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Sample records for liquid phase cyclohexane

  1. Mild ring-opening coupling of liquid-phase cyclohexane to diesel components using sulfated metal oxides.

    PubMed

    Mao, Wei; Ma, Hongzhu; Wang, Bo

    2010-04-15

    We have investigated a mild simple synthesis method for ring-opening coupling of liquid-phase cyclohexane to diesel components using various sulfated metal oxides [SO(4)(2-)/Fe(2)O(3) (SF), SO(4)(2-)/TiO(2) (ST) and SO(4)(2-)/ZrO(2) (SZ)] under low temperature (333K) and atmospheric pressure. Neither solvent nor promoters are needed in the reaction system so as to be a clean approach. Operating under these reaction conditions, a maximum activity of 6% was obtained with SF as catalyst, and a significantly high selectivity of 74.5% for nicer diesel components (n-C(14)-C(18)) was obtained simultaneously. Whereas, ST and SZ displayed low activity for cyclohexane reaction. By utilization of the temperature-programmed desorption of ammonia (NH(3)-TPD) measurement and the N(2) adsorption method, the results suggested that a satisfied acid strength distribution and high density of acid sites appeared in SF catalyst in comparison with other catalysts, which may play an important role in the reaction. PMID:19962237

  2. A shock pressure induced phase transition from liquid to solid of cyclohexane using time-resolved coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Oguchi, Shiro; Sato, Akira; Kondo, Ken-Ichi; Nakamura, Kazutaka

    2007-06-01

    The liquid-solid phase transition of cyclohexane has been studied under laser shock compression up to 3.8 GPa by using nanosecond time-resolved Coherent Anti-stokes Raman Spectroscopy (CARS) and laser shock compression. The shock wave is generated by irradiation of 10 ns pulsed laser beam on the plasma confinement target and its pressure is estimated from a particle velocity, which is measured by optically recording velocity interferometer system (ORVIS). Higher frequency shift of the Raman peaks (ring-breathing, C-C stretching, and CH2 twist modes) was observed at high pressure. At 3.8 GPa, splitting of the peak (CH2 twist mode) due to change in symmetry of surrounding molecules, which corresponds to phase transition to solid IV, was observed at delay time of 20 ns. Rapid liquid-solid phase transition has been directly observed to occur within 20 ns.

  3. Cyclohexane

    Integrated Risk Information System (IRIS)

    Cyclohexane ; CASRN 110 - 82 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

  4. Phase behavior study of polystyrene and deuterated polystyrene in alkyl-cyclohexanes

    NASA Astrophysics Data System (ADS)

    Norman, Zachariah; Powers, Wayne; Ryu, Chang

    2009-03-01

    To advance the controlled chemical modification of polystyrene (PS) and deuterated polystyrene (dPS) in solution, the phase behavior of PS and dPS in alkyl-cyclohexane solvents has been studied. Cloud point measurements have been performed by a house-made turbidity instrument using a picolog thermistor and a laser with a photoelectric cell converted to interface with a picolog TH-03 three channel thermistor converter. Solution phase diagrams for molecular weights of PS varying from 67 thousand to 1.8 million have been presented for methyl cyclohexane, propyl cyclohexane, isopropyl cyclohexane, butyl cyclohexane and isobutyl cyclohexane for the measurements of critical solution temperatures as a function of molecular weight. The theta temperature of polystyrene in each of these solvents has been estimated through extrapolation from the molecular weight dependence of the critical temperatures from the cloud point measurements.

  5. Volumetric, Viscometric, and Ultrasonic Properties of Liquid Mixtures of Cyclohexane with Alkanols at Different Temperatures

    NASA Astrophysics Data System (ADS)

    Ali, Anwar; Tasneem, Shadma; Nabi, Firdosa

    2010-09-01

    The densities (ρ), viscosities (η), and ultrasonic speeds (u) of pure cyclohexane, 1-butanol, 2- butanol, and those of their binary mixtures, with cyclohexane as common component, covering the whole composition range have been measured at 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15 K. From the experimental data the excess molar volume (VE), deviations in isentropic compressibility (Δks), deviations in viscosity (Δη), deviations in ultrasonic speed (Δu), deviations in acoustic impedance (ΔZ), deviations in internal pressure (ΔPi), excess Gibbs free energy of activation (ΔG*E), entropies (ΔS*), and enthalpies (ΔH*) of activation of viscous flow have been determined. The sign and magnitude of these parameters were found to be sensitive towards interactions prevailing in the studied systems. Partial molar volumes (V0φ,2) and partial molar compressibilities (K0φ,2) of 1-butanol and 2-butanol in cyclohexane have also been evaluated. Moreover, VE values were theoretically predicted by using Flory's statistical theory. The variations of derived parameters mentioned above with composition offer a convenient method to study the nature and extent of interactions between the component molecules of the liquid mixtures, not easily obtained by other means

  6. Saturated liquid densities of benzene, cyclohexane, and hexane from 298. 15 to 473. 15 K

    SciTech Connect

    Beg, Shafkat; Tukur, N.M.; Al-Harbi, D.K.; Hamad, E.Z. . Dept. of Chemical Engineering)

    1993-07-01

    The results of measurements of saturated liquid densities using a high-pressure stainless steel pycnometer system over a wide variation of temperature from 298.15 to 473.15 K are presented for benzene, cyclohexane, and hexane. Experimental densities were compared with those predicted by the Spencer-Danner-modified Rackett equation (SDR) and the Hankinson-Brobst-Thompson correlation (HBT). The SDR showed an average deviation of 0.22% while the HBT predicted the densities of the three organic solvents with an average deviation of 0.28%. The data obtained have also been compared with the available data reported in the literature.

  7. Microemulsions with surfactant TX100, cyclohexane, and an ionic liquid investigated by conductance, DLS, FTIR measurements, and study of solvent and rotational relaxation within this microemulsion.

    PubMed

    Pramanik, Rajib; Sarkar, Souravi; Ghatak, Chiranjib; Rao, Vishal Govind; Setua, Palash; Sarkar, Nilmoni

    2010-06-10

    Room-temperature ionic liquids (RTILs), N,N,N-trimethyl-N-propyl ammonium bis(trifluoromethanesulfonyl) imide ([N(3111)][Tf(2)N]), were substituted for polar water and formed nonaqueous microemulsions with cyclohexane by the aid of nonionic surfactant TX-100. The phase behavior of the ternary system was investigated, and microregions of [N(3111)][Tf(2)N]-in-cyclohexane (IL/O), bicontinuous, and cyclohexane-in-[N(3111)][Tf(2)N] (O/IL) were identified by traditional electrical conductivity measurements. Dynamic light scattering (DLS) revealed the formation of the IL microemulsions. The FTIR study of O-H stretching band of TX100 also supports this finding. The dynamics of solvent and rotational relaxation have been investigated in [N(3111)][Tf(2)N]/TX100/cyclohexane microemulsions using steady-state and time-resolved fluorescence spectroscopy as a tool and coumarin 480 (C-480) as a fluorescence probe. The size of the microemulsions increases with gradual addition of [N(3111)][Tf(2)N], which revealed from DLS measurement. This leads to the faster collective motions of cation and anions of [N(3111)][Tf(2)N], which contributes to faster solvent relaxation in microemulsions. PMID:20469906

  8. Mutual diffusion of binary liquid mixtures containing methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride.

    PubMed

    Guevara-Carrion, Gabriela; Janzen, Tatjana; Muñoz-Muñoz, Y Mauricio; Vrabec, Jadran

    2016-03-28

    Mutual diffusion coefficients of all 20 binary liquid mixtures that can be formed out of methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride without a miscibility gap are studied at ambient conditions of temperature and pressure in the entire composition range. The considered mixtures show a varying mixing behavior from almost ideal to strongly non-ideal. Predictive molecular dynamics simulations employing the Green-Kubo formalism are carried out. Radial distribution functions are analyzed to gain an understanding of the liquid structure influencing the diffusion processes. It is shown that cluster formation in mixtures containing one alcoholic component has a significant impact on the diffusion process. The estimation of the thermodynamic factor from experimental vapor-liquid equilibrium data is investigated, considering three excess Gibbs energy models, i.e., Wilson, NRTL, and UNIQUAC. It is found that the Wilson model yields the thermodynamic factor that best suits the simulation results for the prediction of the Fick diffusion coefficient. Four semi-empirical methods for the prediction of the self-diffusion coefficients and nine predictive equations for the Fick diffusion coefficient are assessed and it is found that methods based on local composition models are more reliable. Finally, the shear viscosity and thermal conductivity are predicted and in most cases favorably compared with experimental literature values. PMID:27036455

  9. Mutual diffusion of binary liquid mixtures containing methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride

    NASA Astrophysics Data System (ADS)

    Guevara-Carrion, Gabriela; Janzen, Tatjana; Muñoz-Muñoz, Y. Mauricio; Vrabec, Jadran

    2016-03-01

    Mutual diffusion coefficients of all 20 binary liquid mixtures that can be formed out of methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride without a miscibility gap are studied at ambient conditions of temperature and pressure in the entire composition range. The considered mixtures show a varying mixing behavior from almost ideal to strongly non-ideal. Predictive molecular dynamics simulations employing the Green-Kubo formalism are carried out. Radial distribution functions are analyzed to gain an understanding of the liquid structure influencing the diffusion processes. It is shown that cluster formation in mixtures containing one alcoholic component has a significant impact on the diffusion process. The estimation of the thermodynamic factor from experimental vapor-liquid equilibrium data is investigated, considering three excess Gibbs energy models, i.e., Wilson, NRTL, and UNIQUAC. It is found that the Wilson model yields the thermodynamic factor that best suits the simulation results for the prediction of the Fick diffusion coefficient. Four semi-empirical methods for the prediction of the self-diffusion coefficients and nine predictive equations for the Fick diffusion coefficient are assessed and it is found that methods based on local composition models are more reliable. Finally, the shear viscosity and thermal conductivity are predicted and in most cases favorably compared with experimental literature values.

  10. Fluid Phase Topology of Benzene + Cyclohexane + 1-Propanol at 101.3 kPa

    NASA Astrophysics Data System (ADS)

    Andrade, R. S.; Iglesias, M.

    2015-07-01

    Isobaric vapor-liquid equilibria for the benzene + cyclohexane + 1-propanol ternary mixture were experimentally investigated at atmospheric pressure. Data were tested and considered thermodynamically consistent by means of the McDermott and Ellis method. The experimental results showed that this ternary mixture is completely miscible and exhibits three binary minimum homogeneous azeotropes and a ternary minimum azeotrope at the studied conditions. Satisfactory results were obtained for correlation of equilibrium compositions with the UNIQUAC equation and also for prediction with the UNIFAC method. In both cases, low root-mean-square deviations of the vapor mole fraction and temperature were calculated. The capability of 1-propanol as a modified distillation agent at atmospheric conditions is discussed in terms of thermodynamic topological analysis. However, because of the complex topology of the ternary mixture, it leads to a distillation scheme with two columns specifying ternary azeotrope recycling and difficult operation. Thus, this compound is not recommended as a separation agent for the binary benzene + cyclohexane azeotrope.

  11. The intermolecular vibrational dynamics of substituted benzene and cyclohexane liquids, studied by femtosecond OHD-RIKES

    SciTech Connect

    Castner, E.W. Jr.; Chang, Yong Joon

    1995-06-01

    By using the femtosecond optical-heterodyne detected, Raman-induced Kerr effect spectroscopy (OHD-RIKES), we have studied the intermolecular dynamics of toluene, benzyl alcohol, benzonitrile, cyclohexane, and methylcyclohexane in both the time and frequency domains.

  12. Solubility dynamic of methyl yellow and carbon black in microemulsions and lamellar liquid crystal of water, non ionic surfactants and cyclohexane system

    NASA Astrophysics Data System (ADS)

    Amran, A.; Harfianto, R.; Dewi, W. Y.; Beri, D.; Putra, A.

    2016-02-01

    Solubility dynamics of methyl yellow and carbon black in microemulsions and liquid crystals of water, non-ionic surfactants and cyclohexane system, have been investigated. Actually, solubility dynamics of these dyes both in microemulsion (w/o microemulsions) and the lamellar liquid crystal (LLC) were strongly related to the chemical composition, nature and characteristics of microemulsions and the lamellar liquid crystals.

  13. Gas-phase chemistry during the conversion of cyclohexane to carbon: Flow reactor studies at low and intermediate pressure

    SciTech Connect

    Osterheld, T.H.; Allendorf, M.D.; Larson, R.

    1995-07-01

    The gas-phase branching during the conversion of cyclohexane to solid carbon has been measured in a high-temperature-flow reactor. The experiments show that cyclohexane decomposes into a broad distribution of hydrocarbons that further decompose into the more kinetically stable products hydrogen, methane, acetylene, ethylene, benzene, and PAH. At 1363 K, the evolution to these species occurs quickly. We also observe the buildup of significant amounts of aromatic molecules at later stages in the decomposition, with as much as 15% of the total carbon in PAH and 25% in benzene. At later stages, the gas-phase molecules react slowly, even though the system is not at equilibrium, because of their kinetic stability and the smaller radical pool. The decomposition does not appear to depend sensitively on pressure in the regime of 25 to 250 torr. Thus, to a first approximation, these results can be extrapolated to atmospheric pressure.

  14. Second virial coefficient of bmimBF4/triton X-100/ cyclohexane ionic liquid microemulsion as investigated by microcalorimetry.

    PubMed

    Li, Na; Zhang, Shaohua; Zheng, Liqiang; Gao, Yan'an; Yu, Li

    2008-04-01

    The second virial coefficient of the ionic liquid (IL) microemulsion was obtained for the first time using microcalorimetry. The heat of dilution of the microemulsion solutions was measured by isothermal titration microcalorimetry (ITC), and the second virial coefficient was derived from the heat of dilution and the number density of the IL microemulsion solutions on the basis of a hard-sphere interaction potential assumption and as a function of the second-order polynomial. The validity of the second virial coefficient was confirmed by the percolation behavior of different ionic liquid microemulsion solutions of Triton X-100 in cyclohexane with or without added salts. The information obtained from the second virial coefficient shows that the interactions between ionic liquid microemulsion droplets are much stronger than those for traditional microemulsions, which may be attributed to the relatively larger size of the microemulsion droplets. PMID:18312017

  15. Mise en évidence d'états excités dans les spectres de photoionisation du cyclohexane et du diméthyl 2-2-butane liquides

    NASA Astrophysics Data System (ADS)

    Casanovas, J.; Guelfucci, J. P.; Caselles, O.

    1991-07-01

    Excited states are probably occurring, at an intermediate stage, in the VUV photoionization process of liquid hydrocarbons, as suggested by a Stern-Volmer behaviour when interacting with electron quenchers. They are here detected in the VUV photoionization spectrum of cyclohexane and dimethyl-2-2-butane in liquid phase. Some of the discernable peaks can be assigned as valence and Rydberg states, yet observed in gas phase. Supplementary peaks are observed, the existence of which is to be interpretated. L'existence d'états excités dans le processus de photoionisation VUV des hydrocarbures en phase liquide - précédemment suggérée par l'observation de la loi de Stern-Volmer lors de l'interaction avec des capteurs d'électrons - est ici détectée en traçant le spectre de photoionisation VUV du cyclohexane et du diméthyl-2-2-butane purs en phase liquide. Certains des pics observés coïncident avec les états de valence et de Rydberg de ces mêmes corps en phase gaz. Il apparaît des pics supplémentaires dont la nature doit être précisée.

  16. LIGHT NONAQUEOUS PHASE LIQUIDS

    EPA Science Inventory

    Nonaqueous phase liquids (NAPLS) are hydrocarbons that exist as a separate, immiscible phase when in contact with water and/or air. ifferences in the physical and chemical properties of water and NAPL result in the formation of a physical interface between the liquids which preve...

  17. Dynamic Kerr effect study on six-membered-ring molecular liquids: benzene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, cyclohexene, and cyclohexane.

    PubMed

    Kakinuma, Shohei; Shirota, Hideaki

    2015-04-01

    The intermolecular dynamics of five six-membered-ring molecular liquids having different aromaticities-benzene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, cyclohexene, and cyclohexane-measured by femtosecond Raman-induced Kerr effect spectroscopy have been compared in this study. The line shapes of the Fourier transform low-frequency spectra, which arise from the intermolecular vibrational dynamics, are trapezoidal for benzene and 1,3-cyclohexadiene, triangular for 1,4-cyclohexadiene and cyclohexene, and monomodal for cyclohexane. The trapezoidal shapes of the low-frequency spectra of benzene and 1,3-cyclohexadiene are due to the librational motions of their aromatic planar structures, which cause damped nuclear response features. The time integrals of the nuclear responses of the five liquids correlate to the squares of the polarizability anisotropies of the molecules calculated on the basis of density functional theory. The first moments of the low-frequency spectra roughly linearly correlate to the bulk parameters of the square roots of the surface tensions divided by the densities and the square roots of the surface tensions divided by the molecular weights, but the plots for cyclohexene deviate slightly from the correlations. The picosecond overdamped transients of the liquids are well fitted by a biexponential function. The fast time constants of all of the liquids are approximately 1.1-1.4 ps, and they do not obey the Stokes-Einstein-Debye hydrodynamic model. On the other hand, the slow time constants are roughly linearly proportional to the products of the shear viscosities and the molar volumes. The observed intramolecular vibrational modes at less than 700 cm(-1) for all of the liquids are also assigned on the basis of quantum chemistry calculations. PMID:25741755

  18. Syntheses and crystal structures of benzene-sulfonate and -carboxylate copper polymers and their application in the oxidation of cyclohexane in ionic liquid under mild conditions.

    PubMed

    Hazra, Susanta; Ribeiro, Ana P C; Guedes da Silva, M Fátima C; Nieto de Castro, Carlos A; Pombeiro, Armando J L

    2016-09-21

    The syntheses, crystal structures and catalytic activities of the polymers derived from 2-(2-pyridylmethyleneamino)benzenesulfonic acid (HL), viz. [CuL(H2tma)]n (1) and [{Cu2L2(H2pma)}·(8H2O)]n (2) [H3tma = benzene-1,3,5-tricarboxylic (trimesic) acid and H4pma = benzene-1,2,4,5-tetracarboxylic (pyromellitic) acid], are presented. Despite the comparable combinations and compositions of ligands (sulfonate and carboxylate) in these two polymers the bridging moiety in 1 is sulfonate while in 2 it is carboxylate. Complexes 1 and 2 act as catalysts in the peroxidative oxidation of cyclohexane under mild conditions using either the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] or acetonitrile as the solvent. The ionic liquid medium leads to increases in the yields and in the turnover numbers, achieved in shorter reaction times in comparison with those when using the conventional acetonitrile solvent. A simple recycling of the catalysts in the ionic liquid medium is achieved without loss of activity and selectivity. PMID:27529408

  19. New statistical mechanical model for calculating Kirkwood factors in self-associating liquid systems and its application to alkanol+cyclohexane mixtures

    NASA Astrophysics Data System (ADS)

    Vasiltsova, Tatiana; Heintz, Andreas

    2007-09-01

    A new statistical mechanical model for calculating Kirkwood factors in self-associating molecular liquids and their mixtures with nonassociating components has been developed in a consistent way which is based on an extended version of the Flory-Huggins model taking into account chemical association equilibria. The majority of molecular parameters involved into the theory has been fixed by independent quantum mechanical ab initio calculations of associated molecular clusters. The model is also able to predict other thermodynamic mixture properties such as the enthalpy of mixing and also the infrared absorbance of monomer alcohol species as function of concentration. Experimental results of nine alcohol+cyclohexane mixtures taken from the literature have been used to test the new model. The Kirkwood correlation factor gK, the molar enthalpy of mixing HmE, and the monomer IR absorbance can be described simultaneously in excellent agreement with experimental data covering the whole range of mole fraction including temperature dependence of gK, HmE, and the IR absorbance. Two parameters have been adjusted freely for each system. A third parameter for the nonspecific intermolecular dispersion interactions has been adjusted within a limited range of possible values given by physical arguments. The model opens a new way of a more reliable understanding of structures and equilibrium properties of hydrogen bonded systems in the condensed liquid state.

  20. PHASE CHANGE LIQUIDS

    SciTech Connect

    Susan S. Sorini; John F. Schabron

    2006-03-01

    Work is being performed to develop a new shipping system for frozen environmental samples (or other materials) that uses an optimal phase change liquid (PCL) formulation and an insulated shipping container with an on-board digital temperature data logger to provide a history of the temperature profile within the container during shipment. In previous work, several PCL formulations with temperatures of fusion ranging from approximately -14 to -20 C were prepared and evaluated. Both temperature of fusion and heat of fusion of the formulations were measured, and an optimal PCL formulation was selected. The PCL was frozen in plastic bags and tested for its temperature profile in a cooler using a digital temperature data logger. This testing showed that the PCL formulation can maintain freezer temperatures (< -7 to -20 C) for an extended period, such as the time for shipping samples by overnight courier. The results of the experiments described in this report provide significant information for use in developing an integrated freezer system that uses a PCL formulation to maintain freezer temperatures in coolers for shipping environmental samples to the laboratory. Experimental results show the importance of the type of cooler used in the system and that use of an insulating material within the cooler improves the performance of the freezer system. A new optimal PCL formulation for use in the system has been determined. The new formulation has been shown to maintain temperatures at < -7 to -20 C for 47 hours in an insulated cooler system containing soil samples. These results are very promising for developing the new technology.

  1. Liquid-Phase Adsorption Fundamentals.

    ERIC Educational Resources Information Center

    Cooney, David O.

    1987-01-01

    Describes an experiment developed and used in the unit operations laboratory course at the University of Wyoming. Involves the liquid-phase adsorption of an organic compound from aqueous solution on activated carbon, and is relevant to adsorption processes in general. (TW)

  2. Liquid liquid phase transition in Stillinger Weber silicon

    NASA Astrophysics Data System (ADS)

    Beaucage, Philippe; Mousseau, Normand

    2005-04-01

    It was recently demonstrated that Stillinger-Weber silicon undergoes a liquid-liquid first-order phase transition deep into the supercooled region (Sastry and Angell 2003 Nat. Mater. 2 739). Here we study the effects of perturbations on this phase transition. We show that the order of the liquid-liquid transition changes with negative pressure. We also find that the liquid-liquid transition disappears when the three-body term of the potential is strengthened by as little as 5%. This implies that the details of the potential could affect strongly the nature and even the existence of the liquid-liquid phase.

  3. Effect of water on the solvent relaxation dynamics in an ionic liquid containing microemulsion of 1-butyl-3-methyl imidazolium tetrafluoroborate/TritonX-100/cyclohexane

    NASA Astrophysics Data System (ADS)

    Pramanik, Rajib; Sarkar, Souravi; Ghatak, Chiranjib; Setua, Palash; Rao, Vishal Govind; Sarkar, Nilmoni

    2010-04-01

    The dynamics of solvent and rotational relaxation have been investigated in [bmim][BF 4]/TX-100/cyclohexane microemulsions with addition of water-using steady state and time-resolved fluorescence spectroscopy as a tool and coumarin 480 (C-480) as a fluorescence probe. The added water decreases the size of the microemulsions; consequently solvent relaxation time increases. The rotational relaxation time of C-480 in microemulsions is almost unchanged with increase in amount of water in microemulsions.

  4. Phase equilibria and modeling of pyridinium-based ionic liquid solutions.

    PubMed

    Domańska, Urszula; Królikowski, Marek; Ramjugernath, Deresh; Letcher, Trevor M; Tumba, Kaniki

    2010-11-25

    The phase diagrams of the ionic liquid (IL) N-butyl-4-methylpyridinium bis{(trifluoromethyl)sulfonyl}imide ([BM(4)Py][NTf(2)]) with water, an alcohol (1-butanol, 1-hexanol, 1-octanol, 1-decanol), an aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene), an alkane (n-hexane, n-heptane, n-octane), or cyclohexane have been measured at atmospheric pressure using a dynamic method. This work includes the characterization of the synthesized compound by water content and also by differential scanning calorimetry. Phase diagrams for the binary systems of [BM(4)Py][NTf(2)] with all solvents reveal eutectic systems with regards to (solid-liquid) phase equilibria and show immiscibility in the liquid phase region with an upper critical solution temperature (UCST) in most of the mixtures. The phase equilibria (solid, or liquid-liquid) for the binary systems containing aliphatic hydrocarbons reported here exhibit the lowest solubility and the highest immiscibility gap, a trend which has been observed for all ILs. The reduction of experimental data has been carried out using the nonrandom two-liquid (NRTL) correlation equation. The phase diagrams reported here have been compared with analogous phase diagrams reported previously for systems containing the IL N-butyl-4-methylpyridinium tosylate and other pyridinium-based ILs. The influence of the anion of the IL on the phase behavior has been discussed. PMID:20964426

  5. Liquid-phase chromatography detector

    DOEpatents

    Voigtman, Edward G.; Winefordner, James D.; Jurgensen, Arthur R.

    1983-01-01

    A liquid-phase chromatography detector comprising a flow cell having an inlet tubular conduit for receiving a liquid chromatographic effluent and discharging it as a flowing columnar stream onto a vertically adjustable receiving surface spaced apart from and located vertically below and in close proximity to the discharge end of the tubular conduit; a receiver adapted to receive liquid overflowing from the receiving surface; an exit conduit for continuously removing liquid from the receiver; a light source for focussing fluorescence-producing light pulses on the flowing columnar stream as it passes from the outlet of the conduit to the receiving surface and a fluorescence detector to detect the produced fluorescence; a source of light pulse for producing acoustic waves in the columnar stream as it passes from the conduit outlet to the receiving surface; and a piezoelectric transducer adapted to detect those waves; and a source of bias voltage applied to the inlet tubular conduit and adapted to produce ionization of the liquid flowing through the flow cell so as to produce photocurrents therein and an electrical system to detect and record the photocurrents. This system is useful in separating and detecting individual chemical compounds from mixtures thereof.

  6. Liquid-phase chromatography detector

    DOEpatents

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

    1983-11-08

    A liquid-phase chromatography detector comprises a flow cell having an inlet tubular conduit for receiving a liquid chromatographic effluent and discharging it as a flowing columnar stream onto a vertically adjustable receiving surface spaced apart from and located vertically below and in close proximity to the discharge end of the tubular conduit; a receiver adapted to receive liquid overflowing from the receiving surface; an exit conduit for continuously removing liquid from the receiver; a light source for focusing fluorescence-producing light pulses on the flowing columnar stream as it passes from the outlet of the conduit to the receiving surface and a fluorescence detector to detect the produced fluorescence; a source of light pulse for producing acoustic waves in the columnar stream as it passes from the conduit outlet to the receiving surface; and a piezoelectric transducer adapted to detect those waves; and a source of bias voltage applied to the inlet tubular conduit and adapted to produce ionization of the liquid flowing through the flow cell so as to produce photocurrents therein and an electrical system to detect and record the photocurrents. This system is useful in separating and detecting individual chemical compounds from mixtures thereof. 5 figs.

  7. Models for a liquid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Buldyrev, S. V.; Franzese, G.; Giovambattista, N.; Malescio, G.; Sadr-Lahijany, M. R.; Scala, A.; Skibinsky, A.; Stanley, H. E.

    2002-02-01

    We use molecular dynamics simulations to study two- and three-dimensional models with the isotropic double-step potential which in addition to the hard core has a repulsive soft core of larger radius. Our results indicate that the presence of two characteristic repulsive distances (hard core and soft core) is sufficient to explain liquid anomalies and a liquid-liquid phase transition, but these two phenomena may occur independently. Thus liquid-liquid transitions may exist in systems like liquid metals, regardless of the presence of the density anomaly. For 2D, we propose a model with a specific set of hard core and soft core parameters, that qualitatively reproduces the phase diagram and anomalies of liquid water. We identify two solid phases: a square crystal (high density phase), and a triangular crystal (low density phase) and discuss the relation between the anomalies of liquid and the polymorphism of the solid. Similarly to real water, our 2D system may have the second critical point in the metastable liquid phase beyond the freezing line. In 3D, we find several sets of parameters for which two fluid-fluid phase transition lines exist: the first line between gas and liquid and the second line between high-density liquid (HDL) and low-density liquid (LDL). In all cases, the LDL phase shows no density anomaly in 3D. We relate the absence of the density anomaly with the positive slope of the LDL-HDL phase transition line.

  8. Novel Detection Method of Liquid-Liquid Phase Separation

    NASA Astrophysics Data System (ADS)

    Kato, Hitoshi; Katayanagi, Hideki; Koga, Yoshikata; Nishikawa, Keiko

    2004-12-01

    A novel method of determining a liquid-liquid phase boundary was developed. This method is based on our discovery that a nascent low-density phase is attracted to the center of a Rankine vortex at the onset of phase separation. Thus a liquid-liquid phase boundary is detected easily, rapidly, and accurately. The phase diagrams of the ternary systems NaCl-H2O-1-propanol and NaCl-H2O-1-butanol were obtained by this method. The results matched well with literature values.

  9. Mixed Stationary Liquid Phases for Gas-Liquid Chromatography.

    ERIC Educational Resources Information Center

    Koury, Albert M.; Parcher, Jon F.

    1979-01-01

    Describes a laboratory technique for use in an undergraduate instrumental analysis course that, using the interpretation of window diagrams, prepares a mixed liquid phase column for gas-liquid chromatography. A detailed procedure is provided. (BT)

  10. Spontaneous liquid-liquid phase separation of water.

    PubMed

    Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

    2014-02-01

    We report a molecular dynamics simulation demonstrating a fast spontaneous liquid-liquid phase separation of water and a subsequent slow crystallization to ice. It is found that supercooled water separates rapidly into low- and high-density domains so as to reduce the surface energy in the rectangular simulation cell at certain thermodynamic states. The liquid-liquid phase separation, which is about two orders of magnitude faster than the crystallization, suggests a possibility to observe this phenomenon experimentally. PMID:25353404

  11. Liquid Phase Miscibility Gap Materials

    NASA Technical Reports Server (NTRS)

    Gelles, S. H.; Markworth, A. J.

    1985-01-01

    The manner in which the microstructural features of liquid-phase miscibility gap alloys develop was determined. This will allow control of the microstructures and the resultant properties of these alloys. The long-duration low gravity afforded by the shuttle will allow experiments supporting this research to be conducted with minimal interference from buoyancy effects and gravitationally driven convection currents. Ground base studies were conducted on Al-In, Cu-Pb, and Te-Tl alloys to determine the effect of cooling rate, composition, and interfacial energies on the phase separation and solidification processes that influence the development of microstructure in these alloys. Isothermal and directional cooling experiments and simulations are conducted. The ground based activities are used as a technological base from which flight experiments formulated and to which these flight experiments are compared.

  12. Transient liquid phase ceramic bonding

    DOEpatents

    Glaeser, Andreas M.

    1994-01-01

    Ceramics are joined to themselves or to metals using a transient liquid phase method employing three layers, one of which is a refractory metal, ceramic or alloy. The refractory layer is placed between two metal layers, each of which has a lower melting point than the refractory layer. The three layers are pressed between the two articles to be bonded to form an assembly. The assembly is heated to a bonding temperature at which the refractory layer remains solid, but the two metal layers melt to form a liquid. The refractory layer reacts with the surrounding liquid and a single solid bonding layer is eventually formed. The layers may be designed to react completely with each other and form refractory intermetallic bonding layers. Impurities incorporated into the refractory metal may react with the metal layers to form refractory compounds. Another method for joining ceramic articles employs a ceramic interlayer sandwiched between two metal layers. In alternative embodiments, the metal layers may include sublayers. A method is also provided for joining two ceramic articles using a single interlayer. An alternate bonding method provides a refractory-metal oxide interlayer placed adjacent to a strong oxide former. Aluminum or aluminum alloys are joined together using metal interlayers.

  13. An Equation of State for the Thermodynamic Properties of Cyclohexane

    SciTech Connect

    Zhou, Yong Liu, Jun; Penoncello, Steven G.; Lemmon, Eric W.

    2014-12-15

    An equation of state for cyclohexane has been developed using the Helmholtz energy as the fundamental property with independent variables of density and temperature. Multi-property fitting technology was used to fit the equation of state to data for pρT, heat capacities, sound speeds, virial coefficients, vapor pressures, and saturated densities. The equation of state was developed to conform to the Maxwell criteria for two-phase vapor-liquid equilibrium states, and is valid from the triple-point temperature to 700 K, with pressures up to 250 MPa and densities up to 10.3 mol dm{sup −3}. In general, the uncertainties (k = 2, indicating a level of confidence of 95%) in density for the equation of state are 0.1% (liquid and vapor) up to 500 K, and 0.2% above 500 K, with higher uncertainties within the critical region. Between 283 and 473 K with pressures lower than 30 MPa, the uncertainty is as low as 0.03% in density in the liquid phase. The uncertainties in the speed of sound are 0.2% between 283 and 323 K in the liquid, and 1% elsewhere. Other uncertainties are 0.05% in vapor pressure and 2% in heat capacities. The behavior of the equation of state is reasonable within the region of validity and at higher and lower temperatures and pressures. A detailed analysis has been performed in this article.

  14. Enhanced mineralization of organic compounds in nonaqueous-phase liquids

    SciTech Connect

    Labare, M.P.; Alexander, M.

    1995-11-01

    Biodegradation of phenanthrene, biphenyl, or di(2-ethylhexyl) phthalate initially present in a variety of nonaqueous-phase liquids (NAPLs) was slow in samples of soil and aquifer solids. The NAPLs were hexadecane, dibutyl phthalate, 2, 2, 4 ,4, 6, 8, 8-heptamethylnonane, cyclohexane, commercial oils, crude oil, creosote, and kerosene. Slurrying the soil or aquifer solids markedly enhanced the rate and extent of mineralization of the test compounds initially in many of the NAPLs. Both the low rate and extent of mineralization of the three compounds initially in dibutyl phthalate in soil slurries and of di(2- ethylhexyl) phthalate in heptamethylnonane present in slurries of aquifer solids were increased by inoculation of acclimated microbial cultures. Increasing the NAPL volume decreased phenanthrene biodegradation in soil, but the effect of larger NAPL volume could be alleviated by slurrying and inoculation. The rate or extent of mineralization in aquifer slurries of di(2-ethylhexyi) phthalate initially in some NAPLs was increased by addition of N and P, and inoculation further enhanced the degradation.

  15. Liquid phase sintering of silicon carbide

    DOEpatents

    Cutler, R.A.; Virkar, A.V.; Hurford, A.C.

    1989-05-09

    Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1,600 C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase. 4 figs.

  16. Liquid phase sintering of silicon carbide

    DOEpatents

    Cutler, Raymond A.; Virkar, Anil V.; Hurford, Andrew C.

    1989-01-01

    Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1600.degree. C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase.

  17. Liquid-phase combinatorial synthesis.

    PubMed Central

    Han, H; Wolfe, M M; Brenner, S; Janda, K D

    1995-01-01

    A concept termed liquid-phase combinatorial synthesis (LPCS) is described. The central feature of this methodology is that it combines the advantages that classic organic synthesis in solution offers with those that solid-phase synthesis can provide, through the application of a linear homogeneous polymer. To validate this concept two libraries were prepared, one of peptide and the second of nonpeptide origin. The peptide-based library was synthesized by a recursive deconvolution strategy [Erb, E., Janda, K. D. & Brenner, S. (1994) Proc. Natl. Acad. Sci. USA 91, 11422-11426] and several ligands were found within this library to bind a monoclonal antibody elicited against beta-endorphin. The non-peptide molecules synthesized were arylsulfonamides, a class of compounds of known clinical bactericidal efficacy. The results indicate that the reaction scope of LPCS should be general, and its value to multiple, high-throughput screening assays could be of particular merit, since multimilligram quantities of each library member can readily be attained. PMID:7541541

  18. Modeling liquid-liquid phase transitions and quasicrystal formation

    NASA Astrophysics Data System (ADS)

    Skibinsky, Anna

    In this thesis, studies which concern two different subjects related to phase transitions in fluids and crystalline solids are presented. Condensed matter formation, structure, and phase transitions are modeled using molecular dynamics simulations of simple discontinuous potentials with attractive and repulsive interactions. Novel phase diagrams are proposed for quasicrystals, crystals, and liquids. In the first part of the thesis, the formation of a quasicrystal in a two dimensional monodisperse system is investigated using molecular dynamics simulations of hard sphere particles interacting via a two-dimensional square-well potential. It is found that for certain values of the square-well parameters more than one stable crystalline phase can form. By quenching the liquid phase at a very low temperature, an amorphous phase is obtained. When this the amorphous phase is heated, a quasicrystalline structure with five-fold symmetry forms. From estimations of the Helmholtz potentials of the stable crystalline phases and of the quasicrystal, it is concluded that within a specific temperature range, the observed quasicrystal phase can be the stable phase. The second part of the thesis concerns a study of the liquid-liquid phase transition for a single-component system in three dimensions, interacting via an isotropic potential with a repulsive soft-core shoulder at short distance and an attractive well at an intermediate distance. The potential is similar to potentials used to describe such liquid systems as colloids, protein solutions, or liquid metals. It is shown that the phase diagram for such a potential can have two lines of first-order fluid-fluid phase transitions: one separating a gas and a low-density liquid (LDL), and another between the LDL and a high-density liquid (HDL). Both phase transition lines end in a critical point, a gas-LDL critical point and, depending on the potential parameters, either a gas-HDL critical point or a LDL-HDL critical point. A

  19. Critical behaviour of ionic solutions in non-polar solvents with a liquid - liquid phase transition

    NASA Astrophysics Data System (ADS)

    Schröer, W.; Kleemeier, M.; Plikat, M.; Weiss, V.; Wiegand, S.

    1996-11-01

    Turbidity measurements showing crossover from mean-field to Ising criticality have been reported by Narayanan and Pitzer for the liquid - liquid phase transition in ionic solutions of alkyl-ammonium picrates in higher alcohols. The Ising region was found to increase with the dielectric permittivity D for solvents with 4 < D < 8. It was conjectured that the Ising region becomes too small to be observed for lower values of D, which is in accordance with the finding of mean-field criticality in the system triethylhexylammonium triethylhexylborate 0953-8984/8/47/023/img1 in diphenyl ether 0953-8984/8/47/023/img2, where 0953-8984/8/47/023/img3. In order to check this hypothesis, we investigate solutions of salts in non-protonating solvents with D<2.5. The systems are tetrabutylammonium naphthyl sulphonate 0953-8984/8/47/023/img4 in toluene and tributylheptylammonium dodecyl sulphate 0953-8984/8/47/023/img5 in cyclohexane. The location of the critical points in the corresponding state diagram is in general agreement with the model system of charged hard spheres in a dielectric continuum, i.e. the restricted primitive model (RPM). However, changes of 0953-8984/8/47/023/img6 by minute variations of the salt and of the solvent (toluene, xylene, ethylbenzene) cannot be explained by the RPM. We report measurements of the phase diagram and light-scattering results. The amplitudes of the correlation length are up to an order of magnitude larger than those typically found in non-ionic fluids. For the new systems, but also for the solution of 0953-8984/8/47/023/img7 in 0953-8984/8/47/023/img8, Ising criticality is found in the region of 0953-8984/8/47/023/img9.

  20. Operation with three liquid phases in a staged liquid-liquid contactor

    SciTech Connect

    Leonard, R.A.; Ziegler, A.A.; Wigeland, R.A.; Bane, R.W.; Steindler, M.J.

    1983-03-01

    Operation with three liquid phases was demonstrated in a staged liquid-liquid contactor. The possibility that three liquid phases could be handled in a liquid-liquid contactor normally used with two liquid phases was initially established using a laboratory batch test. Tht three liquid phases were obtained using a thorium flow sheet having high concentrations of both acid and thorium. To analyze the batch test, the concept of a dimensionless dispersion number for use with two liquid phases was extended so that it could be applied to three liquid phases. Based on the batch tests, continuous flow tests were run in a staged liquid-liquid contactor used for solvent extraction. A critical factor in the success of these tests was determining the position of the liquid-liquid interface in the contactor. Thus, a contactor was used which allows the position of the liquid-liquid interface to be adjusted. Actual three-phase operation was demonstrated using a 4-cm annular centrifugal contactor, albeit with a somewhat greater (3 to 4 vol. %) aqueous-phase contamination of the organic exit stream than normal (< 1 vol. %).

  1. A Cu(ii) MOF with a flexible bifunctionalised terpyridine as an efficient catalyst for the single-pot hydrocarboxylation of cyclohexane to carboxylic acid in water/ionic liquid medium.

    PubMed

    Paul, Anup; Ribeiro, Ana P C; Karmakar, Anirban; Guedes da Silva, M Fátima C; Pombeiro, Armando J L

    2016-08-01

    The copper(ii) metal-organic framework (MOF) [Cu(η-1κN,N',N'':2κO,O'-L)(NO3)]n (1) [L = 4-((4-([2,2':6',2''-terpyridin]-4'-yl)benzyl)oxy)benzoate] has been synthesized from a flexible bifunctionalised terpyridine species (HL). It was characterized by elemental, FT-IR, powder and single crystal X-ray diffraction analyses. Single crystal X-ray crystallography of 1 shows a 1D polymeric architecture, whose topological analysis illustrates a uninodal (2)-connected net having topological type 2C1. 1 shows good catalytic activity and selectivity towards the hydrocarboxylation of cyclohexane to cyclohexanecarboxylic acid in water/acetonitrile or water/ionic liquid [BMPyr][NTf2] [BMPyr = 1-butyl-1 methylpyrrolidinium; NTf2 = bis(trifluoromethanesulfonyl)imide] medium. It can be recycled and reused without any significant loss of catalytic efficiency. This study provides the first example of an efficient alkane hydrocarboxylation to carboxylic acid, in an ionic liquid and under mild conditions. PMID:27460349

  2. Randomized Grain Boundary Liquid Crystal Phase

    NASA Astrophysics Data System (ADS)

    Chen, D.; Wang, H.; Li, M.; Glaser, M.; Maclennan, J.; Clark, N.

    2012-02-01

    The formation of macroscopic, chiral domains, in the B4 and dark conglomerate phases, for example, is a feature of bent-core liquid crystals resulting from the interplay of chirality, molecular bend and molecular tilt. We report a new, chiral phase observed in a hockey stick-like liquid crystal molecule. This phase appears below a smectic A phase and cools to a crystal phase. TEM images of the free surface of the chiral phase show hundreds of randomly oriented smectic blocks several hundred nanometers in size, similar to those seen in the twist grain boundary (TGB) phase. However, in contrast to the TGB phase, these blocks are randomly oriented. The characteristic defects in this phase are revealed by freeze-fracture TEM images. We will show how these defects mediate the randomized orientation and discuss the intrinsic mechanism driving the formation of this phase. This work is supported by NSF MRSEC Grant DMR0820579 and NSF Grant DMR0606528.

  3. Phase behavior of ionic liquid crystals

    NASA Astrophysics Data System (ADS)

    Kondrat, S.; Bier, M.; Harnau, L.

    2010-05-01

    Bulk properties of ionic liquid crystals are investigated using density functional theory. The liquid crystal molecules are represented by ellipsoidal particles with charges located in their center or at their tails. Attractive interactions are taken into account in terms of the Gay-Berne pair potential. Rich phase diagrams involving vapor, isotropic and nematic liquid, as well as smectic phases are found. The dependence of the phase behavior on various parameters such as the length of the particles and the location of charges on the particles is studied.

  4. Generic mechanism for generating a liquid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Franzese, Giancarlo; Malescio, Gianpietro; Skibinsky, Anna; Buldyrev, Sergey V.; Stanley, H. Eugene

    2001-02-01

    Recent experimental results indicate that phosphorus-a single-component system-can have a high-density liquid (HDL) and a low-density liquid (LDL) phase. A first-order transition between two liquids of different densities is consistent with experimental data for a variety of materials, including single-component systems such as water, silica and carbon. Molecular dynamics simulations of very specific models for supercooled water, liquid carbon and supercooled silica predict a LDL-HDL critical point, but a coherent and general interpretation of the LDL-HDL transition is lacking. Here we show that the presence of a LDL and a HDL can be directly related to an interaction potential with an attractive part and two characteristic short-range repulsive distances. This kind of interaction is common to other single-component materials in the liquid state (in particular, liquid metals), and such potentials are often used to describe systems that exhibit a density anomaly. However, our results show that the LDL and HDL phases can occur in systems with no density anomaly. Our results therefore present an experimental challenge to uncover a liquid-liquid transition in systems like liquid metals, regardless of the presence of a density anomaly.

  5. Ionic liquid-in-oil microemulsions.

    PubMed

    Eastoe, Julian; Gold, Sarah; Rogers, Sarah E; Paul, Alison; Welton, Tom; Heenan, Richard K; Grillo, Isabelle

    2005-05-25

    Phase stability and small-angle neutron scattering (SANS) data show that surfactant-stabilized nanodomains of a typical ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4]) may be dispersed by the nonionic surfactant Triton-X100 in cyclohexane. Analyses of these SANS data are consistent with the formation of ionic liquid-in-oil microemulsion droplets. PMID:15898765

  6. Phase changes in liquid face seals

    NASA Technical Reports Server (NTRS)

    Hughes, W. F.

    1980-01-01

    Computer program predicts boiling (phase change) in liquid face seals. Program determines if and when boiling occurs, and calculates location of boiling interface, pressure and temperature profiles, and load.

  7. Correlation of three-liquid-phase equilibria involving ionic liquids.

    PubMed

    Rodríguez-Escontrela, I; Arce, A; Soto, A; Marcilla, A; Olaya, M M; Reyes-Labarta, J A

    2016-08-01

    The difficulty in achieving a good thermodynamic description of phase equilibria is finding a model that can be extended to a large variety of chemical families and conditions. This problem worsens in the case of systems containing more than two phases or involving complex compounds such as ionic liquids. However, there are interesting applications that involve multiphasic systems, and the promising features of ionic liquids suggest that they will play an important role in many future processes. In this work, for the first time, the simultaneous correlation of liquid-liquid and liquid-liquid-liquid equilibrium data for ternary systems involving ionic liquids has been carried out. To that end, the phase diagram of the water + [P6 6 6 14][DCA] + hexane system has been determined at 298.15 K and 323.15 K and atmospheric pressure. The importance of this system lies in the possibility of using the surface active ionic liquid to improve surfactant enhanced oil recovery methods. With those and previous measurements, thirteen sets of equilibrium data for water + ionic liquid + oil ternary systems have been correlated. The isoactivity equilibrium condition, using the NRTL model, and some pivotal strategies are proposed to correlate these complex systems. Good agreement has been found between experimental and calculated data in all the regions (one triphasic and two biphasic) of the diagrams. The geometric aspects related to the Gibbs energy of mixing function obtained using the model, together with the minor common tangent plane equilibrium condition, are valuable tools to check the consistency of the obtained correlation results. PMID:27427420

  8. Vapor-liquid phase separator studies

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Lee, J. M.; Kim, Y. I.; Hepler, W. A.; Frederking, T. H. K.

    1983-01-01

    Porous plugs serve as both entropy rejection devices and phase separation components separating the vapor phase on the downstream side from liquid Helium 2 upstream. The liquid upstream is the cryo-reservoir fluid needed for equipment cooling by means of Helium 2, i.e Helium-4 below its lambda temperature in near-saturated states. The topics outlined are characteristic lengths, transport equations and plug results.

  9. Effect of gravity on liquid phase sintering

    NASA Technical Reports Server (NTRS)

    Mookherji, T.; Mcanelly, W. B.; Mckannan, E. C.

    1974-01-01

    The unique conditions offered by the earth orbital environment in material processing involving both solid and liquid phases, such as liquid phase sintering, were studied. An experimental development program involving both test and theoretical work was initiated. Experimental work using material combinations selected such that maximum information about the effect of gravity can be derived has been conducted. Wetting of the solid phase by the liquid during sintering is an important phenomenon in liquid phase sintering, and gravity has influence on both capillary phenomenon and density segregation; hence, material combinations were selected such that these two effects can be suitably studies. The experimental work is meant to form the basis for similar comparative work done under low-g conditions. The part of the model dealing with the capillary phenomenon, as related to liquid phase sintering and the effect of gravity on it, suggest that gravity will have negligible effect on the Bond number and that the cohesive force is dependent on both the amount of liquid phase and the angle of contact.

  10. Liquid-Liquid Phase Transition in Nanoconfined Silicon Carbide.

    PubMed

    Wu, Weikang; Zhang, Leining; Liu, Sida; Ren, Hongru; Zhou, Xuyan; Li, Hui

    2016-03-01

    We report theoretical evidence of a liquid-liquid phase transition (LLPT) in liquid silicon carbide under nanoslit confinement. The LLPT is characterized by layering transitions induced by confinement and pressure, accompanying the rapid change in density. During the layering transition, the proportional distribution of tetracoordinated and pentacoordinated structures exhibits remarkable change. The tricoordinated structures lead to the microphase separation between silicon (with the dominant tricoordinated, tetracoordinated, and pentacoordinated structures) and carbon (with the dominant tricoordinated structures) in the layer close to the walls. A strong layer separation between silicon atoms and carbon atoms is induced by strong wall-liquid forces. Importantly, the pressure confinement phase diagram with negative slopes for LLPT lines indicates that, under high pressure, the LLPT is mainly confinement-induced, but under low pressure, it becomes dominantly pressure-induced. PMID:26859609

  11. Solid-liquid phase transition in argon

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Tang, H. T.

    1978-01-01

    Starting from the Lennard-Jones interatomic potential, a modified cell theory has been used to describe the solid-liquid phase transition in argon. The cell-size variations may be evaluated by a self-consistent condition. With the inclusion of cell-size variations, the transition temperature, the solid and liquid densities, and the liquid-phase radial-distribution functions have been calculated. These ab initio results are in satisfactory agreement with molecular-dynamics calculations as well as experimental data on argon.

  12. Comment on "Spontaneous liquid-liquid phase separation of water".

    PubMed

    Limmer, David T; Chandler, David

    2015-01-01

    Yagasaki et al. [Phys. Rev. E 89, 020301 (2014)] present results from a molecular dynamics trajectory illustrating coarsening of ice, which they interpret as evidence of transient coexistence between two distinct supercooled phases of liquid water. We point out that neither two distinct liquids nor criticality are demonstrated in this simulation study. Instead, the illustrated trajectory is consistent with coarsening behaviors analyzed and predicted in earlier work by others. PMID:25679744

  13. Liquid-phase compositions from vapor-phase analyses

    SciTech Connect

    Davis, W. Jr. ); Cochran, H.D. )

    1990-02-01

    Arsenic normally is not considered to be a contaminant. However, because arsenic was found in many cylinders of UF{sub 6}, including in corrosion products, a study was performed of the distribution of the two arsenic fluorides, AsF{sub 3} and AsF{sub 5}, between liquid and vapor phases. The results of the study pertain to condensation or vaporization of liquid UF{sub 6}. This study includes use of various experimental data plus many extrapolations necessitated by the meagerness of the experimental data. The results of this study provide additional support for the vapor-liquid equilibrium model of J.M. Prausnitz and his coworkers as a means of describing the distribution of various impurities between vapor and liquid phases of UF{sub 6}. Thus, it is concluded that AsF{sub 3} will tend to concentrate in the liquid phase but that the concentration of AsF{sub 5} in the vapor phase will exceed its liquid-phase concentration by a factor of about 7.5, which is in agreement with experimental data. Because the weight of the liquid phase in a condensation operation may be in the range of thousands of times that of the vapor phase, most of any AsF{sub 5} will be in the liquid phase in spite of this separation factor of 7.5. It may also be concluded that any arsenic fluorides fed into a uranium isotope separation plant will either travel with other low-molecular-weight gases or react with materials present in the plant. 25 refs., 3 figs., 6 tabs.

  14. Coexisting Liquid Phases Underlie Nucleolar Subcompartments.

    PubMed

    Feric, Marina; Vaidya, Nilesh; Harmon, Tyler S; Mitrea, Diana M; Zhu, Lian; Richardson, Tiffany M; Kriwacki, Richard W; Pappu, Rohit V; Brangwynne, Clifford P

    2016-06-16

    The nucleolus and other ribonucleoprotein (RNP) bodies are membrane-less organelles that appear to assemble through phase separation of their molecular components. However, many such RNP bodies contain internal subcompartments, and the mechanism of their formation remains unclear. Here, we combine in vivo and in vitro studies, together with computational modeling, to show that subcompartments within the nucleolus represent distinct, coexisting liquid phases. Consistent with their in vivo immiscibility, purified nucleolar proteins phase separate into droplets containing distinct non-coalescing phases that are remarkably similar to nucleoli in vivo. This layered droplet organization is caused by differences in the biophysical properties of the phases-particularly droplet surface tension-which arises from sequence-encoded features of their macromolecular components. These results suggest that phase separation can give rise to multilayered liquids that may facilitate sequential RNA processing reactions in a variety of RNP bodies. PAPERCLIP. PMID:27212236

  15. Existence of a liquid-liquid phase transition in methanol.

    PubMed

    Huš, Matej; Urbic, Tomaz

    2014-12-01

    A simple model is constructed to study the phase diagram and thermodynamic properties of methanol, which is described as a dimer of an apolar sphere mimicking the methyl group and a sphere with core-softened potential as the hydroxyl group. Performing classical Monte Carlo simulations, we obtained the phase diagram, showing a second critical point between two different liquid phases. Evaluating systems with a different number of particles, we extrapolate to infinite size in accordance with Ising universality class to obtain bulk values for critical temperature, pressure, and density. Strong evidence that the structure of the liquid changes upon transition from high- to low-density phase was provided. From the experimentally determined hydrogen bond strength and length in methanol and water, we propose where the second critical point of methanol should be. PMID:25615092

  16. Phase separation in transparent liquid-liquid miscibility gap systems

    NASA Technical Reports Server (NTRS)

    Gelles, S. H.; Bhat, B. N.; Laub, R. J.

    1979-01-01

    A program to be carried out on transparent liquid-phase miscibility gap materials was developed for the purpose of acquiring additional insight into the separation process occurring in these systems. The transparency feature allows the reaction to be viewed directly through light scattering and holographic methods.

  17. Liquid-Liquid phase transition in a single component system

    NASA Astrophysics Data System (ADS)

    Franzese, Giancarlo; Skibinsky, Anna; Buldyrev, Sergey; Stanley, H. Eugene

    2001-06-01

    Recent experimental results indicate that phosphorus, a single-component system, can have a high-density liquid (HDL) and a low-density liquid (LDL) phase. A first-order LDL-HDL transition line ending in a critical point is consistent with experimental data and Molecular Dynamics (MD) simulations for a variety of single-component systems such as water, silica and carbon, but a coherent and general interpretation of the LDL-HDL transition is lacking. By means of MD, we show that the LDL-HDL transition can be directly related to an interaction potential with an attractive part and with not one but `two' preferred short-range repulsive distances. This kind of interaction is common to other single-component materials in the liquid state, in particular liquid metals. For the fisrt time, we show that the LDL-HDL transition can occur in systems with no density anomaly, opening an experimental challenge to uncover a liquid-liquid transition in systems like liquid metals, regardless of the presence of the density anomaly.

  18. Phase separation kinetics in immiscible liquids

    NASA Technical Reports Server (NTRS)

    Sadoway, D. R.

    1986-01-01

    The kinetics of phase separation in the succinonitrile-water system are being investigated. Experiments involve initial physical mixing of the two immiscible liquids at a temperature above the consolute, decreasing the temperature into the miscibility gap, followed by imaging of the resultant microstructure as it evolves with time. Refractive index differences allow documentation of the changing microstructures by noninvasive optical techniques without the need to quench the liquid structures for analysis.

  19. Phase separation kinetics in immiscible liquids

    NASA Technical Reports Server (NTRS)

    Ng, Lee H.; Sadoway, Donald R.

    1987-01-01

    The kinetics of phase separation in the succinonitrile-water system are being investigated. Experiments involve initial physical mixing of the two immiscible liquids at a temperature above the consolute, decreasing the temperature into the miscibility gap, followed by iamging of the resultant microstructure as it evolves with time. Refractive index differences allow documentation of the changing microstructures by noninvasive optical techniques without the need to quench the liquid structures for analysis.

  20. Liquid crystal phase shifters for space applications

    NASA Astrophysics Data System (ADS)

    Woehrle, Christopher D.

    Space communication satellites have historically relied heavily on high gain gimbal dish antennas for performing communications. Reflector dish antennas lack flexibility in anti-jamming capabilities, and they tend to have a high risk associated to them given the need for mechanical mechanisms to beam steer. In recent years, a great amount of investment has been made into phased array antenna technologies. Phased arrays offer increased signal flexibility at reduced financial cost and in system risk. The problem with traditional phased arrays is the significant program cost and overall complexity added to the satellite by integrating antenna elements that require many dedicated components to properly perform adaptive beam steering. Several unique methods have been proposed to address the issues that plague traditional phase shifters slated for space applications. Proposed approaches range from complex mechanical switches (MEMS) and ferroelectric devices to more robust molecular changes. Nematic liquid crystals offer adaptive beam steering capabilities that traditional phased arrays have; however, with the added benefit of reduced system cost, complexity, and increased resilience to space environmental factors. The objective of the work presented is to investigate the feasibility of using nematic liquid crystals as a means of phase shifting individual phased array elements slated for space applications. Significant attention is paid to the survivability and performance of liquid crystal and associated materials in the space environment. Performance regarding thermal extremes and interactions with charged particles are the primary factors addressed.

  1. Polymorphism in glassy silicon: Inherited from liquid-liquid phase transition in supercooled liquid

    NASA Astrophysics Data System (ADS)

    Zhang, Shiliang; Wang, Li-Min; Zhang, Xinyu; Qi, Li; Zhang, Suhong; Ma, Mingzhen; Liu, Riping

    2015-02-01

    Combining molecular dynamics (MD) simulation and Voronoi polyhedral analyses, we discussed the microstructure evolution in liquid and glassy silicon during cooling by focusing on the fraction of various clusters. Liquid-liquid phase transition (LLPT) is detected in supercooled liquid silicon However, freezing the high-density liquid (HDL) to the glassy state is not achieved as the quenching rate goes up to 1014 K/s. The polyamorphism in glassy silicon is found to be mainly associated with low-density liquid (LDL).

  2. Polymorphism in glassy silicon: Inherited from liquid-liquid phase transition in supercooled liquid

    PubMed Central

    Zhang, Shiliang; Wang, Li-Min; Zhang, Xinyu; Qi, Li; Zhang, Suhong; Ma, Mingzhen; Liu, Riping

    2015-01-01

    Combining molecular dynamics (MD) simulation and Voronoi polyhedral analyses, we discussed the microstructure evolution in liquid and glassy silicon during cooling by focusing on the fraction of various clusters. Liquid-liquid phase transition (LLPT) is detected in supercooled liquid silicon However, freezing the high-density liquid (HDL) to the glassy state is not achieved as the quenching rate goes up to 1014 K/s. The polyamorphism in glassy silicon is found to be mainly associated with low-density liquid (LDL). PMID:25716054

  3. Liquid phase sintered compacts in space

    NASA Technical Reports Server (NTRS)

    Mookherji, T. K.; Mcanelly, W. B.

    1974-01-01

    A model that will explain the effect of gravity on liquid phase sintering was developed. Wetting characteristics and density segregation which are the two important phenomena in liquid phase sintering are considered in the model development. Experiments were conducted on some selected material combinations to study the gravity effects on liquid phase sintering, and to verify the validity of the model. It is concluded that: (1) The surface tension forces acting on solid particles in a one-g environment are not appreciably different from those anticipated in a 0.00001g/g sub 0 (or lower) environment. (2) The capillary forces are dependent on the contact angle, the quantity of the liquid phase, and the distance between solid particles. (3) The pores (i.e., bubbles) do not appear to be driven to the surface by gravity-produced buoyancy forces. (4) The length of time to produce the same degree of settling in a low-gravity environment will be increased significantly. (5) A low gravity environment would appear to offer a unique means of satisfactorily infiltrating a larger and/or complex shaped compact.

  4. DENSE NONAQUEOUS PHASE LIQUIDS -- A WORKSHOP SUMMARY

    EPA Science Inventory

    site characterization, and, therefore, DNAPL remediation, can be expected. Dense nonaqueous phase liquids (DNAPLs) in the subsurface are long-term sources of ground-water contamination, and may persist for centuries before dissolving completely in adjacent ground water. In respo...

  5. Vapor-liquid phase separator permeability results

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Frederking, T. H. K.

    1981-01-01

    Continued studies are described in the area of vapor-liquid phase separator work with emphasis on permeabilities of porous sintered plugs (stainless steel, nominal pore size 2 micrometer). The temperature dependence of the permeability has been evaluated in classical fluid using He-4 gas at atmospheric pressure and in He-2 on the basis of a modified, thermosmotic permeability of the normal fluid.

  6. Centrifugal Liquid/Gas Separator With Phase Detectors

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.

    1994-01-01

    Centrifugal liquid/gas separator that includes phase (liquid or gas) detectors helps ensure exclusiveness of each phase at its assigned outlet. Acoustic sensors in centrifugal liquid/gas separator measure speeds of sound in nominally pure liquid and nominally pure gas at liquid and gas outlets respectively. When speed of sound is that of pure liquid or gas, valve opens to let liquid or gas flow out.

  7. Gravitational Role in Liquid Phase Sintering

    NASA Technical Reports Server (NTRS)

    Upadhyaya, Anish; Iacocca, Ronald G.; German, Randall M.

    1998-01-01

    To comprehensively understand the gravitational effects on the evolution of both the microstructure and the macrostructure during liquid phase sintering, W-Ni-Fe alloys with W content varying from 35 to 98 wt.% were sintered in microgravity. Compositions that slump during ground-based sintering also distort when sintered under microgravity. In ground-based sintering, low solid content alloys distort with a typical elephant-foot profile, while in microgravity, the compacts tend to spheroidize. This study shows that microstructural segregation occurs in both ground-based as well as microgravity sintering. In ground-based experiments, because of the density difference between the solid and the liquid phase, the solid content increases from top to the bottom of the sample. In microgravity, the solid content increases from periphery to the center of the samples. This study also shows that the pores during microgravity sintering act as a stable phase and attain anomalous shapes.

  8. Solid drop based liquid-phase microextraction.

    PubMed

    Ganjali, Mohammad Reza; Sobhi, Hamid Reza; Farahani, Hadi; Norouzi, Parviz; Dinarvand, Rassoul; Kashtiaray, Amir

    2010-04-16

    Solid drop based liquid-phase microextraction (SDLPME) is a novel sample preparation technique possessing obvious advantages of simple operation with a high pre-concentration factor, low cost and low consumption of organic solvent. SDLPME coupled with gas chromatography (GC), high-performance liquid chromatography (HPLC), and atomic absorption spectrometry (AAS) has been widely applied to the analyses of a different variety of samples. The basic principles, parameters affecting the extraction efficiency, and the latest applications of SDLPME are reviewed in this article. PMID:19962710

  9. Volumetric Properties of the Mixture 1,3-Dioxane C4H8O2 + C6H12 Cyclohexane (VMSD1511, LB5121_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture 1,3-Dioxane C4H8O2 + C6H12 Cyclohexane (VMSD1511, LB5121_V)' providing data from direct measurement of low-pressure thermodynamic speed of sound at variable mole fraction and constant temperature, in the single-phase region(s).

  10. Volumetric Properties of the Mixture 1,3-Dioxane C4H8O2 + C6H12 Cyclohexane (VMSD1111, LB5124_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture 1,3-Dioxane C4H8O2 + C6H12 Cyclohexane (VMSD1111, LB5124_V)' providing data from direct low-pressure measurement of mass density at variable mole fraction and constant temperature, in the single-phase region(s).

  11. Liquid-phase compositions from vapor-phase analyses

    SciTech Connect

    Davis, W. Jr.; Cochran, H.D.; Leitnaker, J.M.

    1989-09-01

    In the safe handling and processing of uranium hexafluoride (UF{sub 6}), it is often desirable to calculate vapor composition and pressure from known liquid composition and temperature. Furthermore, the ability to use analyses of equilibrium vapor-phase samples to calculate liquid-phase compositions would be economically advantageous to the International Atomic Energy Agency (IAEA) in its international safeguards program and to uranium enrichment operators. The latter technique is projected to save the IAEA on the order of $1500 or more per sample. Either type of calculation could be performed with a multicomponent vapor-liquid equilibrium (VLE) model if this model were shown to apply to UF{sub 6} and its common impurities. This report is concerned with the distribution of four potential impurities in UF{sub 6} between liquid and vapor phases. The impurities are carbon dioxide, sulfur hexafluoride, chloryl fluoride, and Freon-114 (CClF{sub 2}CClF{sub 2}). There are no binary equilibrium data on the first three of these impurities; hence, the VLE calculations are based entirely on the thermodynamic properties of the pure components. There are two sets of binary equilibrium data for the system Freon-114-UF{sub 6} that are analyzed in terms of the model of Prausnitz et al. Calculations based on these data are compared with those based solely on the thermodynamic properties of pure Freon-114 and pure UF{sub 6}. 23 refs., 3 figs., 5 tabs.

  12. Vapor-liquid phase separator studies

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Hepler, W. A.; Frederking, T. H. K.

    1985-01-01

    A study of porous plug use for vapor-liquid phase seperation in spaceborne cryogenic systems was conducted. The three main topics addressed were: (1) the usefulness of porous media in designs that call for variable areas and flow rates; (2) the possibility of prediction of main parameters of porous plugs for a given material; and (3) prediction of all parameters of the plug, including secondary parameters.

  13. Phase Behavior of Perturbed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Kralj, S.; Kutnjak, Z.; Lahajnar, G.; Svetec, M.

    We study theoretically the combined effect of confinement and randomness on LC phase transitions in orientational (isotropic-nematic) and translational (nematic-smectic A) degrees of ordering. We focus to cases where these transitions are of (very) weakly 1st order. An adequate experimental realisation is, e.g., 8CB liquid crystal confined to a Controlled-Pore Glass matrix. Based on universal responses of "hard" and "soft" continuum fields to distortions we derive how different mechanisms influence qualitative and quantitative characteristics of phase transitions under consideration.

  14. Liquid-phase electroepitaxy - Dopant segregation

    NASA Technical Reports Server (NTRS)

    Lagowski, J.; Jastrzebski, L.; Gatos, H. C.

    1980-01-01

    A theoretical model is presented which accounts for the dopant segregation in liquid-phase electroepitaxy in terms of dopant transport in the liquid phase (by electromigration and diffusion), the growth velocity, and the Peltier effect at the substrate-solution interface. The contribution of dopant electromigration to the magnitude of the effective segregation coefficient is dominant in the absence of convection; the contribution of the Peltier effect becomes significant only in the presence of pronounced convection. Quantitative expressions which relate the segregation coefficient to the growth parameters also permit the determination of the diffusion constant and electromigration mobility of the dopant in the liquid phase. The model was found to be in good agreement with the measured segregation characteristics of Sn in the electroepitaxial growth of GaAs from Ga-As solutions. For Sn in Ga-As solution at 900 C the diffusion constant was found to be 4 x 10 to the -5 sq cm/s and the electromigration velocity (toward the substrate with a positive polarity 2 x 10 to the -5 cm/s current density of 10 A/sq cm.

  15. Phase Segregation at the Liquid-Air Interface Prior to Liquid-Liquid Equilibrium.

    PubMed

    Bermúdez-Salguero, Carolina; Gracia-Fadrique, Jesús

    2015-08-13

    Binary systems with partial miscibility segregate into two liquid phases when their overall composition lies within the interval defined by the saturation points; out of this interval, there is one single phase, either solvent-rich or solute-rich. In most systems, in the one-phase regions, surface tension decreases with increasing solute concentration due to solute adsorption at the liquid-air interface. Therefore, the solute concentration at the surface is higher than in the bulk, leading to the hypothesis that phase segregation starts at the liquid-air interface with the formation of two surface phases, before the liquid-liquid equilibrium. This phenomenon is called surface segregation and is a step toward understanding liquid segregation at a molecular level and detailing the constitution of fluid interfaces. Surface segregation of aqueous binary systems of alkyl acetates with partial miscibility was theoretically demonstrated by means of a thermodynamic stability test based on energy minimization. Experimentally, the coexistence of two surface regions was verified through Brewster's angle microscopy. The observations were further interpreted with the aid of molecular dynamics simulations, which show the diffusion of the acetates from the bulk toward the liquid-air interface, where acetates aggregate into acetate-rich domains. PMID:26189700

  16. Liquid-liquid and liquid-solid phase separation and flocculation for a charged colloidal dispersion.

    PubMed

    Lai, S K; Wu, K L

    2002-10-01

    We model the intercolloidal interaction by a hard-sphere Yukawa repulsion to which is added the long-range van der Waals attraction. In comparison with the Derjaguin-Landau-Verwey-Overbeek repulsion, the Yukawa repulsion explicitly incorporates the spatial correlations between colloids and small ions. As a result, the repulsive part can be expressed analytically and has a coupling strength depending on the colloidal volume fraction. By use of this two-body potential of mean force and in conjunction with a second-order thermodynamic perturbation theory, we construct the colloidal Helmholtz free energy and use it to calculate the thermodynamic quantities, pressure and chemical potential, needed in the determination of the liquid-liquid and liquid-solid phase diagrams. We examine, in an aqueous charged colloidal dispersion, the effects of the Hamaker constant and particle size on the conformation of a stable liquid-liquid phase transition calculated with respect to the liquid-solid coexistence phases. We find that there exists a threshold Hamaker constant or particle size whose value demarcates the stable liquid-liquid coexistence phases from their metastable counterparts. Applying the same technique and using the energetic criterion, we extend our calculations to study the flocculation phenomenon in aqueous charged colloids. Here, we pay due attention to determining the loci of a stability curve stipulated for a given temperature T0, and obtain the parametric phase diagram of the Hamaker constant vs the coupling strength or, at given surface potential, the particle size. By imposing T0 to be the critical temperature T(c), i.e., setting k(B)T0 (=k(B)T(c)) equal to a reasonable potential barrier, we arrive at the stability curve that marks the irreversible/reversible phase transition. The interesting result is that there occurs a minimum size for the colloidal particles below (above) which the colloidal dispersion is driven to an irreversible (reversible) phase

  17. Liquid-Liquid Phase Separation of Oil Bodies from Seeds.

    PubMed

    Nykiforuk, Cory L

    2016-01-01

    Fundamentally, oil bodies are discrete storage organelles found in oilseeds, comprising a hydrophobic triacylglycerol core surrounded by a half-unit phospholipid membrane and an outer shell of specialized proteins known as oleosins. Oil bodies possess a number of attributes that were exploited by SemBioSys Genetics to isolate highly enriched fractions of oil bodies through liquid-liquid phase separation for a number of commercial applications. The current chapter provides a general guide for the isolation of oil bodies from Arabidopsis and/or safflower seed, from which protocols can be refined for different oilseed sources. For SemBioSys Genetic's recombinant technology, therapeutic proteins were covalently attached to oleosins or fused in-frame with ligands which bound oil bodies, facilitating their recovery to high levels of purity during "upstream processing" of transformed seed. Core to this technology was oil body isolation consisting of simple manipulation including homogenization of seeds to free the oil bodies, followed by the removal of insoluble fractions, and phase separation to recover the oil bodies. During oil body enrichment (an increase in oil body content concomitant with removal of impurities), a number of options and tips are provided to aid researchers in the manipulation and monitoring of these robust organelles. PMID:26614290

  18. Non-Aqueous Phase Liquid Calculator

    Energy Science and Technology Software Center (ESTSC)

    2004-02-19

    Non-Aqueous Phase Liquid or "NPAL" is a term that most environmental professionals are familiar with because NAPL has been recognized in the literature as a significant source of groundwater contamination. There are two types of NAPL: DNAPL and LNAPL. DNAPL is a ‘dense’ non-aqueous phase liquid. In this context, dense means having a density greater than water (1.0 kg/L). Trichloroethylene (TCE) and tetrachioroethylene (PCE) are examples of DNAPL compounds. A compound that is heaver thanmore » water means this type of NAPL will sink in an aquifer. Conversely, LNAPL is a ‘light’ non-aqueous phase liquid with a density less than water, and will float on top of the aquifer. Examples of LNAPL’s are benzene and toluene. LNAPL or DNAPL often manifest as a complex, multi-component mixture of organic compounds that can occur in environmental media. Complex multi-component mixtures distributed in soil pore-air, pore-water, soil particles and in free phase complicate residual saturation of single and multi component NAPL compounds in soil samples. The model output also includes estimates of the NAPL mass and volume and other physical and chemical properties that may be useful for characterization, modeling, and remedial system design and operation. The discovery of NAPL in the aquifer usually leads to a focused characterization for possible sources of NAPL in the vadose zone using a variety of innovative technologies and characterization methods. Often, the analytical data will indicated the presence of NAPL, yet, the NAPL will go unrecognized. Failure to recognize the NAPL can be attributed to the complicated processes of inter-media transfer or a general lack of knowledge about the physical characteristics of complex organic mixtures in environmental samples.« less

  19. Blue-phase liquid crystal droplets

    PubMed Central

    Martínez-González, José A.; Zhou, Ye; Rahimi, Mohammad; Bukusoglu, Emre; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-01-01

    Blue phases of liquid crystals represent unique ordered states of matter in which arrays of defects are organized into striking patterns. Most studies of blue phases to date have focused on bulk properties. In this work, we present a systematic study of blue phases confined into spherical droplets. It is found that, in addition to the so-called blue phases I and II, several new morphologies arise under confinement, with a complexity that increases with the chirality of the medium and with a nature that can be altered by surface anchoring. Through a combination of simulations and experiments, it is also found that one can control the wavelength at which blue-phase droplets absorb light by manipulating either their size or the strength of the anchoring, thereby providing a liquid–state analog of nanoparticles, where dimensions are used to control absorbance or emission. The results presented in this work also suggest that there are conditions where confinement increases the range of stability of blue phases, thereby providing intriguing prospects for applications. PMID:26460039

  20. MSPD sample preparation approach for reversed-phase liquid chromatographic analysis of pesticide residues in stem of coconut palm.

    PubMed

    Ferreira, Jordana Alves; Santos, Luís Fabrício Santana; Souza, Nicaellen Roberta da Silva; Navickiene, Sandro; de Oliveira, Frederico Alberto; Talamini, Viviane

    2013-08-01

    A method was developed using matrix solid-phase dispersion, together with liquid chromatography with ultraviolet diode array detector for determination of carbofuran, difenoconazole, β-cyfluthrin, spirodiclofen and thiophanate-methyl in stem of coconut palm. The best results were obtained using 2.0 g of stem, 1.6 g of Florisil as sorbent and cyclohexane:acetone mixture (4:1). The method was validated using stem samples spiked with pesticides at four concentration levels (0.05-2.0 μg/g). Average recoveries ranged from 70 % to 114.3 %, with relative standard deviations between 1.2 % and 19.2 %. Detection and quantification limits were in the ranges 0.02-0.03 and 0.05-0.1 μg/g, respectively. PMID:23722654

  1. Wide Angle Liquid Crystal Optical Phased Array

    NASA Technical Reports Server (NTRS)

    Wang, Xing-Hua; Wang, Bin; Bos, Philip J.; Anderson, James E.; Pouch, John J.; Miranda, Felix A.; McManamon, Paul F.

    2004-01-01

    Accurate modeling of a high resolution, liquid crystal (LC) based, optical phased array (OPA) is shown. The simulation shows excellent agreement with a test 2-D LC OPA. The modeling method is extendable to cases where the array element size is close to the wavelength of light. The fringing fields of such a device are first studied, and subsequently reduced. This results in a device that demonstrates plus or minus 7.4 degrees of continuous beam steering at a wavelength of 1550 nm, and a diffraction efficiency (DE) higher than 72%.

  2. Liquid Crystal Phases of Semiflexible Polymers

    NASA Astrophysics Data System (ADS)

    Mackay, Ian; Sullivan, Don

    2012-02-01

    Liquid crystal polymers exhibit orientational order (nematic phase) and position order (smectic phase). Previous work on semiflexible polymers using self consistent field theory studied the isotropic-nematic and nematic-smectic transition for homogenous and diblock copolymers. The nematic phase is stabilized by excluded-volume effects between wormlike cylindrical segments. The smectic phase is further stabilized by excluded-volume effects between terminal end segments. Because models of semiflexible polymers include orientational degrees of freedom, in addition to the usual positional degrees of freedom, they are computationally more demanding to study. Spectral decomposition applied to segment orientations has previously been used to make computation feasible. However this method does not converge well for strongly ordered states, which arise in many real systems. I describe a Crank-Nicolson finite difference method applied to the orientations which is expected to converge well for highly ordered systems. This method also exhibits better numerical stability and accuracy and may thus serve as a better foundation for further studies of highly ordered systems. I also describe a modification to the spectral method which can compute the tilted Smectic C phase.

  3. Liquid-liquid phase transitions and water-like anomalies in liquids

    NASA Astrophysics Data System (ADS)

    Lascaris, Erik

    In this thesis we employ computer simulations and statistical physics to understand the origin of liquid-liquid phase transitions and their relationship with anomalies typical of liquid water. Compared with other liquids, water has many anomalies. For example the density anomaly: when water is cooled below 4 °C the density decreases rather than increases. This and other anomalies have also been found to occur in a few other one-component liquids, sometimes in conjunction with the existence of a liquid-liquid phase transition (LLPT) between a low-density liquid (LDL) and a high-density liquid (HDL). Using simple models we explain how these anomalies arise from the presence of two competing length scales. As a specific example we investigate the cut ramp potential, where we show the importance of "competition" in this context, and how one length scale can sometimes be zero. When there is a clear energetic preference for either LDL or HDL for all pressures and temperatures, then there is insufficient competition between the two liquid structures and no anomalies occur. From the simple models it also follows that anomalies can occur without the presence of a LLPT and vice versa. It remains therefore unclear if water has a LLPT that ends in a liquid-liquid critical point (LLCP), a hypothesis that was first proposed based on simulations of the ST2 water model. We confirm the existence of a LLCP in this model using finite size scaling and the Challa-Landau-Binder parameter, and show that the LLPT is not a liquid-crystal transition, as has recently been suggested. Previous research has indicated the possible existence of a LLCP in liquid silica. We perform a detailed analysis of two different silica models (WAC and BKS) at temperatures much lower than was previously simulated. Within the accessible temperature range we find no LLCP in either model, although in the case of WAC potential it is closely approached. We compare our results with those obtained for other

  4. Detailed Chemical Kinetic Modeling of Cyclohexane Oxidation

    SciTech Connect

    Silke, E J; Pitz, W J; Westbrook, C K; Ribaucour, M

    2006-11-10

    A detailed chemical kinetic mechanism has been developed and used to study the oxidation of cyclohexane at both low and high temperatures. Reaction rate constant rules are developed for the low temperature combustion of cyclohexane. These rules can be used for in chemical kinetic mechanisms for other cycloalkanes. Since cyclohexane produces only one type of cyclohexyl radical, much of the low temperature chemistry of cyclohexane is described in terms of one potential energy diagram showing the reaction of cyclohexyl radical + O{sub 2} through five, six and seven membered ring transition states. The direct elimination of cyclohexene and HO{sub 2} from RO{sub 2} is included in the treatment using a modified rate constant of Cavallotti et al. Published and unpublished data from the Lille rapid compression machine, as well as jet-stirred reactor data are used to validate the mechanism. The effect of heat loss is included in the simulations, an improvement on previous studies on cyclohexane. Calculations indicated that the production of 1,2-epoxycyclohexane observed in the experiments can not be simulated based on the current understanding of low temperature chemistry. Possible 'alternative' H-atom isomerizations leading to different products from the parent O{sub 2}QOOH radical were included in the low temperature chemical kinetic mechanism and were found to play a significant role.

  5. On liquid phases in cometary nuclei

    NASA Astrophysics Data System (ADS)

    Miles, Richard; Faillace, George A.

    2012-06-01

    In this paper we review the relevant literature and investigate conditions likely to lead to melting of H2O ice, methanol (CH3OH) ice, ethane (C2H6) ice and other volatile ices in cometary nuclei. On the basis of a heat balance model which takes account of volatiles loss, we predict the formation of occasional aqueous and hydrocarbon liquid phases in subsurface regions at heliocentric distances, rh of 1-3 AU, and 5-12 AU, respectively. Low triple-point temperatures and low vapour pressures of C2H6, C3H8, and some higher-order alkanes and alkenes, favour liquid phase formation in cometary bodies at high rh. Microporosity and the formation of a stabilization crust occluding the escape of volatiles facilitate liquid-phase formation. Characteristics of the near-surface which favour subsurface melting include; low effective surface emissivity (at low rh), high amorphous carbon content, average pore sizes of ˜10 μm or less, presence of solutes (e.g. CH3OH), mixtures of C2-C6 hydrocarbons (for melting at high rh), diurnal thermal cycling, and slow rotation rate. Applying the principles of soil mechanics, capillary forces are shown to initiate pre-melting phenomena and subsequent melting, which is expected to impart considerable strength of ˜104 Pa in partially saturated layers, reducing porosity and permeability, enhancing thermal conductivity and heat transfer. Diurnal thermal cycling is expected to have a marked effect on the composition and distribution of H2O ice in the near-surface leading to frost heave-type phenomena even where little if any true melting occurs. Where melting does take place, capillary suction in the wetted zone has the potential to enhance heat transfer via capillary wetting in a low-gravity environment, and to modify surface topography creating relatively smooth flat-bottomed features, which have a tendency to be located within small depressions. An important aspect of the "wetted layer" model is the prediction that diurnal melt-freeze cycles

  6. Stable liquid crystalline phases of colloidally dispersed exfoliated layered niobates.

    PubMed

    Nakato, Teruyuki; Miyamoto, Nobuyoshi; Harada, Akiko

    2004-01-01

    Colloidally dispersed niobium oxide nanosheets obtained by exfoliation of layered niobates HNb(3)O(8) and HTiNbO(5) formed stable liquid crystalline phases; their liquid crystallinity was dependent on the niobate species exfoliated. PMID:14737341

  7. Liquid phase stability under an extreme temperature gradient.

    PubMed

    Liang, Zhi; Sasikumar, Kiran; Keblinski, Pawel

    2013-11-27

    Using nonequilibrium molecular dynamics simulations, we subject bulk liquid to a very high-temperature gradient and observe a stable liquid phase with a local temperature well above the boiling point. Also, under this high-temperature gradient, the vapor phase exhibits condensation into a liquid at a temperature higher than the saturation temperature, indicating that the observed liquid stability is not caused by nucleation barrier kinetics. We show that, assuming local thermal equilibrium, the phase change can be understood from the thermodynamic analysis. The observed elevation of the boiling point is associated with the interplay between the "bulk" driving force for the phase change and surface tension of the liquid-vapor interface that suppresses the transformation. This phenomenon is analogous to that observed for liquids in confined geometries. In our study, however, a low-temperature liquid, rather than a solid, confines the high-temperature liquid. PMID:24329454

  8. Liquid Phase Stability Under an Extreme Temperature Gradient

    NASA Astrophysics Data System (ADS)

    Liang, Zhi; Sasikumar, Kiran; Keblinski, Pawel

    2013-11-01

    Using nonequilibrium molecular dynamics simulations, we subject bulk liquid to a very high-temperature gradient and observe a stable liquid phase with a local temperature well above the boiling point. Also, under this high-temperature gradient, the vapor phase exhibits condensation into a liquid at a temperature higher than the saturation temperature, indicating that the observed liquid stability is not caused by nucleation barrier kinetics. We show that, assuming local thermal equilibrium, the phase change can be understood from the thermodynamic analysis. The observed elevation of the boiling point is associated with the interplay between the “bulk” driving force for the phase change and surface tension of the liquid-vapor interface that suppresses the transformation. This phenomenon is analogous to that observed for liquids in confined geometries. In our study, however, a low-temperature liquid, rather than a solid, confines the high-temperature liquid.

  9. Quantum Liquid Crystal Phases in Strongly Correlated Fermionic Systems

    ERIC Educational Resources Information Center

    Sun, Kai

    2009-01-01

    This thesis is devoted to the investigation of the quantum liquid crystal phases in strongly correlated electronic systems. Such phases are characterized by their partially broken spatial symmetries and are observed in various strongly correlated systems as being summarized in Chapter 1. Although quantum liquid crystal phases often involve…

  10. Surfactant mediated liquid phase exfoliation of graphene

    NASA Astrophysics Data System (ADS)

    Narayan, Rekha; Kim, Sang Ouk

    2015-10-01

    Commercialization of graphene based applications inevitably requires cost effective mass production. From the early days of research on graphene, direct liquid phase exfoliation (LPE) of graphite has been considered as the most promising strategy to produce high-quality mono or few-layer graphene sheets in solvent dispersion forms. Substantial success has been achieved thus far in the LPE of graphene employing numerous solvent systems and suitable surfactants. This invited review article principally showcase the recent research progress as well as shortcomings of surfactant assisted LPE of graphene. In particular, a comprehensive assessment of the quality and yield of the graphene sheets produced by different categories of the surfactants are summarized. Future direction of LPE methods is also proposed for the eventual success of commercial applications.

  11. Two-phase liquid-liquid flows generated by impinging liquid jets

    NASA Astrophysics Data System (ADS)

    Tsaoulidis, Dimitrios; Li, Qi; Angeli, Panagiota

    2015-11-01

    Two-phase flows in intensified small-scale systems find increasing applications in (bio)chemical analysis and synthesis, fuel cells, polymerisation, and separation processes (solvent extraction). Current nuclear spent fuel reprocessing separation technologies have been developed many decades ago and have not taken account recent advances on process intensification which can drive down plant size and economics. In this work, intensified impinging jets will be developed to create dispersions by bringing the two liquid phases into contact through opposing small channels. A systematic set of experiments has been undertaken, to investigate the hydrodynamic characteristics, to develop predictive models, and enable comparisons with other contactors. Drop size distribution and mixing intensity will be investigated for liquid-liquid mixtures as a function of various parameters using high speed imaging and conductivity probes.

  12. Replication Experiments in Microgravity Liquid Phase Sintering

    NASA Astrophysics Data System (ADS)

    German, Randall M.; Johnson, John L.

    2016-05-01

    Although considerable experience exists with sintering on Earth, the behavior under reduced gravity conditions is poorly understood. This study analyzes replica microgravity liquid phase sintering data for seven tungsten alloys (35 to 88 wt pct tungsten) sintered for three hold times (1, 180, or 600 minutes) at 1773 K (1500 °C) using 0.002 pct of standard gravity. Equivalent sintering is performed on Earth using the same heating cycles. Microgravity sintering results in a lower density and more shape distortion. For Earth-based sintering, minimized distortion is associated with low liquid contents to avoid solid settling and slumping. Distortion in microgravity sintering involves viscous spreading of the component at points of contact with the containment crucible. Distortion in microgravity is minimized by short hold times; long hold times allow progressive component reshaping toward a spherical shape. Microgravity sintering also exhibits pore coalescence into large, stable voids that cause component swelling. The microgravity sintering results show good replication in terms of mass change and sintered density. Distortion is scattered but statistically similar between the replica microgravity runs. However, subtle factors, not typically of concern on Earth, emerge to influence microgravity sintering, such that ground experiments do not provide a basis to predict microgravity behavior.

  13. Protein Phase Behavior in Aqueous Solutions: Crystallization, Liquid-Liquid Phase Separation, Gels, and Aggregates

    PubMed Central

    Dumetz, André C.; Chockla, Aaron M.; Kaler, Eric W.; Lenhoff, Abraham M.

    2008-01-01

    The aggregates and gels commonly observed during protein crystallization have generally been considered disordered phases without further characterization. Here their physical nature is addressed by investigating protein salting-out in ammonium sulfate and sodium chloride for six proteins (ovalbumin, ribonuclease A, soybean trypsin inhibitor, lysozyme, and β-lactoglobulin A and B) at 4°C, 23°C, and 37°C. When interpreted within the framework of a theoretical phase diagram obtained for colloidal particles displaying short-range attractive interactions, the results show that the formation of aggregates can be interpreted theoretically in terms of a gas-liquid phase separation for aggregates that are amorphous or gel-like. A notable additional feature is the existence of a second aggregation line observed for both ovalbumin and ribonuclease A in ammonium sulfate, interpreted theoretically as the spinodal. Further investigation of ovalbumin and lysozyme reveals that the formation of aggregates can be interpreted, in light of theoretical results from mode-coupling theory, as a kinetically trapped state or a gel phase that occurs through the intermediate of a gas-liquid phase separation. Despite the limitations of simple theoretical models of short-range attractive interactions, such as their inability to reproduce the effect of temperature, they provide a framework useful to describe the main features of protein phase behavior. PMID:18160663

  14. Safety in the Chemical Laboratory: Cyclohexane as a Cryoscopic Solvent.

    ERIC Educational Resources Information Center

    Steffel, Margaret J.

    1981-01-01

    Suggests that cyclohexane be used as a solvent in experiments usually using benzene, which has been placed on the list of chemicals that are confirmed carcinogens. Reasons for selection of cyclohexane and experimental procedures using this solvent are described. (CS)

  15. Dynamic Percolation and Swollen Behavior of Nanodroplets in 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate/Triton X-100/Cyclohexane Microemulsions.

    PubMed

    Rahman, Adhip; Rahman, M Muhibur; Mollah, M Yousuf A; Susan, Md Abu Bin Hasan

    2016-07-21

    Microemulsions comprising an ionic liquid (IL), 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][OTf]), as the polar component, Triton X-100 as a surfactant, and cyclohexane as the nonpolar medium were prepared and characterized. Conductivity and dynamic viscosity data were critically analyzed to confirm dynamic percolation among the droplets that are in continuous motion, aggregation, and fission. The transition from oil-continuous phase to bicontinuous phase was observed at the conductance and viscosity percolation thresholds and sharp changes in the values of conductivity and dynamic viscosity could be identified. Dynamic light scattering measurements revealed swelling of the droplets, which varied within the hydrodynamic diameter range of 10-100 nm. Diffusivity of the droplets suggested less Brownian movement with increased amount of the IL. Moreover, changes in the droplet sizes and diffusivity with increase in IL content supported dynamic percolation within the systems. PMID:27355977

  16. Liquid plasmonics: manipulating surface plasmon polaritons via phase transitions.

    PubMed

    Vivekchand, S R C; Engel, Clifford J; Lubin, Steven M; Blaber, Martin G; Zhou, Wei; Suh, Jae Yong; Schatz, George C; Odom, Teri W

    2012-08-01

    This paper reports the manipulation of surface plasmon polaritons (SPPs) in a liquid plasmonic metal by changing its physical phase. Dynamic properties were controlled by solid-to-liquid phase transitions in 1D Ga gratings that were fabricated using a simple molding process. Solid and liquid phases were found to exhibit different plasmonic properties, where light coupled to SPPs more efficiently in the liquid phase. We exploited the supercooling characteristics of Ga to access plasmonic properties associated with the liquid phase over a wider temperature range (up to 30 °C below the melting point of bulk Ga). Ab initio density functional theory-molecular dynamic calculations showed that the broadening of the solid-state electronic band structure was responsible for the superior plasmonic properties of the liquid metal. PMID:22823536

  17. Computer simulations of liquid silica: Equation of state and liquid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Saika-Voivod, Ivan; Sciortino, Francesco; Poole, Peter H.

    2001-01-01

    We conduct extensive molecular dynamics computer simulations of two models for liquid silica [the model of Woodcock, Angell and Cheeseman, J. Phys. Chem. 65, 1565 (1976); and that of van Beest, Kramer, and van Santen, Phys. Rev. Lett. 64, 1955 (1990)] to determine their thermodynamic properties at low temperature T across a wide density range. We find for both models a wide range of states in which isochores of the potential energy U are a linear function of T3/5, as recently proposed for simple liquids [Rosenfeld and P. Tarazona, Mol. Phys. 95, 141 (1998)]. We exploit this behavior to fit an accurate equation of state to our thermodynamic data. Extrapolation of this equation of state to low T predicts the occurrence of a liquid-liquid phase transition for both models. We conduct simulations in the region of the predicted phase transition, and confirm its existence by direct observation of phase separating droplets of atoms with distinct local density and coordination environments.

  18. Defects and order in liquid crystal phases

    NASA Astrophysics Data System (ADS)

    Jain, Shilpa

    This thesis investigates the partial destruction of ordering in liquid crystalline systems due to the influence of defects and thermal fluctuations. The systems under consideration are hexagonal columnar crystals with crystalline order perpendicular to the columns, and two-dimensional smectics with order perpendicular to the layers. We first study the possibility of reentrant melting of a hexagonal columnar crystal of flexible charged polymers at high enough densities. The Lindemann criterion is employed in determining the melting point. Lattice fluctuations are calculated in the Debye model, and an analogy with the Abrikosov vortex lattice in superconductors is exploited in estimating both the elastic constants of the hexagonal lattice, and the appropriate Lindemann constant. We also discuss the unusual functional integral describing the statistical mechanics of a single polymer in an Einstein cage model using the path-integral formulation. A crossover as a function of an external field along the column axis is discussed as well. Next, we study defects in a columnar crystal in the form of vacancy/interstitial loops or strings of vacancies and interstitials bounded by column "heads" and "tails". These defect strings are oriented by the columnar lattice and can change size and shape by movement of the ends and forming kinks along the length. Hence an analysis in terms of directed living polymers is appropriate to study their size and shape distribution, volume fraction, etc. If the entropy of transverse fluctuations overcomes the string line tension in the crystalline phase, a string proliferation transition occurs, leading to a "supersolid" phase with infinitely long vacancy or interstitial strings. We estimate the wandering entropy and examine the behaviour in the transition regime. We also calculate numerically the line tension of various species of vacancies and interstitials in a triangular lattice for power-law potentials as well as for a modified Bessel

  19. Coal-Face Fracture With A Two-Phase Liquid

    NASA Technical Reports Server (NTRS)

    Collins, E. R., Jr.

    1985-01-01

    In new method for mining coal without explosive, two-phase liquid such as CO2 and water, injected at high pressure into deeper ends of holes drilled in coal face. Liquid permeates coal seam through existing microfractures; as liquid seeps back toward face, pressure eventually drops below critical value at which dissolved gas flashvaporizes, breaking up coal.

  20. Encapsulated ionic liquids (ENILs): from continuous to discrete liquid phase.

    PubMed

    Palomar, Jose; Lemus, Jesus; Alonso-Morales, Noelia; Bedia, Jorge; Gilarranz, Miguel A; Rodriguez, Juan J

    2012-10-14

    Encapsulated ionic liquid (ENIL) material was developed, consisting of ionic liquid (IL) introduced into carbon submicrocapsules. ENILs contain >85% w/w of IL but discretized in submicroscopic encapsulated drops, drastically increasing the surface contact area with respect to the neat fluid. ENIL materials were here tested for gas separation processes, obtaining a drastic increase in mass transfer rate. PMID:22935733

  1. Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model System

    PubMed Central

    Xu, Limei; Buldyrev, Sergey V.; Giovambattista, Nicolas; Stanley, H. Eugene

    2010-01-01

    We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses. PMID:21614201

  2. Liquid Crystals: The Phase of the Future.

    ERIC Educational Resources Information Center

    Ondris-Crawford, Renate; And Others

    1992-01-01

    Liquid crystal displays are currently utilized to convey information via graphic displays. Presents experiments and explanations that employ the concept of liquid crystals to learn concepts related to the various states of matter, electric and magnetic forces, refraction of light, and optics. Discusses applications of liquid crystal technology.…

  3. Images reveal that atmospheric particles can undergo liquid-liquid phase separations.

    PubMed

    You, Yuan; Renbaum-Wolff, Lindsay; Carreras-Sospedra, Marc; Hanna, Sarah J; Hiranuma, Naruki; Kamal, Saeid; Smith, Mackenzie L; Zhang, Xiaolu; Weber, Rodney J; Shilling, John E; Dabdub, Donald; Martin, Scot T; Bertram, Allan K

    2012-08-14

    A large fraction of submicron atmospheric aerosol particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere and the water content of the particles correspondingly changes, these mixed particles can undergo a range of phase transitions, possibly including liquid-liquid phase separation. If liquid-liquid phase separation occurs, the gas-particle partitioning of atmospheric semivolatile organic compounds, the scattering and absorption of solar radiation, and the reactive uptake of gas species on atmospheric particles may be affected, with important implications for climate predictions. The actual occurrence of liquid-liquid phase separation within individual atmospheric particles has been considered uncertain, in large part because of the absence of observations for real-world samples. Here, using optical and fluorescence microscopy, we present images that show the coexistence of two noncrystalline phases for real-world samples collected on multiple days in Atlanta, GA as well as for laboratory-generated samples under simulated atmospheric conditions. These results reveal that atmospheric particles can undergo liquid-liquid phase separations. To explore the implications of these findings, we carried out simulations of the Atlanta urban environment and found that liquid-liquid phase separation can result in increased concentrations of gas-phase NO(3) and N(2)O(5) due to decreased particle uptake of N(2)O(5). PMID:22847443

  4. Effects of Liquid-Phase Composition on Its Migration during Liquid-Phase Sintering of Cemented Carbide

    NASA Astrophysics Data System (ADS)

    Fan, Peng; Guo, Jun; Fang, Zhigang Zak; Prichard, Paul

    2009-08-01

    Functionally graded composite materials (FGM composites) with a gradient of matrix phase can offer improved properties. Liquid-phase sintering is one of the approaches for making such materials with a desired gradient of the matrix phase by controlling the redistribution of the liquid phase during sintering. The present study on cemented carbide, WC-Co, demonstrates that the composition of the liquid phase (cobalt phase) is one of the key factors controlling the liquid redistribution. The dependence of the final gradient of the cobalt phase after sintering on its own chemical composition profile is quantitatively established, enabling the design and manufacture of WC-Co with a cobalt-phase-volume gradient via predesigned gradients of carbon content in the system.

  5. Methods to control phase inversions and enhance mass transfer in liquid-liquid dispersions

    DOEpatents

    Tsouris, Constantinos; Dong, Junhang

    2002-01-01

    The present invention is directed to the effects of applied electric fields on liquid-liquid dispersions. In general, the present invention is directed to the control of phase inversions in liquid-liquid dispersions. Because of polarization and deformation effects, coalescence of aqueous drops is facilitated by the application of electric fields. As a result, with an increase in the applied voltage, the ambivalence region is narrowed and shifted toward higher volume fractions of the dispersed phase. This permits the invention to be used to ensure that the aqueous phase remains continuous, even at a high volume fraction of the organic phase. Additionally, the volume fraction of the organic phase may be increased without causing phase inversion, and may be used to correct a phase inversion which has already occurred. Finally, the invention may be used to enhance mass transfer rates from one phase to another through the use of phase inversions.

  6. Solid-liquid phase boundaries of lens protein solutions.

    PubMed Central

    Berland, C R; Thurston, G M; Kondo, M; Broide, M L; Pande, J; Ogun, O; Benedek, G B

    1992-01-01

    We report measurement of the solid-liquid phase boundary, or liquidus line, for aqueous solutions of three pure calf gamma-crystallin proteins: gamma II, gamma IIIa, and gamma IIIb. We also studied the liquidus line for solutions of native gamma IV-crystallin calf lens protein, which consists of 85% gamma IVa/15% gamma IVb. In all four proteins the liquidus phase boundaries lie higher in temperature than the previously determined liquid-liquid coexistence curves. Thus, over the range of concentration and temperature for which liquid-liquid phase separation occurs, the coexistence of a protein crystal phase with a protein liquid solution phase is thermodynamically stable relative to the metastable separated liquid phases. The location of the liquidus lines clearly divides these four crystallin proteins into two groups: those in which liquidus lines flatten at temperatures greater than 70 degrees C: gamma IIIa and gamma IV, and those in which liquidus lines flatten at temperatures less than 50 degrees C: gamma II and gamma IIIb. We have analyzed the form of the liquidus lines by using specific choices for the structures of the Gibbs free energy in solution and solid phases. By applying the thermodynamic conditions for equilibrium between the two phases to the resulting chemical potentials, we can estimate the temperature-dependent free energy change upon binding of protein and water into the solid phase. PMID:1741375

  7. Structure of liquid phosphorus: A liquid-liquid phase transition via constant-pressure first-principles molecular dynamics

    NASA Astrophysics Data System (ADS)

    Morishita, Tetsuya

    2001-12-01

    Constant-pressure first-principles molecular dynamics simulations have been carried out to study structural phase transitions of liquid black phosphorus. By compressing the tetrahedral molecular liquid (a low-pressure phase), a structural phase transition from the molecular to polymeric liquid (a high-pressure phase) was successfully realized just as observed in the recent experiment by Katayama et al. [Nature 170 (2000) 403]. Structural properties in the polymeric liquid were investigated and it is found that the covalent p-state bonds are dominant within the first nearest neighbors of each atom. However, further compression of the polymeric liquid shows that the covalent bonding is weakened as pressure is increased. As a result, liquid phosphorus becomes similar to the simple liquid in which atoms form a close-packed structure at very high pressure.

  8. Phase behavior of lysozyme solutions in the liquid-liquid phase coexistence region at high hydrostatic pressures.

    PubMed

    Schulze, Julian; Möller, Johannes; Weine, Jonathan; Julius, Karin; König, Nico; Nase, Julia; Paulus, Michael; Tolan, Metin; Winter, Roland

    2016-05-25

    We present results from small-angle X-ray scattering and turbidity measurements on the effect of high hydrostatic pressure on the phase behavior of dense lysozyme solutions in the liquid-liquid phase separation region, and characterize the underlying intermolecular protein-protein interactions as a function of temperature and pressure under charge-screening conditions (0.5 M NaCl). A reentrant liquid-liquid phase separation region is observed at elevated pressures, which may originate in the pressure dependence of the solvent-mediated protein-protein interaction. A temperature-pressure-concentration phase diagram was constructed for highly concentrated lysozyme solutions over a wide range of temperatures, pressures and protein concentrations including the critical region of the liquid-liquid miscibility gap. PMID:27165990

  9. Comparing two tetraalkylammonium ionic liquids. I. Liquid phase structure

    NASA Astrophysics Data System (ADS)

    Lima, Thamires A.; Paschoal, Vitor H.; Faria, Luiz F. O.; Ribeiro, Mauro C. C.; Giles, Carlos

    2016-06-01

    X-ray scattering experiments at room temperature were performed for the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2]. The peak in the diffraction data characteristic of charge ordering in [N1444][NTf2] is shifted to longer distances in comparison to [N1114][NTf2], but the peak characteristic of short-range correlations is shifted in [N1444][NTf2] to shorter distances. Molecular dynamics (MD) simulations were performed for these ionic liquids using force fields available from the literature, although with new sets of partial charges for [N1114]+ and [N1444]+ proposed in this work. The shifting of charge and adjacency peaks to opposite directions in these ionic liquids was found in the static structure factor, S(k), calculated by MD simulations. Despite differences in cation sizes, the MD simulations unravel that anions are allowed as close to [N1444]+ as to [N1114]+ because anions are located in between the angle formed by the butyl chains. The more asymmetric molecular structure of the [N1114]+ cation implies differences in partial structure factors calculated for atoms belonging to polar or non-polar parts of [N1114][NTf2], whereas polar and non-polar structure factors are essentially the same in [N1444][NTf2]. Results of this work shed light on controversies in the literature on the liquid structure of tetraalkylammonium based ionic liquids.

  10. Comparing two tetraalkylammonium ionic liquids. I. Liquid phase structure.

    PubMed

    Lima, Thamires A; Paschoal, Vitor H; Faria, Luiz F O; Ribeiro, Mauro C C; Giles, Carlos

    2016-06-14

    X-ray scattering experiments at room temperature were performed for the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2]. The peak in the diffraction data characteristic of charge ordering in [N1444][NTf2] is shifted to longer distances in comparison to [N1114][NTf2], but the peak characteristic of short-range correlations is shifted in [N1444][NTf2] to shorter distances. Molecular dynamics (MD) simulations were performed for these ionic liquids using force fields available from the literature, although with new sets of partial charges for [N1114](+) and [N1444](+) proposed in this work. The shifting of charge and adjacency peaks to opposite directions in these ionic liquids was found in the static structure factor, S(k), calculated by MD simulations. Despite differences in cation sizes, the MD simulations unravel that anions are allowed as close to [N1444](+) as to [N1114](+) because anions are located in between the angle formed by the butyl chains. The more asymmetric molecular structure of the [N1114](+) cation implies differences in partial structure factors calculated for atoms belonging to polar or non-polar parts of [N1114][NTf2], whereas polar and non-polar structure factors are essentially the same in [N1444][NTf2]. Results of this work shed light on controversies in the literature on the liquid structure of tetraalkylammonium based ionic liquids. PMID:27306015

  11. Liquid-Phase Electroepitaxy of Semiconductors

    NASA Astrophysics Data System (ADS)

    Dost, Sadik

    The chapter presents a review of the growth of single-crystal bulk semiconductors by liquid-phase electroepitaxy (LPEE). Following a short introduction, early modeling and theoretical studies on LPEE are briefly introduced. Recent experimental results on LPEE growth of GaAs/GaInAs single crystals under a static applied magnetic field are discussed in detail. The results of three-dimensional numerical simulations carried out for LPEE growth of GaAs under various electric and magnetic field levels are presented. The effect of magnetic field nonuniformities is numerically examined. Crystal growth experiments show that the application of a static magnetic field in LPEE growth of GaAs increases the growth rate very significantly. A continuum model to predict such high growth rates is also presented. The introduction of a new electric mobility in the model, i.e., the electromagnetic mobility, allows accurate predictions of both the growth rate and the growth interface shape. Space limitation required the citation of a limited number of references related to LPEE [29.1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73]. For details of many aspects of the LPEE growth process and its historical developments, the reader is referred to these references and also others cited therein.

  12. Ferrofluid-based liquid-phase microextraction.

    PubMed

    Shi, Zhi-Guo; Zhang, Yufeng; Lee, Hian Kee

    2010-11-19

    A new mode of liquid-phase microextraction based on a ferrofluid has been developed. The ferrofluid was composed of silica-coated magnetic particles and 1-octanol as the extractant solvent. The 1-octanol was firmly confined within the silica-coated particles, preventing it from being lost during extraction. Sixteen polycyclic aromatic hydrocarbons (PAHs) were used as model compounds in the development and evaluation of the extraction procedure in combination with gas chromatography-mass spectrometry. Parameters affecting the extraction efficiency were investigated in detail. The optimal conditions were as follows: 20mL sample volume, 10mg of the silica-coated magnetic particles (28mg of ferrofluid), agitation at 20Hz, 20min extraction time, and 2min by sonication with 100μL acetonitrile as the final extraction solvent. Under optimal extraction conditions, enrichment factors ranging from 102- to 173-fold were obtained for the analytes. The limits of detection and the limits of quantification were in the range of 16.8 and 56.7pgmL(-1) and 0.06 and 0.19ngmL(-1), respectively. The linearities were between 0.5-100 and 1-100ngmL(-1) for different PAHs. As the ferrofluid can respond to and be attracted by a magnet, the extraction can be easily achieved by reciprocating movement of an external magnet that served to agitate the sample. No other devices were needed in this new approach of extraction. This new technique is affordable, efficient and convenient for microextraction, and offers portability for potential onsite extraction. PMID:20961552

  13. Liquid-Liquid Phase Transformation in Silicon: Evidence from First-Principles Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Jakse, N.; Pasturel, A.

    2007-11-01

    We report results of first principles molecular dynamics simulations that confirm early speculations on the presence of liquid-liquid phase transition in undercooled silicon. However, we find that structural and electronic properties of both low-density liquid (LDL) and high-density liquid (HDL) phases are quite different from those obtained by empirical calculations, the difference being more pronounced for the HDL phase. The discrepancy between quantum and classical simulations is attributed to the inability of empirical potentials to describe changes in chemical bonds induced by density and temperature variations.

  14. Phase Diagram Characterization Using Magnetic Beads as Liquid Carriers.

    PubMed

    Blumenschein, Nicholas; Han, Daewoo; Steckl, Andrew J

    2015-01-01

    Magnetic beads with ~1.9 µm average diameter were used to transport microliter volumes of liquids between contiguous liquid segments with a tube for the purpose of investigating phase change of those liquid segments. The magnetic beads were externally controlled using a magnet, allowing for the beads to bridge the air valve between the adjacent liquid segments. A hydrophobic coating was applied to the inner surface of the tube to enhance the separation between two liquid segments. The applied magnetic field formed an aggregate cluster of magnetic beads, capturing a certain liquid amount within the cluster that is referred to as carry-over volume. A fluorescent dye was added to one liquid segment, followed by a series of liquid transfers, which then changed the fluorescence intensity in the neighboring liquid segment. Based on the numerical analysis of the measured fluorescence intensity change, the carry-over volume per mass of magnetic beads has been found to be ~2 to 3 µl/mg. This small amount of liquid allowed for the use of comparatively small liquid segments of a couple hundred microliters, enhancing the feasibility of the device for a lab-in-tube approach. This technique of applying small compositional variation in a liquid volume was applied to analyzing the binary phase diagram between water and the surfactant C12E5 (pentaethylene glycol monododecyl ether), leading to quicker analysis with smaller sample volumes than conventional methods. PMID:26381055

  15. Transient-Liquid-Phase and Liquid-Film-Assisted Joining ofCeramics

    SciTech Connect

    Sugar, Joshua D.; McKeown, Joseph T.; Akashi, Takaya; Hong, SungM.; Nakashima, Kunihiko; Glaeser, Andreas M.

    2005-02-09

    Two joining methods, transient-liquid-phase (TLP) joining and liquid-film-assisted joining (LFAJ), have been used to bond alumina ceramics. Both methods rely on multilayer metallic interlayers designed to form thin liquid films at reduced temperatures. The liquid films either disappear by interdiffusion (TLP) or promote ceramic/metal interface formation and concurrent dewetting of the liquid film (LFAJ). Progress on extending the TLP method to lower temperatures by combining low-melting-point (<450 C) liquids and commercial reactive-metal brazes is described. Recent LFAJ work on joining alumina to niobium using copper films is presented.

  16. The effect of graphene on liquid-crystalline blue phases

    NASA Astrophysics Data System (ADS)

    Lavrič, M.; Tzitzios, V.; Kralj, S.; Cordoyiannis, G.; Lelidis, I.; Nounesis, G.; Georgakilas, V.; Amenitsch, H.; Zidanšek, A.; Kutnjak, Z.

    2013-09-01

    The stabilization of liquid-crystalline blue phases is recently attracting considerable interest because of the envisioned applications in fast optical displays and tunable photonic crystals. We report on the effect of surface-functionalized graphene nanosheets on the blue phase range of a chiral liquid crystal. Calorimetric and optical measurements, reproducible on heating and cooling, demonstrate that the resulting soft nanocomposite exhibits an increased blue phase temperature stability range for a minute concentration of dispersed graphene. The impact is stronger on the ordered, cubic structured blue phase I. These findings suggest that anisotropic nanoparticles may be of great usefulness for stabilizing blue phases.

  17. Ultra fast polymer network blue phase liquid crystals

    NASA Astrophysics Data System (ADS)

    Hussain, Zakir; Masutani, Akira; Danner, David; Pleis, Frank; Hollfelder, Nadine; Nelles, Gabriele; Kilickiran, Pinar

    2011-06-01

    Polymer-stabilization of blue phase liquid crystal systems within a host polymer network are reported, which enables ultrafast switching flexible displays. Our newly developed method to stabilize the blue phase in an existing polymer network (e.g., that of a polymer network liquid crystal; PNLC) has shown wide temperature stability and fast response speeds. Systems where the blue phase is stabilized in an already existing polymer network are attractive candidates for ultrafast LCDs. The technology also promises to be applied to flexible PNLC and/or polymer dispersed liquid crystal (PDLC) displays using plastic substrate such as polyethylene terephthalate (PET).

  18. Measurements of liquid-phase turbulence in gas-liquid two-phase flows using particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Zhou, Xinquan; Doup, Benjamin; Sun, Xiaodong

    2013-12-01

    Liquid-phase turbulence measurements were performed in an air-water two-phase flow loop with a circular test section of 50 mm inner diameter using a particle image velocimetry (PIV) system. An optical phase separation method--planar laser-induced fluorescence (PLIF) technique—which uses fluorescent particles and an optical filtration technique, was employed to separate the signals of the fluorescent seeding particles from those due to bubbles and other noises. An image pre-processing scheme was applied to the raw PIV images to remove the noise residuals that are not removed by the PLIF technique. In addition, four-sensor conductivity probes were adopted to measure the radial distribution of the void fraction. Two benchmark tests were performed: the first was a comparison of the PIV measurement results with those of similar flow conditions using thermal anemometry from previous studies; the second quantitatively compared the superficial liquid velocities calculated from the local liquid velocity and void fraction measurements with the global liquid flow rate measurements. The differences of the superficial liquid velocity obtained from the two measurements were bounded within ±7% for single-phase flows and two-phase bubbly flows with the area-average void fraction up to 18%. Furthermore, a preliminary uncertainty analysis was conducted to investigate the accuracy of the two-phase PIV measurements. The systematic uncertainties due to the circular pipe curvature effects, bubble surface reflection effects and other potential uncertainty sources of the PIV measurements were discussed. The purpose of this work is to facilitate the development of a measurement technique (PIV-PLIF) combined with image pre-processing for the liquid-phase turbulence in gas-liquid two-phase flows of relatively high void fractions. The high-resolution data set can be used to more thoroughly understand two-phase flow behavior, develop liquid-phase turbulence models, and assess high

  19. Electron-solid and electron-liquid phases in graphene

    NASA Astrophysics Data System (ADS)

    Knoester, M. E.; Papić, Z.; Morais Smith, C.

    2016-04-01

    We investigate the competition between electron-solid and quantum-liquid phases in graphene, which arise in partially filled Landau levels. The differences in the wave function describing the electrons in the presence of a perpendicular magnetic field in graphene with respect to the conventional semiconductors, such as GaAs, can be captured in a form factor which carries the Landau-level index. This leads to a quantitative difference in the electron-solid and -liquid energies. For the lowest Landau level, there is no difference in the wave function of relativistic and nonrelativistic systems. We compute the cohesive energy of the solid phase analytically using a Hartree-Fock Hamiltonian. The liquid energies are computed analytically as well as numerically, using exact diagonalization. We find that the liquid phase dominates in the n =1 Landau level, whereas the Wigner crystal and electron-bubble phases become more prominent in the n =2 and 3 Landau level.

  20. Apparatus for the premixed gas phase combustion of liquid fuels

    SciTech Connect

    Roffe, G.A.; Trucco, H.A.

    1981-04-21

    This invention relates to improvements in the art of liquid fuel combustion and, more particularly, concerns a method and apparatus for the controlled gasification of liquid fuels, the thorough premixing of the then gasified fuel with air and the subsequent gas-phase combustion of the mixture to produce a flame substantially free of soot, carbon monoxide, nitric oxide and unburned fuel.

  1. Solid–Liquid Phase Change Driven by Internal Heat Generation

    SciTech Connect

    John Crepeau; Ali s. Siahpush

    2012-07-01

    This article presents results of solid-liquid phase change, the Stefan Problem, where melting is driven internal heat generation, in a cylindrical geometry. The comparison between a quasi-static analytical solution for Stefan numbers less than one and numerical solutions shows good agreement. The computational results of phase change with internal heat generation show how convection cells form in the liquid region. A scale analysis of the same problem shows four distinct regions of the melting process.

  2. Diffusion mass transport in liquid phase epitaxial growth of semiconductors

    SciTech Connect

    Dost, S.; Qin, Z.; Kimura, M.

    1996-12-01

    A numerical simulation model for the mass transport occurring during the liquid phase epitaxial growth of AlGaAs is presented. The mass transport equations in the liquid and solid phases, and the relationships between concentrations and temperature obtained from the phase diagram constitute the governing equations. These equations together with appropriate interface and boundary conditions were solved numerically by the Finite Element Method. Numerical results show the importance of diffusion into the solid phase, affecting the composition of grown layers. Simulation results agree with experiments.

  3. Gas-Liquid Flows and Phase Separation

    NASA Technical Reports Server (NTRS)

    McQuillen, John

    2004-01-01

    Common issues for space system designers include:Ability to Verify Performance in Normal Gravity prior to Deployment; System Stability; Phase Accumulation & Shedding; Phase Separation; Flow Distribution through Tees & Manifolds Boiling Crisis; Heat Transfer Coefficient; and Pressure Drop.The report concludes:Guidance similar to "A design that operates in a single phase is less complex than a design that has two-phase flow" is not always true considering the amount of effort spent on pressurizing, subcooling and phase separators to ensure single phase operation. While there is still much to learn about two-phase flow in reduced gravity, we have a good start. Focus now needs to be directed more towards system level problems .

  4. Comparison of liquid-phase and gas-phase pure thermal cracking on n-hexadecane

    SciTech Connect

    Wu, G.; Katsumura, Yosuke; Matsuura, Chihiro; Ishigure, Kenkichi; Kubo, Junichi

    1996-12-01

    Thermal cracking of n-hexadecane in the mild temperature (330--375 C) range has been investigated in liquid and gas phases. The kinetic data of liquid-phase cracking are shown to be very similar to those of gas-phase cracking. However, the pattern and distribution of the products are greatly phase dependent. In liquid-phase cracking, there is an equimolar distribution of n-alkane and 1-alkene products in the C{sub 3}--C{sub 13} range at low conversion; when the conversion is increased, more alkanes than alkenes are produced. To the contrary, more alkenes than alkanes are always determined in products from gas-phase cracking. Liquid-phase cracking gives a low selectivity of gas products and a high selectivity of addition compounds (C{sub 18}--C{sub 30}), whereas gas-phase cracking produces a large amount of gas products and no addition compounds. The phase dependence of products can be interpreted in terms of a low concentration of hexadecane, under which {beta}-scission occurs more preferentially than in liquid phase. Reaction mechanisms are suggested based on the product analysis to account for cracking behaviors of liquid-phase and gas-phase cracking.

  5. Liquid phase reaction-bonding of structural ceramics and composites

    SciTech Connect

    Chiang, Y.M. . Dept. of Materials Science and Engineering)

    1988-01-01

    Synthesis of ceramics via the reaction of a solid precursor with either a gas or liquid phase has a number of advantages compared to conventional sintering technology. These advantages are known for gas-phase processes. The authors have explored the potential for synthesizing high performance ceramics in the model system reaction-bonded silicon carbide, in which liquid silicon is used to infiltrate carbonaceous preforms. In this paper results are presented that illustrate the use of alloyed-melts to obtain dense silicon carbide composites with residual refractory silicide phases, such as MoSi/sub 2/, rather than the residual silicon phase which has heretofore limited high temperature properties. Infiltration processing considerations, such as the ultimate infiltration dimensions possible in the presence of simultaneous reaction, are discussed. Microstructure and mechanical properties characterization in the SIC-MoSi/sub 2/ system are presented. Other refractory ceramics systems to which liquid-phase reaction-bonding may be applied are discussed.

  6. The liquid to vapor phase transition in excited nuclei

    SciTech Connect

    Elliott, J.B.; Moretto, L.G.; Phair, L.; Wozniak, G.J.; Beaulieu, L.; Breuer, H.; Korteling, R.G.; Kwiatkowski, K.; Lefort, T.; Pienkowski, L.; Ruangma, A.; Viola, V.E.; Yennello, S.J.

    2001-05-08

    For many years it has been speculated that excited nuclei would undergo a liquid to vapor phase transition. For even longer, it has been known that clusterization in a vapor carries direct information on the liquid-vapor equilibrium according to Fisher's droplet model. Now the thermal component of the 8 GeV/c pion + 197 Au multifragmentation data of the ISiS Collaboration is shown to follow the scaling predicted by Fisher's model, thus providing the strongest evidence yet of the liquid to vapor phase transition.

  7. Structural crossover in a supercooled metallic liquid and the link to a liquid-to-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Lan, S.; Blodgett, M.; Kelton, K. F.; Ma, J. L.; Fan, J.; Wang, X.-L.

    2016-05-01

    Time-resolved synchrotron measurements were carried out to capture the structure evolution of an electrostatically levitated metallic-glass-forming liquid during free cooling. The experimental data shows a crossover in the liquid structure at ˜1000 K, about 115 K below the melting temperature and 150 K above the crystallization temperature. The structure change is characterized by a dramatic growth in the extended-range order below the crossover temperature. Molecular dynamics simulations have identified that the growth of the extended-range order was due to an increased correlation between solute atoms. These results provide structural evidence for a liquid-to-liquid-phase-transition in the supercooled metallic liquid.

  8. Relationship between the liquid liquid phase transition and dynamic behaviour in the Jagla model

    NASA Astrophysics Data System (ADS)

    Xu, Limei; Ehrenberg, Isaac; Buldyrev, Sergey V.; Stanley, H. Eugene

    2006-09-01

    Using molecular dynamics simulations, we study a spherically symmetric 'two-scale' Jagla potential with both repulsive and attractive ramps. This potential displays a liquid-liquid phase transition with a positively sloped coexistence line ending at a critical point well above the equilibrium melting line. We study the dynamic behaviour in the vicinity of this liquid-liquid critical point. Below the critical point, we find that the dynamics in the more ordered high density liquid (HDL) are much slower then the dynamics in the less ordered low density liquid (LDL). Moreover, the behaviour of the diffusion constant and relaxation time in the HDL phase follows approximately an Arrhenius law, while in the LDL phase the slope of the Arrhenius fit increases upon cooling. Above the critical pressure, as we cool the system at constant pressure, the behaviour of the dynamics smoothly changes with temperature. It resembles the behaviour of the LDL at high temperatures and resembles the behaviour of the HDL at low temperatures. This dynamic crossover happens in the vicinity of the Widom line (the extension of the coexistence line into the one-phase region) which also has a positive slope. Our work suggests a possible general relation between a liquid-liquid phase transition and the change in dynamics.

  9. Green aspects, developments and perspectives of liquid phase microextraction techniques.

    PubMed

    Spietelun, Agata; Marcinkowski, Łukasz; de la Guardia, Miguel; Namieśnik, Jacek

    2014-02-01

    Determination of analytes at trace levels in complex samples (e.g. biological or contaminated water or soils) are often required for the environmental assessment and monitoring as well as for scientific research in the field of environmental pollution. A limited number of analytical techniques are sensitive enough for the direct determination of trace components in samples and, because of that, a preliminary step of the analyte isolation/enrichment prior to analysis is required in many cases. In this work the newest trends and innovations in liquid phase microextraction, like: single-drop microextraction (SDME), hollow fiber liquid-phase microextraction (HF-LPME), and dispersive liquid-liquid microextraction (DLLME) have been discussed, including their critical evaluation and possible application in analytical practice. The described modifications of extraction techniques deal with system miniaturization and/or automation, the use of ultrasound and physical agitation, and electrochemical methods. Particular attention was given to pro-ecological aspects therefore the possible use of novel, non-toxic extracting agents, inter alia, ionic liquids, coacervates, surfactant solutions and reverse micelles in the liquid phase microextraction techniques has been evaluated in depth. Also, new methodological solutions and the related instruments and devices for the efficient liquid phase micoextraction of analytes, which have found application at the stage of procedure prior to chromatographic determination, are presented. PMID:24401382

  10. Suppression of phase transitions in a confined rodlike liquid crystal.

    PubMed

    Grigoriadis, Christos; Duran, Hatice; Steinhart, Martin; Kappl, Michael; Butt, Hans-Jürgen; Floudas, George

    2011-11-22

    The nematic-to-isotropic, crystal-to-nematic, and supercooled liquid-to-glass temperatures are studied in the liquid crystal 4-pentyl-4'-cyanobiphenyl (5CB) confined in self-ordered nanoporous alumina. The nematic-to-isotropic and the crystal-to-nematic transition temperatures are reduced linearly with the inverse pore diameter. The finding that the crystalline phase is completely suppressed in pores having diameters of 35 nm and below yields an estimate of the critical nucleus size. The liquid-to-glass temperature is reduced in confinement as anticipated by the model of rotational diffusion within a cavity. These results provide the pertinent phase diagram for a confined liquid crystal and are of technological relevance for the design of liquid crystal-based devices with tunable optical, thermal, and dielectric properties. PMID:21974835

  11. Liquid jet pumps for two-phase flows

    SciTech Connect

    Cunningham, R.G.

    1995-06-01

    Isothermal compression of a bubbly secondary fluid in a mixing-throat and diffuser is described by a one-dimensional flow model of a liquid-jet pump. Friction-loss coefficients used in the four equations may be determined experimentally, or taken from the literature. The model reduces to the liquid-jet gas compressor case if the secondary liquid is zero. Conversely, a zero secondary-gas flow reduces the liquid-jet gas and liquid (LJGL) model to that of the familiar liquid-jet liquid pump. A ``jet loss`` occurs in liquid-jet pumps if the nozzle tip is withdrawn from the entrance plane of the throat, and jet loss is included in the efficiency equations. Comparisons are made with published test data for liquid-jet liquid pumps and for liquid-jet gas compressors. The LJGL model is used to explore jet pump responses to two-phase secondary flows, nozzle-to-throat area ratio, and primary-jet velocity. The results are shown in terms of performance curves versus flow ratios. Predicted peak efficiencies are approximately 50 percent. Under sever operating conditions, LJGL pump performance curves exhibit maximum-flow ratios or cut-offs. Cut-offs occurs when two-phase secondary-flow steams attain sonic values at the entry of the mixing throat. A dimensionless number correlates flow-ratio cut-offs with pump geometry and operating conditions. Throat-entry choking of the secondary flow can be predicted, hence avoided, in designing jet pumps to hand two-phase fluids.

  12. Ambient temperature liquefaction using liquid clathrates: Final technical report

    SciTech Connect

    Atwood, J.L.

    1988-06-22

    New air-stable liquid clathrates based on simple salts were used to effect liquefaction. The quantity of the liquefied products from the liquid clathrates based on (organic base/center dot/H)/sup + -/(Cl-H-Cl)/sup minus/ is among the highest yet observed. Indeed, liquid clathrates based on classic room temperature molten salts such as (pyridinium)(AlCl/sub 4/) have afforded yields of liquid material which may go as high as 70%. The work-up scheme for the (NBu/sub 4/)(Cl-H-Br) liquefaction products has afforded excellent mass balance. The first model hydrogenation runs in a liquid clathrate have been successfully carried out. In the liquid clathrate based on (NBu/sub 4/)(BF/sub 4/) and benzene, Wilkinson's catalyst has given almost complete conversion of cyclohexene to cyclohexane. Studies on the retention of cyclohexene and cyclohexane in the liquid clathrate phase are in progress. Initial indications are that cyclohexene is more compatible with the lower liquid layer than is cyclohexane.

  13. Cyclo-hexane-1-spiro-2'-imidazolidine-5'-spiro-1''-cyclo-hexan-4'-one.

    PubMed

    Kavitha, T; Ponnuswamy, S; Vijayalakshmi, R; Thenmozhi, M; Ponnuswamy, M N

    2010-01-01

    In the title compound, C(13)H(22)N(2)O, the central imidazolidine ring is in an envelope conformation and the two cyclo-hexane rings adopt chair conformations. In the crystal structure, the mol-ecules are linked into centrosymmetric R(2) (2)(8) dimers by pairs of N-H⋯O hydrogen bonds. PMID:21579127

  14. Entropy Calculations for a Supercooled Liquid Crystalline Blue Phase

    ERIC Educational Resources Information Center

    Singh, U.

    2007-01-01

    We observed, using polarized light microscopy, the supercooling of the blue phase (BPI) of cholesteryl proprionate and measured the corresponding liquid crystalline phase transition temperatures. From these temperatures and additional published data we have provided, for the benefit of undergraduate physics students, a nontraditional example…

  15. Polarization-phase filtering of laser images of biological liquids

    NASA Astrophysics Data System (ADS)

    Ushenko, Yu. A.; Sidor, M.

    2013-06-01

    Our work is aimed at searching the possibilities to perform diagnostics and differentiation of structures inherent to liquid-crystal networks of blood plasma with various pathologies (health - breast cancer) by using the method to determine the coordinate distributions of phase shifts (phase maps) between orthogonal components of laser radiation amplitudes with the following statistical, fractal and singular analyses of these distributions.

  16. Low voltage blue phase liquid crystal for spatial light modulators.

    PubMed

    Peng, Fenglin; Lee, Yun-Han; Luo, Zhenyue; Wu, Shin-Tson

    2015-11-01

    We demonstrated a low-voltage polymer-stabilized blue phase liquid crystal (BPLC) for phase-only modulation with a liquid-crystal-on-silicon (LCoS). A new device configuration was developed, which allows the incident laser beam to traverse the BPLC layer four times before exiting the LCoS. As a result, the 2π phase change voltage is reduced to below 24 V in the visible region. The response time remains relatively fast (∼3  ms). The proposed device configuration enables widespread applications of BPLC spatial light modulators. PMID:26512528

  17. Fabrication of Janus droplets by evaporation driven liquid-liquid phase separation.

    PubMed

    Zhang, Qingquan; Xu, Meng; Liu, Xiaojun; Zhao, Wenfeng; Zong, Chenghua; Yu, Yang; Wang, Qi; Gai, Hongwei

    2016-04-11

    We present a universal and scalable method to fabricate Janus droplets based on evaporation driven liquid-liquid phase separation. In this work, the morphologies and chemical properties of separate parts of the Janus droplets can be flexibly regulated, and more complex Janus droplets (such as core-shell Janus droplets, ternary Janus droplets, and multiple Janus droplets) can be constructed easily. PMID:26983706

  18. Phase behavior and dynamics of a cholesteric liquid crystal

    SciTech Connect

    Roy, D.; Fragiadakis, D.; Roland, C. M.; Dabrowski, R.; Dziaduszek, J.; Urban, S.

    2014-02-21

    The synthesis, equation of state, phase diagram, and dielectric relaxation properties are reported for a new liquid crystal, 4{sup ′}-butyl-4-(2-methylbutoxy)azoxybenzene (4ABO5*), which exhibits a cholesteric phase at ambient temperature. The steepness of the intermolecular potential was characterized from the thermodynamic potential parameter, Γ = 4.3 ± 0.1 and the dynamic scaling exponent, γ = 3.5 ± 0.2. The difference between them is similar to that seen previously for nematic and smectic liquid crystals, with the near equivalence of Γ and γ consistent with the near constancy of the relaxation time of 4ABO5* at the cholesteric to isotropic phase transition (i.e., the clearing line). Thus, chirality does not cause deviations from the general relationship between thermodynamics and dynamics in the ordered phase of liquid crystals. The ionic conductivity of 4ABO5* shows strong coupling to the reorientational dynamics.

  19. Fast Method for Computing Chemical Potentials and Liquid-Liquid Phase Equilibria of Macromolecular Solutions.

    PubMed

    Qin, Sanbo; Zhou, Huan-Xiang

    2016-08-25

    Chemical potential is a fundamental property for determining thermodynamic equilibria involving exchange of molecules, such as between two phases of molecular systems. Previously, we developed the fast Fourier transform (FFT)-based method for Modeling Atomistic Protein-crowder interactions (FMAP) to calculate excess chemical potentials according to the Widom insertion. Intermolecular interaction energies were expressed as correlation functions and evaluated via FFT. Here, we extend this method to calculate liquid-liquid phase equilibria of macromolecular solutions. Chemical potentials are calculated by FMAP over a wide range of molecular densities, and the condition for coexistence of low- and high-density phases is determined by the Maxwell equal-area rule. When benchmarked on Lennard-Jones fluids, our method produces an accurate phase diagram at 18% of the computational cost of the current best method. Importantly, the gain in computational speed increases dramatically as the molecules become more complex, leading to many orders of magnitude in speed up for atomistically represented proteins. We demonstrate the power of FMAP by reporting the first results for the liquid-liquid coexistence curve of γII-crystallin represented at the all-atom level. Our method may thus open the door to accurate determination of phase equilibria for macromolecular mixtures such as protein-protein mixtures and protein-RNA mixtures, that are known to undergo liquid-liquid phase separation, both in vitro and in vivo. PMID:27327881

  20. Microgravity Studies of Liquid-Liquid Phase Transitions in Alumina-Yttria Melts

    NASA Technical Reports Server (NTRS)

    Guynes, Buddy (Technical Monitor); Weber, Richard; Nordine, Paul

    2004-01-01

    The scientific objective of this research is to increase the fundamental knowledge base for liquid- phase processing of technologically important oxide materials. The experimental objective is to define conditions and hardware requirements for microgravity flight experiments to test and expand the experimental hypotheses that: 1. Liquid phase transitions can occur in undercooled melts by a diffusionless process. 2. Onset of the liquid phase transition is accompanied by a large change in the temperature dependence of melt viscosity. Experiments on undercooled YAG (Y3A15012)- and rare earth oxide aluminate composition liquids demonstrated a large departure from an Arrhenian temperature dependence of viscosity. Liquid YAG is nearly inviscid at its 2240 K melting point. Glass fibers were pulled from melts undercooled by ca. 600 K indicating that the viscosity is on the order of 100 Pans (1000 Poise) at 1600 K. This value of viscosity is 500 times greater than that obtained by extrapolation of data for temperatures above the melting point of YAG. These results show that the liquids are extremely fragile and that the onset of the highly non-Arrhenian viscosity-temperature relationship occurs at a temperature considerably below the equilibrium melting point of the solid phases. Further results on undercooled alumina-yttria melts containing 23-42 mole % yttrium oxide indicate that a congruent liquid-liquid phase transition occurs in the undercooled liquids. The rates of transition are inconsistent with a diffusion-limited process. This research is directed to investigation of the scientifically interesting phenomena of polyamorphism and fragility in undercooled rare earth oxide aluminum oxide liquids. The results bear on the technologically important problem of producing high value rare earth-based optical materials.

  1. Micellar hexagonal phases in lyotropic liquid crystals

    NASA Astrophysics Data System (ADS)

    Amaral, L. Q.; Gulik, A.; Itri, R.; Mariani, P.

    1992-09-01

    The hexagonal cell parameter a of the system sodium dodecyl lauryl sulfate and water as a function of volume concentration cv in phase Hα shows the functional behavior expected for micelles of finite length: a~c-1/3v. The interpretation of x-ray data based on finite micelles leads to an alternative description of the hexagonal phase Hα: spherocylindrical micelles of constant radius with length that may grow along the range of the Hα phase. Results are compared with recent statistical-mechanical calculations for the isotropic I-Hα transition. The absence of diffraction in the direction perpendicular to the hexagonal plane is ascribed to polydispersity of micellar length, which also is a necessary condition for the occurrence of direct I-Hα transitions.

  2. Determination of organochlorine pesticides in water using solvent cooling assisted dynamic hollow-fiber-supported headspace liquid-phase microextraction.

    PubMed

    Huang, Shih-Pin; Huang, Shang-Da

    2007-12-28

    The organic solvent film formed within a hollow fiber was used as an extraction interface in the headspace liquid-phase microextraction (HS-LPME) of organochlorine pesticides. Some common organic solvents with different vapor pressures (9.33-12,918.9 Pa) were studied as extractants. The results indicated that even the solvent with the highest vapor pressure (cyclohexane) can be used to carry out the extraction successfully. However, those compounds (analytes) with low vapor pressures could not be extracted successfully. In general, the large surface area of the hollow fiber can hasten the extraction speed, but it can increase the risk of solvent loss. Lowering the temperature of the extraction solvent could not only reduce solvent loss (by lowering its vapor pressure) but also extend the feasible extraction time to improve extraction efficiency. In this work, a solvent cooling assisted dynamic hollow-fiber-supported headspace liquid-phase microextraction (SC-DHF-HS-LPME) approach was developed. By lowering the temperature of the solvent, the evaporation can be decreased, the extraction time can be lengthened, and, on the contrary, the equilibrium constant between headspace phase and extraction solvent can be increased. In dynamic LPME, the extracting solvent is held within a hollow fiber, affixed to a syringe needle and placed in the headspace of the sample container. The extracting solvent within the fiber is moved to-and-fro by using a programmable syringe pump. The movement facilitates mass transfer of analyte(s) from the sample to the solvent. Analysis of the extract was carried out by gas chromatography-mass spectrometry (GC-MS). The effects of identity of extraction solvent, extraction temperature, sample agitation, extraction time, and salt concentration on extraction performance were also investigated. Good enrichments were achieved (65-211-fold) with this method. Good repeatabilities of extraction were obtained, with RSD values below 15.2%. Detection

  3. Liquid and Solid Phases of 3He on Graphite

    NASA Astrophysics Data System (ADS)

    Gordillo, M. C.; Boronat, J.

    2016-04-01

    Recent heat-capacity experiments show quite unambiguously the existence of a liquid 3He phase adsorbed on graphite. This liquid is stable at an extremely low density, possibly one of the lowest found in nature. Previous theoretical calculations of the same system, and in strictly two dimensions, agree with the result that this liquid phase is not stable and the system is in the gas phase. We calculated the phase diagram of normal 3He adsorbed on graphite at T =0 using quantum Monte Carlo methods. Considering a fully corrugated substrate, we observe that at densities lower than 0.006 Å-2 the system is a very dilute gas that, at that density, is in equilibrium with a liquid of density 0.014 Å-2 . Our prediction matches very well the recent experimental findings on the same system. On the contrary, when a flat substrate is considered, no gas-liquid coexistence is found, in agreement with previous calculations. We also report results on the different solid structures, and on the corresponding phase transitions that appear at higher densities.

  4. Toward Consistent Terminology for Cyclohexane Conformers in Introductory Organic Chemistry

    ERIC Educational Resources Information Center

    Nelson, Donna J.; Brammer, Christopher N.

    2011-01-01

    Recommended changes in use of cyclohexane conformers and their nomenclature will remedy inconsistencies in cyclohexane conformers and their nomenclature that exist across currently used organic chemistry textbooks. These inconsistencies prompted this logical analysis and the resulting recommendations. Recommended conformer names are "chair",…

  5. Nature of the first-order liquid-liquid phase transition in supercooled silicon

    NASA Astrophysics Data System (ADS)

    Zhao, G.; Yu, Y. J.; Tan, X. M.

    2015-08-01

    The first-order liquid-liquid phase transition in supercooled Si is revisited by long-time first-principle molecular dynamics simulations. As the focus of the present paper, its nature is revealed by analyzing the inherent structures of low-density liquid (LDL) and high-density liquid (HDL). Our results show that it is a transition between a sp3-hybridization LDL and a white-tin-like HDL. This uncovers the origin of the semimetal-metal transition accompanying it and also proves that HDL is the metastable extension of high temperature equilibrium liquid into the supercooled regime. The pressure-temperature diagram of supercooled Si thus can be regarded in some respects as shifted reflection of its crystalline phase diagram.

  6. Containerless Liquid-Phase Processing of Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Weber, J. K. Richard (Principal Investigator); Nordine, Paul C.

    1996-01-01

    The present project builds on the results of research supported under a previous NASA grant to investigate containerless liquid-phase processing of molten ceramic materials. The research used an aero-acoustic levitator in combination with cw CO2 laser beam heating to achieve containerless melting, superheating, undercooling, and solidification of poorly-conducting solids and liquids. Experiments were performed on aluminum oxide, binary aluminum oxide-silicon dioxide materials, and oxide superconductors.

  7. Liquid-phase mixing of bipropellant doublets

    NASA Technical Reports Server (NTRS)

    Hoehn, F. W.; Rupe, J. H.; Sotter, J. G.

    1972-01-01

    Experimental results of unlike doublet mixing are correlated with an analytically derived equation predicting fluid cavitation. The correlation relates the minimum orifice pressure drop required to initiate cavitation, with the system back pressure, cold flow simulant vapor pressure, and the orifice flow discharge and contraction coefficients. Stream flow instabilities are also visually correlated with the onset of cavitation and orifice discharge coefficient measurements. The influence of cavitation on the characteristic phenomenon of hydraulic flip is observed for both circular and noncircular shaped orifices. For certain intermediate orifice lengths, some noncircular shapes are shown to produce more fully developed flows (shorter recovery lengths) and therefore a more cohesive jet, which in turn yields slightly higher cold flow mixing uniformities than circular shaped orifices of equal absolute length. The particular noncircular shaped elements evaluated are shown to be more sensitive to liquid stream misimpingement than the corresponding circular orifices.

  8. Microstructural development in transient liquid-phase bonding

    NASA Astrophysics Data System (ADS)

    Gale, W. F.; Wallach, E. R.

    1991-10-01

    The applicability of conventional models of the transient liquid-phase (TLP) bonding process to the joining of nickel using ternary Ni-Si-B insert metals is considered in this article. It is suggested that diffusion of boron out of the liquid and into the solid substrate before the equilibration of the liquid and solid phases can result in the development of significant boron concentrations in the substrate. This, in turn, leads to the precipitation of boride phases in the substrate during holding at bonding temperatures below the binary nickel-boron eutectic temperature. The formation of boride phases during holding at the bonding temperature is of importance, because first, it is not predicted by the standard models of the TLP process, and second, the borides are not removed by prolonged holding at the bonding temperature and therefore may influence the in-service properties of the joint. In contrast, when bonding above the binary nickel-boron eutectic temperature, localized liquation of the substrate takes place. This liquid region resolidifies following prolonged holding and does not result in the formation of persistent boride phases. Experimental support is presented for the formation of borides during bonding, and characterization of the boride phases formed in the substrate is described.

  9. The Molecular Structure of the Liquid Ordered Phase

    NASA Astrophysics Data System (ADS)

    Lyman, Edward

    2014-03-01

    Molecular dynamics simulations reveal substructures within the liquid-ordered phase of lipid bilayers. These substructures, identified in a 10 μsec all-atom trajectory of liquid-ordered/liquid-disordered coexistence (Lo/Ld) , are composed of saturated hydrocarbon chains packed with local hexagonal order, and separated by interstitial regions enriched in cholesterol and unsaturated chains. Lipid hydrocarbon chain order parameters calculated from the Lo phase are in excellent agreement with 2H NMR measurements; the local hexagonal packing is also consistent with 1H-MAS NMR spectra of the Lo phase, NMR diffusion experiments, and small angle X-ray- and neutron scattering. The balance of cholesterol-rich to local hexagonal order is proposed to control the partitioning of membrane components into the Lo regions. The latter have been frequently associated with formation of so-called rafts, platforms in the plasma membranes of cells that facilitate interaction between components of signaling pathways.

  10. Manipulating Liquids With Acoustic Radiation Pressure Phased Arrays

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C.

    1999-01-01

    High-intensity ultrasound waves can produce the effects of "Acoustic Radiation Pressure" (ARP) and "acoustic streaming." These effects can be used to propel liquid flows and to apply forces that can be used to move or manipulate floating objects or liquid surfaces. NASA's interest in ARP includes the remote-control agitation of liquids and the manipulation of bubbles and drops in liquid experiments and propellant systems. A high level of flexibility is attained by using a high-power acoustic phased array to generate, steer, and focus a beam of acoustic waves. This is called an Acoustic Radiation Pressure Phased Array, or ARPPA. In this approach, many acoustic transducer elements emit wavelets that converge into a single beam of sound waves. Electronically coordinating the timing, or "phase shift," of the acoustic waves makes it possible to form a beam with a predefined direction and focus. Therefore, a user can direct the ARP force at almost any desired point within a liquid volume. ARPPA lets experimenters manipulate objects anywhere in a test volume. This flexibility allow it to be used for multiple purposes, such as to agitate liquids, deploy and manipulate drops or bubbles, and even suppress sloshing in spacecraft propellant tanks.

  11. Liquid-liquid phase separation in supersaturated lysozyme solutions and associated precipitate formation/crystallization

    NASA Astrophysics Data System (ADS)

    Muschol, Martin; Rosenberger, Franz

    1997-08-01

    Using cloud point determinations, the phase boundaries (binodals) for metastable liquid-liquid (L-L) separation in supersaturated hen egg white lysozyme solutions with 3%, 5%, and 7% (w/v) NaCl at pH=4.5 and protein concentrations c between 40 and 400 mg/ml were determined. The critical temperature for the binodal increased approximately linearly with salt concentration. The coexisting liquid phases both remained supersaturated but differed widely in protein concentration. No salt repartitioning was observed between the initial and the two separated liquid phases. After the L-L separation, due to the presence of the high protein concentration phase, crystallization occurred much more rapidly than in the initial solution. At high initial protein concentrations, a metastable gel phase formed at temperatures above the liquid binodal. Both crystal nucleation and gel formation were accelerated in samples that had been cycled through the binodal. Solutions in the gel and L-L regions yielded various types of precipitates. Based on theoretical considerations, previous observations with other proteins, and our experimental results with lysozyme, a generic phase diagram for globular proteins is put forth. A limited region in the (T,c) plane favorable for the growth of protein single crystals is delineated.

  12. Liquid-Liquid Phase Separation in Supersaturated Lysozyme Solutions and Associated Precipitate Formation/Crystallization

    NASA Technical Reports Server (NTRS)

    Muschol, Martin; Rosenberger, Franz

    1997-01-01

    Using cloud point determinations, the phase boundaries (binodals) for metastable liquid-liquid (L-L) separation in supersaturated hen egg white lysozyme solutions with 3%, 5%, and 7% (wlv) NaCl at pH= 4.5 and protein concentrations c between 40 and 400 mg/ml were determined. The critical temperature for the binodal increased approximately linearly with salt concentration. The coexisting liquid phases both remained supersaturated but differed widely in protein concentration. No salt repartitioning was observed between the initial and the two separated liquid phases. After the L-L separation, due to the presence of the high protein concentration phase, crystallization occurred much more rapidly than in the initial solution. At high initial protein concentrations, a metastable gel phase formed at temperatures above the liquid binodal. Both crystal nucleation and gel formation were accelerated in samples that had been cycled through the binodal. Solutions in the gel and L-L regions yielded various types of precipitates. Based on theoretical considerations, previous observations with other proteins, and our experimental results with lysozyme, a generic phase diagram for globular proteins is put forth. A limited region in the (T,c) plane favorable for the growth of protein single crystals is delineated.

  13. Effect of liquid viscosity on wave behavior in gas-liquid two-phase flow

    SciTech Connect

    Kondo, Yoshiyuki; Mori, Koji; Yagishita, Takuya; Nakabo, Akinobu

    1999-07-01

    Measurements of time-spatial distributions of liquid holdups for the vertical upward gas-liquid two-phase flow were carried out by using the supermultiple cross-sectional mean liquid holdup probes (S-CHOP) and the semi-supermultiple point-electrode probes (SS-PEP) in the wide range of superficial gas and liquid velocity, j{sub g} and j{sub {ell}}, and the liquid kinematic viscosities were {nu}{sub {ell}} = 1 x 10{sup {minus}6}, 10 x 10{sup {minus}6} and 20 x 10{sup {minus}6} m{sup 1}/s. The time-spatial maps of wave behavior and the interfacial profiles were presented. Close inspection of these results reveals that there also exist huge waves and disturbance waves in the higher liquid viscosity conditions. To clarify the characteristics of these waves, the wave-vein analysis and the cluster analysis by K-mean algorithm were applied. These methods distinguished huge wave and disturbance wave objectively. The appearance regions of liquid slug, huge wave, and disturbance wave for each liquid viscosity condition were presented and the effects of liquid viscosity on them were discussed. Furthermore, velocity, width and height of these waves were determined, and the effects of liquid viscosity on them were clarified.

  14. Adaptive optics fundus camera using a liquid crystal phase modulator

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tatsuo; Nakazawa, Naoki; Bessho, Kenichiro; Kitaguchi, Yoshiyuki; Maeda, Naoyuki; Fujikado, Takashi; Mihashi, Toshifumi

    2008-05-01

    We have developed an adaptive optics (AO) fundus camera to obtain high resolution retinal images of eyes. We use a liquid crystal phase modulator to compensate the aberrations of the eye for better resolution and better contrast in the images. The liquid crystal phase modulator has a wider dynamic range to compensate aberrations than most mechanical deformable mirrors and its linear phase generation makes it easy to follow eye movements. The wavefront aberration was measured in real time with a sampling rate of 10 Hz and the closed loop system was operated at around 2 Hz. We developed software tools to align consecutively obtained images. From our experiments with three eyes, the aberrations of normal eyes were reduced to less than 0.1 μm (RMS) in less than three seconds by the liquid crystal phase modulator. We confirmed that this method was adequate for measuring eyes with large aberrations including keratoconic eyes. Finally, using the liquid crystal phase modulator, high resolution images of retinas could be obtained.

  15. A novel urea-functionalized surface-confined octadecylimidazolium ionic liquid silica stationary phase for reversed-phase liquid chromatography.

    PubMed

    Zhang, Mingliang; Tan, Ting; Li, Zhan; Gu, Tongnian; Chen, Jia; Qiu, Hongdeng

    2014-10-24

    One-pot synthesis of surface-confined ionic liquid functionalized silica spheres was proposed using N-(3-aminopropyl)imidazole, γ-isopropyltriethoxysilane and 1-bromooctadecane as starting materials. The surface modification of the silica spheres was successful with a high surface density of octadecylimidazolium, enabling the utilization of this new urea-functionalized ionic liquid-grafted silica material as stationary phase for high-performance liquid chromatography in reversed-phase mode. The long aliphatic chain combined with the multiple polar group embedded in the ligands imparted the new stationary phase fine selectivity towards PAH isomers and polar aromatics and higher affinity for phenolic compounds. The unique features of the new material, especially the effect of the urea group on the retention were elucidated by mathematic modeling. PMID:25249489

  16. Two-phase flow characteristics of liquid oxygen flow in low pressure liquid rocket engine

    NASA Astrophysics Data System (ADS)

    Cho, Namkyung; Kim, Seunghan; Kim, Youngmog; Jeong, Sangkwon; Jung, Jeheon

    2004-06-01

    In most cryogenic liquid rocket engines, liquid oxygen manifold and injector are not thermally insulated from room temperature environment for the purpose of reducing system complexity and weight. This feature of cryogenic liquid supply system results in the situation that liquid oxygen flow is vaporized especially in the vicinity of the manifold and the injector wall. The transient two-phase flow tendency is severe for low combustion pressure rocket engine without using turbo-pump. This paper focuses on the two-phase flow phenomena of liquid oxygen in low combustion pressure rocket engine. The KSR-III (Korea Sounding Rocket) engine test data is thoroughly analyzed to estimate the vapor fraction of liquid oxygen flow near the engine manifold and the injector. During the cold flow and the combustion tests of the KSR-III Engine, the static and dynamic pressures are measured at the engine inlet, the liquid oxygen manifold and the combustion chamber. The manifold outer wall and the inner wall temperatures are also measured. In this paper, we present the experimental investigation on the vapor generation, the vapor mass fraction, and the boiling characteristics of the liquid oxygen flow in the engine manifold and injector.

  17. Intrinsic response of polymer liquid crystals in photochemical phase transition

    SciTech Connect

    Ikeda, Tomiki; Sasaki, Takeo; Kim, Haengboo )

    1991-01-24

    Time-resolved measurements were performed on the photochemically induced isothermal phase transition of polymer liquid crystals (PLC) with mesogenic side chains of phenyl benzoate (PAPB3) and cyanobiphenyl (PACB3) under conditions wherein the photochemical reaction of the doped photoresponsive molecule (4-butyl-4-{prime}-methoxyazobenzene, BMAB) was completed within {approximately} 10 ns, and the subsequent phase transition of the matrix PLC from nematic (N) to isotropic (I) state was followed by time-resolved measurements of the birefringence of the system. Formation of a sufficient amount of the cis isomer of BMAB with a single pulse of a laser lowered the N-I phase transition temperature of the mixture, inducing the N-I phase transition of PLCs isothermally in a time range of {approximately} 200 ms. This time range is comparable to that of low molecular weight liquid crystals, indicating that suppression in mobility of mesogens in PLCs does not affect significantly the thermodynamically controlled process.

  18. A model of liquid phase sintering by the homogenization

    NASA Astrophysics Data System (ADS)

    Pernin, Jean-Noël; Clementz, Philippe

    We study the first stage of liquid phase sintering, when the particles rearrangement due to capillary forces is over. We give the boundary value problem satisfied by the displacement field of points of the medium in the phase of elastic compression of solid particles, for given capillary forces acting as a density of external forces, by using the homogenization method and we characterize the mechanical behavior of this constrained medium from the material properties of each elementary components.

  19. Phase behavior and local structure of liquid crystalline polymers

    NASA Astrophysics Data System (ADS)

    Fynewever, Herb

    In this work we use a combination of theory and computer simulation to study the phase behavior of liquid crystalline polymers and the local structure of polymer melts. We review experimental and simulation evidence which shows that long and stiff molecules form orientationally ordered phases at packing fractions intermediate between the liquid and the solid. With the aid of a two-molecule simulation, we are able to apply Onsager's theory [Ann. N. Y. Acad. Sci. 51, 627 (1949)] for liquid crystal formation to flexible molecules without any additional approximations. Our results have a quantitative advantage over other theories in comparison with computer simulation data such as for the liquid-liquid crystal phase diagram. We also study the local structure of polymer melts using a two-molecule simulation to apply the density functional theories of Donley, Curro, and McCoy [J. Chem. Phys. 101 , 3205 (1994)1; and Yethiraj and Woodward [J. Chem. Phys 102 , 5499 (1995)]. The accuracy of these methods rivals that of integral equation theories in their predictions of local order. Further, the two-molecule simulation facilitates a more direct calculation of the equation of state via the monitoring of orientational correlations.

  20. On the phase-field modelling of a miscible liquid/liquid boundary.

    PubMed

    Xie, Ruilin; Vorobev, Anatoliy

    2016-02-15

    Mixing of miscible liquids is essential for numerous processes in industry and nature. Mixing, i.e. interpenetration of molecules through the liquid/liquid boundary, occurs via interfacial diffusion. Mixing can also involve externally or internally driven hydrodynamic flows, and can lead to deformation or disintegration of the liquid/liquid boundary. At the moment, the mixing dynamics remains poorly understood. The classical Fick's law, generally accepted for description of the diffusion process, does not explain the experimental observations, in particular, the recent experiments with dissolution of a liquid solute by a liquid solvent within a horizontal capillary (Stevar and Vorobev, 2012). We present the results of the numerical study aimed at development of an advanced model for the dissolution dynamics of liquid/liquid binary mixtures. The model is based on the phase-field (Cahn-Hilliard) approach that is used as a physics-based model for the thermo- and hydrodynamic evolution of binary mixtures. Within this approach, the diffusion flux is defined through the gradient of chemical potential, and, in particular, includes the effect of barodiffusion. The dynamic interfacial stresses at the miscible interface are also taken into account. The simulations showed that such an approach can accurately reproduce the shape of the solute/solvent boundary, and some aspects of the diffusion dynamics. Nevertheless, all experimentally-observed features of the diffusion motion of the solute/solvent boundary, were not reproduced. PMID:26609922

  1. Stretchable liquid-crystal blue-phase gels

    NASA Astrophysics Data System (ADS)

    Castles, F.; Morris, S. M.; Hung, J. M. C.; Qasim, M. M.; Wright, A. D.; Nosheen, S.; Choi, S. S.; Outram, B. I.; Elston, S. J.; Burgess, C.; Hill, L.; Wilkinson, T. D.; Coles, H. J.

    2014-08-01

    Liquid-crystalline polymers are materials of considerable scientific interest and technological value. An important subset of these materials exhibit rubber-like elasticity, combining the optical properties of liquid crystals with the mechanical properties of rubber. Moreover, they exhibit behaviour not seen in either type of material independently, and many of their properties depend crucially on the particular mesophase employed. Such stretchable liquid-crystalline polymers have previously been demonstrated in the nematic, chiral-nematic, and smectic mesophases. Here, we report the fabrication of a stretchable gel of blue phase I, which forms a self-assembled, three-dimensional photonic crystal that remains electro-optically switchable under a moderate applied voltage, and whose optical properties can be manipulated by an applied strain. We also find that, unlike its undistorted counterpart, a mechanically deformed blue phase exhibits a Pockels electro-optic effect, which sets out new theoretical challenges and possibilities for low-voltage electro-optic devices.

  2. Depositing spacing layers on magnetic film with liquid phase epitaxy

    NASA Technical Reports Server (NTRS)

    Moody, J. W.; Shaw, R. W.; Sanfort, R. M.

    1975-01-01

    Liquid phase epitaxy spacing layer is compatible with systems which are hard-bubble proofed by use of second magnetic garnet film as capping layer. Composite is superior in that: circuit fabrication time is reduced; adherence is superior; visibility is better; and, good match of thermal expansion coefficients is provided.

  3. pH Variance in Aerosols Undergoing Liquid-Liquid Phase Separation

    NASA Astrophysics Data System (ADS)

    Eddingsaas, N. C.; Dallemagne, M.; Huang, X.

    2014-12-01

    The water content of aerosols is largely governed by relative humidity (RH). As the relative humidity decreases, and thus the water content of aerosols, a number of processes occur including the shrinking of aerosols, the increase in concentration of components, and potentially the formation of liquid liquid phase separation (llps) due to the salting out of inorganic salts. The most ubiquitous salt in atmospheric aerosols is ammonium sulfate which results in many aerosols to be at least mildly acidic. However, during llps, the pH of the different phases is not necessarily the same. Many reactions that take place within atmospheric aerosols are acid catalyzed so a better understanding of the pH of the individual phases as well as the interface between the phases is important to understanding aerosol processing and aging. Through the use of pH sensitive dyes and confocal microscopy we have directly measured the pH of micron sized model aerosols during high RH where the aerosols are in a single phase, at intermediate while the aerosols are in llps, and low RH where the aerosols consist of one liquid phase and one solid phase. We will discuss the variation in RH during these different phase states in the presence and absence of excess sulfuric acid. We will also discuss how this variation in pH affects aging of aerosols.

  4. Cyclohexane triones, novel membrane-active antibacterial agents.

    PubMed Central

    Lloyd, W J; Broadhurst, A V; Hall, M J; Andrews, K J; Barber, W E; Wong-Kai-In, P

    1988-01-01

    The cyclohexane triones are a novel group of synthetic antibacterial agents that are active against gram-positive bacteria, Haemophilus influenzae, and Mycobacterium smegmatis. In general, these compounds behaved in a manner similar to that of hexachlorophene, inhibiting the transport of low-molecular-weight hydrophilic substances into bacteria. Unlike cationic detergents, such as chlorhexidine, they did not cause disruption of the bacterial cytoplasmic membrane over a short time period. The most potent antibacterial cyclohexane trione studied had a reduced ability to inhibit solute transport in comparison with certain less active analogs. Cyclohexane triones may express more than a single type of antibacterial effect. PMID:3137860

  5. Novel biodegradation pathways of cyclohexane by Rhodococcus sp. EC1.

    PubMed

    Yi, Taewoo; Lee, Eun-Hee; Ahn, Yun Gyong; Hwang, Geum-Sook; Cho, Kyung-Suk

    2011-07-15

    The metabolism of cyclohexanes by Rodococcus sp. EC1 was investigated using a sequential tracking method of degradation intermediate. Evidence for the formation of cyclohexanol, cyclohexaone, 2-cyclohexen-1-one, and phenol was presented. EC1 metabolized cyclohexane to phenol by aromatization of 2-cyclohexen-1-one, and furthermore gamma-butyrolactone as an intermediate of 2-cyclohexen-1-one was formed. Aromatization by EC1 was confirmed using tetrahydrofuran. Tetrahydrofuran was metabolized through aromatization reaction, involving furan and 2,3-dihydrofuran as key intermediates. EC1 can degrade cyclohexane and tetrahydrofuran in aromatization via desaturation. PMID:21571424

  6. Liquid-liquid phase separation in heavy-metal fluoride glass

    SciTech Connect

    Suscavaye, M.J.; El-Bayoumi, O.H.

    1985-09-01

    The microstructure of heavy-metal fluoride glass of composition 28.5CdF/sub 2/. 5.0LiF.28.5AlF/sub 3/.38PbF/sub 2/ was investigated using scanning electron microscopy and energy-dispersive X-ray techniques. Liquid-liquid phase separation was observed in crucible-cooled glass samples. The volume fraction of the dispersed glass phase increased substantially as a result of heating the sample at 309/sup 0/C for 1 h.

  7. Liquid-gas phase transition in nuclear matter including strangeness

    SciTech Connect

    Wang, P.; Leinweber, D.B.; Williams, A.G.; Thomas, A.W.

    2004-11-01

    We apply the chiral SU(3) quark mean field model to study the properties of strange hadronic matter at finite temperature. The liquid-gas phase transition is studied as a function of the strangeness fraction. The pressure of the system cannot remain constant during the phase transition, since there are two independent conserved charges (baryon and strangeness number). In a range of temperatures around 15 MeV (precise values depending on the model used) the equation of state exhibits multiple bifurcates. The difference in the strangeness fraction f{sub s} between the liquid and gas phases is small when they coexist. The critical temperature of strange matter turns out to be a nontrivial function of the strangeness fraction.

  8. Anomalous properties and the liquid-liquid phase transition in gallium.

    PubMed

    Li, Renzhong; Sun, Gang; Xu, Limei

    2016-08-01

    A group of materials including water and silicon exhibit many anomalous behaviors, e.g., density anomaly and diffusivity anomaly (increase upon compression). These materials are hypothesized to have a liquid-liquid phase transition (LLPT) and the critical fluctuation in the vicinity of the liquid-liquid critical point is considered as the origin of different anomalies. Liquid gallium was also reported to have a LLPT, yet whether it shows similar water-like anomalies is not yet studied. Using molecular dynamics simulations on a modified embedded-atom model, we study the thermodynamic, dynamic, and structural properties of liquid gallium as well as its LLPT. We find that, similar to water-like materials predicted to have the LLPT, gallium also shows different anomalous behaviors (e.g., density anomaly, diffusivity anomaly, and structural anomaly). We also find that its thermodynamic and structural response functions are continuous and show maxima in the supercritical region, the loci of which asymptotically approach to the other and merge to the Widom line. These phenomena are consistent with the supercritical phenomenon in a category of materials with a liquid-liquid critical point, which could be common features in most materials with a LLPT. PMID:27497564

  9. Anomalous properties and the liquid-liquid phase transition in gallium

    NASA Astrophysics Data System (ADS)

    Li, Renzhong; Sun, Gang; Xu, Limei

    2016-08-01

    A group of materials including water and silicon exhibit many anomalous behaviors, e.g., density anomaly and diffusivity anomaly (increase upon compression). These materials are hypothesized to have a liquid-liquid phase transition (LLPT) and the critical fluctuation in the vicinity of the liquid-liquid critical point is considered as the origin of different anomalies. Liquid gallium was also reported to have a LLPT, yet whether it shows similar water-like anomalies is not yet studied. Using molecular dynamics simulations on a modified embedded-atom model, we study the thermodynamic, dynamic, and structural properties of liquid gallium as well as its LLPT. We find that, similar to water-like materials predicted to have the LLPT, gallium also shows different anomalous behaviors (e.g., density anomaly, diffusivity anomaly, and structural anomaly). We also find that its thermodynamic and structural response functions are continuous and show maxima in the supercritical region, the loci of which asymptotically approach to the other and merge to the Widom line. These phenomena are consistent with the supercritical phenomenon in a category of materials with a liquid-liquid critical point, which could be common features in most materials with a LLPT.

  10. Liquid-liquid phase separation of freely falling undercooled ternary Fe-Cu-Sn alloy

    PubMed Central

    Wang, W .L.; Wu, Y. H.; Li, L. H.; Zhai, W.; Zhang, X. M.; Wei, B.

    2015-01-01

    The active modulation and control of the liquid phase separation for high-temperature metallic systems are still challenging the development of advanced immiscible alloys. Here we present an attempt to manipulate the dynamic process of liquid-liquid phase separation for ternary Fe47.5Cu47.5Sn5 alloy. It was firstly dispersed into numerous droplets with 66 ~ 810 μm diameters and then highly undercooled and rapidly solidified under the containerless microgravity condition inside drop tube. 3-D phase field simulation was performed to explore the kinetic evolution of liquid phase separation. Through regulating the combined effects of undercooling level, phase separation time and Marangoni migration, three types of separation patterns were yielded: monotectic cell, core shell and dispersive structures. The two-layer core-shell morphology proved to be the most stable separation configuration owing to its lowest chemical potential. Whereas the monotectic cell and dispersive microstructures were both thermodynamically metastable transition states because of their highly active energy. The Sn solute partition profiles of Fe-rich core and Cu-rich shell in core-shell structures varied only slightly with cooling rate. PMID:26552711

  11. Liquid-liquid phase separation of freely falling undercooled ternary Fe-Cu-Sn alloy.

    PubMed

    Wang, W L; Wu, Y H; Li, L H; Zhai, W; Zhang, X M; Wei, B

    2015-01-01

    The active modulation and control of the liquid phase separation for high-temperature metallic systems are still challenging the development of advanced immiscible alloys. Here we present an attempt to manipulate the dynamic process of liquid-liquid phase separation for ternary Fe47.5Cu47.5Sn5 alloy. It was firstly dispersed into numerous droplets with 66 ~ 810 μm diameters and then highly undercooled and rapidly solidified under the containerless microgravity condition inside drop tube. 3-D phase field simulation was performed to explore the kinetic evolution of liquid phase separation. Through regulating the combined effects of undercooling level, phase separation time and Marangoni migration, three types of separation patterns were yielded: monotectic cell, core shell and dispersive structures. The two-layer core-shell morphology proved to be the most stable separation configuration owing to its lowest chemical potential. Whereas the monotectic cell and dispersive microstructures were both thermodynamically metastable transition states because of their highly active energy. The Sn solute partition profiles of Fe-rich core and Cu-rich shell in core-shell structures varied only slightly with cooling rate. PMID:26552711

  12. Liquid-liquid phase separation of freely falling undercooled ternary Fe-Cu-Sn alloy

    NASA Astrophysics Data System (ADS)

    Wang, W. L.; Wu, Y. H.; Li, L. H.; Zhai, W.; Zhang, X. M.; Wei, B.

    2015-11-01

    The active modulation and control of the liquid phase separation for high-temperature metallic systems are still challenging the development of advanced immiscible alloys. Here we present an attempt to manipulate the dynamic process of liquid-liquid phase separation for ternary Fe47.5Cu47.5Sn5 alloy. It was firstly dispersed into numerous droplets with 66 ~ 810 μm diameters and then highly undercooled and rapidly solidified under the containerless microgravity condition inside drop tube. 3-D phase field simulation was performed to explore the kinetic evolution of liquid phase separation. Through regulating the combined effects of undercooling level, phase separation time and Marangoni migration, three types of separation patterns were yielded: monotectic cell, core shell and dispersive structures. The two-layer core-shell morphology proved to be the most stable separation configuration owing to its lowest chemical potential. Whereas the monotectic cell and dispersive microstructures were both thermodynamically metastable transition states because of their highly active energy. The Sn solute partition profiles of Fe-rich core and Cu-rich shell in core-shell structures varied only slightly with cooling rate.

  13. Electrically tunable holographic polymer templated blue phase liquid crystal grating

    NASA Astrophysics Data System (ADS)

    He, Zheng-Hong; Chen, Chao-Ping; Zhu, Ji-Liang; Yuan, Ya-Chao; Li, Yan; Hu, Wei; Li, Xiao; Li, Hong-Jing; Lu, Jian-Gang; Su, Yi-Kai

    2015-06-01

    In this paper, we demonstrate an alternative approach to fabricating an electrically tunable holographic polymer templated blue phase liquid crystal grating. This grating is obtained by preforming a polymer template comprised of periodic fringes, and then refilling it with a blue phase liquid crystal. Compared with conventional holographic polymer dispersed liquid crystal gratings, our grating can remarkably reduce its switching voltage from 200 V to 43 V while maintaining a sub-millisecond response time. The holographic polymer templated blue phase liquid crystal (HPTBPLC) grating is free from electrode patterning, thus leading to a lower cost and more flexible applications. Project supported by the National Basic Research Program of China (Grant No. 2013CB328804), the National Natural Science Foundation of China (Grant No. 61307028), the Funds from the Science and Technology Commission of Shanghai Municipality (Grant Nos. 11JC1405300, 13ZR1420000, and 14ZR1422300), and the Fundamental Research Funds for the Central Universities, China (Grant No. XDJK 2011C047).

  14. 4He glass phase: A model for liquid elements

    NASA Astrophysics Data System (ADS)

    Tournier, Robert F.; Bossy, Jacques

    2016-08-01

    The specific heat of liquid helium confined under pressure in nanoporous material and the formation, in these conditions, of a glass phase accompanied by latent heat are known. These properties are in good agreement with a recent model predicting, in liquid elements, the formation of ultrastable glass having universal thermodynamic properties. The third law of thermodynamics involves that the specific heat decreases at low temperatures and consequently the effective transition temperature of the glass increases up to the temperature where the frozen enthalpy becomes equal to the predicted value. The glass residual entropy is about 23.6% of the melting entropy.

  15. Gravitational contributions to microstructural coarsening in liquid phase sintering

    NASA Technical Reports Server (NTRS)

    Kipphut, C. M.; Kishi, T.; Bose, A.; German, R. M.

    1987-01-01

    Preliminary experiments for determining the role of gravity in liquid phase sintering have been carried out. Tungsten heavy alloys were selected for this investigation because of the large density difference between solid and liquid, extensive interest in the alloys and considerable data on these alloys. By identifying and isolating the role that gravity plays in shape distortion and microstructural coarsening, further insight into the mechanisms of coarsening kinetics may be realized. Improvements in mechanical properties, shape complexity, and dimensional stability may be realized in the future from low gravity sintering.

  16. String theory, quantum phase transitions, and the emergent Fermi liquid.

    PubMed

    Cubrović, Mihailo; Zaanen, Jan; Schalm, Koenraad

    2009-07-24

    A central problem in quantum condensed matter physics is the critical theory governing the zero-temperature quantum phase transition between strongly renormalized Fermi liquids as found in heavy fermion intermetallics and possibly in high-critical temperature superconductors. We found that the mathematics of string theory is capable of describing such fermionic quantum critical states. Using the anti-de Sitter/conformal field theory correspondence to relate fermionic quantum critical fields to a gravitational problem, we computed the spectral functions of fermions in the field theory. By increasing the fermion density away from the relativistic quantum critical point, a state emerges with all the features of the Fermi liquid. PMID:19556462

  17. Elastic response and phase behavior in binary liquid crystal mixtures.

    PubMed

    Sidky, Hythem; Whitmer, Jonathan K

    2016-05-11

    Utilizing density-of-states simulations, we perform a full mapping of the phase behavior and elastic responses of binary liquid crystalline mixtures represented by the multicomponent Lebwohl-Lasher model. Our techniques are able to characterize the complete phase diagram, including nematic-nematic phase separation predicted by mean-field theories, but previously not observed in simulations. Mapping this phase diagram permits detailed study of elastic properties across the miscible nematic region. Importantly, we observe for the first time local phase separation and disordering driven by the application of small linear perturbations near the transition temperature and more significantly through nonlinear stresses. These findings are of key importance in systems of blended nematics which contain particulate inclusions, or are otherwise confined. PMID:27093188

  18. Induced smectic phases of stoichiometric liquid crystal mixtures.

    PubMed

    Sugisawa, Shin-Ya; Tabe, Yuka

    2016-03-16

    We revealed the detailed structures of induced smectic liquid crystal (LC) phases composed of a binary mixture of charge-transfer (CT) LC substances. Although neither of the constituents had highly ordered smectic phases, the mixture exhibited smectic-E (SmE) or smectic-B (SmB) phases when mixed at ratios of 1 : 1 and 2 : 3, respectively. The results of polarized optical microscopy, differential scanning calorimetry, X-ray diffraction, and infrared spectroscopy indicated that the induced smectic phases were stabilized by an exquisite balance between the CT interactions, dipolar interactions, and excluded volume effects. We proposed a possible model for the molecular arrangements in the SmE and SmB phases, which consistently explained the experimental results including the stoichiometric ratios. PMID:26898174

  19. Thermal Vibrational Convection in a Two-phase Stratified Liquid

    NASA Technical Reports Server (NTRS)

    Chang, Qingming; Alexander, J. Iwan D.

    2007-01-01

    The response of a two-phase stratified liquid system subject to a vibration parallel to an imposed temperature gradient is analyzed using a hybrid thermal lattice Boltzmann method (HTLB). The vibrations considered correspond to sinusoidal translations of a rigid cavity at a fixed frequency. The layers are thermally and mechanically coupled. Interaction between gravity-induced and vibration-induced thermal convection is studied. The ability of applied vibration to enhance the flow, heat transfer and interface distortion is investigated. For the range of conditions investigated, the results reveal that the effect of vibrational Rayleigh number and vibrational frequency on a two-phase stratified fluid system is much different than that for a single-phase fluid system. Comparisons of the response of a two-phase stratified fluid system with a single-phase fluid system are discussed.

  20. Superfluid helium 2 liquid-vapor phase separation: Technology assessment

    NASA Technical Reports Server (NTRS)

    Lee, J. M.

    1984-01-01

    A literature survey of helium 2 liquid vapor phase separation is presented. Currently, two types of He 2 phase separators are being investigated: porous, sintered metal plugs and the active phase separator. The permeability K(P) shows consistency in porous plug geometric characterization. Both the heat and mass fluxes increase with K(P). Downstream pressure regulation to adjust for varying heat loads and both temperatures is possible. For large dynamic heat loads, the active phase separator shows a maximum heat rejection rate of up to 2 W and bath temperature stability of 0.1 mK. Porous plug phase separation performance should be investigated for application to SIRTF and, in particular, that plugs of from 10 to the minus ninth square centimeters to 10 to the minus eighth square centimeters in conjunction with downstream pressure regulation be studied.

  1. Polycontinuous Lyotropic Liquid Crystalline Network Phases from Gemini Dicarboxylate Surfactants

    NASA Astrophysics Data System (ADS)

    Mahanthappa, Mahesh; Sorenson, Gregory; Schmitt, Adam

    2015-03-01

    Arising from the water concentration-dependent self-assembly of amphiphilic molecules, lyotropic liquid crystals (LLCs) form a wide variety of structurally periodic nanoscale morphologies including discontinuous micellar phases (I), hexagonally-packed cylinders (C), and lamellar (L) phases. In intermediate amphiphile concentration windows between the L and C phases, one typically observes three bicontinuous cubic network phases: gyroid (G), diamond (D), and primitive (P). Recent theoretical work has suggested the possible stability of a variety of non-cubic network phase LLCs, yet none of these phases have been previously observed. In this presentation, we describe the experimental discovery of the first triply periodic network phase LLC with 3D-hexagonal symmetry (space group #193) in binary mixtures of water with a simple gemini dicarboxylate surfactant based on dodecanoic acid. Using a combination of SAXS and rheological methods, we structurally characterize this new phase and show that it is comprised of three interpenetrating lipidic networks of 3-fold connectors in a matrix of water. This finding highlights the unusual aqueous phase behavior of gemini surfactants and suggests new methods for discovering and stabilizing new network phase LLCs beyond the gyroid.

  2. Glass and liquid phase diagram of a polyamorphic monatomic system

    NASA Astrophysics Data System (ADS)

    Reisman, Shaina; Giovambattista, Nicolas

    2013-02-01

    We perform out-of-equilibrium molecular dynamics (MD) simulations of a monatomic system with Fermi-Jagla (FJ) pair potential interactions. This model system exhibits polyamorphism both in the liquid and glass state. The two liquids, low-density (LDL) and high-density liquid (HDL), are accessible in equilibrium MD simulations and can form two glasses, low-density (LDA) and high-density amorphous (HDA) solid, upon isobaric cooling. The FJ model exhibits many of the anomalous properties observed in water and other polyamorphic liquids and thus, it is an excellent model system to explore qualitatively the thermodynamic properties of such substances. The liquid phase behavior of the FJ model system has been previously characterized. In this work, we focus on the glass behavior of the FJ system. Specifically, we perform systematic isothermal compression and decompression simulations of LDA and HDA at different temperatures and determine "phase diagrams" for the glass state; these phase diagrams varying with the compression/decompression rate used. We obtain the LDA-to-HDA and HDA-to-LDA transition pressure loci, PLDA-HDA(T) and PHDA-LDA(T), respectively. In addition, the compression-induced amorphization line, at which the low-pressure crystal (LPC) transforms to HDA, PLPC-HDA(T), is determined. As originally proposed by Poole et al. [Phys. Rev. E 48, 4605 (1993)], 10.1103/PhysRevE.48.4605 simulations suggest that the PLDA-HDA(T) and PHDA-LDA(T) loci are extensions of the LDL-to-HDL and HDL-to-LDL spinodal lines into the glass domain. Interestingly, our simulations indicate that the PLPC-HDA(T) locus is an extension, into the glass domain, of the LPC metastability limit relative to the liquid. We discuss the effects of compression/decompression rates on the behavior of the PLDA-HDA(T), PHDA-LDA(T), PLPC-HDA(T) loci. The competition between glass polyamorphism and crystallization is also addressed. At our "fast rate," crystallization can be partially suppressed and the

  3. Glass and liquid phase diagram of a polyamorphic monatomic system.

    PubMed

    Reisman, Shaina; Giovambattista, Nicolas

    2013-02-14

    We perform out-of-equilibrium molecular dynamics (MD) simulations of a monatomic system with Fermi-Jagla (FJ) pair potential interactions. This model system exhibits polyamorphism both in the liquid and glass state. The two liquids, low-density (LDL) and high-density liquid (HDL), are accessible in equilibrium MD simulations and can form two glasses, low-density (LDA) and high-density amorphous (HDA) solid, upon isobaric cooling. The FJ model exhibits many of the anomalous properties observed in water and other polyamorphic liquids and thus, it is an excellent model system to explore qualitatively the thermodynamic properties of such substances. The liquid phase behavior of the FJ model system has been previously characterized. In this work, we focus on the glass behavior of the FJ system. Specifically, we perform systematic isothermal compression and decompression simulations of LDA and HDA at different temperatures and determine "phase diagrams" for the glass state; these phase diagrams varying with the compression/decompression rate used. We obtain the LDA-to-HDA and HDA-to-LDA transition pressure loci, P(LDA-HDA)(T) and P(HDA-LDA)(T), respectively. In addition, the compression-induced amorphization line, at which the low-pressure crystal (LPC) transforms to HDA, P(LPC-HDA)(T), is determined. As originally proposed by Poole et al. [Phys. Rev. E 48, 4605 (1993)] simulations suggest that the P(LDA-HDA)(T) and P(HDA-LDA)(T) loci are extensions of the LDL-to-HDL and HDL-to-LDL spinodal lines into the glass domain. Interestingly, our simulations indicate that the P(LPC-HDA)(T) locus is an extension, into the glass domain, of the LPC metastability limit relative to the liquid. We discuss the effects of compression/decompression rates on the behavior of the P(LDA-HDA)(T), P(HDA-LDA)(T), P(LPC-HDA)(T) loci. The competition between glass polyamorphism and crystallization is also addressed. At our "fast rate," crystallization can be partially suppressed and the glass

  4. Evidence of a liquid-liquid phase transition in hot dense hydrogen.

    PubMed

    Dzyabura, Vasily; Zaghoo, Mohamed; Silvera, Isaac F

    2013-05-14

    We use pulsed-laser heating of hydrogen at static pressures in the megabar pressure region to search for the plasma phase transition to liquid atomic metallic hydrogen. We heat our samples substantially above the melting line and observe a plateau in a temperature vs. laser power curve that otherwise increases with power. This anomaly in the heating curve appears correlated with theoretical predictions for the plasma phase transition. PMID:23630287

  5. Plasmas in Multiphase Media: Bubble Enhanced Discharges in Liquids and Plasma/Liquid Phase Boundaries

    SciTech Connect

    Kushner, Mark Jay

    2014-07-10

    In this research project, the interaction of atmospheric pressure plasmas with multi-phase media was computationally investigated. Multi-phase media includes liquids, particles, complex materials and porous surfaces. Although this investigation addressed fundamental plasma transport and chemical processes, the outcomes directly and beneficially affected applications including biotechnology, medicine and environmental remediation (e.g., water purification). During this project, we made advances in our understanding of the interaction of atmospheric pressure plasmas in the form of dielectric barrier discharges and plasma jets with organic materials and liquids. We also made advances in our ability to use computer modeling to represent these complex processes. We determined the method that atmospheric pressure plasmas flow along solid and liquid surfaces, and through endoscopic like tubes, deliver optical and high energy ion activation energy to organic and liquid surfaces, and produce reactivity in thin liquid layers, as might cover a wound. We determined the mechanisms whereby plasmas can deliver activation energy to the inside of liquids by sustaining plasmas in bubbles. These findings are important to the advancement of new technology areas such as plasma medicine

  6. Phase-Changing Ionic Liquids: CO2 Capture with Ionic Liquids Involving Phase Change

    SciTech Connect

    2010-07-01

    IMPACCT Project: Notre Dame is developing a new CO2 capture process that uses special ionic liquids (ILs) to remove CO2 from the gas exhaust of coal-fired power plants. ILs are salts that are normally liquid at room temperature, but Notre Dame has discovered a new class of ILs that are solid at room temperature and change to liquid when they bind to CO2. Upon heating, the CO2 is released for storage, and the ILs re-solidify and donate some of the heat generated in the process to facilitate further CO2 release. These new ILs can reduce the energy required to capture CO2 from the exhaust stream of a coal-fired power plant when compared to state-ofthe- art technology.

  7. Surface order at surfactant-laden interfaces between isotropic liquid crystals and liquid phases with different polarity

    NASA Astrophysics Data System (ADS)

    Feng, Xunda; Bahr, Christian

    2011-03-01

    We present an ellipsometry study of the interface between thermotropic liquid crystals and liquid phases consisting of various binary mixtures of water and glycerol. The liquid-crystal samples contain a small constant amount of a surfactant which induces a homeotropic anchoring at the interface. We determine the smectic or nematic order at the interface in the temperature range above the liquid-crystal-isotropic transition while the water to glycerol ratio is varied, corresponding to a systematic modification of the polarity of the liquid phase. The surface-induced order becomes less pronounced with increasing glycerol concentration in the liquid phase. The observed behavior is compared with previous studies in which the surfactant concentration in the liquid-crystal bulk phase was varied. The results indicate that in both cases the magnitude of the surfactant coverage at the interface is the key quantity which determines the liquid-crystal surface order at the interface.

  8. Structure, Hydrodynamics, and Phase Transition of Freely Suspended Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Clark, Noel A.

    2000-01-01

    Smectic liquid crystals are phases of rod shaped molecules organized into one dimensionally (1D) periodic arrays of layers, each layer being between one and two molecular lengths thick. In the least ordered smectic phases, the smectics A and C, each layer is a two dimensional (2D) liquid. Additionally there are a variety of more ordered smectic phases having hexatic short range translational order or 2D crystalline quasi long range translational order within the layers. The inherent fluid-layer structure and low vapor pressure of smectic liquid crystals enable the long term stabilization of freely suspended, single component, layered fluid films as thin as 30A, a single molecular layer. The layering forces the films to be an integral number of smectic layers thick, quantizing their thickness in layer units and forcing a film of a particular number of layers to be physically homogeneous with respect to its layer structure over its entire area. Optical reflectivity enables the precise determination of the number of layers. These ultrathin freely suspended liquid crystal films are structures of fundamental interest in condensed matter and fluid physics. They are the thinnest known stable condensed phase fluid structures and have the largest surface-to-volume ratio of any stable fluid preparation, making them ideal for the study of the effects of reduced dimensionality on phase behavior and on fluctuation and interface phenomena. Their low vapor pressure and quantized thickness enable the effective use of microgravity to extend the study of basic capillary phenomena to ultrathin fluid films. Freely suspended films have been a wellspring of new liquid crystal physics. They have been used to provide unique experimental conditions for the study of condensed phase transitions in two dimensions. They are the only system in which the hexatic has been unambiguously identified as a phase of matter, and the only physical system in which fluctuations of a 2D XY system and

  9. Common path point diffraction interferometer using liquid crystal phase shifting

    NASA Technical Reports Server (NTRS)

    Mercer, Carolyn R. (Inventor)

    1997-01-01

    A common path point diffraction interferometer uses dyed, parallel nematic liquid crystals which surround an optically transparent microsphere. Coherent, collimated and polarized light is focused on the microsphere at a diameter larger than that of the microsphere. A portion of the focused light passes through the microsphere to form a spherical wavefront reference beam and the rest of the light is attenuated by the dyed liquid crystals to form an object beam. The two beams form an interferogram which is imaged by a lens onto an electronic array sensor and into a computer which determines the wavefront of the object beam. The computer phase shifts the interferogram by stepping up an AC voltage applied across the liquid crystals without affecting the reference beam.

  10. Dynamical and structural heterogeneities close to liquid-liquid phase transitions: The case of gallium

    NASA Astrophysics Data System (ADS)

    Antonelli, Alex; Cajahuaringa, Samuel; de Koning, Maurice

    2013-03-01

    Liquid-liquid phase transitions (LLPT) have been proposed in order to explain the thermodynamic anomalies exhibited by some liquids. Recently, it was found, through molecular dynamics simulations, that liquid elemental gallium, described by a modified embedded-atom model, exhibits a LLPT between a high-density liquid (HDL) and a low-density liquid (LDL), about 60 K below the melting temperature. In this work, we studied the dynamics of supercooled liquid gallium close to the LLPT. Our results show a large increase in the plateau of the self-intermediate scattering function (β-relaxation process) and in the non-Gaussian parameter, indicating a pronounced dynamical heterogeneity upon the onset of the LLPT. The dynamical heterogeneity of the LDL is closely correlated to its structural heterogeneity, since the fast diffusing atoms belong to high-density domains of predominantly 9-fold coordinated atoms, whereas the slow diffusing ones are mostly in low-density domains of 8-fold coordinated atoms. The energetics suggests that the reason for the sluggish dynamics of LDL is due to its larger cohesive energy as compared to that of the HDL. Work supported by FAPESP, CNPq, CAPES, and FAEPEX/UNICAMP

  11. Liquid-phase sintering of iron aluminide-bonded ceramics

    SciTech Connect

    Schneibel, J.H.; Carmichael, C.A.

    1995-12-31

    Iron aluminide intermetallics exhibit excellent oxidation and sulfidation resistance and are therefore considered as the matrix in metal matrix composites, or the binder in hard metals or cermets. In this paper the authors discuss the processing and properties of liquid-phase sintered iron aluminide-bonded ceramics. It is found that ceramics such as TiB{sub 2}, ZrB{sub 2}, TiC, and WC may all be liquid phase-sintered. nearly complete densification is achieved for ceramic volume fractions ranging up to 60%. Depending on the composition, room temperature three point-bend strengths and fracture toughnesses reaching 1,500 MPa and 30 MPa m{sup 1/2}, respectively, have been found. Since the processing was carried out in a very simple manner, optimized processing is likely to result in further improvements.

  12. Liquid phase oxidation chemistry in continuous-flow microreactors.

    PubMed

    Gemoets, Hannes P L; Su, Yuanhai; Shang, Minjing; Hessel, Volker; Luque, Rafael; Noël, Timothy

    2016-01-01

    Continuous-flow liquid phase oxidation chemistry in microreactors receives a lot of attention as the reactor provides enhanced heat and mass transfer characteristics, safe use of hazardous oxidants, high interfacial areas, and scale-up potential. In this review, an up-to-date overview of both technological and chemical aspects of liquid phase oxidation chemistry in continuous-flow microreactors is given. A description of mass and heat transfer phenomena is provided and fundamental principles are deduced which can be used to make a judicious choice for a suitable reactor. In addition, the safety aspects of continuous-flow technology are discussed. Next, oxidation chemistry in flow is discussed, including the use of oxygen, hydrogen peroxide, ozone and other oxidants in flow. Finally, the scale-up potential for continuous-flow reactors is described. PMID:26203551

  13. Densification and shape distortion in liquid-phase sintering

    SciTech Connect

    Liu, J.; German, R.M.

    1999-12-01

    Densification and dimensional control are important aspects of liquid-phase sintering. The capillary force and the solid bonding affect both densification and shape preservation. Capillarity, which is orientated isotropically, causes uniform shrinkage and holds grains together to preserve the component shape in the early stage of sintering. On the other hand, solid bonding resists viscous flow and inhibits densification and shape distortion. The capillary force decreases with densification and approaches zero as pores are eliminated. Thus, shape retention eventually requires solid-grain bonding. The solid-grain bonding provides compact rigidity, which is represented by compact strength. Shape distortion occurs when the compact loses its strength. For every situation, there is a critical compact strength above which no shape distortion occurs. Distortion in liquid-phase sintering indicates that the compact strength passed below a critical level.

  14. Transport Phenomena in Liquid Phase Diffusion Growth of Silicon Germanium

    NASA Astrophysics Data System (ADS)

    Armour, Neil Alexander

    Silicon Germanium, SiGe, is an important emerging semiconductor material. In order to optimize growth techniques for SiGe production, such as Liquid Phase Diffusion, LPD, or Melt Replenishment Czochralski, a good understanding of the transport phenomena in the melt is required. In the context of the Liquid Phase Diffusion growth technique, the transport phenomena of silicon in a silicon-germanium melt has been explored. Experiments isolating the dissolution and transport of silicon into a germanium melt have been conducted under a variety of flow conditions. Preliminary modeling of these experiments has also been conducted and agreement with experiments has been shown. In addition, full LPD experiments have also been conducted under varying flow conditions. Altered flow conditions were achieved through the application of a variety of magnetic fields. Through the experimental and modeling work better understanding of the transport mechanisms at work in a silicon-germanium melt has been achieved.

  15. Powder metallurgy: Solid and liquid phase sintering of copper

    NASA Technical Reports Server (NTRS)

    Sheldon, Rex; Weiser, Martin W.

    1993-01-01

    Basic powder metallurgy (P/M) principles and techniques are presented in this laboratory experiment. A copper based system is used since it is relatively easy to work with and is commercially important. In addition to standard solid state sintering, small quantities of low melting metals such as tin, zinc, lead, and aluminum can be added to demonstrate liquid phase sintering and alloy formation. The Taguchi Method of experimental design was used to study the effect of particle size, pressing force, sintering temperature, and sintering time. These parameters can be easily changed to incorporate liquid phase sintering effects and some guidelines for such substitutions are presented. The experiment is typically carried out over a period of three weeks.

  16. Study on the mechanism of liquid phase sintering (M-12)

    NASA Technical Reports Server (NTRS)

    Kohara, S.

    1993-01-01

    The objectives were to (1) obtain the data representing the growth rate of solid particles in a liquid matrix without the effect of gravity; and (2) reveal the growth behavior of solid particles during liquid phase sintering using the data obtained. Nickel and tungsten are used as the constituent materials in liquid phase sintering. The properties of the constituent metals are given. When a compact of the mixture of tungsten and nickel powders is heated and kept at 1550 C, nickel melts down but tungsten stays solid. As the density of tungsten is much greater than that of nickel, the sedimentation of tungsten particles occurs in the experiment on Earth. The difference between the experiments on Earth and in space is illustrated. The tungsten particles sink to the bottom and are brought into contact with each other. The resulting pressure at the contact point causes the accelerated dissolution of tungsten. Consequently, flat surfaces are formed at the contact sites. As a result of dissolution and reprecipitation of tungsten, the shape of particles changes to a polygon. This phenomenon is called 'flattening.' An example of flattening of tungsten particles is shown. Thus, the data obtained by the experiment on Earth may not represent the exact growth behavior of the solid particles in a liquid matrix. If the experiments were done in a microgravity environment, the data corresponding to the theoretical growth behavior of solid particles could be achieved.

  17. Phase-locked measurements of gas-liquid horizontal flows

    NASA Astrophysics Data System (ADS)

    Zadrazil, Ivan; Matar, Omar; Markides, Christos

    2014-11-01

    A flow of gas and liquid in a horizontal pipe can be described in terms of various flow regimes, e.g. wavy stratified, annular or slug flow. These flow regimes appear at characteristic gas and liquid Reynolds numbers and feature unique wave phenomena. Wavy stratified flow is populated by low amplitude waves whereas annular flow contains high amplitude and long lived waves, so called disturbance waves, that play a key role in a liquid entrainment into the gas phase (droplets). In a slug flow regime, liquid-continuous regions travel at high speeds through a pipe separated by regions of stratified flow. We use a refractive index matched dynamic shadowgraphy technique using a high-speed camera mounted on a moving robotic linear rail to track the formation and development of features characteristic for the aforementioned flow regimes. We show that the wave dynamics become progressively more complex with increasing liquid and gas Reynolds numbers. Based on the shadowgraphy measurements we present, over a range of conditions: (i) phenomenological observations of the formation, and (ii) statistical data on the downstream velocity distribution of different classes of waves. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

  18. Confinement-driven phase separation of quantum liquid mixtures.

    PubMed

    Prisk, T R; Pantalei, C; Kaiser, H; Sokol, P E

    2012-08-17

    We report small-angle neutron scattering studies of liquid helium mixtures confined in Mobil Crystalline Material-41 (MCM-41), a porous silica glass with narrow cylindrical nanopores (d=3.4 nm). MCM-41 is an ideal model adsorbent for fundamental studies of gas sorption in porous media because its monodisperse pores are arranged in a 2D triangular lattice. The small-angle scattering consists of a series of diffraction peaks whose intensities are determined by how the imbibed liquid fills the pores. Pure (4)He adsorbed in the pores show classic, layer-by-layer film growth as a function of pore filling, leaving the long range symmetry of the system intact. In contrast, the adsorption of (3)He-(4)He mixtures produces a structure incommensurate with the pore lattice. Neither capillary condensation nor preferential adsorption of one helium isotope to the pore walls can provide the symmetry-breaking mechanism. The scattering is consistent with the formation of randomly distributed liquid-liquid microdomains ∼2.3 nm in size, providing evidence that confinement in a nanometer scale capillary can drive local phase separation in quantum liquid mixtures. PMID:23006380

  19. Vortex motion phase separator for zero gravity liquid transfer

    NASA Technical Reports Server (NTRS)

    Howard, Frank S. (Inventor); Fraser, Wilson M., Jr. (Inventor)

    1989-01-01

    A vortex motion phase separator is disclosed for transferring a liquid in a zero gravity environment while at the same time separating the liquid from vapors found within either the sender or the receiving tanks. The separator comprises a rigid sender tank having a circular cross-section and rigid receiver tank having a circular cross-section. A plurality of ducts connects the sender tank and the receiver tank. Disposed within the ducts connecting the receiver tank and the sender tank is a pump and a plurality of valves. The pump is powered by an electric motor and is adapted to draw either the liquid or a mixture of the liquid and the vapor from the sender tank. Initially, the mixture drawn from the sender tank is directed through a portion of the ductwork and back into the sender tank at a tangent to the inside surface of the sender tank, thereby creating a swirling vortex of the mixture within the sender tank. As the pumping action increases, the speed of the swirling action within the sender tank increases creating an increase in the centrifugal force operating on the mixture. The effect of the centrifugal force is to cause the heavier liquid to migrate to the inside surface of the sender tank and to separate from the vapor. When this separation reaches a predetermined degree, control means is activated to direct the liquid conveyed by the pump directly into the receiver tank. At the same time, the vapor within the receiver tank is directed from the receiver tank back into the sender tank. This flow continues until substantially all of the liquid is transferred from the sender tank to the receiver tank.

  20. Dynamic evolution of liquid-liquid phase separation during continuous cooling

    SciTech Connect

    Imhoff, S. D.; Gibbs, P. J.; Katz, M. R.; Ott, T. J.; Patterson, B. M.; Lee, W. -K.; Fezzaa, K.; Cooley, J. C.; Clarke, A. J.

    2015-03-01

    Solidification from a multiphase fluid involves many unknown quantities due to the difficulty of predicting the impact of fluid flow on chemical partitioning. Real-time x-ray radiography has been used to observe liquideliquid phase separation in Al90In10 prior to solidification. Quantitative image analysis has been used to measure the motion and population characteristics of the dispersed indium-rich liquid phase during cooling. Here we determine that the droplet growth characteristics resemble well known steady-state coarsening laws with likely enhancement by concurrent growth due to supersaturation. Simplistic views of droplet motion are found to be insufficient until late in the reaction due to a hydrodynamic instability caused by the large density difference between the dispersed and matrix liquid phases.

  1. Oxidation Protection of Uranium Nitride Fuel using Liquid Phase Sintering

    SciTech Connect

    Dr. Paul A. Lessing

    2012-03-01

    Two methods are proposed to increase the oxidation resistance of uranium nitride (UN) nuclear fuel. These paths are: (1) Addition of USi{sub x} (e.g. U3Si2) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with various compounds (followed by densification via Spark Plasma Sintering or Liquid Phase Sintering) that will greatly increase oxidation resistance. The advantages (high thermal conductivity, very high melting point, and high density) of nitride fuel have long been recognized. The sodium cooled BR-10 reactor in Russia operated for 18 years on uranium nitride fuel (UN was used as the driver fuel for two core loads). However, the potential advantages (large power up-grade, increased cycle lengths, possible high burn-ups) as a Light Water Reactor (LWR) fuel are offset by uranium nitride's extremely low oxidation resistance (UN powders oxidize in air and UN pellets decompose in hot water). Innovative research is proposed to solve this problem and thereby provide an accident tolerant LWR fuel that would resist water leaks and high temperature steam oxidation/spalling during an accident. It is proposed that we investigate two methods to increase the oxidation resistance of UN: (1) Addition of USi{sub x} (e.g. U{sub 3}Si{sub 2}) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with compounds (followed by densification via Spark Plasma Sintering) that will greatly increase oxidation resistance.

  2. Liquid phase coating to produce controlled-release alginate microspheres.

    PubMed

    Chan, Lai Wah; Liu, Xiaohua; Heng, Paul Wan Sia

    2005-12-01

    This study explored a liquid phase coating technique to produce polymethyl methacrylate (PMMA)-coated alginate microspheres. Alginate microspheres with a mean diameter of 85.6 microm were prepared using an emulsification method. The alginate microspheres, as cores, were then coated with different types of PMMA by a liquid phase coating technique. The release characteristics of these coated microspheres in simulated gastric (SGF) and intestinal (SIF) fluids and the influence of drug load on encapsulation efficiency were studied. The release of paracetamol, as a model hydrophilic drug, from the coated microspheres in SGF and SIF was greatly retarded. Release rates of Eudragit RS100-coated microspheres in SGF and SIF were similar as the rate-controlling polymer coat was insoluble in both media. Drug release from Eudragit S100-coated microspheres was more sustained in SGF than in SIF, due to the greater solubility of the coating polymer in media with pH greater than 7.0. The drug release rate was affected by the core:coat ratio. Drug release from the coated microspheres was best described by the Higuchi's square root model. The liquid phase coating technique developed offers an efficient method of coating small microspheres with markedly reduced drug loss and possible controlled drug release. PMID:16423760

  3. ENHANCED SOURCE REMOVAL OF NONAQUEOUS PHASE LIQUID CONTAMINANTS BY CHEMICAL-BASED FLOODING

    EPA Science Inventory

    Nonaqueous phase liquids (NAPLs) such as gasoline and halogenated solvents (trichloroethylene (TCE) and teterachloroethylene (PCE), etc) enter the subsurface after a spill, or from leaking underground storage tanks. The presence of residual dense nonaqueous phase liquids (DNAPL) ...

  4. Modeling the solid-liquid phase transition in saturated triglycerides

    NASA Astrophysics Data System (ADS)

    Pink, David A.; Hanna, Charles B.; Sandt, Christophe; MacDonald, Adam J.; MacEachern, Ronald; Corkery, Robert; Rousseau, Dérick

    2010-02-01

    We investigated theoretically two competing published scenarios for the melting transition of the triglyceride trilaurin (TL): those of (1) Corkery et al. [Langmuir 23, 7241 (2007)], in which the average state of each TL molecule in the liquid phase is a discotic "Y" conformer whose three chains are dynamically twisted, with an average angle of ˜120° between them, and those of (2) Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid-state conformation of the TL molecule in the liquid phase is a nematic h∗-conformer whose three chains are in a modified "chair" conformation. We developed two competing models for the two scenarios, in which TL molecules are in a nematic compact-chair (or "h") conformation, with extended, possibly all-trans, chains at low-temperatures, and in either a Y conformation or an h∗ conformation in the liquid state at temperatures higher than the phase-transition temperature, T∗=319 K. We defined an h-Y model as a realization of the proposal of Corkery et al. [Langmuir 23, 7241 (2007)], and explored its predictions by mapping it onto an Ising model in a temperature-dependent field, performing a mean-field approximation, and calculating the transition enthalpy ΔH. We found that the most plausible realization of the h-Y model, as applied to the solid-liquid phase transition in TL, and likely to all saturated triglycerides, gave a value of ΔH in reasonable agreement with the experiment. We then defined an alternative h-h∗ model as a realization of the proposal of Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid phase exhibits an average symmetry breaking similar to an h conformation, but with twisted chains, to see whether it could describe the TL phase transition. The h-h∗ model gave a value of ΔH that was too small by a factor of ˜3-4. We also predicted the temperature dependence of the 1132 cm-1 Raman band for both models, and performed measurements of the ratios of three TL Raman

  5. Electrostatic levitation studies of supercooled liquids and metastable solid phases

    NASA Astrophysics Data System (ADS)

    Rustan, Gustav Errol

    been carried out to study the metastable phase formation in an Fe83B17 near eutectic alloy. Initial supercooling measurements using the ISU-ESL identified the formation of three metastable phases: a precipitate phase that shows stable coexistence with the deeply supercooled liquid, and two distinct bulk solidification phases. To identify the structure of the metastable phases, the Washington University Beamline ESL (WU-BESL) has been used to perform in-situ high energy x-ray diffraction measurements of the metastable phases. Based on the x-ray results, the precipitate phase has been identified as bcc-Fe, and the more commonly occurring bulk solidification product has been found to be a two-phase mixture of Fe23B6 plus fcc-Fe, which appears, upon cooling, to transform into a three phase mixture of Fe23B6, bcc-Fe, and an as-yet unidentified phase, with the transformation occurring at approximately the expected fcc-to-bcc transformation temperature of pure Fe. To further characterize the multi-phase metastable alloy, the ISU-ESL has been used to perform measurements of volume thermal expansion via the videographic technique, as well as RF susceptibility via the TDO technique. The results of the thermal expansion and susceptibility data have been found to be sensitive indicators of additional structural changes that may be occurring in the metastable solid at temperatures below 1000 K, and the susceptibility data has revealed that three distinct ferromagnetic phase transitions take place within the multi-phase mixture. Based on these results, it has been hypothesized that there may be an additional transformation taking place that leads to the formation of either bct- or o-Fe3B in addition to the Fe23B6 phase, although further work is required to test this hypothesis.

  6. Ionic liquids in refinery desulfurization: comparison between biphasic and supported ionic liquid phase suspension processes.

    PubMed

    Kuhlmann, Esther; Haumann, Marco; Jess, Andreas; Seeberger, Andreas; Wasserscheid, Peter

    2009-01-01

    The desulfurization of fuel compounds in the presence of ionic liquids is reported. For this purpose, the desulfurization efficiency of a variety of imidazolium phosphate ionic liquids has been tested. Dibenzothiophene/dodecane and butylmercaptan/decane mixtures were used as model systems. Single-stage extractions reduced the sulfur content from 500 ppm to 200 ppm. In multistage extractions the sulfur content could be lowered to less than 10 ppm within seven stages. Regeneration of the ionic liquid was achieved by distillation or re-extraction procedures. Supported ionic liquid phase (SILP) materials, obtained by dispersing the ionic liquid as a thin film on highly porous silica, exhibited a significantly higher extraction performance owing to their larger surface areas, reducing the sulfur content to less than 100 ppm in one stage. Multistage extraction with these SILP materials reduced the sulfur level to 50 ppm in the second stage. The SILP technology offers very efficient utilization of ionic liquids and circumvents mass transport limitations because of the small film thickness and large surface area, and allows application of the simple packed-bed column extraction technique. PMID:19798713

  7. Pressure-energy correlations in liquids. IV. ``Isomorphs'' in liquid phase diagrams

    NASA Astrophysics Data System (ADS)

    Gnan, Nicoletta; Schrøder, Thomas B.; Pedersen, Ulf R.; Bailey, Nicholas P.; Dyre, Jeppe C.

    2009-12-01

    This paper is the fourth in a series devoted to identifying and explaining the properties of strongly correlating liquids, i.e., liquids where virial and potential energy correlate better than 90% in their thermal equilibrium fluctuations in the N V T ensemble. For such liquids we here introduce the concept of "isomorphic" curves in the phase diagram. A number of thermodynamic, static, and dynamic isomorph invariants are identified. These include the excess entropy, the isochoric specific heat, reduced-unit static and dynamic correlation functions, as well as reduced-unit transport coefficients. The dynamic invariants apply for both Newtonian and Brownian dynamics. It is shown that after a jump between isomorphic state points the system is instantaneously in thermal equilibrium; consequences of this for generic aging experiments are discussed. Selected isomorph predictions are validated by computer simulations of the Kob-Andersen binary Lennard-Jones mixture, which is a strongly correlating liquid. The final section of the paper relates the isomorph concept to phenomenological melting rules, Rosenfeld's excess entropy scaling, Young and Andersen's approximate scaling principle, and the two-order parameter maps of Debenedetti and co-workers. This section also shows how the existence of isomorphs implies an "isomorph filter" for theories for the non-Arrhenius temperature dependence of viscous liquids' relaxation time, and it explains isochronal superposition for strongly correlating viscous liquids.

  8. Influence of phase delay profile on diffraction efficiency of liquid crystal optical phased array

    NASA Astrophysics Data System (ADS)

    Xu, Lin; Zhang, Jian; Wu, Li Ying

    2009-06-01

    The hardware structure and driving voltage of liquid crystal optical phased array (LCOPA) devices determine the produced phase delay characteristics. The phase delay profile influences directly the device's diffraction efficiency. In this paper, a sawtooth-shaped phase delay model of LCOPA was proposed to analyze quantitatively the influence factors of diffraction efficiency employing Fourier optics theory. Analysis results show that flyback region size is the main factor that affects diffraction efficiency. The influence extent varies with different maximum-phase-delays and grating periods. There exists an optimized curve between maximum-phase-delay and flyback region, and between maximum-phase-delay and grating period, individually. The smaller the grating period is or the larger the flyback region is, the more evident the optimization effect becomes, and the maximum increase ratio is up to 16%. Some feasible experiments were done to test theoretical analysis, and the experimental results agreed with the analysis results.

  9. Variation in pH of Model Secondary Organic Aerosol during Liquid-Liquid Phase Separation.

    PubMed

    Dallemagne, Magda A; Huang, Xiau Ya; Eddingsaas, Nathan C

    2016-05-12

    The majority of atmospheric aerosols consist of both organic and inorganic components. At intermediate relative humidity (RH), atmospheric aerosol can undergo liquid-liquid phase separation (LLPS) in which the organic and inorganic fractions segregate from each other. We have extended the study of LLPS to the effect that phase separation has on the pH of the overall aerosols and the pH of the individual phases. Using confocal microscopy and pH sensitive dyes, the pH of internally mixed model aerosols consisting of polyethylene glycol 400 and ammonium sulfate as well as the pH of the organic fraction during LLPS have been directly measured. During LLPS, the pH of the organic fraction was observed to increase to 4.2 ± 0.2 from 3.8 ± 0.1 under high RH when the aerosol was internally mixed. In addition, the high spatial resolution of the confocal microscope allowed us to characterize the composition of each of the phases, and we have observed that during LLPS the organic shell still contains large quantities of water and should be characterized as an aqueous organic-rich phase rather than simply an organic phase. PMID:27082856

  10. Metabolism of Cyclohexane Carboxylic Acid by Alcaligenes Strain W1

    PubMed Central

    Taylor, David G.; Trudgill, Peter W.

    1978-01-01

    Thirty-three microorganisms capable of growth with cyclohexane carboxylate as the sole source of carbon were isolated from mud, water, and soil samples from the Aberystwyth area. Preliminary screening and whole-cell oxidation studies suggested that, with one exception, all of the strains metabolized the growth substrate by beta-oxidation of the coenzyme A ester. This single distinctive strain, able to oxidize rapidly trans-4-hydroxycyclohexane carboxylate, 4-ketocyclohexane carboxylate, p-hydroxybenzoate, and protocatechuate when grown with cyclohexane carboxylate, was classified as a strain of Alcaligenes and given the number W1. Enzymes capable of converting cyclohexane carboxylate to p-hydroxybenzoate were induced by growth with the alicyclic acid and included the first unambiguous specimen of a cyclohexane carboxylate hydroxylase. Because it is a very fragile protein, attempts to stabilize the cyclohexane carboxylate hydroxylase so that a purification procedure could be developed have consistently failed. In limited studies with crude cell extracts, we found that hydroxylation occurred at the 4 position, probably yielding the trans isomer of 4-hydroxycyclohexane carboxylate. Simultaneous measurement of oxygen consumption and reduced nicotinamide adenine dinucleotide oxidation, coupled with an assessment of reactant stoichiometry, showed the enzyme to be a mixed-function oxygenase. Mass spectral analysis enabled the conversion of cyclohexane carboxylate to p-hydroxybenzoate by cell extracts to be established unequivocally, and all of our data were consistent with the pathway: cyclohexane carboxylate → trans-4-hydroxycyclohexane carboxylate → 4-ketocyclohexane carboxylate → p-hydroxybenzoate. The further metabolism of p-hydroxybenzoate proceeded by meta fission and by the oxidative branch of the 2-hydroxy-4-carboxymuconic semialde-hyde-cleaving pathway. PMID:207665

  11. Liquid-Liquid Phase Transition and Its Phase Diagram in Deeply-Cooled Heavy Water Confined in a Nanoporous Silica Matrix.

    PubMed

    Wang, Zhe; Ito, Kanae; Leão, Juscelino B; Harriger, Leland; Liu, Yun; Chen, Sow-Hsin

    2015-06-01

    Using neutron diffraction technique, we measure the average density of the heavy water confined in a nanoporous silica matrix, MCM-41, over the pressure-temperature plane. The result suggests the existence of a line of liquid-liquid phase transition with its end point at 1.29 ± 0.34 kbar and 213 ± 3 K in a fully hydrated sample. This point would be the liquid-liquid critical point (LLCP) according to the "liquid-liquid critical point" scenario. The phase diagram of the deeply cooled confined heavy water is then discussed. Moreover, in a partially hydrated sample, the phase transition completely disappears. This result shows that it is the free water part, rather than the bound water part, of the confined water that undergoes a liquid-liquid transition. PMID:26266493

  12. Viscosity of the entangled-vortex-liquid phase

    SciTech Connect

    Cates, M.E. )

    1992-06-01

    The entangled-flux-line liquid phase of high-temperature superconductors is considered. This is a phase of directed, mutually avoiding polymerlike flux lines which are strongly entangled. However, there is a finite rate constant for topological reconnection of the flux lines. The viscosity {eta} of the phase is discussed using a simplified model, following that recently developed by Marchetti and Nelson (Phys. Rev. B 42, 9938 (1990)). We find, as did these authors, a result of the form {eta}={eta}{sub 0}{ital e}{sup {ital U}/{ital k}{ital T}}. However, our estimate for {ital U} is one-third of their value; the difference could be significant when the activation energy for flux-line reconnection is large.

  13. Luttinger liquid with complex forward scattering: Robustness and Berry phase

    NASA Astrophysics Data System (ADS)

    Dóra, Balázs; Moessner, Roderich

    2016-02-01

    Luttinger liquids (LLs) are one-dimensional systems with well-understood instabilities due to Umklapp or backscattering. We study a generalization of the Luttinger model, which incorporates a time reversal symmetry breaking interaction producing a complex forward scattering amplitude (g2 process). The resulting low energy state is still a LL and belongs to the family of interacting Schulz-Shastry models. Remarkably, it becomes increasingly robust against additional perturbations—for purely imaginary g2, both Umklapp and local backscattering are always irrelevant. Changing the phase of the interaction generates a nontrivial Berry phase, with a universal geometric phase difference between ground and a one boson excited state depending only on the LL parameter.

  14. Printing nanoparticles from the liquid and gas phases using nanoxerography

    NASA Astrophysics Data System (ADS)

    Barry, Chad R.; Steward, Michael G.; Lwin, Nyein Z.; Jacobs, Heiko O.

    2003-10-01

    This paper reports on the directed self-assembly of nanoparticles onto charged surface areas with a resolution of 200 nm from the liquid phase and 100 nm from the gas phase. The charged areas required for this type of nanoxerographic printing were fabricated using a parallel method that employs a flexible, electrically conductive, electrode to charge a thin-film electret. As electrodes, we used metal-coated polymeric stamps and 10 µm thick doped silicon wafers carrying a pattern in topography. Each electrode was brought in contact with a thin-film electret on an n-doped silicon substrate. The charge pattern was transferred into the thin-film electret by applying a voltage pulse between the conductive electrode and the silicon substrate. Areas as large as 1 cm2 were patterned with charge with 100 nm scale resolution in 10 s. These charge patterns attract nanoparticles. A liquid-phase assembly process where electrostatic forces compete with disordering forces due to ultrasonication has been developed to assemble nanoparticles onto charged based receptors in 10 s from a liquid suspension. A gas-phase assembly process was developed that uses a transparent particle assembly module to direct particles towards the charged surface while monitoring the total charge of assembled particles. Nanoparticles were generated using a tube furnace by evaporation and condensation at the outlet. The electrostatically directed assembly of 10-100 nm sized metal (gold, silver) and 30 nm sized carbon particles was accomplished with a resolution 500-1000 times greater than the resolution of existing xerographic printers.

  15. Amphitropic liquid crystal phases from polyhydroxy sugar surfactants: Fundamental studies

    NASA Astrophysics Data System (ADS)

    Abou Zied, Osama K.; Hashim, Rauzah; Timimi, B. A.

    2015-03-01

    The self-assembly phenomena on a special class of poly-hydroxy sugar surfactant have been studied extensively. This class of material is classified as amphitropic liquid crystals since they exhibit both thermotropic and lyotropic liquid crystalline properties. Hence the potential applications of these non-ionic surfactants are more versatile than those from the conventional lyotropic liquid crystals including those from thermotropic phases, but the latters are yet to be realized. Unfortunately, due to the lack of interest (or even awareness), fundamental studies in thermotropic glycolipids are scanty to support application development, and any tangible progress is often mired by the complexity of the sugar stereochemistry. However, some applications may be pursued from these materials by taking the advantage of the sugar chirality and the tilted structure of the lipid organization which implies ferroelectric behavior. Here, we present our studies on the stereochemical diversity of the sugar units in glycosides that form the thermotropic/lyotropic phases. The structure to property relationship compares different chain designs and other popular polyhydroxy compounds, such as monooleins and alkylpolyglucosides. Different structural properties of these glycosides are discussed with respect to their self-assembly organization and potential applications, such as delivery systems and membrane mimetic study.

  16. Stretchable liquid-crystal blue-phase gels.

    PubMed

    Castles, F; Morris, S M; Hung, J M C; Qasim, M M; Wright, A D; Nosheen, S; Choi, S S; Outram, B I; Elston, S J; Burgess, C; Hill, L; Wilkinson, T D; Coles, H J

    2014-08-01

    Liquid-crystalline polymers are materials of considerable scientific interest and technological value. An important subset of these materials exhibit rubber-like elasticity, combining the optical properties of liquid crystals with the mechanical properties of rubber. Moreover, they exhibit behaviour not seen in either type of material independently, and many of their properties depend crucially on the particular mesophase employed. Such stretchable liquid-crystalline polymers have previously been demonstrated in the nematic, chiral-nematic, and smectic mesophases. Here, we report the fabrication of a stretchable gel of blue phase I, which forms a self-assembled, three-dimensional photonic crystal that remains electro-optically switchable under a moderate applied voltage, and whose optical properties can be manipulated by an applied strain. We also find that, unlike its undistorted counterpart, a mechanically deformed blue phase exhibits a Pockels electro-optic effect, which sets out new theoretical challenges and possibilities for low-voltage electro-optic devices. PMID:24880732

  17. Modified phase-field-crystal model for solid-liquid phase transitions

    NASA Astrophysics Data System (ADS)

    Guo, Can; Wang, Jincheng; Wang, Zhijun; Li, Junjie; Guo, Yaolin; Tang, Sai

    2015-07-01

    A modified phase-field-crystal (PFC) model is proposed to describe solid-liquid phase transitions by reconstructing the correlation function. The effects of fitting parameters of our modified PFC model on the bcc-liquid phase diagram, numerical stability, and solid-liquid interface properties during planar interface growth are examined carefully. The results indicate that the increase of the correlation function peak width at k =km will enhance the stability of the ordered phase, while the increase of peak height at k =0 will narrow the two-phase coexistence region. The third-order term in the free-energy function and the short wave-length of the correlation function have significant influences on the numerical stability of the PFC model. During planar interface growth, the increase of peak width at k =km will decrease the interface width and the velocity coefficient C , but increase the anisotropy of C and the interface free energy. Finally, the feasibility of the modified phase-field-crystal model is demonstrated with a numerical example of three-dimensional dendritic growth of a body-centered-cubic structure.

  18. Modified phase-field-crystal model for solid-liquid phase transitions.

    PubMed

    Guo, Can; Wang, Jincheng; Wang, Zhijun; Li, Junjie; Guo, Yaolin; Tang, Sai

    2015-07-01

    A modified phase-field-crystal (PFC) model is proposed to describe solid-liquid phase transitions by reconstructing the correlation function. The effects of fitting parameters of our modified PFC model on the bcc-liquid phase diagram, numerical stability, and solid-liquid interface properties during planar interface growth are examined carefully. The results indicate that the increase of the correlation function peak width at k=k(m) will enhance the stability of the ordered phase, while the increase of peak height at k=0 will narrow the two-phase coexistence region. The third-order term in the free-energy function and the short wave-length of the correlation function have significant influences on the numerical stability of the PFC model. During planar interface growth, the increase of peak width at k=k(m) will decrease the interface width and the velocity coefficient C, but increase the anisotropy of C and the interface free energy. Finally, the feasibility of the modified phase-field-crystal model is demonstrated with a numerical example of three-dimensional dendritic growth of a body-centered-cubic structure. PMID:26274309

  19. Microstructural control of silicon carbide via liquid phase sintering

    NASA Astrophysics Data System (ADS)

    Mrotek, Sharon Robinson

    Silicon carbide ceramics with various microstructures were fabricated by controlling the amount and composition of a Y2O3-Al 2O3 liquid phase, crystallographic phase of the starting powders, trace impurities in those powders, and time and temperature of sintering and post- sintering heat-treatments. Alpha and beta SiC "seeds" were used to control grain growth during sintering. The grain size distribution and aspect ratio of the grains were determined through microstructural analysis of polished and etched samples. TEM was used in conjunction with EDS to determine the distribution of the sintering aids in the grains and the grain boundaries. Additionally, the final phase content of the samples was determined via x-ray diffraction. The fracture toughness and hardness were measured to evaluate the relative effects of the microstructural variations on the mechanical properties. Alpha silicon carbide samples exhibited a fine grained, equiaxed microstructure. Under appropriate conditions, samples prepared from beta-SiC powders underwent a phase transformation to alpha-SiC accompanied by the growth of elongated platelet grains. The addition of alpha seeds to the beta powder reduced the size of the platelets compared to unseeded samples of the same composition. If the beta to alpha phase transformation did not occur, the beta samples developed an equiaxed microstructure. The grain size of all samples decreased with increasing amounts of sintering additives. The beta to alpha phase transformation, required to obtain an elongated grain microstructure, was catalyzed by the presence of sufficient amounts of aluminum. If insufficient Al impurity was present in the powder, purposeful additions of Al metal could induce the phase transformation. Examination of the sintering progression over time indicated that the phase transformation occurred late in the sintering process and appeared to occur via a solution/reprecipitation mechanism. Post-sintering heat treatments were also used

  20. Effect of dimensionality on vapor-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Singh, Sudhir Kumar

    2014-04-01

    Dimensionality play significant role on `phase transitions'. Fluids in macroscopic confinement (bulk or 3-Dimensional, 3D) do not show significant changes in their phase transition properties with extent of confinement, since the number of molecules away from the surrounding surfaces is astronomically higher than the number of molecules in close proximity of the confining surfaces. In microscopic confinement (quasi 3D to quasi-2D), however, the number of molecules away from the close proximity of the surface is not as high as is the case with macroscopic (3D) confinement. Hence, under the same thermodynamic conditions `phase transition' properties at microscopic confinement may not remain the same as the macroscopic or 3D values. Phase transitions at extremely small scale become very sensitive to the dimensions as well as the surface characteristics of the system. In this work our investigations reveal the effect of dimensionality on the phase transition from 3D to quasi-2D to 2D behavior. We have used grand canonical transition matrix Monte Carlo simulation to understand the vapor-liquid phase transitions from 3D to quasi-2D behavior. Such studies can be helpful in understanding and controlling the fluid film behaviour confined between solid surfaces of few molecular diameters, for example, in lubrication applications.

  1. Liquid Crystal Phase Behaviour of Attractive Disc-Like Particles

    PubMed Central

    Wu, Liang; Jackson, George; Müller, Erich A.

    2013-01-01

    We employ a generalized van der Waals-Onsager perturbation theory to construct a free energy functional capable of describing the thermodynamic properties and orientational order of the isotropic and nematic phases of attractive disc particles. The model mesogen is a hard (purely repulsive) cylindrical disc particle decorated with an anisotropic square-well attractive potential placed at the centre of mass. Even for isotropic attractive interactions, the resulting overall inter-particle potential is anisotropic, due to the orientation-dependent excluded volume of the underlying hard core. An algebraic equation of state for attractive disc particles is developed by adopting the Onsager trial function to characterize the orientational order in the nematic phase. The theory is then used to represent the fluid-phase behaviour (vapour-liquid, isotropic-nematic, and nematic-nematic) of the oblate attractive particles for varying values of the molecular aspect ratio and parameters of the attractive potential. When compared to the phase diagram of their athermal analogues, it is seen that the addition of an attractive interaction facilitates the formation of orientationally-ordered phases. Most interestingly, for certain aspect ratios, a coexistence between two anisotropic nematic phases is exhibited by the attractive disc-like fluids. PMID:23965962

  2. Effect of dimensionality on vapor-liquid phase transition

    SciTech Connect

    Singh, Sudhir Kumar

    2014-04-24

    Dimensionality play significant role on ‘phase transitions’. Fluids in macroscopic confinement (bulk or 3-Dimensional, 3D) do not show significant changes in their phase transition properties with extent of confinement, since the number of molecules away from the surrounding surfaces is astronomically higher than the number of molecules in close proximity of the confining surfaces. In microscopic confinement (quasi 3D to quasi-2D), however, the number of molecules away from the close proximity of the surface is not as high as is the case with macroscopic (3D) confinement. Hence, under the same thermodynamic conditions ‘phase transition’ properties at microscopic confinement may not remain the same as the macroscopic or 3D values. Phase transitions at extremely small scale become very sensitive to the dimensions as well as the surface characteristics of the system. In this work our investigations reveal the effect of dimensionality on the phase transition from 3D to quasi-2D to 2D behavior. We have used grand canonical transition matrix Monte Carlo simulation to understand the vapor–liquid phase transitions from 3D to quasi-2D behavior. Such studies can be helpful in understanding and controlling the fluid film behaviour confined between solid surfaces of few molecular diameters, for example, in lubrication applications.

  3. A polarization independent liquid crystal phase modulation adopting surface pinning effect of polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Tsou, Yu-Shih

    2011-12-01

    A polarization-independent liquid crystal (LC) phase modulation using the surface pinning effect of polymer dispersed liquid crystals (SP-PDLC) is demonstrated. In the bulk region of the SP-PDLC, the orientations of LC directors are randomly dispersed; thus, any polarization of incident light experiences the same averaged refractive index. In the regions near glass substrates, the LC droplets are pinned. The orientations of top and bottom droplets are orthogonal. Two eigen-polarizations of an incident light experience the same phase shift. As a result, the SP-PDLC is polarization independent. Polarizer-free microlens arrays of SP-PDLC are also demonstrated. The SP-PDLC has potential for application in spatial light modulators, laser beam steering, and electrically tunable microprisms.

  4. Metastable liquid-liquid phase separation and criticality in water-like models

    NASA Astrophysics Data System (ADS)

    Singh, Rakesh; Biddle, John; Debenedetti, Pablo; Anisimov, Mikhail

    Water shows intriguing thermodynamic and dynamic anomalies in the supercooled liquid state. A possible explanation of the origin of these anomalies lies in the existence of a metastable first order liquid-liquid phase transition (LLPT) between two (high and low density) forms of liquid water. Unambiguous experimental proof of existence of LLPT in bulk supercooled water is so far hampered by ultra-fast ice crystallization. Computer simulations of water models are therefore crucial for exploring the possibility of LLPT in deeply supercooled water. We present computer simulation results that elucidate the possibility of a metastable LLPT in one of the most accurate atomistic models of water, TIP4P/2005. To describe the computed properties, we have applied two-state thermodynamics, viewing water as a non-ideal mixture of two inter-convertible states. The thermodynamic behavior of the model in the one-phase region suggests the existence of energy-driven LLPT. We compare the behavior of TIP4P/2005 with other popular water models, and with real water, all of which are well-described by two-state thermodynamics. Additionally, we also elucidate the relation between the phenomenological order parameter of the two-state thermodynamics and the microscopic nature of the low-density structure.

  5. Supercritical phenomenon of hydrogen beyond the liquid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Li, Renzhong; Chen, Ji; Li, Xinzheng; Wang, Enge; Xu, Limei

    2015-06-01

    Using ab initio molecular dynamics simulation, we investigate the supercritical phenomenon associated with the liquid-liquid phase transition of hydrogen by studying the isothermal response functions, such as electric conductivity, molecular dissociation coefficient and isothermal compressibility, with respect to pressure. We find that, along each isotherm in the supercritical region, each of these response functions shows a maximum, the location of which is different for different response functions. As temperature decreases, the loci of these maxima asymptotically converge to a line of zero ordering field, known as the Widom line along which the magnitude of the response function maxima becomes larger and larger until it diverges as the critical point is approached. Thus, our study provides a possible way to locate the liquid-liquid critical point of hydrogen from the supercritical region at lower pressures. It also indicates that the supercritical phonomenon near the critical point of hydrogen is a rather general feature of second-order phase transition, it is not only true for classical systems with weak interactions but also true for highly condensed system with strong inter-atomic interactions.

  6. Crystallization and Phase Changes in Paracetamol from the Amorphous Solid to the Liquid Phase

    PubMed Central

    2014-01-01

    For the case of paracetamol, we show how terahertz time-domain spectroscopy can be used to characterize the solid and liquid phase dynamics. Heating of supercooled amorphous paracetamol from 295 K in a covered sample under vacuum leads to its crystallization at 330 K. First, form III is formed followed by the transformation of form III to form II at 375 K, to form I at 405 K, and finally melting is observed around 455 K. We discuss the difference between the featureless spectra of the supercooled liquid and its liquid melt. Lastly, we studied the onset of crystallization from the supercooled liquid in detail and quantified its kinetics based on the Avrami–Erofeev model. We determined an effective rate constant of k = 0.056 min–1 with a corresponding onset of crystallization at T = 329.5 K for a heating rate of 0.4 K min–1. PMID:24579729

  7. Crystallization and phase changes in paracetamol from the amorphous solid to the liquid phase.

    PubMed

    Sibik, Juraj; Sargent, Michael J; Franklin, Miriam; Zeitler, J Axel

    2014-04-01

    For the case of paracetamol, we show how terahertz time-domain spectroscopy can be used to characterize the solid and liquid phase dynamics. Heating of supercooled amorphous paracetamol from 295 K in a covered sample under vacuum leads to its crystallization at 330 K. First, form III is formed followed by the transformation of form III to form II at 375 K, to form I at 405 K, and finally melting is observed around 455 K. We discuss the difference between the featureless spectra of the supercooled liquid and its liquid melt. Lastly, we studied the onset of crystallization from the supercooled liquid in detail and quantified its kinetics based on the Avrami-Erofeev model. We determined an effective rate constant of k = 0.056 min(-1) with a corresponding onset of crystallization at T = 329.5 K for a heating rate of 0.4 K min(-1). PMID:24579729

  8. Phase transition dynamics of liquid phase precipitation from a supersaturated gas mixture.

    PubMed

    Pines, V; Zlatkowski, M; Chait, A

    2004-11-01

    This work presents a self-consistent description of phase transition dynamics of disperse liquid phase precipitating from a supersaturated gas mixture. The unified approach integrates the macroscale transport phenomena of cloud dynamics with the essential microphysical kinetic processes of droplet condensation, evaporation, and droplet collisions simultaneously taking place in stochastic population of liquid droplets. A complete set of governing equations with well-defined dissipative fluxes and kinetic rates is derived for phase transition dynamics from nucleation to postnucleation to coarsening stages. The local thermodynamics of precipitating system, which is considered as ternary mixture of disperse liquid phase and water vapor with dry air, is redefined to explicitly include on equal basis both the vapor content and liquid content into the fundamental thermodynamic relations and equation of state. The molecular kinetic flux regularization method for growth of submicron droplets is reexamined to include, among others, significant contribution of vapor molecular energy flux into total heat flux, resulting in new expressions for the droplet temperature, growth rate, and effective diffusion coefficients. The local kinetic rates are determined on the basis of microscale kinetic equation for the droplet distribution function. This is in contrast to commonly used semiempirical parametrization schemes for kinetic rates with adjustable parameters, wherein the probabilistic aspects of microphysical processes are not rigorously addressed. Stochastic diffusion interactions among droplets competing for the available water vapor and modifications in the kinetic equation for droplets growing in stochastic population with direct long-range diffusion interactions amongst them are discussed and formulated as well. PMID:15527359

  9. Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics

    NASA Astrophysics Data System (ADS)

    Griffin, DeVon W.; Marshall, Keneth L.

    2002-11-01

    The initial focus of this project was to eliminate both of these problems in the Liquid Crystal Point-Diffraction Interferometer (LCPDI). Progress toward that goal will be described, along with the demonstration of a phase shifting Liquid Crystal Shearing Interferometer (LCSI) that was developed as part of this work. The latest LCPDI, other than a lens to focus the light from a test section onto a diffracting microsphere within the interferometer and a collimated laser for illumination, the pink region contained within the glass plates on the rod-mounted platform is the complete interferometer. The total width is approximately 1.5 inches with 0.25 inches on each side for bonding the electrical leads. It is 1 inch high and there are only four diffracting microspheres within the interferometer. As a result, it is very easy to align, achieving the first goal. The liquid crystal electro-optical response time is a function of layer thickness, with thinner devices switching faster due to a reduction in long-range viscoelastic forces between the LC molecules. The LCPDI has a liquid crystal layer thickness of 10 microns, which is controlled by plastic or glass microspheres embedded in epoxy 'pads' at the corners of the device. The diffracting spheres are composed of polystyrene/divinyl benzene polymer with an initial diameter of 15 microns. The spheres deform slightly when the interferometer is assembled to conform to the spacing produced by the microsphere-filled epoxy spacer pads. While the speed of this interferometer has not yet been tested, previous LCPDIs fabricated at the Laboratory for Laser Energetics switched at a rate of approximately 3.3 Hz, a factor of 10 slower than desired. We anticipate better performance when the speed of these interferometers is tested since they are approximately three times thinner. Phase shifting in these devices is a function of the AC voltage level applied to the liquid crystal. As the voltage increases, the dye in the liquid crystal

  10. Droplet ignition and combustion including liquid-phase heating

    SciTech Connect

    Shaygan, N.; Prakash, S.

    1995-07-01

    Heating, ignition, and the subsequent combustion of a liquid droplet are studied in a hot stagnant environment. The transient, coupled liquid-gas phase problem of droplet combustion in one dimension is solved numerically. The pressure is assumed to be uniform and constant. This assumption is utilized in a novel way to formulate and solve the continuity equation. It is found that ignition occurs as soon as suitable conditions develop in the neighborhood of the droplet. In fact, the droplet surface heating is intimately connected with ignition. These general conclusions are found to be true for a volatile (n-heptane) as well as for a less volatile fuel (n-hexadecane). It is also found that the radial velocity produced by the evaporation and combustion of the droplet, leads to a local Reynolds number of order one. Hence, convective effects are as important as diffusion effects.

  11. Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics

    NASA Technical Reports Server (NTRS)

    Griffin, DeVon W.; Marshall, Keneth L.

    2002-01-01

    The initial focus of this project was to eliminate both of these problems in the Liquid Crystal Point-Diffraction Interferometer (LCPDI). Progress toward that goal will be described, along with the demonstration of a phase shifting Liquid Crystal Shearing Interferometer (LCSI) that was developed as part of this work. The latest LCPDI, other than a lens to focus the light from a test section onto a diffracting microsphere within the interferometer and a collimated laser for illumination, the pink region contained within the glass plates on the rod-mounted platform is the complete interferometer. The total width is approximately 1.5 inches with 0.25 inches on each side for bonding the electrical leads. It is 1 inch high and there are only four diffracting microspheres within the interferometer. As a result, it is very easy to align, achieving the first goal. The liquid crystal electro-optical response time is a function of layer thickness, with thinner devices switching faster due to a reduction in long-range viscoelastic forces between the LC molecules. The LCPDI has a liquid crystal layer thickness of 10 microns, which is controlled by plastic or glass microspheres embedded in epoxy 'pads' at the corners of the device. The diffracting spheres are composed of polystyrene/divinyl benzene polymer with an initial diameter of 15 microns. The spheres deform slightly when the interferometer is assembled to conform to the spacing produced by the microsphere-filled epoxy spacer pads. While the speed of this interferometer has not yet been tested, previous LCPDIs fabricated at the Laboratory for Laser Energetics switched at a rate of approximately 3.3 Hz, a factor of 10 slower than desired. We anticipate better performance when the speed of these interferometers is tested since they are approximately three times thinner. Phase shifting in these devices is a function of the AC voltage level applied to the liquid crystal. As the voltage increases, the dye in the liquid crystal

  12. Supersolidus Liquid Phase Sintering Modeling of Inconel 718 Superalloy

    NASA Astrophysics Data System (ADS)

    Levasseur, David; Brochu, Mathieu

    2016-02-01

    Powder metallurgy of Inconel 718 superalloy is advantageous as a near-net shape process for complex parts to reduce the buy-to-fly ratio and machining cost. However, sintering Inconel 718 requires the assistance of supersolidus liquid formation to achieve near full density and involves the risk of distortion at high temperatures. The present work is focused on modeling the onset of sintering and distortion as a function of temperature, grain size, and part geometry for Inconel 718. Using experimental sintering results and data available in the literature, the supersolidus liquid phase sintering of Inconel 718 was modeled. The model was used to define a processing window where part distortion would be avoided.

  13. Disappearance of Widom Line for Liquid-Liquid Phase Transition with Horizontal Coexistence Line

    NASA Astrophysics Data System (ADS)

    Luo, Jiayuan; Xu, Limei; Buldyrev, Sergey; Angell, Austen; Stanley, Gene

    2012-02-01

    The study of spherically symmetric two-scale Jagla model with both repulsive and attractive ramps has been very successful in demonstrating the anomalous behavior of liquids (especially water) and its relation with respect to the existence of a liquid-liquid (LL) critical point. However, the co-existence line of Jagla model shows a positive slope, which is opposite to what has been found in the simulations of water. To more convincingly link the result of the study on Jagla model with that of water, we applied discrete molecular dynamics to Gibson and Wilding's modified Jagla model and found that by shrinking both the attractive and repulsive ramps, the slope of the coexistence line can be reduced to zero. However, at these values of the parameters, the LL critical point becomes completely unstable with respect to crystal and glass. We further studied the Widom line, defined as extreme of response functions and also continuation of the coexistence line into one phase region, and found Widom line disappeared in the case of zero slope of the coexistence line, due to the equal enthalpy of low-density liquid (LDL) and high-density liquid (HDL).

  14. Liquid-phase chemical sensing using lateral mode resonant cantilevers.

    PubMed

    Beardslee, L A; Demirci, K S; Luzinova, Y; Mizaikoff, B; Heinrich, S M; Josse, F; Brand, O

    2010-09-15

    Liquid-phase operation of resonant cantilevers vibrating in an out-of-plane flexural mode has to date been limited by the considerable fluid damping and the resulting low quality factors (Q factors). To reduce fluid damping in liquids and to improve the detection limit for liquid-phase sensing applications, resonant cantilever transducers vibrating in their in-plane rather than their out-of-plane flexural resonant mode have been fabricated and shown to have Q factors up to 67 in water (up to 4300 in air). In the present work, resonant cantilevers, thermally excited in an in-plane flexural mode, are investigated and applied as sensors for volatile organic compounds in water. The cantilevers are fabricated using a complementary metal oxide semiconductor (CMOS) compatible fabrication process based on bulk micromachining. The devices were coated with chemically sensitive polymers allowing for analyte sorption into the polymer. Poly(isobutylene) (PIB) and poly(ethylene-co-propylene) (EPCO) were investigated as sensitive layers with seven different analytes screened with PIB and 12 analytes tested with EPCO. Analyte concentrations in the range of 1-100 ppm have been measured in the present experiments, and detection limits in the parts per billion concentration range have been estimated for the polymer-coated cantilevers exposed to volatile organics in water. These results demonstrate significantly improved sensing properties in liquids and indicate the potential of cantilever-type mass-sensitive chemical sensors operating in their in-plane rather than out-of-plane flexural modes. PMID:20715842

  15. Quantum Control of Femtochemistry in the Gas Phase, Liquid Phase and on Surfaces

    NASA Astrophysics Data System (ADS)

    Gerber, Gustav

    2008-03-01

    By using coherent control techniques we control the behavior of quantum systems on their natural fs-time scale by applying ultrashort coherent light fields in the wavelength range from the IR to the UV. These laser pulses can be variably shaped in space and time using a laser pulse shaper consisting of a liquid-crystal display [1]. Laser-optimized femtochemistry in the gas phase and liquid phase is one field in which this new technique is successfully employed. Automated optimization of branching ratios and total product yields of gas phase photodissociation reactions as well as chemically selective molecular excitation in the liquid phase is performed [2][3]. Structural changes of a molecule in the liquid phase have been controlled by laser-optimized photoisomerization of a cyanine dye molecule [4] and of retinal in bacteriorhodopsin [5]. So far, optimal control techniques have been restricted to gas phase and condensed phase optimization experiments. Recently we have demonstrated femtosecond laser-assisted catalytic reactions on a Pd(100) single crystal surface. By applying a closed-loop optimal control scheme, we manipulate these reactions and selectively optimize the ratio of different bond-forming reaction channels, in contrast to previous quantum control experiments aiming at bond-cleavage. The results represent a first step towards selective photocatalysis of molecules. [1] T. Baumert et al, Appl. Phys. B 65, 779 (1997) [2] A. Assion et al, Science 282, 919(1998); T. Brixner et al, J. Mod. Opt. 50, 539 (2003) [3] T. Brixner et al, Nature, Vol. 414, 57 (2001) and J. Chem. Phys. 118, 3692 (2003) [4] G. Krampert et al, Phys. Rev. Lett. 94, 068305 (2005) [5] G. Vogt et al, Chem. Phys. Lett. 433, 211 (2006) P. Nuernberger et al, Phys. Chem. Chem. Phys. 9, 2470 (2007)

  16. Liquid-Liquid Phase Transitions of Phosphorus via Constant-Pressure First-Principles Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Morishita, Tetsuya

    2001-09-01

    Pressure-induced phase transitions in liquid phosphorus have been studied by constant-pressure first-principles molecular dynamics simulations. By compressing a low-pressure liquid which consists of the tetrahedral P4 molecules, a structural phase transition from the molecular to polymeric liquid (a high-pressure phase) observed in the recent experiment by Katayama et al. [Nature (London) 403, 170 (2000)] was successfully realized. It is found that this transition is caused by a breakup of the tetrahedral molecules with large volume contraction. The same transition is also realized by heating. This indicates that only the polymeric liquid can stably exist at high temperature.

  17. Ionic liquid based hollow fiber supported liquid phase microextraction of ultraviolet filters.

    PubMed

    Ge, Dandan; Lee, Hian Kee

    2012-03-16

    Hollow fiber protected liquid phase microextraction using an ionic liquid as supported phase and acceptor phase (IL-HF-LPME) is proposed for the determination of four ultraviolet (UV) filters (benzophenone, 3-(4-methylbenzylidene)-camphor, 2-hydroxy-4-methoxybenzophenone and 2,4-dihydroxybenzophenone) in water samples for the first time. In the present study, four different ILs 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate) [HMIM][FAP], 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate [BMPL][FAP], 1-butyl-3-methylimidazolium phosphate ([BMIM][PO(4)]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF(6)]) were evaluated as extraction solvent. Only [HMIM][FAP] showed high chemical affinity to the analytes which permits a selective isolation of the UV filters from the sample matrix, allowing also their preconcentration. IL-HF-LPME and high performance liquid chromatography provides repeatability from 1.1% to 8.2% and limits of detection between 0.3 and 0.5 ng/ml. Real water samples spiked with the analytes extracted were analyzed, and yielded relative recoveries ranging from 82.6% to 105.9%. PMID:22307149

  18. Two-phase, gas-liquid flows in static mixers

    SciTech Connect

    Shah, N.F.; Kale, D.D. )

    1992-02-01

    This paper reports that static mixers are used for many gas-liquid two-phase operations. some of the typical applications are processing of natural gas to remove hydrogen sulfide or carbon dioxide, waste water treatment, dissolution of gases, hydrogenation, chlorination, and so on. They have experimentally studied the pressure drop for oxygen-water system in a bubble column packed with Sulzer-Koch-type mixing elements. They observed that the ratio of pressure drop through the packed bubble column to that through the unpacked one was slightly greater than one. The suitability of static mixers to mix fluids of very widely different viscosities has been demonstrated. Two-phase operations in polymer industry involve very viscous fluids. Due to the high viscosity of these fluids, the flow will be predominantly in laminar region for both fluids. There are no data on gas-liquid two-phase systems incorporating viscous Newtonian and non-Newtonian fluids where flows are predominantly in laminar region.

  19. System for exchange of hydrogen between liquid and solid phases

    DOEpatents

    Reilly, J.J.; Grohse, E.W.; Johnson, J.R.; Winsche, W.E.

    1985-02-22

    The reversible reaction M + x/2 H/sub 2/ reversible MH/sub x/, wherein M is a reversible metal hydride former that forms a hydride MH/sub x/ in the presence of H/sub 2/, generally used to store and recall H/sub 2/, is found to proceed under an inert liquid, thereby reducing contamination, providing better temperature control, providing in situ mobility of the reactants, and increasing flexibility in process design. Thus, a slurry of particles of a metal hydride former with an inert solvent is subjected to a temperature and pressure controlled atmosphere containing H/sub 2/, to store hydrogen and to release previously stored hydrogen. The direction of the flow of the H/sub 2/ through the liquid is dependent upon the H/sub 2/ pressure in the gas phase at a given temperature. When the actual H/sub 2/ pressure is above the equilibrium absorption pressure of the respective hydride the reaction proceeds to the right, i.e., the metal hydride is formed and hydrogen is stored in the solid particle. When the actual pressure in the gas phase is below the equilibrium dissociation pressure of the respective hydride the reaction proceeds to the left, the metal hydride is decomposed and hydrogen is released into the gas phase.

  20. System for exchange of hydrogen between liquid and solid phases

    DOEpatents

    Reilly, James J.; Grohse, Edward W.; Johnson, John R.; Winsche, deceased, Warren E.

    1988-01-01

    The reversible reaction M+x/2 H.sub.2 .rarw..fwdarw.MH.sub.x, wherein M is a reversible metal hydride former that forms a hydride MH.sub.x in the presence of H.sub.2, generally used to store and recall H.sub.2, is found to proceed under an inert liquid, thereby reducing contamination, providing better temperature control, providing in situ mobility of the reactants, and increasing flexibility in process design. Thus, a slurry of particles of a metal hydride former with an inert solvent is subjected to a temperature and pressure controlled atmosphere containing H.sub.2, to store hydrogen and to release previously stored hydrogen. The direction of the flow of the H.sub.2 through the liquid is dependent upon the H.sub.2 pressure in the gas phase at a given temperature. When the actual H.sub.2 pressure is above the equilibrium absorption pressure of the respective hydride the reaction proceeds to the right, i.e., the metal hydride is formed and hydrogen is stored in the solid particles. When the actual pressure in the gas phase is below the equilibrium dissociation pressure of the respective hydride the reaction proceeds to the left, the metal hydride is decomposed and hydrogen is released into the gas phase.

  1. An experimental investigation of two-phase liquid oxygen pumping

    NASA Technical Reports Server (NTRS)

    Gross, L. A.

    1973-01-01

    The results of an experimental program to explore the feasibility of pumping two-phase oxygen (liquid and gas) at the pump inlet are reported. Twenty-one cavitation tests were run on a standard J-2 oxygen pump at the MSFC Components Test Laboratory. All tests were run with liquid oxygen 5 to 10 K above the normal boiling point temperature. During ten tests run at approximately at the pump inlet were noted before complete pump performance 50 percent of the nominal operating speed, two phase conditions were achieved. Vapor volumes of 40 to 50 percent at the pump inlet were noted before complete pump performance loss. The experimental results compared to predictions. Nine cavitation tests run at the nominal pump speed over a 5 K temperature range showed progressively lower net positive suction head (NPSH) requirements as temperature was increased. Two-phase operation was not achieved. The temperature varying NPSH data were used to calculate thermodynamic effects on NPSH, and the results were compared to existing data.

  2. Glucose- and Cellulose-Derived Ni/C-SO3H Catalysts for Liquid Phase Phenol Hydrodeoxygenation

    SciTech Connect

    Kasakov, Stanislav; Zhao, Chen; Barath, Eszter; Chase, Zizwe A.; Fulton, John L.; Camaioni, Donald M.; Vjunov, Aleksei; Shi, Hui; Lercher, Johannes A.

    2015-01-19

    Sulfonated carbons were explored as functionalized supports for Ni nanoparticles to hydrodeoxygenate (HDO) phenol. Both hexadecane and water were used as solvents. The dual-functional Ni catalysts supported on sulfonated carbon (Ni/C-SO3H) showed high rates for phenol hydrodeoxygenation in liquid hexadecane, but not in water. Glucose and cellulose were precursors to the carbon supports. Changes in the carbons resulting from sulfonation of the carbons resulted in variations of carbon sheet structures, morphologies and the surface concentrations of acid sites. While the C-SO3H supports were active for cyclohexanol dehydration in hexadecane and water, Ni/C-SO3H only catalyzed the reduction of phenol to cyclohexanol in water. The state of 3 – 5 nm grafted Ni particles was analyzed by in situ X-ray absorption spectroscopy. The results show that the metallic Ni was rapidly formed in situ without detectable leaching to the aqueous phase, suggesting that just the acid functions on Ni/C-SO3H are inhibited in presence of water. Using in situ IR spectroscopy, it was shown that even in hexadecane, phenol HDO is limited by the dehydration step. Thus, phenol HDO catalysis was further improved by physically admixing C-SO3H with the Ni/C-SO3H catalyst to balance the two catalytic functions. The minimum addition of 7 wt.% C-SO3H to the most active of the Ni/C-SO3H catalysts enabled nearly quantitative conversion of phenol and the highest selectivity (90%) towards cyclohexane in 6 h, at temperatures as low as 473 K, suggesting that the proximity to Ni limits the acid properties of the support.

  3. NGNP Process Heat Utilization: Liquid Metal Phase Change Heat Exchanger

    SciTech Connect

    Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson

    2008-09-01

    One key long-standing issue that must be overcome to fully realize the successful growth of nuclear power is to determine other benefits of nuclear energy apart from meeting the electricity demands. The Next Generation Nuclear Plant (NGNP) will most likely be producing electricity and heat for the production of hydrogen and/or oil retrieval from oil sands and oil shale to help in our national pursuit of energy independence. For nuclear process heat to be utilized, intermediate heat exchange is required to transfer heat from the NGNP to the hydrogen plant or oil recovery field in the most efficient way possible. Development of nuclear reactor - process heat technology has intensified the interest in liquid metals as heat transfer media because of their ideal transport properties. Liquid metal heat exchangers are not new in practical applications. An important rational for considering liquid metals is the potential convective heat transfer is among the highest known. Thus explains the interest in liquid metals as coolant for intermediate heat exchange from NGNP. For process heat it is desired that, intermediate heat exchangers (IHX) transfer heat from the NGNP in the most efficient way possible. The production of electric power at higher efficiency via the Brayton Cycle, and hydrogen production, requires both heat at higher temperatures and high effectiveness compact heat exchangers to transfer heat to either the power or process cycle. Compact heat exchangers maximize the heat transfer surface area per volume of heat exchanger; this has the benefit of reducing heat exchanger size and heat losses. High temperature IHX design requirements are governed in part by the allowable temperature drop between the outlet and inlet of the NGNP. In order to improve the characteristics of heat transfer, liquid metal phase change heat exchangers may be more effective and efficient. This paper explores the overall heat transfer characteristics and pressure drop of the phase change

  4. Phase Behavior and Collective Dynamics of Liquid Water

    NASA Astrophysics Data System (ADS)

    Sastry, Srikanth

    The unusual properties of liquid water have been analyzed predominantly in terms of the hydrogen bond network which characterizes its microscopic structure. Properties of the hydrogen bond network, with physically motivated additional assumptions, have been shown to describe well most static and dynamic properties of water. However, there are important exceptions where no conclusive analysis in terms of the hydrogen bond network has been carried out. Two such exceptions are addressed in this thesis. The phase behaviour of water--in particular the limiting behavior of the metastable continuations of the liquid--is an open question. To explain the apparent divergence of many thermodynamic and microscopic quantities on supercooling, Speedy and Angell proposed that these divergences are due to an absolute limit of stability of the liquid phase, conjecturing further that such limits of stability form a continuous reentrant locus in the P-T plane. In an attempt to address this conjecture on the basis of microscopic behavior in water, a lattice gas model is developed, which exhibits water-like behavior and has phases corresponding to the real system. The liquid gas spinodal is seen to be reentrant, in accordance with the stability limit conjecture. However, the limit of stability upon supercooling in the model, while consistent with experiments, is found to differ qualitatively from the prediction, displaying no singular behavior of thermodynamic quantities. In computer and experimental studies of sound propagation in water at high wavenumbers, the sound velocity is found to be about twice the hydrodynamic value. It was proposed that this mode propagates on the hydrogen bond network and occurs due to the connectivity properties of the network. This question is studied through Molecular Dynamics simulations of the liquid and normal model analysis of inherent structures. The results show that only one longitudinal sound mode is present. However, an attempt is made to go

  5. A novel procedure for phase separation in dispersive liquid-liquid microextraction based on solidification of the aqueous phase.

    PubMed

    March, J G; Cerdà, V

    2016-08-15

    In this paper, an alternative for handling the organic phase after a dispersive liquid-liquid microextraction using organic solvents lighter than water is presented. It is based on solidification (at -18°C) of the aqueous phase obtained after centrifugation, and the decantation, collection and analysis of the liquid organic layer. The extraction of nicotine in toluene, and its determination in eggplant samples was conducted as a proof of concept. The study has been carried out using standards prepared in water and the formation of the dispersion was assisted by sonication. The organic extract was analysed using gas chromatography coupled to mass spectrometry. Satisfactory analytical figures of merit as: limit of detection (0.4µgL(-1), 2ngg(-1) wet sample), limit of quantification (1.2µgL(-1), 6.5ngg(-1) wet sample), within-day precision (RSD=7%), and linearity interval (up to 384µgL(-1) nicotine) were achieved. It constituted a contribution to the handling of organic extracts after microextraction processes. PMID:27260454

  6. Liquid/solid/dual phase xenon γ-ray detectors

    NASA Astrophysics Data System (ADS)

    van Sonsbeek, R.; Bom, V. R.; van Eijk, C. W. E.; Hollander, R. W.; Meijvogel, K.; Okx, W. J. C.

    1994-09-01

    It is recognized by various groups in the world that liquid xenon (LXe) is an interesting medium for the detection of γ-rays. In spite of all the experimental and theoretical effort expended during recent years, the processes that take place in this medium are not yet fully understood. We have obtained some preliminary results using an ionization chamber with a Frisch grid. This chamber could be filled with LXe and with solid xenon (SXe). We also investigated dual phase (GXe/SXe) systems. Our study will be continued with a newly developed detection cell described in this article.

  7. Vapors-liquid phase separator. [infrared telescope heat sink

    NASA Technical Reports Server (NTRS)

    Frederking, T. H. K.; Brown, G. S.; Chuang, C.; Kamioka, Y.; Kim, Y. I.; Lee, J. M.; Yuan, S. W. K.

    1980-01-01

    The use of porous plugs, mostly with in the form of passive devices with constant area were considered as vapor-liquid phase separators for helium 2 storage vessels under reduced gravity. The incorporation of components with variable cross sectional area as a method of flow rate modification was also investigated. A particular device which uses a shutter-type system for area variation was designed and constructed. This system successfully permitted flor rate changes of up to plus or minus 60% from its mean value.

  8. Environmental information volume: Liquid Phase Methanol (LPMEOH{trademark}) project

    SciTech Connect

    1996-05-01

    The purpose of this project is to demonstrate the commercial viability of the Liquid Phase Methanol Process using coal-derived synthesis gas, a mixture of hydrogen and carbon monoxide. This report describes the proposed actions, alternative to the proposed action, the existing environment at the coal gasification plant at Kingsport, Tennessee, environmental impacts, regulatory requirements, offsite fuel testing, and DME addition to methanol production. Appendices include the air permit application, solid waste permits, water permit, existing air permits, agency correspondence, and Eastman and Air Products literature.

  9. Liquid phase synthesis of copper indium diselenide nanoparticles

    SciTech Connect

    Jakhmola, Priyanka; Agarwal, Garima; Jha, Prafulla K.; Bhatnagar, S. P.

    2014-04-24

    Nanoparticles of Copper Indium diselenide (CuInSe{sub 2}), belongs to I-III-VI{sub 2} family has been synthesized via liquid phase route using ethylenediamine as a solvent. Characterization of as-grown particles is done by XRD, HRTEM, DLS, optical microscopy and UV-Vis spectroscopy. X-ray diffraction pattern confirmed that the CuInSe2 nanoparticles obtained reveals chalcopyrite structure. Particle size evaluated from dynamic light scattering of as grown particle possessing radius of 90 nm. The bandgap of 1.05eV is obtained from UV-Vis spectrum which will applicable to the solar cell devices.

  10. Geometrically-frustrated pseudogap phase of Coulomb liquids

    NASA Astrophysics Data System (ADS)

    Pramudya, Y.; Terletska, H.; Pankov, S.; Manousakis, E.; Dobrosavljević, V.

    2012-06-01

    We study a class of models with long-range repulsive interactions of the generalized Coulomb form V(r)∼1/rα. We show that decreasing the interaction exponent in the regime αliquid then survives in a broad pseudogap phase found at T>Tc, which is characterized by an unusual temperature dependence of all quantities. In contrast, the leading critical behavior very close to the charge-ordering temperature remains identical as in models with short-range interactions.

  11. Investigating materials formation with liquid-phase and cryogenic TEM

    NASA Astrophysics Data System (ADS)

    de Yoreo, J. J.; N. A. J. M., Sommerdijk

    2016-08-01

    The recent advent of liquid-phase transmission electron microscopy (TEM) and advances in cryogenic TEM are transforming our understanding of the physical and chemical mechanisms underlying the formation of materials in synthetic, biological and geochemical systems. These techniques have been applied to study the dynamic processes of nucleation, self-assembly, crystal growth and coarsening for metallic and semiconductor nanoparticles, (bio)minerals, electrochemical systems, macromolecular complexes, and organic and inorganic self-assembling systems. New instrumentation and methodologies that are currently on the horizon promise new opportunities for advancing the science of materials synthesis.

  12. Liquid-Phase Processing of Barium Titanate Thin Films

    NASA Astrophysics Data System (ADS)

    Harris, David Thomas

    Processing of thin films introduces strict limits on the thermal budget due to substrate stability and thermal expansion mismatch stresses. Barium titanate serves as a model system for the difficulty in producing high quality thin films because of sensitivity to stress, scale, and crystal quality. Thermal budget restriction leads to reduced crystal quality, density, and grain growth, depressing ferroelectric and nonlinear dielectric properties. Processing of barium titanate is typically performed at temperatures hundreds of degrees above compatibility with metalized substrates. In particular integration with silicon and other low thermal expansion substrates is desirable for reductions in costs and wider availability of technologies. In bulk metal and ceramic systems, sintering behavior has been encouraged by the addition of a liquid forming second phase, improving kinetics and promoting densification and grain growth at lower temperatures. This approach is also widespread in the multilayer ceramic capacitor industry. However only limited exploration of flux processing with refractory thin films has been performed despite offering improved dielectric properties for barium titanate films at lower temperatures. This dissertation explores physical vapor deposition of barium titanate thin films with addition of liquid forming fluxes. Flux systems studied include BaO-B2O3, Bi2O3-BaB2O 4, BaO-V2O5, CuO-BaO-B2O3, and BaO-B2O3 modified by Al, Si, V, and Li. Additions of BaO-B2O3 leads to densification and an increase in average grain size from 50 nm to over 300 nm after annealing at 900 °C. The ability to tune permittivity of the material improved from 20% to 70%. Development of high quality films enables engineering of ferroelectric phase stability using residual thermal expansion mismatch in polycrystalline films. The observed shifts to TC match thermodynamic calculations, expected strain from the thermal expansion coefficients, as well as x-ray diffract measurements

  13. Three-dimensional colloidal crystals in liquid crystalline blue phases

    PubMed Central

    Ravnik, Miha; Alexander, Gareth P.; Yeomans, Julia M.; Žumer, Slobodan

    2011-01-01

    Applications for photonic crystals and metamaterials put stringent requirements on the characteristics of advanced optical materials, demanding tunability, high Q factors, applicability in visible range, and large-scale self-assembly. Exploiting the interplay between structural and optical properties, colloidal lattices embedded in liquid crystals (LCs) are promising candidates for such materials. Recently, stable two-dimensional colloidal configurations were demonstrated in nematic LCs. However, the question as to whether stable 3D colloidal structures can exist in an LC had remained unanswered. We show, by means of computer modeling, that colloidal particles can self-assemble into stable, 3D, periodic structures in blue phase LCs. The assembly is based on blue phases providing a 3D template of trapping sites for colloidal particles. The particle configuration is determined by the orientational order of the LC molecules: Specifically, face-centered cubic colloidal crystals form in type-I blue phases, whereas body-centered crystals form in type-II blue phases. For typical particle diameters (approximately 100 nm) the effective binding energy can reach up to a few 100 kBT, implying robustness against mechanical stress and temperature fluctuations. Moreover, the colloidal particles substantially increase the thermal stability range of the blue phases, for a factor of two and more. The LC-supported colloidal structure is one or two orders of magnitude stronger bound than, e.g., water-based colloidal crystals. PMID:21368186

  14. Effect of temperature in reversed phase liquid chromatography.

    PubMed

    Guillarme, D; Heinisch, S; Rocca, J L

    2004-10-15

    The high temperature liquid chromatography (HTLC) reveals interesting chromatographic properties but even now, it misses some theoretical aspects concerning the influence of high temperature on thermodynamic and kinetic aspects of chromatography: such a knowledge is very essential for method development. In this work, the effect of temperature on solute behavior has been studied using various stationary phases which are representative of the available thermally stable materials present on the market. The thermodynamic properties were evaluated by using different mobile phases: acetonitrile-water, methanol-water and pure water. The obtained results were discussed on the basis of both type of mobile phases and type of stationary phases. Type of mobile phase was found to play an important role on the retention of solutes. The kinetic aspect was studied at various temperatures ranging from ambient temperature to high temperature (typically from about 30 to 200 degrees C) by fitting the experimental data with the Knox equation and it was shown that the efficiency is improved significantly when the temperature is increased. In this paper, we also discussed the problem of temperature control for thermostating columns which may represent a significant source of peak broadening: by taking into account the three main parameters such as heat transfer, pressure drop and band broadening resulting from the preheating tube, suitable rules are set up for a judicious choice of the column internal diameter. PMID:15527119

  15. Characterization of predominantly hydrophobic poly(styrene)-poly(ethylene oxide) copolymers at air/water and cyclohexane/water interfaces

    SciTech Connect

    Gragson, D.E.; Jensen, J.M.; Baker, S.M.

    1999-09-14

    Interfacial tension measurements are employed to explore the spreading behavior of predominantly hydrophobic poly(styrene)--poly(ethylene oxide), PS-PEO, diblock copolymers at air/water and cyclohexane/water interfaces. Two copolymers with 7%- and 15.5%-PEO are examined in this study. The former is expected to have a PS block limiting area in air roughly equal to the limiting PEO pancake area, whereas the latter is expected to have a limiting PS block area in air approximately 3 times smaller than the limiting PEO pancake area. At the air/water interface, the 7%-PEO copolymer does not spread well, which is attributed to interference from the hydrophobic PS block. In contrast, the 7%-PEO copolymer spreads well at the cyclohexane/water interface, producing an isotherm with a terminating mean molecular area 3 times smaller than that obtained at the air/water interface. The 15.5%-PEO copolymer spreads well at both the air/water ad cyclohexane/water interfaces due to less interference from the smaller hydrophobic PS block. These observations are compared to compression isotherms, and the results are discussed in terms of the solvating nature of the adjacent cyclohexane phase for the PS block.

  16. Extraction of proteins with ionic liquid aqueous two-phase system based on guanidine ionic liquid.

    PubMed

    Zeng, Qun; Wang, Yuzhi; Li, Na; Huang, Xiu; Ding, Xueqin; Lin, Xiao; Huang, Songyun; Liu, Xiaojie

    2013-11-15

    Eight kinds of green ionic liquids were synthesized, and an ionic liquid aqueous two-phase system (ILATPS) based on 1,1,3,3-tetramethylguandine acrylate (TMGA) guanidine ionic liquid was first time studied for the extraction of proteins. Single factor experiments proved that the extraction efficiency of bovine serum albumin (BSA) was influenced by the mass of IL, K2HPO4 and BSA, also related to the separation time and temperature. The optimum conditions were determined through orthogonal experiment by the five factors described above. The results showed that under the optimum conditions, the extraction efficiency could reach up to 99.6243%. The relative standard deviations (RSD) of extraction efficiencies in precision experiment, repeatability experiment and stability experiment were 0.8156% (n=5), 1.6173% (n=5) and 1.6292% (n=5), respectively. UV-vis and FT-IR spectra confirmed that there were no chemical interactions between BSA and ionic liquid in the extraction process, and the conformation of the protein was not changed after extraction. The conductivity, DLS and TEM were combined to investigate the microstructure of the top phase and the possible mechanism for the extraction. The results showed that hydrophobic interaction, hydrogen bonding interaction and the salt out effect played important roles in the transferring process, and the aggregation and embrace phenomenon was the main driving force for the separation. All these results proved that guanidine ionic liquid-based ATPSs have the potential to offer new possibility in the extraction of proteins. PMID:24148423

  17. Liquid-liquid phase separation in aerosol particles: Imaging at the Nanometer Scale

    SciTech Connect

    O'Brien, Rachel; Wang, Bingbing; Kelly, Stephen T.; Lundt, Nils; You, Yuan; Bertram, Allan K.; Leone, Stephen R.; Laskin, Alexander; Gilles, Mary K.

    2015-04-21

    Atmospheric aerosols can undergo phase transitions including liquid-liquid phase separation (LLPS) while responding to changes in the ambient relative humidity (RH). Here, we report results of chemical imaging experiments using environmental scanning electron microscopy (ESEM) and scanning transmission x-ray microscopy (STXM) to investigate the LLPS of micron sized particles undergoing a full hydration-dehydration cycle. Internally mixed particles composed of ammonium sulfate (AS) and either: limonene secondary organic carbon (LSOC), a, 4-dihydroxy-3-methoxybenzeneaceticacid (HMMA), or polyethylene glycol (PEG-400) were studied. Events of LLPS with apparent core-shell particle morphology were observed for all samples with both techniques. Chemical imaging with STXM showed that both LSOC/AS and HMMA/AS particles were never homogeneously mixed for all measured RH’s above the deliquescence point and that the majority of the organic component was located in the shell. The shell composition was estimated as 65:35 organic: inorganic in LSOC/AS and as 50:50 organic: inorganic for HMMA/AS. PEG-400/AS particles showed fully homogeneous mixtures at high RH and phase separated below 89-92% RH with an estimated 50:50% organic to inorganic mix in the shell. These two chemical imaging techniques are well suited for in-situ analysis of the hygroscopic behavior, phase separation, and surface composition of collected ambient aerosol particles.

  18. Growth Kinetics of Intracellular RNA/Protein Droplets: Signature of a Liquid-Liquid Phase Transition?

    NASA Astrophysics Data System (ADS)

    Berry, Joel; Weber, Stephanie C.; Vaidya, Nilesh; Zhu, Lian; Haataja, Mikko; Brangwynne, Clifford P.

    2015-03-01

    Nonmembrane-bound organelles are functional, dynamic assemblies of RNA and/or protein that can self-assemble and disassemble within the cytoplasm or nucleoplasm. The possibility that underlying intracellular phase transitions may drive and mediate the morphological evolution of some membrane-less organelles has been supported by several recent studies. In this talk, results from a collaborative experimental-theoretical study of the growth and dissolution kinetics of nucleoli and extranucleolar droplets (ENDs) in C. elegans embryos will be presented. We have employed Flory-Huggins solution theory, reaction-diffusion kinetics, and quantitative statistical dynamic scaling analysis to characterize the specific growth mechanisms at work. Our findings indicate that both in vivo and in vitro droplet scaling and growth kinetics are consistent with those resulting from an equilibrium liquid-liquid phase transition mediated by passive nonequilibrium growth mechanisms - simultaneous Brownian coalescence and Ostwald ripening. This supports a view in which cells can employ phase transitions to drive structural organization, while utilizing active processes, such as local transcriptional activity, to fine tune the kinetics of these phase transitions in response to given conditions.

  19. Olefin Epoxidation in Aqueous Phase Using Ionic-Liquid Catalysts.

    PubMed

    Cokoja, Mirza; Reich, Robert M; Wilhelm, Michael E; Kaposi, Marlene; Schäffer, Johannes; Morris, Danny S; Münchmeyer, Christian J; Anthofer, Michael H; Markovits, Iulius I E; Kühn, Fritz E; Herrmann, Wolfgang A; Jess, Andreas; Love, Jason B

    2016-07-21

    Hydrophobic imidazolium-based ionic liquids (IL) act as catalysts for the epoxidation of unfunctionalized olefins in water using hydrogen peroxide as oxidant. Although the catalysts are insoluble in both the substrate and in water, surprisingly, they are very well soluble in aqueous H2 O2 solution, owing to perrhenate-H2 O2 interactions. Even more remarkably, the presence of the catalyst also boosts the solubility of substrate in water. This effect is crucially dependent on the cation design. Hence, the imidazolium perrhenates enable both the transfer of hydrophobic substrate into the aqueous phase, and serve as actual catalysts, which is unprecedented. At the end of the reaction and in absence of H2 O2 the IL catalyst forms a third phase next to the lipophilic product and water and can easily be recycled. PMID:27219852

  20. Volume phase transitions of cholesteric liquid crystalline gels.

    PubMed

    Matsuyama, Akihiko

    2015-05-01

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels. PMID:25956120

  1. Volume phase transitions of cholesteric liquid crystalline gels

    SciTech Connect

    Matsuyama, Akihiko

    2015-05-07

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  2. The Nematic Phases of Bent-Core Liquid Crystals

    PubMed Central

    Gleeson, Helen F; Kaur, Sarabjot; Görtz, Verena; Belaissaoui, Abdel; Cowling, Stephen; Goodby, John W

    2014-01-01

    Over the last ten years, the nematic phases of liquid crystals formed from bent-core structures have provoked considerable research because of their remarkable properties. This Minireview summarises some recent measurements of the physical properties of these systems, as well as describing some new data. We concentrate on oxadiazole-based materials as exemplars of this class of nematogens, but also describe some other bent-core systems. The influence of molecular structure on the stability of the nematic phase is described, together with progress in reducing the nematic transition temperatures by modifications to the molecular structure. The physical properties of bent-core nematic materials have proven difficult to study, but patterns are emerging regarding their optical and dielectric properties. Recent breakthroughs in understanding the elastic and flexoelectric behaviour are summarised. Finally, some exemplars of unusual electric field behaviour are described. PMID:24700653

  3. Volume phase transitions of cholesteric liquid crystalline gels

    NASA Astrophysics Data System (ADS)

    Matsuyama, Akihiko

    2015-05-01

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  4. Phase Ordering in Mixtures of Liquid Crystals and Nanoparticles

    NASA Astrophysics Data System (ADS)

    Rožič, Brigita; Jagodič, Marko; Gyergyek, Sašo; Lahajnar, Gojmir; Popa-Nita, Vlad; Jagličić, Zvonko; Drofenik, Mihael; Kutnjak, Zdravko; Kralj, Samo

    We have studied the coupling interaction between liquid crystal (LC) molecules and nanoparticles (NPs) in LC=NPs mixtures. Using a simple phenomenological approach, possible structures of the coupling term are derived for strongly anisotropic NPs. The coupling terms include (i) an interaction term promoting the mutual ordering of the LC molecules and the NPs, and (ii) the Flory-Huggins-type term enforcing the phase separation. Both contributions exhibit the same scaling dependence on the diameter of the NPs. However, these terms only exist for a finite degree of nematic LC ordering. The magnetic response due to the LC-NPs coupling is probed experimentally for a mixture of weakly anisotropic magnetic NPs and a ferroelectric LC. A finite coupling effect was observed in the ferroelectric LC phase, suggesting such systems can be used as soft magnetoelectrics.

  5. Experimental investigation of bioethanol liquid phase dehydration using natural clinoptilolite

    PubMed Central

    Karimi, Samira; Ghobadian, Barat; Omidkhah, Mohammad-Reza; Towfighi, Jafar; Tavakkoli Yaraki, Mohammad

    2016-01-01

    An experimental study of bioethanol adsorption on natural Iranian clinoptilolite was carried out. Dynamic breakthrough curves were used to investigate the best adsorption conditions in bioethanol liquid phase. A laboratory setup was designed and fabricated for this purpose. In order to find the best operating conditions, the effect of liquid pressure, temperature and flow rate on breakthrough curves and consequently, maximum ethanol uptake by adsorbent were studied. The effects of different variables on final bioethanol concentration were investigated using Response Surface Methodology (RSM). The results showed that by working at optimum condition, feed with 96% (v/v) initial ethanol concentration could be purified up to 99.9% (v/v). In addition, the process was modeled using Box–Behnken model and optimum operational conditions to reach 99.9% for final ethanol concentration were found equal to 10.7 °C, 4.9 bar and 8 mL/min for liquid temperature, pressure and flow rate, respectively. Therefore, the selected natural Iranian clinoptilolite was found to be a promising adsorbent material for bioethanol dehydration process. PMID:27222748

  6. Experimental investigation of bioethanol liquid phase dehydration using natural clinoptilolite.

    PubMed

    Karimi, Samira; Ghobadian, Barat; Omidkhah, Mohammad-Reza; Towfighi, Jafar; Tavakkoli Yaraki, Mohammad

    2016-05-01

    An experimental study of bioethanol adsorption on natural Iranian clinoptilolite was carried out. Dynamic breakthrough curves were used to investigate the best adsorption conditions in bioethanol liquid phase. A laboratory setup was designed and fabricated for this purpose. In order to find the best operating conditions, the effect of liquid pressure, temperature and flow rate on breakthrough curves and consequently, maximum ethanol uptake by adsorbent were studied. The effects of different variables on final bioethanol concentration were investigated using Response Surface Methodology (RSM). The results showed that by working at optimum condition, feed with 96% (v/v) initial ethanol concentration could be purified up to 99.9% (v/v). In addition, the process was modeled using Box-Behnken model and optimum operational conditions to reach 99.9% for final ethanol concentration were found equal to 10.7 °C, 4.9 bar and 8 mL/min for liquid temperature, pressure and flow rate, respectively. Therefore, the selected natural Iranian clinoptilolite was found to be a promising adsorbent material for bioethanol dehydration process. PMID:27222748

  7. Searching for dark matter with single phase liquid argon

    NASA Astrophysics Data System (ADS)

    Caldwell, Thomas S., Jr.

    The first hint that we fail to understand the nature of a large fraction of the gravitating matter in the universe came from Fritz Zwicky's measurements of the velocity distribution of the Coma cluster in 1933. Using the Virial theorem, Zwicky found that galaxies in the cluster were orbiting far too fast to remain gravitationally bound when their mass was estimated by the brightness of the visible matter. This led to the postulation that some form of non-luminous dark matter is present in galaxies comprising a large fraction of the galactic mass. The nature of this dark matter remains yet unknown over 80 years after Zwicky's measurements despite the efforts of many experiments. Dark matter is widely believed to be a beyond the Standard Model particle which brings the dark matter problem into the realm of particle physics. Supersymmetry is one widely explored extension of the Standard model, from which particles meeting the constraints on dark matter properties can naturally arise. These particles are generically termed weakly interacting massive particles (WIMPs), and are a currently favored dark matter candidate. A variety of experimental efforts are underway aimed towards direct detection of dark matter through observation of rare scattering of WIMPs in terrestrial detectors. Single phase liquid argon detectors are an appealing WIMP detection technique due to the scintillation properties of liquid argon and the scalability of the single phase approach. The MiniCLEAN dark matter detector is a single phase liquid argon scintillation scintillation detector with a 500 kg active mass. The modular design offers 4pi coverage with 92 optical cassettes, each containing TPB coated acrylic and a cryogenic photomultiplier tube. The MiniCLEAN detector has recently completed construction at SNOLAB. The detector is currently being commissioned, and will soon begin operation with the liquid argon target. Utilizing advanced pulse-shape discrimination techniques, MiniCLEAN will

  8. Spin liquid phases of large spin Mott insulating ultracold atoms

    NASA Astrophysics Data System (ADS)

    Rutkowski, Todd C.; Lawler, Michael J.

    2015-03-01

    Understanding exotic forms of magnetism, primarily those driven by large spin fluctuations such as the quantum spin liquid state, is a major goal of condensed matter physics. But, the relatively small number of viable candidate materials poses a difficulty. We believe this problem can be solved by Mott insulating ultracold atoms with large spin moments that interact via whole-atom exchange. The large spin fluctuations of this exchange could stabilize exotic physics similar to condensed matter systems, all in an extremely tunable environment. We have approached the problem by performing a mean field theory for spin-f bosons in an optical lattice which is exact in the large-f limit. This setting is similar to that of SU(N) magnetism proposed for alkali-earth atoms but without the SU(N) symmetry. We find that states with long-range order, such as the spin nematic phase of f = 1 Na atoms, become highly entangled spin-liquid-like states for f = 3 Cr atoms. This is evidence that the magnetic phase diagram for Mott insulating atoms at larger spins generically contains exotic forms of magnetism.

  9. Comparing two tetraalkylammonium ionic liquids. II. Phase transitions.

    PubMed

    Lima, Thamires A; Paschoal, Vitor H; Faria, Luiz F O; Ribeiro, Mauro C C; Ferreira, Fabio F; Costa, Fanny N; Giles, Carlos

    2016-06-14

    Phase transitions of the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2], were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements, and Raman spectroscopy. XRD and Raman spectra were obtained as a function of temperature at atmospheric pressure, and also under high pressure at room temperature using a diamond anvil cell (DAC). [N1444][NTf2] experiences glass transition at low temperature, whereas [N1114][NTf2] crystallizes or not depending on the cooling rate. Both the ionic liquids exhibit glass transition under high pressure. XRD and low-frequency Raman spectra provide a consistent physical picture of structural ordering-disordering accompanying the thermal events of crystallization, glass transition, cold crystallization, pre-melting, and melting. Raman spectra in the high-frequency range of some specific cation and anion normal modes reveal conformational changes of the molecular structures along phase transitions. PMID:27306016

  10. Stabilizing blue phase liquid crystals with linearly polarized UV light

    NASA Astrophysics Data System (ADS)

    Xu, Daming; Yuan, Jiamin; Schadt, Martin; Yan, Jing; Wu, Shin-Tson

    2015-03-01

    Polymer-stabilized blue-phase liquid crystal (PS-BPLC) has become an increasingly important technology trend for information display and photonic applications. BPLC exhibits several attractive features, such as reasonably wide temperature range, submillisecond gray-to-gray response time, no need for alignment layer, optically isotropic voltageoff state, and large cell gap tolerance when an in-plane switching (IPS) cell is employed. However, some bottlenecks such as high operation voltage, relatively low transmittance, and noticeable hysteresis and prolonged response time at high field region for IPS mode, still remain to be overcome before widespread application of BPLC can be realized. To reduce operation voltage, both new BPLC materials and new device structures have been investigated. In this paper, we demonstrate the stabilization a photopolymer-embedded blue phase liquid crystal precursor using a linearly polarized UV light for first time. When the UV polarization axis is perpendicular to the stripe electrodes of an IPS cell, anisotropic polymer networks are formed through the linear photo-polymerization process and the electrostriction effect is suppressed. As a result, the measured hysteresis is dramatically reduced from 6.95% to 0.36% and the response time shortened by ~2X compared to unpolarized UV exposure. To induce larger anisotropy in polymer networks for mitigating the electrostriction effect, high-intensity linearly polarized UV exposure is preferred. It is foreseeable this method will guide future BPLC device and material development as well as manufacturing process. The dawn of BPLCD is near.

  11. Surface confined ionic liquid as a stationary phase for HPLC

    SciTech Connect

    Wang, Qian; Baker, Gary A; Baker, Sheila N; Colon, Luis

    2006-01-01

    Trimethoxysilane ionosilane derivatives of room temperature ionic liquids based on alkylimidazolium bromides were synthesized for attachment to silica support material. The derivatives 1-methyl-3-(trimethoxysilylpropyl)imidazolium bromide and 1-butyl-3-(trimethoxysilylpropyl)imidazolium bromide were used to modify the surface of 3 {micro}m diameter silica particles to act as the stationary phase for HPLC. The modified particles were characterized by thermogravimetric analysis (TGA) and {sup 13}C and {sup 29}Si NMR spectroscopies. The surface modification procedure rendered particles with a surface coverage of 0.84 {micro}mol m{sup -2} for the alkylimidazolium bromide. The ionic liquid moiety was predominantly attached to the silica surface through two siloxane bonds of the ionosilane derivative (63%). Columns packed with the modified silica material were tested under HPLC conditions. Preliminary evaluation of the stationary phase for HPLC was performed using aromatic carboxylic acids as model compounds. The separation mechanism appears to involve multiple interactions including ion exchange, hydrophobic interaction, and other electrostatic interactions.

  12. Comparing two tetraalkylammonium ionic liquids. II. Phase transitions

    NASA Astrophysics Data System (ADS)

    Lima, Thamires A.; Paschoal, Vitor H.; Faria, Luiz F. O.; Ribeiro, Mauro C. C.; Ferreira, Fabio F.; Costa, Fanny N.; Giles, Carlos

    2016-06-01

    Phase transitions of the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2], were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements, and Raman spectroscopy. XRD and Raman spectra were obtained as a function of temperature at atmospheric pressure, and also under high pressure at room temperature using a diamond anvil cell (DAC). [N1444][NTf2] experiences glass transition at low temperature, whereas [N1114][NTf2] crystallizes or not depending on the cooling rate. Both the ionic liquids exhibit glass transition under high pressure. XRD and low-frequency Raman spectra provide a consistent physical picture of structural ordering-disordering accompanying the thermal events of crystallization, glass transition, cold crystallization, pre-melting, and melting. Raman spectra in the high-frequency range of some specific cation and anion normal modes reveal conformational changes of the molecular structures along phase transitions.

  13. Unusual liquid-liquid phase transition in aqueous mixtures of a well-known dendrimer.

    PubMed

    da Costa, Viviana C P; Annunziata, Onofrio

    2015-11-21

    Liquid-liquid phase separation (LLPS) has been extensively investigated for polymer and protein solutions due to its importance in mixture thermodynamics, separation science and self-assembly processes. However, to date, no experimental studies have been reported on LLPS of dendrimer solutions. Here, it is shown that LLPS of aqueous solutions containing a hydroxyl-functionalized poly(amido amine) dendrimer of fourth generation is induced in the presence of sodium sulfate. Both the LLPS temperature and salt-dendrimer partitioning between the two coexisting phases at constant temperature were measured. Interestingly, our experiments show that LLPS switches from being induced by cooling to being induced by heating as the salt concentration increases. The two coexisting phases also show opposite temperature response. Thus, this phase transition exhibits a simultaneous lower and upper critical solution temperature-type behavior. Dynamic light-scattering and dye-binding experiments indicate that no appreciable conformational change occurs as the salt concentration increases. To explain the observed phase behavior, a thermodynamic model based on two parameters was developed. The first parameter, which describes dendrimer-dendrimer interaction energy, was determined by isothermal titration calorimetry. The second parameter describes the salt salting-out strength. By varying the salting-out parameter, it is shown that the model achieves agreement not only with the location of the experimental binodal at 25 °C but also with the slope of this curve around the critical point. The proposed model also predicts that the unusual temperature behavior of this phase transition can be described as the net result of two thermodynamic factors with opposite temperature responses: salt thermodynamic non-ideality and salting-out strength. PMID:26451401

  14. Application of Ionic Liquids in High Performance Reversed-Phase Chromatography

    PubMed Central

    Wang, Ye; Tian, Minglei; Bi, Wentao; Row, Kyung Ho

    2009-01-01

    Ionic liquids, considered “green” chemicals, are widely used in many areas of analytical chemistry due to their unique properties. Recently, ionic liquids have been used as a kind of novel additive in separation and combined with silica to synthesize new stationary phase as separation media. This review will focus on the properties and mechanisms of ionic liquids and their potential applications as mobile phase modifier and surface-bonded stationary phase in reversed-phase high performance liquid chromatography (RP-HPLC). Ionic liquids demonstrate advantages and potential in chromatographic field. PMID:19582220

  15. Liquid crystal gratings from nematic to blue phase

    NASA Astrophysics Data System (ADS)

    Lu, Yan-qing; Hu, Wei; Lin, Xiao-wen; Srivastava, Abhishek; Chigrinov, Vladimir G.

    2012-10-01

    Some of our recent progress on liquid crystal (LC) gratings, from nematic to blue phase, is reviewed in this invited talk. The first kind of grating is fabricated by periodically adjusting the LC directors to form alternate micro phase retarders and polarization rotators in a cell placed between crossed polarizers. The second one is demonstrated by means of photoalignment technique with alternate orthogonal homogeneously-aligned domains. To improve the response time of the gratings, several approaches are also proposed by using dual-frequency addressed nematic LC, ferroelectric LC and blue phase LC, which shows great performance including high transmittance, polarization independency and submillisecond response. At last, to obtain other controllable LC microstructures rather than simple 1D/2D gratings, we develop a micro-lithography system with a digital micro-mirror device as dynamic mask forms. It may instantly generate arbitrary micro-images on photoalignment layers and further guides the LC molecule orientations. Besides normal phase gratings, more complex patterns such as quasicrystal structures are demonstrated. Some new applications such as tunable multiport optical switching and vector beam generations are expected.

  16. Evidence for liquid phase reactions during single bubble acoustic cavitation.

    PubMed

    Troia, A; Madonna Ripa, D; Lago, S; Spagnolo, R

    2004-07-01

    We extended the recent experiment by Lepoint et al. [Sonochemistry and Sonoluminescence, NATO ASI Series, Series C 524, Kluwer Academic Publishers, Dordrecht/Boston/London, 1999, p. 285], involving a so-called single bubble sonochemistry process, to a three-phase system. We have found experimental evidence that a single cavitating bubble can activate the oxidation of I- ions after the injection of a CCl4 liquid drop in the bubble trapping apparatus. The solvent drop (CCl4 is almost water insoluble) is pushed towards the bubble position and forms a thin film on the bubble surface. When the acoustic pressure drive is increased above 100 kPa, the three-phase system gives rise to a dark filament, indicating the complexation reaction between starch (added to the water phase) and I2. I2 species is the product of surface reactions involving bubble-induced decomposition of CCl4. Further increase of the acoustic drive causes the thin CCl4 film to separate from the bubble and stops I2 production. The study of the chemical activity of this three-phase system could give new advances on dynamics of the bubble collapse. PMID:15157862

  17. Phase-Shifting Liquid Crystal Point-Diffraction Interferometry

    NASA Technical Reports Server (NTRS)

    Griffin, DeVon W.; Marshall, Kenneth L.; Mercer, Carolyn R.

    2000-01-01

    , the limited spatial resolution and the methods required for data reduction suggest that a more useful instrument needs to be developed. The category of interferometers known as common path interferometers can eliminate much of the vibration sensitivity associated with traditional interferometry as described above. In these devices, division of the amplitude of the wavefront following the test section produces the reference beam. Examples of these instruments include shearing and point diffraction interferometers. In the latter case, shown schematically, a lens focuses light passing through the test section onto a small diffracting object. Such objects are typically either a circle of material on a high quality glass plate or a small sphere in a glass cell. The size of the focused spot is several times larger than the object so that the light not intercepted by the diffracting object forms the test beam while the diffracted light generates a spherical reference beam. While this configuration is mechanically stable, phase shifting one beam with respect to the other is difficult due to the common path. Phase shifting enables extremely accurate measurements of the phase of the interferogram using only gray scale intensity measurements and is the de facto standard of industry. Mercer and Creath 2 demonstrated phase shifting in a point diffraction interferometer using a spherical spacer in a liquid crystal cell as the diffracting object. By changing the voltage across the cell, they were able to shift the phase of the undiffracted beam relative to the reference beam generated by diffraction from the sphere. While they applied this technology to fluid measurements, the device shifted phase so slowly that it was not useful for studying transient phenomena. We have identified several technical problems that precluded operation of the device at video frame rates and intend to solve them to produce a phase-shifting liquid crystal point-diffraction interferometer operating at

  18. Liquid mixture convection during phase separation in a temperature gradient

    NASA Astrophysics Data System (ADS)

    Lamorgese, A. G.; Mauri, R.

    2011-03-01

    We simulate the phase separation of a low-viscosity binary mixture, assuming that the fluid system is confined between two walls that are cooled down to different temperatures below the critical point of the mixture, corresponding to quenches within the unstable range of its phase diagram. Spinodal decomposition patterns for off-critical mixtures are studied numerically in two dimensions in the creeping flow limit and for a large Lewis number, together with their dependence on the fluidity coefficient. Our numerical results reproduce the large-scale unidirectional migration of phase-separating droplets that was observed experimentally by Califano et al. ["Large-scale, unidirectional convection during phase separation of a density-matched liquid mixture," Phys. Fluids 17, 094109 (2005)], who measured typical speeds that are quite larger than the Marangoni velocity. To understand this finding, we then studied the temperature-gradient-induced motion of an isolated droplet of the minority phase embedded in a continuous phase, showing that when the drop is near local equilibrium, its speed is of the same order as the Marangoni velocity, i.e., it is proportional to the unperturbed temperature gradient and the fluidity coefficient. However, far from local equilibrium, i.e., for very large unperturbed temperature gradients, the drop first accelerates to a speed that is larger than the Marangoni velocity, then, later, it decelerates, exhibiting an increase-decrease behavior, as described by Yin et al. ["Thermocapillary migration of nondeformable drops," Phys. Fluids 20, 082101 (2008)]. Such behavior is due to the large nonequilibrium, Korteweg-driven convection, which at first accelerates the droplets to relatively large velocities, and then tends to induce an approximately uniform inside temperature distribution so that the drop experiences an effective temperature gradient that is much smaller than the unperturbed one and, consequently, decelerates.

  19. Kinetics of diffusional droplet growth in a liquid/liquid two-phase system

    NASA Technical Reports Server (NTRS)

    Glickman, M. E.; Fradkov, V. E.

    1995-01-01

    A new powerful experimental technique based on holographic observations, developed at the NASA Marshall Space Flight Center, now permits observation of small liquid droplets coarsening. This technique was developed and used for mixed-dimensional coarsening studies. Experiments were conducted on an isopycnic two-phase alloy of succinonitrile and water, annealed isothermally over a four-month period. The succinonitrile-rich droplets precipitate from a water-rich liquid matrix having a density very close to that of the droplets. The matrix and droplets, however, have different optical indices. The results of these experiments, along with the results of computer simulation based on the quasi-static diffusion approximation developed at Rensselaer are reported. These results were published recently. Copies of these papers are attached to this report.

  20. Continuous cyclohexane oxidation to cyclohexanol using a novel cytochrome P450 monooxygenase from Acidovorax sp. CHX100 in recombinant P. taiwanensis VLB120 biofilms.

    PubMed

    Karande, Rohan; Debor, Linde; Salamanca, Diego; Bogdahn, Fabian; Engesser, Karl-Heinrich; Buehler, Katja; Schmid, Andreas

    2016-01-01

    The applications of biocatalysts in chemical industries are characterized by activity, selectivity, and stability. One key strategy to achieve high biocatalytic activity is the identification of novel enzymes with kinetics optimized for organic synthesis by Nature. The isolation of novel cytochrome P450 monooxygenase genes from Acidovorax sp. CHX100 and their functional expression in recombinant Pseudomonas taiwanensis VLB120 enabled efficient oxidation of cyclohexane to cyclohexanol. Although initial resting cell activities of 20 U gCDW (-1) were achieved, the rapid decrease in catalytic activity due to the toxicity of cyclohexane prevented synthetic applications. Cyclohexane toxicity was reduced and cellular activities stabilized over the reaction time by delivering the toxic substrate through the vapor phase and by balancing the aqueous phase mass transfer with the cellular conversion rate. The potential of this novel CYP enzyme was exploited by transferring the shake flask reaction to an aqueous-air segmented flow biofilm membrane reactor for maximizing productivity. Cyclohexane was continuously delivered via the silicone membrane. This ensured lower reactant toxicity and continuous product formation at an average volumetric productivity of 0.4 g L tube (-1) h(-1) for several days. This highlights the potential of combining a powerful catalyst with a beneficial reactor design to overcome critical issues of cyclohexane oxidation to cyclohexanol. It opens new opportunities for biocatalytic transformations of compounds which are toxic, volatile, and have low solubility in water. PMID:26153144

  1. Comparison of electrical and optical characteristics in gas-phase and gas-liquid phase discharges

    NASA Astrophysics Data System (ADS)

    Qazi, H. I. A.; Nie, Qiu-Yue; Li, He-Ping; Zhang, Xiao-Fei; Bao, Cheng-Yu

    2015-12-01

    This paper presents an AC-excited argon discharge generated using a gas-liquid (two-phase) hybrid plasma reactor, which mainly consists of a powered needle electrode enclosed in a conical quartz tube and grounded deionized water electrode. The discharges in the gas-phase, as well as in the two-phase, exhibit two discharge modes, i.e., the low current glow-like diffuse mode and the high current streamer-like constrict mode, with a mode transition, which exhibits a negative resistance of the discharges. The optical emission spectral analysis shows that the stronger diffusion of the water vapor into the discharge region in the two-phase discharges boosts up the generation of OH (A-X) radicals, and consequently, leads to a higher rotational temperature in the water-phase plasma plume than that of the gas-phase discharges. Both the increase of the power input and the decrease of the argon flow rate result in the increase of the rotational temperature in the plasma plume of the water-phase discharge. The stable two-phase discharges with a long plasma plume in the water-phase under a low power input and gas flow rate may show a promising prospect for the degradation of organic pollutants, e.g., printing and dyeing wastewater, in the field of environmental protection.

  2. Comparison of electrical and optical characteristics in gas-phase and gas-liquid phase discharges

    SciTech Connect

    Qazi, H. I. A.; Li, He-Ping Zhang, Xiao-Fei; Bao, Cheng-Yu; Nie, Qiu-Yue

    2015-12-15

    This paper presents an AC-excited argon discharge generated using a gas-liquid (two-phase) hybrid plasma reactor, which mainly consists of a powered needle electrode enclosed in a conical quartz tube and grounded deionized water electrode. The discharges in the gas-phase, as well as in the two-phase, exhibit two discharge modes, i.e., the low current glow-like diffuse mode and the high current streamer-like constrict mode, with a mode transition, which exhibits a negative resistance of the discharges. The optical emission spectral analysis shows that the stronger diffusion of the water vapor into the discharge region in the two-phase discharges boosts up the generation of OH (A–X) radicals, and consequently, leads to a higher rotational temperature in the water-phase plasma plume than that of the gas-phase discharges. Both the increase of the power input and the decrease of the argon flow rate result in the increase of the rotational temperature in the plasma plume of the water-phase discharge. The stable two-phase discharges with a long plasma plume in the water-phase under a low power input and gas flow rate may show a promising prospect for the degradation of organic pollutants, e.g., printing and dyeing wastewater, in the field of environmental protection.

  3. Liquid/liquid metal extraction: Phase diagram topology resulting from molecular interactions between extractant, ion, oil and water

    NASA Astrophysics Data System (ADS)

    Bauer, C.; Bauduin, P.; Dufrêche, J. F.; Zemb, T.; Diat, O.

    2012-11-01

    We consider the class of surfactants called "extractants" since they specifically interact with some cations and are used in liquid-liquid separation processes. We review here features of water-poor reverse micelles in water/oil/ extractant systems as determined by combined structural studies including small angle scattering techniques on absolute scale. Origins of instabilities, liquid-liquid separation as well as emulsification failure are detected. Phase diagrams contain the same multi-phase domains as classical microemulsions, but special unusual features appear due to the high spontaneous curvature directed towards the polar cores of aggregates as well as rigidity of the film made by extracting molecules.

  4. Liquid-liquid phase separation on melts and glasses in ferric ferrous oxide-silica system

    SciTech Connect

    Yasumori, A.; Koike, A.; Kameshima, Y.; Okada, K.; Yano, T.; Yamane, M.; Inoue, S.

    1997-12-31

    The existence of liquid-liquid miscibility gap in ferric ferrous oxide-silica system has been reported, however, the phase separation phenomena and the derived morphology of the phase separated glasses are uncertain. In this study, the melt-quenched samples of 5 Fe{sub 3}O{sub 4}-95 SiO{sub 2} and 15 Fe{sub 3}O{sub 4}-085 SiO{sub 2} (mol%) were prepared by melting at 2,300 C or 2,200 C (expected to be above miscibility gap), and subsequently at 1,800 C or 1,750 C (in immiscible region) by use of infrared image furnace and quenching at the rate of {approx}10{sup 2} K/sec. The glassy materials exhibited phase separation having discrete spherical particles or interconnected structure due to the composition, melting temperature and time. Also, the segregation of Fe component occurred during melting, which was caused by the difference of specific gravity of components in the melt.

  5. Feasibility assessment for a novel reverse-phase wet granulation process: the effect of liquid saturation and binder liquid viscosity.

    PubMed

    Wade, J B; Martin, G P; Long, D F

    2014-11-20

    A novel reverse-phase wet granulation process was developed and the feasibility of the process compared to a conventional wet granulation process. The reverse-phase granulation approach involves the immersion of the dry powder formulation into the binder liquid followed by controlled breakage to form granules. Conventional wisdom would warn against this approach due to the initial formation of a slurry or over-wetted powder formulation. However, a feasibility assessment of the novel approach was motivated by the potential advantages of eliminating traditional granule nucleation variables and reducing risk of uncontrolled granule growth. The effects of liquid saturation and binder liquid viscosity on the physical properties of granules formed using both the reverse-phase and conventional granulation processes were compared. Liquid saturation significantly affected the physical properties of granules prepared using both processes. At liquid saturation up to ∼1 the reverse-phase process typically resulted in larger, less porous granules than the conventional process. However, at a liquid saturation >1.1 the conventional process exhibited uncontrolled growth and significantly larger granule size as a result of decreased intragranular porosity. The response to liquid saturation was seen as a steady growth mechanism for the reverse-phase process compared to an induction growth mechanism for the conventional process, indicating potential robustness advantages of the reverse-phase approach. Despite institutional perceptions to the contrary, the reverse-phase process was shown to be feasible and merits further detailed investigation. PMID:25218187

  6. Effects of cyclohexane, an industrial solvent, on the yeast Saccharomyces cerevisiae and on isolated yeast mitochondria

    SciTech Connect

    Uribe, S.; Rangel, P.; Espinola, G.; Aguirre, G. )

    1990-07-01

    Little information on the effects of cyclohexane at the cellular or subcellular level is available. In Saccharomyces cerevisiae, cyclohexane inhibited respiration and diverse energy-dependent processes. In mitochondria isolated from S. cerevisiae, oxygen uptake and ATP synthesis were inhibited, although ATPase activity was not affected. Cyclohexane effects were similar to those reported for beta-pinene and limonene, suggesting that the cyclohexane ring in these monoterpenes may be a determinant for their biological activities.

  7. Method for forming single phase, single crystalline 2122 BCSCO superconductor thin films by liquid phase epitaxy

    NASA Technical Reports Server (NTRS)

    Pandey, Raghvendra K. (Inventor); Raina, Kanwal (Inventor); Solayappan, Narayanan (Inventor)

    1994-01-01

    A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83 K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

  8. Imidazoline type stationary phase for hydrophilic interaction chromatography and reversed-phase liquid chromatography.

    PubMed

    Li, Yuanyuan; Feng, Yaoyao; Chen, Tong; Zhang, Haixia

    2011-09-01

    An imidazoline was prepared by solvent-free microwave-assisted organic synthesis and immobilized on porous silica particles by polymerization. The resulting material was composed of both hydrophobic alkyl ester chains and hydrophilic imidazoline rings, which gave it both hydrophilic interaction and reversed-phase characteristics. The titration curve suggests that the new material has buffering capacity and acquires increasing positive charge over the pH range 9-4, and is "zwitterionic" in the upper part of this pH range. Through investigating the effect of column temperature, the water content, pH and ion strength of mobile phase on the retention time of polar compounds in highly organic eluents, it was found that the new material could be used as a hydrophilic interaction liquid chromatography (HILIC) stationary phase which involved a complex retention process consisting of partitioning, surface adsorption and electrostatic interactions. In addition, the retention behavior of aromatic compounds in different mobile phase conditions was also studied, which showed the new material mainly exhibited a partitioning mechanism in the reversed-phase liquid chromatography (RPLC) mode. The separation of six water-soluble vitamins and five aromatic compounds were achieved by using the new material in the HILIC and RPLC modes, respectively. PMID:21543075

  9. The Frozen State in the Liquid Phase of Side-Chain Liquid-Crystal Polymers

    NASA Astrophysics Data System (ADS)

    Mendil, H.; Noirez, L.; Baroni, P.; Grillo, I.

    2006-02-01

    Quenched isotropic melts of side-chain liquid-crystal polymers reveal surprisingly an anisotropic polymer conformation. This small-angle neutron-scattering (SANS) result is consistent with the identification of a macroscopic, solidlike response in the isotropic phase. Both experiments (rheology and SANS) indicate that the polymer system appears frozen on millimeter length scales and at the time scales of the observation. This result implies that the flow behavior is not the terminal behavior and that cross-links or entanglements are not a necessary condition to provide elasticity in melts.

  10. A phase-stepped point diffraction interferometer using liquid crystals

    NASA Technical Reports Server (NTRS)

    Mercer, Carolyn R.; Creath, Katherine; Rashidnia, Nasser

    1995-01-01

    A new instrument, the liquid crystal point diffraction interferometer (LCPDI), has been developed for the measurement of phase objects. This instrument maintains the compact, robust design of Linnik's point diffraction interferometer (PDI) and adds to it phase stepping capability for quantitative interferogram analysis. The result is a compact, simple to align, environmentally insensitive interferometer capable of accurately measuring optical wavefronts with high data density and with automated data reduction. The design of the LCPDI is briefly discussed. An algorithm is presented for eliminating phase measurement error caused by object beam intensity variation from frame-to-frame. The LCPDI is demonstrated by measuring the temperature distribution across a heated chamber filled with silicone oil. The measured results are compared to independently measured results and show excellent agreement with them. It is expected that this instrument will have application in the fluid sciences as a diagnostic tool, particularly in space based applications where autonomy, robustness, and compactness are desirable qualities. It should also be useful for the testing of optical elements, provided a master is available for comparison.

  11. Two-phase and three-phase liquid-phase microextraction of hydrochlorothiazide and triamterene in urine samples.

    PubMed

    Ahmad Panahi, Homayon; Ejlali, Maryam; Chabouk, Monireh

    2016-07-01

    This paper reports the applicability of two-phase and three-phase hollow fiber based liquid-phase microextraction (HF-LPME) for the extraction of hydrochlorothiazide (HYD) and triamterene (TRM) from human urine. The HYD in two-phase HF-LPME is extracted from 24 mL of the aqueous sample into an organic phase with microliter volume located inside the pores and lumen of a polypropylene hollow fiber as acceptor phase, but the TRM in three-phase HF-LPME is extracted from aqueous donor phase to organic phase and then back-extracted to the aqueous acceptor phase, which can be directly injected into HPLC for analysis. Under optimized conditions preconcentration factors of HYD and TRM were obtained as 128 and 239, respectively. The calibration curves were linear (R(2)  ≥ 0.995) in the concentration range of 1.0-100 µg/L for HYD and 2.0-100 µg/L for TRM. The limits of detection for HYD and TRM were 0.5 µg/L. The intra-day and inter-day RSD based on four replicates were obtained as ≤5.8 and ≤9.3%, respectively. The methods were successfully applied for determining the concentration of the drugs in urine samples. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26542449

  12. Structure analysis of turbulent liquid phase by POD and LSE techniques

    SciTech Connect

    Munir, S. Muthuvalu, M. S.; Siddiqui, M. I.; Heikal, M. R. Aziz, A. Rashid A.

    2014-10-24

    In this paper, vortical structures and turbulence characteristics of liquid phase in both single liquid phase and two-phase slug flow in pipes were studied. Two dimensional velocity vector fields of liquid phase were obtained by Particle image velocimetry (PIV). Two cases were considered one single phase liquid flow at 80 l/m and second slug flow by introducing gas at 60 l/m while keeping liquid flow rate same. Proper orthogonal decomposition (POD) and Linear stochastic estimation techniques were used for the extraction of coherent structures and analysis of turbulence in liquid phase for both cases. POD has successfully revealed large energy containing structures. The time dependent POD spatial mode coefficients oscillate with high frequency for high mode numbers. The energy distribution of spatial modes was also achieved. LSE has pointed out the coherent structured for both cases and the reconstructed velocity fields are in well agreement with the instantaneous velocity fields.

  13. Phase behavior and rheological analysis of reverse liquid crystals and W/I2 and W/H2 gel emulsions using an amphiphilic block copolymer.

    PubMed

    May, Anna; Aramaki, Kenji; Gutiérrez, José María

    2011-03-15

    This article reports the phase behavior determi-nation of a system forming reverse liquid crystals and the formation of novel disperse systems in the two-phase region. The studied system is formed by water, cyclohexane, and Pluronic L-121, an amphiphilic block copolymer considered of special interest due to its aggregation and structural properties. This system forms reverse cubic (I2) and reverse hexagonal (H2) phases at high polymer concentrations. These reverse phases are of particular interest since in the two-phase region, stable high internal phase reverse emulsions can be formed. The characterization of the I2 and H2 phases and of the derived gel emulsions was performed with small-angle X-ray scattering (SAXS) and rheometry, and the influence of temperature and water content was studied. The H2 phase experimented a thermal transition to an I2 phase when temperature was increased, which presented an Fd3m structure. All samples showed a strong shear thinning behavior from low shear rates. The elastic modulus (G') in the I2 phase was around 1 order of magnitude higher than in the H2 phase. G' was predominantly higher than the viscous modulus (G''). In the gel emulsions, G' was nearly frequency-independent, indicating their gel type nature. Contrarily to water-in-oil (W/O) normal emulsions, in W/I2 and W/H2 gel emulsions, G', the complex viscosity (|η*|), and the yield stress (τ0) decreased with increasing water content, since the highly viscous microstructure of the continuous phase was responsible for the high viscosity and elastic behavior of the emulsions, instead of the volume fraction of dispersed phase and droplet size. A rheological analysis, in which the cooperative flow theory, the soft glass rheology model, and the slip plane model were analyzed and compared, was performed to obtain one single model that could describe the non-Maxwellian behavior of both reverse phases and highly concentrated emulsions and to characterize their microstructure with

  14. RNA footprinting analysis using ion pair reverse phase liquid chromatography.

    PubMed Central

    Dickman, Mark J; Conroy, Matthew J; Grasby, Jane A; Hornby, David P

    2002-01-01

    Hydroxyl radical footprinting is a powerful technique often employed in characterization of the tertiary interactions between proteins and nucleic acids. Following the generation of a nucleic acid "ladder" either by chemical or enzymatic reactions, the radiolabeled products are traditionally separated by denaturing gel electrophoresis and further quantified by phosphorimaging techniques. Here we report the use of ion pair reverse phase liquid chromatography to analyze the products of an RNA footprinting reaction using fluorescently labeled RNA molecules. This technique offers several advantages over existing procedures, including rapid analysis, automation, and direct quantification of the cleavage products without the need to employ radiolabeling. To illustrate the resolving power of this technique, we have analyzed the products of base hydrolysis, generated from a fluorescently labeled RNA molecule and have subsequently used this method to define the solvent accessibility of the substrate strand as it docks with the hairpin ribozyme. PMID:11911369

  15. Phase diagrams of orientational transitions in absorbing nematic liquid crystals

    SciTech Connect

    Zolot’ko, A. S. Ochkin, V. N.; Smayev, M. P.; Shvetsov, S. A.

    2015-05-15

    A theory of orientational transitions in nematic liquid crystals (NLCs), which employs the expansion of optical torques acting on the NLC director with respect to the rotation angle, has been developed for NLCs with additives of conformationally active compounds under the action of optical and low-frequency electric and magnetic fields. Phase diagrams of NLCs are constructed as a function of the intensity and polarization of the light field, the strength of low-frequency electric field, and a parameter that characterizes the feedback between the rotation of the NLC director and optical torque. Conditions for the occurrence of first- and second-order transitions are determined. The proposed theory agrees with available experimental data.

  16. Isotropic and nematic liquid crystalline phases of adaptive rotaxanes

    NASA Astrophysics Data System (ADS)

    He, Hao; Sevick, Edith M.; Williams, David R. M.

    2016-03-01

    We describe the thermodynamics of a solution of rotaxanes which can change their length from a short state of length L to a long state of length qL in response to their surrounding environment. We call these rotaxanes "adaptive." We show that such a system can exhibit both isotropic and nematic liquid crystalline phases. The system shows several interesting kinds of behaviour. First we predict that the fraction of short-length rotaxanes increases linearly with concentration and is a maximum at the critical concentration that marks the isotropic to nematic transition. Second, the critical concentration shows a minimum at a certain value of q. Our model suggests that the effect of adaptive length changes is most dramatic at small q and where the long state is slightly favoured.

  17. Orientational Phase Ordering in Disordered Liquid Crystalline Heteropolymers

    NASA Astrophysics Data System (ADS)

    Gutman, Lorin; Shakhnovich, Eugene I.

    2000-03-01

    Liquid-crystalline disordered heteropolymers (DLCPs) are studied by a novel creation-annihilation method and replica field theory. The 0 disorder limit of theory is the non-perturbative (A. M. Gupta and S. F. Edwards J. Chem. Phys., 98, 1588, (1993)) result for long homopolymer chains. Sequence disorder, alignment propensity, stiffness and lyotropic effects on orientational phase ordering and coexistence width are studied numerically by unconstrained iteration of principal axis of segment orientational tensors; It is shown that sequence heterogeneity impacts strongly the density order/disorder threshold and the Maxwell construction shows a three fold increase in coexistence width compared with the homopolymer analogue. The non-equilibrium meta-stable domain scale, obtained by calculation of Doring free energy from field theory and nucleation theory is of the order of μ m, in agreement with recent experiments on DLCPs.

  18. Thermal conductivity of alternative refrigerants in the liquid phase

    SciTech Connect

    Yata, J.; Hori, M.; Kobayashi, K.; Minamiyama, T.

    1996-05-01

    Measurements of the thermal conductivity of five alternative refrigerants, namely, difluoromethane (HFC-32), pentafluoroethane (HFC-125), 1,1,1-trifluorethane (HFC-143a), and dichloropentafluoropropanes (HCFC-225ca and HCFC-225cb), are carried out in the liquid phase. The range of temperature is 253-324 K for HFC-32, 257-305 K for HFC-125, 268-314 K for HFC-134a, 267-325 K for HCF-225ca, and 286-345 K for HCFC-225cb. The pressure range is from saturation to 30 MPa. The reproducibility of the data is better than 0.5%, and the accuracy of the data is estimated to be of the order of 1%. The experimental results for the thermal conductivity of each substance are correlated by an equation which is a function of temperature and pressure. A short discussion is given to the comparison of the present results with literature values for HFC-125. The saturated liquid thermal conductivity values of HFC-32, HFC-125, and HFC-143a are compared with those of chlorodifluoromethane (HCFC-22) and tetrafluoroethane (HFC-134a) and it is shown that the value of HFC-32 is highest, while that of HFC-125 is lowest, among these substances. The dependence of thermal conductivity on number of fluorine atoms among the refrigerants with the same number of carbon and hydrogen atoms is discussed.

  19. Non-aqueous phase liquid spreading during soil vapor extraction

    NASA Astrophysics Data System (ADS)

    Kneafsey, Timothy J.; Hunt, James R.

    2004-02-01

    Many non-aqueous phase liquids (NAPLs) are expected to spread at the air-water interface, particularly under non-equilibrium conditions. In the vadose zone, this spreading should increase the surface area for mass transfer and the efficiency of volatile NAPL recovery by soil vapor extraction (SVE). Observations of spreading on water wet surfaces led to a conceptual model of oil spreading vertically above a NAPL pool in the vadose zone. Analysis of this model predicts that spreading can enhance the SVE contaminant recovery compared to conditions where the liquid does not spread. Experiments were conducted with spreading volatile oils hexane and heptane in wet porous media and capillary tubes, where spreading was observed at the scale of centimeters. Within porous medium columns up to a meter in height containing stagnant gas, spreading was less than ten centimeters and did not contribute significantly to hexane volatilization. Water film thinning and oil film pinning may have prevented significant oil film spreading, and thus did not enhance SVE at the scale of a meter. The experiments performed indicate that volatile oil spreading at the field scale is unlikely to contribute significantly to the efficiency of SVE.

  20. Non-Fermi liquid phase in metallic Skyrmion crystals

    NASA Astrophysics Data System (ADS)

    Watanabe, Haruki; Parameswaran, Siddharth; Raghu, Srinivas; Vishwanath, Ashvin

    2014-03-01

    Motivated by reports of a non-Fermi liquid state in MnSi, we examine the effect of coupling phonons of an incommensurate skyrmion crystal (SkX) to conduction electrons. We find that non-Fermi liquid behavior emerges in both two and three dimensions over the entire phase, due to an anomalous electron-phonon coupling that is linked to the net skyrmion density. A small parameter, the spiral wave vector in lattice units, allows us to exercise analytic control and ignore Landau damping of phonons over a wide energy range. At the lowest energy scales the problem is similar to electrons coupled to a gauge field. The best prospects for realizing these effects is in short period skyrmion lattice systems such as MnGe or epitaxial MnSi films. We also compare our results with the unusual T 3 / 2 scaling of temperature dependent resistivity seen in high pressure experiments on MnSi. We acknowledge support from the NSF via Grant DMR-0645691, the DOE Office of Basic Energy Sciences via contract DE-AC02-76SF00515, and the Simons, Templeton, and Alfred P. Sloan Foundations.

  1. Semiphenomenological model for gas-liquid phase transitions.

    PubMed

    Benilov, E S; Benilov, M S

    2016-03-01

    We examine a rarefied gas with inter-molecular attraction. It is argued that the attraction force amplifies random density fluctuations by pulling molecules from lower-density regions into high-density regions and thus may give rise to an instability. To describe this effect, we use a kinetic equation where the attraction force is taken into account in a way similar to how electromagnetic forces in plasma are treated in the Vlasov model. It is demonstrated that the instability occurs when the temperature T is lower than a certain threshold value T(s) depending on the gas density. It is further shown that, even if T is only marginally lower than T(s), the instability generates clusters with density much higher than that of the gas. These results suggest that the instability should be interpreted as a gas-liquid phase transition, with T(s) being the temperature of saturated vapor and the high-density clusters representing liquid droplets. PMID:27078333

  2. Solvent systems for countercurrent chromatography: an aqueous two phase liquid system based on a room temperature ionic liquid.

    PubMed

    Ruiz-Angel, Maria Jose; Pino, Veronica; Carda-Broch, Samuel; Berthod, Alain

    2007-06-01

    A new aqueous two phase liquid system (ATPS) based on the ionic liquid 1-butyl-3-methyl imidazolium chloride (BMIM Cl), potassium dibasic phosphate (K(2)HPO(4)) and water was recently proposed in the literature. The full phase diagram of this ATPS was prepared and some tie lines were fully determined. It was compared to classical ATPSs based on polyethylene glycol with an average molecular mass of 1000 (PEG 1000) and 10,000 (PEG 10000) and K(2)HPO(4). Two countercurrent chromatography (CCC) columns, a hydrostatic Sanki and a J type hydrodynamic CCC columns were used to test the liquid phase retention of these ATPSs in all possible configurations. It was found that the BMIM Cl ATPS liquid phases were much easier to retain in the two CCC columns than the PEG 1000 ATPS phases. Using protein and alcohol solutes, it was established that the BMIM Cl ATPS has a polarity completely different from that of the PEG 1000 ATPS. For example, ovalbumin partitions equally between the two phases of the PEG 1000 ATPS (K(D)=1.4) when it is completely located in the BMIM Cl upper phase of the ionic liquid ATPS (K(D)=180). The discrimination factor of the ionic liquid system and its intrinsic hydrophobicity were respectively found three times higher and ten times lower than the respective values of the PEG 1000 ATPS. PMID:17166506

  3. Synthesis, structure and phase behavior of liquid crystalline polyurethanes

    SciTech Connect

    Papadimitrakopoulos, F.

    1993-01-01

    This dissertation describes the synthesis, structure and phase behavior of polyurethanes based on the mesogenic biphenol 4,4'-bis (6-hydroxyhexoxy)biphenyl (BHHBP) and meta substituted tolylene/phenylene diisocynates. The structure-property relationships were determined as a function of hydrogen-bonding, the position of the methyl group in the tolylene diisocyanate moiety (TDI) and the biphenol moiety. The liquid crystalline phase (mesophase) and crystalline phase were investigated primarily with differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and infrared spectroscopy. The influence of H-bonding on the structure and phase behavior of 1,4-LCPU-6 was determined by the synthesis of high molecular weight N-Methyl2,4-LCPU-65, using a novel high temperature polymerization of a biscarbamoyl chloride with the BHHBP mesogenic diol. In contrast to the regular ([alpha], [omega]-hexane diol) based polyurethanes (PUs), BHHBP derived polyurethanes (LCPUs) crystallize rapidly from their melts. Hexafluoroisopropanol fast solvent-evaporation casting or rapid cooling from the melt resulted in thin films or bulk samples with a glassy mesophase morphology. During the subsequent heating scan, the mesophase to crystal transition occurs. Highly oriented fibers were obtained for the mesogenic polyurethanes. Atomistic molecular simulations coupled with X-ray intensity refinement allowed determination of the crystalline chain conformation and packing characteristics for the 2,6-LCPU-6 and 1,3-LCPU-6 (2,6-TDI and 1,3-Phenylene Diisocynate (1,3-PDI) derived LCPUs). On the basis of structural similarity and well resolved WAXS powder patterns similar analysis was extended to the regular polyurethanes as well (2,6-PU-6 and 1,3-PU-6). The good correlation polymers suggest that melting is primarily controlled by the dissociation of H-bonds in the ordered domains.

  4. Low Density Phases in a Uniformly Charged Liquid

    NASA Astrophysics Data System (ADS)

    Knüpfer, Hans; Muratov, Cyrill B.; Novaga, Matteo

    2016-07-01

    This paper is concerned with the macroscopic behavior of global energy minimizers in the three-dimensional sharp interface unscreened Ohta-Kawasaki model of diblock copolymer melts. This model is also referred to as the nuclear liquid drop model in the studies of the structure of highly compressed nuclear matter found in the crust of neutron stars, and, more broadly, is a paradigm for energy-driven pattern forming systems in which spatial order arises as a result of the competition of short-range attractive and long-range repulsive forces. Here we investigate the large volume behavior of minimizers in the low volume fraction regime, in which one expects the formation of a periodic lattice of small droplets of the minority phase in a sea of the majority phase. Under periodic boundary conditions, we prove that the considered energy {Γ}-converges to an energy functional of the limit "homogenized" measure associated with the minority phase consisting of a local linear term and a non-local quadratic term mediated by the Coulomb kernel. As a consequence, asymptotically the mass of the minority phase in a minimizer spreads uniformly across the domain. Similarly, the energy spreads uniformly across the domain as well, with the limit energy density minimizing the energy of a single droplet per unit volume. Finally, we prove that in the macroscopic limit the connected components of the minimizers have volumes and diameters that are bounded above and below by universal constants, and that most of them converge to the minimizers of the energy divided by volume for the whole space problem.

  5. Redistribution of black carbon in aerosol particles undergoing liquid-liquid phase separation

    NASA Astrophysics Data System (ADS)

    Brunamonti, S.; Krieger, U. K.; Marcolli, C.; Peter, T.

    2015-04-01

    Atmospheric black carbon (BC) is a major anthropogenic greenhouse agent, yet substantial uncertainties obstruct understanding its radiative forcing. Particularly debated is the extent of the absorption enhancement by internally compared to externally mixed BC, which critically depends on the interior morphology of the BC-containing particles. Here we suggest that a currently unaccounted morphology, optically very different from the customary core-shell and volume-mixing assumptions, likely occurs in aerosol particles undergoing liquid-liquid phase separation (LLPS). Using Raman spectroscopy on micrometer-sized droplets, we show that LLPS of an organic/inorganic model system drives redistribution of BC into the outer (organic) phase of the host particle. This results in an inverted core-shell structure, in which a transparent aqueous core is surrounded by a BC-containing absorbing shell. Based on Mie theory calculations, we estimate that such a redistribution can increase the absorption efficiency of internally mixed BC aerosols by up to 25% compared to the core-shell approximation.

  6. Interplay of the Glass Transition and the Liquid-Liquid Phase Transition in Water

    PubMed Central

    Giovambattista, Nicolas; Loerting, Thomas; Lukanov, Boris R.; Starr, Francis W.

    2012-01-01

    Water has multiple glassy states, often called amorphous ices. Low-density (LDA) and high-density (HDA) amorphous ice are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation connects to a first-order liquid-liquid phase transition (LLPT) above the glass transition temperature Tg. Direct experimental evidence of the LLPT is challenging to obtain, since the LLPT occurs at conditions where water rapidly crystallizes. In this work, we explore the implications of a LLPT on the pressure dependence of Tg(P) for LDA and HDA by performing computer simulations of two water models – one with a LLPT, and one without. In the absence of a LLPT, Tg(P) for all glasses nearly coincide. When there is a LLPT, different glasses exhibit dramatically different Tg(P) which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario including a LLPT. PMID:22550566

  7. Methylammonium formate as a mobile phase modifier for reversed-phase liquid chromatography

    PubMed Central

    Grossman, Shau; Danielson, Neil D.

    2009-01-01

    Although alkylammonium ionic liquids such as ethylammonium nitrate and ethylammonium formate have been used as mobile phase “solvents” for liquid chromatography (LC), we have shown that methylammonium formate (MAF), in part because of its lower viscosity, can be an effective replacement for methanol (MeOH) in reversed-phase LC. Plots of log retention factor versus the fraction of MeOH and MAF in the mobile phase indicate quite comparable solvent strength slope values of 2.50 and 2.05, respectively. Using a polar endcapped C18 column, furazolidone and nitrofurantoin using 20% MAF-80% water could be separated in 22 min but no baseline separation was possible using MeOH as the modifier, even down to 10%. Suppression of silanol peak broadening effects by MAF is important permitting a baseline separation of pyridoxine, thiamine, and nicotinamide using 5% MAF-95% water at 0.7 mL/min. Using 5% MeOH-95% water, severe peak broadening for thiamine is evident. The compatibility of MAF as a mobile phase modifer for LC with mass spectrometry detection of water soluble vitamins is also shown. PMID:18849044

  8. Extensive database of liquid phase diffusion coefficients of some frequently used test molecules in reversed-phase liquid chromatography and hydrophilic interaction liquid chromatography.

    PubMed

    Song, Huiying; Vanderheyden, Yoachim; Adams, Erwin; Desmet, Gert; Cabooter, Deirdre

    2016-07-15

    Diffusion plays an important role in all aspects of band broadening in chromatography. An accurate knowledge of molecular diffusion coefficients in different mobile phases is therefore crucial in fundamental column performance studies. Correlations available in literature, such as the Wilke-Chang equation, can provide good approximations of molecular diffusion under reversed-phase conditions. However, these correlations have been demonstrated to be less accurate for mobile phases containing a large percentage of acetonitrile, as is the case in hydrophilic interaction liquid chromatography. A database of experimentally measured molecular diffusion coefficients of some 45 polar and apolar compounds that are frequently used as test molecules under hydrophilic interaction liquid chromatography and reversed-phase conditions is therefore presented. Special attention is given to diffusion coefficients of polar compounds obtained in large percentages of acetonitrile (>90%). The effect of the buffer concentration (5-10mM ammonium acetate) on the obtained diffusion coefficients is investigated and is demonstrated to mainly influence the molecular diffusion of charged molecules. Diffusion coefficients are measured using the Taylor-Aris method and hence deduced from the peak broadening of a solute when flowing through a long open tube. The validity of the set-up employed for the measurement of the diffusion coefficients is demonstrated by ruling out the occurrence of longitudinal diffusion, secondary flow interactions and extra-column effects, while it is also shown that radial equilibration in the 15m long capillary is effective. PMID:27240944

  9. Graphene via sonication assisted liquid-phase exfoliation.

    PubMed

    Ciesielski, Artur; Samorì, Paolo

    2014-01-01

    Graphene, the 2D form of carbon based material existing as a single layer of atoms arranged in a honeycomb lattice, has set the science and technology sectors alight with interest in the last decade in view of its astounding electrical and thermal properties, combined with its mechanical stiffness, strength and elasticity. Two distinct strategies have been undertaken for graphene production, i.e. the bottom-up and the top-down. The former relies on the generation of graphene from suitably designed molecular building blocks undergoing chemical reaction to form covalently linked 2D networks. The latter occurs via exfoliation of graphite into graphene. Bottom-up techniques, based on the organic syntheses starting from small molecular modules, when performed in liquid media, are both size limited, because macromolecules become more and more insoluble with increasing size, and suffer from the occurrence of side reactions with increasing molecular weight. Because of these reasons such a synthesis has been performed more and more on a solid (ideally catalytically active) surface. Substrate-based growth of single layers can be done also by chemical vapor deposition (CVD) or via reduction of silicon carbide, which unfortunately relies on the ability to follow a narrow thermodynamic path. Top-down approaches can be accomplished under different environmental conditions. Alongside the mechanical cleavage based on the scotch tape approach, liquid-phase exfoliation (LPE) methods are becoming more and more interesting because they are extremely versatile, potentially up-scalable, and can be used to deposit graphene in a variety of environments and on different substrates not available using mechanical cleavage or growth methods. Interestingly, LPE can be applied to produce different layered systems exhibiting different compositions such as BN, MoS2, WS2, NbSe2, and TaS2, thereby enabling the tuning of numerous physico-chemical properties of the material. Furthermore, LPE can be

  10. The Influence of Disorder on Thermotropic Nematic Liquid Crystals Phase Behavior

    PubMed Central

    Popa-Nita, Vlad; Gerlič, Ivan; Kralj, Samo

    2009-01-01

    We review the theoretical research on the influence of disorder on structure and phase behavior of condensed matter system exhibiting continuous symmetry breaking focusing on liquid crystal phase transitions. We discuss the main properties of liquid crystals as adequate systems in which several open questions with respect to the impact of disorder on universal phase and structural behavior could be explored. Main advantages of liquid crystalline materials and different experimental realizations of random field-type disorder imposed on liquid crystal phases are described. PMID:19865529

  11. Phase-Shifting Liquid Crystal Point-Diffraction Interferometry

    NASA Technical Reports Server (NTRS)

    Griffin, DeVon W.; Marshall, Kenneth L.; Mercer, Carolyn R.

    2000-01-01

    , the limited spatial resolution and the methods required for data reduction suggest that a more useful instrument needs to be developed. The category of interferometers known as common path interferometers can eliminate much of the vibration sensitivity associated with traditional interferometry as described above. In these devices, division of the amplitude of the wavefront following the test section produces the reference beam. Examples of these instruments include shearing and point diffraction interferometers. In the latter case, shown schematically, a lens focuses light passing through the test section onto a small diffracting object. Such objects are typically either a circle of material on a high quality glass plate or a small sphere in a glass cell. The size of the focused spot is several times larger than the object so that the light not intercepted by the diffracting object forms the test beam while the diffracted light generates a spherical reference beam. While this configuration is mechanically stable, phase shifting one beam with respect to the other is difficult due to the common path. Phase shifting enables extremely accurate measurements of the phase of the interferogram using only gray scale intensity measurements and is the de facto standard of industry. Mercer and Creath 2 demonstrated phase shifting in a point diffraction interferometer using a spherical spacer in a liquid crystal cell as the diffracting object. By changing the voltage across the cell, they were able to shift the phase of the undiffracted beam relative to the reference beam generated by diffraction from the sphere. While they applied this technology to fluid measurements, the device shifted phase so slowly that it was not useful for studying transient phenomena. We have identified several technical problems that precluded operation of the device at video frame rates and intend to solve them to produce a phase-shifting liquid crystal point-diffraction interferometer operating at

  12. Determination of liquid-liquid critical point composition using 90∘ laser light scattering

    NASA Astrophysics Data System (ADS)

    Williamson, J. Charles; Brown, Allison M.; Helvie, Elise N.; Dean, Kevin M.

    2016-04-01

    Despite over a century of characterization efforts, liquid-liquid critical point compositions are difficult to identify with good accuracy. Reported values vary up to 10% for even well-studied systems. Here, a technique is presented for high-precision determination of the critical composition of a partially miscible binary liquid system. Ninety-degree laser light-scattering intensities from single-phase samples are analyzed using an equation derived from nonclassical power laws and the pseudospinodal approximation. Results are reported for four liquid-liquid systems (aniline + hexane, isobutyric acid + water, methanol + cyclohexane, and methanol + carbon disulfide). Compared to other methods, the 90∘ light-scattering approach has a strong dependence on composition near the critical point, is less affected by temperature fluctuations, and is insensitive to the presence of trace impurities in the samples. Critical compositions found with 90∘ light scattering are precise to the parts-per-thousand level and show long-term reproducibility.

  13. Liquid phase deposition synthesis of hexagonal molybdenum trioxide thin films

    SciTech Connect

    Deki, Shigehito; Beleke, Alexis Bienvenu; Kotani, Yuki; Mizuhata, Minoru

    2009-09-15

    Hexagonal molybdenum trioxide thin films with good crystallinity and high purity have been fabricated by the liquid phase deposition (LPD) technique using molybdic acid (H{sub 2}MoO{sub 4}) dissolved in 2.82% hydrofluoric acid (HF) and H{sub 3}BO{sub 3} as precursors. The crystal was found to belong to a hexagonal hydrate system MoO{sub 3}.nH{sub 2}O (napprox0.56). The unit cell lattice parameters are a=10.651 A, c=3.725 A and V=365.997 A{sup 3}. Scanning electron microscope (SEM) images of the as-deposited samples showed well-shaped hexagonal rods nuclei that grew and where the amount increased with increase in reaction time. X-ray photon electron spectroscopy (XPS) spectra showed a Gaussian shape of the doublet of Mo 3d core level, indicating the presence of Mo{sup 6+} oxidation state in the deposited films. The deposited films exhibited an electrochromic behavior by lithium intercalation and deintercalation, which resulted in coloration and bleaching of the film. Upon dehydration at about 450 deg. C, the hexagonal MoO{sub 3}.nH{sub 2}O was transformed into the thermodynamically stable orthorhombic phase. - Abstract: SEM photograph of typical h-MoO{sub 3}.nH{sub 2}O thin film nuclei obtained after 36 h at 40 deg. C by the LPD method. Display Omitted

  14. An overview of multidimensional liquid phase separations in food analysis.

    PubMed

    Franco, Maraíssa Silva; Padovan, Rodrigo Nogueira; Fumes, Bruno Henrique; Lanças, Fernando Mauro

    2016-07-01

    Food safety is a priority public health concern that demands analytical methods capable to detect low concentration level of contaminants (e.g. pesticides and antibiotics) in different food matrices. Due to the high complexity of these matrices, a sample preparation step is in most cases mandatory to achieve satisfactory results being usually tedious, lengthy, and prone to the introduction of errors. For this reason, many research groups have focused efforts on the development of online systems capable to do the cleanup, concentration, and separation steps at once through multidimensional separation techniques (MDS). Among several possible setups, the most popular are the multidimensional chromatographic techniques (MDC) that consist in combining more than one mobile and/or stationary phase to provide a satisfactory separation. In the present review, we selected a variety of multidimensional separation systems used for food contaminant analysis in order to discuss the instrumentation aspects, the concept of orthogonality, column approaches used in these systems, and new materials that can be used in these columns. Selected classes of contaminants present in food matrices are introduced and discussed as example of the potential applications of multidimensional liquid phase separation techniques in food safety. PMID:27030380

  15. Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy

    PubMed Central

    Zhou, Shengqiang; Liu, Fang; Prucnal, S.; Gao, Kun; Khalid, M.; Baehtz, C.; Posselt, M.; Skorupa, W.; Helm, M.

    2015-01-01

    Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability. PMID:25660096

  16. Tertiary phase diagram of cellulose, ionic liquid and organic solvent

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Henderson, Doug; Tyagi, Madhusudan; Mao, Yimin; Briber, Robert M.; Wang, Howard

    Cellulose is the most abundant natural polymer on earth, and widely used in products from clothing to paper. Fundamental understanding of molecular solutions of cellulose is the key to realize advanced technologies beyond cellulose fibers. It has been reported that certain ionic liquid/organic solvent mixtures dissolve cellulose. In this study, the tertiary phase diagram of microcrystalline cellulose, 1-Ethyl-3-methylimidazolium acetate (EMIMAc), and dimethylformamide (DMF) mixtures has been determined using optical cloud point method and small angle neutron scattering (SANS). Data indicate that a molar ratio of EMIMAc to cellulose repeating unit equal or greater than 3 is necessary but not sufficient in forming one-phase homogeneous solutions. A miscibility gap exists in the dilute regime, where a minimum of 5 mol% of EMIM Ac in DMF is needed to form homogenous solutions. SANS show that cellulose chains adopt Gaussian-like conformation in homogenous solutions. The solutions exhibit the characteristics of upper critical solution temperature. Clustering of cellulose chains occurs at low EMIMAc/DMF or EMIMAc/cellulose ratio, or at low temperatures. The mechanism of cellulose dissolution in tertiary mixture is discussed.

  17. Impedance Spectroscopy of Liquid-Phase Sintered Silicon Carbide

    SciTech Connect

    McLachlan, D.S.; Sauti, G.; Vorster, A.; Hermann, M.

    2004-02-26

    Liquid-Phase Sintered Silicon Carbide (LPSSiC) materials were produced with different Y2O3: Al2O3 and Y2O3: SiO2 sintering additive ratios. Densification was achieved by hot pressing (HP). The ratio of the polytypes and the amount and crystalline composition of the grain boundary phases was determined using Rietveld analysis. Microstructures of the materials were related to the mechanical properties (hardness, fracture toughness and strength), which are not presented. The impedance Spectroscopy measurements were made at temperatures between 100 deg. C and 400 deg. C and analyzed using Effective Media Theories and the Brick Layer Model. In some cases, in order to correctly fit the results, it was necessary to use or model the frequency dependence of the conductivity or dielectric constant of the SiC grains using various theoretical models. The impedance arcs for the SiC grains in the different samples varied widely, probably more due to the 'semiconductor' doping of the grains or nonstoichiometry, than the SiC polytypes in the grains. The SiC grains all showed an Arrhenius behavior with energy gaps in the range 0.3 to 0.5eV.

  18. Debris cloud characterization in the liquid-vapor phase

    SciTech Connect

    Chhabildas, L.C.; Boslough, M.B.; Reinhart, W.D.; Hall, C.A.

    1993-10-01

    A series of experiments has been performed on the Sandia Hypervelocity Launcher to impact a 1.25-mm thick aluminum bumper by an aluminum flier plate 17-mm diameter by 0.92-mm thick over the velocity range of 5 km/s to 11 km/s. Radiographic techniques were employed to record the debris cloud generated upon impact. The shape of the debris cloud is found to depend on the flier plate tilt. Generally the data indicate a central core of higher density surrounded by a diffused layer. These experiments allow measurements of debris cloud expansion velocities as the material undergoes a phase change from solid fragments at impact velocities of 5 km/s to a mixture of liquid and vapor phase at higher impact velocities. The expansion velocity of the debris cloud increases with increasing impact velocity, with the high-density leading edge traveling faster than the impact velocity. There is a difference between the X-ray and photographic measurements of expansion velocities at higher impact velocities. This is believed to be due to the presence of very low- density vapor in the photographic records that are not detected using X-ray techniques.

  19. Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy.

    PubMed

    Zhou, Shengqiang; Liu, Fang; Prucnal, S; Gao, Kun; Khalid, M; Baehtz, C; Posselt, M; Skorupa, W; Helm, M

    2015-01-01

    Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability. PMID:25660096

  20. Impedance Spectroscopy of Liquid-Phase Sintered Silicon Carbide

    NASA Astrophysics Data System (ADS)

    McLachlan, D. S.; Sauti, G.; Vorster, A.; Hermann, M.

    2004-02-01

    Liquid-Phase Sintered Silicon Carbide (LPSSiC) materials were produced with different Y2O3: Al2O3 and Y2O3: SiO2 sintering additive ratios. Densification was achieved by hot pressing (HP). The ratio of the polytypes and the amount and crystalline composition of the grain boundary phases was determined using Rietveld analysis. Microstructures of the materials were related to the mechanical properties (hardness, fracture toughness and strength), which are not presented. The impedance Spectroscopy measurements were made at temperatures between 100°C and 400°C and analyzed using Effective Media Theories and the Brick Layer Model. In some cases, in order to correctly fit the results, it was necessary to use or model the frequency dependence of the conductivity or dielectric constant of the SiC grains using various theoretical models. The impedance arcs for the SiC grains in the different samples varied widely, probably more due to the "semiconductor" doping of the grains or nonstoichiometry, than the SiC polytypes in the grains. The SiC grains all showed an Arrhenius behavior with energy gaps in the range 0.3 to 0.5eV.

  1. Reversible Nanoparticle Cubic Lattices in Blue Phase Liquid Crystals.

    PubMed

    Gharbi, Mohamed Amine; Manet, Sabine; Lhermitte, Julien; Brown, Sarah; Milette, Jonathan; Toader, Violeta; Sutton, Mark; Reven, Linda

    2016-03-22

    Blue phases (BPs), a distinct class of liquid crystals (LCs) with 3D periodic ordering of double twist cylinders involving orthogonal helical director twists, have been theoretically studied as potential templates for tunable colloidal crystals. Here, we report the spontaneous formation of thermally reversible, cubic crystal nanoparticle (NP) assemblies in BPs. Gold NPs, functionalized to be highly miscible in cyanobiphenyl-based LCs, were dispersed in BP mixtures and characterized by polarized optical microscopy and synchrotron small-angle X-ray scattering (SAXS). The NPs assemble by selectively migrating to periodic strong trapping sites in the BP disclination lines. The NP lattice, remarkably robust given the small particle size (4.5 nm diameter), is commensurate with that of the BP matrix. At the BP I to BP II phase transition, the NP lattice reversibly switches between two different cubic structures. The simultaneous presence of two different symmetries in a single material presents an interesting opportunity to develop novel dynamic optical materials. PMID:26900753

  2. Purification of flavonoids from licorice using an off-line preparative two-dimensional normal-phase liquid chromatography/reversed-phase liquid chromatography method.

    PubMed

    Fan, Yunpeng; Fu, Yanhui; Fu, Qing; Cai, Jianfeng; Xin, Huaxia; Dai, Mei; Jin, Yu

    2016-07-01

    An orthogonal (71.9%) off-line preparative two-dimensional normal-phase liquid chromatography/reversed-phase liquid chromatography method coupled with effective sample pretreatment was developed for separation and purification of flavonoids from licorice. Most of the nonflavonoids were firstly removed using a self-made Click TE-Cys (60 μm) solid-phase extraction. In the first dimension, an industrial grade preparative chromatography was employed to purify the crude flavonoids. Click TE-Cys (10 μm) was selected as the stationary phase that provided an excellent separation with high reproducibility. Ethyl acetate/ethanol was selected as the mobile phase owing to their excellent solubility for flavonoids. Flavonoids co-eluted in the first dimension were selected for further purification using reversed-phase liquid chromatography. Multiple compounds could be isolated from one normal-phase fraction and some compounds with bad resolution in one-dimensional liquid chromatography could be prepared in this two-dimensional system owing to the orthogonal separation. Moreover, this two-dimensional liquid chromatography method was beneficial for the preparation of relatively trace flavonoid compounds, which were enriched in the first dimension and further purified in the second dimension. Totally, 24 flavonoid compounds with high purity were obtained. The results demonstrated that the off-line two-dimensional liquid chromatography method was effective for the preparative separation and purification of flavonoids from licorice. PMID:27214649

  3. Enhancement of gas-phase diffusion in the presence of liquid

    NASA Astrophysics Data System (ADS)

    Webb, S.; Angert, A.

    2003-04-01

    Gas diffusion in porous media occurs in both the gas and liquid phases. In many instances, gas diffusion in the liquid phase is ignored. However, under many conditions, gas diffusion in the liquid phase may be more important than gas diffusion in the gas phase. Two different cases will be examined in this work. The first case is a continuous liquid path between the gas concentrations of interest modeled after Jury et al. (1984). The second case is the situation at low liquid saturation where liquid islands exist. For the first case, Jury's model can be rewritten as a ratio of the total gas diffusion in the gas and liquid phases to that just in the gas phase. The liquid diffusion coefficient is approximately 10-4 times the gas diffusion coefficient consistent with Jury et al. (1984). The ratio of total diffusion to gas-phase diffusion is then only a function of Henry's constant and the liquid saturation. For higher values of Henry's constant, such as for CO2 and O2, the effect of diffusion in the liquid phase is small except at high liquid saturations. For small values of Henry's constant, such as for some VOCs and explosive compounds, diffusion in the liquid phase dominates for low and moderate liquid saturation values. The second case is the enhancement of diffusion caused by liquid islands at low liquid saturation. Enhanced vapor diffusion across liquid islands has been observed and modeled by Webb and Ho (1999), where condensation and evaporation occur on opposite ends of the liquid island. Vapor diffusion enhancement of up to a factor of 10 has been observed. Similarly, gas can diffuse through the liquid island. For high values of Henry's constant, gas diffusion through liquid islands is negligible and can be ignored. For small values of Henry's constant, diffusion through liquid islands may be much greater than diffusion through gas, so the rate is enhanced. The work was sponsored by the Geneva International Center for Humanitarian Demining (GICHD) under the

  4. Phase separations in mixtures of a liquid crystal and a nanocolloidal particle

    NASA Astrophysics Data System (ADS)

    Matsuyama, Akihiko

    2009-11-01

    We present a mean field theory to describe phase separations in mixtures of a liquid crystal and a nanocolloidal particle. By taking into account a nematic, a smectic A ordering of the liquid crystal, and a crystalline ordering of the nanoparticle, we calculate the phase diagrams on the temperature-concentration plane. We predict various phase separations, such as a smectic A-crystal phase separation and a smectic A-isotropic-crystal triple point, etc., depending on the interactions between the liquid crystal and the colloidal surface. Inside binodal curves, we find new unstable and metastable regions, which are important in the phase ordering dynamics. We also find a crystalline ordering of the nanoparticles dispersed in a smectic A phase and a nematic phase. The cooperative phenomena between liquid-crystalline ordering and crystalline ordering induce a variety of phase diagrams.

  5. Phase separations in mixtures of a liquid crystal and a nanocolloidal particle.

    PubMed

    Matsuyama, Akihiko

    2009-11-28

    We present a mean field theory to describe phase separations in mixtures of a liquid crystal and a nanocolloidal particle. By taking into account a nematic, a smectic A ordering of the liquid crystal, and a crystalline ordering of the nanoparticle, we calculate the phase diagrams on the temperature-concentration plane. We predict various phase separations, such as a smectic A-crystal phase separation and a smectic A-isotropic-crystal triple point, etc., depending on the interactions between the liquid crystal and the colloidal surface. Inside binodal curves, we find new unstable and metastable regions, which are important in the phase ordering dynamics. We also find a crystalline ordering of the nanoparticles dispersed in a smectic A phase and a nematic phase. The cooperative phenomena between liquid-crystalline ordering and crystalline ordering induce a variety of phase diagrams. PMID:19947706

  6. Two-Phase Model of Liquid-Liquid Interactions With Interface Capturing: Application to Water Assisted Injection Molding

    NASA Astrophysics Data System (ADS)

    Silva, Luisa; Lanrivain, Rodolphe; Zerguine, Walid; Rodriguez-Villa, Andrès; Coupez, Thierry

    2007-05-01

    In this paper, a two phase model to compute liquid-liquid flows is presented. We consider that one phase is a highly viscous thermodependent liquid (polymer phase), whereas the second one is a low viscosity low temperature fluid (water). The first part of this paper concerns capture of the interface between the water and the polymer (or determination of the phase field function). Classical VOF and Level set techniques have been implemented and were ameliorated using mesh adaptation techniques. To accurately determine the velocity field, a two-phase formulation is considered, based in the theory of mixtures, and we introduce a scalar parameter, the phase fraction quantifying the presence of each phase in each point of the computational domain. A friction type coupling between both phases is retained. Using the mixed finite element method within an eulerian framework, we calculate in a single system the whole kinematic variables for both liquids (velocity and pressure of each phase). Results are shown, for 2D and 3D parts.

  7. Liquid crystal phases of two-dimensional dipolar gases and Berezinskii-Kosterlitz-Thouless melting

    PubMed Central

    Wu, Zhigang; Block, Jens K.; Bruun, Georg M.

    2016-01-01

    Liquid crystals are phases of matter intermediate between crystals and liquids. Whereas classical liquid crystals have been known for a long time and are used in electro-optical displays, much less is known about their quantum counterparts. There is growing evidence that quantum liquid crystals play a central role in many electron systems including high temperature superconductors, but a quantitative understanding is lacking due to disorder and other complications. Here, we analyse the quantum phase diagram of a two-dimensional dipolar gas, which exhibits stripe, nematic and supersolid phases. We calculate the stiffness constants determining the stability of the nematic and stripe phases, and the melting of the stripes set by the proliferation of topological defects is analysed microscopically. Our results for the critical temperatures of these phases demonstrate that a controlled study of the interplay between quantum liquid and superfluid phases is within experimental reach for the first time, using dipolar gases. PMID:26750156

  8. Liquid crystal phases of two-dimensional dipolar gases and Berezinskii-Kosterlitz-Thouless melting

    NASA Astrophysics Data System (ADS)

    Wu, Zhigang; Block, Jens K.; Bruun, Georg M.

    2016-01-01

    Liquid crystals are phases of matter intermediate between crystals and liquids. Whereas classical liquid crystals have been known for a long time and are used in electro-optical displays, much less is known about their quantum counterparts. There is growing evidence that quantum liquid crystals play a central role in many electron systems including high temperature superconductors, but a quantitative understanding is lacking due to disorder and other complications. Here, we analyse the quantum phase diagram of a two-dimensional dipolar gas, which exhibits stripe, nematic and supersolid phases. We calculate the stiffness constants determining the stability of the nematic and stripe phases, and the melting of the stripes set by the proliferation of topological defects is analysed microscopically. Our results for the critical temperatures of these phases demonstrate that a controlled study of the interplay between quantum liquid and superfluid phases is within experimental reach for the first time, using dipolar gases.

  9. Liquid crystal phases of two-dimensional dipolar gases and Berezinskii-Kosterlitz-Thouless melting.

    PubMed

    Wu, Zhigang; Block, Jens K; Bruun, Georg M

    2016-01-01

    Liquid crystals are phases of matter intermediate between crystals and liquids. Whereas classical liquid crystals have been known for a long time and are used in electro-optical displays, much less is known about their quantum counterparts. There is growing evidence that quantum liquid crystals play a central role in many electron systems including high temperature superconductors, but a quantitative understanding is lacking due to disorder and other complications. Here, we analyse the quantum phase diagram of a two-dimensional dipolar gas, which exhibits stripe, nematic and supersolid phases. We calculate the stiffness constants determining the stability of the nematic and stripe phases, and the melting of the stripes set by the proliferation of topological defects is analysed microscopically. Our results for the critical temperatures of these phases demonstrate that a controlled study of the interplay between quantum liquid and superfluid phases is within experimental reach for the first time, using dipolar gases. PMID:26750156

  10. Preparation and evaluation of surface-bonded tricationic ionic liquid silica as stationary phases for high-performance liquid chromatography.

    PubMed

    Qiao, Lizhen; Shi, Xianzhe; Lu, Xin; Xu, Guowang

    2015-05-29

    Two tricationic ionic liquids were prepared and then bonded onto the surface of supporting silica materials through "thiol-ene" click chemistry as new stationary phases for high-performance liquid chromatography. The obtained columns of tricationic ionic liquids were evaluated respectively in the reversed-phase liquid chromatography (RPLC) mode and hydrophilic interaction liquid chromatography (HILIC) mode, and possess ideal column efficiency of 80,000 plates/m in the RPLC mode with naphthalene as the test solute. The tricationic ionic liquid stationary phases exhibit good hydrophobic and shape selectivity to hydrophobic compounds, and RPLC retention behavior with multiple interactions. In the HILIC mode, the retention and selectivity were evaluated through the efficient separation of nucleosides and bases as well as flavonoids, and the typical HILIC retention behavior was demonstrated by investigating retention changes of hydrophilic solutes with water volume fraction in mobile phase. The results show that the tricationic ionic liquid columns possess great prospect for applications in analysis of hydrophobic and hydrophilic samples. PMID:25890438

  11. Nanoparticle-induced widening of the temperature range of liquid-crystalline blue phases

    NASA Astrophysics Data System (ADS)

    Karatairi, Eva; Rožič, Brigita; Kutnjak, Zdravko; Tzitzios, Vassilios; Nounesis, George; Cordoyiannis, George; Thoen, Jan; Glorieux, Christ; Kralj, Samo

    2010-04-01

    Liquid-crystalline blue phases exhibit exceptional properties for applications in the display and sensor industry. However, in single component systems, they are stable only for very narrow temperature range between the isotropic and the chiral nematic phase, a feature that severely hinders their applicability. Systematic high-resolution calorimetric studies reveal that blue phase III is effectively stabilized in a wide temperature range by mixing surface-functionalized nanoparticles with chiral liquid crystals. This effect is present for two liquid crystals, yielding a robust method to stabilize blue phases, especially blue phase III. Theoretical arguments show that the aggregation of nanoparticles at disclination lines is responsible for the observed effects.

  12. Switchable liquid-crystal phase-shift mask for super-resolution photolithography based on Pancharatnam-Berry phase

    NASA Astrophysics Data System (ADS)

    Glazar, Nikolaus; Culbreath, Christopher; Li, Yannian; Yokoyama, Hiroshi

    2015-11-01

    We present a novel liquid-crystal-based phase-shift mask that utilizes the Pancharatnam-Berry phase for super-resolution photolithography. Using an automated maskless photoalignment technique, we pattern an azobenzene alignment layer in a nematic liquid-crystal cell to fabricate the mask. Since the image is formed by phase cancellation, the minimum feature size is not restricted by the diffraction limit; here, we obtain submicron features. The liquid-crystal properties of the cell allow the mask to be switched on and off by applying a voltage. The cost effectiveness and flexibility of this technique make it a promising new technology for photolithography.

  13. Ultrasonic velocity and absorption study of binary mixtures of cyclohexane with acrylonitrile by interferometric method at different frequencies

    NASA Astrophysics Data System (ADS)

    Pawar, N. R.; Chimankar, O. P.; Bhandakkar, V. D.; Padole, N. N.

    2012-12-01

    The ultrasonic velocity (u), absorption (α), density (ρ), and viscosity (η) has been measured at different frequencies (1MHz to 10MHz) in the binary mixtures of cyclohexane with acrylonitriile over the entire range of composition at temperature 303K. Vander Waal's constant (b), adiabatic compressibility (βa), acoustic impedance (Z), molar volume (V), free length (Lf), free volume, internal pressure, intermolecular radius and relative association have been also calculated. A special application for acrylonitrile is in the manufacture of carbon fibers. These are produced by paralysis of oriented poly acrylonitrile fibers and are used to reinforce composites for high-performance applications in the aircraft, defense and aerospace industries. Other applications of acrylonitrile are in the production of fatty amines, ion exchange resins and fatty amine amides used in cosmetics, adhesives, corrosion inhibitors and water-treatment resins. Cyclohexane derivatives can be used for the synthesis of pharmaceuticals, dyes, herbicides, plant growth regulator, plasticizers, rubber chemicals, nylon, cyclamens and other organic compounds. In the view of these extensive applications of acrylonitrile and cyclohexane in the engineering process, textile and pharmaceutical industries present study provides qualitative information regarding the nature and strength of interaction in the liquid mixtures through derive parameters from ultrasonic velocity and absorption measurement.

  14. The Boson peak in confined water: An experimental investigation of the liquid-liquid phase transition hypothesis

    NASA Astrophysics Data System (ADS)

    Mallamace, Francesco; Corsaro, Carmelo; Mallamace, Domenico; Wang, Zhe; Chen, Sow-Hsin

    2015-10-01

    The Boson peak (BP) of deeply cooled confined water is studied by using inelastic neutron scattering (INS) in a large interval of the ( P, T) phase plane. By taking into account the different behavior of such a collective vibrational mode in both strong and fragile glasses as well as in glass-forming materials, we were able to determine the Widom line that characterizes supercooled bulk water within the frame of the liquid-liquid phase transition (LLPT) hypothesis. The peak frequency and width of the BP correlated with the water polymorphism of the LLPT scenario, allowing us to distinguish the "low-density liquid" (LDL) and "high-density liquid" (HDL) phases in deeply cooled bulk water.Moreover, the BP properties afford a further confirmation of theWidom line temperature T W as the ( P, T) locus in which the local structure of water transforms from a predominately LDL form to a predominately HDL form.

  15. Liquid-liquid phase equilibrium and core-shell structure formation in immiscible Al-Bi-Sn alloys

    NASA Astrophysics Data System (ADS)

    Li, Mingyang; Jia, Peng; Sun, Xiaofei; Geng, Haoran; Zuo, Min; Zhao, Degang

    2016-04-01

    In this paper, the liquid-phase separation of ternary immiscible Al45Bi19.8Sn35.2 and Al60Bi14.4Sn25.6 melts was studied with resistivity and thermal analysis methods at different temperature. The resistivity-temperature curves appear abrupt and anomalously change with rising temperature, corresponding to the anomalous and low peak of melting process in DSC curves, indicative of the occurrence of the liquid-phase separation. The anomalous behavior of the resistivity temperature dependence is attributable to concentration-concentration fluctuations. The effect of composition and melt temperature on the liquid-phase separation and core-shell structure formation in immiscible Al-Bi-Sn alloys was studied. The liquid-phase separation and formation of the core-shell structure in immiscible Al-Bi-Sn alloys are readily acquired when the alloy compositions fall into liquid miscibility gap. What's more, the cross-sectional structure changes from irregular, dispersed to core-type shapes under the actions of Marangoni motion with increasing melt temperature. This study provides some clues for the preparation of core-shell microspheres of immiscible Al-Bi-Sn alloys via liquid-phase separation.

  16. Evidence of a Liquid-Liquid Phase Transition Hot Dense Hydrogen

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac; Dzyabura, Vasily; Zaghoo, Mohamed

    2013-03-01

    We use pulsed laser heating of hydrogen at static pressures in the megabar pressure region generated in a diamond anvil cell to search for the plasma phase transition (PPT) to liquid atomic metallic hydrogen. Heating the sample substantially above the melting line we observe a plateau in a temperature vs laser power curve that otherwise increases with power. This anomaly in the heating curve is closely correlated with theoretical predictions for the PPT, falling within the theoretically predicted range and having a negative slope with increasing pressure. Details will be presented. The NSF, grant DMR-0804378 and the DOE Stockpile Stewardship Academic Alliance program, grant DE-FG52-10NA29656 supported this research.

  17. Crosslinked polymeric ionic liquids as solid-phase microextraction sorbent coatings for high performance liquid chromatography.

    PubMed

    Yu, Honglian; Merib, Josias; Anderson, Jared L

    2016-03-18

    Neat crosslinked polymeric ionic liquid (PIL) sorbent coatings for solid-phase microextraction (SPME) compatible with high-performance liquid chromatography (HPLC) are reported for the first time. Six structurally different PILs were crosslinked to nitinol supports and applied for the determination of select pharmaceutical drugs, phenolics, and insecticides. Sampling conditions including sample solution pH, extraction time, desorption solvent, desorption time, and desorption solvent volume were optimized using design of experiment (DOE). The developed PIL sorbent coatings were stable when performing extractions under acidic pH and remained intact in various organic desorption solvents (i.e., methanol, acetonitrile, acetone). The PIL-based sorbent coating polymerized from the IL monomer 1-vinyl-3-(10-hydroxydecyl) imidazolium chloride [VC10OHIM][Cl] and IL crosslinker 1,12-di(3-vinylbenzylimidazolium) dodecane dichloride [(VBIM)2C12] 2[Cl] exhibited superior extraction performance compared to the other studied PILs. The extraction efficiency of pharmaceutical drugs and phenolics increased when the film thickness of the PIL-based sorbent coating was increased while many insecticides were largely unaffected. Satisfactory analytical performance was obtained with limits of detection (LODs) ranging from 0.2 to 2 μg L(-1) for the target analytes. The accuracy of the analytical method was examined by studying the relative recovery of analytes in real water samples, including tap water and lake water, with recoveries varying from 50.2% to 115.9% and from 48.8% to 116.6%, respectively. PMID:26896916

  18. Characterization of annular two-phase gas-liquid flows in microgravity

    NASA Technical Reports Server (NTRS)

    Bousman, W. Scott; Mcquillen, John B.

    1994-01-01

    A series of two-phase gas-liquid flow experiments were developed to study annular flows in microgravity using the NASA Lewis Learjet. A test section was built to measure the liquid film thickness around the perimeter of the tube permitting the three dimensional nature of the gas-liquid interface to be observed. A second test section was used to measure the film thickness, pressure drop and wall shear stress in annular microgravity two-phase flows. Three liquids were studied to determine the effects of liquid viscosity and surface tension. The result of this study provide insight into the wave characteristics, pressure drop and droplet entrainment in microgravity annular flows.

  19. Non-equilibrium phase transitions in a liquid crystal

    NASA Astrophysics Data System (ADS)

    Dan, K.; Roy, M.; Datta, A.

    2015-09-01

    The present manuscript describes kinetic behaviour of the glass transition and non-equilibrium features of the "Nematic-Isotropic" (N-I) phase transition of a well known liquid crystalline material N-(4-methoxybenzylidene)-4-butylaniline from the effects of heating rate and initial temperature on the transitions, through differential scanning calorimetry (DSC), Fourier transform infrared and fluorescence spectroscopy. Around the vicinity of the glass transition temperature (Tg), while only a change in the baseline of the ΔCp vs T curve is observed for heating rate (β) > 5 K min-1, consistent with a glass transition, a clear peak for β ≤ 5 K min-1 and the rapid reduction in the ΔCp value from the former to the latter rate correspond to an order-disorder transition and a transition from ergodic to non-ergodic behaviour. The ln β vs 1000/T curve for the glass transition shows convex Arrhenius behaviour that can be explained very well by a purely entropic activation barrier [Dan et al., Eur. Phys. Lett. 108, 36007 (2014)]. Fourier transform infrared spectroscopy indicates sudden freezing of the out-of-plane distortion vibrations of the benzene rings around the glass transition temperature and a considerable red shift indicating enhanced coplanarity of the benzene rings and, consequently, enhancement in the molecular ordering compared to room temperature. We further provide a direct experimental evidence of the non-equilibrium nature of the N-I transition through the dependence of this transition temperature (TNI) and associated enthalpy change (ΔH) on the initial temperature (at fixed β-values) for the DSC scans. A plausible qualitative explanation based on Mesquita's extension of Landau-deGennes theory [O. N. de Mesquita, Braz. J. Phys. 28, 257 (1998)] has been put forward. The change in the molecular ordering from nematic to isotropic phase has been investigated through fluorescence anisotropy measurements where the order parameter, quantified by the

  20. Molecular dynamics study of cyclohexane interconversion

    NASA Astrophysics Data System (ADS)

    Wilson, Michael A.; Chandler, David

    1990-12-01

    Classical molecular dynamics calculations are reported for one C 6H 12 molecule in a bath of 250 CS 2 molecules at roomtemperature and liquid densities of 1.0, 1.3, 1.4 and 1.5 g/cm 3. The solvent contribution to the free energy of activation for the chair-boat isomerization has been determined to high accuracy. The transmission coefficient and reactive flux correlation functions have also been computed. The results obtained agree with earlier conclusions drawn from RISM integral equation calculations and stochastic molecular dynamics calculations. Namely, the solvent effect on the rate manifests a qualitative breakdown of transition state theory and the RRKM picture of unimolecular kinetics. Analysis of the activated trajectories indicate a significant degree of quasiperiodicity.

  1. Phase Transition and Dynamics in Imidazolium-Based Ionic Liquid Crystals through a Metastable Highly Ordered Smectic Phase.

    PubMed

    Nozaki, Yoko; Yamaguchi, Keito; Tomida, Kenji; Taniguchi, Natsumi; Hara, Hironori; Takikawa, Yoshinori; Sadakane, Koichiro; Nakamura, Kenji; Konishi, Takashi; Fukao, Koji

    2016-06-16

    The phase transition behavior and dynamics of ionic liquid crystals, 1-methyl-3-alkylimidazolium tetrafluoroborate with various alkyl chain lengths, were investigated by X-ray scattering, differential scanning calorimetry, optical microscopy, and dielectric relaxation spectroscopy to elucidate the mechanism of their structural and phase changes. A metastable phase was found to appear via a supercooled smectic phase on cooling. In the metastable phase, disorder in the smectic phase is partially frozen; thus, the phase has order higher than that of the smectic phase but lower than that of the crystalline phase. During the subsequent heating process, the frozen disorder activates, and a crystalline phase appears in the supercooled smectic phase before entering the smectic phase. The relationship between the phase behavior and the dynamics of charge carriers such as ions is also discussed. PMID:27195480

  2. Liquid-vapor phase equilibrium in a tin-selenium system

    NASA Astrophysics Data System (ADS)

    Volodin, V. N.; Burabaeva, N. M.; Trebukhov, S. A.

    2014-12-01

    Based on the pressure of the saturated vapor and components over liquid alloys in a tin-selenium system, determined using the boiling points approach (isothermal variant), its boiling point and corresponding vapor phase composition are calculated in the region of liquid solutions. The phase diagram is supple-mented with the liquid-vapor phase transition under atmospheric pressure and in vacuums of 100 and 10 Pa with the boundaries of the region in which the regions of liquid and vapor coexist being determined.

  3. Laser-induced separation of hydrogen isotopes in the liquid phase

    DOEpatents

    Freund, Samuel M.; Maier, II, William B.; Beattie, Willard H.; Holland, Redus F.

    1980-01-01

    Hydrogen isotope separation is achieved by either (a) dissolving a hydrogen-bearing feedstock compound in a liquid solvent, or (b) liquefying a hydrogen-bearing feedstock compound, the liquid phase thus resulting being kept at a temperature at which spectral features of the feedstock relating to a particular hydrogen isotope are resolved, i.e., a clear-cut isotope shift is delineated, irradiating the liquid phase with monochromatic radiation of a wavelength which at least preferentially excites those molecules of the feedstock containing a first hydrogen isotope, inducing photochemical reaction in the excited molecules, and separating the reaction product containing the first isotope from the liquid phase.

  4. A binary phase field crystal study for liquid phase heteroepitaxial growth

    NASA Astrophysics Data System (ADS)

    Lu, Yanli; Peng, Yingying; Chen, Zheng

    2016-09-01

    The liquid phase heteroepitaxial growth on predefined crystalline substrate is studied with binary phase field crystal (PFC) model. The purpose of this paper focuses on changes of the morphology of epitaxial films, influences of substrate vicinal angles on epitaxial growth, characteristics of islands growth on both sides of the substrate as well. It is found that the morphology of epitaxial films undergoes the following transitions: layer-by-layer growth, islands formation, mismatch dislocations nucleation and climb towards the film-substrate interface. Meanwhile, the density of steps and islands has obviously direct ratio relations with the vicinal angles. Also, preferential regions are found when islands grow on both sides of the substrate. For thinner substrate, the arrangement of islands is more orderly and the appearance of preferential growth is more obvious than that of thicker substrate. Also, the existing of preferential regions is much more valid for small substrate vicinal angles in contrast for big substrate vicinal angles.

  5. Adsorption of isopropanol and cyclohexane on zinc oxide

    NASA Astrophysics Data System (ADS)

    Bratchikova, I. G.; Pylinina, A. I.; Platonov, E. A.; Danilova, M. N.; Isaeva, N. Yu.; Yagodovskii, V. D.

    2015-01-01

    Adsorption isotherms of isopropanol and cyclohexane are obtained in the range of 234-303 K on an initial surface of zinc oxide and after its treatment with glow-discharge plasma in O2 and high-frequency plasma in Ar. The values of isosteric heat and adsorption entropy are shown to be only slightly affected by these treatments. It is found that the acidity of the surface increases by 38 and 97%, respectively, and the acidic sites are not adsorption sites for either adsorbate. At low degrees of occupation, the adsorption isotherms of (CH3)2CHOH are described by an equation of induced adsorption whose parameters are dependent on the plasma-chemical treatments. It is concluded that adsorbed isopropanol particles exist in positively and negatively charged forms. The adsorption of cyclohexane is described by the Hill-de Boer equation for the initial ZnO surface, and by the Langmuir equation after plasma-chemical treatments.

  6. Separation of gas from liquid in a two-phase flow system

    NASA Technical Reports Server (NTRS)

    Hayes, L. G.; Elliott, D. G.

    1973-01-01

    Separation system causes jets which leave two-phase nozzles to impinge on each other, so that liquid from jets tends to coalesce in center of combined jet streams while gas phase is forced to outer periphery. Thus, because liquid coalescence is achieved without resort to separation with solid surfaces, cycle efficiency is improved.

  7. Centrifugal contactor with liquid mixing and flow control vanes and method of mixing liquids of different phases

    SciTech Connect

    Jubin, R.T.; Randolph, J.D.

    1991-06-18

    This patent describes a centrifugal contactor for solvent extraction systems. The centrifugal contactor is provided with an annular vertically oriented mixing chamber between the rotor housing and the rotor for mixing process liquids such as the aqueous and organic phases of the solvent extraction process used for nuclear fuel reprocessing. A set of stationary helically disposed vanes carried by the housing is in the lower region of the mixing chamber at a location below the process-liquid inlets for the purpose of urging the liquids in an upward direction toward the inlets and enhancing the mixing of the liquids and mass transfer between the liquids. The upper region of the mixing vessel above the inlets for the process liquids is also provided with a set helically disposed vanes carried by the housing for urging the process liquids in a downward direction when the liquid flow rates through the inlets are relatively high and the liquids contact the vane set in the upper region. The use of these opposing vane sets in the mixing zone maintains the liquid in the mixing zone at suitable levels.

  8. A polarization-independent liquid crystal phase modulation using polymer-network liquid crystal with orthogonal alignment layers

    NASA Astrophysics Data System (ADS)

    Chen, Ming-Syuan; Lin, Wei-Chih; Tsou, Yu-Shih; Lin, Yi-Hsin

    2012-10-01

    A polarization-independent liquid crystal (LC) phase modulation using polymer-network liquid crystals with orthogonal alignments layers (T-PNLC) is demonstrated. T-PNLC consists of three layers. LC directors in the two layers near glass substrates are orthogonal to each other. In the middle layer, LC directors are perpendicular to the glass substrate. The advantages of such T-PNLC include polarizer-free, larger phase shift (~0.4π rad) than the residual phase type (<0.05π rad), and low operating voltage (< 30Vrms). It does not require bias voltage for avoiding scattering because the refractive index of liquid crystals matches that of polymers. The phase shift of T-PNLC is affected by the cell gap and the curing voltages. The potential applications are laser beam steering, spatial light modulators and electrically tunable micro-lens arrays.

  9. Numerical Modeling of Liquid-Vapor Phase Change

    NASA Technical Reports Server (NTRS)

    Esmaeeli, Asghar; Arpaci, Vedat S.

    2001-01-01

    We implemented a two- and three-dimensional finite difference/front tracking technique to solve liquid-vapor phase change problems. The mathematical and the numerical features of the method were explained in great detail in our previous reports, Briefly, we used a single formula representation which incorporated jump conditions into the governing equations. The interfacial terms were distributed as singular terms using delta functions so that the governing equations would be the same as conventional conservation equations away from the interface and in the vicinity of the interface they would provide correct jump conditions. We used a fixed staggered grid to discretize these equations and an unstructured grid to explicitly track the front. While in two dimensions the front was simply a connection of small line segments, in three dimensions it was represented by a connection of small triangular elements. The equations were written in conservative forms and during the course of computations we used regriding to control the size of the elements of the unstructured grid. Moreover, we implemented a coalescence in two dimensions which allowed the merging of different fronts or two segments of the same front when they were sufficiently close. We used our code to study thermocapillary migration of bubbles, burst of bubbles at a free surface, buoyancy-driven interactions of bubbles, evaporation of drops, rapid evaporation of an interface, planar solidification of an undercooled melt, dendritic solidification, and a host of other problems cited in the reference.

  10. Liquid-vapor phase diagram of metals using EAM potential

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Chandrani

    2013-02-01

    Pair-wise additive potentials are not adequate to describe the properties of metallic systems since many body effects are completely ignored in that approximation. In this regard, the embedded atom method is more appropriate because, in addition to the pair interaction, the total energy includes an embedding energy which is the energy required to add an impurity atom to the host electron fluid. Thus EAM takes into account the many body effects to some extent. We use the Cai and Ye's EAM potential to predict the liquid vapor phase diagram and critical constants of Aluminum and Copper within a perturbation theory approach. In this method, free energy of a fluid molecule, trapped in a cage formed by its nearest neighbors, is expanded about a hard sphere reference system. The first order correction term is calculated in terms of the zero temperature isotherm of the solid obtained using the EAM potential. Higher order correction terms are added to account for the deviation of the behavior of the real fluid from the reference hard sphere fluid.

  11. Gravitational effects on microstructural development in liquid phase sintered materials

    SciTech Connect

    Courtney, T.H.

    1996-09-01

    In this review the author has tried to place in perspective differing viewpoints concerning the effect of gravity in LPS. Gravity induced settling can be roughly separated into two stages; free settling of isolated particles and skeletal settling of a connected solid structure. There is disagreement over the solid phase volume fraction needed to establish a skeletal structure. The author noted that such a criterion can only be determined by examination of structures sintered for times less than that at which skeletal settling commences. If this protocol is not followed, the measured critical volume fraction is greater than the one at which a skeleton first forms. The author reviewed two mechanisms for skeletal settling. While the process is complicated, previous work strongly suggests that particles are, more-or-less, extricated from the skeleton one at a time. They then settle a distance comparable to the interparticle spacing. Repetition leads to the slow slumping observed, for example, in heavy metals. Conversely, extrication in Fe-Cu alloys leads to floating of Fe particles. Details of the extrication process have not yet been clarified, and continued work in this area might be fruitful. The author also noted that a recent model put forth to describe skeletal settling in LPS systems seems physically unrealistic. In addition, the physics underlying the model do not apply to a system in which the solid has a lesser density than the liquid.

  12. Self-Sputtering of Solid and Liquid Phase Tin

    NASA Astrophysics Data System (ADS)

    Coventry, M. D.; Tomchik, C. A.; Ruzic, D. N.

    2004-11-01

    The absolute self-sputtering yields of solid and liquid-phase Sn have been measured for incident ions with energies of 300 to 1000 eV at 45^o using the Ion-surface InterAction eXperiment (IIAX). A Sn divertor^1 would experience self-bombardment from redepositing Sn ions, and its use may be limited by a temperature-enhanced self-sputtering yield. Thus, an understanding of any temperature dependence is a key to predictive modeling of such a device. IIAX uses a Colutron^2 ion source to produce a velocity-filtered Sn^+ beam for sample irradiation. Experiments were carried out with sample temperatures ranging from room temperature to 380^oC. A quartz-crystal microbalance (QCM) monitors sputtering by direct collection of ejected and reflected material; background noise is removed using a reference crystal. VFTRIM^3, which cannot simulate temperature, was used for comparison to recorded data and for data analysis. Hybrid Molecular-Dynamic/Monte Carlo simulations which include temperature effects^4 were also investigated. [1] Brooks, J.N. Fus. Eng. Des. 60 (2002) 515-526. [2] Menzinger, M. and Wahlin, L. Rev. Sci. Instrum. 40 (1969) 102-105. [3] Ruzic, D.N. Nuc. Instrum. Meth. Phys. Res. 47 (1990) 118-125. [4] Allain, J.P., D.N. Ruzic, submitted to Nuc. Instrum. Meth. B, January 2004

  13. Thermodynamic and kinetic simulation of transient liquid-phase bonding

    NASA Astrophysics Data System (ADS)

    Lindner, Brad

    The use of numeric computational methods for the simulation of materials systems is becoming more prevalent and an understanding of these tools may soon be a necessity for Materials Engineers and Scientists. The applicability of numerical simulation methods to transient liquid-phase (TLP) bonding is evaluated using a type 316L/MBF-51 material system. The comparisons involve the calculation of bulk diffusivities, tracking of interface positions during dissolution, widening, and isothermal solidification stages, as well as comparison of elemental composition profiles. The simulations were performed with Thermo-Calc and DICTRA software packages and the experiments with differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and optical microscopic methods. Analytical methods are also discussed to enhance understanding. The results of the investigation show that while general agreement between simulations and experiments can be obtained, assumptions made with the simulation programs may cause difficulty in interpretation of the results unless the user has sufficient, mathematical, thermodynamic, kinetic, and simulation background.

  14. Dynamic equilibrium dissolution of complex nonaqueous phase liquid mixtures into the aqueous phase.

    PubMed

    Schluep, Mathias; Gälli, René; Imboden, Dieter M; Zeyer, Josef

    2002-07-01

    Human health risks posed by hazardous substances seeping from a pool of nonaqueous phase liquids (NAPLs) into groundwater change over time because the more soluble compounds such as benzene, toluene, ethylbenzene, and xylene (BTEX) dissolve faster into the aqueous phase than less soluble compounds such as polycyclic aromatic hydrocarbons (PAH). Long-term dissolution from diesel fuel into the aqueous phase was determined experimentally in a continuous flow-through system using the slow-stirring method. The data obtained are interpreted using a dynamic equilibrium dissolution model based on Raoult's law. The predicted temporal development of aqueous concentrations are in good agreement with the experimental results. When a compound in the NAPL approaches complete depletion, a tailing behavior is observed, which is assigned to nonequilibrium effects, such as mass transfer limitations in the NAPL phase. The model predicted an increase of the mean molar mass of the diesel fuel of 1.5% over the entire experimental period. It should be noted that, if the dissolution process were to proceed further, the change in the mean molar mass could become significant and render the simple model inaccurate. Yet the simple model supports the assessment of initial action after a contamination event as well as the planning of long-term remedial strategies. PMID:12109733

  15. Nanoparticles for Nonaqueous-phase liquids (NAPLs) Remediation

    NASA Astrophysics Data System (ADS)

    Jiemvarangkul, Pijit

    Nanotechnology has gained attention in various fields of science and engineering for more than decades. Many nanotechnologies using nanosorbents, nanosensors, and nanoparticles have been developed, studied, and used to solve environmental problems. This dissertation contributes to the applications of two types of nanoparticles: 1) using zero valent iron nanoparticle technology (nZVI) for treatment of groundwater contaminated by chlorinated hydrocarbons and study effect of polyelectrolyte polymers on enhancing the mobility of nZVI in porous media and 2) testing a new type of nanoparticle, nano-scale calcium peroxide (CaO2) particles (nano-peroxide); particles have been synthesized and preliminarily tests on their chemical properties and oxidizing reactions with petroleum hydrocarbons investigated. Trichloroethylene (TCE) is one of the high toxic, dense, non-aqueous phase liquids (DNAPLs) and it is one of the major problems of groundwater contamination. The direct reaction of nano-scale zerovalent iron (nZVI) particles and TCE liquid phase batch experiments shows that nZVI has capability to remove pure phase TCE and there is the reduction reaction occurred with reaction byproduct. Mass balance of nZVI-TCE reaction demonstrates that 7--9 % TCE mass was trapped in 1 g of nZVI sludge indicating that absorption occurred during the removal process confirming the absorption of TCE into nZVI sludge. The reaction and absorption abilities of nZVI are depended upon its surface areas. Increasing amount of nZVI reduces the space of batch experiment systems, so TCE removal efficiency of nZVI is decreased. These experiments show the practicability of using nZVI to directly remove TCE from contaminated groundwater. The transport of nanoscale zero-valent iron (nZVI) particles stabilized by three polyelectrolytes: polyvinyl alcohol-co-vinyl acetate-co-itaconic acid (PV3A), poly(acrylic acid) (PAA) and soy proteins were examined. The study shows the increase in nZVI mobility by

  16. Metastable liquid-liquid phase transition in a single-component system with only one crystal phase and no density anomaly

    NASA Astrophysics Data System (ADS)

    Franzese, G.; Malescio, G.; Skibinsky, A.; Buldyrev, S. V.; Stanley, H. E.

    2002-11-01

    We investigate the phase behavior of a single-component system in three dimensions with spherically-symmetric, pairwise-additive, soft-core interactions with an attractive well at a long distance, a repulsive soft-core shoulder at an intermediate distance, and a hard-core repulsion at a short distance, similar to potentials used to describe liquid systems such as colloids, protein solutions, or liquid metals. We showed [Nature (London) 409, 692 (2001)] that, even with no evidence of the density anomaly, the phase diagram has two first-order fluid-fluid phase transitions, one ending in a gas-low-density-liquid (LDL) critical point, and the other in a gas-high-density-liquid (HDL) critical point, with a LDL-HDL phase transition at low temperatures. Here we use integral equation calculations to explore the three-parameter space of the soft-core potential and perform molecular dynamics simulations in the interesting region of parameters. For the equilibrium phase diagram, we analyze the structure of the crystal phase and find that, within the considered range of densities, the structure is independent of the density. Then, we analyze in detail the fluid metastable phases and, by explicit thermodynamic calculation in the supercooled phase, we show the absence of the density anomaly. We suggest that this absence is related to the presence of only one stable crystal structure.

  17. Analog optical phase modulator based on chiral smectic and polymer cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Stockley, Jay E.; Sharp, Gary D.; Serati, Steven A.; Johnson, Kristina M.

    1995-12-01

    A high-speed analog optical phase modulator based on chiral smectic and cholesteric liquid crystals is discussed. The chiral smectic liquid-crystal device functions as a variable-orientation half-wave retarder, whereas the polymer cholesteric liquid-crystal film acts as a polarization-preserving mirror. We use circular Jones calculus to describe optical phase modulation, using a half-wave retarder of variable orientation acting on circularly polarized light. The phase induced by this modulator is achromatic. Analog phase modulation of nearly 360deg is demonstrated with a device switching time of 200 mu s at 25degC .

  18. Phase and Topological Behavior of Lyotropic Chromonic Liquid Crystals in Double Emulsions

    NASA Astrophysics Data System (ADS)

    Davidson, Zoey S.; Jeong, Joonwoo; Tu, Fuquan; Lohr, Matt; Lee, Daeyeon; Collings, Peter J.; Lubensky, Tom C.; Yodh, A. G.

    2013-03-01

    Lyotropic chromonic liquid crystals, assembled by non-covalent interactions, have fascinating temperature- and concentration-dependent phase behavior. Using water-oil-water double emulsions, we are able control the inner droplet chromonic phase concentration by osmosis through the oil phase. We then study the configurations of the chromonic liquid crystal phases in droplets by varying the oil types, oil soluble surfactants, and inner droplet diameter. We employ polarization microscopy to observe resulting nematic and columnar phases of Sunset Yellow FCF, and we deduce the liquid crystal configuration of both phases within the droplets. Simulations based on Jones matrices confirm droplet appearance, and preliminary observations of chromonic liquid crystal shells in oil-water-oil double emulsions are reported. Supported by UPenn MRSEC DMR 11-20901 and NSF DMR 12-05463

  19. Chromatographic sample collection from two-phase (gas+liquid) flows.

    PubMed

    Bruno, Thomas J; Windom, Bret C

    2011-12-01

    A particularly challenging sample presentation in analytical chemistry is a flowing stream that consists of both a gas and liquid phase, combined with the common situation in which a reliable analysis is needed for both phases, separately. In these cases, the vapor and liquid must be physically separated (without change to either), before the individual phases can be collected and analyzed. It is not possible to analyze two-phase flows otherwise. Although the two phases are at equilibrium, it is imperative that no liquid contaminate the vapor, and no vapor be entrained in the liquid at a given temperature and pressure. In this paper, we describe a simple on-line device that can individually separate and collect the vapor and liquid phases of a two-phase flow. The apparatus, which we call P(2)SC, uses an adaptation of the branch point separator, with vapor collection done downstream in a metal bellows. The liquid collection is done in a length of Teflon tube. The separated vapor and liquid phases are then easily transferred into any desired analytical instrument with a syringe, although any sample introduction method, such as a valve, could be used as well. We discuss the application of this device with a stream of thermally stressed rocket kerosene. PMID:22036084

  20. Microstructural change during (liquid phase sintering) of W-Ni-Fe alloy

    SciTech Connect

    Park, J.K.; Eun, K.Y. ); Kang, S.L

    1989-05-01

    The changes of bulk density and microstructures during heating and liquid phase sintering of 98W-1Ni-1Fe compacts prepared from 1 and 5 {mu}m W powders have been observed in order to characterize the densification behavior. The compact prepared from a fine (1 {mu}m) W powder begins to densify rapidly at about 1200{degrees}C in the solid state during heating, attaining about 95 pct density upon reaching the liquid phase sintering temperature of 1460{degrees}C. The compact prepared from a coarse (5 {mu}m) W powder begins to densify rapidly at about 1400{degrees}C in the solid state, attaining about 87 pct density upon reaching the liquid phase sintering temperature. Thus, the skeleton of grains is already formed prior to liquid formation. During the isothermal liquid phase sintering, substantial grain growth occurs, and the liquid flows into both open and closed pores, filling them sequentially from the regions with small cross-sections. The grains subsequently grow into the liquid pockets which have been formed at the pore sites. The sequential pore filling by first liquid thus is shown to be the dominant densification process during the liquid phase sintering of this alloy.

  1. Method and device for removing a non-aqueous phase liquid from a groundwater system

    DOEpatents

    Looney, Brian B.; Rossabi, Joseph; Riha, Brian D.

    2002-01-01

    A device for removing a non-aqueous phase liquid from a groundwater system includes a generally cylindrical push-rod defining an internal recess therein. The push-rod includes first and second end portions and an external liquid collection surface. A liquid collection member is detachably connected to the push-rod at one of the first and second end portions thereof. The method of the present invention for removing a non-aqueous phase liquid from a contaminated groundwater system includes providing a lance including an external hydrophobic liquid collection surface, an internal recess, and a collection chamber at the bottom end thereof. The lance is extended into the groundwater system such that the top end thereof remains above the ground surface. The liquid is then allowed to collect on the liquid collection surface, and flow downwardly by gravity into the collection chamber to be pumped upwardly through the internal recess in the lance.

  2. A Liquid-Liquid Thermoelectric Heat Exchanger as a Heat Pump for Testing Phase Change Material Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Sheth, Rubik B.; Makinen, Janice; Le, Hung V.

    2016-01-01

    The primary objective of the Phase Change HX payload on the International Space Station (ISS) is to test and demonstrate the viability and performance of Phase Change Material Heat Exchangers (PCM HX). The system was required to pump a working fluid through a PCM HX to promote the phase change material to freeze and thaw as expected on Orion's Multipurpose Crew Vehicle. Due to limitations on ISS's Internal Thermal Control System, a heat pump was needed on the Phase Change HX payload to help with reducing the working fluid's temperature to below 0degC (32degF). This paper will review the design and development of a TEC based liquid-liquid heat exchanger as a way to vary to fluid temperature for the freeze and thaw phase of the PCM HX. Specifically, the paper will review the design of custom coldplates and sizing for the required heat removal of the HX.

  3. Quenching of singlet molecular oxygen ( sup 1. Delta. sub g O sub 2 ) in silica gel/cyclohexane heterogeneous systems. A direct time-resolved study

    SciTech Connect

    Iu, Kaikong; Thomas, J.K. )

    1990-04-25

    Direct time-resolved studies of singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}) phosphorescence ({sup 3}{Sigma}{sub g} {sup {minus}}O{sub 2} ({nu} = 0) {l arrow} {sup 1}{Delta}{sub g}O{sub 2} ({nu} = 0); 1,270 nm) in heterogeneous silica gel/cyclohexane systems are presented. Singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}) is created through a photosensitization process on silica gel surfaces. The experimental results show that the lifetimes of singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}) in both porous and compressed fumed silica/gel cyclohexane systems are significantly less than that in liquid cyclohexane. The shortened singlet molecular oxygen lifetime is due mainly to quenching by adsorbed water and silanol groups on the silica gel surface. In addition, monoamines coadsorbed on the silica gel surface do not quench singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}); however, diamines such as DABCO or piperazine maintain their quenching activity, but the quenching kinetics are not of the Stern-Volmer type. The singlet molecular oxygen lifetime increases on loading the porous silica gel/cyclohexane system with monoamine. Coadsorption of piperazine increases quenching of {sup 1}{Delta}{sub g} O{sub 2} by DABCO.

  4. Two phase flow of liquids in a narrow gap: Phase interference and hysteresis

    NASA Astrophysics Data System (ADS)

    Raza, Salim; Hejazi, S. Hossein; Gates, Ian D.

    2016-07-01

    Co-current flow of two immiscible liquids, such as oil and water in a planar fracture, exhibits nonlinear structures which become important in many natural and engineering systems such as subsurface flows, multiphase flows in lubrication joints, and coating flows. In this context, co-current flow of oil and water with variable rates is experimentally studied in a Hele-Shaw cell, various flow regimes are classified, and relative permeabilities for the phases are analysed thoroughly. Similar to multiphase pipe flows, multiphase flow in planar gaps shows various flow regimes, each having different flow rate/pressure gradient behaviour. As well as recovering the known results in the immiscible displacements in Hele-Shaw cell where the fluid-fluid interface remains stable/unstable for favorable/adverse viscosity ratios, it is found that the co-current flow of two fluids with different viscosities results in three distinct flow regimes. Before breakthrough of non-wetting phase, i.e, water, a "linear displacement" flow regime initially establishes at very low water injection rates. This stable movement turns into a "fingering advancement" flow regime at high water flow rates and Saffman-Taylor instability develops normal to the direction of the flow. After the breakthrough, a "droplet formation" flow regime is identified where the droplets of wetting phase, oil, are trapped in the water phase. For subsurface flow applications, we quantify these regimes through relative permeability curves. It is reported that as the water flow rate increases, the relative permeabilities and flow channels become smooth and regular. This behaviour of relative permeability and saturations shows dominance of capillary forces at low flow rates and viscous forces at higher flow rates. Variable injection rates provide the interface structures for both drainage and imbibition process, where the wetting phase saturation decreases and increases respectively. It is shown that relative permeability

  5. Rapid removal of nitrobenzene in a three-phase ozone loaded system with gas-liquid-liquid

    USGS Publications Warehouse

    Li, Shiyin; Zhu, Jiangpeng; Wang, Guoxiang; Ni, Lixiao; Zhang, Yong; Green, Christopher T.

    2015-01-01

    This study explores the removal rate of nitrobenzene (NB) using a new gas-liquid-liquid (G-L-L) three-phase ozone loaded system consisting of a gaseous ozone, an aqueous solvent phase, and a fluorinated solvent phase (perfluorodecalin, or FDC). The removal rate of NB was quantified in relation to six factors including 1) initial pH, 2) initial NB dosage, 3) gaseous ozone dosage, 4) free radical scavenger, 5) FDC pre-aerated gaseous ozone, and 6) reuse of FDC. The NB removal rate is positively affected by the first three factors. Compared with the conventional gas-liquid (water) (G-L) two-phase ozonation system, the free radical scavenger (tertiary butyl alcohol) has much less influence on the removal rate of NB in the G-L-L system. The FDC loaded ozone acts as an ozone reservoir and serves as the main reactive phase in the G-L-L three-phase system. The reuse of FDC has little influence on the removal rate of NB. These experimental results suggest that the oxidation efficiency of ozonation in the G-L-L three-phase system is better than that in the conventional G-L two-phase system.

  6. Determination of Atmospheric Hydroxyl Radical by Liquid Phase Scrubbing and High Performance Liquid Chromatography.

    NASA Astrophysics Data System (ADS)

    Chen, Xiaohui

    A new in situ method for determining atmospheric hydroxyl radical (OH) was developed. This method is based on liquid phase scrubbing technique and high performance liquid chromatography (LPS-HPLC). The sampling system employs glass bubblers to trap atmospheric OH into a buffered solution containing the chemical probe, salicylic acid (o-hydroxybenzoic acid, OHBA). The reaction of OHBA with OH produces a stable fluorescent product, 2,5-dihydroxybenzoic acid (2,5-DHBA), which is determined by reverse phase HPLC and fluorescence detection. The atmospheric OH concentration ( (OH)) is inferred from the resulting 2,5-DHBA amount in the aqueous scrubbing solution, fraction of 2,5-DHBA in the products, air sampling flow rate, sampling time, local pressure and temperature, etc. HPLC separation efficiency and fluorescence detection sensitivity for 2,5-DHBA have been studied. The results indicate that: the reagent blank can be controlled by suitable recrystallization; pH affects both separation and detection processes; the fluorometer should be adjusted to reach its highest signal-to-noise ratio by light source selection, flow cell size selection, wavelength selection, etc. Preliminary column switch experiments reveal the possibility to automate the whole sampling and detection system to enhance the temporal resolution. During an intercomparison of tropospheric OH measurement techniques at the Caribou site, CO (relatively unpolluted air) in Fall 1993, overlapping data were obtained with long path absorption and ion-assisted coupled with MS methods. LPS -HPLC day-time (OH) s, which range from {< }10^6 to 6times10 ^6 radicals/cm^3, agree well with those derived from the other two methods, especially the latter. LPS-HPLC (OH) depends linearly on the combined effects of solar flux, ozone and water vapor, however, it has a nonlinear dependence on NO _{x} and hydrocarbons. These results are consistent with that predicted from photochemical models. Experimental results and model

  7. Chiral liquid crystals: the vestigial chiral phases of T, O, I matter

    NASA Astrophysics Data System (ADS)

    Nissinen, Jaakko; Liu, Ke; Slager, Robert-Jan; Wu, Kai; Zaanen, Jan

    We show how chiral order develops in vestigial isotropic phases of T , O and I liquid crystalline systems in three dimensions. The liquid crystal phases are realized in a lattice model of orientational degrees of freedom with point group symmetries G ⊂ O (3) , represented as O (3) -rotors coupled to G gauge fields. The model incorporates also disclinations via the gauge fields, features an ordered nematic phase with unbroken G rotations at low temperatures and a high temperature isotropic liquid phase. We observe an intermediate phase with spontaneous chirality but isotropic SO (3) symmetry (a liquid) for the gauge groups T, O, and I, the proper symmetry groups of the tetrahedron, cube and icosahedron, respectively. For the other subgroups of SO (3) , Cn <= ∞ and Dn <= ∞, there is generically only a single phase transition from the nematic phase to the isotropic liquid. We discuss the nature of the phase transitions and conditions under which the chiral phase is stabilized by the nematic order parameter fluctuations. The nature of the vestigial chiral phase is reminiscent of the so-called Ising nematic phase in iron based superconductors. Research supported by the Netherlands foundation for Fundamental Research of Matter (FOM).

  8. Sedimentation of a two-dimensional colloidal mixture exhibiting liquid-liquid and gas-liquid phase separation: a dynamical density functional theory study.

    PubMed

    Malijevský, Alexandr; Archer, Andrew J

    2013-10-14

    We present dynamical density functional theory results for the time evolution of the density distribution of a sedimenting model two-dimensional binary mixture of colloids. The interplay between the bulk phase behaviour of the mixture, its interfacial properties at the confining walls, and the gravitational field gives rise to a rich variety of equilibrium and non-equilibrium morphologies. In the fluid state, the system exhibits both liquid-liquid and gas-liquid phase separation. As the system sediments, the phase separation significantly affects the dynamics and we explore situations where the final state is a coexistence of up to three different phases. Solving the dynamical equations in two-dimensions, we find that in certain situations the final density profiles of the two species have a symmetry that is different from that of the external potentials, which is perhaps surprising, given the statistical mechanics origin of the theory. The paper concludes with a discussion on this. PMID:24116640

  9. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide

    PubMed Central

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-01-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25–60 oC) and frequency range (100 Hz–2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB. PMID:27555475

  10. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide.

    PubMed

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-01-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25-60 (o)C) and frequency range (100 Hz-2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB. PMID:27555475

  11. Double-twist cylinders in liquid crystalline cholesteric blue phases observed by transmission electron microscopy.

    PubMed

    Tanaka, Shu; Yoshida, Hiroyuki; Kawata, Yuto; Kuwahara, Ryusuke; Nishi, Ryuji; Ozaki, Masanori

    2015-01-01

    Cholesteric blue phases are liquid crystalline phases in which the constituent rod-like molecules spontaneously form three-dimensional, helical structures. Despite theoretical predictions that they are composed of cylindrical substructures within which the liquid crystal molecules are doubly twisted, real space observation of the arrangement of such structures had not been performed. Through transmission electron microscopy of photopolymerized blue phases with controlled lattice plane orientations, we report real space observation and comparison of the lattice structures of blue phases I and II. The two systems show distinctly different contrasts, reflecting the theoretically predicted, body centred and simple cubic arrangement of the double-twist cylinders. Transmission electron microscopy also reveals different tendencies of the two blue phases to align on unidirectionally rubbed surfaces. We thus show that TEM observation of alignment-controlled, photopolymerized liquid crystals can be a powerful tool to investigate complex liquid crystalline order. PMID:26530779

  12. Double-twist cylinders in liquid crystalline cholesteric blue phases observed by transmission electron microscopy

    PubMed Central

    Tanaka, Shu; Yoshida, Hiroyuki; Kawata, Yuto; Kuwahara, Ryusuke; Nishi, Ryuji; Ozaki, Masanori

    2015-01-01

    Cholesteric blue phases are liquid crystalline phases in which the constituent rod-like molecules spontaneously form three-dimensional, helical structures. Despite theoretical predictions that they are composed of cylindrical substructures within which the liquid crystal molecules are doubly twisted, real space observation of the arrangement of such structures had not been performed. Through transmission electron microscopy of photopolymerized blue phases with controlled lattice plane orientations, we report real space observation and comparison of the lattice structures of blue phases I and II. The two systems show distinctly different contrasts, reflecting the theoretically predicted, body centred and simple cubic arrangement of the double-twist cylinders. Transmission electron microscopy also reveals different tendencies of the two blue phases to align on unidirectionally rubbed surfaces. We thus show that TEM observation of alignment-controlled, photopolymerized liquid crystals can be a powerful tool to investigate complex liquid crystalline order. PMID:26530779

  13. Double-twist cylinders in liquid crystalline cholesteric blue phases observed by transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Tanaka, Shu; Yoshida, Hiroyuki; Kawata, Yuto; Kuwahara, Ryusuke; Nishi, Ryuji; Ozaki, Masanori

    2015-11-01

    Cholesteric blue phases are liquid crystalline phases in which the constituent rod-like molecules spontaneously form three-dimensional, helical structures. Despite theoretical predictions that they are composed of cylindrical substructures within which the liquid crystal molecules are doubly twisted, real space observation of the arrangement of such structures had not been performed. Through transmission electron microscopy of photopolymerized blue phases with controlled lattice plane orientations, we report real space observation and comparison of the lattice structures of blue phases I and II. The two systems show distinctly different contrasts, reflecting the theoretically predicted, body centred and simple cubic arrangement of the double-twist cylinders. Transmission electron microscopy also reveals different tendencies of the two blue phases to align on unidirectionally rubbed surfaces. We thus show that TEM observation of alignment-controlled, photopolymerized liquid crystals can be a powerful tool to investigate complex liquid crystalline order.

  14. Liquid electrode

    DOEpatents

    Ekechukwu, Amy A.

    1994-01-01

    A dropping electrolyte electrode for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions.

  15. Reactive Species Processes in Plasma-, Gas-, and Liquid-Phase

    NASA Astrophysics Data System (ADS)

    Reuter, Stephan; Winter, Joern; Hammer, Malte; Schmidt-Bleker, Ansgar; Iseni, Sylvain; Tresp, Helena; Dünnbier, Mario; Masur, Kai; Wende, Kristian; Weltmann, Klaus-Dieter

    2013-09-01

    Especially for the field of plasma medicine, plasmas interacting with liquids are of great interest for environmental, chemical, and biomedical applications. In this work we present optical diagnostics on atmospheric pressure plasma jets interacting with liquids. Combining the diagnostic results with numerical simulations yields an understanding of fundamental processes such as air species diffusion into the jet effluents or the influence on humidity. Especially for plasma treatment of physiological liquids in ambient air, atmospheric species play a key role. To achieve a desired reactive component output, the generation processes from these ambient air species are controlled. Plasma jets are characterized by planar laser induced fluorescence spectroscopy, by absorption and emission spectroscopy, and by flow simulations. With the gained knowledge we are able to tailor the reactive component composition and to influence plasma jet-liquid interaction. We show that reactive species generation within plasma treated liquid can be tuned and apply the findings to biological cells to investigate the effect of reactive oxygen and nitrogen species (RONS). The plasma treated liquids are investigated regarding their pH value, OH radicals, nitrate and nitrite, and H2O2 content. From the tailored plasma treatment a significant insight into the relevant transport processes in plasma treatment of liquids has been gained. Support by the German BMBF 03Z2DN11&12 is acknowledged.

  16. Blue phase liquid crystalline polymers and its application in manned spacecraft

    NASA Astrophysics Data System (ADS)

    Zhang, Dongpu; Xu, Fang; Li, Wangling; Guo, Weiguo

    2014-11-01

    As novel Liquid Crystal Display (LCD) materials, blue phase liquid crystalline polymers have attracted considerable attention and interests, mainly because of their unique properties, including wide angle of view, fast response times and selective reflection of light. Blue phases are mesophases usually exhibited by highly chiral materials and commonly occur in a narrow temperature range below the isotropic phase.They are optically active and non-birefringent, while exhibit Bragg diffraction of light in the visible wavelength. So they can improve and enhance the performances of liquid crystal display in manned spacecraft. The development and recent advances are reviewed with a brief introduction of the history of the blue phase studies. Some special properties are analyzed especially the frustration in the double twist molecular alignment. The application prospect of blue phase liquid crystalline polymers in manned spacecraft are discussed. Because of high resolution, high response speed, low power, low weight and small footprint, blue phase liquid crystal displays can meet the technique requirements on displays in our future manned spacecrafts, especially space station. Blue phase liquid crystalline polymers have more superior performances on viewing angle. Thus, blue phase LCD is a better choice to improve the viewing angle in manned spacecrafts.

  17. Liquid Phase Sintering of Boron-Containing Powder Metallurgy Steel with Chromium and Carbon

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Wei; Fan, Yu-Chi; Huang, Her-Yueh; Cai, Wen-Zhang

    2015-11-01

    Liquid phase sintering is an effective method to improve the densification of powder metallurgy materials. Boron is an excellent alloying element for liquid phase sintering of Fe-based materials. However, the roles of chromium and carbon, and particularly that of the former, on liquid phase sintering are still undetermined. This study demonstrated the effects of chromium and carbon on the microstructure, elemental distribution, boride structure, liquid formation, and densification of Fe-B-Cr and Fe-B-Cr-C steels during liquid phase sintering. The results showed that steels with 0.5 wt pct C densify faster than those without 0.5 wt pct C. Moreover, although only one liquid phase forms in Fe-B-Cr steel, adding 0.5 wt pct C reduces the formation temperature of the liquid phase by about 50 K (°C) and facilitates the formation of an additional liquid, resulting in better densification at 1473 K (1200 °C). In both Fe-B-Cr and Fe-B-Cr-C steels, increasing the chromium content from 1.5 to 3 wt pct raises the temperature of liquid formation by about 10 K (°C). Thermodynamic simulations and experimental results demonstrated that carbon atoms dissolved in austenite facilitate the eutectic reaction and reduce the formation temperature of the liquid phase. In contrast, both chromium and molybdenum atoms dissolved in austenite delay the eutectic reaction. Furthermore, the 3Cr-0.5Mo additive in the Fe-0.4B steel does not change the typical boride structure of M2B. With the addition of 0.5 wt pct C, the crystal structure is completely transformed from M2B boride to M3(B,C) boro-carbide.

  18. New methods and materials for solid phase extraction and high performance liquid chromatography

    SciTech Connect

    Dumont, P.J.

    1996-04-23

    This paper describes methods for solid phase extraction and high performance liquid chromatography (HPLC). The following are described: Effects of Resin Sulfonation on the Retention of Polar Organic Compounds in Solid Phase Extraction; Ion-Chromatographic Separation of Alkali Metals In Non-Aqueous Solvents; Cation-Exchange Chromatography in Non-Aqueous Solvents; and Silicalite As a Stationary Phase For HPLC.

  19. 40 CFR 227.32 - Liquid, suspended particulate, and solid phases of a material.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... solid phases of a material. 227.32 Section 227.32 Protection of Environment ENVIRONMENTAL PROTECTION... MATERIALS Definitions § 227.32 Liquid, suspended particulate, and solid phases of a material. (a) For the... obtained above prior to centrifugation and filtration. The solid phase includes all material settling...

  20. 40 CFR 227.32 - Liquid, suspended particulate, and solid phases of a material.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... solid phases of a material. 227.32 Section 227.32 Protection of Environment ENVIRONMENTAL PROTECTION... MATERIALS Definitions § 227.32 Liquid, suspended particulate, and solid phases of a material. (a) For the... obtained above prior to centrifugation and filtration. The solid phase includes all material settling...

  1. 40 CFR 227.32 - Liquid, suspended particulate, and solid phases of a material.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... solid phases of a material. 227.32 Section 227.32 Protection of Environment ENVIRONMENTAL PROTECTION... MATERIALS Definitions § 227.32 Liquid, suspended particulate, and solid phases of a material. (a) For the... obtained above prior to centrifugation and filtration. The solid phase includes all material settling...

  2. 40 CFR 227.32 - Liquid, suspended particulate, and solid phases of a material.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... solid phases of a material. 227.32 Section 227.32 Protection of Environment ENVIRONMENTAL PROTECTION... MATERIALS Definitions § 227.32 Liquid, suspended particulate, and solid phases of a material. (a) For the... obtained above prior to centrifugation and filtration. The solid phase includes all material settling...

  3. Applications of liquid-phase microextraction techniques in natural product analysis: a review.

    PubMed

    Yan, Yunyan; Chen, Xuan; Hu, Shuang; Bai, Xiaohong

    2014-11-14

    Over the last years, liquid-phase microextraction (LPME) as a simple, rapid, practical and effective sample-preparation technique, coupled with various instrumental analytical methods, has been increasingly and widely used to research and determine trace or ultra-micro-levels of both inorganic and organic analytes from different matrix-complex samples. In this review, different kinds of LPMEs such as single drop liquid-phase microextraction, dispersive liquid-liquid microextraction, and hollow fibre liquid-phase microextraction are summarized and recent applications of LPMEs in trace compounds in vivo and in vitro from different natural product matrice analysis such as tea, vegetables, seeds, herbs, and galenical are also discussed. Finally, future developments and applications of LPMEs in complex sample analysis are prospected. PMID:25441339

  4. Phase and interphase behavior of discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Moreno-Razo, J. Antonio; Cienegas-Caceres, Octavio; Díaz-Herrera, Enrique; Quintana, Jacqueline

    2008-03-01

    We present the phase diagram of Gay-Berne potential for discotic symmetry using a particular set of parameters. We show evidence of isotropic, nematic and columnar phases. These results were obtained using two different Molecular Dynamics ensembles to get complementary information. The canonical ensemble to produce interphases between coexisting phases and isothermal-isobaric ensemble to calculate homogeneous properties. The phase diagram was constructed using 2048 particles. For the lower part of the phase diagram, corresponding to low range of temperatures, we present evidence of coexistence lines for isotropic and columnar phases, We support our conclusions on distribution functions and nematic order parameter results.

  5. Paraelectric-antiferroelectric phase transition in achiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Pociecha, Damian; Gorecka, Ewa; Čepič, Mojca; Vaupotič, Nataša; Gomola, Kinga; Mieczkowski, Jozef

    2005-12-01

    Critical freezing of molecular rotation in an achiral smectic phase, which leads to polar ordering through the second order paraelectric-antiferroelectric (Sm-A→Sm-APA) phase transition is studied theoretically and experimentally. Strong softening of the polar mode in the Sm-A phase and highly intensive dielectric mode in the Sm-APA phase are observed due to weak antiferroelectric interactions in the system. In the Sm-APA phase the dielectric response behaves critically upon biasing by a dc electric field. Such a behavior is found general for the antiferroelectric smectic phase with significant quadrupolar interlayer coupling.

  6. Formation of binary phase gratings in photopolymer-liquid crystal composites by a surface-controlled anisotropic phase separation

    SciTech Connect

    Park, Jae-Hong; Khoo, Iam Choon; Yu, Chang-Jae; Jung, Min-Sik; Lee, Sin-Doo

    2005-01-10

    We report on formation of binary phase gratings in photopolymer-liquid crystal (PLC) composites using a surface-controlled phase separation method. The binary nature of the PLC phase gratings is produced by employing a single step photo-ablation through an amplitude photomask which precisely controls the interfacial interactions between the LC and the photopolymer on the alignment layer. A subsequent illumination of the ultraviolet light onto the whole PLC promotes an anisotropic phase separation resulting in the formation of distinct binary patterns for the PLC structure. The electrically tunable diffraction properties of the binary phase gratings are presented.

  7. LETTER TO THE EDITOR: Density minimum and liquid liquid phase transition

    NASA Astrophysics Data System (ADS)

    Poole, Peter H.; Saika-Voivod, Ivan; Sciortino, Francesco

    2005-11-01

    We present a high-resolution computer simulation study of the equation of state of ST2 water, evaluating the liquid-state properties at 2718 state points, and precisely locating the liquid-liquid critical point (LLCP) occurring in this model. We are thereby able to reveal the interconnected set of density anomalies, spinodal instabilities and response function extrema that occur in the vicinity of an LLCP for the case of a realistic, off-lattice model of a liquid with local tetrahedral order. In particular, we unambiguously identify a density minimum in the liquid state, define its relationship to other anomalies, and show that it arises due to the approach of the liquid structure to a defect-free random tetrahedral network of hydrogen bonds.

  8. A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Chen, Ming-Syuan; Lin, Wei-Chih; Tsou, Yu-Shih

    2012-07-01

    A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell (T-PNLC) is demonstrated. T-PNLC consists of three layers. Liquid crystal (LC) directors in the two layers near glass substrates are orthogonal to each other and those two layers modulate two eigen-polarizations of an incident light. As a result, two eigen-polarizations of an incident light experience the same phase shift. In the middle layer, LC directors are perpendicular to the glass substrate and contribute no phase shift. The phase shift of T-PNLC is electrically tunable and polarization-independent. T-PNLC does not require any bias voltage for operation. The phase shift is 0.28 π rad for the voltage of 30 Vrms. By measuring and analyzing the optical phase shift of T-PNLC at the oblique incidence of transverse magnetic wave, the pretilt angle of LC directors and the effective thickness of three layers are obtained and discussed. The potential applications are spatial light modulators, laser beam steering, and micro-lens arrays.

  9. Properties of columns with several pyridinium and imidazolium ionic liquid stationary phases.

    PubMed

    Shashkov, M V; Sidelnikov, V N

    2013-09-27

    Recent advances in the development of new liquid phases (ILs) made it possible to use some classes of ILs as polar stationary liquid phases (SLP). In our days only alkylimidazolium- and alkylphosphonium-based ILs are widely used as polar SLP. In present work some other types of ILs - pyridinium and cyanopropyl/hydroxypropyl imidazolium were investigated as SLP. Columns with efficiencies 2000-2500 plates/m by high-pressure static method were prepared. Polarity and selectivity of these phases were measured. Selectivity was described in terms of intermolecular interactions by using Abraham solvatation parameter model. The set of the regularities between cation structure of ionic liquid and selectivity has been shown. The number and position of methyl groups in ionic liquid pyridinium ring were shown to have the sufficient influence on all type of molecular interactions. Finally the resolutions of test mixture for the several ionic liquid SLP were obtained. For columns with some ionic liquids the dependencies of the height equivalent to a theoretical plate (HETP) and sample loading capacity were obtained and compared with the conventional phases. It was found that the optimal efficiency for the IL columns is attained at lower carrier gas velocities in comparison with traditional phases. Nevetheless sample loading capacity of IL phases is comparable to those of conventional GC phases. PMID:23958690

  10. Quasi-liquid layer theory based on the bulk first-order phase transition

    SciTech Connect

    Ryzhkin, I. A. Petrenko, V. F.

    2009-01-15

    The theory of the superionic phase transition (bulk first-order transition) proposed in [1] is used to explain the existence of a quasi-liquid layer at an ice surface below its melting point. An analytical expression is derived for the quasi-liquid layer thickness. Numerical estimates are made and compared with experiment. Distinction is made between the present model and other quasi-liquid layer theories.

  11. An Amide-Functionalized Dynamic Metal-Organic Framework Exhibiting Visual Colorimetric Anion Exchange and Selective Uptake of Benzene over Cyclohexane.

    PubMed

    Karmakar, Avishek; Desai, Aamod V; Manna, Biplab; Joarder, Biplab; Ghosh, Sujit K

    2015-05-01

    A novel porous metal-organic framework (MOF) architecture is formed by a neutral amide-functionalized ligand and copper(II). Upon desolvation, this compound undergoes a dynamic structural transformation from a one-dimensional (1D) porous phase to a two-dimensional (2D) non-porous phase that shows selective uptake of benzene over cyclohexane. The as-synthesized compound also acts as a visual colorimetric anion sensor for thiocyanate. PMID:25808598

  12. Polyaromatic hydrocarbons do not disturb liquid-liquid phase coexistence, but increase the fluidity of model membranes.

    PubMed

    Liland, Nina S; Simonsen, Adam C; Duelund, Lars; Torstensen, Bente E; Berntssen, Marc H G; Mouritsen, Ole G

    2014-12-01

    Polyaromatic hydrocarbons (PAHs) is a group of compounds, many of which are toxic, formed by incomplete combustion or thermal processing of organic material. They are highly lipophilic and thus present in some seed oils used for human consumption as well as being increasingly common in aquaculture diets due to inclusion of vegetable oils. Cytotoxic effects of PAHs have been thought to be partly due to a membrane perturbing effect of these compounds. A series of studies were here performed to examine the effects of three different PAHs (naphthalene, phenanthrene and benzo[a]pyrene) with different molecular sizes (two, three and five rings, respectively) and fat solubility (Kow 3.29, 4.53 and 6.04, respectively) on membrane models. The effects of PAHs on liquid-liquid phase coexistence in solid-supported lipid bilayers (dioleoylphosphocholine:dipalmitoylphosphatidylcholine:cholesterol) were assessed using fluorescence microscopy. Benzo[a]pyrene had a slight affinity for the liquid-ordered phase, but there were no effects of adding any of the other PAHs on the number or size of the liquid domains (liquid-ordered and liquid-disordered). Benzo[a]pyrene and phenanthrene, but not naphthalene, lowered the transition temperature (Tm) and the enthalpy (ΔH) characterising the transition from the solid to the liquid-crystalline phase in DPPC vesicles. The membrane effects of the PAH molecules are likely related to size, with bigger and more fat-soluble molecules having a fluidising effect when embedded in the membrane, possibly causing some of the observed toxic effects in fish exposed to these contaminants. PMID:25181555

  13. Light-Weight, Single-Phase, Liquid-Cooled Cold Plate (Presentation)

    SciTech Connect

    Narumanchi, S.

    2013-07-01

    This presentation, 'Light-Weight, Low-Cost, Single-Phase Liquid-Cooled Cold Plate,' directly addresses program goals of increased power density, specific power, and lower cost of power electronics components through improved thermal management.

  14. Light-Weight, Low-Cost, Single-Phase, Liquid-Cooled Cold Plate (Presentation)

    SciTech Connect

    Narumanchi, S.

    2013-07-01

    This presentation, 'Light-Weight, Low-Cost, Single-Phase Liquid-Cooled Cold Plate,' directly addresses program goals of increased power density, specific power, and lower cost of power electronics components through improved thermal management.

  15. MEASUREMENT OF MASS TRANSFER RATES FOR SURFACTANT-ENHANCED SOLUBILIZATION OF NONAQUEOUS PHASE LIQUIDS. (R825405)

    EPA Science Inventory

    Surfactant-enhanced solubilization of residual, nonaqueous-phase liquid (NAPL) contaminants is an emerging, subsurface remediation technology. The potential for nonequilibrium conditions is investigated for surfactant-enhanced solubilization of a NAPL, trichloroethylene (TCE), in...

  16. Electrically tunable refractive index in the dark conglomerate phase of a bent-core liquid crystal

    NASA Astrophysics Data System (ADS)

    Nagaraj, M.; Görtz, V.; Goodby, J. W.; Gleeson, H. F.

    2014-01-01

    Here we report an electrically tunable refractive index observed in an isotropic liquid crystal phase known as the dark conglomerate (DC) phase. This unusual change in the refractive index which has not been reported before in the DC phase of other bent-core liquid crystals occurs because of a series of electric-field-driven transformations that take place in the DC phase of the studied bent-core liquid crystal. These transformations give rise to a decrease in the refractive index of the system, when an electric field is applied across the device, and no change in the birefringence is seen during such behavior. The electro-optic phenomenon is described in detail and the possibility of exploiting this for a number of liquid crystal based device applications is discussed.

  17. A Study of the Liquid-Liquid Partitioning Process Using Reverse-Phase Liquid Chromatography: An Undergraduate Analytical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Lochmuller, C. H.; And Others

    1980-01-01

    Presents an undergraduate analytical chemistry experiment that promotes an interpretation of the molecular aspects of solute partitioning, enhancing student understanding of separation science and liquid chromatography. (CS)

  18. Active role of the liquid phase of developer in revealing surface flaws by capillary methods

    SciTech Connect

    Prokhorenko, P.P.; Dezhkunov, N.V.; Stoicheva, I.V.

    1988-08-01

    The article investigates the interaction of two chemically nonreacting liquids after they have been brought into contact with each other in a capillary. It is established that the liquid phase of the developer is not only a passive carrier of the developing component but also exerts an active influence on the process of development, and consequently, on the detectability of flaws.

  19. Investigating the Retention Mechanisms of Liquid Chromatography Using Solid-Phase Extraction Cartridges

    ERIC Educational Resources Information Center

    O'Donnell, Mary E.; Musial, Beata A.; Bretz, Stacey Lowery; Danielson, Neil D.; Ca, Diep

    2009-01-01

    Liquid chromatography (LC) experiments for the undergraduate analytical laboratory course often illustrate the application of reversed-phase LC to solve a separation problem, but rarely compare LC retention mechanisms. In addition, a high-performance liquid chromatography instrument may be beyond what some small colleges can purchase. Solid-phase…

  20. A Liquid-to-Solid Phase Transition of the ALS Protein FUS Accelerated by Disease Mutation.

    PubMed

    Patel, Avinash; Lee, Hyun O; Jawerth, Louise; Maharana, Shovamayee; Jahnel, Marcus; Hein, Marco Y; Stoynov, Stoyno; Mahamid, Julia; Saha, Shambaditya; Franzmann, Titus M; Pozniakovski, Andrej; Poser, Ina; Maghelli, Nicola; Royer, Loic A; Weigert, Martin; Myers, Eugene W; Grill, Stephan; Drechsel, David; Hyman, Anthony A; Alberti, Simon

    2015-08-27

    Many proteins contain disordered regions of low-sequence complexity, which cause aging-associated diseases because they are prone to aggregate. Here, we study FUS, a prion-like protein containing intrinsically disordered domains associated with the neurodegenerative disease ALS. We show that, in cells, FUS forms liquid compartments at sites of DNA damage and in the cytoplasm upon stress. We confirm this by reconstituting liquid FUS compartments in vitro. Using an in vitro "aging" experiment, we demonstrate that liquid droplets of FUS protein convert with time from a liquid to an aggregated state, and this conversion is accelerated by patient-derived mutations. We conclude that the physiological role of FUS requires forming dynamic liquid-like compartments. We propose that liquid-like compartments carry the trade-off between functionality and risk of aggregation and that aberrant phase transitions within liquid-like compartments lie at the heart of ALS and, presumably, other age-related diseases. PMID:26317470

  1. Use of free silicon in liquid phase sintering of silicon nitrides and sialons

    DOEpatents

    Raj, Rishi; Baik, Sunggi

    1985-11-12

    This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic.

  2. Handling of liquid holdup in Duyong two-phase flow pipeline system

    SciTech Connect

    Saad, M.R.; Singh, B. )

    1988-01-01

    This paper deals with the handling of liquids in the multi-phase flow pipeline system within Carigali's Duyong Offshore Gas Complex and the Onshore Gas Terminal, in Kerteh, Terongganu. The data and operations experience gathered necessitate changes to the operating procedures originally identified during the design phase. This is to ensure more efficient handling of liquid hold-up in the pipeline during low gas flowrates.

  3. Use of free silicon in liquid phase sintering of silicon nitrides and sialons

    DOEpatents

    Raj, R.; Baik, S.

    1985-11-12

    This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic. 4 figs.

  4. Evaluation of Mercury in Liquid Waste Processing Facilities - Phase I Report

    SciTech Connect

    Jain, V.; Occhipinti, J.; Shah, H.; Wilmarth, B.; Edwards, R.

    2015-07-01

    This report provides a summary of Phase I activities conducted to support an Integrated Evaluation of Mercury in Liquid Waste System (LWS) Processing Facilities. Phase I activities included a review and assessment of the liquid waste inventory and chemical processing behavior of mercury using a system by system review methodology approach. Gaps in understanding mercury behavior as well as action items from the structured reviews are being tracked. 64% of the gaps and actions have been resolved.

  5. Evaluation of mercury in liquid waste processing facilities - Phase I report

    SciTech Connect

    Jain, V.; Occhipinti, J. E.; Shah, H.; Wilmarth, W. R.; Edwards, R. E.

    2015-07-01

    This report provides a summary of Phase I activities conducted to support an Integrated Evaluation of Mercury in Liquid Waste System (LWS) Processing Facilities. Phase I activities included a review and assessment of the liquid waste inventory and chemical processing behavior of mercury using a system by system review methodology approach. Gaps in understanding mercury behavior as well as action items from the structured reviews are being tracked. 64% of the gaps and actions have been resolved.

  6. Study of surface-bonded dicationic ionic liquids as stationary phases for hydrophilic interaction chromatography.

    PubMed

    Qiao, Lizhen; Li, Hua; Shan, Yuanhong; Wang, Shuangyuan; Shi, Xianzhe; Lu, Xin; Xu, Guowang

    2014-02-21

    In the present study, several geminal dicationic ionic liquids based on 1,4-bis(3-allylimidazolium)butane and 1,8-bis(3-allylimidazolium)octane in combination with different anions bromide and bis(trifluoromethanesulphonyl)imide were prepared and then bonded to the surface of 3-mercaptopropyl modified silica materials through the "thiol-ene" click chemistry as stationary phases for hydrophilic interaction chromatography (HILIC). Compared with their monocationic analogues, the dicationic ionic liquids stationary phases presented effective retention and good selectivity for typical hydrophilic compounds under HILIC mode with the column efficiency as high as 130,000 plates/m. Moreover, the influence of different alkyl chain spacer between dications and combined anions on the retention behavior and selectivity of the dicationic ionic liquids stationary phases under HILIC mode was displayed. The results indicated that the longer linkage chain would decrease the hydrophilicity and retention on the dicationic ionic liquid stationary phase, and while differently combined anions had no difference due to the exchangeability under the common HILIC mobile phase with buffer salt. Finally, the retention mechanism was investigated by evaluating the effect of chromatographic factors on retention, including the water content in the mobile phase, the mobile phase pH and buffer salt concentration. The results showed that the dicationic ionic liquids stationary phases presented a mixed-mode retention behavior with HILIC mechanism and anion exchange. PMID:24484692

  7. Amphiphilic Liquid Crystal Exhibiting the Smectic A to Smectic C Phase Transition without Layer Contraction

    NASA Astrophysics Data System (ADS)

    Ishida, Norihiro; Takanishi, Yoichi; Yamamoto, Jun; Yoshizawa, Atsushi

    2011-02-01

    We prepared an amphiphilic liquid crystal composed of a semiperfluorinated alkyl chain and a 2,3-difluoro-1,4-diphenylbenzene core, and investigated its physical properties using polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction analysis. The compound was found to exhibit the smectic A to smectic C phase transition without layer contraction. The compound doped with a ferroelectric liquid crystal exhibited a fast electro-optical switching with a response time of 10 µs in the chiral smectic A phase in spite of the absence of a chiral smectic C phase. The phase transition behavior is interpreted using the de Vries cone model.

  8. A two-phase model for subcooled and superheated liquid jets

    SciTech Connect

    Muralidhar, R.; Jersey, G.R.; Krambeck, F.J.; Sundaresan, S.

    1995-12-31

    This paper describes a two-phase jet model for predicting the liquid rainout (capture) and composition of subcooled and superheated HF/additive pressurized liquid releases. The parent droplets of the release mixture constitute the fist phase. The second phase can in general be a vapor-liquid fog. The drops are not in equilibrium with the fog phase with which they exchange mass and energy. The fog at any location is assumed to be in local equilibrium. Correlations are developed for predicting the initial drop size for hydrodynamic breakup of jets. Applications are discussed in this paper for HF/additive mixtures. The fog phase calculations account for HF oligomerization and HF-water complex formation in the vapor phase and equilibrium between the liquid and vapor in the fog. The model incorporates jet trajectory calculations and hence can predict the amount of liquid rained out (liquid capture) and the capture distance. The HF captures predicted by the model for various release conditions are in agreement with small and large scale release experiments.

  9. Phase grating wavefront curvature sensor based on liquid crystal spatial light modulator

    NASA Astrophysics Data System (ADS)

    Chen, Bo; Li, Xiaoyang; Yang, Xu

    2015-08-01

    The phase grating wavefront curvature sensor based on liquid crystal spatial light modulator is introduced. A close-loop phase retrieval method based on Eigen functions of Laplacian is proposed, and its accuracy and efficiency are analyzed through numerical experiments of atmospheric phase retrieval. The results show that the close-loop phase retrieval method has a high accuracy. Moreover, it is stable regardless of modal cross coupling.

  10. [Preparation of triterpene saponins from Platycodon grandiflorum by two-dimensional hydrophilic interaction liquid chromatography-reversed phase liquid chromatography].

    PubMed

    Xing, Qianqian; Fu, Qing; Jin, Yu; Liang, Xinmiao

    2014-07-01

    A two-dimensional (2-D) preparative liquid chromatography method was developed for the preparation of triterpene saponins from Platycodon grandiflorum using hydrophilic interaction liquid chromatography (HILIC) coupled with reversed phase liquid chromatography (RPLC). At first, the crude extract was obtained from Platycodon grandiflorum by boiled alcohol precipitation. Then, the concentrated crude extracts were continuously pretreated using solid phase extraction (SPE) under reversed-phase and hydrophilic-phase modes to remove the impurities. Subsequently, XAmide column (150 mm x 20 mm, 5 microm) was selected to separate the triterpene saponin constituents under HILIC mode using water and acetonitrile as mobile phases. From 6 min to 25 min, each fraction was collected per minute under time-triggered mode and 20 fractions were collected. The 18th fraction (JG23) was selected for further purification. The column of Atlantis PrepT3 (100 mm x 30 mm, 5 microm) was chosen and two monomeric compounds were obtained. The two compounds with over 90% purity were identified as deapiplatycoside E and platycoside E with mass spectrometry (MS) and nuclear magnetic resonance (NMR). This 2-D HILIC-RPLC method with high orthogonality can be used in the preparation of triterpene saponins from natural products. PMID:25255571

  11. Chromatographic evaluation of a newly designed peptide-silica stationary phase in reverse phase liquid chromatography and hydrophilic interaction liquid chromatography: mixed mode behavior.

    PubMed

    Ray, Sudipta; Takafuji, Makoto; Ihara, Hirotaka

    2012-11-30

    The short peptide Boc-Phe-Aib-Phe-OH was synthesized and immobilized onto porous silica using grafting methodology. The resulting peptide-bonded silica was characterized using DRIFT-mode FT-IR, elemental analysis, thermogravimetric analysis, solid state C(13) NMR spectroscopy and the successful immobilization of the peptide on the silica support was confirmed. This grafted phase was packed into a stainless steel column and used for mixed-mode chromatography such as reversed-phase high-performance liquid chromatography and hydrophilic interaction liquid chromatography for the efficient separation of hydrophobic compounds, small polar molecules, and drug molecules. Compared with ODS and phenyl columns, this new stationary phase shows considerably higher molecular-planarity selectivity towards polyaromatic hydrocarbons and also available for separation of nucleo-analytes and sulfa-drug molecules in a hydrophilic interaction liquid chromatography mode. The multiple interactions induced by polar carbonyl group and hydrophobic phenyl group allow this peptide-modified silica to serve as a multi-mode stationary phase in high performance liquid chromatography. PMID:23116801

  12. Modeling the gas-particle partitioning of secondary organic aerosol: the importance of liquid-liquid phase separation

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Seinfeld, J. H.

    2012-01-01

    The partitioning of semivolatile organic compounds between the gas phase and aerosol particles is an important source of secondary organic aerosol (SOA). Gas-particle partitioning of organic and inorganic species is influenced by the physical state and water content of aerosols, and therefore ambient relative humidity (RH), as well as temperature and organic loading levels. We introduce a novel combination of the thermodynamic models AIOMFAC (for liquid mixture non-ideality) and EVAPORATION (for pure compound vapor pressures) with oxidation product information from the Master Chemical Mechanism (MCM) for the computation of gas-particle partitioning of organic compounds and water. The presence and impact of a liquid-liquid phase separation in the condensed phase is calculated as a function of variations in relative humidity, organic loading levels, and associated changes in aerosol composition. We show that a complex system of water, ammonium sulfate, and SOA from the ozonolysis of α-pinene exhibits liquid-liquid phase separation over a wide range of relative humidities (simulated from 30% to 99% RH). Since fully coupled phase separation and gas-particle partitioning calculations are computationally expensive, different simplified model approaches are tested with regards to computational costs and accuracy of predictions compared to the benchmark calculation. Both forcing a liquid one-phase aerosol considering non-ideal mixing or assuming an ideal mixture bear the potential for vastly incorrect partitioning predictions. Assuming an ideal mixture leads to substantial overestimation of the particulate organic mass, at high RH by more than 200%. Moreover, the simplified one-phase cases stress two key points for accurate gas-particle partitioning calculations: (1) non-ideality in the condensed phase needs to be considered and (2) liquid-liquid phase separation is a consequence of considerable deviations from ideal mixing in solutions containing inorganic ions and

  13. Modeling the gas-particle partitioning of secondary organic aerosol: the importance of liquid-liquid phase separation

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Seinfeld, J. H.

    2012-05-01

    The partitioning of semivolatile organic compounds between the gas phase and aerosol particles is an important source of secondary organic aerosol (SOA). Gas-particle partitioning of organic and inorganic species is influenced by the physical state and water content of aerosols, and therefore ambient relative humidity (RH), as well as temperature and organic loading levels. We introduce a novel combination of the thermodynamic models AIOMFAC (for liquid mixture non-ideality) and EVAPORATION (for pure compound vapor pressures) with oxidation product information from the Master Chemical Mechanism (MCM) for the computation of gas-particle partitioning of organic compounds and water. The presence and impact of a liquid-liquid phase separation in the condensed phase is calculated as a function of variations in relative humidity, organic loading levels, and associated changes in aerosol composition. We show that a complex system of water, ammonium sulfate, and SOA from the ozonolysis of α-pinene exhibits liquid-liquid phase separation over a wide range of relative humidities (simulated from 30% to 99% RH). Since fully coupled phase separation and gas-particle partitioning calculations are computationally expensive, several simplified model approaches are tested with regard to computational costs and accuracy of predictions compared to the benchmark calculation. It is shown that forcing a liquid one-phase aerosol with or without consideration of non-ideal mixing bears the potential for vastly incorrect partitioning predictions. Assuming an ideal mixture leads to substantial overestimation of the particulate organic mass, by more than 100% at RH values of 80% and by more than 200% at RH values of 95%. Moreover, the simplified one-phase cases stress two key points for accurate gas-particle partitioning calculations: (1) non-ideality in the condensed phase needs to be considered and (2) liquid-liquid phase separation is a consequence of considerable deviations from ideal

  14. Collisions of low-energy electrons with cyclohexane

    SciTech Connect

    Barbosa, Alessandra Souza; Bettega, Márcio H. F.

    2014-12-28

    We report calculated cross sections for elastic scattering of low-energy electrons by cyclohexane (c-C{sub 6}H{sub 12}). We employed the Schwinger multichannel method implemented with norm-conserving pseudopotentials in the static-exchange and static-exchange plus polarization approximations, for impact energies up to 30 eV. We compare our calculated integral cross section with experimental total cross sections available in the literature. We also compare our calculated differential cross sections (DCSs) with experimental results for benzene and experimental and theoretical results for 1,4-dioxane, in order to investigate the similarities between those molecules under electron collisions. Although benzene is a cyclic six-carbon molecule, as cyclohexane, we found that the differential cross sections of the latter are more similar to those of 1,4-dioxane than those of benzene. These similarities suggest that the geometry may play an important role in the behavior of the DCSs of these molecules. Our integral cross section displays a broad structure at around 8.5 eV, in agreement with the total cross section experimental data of 8 eV and vibrational excitation data of 7.5 eV. The present integral cross section also shows the presence of a Ramsauer-Townsend minimum at around 0.12 eV. In general, our integral cross section shows a qualitative agreement with the experimental total cross section.

  15. A study of separation selectivity using embedded ester-bonded stationary phases for liquid chromatography.

    PubMed

    Bocian, Szymon; Krzemińska, Katarzyna; Buszewski, Bogusław

    2016-07-01

    A new type of stationary bonded phase for liquid chromatography with various functional groups bonded to diol-modified silica via ester bond was synthesized. The structures of the proposed stationary phases contain: alkyl chains (C10, C18), phenyl, and cholesterol groups. The structures of the synthesized materials were confirmed by different physico-chemical techniques such as elemental analysis, infrared spectroscopy (FTIR), (13)C CP/MAS NMR and liquid chromatography under reversed phase conditions (RP) and with hydrophilic interaction liquid chromatography (HILIC). Depending on the type of functionalities bonded to the Diol-Ester, the stationary phases are capable of separating various groups of compounds in RP and HILC, even using pure water as a mobile phase. PMID:27170946

  16. Temperature tuning of lasing emission from dye-doped liquid crystal at intermediate twisted phase

    NASA Astrophysics Data System (ADS)

    Liao, Kuan-Cheng; Lin, Ja-Hon; Jian, Li-Hao; Chen, Yao-Hui; Wu, Jin-Jei

    2015-07-01

    Temperature tuning of lasing emission from dye-doped cholesteric liquid crystal (CLC) at intermediate twisted phase has been demonstrated in this work. With heavily doping of 42.5% chiral molecules into the nematic liquid crystals, the shifts of photonic bandgap versus temperature is obviously as thermal controlling of the sample below the certain value. By the differential scanning calorimetr measuremet, we demonstrate the phase transition from the CLC to the smectic phase when the temperature is lowered to be about 15°C. Between CLC and smectic phase, the liquid crystal mixtures are operated at intermediate twisted phase that can be used the temperature related refractive mirror. After pump by the Q-switched Nd:YAG laser, the lasing emission from this dye doped LC mixtures has been demonstrated whose emission wavelength can be tuned from 566 to 637 nm with 1.4°C variation.

  17. Phase diagrams of mixtures of a polymer and a cholesteric liquid crystal under an external field

    SciTech Connect

    Matsuyama, Akihiko

    2014-11-14

    We present a mean field theory to describe phase behaviors in mixtures of a polymer and a cholesteric liquid crystal under an external magnetic or electric field. Taking into account a chiral coupling between a polymer and a liquid crystal under the external field, we examine twist-untwist phase transitions and phase separations in the mixtures. It is found that a cholesteric-nematic phase transition can be induced by not only the external field but also concentration and temperature. Depending on the strength of the external field, we predict cholesteric-paranematic (Ch+pN), nematic-paranematic (N+pN), cholesteric-nematic (Ch+N) phase separations, etc., on the temperature-concentration plane. We also discuss mixtures of a non-chiral nematic liquid crystal and a chiral dopant.

  18. Student Understanding of Liquid-Vapor Phase Equilibrium

    ERIC Educational Resources Information Center

    Boudreaux, Andrew; Campbell, Craig

    2012-01-01

    Student understanding of the equilibrium coexistence of a liquid and its vapor was the subject of an extended investigation. Written assessment questions were administered to undergraduates enrolled in introductory physics and chemistry courses. Responses have been analyzed to document conceptual and reasoning difficulties in sufficient detail to…

  19. Analysis of Developing Gas/liquid Two-Phase Flows

    SciTech Connect

    Elena A. Tselishcheva; Michael Z. Podowski; Steven P. Antal; Donna Post Guillen; Matthias Beyer; Dirk Lucas

    2010-06-01

    The goal of this work is to develop a mechanistically based CFD model that can be used to simulate process equipment operating in the churn-turbulent regime. The simulations were performed using a state-of-the-art computational multiphase fluid dynamics code, NPHASE–CMFD [Antal et al,2000]. A complete four-field model, including the continuous liquid field and three dispersed gas fields representing bubbles of different sizes, was first carefully tested for numerical convergence and accuracy, and then used to reproduce the experimental results from the TOPFLOW test facility at Forschungszentrum Dresden-Rossendorf e.V. Institute of Safety Research [Prasser et al,2007]. Good progress has been made in simulating the churn-turbulent flows and comparison the NPHASE-CMFD simulations with TOPFLOW experimental data. The main objective of the paper is to demonstrate capability to predict the evolution of adiabatic churn-turbulent gas/liquid flows. The proposed modelling concept uses transport equations for the continuous liquid field and for dispersed bubble fields [Tselishcheva et al, 2009]. Along with closure laws based on interaction between bubbles and continuous liquid, the effect of height on air density has been included in the model. The figure below presents the developing flow results of the study, namely total void fraction at different axial locations along the TOPFLOW facility test section. The complete model description, as well as results of simulations and validation will be presented in the full paper.

  20. Liquid-crystal phase grating based on in-plane switching.

    PubMed

    Fujieda, I

    2001-12-01

    A simple phase grating is constructed by insertion of a liquid-crystal layer between two glass plates, upon one of which a pair of transparent interdigitated electrodes is formed. With a bias application, liquid-crystal molecules align themselves along the electric field lines, which are substantially parallel to the glass plates. By controlling the degree of this in-plane switching for the liquid-crystal molecules, one can generate various phase-shift distributions for the light passing through the device. The grating characteristics are altered accordingly. Versatile design and ease of fabrication are potential advantages of this device for some future applications. PMID:18364930

  1. Measuring gas-liquid partition coefficients of aroma compounds by solid phase microextraction, sampling either headspace or liquid.

    PubMed

    Lloyd, Nathan W; Dungan, Stephanie R; Ebeler, Susan E

    2011-08-21

    Hydrophobic compounds are important odorants and nutrients in foods and beverages, as well as environmental contaminants and pharmaceuticals. Factors influencing their partitioning within multi-component systems and/or from the bulk liquid phase to the air are critical for understanding aroma quality and nutrient bioavailability. The equilibrium partitioning of hydrophobic analytes between air and water was analyzed using solid phase microextraction (SPME) in the headspace (HS-SPME) and via direct immersion in the liquid (DI-SPME). The compounds studied serve as models for hydrophobic aroma compounds covering a range of air-water partition coefficients that extends over four orders of magnitude. By varying the total amount of analyte as well as the ratio of vapor to liquid in the closed, static system, the partition coefficient, K(vl), can be determined without the need for an external calibration, eliminating many potential systematic errors. K(vl) determination using DI-SPME in this manner has not been demonstrated before. There was good agreement between results determined by DI-SPME and by HS-SPME over the wide range of partitioning behavior studied. This shows that these two methods are capable of providing accurate, complementary measurements. Precision in K(vl) determination depends strongly on K(vl) magnitude and the ratio of the air and liquid phases. PMID:21727981

  2. Two-phase stopped-flow measurement of the protonation of tetraphenylporphyrin at the liquid-liquid interface.

    PubMed

    Nagatani, H; Watarai, H

    1996-04-01

    The formation rate of the protonated form of tetraphenylporphyrin (TPP) in a dispersed two-phase system composed of dodecane and aqueous trichloroacetic acid (TCA) was studied by means of a stopped-flow method. The protonation reaction took place at the liquid-liquid interface, and the diprotonated TPP (H(2)TPP(2+)) formed was adsorbed there. In order to determine the rate-determining process, changes in absorbance at the absorption maximum wavelengths of TPP and H(2)TPP(2+) were analyzed. The obtained rate constant for the decrease of TPP in the organic phase, 21 ± 2 s(-1), was in agreement with that for the increase of diprotonated TPP at the interface, 20 ± 3 s(-1). The observed rate constants did not show any dependence on concentrations of both TPP and the acid. The experimental results suggested the rate-determining step to be the molecular diffusion process of TPP in the stagnant layer in the organic phase side at the liquid-liquid interface, and the thickness of the stagnant layer was estimated as 1.4 × 10(-4) cm. PMID:21619156

  3. Pair interactions among ternary DPPC/POPC/cholesterol mixtures in liquid-ordered and liquid-disordered phases.

    PubMed

    Yang, Jing; Martí, Jordi; Calero, Carles

    2016-05-18

    Saturated phospholipids, unsaturated phospholipids, and cholesterol are essential components of cell membranes, making the understanding of their mutual interactions of great significance. We have performed microsecond molecular dynamics simulations on the ternary mixtures of DPPC/POPC/cholesterol to systematically examine lipid-lipid and cholesterol-lipid interactions in the liquid-ordered and the liquid-disordered phases. The results show that there exists a competition between the tighter packing of cholesterol-lipid and the looser packing of lipid-lipid as the membrane changes from the liquid-disordered phase to the liquid-ordered phase. Depending on the lipid saturation, the favor of lipid-lipid interactions is in the order of saturated-saturated > monounsaturated-monounsaturated > saturated-monounsaturated. Cholesterol-saturated lipid interactions are more favorable than cholesterol-monounsaturated lipid ones. The results are consistent with the push-pull forces derived from experiments and give general insights into the interactions among membrane components. PMID:27103534

  4. Solid-liquid phase equilibrium for binary Lennard-Jones mixtures

    NASA Astrophysics Data System (ADS)

    Hitchcock, Monica R.; Hall, Carol K.

    1999-06-01

    Solid-liquid phase diagrams are calculated for binary mixtures of Lennard-Jones spheres using Monte Carlo simulation and the Gibbs-Duhem integration technique of Kofke. We calculate solid-liquid phase diagrams for the model Lennard-Jones mixtures: argon-methane, krypton-methane, and argon-krypton, and compare our simulation results with experimental data and with Cottin and Monson's recent cell theory predictions. The Lennard-Jones model simulation results and the cell theory predictions show qualitative agreement with the experimental phase diagrams. One of the mixtures, argon-krypton, has a different phase diagram than its hard-sphere counterpart, suggesting that attractive interactions are an important consideration in determining solid-liquid phase behavior. We then systematically explore Lennard-Jones parameter space to investigate how solid-liquid phase diagrams change as a function of the Lennard-Jones diameter ratio, σ11/σ22, and well-depth ratio, ɛ11/ɛ22. This culminates in an estimate of the boundaries separating the regions of solid solution, azeotrope, and eutectic solid-liquid phase behavior in the space spanned by σ11/σ22 and ɛ11/ɛ22 for the case σ11/σ22<0.85.

  5. Two-Dimensional Numerical Simulation of Boiling Two-Phase Flow of Liquid Nitrogen

    NASA Astrophysics Data System (ADS)

    Ishimoto, Jun; Oike, Mamoru; Kamijo, Kenjiro

    Two-dimensional characteristics of the boiling two-phase flow of liquid nitrogen in a duct flow are numerically investigated to contribute to the further development of new high-performance cryogenic engineering applications. First, the governing equations of the boiling two-phase flow of liquid nitrogen based on the unsteady drift-flux model are presented and several flow characteristics are numerically calculated taking account the effect of cryogenic flow states. Based on the numerical results, a two-dimensional structure of the boiling two-phase flow of liquid nitrogen is shown in detail, and it is found that the phase change of liquid nitrogen occurs in quite a short time interval compared with that of two-phase pressurized water at high temperature. Next, it is clarified that the distributions of pressure and the void fraction in a two-phase flow show a tendency different from those of fluids at room temperature because of the decrease in sound velocity due to large compressibility and the rapid phase change velocity in a cryogenic two-phase mixture flow. According to these numerical results, the fundamental characteristics of the cryogenic two-phase flow are predicted. The numerical results obtained will contribute to advanced cryogenic industrial applications.

  6. The liquid protein phase in crystallization: a case study—intact immunoglobulins

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Yurii G.; Malkin, Alexander J.; McPherson, Alexander

    2001-11-01

    A common observation by protein chemists has been the appearance, for many proteins in aqueous solutions, of oil like droplets, or in more extreme cases the formation of a second oil like phase. These may accompany the formation of precipitate in "salting out" or "salting in' procedures, but more commonly appear in place of any precipitate. Such phase separations also occur, with even greater frequency, in the presence of polymeric precipitants such as polyethyleneglycol (PEG). In general the appearance of a second liquid phase has been taken as indicative of protein aggregation, though an aggregate state distinctly different from that characteristic of amorphous precipitate. While the latter is thought to be composed of linear and branched assemblies, polymers of a sort, the oil phase suggests a more compact, three-dimensional, but fluid state. An important property of an alternate, fluid phase is that it can mediate transitions between other states, for example, between protein molecules free in solution and protein molecules immobilized in amorphous precipitate or crystals. The "liquid protein" phase can be readily observed in many crystallization experiments either prior to the appearance of visible crystals, or directly participating in the crystal growth process. In some cases the relationship between the liquid phase and developing crystals is intimate. Crystals grow directly from the liquid phase, or appear only after the visible formation of the liquid phase. We describe here our experience with a class of macromolecules, immunoglobulins, and particularly IDEC-151, an IgG specific for CD4 on human lymphocytes. This protein has been crystallized from a Jeffamine-LiSO 4 mother liquor and, its crystallization illustrates many of the features associated with the liquid protein, or protein rich phase.

  7. Ultrahigh-vacuum chamber equipped with a reaction cell for studying liquid-phase catalytic reactions

    NASA Astrophysics Data System (ADS)

    Gardin, Denis E.; Somorjai, Gabor A.

    1993-05-01

    We describe the construction and operation of a liquid-phase reaction cell designed in our laboratory that is attached to an ultrahigh-vacuum (UHV) chamber equipped with the traditional surface science techniques for structure and composition analysis. The sample surface can be prepared and characterized in the UHV chamber prior to transfer in the liquid-phase reaction cell. The transfer has been designed so that there is no loss of the UHV chamber vacuum integrity, as few parts as possible come into contact with the liquid, the surface stays clean during the transfer. The liquid-phase reaction cell itself is designed to study liquid-phase hydrogenation reactions at pressures up to 2 atm and temperatures up to 70 °C. A 1-mm-diam liquid jet with a velocity up to 6 m/s is produced by a gear pump that is incident on the sample surface to allow good mass transfer at the liquid-solid interface. The progress of the reaction is followed by gas chromatography. We report the reaction rate data for the hydrogenation of cyclohexene on a platinum foil.

  8. Ultrahigh-vacuum chamber equipped with a reaction cell for studying liquid-phase catalytic reactions

    SciTech Connect

    Gardin, D.E.; Somorjai, G.A. )

    1993-05-01

    We describe the construction and operation of a liquid-phase reaction cell designed in our laboratory that is attached to an ultrahigh-vacuum (UHV) chamber equipped with the traditional surface science techniques for structure and composition analysis. The sample surface can be prepared and characterized in the UHV chamber prior to transfer in the liquid-phase reaction cell. The transfer has been designed so that there is no loss of the UHV chamber vacuum integrity, as few parts as possible come into contact with the liquid, the surface stays clean during the transfer. The liquid-phase reaction cell itself is designed to study liquid-phase hydrogenation reactions at pressures up to 2 atm and temperatures up to 70 [degree]C. A 1-mm-diam liquid jet with a velocity up to 6 m/s is produced by a gear pump that is incident on the sample surface to allow good mass transfer at the liquid-solid interface. The progress of the reaction is followed by gas chromatography. We report the reaction rate data for the hydrogenation of cyclohexene on a platinum foil.

  9. Stable non-Fermi-liquid phase of itinerant spin-orbit coupled ferromagnets

    NASA Astrophysics Data System (ADS)

    Bahri, Yasaman; Potter, Andrew C.

    2015-07-01

    Direct (nongradient) coupling between a gapless bosonic field and a Fermi surface results in the destruction of Landau quasiparticles and a breakdown of Fermi liquid theory. Such a non-Fermi-liquid phase arises in spin-orbit coupled ferromagnets with spontaneously broken continuous symmetries due to strong coupling between rotational Goldstone modes and itinerant electrons. These systems provide an experimentally accessible context for studying non-Fermi-liquid physics. Possible examples include low-density Rashba coupled electron gases, which have a natural tendency towards spontaneous ferromagnetism, or topological insulator surface states with proximity-induced ferromagnetism. Crucially, unlike the related case of a spontaneous nematic distortion of the Fermi surface, for which controlled field theory calculations predict that the non-Fermi-liquid regime will be masked by a superconducting dome, we show that the non-Fermi-liquid phase in spin-orbit coupled ferromagnets is stable.

  10. Stable non-Fermi liquid phase of itinerant spin-orbit coupled ferromagnets

    NASA Astrophysics Data System (ADS)

    Bahri, Yasaman; Potter, Andrew

    2015-03-01

    Direct coupling between gapless bosons and a Fermi surface results in the destruction of Landau quasiparticles and a breakdown of Fermi liquid theory. Such a non-Fermi liquid phase arises in spin-orbit coupled ferromagnets with spontaneously broken continuous symmetries due to strong coupling between rotational Goldstone modes and itinerant electrons. These systems provide an experimentally accessible context for studying non-Fermi liquid physics. Possible examples include low-density Rashba coupled electron gases, which have a natural tendency towards spontaneous ferromagnetism, or topological insulator surface states with proximity-induced ferromagnetism. Crucially, unlike the related case of a spontaneous nematic distortion of the Fermi surface, for which the non-Fermi liquid regime is expected to be masked by a superconducting dome, we show that the non-Fermi liquid phase in spin-orbit coupled ferromagnets is stable.

  11. Cobalt-promoted Iron Oxide Nanoparticles for the Selective Oxidative Dehydrogenation of Cyclohexane

    NASA Astrophysics Data System (ADS)

    Rutter, Matthew

    -Ray Photoelectron Spectroscopy (XPS), BET N2 Physisorption, and CO Temperature Programmed Reduction (CO-TPR). These characterizations helped us to correlate the selectivity and activity data for each catalyst in an attempt to understand what roles the surface species played. It was found that iron oxide nanoparticles doped with 2-10 mol% cobalt formed a stable surface phase, enriched in Co (20 at%), independent of the bulk concentration. XPS measurements indicate this phase is rich in octahedral Co2+ cations. The selectivity to benzene was much higher in the Co-promoted iron oxide samples. This high concentration of octahedral cobalt(II) cations appear to have a strong promotional effect on the weakly held surface oxygen sites which have been shown previously to be the active sites for this reaction. Addition of cobalt also promoted the activity of the iron oxide nanoparticles; and stabilized them against particle growth under the reaction conditions, typically held at several different temperatures up to 370 °C, in a mixture of 0.4% cyclohexane and 4% oxygen, for several hours.

  12. Influence of ester functional groups on the liquid-phase structure and solvation properties of imidazolium-based ionic liquids.

    PubMed

    Pensado, Alfonso S; Pádua, Agílio A H; Costa Gomes, Margarida F

    2011-04-14

    The incorporation of ester functions in the side chains in 1-alkyl-3-methylimidazolium cations seems to increase the biodegradability of these ionic liquids. We study here how the presence of ester functional groups affects the liquid-state structure (namely, the microphase segregation between polar and nonpolar domains in these ionic liquids) and the way in which the solvation of gases can be understood in these solvents. We use molecular simulation to study the structure of the ionic liquids 3-methyl-1-(pentoxycarbonylmethyl)imidazolium octylsulfate, [C(1)COOC(5)C(1)im][C(8)SO(4)]; and 3-methyl-1-(pentoxycarbonylmethyl)imidazolium bis(trifluoromethylsulfonyl)imide, [C(1)COOC(5)C(1)im][NTf(2)] in the liquid phase and to assess the molecular mechanisms of solvation of carbon dioxide and ethane. The presence of ester functions influences the relative size of the polar and nonpolar domains in the ionic liquids, but does not significantly affect the solvation of gases. PMID:21391547

  13. Gold nanoparticle decorated graphene oxide/silica composite stationary phase for high-performance liquid chromatography.

    PubMed

    Liang, Xiaojing; Wang, Xusheng; Ren, Haixia; Jiang, Shengxiang; Wang, Licheng; Liu, Shujuan

    2014-06-01

    In the initial phase of this study, graphene oxide (GO)/silica was fabricated by assembling GO onto the silica particles, and then gold nanoparticles (GNPs) were used to modify the GO/silica to prepare a novel stationary phase for high-performance liquid chromatography. The new stationary phase could be used in both reversed-phase chromatography and hydrophilic interaction liquid chromatography modes. Good separations of alkylbenzenes, isomerides, amino acids, nucleosides, and nucleobases were achieved in both modes. Compared with the GO/silica phase and GNPs/silica phase, it is found that except for hydrophilicity, large π-electron systems, hydrophobicity, and coordination functions, this new stationary phase also exhibited special separation performance due to the combination of 2D GO with zero-dimensional GNPs. PMID:24723561

  14. Facile preparation of highly-dispersed cobalt-silicon mixed oxide nanosphere and its catalytic application in cyclohexane selective oxidation

    PubMed Central

    2011-01-01

    Highly dispersed cobalt-silicon mixed oxide [Co-SiO2] nanosphere was successfully prepared with a modified reverse-phase microemulsion method. This material was characterized in detail by X-ray diffraction, transmission electron microscopy, Fourier transform infrared, ultraviolet-visible diffuse reflectance spectra, X-ray absorption spectroscopy near-edge structure, and N2 adsorption-desorption measurements. High valence state cobalt could be easily obtained without calcination, which is fascinating for the catalytic application for its strong oxidation ability. In the selective oxidation of cyclohexane, Co-SiO2 acted as an efficient catalyst, and good activity could be obtained under mild conditions. PMID:22067075

  15. Magnetohydrodynamic generators using two-phase liquid-metal flows

    NASA Technical Reports Server (NTRS)

    Petrick, M.

    1969-01-01

    Two-phase flow generator cycle of a magnetohydrodynamic /MHD/ generator uses a working fluid which is compressible and treated as an expanding gas. The two-phase mixture passes from the heat source through the MHD generator, where the expansion process takes place and the electrical energy is extracted.

  16. Phase equilibria and modeling of ammonium ionic liquid, C2NTf2, solutions.

    PubMed

    Domańska, Urszula; Marciniak, Andrzej; Królikowski, Marek

    2008-01-31

    Novel quaternary ammonium ionic liquid, ethyl(2-hydroxyethyl)dimethylammonium bis(trifluomethylsulfonyl)imide (C2NTf2), has been prepared from N,N-dimethylethanolamine as a substrate. The paper includes a specific basic characterization of the synthesized compound by NMR and the basic thermophysical properties: the melting point, enthalpy of fusion, enthalpy of solid-solid phase transition, glass transition determined by the differential scanning calorimetry (DSC), temperature of decomposition, and water content. The density of the new compound was measured. The solid-liquid or liquid-liquid phase equilibria of binary mixtures containing {C2NTf2+water or an alcohol (propan-1-ol, butan-1-ol, hexan-1-ol, octan-1-ol, decan-1-ol), aromatic hydrocarbons (benzene, toluene), aliphatic hydrocarbons (n-hexane, n-octane), dimethylsulfoxide (DMSO), or tetrahydrofuran (THF)} have been measured by a dynamic method in a wide range of temperatures from 230 to 430 K. These data were correlated by means of the nonrandom two-liquid (NRTL) equation utilizing temperature-dependent parameters derived from the solid-liquid or liquid-liquid equilibrium. From the solubility results, the negative value of the partition coefficient of ionic liquid in binary system octan-1-ol/water (log P) at 298.15 K has been calculated. PMID:18179194

  17. Dynamic evolution of liquid–liquid phase separation during continuous cooling

    SciTech Connect

    Imhoff, Seth D.; Gibbs, Paul J.; Katz, Martha R.; Ott, Thomas J.; Patterson, Brian M.; Lee, Wah-Keat; Fezzaa, Kamel; Cooley, Jason C.; Clarke, Amy J.

    2015-01-06

    Solidification from a multiphase fluid involves many unknown quantities due to the difficulty of predicting the impact of fluid flow on chemical partitioning. Real-time x-ray radiography was used to observe liquid-liquid phase separation in Al90In10 prior to solidification. Quantitative image analysis was used to measure the motion and population characteristics of the dispersed indium-rich liquid phase during cooling. Here we determine that the droplet growth characteristics resemble well known steady-state coarsening laws with likely enhancement by concurrent growth due to supersaturation. Simplistic views of droplet motion are found to be insufficient until late in the reaction due to a hydrodynamic instability caused by the large density difference between the dispersed and matrix liquid phases.

  18. Symmetric Z2 spin liquids and their neighboring phases on triangular lattice

    NASA Astrophysics Data System (ADS)

    Lu, Yuan-Ming

    2016-04-01

    Motivated by recent numerical discovery of a gapped spin liquid phase in spin-1 /2 triangular-lattice J1-J2 Heisenberg model, we classify symmetric Z2 spin liquids on triangular lattice in the Abrikosov-fermion representation. We find 20 phases with distinct spinon symmetry quantum numbers, eight of which have their counterparts in the Schwinger-boson representation. Among them we identify two promising candidates (#1 and #20), which can realize a gapped Z2 spin liquid with up to next nearest neighbor mean-field amplitudes. We analyze their neighboring magnetic orders and valence bond solid patterns, and find one state (#20) that is connected to 120-degree Neel order by a continuous quantum phase transition. We also identify gapped nematic Z2 spin liquids in the neighborhood of the symmetric states and find three promising candidates (#1, #6, and #20).

  19. Dynamic evolution of liquid–liquid phase separation during continuous cooling

    DOE PAGESBeta

    Imhoff, Seth D.; Gibbs, Paul J.; Katz, Martha R.; Ott, Thomas J.; Patterson, Brian M.; Lee, Wah-Keat; Fezzaa, Kamel; Cooley, Jason C.; Clarke, Amy J.

    2015-01-06

    Solidification from a multiphase fluid involves many unknown quantities due to the difficulty of predicting the impact of fluid flow on chemical partitioning. Real-time x-ray radiography was used to observe liquid-liquid phase separation in Al90In10 prior to solidification. Quantitative image analysis was used to measure the motion and population characteristics of the dispersed indium-rich liquid phase during cooling. Here we determine that the droplet growth characteristics resemble well known steady-state coarsening laws with likely enhancement by concurrent growth due to supersaturation. Simplistic views of droplet motion are found to be insufficient until late in the reaction due to a hydrodynamicmore » instability caused by the large density difference between the dispersed and matrix liquid phases.« less

  20. Liquid nanodroplet formation through phase explosion mechanism in laser-irradiated metal targets

    NASA Astrophysics Data System (ADS)

    Mazzi, Alberto; Gorrini, Federico; Miotello, Antonio

    2015-09-01

    Some quantitative aspects of laser-irradiated pure metals, while approaching phase explosion, are still not completely understood. Here, we develop a model that describes the main quantities regulating the liquid-vapor explosive phase transition and the expulsion of liquid nanodroplets that, by solidifying, give rise to nanoparticle formation. The model combines both a thermodynamics description of the explosive phase change and a Monte Carlo simulation of the randomly generated critical vapor bubbles. The calculation is performed on a set of seven metals (Al, Fe, Co, Ni, Cu, Ag, and Au) which are frequently used in pulsed laser ablation experiments. Our final predictions about the size distribution of the liquid nanodroplets and the number ratio of liquid/vapor ejected atoms are compared, whenever possible, with available molecular dynamics simulations and experimental data.

  1. Cyclohexane, a Potential Drug of Abuse with Pernicious Effects on the Brain

    PubMed Central

    Campos-Ordonez, Tania; Gonzalez-Perez, Oscar

    2016-01-01

    Cyclohexane is a volatile solvent used as a harmless substitute for dangerous organic solvents in several products, such as paint thinners, gasoline and adhesives. Many of these products are used as drugs of abuse and can severely damage neural tissue and impair neurological functions. However, there is very little information on the effects of cyclohexane on the brain. In humans, cyclohexane produces headaches, sleepiness, dizziness, limb weakness, motor changes, and verbal memory impairment. Recent studies in mice have demonstrated behavioral alterations, reactive gliosis, microglial reactivity, and oxidative stress in the brains of cyclohexane-exposed animals. This indicates that cyclohexane may represent a potential problem for public health. Therefore, studies are needed to clarify the neurobiological effects of this volatile compound, including the cellular and molecular mechanisms of neurotoxicity, and to minimize the human health risk posed by the intentional or accidental inhalation of this potential drug of abuse. PMID:26779017

  2. Cyclohexane, a Potential Drug of Abuse with Pernicious Effects on the Brain.

    PubMed

    Campos-Ordonez, Tania; Gonzalez-Perez, Oscar

    2015-01-01

    Cyclohexane is a volatile solvent used as a harmless substitute for dangerous organic solvents in several products, such as paint thinners, gasoline and adhesives. Many of these products are used as drugs of abuse and can severely damage neural tissue and impair neurological functions. However, there is very little information on the effects of cyclohexane on the brain. In humans, cyclohexane produces headaches, sleepiness, dizziness, limb weakness, motor changes, and verbal memory impairment. Recent studies in mice have demonstrated behavioral alterations, reactive gliosis, microglial reactivity, and oxidative stress in the brains of cyclohexane-exposed animals. This indicates that cyclohexane may represent a potential problem for public health. Therefore, studies are needed to clarify the neurobiological effects of this volatile compound, including the cellular and molecular mechanisms of neurotoxicity, and to minimize the human health risk posed by the intentional or accidental inhalation of this potential drug of abuse. PMID:26779017

  3. Revisiting the formation of cyclic clusters in liquid ethanol.

    PubMed

    Balanay, Mannix P; Kim, Dong Hee; Fan, Haiyan

    2016-04-21

    The liquid phase of ethanol in pure and in non-polar solvents was studied at room temperature using Fourier transform infrared (FT-IR) and (1)H nuclear magnetic resonance (NMR) spectroscopies together with theoretical approach. The FT-IR spectra for pure ethanol and solution in cyclohexane at different dilution stages are consistent with (1)H NMR results. The results from both methods were best explained by the results of the density functional theory based on a multimeric model. It is suggested that cyclic trimers and tetramers are dominated in the solution of cyclohexane/hexane with the concentration greater than 0.5M at room temperature. In liquid ethanol, while the primary components at room temperature are cyclic trimers and tetramers, there is a certain amount (∼14%) of open hydroxide group representing the existence of chain like structures in the equilibria. The cyclic cluster model in the liquid and concentrated solution phase (>0.5M) can be used to explain the anomalously lower freezing point of ethanol (159 K) than that of water (273 K) at ambient conditions. In addition, (1)H NMR at various dilution stages reveals the dynamics for the formation of cyclic clusters. PMID:27389215

  4. Revisiting the formation of cyclic clusters in liquid ethanol

    NASA Astrophysics Data System (ADS)

    Balanay, Mannix P.; Kim, Dong Hee; Fan, Haiyan

    2016-04-01

    The liquid phase of ethanol in pure and in non-polar solvents was studied at room temperature using Fourier transform infrared (FT-IR) and 1H nuclear magnetic resonance (NMR) spectroscopies together with theoretical approach. The FT-IR spectra for pure ethanol and solution in cyclohexane at different dilution stages are consistent with 1H NMR results. The results from both methods were best explained by the results of the density functional theory based on a multimeric model. It is suggested that cyclic trimers and tetramers are dominated in the solution of cyclohexane/hexane with the concentration greater than 0.5M at room temperature. In liquid ethanol, while the primary components at room temperature are cyclic trimers and tetramers, there is a certain amount (˜14%) of open hydroxide group representing the existence of chain like structures in the equilibria. The cyclic cluster model in the liquid and concentrated solution phase (>0.5M) can be used to explain the anomalously lower freezing point of ethanol (159 K) than that of water (273 K) at ambient conditions. In addition, 1H NMR at various dilution stages reveals the dynamics for the formation of cyclic clusters.

  5. Heterogeneity of the Liquid Phase, and Vapor Separation in Los Azufres (Mexico) Geothermal Reservoir

    SciTech Connect

    Nieva, D.; Quijano, L.; Garfias, A.; Barragan, R.M.; Laredo, F.

    1983-12-15

    Data of chemical and isotopic composition of fluids from Los Azufres geothermal wells is interpreted in order to characterize the composition of the liquid phase, and to define the relation between this phase and fluids from steam-producing wells. Chemical and specific enthalpy data show that most wells considered are fed a mixture of steam and liquid. Thus, flashing occurs in the formation. This poses a problem on the interpretation of isotopic data, because the composition of the feeding mixture need not be representative of the composition of the liquid phase in the reservoir. Two extreme alternatives for the interpretation of isotopic data are considered. In the first alternative the composition of the total discharge is considered to be the same as that of the liquid in the reservoir. In the second alternative the feeding fluid is considered to be a mixture of the liquid phase in the reservoir and the calculated fraction of steam. In addition, this steam is assumed to separate from a much larger mass of that liquid phase at the downhole temperature. The contribution of steam is then subtracted from the total discharge to yield the composition of the liquid phase. Using data for silica concentration in total discharge and separated water, the chloride concentration in the reservoir liquid is calculated. This result is used to calculate the fraction of steam in the feeding mixture of each well. The isotopic data is then corrected as proposed for the second alternative, to yield the composition of the liquid phase. Comparison of the corrected and uncorrected isotopic values shows that the correction has an important effect only when the steam mass fraction in the feeding mixture is large (> 20%). The correction tends to reduce the dispersion of data points in a {delta} D vs {delta}{sup 18}O diagram. Points representing composition of liquid phase show an approximately linear distribution, suggesting a process of mixing of two fluids. Available data appears to

  6. Quark-Gluon Soup -- The Perfectly Liquid Phase of QCD

    NASA Astrophysics Data System (ADS)

    Heinz, Ulrich

    2015-03-01

    At temperatures above about 150 MeV and energy densities exceeding 500 MeV/fm3, quarks and gluons exist in the form of a plasma of free color charges that is about 1000 times hotter and a billion times denser than any other plasma ever created in the laboratory. This quark-gluon plasma (QGP) turns out to be strongly coupled, flowing like a liquid. About 35 years ago, the nuclear physics community started a program of relativistic heavy-ion collisions with the goal of producing and studying QGP under controlled laboratory conditions. This article recounts the story of its successful creation in collider experiments at Brookhaven National Laboratory and CERN and the subsequent discovery of its almost perfectly liquid nature, and reports on the recent quantitatively precise determination of its thermodynamic and transport properties.

  7. Controlled Electrochemical Deformation of Liquid-Phase Gallium.

    PubMed

    Chrimes, Adam F; Berean, Kyle J; Mitchell, Arnan; Rosengarten, Gary; Kalantar-zadeh, Kourosh

    2016-02-17

    Pure gallium is a soft metal with a low temperature melting point of 29.8 °C. This low melting temperature can potentially be employed for creating optical components with changeable configurations on demand by manipulating gallium in its liquid state. Gallium is a smooth and highly reflective metal that can be readily maneuvered using electric fields. These features allow gallium to be used as a reconfigurable optical reflector. This work demonstrates the use of gallium for creating reconfigurable optical reflectors manipulated through the use of electric fields when gallium is in a liquid state. The use of gallium allows the formed structures to be frozen and preserved as long as the temperature of the metal remains below its melting temperature. The lens can be readily reshaped by raising the temperature above the melting point and reapplying an electric field to produce a different curvature of the gallium reflector. PMID:26820807

  8. Directed liquid phase assembly of highly ordered metallic nanoparticle arrays

    DOE PAGESBeta

    Wu, Yueying; Dong, Nanyi; Fu, Shaofang; Fowlkes, Jason D.; Kondic, Lou; Vincenti, Maria A.; de Ceglia, Domenico; Rack, Philip D.

    2014-04-01

    Directed assembly of nanomaterials is a promising route for the synthesis of advanced materials and devices. We demonstrate the directed-assembly of highly ordered two-dimensional arrays of hierarchical nanostructures with tunable size, spacing and composition. The directed assembly is achieved on lithographically patterned metal films that are subsequently pulse-laser melted; during the brief liquid lifetime, the pattened nanostructures assemble into highly ordered primary and secondary nanoparticles, with sizes below that which was originally patterned. Complementary fluid-dynamics simulations emulate the resultant patterns and show how the competition of capillary forces and liquid metal–solid substrate interaction potential drives the directed assembly. Lastly, asmore » an example of the enhanced functionality, a full-wave electromagnetic analysis has been performed to identify the nature of the supported plasmonic resonances.« less

  9. Directed liquid phase assembly of highly ordered metallic nanoparticle arrays

    SciTech Connect

    Wu, Yueying; Dong, Nanyi; Fu, Shaofang; Fowlkes, Jason D.; Kondic, Lou; Vincenti, Maria A.; de Ceglia, Domenico; Rack, Philip D.

    2014-04-01

    Directed assembly of nanomaterials is a promising route for the synthesis of advanced materials and devices. We demonstrate the directed-assembly of highly ordered two-dimensional arrays of hierarchical nanostructures with tunable size, spacing and composition. The directed assembly is achieved on lithographically patterned metal films that are subsequently pulse-laser melted; during the brief liquid lifetime, the pattened nanostructures assemble into highly ordered primary and secondary nanoparticles, with sizes below that which was originally patterned. Complementary fluid-dynamics simulations emulate the resultant patterns and show how the competition of capillary forces and liquid metal–solid substrate interaction potential drives the directed assembly. Lastly, as an example of the enhanced functionality, a full-wave electromagnetic analysis has been performed to identify the nature of the supported plasmonic resonances.

  10. Versatile ligands for high-performance liquid chromatography: An overview of ionic liquid-functionalized stationary phases.

    PubMed

    Zhang, Mingliang; Mallik, Abul K; Takafuji, Makoto; Ihara, Hirotaka; Qiu, Hongdeng

    2015-08-01

    Ionic liquids (ILs), a class of unique substances composed purely by cation and anions, are renowned for their fascinating physical and chemical properties, such as negligible volatility, high dissolution power, high thermal stability, tunable structure and miscibility. They are enjoying ever-growing applications in a great diversity of disciplines. IL-modified silica, transforming the merits of ILs into chromatographic advantages, has endowed the development of high-performance liquid chromatography (HPLC) stationary phase with considerable vitality. In the last decade, IL-functionalized silica stationary phases have evolved into a series of branches to accommodate to different HPLC modes. An up-to-date overview of IL-immobilized stationary phases is presented in this review, and divided into five parts according to application mode, i.e., ion-exchange, normal-phase, reversed-phase, hydrophilic interaction and chiral recognition. Specific attention is channeled to synthetic strategies, chromatographic behavior and separation performance of IL-functionalized silica stationary phases. PMID:26320781

  11. Ionic liquid-modified materials for solid-phase extraction and separation: a review.

    PubMed

    Vidal, Lorena; Riekkola, Marja-Liisa; Canals, Antonio

    2012-02-17

    In recent years, materials science has propelled to the research forefront. Ionic liquids with unique and fascinating properties have also left their footprints to the developments of materials science during the last years. In this review we highlight some of their recent advances and provide an overview at the current status of ionic liquid-modified materials applied in solid-phase extraction, liquid and gas chromatography and capillary electrochromatography with reference to recent applications. In addition, the potential of ionic liquids in the modification of capillary inner wall in capillary electrophoresis is demonstrated. The main target material modified with ionic liquids is silica, but polymers and monoliths have recently joined the studies. Although imidazolium is still clearly the most commonly used ionic liquid for the covalently modification of materials, the exploitation of pyridinium and phosphonium will most probably increase in the future. PMID:22244164

  12. A neutralization charge detection method for detecting ions under ambient and liquid-phase conditions.

    PubMed

    Chang, Ko-Keng; Cai, Yi-Hong; Chen, Chung-Hsuan; Wang, Yi-Sheng

    2016-04-14

    The neutralization charge detection method detects induction signals produced from the neutralization of electric charges of ions at metal surfaces. The signals are intense and can propagate through phase boundaries for detection. The detection method can detect ions under ambient and liquid-phase conditions with high senstivity and fast response time. PMID:26996136

  13. PARTITIONING TRACERS FOR IN SITU DETECTION AND QUANTIFICATION OF DENSE NONAQUEOUS PHASE LIQUIDS IN GROUNDWATER SYSTEMS

    EPA Science Inventory

    The overall goal of the proposed project is to explore the use of partitioning tracers to characterize dense nonaqueous phase liquids (DNAPLs) in aquifer systems. Bulk-phase partitioning tracers will be investigated to detect and determine DNAPL saturation, while interface partit...

  14. SYNTHESIS REPORT ON FIVE DENSE, NONAQUEOUS-PHASE LIQUID (DNAPL) REMEDIATION PROJECTS

    EPA Science Inventory

    Dense non-aqueous phase liquid (DNAPL) poses a difficult problem for subsurface remediation because it serves as a continuing source to dissolved phase ground water contamination and is difficult to remove from interstitial pore space or bedrock fractures in the subsurface. Numer...

  15. Two parametric flow measurement in gas-liquid two-phase flow

    NASA Astrophysics Data System (ADS)

    Chen, Z.; Chen, C.; Xu, Y.; Zhao, Z.

    The importance and current development of two parametric measurement during two-phase flow are briefly reviewed in this paper. Gas-liquid two-phase two parametric metering experiments were conducted by using an oval gear meter and a sharp edged orifice mounted in series in a horizontal pipe. Compressed air and water were used as gas and liquid phases respectively. The correlations, which can be used to predict the total flow rate and volumetric quality of two-phase flow or volumetric flow rate of each phase, have also been proposed in this paper. Comparison of the calculated values of flow rate of each phase from the correlations with the test data showed that the root mean square fractional deviation for gas flow rate is 2.9 percent and for liquid flow rate 4.4 percent. The method proposed in this paper can be used to measure the gas and liquid flow rate in two-phase flow region without having to separate the phases.

  16. Models of retention of adamantylamidrazones in reversed-phase high-performance liquid chromatography

    NASA Astrophysics Data System (ADS)

    Prokopov, S. V.; Kurbatova, S. V.

    2011-05-01

    Rules governing the chromatographic behavior of some amidrazones of the adamantane series were studied under the conditions of reversed-phase high-performance liquid chromatography. The characteristics of the retention of sorbates in elution by aqueous-acetonitrile phases with various compositions were calculated. Correlations between the structure and physicochemical characteristics of sorbate molecules and their retention were studied.

  17. Characterization of rhamnolipids by liquid chromatography/mass spectrometry after solid-phase extraction.

    PubMed

    Behrens, Beate; Engelen, Jeannine; Tiso, Till; Blank, Lars Mathias; Hayen, Heiko

    2016-04-01

    Rhamnolipids are surface-active agents with a broad application potential that are produced in complex mixtures by bacteria of the genus Pseudomonas. Analysis from fermentation broth is often characterized by laborious sample preparation and requires hyphenated analytical techniques like liquid chromatography coupled to mass spectrometry (LC-MS) to obtain detailed information about sample composition. In this study, an analytical procedure based on chromatographic method development and characterization of rhamnolipid sample material by LC-MS as well as a comparison of two sample preparation methods, i.e., liquid-liquid extraction and solid-phase extraction, is presented. Efficient separation was achieved under reversed-phase conditions using a mixed propylphenyl and octadecylsilyl-modified silica gel stationary phase. LC-MS/MS analysis of a supernatant from Pseudomonas putida strain KT2440 pVLT33_rhlABC grown on glucose as sole carbon source and purified by solid-phase extraction revealed a total of 20 congeners of di-rhamnolipids, mono-rhamnolipids, and their biosynthetic precursors 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs) with different carbon chain lengths from C8 to C14, including three rhamnolipids with uncommon C9 and C11 fatty acid residues. LC-MS and the orcinol assay were used to evaluate the developed solid-phase extraction method in comparison with the established liquid-liquid extraction. Solid-phase extraction exhibited higher yields and reproducibility as well as lower experimental effort. Graphical Abstract ᅟ. PMID:26879646

  18. Characterization of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][Tf2N])∕TX-100∕cyclohexane ternary microemulsion: investigation of photoinduced electron transfer in this RTIL containing microemulsion.

    PubMed

    Sarkar, Souravi; Pramanik, Rajib; Ghatak, Chiranjib; Rao, Vishal Govind; Sarkar, Nilmoni

    2011-02-21

    In this study we have characterized a ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethyl- sulfonyl)imide containing ternary nonaqueous microemulsion ([Emim][Tf(2)N]∕∕TX-100∕cyclo- hexane). The phase behavior and dynamic light scattering study show that the [Emim][Tf(2)N]∕TX-100∕cyclohexane three component system can form microemulsion with [Emim][Tf(2)N] as polar core at suitable condition. We have investigated photoinduced electron transfer (PET) using dimethyl aniline as electron donor and several Coumarin dyes as electron acceptor molecules at two different R values (R = [ionic liquid]∕[surfactant]) to observe how the dynamics of the PET rate is affected in this type of confined microenvironment compared to that of the PET dynamics in neat ionic liquid and other pure solvent media. The plot of observed k(q) values with the free energy change (ΔG(0)) for electron transfer reaction shows an apparent inversion in the observed rate as predicted by the Marcus theory. PMID:21341859

  19. Characterization of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][Tf2N])/TX-100/cyclohexane ternary microemulsion: Investigation of photoinduced electron transfer in this RTIL containing microemulsion

    NASA Astrophysics Data System (ADS)

    Sarkar, Souravi; Pramanik, Rajib; Ghatak, Chiranjib; Rao, Vishal Govind; Sarkar, Nilmoni

    2011-02-01

    In this study we have characterized a ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethyl- sulfonyl)imide containing ternary nonaqueous microemulsion ([Emim][Tf2N]//TX-100/cyclo- hexane). The phase behavior and dynamic light scattering study show that the [Emim][Tf2N]/TX-100/cyclohexane three component system can form microemulsion with [Emim][Tf2N] as polar core at suitable condition. We have investigated photoinduced electron transfer (PET) using dimethyl aniline as electron donor and several Coumarin dyes as electron acceptor molecules at two different R values (R = [ionic liquid]/[surfactant]) to observe how the dynamics of the PET rate is affected in this type of confined microenvironment compared to that of the PET dynamics in neat ionic liquid and other pure solvent media. The plot of observed kq values with the free energy change (ΔG0) for electron transfer reaction shows an apparent inversion in the observed rate as predicted by the Marcus theory.

  20. A compensation method for the full phase retardance nonuniformity in phase-only liquid crystal on silicon spatial light modulators.

    PubMed

    Teng, Long; Pivnenko, Mike; Robertson, Brian; Zhang, Rong; Chu, Daping

    2014-10-20

    A simple and efficient compensation method for the full correction of both the anisotropic and isotropic nonuniformity of the light phase retardance in a liquid crystal (LC) layer is presented. This is achieved by accurate measurement of the spatial variation of the LC layer's thickness with the help of a calibrated liquid crystal wedge, rather than solely relying on the light intensity profile recorded using two crossed polarizers. Local phase retardance as a function of the applied voltage is calculated with its LC thickness and a set of reference data measured from the intensity of the reflected light using two crossed polarizers. Compensation of the corresponding phase nonuniformity is realized by applying adjusted local voltage signals for different grey levels. To demonstrate its effectiveness, the proposed method is applied to improve the performance of a phase-only liquid crystal on silicon (LCOS) spatial light modulator (SLM). The power of the first diffraction order measured with the binary phase gratings compensated by this method is compared with that compensated by the conventional crossed-polarizer method. The results show that the phase compensation method proposed here can increase the dynamic range of the first order diffraction power significantly from 15~21 dB to over 38 dB, while the crossed-polarizer method can only increase it to 23 dB. PMID:25401672

  1. An immersed boundary-thermal lattice Boltzmann method for solid-liquid phase change

    NASA Astrophysics Data System (ADS)

    Huang, Rongzong; Wu, Huiying

    2014-11-01

    In this work, an immersed boundary-thermal lattice Boltzmann method (IB-TLBM) is proposed to simulate solid-liquid phase change problems. To treat the velocity and temperature boundary conditions on the solid-liquid interface, immersed boundary method (IBM) is adopted, in which the solid-liquid interface is represented as a sharp interface rather than a diffusive interface and is tracked explicitly by Lagrangian grid. The surface forces along the immersed boundary, including the “momentum force” for velocity boundary condition and the “energy force” for temperature boundary condition, are calculated by the direct-forcing scheme. The moving velocity of solid-liquid interface induced by phase change is calculated by the amount of latent heat absorbed or released in a time step directly, with no need to compute temperature gradients in solid and liquid phases separately. The temperature on the solid-liquid interface is specified as the melting temperature, which means phase change happens at a constant temperature. As the solid-liquid interface evolves with time, the identification of phase of Eulerian points and the rearrangement of Lagrangian points are also considered. With regard to the velocity and temperature fields, passive scalar thermal lattice Boltzmann method (TLBM) with multiple-relaxation-time (MRT) collision schemes is adopted. Numerical examples, including conduction-induced melting in a semi-infinite space and melting in a square cavity, are carried out to verify the present method and good results are obtained. As a further application, melting in a circular cylinder with considering the motion of solid phase is simulated successfully by the present method; numerical results show that the motion of solid phase accelerates the melting process obviously.

  2. Optical studies on smectic phases in binary mixture of liquid crystals

    NASA Astrophysics Data System (ADS)

    Govindaiah, T. N.; Sreepad, H. R.; Nagaraja, N.; Sridhara, G. R.; Ravi, H. R.

    2015-06-01

    The binary mixture of two non-mesogenic compounds viz., Didodecyl dimethyl ammonium bromide (DDAB) and ethylene glycol (EG) exhibits different liquid crystalline phase's at large range of concentrations and temperature. The concentrations with lower / higher percentage of DDAB exhibit I-SmA-SmC*-SmE-K sequentially when the specimen is cooled from isotropic phase. Different liquid crystalline phases observed in the mixture were studied using DSC, X-ray, and Optical microscopic techniques. The temperature variations of optical anisotropy have also been discussed.

  3. Transitional liquid crystalline phases between the hexagonal and lamellar phases in ternary cesium N-tetradecanoate-water-additive mixtures

    SciTech Connect

    Blackburn, J.C.; Kilpatrick, P.K. )

    1993-04-01

    The effects of added salt (CsOH, CsCl), long-chain carboxylic acid, and long-chain alcohol on the lyotropic liquid crystalline phase behavior in the cesium n-tetradecanoate (CsTD)-water system is reported. The transitional region between the hexagonal (H) and lamellar (L) phases was the compositional range of focus. Three transitional phases were observed: (i) the ribbon (R) phase, a biaxial phase consisting of cylinders of ellipsoidal cross section; (ii) the viscous isotropic (VI) phase, an isotropic phase thought to consist of interconnected rods on an Ia3d lattice; and (iii) the intermediate (Int) phase, a uniaxial anisotropic phase thought to consist of interconnected rods on a planar lattice. The effect of the additives was to decrease the interfacial curvature of the surfactant head group layer by varying head group repulsion and by varying the surfactant tail volume relative to the surfactant head group area. These changes resulted in formation of transitional phases seeming to possess curvature between that of the cylindrical H phase and the planar L phase. The ionic repulsion between carboxylate head groups was reduced by the addition of CsOH or CsCl, and resulted in destabilization of the VI phase and the formation of the anisotropic Int phase. With the addition of cosurfactants, n-tetradecanoic acid (TDA) and 1-tetradecanol (TDOH), no Int phase was observed. With 7 wt% added TDA the R phase was stabilized up to temperatures of 336 K, above the 330 K temperature limit in the binary CsTD-D[sub 2]O system. In all four systems, sufficient additive (5-10 wt%) resulted in a transition to the L phase, which was stable over a large portion of the compositional range. In order of apparently decreasing mean curvature, the phase sequence is: hexagonal, ribbon, viscous isotropic, intermediate, and lamellar.

  4. Phase equilibria and liquid phase epitaxy growth of PbSnSeTe lattice matched to PbSe

    NASA Technical Reports Server (NTRS)

    Mccann, Patrick J.; Fonstad, Clifton G.; Fuchs, Jacob; Feit, Ze'ev

    1987-01-01

    The necessary phase diagram data for growing lattice-matched layers of PbSnSeTe on PbSe are presented. Solid compounds of Pb(1-x)Sn(x)Se(1-y)Te(y) lattice-matched to PbSe were grown from liquid melts consisting of (Pb/1-x/Sn/x/)(1-z)(Se/1-y/Te/y/)(z); phase equilibria data were determined together with liquidus data for values of x(liquid) from 0 to 40 percent and y(liquid) from 0 to 40 percent for temperatures between 450 and 540 C. It was found that relatively large amounts of Te must be added to the melt to achieve lattice matching because of its low segregation coefficient relative to Se. A significant lattice-pulling effect was discovered for the 5-percent Sn case, and a similar effect is expected for the 10- and 20-percent Sn cases.

  5. Magnetic microemulsions based on magnetic ionic liquids.

    PubMed

    Klee, Andreas; Prevost, Sylvain; Kunz, Werner; Schweins, Ralf; Kiefer, Klaus; Gradzielski, Michael

    2012-11-28

    Microemulsions with magnetic properties were formed by employing a magnetic room temperature ionic liquid (MRTIL) as polar phase, cyclohexane as oil, and an appropriate mixture of ionic surfactant and decanol as a cosurfactant. By means of small-angle neutron scattering (SANS) and electric conductivity the microemulsion structure could be confirmed, where the classical structural sequence of oil-continuous-bicontinuous-polar phase continuous is observed with increasing ratio [polar phase]/[oil]. Accordingly a maximum of the structural size is observed at about equal volumes of oil and MRTIL contained. Therefore this system is structurally the same as normal microemulsions but with the magnetic properties added to it by the incorporation into the systems formulation. PMID:23060241

  6. Energy landscape view of phase transitions and slow dynamics in thermotropic liquid crystals

    PubMed Central

    Chakrabarti, Dwaipayan; Bagchi, Biman

    2006-01-01

    Thermotropic liquid crystals are known to display rich phase behavior on temperature variation. Although the nematic phase is orientationally ordered but translationally disordered, a smectic phase is characterized by the appearance of a partial translational order in addition to a further increase in orientational order. In an attempt to understand the interplay between orientational and translational order in the mesophases that thermotropic liquid crystals typically exhibit upon cooling from the high-temperature isotropic phase, we investigate the potential energy landscapes of a family of model liquid crystalline systems. The configurations of the system corresponding to the local potential energy minima, known as the inherent structures, are determined from computer simulations across the mesophases. We find that the depth of the potential energy minima explored by the system along an isochor grows through the nematic phase as temperature drops in contrast to its insensitivity to temperature in the isotropic and smectic phases. The onset of the growth of the orientational order in the parent phase is found to induce a translational order, resulting in a smectic-like layer in the underlying inherent structures; the inherent structures, surprisingly, never seem to sustain orientational order alone if the parent nematic phase is sandwiched between the high-temperature isotropic phase and the low-temperature smectic phase. The Arrhenius temperature dependence of the orientational relaxation time breaks down near the isotropic–nematic transition. We find that this breakdown occurs at a temperature below which the system explores increasingly deeper potential energy minima. PMID:16648269

  7. Poly(L-lactic acid)-modified silica stationary phase for reversed-phase and hydrophilic interaction liquid chromatography.

    PubMed

    Ohyama, Kaname; Takasago, Shizuka; Kishikawa, Naoya; Kuroda, Naotaka

    2015-03-01

    Poly(L-lactic acid) is a linear aliphatic thermoplastic polyester that can be produced from renewable resources. A poly(L-lactic acid)-modified silica stationary phase was newly prepared by amide bond reaction between amino groups on aminopropyl silica and carboxylic acid groups at the end of the poly(L-lactic acid) chain. The poly(L-lactic acid)-silica column was characterized in reversed-phase liquid chromatography and hydrophilic interaction liquid chromatography with the use of different mobile phase compositions. The poly(L-lactic acid)-silica column was found to work in both modes, and the retention of test compounds depending on acetonitrile content exhibited "U-shaped" curves, which was an indicator of reversed-phase liquid chromatography/hydrophilic interaction liquid chromatography mixed-mode retention behavior. In addition, carbonyl groups included into the poly(L-lactic acid) backbone work as an electron-accepting group toward a polycyclic aromatic hydrocarbon and provide π-π interactions. PMID:25546473

  8. Migration of liquid phase from the primary/peritectic interface in a temperature gradient

    NASA Astrophysics Data System (ADS)

    Peng, Peng; Li, XinZhong; Su, YanQing; Guo, JingJie

    2016-07-01

    The migration of the liquid droplets from the primary α/peritectic β interface at the peritectic temperature TP has been observed and analyzed in a Sn-Ni peritectic alloy. During the isothermal annealing stage of the interrupted directional solidification, a concentration gradient is established across the liquid droplets along the direction of the temperature gradient due to the temperature gradient zone melting. Simultaneous remelting/resolidification at the top/bottom of the liquid droplets by this concentration gradient have been confirmed to lead to migration of these droplets towards higher temperatures. The dependence of the migration distance of the liquid droplets on isothermal annealing time has been well predicted. Furthermore, since the lengths of the liquid droplet are not uniform along the direction of the temperature gradient, the remelting/resolidification rates which are dependent on the local morphology of liquid droplet are different at different local positions of the liquid droplets. It has been demonstrated that the morphology of the liquid droplet was also influenced by the morphologies of the liquid phase themselves. Therefore, the morphology of the liquid droplet itself changes from spherical to some kinds of irregular shapes during its migration.

  9. Giant Magnetic Field-induced Phase Transitions in Dimeric Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Salili, Seyyed Muhammad; Salamonczyk, Miroslaw; Tamba, Maria-Gabriela; Sprunt, Samuel; Mehl, Georg; Jakli, Antal; Gleeson, James; Kent Group Collaboration; Hull Group Collaboration

    Liquid crystals are responsive to external fields such as electric, magnetic fields. The first experimental observation of dependence of isotropic to nematic phase transition on the applied magnetic field was done using a strong magnetic field on bent-core nematogens and the phase transition temperature exhibited an upshift of 0.7 C at B =30 T. We report on measurements of giant magnetic field-induced isotropic-nematic transition of chainsticks (nunchuks) type dimeric liquid crystals. Upon using the B =25 T split-helix resistive solenoid magnet at NHMFL, we have observed up to 18 C upshift of the isotropic to nematic phase transition temperature at B =22T. We discuss the results within the context of differential thermodynamic potential and the two basic mean-field theories. To our knowledge, this is the first observation of such huge shifts in the phase transitions of thermotropic liquid ctystals

  10. Glucaminium ionic liquid-functionalized stationary phase for the separation of nucleosides in hydrophilic interaction chromatography.

    PubMed

    Jiang, Qiong; Zhang, Mingliang; Wang, Xusheng; Guo, Yong; Qiu, Hongdeng; Zhang, Shusheng

    2015-10-01

    A glucaminium-based ionic liquid stationary phase was prepared via facile epoxy-amine reaction and subsequent quaternization. Successful immobilization of glucaminium-based ionic liquid onto silica surface was validated by elemental analysis and infrared spectroscopy. The new stationary phase was evaluated for the separation of nucleosides in hydrophilic interaction liquid chromatography (HILIC). Effects of various factors, such as acetonitrile concentration, salt concentration, pH value, as well as column temperature, on the chromatographic behavior toward nucleosides were studied in detail. The results indicated that this new stationary phase can be used for separation of water-soluble polar substances in HILIC mode. The retention of solutes on the stationary phase was influenced by a mixed-mode retention mechanism with a combination of adsorptive and partitioning interactions. PMID:26231689

  11. Topology-driven quantum phase transitions in time-reversal-invariant anyonic quantum liquids

    NASA Astrophysics Data System (ADS)

    Gils, Charlotte; Trebst, Simon; Kitaev, Alexei; Ludwig, Andreas W. W.; Troyer, Matthias; Wang, Zhenghan

    2009-11-01

    Indistinguishable particles in two dimensions can be characterized by anyonic quantum statistics, which is more general than that of bosons or fermions. Anyons emerge as quasiparticles in fractional quantum Hall states and in certain frustrated quantum magnets. Quantum liquids of anyons show degenerate ground states, where the degeneracy depends on the topology of the underlying surface. Here, we present a new type of continuous quantum phase transition in such anyonic quantum liquids, which is driven by quantum fluctuations of the topology. The critical state connecting two anyonic liquids on surfaces with different topologies is reminiscent of the notion of a `quantum foam' with fluctuations on all length scales. This exotic quantum phase transition arises in a microscopic model of interacting anyons for which we present an exact solution in a linear geometry. We introduce an intuitive physical picture of this model that unifies string nets and loop gases, and provide a simple description of topological quantum phases and their phase transitions.

  12. Transient liquid-phase bonding in the Ni-Al-B system

    NASA Astrophysics Data System (ADS)

    Campbell, C. E.; Boettinger, W. J.

    2000-11-01

    Transient liquid-phase (TLP) bonding experiments were performed using a Ni-10.3 at. pct Al alloy and a Ni-10 at. pct B filler material, and the results were compared to simulations performed using the finite-difference diffusion code, DICTRA. For the simulations, a thermodynamic assessment of the Ni-Al-B system was used to define the phase diagram and the thermodynamic factors of the diffusion coefficients. Composition-dependent diffusion mobilities were assessed for the ternary system. Predicted liquid widths as functions of time were in good agreement with the experiments. The calculated and experimental Al composition profiles agree in the matrix but not in the liquid. The simulations qualitatively predicted the observed precipitation and later dissolution of the intermetallic τ phase (Ni20Al3B6) in the base material. This research demonstrated the potential for modeling the formation of spurious phases during TLP bonding of practical superalloy systems.

  13. Automated screening of reversed-phase stationary phases for small-molecule separations using liquid chromatography with mass spectrometry.

    PubMed

    Appulage, Dananjaya K; Wang, Evelyn H; Carroll, Frances; Schug, Kevin A

    2016-05-01

    There are various reversed-phase stationary phases that offer significant differences in selectivity and retention. To investigate different reversed-phase stationary phases (aqueous stable C18 , biphenyl, pentafluorophenyl propyl, and polar-embedded alkyl) in an automated fashion, commercial software and associated hardware for mobile phase and column selection were used in conjunction with liquid chromatography and a triple quadrupole mass spectrometer detector. A model analyte mixture was prepared using a combination of standards from varying classes of analytes (including drugs, drugs of abuse, amino acids, nicotine, and nicotine-like compounds). Chromatographic results revealed diverse variations in selectivity and peak shape. Differences in the elution order of analytes on the polar-embedded alkyl phase for several analytes showed distinct selectivity differences compared to the aqueous C18 phase. The electron-rich pentafluorophenyl propyl phase showed unique selectivity toward protonated amines. The biphenyl phase provided further changes in selectivity relative to C18 with a methanolic phase, but it behaved very similarly to a C18 when an acetonitrile-based mobile phase was evaluated. This study shows the value of rapid column screening as an alternative to excessive mobile phase variation to obtain suitable chromatographic settings for analyte separation. PMID:26959840

  14. Diffuse-interface modeling of liquid-vapor phase separation in a van der Waals fluid

    NASA Astrophysics Data System (ADS)

    Lamorgese, A. G.; Mauri, R.

    2009-04-01

    We simulate liquid-vapor phase separation in a van der Waals fluid that is deeply quenched into the unstable range of its phase diagram. Our theoretical approach follows the diffuse-interface model, where convection induced by phase change is accounted for via a nonequilibrium (Korteweg) force expressing the tendency of the liquid-vapor system to minimize its free energy. Spinodal decomposition patterns for critical and off-critical van der Waals fluids are studied numerically, revealing the scaling laws of the characteristic length scale and composition of single-phase microdomains, together with their dependence on the Reynolds number. Unlike phase separation of viscous binary mixtures, here local equilibrium is reached almost immediately after single-phase domains start to form. In addition, as predicted by scaling laws, such domains grow in time like t2/3. Comparison between 2D and 3D results reveals that 2D simulations capture, even quantitatively, the main features of the phenomenon.

  15. Ecotoxicology of heavy metals: Liquid-phase extraction by nanosorbents

    NASA Astrophysics Data System (ADS)

    Burakov, A.; Romantsova, I.; Babkin, A.; Neskoromnaya, E.; Kucherova, A.; Kashevich, Z.

    2015-11-01

    The paper considers the problem of extreme toxicity heavy metal compounds dissolved in wastewater and liquid emissions of industrial enterprises to living organisms and environment as a whole. The possibility of increasing extraction efficiency of heavy metal ions by sorption materials was demonstrated. The porous space of the latter was modified by carbon nanotubes (CNTs) during process of the chemical vapour deposition (CVD) of carbon on metal oxide catalysts. The increasing of the sorption capacity (10-30%) and the sorption rate of nanomodified activated carbons in comparison with standard materials in the example of absorption of Co2+ and Ni2+ ions from aqueous solutions was proven.

  16. Onset of Convection in Two Liquid Layers with Phase Change

    SciTech Connect

    McFadden, G B; Coriell, S R; Gurski, K F; Cotrell, D L

    2006-09-14

    We perform linear stability calculations for horizontal fluid bilayers that can undergo a phase transformation, taking into account both buoyancy effects and thermocapillary effects in the presence of a vertical temperature gradient. We compare the familiar case of the stability of two immiscible fluids in a bilayer geometry with the less-studied case that the two fluids represent different phases of a single-component material, e.g., the water-steam system. The two cases differ in their interfacial boundary conditions: the condition that the interface is a material surface is replaced by the continuity of mass flux across the interface, together with an assumption of thermodynamic equilibrium that in the linearized equations represents the Clausius-Clapeyron relation relating the interfacial temperature and pressures. For the two-phase case, we find that the entropy difference between the phases plays a crucial role in determining the stability of the system. For small values of the entropy difference between the phases, the two-phase system can be linearly unstable to either heating from above or below. The instability is due to the Marangoni effect in combination with the effects of buoyancy (for heating from below). For larger values of the entropy difference the two-phase system is unstable only for heating from below, and the Marangoni effect is masked by effects of the entropy difference. To help understand the mechanisms driving the instability on heating from below we have performed both long-wavelength and short-wavelength analyses of the two-phase system. The short-wavelength analysis shows that the instability is driven by a coupling between the flow normal to the interface and the latent heat generation at the interface. The mechanism for the large wavelength instability is more complicated, and the detailed form of the expansion is found to depend on the Crispation and Bond numbers as well as the entropy difference. The two-phase system allows a

  17. Liquid-Phase Deposition of CIS Thin Layers: Final Report, February 2003--July 2005

    SciTech Connect

    Ernst, F.; Pirouz, P.

    2006-02-01

    The goal of this project was to fabricate single-phase CIS (a-Cu-In-Se, stoichiometric composition: CuInSe2) thin films for photovoltaic applications from a liquid phase - a Cu-In-Se melt of appropriate composition. This approach of liquid-phase deposition (LPD) is based on the new phase diagram we have established for Cu-In-Se, the first complete equilibrium phase diagram of this system. The liquidus projection exhibits four composition fields in which the primary solid phase, i.e., the first solid material that forms on cooling down from an entirely liquid state, is a-CuInSe2. Remarkably, none of the four composition fields is anywhere near the stoichiometric composition (CuInSe2) of a-CuInSe2. The results demonstrate that the proposed technique is indeed capable of producing films with a particularly large grain size and a correspondingly low density of grain boundaries. To obtain films sufficiently thin for solar cell applications and with a sufficiently smooth surface, it is advantageous to employ a sliding boat mechanism. Future work on liquid-phase deposition of CIS should focus on the interaction between the melt and the substrate surface, the resulting CIS interfaces, the surface morphology of the LPD-grown films, and, of course, the electronic properties of the material.

  18. Adsorption of benzene, cyclohexane and hexane on ordered mesoporous carbon.

    PubMed

    Wang, Gang; Dou, Baojuan; Zhang, Zhongshen; Wang, Junhui; Liu, Haier; Hao, Zhengping

    2015-04-01

    Ordered mesoporous carbon (OMC) with high specific surface area and large pore volume was synthesized and tested for use as an adsorbent for volatile organic compound (VOC) disposal. Benzene, cyclohexane and hexane were selected as typical adsorbates due to their different molecular sizes and extensive utilization in industrial processes. In spite of their structural differences, high adsorption amounts were achieved for all three adsorbates, as the pore size of OMC is large enough for the access of these VOCs. In addition, the unusual bimodal-like pore size distribution gives the adsorbates a higher diffusion rate compared with conventional adsorbents such as activated carbon and carbon molecular sieve. Kinetic analysis suggests that the adsorption barriers mainly originated from the difficulty of VOC vapor molecules entering the pore channels of adsorbents. Therefore, its superior adsorption ability toward VOCs, together with a high diffusion rate, makes the ordered mesoporous carbon a promising potential adsorbent for VOC disposal. PMID:25872710

  19. Novel cyclohexane monooxygenase from Acidovorax sp. CHX100.

    PubMed

    Salamanca, Diego; Karande, Rohan; Schmid, Andreas; Dobslaw, Daniel

    2015-08-01

    Acidovorax sp. CHX100 has a remarkable ability for growth on short cycloalkanes (C5-C8) as a sole source of carbon and energy under aerobic conditions via an uncharacterized mechanism. Transposon mutagenesis of Acidovorax sp. CHX100 revealed a novel cytochrome P450 monooxygenase (CYP450chx) which catalyzed the transformation of cyclohexane to cyclohexanol. Primer walking methods categorized CYP450chx as cytochrome P450 class I taking into account its operon structure: monooxygenase, FAD oxidoreductase, and ferredoxin. CYP450chx was successfully cloned and expressed in Escherichia coli JM109. The activity of CYP450chx was demonstrated by means of the indole co-oxidation. Biotransformation capability of CYP450chx was confirmed through the catalysis of cycloalkanes (C5-C8) to their respective cyclic alcohols. PMID:25935342

  20. Dimple coalescence and liquid droplets distributions during phase separation in a pure fluid under microgravity.

    PubMed

    Oprisan, Ana; Oprisan, Sorinel A; Hegseth, John J; Garrabos, Yves; Lecoutre-Chabot, Carole; Beysens, Daniel

    2014-09-01

    Phase separation has important implications for the mechanical, thermal, and electrical properties of materials. Weightless conditions prevent buoyancy and sedimentation from affecting the dynamics of phase separation and the morphology of the domains. In our experiments, sulfur hexafluoride (SF6) was initially heated about 1K above its critical temperature under microgravity conditions and then repeatedly quenched using temperature steps, the last one being of 3.6 mK, until it crossed its critical temperature and phase-separated into gas and liquid domains. Both full view (macroscopic) and microscopic view images of the sample cell unit were analyzed to determine the changes in the distribution of liquid droplet diameters during phase separation. Previously, dimple coalescences were only observed in density-matched binary liquid mixture near its critical point of miscibility. Here we present experimental evidences in support of dimple coalescence between phase-separated liquid droplets in pure, supercritical, fluids under microgravity conditions. Although both liquid mixtures and pure fluids belong to the same universality class, both the mass transport mechanisms and their thermophysical properties are significantly different. In supercritical pure fluids the transport of heat and mass are strongly coupled by the enthalpy of condensation, whereas in liquid mixtures mass transport processes are purely diffusive. The viscosity is also much smaller in pure fluids than in liquid mixtures. For these reasons, there are large differences in the fluctuation relaxation time and hydrodynamics flows that prompted this experimental investigation. We found that the number of droplets increases rapidly during the intermediate stage of phase separation. We also found that above a cutoff diameter of about 100 microns the size distribution of droplets follows a power law with an exponent close to -2, as predicted from phenomenological considerations. PMID:25260326

  1. Heat of Mixing and Solution of 1,3-Dioxane C4H8O2 + C6H12 Cyclohexane (HMSD1111, LB4308_H)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Heat of Mixing and Solution of 1,3-Dioxane C4H8O2 + C6H12 Cyclohexane (HMSD1111, LB4308_H)' providing data from direct low-pressure calorimetric measurement of molar excess enthalpy at variable mole fraction and constant temperature.

  2. Volumetric Properties of the Mixture 1,3-Dioxane C4H8O2 + C6H12 Cyclohexane (VMSD1212, LB5126_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture 1,3-Dioxane C4H8O2 + C6H12 Cyclohexane (VMSD1212, LB5126_V)' providing data by calculation of molar excess volume from low-pressure density measurements at variable mole fraction and constant temperature.

  3. Phase diagrams for the blue phases of highly chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Bowling, Miriam B.; Collings, Peter J.; Booth, Christopher J.; Goodby, John W.

    1993-11-01

    Polarizing microscopy and optical-activity measurements are used to determine the phase diagram for the blue phases of chiral-racemic mixtures of terephthaloyloxy-bis-4-(2'-methylbutyl) benzoate. Contrary to an earlier report, it is the second blue phase (BP II) rather than the first blue phase (BP I) that is not stable relative to the other blue phases at high chirality. With this development, all phase diagrams for the blue phases reported to date have the same topology. Using similar data for two other highly chiral systems, it is found that a simple scaling of the temperature and chiral-fraction axes produces phase diagrams in quantitative agreement with the present results. Thus, in spite of differences in molecular structure, the number of chiral centers, and phase-transition temperatures, these three systems possess remarkably similar phase diagrams and lend evidence for a universal phase diagram for the blue phases.

  4. Micellar structures in lyotropic liquid crystals and phase transitions

    NASA Astrophysics Data System (ADS)

    Saupe, A.; Xu, S. Y.; Plumley, Sulakshana; Zhu, Y. K.; Photinos, P.

    1991-05-01

    The formation of micellar nematics is discussed with emphasis on the transitions between nematic phases and nematic-smectic transitions. Phase diagrams for MTAB/l-decanol/D,O systems show a direct transition between uniaxial nematics. Electrical conductivity and birefringence measurements on a mixture of sodium decylsulfate. 1-decanol, D,O demonstrate, on the other hand, the existence of a biaxial nemantic range that separates the Uniaxial nematics. On a mixture of cesium perflouroctanoate and H 2O the electrical conductivity and rotational viscosity are used to discuss the relevant features of nematic-lamellar-smectic transitions. The formation of elongated ribbon-like micelles at the nematic-smectic transition is suggested. Transitions between different nematic phases in the MTAB system may be connected with a structural change from long micelles with a fairly circular cross section to similar micelles with a more elliptical cross section.

  5. A liquid/gas phase separator for He-I and He-II

    NASA Technical Reports Server (NTRS)

    Shirron, P. J.; Zahniser, J. L.; Dipirro, M. J.

    1991-01-01

    A liquid/gas phase separator has been developed which separates both liquid He-I and He-II from their vapor. The phase separator was designed for the Superfluid Helium On Orbit Transfer (SHOOT) Flight Demonstration both to cool the liquid He after launch (at temperatures between 2.8 and 4.3 K) to the operating temperature of 1.4 K and as a low rate vent on orbit to maintain operating temperature. The phase separator is made of high-purity copper disks held apart by 6 micron Kevlar fibers. It works on the principle of conducting heat from within the dewar to vaporize liquid as it is throttled in the slits to efficiently cool the remaining liquid. Laboratory tests have demonstrated perfect phase separation for both He at its saturated vapor pressure from 1.2 to 4.3 K and for He-II at 2.13 K at pressures from 4.6 to 112 kPa. The performance of this phase separator during lab testing as well as expected performance in space is discussed.

  6. IMPROVING LIQUID CRYSTAL-BASED BIOSENSING IN AQUEOUS PHASES

    PubMed Central

    Iglesias, Wilder; Abbott, Nicholas L.; Mann, Elizabeth K.; Jákli, Antal

    2012-01-01

    Liquid crystal (LC)-based biological sensors permit the study of aqueous biological samples without the need for the labeling of biological species with fluorescent dyes (which can be laborious and change the properties of the biological sample under study). To date, studies of LC-based biosensors have explored only a narrow range of the liquid crystal/alignment layer combinations essential to their operation. Here we report a study of the role of LC elastic constants and the surface anchoring energy in determining the sensitivity of LC-based biosensors. By investigating a mixture of rod-shape and bent-shape mesogens, and three different alignment layers, we were able to widen the useful detection range of a LC-based sensor by providing an almost linear mapping of effective birefringence with concentration between 0.05 and 1mM of an anionic surfactant (model target analyte). These studies pave the way for optimization of LC-based biosensors and reveal the importance of the choice of both the LC material and the alignment layer in determining sensor properties. PMID:23157269

  7. Improving liquid-crystal-based biosensing in aqueous phases.

    PubMed

    Iglesias, Wilder; Abbott, Nicholas L; Mann, Elizabeth K; Jákli, Antal

    2012-12-01

    Liquid crystal (LC)-based biological sensors permit the study of aqueous biological samples without the need for the labeling of biological species with fluorescent dyes (which can be laborious and change the properties of the biological sample under study). To date, studies of LC-based biosensors have explored only a narrow range of the liquid crystal/alignment layer combinations essential to their operation. Here, we report a study of the role of LC elastic constants and the surface anchoring energy in determining the sensitivity of LC-based biosensors. By investigating a mixture of rod-shape and bent-shape mesogens, and three different alignment layers, we were able to widen the useful detection range of a LC-based sensor by providing an almost-linear mapping of effective birefringence with anionic surfactant concentrations between 0.05 mM and 1 mM (model target analyte). These studies pave the way for optimization of LC-based biosensors and reveal the importance of the choice of both the LC material and the alignment layer in determining sensor properties. PMID:23157269

  8. Chromonic liquid crystalline nematic phase exhibited in binary mixture of two liquid crystals

    SciTech Connect

    Govindaiah, T. N. Sreepad, H. R.; Sridhar, K. N.; Sridhara, G. R.; Nagaraja, N.

    2015-06-24

    A binary mixture of abietic acid and orthophosphoric acid (H{sub 3}PO{sub 4}) exhibits co-existence of biphasic region of Nematic+Isotropic (N+I), lyotropic Nematic (ND) and Smectic-G (SmG) phases. The mixture exhibits N+I, N and SmG phases at different concentrations and at different temperatures. Mixtures with all concentrations of abietic acid exhibit I→N+I→N→SmG phases sequentially when the specimen is cooled from its isotropic melt. These phases have been characterized by using differential scanning calorimetric, X-ray diffraction, and optical texture studies.

  9. Pressureless Reaction Sintering of AlON using Aluminum Orthophosphate as a Transient Liquid Phase

    SciTech Connect

    Michael Bakas; Henry Chu

    2009-01-01

    Use of aluminum oxynitride (AlON) in transparent armor systems has been difficult due to the expense and limitations of the processing methods currently necessary to achieve transparency. Development of a pressureless processing method based on direct reaction sintering of alumina and aluminum nitride powders would reduce costs and provide a more flexible and practical manufacturing method. It may be possible to develop such a processing method using liquid phase sintering; as long as the liquid phase does not remain in the final sample. AlPO4 forms a liquid phase with Al2O3 and AlN at the temperatures required to sinter AlON, and slowly decomposes into P2O5 and alumina. Therefore, it was investigated as a possible transient liquid phase for reaction-sintered AlON. Small compacts of alumina and aluminum nitride with up to of 15wt% AlPO4 additive were pressed and sintered. It was found that AlPO4 formed the requisite transient liquid phase, and it was possible to adjust the process to produce AlON samples with good transmission and densities of 3.66-3.67 g/cc. XRD confirmed the samples formed were AlON, with no trace of any remaining phosphate phases or excess alumina or aluminum nitride. Based on the results, it was concluded that AlPO4 could be utilized as a transient liquid phase to improve the density and transmission of AlON produced by pressureless reaction sintering.

  10. Hydrodynamics and energy consumption studies in a three-phase liquid circulating three-phase fluid bed contactor

    SciTech Connect

    Rusumdar, Ahmad J; Abuthalib, A.; Mohan, Vaka Murali; Srinivasa Kumar, C.; Sujatha, V.; Rajendra Prasad, P.

    2009-07-15

    The hydrodynamics and energy consumption have been studied in a cold flow, bubbling and turbulent, pressurized gas-liquid-solid three-phase fluidized bed (0.15 m ID x 1 m height) with concurrent gas-liquid up flow is proposed with the intention of increasing the gas hold up. The hydrodynamic behaviour is described and characterised by some specific gas and liquid velocities. Particles are easily fluidized and can be uniformly distributed over the whole height of the column. The effect of parameters like liquid flow rate, gas flow rate, particle loading, particle size, and solid density on gas hold up and effect of gas flow rate, solid density and particle size on solid hold up, energy consumption and minimum fluidization velocity has been studied. At the elevated pressures a superior method for better prediction of minimum fluidization velocity and terminal settling velocities has been adopted. The results have been interpreted with Bernoulli's theorem and Richardson-Zaki equation. Based on the assumption of the gas and liquid as a pretend fluid, a simplification has been made to predict the particle terminal settling velocities. The Richardson-Zaki parameter n' was compared with Renzo's results. A correlation has been proposed with the experimental results for the three-phase fluidization. (author)

  11. Absence of a Spin Liquid Phase in the Hubbard Model on the Honeycomb Lattice

    PubMed Central

    Sorella, Sandro; Yunoki, Seiji

    2012-01-01

    A spin liquid is a novel quantum state of matter with no conventional order parameter where a finite charge gap exists even though the band theory would predict metallic behavior. Finding a stable spin liquid in two or higher spatial dimensions is one of the most challenging and debated issues in condensed matter physics. Very recently, it has been reported that a model of graphene, i.e., the Hubbard model on the honeycomb lattice, can show a spin liquid ground state in a wide region of the phase diagram, between a semi-metal (SM) and an antiferromagnetic insulator (AFMI). Here, by performing numerically exact quantum Monte Carlo simulations, we extend the previous study to much larger clusters (containing up to 2592 sites), and find, if any, a very weak evidence of this spin liquid region. Instead, our calculations strongly indicate a direct and continuous quantum phase transition between SM and AFMI. PMID:23251778

  12. Characterizing the correlations between local phase fractions of gas-liquid two-phase flow with wire-mesh sensor.

    PubMed

    Tan, C; Liu, W L; Dong, F

    2016-06-28

    Understanding of flow patterns and their transitions is significant to uncover the flow mechanics of two-phase flow. The local phase distribution and its fluctuations contain rich information regarding the flow structures. A wire-mesh sensor (WMS) was used to study the local phase fluctuations of horizontal gas-liquid two-phase flow, which was verified through comparing the reconstructed three-dimensional flow structure with photographs taken during the experiments. Each crossing point of the WMS is treated as a node, so the measurement on each node is the phase fraction in this local area. An undirected and unweighted flow pattern network was established based on connections that are formed by cross-correlating the time series of each node under different flow patterns. The structure of the flow pattern network reveals the relationship of the phase fluctuations at each node during flow pattern transition, which is then quantified by introducing the topological index of the complex network. The proposed analysis method using the WMS not only provides three-dimensional visualizations of the gas-liquid two-phase flow, but is also a thorough analysis for the structure of flow patterns and the characteristics of flow pattern transition. This article is part of the themed issue 'Supersensing through industrial process tomography'. PMID:27185959

  13. On-line comprehensive two-dimensional normal-phase liquid chromatography×reversed-phase liquid chromatography for preparative isolation of toad venom.

    PubMed

    Li, Jia-Fu; Fang, Hua; Yan, Xia; Chang, Fang-Rong; Wu, Zhen; Wu, Yun-Long; Qiu, Ying-Kun

    2016-07-22

    An on-line comprehensive preparative two-dimensional normal-phase liquid chromatography×reversed-phase liquid chromatography (2D NPLC×RPLC) system was constructed with a newly developed vacuum evaporation assisted adsorption (VEAA) interface, allowing fast removal of NPLC solvent in the vacuum condition and successfully solving the solvent incompatibility problem between NPLC and RPLC. The system achieved on-line solvent exchange within the two dimensions and its performance was illustrated by gram-scale isolation of crude extract from the venom of Bufo bufo gargarizans. Within separation time of ∼20h, 19 compounds were obtained with high purity in a single run. With the VEAA interface, the 2D system exhibited apparent advantages in separation efficiency and automation compared with conventional methods, indicating its promising application in the routine separation process for complicated natural products. PMID:27328884

  14. A vacuum assisted dynamic evaporation interface for two-dimensional normal phase/reverse phase liquid chromatography.

    PubMed

    Ding, Kun; Xu, Yuan; Wang, Hua; Duan, Chunfeng; Guan, Yafeng

    2010-08-20

    A vacuum assisted dynamic solvent evaporation interface for coupling of two-dimensional normal phase/reverse phase liquid chromatography was developed and evaluated. A normal-phase liquid chromatographic (NPLC) column of a 250mmx4.6mm I.D. 5microm CN phase was used as the first dimension, and a reversed-phase liquid chromatographic (RPLC) column of 250mmx4.6mm I.D. 5micromC(18) phase was used as the second dimension. The eluent from the first dimension flowed into a fraction loop, and the solvent in the eluent was dynamically evaporated and removed by vacuum as it was entering the fraction loop of the interface. The non-evaporable analytes was retained and enriched in about 5-25microL solution within the loop. Up to 1mL/min of mobile phase from the first dimension can be evaporated and removed dynamically by the interface. The mobile phase from the second dimension then entered the loop, and dissolved the concentrated analytes retained inside the loop, and carried them onto the second dimension column for further separation. The operation conditions of the two dimensions were independent from each other, and both dimensions were operated at their optimal chromatographic conditions. We evaluated the interface by controlling the loop temperature in a water bath at normal temperature, and investigated the sample losses by using standard samples with different boiling points. It was found that the sample loss due to evaporation in the interface was negligible for non-volatile samples or for components with boiling point above 340 degrees C. The interface realizes fast solvent removal of mL volume of fraction and concentration of the fraction into tenth of microL volume, and injection of the concentrated fraction on the secondary column. The chromatographic performance of the two-dimensional LC system was enhanced without compromise of separation efficiency and selectivity on each dimension. PMID:20630530

  15. Automated hollow-fiber liquid-phase microextraction followed by liquid chromatography with mass spectrometry for the determination of benzodiazepine drugs in biological samples.

    PubMed

    Nazaripour, Ali; Yamini, Yadollah; Ebrahimpour, Behnam; Fasihi, Javad

    2016-07-01

    In this study, two-phase hollow-fiber liquid-phase microextraction and three-phase hollow-fiber liquid-phase microextraction based on two immiscible organic solvents were compared for extraction of oxazepam and Lorazepam. Separations were performed on a liquid chromatography with mass spectrometry instrument. Under optimal conditions, three-phase hollow-fiber liquid-phase microextraction based on two immiscible organic solvents has a better extraction efficiency. In a urine sample, for three-phase hollow fiber liquid-phase microextraction based on two immiscible organic solvents, the calibration curves were found to be linear in the range of 0.6-200 and 0.9-200 μg L(-1) and the limits of detection were 0.2 and 0.3 μg L(-1) for oxazepam and lorazepam, respectively. For two-phase hollow fiber liquid-phase microextraction, the calibration curves were found to be linear in the range of 1-200 and 1.5-200 μg L(-1) and the limits of detection were 0.3 and 0.5 μg L(-1) for oxazepam and lorazepam, respectively. In a urine sample, for three-phase hollow-fiber-based liquid-phase microextraction based on two immiscible organic solvents, relative standard deviations in the range of 4.2-4.5% and preconcentration factors in the range of 70-180 were obtained for oxazepam and lorazepam, respectively. Also for the two-phase hollow-fiber liquid-phase microextraction, preconcentration factors in the range of 101-257 were obtained for oxazepam and lorazepam, respectively. PMID:27144369

  16. Migration of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling.

    PubMed

    Peng, Hao; Ding, Guoliang; Hu, Haitao

    2011-01-01

    The migration characteristics of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling were investigated experimentally. Four types of carbon nanotubes with the outside diameters from 15 to 80 nm and the lengths from 1.5 to 10 μm were used in the experiments. The refrigerants include R113, R141b and n-pentane. The oil concentration is from 0 to 10 wt.%, the heat flux is from 10 to 100 kW·m-2, and the initial liquid-level height is from 1.3 to 3.4 cm. The experimental results indicate that the migration ratio of carbon nanotube increases with the increase of the outside diameter or the length of carbon nanotube. For the fixed type of carbon nanotube, the migration ratio decreases with the increase of the oil concentration or the heat flux, and increases with the increase of the initial liquid-level height. The migration ratio of carbon nanotube increases with the decrease of dynamic viscosity of refrigerant or the increase of liquid phase density of refrigerant. A model for predicting the migration ratio of carbon nanotubes in the refrigerant-based nanofluid pool boiling is proposed, and the predictions agree with 92% of the experimental data within a deviation of ±20%. PMID:21711730

  17. Migration of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling

    PubMed Central

    2011-01-01

    The migration characteristics of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling were investigated experimentally. Four types of carbon nanotubes with the outside diameters from 15 to 80 nm and the lengths from 1.5 to 10 μm were used in the experiments. The refrigerants include R113, R141b and n-pentane. The oil concentration is from 0 to 10 wt.%, the heat flux is from 10 to 100 kW·m-2, and the initial liquid-level height is from 1.3 to 3.4 cm. The experimental results indicate that the migration ratio of carbon nanotube increases with the increase of the outside diameter or the length of carbon nanotube. For the fixed type of carbon nanotube, the migration ratio decreases with the increase of the oil concentration or the heat flux, and increases with the increase of the initial liquid-level height. The migration ratio of carbon nanotube increases with the decrease of dynamic viscosity of refrigerant or the increase of liquid phase density of refrigerant. A model for predicting the migration ratio of carbon nanotubes in the refrigerant-based nanofluid pool boiling is proposed, and the predictions agree with 92% of the experimental data within a deviation of ±20%. PMID:21711730

  18. Molecular dynamics simulations of pressure shocks in liquid phase nitromethane

    NASA Astrophysics Data System (ADS)

    McNatt, Michael David

    The dynamic energy transfer processes present in liquid nitromethane (NM) under pressure shock loading conditions have been investigated by nonequilibrium molecular dynamics methods using a previously developed, fully flexible NM force field (Sorescu, D. C.; Rice, B. M.; Thompson, D. L. J. Phys. Chem. B 2000, 104, 8406). Generally good qualitative agreement with the corresponding experimental values was found for sound speeds (C) as a function of temperature. This is true as well for the PVT Hugoniot data calculated for the shock compressed zones behind our simulated shock fronts. The predicted C( T) are, however, ˜13--30% higher than experiment (Lysne, P. C.; Hardesty, D. R. J. Chem. Phys. 1973, 59, 6512) and our predicted densities for the shock compressed area behind fronts are consistently 4--10% lower than experiment (Winey, J. M.; Duvall, G. E.; Knudson, M. D.; Gupta, Y. M. J. Chem. Phys. 2000, 113, 7492). Accurate Hugoniot pressures are predicted by our simulations at all three initial temperatures (T i) studied. The Ti simulated for this work (255, 300, 350 K) span virtually the entire experimental ambient pressure liquid temperature range of NM (˜ 244--373 K). Thus combining and comparing our results with those of Winey et al. based on empirical equations of state work, opens up a considerable range of possible further tests and developments of our NM force field. This is particularly important in regards to the intermolecular force field due to its intended purpose of being applicable to a wide range of nitro and nitramine energetic compounds. Also, within the timeframes of our simulations (< 10 ps) the kinetic energy behind our shock fronts does not achieve equilibrium conditions as determined by the classical theory of equipartition.

  19. Direct molecular dynamics simulation of liquid-solid phase equilibria for two-component plasmas.

    PubMed

    Schneider, A S; Hughto, J; Horowitz, C J; Berry, D K

    2012-06-01

    We determine the liquid-solid phase diagram for carbon-oxygen and oxygen-selenium plasma mixtures using two-phase molecular dynamics simulations. We identify liquid, solid, and interface regions using a bond angle metric. To study finite-size effects, we perform 27,648- and 55,296-ion simulations. To help monitor nonequilibrium effects, we calculate diffusion constants D(i). For the carbon-oxygen system we find that D(O) for oxygen ions in the solid is much smaller than D(C) for carbon ions and that both diffusion constants are 80 or more times smaller than diffusion constants in the liquid phase. There is excellent agreement between our carbon-oxygen phase diagram and that predicted by Medin and Cumming. This suggests that errors from finite-size and nonequilibrium effects are small and that the carbon-oxygen phase diagram is now accurately known. The oxygen-selenium system is a simple two-component model for more complex rapid proton capture nucleosynthesis ash compositions for an accreting neutron star. Diffusion of oxygen, in a predominantly selenium crystal, is remarkably fast, comparable to diffusion in the liquid phase. We find a somewhat lower melting temperature for the oxygen-selenium system than that predicted by Medin and Cumming. This is probably because of electron screening effects. PMID:23005226

  20. Direct molecular dynamics simulation of liquid-solid phase equilibria for two-component plasmas

    NASA Astrophysics Data System (ADS)

    Schneider, A. S.; Hughto, J.; Horowitz, C. J.; Berry, D. K.

    2012-06-01

    We determine the liquid-solid phase diagram for carbon-oxygen and oxygen-selenium plasma mixtures using two-phase molecular dynamics simulations. We identify liquid, solid, and interface regions using a bond angle metric. To study finite-size effects, we perform 27 648- and 55 296-ion simulations. To help monitor nonequilibrium effects, we calculate diffusion constants Di. For the carbon-oxygen system we find that DO for oxygen ions in the solid is much smaller than DC for carbon ions and that both diffusion constants are 80 or more times smaller than diffusion constants in the liquid phase. There is excellent agreement between our carbon-oxygen phase diagram and that predicted by Medin and Cumming. This suggests that errors from finite-size and nonequilibrium effects are small and that the carbon-oxygen phase diagram is now accurately known. The oxygen-selenium system is a simple two-component model for more complex rapid proton capture nucleosynthesis ash compositions for an accreting neutron star. Diffusion of oxygen, in a predominantly selenium crystal, is remarkably fast, comparable to diffusion in the liquid phase. We find a somewhat lower melting temperature for the oxygen-selenium system than that predicted by Medin and Cumming. This is probably because of electron screening effects.