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Sample records for phase separated thermotropic

  1. Thermotropic Uniaxial and Biaxial Nematic and Smectic Phases in Bent-Core Mesogens

    SciTech Connect

    Prasad, Venna; Kang, Shin-Woong; Suresh, K.A.; Joshi, Leela; Wang, Qingbing; Kumar, Satyendra

    2010-07-20

    Two azo substituted achiral bent-core mesogens have been synthesized. Optical polarizing microscopy and synchrotron X-ray scattering studies of both compounds reveal the existence of the thermotropic uniaxial and biaxial nematic and three smectic phases at different temperatures in these single component small molecule systems. The transition from the uniaxial to biaxial nematic phase is confirmed to be second order. The transitions from the biaxial nematic to the underlying smectic phase and between the smectic phases have barely discernible heat capacity signatures and thus are also second order.

  2. 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

  3. Formation of a Double Diamond Cubic Phase by Thermotropic Liquid Crystalline Self-Assembly of Bundled Bolaamphiphiles.

    PubMed

    Zeng, Xiangbing; Prehm, Marko; Ungar, Goran; Tschierske, Carsten; Liu, Feng

    2016-07-11

    A quaternary amphiphile with swallow-tail side groups displays a new bicontinuous thermotropic cubic phase with symmetry Pn3‾ m and formed by two interpenetrating networks where cylindrical segments are linked by H bonds at tetrahedral junctions. Each network segment contains two bundles, each containing 12 rod-like mesogens, lying along the segment axis. This assembly leads to the first thermotropic structure of the "double diamond" type. A quantitative geometric model is proposed to explain the occurrence of this rare phase. PMID:27270840

  4. Alkyl-bis(imidazolium) salts: a new amphiphile platform that forms thermotropic and non-aqueous lyotropic bicontinuous cubic phases

    SciTech Connect

    Robertson, LA; Schenkel, MR; Wiesenauer, BR; Gin, DL

    2013-01-01

    New ionic amphiphiles with a hexyl-bridged bis(imidazolium) headgroup; Br-, BF4-, or Tf2N- anions; and a long n-alkyl tail can form thermotropic bicontinuous cubic liquid crystal phases in neat form and/or lyotropic bicontinuous cubic phases with several non-aqueous solvents or water.

  5. Antifreeze glycoproteins inhibit leakage from liposomes during thermotropic phase transitions.

    PubMed Central

    Hays, L M; Feeney, R E; Crowe, L M; Crowe, J H; Oliver, A E

    1996-01-01

    Antifreeze glycoproteins (AFGPs), found in the blood of polar fish at concentrations as high as 35 g/liter, are known to prevent ice crystal growth and depress the freezing temperature of the blood. Previously, Rubinsky et al. [Rubinsky, B., Mattioli, M., Arav, A., Barboni, B. & Fletcher, G. L. (1992) Am. J. Physiol. 262, R542-R545] provided evidence that AFGPs block ion fluxes across membranes during cooling, an effect that they ascribed to interactions with ion channels. We investigated the effects of AFGPs on the leakage of a trapped marker from liposomes during chilling. As these liposomes are cooled through the transition temperature, they leak approximately 50% of their contents. Addition of less than 1 mg/ml of AFGP prevents up to 100% of this leakage, both during chilling and warming through the phase transition. This is a general effect that we show here applies to liposomes composed of phospholipids with transition temperatures ranging from 12 degrees C to 41 degrees C. Because these results were obtained with liposomes composed of phospholipids alone, we conclude that the stabilizing effects of AFGPs on intact cells during chilling reported by Rubinsky et al. may be due to a nonspecific effect on the lipid components of native membranes. There are other proteins that prevent leakage, but only under specialized conditions. For instance, antifreeze proteins, bovine serum albumin, and ovomucoid all either have no effect or actually induce leakage. Following precipitation with acetone, all three proteins inhibited leakage, although not to the extent seen with AFGPs. Alternatively, there are proteins such as ovotransferrin that have no effect on leakage, either before or after acetone precipitation. PMID:8692905

  6. Induction of thermotropic bicontinuous cubic phases in liquid-crystalline ammonium and phosphonium salts.

    PubMed

    Ichikawa, Takahiro; Yoshio, Masafumi; Hamasaki, Atsushi; Taguchi, Satomi; Liu, Feng; Zeng, Xiang-bing; Ungar, Goran; Ohno, Hiroyuki; Kato, Takashi

    2012-02-01

    Two series of wedge-shaped onium salts, one ammonium and the other phosphonium, having 3,4,5-tris(alkyloxy)benzyl moieties, exhibit thermotropic bicontinuous "gyroid" cubic (Cub(bi)) and hexagonal columnar liquid-crystalline (LC) phases by nanosegregation between ionophilic and ionophobic parts. The alkyl chain lengths on the cationic moieties, anion species, and alkyl chain lengths on the benzyl moieties have crucial effects on their thermotropic phase behavior. For example, triethyl-[3,4,5-tris(dodecyloxy)benzyl]ammonium hexafluorophosphate forms the thermotropic Ia3d Cub(bi) LC phase, whereas an analogous compound with trifluoromethanesulfonate anion shows no LC properties. Synchrotron small-angle diffraction intensities from the Ia3d Cub(bi) LC materials provide electron density maps in the bulk state. The resulting maps show convincingly that the Ia3d Cub(bi) structure is composed of three-dimensionally interconnected ion nanochannel networks surrounded by aliphatic domains. A novel differential mapping technique has been applied successfully. The map of triethyl-[3,4,5-tris(decyloxy)benzyl]ammonium tetrafluoroborate has been subtracted from that of the analogous ammonium salt with hexafluorophosphate anion in the Ia3d Cub(bi) phases. The differential map shows that the counteranions are located in the core of the three-dimensionally interconnected nanochannel networks. Changing from trimethyl- via triethyl- to tripropylammonium cation changes the phase from columnar to Cub(bi) to no mesophase, respectively. This sensitivity to the widened shape for the narrow end of the molecule is explained successfully by the previously proposed semiquantitative geometric model based on the radial distribution of volume in wedge-shaped molecules. The LC onium salts dissolve lithium tetrafluoroborate without losing the Ia3d Cub(bi) LC phase. The Cub(bi) LC materials exhibit efficient ion-transporting behavior as a result of their 3D interconnected ion nanochannel networks

  7. Structure and Thermotropic phase Behavior of Fluorinated Phospholipid Bilayers: A combined Attenuated Total Reflection FTIR Spectroscopy and Imaging Ellipsometry Study

    PubMed Central

    Schuy, Steffen; Faiss, Simon; Yoder, Nicholas C.; Kalsani, Venkateshwarlu; Kumar, Krishna; Janshoff, Andreas; Vogel, Reiner

    2008-01-01

    Lipid bilayers consisting of lipids with terminally perfluoroalkylated chains have remarkable properties. They exhibit increased stability and phase-separated nanoscale patterns in mixtures with nonfluorinated lipids. In order to understand the bilayer properties that are responsible for this behavior, we have analyzed the structure of solid-supported bilayers composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and of a DPPC analogue with 6 terminal perfluorinated methylene units (F6-DPPC). Polarized attenuated total reflection Fourier-transform infrared spectroscopy indicates that for F6-DPPC, the tilt of the lipid acyl chains to the bilayer normal is increased to 39° as compared to 21° for native DPPC, for both lipids in the gel phase. This substantial increase of the tilt angle is responsible for a decrease of the bilayer thickness from 5.4 nm for DPPC to 4.5 nm for F6-DPPC, as revealed by temperature-controlled imaging ellipsometry on microstructured lipid bilayers and solution atomic force microscopy. During the main phase transition from the gel to the fluid phase, both the relative bilayer thickness change and the relative area change are substantially smaller for F6-DPPC than for DPPC. In light of these structural and thermotropic data, we propose a model in which the higher acyl-chain tilt angle in F6-DPPC is the result of a conformational rearrangement to minimize unfavorable fluorocarbon–hydrocarbon interactions in the center of the bilayer due to chain staggering. PMID:18563929

  8. Nonionic diethanolamide amphiphiles with isoprenoid-type hydrocarbon chains: thermotropic and lyotropic liquid crystalline phase behaviour

    SciTech Connect

    Sagnella, Sharon M.; Conn, Charlotte E.; Krodkiewska, Irena; Drummond, Calum J.

    2014-09-24

    The thermotropic and lyotropic liquid crystalline phase behaviour of a series of diethanolamide amphiphiles with isoprenoid-type hydrocarbon chains (geranoyl, H-farnesoyl, and phytanoyl) has been investigated. When neat, both H-farnesoyl and phytanoyl diethanolamide form a smectic liquid crystalline structure at sub-zero temperatures. In addition, all three diethanolamides exhibit a glass transition temperature at around -73 C. Geranoyl diethanolamide forms a lamellar crystalline phase with a lattice parameter of 17.4 {angstrom} following long term storage accompanied by the loss of the glass transition. In the presence of water, H-farnesoyl and phytanoyl diethanolamide form lyotropic liquid crystalline phases, whilst geranoyl diethanolamide forms an L{sub 2} phase. H-farnesoyl diethanolamide forms a fluid lamellar phase (L{sub {alpha}}) at room temperature and up to {approx} 40 C. Phytanoyl diethanolamide displays a rich mesomorphism forming the inverse diamond (Q{sub II}{sup D}) and gyroid (Q{sub II}{sup G}) bicontinuous cubic phases in addition to an L{sub {alpha}} phase.

  9. Effect of a glucose-triazole-hydrogenated cardanol conjugate on lipid bilayer membrane organization and thermotropic phase transition

    NASA Astrophysics Data System (ADS)

    Swain, Jitendriya; Kamalraj, M.; Surya Prakash Rao, H.; Mishra, Ashok K.

    2015-02-01

    This work focuses on the membrane perturbation, solubilisation and thermotropic phase transition process of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) MLVs induced by a glucose-triazole-hydrogenated cardanol conjugate (GTHCC). GTHCC is a recently introduced non toxic sugar derivative. Differential scanning calorimetry (DSC) and fluorescence molecular probe based techniques have been used to understand the concentration dependent membrane perturbation, solubilisation and thermotropic phase transition process of DPPC MLVs. The phase transition temperature of DPPC MLVs decreases with increase in mol% of GTHCC. At higher concentration above 10 mol%, GTHCC was significantly perturbed the membrane organization. The intrinsic fluorescence of GTHCC is also found to be sensitive towards phase behaviour and changes in membrane organization of DPPC MLVs.

  10. Effect of Phase Transition on the Rheology of Model Thermotropic Liquid Crystalline Polymers

    NASA Astrophysics Data System (ADS)

    Zhou, Weijun; Kornfield, Julie A.

    1998-03-01

    Despite their important material properties, rheological studies of thermotropic liquid crystalline polymers (TLCPs) have not received much attention due to experimental difficulties. In this report, we describe the rheology of a model TLCP, which has good thermal stability and low isotropization temperature (DHMS-7,9, T_m=90^circC, T_xn=120^circC, T_ni=197^circC, where T_xn is the transition temperature between an unidentified mesophase to nematic phase). Systematic studies were carried out on DHMS-7,9 as a function of temperature and Mw (M_w=11K to 65K). Oscillatory dynamic moduli (G^') showed a plateau at an intermediate frequency at temperature below 120^circC , but no plateau for G^' was observed over the whole frequency range studied above 120^circC. We also studied the corresponding textural behavior by rheological-microscopy at different temperature with a home-made flow cell attached to a polarized light microscopy. It was recently reported that this TLCP exhibits different flow-aligning behavior in the mesophase by X-ray diffraction (Log-rolling alignment below 120^circC and typical flow alignment above 120^circC). Currently, we are investigating the origin of this flow behavior.

  11. Thermotropic liquid crystals from biomacromolecules

    PubMed Central

    Liu, Kai; Chen, Dong; Marcozzi, Alessio; Zheng, Lifei; Su, Juanjuan; Pesce, Diego; Zajaczkowski, Wojciech; Kolbe, Anke; Pisula, Wojciech; Müllen, Klaus; Clark, Noel A.; Herrmann, Andreas

    2014-01-01

    Complexation of biomacromolecules (e.g., nucleic acids, proteins, or viruses) with surfactants containing flexible alkyl tails, followed by dehydration, is shown to be a simple generic method for the production of thermotropic liquid crystals. The anhydrous smectic phases that result exhibit biomacromolecular sublayers intercalated between aliphatic hydrocarbon sublayers at or near room temperature. Both this and low transition temperatures to other phases enable the study and application of thermotropic liquid crystal phase behavior without thermal degradation of the biomolecular components. PMID:25512508

  12. Differential scanning calorimetry of thermotropic phase transitions in vitaminylated lipids: aqueous dispersions of N-biotinyl phosphatidylethanolamines.

    PubMed Central

    Swamy, M. J.; Angerstein, B.; Marsh, D.

    1994-01-01

    The thermotropic phase behavior of a homologous series of saturated diacyl phosphatidylethanolamines in which the headgroup is N-derivatized with biotin has been investigated by differential scanning calorimetry. In 1 M NaCl, derivatives with acyl chainlengths from C(12:0) to C(20:0) all exhibit sharp chain-melting phase transitions, which are reversible with a hysteresis of 1.5 degrees or less, except for the C(12:0) lipid which has a transition temperature below 0 degree C. The transition enthalpy and the transition entropy depend approximately linearly on the lipid chainlength, with incremental values per CH2 group that are very similar to those obtained for the corresponding underivatized phosphatidylethanolamines in aqueous dispersion. The chainlength-independent contribution to the transition enthalpy is significantly smaller than that for the underivatized phosphatidylethanolamines, and that for the transition entropy is much smaller; the latter suggesting that the N-biotinylated phosphatidylethanolamine headgroups are differently hydrated from those of the underivatized lipids. The gel-to-fluid phase transition temperatures of the N-biotinylated lipids are lower than those of the parent phosphatidylethanolamines, and their chainlength dependence conforms well with that predicted by assuming that the transition enthalpy and entropy are linearly dependent on chainlength. Although the chain-melting phase behavior is generally similar to that of the parent phosphatidylethanolamines, the gel phases (and the fluid phases in the case of chainlengths C(12:0) to C(16:0)) have a different lyotropic structure in the two cases, and this is reflected in the chainlength-independent contributions to the thermodynamic parameters. In the absence of salt, the thermotropic phase behavior of aqueous dispersions of the N-biotinyl phosphatidylethanolamines is considerably more complex. The transition temperatures are consistently lower than those in 1 M NaCI, but the transitions

  13. Alpha-synuclein and familial variants affect the chain order and the thermotropic phase behavior of anionic lipid vesicles.

    PubMed

    Pantusa, Manuela; Vad, Brian; Lillelund, Ove; Kjær, Lars; Otzen, Daniel; Bartucci, Rosa

    2016-09-01

    Alpha-synuclein (aSN) is a presynaptic protein with a pathological role in Parkinson's disease (PD). The mutants A30P, E46K and A53T are involved in PD early-onset forms. aSN is natively unfolded but can self-assemble to oligomers and fibrils and binds anionic membranes in a helical conformation. We study the influence of wild-type (wt) aSN and familial variants on the chain order and thermotropic phase behavior of anionic dimyristoylphosphatidylglycerol (DMPG) bilayers by using electron spin resonance and calorimetry, respectively. The alpha-helical conformation of the proteins in the membrane-bound state is assessed by circular dichroism thermal scans. wt and mutated aSN upon binding to fluid DMPG vesicles progressively increase chain order. Lipid:protein molar binding stoichiometries correspond to 50 for A30P, 35-36 for aSN and A53T, 30 for E46K. The temperature range over which the variants assume the α-helical fold correlates directly with the density of proteins on vesicle surfaces. All variants preserve the characteristic chain flexibility gradient and impart motional restriction in the lipid chain. This is evident at the first CH2 segments and is markedly reduced at the chain termini, disappearing completely for A30P. The proteins slightly reduce DMPG main transition temperature, revealing preferential affinity for the fluid phase, and broaden the transition, promoting gel-fluid phase coexistence. The overall results are consistent with protein surface association in which the degree of binding correlates with the degree of folding and perturbation of the membrane bilayer. However, the degree of binding of monomer to membrane does not correlate directly with aSN toxicity in vivo. PMID:27177693

  14. The elusive thermotropic biaxial nematic phase in rigid bent-core molecules

    NASA Astrophysics Data System (ADS)

    Acharya, Bharat R.; Primak, Andrew; Dingemans, Theo J.; Samulski, Edward T.; Kumar, Satyendra

    2003-08-01

    The biaxial nematic liquid crystalline phase was predicted several decades ago. Several vigorous attempts to find it in various systems resulted in mis-identifications. The results of X-ray diffraction and optical texture studies of the phases exhibited by rigid bent-core molecules derived from 2,5-bis-(p-hydroxyphenyl)-1,3,4-oxadiazole reveal that the biaxial nematic phase is formed by three compounds of this type. X-ray diffraction studies reveal that the nematic phase of these compounds has the achiral symmetry D2h, in which the overall long axes of the molecules are oriented parallel to each other to define the major axis of the biaxial phase. The apex of the bent-cores de- fines the minor axis of this phase along which the planes containing the bent-cores of neighboring molecules are oriented parallel to each other.

  15. 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

  16. Phase states and thermomorphologic, thermotropic, and magnetomorphologic properties of lyotropic mesophases: Sodium lauryl sulphate-water-1-decanol liquid-crystalline system

    NASA Astrophysics Data System (ADS)

    Özden, Pınar; Nesrullajev, Arif; Oktik, Şener

    2010-12-01

    Phase states in sodium lauryl sulphate-water-1-decanol lyotropic liquid-crystalline system have been investigated for different temperature ranges. The dependence of triangle phase diagram types, phase boundaries, and sequence of lyotropic mesophases vs temperature has been found. The thermomorphologic, thermotropic, and magnetomorphologic properties of hexagonal E, lamellar D, nematic-calamitic NC , nematic-discotic ND , and biaxial nematic Nbx mesophases have been studied in detail. Dynamics of transformations of magnetically induced textures has been investigated. Peculiarities of typical and magnetically induced textures have been investigated in detail. Triangle phase diagrams of sodium lauryl sulphate-water-1-decanol lyotropic liquid-crystalline system for different temperatures and typical and magnetically induced textures of E, D, NC , ND , and Nbx mesophases are presented.

  17. Process for phase separation

    DOEpatents

    Comolli, Alfred G.

    1979-01-01

    This invention provides a continuous process for separating a gaseous phase from a hydrocarbon liquid containing carbonaceous particulates and gases. The liquid is fed to a cylindrical separator, with the gaseous phase being removed therefrom as an overhead product, whereas the hydrocarbon liquid and the particulates are withdrawn as a bottoms product. By feeding the liquid tangentially to the separator and maintaining a particulate-liquid slurry downward velocity of from about 0.01 to about 0.25 fps in the separator, a total solids weight percent in the slurry of from about 0.1 to about 30%, a slurry temperature of from about 550.degree. to about 900.degree. F., a slurry residence time in the separator of from about 30 to about 360 seconds, and a length/diameter ratio for the separator of from about 20/1 to about 50/1, so that the characterization factor, .alpha., defined as ##STR1## DOES NOT EXCEED ABOUT 48 (.degree.R sec.sup.2)/ft, the deposit of carbonaceous materials on the interior surface of the separator may be substantially eliminated.

  18. Low gravity phase separator

    NASA Technical Reports Server (NTRS)

    Smoot, G. F.; Pope, W. L.; Smith, L. (Inventor)

    1977-01-01

    An apparatus is described for phase separating a gas-liquid mixture as might exist in a subcritical cryogenic helium vessel for cooling a superconducting magnet at low gravity such as in planetary orbit, permitting conservation of the liquid and extended service life of the superconducting magnet.

  19. Microgravity Passive Phase Separator

    NASA Technical Reports Server (NTRS)

    Paragano, Matthew; Indoe, William; Darmetko, Jeffrey

    2012-01-01

    A new invention disclosure discusses a structure and process for separating gas from liquids in microgravity. The Microgravity Passive Phase Separator consists of two concentric, pleated, woven stainless- steel screens (25-micrometer nominal pore) with an axial inlet, and an annular outlet between both screens (see figure). Water enters at one end of the center screen at high velocity, eventually passing through the inner screen and out through the annular exit. As gas is introduced into the flow stream, the drag force exerted on the bubble pushes it downstream until flow stagnation or until it reaches an equilibrium point between the surface tension holding bubble to the screen and the drag force. Gas bubbles of a given size will form a front that is moved further down the length of the inner screen with increasing velocity. As more bubbles are added, the front location will remain fixed, but additional bubbles will move to the end of the unit, eventually coming to rest in the large cavity between the unit housing and the outer screen (storage area). Owing to the small size of the pores and the hydrophilic nature of the screen material, gas does not pass through the screen and is retained within the unit for emptying during ground processing. If debris is picked up on the screen, the area closest to the inlet will become clogged, so high-velocity flow will persist farther down the length of the center screen, pushing the bubble front further from the inlet of the inner screen. It is desired to keep the velocity high enough so that, for any bubble size, an area of clean screen exists between the bubbles and the debris. The primary benefits of this innovation are the lack of any need for additional power, strip gas, or location for venting the separated gas. As the unit contains no membrane, the transport fluid will not be lost due to evaporation in the process of gas separation. Separation is performed with relatively low pressure drop based on the large surface

  20. Surface alignment, anchoring transitions, optical properties, and topological defects in the nematic phase of thermotropic bent-core liquid crystal A131

    NASA Astrophysics Data System (ADS)

    Senyuk, B.; Wonderly, H.; Mathews, M.; Li, Q.; Shiyanovskii, S. V.; Lavrentovich, O. D.

    2010-10-01

    We study optical, structural, and surface anchoring properties of thermotropic nematic bent-core material A131. The focus is on the features associated with orientational order as the material has been reported to exhibit not only the usual uniaxial nematic but also the biaxial nematic phase. We demonstrate that A131 experiences a surface anchoring transition from a perpendicular to tilted alignment when the temperature decreases. The features of the tilted state are consistent with surface-induced birefringence associated with smectic layering near the surface and a molecular tilt that changes along the normal to the substrates. The surface-induced birefringence is reduced to zero by a modest electric field that establishes a uniform uniaxial nematic state. Both refractive and absorptive optical properties of A131 are consistent with the uniaxial order. We found no evidence of the “polycrystalline” biaxial behavior in the cells placed in crossed electric and magnetic fields. We observe stable topological point defects (boojums and hedgehogs) and nonsingular “escaped” disclinations pertinent only to the uniaxial order. Finally, freely suspended films of A131 show uniaxial nematic and smectic textures; a decrease in the film thickness expands the temperature range of stability of smectic textures, supporting the idea of surface-induced smectic layering. Our conclusion is that A131 features only a uniaxial nematic phase and that the apparent biaxiality is caused by subtle surface effects rather than by the bulk biaxial phase.

  1. Three phase downhole separator process

    DOEpatents

    Cognata, Louis John

    2008-06-24

    Three Phase Downhole Separator Process (TPDSP) is a process which results in the separation of all three phases, (1) oil, (2) gas, and (3) water, at the downhole location in the well bore, water disposal injection downhole, and oil and gas production uphole.

  2. Microcellular foams via phase separation

    SciTech Connect

    Young, A.T.

    1985-01-01

    A study of wide variety of processes for making plastic foams shows that phase separation processes for polymers from solutions offers the most viable methods for obtaining rigid plastic foams which met the physical requirements for fusion target designs. Four general phase separation methods have been shown to give polymer foams with densities less than 0.1 g/cm/sup 3/ and cell sizes of 30..mu..m or less. These methods involve the utilization of non-solvent, chemical or thermal cooling processes to achieve a controlled phase separation wherein either two distinct phases are obtained where the polymer phase is a continuous phase or two bicontinuous phases are obtained where both the polymer and solvent are interpenetrating, continuous, labyrinthine phases. Subsequent removal of the solvent gives the final foam structure.

  3. Role of Molecular Structure on X-ray Diffraction in Thermotropic Uniaxial and Biaxial Nematic Liquid Crystal Phases

    SciTech Connect

    Acharya, Bharat R.; Kang, Shin-Woong; Prasad, Veena; Kumar, Satyendra

    2009-08-27

    X-ray diffraction is one of the most definitive methods to determine the structure of condensed matter phases, and it has been applied to unequivocally infer the structures of conventional calamitic and lyotropic liquid crystals. With the advent of bent-core and tetrapodic mesogens and the discovery of the biaxial nematic phase in them, the experimental results require more careful interpretation and analysis. Here, we present ab-initio calculations of X-ray diffraction patterns in the isotropic, uniaxial nematic, and biaxial nematic phases of bent-core mesogens. A simple Meier-Saupe-like molecular distribution function is employed to describe both aligned and unaligned mesophases. The distribution function is decomposed into two, polar and azimuthal, distribution functions to calculate the effect of the evolution of uniaxial and biaxial nematic orientational order. The calculations provide satisfactory semiquantitative interpretations of experimental results. The calculations presented here should provide a pathway to more refined and quantitative analysis of X-ray diffraction data from the biaxial nematic phase.

  4. Role of Molecular Structure on X-ray Diffraction in Uniaxial and Biaxial Phases of Thermotropic Liquid Crystals

    SciTech Connect

    Acharya, Bharat R.; Kang, Shin-Woong; Prasad, Veena; Kumar, Satyendra

    2009-04-29

    X-ray diffraction is one of the most definitive methods to determine the structure of condensed matter phases, and it has been applied to unequivocally infer the structures of conventional calamitic and lyotropic liquid crystals. With the advent of bent-core and tetrapodic mesogens and the discovery of the biaxial nematic phase in them, the experimental results require more careful interpretation and analysis. Here, we present ab-initio calculations of X-ray diffraction patterns in the isotropic, uniaxial nematic, and biaxial nematic phases of bent-core mesogens. A simple Meier-Saupe-like molecular distribution function is employed to describe both aligned and unaligned mesophases. The distribution function is decomposed into two, polar and azimuthal, distribution functions to calculate the effect of the evolution of uniaxial and biaxial nematic orientational order. The calculations provide satisfactory semiquantitative interpretations of experimental results. The calculations presented here should provide a pathway to more refined and quantitative analysis of X-ray diffraction data from the biaxial nematic phase.

  5. Surface alignment, anchoring transitions, optical properties, and topological defects in the thermotropic nematic phase of organo-siloxane tetrapodes.

    PubMed

    Kim, Young-Ki; Senyuk, Bohdan; Shin, Sung-Tae; Kohlmeier, Alexandra; Mehl, Georg H; Lavrentovich, Oleg D

    2014-01-21

    We perform optical, surface anchoring, and textural studies of an organo-siloxane "tetrapode" material in the broad temperature range of the nematic phase. The optical, structural, and topological features are compatible with the uniaxial nematic order rather than with the biaxial nematic order, in the entire nematic temperature range -25 °C < T < 46 °C studied. For homeotropic alignment, the material experiences surface anchoring transition, but the director can be realigned into an optically uniaxial texture by applying a sufficiently strong electric field. The topological features of textures in cylindrical capillaries, in spherical droplets and around colloidal inclusions are consistent with the uniaxial character of the long-range nematic order. In particular, we observe isolated surface point defects - boojums and bulk point defects - hedgehogs that can exist only in the uniaxial nematic liquid crystal. PMID:24651889

  6. Imaging the oxidation effects of the Fenton reaction on phospholipids at the interface between aqueous phase and thermotropic liquid crystals.

    PubMed

    Zhang, Minmin; Jang, Chang-Hyun

    2015-08-01

    The lipid peroxidation process has attracted much attention because of the growing evidence of its involvement in the pathogenesis of age-related diseases. Herein, we report a simple, label-free method to study the oxidation of phospholipids by the Fenton reaction at the interface between an aqueous phase and immiscible liquid crystals (LCs). The different images produced by the orientation of 4-cyano-4'-pentylbiphenyl (5CB) corresponded to the presence or absence of oxidized 1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (DOPG). The oxidation effects of the Fenton reaction on DOPG were evaluated by monitoring the orientational response of liquid crystals upon contact with the oxidized DOPG solutions. DOPG was oxidized into chain-changed products containing hydroxy, carbonyl, or aldehyde groups, resulting in the rearrangement of the phospholipid layer. This induced the orientational transition of LCs from homeotropic to planar states; therefore, a dark to bright optical shift was observed. This shift was due to the Fenton reaction preventing DOPG to induce the orientational alignment of LCs at the aqueous/LC interface. We also used an ultraviolet spectrophotometer to confirm the effects of oxidation on phospholipids by the Fenton reaction. Using this simple method, a new approach for investigating phospholipid oxidation was established with high resolution and easy accessibility. PMID:25656072

  7. Two-Phase Flow Separator Investigation

    NASA Video Gallery

    The goal of the Two-Phase Flow Separator investigation is to help increase understanding of how to separate gases and liquids in microgravity. Many systems on the space station contain both liquids...

  8. Binary Colloidal Alloy Test-5: Phase Separation

    NASA Technical Reports Server (NTRS)

    Lynch, Matthew; Weitz, David A.; Lu, Peter J.

    2008-01-01

    The Binary Colloidal Alloy Test - 5: Phase Separation (BCAT-5-PhaseSep) experiment will photograph initially randomized colloidal samples onboard the ISS to determine their resulting structure over time. This allows the scientists to capture the kinetics (evolution) of their samples, as well as the final equilibrium state of each sample. BCAT-5-PhaseSep studies collapse (phase separation rates that impact product shelf-life); in microgravity the physics of collapse is not masked by being reduced to a simple top and bottom phase as it is on Earth.

  9. Mechanisms and Consequences of Macromolecular Phase Separation.

    PubMed

    Bergeron-Sandoval, Louis-Philippe; Safaee, Nozhat; Michnick, Stephen W

    2016-05-19

    Over a century ago, colloidal phase separation of matter into non-membranous bodies was recognized as a fundamental organizing principal of cell "protoplasm." Recent insights into the molecular properties of such phase-separated bodies present challenges to our understanding of cellular protein interaction networks, as well as opportunities for interpreting and understanding of native and pathological genetic and molecular interactions. Here, we briefly review examples of and discuss physical principles of phase-separated cellular bodies and then reflect on how knowledge of these principles may direct future research on their functions. PMID:27203111

  10. Study Of Phase Separation In Glass

    NASA Technical Reports Server (NTRS)

    Neilson, George F.; Weinberg, Michael C.; Smith, Gary L.

    1989-01-01

    Report describes an experimental study of effect of hydroxide content on phase separation in soda/silica glasses. Ordinary and gel glasses melted at 1,565 degree C, and melts stirred periodically. "Wet" glasses produced by passing bubbles of N2 saturated with water through melts; "dry" glasses prepared in similar manner, except N2 dried before passage through melts. Analyses of compositions of glasses performed by atomic-absorption and index-of-refraction measurements. Authors conclude hydroxide speeds up phase separation, regardless of method (gel or ordinary) by which glass prepared. Eventually helps material scientists to find ways to control morphology of phase separation.

  11. Thermodynamic modeling of phase separation in manganites

    NASA Astrophysics Data System (ADS)

    Sacanell, J.; Parisi, F.; Campoy, J. C. P.; Ghivelder, L.

    2006-01-01

    We present a phenomenological model based on the thermodynamics of the phase separated state of manganites, accounting for its static and dynamic properties. Through calorimetric measurements on La0.225Pr0.4Ca0.375MnO3 the low temperature free energies of the coexisting ferromagnetic and charge ordered phases are evaluated. The phase separated state is modeled by free energy densities uniformly spread over the sample volume. The calculations contemplate the out of equilibrium features of the coexisting phase regime, to allow a comparison between magnetic measurements and the predictions of the model. A phase diagram including the static and dynamic properties of the system is constructed, showing the existence of blocked and unblocked regimes which are characteristics of the phase separated state in manganites.

  12. Polymer solution phase separation: Microgravity simulation

    NASA Technical Reports Server (NTRS)

    Cerny, Lawrence C.; Sutter, James K.

    1989-01-01

    In many multicomponent systems, a transition from a single phase of uniform composition to a multiphase state with separated regions of different composition can be induced by changes in temperature and shear. The density difference between the phase and thermal and/or shear gradients within the system results in buoyancy driven convection. These differences affect kinetics of the phase separation if the system has a sufficiently low viscosity. This investigation presents more preliminary developments of a theoretical model in order to describe effects of the buoyancy driven convection in phase separation kinetics. Polymer solutions were employed as model systems because of the ease with which density differences can be systematically varied and because of the importance of phase separation in the processing and properties of polymeric materials. The results indicate that the kinetics of the phase separation can be performed viscometrically using laser light scattering as a principle means of following the process quantitatively. Isopycnic polymer solutions were used to determine the viscosity and density difference limits for polymer phase separation.

  13. Orientational behaviour of thermotropic and lyotropic liquid crystal polymer systems under shear flow

    NASA Astrophysics Data System (ADS)

    Andresen, E. M.; Mitchell, G. R.

    1998-08-01

    A comparison is made of the development of global orientation during shearing of lyotropic solutions of hydroxypropylcellulose with that observed for the thermotropic phase of hydroxypropylcellulose. At shear rates > 10 s-1 the behaviour of the two systems is similar, both during steady-state shear, and in terms of relaxation following cessation of shear flow. At low shear rates, the levels of orientation observed for the thermotropic system are substantially greater than observed for the lyotropic solutions. The relationship of these differences to variations in molecular parameters, viscous stress and to director tumbling is discussed.

  14. 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.

  15. 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 .

  16. Phase Separation in Solutions of Monoclonal Antibodies

    NASA Astrophysics Data System (ADS)

    Benedek, George; Wang, Ying; Lomakin, Aleksey; Latypov, Ramil

    2012-02-01

    We report the observation of liquid-liquid phase separation (LLPS) in a solution of humanized monoclonal antibodies, IgG2, and the effects of human serum albumin, a major blood protein, on this phase separation. We find a significant reduction of phase separation temperature in the presence of albumin, and a preferential partitioning of the albumin into the antibody-rich phase. We provide a general thermodynamic analysis of the antibody-albumin mixture phase diagram and relate its features to the magnitude of the effective inter-protein interactions. Our analysis suggests that additives (HSA in this report), which have moderate attraction with antibody molecules, may be used to forestall undesirable protein condensation in antibody solutions. Our findings are relevant to understanding the stability of pharmaceutical solutions of antibodies and the mechanisms of cryoglobulinemia.

  17. Phase separations in a copolymer copolymer mixture

    NASA Astrophysics Data System (ADS)

    Zhang, Jin-Jun; Jin, Guojun; Ma, Yuqiang

    2006-01-01

    We propose a three-order-parameter model to study the phase separations in a diblock copolymer-diblock copolymer mixture. The cell dynamical simulations provide rich information about the phase evolution and structural formation, especially the appearance of onion-rings. The parametric dependence and physical reason for the domain growth of onion-rings are discussed.

  18. Thermotropic phase properties of 1,2-di-O-tetradecyl-3-O-(3-O-methyl- beta-D-glucopyranosyl)-sn-glycerol.

    PubMed Central

    Trouard, T P; Mannock, D A; Lindblom, G; Rilfors, L; Akiyama, M; McElhaney, R N

    1994-01-01

    The hydration properties and the phase structure of 1,2-di-O-tetradecyl-3-O(3-O-methyl-beta-D-glucopyranosyl)-sn-glycerol (3-O-Me-beta-D-GlcDAIG) in water have been studied via differential scanning calorimetry, 1H-NMR and 2H-NMR spectroscopy, and x-ray diffraction. Results indicate that this lipid forms a crystalline (Lc) phase up to temperatures of 60-70 degrees C, where a transition through a metastable reversed hexagonal (Hll) phase to a reversed micellar solution (L2) phase occurs. Experiments were carried out at water concentrations in a range from 0 to 35 wt%, which indicate that all phases are poorly hydrated, taking up < 5 mol water/mol lipid. The absence of a lamellar liquid crystalline (L alpha) phase and the low levels of hydration measured in the discernible phases suggest that the methylation of the saccharide moiety alters the hydrogen bonding properties of the headgroup in such a way that the 3-O-Me-beta-D-GlcDAIG headgroup cannot achieve the same level of hydration as the unmethylated form. Thus, in spite of the small increase in steric bulk resulting from methylation, there is an increase in the tendency of 3-O-Me-beta-D-GlcDAIG to form nonlamellar structures. A similar phase behavior has previously been observed for the Acholeplasma laidlawii A membrane lipid 1,2-diacyl-3-O-(6-O-acyl-alpha-D-glucopyranosyl)-sn-glycerol in water (Lindblom et al. 1993. J. Biol. Chem. 268:16198-16207). The phase behavior of the two lipids suggests that hydrophobic substitution of a hydroxyl group in the sugar ring of the glucopyranosylglycerols has a very strong effect on their physicochemical properties, i.e., headgroup hydration and the formation of different lipid aggregate structures. PMID:7811919

  19. Electronic phase separation in iron pnictides

    NASA Astrophysics Data System (ADS)

    Sboychakov, A. O.; Rozhkov, A. V.; Kugel, K. I.; Rakhmanov, A. L.; Nori, Franco

    2013-11-01

    A mechanism for electronic phase separation in iron pnictides is proposed. It is based on the competition between commensurate and incommensurate spin-density-wave phases in a system with an imperfect doping-dependent nesting of a multisheeted Fermi surface. We model the Fermi surface by two elliptical electron pockets and three circular hole pockets. The interaction between a charge carrier in a hole band and a carrier in an electron band leads to the formation of spin-density-wave order. The commensurate spin density wave in the parent compound transforms to the incommensurate phase when doping is introduced. We show that, for certain parameter values, the uniform state is unstable with respect to phase separation. The resulting inhomogeneous state consists of regions of commensurate and incommensurate spin-density-wave phases. Our results are in qualitative agreement with recent observations of incommensurate spin density waves and electronic inhomogeneity in iron pnictides.

  20. Tuning Membrane Phase Separation Using Nonlipid Amphiphiles

    PubMed Central

    Muddana, Hari S.; Chiang, Homer H.; Butler, Peter J.

    2012-01-01

    Lipid phase separation may be a mechanism by which lipids participate in sorting membrane proteins and facilitate membrane-mediated biochemical signaling in cells. To provide new tools for membrane lipid phase manipulation that avoid direct effects on protein activity and lipid composition, we studied phase separation in binary and ternary lipid mixtures under the influence of three nonlipid amphiphiles, vitamin E (VE), Triton-X (TX)-100, and benzyl alcohol (BA). Mechanisms of additive-induced phase separation were elucidated using coarse-grained molecular dynamics simulations of these additives in a liquid bilayer made from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-diundecanoyl-sn-glycero-phosphocholine (DUPC). From simulations, the additive's partitioning preference, changes in membrane thickness, and alterations in lipid order were quantified. Simulations showed that VE favored the DPPC phase but partitioned predominantly to the domain boundaries and lowered the tendency for domain formation, and therefore acted as a linactant. This simulated behavior was consistent with experimental observations in which VE promoted lipid mixing and dispersed domains in both gel/liquid and liquid-ordered/liquid-disordered systems. From simulation, BA partitioned predominantly to the DUPC phase, decreased lipid order there, and thinned the membrane. These actions explain why, experimentally, BA promoted phase separation in both binary and ternary lipid mixtures. In contrast, TX, a popular detergent used to isolate raft membranes in cells, exhibited equal preference for both phases, as demonstrated by simulations, but nonetheless, was a strong domain promoter in all lipid mixtures. Further analysis showed that TX increased membrane thickness of the DPPC phase to a greater extent than the DUPC phase and thus increased hydrophobic mismatch, which may explain experimental observation of phase separation in the presence of TX. In summary, these nonlipid amphiphiles

  1. 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.

  2. Liquid crystalline thermotropic and lyotropic nanohybrids

    NASA Astrophysics Data System (ADS)

    Saliba, Sarmenio; Mingotaud, Christophe; Kahn, Myrtil L.; Marty, Jean-Daniel

    2013-07-01

    This review is meant to give the reader an insight into hybrids incorporating different types of nanoparticles, e.g. metallic or metal oxides, within different types of lyotropic and thermotropic liquid crystals, from relatively small calamitic molecules to the larger discotics and polymers. In particular, this review highlights the importance of nanoparticle-liquid crystal interactions in accessing hybrid materials that exhibit synergetic properties.

  3. Does dynamic vulcanization induce phase separation?

    PubMed

    Abolhasani, Mohammad Mahdi; Zarejousheghani, Fatemeh; Naebe, Minoo; Guo, Qipeng

    2014-08-14

    Immiscible and miscible blends of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) were subjected to dynamic vulcanization to investigate the effect of crosslinking on phase separation. As a result of different processability, mixing torque behavior of miscible and immiscible blends was significantly different from one another. Scanning electron microscopy (SEM) was used to investigate the morphology of the system. After dynamic vulcanization, submicron ACM droplets were observed in the samples near the binodal curve of the system under mixing conditions. Small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) analysis were used to investigate the effect of dynamic vulcanization on the lamellar structure of the system. It was shown that for samples near the boundary of phase separation, increasing the crosslink density led to a decrease in the lamellar long period (L) as a sign of increment of crosslink density induced phase decomposition. Effects of shear rate on the final morphology of the system were investigated by changing the mixing temperature and by comparing the results of dynamic vulcanization at one phase and two phase regions. PMID:24957793

  4. Crystallization And Phase Separation In Fluoride Glasses

    NASA Astrophysics Data System (ADS)

    Boehm, L.; Chung, K.-H.; Crichton, S. N.; Moynihan, C. T.

    1987-01-01

    We report here two studies relevant to these phenomena. Phase separation was unambiguously shown to occur in a ZrF4-based glass containing a small amount of PbF2 and prepared under a chloride-containing reactive atmosphere. Partial replacement of ZrF4 by HfF4 in a ZBLAN glass appears to improve the resistance to crystallization. The reason for this improvement seems to be a change in the crystalline phases and compositions first appearing on reheating.

  5. Thermocapillary-Induced Phase Separation with Coalescence

    NASA Technical Reports Server (NTRS)

    Davis, Robert H.

    2003-01-01

    Research has been undertaken on interactions of two or more deformable drops (or bubbles) in a viscous fluid and subject to a temperature, gravitational, or flow field. An asymptotic theory for nearly spherical drops shows that small deformations reduce the coalescence and phase separation rates. Boundary-integral simulations for large deformations show that bubbles experience alignment and enhanced coalescence, whereas more viscous drops may break as a result of hydrodynamic interactions. Experiments for buoyancy motion confirm these observations. Simulations of the sedimentation of many drops show clustering phenomena due to deformations, which lead to enhanced phase separation rates, and simulations of sheared emulsions show that deformations cause a reduction in the effective viscosity.

  6. 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.

  7. 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.

  8. Experimental study of phase separation in dividing two phase flow

    SciTech Connect

    Qian Yong; Yang Zhilin; Xu Jijun

    1996-12-31

    Experimental study of phase separation of air-water two phase bubbly, slug flow in the horizontal T-junction is carried out. The influences of the inlet mass quality X1, mass extraction rate G3/G1, and fraction of extracted liquid QL3/QL1 on phase separation characteristics are analyzed. For the first time, the authors have found and defined pulsating run effect by the visual experiments, which show that under certain conditions, the down stream flow of the T-junction has strangely affected the phase redistribution of the junction, and firstly point out that the downstream geometric condition is very important to the study of phase separation phenomenon of two-phase flow in a T-junction. This kind of phenomenon has many applications in the field of energy, power, petroleum and chemical industries, such as the loss of coolant accident (LOCA) caused by a small break in a horizontal coolant pipe in nuclear reactor, and the flip-flop effect in the natural gas transportation pipeline system, etc.

  9. Phase separation of comb polymer nanocomposite melts.

    PubMed

    Xu, Qinzhi; Feng, Yancong; Chen, Lan

    2016-02-01

    In this work, the spinodal phase demixing of branched comb polymer nanocomposite (PNC) melts is systematically investigated using the polymer reference interaction site model (PRISM) theory. To verify the reliability of the present method in characterizing the phase behavior of comb PNCs, the intermolecular correlation functions of the system for nonzero particle volume fractions are compared with our molecular dynamics simulation data. After verifying the model and discussing the structure of the comb PNCs in the dilute nanoparticle limit, the interference among the side chain number, side chain length, nanoparticle-monomer size ratio and attractive interactions between the comb polymer and nanoparticles in spinodal demixing curves is analyzed and discussed in detail. The results predict two kinds of distinct phase separation behaviors. One is called classic fluid phase boundary, which is mediated by the entropic depletion attraction and contact aggregation of nanoparticles at relatively low nanoparticle-monomer attraction strength. The second demixing transition occurs at relatively high attraction strength and involves the formation of an equilibrium physical network phase with local bridging of nanoparticles. The phase boundaries are found to be sensitive to the side chain number, side chain length, nanoparticle-monomer size ratio and attractive interactions. As the side chain length is fixed, the side chain number has a large effect on the phase behavior of comb PNCs; with increasing side chain number, the miscibility window first widens and then shrinks. When the side chain number is lower than a threshold value, the phase boundaries undergo a process from enlarging the miscibility window to narrowing as side chain length increases. Once the side chain number overtakes this threshold value, the phase boundary shifts towards less miscibility. With increasing nanoparticle-monomer size ratio, a crossover of particle size occurs, above which the phase separation

  10. Arrested segregative phase separation in capillary tubes.

    PubMed

    Tromp, R Hans; Lindhoud, Saskia

    2006-09-01

    Phase separation in a capillary tube with one of the phases fully wetting the capillary wall is arrested when the typical size of the phase domains reaches the value of the diameter of the tube. The arrested state consists of an alternating sequence of concave-capped and convex-capped cylindrical domains, called "plugs," "bridges," or "lenses," of wetting and nonwetting phase, respectively. A description of this arrested plug state for an aqueous mixture of two polymer solutions is the subject of this work. A phase separating system consisting of two incompatible polymers dissolved in water was studied. The phase volume ratio was close to unity. The initial state from which plugs evolve is characterized by droplets of wetting phase in a continuous nonwetting phase. Experiments show the formation of plugs by a pathway that differs from the theoretically well-described instabilities in the thickness of a fluid thread inside a confined fluid cylinder. Plugs appear to form after the wetting layer (the confined fluid cylinder) has become unstable after merging of droplet with the wetting layer. The relative density of the phases could be set by the addition of salt, enabling density matching. As a consequence, the capillary length can in principle be made infinitely large and the Bond number (which represents the force of gravity relative to the capillary force) zero, without considerably changing the interfacial tension. Using the possibility of density matching, the relations among capillary length and capillary diameter on the one hand, and the presence of plugs and their average size on the other were studied. It was found that stable plugs are present when the capillary radius does not exceed a certain value, which is probably smaller than the capillary length. However, the average plug size is independent of capillary length. At constant capillary length, average plug size was found to scale with the capillary diameter to a power 1.3, significantly higher than the

  11. Wetting and phase separation in soft adhesion

    PubMed Central

    Jensen, Katharine E.; Sarfati, Raphael; Style, Robert W.; Boltyanskiy, Rostislav; Chakrabarti, Aditi; Chaudhury, Manoj K.; Dufresne, Eric R.

    2015-01-01

    In the classic theory of solid adhesion, surface energy drives deformation to increase contact area whereas bulk elasticity opposes it. Recently, solid surface stress has been shown also to play an important role in opposing deformation of soft materials. This suggests that the contact line in soft adhesion should mimic that of a liquid droplet, with a contact angle determined by surface tensions. Consistent with this hypothesis, we observe a contact angle of a soft silicone substrate on rigid silica spheres that depends on the surface functionalization but not the sphere size. However, to satisfy this wetting condition without a divergent elastic stress, the gel phase separates from its solvent near the contact line. This creates a four-phase contact zone with two additional contact lines hidden below the surface of the substrate. Whereas the geometries of these contact lines are independent of the size of the sphere, the volume of the phase-separated region is not, but rather depends on the indentation volume. These results indicate that theories of adhesion of soft gels need to account for both the compressibility of the gel network and a nonzero surface stress between the gel and its solvent. PMID:26553989

  12. Phase Separation: Linking Cellular Compartmentalization to Disease.

    PubMed

    Aguzzi, Adriano; Altmeyer, Matthias

    2016-07-01

    Eukaryotic cells are complex structures capable of coordinating numerous biochemical reactions in space and time. Key to such coordination is the subdivision of intracellular space into functional compartments. Compartmentalization can be achieved by intracellular membranes, which surround organelles and act as physical barriers. In addition, cells have developed sophisticated mechanisms to partition their inner substance in a tightly regulated manner. Recent studies provide compelling evidence that membraneless compartmentalization can be achieved by liquid demixing, a process culminating in liquid-liquid phase separation and the formation of phase boundaries. We discuss how this emerging concept may help in understanding dynamic reorganization of subcellular space and highlight its potential as a framework to explain pathological protein assembly in cancer and neurodegeneration. PMID:27051975

  13. Phase behaviour and phase separation kinetics measurement using acoustic arrays

    NASA Astrophysics Data System (ADS)

    Khammar, M.; Shaw, J. M.

    2011-10-01

    Speed of sound and acoustic wave attenuation are sensitive to fluid phase composition and to the presence of liquid-liquid interfaces. In this work, the use of an acoustic array comprising 64 elements as a non-intrusive sensor for liquid-liquid interface, phase separation kinetics measurement in bulk fluids, and local composition measurement in porous media is illustrated. Three benchmark examples: the phase behaviour of methanol + mixed hexanes and methanol + heptane mixtures at 25.0 °C and 1 bar, and Athabasca bitumen + heptane in a synthetic silica porous medium at 22.5 °C and 1 bar, illustrate the accuracy of liquid-liquid interface and potential research and industrial applications of the technique. Liquid-liquid interfaces can be detected independently using both speed of sound and acoustic wave attenuation measurements. The precision of the interface location measurement is 300 μm. As complete scans can be performed at a rate of 1 Hz, phase separation kinetics and diffusion of liquids within porous media are readily tracked. The technique is expected to find application where the fluids or porous media are opaque to visible light and where other imaging techniques are not readily applied, or are too costly. A current limitation is that the acoustic probes must be cooled to less than 315 K in order for them to operate.

  14. Jahn-Teller solitons, structural phase transitions, and phase separation.

    PubMed

    Clougherty, Dennis P

    2006-02-01

    It is demonstrated that under common conditions a molecular solid subject to Jahn-Teller interactions supports stable Q-ball-like nontopological solitons. Such solitons represent a localized lump of excess electric charge in periodic motion accompanied by a time-dependent shape distortion of a set of adjacent molecules. The motion of the distortion can correspond to a true rotation or to a pseudorotation about the symmetric shape configuration. These solitons are stable for Jahn-Teller coupling strengths below a critical value; however, as the Jahn-Teller coupling approaches this critical value, the size of the soliton diverges signaling an incipient structural phase transition. The soliton phase mimics features commonly attributed to phase separation in complex solids. PMID:16486846

  15. Jahn-Teller Solitons, Structural Phase Transitions, and Phase Separation

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.

    2006-02-01

    It is demonstrated that under common conditions a molecular solid subject to Jahn-Teller interactions supports stable Q-ball-like nontopological solitons. Such solitons represent a localized lump of excess electric charge in periodic motion accompanied by a time-dependent shape distortion of a set of adjacent molecules. The motion of the distortion can correspond to a true rotation or to a pseudorotation about the symmetric shape configuration. These solitons are stable for Jahn-Teller coupling strengths below a critical value; however, as the Jahn-Teller coupling approaches this critical value, the size of the soliton diverges signaling an incipient structural phase transition. The soliton phase mimics features commonly attributed to phase separation in complex solids.

  16. Griffiths phase and temporal effects in phase separated manganites

    NASA Astrophysics Data System (ADS)

    Krivoruchko, V. N.; Marchenko, M. A.

    2016-08-01

    Phenomenological description of relaxation phenomena in magnetic and transport properties of perovskite manganites has been presented. The approach is based on generalization of some hypotheses appropriate to the Preisach picture of magnetization process for half-metallic ferromagnets and on an assumption that in doped manganites the phase separated state exists near the magnetic ordering temperature. For systems with the percolation type of a ferromagnet-paramagnet transition, distinctive features in relaxation of magnetization and resistivity have been found. The relaxation is shown to be most pronounced near the transition temperature, and to be an approximately logarithmic function of time. The theoretical results replicate a broad spectrum of behavior observed experimentally on time dependence of magnetization and resistivity of CMR systems and allow a direct comparison with available experimental data. We propose an additional experimental test to distinguish between the percolation scenario of magnetic and transport transitions in doped manganites, and the ferromagnetic polaron picture. In particular, an anomalously slow relaxation to zero of the order parameter can be considered as a key feature of the Griffiths-like phase transition in doped manganites. It is also shown that a system with the Griffiths-like state will exhibit nonequilibrium aging and rejuvenation phenomena, which in many aspects resemble that of a spin glass. We hope that experimental observation of a set of time decay properties will provide a settlement of apparently conflicting results obtained for different characteristics of phase-separated manganites.

  17. Gelation and phase separation of attractive colloids

    NASA Astrophysics Data System (ADS)

    Lu, Peter James

    2008-07-01

    I present several scientific and technical contributions in this thesis. I demonstrate that the gelation of spherical particles with isotropic, short-range attractive interactions is initiated by spinodal decomposition, a thermodynamic instability that triggers the formation of clusters that span and dynamically arrest to create a gel. This simple, universal gelation picture does not depend on microscopic system-specific details---thus broadly describing any particle system with short-range attractions---and suggests that gelation, often considered a purely kinetic phenomenon, is in fact a direct consequence of equilibrium liquid-gas phase separation. I also demonstrate that spherical particles with isotropic attractive interactions exhibit a stable phase---a fluid of particle clusters---that persists on experimental timescales even in the absence of any long-range Coulombic charge repulsion; this contrasts some expectations based on simulation and theory. I describe a new capability I created by integrating accelerated image processing software that I wrote into a high-speed confocal microscope system that I developed: active target-locking, the ability to follow freely-moving complex objects within a microscope sample, even as they change size, shape, and orientation---in real time. Finally, I report continuous, month-long observations of near-critical spinodal decomposition of colloids with isotropic attractions, aboard the International Space Station. I also include detailed descriptions, with examples and illustrations, of the tools and techniques that I have developed to produce these results.

  18. Separation of aqueous two-phase polymer systems in microgravity

    NASA Technical Reports Server (NTRS)

    Vanalstine, J. M.; Harris, J. M.; Synder, S.; Curreri, P. A.; Bamberger, S. B.; Brooks, D. E.

    1984-01-01

    Phase separation of polymer systems in microgravity is studied in aircraft flights to prepare shuttle experiments. Short duration (20 sec) experiments demonstrate that phase separation proceeds rapidly in low gravity despite appreciable phase viscosities and low liquid interfacial tensions (i.e., 50 cP, 10 micro N/m). Ostwald ripening does not appear to be a satisfactory model for the phase separation mechanism. Polymer coated surfaces are evaluated as a means to localize phases separated in low gravity. Contact angle measurements demonstrate that covalently coupling dextran or PEG to glass drastically alters the 1-g wall wetting behavior of the phases in dextran-PEG two phase systems.

  19. D-Limonene as a Chiral Dopant for Thermotropic Liquid Crystalline Systems

    NASA Astrophysics Data System (ADS)

    Zola, Rafael S.; Hurley, Shawn; Yang, Deng-Ke

    2011-06-01

    We used the chiral molecule D-limonene to induce thermotropic cholesteric phases. The methods used to characterize the chiral nematic phase and its features are given. We substituted D-limonene for conventional synthesized chiral dopants in the twisted nematic (TN) displays and showed an improvement in the response time. Despite the large number of synthesized chiral dopants, D-limonene can be used as a dopant for making cholesteric phases having the advantage of being a naturally occurring substance. It is surprising how many more synthesized chiral molecules have been used as the liquid crystal field moves forward in comparison to naturally occurring molecules.

  20. Surfactant-induced nematic wetting layer at a thermotropic liquid crystal/water interface.

    PubMed

    Bahr, Ch

    2006-03-01

    An ellipsometric study of the interface between a thermotropic liquid crystal and water near the nematic-isotropic phase transition of the liquid crystal is presented. At temperatures above the transition, a nematic wetting layer appears at the interface if the water phase contains a surfactant inducing a homeotropic alignment of the nematic phase. The detailed behavior is significantly influenced by the concentration of the surfactant. The results can be described by a Landau model of nematic wetting in which the surfactant concentration tunes the magnitude of an ordering interface potential. PMID:16605490

  1. A quantitative assessment of chemical perturbations in thermotropic cyanobiphenyls.

    PubMed

    Guerra, Sebastiano; Dutronc, Thibault; Terazzi, Emmanuel; Guénée, Laure; Piguet, Claude

    2016-05-25

    Chemical programming of the temperature domains of existence of liquid crystals is greatly desired by both academic workers and industrial partners. This contribution proposes to combine empirical approaches, which rely on systematic chemical substitutions of mesogenic molecules followed by thermal characterizations, with a rational thermodynamic assessment of the effects induced by chemical perturbations. Taking into account the similarities which exist between temperature-dependent cohesive Gibbs free energy densities (CFEDs) and pressure-temperature phase diagrams modeled with the Clapeyron equation, chemical perturbations are considered as pressure increments along phase boundaries, which control the thermotropic liquid crystalline properties. Taking the familiar calamitic amphiphilic cyanobiphenyl-type mesogens as models, the consequences of (i) methyl substitution of the aromatic polar heads and (ii) connections of bulky silyl groups at the termini of the apolar flexible alkyl chain on the melting and clearing temperatures are quantitatively analyzed. Particular efforts were focused on the translation of the thermodynamic rationalization into a predictive tool accessible to synthetic chemists mainly interested in designing liquid crystals with specific technological applications. PMID:27173940

  2. Stereochemical control of nonamphiphilic lyotropic liquid crystals: chiral nematic phase of assemblies separated by six nanometers of aqueous solvents.

    PubMed

    Yang, Sijie; Wang, Bing; Cui, Dawei; Kerwood, Deborah; Wilkens, Stephan; Han, Junjie; Luk, Yan-Yeung

    2013-06-13

    Unlike conventional thermotropic and lyotropic liquid crystals, nonamphiphilic lyotropic liquid crystals consist of hydrated assemblies of nonamphiphilic molecules that are aligned with a separation of about 6 nm between assemblies in an aqueous environment. This separation raises the question of how chirality, either from chiral mesogens or chiral dopants, would impact the phase as the assemblies that need to interact with each other are about 6 nm apart. Here, we report the synthesis of three stereoisomers of disodium chromonyl carboxylate, 5'DSCG-diviol, and the correlation between the molecular structure, bulk assembly, and liquid crystal formation. We observed that the chiral isomers (enantiomers 5'DSCG-(R,R)-diviol and 5'DSCG-(S,S)-diviol) formed liquid crystals while the achiral isomer 5'DSCG-meso-diviol did not. Circular dichroism indicated a chiral conformation with bisignate cotton effect. The nuclear Overhauser effect in proton NMR spectroscopy revealed conformations that are responsible for liquid crystal formation. Cryogenic transmission electron microscopy showed that chiral 5'DSCG-diviols form assemblies with crossings. Interestingly, only planar alignment of the chiral nematic phase was observed in liquid crystal cells with thin spacers. The homeotropic alignment that permitted a fingerprint texture was obtained only when the thickness of the liquid crystal cell was increase to above ~500 μm. These studies suggest that hydrated assemblies of chiral 5'DSCG-diviol can interact with each other across a 6 nm separation in an aqueous environment by having a twist angle of about 0.22° throughout the sample between the neighboring assemblies. PMID:23688325

  3. Thermotropic nematic order upon nanocapillary filling

    NASA Astrophysics Data System (ADS)

    Huber, Patrick; Busch, Mark; Całus, Sylwia; Kityk, Andriy V.

    2013-04-01

    Optical birefringence and light absorption measurements reveal four regimes for the thermotropic behavior of a nematogen liquid (7CB) upon sequential filling of parallel-aligned capillaries of 12 nm diameter in a monolithic, mesoporous silica membrane. No molecular reorientation is observed for the first adsorbed monolayer. In the film-condensed state (up to 1 nm thickness), a weak, continuous paranematic-to-nematic (P-N) transition is found, which is shifted by 10 K below the discontinuous bulk transition at TIN=305 K. The capillary-condensed state exhibits a more pronounced, albeit still continuous P-N reordering, located 4 K below TIN. This shift vanishes abruptly upon complete filling of the capillaries. It could originate in competing anchoring conditions at the free inner surfaces and at the pore walls or result from the 10-MPa tensile pressure release associated with the disappearance of concave menisci in the confined liquid upon complete filling. The study documents that the thermo-optical properties of nanoporous systems (or single nanocapillaries) can be tailored over a surprisingly wide range simply by variation of the filling fraction with liquid crystals.

  4. Thermotropic nematic order upon nanocapillary filling.

    PubMed

    Huber, Patrick; Busch, Mark; Całus, Sylwia; Kityk, Andriy V

    2013-04-01

    Optical birefringence and light absorption measurements reveal four regimes for the thermotropic behavior of a nematogen liquid (7CB) upon sequential filling of parallel-aligned capillaries of 12 nm diameter in a monolithic, mesoporous silica membrane. No molecular reorientation is observed for the first adsorbed monolayer. In the film-condensed state (up to 1 nm thickness), a weak, continuous paranematic-to-nematic (P-N) transition is found, which is shifted by 10 K below the discontinuous bulk transition at T(IN)=305 K. The capillary-condensed state exhibits a more pronounced, albeit still continuous P-N reordering, located 4 K below T(IN). This shift vanishes abruptly upon complete filling of the capillaries. It could originate in competing anchoring conditions at the free inner surfaces and at the pore walls or result from the 10-MPa tensile pressure release associated with the disappearance of concave menisci in the confined liquid upon complete filling. The study documents that the thermo-optical properties of nanoporous systems (or single nanocapillaries) can be tailored over a surprisingly wide range simply by variation of the filling fraction with liquid crystals. PMID:23679431

  5. Phase Separation in Cuprate Superconductors - Proceedings of the Workshop

    NASA Astrophysics Data System (ADS)

    Müller, K. A.; Benedek, G.

    1993-01-01

    The Table of Contents for the full book PDF is as follows: * Preface and Scope * Frustrated Phase Separation and High Temperature Superconductivity * Phase Separation and Photo-Induced High Tc Superconductivity in the Cuprates * Neutron Scattering Studies of the Spin Dynamics in La2-xSrxCuO4 * Percolative Phase Separation and High Tc Superconductivity * Phase Separation in Cuprate Superconductors from NMR and Microwave Absorption Measurements * Electronic Structure and Phase Separation in Superconducting Cuprates * The Virtual Exciton Mechanism of Superconductivity * Linear Arrays of Non Homogeneous Cu Sites in the CuO2 Plane: A New Scenario for Pairing Mechanisms in a Corrugated-Iron-Like Plane * Phase Separation, Structure and Superconductivity in Oxygen-Annealed La2CuO4+δ * Phase Separation in La2-xSrxCuO4 and YBa2Cu3Ox Studied by Mössbauer Spectroscopy * Phase Diagram and Transport Studies on La2-xSrxCuO4 * Static and Dynamic Transport Aspects of Phase Separation * Phase Separation in the Superconducting La2Cu4+δ Phases (0 < δ < 0.09) Prepared by Electrochemical Oxidation * Neutron Scattering Study of the YBa2Cu3O6+x System * NMR Investigation of Low Energy Excitations in YBa2Cu3O6+x Single Crystals * Aspects of the Spin Dynamics in the Cuprate Superconductors * Oxygen Order and Spin Structure in YBa2Cu3Ox Deduced from Copper NMR and NQR * Static and Dynamic Magnetic Properties of Ba, Cu and O in YBa2Cu4O8 and Y2Ba4Cu7O15.1 * Positional Splitting of Apex Oxygen and Nonlinear Excitations in Cuprates * Cooper Pair Formation by Distortive Electron-Lattice Coupling * Bipolaronic Charge Density Waves, Polaronic Spin Density Waves, and High Tc Superconductivity * Phase Separation as Result of a Thermodynamical Variational Method for the Emery Model * General Discussion led by G. Benedek and K. A. Müller

  6. Capillary electrokinetic separations: Influence of mobile phase composition on performance

    SciTech Connect

    Sepaniak, M.J.; Swaile, D.F.; Powell, A.C.; Cole, R.O.

    1990-01-01

    The composition of the mobile phase employed in capillary zone electrophoresis and the related technique, micellar electrokinetic capillary chromatography, is an important factor in determining separation performance. The influences of ionic salt, surfactant, and organic solvent mobile phase additives on separation efficiency, retention, and elution range are discussed and demonstrated. 23 refs., 2 figs., 2 tabs.

  7. Thermotropic and lyotropic behaviour of new liquid-crystalline materials with different hydrophilic groups: synthesis and mesomorphic properties

    PubMed Central

    Kašpar, Miroslav; Hamplová, Věra; Dawin, Ute; Giesselmann, Frank

    2013-01-01

    Summary Several new calamitic liquid-crystalline (LC) materials with flexible hydrophilic chains, namely either hydroxy groups or ethylene glycol units, or both types together, have been synthesized in order to look for new functional LC materials exhibiting both, thermotropic and lyotropic behaviour. Such materials are of high potential interest for challenging issues such as the self-organization of carbon nanotubes or various nanoparticles. Thermotropic mesomorphic properties have been studied by using polarizing optical microscopy, differential scanning calorimetry and X-ray scattering. Four of these nonchiral and chiral materials exhibit nematic and chiral nematic phases, respectively. For some molecular structures, smectic phases have also been detected. A contact sample of one of the prepared compounds with diethylene glycol clearly shows the lyotropic behaviour; namely a lamellar phase was observed. The relationship between the molecular structure and mesomorphic properties of these new LCs with hydrophilic chains is discussed. PMID:23504455

  8. 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.

  9. 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

  10. Stable phase separation and heterogeneity away from the coexistence curve

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, T. R.; Belitz, D.

    2016-04-01

    Phase separation, i.e., the coexistence of two different phases, is observed in many systems away from the coexistence curve of a first-order transition, leading to a stable heterogeneous phase or region. Examples include various quantum ferromagnets, heavy-fermion systems, rare-earth nickelates, and others. These observations seem to violate basic notions of equilibrium thermodynamics, which state that phase separation can occur only on the coexistence curve. We show theoretically that quenched disorder allows for phase separation away from the coexistence curve even in equilibrium due to the existence of stable minority-phase droplets within the majority phase. Our scenario also answers a related question: How can a first-order transition remain sharp in the presence of quenched disorder without violating the rigorous lower bound ν ≥2 /d for the correlation-length exponent? We discuss this scenario in the context of experimental results for a large variety of systems.

  11. 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.

  12. Colossal piezoresistance in phase separated manganites.

    PubMed

    Tosado, Jacob; Dhakal, Tara; Biswas, Amlan

    2009-05-13

    We have measured the strain dependent transport properties of phase separated manganite thin films. We subjected (La(1-y)Pr(y))(1-x)Ca(x)MnO(3) thin films grown on NdGaO(3)(110) substrates to direct external mechanical stress using a three-point beam bending method. The resultant change in resistance reveals a colossal piezoresistance (CPR) in manganites. Our experiments reveal that phase separation is a necessary but not sufficient condition for CPR. The maximum CPR is observed only when the phase boundaries are free to move in the fluid-like phase separated state. Our results show that both long-range strain interactions and quenched disorder play an important role in micrometer scale phase separation in manganites, albeit in different temperature ranges. PMID:21825473

  13. Oscillatory Shear Alignment and Rheology of a Main-chain Thermotropic Liquid Crystalline Polymer.

    NASA Astrophysics Data System (ADS)

    Kornfield, Julia A.; Zhou, Weijun; Ugaz, Victor M.; Vaish, Nitin; Burghardt, Wesley R.

    2000-03-01

    Orientational flipping is well known in lamellar block copolymers under oscillatory shear. For thermotropic LCPs, two different orientation states have also been reported under steady shear -- oriented either along the flow direction (``parallel'') or along the vorticity direction (``perpendicular''). Here we examine the oscillatory shear behavior of a model thermotropic LCP (DHMS-7,9, T_m=90^circC, T_xn=120^circC, T_ni=192^circC, where T_xn is the transition temperature between an unidentified mesophase ``Phase X'' to nematic phase), which exhibits this type of orientational flipping. Systematic studies have been carried out on DHMS-7,9 as a function of temperature, frequency, and strain amplitude. In the nematic phase, oscillatory shear induces parallel alignment. However, in Phase X, qualitatively different alignment behavior was observed: low frequency and large strain amplitude promote perpendicular alignment, while high frequency and small strain amplitude induce parallel orientation. A possible explanation of this anomalous shear alignment behavior will be provided.

  14. Phase Separators And Fountain-Effect Pumps For He 11

    NASA Technical Reports Server (NTRS)

    Whitehouse, Paul L.

    1989-01-01

    Fused-glass microchannel arrays for use as HE 11 phase separators and fountain-effect pumps. Microchannel devices for use in low-gravity storage and cooling systems containing superfluid helium. Phase separators and pumps take advantage of thermomechanical effect peculiar to He 11 in restricted spaces. By creating thermal gradient in porous plug, direction of flow reversed, turning phase separator into pump. However, addition of heat disadvantage. Thermal gradient created by using Peltier effect to transfer heat across array, removing heat from He 11 supply and overcoming undesirable addition of heat.

  15. Phase separation and the formation of cellular bodies

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Broedersz, Chase P.; Meir, Yigal; Wingreen, Ned S.

    Cellular bodies in eukaryotic cells spontaneously assemble to form cellular compartments. Among other functions, these bodies carry out essential biochemical reactions. Cellular bodies form micron-sized structures, which, unlike canonical cell organelles, are not surrounded by membranes. A recent in vitro experiment has shown that phase separation of polymers in solution can explain the formation of cellular bodies. We constructed a lattice-polymer model to capture the essential mechanism leading to this phase separation. We used both analytical and numerical tools to predict the phase diagram of a system of two interacting polymers, including the concentration of each polymer type in the condensed and dilute phase.

  16. Separation of Chloroplast Pigments Using Reverse Phase Chromatography.

    ERIC Educational Resources Information Center

    Reese, R. Neil

    1997-01-01

    Presents a protocol that uses reverse phase chromatography for the separation of chloroplast pigments. Provides a simple and relatively safe procedure for use in teaching laboratories. Discusses pigment extraction, chromatography, results, and advantages of the process. (JRH)

  17. 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.

  18. Phase separation in the crust of accreting neutron stars.

    PubMed

    Horowitz, C J; Berry, D K; Brown, E F

    2007-06-01

    Nucleosynthesis, on the surface of accreting neutron stars, produces a range of chemical elements. We perform molecular dynamics simulations of crystallization to see how this complex composition forms new neutron star crust. We find chemical separation, with the liquid ocean phase greatly enriched in low atomic number elements compared to the solid crust. This phase separation should change many crust properties such as the thermal conductivity and shear modulus. PMID:17677319

  19. Phase-Locked Semiconductor Lasers With Separate Contacts

    NASA Technical Reports Server (NTRS)

    Katz, Joseph; Yariv, Amnon; Margalit, Shlomo

    1988-01-01

    Individual current feeds enable better uniformity and flexible control. Separate contacts for lasers in array enable control of output radiation pattern and compensation of manufacturing nonuniformities among lasers. Concept of separate current control described for two-laser array in "Semiconductor Laser Phased Array" (NPO-15963).

  20. Protein crystals on phase-separating model membranes

    NASA Astrophysics Data System (ADS)

    Manley, Suliana; Horton, Margaret; Leszczynski, Szymon; Gast, Alice

    2006-03-01

    We study the interplay between the crystallization of proteins tethered to membranes and separation within the membranes of giant unilamellar vesicles (GUVs) composed of DOPC, sphingomyelin (SM), and cholesterol. These model membranes phase separate into coexisting liquid domains below a miscibility transition temperature. This phase separation captures some aspects of the formation of lipid rafts in cell membranes and demonstrates the influence of membrane composition on raft formation. Real cell membranes have a much more complicated structure. There are additional physical constraints present in cell membranes, such as their attachment to the cytoskeleton and the presence of membrane bound proteins. The self-association of membrane proteins can influence the membrane phase behavior. We begin to investigate these effects on model tethered protein- loaded membranes by incorporating a small amount of biotin-X- DPPE into our GUVs. The biotinylated lipid partitions into a cholesterol-poor phase; thus, streptavidin binds preferentially to one of the membrane phases. As streptavidin assembles to form crystalline domains, it restricts the membrane mobility. We examine the effect of this protein association on lipid phase separation, as well as the effect of the lipid phase separation on the crystallization of the tethered proteins.

  1. A Simple Algorithm for Calculation of Phase Separation.

    ERIC Educational Resources Information Center

    Eubank, Philip T.; Barrufet, Maria A.

    1988-01-01

    Describes an algorithm that provides more rapid convergence for more complicated forms of phase separation requiring the use of a digital computer. Demonstrates that this "inside-out" algorithm remains efficient for determination of the equilibrium states for any type of phase transition for a binary system. (CW)

  2. Texas A&M vortex type phase separator

    NASA Astrophysics Data System (ADS)

    Best, Frederick

    2000-01-01

    Phase separation is required for regenerative biological and chemical process systems as well as thermal transport and rejection systems. Liquid and gas management requirements for future spacecraft will demand small, passive systems able to operate over wide ranges of inlet qualities. Conservation and recycling of air and water is a necessary part of the construction and operation of the International Space Station as well as future long duration space missions. Space systems are sensitive to volume, mass, and power. Therefore, it is necessary to develop a method to recycle wastewater with minimal power consumption. Regenerative life support systems currently being investigated require phase separation to separate the liquid from the gas produced. The microgravity phase separator designed and fabricated at Texas A&M University relies on centripetal driven buoyancy forces to form a gas-liquid vortex within a fixed, right-circular cylinder. Two-phase flow is injected tangentially along the inner wall of this cylinder producing a radial acceleration gradient. The gradient produced from the intrinsic momentum of the injected mixture results in a rotating flow that drives the buoyancy process by the production of a hydrostatic pressure gradient. Texas A&M has flown several KC-135 flights with separator. These flights have included scaling studies, stability and transient investigations, and tests for inventory instrumentation. Among the hardware tested have been passive devices for separating mixed vapor/liquid streams into single-phase streams of vapor only and liquid only. .

  3. Simultaneous Vapor Deposition and Phase Separation of Polymer Films

    NASA Astrophysics Data System (ADS)

    Tao, Ran; Anthamatten, Mitchell

    2012-02-01

    Initiated chemical vapor deposition (iCVD) is a solventless, free radical technique used predominately to deposit homogeneous films of linear and crosslinked polymers directly from gas phase feeds. The major goal of this research is to force and arrest phase separation of deposited species by co-depositing non-reactive molecules (porogens) with reactive monomers and crosslinkers. We introduce these species during iCVD to force and quench polymer induced phase separation (PIPS) during film growth as a step toward tunable pore-size, density, and morphology. Polymerization, crosslinking and PIPS are intended to occur simultaneously on the substrate, resulting in a vitrified microstructure. Cahn-Hilliard theory predicts that the length scale of phase separation depends on the polymer-porogen interaction energy, the polymerization rate and the species' mobility. A series of films were grown by varying deposition rate, porogen type, and reagent flowrates. Crosslinkers were introduced to limit the growth of phase separated domains and to provide mechanical support during porogen removal. To elucidate how phase separation competes with polymerization and film growth, deposited films were studied using a combination of electron microscopy, profilometry and spectroscopic techniques.

  4. 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.

  5. Continuous flow system for controlling phases separation near λ transition

    SciTech Connect

    Chorowski, M.; Poliński, J.; Kempiński, W.; Trybuła, Z.; Łoś, Sz.; Chołast, K.; Kociemba, A.

    2014-01-29

    As demands on 3He are increasing and conventional 3He production through tritium decay is decreasing, alternative 3He production methods are becoming economically viable. One such possibility is to use entropy filters for extraction of the 3He isotope from natural gas. According to the phase diagram of the 3He, its solidification is impossible by only lowering of the temperature. Hence during the cooling process at stable pressure we can reach λ-point and pass to the special phase - He II. The total density of HeII is a sum of the two phases: normal the superfluid ones. It is possible to separate these two phases with an entropy filter - the barrier for the classically-behaving normal phase. This barrier can also be used to separate the two main isotopes of He: 4He and 3He, because at temperatures close to the 4He-λ-point the 3He isotope is part of the normal phase. The paper presents continuous flow schemes of different separation methods of 3He from helium commodity coming from natural gas cryogenic processing. An overall thermodynamic efficiency of the 3He/4He separation process is presented. A simplified model of continuous flow HeI -HeII recuperative heat exchanger is given. Ceramic and carbon porous plugs have been tested in entropy filter applications.

  6. Phase-separation inhibitors and prevention of selenite cataract.

    PubMed Central

    Clark, J I; Steele, J E

    1992-01-01

    The variation of the phase-separation temperature (Tc) was studied in lenses during formation of cataracts induced by a subcutaneous injection of sodium selenite. In normal control animals, the Tc decreased monotonically with increasing age. Approximately 2 days after administration of the selenite the Tc decreased sharply to a minimum, and then at day 4 the Tc increased dramatically toward body temperature. Mature irreversible cataracts formed approximately 6 days after injection of the selenite. Intraperitoneal administration of WR-77913, a phase-separation inhibitor, prevented the abnormal variation of Tc in vivo. When injected into control animals without selenite, WR-77913 produced no abnormal variation in Tc. The results confirm that Tc is a sensitive measure of early changes in the lens and that opacification associated with abnormal variation in Tc can be prevented in vivo by using a phase-separation inhibitor. Images PMID:1311849

  7. Phase separation and emergent structures in an active nematic fluid

    PubMed Central

    Putzig, Elias; Baskaran, Aparna

    2015-01-01

    We consider a phenomenological continuum theory for an active nematic fluid and show that there exists a universal, model independent instability which renders the homogeneous nematic state unstable to order fluctuations. Using numerical and analytic tools we show that, in the vicinity of a critical point, this instability leads to a phase separated state in which the ordered regions form bands in which the direction of nematic order is perpendicular to the direction of density gradient. We argue that the underlying mechanism that leads to this phase separation is a universal feature of active fluids of different symmetries. PMID:25375491

  8. Phase separation of X-irradiated lenses of rabbit

    SciTech Connect

    Clark, J.I.; Giblin, F.J.; Reddy, V.N.; Benedek, G.B.

    1982-02-01

    The phase separation temperature (Tcat) was studied as a function of time (age) after the administration of a single dose of radiation (2000 rad), which induces cataract in the rabbit lens. In the normal unirradiated lens, Tcat decreases linearly with age at a rate (DTcat/dt) approximately 2.2 degrees/week. In the irradiated lens, Tcat initially decreases with age much less than the normal lens, then rises sharply with age at the time of the appearance of opacity in the living rabbit eye. We suggest that the phase separation temperature may serve as a sensitive and early indicator of cataractogenic processes in the lens.

  9. Phase separation in thin films: Effect of temperature gradients

    NASA Astrophysics Data System (ADS)

    Jaiswal, Prabhat K.; Puri, Sanjay; Binder, Kurt

    2013-09-01

    We study the phase-separation kinetics of a binary (AB) mixture confined in a thin film of thickness D with a temperature gradient. Starting from a Kawasaki-exchange kinetic Ising model, we use a master-equation approach to systematically derive an extension of the Cahn-Hilliard model for this system. We study the effect of temperature gradients perpendicular to the film with “neutral” (no preference for either A or B) surfaces. We highlight the rich phenomenology and pattern dynamics which arises from the interplay of phase separation and the temperature gradient.

  10. Separation of synchronous sources through phase locked matrix factorization.

    PubMed

    Almeida, Miguel S B; Vigário, Ricardo; Bioucas-Dias, José

    2014-10-01

    In this paper, we study the separation of synchronous sources (SSS) problem, which deals with the separation of sources whose phases are synchronous. This problem cannot be addressed through independent component analysis methods because synchronous sources are statistically dependent. We present a two-step algorithm, called phase locked matrix factorization (PLMF), to perform SSS. We also show that SSS is identifiable under some assumptions and that any global minimum of PLMFs cost function is a desirable solution for SSS. We extensively study the algorithm on simulated data and conclude that it can perform SSS with various numbers of sources and sensors and with various phase lags between the sources, both in the ideal (i.e., perfectly synchronous and nonnoisy) case, and with various levels of additive noise in the observed signals and of phase jitter in the sources. PMID:25291741

  11. Phase separation in biological membranes: integration of theory and experiment

    PubMed Central

    Elson, Elliot L.; Fried, Eliot; Dolbow, John E.; Genin, Guy M.

    2013-01-01

    Lipid bilayer model membranes can undergo transitions between ordered and disordered phases, and membranes that contain a mixture of lipid species can undergo phase separations. Studies of these transformations are of interest for what they can tell us about the interaction energies of lipid molecules of different species and conformations. Nanoscopic phases can provide a model for membrane rafts, which have important biological functions in cell membranes. Important questions are whether lipid nanodomains can exist in stable equilibrium in membranes and what is the distribution of their sizes in membranes of different composition. It is also important to know the lifetimes of nanodomains. Theoretical methods have supplied much important information on these questions, but better experimental methods are needed to detect and characterize nanodomains under normal membrane conditions. This review summarizes linkages between theoretical and experimental studies of phase separation in lipid bilayer model membranes. PMID:20192775

  12. Phase Separation kinetics in an Fe-Cr-Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Chao, J.

    2012-01-01

    The {alpha}-{alpha}{prime} phase separation kinetics in a commercial Fe-20 wt.% Cr-6 wt.% Al oxide dispersion-strengthened PM 2000{trademark} steel have been characterized with the complementary techniques atom probe tomography and thermoelectric power measurements during isothermal aging at 673, 708, and 748 K for times up to 3600 h. A progressive decrease in the Al content of the Cr-rich {alpha}{prime} phase was observed at 708 and 748 K with increasing time, but no partitioning was observed at 673 K. The variation in the volume fraction of the {alpha}{prime} phase well inside the coarsening regime, along with the Avrami exponent 1.2 and activation energy 264 kJ mol{sup -1}, obtained after fitting the experimental results to an Austin-Rickett type equation, indicates that phase separation in PM 2000{trademark} is a transient coarsening process with overlapping nucleation, growth, and coarsening stages.

  13. Phase transition in Caenorhabditis elegans: A classical oil-water phase separation?

    NASA Astrophysics Data System (ADS)

    Weber, Christoph; Tony Hyman Collaboration; Andrés Delgadillo Collaboration; Frank Jülicher Team

    2014-03-01

    In Caenorhabditis elegans droplets form before the cell divides. These droplets, also referred to as P-granules, consist of a variety of unstructured proteins and mRNA. Brangwynne et al. [Science, 2009] showed that the P-granules exhibit fluid-like behavior and that the phase separation is controlled spatially by a gradient of a component called Mex-5. It is believed that this system exhibits the same characteristics as a classical oil-water phase separation. Here we report the recent experimental investigations on the phase separation in Caenorhabditis elegans and compare our findings with a classical oil-water phase separation. Specifically, we consider the underlying coarsening mechanisms as well as the impact of temperature and species composition. Finally, we present a preliminary model incorporating the characteristics of the phase separation kinetics for Caenorhabditis elegans.

  14. Thermotropic phase transitions in Pb1-xSrx(Al1/3Nb2/3)0.1(Zr0.52Ti0.48)0.9O3 ceramics: Temperature dependent dielectric permittivity and Raman scattering

    NASA Astrophysics Data System (ADS)

    Li, C. Q.; Peng, L.; Wang, P.; Jiang, K.; Liu, A. Y.; Hu, Z. G.; Chu, J. H.

    2015-06-01

    The phase transitions of Pb1-xSrx(Al1/3Nb2/3)0.1(Zr0.52Ti0.48)0.9O3 (Sr-modified PAN-PZT) ceramics with Sr compositions of x = 2%, 5%, 10% and 15% have been investigated using X-ray diffraction (XRD), temperature dependent dielectric permittivity and Raman scattering. The XRD analysis show that the phase transition occurs between Sr composition of 5% and 10%. Based on the broad dielectric peaks at 100 Hz, the diffused phase transition from tetragonal (T) to cubic (C) structure shifts to lower temperature with increasing Sr composition. The dramatic changes of wavenumber and full width at half-maximum (FWHM) for E(TO4)' softing mode can be observed at morphotropic phase boundary (MPB). Moreover, the MPB characteristic shows a wider and lower trend of temperature region with increasing Sr composition. It could be ascribed to the diminishment of the energy barrier and increment of A-cation entropy. Therefore, the Sr-modified PAN-PZT ceramics unambiguously undergo two successive structural transitions (rhombohedral-tetragonal-cubic phase) with temperature from 80 to 750 K. Correspondingly, the phase diagram of Sr-modified PAN-PZT ceramics can be well depicted.

  15. Ruthenium Behavior at Phase Separation of Borosilicate Glass-12259

    SciTech Connect

    Enokida, Youichi; Sawada, Kayo

    2012-07-01

    The Rokkasho reprocessing plant (RRP) located in Aomori, Japan, vitrifies high level waste (HLW) into a borosilicate glass. The HLW is generated from the reprocessing of spent fuel and contains ruthenium (Ru) and other platinum group metals (PGMs). Based on the recent consequences after a huge earthquake that occurred in Japan, a hypothetical blackout was postulated for the RRP to address additional safety analysis requirements. During a prolonged blackout, the borosilicate glass could phase separate due to cooling of the glass in the melter. The Ru present in the glass matrix could migrate into separate phases and impact the durability of the borosilicate glass. The durability of the glass is important for quality assurance and performance assessment of the vitrified HLW. A fundamental study was performed at an independent university to understand the impact of a prolonged blackout. Simulated HLW glasses were prepared for the RRP, and the Ru behavior in phase separated glasses was studied. The simulated HLW glasses contained nonradioactive elements and PGMs. The glass compositions were then altered to enhance the formation of the phase-separated glasses when subjected to thermal treatment at 700 deg. C for 24 hours. The synthesized simulated glasses contained 1.1 % Ru by weight as ruthenium dioxide (RuO{sub 2}). A portion of the RuO{sub 2} formed needle-shaped crystals in the glass specimens. After the thermal treatment, the glass specimen had separated into two phases. One of the two phases was a B{sub 2}O{sub 3} rich phase, and the other phase was a SiO{sub 2} rich phase. The majority of the chemical species in the B{sub 2}O{sub 3} rich phase was leached away with the Material Characterization Center-3 (MCC-3) protocol standardized by the Pacific Northwest National Laboratory using an aqueous low-concentrated nitric acid solution, but the leaching of the Ru fraction was very limited; less than 1% of the original Ru content. The Ru leaching was much less than

  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. Microscale extraction and phase separation using a porous capillary.

    PubMed

    Phillips, Thomas W; Bannock, James H; deMello, John C

    2015-07-21

    We report the use of a porous polytetrafluoroethylene capillary for the inline separation of liquid-liquid segmented flows, based on the selective wetting and permeation of the porous capillary walls by one of the liquids. Insertion of a narrow flow restriction at the capillary outlet allows the back pressure to be tuned for multiple liquid-liquid combinations and flow conditions. In this way, efficient separation of aqueous-organic, aqueous-fluorous and organic-fluorous segmented flows can be readily achieved over a wide range of flow rates. The porous-capillary-separator enables the straightforward regeneration of a continuous flow from a segmented flow, and may be applied to various applications, including inline analysis, biphasic reactions, and purification. As a demonstration of the latter, we performed a simple inline aqueous-organic extraction of the pH indicator 2,6-dichloroindophenol. An aqueous solution of the conjugate base was mixed with hydrochloric acid in continuous flow to protonate the indicator and render it organic-soluble. The indicator was then extracted from the aqueous feed into chloroform using a segmented flow. The two liquids were finally separated inline using a porous PTFE capillary, with the aqueous phase emerging as a continuous stream from the separator outlet. UV-visible absorption spectroscopy showed the concentration of indicator in the outflowing aqueous phase to be less than one percent of its original value, confirming the efficacy of the extraction and separation process. PMID:26054926

  18. Demixing kinetics of phase separated polymer solutions in microgravity

    NASA Technical Reports Server (NTRS)

    Brooks, D. E.; Bamberger, S. B.; Harris, J. M.; Vanalstine, J.; Snyder, R. S.

    1988-01-01

    Phase separated solutions of two neutral polymers in buffer provide a useful and versatile medium for the partition separation of biological cells. However, the efficiency of such separations is orders of magnitude lower than the thermodynamic limit. To test the hypothesis that this inefficiency is at least partially due to the convection and sedimentation that occur during the gravity driven demixing that follows introduction of cells to the systems, a series of experiments were begun aimed at performing cell partition in a low g environment. Demixing of isopycnic three polymer solvent systems was studied, experiments were performed on KC-135 aircraft and one shuttle middeck experiment was completed. Analysis of the results of these experiments and comparisons with the predictions of scaling relations for the dependence of phase domain size on time, derived for a number of possible demixing mechanisms, are presented.

  19. Confined phase separation in SiOX nanometric thin layers

    NASA Astrophysics Data System (ADS)

    Roussel, M.; Talbot, E.; Pareige, C.; Pratibha Nalini, R.; Gourbilleau, F.; Pareige, P.

    2013-11-01

    Phase separation in silicon-rich silica/silica multilayers was investigated using Atom Probe Tomography and Atomistic Kinetic Monte Carlo simulation. It is shown that the thickness of silicon-rich silicon oxide sublayers plays an important role during phase transformation. It determines the morphology of Si-rich phase formed after subsequent annealing, which is of prime interest for microelectronic and optoelectronic applications. Monte Carlo simulation reveals that the formation of isolated Si clusters can be achieved even in the case of spinodal decomposition and is directly related to the ratio between the spinodal wavelength and the sublayer thickness.

  20. Assemblages: Functional units formed by cellular phase separation

    PubMed Central

    Wright, Peter E.

    2014-01-01

    The partitioning of intracellular space beyond membrane-bound organelles can be achieved with collections of proteins that are multivalent or contain low-complexity, intrinsically disordered regions. These proteins can undergo a physical phase change to form functional granules or other entities within the cytoplasm or nucleoplasm that collectively we term “assemblage.” Intrinsically disordered proteins (IDPs) play an important role in forming a subset of cellular assemblages by promoting phase separation. Recent work points to an involvement of assemblages in disease states, indicating that intrinsic disorder and phase transitions should be considered in the development of therapeutics. PMID:25179628

  1. Diagnostic immunoassay by solid phase separation for digoxin

    SciTech Connect

    Grenier, F.C.; Pry, T.A.; Kolaczkowski, L.

    1988-11-29

    A method is described for conducting a diagnostic immunoassay for digoxin, comprising: (a) forming a reaction mixture of a test sample with a molar excess of labeled anti-digoxin antibodies whereby the labeled antibodies are capable of forming complex with digoxin present in the sample; (b) contacting the reaction mixture with a solid phase material having immobilized thereon a compound; (c) separating the solid phase material from the reaction mixture; and (d) determining the presence of digoxin in the test sample by measuring the amount of complex present in the liquid phase.

  2. The thermotropic behavior of dipalmitoyl phosphatidylcholine bilayers. A Fourier transform infrared study of specifically labeled lipids.

    PubMed Central

    Cameron, D G; Casal, H L; Mantsch, H H; Boulanger, Y; Smith, I C

    1981-01-01

    Fourier transform infrared spectroscopy has been used to study the thermotropic behavior of hydrated multibilayers of specifically deuterated derivatives of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. It is shown that throughout the gel phase there is little or no conformational disorder introduced into the acyl chains. The pretransition effect is greatest in the central segments of the acyl chains, demonstrating that the interchain interactions are more pronounced in this region than in the center of the bilayer and suggesting the presence, in the gel phase, of a "plateau" in the strength of the interchain interactions. As the temperature is reduced, the rate of rotation of the terminal methyl group decreases steadily; below 0 degree C the conformation is rigid on the infrared time scale. PMID:6894878

  3. Analysis of Phase Separation in Czochralski Grown Single Crystal Ilmenite

    NASA Technical Reports Server (NTRS)

    Wilkins, R.; Powell, Kirk St. A.; Loregnard, Kieron R.; Lin, Sy-Chyi; Muthusami, Jayakumar; Zhou, Feng; Pandey, R. K.; Brown, Geoff; Hawley, M. E.

    1998-01-01

    Ilmenite (FeTiOs) is a wide bandgap semiconductor with an energy gap of 2.58 eV. Ilmenite has properties suited for radiation tolerant applications, as well as a variety of other electronic applications. Single crystal ilmenite has been grown from the melt using the Czochralski method. Growth conditions have a profound effect on the microstructure of the samples. Here we present data from a variety of analytical techniques which indicate that some grown crystals exhibit distinct phase separation during growth. This phase separation is apparent for both post-growth annealed and unannealed samples. Under optical microscopy, there appear two distinct areas forming a matrix with an array of dots on order of 5 pm diameter. While appearing bright in the optical micrograph, atomic force microscope (AFM) shows the dots to be shallow pits on the surface. Magnetic force microscope (MFM) shows the dots to be magnetic. Phase identification via electron microprobe analysis (EMPA) indicates two major phases in the unannealed samples and four in the annealed samples, where the dots appear to be almost pure iron. This is consistent with micrographs taken with a scanning probe microscope used in the magnetic force mode. Samples that do not exhibit the phase separation have little or no discernible magnetic structure detectable by the MFM.

  4. Prediction of phase separation during the drying of polymer shells

    SciTech Connect

    Wilemski, G.; Cook, R.; Boone, T.; Cheung, L.; Nelson, D.

    1995-12-01

    During the drying of polymer shells formed by microencapsulation, vacuole formation is believed to occur as a result of phase separation. To better understand and control this process, we have used a multicomponent diffusion formalism to predict compositional changes in the layer as organic solvents diffuse out and water diffuses into the layer. Formation of thermodynamically unstable compositions can lead to phase separation by condensation of water on submicron foreign particles present in the shell wall. We used statistical mechanics, the UNIFAP methodology, and empirical data to deduce the required values of transport coefficients and equilibrium phase compositions. The results suggest that vacuole formation can be eliminated or reduced by removing submicron and larger particles from the shell wall and by using solvents with lower intrinsic water solubilities. 21 refs., 7 figs.

  5. A phase-separation kinetic model for coke formation

    SciTech Connect

    Wiehe, I.A. . Corporate Research Lab.)

    1993-11-01

    Coke formation during the thermolysis of petroleum residua is postulated to occur by a mechanism that involves the liquid-liquid phase separation of reacted asphaltenes to form a phase that is lean in abstractable hydrogen. This mechanism provides the basis of a model that quantitatively describes the kinetics for the thermolysis of Cold Lake vacuum residuum and its deasphalted oil in an open-tube reactor at 400 C. The previously unreacted asphaltenes were found to be the fraction with the highest rate of thermal reaction but with the least extent of reaction. This not only described the appearance and disappearance of asphaltenes but also quantitatively described the variation in molecular weight and hydrogen content of the asphaltenes with reaction time. Further evidence of the liquid-liquid phase separation was the observation of spherical particles of liquid crystalline coke and the preferential conversion of the most associated asphaltenes to coke.

  6. A phase separation kinetic model for coke formation

    SciTech Connect

    Wiehe, I.A.

    1993-12-31

    Coke formation during the thermolysis of petroleum residua is postulated to occur by a mechanism that involves the liquid-liquid phase separation of reacted asphaltenes to form a phase that is lean in abstractable hydrogen. This mechanism provides the basis of a model the quantitatively describes the kinetics for the thermolysis of Cold Lake vacuum residuum and its deasphalted oil in an open tube reactor at 400{degrees}C. The previously unreacted asphaltenes were found to be the fraction with the highest rate of thermal reaction but with the least extent of reaction. Further evidence of the liquid-liquid phase separation was the observation of spherical particles of liquid crystalline coke and the preferential conversion of the most associated asphaltenes to coke.

  7. Metallic and semiconducting carbon nanotubes separation using an aqueous two-phase separation technique: a review

    NASA Astrophysics Data System (ADS)

    Tang, Malcolm S. Y.; Ng, Eng-Poh; Juan, Joon Ching; Ooi, Chien Wei; Ling, Tau Chuan; Woon, Kai Lin; Loke Show, Pau

    2016-08-01

    It is known that carbon nanotubes show desirable physical and chemical properties with a wide array of potential applications. Nonetheless, their potential has been hampered by the difficulties in acquiring high purity, chiral-specific tubes. Considerable advancement has been made in terms of the purification of carbon nanotubes, for instance chemical oxidation, physical separation, and myriad combinations of physical and chemical methods. The aqueous two-phase separation technique has recently been demonstrated to be able to sort carbon nanotubes based on their chirality. The technique requires low cost polymers and salt, and is able to sort the tubes based on their diameter as well as metallicity. In this review, we aim to provide a review that could stimulate innovative thought on the progress of a carbon nanotubes sorting method using the aqueous two-phase separation method, and present possible future work and an outlook that could enhance the methodology.

  8. Metallic and semiconducting carbon nanotubes separation using an aqueous two-phase separation technique: a review.

    PubMed

    Tang, Malcolm S Y; Ng, Eng-Poh; Juan, Joon Ching; Ooi, Chien Wei; Ling, Tau Chuan; Woon, Kai Lin; Show, Pau Loke

    2016-08-19

    It is known that carbon nanotubes show desirable physical and chemical properties with a wide array of potential applications. Nonetheless, their potential has been hampered by the difficulties in acquiring high purity, chiral-specific tubes. Considerable advancement has been made in terms of the purification of carbon nanotubes, for instance chemical oxidation, physical separation, and myriad combinations of physical and chemical methods. The aqueous two-phase separation technique has recently been demonstrated to be able to sort carbon nanotubes based on their chirality. The technique requires low cost polymers and salt, and is able to sort the tubes based on their diameter as well as metallicity. In this review, we aim to provide a review that could stimulate innovative thought on the progress of a carbon nanotubes sorting method using the aqueous two-phase separation method, and present possible future work and an outlook that could enhance the methodology. PMID:27396920

  9. Phase discrimination method for simultaneous two-phase separation in time-resolved stereo PIV measurements

    NASA Astrophysics Data System (ADS)

    Cheng, Y.; Pothos, S.; Diez, F. J.

    2010-12-01

    A phase discrimination method for two-phase PIV is presented that is capable of simultaneously separating the two phases from time-resolved stereoscopic PIV images taken in a particle-laden jet. The technique developed expands on previous work done by Khalitov and Longmire (Exp Fluids 32:252-268, 2002), where by means of image processing techniques, a raw two-phase PIV image can be separated into two single-phase images according to particle size and intensity distributions. The technique is expanded through the use of three new image processing algorithms to separate particles of similar size (up to an order of magnitude better than published work) for fields of view much larger than previously considered. It also addresses the known problem of noisy background images produced by high-speed CMOS cameras, which makes the particle detection and separation from the noisy background difficult, through the use of a novel fast Fourier transform background filter.

  10. Polymerization-Induced Phase Separation in Vinyl Ester Resins

    NASA Astrophysics Data System (ADS)

    Ganglani, Manisha; Torkelson, John; Carr, Stephen

    2000-03-01

    In certain multi-component, crosslinking polymer systems, phase separation is induced by polymerization, a process call polymerization-induced phase separation (PIPS) in which there exists a competition between reaction rate and phase separation rate. The final morphology and properties of a system that experiences PIPS depend on the outcome of this competition. Thus, by controlling these rates, it would be possible to control end properties. In fact, this theory has been applied for the creation of polymer-dispersed liquid crystals (PDLCs) where cure occurs via condensation reactions or via free radical polymerization initiated by UV light. This research examines PIPS in the vinyl ester (VE) resins, which are popular as matrix materials in polymer composites. Cure of the VE resins is more complicated because it uses initiators and therefore requires more time and offers less control than cure by photopolymerization. To better understand the PIPS process in the VE resins, this research separates the two competitive effects and examines each one in turn. Initial experiments use a model system to focus on the effect of PIPS in the absence of crosslinking.

  11. 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

  12. Evidence of Phase Separation during Vapor Deposition Polymerization

    NASA Astrophysics Data System (ADS)

    Tao, Ran; Anthamatten, Mitchell

    2013-03-01

    Initiated chemical vapor deposition (iCVD) is a solventless, free radical technique predominately used to deposit homogeneous films of linear and crosslinked polymers directly from gas phase feeds. We are developing multicomponent iCVD techniques to induce phase separation during film growth. Small molecule porogens and crosslinkers are introduced into the iCVD process during film growth of poly(glycidyl methacrylate). Analogous to well established polymerization induced phase separation (PIPS) processes, porogens, such as dimethyl phthalate, are well mixed at the growing gas-film interface but are immiscible with high molecular weight polymer. Polymerization, crosslinking and PIPS are intended to occur simultaneously on the substrate, resulting in a vitrified microstructure. A series of films were grown by varying deposition rate, porogen type, and reagent flowrates. Deposited films were studied by electron microscopy and spectroscopic techniques. Experiments are compared to Cahn-Hilliard theory predictions that relate the length and time scale of the phase separation to the polymer-porogen interaction energy, the rate of polymerization and the species mobility.

  13. Phase separation in solutions with specific and nonspecific interactions

    SciTech Connect

    Jacobs, William M.; Frenkel, Daan; Oxtoby, David W.

    2014-05-28

    Protein solutions, which tend to be thermodynamically stable under physiological conditions, can demix into protein-enriched and protein-depleted phases when stressed. Using a lattice-gas model of proteins with both isotropic and specific, directional interactions, we calculate the critical conditions for phase separation for model proteins with up to four patches via Monte Carlo simulations and statistical associating fluid theory. Given a fixed specific interaction strength, the critical value of the isotropic energy, which accounts for dispersion forces and nonspecific interactions, measures the stability of the solution with respect to nonspecific interactions. Phase separation is suppressed by the formation of protein complexes, which effectively passivate the strongly associating sites on the monomers. Nevertheless, we find that protein models with three or more patches can form extended aggregates that phase separate despite the assembly of passivated complexes, even in the absence of nonspecific interactions. We present a unified view of the critical behavior of model fluids with anisotropic interactions, and we discuss the implications of these results for the thermodynamic stability of protein solutions.

  14. Separate-contact phase-locked semiconductor laser arrays

    NASA Technical Reports Server (NTRS)

    Katz, J.; Kapon, E.; Lindsey, C.; Margalit, S.; Yariv, A.

    1985-01-01

    The novel optoelectronic devices discussed, phase-locked semiconductor laser arrays with separate contacts can perform a variety of near field and far field pattern tailoring functions and control mutual coherence among array elements, as well as lasing wavelength selectivity and tunability. Attention is presently given to experimental results from such arrays, which indicate that the threshold currents of the 4-micron wide lasers employed are typically 60 mA. The separate contacts to each one of them are provided by means of two-level metallization.

  15. Re-entrant phase behavior for systems with competition between phase separation and self-assembly

    NASA Astrophysics Data System (ADS)

    Reinhardt, Aleks; Williamson, Alexander J.; Doye, Jonathan P. K.; Carrete, Jesús; Varela, Luis M.; Louis, Ard A.

    2011-03-01

    In patchy particle systems where there is a competition between the self-assembly of finite clusters and liquid-vapor phase separation, re-entrant phase behavior can be observed, with the system passing from a monomeric vapor phase to a region of liquid-vapor phase coexistence and then to a vapor phase of clusters as the temperature is decreased at constant density. Here, we present a classical statistical mechanical approach to the determination of the complete phase diagram of such a system. We model the system as a van der Waals fluid, but one where the monomers can assemble into monodisperse clusters that have no attractive interactions with any of the other species. The resulting phase diagrams show a clear region of re-entrance. However, for the most physically reasonable parameter values of the model, this behavior is restricted to a certain range of density, with phase separation still persisting at high densities.

  16. Growth and Morphology of Phase Separating Supercritical Fluids

    NASA Technical Reports Server (NTRS)

    Hegseth, John; Beysens, Daniel; Perrot, Francoise; Nikolayev, Vadim; Garrabos, Yves

    1996-01-01

    The scientific objective is to study the relation between the morphology and the growth kinetics of domains during phase separation. We know from previous experiments performed near the critical point of pure fluids and binary liquids that there are two simple growth laws at late times. The 'fast' growth appears when the volumes of the phases are nearly equal and the droplet pattern is interconnected. In this case the size of the droplets grows linearly in time. The 'slow' growth appears when the pattern of droplets embedded in the majority phase is disconnected. In this case the size of the droplets increases in proportion to time to the power 1/3. The volume fraction of the minority phase is a good candidate to determine this change of behavior. All previous attempts to vary the volume fraction in a single experimental cell have failed because of the extreme experimental difficulties.

  17. 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.

  18. Lattice-gas models of phase separation: interfaces, phase transitions, and multiphase flow

    SciTech Connect

    Rothman, D.H. ); Zaleski, S. )

    1994-10-01

    Momentum-conserving lattice gases are simple, discrete, microscopic models of fluids. This review describes their hydrodynamics, with particular attention given to the derivation of macroscopic constitutive equations from microscopic dynamics. Lattice-gas models of phase separation receive special emphasis. The current understanding of phase transitions in these momentum-conserving models is reviewed; included in this discussion is a summary of the dynamical properties of interfaces. Because the phase-separation models are microscopically time irreversible, interesting questions are raised about their relationship to real fluid mixtures. Simulation of certain complex-fluid problems, such as multiphase flow through porous media and the interaction of phase transitions with hydrodynamics, is illustrated.

  19. Phase-locked semiconductor laser array with separate contacts

    NASA Technical Reports Server (NTRS)

    Katz, J.; Kapon, E.; Lindsey, C.; Margalit, S.; Shreter, U.; Yariv, A.

    1983-01-01

    A new monolithic phase-locked semiconductor laser array has been fabricated. Employing two-level metallization, each of the eight elements in the array has a separate contact, thus making it possible to compensate for device nonuniformities and control the near-field and far-field patterns. Threshold currents are approximately 60 mA for each 5-micron-wide laser in the array. Phase locking has been observed via the narrowing of the far-field pattern. Experimental results are compared to those obtained from the same arrays operated with all the lasers connected in parallel.

  20. Correlated lateral phase separations in stacks of lipid membranes

    NASA Astrophysics Data System (ADS)

    Hoshino, Takuma; Komura, Shigeyuki; Andelman, David

    2015-12-01

    Motivated by the experimental study of Tayebi et al. [Nat. Mater. 11, 1074 (2012)] on phase separation of stacked multi-component lipid bilayers, we propose a model composed of stacked two-dimensional Ising spins. We study both its static and dynamical features using Monte Carlo simulations with Kawasaki spin exchange dynamics that conserves the order parameter. We show that at thermodynamical equilibrium, due to strong inter-layer correlations, the system forms a continuous columnar structure for any finite interaction across adjacent layers. Furthermore, the phase separation shows a faster dynamics as the inter-layer interaction is increased. This temporal behavior is mainly due to an effective deeper temperature quench because of the larger value of the critical temperature, Tc, for larger inter-layer interaction. When the temperature ratio, T/Tc, is kept fixed, the temporal growth exponent does not increase and even slightly decreases as a function of the increased inter-layer interaction.

  1. Exploration of phase separation in heterogeneous lipid monolayers

    NASA Astrophysics Data System (ADS)

    Decaro, Curt; Bera, Sambhunath; Jiang, Zhang; Mukhopadhyay, Mrinmay; Thompson, Carol

    2012-02-01

    A Langmuir monolayer is a well established model of a single leaflet of a lipid membrane. In this work, we investigate the phase separation behavior of a model Langmuir monolayer as a function of both Langmuir surface pressure and ratio of saturated lipid : unsaturated lipid : cholesterol. The specifics of domain separation behavior, or ``rafting,'' in membranes are generally thought to be responsible for much of the behavior of living membranes, specifically in protein integration and transport. Off-specular x-ray scattering is used to probe in-plane structure of the membrane at the sub-micron scale. Additionally, atomic force microscopy imaging is taken on samples transferred to a rigid support. In-plane order is found to grow as a function of surface pressure. Also, the in-plane order is found to depend on cholesterol concentration in the monolayer. The phase space of the in-plane order as a function of lipid and cholesterol concentration is presented.

  2. Fibril Formation and Phase Separation in Aqueous Cellulose Ethers

    NASA Astrophysics Data System (ADS)

    Maxwell, Amanda; Schmidt, Peter; McAllister, John; Lott, Joseph; Bates, Frank; Lodge, Timothy

    Aqueous solutions of many cellulose ethers are known to undergo thermoreversible gelation and phase separation upon heating to form turbid hydrogels, but the mechanism and resulting structures have not been well understood. Turbidity, light scattering and small-angle neutron scattering (SANS) are used to show that hydroxypropyl methylcellulose (HPMC) chains are dissolved in water below 50 °C and undergo phase separation at higher temperatures. At 70 °C, at sufficiently high concentrations in water, HPMC orders into fibrillar structures with a well-defined radius of 18 +/- 2 nm, as characterized by cryogenic transmission electron microscopy and SANS. The HPMC fibril structure is independent of concentration and heating rate. However, HPMC fibrils do not form a percolating network as readily as is seen in methylcellulose, resulting in a lower hot-gel modulus, as demonstrated by rheology.

  3. Phase separation of metallic hydrogen-helium alloys

    NASA Technical Reports Server (NTRS)

    Straus, D. M.; Ashcroft, N. W.; Beck, H.

    1976-01-01

    Calculations are presented for the thermodynamic functions and phase separation boundaries of solid metallic hydrogen helium alloys at temperatures between 0 K and 19,000 K and at pressures between 15 and 90 megabars. Expressions for the band structure energy of a randomly disordered alloy (including third order in the electron ion interaction) are derived and evaluated. Short and long range order are included by the quasi-chemical method, and lattice dynamics in the virtual crystal harmonic approximation. We conclude that at temperatures below 4,000 K there is complete phase separation of hydrogen helium alloys, and that a miscibility gap remains at the highest temperatures and pressures considered. The relevance of these results to models of the deep interior of Jupiter is briefly discussed.

  4. Phase separation of metallic hydrogen-helium alloys

    NASA Technical Reports Server (NTRS)

    Straus, D. M.; Ashcroft, N. W.; Beck, H.

    1977-01-01

    Calculations are presented for the thermodynamic functions and phase-separation boundaries of solid metallic hydrogen-helium alloys at temperatures between zero and 19,000 K and at pressures between 15 and 90 Mbar. Expressions for the band-structure energy of a randomly disordered alloy (including third order in the electron-ion interaction) are derived and evaluated. Short- and long-range orders are included by the quasi-chemical method, and lattice dynamics in the virtual-crystal harmonic approximation. It is concluded that at temperatures below 4000 K, there is essentially complete phase separation of hydrogen-helium alloys and that a miscibility gap remains at the highest temperatures and pressures considered. The relevance of these results to models of the deep interior of Jupiter is briefly discussed.

  5. Separation of granulocytes from whole blood by leukoadhesion, phase 1

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Capillary glass tubes are investigated for the separation and retrieval of large quantities of viable granulocytes and monocytes from whole blood on a continuous basis from a single donor. This effort represented the feasibility demonstration of a three phase program for development of a capillary tube cell separation device. The activity included the analysis and parametric laboratory testing with subscale models required to design a prototype device. Capillary tubes 40 cm long with a nominal 0.030 cm internal diameter yielded the highest total process efficiency. Recovery efficiencies as high as 89% of the adhering cell population were obtained. Granulocyte phagocytosis of latex particles indicated approximately 90% viability. Monocytes recovered from the separation column retained their capability to stimulate human bone marrow colony growth, as demonstrated in an in vitro cell culture assay.

  6. Rationale for two phase polymer system microgravity separation experiments

    NASA Technical Reports Server (NTRS)

    Brooks, D. E.; Bamberger, S. B.; Harris, J. M.; Vanalstine, J.

    1984-01-01

    The two-phase systems that result when aqueous solutions of dextran and poly(ethylene glycol) are mixed at concentrations above a few percent are discussed. They provide useful media for the partition and isolation of macromolecules and cell subpopulations. By manipulating their composition, separations based on a variety of molecular and surface properties are achieved, including membrane hydrophobic properties, cell surface charge, and membrane antigenicity. Work on the mechanism of cell partition shows there is a randomizing, nonthermal energy present which reduces separation resolution. This stochastic energy is probably associated with hydrodynamic interactions present during separation. Because such factors should be markedly reduced in microgravity, a series of shuttle experiments to indicate approaches to increasing the resolution of the procedure are planned.

  7. Waves at the nematic-isotropic interface: Thermotropic nematogen-non-nematogen mixtures

    NASA Astrophysics Data System (ADS)

    Popa-Nita, V.; Sluckin, T. J.; Kralj, S.

    2005-06-01

    We develop a theory for surface modes at the nematic-isotropic interface in thermotropic nematogen-non-nematogen mixtures. We employ the dynamical generalization of the Landau-de Gennes model for the orientational (nonconserved) order parameter, coupled with the Cahn-Hilliard equation for concentration (conserved parameter), and include hydrodynamic degrees of freedom. The theory uses a generalized form of the Landau-de Gennes free-energy density to include the coupling between the concentration of the non-nematogen fluid and the orientational order parameter. Two representative phase diagrams are shown. The method of matched asymptotic expansions is used to obtain a generalized dispersion relation. Further analysis is made in particular cases. Orientational order parameter relaxation dominates in the short-wavelength limit, while in the long-wavelength limit viscous damping processes become important. There is an intermediate region (depending on the temperature) in which the interaction between conserved parameter dynamics and hydrodynamics is important.

  8. Activity induced phase separation in particles and (bio)polymers

    NASA Astrophysics Data System (ADS)

    Grosberg, Alexander

    It was recently shown that the non-equilibrium steady state of the mixture of two types of particles exposed to two different thermostats can phase separate (A.Y.Grosberg, J.-F.Joanny, PRE, v. 91, 032118, 2015). similar result is valid also in the case when particles in question are monomers of two different polymer chains, or blocks of a co-polymer. We discuss the implications of these results for the physics of chromatin.

  9. Separating homeologs by phasing in the tetraploid wheat transcriptome

    PubMed Central

    2013-01-01

    Background The high level of identity among duplicated homoeologous genomes in tetraploid pasta wheat presents substantial challenges for de novo transcriptome assembly. To solve this problem, we develop a specialized bioinformatics workflow that optimizes transcriptome assembly and separation of merged homoeologs. To evaluate our strategy, we sequence and assemble the transcriptome of one of the diploid ancestors of pasta wheat, and compare both assemblies with a benchmark set of 13,472 full-length, non-redundant bread wheat cDNAs. Results A total of 489 million 100 bp paired-end reads from tetraploid wheat assemble in 140,118 contigs, including 96% of the benchmark cDNAs. We used a comparative genomics approach to annotate 66,633 open reading frames. The multiple k-mer assembly strategy increases the proportion of cDNAs assembled full-length in a single contig by 22% relative to the best single k-mer size. Homoeologs are separated using a post-assembly pipeline that includes polymorphism identification, phasing of SNPs, read sorting, and re-assembly of phased reads. Using a reference set of genes, we determine that 98.7% of SNPs analyzed are correctly separated by phasing. Conclusions Our study shows that de novo transcriptome assembly of tetraploid wheat benefit from multiple k-mer assembly strategies more than diploid wheat. Our results also demonstrate that phasing approaches originally designed for heterozygous diploid organisms can be used to separate the close homoeologous genomes of tetraploid wheat. The predicted tetraploid wheat proteome and gene models provide a valuable tool for the wheat research community and for those interested in comparative genomic studies. PMID:23800085

  10. Phase separation and coarsening in electrostatically driven granular media.

    SciTech Connect

    Aranson, I. S.; Meerson, B.; Sasorov, P. V.; Vinokur, V. M.; Materials Science Division; Hebrew Univ. of Jerusalem; Inst. of Theoretical and Experimental Physics

    2002-05-20

    A continuum model for the phase separation and coarsening in electrostatically driven granular media is formulated in terms of a Ginzburg-Landau equation subject to conservation of the total number of grains. In the regime of well-developed clusters, the continuum model is used to derive 'sharp-interface' equations that govern the dynamics of the interphase boundary. The model captures the essential physics of this system.

  11. Ligand-Driven Phase Separation in Binary Particle Brush Materials

    NASA Astrophysics Data System (ADS)

    Bockstaller, Michael; Schmitt, Michael; Zhang, Jianan; Yan, Jiajun; Matyjaszewski, Krzysztof

    The tethering of polymer chains to the surface of nanoparticles (to form so-called `particle brush materials') has emerged as an effective means to enable the bottom-up assembly of one-component hybrid materials with controlled microstructure and improved mechanical stability as well as novel optical or acoustic properties. The polymer-like interactions and response of these particle-brush materials suggest intriguing new opportunities to control structure formation in multicomponent particle mixtures. This contribution will demonstrate that polymer-ligand interactions can drive phase separation processes in mixed particle systems that share analogies to those of regular binary polymer blends. The role of particle size, density and degree of polymerization of tethered chains as well as the interaction parameter between the distinct tethered chains on the mechanism and kinetics of phase separation processes in mixed particle brush systems will be discussed. Ligand-driven phase separation will be shown to enable the efficient fabrication of monochromatic domain structured in mixed quantum dot systems that might find application in next generation quantum dot-enabled LEDs. Support by the National Science Foundation (via Grant DMR-1410845) is gratefully acknowledged.

  12. Phase-separation models for swimming enhancement in complex fluids

    NASA Astrophysics Data System (ADS)

    Man, Yi; Lauga, Eric

    2015-08-01

    Swimming cells often have to self-propel through fluids displaying non-Newtonian rheology. While past theoretical work seems to indicate that stresses arising from complex fluids should systematically hinder low-Reynolds number locomotion, experimental observations suggest that locomotion enhancement is possible. In this paper we propose a physical mechanism for locomotion enhancement of microscopic swimmers in a complex fluid. It is based on the fact that microstructured fluids will generically phase-separate near surfaces, leading to the presence of low-viscosity layers, which promote slip and decrease viscous friction near the surface of the swimmer. We use two models to address the consequence of this phase separation: a nonzero apparent slip length for the fluid and then an explicit modeling of the change of viscosity in a thin layer near the swimmer. Considering two canonical setups for low-Reynolds number locomotion, namely the waving locomotion of a two-dimensional sheet and that of a three-dimensional filament, we show that phase-separation systematically increases the locomotion speeds, possibly by orders of magnitude. We close by confronting our predictions with recent experimental results.

  13. Phase-separation models for swimming enhancement in complex fluids.

    PubMed

    Man, Yi; Lauga, Eric

    2015-08-01

    Swimming cells often have to self-propel through fluids displaying non-Newtonian rheology. While past theoretical work seems to indicate that stresses arising from complex fluids should systematically hinder low-Reynolds number locomotion, experimental observations suggest that locomotion enhancement is possible. In this paper we propose a physical mechanism for locomotion enhancement of microscopic swimmers in a complex fluid. It is based on the fact that microstructured fluids will generically phase-separate near surfaces, leading to the presence of low-viscosity layers, which promote slip and decrease viscous friction near the surface of the swimmer. We use two models to address the consequence of this phase separation: a nonzero apparent slip length for the fluid and then an explicit modeling of the change of viscosity in a thin layer near the swimmer. Considering two canonical setups for low-Reynolds number locomotion, namely the waving locomotion of a two-dimensional sheet and that of a three-dimensional filament, we show that phase-separation systematically increases the locomotion speeds, possibly by orders of magnitude. We close by confronting our predictions with recent experimental results. PMID:26382500

  14. Novel Resistive Switching Behavior in Phase Separated Manganites

    NASA Astrophysics Data System (ADS)

    Guo, Hangwen; Ward, T. Zac; Sun, Dali; Snijders, Paul C.; Gai, Zheng; Shen, Jian

    2011-03-01

    Electronic phase separation plays a key role in many novel phenomena in complex materials. Manganites are a prime example of this class of materials and have recently come under increase scrutiny for possible application in resistive random-access memory (RRAM) technology. Here, we will discuss our recent work on spatially confined La5/8-xPrxCa3/8MnO3. We have discovered that it is possible to drive single electronic domain formation/annihilation through electric field pulsing. By measuring the I-V curve, we find such resistive switching is different from normal RRAM mechanisms in manganites and is closely related to the nature of electronic phase separation. These findings open these systems to a new understanding of the nature of electronic phase separation and begin the development of manganites for future applications in RRAM devices. Research sponsored by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy.

  15. Phase separated microstructure and dynamics of polyurethane elastomers under strain

    NASA Astrophysics Data System (ADS)

    Iacob, Ciprian; Padsalgikar, Ajay; Runt, James

    The molecular mobility of polyurethane elastomers is of the utmost importance in establishing physical properties for uses ranging from automotive tires and shoe soles to more sophisticated aerospace and biomedical applications. In many of these applications, chain dynamics as well as mechanical properties under external stresses/strains are critical for determining ultimate performance. In order to develop a more complete understanding of their mechanical response, we explored the effect of uniaxial strain on the phase separated microstructure and molecular dynamics of the elastomers. We utilize X-ray scattering to investigate soft segment and hard domain orientation, and broadband dielectric spectroscopy for interrogation of the dynamics. Uniaxial deformation is found to significantly perturb the phase-separated microstructure and chain orientation, and results in a considerable slowing down of the dynamics of the elastomers. Attenuated total reflectance Fourier transform infrared spectroscopy measurements of the polyurethanes under uniaxial deformation are also employed and the results are quantitatively correlated with mechanical tensile tests and the degree of phase separation from small-angle X-ray scattering measurements.

  16. Anisotropic phase separation in amorphous Fe--Ge alloys

    SciTech Connect

    Regan, M.J.; Bienenstock, A.

    1993-04-01

    Magnetron sputtered amorphous Fe{sub x}Ge{sub 100-x} films have been examined with anomalous small-angle x-ray scattering (ASAXS) in an attempt to characterize composition fluctuations which have been previously reported in this system. Films grown under various deposition conditions have been studied, with the scattering vector both in and oblique to the plane of the films, to search for anisotropy. By manipulating the deposited power flux and rates of growth, films which have the same composition can be grown to different states of phase separation. The total correlation functions have been calculated from the oblique scattering experiments. The anisotropy can be successfully modeled as a close-packing of oriented prolate ellipsoidal particles, with the elongated axis along the direction of film growth. A method for using these measurements to determine the compositions of the phase-separating species has been developed and utilized. The results indicate phase separation into a-Ge and a-FeGe{sub 2} for the a-Fe{sub x}Ge{sub 100-x} (x<33) alloy.

  17. Anisotropic phase separation in amorphous Fe--Ge alloys

    SciTech Connect

    Regan, M.J.; Bienenstock, A.

    1993-04-01

    Magnetron sputtered amorphous Fe[sub x]Ge[sub 100-x] films have been examined with anomalous small-angle x-ray scattering (ASAXS) in an attempt to characterize composition fluctuations which have been previously reported in this system. Films grown under various deposition conditions have been studied, with the scattering vector both in and oblique to the plane of the films, to search for anisotropy. By manipulating the deposited power flux and rates of growth, films which have the same composition can be grown to different states of phase separation. The total correlation functions have been calculated from the oblique scattering experiments. The anisotropy can be successfully modeled as a close-packing of oriented prolate ellipsoidal particles, with the elongated axis along the direction of film growth. A method for using these measurements to determine the compositions of the phase-separating species has been developed and utilized. The results indicate phase separation into a-Ge and a-FeGe[sub 2] for the a-Fe[sub x]Ge[sub 100-x] (x<33) alloy.

  18. Source separation and clustering of phase-locked subspaces.

    PubMed

    Almeida, Miguel; Schleimer, Jan-Hendrik; Bioucas-Dias, José Mario; Vigário, Ricardo

    2011-09-01

    It has been proven that there are synchrony (or phase-locking) phenomena present in multiple oscillating systems such as electrical circuits, lasers, chemical reactions, and human neurons. If the measurements of these systems cannot detect the individual oscillators but rather a superposition of them, as in brain electrophysiological signals (electro- and magneoencephalogram), spurious phase locking will be detected. Current source-extraction techniques attempt to undo this superposition by assuming properties on the data, which are not valid when underlying sources are phase-locked. Statistical independence of the sources is one such invalid assumption, as phase-locked sources are dependent. In this paper, we introduce methods for source separation and clustering which make adequate assumptions for data where synchrony is present, and show with simulated data that they perform well even in cases where independent component analysis and other well-known source-separation methods fail. The results in this paper provide a proof of concept that synchrony-based techniques are useful for low-noise applications. PMID:21791409

  19. Uphill diffusion and phase separation in partially miscible multicomponent mixtures

    NASA Astrophysics Data System (ADS)

    He, Ping; Raghavan, Ashwin; Ghoniem, Ahmed

    2015-11-01

    The partially miscible multicomponent mixtures, which are frequently encountered in green chemistry processes, often exhibit complicated behaviors, and are critical to the production rate, energy efficiency, and pollution controls. Recent studies have been mainly focused on phase behaviors. However, the coupled phase equilibrium and transport process, which may be the answer to phase separations observed in experiments, is not well researched. Here, we present a numerical and theoretical study on coupled mixing of heavy oil and supercritical water, and the results of our state-of-art modeling agree with experimental measurements. We find that due to the non-ideal diffusion driving force, (1) strong uphill diffusion of heavy oil fractions occurs, (2) a new heavy oil phase is separated starting from the plait point, and heavy fractions become highly concentrated, and (3) water diffusion initially overshoots in oil, and is expelled lately. Finally, we conclude our analysis applicable to different molecules and conditions. The authors thank Saudi Aramco for supporting this work (contract number 6600023444).

  20. Quadruple-junction lattice coherency and phase separation in a binary-phase system

    NASA Astrophysics Data System (ADS)

    Chung, Sung-Yoon; Choi, Si-Young; Kim, Jin-Gyu; Kim, Young-Min

    2015-09-01

    If each phase has an identical crystal structure and small misfit in the lattice parameters in a binary-phase crystalline system, coherent phase boundaries usually form during separation. Although there have been numerous studies on the effect of coherency elastic energy, no attempt has been made to demonstrate how the phase-separation behaviour varies when multiple interfaces meet at a junction. Here we show that a comprehensively different phase-separation morphology is induced, to release the high coherency strain confined to quadruple junctions. High-temperature in-situ transmission electron microscopy reveals that phase boundaries with a new crystallographic orientation emerge over twinned crystals to provide strain relaxation at quadruple junctions. The high coherency strain and the formation of different phase boundaries can be understood in terms of the force equilibrium between interface tensions at a junction point. Visualizing the quadruple points at atomic resolution, our observations emphasize the impact of multiple junctions on the morphology evolution during phase separation.

  1. Quadruple-junction lattice coherency and phase separation in a binary-phase system

    PubMed Central

    Chung, Sung-Yoon; Choi, Si-Young; Kim, Jin-Gyu; Kim, Young-Min

    2015-01-01

    If each phase has an identical crystal structure and small misfit in the lattice parameters in a binary-phase crystalline system, coherent phase boundaries usually form during separation. Although there have been numerous studies on the effect of coherency elastic energy, no attempt has been made to demonstrate how the phase-separation behaviour varies when multiple interfaces meet at a junction. Here we show that a comprehensively different phase-separation morphology is induced, to release the high coherency strain confined to quadruple junctions. High-temperature in-situ transmission electron microscopy reveals that phase boundaries with a new crystallographic orientation emerge over twinned crystals to provide strain relaxation at quadruple junctions. The high coherency strain and the formation of different phase boundaries can be understood in terms of the force equilibrium between interface tensions at a junction point. Visualizing the quadruple points at atomic resolution, our observations emphasize the impact of multiple junctions on the morphology evolution during phase separation. PMID:26346223

  2. Phase diagram of van der Waals-like phase separation in a driven granular gas.

    PubMed

    Khain, Evgeniy; Meerson, Baruch; Sasorov, Pavel V

    2004-11-01

    Equations of granular hydrostatics are used to compute the phase diagram of the recently discovered van der Waals-like phase separation in a driven granular gas. The model two-dimensional system consists of smooth hard disks in a rectangular box, colliding inelastically with each other and driven by a "thermal" wall at zero gravity. The spinodal line and the critical point of the phase separation are determined. Close to the critical point, the spinodal and binodal (coexistence) lines are determined analytically. Effects of the finite size of the confining box in the direction parallel to the thermal wall are investigated. These include suppression of the phase separation by heat conduction in the lateral direction and a change from supercritical to subcritical bifurcation. PMID:15600606

  3. Separable pairing force for relativistic quasiparticle random-phase approximation

    SciTech Connect

    Tian Yuan; Ma Zhongyu; Ring, Peter

    2009-06-15

    We have introduced a separable pairing force, which was adjusted to reproduce the pairing properties of the Gogny force in nuclear matter. This separable pairing force is able to describe in relativistic Hartree-Bogoliubov (RHB) calculations the pairing properties in the ground state of finite nuclei on almost the same footing as the original Gogny interaction. In this work we investigate excited states using the Relativistic Quasiparticle Random-Phase Approximation (RQRPA) with the same separable pairing force. For consistency the Goldstone modes and the convergence with various cutoff parameters in this version of RQRPA are studied. The first excited 2{sup +} states for the chain of Sn isotopes with Z=50 and the chain of isotones with N=82 isotones are calculated in RQRPA together with the 3{sup -} states of Sn isotopes. By comparing our results with experimental data and with the results of the original Gogny force we find that this simple separable pairing interaction is very successful in depicting the pairing properties of vibrational excitations.

  4. Silk fibroin gelation via non-solvent induced phase separation.

    PubMed

    Kasoju, Naresh; Hawkins, Nicholas; Pop-Georgievski, Ognen; Kubies, Dana; Vollrath, Fritz

    2016-03-01

    Tissue engineering benefits from novel materials with precisely tunable physical, chemical and mechanical properties over a broad range. Here we report a practical approach to prepare Bombyx mori silk fibroin hydrogels using the principle of non-solvent induced phase separation (NIPS). A combination of reconstituted silk fibroin (RSF) and methanol (non-solvent), with a final concentration of 2.5% w/v and 12.5% v/v respectively, maintained at 22 °C temperature turned into a hydrogel within 10 hours. Freeze-drying of this gel gave a foam with a porosity of 88%, a water uptake capacity of 89% and a swelling index of 8.6. The gelation kinetics and the loss tangent of the gels were investigated by rheometry. The changes in the morphology of the porous foams were visualized by SEM. The changes in RSF chemical composition and the relative fraction of its secondary structural elements were analyzed by ATR-FTIR along with Fourier self-deconvolution. And, the changes in the glass transition temperature, specific heat capacity and the relative fraction of crystallinity of RSF were determined by TM-DSC. Data suggested that RSF-water-methanol behaved as a polymer-solvent-non-solvent ternary phase system, wherein the demixing of the water-methanol phases altered the thermodynamic equilibrium of RSF-water phases and resulted in the desolvation and eventual separation of the RSF phase. Systematic analysis revealed that both gelation time and the properties of hydrogels and porous foams could be controlled by the ratios of RSF and non-solvent concentration as well as by the type of non-solvent and incubation temperature. Due to the unique properties we envisage that the herein prepared NIPS induced RSF hydrogels and porous foams can possibly be used for the encapsulation of cells and/or for the controlled release of both hydrophilic and hydrophobic drugs. PMID:26730413

  5. Phase Separation of Model Segmented Poly(Carbonate Urethanes)

    NASA Astrophysics Data System (ADS)

    Hernandez, Rebeca; Hung, Elena; Runt, James

    2006-03-01

    The present paper focuses on the phase separated morphology and segment demixing of model poly(carbonate urethanes) [PCU] with hard segment contents ranging from 30 -- 65% and soft segments composed of 1,6 poly(hexamethylene carbonate) [MW = 1K]. Hard segments were formed from 4,4'-methylenediphenyl diisocyanate and 1,4 butanediol. This family of materials represents a recent approach in the development of polyurethanes with improved long-term biostability, and is under clinical investigation in a number of biomedical devices. Only a single glass transition temperature was observed for each copolymer, increasing in temperature with increasing hard segment content. However, loss spectra from dynamic mechanical analysis showed clear evidence of two mixed phases. The results of small-angle X-ray scattering and tapping mode AFM experiments were consistent with these observations and will be discussed. Finally, these results will be compared with initial findings on phase separation in another family of polyurethane copolymers of current interest as blood-contact materials in biomedical devices having mixed poly(dimethylsiloxane) -- poly(hexamethyleneoxide) soft segments.

  6. The phase reversal phenomenon at flow separation and reattachment

    NASA Technical Reports Server (NTRS)

    Stack, J. Pete; Mangalam, S. M.; Kalburgi, V.

    1988-01-01

    Tests were conducted on two different airfoils, one of them in a low-turbulence tunnel, to detect laminar separation and turbulent reattachment locations. A 'nonintrusive' multielement sensor consisting of a large number of closely spaced individual nickel films was vacuum deposited on a thin substrate and bonded to the airfoil model surface. Each sensor element was a part of an independent constant temperature anemometer system. Time history as well as spectral analysis of signals from surface film gauges were used to determine the surface shear flow characteristics. A major breakthrough was achieved with the discovery of phase reversal in low-frequency dynamic shear stress signals across regions of flow separation and reattachment.

  7. Self-assembly of amorphous biophotonic nanostructures by phase separation

    SciTech Connect

    Dufresne, Eric R.; Noh, Heeso; Saranathan, Vinodkumar; Mochrie, Simon G.J.; Cao, Hui; Prum, Richard O.

    2009-04-23

    Some of the most vivid colors in the animal kingdom are created not by pigments, but by wavelength-selective scattering of light from nanostructures. Here we investigate quasi-ordered nanostructures of avian feather barbs which produce vivid non-iridescent colors. These {beta}-keratin and air nanostructures are found in two basic morphologies: tortuous channels and amorphous packings of spheres. Each class of nanostructure is isotropic and has a pronounced characteristic length scale of variation in composition. These local structural correlations lead to strong backscattering over a narrow range of optical frequencies and little variation with angle of incidence. Such optical properties play important roles in social and sexual communication. To be effective, birds need to precisely control the development of these nanoscale structures, yet little is known about how they grow. We hypothesize that multiple lineages of birds have convergently evolved to exploit phase separation and kinetic arrest to self-assemble spongy color-producing nanostructures in feather barbs. Observed avian nanostructures are strikingly similar to those self-assembled during the phase separation of fluid mixtures; the channel and sphere morphologies are characteristic of phase separation by spinodal decomposition and nucleation and growth, respectively. These unstable structures are locked-in by the kinetic arrest of the {beta}-keratin matrix, likely through the entanglement or cross-linking of supermolecular {beta}-keratin fibers. Using the power of self-assembly, birds can robustly realize a diverse range of nanoscopic morphologies with relatively small physical and chemical changes during feather development.

  8. Phase Separation of Superconducting Phases in the Penson-Kolb-Hubbard Model

    NASA Astrophysics Data System (ADS)

    Jerzy Kapcia, Konrad; Czart, Wojciech Robert; Ptok, Andrzej

    2016-04-01

    In this paper, we determine the phase diagrams (for T = 0 as well as T > 0) of the Penson-Kolb-Hubbard model for two dimensional square lattice within Hartree-Fock mean-field theory focusing on an investigation of superconducting phases and on a possibility of the occurrence of the phase separation. We obtain that the phase separation, which is a state of coexistence of two different superconducting phases (with s- and η-wave symmetries), occurs in definite ranges of the electron concentration. In addition, increasing temperature can change the symmetry of the superconducting order parameter (from η-wave into s-wave). The system considered exhibits also an interesting multicritical behaviour including bicritical points. The relevance of the results to experiments for real materials is also discussed.

  9. 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.

  10. Nanopatterns by phase separation of patterned mixed polymer monolayers

    DOEpatents

    Huber, Dale L; Frischknecht, Amalie

    2014-02-18

    Micron-size and sub-micron-size patterns on a substrate can direct the self-assembly of surface-bonded mixed polymer brushes to create nanoscale patterns in the phase-separated mixed polymer brush. The larger scale features, or patterns, can be defined by a variety of lithographic techniques, as well as other physical and chemical processes including but not limited to etching, grinding, and polishing. The polymer brushes preferably comprise vinyl polymers, such as polystyrene and poly(methyl methacrylate).

  11. Phase/Shape Transitions and the Two Neutron Separation Energies

    SciTech Connect

    Zamfir, N. V.; Anghel, Sabina; Cata-Danil, G.

    2008-11-11

    We investigated the evolution of experimental two-neutron separation energies (S{sub 2n}) along the isotopic chains for the even-even nuclei. In order to enhance the sensitivity of our search, differential variation of the S{sub 2n} has been investigated. The emphasis is on finding nonmonotonic behaviors which can be correlated with phase/shape transition. Correlations of the ground state S{sub 2n} values with the excited states energies R{sub 4/2} ratio are also discussed.

  12. Accelerated sintering in phase-separating nanostructured alloys

    PubMed Central

    Park, Mansoo; Schuh, Christopher A.

    2015-01-01

    Sintering of powders is a common means of producing bulk materials when melt casting is impossible or does not achieve a desired microstructure, and has long been pursued for nanocrystalline materials in particular. Acceleration of sintering is desirable to lower processing temperatures and times, and thus to limit undesirable microstructure evolution. Here we show that markedly enhanced sintering is possible in some nanocrystalline alloys. In a nanostructured W–Cr alloy, sintering sets on at a very low temperature that is commensurate with phase separation to form a Cr-rich phase with a nanoscale arrangement that supports rapid diffusional transport. The method permits bulk full density specimens with nanoscale grains, produced during a sintering cycle involving no applied stress. We further show that such accelerated sintering can be evoked by design in other nanocrystalline alloys, opening the door to a variety of nanostructured bulk materials processed in arbitrary shapes from powder inputs. PMID:25901420

  13. Phase separation as a key to a thermoelectric high efficiency.

    PubMed

    Schwall, Michael; Balke, Benjamin

    2013-02-14

    This work elucidates the possible reasons for the outstanding, but never reproduced thermoelectric properties of the doped Ti(0.5)Zr(0.25)Hf(0.25)NiSn Heusler compounds. The structural investigations done via synchrotron X-ray diffraction measurements and scanning electron microscope measurements, which clearly show that the microstructure consists of three temperature stable C1(b) phases with possible semi-coherent interfaces, are presented. The exceptional thermoelectric properties are due to this intrinsic phase separation. It is possible to reproduce the high Figure of Merit values with ZT = 1.2 at 830 K. Furthermore, the influence of doping different elements on the Sn position in this Heusler material system is investigated. PMID:23247074

  14. Accelerated sintering in phase-separating nanostructured alloys.

    PubMed

    Park, Mansoo; Schuh, Christopher A

    2015-01-01

    Sintering of powders is a common means of producing bulk materials when melt casting is impossible or does not achieve a desired microstructure, and has long been pursued for nanocrystalline materials in particular. Acceleration of sintering is desirable to lower processing temperatures and times, and thus to limit undesirable microstructure evolution. Here we show that markedly enhanced sintering is possible in some nanocrystalline alloys. In a nanostructured W-Cr alloy, sintering sets on at a very low temperature that is commensurate with phase separation to form a Cr-rich phase with a nanoscale arrangement that supports rapid diffusional transport. The method permits bulk full density specimens with nanoscale grains, produced during a sintering cycle involving no applied stress. We further show that such accelerated sintering can be evoked by design in other nanocrystalline alloys, opening the door to a variety of nanostructured bulk materials processed in arbitrary shapes from powder inputs. PMID:25901420

  15. 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.

  16. 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

  17. Studies on Phase Separation in a-PMMA/PEG Gels

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoliang

    2005-03-01

    Stereo-irregular atactic poly(methyl methacrylate) (a-PMMA) is known incapable of forming gels in common solvents, irrespective of the solvent quality. However, we recently found a rigid opaque thermal-reversible a-PMMA gel in the solvent of the polyethyl glycol oligomer (PEG) (the PEG molecule mass differ from 400 to 4000 were used). FT-IR, dynamic mechanical temperature analysis and Solid state NMR measurements were used to study the gel properties and gelation mechanism. The in situ IR studies in a-PMMA/PEG gel suggested that some a-PMMA segments were in the aggregated state in solution, which became a node in the solution. With decreasing temperature, the fraction of aggregated a-PMMA in solution increases, resulting in the formation of physical network finally. Spin diffusion was used to determine the size (ξ) of domains in the gels. We found that, a-PMMA/PEG4000 was miscible (ξ ˜ 9nm), while a-PMMA/PEG1000 was micro phase separated (ξ ˜ 57nm) and a-PMMA/PEG400 was macro phase separated (ξ > 300nm). The a-PMMA self-aggregation was attributed to the depletion interaction that becomes important in the case of middle-sized solvents.

  18. Phase Separation in Lean-Grade Duplex Stainless Steel 2101

    NASA Astrophysics Data System (ADS)

    Garfinkel, David A.; Poplawsky, Jonathan D.; Guo, Wei; Young, George A.; Tucker, Julie D.

    2015-08-01

    The use of duplex stainless steels (DSS) in nuclear power generation systems is limited by thermal instability that leads to embrittlement in the temperature range of 204°C to 538°C. New lean-grade alloys, such as 2101, offer the potential to mitigate these effects. Thermal embrittlement was quantified through impact toughness and hardness testing on samples of alloy 2101 after aging at 427°C for various durations (1-10,000 h). Additionally, atom probe tomography (APT) was utilized in order to observe the kinetics of α-α' separation and G-phase formation. Mechanical testing and APT data for two other DSS alloys, 2003 and 2205, were used as a reference to 2101. The results show that alloy 2101 exhibits superior performance compared to the standard-grade DSS alloy 2205 but inferior to the lean-grade alloy 2003 in mechanical testing. APT data demonstrate that the degree of α-α' separation found in alloy 2101 closely resembles that of 2205 and greatly exceeds 2003. Additionally, contrary to what was observed in 2003, 2101 demonstrated G-phase like precipitates after long aging times, although precipitates were not as abundant as was observed in 2205.

  19. Phase Separation in Lean Grade Duplex Stainless Steel 2101

    SciTech Connect

    Garfinkel, D.; Poplawsky, Jonathan D.; Guo, Wei; Young, Jr., George A.; Tucker, Julie

    2015-08-19

    The use of duplex stainless steels (DSS) in nuclear power generation systems is limited by thermal instability that leads to embrittlement in the temperature range of 204°C - 538°C. New lean grade alloys, such as 2101, offer the potential to mitigate these effects. Thermal embrittlement was quantified through impact toughness and hardness testing on samples of alloy 2101 after aging at 427°C for various durations (1-10,000 hours). Additionally, atom probe tomography (APT) was utilized in order to observe the kinetics of α-α’ separation and G-phase formation. Mechanical testing and APT data for two other DSS alloys, 2003 and 2205 were used as a reference to 2101. The results show that alloy 2101 exhibits superior performance compared to the standard grade DSS alloy, 2205, but inferior to the lean grade alloy, 2003, in mechanical testing. APT data demonstrates that the degree of α-α’ separation found in alloy 2101 closely resembles that of 2205, and greatly exceeds 2003. Additionally, contrary to what was observed in 2003, 2101 demonstrated G-phase like precipitates after long aging times, though precipitates were not as abundant as was observed in 2205.

  20. Phase Separation in Lean Grade Duplex Stainless Steel 2101

    DOE PAGESBeta

    Garfinkel, D.; Poplawsky, Jonathan D.; Guo, Wei; Young, Jr., George A.; Tucker, Julie

    2015-08-19

    The use of duplex stainless steels (DSS) in nuclear power generation systems is limited by thermal instability that leads to embrittlement in the temperature range of 204°C - 538°C. New lean grade alloys, such as 2101, offer the potential to mitigate these effects. Thermal embrittlement was quantified through impact toughness and hardness testing on samples of alloy 2101 after aging at 427°C for various durations (1-10,000 hours). Additionally, atom probe tomography (APT) was utilized in order to observe the kinetics of α-α’ separation and G-phase formation. Mechanical testing and APT data for two other DSS alloys, 2003 and 2205 weremore » used as a reference to 2101. The results show that alloy 2101 exhibits superior performance compared to the standard grade DSS alloy, 2205, but inferior to the lean grade alloy, 2003, in mechanical testing. APT data demonstrates that the degree of α-α’ separation found in alloy 2101 closely resembles that of 2205, and greatly exceeds 2003. Additionally, contrary to what was observed in 2003, 2101 demonstrated G-phase like precipitates after long aging times, though precipitates were not as abundant as was observed in 2205.« less

  1. The mechanical properties of phase separated protein droplets

    NASA Astrophysics Data System (ADS)

    Jawerth, Louise; Ijavi, Mahdiye; Patel, Avinash; Saha, Shambaditya; Jülicher, Frank; Hyman, Anthony

    In vivo, numerous proteins associate into liquid compartments by de-mixing from the surrounding solution, similar to oil molecules in water. Many of these proteins and their corresponding liquid compartments play a crucial role in important biological processes, for instance germ line specification in C. elegans or in neurodegenerative diseases such as Amyotrophic lateral sclerosis (ALS). However, despite their importance, very little is known about the physical properties of the resulting droplets as well as the physical mechanisms that control their phase separation from solution. To gain a deeper understanding of these aspects, we study a few such proteins in vitro. When these proteins are purified and added to a physiological buffer, they phase separate into droplets ranging in size from a few to tens of microns with liquid-like behavior similar to their physiological counterparts. By attaching small beads to the surface of the droplets, we can deform the droplets by manipulating the beads directly using optical tweezers. By measuring the force required to deform the droplets we determine their surface tension, elasticity and viscosity as well as the frequency response of these properties. We also measure these properties using passive micro-rheology.

  2. Correlated lateral phase separations in stacks of lipid membranes

    SciTech Connect

    Hoshino, Takuma; Komura, Shigeyuki; Andelman, David

    2015-12-28

    Motivated by the experimental study of Tayebi et al. [Nat. Mater. 11, 1074 (2012)] on phase separation of stacked multi-component lipid bilayers, we propose a model composed of stacked two-dimensional Ising spins. We study both its static and dynamical features using Monte Carlo simulations with Kawasaki spin exchange dynamics that conserves the order parameter. We show that at thermodynamical equilibrium, due to strong inter-layer correlations, the system forms a continuous columnar structure for any finite interaction across adjacent layers. Furthermore, the phase separation shows a faster dynamics as the inter-layer interaction is increased. This temporal behavior is mainly due to an effective deeper temperature quench because of the larger value of the critical temperature, T{sub c}, for larger inter-layer interaction. When the temperature ratio, T/T{sub c}, is kept fixed, the temporal growth exponent does not increase and even slightly decreases as a function of the increased inter-layer interaction.

  3. Binary-liquid phase separation of lens protein solutions.

    PubMed Central

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

    1991-01-01

    We have determined the coexistence curves (plots of phase-separation temperature T versus protein concentration C) for aqueous solutions of purified calf lens proteins. The proteins studied, calf gamma IIIa-, gamma IIIb-, and gamma IVa-crystallin, have very similar amino acid sequences and three-dimensional structures. Both ascending and descending limbs of the coexistence curves were measured. We find that the coexistence curves for each of these proteins and for gamma II-crystallin can be fit, near the critical point, to the function /(Cc-C)/Cc/ = A [(Tc - T)/Tc]beta, where beta = 0.325, Cc is the critical protein concentration in mg/ml, Tc is the critical temperature for phase separation in K, and A is a parameter that characterizes the width of the coexistence curve. We find that A and Cc are approximately the same for all four coexistence curves (A = 2.6 +/- 0.1, Cc = 289 +/- 20 mg/ml), but that Tc is not the same. For gamma II- and gamma IIIb-crystallin, Tc approximately 5 degrees C, whereas for gamma IIIa- and gamma IVa-crystallin, Tc approximately 38 degrees C. By comparing the published protein sequences for calf, rat, and human gamma-crystallins, we postulate that a few key amino acid residues account for the division of gamma-crystallins into low-Tc and high-Tc groups. Images PMID:2062844

  4. Quantitative analysis of aqueous phase composition of model dentin adhesives experiencing phase separation

    PubMed Central

    Ye, Qiang; Park, Jonggu; Parthasarathy, Ranganathan; Pamatmat, Francis; Misra, Anil; Laurence, Jennifer S.; Marangos, Orestes; Spencer, Paulette

    2013-01-01

    There have been reports of the sensitivity of our current dentin adhesives to excess moisture, for example, water-blisters in adhesives placed on over-wet surfaces, and phase separation with concomitant limited infiltration of the critical dimethacrylate component into the demineralized dentin matrix. To determine quantitatively the hydrophobic/hydrophilic components in the aqueous phase when exposed to over-wet environments, model adhesives were mixed with 16, 33, and 50 wt % water to yield well-separated phases. Based upon high-performance liquid chromatography coupled with photodiode array detection, it was found that the amounts of hydrophobic BisGMA and hydrophobic initiators are less than 0.1 wt % in the aqueous phase. The amount of these compounds decreased with an increase in the initial water content. The major components of the aqueous phase were hydroxyethyl methacrylate (HEMA) and water, and the HEMA content ranged from 18.3 to 14.7 wt %. Different BisGMA homologues and the relative content of these homologues in the aqueous phase have been identified; however, the amount of crosslinkable BisGMA was minimal and, thus, could not help in the formation of a crosslinked polymer network in the aqueous phase. Without the protection afforded by a strong crosslinked network, the poorly photoreactive compounds of this aqueous phase could be leached easily. These results suggest that adhesive formulations should be designed to include hydrophilic multimethacrylate monomers and water compatible initiators. PMID:22331596

  5. Dual Phase Membrane for High Temperature CO2 Separation

    SciTech Connect

    Jerry Lin

    2007-06-30

    This project aimed at synthesis of a new inorganic dual-phase carbonate membrane for high temperature CO{sub 2} separation. Metal-carbonate dual-phase membranes were prepared by the direct infiltration method and the synthesis conditions were optimized. Permeation tests for CO{sub 2} and N{sub 2} from 450-750 C showed very low permeances of those two gases through the dual-phase membrane, which was expected due to the lack of ionization of those two particular gases. Permeance of the CO{sub 2} and O{sub 2} mixture was much higher, indicating that the gases do form an ionic species, CO{sub 3}{sup 2-}, enhancing transport through the membrane. However, at temperatures in excess of 650 C, the permeance of CO{sub 3}{sup 2-} decreased rapidly, while predictions showed that permeance should have continued to increase with temperature. XRD data obtained from used membrane indicated that lithium iron oxides formed on the support surface. This lithium iron oxide layer has a very low conductivity, which drastically reduces the flow of electrons to the CO{sub 2}/O{sub 2} gas mixture; thus limiting the formation of the ionic species required for transport through the membrane. These results indicated that the use of stainless steel supports in a high temperature oxidative environment can lead to decreased performance of the membranes. This revelation created the need for an oxidation resistant support, which could be gained by the use of a ceramic-type membrane. Work was extended to synthesize a new inorganic dual-phase carbonate membrane for high temperature CO{sub 2} separation. Helium permeance of the support before and after infiltration of molten carbonate are on the order of 10{sup -6} and 10{sup -10} moles/m{sup 2} {center_dot} Pa {center_dot} s respectively, indicating that the molten carbonate is able to sufficiently infiltrate the membrane. It was found that La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (LSCF) was a suitable candidate for the support

  6. Phase Separation from Electron Confinement at Oxide Interfaces.

    PubMed

    Scopigno, N; Bucheli, D; Caprara, S; Biscaras, J; Bergeal, N; Lesueur, J; Grilli, M

    2016-01-15

    Oxide heterostructures are of great interest for both fundamental and applicative reasons. In particular, the two-dimensional electron gas at the LaAlO_{3}/SrTiO_{3} or LaTiO_{3}/SrTiO_{3} interfaces displays many different properties and functionalities. However, there are clear experimental indications that the interface electronic state is strongly inhomogeneous and therefore it is crucial to investigate possible intrinsic mechanisms underlying this inhomogeneity. Here, the electrostatic potential confining the electron gas at the interface is calculated self-consistently, finding that such confinement may induce phase separation, to avoid a thermodynamically unstable state with a negative compressibility. This provides a robust mechanism for the inhomogeneous character of these interfaces. PMID:26824560

  7. Ostwald-Driven Phase Separation in Bimetallic Nanoparticle Assemblies.

    PubMed

    Prévot, Geoffroy; Nguyen, Nhat Tai; Alloyeau, Damien; Ricolleau, Christian; Nelayah, Jaysen

    2016-04-26

    The compositional stability of bimetallic nanoparticles (NPs) is crucial for many applications. We have studied the coarsening of amorphous carbon-supported Au-Pd NPs during annealing at 873 K. Using scanning transmission electron microscopy and energy-dispersive spectroscopy measurements, we show that, despite a complete miscibility of the two metals, the particle assembly undergoes a phase separation during annealing, which leads to two distinct populations: Au-rich NPs with a mean radius of 3.5 nm and large Pd-rich NPs with a mean radius of 25 nm. Thermodynamic calculations and kinetic Monte Carlo simulations explain this behavior that is driven by the competition between surface and mixing energy and by the different mobilities of the two atomic species. PMID:26989906

  8. The evolutionary significance of phase-separated microsystems

    NASA Technical Reports Server (NTRS)

    Fox, S. W.

    1976-01-01

    The source, preparation, and properties of phase-separated systems such as lipid layers, coacervate droplets, sulphobes, and proteinoid microspheres are reviewed. These microsystems are of interest as partial models for the cell and as partial or total models for the protocell. Conceptual benefits from the study of such models include clues to experiments on origins, insights into principles of action, and, in some instances, presumable models of the origin of the protocell. The benefits to evolution of organized chemical units are many, and can in part be analyzed. Ease of formation suggests that such units would have arisen early in primordial organic evolution. Integration of these various concepts and the results of consequent experiments have contributed to the developing theory of the origins of primordial and contemporary life.

  9. Phase separated membrane bioreactor - Results from model system studies

    NASA Technical Reports Server (NTRS)

    Petersen, G. R.; Seshan, P. K.; Dunlop, E. H.

    1989-01-01

    The operation and evaluation of a bioreactor designed for high intensity oxygen transfer in a microgravity environment is described. The reactor itself consists of a zero headspace liquid phase separated from the air supply by a long length of silicone rubber tubing through which the oxygen diffuses in and the carbon dioxide diffuses out. Mass transfer studies show that the oxygen is film diffusion controlled both externally and internally to the tubing and not by diffusion across the tube walls. Methods of upgrading the design to eliminate these resistances are proposed. Cell growth was obtained in the fermenter using Saccharomyces cerevisiae showing that this concept is capable of sustaining cell growth in the terrestrial simulation.

  10. Model system studies with a phase separated membrane bioreactor

    NASA Technical Reports Server (NTRS)

    Petersen, G. R.; Seshan, P. K.; Dunlop, Eric H.

    1989-01-01

    The operation and evaluation of a bioreactor designed for high intensity oxygen transfer in a microgravity environment is described. The reactor itself consists of a zero headspace liquid phase separated from the air supply by a long length of silicone rubber tubing through which the oxygen diffuses in and the carbon dioxide diffuses out. Mass transfer studies show that the oxygen is film diffusion controlled both externally and internally to the tubing and not by diffusion across the tube walls. Methods of upgrading the design to eliminate these resistances are proposed. Cell growth was obtained in the fermenter using Saccharomyces cerevisiae showing that this concept is capable of sustaining cell growth in the terrestial simulation.

  11. Micro-phase Separation via Spinodal-like Decomposition in Hexamethylynediisocyanate (HDI)-polyurea

    SciTech Connect

    Kulkarni, Amit S.; Beaucage, Gregory; Wilkes, Garth L.; Das, Sudipto; Yilgor, Iskander

    2012-04-03

    We found that micro-phase separation in hexamethylynediisocyanate-polyurea was studied using small-angle X-ray scattering and infrared absorption. Moreover, it was found that phase separation in this system followed spinodal-like decomposition on a 3–4 nm size scale with phase separation occuring on a time scale of days.

  12. Structural and thermotropic properties of synthetic C16:0 (palmitoyl) ceramide: effect of hydration.

    PubMed

    Shah, J; Atienza, J M; Duclos, R I; Rawlings, A V; Dong, Z; Shipley, G G

    1995-09-01

    Differential scanning calorimetry (DSC) and X-ray diffraction techniques have been used to investigate the structure and thermotropic properties of synthetic, non-hydroxy fatty acid (16:0) ceramide (NFA(C16)CER) as a function of hydration. Anhydrous NFA(C16)CER shows a single, broad endothermic transition at 95.4 degrees C (delta H = 10.4 kcal/mol). On hydration, a broad exothermic transition appears at approximately 50-70 degrees C while the main endothermic transition decreases to 90.0 degrees C (delta H = 13.8 kcal/mol). The enthalpy of the exothermic transition increases with hydration to a maximum value, delta H = 4.8 kcal/mol. This polymorphic phase behavior depends on the low temperature incubation time and prior cooling rate. X-ray diffraction of fully hydrated NFA(C16)CER at 26 degrees C, shows a well-ordered lamellar phase with a bilayer periodicity d = 46.9 A. At 68 degrees C, above the first exothermic transition, X-ray diffraction shows again a lamellar phase with reduced bilayer periodicity d = 41.8 A and an increased number of both lamellar and wide-angle reflections indicative of enhanced layer and chain packing order, respectively. At 90.0 degrees C, above the main transition, the diffraction pattern shows a broad, intense reflection at 29.9 A and a diffuse reflection at 4.6 A, indicative of a melted chain phase. On cooling, NFA(C16)CER exhibits polymorphic phase behavior involving the conversion of the melted chain phase to a metastable bilayer phase. On heating, this metastable phase undergoes an exothermic transition to a stable bilayer phase; on further heating, NFA(C16)CER converts endothermically to the melted-chain phase.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8558082

  13. Evolution of a phase separated gravity independent bioreactor

    NASA Technical Reports Server (NTRS)

    Villeneuve, Peter E.; Dunlop, Eric H.

    1992-01-01

    The evolution of a phase-separated gravity-independent bioreactor is described. The initial prototype, a zero head-space manifold silicone membrane based reactor, maintained large diffusional resistances. Obtaining oxygen transfer rates needed to support carbon-recycling aerobic microbes is impossible if large resistances are maintained. Next generation designs (Mark I and II) mimic heat exchanger design to promote turbulence at the tubing-liquid interface, thereby reducing liquid and gas side diffusional resistances. While oxygen transfer rates increased by a factor of ten, liquid channeling prevented further increases. To overcome these problems, a Mark III reactor was developed which maintains inverted phases, i.e., media flows inside the silicone tubing, oxygen gas is applied external to the tubing. This enhances design through changes in gas side driving force concentration and liquid side turbulence levels. Combining an applied external pressure of 4 atm with increased Reynolds numbers resulted in oxygen transfer intensities of 232 mmol O2/l per hr (1000 times greater than the first prototype and comparable to a conventional fermenter). A 1.0 liter Mark III reactor can potentially deliver oxygen supplies necessary to support cell cultures needed to recycle a 10-astronaut carbon load continuously.

  14. DUAL PHASE MEMBRANE FOR HIGH TEMPERATURE CO2 SEPARATION

    SciTech Connect

    Jerry Y.S. Lin; Seungjoon Chung; Matthew Anderson

    2005-12-01

    This project is intended to expand upon the previous year's research en route to the development of a sustainable dual phase membrane for CO{sub 2} separation. It was found that the pores within the supports had to be less than 9 {micro}m in order to maintain the stability of the dual phase membrane. Pores larger than 9 {micro}m would be unable to hold the molten carbonate phase in place, rendering the membrane ineffective. Calculations show that 80% of the pore volume of the 0.5 media grade metal support was filled with the molten carbonate. Information obtained from EDS and SEM confirmed that the molten carbonate completely infiltrated the pores on both the contact and non-contact size of the metal support. Permeation tests for CO{sub 2} and N{sub 2} at 450-750 C show very low permeance of those two gases through the dual phase membrane, which was expected due to the lack of ionization of those two gases. Permeance of the CO{sub 2} and O{sub 2} mixture was much higher, indicating that the gases do form an ionic species, CO{sub 3}{sup 2-}, enhancing transport through the membrane. However, at temperatures in excess of 650 C, the permeance of CO{sub 3}{sup 2-} decreased quite rapidly, while predictions showed that permeance should have continued to increase. XRD data obtained form the surface of the membrane indicated the formation of lithium iron oxides on the support. This layer has a very low conductivity, which drastically reduces the flow of electrons to the CO{sub 2}/O{sub 2} gas mixture, limiting the formation of the ionic species. These results indicate that the use of stainless steel supports in a high temperature oxidative environment can lead to decreased performance of the membranes. This revelation has created the need for an oxidation resistant support, which can be gained by the use of a ceramic-type membrane. Future research efforts will be directed towards preparation of a new ceramic-carbonate dual phase membrane. The membrane will based on an

  15. 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

  16. Influence of Simple Electrolytes on the Orientational Ordering of Thermotropic Liquid Crystals at Aqueous Interfaces

    PubMed Central

    Carlton, Rebecca J.; Gupta, Jugal K.; Swift, Candice L.; Abbott, Nicholas L.

    2011-01-01

    We report orientational anchoring transitions at aqueous interfaces of a water-immiscible, thermotropic liquid crystal (LC; nematic phase of 4′-pentyl-4-cyanobiphenyl) that are induced by changes in pH of the aqueous solution and the addition of simple electrolytes (NaCl) to the aqueous phase. Whereas measurements of the zeta potential on the aqueous side of the interface of LC-in-water emulsions prepared with 5CB confirm pH-dependent formation of an electrical double layer extending into the aqueous phase, quantification of the orientational ordering of the LC leads to the proposition that an electrical double layer is also formed on the LC-side of the interface with an internal electric field that drives the LC anchoring transition. Further support for this conclusion is obtained from measurements of the dependence of LC ordering on pH and ionic strength, as well as a simple model based on the Poisson-Boltzmann equation from which we calculate the contribution of an electrical double layer to the orientational anchoring energy of the LC. Overall, the results presented herein provide new fundamental insights into ionic phenomena at LC-aqueous interfaces, and expand the range of solutes known to cause orientational anchoring transitions at LC-aqueous interfaces beyond previously examined amphiphilic adsorbates. PMID:22106820

  17. Research on the two-phase flow and separation mechanism in the oil-gas cyclone separator

    NASA Astrophysics Data System (ADS)

    Wang, L. Z.; Gao, X.; Feng, J. M.; Peng, X. Y.

    2015-08-01

    The cyclone separator has attracted increasing attention due to its small size, rapid construction and high separation efficiency. This study investigated its gas-liquid two-phase flow and separation characteristics experimentally and numerically. A numerical model of two- phase flow in the cyclone separator was proposed using the Euler-Lagrange method. The distribution of pressure, tangential and axial velocity in the gas-phase flow field was obtained, and the oil droplet movement was traced. Separation efficiency was also studied experimentally, and the diameter distributions of oil droplets at the inlet and the outlet of the separator were measured by a Malvern laser particle size analyser to verify the simulation model. Based on high-speed photography technology, the oil film distribution and flow pattern on the wall of the cyclone separator were visualised. The variation of oil-gas two-phase flow in the cyclone separator was compared under various inlet flow rates. Based on the results, an improved structure was proposed, and the performance of the improved separator was investigated experimentally.

  18. Dual Phase Membrane for High Temperature CO2 Separation

    SciTech Connect

    Jerry Y.S. Lin; Matthew Anderson

    2006-09-29

    Dual-phase membranes consisting of stainless steel supports infiltrated with molten carbonate have been shown to be selective to CO{sub 2} at high temperatures (400-650 C). However, over time at high temperatures, the formation of iron oxides on the surface of the stainless steel supports render the membranes ineffective. This report details synthesis and characteristics of dual-phase carbonate membrane with an oxidation resistant perovskite type ceramic (lanthanum-strontium-cobaltite-iron; LSCF) support. Porous LSCF supports were prepared from its powder synthesized by the citrate method. Both steady state permeation and mercury porosimetry confirmed that the LSCF membrane sintered at 900 C has pores large enough to absorb molten carbonate, yet small enough to retain the molten carbonate under high pressure conditions. Results of XRD analysis have shown that LSCF and the molten carbonate mixture do not react with each other at temperatures below 700 C. Four-point method conductivity tests indicate that the support material has sufficiently high electronic conductivity for this application. Li-Na-K carbonate was coated to the porous LSCF support by a liquid infiltration method. Helium permeance of the support before and after infiltration of molten carbonate are on the order of 10{sup -6} and 10{sup -10} moles/m{sup 2} {center_dot} Pa {center_dot} s respectively, indicating that the molten carbonate is able to sufficiently infiltrate the membrane. Preliminary high temperature permeation experiments indicate that the membrane does separate CO{sub 2} in the presence of O{sub 2}, with a maximum flux of 0.623 ml/cm{sup 2} {center_dot} min obtained at 850 C.

  19. Nanoparticle-Mediated, Light-Induced Phase Separations.

    PubMed

    Neumann, Oara; Neumann, Albert D; Silva, Edgar; Ayala-Orozco, Ciceron; Tian, Shu; Nordlander, Peter; Halas, Naomi J

    2015-12-01

    Nanoparticles that both absorb and scatter light, when dispersed in a liquid, absorb optical energy and heat a reduced fluid volume due to the combination of multiple scattering and optical absorption. This can induce a localized liquid-vapor phase change within the reduced volume without the requirement of heating the entire fluid. For binary liquid mixtures, this process results in vaporization of the more volatile component of the mixture. When subsequently condensed, these two steps of vaporization and condensation constitute a distillation process mediated by nanoparticles and driven by optical illumination. Because it does not require the heating of a large volume of fluid, this process requires substantially less energy than traditional distillation using thermal sources. We investigated nanoparticle-mediated, light-induced distillation of ethanol-H2O and 1-propanol-H2O mixtures, using Au-SiO2 nanoshells as the absorber-scatterer nanoparticle and nanoparticle-resonant laser irradiation to drive the process. For ethanol-H2O mixtures, the mole fraction of ethanol obtained in the light-induced process is substantially higher than that obtained by conventional thermal distillation, essentially removing the ethanol-H2O azeotrope that limits conventional distillation. In contrast, for 1-propanol-H2O mixtures the distillate properties resulting from light-induced distillation were very similar to those obtained by thermal distillation. In the 1-propanol-H2O system, a nanoparticle-mediated, light-induced liquid-liquid phase separation was also observed. PMID:26535465

  20. 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

  1. Phase separation in antisymmetric films: A molecular dynamics study

    SciTech Connect

    Krishnan, Raishma; Puri, Sanjay; Jaiswal, Prabhat K.

    2013-11-07

    We have used molecular dynamics (MD) simulations to study phase-separation kinetics in a binary fluid mixture (AB) confined in an antisymmetric thin film. One surface of the film (located at z = 0) attracts the A-atoms, and the other surface (located at z = D) attracts the B-atoms. We study the kinetic processes which lead to the formation of equilibrium morphologies subsequent to a deep quench below the miscibility gap. In the initial stages, one observes the formation of a layered structure, consisting of an A-rich layer followed by a B-rich layer at z = 0; and an analogous structure at z = D. This multi-layered morphology is time-dependent and propagates into the bulk, though it may break up into a laterally inhomogeneous structure at a later stage. We characterize the evolution morphologies via laterally averaged order parameter profiles; the growth laws for wetting-layer kinetics and layer-wise length scales; and the scaling properties of layer-wise correlation functions.

  2. Dual Phase Membrane for High temperature CO2 Separation

    SciTech Connect

    Jerry Y.S. Lin; Matthew Anderson

    2005-12-01

    Research in the previous years in this project found that stainless steel supports are oxidized during high temperature, dual phase membrane separation of carbon dioxide (with oxygen). Consequently, a new material has been sought to alleviate the problems with oxidation. Lanthanum cobaltite oxide is a suitable candidate for the support material in the dual phase membrane due to its oxidation resistance and electronic conductivity. Porous lanthanum cobaltite membranes were prepared via the citrate method, using nitrate metal precursors as the source of La, Sr, Co and Fe. The material was prepared and ground into a powder, which was subsequently pressed into disks for sintering at 900 C. Conductivity measurements were evaluated using the four-probe DC method. Support pore size was determined by helium permeation. Conductivity of the lanthanum cobaltite material was found to be at a maximum of 0.1856 S/cm at 550 C. The helium permeance of the lanthanum cobaltite membranes for this research was on the order of 10{sup -6} moles/m{sup 2} {center_dot} Pa {center_dot} s, proving that the membranes are porous after sintering at 900 C. The average pore size based on steady state helium permeance measurements was found to be between 0.37 and 0.57 {micro}m. The lanthanum cobaltite membranes have shown to have desired porosity, pore size and electric conductivity as the support for the dual-phase membranes. Molten carbonate was infiltrated to the pores of lanthanum cobaltite membranes support. After infiltration with molten carbonate, the helium permeance of the membranes decreased by three orders of magnitude to 10{sup -9} moles/m{sup 2} {center_dot} Pa {center_dot} s. This number, however, is one order of magnitude larger than the room temperate permeance of the stainless steel supports after infiltration with molten carbonate. Optimization of the dip coating process with molten carbonate will be evaluated to determine if lower permeance values can be obtained with the

  3. Effect of OH content on phase separation behavior of soda-silica glasses

    NASA Technical Reports Server (NTRS)

    Neilson, G. F.; Weinberg, M. C.; Smith, G. L.

    1986-01-01

    The kinetics of phase separation in a gel and ordinary soda-silica glass are followed by use of small angle X-ray scattering. Also, the influence of OH on the phase separation behavior is studied. It is found that OH accelerates the growth of the secondary phase, and that gel and ordinary glasses of similar composition and OH concentration exhibit similar phase separation characteristics.

  4. Solidification Behavior of Polymer Solution during Membrane Preparation by Thermally Induced Phase Separation

    PubMed Central

    Ishigami, Toru; Nii, Yoko; Ohmukai, Yoshikage; Rajabzadeh, Saeid; Matsuyama, Hideto

    2014-01-01

    The solidification behavior of poly(vinylidene fluoride) (PVDF) solution during membrane preparation by thermally induced phase separation (TIPS) was investigated. Apparatus newly developed in our laboratory was used to quantitatively measure membrane stiffness during phase separation. In this apparatus, a cooling polymer solution, placed on a stage, is moved upwards and the surface of the polymer solution contacts a sphere attached to the tip of a needle. The displacement of a blade spring attached to the needle is then measured by a laser displacement sensor. Different phase separation modes, such as liquid-liquid (L-L) phase separation and solid-liquid (S-L) phase separation (polymer crystallization) were investigated. In the case of S-L phase separation, the stiffness of the solution surface began to increase significantly just before termination of crystallization. In contrast, L-L phase separation delayed solidification of the solution. This was because mutual contact of the spherulites was obstructed by droplets of polymer-lean phase formed during L-L phase separation. Thus, the solidification rate was slower for the L-L phase separation system than for the S-L phase separation system. PMID:24957124

  5. Dissipative particle dynamics simulation study on the binary mixture phase separation coupled with polymerization.

    PubMed

    Liu, Hong; Qian, Hu-Jun; Zhao, Ying; Lu, Zhong-Yuan

    2007-10-14

    The influence of polymerization on the phase separation of binary immiscible mixtures has been investigated by the dissipative particle dynamics simulations in two dimensions. During polymerization, the bulk viscosity increases, which consequently slows down the spinodal decomposition process. The domain size growth is monitored in the simulations. The absence of 23 exponent for inertial hydrodynamic mechanism clearly reflects the suppressing effect of polymerization on the phase separation. Due to the increasing viscosity, the individual phase may be trapped in a metastable stage instead of the lamellar morphology identified for symmetric mixtures. Moreover, the polymerization induced phase separation in the binary miscible mixture has been studied. The domain growth is strongly dependent on the polymerization probability, which is naturally related to the activation energy for polymerization. The observed complex phase separation behavior is attributed to the interplay between the increasing thermodynamic driving force for phase separation and the increasing viscosity that suppresses phase separation as the polymerization proceeds. PMID:17935435

  6. Selective Metal Deposition on a Phase-Separated Polymer Blend Surface

    NASA Astrophysics Data System (ADS)

    Tsujioka, Tsuyoshi; Yamaguchi, Koji

    2013-07-01

    We report selective metal deposition on a phase-separated polymer blend surface. A polymer blend film consisting of polystyrene (PS) and a polystyrene-block-polybutadiene copolymer (PS-BR) was annealed, and a micro-phase-separated film was obtained. Pb was evaporated onto the phase-separated surface without an evaporation mask and was selectively deposited on the PS phase but not on the PS-BR phase. We achieved fine metal patterns corresponding to the microphase separation. This result suggests a novel method of preparing fine metal patterns for electronics and photonics.

  7. Carbon Dioxide Separation from Flue Gas by Phase Enhanced Absorption

    SciTech Connect

    Tim Fout

    2007-06-30

    A new process, phase enhanced absorption, was invented. The method is carried out in an absorber, where a liquid carrier (aqueous solution), an organic mixture (or organic compound), and a gas mixture containing a gas to be absorbed are introduced from an inlet. Since the organic mixture is immiscible or at least partially immiscible with the liquid carrier, the organic mixture forms a layer or small parcels between the liquid carrier and the gas mixture. The organic mixture in the absorber improves mass transfer efficiency of the system and increases the absorption rate of the gas. The organic mixture serves as a transportation media. The gas is finally accumulated in the liquid carrier as in a conventional gas-liquid absorption system. The presence of the organic layer does not hinder the regeneration of the liquid carrier or recovery of the gas because the organic layer is removed by a settler after the absorption process is completed. In another aspect, the system exhibited increased gas-liquid separation efficiency, thereby reducing the costs of operation and maintenance. Our study focused on the search of the organic layer or transportation layer to enhance the absorption rate of carbon dioxide. The following systems were studied, (1) CO{sub 2}-water system and CO{sub 2}-water-organic layer system; (2) CO{sub 2}-Potassium Carbonate aqueous solution system and CO{sub 2}-Potassium Carbonate aqueous solution-organic layer system. CO{sub 2}-water and CO{sub 2}-Potassium Carbonate systems are the traditional gas-liquid absorption processes. The CO{sub 2}-water-organic layer and CO{sub 2}-Potassium Carbonate-organic layer systems are the novel absorption processes, phase enhanced absorption. As we mentioned early, organic layer is used for the increase of absorption rate, and plays the role of transportation of CO{sub 2}. Our study showed that the absorption rate can be increased by adding the organic layer. However, the enhanced factor is highly depended on the

  8. Fluid Phase Separation (FPS) experiment for flight on a space shuttle Get Away Special (GAS) canister

    NASA Technical Reports Server (NTRS)

    Peters, Bruce; Wingo, Dennis; Bower, Mark; Amborski, Robert; Blount, Laura; Daniel, Alan; Hagood, Bob; Handley, James; Hediger, Donald; Jimmerson, Lisa

    1990-01-01

    The separation of fluid phases in microgravity environments is of importance to environmental control and life support systems (ECLSS) and materials processing in space. A successful fluid phase separation experiment will demonstrate a proof of concept for the separation technique and add to the knowledge base of material behavior. The phase separation experiment will contain a premixed fluid which will be exposed to a microgravity environment. After the phase separation of the compound has occurred, small samples of each of the species will be taken for analysis on the Earth. By correlating the time of separation and the temperature history of the fluid, it will be possible to characterize the process. The experiment has been integrated into space available on a manifested Get Away Special (GAS) experiment, CONCAP 2, part of the Consortium for Materials Complex Autonomous Payload (CAP) Program, scheduled for STS-42. The design and the production of a fluid phase separation experiment for rapid implementation at low cost is presented.

  9. Crystalline Phase Separation in Phosphate Containing Waste Glasses: Relevance to INEEL HAW

    SciTech Connect

    Jantzen, C.M.

    2000-09-21

    As part of the Tanks Focus Area's (TFA) effort to increase waste loading for high-level waste vitrification at various facilities in the Department of Energy (DOE) complex, the occurrence of phase separation in waste glasses spanning the Savannah River Site (SRS) and Idaho National Engineering and Environmental Laboratory (INEEL) composition ranges have been studied. The type of phase separation that occurs in the phosphate rich borosilicate waste glasses, such as those investigated for INEEL, crystallizes upon cooling. This type of phase separation mechanism is less well studied than amorphous phase separation in phosphate poor borosilicate waste glasses. Therefore, the type of phase separation, extent, and impact of phase separation on glass durability for a series of INEEL-type glasses were examined and the data statistically analyzed in this study.

  10. A novel route for fabricating metal-polymer composite nanoparticles with phase-separated structures.

    PubMed

    Yabu, Hiroshi; Koike, Kazutaka; Motoyoshi, Kiwamu; Higuchi, Takeshi; Shimomura, Masatsugu

    2010-07-15

    Au nanoparticles (NPs) and polymer composite particles with phase-separation structures were prepared based on phase separation structures. Au NPs were successfully synthesized in amphiphilic block-copolymer micelles, and then composite particles were formed by a simple solvent evaporation process from Au NPs and polymer solution. The phase separated structures (Janus and Core-shell) were controlled by changing the combination of polymers having differing hydrophobicity. PMID:21567522

  11. A novel mechanical model for phase-separation in debris flows

    NASA Astrophysics Data System (ADS)

    Pudasaini, Shiva P.

    2015-04-01

    Understanding the physics of phase-separation between solid and fluid phases as a two-phase mass moves down slope is a long-standing challenge. Here, I propose a fundamentally new mechanism, called 'separation-flux', that leads to strong phase-separation in avalanche and debris flows. This new model extends the general two-phase debris flow model (Pudasaini, 2012) to include a separation-flux mechanism. The new flux separation mechanism is capable of describing and controlling the dynamically evolving phase-separation, segregation, and/or levee formation in a real two-phase, geometrically three-dimensional debris flow motion and deposition. These are often observed phenomena in natural debris flows and industrial processes that involve the transportation of particulate solid-fluid mixture material. The novel separation-flux model includes several dominant physical and mechanical aspects that result in strong phase-separation (segregation). These include pressure gradients, volume fractions of solid and fluid phases and their gradients, shear-rates, flow depth, material friction, viscosity, material densities, boundary structures, gravity and topographic constraints, grain shape, size, etc. Due to the inherent separation mechanism, as the mass moves down slope, more and more solid particles are brought to the front, resulting in a solid-rich and mechanically strong frontal surge head followed by a weak tail largely consisting of the viscous fluid. The primary frontal surge head followed by secondary surge is the consequence of the phase-separation. Such typical and dominant phase-separation phenomena are revealed here for the first time in real two-phase debris flow modeling and simulations. However, these phenomena may depend on the bulk material composition and the applied forces. Reference: Pudasaini, Shiva P. (2012): A general two-phase debris flow model. J. Geophys. Res., 117, F03010, doi: 10.1029/2011JF002186.

  12. On the phase form of a deformation quantization with separation of variables

    NASA Astrophysics Data System (ADS)

    Karabegov, Alexander

    2016-06-01

    Given a star product with separation of variables on a pseudo-Kähler manifold, we obtain a new formal (1, 1)-form from its classifying form and call it the phase form of the star product. The cohomology class of a star product with separation of variables equals the class of its phase form. We show that the phase forms can be arbitrary and they bijectively parametrize the star products with separation of variables. We also describe the action of a change of the formal parameter on a star product with separation of variables, its formal Berezin transform, classifying form, phase form, and canonical trace density.

  13. Structure and thermotropic properties of 1-stearoyl-2-acetyl-phosphatidylcholine bilayer membranes.

    PubMed

    Shah, J; Duclos, R I; Shipley, G G

    1994-05-01

    The structural and thermotropic properties of 1-stearoyl-2-acetyl-phosphatidylcholine (C(18):C(2)-PC) were studied as a function of hydration. A combination of differential scanning calorimetry and x-ray diffraction techniques have been used to investigate the phase behavior of C(18):C(2)-PC. At low hydration (e.g., 20% H2O), the differential scanning calorimetry heating curve shows a single reversible endothermic transition at 44.6 degrees C with transition enthalpy delta H = 6.4 kcal/mol. The x-ray diffraction pattern at -8 degrees C shows a lamellar structure with a small bilayer periodicity d = 46.3 A and two wide angle reflections at 4.3 and 3.95 A, characteristic of a tilted chain, L beta' bilayer gel structure. Above the main transition temperature, a liquid crystalline L alpha phase is observed with d = 53.3 A. Electron density profiles at 20% hydration suggest that C(18):C(2)-PC forms a fully interdigitated bilayer at -8 degrees C and a noninterdigitated, liquid crystalline phase above its transition temperature (T > Tm). Between 30 and 50% hydration, on heating C(18):C(2)-PC converts from a highly ordered, fully interdigitated gel phase (L beta') to a less ordered, interdigitated gel phase (L beta), which on further heating converts to a noninterdigitated liquid crystalline L alpha phase. However, the fully hydrated (> 60% H2O) C(18):C(2)-PC, after incubation at 0 degrees C, displays three endothermic transitions at 8.9 degrees C (transition I, delta H = 1.6 kcal/mol), 18.0 degrees C (transition II), and 20.1 degrees C (transition III, delta HII+III = 4.8 kcal/mol). X-ray diffraction at -8 degrees C again showed a lamellar gel phase (L beta') with a small periodicity d = 52.3 A. At 14 degrees C a less ordered, lamellar gel phase (L beta) is observed with d = 60.5 A. However, above the transition III, a broad, diffuse reflection is observed at approximately 39 A, consistent with the presence of a micellar phase. The following scheme is proposed for

  14. On separability of A-phases during the cyclic alternating pattern.

    PubMed

    Mendez, M O; Alba, A; Chouvarda, I; Milioli, G; Grassi, A; Terzano, M G; Parrino, L

    2014-01-01

    A statistical analysis of the separability of EEG A-phases, with respect to basal activity, is presented in this study. A-phases are short central events that build up the Cyclic Alternating Pattern (CAP) during sleep. The CAP is a brain phenomenon which is thought to be related to the construction, destruction and instability of sleep stages dynamics. From the EEG signals, segments obtained around the onset and offset of the A-phases were used to evaluate the separability between A-phases and basal sleep stage oscillations. In addition, a classifier was trained to separate the different A-phase types (A1, A2 and A3). Temporal, energy and complexity measures were used as descriptors for the classifier. The results show a percentage of separation between onset and preceding basal oscillations higher than 85 % for all A-phases types. For Offset separation from following baseline, the accuracy is higher than 80 % but specificity is around 75%. Concerning to A-phase type separation, A1-phase and A3-phase are well separated with accuracy higher than 80, while A1 and A2-phases show a separation lower than 50%. These results encourage the design of automatic classifiers for Onset detection and for separating among A-phases type A1 and A3. On the other hand, the A-phase Offsets present a smooth transition towards the basal sleep stage oscillations, and A2-phases are very similar to A1-phases, suggesting that a high uncertainty may exist during CAP annotation. PMID:25570436

  15. Comprehensive study on the light shielding potential of thermotropic layers for the development of new materials.

    PubMed

    Gruber, D P; Winkler, G; Resch, K

    2015-01-10

    In recent years thermotropic overheating protection glazings have been the focus for both solar thermal collector technology and architecture. A thermotropic glazing changes its light transmittance from highly transparent to light diffusing upon reaching a certain threshold temperature autonomously and reversibly. In thermotropic systems with fixed domains (TSFD) the scattering domains are embedded in a polymer matrix, which exhibits a sudden change of the refractive index upon reaching a threshold temperature. The aim of the present study was to comprehensively investigate the light shielding characteristics and potential of TSFD materials by applying simulation of light scattering in particle-filled layers. In random walk simulations a variety of parameters were varied systematically, and the effect on the light transmission behavior of TSFD was studied. The calculation steps of the simulation process are shown in detail. The simulations demonstrate that there is great potential for the production of functional materials with high overheating protection efficiency. PMID:25967611

  16. 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.

  17. 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.

  18. Two-phase, passive separator-and-filter assembly

    NASA Technical Reports Server (NTRS)

    Erickson, A. C.; Porter, F. J., Jr.

    1974-01-01

    Assembly separates liquid from gas by passive hydrophilic/hydrophobic material approach. Apparatus is comprised of porous glass hydrophilic tubes. Quantity, lateral size, and pore size of glass tubes are determined by particular design requirements with regard to water rate, water quality contamination level, application endurance life, and operating differential pressure level.

  19. Separations/pretreatment considerations for Hanford privatization phase 2

    SciTech Connect

    Hunt, R.D.; McGinnis, C.P.; Welch, T.D.

    1998-05-01

    The Tank Focus Area is funded to develop, demonstrate, and deploy technologies that will assist in the treatment and closure of its nuclear waste tanks. Pretreatment technologies developed to support the privatization effort by the Department of Energy are reviewed. Advancements in evaporation, solid-liquid separation, sludge treatment, solids controls, sodium management, and radionuclide removal are considered.

  20. Phase separation in lipid bilayers triggered by low pH

    SciTech Connect

    Suresh, Swetha; Edwardson, J. Michael

    2010-09-03

    Research highlights: {yields} Lipid bilayers have been imaged by atomic force microscopy (AFM). {yields} At pH 5 phase separation occurs in lipid bilayers containing mixed acyl chains. {yields} Phase separation does not occur when lipids have only unsaturated chains. {yields} Phase separation might drive protein clustering during endocytosis. -- Abstract: Endocytosis involves the capture of membrane from the cell surface in the form of vesicles, which become rapidly acidified to about pH 5. Here we show using atomic force microscopy (AFM) imaging that this degree of acidification triggers phase separation in lipid bilayers containing mixed acyl chains (e.g. palmitoyl/oleoyl) or complex mixtures (e.g. total brain extract) but not in bilayers containing only lipids with unsaturated chains (e.g. dioleoyl). Since mixed-chain lipids are major constituents of the outer leaflet of the plasma membrane, the type of phase separation reported here might support protein clustering and signaling during endocytosis.

  1. Vertical phase separation in bulk heterojunction solar cells formed by in situ polymerization of fulleride

    PubMed Central

    Zhang, Lipei; Xing, Xing; Zheng, Lingling; Chen, Zhijian; Xiao, Lixin; Qu, Bo; Gong, Qihuang

    2014-01-01

    Vertical phase separation of the donor and the acceptor in organic bulk heterojunction solar cells is crucial to improve the exciton dissociation and charge transport efficiencies. This is because whilst the exciton diffusion length is limited, the organic film must be thick enough to absorb sufficient light. However, it is still a challenge to control the phase separation of a binary blend in a bulk heterojunction device architecture. Here we report the realization of vertical phase separation induced by in situ photo-polymerization of the acrylate-based fulleride. The power conversion efficiency of the devices with vertical phase separation increased by 20%. By optimising the device architecture, the power conversion efficiency of the single junction device reached 8.47%. We believe that in situ photo-polymerization of acrylate-based fulleride is a universal and controllable way to realise vertical phase separation in organic blends. PMID:24861168

  2. Timing of traffic lights and phase separation in two-dimensional traffic flow

    NASA Astrophysics Data System (ADS)

    Sun, Duo; Jiang, Rui; Wang, Bing-Hong

    2010-02-01

    In this paper, we study the effects of traffic light period in two-dimensional Biham-Middleton-Levine (BML) traffic flow model. It is found that a phase separation phenomenon, in which the system separates into coexistence of free flow and jam, could be observed in intermediate vehicle density range when traffic light period T⩾4. We have explained the reason of occurrence of phase separation and investigated its behavior in different traffic light period.

  3. 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.

  4. 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

  5. Self-Organisation, Thermotropic and Lyotropic Properties of Glycolipids Related to their Biological Implications

    PubMed Central

    Garidel, Patrick; Kaconis, Yani; Heinbockel, Lena; Wulf, Matthias; Gerber, Sven; Munk, Ariane; Vill, Volkmar; Brandenburg, Klaus

    2015-01-01

    Glycolipids are amphiphilic molecules which bear an oligo- or polysaccharide as hydrophilic head group and hydrocarbon chains in varying numbers and lengths as hydrophobic part. They play an important role in life science as well as in material science. Their biological and physiological functions are quite diverse, ranging from mediators of cell-cell recognition processes, constituents of membrane domains or as membrane-forming units. Glycolipids form an exceptional class of liquid-crystal mesophases due to the fact that their self-organisation obeys more complex rules as compared to classical monophilic liquid-crystals. Like other amphiphiles, the supra-molecular structures formed by glycolipids are driven by their chemical structure; however, the details of this process are still hardly understood. Based on the synthesis of specific glycolipids with a clearly defined chemical structure, e.g., type and length of the sugar head group, acyl chain linkage, substitution pattern, hydrocarbon chain lengths and saturation, combined with a profound physico-chemical characterisation of the formed mesophases, the principles of the organisation in different aggregate structures of the glycolipids can be obtained. The importance of the observed and formed phases and their properties are discussed with respect to their biological and physiological relevance. The presented data describe briefly the strategies used for the synthesis of the used glycolipids. The main focus, however, lies on the thermotropic as well as lyotropic characterisation of the self-organised structures and formed phases based on physico-chemical and biophysical methods linked to their potential biological implications and relevance. PMID:26464591

  6. A neon-E rich phase in Orgueil - Results obtained on density separates

    NASA Astrophysics Data System (ADS)

    Eberhardt, P.; Jungck, M. H. A.; Meier, F. O.; Niederer, F. R.

    1981-09-01

    A stepwise heating technique was used on eight density separates from the neon-E rich phase G4j of the carbonaceous chondrite Orgueil to measure He, Ne and Ar. The density separation technique was found to further enrich the Ne-E carrier phases, allowing the Ne-E to be identified as virtually pure Ne-22. At least two separable carrier phases exist: (1) the l-carrier phase, which releases its Ne-E at temperatures below 900 C and is heavily enriched in the low-density separate; and (2) the h-carrier phase. The h-carrier is found to be highly retentive, with release temperatures above 900 C, and is associated with higher-density material. It is concluded that Ne-E and its carrier phases are probably of presolar origin.

  7. Technical status report on the prediction of amorphous phase separation in multicomponent borosilicate glasses. Revision 0

    SciTech Connect

    Peeler, D.K.

    1998-12-31

    This status report describes the current status for predicting of amorphous phase separation in multicomponent borosilicate glasses and the two major development criteria (composition and thermal history). The goal of this subtask is to perform targeted research activities to define and, where applicable, extend the boundaries of existing phase stability models that restrict HLW glass waste loading. Specifically, the focus will be on delimiting boundaries for immiscible phase separation. The development of data, understanding, and quantitative description for composition and kinetic effects on the development of amorphous phase separation will continue in FY98. This effort will provide insight into the compositional effects on phase stability and will lead to a better understanding of the methods used to predict the development of amorphous phase separation in HLW glasses.

  8. Registered and Antiregistered Phase Separation of Mixed Amphiphilic Bilayers

    PubMed Central

    Williamson, John J.; Olmsted, Peter D.

    2015-01-01

    We derive a mean-field free energy for the phase behavior of coupled bilayer leaflets, which is implicated in cellular processes and important to the design of artificial membranes. Our model accounts for amphiphile-level structural features, particularly hydrophobic mismatch, which promotes antiregistration, in competition with the direct transmidplane coupling usually studied, which promotes registration. We show that the phase diagram of coupled leaflets allows multiple metastable coexistences, and we illustrate the kinetic implications of this with a detailed study of a bilayer of equimolar overall composition. For approximate parameters estimated to apply to phospholipids, equilibrium coexistence is typically registered, but metastable antiregistered phases can be kinetically favored by hydrophobic mismatch. Thus, a bilayer in the spinodal region can require nucleation to equilibrate, in a novel manifestation of Ostwald’s rule of stages. Our results provide a framework for understanding disparate existing observations in the literature, elucidating a subtle competition of couplings and a key role for phase-transition kinetics in bilayer phase behavior. PMID:25902436

  9. Detection of phase separation in fluid phosphatidylserine/phosphatidylcholine mixtures.

    PubMed

    Hinderliter, A K; Huang, J; Feigenson, G W

    1994-11-01

    The nonideal mixing of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine, (16:0, 18:1)PS, and 1,2-didodecenoyl-sn-glycero-3-phosphocholine, (12:1, 12:1)PC, in fluid lamellar model membranes was studied by measuring binding of aqueous Ca2+ ions and by x-ray diffraction. A region of two-phase coexistence was found by invariance of the aqueous concentration and by the appearance of two sets of lamellar spacings. The phases were identified as fluid from the diffuse x-ray diffraction in the wide-angle region. The width of the two-phase coexistence region was greater at higher ionic strength. In 800 mM KCl, the phase boundaries were at PS mole fraction 0.5 and 0.8. In 100 mM KCl, the phase boundaries were at PS mole fraction 0.52 and 0.62. Monte Carlo simulations of the lateral distributions of these PS/PC mixtures show pronounced clustering of the lipids. PMID:7858127

  10. Demixing kinetics of phase separated polymer solutions in microgravity. [cell separation

    NASA Technical Reports Server (NTRS)

    Brooks, D. E.; Bamberger, S. B.; Harris, J. M.; Vanalstine, J.; Snyder, R. S.

    1987-01-01

    In preparation for performing cell partitioning in space the demixing behavior of aqueous two phase systems containing dextran and poly(ethylene glycol) in microgravity was modeled with an isopycnic system and studied on aircraft flights and on STS 51-D. In all types of experiments demixing occurs, eventually producing one phase localized around the wall of the container with the other internalized within it. The demixing kinetics were analyzed in each case.

  11. Controllable Phase Separation by Boc-Modified Lipophilic Acid as a Multifunctional Extractant.

    PubMed

    Tao, Kai; Adler-Abramovich, Lihi; Gazit, Ehud

    2015-01-01

    While phase separation of immiscible liquid-liquid systems has become increasingly significant in diverse areas, the irreversible nature limits their further application in controllable extraction-concentration or capture-release fields. There is a need for the development of simple, efficient and reversible methods for numerous research and industrial extraction and separation applications. We envisioned Boc-modified lipophilic acids as a simple model for such use based on the studies of the multi-phase transitions of Boc-modified supramolecular polymeric systems. Here, we demonstrate that in the presence of Boc-7-aminoheptanoic acid (Boc-7), phase separation occurs in mixtures of miscible organic solvent and water. The separation behavior was confirmed by differential colorimetric development in aqueous and organic phases using methyl orange staining assays. Component substitution experiments verified that the phase separation results from the subtle balance between the aggregation and the solvation forces of Boc-7, and is reversible by adjusting the solution pH. Owing to the intrinsic hydrophobic properties of the organic phase and the hydrogen bonding-forming ability of the carboxyl group of Boc-7, the phase separation system captures and releases Sudan Red, fluorescein, and streptavidin in a controllable manner. Consequently, a reversible and simple phase separation system can be designed as a multifunctional extractant. PMID:26627307

  12. Controllable Phase Separation by Boc-Modified Lipophilic Acid as a Multifunctional Extractant

    PubMed Central

    Tao, Kai; Adler-Abramovich, Lihi; Gazit, Ehud

    2015-01-01

    While phase separation of immiscible liquid-liquid systems has become increasingly significant in diverse areas, the irreversible nature limits their further application in controllable extraction-concentration or capture-release fields. There is a need for the development of simple, efficient and reversible methods for numerous research and industrial extraction and separation applications. We envisioned Boc-modified lipophilic acids as a simple model for such use based on the studies of the multi-phase transitions of Boc-modified supramolecular polymeric systems. Here, we demonstrate that in the presence of Boc-7-aminoheptanoic acid (Boc-7), phase separation occurs in mixtures of miscible organic solvent and water. The separation behavior was confirmed by differential colorimetric development in aqueous and organic phases using methyl orange staining assays. Component substitution experiments verified that the phase separation results from the subtle balance between the aggregation and the solvation forces of Boc-7, and is reversible by adjusting the solution pH. Owing to the intrinsic hydrophobic properties of the organic phase and the hydrogen bonding-forming ability of the carboxyl group of Boc-7, the phase separation system captures and releases Sudan Red, fluorescein, and streptavidin in a controllable manner. Consequently, a reversible and simple phase separation system can be designed as a multifunctional extractant. PMID:26627307

  13. Controllable Phase Separation by Boc-Modified Lipophilic Acid as a Multifunctional Extractant

    NASA Astrophysics Data System (ADS)

    Tao, Kai; Adler-Abramovich, Lihi; Gazit, Ehud

    2015-12-01

    While phase separation of immiscible liquid-liquid systems has become increasingly significant in diverse areas, the irreversible nature limits their further application in controllable extraction-concentration or capture-release fields. There is a need for the development of simple, efficient and reversible methods for numerous research and industrial extraction and separation applications. We envisioned Boc-modified lipophilic acids as a simple model for such use based on the studies of the multi-phase transitions of Boc-modified supramolecular polymeric systems. Here, we demonstrate that in the presence of Boc-7-aminoheptanoic acid (Boc-7), phase separation occurs in mixtures of miscible organic solvent and water. The separation behavior was confirmed by differential colorimetric development in aqueous and organic phases using methyl orange staining assays. Component substitution experiments verified that the phase separation results from the subtle balance between the aggregation and the solvation forces of Boc-7, and is reversible by adjusting the solution pH. Owing to the intrinsic hydrophobic properties of the organic phase and the hydrogen bonding-forming ability of the carboxyl group of Boc-7, the phase separation system captures and releases Sudan Red, fluorescein, and streptavidin in a controllable manner. Consequently, a reversible and simple phase separation system can be designed as a multifunctional extractant.

  14. Effect of confinement on phase-separation and superfluid transition in ^3 He-^4 He mixtures

    NASA Astrophysics Data System (ADS)

    Shenoy, V. B.; Saam, W. F.

    1996-03-01

    We derive the phase diagram of ^3 He - ^4 He mixtures confined between parallel plates within phenomelogical Landau theory. The analyses focus on the effect of the separation between the plates and the magnitude of surface field ( which is a measure of preference for ^4He rich phase) on phase-separation and superfluid transition in the confined mixtures. Connection to recent experiments on He mixtures in aerogel is made.

  15. Thermoresponsive Toughening with Crack Bifurcation in Phase-Separated Hydrogels under Isochoric Conditions.

    PubMed

    Guo, Hui; Sanson, Nicolas; Hourdet, Dominique; Marcellan, Alba

    2016-07-01

    A novel mode of gel toughening displaying crack bifurcation is highlighted in phase-separated hydrogels. By exploring original covalent network topologies, phase-separated gels under isochoric conditions demonstrate advanced thermoresponsive mechanical properties: excellent fatigue resistance, self-healing, and remarkable fracture energies. Beyond the phase-transition temperature, the fracture proceeds by a systematic crack-bifurcation process, unreported so far in gels. PMID:27159115

  16. Impact of immobilized polysaccharide chiral stationary phases on enantiomeric separations.

    PubMed

    Ali, Imran; Aboul-Enein, Hassan Y

    2006-04-01

    Immobilized polysaccharide-based chiral stationary phases (CSPs) are gaining importance in the resolution of racemic compounds due to their stable nature on working with normal solvents and those prohibited for use with coated phases (tetrahydrofuran, chloroform, dichloromethane, acetone, 1,4-dioxane, ethyl acetate, and certain other ethers). This review discusses the use of immobilized polysaccharide CSPs in the chiral resolution of various racemates by liquid chromatography. The discussion includes immobilization methodologies, enantioselectivities, efficiencies, and a comparison of chiral recognition capabilities of coated vs. immobilized CSPs. Some applications of immobilized CSPs to the chiral resolution of racemic compounds are also presented. PMID:16830488

  17. Phase separation in the t-J model. [in theory of high-temperature superconductors

    NASA Technical Reports Server (NTRS)

    Emery, V. J.; Lin, H. Q.; Kivelson, S. A.

    1990-01-01

    A detailed understanding of the motion of 'holes' in an antiferromagnet is of fundamental importance for the theory of high-temperature superconductors. It is shown here that, for the t-J model, dilute holes in an antiferromagnet are unstable against phase separation into a hole-rich and a no-hole phase. When the spin-exchange interaction J exceeds a critical value Jc, the hole-rich phase has no electrons. It is proposed that, for J slightly less than Jc, the hole-rich phase is a low-density superfluid of electron pairs. Phase separation in related models is briefly discussed.

  18. Simulation of Reaction-Induced Phase Separation in Surface Alloy

    NASA Astrophysics Data System (ADS)

    Zvejnieks, G.; Tornau, E. E.

    2008-03-01

    Using kinetic Monte Carlo method we simulate the dynamics of biatomic Au0.3Ni0.7 surface alloy separation on Ni(111) due to Ni(CO)4 out-reaction. The experiment of Vestergaard et al. is modeled by counterbalancing dynamical processes and interactions between reactants. The simulations demonstrate step flow rate increase with CO coverage, cCO, in qualitative agreement with the experiment only for cCO ≲ 0.45 monolayer. Moreover, we demonstrate both CO influence on reaction process and Au domain formation.

  19. Conserved interdomain linker promotes phase separation of the multivalent adaptor protein Nck

    PubMed Central

    Banjade, Sudeep; Wu, Qiong; Mittal, Anuradha; Peeples, William B.; Pappu, Rohit V.; Rosen, Michael K.

    2015-01-01

    The organization of membranes, the cytosol, and the nucleus of eukaryotic cells can be controlled through phase separation of lipids, proteins, and nucleic acids. Collective interactions of multivalent molecules mediated by modular binding domains can induce gelation and phase separation in several cytosolic and membrane-associated systems. The adaptor protein Nck has three SRC-homology 3 (SH3) domains that bind multiple proline-rich segments in the actin regulatory protein neuronal Wiskott-Aldrich syndrome protein (N-WASP) and an SH2 domain that binds to multiple phosphotyrosine sites in the adhesion protein nephrin, leading to phase separation. Here, we show that the 50-residue linker between the first two SH3 domains of Nck enhances phase separation of Nck/N-WASP/nephrin assemblies. Two linear motifs within this element, as well as its overall positively charged character, are important for this effect. The linker increases the driving force for self-assembly of Nck, likely through weak interactions with the second SH3 domain, and this effect appears to promote phase separation. The linker sequence is highly conserved, suggesting that the sequence determinants of the driving forces for phase separation may be generally important to Nck functions. Our studies demonstrate that linker regions between modular domains can contribute to the driving forces for self-assembly and phase separation of multivalent proteins. PMID:26553976

  20. Graphene oxide membrane for liquid phase organic molecular separation

    NASA Astrophysics Data System (ADS)

    Liu, Renlong; Arabale, Girish; Kim, Jinseon; Sun, Ke; Lee, Yongwoon; Ryu, Changkook; Lee, Changgu

    2015-03-01

    The selective permeation of organic solvents and water through graphene oxide (GO) membranes has been demonstrated. Water was found to permeate through GO membranes faster than various alcohols. The permeation rates of propanol are about 80 times lower than that of water. Taking advantage of the differences in the permeation rates, we separated water from the alcohols and obtained alcohols with high purity. For ethanol and 1-propanol, binary solutions of the alcohol and water were filtered efficiently to produce alcohols with concentration of about 97%. However, the selectivity of the filtration of methanol is significantly lower than those of the other alcohols. To understand the mechanism we followed the structural changes in the GO membranes by X-Ray diffraction analysis. From the X-ray diffraction results we speculate that the selectivity of the permeation of water and alcohols is closely related to the molecular sizes of the solvents and their polarity. In order to demonstrate the potential applications of this process for the selective removal of water from aqueous organic mixtures, we performed the separation of water from a bio-oil containing 73% of water. The majority of the water was filtered out resulting in a higher purity bio-oil.

  1. 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

  2. Monte Carlo simulations of the phase separation of a copolymer blend in a thin film.

    PubMed

    Wang, Zhexiao; Shao, Jing; Pan, Heng; Feng, Xiaoshuang; Chen, Peng; Xia, Ru; Wu, Xiangsong; Qian, Jiasheng

    2015-02-23

    Monte Carlo simulations were carried out to study the phase separation of a copolymer blend comprising an alternating copolymer and/or block copolymer in a thin film, and a phase diagram was constructed with a series of composed recipes. The effects of composition and segregation strength on phase separation were discussed in detail. The chain conformation of the block copolymer and alternating copolymer were investigated with changes of the segregation strength. Our simulations revealed that the segment distribution along the copolymer chain and the segregation strength between coarse-grained beads are two important parameters controlling phase separation and chain conformation in thin films of a copolymer blend. A well-controlled phase separation in the copolymer blend can be used to fabricate novel nanostructures. PMID:25504337

  3. Hydration and phase separation of polyethylene glycol in copolymers of tyrosine derived carbonates.

    NASA Astrophysics Data System (ADS)

    Sanjeeva Murthy, N.; Wang, Wenjie; Kohn, Joachim

    2009-03-01

    Effect of PEG fraction and its block size on the temperature-induced phase transitions and the hydration-induced phase separation were investigated in a copolymer of desaminotyrosyl tyrosine ethyl ester (DTE) and PEG using simultaneous SAXS/WAXS/DSC. The PEG segments crystallized when the block size was at least 2000 Daltons and present at ˜ 40 wt%, and raised the Tg of the polymer by ˜ 15 ^oC. The PEG blocks in dry polymers with up to 50 wt% PEG, even when crystalline, were found to be uniformly distributed with no evidence of phase separation at 10 nm length scales. The non-iodinated PEG-rich sample with 30 mole% PEG2k showed the lower critical solution temperature (LCST) behavior with PEG blocks forming a separate phase above -21 ^oC. In the iodinated version of this polymer, the PEG2k blocks were phase separated in the solid phase. In all samples, whether PEG was crystalline or not, hydration induced PEG to separate into 15 nm hydrated domains. Phase behavior was dependent on whether poly(DTE) or the PEG was the major (matrix) phase. Changes in the mobility of the chains brought about by water-mediated hydrogen-bonding, and modulated by heat, appear to be the common underlying explanation for the range of observed phase behavior.

  4. A REVIEW OF THE EARLY DEVELOPMENT OF THE THERMODYNAMICS OF THE COMPLEX COACERVATION PHASE SEPARATION

    PubMed Central

    Veis, Arthur

    2011-01-01

    Coacervation was defined as the phenomenon in which a colloidal dispersion separated into colloid-rich (the coacervate), and colloid-poor phases, both with the same solvent. Complex coacervation covered the situation in which a mixture of two polymeric polyions with opposite charge separated into liquid dilute and concentrated phases, in the same solvent, with both phases, at equilibrium, containing both polyions. Voorn and Overbeek provided the first theoretical analysis of complex coacervation by applying Flory-Huggins polymer statistics to model the random mixing of the polyions and their counter ions in solution, assuming completely random mixing of the polyions in each phase, with the electrostatic free energy, ΔGelect, providing the driving force. However, experimentally complete randomness does not apply: polyion size, heterogeneity, chain stiffness and charge density (σ) all affect the equilibrium phase separation and phase concentrations. Moreover, in pauci-disperse systems multiple phases are often observed. As an alternative, Veis and Aranyi proposed the formation of charge paired Symmetrical Aggregates (SA) as an initial step, followed by phase separation driven by the interaction parameter, χ23, combining both entropy and enthalpy factors other than the ΔGelect electrostatic term. This two stage path to equilibrium phase separation allows for understanding and quantifying and modeling the diverse aggregates produced by interactions between polyampholyte molecules of different charge density, σ, and intrinsic polyion structure. PMID:21377640

  5. Phase separation of biphasic mixture of active Janus colloids

    NASA Astrophysics Data System (ADS)

    Yan, Jing; Han, Ming; Luijten, Erik; Granick, Steve

    2014-03-01

    Recently there is a surge of interest in the phase behavior of active matter in which building blocks display self-propelling motion. Although much has been known from theory and simulation, experimental examples are very rare. Specifically, the epitomic problem of a binary mixture of active matter defies any experiment or theory so far. Here we present an experimental realization of binary mixture of particles, which only acquires activity when they collisionally interact with the opposite kind. We used a system in which the only difference in the two particles is the phase in their cyclic motion, precluding any artifact due to difference in interparticle potential. We observe phenomena strikingly similar to spinodal decomposition of molecular system, in addition to new features due to the nonequilibrium nature of the system. We derived a general, effective Flory-Huggins theory for spinodal decomposition of bicomponent active system, and rationalized the 1/3 power law growth of the domain size in regions where thermodynamic analogy is valid. The system also presents a plethora of nonequilibrium phenomena such as critical fluctuation, lane formation, and dynamic absorbing state in different parameter space.

  6. A fuzzy controlled three-phase centrifuge for waste separation

    SciTech Connect

    Parkinson, W.J.; Smith, R.E.; Miller, N.

    1998-02-01

    The three-phase centrifuge technology discussed in this paper was developed by Neal Miller, president of Centech, Inc. The three-phase centrifuge is an excellent device for cleaning up oil field and refinery wastes which are typically composed of hydrocarbons, water, and solids. The technology is unique. It turns the waste into salable oil, reusable water, and landfill-able solids. No secondary waste is produced. The problem is that only the inventor can set up and run the equipment well enough to provide an optimal cleanup. Demand for this device has far exceeded a one man operation. There is now a need for several centrifuges to be operated at different locations at the same time. This has produced a demand for an intelligent control system, one that could replace a highly skilled operator, or at least supplement the skills of a less experienced operator. The control problem is ideally suited to fuzzy logic, since the centrifuge is a highly complicated machine operated entirely by the skill and experience of the operator. A fuzzy control system was designed for and used with the centrifuge.

  7. Rubber-modified epoxies: Analysis of the phase-separation process

    SciTech Connect

    Verchere, D.; Sautereau, H.; Pascault, J.P.; Moschiar, S.M.; Riccardi, C.C.; Williams, R.J.J.

    1993-12-31

    The phase-separation process of a diepoxide based on bisphenol A diglycidyl ether cured with a cycloaliphatic diamine in the presence of an epoxy-terminated butadiene-acrylonitrile random copolymer (ETBN) was experimentally studied and theoretically simulated. The increase in the average molecular weight of the epoxy-amine polymer is shown to be the main thermodynamic factor leading to phase separation. The competition between nucleation-growth and spinodal decomposition is analyzed. Low values of interfacial tensions and polymerization rates favor the first mechanism in most cases. A secondary phase separation must occur inside the dispersed particles, leading to a segregated epoxy-amine phase. The theoretical simulation explains the increase of the average diameter of dispersed-phase particles with increasing polymerization temperature. The volume fraction of dispersed phase is the dominating factor affecting fracture toughness. 49 refs., 16 figs.

  8. Cell separations and the demixing of aqueous two phase polymer solutions in microgravity

    NASA Technical Reports Server (NTRS)

    Brooks, Donald E.; Bamberger, Stephan; Harris, J. M.; Van Alstine, James M.

    1991-01-01

    Partition in phase separated aqueous polymer solutions is a cell separation procedure thought to be adversely influenced by gravity. In preparation for performing cell partitioning experiments in space, and to provide general information concerning the demixing of immiscible liquids in low gravity, a series of phase separated aqueous polymer solutions have been flown on two shuttle flights. Fluorocarbon oil and water emulsions were also flown on the second flight. The aqueous polymer emulsions, which in one g demix largely by sedimentation and convection due to the density differences between the phases, demixed more slowly than on the ground and the final disposition of the phases was determined by the wetting of the container wall by the phases. The demixing behavior and kinetics were influenced by the phase volume ratio, physical properties of the systems and chamber wall interaction. The average domain size increased linearly with time as the systems demixed.

  9. Numerical Study of Gas-Phase Flow in a Cyclone Separator

    NASA Astrophysics Data System (ADS)

    Shi, Ya-Ping; Qu, Biao; Huang, Shan; Niu, Xiao-Dong

    2016-06-01

    To investigate separation efficiency of a cyclone separator at different operating parameters, in this paper we use Fluent software to numerically study the three dimensional gas-solid two-phase flows in the cyclone separator. The present work mainly consists four parts. Firstly we investigates the accuracy of different turbulent models including the standard k-ɛ model, RNG k-ɛ model, Realizable k-ɛ model and Reynolds stress equation model (RSM), and finds that the RSM turbulence model gives a good comparison between the numerical results and the experimental results. Secondly, the gas phase flow rate, pressure, and turbulent distribution in the cyclone separator are explored numerically in detail with the RSM model. Thirdly, on the base of the gas flow results, gas-solid two phase flows in the cyclone separator are studied by coupling the random trajectory model in the Lagrangian coordinates so that the particle trajectories in separator are displayed. Finally, effects of particle size and velocity at the cyclone separator inlet on the separation efficiency are analyzed. Numerical results show that when the particle velocity is higher and particle size is larger at the inlet, the separation efficiency is better. However, when the particle velocity and size approach their threshold values, the separation efficiency will not change.

  10. Soft nanostructuring of YBCO Josephson junctions by phase separation.

    PubMed

    Gustafsson, D; Pettersson, H; Iandolo, B; Olsson, E; Bauch, T; Lombardi, F

    2010-12-01

    We have developed a new method to fabricate biepitaxial YBa2 Cu3 O7-δ (YBCO) Josephson junctions at the nanoscale, allowing junctions widths down to 100 nm and simultaneously avoiding the typical damage in grain boundary interfaces due to conventional patterning procedures. By using the competition between the superconducting YBCO and the insulating Y2 BaCuO5 phases during film growth, we formed nanometer sized grain boundary junctions in the insulating Y2 BaCuO5 matrix as confirmed by high-resolution transmission electron microscopy. Electrical transport measurements give clear indications that we are close to probing the intrinsic properties of the grain boundaries. PMID:21080664

  11. Hierarchical multiscale hyperporous block copolymer membranes via tunable dual-phase separation.

    PubMed

    Yoo, Seungmin; Kim, Jung-Hwan; Shin, Myoungsoo; Park, Hyungmin; Kim, Jeong-Hoon; Lee, Sang-Young; Park, Soojin

    2015-07-01

    The rational design and realization of revolutionary porous structures have been long-standing challenges in membrane science. We demonstrate a new class of amphiphilic polystyrene-block-poly(4-vinylpyridine) block copolymer (BCP)-based porous membranes featuring hierarchical multiscale hyperporous structures. The introduction of surface energy-modifying agents and the control of major phase separation parameters (such as nonsolvent polarity and solvent drying time) enable tunable dual-phase separation of BCPs, eventually leading to macro/nanoscale porous structures and chemical functionalities far beyond those accessible with conventional approaches. Application of this BCP membrane to a lithium-ion battery separator affords exceptional improvement in electrochemical performance. The dual-phase separation-driven macro/nanopore construction strategy, owing to its simplicity and tunability, is expected to be readily applicable to a rich variety of membrane fields including molecular separation, water purification, and energy-related devices. PMID:26601212

  12. Crystal Morphology Control By Melt Phase Separation in Biodegradable Polymer Blends

    NASA Astrophysics Data System (ADS)

    Akpalu, Y. A.; Meredith, J. C.; Amis, E. J.

    2001-03-01

    The effect of lower critical solution temperature (LCST) phase separation on the crystallization of poly(ɛ-caprolactone) PCL in PCL/poly(D,L-lactide) (PDLA) blends is studied by simultaneous small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS). Phase separation is induced by controlled temperature jumps into the LCST (two-phase) region, which is above the melting temperature (60 ^oC) of PCL and the glass transition temperature (50 ^oC) of PDLA. We have followed the nanoscale structural changes (< 100 nm) during subsequent crystallization at 45 ^oC of critical (0.36 PCL) and off-critical (0.50 PCL) blend compositions in both one-phase and two-phase melts. The spherulite morphology (1-100 μm) is examined with optical microscopy. When crystallization follows LCST phase separation, the shape, size and distribution of the spherulites depends on the extent of melt phase separation. In our x-ray measurements, the WAXS crystallinity of PCL is less than 40 % for the temperature range of interest. We perform a correlation function and intensity model analysis of our SAXS data to obtain morphological variables that characterize the intraspherulitic morphology. These morphological variables are relatively constant during crystallization and are also independent of melt phase separation. On the other hand, the ultimate crystallinity, the crystallization rate and the intraspherulitic concentration of PDLA depend on the extent of melt phase separation. In 0.36 PCL the ultimate crystallinity can be reduced by 50 %. To the best of our knowledge, this is the first use of simultaneous SAXS/WAXS to investigate the effect on melt phase separation and blending on the crystal morphology independently.

  13. Multimodal Responses of Self-Organized Circuitry in Electronically Phase Separated Materials

    DOE PAGESBeta

    Herklotz, Andreas; Guo, Hangwen; Wong, Anthony T.; Lee, Ho Nyung; Rack, Philip D.; Ward, Thomas Z.

    2016-07-13

    When confining an electronically phase we separated manganite film to the scale of its coexisting self-organized metallic and these insulating domains allows resistor-capacitor circuit-like responses while providing both electroresistive and magnetoresistive switching functionality.

  14. Fingerprints of intrinsic phase separation: magnetically doped two-dimensional electron gas.

    PubMed

    Terletska, H; Dobrosavljević, V

    2011-05-01

    In addition to Anderson and Mott localization, intrinsic phase separation has long been advocated as the third fundamental mechanism controlling the doping-driven metal-insulator transitions. In electronic system, where charge neutrality precludes global phase separation, it may lead to various inhomogeneous states and dramatically affect transport. Here we theoretically predict the precise experimental signatures of such phase separation-driven metal-insulator transitions. We show that anomalous transport is expected in an intermediate regime around the transition, displaying very strong temperature and magnetic field dependence but very weak density dependence. Our predictions find striking agreement with recent experiments on Mn-doped CdTe quantum wells, a system where we identify the microscopic origin for intrinsic phase separation. PMID:21635108

  15. An asymmetric tubular ceramic-carbonate dual phase membrane for high temperature CO2 separation.

    PubMed

    Dong, Xueliang; Ortiz Landeros, José; Lin, Y S

    2013-10-25

    For the first time, a tubular asymmetric ceramic-carbonate dual phase membrane was prepared by a centrifugal casting technique and used for high temperature CO2 separation. This membrane shows high CO2 permeation flux and permeance. PMID:24022119

  16. The effect of liquid-liquid phase separation of glass on the properties and crystallization behavior

    NASA Technical Reports Server (NTRS)

    Li, J. Z.

    1985-01-01

    A theoretical discussion is given of the phase separation mechanism of amorphous materials. This includes nucleus growth, spinoidal decomposition, and nuclei agglomeration and coarsening. Various types of glass are analyzed.

  17. Chirality Separation of Single-Wall Carbon Nanotubes using Aqueous Two-Phase Extraction

    NASA Astrophysics Data System (ADS)

    Fagan, Jeffrey

    2014-03-01

    Aqueous two-phase extraction (ATPE) was recently demonstrated to enable the separation of individual species of single-wall carbon nanotubes (SWCNTs) across the separated phases. In this presentation I will describe the use of a dextran - polyethylene glycol aqueous two-phase system along with a separation scheme of varying surfactant concentrations to enable isolation at high purity of specific small diameter SWCNT species. Separation by ATPE is rapid and robust, with a remarkable tunability that allows isolation of most single nanotube chiralities at high purity. Choice of surfactant(s), temperature, polymer concentrations, and the addition of small molecule salts can all be used to tune the exact partitioning of single SWCNT species between the two phases.

  18. Rheological monitoring of phase separation induced by chemical reaction in thermoplastic-modified epoxy

    SciTech Connect

    Vinh-Tung, C.; Lachenal, G.; Chabert, B.

    1996-12-31

    The phase separation induced by chemical reaction in blends of tetraglycidyl-diaminodiphenylmethane epoxy resin with an aromatic diamine hardener and a thermoplastic was monitored. Rheological measurements and morphologies are described.

  19. 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

  20. Silica-based polypeptide-monolithic stationary phase for hydrophilic chromatography and chiral separation.

    PubMed

    Zhao, Licong; Yang, Limin; Wang, Qiuquan

    2016-05-13

    Glutathione (GSH)-, somatostatin acetate (ST)- and ovomucoid (OV)-functionalized silica-monolithic stationary phases were designed and synthesized for HILIC and chiral separation using capillary electrochromatography (CEC). GSH, ST and OV were covalently incorporated into the silica skeleton via the epoxy ring-opening reaction between their amino groups and the glycidyl moiety in γ-glycidoxypropyltrimethoxysilane (GPTMS) together with polycondensation and copolymerization of tetramethyloxysilane and GPTMS. Not only could the direction and electroosmotic flow magnitude on the prepared GSH-, ST- and OV-silica hybrid monolithic stationary phases be controlled by the pH of the mobile phase, but also a typical HILIC behavior was observed so that the nucleotides and HPLC peptide standard mixture could be baseline separated using an aqueous mobile phase without any acetonitrile during CEC. Moreover, the prepared monolithic columns had a chiral separation ability to separate dl-amino acids. The OV-silica hybrid monolithic column was most effective in chiral separation and could separate dl-glutamic acid (Glu) (the resolution R=1.07), dl-tyrosine (Tyr) (1.57) and dl-histidine (His) (1.06). Importantly, the chiral separation ability of the GSH-silica hybrid monolithic column could be remarkably enhanced when using gold nanoparticles (AuNPs) to fabricate an AuNP-mediated GSH-AuNP-GSH-silica hybrid monolithic column. The R of dl-Glu, dl-Tyr and dl-His reached 1.19, 1.60 and 2.03. This monolithic column was thus applied to separate drug enantiomers, and quantitative separation of all four R/S drug enantiomers were achieved with R ranging from 4.36 to 5.64. These peptide- and protein-silica monolithic stationary phases with typical HILIC separation behavior and chiral separation ability implied their promise for the analysis of not only the future metabolic studies, but also drug enantiomers recognition. PMID:27083263

  1. Phase separation between conductive and insulative materials induced by the electric field.

    PubMed

    Nagamine, Yuko

    2016-07-01

    To demonstrate that phase separation is a main mechanism of pattern formation for one of the spatiotemporal patterns emerging in the Ag and Sb electrodeposition system, I performed numerical simulations to model the mixed system of conductive and insulative materials under a steady electric field. For such a dissipative system, I derived the extended Cahn-Hilliard equation using Onsager's variational principle. My results demonstrate that conductive and insulative materials phase separate spatially under the constant-current mode. PMID:27575064

  2. Phase separation between conductive and insulative materials induced by the electric field

    NASA Astrophysics Data System (ADS)

    Nagamine, Yuko

    2016-07-01

    To demonstrate that phase separation is a main mechanism of pattern formation for one of the spatiotemporal patterns emerging in the Ag and Sb electrodeposition system, I performed numerical simulations to model the mixed system of conductive and insulative materials under a steady electric field. For such a dissipative system, I derived the extended Cahn-Hilliard equation using Onsager's variational principle. My results demonstrate that conductive and insulative materials phase separate spatially under the constant-current mode.

  3. Space cryogenics components based on the thermomechanical effect - Vapor-liquid phase separation

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    Applications of the thermomechanical effect has been qualified including incorporation in large-scale space systems in the area of vapor-liquid phase separation (VLPS). The theory of the porous-plug phase separator is developed for the limit of a high thermal impedance of the solid-state grains. Extensions of the theory of nonlinear turbulent flow are presented based on experimental results.

  4. In situ x-ray scattering study of a main-chain thermotropic liquid crystalline polymer under oscillatory shear flow

    NASA Astrophysics Data System (ADS)

    Vaish, Nitin; Burghardt, Wesley R.; Zhou, Weijun; Kornfield, Julia A.

    2000-03-01

    Liquid crystalline polymers (LCPs) have been the subject of extensive studies because of potential commercial applications and scientific challenges. The excellent mechanical properties of LCPs arise from highly anisotropic molecular structure, which develops as a complex interplay between molecular dynamics and the applied flow field. We study the behavior of model thermotropic main-chain LCP (DHMS-7,9) under oscillatory shear flow using in situ X-ray scattering techniques. Experiments were done in nematic (140^o C) and x-phase (110^o C) to study the effects of frequency (0.5 - 50 rps) and strain amplitude (50 200In nematic phase, strong alignment in the flow direction (‘parallel’) was observed. The steady state was reached quickly either at high strain amplitudes or high frequencies. In x-phase, molecules aligned in flow direction at high strain levels or oscillation frequency, while alignment in vorticity (‘perpendicular’) direction was observed at low strain amplitude or frequency. In addition, we present the flipping of orientation from parallel to perpendicular alignment as a result of step change in temperature from 140^o C to 110^o C and oscillatory motion from a pre-aligned parallel state in x-phase.

  5. Sintered plug flow modulation of a vapor-liquid phase separator for a helium II vessel

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    Presented is a system for modulation of a superfluid (helium II) flow in a vapor-liquid phase separator, for use in cryogenic storage tanks in future space missions. The system consists of a semicircular mechanically operated shutter, downstream of the separator plug, rotated at 0.1 rpm to control the operational surface area of the separator. The mass flow rate was varied from 10 to 22 mg/s. Pressure gradients across the plug are also discussed.

  6. 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

  7. Use of Solid Phase Extraction in the Biochemistry Laboratory to Separate Different Lipids

    ERIC Educational Resources Information Center

    Flurkey, William H.

    2005-01-01

    Solid-phase extraction (SPE) was used to demonstrate how various lipids and lipid classes could be separated in a biochemistry laboratory setting. Three different SPE methods were chosen on their ability to separate a lipid mixture, consisting of a combination of a either a fatty acid, a triacylglycerol, a mono- or diacylglycerol, phospholipid,…

  8. Suppression of turbulent energy cascade due to phase separation in homogenous binary mixture fluid

    NASA Astrophysics Data System (ADS)

    Takagi, Youhei; Okamoto, Sachiya

    2015-11-01

    When a multi-component fluid mixture becomes themophysically unstable state by quenching from well-melting condition, phase separation due to spinodal decomposition occurs, and a self-organized structure is formed. During phase separation, free energy is consumed for the structure formation. In our previous report, the phase separation in homogenous turbulence was numerically simulated and the coarsening process of phase separation was discussed. In this study, we extended our numerical model to a high Schmidt number fluid corresponding to actual polymer solution. The governing equations were continuity, Navier-Stokes, and Chan-Hiliard equations as same as our previous report. The flow filed was an isotropic homogenous turbulence, and the dimensionless parameters in the Chan-Hilliard equation were estimated based on the thermophysical condition of binary mixture. From the numerical results, it was found that turbulent energy cascade was drastically suppressed in the inertial subrange by phase separation for the high Schmidt number flow. By using the identification of turbulent and phase separation structure, we discussed the relation between total energy balance and the structures formation processes. This study is financially supported by the Grand-in-Aid for Young Scientists (B) (No. T26820045) from the Ministry of Education, Cul-ture, Sports, Science and Technology of Japan.

  9. Selection of thermotropic liquid crystalline polymers for rotational molding

    NASA Astrophysics Data System (ADS)

    Scribben, Eric

    Thermotropic liquid crystalline polymers (TLCPs) possess a number of physical and mechanical properties such as: excellent chemical resistance, low permeability, low coefficient of thermal expansion, high tensile strength and modulus, and good impact resistance, which make them desirable for use in the storage of cryogenic fluids. Rotational molding was selected as the processing method for these containers because it is convenient for manufacturing large storage vessels from thermoplastics. Unfortunately, there are no reports of successful TLCP rotational molding in the technical literature. The only related work reported involved the static coalescence of two TLCP powders, where three key results were reported that were expected to present problems that preclude the rotational molding process. The first result was that conventional grinding methods produced powders that were composed of high aspect ratio particles. Secondly, coalescence was observed to be either slow or incomplete and speculated that the observed difficulties with coalescence may be due to large values of the shear viscosity at low deformation rates. Finally, complete densification was not observed for the high aspect ratio particles. However, the nature of these problems were not evaluated to determine if they did, in fact, create processing difficulties for rotational molding or if it was possible to develop solutions to the problems to achieve successful rotational molding. This work is concerned with developing a resin selection method to identify viable TLCP candidates and establish processing conditions for successful rotational molding. This was accomplished by individually investigating each of the phenomenological steps of rotational molding to determine the requirements for acceptable performance in, or successful completion of, each step. The fundamental steps were: the characteristics and behavior of the powder in solids flow, the coalescence behavior of isolated particles, and the

  10. Phase separation induced molecular fractionation of gum arabic--sugar beet pectin systems.

    PubMed

    Mao, Peng; Zhao, Meng; Zhang, Fan; Fang, Yapeng; Phillips, Glyn O; Nishinari, Katsuyoshi; Jiang, Fatang

    2013-10-15

    This paper investigates the phase separation and phase separation-induced fractionation of gum arabic (GA)/sugar beet pectin (SBP) mixed solutions. A phase diagram, including cloud and binodal curves, was established by visual observation and phase composition analysis. The deviation of the binodal curve from the cloud curve was a result of phase separation-induced fractionation of polydisperse GA and SBP molecules. Fractionation of GA increased the content of arabinogalactan-protein complex (AGP) from ca. 13% to 27%. The fractionated GA (FGA) showed improved emulsifying functionality, whereas the fractionated SBP (FSBP) had a reduced emulsifying functionality. The changes in emulsifying efficiency can be explained by interfacial adsorption behaviors at the oil-water interface as indicated by interfacial tension measurements. PMID:23987401

  11. Phase separation of cesium from lead borosilicate glass by heat treatment under a reducing atmosphere.

    PubMed

    Xu, Zhanglian; Okada, Takashi; Nishimura, Fumihiro; Yonezawa, Susumu

    2016-11-01

    A phase-separation technique for removing sodium from glass using a heat-treatment method under a reducing atmosphere was previously developed for sodium recovery from waste glass. In this study, this technique was applied to cesium-containing lead borosilicate glass to concentrate the cesium in phase-separated sodium-rich materials for efficient cesium extraction. The theoretical phase-separation temperature of the sodium-rich phase was simulated by thermodynamic equilibrium calculations and was predicted to occur below 700°C for lead borosilicate glass. Experimentally, a simulated lead borosilicate glass was melted at 1000°C and subsequently annealed below 700°C under a CO-containing reducing atmosphere. The phase separation of cesium was found to occur with sodium enrichment on the glass surface that was in contact with the gas phase, promoting cesium extraction from the treated glass using water. The cesium extraction efficiency was affected by the surface area of the treated glass that was in contact with water, and under the examined conditions, the cesium extraction efficiency was up to 66%. Phase separation using reductive heat treatment, combined with a water leaching technique, is suggested to be effective for extracting cesium incorporated in borosilicate glass waste. PMID:27368086

  12. The Two-Phase Flow Separator Experiment Breadboard Model: Reduced Gravity Aircraft Results

    NASA Technical Reports Server (NTRS)

    Rame, E; Sharp, L. M.; Chahine, G.; Kamotani, Y.; Gotti, D.; Owens, J.; Gilkey, K.; Pham, N.

    2015-01-01

    Life support systems in space depend on the ability to effectively separate gas from liquid. Passive cyclonic phase separators use the centripetal acceleration of a rotating gas-liquid mixture to carry out phase separation. The gas migrates to the center, while gas-free liquid may be withdrawn from one of the end plates. We have designed, constructed and tested a breadboard that accommodates the test sections of two independent principal investigators and satisfies their respective requirements, including flow rates, pressure and video diagnostics. The breadboard was flown in the NASA low-gravity airplane in order to test the system performance and design under reduced gravity conditions.

  13. Extent and mechanism of phase separation during the extrusion of calcium phosphate pastes.

    PubMed

    O'Neill, Rory; McCarthy, Helen O; Cunningham, Eoin; Montufar, Edgar; Ginebra, Maria-Pau; Wilson, D Ian; Lennon, Alex; Dunne, Nicholas

    2016-02-01

    The aim of this study was to increase understanding of the mechanism and dominant drivers influencing phase separation during ram extrusion of calcium phosphate (CaP) paste for orthopaedic applications. The liquid content of extrudate was determined, and the flow of liquid and powder phases within the syringe barrel during extrusion were observed, subject to various extrusion parameters. Increasing the initial liquid-to-powder mass ratio, LPR, (0.4-0.45), plunger rate (5-20 mm/min), and tapering the barrel exit (45°-90°) significantly reduced the extent of phase separation. Phase separation values ranged from (6.22 ± 0.69 to 18.94 ± 0.69 %). However altering needle geometry had no significant effect on phase separation. From powder tracing and liquid content determination, static zones of powder and a non-uniform liquid distribution was observed within the barrel. Measurements of extrudate and paste LPR within the barrel indicated that extrudate LPR remained constant during extrusion, while LPR of paste within the barrel decreased steadily. These observations indicate the mechanism of phase separation was located within the syringe barrel. Therefore phase separation can be attributed to either; (1) the liquid being forced downstream by an increase in pore pressure as a result of powder consolidation due to the pressure exerted by the plunger or (2) the liquid being drawn from paste within the barrel, due to suction, driven by dilation of the solids matrix at the barrel exit. Differentiating between these two mechanisms is difficult; however results obtained suggest that suction is the dominant phase separation mechanism occurring during extrusion of CaP paste. PMID:26704546

  14. Influence of Specific Anions on the Orientational Ordering of Thermotropic Liquid Crystals at Aqueous Interfaces

    PubMed Central

    Carlton, Rebecca J.; Ma, C. Derek; Gupta, Jugal K.; Abbott, Nicholas L.

    2012-01-01

    We report that specific anions (of sodium salts) added to aqueous phases at molar concentrations can trigger rapid, orientational ordering transitions in water-immiscible, thermotropic liquid crystals (LCs; e.g., nematic phase of 4′-pentyl-4-cyanobiphenyl, 5CB) contacting the aqueous phases. Anions classified as chaotropic, specifically iodide, perchlorate and thiocyanate, cause 5CB to undergo continuous, concentration-dependent transitions from planar to homeotropic (perpendicular) orientations at LC-aqueous interfaces within 20 s of addition of the anions. In contrast, anions classified as relatively more kosmotropic in nature (fluoride, sulfate, phosphate, acetate, chloride, nitrate, bromide, and chlorate) do not perturb the LC orientation from that observed without added salts (i.e., planar orientation). Surface pressure-area isotherms of Langmuir films of 5CB supported on aqueous salt solutions reveal ion-specific effects ranking in a manner similar to the LC ordering transitions. Specifically, chaotropic salts stabilized monolayers of 5CB to higher surface pressures and areal densities (12.6 mN/m at 27 Å2/molec. for NaClO4) and thus smaller molecular tilt angles (30° from the surface normal for NaClO4) than kosmotropic salts (5.0 mN/m at 38 Å2/molec. with a corresponding tilt angle of 53° for NaCl). These results and others reported herein suggest that anion-specific interactions with 5CB monolayers lead to bulk LC ordering transitions. Support for the proposition that these ion-specific interactions involve the nitrile group was obtained by using a second LC with nitrile groups (E7; ion-specific effects similar to 5CB were observed) and a third LC with fluorine-substituted aromatic groups (TL205; weak dipole and no ion-specific effects were measured). Finally, we also establish that anion-induced orientational transitions in micrometer-thick LC films involve a change in the easy axis of the LC. Overall, these results provide new insights into ionic

  15. Double-antibody solid-phase radioimmunoassay: a simplified phase-separation procedure applied to various ligands

    SciTech Connect

    Tevaarwerk, G.J.M.; Boyle, D.A.; Hurst, C.J.; Anguish, I.; Uksik, P.

    1980-06-01

    The purpose was to develop a simplified and reliable method of separating free from antibody-bound ligand using a precipitating antibody linked to a cellulose derivative. Dose-response curves and control sera were set up in parallel for various pituitary and placental polypeptides, steroid hormones, insulin, glucagon, triiodothyronine, thyroxine, angiotensin I, calcitonin, gastrin, cyclic AMP, and digoxin. After first-antibody reactions had reached equilibrium, free and bound ligand were separated using a double-antibody solid-phase system in parallel with conventional methods, including dextran-coated charcoal, double-antibody precipitation, single-antibody solid phase, organic solvents, salt precipitation, and anion-exchange resins. The effect of variations in temperature, incubation time, protein content, pH, and amount of separating material added were studied. The results showed that separation was complete within 1 hr for small ligand molecules and within 2 hr for larger ones. Dose-response curves and control-sera results closely paralleled those obtained with conventional methods. The method was not affected by moderate variations in incubation variables. Nonspecific binding was less than 3% in all assays, while intra-assay and interassay coefficients of variation were similar to those obtained with conventional phase-separation methods. It is concluded that the method is a simple and rapid alternative phase-separation system. It has the advantage of being free from common nonspecific intersample variations, and can be applied to any assay system based on rabbit or guinea pig antibodies without preliminay time- or reagent-consuming titration or adjustments to establish optimum phase-separating conditions.

  16. Method and apparatus for centrifugal separation of dispersed phase from a continuous liquid phase

    SciTech Connect

    Ryan, D.G.

    1986-12-16

    A method is described of treating a hydrocarbon oil mixture boiling in the lubricating oil range and containing wax particles, for separating wax particles from the oil mixture, comprising the steps of: centrifugating the oil mixture to be treated in a centrifugal separation device, for separating a quantity of the wax particles from the oil mixture; introducing free excess charge which is net unipolar into the oil mixture, whereby charge transfers to wax particles in the oil mixture; and collecting charged wax particles, for separation from the oil mixture.

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. Hierarchical multiscale hyperporous block copolymer membranes via tunable dual-phase separation

    PubMed Central

    Yoo, Seungmin; Kim, Jung-Hwan; Shin, Myoungsoo; Park, Hyungmin; Kim, Jeong-Hoon; Lee, Sang-Young; Park, Soojin

    2015-01-01

    The rational design and realization of revolutionary porous structures have been long-standing challenges in membrane science. We demonstrate a new class of amphiphilic polystyrene-block-poly(4-vinylpyridine) block copolymer (BCP)–based porous membranes featuring hierarchical multiscale hyperporous structures. The introduction of surface energy–modifying agents and the control of major phase separation parameters (such as nonsolvent polarity and solvent drying time) enable tunable dual-phase separation of BCPs, eventually leading to macro/nanoscale porous structures and chemical functionalities far beyond those accessible with conventional approaches. Application of this BCP membrane to a lithium-ion battery separator affords exceptional improvement in electrochemical performance. The dual-phase separation–driven macro/nanopore construction strategy, owing to its simplicity and tunability, is expected to be readily applicable to a rich variety of membrane fields including molecular separation, water purification, and energy-related devices. PMID:26601212

  2. Nucleation pathway and kinetics of phase-separating active Brownian particles.

    PubMed

    Richard, David; Löwen, Hartmut; Speck, Thomas

    2016-06-28

    Suspensions of purely repulsive but self-propelled Brownian particles might undergo phase separation, a phenomenon that strongly resembles the phase separation of passive particles with attractions. Here we employ computer simulations to study the nucleation kinetics and the microscopic pathway active Brownian disks take in two dimensions when quenched from the homogeneous suspension to propulsion speeds beyond the binodal. We find the same qualitative behavior for the nucleation rate as a function of density as for a passive suspension undergoing liquid-vapor separation, suggesting that the scenario of an effective free energy also extends to the kinetics of phase separation. We study the transition in more detail through a committor analysis and find that transition states are best described by a combination of cluster size and the radial polarization of particles in the cluster. PMID:27126952

  3. Separation of electrostatic and magnetic phase shifts using a modified transport-of-intensity equation.

    PubMed

    Humphrey, E; Phatak, C; Petford-Long, A K; De Graef, M

    2014-04-01

    We introduce a new approach for the separation of the electrostatic and magnetic components of the electron wave phase shift, based on the transport-of-intensity equation (TIE) formalism. We derive two separate TIE-like equations, one for each of the phase shift components. We use experimental results on FeCoB and Permalloy patterned islands to illustrate how the magnetic and electrostatic longitudinal derivatives can be computed. The main advantage of this new approach is the fact that the differences in the power spectra of the two phase components (electrostatic phase shifts often have significant power in the higher frequencies) can be accommodated by the selection of two different Tikhonov regularization parameters for the two phase reconstructions. The extra computational demands of the method are more than compensated by the improved phase reconstruction results. PMID:24513573

  4. 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.

  5. Extraction of complementary from non-complementary DNA sequences through phase separation and centrifugation

    NASA Astrophysics Data System (ADS)

    Robins, Taiquitha; McPherson, Dacia; Zhu, Chenhui; Moran, Mark; Walba, Dave; Zanchetta, Giuliano; Bellini, Tommaso; Clark, Noel

    2008-03-01

    Double stranded deoxyribonucleic acid (DNA) is known to form lyotropic liquid crystal (LC) phases, nematic and then columnar with increasing DNA concentration in water. Single stranded (DNA) does not form liquid crystal phases. We study the phase separation of both long (900bp) and short (6-20bp) DNA. In the mixture solution of a self complementary sequences (scDNA) and non complementary sequences (nscDNA), the scDNA forms DNA double helices and hence forms LC phases while the nscDNA stays in the isotropic phase, the LC appearing in the form of phase separated droplets. We report results of the use of centrifugation to produce complete spatial segregation of complementary and noncomplementary DNA, based on their different LC-formation tendencies.

  6. Spectromicroscopy of electronic phase separation in KxFe2−ySe2 superconductor

    PubMed Central

    Bendele, M.; Barinov, A.; Joseph, B.; Innocenti, D.; Iadecola, A.; Bianconi, A.; Takeya, H.; Mizuguchi, Y.; Takano, Y.; Noji, T.; Hatakeda, T.; Koike, Y.; Horio, M.; Fujimori, A.; Ootsuki, D.; Mizokawa, T.; Saini, N. L.

    2014-01-01

    Structural phase separation in AxFe2−ySe2 system has been studied by different experimental techniques, however, it should be important to know how the electronic uniformity is influenced, on which length scale the electronic phases coexist, and what is their spatial distribution. Here, we have used novel scanning photoelectron microscopy (SPEM) to study the electronic phase separation in KxFe2−ySe2, providing a direct measurement of the topological spatial distribution of the different electronic phases. The SPEM results reveal a peculiar interconnected conducting filamentary phase that is embedded in the insulating texture. The filamentary structure with a particular topological geometry could be important for the high Tc superconductivity in the presence of a phase with a large magnetic moment in AxFe2−ySe2 materials. PMID:24998816

  7. 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.

  8. Phase-Field Simulation of the Separation Kinetics of a Nanoscale Phase in a Fe-Cr Alloy

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Li, Yongsheng; Wu, Xingchao; Hou, Zhiyuan; Hu, Kai

    2016-05-01

    The separation of a Cr-enriched nanometer-scale α' phase can induce the embrittlement of Fe-Cr alloys at high temperature, and the separation kinetics of the α' phase determines its spatial morphology. The quantitative kinetics of the α' phase formed by spinodal decomposition was studied in a Fe-42 at.% Cr alloy by phase-field simulation at various aging temperatures; the temporal morphology, average particle radius, volume fraction, particle number density, and particle size distribution of α' phase were investigated. The results indicate that the coarsening rate of the α' phase increases with increasing aging temperature, and the particle number density shows a large slope in the coarsening stage at higher aging temperature. The particle size distribution also demonstrates faster growth and coarsening rates of the α' phase at higher aging temperature. The mutual effects of supercooling and diffusion during phase decomposition result in a highest decomposition rate at 725 K than that of 700 and 750 K in the Fe-42 at.% Cr alloy. The simulation results of the kinetics of the Cr-enriched α' phase provide a basic understanding of the thermal aging and morphology evolution of Fe-Cr alloys.

  9. Nanoscopy of Phase Separation in InxGa1-xN Alloys.

    PubMed

    Abate, Yohannes; Seidlitz, Daniel; Fali, Alireza; Gamage, Sampath; Babicheva, Viktoriia; Yakovlev, Vladislav S; Stockman, Mark I; Collazo, Ramon; Alden, Dorian; Dietz, Nikolaus

    2016-09-01

    Phase separations in ternary/multinary semiconductor alloys is a major challenge that limits optical and electronic internal device efficiency. We have found ubiquitous local phase separation in In1-xGaxN alloys that persists to nanoscale spatial extent by employing high-resolution nanoimaging technique. We lithographically patterned InN/sapphire substrates with nanolayers of In1-xGaxN down to few atomic layers thick that enabled us to calibrate the near-field infrared response of the semiconductor nanolayers as a function of composition and thickness. We also developed an advanced theoretical approach that considers the full geometry of the probe tip and all the sample and substrate layers. Combining experiment and theory, we identified and quantified phase separation in epitaxially grown individual nanoalloys. We found that the scale of the phase separation varies widely from particle to particle ranging from all Ga- to all In-rich regions and covering everything in between. We have found that between 20 and 25% of particles show some level of Ga-rich phase separation over the entire sample region, which is in qualitative agreement with the known phase diagram of In1-xGaxN system. PMID:27533107

  10. Characterization of thermotropism in primary roots of maize: dependence on temperature and temperature gradient, and interaction with gravitropism

    NASA Technical Reports Server (NTRS)

    Poff, K. L.

    1991-01-01

    Thermotropism in primary roots of Zea mays L. was studied with respect to gradient strength (degrees C cm-1), temperature of exposure within a gradient, pre-treatment temperature, and gravitropic stimulation. The magnitude of the response decreased with gradient strength. Maximum thermotropism was independent of gradient strength and pre-treatment temperature. The range of temperature for positive and negative thermotropism did not change with pre-treatment temperature. However, the exact range of temperatures for positive and negative thermotropism varied with gradient strengths. In general, temperatures of exposure lower than 25 degrees C resulted in positive tropic responses while temperatures of exposure of 39 degrees C or more resulted in negative tropic responses. Thermotropism was shown to modify and reverse the normal gravitropic curvature of a horizontal root when thermal gradients were applied opposite the 1 g vector. It is concluded that root thermotropism is a consequence of thermal sensing and that the curvature of the primary root results from the interaction of the thermal and gravitational sensing systems.

  11. Phase Separation on Bicontinuous Cubic Membranes: Symmetry Breaking, Reentrant, and Domain Faceting

    NASA Astrophysics Data System (ADS)

    Paillusson, Fabien; Pennington, Matthew R.; Kusumaatmaja, Halim

    2016-07-01

    We study the phase separation of binary lipid mixtures that form bicontinuous cubic phases. The competition between the nonuniform Gaussian membrane curvature and line tension leads to a very rich phase diagram, where we observe symmetry breaking of the membrane morphologies and reentrant phenomena due to the formation of bridges between segregated domains. Upon increasing the line tension contribution, we also find faceting of lipid domains that we explain using a simple argument based on the symmetry of the underlying surface and topology.

  12. Phase separation as a strategy toward controlling dilution effects in macrocyclic Glaser-Hay couplings.

    PubMed

    Bédard, Anne-Catherine; Collins, Shawn K

    2011-12-14

    Macrocycles are abundant in numerous chemical applications, however the traditional strategy for the preparation of these compounds remains cumbersome and environmentally damaging; involving tedious reaction set-ups and extremely dilute reaction media. The development of a macrocyclization strategy conducted at high concentrations is described which exploits phase separation of the catalyst and substrate, as a strategy to control dilution effects. Sequestering a copper catalyst in a highly polar and/or hydrophilic phase can be achieved using a hydrophilic ligand, T-PEG(1900), a PEGylated TMEDA derivative. Similarly, phase separation is possible when suitable copper complexes are soluble in PEG(400), a green and efficient solvent which can be utilized in biphasic mixtures for promoting macrocyclization at high concentrations. The latter phase separation technique can be exploited for the synthesis of a wide range of industrially relevant macrocycles with varying ring sizes and functional groups. PMID:22029394

  13. Effects of Fe/C phase separation on the ages of white dwarfs

    NASA Technical Reports Server (NTRS)

    Xu, Z. W.; Van Horn, H. M.

    1992-01-01

    The energy release associated with the phase separation of Fe from C in a predominantly C white dwarf is calculated. The total gravitational-plus-internal energy differences between models of homogeneous compositions and those wth Fe-enriched cores are computed. In the unlikely case where the core is pure Fe, a substantial extension of the white dwarf cooling times is found, even with the small cosmic abundance of this element. For the more realistic core compositions that result if the Fe/C phase diagram is either of the spindle or of the azeotropic type, the energy release is still sufficient to prolong the cooling times by about 0.6 Gyr, comparable to that produced by C/O phase separation. Phase separation is found to produce an appreciable 'bump' in the luminosity function, although not one large enough to exceed the observational errors at low luminosities.

  14. 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

  15. Hydrogen isotope systematics of phase separation in submarine hydrothermal systems: Experimental calibration and theoretical models

    USGS Publications Warehouse

    Berndt, M.E.; Seal, R.R., II; Shanks, Wayne C., III; Seyfried, W.E., Jr.

    1996-01-01

    Hydrogen isotope fractionation factors were measured for coexisting brines and vapors formed by phase separation of NaCl/H2O fluids at temperatures ranging from 399-450??C and pressures from 277-397 bars. It was found that brines are depleted in D compared to coexisting vapors at all conditions studied. The magnitude of hydrogen isotope fractionation is dependent on the relative amounts of Cl in the two phases and can be empirically correlated to pressure using the following relationship: 1000 ln ??(vap-brine) = 2.54(??0.83) + 2.87(??0.69) x log (??P), where ??(vap-brine) is the fractionation factor and ??P is a pressure term representing distance from the critical curve in the NaCl/H2O system. The effect of phase separation on hydrogen isotope distribution in subseafloor hydrothermal systems depends on a number of factors, including whether phase separation is induced by heating at depth or by decompression of hydrothermal fluids ascending to the seafloor. Phase separation in most subseafloor systems appears to be a simple process driven by heating of seawater to conditions within the two-phase region, followed by segregation and entrainment of brine or vapor into a seawater dominated system. Resulting vent fluids exhibit large ranges in Cl concentration with no measurable effect on ??D. Possible exceptions to this include hydrothermal fluids venting at Axial and 9??N on the East Pacific Rise. High ??D values of low Cl fluids venting at Axial are consistent with phase separation taking place at relatively shallow levels in the oceanic crust while negative ??D values in some low Cl fluids venting at 9??N suggest involvement of a magmatic fluid component or phase separation of D-depleted brines derived during previous hydrothermal activity.

  16. Characterization of fish gelatin-gum arabic complex coacervates as influenced by phase separation temperature.

    PubMed

    Anvari, Mohammad; Pan, Cheol-Ho; Yoon, Won-Byong; Chung, Donghwa

    2015-08-01

    The rheological and structural characteristics of fish gelatin (FG)-gum arabic (GA) complex coacervate phase, separated from an aqueous mixture of 1% FG and 1% GA at pH 3.5, were investigated as influenced by phase separation temperature. Decreasing the phase separation temperature from 40 to 10 °C lead to: (1) the formation of a coacervate phase with a larger volume fraction and higher biopolymer concentrations, which is more viscous, more structural resistant at low shear rates, more shear-thinning at high shear rates, and more condensed in microstructure, (2) a solid-like elastic behavior of the phase separated at 10 °C at a high oscillatory frequency, (3) the increase in gelling and melting temperatures of the coacervate phase (3.7-3.9 °C and 6.2-6.9 °C, respectively), (4) the formation of a more rigid and thermo-stable coacervate gel. The coacervate phase is regarded as a homogeneously networked biopolymer matrix dispersed with water vacuoles and its gel as a weak physical gel reinforced by FG-GA attractive electrostatic interactions. PMID:26054661

  17. Separation performance of guanidinium-based ionic liquids as stationary phases for gas chromatography.

    PubMed

    Qiao, Lizhen; Lu, Kai; Qi, Meiling; Fu, Ruonong

    2013-02-01

    Room temperature ionic liquids (RTILs) as stationary phases for gas chromatography (GC) have made great achievements in both research and applications over the last decades. Until now, all of the RTIL stationary phases reported have involved imidazolium, ammonium, pyrrolidinium, and phosphonium-based RTILs, and however, no publications are available using guanidinium-based ionic liquids (GBILs) as GC stationary phases except two preliminary reports from our group. In the present work, three hexaalkyl GBILs stationary phases, namely N, N,N',N'-tetramethyl-N″, N″-dioctylguanidinum hexafluophosphate (DOTMG-PF(6)), N,N,N',N'-tetramethyl-N″, N″-dioctylguanidinium bis (trifluoromethylsulfonyl) imide (DOTMG-NTf(2)), and N,N,N',N'-tetraoctyl-N″, N″-dimethylguanidinium bis (trifluoromethylsulfonyl) imide (TODMG-NTf(2)), were synthesized and used as stationary phases for GC separation after they were statically coated onto the inner walls of fused-silica capillary columns. The evaluation of DOTMG-PF(6) and TODMG-NTf(2) as GC stationary phases is reported here for the first time, whereas additional results on the DOTMG-NTf(2) stationary phase are added here on the basis of our previous report. In this work, McReynolds constants and Abraham solvation system constants are used to evaluate the average polarity and the solvation properties of the GBILs stationary phases for GC separation, respectively. The results show that the GBILs stationary phases exhibit medium polarity with an average polarity of 293-390, and that the major molecular interactions of the GBILs with analytes are dipole/polarizable interactions, H-bond basicity and dispersion forces, etc. After this, the separation performance and thermal stability of the GBILs stationary phases were evaluated, showing that these stationary phases achieve excellent separation for analytes of great variety covering hydrocarbons, alcohols, esters, aldehydes, ketones, amines, amides and aromatics, and exhibit

  18. Evaluation of the Sensitivity of Two-Phase Flow Model for the Steam Separator Analysis

    SciTech Connect

    Michio Murase; Masao Chaki

    2006-07-01

    Reducing of the pressure losses of steam separator systems of boiling water reactor (BWR) plants is useful to reduce the required pump head and enhance core stability design margin. The need to reduce the pressure losses of steam separator systems is especially important in BWR plants that have high power density cores and natural circulation systems. The core flow rate of a BWR plant with a natural circulation system is affected by the pressure losses of steam separator systems. In BWR plants with high power density cores, the core stability design margin is affected by these pressure losses. Generally, reducing the pressure losses of the steam separator systems leads to increased carry-under and carryover. Reducing the pressure losses while keeping the characteristics of both carry-under and carryover is desired, so many studies have been done. The steam separator of a BWR plant consists of a standpipe section, a swirl vane section and three-barrel sections. Two-phase flow of steam and water enters the steam separator through the standpipe section and reaches the swirl vane section. In the swirl vane section, the two-phase flow is given centrifugal force and is basically separated into steam and water. Therefore investigating the two-phase flow characteristics of the swirl vane section is very important. After the swirl vane section, the two-phase flow enters the barrel sections. Each barrel has a pick-off ring. The water in the barrel section is mainly removed by these pick-off rings because the water mainly flows upward as a liquid film in the barrel section due to the centrifugal force given in the swirl vane section. We researched the effect of using the drag force model of the swirling two-phase flow in analyzing a steam separator and we found that the drag force model greatly affects the results of the analysis. (authors)

  19. Ternary Phase-Separation Investigation of Sol-Gel Derived Silica from Ethyl Silicate 40

    PubMed Central

    Wang, Shengnan; Wang, David K.; Smart, Simon; Diniz da Costa, João C.

    2015-01-01

    A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H2O/Si ratios. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H2O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification. PMID:26411484

  20. Ternary Phase-Separation Investigation of Sol-Gel Derived Silica from Ethyl Silicate 40.

    PubMed

    Wang, Shengnan; Wang, David K; Smart, Simon; da Costa, João C Diniz

    2015-01-01

    A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H2O/Si ratios. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H2O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification. PMID:26411484

  1. Phase Separation in La-Containing Sodium Alumino-Borosilicate Glasses

    SciTech Connect

    Li, Liyu; Qian, Maoxu; Li, Hong; Strachan, Denis M.

    2001-01-13

    La (III) is considered as a surrogate for Pu (III) in the development of radioactive waste glasses. The addition of La (III) in some sodium alumino-borosilicate glasses causes phase separation, but in others, it causes crystallization of sodium lanthanum silicate. In this study, we characterize some clear glasses and some phase-separated La-containing glasses using optical microscopy, X-ray diffraction, and transmission electron microscopy. The baseline glass (without La2O3) in which phase separation first occurs with the addition of La2O3 is more heterogeneous than the baseline glass in which crystallization first occurs with the addition of La2O3. They all consist of two portions: a borate portion and a silicate portion. As La2O3 is added, it is incorporated in the borate portion first, and causes a phase rich in La and B separated from the melt. Increasing excess Na, i.e., Na-Al, or excess Al, i.e., Al-Na, can suppress the phase separation. When more La2O3 is added, it is incorporated in the silicate portion, and causes the crystallization of sodium lanthanum silicate in the melt.

  2. Movie of phase separation during physics of colloids in space experiment

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Still photographs taken over 16 hours on Nov. 13, 2001, on the International Space Station have been condensed into a few seconds to show the de-mixing -- or phase separation -- process studied by the Experiment on Physics of Colloids in Space. Commanded from the ground, dozens of similar tests have been conducted since the experiment arrived on ISS in 2000. The sample is a mix of polymethylmethacrylate (PMMA or acrylic) colloids, polystyrene polymers and solvents. The circular area in the video is 2 cm (0.8 in.) in diameter. The phase separation process occurs spontaneously after the sample is mechanically mixed. The evolving lighter regions are rich in colloid and have the structure of a liquid. The dark regions are poor in colloids and have the structure of a gas. This behavior carnot be observed on Earth because gravity causes the particles to fall out of solution faster than the phase separation can occur. While similar to a gas-liquid phase transition, the growth rate observed in this test is different from any atomic gas-liquid or liquid-liquid phase transition ever measured experimentally. Ultimately, the sample separates into colloid-poor and colloid-rich areas, just as oil and vinegar separate. The fundamental science of de-mixing in this colloid-polymer sample is the same found in the annealing of metal alloys and plastic polymer blends. Improving the understanding of this process may lead to improving processing of these materials on Earth.

  3. Phase separation during the Experiment on Physics of Colloids in Space

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Still photographs taken over 16 hours on Nov. 13, 2001, on the International Space Station have been condensed into a few seconds to show the de-mixing -- or phase separation -- process studied by the Experiment on Physics of Colloids in Space. Commanded from the ground, dozens of similar tests have been conducted since the experiment arrived on ISS in 2000. The sample is a mix of polymethylmethacrylate (PMMA or acrylic) colloids, polystyrene polymers and solvents. The circular area is 2 cm (0.8 in.) in diameter. The phase separation process occurs spontaneously after the sample is mechanically mixed. The evolving lighter regions are rich in colloid and have the structure of a liquid. The dark regions are poor in colloids and have the structure of a gas. This behavior carnot be observed on Earth because gravity causes the particles to fall out of solution faster than the phase separation can occur. While similar to a gas-liquid phase transition, the growth rate observed in this test is different from any atomic gas-liquid or liquid-liquid phase transition ever measured experimentally. Ultimately, the sample separates into colloid-poor and colloid-rich areas, just as oil and vinegar separate. The fundamental science of de-mixing in this colloid-polymer sample is the same found in the annealing of metal alloys and plastic polymer blends. Improving the understanding of this process may lead to improving processing of these materials on Earth.

  4. Ternary Phase-Separation Investigation of Sol-Gel Derived Silica from Ethyl Silicate 40

    NASA Astrophysics Data System (ADS)

    Wang, Shengnan; Wang, David K.; Smart, Simon; Diniz da Costa, João C.

    2015-09-01

    A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H2O/Si ratios. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H2O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification.

  5. Phase separation and ordering in InGaAs and InGaAs materials. Final report

    SciTech Connect

    Not Available

    1995-02-23

    This report highlights the advances in the understanding of phase separation and atomic ordering in mixed III-V layers. Specifically, the following issues were addressed in the grant period (August 1987 to February 1992): (1) bulk vs surface phase separation; (2) influence of growth technique on phase separation; (3) origin of coarse contrast modulations; (4) influence of dopant diffusion on phase separated microstructures; (5) influence of annealing on carrier mobility in InGaAsP layers; (6) co-existence of CuPt-type ordering and phase separation; (7) influence of growth conditions on ordering; (8) influence of surface reconstruction on atomic ordering.

  6. Grafted nanoparticles as soft patchy colloids: Self-assembly versus phase separation

    SciTech Connect

    Mahynski, Nathan A.; Panagiotopoulos, Athanassios Z.

    2015-02-21

    We investigate the thermodynamic behavior of a model polymer-grafted nanoparticle (GNP) system on a fine lattice, using grand canonical Monte Carlo simulations, to compare and contrast the validity of two different models for GNPs: “nanoparticle amphiphiles” versus “patchy particles.” In the former model, continuous self-assembly processes are expected to dominate the system, whereas the latter are characterized by first-order phase separation into novel equilibrium phases such as “empty liquids.” We find that, in general, considering GNPs as amphiphiles within the framework of a recent mean-field theory [Pryamtisyn et al., J. Chem. Phys. 131, 221102 (2009)] provides a qualitatively accurate description of the thermodynamics of GNP systems, revealing either first-order phase separation into two isotropic phases or continuous self-assembly. Our model GNPs display no signs of empty liquid formation, suggesting that these nanoparticles do not provide a route to such phases.

  7. Kinetics of symmetry and asymmetry in a phase-separating bilayer membrane

    NASA Astrophysics Data System (ADS)

    Williamson, J. J.; Olmsted, P. D.

    2015-11-01

    We simulate a phase-separating bilayer in which the leaflets experience a direct coupling favoring local compositional symmetry ("registered" bilayer phases), and an indirect coupling due to hydrophobic mismatch that favors strong local asymmetry ("antiregistered" bilayer phases). For wide ranges of overall leaflet compositions, multiple competing states are possible. For estimated physical parameters, a quenched bilayer may first evolve toward a metastable state more asymmetric than if the leaflets were uncorrelated; subsequently, it must nucleate to reach its equilibrium, more symmetric, state. These phase-transition kinetics exhibit characteristic signatures through which fundamental and opposing interleaflet interactions may be probed. We emphasize how bilayer phase diagrams with a separate axis for each leaflet can account for overall and local symmetry or asymmetry, and capture a range of observations in the experiment and simulation literature.

  8. Separating pairing from quantum phase coherence dynamics above the superconducting transition by femtosecond spectroscopy

    PubMed Central

    Madan, I.; Kurosawa, T.; Toda, Y.; Oda, M.; Mertelj, T.; Kusar, P.; Mihailovic, D.

    2014-01-01

    In classical superconductors an energy gap and phase coherence appear simultaneously with pairing at the transition to the superconducting state. In high-temperature superconductors, the possibility that pairing and phase coherence are distinct and independent processes has led to intense experimental search of their separate manifestations. Using femtosecond spectroscopy methods we now show that it is possible to clearly separate fluctuation dynamics of the superconducting pairing amplitude from the phase relaxation above the critical transition temperature. Empirically establishing a close correspondence between the superfluid density measured by THz spectroscopy and superconducting optical pump-probe response over a wide region of temperature, we find that in differently doped Bi2Sr2CaCu2O8+δ crystals the pairing gap amplitude monotonically extends well beyond Tc, while the phase coherence shows a pronounced power-law divergence as T → Tc, thus showing that phase coherence and gap formation are distinct processes which occur on different timescales. PMID:25014162

  9. Design and Development of Gas-Liquid Cylindrical Cyclone Compact Separators for Three-Phase Flow

    SciTech Connect

    Mohan, Ram S.; Shoham, Ovadia

    1999-10-28

    The objective of this five-year project (October, 1997--September, 2002) is to expand the current research activities of Tulsa University Separation Technology Projects (TUSTP) to multiphase oil/water/gas separation. This project will be executed in two phases. Phase I (1997--2000) will focus on the investigations of the complex multiphase hydrodynamic flow behavior in a three-phase Gas-Liquid Cylindrical Cyclone (GLCC) Separator. The activities of this phase will include the development of a mechanistic model, a computational fluid dynamics (CFD) simulator, and detailed experimentation on the three-phase GLCC. The experimental and CFD simulation results will be suitably integrated with the mechanistic model. In Phase II (2000--2002), the developed GLCC separator will be tested under high pressure and real crudes conditions. This is crucial for validating the GLCC design for field application and facilitating easy and rapid technology deployment. Design criteria for industrial applications will be developed based on these results and will be incorporated into the mechanistic model by TUSTP.

  10. Design and Development of Gas-Liquid Cylindrical Cyclone Compact Separators for Three-Phase Flow

    SciTech Connect

    Mohan, R.S.; Shoham, O.

    2001-01-18

    The objective of this five-year project (October 1997 - September 2002) was to expand the current research activities of Tulsa University Separation Technology Projects (TUSTP) to multiphase oil/water/gas separation. This project was executed in two phases. Phase I (1997 - 2000) focused on the investigations of the complex multiphase hydrodynamic flow behavior in a three-phase Gas-Liquid Cylindrical Cyclone (GLCC) Separator. The activities of this phase included the development of a mechanistic model, a computational fluid dynamics (CFD) simulator, and detailed experimentation on the three-phase GLCC. The experimental and CFD simulation results will be suitably integrated with the mechanistic model. In Phase II (2000 - 2002), the developed GLCC separator will be tested under high pressure and real crude conditions. This is crucial for validating the GLCC design for field application and facilitating easy and rapid technology deployment. Design criteria for industrial applications will be developed based on these results and will be incorporated into the mechanistic model by TUSTP.

  11. D0 Silicon Upgrade: Calc. to Determine Need for a N2 Phase Separator

    SciTech Connect

    Rucinski, Russ; /Fermilab

    1995-04-07

    A nitrogen phase separator is recommended on the liquid supply line at the helium refrigerator plant. This engineering note documents the calculations done to reach that conclusion. The steady state liquid nitrogen consumption rate for the refrigerator, VLPC and solenoid systems is about 30 gal/hr. The estimated heat leak for the piping run to the refrigerator location is 50 watts. The calculated quality at the refrigerator was 0.032. Given this quality, a two phase flow model based on Lockhart-Martinelli and also incorporating Baker diagram nomenclature was run on TK solver. The result of this program was that without the use of a phase separator we could expect a slug flow pattern with a volume fraction of gas of 65%. Based on this, I recommend that we use a phase separator to siphon off the gas before the nitrogen is sent to a standard saver type subcooler. Including the phase separator will help ensure proper operation of the subcooler. The subcooler will help us attempt to deliver single phase liquid to the nitrogen control valves.

  12. Design and Development of Gas-Liquid Cylindrical Cyclone Compact Separators for Three-Phase Flow

    SciTech Connect

    Mohan, R.S.; Shoham, O.

    2001-01-10

    The objective of this five-year project (October 1997--September 2002) was to expand the current research activities of Tulsa University Separation Technology Projects (TUSTP) to multiphase oil/water/gas separation. This project was executed in two phases. Phase I (1997--2000) focused on the investigations of the complex multiphase hydrodynamic flow behavior in a three-phase Gas-Liquid Cylindrical Cyclone (GLCC) Separator. The activities of this phase included the development of a mechanistic model, a computational fluid dynamics (CFD) simulator, and detailed experimentation on the three-phase GLCC. The experimental and CFD simulation results will be suitably integrated with the mechanistic model. In Phase II (2000--2002), the developed GLCC separator will be tested under high pressure and real crude conditions. This is crucial for validating the GLCC design for field application and facilitating easy and rapid technology deployment. Design criteria for industrial applications will be developed based on these results and will be incorporated into the mechanistic model by TUSTP.

  13. Control of Polymer Phase Separation by Roughness Transfer Printing for 2D Microlens Arrays.

    PubMed

    Zhang, Xinyue; Gao, Naiwei; He, Yonglin; Liao, Shenglong; Zhang, Shiming; Wang, Yapei

    2016-07-01

    Great efforts have been devoted to the control of phase separation between blended polymers in terms of the advantages for engineering functional topologies. A simple and straightforward pathway through roughness transfer printing (RTP) is proposed to realize the control of polymer phase separation. The additional roughness difference, which is introduced by trace agarose transferred from a hydrogel stamp, offers a great effect on the rate of nucleation and coalescence orientation of polymethylmethacrylate (PMMA) protrusions grown from a polydimethylsiloxane (PDMS) network. Using a particular topography of agarose stamp and a proper growth time in toluene atmosphere, a 2D microlens array with high uniformity is obtained that shows great potential for optical applications. Moreover, the control of polymer phase separation was successfully extended to the collection and identification of fingerprints with a high degree of replication. PMID:27254465

  14. Device for two-dimensional gas-phase separation and characterization of ion mixtures

    DOEpatents

    Tang, Keqi; Shvartsburg, Alexandre A.; Smith, Richard D.

    2006-12-12

    The present invention relates to a device for separation and characterization of gas-phase ions. The device incorporates an ion source, a field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer, an ion mobility spectrometry (IMS) drift tube, and an ion detector. In one aspect of the invention, FAIMS operating voltages are electrically floated on top of the IMS drift voltage. In the other aspect, the FAIMS/IMS interface is implemented employing an electrodynamic ion funnel, including in particular an hourglass ion funnel. The present invention improves the efficiency (peak capacity) and sensitivity of gas-phase separations; the online FAIMS/IMS coupling creates a fundamentally novel two-dimensional gas-phase separation technology with high peak capacity, specificity, and exceptional throughput.

  15. Theory of spatiotemporally resolved spectroscopy for phase-separation dynamics in electron-hole systems

    NASA Astrophysics Data System (ADS)

    Ishikawa, Akira

    2013-02-01

    Phase separation such as the formation of electron-hole droplets has been observed in semiconductor electron-hole systems. In such conventional experiments, the information averaged in real space was obtained. However, in recent years, optical-near-field techniques have enabled us to acquire spatial information. In this study, I propose a theoretical formulation of spatiotemporal dynamics and spatiotemporally resolved optical response of the gas-liquid phase separation in electron-hole systems. In addition, the nature of the nonequilibrium open system is an essential point in electron-hole systems. Therefore, I investigate the effect of the finite lifetime of electron-hole pairs on phase-separation dynamics. Contribution to the Topical Issue "Excitonic Processes in Condensed Matter, Nanostructured and Molecular Materials", edited by Maria Antonietta Loi, Jasper Knoester and Paul H. M. van Loosdrecht.

  16. Viscosity and phase separations of binary CO-He and CO-Ar mixtures

    NASA Astrophysics Data System (ADS)

    Rademacher, N.; Bayarjargal, L.; Morgenroth, W.; Ciezak-Jenkins, J. A.; Winkler, B.

    2015-01-01

    Binary mixtures of 10 and 25 vol% CO in He and 10 vol% CO in Ar have been studied at high pressures and ambient temperature in diamond anvil cells. Phase separations were observed at 5.7(3) GPa, 3.6(2) GPa and 1.6(1) GPa. Earlier studies of ?-He mixtures of comparable concentrations revealed phase separations at significantly larger pressures, while ?-Ar mixtures separate at pressures comparable to those observed in the CO-Ar system here. The viscosity of a CO-rich fluid phase was determined by measuring the velocities of rising He bubbles. After corrections for the influence of the finite container size and of remaining helium in CO, the viscosity of the CO-rich fluid at 3.8(1) GPa was ≈3(1) mPa s, similar to what would be expected for isoelectronic liquid ? under the same conditions.

  17. Influence of red blood cell clustering on phase separation in capillary networks

    NASA Astrophysics Data System (ADS)

    Podgorski, Thomas; Boucly, Celine; Coupier, Gwennou

    2014-11-01

    We investigate the flow of red blood cell suspensions in microfluidic bifurcations and capillary networks. At strong degrees of confinement, such as those encountered in the microcirculation, phase separation takes place at bifurcations of the network, leading to strong heterogeneities and fluctuations of the hematocrit (blood cell concentration). We highlight the influence of the mechanical properties of cells : an increase of membrane or cytoplasm rigidity, as can happen in pathologies such as sickle cell disease tends to reduce the phase separation. The influence of the attractive interaction between cells, that leads to clustering (rouleau formation) was also investigated by varying the concentration of macromolecules in the solution (dextran or fibrinogen). We show that hydrodynamic stresses in bifurcations can lead to rupture of clusters at a critical speed which increases with interaction energy. Overall, the clustering phenomenon tends to increase phase separation and hematocrit heterogeneities.

  18. 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

  19. Exploring the dynamics of phase separation in colloid-polymer mixtures with long range attraction.

    PubMed

    Sabin, Juan; Bailey, Arthur E; Frisken, Barbara J

    2016-06-28

    We have studied the kinetics of phase separation and gel formation in a low-dispersity colloid - non-adsorbing polymer system with long range attraction using small-angle light scattering. This system exhibits two-phase and three-phase coexistence of gas, liquid and crystal phases when the strength of attraction is between 2 and 4kBT and gel phases when the strength of attraction is increased. For those samples that undergo macroscopic phase separation, whether to gas-crystal, gas-liquid or gas-liquid-crystal coexistence, we observe dynamic scaling of the structure factor and growth of a characteristic length scale that behaves as expected for phase separation in fluids. In samples that gel, the power law associated with the growth of the dominant length scale is not equal to 1/3, but appears to depend mainly on the strength of attraction, decreasing from 1/3 for samples near the coexistence region to 1/27 at 8kBT, over a wide range of colloid and polymer concentrations. PMID:27242183

  20. pn-homojunction organic solar cells formed in phase-separated co-deposited films

    NASA Astrophysics Data System (ADS)

    Kubo, Masayuki; Kaji, Toshihiko; Hiramoto, Masahiro

    2013-12-01

    Simultaneous control of the doping and phase-separation in organic co-deposited films consisting of metal-free phthalocyanine and fullerene was performed. The doping was used to form pn-homojunctions in the phase-separated co-deposited films. The diffusion length of the minority carriers reached 0.3 μm allowing the fabrication of very thick cells up to 0.5 μm thick. It was shown that suppression of the interfacial recombination processes is crucial for obtaining cells with high performance.

  1. Controlling phase separation of binary Bose-Einstein condensates via mixed-spin-channel Feshbach resonance

    SciTech Connect

    Tojo, Satoshi; Taguchi, Yoshihisa; Masuyama, Yuta; Hayashi, Taro; Hirano, Takuya; Saito, Hiroki

    2010-09-15

    We investigate controlled phase separation of a binary Bose-Einstein condensate in the proximity of a mixed-spin-channel Feshbach resonance in the |F=1,m{sub F}=+1> and |F=2,m{sub F}=-1> states of {sup 87}Rb at a magnetic field of 9.10 G. Phase separation occurs on the lower-magnetic-field side of the Feshbach resonance while the two components overlap on the higher-magnetic-field side. The Feshbach resonance curve of the scattering length is obtained from the shape of the atomic cloud by comparison with the numerical analysis of coupled Gross-Pitaevskii equations.

  2. Influence of recrystallization on phase separation kinetics of oxide dispersion strengthened Fe Cr Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Pimentel, G.; Chao, J.

    2012-01-01

    The effect of different starting microstructures on the kinetics of Fe-rich ({alpha}) and Cr-rich ({alpha}') phase separation during aging of Fe-Cr-Al oxide dispersion strengthened (ODS) alloys has been analyzed with a combination of atom probe tomography and thermoelectric power measurements. The results revealed that the high recrystallization temperature necessary to produce a coarse grained microstructure in Fe-base ODS alloys affects the randomness of Cr-atom distributions and defect density, which consequently affect the phase separation kinetics at low annealing temperatures.

  3. Phase separation in the trapped spinor gases with anisotropic spin-spin interaction

    NASA Astrophysics Data System (ADS)

    Hao, Y.; Zhang, Y.; Liang, J. Q.; Chen, S.

    2007-09-01

    We investigate the effect of the anisotropic spin-spin interaction on the ground state density distribution of the one dimensional spin-1 bosonic gases within a modified Gross-Pitaevskii theory both in the weakly interaction regime and in the Tonks-Girardeau (TG) regime. We find that for ferromagnetic spinor gas the phase separation occurs even for weak anisotropy of the spin-spin interaction, which becomes more and more obvious and the component of mF=0 diminishes as the anisotropy increases. However, no phase separation is found for anti-ferromagnetic spinor gas in both regimes.

  4. An atom probe perspective on phase separation and precipitation in duplex stainless steels

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Garfinkel, David A.; Tucker, Julie D.; Haley, Daniel; Young, George A.; Poplawsky, Jonathan D.

    2016-06-01

    Three-dimensional chemical imaging of Fe–Cr alloys showing Fe-rich (α)/Cr-rich (α‧) phase separation is reported using atom probe tomography techniques. The extent of phase separation, i.e., amplitude and wavelength, has been quantitatively assessed using the Langer-Bar-on-Miller, proximity histogram, and autocorrelation function methods for two separate Fe–Cr alloys, designated 2101 and 2205. Although the 2101 alloy possesses a larger wavelength and amplitude after annealing at 427 °C for 100–10 000 h, it exhibits a lower hardness than the 2205 alloy. In addition to this phase separation, ultra-fine Ni–Mn–Si–Cu-rich G-phase precipitates form at the α/α‧ interfaces in both alloys. For the 2101 alloy, Cu clusters act to form a nucleus, around which a Ni–Mn–Si shell develops during the precipitation process. For the 2205 alloy, the Ni and Cu atoms enrich simultaneously and no core–shell chemical distribution was found. This segregation phenomenon may arise from the exact Ni/Cu ratio inside the ferrite. After annealing for 10 000 h, the number density of the G-phase within the 2205 alloy was found to be roughly one order of magnitude higher than in the 2101 alloy. The G-phase precipitates have an additional deleterious effect on the thermal embrittlement, as evaluated by the Ashby–Orowan equation, which explains the discrepancy between the hardness and the rate of phase separation with respect to annealing time (Gladman T 1999 Mater. Sci. Tech. Ser. 15 30–36). ).

  5. An atom probe perspective on phase separation and precipitation in duplex stainless steels

    DOE PAGESBeta

    Garfinkel, David A.; Tucker, Julie D.; Haley, Daniel A.; Young, George A.; Guo, Wei; Poplawsky, Jonathan D.

    2016-05-16

    Here, three-dimensional chemical imaging of Fe–Cr alloys showing Fe-rich (α)/Cr-rich (α') phase separation is reported using atom probe tomography techniques. The extent of phase separation, i.e., amplitude and wavelength, has been quantitatively assessed using the Langer-Bar-on-Miller, proximity histogram, and autocorrelation function methods for two separate Fe–Cr alloys, designated 2101 and 2205. Although the 2101 alloy possesses a larger wavelength and amplitude after annealing at 427 °C for 100–10 000 h, it exhibits a lower hardness than the 2205 alloy. In addition to this phase separation, ultra-fine Ni–Mn–Si–Cu-rich G-phase precipitates form at the α/α' interfaces in both alloys. For the 2101more » alloy, Cu clusters act to form a nucleus, around which a Ni–Mn–Si shell develops during the precipitation process. For the 2205 alloy, the Ni and Cu atoms enrich simultaneously and no core–shell chemical distribution was found. This segregation phenomenon may arise from the exact Ni/Cu ratio inside the ferrite. After annealing for 10 000 h, the number density of the G-phase within the 2205 alloy was found to be roughly one order of magnitude higher than in the 2101 alloy. The G-phase precipitates have an additional deleterious effect on the thermal embrittlement, as evaluated by the Ashby–Orowan equation, which explains the discrepancy between the hardness and the rate of phase separation with respect to annealing time (Gladman T 1999 Mater. Sci. Tech. Ser. 15 30–36).« less

  6. An atom probe perspective on phase separation and precipitation in duplex stainless steels.

    PubMed

    Guo, Wei; Garfinkel, David A; Tucker, Julie D; Haley, Daniel; Young, George A; Poplawsky, Jonathan D

    2016-06-24

    Three-dimensional chemical imaging of Fe-Cr alloys showing Fe-rich (α)/Cr-rich (α') phase separation is reported using atom probe tomography techniques. The extent of phase separation, i.e., amplitude and wavelength, has been quantitatively assessed using the Langer-Bar-on-Miller, proximity histogram, and autocorrelation function methods for two separate Fe-Cr alloys, designated 2101 and 2205. Although the 2101 alloy possesses a larger wavelength and amplitude after annealing at 427 °C for 100-10 000 h, it exhibits a lower hardness than the 2205 alloy. In addition to this phase separation, ultra-fine Ni-Mn-Si-Cu-rich G-phase precipitates form at the α/α' interfaces in both alloys. For the 2101 alloy, Cu clusters act to form a nucleus, around which a Ni-Mn-Si shell develops during the precipitation process. For the 2205 alloy, the Ni and Cu atoms enrich simultaneously and no core-shell chemical distribution was found. This segregation phenomenon may arise from the exact Ni/Cu ratio inside the ferrite. After annealing for 10 000 h, the number density of the G-phase within the 2205 alloy was found to be roughly one order of magnitude higher than in the 2101 alloy. The G-phase precipitates have an additional deleterious effect on the thermal embrittlement, as evaluated by the Ashby-Orowan equation, which explains the discrepancy between the hardness and the rate of phase separation with respect to annealing time (Gladman T 1999 Mater. Sci. Tech. Ser. 15 30-36). PMID:27181108

  7. Phase separation in aqueous solutions of lens gamma-crystallins: special role of gamma s.

    PubMed Central

    Liu, C; Asherie, N; Lomakin, A; Pande, J; Ogun, O; Benedek, G B

    1996-01-01

    We have studied liquid-liquid phase separation in aqueous ternary solutions of calf lens gamma-crystallin proteins. Specifically, we have examined two ternary systems containing gamma s--namely, gamma IVa with gamma s in water and gamma II with gamma s in water. For each system, the phase-separation temperatures (Tph (phi)) alpha as a function of the overall protein volume fraction phi at various fixed compositions alpha (the "cloud-point curves") were measured. For the gamma IVa, gamma s, and water ternary solution, a binodal curve composed of pairs of coexisting points, (phi I, alpha 1) and (phi II, alpha II), at a fixed temperature (20 degrees C) was also determined. We observe that on the cloud-point curve the critical point is at a higher volume fraction than the maximum phase-separation temperature point. We also find that typically the difference in composition between the coexisting phases is at least as significant as the difference in volume fraction. We show that the asymmetric shape of the cloud-point curve is a consequence of this significant composition difference. Our observation that the phase-separation temperature of the mixtures in the high volume fraction region is strongly suppressed suggests that gamma s-crystallin may play an important role in maintaining the transparency of the lens. PMID:8552642

  8. Phase separation of a hexacyanoferrate-bridged coordination framework under electrochemical na-ion insertion.

    PubMed

    Kajiyama, Satoshi; Mizuno, Yoshifumi; Okubo, Masashi; Kurono, Ryosuke; Nishimura, Shin-ichi; Yamada, Atsuo

    2014-03-17

    Phase separation and transformation induced by electrochemical ion insertion are key processes in achieving efficient energy storage. Exploration of novel insertion electrode materials/reactions is particularly important to unravel the atomic/molecular-level mechanism and improve the electrochemical properties. Here, we report the unconventional phase separation of a cyanide-bridged coordination polymer, Eu[Fe(CN)6]·4H2O, under electrochemical Na-ion insertion. Detailed structural analyses performed during the electrochemical reaction revealed that, in contrast to conventional electrochemical phase separation induced by the elastic interaction between nearest neighbors, the phase separation of NaxEu[Fe(CN)6]·4H2O is due to a long-range interaction, namely, cooperative rotation ordering of hexacyanoferrates. Kolmogorov-Johnson-Mehl-Avrami analysis showed that the activation energy for the phase boundary migration in NaxEu[Fe(CN)6]·4H2O is lower than that in other conventional electrode materials such as Li(1-x)FePO4. PMID:24588620

  9. Thermal vacancies and phase separation in bcc mixtures of helium-3 and helium-4

    SciTech Connect

    Fraass, Benedick Andrew

    1980-01-01

    Thermal vacancy concentrations in crystals of /sup 3/He-/sup 4/He mixtures have been determined. A new x-ray diffractometer-position sensitive detector system is used to make measurements of the absolute lattice parameter of the helium crystals with an accuracy of 300 ppM, and measurements of changes in lattice parameters to better than 60 ppM. The phase separation of the concentrated /sup 3/He-/sup 4/He mixtures has been studied in detail with the x-ray measurements. Vacancy concentrations in crystals with 99%, 51%, 28%, 12%, and 0% /sup 3/He have been determined. Phase separation has been studied in mixed crystals with concentrations of 51%, 28%, and 12% /sup 3/He and melting pressures between 3.0 and 6.1 MPa. The phase separation temperatures determined in this work are in general agreement with previous work. The pressure dependence of T/sub c/, the phase separation temperature for a 50% mixture, is found to be linear: dT/sub c//dP = -34 mdeg/MPa. The x-ray measurements are used to make several comments on the low temperature phase diagram of the helium mixtures.

  10. Inherent structures of phase-separating binary mixtures: Nucleation, spinodal decomposition, and pattern formation

    NASA Astrophysics Data System (ADS)

    Sarkar, Sarmistha; Bagchi, Biman

    2011-03-01

    An energy landscape view of phase separation and nonideality in binary mixtures is developed by exploring their potential energy landscape (PEL) as functions of temperature and composition. We employ molecular dynamics simulations to study a model that promotes structure breaking in the solute-solvent parent binary liquid, at low temperatures. The PEL of the system captures the potential energy distribution of the inherent structures (IS) of the system and is obtained by removing the kinetic energy (including that of intermolecular vibrations). The broader distribution of the inherent structure energy for structure breaking liquid than that of the structure making liquid demonstrates the larger role of entropy in stabilizing the parent liquid of the structure breaking type of binary mixtures. At high temperature, although the parent structure of the structure breaking binary mixture is homogenous, the corresponding inherent structure is found to be always phase separated, with a density pattern that exhibits marked correlation with the energy of its inherent structure. Over a broad range of intermediate inherent structure energy, bicontinuous phase separation prevails with interpenetrating stripes as signatures of spinodal decomposition. At low inherent structure energy, the structure is largely phase separated with one interface where as at high inherent structure energy we find nucleation type growth. Interestingly, at low temperature, the average inherent structure energy () exhibits a drop with temperature which signals the onset of crystallization in one of the phases while the other remains in the liquid state. The nonideal composition dependence of viscosity is anticorrelated with average inherent structure energy.

  11. The role of Gauss curvature in a membrane phase separation problem

    NASA Astrophysics Data System (ADS)

    Gillmor, Susan; Lee, Jieun; Ren, Xiaofeng

    2011-12-01

    Consider a two-phase lipid vesicle. Below the transition temperature, the phases separate into non-connecting domains that coarsen into larger areas. The free energy of phase properties determines the length of the boundaries separating the regions. The two phases correspond to different lipid compositions, and in cells, this fluctuation in composition is a dynamic process vital to its function. We prove that a small patch of the minority lipids forms at a point of the membrane where the Gauss curvature attains a maximum. This patch has a round shape approximately and its boundary has a constant geodesic curvature. The proof consists of three steps. The construction of a family of good approximate solutions, an improvement of the approximate solutions so that their geodesic curvature is a constant modulo translation, and the identification of an exact solution from the family of the improved approximate solutions. Our theoretical results are supported by vesicle experiments.

  12. 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

  13. Phase Separation and Pair Condensation in a Spin-Imbalanced 2D Fermi Gas.

    PubMed

    Mitra, Debayan; Brown, Peter T; Schauß, Peter; Kondov, Stanimir S; Bakr, Waseem S

    2016-08-26

    We study a two-component quasi-two-dimensional Fermi gas with imbalanced spin populations. We probe the gas at different interaction strengths and polarizations by measuring the density of each spin component in the trap and the pair momentum distribution after time of flight. For a wide range of experimental parameters, we observe in-trap phase separation characterized by the appearance of a spin-balanced core surrounded by a polarized gas. Our momentum space measurements indicate pair condensation in the imbalanced gas even for large polarizations where phase separation vanishes, pointing to the presence of a polarized pair condensate. Our observation of zero momentum pair condensates in 2D spin-imbalanced gases opens the way to explorations of more exotic superfluid phases that occupy a large part of the phase diagram in lower dimensions. PMID:27610853

  14. Nonmagnetic Insulator State in Na1CoO2 and Phase Separation of Na Vacancies

    NASA Astrophysics Data System (ADS)

    de Vaulx, C.; Julien, M.-H.; Berthier, C.; Horvatić, M.; Bordet, P.; Simonet, V.; Chen, D. P.; Lin, C. T.

    2005-10-01

    Crystallographic, magnetic, and NMR properties of a NaxCoO2 single crystal with x≃1 are presented. We identify the stoichiometric Na1CoO2 phase, which is shown to be a nonmagnetic insulator, as expected for homogeneous planes of Co3+ ions with S=0. In addition, we present evidence that, because of slight average Na deficiency, chemical and electronic phase separation leads to a segregation of Na vacancies into the well-defined, magnetic, Na0.8CoO2 phase. The importance of phase separation is discussed in the context of magnetic order for x≃0.8 and the occurrence of a metal-insulator transition for x→1.

  15. Stress reduction in phase-separated, cross-linked networks: influence of phase structure and kinetics of reaction

    PubMed Central

    Szczepanski, Caroline R.; Stansbury, Jeffrey W.

    2014-01-01

    A mechanism for polymerization shrinkage and stress reduction was developed for heterogeneous networks formed via ambient, photo-initiated polymerization-induced phase separation (PIPS). The material system used consists of a bulk homopolymer matrix of triethylene glycol dimethacrylate (TEGDMA) modified with one of three non-reactive, linear prepolymers (poly-methyl, ethyl and butyl methacrylate). At higher prepolymer loading levels (10–20 wt%) an enhanced reduction in both shrinkage and polymerization stress is observed. The onset of gelation in these materials is delayed to a higher degree of methacrylate conversion (~15–25%), providing more time for phase structure evolution by thermodynamically driven monomer diffusion between immiscible phases prior to network macro-gelation. The resulting phase structure was probed by introducing a fluorescently tagged prepolymer into the matrix. The phase structure evolves from a dispersion of prepolymer at low loading levels to a fully co-continuous heterogeneous network at higher loadings. The bulk modulus in phase separated networks is equivalent or greater than that of poly(TEGDMA), despite a reduced polymerization rate and cross-link density in the prepolymer-rich domains. PMID:25418999

  16. Analysis of Phase Separation in High Performance PbTe–PbS Thermoelectric Materials

    SciTech Connect

    Girard, Steven N.; Schmidt-Rohr, Klaus; Chasapis, Thomas C.; Hatzikraniotis, Euripides; Njegic, B.; Levin, E. M.; Rawal, A.; Paraskevopoulos, Konstantios M.; Kanatzidis, Mercouri G.

    2013-02-11

    Phase immiscibility in PbTe–based thermoelectric materials is an effective means of top-down synthesis of nanostructured composites exhibiting low lattice thermal conductivities. PbTe1-x Sx thermoelectric materials can be synthesized as metastable solid solution alloys through rapid quenching. Subsequent post-annealing induces phase separation at the nanometer scale, producing nanostructures that increase phonon scattering and reduce lattice thermal conductivity. However, there has yet to be any study investigating in detail the local chemical structure of both the solid solution and nanostructured variants of this material system. Herein, quenched and annealed (i.e., solid solution and phase-separated) samples of PbTe–PbS are analyzed by in situ high-resolution synchrotron powder X-ray diffraction, solid-state 125Te nuclear magnetic resonance (NMR), and infrared (IR) spectroscopy analysis. For high concentrations of PbS in PbTe, e.g., x >16%, NMR and IR analyses reveal that rapidly quenched samples exhibit incipient phase separation that is not detected by state-of-the-art synchrotron X-ray diffraction, providing an example of a PbTe thermoelectric “alloy” that is in fact phase inhomogeneous. Thermally-induced PbS phase separation in PbTe–PbS occurs close to 200 °C for all compositions studied, and the solubility of the PbS phase in PbTe at elevated temperatures >500 °C is reported. The findings of this study suggest that there may be a large number of thermoelectric alloy systems that are phase inhomogeneous or nanostructured despite adherence to Vegard's Law of alloys, highlighting the importance of careful chemical characterization to differentiate between thermoelectric alloys and composites.

  17. Cell separation in immunoaffinity partition in aqueous polymer two-phase systems

    NASA Technical Reports Server (NTRS)

    Karr, Laurel J.; Van Alstine, James M.; Snyder, Robert S.; Shafer, Steven G.; Harris, J. Milton

    1989-01-01

    Two methods for immunoaffinity partitioning are described. One technique involves the covalent coupling of poly (ethylene glycol) (PEG) to immunoglobulin G antibody preparations. In the second method PEG-modified Protein A is used to complex with cells and unmodified antibody. The effects of PEG molecular weight, the degree of modification, and varying phase system composition on antibody activity and its affinity for the upper phase are studied. It is observed that both methods resulted in effective cell separation.

  18. Electrostatic interactions and aqueous two-phase separation modes of aqueous mixed oppositely charged surfactants system.

    PubMed

    Hao, Li-Sheng; Gui, Yuan-Xiang; Chen, Yan-Mei; He, Shao-Qing; Nan, Yan-Qing; You, Yi-Lan

    2012-08-30

    Electrostatic interactions play an important role in setting the aqueous two-phase separation behaviors of mixtures of oppositely charged surfactants. The aqueous mixture of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfonate (AS) is actually a five-component system, comprised of CTAB, AS, complex salt (cetyltrimethylammonium dodecylsulfonate, abbreviated as CTA(+)AS(-)), NaBr, and water. In the three-dimensional pyramid phase diagram, the aqueous two-phase region with excess AS or with excess CTAB extends successively from the region very near to the NaBr-H2O line through the CTAB-AS-H2O conventional mixing plane to the CTA(+)AS(-)-AS-H2O side plane or to the CTA(+)AS(-)-CTAB-H2O side plane, respectively. Large or small molar ratios between the counterions and their corresponding surfactant ions for oppositely charged surfactants located in the NaBr side or the CTA(+)AS(-) side of the pyramid imply strong or weak electrostatic screening. Electrostatic screening of counterions alters the electrostatic attractions between the oppositely charged head groups or the electrostatic repulsions between the like-charged head groups in excess, and the electrostatic free energy of aggregation thus affects the aqueous two-phase separation modes. Composition analysis, rheological property investigation, and TEM images suggest that there are two kinds of aqueous two-phase systems (ATPSs). On the basis of these experimental results and Kaler's cell model, two kinds of phase separation modes were proposed. Experimental results also indicate that all of the top phases are surfactant-rich, and all of the bottom phases are surfactant-poor; the density difference between the top phase and the bottom phase in one ATPS is very small; the interfacial tension (σ) of the ATPS is ultralow. PMID:22856887

  19. A Preliminary Assessment of Phase Separator Ground-Based and Reduced-Gravity Testing for ALS Systems

    NASA Technical Reports Server (NTRS)

    Hall, Nancy Rabel

    2006-01-01

    A viewgraph presentation of phase separator ground-based and reduced-gravity testing for Advanced Life Support (ALS) systems is shown. The topics include: 1) Multiphase Flow Technology Program; 2) Types of Separators; 3) MOBI Phase Separators; 4) Experiment set-up; and 5) Preliminary comparison/results.

  20. Separable phases of light-evoked depolarizations in the retina of Strombus.

    PubMed

    Quandt, F N; Gillary, H L

    1980-02-01

    The waveforms of light-evoked depolarizations in Strombus retinal neurones can exhibit two sequential peaks or phases, the relative amplitudes of which vary with changes in stimulus intensity and interstimulus interval. Experiments employing either the passage of constant intracellular current or voltage clamp techniques indicate that both phases reverse polarity at intracellular potentials less negative than the resting potential. The potential at which the first phase reverses its polarity is considerably more positive than that of the second phase. The results indicate that the light-evoked depolarizations are generated by at least two different processes; these appear to be separate conductance changes, neither of which is voltage dependent. Under certain conditions, the second phase was inhibited by high extracellular concentrations of Mg2+, indicating that it may arise as a result of chemically mediated synaptic transmission. The first phase did not show such inhibition and appears to be caused by the direct action of light on the cell. PMID:7365412

  1. Investigation of high velocity separator for particle removal in coal gasification plants. Phase II report

    SciTech Connect

    Linhardt, H.D.

    1980-01-15

    This report summarizes the results of Phase II of the High Velocity Particle Separator Program performed under Contract EF-77-C-01-2709. This high velocity wedge separator has the potential to reduce equipment size and cost of high temperature and pressurized particulate removal equipment for coal derived gases. Phase II has been directed toward testing and detailed conceptual design of an element suitable for a commercial scale high temperature, high pressure particle separator (HTPS). Concurrently, Phase IA has been conducted, which utilized the ambient analog method (AAM) for aerodynamic and collection performance investigation of each HTPS configuration prior and during hot testing. This report summarizes the results of Phase IA and II. The AAM effort established correlation of theoretical analysis and experiment for HTPS pressure drop, purge flow ratio and collection efficiency potential. Task I defined the initial test conditions to be the contract design point of 1800/sup 0/F and 350 psia. The 1800/sup 0/F, 350 psia testing represents the main high temperature testing with coal-derived particulates in the 2 to 10 micron range. Phase IA and Phase II have demonstrated efficient particle collection with acceptable pressure drop. In view of these encouraging results, it is reasonable to apply the developed technology toward future hot gas particulate cleanup requirements.

  2. Photopolymerization-induced crystallization and phase separation in poly(ethylene oxide)/triacrylate blends

    SciTech Connect

    Park, Soo Jeoung; Kyu, Thein

    2008-12-28

    The present article describes experimental and theoretical investigations of miscibility and crystallization behavior of blends of poly(ethylene oxide) (PEO) and triacrylate monomer (TA) using differential scanning calorimetry and optical microscopy. The PEO/TA blends manifested a single T{sub g} varying systematically with composition suggestive of a miscible character in their amorphous states. Moreover, there occurs melting point depression of PEO crystals with increasing TA. A phase diagram was subsequently established that exhibited a solid+liquid coexistence region bound by the liquidus and solidus lines, followed by an upper critical solution temperature (UCST) at a lower temperature. The emerging phase morphology was investigated to verify the coexistence regions. Upon photopolymerization in the isotropic melt above the melting point depression curve, both the UCST and the melting temperatures move upward and eventually surpass the reaction temperature, resulting in phase separation as well as crystallization of PEO driven by the changing supercooling, i.e., the thermodynamic driving force. Of particular interest is the interplay between photopolymerization-induced phase separation and crystallization, which eventually determines the final phase morphology of the PEO/TA blend such as crystalline lamellae, sheaf, or spherulites in isotropic liquid, phase separated domains, and viscous fingering liquids.

  3. 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.

  4. 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.

  5. Novel Approach for Developing Dual-Phase Ceramic Membranes for Oxygen Separation through Beneficial Phase Reaction.

    PubMed

    Zhang, Zhenbao; Zhou, Wei; Chen, Yubo; Chen, Dengjie; Chen, Jiawei; Liu, Shaomin; Jin, Wanqin; Shao, Zongping

    2015-10-21

    A novel method based on beneficial phase reaction for developing composite membranes with high oxygen permeation flux and favorable stability was proposed in this work. Various Ce0.8Sm0.2O2-δ (SDC) + SrCO3+Co3O4 powders with different SDC contents were successfully fabricated into membranes through high temperature phase reaction. The X-ray diffraction (XRD) measurements suggest that the solid-state reaction between the SDC, SrCO3 and Co3O4 oxides occurred at the temperature for membrane sintering, leading to the formation of a highly conductive tetragonal perovskite phase SmxSr1-xCoO3-δ. The morphology and elemental distribution of the dual-phase membranes were characterized using back scattered scanning electron microscopy and energy dispersive X-ray spectroscopy (BSEM-EDX). The oxygen bulk diffusivity and surface exchange properties of the materials were investigated via the electrical conductivity relaxation technique, which supported the formation of conductive phases. The SDC+20 wt % SrCO3+10.89 wt % Co3O4 membrane exhibited the highest permeation flux among the others, reaching 0.93 mL cm(-2) min(-1) [STP = standard temperature and pressure] under an air/helium gradient at 900 °C for a membrane with a thickness of 0.5 mm. In addition, the oxygen permeation flux remained stable during the long-time test. The results demonstrate the beneficial phase reaction as a practical method for the development of high-performance dual-phase ceramic membranes. PMID:26419767

  6. The use of aqueous PEG/dextran phase separation for the preparation of dextran microspheres.

    PubMed

    Stenekes, R J; Franssen, O; van Bommel, E M; Crommelin, D J; Hennink, W E

    1999-06-10

    A novel procedure to prepare dextran microspheres, without the use of organic solvents was developed. The method is based on phase separation which occurs in aqueous solutions of PEG and methacrylated dextran (dexMA). After stirring this two phase system a water-in-water emulsion is formed. When dexMA forms the discontinuous phase, dextran microspheres can be obtained by polymerization of the methacryloyl groups attached to dextran. The aim of this study was to gain insight into the formulation parameters that affect the particle characteristics. Therefore, it was necessary to establish dexMA/PEG/water phase diagrams. Lower polymer molecular weights and higher degrees of MA substitution resulted in less pronounced phase separation (binodal shifts to higher concentrations). The volume weight mean microsphere diameter varied between 2.5 and 20 microm, depending on the viscosities of both phases and the PEG/dexMA volume ratio. A more viscous continuous phase and/or a less viscous discontinuous phase resulted in smaller microspheres. Furthermore, the particle size increased with decreasing PEG/dexMA volume ratios. The particle characteristics, like cross-link density, initial water content and size can be tailored by adjusting the formulation parameters. PMID:10361149

  7. Understanding the mechanism of LCST phase separation of mixed ionic liquids in water by MD simulations.

    PubMed

    Zhao, Yuling; Wang, Huiyong; Pei, Yuanchao; Liu, Zhiping; Wang, Jianji

    2016-08-17

    Recently, it has been found experimentally that two different amino acid ionic liquids (ILs) can be mixed to show unique lowest critical solution temperature (LCST) phase separation in water. However, little is known about the mechanism of phase separation in these IL/water mixtures at the molecular level. In this work, five kinds of amino acid ILs were chosen to study the mechanism of LCST-type phase separation by molecular dynamics (MD) simulations. Toward this end, a series of all-atom MD simulations were carried out on the ternary mixtures consisting of two different ILs and water at different temperatures. The various interaction energies and radial distribution functions (RDFs) were calculated and analyzed for these mixed systems. It was found that for amino acid ILs, the -NH2 or -COOH group of one anion could have a hydrogen bonding interaction with the -COO(-) group of another anion. With the increase of temperature, this kind of hydrogen bonding interaction between anions was strengthened and then the anion-H2O electrostatic interaction was weakened, which led to the LCST-type phase separation of the mixed ILs in water. In addition, a series of MD simulations for [P6668]1[Lys]n[Asp]1-n/H2O systems were also performed to study the effect of the mixing ratio of ILs on phase separation. It was also noted that the experimental critical composition corresponding to the lowest critical solution temperature was well predicted from the total electrostatic interaction energies as a function of mole fraction of [P6668][Lys] in these systems. The conclusions drawn from this study may provide new insight into the LCST-type phase behavior of ILs in water, and motivate further studies on practical applications. PMID:27498928

  8. Numerical simulation of gas-solid two-phase flow in U-beam separator

    NASA Astrophysics Data System (ADS)

    Zhou, X. Y.; Zhang, H. Z.; Chen, X. P.; Ruan, J. M.; Dou, H. S.

    2015-01-01

    Numerical simulation is carried out for gas-solid two-phase flow in a U-beam separator. In this study, the U-beam is altered with the inlet fins in order to improve the performance of the separator. The inlet fin angle of the separator are 30°, 35°, 40°, 45°, 50°, 55 ° and 60°. The governing equations are the Reynolds-Averaged Navier-Stokes equation with the standard k-epsilon model and the discrete phase model (DPM) describing the discrete two - phase flow as well as stochastic tracking model. Results show that the pressure drop deviation with fins is within 3% from those without fins. It is found that there is a maximum separation efficiency at the fin angle of 35°. Fin induces generation of a stagnation region which could collect particles and lead to change of vortical structures. The fin induced flow also causes the turbulent intensity inside the baffle to decrease to facilitate separation.

  9. Size-exclusion capillary electrochromatographic separation of polysaccharides using polymeric stationary phases.

    PubMed

    Mistry, Kavita; Krull, Ira; Grinberg, Nelu

    2003-06-01

    We report the successful size-based separations of large, neutral polysaccharides using capillary electrochromatography (CEC). As the polysaccharides possessed little chromophore for photometric detection, two separate approaches were taken. In the first approach, indirect detection was combined with size-exclusion chromatography using a sulfonated polystyrene/divinylbenzene stationary phase. The separations were performed using a 300 A pore size stationary phase under aqueous conditions. Non-size based interactions were minimal using this material, resulting in an effective calibration range of molecular masses 180 to 112 000 g.mol(-1) for pullulans. In the second approach, the polysaccharides were derivatized with phenylisocyanate and were subsequently separated on columns made using a combination of high capacity ion-exchanger and a neutral polystyrene/divinylbenzene material of various pore sizes. The sulfonated ion-exchange phase provided the electroosmotic flow, while the mixed pore size material provided the extended calibration range. The linear range for this primarily nonaqueous system using tetrahydrofuran was determined to be from molecular masses 738 to 404 000 g.mol(-1) of the original, untagged pullulan. This approach overcame the limited solubility issue associated with analysis of some polysaccharides. Analysis of pullulan and amylose samples by CEC correlated well with results obtained by conventional high-performance liquid chromatography (HPLC). The size-exclusion electrochromatographic separations provide an alternative mode for determining the relative molecular weights of polysaccharides with reduced sample and solvent consumption, as well as analysis times. PMID:12783452

  10. Immobilization and recovery of thorium, a neptunium surrogate, using phase-separated glasses

    SciTech Connect

    Meaker, T.F.; Karraker, D.; Tosten, M.; Pareizs, J.M.; Ramsey, W.G.

    1997-12-31

    The Savannah River Site has the majority of the United States` supply of neptunium currently stored in an acid solution in one of their canyon facilities. A program is being developed that could be utilized to ship this material, as glass, to Oak Ridge National Laboratory where the Np could be leached from the glass, purified by ion exchange and made into target material for the production of Pu-238. Ion exchange purification dictates no material be in the leachate making the isolation of the Np difficult. The authors have developed a process using thorium as a surrogate for Np that could immobilize the Np into a soda borosilicate glass for shipment. To achieve recovery of the Np, the glass can be phase separated prior to leaching with nitric acid. Phase separation would produce a Np-rich sodium-borate phase and a Si-rich phase similar to a Vycor{reg_sign} glass. The nitric acid selectively attacks the sodium-borate phase allowing high Np recovery in a solution that contains only sodium and boron. These can be easily separated from Np by ion exchange. Essentially all of the silicon which would interfere with ion exchange by precipitation is retained in the Vycor{reg_sign}-type phase. This technology may also be applied to other actinides stored in relatively pure solutions. This paper will report the optimization of variables for maximizing Th (a Np surrogate) recovery while minimizing Si release. Th solubility in glass, heat treatment conditions and leaching parameters will be discussed. Transmission Electron Microscopy (TEM) with energy dispersive spectroscopy (EDS) data will be included to show phase separation after heat treatment.

  11. A Classroom Demonstration of Water-Induced Phase Separation of Alcohol-Gasoline Biofuel Blends

    ERIC Educational Resources Information Center

    Mueller, Sherry A.; Anderson, James E.; Wallington, Timothy J.

    2009-01-01

    A significant issue associated with ethanol-gasoline blends is the phase separation that occurs with the addition of small volumes of water, producing an ethanol-deficient gasoline layer and an ethanol-rich aqueous layer. The gasoline layer may have a lower-than-desired octane rating due to the decrease in ethanol content, resulting in engine…

  12. Formation and Maturation of Phase-Separated Liquid Droplets by RNA-Binding Proteins.

    PubMed

    Lin, Yuan; Protter, David S W; Rosen, Michael K; Parker, Roy

    2015-10-15

    Eukaryotic cells possess numerous dynamic membrane-less organelles, RNP granules, enriched in RNA and RNA-binding proteins containing disordered regions. We demonstrate that the disordered regions of key RNP granule components and the full-length granule protein hnRNPA1 can phase separate in vitro, producing dynamic liquid droplets. Phase separation is promoted by low salt concentrations or RNA. Over time, the droplets mature to more stable states, as assessed by slowed fluorescence recovery after photobleaching and resistance to salt. Maturation often coincides with formation of fibrous structures. Different disordered domains can co-assemble into phase-separated droplets. These biophysical properties demonstrate a plausible mechanism by which interactions between disordered regions, coupled with RNA binding, could contribute to RNP granule assembly in vivo through promoting phase separation. Progression from dynamic liquids to stable fibers may be regulated to produce cellular structures with diverse physiochemical properties and functions. Misregulation could contribute to diseases involving aberrant RNA granules. PMID:26412307

  13. Realization of a universal and phase-covariant quantum cloning machine in separate cavities

    SciTech Connect

    Fang Baolong; Song Qingming; Ye Liu

    2011-04-15

    We present a scheme to realize a special quantum cloning machine in separate cavities. The quantum cloning machine can copy the quantum information from a photon pulse to two distant atoms. Choosing the different parameters, the method can perform optimal symmetric (asymmetric) universal quantum cloning and optimal symmetric (asymmetric) phase-covariant cloning.

  14. Twentieth international symposium on electro- and liquid-phase separation techniques (ITP2013): highlights.

    PubMed

    Cifuentes, Alejandro; Hernández-Borges, Javier

    2014-01-01

    The 20th edition of the International Symposium on Electro- and Liquid-Phase Separation Techniques (ITP2013) took place on October 6-9, 2013, at Puerto de la Cruz in Tenerife, Canary Islands (Spain). This article reviews the highlights of this new edition of the symposia, also including the different activities that took place as well as the awards presented. PMID:24339404

  15. Influence of filler particle and clusters on phase separation in binary polymer blends

    SciTech Connect

    Jiang, Yi; Saxena, A. B.; Lookman, T.; Douglas, J. F.

    2001-01-01

    Polymer materials are rarely used in their pure form in applications. They are often filled with additives that improve their processability and mechanical or electrical properties. An understanding of the polymer-filler interaction and the ramifications for the properties of filled polymer blends is a matter of significant practical interest. Phase separation plays an important role in determining the morphology and properties of filled polymer composites, which usually are a blend of various macromolecular fluids, and additive particles. Despite the wide application of these blends, the development and the stability of the phase separating morphology are not fully understood. In particular, the interference of the filler induced composition waves remains unexplored. The presence of a surface induces a composition wave, which consists of stripes parallel to the surface and only exists close to the surface. The morphologies in the bulk take form of the characteristic spinodal decomposition patterns, i.e. the convoluted stripes. This surface directed phase separation has been studied both theoretically and experimentally. Recent numerical results show that an immobile spherical filler particle introduces transient target patterns in two-dimensional polymer thin films, and experimental results have confirmed the observations. The authors report simulation results of the effect of filler geometry on phase separation morphology, focusing on the interference of the composition waves on the stability of two-dimensional polymer blends (polymer thin films).

  16. Simplified thermodynamic functions for vapor-liquid phase separation and fountain effect pumps

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    He-4 fluid handling devices near 2 K require novel components for non-Newtonian fluid transport in He II. Related sizing of devices has to be based on appropriate thermophysical property functions. The present paper presents simplified equilibrium state functions for porous media components which serve as vapor-liquid phase separators and fountain effect pumps.

  17. The question of dispersive kinetics for the initial phase of charge separation in bacterial reaction centers

    SciTech Connect

    Small, G.J.; Hayes, J.M.; Silbey, R.J.

    1992-09-17

    Recently, femtosecond time domain data have raised the possibility that the kinetics of the initial phase of charge separation could be dispersive due to the glasslike structural heterogeneity of proteins. Guided by spectral hole burning data, we have derived simple theoretical rate expressions which allow the question posed in the title to be explored. 27 refs., 1 fig., 2 tabs.

  18. Phase separation and direct magnetocaloric effect in La0.5Ca0.5MnO3 manganite

    NASA Astrophysics Data System (ADS)

    Amirzadeh, P.; Ahmadvand, H.; Kameli, P.; Aslibeiki, B.; Salamati, H.; Gamzatov, A. G.; Aliev, A. M.; Kamilov, I. K.

    2013-03-01

    A series of phase separated La0.5Ca0.5MnO3 manganite samples with different grain sizes were studied by ac susceptibility, direct magnetocaloric effect (ΔT), and heat capacity measurements. The ac susceptibility shows that fractions of ferromagnetic and antiferromagnetic phases and consequently the phase separated state can be controlled by means of sintering temperature. Lower sintering temperature leads to a ferromagnetic state, while higher sintering temperature increases antiferromagnetic phase fraction, resulting in a phase separated state. In the phase separated samples, ΔT shows a conventional positive peak near TC and an anomalous positive peak at lower temperature near TN. The anomalous positive peak appears at higher magnetic field and is accompanied with thermal hysteresis. It is suggested that the anomalous magnetocaloric behaviors result from phase separation and first order magnetostructural phase transition. This study shows that direct magnetocaloric effect is a useful technique for the study of manganites.

  19. Advanced flight hardware for organic separations using aqueous two-phase partitioning

    NASA Astrophysics Data System (ADS)

    Deuser, Mark S.; Vellinger, John C.; Weber, John T.

    1996-03-01

    Separation of cells and cell components is the limiting factor in many biomedical research and pharmaceutical development processes. Aqueous Two-Phase Partitioning (ATPP) is a unique separation technique which allows purification and classification of biological materials. SHOT has employed the ATPP process in separation equipment developed for both space and ground applications. Initial equipment development and research focused on the ORganic SEParation (ORSEP) space flight experiments that were performed on suborbital rockets and the shuttle. ADvanced SEParations (ADSEP) technology was developed as the next generation of ORSEP equipment through a NASA Small Business Innovation Research (SBIR) contract. Under the SBIR contract, a marketing study was conducted, indicating a growing commercial market exists among biotechnology firms for ADSEP equipment and associated flight research and development services. SHOT is preparing to begin manufacturing and marketing laboratory versions of the ADSEP hardware for the ground-based market. In addition, through a self-financed SBIR Phase III effort, SHOT is fabricating and integrating the ADSEP flight hardware for a commercially-driven SPACEHAB 04 experiment that will be the initial step in marketing space separations services. The ADSEP ground-based and microgravity research is expected to play a vital role in developing important new biomedical and pharmaceutical products.

  20. He II Liquid/Vapor Phase Separator for Large Dynamic Range Operation

    NASA Technical Reports Server (NTRS)

    Nakano, A.; Petrac, D.

    1995-01-01

    A phase separator, which separates helium vapor from liquid superfluid helium (He II), is an indispensable device for space cryogenics. The most recent approach to the Space Infrared Telescope Facility (SIRTF) uses a new design concept in which only the detector package is cold at launch, the remainder of the telescope being subsequently cooled to operating temperature on orbit. Therefore, a large dynamic operational range is required of the cryogen system. This is a report of initial laboratory test results with candidate porous plugs as phase separators. Mass flow rates and pressure and temperature differences across a porous plug were measured in this experiment. Relatively large mass flow rates were observed even at small pressure differences. In the high mass flow rate region, a hysteresis was observed with increases and decreases of the pressure difference. A linear theory is proposed and compared with experimental data to explain several phenomena observed in this system.

  1. Development of experiment and theory to detect and predict ligand phase separation on silver nanoparticles.

    PubMed

    Farrell, Zachary; Merz, Steve; Seager, Jon; Dunn, Caroline; Egorov, Sergei; Green, David L

    2015-05-26

    MALDI mass-spectrometry measurements are combined with self-consistent mean-field (SCF) calculations to detect and predict ligand phase separation on Ag nanoparticles. The experimental and theoretical techniques complement each other by enabling quantification of the nearest-neighbor distribution of a ligand mixture in a monolayer shell. By tracking a characteristic metallic fragment family, analysis of a MALDI spectrum produces a frequency distribution corresponding to specific ligand patterning. Inherent to the SCF calculation is the enumeration of local interactions that dictate ligand assembly. Interweaving MALDI and SCF facilitates a comparison between the experimentally and theoretically derived frequency distributions as well as their deviation from a well-mixed state. Thus, we combine these techniques to detect and predict phase separation in monolayers that mix uniformly or experience varying degrees of de-mixing, including microphase separation and stripe formation. Definition of MALDI removed as this is a commonly recognized technique. PMID:25882701

  2. Confined phase separation in SiO{sub X} nanometric thin layers

    SciTech Connect

    Roussel, M.; Talbot, E.; Pareige, C.; Pareige, P.; Pratibha Nalini, R.; Gourbilleau, F.

    2013-11-11

    Phase separation in silicon-rich silica/silica multilayers was investigated using Atom Probe Tomography and Atomistic Kinetic Monte Carlo simulation. It is shown that the thickness of silicon-rich silicon oxide sublayers plays an important role during phase transformation. It determines the morphology of Si-rich phase formed after subsequent annealing, which is of prime interest for microelectronic and optoelectronic applications. Monte Carlo simulation reveals that the formation of isolated Si clusters can be achieved even in the case of spinodal decomposition and is directly related to the ratio between the spinodal wavelength and the sublayer thickness.

  3. Phase Separation on Bicontinuous Cubic Membranes: Symmetry Breaking, Reentrant, and Domain Faceting.

    PubMed

    Paillusson, Fabien; Pennington, Matthew R; Kusumaatmaja, Halim

    2016-07-29

    We study the phase separation of binary lipid mixtures that form bicontinuous cubic phases. The competition between the nonuniform Gaussian membrane curvature and line tension leads to a very rich phase diagram, where we observe symmetry breaking of the membrane morphologies and reentrant phenomena due to the formation of bridges between segregated domains. Upon increasing the line tension contribution, we also find faceting of lipid domains that we explain using a simple argument based on the symmetry of the underlying surface and topology. PMID:27517794

  4. Chromatographic separation of phenylpropanol enantiomers on a quinidine carbamate-type chiral stationary phase

    SciTech Connect

    Asnin, Leonid; Guiochon, Georges A

    2005-07-01

    The retention and the separation of the enantiomers of 1-phenylpropanol (1PP), 2-phenylpropanol (2PP), and 3-chloro-1-phenylpropanol (3CPP) on silica-bonded quinidine carbamate under normal phase HPLC conditions were investigated. A relatively high selectivity of the stationary phase for 3CPP and 1PP ({alpha} {approx} 1.07-1.09) was achieved with eluents containing ethyl acetate as the polar modifier. These mobile phases were examined in detail. Based on the set of chromatographic and thermodynamic data collected, conclusions regarding the mechanism of enantioselectivity and the structure of the selector chiral center are made.

  5. [Separation of bases, phenols and pharmaceuticals on ionic liquid-modified silica stationary phase with pure water as mobile phase].

    PubMed

    Wang, Xusheng; Qiu, Hongdeng; Liu, Xia; Jiang, Shengxiang

    2011-03-01

    N-methylimidazolium ionic liquid (IL) -modified silica was prepared with the reaction of 3-chloropropyl modified silica and N-methylimidazole using toluene as solvent. Based on the multiple interactions between N-methylimidazolium IL-modified silica and analytes such as hydrophobic interaction, electrostatic attraction, repulsion interaction, hydrogen-bonding, etc., the bases (cytosine, thymine, 2-aminopyrimidine and 6-chloroguanine), phenols (m-aminophenol, resorcinol and m-nitrophenol) and three pharmaceuticals (moroxydine hydrochloride, acyclovir and cephalexin hydrate) were separated successfully with only pure water as the mobile phase. These chromatographic separations are environmental friendly, economical and convenient, without any organic solvent or buffer additive. The retention mechanism of these samples on the stationary phase was also investigated. PMID:21657060

  6. Slow Phase Separation in Mixed Columnar Phases of NanoDNA and Chromonic Dye

    NASA Astrophysics Data System (ADS)

    Smith, Gregory; Yi, Youngwoo; Walba, David; Clark, Noel

    2014-03-01

    The architecture of a DNA duplex with its externally exposed charged phosphate backbone and internally hidden aromatic bases, hydrophobically stacked at a spacing of 3.4 Å, is strikingly similar to aggregates of Liquid Crystal (LC) forming chromonic dyes such as Sunset Yellow (SSY). One might naturally question whether a DNA-like molecular column can be assembled from a subunit resembling a chromonic dye. Because little is known about direct mixtures of chromonics with DNA and how such a mixture might form mixed LC phases, we mixed blunt-end 12mer NanoDNA (GCGCTTAAGCGC) with SSY, both of these molecular species independently having well-described LC behavior. Observed mixtures are remarkably miscible, exhibiting a mixed chiral nematic phase with Grandjean texture that is distinct from SSY and DNA nematic forms. On transition to the columnar phase when the molecular species fractions are very close in proportion (about 1:1.3 DNA:SSY by weight) the columnar phase exhibits a slow but thermally reversible demixing to produce a striated texture whose assembly is guided by the columnar director structure. Grant support: NSF DRM 1207606 and NSF MRSEC DRM 0820579.

  7. Test Plan for Effect of Phase Separation on Optimization of Waste Loading in High-Level Waste

    SciTech Connect

    Jantzen, C.M.

    1999-10-04

    Several types of phase transformations can occur in glass. The most commonly occurring phase transformations are crystallization and/or liquid-liquid phase separation. Crystallization is the growth of a crystalline phase(s) which may or may not have the same composition as the original liquid.

  8. Direct Observation of Smectic Layers in Thermotropic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Gao, M.; Diorio, N.; Weissflog, W.; Baumeister, U.; Sprunt, S.; Gleeson, J. T.; Jákli, A.

    2012-09-01

    We demonstrate subnanometer resolution cryo-TEM imaging of smectic layers in the smectic and nematic phases of two bent-core liquid crystals. Our results show perfect periodicity over several hundred layers in the smectic phase and also provide the first direct evidence of smectic clusters on length scales of 30-50 nm in a nematic liquid crystal. The results are corroborated with small angle x-ray scattering measurements. The observation of smectic clusters in the nematic phase is of special interest in bent-core liquid crystals, where the smectic clusters are stable over wide temperature ranges, in contrast to the well-known pretransitional “cybotactic” clusters that appear only in the vicinity of a bulk smectic phase. The means to characterize and manipulate this nanoscale molecular order could open up completely new liquid crystal-based technologies.

  9. PHASE SEPARATION IN PM 2000 FE-BASE ODS ALLOY: EXPERIMENTAL STUDY AT THE ATOMIC LEVEL

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Russell, Kaye F; Chao, J.; Gonzalez-Carrasco, J. L.

    2008-01-01

    The coarsening of the three-dimensional microstructure resulting from phase separation during ageing at 748 K of a Fe-based PM 2000{trademark} oxide dispersion strengthened (ODS) steel has been investigated by atom probe tomography and hardness measurements. Phase separation resulted in the formation of isolated particles of the chromium-enriched {alpha}{prime} phase. The aluminum and titanium were found to preferential partition to the iron-rich {alpha} phase. The partitioning of aluminum is consistent with theoretical calculations. The change in the scale of the chromium-enriched {alpha}{prime} phase was found to fit a power law with a time exponent of 0.32 in accordance with that predicted by the classical Lifshitz, Slyozov and Wagner (LSW) theory. The solute concentrations of the coexisting {alpha} and {alpha}{prime} phases were estimated from concentration frequency distributions with the Langer-Bar-on-Miller (LBM) method and proximity histograms. The hardness was linearly related to the chromium content of the {alpha}{prime} phase.

  10. Homogeneous, single-phase hydroformylation of olefins using ionic phosphines and novel catalyst/product separation

    SciTech Connect

    Abatjoglou, A.G.; Peterson, R.R.; Bryant, D.R.

    1995-12-01

    A high efficiency low pressure hydroformylation process for higher molecular weight olefins has been developed using rhodium/ionic phosphine catalyst. Catalyst solubilization in the non-polar reactants and products is achieved using specialized solubilizing agents, such as N-methyl pyrrolidone (NMP), yielding single-phase systems. Separation of catalyst from product is induced by the addition of small amounts of water outside the hydroformylation reactor. Under the two-phase conditions, most of the catalyst components are found in the polar NMP/water phase, and the products (aldehydes, olefins, reaction byproducts) in a separate, non-polar, phase. The catalyst phase is recycled to the reactors after thorough drying to ensure a single homogeneous phase at reaction conditions. Traces of catalyst and solubilizing agent are effectively recovered from the product and recycled. A major advantage of this process, over water-based two-phase systems, is the high catalytic reactivities and concomitant high olefin efficiencies (>90%) which are achieved with olefins of low, water solubility.

  11. Formation of Asymmetrical Structured Silica Controlled by a Phase Separation Process and Implication for Biosilicification

    PubMed Central

    Shi, Jia-Yuan; Yao, Qi-Zhi; Li, Xi-Ming; Zhou, Gen-Tao; Fu, Sheng-Quan

    2013-01-01

    Biogenetic silica displays intricate patterns assembling from nano- to microsize level and interesting non-spherical structures differentiating in specific directions. Several model systems have been proposed to explain the formation of biosilica nanostructures. Of them, phase separation based on the physicochemical properties of organic amines was considered to be responsible for the pattern formation of biosilica. In this paper, using tetraethyl orthosilicate (TEOS, Si(OCH2CH3)4) as silica precursor, phospholipid (PL) and dodecylamine (DA) were introduced to initiate phase separation of organic components and influence silica precipitation. Morphology, structure and composition of the mineralized products were characterized using a range of techniques including field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), infrared spectra (IR), and nitrogen physisorption. The results demonstrate that the phase separation process of the organic components leads to the formation of asymmetrically non-spherical silica structures, and the aspect ratios of the asymmetrical structures can be well controlled by varying the concentration of PL and DA. On the basis of the time-dependent experiments, a tentative mechanism is also proposed to illustrate the asymmetrical morphogenesis. Therefore, our results imply that in addition to explaining the hierarchical porous nanopatterning of biosilica, the phase separation process may also be responsible for the growth differentiation of siliceous structures in specific directions. Because organic amine (e.g., long-chair polyamines), phospholipids (e.g., silicalemma) and the phase separation process are associated with the biosilicification of diatoms, our results may provide a new insight into the mechanism of biosilicification. PMID:23585878

  12. Formation of asymmetrical structured silica controlled by a phase separation process and implication for biosilicification.

    PubMed

    Shi, Jia-Yuan; Yao, Qi-Zhi; Li, Xi-Ming; Zhou, Gen-Tao; Fu, Sheng-Quan

    2013-01-01

    Biogenetic silica displays intricate patterns assembling from nano- to microsize level and interesting non-spherical structures differentiating in specific directions. Several model systems have been proposed to explain the formation of biosilica nanostructures. Of them, phase separation based on the physicochemical properties of organic amines was considered to be responsible for the pattern formation of biosilica. In this paper, using tetraethyl orthosilicate (TEOS, Si(OCH2CH3)4) as silica precursor, phospholipid (PL) and dodecylamine (DA) were introduced to initiate phase separation of organic components and influence silica precipitation. Morphology, structure and composition of the mineralized products were characterized using a range of techniques including field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), infrared spectra (IR), and nitrogen physisorption. The results demonstrate that the phase separation process of the organic components leads to the formation of asymmetrically non-spherical silica structures, and the aspect ratios of the asymmetrical structures can be well controlled by varying the concentration of PL and DA. On the basis of the time-dependent experiments, a tentative mechanism is also proposed to illustrate the asymmetrical morphogenesis. Therefore, our results imply that in addition to explaining the hierarchical porous nanopatterning of biosilica, the phase separation process may also be responsible for the growth differentiation of siliceous structures in specific directions. Because organic amine (e.g., long-chair polyamines), phospholipids (e.g., silicalemma) and the phase separation process are associated with the biosilicification of diatoms, our results may provide a new insight into the mechanism of biosilicification. PMID:23585878

  13. Phase separation of polymer mixtures induced by light and heat: a comparative study by light scattering

    NASA Astrophysics Data System (ADS)

    Ochi, Yuki; Kawakubo, Rie; Van-Pham, Dan-Thuy; Kitamura, Yuki; Nakanishi, Hideyuki; Norisuye, Tomohisa; Tran-Cong-Miyata, Qui

    2015-12-01

    Phase separation of binary blends composed of a polystyrene derivative (PS) and poly (vinyl methyl ether) (PVME) with a lower critical solution temperature (LCST) was experimentally induced by two different methods: heating and UV light irradiation. Using laser light scattering combined with the temperature jump (T-jump) technique, it was demonstrated that in the case of heating, the mixture undergoes phase separation via the nucleation-and-growth (NG) and the spinodal decomposition (SN) processes under shallow and deep quenches, respectively. Particularly, the crossover from the spinodal decomposition to the nucleation-and-growth process was observed at long time under a deep T-jump by light-scattering experiments. On the other hand, in the photo-crosslink case, the PS/PVME blends undergo a nucleation-and-growth process upon irradiation with weak light intensity, whereas the mixture exhibits the spinodal decomposition under irradiation with strong light intensity. From the analysis of the light-scattering data obtained for the blends under the photo-crosslink, the kinetic data reveal the suppression of morphologies having large characteristic length scales. This feature clearly differs from the phase separation induced by heating where no mode-suppression process was observed. It was also found that distribution of the characteristic length scales (the regularity) of the morphology becomes narrow as the phase separation proceeds for reacting blends, whereas it becomes broader as the phase separation proceeds by heating, revealing the important roles of reaction in the suppression of fluctuations with long wavelengths. These experimental results establish a method to control the length scales and the regularity of the morphology of polymer blends by chemical reaction.

  14. Asymmetrical phase separation and gelation in binary mixtures of oppositely charged colloids

    NASA Astrophysics Data System (ADS)

    Zong, Yiwu; Yuan, Guangcui; Han, Charles C.

    2016-07-01

    Two types of colloidal particles, which are nearly the same in chemical composition but carry opposite surface charges, are mixed in water. Depending on the relative proportion of the oppositely charged particles, the process of aggregation leads to the formation of discrete clusters of various sizes in dilute dispersions, and to the development of particle gel networks in more concentrated systems. Due to the significant difference in the absolute values of surface charges (negative particle: -48 mV, positive particle: +24 mV), the phase separation and the gelation behaviors are asymmetric with respect to the mixing ratio. Mixtures with excess negative particles are more stable, while mixtures with excess positive particles are easily affected by phase separation. The hetero-aggregation triggered by the addition of microscopically large macro-ions is similar to what is often observed in a mono-component charged colloidal system, i.e., phase separation occurs through addition of small electrolyte ions. Within the concentration region investigated here, it is clear that the gel line is buried inside the phase separation region. Gelation occurs only when the number and size of the clusters are large and big enough to connect up into a space-spanning network. Our results indicate that, in this binary mixture of oppositely charged colloids, although the interaction between unlike species is attractive and that between like species is repulsive, the onset of gelation is in fact governed by the equilibrium phase separation, as in the case of purely attractive systems with short-range isotropic interaction.

  15. Phase Separation Dynamics of Polymer Blend Films Containing Polymer-Grafted Nanoparticles

    NASA Astrophysics Data System (ADS)

    Chung, H.-J.; Ohno, K.

    2005-03-01

    Polymer blends containing nanoparticles (NP) are important in advanced technologies including opto-electronic and biosensor devices. Upon adding methyl-terminated silica NP's [22nm (NPA)] at dilute concentrations, PMMA:SAN (50:50) films (650nm) undergo early, intermediate and late stages of morphology development, similar to a PMMA:SAN film (Wang & Composto, JCP (2000)). NP's partition into the PMMA-rich phase, and slow down the kinetics of domain growth. This result is consistent with a coalescence model that predicts ξ˜ (1 / η)^1/3 t^1/3, where ξ and η are the correlation length and PMMA viscosity, respectively (Chung et al., EPL (2004)). Although the bulk η agrees with this model, a microscopic understanding of the phase separation mechanism requires knowledge of polymer-NP and NP-NP interactions. To address this issue, well-characterized silica NP's (15 nm) with densely grafted PMMA [Mw = 1.8K (NPB) and 21K (NPC)] are employed as non-interacting fillers in the PMMA-rich phase. The impact of PMMA-grafted NP on the phase separation dynamics in films, as well as the rheology of PMMA/NP composites, is investigated. Specifically, phase separation was slowest for NPB relative to films containing NPA and NPC. These studies show that wetting and domain coarsening in polymer blend films can be controlled by the judicial addition of surface modified NP.

  16. Lateral phase separation of mixed polymer brushes on planar and spherical surfaces

    NASA Astrophysics Data System (ADS)

    van Lehn, Reid; Alexander-Katz, Alfredo

    2012-02-01

    A mixed polymer brush consists of two (or more) polymer species grafted to a surface at a high density, inducing the polymers to highly stretch to maximize favorable solvent interactions while minimizing polymer overlap. The enthalpic and entropic interactions between the different polymers give rise to lateral phase behavior on the surface. Understanding this phase separation behavior is interesting for applications in nanotemplating and controlled protein adsorption. In this work, we present a novel theoretical model to quickly predict lateral phase separated morphologies of mixed polymer brushes on planar, cylindrical and spherical surfaces. The model combines a Flory-Huggins model for enthalpic interactions between the polymer components with an Alexander-de Gennes model for the entropy of the brush layers. When there is a length difference between the polymer components, these two interactions along with the conformational entropy of the system lead to a range of morphologies including stripes, dimples, mixing, and complete phase separation. The computational efficiency of this model allows for phase diagrams to be generated with great accuracy. The results of our model thus allow for the fast prediction of lateral morphologies on different geometries.

  17. Phase separation in lead zirconate titanate and bismuth titanate during electrical shorting and fatigue

    NASA Astrophysics Data System (ADS)

    Lou, Xiaojie; Hu, Xiaobing; Zhang, Ming; Morrison, F. D.; Redfern, S. A. T.; Scott, J. F.

    2006-02-01

    Micro-Raman and electron microprobe techniques are used to show that lead zirconate titanate and samarium-doped bismuth titanate undergo local phase transformations and separation during electrical shorting and in the dendritic precursors to microshorts caused by bipolar fatigue. These precursors for shorts, consisting of dark filaments, were studied just before they completely shorted the sample. The aim of the study was to compare electrical breakdown and breakdown precursors in ABO3 perovskite oxides and related Aurivillius phase layer structures with Bi (A site) substitution and with B-site substitution (e.g., Ti for Zr in PZT). The observation of phase separation and decomposition is related to congruent and incongruent meltings in these materials. Dendritelike shorts and short precursors of a few microns in diameter, produced by extreme bipolar voltage cycling fatigue, are mapped spectroscopically in 1 μm2 areas and exhibit almost pure regions of α-PbO, β-PbO, and rutile TiO2. The α-β PbO phase boundary runs from 500 °C at 1 atm to room temperature at 0.4 GPa, easily accessible temperatures and pressures in the dynamical process. Similarly, under large dc voltages the Sm-doped bismuth titanate transforms from a layered-perovskite structure to a pyrochlore structure during filamentary electrical breakdown, with the loss of Bi. The interfacial phase separation has been attributed to the combination of defect aggregation and thermal decomposition effects.

  18. Extraordinary phase separation and segregation in vent fluids from the southern East Pacific Rise

    USGS Publications Warehouse

    Von Damm, K. L.; Lilley, M.D.; Shanks, Wayne C.; Brockington, M.; Bray, A.M.; O'Grady, K. M.; Olson, E.; Graham, A.; Proskurowski, G.

    2003-01-01

    The discovery of Brandon vent on the southern East Pacific Rise is providing new insights into the controls on midocean ridge hydrothermal vent fluid chemistry. The physical conditions at the time ofsampling (287 bar and 405??C) place the Brandon fluids very close to the critical point of seawater (298 bar and 407??C). This permits in situ study of the effects of near criticalphenomena, which are interpreted to be the primary cause of enhanced transition metal transport in these fluids. Of the five orifices on Brandon sampled, three were venting fluids with less than seawater chlorinity, and two were venting fluids with greater than seawater chlorinity. The liquid phase orifices contain 1.6-1.9 times the chloride content of the vapors. Most other elements, excluding the gases, have this same ratio demonstrating the conservative nature of phase separation and the lack of subsequent water-rock interaction. The vapor and liquid phases vent at the same time from orifices within meters of each other on the Brandon structure. Variations in fluid compositions occur on a time scale of minutes. Our interpretation is that phase separation and segregation must be occurring 'real time' within the sulfide structure itself. Fluids from Brandon therefore provide an unique opportunity to understand in situ phase separation without the overprinting of continued water-rock interaction with the oceanic crust, as well as critical phenomena. ?? 2002 Elsevier Science B.V. All rights reserved.

  19. Phase separation of electrons strongly coupled with phonons in cuprates and manganites

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sasha

    2009-03-01

    Recent advanced Monte Carlo simulations have not found superconductivity and phase separation in the Hubbard model with on-site repulsive electron-electron correlations. I argue that microscopic phase separations in cuprate superconductors and colossal magnetoresistance (CMR) manganites originate from a strong electron-phonon interaction (EPI) combined with unavoidable disorder. Attractive electron correlations, caused by an almost unretarded EPI, are sufficient to overcome the direct inter-site Coulomb repulsion in these charge-transfer Mott-Hubbard insulators, so that low energy physics is that of small polarons and small bipolarons. They form clusters localized by disorder below the mobility edge, but propagate as the Bloch states above the mobility edge. I identify the Froehlich EPI as the most essential for pairing and phase separation in superconducting layered cuprates. The pairing of oxygen holes into heavy bipolarons in the paramagnetic phase (current-carrier density collapse (CCDC)) explains also CMR and high and low-resistance phase coexistence near the ferromagnetic transition of doped manganites.

  20. Measurement of countercurrent phase separation and distribution in a two-dimensional test section

    SciTech Connect

    Bukhari, K M; Lahey, Jr, R T

    1984-01-01

    The degree of phase separation that occurs in the core of a pressurized water reactor (PWR) during various postulated accidents is an important consideration for studying the course of events during such accidents. The dependence of countercurrent phase separation and distribution phenomena on flow quality, mass flux and system geometry was studied experimentally in a two-dimensional (2-D) test section. A two-phase (air/water) mixture flowed upwards and single-phase water flowed downward along one side of the test section. This countercurrent flow configuration was intended to simulate the so-called chimney effect in the diabatic JAERI 2-D experiments in Japan. A large air/water loop used with a 91.44 cm x 91.44 cm x 1.27 cm test section to study phase separation and distribution effects. A traversing single beam gamma-densitometer was used to measure the chordal average void fractions at several elevations along the test section. Cross-plots between various flow conditions and geometries were made. An error analysis giving the total error in the void fraction measurements was also performed. High speed photographs were also made of the flow structure, to provide information on flow regimes. The photographic records and the void fraction and hydraulic inflow/outflow data are presented in a form suitable for the assessment of advanced generation computer codes (e.g., TRAC).

  1. Dispersions of Semiconductor Nanoparticles in Thermotropic Liquid Crystal: From Optical Modification to Assisted Self-Assembly

    NASA Astrophysics Data System (ADS)

    Rodarte, Andrea L.

    The interaction of semiconducting quantum dot nanoparticles (QDs) within thermotropic liquid crystalline (LC) materials are studied in this thesis. LC materials are ideal for bottom-up organization of nanoparticles as an active matrix that can be externally manipulated via electric or magnetic fields. In addition, the optical properties of QDs can be modified by the surrounding LC resulting in novel devices such as a quantum dot/liquid crystal laser. The first system studies the dispersion of spherical nanoparticles in the phase. The dispersion is investigated with the use of polarized optical microscopy, fluorescence microscopy and confocal scanning microscopy. Quantum dots well dispersed in the isotropic phase are expelled from ordered domains of LC at the phase transition. Under controlled conditions, the majority of QDs in the system can form ordered three dimensional assemblies that are situated at defect points in the liquid crystal. The internal order of the assemblies is probed utilizing Forster resonance energy transfer (FRET), combined with small angle X-ray scattering (SAXS). Furthermore, the location of these assemblies can be predetermined with the use of beads as defect nucleation points in the cell. The interaction of QDs in a cholesteric liquid crystal (CLC) is also investigated. The reflection band created by the periodic change of index of refraction in a planar aligned CLC acts as a 1-D photonic cavity when the CLC is doped with a low concentration of QDs. A Cano-wedge cell varies the pitch of the CLC leading to the formation of Grandjean steps. This spatially tunes the photonic stop band, changing the resonance condition and continuously altering both the emission wavelength and polarization state of the QD ensemble. Using high resolution spatially and spectrally resolved photoluminescence measurements, the emission is shown to be elliptically polarized and that the tilt of the ellipse, while dependent on the emission wavelength, additionally

  2. Chemical ordering suppresses large-scale electronic phase separation in doped manganites

    NASA Astrophysics Data System (ADS)

    Zhu, Yinyan; Du, Kai; Niu, Jiebin; Lin, Lingfang; Wei, Wengang; Liu, Hao; Lin, Hanxuan; Zhang, Kai; Yang, Tieying; Kou, Yunfang; Shao, Jian; Gao, Xingyu; Xu, Xiaoshan; Wu, Xiaoshan; Dong, Shuai; Yin, Lifeng; Shen, Jian

    2016-04-01

    For strongly correlated oxides, it has been a long-standing issue regarding the role of the chemical ordering of the dopants on the physical properties. Here, using unit cell by unit cell superlattice growth technique, we determine the role of chemical ordering of the Pr dopant in a colossal magnetoresistant (La1-yPry)1-xCaxMnO3 (LPCMO) system, which has been well known for its large length-scale electronic phase separation phenomena. Our experimental results show that the chemical ordering of Pr leads to marked reduction of the length scale of electronic phase separations. Moreover, compared with the conventional Pr-disordered LPCMO system, the Pr-ordered LPCMO system has a metal-insulator transition that is ~100 K higher because the ferromagnetic metallic phase is more dominant at all temperatures below the Curie temperature.

  3. A model of attractive interactions to account for fluid-fluid phase separation of protein solutions

    NASA Astrophysics Data System (ADS)

    Malfois, Marc; Bonneté, Françoise; Belloni, Luc; Tardieu, Annette

    1996-08-01

    Concentrated γ-crystallin and lysozyme solutions have been reported to undergo a fluid-fluid phase separation when cooled below a critical temperature. This behavior is under control of the weak forces acting in solution between macromolecules. We have used small angle x-ray scattering at the synchrotron radiation facility LURE (Orsay, France) to analyze the interaction potentials. A model of attractive interactions which depends upon three parameters, protein diameter, potential depth, and range, is able to account for both the x-ray structure factors measured at high temperature and for the low temperature phase separation. Although van der Waals forces could be at the origin of the attractive interaction potentials, other more specific effects also contribute to the protein phase diagrams.

  4. Supercooling transition in phase separated manganite thin films: An electrical transport study

    SciTech Connect

    Singh, Sandeep; Kumar, Pawan; Siwach, P. K.; Singh, H. K.; Tyagi, Pawan Kumar

    2014-05-26

    The impact of variation in the relative fractions of the ferromagnetic metallic and antiferromagnetic/charge ordered insulator phases on the supercooling/superheating transition in strongly phase separated system, La{sub 5/8−y}Pr{sub y}Ca{sub 3/8}MnO{sub 3} (y ≈ 0.4), has been studied employing magnetotransport measurements. Our study clearly shows that the supercooling transition temperature is non-unique and strongly depends on the magneto-thermodynamic path through which the low temperature state is accessed. In contrast, the superheating transition temperature remains constant. The thermo-magnetic hysteresis, the separation of the two transitions and the associated resistivity, all are functions of the relative fraction of the coexisting phases.

  5. Vacancy-mediated fcc/bcc phase separation in Fe1 -xNix ultrathin films

    NASA Astrophysics Data System (ADS)

    Menteş, T. O.; Stojić, N.; Vescovo, E.; Ablett, J. M.; Niño, M. A.; Locatelli, A.

    2016-08-01

    The phase separation occurring in Fe-Ni thin films near the Invar composition is studied by using high-resolution spectromicroscopy techniques and density functional theory calculations. Annealed at temperatures around 300 ∘C ,Fe0.70Ni0.30 films on W(110) break into micron-sized bcc and fcc domains with compositions in agreement with the bulk Fe-Ni phase diagram. Ni is found to be the diffusing species in forming the chemical heterogeneity. The experimentally determined energy barrier of 1.59 ±0.09 eV is identified as the vacancy formation energy via density functional theory calculations. Thus, the principal role of the surface in the phase separation process is attributed to vacancy creation without interstitials.

  6. Effect of solvent annealing on phase separation of donor/acceptor species in organic mixtures

    NASA Astrophysics Data System (ADS)

    Cezza, Miriam; Shao, Qian; Guo, Shy-Hauh; Phaneuf, Raymond J.

    2013-03-01

    Studies on phase separation of mixtures of tetranitro zinc- phthalocyanine (tn-ZnPc) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were performed in which we controlled the evaporation rate of the solvent (chloroform). Phase-contrast AFM analysis reveals that slowing down the evaporation rate of the solvent facilitates the nucleation of the donor component, and the two components phase-separate. The size of the molecular agglomerates and single small particles decreases for slow solvent evaporation and the density of small particles per unit area increases by an order of magnitude over the range studied. Work supported by the NSF-MRSEC at the University of Maryland #DMR0520471.

  7. Long-term stability of phase-separated half-Heusler compounds.

    PubMed

    Krez, J; Balke, B; Ouardi, S; Selle, S; Höche, T; Felser, C; Hermes, W; Schwind, M

    2015-11-28

    Half-Heusler (HH) compounds have shown high figure of merit up to 1.5. Here, we address the long-term stability of n- and p-type HH materials. For this purpose, we investigated HH materials based on the Ti0.3Zr0.35Hf0.35NiSn-system after 500 cycles (1700 h) from 373 to 873 K. Both compounds exhibit a maximum Seebeck coefficient of |α|≈ 210 μV K(-1) and a phase separation into two HH phases. The dendritic microstructure is temperature resistant and upon cycling the changes in the microstructure are so marginal that the low thermal conductivity values (κ < 4 W m(-1) K(-1)) could be maintained. Our results emphasize that phase-separated HH compounds are suitable low cost materials and can lead to enhanced thermoelectric efficiencies beyond the set benchmark for industrial applications. PMID:26488053

  8. Chemical ordering suppresses large-scale electronic phase separation in doped manganites

    PubMed Central

    Zhu, Yinyan; Du, Kai; Niu, Jiebin; Lin, Lingfang; Wei, Wengang; Liu, Hao; Lin, Hanxuan; Zhang, Kai; Yang, Tieying; Kou, Yunfang; Shao, Jian; Gao, Xingyu; Xu, Xiaoshan; Wu, Xiaoshan; Dong, Shuai; Yin, Lifeng; Shen, Jian

    2016-01-01

    For strongly correlated oxides, it has been a long-standing issue regarding the role of the chemical ordering of the dopants on the physical properties. Here, using unit cell by unit cell superlattice growth technique, we determine the role of chemical ordering of the Pr dopant in a colossal magnetoresistant (La1−yPry)1−xCaxMnO3 (LPCMO) system, which has been well known for its large length-scale electronic phase separation phenomena. Our experimental results show that the chemical ordering of Pr leads to marked reduction of the length scale of electronic phase separations. Moreover, compared with the conventional Pr-disordered LPCMO system, the Pr-ordered LPCMO system has a metal–insulator transition that is ∼100 K higher because the ferromagnetic metallic phase is more dominant at all temperatures below the Curie temperature. PMID:27053071

  9. Manipulating electronic phase separation in strongly correlated oxides with an ordered array of antidots

    PubMed Central

    Zhang, Kai; Du, Kai; Liu, Hao; Zhang, X.-G.; Lan, Fanli; Lin, Hanxuan; Wei, Wengang; Zhu, Yinyan; Kou, Yunfang; Shao, Jian; Niu, Jiebin; Wang, Wenbin; Wu, Ruqian; Yin, Lifeng; Plummer, E. W.; Shen, Jian

    2015-01-01

    The interesting transport and magnetic properties in manganites depend sensitively on the nucleation and growth of electronic phase-separated domains. By fabricating antidot arrays in La0.325Pr0.3Ca0.375MnO3 (LPCMO) epitaxial thin films, we create ordered arrays of micrometer-sized ferromagnetic metallic (FMM) rings in the LPCMO films that lead to dramatically increased metal–insulator transition temperatures and reduced resistances. The FMM rings emerge from the edges of the antidots where the lattice symmetry is broken. Based on our Monte Carlo simulation, these FMM rings assist the nucleation and growth of FMM phase domains increasing the metal–insulator transition with decreasing temperature or increasing magnetic field. This study points to a way in which electronic phase separation in manganites can be artificially controlled without changing chemical composition or applying external field. PMID:26195791

  10. High-capacity stationary phases containing heavy atoms for HPLC separation of fullerenes

    SciTech Connect

    Kimata, Kazuhiro |; Hirose, Tsunehisa; Moriuchi, Kouji; Hosoya, Ken; Araki, Takeo; Tanaka, Nobuo

    1995-08-01

    A high-capacity stationary phase for the separation of fullerenes was prepared by immobilizing 3-[(pentabromobenzyl)oxy]propylsilyl (PBB) groups onto silica surfaces. The stationary phase was developed by a reciprocal approach. This was possible by finding the structure of solvents that provided high solubilities as well as high eluent strength for chromatographic elution of fullerenes. The increased solubility and increased eluent strength for C{sub 60} seen with solvents containing heavy heteroatoms suggested the preferential interaction of C{sub 60} with such solvent molecules. The stationary phases containing sulfur, chlorine, or bromine in fact resulted in longer retention of fullerenes. The PBB silica showed high retentivity with excellent efficiency for fullerenes, permitting the use of solvents providing high solubilities, such as carbon disulfide and 1,2,4-trichlorobenzene for gramscale separations with ordinary HPLC equipment. 22 refs., 6 figs., 3 tabs.

  11. Dynamics of phase separation in polymer blends studied by ultrafast scanning calorimetry

    NASA Astrophysics Data System (ADS)

    Zhou, Dongshan; Wei, Lai; Luo, Shaochuan; Jiang, Jing; Wang, Xiaoliang; Xue, Gi

    2015-03-01

    Phase separation in polymer blends has been widely studied in material science due to the special microstructures they may form during the processes. The recently developed ultrafast scanning calorimetry (UFSC) with heating and cooling rates up to 10E5 K/s provides better chance to follow the fast de-mixing of polymer blends occurring in sub-milliseconds. In this work, the dynamics of phase separation in several proportions of poly(styrene) and poly(vinyl methyl ether) (PS/PVME) blends with different molecular weights were studied using UFSC. It shows that the phase diagrams of the blend can be easily built and that the de-mixing level can be well controlled by the fast heating and quenching program the UFSC offers. The authors appreciate the financial support of National Basic Research Program of China (973 program, 2012CB821503) and the NSF of China (21274059 and 21027006).

  12. 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

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

    PubMed

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

    2015-07-21

    Countercurrent separation (CCS) utilizes the differential partitioning behavior of analytes between two immiscible liquid phases. We introduce the first platform ("CherryOne") capable of real-time monitoring, metering, and control of the dynamic liquid-liquid CCS process. Automated phase monitoring and volumetrics are made possible with an array of sensors, including the new permittivity-based phase metering apparatus (PMA). Volumetric data for each liquid phase are converted into a dynamic real-time display of stationary phase retention (Sf) and eluent partition coefficients (K), which represent critical parameters of CCS reproducibility. When coupled with the elution-extrusion operational mode (EECCC), automated Sf and K determination empowers untargeted and targeted applications ranging from metabolomic analysis to preparative purifications. PMID:26152934

  14. DESIGN AND DEVELOPMENT OF GAS-LIQUID CYLINDRICAL CYCLONE COMPACT SEPARATORS FOR THREE-PHASE FLOW

    SciTech Connect

    Dr. Ram S. Mohan; Dr. Ovadia Shoham

    2000-04-28

    The objective of this five-year project (October, 1997-September, 2002) is to expand the current research activities of Tulsa University Separation Technology Projects (TUSTP) to multiphase oil/water/gas separation. This project will be executed in two phases. Phase I (1997-2000) will focus on the investigations of the complex multiphase hydrodynamic flow behavior in a three-phase Gas-Liquid Cylindrical Cyclone (GLCC{copyright}) Separator. The activities of this phase will include the development of a mechanistic model, a computational fluid dynamics (CFD) simulator, and detailed experimentation on the three-phase GLCC{copyright}. The experimental and CFD simulation results will be suitably integrated with the mechanistic model. In Phase II (2000-2002), the developed GLCC{copyright} separator will be tested under high pressure and real crudes conditions. This is crucial for validating the GLCC{copyright} design for field application and facilitating easy and rapid technology deployment. Design criteria for industrial applications will be developed based on these results and will be incorporated into the mechanistic model by TUSTP. This report presents a brief overview of the activities and tasks accomplished during the first half year (October 1, 1999-March 31, 2000) of the budget period (October 1, 1999-September 30, 2000). The total tasks of the budget period are given initially, followed by the technical and scientific results achieved till date. The report concludes with a detailed description of the plans for the conduct of the project for the second half year (April 1, 2000-September 30, 2000) of the current budget period.

  15. Architecture Study on Telemetry Coverage for Immediate Post-Separation Phase

    NASA Technical Reports Server (NTRS)

    Cheung, Kar-Ming; Lee, Charles H.; Kellogg, Kent H.; Stocklin, Frank J.; Zillig, David J.; Fielhauer, Karl B.

    2008-01-01

    This paper presents the preliminary results of an architecture study that provides continuous telemetry coverage for NASA missions for immediate post-separation phase. This study is a collaboration effort between Jet Propulsion Laboratory (JPL), Goddard Space Flight Center (GSFC), and Applied Physics Laboratory (APL). After launch when the spacecraft separated from the upper stage, the spacecraft typically executes a number of mission-critical operations prior to the deployment of solar panels and the activation of the primary communication subsystem. JPL, GSFC, and APL have similar design principle statements that require continuous coverage of mission-critical telemetry during the immediate post-separation phase. To conform to these design principles, an architecture that consists of a separate spacecraft transmitter and a robust communication network capable of tracking the spacecraft signals is needed.This paper presents the preliminary results of an architecture study that provides continuous telemetry coverage for NASA missions for immediate post-separation phase. This study is a collaboration effort between Jet Propulsion Laboratory (JPL), Goddard Space Flight Center (GSFC), and Applied Physics Laboratory (APL). After launch when the spacecraft separated from the upper stage, the spacecraft typically executes a number of mission-critical operations prior to the deployment of solar panels and the activation of the primary communication subsystem. JPL, GSFC, and APL have similar design principle statements that require continuous coverage of mission-critical telemetry during the immediate post-separation phase. To conform to these design principles, an architecture that consists of a separate spacecraft transmitter and a robust communication network capable of tracking the spacecraft signals is needed. The main results of this study are as follows: 1) At low altitude (< 10000 km) when most post-separation critical operations are executed, Earth-based network

  16. Stability and Oil Migration of Oil-in-Water Emulsions Emulsified by Phase-Separating Biopolymer Mixtures.

    PubMed

    Yang, Nan; Mao, Peng; Lv, Ruihe; Zhang, Ke; Fang, Yapeng; Nishinari, Katsuyoshi; Phillips, Glyn O

    2016-08-01

    Oil-in-water (O/W) emulsions with varying concentration of oil phase, medium-chain triglyceride (MCT), were prepared using phase-separating gum arabic (GA)/sugar beet pectin (SBP) mixture as an emulsifier. Stability of the emulsions including emulsion phase separation, droplet size change, and oil migration were investigated by means of visual observation, droplet size analysis, oil partition analysis, backscattering of light, and interfacial tension measurement. It was found that in the emulsions prepared with 4.0% GA/1.0% SBP, when the concentration of MCT was greater than 2.0%, emulsion phase separation was not observed and the emulsions were stable with droplet size unchanged during storage. This result proves the emulsification ability of phase-separating biopolymer mixtures and their potential usage as emulsifiers to prepare O/W emulsion. However, when the concentration of MCT was equal or less than 2.0%, emulsion phase separation occurred after preparation resulting in an upper SBP-rich phase and a lower GA-rich phase. The droplet size increased in the upper phase whereas decreased slightly in the lower phase with time, compared to the freshly prepared emulsions. During storage, the oil droplets exhibited a complex migration process: first moving to the SBP-rich phase, then to the GA-rich phase and finally gathering at the interface between the two phases. The mechanisms of the emulsion stability and oil migration in the phase-separated emulsions were discussed. PMID:27384744

  17. Graphitic carbon nitride as high-resolution stationary phase for gas chromatographic separations.

    PubMed

    Zheng, Yunzhong; Qi, Meiling; Fu, Ruonong

    2016-07-01

    This work presents the first example of utilization of graphitic carbon nitride (g-C3N4) as stationary phase for capillary gas chromatographic (GC) separations. The statically coated g-C3N4 column showed the column efficiencies of 3760 plates/m and weak polarity. Its resolving capability and retention behaviours were investigated by using the Grob test mixture, and mixtures of diverse types of analytes, and structural and positional isomers. The results showed superior separation performance of the g-C3N4 stationary phase for some critical analytes and preferential retention for aromatic analytes. Specifically, it exhibited high-resolution capability for aromatic and aliphatic isomers such as methylnaphthalenes and dimethylnaphthalenes, phenanthrene and anthracene and alkane isomers. In addition, g-C3N4 column showed excellent thermal stability up to 280°C and good repeatability with relative standard deviation (RSD) values less than 0.09% for intra-day, below 0.23% for inter-day and in the range of 1.9-8.4% for between-column, respectively. The advantageous separation performance shows the potential of g-C3N4 and related materials as stationary phase in GC and other separation technologies. PMID:27266332

  18. Search for improved fluorinated stationary phases for separation of fluorine-containing pharmaceuticals from their desfluoro analogs.

    PubMed

    Regalado, Erik L; Makarov, Alexey A; McClain, Ray; Przybyciel, Matthew; Welch, Christopher J

    2015-02-01

    Evaluation of a several fluorine-containing stationary phases for the chromatographic separation of fluorine-containing pharmaceuticals from their corresponding desfluoro analogs revealed a number of perfluoroaryl and perfluoroalky stationary phases that afford good separations. These fluorous stationary phases exhibit greater retention for the fluorine-containing compounds relative to the H-containing analogs, consistent with a fluorophilic retention mechanism. While both perfluoroalkyl and perfluoroaryl stationary phases afford adequate resolution, the perfluoroaryl columns generally exhibit superior separation factor (α) and peak efficiency (N), resulting in faster baseline separations, with the Hypersil Gold PFP and Poroshell 120 PFP columns providing the best overall performance for the test group studied. PMID:25595532

  19. 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

  20. Architecture Study on Telemetry Coverage for Immediate Post-Separation Phase

    NASA Technical Reports Server (NTRS)

    Cheung, Kar-Ming; Lee, Charles; Kellogg, Kent; Stocklin, Frank; Zillig, David; Fielhauer, Karl

    2008-01-01

    This document is the viewgraphs that accompanies a paper that presents the preliminary results of an architecture study that provides continuous telemetry coverage for NASA missions for immediate post-separation phase. After launch when the spacecraft separated from the upper stage, the spacecraft typically executes a number of mission-critical operations prior to the deployment of solar panels and the activation of the primary communication subsystem. JPL, GSFC, and APL have similar design principle statements that require continuous coverage of mission-critical telemetry during the immediate post-separation phase. To conform to these design principles, an architecture that consists of a separate spacecraft transmitter and a robust communication network capable of tracking the spacecraft signals is needed. The main results of this study are as follows: 1) At low altitude (< 10000 km) when most post-separation critical operations are executed, Earth-based network (e.g. Deep Space Network (DSN)) can only provide limited coverage, whereas space-based network (e.g. Space Network (SN)) can provide continuous coverage. 2) Commercial-off-the-shelf SN compatible transmitters are available for small satellite applications. In this paper we present the detailed coverage analysis of Earth-based and Space-based networks. We identify the key functional and performance requirements of the architecture, and describe the proposed selection criteria of the spacecraft transmitter. We conclude the paper with a proposed forward plan.

  1. Facile synthesis of gradient mesoporous carbon monolith based on polymerization-induced phase separation

    NASA Astrophysics Data System (ADS)

    Xu, Shunjian; Luo, Yufeng; Zhong, Wei; Xiao, Zonghu; Luo, Yongping; Ou, Hui; Zhao, Xing-Zhong

    2014-06-01

    In this paper, a gradient mesoporous carbon (GMC) monolith derived from the mixtures of phenolic resin (PF) and ethylene glycol (EG) was prepared by a facile route based on polymerization-induced phase separation under temperature gradient (TG). A graded biphasic structure of PF-rich and EG-rich phases was first formed in preform under a TG, and then the preform was pyrolyzed to obtain the GMC monolith. The TG is mainly induced by the thermal resistance of the preferential phase separation layer at high temperature region. The pore structure of the monolith changes gradually along the TG direction. When the TG varies from 58°C to 29°C, the pore size, apparent porosity and specific surface area of the monolith range respectively from 18 nm to 83 nm, from 32% to 39% and from 140.5 m2/g to 515.3 m2/g. The gradient porous structure of the monolith is inherited from that of the preform, which depends on phase separation under TG in the resin mixtures. The pyrolysis mainly brings about the contraction of the pore size and wall thickness as well as the transformation of polymerized PF into glassy carbon.

  2. Separation of dialkyl sulfides by metallo-mesogenic stationary phases for complexation gas chromatography.

    PubMed

    Chen, Jian-Lian; Liu, Chuen-Ying

    2007-08-17

    A copper mesogenic side-chain polymer (P-C(15)CuC(18)) was cross-linked onto the capillary wall as a stationary film for gas chromatography (GC) separation of alkyl sulfides. These organic sulfides are of interest for their large health impact because of their wide range of volatiles and high reactivities toward metals. Different GC parameters for optimal separation efficiency are discussed for use with a mesogenic polymer column along with flame photometric detection (FPD). Both the carrier gas flow-rate and column temperature were studied to determine the relationship of plate height to the chemical structure of the solutes, as well as to determine the morphology of the mesogenic polymer. Van 't Hoff plots show phase transitions of the stationary mesophase as the column temperature was varied. The results reveal that the separation mechanism might be based on ligand exchange and polarity interaction between the analytes and the stationary phase, with the vapor pressure of the analytes also being important. The former interaction dominates in the lamellar crystalline phase and the latter interaction dominates in the hexagonal columnar-discotic phase. With high reproducibility for retention time (RSD< or =0.37%) and for peak area (RSD< or =5.16%), the GC-FPD system produced linear calibration graphs (r> or =0.9918) for the determination of 13 sulfides with a detection limit below 2.5 ng. PMID:17568598

  3. Polymer depletion-driven cluster aggregation and initial phase separation in charged nanosized colloids.

    PubMed

    Gögelein, Christoph; Nägele, Gerhard; Buitenhuis, Johan; Tuinier, Remco; Dhont, Jan K G

    2009-05-28

    We study polymer depletion-driven cluster aggregation and initial phase separation in aqueous dispersions of charge-stabilized silica spheres, where the ionic strength and polymer (dextran) concentration are systematically varied, using dynamic light scattering and visual observation. Without polymers and for increasing salt and colloid content, the dispersions become increasingly unstable against irreversible cluster formation. By adding nonadsorbing polymers, a depletion-driven attraction is induced, which lowers the stabilizing Coulomb barrier and enhances the cluster growth rate. The initial growth rate increases with increasing polymer concentration and decreases with increasing polymer molar mass. These observations can be quantitatively understood by an irreversible dimer formation theory based on the classical Derjaguin, Landau, Verwey, and Overbeek pair potential, with the depletion attraction modeled by the Asakura-Oosawa-Vrij potential. At low colloid concentration, we observe an exponential cluster growth rate for all polymer concentrations considered, indicating a reaction-limited aggregation mechanism. At sufficiently high polymer and colloid concentrations, and lower salt content, a gas-liquidlike demixing is observed initially. Later on, the system separates into a gel and fluidlike phase. The experimental time-dependent state diagram is compared to the theoretical equilibrium phase diagram obtained from a generalized free-volume theory and is discussed in terms of an initial reversible phase separation process in combination with irreversible aggregation at later times. PMID:19485479

  4. 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.

  5. Surface modification of polytetrafluoroethylene column for two-stationary phase separations by counter-current chromatography.

    PubMed

    Quan, Kai-jun; Huang, Xin-yi; Li, Xiao-ting; Wang, Gao-hong; Liu, Yan-juan; Duan, Wen-da; Di, Duo-long

    2015-11-27

    To improve the separation capability of CCC, a novel solid-liquid two-stationary phases CCC (ASP-CCC) column was prepared employing graphene oxide (GO) conjugated poly-dopamine (PD) coating (GO/PD) as auxiliary stationary phase (ASP). The results of Scanning electron microscopy (SEM), contact angle and X-ray photoelectron spectroscopy (XPS) indicated that nanostructured GO and PD were successfully grafted on the inner wall of the PTFE column. Three alkaloid compounds were selected as the target analytes to evaluate the performance of the novel column. Because of the intermolecular force (hydrogen bond, electrostatic interaction and π-π interaction) between the ASP and model compounds, three analytes were well separated with this novel ASP-CCC column. Additionally, the novel column exhibited higher stationary phase retention ratio, about 8%, than original column without changing the chromatographic condition. Furthermore, the eluotropic sequence of analytes on novel column was in accordance with that in the original column. This suggested that the novel column is a CCC column with auxiliary stationary phase (ASP) in its own right, and the present separation mode is the combination of partition chromatography and adsorption chromatography. PMID:26518492

  6. Phase Separation of Silicon-Containing Polymer/Polystyrene Blends in Spin-Coated Films.

    PubMed

    Li, Yang; Hu, Kai; Han, Xiao; Yang, Qinyu; Xiong, Yifeng; Bai, Yuhang; Guo, Xu; Cui, Yushuang; Yuan, Changsheng; Ge, Haixiong; Chen, Yanfeng

    2016-04-19

    In this Article, two readily available polymers that contain silicon and have different surface tensions, polydimethylsiloxane (PDMS) and polyphenylsilsequioxane (PPSQ), were used to produce polymer blends with polystyrene (PS). Spin-coated thin films of the polymer blends were treated by O2 reactive-ion etching (RIE). The PS constituent was selectively removed by O2 RIE, whereas the silicon-containing phase remained because of the high etching resistance of silicon. This selective removal of PS substantially enhanced the contrast of the phase separation morphologies for better scanning electron microscope (SEM) and atomic force microscope (AFM) measurements. We investigated the effects of the silicon-containing constituents, polymer blend composition, concentration of the polymer blend solution, surface tension of the substrate, and the spin-coating speed on the ultimate morphologies of phase separation. The average domain size, ranging from 100 nm to 10 μm, was tuned through an interplay of these factors. In addition, the polymer blend film was formed on a pure organic layer, through which the aspect ratio of the phase separation morphologies was further amplified by a selective etching process. The formed nanostructures are compatible with existing nanofabrication techniques for pattern transfer onto substrates. PMID:27052643

  7. Ion-exchange vs reversed-phase chromatography for separation and determination of basic psychotropic drugs.

    PubMed

    Petruczynik, Anna; Wróblewski, Karol; Deja, Michał; Waksmundzka-Hajnos, Monika

    2015-11-01

    Ion exchange chromatography, an alternative to reversed-phase (RP) chromatography, is described in this paper. We aimed to obtain optimal conditions for the separation of basic drugs because silica-based RP stationary phases show silanol effect and make the analysis of basic analytes hardly possible. The retention, separation selectivity, symmetry of peaks and system efficiency were examined in different eluent systems containing different types of buffers at acidic pH and with the addition of organic modifiers: methanol and acetonitrile. The obtained results reveal a large influence of the salt cation used for buffer preparation and the type of organic modifier on the retention behavior of the analytes. These results were also compared with those obtained on an XBridge C18 column. The obtained results demonstrated that SCX stationary phases can be successfully used as alternatives to C18 stationary phases in the separation of basic compounds. The most selective and efficient chromatographic systems were applied for the quantification of some psychotropic drugs in fortified human serum samples. PMID:25944095

  8. Evolution of Surface Structure and Phase Separation in GaInAsSb

    SciTech Connect

    C.J. Vineis; C.A. Wang; D.R. Calawa

    2000-08-21

    Atomic force microscopy was used to study changes in the surface step structure of GaInAsSb layers with varying degrees of phase separation. The layers were grown by organometallic vapor phase epitaxy on (001) GaSb substrates with 2{sup o} miscut angles toward (-1-11)A, (1-11)B, and (101). Alloy decomposition was observed by contrast modulations in plan-view transmission electron microscopy, and broadening in x-ray diffraction and photoluminescence peaks. GaInAsSb layers with a minimal degree of phase separation exhibit a step-bunched step structure. A gradual degradation in the periodicity of the step structure is observed as the alloy decomposes into GaAs- and InSb-rich regions. The surface eventually develops trenches to accommodate the local strain associated with composition variations, which are on the order of a few percent. The surface composition is affected by substrate miscut angle, and although phase separation cannot be eliminated, its extent can be reduced by growing on substrates miscut toward (1-11)B.

  9. Morphology Mapping of Phase-Separated Polymer Films Using Nanothermal Analysis

    SciTech Connect

    Nikiforov, Maxim; Gam, Sangah; Jesse, Stephen; Composto, Russel C; Kalinin, Sergei V

    2010-01-01

    Polymers films are attractive, in part, because their physical properties can be tuned by blending polymer with complementary characteristics. However, blending is typically challenging because most polymers will undergo phase separation, resulting in unpredictable behavior. Here, we introduce band excitation nanothermal analysis (BE-NanoTA) as a nondestructive AFM-based technique for mapping the near surface, thermal properties of polymeric coatings. BE-NanoTA was used to investigate phase separation and domain growth in poly(styrene-ran-acrylonitrile):poly(methyl methacrylate) SAN:PMMA films. The size and shape of PMMA-rich domains are consistent with prior measurements on the same system using a destructive method, namely UV-ozone etching of PMMA followed by topography mapping using standard AFM. Moreover, new insights into the mechanism of phase separation were uncovered including the observation of SAN- and PMMA-rich channels near the surface at early times as well as small SAN-rich domains trapped within large PMMA domains during intermediate times. Because it is nondestructive, BE-NanoTA can be used to explore in situ phase evolution in soft matter systems (e.g., polymer nanocomposites) which do not lend themselves to the UV-ozone etching method

  10. Evidence that oleic acid exists in a separate phase within stratum corneum lipids

    SciTech Connect

    Ongpipattanakul, B.; Burnette, R.R.; Potts, R.O.; Francoeur, M.L. )

    1991-03-01

    Oleic acid is known to be a penetration enhancer for polar to moderately polar molecules. A mechanism related to lipid phase separation has been previously proposed by this laboratory to explain the increases in skin transport. In the studies presented here, Fourier transform infrared spectroscopy (FT-IR) was utilized to investigate whether or not oleic acid exists in a separate phase within stratum corneum (SC) lipids. Per-deuterated oleic acid was employed allowing the conformational phase behavior of the exogenously added fatty acid and the endogenous SC lipids to be monitored independently of each other. The results indicated that oleic acid exerts a significant effect on the SC lipids, lowering the lipid transition temperature (Tm) in addition to increasing the conformational freedom or flexibility of the endogenous lipid alkyl chains above their Tm. At temperatures lower than Tm, however, oleic acid did not significantly change the chain disorder of the SC lipids. Similar results were obtained with lipids isolated from the SC by chloroform:methanol extraction. Oleic acid, itself, was almost fully disordered at temperatures both above and below the endogenous lipid Tm in the intact SC and extracted lipid samples. This finding suggested that oleic acid does exist as a liquid within the SC lipids. The coexistence of fluid oleic acid and ordered SC lipids, at physiological temperatures, is consistent with the previously proposed phase-separation transport mechanism for enhanced diffusion.

  11. Zero-g experiments with a He II active phase separator for space application

    NASA Technical Reports Server (NTRS)

    Denner, H. D.; Klipping, G.; Lueders, K.; Ruppert, U.; Stahnke, F.; Szuecs, Z.; Elleman, D.; Petrac, D.

    1984-01-01

    An active phase separator (APS) for temperature control of He II space cooling systems was tested in a zero-g environment during a series of parabolic flights on a NASA KC 135 aircraft. The APS provides for liquid-gas separation and features an annular gap, a downstream heat exchanger and an upstream ball closure. The apparatus was operated during acceleration and floating and in two different heat load situations. The tests confirmed that adequate mass flow rates could be maintained using a vacuum pump to simulate space vacuum and that residual liquid could be evaporated from the heat exchanger after closing a ball valve to seal off flows.

  12. Spin Waves, Phase Separation, and Interphase Boundaries in Double Exchange Magnets.

    NASA Astrophysics Data System (ADS)

    Golosov, D. I.

    2002-03-01

    We study a classical double exchange magnet with direct antiferromagnetic superexchange coupling, J, between the localized spins. It is shown that the de-stabilization of the ferromagnetic ground state with increasing J leads to phase separation; the latter always preempts the spin-wave instability (softening of the magnon spectrum). It is also found that the boundaries separating the ferromagnetic and antiferromagnetic areas of the sample tend to be abrupt. We expect these results (which were obtained for a two-dimensional system) to persist in 3D as well. Reference: preprint cond-mat/0110322 (to be published in J. Appl. Phys.)

  13. From Phase to Microphase Separation in Flocking Models: The Essential Role of Nonequilibrium Fluctuations

    NASA Astrophysics Data System (ADS)

    Solon, Alexandre P.; Chaté, Hugues; Tailleur, Julien

    2015-02-01

    We show that the flocking transition in the Vicsek model is best understood as a liquid-gas transition, rather than an order-disorder one. The full phase separation observed in flocking models with Z2 rotational symmetry is, however, replaced by a microphase separation leading to a smectic arrangement of traveling ordered bands. Remarkably, continuous deterministic descriptions do not account for this difference, which is only recovered at the fluctuating hydrodynamics level. Scalar and vectorial order parameters indeed produce different types of number fluctuations, which we show to be essential in selecting the inhomogeneous patterns. This highlights an unexpected role of fluctuations in the selection of flock shapes.

  14. Inherent structures of phase-separating binary mixtures: nucleation, spinodal decomposition, and pattern formation.

    PubMed

    Sarkar, Sarmistha; Bagchi, Biman

    2011-03-01

    An energy landscape view of phase separation and nonideality in binary mixtures is developed by exploring their potential energy landscape (PEL) as functions of temperature and composition. We employ molecular dynamics simulations to study a model that promotes structure breaking in the solute-solvent parent binary liquid, at low temperatures. The PEL of the system captures the potential energy distribution of the inherent structures (IS) of the system and is obtained by removing the kinetic energy (including that of intermolecular vibrations). The broader distribution of the inherent structure energy for structure breaking liquid than that of the structure making liquid demonstrates the larger role of entropy in stabilizing the parent liquid of the structure breaking type of binary mixtures. At high temperature, although the parent structure of the structure breaking binary mixture is homogenous, the corresponding inherent structure is found to be always phase separated, with a density pattern that exhibits marked correlation with the energy of its inherent structure. Over a broad range of intermediate inherent structure energy, bicontinuous phase separation prevails with interpenetrating stripes as signatures of spinodal decomposition. At low inherent structure energy, the structure is largely phase separated with one interface where as at high inherent structure energy we find nucleation type growth. Interestingly, at low temperature, the average inherent structure energy () exhibits a drop with temperature which signals the onset of crystallization in one of the phases while the other remains in the liquid state. The nonideal composition dependence of viscosity is anticorrelated with average inherent structure energy. PMID:21517506

  15. Fatty Acid Chain Length Dependence of Phase Separation Kinetics in Stratum Corneum Models by IR Spectroscopy.

    PubMed

    Mendelsohn, Richard; Rabie, Emann; Walters, Russel M; Flach, Carol R

    2015-07-30

    The main barrier to permeability in human skin resides in the stratum corneum (SC), a layered structure consisting of anucleated, flattened cells (corneocytes) embedded in a heterogeneous lamellar lipid matrix. While lipid structures and packing propensities in the SC and in SC models have been extensively investigated, only limited data are available concerning the kinetics and mechanism of formation of lamellar phases and particular lipid packing motifs. In our prior investigation, kinetic IR spectroscopy measurements probed the temporal sequence of phase separation leading to ordered structures in a three component SC model of equimolar structurally heterogeneous ceramide[NS], chain perdeuterated stearic acid, and cholesterol. In the current work, the phase separation kinetic effects of specific fatty acid chain lengths with a synthetic structurally homogeneous ceramide[NS] in similar ternary mixtures are examined. These are compared with a mixture containing ceramide[NS] with an unsaturated acid chain. The kinetic events are sensitive to the difference in chain lengths between the ceramide acid chain and the fatty acid as well as to the presence of unsaturation in the former. The observed kinetic behaviors span a wide range of phase separation times, ranging from the formation of a solid solution stable for at least 200 h, to a system in which an orthorhombic fatty acid structure is essentially completely formed within the time resolution of the experiment (15 min). The data seem to offer some features of a spinodal phase separation at relatively short times. Overall the approach offers a possible means for addressing several unanswered questions pertinent to skin pharmacology, such as the roles of a wide variety of ceramide and fatty acid species and the design of therapeutic interventions for repair of pathological conditions of the SC. PMID:26131756

  16. The effect of charge separation on the phase behavior of dipolar colloidal rods.

    PubMed

    Rutkowski, David M; Velev, Orlin D; Klapp, Sabine H L; Hall, Carol K

    2016-06-14

    Colloids with anisotropic shape and charge distribution can assemble into a variety of structures that could find use as novel materials for optical, photonic, electronic and structural applications. Because experimental characterization of the many possible types of multi-shape and multipolar colloidal particles that could form useful structures is difficult, the search for novel colloidal materials can be enhanced by simulations of colloidal particle assembly. We have simulated a system of dipolar colloidal rods at fixed aspect ratio using discontinuous molecular dynamics (DMD) to investigate how the charge separation of an embedded dipole affects the types of assemblies that occur. Each dipolar rod is modeled as several overlapping spheres fixed in an elongated shape to represent excluded volume and two smaller, embedded spheres to represent the charges that make up the extended dipole. Large charge separations predominately form structures where the rods link head-to-tail while small charge separations predominately form structures where the rods stack side-by-side. Rods with small charge separations tend to form dense aggregates while rods with large charge separations tend to form coarse gel-like structures. Structural phase boundaries between fluid, string-fluid, and "gel" (networked) phases are mapped out and characterized as to whether they have global head-to-tail or global side-by-side order. A structural coarsening transition is observed for particles with large charge separations in which the head-tail networks thicken as temperature is lowered due to an increased tendency to form side-by-side structures. Triangularly connected networks form at small charge separations; these may be useful for encapsulating smaller particles. PMID:27151445

  17. 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.

  18. Selectivity differences of water-soluble vitamins separated on hydrophilic interaction stationary phases.

    PubMed

    Yang, Yuanzhong; Boysen, Reinhard I; Hearn, Milton T W

    2013-06-01

    In this study, the retention behavior and selectivity differences of water-soluble vitamins were evaluated with three types of polar stationary phases (i.e. an underivatized silica phase, an amide phase, and an amino phase) operated in the hydrophilic interaction chromatographic mode with ESI mass spectrometric detection. The effects of mobile phase composition, including buffer pH and concentration, on the retention and selectivity of the vitamins were investigated. In all stationary phases, the neutral or weakly charged vitamins exhibited very weak retention under each of the pH conditions, while the acidic and more basic vitamins showed diverse retention behaviors. With the underivatized silica phase, increasing the salt concentration of the mobile phase resulted in enhanced retention of the acidic vitamins, but decreased retention of the basic vitamins. These observations thus signify the involvement of secondary mechanisms, such as electrostatic interaction in the retention of these analytes. Under optimized conditions, a baseline separation of all vitamins was achieved with excellent peak efficiency. In addition, the effects of water content in the sample on retention and peak efficiency were examined, with sample stacking effects observed when the injected sample contained a high amount of water. PMID:23554360

  19. Preferential localization of Lactococcus lactis cells entrapped in a caseinate/alginate phase separated system.

    PubMed

    Léonard, Lucie; Gharsallaoui, Adem; Ouaali, Fahima; Degraeve, Pascal; Waché, Yves; Saurel, Rémi; Oulahal, Nadia

    2013-09-01

    This study aimed to entrap bioprotective lactic acid bacteria in a sodium caseinate/sodium alginate aqueous two-phase system. Phase diagram at pH=7 showed that sodium alginate and sodium caseinate were not miscible when their concentrations exceeded 1% (w/w) and 6% (w/w), respectively. The stability of the caseinate/alginate two-phase system was also checked at pH values of 6.0 and 5.5. Lactococcus lactis subsp. lactis LAB3 cells were added in a 4% (w/w) caseinate/1.5% (w/w) alginate two-phase system at pH=7. Fluorescence microscopy allowed to observe that the caseinate-rich phase formed droplets dispersed in a continuous alginate-rich phase. The distribution of bacteria in such a system was observed by epifluorescence microscopy: Lc. lactis LAB3 cells stained with Live/Dead(®) Baclight kit™ were located exclusively in the protein phase. Since zeta-potential measurements indicated that alginate, caseinate and bacterial cells all had an overall negative charge at pH 7, the preferential adhesion of LAB cells was assumed to be driven by hydrophobic effect or by depletion phenomena in such biopolymeric systems. Moreover, LAB cells viability was significantly higher in the ternary mixture obtained in the presence of both caseinate and alginate than in single alginate solution. Caseinate/alginate phase separated systems appeared thus well suited for Lc. lactis LAB3 cells entrapment. PMID:23665092

  20. Atomistic Simulations of a Thermotropic Biaxial Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Peláez, Jorge; Wilson, Mark R.

    2006-12-01

    We have performed molecular dynamics simulations of a 2,5-bis-(p-hydroxyphenyl)-1,3,4-oxadiazole mesogen (ODBP-Ph-C7) at a fully atomistic level for a range of temperatures within the region that has experimentally been assigned to a biaxial nematic phase. Analysis of the data shows that the simulated nematic phase is biaxial but that the degree of biaxiality is small. The simulations show also the formation of ferroelectric domains in the nematic where the molecular short axis is aligned with the oxadiazole dipoles parallel to each other. Removal of electrostatic interactions leads to destabilization of ferroelectric domains and destabilization of the biaxiality. An additional simulation shows the slow growth of a mesophase directly from the isotropic fluid over a period of approximately 50 ns. This is the first time this has been achieved within the framework of an all-atom model.

  1. Thermotropic nanostructured "gel in gel" systems for improved oil recovery and water shutoff

    NASA Astrophysics Data System (ADS)

    Altunina, L. K.; Kuvshinov, V. A.; Stasyeva, L. A.

    2015-10-01

    Thermotropic nanostructured system with two gel-forming components has been created based on inorganic hydroxypolymer and organic polymer with a lower critical solution temperature of "aluminum salt-cellulose ether-carbamide-water", forming at heating a bound-dispersed nano-sized "gel in gel" structure. The studies on the kinetics of gelation and rheological properties of solutions and gels in this system have shown that the gels have a higher viscosity and elasticity and thereby are promising for creating deflecting screens in oil reservoirs, redistribution of filtration flows, improved oil recovery and for water shutoff.

  2. Phase separation in InGaN/GaN multiple quantum wells

    SciTech Connect

    McCluskey, M.D.; Romano, L.T.; Krusor, B.S.; Bour, D.P.; Johnson, N.M.; Brennan, S.

    1998-04-01

    Evidence is presented for phase separation in In{sub 0.27}Ga{sub 0.73}N/GaN multiple quantum wells. After annealing for 40 h at a temperature of 950{degree}C, the absorption threshold at 2.95 eV is replaced by a broad peak at 2.65 eV. This peak is attributed to the formation of In-rich InGaN phases in the active region. X-ray diffraction measurements show a shift in the diffraction peaks toward GaN, consistent with the formation of an In-poor phase. A diffraction peak corresponding to an In-rich phase is also present in the annealed material. Nanoscale In-rich InGaN precipitates are observed by transmission electron microscopy and energy dispersive x-ray chemical analysis. {copyright} {ital 1998 American Institute of Physics.}

  3. Phase Separation Kinetics of a Binary Polymer Blend with Added Random Copolymer

    NASA Astrophysics Data System (ADS)

    Waldow, Dean; Barham, Bethany; Halasa, Adel

    1998-03-01

    The phase separation kinetics of a polymer blend with increasing amounts of random copolymer was studied using wide angle light scattering. The system is a blend of polystyrene and polybutadiene, and the copolymer is an asymmetric random styrene-butadiene copolymer (80/20). The composition of the blend is near critical and the weight percentages of the added copolymer vary from 0.0 to 2.5 percent. The temperature of the cloud point increases with increasing copolymer amount indicating a destabilizing effect. Light scattering data was collected while temperature was jumped from the one-phase region into the two-phase region near the phase boundary. Early stage and intermediate stage kinetics were analyzed using Cahn-Hillard-Cook theory and scaling theory. The early stage kinetics indicate a slowing of the diffusion constants with added copolymer, and the intermediate stage kinetics suggest that the scaling theory doesn't accurately describe the data.

  4. Calix[4]pyrroles: highly selective stationary phases for gas chromatographic separations.

    PubMed

    Fan, Jing; Wang, Zhenzhong; Li, Qian; Qi, Meiling; Shao, Shijun; Fu, Ruonong

    2014-10-01

    Calix[4]pyrroles offer a great potential as stationary phases for gas chromatography (GC) due to their unique structures and physicochemical properties. Herein we present the first report of using two calix[4]pyrroles, namely meso-tetra-cyclohexylcalix[4]pyrrole (THCP) and meso-octamethylcalix[4]pyrrole (OMCP). These stationary phases were statically coated onto capillary columns and investigated in terms of column efficiency, polarity, separation performance, thermal stability and repeatability. The columns achieved column efficiencies of 2200-3000plates/m and exhibited nonpolar nature with an average polarity of 67 for THCP and 64 for OMCP, respectively. THCP stationary phase shows high selectivity for analytes of different polarity and exhibits nice peak shapes, especially for aldehydes, alcohols and anilines that are prone to severe peak tailing in GC analysis. Interestingly, THCP stationary phase possesses superior resolving ability for aniline and benzenediol positional isomers while OMCP shows preferential selectivity for nonpolar analytes such as hexane isomers. Moreover, calix[4]pyrrole columns also have good thermal stability up to 260°C and repeatability with a relative standard deviation (RSD%) of less than 0.10% for run-to-run and less than 5.2% for column-to-column. This work demonstrates the unique separation performance of calix[4]pyrroles and their promising future as a new class of GC stationary phases. PMID:25173993

  5. Phase separation in vacuum codeposited pentacene/6,13-pentacenequinone thin films

    SciTech Connect

    Salzmann, Ingo; Opitz, Ricarda; Rogaschewski, Siegfried; Rabe, Juergen P.; Koch, Norbert; Nickel, Bert

    2007-05-01

    Pentacene (P) and 6,13-pentacenequinone (PQ) have been vacuum codeposited onto SiO{sub 2} in order to control phase separation in thin films for the application as bulk heterojunctions in organic photovoltaic devices. Structural investigations by means of scanning electron microscopy (SEM) and atomic force microscopy revealed pronounced phase separation of the two materials at length scales that turned out to be tunable by the variation of the deposition rate. X-ray diffraction provided evidence for polymorphism in pure films of P and PQ on SiO{sub 2}. While pure films exhibited both the bulk and thin-film phase, the bulk phase is mainly suppressed within the co-deposited films (P+PQ). This was corroborated by Fourier-transform infrared spectroscopy results. SEM investigations of pure and codeposited films indicated that PQ bulk crystallites of up to 200 nm height form continuous paths to the substrate and grow within a matrix formed of P and PQ thin-film phases. The obtained heterojunction morphologies thus appear interesting for the application in organic-based photovoltaic cells.

  6. The rheology and phase separation kinetics of mixed-matrix membrane dopes

    NASA Astrophysics Data System (ADS)

    Olanrewaju, Kayode Olaseni

    Mixed-matrix hollow fiber membranes are being developed to offer more efficient gas separations applications than what the current technologies allow. Mixed-matrix membranes (MMMs) are membranes in which molecular sieves incorporated in a polymer matrix enhance separation of gas mixtures based on the molecular size difference and/or adsorption properties of the component gases in the molecular sieve. The major challenges encountered in the efficient development of MMMs are associated with some of the paradigm shifts involved in their processing, as compared to pure polymer membranes. For instance, mixed-matrix hollow fiber membranes are prepared by a dry-wet jet spinning method. Efficient large scale processing of hollow fibers by this method requires knowledge of two key process variables: the rheology and kinetics of phase separation of the MMM dopes. Predicting the rheological properties of MMM dopes is not trivial; the presence of particles significantly affects neat polymer membrane dopes. Therefore, the need exists to characterize and develop predictive capabilities for the rheology of MMM dopes. Furthermore, the kinetics of phase separation of polymer solutions is not well understood. In the case of MMM dopes, the kinetics of phase separation are further complicated by the presence of porous particles in a polymer solution. Thus, studies on the phase separation kinetics of polymer solutions and suspensions of zeolite particles in polymer solutions are essential. Therefore, this research thesis aims to study the rheology and phase separation kinetics of mixed-matrix membrane dopes. In our research efforts to develop predictive models for the shear rheology of suspensions of zeolite particles in polymer solutions, it was found that MFI zeolite suspensions have relative viscosities that dramatically exceed the Krieger-Dougherty predictions for hard sphere suspensions. Our investigations showed that the major origin of this discrepancy is the selective

  7. 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.

  8. Dynamical Clustering and Phase Separation in Suspensions of Self-Propelled Colloidal Particles

    NASA Astrophysics Data System (ADS)

    Buttinoni, Ivo; Bialké, Julian; Kümmel, Felix; Löwen, Hartmut; Bechinger, Clemens; Speck, Thomas

    2013-06-01

    We study experimentally and numerically a (quasi-)two-dimensional colloidal suspension of self-propelled spherical particles. The particles are carbon-coated Janus particles, which are propelled due to diffusiophoresis in a near-critical water-lutidine mixture. At low densities, we find that the driving stabilizes small clusters. At higher densities, the suspension undergoes a phase separation into large clusters and a dilute gas phase. The same qualitative behavior is observed in simulations of a minimal model for repulsive self-propelled particles lacking any alignment interactions. The observed behavior is rationalized in terms of a dynamical instability due to the self-trapping of self-propelled particles.

  9. Observations of homogeneous phase separation in liquid He3-He4 mixtures

    NASA Technical Reports Server (NTRS)

    Hoffer, J. K.; Campbell, L. J.; Bartlett, R. J.

    1980-01-01

    The so-called miscibility gap that exists below the critical point in liquid He-3 - H-4 mixtures makes it possible to study binary phase composition, and the ensuing dispersions, in a system possessing an additional order parameter in one of the components. The physical behavior of a superfluid dispersion produced by pressure quenching an He-3 - He-4 mixture into the miscibility gap is described. The description applies both to quenches of homogeneous and phase-separated initial states in various regions of the miscibility gap.

  10. CFD simulation of single-phase and two-phase flow in gas-liquid cylindrical cyclone separators

    SciTech Connect

    Erdal, F.M.; Shirazi, S.A.; Shoham, O.; Kouba, G.E.

    1996-12-31

    The petroleum industry has shown interest in utilizing the Gas Liquid Cylindrical Cyclone (GLCC) separator as an alternative to the vessel-type separator. Thus, it is important to develop predictive tools for design and to be able to improve the technology of the GLCC. Previous studies have resulted in mechanistic models capable of predicting the operational envelope for liquid carry-over. However, these models do not address details of the complex flow field in the GLCC and related phenomena such as gas carry-under. This paper presents computational fluid dynamics (CFD) simulations of single-phase and- two-phase flow in several GLCC configurations. The CFD simulations are compared with experimental data including tangential velocity profiles and tangential velocity decay. Good agreement is observed between the data and the simulations. An axisymmetric flow model for the GLCC is also developed. The axisymmetric model, which is computationally efficient, gives good results as compared to the three-dimensional simulations. Preliminary two-phase flow simulations are also performed to predict the gas void fraction distribution in the GLCC.

  11. Soft-shear induced phase-separated nanoparticle string-structures in polymer thin films.

    PubMed

    Zhang, Ren; Lee, Bongjoon; Bockstaller, Michael R; Al-Enizi, Abdullah M; Elzatahry, Ahmed; Berry, Brian C; Karim, Alamgir

    2016-04-12

    Application of shear stress has been shown to unidirectionally orient the microstructures of block copolymers and polymer blends. In the present work, we study the phase separation of a novel nanoparticle (NP)-polymer blend thin film system under shear using a soft-shear dynamic zone annealing (DZA-SS) method. The nanoparticles are densely grafted with polymer chains of chemically dissimilar composition from the matrix polymer, which induces phase separation upon thermal annealing into concentrated nanoparticle domains. We systematically examine the influence of DZA-SS translation speed and thus the effective shear rate on nanoparticle domain elongation and compare this with the counterpart binary polymer blend behavior. Unidirectionally aligned nanoparticle string-domains are fabricated in the presence of soft-shear in confined thin film geometry. We expect this DZA-SS method to be applicable to various NP-polymer blends towards unidirectionally aligned nanoparticle structures, which are important to functional nanoparticle structure fabrication. PMID:26814827

  12. Molecular dynamics study of phase separation in fluids with chemical reactions

    NASA Astrophysics Data System (ADS)

    Krishnan, Raishma; Puri, Sanjay

    2015-11-01

    We present results from the first d =3 molecular dynamics (MD) study of phase-separating fluid mixtures (AB) with simple chemical reactions (A ⇌B ). We focus on the case where the rates of forward and backward reactions are equal. The chemical reactions compete with segregation, and the coarsening system settles into a steady-state mesoscale morphology. However, hydrodynamic effects destroy the lamellar morphology which characterizes the diffusive case. This has important consequences for the phase-separating structure, which we study in detail. In particular, the equilibrium length scale (ℓeq) in the steady state suggests a power-law dependence on the reaction rate ɛ :ℓeq˜ɛ-θ with θ ≃1.0 .

  13. Separation of basic oligopeptides by ion-pairing reversed-phase chromatography

    NASA Astrophysics Data System (ADS)

    Xie, Wenchun

    The present thesis consist of five chapters. Chapter I introduces background information on the ion-pairing reversed-phase chromatography and liquid chromatography in the critical condition. Chapter II decribes our study on the isocratic separation of oligolysine (dp = 2 to 8) using a fixed content of acetonitrile (ACN) (23%) and different concentrations of HFBA in the mobile phase (0.6-30.6 mM) on a Waters XBridge Shield RP18® column. We found that the retention time of oligolysine increases as the dp increases, because of an increased number of HFBA bound to the peptides. Furthermore, when [HFBA] increased, the retention time increased at different rates. The greater the dp, the faster the rate. Based on a closed pairing model that presumes an equilibrium between an unpaired state and the paired state with a fixed number of HFBA molecules, an equation was derived for the retention factor of oligolysine. In Chapter III, we compare retention behaviors of oligolysine (dp = 2 to 8) and oligoarginine (dp = 2 to 8) when they are separated on the Waters XBridge Shield RP18® using fixed a ACN content (23%) and difference concentrations of HFBA (0.4-30.6 mM) in the mobile phase. The retention time of oligoarginine also increased at different rates as [HFBA] increased. The greater the dp, the faster the rate. The retention time of oligolysine is shorter than that of oligarginine having the dame dp. We applied Eq.1 to analyze the plot of ln k as a function of [HFBA] for each oligopeptide component to obtain the values for n, Kip,m, and βKd,ip. For oligolysine, n increases linearly as dp increase and oligoarginine exhibits an accelerated increase in n as dp rises. The plot of ln βKd,ip against dp followed a linear relationship for both peptides. In Chapter IV, we study the effect of mobile phase composition on the retention of oligolysine (dp = 2 to 8) on the Waters XBridge Shield RP18 ®. The ACN content was changed from 20% to 33% and the HFBA concentration from 0.7 to

  14. Influence of phase separation on the devitrification of 45S5 bioglass.

    PubMed

    Golovchak, R; Thapar, P; Ingram, A; Savytskii, D; Jain, H

    2014-11-01

    The devitrification of the 45S5 variety of bioactive glasses (BGs) in relation to phase separation is studied with scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry and positron annihilation lifetime spectroscopy techniques. It is shown that the type of phase separation (such as spinodal vs. droplet-like) has a pronounced effect on the activation energy of viscous flow and crystallization, the onset temperature of crystallization and the void size distribution at the nanoscale. Generally, the Johnson-Mehl-Avrami (JMA) relation does not describe crystallization kinetics in bulk 45S5 BG. However, for powder samples (<300 μm) the difference in crystallization kinetics, which is surface-driven for the two kinds of glasses, becomes much smaller, and can be described with the JMA relation under some circumstances. PMID:25072619

  15. Tunable tissue scaffolds fabricated by in situ crosslink in phase separation system

    PubMed Central

    Liu, Xifeng; Chen, Wenjian; Gustafson, Carl T.; Miller, A. Lee; Waletzki, Brian E.; Yaszemski, Michael J.; Lu, Lichun

    2015-01-01

    Three-dimensional (3-D) scaffolds with intrinsic porous structures are desirable in various tissue regeneration applications. In this study, a unique method that combines thermally induced phase separation with a photocrosslinking process was developed for the fabrication of 3-D crosslinked polymer scaffolds with densely interconnected porous structures. Biodegradable poly(propylene fumarate)-co-poly(L-lactic acid) with crosslinkable fumarate bonds were used as the structural polymer material and a dioxane/water binary system was applied for the phase separation. By altering the polymer composition (9, 5 and 3 wt%), different types of scaffolds with distinct morphology, mechanical strength, degradation rate, cell growth and morphology, and extracellular matrix production were fabricated. These crosslinked 3-D porous scaffolds with tunable strength and biological responses show promise for potential applications in regenerative therapies, including bone and neural tissue engineering. PMID:26989479

  16. Homeotropically aligning phase separated columnar structures for fabrication of flexible electrooptical devices

    NASA Astrophysics Data System (ADS)

    Acharya, Bharat R.; Choi, Hyunchul; Srinivasarao, Mohan; Kumar, Satyendra

    2011-11-01

    A method of achieving homeotropic alignment of liquid crystals (LCs) by ultraviolet light induced phase separation of LC from its mixture with photo-curable pre-polymer is reported. Vertical polymer columns and micro-fibrils developed during the phase separation promote homeotropic alignment of the LC director (i.e., alignment perpendicular to the LC-substrate interface), suitable for devices based on LCs possessing negative dielectric anisotropy. These vertical structures extend between two substrates and permit the fabrication of highly flexible electro-optical devices with high contrast coupled with fast response times. This simple single-step technique eliminates the need for the traditional polymer alignment layer pre-deposited on substrates.

  17. Synthesis of semicrystalline nanocapsular structures obtained by Thermally Induced Phase Separation in nanoconfinement

    PubMed Central

    Torino, Enza; Aruta, Rosaria; Sibillano, Teresa; Giannini, Cinzia; Netti, Paolo A.

    2016-01-01

    Phase separation of a polymer solution exhibits a peculiar behavior when induced in a nanoconfinement. The energetic constraints introduce additional interactions between the polymer segments that reduce the number of available configurations. In our work, this effect is exploited in a one-step strategy called nanoconfined-Thermally Induced Phase Separation (nc-TIPS) to promote the crystallization of polymer chains into nanocapsular structures of controlled size and shell thickness. This is accomplished by performing a quench step of a low-concentrated PLLA-dioxane-water solution included in emulsions of mean droplet size <500 nm acting as nanodomains. The control of nanoconfinement conditions enables not only the production of nanocapsules with a minimum mean particle diameter of 70 nm but also the tunability of shell thickness and its crystallinity degree. The specific properties of the developed nanocapsular architectures have important implications on release mechanism and loading capability of hydrophilic and lipophilic payload compounds. PMID:27604818

  18. Synthesis of semicrystalline nanocapsular structures obtained by Thermally Induced Phase Separation in nanoconfinement.

    PubMed

    Torino, Enza; Aruta, Rosaria; Sibillano, Teresa; Giannini, Cinzia; Netti, Paolo A

    2016-01-01

    Phase separation of a polymer solution exhibits a peculiar behavior when induced in a nanoconfinement. The energetic constraints introduce additional interactions between the polymer segments that reduce the number of available configurations. In our work, this effect is exploited in a one-step strategy called nanoconfined-Thermally Induced Phase Separation (nc-TIPS) to promote the crystallization of polymer chains into nanocapsular structures of controlled size and shell thickness. This is accomplished by performing a quench step of a low-concentrated PLLA-dioxane-water solution included in emulsions of mean droplet size <500 nm acting as nanodomains. The control of nanoconfinement conditions enables not only the production of nanocapsules with a minimum mean particle diameter of 70 nm but also the tunability of shell thickness and its crystallinity degree. The specific properties of the developed nanocapsular architectures have important implications on release mechanism and loading capability of hydrophilic and lipophilic payload compounds. PMID:27604818

  19. Insertion of interlayers in efficient polymer-based organic solar cells for control of phase separation

    NASA Astrophysics Data System (ADS)

    Taima, Tetsuya; Tanaka, Jun; Kuwabara, Takayuki; Takahashi, Kohshin

    2016-02-01

    To improve the solar cell performance of polymer-based organic solar cells, the control of phase separation in the bulk heterojunction (BHJ) layer is important. In the case of a thienothiophene-benzodithiophene-based polymer (PTB7)-based solar cell, 1,8-diiodoctane (DIO) is added into the chlorobenzene solvent. However, it is well known that DIO addition causes degradation in long-term operation. Here, we try to improve the performance of the PTB7-based BHJ solar cell by controlling the phase separation in the BHJ layer through the insertion of an inorganic semiconducting copper iodide (CuI) interlayer between the BHJ layer and indium tin oxide. The power conversion efficiency of the PTB7-based solar cell is improved from 3.5 to 3.9% upon inserting the CuI interlayer without DIO addition.

  20. Morphology and Composition of Structured, Phase-Separated Behenic Acid-Perfluorotetradecanoic Acid Monolayer Films.

    PubMed

    Rehman, Jeveria; Araghi, Hessamaddin Younesi; He, Anqiang; Paige, Matthew F

    2016-05-31

    The phase separation of immiscible surfactants in mixed monolayer films provides an approach to physically manipulate important properties of thin films, including surface morphology, microscale composition, and mechanical properties. In this work, we predict, based upon existing miscibility studies and their thermodynamic underpinnings described in the literature, the miscibility and film morphology of mixed monolayers comprised of behenic acid (C21H43COOH) and perfluorotetradecanoic acid (C13F27COOH) in various molar ratios. Predictions are tested using a combination of experimental surface characterization methods for probing miscibility and film morphology at the solid/air and air/water interfaces. Film components were immiscible and phase-separated into chemically well-defined domains under a variety of experimental conditions, with monolayer morphology consistent with initial predictions. The extensibility of these basic predictions to other systems is discussed in the context of using these works for different perfluorinated surfactant molecules. PMID:27163482

  1. Fabrication of microchannels by space-selective control of phase separation in glass.

    PubMed

    Yu, Yongze; Chen, Yeqin; Chen, Jiejie; Lv, Shichao; Feng, Xu; Qi, Yuzhong; Qiu, Jianrong; Zhou, Shifeng

    2016-07-15

    Microchannels have important scientific applications in many fields, because they enable precise control, manipulation, and analysis of fluid on a micrometer scale. Herein, we demonstrate an effective strategy for fabrication of microchannels, based on the space-selective phase separation in glass induced by a femtosecond laser. The proposed method shows its abilities in fabrication of three-dimensional microchannels with ∼5  mm length scale and a uniform cross section. Moreover, we also achieve the modulation of the morphology on the inner surface of microchannels by using objective lenses with various numerical-apertures. The physical mechanism of the phase separation and microstructure evolution is discussed. Our method provides new opportunities to fabricate microchannels with complex structures and multifunctional integration. PMID:27420538

  2. Using Image Processing Techniques for Cluster Analysis, and Droplet Formation in Phase Separating Fluids

    NASA Astrophysics Data System (ADS)

    Smith, Gregory; Oprisan, Ana; Hegseth, John; Oprisan, Sorinel; Lecoutre, Carole; Garrabos, Yves; Beysens, Daniel

    2009-03-01

    A series of experiments were performed using the Alice II apparatus in microgravity to study phase separation near critical temperature. Using image analysis techniques, we were able to obtain quantitative information regarding the morphology of gas-liquid interface near critical point of pure SF6 fluid in microgravity. Growth laws for liquid and gas clusters were extracted based on image segmentation both with thresholding and k-means clustering. By measuring the image features we analyzed the formation of spherical droplets during late stage of phase separation for a series of full view images. The growth of a wetting layer around the border of the cell containing the fluid was also investigated using image processing techniques.

  3. Molecular dynamics study of phase separation in fluids with chemical reactions.

    PubMed

    Krishnan, Raishma; Puri, Sanjay

    2015-11-01

    We present results from the first d=3 molecular dynamics (MD) study of phase-separating fluid mixtures (AB) with simple chemical reactions (A⇌B). We focus on the case where the rates of forward and backward reactions are equal. The chemical reactions compete with segregation, and the coarsening system settles into a steady-state mesoscale morphology. However, hydrodynamic effects destroy the lamellar morphology which characterizes the diffusive case. This has important consequences for the phase-separating structure, which we study in detail. In particular, the equilibrium length scale (ℓ(eq)) in the steady state suggests a power-law dependence on the reaction rate ε:ℓ(eq)∼ε(-θ) with θ≃1.0. PMID:26651704

  4. Influence of Soft Segment Composition on Phase Separated Microstructure of PDMS-Based Multiblock Polyurethane Copolymers.

    NASA Astrophysics Data System (ADS)

    Choi, Taeyi; Weksler, Jadwiga; Padsalgikar, Ajay; Runt, James

    2008-03-01

    Multiblock polyurethane (PU) copolymers with polydimethylsiloxane (PDMS) based soft segments possess intriguing microphase separation behavior and excellent biocompatibility. In this study we investigate the microphase-separated structure of PDMS-PUs with various well-defined soft segment compositions, which is closely connected to the structural and surface properties of these copolymers. The PDMS-PUs are shown to exhibit a three phase, core-shell like morphology. Intra- and intercomponent hydrogen bonding was explored using FTIR spectroscopy and quantitative analysis of hard/soft segment mixing was determined by small-angle X-ray scattering. The presentation will focus on the latest findings, particularly the role of PDMS in controlling the details of the microphase-separated texture.

  5. Quasiequilibrium states in thermotropic liquid crystals studied by multiple-quantum NMR

    NASA Astrophysics Data System (ADS)

    Buljubasich, L.; Monti, G. A.; Acosta, R. H.; Bonin, C. J.; González, C. E.; Zamar, R. C.

    2009-01-01

    Previous work showed that by means of the Jeener-Broekaert (JB) experiment, two quasiequilibrium states can be selectively prepared in the proton spin system of thermotropic nematic liquid crystals (LCs) in a strong magnetic field. The similarity of the experimental results obtained in a variety of LC in a broad Larmor frequency range, with crystal hydrates, supports the assumption that also in LC the two spin reservoirs, into which the Zeeman order is transferred, originate in the dipolar energy and that they are associated with a separation in energy scales: A constant of motion related to the stronger dipolar interactions (S), and a second one (W) corresponding to the secular part of the weaker dipolar interactions with regard to the Zeeman and the strong dipolar part. We study the nature of these quasi-invariants in nematic 5CB (4'-pentyl-4-biphenyl-carbonitrile) and measure their relaxation times by encoding the multiple-quantum coherences of the states following the JB pulse pair on two orthogonal bases, Z and X. The experiments were also performed in powder adamantane at 301K which is used as a reference compound having only one dipolar quasi-invariant. We show that the evolution of the quantum states during the buildup of the quasiequilibrium state in 5CB prepared under the S condition is similar to the case of powder adamantane and that their quasiequilibrium density operators have the same tensor structure. In contrast, the second constant of motion, whose explicit operator form is not known, involves a richer composition of multiple-quantum coherences of even order on the X basis, in consistency with the truncation inherent in its definition. We exploited the exclusive presence of coherences of ±4,±6,±8, besides 0 and ±2 under the W condition to measure the spin-lattice relaxation time TW accurately, so avoiding experimental difficulties that usually impair dipolar order relaxation measurement such as Zeeman contamination at high fields and also

  6. Reprint of: self-assembly of nanoparticles employing polymerization-induced phase separation.

    PubMed

    Williams, Roberto J J; Hoppe, Cristina E; Zucchi, Ileana A; Romeo, Hernán E; dell'Erba, Ignacio E; Gómez, María L; Puig, Julieta; Leonardi, Agustina B

    2015-06-01

    Nanoparticles (NPs) may be homogeneously dispersed in the precursors of a polymer (reactive solvent) by an adequate selection of their stabilizing ligands. However, the dispersion can become metastable or unstable in the course of polymerization. If this happens, NP-rich domains can be segregated by a process called polymerization-induced phase separation (PIPS). This occurs mainly due to the decrease in the entropic contribution of the reactive solvent to the free energy of mixing (increase in its average size) and, for a reactive solvent generating a cross-linked polymer, the additional contribution of the elastic energy in the post-gel stage. The extent of PIPS will depend on the competition between phase separation and polymerization rates. It can be completely avoided, limited to a local scale or conveyed to generate different types of NPs' aggregates such as crystalline platelets, self-assembled structures with a hierarchical order and partitioning at the interface, and bidimensional patterns of NPs at the film surface. The use of a third component in the initial formulation such as a linear polymer or a block copolymer, provides the possibility of generating an internal template for the preferential location and self-assembly of phase-separated NPs. Some illustrative examples of morphologies generated by PIPS in solutions of NPs in reactive solvents, are analyzed in this feature article. PMID:25736431

  7. Self-assembly of nanoparticles employing polymerization-induced phase separation.

    PubMed

    Williams, Roberto J J; Hoppe, Cristina E; Zucchi, Ileana A; Romeo, Hernán E; dell'Erba, Ignacio E; Gómez, María L; Puig, Julieta; Leonardi, Agustina B

    2014-10-01

    Nanoparticles (NPs) may be homogeneously dispersed in the precursors of a polymer (reactive solvent) by an adequate selection of their stabilizing ligands. However, the dispersion can become metastable or unstable in the course of polymerization. If this happens, NP-rich domains can be segregated by a process called polymerization-induced phase separation (PIPS). This occurs mainly due to the decrease in the entropic contribution of the reactive solvent to the free energy of mixing (increase in its average size) and, for a reactive solvent generating a cross-linked polymer, the additional contribution of the elastic energy in the post-gel stage. The extent of PIPS will depend on the competition between phase separation and polymerization rates. It can be completely avoided, limited to a local scale or conveyed to generate different types of NPs' aggregates such as crystalline platelets, self-assembled structures with a hierarchical order and partitioning at the interface, and bidimensional patterns of NPs at the film surface. The use of a third component in the initial formulation such as a linear polymer or a block copolymer, provides the possibility of generating an internal template for the preferential location and self-assembly of phase-separated NPs. Some illustrative examples of morphologies generated by PIPS in solutions of NPs in reactive solvents, are analyzed in this feature article. PMID:25014172

  8. Experimental evidence for phase separation in hydrogen-helium mixtures at Jovian planet conditions

    NASA Astrophysics Data System (ADS)

    Collins, G. W.; Brygoo, S.; Millot, M.; Rygg, J. R.; Celliers, P. M.; Eggert, J.; Boehly, T. R.; Jeanloz, R.; Loubeyre, P.

    2015-11-01

    Whether or not H-He mixtures phase separate in Jovian planets is important to our understanding of the structure and evolution of Jupiter and Saturn. Also integral to such planet models, as well as mechanisms for H-He phase separation, are the insulating-to-conducting and the molecular-to-atomic-hydrogen transitions in the H-He mixture. Coupling static and dynamic compression techniques has allowed us to make the first thermodynamic and transport measurements of H-He mixtures at deep Jovian planet conditions. These data provide evidence that the H-He fluid demixes at the high pressures and temperatures expected to exist deep inside Saturn and Jupiter. This phase separation may result in the differentiation of heavier helium clusters, leading to helium rain in the deep interior of Saturn and perhaps even in a significant outer layer of Jupiter. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory in part under Contract W-7405-Eng-48 and in part under Contract DE-AC52-07NA27344.

  9. Controlling Phase Separation of Tough Interpenetrating Polymer Networks via Addition of Amphiphilic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Rohde, Brian; Krishnamoorti, Ramanan; Robertson, Megan

    Interpenetrating polymer networks (IPNs) offer a unique way to combine the mechanical properties of two thermoset systems. Often used to create a material that possesses both high toughness and tensile properties, here we use polydicyclopentadiene, cured via ring opening metathesis polymerization, to contribute high toughness and diglycidyl ether of bisphenol A cured via anhydride chemistry to contribute high tensile strength and modulus. As the uncompatibilized system reacts in the presence of one another, mesoscopic phase separation occurs and dictates the overall efficacy of combining mechanical properties. To control phase separation and drive the system towards more mechanically robust nanostructed IPNs, amphiphilic block copolymers of polybutadiene- b-polyethylene oxide, where one block possesses strong affinity to polyDCPD and the other the DGEBA, were added to the system. Here we present a systematic study of the influence of block copolymer composition in the overall blend on degree of phase separation and morphology using a combination of small-angle x-ray scattering (SAXS) and scanning electron microscopy (SEM) techniques. The resultant mechanical properties are then explored in an effort to link mechanical properties to blend morphology.

  10. 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.

  11. Microfluidic Production of Semipermeable Microcapsules by Polymerization-Induced Phase Separation.

    PubMed

    Kim, Bomi; Jeon, Tae Yoon; Oh, You-Kwan; Kim, Shin-Hyun

    2015-06-01

    Semipermeable microcapsules are appealing for controlled release of drugs, study of cell-to-cell communication, and isolation of enzymes or artificial catalysts. Here, we report a microfluidic strategy for creating monodisperse microcapsules with size-selective permeability using polymerization-induced phase separation. Monodisperse water-in-oil-in-water (W/O/W) double-emulsion drops, whose ultrathin middle layer is composed of photocurable resin and inert oil, are generated in a capillary microfluidic device, and irradiated by UV light. Upon UV illumination, the monomers are photopolymerized, which leads to phase separation between the polymerized resin and the oil within the ultrathin shell. Subsequent dissolution of the oil leaves behind regular pores in the polymerized membrane that interconnect the interior and exterior of the microcapsules, thereby providing size-selective permeability. The degree of phase separation can be further tuned by adjusting the fraction of oil in the shell or the affinity of the oil to the monomers, thereby enabling the control of the cutoff value of permeation. High mechanical stability and chemical resistance of the microcapsules, as well as controllable permeability and high encapsulation efficiency, will provide new opportunity in a wide range of applications. PMID:26020458

  12. Controlling Phase Separation of Interpenetrating Polymer Networks by Addition of Block Copolymers

    NASA Astrophysics Data System (ADS)

    Rohde, Brian; Krishnamoorti, Ramanan; Robertson, Megan

    2015-03-01

    Interpenetrating polymer networks (IPNs) offer a unique way to produce mechanically superior thermoset blends relative to the neat components. In this study, IPNs were prepared consisting of polydicyclopentadiene (polyDCPD), contributing high fracture toughness, and an epoxy resin (the diglycidyl ether of bisphenol A cured with nadic methyl anhydride), contributing high tensile strength and modulus. In the absence of compatibilization, the simultaneous curing of the networks leads to a macroscopically phase separated blend that exhibits poor mechanical behavior. To control phase separation and drive the system towards more mechanically robust nanostructured IPNs, block copolymers were designed to compatibilize this system, where one block possesses affinity to polyDCPD (polynorbornene in this study) and the other block possesses affinity to DGEBA (poly(ɛ-caprolactone) in this study). The influence of the block copolymer composition on the degree of phase separation and interfacial adhesion in the IPN was studied using a combination of small-angle scattering and imaging techniques. The resultant mechanical properties were explored and structure-property relationships were developed in this blend system.

  13. Phase separation and rotor self-assembly in active particle suspensions

    PubMed Central

    Schwarz-Linek, J.; Valeriani, C.; Cacciuto, A.; Cates, M. E.; Marenduzzo, D.; Morozov, A. N.; Poon, W. C. K.

    2012-01-01

    Adding a nonadsorbing polymer to passive colloids induces an attraction between the particles via the “depletion” mechanism. High enough polymer concentrations lead to phase separation. We combine experiments, theory, and simulations to demonstrate that using active colloids (such as motile bacteria) dramatically changes the physics of such mixtures. First, significantly stronger interparticle attraction is needed to cause phase separation. Secondly, the finite size aggregates formed at lower interparticle attraction show unidirectional rotation. These micro-rotors demonstrate the self-assembly of functional structures using active particles. The angular speed of the rotating clusters scales approximately as the inverse of their size, which may be understood theoretically by assuming that the torques exerted by the outermost bacteria in a cluster add up randomly. Our simulations suggest that both the suppression of phase separation and the self-assembly of rotors are generic features of aggregating swimmers and should therefore occur in a variety of biological and synthetic active particle systems. PMID:22392986

  14. Lamellar, micro-phase separated blends of methyl cellulose and dendritic polyethylene glycol, POSS-PEG.

    PubMed

    Chinnam, Parameswara Rao; Mantravadi, Ramya; Jimenez, Jayvic C; Dikin, Dmitriy A; Wunder, Stephanie L

    2016-01-20

    Blends of methyl cellulose (MC) and liquid pegylated polyoctahedralsilsesquioxane (POSS-PEG) were prepared from non-gelled, aqueous solutions at room temperature (RT), which was below their gel temperatures (Tm). Lamellar, fibrillated films (pure MC) and increasingly micro-porous morphologies with increasing POSS-PEG content were formed, which had RT moduli between 1 and 5GPa. Evidence of distinct micro-phase separated MC and POSS-PEG domains was indicated by the persistence of the MC and POSS-PEG (at 77K) crystal structures in the X-ray diffraction data, and scanning transmission electron images. Mixing of MC and POSS-PEG in the interface region was indicated by suppression of crystallinity in the POSS-PEG, and increases/decreases in the glass transition temperatures (Tg) of POSS-PEG/MC in the blends compared with the pure components. These interface interactions may serve as cross-link sites between the micro-phase separated domains that permit incorporation of high amounts of POSS-PEG in the blends, prevent macro-phase separation and result in rubbery material properties (at high POSS-PEG content). Above Tg/Tm of POSS-PEG, the moduli of the blends increase with MC content as expected. However, below Tg/Tm of POSS-PEG, the moduli are greater for blends with high POSS-PEG content, suggesting that it behaves like semi-crystalline polyethylene oxide reinforced with silica (SiO1.5). PMID:26572324

  15. Phase Separation Kinetics in Isopycnic Mixtures of H2O/CO2/Ethoxylated Alcohol Surfactants

    NASA Technical Reports Server (NTRS)

    Lesemann, Markus; Paulaitis, Michael E.; Kaler, Eric W.

    1999-01-01

    Ternary mixtures of H2O and CO2 with ethoxylated alcohol (C(sub i)E(sub j)) surfactants form three coexisting liquid phases at conditions where two of the phases have equal densities (isopycnic phases). Isopycnic phase behavior has been observed for mixtures containing C8E5, C10E6, and C12E6 surfactants, but not for those mixtures containing either C4E1 or C8E3 surfactants. Pressure-temperature (PT) projections for this three-phase equilibrium were determined for H2O/CO2/C8E5 and H2O/CO2/C10E6 mixtures at temperatures from approximately 25 to 33 C and pressures between 90 and 350 bar. Measurements of the microstructure in H2O/CO2/C12E6 mixtures as a function of temperature (25-31 C), pressure (63.1-90.7 bar), and CO2 composition (0-3.9 wt%) have also been carried out to show that while micellar structure remains essentially un-changed, critical concentration fluctuations increase as the phase boundary and plait point are approached. In this report, we present our first measurements of the kinetics of isopycnic phase separation for ternary mixtures of H2O/CO2/C8E5.

  16. Effect of electric field and strain on the magnetic properties of phase separated manganites

    NASA Astrophysics Data System (ADS)

    Grant, Daniel M.

    Perovskite manganese oxide (manganites) have attracted research attention due to a wide variety of complex behaviors observed, including colossal responses to external perturbations. More recent work has focused on the competing ground states and the coexistence of magnetic and non-magnetic phases in manganites. Anisotropic resistance changes have been observed in high quality thin film manganites, possibly due to dielectrophoresis, upon application of an electric field. Dielectrophoresis is usually observed in fluid-like systems in an electric field but is surprisingly useful in explaining the transport properties of manganites due to the fluid-like behavior of competing phases. A main goal of this dissertation is to explore the role of magnetic interactions on the dielectrophoresis effects on ferromagnetic metallic regions in phase separated manganite thin films. The combined effect of electric and magnetic fields in these manganites could reveal a novel form of magnetoelectric effect. In one set of experiments, a magnetic field decreased the amount of time needed for the dielectrophoresis to lead to a large drop in the resistance along one direction, showing the importance of magnetic interactions in dielectrophoresis. In another set of experiments, breaking down the large resistance of a manganite sample produced a small change in coercive field, further confirming the relationship between electric and magnetic effects in manganites. However, the largest effect on the magnetic properties of the thin films was from confinement of the competing phases in micrometer scale structures fabricated on the thin films. Coercive field increases of about 100- 400% were observed in a certain range of film thicknesses. To analyze such behavior in manganites, high quality thin films of the phase-separated manganite (La1-xPrx)1-yCa yMnO3 (LPCMO) were grown on NdGaO3 (NGO) substrates using pulsed laser deposition. Mangetotransport, magnetization, and scanning probe microscopy

  17. Investigating hygroscopic behavior and phase separation of organic/inorganic mixed phase aerosol particles with FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Zawadowicz, M. A.; Cziczo, D. J.

    2013-12-01

    Atmospheric aerosol particles can be composed of inorganic salts, such as ammonium sulfate and sodium chloride, and therefore exhibit hygroscopic properties. Many inorganic salts have very well-defined deliquescence and efflorescence points at which they take up and lose water, respectively. For example, the deliquescence relative humidity of pure ammonium sulfate is about 80% and its efflorescence point is about 35%. This behavior of ammonium sulfate is important to atmospheric chemistry because some reactions, such as the hydrolysis of nitrogen pentoxide, occur on aqueous but not crystalline surfaces. Deliquescence and efflorescence of simple inorganic salt particles have been investigated by a variety of methods, such as IR spectroscopy, tandem mobility analysis and electrodynamic balance. Field measurements have shown that atmospheric aerosol are not typically a single inorganic salt, instead they often contain organic as well as inorganic species. Mixed inorganic/organic aerosol particles, while abundant in the atmosphere, have not been studied as extensively. Many recent studies have focused on microscopy techniques that require deposition of the aerosol on a glass slide, possibly changing its surface properties. This project investigates the deliquescence and efflorescence points, phase separation and ability to exchange gas-phase components of mixed organic and inorganic aerosol using a flow tube coupled with FTIR spectroscopy. Ammonium sulfate aerosol mixed with organic polyols with different O:C ratios, including glycerol, 1,2,6-hexanetriol, 1,4-butanediol and 1,5-pentanediol have been investigated. This project aims to study gas-phase exchange in these aerosol systems to determine if exchange is impacted when phase separation occurs.

  18. Phase separation and atomic ordering in indium gallium nitride epitaxial layers

    NASA Astrophysics Data System (ADS)

    Rao, Manu

    Phase separation and atomic ordering were investigated in InGaN layers grown by metalorganic chemical vapor deposition on (0001) sapphire substrates. Transmission electron microscopy (TEM) of InGaN layers during their early stages of growth reveal 2-D quantum rings that form spontaneously. In thick layers at InN contents of 3%, planview TEM images show a random distribution of atomic species and selected area diffraction (SAD) patterns do not exhibit satellite spots continuous to Bragg reflections. InN contents of 12% result in a speckled microstructure and satellites are present in SAD patterns. No satellites are observed along the [0001] direction, implying that phase separation is two-dimensional in nature and may occur on the surface while the layer is growing. These results are indicative of composition modulations lying in the (0001) growth plane. Samples containing InN fractions of between 22 and 34% exhibit microstructures having stronger contrast variations and SAD patterns with satellites further spaced from fundamental reflections. In cross-sectional TEM images, contrast striations oriented along [0001] are present except near the InGaN/GaN interface. The spacing of these striations is comparable to the composition modulation wavelengths calculated from SADPs and decreases with increasing InN content. Similarly, plan view TEM images taken from very thin specimens exhibit a domain structure with well aligned stripes within the domains. Increasing the growth rate from 400nm/h to 900nm/h results in a reduction in the intensity of satellite spots, indicating that the amplitude of composition modulations is reduced. The absence of contrast near the InGaN/GaN interface suggest reduced In incorporation, resulting in the absence of phase separation. Reduced In incorporation is confirmed by high angle angular dark field (HAADF) imaging and energy dispersive x-ray spectroscopy (EDS). X-ray diffraction and photoluminescence data are consistent with the occurrence

  19. On-Chip Pressure Generation for Driving Liquid Phase Separations in Nanochannels.

    PubMed

    Xia, Ling; Choi, Chiwoong; Kothekar, Shrinivas C; Dutta, Debashis

    2016-01-01

    In this Article, we describe the generation of pressure gradients on-chip for driving liquid phase separations in submicrometer deep channels. The reported pressure-generation capability was realized by applying an electrical voltage across the interface of two glass channel segments with different depths. A mismatch in the electroosmotic flow rate at this junction led to the generation of pressure-driven flow in our device, a fraction of which was then directed to an analysis channel to carry out the desired separation. Experiments showed the reported strategy to be particularly conducive for miniaturization of pressure-driven separations yielding flow velocities in the separation channel that were nearly unaffected upon scaling down the depth of the entire fluidic network. Moreover, the small dead volume in our system allowed for high dynamic control over this pressure gradient, which otherwise was challenging to accomplish during the sample injection process using external pumps. Pressure-driven velocities up to 3.1 mm/s were realized in separation ducts as shallow as 300 nm using our current design for a maximum applied voltage of 3 kV. The functionality of this integrated device was demonstrated by implementing a pressure-driven ion chromatographic analysis that relied on analyte interaction with the nanochannel surface charges to yield a nonuniform solute concentration across the channel depth. Upon coupling such analyte distribution to the parabolic pressure-driven flow profile in the separation duct, a mixture of amino acids could be resolved. The reported assay yielded a higher separation resolution compared to its electrically driven counterpart in which sample migration was realized using electroosmosis/electrophoresis. PMID:26636608

  20. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs

    SciTech Connect

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K.; Ruegg, Christian; Susner, Michael A.; Sefat, Athena S.; Zhigadlo, Nikolai D.; Morenzoni, Elvezio

    2015-09-08

    We report that the recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5≲ p ≲ 7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc3.2 as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs.

  1. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs.

    PubMed

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K; Rüegg, Christian; Susner, Michael A; Sefat, Athena S; Zhigadlo, Nikolai D; Morenzoni, Elvezio

    2015-01-01

    The recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5 < or ~  p < or ~ 7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc(3.2) as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs. PMID:26346548

  2. The relationship between oxygen permeability and phase separation morphology of the multicomponent silicone hydrogels.

    PubMed

    Zhao, Zhengbai; Xie, Haijiao; An, Shuangshuang; Jiang, Yong

    2014-12-18

    In this article, the multicomponent copolymers were prepared by the copolymerization of two hydrophobic silicon-containing monomers bis(trimethylsilyloxy) methylsilylpropyl glycerol methacrylate (SiMA) and tris(trimethylsiloxy)-3-methacryloxypropylsilane (TRIS) with three hydrophilic monomers 2-hydroxyethyl methacrylate, N-vinylpyrrolidone, and N,N-dimethyl acrylamide. The copolymers were hydrated to form transparent silicone hydrogels. The oxygen permeability coefficients (Dk) of hydrogels were measured, and their relationships with the equilibrium water contents (EWC) and the types and contents of silicon containing monomers as well as the phase separation structures of silicone hydrogels were analyzed in detail. The results showed that the EWC decreased as the increase of SiMA content. The relationship between Dk and SiMA content, as well as that between Dk and EWC, showed inverted bell curve distributions, which meant two main factors, i.e., silicon-oxygen bond in silicone and water in hydrogel, contributed to oxygen permeation and followed a mutual inhibition competition mechanism. The internal morphologies of the hydrogels were observed by transmission electron microscope, and the results showed that the hydrogels presented two different phase separation structures depending on the types of the silicon-containing monomers. The silicone phase in SiMA containing hydrogel presented to be a granular texture, while the silicone phase in TRIS containing hydrogel formed a fibrous texture which resulted in a higher Dk value. These results could help to design a silicone hydrogel with better properties and wider application. PMID:25423615

  3. Electronic phase separation at the LaAlO₃/SrTiO₃ interface.

    PubMed

    Ariando; Wang, X; Baskaran, G; Liu, Z Q; Huijben, J; Yi, J B; Annadi, A; Barman, A Roy; Rusydi, A; Dhar, S; Feng, Y P; Ding, J; Hilgenkamp, H; Venkatesan, T

    2011-01-01

    There are many electronic and magnetic properties exhibited by complex oxides. Electronic phase separation (EPS) is one of those, the presence of which can be linked to exotic behaviours, such as colossal magnetoresistance, metal-insulator transition and high-temperature superconductivity. A variety of new and unusual electronic phases at the interfaces between complex oxides, in particular between two non-magnetic insulators LaAlO(3) and SrTiO(3), have stimulated the oxide community. However, no EPS has been observed in this system despite a theoretical prediction. Here, we report an EPS state at the LaAlO(3)/SrTiO(3) interface, where the interface charges are separated into regions of a quasi-two-dimensional electron gas, a ferromagnetic phase, which persists above room temperature, and a (superconductor like) diamagnetic/paramagnetic phase below 60 K. The EPS is due to the selective occupancy (in the form of 2D-nanoscopic metallic droplets) of interface sub-bands of the nearly degenerate Ti orbital in the SrTiO(3). The observation of this EPS demonstrates the electronic and magnetic phenomena that can emerge at the interface between complex oxides mediated by the Ti orbital. PMID:21304517

  4. Buckling, driven by constrained phase separation, of toroid-shaped hydrogels

    NASA Astrophysics Data System (ADS)

    Dimitriyev, Michael S.; Chang, Ya-Wen; Souslov, Anton; Fernandez-Nieves, Alberto; Goldbart, Paul M.

    We investigate the buckling process observed in connection with the temperature-induced shrinking of an elastic toroid composed of hydrogel. Hydrogels are polymeric network media that become swollen when mixed with water, provided the temperature is low enough. As the temperature is increased beyond a certain point, such gels undergo a first-order de-swelling transition to a de-mixed state, in which the network segregates from the water, resulting in a shrunken phase. It is known that the rapid heating of swollen hydrogels beyond the de-swelling transition results in the formation of a shrunken-phase boundary region, or shell. This shell hinders the expulsion of fluid associated with the equilibration of the sample interior, and gives rise to a prolonged period of coexistence between shrunken and swollen domains in the interior of the sample. In contrast with the spherical case, toroidal samples have been observed to undergo a constrained phase separation that is accompanied by a global buckling (or ``Pringling'') deformation of the sample shape. We present a model of hydrogel toroid Pringling in which such deformations are driven by this phase separation process.

  5. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs

    PubMed Central

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K.; Rüegg, Christian; Susner, Michael A.; Sefat, Athena S.; Zhigadlo, Nikolai D.; Morenzoni, Elvezio

    2015-01-01

    The recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p  3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p  7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc  1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5  p  7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs. PMID:26346548

  6. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs

    DOE PAGESBeta

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K.; Ruegg, Christian; Susner, Michael A.; Sefat, Athena S.; Zhigadlo, Nikolai D.; et al

    2015-09-08

    We report that the recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreasesmore » upon increasing the pressure. In the intermediate pressure region (3.5≲ p ≲ 7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc3.2 as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs.« less

  7. Application of capillary fluid management techniques to the design of a phase separating microgravity bioreactor

    NASA Technical Reports Server (NTRS)

    Finger, Barry W.; Neville, Gale E., Jr.; Sager, John C.

    1993-01-01

    Manned space missions require the development of compact, efficient, and reliable life support systems. A number of aqueous biological conversion processes are associated with bioregenerative life support systems. Vessels, or bioreactors, capable of supporting these processes in microgravity must be developed. An annular flow bioreactor has been conceived. It has the potential to incorporate containment, phase separation, gas exchange, and illumination into a single vessel. The bioreactor utilizes capillary fluid management techniques and is configured as a cylindrical tube in which a two-phase liquid-gas flow is maintained. Vanes placed around the inner perimeter enhance capillary forces and cause the liquid phase to attach and flow along the interior surface of the tube. No physical barrier is required to complete phase separation. It is shown analytically that liquid film thickness is limited only by vane geometry and that an annular flow bioreactor capable of managing 284 liters would occupy 0.7 cubic m, less than half the volume of a Spacelab experiment rack.

  8. 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

  9. Magnetic-field-induced nematic-nematic phase separation and droplet formation in colloidal goethite.

    PubMed

    van den Pol, E; Verhoeff, A A; Lupascu, A; Diaconeasa, M A; Davidson, P; Dozov, I; Kuipers, B W M; Thies-Weesie, D M E; Vroege, G J

    2011-05-18

    We demonstrate the suitability of polarization microscopy to study the recently discovered (parallel) nematic-(perpendicular) nematic phase separation. This novel type of phase transition is induced by applying an external magnetic field to a nematic liquid crystal of boardlike colloidal goethite and is due to an interplay between the intrinsic magnetic properties of goethite and the collective effect of liquid crystal formation. It is shown that the intense ochre colour of goethite does not preclude the use of polarization microscopy and interference colours, and that dichroism can give valuable qualitative information on the nature of the phases, their anchoring and their sedimentation and order parameter profiles. We also apply these techniques to study 'nematic-nematic tactoids': nematic droplets sedimenting within a nematic medium with mutually perpendicular orientations. PMID:21525548

  10. 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.

  11. 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.

  12. 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

  13. Oscillatory phase separation in giant lipid vesicles induced by transmembrane osmotic differentials.

    PubMed

    Oglęcka, Kamila; Rangamani, Padmini; Liedberg, Bo; Kraut, Rachel S; Parikh, Atul N

    2014-01-01

    Giant lipid vesicles are closed compartments consisting of semi-permeable shells, which isolate femto- to pico-liter quantities of aqueous core from the bulk. Although water permeates readily across vesicular walls, passive permeation of solutes is hindered. In this study, we show that, when subject to a hypotonic bath, giant vesicles consisting of phase separating lipid mixtures undergo osmotic relaxation exhibiting damped oscillations in phase behavior, which is synchronized with swell-burst lytic cycles: in the swelled state, osmotic pressure and elevated membrane tension due to the influx of water promote domain formation. During bursting, solute leakage through transient pores relaxes the pressure and tension, replacing the domain texture by a uniform one. This isothermal phase transition--resulting from a well-coordinated sequence of mechanochemical events--suggests a complex emergent behavior allowing synthetic vesicles produced from simple components, namely, water, osmolytes, and lipids to sense and regulate their micro-environment. PMID:25318069

  14. Microphase-Separated PE/PEO Thin Films Prepared by Plasma-Assisted Vapor Phase Deposition.

    PubMed

    Choukourov, Andrei; Gordeev, Ivan; Ponti, Jessica; Uboldi, Chiara; Melnichuk, Iurii; Vaidulych, Mykhailo; Kousal, Jaroslav; Nikitin, Daniil; Hanyková, Lenka; Krakovský, Ivan; Slavínská, Danka; Biederman, Hynek

    2016-03-01

    Immiscible polymer blends tend to undergo phase separation with the formation of nanoscale architecture which can be used in a variety of applications. Different wet-chemistry techniques already exist to fix the resultant polymeric structure in predictable manner. In this work, an all-dry and plasma-based strategy is proposed to fabricate thin films of microphase-separated polyolefin/polyether blends. This is achieved by directing (-CH2-)100 and (-CH2-CH2-O-)25 oligomer fluxes produced by vacuum thermal decomposition of poly(ethylene) and poly(ethylene oxide) onto silicon substrates through the zone of the glow discharge. The strategy enables mixing of thermodynamically incompatible macromolecules at the molecular level, whereas electron-impact-initiated radicals serve as cross-linkers to arrest the subsequent phase separation at the nanoscale. The mechanism of the phase separation as well as the morphology of the films is found to depend on the ratio between the oligomeric fluxes. For polyolefin-rich mixtures, polyether molecules self-organize by nucleation and growth into spherical domains with average height of 22 nm and average diameter of 170 nm. For equinumerous fluxes and for mixtures with the prevalence of polyethers, spinodal decomposition is detected that results in the formation of bicontinuous structures with the characteristic domain size and spacing ranging between 5 × 10(1) -7 × 10(1) nm and 3 × 10(2)-4 × 10(2) nm, respectively. The method is shown to produce films with tunable wettability and biologically nonfouling properties. PMID:26953817

  15. Magnetic orderings and phase separations in a simple model of insulating systems

    NASA Astrophysics Data System (ADS)

    Kapcia, Konrad Jerzy; Murawski, Szymon; Kłobus, Waldemar; Robaszkiewicz, Stanisław

    2015-11-01

    A simple effective model for a description of magnetically ordered narrow-band insulators is studied. The Hamiltonian considered consists of the effective on-site interaction (U) and intersite magnetic exchange interactions (Jz, Jxy) between nearest-neighbours. The phase diagrams and properties of this model for arbitrary chemical potential μ and arbitrary electron density n have been determined within several approaches: (i) the variational method (which treats the on-site interaction term exactly and the intersite interactions within the mean-field approximation) for any Jz ,Jxy ≠ 0 (exact in the limit of infinite dimensions), (ii) the Monte Carlo simulations on a square lattice with periodic boundary conditions for Jxy = 0, and (iii) other approximate methods (inter alia: random phase approximation and spin-wave approximation) as well as (iv) rigorous treatment to obtain results concerning the ground state phase diagrams (the two last also for Jz ,Jxy ≠ 0). The investigations of the general case show that, depending on the values of interaction parameters and electron concentration n, the system can exhibit not only homogeneous phases: (anti-)ferromagnetic (Fα, α = z , xy) and nonordered (NO), but also phase separated states (PSα: Fα/NO). For a fixed n one finds the following phase transitions (both continuous and discontinuous ones) and their sequences, which can occur with increasing temperature: Fα → NO, PSα → NO, PSα →Fα → NO, PSα →Fα →PSα → NO. The system analysed exhibits also tricritical behaviour.

  16. Phase-separated, epitaxial composite cap layers for electronic device applications and method of making the same

    DOEpatents

    Aytug, Tolga; Paranthaman, Mariappan Parans; Polat, Ozgur

    2012-07-17

    An electronic component that includes a substrate and a phase-separated layer supported on the substrate and a method of forming the same are disclosed. The phase-separated layer includes a first phase comprising lanthanum manganate (LMO) and a second phase selected from a metal oxide (MO), metal nitride (MN), a metal (Me), and combinations thereof. The phase-separated material can be an epitaxial layer and an upper surface of the phase-separated layer can include interfaces between the first phase and the second phase. The phase-separated layer can be supported on a buffer layer comprising a composition selected from the group consisting of IBAD MgO, LMO/IBAD-MgO, homoepi-IBAD MgO and LMO/homoepi-MgO. The electronic component can also include an electronically active layer supported on the phase-separated layer. The electronically active layer can be a superconducting material, a ferroelectric material, a multiferroic material, a magnetic material, a photovoltaic material, an electrical storage material, and a semiconductor material.

  17. Activity mediated phase separation: Can we understand phase behavior of the nonequilibrium problem from an equilibrium approach?

    PubMed

    Trefz, Benjamin; Das, Subir K; Egorov, Sergei A; Virnau, Peter; Binder, Kurt

    2016-04-14

    We present results for structure and dynamics of mixtures of active and passive particles, from molecular dynamics (MD) simulations and integral equation theory (IET) calculations, for a physically motivated model. The perfectly passive limit of the model corresponds to the phase-separating Asakura-Oosawa model for colloid-polymer mixtures in which, for the present study, the colloids are made self-propelling by introducing activity in accordance with the well known Vicsek model. Such activity facilitates phase separation further, as confirmed by our MD simulations and IET calculations. Depending upon the composition of active and passive particles, the diffusive motion of the active species can only be realized at large time scales. Despite this, we have been able to construct an equilibrium approach to obtain the structural properties of such inherently out-of-equilibrium systems. In this method, effective inter-particle potentials were constructed via IET by taking structural inputs from the MD simulations of the active system. These potentials in turn were used in passive MD simulations, results from which are observed to be in fair agreement with the original ones. PMID:27083747

  18. Activity mediated phase separation: Can we understand phase behavior of the nonequilibrium problem from an equilibrium approach?

    NASA Astrophysics Data System (ADS)

    Trefz, Benjamin; Das, Subir K.; Egorov, Sergei A.; Virnau, Peter; Binder, Kurt

    2016-04-01

    We present results for structure and dynamics of mixtures of active and passive particles, from molecular dynamics (MD) simulations and integral equation theory (IET) calculations, for a physically motivated model. The perfectly passive limit of the model corresponds to the phase-separating Asakura-Oosawa model for colloid-polymer mixtures in which, for the present study, the colloids are made self-propelling by introducing activity in accordance with the well known Vicsek model. Such activity facilitates phase separation further, as confirmed by our MD simulations and IET calculations. Depending upon the composition of active and passive particles, the diffusive motion of the active species can only be realized at large time scales. Despite this, we have been able to construct an equilibrium approach to obtain the structural properties of such inherently out-of-equilibrium systems. In this method, effective inter-particle potentials were constructed via IET by taking structural inputs from the MD simulations of the active system. These potentials in turn were used in passive MD simulations, results from which are observed to be in fair agreement with the original ones.

  19. High-pressure light scattering apparatus to study pressure-induced phase separation in polymer solutions

    NASA Astrophysics Data System (ADS)

    Xiong, Yan; Kiran, Erdogan

    1998-03-01

    A new high-pressure time- and angle-resolved light scattering apparatus has been developed to study the kinetics of phase separation in polymer solutions and other fluid mixtures under pressure at near- and supercritical conditions. The system consists of a high-pressure polymer loading chamber, a solvent charge line, a variable-volume scattering cell (with a built-in movable piston connected to a pressure generator, and an expansion rod driven by an air-actuated diaphragm), and a recirculation pump which are all housed in a temperature-controlled oven. The system is operable at pressures up to 70 MPa, and temperatures up to 473 K. The scattering cell is a short path-length cell made of two flat sapphire windows that are separated by 250 μm. It is designed to permit measurements of transmitted and scattered light intensities over an angle range from 0° to 30°. A linear image sensor with 256 elements is used to monitor the time evolution of the scattered light intensities at different angles. With this sensor, the angle range from 2° to 13° is scanned at a sampling rate of 3.2 ms/scan. The pressure quenches are achieved by movement of the air-actuated movable expansion rod, or by the movement of the piston with the aid of the pressure generator to bring about either rapid (at rates approaching 2000 MPa/s) or slow pressure changes in the system. Quench depth is also adjustable, and very deep (70 MPa) or very shallow (as low as 0.1 MPa) pressure quenches are readily achievable. The temperature and the pressure of the solution in the scattering cell, and the transmitted and scattered light intensities at different angles are recorded in real time through a computerized data acquisition system before and during phase separation. The experimental system is especially suited to follow the kinetics of phase separation in polymer solutions and to assess the metastable and unstable regions where phase separation proceeds by the nucleation and growth, and the spinodal

  20. Relaxations and nano-phase-separation in ultraviscous heptanol-alkyl halide mixture

    NASA Astrophysics Data System (ADS)

    Power, G.; Vij, J. K.; Johari, G. P.

    2007-01-01

    To gain insight into the effects of liquid-liquid phase separation on molecular relaxation behavior we have studied an apparently homogeneous mixture of 5-methyl-2-hexanol and isoamylbromide by dielectric spectroscopy over a broad temperature range. It shows two relaxation regions, widely separated in frequency and temperature, with the low-frequency relaxation due to the alcohol and the high-frequency relaxation due to the halide. In the mixture, the equilibrium dielectric permittivity ɛs of the alcohol is 41% of the pure state at 155.7K and ɛs of isoamylbromide is ˜86% of the pure state at 128.7K. The difference decreases for the alcohol component with decreasing temperature and increases for the isoamylbromide component. The relaxation time τ of 5-methyl-2-hexanol in the mixture at 155.7K is over five orders of magnitude less than in the pure state, and this difference increases with decreasing temperature, but τ of isoamylbromide in the mixture is marginally higher than in the pure liquid. This shows that the mixture would have two Tg's corresponding to its τ of 103s, with values of ˜121K for its 5-methyl-2-hexanol component and ˜108K for its isoamylbromide component. It is concluded that the mixture phase separates in submicron or nanometer-size aggregates of the alcohol in isoamylbromide, without affecting the latter's relaxation kinetics, while its own ɛs and τ decrease markedly.

  1. Normal Gravity Testing of a Microchannel Phase Separator for In Situ Resource Utilization

    NASA Technical Reports Server (NTRS)

    TeGrotenhuis, Ward E.; Stenkamp, Victoria S.; McQuillen, John (Technical Monitor)

    2001-01-01

    A microchannel separator, with 2.7 millimeters as the smallest dimension, was tested, and a pore throat structure captured and removed liquid from a gas-liquid stream. The microchannel device was tested over a of gas and liquid flow rates ranging from 0.0005 up to 0. 14 volume fraction of liquid. Four liquids were tested with air. The biggest factor affecting the throughput is the capacity of liquid flow through the pore throat, which is dictated by permeability, liquid viscosity, flow area, pore throat thickness, and pressure difference across the pore throat. Typically, complete separation of gas and liquid fractions was lost when the liquid flow rate reached about 40 to 60% of the pore throat capacity. However, this could occur over a range of 10 to 90% utilization of pore throat capacity. Breakthrough occurs in the microchannel phase separator at conditions similar to the annular to plug flow transition of two-phase microgravity pipe flow implying that operating in the proper flow regime is crucial. Analysis indicates that the Bond number did not affect performance, supporting the premise that hydrodynamic, interfacial, and capillary forces are more important than gravity. However, the relative importance of gravity is better discerned through testing under reduced gravity conditions.

  2. Synthesis of a mixed-model stationary phase derived from glutamine for HPLC separation of structurally different biologically active compounds: HILIC and reversed-phase applications.

    PubMed

    Aral, Tarık; Aral, Hayriye; Ziyadanoğulları, Berrin; Ziyadanoğulları, Recep

    2015-01-01

    A novel mixed-mode stationary phase was synthesised starting from N-Boc-glutamine, aniline and spherical silica gel (4 µm, 60 Å). The prepared stationary phase was characterized by IR and elemental analysis. The new stationary phase bears an embedded amide group into phenyl ring, highly polar a terminal amide group and non-polar groups (phenyl and alkyl groups). At first, this new mixed-mode stationary phase was used for HILIC separation of four nucleotides and five nucleosides. The effects of different separation conditions, such as pH value, mobile phase and temperature, on the separation process were investigated. The optimum separation for nucleotides was achieved using HILIC isocratic elution with aqueous mobile phase and acetonitrile with 20°C column temperature. Under these conditions, the four nucleotides could be separated and detected at 265 nm within 14 min. Five nucleosides were separated under HILIC isocratic elution with aqueous mobile phase containing pH=3.25 phosphate buffer (10mM) and acetonitrile with 20°C column temperature and detected at 265 nm within 14 min. Chromatographic parameters as retention factor, selectivity, theoretical plate number and peak asymmetry factor were calculated for the effect of temperature and water content in mobile phase on the separation process. The new column was also tested for nucleotides and nucleosides mixture and six analytes were separated in 10min. The chromatographic behaviours of these polar analytes on the new mixed-model stationary phase were compared with those of HILIC columns under similar conditions. Further, phytohormones and phenolic compounds were separated in order to see influence of the new stationary phase in reverse phase conditions. Eleven plant phytohormones were separated within 13 min using RP-HPLC gradient elution with aqueous mobile phase containing pH=2.5 phosphate buffer (10mM) and acetonitrile with 20°C column temperature and detected at 230 or 278 nm. The best separation

  3. Ordering Transitions Triggered by Specific Binding of Vesicles to Protein-Decorated Interfaces of Thermotropic Liquid Crystals

    PubMed Central

    Tan, Lie Na; Orler, Victor J.; Abbott, Nicholas L.

    2012-01-01

    We report that specific binding of ligand-functionalized (biotinylated) phospholipid vesicles (diameter = 120 ± 19 nm) to a monolayer of proteins (streptavidin or anti-biotin antibody) adsorbed at an interface between an aqueous phase and an immiscible film of a thermotropic liquid crystal (LC) (nematic 4′-pentyl-4-cyanobiphenyl (5CB)) triggers a continuous orientational ordering transition (continuous change in the tilt) in the LC. Results presented in this paper indicate that, following the capture of the vesicles at the LC interface via the specific binding interaction, phospholipids are transferred from the vesicles onto the LC interface to form a monolayer, reorganizing and partially displacing proteins from the LC interface. The dynamics of this process are accelerated substantially by the specific binding event relative to a protein-decorated interface of a LC that does not bind the ligands presented by vesicles. The observation of the continuous change in the ordering of the LC, when combined with other results presented in this paper, is significant as it is consistent with the presence of sub-optical domains of proteins and phospholipids on the LC interface. An additional significant hypothesis that emerges from the work reported in this paper is that the ordering transition of the LC is strongly influenced by the bound state of the protein adsorbed on the LC interface, as evidenced by the influence on the LC of (i) “crowding” of the protein within a monolayer formed at the LC interface and (ii) aging of the proteins on the LC interface. Overall, these results demonstrate that ordering transitions in LCs can be used to provide fundamental insights into the competitive adsorption of proteins and lipids at oil-water interfaces, and that LC ordering transitions have the potential to be useful for reporting specific binding events involving vesicles and proteins. PMID:22372743

  4. Pattern Polymerization-Induced Phase Separation in a Polymer-Dispersed Liquid Crystal System

    NASA Astrophysics Data System (ADS)

    Kyu, Thein

    2002-03-01

    Liquid crystal (LC)/polymer composite films have gained attention increasingly due to their applications in flat panel displays and shutters. Photopolymerization is a preferred method to produce LC/polymer composite films from mixtures of reactive monomers and LCs. On the basis of the combined Flory-Huggins free energy for isotropic mixing and Maier-Saupe free energy for nematic ordering along with the elastic free energy of the network, phase diagrams have been established by solving self-consistently. A theoretical simulation has been modeled by incorporating the kinetics of crosslinking reaction into the time-dependent Ginzburg-Landau (TDGL-model C) equations to elucidate the emergence of nematic domains during photopolymerization induced phase separation in electrically switchable holographic polymer-dispersed liquid crystals (H-PDLC). The simulated morphological patterns in the concentration and orientation order parameter fields show discrete layers of liquid crystal droplets alternating periodically with polymer network-rich layers. Furthermore, we recognized the potential for producing electrically tunable microlens from PDLC systems through pattern-photopolymerization-induced phase separation by means of the interference of two horizontal waves and two vertical waves. Our simulation revealed that the emerged LC microlens are of the order of a few hundred nanometers. These LC microlens are not only uniformed in size, but also form in regular arrays, reminiscence of the compound eyes found in flies, ants, and wasps. Supported by ALCOM, NSF DMR 99-03519, and OBR.

  5. First calculation of phase and coherence of longitudinally separated L-band equatorial ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Shume, E. B.; Mannucci, A. J.

    2013-07-01

    We present the first calculation of phase and coherence of cross-wavelet transform applied to longitudinally separated L-band equatorial ionospheric scintillation observations received from Geostationary Earth Orbit (GEO) satellites. The phase and coherence analysis were employed on two pairs of observations: (1) São Luís and Rio Branco and (2) Alta Floresta and Huancayo. For these case studies, in statistically significant and high-coherence regions, scintillation observations over São Luís (Alta Floresta) lead that of Rio Branco (Huancayo) by ˜2 to 3 h with a 95%frequency. If L-band scintillation happens over São Luís (Alta Floresta), there is a 95%likelihood that scintillation would happen to the west over Rio Branco (Huancayo) after ˜2 to 3 h, suggesting that a forecast can be made ahead of scintillation occurrences. The phase and coherence relationships between the longitudinally separated scintillation-producing regions can be connected to the large-scale wave structures which are reported to be related to the generation of equatorial spread F and scintillation.

  6. Direct single-shot phase retrieval for separated objects (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Leshem, Ben; Xu, Rui; Miao, Jianwei; Nadler, Boaz; Oron, Dan; Dudovich, Nirit; Raz, Oren

    2016-03-01

    The phase retrieval problem arises in various fields ranging from physics and astronomy to biology and microscopy. Computational reconstruction of the Fourier phase from a single diffraction pattern is typically achieved using iterative alternating projections algorithms imposing a non-convex computational challenge. A different approach is holography, relying on a known reference field. Here we present a conceptually new approach for the reconstruction of two (or more) sufficiently separated objects. In our approach we combine the constraint the objects are finite as well as the information in the interference between them to construct an overdetermined set of linear equations. We show that this set of equations is guaranteed to yield the correct solution almost always and that it can be solved efficiently by standard numerical algebra tools. Essentially, our method combine commonly used constraint (that the object is finite) with a holographic approach (interference information). It differs from holographic methods in the fact that a known reference field is not required, instead the unknown objects serve as reference to one another (hence blind holography). Our method can be applied in a single-shot for two (or more) separated objects or with several measurements with a single object. It can benefit phase imaging techniques such as Fourier phytography microscopy, as well as coherent diffractive X-ray imaging in which the generation of a well-characterized, high resolution reference beam imposes a major challenge. We demonstrate our method experimentally both in the optical domain and in the X-ray domain using XFEL pulses.

  7. Density functional theory of gas-liquid phase separation in dilute binary mixtures.

    PubMed

    Okamoto, Ryuichi; Onuki, Akira

    2016-06-22

    We examine statics and dynamics of phase-separated states of dilute binary mixtures using density functional theory. In our systems, the difference of the solvation chemical potential between liquid and gas [Formula: see text] (the Gibbs energy of transfer) is considerably larger than the thermal energy [Formula: see text] for each solute particle and the attractive interaction among the solute particles is weaker than that among the solvent particles. In these conditions, the saturated vapor pressure increases by [Formula: see text], where [Formula: see text] is the solute density added in liquid. For [Formula: see text], phase separation is induced at low solute densities in liquid and the new phase remains in gaseous states, even when the liquid pressure is outside the coexistence curve of the solvent. This explains the widely observed formation of stable nanobubbles in ambient water with a dissolved gas. We calculate the density and stress profiles across planar and spherical interfaces, where the surface tension decreases with increasing interfacial solute adsorption. We realize stable solute-rich bubbles with radius about 30 nm, which minimize the free energy functional. We then study dynamics around such a bubble after a decompression of the surrounding liquid, where the bubble undergoes a damped oscillation. In addition, we present some exact and approximate expressions for the surface tension and the interfacial stress tensor. PMID:27115676

  8. Depletion induced isotropic-isotropic phase separation in suspensions of rod-like colloids.

    PubMed

    Jungblut, S; Tuinier, R; Binder, K; Schilling, T

    2007-12-28

    When non-adsorbing polymers are added to an isotropic suspension of rod-like colloids, the colloids effectively attract each other via depletion forces. We performed Monte Carlo simulations to study the phase diagram of such rod-polymer mixture. The colloidal rods were modeled as hard spherocylinders; the polymers were described as spheres of the same diameter as the rods. The polymers may overlap with no energy cost, while the overlap of polymers and rods is forbidden. Large amounts of depletant cause phase separation of the mixture. We estimated the phase boundaries of isotropic-isotropic coexistence both in the bulk and in confinement. To determine the phase boundaries we applied the grand canonical ensemble using successive umbrella sampling [J. Chem. Phys. 120, 10925 (2004)], and we performed a finite size scaling analysis to estimate the location of the critical point. The results are compared with predictions of the free volume theory developed by Lekkerkerker and Stroobants [Nuovo Cimento D 16, 949 (1994)]. We also give estimates for the interfacial tension between the coexisting isotropic phases and analyze its power-law behavior on the approach of the critical point. PMID:18163708

  9. Roles of Interleaflet Coupling and Hydrophobic Mismatch in Lipid Membrane Phase-Separation Kinetics.

    PubMed

    Fowler, Philip W; Williamson, John J; Sansom, Mark S P; Olmsted, Peter D

    2016-09-14

    Characterizing the nanoscale dynamic organization within lipid bilayer membranes is central to our understanding of cell membranes at a molecular level. We investigate phase separation and communication across leaflets in ternary lipid bilayers, including saturated lipids with between 12 and 20 carbons per tail. Coarse-grained molecular dynamics simulations reveal a novel two-step kinetics due to hydrophobic mismatch, in which the initial response of the apposed leaflets upon quenching is to increase local asymmetry (antiregistration), followed by dominance of symmetry (registration) as the bilayer equilibrates. Antiregistration can become thermodynamically preferred if domain size is restricted below ∼20 nm, with implications for the symmetry of rafts and nanoclusters in cell membranes, which have similar reported sizes. We relate our findings to theory derived from a semimicroscopic model in which the leaflets experience a "direct" area-dependent coupling, and an "indirect" coupling that arises from hydrophobic mismatch and is most important at domain boundaries. Registered phases differ in composition from antiregistered phases, consistent with a direct coupling between the leaflets. Increased hydrophobic mismatch purifies the phases, suggesting that it contributes to the molecule-level lipid immiscibility. Our results demonstrate an interplay of competing interleaflet couplings that affect phase compositions and kinetics, and lead to a length scale that can influence lateral and transverse bilayer organization within cells. PMID:27574865

  10. Phase separation of signaling molecules promotes T cell receptor signal transduction.

    PubMed

    Su, Xiaolei; Ditlev, Jonathon A; Hui, Enfu; Xing, Wenmin; Banjade, Sudeep; Okrut, Julia; King, David S; Taunton, Jack; Rosen, Michael K; Vale, Ronald D

    2016-04-29

    Activation of various cell surface receptors triggers the reorganization of downstream signaling molecules into micrometer- or submicrometer-sized clusters. However, the functional consequences of such clustering have been unclear. We biochemically reconstituted a 12-component signaling pathway on model membranes, beginning with T cell receptor (TCR) activation and ending with actin assembly. When TCR phosphorylation was triggered, downstream signaling proteins spontaneously separated into liquid-like clusters that promoted signaling outputs both in vitro and in human Jurkat T cells. Reconstituted clusters were enriched in kinases but excluded phosphatases and enhanced actin filament assembly by recruiting and organizing actin regulators. These results demonstrate that protein phase separation can create a distinct physical and biochemical compartment that facilitates signaling. PMID:27056844

  11. Engineering Cyclodextrin Clicked Chiral Stationary Phase for High-Efficiency Enantiomer Separation

    PubMed Central

    Tang, Jian; Zhang, Shapopeng; Lin, Yuzhou; Zhou, Jie; Pang, Limin; Nie, Xuemei; Zhou, Baojing; Tang, Weihua

    2015-01-01

    The separation of racemic molecules is of crucial significance not only for fundamental research but also for technical application. Enantiomers remain challenging to be separated owing to their identical physical and chemical properties in achiral environments. Chromatographic techniques employing chiral stationary phases (CSPs) have been developed as powerful tools for the chiral analysis and preparation of pure enantiomers, most of which are of biological and pharmaceutical interests. Here we report our efforts in developing high-performance phenylcarbamated cyclodextrin (CD) clicked CSPs. Insights on the impact of CD functionalities in structure design are provided. High-efficiency enantioseparation of a range of aryl alcohols and flavanoids with resolution values (Rs) over 10 were demonstrated by per(3-chloro-4-methyl)phenylcarbamated CD clicked CSP. Comparison study and molecular simulations suggest the improved enantioselectivity was attributed to higher interactions energy difference between the complexes of enantiomers and CSPs with phenylcarbamated CD bearing 3-chloro and 4-methyl functionalities. PMID:26235204

  12. Engineering Cyclodextrin Clicked Chiral Stationary Phase for High-Efficiency Enantiomer Separation

    NASA Astrophysics Data System (ADS)

    Tang, Jian; Zhang, Shapopeng; Lin, Yuzhou; Zhou, Jie; Pang, Limin; Nie, Xuemei; Zhou, Baojing; Tang, Weihua

    2015-08-01

    The separation of racemic molecules is of crucial significance not only for fundamental research but also for technical application. Enantiomers remain challenging to be separated owing to their identical physical and chemical properties in achiral environments. Chromatographic techniques employing chiral stationary phases (CSPs) have been developed as powerful tools for the chiral analysis and preparation of pure enantiomers, most of which are of biological and pharmaceutical interests. Here we report our efforts in developing high-performance phenylcarbamated cyclodextrin (CD) clicked CSPs. Insights on the impact of CD functionalities in structure design are provided. High-efficiency enantioseparation of a range of aryl alcohols and flavanoids with resolution values (Rs) over 10 were demonstrated by per(3-chloro-4-methyl)phenylcarbamated CD clicked CSP. Comparison study and molecular simulations suggest the improved enantioselectivity was attributed to higher interactions energy difference between the complexes of enantiomers and CSPs with phenylcarbamated CD bearing 3-chloro and 4-methyl functionalities.

  13. Thermal conductivity and phase separation of the crust of accreting neutron stars.

    PubMed

    Horowitz, C J; Caballero, O L; Berry, D K

    2009-02-01

    Recently, crust cooling times have been measured for neutron stars after extended outbursts. These observations are very sensitive to the thermal conductivity kappa of the crust and strongly suggest that kappa is large. We perform molecular dynamics simulations of the structure of the crust of an accreting neutron star using a complex composition that includes many impurities. The composition comes from simulations of rapid proton capture nucleosynthesis followed by electron captures. We find that the thermal conductivity is reduced by impurity scattering. In addition, we find phase separation. Some impurities with low atomic number Z are concentrated in a subregion of the simulation volume. For our composition, the solid crust must separate into regions of different compositions. This could lead to an asymmetric star with a quadrupole deformation. Observations of crust cooling can constrain impurity concentrations. PMID:19391802

  14. N-block separable random phase approximation: dipole oscillations in sodium clusters and {C}_{60} fullerene

    NASA Astrophysics Data System (ADS)

    Palade, D. I.; Baran, V.

    2016-09-01

    We generalize the schematic model based on the Random Phase Approximation (RPA) with separable interaction, to a collection of subspaces of ph excitations which interact with different coupling constants. This ansatz notably lowers the numerical effort involved, by reducing the RPA eigenvalue problem to a finite small dimensional system of equation. We derive the associated dispersion relation and the normalization condition for the newly defined unknowns of the system. In contrast with the standard separable approach, the present formalism is able to describe more than one collective excitation even in the degenerate limit, giving also access to the nature of the resonance. The theoretical framework is tested investigating the dipolar oscillations in various neutral and singly charged sodium clusters and C 60 fullerene with results in good agreement with full RPA calculations and experimental data. It is proven that the 40 eV resonance present in photoabsorption spectra of C 60 is a localized surface plasmon.

  15. Fluid Phase Separation (FPS) experiment for flight on the shuttle in a Get Away Special (GAS) canister: Design and fabrication

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The separation of fluid phases in microgravity environments is of importance to environmental control and life support systems (ECLSS) and materials processing in space. A successful fluid phase separation experiment will demonstrate a proof of concept for the separation technique and add to the knowledge base of material behavior. The phase separation experiment will contain a premixed fluid that will be exposed to a microgravity environment. After the phase separation of the compound has occurred, small samples of each of the species will be taken for analysis on Earth. By correlating the time of separation and the temperature history of the fluid, it will be possible to characterize the process. The phase separation experiment is totally self-contained, with three levels of containment on all fluids, and provides all necessary electrical power and control. The controller regulates the temperature of the fluid and controls data logging and sampling. An astronaut-activated switch will initiate the experiment and an unmaskable interrupt is provided for shutdown. The experiment has been integrated into space available on a manifested Get Away Special (GAS) experiment, CONCAP 2, part of the Consortium for Materials Complex Autonomous Payload (CAP) Program, scheduled for STS 42 in April 1991. Presented here are the design and the production of a fluid phase separation experiment for rapid implementation at low cost.

  16. Phase separation in thermal systems: a lattice Boltzmann study and morphological characterization.

    PubMed

    Gan, Yanbiao; Xu, Aiguo; Zhang, Guangcai; Li, Yingjun; Li, Hua

    2011-10-01

    We investigate thermal and isothermal symmetric liquid-vapor separations via a fast Fourier transform thermal lattice Boltzmann (FFT-TLB) model. Structure factor, domain size, and Minkowski functionals are employed to characterize the density and velocity fields, as well as to understand the configurations and the kinetic processes. Compared with the isothermal phase separation, the freedom in temperature prolongs the spinodal decomposition (SD) stage and induces different rheological and morphological behaviors in the thermal system. After the transient procedure, both the thermal and isothermal separations show power-law scalings in domain growth, while the exponent for thermal system is lower than that for isothermal system. With respect to the density field, the isothermal system presents more likely bicontinuous configurations with narrower interfaces, while the thermal system presents more likely configurations with scattered bubbles. Heat creation, conduction, and lower interfacial stresses are the main reasons for the differences in thermal system. Different from the isothermal case, the release of latent heat causes the changing of local temperature, which results in new local mechanical balance. When the Prandtl number becomes smaller, the system approaches thermodynamical equilibrium much more quickly. The increasing of mean temperature makes the interfacial stress lower in the following way: σ=σ(0)[(T(c)-T)/(T(c)-T(0))](3/2), where T(c) is the critical temperature and σ(0) is the interfacial stress at a reference temperature T(0), which is the main reason for the prolonged SD stage and the lower growth exponent in the thermal case. Besides thermodynamics, we probe how the local viscosities influence the morphology of the phase separating system. We find that, for both the isothermal and thermal cases, the growth exponents and local flow velocities are inversely proportional to the corresponding viscosities. Compared with the isothermal case, the

  17. Separation of transition and heavy metals using stationary phase gradients and thin layer chromatography.

    PubMed

    Stegall, Stacy L; Ashraf, Kayesh M; Moye, Julie R; Higgins, Daniel A; Collinson, Maryanne M

    2016-05-13

    Stationary phase gradients for chelation thin layer chromatography (TLC) have been investigated as a tool to separate a mixture of metal ions. The gradient stationary phases were prepared using controlled rate infusion (CRI) from precursors containing mono-, bi-, and tri-dentate ligands, specifically 3-aminopropyltriethoxysilane, N-[3-(trimethoxysilyl)propyl] ethylenediamine, and N-[3-(trimethoxysilyl)propyl] diethylenetriamine. The presence and the extent of gradient formation were confirmed using N1s X-ray photoelectron spectroscopy (XPS). XPS results showed that the degree of modification was dependent on the aminosilane precursor, its concentration, and the rate of infusion. The separation of four transition and heavy metals (Co(2+), Pb(2+), Cu(2+), and Fe(3+)) on gradient and uniformly modified plates was compared using a mobile phase containing a stronger chelating agent, ethylenediaminetetraacetic acid (EDTA). The retention of the metal ions was manipulated by varying the surface concentration of the chelating ligands. The order of retention on unmodified plates and on plates modified with a monodentate ligand was Fe(3+)>Cu(2+)∼Pb(2+)∼Co(2+), while the order of retention on plates modified with bi- and tri-dentate ligands was Fe(3+)>Cu(2+)>Pb(2+)∼Co(2+). Fe(3+) and Cu(2+) were much more sensitive to the concentration of chelating ligand on the surface (displaying lower Rf values with increasing ligand concentration) than Pb(2+) and Co(2+). Complete separation was achieved using a high concentration of the tridentate ligand coupled with a longer time for modification, yielding a retention order of Fe(3+)>Cu(2+)>Co(2+)>Pb(2+). PMID:27090390

  18. Carbide derived carbon from MAX-phases and their separation applications

    NASA Astrophysics Data System (ADS)

    Hoffman, Elizabeth N.

    Improved sorbents with increased selectivity and permeability are needed to meet growing energy and environmental needs. New forms of carbon based sorbents have been discovered recently, including carbons produced by etching metals from metal carbides, known as carbide derived carbons (CDCs). A common method for the synthesis of CDC is by chlorination at elevated temperatures. The goal of this work is to synthesize CDC from ternary carbides and to explore the links between the initial carbide chemistry and structure with the resulting CDCs properties, including porosity. CDC was produced from MAX-phase carbides, in particular Ti3SiC 2, Ti3AlC2, Ti2AlC, and Ta2AlC. Additionally, CDC was produced from Ta-based binary carbides, TaC and Ta 2C, and one carbo-nitride Ti2AlC0.5N0.5. The CDC structure was characterized using XRD, Raman microspectroscopy, and HRTEM. Porosity characterization was performed using sorption analysis with both Ar and N2 as adsorbates. It was determined the microporosity of CDC is related to the density of the initial carbide. The layered structure of the MAX-phase carbides lent toward the formation of larger mesopores within the resulting CDCs, while the amount of mesopores was dependent on the chemistry of the carbide. Furthermore, CDC produced from carbides with extremely high theoretical porosity resulted in small specific surface areas due to a collapse of the carbon structure. To expand the potential applications for CDC beyond powder and bulk forms, CDC membranes were produced from a thin film of TiC deposited by magnetron sputtering onto porous ceramic substrates. The TiC thin film was subsequently chlorinated to produce a bilayer membrane with CDC as the active layer. Both gases and liquids are capable of passing the membrane. The membrane separates based on selective adsorption, rather than a size separation molecular sieving effect. Two applications for CDC produced from MAX-phases were investigated: protein adsorption and gas

  19. Dimensionality dependence of aging in kinetics of diffusive phase separation: Behavior of order-parameter autocorrelation

    NASA Astrophysics Data System (ADS)

    Midya, Jiarul; Majumder, Suman; Das, Subir K.

    2015-08-01

    Behavior of two-time autocorrelation during the phase separation in solid binary mixtures is studied via numerical solutions of the Cahn-Hilliard equation as well as Monte Carlo simulations of the Ising model. Results are analyzed via state-of-the-art methods, including the finite-size scaling technique. Full forms of the autocorrelation in space dimensions 2 and 3 are obtained empirically. The long-time behavior is found to be power law, with exponents unexpectedly higher than the ones for the ferromagnetic ordering. Both Cahn-Hilliard and Ising models provide consistent results.

  20. Dimensionality dependence of aging in kinetics of diffusive phase separation: Behavior of order-parameter autocorrelation.

    PubMed

    Midya, Jiarul; Majumder, Suman; Das, Subir K

    2015-08-01

    Behavior of two-time autocorrelation during the phase separation in solid binary mixtures is studied via numerical solutions of the Cahn-Hilliard equation as well as Monte Carlo simulations of the Ising model. Results are analyzed via state-of-the-art methods, including the finite-size scaling technique. Full forms of the autocorrelation in space dimensions 2 and 3 are obtained empirically. The long-time behavior is found to be power law, with exponents unexpectedly higher than the ones for the ferromagnetic ordering. Both Cahn-Hilliard and Ising models provide consistent results. PMID:26382361

  1. Phase separation on the sphere: Patchy particles and self-assembly

    NASA Astrophysics Data System (ADS)

    Bott, M. C.; Brader, J. M.

    2016-07-01

    Motivated by observations of heterogeneous domain structure on the surface of cells, we consider a minimal model to describe the dynamics of phase separation on the surface of a spherical particle. Finite-size effects on the curved particle surface lead to the formation of long-lived, metastable states for which the density is distributed in patches over the particle surface. We study the time evolution and stability of these states as a function of both the particle size and the thermodynamic parameters. Finally, by connecting our findings with studies of patchy particles, we consider the implications for self-assembly in many-particle systems.

  2. Evolution of pattern complexity in the Cahn-Hilliard theory of phase separation

    SciTech Connect

    Gameiro, Marcio; Mischaikow, Konstantin; Wanner, Thomas . E-mail: wanner@math.gmu.edu

    2005-02-01

    Phase separation processes in compound materials can produce intriguing and complicated patterns. Yet, characterizing the geometry of these patterns quantitatively can be quite challenging. In this paper we propose the use of computational algebraic topology to obtain such a characterization. Our method is illustrated for the complex microstructures observed during spinodal decomposition and early coarsening in both the deterministic Cahn-Hilliard theory, as well as in the stochastic Cahn-Hilliard-Cook model. While both models produce microstructures that are qualitatively similar to the ones observed experimentally, our topological characterization points to significant differences. One particular aspect of our method is its ability to quantify boundary effects in finite size systems.

  3. Hydrogen and dry ice production through phase equilibrium separation and methane reforming

    NASA Astrophysics Data System (ADS)

    Posada, Alberto; Manousiouthakis, Vasilios

    A clean hydrogen (99.9999%) and dry ice production process is proposed, which is based on phase equilibrium (PE) separation and methane reforming. Heat and power integration studies are carried out for the proposed process, by formulating and solving the minimum hot/cold/electric utility cost problem for the associated heat exchange network. The optimum operating cost of the proposed process is shown to be lower than the corresponding cost of the conventional PSA (pressure swing adsorption) based process, if the produced dry ice is sold for as low as 2 cents kg-dry-ice -1 or if an equivalent CO 2 sequestration credit is conceded.

  4. Phase separation in mixtures of ionized iron in a hydrogen plasma

    PubMed Central

    Alder, B. J.; Pollock, E. L.; Hansen, J. P.

    1980-01-01

    The accuracy of the hypernetted chain theory for mixtures of iron nuclei and protons in a charge-neutralizing background is demonstrated by comparison with molecular dynamics calculations. Near critical conditions the Debye-Hückel approximation fails to converge, even with second-order concentration corrections. The critical conditions, determined by assuming a uniform electron gas background, have a critical temperature more than a factor of 2 lower than present estimates of interior solar conditions. Qualitative arguments are made that including the polarization of the electron gas background would not change this result significantly and thus phase separation of iron in the interior of the sun is unlikely. PMID:16592905

  5. Fabrication of triple layered vascular scaffolds by combining electrospinning, braiding, and thermally induced phase separation

    NASA Astrophysics Data System (ADS)

    Mi, Hao-Yang; Jing, Xin; Yu, Emily; McNulty, Jason; Turng, Lih-Sheng

    2015-12-01

    Triple layered small diameter vascular scaffolds, which consisted of thermoplastic polyurethane (TPU) and silk, were fabricated in this study for the first time by combining electrospinning, braiding, and thermally induced phase separation methods. These novel vascular scaffolds, which possess three layers of different structures (nanofibrous inner layer, woven silk filament middle layer, and porous outer layer) have a desired toe region in the tensile test and sufficient suture retention and burst pressure for vascular graft applications. The endothelia cell culture tests showed that a cell layer could form on the inner surface of a scaffold with high cell viability. Furthermore, the cells showed favorable morphology on the scaffold.

  6. Phase separation on the sphere: Patchy particles and self-assembly.

    PubMed

    Bott, M C; Brader, J M

    2016-07-01

    Motivated by observations of heterogeneous domain structure on the surface of cells, we consider a minimal model to describe the dynamics of phase separation on the surface of a spherical particle. Finite-size effects on the curved particle surface lead to the formation of long-lived, metastable states for which the density is distributed in patches over the particle surface. We study the time evolution and stability of these states as a function of both the particle size and the thermodynamic parameters. Finally, by connecting our findings with studies of patchy particles, we consider the implications for self-assembly in many-particle systems. PMID:27575175

  7. Atomic force microscopy studies of domain structures in phase-separated monolayers

    NASA Astrophysics Data System (ADS)

    Xiao, Shou-Jun; Wu, Hai-Ming; Yang, Xiao-Min; Wei, Yu; Tai, Zi-Hou; Sun, Xing-Zhong

    1994-10-01

    Domain structures were studied with atomic force microscopy (AFM) in binary phase-separated monolayer films composed of 5, 10, 15-triphenyl-20-(4-dl-α-phenylalanylamindo) phenyl porphyrin (TPPP) and one of a series of fatty acids which are arachidic acid (AA), palmitic acid (PA), and lauric acid (LA). The liquid-condensed (LC) domain structures of AA and PA were observed in their corresponding mixed monolayers. However, instead of the fatty acid domain, a liquid-expanded (LE) domain structure of TPPP appears in the mixed monolayer of LA/TPPP.

  8. Interfacial structuring in a phase-separating mixed biopolymer solution containing colloidal particles.

    PubMed

    Firoozmand, Hassan; Murray, Brent S; Dickinson, Eric

    2009-02-01

    We report confocal microscopy observations of the spatial distribution of monodisperse charge-stabilized colloidal particles (amphoteric polystyrene latex) incorporated within a spinodal-type phase-separating system of mixed biopolymers (gelatin + oxidized starch). Images from samples aged at 40 degrees C demonstrate a strong tendency for the added particles to accumulate at the liquid-liquid interface and to influence the rate of coarsening of the complex bicontinuous microstructure. Large variations in the local curvature of particle-rich interfacial regions are suggestive of a liquid-liquid boundary that is substantially viscoelastic. PMID:19138064

  9. Separation studies of As(III), Sb(III) and Bi(III) by reversed-phase paper chromatographic technique

    SciTech Connect

    Raman, B.; Shinde, V.M.

    1987-07-01

    Reversed-phase paper chromatographic separations of As(III), Sb(III) and Bi(III) have been carried out on Whatman No 1 filter paper impregnated with triphenylphosphine oxide as stationary phase and using organic complexing agents such as sodium acetate, sodium succinate and sodium malonate solutions as active mobile phases. Results for the separation of binary and ternary mixtures are reported and the method has been successfully applied to the separation and detection of these elements present in real samples and at ppm level concentration.

  10. EXOPLANET ALBEDO SPECTRA AND COLORS AS A FUNCTION OF PLANET PHASE, SEPARATION, AND METALLICITY

    SciTech Connect

    Cahoy, Kerri L.; Marley, Mark S.; Fortney, Jonathan J.

    2010-11-20

    First generation space-based optical coronagraphic telescopes will obtain images of cool gas- and ice-giant exoplanets around nearby stars. Exoplanets lying at planet-star separations larger than about 1 AU-where an exoplanet can be resolved from its parent star-have spectra that are dominated by reflected light to beyond 1 {mu}m and punctuated by molecular absorption features. Here, we consider how exoplanet albedo spectra and colors vary as a function of planet-star separation, metallicity, mass, and observed phase for Jupiter and Neptune analogs from 0.35 to 1 {mu}m. We model Jupiter analogs with 1x and 3x the solar abundance of heavy elements, and Neptune analogs with 10x and 30x the solar abundance of heavy elements. Our model planets orbit a solar analog parent star at separations of 0.8 AU, 2 AU, 5 AU, and 10 AU. We use a radiative-convective model to compute temperature-pressure profiles. The giant exoplanets are found to be cloud-free at 0.8 AU, possess H{sub 2}O clouds at 2 AU, and have both NH{sub 3} and H{sub 2}O clouds at 5 AU and 10 AU. For each model planet we compute moderate resolution (R = {lambda}/{Delta}{lambda} {approx} 800) albedo spectra as a function of phase. We also consider low-resolution spectra and colors that are more consistent with the capabilities of early direct imaging capabilities. As expected, the presence and vertical structure of clouds strongly influence the albedo spectra since cloud particles not only affect optical depth but also have highly directional scattering properties. Observations at different phases also probe different volumes of atmosphere as the source-observer geometry changes. Because the images of the planets themselves will be unresolved, their phase will not necessarily be immediately obvious, and multiple observations will be needed to discriminate between the effects of planet-star separation, metallicity, and phase on the observed albedo spectra. We consider the range of these combined effects on

  11. Oleic- and Docosahexaenoic Acid-Containing Phosphatidylethanolamines Differentially Phase Separate from Sphingomyelin

    PubMed Central

    Shaikh, Saame Raza; LoCascio, Daniel S.; Soni, Smita P.; Wassall, Stephen R.; Stillwell, William

    2009-01-01

    A central tenet of the lipid raft model is the existence of non-raft domains. In support of this view, we have established in model membranes that a phosphatidylethanolamine (PE)-containing docosahexaenoic acid (DHA) forms organizationally distinct non-raft domains in the presence of sphingomyelin (SM) and cholesterol (Chol). We have shown that formation of DHA-rich domains is driven by unfavorable molecular interactions between the rigid Chol molecule and the highly flexible DHA acyl chain. However, the molecular interactions between SM and the DHA-containing PE, which could also contribute to the formation of DHA-rich non-raft domains, have not been sufficiently investigated. To address this issue, we use differential scanning calorimetry (DSC) to study the phase behavior of mixtures of SM with either 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphoethanolamine (16:0-22:6PE) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (16:0-18:1PE), an oleic acid (OA)-containing control, over a wide range of concentrations. Deconvolution of binary DSC scans shows that both 16:0-22:6PE and 16:0-18:1PE phase separate from SM. Analysis of transition temperatures and partial phase diagrams, constructed from the DSC scans for the first time, show that 16:0-22:6PE displays greater non-ideal mixing with SM compared to 16:0-18:1PE. Our findings support a model in which DHA- and OA-containing PEs differentially phase separate from SM over a wide range of molar ratios to initiate the formation of non-raft domains, which is greatly enhanced by DHA, but not OA, in the presence of cholesterol. PMID:19735642

  12. Microcanonical thermostatistics as foundation of thermodynamics: The microscopic origin of condensation and phase separations

    NASA Astrophysics Data System (ADS)

    Gross, D. H. E.

    2005-10-01

    Conventional thermo-statistics address infinite homogeneous systems within the canonical ensemble. However, some 150 years ago the original motivation of thermodynamics was the description of steam engines, i.e., boiling water. Its essential physics is the separation of the gas phase from the liquid. Of course, boiling water is inhomogeneous and as such cannot be treated by canonical thermo-statistics. Then it is not astonishing that a phase transition of first order is signaled canonically by a Yang Lee singularity. Thus it is only treated correctly by microcanonical Boltzmann Planck statistics. This is elaborated in the present article. It turns out that the Boltzmann Planck statistics is much richer and gives fundamental insight into statistical mechanics and especially into entropy. This can even be done to some extend rigorously and analytically. The microcanonical entropy has a very simple physical meaning: It measures the microscopic uncertainty that we have about the system, i.e., the number of points in 6N-dim phase, which are consistent with our information about the system. It can rigorously be split into an ideal-gas part and a configuration part which contains all the physics and especially is responsible for all phase transitions. The deep and essential difference between “extensive” and “intensive” control parameters, i.e., microcanonical and canonical statistics, is exemplified by rotating, self-gravitating systems.

  13. Mapping Liquid-liquid protein phase separation using ultra-fast-scanning fluorescence correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Wei, Ming-Tzo; Elbaum-Garfinkle, Shana; Arnold, Craig B.; Priestley, Rodney D.; Brangwynne, Clifford P.

    Intrinsically disordered proteins (IDPs) are an understudied class of proteins that play important roles in a wide variety of biological processes in cells. We've previously shown that the C. elegans IDP LAF-1 phase separates into P granule-like droplets in vitro. However, the physics of the condensed phase remains poorly understood. Here, we use a novel technique, ultra-fast-scanning fluorescence correlation spectroscopy, to study the nano-scale rheological properties of LAF-1 droplets. Ultra-fast-scanning FCS uses a tunable acoustic gradient index of refraction (TAG) lens with an oil immersion objective to control axial movement of the focal point over a length of several micrometers at frequencies of 70kHz. Using ultra-fast-scanning FCS allows for the accurate determination of molecular concentrations and their diffusion coefficient, when the particle is passing through an excitation volume. Our work reveals an asymmetric LAF-1 phase diagram, and demonstrates that LAF-1 droplets are purely viscous phases which are highly tunable by salt concentration.

  14. Direct single-shot phase retrieval from the diffraction pattern of separated objects

    PubMed Central

    Leshem, Ben; Xu, Rui; Dallal, Yehonatan; Miao, Jianwei; Nadler, Boaz; Oron, Dan; Dudovich, Nirit; Raz, Oren

    2016-01-01

    The non-crystallographic phase problem arises in numerous scientific and technological fields. An important application is coherent diffractive imaging. Recent advances in X-ray free-electron lasers allow capturing of the diffraction pattern from a single nanoparticle before it disintegrates, in so-called ‘diffraction before destruction' experiments. Presently, the phase is reconstructed by iterative algorithms, imposing a non-convex computational challenge, or by Fourier holography, requiring a well-characterized reference field. Here we present a convex scheme for single-shot phase retrieval for two (or more) sufficiently separated objects, demonstrated in two dimensions. In our approach, the objects serve as unknown references to one another, reducing the phase problem to a solvable set of linear equations. We establish our method numerically and experimentally in the optical domain and demonstrate a proof-of-principle single-shot coherent diffractive imaging using X-ray free-electron lasers pulses. Our scheme alleviates several limitations of current methods, offering a new pathway towards direct reconstruction of complex objects. PMID:26899582

  15. Phase transition ordering-separation: A new approach to heat treatment of alloys

    NASA Astrophysics Data System (ADS)

    Ustinovshchikov, Yu. I.

    2015-09-01

    The problems of the consequence of heat treatment of alloys performed using the concept of an ordering-separation phase transition are considered. Fe50Cr50 and Ni88Al12 alloys and U13 steel are used as examples to show that this transition occurs at a temperature specific for each system, and a change in the sign of the chemical interaction between alloy component atoms changes the direction of diffusion fluxes in alloys into the opposite direction, which changes the type of microstructure. The detection of this phase transition radically changes the generally accepted concepts of heat treatment of alloys. This finding calls for transmission electron microscopy investigations to modify the phase diagrams where this phase transition was detected. It is concluded that quenching of alloys from a so-called solid-solution field, which is usually performed before tempering (aging), is an unnecessary and useless operation, since the final structure of an alloy forms upon tempering (aging) irrespective of the structure existing before this heat treatment.

  16. Epitaxy, phase separation and band-edge emission of spontaneously formed InGaN nanorods

    NASA Astrophysics Data System (ADS)

    De, Arpan; Shivaprasad, S. M.

    2016-09-01

    An In-flux dependent study of the nature of epitaxy, compositional phase separation and band-edge emission of spontaneously formed c-oriented InGaN nanorods on c-sapphire is performed. At higher In flux-rates, m-faceted thick nanorods (≈700 nm) form with two in-plane epitaxial orientations, and display compositional phases with In composition varying from 14 to 63%. In these rods, photo-luminescent (PL) emission is seen to originate only from the localized high-In phase (63%) that is embedded in the low-In (14%) InGaN matrix. As the In flux-rate is reduced, nanorods of smaller diameter (≈60 nm) and a coalesced nanorod network are formed, with In incorporation of 15% and 9%, respectively. These faceted, c-aligned thinner nanorods are of a single compositional phase and epitaxy and display room-temperature PL emission. Optical absorption and emission properties of these nanostructures follow Vegard’s law of band-gaps, and the observed bowing parameter and Stokes shifts correlate to the observed compositional inhomogeneity and carrier localization.

  17. Direct single-shot phase retrieval from the diffraction pattern of separated objects

    DOE PAGESBeta

    Leshem, Ben; Xu, Rui; Dallal, Yehonatan; Miao, Jianwei; Nadler, Boaz; Oron, Dan; Dudovich, Nirit; Raz, Oren

    2016-02-22

    The non-crystallographic phase problem arises in numerous scientific and technological fields. An important application is coherent diffractive imaging. Recent advances in X-ray free-electron lasers allow capturing of the diffraction pattern from a single nanoparticle before it disintegrates, in so-called ‘diffraction before destruction’ experiments. Presently, the phase is reconstructed by iterative algorithms, imposing a non-convex computational challenge, or by Fourier holography, requiring a well-characterized reference field. Here we present a convex scheme for single-shot phase retrieval for two (or more) sufficiently separated objects, demonstrated in two dimensions. In our approach, the objects serve as unknown references to one another, reducing themore » phase problem to a solvable set of linear equations. We establish our method numerically and experimentally in the optical domain and demonstrate a proof-of-principle single-shot coherent diffractive imaging using X-ray free-electron lasers pulses. Lastly, our scheme alleviates several limitations of current methods, offering a new pathway towards direct reconstruction of complex objects.« less

  18. Direct single-shot phase retrieval from the diffraction pattern of separated objects.

    PubMed

    Leshem, Ben; Xu, Rui; Dallal, Yehonatan; Miao, Jianwei; Nadler, Boaz; Oron, Dan; Dudovich, Nirit; Raz, Oren

    2016-01-01

    The non-crystallographic phase problem arises in numerous scientific and technological fields. An important application is coherent diffractive imaging. Recent advances in X-ray free-electron lasers allow capturing of the diffraction pattern from a single nanoparticle before it disintegrates, in so-called 'diffraction before destruction' experiments. Presently, the phase is reconstructed by iterative algorithms, imposing a non-convex computational challenge, or by Fourier holography, requiring a well-characterized reference field. Here we present a convex scheme for single-shot phase retrieval for two (or more) sufficiently separated objects, demonstrated in two dimensions. In our approach, the objects serve as unknown references to one another, reducing the phase problem to a solvable set of linear equations. We establish our method numerically and experimentally in the optical domain and demonstrate a proof-of-principle single-shot coherent diffractive imaging using X-ray free-electron lasers pulses. Our scheme alleviates several limitations of current methods, offering a new pathway towards direct reconstruction of complex objects. PMID:26899582

  19. Facet-controlled phase separation in supersaturated Au-Ni nanoparticles upon shape equilibration

    SciTech Connect

    Herz, A. E-mail: dong.wang@tu-ilmenau.de; Rossberg, D.; Hentschel, M.; Theska, F.; Wang, D. E-mail: dong.wang@tu-ilmenau.de; Schaaf, P.; Friák, M.; Holec, D.; Šob, M.; Schneeweiss, O.

    2015-08-17

    Solid-state dewetting is used to fabricate supersaturated, submicron-sized Au-Ni solid solution particles out of thin Au/Ni bilayers by means of a rapid thermal annealing technique. Phase separation in such particles is studied with respect to their equilibrium crystal (or Wulff) shape by subsequent annealing at elevated temperature. It is found that (100) faceting planes of the equilibrated particles are enriched with Ni and (111) faces with Au. Both phases are considered by quantum-mechanical calculations in combination with an error-reduction scheme that was developed to compensate for a missing exchange-correlation potential that would reliably describe both Au and Ni. The observed phase configuration is then related to the minimization of strongly anisotropic elastic energies of Au- and Ni-rich phases and results in a rather unique nanoparticle composite state that is characterized by nearly uniform value of elastic response to epitaxial strains all over the faceted surface. The same conclusion is yielded also by evaluating bi-axial elastic moduli when employing interpolated experimental elastic constants. This work demonstrates a useful route for studying features of physical metallurgy at the mesoscale.

  20. Haloing in bimodal magnetic colloids: the role of field-induced phase separation.

    PubMed

    Magnet, C; Kuzhir, P; Bossis, G; Meunier, A; Suloeva, L; Zubarev, A

    2012-07-01

    If a suspension of magnetic micrometer-sized and nanosized particles is subjected to a homogeneous magnetic field, the nanoparticles are attracted to the microparticles and form thick anisotropic halos (clouds) around them. Such clouds can hinder the approach of microparticles and result in effective repulsion between them [M. T. López-López, A. Yu. Zubarev, and G. Bossis, Soft Matter 6, 4346 (2010)]. In this paper, we present detailed experimental and theoretical studies of nanoparticle concentration profiles and of the equilibrium shapes of nanoparticle clouds around a single magnetized microsphere, taking into account interactions between nanoparticles. We show that at a strong enough magnetic field, the ensemble of nanoparticles experiences a gas-liquid phase transition such that a dense liquid phase is condensed around the magnetic poles of a microsphere while a dilute gas phase occupies the rest of the suspension volume. Nanoparticle accumulation around a microsphere is governed by two dimensionless parameters--the initial nanoparticle concentration (φ(0)) and the magnetic-to-thermal energy ratio (α)--and the three accumulation regimes are mapped onto a α-φ(0) phase diagram. Our local thermodynamic equilibrium approach gives a semiquantitative agreement with the experiments on the equilibrium shapes of nanoparticle clouds. The results of this work could be useful for the development of the bimodal magnetorheological fluids and of the magnetic separation technologies used in bioanalysis and water purification systems. PMID:23005414