Sample records for liquid phase transition

  1. Liquid-gas phase transition in hypernuclei

    NASA Astrophysics Data System (ADS)

    Mallik, S.; Chaudhuri, G.

    2015-05-01

    The fragmentation of excited hypernuclear systems formed in heavy ion collisions has been described by the canonical thermodynamical model extended to three-component systems. The multiplicity distribution of the fragments has been analyzed in detail and it has been observed that the hyperons tend to get attached to the heavier fragments. Another important observation is the phase coexistence of the hyperons, a phenomenon which is linked to the liquid-gas phase transition in strange matter.

  2. Theory of Banana Liquid Crystal Phases and Phase Transitions

    E-print Network

    Tom Lubensky; Leo Radzihovsky

    2002-05-08

    We study phases and phase transitions that can take place in the newly discovered banana (bow-shaped or bent-core) liquid crystal molecules. We show that to completely characterize phases exhibited by such bent-core molecules a third-rank tensor $T^{ijk}$ order parameter is necessary in addition to the vector and the nematic (second-rank) tensor order parameters. We present an exhaustive list of possible liquid phases, characterizing them by their space-symmetry group and order parameters, and catalog the universality classes of the corresponding phase transitions that we expect to take place in such bent-core molecular liquid crystals. In addition to the conventional liquid-crystal phases such as the nematic phase, we predict the existence of novel liquid phases, including the spontaneously chiral nematic $(N_T + 2)^*$ and chiral polar $(V_T + 2)^*$ phases, the orientationally-ordered but optically isotropic tetrahedratic $T$ phase, and a novel nematic $N_T$ phase with $D_{2d}$ symmetry that is neither uniaxial nor biaxial. Interestingly, the Isotropic-Tetrahedratic transition is {\\em continuous} in mean-field theory, but is likely driven first-order by thermal fluctuations. We conclude with a discussion of smectic analogs of these phases and their experimental signatures.

  3. Spin liquids, exotic phases and phase transitions

    E-print Network

    Ran, Ying

    2007-01-01

    Spin liquid, or featureless Mott-Insulator, is a theoretical state of matter firstly motivated from study on High-Tc superconductor. The most striking property of spin liquids is that they do not break any physical symmetry, ...

  4. Nonextensive nuclear liquid-gas phase transition

    NASA Astrophysics Data System (ADS)

    Lavagno, A.; Pigato, D.

    2013-10-01

    We study an effective relativistic mean-field model of nuclear matter with arbitrary proton fraction at finite temperature in the framework of nonextensive statistical mechanics, characterized by power-law quantum distributions. We investigate the presence of thermodynamic instability in a warm and asymmetric nuclear medium and study the consequent nuclear liquid-gas phase transition by requiring the Gibbs conditions on the global conservation of baryon number and electric charge fraction. We show that nonextensive statistical effects play a crucial role in the equation of state and in the formation of mixed phase also for small deviations from the standard Boltzmann-Gibbs statistics.

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

    PubMed

    Huš, Matej; Urbic, Tomaz

    2014-12-01

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

  6. Computer simulations of liquid silica: Equation of state and liquid-liquid phase transition Ivan Saika-Voivod,1

    E-print Network

    Sciortino, Francesco

    phase separation, in which two liquids of distinct chemical composition coexist, are com- mon the onset of liquid­liquid phase separation has been determined 13 , as well as a character- istic patternComputer simulations of liquid silica: Equation of state and liquid-liquid phase transition Ivan

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  8. Phase Transitions and recent advances in liquid-crystals research

    Microsoft Academic Search

    M. B. Pandey; R. Dhar; V. K. Wadhawan

    2009-01-01

    During the past few years, the journal Phase Transitions has attracted a good number of articles from the liquid-crystals community. On the occasion of the 30th anniversary of the journal, we give an overview of the recent developments and the likely future of the field of liquid crystals, with special reference to some of the articles that appeared in this

  9. Phase transitions for a collective coordinate coupled to Luttinger liquids.

    PubMed

    Horovitz, Baruch; Giamarchi, Thierry; Le Doussal, Pierre

    2013-09-13

    We study various realizations of collective coordinates, e.g., the position of a particle, the charge of a Coulomb box, or the phase of a Bose or a superconducting condensate, coupled to Luttinger liquids with N flavors. We find that for a Luttinger parameter (1/2)phase transition from a delocalized phase into a phase with a periodic potential at strong coupling. In the delocalized phase the dynamics is dominated by an effective mass, i.e., diffusive in imaginary time, while on the transition line it becomes dissipative. At K=(1/2) there is an additional transition into a localized phase with no diffusion at zero temperature. PMID:24074101

  10. Phase Transitions for a Collective Coordinate Coupled to Luttinger Liquids

    NASA Astrophysics Data System (ADS)

    Horovitz, Baruch; Giamarchi, Thierry; Le Doussal, Pierre

    2013-09-01

    We study various realizations of collective coordinates, e.g., the position of a particle, the charge of a Coulomb box, or the phase of a Bose or a superconducting condensate, coupled to Luttinger liquids with N flavors. We find that for a Luttinger parameter (1/2)phase transition from a delocalized phase into a phase with a periodic potential at strong coupling. In the delocalized phase the dynamics is dominated by an effective mass, i.e., diffusive in imaginary time, while on the transition line it becomes dissipative. At K=(1/2) there is an additional transition into a localized phase with no diffusion at zero temperature.

  11. Synthesis and Liquid Crystal Phase Transitions of Zirconium Phosphate Disks 

    E-print Network

    Shuai, Min

    2013-05-07

    -shaped nanoparticles, and use it for the study of self-assembly and discotic liquid crystal phase transitions of discotic particles. The work was introduced by the control over the size and polydispersity of zirconium phosphate (ZrP) disks through synthesis...

  12. The liquid-liquid phase transition in silicon revealed by snapshots of valence electrons

    PubMed Central

    Beye, Martin; Sorgenfrei, Florian; Schlotter, William F.; Wurth, Wilfried; Föhlisch, Alexander

    2010-01-01

    The basis for the anomalies of water is still mysterious. Quite generally tetrahedrally coordinated systems, also silicon, show similar thermodynamic behavior but lack—like water—a thorough explanation. Proposed models—controversially discussed—explain the anomalies as a remainder of a first-order phase transition between high and low density liquid phases, buried deeply in the “no man’s land”—a part of the supercooled liquid region where rapid crystallization prohibits any experimental access. Other explanations doubt the existence of the phase transition and its first-order nature. Here, we provide experimental evidence for the first-order-phase transition in silicon. With ultrashort optical pulses of femtosecond duration we instantaneously heat the electronic system of silicon while the atomic structure as defined by the much heavier nuclear system remains initially unchanged. Only on a picosecond time scale the energy is transferred into the atomic lattice providing the energy to drive the phase transitions. With femtosecond X-ray pulses from FLASH, the free-electron laser at Hamburg, we follow the evolution of the valence electronic structure during this process. As the relevant phases are easily distinguishable in their electronic structure, we track how silicon melts into the low-density-liquid phase while a second phase transition into the high-density-liquid phase only occurs after the latent heat for the first-order phase transition has been transferred to the atomic structure. Proving the existence of the liquid-liquid phase transition in silicon, the hypothesized liquid-liquid scenario for water is strongly supported. PMID:20805512

  13. Detection of First-Order Liquid\\/Liquid Phase Transitions in Yttrium Oxide Aluminum Oxide Melts

    Microsoft Academic Search

    G. N. Greaves; M. C. Wilding; S. Fearn; D. Langstaff; F. Kargl; S. Cox; Q. Vu Van; O. Majérus; C. J. Benmore; R. Weber; C. M. Martin; L. Hennet

    2008-01-01

    We combine small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) with aerodynamic levitation techniques to study in situ phase transitions in the liquid state under contactless conditions. At very high temperatures, yttria-alumina melts show a first-order transition, previously inferred from phase separation in quenched glasses. We show how the transition coincides with a narrow and reversible maximum in SAXS

  14. Volume phase transitions of cholesteric liquid crystalline gels

    NASA Astrophysics Data System (ADS)

    Matsuyama, Akihiko

    2015-05-01

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

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

    NASA Technical Reports Server (NTRS)

    Clark, Noel A.

    2000-01-01

    Smectic liquid crystals are phases of rod shaped molecules organized into one dimensionally (1D) periodic arrays of layers, each layer being between one and two molecular lengths thick. In the least ordered smectic phases, the smectics A and C, each layer is a two dimensional (2D) liquid. Additionally there are a variety of more ordered smectic phases having hexatic short range translational order or 2D crystalline quasi long range translational order within the layers. The inherent fluid-layer structure and low vapor pressure of smectic liquid crystals enable the long term stabilization of freely suspended, single component, layered fluid films as thin as 30A, a single molecular layer. The layering forces the films to be an integral number of smectic layers thick, quantizing their thickness in layer units and forcing a film of a particular number of layers to be physically homogeneous with respect to its layer structure over its entire area. Optical reflectivity enables the precise determination of the number of layers. These ultrathin freely suspended liquid crystal films are structures of fundamental interest in condensed matter and fluid physics. They are the thinnest known stable condensed phase fluid structures and have the largest surface-to-volume ratio of any stable fluid preparation, making them ideal for the study of the effects of reduced dimensionality on phase behavior and on fluctuation and interface phenomena. Their low vapor pressure and quantized thickness enable the effective use of microgravity to extend the study of basic capillary phenomena to ultrathin fluid films. Freely suspended films have been a wellspring of new liquid crystal physics. They have been used to provide unique experimental conditions for the study of condensed phase transitions in two dimensions. They are the only system in which the hexatic has been unambiguously identified as a phase of matter, and the only physical system in which fluctuations of a 2D XY system and Kosterlitz Thouless phase transition has been observed and 2D XY quasi long range order verified. Smectic films have enabled the precise determination of smectic layer electron density and positional fluctuation profile and have been used to show that the interlayer interactions in anti-ferroelectric tilted smectics do not extend significantly beyond nearest neighbors. The interactions which are operative in liquid crystals are generally weak in comparison to those in crystalline phases, leading to the facile manipulation of the order in liquid crystals by external agents such as applied fields and surfaces. Effects arising from weak ordering are significantly enhanced in ultrathin free films and filaments wherein the intermolecular coupling is effectively reduced by loss of neighbors. Over the past four years this research, which we now detail, has produced a host of exciting new discoveries and unexpected results, maintaining the position of the study of freely suspended liquid crystal structures as one of most exciting and fruitful areas of complex fluid physics. In addition, several potentially interesting microgravity free film experiments have been identified.

  16. Liquid–liquid phase transition in compressed hydrogen from first-principles simulations

    PubMed Central

    Scandolo, Sandro

    2003-01-01

    The properties of compressed liquid hydrogen, the most abundant fluid in the universe, have been investigated by means of first-principles molecular dynamics at pressures between 75 and 175 GPa and temperatures closer to the freezing line than so far reported in shock-wave experiments. Evidence for a liquid–liquid transition between a molecular and a dissociated phase is provided. The transition is accompanied by a 6% increase in density and by metallization. This finding has important implications for our understanding of the interiors of giant planets and supports predictions of a quantum fluid state at low temperatures. PMID:12626753

  17. Liquid-liquid phase transition in quasi-two-dimensional supercooled silicon.

    PubMed

    Zhang, K; Li, H; Jiang, Y Y

    2014-09-01

    Anomalies of the local structural order in quasi-two-dimensional liquid silicon upon cooling are investigated. Results show that the appearance of the left subpeak in pair correlation functions is the signature of the liquid-liquid phase transition (LLPT). The structural origin of the LLPT is the formation of a crystal-like ordered structure with a short-range scale, which in turn forms the local well-organized paracrystalline region. Unlike in the bulk liquid silicon, the stages of the LLPT and liquid-solid phase transition (LSPT) in the quasi-two-dimensional liquid silicon do not overlap. The crystal-like ordered structures formed in the LLPT are precursors which are prepared for the subsequent LSPT. Also observed was a strong interconnection between the local well-organized paracrystalline region and the transition from the typical metal to the semimetal in the two-dimensional silicon. This study will aid in better understanding of the essential phase change in two-dimensional liquid silicon. PMID:25050842

  18. Ultrafast dynamics of the laser-induced solid-to-liquid phase transition in aluminum

    E-print Network

    Mazur, Eric

    for aluminum by optical exper- iments that demonstrated transition of the optical properties from solid properties during the solid-to-liquid phase transition in aluminum agree with the results obtained to the conclusion that the laser-induced, solid-to-liquid phase transition in aluminum is a thermal process. #12

  19. Liquid-crystal-anchoring transitions at surfaces created by polymerization-induced phase separation

    E-print Network

    Srinivasarao, Mohan

    Liquid-crystal-anchoring transitions at surfaces created by polymerization-induced phase separation surfaces created by polymerization-induced phase separation is presented. This transition is unusual-dispersed liquid-crystal films is explained, and observations provide a pathway to control properties. S1063-651X

  20. Bubbles in liquids with phase transition. Part 1. On phase change of a single vapor bubble in liquid water

    NASA Astrophysics Data System (ADS)

    Dreyer, Wolfgang; Duderstadt, Frank; Hantke, Maren; Warnecke, Gerald

    2012-11-01

    In the forthcoming second part of this paper a system of balance laws for a multi-phase mixture with many dispersed bubbles in liquid is derived where phase transition is taken into account. The exchange terms for mass, momentum and energy explicitly depend on evolution laws for total mass, radius and temperature of single bubbles. Therefore in the current paper we consider a single bubble of vapor and inert gas surrounded by the corresponding liquid phase. The creation of bubbles, e.g. by nucleation is not taken into account. We study the behavior of this bubble due to condensation and evaporation at the interface. The aim is to find evolution laws for total mass, radius and temperature of the bubble, which should be as simple as possible but consider all relevant physical effects. Special attention is given to the effects of surface tension and heat production on the bubble dynamics as well as the propagation of acoustic elastic waves by including slight compressibility of the liquid phase. Separately we study the influence of the three phenomena heat conduction, elastic waves and phase transition on the evolution of the bubble. We find ordinary differential equations that describe the bubble dynamics. It turns out that the elastic waves in the liquid are of greatest importance to the dynamics of the bubble radius. The phase transition has a strong influence on the evolution of the temperature, in particular at the interface. Furthermore the phase transition leads to a drastic change of the water content in the bubble. It is shown that a rebounding bubble is only possible, if it contains in addition an inert gas. In Part 2 of the current paper the equations derived are sought in order to close the system of equations for multi-phase mixture balance laws for dispersed bubbles in liquids involving phase change.

  1. Thermal-induced simultaneous liquid–liquid phase separation and liquid–solid transition in aqueous polyurethane dispersions

    Microsoft Academic Search

    Samy A. Madbouly; Joshua U. Otaigbe; Ajaya K. Nanda; Douglas A. Wicks

    2005-01-01

    Thermal-induced simultaneous phase separation and liquid–solid transition (gelation) in waterborne polyurethane dispersions has been detected morphologically and rheologically. The viscoelastic material functions, such as dynamic shear moduli, G? and G? complex shear viscosity, ?* and loss tangent, tan? were found to be very sensitive to the structure evolution during the gelation process and the subsequent formation of a fractal polymer

  2. Modelling and Numerical Simulation of Liquid-Vapor Phase Transition

    E-print Network

    Paris-Sud XI, Université de

    of pressurized water reactors in the nuclear industry. Indeed, understanding the triggering of boiling crisis-Phase Model We assume that we are far from the critical point, thus the vapor (resp. liquid) phase can the triple Corresponding author is Gloria FACCANONI E-mail: gloria@cmap.polytechnique.fr, WWW: http

  3. Density and phase transition study of the liquid crystal compound 50.16

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Debanjan; Bhattacharjee, Ayon

    2015-05-01

    Density and phase transition study for a liquid crystalline compound (50.16) is reported in this paper. This liquid crystalline compound as it is highly skewed in alkyl chain length. We experimentally measured the phase transition temperatures for the compound using a polarizing optical microscopy and differential scanning calorimeter. The densities of this liquid crystalline compound across all its phases as a function of temperature were measured using a capillary type dilatometer. The densities of the liquid crystals were calculated by correcting for the expansion of the glass capillary tube. These methods were found to be highly suitable for the calculation the phase transition and density of liquid crystalline with respect to temperature. The density data was used to calculate several parameters that provide an understanding of the phase behavior in such skewed liquid crystalline compounds.

  4. Static and dynamical inhomogeneity at liquid - liquid phase transition of Se-Te mixtures

    NASA Astrophysics Data System (ADS)

    Kajihara, Y.; Inui, M.; Matsuda, K.; Ishikawa, D.; Tsutsui, S.; Baron, A. Q. R.

    2011-05-01

    We have carried out x-ray transmission and small-angle x-ray scattering (SAXS) measurements of liquid Se70-Te30 mixture up to 1000 °C and 100MPa and inelastic x-ray scattering (IXS) measurement of liquid Se50-Te50 mixture at SPring-8 in Japan. In this paper, we report the preliminary results. In liquid Se70Te30 at 6MPa, with increasing temperature from 400 °C, the density first normaly decreases but anomalously increases from 650 °C. This anomalous density behaviour can be interpreted that the sample exhibits continuous transition from low-density phase to high-density one in this temperature region. As a proof of that, the zero-wavenumber-limit of SAXS intensity I(0) increases and shows maximum in this region, which means that the static density inhomogeneity arises due to phase transition. When the pressure is elevated, the density and I(0) curves shift to lower temperature side. The velocity of acoustic mode in Se50-Te50 estimated by IXS data is much higher than the ultrasonic sound velocity (so-called "fast sound" state) and the temperature dependences of the two velocities are totally different. But the ratio of the two velocities, the strength of "fast sound", seems to increase with approaching to the transition region and thus it seems to be a good sign of dynamical inhomogeneity.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  6. A liquid vapor phase transition in quantum statistical F. Baffioni, T. Kuna, I. Merola, and E. Presutti

    E-print Network

    A liquid vapor phase transition in quantum statistical mechanics F. Baffioni, T. Kuna, I. Merola, and E. Presutti Abstract. We prove a liquid vapor phase transition for a quantum system of particles the van der Waals theory of liquid vapor phase transitions, and indeed the limit 0, after

  7. Nuclear symmetry energy effects on liquid-gas phase transition in hot asymmetric nuclear matter

    E-print Network

    Bharat K. Sharma; Subrata Pal

    2010-01-14

    The liquid-gas phase transition in hot asymmetric nuclear matter is investigated within relativistic mean-field model using the density dependence of nuclear symmetry energy constrained from the measured neutron skin thickness of finite nuclei. We find symmetry energy has a significant influence on several features of liquid-gas phase transition. The boundary and area of the liquid-gas coexistence region, the maximal isospin asymmetry and the critical values of pressure and isospin asymmetry all of which systematically increase with increasing softness in the density dependence of symmetry energy. The critical temperature below which the liquid-gas mixed phase exists is found higher for a softer symmetry energy.

  8. Phase Transition and Separation for Mixture of Liquid He-3 and He-4

    E-print Network

    Tian Ma; Shouhong Wang

    2008-05-31

    This article introduces a dynamical Ginzburg-Landau phase transition/separation model for the mixture of liquid helium-3 and helium-4, using a unified dynamical Ginzburg-Landau model for equilibrium phase transitions. The analysis of this model leads to three critical length scales L1 < L2 < L3, detailed theoretical phase diagrams and transition properties with different length scales of the container.

  9. Quantum phase transition from an antiferromagnet to a spin liquid in a metal

    E-print Network

    Grover, Tarun

    We study quantum phase transitions from easy-plane antiferromagnetic metals to paramagnetic metals in Kondo-Heisenberg lattice systems. If the paramagnetic metal is a fractionalized Fermi liquid then the universal critical ...

  10. The Nuclear Liquid-Gas Phase Transition: Q.E.D

    E-print Network

    V. E. Viola

    2003-11-11

    For the past decade, intense experimental effort has been devoted to the search for a liquid-gas phase transition in highly excited nuclei. Now, synthesis of the large body of existing multifragmentation data provides a strong case for identification of this phenomenon. In this presentation we discuss several salient features of the data that support their interpretation in terms of a spinodal liquid-gas phase transition.

  11. Third-order gas-liquid phase transition and the nature of Andrews critical Tian Ma and Shouhong Wang

    E-print Network

    Wang, Shouhong

    Third-order gas-liquid phase transition and the nature of Andrews critical point Tian Ma-order gas-liquid phase transition and the nature of Andrews critical point Tian Ma1 and Shouhong Wang2 1 is to study the nature of the Andrews critical point in the gas-liquid transition in a physical

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

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac; Dzyabura, Vasily; Zaghoo, Mohamed

    2013-03-01

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

  13. A Calorimetric Study of Liquid Crystal Phase Transitions in Restrictive Geometries

    Microsoft Academic Search

    Germano Silvio Iannacchione

    1993-01-01

    A considerable amount of experimental and theoretical efforts have been applied to the study of confined liquid crystals. This has been motivated by the obvious interest for industrial applications and by the fundamental scientific questions that these systems address. This work details a calorimetric study of three phase transitions for liquid crystals confined within submicron size cylindrical cavities and random

  14. Phase transition altering the symmetry of topological point defects (hedgehogs) in a nematic liquid crystal

    E-print Network

    Lavrentovich, Oleg D.

    Phase transition altering the symmetry of topological point defects (hedgehogs) in a nematic liquid defect (hedgehog) at the center of the drop. The transition occurred as a result of a change did not change) and involved transformation of a radial hedgehog to a hyperbolic one, accompanied

  15. The complement: a solution to liquid drop finite size effects in phase transitions

    E-print Network

    L. G. Moretto; K. A. Bugaev; J. B. Elliott; R. Ghetti; J. Helgesson; L. Phair

    2005-04-07

    The effects of the finite size of a liquid drop undergoing a phase transition are described in terms of the complement, the largest (but still mesoscopic) drop representing the liquid in equilibrium with the vapor. Vapor cluster concentrations, pressure and density from fixed mean density lattice gas (Ising) model calculations are explained in terms of the complement. Accounting for this finite size effect is key to determining the infinite nuclear matter phase diagram from experimental data.

  16. Dielectric study of the SAd -SA2 phase transition of new thermotropic liquid crystals

    E-print Network

    Boyer, Edmond

    ). In anisotropic phases, the per- mittivities s*(E//n) and 8*-(E 1 n) are obtained when the applied electric field is parallel or perpendicular to the director n respectively. A magnetic field of 1.2 T is used to orient903 Dielectric study of the SAd - SA2 phase transition of new thermotropic liquid crystals N. R

  17. Calorimetric Studies of the Smectic A to Isotropic Phase Transition of Liquid Crystals in Confied Media

    Microsoft Academic Search

    Indira Weerasekera; Karl M. Unruh

    1996-01-01

    The first order transition from the smectic A to isotropic phase of the liquid crystals 4-10-alkoxy-4'-cyanobiphenyl and 4-10-alkyl-4'-cyanobipenyl confined within nanometer sized silica glass pores has been studied as a function of the mean radii of the confining pores by differential scanning calorimetry. The transition temperatures and the latent heats of transition were found to be size dependent, and in

  18. The gas-liquid phase-transition singularities in the framework of the liquid-state integral equation formalism

    Microsoft Academic Search

    Gari Sarkisov; Enrique Lomba

    2005-01-01

    The singularities of various liquid-state integral equations derived from the Ornstein-Zernike relation and its temperature derivatives, have been investigated in the liquid-vapor transition region. As a general feature, it has been found that the existence of a nonsolution curve on the vapor side of the phase diagram, on which both the direct and the total correlation functions become complex-with a

  19. Liquid-liquid phase transition in aqueous solutions of n-hydrocarbons and amphiphiles

    NASA Astrophysics Data System (ADS)

    Mirgorod, Yu. A.

    2010-10-01

    Phase transitions in ensembles of water clusters in aqueous solutions of C11-C28 n-hydrocarbons and C2-C12 amphiphiles have been studied as dependent on the concentration and size of dissolved molecules. A critical size (approximately corresponding to the volume of undecane molecule) for water clusters is determined, which triggers the phase transition that leads to the formation of bistable amphiphile micelles.

  20. Two transitions between isotropic and nematic phases in confined liquid crystals.

    PubMed

    Emelyanenko, Alexander V; Aya, Satoshi; Sasaki, Yuji; Araoka, Fumito; Ema, Kenji; Ishikawa, Ken; Takezoe, Hideo

    2011-10-01

    The molecular mean-field theory for the nematic-isotropic (N-Iso) phase transition in the vicinity of the surface is derived. We have shown that the nematic order parameter in liquid crystal near the surface is generally different from that in the bulk. It is never equal to zero if the anisotropic interaction with the surface is present. At the same time, transition from the phase with large nematic order parameter at the surface to the phase with small nematic order parameter at the surface is possible on heating. This surface transition always happens at higher temperatures than N-Iso phase transition related to the bulk. The theoretical prediction was well reproduced experimentally. PMID:22181151

  1. The Phase Transition between Chiral Nematic and Smectic A * Liquid Crystals

    Microsoft Academic Search

    PATRICIA BAUMAN; M. CARME CALDERER; CHUN LIU; DANIEL PHILLIPS

    2002-01-01

    In this paper we study the Landau-de Gennes free energy used to describe the transition between chiral nematic and smectic\\u000a A liquid crystal phases. We consider the phenomenology of the transition and discuss the behavior of the material constants.\\u000a Within the present mathematical framework, the physically observed growth behavior of the twist and bend Frank constants, K\\u000a 2 and K

  2. Phonon self-energies and phase transitions in a prototype discotic liquid crystal M. Nollmann1

    E-print Network

    Nollmann, Marcelo

    , and basic aspects of the application of the con- tinuum and mean-field theories to them remain to be tested and the predictions of the mean-field Maier-Saupe theory 1 . Experiments of this sort exploit the fact that specificPhonon self-energies and phase transitions in a prototype discotic liquid crystal M. No¨llmann1

  3. Liquid-liquid phase transition model incorporating evidence for ferroelectric state near the lambda-point anomaly in supercooled water

    E-print Network

    Peter O. Fedichev; Leonid I. Menshikov

    2012-01-30

    We propose a unified model combining the first-order liquid-liquid and the second-order ferroelectric phase transitions models and explaining various features of the $\\lambda$-point of liquid water within a single theoretical framework. It becomes clear within the proposed model that not only does the long-range dipole-dipole interaction of water molecules yield a large value of dielectric constant $\\epsilon$ at room temperatures, our analysis shows that the large dipole moment of the water molecules also leads to a ferroelectric phase transition at a temperature close to the lambda-point. Our more refined model suggests that the phase transition occurs only in the low density component of the liquid and is the origin of the singularity of the dielectric constant recently observed in experiments with supercooled liquid water at temperature T~233K. This combined model agrees well with nearly every available set of experiments and explains most of the well-known and even recently obtained results of MD simulations.

  4. Middle phase microemulsion to liquid crystal transition in surfactant systems for EOR

    SciTech Connect

    Hackett, J.L.; Miller, C.A.

    1986-01-01

    The phase behavior of two anionic surfactant systems, one containing a commercial alpha olefin sulfonate, and the other pure sodium dodecyl sulfate (SDS), was determined in the region where a transition from microemulsion to liquid crystalline phases occurred with decreasing alcohol content and decreasing temperature. A general and rather complex pattern of phase behavior was seen which included a four-phase coexistence region of brine, microemulsion, lamellar liquid crystal, and oil and two three-phase regions containing both microemulsion and liquid crystal. In much of the four-phase region, complete separation of the phases did not occur even after equilibration for a year or more at constant temperature. Instead, oil and brine we observed to coexist with stable birefringent dispersions which, at least for some compositions, apparently contained three phases: microemulsion, liquid crystal, and oil. Solubilization of brine was uniformly low in the phases making up the dispersions. The dispersions in the SDS system exhibited non-Newtonian behavior with apparent viscosities in the range of 50-100 mPa . s at a shear rate of 10 sec/sup -1/. Microemulsion viscosities in the same system were about an order of magnitude lower. No plugging or other adverse behavior was seen when such dispersions flowed at a velocity of 10/sup -5/ m/s (3 ft/day) through a model porous medium having pore sizes comparable to those in reservoirs. In preliminary experiments, selected dispersions appeared to be capable of displacing oil from the same model porous medium.

  5. Observation of surface and bulk phase transitions in nematic liquid crystals.

    PubMed

    Boamfa, M I; Kim, M W; Maan, J C; Rasing, Th

    2003-01-01

    The behaviour of liquid crystal (LC) molecules near a surface is of both fundamental and technological interest: it gives rise to various surface phase-transition and wetting phenomena, and surface-induced ordering of the LC molecules is integral to the operation of LC displays. Here we report the observation of a pure isotropic-nematic (IN) surface phase transition-clearly separated from the bulk IN transition-in a nematic LC on a substrate. Differences in phase behaviour between surface and bulk are expected, but have hitherto proved difficult to distinguish, owing in part to the close proximity of their transition temperatures. We have overcome these difficulties by using a mixture of nematic LCs: small, surface-induced composition variations lead to complete separation of the surface and bulk transitions, which we then study independently as a function of substrate and applied magnetic field. We find the surface IN transition to be of first order on surfaces with a weak anchoring energy and continuous on surfaces with a strong anchoring. We show that the presence of high magnetic fields does not change the surface IN transition temperature, whereas the bulk IN transition temperature increases with field. We attribute this to the interaction energy between the surface and bulk phases, which is tuned by magnetic-field-induced order in the surface-wetting layer. PMID:12520297

  6. Investigating the solid-liquid phase transition of water nanofilms using the generalized replica exchange method

    SciTech Connect

    Lu, Qing [Division of Materials Science and Engineering, Boston University, Brookline, Massachusetts 02446 (United States); Kim, Jaegil; Straub, John E., E-mail: straub@bu.edu [Department of Chemistry, Boston University, Boston, Massachusetts 02215 (United States); Farrell, James D.; Wales, David J. [University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW (United Kingdom)

    2014-11-14

    The generalized Replica Exchange Method (gREM) was applied to study a solid-liquid phase transition in a nanoconfined bilayer water system using the monatomic water (mW) model. Exploiting optimally designed non-Boltzmann sampling weights with replica exchanges, gREM enables an effective sampling of configurations that are metastable or unstable in the canonical ensemble via successive unimodal energy distributions across phase transition regions, often characterized by S-loop or backbending in the statistical temperature. Extensive gREM simulations combined with Statistical Temperature Weighted Histogram Analysis Method (ST-WHAM) for nanoconfined mW water at various densities provide a comprehensive characterization of diverse thermodynamic and structural properties intrinsic to phase transitions. Graph representation of minimized structures of bilayer water systems determined by the basin-hopping global optimization revealed heterogeneous ice structures composed of pentagons, hexagons, and heptagons, consistent with an increasingly ordered solid phase with decreasing density. Apparent crossover from a first-order solid-liquid transition to a continuous one in nanoconfined mW water with increasing density of the system was observed in terms of a diminishing S-loop in the statistical temperature, smooth variation of internal energies and heat capacities, and a characteristic variation of lateral radial distribution functions, and transverse density profiles across transition regions.

  7. DYNAMIC MODELING STRATEGY FOR FLOW REGIME TRANSITION IN GAS-LIQUID TWO-PHASE FLOWS

    SciTech Connect

    X. Wang; X. Sun; H. Zhao

    2011-09-01

    In modeling gas-liquid two-phase flows, the concept of flow regime has been used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are often flow regime dependent. Currently, the determination of the flow regimes is primarily based on flow regime maps or transition criteria, which are developed for steady-state, fully-developed flows and widely applied in nuclear reactor system safety analysis codes, such as RELAP5. As two-phase flows are observed to be dynamic in nature (fully-developed two-phase flows generally do not exist in real applications), it is of importance to model the flow regime transition dynamically for more accurate predictions of two-phase flows. The present work aims to develop a dynamic modeling strategy for determining flow regimes in gas-liquid two-phase flows through the introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation and destruction of the interfacial area, such as the fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation; and fluid particle coalescence and condensation, respectively. For the flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shape (which are correlated), namely small bubbles and large bubbles. A preliminary approach to dynamically identifying the flow regimes is provided, in which discriminators are based on the predicted information, such as the void fraction and interfacial area concentration of small bubble and large bubble groups. This method is expected to be applied to computer codes to improve their predictive capabilities of gas-liquid two-phase flows, in particular for the applications in which flow regime transition occurs.

  8. Novel Ferroelectric Liquid Crystal Mode for Active Matrix Liquid Crystal Display Using Cholesteric Chiral Smectic C Phase Transition Material

    Microsoft Academic Search

    Yasufumi Asao; Takeshi Togano; Masahiro Terada; Takashi Moriyama; Shinichi Nakamura; Jun Iba

    1999-01-01

    We propose a novel ferroelectric liquid crystal (FLC) mode which is capable of gray-scale display with an active device such as a thin-film transistor (TFT). This technology is based on the monostable FLC mode, which is obtained from a material with cholesteric chiral smectic C (Ch SmC*) phase transition sequences and by applying a low DC voltage only near the

  9. Pinball liquid phase from Hund's coupling in frustrated transition-metal oxides

    NASA Astrophysics Data System (ADS)

    Ralko, Arnaud; Merino, Jaime; Fratini, Simone

    2015-04-01

    The interplay of nonlocal Coulomb repulsion and Hund's coupling in the d -orbital manifold in frustrated triangular lattices is analyzed by a multiband extended Hubbard model. We find a rich phase diagram with several competing phases, including a robust pinball liquid phase, which is an unconventional metal characterized by threefold charge order, bad metallic behavior, and the emergence of high-spin local moments. Our results naturally explain the anomalous charge-ordered metallic state observed in the triangular layered compound AgNiO2. The potential relevance to other triangular transition-metal oxides is discussed.

  10. Description of liquid-gas phase transition in the frame of continuum mechanics

    NASA Astrophysics Data System (ADS)

    Vilchevskaya, Elena N.; Ivanova, Elena A.; Altenbach, Holm

    2014-03-01

    A new method of describing the liquid-gas phase transition is presented. It is assumed that the phase transition is characterized by a significant change of the particle density distribution as a result of energy supply at the boiling point that leads to structural changes but not to heating. Structural changes are described by an additional state characteristics of the system—the distribution density of the particles which is presented by an independent balance equation. The mathematical treatment is based on a special form of the internal energy and a source term in the particle balance equation. The presented method allows to model continua which have different specific heat capacities in liquid and in gas state.

  11. Isotropic-to-nematic phase transition of liquid crystals confined in nanoemulsion droplets

    NASA Astrophysics Data System (ADS)

    Bono, S.; Takanishi, Y.; Yamamoto, J.

    2015-01-01

    We fabricated liquid crystalline nanoemulsions (LCNEs) by introducing low molecular weight liquid crystals (LMWLCs) into the core of nanoemulsions, and investigated the phase transition behavior of LMWLCs in the core part with the various weight ratios of LMWLCs to surfactants. The polarized dynamic light scattering measurement was performed to estimate the radii of LCNEs, and it is found that their radii can be controlled by the weight ratio of LMLCs to surfactant polymers. In the depolarized light scattering, it was revealed that the order of the isotropic-nematic phase transition behavior changes from the first order to biased second order with decreasing radius of LCNEs because of the three-dimensional confinement effect surrounded by an anchoring surface.

  12. Paranematic–nematic phase transition in liquid crystalline elastomers: a H-NMR study

    Microsoft Academic Search

    Valentina Domenici; Bostjan Zalar

    2010-01-01

    In this study, selectively deuterium-labelled monodomain liquid single crystalline elastomers have been investigated by means of H-NMR spectroscopy. The analysis of the spectral features as well as the study of the orientational properties in the paranematic and nematic phases confirmed the supercriticality of the paranematic–nematic transition as an intrinsic property of these systems. Moreover, the combined study of the spin–spin

  13. On the size dependences of the crystal-liquid phase transition parameters

    NASA Astrophysics Data System (ADS)

    Magomedov, M. N.

    2014-05-01

    A comparatively simple method is proposed for calculating the size dependences of the latent heat, volume jumps, and the interfacial surface energy for the crystal-liquid phase transition proceeding from the results of experiments (real or computer) on determining size dependences of the melting point and the crystallization temperature. The method is tested on the basis of computer simulation data for copper, gold, aluminum, and nickel nanoparticles and experimental data for tin.

  14. Time resolved photoelectron spectroscopy of germanium and silicon during the solid to the liquid state phase transition

    Microsoft Academic Search

    G. Gantner; H.-G. Boyen; P. Oelhafen

    1996-01-01

    Photoelectron spectroscopy of liquid silicon and germanium has been performed by using a new technique based on laser-pulse induced melting of sample surfaces and time resolved detection of the photoelectrons. With this method it has, for the first time, been possible to observe the solid to liquid phase transition of silicon, an element with a vapor pressure in the liquid

  15. Pressure Dependence of the Liquid–Liquid Phase Transition of Nanopore Water Doped Slightly with Hydroxylamine, and a Phase Behavior Predicted for Pure Water

    NASA Astrophysics Data System (ADS)

    Nagoe, Atsushi; Iwaki, Shinji; Oguni, Masaharu; Tôzaki, Ken-ichi

    2014-09-01

    Phase transition behaviors of confined pure water and confined water doped with a small amount of hydroxylamine (HA) with a mole fraction of xHA = 0.03 were examined by high-pressure differential thermal analyses at 0.1, 50, 100, and 150 MPa; the average diameters of silica pores used were 2.0 and 2.5 nm. A liquid–liquid phase transition (LLPT) of the confined HA-doped water was clearly observed and its pressurization effect could be evaluated, unlike in the experiments on undoped water. It was found that pressurization causes the transition temperature (Ttrs) to linearly decrease, indicating that the low-temperature phase has a lower density than the high-temperature one. Transition enthalpy (?trsH) decreased steeply with increasing pressure. Considering the linear decrease in Ttrs with increasing pressure, the steep decrease in ?trsH indicates that the LLPT effect of the HA-doped water attenuates with pressure. We present a new scenario of the phase behavior concerning the LLPT of pure water based on the analogy from the behavior of slightly HA-doped water, where a liquid–liquid critical point (LLCP) and a coexistence line are located in a negative-pressure regime but not in a positive-pressure one. It is reasonably understood that doping a small amount of HA into water results in negative chemical pressurization and causes the LLPT to occur even at ambient pressure.

  16. Surface Specularity as an Indicator of Shock-induced Solid-liquid Phase Transitions in Tin

    SciTech Connect

    G. D. Stevens, S. S. Lutz, B. R. Marshall, W.D. Turley, et al.

    2007-12-01

    When highly polished metal surfaces melt upon release after shock loading, they exhibit features that suggest significant surface changes accompany the phase transition. The reflection of light from such surfaces changes from specular (pre-shock) to diffuse upon melting. Typical of this phenomenon is the loss of signal light in velocity interferometer system for any reflector (VISAR) measurements, which usually occurs at pressures high enough to melt the free surface. Unlike many other potential material phase-sensitive diagnostics (e.g., reflectometry, conductivity), that show relatively small (1%-10%) changes, the specularity of reflection provides a more sensitive and definitive (>10x) indication of the solid-liquid phase transition. Data will be presented that support the hypothesis that specularity changes indicate melt in a way that can be measured easily and unambiguously.

  17. Liquid–solid phase transition of hydrogen and deuterium in silica aerogel

    SciTech Connect

    Van Cleve, E.; Worsley, M. A.; Kucheyev, S. O., E-mail: kucheyev@llnl.gov [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

    2014-10-28

    Behavior of hydrogen isotopes confined in disordered low-density nanoporous solids remains essentially unknown. Here, we use relaxation calorimetry to study freezing and melting of H{sub 2} and D{sub 2} in an ?85%-porous base-catalyzed silica aerogel. We find that liquid–solid transition temperatures of both isotopes inside the aerogel are depressed. The phase transition takes place over a wide temperature range of ?4?K and non-trivially depends on the liquid filling fraction, reflecting the broad pore size distribution in the aerogel. Undercooling is observed for both H{sub 2} and D{sub 2} confined inside the aerogel monolith. Results for H{sub 2} and D{sub 2} are extrapolated to tritium-containing hydrogens with the quantum law of corresponding states.

  18. Near infrared light-driven liquid crystal phase transition enabled by hydrophobic mesogen grafted plasmonic gold nanorods.

    PubMed

    Gutierrez-Cuevas, Karla G; Wang, Ling; Xue, Chenming; Singh, Gautam; Kumar, Satyendra; Urbas, Augustine; Li, Quan

    2015-06-01

    Light-driven phase transition in liquid crystals is a fascinating endeavour from both scientific and technological points of view. Here we demonstrate the proof-of-principle that the photothermal effect of organo-soluble plasmonic gold nanorods can introduce the phase transition of thermotropic liquid crystals upon near infrared laser irradiation. Interestingly, the reverse process occurs when the laser is switched off. PMID:25989830

  19. Solvent effect on phase transition of lyotropic rigid-chain liquid crystal polymer studied by dissipative particle dynamics.

    PubMed

    Zhao, Tongyang; Wang, Xiaogong

    2013-01-14

    Effect of solvent quality on phase transition of lyotropic rigid-chain liquid crystal polymer is studied by dissipative particle dynamics simulation. A rod composed of fused DPD particles is used to represent the solvated rigid polymer. The effect of solvent quality is investigated by adjusting the repulsion parameter between the rods and solvent particles. The simulation shows that the solvent quality has significant influences on the phase transition behavior of the system and the influences are also closely related with the concentrations before the solvent becomes extremely poor. The influences of the solvent quality are attributed to the interplay between the immiscibility-induced phase separation and nematic-isotropic phase transition, which can be described by the binodal lines and nematic-isotropic transition lines in the phase diagrams. If a system is located in the one phase region, it will undergo a typical nematic to isotropic phase transition as the temperature increases. If a system is located in the biphasic region, there are two different types of nematic-isotropic phase transitions depending on whether the transition temperature from the biphasic region to isotropic phase region is lower or higher than the nematic-isotropic transition temperature of the concentrated phase. The first type corresponds to the transition from the biphasic region to the isotropic one phase region and the second type is attributed to the nematic-isotropic phase transition that occurs in the concentrated phase. PMID:23320724

  20. X-Ray Study of Phase Transition and Structures of Some Columnar Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Dai, Song

    1995-01-01

    Three series of columnar discotic liquid crystals with different cores and lengths of side chains have been studied by use of X-ray diffraction. Overlapping diffraction peaks have been decomposed by use of a peak model. The measured d-spacings were indexed for the mesophases and some crystal phases. Radial distribution functions (RDF) along the columnar axes were calculated approximately. Octaether derivatives of tetrabenzocyclododecatetraene with n = 12, 13, 14, 15 carbon atoms in the side chains exhibit a hexagonal mesophase to centered rectangular mesophase transition without observable transition heat. It is found that the transitions take place over a wide temperature range (maximum 20^circC) n = 13 and 14. This transition range is really an intermediate phase which is neither hexagonal nor centred rectangular, but rather oblique. This series of specimens also shows crystal to crystal transitions with small transition heats. Detailed X-ray diffraction scans indicate that these transitions also occur over a temperature range (maximum 10 ^circC) and the transition is not a sudden transition as a function of temperature. Hexa-n-alcanoyloxy triphenylenes with side chain carbon atom number n = 6, 8, 10, 12 have been studied. HAT -C8 shows solid polymorphism between 80^ circC and 26^circC. HAT -C10 has two mesophases with small differences in their diffraction pattern. HAT-C12 had been reported to have three mesophases on cooling from 125^circ C to 70^circC, but the corresponding diffraction patterns are not stable. The stable patterns obtained above 70^circ C are those of the isotropic liquid. At 70 ^circC, the specimen does show a stable mesophase pattern corresponding to the D_0 phase. Benzene twins based on hexa-hydrobenzene hexa -n-heptanoate (R = C_6 H _{13}) also have been studied. These twins consists of two benzene rings joined by a long flexible spacer rm C_{n-2}H_ {2n-1}(COO)_2 with R as the side chains. TWINS-S6, 8 show a complex diffraction pattern in their mesophase temperature range. No mesophase is observed by X-rays. TWINS-S12, 14 show a simple mesophase diffraction pattern in the mesophase temperature range.

  1. Contact line motion in confined liquid-gas systems: Slip versus phase transition

    NASA Astrophysics Data System (ADS)

    Xu, Xinpeng; Qian, Tiezheng

    2010-11-01

    In two-phase flows, the interface intervening between the two fluid phases intersects the solid wall at the contact line. A classical problem in continuum fluid mechanics is the incompatibility between the moving contact line and the no-slip boundary condition, as the latter leads to a nonintegrable stress singularity. Recently, various diffuse-interface models have been proposed to explain the contact line motion using mechanisms missing from the sharp-interface treatments in fluid mechanics. In one-component two-phase (liquid-gas) systems, the contact line can move through the mass transport across the interface while in two-component (binary) fluids, the contact line can move through diffusive transport across the interface. While these mechanisms alone suffice to remove the stress singularity, the role of fluid slip at solid surface needs to be taken into account as well. In this paper, we apply the diffuse-interface modeling to the study of contact line motion in one-component liquid-gas systems, with the fluid slip fully taken into account. The dynamic van der Waals theory has been presented for one-component fluids, capable of describing the two-phase hydrodynamics involving the liquid-gas transition [A. Onuki, Phys. Rev. E 75, 036304 (2007)]. This theory assumes the local equilibrium condition at the solid surface for density and also the no-slip boundary condition for velocity. We use its hydrodynamic equations to describe the continuum hydrodynamics in the bulk region and derive the more general boundary conditions by introducing additional dissipative processes at the fluid-solid interface. The positive definiteness of entropy production rate is the guiding principle of our derivation. Numerical simulations based on a finite-difference algorithm have been carried out to investigate the dynamic effects of the newly derived boundary conditions, showing that the contact line can move through both phase transition and slip, with their relative contributions determined by a competition between the two coexisting mechanisms in terms of entropy production. At temperatures very close to the critical temperature, the phase transition is the dominant mechanism, for the liquid-gas interface is wide and the density ratio is close to 1. At low temperatures, the slip effect shows up as the slip length is gradually increased. The observed competition can be interpreted by the Onsager principle of minimum entropy production.

  2. Phases and phase transitions of polymeric liquid crystals: A high resolution x ray diffraction and light scattering study

    NASA Astrophysics Data System (ADS)

    Nachaliel, Ehud

    1991-03-01

    Liquid crystal polymers (LCP) were compared with monomeric liquid crystals (MLC) by means of high-resolution x-ray (HIREX) and light scattering (LIS). Both HIREX and LIS were used to study the nematic-smectic(sub a) phase transition of P4.1 polysiloxane; the following critical exponents were determined: nu(sub parallel) = 0.77 +/-0.05; nu(sub normal) = 0.57 +/-0.08; gamma = 1.3 +/-0.10. The bare correlation lengths were found to be: xi(sup 0)(sub parallel) = 3.27 +/-0.08; xi(sup 0)(sub normal)q(sub 0) = 1.09 +/-0.14 which are unusually large in comparison with MLC. LIS experiments confirmed these values and indicated 'cross over' of nu(sub parallel) from 0.77 to 0.53. These results are typical of a system near to a tricritical point. HIREX was used to study the nematic-smectic(sub c) phase transition in C6-polysiloxane; the results were a good fit to Chen and Lubensky's mean field theory but the correlation lengths saturated near the transition to the nematic phase. A study of the smectic(sub a) phase of PA6 polyacrylate, near the transition to the nematic phase, showed that, except very close to the transition, the first and second harmonics of the x-ray structure factor were found to be consistent with the harmonic theory of de Gennes and Caille. This is thought to indicate the importance of anharmonic corrections near the phase transition. Fits to the experimental data yielded the compressibility constant, B and the splay elastic constant, K(sub s). B was found to obey a power law: B varies as t(sup phi) in which phi = 0.82 +/-0.08. In good agreement with theoretical predictions using exponents from the literature, but in disagreement with previous experimental results on MLC's. The splay elastic constant K(sub s) has roughly the same magnitude as in MLC's but tends to decrease by approximately 50% upon approaching the transition from below. This temperature dependence might give further evidence for the importance of anharmonicity in the system. Finally, the smectic(sub c) phase of C6 polysiloxane was studied, using HIREX. The tilt angle was found to decrease continuously upon decreasing temperature. This behavior, opposite to that observed in MLC's is caused by the stiffening in the plymeric backbone and spacers.

  3. Molecular Evolution of Poly(2-isopropyl-2-oxazoline) Aqueous Solution during the Liquid-Liquid Phase Separation and Phase Transition Process.

    PubMed

    Li, Tianjiao; Tang, Hui; Wu, Peiyi

    2015-06-23

    A detailed phase transition process of poly(2-isopropyl-2-oxazoline) (PIPOZ) in aqueous solution was investigated by means of DSC, temperature-variable (1)H NMR, Raman, optical micrographs, and FT-IR spectroscopy measurements. Gradual phase separation accompanied by large dehydration degree and big conformational changes above the lower critical solution temperature (LCST) and facile reversibility were identified. Based on the two-dimensional correlation (2Dcos) and perturbation correlation moving window (PCMW) analyses, the sequence order of chemical group motions in phase transition process was elucidated. Additionally, a newly assigned CH3···O?C intermolecular hydrogen bond at 3008 cm(-1) in the PIPOZ system provides extra information on the interactions between C-H and C?O groups. The formation of cross-linking "bridging" hydrogen bonds C?O···D-O-D···O?C (1631 cm(-1)) is proposed as the key process to induce the liquid-liquid phase separation and polymer-rich phase formation of PIPOZ solution. With slow heating, more and more "bridging" hydrogen bonds were formed and D2O were expelled with an ordered and mostly all-trans conformation adopted in the PIPOZ chains. On the basis of these observations, a physical picture on the molecular evolution of PIPOZ solution during the phase transition process has been derived. PMID:26024150

  4. Phase transitions in nuclear physics

    SciTech Connect

    Moretto, L.G.; Phair, L.; Wozniak, G.J.

    1997-08-01

    A critical overview of the low energy phase transitions in nuclei is presented with particular attention to the 2nd (1st) order pairing phase transitions, and to the 1st order liquid-vapor phase transition. The role of fluctuations in washing out these transitions is discussed and illustrated with examples. A robust indicator of phase coexistence in multifragmentation is presented.

  5. Method and apparatus for acoustic plate mode liquid-solid phase transition detection

    NASA Astrophysics Data System (ADS)

    Blair, D. S.; Frye, G. C.; Hughes, R. C.; Martin, S. J.; Ricco, A. J.

    1990-05-01

    A method and apparatus for sensing a liquid-solid phase transition event is provided which comprises an acoustic plate mode detecting element placed in contact with a liquid or solid material which generates a high-frequency acoustic wave that is attenuated to an extent based on the physical state of the material in contact with the detecting element. The attenuation caused by the material in contact with the acoustic plate mode detecting element is used to determine the physical state of the material being detected. The method and device are particularly suited for detecting conditions such as the icing and deicing of wings of an aircraft. In another aspect of the present invention, a method is provided wherein the adhesion of a solid material to the detecting element can be measured using the apparatus of the invention.

  6. Method and apparatus for acoustic plate mode liquid-solid phase transition detection

    DOEpatents

    Blair, Dianna S. (Albuquerque, NM); Freye, Gregory C. (Cedar Crest, NM); Hughes, Robert C. (Albuquerque, NM); Martin, Stephen J. (Albuquerque, NM); Ricco, Antonio J. (Albuquerque, NM)

    1993-01-01

    A method and apparatus for sensing a liquid-solid phase transition event is provided which comprises an acoustic plate mode detecting element placed in contact with a liquid or solid material which generates a high-frequency acoustic wave that is attenuated to an extent based on the physical state of the material is contact with the detecting element. The attenuation caused by the material in contact with the acoustic plate mode detecting element is used to determine the physical state of the material being detected. The method and device are particularly suited for detecting conditions such as the icing and deicing of wings of an aircraft. In another aspect of the present invention, a method is provided wherein the adhesion of a solid material to the detecting element can be measured using the apparatus of the invention.

  7. Liquid-solid phase transition alloy as reversible and rapid molding bone cement.

    PubMed

    Yi, Liting; Jin, Chao; Wang, Lei; Liu, Jing

    2014-12-01

    Acrylic bone cement has been an essential non-metallic implant used as fixing agent in the cemented total joint arthroplasty (THA). However, the currently available materials based mainly on polymethylmethacrylate (PMMA) still encounter certain limitations, such as time-consuming polymerization, thermal and chemical necrosis and troublesome revision procedure. Here from an alternative way, we proposed for the first time to adopt the injectable alloy cement to address such tough issues through introducing its unique liquid-solid phase transition mechanism. A typical cement along this way is thus made of an alloy Bi/In/Sn/Zn with a specifically designed low melting point 57.5 °C, which enables its rapid molding into various desired shapes with high plasticity and ultimate metallic behaviors. The fundamental characteristics including the mechanical strength, biocompatibility and phase transition-induced thermal effects have been clarified to demonstrate the importance of such alloy as unconventional cement with favorable merits. In addition, we also disclosed its advantage as an excellent contrast agent for radiation imaging on the bone interior structure which is highly beneficial for guiding the surgery and monitoring the therapeutic effects. Particularly, the proposed alloy cement with reversible phase transition feature significantly simplifies the revision of the cement and prosthesis. This study opens the way for employing the injectable alloy materials as reversible bone cement to fulfill diverse clinical needs in the coming time. PMID:25239039

  8. Dynamics of isothermal phase transition of liquid crystal with zero anchoring

    NASA Astrophysics Data System (ADS)

    Fu, Jinxin; Nayani, Karthik; Park, Jung Ok; Srinivasarao, Mohan

    2015-03-01

    Liquid crystal (LC) is an ideal system to mimic the cosmological symmetry breaking in the laboratory. The formation of LC string defects in film and bubble has been shown to be analogous to the formation of cosmic strings previously. Here we study the dynamics of LC isothermal transition from isotropic to nematic phase in a three-dimensionally isotropic environment, which enables us to observe the simultaneous symmetry breaking of matter without any external heat transfer or anchoring boundary condition. The isothermal phase transition is realized by the photochemical conversion of the trans-form to the cis-form of an Azobenzene compound that is added into liquid crystal E7. And a medium composed of carbopol and SDS surfactant provides the zero anchoring. The dynamics of the nucleation of LC and defects are studied under microscope with high-speed camera. This work was supported a grant from the U.S. Office of Basic Energy Sciences, Department of Energy; Grant No. DE-SC0001412

  9. Free energy surface of ST2 water near the liquid-liquid phase transition Peter H. Poole, Richard K. Bowles, Ivan Saika-Voivod, and Francesco Sciortino

    E-print Network

    Sciortino, Francesco

    Free energy surface of ST2 water near the liquid-liquid phase transition Peter H. Poole, Richard K://jcp.aip.org/about/rights_and_permissions #12;THE JOURNAL OF CHEMICAL PHYSICS 138, 034505 (2013) Free energy surface of ST2 water near umbrella sampling Monte Carlo simulations to evaluate the free energy surface of the ST2 model of water

  10. Phase Transitions, Crystallization Behaviors and Structure of a Nonracemic Chiral Main-Chain Liquid Crystalline Polyester

    NASA Astrophysics Data System (ADS)

    Jin, Shi; Bai, Feng; Li, Christopher Y.; Harris, Frank W.; Cheng, S. Z. D.

    2002-03-01

    A nonracemic chiral main-chain liquid crystalline (LC) polyester [PET(R*)-7] has been synthesized using condensation reaction of an AB type monomer. Multiple phase transitions have been found during cooling and heating at different rates in differential scanning calorimetry measurements. Wide-angle X-ray diffraction (WAXD) experiments have shown that the phase transition swquence is from a highly ordered smectic phase -SmC* (139 °C) - SmA* (199 °C) TGBA ( 206 °C) isotropic with increasing temperature. Flat-on and twisted helical single crystals can be grown thermotropically from the LC state. Both types of crystals possess the identical monoclinic unit cell: a = 1.04 nm, b = 0.450 nm, c= 5.59 nm and g = 84.2 °. All helical crystals show a right-hand twist with pitch lengths of ranging between 0.5 - 5 mm. These single crystals can also be obtained by evaporating solvent from solution. PET(R*)-7 crystallizes much faster in its orientated form. It has been found that the orientation of crystals can be manipulated by the nature of phase from which they grow. The c-axis of crystals is along the fiber axis when crystallization occurs in the SmA* phase, while the c-axis of crystals is along the direction of the SmC* layer normal when crystallization takes place in the SmC* phase. An interesting observation is that macroscopic LC quasi-monodomains can be obtained by applying a mechanical external field. Detailed WAXD results indicate that they are SmC* quasi-monodomains. A quasi-monodomain can crystallize into a single-crystal-like structure.

  11. Synergy in lipofection by cationic lipid mixtures: Superior activity at the gel-liquid crystalline phase transition

    PubMed Central

    Koynova, Rumiana; Wang, Li; MacDonald, Robert C.

    2008-01-01

    Some mixtures of two cationic lipids including phospholipid compounds (O-ethylphosphatidylcholines), as well as common, commercially available cationic lipids, such as dimethylammonium bromides and trimethylammonium propanes, deliver therapeutic DNA considerably more efficiently than do the separate molecules. In an effort to rationalize this widespread “mixture synergism”, we examined the phase behavior of the cationic lipid mixtures and constructed their binary phase diagrams. Among a group of more than 50 formulations, the compositions with maximum delivery activity resided unambiguously in the solid-liquid crystalline two-phase region at physiological temperature. Thus, the transfection efficacy of formulations exhibiting solid-liquid crystalline phase coexistence is more than 5× higher than that of formulations in the gel (solid) phase, and over twice that of liquid crystalline formulations; phase coexistence occurring at physiological temperature thus appears to contribute significantly to mixture synergism. This relationship between delivery activity and physical property can be rationalized on the basis of the known consequences of lipid phase transitions, namely the accumulation of defects and increased disorder at solid-liquid crystalline phase boundaries. Packing defects at the borders of coexisting solid and liquid crystalline domains, as well as large local density fluctuations, could be responsible for the enhanced fusogenicity of mixtures. This study leads to the important conclusion that manipulating the composition of the lipid carriers so their phase transition takes place at physiological temperature can enhance their delivery efficacy. PMID:17571876

  12. Separation of rare earths from transition metals by liquid-liquid extraction from a molten salt hydrate to an ionic liquid phase.

    PubMed

    Rout, Alok; Binnemans, Koen

    2014-02-28

    The solvent extraction of trivalent rare-earth ions and their separation from divalent transition metal ions using molten salt hydrates as the feed phase and an undiluted fluorine-free ionic liquid as the extracting phase were investigated in detail. The extractant was tricaprylmethylammonium nitrate, [A336][NO3], and the hydrated melt was calcium nitrate tetrahydrate, Ca(NO3)2·4H2O. The extraction behavior of rare-earth ions was studied for solutions of individual elements, as well as for mixtures of rare earths in the hydrated melt. The influence of different extraction parameters was investigated: the initial metal loading in the feed phase, percentage of water in the feed solution, equilibration time, and the type of hydrated melt. The extraction of rare earths from Ca(NO3)2·4H2O was compared with extraction from CaCl2·4H2O by [A336][Cl] (Aliquat 336). The nitrate system was found to be the better one. The extraction and separation of rare earths from the transition metals nickel, cobalt and zinc were also investigated. Remarkably high separation factors of rare-earth ions over transition metal ions were observed for extraction from Ca(NO3)2·4H2O by the [A336][NO3] extracting phase. Furthermore, rare-earth ions could be separated efficiently from transition metal ions, even in melts with very high concentrations of transition metal ions. Rare-earth oxides could be directly dissolved in the Ca(NO3)2·4H2O phase in the presence of small amounts of Al(NO3)3·9H2O or concentrated nitric acid. The efficiency of extraction after dissolving the rare-earth oxides in the hydrated nitrate melt was identical to extraction from solutions with rare-earth nitrates dissolved in the molten phase. The stripping of the rare-earth ions from the loaded ionic liquid phase and the reuse of the recycled ionic liquid were also investigated in detail. PMID:24352299

  13. Studies of molecular monolayers at air-liquid interfaces by second harmonic generation: question of orientational phase transition

    SciTech Connect

    Rasing, T.; Shen, Y.R.; Kim, M.W.; Grubb, S.; Bock, J.

    1985-06-01

    Insoluble molecular monolayers at gas-liquid interfaces provide an insight to the understanding of surfactants, wetting, microemulsions and membrane structures and offer a possibility to study the rich world of 2-dimensional phase transitions. In the interpretation of the observed properties of these systems various assumptions about the molecular orientation are often made, but so far few clear experimental data exist. In this paper we will show how optical second harmonic generation (SHG) can be used to measure the molecular orientation of monolayers of surfactant molecules at water-air interfaces. By simultaneously measuring the surface pressure versus surface molecular area we can show for the first time that the observed liquid condensed-liquid expanded transition is an orientational phase transition. 7 refs., 4 figs.

  14. Calorimetric study of the isotropic to nematic phase transition in an aligned liquid crystal nano?colloidal gel

    Microsoft Academic Search

    F. Crucenau; D. Liang; R. L. Leheny; G. S. Iannacchione

    2008-01-01

    A high?resolution calorimetric study of the specific heat (Cp) has been carried out for the isotropic to nematic phase transition in an aligned liquid crystal (octylcyanobiphenyl ? 8CB) and aerosil nano?colloid gel. A stable alignment was achieved by repeated thermal cycling of the samples in the presence of a strong uniform magnetic field, which introduces anisotropy to the quenched random

  15. Traveling Waves, Riemann Problems and Computations of a Model of the Dynamics of Liquid\\/Vapor Phase Transitions

    Microsoft Academic Search

    Haitao Fan

    1998-01-01

    A model for the liquid\\/vapor phase transitions in a shock tube is discussed. Computations for the one-dimensional isothermal case is carried out to show that this model exhibits one-dimensional wave patterns observed in actual experiments. The existence of traveling waves under two different scalings are studied. For the first scaling, where the diffusion of different phases is very small relative

  16. Effects of Kinetic Roughening and Liquid-Liquid Phase Transition on Lysozyme Crystal Growth Velocities

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Konnert, John; Forsythe, Elizabeth L.; Pusey, Marc L.

    2004-01-01

    We measured the growth velocities of the (110) face of tetragonal lysozyme, V (centimeters per second), at four different concentrations, c (milligrams per milliliter), as the solution temperature, T (Centigrade), was reduced. For a broad range of T dependent on c, we find that the growth velocities increased as the solution temperature was reduced. The initial increase in V is well characterized by the 2D nucleation model for crystal growth, yielding the magnitude of an effective barrier for growth, gamma(sub s) = 1.2 plus or minus 0.1 x 10(exp -13) erg/molecule. Below certain temperatures, T(sub cr), dependent on c, however, a kinetic roughening hypothesis that considers the continuous addition of molecules anywhere on the crystal surface better describes the observed growth velocities. The application of the continuous growth model, up to the solution cloud-point temperatures, T(sub cl), enabled the determinations of the crossover concentration, c(sub r), from estimated values of T(sub cr). For all conditions presented, we find that the crossover from growth by 2D nucleation to continuous addition occurs at a supersaturation, sigma (sub c), = 2.0 plus or minus 0.1. Moreover, we find the energy barrier for the continuous addition, E(sub c), within the temperature range T(sub cl) less than T less than T less than T (sub cr), to be 6 plus or minus 1 x 10(exp -13) erg/molecule. Further reduction of T below approximately 2-3 C of T(sub cl), also revealed a rapid slowing of crystal growth velocities. From quasi-elastic light scattering investigations, we find that the rapid diminishment of crystal growth velocities can be accounted for by the phase behavior of lysozyme solutions. Namely, we find the reversible formation of dense fluid proto-droplets comprised of lysozyme molecules to occur below approximately 0.3 C of T(sub cl). Hence, the rapid slowing of growth velocities may occur as a result of the sudden depletion of "mobile" molecules within crystal growth solutions as dense fluid proto-droplets form.

  17. A calorimetric study of liquid crystalline phase transitions in confined geometries

    Microsoft Academic Search

    Indira Amarangani Weerasekera

    1998-01-01

    The behavior of the mesophase to isotropic transitions of liquid crystals in confined geometries has been studied using differential scanning calorimetry in an effort to understand the effects of finite size on the transition temperature and the latent heat. Liquid crystals 4-5-alkyl-4sp'-cyanobiphenyl, 4-10-alkyl-4sp '-cyanobiphenyl, 4-5-alkoxy-4sp'-cyanobiphenyl, and 4-10-alkoxy-4sp'-cyanobiphenyl were confined in a series of porous silica glasses with mean pore radii

  18. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model.

    PubMed

    Butlitsky, M A; Zelener, B B; Zelener, B V

    2014-07-14

    A two-component plasma model, which we called a "shelf Coulomb" model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The "shelf Coulomb" model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ? parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ? and ? = ?e(2)n(1/3) (where ? = 1/kBT, n is the particle's density, kB is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ? and ? parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ?(crit) ? 13(T(*)(crit) ? 0.076), ?(crit) ? 1.8(v(*)(crit) ? 0.17), P(*)(crit) ? 0.39, where specific volume v* = 1/?(3) and reduced temperature T(*) = ?(-1). PMID:25028031

  19. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model

    SciTech Connect

    Butlitsky, M. A.; Zelener, B. V. [Joint Institute for High Temperature of Russian Academy of Science, 125412, Russia, Moscow, Izhorskaya str. 13/2 (Russian Federation); Zelener, B. B. [Joint Institute for High Temperature of Russian Academy of Science, 125412, Russia, Moscow, Izhorskaya str. 13/2 (Russian Federation); Moscow Engineering Physics Institute, 115409, Russia, Moscow, Kashirskoe sh. 31 (Russian Federation)

    2014-07-14

    A two-component plasma model, which we called a “shelf Coulomb” model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The “shelf Coulomb” model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ? parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ? and ? = ?e{sup 2}n{sup 1/3} (where ? = 1/k{sub B}T, n is the particle's density, k{sub B} is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ? and ? parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ?{sub crit}?13(T{sub crit}{sup *}?0.076),?{sub crit}?1.8(v{sub crit}{sup *}?0.17),P{sub crit}{sup *}?0.39, where specific volume v* = 1/?{sup 3} and reduced temperature T{sup *} = ?{sup ?1}.

  20. Nuclear liquid-gas phase transition at large N{sub c} in the van der Waals approximation

    SciTech Connect

    Torrieri, Giorgio; Mishustin, Igor [FIAS, J. W. Goethe Universitaet, Max von Laue-Strasse 1, D-60438 Frankfurt am Main (Germany)

    2010-11-15

    We examine the nuclear liquid-gas phase transition at a large number of colors (N{sub c}) within the framework of the van der Waals (VdW) We argue that the VdW equation is appropriate for describing internucleon forces, and discuss how each parameter scales with N{sub c}. We demonstrate that N{sub c}=3 (our world) is not large with respect to the other dimensionless scale relevant to baryonic matter, the number of neighbors in a dense system N{sub N}. Consequently, we show that the liquid-gas phase transition looks dramatically different at N{sub c{yields}{infinity}} with respect to our world: The critical-point temperature becomes of the order of {Lambda}{sub QCD} rather than below it. The critical-point density becomes of the order of the baryonic density, rather than an order of magnitude below it. These are precisely the characteristics usually associated with the ''quarkyonic phase.'' We therefore conjecture that quarkyonic matter is simply the large-N{sub c} limit of the nuclear liquid, and the interplay between N{sub c} and N{sub N} is the reason that the nuclear liquid in our world is so different from quarkyonic matter. We conclude by suggesting ways in which our conjecture can be tested in future lattice measurements.

  1. Reversible temperature regulation of electrical and thermal conductivity using liquid-solid phase transitions.

    PubMed

    Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

    2011-01-01

    Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions. PMID:21505445

  2. Reversible temperature regulation of electrical and thermal conductivity using liquid–solid phase transitions

    PubMed Central

    Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

    2011-01-01

    Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions. PMID:21505445

  3. Search for the First-Order Liquid-to-Liquid Phase Transition in Low-Temperature Confined Water by Neutron Scattering

    SciTech Connect

    Chen, Sow-Hsin [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT); Wang, Zhe [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT); Kolesnikov, Alexander I [ORNL] [ORNL; Zhang, Yang [ORNL] [ORNL; Liu, Kao-Hsiang [National Taiwan University] [National Taiwan University

    2013-01-01

    It has been conjectured that a 1st order liquid-to-liquid (L-L) phase transition (LLPT) between high density liquid (HDL) and low density liquid (LDL) in supercooled water may exist, as a thermodynamic extension to the liquid phase of the 1st order transition established between the two bulk solid phases of amorphous ice, the high density amorphous ice (HDA) and the low density amorphous ice (LDA). In this paper, we first recall our previous attempts to establish the existence of the 1st order L-L phase transition through the use of two neutron scattering techniques: a constant Q elastic diffraction study of isobaric temperature scan of the D2O density, namely, the equation of state (EOS) measurements. A pronounced density hysteresis phenomenon in the temperature scan of the density above P = 1500 bar is observed which gives a plausible evidence of crossing the 1st order L-L phase transition line above this pressure; an incoherent quasi-elastic scattering measurements of temperature-dependence of the alpha-relaxation time of H2O at a series of pressures, namely, the study of the Fragile-to-Strong dynamic crossover (FSC) phenomenon as a function of pressure which we interpreted as the results of crossing the Widom line in the one-phase region. In this new experiment, we used incoherent inelastic neutron scattering (INS) to measure the density of states (DOS) of H atoms in H2O molecules in confined water as function of temperature and pressure, through which we may be able to follow the emergence of the LDL and HDL phases at supercooled temperature and high pressures. We here report for the first time the differences of librational and translational DOSs between the hypothetical HDL and LDL phases, which are similar to the corresponding differences between the well-established HDA and LDA ices. This is plausible evidence that the HDL and LDL phases are the thermodynamic extensions of the corresponding amorphous solid water HDA and LDA ices.

  4. Effect of fatty acyl chain length and structure on the lamellar gel to liquid-crystalline and lamellar to reversed hexagonal phase transitions of aqueous phosphatidylethanolamine dispersions

    SciTech Connect

    Lewis, R.N.A.H.; Mannock, D.A.; McElhaney, R.N.; Turner, D.C.; Gruner, S.M. (Univ. of Alberta, Edmonton (Canada))

    1989-01-24

    The lamellar gel/liquid-crystalline and the lamellar liquid-crystalline/reversed hexagonal phase transitions of aqueous dispersions of a number of synthetic phosphatidylethanolamines containing linear saturated, branched chain, and alicyclic fatty acyl chains of varying length were studied by differential scanning calorimetry, {sup 31}P nuclear magnetic resonance spectroscopy, and X-ray diffraction. For any given homologous series of phosphatidylethanolamines containing a single chemical class of fatty acids, the lamellar gel/liquid-crystalline phase transition temperature increases and the lamellar liquid-crystalline/reversed hexagonal phase transition temperature decreases with increases in hydrocarbon chain length. For a series of phosphatidylethanolamines of the same hydrocarbon chain length but with different chemical structures, both the lamellar gel/liquid-crystalline and the lamellar liquid-crystalline/reversed hexagonal phase transition temperatures vary markedly and in the same direction. These results suggest that for any given hydrocarbon chain length, there may be a critical thickness at which the liquid-crystalline phosphatidylethanolamine bilayer becomes unstable with respect to inverted nonbilayer phases such as the H{sub II} phase and that the temperature at which this critical thickness is reached is dependent upon that bilayers proximity to the hydrocarbon chain-melting phase transition temperature.

  5. The nuclear liquid-gas phase transition within Fermionic Molecular Dynamics

    E-print Network

    J. Schnack; H. Feldmeier

    1997-03-19

    The time evolution of excited nuclei, which are in equilibrium with the surrounding vapour, is investigated. It is shown that the finite nuclear systems undergo a first oder phase transition. The caloric curve is presented for excited Oxygen, Magnesium, Aluminum and Calcium and the critical temperature is estimated for Oxygen.

  6. Fluctuations and Criticality of a Granular Solid-Liquid-Like Phase Transition

    NASA Astrophysics Data System (ADS)

    Castillo, Gustavo; Mujica, Nicolás; Soto, Rodrigo

    2012-08-01

    We present an experimental study of density and order fluctuations in the vicinity of the solid-liquid-like transition that occurs in a vibrated quasi-two-dimensional granular system. The two-dimensional projected static and dynamic correlation functions are studied. We show that density fluctuations, characterized through the structure factor, increase in size and intensity as the transition is approached, but they do not change significantly at the transition itself. The dense, metastable clusters, which present square symmetry, also increase their local order in the vicinity of the transition. This is characterized through the bond-orientational order parameter Q4, which in Fourier space shows an Ornstein-Zernike-like behavior. Depending on the filling density and vertical height, the transition can be of first- or second-order type. In the latter case, the associated correlation length ?4, the relaxation time ?4, the zero k limit of Q4 fluctuations (static susceptibility), the pair correlation function of Q4, and the amplitude of the order parameter obey critical power laws, with saturations due to finite size effects. Their respective critical exponents are ??=1, ??=2, ?=1, ?=0.67, and ?=1/2, whereas the dynamical critical exponent z=??/??=2. These results are consistent with model C of dynamical critical phenomena, valid for a nonconserved critical order parameter (bond-orientation order) coupled to a conserved field (density).

  7. Thermally induced structural changes of acetaminophen in phase transition between the solid and liquid states monitored by combination analysis of FT-IR\\/DSC microscopic system

    Microsoft Academic Search

    S.-Y Lin; S.-L Wang; Y.-D Cheng

    2000-01-01

    The molecular structure of acetaminophen in solid\\/liquid phase transition states was simply investigated by Fourier transform infrared (FT-IR) microspectroscopy equipped with differential scanning calorimetry (DSC). The result indicated that the intermolecular hydrogen bonds in the solid-state acetaminophen molecules were dramatically broken from 165°C, and loosened its molecular structure and packing to induce the phase transition between solid and liquid states.

  8. Liquid-gas and superconducting phase transitions of nuclear matter calculated with real time Green's function methods and Skyrme interactions

    SciTech Connect

    Su, R.K.; Yang, S.D.; Kuo, T.T.S.

    1987-04-01

    Real-time finite temperature Green's function methods with pair cutoff approximations are applied to the calculation of the equation of state of symmetric nuclear matter. The liquid-gas and the superconducting second-order phase transitions of nuclear matter are studied using, respectively, the normal and abnormal pair cutoff approximations. Several versions of the Skyrme effective interactions are employed. Significant differences are found between the pressure-density isotherms at finite temperature given by different Skyrme interactions, although they give quite similar ground state nuclear matter properties. The critical temperatures k/sub B/T/sub c//sup (1)/ for the liquid-gas phase transition given by various Skyrme interactions range from approx.15 to approx.20 MeV. A strong dependence of k/sub B/T/sub c//sup (1)/ on the combination 3t/sub 1/+5t/sub 2/, t/sub 1/ and t/sub 2/ being two parameters of the Skyrme interaction, is observed. For nuclear matter at normal density, nonvanishing energy gap is obtained only for the Skyrme interactions SkI and SkVI. The critical temperatures for the superconducting second-order phase transitions for these two cases are, respectively, 0.5 and 0.345 MeV. Dependence of the energy gap on the nuclear matter density is discussed.

  9. Molecular Dynamics Simulation of Argon in Solid-Liquid Phase Transition Region

    NASA Astrophysics Data System (ADS)

    Özgen, Soner; Kuzucu, Veysel; Adigüzel, Osman

    1997-10-01

    The microstructure of 256 argon atoms located on ideal fcc lattice sites on which periodic boundary conditions have been applied at the vicinity of transition temperature has been investigated. The forces among atoms have been derived from Lennard-Jones potential energy function and the equations of motion of the system have been solved by using the Verlet algorithm. The variations in microstructure have been investigated by means of radial distribution function and real-space atomic trajectories. It has been found from the results of simulation at zero pressure that solid-liquid transition temperature is 86K, the change of enthalpy is 1202 J/mol and relative volume change is 0.14.

  10. Liquid-solid and solid-solid phase transition of monolayer water: high-density rhombic monolayer ice.

    PubMed

    Kaneko, Toshihiro; Bai, Jaeil; Yasuoka, Kenji; Mitsutake, Ayori; Zeng, Xiao Cheng

    2014-05-14

    Liquid-solid and solid-solid phase transitions of a monolayer water confined between two parallel hydrophobic surfaces are studied by molecular dynamics simulations. The solid phase considered is the high-density rhombic monolayer ice. Based on the computed free energy surface, it is found that at a certain width of the slit nanopore, the monolayer water exhibits not only a high freezing point but also a low energy barrier to crystallization. Moreover, through analyzing the oxygen-hydrogen-oxygen angle distribution and oxygen-hydrogen radial distribution, the high-density monolayer ice is classified as either a flat ice or a puckered ice. The transition between a flat ice and a puckered ice reflects a trade-off between the water-wall interactions and the electrostatic interactions among water molecules. PMID:24832288

  11. Liquid-solid and solid-solid phase transition of monolayer water: High-density rhombic monolayer ice

    NASA Astrophysics Data System (ADS)

    Kaneko, Toshihiro; Bai, Jaeil; Yasuoka, Kenji; Mitsutake, Ayori; Zeng, Xiao Cheng

    2014-05-01

    Liquid-solid and solid-solid phase transitions of a monolayer water confined between two parallel hydrophobic surfaces are studied by molecular dynamics simulations. The solid phase considered is the high-density rhombic monolayer ice. Based on the computed free energy surface, it is found that at a certain width of the slit nanopore, the monolayer water exhibits not only a high freezing point but also a low energy barrier to crystallization. Moreover, through analyzing the oxygen-hydrogen-oxygen angle distribution and oxygen-hydrogen radial distribution, the high-density monolayer ice is classified as either a flat ice or a puckered ice. The transition between a flat ice and a puckered ice reflects a trade-off between the water-wall interactions and the electrostatic interactions among water molecules.

  12. Morphogenesis of defects and tactoids during isotropic-nematic phase transition in self-assembled lyotropic chromonic liquid crystals.

    PubMed

    Kim, Young-Ki; Shiyanovskii, Sergij V; Lavrentovich, Oleg D

    2013-10-01

    We explore the structure of nuclei and topological defects in the first-order phase transition between the nematic (N) and isotropic (I) phases in lyotropic chromonic liquid crystals (LCLCs). The LCLCs are formed by self-assembled molecular aggregates of various lengths and show a broad biphasic region. The defects emerge as a result of two mechanisms: (1) surface-anisotropy that endows each N nucleus ('tactoid') with topological defects thanks to preferential (tangential) orientation of the director at the closed I-N interface, and (2) Kibble mechanism with defects forming when differently oriented N tactoids merge with each other. Different scenarios of phase transition involve positive (N-in-I) and negative (I-in-N) tactoids with nontrivial topology of the director field and also multiply connected tactoid-in-tactoid configurations. The closed I-N interface limiting a tactoid shows a certain number of cusps; the lips of the interface on the opposite sides of the cusp make an angle different from ?. The N side of each cusp contains a point defect-boojum. The number of cusps shows how many times the director becomes perpendicular to the I-N interface when one circumnavigates the closed boundary of the tactoid. We derive conservation laws that connect the number of cusps c to the topological strength m of defects in the N part of the simply connected and multiply connected tactoids. We demonstrate how the elastic anisotropy of the N phase results in non-circular shape of the disclination cores. A generalized Wulff construction is used to derive the shape of I and N tactoids as a function of I-N interfacial tension anisotropy in the approximation of frozen director field of various topological charges m. The complex shapes and structures of tactoids and topological defects demonstrate an important role of surface anisotropy in morphogenesis of phase transitions in liquid crystals. PMID:24025849

  13. Structural Formation Process of Microphase Separated Films with Liquid Crystalline Phase Transition

    NASA Astrophysics Data System (ADS)

    Komura, Motonori; Iyoda, Tomokazu

    2008-03-01

    Ordered nanostructures arising from the microphase separation of block copolymers have driven one to fabricate nanofunctional materials as fundamental technology of the coming electronic and photonic materials. Thin films of a series of newly designed amphiphilic block copolymer consisting of hydrophilic polyethylene oxide (PEO) and hydrophobic polymethacrylate with azobenzene-mesogen in side-chain (PMA(Az)) show highly ordered microphase separation with PEO cylinders perpendicularly oriented to the film surface. In the present report, we investigated a structural formation process of the microphase separated films by temperature controlled atomic force microscopy (AFM) and grazing incidence small angle X-ray scattering (GISAXS). These measurements revealed that homeotropic alignments of Az liquid crystalline layers predominated the cylinder orientation, which corresponded to a <110> direction of body centered cubic structure under annealing condition, in disagreement with cylinder orientation of order-order transition of traditional block copolymers.

  14. Models for the phase transition between a Fermi liquid and fractional Chern insulator

    NASA Astrophysics Data System (ADS)

    Moore, Joel; Zaletel, Michael; Parameswaran, Siddharth

    2014-03-01

    A partially filled band with nonzero Chern density can support fractional quantum Hall states (``fractional Chern insulators'') as a consequence of repulsive interactions between electrons. In the absence of this repulsion, the ground state is generically a simple band metal with an anomalous Hall effect. There are several possible scenarios for a second-order transition between metallic and quantum Hall states, which can be approached as a composite-fermion band crossing, a coupling between Luttinger liquids, or via a parton construction. We discuss the extent to which these scenarios lead to different predictions and test those predictions by density-matrix renormalization group calculations. The authors acknowledge support from NSF DMR-1206515 (J.E.M. and M.Z.) and a Simons Foundation postdoctoral fellowship (S.P.).

  15. Nanosecond Ultrasonics to Study Phase Transitions in Solid and Liquid Systems at High Pressure and Temperature

    SciTech Connect

    Bonner, B P; Berge, P A; Carlson, S C; Farber, D L; Akella, J

    2007-03-21

    This report describes the development of a high-frequency ultrasonic measurement capability for application to the study of phase transitions at elevated pressure and temperature. We combined expertise in various aspects of static high-pressure technique with recent advances in wave propagation modeling, ultrasonic transducer development, electronic methods and broadband instrumentation to accomplish the goals of this project. The transduction and electronic systems have a demonstrated bandwidth of 400 MHz, allowing investigations of phenomena with characteristic times as short as 2.5 nS. A compact, pneumatically driven moissanite anvil cell was developed and constructed for this project. This device generates a high-pressure environment for mm dimension samples to pressures of 3 GPa. Ultrasonic measurements were conducted in the moissanite cell, an LLNL multi-anvil device and in a modified piston cylinder device. Measurements for water, and elemental tantalum, tin and cerium demonstrate the success of the methods. The {gamma}-{alpha} phase transition in cerium was clearly detected at {approx}0.7 GPa with 75 MHz longitudinal waves. These results have direct application to important problems in LLNL programs, as well as seismology and planetary science.

  16. Phase transition of a quaternary ammonium Gemini surfactant induced by minor structural changes of protic ionic liquids.

    PubMed

    Li, Qintang; Wang, Xudong; Yue, Xiu; Chen, Xiao

    2014-02-18

    The aggregation behaviors of a Gemini surfactant [C12H25(CH3)2N(+)(CH2)2N(+)(CH3)2C12H25]Br2(-) (12-2-12) in two protic ionic liquids (PILs), propylammonium nitrate (PAN) and butylammonium nitrate (BAN), were investigated by means of several experimental techniques including small and wide-angle X-ray scattering, the polarized optical microscopy and the rheological measurement. Compared to those in ethylammonium nitrate (EAN), the minor structural changes with only one or two methylene units (-CH2-) increase in cationic chain length of PIL, result in a dramatic phase transition of formed aggregates. The critical micellization concentration was increased in PAN, while no micelle formation was detected in BAN. A normal hexagonal phase was observed in the 12-2-12/PAN system, while the normal hexagonal, bicontinuous cubic, and lamellar phases were mapped in the 12-2-12/BAN system. Such aggregation behavior changes can be ascribed to the weaker solvophobic interactions of 12-2-12 in PAN and BAN. The unique molecular structure of 12-2-12 is also an important factor to highlight such a dramatic phase transition due to the PIL structure change. PMID:24455981

  17. Structural transitions in liquid cesium

    NASA Astrophysics Data System (ADS)

    Belashchenko, D. K.

    2014-09-01

    Two series of models of liquid cesium at temperatures of 493 and 623 K and pressures lower than 18 GPa are constructed by means of molecular dynamics using the potential of the embedded atom model. The thermodynamic properties of the models, pair correlation functions, pair radial distribution functions, structure factors, coordination numbers, and distributions of the Voronoi polyhedra and Delaunay simplexes are analyzed. No indications of structural transitions in liquid cesium of the first-order phase transition type are observed near a pressure of 3.9 GPa. Divergences from the results of some X-ray diffraction studies could be due to incorrect determination of the coordination numbers via the standard method because of the strong asymmetry of the first peaks of the pair radial distribution functions.

  18. Nanoscale Thermotropic Phase Transitions Enhance Photothermal Microscopy Signals

    E-print Network

    Boyer, Edmond

    1 Nanoscale Thermotropic Phase Transitions Enhance Photothermal Microscopy Signals A. Nicholas G phase transition, we demonstrate a 40-fold signal-to-noise ratio enhancement for gold nanoparticles microscopy, nanoparticles, thermotropic phase transition, liquid crystals, single molecule detection. #12

  19. Hidden non-Fermi liquid behavior caused by magnetic phase transition in Ni-doped Ba-122 pnictides

    PubMed Central

    Lee, Seokbae; Choi, Ki-Young; Jung, Eilho; Rho, Seulki; Shin, Soohyeon; Park, Tuson; Hwang, Jungseek

    2015-01-01

    We studied two BaFe2?xNixAs2 (Ni-doped Ba-122) single crystals at two different doping levels (underdoped and optimally doped) using an optical spectroscopic technique. The underdoped sample shows a magnetic phase transition around 80?K. We analyze the data with a Drude-Lorentz model with two Drude components (D1 and D2). It is known that the narrow D1 component originates from electron carriers in the electron-pockets and the broad D2 mode is from hole carriers in the hole-pockets. While the plasma frequencies of both Drude components and the static scattering rate of the broad D2 component show negligible temperature dependencies, the static scattering rate of the D1 mode shows strong temperature dependence for the both samples. We observed a hidden quasi-linear temperature dependence in the scattering rate of the D1 mode above and below the magnetic transition temperature while in the optimally doped sample the scattering rate shows a more quadratic temperature dependence. The hidden non-Fermi liquid behavior in the underdoped sample seems to be related to the magnetic phase of the material. PMID:26184412

  20. A Novel Liquid-Liquid Transition in Undercooled Ti-Zr-Ni Liquids

    NASA Technical Reports Server (NTRS)

    Lee, G. W.; Gangopadhyay, A. K.; Kelton, K. F.; Bradshaw, R. C.; Hyers, R. W.; Rathz, T. J.; Rogers, J. R.

    2004-01-01

    If crystallization can be avoided, liquids enter a metastable (undercooled) state below their equilibrium liquidus temperatures, T(sub l), finally 'freezing' into a glass below a characteristic temperature called the glass transition temperature, T(sub g). In rare cases, the undercooled liquid may undergo a liquid-liquid phase transition (liquid polymorphism) before entering the glassy state. This has been suggested from experimental studies of H2O and Si. Such phase transitions have been predicted in some stable liquids, ie. above T(sub l) at atmospheric pressure, for SiO2 and BeF2, but these have not been verified experimentally. They have been observed in liquids of P, Si and C, but only under high pressure. In this letter we present the first experimental evidence for a phase transition in a low viscosity metallic liquid that is driven by an approach to a constant entropy configuration state and correlated with a growing icosahedral order in the liquid. A maximum in the specific heat at constant pressure, similar to what is normally observed near T(sub g), is reported for undercooled liquids of quasicrystal-forming Ti-Zr-Ni alloys. A two-state excitation model that includes cooperativity by incorporating a temperature-dependent excitation energy, fits the specific heat data well, signaling a phase transition. An inflection in the liquid density with decreasing temperature instead of a discontinuity indicates that this is not a typical first order phase transition; it could be a weakly first order or higher order transition. While showing many similarities to a glass transition, this liquid-liquid phase transition occurs in a mobile liquid, making it novel.

  1. Effect of particle geometry on phase transitions in two-dimensional liquid crystals.

    PubMed

    Martínez-Ratón, Yuri; Velasco, Enrique; Mederos, Luis

    2005-02-01

    Using a version of density-functional theory which combines Onsager approximation and fundamental-measure theory for spatially nonuniform phases, we have studied the phase diagram of freely rotating hard rectangles and hard discorectangles. We find profound differences in the phase behavior of these models, which can be attributed to their different packing properties. Interestingly, bimodal orientational distribution functions are found in the nematic phase of hard rectangles, which cause a certain degree of biaxial order, albeit metastable with respect to spatially ordered phases. This feature is absent in discorectangles, which always show unimodal behavior. This result may be relevant in the light of recent experimental results which have confirmed the existence of biaxial phases. We expect that some perturbation of the particle shapes (either a certain degree of polydispersity or even bimodal dispersity in the aspect ratios) may actually destabilize spatially ordered phases thereby stabilizing the biaxial phase. PMID:15740404

  2. Effect of particle geometry on phase transitions in two-dimensional liquid crystals

    NASA Astrophysics Data System (ADS)

    Martínez-Ratón, Yuri; Velasco, Enrique; Mederos, Luis

    2005-02-01

    Using a version of density-functional theory which combines Onsager approximation and fundamental-measure theory for spatially nonuniform phases, we have studied the phase diagram of freely rotating hard rectangles and hard discorectangles. We find profound differences in the phase behavior of these models, which can be attributed to their different packing properties. Interestingly, bimodal orientational distribution functions are found in the nematic phase of hard rectangles, which cause a certain degree of biaxial order, albeit metastable with respect to spatially ordered phases. This feature is absent in discorectangles, which always show unimodal behavior. This result may be relevant in the light of recent experimental results which have confirmed the existence of biaxial phases. We expect that some perturbation of the particle shapes (either a certain degree of polydispersity or even bimodal dispersity in the aspect ratios) may actually destabilize spatially ordered phases thereby stabilizing the biaxial phase.

  3. Soft perforation of planar bilayer lipid membranes of dipalmitoylphosphatidylcholine at the temperature of the phase transition from the liquid crystalline to the gel state

    Microsoft Academic Search

    Valerij F. Antonov; Andrej A. Anosov; Vladimir P. Norik; Elena Yu. Smirnova

    2005-01-01

    In contrast to the widely used method of electroporation, the method of soft perforation of lipid bilayers is proposed. It is based on the structural rearrangement of the lipid bilayer formed from disaturated phospholipids at the temperature of the phase transition from the liquid crystalline state to the gel state. This allows us to obtain a lipid pore population without

  4. DNA-induced 2D-to-1D Phase Transition of Nanoparticle Assemblies at Liquid-Vapor Interface

    NASA Astrophysics Data System (ADS)

    Srivastava, Sunita; Nykypanchuk, Dmytro; Fukuto, Masafumi; Gang, Oleg

    2012-02-01

    We have investigated the structure formation and development for two-dimensional assembly of DNA functionalized nanoparticles at liquid-vapor interface. The adsorption of negatively charged DNA-coated particle to the interface was triggered by a positively charged lipid layer. A normal and in-plane structure of the nanoparticle monolayer were probed using in-situ surface scattering methods, x-ray reflectivity and grazing incidence small angle x-ray scattering. We observed the formation of the hexagonally closed packed (HCP) 2D lattice of nanoparticles due to a combination of electrostatic surface-to-particle attraction and interparticle repulsion. Upon an onset of DNA hybridization between particles the phase transition from HCP order to 1D crystalline structure was observed. The control on the interparticle spacing and monolayer confinement were also examined by changing a salt concentration. Our studies demonstrate novel mechanism for transition from ordered 2D to ordered 1D structure due to the domination of DNA-induced attraction over an electrostatic repulsion and open a route for nano-structure manipulations at the interfaces.

  5. Journal of Statistical Physics, Vol. 94, Nos. 56, 1999 Liquid Vapor Phase Transitions for Systems with

    E-print Network

    Lebowitz, Joel

    with low density expansions, to accurately describe the observed behavior of gases. Furthermore agreement with those of liquids in the ranges of temperatures and pressures where boiling and condensation to Ising spins). These systems can be thought of as idealizations of real fluids in which however

  6. LiquidVapor Phase Transitions for Systems with Finite Range Interactions

    E-print Network

    by comparison of experiment with low density expansions, accurately describe the behavior of both gases and liquids in the ranges of temperatures and pressures where boiling and condensation takes place. In fact). These systems can be thought of as idealiza­ tions of real fluids in which however the natural continuous

  7. Molecular Order, Phase Transitions and Chain Mobility in Liquid Crystalline Copolyesters

    Microsoft Academic Search

    Stefan Buchner; Di Chen; Rainer Gehrke; Hans Gerhard Zachmann

    1988-01-01

    Poly (ethylene naphthalene-2,6-dicarboxylate) (PEN) and copolyesters of PEN and p-hydroxybenzoic acid (PHB) containing different amounts of PHB ranging from 10 to 90 mole-% were synthesized and studied by wide angle X-ray scattering employing synchrotron radiation, by DSC and microscopically. The copolyesters form liquid crystalline states if their content of PHB exceeds 30 %. In the materials containing up to 50

  8. Molecular Dynamics Simulation of Argon in Solid-Liquid Phase Transition Region

    Microsoft Academic Search

    Soner Özgen; Veysel Kuzucu; Osman Adigüzel

    1997-01-01

    The microstructure of 256 argon atoms located on ideal fcc lattice sites on which periodic boundary conditions have been applied at the vicinity of transition temperature has been investigated. The forces among atoms have been derived from Lennard-Jones potential energy function and the equations of motion of the system have been solved by using the Verlet algorithm. The variations in

  9. Smectic-A and smectic-C phases and phase transitions in 8? S5 liquid-crystal-aerosil gels

    E-print Network

    Garland, Carl W.

    High-resolution x-ray scattering studies of the nonpolar thermotropic liquid crystal 4-n-pentylphenylthiol-4?-n-octyloxybenzoate (8? S5) in aerosil gel nanonetworks reveal that the aerosil-induced disorder significantly ...

  10. A Liquid-Liquid Transition in an Undercooled Ti-Zr-Ni Liquid

    NASA Technical Reports Server (NTRS)

    Lee, G. W.; Gangopadhyay, A. K.; Kelton, K. F.; Hyers, R. W.; Rathz, T. J.; Rogers, J. R.

    2003-01-01

    If crystallization can be avoided, liquids enter a metastable (undercooled) state below their equilibrium liquidus temperatures, TI, finally freezing into a glass below a characteristic temperature called the glass transition temperature, T,. In rare cases, the undercooled liquid may undergo a liquid-liquid phase transition (liquid polymorphism) before entering the glassy state. This has been suggested from experimental studies of HzO and Si4. Such phase transitions have been predicted in some stable liquids, i.e. above TI at atmospheric pressure, for Si02 and BeF;, but these have not been verified experimentally. They have been observed in liquids of P7, Sis and C9, but only under high pressure. All of these transitions are driven by an anomalous density change, i.e. change in local structure, with temperature or pressure. In this letter we present the first experimental evidence for a phase transition in a low viscosity liquid that is not driven by an anomalous density change, but by an approach to a constant configuration state. A maximum in the specific heat at constant pressure, similar to what is normally observed near T,, is reported here for undercooled low viscosity liquids of quasicrystal- forming Ti-Zr-Ni alloys. that includes cooperativity, by incorporating a temperature dependent excitation energy fits the data well, signaling a phase transition.

  11. Confinement Effects on Photoalignment, Photochemical Phase Transition, and Thermochromic Behavior of Liquid Crystalline

    E-print Network

    Zhao, Yue

    , which is at the origin of the thermochromic property. The common cause of these confinement effects- tion with linearly polarized light. For amorphous poly- mers, if a photoinduced orientation is obtained groups in a LC phase.6,15,16 The second feature of LC azobenzene poly- mers is the photochemically

  12. Volume phase transitions of biaxial nematic elastomers.

    PubMed

    Matsuyama, Akihiko

    2012-01-01

    We present a mean-field theory to describe biaxial nematic phases of side-chain liquid crystalline elastomers. Novel biaxial nematic phases are theoretically predicted in a side-chain liquid crystalline polymer and gel, where side chains (mesogens) and rigid-backbone chains favor mutually perpendicular orientations. We calculate uniaxial and biaxial orientational order parameters and examine deformations of the gel and stable biaxial nematic phases of the liquid crystalline gel dissolved in isotropic solvents. We predict first-order uniaxial-biaxial nematic phase transitions of the gel and the volume of the gel is discontinuously changed at the phase transition temperature. PMID:22400583

  13. Iron-histidine resonance raman band of deoxyheme proteins: effects of anharmonic coupling and glass-liquid phase transition

    PubMed Central

    Bitler, A; Stavrov, SS

    1999-01-01

    Weak anharmonic coupling of two soft molecular vibrations is shown to cause pronounced temperature dependence of the corresponding resonance Raman bands. The developed theory is used to interpret the temperature dependence of the iron-histidine band of deoxyheme proteins and model compounds. It is shown that anharmonic coupling of the iron-histidine and heme doming vibrations must cause pronounced broadening of the band, its asymmetry, and shift of its maximum to the red upon heating. It also can lead to a structured shape of this band at room temperature. Proper consideration of the anharmonic coupling allows simulation of the temperature dependence of the iron-histidine band shape of horse heart myoglobin in the temperature interval of 10-300 K, using the minimum number of necessary parameters. Analysis of this temperature dependence clearly shows that the iron-histidine band of deoxyheme proteins is sensitive to the glass-liquid phase transition in the protein hydration shell, which takes place at 160-190 K. PMID:10545375

  14. Aggregation, percolation and phase transitions in nematic liquid crystal EBBA doped with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Goncharuk, A. I.; Lebovka, N. I.; Lisetski, L. N.; Minenko, S. S.

    2009-08-01

    Electrical conductivity, optical transmittance and microstructure of multiwalled carbon nanotubes (MWCNTs) dispersed in nematic liquid crystal 4-ethoxybenzylidene-4'-n-butylaniline (EBBA) were studied in the temperature range between 287 and 363 K. The concentration C of MWCNTs was varied within 0.01-1% wt. The percolation threshold with a noticeable increase in electrical conductivity (by many orders of magnitude) was observed in the vicinity of C ? 0.1% wt. The heating-cooling hysteretic behaviour of electrical conductivity and optical transmittance thermal pre-history effects were studied. These effects reflected strong agglomeration and rearrangement of nanotubes during the thermal incubation. The estimates show that transient behaviour during the thermal incubation can be caused by Brownian motion of MWCNTs. The solidification of MWCNT + EBBA composite in the nematic range extended by conditions of supercooling was also studied as a function of temperature using electrical conductivity measurements. The solidification lag-time dependence on supercooling temperature followed the classical heterogeneous nucleation law, with MWCNTs serving as centres of EBBA solidification.

  15. Compound nuclear decay and the liquid to vapor phase transition: a physical picture

    E-print Network

    L. G. Moretto; J. B. Elliott; L. Phair

    2005-07-08

    Analyses of multifragmentation in terms of the Fisher droplet model (FDM) and the associated construction of a nuclear phase diagram bring forth the problem of the actual existence of the nuclear vapor phase and the meaning of its associated pressure. We present here a physical picture of fragment production from excited nuclei that solves this problem and establishes the relationship between the FDM and the standard compound nucleus decay rate for rare particles emitted in first-chance decay. The compound thermal emission picture is formally equivalent to a FDM-like equilibrium description and avoids the problem of the vapor while also explaining the observation of Boltzmann-like distribution of emission times. In this picture a simple Fermi gas thermometric relation is naturally justified and verified in the fragment yields and time scales. Low energy compound nucleus fragment yields scale according to the FDM and lead to an estimate of the infinite symmetric nuclear matter critical temperature between 18 and 27 MeV depending on the choice of the surface energy coefficient of nuclear matter.

  16. Liquid-liquid-solid transition in viscoelastic liquids

    PubMed Central

    Zubelewicz, Aleksander

    2013-01-01

    Liquid-liquid-solid transitions (LLST) are known to occur in confined liquids, exist in supercooled liquids and emerge in liquids driven from equilibrium. Molecular dynamics (MD) simulations claim many successes in forecasting the phenomena. The transitions are also studied in the framework of thermodynamics based methods and minimalistic models. In here, the proposed approach is derived in the framework of continuum and includes spatial and temporal dynamic heterogeneities; the approach is meant to capture the material behavior at small scales. We conjecture that the liquid-like and solid-like behaviors are dissimilar enough for the two to be governed by different constitutive relations. In this way, we gain additional degree of freedom, which is found essential when predicting the transitional phenomena. As a result, we derive the LLST criteria for liquids in equilibrium, during steady flow and at transient conditions. Lastly, we forecast short-lived LLSTs in human blood during cardiac cycle. PMID:23429528

  17. Wetting and layering transitions in liquid crystals

    NASA Astrophysics Data System (ADS)

    Somoza, A. M.; Mederos, L.; Sullivan, D. E.

    1995-11-01

    Interfacial structure in the isotropic phase of a liquid-crystalline material near a wall is studied by a mean-field density-functional theory. With increasing strength of the wall anchoring potential, the theory predicts a first-order transition from incomplete to complete wetting by the smectic-A phase at bulk isotropic-smectic coexistence, with an associated prewetting transition occurring away from bulk coexistence. The incomplete wetting case is accompanied by a small number (between 0 and and 2) of discrete layer transitions, while an infinite number of such transitions occurs at complete wetting. An analysis of the underlying physical mechanisns for layer transitions reveals that these transitions tend to disappear as the system is moved both sufficiently close to and sufficiently far from the bulk isotropic-nematic-smectic-A triple point by varying the model coupling parameters. These results reconcile findings from previous theories and experiments.

  18. Liquid-Liquid Extraction Using the Composition-Induced Phase Separation Process

    E-print Network

    Vladimirova, Natalia

    Liquid-Liquid Extraction Using the Composition-Induced Phase Separation Process Rajan Gupta York 10031 This paper describes a new separation process of liquid-liquid extraction. It consists is similar to the phase transition extraction, which was described in a previous paper, where the liquid

  19. Order-parameter-aided temperature-accelerated sampling for the exploration of crystal polymorphism and solid-liquid phase transitions

    PubMed Central

    Yu, Tang-Qing; Chen, Pei-Yang; Chen, Ming; Samanta, Amit; Vanden-Eijnden, Eric; Tuckerman, Mark

    2014-01-01

    The problem of predicting polymorphism in atomic and molecular crystals constitutes a significant challenge both experimentally and theoretically. From the theoretical viewpoint, polymorphism prediction falls into the general class of problems characterized by an underlying rough energy landscape, and consequently, free energy based enhanced sampling approaches can be brought to bear on the problem. In this paper, we build on a scheme previously introduced by two of the authors in which the lengths and angles of the supercell are targeted for enhanced sampling via temperature accelerated adiabatic free energy dynamics [T. Q. Yu and M. E. Tuckerman, Phys. Rev. Lett. 107, 015701 (2011)]. Here, that framework is expanded to include general order parameters that distinguish different crystalline arrangements as target collective variables for enhanced sampling. The resulting free energy surface, being of quite high dimension, is nontrivial to reconstruct, and we discuss one particular strategy for performing the free energy analysis. The method is applied to the study of polymorphism in xenon crystals at high pressure and temperature using the Steinhardt order parameters without and with the supercell included in the set of collective variables. The expected fcc and bcc structures are obtained, and when the supercell parameters are included as collective variables, we also find several new structures, including fcc states with hcp stacking faults. We also apply the new method to the solid-liquid phase transition in copper at 1300 K using the same Steinhardt order parameters. Our method is able to melt and refreeze the system repeatedly, and the free energy profile can be obtained with high efficiency. PMID:24907992

  20. Order-parameter-aided temperature-accelerated sampling for the exploration of crystal polymorphism and solid-liquid phase transitions

    SciTech Connect

    Yu, Tang-Qing, E-mail: tangqing.yu@nyu.edu; Vanden-Eijnden, Eric, E-mail: eve2@cims.nyu.edu [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States); Chen, Pei-Yang; Chen, Ming [Department of Chemistry, New York University, New York, New York 10003 (United States); Samanta, Amit [Program in Applied and Computational Mathematics, Princeton University, Princeton, New Jersey 08544, USA and Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Tuckerman, Mark, E-mail: mark.tuckerman@nyu.edu [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States); Department of Chemistry, New York University, New York, New York 10003 (United States); NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062 (China)

    2014-06-07

    The problem of predicting polymorphism in atomic and molecular crystals constitutes a significant challenge both experimentally and theoretically. From the theoretical viewpoint, polymorphism prediction falls into the general class of problems characterized by an underlying rough energy landscape, and consequently, free energy based enhanced sampling approaches can be brought to bear on the problem. In this paper, we build on a scheme previously introduced by two of the authors in which the lengths and angles of the supercell are targeted for enhanced sampling via temperature accelerated adiabatic free energy dynamics [T. Q. Yu and M. E. Tuckerman, Phys. Rev. Lett. 107, 015701 (2011)]. Here, that framework is expanded to include general order parameters that distinguish different crystalline arrangements as target collective variables for enhanced sampling. The resulting free energy surface, being of quite high dimension, is nontrivial to reconstruct, and we discuss one particular strategy for performing the free energy analysis. The method is applied to the study of polymorphism in xenon crystals at high pressure and temperature using the Steinhardt order parameters without and with the supercell included in the set of collective variables. The expected fcc and bcc structures are obtained, and when the supercell parameters are included as collective variables, we also find several new structures, including fcc states with hcp stacking faults. We also apply the new method to the solid-liquid phase transition in copper at 1300 K using the same Steinhardt order parameters. Our method is able to melt and refreeze the system repeatedly, and the free energy profile can be obtained with high efficiency.

  1. Comparison between Protein-Polyethylene Glycol (PEG) Interactions and the Effect of PEG on Protein-Protein Interactions Using the Liquid-Liquid Phase Transition

    E-print Network

    Annunziata, Onofrio

    Comparison between Protein-Polyethylene Glycol (PEG) Interactions and the Effect of PEG on Protein-ProteinVember 18, 2006 Phase transitions of protein aqueous solutions are important for protein crystallization and biomaterials science in general. One source of thermodynamic complexity in protein solutions and their phase

  2. CdSe nanoparticles dispersed in ferroelectric smectic liquid crystals: effects upon the smectic order and the smectic-A to chiral smectic-C phase transition.

    PubMed

    Thanassoulas, Angelos; Karatairi, Eva; Cordoyiannis, George; Kutnjak, Zdravko; Tzitzios, Vassilios; Lelidis, Ioannis; Nounesis, George

    2013-09-01

    Spherical CdSe nanoparticles, surface-treated with oleylamine and tri-octylphosphine, dispersed in ferroelectric liquid crystals, can efficiently target disclination lines, substantially altering the macroscopic properties of the host compound. Here we present an ac calorimetry and x-ray diffraction study demonstrating that for a large range of nanoparticle concentrations the smectic-A layer thickness increases monotonically. This provides evidence for enhanced accumulation of nanoparticles at the smectic layers. Our results for the Smectic-A (SmA) to chiral smectic-C (SmC) phase transition of the liquid crystal S-(+)4-(2'-methylbutyl)phenyl-4'-n-octylbiphenyl-4-carboxylate (CE8) reveal that the character of the transition is profoundly changed as a function of the nanoparticle concentration. Large transition temperature shifts are recorded. Moreover, the heat-capacity peaks exhibit a crossover trend to a step-like anomaly. This behavior may be linked to the weakening of the SmA and SmC order parameter coupling responsible for the observed near-tricritical, mean-field character of the transition in bulk CE8. At lower temperatures, the presence of nanoparticles disrupts the phase sequence involving the tilted hexatic phases most likely by obstructing the establishment of long-range bond-orientational order. PMID:24125282

  3. Phase Transitions in Materials

    NASA Astrophysics Data System (ADS)

    Fultz, Brent

    2014-08-01

    Part I. Basic Thermodynamics and Kinetics of Phase Transformations: 1. Introduction; 2. Essentials of T-c phase diagrams; 3. Diffusion; 4. Nucleation; 5. Effects of diffusion and nucleation on phase transformations; Part II. The Atomic Origins of Thermodynamics and Kinetics: 6. Energy; 7. Entropy; 8. Pressure; 9. Atom movements with the vacancy mechanism; Part III. Types of Phase Transformations: 10. Melting; 11. Transformations involving precipitates and interfaces; 12. Spinodal decomposition; 13. Phase field theory; 14. Method of concentration waves and chemical ordering; 15. Diffusionless transformations; 16. Thermodynamics of nanomaterials; 17. Magnetic and electronic phase transitions; 18. Phase transitions in quantum materials; Part IV. Advanced Topics; 19. Low temperature analysis of phase boundaries; 20. Cooperative behavior near a critical temperature; 21. Elastic energy of solid precipitates; 22. Statistical kinetics of ordering transformations; 23. Diffusion, dissipation, and inelastic scattering; 24. Vibrational thermodynamics of materials at high temperatures.

  4. Cross-dimensional phase transition from an array of 1D Luttinger liquids to a 3D Bose-Einstein condensate

    E-print Network

    Andreas Vogler; Ralf Labouvie; Giovanni Barontini; Sebastian Eggert; Vera Guarrera; Herwig Ott

    2014-10-07

    We study the thermodynamic properties of a 2D array of coupled one-dimensional Bose gases. The system is realized with ultracold bosonic atoms loaded in the potential tubes of a two-dimensional optical lattice. For negligible coupling strength, each tube is an independent weakly interacting 1D Bose gas featuring Tomonaga Luttinger liquid behavior. By decreasing the lattice depth, we increase the coupling strength between the 1D gases and allow for the phase transition into a 3D condensate. We extract the phase diagram for such a system and compare our results with theoretical predictions. Due to the high effective mass across the periodic potential and the increased 1D interaction strength, the phase transition is shifted to large positive values of the chemical potential. Our results are prototypical to a variety of low-dimensional systems, where the coupling between the subsystems is realized in a higher spatial dimension such as coupled spin chains in magnetic insulators.

  5. Insights into phase transition kinetics from colloid science

    Microsoft Academic Search

    Valerie J. Anderson; Henk N. W. Lekkerkerker

    2002-01-01

    Colloids display intriguing transitions between gas, liquid, solid and liquid crystalline phases. Such phase transitions are ubiquitous in nature and have been studied for decades. However, the predictions of phase diagrams are not always realized; systems often become undercooled, supersaturated, or trapped in gel-like states. In many cases the end products strongly depend on the starting position in the phase

  6. Nature of the liquid crystalline phase transitions in the cesium pentadecafluorooctanoate (CsPFO)-water system: the nematic-to-isotropic transition.

    PubMed

    Jolley, K W; Smith, M H; Boden, N; Henderson, J R

    2001-05-01

    Deuterium NMR spectroscopy of 2H2O has been used to monitor the magnetic-field-induced order on approaching a transition to a nematic phase in isotropic solutions of disklike micelles of cesium pentadecafluorooctanoate. Highly accurate data on the phase boundaries and spinodals have been obtained for solutions with volume fraction concentration straight phi between 0.078 and 0.201. The quantity TIN-T*, where T* is the spinodal limit of the isotropic phase and TIN is the temperature at which the nematic phase first appears on cooling, decreases linearly with decreasing concentration, extrapolating to zero only at zero concentration. Thus, there is no evidence to support the presence of a Landau point along the transition line as has previously been conjectured. The values for (TIN-T*)/TIN are in the range 10(-5)-10(-4), up to two orders of magnitude smaller than corresponding values reported for calamitic thermotropic nematics. The transition gap (phiNI-phiIN)/phiIN approximately 0.33% for phi<0.20 is also very small, although finite as required for a first-order phase transition. These data, when combined with previously measured properties, present an intriguing picture of the isotropic-to-nematic phase transition in a paradigmatic system of self-assembled diskotic particles. However, it is not completely clear, within the context of current theoretical understanding, whether the behavior of this system is explicable by hard-particle models, or if the self-assembly plays a crucial role in weakening the phase transition. PMID:11414919

  7. Metastable liquid-liquid transition in a molecular model of water.

    PubMed

    Palmer, Jeremy C; Martelli, Fausto; Liu, Yang; Car, Roberto; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2014-06-19

    Liquid water's isothermal compressibility and isobaric heat capacity, and the magnitude of its thermal expansion coefficient, increase sharply on cooling below the equilibrium freezing point. Many experimental, theoretical and computational studies have sought to understand the molecular origin and implications of this anomalous behaviour. Of the different theoretical scenarios put forward, one posits the existence of a first-order phase transition that involves two forms of liquid water and terminates at a critical point located at deeply supercooled conditions. Some experimental evidence is consistent with this hypothesis, but no definitive proof of a liquid-liquid transition in water has been obtained to date: rapid ice crystallization has so far prevented decisive measurements on deeply supercooled water, although this challenge has been overcome recently. Computer simulations are therefore crucial for exploring water's structure and behaviour in this regime, and have shown that some water models exhibit liquid-liquid transitions and others do not. However, recent work has argued that the liquid-liquid transition has been mistakenly interpreted, and is in fact a liquid-crystal transition in all atomistic models of water. Here we show, by studying the liquid-liquid transition in the ST2 model of water with the use of six advanced sampling methods to compute the free-energy surface, that two metastable liquid phases and a stable crystal phase exist at the same deeply supercooled thermodynamic condition, and that the transition between the two liquids satisfies the thermodynamic criteria of a first-order transition. We follow the rearrangement of water's coordination shell and topological ring structure along a thermodynamically reversible path from the low-density liquid to cubic ice. We also show that the system fluctuates freely between the two liquid phases rather than crystallizing. These findings provide unambiguous evidence for a liquid-liquid transition in the ST2 model of water, and point to the separation of time scales between crystallization and relaxation as being crucial for enabling it. PMID:24943954

  8. Metastable liquid-liquid transition in a molecular model of water

    NASA Astrophysics Data System (ADS)

    Palmer, Jeremy C.; Martelli, Fausto; Liu, Yang; Car, Roberto; Panagiotopoulos, Athanassios Z.; Debenedetti, Pablo G.

    2014-06-01

    Liquid water's isothermal compressibility and isobaric heat capacity, and the magnitude of its thermal expansion coefficient, increase sharply on cooling below the equilibrium freezing point. Many experimental, theoretical and computational studies have sought to understand the molecular origin and implications of this anomalous behaviour. Of the different theoretical scenarios put forward, one posits the existence of a first-order phase transition that involves two forms of liquid water and terminates at a critical point located at deeply supercooled conditions. Some experimental evidence is consistent with this hypothesis, but no definitive proof of a liquid-liquid transition in water has been obtained to date: rapid ice crystallization has so far prevented decisive measurements on deeply supercooled water, although this challenge has been overcome recently. Computer simulations are therefore crucial for exploring water's structure and behaviour in this regime, and have shown that some water models exhibit liquid-liquid transitions and others do not. However, recent work has argued that the liquid-liquid transition has been mistakenly interpreted, and is in fact a liquid-crystal transition in all atomistic models of water. Here we show, by studying the liquid-liquid transition in the ST2 model of water with the use of six advanced sampling methods to compute the free-energy surface, that two metastable liquid phases and a stable crystal phase exist at the same deeply supercooled thermodynamic condition, and that the transition between the two liquids satisfies the thermodynamic criteria of a first-order transition. We follow the rearrangement of water's coordination shell and topological ring structure along a thermodynamically reversible path from the low-density liquid to cubic ice. We also show that the system fluctuates freely between the two liquid phases rather than crystallizing. These findings provide unambiguous evidence for a liquid-liquid transition in the ST2 model of water, and point to the separation of time scales between crystallization and relaxation as being crucial for enabling it.

  9. Phase transition and lattice distortion in the proposed spin-liquid system {kappa}-(BEDT-TTF){sub 2}Cu{sub 2}(CN){sub 3}.

    SciTech Connect

    Lang, M.; Manna, R. S.; de Souza, M.; Bruhl, A.; Schlueter, J. A.; Materials Science Division; Goethe-Univ.

    2010-01-01

    We report measurements of the uniaxial coefficients of thermal expansion {alpha}{sub i} and the specific heat C on the spin-liquid candidate {kappa}-(BEDT-TTF){sub 2}Cu{sub 2}(CN){sub 3}. We observe anomalous and strongly anisotropic in-plane expansivities, implying (i) distinct T-induced b-c lattice distortions and (ii) an increase in the ratio of the hopping amplitudes t{prime}/t upon cooling into the low-temperature regime. Most importantly, the {alpha}{sub i} data reveal clear evidence for a second-order phase transition around 6 K, accompanied by distinct lattice effects. By using a Grueneisen-scaling Ansatz, we are able to extract the corresponding anomaly to the specific heat. Estimates of the entropy indicate that spin degrees of freedom alone cannot account for the phase transition anomaly, suggesting that charge degrees of freedom are involved.

  10. Nature of the liquid crystalline phase transitions in the cesium pentadecafluorooctanoate (CsPFO)-water system: The nematic-to-isotropic transition

    Microsoft Academic Search

    K. W. Jolley; M. H. Smith; N. Boden; J. R. Henderson

    2001-01-01

    Deuterium NMR spectroscopy of 2H2O has been used to monitor the magnetic-field-induced order on approaching a transition to a nematic phase in isotropic solutions of disklike micelles of cesium pentadecafluorooctanoate. Highly accurate data on the phase boundaries and spinodals have been obtained for solutions with volume fraction concentration phi between 0.078 and 0.201. The quantity TIN-T*, where T* is the

  11. Phase transitions, intermolecular interactions and electrical conductivity behavior in carbon multiwalled nanotubes/nematic liquid crystal composites

    NASA Astrophysics Data System (ADS)

    Lebovka, N.; Dadakova, T.; Lysetskiy, L.; Melezhyk, O.; Puchkovska, G.; Gavrilko, T.; Baran, J.; Drozd, M.

    2008-09-01

    The phase transitions, intermolecular interactions and electrical percolation behavior in the composites of multiwalled carbon nanotubes (MWNTs) and nematic LC ( p-ethoxybenzylidene- p'-butylaniline, EBBA) are experimentally investigated in this work. The concentration of nanotubes was between 0 and 1% (wt), and the temperature interval was 273-363 K. The experimental data of differential scanning calorimetry (DSC) and FTIR adsorption spectra evidence the presence of strong interactions inside MWNTs/EBBA nanocomposites. An increase of both isotropic-to-nematic (by 0.5-1 K) and nematic-to-crystalline (by 1.5-3 K) phase transition temperatures was observed for EBBA filled with MWNTs. The FTIR spectroscopic data evidence an enhancement of the strong binding interaction between MWNTs and EBBA with increase of the concentration of MWNTs. It was shown that intermolecular interactions affect noticeably the electrical conductivity of MWNTs/EBBA composites. The percolation transition from non-conductive to high conductive state, and the effect of positive temperature coefficient (PTC effect) were observed at MWNT concentrations exceeding 0.05-0.1 wt.% Within the nematic phase temperature range, the electrical conductivity of the composites reveals a noticeable heating-cooling hysteresis and follows Arrhenius behavior. The activation energy decreases when MWNTs concentration increases, which supports the dominating role of the junction mechanism related to the thermal motion of nanotubes. The electric field dependence of the electrical conductivity was explained by the existence of the field-enhanced charge transport through hopping junctions in the LC gaps.

  12. Reversible suppression of second harmonic generation in dye-doped liquid crystal by light-induced thermal phase transition on sub-micrometer scale

    NASA Astrophysics Data System (ADS)

    Zhuo, Guan-Yu; Chen, Kuan-Chieh; Lai, Kai-Wen; Wang, Chao-Ran; Chao, Chih-Yu; Chu, Shi-Wei

    2015-02-01

    Optically controllable signals are fundamental to various applications from communication to super-resolution imaging. However, literature on non-fluorescent, nonlinear optical signals that can be reversibly turned on/off on a sub-micrometer scale is scant. In this work, we experimentally demonstrate a scheme for the reversible suppression of second harmonic generation (SHG) based on dye-doped nematic liquid crystal molecules. Under a pump (suppressing SHG) and probe (generating SHG) setup with a tightly focusing microscope and a time-gated detection, outstanding modulation depth (>80%) has been realized. Surprisingly, the mechanism of liquid crystal SHG switch on a sub-micrometer scale was found to be light-induced thermal phase transition as against optical Frederick's transition. Quantitative analysis of the optical nonlinearity ? ( 2 ) versus local heating shows an excellent agreement of SHG signal suppression as well as its dependence on the liquid crystal molecular order and phase change. Our work provides an innovative example of applying nonlinear optical properties of soft materials, and can be further optimized for all-optical modulation applications.

  13. NUCLEATION OF SUPERFLUID TRANSITIONS IN LIQUID HELIUM MIXTURES

    E-print Network

    Boyer, Edmond

    59 NUCLEATION OF SUPERFLUID TRANSITIONS IN LIQUID HELIUM MIXTURES J. P. ROMAGNAN and J. P. LAHEURTE très fortement vers 1,1 (K). Abstract. 2014 Superfluid transitions in liquid helium mixtures Physics Abstracts 7.4H0 - 7.700 1. Introduction. - The study of superfluid and phase separation

  14. Viscosity near phase transitions

    E-print Network

    Antonio Dobado; Felipe J. Llanes-Estrada; Juan M. Torres-Rincon

    2010-09-30

    Probably the most enticing observation in theoretical physics during the last decade was the discovery of the great amount of consequences obtained from the AdS/CFT conjecture put forward by Maldacena. In this work we review how this correspondence can be used to address hydrodynamic properties such as the viscosity of some strongly interacting systems. We also employ the Boltzmann equation for those systems closer to low-energy QCD, and argue that this kind of transport coefficients can be related to phase transitions, in particular the QGP/hadronic phase transition studied in heavy ion collisions.

  15. Fluctuations at phase transitions

    E-print Network

    Rivers, R J

    1994-01-01

    We use the closed time-path formalism to calculate fluctuations at phase transitions, both in and out of equilibrium. Specifically, we consider the creation of vortices by fluctuations, of relevance to the early universe and to ^{4}He superfluidity. (Invited talk to Nato Advanced Research Workshop on Electroweak Physics and the Early Universe, Sintra (Portugal), March 1994)

  16. String mediated phase transitions

    NASA Technical Reports Server (NTRS)

    Copeland, ED; Haws, D.; Rivers, R.; Holbraad, S.

    1988-01-01

    It is demonstrated from first principles how the existence of string-like structures can cause a system to undergo a phase transition. In particular, the role of topologically stable cosmic string in the restoration of spontaneously broken symmetries is emphasized. How the thermodynamic properties of strings alter when stiffness and nearest neighbor string-string interactions are included is discussed.

  17. Thermal and Structural Study on Liquid-Crystalline Phase Transitions in bis-Alkyl Trimethyl Ammonium Dichromates

    Microsoft Academic Search

    Nathalie Fossé; Jean Yves Mevellec; Luc Brohan

    2000-01-01

    A series of bis-alkyltrimethylammonium dichromates (CnH2n+1(CH3)3 N)2 Cr2O7· x H2O (where n = 8, 10, 12, 14, 16, 18, and 0?x?2) compounds (ATMACr) was synthesized from alkyltrimethylammonium bromide and K2Cr2O7. The phase transitions and mesogenicity of these substances were studied by X-ray diffraction, DSC measurements, and FT-IR observations. In the series of hydrated ATMACr compounds, the decreasing of the ?SSm-I

  18. Mathematical Modeling and Numerical Simulation of Liquid-Solid and Solid-Liquid Phase Change

    E-print Network

    Joy, Aaron

    2013-08-31

    This thesis presents numerical simulations of liquid-solid and solid-liquid phase change processes using mathematical models in Lagrangian and Eulerian descriptions. The mathematical models are derived by assuming a smooth interface (or transition...

  19. Bond orientational order in liquids: Towards a unified description of water-like anomalies, liquid-liquid transition, glass transition, and crystallization: Bond orientational order in liquids.

    PubMed

    Tanaka, Hajime

    2012-10-01

    There are at least three fundamental states of matter, depending upon temperature and pressure: gas, liquid, and solid (crystal). These states are separated by first-order phase transitions between them. In both gas and liquid phases a complete translational and rotational symmetry exist, whereas in a solid phase both symmetries are broken. In intermediate phases between liquid and solid, which include liquid crystal and plastic crystal phases, only one of the two symmetries is preserved. Among the fundamental states of matter, the liquid state is the most poorly understood. We argue that it is crucial for a better understanding of liquids to recognize that a liquid generally has the tendency to have a local structural order and its presence is intrinsic and universal to any liquid. Such structural ordering is a consequence of many-body correlations, more specifically, bond angle correlations, which we believe are crucial for the description of the liquid state. We show that this physical picture may naturally explain difficult unsolved problems associated with the liquid state, such as anomalies of water-type liquids (water, Si, Ge, ...), liquid-liquid transition, liquid-glass transition, crystallization and quasicrystal formation, in a unified manner. In other words, we need a new order parameter representing a low local free-energy configuration, which is a bond orientational order parameter in many cases, in addition to a density order parameter for the physical description of these phenomena. Here we review our two-order-parameter model of liquid and consider how transient local structural ordering is linked to all of the above-mentioned phenomena. The relationship between these phenomena is also discussed. PMID:23104614

  20. Fragile-to-fragile liquid transition at Tg and stable-glass phase nucleation rate maximum at the Kauzmann temperature TK

    NASA Astrophysics Data System (ADS)

    Tournier, Robert F.

    2014-12-01

    An undercooled liquid is unstable. The driving force of the glass transition at Tg is a change of the undercooled-liquid Gibbs free energy. The classical Gibbs free energy change for a crystal formation is completed including an enthalpy saving. The crystal growth critical nucleus is used as a probe to observe the Laplace pressure change ?p accompanying the enthalpy change -Vm×?p at Tg where Vm is the molar volume. A stable glass-liquid transition model predicts the specific heat jump of fragile liquids at T?Tg, the Kauzmann temperature TK where the liquid entropy excess with regard to crystal goes to zero, the equilibrium enthalpy between TK and Tg, the maximum nucleation rate at TK of superclusters containing magic atom numbers, and the equilibrium latent heats at Tg and TK. Strong-to-fragile and strong-to-strong liquid transitions at Tg are also described and all their thermodynamic parameters are determined from their specific heat jumps. The existence of fragile liquids quenched in the amorphous state, which do not undergo liquid-liquid transition during heating preceding their crystallization, is predicted. Long ageing times leading to the formation at TK of a stable glass composed of superclusters containing up to 147 atom, touching and interpenetrating, are evaluated from nucleation rates. A fragile-to-fragile liquid transition occurs at Tg without stable-glass formation while a strong glass is stable after transition.

  1. Fragile-to-fragile Liquid Transition at Tg and Stable-Glass Phase Nucleation Rate Maximum at the Kauzmann Temperature TK

    E-print Network

    Robert Felix Tournier

    2015-02-23

    An undercooled liquid is unstable. The driving force of the glass transition at Tg is a change of the undercooled-liquid Gibbs free energy. The classical Gibbs free energy change for a crystal formation is completed including an enthalpy saving. The crystal growth critical nucleus is used as a probe to observe the Laplace pressure change Dp accompanying the enthalpy change -Vm *Dp at Tg where Vm is the molar volume. A stable glass-liquid transition model predicts the specific heat jump of fragile liquids at temperatures smaller than Tg, the Kauzmann temperature TK where the liquid entropy excess with regard to crystal goes to zero, the equilibrium enthalpy between TK and Tg, the maximum nucleation rate at TK of superclusters containing magic atom numbers, and the equilibrium latent heats at Tg and TK. Strong-to-fragile and strong-to-strong liquid transitions at Tg are also described and all their thermodynamic parameters are determined from their specific heat jumps. The existence of fragile liquids quenched in the amorphous state, which do not undergo liquid-liquid transition during heating preceding their crystallization, is predicted. Long ageing times leading to the formation at TK of a stable glass composed of superclusters containing up to 147 atoms, touching and interpenetrating, are evaluated from nucleation rates. A fragile-to-fragile liquid transition occurs at Tg without stable-glass formation while a strong glass is stable after transition.

  2. Emergence and Phase Transitions

    NASA Astrophysics Data System (ADS)

    Sikkema, Arnold

    2006-05-01

    Phase transitions are well defined in physics through concepts such as spontaneous symmetry breaking, order parameter, entropy, and critical exponents. But emergence --- also exhibiting whole-part relations (such as top-down influence), unpredictability, and insensitivity to microscopic detail --- is a loosely-defined concept being used in many disciplines, particularly in psychology, biology, philosophy, as well as in physics[1,2]. I will review the concepts of emergence as used in the various fields and consider the extent to which the methods of phase transitions can clarify the usefulness of the concept of emergence both within the discipline of physics and beyond.1. Robert B. Laughlin, A Different Universe: Reinventing Physics from the Bottom Down (New York: Basic Books, 2005). 2. George F.R. Ellis, ``Physics and the Real World'', Physics Today, vol. 58, no. 7 (July 2005) pp. 49-54.

  3. Phase Transition Taylor Test

    NASA Astrophysics Data System (ADS)

    Zhang, Xinghua

    2005-07-01

    In this article, the Taylor impact test is applied to investigate the dynamic phase transformation behavior of NiTi alloy, which we call it the phase transition Taylor test (PTTT). The symmetry impact configuration is applied in the study at impact velocity range from 47m/s to 175m/s by using a light gas gun facility in this lab. The NiTi alloy is treated in the state of shape memory effect (SME). The shape of the recovered samples is substantially different from that of traditional elastic-plastic Taylor test. The recovered NiTi bar can be divided into three deformation regions from the impact surface: the main deformation region with homogeneous deformation, the gradient deformation region and the elastic region successively, which correspond to the martensitic phase, mixed phase and austenite, respectively. The different deformation regions demonstrate the interaction between the dynamic phase boundary and the rarefaction wave reflected from the free end of the bar. Simulation with the macroscopic phase boundary propagation theory[1]is in good agreement with the experimental measurement. [1] Dai X et al, International Journal of Impact Engineering, 30(4)(2004), 385.

  4. Evidence of liquid-liquid transition in glass-forming La50Al35Ni15 melt above liquidus temperature.

    PubMed

    Xu, Wei; Sandor, Magdalena T; Yu, Yao; Ke, Hai-Bo; Zhang, Hua-Ping; Li, Mao-Zhi; Wang, Wei-Hua; Liu, Lin; Wu, Yue

    2015-01-01

    Liquid-liquid transition, a phase transition of one liquid phase to another with the same composition, provides a key opportunity for investigating the relationship between liquid structures and dynamics. Here we report experimental evidences of a liquid-liquid transition in glass-forming La50Al35Ni15 melt above its liquidus temperature by (27)Al nuclear magnetic resonance including the temperature dependence of cage volume fluctuations and atomic diffusion. The observed dependence of the incubation time on the degree of undercooling is consistent with a first-order phase transition. Simulation results indicate that such transition is accompanied by the change of bond-orientational order without noticeable change in density. The temperature dependence of atomic diffusion revealed by simulations is also in agreement with experiments. These observations indicate the need of two-order parameters in describing phase transitions of liquids. PMID:26165855

  5. Integrated modeling of CO2 storage and leakage scenarios including transitions between super- and sub-critical conditions, and phase change between liquid and gaseous CO2

    SciTech Connect

    Pruess, K.

    2011-05-15

    Storage of CO{sub 2} in saline aquifers is intended to be at supercritical pressure and temperature conditions, but CO{sub 2} leaking from a geologic storage reservoir and migrating toward the land surface (through faults, fractures, or improperly abandoned wells) would reach subcritical conditions at depths shallower than 500-750 m. At these and shallower depths, subcritical CO{sub 2} can form two-phase mixtures of liquid and gaseous CO{sub 2}, with significant latent heat effects during boiling and condensation. Additional strongly non-isothermal effects can arise from decompression of gas-like subcritical CO{sub 2}, the so-called Joule-Thomson effect. Integrated modeling of CO{sub 2} storage and leakage requires the ability to model non-isothermal flows of brine and CO{sub 2} at conditions that range from supercritical to subcritical, including three-phase flow of aqueous phase, and both liquid and gaseous CO{sub 2}. In this paper, we describe and demonstrate comprehensive simulation capabilities that can cope with all possible phase conditions in brine-CO{sub 2} systems. Our model formulation includes: (1) an accurate description of thermophysical properties of aqueous and CO{sub 2}-rich phases as functions of temperature, pressure, salinity and CO{sub 2} content, including the mutual dissolution of CO{sub 2} and H{sub 2}O; (2) transitions between super- and subcritical conditions, including phase change between liquid and gaseous CO{sub 2}; (3) one-, two-, and three-phase flow of brine-CO{sub 2} mixtures, including heat flow; (4) non-isothermal effects associated with phase change, mutual dissolution of CO{sub 2} and water, and (de-) compression effects; and (5) the effects of dissolved NaCl, and the possibility of precipitating solid halite, with associated porosity and permeability change. Applications to specific leakage scenarios demonstrate that the peculiar thermophysical properties of CO{sub 2} provide a potential for positive as well as negative feedbacks on leakage rates, with a combination of self-enhancing and self-limiting effects. Lower viscosity and density of CO{sub 2} as compared to aqueous fluids provides a potential for self-enhancing effects during leakage, while strong cooling effects from liquid CO{sub 2} boiling into gas, and from expansion of gas rising towards the land surface, act to self-limit discharges. Strong interference between fluid phases under three-phase conditions (aqueous - liquid CO{sub 2} - gaseous CO{sub 2}) also tends to reduce CO{sub 2} fluxes. Feedback on different space and time scales can induce non-monotonic behavior of CO{sub 2} flow rates.

  6. Liquid to quasicrystal transition in bilayer water.

    PubMed

    Johnston, Jessica C; Kastelowitz, Noah; Molinero, Valeria

    2010-10-21

    The phase behavior of confined water is a topic of intense and current interest due to its relevance in biology, geology, and materials science. Nevertheless, little is known about the phases that water forms even when confined in the simplest geometries, such as water confined between parallel surfaces. Here we use molecular dynamics simulations to compute the phase diagram of two layers of water confined between parallel non hydrogen bonding walls. This study shows that the water bilayer forms a dodecagonal quasicrystal, as well as two previously unreported bilayer crystals, one tiled exclusively by pentagonal rings. Quasicrystals, structures with long-range order but without periodicity, have never before been reported for water. The dodecagonal quasicrystal is obtained from the bilayer liquid through a reversible first-order phase transition and has diffusivity intermediate between that of the bilayer liquid and ice phases. The water quasicrystal and the ice polymorphs based on pentagons are stabilized by compression of the bilayer and are not templated by the confining surfaces, which are smooth. This demonstrates that these novel phases are intrinsically favored in bilayer water and suggests that these structures could be relevant not only for confined water but also for the wetting and properties of water at interfaces. PMID:20969412

  7. Liquid-liquid transition in supercooled water suggested by microsecond simulations.

    PubMed

    Li, Yaping; Li, Jicun; Wang, Feng

    2013-07-23

    The putative liquid-liquid phase transition in supercooled water has been used to explain many anomalous behaviors of water. However, no direct experimental verification of such a phase transition has been accomplished, and theoretical studies from different simulations contradict each other. We investigated the putative liquid-liquid phase transition using the Water potential from Adaptive Force Matching for Ice and Liquid (WAIL). The simulation reveals a first-order phase transition in the supercooled regime with the critical point at ~207 K and 50 MPa. Normal water is high-density liquid (HDL). Low-density liquid (LDL) emerges at lower temperatures. The LDL phase has a density only slightly larger than that of the ice-Ih and shows more long-range order than HDL. However, the transformation from LDL to HDL is spontaneous across the first-order phase transition line, suggesting the LDL configuration is not poorly formed nanocrystalline ice. It has been demonstrated in the past that the WAIL potential provides reliable predictions of water properties such as melting temperature and temperature of maximum density. Compared with other simple water potentials, WAIL is not biased by fitting to experimental properties, and simulation with this potential reflects the prediction of a high-quality first-principle potential energy surface. PMID:23836647

  8. Quantum Nature of a Nuclear Phase Transition

    SciTech Connect

    Bonasera, A. [Cyclotron Institute, Texas A and M, College Station, Texas 77843 (United States); Laboratori Nazionali del Sud, INFN, via Santa Sofia, 62, 95123 Catania (Italy); Libera Universita Kore di Enna, 94100 Enna (Italy); Chen, Z.; Wada, R.; Hagel, K.; Natowitz, J.; Sahu, P.; Qin, L.; Materna, T. [Cyclotron Institute, Texas A and M, College Station, Texas 77843 (United States); Kowalski, S. [Institute of Physics, Silesia University, Katowice (Poland); Keutgen, Th. [Institut de Physique Nucleaire and FNRS, Universite Catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Nakagawa, T. [Riken, 2-1 Hirosawa, Wako-shi, Saitama, Japan 351-0198 (Japan)

    2008-09-19

    At finite temperatures and low densities, nuclei may undergo a phase change similar to a classical liquid-gas phase transition. Temperature is the control parameter while density and pressure are the conjugate variables. In the nucleus the difference between the proton and neutron concentrations acts as an additional order parameter, for which the symmetry potential is the conjugate variable. We present experimental results which reveal the N/Z dependence of the phase transition and discuss possible implications of these observations in terms of the Landau free energy description of critical phenomena.

  9. Anchoring transition in confined discotic columnar liquid crystal films

    NASA Astrophysics Data System (ADS)

    Brunet, Thomas; Thiebaut, Olivier; Charlet, Émilie; Bock, Harald; Kelber, Julien; Grelet, Éric

    2011-01-01

    We report the achievement of ultrathin films (down to 25 nm thick) of thermotropic columnar liquid crystals in homeotropic alignment (columns normal to the interface) confined between a glass slide and a thin metallic electrode (about 150 nm thick). The face-on orientation of the discotic compound is obtained by anchoring transition of a columnar liquid crystalline phase from a degenerate planar orientation to the homeotropic alignment without any phase transition to the isotropic liquid phase. The kinetic dependence on temperature of such anchoring transition is investigated revealing various diffusive growth regimes of the homeotropic domains. Finally, confining effects are also considered by varying the thickness of the columnar liquid crystal film to reach the typical value required in organic solar cells thus demonstrating the reliability of such alignment process in a photovoltaic context.

  10. Smectic layer transitions at the surface of an isotropic liquid

    NASA Astrophysics Data System (ADS)

    Somoza, A. M.; Mederos, L.; Sullivan, D. E.

    1994-06-01

    A density-functional theory of the interface between a liquid crystal and a wall predicts a first-order wetting transition by the smectic-A phase when the bulk liquid is isotropic. This is preceded by a prewetting transition away from bulk coexistence. The incomplete and complete wetting regimes are accompanied by a finite and an infinite number of layer transitions, respectively. The layering mechanism shows that the transitions can disappear both very near and far from the isotropic-nematic-smectic-A triple point. These results reconcile findings from previous theories and experiments.

  11. Thermal- and photo-induced phase-transition behaviors of a tapered dendritic liquid crystal with photochromic azobenzene mesogens and a bicyclic chiral center.

    PubMed

    Kim, Dae-Yoon; Lee, Sang-A; Choi, Yu-Jin; Hwang, Seok-Ho; Kuo, Shiao-Wei; Nah, Changwoon; Lee, Myong-Hoon; Jeong, Kwang-Un

    2014-05-01

    A ribbon-shaped chiral liquid crystalline (LC) dendrimer with photochromic azobenzene mesogens and an isosorbide chiral center (abbreviated as AZ3 DLC) was successfully synthesized and its major phase transitions were studied by using differential scanning calorimetry (DSC) and linear polarized optical microscopy (POM). Its ordered structures at different temperatures were further identified through structure-sensitive diffraction techniques. Based on the experimental results, it was found that the AZ3 DLC molecule exhibited the low-ordered chiral smectic (Sm*) LC phase with 6.31?nm periodicity at a high-temperature phase region. AZ3 DLC showed the reversible photoisomerization in both organic solvents and nematic (N) LC media. As a chiral-inducing agent, it exhibited a good solubility, a high helical-twisting power, and a large change in the helical-twisting power due to its photochemical isomerization in the commercially available N LC hosts. Therefore, we were able to reversibly "remote-control" the colors in the whole visible region by finely tuning the helical pitch of the spontaneously formed helical superstructures. PMID:24665056

  12. The putative liquid-liquid transition is a liquid-solid transition in atomistic models of water. II

    SciTech Connect

    Limmer, David T.; Chandler, David, E-mail: chandler@berkeley.edu [Department of Chemistry, University of California, Berkeley, California 94720 (United States)

    2013-06-07

    This paper extends our earlier studies of free energy functions of density and crystalline order parameters for models of supercooled water, which allows us to examine the possibility of two distinct metastable liquid phases [D. T. Limmer and D. Chandler, J. Chem. Phys.135, 134503 (2011) and preprint http://arxiv.org/abs/arXiv:1107.0337 (2011)]. Low-temperature reversible free energy surfaces of several different atomistic models are computed: mW water, TIP4P/2005 water, Stillinger-Weber silicon, and ST2 water, the last of these comparing three different treatments of long-ranged forces. In each case, we show that there is one stable or metastable liquid phase, and there is an ice-like crystal phase. The time scales for crystallization in these systems far exceed those of structural relaxation in the supercooled metastable liquid. We show how this wide separation in time scales produces an illusion of a low-temperature liquid-liquid transition. The phenomenon suggesting metastability of two distinct liquid phases is actually coarsening of the ordered ice-like phase, which we elucidate using both analytical theory and computer simulation. For the latter, we describe robust methods for computing reversible free energy surfaces, and we consider effects of electrostatic boundary conditions. We show that sensible alterations of models and boundary conditions produce no qualitative changes in low-temperature phase behaviors of these systems, only marginal changes in equations of state. On the other hand, we show that altering sampling time scales can produce large and qualitative non-equilibrium effects. Recent reports of evidence of a liquid-liquid critical point in computer simulations of supercooled water are considered in this light.

  13. Quantum phase transition in space

    SciTech Connect

    Damski, Bogdan [Los Alamos National Laboratory; Zurek, Wojciech H [Los Alamos National Laboratory

    2008-01-01

    A quantum phase transition between the symmetric (polar) phase and the phase with broken symmetry can be induced in a ferromagnetic spin-1 Bose-Einstein condensate in space (rather than in time). We consider such a phase transition and show that the transition region in the vicinity of the critical point exhibits scalings that reflect a compromise between the rate at which the transition is imposed (i.e., the gradient of the control parameter) and the scaling of the divergent healing length in the critical region. Our results suggest a method for the direct measurement of the scaling exponent {nu}.

  14. Liquid Phase Heating Systems 

    E-print Network

    Mordt, E. H.

    1979-01-01

    Temperature Water (HTW) central district heating systems are far superior to steam systems in large, spread out installations such as airports, universities and office complexes. Water, pressurized to keep it in the liquid state, is distributed at 400o...

  15. Liquid-liquid transition in ST2 water

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Palmer, Jeremy C.; Panagiotopoulos, Athanassios Z.; Debenedetti, Pablo G.

    2012-12-01

    We use the weighted histogram analysis method [S. Kumar, D. Bouzida, R. H. Swendsen, P. A. Kollman, and J. M. Rosenberg, J. Comput. Chem. 13, 1011 (1992), 10.1002/jcc.540130812] to calculate the free energy surface of the ST2 model of water as a function of density and bond-orientational order. We perform our calculations at deeply supercooled conditions (T = 228.6 K, P = 2.2 kbar; T = 235 K, P = 2.2 kbar) and focus our attention on the region of bond-orientational order that is relevant to disordered phases. We find a first-order transition between a low-density liquid (LDL, ? ? 0.9 g/cc) and a high-density liquid (HDL, ? ? 1.15 g/cc), confirming our earlier sampling of the free energy surface of this model as a function of density [Y. Liu, A. Z. Panagiotopoulos, and P. G. Debenedetti, J. Chem. Phys. 131, 104508 (2009), 10.1063/1.3229892]. We demonstrate the disappearance of the LDL basin at high pressure and of the HDL basin at low pressure, in agreement with independent simulations of the system's equation of state. Consistency between directly computed and reweighted free energies, as well as between free energy surfaces computed using different thermodynamic starting conditions, confirms proper equilibrium sampling. Diffusion and structural relaxation calculations demonstrate that equilibration of the LDL phase, which exhibits slow dynamics, is attained in the course of the simulations. Repeated flipping between the LDL and HDL phases in the course of long molecular dynamics runs provides further evidence of a phase transition. We use the Ewald summation with vacuum boundary conditions to calculate long-ranged Coulombic interactions and show that conducting boundary conditions lead to unphysical behavior at low temperatures.

  16. Liquid-liquid transition in ST2 water.

    PubMed

    Liu, Yang; Palmer, Jeremy C; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2012-12-01

    We use the weighted histogram analysis method [S. Kumar, D. Bouzida, R. H. Swendsen, P. A. Kollman, and J. M. Rosenberg, J. Comput. Chem. 13, 1011 (1992)] to calculate the free energy surface of the ST2 model of water as a function of density and bond-orientational order. We perform our calculations at deeply supercooled conditions (T = 228.6 K, P = 2.2 kbar; T = 235 K, P = 2.2 kbar) and focus our attention on the region of bond-orientational order that is relevant to disordered phases. We find a first-order transition between a low-density liquid (LDL, ? ? 0.9 g/cc) and a high-density liquid (HDL, ? ? 1.15 g/cc), confirming our earlier sampling of the free energy surface of this model as a function of density [Y. Liu, A. Z. Panagiotopoulos, and P. G. Debenedetti, J. Chem. Phys. 131, 104508 (2009)]. We demonstrate the disappearance of the LDL basin at high pressure and of the HDL basin at low pressure, in agreement with independent simulations of the system's equation of state. Consistency between directly computed and reweighted free energies, as well as between free energy surfaces computed using different thermodynamic starting conditions, confirms proper equilibrium sampling. Diffusion and structural relaxation calculations demonstrate that equilibration of the LDL phase, which exhibits slow dynamics, is attained in the course of the simulations. Repeated flipping between the LDL and HDL phases in the course of long molecular dynamics runs provides further evidence of a phase transition. We use the Ewald summation with vacuum boundary conditions to calculate long-ranged Coulombic interactions and show that conducting boundary conditions lead to unphysical behavior at low temperatures. PMID:23231249

  17. Activation energy of liquid-phase hydrogenation of 1-hexyne over transition metals at elevated hydrogen pressures

    SciTech Connect

    Sokol'skii, D.V.; Ualikhanova, A.

    1983-02-20

    The apparent activation energies of hydrogenation of 1-hexyne in presence of transition metals are in the range 16-51 kJ/mole and depend on the nature of the metal, the support, and the solvent. The activation energies of hydrogenation of 1-hexyne in presence of transition elements are not altered significantly when the reaction order with respect to hydrogen changes from one to zero.

  18. Continuous transitions between composite Fermi liquid and Landau Fermi liquid: A route to fractionalized Mott insulators

    E-print Network

    Barkeshli, Maissam

    One of the most successful theories of a non-Fermi-liquid metallic state is the composite Fermi-liquid (CFL) theory of the half-filled Landau level. In this paper, we study continuous quantum phase transitions out of the ...

  19. PHASE TRANSITIONS, CRITICAL PHENOMENA AND EXACTLY SOLVABLE LATTICE MODELS

    E-print Network

    Pearce, Paul A.

    : pap@mundoe.maths.mu.oz.au 1 #12;P T Critical Point Triple Point Gas Liquid Solid Fluid 1 Atm 100 C0 C coexistence at the triple point. The liquid/gas transition line terminates in a critical point. Beyond of common everyday expe- rience. If we boil a kettle of water we observe a change of phase from a liquid

  20. A reactive force field simulation of liquidliquid phase transitions in phosphorus

    E-print Network

    A reactive force field simulation of liquid­liquid phase transitions in phosphorus P. Ballone 2004; accepted 6 August 2004 A force field model of phosphorus has been developed based on density-ray diffraction measurements1 have identified a liquid-liquid phase transition in phosphorus occurring at high

  1. Spinfluid Phase Transitions

    E-print Network

    Marcus S. Cohen

    2009-07-10

    We start with the spinfluid: a nearly-homogeneous, 8-spinor medium, with small local eddies and twists. As it expends, these seed a raft of intersecting codimension-J singularities: a spinfoam. As this expands, the energy trapped in each (4-J) brane varies as the Jth power of the scale factor. Summing on J=(0,1,2,3,4) creates a quartic dilation potential with either 1 or 2 minima: preferred length and mass scales. The spinfoam expands forever with 1 minimum, but recontracts with 2. To quantize it, we take a canonical ensemble of spinfoams, immersed in a heat bath of vacuum spinors, whose microstates vastly outnumber the matter states. It's evolution is governed by a free energy which admits phase transitions at two critical scale, separated by a triple point.Their critical droplets correspond to the varieties of leptons and hadrons.We identify the first as inflation, the second as baryogenesis; and the heat bath of vacuum spinors as dark energy.

  2. Phase transitions and non-Fermi-liquid behavior in UCu5-xPdx at low temperatures

    Microsoft Academic Search

    R. Vollmer; T. Pietrus; H. V. Löhneysen; R. Chau; M. B. Maple

    2000-01-01

    We report on measurements of the specific heat C and susceptibility chi on UCu5-xPdx (x=0, 1, 1.25, 1.5, 2). For 1<=x<=1.5, the results suggest that non-Fermi-liquid behavior, i.e., a divergence of C\\/T and chi towards low temperatures, gives way to spin-glass freezing for x=1 and x=1.5, whereas no indication of a magnetically ordered ground state is observed for x=1.25 down

  3. Behavior of Supercooled Aqueous Solutions Stemming from Hidden Liquid-Liquid Transition in Water

    E-print Network

    John W. Biddle; Vincent Holten; Mikhail A. Anisimov

    2014-08-21

    A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid-liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid-liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H2O-NaCl and H2O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter, to be consistent with the presence of the metastable liquid-liquid transition. We suggest an interpretation of the liquid-liquid transition in aqueous solutions of glycerol, recently observed by Murata and Tanaka, elucidating the non-conserved nature of the order parameter, its coupling with density and concentration, and the peculiarity of "spinodal decomposition without phase separation". We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases.

  4. Contact resistivity decrease at a metal/semiconductor interface by a solid-to-liquid phase transitional metallo-organic silver.

    PubMed

    Shin, Dong-Youn; Seo, Jun-Young; Kang, Min Gu; Song, Hee-eun

    2014-09-24

    We present a new approach to ensure the low contact resistivity of a silver paste at a metal/semiconductor interface over a broad range of peak firing temperatures by using a solid-to-liquid phase transitional metallo-organic silver, that is, silver neodecanoate. Silver nanoclusters, thermally derived from silver neodecanoate, are readily dissolved into the melt of metal oxide glass frit even at low temperatures, at which point the molten metal oxide glass frit lacks the dissociation capability of bulk silver into Ag(+) ions. In the presence of O(2-) ions in the melt of metal oxide glass frit, the redox reaction from Ag(+) to Ag(0) augments the noble-metal-assisted etching capability to remove the passivation layer of silicon nitride. Moreover, during the cooling stage, the nucleated silver atoms enrich the content of silver nanocolloids in the solidified metal oxide glass layer. The resulting contact resistivity of silver paste with silver neodecanoate at the metal/semiconductor interface thus remains low-between 4.12 and 16.08 m? cm(2)-whereas without silver neodecanoate, the paste exhibits a contact resistivity between 2.61 and 72.38 m? cm(2) in the range of peak firing temperatures from 750 to 810 °C. The advantage of using silver neodecanoate in silver paste becomes evident in that contact resistivity remains low over the broad range of peak firing temperatures, thus providing greater flexibility with respect to the firing temperature required in silicon solar cell applications. PMID:25182502

  5. DNA-gelatin complex coacervation, UCST and first-order phase transition of coacervate to anisotropic ion gel in 1-methyl-3-octylimidazolium chloride ionic liquid solutions.

    PubMed

    Rawat, Kamla; Aswal, V K; Bohidar, H B

    2012-12-27

    Study of kinetics of complex coacervation occurring in aqueous 1-octyl-3-methylimidazolium chloride ionic liquid solution of low charge density polypeptide (gelatin A) and 200 base pair DNA, and thermally activated coacervate into anisotropic gel transition, is reported here. Associative interaction between DNA and gelatin A (GA) having charge ratio (DNA:GA = 16:1) and persistence length ratio (5:1) was studied at fixed DNA (0.005% (w/v)) and varying GA concentration (C(GA) = 0-0.25% (w/v)). The interaction profile was found to be strongly hierarchical and revealed three distinct binding regions: (i) Region I showed DNA-condensation (primary binding) for C(GA) < 0.10% (w/v), the DNA ? potential decrease from -80 to -5 mV (95%) (partial charge neutralization), and a size decrease by ?60%. (ii) Region II (0.10 < C(GA) < 0.15% (w/v)) indicated secondary binding, a 4-fold turbidity increase, a ? potential decrease from -5 to 0 mV (complete charge neutralization), which resulted in the appearance of soluble complexes and initiation of coacervation. (iii) Region III (0.15 < C(GA) < 0.25% (w/v)) revealed growth of insoluble complexes followed by precipitation. The hydration of coacervate was found to be protein concentration specific in Raman studies. The binding profile of DNA-GA complex with IL concentration revealed optimum IL concentration (=0.05% (w/v)) was required to maximize the interactions. Small angle neutron scattering (SANS) data of coacervates gave static structure factor profiles, I(q) versus wave vector q, that were remarkably similar and invariant of protein concentration. This data could be split into two distinct regions: (i) for 0.0173 < q < 0.0353 Å(-1), I(q) ~ q(-?) with ? = 1.35-1.67, and (ii) for 0.0353 < q < 0.35 Å(-1), I(q) = I(0)/(1 + q(2)?(2)). The correlation length found was ? = 2 ± 0.1 nm independent of protein concentration. The viscoelastic length (?8 nm) was found to have value close to the persistence length of the protein (?10 nm). Rheology data indicated that the coacervate phase resided close to the gelation state of the protein. Thus, on a heating-cooling cycle (heating to 50 °C followed by cooling to 20 °C), the heterogeneous coacervate exhibited an irreversible first-order phase transition to an anisotropic ion gel. This established a coacervate-ion gel phase diagram having a well-defined UCST. PMID:23194173

  6. The topological susceptibility from grand canonical simulations in the interacting instanton liquid model: chiral phase transition and axion mass

    E-print Network

    Olivier Wantz; E. P. S. Shellard

    2010-01-14

    This is the last in a series of papers on the topological susceptibility in the interacting instanton liquid model (IILM). We will derive improved finite temperature interactions to study the thermodynamic limit of grand canonical Monte Carlo simulations in the quenched and unquenched case with light, physical quark masses. In particular, we will be interested in chiral symmetry breaking. The paper culminates by giving, for the first time, a well-motivated temperature-dependent axion mass. Especially, this work finally provides a computation of the axion mass in the low temperature regime, $m^2_a f^2_a = 1.46 10^{-3}\\Lambda^4 \\frac{1+0.50 T/\\Lambda}{1+(3.53 T/\\Lambda)^{7.48}}$. It connects smoothly to the high temperature dilute gas approximation; the latter is improved by including quark threshold effects. To compare with earlier studies, we also provide the usual power-law $m^2_a = \\frac{\\alpha_a \\Lambda^4}{f_a^2 (T/\\Lambda)^n}$, where $\\Lambda=400\\units{MeV}$, $n=6.68$ and $\\alpha=1.68 10^{-7}$.

  7. Liquid-Liquid Two-Phase Flow Systems Neima Brauner

    E-print Network

    Brauner, Neima

    with a complete separation of the liquids may prevail for some limited range of relatively low flow rates where2.22.2323 1 #12;Liquid-Liquid Two-Phase Flow Systems Neima Brauner School of Engineering, Tel-Aviv University Tel-Aviv 69978, Israel 1 General Description of Liquid-Liquid Flows: Flow Patterns Flows of two

  8. Kinetics and mechanism of the barotropic lamellar gel/lamellar liquid crystal phase transition in fully hydrated dihexadecylphosphatidylethanolamine: a time-resolved x-ray diffraction study using pressure jump.

    PubMed Central

    Cheng, A; Hummel, B; Mencke, A; Caffrey, M

    1994-01-01

    The kinetics and mechanism of the barotropic lamellar gel (L beta')/lamellar liquid crystal (L alpha) phase transition in fully hydrated 1,2-dihexadecyl-sn-glycero-3-phosphoethanolamine (DHPE) has been studied using time-resolved x-ray diffraction (TRXRD). The phase transition was induced by pressure jumps of varying amplitudes in both the pressurization and depressurization directions at controlled temperature (78 degrees C). Both low- and wide-angle diffracted x rays were recorded simultaneously in live time using an x-ray-sensitive image intensifier coupled to a CCD camera and Super-VHS videotape recorder. Such an arrangement allowed for the direct and quantitative characterization of the long- (lamellar repeat spacing) and short-range order (chain packing) during a kinetic experiment. The image-processed live-time x-ray diffraction data were fitted using a nonlinear least-squares model, and the parameters of the fits were monitored continuously throughout the transition. The pressure-induced transitions from the L alpha to the L beta' phase and from the L beta' to the L alpha phase was two-state (no formation of intermediates apparent during the transition) to within the sensitivity limits of the method. The corresponding transit time (the time during which both phases coexist) associated with the long- and short-range order of the pressurization-induced L alpha-to-L beta' phase transition decreased to a limiting value of approximately 50 ms with increasing pressure jump amplitude. This limiting value was close to the response time of the detector/recording system. Thus, the intrinsic transit time of this transition in fully hydrated DHPE at 78 degrees C was less than or equal to 50 ms. In contrast, the depressurization-induced L beta'-to-L alpha phase transition was slower, taking approximately 1 s to complete, and occurred with no obvious dependence of the transit time on pressure jump amplitude. In the depressurization jump experiment, the lipid responded rapidly to the pressure jump in the L beta' phase up to the rate-determining L beta'-to-L alpha transition. Such behavior was examined carefully, as it could complicate the interpretation of phase transition kinetic measurements. Images FIGURE 1 PMID:7918998

  9. Liquid-Phase Adsorption Fundamentals.

    ERIC Educational Resources Information Center

    Cooney, David O.

    1987-01-01

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

  10. Texture transitions in the liquid crystalline alkyloxybenzoic acid 6OBAC

    E-print Network

    A. Sparavigna; A. Mello; B. Montrucchio

    2006-09-01

    The 4,n-alkyloxybenzoic acid 6OBAC has a very rich variety of crystalline structures and two nematic sub-phases, characterised by different textures. It is a material belonging to a family of liquid crystals formed by hydrogen bonded molecules, the 4,n-alkyloxybenzoic acids indicates the homologue number). The homologues with n ranging from 7 to 13 display both smectic C and N phases. In spite of the absence of a smectic phase, 6OBAC exhibits two sub-phases with different textures, as it happens in other materials of the homologue series which possess the smectic phase. This is the first material that exhibits a texture transition in a nematic phase directly originated from a crystal phase. Here we present the results of an image processing assisted optical investigation to characterise the textures and the transitions between textures. This processing is necessary to discriminate between crystal modifications and nematic sub-phases.

  11. Lattice effects and entropy release at the low-temperature phase transition in the spin-liquid candidate kappa-(BEDT-TTF){sub 2}Cu{sub 2}(CN){sub 3}.

    SciTech Connect

    Manna, R. S.; de Souza, M.; Bruhl, A.; Schlueter, J. A.; Lang, M.; Materials Science Division; Goethe-Univ.

    2010-01-08

    The spin-liquid candidate {kappa}-(BEDT-TTF){sub 2}Cu{sub 2}(CN){sub 3} has been studied by measuring the uniaxial expansion coefficients {alpha}{sub i}, the specific heat, and magnetic susceptibility. Special emphasis was placed on the mysterious anomaly around 6K - a potential spin-liquid instability. Distinct and strongly anisotropic lattice effects have been observed at 6K, clearly identifying this feature as a second-order phase transition. Owing to the large anomalies in {alpha}{sub i}, the application of Grueneisen scaling has enabled us to determine the corresponding specific heat contribution and the entropy release. Comparison of the latter with available spin models suggests that spin degrees of freedom alone cannot account for the phase transition. Scenarios, involving charge degrees of freedom, are discussed.

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

    SciTech Connect

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

    2012-07-30

    A large fraction of submicron atmospheric particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere, 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 semi-volatile organic compounds, the scattering and absorption of solar radiation, and the uptake of reactive gas species on atmospheric particles will be affected, with important implications for climate predictions. The actual occurrence of these types of phase transitions 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 observe the coexistence of two non-crystalline phases in particles generated from real-world samples collected on multiple days in Atlanta, Georgia, and in particles generated in the laboratory using atmospheric conditions. These results reveal that atmospheric particles can undergo liquid-liquid phase separations. Using a box model, we show that liquid-liquid phase separation can result in increased concentrations of gas-phase NO3 and N2O5 in the Atlanta region, due to decreased particle uptake of N2O5.

  13. A Demonstration of the Continuous Phase (Second-Order) Transition of a Binary Liquid System in the Region around Its Critical Point

    ERIC Educational Resources Information Center

    Johnson, Michael R.

    2006-01-01

    In most general chemistry and introductory physical chemistry classes, critical point is defined as that temperature-pressure point on a phase diagram where the liquid-gas interface disappears, a phenomenon that generally occurs at relatively high temperatures or high pressures. Two examples are: water, with a critical point at 647 K (critical…

  14. Two Phase Flow Mapping and Transition Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Parang, Masood; Chao, David F.

    1998-01-01

    In this paper, recent microgravity two-phase flow data for air-water, air-water-glycerin, and air- water-Zonyl FSP mixtures are analyzed for transition from bubbly to slug and from slug to annular flow. It is found that Weber number-based maps are inadequate to predict flow-pattern transition, especially over a wide range of liquid flow rates. It is further shown that slug to annular flow transition is dependent on liquid phase Reynolds number at high liquid flow rate. This effect may be attributed to growing importance of liquid phase inertia in the dynamics of the phase flow and distribution. As a result a new form of scaling is introduced to present data using liquid Weber number based on vapor and liquid superficial velocities and Reynolds number based on liquid superficial velocity. This new combination of the dimensionless parameters seem to be more appropriate for the presentation of the microgravity data and provides a better flow pattern prediction and should be considered for evaluation with data obtained in the future. Similarly, the analysis of bubble to slug flow transition indicates a strong dependence on both liquid inertia and turbulence fluctuations which seem to play a significant role on this transition at high values of liquid velocity. A revised mapping of data using a new group of dimensionless parameters show a better and more consistent description of flow transition over a wide range of liquid flow rates. Further evaluation of the proposed flow transition mapping will have to be made after a wider range of microgravity data become available.

  15. Lithium iodate: Phase transitions revisited

    NASA Astrophysics Data System (ADS)

    Crettez, Jean-Michel; Coquet, Etienne; Michaux, Bernard; Pannetier, Jean; Bouillot, Jacques; Orlans, Patrick; Nonat, André; Mutin, Jean-Claude

    1987-03-01

    The sequence of phase transitions of lithium iodate powders has been investigated by neutron thermodiffractometry. Upon heating, powders obtained by grinding hexagonal crystals exhibit the well known ? ? ? ? ? sequence. The intermediate orthorhombic phase ? is never observed as a single phase but always coexists either with ? or with ?-LiIO 3. The transition temperatures and the ? ? ? transformation rate are found to be strongly dependent on the crystallite dimension, especially for grain sizes smaller than 100 ?m. The hysteresis of the reversible ? ? ? transition, the kinetics of both ? ? ? and ? ? ? transitions, and the influence of proton contamination are also investigated. Contrary to this, natural powders obtained by fast evaporation of an aqueous solution do not exhibit any intermediate phase and transform directly from ? to the ? tetragonal modification. Further DTA and X-ray investigations show that the occurrence of the ? phase is related to the mechanical treatment of the sample (grinding, polishing…), i.e. to the presence of defects. Previous literature data are reviewed and the apparent discrepancies concerning the transition processes are elucidated on the basis of the present results.

  16. Zero-temperature properties of matter and the quantum theorem of corresponding states: the liquid-to-crystal phase transition for Fermi and Bose systems

    Microsoft Academic Search

    L. H. Nosanow; L. J. Parish; F. J. Pinski

    1975-01-01

    The zero-temperature properties of matter with an interaction pair potential of the Lennard-Jones form are studied in the context of the quantum theorem of corresponding states. In particular, the phase transition between the fluid and crystalline phases is studied for systems obeying either Fermi-Dirac or Bose-Einstein statistics. It is found that the solidification pressure of a Fermi system is much

  17. Low voltage blue-phase liquid crystal displays Linghui Rao,1

    E-print Network

    Wu, Shin-Tson

    Low voltage blue-phase liquid crystal displays Linghui Rao,1 Zhibing Ge,1 Shin-Tson Wu,1,a of the emerging blue-phase liquid crystal displays BP-LCDs . Simulation results indicate that the generated-effect-induced isotropic-to-anisotropic transition in blue-phase liquid crystal BPLC 1­6 has potential to become next

  18. Phase Transition in Reconstituted Chromatin

    E-print Network

    Tonau Nakai; Kohji Hizume; Shige. H. Yoshimura; Kunio Takeyasu; Kenichi Yoshikawa

    2004-09-10

    By observing reconstituted chromatin by fluorescence microscopy (FM) and atomic force microscopy (AFM), we found that the density of nucleosomes exhibits a bimodal profile, i.e., there is a large transition between the dense and dispersed states in reconstituted chromatin. Based on an analysis of the spatial distribution of nucleosome cores, we deduced an effective thermodynamic potential as a function of the nucleosome-nucleosome distance. This enabled us to interpret the folding transition of chromatin in terms of a first-order phase transition. This mechanism for the condensation of chromatin is discussed in terms of its biological significance.

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

    ERIC Educational Resources Information Center

    Koury, Albert M.; Parcher, Jon F.

    1979-01-01

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

  20. Electrical Dissipation Measurement of Polymer Phase Transitions

    NASA Technical Reports Server (NTRS)

    Long, E. R., R; Schuszler, A., II

    1983-01-01

    Technique measures solid/solid, glass/rubber, and liquid/liquid transition temperatures in polymers having dipole moments. Technique based on change in dipole packing that occurs with each transition and measured as change in electrical dissipation factor. Change in dipole packing occuring with each transition sensed by effect on dissipation factor.

  1. Phase transitions in nuclear matter

    SciTech Connect

    Glendenning, N.K.

    1984-11-01

    The rather general circumstances under which a phase transition in hadronic matter at finite temperature to an abnormal phase in which baryon effective masses become small and in which copious baryon-antibaryon pairs appear is emphasized. A preview is also given of a soliton model of dense matter, in which at a density of about seven times nuclear density, matter ceases to be a color insulator and becomes increasingly color conducting. 22 references.

  2. Coexistence of an ordered anisotropic phase and a liquid expanded phase in an amphiphilic monolayer

    E-print Network

    Paris-Sud XI, Université de

    2277 Coexistence of an ordered anisotropic phase and a liquid expanded phase in an amphiphilic. - Nous présentons une étude expérimentale d'une transition de phase d'une monocouche d'amphiphiles amphiphiles. We have combined measurement of surface tension isotherms, ellipsometry and observations

  3. Symmetry structure and phase transitions

    E-print Network

    Ashok Goyal; Meenu Dahiya; Deepak Chandra

    2002-01-22

    We study chiral symmetry structure at finite density and temperature in the presence of external magnetic field and gravity, a situation relevant in the early Universe and in the core of compact stars. We then investigate the dynamical evolution of phase transition in the expanding early Universe and possible formation of quark nuggets and their survival.

  4. Modelling and Control of Two-Phase Phenomena: Liquid-Liquid Two-Phase Flow Systems

    E-print Network

    Brauner, Neima

    with a complete separation of the liquids may prevail for some limited range of relatively low flow rates whereModelling and Control of Two-Phase Phenomena: Liquid-Liquid Two-Phase Flow Systems Neima Brauner School of Engineering, Tel-Aviv University Tel-Aviv 69978, Israel 1 General Description of Liquid-Liquid

  5. Phase transitions in wave turbulence.

    PubMed

    Vladimirova, Natalia; Derevyanko, Stanislav; Falkovich, Gregory

    2012-01-01

    We consider turbulence within the Gross-Pitaevsky model and look into the creation of a coherent condensate via an inverse cascade originating at small scales. The growth of the condensate leads to a spontaneous breakdown of statistical symmetries of overcondensate fluctuations: First, isotropy is broken, then a series of phase transitions marks the changing symmetry from twofold to threefold to fourfold. We describe respective anisotropic flux flows in the k space. At the highest level reached, we observe a short-range positional and long-range orientational order (as in a hexatic phase). In other words, the more one pumps the system, the more ordered the system becomes. The phase transitions happen when the system is pumped by an instability term and does not occur when pumped by a random force. We thus demonstrate nonuniversality of an inverse-cascade turbulence with respect to the nature of small-scale forcing. PMID:22400497

  6. Temperature- and pressure-induced phase transitions in cyclobutanol

    NASA Astrophysics Data System (ADS)

    Cheng, Xuerui; Li, Junyu; Chen, Liucheng; Zhu, Xiang; Yuan, Chaosheng; Wang, Yongqiang; Su, Lei

    2015-07-01

    The phase transition and polymorphism of cyclobutanol (C4H8O) has been investigated at low temperature and high pressure. Differential scanning calorimetry (DSC) and Raman spectra reveal that a supercooled state is observed during the cooling process, while crystalline state is formed in the heating process. We also present pressure-induced phase transition of cyclobutanol by means of Raman and infrared spectroscopy. The results indicate that cyclobutanol undergoes two phase transformations during compression to 11.4 GPa. At around 0.9 GPa, the liquid cyclobutanol transforms to a solid crystal structure. Further compression to 1.4 GPa, another fully ordered crystalline phase is observed. Simultaneously, conformational change is observed accompanied by phase transition. In addition, the red shift of the O-H stretching modes with pressure suggests the ordered crystalline phases are characterized by the formation of hydrogen-bonded molecular chains. Finally, the phase transitions under high pressure or low temperature are reversible.

  7. Behavior of supercooled aqueous solutions stemming from hidden liquid-liquid transition in water.

    PubMed

    Biddle, John W; Holten, Vincent; Anisimov, Mikhail A

    2014-08-21

    A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid-liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid-liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H2O-NaCl and H2O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter [J. Phys. Chem. B 104, 8563 (2000)], to be consistent with the presence of the metastable liquid-liquid transition. We elucidate the non-conserved nature of the order parameter (extent of "reaction" between two alternative structures of water) and the consequences of its coupling with conserved properties (density and concentration). We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases. PMID:25149798

  8. Transient liquid phase ceramic bonding

    DOEpatents

    Glaeser, Andreas M. (Berkeley, CA)

    1994-01-01

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

  9. Decoherence after a phase transition

    E-print Network

    Lombardo, F C; Rivers, R J

    2001-01-01

    We analyze the onset of classical behaviour after a second-order phase transition in quantum field theory. We consider a scalar theory in which the system-field interacts with its environment, represented both by further scalar fields and by its own short-wavelength modes. We compute the decoherence time for the system-field modes and compare it with the other time scales of the model. Within our approximations we see that the long-wavelength modes have decohered by the time that the transition has been first implemented (the spinodal time)

  10. Quantum phase transition with a simple variational ansatz

    NASA Astrophysics Data System (ADS)

    Lutsyshyn, Y.; Astrakharchik, G. E.; Cazorla, C.; Boronat, J.

    2014-12-01

    We study the zero-temperature quantum phase transition between liquid and hcp solid 4He. We use the variational method with a simple yet exchange-symmetric and fully explicit wave function. It is found that the optimized wave function undergoes spontaneous symmetry breaking and describes the quantum solidification of helium at 22 atm. The explicit form of the wave function allows us to consider various contributions to the phase transition. We find that the employed wave function is an excellent candidate for describing both a first-order quantum phase transition and the ground state of a Bose solid.

  11. Wetting transitions in two-, three-, and four-phase systems.

    PubMed

    Hejazi, Vahid; Nosonovsky, Michael

    2012-01-31

    We discuss wetting of rough surfaces with two-phase (solid-liquid), three-phase (solid-water-air and solid-oil-water), and four-phase (solid-oil-water-air) interfaces mimicking fish scales. We extend the traditional Wenzel and Cassie-Baxter models to these cases. We further present experimental observations of two-, three-, and four-phase systems in the case of metal-matrix composite solid surfaces immersed in water and in contact with oil. Experimental observations show that wetting transitions can occur in underwater oleophobic systems. We also discuss wetting transitions as phase transitions using the phase-field approach and show that a phenomenological gradient coefficient is responsible for wetting transition, energy barriers, and wetting/dewetting asymmetry (hysteresis). PMID:22054126

  12. Kinetics of the barotropic ripple (P beta')/lamellar liquid crystal (L alpha) phase transition in fully hydrated dimyristoylphosphatidylcholine (DMPC) monitored by time-resolved x-ray diffraction.

    PubMed Central

    Caffrey, M; Hogan, J; Mencke, A

    1991-01-01

    We present here the first study of the use of a pressure-jump to induce the ripple (P beta')/lamellar liquid crystal (L alpha) phase transition in fully hydrated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The transition was monitored by using time-resolved x-ray diffraction (TRXRD). Applying a pressure-jump from atmospheric to 11.3 MPa (1640 psig, 111.6 atm) in 2.5 s induces the L alpha to P beta' phase transition which takes place in two stages. The lamellar repeat spacing initially increases from a value of 66.0 +/- 0.1 A (n = 4) to a maximum value of 70.3 +/- 0.8 A (n = 4) after 10 s and after a further 100-150 s decreases slightly to 68.5 +/- 0.3 A (n = 4). The reverse transition takes place following a pressure jump in 5.5 s from 11.3 MPa to atmospheric pressure. Again, the transition occurs in two stages with the repeat spacing steadily decreasing from an initial value of 68.5 +/- 0.3 A (n = 3) to a minimum value of 66.6 +/- 0.3 A (n = 3) after 50 s and then increasing by approximately 0.5 A over a period of 100 s. The transition temperature increases linearly with pressure up to 14.1 MPa in accordance with the Clapeyron relation, giving a dT/dP value of 0.285 degrees C/MPa (28.5 degrees C/kbar) and an associated volume change of 40 microliters/g. A dynamic compressibility of 0.13 +/- 0.01 A/MPa has been determined for the L alpha phase. This value is compared with the equilibrium compressibilities of bilayer and nonbilayer phases reported in the literature. The results suggest testable mechanisms for the pressure-induced transition involving changes in periodicity, phase hydration, chain order, and orientation. A more complete understanding of the transition mechanism will require improvement in detector spatial resolution and sensitivity, and data on the pressure sensitivity of phase hydration. PMID:1912281

  13. Liquid phase sintering in microgravity

    NASA Astrophysics Data System (ADS)

    Smith, J.; Lundquist, C.; Riley, M.; Robinson, R.

    Liquid Phase Sintering (LPS) experiments have been conducted on four suborbital rockets, six Space Shuttle missions and two missions to the Mir Space Station by our research group. These missions began in 1989, spanning over 10 years. This paper will overview the many separate and interesting research and technical challenges faced in these missions and review the many published models developed to date by our group. The principle finding is that microgravity materials made using typical liquid phase sintering approaches are inferior to those made on earth. This results from pressing the green, presintered compact from their constituent powders, Fe and Co base materials with a Cu additive phase, producing composites that have solid volume fractions of 70-80%, with the balance either vacuum filled pores or entrapped gas. During LPS, the compact is processed above the melting point of the additive phase, producing a three-phase system. On earth, the entrapped gas is rapidly eliminated, and particle rearrangement is principally by buoyancy driven convection. In microgravity, this is not the case. In microgravity systems, all three phases exist concurrently, and the gas phase is not eliminated by buoyancy driven convection. Instead, the gas phase alters the free energy of the composite producing a variety of transport processes not typically seen in the earth based experiments, a positive result. Microgravity experiments slow down the typically fast acting rearrangement phase, permitting detailed study of the rapid processes taking place on earth in the first few seconds to minutes of LPS. Results from space processing have lead to a reconsideration of unit gravity models during the rearrangement stage. It has lead to a new model to explain the initiation of pore metamorphosis in LPS sample processed in microgravity, where pore breakup, coalescence and filling were found. Diffusion controlled grain growth in mutually soluble alloy phase systems, such as Co-Cu, was observed for the first time and a shrinking core model developed that successfully modeled this aspect of grain growth. In the absence of gravity, the grain coarsening model should follow the Lifshitz-Slyozov and Wagner (LSW) theory. Our extensive analysis of over 200 samples has shown that, contrary to expectation, there was an enhancement in particle coarsening with a decrease in the volume fraction of solid. The agglomerated microstructures exhibited a higher grain growth constant consistent with their higher 3D coordination number. Though buoyancy driven convection is eliminated, Brownian motion is not and becomes dominate in microgravity. This driving force leads to agglomeration and the need to use the Lifshitz-Slyozov Encounter Modified (LSEM) model to correctly model the results. Many papers on these phenomena h ve appeared in the literature and will be summarized anda presented along with a discussion of systems and subsystems needed to successfully conduct high temperature microgravity research on the fundamental mechanisms associated with LPS.

  14. Liquid phase sintering of silicon carbide

    DOEpatents

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

    1989-05-09

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

  15. Porous Liquid Phases for Indented Colloids with Depletion Interactions

    NASA Astrophysics Data System (ADS)

    Ashton, Douglas J.; Jack, Robert L.; Wilding, Nigel B.

    2015-06-01

    We study indented spherical colloids, interacting via depletion forces. These systems exhibit liquid-vapor phase transitions whose properties are determined by a combination of strong "lock-and-key" bonds and weaker nonspecific interactions. As the propensity for lock-and-key binding increases, the critical point moves to significantly lower density, and the coexisting phases change their structure. In particular, the liquid phase is porous, exhibiting large percolating voids. The properties of this system depend strongly on the topological structure of an underlying bond network: we comment on the implications of this fact for the assembly of equilibrium states with controlled porous structures.

  16. New materials for solar thermal storage—solid\\/liquid transitions in fatty acid esters

    Microsoft Academic Search

    R Nikoli?; M Marinovi?-Cincovi?; S Gadžuri?; I. J Zsigrai

    2003-01-01

    Solid\\/liquid transitions were studied by DSC measurements in the following fatty acid esters: methyl stearate, methyl palmitate, cetyl stearate, cetyl palmitate and their binary mixtures. Four systems, with phase transition temperature close to room temperature and with high enthalpy of transition and low hysteresis, were selected for further studies relevant to passive solar thermal storage. The selected systems were: methyl

  17. Liquid-crystal transitions: a first-principles multiscale approach.

    PubMed

    Shreif, Z; Pankavich, S; Ortoleva, P

    2009-09-01

    A rigorous theory of liquid-crystal transitions is developed starting from the Liouville equation. The starting point is an all-atom description and a set of order-parameter field variables that are shown to evolve slowly via Newton's equations. The separation of time scales between that of atomic collision or vibrations and the order-parameter fields enables the derivation of rigorous equations for stochastic order-parameter field dynamics. When the fields provide a measure of the spatial profile of the probability of molecular position, orientation, and internal structure, a theory of liquid-crystal transitions emerges. The theory uses the all-atom/continuum approach developed earlier to obtain a functional generalization of the Smoluchowski equation wherein key atomic details are embedded. The equivalent nonlocal Langevin equations are derived, and the computational aspects are discussed. The theory enables simulations that are much less computationally intensive than molecular dynamics and thus does not require oversimplification of the system's constituent components. The equations obtained do not include factors that require calibration and can thus be applicable to various phase transitions which overcomes the limitations of phenomenological field models. The relation of the theory to phenomenological descriptions of nematic and smectic phase transitions, and the possible existence of other types of transitions involving intermolecular structural parameters are discussed. PMID:19905127

  18. Liquid phase chromatography on microchips.

    PubMed

    Kutter, Jörg P

    2012-01-20

    Over the past twenty years, the field of microfluidics has emerged providing one of the main enabling technologies to realize miniaturized chemical analysis systems, often referred to as micro-Total Analysis Systems (uTAS), or, more generally, Lab-on-a-Chip Systems (LOC) [1,2]. While microfluidics was driven forward a lot from the engineering side, especially with respect to ink jet and dispensing technology, the initial push and interest from the analytical chemistry community was through the desire to develop miniaturized sensors, detectors, and, very early on, separation systems. The initial almost explosive development of, in particular, chromatographic separation systems on microchips, has, however, slowed down in recent years. This review takes a closer, critical look at how liquid phase chromatography has been implemented in miniaturized formats over the past several years, what is important to keep in mind when developing or working with separations in a miniaturized format, and what challenges and pitfalls remain. PMID:22071425

  19. EPR investigation of phase transitions in amphiphilic systems D.D. Lasi010D

    E-print Network

    Paris-Sud XI, Université de

    737 EPR investigation of phase transitions in amphiphilic systems D.D. Lasi010D Institute J. Stefan amphiphiles utilisant de l'acide palmitique marqué. Deux des systèmes ne présentent pas de changement-cristal liquide. Une transition supplémentaire est observée dans la phase cristal liquide du système amphiphile

  20. Thermodynamics and phase transitions in two-dimensional Yukawa systems

    NASA Astrophysics Data System (ADS)

    Vaulina, O. S.; Koss, X. G.

    2014-10-01

    The results of numerical simulations of strongly-coupled two-dimensional dissipative Yukawa systems are presented. The thermodynamic characteristics of these systems were studied, namely the internal energy, the specific heat and the entropy. For the first time, it is discovered that the considered characteristics have two singular points on the melting line; one of these points corresponds to the first-order phase transition from crystal to the hexatic phase, and another point corresponds to the second-order phase transition from the hexatic phase to the isotropic liquid. The obtained results are compared to the existing numerical and analytical data.

  1. Chemistry of polynuclear transition-metal complexes in ionic liquids.

    PubMed

    Ahmed, Ejaz; Ruck, Michael

    2011-10-01

    Transition-metal chemistry in ionic liquids (IL) has achieved intrinsic fascination in the last few years. The use of an IL as environmental friendly solvent, offers many advantages over traditional materials synthesis methods. The change from molecular to ionic reaction media leads to new types of materials being accessible. Room-temperature IL have been found to be excellent media for stabilising transition-metal clusters in solution and to crystallise homo- and heteronuclear transition-metal complexes and clusters. Furthermore, the use of IL as solvent provides the option to replace high-temperature routes, such as crystallisation from the melt or gas-phase deposition, by convenient room- or low-temperature syntheses. Inorganic IL composed of alkali metal cations and polynuclear transition-metal cluster anions are also known. Each of these areas will be discussed briefly in this contribution. PMID:21743925

  2. Liquid-phase sintering of ceramics

    SciTech Connect

    Marion, J.E.; Hsueh, C.H.; Evans, A.G.

    1987-10-01

    Expressions for the sintering rate in liquid-phase sintering are derived for coupled-interface dissolution and liquid-phase diffusion. The analysis reveals the important role of stress gradients in the grain boundary phase and also shows that such gradients cannot be supplied by liquid-phase flow. Stress-supporting structure in the grain boundary phase is thus implied. The probable existence of such structure is revealed by diffuse dark-field scattering studies, using transmission electron microscopy, on partially sintered alumina/anorthite bodies.

  3. Phases and phase transitions in disordered quantum systems

    NASA Astrophysics Data System (ADS)

    Vojta, Thomas

    2013-08-01

    These lecture notes give a pedagogical introduction to phase transitions in disordered quantum systems and to the exotic Griffiths phases induced in their vicinity. We first review some fundamental concepts in the physics of phase transitions. We then derive criteria governing under what conditions spatial disorder or randomness can change the properties of a phase transition. After introducing the strong-disorder renormalization group method, we discuss in detail some of the exotic phenomena arising at phase transitions in disordered quantum systems. These include infinite-randomness criticality, rare regions and quantum Griffiths singularities, as well as the smearing of phase transitions. We also present a number of experimental examples.

  4. Microemulsion to liquid crystal transition in two anionic surfactant systems

    SciTech Connect

    Hackett, J.L.; Miller, C.A.

    1988-08-01

    The phase behavior of two anionic surfactant systems, one containing a commercial alpha olefin sulfonate (AOS) and the other containing pure sodium dodecyl sulfate (SDS), was determined in the region where a transition from microemulsion to liquid-crystalline phases occurred with decreasing alcohol content and temperature. A general and rather complex pattern of phase behavior was seen that included a four-phase coexistence region of brine, microemulsion, lamellar liquid crystal, and oil, and two three-phase regions containing both microemulsion and liquid crystal. In much of the four-phase region, complete separation of the phases did not occur even after equilibration for 1 year or more at constant temperature. Instead, oil and brine were observed to coexist with stable birefringent dispersions that (for some compositions at least) apparently contained three phases: microemulsion, liquid crystal, and oil. Solubilization of brine was uniformly low in the phases making up the dispersions. The dispersions in the SDS system exhibited non-Newtonian behavior with apparent viscosities in the range of 50 to 100 mPa . s (50 to 100 cp) at a shear rate of 10 seconds/sup -1/. Microemulsion viscosities in the same system were about an order of magnitude lower. No plugging or other adverse behavior was seen when such dispersions flowed at a velocity of 10/sup -5/ m/s (3 ft/D) through a model porous medium having pore sizes comparable with those in reservoirs. In preliminary experiments, selected dispersions appeared to be capable of displacing oil from the same model porous medium.

  5. Work and quantum phase transitions: quantum latency.

    PubMed

    Mascarenhas, E; Bragança, H; Dorner, R; França Santos, M; Vedral, V; Modi, K; Goold, J

    2014-06-01

    We study the physics of quantum phase transitions from the perspective of nonequilibrium thermodynamics. For first-order quantum phase transitions, we find that the average work done per quench in crossing the critical point is discontinuous. This leads us to introduce the quantum latent work in analogy with the classical latent heat of first order classical phase transitions. For second order quantum phase transitions the irreversible work is closely related to the fidelity susceptibility for weak sudden quenches of the system Hamiltonian. We demonstrate our ideas with numerical simulations of first, second, and infinite order phase transitions in various spin chain models. PMID:25019721

  6. Phase transitions in the assembly of multivalent signalling proteins

    SciTech Connect

    Li, Pilong; Banjade, Sudeep; Cheng, Hui-Chun; Kim, Soyeon; Chen, Baoyu; Guo, Liang; Llaguno, Marc; Hollingsworth, Javoris V.; King, David S.; Banani, Salman F.; Russo, Paul S.; Jiang, Qiu-Xing; Nixon, B. Tracy; Rosen, Michael K. (IIT); (UCB); (LSU); (UTSMC); (Penn)

    2013-04-08

    Cells are organized on length scales ranging from angstrom to micrometers. However, the mechanisms by which angstrom-scale molecular properties are translated to micrometer-scale macroscopic properties are not well understood. Here we show that interactions between diverse synthetic, multivalent macromolecules (including multi-domain proteins and RNA) produce sharp liquid-liquid-demixing phase separations, generating micrometer-sized liquid droplets in aqueous solution. This macroscopic transition corresponds to a molecular transition between small complexes and large, dynamic supramolecular polymers. The concentrations needed for phase transition are directly related to the valency of the interacting species. In the case of the actin-regulatory protein called neural Wiskott-Aldrich syndrome protein (N-WASP) interacting with its established biological partners NCK and phosphorylated nephrin1, the phase transition corresponds to a sharp increase in activity towards an actin nucleation factor, the Arp2/3 complex. The transition is governed by the degree of phosphorylation of nephrin, explaining how this property of the system can be controlled to regulatory effect by kinases. The widespread occurrence of multivalent systems suggests that phase transitions may be used to spatially organize and biochemically regulate information throughout biology.

  7. Fluctuations and Phase Transition Dynamics

    E-print Network

    Rivers, R J

    2000-01-01

    Kibble and Zurek have provided a unifying causal picture for the appearance of classical defects like cosmic strings or vortices at the onset of phase transitions in relativistic QFT and condensed matter systems respectively. In condensed matter the predictions are partially supported by agreement with experiments in superfluid helium. We provide an alternative picture for the initial appearance of defects that supports the experimental evidence. When the original predictions fail, this is understood, in part, as a consequence of thermal fluctuations (noise), which play a comparable role in both condensed matter and QFT.

  8. Brain Performance versus Phase Transitions

    PubMed Central

    Torres, Joaquín J.; Marro, J.

    2015-01-01

    We here illustrate how a well-founded study of the brain may originate in assuming analogies with phase-transition phenomena. Analyzing to what extent a weak signal endures in noisy environments, we identify the underlying mechanisms, and it results a description of how the excitability associated to (non-equilibrium) phase changes and criticality optimizes the processing of the signal. Our setting is a network of integrate-and-fire nodes in which connections are heterogeneous with rapid time-varying intensities mimicking fatigue and potentiation. Emergence then becomes quite robust against wiring topology modification—in fact, we considered from a fully connected network to the Homo sapiens connectome—showing the essential role of synaptic flickering on computations. We also suggest how to experimentally disclose significant changes during actual brain operation. PMID:26193453

  9. 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.

  10. Energy Landscape of Zirconia Phase Transitions.

    PubMed

    Guan, Shu-Hui; Zhang, Xiao-Jie; Liu, Zhi-Pan

    2015-07-01

    The solid-phase transitions of zirconia are important phenomena for many industrial applications. Because of the lack of tools for resolving the atom displacement pattern, the transition kinetics has been disputed for over 60 years. Here, first-principles-based stochastic surface walking (SSW) pathway sampling is utilized for resolving the mechanism of ZrO2 tetragonal-to-monoclinic solid-phase transition. Two types of lattice and atom correspondence allowed in phase transition are determined for the first time from energy criterion, which are originated from two nearly energy-degenerate lowest-transition pathways and one stress-induced ferroelastic transition channel of tetragonal phase. An orthorhombic crystal phase (Pbc2/1) is discovered to be a trapping state at low temperatures in phase transition, the presence of which does not create new orientation relation but deters transformation toughening significantly. This new finding may facilitate the design of new functional oxide materials in ceramic industry. PMID:26075311

  11. Temperature-Induced Phase Transitions in Nematode Lipids and Their Influence on Respiration

    PubMed Central

    Lyons, J. M.; Keith, A. D.; Thomason, I. J.

    1975-01-01

    Temperature-induced phase transitions estimated by electron spin resonance (ESR) technique were ohscrved in the lipids of several nematode species. In both Meloidogyne javanica and Caenorhahditis elegans, there was a phase transition in their phospholipids from a liquid-crystalline state to a solid gel state at about 10 C. Aphelenchus avenae also had a phase transition, but at about 20 C. With this species, the spin-label motion parameters indicated the transition was from the liquid-crystalline state below 20 C to a more liquid or disordered state above 20 C. Anguina tritici and Meloidogyne hapla, in contrast, had no phase transitions over the entire temperature range studied. Each phase transition detected by ESR was reflected in the respiratory rates of the nematodes, and the temperature of the transition coincides with the environmental adaptation of these species. PMID:19308140

  12. Liquid Crystalline Polymer Vesicles: Thermotropic Phases in Lyotropic Structures

    E-print Network

    Lin Jia; Min-Hui Li

    2015-03-04

    This paper reviews the research work on the liquid crystalline (LC) polymer vesicles (polymersomes), where the thermotropic nematic and smectic phases are displayed in the lyotropic bilayer polymer membrane. LC polymersomes possess the properties of both liquid crystals and polymers, the two essential soft matters. LC polymersomes offer, on the one hand, novel examples of the interplay between orientational order and the curved geometry of a two dimensional membrane. Spherical, ellipsoidal and tetrahedral vesicles are discussed. On the other hand, LC polymersomes enable novel design of stimuli-responsive polymersomes using intramolecular conformational transition from nematic to isotropic phase of LC blocks. Photo-responsive polymersome bursting is highlighted.

  13. Phase transitions in alkylammonium halogenoantimonates and bismuthates

    Microsoft Academic Search

    Ryszard Jakubas; Lucjan Sobczyk

    1990-01-01

    A review of the results of studies on the structure, phase transitions and physical properties of alkylammonium halogenoantimonates (III) and bismuthates (III) is presented. The crystals of these compounds are characterized by a variety of anionic structures and show a number of phase transitions including those to polar phases. We concentrate here mainly on dielectric and pyroelectric properties, spontaneous polarization

  14. Using Peltier Cells to Study Solid-Liquid-Vapour Transitions and Supercooling

    ERIC Educational Resources Information Center

    Torzo, Giacomo; Soletta, Isabella; Branca, Mario

    2007-01-01

    We propose an apparatus for teaching experimental thermodynamics in undergraduate introductory courses, using thermoelectric modules and a real-time data acquisition system. The device may be made at low cost, still providing an easy approach to the investigation of liquid-solid and liquid-vapour phase transitions and of metastable states…

  15. Quantitative Evaluation of Colloidal Stability of Antibody Solutions using PEG-Induced Liquid-Liquid Phase Separation

    E-print Network

    Benedek, George B.

    pathways including crystallization, colloidal aggregation, and liquid-liquid phase separation (LLPS) can. KEYWORDS: antibody, PEG, liquid-liquid phase separation, colloidal stability, binding energy 1 of protein condensation such as crystallization, aggregation, gelation, and liquid-liquid phase separation

  16. Dipole-induced dipole light scattering in supercooled liquids near the liquid-glass transition

    NASA Astrophysics Data System (ADS)

    Bykhovskii, Alexis D.; Pick, Robert M.

    1994-05-01

    The integrated intensity produced by the dipole-induced dipole (DID) light scattering mechanism in a Lennard-Jones fluid is investigated for different points of the phase diagram corresponding to the normal and undercooled liquid at zero pressure. The exactly computed intensity is compared to the full Kirkwood superposition approximation (KSA) and its so-called Stephen approximation. The latter gives one or two orders of magnitude too large results, while the former is in much better agreement with the exact computation up to large reduced density values. On the basis of the mode coupling theory of the glass transition, it is argued that, in the vicinity of this transition, in real glass forming isotropic molecular liquids for which DID is the only light scattering mechanism, both a dynamical extension of the KSA and its Stephen approximation should yield dynamical spectra proportional to the real ones.

  17. Surface Premelting Coupled with Bulk Phase Transitions in Colloidal Crystals

    NASA Astrophysics Data System (ADS)

    Li, Bo; Wang, Feng; Zhou, Di; Cao, Xin; Peng, Yi; Ni, Ran; Liao, Maijia; Han, Yilong

    2015-03-01

    Colloids have been used as outstanding model systems for the studies of various phase transitions in bulk, but not at interface yet. Here we obtained equilibrium crystal-vapor interfaces using tunable attractive colloidal spheres and studied the surface premelting at the single-particle level by video microscopy. We found that monolayer crystals exhibit a bulk isostructural solid-solid transition which triggers the surface premelting. The premelting is incomplete due to the interruption of a mechanical-instability-induced bulk melting. By contrast, two- or multilayer crystals do not have the solid-solid transition and the mechanical instability, hence they exhibit complete premelting with divergent surface-liquid thickness. These novel interplays between bulk and surface phase transitions cast new lights for both types of transitions.

  18. Phase-separation of miscible liquids in a centrifuge

    NASA Astrophysics Data System (ADS)

    Tsori, Yoav; Leibler, Ludwik

    2007-09-01

    We show that a liquid mixture in the thermodynamically stable homogeneous phase can undergo a phase-separation transition when rotated at sufficiently high frequency ?. This phase-transition is different from the usual case where two liquids are immiscible or where the slow sedimentation process of one component (e.g. a polymer) is accelerated due to centrifugation. For a binary mixture, the main coupling is due to a term ???(, where ? ? is the difference between the two liquid densities and r the distance from the rotation axis. Below the critical temperature there is a critical rotation frequency ?, below which smooth density gradients occur. When ?>?, we find a sharp interface between the low density liquid close to the center of the centrifuge and a high density liquid far from the center. These findings may be relevant to various separation processes and to the control of chemical reactions, in particular their kinetics. To cite this article: Y. Tsori, L. Leibler, C. R. Physique 8 (2007).

  19. Phase-separation of miscible liquids in a centrifuge

    E-print Network

    Yoav Tsori; Ludwik Leibler

    2007-12-18

    We show that a liquid mixture in the thermodynamically stable homogeneous phase can undergo a phase-separation transition when rotated at sufficiently high frequency $\\omega$. This phase-transition is different from the usual case where two liquids are immiscible or where the slow sedimentation process of one component (e.g. a polymer) is accelerated due to centrifugation. For a binary mixture, the main coupling is due to a term $\\propto \\Delta\\rho(\\omega r)^2$, where $\\Delta\\rho$ is the difference between the two liquid densities and $r$ the distance from the rotation axis. Below the critical temperature there is a critical rotation frequency $\\omega_c$, below which smooth density gradients occur. When $\\omega>\\omega_c$, we find a sharp interface between the low density liquid close to the center of the centrifuge and a high density liquid far from the center. These findings may be relevant to various separation processes and to the control of chemical reactions, in particular their kinetics.

  20. Topological phase transitions in the gauged BPS baby Skyrme model

    E-print Network

    C. Adam; C. Naya; T. Romanczukiewicz; J. Sanchez-Guillen; A. Wereszczynski

    2015-01-15

    We demonstrate that the gauged BPS baby Skyrme model with a double vacuum potential allows for phase transitions from a non-solitonic to a solitonic phase, where the latter corresponds to a ferromagnetic liquid. Such a transition can be generated by increasing the external pressure $P$ or by turning on an external magnetic field $H$. As a consequence, the topological phase where gauged BPS baby skyrmions exist, is a higher density phase. For smaller densities, obtained for smaller values of $P$ and $H$, a phase without solitons is reached. We find the critical line in the $P,H$ parameter space. Furthermore, in the soliton phase, we find the equation of state for the baby skyrmion matter $V=V(P,H)$ at zero temperature, where $V$ is the "volume", i.e., area of the solitons.

  1. Topological phase transitions in the gauged BPS baby Skyrme model

    E-print Network

    Adam, C; Romanczukiewicz, T; Sanchez-Guillen, J; Wereszczynski, A

    2015-01-01

    We demonstrate that the gauged BPS baby Skyrme model with a double vacuum potential allows for phase transitions from a non-solitonic to a solitonic phase, where the latter corresponds to a ferromagnetic liquid. Such a transition can be generated by increasing the external pressure $P$ or by turning on an external magnetic field $H$. As a consequence, the topological phase where gauged BPS baby skyrmions exist, is a higher density phase. For smaller densities, obtained for smaller values of $P$ and $H$, a phase without solitons is reached. We find the critical line in the $P,H$ parameter space. Furthermore, in the soliton phase, we find the equation of state for the baby skyrmion matter $V=V(P,H)$ at zero temperature, where $V$ is the "volume", i.e., area of the solitons.

  2. Topological phase transitions in the gauged BPS baby Skyrme model

    NASA Astrophysics Data System (ADS)

    Adam, C.; Naya, C.; Romanczukiewicz, T.; Sanchez-Guillen, J.; Wereszczynski, A.

    2015-05-01

    We demonstrate that the gauged BPS baby Skyrme model with a double vacuum potential allows for phase transitions from a non-solitonic to a solitonic phase, where the latter corresponds to a ferromagnetic liquid. Such a transition can be generated by increasing the external pressure P or by turning on an external magnetic field H. As a consequence, the topological phase where gauged BPS baby skyrmions exist, is a higher density phase. For smaller densities, obtained for smaller values of P and H, a phase without solitons is reached. We find the critical line in the P, H parameter space. Furthermore, in the soliton phase, we find the equation of state for the baby skyrmion matter V = V( P,H) at zero temperature, where V is the "volume", i.e., area of the solitons.

  3. Freedericksz Transitions in Nematic and Cholesteric Liquid Crystal Droplets: Determination of K24 Elastic Constant

    Microsoft Academic Search

    S. Žumer; S. Kralj; J. Bezi?

    1992-01-01

    Field induced structural (Freedericksz) transitions in supramicron nematic and cholesteric liquid crystal droplets embedded in a solid matrix are theoretically analysed. Taking into account the elastic, surface, and field free energy contributions, the equilibrium structures and phase diagrams are obtained. The predicted strong dependence of the radial - axial structural transition on the value of the saddlesplay splay elastic constant

  4. 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

  5. Phase transitions in human IgG solutions.

    PubMed

    Wang, Ying; Lomakin, Aleksey; Latypov, Ramil F; Laubach, Jacob P; Hideshima, Teru; Richardson, Paul G; Munshi, Nikhil C; Anderson, Kenneth C; Benedek, George B

    2013-09-28

    Protein condensations, such as crystallization, liquid-liquid phase separation, aggregation, and gelation, have been observed in concentrated antibody solutions under various solution conditions. While most IgG antibodies are quite soluble, a few outliers can undergo condensation under physiological conditions. Condensation of IgGs can cause serious consequences in some human diseases and in biopharmaceutical formulations. The phase transitions underlying protein condensations in concentrated IgG solutions is also of fundamental interest for the understanding of the phase behavior of non-spherical protein molecules. Due to the high solubility of generic IgGs, the phase behavior of IgG solutions has not yet been well studied. In this work, we present an experimental approach to study IgG solutions in which the phase transitions are hidden below the freezing point of the solution. Using this method, we have investigated liquid-liquid phase separation of six human myeloma IgGs and two recombinant pharmaceutical human IgGs. We have also studied the relation between crystallization and liquid-liquid phase separation of two human cryoglobulin IgGs. Our experimental results reveal several important features of the generic phase behavior of IgG solutions: (1) the shape of the coexistence curve is similar for all IgGs but quite different from that of quasi-spherical proteins; (2) all IgGs have critical points located at roughly the same protein concentration at ~100 mg/ml while their critical temperatures vary significantly; and (3) the liquid-liquid phase separation in IgG solutions is metastable with respect to crystallization. These features of phase behavior of IgG solutions reflect the fact that all IgGs have nearly identical molecular geometry but quite diverse net inter-protein interaction energies. This work provides a foundation for further experimental and theoretical studies of the phase behavior of generic IgGs as well as outliers with large propensity to condense. The investigation of the phase diagram of IgG solutions is of great importance for the understanding of immunoglobulin deposition diseases as well as for the understanding of the colloidal stability of IgG pharmaceutical formulations. PMID:24089716

  6. Phase transitions in human IgG solutions

    PubMed Central

    Wang, Ying; Lomakin, Aleksey; Latypov, Ramil F.; Laubach, Jacob P.; Hideshima, Teru; Richardson, Paul G.; Munshi, Nikhil C.; Anderson, Kenneth C.; Benedek, George B.

    2013-01-01

    Protein condensations, such as crystallization, liquid-liquid phase separation, aggregation, and gelation, have been observed in concentrated antibody solutions under various solution conditions. While most IgG antibodies are quite soluble, a few outliers can undergo condensation under physiological conditions. Condensation of IgGs can cause serious consequences in some human diseases and in biopharmaceutical formulations. The phase transitions underlying protein condensations in concentrated IgG solutions is also of fundamental interest for the understanding of the phase behavior of non-spherical protein molecules. Due to the high solubility of generic IgGs, the phase behavior of IgG solutions has not yet been well studied. In this work, we present an experimental approach to study IgG solutions in which the phase transitions are hidden below the freezing point of the solution. Using this method, we have investigated liquid-liquid phase separation of six human myeloma IgGs and two recombinant pharmaceutical human IgGs. We have also studied the relation between crystallization and liquid-liquid phase separation of two human cryoglobulin IgGs. Our experimental results reveal several important features of the generic phase behavior of IgG solutions: (1) the shape of the coexistence curve is similar for all IgGs but quite different from that of quasi-spherical proteins; (2) all IgGs have critical points located at roughly the same protein concentration at ?100 mg/ml while their critical temperatures vary significantly; and (3) the liquid-liquid phase separation in IgG solutions is metastable with respect to crystallization. These features of phase behavior of IgG solutions reflect the fact that all IgGs have nearly identical molecular geometry but quite diverse net inter-protein interaction energies. This work provides a foundation for further experimental and theoretical studies of the phase behavior of generic IgGs as well as outliers with large propensity to condense. The investigation of the phase diagram of IgG solutions is of great importance for the understanding of immunoglobulin deposition diseases as well as for the understanding of the colloidal stability of IgG pharmaceutical formulations. PMID:24089716

  7. [Solubility and phase transitions in the water-protein-salt system].

    PubMed

    Rozhkov, S P

    2006-01-01

    The previously derived formulas for the curves corresponding to sol-gel, liquid-liquid, and liquid-solid phase transitions, which correlate the critical molar composition of the water-protein-salt system with individual characteristic features of its component (protein charge z, the number of ions adsorbed v, the function of electrolyte activity A) are presented as curves in ordinary coordinates of protein solubility logS against salt concentration m3. Tendencies in changes in phase transition lines versus the v, z, and v/z ratio have been determined. Correlations of the salting-out curve and the salting-out coefficient with phase transitions are discussed. PMID:17131819

  8. Game Theory and Topological Phase Transition

    E-print Network

    Tieyan Si

    2008-03-29

    Phase transition is a war game. It widely exists in different kinds of complex system beyond physics. Where there is revolution, there is phase transition. The renormalization group transformation, which was proved to be a powerful tool to study the critical phenomena, is actually a game process. The phase boundary between the old phase and new phase is the outcome of many rounds of negotiation between the old force and new force. The order of phase transition is determined by the cutoff of renormalization group transformation. This definition unified Ehrenfest's definition of phase transition in thermodynamic physics. If the strategy manifold has nontrivial topology, the topological relation would put a constrain on the surviving strategies, the transition occurred under this constrain may be called a topological one. If the strategy manifold is open and noncompact, phase transition is simply a game process, there is no table for topology. An universal phase coexistence equation is found, it sits at the Nash equilibrium point. Inspired by the fractal space structure demonstrated by renormalization group theory, a conjecture is proposed that the universal scaling law of a general phase transition in a complex system comes from the coexistence equation around Nash equilibrium point. Game theory also provide us new understanding to pairing mechanism and entanglement in many body physics.

  9. Prediction of EPR spectra of liquid crystals with doped spin probes from fully atomistic molecular dynamics simulations: exploring molecular order and dynamics at the phase transition.

    PubMed

    Kuprusevicius, Egidisus; Edge, Ruth; Gopee, Hemant; Cammidge, Andrew N; McInnes, Eric J L; Wilson, Mark R; Oganesyan, Vasily S

    2010-10-11

    Liquid crystals spin their secrets: Electron paramagnetic resonance (EPR) spectra are predicted directly and completely from fully atomistic molecular dynamics (MD) simulations of 4-cyano-4-n-pentylbiphenyl (5CB) nematic liquid crystals with a doped nitroxide spin probe (depicted in yellow; red curve = simulated and blue curve = measured EPR spectrum). PMID:20827705

  10. Phase transitions in the web of science

    NASA Astrophysics Data System (ADS)

    Phillips, J. C.

    2015-06-01

    The Internet age is changing the structure of science, and affecting interdisciplinary interactions. Publication profiles connecting mathematics with molecular biology and condensed matter physics over the last 40 years exhibit common phase transitions indicative of the critical role played by specific interdisciplinary interactions. The strengths of the phase transitions quantify the importance of interdisciplinary interactions.

  11. Shape phase transition and phase coexistence in odd Sm nuclei

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Pan, Feng; Liu, Yu-Xin; Luo, Yan-An; Draayer, J. P.

    2013-07-01

    The shape phase transition and the associated phase coexistence in the odd Sm isotopes are investigated. Through analyzing two-neutron separation energies and the low-lying spectra of the odd Sm isotopes, it is found that the spherical to axially deformed shape phase transition does occur in the odd Sm nuclei just as their neighboring even Sm nuclei. The phase coexistence in 151Sm, which lies close to the critical point, is revealed.

  12. A thermodynamically consistent Ginzburg-Landau model for superfluid transition in liquid helium

    E-print Network

    Alessia Berti; Valeria Berti

    2012-11-15

    In this paper we propose a thermodynamically consistent model for superfluid-normal phase transition in liquid helium, accounting for variations of temperature and density. The phase transition is described by means of an order parameter, according to the Ginzburg-Landau theory, emphasizing the analogies between superfluidity and superconductivity. The normal component of the velocity is assumed to be compressible and the usual phase diagram of liquid helium is recovered. Moreover, the continuity equation leads to a dependence between density and temperature in agreement with the experimental data.

  13. Binary Solid-Liquid Phase Equilibria

    ERIC Educational Resources Information Center

    Ellison, Herbert R.

    1978-01-01

    Indicates some of the information that may be obtained from a binary solid-liquid phase equilibria experiment and a method to write a computer program that will plot an ideal phase diagram to which the experimental results may be compared. (Author/CP)

  14. Switchable thermal antenna by phase transition

    E-print Network

    Ben-Abdallah, Philippe; Besbes, Mondher

    2013-01-01

    We introduce a thermal antenna which can be actively switched by phase transition. The source makes use of periodically patterned vanadium dioxide, a metal-insulator phase transition material which supports a surface phonon-polariton (SPP) in the infrared range in its crystalline phase. Using electrodes properly registred with respect to the pattern, the phase transition of VO2 can be localy triggered within few microseconds and the SPP can be diffracted making the thermal emission highly directionnal. This switchable antenna could find broad applications in the domain of active thermal coatings or in those of infrared spectroscopy and sensing.

  15. Liquid crystal orientation transition on microtextured substrates.

    PubMed

    Zhang, Baoshe; Lee, Fuk Kay; Tsui, Ophelia K C; Sheng, Ping

    2003-11-21

    A uniform alignment of liquid crystal (LC) with finite pretilt was observed on microtextured substrates that were lithographically fabricated with alternating horizontal and vertical corrugations. As the period of alternation was decreased toward 0.8 microm, the nematic LC alignment on these substrates changed from inhomogeneous in plane, copying the substrate corrugations, to a uniform configuration with a large pretilt of approximately 40 degrees. This transition is pertinent to a frustrated boundary wherein a lowering in the LC elastic energy due to spatial variation in the LC orientation compromises an increase in the surface anchoring energy. A model based on this idea demonstrates good agreement with the experiment. This result may open up a new arena for tailoring substrate characteristics for LC alignment. PMID:14683312

  16. Synthetic gauge fields stabilize a chiral spin liquid phase

    E-print Network

    Gang Chen; Kaden R. A. Hazzard; Ana Maria Rey; Michael Hermele

    2015-01-16

    We calculate the phase diagram of the SU($N$) Hubbard model describing fermionic alkaline earth atoms in a square optical lattice with on-average one atom per site, using a slave-rotor mean-field approximation. We find that the chiral spin liquid predicted for $N\\ge5$ and large interactions passes through a fractionalized state with a spinon Fermi surface as interactions are decreased before transitioning to a weakly interacting metal. We also show that by adding an artificial uniform magnetic field with flux per plaquette $2\\pi/N$, the chiral spin liquid becomes the ground state for all $N\\ge 3$ at large interactions, persists to weaker interactions, and its spin gap increases, suggesting that the spin liquid physics will persist to higher temperatures. We discuss potential methods to realize the artificial gauge fields and detect the predicted phases.

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

    PubMed Central

    Popa-Nita, Vlad; Gerli?, 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

  18. Order parameter free enhanced sampling of the vapor-liquid transition using the generalized replica exchange method

    E-print Network

    Straub, John E.

    Order parameter free enhanced sampling of the vapor-liquid transition using the generalized replica://jcp.aip.org/authors #12;THE JOURNAL OF CHEMICAL PHYSICS 138, 104119 (2013) Order parameter free enhanced sampling-liquid phase transition in Lennard-Jones fluids. Merging an optimally designed generalized ensemble sampling

  19. Toward a complete description of nucleation and growth in liquid-liquid phase separation

    E-print Network

    Paris-Sud XI, Université de

    Toward a complete description of nucleation and growth in liquid-liquid phase separation Short separation mechanism of a binary liquid mixture off-critically quenched in its miscibility gap is nucleation separates in two phases. This liquid-liquid phase separation gives the opportunity to observe the pathway

  20. Optical sensor for characterizing the phase transition in salted solutions.

    PubMed

    Claverie, Rémy; Fontana, Marc D; Duri?kovi?, Ivana; Bourson, Patrice; Marchetti, Mario; Chassot, Jean-Marie

    2010-01-01

    We propose a new optical sensor to characterize the solid-liquid phase transition in salted solutions. The probe mainly consists of a Raman spectrometer that extracts the vibrational properties from the light scattered by the salty medium. The spectrum of the O-H stretching band was shown to be strongly affected by the introduction of NaCl and the temperature change as well. A parameter SD defined as the ratio of the integrated intensities of two parts of this band allows to study the temperature and concentration dependences of the phase transition. Then, an easy and efficient signal processing and the exploitation of a modified Boltzmann equation give information on the phase transition. Validations were done on solutions with varying concentration of NaCl. PMID:22319327

  1. Interplay between chiral and deconfinement phase transitions

    E-print Network

    Fukun Xu; Tamal K. Mukherjee; Huan Chen; Mei Huang

    2011-01-15

    By using the dressed Polyakov loop or dual chiral condensate as an equivalent order parameter of the deconfinement phase transition, we investigate the relation between the chiral and deconfinement phase transitions at finite temperature and density in the framework of three-flavor Nambu--Jona-Lasinio (NJL) model. It is found that in the chiral limit, the critical temperature for chiral phase transition coincides with that of the dressed Polyakov loop in the whole $(T,\\mu)$ plane. In the case of explicit chiral symmetry breaking, it is found that the phase transitions are flavor dependent. For each flavor, the transition temperature for chiral restoration $T_c^{\\chi}$ is smaller than that of the dressed Polyakov loop $T_c^{{\\cal D}}$ in the low baryon density region where the transition is a crossover, and, the two critical temperatures coincide in the high baryon density region where the phase transition is of first order. Therefore, there are two critical end points, i.e, $T_{CEP}^{u,d}$ and $T_{CEP}^{s}$ at finite density. We also explain the feature of $T_c^{\\chi}=T_c^{\\cal D}$ in the case of 1st and 2nd order phase transitions, and $T_c^{\\chi}

  2. Escape configuration lattice near the nematic-isotropic transition: Tilt analogue of blue phases

    E-print Network

    Buddhapriya Chakrabarti; Yashodhan Hatwalne; N. V. Madhusudana

    2006-04-28

    We predict the possible existence of a new phase of liquid crystals near the nematic-isotropic ($ NI $) transition. This phase is an achiral, tilt-analogue of the blue phase and is composed of a lattice of {\\em double-tilt}, escape-configuration cylinders. We discuss the structure and the stability of this phase and provide an estimate of the lattice parameter.

  3. Phase transitions in the early universe

    NASA Astrophysics Data System (ADS)

    Wainwright, Carroll L.

    I explore the theory and computation of early-Universe finite-temperature phase transitions involving scalar fields. I focus primarily on the electroweak phase transition, but some of the methods I develop are applicable to any scalar-field cosmological phase transition (such as the computation of the lifetime of zero-temperature metastable vacua). I begin by examining phase transition thermodynamics with many extra coupled degrees of freedom, finding that such transitions have the potential to produce large amounts of entropy and can significantly dilute the concentration of thermal relic species (e.g., dark matter). I then detail a novel algorithm for calculating instanton solutions with multiple dynamic scalar fields, and present a computational package which implements the algorithm and computes the finite-temperature phase structure. Next, I discuss theoretical and practical problems of gauge dependence in finite-temperature effective potentials, using the Abelian Higgs and Abelian Higgs plus singlet models to show the severity of the problem. Finally, I apply the aforementioned algorithm to the electroweak phase transition in the next-to-minimal supersymmetric standard model (NMSSM). My collaborators and I find viable regions of the NMSSM which contain a strongly first-order phase transition and large enough CP violation to support electroweak baryogenesis, evade electric dipole moment constraints, and provide a dark matter candidate which could produce the observed 130 GeV gamma-ray line observed in the galactic center by the Fermi Gamma-ray Space Telescope.

  4. 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.

  5. 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.

  6. Photopyroelectric method using a thermal wave resonator cavity for detection of phase transitions in agar

    Microsoft Academic Search

    R. Medina-Esquivel; J. M. Yanez-Limon; Juan J. Alvarado-Gil

    2005-01-01

    In this work, the Photopyroelectric (PPE) technique using a Thermal Wave Resonator Cavity (TWRC) is used to measure the thermal diffusivity of agar. We, determine the liquid to gel phase transition temperature as a function of agar concentration, detecting a shift in that temperature. As agar concentration decreases, the phase transition temperatures get lower. The thermal diffusivity of agar as

  7. EPR investigations of phase transitions in amphiphilic systems using hydrophilic spin probes

    E-print Network

    Paris-Sud XI, Université de

    1653 EPR investigations of phase transitions in amphiphilic systems using hydrophilic spin probes D trois systèmes amphiphiles. On a déterminé le partage des molécules sondes hydrophiles entre l'eau et l-gel and gel-liquid crystal phase transitions in three amphiphilic systems. The partition of the small

  8. Phase transition of poly(N-isopropylacrylamide) in aqueous protic ionic liquids: kosmotropic versus chaotropic anions and their interaction with water.

    PubMed

    Debeljuh, Natalie J; Sutti, Alessandra; Barrow, Colin J; Byrne, Nolene

    2013-07-18

    We have investigated the influence of a series of triethylammonium-based protic ionic liquid-water solutions on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAM). We find that kosmotropic anions lower the LCST of PNIPAM more dramatically when compared with chaotropic anions. In addition, we have probed the solvent properties of the hydrated protic ionic liquid solutions using (1)H NMR, polarity measurements, and solvatochromic analysis of the Kamlet-Taft parameters, ? and ?*. We find that the hydrogen bond character--more specifically, the interactions between water and pIL--is the dominant parameter responsible for lowering the LCST of PNIPAM. We have added choline dihydrogen phosphate (choline dhp) into this study on the basis of positive results from previously reported protein folding studies using this ionic liquid. PMID:23758528

  9. Isotropic-nematic phase transition in aqueous sepiolite suspensions.

    PubMed

    Woolston, Phillip; van Duijneveldt, Jeroen S

    2015-01-01

    Aqueous suspensions of sepiolite clay rods in water tend to form gels on increase of concentration. Here it is shown how addition of a small amount (0.1% of the clay mass) of a common stabiliser for clay suspensions, sodium polyacrylate, can allow the observation of an isotropic-nematic liquid crystal phase transition. This transition was found to move to higher clay concentrations upon adding NaCl, with samples containing 10(-3) M salt or above only displaying a gel phase. Even samples that initially formed liquid crystals had a tendency to form gels after several weeks, possibly due to Mg(2+) ions leaching from the clay mineral. PMID:25313468

  10. SIMMER-II analysis of transition-phase experiments

    SciTech Connect

    Wehner, T.R.; Bell, C.R.

    1985-01-01

    Analyses of Los Alamos transition-phase experiments with the SIMMER-II computer code are reported. These transient boilup experiments simulated the recriticality-induced transient motion of a boiling pool of molten fuel, molten steel and steel vapor, within a subassembly duct in a liquid-metal fast breeder reactor during the transition phase of a core-disruptive accident. The two purposes of these experiments were to explore and reach a better understanding of fast reactor safety issues, and to provide data for SIMMER-II verification. Experimental data, consisting of four pressure traces and a high-speed movie, were recorded for four sets of initial conditions. For three of the four cases, SIMMER-II-calculated pressures compared reasonably well with the experimental pressures. After a modification to SIMMER-II's liquid-vapor drag correlation, the comparison for the fourth case was reasonable also. 12 refs., 4 figs.

  11. Cluster emission and phase transition behaviours in nuclear disassembly

    NASA Astrophysics Data System (ADS)

    Ma, Y. G.

    2001-12-01

    The features of the emissions of light particles (LP), charged particles (CP), intermediate mass fragments (IMF) and the largest fragment (MAX) are investigated for 129Xe as functions of temperature and 'freeze-out' density in the frameworks of the isospin-dependent lattice gas model and the classical molecular dynamics model. Definite turning points for the slopes of average multiplicity of LP, CP and IMF, and of the mean mass of the largest fragment Amax are shown around a liquid-gas phase transition temperature and while the largest variances of the distributions of LP, CP, IMF and MAX appear there. It indicates that the cluster emission rate can be taken as a probe of nuclear liquid-gas phase transition. Furthermore, the largest fluctuation is simultaneously accompanied at the point of the phase transition as can be noted by investigating both the variances of their cluster multiplicity or mass distributions and the Campi scatter plots within the lattice gas model and the molecular dynamics model, which is consistent with the result of the traditional thermodynamical theory when a phase transition occurs.

  12. The phase diagram of molybdenum at extreme conditions and the role of local liquid structures

    SciTech Connect

    Ross, M

    2008-08-15

    Recent DAC measurements made of the Mo melting curve by the x-ray diffraction studies confirms that, up to at least 110 GPa (3300K) melting is directly from bcc to liquid, evidence that there is no basis for a speculated bcc-hcp or fcc transition. An examination of the Poisson Ratio, obtained from shock sound speed measurements, provides evidence that the 210 GPa (4100K) transition detected from shock experiments is a continuation of the bcc-liquid melting, but is from a bcc-to a solid-like mixed phase rather than to liquid. Calculations, modeled to include the free energy of liquid local structures, predict that the transition from the liquid to the mixed phase is near 150 GPa(3500K). The presence of local structures provides the simplest and most direct explanation for the Mo phase diagram, and the low melting slopes.

  13. Is there a third order phase transition for supercritical fluids?

    SciTech Connect

    Zhu, Jinglong [LMAM and School of Mathematical Sciences, Peking University, Beijing (China) [LMAM and School of Mathematical Sciences, Peking University, Beijing (China); Beijing International Center for Mathematical Research, Peking University, Beijing (China); Zhang, Pingwen [LMAM and School of Mathematical Sciences, Peking University, Beijing (China)] [LMAM and School of Mathematical Sciences, Peking University, Beijing (China); Wang, Han, E-mail: han.wang@fu-berlin.de; Site, Luigi Delle, E-mail: luigi.dellesite@fu-berlin.de [Institute for Mathematics, Freie Universität Berlin (Germany)

    2014-01-07

    We prove that according to Molecular Dynamics (MD) simulations of liquid mixtures of Lennard-Jones (L-J) particles, there is no third order phase transition in the supercritical regime beyond Andrew's critical point. This result is in open contrast with recent theoretical studies and experiments which instead suggest not only its existence but also its universality regarding the chemical nature of the fluid. We argue that our results are solid enough to go beyond the limitations of MD and the generic character of L-J models, thus suggesting a rather smooth liquid-vapor thermodynamic behavior of fluids in supercritical regime.

  14. Quantum phase transition in a graphene model

    NASA Astrophysics Data System (ADS)

    Hands, Simon; Strouthos, Costas

    2009-03-01

    We present results for the equation of state of a graphene-like model in an effort to understand the properties of its quantum phase transition. The Nf fermion species interact through a three dimensional instantaneous Coulomb potential. Since there are no reliable analytical tools that work for all values of Nf and the coupling constant g, we rely on Monte Carlo simulations to calculate the critical properties of the model near the phase transition. We consider the four-component formulation for the fermion fields, which arises naturally as the continuum limit of the staggered fermion construction in (2 + 1) dimensions. In the limit of infinitely strong Coulomb interaction, the system undergoes a quantum phase transition at a critical number of fermion species Nfc approx 4.7. We also calculate the values of the critical exponents at the quantum phase transition.

  15. Phase transition phenomenon: A compound measure analysis

    NASA Astrophysics Data System (ADS)

    Kang, Bo Soo; Park, Chanhi; Ryu, Doojin; Song, Wonho

    2015-06-01

    This study investigates the well-documented phenomenon of phase transition in financial markets using combined information from both return and volume changes within short time intervals. We suggest a new measure for the phase transition behaviour of markets, calculated as a return distribution conditional on local variance in volume imbalance, and show that this measure successfully captures phase transition behaviour under various conditions. We analyse the intraday trade and quote dataset from the KOSPI 200 index futures, which includes detailed information on the original order size and the type of each initiating investor. We find that among these two competing factors, the submitted order size yields more explanatory power on the phenomenon of market phase transition than the investor type.

  16. Critical behaviours of contact near phase transitions

    PubMed Central

    Chen, Y.-Y.; Jiang, Y.-Z.; Guan, X.-W.; Zhou, Qi

    2014-01-01

    A central quantity of importance for ultracold atoms is contact, which measures two-body correlations at short distances in dilute systems. It appears in universal relations among thermodynamic quantities, such as large momentum tails, energy and dynamic structure factors, through the renowned Tan relations. However, a conceptual question remains open as to whether or not contact can signify phase transitions that are insensitive to short-range physics. Here we show that, near a continuous classical or quantum phase transition, contact exhibits a variety of critical behaviours, including scaling laws and critical exponents that are uniquely determined by the universality class of the phase transition, and a constant contact per particle. We also use a prototypical exactly solvable model to demonstrate these critical behaviours in one-dimensional strongly interacting fermions. Our work establishes an intrinsic connection between the universality of dilute many-body systems and universal critical phenomena near a phase transition. PMID:25346226

  17. Consistent lattice Boltzmann equations for phase transitions

    NASA Astrophysics Data System (ADS)

    Siebert, D. N.; Philippi, P. C.; Mattila, K. K.

    2014-11-01

    Unlike conventional computational fluid dynamics methods, the lattice Boltzmann method (LBM) describes the dynamic behavior of fluids in a mesoscopic scale based on discrete forms of kinetic equations. In this scale, complex macroscopic phenomena like the formation and collapse of interfaces can be naturally described as related to source terms incorporated into the kinetic equations. In this context, a novel athermal lattice Boltzmann scheme for the simulation of phase transition is proposed. The continuous kinetic model obtained from the Liouville equation using the mean-field interaction force approach is shown to be consistent with diffuse interface model using the Helmholtz free energy. Density profiles, interface thickness, and surface tension are analytically derived for a plane liquid-vapor interface. A discrete form of the kinetic equation is then obtained by applying the quadrature method based on prescribed abscissas together with a third-order scheme for the discretization of the streaming or advection term in the Boltzmann equation. Spatial derivatives in the source terms are approximated with high-order schemes. The numerical validation of the method is performed by measuring the speed of sound as well as by retrieving the coexistence curve and the interface density profiles. The appearance of spurious currents near the interface is investigated. The simulations are performed with the equations of state of Van der Waals, Redlich-Kwong, Redlich-Kwong-Soave, Peng-Robinson, and Carnahan-Starling.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  19. Deconfining phase transition in lattice quantum chromodynamics

    SciTech Connect

    Gottlieb, S.A.; Kuti, J.; Toussaint, D.; Kennedy, A.D.; Meyer, S.; Pendleton, B.J.; Sugar, R.L.

    1986-06-01

    We present a large-scale Monte Carlo calculation of the deconfining phase transition temperature in lattice quantum chromodynamics without fermions. Using the Wilson action, the transition temperature as a function of the lattice coupling g-italic is consistent with scaling behavior dictated by the perturbative ..beta.. function for 6/g-italic/sup 2/>6.15.

  20. Quantum phase transitions in rotating nuclei

    SciTech Connect

    Nazmitdinov, R. G. [Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna (Russian Federation); Departament de Fisica, UIB, E-07122 Palma de Mallorca (Spain); Kvasil, J. [Institute of Particle and Nuclear Physics, Charles University, V. Holesovickach 2, CZ-18000 Praha 8 (Czech Republic)

    2009-01-28

    We extend the classical Landau theory for rotating nuclei and show that the backbending in {sup 162}Yb, that comes about as a result of the two-quasiparticle alignment, is identified with the second order phase transition. We found that the backbending in {sup 156}Dy, caused by the instability of {gamma}-vibrations in the rotating frame, corresponds to the first order phase transition.

  1. First Order Phase Transitions in Gravitational Collapse

    E-print Network

    P. Bizo?; T. Chmaj

    1998-01-31

    In recent numerical simulations of spherically symmetric gravitational collapse a new type of critical behaviour, dominated by a sphaleron solution, has been found. In contrast to the previously studied models, in this case there is a finite gap in the spectrum of black-hole masses which is reminiscent of a first order phase transition. We briefly summarize the essential features of this phase transition and describe the basic heuristic picture underlying the numerical phenomenology.

  2. Liquid phase sintered compacts in space

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  3. DENSE NONAQUEOUS PHASE LIQUIDS -- A WORKSHOP SUMMARY

    EPA Science Inventory

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

  4. 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.

  5. Optically binary liquid crystalline blue phases induced by one-armed cholesterol-linked azobenzene molecules.

    PubMed

    Yin, Leicheng; Wu, Yeping; Gao, Jiangang; Ma, Jiajun; Hu, Zhijia; Zou, Gang; Zhang, Qijin

    2015-08-14

    A series of one-armed cholesterol-linked azobenzene molecules named CholXAzo with different spacers were synthesized, in which Chol6Azo was found to have induced blue phases (BPs) with a concentration of 4.0 wt%. Under irradiation of 385 nm UV light with a density of 15.0 mW cm(-2), photo-responsive behaviour of the 4.0 wt% Chol6Azo doped sample named B3 shows a sensitive temperature dependence, which means that at 38.0 °C a phase transition from BPs to the isotropic phase is induced; however, at 33.0 °C, this phase transition does not take place. Results from the research show that the optically binary phase transition behaviour of B3 is sensitive to the isomerization degree of Chol6Azo, which is closely related to the stability of the BP structure and there is a critical isomerization degree of 13.7% for the phase transition of the B3 liquid crystals. Further POM observation shows that the liquid crystal samples doped with different concentrations of Chol6Azo have an increasing transition temperature for photo-induced phase transition from the BP to the isotropic phase along with the increasing concentration of Chol6Azo, which are found to have the same changing tendency with phase transition temperature from the isotropic phase to BPs and a phase diagram is made to map the optically binary behaviour of Chol6Azo doped blue phase liquid crystals. At last, a simple pattern with the BP and the isotropic phase arranged at an interval was made in this optically binary liquid crystalline blue phase under a suitable photomask. PMID:26144839

  6. Reversible Hydrophobic-Hydrophilic Transition of Ionic Liquids Driven by Carbon Dioxide.

    PubMed

    Xiong, Dazhen; Cui, Guokai; Wang, Jianji; Wang, Huiyong; Li, Zhiyong; Yao, Kaisheng; Zhang, Suojiang

    2015-06-15

    Ionic liquids (ILs) with a reversible hydrophobic-hydrophilic transition were developed, and they exhibited unique phase behavior with H2 O: monophase in the presence of CO2 , but biphase upon removal of CO2 at room temperature and atmospheric pressure. Thus, coupling of reaction, separation, and recovery steps in sustainable chemical processes could be realized by a reversible liquid-liquid phase transition of such IL-H2 O mixtures. Spectroscopic investigations and DFT calculations showed that the mechanism behind hydrophobic-hydrophilic transition involved reversible reaction of CO2 with anion of the ILs and formation of hydrophilic ammonium salts. These unique IL-H2 O systems were successfully utilized for facile one-step synthesis of Au porous films by bubbling CO2 under ambient conditions. The Au porous films and the ILs were then separated simultaneously from aqueous solutions by bubbling N2 , and recovered ILs could be directly reused in the next process. PMID:25925191

  7. Size dependence of phase transitions in aerosol nanoparticles.

    PubMed

    Cheng, Yafang; Su, Hang; Koop, Thomas; Mikhailov, Eugene; Pöschl, Ulrich

    2015-01-01

    Phase transitions of nanoparticles are of fundamental importance in atmospheric sciences, but current understanding is insufficient to explain observations at the nano-scale. In particular, discrepancies exist between observations and model predictions of deliquescence and efflorescence transitions and the hygroscopic growth of salt nanoparticles. Here we show that these discrepancies can be resolved by consideration of particle size effects with consistent thermodynamic data. We present a new method for the determination of water and solute activities and interfacial energies in highly supersaturated aqueous solution droplets (Differential Köhler Analysis). Our analysis reveals that particle size can strongly alter the characteristic concentration of phase separation in mixed systems, resembling the influence of temperature. Owing to similar effects, atmospheric secondary organic aerosol particles at room temperature are expected to be always liquid at diameters below ~20?nm. We thus propose and demonstrate that particle size should be included as an additional dimension in the equilibrium phase diagram of aerosol nanoparticles. PMID:25586967

  8. Novel liquid-liquid transition in the liquid Se-GeSe system

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Y.

    2011-05-01

    The sound velocity in the liquid Se-SeGe system under the saturated vapor pressure was measured at every 1 degree. A minimum in the sound velocity as a function of temperature has been observed for alloys with 12.5 to 45 at.% Ge, which suggests that the crossover liquid-liquid transition occurs in the liquid around GeSe2. In addition to the minimum, it has been found for alloys with 15 to 27.5 at.% Ge that the sound velocity decreases rather stepwise. The reproducibility has been checked for different samples with the same composition and for different ultrasonic transducers. The decrease occurs in a very narrow temperature interval, a few degrees, and shows hysteresis depending on thermal treatments. The position of this temperature region lowers with increasing Ge concentration, and appears to merge into a minimum in the sound velocity around GeSe2. Novel structural changes, being the first order in nature, occur slightly below the crossover transition.

  9. Phase transitions in ammonium perchlorate to 26 GPA and 700 K in a diamond anvil cell

    SciTech Connect

    Foltz, M.F.; Maienschein, J.L.

    1995-07-10

    Ammonium perchlorate (AP) showed previously unreported phase behavior when studied in a diamond anvil cell (DAC) at high temperature (to 693 K) and high pressure (to {approximately}26 GPa). Liquid droplets, observed above the known 513 K orthorhombic-to-cubic phase transition, are interpreted as the onset to melting. The melting point decreased with increasing pressure. Mid-infrared FTIR spectra of the residue showed only AP. The AP melt may contribute to shock insensitivity of AP-based propellants. Gas formation was seen at higher temperatures. A phase diagram was constructed using the appearance of liquid and gas as solid-liquid and liquid-gas transitions. Preliminary pressurized differential scanning calorimetry data showed a weak pressure dependence (to {approximately}6.9 MPa) for the orthorhombic-to-cubic phase transition.

  10. Extended ensemble theory, spontaneous symmetry breaking, and phase transitions

    NASA Astrophysics Data System (ADS)

    Xiao, Ming-wen

    2006-09-01

    In this paper, as a personal review, we suppose a possible extension of Gibbs ensemble theory so that it can provide a reasonable description of phase transitions and spontaneous symmetry breaking. The extension is founded on three hypotheses, and can be regarded as a microscopic edition of the Landau phenomenological theory of phase transitions. Within its framework, the stable state of a system is determined by the evolution of order parameter with temperature according to such a principle that the entropy of the system will reach its minimum in this state. The evolution of order parameter can cause a change in representation of the system Hamiltonian; different phases will realize different representations, respectively; a phase transition amounts to a representation transformation. Physically, it turns out that phase transitions originate from the automatic interference among matter waves as the temperature is cooled down. Typical quantum many-body systems are studied with this extended ensemble theory. We regain the Bardeen Cooper Schrieffer solution for the weak-coupling superconductivity, and prove that it is stable. We find that negative-temperature and laser phases arise from the same mechanism as phase transitions, and that they are unstable. For the ideal Bose gas, we demonstrate that it will produce Bose Einstein condensation (BEC) in the thermodynamic limit, which confirms exactly Einstein's deep physical insight. In contrast, there is no BEC either within the phonon gas in a black body or within the ideal photon gas in a solid body. We prove that it is not admissible to quantize the Dirac field by using Bose Einstein statistics. We show that a structural phase transition belongs physically to the BEC happening in configuration space, and that a double-well anharmonic system will undergo a structural phase transition at a finite temperature. For the O(N)-symmetric vector model, we demonstrate that it will yield spontaneous symmetry breaking and produce Goldstone bosons; and if it is coupled with a gauge field, the gauge field will obtain a mass (Higgs mechanism). Also, we show that an interacting Bose gas is stable only if the interaction is repulsive. For the weak interaction case, we find that the BEC is a '?-transition' and its transition temperature can be lowered by the repulsive interaction. In connection with liquid 4He, it is found that the specific heat at constant pressure CP will show a T3 law at low temperatures, which is in agreement with the experiment. If the system is further cooled down, the theory predicts that CP will vanish linearly as T\\rightarrow 0 , which is anticipating experimental verifications.

  11. Phase Transition Induced Fission in Lipid Vesicles

    E-print Network

    C. Leirer; B. Wunderlich; V. M. Myles; M. F. Schneider

    2010-05-24

    In this work we demonstrate how the first order phase transition in giant unilamellar vesicles (GUVs) can function as a trigger for membrane fission. When driven through their gel-fluid phase transition GUVs exhibit budding or pearl formation. These buds remain connected to the mother vesicle presumably by a small neck. Cooling these vesicles from the fluid phase (T>Tm) through the phase transition into the gel state (T

  12. The cosmological QCD phase transition revisited

    NASA Astrophysics Data System (ADS)

    Boeckel, Tillmann; Schettler, Simon; Schaffner-Bielich, Jürgen

    2011-04-01

    The QCD phase diagram might exhibit a first order phase transition for large baryochemical potentials. We explore the cosmological implications of such a QCD phase transition in the early universe. We propose that the large baryon-asymmetry is diluted by a little inflation where the universe is trapped in a false vacuum state of QCD. The little inflation is stopped by bubble nucleation which leads to primordial production of the seeds of extragalactic magnetic fields, primordial black holes and gravitational waves. In addition the power spectrum of cold dark matter can be affected up to mass scales of 109M. The imprints of the cosmological QCD phase transition on the gravitational wave background can be explored with the future gravitational wave detectors LISA and BBO and with pulsar timing.

  13. Microgravity Two-Phase Flow Transition

    NASA Technical Reports Server (NTRS)

    Parang, M.; Chao, D.

    1999-01-01

    Two-phase flows under microgravity condition find a large number of important applications in fluid handling and storage, and spacecraft thermal management. Specifically, under microgravity condition heat transfer between heat exchanger surfaces and fluids depend critically on the distribution and interaction between different fluid phases which are often qualitatively different from the gravity-based systems. Heat transfer and flow analysis in two-phase flows under these conditions require a clear understanding of the flow pattern transition and development of appropriate dimensionless scales for its modeling and prediction. The physics of this flow is however very complex and remains poorly understood. This has led to various inadequacies in flow and heat transfer modeling and has made prediction of flow transition difficult in engineering design of efficient thermal and flow systems. In the present study the available published data for flow transition under microgravity condition are considered for mapping. The transition from slug to annular flow and from bubbly to slug flow are mapped using dimensionless variable combination developed in a previous study by the authors. The result indicate that the new maps describe the flow transitions reasonably well over the range of the data available. The transition maps are examined and the results are discussed in relation to the presumed balance of forces and flow dynamics. It is suggested that further evaluation of the proposed flow and transition mapping will require a wider range of microgravity data expected to be made available in future studies.

  14. Disorder driven quantum phase transitions in transition metal oxides

    Microsoft Academic Search

    Kohjiro Kobayashi; Nandini Trivedi

    2007-01-01

    We investigate the effect of disorder on a class of transition metal oxides described by a single orbital Hubbard model at half filling and away from half filling. The phases are characterized by the nature of the electronic and spin excitations. We calculate the local density of states, frequency and temperature-dependent conductivity and spin susceptibility as functions of disorder and

  15. Influence of Fluid Flow Distribution in MicroChannel Arrays to Phase Transition Processes

    Microsoft Academic Search

    J. J. Brandner; S. Maikowske

    2012-01-01

    Microstructured heat exchangers are well suited for such phase transition processes as evaporation of liquids due to their heat transfer capabilities, being two to three orders of magnitude higher than those of conventional heat transfer devices. Controlling liquid evaporation inside micro-channels to provide full evaporation in a stable way is not trivial. In most cases, such instabilities as slug flow,

  16. How pre-melting on surrounding interfaces broadens solidliquid phase transitions

    E-print Network

    Loss, Daniel

    . The domains melt gradually below the bulk melting point of alkane. They coexist with a `pre-molten' liquid or confinement, every solid will melt (partially) and spread out at temperatures below its bulk melting pointARTICLES How pre-melting on surrounding interfaces broadens solid­liquid phase transitions HANS

  17. ATOMIC AND MOLECULAR PHYSICS: High-Temperature Raman Investigation on Phase Transition of LBO Crystal

    NASA Astrophysics Data System (ADS)

    Zhang, Xia; Wan, Song-Ming; Yin, Shao-Tang; You, Jing-Lin

    2009-11-01

    The high-temperature Raman spectroscopy technique is applied to investigate the phase transition of LiB3O5 crystal. The result shows that the crystal is stable in the range of 293-893 K. When the temperature increases up to above 1107K, the phase transition occurs. In the liquid phase, Li2B4O7 crystal precipitates out. Up to 1173K, the Li2B4O7 crystal disappears in the melt.

  18. Chemical reaction models for non-equilibrium phase transitions

    Microsoft Academic Search

    F. Schlögl

    1972-01-01

    Chemical model reactions are discussed the steady states of which show the phenomenon of non equilibrium phase transitions. One example shows a phase transition of second order, another one shows a phase transition of first order. If diffusion occurs in the case of first order transition, coexistence of two phases in different domains is possible. For plane boundary layers between

  19. Multiplicative Noise and Second Order Phase Transitions

    NASA Astrophysics Data System (ADS)

    Manor, Alon; Shnerb, Nadav M.

    2009-07-01

    The scale-free distribution of cluster sizes in continuous phase transitions is linked to the law of proportional effect. A numerical study of a two-dimensional Ising model suggests that a cluster size undergoes a multiplicative birth-death process. At the transition the ratio between birth and death rates approaches unity for large clusters, and the resulting steady state shows a power-law behavior. The percolation dynamic, on the other hand, yields a geometric phase transition without ergodicity breaking, where large-scale merging and splitting of clusters dominate the distribution. Instead of short-range birth-death jumps, the percolation transition is characterized by Lévi flights along the cluster-size axis.

  20. Partitioning of transition metals between diopside and coexisting silicate liquids. I - Nickel, cobalt, and manganese

    NASA Technical Reports Server (NTRS)

    Lindstrom, D. J.; Weill, D. F.

    1978-01-01

    Distribution coefficients have been found for the partitioning of Ni, Co, and Mn between calcium-rich clinopyroxenes and coexisting silicate liquids. Values are found for the 1110-1360 C temperature range. The breakdown of Henry's Law was not observed. The measured clinopyroxene/liquid distribution coefficients ranged from 1.5-14.0 for Ni, 0.5-2.0 for Co, and 0.3-1.2 for Mn. Analyses of pyroxenes grown from charges differing in the amounts of transition metals indicate that Ni and Co occupy the M1 site of diopside and that Mn occupies the M1 and M2 sites. Equilibrium constants were found in terms of the activities of the components in the liquid and solid phases. These activities are based on the mole fractions. An activity/concentration model was used for the liquid phase in order to explain the variations in the clinopyroxene/liquid coefficients due to bulk composition.

  1. Orientational phase transitions in alloys

    Microsoft Academic Search

    M. L. Saboungi; G. K. Johnson; D. L. Price

    1992-01-01

    Plastic crystal behavior is observed in semiconducting CsPb and NaSn at high temperature (600 and 500 C, respectively). This behavior is associated with Mâ⁴⁻ or AâMâ structural units orientationally disordering about 50 C below the melting point where translational disorder sets in. This orientational disorder is different in the two phases, exhibiting jump reorientations in CsPb and a more isotropic

  2. Holographic Phase Transitions with Fundamental Matter

    SciTech Connect

    Mateos, David [Department of Physics, University of California, Santa Barbara, California 93106-9530 (United States); Myers, Robert C.; Thomson, Rowan M. [Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2J 2Y5 (Canada); Department of Physics, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

    2006-09-01

    The holographic dual of a finite-temperature gauge theory with a small number of flavors typically contains D-brane probes in a black hole background. At low temperature, the branes sit outside the black hole and the meson spectrum is discrete and possesses a mass gap. As the temperature increases, the branes approach a critical solution. Eventually, they fall into the horizon and a phase transition occurs. In the new phase, the meson spectrum is continuous and gapless. At large N{sub c} and large 't Hooft coupling, we show that this phase transition is always first order. In confining theories with heavy quarks, it occurs above the deconfinement transition for the glue.

  3. LIQUID PHASE SINTERED METAL MATRIX COMPOSITE MATERIALS

    Microsoft Academic Search

    S. J. Yankee; G. M. Janowski; B. J. Pletka

    1990-01-01

    Iron-base and aluminum-base composite materials reinforced with various ceramic particulates have been fabricated via powder metallurgy and liquid phase sintering. The advantage of this manufacturing route is that conventional powder metallurgy processing equipment can be used to fabricate metal matrix\\/ceramic composites. Furthermore, this approach makes it possible to manufacture these composites to near-net-shape. A number of matrix\\/ceramic combinations have been

  4. Late-time cosmological phase transitions

    SciTech Connect

    Schramm, D.N. (Chicago Univ., IL (USA) Fermi National Accelerator Lab., Batavia, IL (USA))

    1990-11-01

    It is shown that the potential galaxy formation and large-scale structure problems of objects existing at high redshifts (Z {approx gt} 5), structures existing on scales of 100M pc as well as velocity flows on such scales, and minimal microwave anisotropies ({Delta}T/T) {approx lt} 10{sup {minus}5} can be solved if the seeds needed to generate structure form in a vacuum phase transition after decoupling. It is argued that the basic physics of such a phase transition is no more exotic than that utilized in the more traditional GUT scale phase transitions, and that, just as in the GUT case, significant random gaussian fluctuations and/or topological defects can form. Scale lengths of {approximately}100M pc for large-scale structure as well as {approximately}1 M pc for galaxy formation occur naturally. Possible support for new physics that might be associated with such a late-time transition comes from the preliminary results of the SAGE solar neutrino experiment, implying neutrino flavor mixing with values similar to those required for a late-time transition. It is also noted that a see-saw model for the neutrino masses might also imply a tau neutrino mass that is an ideal hot dark matter candidate. However, in general either hot or cold dark matter can be consistent with a late-time transition. 47 refs., 2 figs.

  5. The ?–? phase transition in volcanic cristobalite

    PubMed Central

    Damby, David E.; Llewellin, Edward W.; Horwell, Claire J.; Williamson, Ben J.; Najorka, Jens; Cressey, Gordon; Carpenter, Michael

    2014-01-01

    Cristobalite is a common mineral in volcanic ash produced from dome-forming eruptions. Assessment of the respiratory hazard posed by volcanic ash requires understanding the nature of the cristobalite it contains. Volcanic cristobalite contains coupled substitutions of Al3+ and Na+ for Si4+; similar co-substitutions in synthetic cristobalite are known to modify the crystal structure, affecting the stability of the ? and ? forms and the observed transition between them. Here, for the first time, the dynamics and energy changes associated with the ?–? phase transition in volcanic cristobalite are investigated using X-ray powder diffraction with simultaneous in situ heating and differential scanning calorimetry. At ambient temperature, volcanic cristobalite exists in the ? form and has a larger cell volume than synthetic ?-cristobalite; as a result, its diffraction pattern sits between ICDD ?- and ?-cristobalite library patterns, which could cause ambiguity in phase identification. On heating from ambient temperature, volcanic cristobalite exhibits a lower degree of thermal expansion than synthetic cristobalite, and it also has a lower ?–? transition temperature (?473?K) compared with synthetic cristobalite (upwards of 543?K); these observations are discussed in relation to the presence of Al3+ and Na+ defects. The transition shows a stable and reproducible hysteresis loop with ? and ? phases coexisting through the transition, suggesting that discrete crystals in the sample have different transition temperatures. PMID:25242910

  6. Spin-gap phases in Tomonaga-Luttinger liquids

    NASA Astrophysics Data System (ADS)

    Nakamura, Masaaki; Kitazawa, Atsuhiro; Nomura, Kiyohide

    1999-09-01

    We give details of the analysis of critical properties of spin-gap phases in one-dimensional lattice electron models. In Tomonaga-Luttinger (TL) liquid theory, the spin-gap instability occurs when the backward scattering changes from repulsive to attractive. This transition point is shown to be equivalent to that of the level-crossing of the singlet and triplet excitation spectra, using the c=1 conformal field theory and the renormalization group. Based on this notion, the transition point between the TL liquid and the spin-gap phases can be determined with high-accuracy from the numerical data of finite-size clusters. We also discuss the boundary conditions and discrete symmetries to extract these excitation spectra. This technique is applied to the extended Hubbard model, the t-J model, and the t-J-J' model, and their phase diagrams are obtained. We also discuss the relation between our results and analytical solutions in weak-coupling and low-density limits.

  7. How many phases and phase transitions do exist in Gibbs adsorption layers at the air-water interface?

    PubMed

    Hossain, Md Mufazzal; Iimura, Ken-Ichi; Kato, Teiji

    2007-02-15

    Four different phases and four different first-order phase transitions have been shown to exist in Gibbs adsorption layers of mixtures containing n-hexadecyl dihydrogen phosphate (n-HDP) and L-arginine (L-arg) at a molar ratio of 1:2. These conclusions have been made from surface pressure-time (pi-t) adsorption isotherms measured with a film balance and from monolayer morphology observed with a Brewster angle microscopy (BAM). The observed four phases are gas (G), liquid expanded (LE), liquid condensed (LC) and LC' phases. Three first-order phase transitions are G-LE, LE-LC and LC-LC'. However, the thermodynamically allowed G-LC phase transition in a 1.2 x 10(-4) M mixture at 2 degrees C, which is below the so-called triple point, is kinetically separated into the G-LE and LE-LC phase transitions. The most interesting observation is that the homogeneous LC phase shows a new first-order phase transition named as LC-LC' at 2 or 5 degrees C. The LE and LC phases represent circular and fractal shaped domains, respectively, whereas the LC' phase shows very bright, anisotropic and characteristic shaped domains. PMID:17125781

  8. Phase Transitions with Subnucleonic Degrees of Freedom

    SciTech Connect

    Rapp, R. [Cyclotron Institute and Physics Department, Texas A and M University, College Station, Texas 77843-3366 (United States)

    2008-01-24

    We first give a short and elementary overview of standard-model phase transitions (electroweak and strong) with emphasis on how they generated the visible mass in the early universe. Subsequently, we focus on transitions associated with the strong interaction, in particular the mechanisms and observable consequences of spontaneous chiral symmetry breaking and its restoration. Recent advances in the interpretation of dilepton spectra in relativistic heavy-ion collisions, which provide the unique opportunity to study QCD phase changes in the laboratory, are discussed.

  9. Queueing Phase Transition: Theory of Translation

    NASA Astrophysics Data System (ADS)

    Romano, M. Carmen; Thiel, Marco; Stansfield, Ian; Grebogi, Celso

    2009-05-01

    We study the current of particles on a lattice, where to each site a different hopping probability has been associated and the particles can move only in one direction. We show that the queueing of the particles behind a slow site can lead to a first-order phase transition, and derive analytical expressions for the configuration of slow sites for this to happen. We apply this stochastic model to describe the translation of mRNAs. We show that the first-order phase transition, uncovered in this work, is the process responsible for the classification of the proteins having different biological functions.

  10. Dimension changing phase transitions in instanton crystals

    NASA Astrophysics Data System (ADS)

    Kaplunovsky, Vadim; Sonnenschein, Jacob

    2014-04-01

    We investigate lattices of instantons and the dimension-changing transitions between them. Our ultimate goal is the 3D ? 4D transition, which is holographically dual to the phase transition between the baryonic and the quarkyonic phases of cold nuclear matter. However, in this paper (just as in [1]) we focus on lower dimensions — the 1D lattice of instantons in a harmonic potential V ? , and the zigzag-shaped lattice as a first stage of the 1D ? 2D transition. We prove that in the low- and moderate-density regimes, interactions between the instantons are dominated by two-body forces. This drastically simplifies finding the ground state of the instantons' orientations, so we made a numeric scan of the whole orientation space instead of assuming any particular ansatz. We find that depending on the M 2 /M 3 /M 4 ratios, the ground state of instanton orientations can follow a wide variety of patterns. For the straight 1D lattices, we found orientations periodically running over elements of a , Klein, prismatic, or dihedral subgroup of the , as well as irrational but link-periodic patterns. For the zigzag-shaped lattices, we detected 4 distinct orientation phases — the anti-ferromagnet, another abelian phase, and two non-abelian phases. Allowing the zigzag amplitude to vary as a function of increasing compression force, we obtained the phase diagrams for the straight and zigzag-shaped lattices in the (force , M 3 /M 4), (chemical potential , M 3 /M 4), and (density , M 3 /M 4) planes. Some of the transitions between these phases are second-order while others are first-order. Our techniques can be applied to other types of non-abelian crystals.

  11. Convex Arrhenius behaviour in a nematic-isotropic phase transition

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    Convex Arrhenius behaviour, rare in transitions between equilibrium phases of pure systems, is observed in the plot of heating rate (? = \\frac{\\text{d}T}{\\text{d}t}) vs. temperature (T) for Nematic-Isotropic (N-I) transition of liquid crystalline MBBA through Differential Scanning Calorimetry (DSC). The plot is best fit by a monomolecular growth function, using which an entropy-driven activation barrier, increasing non-linearly with temperature, is obtained. Fourier Transform Infrared (FTIR) studies of MBBA around the N-I transition temperature (T_c) show increase in out-of-plane benzene ring distortions and decrease in order along the C=N-C axis, consistent with DSC results of conformational entropy-driven barrier.

  12. Viscosity and thermal conductivity effects at first-order phase transitions in heavy-ion collisions

    E-print Network

    D. N. Voskresensky; V. V. Skokov

    2010-12-22

    Effects of viscosity and thermal conductivity on the dynamics of first-order phase transitions are studied. The nuclear gas-liquid and hadron-quark transitions in heavy-ion collisions are considered. We demonstrate that at non-zero thermal conductivity, $\\kappa \

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

    NASA Astrophysics Data System (ADS)

    Reisman, Shaina; Giovambattista, Nicolas

    2013-02-01

    We perform out-of-equilibrium molecular dynamics (MD) simulations of a monatomic system with Fermi-Jagla (FJ) pair potential interactions. This model system exhibits polyamorphism both in the liquid and glass state. The two liquids, low-density (LDL) and high-density liquid (HDL), are accessible in equilibrium MD simulations and can form two glasses, low-density (LDA) and high-density amorphous (HDA) solid, upon isobaric cooling. The FJ model exhibits many of the anomalous properties observed in water and other polyamorphic liquids and thus, it is an excellent model system to explore qualitatively the thermodynamic properties of such substances. The liquid phase behavior of the FJ model system has been previously characterized. In this work, we focus on the glass behavior of the FJ system. Specifically, we perform systematic isothermal compression and decompression simulations of LDA and HDA at different temperatures and determine "phase diagrams" for the glass state; these phase diagrams varying with the compression/decompression rate used. We obtain the LDA-to-HDA and HDA-to-LDA transition pressure loci, PLDA-HDA(T) and PHDA-LDA(T), respectively. In addition, the compression-induced amorphization line, at which the low-pressure crystal (LPC) transforms to HDA, PLPC-HDA(T), is determined. As originally proposed by Poole et al. [Phys. Rev. E 48, 4605 (1993)], 10.1103/PhysRevE.48.4605 simulations suggest that the PLDA-HDA(T) and PHDA-LDA(T) loci are extensions of the LDL-to-HDL and HDL-to-LDL spinodal lines into the glass domain. Interestingly, our simulations indicate that the PLPC-HDA(T) locus is an extension, into the glass domain, of the LPC metastability limit relative to the liquid. We discuss the effects of compression/decompression rates on the behavior of the PLDA-HDA(T), PHDA-LDA(T), PLPC-HDA(T) loci. The competition between glass polyamorphism and crystallization is also addressed. At our "fast rate," crystallization can be partially suppressed and the glass phase diagram can be related directly with the liquid phase diagram. However, at our "slow rate," crystallization cannot be prevented at intermediate temperatures, within the glass region. In these cases, multiple crystal-crystal transformations are found upon compression/decompression (polymorphism).

  14. Multiple interfaces in diffusional phase transitions in binary mesogen-nonmesogen mixtures undergoing metastable phase separations.

    PubMed

    Soulé, Ezequiel R; Lavigne, Cyrille; Reven, Linda; Rey, Alejandro D

    2012-07-01

    Theory and simulations of simultaneous chemical demixing and phase ordering are performed for a mixed order parameter system with an isotropic-isotropic (I-I) phase separation that is metastable with respect to an isotropic-nematic (I-N) phase-ordering transition. Under certain conditions, the disordered phase transforms into an ordered phase via the motion of a double front containing a metastable phase produced by I-I demixing, a thermodynamically driven mechanism not previously reported. Different kinetic regimes are found depending on the location of the initial conditions in the thermodynamic phase diagram and the ratio between diffusional and nematic phase-ordering mobilities. For a diffusional process, depending if the temperature is above or below the critical codissolution point, an inflection point or a phase separation takes place in the depletion layer. This phase separation leads to the formation of a second interface where the separation of the two metastable isotropic phases grows monotonically with time. The observed deviations from the typical Fickian concentration profiles are associated with strong positive deviations of the mixture from ideality due to couplings between concentration and nematic ordering. Although systems of interest include liquid-crystalline nanocomposites, this mechanism may apply to any mixture that can undergo an order-disorder transition and demix. PMID:23005428

  15. Multiple interfaces in diffusional phase transitions in binary mesogen-nonmesogen mixtures undergoing metastable phase separations

    NASA Astrophysics Data System (ADS)

    Soulé, Ezequiel R.; Lavigne, Cyrille; Reven, Linda; Rey, Alejandro D.

    2012-07-01

    Theory and simulations of simultaneous chemical demixing and phase ordering are performed for a mixed order parameter system with an isotropic-isotropic (I-I) phase separation that is metastable with respect to an isotropic-nematic (I-N) phase-ordering transition. Under certain conditions, the disordered phase transforms into an ordered phase via the motion of a double front containing a metastable phase produced by I-I demixing, a thermodynamically driven mechanism not previously reported. Different kinetic regimes are found depending on the location of the initial conditions in the thermodynamic phase diagram and the ratio between diffusional and nematic phase-ordering mobilities. For a diffusional process, depending if the temperature is above or below the critical codissolution point, an inflection point or a phase separation takes place in the depletion layer. This phase separation leads to the formation of a second interface where the separation of the two metastable isotropic phases grows monotonically with time. The observed deviations from the typical Fickian concentration profiles are associated with strong positive deviations of the mixture from ideality due to couplings between concentration and nematic ordering. Although systems of interest include liquid-crystalline nanocomposites, this mechanism may apply to any mixture that can undergo an order-disorder transition and demix.

  16. Elastic anomalies at phase transitions in multiferroics

    NASA Astrophysics Data System (ADS)

    Pirozerskii, A. L.; Charnaya, E. V.; Gabbasova, K. R.; Bugaev, A. S.

    2014-09-01

    The temperature dependences of the elastic modulus in multiferroics-magnetoelectrics are analyzed, in which magnetic and ferroelectric orderings appear as the result of two successive phase transitions. The analytical relationships for the elastic modulus near the phase transitions to ordered states are obtained for the cases of either linear-quadratic or biquadratic contributions to magneto- and electroelastic coupling. The explicit dependence of the elastic modulus in the multiferroic phase on the magnetoelectric coupling constant was found. It is shown that the characteristic elastic properties in multiferroics can be treated using the Landau theory without taking into account fluctuations. The analysis includes changes in the phase diagrams due to the magneto- and electroelastic coupling.

  17. Orientational phase transitions in alloys

    SciTech Connect

    Saboungi, M.L.; Johnson, G.K.; Price, D.L.

    1992-09-22

    Plastic crystal behavior is observed in semiconducting CsPb and NaSn at high temperature (600 and 500 C, respectively). This behavior is associated with M{sub 4}{sup 4{minus}} or A{sub 4}M{sub 4} structural units orientationally disordering about 50 C below the melting point where translational disorder sets in. This orientational disorder is different in the two phases, exhibiting jump reorientations in CsPb and a more isotropic behavior in NaSn. In other Zintl compounds such as KPb, there is a single melting point where orientational and translational disorder sets in simultaneously; the classification of the different Zintl compounds into these two different kinds of behavior will require calorimetry or neutron diffraction below the melting point. (DLC)

  18. Phase Separation Kinetics of a Liquid Crystal-Polymer Mixture

    Microsoft Academic Search

    J. Y. Kim; P. Palffy-muhoray

    1991-01-01

    Epoxy-based polymer-dispersed liquid crystal (PDLC) materials composed of the liquid crystal E-7, the epoxy Epon 828, and the curing agent Capcure 3–800 are formed via polymerization induced phase separation of the liquid crystal and the polymer. As the polymer reacts with the curing agent, the liquid crystal and the polymer become immiscible and the system phase separates with the liquid

  19. Phase diagrams of mixtures of a polymer and a cholesteric liquid crystal under an external field.

    PubMed

    Matsuyama, Akihiko

    2014-11-14

    We present a mean field theory to describe phase behaviors in mixtures of a polymer and a cholesteric liquid crystal under an external magnetic or electric field. Taking into account a chiral coupling between a polymer and a liquid crystal under the external field, we examine twist-untwist phase transitions and phase separations in the mixtures. It is found that a cholesteric-nematic phase transition can be induced by not only the external field but also concentration and temperature. Depending on the strength of the external field, we predict cholesteric-paranematic (Ch+pN), nematic-paranematic (N+pN), cholesteric-nematic (Ch+N) phase separations, etc., on the temperature-concentration plane. We also discuss mixtures of a non-chiral nematic liquid crystal and a chiral dopant. PMID:25399158

  20. Assessment of the thermal-hydraulic technology of the transition phase of a core-disruptive accident in a LMFBR

    SciTech Connect

    Greene, G.A.; Ginsberg, T.; Kazimi, M.S.

    1982-11-01

    The technology of thermal hydraulic aspects of the transition phase accident sequence in liquid metal fast breeder reactors has been reviewed. Previous analyses of the transition phase accident sequence have been reviewed and the current understanding of major thermal hydraulic phenomenology has been assessed. As a result of the foregoing, together with a scoping analysis of the transition phase accident sequence, major transition phase issues have been defined and research needs have been identified. The major conclusion of transition phase scoping analysis is that fuel dispersal cannot be relied upon to rule out the possibility of recriticalities during this stage of the accident.

  1. Porcupine-like horseshoes: Transitivity, Lyapunov spectrum, and phase transitions

    E-print Network

    Díaz, L J

    2010-01-01

    We study a partially hyperbolic and topologically transitive local diffeomorphism $F$ that is a skew-product over a horseshoe map. This system is derived from a homoclinic class and contains infinitely many hyperbolic periodic points of different indices and hence is not hyperbolic. The associated transitive invariant set $\\Lambda$ possesses a very rich fiber structure, it contains uncountably many trivial and uncountably many non-trivial fibers. Moreover, the spectrum of the central Lyapunov exponents of $F|_{\\Lambda}$ contains a gap and hence gives rise to a first order phase transition. A major part of the proofs relies on the analysis of an associated iterated function system that is genuinely non-contracting.

  2. Late Time Phase Transition as Dark Energy

    Microsoft Academic Search

    A. de la Macorra

    2003-01-01

    We study the possibility that the quintessence field responsible for the dark energy and the present day acceleration of the universe is given by a condensate field generated at a late phase transition scale determined by the condensation scale. We show that the quintessence field can be described naturally by the condensates of a non-abelian gauge group. The non-perturbative effects

  3. Passive Supporters of Terrorism and Phase Transitions

    E-print Network

    August, Friedrich; Delitzscher, Sascha; Hiller, Gerald; Krueger, Tyll

    2010-01-01

    We discuss some social contagion processes to describe the formation and spread of radical opinions. The dynamics of opinion spread involves local threshold processes as well as mean field effects. We calculate and observe phase transitions in the dynamical variables resulting in a rapidly increasing number of passive supporters. This strongly indicates that military solutions are inappropriate.

  4. Phase transitions in an alternating superlattice

    Microsoft Academic Search

    M. Saber; A. Ainane; K. Bärner

    2007-01-01

    Within the effective field theory with a probability distribution technique that accounts for the self spin correlation functions, we examine the phase transition properties of a ferroelectric superlattice with two alternating layers A and B described by a transverse spin-1\\/2 Ising model. The equations that determine the Curie temperature Tc and the polarization have been obtained. The effects of the

  5. Solitonic Phase Transitions of Galilean Black Holes

    E-print Network

    R. B. Mann

    2009-03-25

    Planar black holes with Galilean asymptotics have been proposed as the holographic dual of a non-relativistic conformal field theory at finite temperature. I show that these objects can undergo a phase transition at low temperature to a new type of soliton with the same asymptotic structure. The strength of the chemical potential is induced by the scale of the soliton.

  6. Double-Diffusive Layers and Phase Transitions

    NASA Astrophysics Data System (ADS)

    Dude, Sabine; Hansen, Ulrich

    2015-04-01

    Researching the thermal evolution of the Earth's mantle on numerical base is very challenging. During the last decade different approaches are put forward in oder to understand the picture of the today's Earth's mantle. One way is to incorporate all the known features and physics (plate tectonics, phase transitions, CMB-topography, ...) into numerical models and make them as complex (or 'complete') as possible to capture Earth's mantle processes and surface signals. Another way is, to take a step back and look at less complex models which account for single processes and their interaction and evolution. With these 'simpler' models one is able look in detail into the physical processes and dependencies on certain parameters. Since the knowledge of slab stagnation in the transitions zone of the Earth's mantle the question whether the mantle is or at least has been layered to some degree is still under debate. On this basis we address two important features that lead to layered mantle convection and may affect each other and with this the thermal evolution of the mantle. It is commonly known the main mantle mineral olivine pass through various phase changes with depth [1]. Detailed numerical studies had been carried out to ascertain the influence on convective motion and planetary evolution [2]. It is still heavily discussed whether the endothermic phase change at 660km depth can lead an isolated lower mantle. Most of the numerical studies favour a model which has phases of layering that are disrupted by catastrophic events. In the last years double-diffusive convection has also been intensively studied with regard to planetary mantle evolution such as pile formation and core-mantle boundary topography [3]. However, another striking feature still posing open questions are evolving layers self-organised from a previous non layered state. Considering a chemical component that influences the density of a fluid in addition to the temperature leads to dynamical phenomena that have no counterpart in pure thermal convection. In oder to determine the interaction of double-diffusive layers with a phase transition we carried out numerical simulations ranging from exothermic to endothermic conditions. Taking into account a depth and temperature dependence of the phase transition the results show that on the one hand double-diffusive layering is strongly affected by the presence of phase transition but on the other hand the equilibrium position of the phase transition is shifted depending on the properties of the considered transition. In addition to that we incorporate the chemical dependence of the phase change and determine the influence on the layer growth and the overall dynamics. References [1] Schubert, G., Yuen, D. A., Turcotte, D. L., Role of Phase Transitions in a Dynamic Mantle. Geophys. J. Roy. Astron. Soc., 42:705-735, 1975. [2] Christensen, U., Effects of Phase Transitions on Mantle Convection. Ann. Rev. Earth Planet. Sci., 23:65-88, 1995. [3] Tackley, P. J. Dynamics and evolution of the deep mantle resulting from thermal, chemical, phase and melting effects. Earth-Sci. Rev., 110:1-25, 2012.

  7. Nonuniversal surface behavior of dynamic phase transitions

    NASA Astrophysics Data System (ADS)

    Riego, Patricia; Berger, Andreas

    2015-06-01

    We have studied the dynamic phase transition (DPT) of the kinetic Ising model in systems with surfaces within the mean-field approximation. Varying the surface exchange coupling strength Js, the amplitude of the externally applied oscillating field h0, and its period P , we explore the dynamic behavior of the layer-dependent magnetization and the associated DPTs. The surface phase diagram shows several features that resemble those of the equilibrium case, with an extraordinary bulk transition and a surface transition for high Js values, independent from the value of h0. For low Js, however, h0 is found to be a crucial parameter that leads to nonuniversal surface behavior at the ordinary bulk transition point. Specifically, we observed here a bulk-supported surface DPT for high field amplitudes h0 and correspondingly short critical periods Pc, whereas this surface transition simultaneous to the bulk one is suppressed for slow critical dynamics occurring for low values of h0. The suppression of the DPT for low h0 not only occurs for the topmost surface layer, but also affects a significant number of subsurface layers. We find that the key physical quantity that explains this nonuniversal behavior is the time correlation between the dynamic surface and bulk magnetizations at the bulk critical point. This time correlation has to pass a threshold value to trigger a bulk-induced DPT in the surface layers. Otherwise, dynamic phase transitions are absent at the surface in stark contrast to the equilibrium behavior of the corresponding thermodynamic Ising model. Also, we have analyzed the penetration depth of the dynamically ordered phase for the surface DPT that occurs for large Js values. Here we find that the penetration depth depends strongly on Js and behaves identically to the corresponding equilibrium Ising model.

  8. Does Sex Induce a Phase Transition?

    E-print Network

    de Oliveira, P M C; Stauffer, D; Cebrat, S; Pekalski, A; 10.1140/epjb/e2008-00229-3

    2009-01-01

    We discovered a dynamic phase transition induced by sexual reproduction. The dynamics is a pure Darwinian rule with both fundamental ingredients to drive evolution: 1) random mutations and crossings which act in the sense of increasing the entropy (or diversity); and 2) selection which acts in the opposite sense by limiting the entropy explosion. Selection wins this competition if mutations performed at birth are few enough. By slowly increasing the average number m of mutations, however, the population suddenly undergoes a mutational degradation precisely at a transition point mc. Above this point, the "bad" alleles spread over the genetic pool of the population, overcoming the selection pressure. Individuals become selectively alike, and evolution stops. Only below this point, m < mc, evolutionary life is possible. The finite-size-scaling behaviour of this transition is exhibited for large enough "chromosome" lengths L. One important and surprising observation is the L-independence of the transition curv...

  9. Size dependence of phase transitions in aerosol nanoparticles

    NASA Astrophysics Data System (ADS)

    Cheng, Yafang; Su, Hang; Koop, Thomas; Mikhailov, Eugene; Pöschl, Ulrich

    2015-04-01

    Phase transitions of nanoparticles are of fundamental importance in atmospheric sciences. Current understanding is insufficient to explain observations at the nano-scale. In particular, discrepancies exist between observations and model predictions of deliquescence and efflorescence transitions and the hygroscopic growth of salt nanoparticles. Here we show that these discrepancies can be resolved by consideration of particle size effects with consistent thermodynamic data. We present a new method for the determination of water and solute activities and interfacial energies in highly supersaturated aqueous solution droplets. Our analysis reveals that particle size can strongly alter the characteristic concentration of phase separation in mixed systems, resembling the influence of temperature. Due to similar effects, atmospheric secondary organic aerosol particles at room temperature are expected to be always liquid at diameters below ~20 nm. We thus propose and demonstrate that particle size should be included as an additional dimension in the equilibrium phase diagram of aerosol nanoparticles. Reference: Cheng, Y. et al. Size dependence of phase transitions in aerosol nanoparticles. Nature Communications. 5:5923 doi: 10.1038/ncomms6850 (2015).

  10. Evidence for liquid water during the high-density to low-density amorphous ice transition

    PubMed Central

    Kim, Chae Un; Barstow, Buz; Tate, Mark W.; Gruner, Sol M.

    2009-01-01

    Polymorphism of water has been extensively studied, but controversy still exists over the phase transition between high-density amorphous (HDA) and low-density amorphous (LDA) ice. We report the phase behavior of HDA ice inside high-pressure cryocooled protein crystals. Using X-ray diffraction, we demonstrate that the intermediate states in the temperature range from 80 to 170 K can be reconstructed as a linear combination of HDA and LDA ice, suggesting a first-order transition. We found evidence for a liquid state of water during the ice transition based on the protein crystallographic data. These observations open the possibility that the HDA ice induced by high-pressure cryocooling is a genuine glassy form of high-density liquid. PMID:19258453

  11. Ion induced lamellar-lamellar phase transition in charged surfactant systems

    NASA Astrophysics Data System (ADS)

    Harries, Daniel; Podgornik, Rudi; Parsegian, V. Adrian; Mar-Or, Etay; Andelman, David

    2006-06-01

    We propose a model for the liquid-liquid (L??L?') phase transition observed in osmotic pressure measurements of certain charged lamellae-forming amphiphiles. The model free energy combines mean-field electrostatic and phenomenological nonelectrostatic interactions, while the number of dissociated counterions is treated as a variable degree of freedom that is determined self-consistently. The model, therefore, joins two well-known theories: the Poisson-Boltzmann theory for ionic solutions between charged lamellae and the Langmuir-Frumkin-Davies adsorption isotherm modified to account for charged adsorbing species. Minimizing the appropriate free energy for each interlamellar spacing, we find the ionic density profiles and the resulting osmotic pressure. While in the simple Poisson-Boltzmann theory the osmotic pressure isotherms are always smooth, we observe a discontinuous liquid-liquid phase transition when the Poisson-Boltzmann theory is self-consistently augmented by the Langmuir-Frumkin-Davies adsorption. This phase transition depends on the area per amphiphilic head group, as well as on nonelectrostatic interactions of the counterions with the lamellae and interactions between counterion-bound and counterion-dissociated surfactants. Coupling the lateral phase transition in the bilayer plane with electrostatic interactions in the bulk, our results offer a qualitative explanation for the existence of the L??L?' phase transition of didodecyldimethylammonium bromide (DDABr), but the transition's apparent absence for the chloride and the iodide homologs. More quantitative comparisons with experiment require better understanding of the microscopic basis of the phenomenological model parameters.

  12. Quantum phase transitions in semilocal quantum liquids

    E-print Network

    Iqbal, Nabil

    We consider several types of quantum critical phenomena from finite-density gauge-gravity duality which to different degrees lie outside the Landau-Ginsburg-Wilson paradigm. These include: (i) a “bifurcating” critical ...

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

    NASA Astrophysics Data System (ADS)

    Rustan, Gustav Errol

    A new laboratory has been developed at Iowa State University (ISU) to be used for the study of high temperature liquids and solids, with particular focus on the supercooling of liquids and their metastable solidification products. This new laboratory employs the electrostatic levitation (ESL) technique, in which a charged sample is suspended between a set of electrodes to achieve non-contact handling. Owing to the elimination of a crucible, high temperature processing of samples can be achieved with reduced levels of contamination and heterogeneous nucleation. Because of the reduction in heterogeneous nucleation, samples can be supercooled well below their equilibrium melting temperature, opening the door to a wide range of measurements on supercooled liquids. Measurements methods have been implemented for the characterization of thermophysical properties such as: volume/density, ratio of specific heat to total hemispherical emissivity, surface tension, viscosity, electrical resistivity, and magnetic susceptibility. For measurements of electrical resistivity and magnetic susceptibility, a new method has been developed at ISU based on the tunnel diode oscillator (TDO) technique. The TDO technique uses the negative differential resistance of a tunnel diode to drive an LC tank circuit into self-sustained oscillation at the resonant LC frequency. The LC tank is inductively coupled to the samples under study, and changes in the electrical resistivity or magnetic susceptibility of the sample are manifested as changes in the resonant frequency. By measuring the frequency shifts of the TDO, insights can be made into changes in the material's electrical and magnetic properties. This method has been validated by performing resistivity measurements on a sample of high purity Zr, and by performing measurements on the ferromagnetic transition in a low-carbon steel ball bearing. In addition to the development of the laboratory and its supporting instrumentation, an effort has been carried out to study the metastable phase formation in an Fe83B17 near eutectic alloy. Initial supercooling measurements using the ISU-ESL identified the formation of three metastable phases: a precipitate phase that shows stable coexistence with the deeply supercooled liquid, and two distinct bulk solidification phases. To identify the structure of the metastable phases, the Washington University Beamline ESL (WU-BESL) has been used to perform in-situ high energy x-ray diffraction measurements of the metastable phases. Based on the x-ray results, the precipitate phase has been identified as bcc-Fe, and the more commonly occurring bulk solidification product has been found to be a two-phase mixture of Fe23B6 plus fcc-Fe, which appears, upon cooling, to transform into a three phase mixture of Fe23B6, bcc-Fe, and an as-yet unidentified phase, with the transformation occurring at approximately the expected fcc-to-bcc transformation temperature of pure Fe. To further characterize the multi-phase metastable alloy, the ISU-ESL has been used to perform measurements of volume thermal expansion via the videographic technique, as well as RF susceptibility via the TDO technique. The results of the thermal expansion and susceptibility data have been found to be sensitive indicators of additional structural changes that may be occurring in the metastable solid at temperatures below 1000 K, and the susceptibility data has revealed that three distinct ferromagnetic phase transitions take place within the multi-phase mixture. Based on these results, it has been hypothesized that there may be an additional transformation taking place that leads to the formation of either bct- or o-Fe3B in addition to the Fe23B6 phase, although further work is required to test this hypothesis.

  14. Light clusters, pasta phases, and phase transitions in core-collapse supernova matter

    NASA Astrophysics Data System (ADS)

    Pais, Helena; Chiacchiera, Silvia; Providência, Constança

    2015-05-01

    The pasta phase in core-collapse supernova matter (finite temperatures and fixed proton fractions) is studied within relativistic mean-field models. Three different calculations are used for comparison: the Thomas-Fermi, the coexisting phases, and the compressible liquid drop approximations. The effects of including light clusters in nuclear matter and the densities at which the transitions between pasta configurations and to uniform matter occur are also investigated. The free energy, pressure, entropy, and chemical potentials in the range of particle number densities and temperatures expected to cover the pasta region are calculated. Finally, a comparison with a finite-temperature Skyrme-Hartree-Fock calculation is drawn.

  15. TheLiquidPhase: Countercurrent Chromatography

    NSDL National Science Digital Library

    TheLiquidPhase is a community portal, or wiki, dedicated to the proliferation of knowledge and good technique in countercurrent chromatography (CCC). It has been organized to help prospective users of CCC learn about its potential and to provide a virtual meeting place for discussions among experienced users of the technique. There are pages explaining CCC, how to get started, and describing a typical setup; sections devoted to solvent systems, modes of operation, and CCC chromatograms; an undergraduate chemistry lab experiment using CCC; lists of manufacturers and distributors; a bibliography, and an alphabetical index.

  16. Search for Electronic Phase Separation at Quantum Phase Transitions

    Microsoft Academic Search

    C. Pfleiderer; P. Böni; C. Franz; T. Keller; A. Neubauer; P. G. Niklowitz; P. Schmakat; M. Schulz; Y.-K. Huang; J. A. Mydosh; M. Vojta; W. Duncan; F. M. Grosche; M. Brando; M. Deppe; C. Geibel; F. Steglich; A. Krimmel; A. Loidl

    2010-01-01

    Phase separation and extreme sensitivity to disorder and defects are key features of electronic order near quantum phase transitions.\\u000a Neutron depolarization imaging and neutron Larmor diffraction are new experimental techniques capable of providing detailed\\u000a real-space and reciprocal-space information, respectively, on the existence and nature of phase separations. Proof-of-principle\\u000a depolarization imaging in Pd1?x\\u000a Ni\\u000a x\\u000a , CePd1?x\\u000a Rh\\u000a x\\u000a and NbFe2

  17. Dynamics of the chiral phase transition

    E-print Network

    van Hees, H; Meistrenko, A; Greiner, C

    2013-01-01

    The intention of this study is the search for signatures of the chiral phase transition in heavy-ion collisions. To investigate the impact of fluctuations, e.g., of the baryon number, at the transition or at a critical point, the linear sigma model is treated in a dynamical (3+1)-dimensional numerical simulation. Chiral fields are approximated as classical mean fields, and quarks are described as quasi particles in a Vlasov equation. Additional dynamics is implemented by quark-quark and quark-sigma-field interactions. For a consistent description of field-particle interactions, a new Monte-Carlo-Langevin-like formalism has been developed and is discussed.

  18. Dynamics of the chiral phase transition

    E-print Network

    H. van Hees; C. Wesp; A. Meistrenko; C. Greiner

    2013-11-26

    The intention of this study is the search for signatures of the chiral phase transition in heavy-ion collisions. To investigate the impact of fluctuations, e.g., of the baryon number, at the transition or at a critical point, the linear sigma model is treated in a dynamical (3+1)-dimensional numerical simulation. Chiral fields are approximated as classical mean fields, and quarks are described as quasi particles in a Vlasov equation. Additional dynamics is implemented by quark-quark and quark-sigma-field interactions. For a consistent description of field-particle interactions, a new Monte-Carlo-Langevin-like formalism has been developed and is discussed.

  19. How Phase Transitions induce classical behaviour

    E-print Network

    Rivers, R J

    2004-01-01

    We continue the analysis of the onset of classical behaviour in a scalar field after a continuous phase transition, in which the system-field, the long wavelength order parameter of the model, interacts with an environment, of its own short-wavelength modes and other fields, neutral and charged, with which it is expected to interact. We compute the decoherence time for the system-field modes from the master equation and directly from the decoherence functional (with identical results). In simple circumstances the order parameter field is classical by the time the transition is complete.

  20. Phase Transitions in Paradigm Shift Models

    PubMed Central

    Chae, Huiseung; Yook, Soon-Hyung; Kim, Yup

    2013-01-01

    Two general models for paradigm shifts, deterministic propagation model (DM) and stochastic propagation model (SM), are proposed to describe paradigm shifts and the adoption of new technological levels. By defining the order parameter based on the diversity of ideas, , it is studied when and how the phase transition or the disappearance of a dominant paradigm occurs as a cost in DM or an innovation probability in SM increases. In addition, we also investigate how the propagation processes affect the transition nature. From analytical calculations and numerical simulations is shown to satisfy the scaling relation for DM with the number of agents . In contrast, in SM scales as . PMID:23951043

  1. Dimensional phase transition in small Yukawa clusters

    SciTech Connect

    Sheridan, T. E.; Wells, K. D. [Department of Physics and Astronomy, Ohio Northern University, Ada, Ohio 45810 (United States)

    2010-01-15

    We investigate the one- to two-dimensional zigzag transition in clusters consisting of a small number of particles interacting through a Yukawa (Debye) potential and confined in a two-dimensional biharmonic potential well. Dusty (complex) plasma clusters with n<=19 monodisperse particles are characterized experimentally for two different confining wells. The well anisotropy is accurately measured, and the Debye shielding parameter is determined from the longitudinal breathing frequency. Debye shielding is shown to be important. A model for this system is used to predict equilibrium particle configurations. The experiment and model exhibit excellent agreement. The critical value of n for the zigzag transition is found to be less than that predicted for an unshielded Coulomb interaction. The zigzag transition is shown to behave as a continuous phase transition from a one-dimensional to a two-dimensional state, where the state variables are the number of particles, the well anisotropy and the Debye shielding parameter. A universal critical exponent for the zigzag transition is identified for transitions caused by varying the Debye shielding parameter.

  2. Transport, phase transitions, and wetting in micro/nanochannels: a phase field/DDFT approach.

    PubMed

    Mickel, Walter; Joly, Laurent; Biben, Thierry

    2011-03-01

    While the flow of a liquid in a macroscopic channel is usually described using hydrodynamics with no-slip boundary conditions at the walls of the channel, transport phenomena in microchannels involve physics at many different scales due to the interplay between the micrometric section of the channel and the micro- or nanometric roughness of the boundaries. Roughness can have many different effects such as increasing the friction between the liquid and the walls (leading to the macroscopic no-slip boundary condition) or on the contrary reduce it thanks to the Wenzel-Cassie-Baxter wetting transition induced by capillarity. Here we detail a phase-field/dynamic density functional theory model able to account for the wetting transitions, the resulting friction between the wall and the fluid, and compressible hydrodynamics at high viscosity contrast. PMID:21384948

  3. Phase liquid turbulence as novel quantum approach

    E-print Network

    Sergey Kamenshchikov

    2015-03-03

    In this paper we consider a nonlinear stochastic approach to the description of quantum systems. It is shown that a possibility to derive quantum properties - spectrum quantization, zero point positive energy and uncertainty relations, exists in frame of Zaslavsky phase liquid. This liquid is considered as a projection of continuous turbulent medium into a Hilbert phase space.It has isotropic minimal diffusion defined by Planck constant.Areas of probability condensation may produce clustering centers: quasi stable particles-attractors which preserve boundaries and scale-free fractal transport properties.The stability of particles has been shown in frame of the first order perturbation theory. Quantum peculiarities of considered systems have been strictly derived from markovian Fokker-Planck equation. It turned out that the positive zero point energy has volumetric properties and grows for higher time resolutions. We have shown that a quasi stable attractor may be applied as a satisfactory model of an elementary quantum system. The conditions of attractor stability are defined on the basis of Nonlinear Prigogine Theorem. Finally the integrity of classical and quantum approaches is recovered: existence of particles is derived in terms of Zaslavsky quantum fluid.

  4. Investigating polaron phase transitions with polar molecules

    E-print Network

    Herrera, Felipe; Krems, Roman V; Berciu, Mona

    2013-01-01

    We determine the phase diagram of a polaron model with mixed breathing-mode and Su-Schrieffer-Heeger couplings and show that it has two sharp transitions, in contrast to pure models which exhibit one (for Su-Schrieffer-Heeger coupling) or no (for breathing-mode coupling) transition. Our results indicate that the physics of realistic mixed polaron models is much richer than that of simplified models. We then show that ultracold molecules trapped in optical lattices can be used to study precisely this mixed Hamiltonian, and that the relative contributions of the two couplings can be tuned with external electric fields. The parameters of current experimental set-ups place them in the region where one of the transitions occurs. We propose a scheme to measure the polaron dispersion using stimulated Raman spectroscopy.

  5. Dynamical quantum phase transitions: scaling and universality

    E-print Network

    Markus Heyl

    2015-05-10

    Dynamical quantum phase transitions (DQPTs) at critical times appear as non-analyticities during nonequilibrium quantum real-time evolution. Although there is evidence for a close relationship between DQPTs and equilibrium phase transitions, a major challenge is still to connect to fundamental concepts such as scaling and universality. In this work, renormalization group transformations in complex parameter space are formulated for quantum quenches in Ising models showing that the DQPTs are critical points associated with unstable fixed points of equilibrium Ising models. Therefore, these DQPTs obey scaling and universality. On the basis of numerical simulations, signatures of these DQPTs in the dynamical buildup of spin correlations are found with an associated power-law scaling determined solely by the fixed point's universality class. An outlook is given on how to explore this dynamical scaling experimentally in systems of trapped ions.

  6. A compressible mixture model with phase transition

    NASA Astrophysics Data System (ADS)

    Dreyer, Wolfgang; Giesselmann, Jan; Kraus, Christiane

    2014-04-01

    We introduce a new thermodynamically consistent diffuse interface model of Allen-Cahn/Navier-Stokes type for multi-component flows with phase transitions and chemical reactions. For the introduced diffuse interface model, we investigate physically admissible sharp interface limits by matched asymptotic techniques. We consider two scaling regimes, i.e. a non-dissipative and a dissipative regime, where we recover in the sharp interface limit a generalized Allen-Cahn/Euler system for mixtures with chemical reactions in the bulk phases equipped with admissible interfacial conditions. The interfacial conditions satisfy, for instance, a Young-Laplace and a Stefan type law.

  7. Topological phase transition in a discrete quasicrystal.

    PubMed

    Sagi, Eran; Eisenberg, Eli

    2014-07-01

    We investigate a two-dimensional tiling model. Even though the degrees of freedom in this model are discrete, it has a hidden continuous global symmetry in the infinite lattice limit, whose corresponding Goldstone modes are the quasicrystalline phasonic degrees of freedom. We show that due to this continuous symmetry and despite the apparent discrete nature of the model, a topological phase transition from a quasi-long-range ordered to a disordered phase occurs at a finite temperature, driven by vortex proliferation. We argue that some of the results are universal properties of two-dimensional systems whose ground state is a quasicrystalline state. PMID:25122249

  8. Topological phase transition in a discrete quasicrystal

    NASA Astrophysics Data System (ADS)

    Sagi, Eran; Eisenberg, Eli

    2014-07-01

    We investigate a two-dimensional tiling model. Even though the degrees of freedom in this model are discrete, it has a hidden continuous global symmetry in the infinite lattice limit, whose corresponding Goldstone modes are the quasicrystalline phasonic degrees of freedom. We show that due to this continuous symmetry and despite the apparent discrete nature of the model, a topological phase transition from a quasi-long-range ordered to a disordered phase occurs at a finite temperature, driven by vortex proliferation. We argue that some of the results are universal properties of two-dimensional systems whose ground state is a quasicrystalline state.

  9. correlation effects in topological phase transitions

    NASA Astrophysics Data System (ADS)

    Hung, Hsiang-Hsuan; Chua, Victor; Wang, Lei; Fiete, Gregory

    2014-03-01

    We study topological insulators/trivial insulators topological phase transitions in the Kane-Mele-Hubbard model using the projective quantum Monte Carlo method. We numerically compute the topological invariants and study topological phase transitions under correlation. We find that quantum fluctuation effects from interactions can act both to stabilize and destabilize topological phases, depending on the details of the model. When the one-body terms break the lattice symmetry, e.g. bond dimerization breaks the rotational symmetry in the Kane-Mele model, the Hubbard interaction destabilizes the topological insulator phase. On the other hand, when the one-body terms (e.g. the third-nearest neighbor hopping) preserves the lattice symmetry, the interaction stabilizes the topological phase. This work was supported by ARO Grant No. W911NF- 09-1-0527, NSF Grant No. DMR-0955778, and by grant W911NF-12-1-0573 from the Army Research Office with funding from the DARPA OLE Program.

  10. Molecular Simulation of Henry's Constant at Vapor-Liquid and Liquid-Liquid Phase Richard J. Sadus

    E-print Network

    Molecular Simulation of Henry's Constant at Vapor-Liquid and Liquid-Liquid Phase Boundaries Richard to determine Henry's constant from the residual chemical potential at infinite dilution at the vapor-liquid coexistence. 1. Introduction Henry's constant is a well-known measure of a solute's solubility in a particular

  11. An improved model for the transit entropy of monatomic liquids

    SciTech Connect

    Wallace, Duane C [Los Alamos National Laboratory; Chisolm, Eric D [Los Alamos National Laboratory; Bock, Nicolas [Los Alamos National Laboratory

    2009-01-01

    In the original formulation of V-T theory for monatomic liquid dynamics, the transit contribution to entropy was taken to be a universal constant, calibrated to the constant-volume entropy of melting. This model suffers two deficiencies: (a) it does not account for experimental entropy differences of {+-}2% among elemental liquids, and (b) it implies a value of zero for the transit contribution to internal energy. The purpose of this paper is to correct these deficiencies. To this end, the V-T equation for entropy is fitted to an overall accuracy of {+-}0.1% to the available experimental high temperature entropy data for elemental liquids. The theory contains two nuclear motion contributions: (a) the dominant vibrational contribution S{sub vib}(T/{theta}{sub 0}), where T is temperature and {theta}{sub 0} is the vibrational characteristic temperature, and (b) the transit contribution S{sub tr}(T/{theta}{sub tr}), where {theta}{sub tr} is a scaling temperature for each liquid. The appearance of a common functional form of S{sub tr} for all the liquids studied is a property of the experimental data, when analyzed via the V-T formula. The resulting S{sub tr} implies the correct transit contribution to internal energy. The theoretical entropy of melting is derived, in a single formula applying to normal and anomalous melting alike. An ab initio calculation of {theta}{sub 0}, based on density functional theory, is reported for liquid Na and Cu. Comparison of these calculations with the above analysis of experimental entropy data provides verification of V-T theory. In view of the present results, techniques currently being applied in ab initio simulations of liquid properties can be employed to advantage in the further testing and development of V-T theory.

  12. PIV measurements in a liquid–liquid system at volume percentages up to 10% dispersed phase

    Microsoft Academic Search

    Fredrik J. E. Svensson; Anders Rasmuson

    2006-01-01

    In this study the effect of the volume percentage dispersed phase on the flow structure in an immiscible liquid–liquid system is investigated. A model system, consisting of two refraction index matched liquids, is presented along with velocity measurements of the continuous phase utilising the particle image velocimetry technique. Velocity fields at three locations have been measured inside a baffled cylindrical

  13. Matrix Product States and Quantum Phase Transitions

    E-print Network

    K. Heshami; S. Raeisi

    2009-09-16

    We have developed a new approach based on matrix product representations of ground states to study Quantum Phase Transitions (QPT). As confirmation of the power of our approach we have analytically analyzed the XXZ spin-one chain with uniaxial single-ion-type anisotropy and our results compare favourably with previous numerical studies. In addition, our description lets to know which part of parameters space of the Hamiltonian is most likely to be exactly solvable.

  14. Deconfinement phase transition in mirror of symmetries

    Microsoft Academic Search

    M. N. Chernodub; A. Nakamura; V. I. Zakharov

    2011-01-01

    We argue that the deconfinement phase transition in Yang-Mills theories can be viewed as a change of effective non-perturbative\\u000a degrees of freedom and of symmetries of their interactions. In short, the strings in four dimensions (4d) at temperatures\\u000a below the critical temperature T\\u000a c are replaced by particles, or field theories in 3d at T > T\\u000a c. The picture

  15. On Phase Transitions in Coupled Map Lattices

    Microsoft Academic Search

    W. Just; F. Schmüser

    2005-01-01

    Coupled map lattices are a paradigm for studying fundamental questions in spatially extended dynamical systems. Within this\\u000a tutorial we focus on qualitative changes of the motion which are intimately related with the limit of large system size. Similar\\u000a to equilibrium phase transitions, such qualitative changes are an ubiquitous feature of dynamical systems with a large number\\u000a of degrees of freedom.

  16. Nature and measure of entanglement in quantum phase transitions

    NASA Astrophysics Data System (ADS)

    Somma, Rolando; Ortiz, Gerardo; Barnum, Howard; Knill, Emanuel; Viola, Lorenza

    2003-03-01

    Characterizing and quantifying entanglement of quantum states in many-particle systems is at the core of a full understanding of the nature of quantum phase transitions in matter. Entanglement is a relative notion and, although many measures of entanglement have been defined in the literature, assessing the utility of those measures to characterize quantum phase transitions is still an open problem. We introduce a new measure, based on a different concept of entanglement, which allows us to identify the transition. The traditional concept of entanglement refers to the property of many-parties states which cannot be expressed as a product of states of each party. We have recently [1] introduced a different concept of entanglement which makes no reference to the subsystem decomposition of the total Hilbert space and which reduces to the traditional concept in the case of two parties. In our framework an extremal (pure) quantum state is unentangled with respect to an algebra of observables if it induces an extremal state (set of expectation values) on that algebra. This identifies pure unentangled states with generalized coherent states of the algebra (mixed states will be unentangled if they are convex combinations of pure unentangled states). For example, a Slater determinant, i.e., a state of free spinless fermions (Fermi liquid), is unentangled with respect to the algebra generated by the bilinear fermionic operators c^i cj (algebra U(N)) but it is, in general, entangled with respect to the Pauli (spin 1/2) algebra. This concept leads to the definition of a "Purity" relative to a given subalgebra as a measure of entanglement. We will show how this measure applies to the study of different types of phase transitions. In particular, we will apply this concept to Ising-like and Kosterlitz-Thouless transitions in models of interest in condensed matter physics. [1] H. Barnum, E. Knill, G. Ortiz, and L. Viola (2002), quant-ph/0207149.

  17. Modeling the Polydomain–Monodomain transition of Liquid Crystal Elastomers

    PubMed Central

    Whitmer, Jonathan K.; Roberts, Tyler F.; Shekhar, Raj; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-01-01

    We study the mechanism of the polydomain–monodomain transition in liquid crystalline elastomers at the molecular scale. A coarse-grained model is proposed in which mesogens are described as ellipsoidal particles. Molecular dynamics simulations are used to examine the transition from a polydomain state to a monodomain state in the presence of uniaxial strain. Our model demonstrates soft elasticity, similar to that exhibited by side-chain elastomers in the literature. By analysing the growth dynamics of nematic domains during uniaxial extension, we provide direct evidence that at a molecular level the polydomain–monodomain transition proceeds through cluster rotation and domain growth. PMID:23496448

  18. Liquid-phase separation in glass-forming systems

    Microsoft Academic Search

    P. F. James

    1975-01-01

    This review is concerned with the process of liquid-phase separation in glass-forming systems. In the first part a general account of phase equilibria is presented together with a discussion of the thermodynamic behaviour of systems exhibiting liquid-liquid immiscibility. The estimation of free energies from phase-boundary data and the location of the spinodal boundary are briefly considered. The origin of immiscibility

  19. Fixed volume versus fixed pressure liquid-vapor transition

    NASA Astrophysics Data System (ADS)

    Calecki, D.; Lederer, D.; Roulet, B.; Diu, B.; Guthmann, C.

    2010-12-01

    We consider the equilibrium conditions for nucleation at the liquid-vapor transition at fixed volume in contrast to the traditional fixed pressure treatment. Significant differences appear, particularly for the stability of the diphasic states, which strongly depends on the external conditions.

  20. Simple theory of transitions between smectic, nematic, and isotropic phases.

    PubMed

    Emelyanenko, A V; Khokhlov, A R

    2015-05-28

    The transitions between smectic, nematic, and isotropic phases are investigated in the framework of a unified molecular-statistical approach. The new translational order parameter is different from the one introduced in K. Kobayashi [Phys. Lett. A 31, 125 (1970)] and W. L. McMillan [Phys. Rev. A 4, 1238 (1971)]. The variance of the square sine of intermolecular shift angle along the director is introduced to take self-consistently into account the most probable location of the molecules with respect to each other, which is unique for every liquid crystal (LC) material and is mainly responsible for the order parameters and phase sequences. The mean molecular field was treated in terms of only two parameters specific to any intermolecular potential of elongated molecules: (1) its global minimum position with respect to the shift of two interacting molecules along the director and (2) its inhomogeneity/anisotropy ratio. A simple molecular model is also introduced, where the global minimum position is determined by the linking groups elongation ?/d, while the inhomogeneity/anisotropy ratio G?/G? is determined by the ratio of electrostatic and dispersion contributions. All possible phase sequences, including abrupt/continuous transformation between the smectic and nematic states and the direct smectic-isotropic phase transition, are predicted. The theoretical prediction is in a good agreement with experimental data for some simple materials correlating with our molecular model, but it is expected to be valid for any LC material. PMID:26026463

  1. Solid-Hexatic-Liquid Transition at Two-Dimensional Melting of Plasma-Dust Monolayer

    NASA Astrophysics Data System (ADS)

    Petrov, Oleg; Vasiliev, Mikhail; Tun, Ye; Stacenko, Konstantin; Vaulina, Olga; Vasilieva, Elena; Lisin, Evgeny; Myasnikov, Maxim; Fortov, Vladimir

    2014-10-01

    According to the Berezinskii-Kosterlitz-Thouless (BKT) theory based on unbinding of topological defects (dislocations and disclinations), the 2D system supports a two-stage transition from a crystal phase to a liquid state of a system via the formation of the intermediate, hexatic phase. Here we present new results of an experimental study of the change of translational and orientational order and topological defects, the excess of entropy and the pair interactions at 2D melting of dust monolayer in rf discharge plasma. The experimental results have revealed the existence of hexatic phase as well as solid-to-hexatic phase and hexatic-to-liquid transitions. The pair correlation and bond-angular correlation functions, the number of topological defects, the pair potentials and the excess entropy are measured and analyzed. The bond-orientational correlation functions show a clear solid-to-hexatic-to-fluid transition, in perfect agreement with the BKT theory. The spatial distribution of pair interparticle interaction forces was recovered by the original method based on solving the inverse problem using Langevin equations. The measured phase-state points with the theoretical phase diagram of two-dimensional Yukawa system have been obtained. This work was partially supported by the Russian Foundation for Basic Research (Projects No. 13-02-01393 and 13-02-12256) and by the Program of the Presidium of RAS ``Matter under High Energy Densities.''

  2. The puzzling first-order phase transition in water-glycerol mixtures.

    PubMed

    Popov, Ivan; Greenbaum Gutina, Anna; Sokolov, Alexei P; Feldman, Yuri

    2015-07-21

    Over the last decade, discussions on a possible liquid-liquid transition (LLT) have strongly intensified. The LLT proposed by several authors focused mostly on explaining the anomalous properties of water in a deeply supercooled state. However, there have been no direct experimental observations yet of LLT in bulk water in the so-called 'no man's land', where water exists only in the crystalline states. Recently, a novel experimental strategy to detect LLT in water has been employed using water-glycerol (W-G) mixtures, because glycerol can generate a strong hindrance for water crystallization. As a result, the observed first-order phase transition at a concentration of glycerol around cg? 20 mol% was ascribed to the LLT. Here we show unambiguously that the first order phase transition in W-G mixtures is caused by the ice formation. We provide additional dielectric measurements, applying specific annealing temperature protocols in order to reinforce this conclusion. We also provide an explanation, why such a phase transition occurs only in the narrow glycerol concentration range. These results clearly demonstrate the danger of analysis of phase-separating liquids to gain better insights into water dynamics. These liquids have complex phase behavior that is affected by temperature, phase stability and segregation, viscosity and nucleation, and finally by crystallization, that might lead to significant misinterpretations. PMID:26100246

  3. Nonequilibrium thermodynamic fluctuations and phase transition in black holes

    SciTech Connect

    Su, R. (China Center of Advanced Science and Technology (World Laboratory), P.O. Box 8730, Beijing, People's Republic of China and Department of Physics, Fudan University, Shanghai 200433 (China)); Cai, R. (Department of Physics, Fudan University, Shanghai 200433 (China)); Yu, P.K.N. (Department of Physics and Materials Science, City Polytechnic of Hong Kong, Kowloon Tong, Kowloon (Hong Kong))

    1994-08-15

    Landau nonequilibrium fluctuation and phase transition theory is applied to the discussion of the phase transition of black holes. Some second moments of relevant thermodynamical quantities for Kerr-Newman black holes are estimated. A theorem governing the divergence of some second moments and the occurrence of the phase transition in black holes is given.

  4. Phases and phase transitions in a dipolar ferromagnetic spinor gas

    NASA Astrophysics Data System (ADS)

    Stamper-Kurn, Dan

    2008-05-01

    In the regime of quantum degeneracy, a gas of spin-1 rubidium atoms is predicted to become simultaneously superfluid and magnetically ordered. We have studied such a gas using dispersive imaging to measure the complete vector magnetization in situ. I will present three main findings from our work. First, we have studied the dynamics of a gas that is suddenly quenched across a symmetry-breaking phase transition, characterizing the spectrum of dynamic instabilities and quantifying the symmetry-breaking seed that is predicted to arise due to quantum spin fluctuations. Second, we have ascertained that magnetic dipole interactions are an important influence on this spin-1 gas. Third, we have explored the equilibrium phase diagram for this gas, finding that a robust inhomogeneous but spatially structured spin texture arises in steady state below the apparent Bose-Einstein condensation transition temperature.

  5. Transient liquid phase bonding of intermetallics

    NASA Astrophysics Data System (ADS)

    Guan, Yimin

    The present work was undertaken to examine the applicability of transient liquid phase bonding to structural intermetallics. This research was based on an investigation of the mechanisms governing microstructural development in the joint and adjacent substrates during the joining process. The bonding systems investigated included polycrystalline NiAl/Cu/Ni, polycrystalline NiAl/Cu/superalloys (Martin-Marietta (MM)-247, Inconel (IN) 718 and Nimonic 90), single-crystal NiAl (with 1.5 at % Hf) joined to MM-247 using different filler metals (Cu foil, powder filler metal and electro-plated thin Cu film), and martensitic NiAl joined with martensitic NiTi using Cu foil and specially designed powder filler metals. In polycrystalline NiAl/Cu/Ni bonds, the mechanism of isothermal solidification is considered. Changes in the microstructure of the bond centerline due to element redistribution are discussed. The precipitation of both L1sb2 type gammasp' and B2 type beta phase at the joint centerline is investigated. The formation of martensitic L1sb0 type NiAl is also examined. The mechanical properties of the joints are investigated using shear strength and microhardness tests. In TLP bonding of polycrystalline NiAl with MM-247, both the epitaxial growth of the beta phase NiAl into the joint and the formation of non-epitaxial beta-phase layers are considered. The formation of second-phases, including the gammasp' phase, carbides, and sigma-phase intermetallics is also examined. Bond-line and adjacent substrate microstructures for the NiAl/Cu/MM-247 bonds are correlated with joint mechanical properties determined by room temperature shear testing. Single-crystal NiAl (1.5 at % Hf)/Cu/MM-247 joints are examined and compared with polycrystalline NiAl/Cu/MM247 joints. The effect of Hf on the microstructure of joints is investigated. The influence of different filler metals (i.e., wide-gap powder filler metal and electro-plated thin film filler metal) on the joining process is also considered. In TLP bonding of martensitic NiAl with martensitic NiTi, the formation Ti depletion region was observed while using Cu foil as the filler metal. Alternative filler metals were successfully used to solve this problem. According to the experimental results, standard TLP bonding models cannot be applied to the bonding systems in this research. The influence of second phase formation on TLP models is discussed.

  6. Phase transitions and size scaling of membrane-less organelles

    PubMed Central

    2013-01-01

    The coordinated growth of cells and their organelles is a fundamental and poorly understood problem, with implications for processes ranging from embryonic development to oncogenesis. Recent experiments have shed light on the cell size–dependent assembly of membrane-less cytoplasmic and nucleoplasmic structures, including ribonucleoprotein (RNP) granules and other intracellular bodies. Many of these structures behave as condensed liquid-like phases of the cytoplasm/nucleoplasm. The phase transitions that appear to govern their assembly exhibit an intrinsic dependence on cell size, and may explain the size scaling reported for a number of structures. This size scaling could, in turn, play a role in cell growth and size control. PMID:24368804

  7. Study of cerium phase transitions in shock wave experiments

    SciTech Connect

    Zhernokletov, M. V., E-mail: root@gdd.vniief.ru; Kovalev, A. E.; Komissarov, V. V.; Novikov, M. G. [All-Russia Research Institute of Experimental Physics (VNIIEF), Russian Federal Nuclear Center (Russian Federation); Zocher, M. A., E-mail: zocher@lanl.gov; Cherne, F. J., E-mail: cherne@lanl.gov [Los Alamos National Laboratory (United States)

    2011-02-15

    Cerium has a complex phase diagram that is explained by the presence of structural phase transitions. Experiments to measure the sound velocities in cerium by two methods were carried out to determine the onset of cerium melting on the Hugoniot. In the pressure range 4-37 GPa, the sound velocity in cerium samples was measured by the counter release method using manganin-based piezoresistive gauges. In the pressure range 35-140 GPa, the sound velocity in cerium was measured by the overtaking release method using carbogal and tetrachloromethane indicator liquids. The samples were loaded with plane shock wave generators using powerful explosive charges. The onset of cerium melting on the Hugoniot at a pressure of about 13 GPa has been ascertained from the measured elastic longitudinal and bulk sound velocities.

  8. Study of cerium phase transitions in shock wave experiments

    NASA Astrophysics Data System (ADS)

    Zhernokletov, M. V.; Kovalev, A. E.; Komissarov, V. V.; Novikov, M. G.; Zocher, M. A.; Cherne, F. J.

    2011-02-01

    Cerium has a complex phase diagram that is explained by the presence of structural phase transitions. Experiments to measure the sound velocities in cerium by two methods were carried out to determine the onset of cerium melting on the Hugoniot. In the pressure range 4-37 GPa, the sound velocity in cerium samples was measured by the counter release method using manganin-based piezoresistive gauges. In the pressure range 35-140 GPa, the sound velocity in cerium was measured by the overtaking release method using carbogal and tetrachloromethane indicator liquids. The samples were loaded with plane shock wave generators using powerful explosive charges. The onset of cerium melting on the Hugoniot at a pressure of about 13 GPa has been ascertained from the measured elastic longitudinal and bulk sound velocities.

  9. Phase Transition of High Carbon Steel Demonstration

    NSDL National Science Digital Library

    The Materials Science and Technology Teacher's Workshop (MAST) provides this demonstration on the phase transition of high carbon steel. The crystalline structure of iron is different at different temperatures, and high-carbon steel alloys undergo a transformation from BCC to FCC in a very small temperature range. An interesting application of this theory is in determining the maximum temperature to which a piece of steel has been heated before it changes phases. In this module, a piece of piano wire is heated and phase changes are observed through the changes in length and magnetic properties of the wire.The lesson includes a step by step explanation of the laboratory procedure. Discussion questions are also included.

  10. CARBON DIOXIDE SEPARATION BY PHASE ENHANCED GAS-LIQUID ABSORPTION

    SciTech Connect

    Liang Hu

    2004-09-30

    A new process called phase enhanced gas-liquid absorption has been developed in its early stage. It was found that adding another phase into the absorption system of gas/aqueous phase could enhance the absorption rate. A system with three phases was studied. In the system, gas phase was carbon dioxide. Two liquid phases were used. One was organic phase. Another was aqueous phase. By addition of organic phase into the absorption system of CO{sub 2}-aqueous phase, the absorption rate of CO{sub 2} was increased significantly. CO{sub 2} finally accumulated into aqueous phase. The experimental results proved that (1) Absorption rate of carbon dioxide was enhanced by adding organic phase into gas aqueous phase system; (2) Organic phase played the role of transportation of gas solute (CO{sub 2}). Carbon dioxide finally accumulated into aqueous phase.

  11. Epigenetics and locust life phase transitions.

    PubMed

    Ernst, Ulrich R; Van Hiel, Matthias B; Depuydt, Geert; Boerjan, Bart; De Loof, Arnold; Schoofs, Liliane

    2015-01-01

    Insects are one of the most successful classes on Earth, reflected in an enormous species richness and diversity. Arguably, this success is partly due to the high degree to which polyphenism, where one genotype gives rise to more than one phenotype, is exploited by many of its species. In social insects, for instance, larval diet influences the development into distinct castes; and locust polyphenism has tricked researchers for years into believing that the drastically different solitarious and gregarious phases might be different species. Solitarious locusts behave much as common grasshoppers. However, they are notorious for forming vast, devastating swarms upon crowding. These gregarious animals are shorter lived, less fecund and transmit their phase characteristics to their offspring. The behavioural gregarisation occurs within hours, yet the full display of gregarious characters takes several generations, as does the reversal to the solitarious phase. Hormones, neuropeptides and neurotransmitters influence some of the phase traits; however, none of the suggested mechanisms can account for all the observed differences, notably imprinting effects on longevity and fecundity. This is why, more recently, epigenetics has caught the interest of the polyphenism field. Accumulating evidence points towards a role for epigenetic regulation in locust phase polyphenism. This is corroborated in the economically important locust species Locusta migratoria and Schistocerca gregaria. Here, we review the key elements involved in phase transition in locusts and possible epigenetic regulation. We discuss the relative role of DNA methylation, histone modification and small RNA molecules, and suggest future research directions. PMID:25568455

  12. Transitional Bubble in Periodic Flow Phase Shift

    NASA Technical Reports Server (NTRS)

    Talan, M.; Hourmouziadis, Jean

    2004-01-01

    One particular characteristic observed in unsteady shear layers is the phase shift relative to the main flow. In attached boundary layers this will have an effect both on the instantaneous skin friction and heat transfer. In separation bubbles the contribution to the drag is dominated by the pressure distribution. However, the most significant effect appears to be the phase shift on the transition process. Unsteady transition behaviour may determine the bursting of the bubble resulting in an un-recoverable full separation. An early analysis of the phase shift was performed by Stokes for the incompressible boundary layer of an oscillating wall and an oscillating main flow. An amplitude overshoot within the shear layer as well as a phase shift were observed that can be attributed to the relatively slow diffusion of viscous stresses compared to the fast change of pressure. Experiments in a low speed facility with the boundary layer of a flat plate were evaluated in respect to phase shift. A pressure distribution similar to that on the suction surface of a turbomachinery aerofoil was superimposed generating a typical transitional separation bubble. A periodically unsteady main flow in the suction type wind tunnel was introduced via a rotating flap downstream of the test section. The experiments covered a range of the three similarity parameters of momentum-loss-thickness Reynolds-number of 92 to 226 and Strouhal-number (reduced frequency) of 0.0001 to 0.0004 at the separation point, and an amplitude range up to 19 %. The free stream turbulence level was less than 1% .Upstream of the separation point the phase shift in the laminar boundary layer does not appear to be affected significantly bay either of the three parameters. The trend perpendicular to the wall is similar to the Stokes analysis. The problem scales well with the wave velocity introduced by Stokes, however, the lag of the main flow near the wall is less than indicated analytically. The separation point comes closest to the Stokes analysis but the phase is still 20 degrees lower at the wall.

  13. Hygroscopic Influence on the Semisolid-to-Liquid Transition of Secondary Organic Materials.

    PubMed

    Bateman, Adam P; Bertram, Allan K; Martin, Scot T

    2015-05-14

    The effect of relative humidity (RH) on the rebound of particles composed of isoprene, ?-pinene, and toluene secondary organic materials (SOMs) was studied. A three-arm impaction apparatus was used to study rebound from 5 to 95% RH at 298 K. Calibration experiments using sucrose particles of variable but known viscosities showed that the transition from rebounding to adhering particles occurred for a change in viscosity from 100 to 1 Pa s, corresponding to a transition from semisolid to liquid material. The experimentally determined rebound fractions of the studied SOMs were compared with results from a model of the rebound processes of hard particles, taking into account the particle kinetic energy, van der Waals forces, and RH-dependent capillary forces. For low RH values, the hard-particle model explained the diameter-dependent rebound behavior for all studied SOMs. For elevated RH, however, the experimental observations deviated from the model predictions. On the basis of the calibration experiments using sucrose particles as well as a comparison between the observations and the predictions of the hard-particle model, the interpretation is made that a semisolid-to-liquid transition occurred at elevated RH. Material softening, increased adhesion, or a combination of the two implied the action of additional modes of energy relaxation that were not included in the hard-particle model. The RH threshold for the semisolid-to-liquid phase transition was 40% RH for isoprene SOM, 70% for toluene SOM, and 70% for ?-pinene SOM. A correlation between the rebound fraction and the hygroscopic growth factor G was demonstrated, implying that absorbed water volume was a dominant governing factor of the semisolid-to-liquid transition for the studied classes of SOM. Simple heuristic rules based on G of 1.15 for the semisolid-to-liquid phase transition could be used for prognostication of the SOM phase in modeling applications at 298 K. With respect to atmospheric processes, the findings of this study suggest that both the chemical composition and the RH influence the phase state of organic particles. The findings can explain reports of solid organic particles for terpene-dominant conditions of a boreal forest at low RH compared to reports of liquid organic particles for isoprene-dominant tropical forests at high RH. PMID:25397730

  14. Magnetoelastic effects on antiferromagnetic phase transitions (invited)

    SciTech Connect

    Wolf, W.P.; Huan, C.H.A.

    1988-04-15

    The effect of elastic strains on antiferromagnetic phase transitions is considered. For cases in which the magnetic and chemical unit cells coincide, the combination of a strain and an applied field is found to lead to the possibility of a linear magnetoelastic (LME) coupling which may induce antiferromagnetic order, even in the normally paramagnetic phase. Such an effect can, in principle, destroy any second-order phase transition. An order of magnitude estimate shows that the effect is small but not negligible, and that it may explain a number of unusual effects observed in dysprosium aluminum garnet, including anomalous neutron scattering, magnetic hysteresis and magnetostriction. Similar strain-induced effects may be important in many other antiferromagnets, including CoF/sub 2/, FeF/sub 2/, MnF/sub 2/, and ..cap alpha..Fe/sub 2/O/sub 3/, as well as in mixed crystals with the same structures. Strain gradients may produce similar effects in other antiferromagnets which are magnetoelectric, including DyPO/sub 4/, DyAlO/sub 3/, and Cr/sub 2/O/sub 3/.

  15. Topological Phase Transition without Gap Closing

    PubMed Central

    Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

    2013-01-01

    Topological phase transition is accompanied with a change of topological numbers. According to the bulk-edge correspondence, the gap closing and the breakdown of the adiabaticity are necessary at the phase transition point to make the topological number ill-defined. However, the gap closing is not always needed. In this paper, we show that two topological distinct phases can be continuously connected without gap closing, provided the symmetry of the system changes during the process. Here we propose the generic principles how this is possible by demonstrating various examples such as 1D polyacetylene with the charge-density-wave order, 2D silicene with the antiferromagnetic order, 2D silicene or quantum well made of HgTe with superconducting proximity effects and 3D superconductor Cu doped Bi2Se3. It is argued that such an unusual phenomenon can occur when we detour around the gap closing point provided the connection of the topological numbers is lost along the detour path. PMID:24071900

  16. Topological phase transition without gap closing.

    PubMed

    Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

    2013-01-01

    Topological phase transition is accompanied with a change of topological numbers. According to the bulk-edge correspondence, the gap closing and the breakdown of the adiabaticity are necessary at the phase transition point to make the topological number ill-defined. However, the gap closing is not always needed. In this paper, we show that two topological distinct phases can be continuously connected without gap closing, provided the symmetry of the system changes during the process. Here we propose the generic principles how this is possible by demonstrating various examples such as 1D polyacetylene with the charge-density-wave order, 2D silicene with the antiferromagnetic order, 2D silicene or quantum well made of HgTe with superconducting proximity effects and 3D superconductor Cu doped Bi2Se3. It is argued that such an unusual phenomenon can occur when we detour around the gap closing point provided the connection of the topological numbers is lost along the detour path. PMID:24071900

  17. Stochastic resonance at nonequilibrium phase transitions

    NASA Astrophysics Data System (ADS)

    Skokov, V. N.; Koverda, V. P.; Vinogradov, A. V.; Reshetnikov, A. V.

    2015-07-01

    Thermal pulsations in a transition from a nucleate to a film regime of water boiling on a wire heater with a periodic Joule heat release have been studied experimentally. At frequencies of the periodic action smaller than 0.1 Hz the intermittency of the nucleate and film boiling regimes was observed. In this case the amplitude of thermal pulsations increased. The experiments with an additional noise source were carried out. With an increase in the intensity of the noise the power of the output periodic mode increased and reaching the maximum began to decrease. The results are interpreted as stochastic resonance when the periodic component of pulsations increases in the presence of noise. The results show that in a complex system with nonequilibrium phase transitions there can occur both the extreme fluctuations with 1 / f power spectrum and stochastic resonance under external periodic action.

  18. On the transition between two-phase and single-phase interface dynamics in multicomponent fluids at supercritical pressures

    NASA Astrophysics Data System (ADS)

    Dahms, Rainer N.; Oefelein, Joseph C.

    2013-09-01

    A theory that explains the operating pressures where liquid injection processes transition from exhibiting classical two-phase spray atomization phenomena to single-phase diffusion-dominated mixing is presented. Imaging from a variety of experiments have long shown that under certain conditions, typically when the pressure of the working fluid exceeds the thermodynamic critical pressure of the liquid phase, the presence of discrete two-phase flow processes become diminished. Instead, the classical gas-liquid interface is replaced by diffusion-dominated mixing. When and how this transition occurs, however, is not well understood. Modern theory still lacks a physically based model to quantify this transition and the precise mechanisms that lead to it. In this paper, we derive a new model that explains how the transition occurs in multicomponent fluids and present a detailed analysis to quantify it. The model applies a detailed property evaluation scheme based on a modified 32-term Benedict-Webb-Rubin equation of state that accounts for the relevant real-fluid thermodynamic and transport properties of the multicomponent system. This framework is combined with Linear Gradient Theory, which describes the detailed molecular structure of the vapor-liquid interface region. Our analysis reveals that the two-phase interface breaks down not necessarily due to vanishing surface tension forces, but due to thickened interfaces at high subcritical temperatures coupled with an inherent reduction of the mean free molecular path. At a certain point, the combination of reduced surface tension, the thicker interface, and reduced mean free molecular path enter the continuum length scale regime. When this occurs, inter-molecular forces approach that of the multicomponent continuum where transport processes dominate across the interfacial region. This leads to a continuous phase transition from compressed liquid to supercritical mixture states. Based on this theory, a regime diagram for liquid injection is developed that quantifies the conditions under which classical sprays transition to dense-fluid jets. It is shown that the chamber pressure required to support diffusion-dominated mixing dynamics depends on the composition and temperature of the injected liquid and ambient gas. To illustrate the method and analysis, we use conditions typical of diesel engine injection. We also present a companion set of high-speed images to provide experimental validation of the presented theory. The basic theory is quite general and applies to a wide range of modern propulsion and power systems such as liquid rockets, gas turbines, and reciprocating engines. Interestingly, the regime diagram associated with diesel engine injection suggests that classical spray phenomena at typical injection conditions do not occur.

  19. 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

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

    E-print Network

    Dennis P. Clougherty

    2006-02-01

    It is demonstrated that under common conditions a molecular solid subject to Jahn-Teller interactions supports stable Q-ball-like non-topological 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 pseudo-rotation 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.

  1. Swarms, phase transitions, and collective intelligence

    SciTech Connect

    Millonas, M.M. [Texas Univ., Austin, TX (United States). Dept. of Physics

    1992-12-31

    A model of the collective behavior of a large number of locally acting organisms is proposed. The model is intended to be realistic, but turns out to fit naturally into the category of connectionist models, Like all connectionist models, its properties can be divided into the categories of structure, dynamics, and learning. The space in which the organisms move is discretized, and is modeled by a lattice of nodes, or cells. Each cell hag a specified volume, and is connected to other cells in the space in a definite way. Organisms move probabilistically between local cells in this space, but with weights dependent on local morphogenic substances, or morphogens. The morphogens are in turn are effected by the passage of an organism. The evolution of the morphogens, and the corresponding constitutes of the organisms constitutes the collective behavior of the group. The generic properties of such systems are analyzed, and a number of results are obtained. The model has various types of phase transitions and self-organizing properties controlled both by the level of the noise, and other parameters. It is hoped that the present mode; might serve as a paradigmatic example of a complex cooperative system in nature. In particular this model can be used to explore the relation of phase transitions to at least three important issues encountered in artificial life. Firstly, that of emergence as complex adaptive behavior. Secondly, as an exploration of second order phase transitions in biological systems. Lastly, to derive behavioral criteria for the evolution of collective behavior in social organisms. The model is then applied to the specific case of ants moving on a lattice. The local behavior of the ants is inspired by the actual behavior observed in the laboratory, and analytic results for the collective behavior are compared to the corresponding laboratory results. Monte carlo simulations are used as illustrations.

  2. Swarms, phase transitions, and collective intelligence

    SciTech Connect

    Millonas, M.M. (Texas Univ., Austin, TX (United States). Dept. of Physics)

    1992-01-01

    A model of the collective behavior of a large number of locally acting organisms is proposed. The model is intended to be realistic, but turns out to fit naturally into the category of connectionist models, Like all connectionist models, its properties can be divided into the categories of structure, dynamics, and learning. The space in which the organisms move is discretized, and is modeled by a lattice of nodes, or cells. Each cell hag a specified volume, and is connected to other cells in the space in a definite way. Organisms move probabilistically between local cells in this space, but with weights dependent on local morphogenic substances, or morphogens. The morphogens are in turn are effected by the passage of an organism. The evolution of the morphogens, and the corresponding constitutes of the organisms constitutes the collective behavior of the group. The generic properties of such systems are analyzed, and a number of results are obtained. The model has various types of phase transitions and self-organizing properties controlled both by the level of the noise, and other parameters. It is hoped that the present mode; might serve as a paradigmatic example of a complex cooperative system in nature. In particular this model can be used to explore the relation of phase transitions to at least three important issues encountered in artificial life. Firstly, that of emergence as complex adaptive behavior. Secondly, as an exploration of second order phase transitions in biological systems. Lastly, to derive behavioral criteria for the evolution of collective behavior in social organisms. The model is then applied to the specific case of ants moving on a lattice. The local behavior of the ants is inspired by the actual behavior observed in the laboratory, and analytic results for the collective behavior are compared to the corresponding laboratory results. Monte carlo simulations are used as illustrations.

  3. Phase Stability of Lithiated Transition Metal Oxides

    Microsoft Academic Search

    Alexander I. Landa; Chun-Chieh Chang; Prashant N. Kumta; Levente Vitos; Igor A. Abrikosov

    2002-01-01

    There is significant interest in LiCoO2 and LiMnO2 primarily for use in Li-ion batteries. However LiMnO2 is unstable and a prediction of the structural stability and the phase transitions in the LiMnO_2-LiCoO2 system would be very useful. In this presentation we report the results of the full charge density exact muffin-tin orbital studies conducted on the orthorhombic, monoclinic and rhombohedral

  4. Quasinormal modes and thermodynamic phase transitions

    SciTech Connect

    Berti, Emanuele; Cardoso, Vitor [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States); Centro Multidisciplinar de Astrofisica - CENTRA, Dept. de Fisica, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal) and Dept. of Physics and Astronomy, University of Mississippi, University, Mississippi 38677-1848 (United States)

    2008-04-15

    It has recently been suggested that scalar, Dirac, and Rarita-Schwinger perturbations are related to thermodynamic phase transitions of charged (Reissner-Nordstroem) black holes. In this Brief Report we show that this result is probably a numerical coincidence, and that the conjectured correspondence does not straightforwardly generalize to other metrics, such as Kerr or Schwarzschild (anti-)de Sitter. Our calculations do not rule out a relation between dynamical and thermodynamical properties of black holes, but they suggest that such a relation is nontrivial.

  5. Bound entanglement in quantum phase transitions

    SciTech Connect

    Baghbanzadeh, S.; Alipour, S. [Department of Physics, Sharif University of Technology, Post Office Box 11155-9161, Tehran (Iran, Islamic Republic of); Rezakhani, A. T. [Department of Chemistry and Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, California 90089 (United States)

    2010-04-15

    We investigate quantum phase transitions in which a change in the type of entanglement from bound entanglement to either free entanglement or separability may occur. In particular, we present a theoretical method to construct a class of quantum spin-chain Hamiltonians that exhibit this type of quantum criticality. Given parameter-dependent two-site reduced density matrices (with prescribed entanglement properties), we lay out a reverse construction for a compatible pure state for the whole system, as well as a class of Hamiltonians for which this pure state is a ground state. This construction is illustrated through several examples.

  6. Chiral Phase Transition from String Theory

    SciTech Connect

    Parnachev, Andrei; Sahakyan, David A. [Department of Physics, Rutgers University, Piscataway, New Jersey 08854-8019 (United States)

    2006-09-15

    The low energy dynamics of a certain D-brane configuration in string theory is described at weak t'Hooft coupling by a nonlocal version of the Nambu-Jona-Lasinio model. We study this system at finite temperature and strong t'Hooft coupling, using the string theory dual. We show that for sufficiently low temperatures chiral symmetry is broken, while for temperatures larger then the critical value, it gets restored. We compute the latent heat and observe that the phase transition is of the first order.

  7. Chiral phase transition from string theory.

    PubMed

    Parnachev, Andrei; Sahakyan, David A

    2006-09-15

    The low energy dynamics of a certain D-brane configuration in string theory is described at weak t'Hooft coupling by a nonlocal version of the Nambu-Jona-Lasinio model. We study this system at finite temperature and strong t'Hooft coupling, using the string theory dual. We show that for sufficiently low temperatures chiral symmetry is broken, while for temperatures larger then the critical value, it gets restored. We compute the latent heat and observe that the phase transition is of the first order. PMID:17025875

  8. Quantum Phase Transitions and Bipartite Entanglement

    E-print Network

    Lian-Ao Wu; Marcelo S. Sarandy; Daniel A. Lidar

    2004-12-17

    We develop a general theory of the relation between quantum phase transitions (QPTs) characterized by nonanalyticities in the energy and bipartite entanglement. We derive a functional relation between the matrix elements of two-particle reduced density matrices and the eigenvalues of general two-body Hamiltonians of $d$-level systems. The ground state energy eigenvalue and its derivatives, whose non-analyticity characterizes a QPT, are directly tied to bipartite entanglement measures. We show that first-order QPTs are signalled by density matrix elements themselves and second-order QPTs by the first derivative of density matrix elements. Our general conclusions are illustrated via several quantum spin models.

  9. Is ``metamictization`` of zircon a phase transition?

    SciTech Connect

    Salje, E.K.H.; Chrosch, J. [Univ. of Cambridge (United Kingdom). Dept. of Earth Sciences; Ewing, R.C. [Univ. of Michigan, Ann Arbor, MI (United States)

    1999-07-01

    Metamictization is the transition from the crystalline to an aperiodic or amorphous state due to alpha-decay event damage from constituent radionuclides ({sup 238}U, {sup 235}U, and {sup 232}Th) and their daughters. However, this transformation in minerals is part of a larger class of radiation-induced transformations to the amorphous state that has received considerable recent attention as a result of ion- and electron-beam experiments on metals, intermetallics, simple oxides, and complex ceramics and minerals. Diffuse X-ray scattering from single crystals of metamict zircon reveals residual crystallinity even at high fluences (up to 7.2 {times} 10{sup 18} {alpha}-decay events/g). The experimental evidence does not suggest that radiation-induced amorphization is a phase transition. The observations are in good agreement with a nonconvergent, heterogeneous model of amorphization in which damage production is a random process of cascade formation and overlap at increasing fluence. Instead of an amorphization transition, the existence of a percolation transition is postulated. At the level of radiation damage near the percolation point, the heterogeneous strain broadening of X-ray diffraction profiles is reduced whereas the particle-size broadening increases. Simultaneously, the macroscopic swelling of the zircon becomes larger than the maximum expansion of the unit-cell parameters. A suitable empirical parameter that characterizes this transition is the flux, D{sub s}, at which the macroscopic expansion is identical to the maximum expansion of the crystallographic unit cell. In zircon, D{sub s} = 3.5{center_dot}10{sup 18} {alpha}-decay events/g.

  10. Continuous or catastrophic solid-liquid transition in jammed systems

    NASA Astrophysics Data System (ADS)

    Coussot, P.; Roussel, N.; Jarny, S.; Chanson, H.

    2005-01-01

    Pasty materials encountered in industry and in earth science are intermediate between solids and liquids either in terms of their internal structure (disordered but jammed) or from a mechanical point of view. Our results indicate that the apparent behavior of a particulate system (soils, suspensions, clays, etc.) can range from liquid-like to soil or solid-like depending on the relative importance of the energy supplied to it and its "state of jamming" which evolves in time, and the transition from one state to another may appear either continuous or catastrophic.

  11. Quantum critical phase and Lifshitz transition in an extended periodic Anderson model.

    PubMed

    Laad, M S; Koley, S; Taraphder, A

    2012-06-13

    We study the quantum phase transition in f-electron systems as a quantum Lifshitz transition driven by selective-Mott localization in a realistic extended Anderson lattice model. Using dynamical mean-field theory (DMFT), we find that a quantum critical phase with anomalous ?/T scaling separates a heavy Landau-Fermi liquid from ordered phase(s). This non-Fermi liquid state arises from a lattice orthogonality catastrophe originating from orbital-selective Mott localization. Fermi surface reconstruction occurs via the interplay between and penetration of the Green function zeros to the poles, leading to violation of Luttinger's theorem in the strange metal. We show how this naturally leads to scale-invariant responses in transport. Thus, our work represents a specific DMFT realization of the hidden-FL and FL* theories, and holds promise for the study of 'strange' metal phases in quantum matter. PMID:22589244

  12. Equation of state of nuclear matter in the first order phase transition

    E-print Network

    Toshiki Maruyama; Toshitaka Tatsumi; Satoshi Chiba

    2009-01-13

    We investigate the properties of nuclear matter at the first-order phase transitions (FOPT) such as liquid-gas phase transition, kaon condensation, and hadron-quark phase transition. As a general feature of the FOPT of matter consisting of many species of charged particles, there appears a mixed phases with regular structures called "pasta" due to the balance of the Coulomb repulsion and the surface tension between two phases. The equation of state (EOS) of mixed phase is different from those obtained by a bulk application of Gibbs conditions or by the Maxwell construction due to the effects of the non-uniform structure. We show that the charge screening and strong surface tension make the EOS close to that of the Maxwell construction.

  13. Polyaromatic hydrocarbons do not disturb liquid-liquid phase coexistence, but increase the fluidity of model membranes.

    PubMed

    Liland, Nina S; Simonsen, Adam C; Duelund, Lars; Torstensen, Bente E; Berntssen, Marc H G; Mouritsen, Ole G

    2014-12-01

    Polyaromatic hydrocarbons (PAHs) is a group of compounds, many of which are toxic, formed by incomplete combustion or thermal processing of organic material. They are highly lipophilic and thus present in some seed oils used for human consumption as well as being increasingly common in aquaculture diets due to inclusion of vegetable oils. Cytotoxic effects of PAHs have been thought to be partly due to a membrane perturbing effect of these compounds. A series of studies were here performed to examine the effects of three different PAHs (naphthalene, phenanthrene and benzo[a]pyrene) with different molecular sizes (two, three and five rings, respectively) and fat solubility (Kow 3.29, 4.53 and 6.04, respectively) on membrane models. The effects of PAHs on liquid-liquid phase coexistence in solid-supported lipid bilayers (dioleoylphosphocholine:dipalmitoylphosphatidylcholine:cholesterol) were assessed using fluorescence microscopy. Benzo[a]pyrene had a slight affinity for the liquid-ordered phase, but there were no effects of adding any of the other PAHs on the number or size of the liquid domains (liquid-ordered and liquid-disordered). Benzo[a]pyrene and phenanthrene, but not naphthalene, lowered the transition temperature (Tm) and the enthalpy (?H) characterising the transition from the solid to the liquid-crystalline phase in DPPC vesicles. The membrane effects of the PAH molecules are likely related to size, with bigger and more fat-soluble molecules having a fluidising effect when embedded in the membrane, possibly causing some of the observed toxic effects in fish exposed to these contaminants. PMID:25181555

  14. Phase-Field Method of Phase Transitions/Domain Structures in Ferroelectric Thin Films: A Review

    E-print Network

    Chen, Long-Qing

    phase transitions and domain stability in ferroelectric thin films and superlattices. It is dem the same probability of forming in a parent phase below the ferro- electric transition temperaturePhase-Field Method of Phase Transitions/Domain Structures in Ferroelectric Thin Films: A Review

  15. Fatty-acid monolayers at the nematic/water interface: phases and liquid-crystal alignment.

    PubMed

    Price, Andrew D; Schwartz, Daniel K

    2007-02-01

    The two-dimensional (2D) phases of fatty-acid monolayers (hexadecanoic, octadecanoic, eicosanoic, and docosanoic acids) have been studied at the interface of a nematic liquid crystal (LC) and water. When observed between crossed polarizers, the LC responds to monolayer structure owing to mesoscopic alignment of the LC by the adsorbed molecules. Similar to Langmuir monolayers at the air/water interface, the adsorbed monolayer at the nematic/water interface displays distinct thermodynamic phases. Observed are a 2D gas, isotropic liquid, and two condensed mesophases, each with a characteristic anchoring of the LC zenithal tilt and azimuth. By varying the monolayer temperature and surface concentration we observe reversible first-order phase transitions from vapor to liquid and from liquid to condensed. A temperature-dependent transition between two condensed phases appears to be a reversible swiveling transition in the tilt azimuth of the monolayer. Similar to monolayers at the air/water interface, the temperature of the gas/liquid/condensed triple-point temperature increased by about 10 degrees C for a two methylene group increase in chain length. However, the absolute value of the triple-point temperatures are depressed by about 40 degrees C compared to those of analogous monolayers at the air/water interface. We also observe a direct influence by the LC layer on the mesoscopic and macroscopic structure of the monolayer by analyzing the shapes and internal textures of gas domains in coexistence with a 2D liquid. An effective anisotropic line tension arises from elastic forces owing to deformation of the nematic director across phase boundaries. This results in the deformation of the domain from circular to elongated, with a distinct singularity. The LC elastic energy also gives rise to transition zones displaying mesoscopic realignment of the director tilt or azimuth between adjacent regions with a sudden change in anchoring. PMID:17266255

  16. Pressure induced quantum phase transitions in metallic oxides and pnictides

    NASA Astrophysics Data System (ADS)

    Fallah Tafti, Fazel

    Quantum phase transitions occur as a result of competing ground states. The focus of the present work is to understand quantum criticality and its consequences when the competition is between insulating and metallic ground states. Metal-insulator transitions are studied by means of electronic transport measurements and quantum critical points are approached by applying hydrostatic pressure in two different compounds namely Eu2Ir22O 7 and FeCrAs. The former is a ternary metal oxide and the latter is a ternary metal pnictide. A major component of this work was the development of the ultra-high pressure measurements by means of Anvil cells. A novel design is introduced which minimizes the alignment accessory components hence, making the cell more robust and easier to use. Eu2Ir22O7 is a ternary metal oxide and a member of the pyrochlore iridate family. Resistivity measurements under pressure in moissanite anvil cells show the evolution of the ground state of the system from insulating to metallic. The quantum phase transition at Pc ˜ 6 GPa appears to be continuous. A remarkable correspondence is revealed between the effect of the hydrostatic pressure on Eu2Ir22O7 and the effect of chemical pressure by changing the R size in the R2Ir2O7 series. This suggests that in both cases the tuning parameter controls the t2g bandwidth of the iridium 5d electrons. Moreover, hydrostatic pressure unveils a curious cross-over from incoherent to conventional metallic behaviour at a T* > 150 K in the neighbourhood of Pc, suggesting a connection between the high and low temperature phases. The possibility of a topological semi-metallic ground state, predicted in recent theoretical studies, is explained. FeCrAs is a ternary metal pnictide with Fermi liquid specific heat and susceptibility behaviour but non-metallic non-Fermi liquid resistivity behaviour. Characteristic properties of the compound are explained and compared to those of superconducting pnictides. Antiferromagnetic (AFM) order sets in at ˜125 K with the magnetic moments residing on the Cr site. Pressure measurements are carried out in moissanite and diamond anvil cells in order to suppress the AFM order and resolve the underlying electronic transport properties. While AFM order is destroyed by pressure, the non-metallic non-Fermi liquid behaviour is shown to be robust against pressure.

  17. Liquid crystal based phase shifters in 60 GHz band

    Microsoft Academic Search

    S. Bulja; D. Mirshekar-Syahkal; M. Yazdanpanahi; R. James; S. E. Day; F. A. Fernandez

    2010-01-01

    Preliminary structures and performance results of two different 60 GHz band planar phase shifters using liquid crystal (LC) are presented. The first phase shifter is based on a meandered microstrip line structure with the conductor pattern exposed to a layer of a nematic LC, while the second phase shifter is based on the reflection type microstrip line phase shifter structure

  18. Electronic phase transitions in ultrathin magnetite films.

    PubMed

    Bernal-Villamil, I; Gallego, S

    2015-07-29

    Magnetite (Fe3O4) shows singular electronic and magnetic properties, resulting from complex electron-electron and electron-phonon interactions that involve the interplay of charge, orbital and spin degrees of freedom. The Verwey transition is a manifestation of these interactions, with a puzzling connection between the low temperature charge ordered state and the dynamic charge fluctuations still present above the transition temperature. Here we explore how these rich physical phenomena are affected by thin film geometries, particularly focusing on the ultimate size limit defined by thicknesses below the minimum bulk unit cell. On one hand, we address the influence of extended defects, such as surfaces or antiphase domains, on the novel features exhibited by thin films. On the other, we try to isolate the effect of the reduced thickness on the electronic and magnetic properties. We will show that a distinct phase diagram and novel charge distributions emerge under reduced dimensions, while holding the local high magnetic moments. Altogether, thin film geometries offer unique possibilities to understand the complex interplay of short- and long-range orders in the Verwey transition. Furthermore, they arise as interesting candidates for the exploitation of the rich physics of magnetite in devices that demand nanoscale geometries, additionally offering novel functionalities based on their distinct properties with respect to the bulk form. PMID:26153727

  19. Gravitational waves from the electroweak phase transition

    NASA Astrophysics Data System (ADS)

    Leitao, Leonardo; Mégevand, Ariel; Sánchez, Alejandro D.

    2012-10-01

    We study the generation of gravitational waves in the electroweak phase transition. We consider a few extensions of the Standard Model, namely, the addition of scalar singlets, the minimal supersymmetric extension, and the addition of TeV fermions. For each model we consider the complete dynamics of the phase transition. In particular, we estimate the friction force acting on bubble walls, and we take into account the fact that they can propagate either as detonations or as deflagrations preceded by shock fronts, or they can run away. We compute the peak frequency and peak intensity of the gravitational radiation generated by bubble collisions and turbulence. We discuss the detectability by proposed spaceborne detectors. For the models we considered, runaway walls require significant fine tuning of the parameters, and the gravitational wave signal from bubble collisions is generally much weaker than that from turbulence. Although the predicted signal is in most cases rather low for the sensitivity of LISA, models with strongly coupled extra scalars reach this sensitivity for frequencies f ~ 10-4 Hz, and give intensities as high as h2?GW ~ 10-8.

  20. Exotic quantum phase transitions of strongly interacting topological insulators

    NASA Astrophysics Data System (ADS)

    Slagle, Kevin; You, Yi-Zhuang; Xu, Cenke

    2015-03-01

    Using determinant quantum Monte Carlo simulations, we demonstrate that an extended Hubbard model on a bilayer honeycomb lattice has two novel quantum phase transitions. The first is a quantum phase transition between the weakly interacting gapless Dirac fermion phase and a strongly interacting fully gapped and symmetric trivial phase, which cannot be described by the standard Gross-Neveu model. The second is a quantum critical point between a quantum spin Hall insulator with spin Sz conservation and the previously mentioned strongly interacting fully gapped phase. At the latter quantum critical point the single-particle excitations remain gapped, while spin and charge gaps both close. We argue that the first quantum phase transition is related to the Z16 classification of the topological superconductor 3He-B phase with interactions, while the second quantum phase transition is a topological phase transition described by a bosonic O (4 ) nonlinear sigma model field theory with a ? term.

  1. Phase Separation of Liquid Crystals in Polymers

    Microsoft Academic Search

    John L. West

    1988-01-01

    New optoelectronic materials based on polymer dispersed liquid crystals (PDLC) show great potential for application in displays, temperature sensors, optical computing and for solar energy control. We report liquid crystal, termoset or thermoplastic materials. PDLC materials may be formed by several different processes. The liquid crystal may be dissolved in low molecular weight polymer precursors, in a thermoplastic melt or

  2. Liquid Crystals: The Phase of the Future.

    ERIC Educational Resources Information Center

    Ondris-Crawford, Renate; And Others

    1992-01-01

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

  3. Experimental study of solid–liquid phase change in a spiral thermal energy storage unit

    Microsoft Academic Search

    J Banaszek; R Domañski; M Rebow; F El-Sagier

    1999-01-01

    A new idea on the use of a vertical spiral heat exchanger in a latent heat thermal energy storage system is analyzed experimentally. In this context, two important subjects are addressed. The first one is the temporal behavior of a phase change medium undergoing a non-isothermal solid–liquid phase change transition during its two-side heating or cooling by a working fluid

  4. Self-focusing of laser light in the isotropic phase of a nematic liquid crystal

    Microsoft Academic Search

    D. V. G. L. Narasimha Rao; S. Jayaraman

    1973-01-01

    Self-focusing of ruby laser light is studied as a function of sample length and temperature in the isotropic phase of nematic liquid-crystal MBBA. The critical power for self-focusing, 0.36 kW, observed near the phase transition temperature is a factor of 20 times less than that for CS2. The corresponding nonlinear index 4.4 × 10?10 esu is the largest value known

  5. Liquid-Phase Processing of Barium Titanate Thin Films

    NASA Astrophysics Data System (ADS)

    Harris, David Thomas

    Processing of thin films introduces strict limits on the thermal budget due to substrate stability and thermal expansion mismatch stresses. Barium titanate serves as a model system for the difficulty in producing high quality thin films because of sensitivity to stress, scale, and crystal quality. Thermal budget restriction leads to reduced crystal quality, density, and grain growth, depressing ferroelectric and nonlinear dielectric properties. Processing of barium titanate is typically performed at temperatures hundreds of degrees above compatibility with metalized substrates. In particular integration with silicon and other low thermal expansion substrates is desirable for reductions in costs and wider availability of technologies. In bulk metal and ceramic systems, sintering behavior has been encouraged by the addition of a liquid forming second phase, improving kinetics and promoting densification and grain growth at lower temperatures. This approach is also widespread in the multilayer ceramic capacitor industry. However only limited exploration of flux processing with refractory thin films has been performed despite offering improved dielectric properties for barium titanate films at lower temperatures. This dissertation explores physical vapor deposition of barium titanate thin films with addition of liquid forming fluxes. Flux systems studied include BaO-B2O3, Bi2O3-BaB2O 4, BaO-V2O5, CuO-BaO-B2O3, and BaO-B2O3 modified by Al, Si, V, and Li. Additions of BaO-B2O3 leads to densification and an increase in average grain size from 50 nm to over 300 nm after annealing at 900 °C. The ability to tune permittivity of the material improved from 20% to 70%. Development of high quality films enables engineering of ferroelectric phase stability using residual thermal expansion mismatch in polycrystalline films. The observed shifts to TC match thermodynamic calculations, expected strain from the thermal expansion coefficients, as well as x-ray diffract measurements . Our system exhibits flux-film-substrate interactions that can lead to dramatic changes to the microstructure. This effect is especially pronounced onc -sapphire, with Al diffusion from the substrate leading to formation of an epitaxial BaAl2O4 second phase at the substrate-film interface. The formation of this second phase in the presence of a liquid phase seeds {111} twins that drive abnormal grain growth. The orientation of the sapphire substrate determines the BaAl2O 4 morphology, enabling control the abnormal grain growth behavior. CuO additions leads to significant grain growth at 900 °C, with average grain size approaching 500 nm. The orthorhombic-tetragonal phase transition is clearly observable in temperature dependent measurements and both linear and nonlinear dielectric properties are improved. All films containing CuO are susceptible to aging. A number of other systems were investigated for efficacy at temperatures below 900 °C. Pulsed laser deposition was used to study flux + BaTiO 3 targets, layered flux films, and in situ liquids. RF-magnetron sputtering using a dual-gun approach was used to explore integration on flexible foils with Ba1-xSrxTiO3. Many of these systems were based on the BaO-B2O3 system, which has proven effective in thin films, multilayer ceramic capacitors, and bulk ceramics. Modifiers allow tailoring of the microstructure at 900 °C, however no compositions were found, and no reports exist in the open literature, that provide significant grain growth or densification below 900 °C. Liquid phase fluxes offer a promising path forward for low temperature processing of barium titanate, with the ultimate goal of integration with metalized silicon substrates. This work demonstrates significant improvements to dielectric properties and the necessity of understanding interactions in the film-flux-substrate system.

  6. Viscosity and thermal conductivity effects at first-order phase transitions in heavy-ion collisions

    SciTech Connect

    Voskresensky, D. N., E-mail: D.Voskresensky@gsi.de [National Research Nuclear University 'MEPhI' (Russian Federation); Skokov, V. V., E-mail: V.Skokov@gsi.de [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH (Germany)

    2012-06-15

    Effects of viscosity and thermal conductivity on the dynamics of first-order phase transitions are studied. The nuclear gas-liquid and hadron-quark transitions in heavy-ion collisions are considered. We demonstrate that at nonzero thermal conductivity, {kappa} {ne} 0, onset of spinodal instabilities occurs on an isothermal spinodal line, whereas for {kappa} = 0 instabilities take place at lower temperatures, on an adiabatic spinodal.

  7. Membrane Phase Transitions are Responsible for Imbibitional Damage in Dry Pollen

    Microsoft Academic Search

    John H. Crowe; Folkert A. Hoekstra; Lois M. Crowe

    1989-01-01

    We have found that the most probable cause of the leakage seen when dry cells or organisms such as seeds, pollen, or yeast cells are plunged into water is a gel to liquid crystalline phase transition in membrane phospholipids accompanying rehydration. By using Fourier transform infrared spectroscopy we have recorded infrared spectra of CH2 stretching vibrations in dry and partially

  8. Does sex induce a phase transition?

    NASA Astrophysics Data System (ADS)

    de Oliveira, P. M. C.; Moss de Oliveira, S.; Stauffer, D.; Cebrat, S.; P?kalski, A.

    2008-05-01

    We discovered a dynamic phase transition induced by sexual reproduction. The dynamics is a pure Darwinian rule applied to diploid bit-strings with both fundamental ingredients to drive Darwin's evolution: (1) random mutations and crossings which act in the sense of increasing the entropy (or diversity); and (2) selection which acts in the opposite sense by limiting the entropy explosion. Selection wins this competition if mutations performed at birth are few enough, and thus the wild genotype dominates the steady-state population. By slowly increasing the average number m of mutations, however, the population suddenly undergoes a mutational degradation precisely at a transition point mc. Above this point, the “bad” alleles (represented by 1-bits) spread over the genetic pool of the population, overcoming the selection pressure. Individuals become selectively alike, and evolution stops. Only below this point, m < mc, evolutionary life is possible. The finite-size-scaling behaviour of this transition is exhibited for large enough “chromosome” lengths L, through lengthy computer simulations. One important and surprising observation is the L-independence of the transition curves, for large L. They are also independent on the population size. Another is that mc is near unity, i.e. life cannot be stable with much more than one mutation per diploid genome, independent of the chromosome length, in agreement with reality. One possible consequence is that an eventual evolutionary jump towards larger L enabling the storage of more genetic information would demand an improved DNA copying machinery in order to keep the same total number of mutations per offspring.

  9. Second-order phase transitions, L. Landau and his successors

    E-print Network

    Y. Mnyukh

    2011-02-05

    There are only two ways for solid-state phase transitions to be compliant with thermodynamics: emerging of infinitesimal quantity of the new phase, or infinitesimal "qualitative" change occurring uniformly throughout the bulk at a time. The suggested theories of phase transitions are checked here for that compliance and in historical perspective. While introducing the theory of "continuous" second-order phase transitions, L. Landau claimed that they "may also exist" along with the majority of first order phase transitions, the latter being "discontinuous", displaying "jumps" of their physical properties; the fundamental differences between the two types were specified. But his theoretical successors disregarded these irreconcilable differences, incorrectly presenting all phase transitions as a cooperative phenomenon treatable by statistical mechanics. In the meantime, evidence has been mounted that all phase transitions have a nucleation-and-growth mechanism, thus making the above classification unneeded.

  10. Surface entropy of liquid transition and noble metals

    NASA Astrophysics Data System (ADS)

    Gosh, R. C.; Das, Ramprosad; Sen, Sumon C.; Bhuiyan, G. M.

    2015-07-01

    Surface entropy of liquid transition and noble metals has been investigated using an expression obtained from the hard-sphere (HS) theory of liquid. The expression is developed from the Mayer's extended surface tension formula [Journal of Non-Crystalline Solids 380 (2013) 42-47]. For interionic interaction in metals, Brettonet-Silbert (BS) pseudopotentials and embedded atom method (EAM) potentials have been used. The liquid structure is described by the variational modified hypernetted chain (VMHNC) theory. The essential ingredient of the expression is the temperature dependent effective HS diameter (or packing fraction), which is calculated from the aforementioned potentials together with the VMHNC theory. The obtained results for the surface entropy using the effective HS diameter are found to be good in agreement with the available experimental as well as other theoretical values.

  11. Liquid-liquid Phase Separation in Aerosols: Model Predictions, Laboratory and Field Observations

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Seinfeld, J.

    2012-12-01

    Atmospheric aerosol particles composed of a variety of organic compounds, water, and dissolved inorganic ions exhibit changes in water content, phase state and mixing properties in response to variations in relative humidity (RH) and temperature of the environment. Liquid-liquid phase separation may occur in partially liquid aerosol particles as a consequence of changes in composition, most prominently water content. A liquid-liquid phase separation manifests the presence of limited miscibility among the solution constituents indicating significant non-ideality in the condensed phase, which is caused by unfavorable interactions between water molecules, inorganic ions, and organic compounds; especially in the presence of rather hydrophobic organics with low O:C atomic ratios. An increasing number of laboratory experiments and thermodynamic modeling studies suggest that liquid-liquid phase separation is expected to be present over a wide range of RH for typical organic:inorganic ratios of aged tropospheric aerosol. Recent data from field observations in the Los Angeles basin and other ambient observations, including droplet experiments from filter sample extracts, provide evidence for the presence of phase separations in ambient aerosol particles. We present an overview on liquid-liquid phase separation related to aerosols and organic-inorganic model systems based on thermodynamic theory, detailed calculations, laboratory experiments, and indirect evidence from field observations. There are several potentially important impacts of liquid-liquid phase separation on the distribution of semivolatile organic and inorganic compounds, the equilibration timescale of gas-particle partitioning, and consequences for particle-phase chemistry. We discuss important aspects related to the computational challenges and costs of predicting and representing phase separations in detailed physicochemical models and present a new algorithm designed for complex systems of many components.

  12. Continuous Mott transition between a metal and a quantum spin liquid

    NASA Astrophysics Data System (ADS)

    Mishmash, Ryan V.; González, Iván; Melko, Roger G.; Motrunich, Olexei I.; Fisher, Matthew P. A.

    2015-06-01

    More than half a century after first being proposed by Sir Nevill Mott, the deceptively simple question of whether the interaction-driven electronic metal-insulator transition may be continuous remains enigmatic. Recent experiments on two-dimensional materials suggest that when the insulator is a quantum spin liquid, lack of magnetic long-range order on the insulating side may cause the transition to be continuous, or only very weakly first order. Motivated by this, we study a half-filled extended Hubbard model on a triangular lattice strip geometry. We argue, through use of large-scale numerical simulations and analytical bosonization, that this model harbors a continuous (Kosterlitz-Thouless-like) quantum phase transition between a metal and a gapless spin liquid characterized by a spinon Fermi surface, i.e., a "spinon metal." These results may provide a rare insight into the development of Mott criticality in strongly interacting two-dimensional materials and represent one of the first numerical demonstrations of a Mott insulating quantum spin liquid phase in a genuinely electronic microscopic model.

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

    SciTech Connect

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

    2005-02-09

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

  14. Reply to "Comment on 'Spontaneous liquid-liquid phase separation of water'?".

    PubMed

    Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

    2015-01-01

    Two different scenarios have been proposed on the phase separation occurring in the deeply supercooled liquid water. We discuss what we can derive from our simulation results for the two scenarios and propose a way for future investigation. We also demonstrate that the phase separation in the supercooled liquid water looks like the separation of liquid water and vapor just below the conventional critical point. PMID:25679745

  15. Phase Transitions of Nanoemulsions Using Ultrasound: Experimental Observations

    PubMed Central

    Singh, Ram; Husseini, Ghaleb A.; Pitt, William G.

    2012-01-01

    The ultrasound-induced transformation of perfluorocarbon liquids to gases is of interest in the area of drug and gene delivery. In this study, three independent parameters (temperature, size, and perfluorocarbon species) were selected to investigate the effects of 476-kHz and 20-kHz ultrasound on nanoemulsion phase transition. Two levels of each factor (low and high) were considered at each frequency. The acoustic intensities at gas bubble formation and at the onset of inertial cavitation were recorded and subsequently correlated with the acoustic parameters. Experimental data showed that low frequencies are more effective in forming and collapsing a bubble. Additionally, as the size of the emulsion droplet increased, the intensity required for bubble formation decreased. As expected, perfluorohexane emulsions require greater intensity to form cavitating bubbles than perfluoropentane emulsions. PMID:22444691

  16. The liquid-to-solid transition in stereodeposition techniques

    NASA Astrophysics Data System (ADS)

    Crockett, Robert Sinclair

    Stereodeposition is a freeform fabrication technique which accomplishes the computer-controlled, layerwise buildup of an object through direct placement of a fluid which rapidly solidifies. Current materials compatible with stereodeposition include functional ceramics and metals, engineering polymers, and composites. The key to this flexibility is stereodeposition's ability to operate under a wide range of liquid-to-solid transformation rates. Understanding and controlling the material parameters involved in the liquid-to-solid transition is critical, as solidification ultimately impacts the precision and quality of the final object. A model of the liquid-to-solid transition has been developed in which a bead spreading on a curved surface is followed as a series of state "snapshots", whereby an applied force produces an incremental bead motion in an increment of time. This approach differs from most liquid spreading models, but allows flexibility in the time and geometry dependence of forces associated with a solidifying stereodeposition liquid. The model predicts bead contact angle as a function of time based on initial liquid properties (surface tension, viscosity, yield strength) and the solidification strategy employed, namely rheology control, mass transfer, or thermal transfer. Three parameter groupings are identified: alpha, which controls final contact angle, beta, which controls spreading rate, and delta, which controls amount of liquid transformation occurring during spreading. To validate the model, dynamic measurements are performed on the spreading of slurries of silica particles in various liquids. The model is found to predict the early stage of spreading (<5 s) under one of the two proposed boundary conditions, and is shown to be equivalent in the limit to the more traditional dynamic wetting models employing an energy rate balance. An explanation is presented for the failure of the model to accurately predict the final contact angle for highly shear-thinning slurries. The results of the model are applied to operational stereodeposition systems. Placement on a graphical representation of the alpha,\\ beta, and delta parameter space provides insight as to how the initial liquid conditions, modified by solidification strategies, will impact the ultimate freeforming characteristics such as object resolution, flaws, and gaps; from this, potential modifications can be identified.

  17. Zipf's law from a communicative phase transition

    NASA Astrophysics Data System (ADS)

    Ferrer I Cancho, R.

    2005-10-01

    Here we present a new model for Zipf's law in human word frequencies. The model defines the goal and the cost of communication using information theory. The model shows a continuous phase transition from a no communication to a perfect communication phase. Scaling consistent with Zipf's law is found in the boundary between phases. The exponents are consistent with minimizing the entropy of words. The model differs from a previous model [Ferrer i Cancho, Solé, Proc. Natl. Acad. Sci. USA 100, 788 791 (2003)] in two aspects. First, it assumes that the probability of experiencing a certain stimulus is controlled by the internal structure of the communication system rather than by the probability of experiencing it in the `outside' world, which makes it specially suitable for the speech of schizophrenics. Second, the exponent ? predicted for the frequency versus rank distribution is in a range where ?>1, which may explain that of some schizophrenics and some children, with ?=1.5-1.6. Among the many models for Zipf's law, none explains Zipf's law for that particular range of exponents. In particular, two simplistic models fail to explain that particular range of exponents: intermittent silence and Simon's model. We support that Zipf's law in a communication system may maximize the information transfer under constraints.

  18. Glass Transition by Gelation in a Phase Separating Binary Alloy

    E-print Network

    Baumer, Richard E.

    We use molecular dynamics simulations to show that glass transition in a model phase separating amorphous alloy, Cu50Nb50, occurs by gelation. At the glass transition, a mechanically stiff, percolating network of atoms ...

  19. Blue phase liquid crystal: strategies for phase stabilization and device development

    NASA Astrophysics Data System (ADS)

    Asiqur Rahman, MD; Mohd Said, Suhana; Balamurugan, S.

    2015-06-01

    The blue phase liquid crystal (BPLC) is a highly ordered liquid crystal (LC) phase found very close to the LC–isotropic transition. The BPLC has demonstrated potential in next-generation display and photonic technology due to its exceptional properties such as sub-millisecond response time and wide viewing angle. However, BPLC is stable in a very small temperature range (0.5–1 °C) and its driving voltage is very high (?100 V). To overcome these challenges recent research has focused on solutions which incorporate polymers or nanoparticles into the blue phase to widen the temperature range from around few °C to potentially more than 60 °C. In order to reduce the driving voltage, strategies have been attempted by modifying the device structure by introducing protrusion or corrugated electrodes and vertical field switching mechanism has been proposed. In this paper the effectiveness of the proposed solution will be discussed, in order to assess the potential of BPLC in display technology and beyond.

  20. Analogies between granular jamming and the liquid-glass transition.

    PubMed

    Silbert, Leonardo E; Erta?, Deniz; Grest, Gary S; Halsey, Thomas C; Levine, Dov

    2002-05-01

    Based on large-scale, three-dimensional chute flow simulations of granular systems, we uncover strong analogies between the jamming of the grains and the liquid-glass transition. The angle of inclination theta in the former transition appears as an analog of temperature T in the latter. The transition is manifested in the development of a plateau in the contact normal force distribution P(f) at small forces, the splitting of the second peak in the pair-correlation function g(r), and increased fluctuations of the system energy. The static state also exhibits history dependence, akin to the quench-rate dependence of structural properties of glasses, due to the hyperstaticity of the contact network. PMID:12059551

  1. Discontinuous anchoring transition and photothermal switching in composites of liquid crystals and conducting polymer nanofibers

    NASA Astrophysics Data System (ADS)

    Rasna, M. V.; Zuhail, K. P.; Manda, R.; Paik, P.; Haase, W.; Dhara, Surajit

    2014-05-01

    We prepared nanocomposites of a nematic liquid crystal and nanofibers of a conducting polymer (polyaniline). All the nanocomposites exhibit a discontinuous surface anchoring transition from planar to homeotropic in the nematic phase on a perfluoropolymer coated surface with a thermal hysteresis (?5.3?C). We observe a relatively large bistable conductivity and demonstrate a light driven switching of conductivity and dielectric constant in dye doped nanocomposites in the thermal hysteresis (bistable) region. The experimental results have been explained based on the reorientation of the nanofibers driven by the anchoring transition of the nematic liquid crystal. We show a significant enhancement of the bistable temperature range (?13?C) by an appropriate choice of compound in the binary system.

  2. Phase Transitions and the Perfectness of Fluids

    E-print Network

    Jiunn-Wei Chen; Mei Huang; Yen-Han Li; Eiji Nakano; Di-Lun Yang

    2008-10-11

    We calculate the ratio eta/s, the shear viscosity (eta) to entropy density (s), which characterizes how perfect a fluid is, in weakly coupled real scalar field theories with different types of phase transitions. The mean-field results of the eta/s behaviors agree with the empirical observations in atomic and molecular systems such as water, He, N, and all the matters with data available in the NIST database. These behaviors are expected to be the same in N component scalar theories with an O(N) symmetry. We speculate these eta/s behaviors are general properties of fluid shared by QCD and cold atoms. Finally, we clarify some issues regarding counterexamples of the conjectured universal eta/s bound found in Refs.[16,17].

  3. MAGNETIC FIELDS FROM QCD PHASE TRANSITIONS

    SciTech Connect

    Tevzadze, Alexander G. [Faculty of Exact and Natural Sciences, Javakhishvili Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi 0128 (Georgia); Kisslinger, Leonard; Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Brandenburg, Axel, E-mail: aleko@tevza.org [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

    2012-11-01

    We study the evolution of QCD phase transition-generated magnetic fields (MFs) in freely decaying MHD turbulence of the expanding universe. We consider an MF generation model that starts from basic non-perturbative QCD theory and predicts stochastic MFs with an amplitude of the order of 0.02 {mu}G and small magnetic helicity. We employ direct numerical simulations to model the MHD turbulence decay and identify two different regimes: a 'weakly helical' turbulence regime, when magnetic helicity increases during decay, and 'fully helical' turbulence, when maximal magnetic helicity is reached and an inverse cascade develops. The results of our analysis show that in the most optimistic scenario the magnetic correlation length in the comoving frame can reach 10 kpc with the amplitude of the effective MF being 0.007 nG. We demonstrate that the considered model of magnetogenesis can provide the seed MF for galaxies and clusters.

  4. A Susy Phase Transition as Central Engine

    E-print Network

    L. Clavelli

    2005-01-10

    For several decades the energy source powering supernovae and gamma ray bursts has been a troubling mystery. Many articles on these phenomena have been content to model the consequences of an unknown "central engine" depositing a large amount of energy in a small region. In the case of supernovae this is somewhat unsettling since the type 1a supernovae are assumed to be "standardizable candles" from which important information concerning the dark energy can be derived. It should be expected that a more detailed understanding of supernovae dynamics could lead to a reduction of the errors in this relationship. Similarly, the current state of the standard model theory of gamma ray bursts, which in some cases have been associated with supernovae, has conceptual gaps not only in the central engine but also in the mechanism for jet collimation and the lack of baryon loading. We discuss here the Supersymmetric (susy) phase transition model for the central engine.

  5. A Susy Phase Transition as Central Engine

    E-print Network

    Clavelli, L

    2005-01-01

    For several decades the energy source powering supernovae and gamma ray bursts has been a troubling mystery. Many articles on these phenomena have been content to model the consequences of an unknown "central engine" depositing a large amount of energy in a small region. In the case of supernovae this is somewhat unsettling since the type 1a supernovae are assumed to be "standardizable candles" from which important information concerning the dark energy can be derived. It should be expected that a more detailed understanding of supernovae dynamics could lead to a reduction of the errors in this relationship. Similarly, the current state of the standard model theory of gamma ray bursts, which in some cases have been associated with supernovae, has conceptual gaps not only in the central engine but also in the mechanism for jet collimation and the lack of baryon loading. We discuss here the Supersymmetric (susy) phase transition model for the central engine.

  6. Experimental Investigations of Magnetic Phase Transitions

    NASA Astrophysics Data System (ADS)

    Brug, James Alexander

    Our understanding of magnetic phase transitions has progressed rapidly in recent years, and one material that is currently of theoretical interest is the metamagnet, dysprosium aluminum garnet (DAG). This is a well understood, model system that can be used to test theories of tricritical behavior. However, the experimental investigation of this material requires high resolution measurements and in this thesis several experimental methods were developed for this purpose. Methods of measuring magnetic properties using optical techniques were investigated as they allow small regions of the sample to be measured and thereby reduce the rounding effects produced by nonuniform samples. An apparatus for measuring the Faraday rotation was developed to measure the magnetization of samples in the shape of thin plates and spheres. In addition, a method of measuring the light scattered from domains in spherical samples was developed to locate the first-order phase boundaries. The shape of the sample was important as effects due to inhomogeneous demagnetizing fields were observed for nonellipsoidal samples. A computer model using finite elements investigated this effect and general predictions were made of the size of these effects in materials with different equations of state and sample shapes. This method was also used to investigate the effects of imperfections (pores, surface pits) on magnetic measurements. A method of measurement using mutual inductance coils was constructed to measure the a.c. susceptibility. In addition to measurements of the susceptibility at various frequencies, the out-of-phase component of the susceptibility was found to give a sensitive measurement of the location of the phase transition. The above methods were used to investigate the behavior of DAG near its tricritical point. The general behavior that was measured was consistent with previous investigations. However, close to the tricritical point, previously unreported domain-like states and very long relaxation times (>0.1 seconds) were observed and these precluded simple analysis of the results. Current models of tricritical behavior do not take into account these processes and, therefore, the measurements of this thesis indicate the need for new theoretical developements.

  7. Topological and geometrical aspects of phase transitions

    NASA Astrophysics Data System (ADS)

    Santos, F. A. N.; Rehn, J. A.; Coutinho-Filho, M. D.

    2014-03-01

    In the first part of this review, we use a topological approach to describe the frustration- and field-induced phase transitions exhibited by the infinite-range XY model on the AB2 chain, including noncollinear spin structures. For this purpose, we have computed the Euler characteristic, ?, as well as other topological invariants, which are found to behave similarly as a function of the energy level in the context of Morse theory. Our findings and those available in the literature suggest that the cusp-like singularity exhibited by ? at the critical energy, Ec, put together with the divergence of the density of Jacobian's critical points emerge as necessary and sufficient conditions for the occurrence of finite-temperature topology-induced phase transitions. In the second part, we present an alternative solution of the Ising chain in a field under free and periodic boundary conditions, in the microcanonical, canonical, and grand canonical ensembles, from a unified combinatorial and topological perspective. In particular, the computation of the per-site entropy as a function of the energy unveils a residual value for critical values of the magnetic field, a phenomenon for which we provide a topological interpretation and a connection with the Fibonacci sequence. We also show that, in the thermodynamic limit, the per-site microcanonical entropy is equal to the logarithm of the per-site Euler characteristic. Finally, we emphasize that our combinatorial approach to the canonical ensemble allows exact computation of the thermally averaged value (T) of the Euler characteristic; our results show that the conjecture (Tc)= 0, where Tc is the critical temperature, is valid for the Ising chain.

  8. Thick strings, the liquid crystal blue phase, and cosmological large-scale structure

    NASA Technical Reports Server (NTRS)

    Luo, Xiaochun; Schramm, David N.

    1992-01-01

    A phenomenological model based on the liquid crystal blue phase is proposed as a model for a late-time cosmological phase transition. Topological defects, in particular thick strings and/or domain walls, are presented as seeds for structure formation. It is shown that the observed large-scale structure, including quasi-periodic wall structure, can be well fitted in the model without violating the microwave background isotropy bound or the limits from induced gravitational waves and the millisecond pulsar timing. Furthermore, such late-time transitions can produce objects such as quasars at high redshifts. The model appears to work with either cold or hot dark matter.

  9. Using Peltier cells to study solid liquid vapour transitions and supercooling

    NASA Astrophysics Data System (ADS)

    Torzo, Giacomo; Soletta, Isabella; Branca, Mario

    2007-05-01

    We propose an apparatus for teaching experimental thermodynamics in undergraduate introductory courses, using thermoelectric modules and a real-time data acquisition system. The device may be made at low cost, still providing an easy approach to the investigation of liquid solid and liquid vapour phase transitions and of metastable states (supercooling). The thermoelectric module (a technological evolution of the thermocouple) is by itself an interesting subject that offers a clear example of both thermo-electric (Seebeck effect) and electro-thermal (Peltier effect) energy transformation. We report here some cooling/heating measurements for several liquids and mixtures, including water, salt/water, ethanol/water and sodium acetate, showing how to evaluate the phenomena of freezing point depression and elevation, and how to evaluate the water latent heat.

  10. The liquid-liquid transition in supercooled ST2 water: a comparison between umbrella sampling and well-tempered metadynamics.

    PubMed

    Palmer, Jeremy C; Car, Roberto; Debenedetti, Pablo G

    2013-01-01

    We investigate the metastable phase behaviour of the ST2 water model under deeply supercooled conditions. The phase behaviour is examined using umbrella sampling (US) and well-tempered metadynamics (WT-MetaD) simulations to compute the reversible free energy surface parameterized by density and bond-orientation order. We find that free energy surfaces computed with both techniques clearly show two liquid phases in coexistence, in agreement with our earlier US and grand canonical Monte Carlo calculations [Y. Liu, J. C. Palmer, A. Z. Panagiotopoulos and P. G. Debenedetti, J Chem Phys, 2012, 137, 214505; Y. Liu, A. Z. Panagiotopoulos and P. G. Debenedetti, J Chem Phys, 2009, 131, 104508]. While we demonstrate that US and WT-MetaD produce consistent results, the latter technique is estimated to be more computationally efficient by an order of magnitude. As a result, we show that WT-MetaD can be used to study the finite-size scaling behaviour of the free energy barrier separating the two liquids for systems containing 192, 300 and 400 ST2 molecules. Although our results are consistent with the expected N(2/3) scaling law, we conclude that larger systems must be examined to provide conclusive evidence of a first-order phase transition and associated second critical point. PMID:24640486

  11. Quantum phase transition of condensed bosons in optical lattices

    E-print Network

    Jun-Jun Liang; J. -Q. Liang; W. -M. Liu

    2004-03-23

    In this paper we study the superfluid-Mott-insulator phase transition of ultracold dilute gas of bosonic atoms in an optical lattice by means of Green function method and Bogliubov transformation as well. The superfluid- Mott-insulator phase transition condition is determined by the energy-band structure with an obvious interpretation of the transition mechanism. Moreover the superfluid phase is explained explicitly from the energy spectrum derived in terms of Bogliubov approach.

  12. Gravitational waves from global second order phase transitions

    SciTech Connect

    Jr, John T. Giblin [Department of Physics, Kenyon College, 201 North College Rd, Gambier, OH 43022 (United States); Price, Larry R.; Siemens, Xavier; Vlcek, Brian, E-mail: giblinj@kenyon.edu, E-mail: larryp@caltech.edu, E-mail: siemens@gravity.phys.uwm.edu, E-mail: bvlcek@uwm.edu [Center for Gravitation and Cosmology, Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI 53201 (United States)

    2012-11-01

    Global second-order phase transitions are expected to produce scale-invariant gravitational wave spectra. In this manuscript we explore the dynamics of a symmetry-breaking phase transition using lattice simulations. We explicitly calculate the stochastic gravitational wave background produced during the transition and subsequent self-ordering phase. We comment on this signal as it compares to the scale-invariant spectrum produced during inflation.

  13. Quantum phase transition as an interplay of Kitaev and Ising interactions

    E-print Network

    A. Langari; A. Mohammad-Aghaei; R. Haghshenas

    2014-10-08

    We study the interplay between the Kitaev and Ising interactions on both ladder and two dimensional lattices. We show that the ground state of the Kitaev ladder is a symmetry-protected topological (SPT) phase, which is protected by a $\\mathbb{Z}_2 \\times \\mathbb{Z}_2$ symmetry. It is confirmed by the degeneracy of the entanglement spectrum and non-trivial phase factors (inequivalent projective representations of the symmetries), which are obtained within infinite matrix-product representation of numerical density matrix renormalization group. We derive the effective theory to describe the topological phase transition on both ladder and two-dimensional lattices, which is given by the transverse field Ising model with/without next-nearest neighbor coupling. The ladder has three phases, namely, the Kitaev SPT, symmetry broken ferro/antiferromagnetic order and classical spin-liquid. The non-zero quantum critical point and its corresponding central charge are provided by the effective theory, which are in full agreement with the numerical results, i.e., the divergence of entanglement entropy at the critical point, change of the entanglement spectrum degeneracy and a drop in the ground-state fidelity. The central charge of the critical points are either c=1 or c=2, with the magnetization and correlation exponents being 1/4 and 1/2, respectively. In the absence of frustration, the 2D lattice shows a topological phase transition from the $\\mathbb{Z}_2$ spin-liquid state to the long-range ordered Ising phase at finite ratio of couplings, while in the presence of frustration, an order-by-disorder transition is induced by the Kitaev term. The 2D classical spin-liquid phase is unstable against the addition of Kitaev term toward an ordered phase before the transition to the $\\mathbb{Z}_2$ spin-liquid state.

  14. Survey of CRISM Transition Phase Observations

    NASA Astrophysics Data System (ADS)

    Seelos, F. P.; Murchie, S. L.; Choo, T. H.; McGovern, J. A.

    2006-12-01

    The Mars Reconnaissance Orbiter (MRO) transition phase extends from the end of aerobraking (08/30/06) to the start of the Primary Science Phase (PSP) (11/08/2006). Within this timeframe, the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) will acquire Mars scene observations in association with the deployment of the telescope cover (09/27/06) and during the operational checkout of the full science payload (09/29/06 - 10/05/06). The CRISM cover opening sequence includes scene observations that will be used to verify deployment and to validate the on-orbit instrument wavelength calibration. The limited cover opening observation set consists of: 1. A hyperspectral nadir scan acquired as the cover is deployed (first light) 2. A single targeted (gimbaled) hyperspectral observation in the northern plains 3. A restricted duration nadir multispectral strip The high level objectives for the science payload checkout are to obtain observations in support of in-flight wavelength, radiometric, and geometric instrument calibration, to acquire data that will contribute to the development of a first-order hyperspectral atmospheric correction, and to exercise numerous spacecraft and instrument observing modes and strategies that will be employed during PSP. The science payload checkout also enables a unique collaboration between the Mars Express OMEGA and CRISM teams, with both spectrometers slated to observe common target locations with a minimal time offset for the purpose of instrument cross-calibration. The priority CRISM observations for the payload checkout include: 1. Multispectral nadir and hyperspectral off-nadir targeted observations in support of the cross-calibration experiment with OMEGA 2. Terminator-to-terminator multispectral data acquisition demonstrating the strategy that will be used to construct the global multispectral survey map 3. Terminator-to-terminator atmospheric emission phase function (EPF) data acquisition demonstrating the observation sequence at the core of the atmospheric monitoring and seasonal change campaigns 4. A hyperspectral nadir observation from a spectrally bland region that will contribute to an improved flat field correction 5. An extended hyperspectral nadir scan with a large variation in atmospheric path length to establish a CRISM-tailored aerosol scaling spectrum 6. Nadir and off-nadir multispectral and hyperspectral coordinated observations with HiRISE and CTX to demonstrate this fundamental operational capability and to assess relative alignment 7. A hyperspectral targeted observation in support of Phoenix landing site selection 8. Initial observation of spatially extensive spectrally compelling regions such as Meridiani Planum and Nili Fossae The CRISM observations planned for the transition phase will allow for robust on-orbit validation of the instrument wavelength, radiometric, and geometric calibration. These observations also comprise an accurate sampling of the observing modes and strategies that will be employed in PSP. The spatial and spectral characteristics of the CRISM transition phase data products will be presented in the context of the CRISM science objectives.

  15. Structural phase transition of vanadium at 69 GPa.

    PubMed

    Ding, Yang; Ahuja, Rajeev; Shu, Jinfu; Chow, Paul; Luo, Wei; Mao, Ho-kwang

    2007-02-23

    A phase transition was observed at 63-69 GPa and room temperature in vanadium with synchrotron x-ray diffraction. The transition is characterized as a rhombohedral lattice distortion of the body-centered-cubic vanadium without a discontinuity in the pressure-volume data, thus representing a novel type of transition that has never been observed in elements. Instead of driven by the conventional s-d electronic transition mechanism, the phase transition could be associated with the softening of C44 trigonal elasticity tensor that originates from the combination of Fermi surface nesting, band Jahn-Teller distortion, and electronic topological transition. PMID:17359109

  16. Physico-Chemical Properties and Phase Behaviour of Pyrrolidinium-Based Ionic Liquids

    PubMed Central

    Doma?ska, Urszula

    2010-01-01

    A review of the relevant literature on 1-alkyl-1-methylpyrrolidinium-based ionic liquids has been presented. The phase diagrams for the binary systems of {1-ethyl-1-methylpyrrolidinium trifluoromethanesulfonate (triflate) [EMPYR][CF3SO3] + water, or + 1-butanol} and for the binary systems of {1-propyl-1-methylpyrrolidinium trifluoromethanesulfonate (triflate) [PMPYR][CF3SO3] + water, or + an alcohol (1-butanol, 1-hexanol, 1-octanol, 1-decanol)} have been determined at atmospheric pressure using a dynamic method. The influence of alcohol chain length was discussed for the [PMPYR][CF3SO3]. A systematic decrease in the solubility was observed with an increase of the alkyl chain length of an alcohol. (Solid + liquid) phase equilibria with complete miscibility in the liquid phase region were observed for the systems involving water and alcohols. The solubility of the ionic liquid increases as the alkyl chain length on the pyrrolidinium cation increases. The correlation of the experimental data has been carried out using the Wilson, UNIQUAC and the NRTL equations. The phase diagrams reported here have been compared to the systems published earlier with the 1-alkyl-1-methylpyrrolidinium-based ionic liquids. The influence of the cation and anion on the phase behaviour has been discussed. The basic thermal properties of pure ILs, i.e., melting temperature and the enthalpy of fusion, the solid-solid phase transition temperature and enthalpy have been measured using a differential scanning microcalorimetry technique. PMID:20480044

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

    Microsoft Academic Search

    J. M. Lee

    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

  18. Dissolution of Trapped Nonaqueous Phase Liquids: Mass Transfer Characteristics

    Microsoft Academic Search

    Cass T. Miller; MICHELE M. POIRIER-MCNEILL; Alex S. Mayer

    1990-01-01

    Many groundwater contamination incidents begin with the release of an essentially immiscible fluid into the subsurface environment. Once in the subsurface, an immiscible fluid participates in a complex pattern of transport processes. For immiscible fluids that are commonly found in contaminated groundwater environments the interphase mass transfer between the nonaqueous phase liquids (NAPLs) phase and the aqueous phase is an

  19. Dissolution of trapped nonaqueous phase liquids: Mass transfer characteristics

    Microsoft Academic Search

    Cass T. Miller; M. M. Poirier-McNeill; Alex S. Mayer

    1990-01-01

    Many groundwater contamination incidents begin with the release of an essentially immiscible fluid into the subsurface environment. Once in the subsurface, an immiscible fluid participates in a complex pattern of transport processes. For immiscible fluids that are commonly found in contaminated groundwater environments the interphase mass transfer between the nonaqueous phase liquids (NAPLs) phase and the aqueous phase is an

  20. Mesoscale modeling of phase transition dynamics of thermoresponsive polymers

    E-print Network

    Li, Zhen; Li, Xuejin; Karniadakis, George Em

    2015-01-01

    We present a non-isothermal mesoscopic model for investigation of the phase transition dynamics of thermoresponsive polymers. Since this model conserves energy in the simulations, it is able to correctly capture not only the transient behavior of polymer precipitation from solvent, but also the energy variation associated with the phase transition process. Simulations provide dynamic details of the thermally induced phase transition and confirm two different mechanisms dominating the phase transition dynamics. A shift of endothermic peak with concentration is observed and the underlying mechanism is explored.

  1. Mesoscale modeling of phase transition dynamics of thermoresponsive polymers.

    PubMed

    Li, Zhen; Tang, Yu-Hang; Li, Xuejin; Karniadakis, George Em

    2015-06-25

    We present a non-isothermal mesoscopic model for investigation of the phase transition dynamics of thermoresponsive polymers. Since this model conserves energy in the simulations, it is able to correctly capture not only the transient behavior of polymer precipitation from solvent, but also the energy variation associated with the phase transition process. Simulations provide dynamic details of the thermally induced phase transition and confirm two different mechanisms dominating the phase transition dynamics. A shift of endothermic peak with concentration is observed and the underlying mechanism is explored. PMID:26062446

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

    NASA Astrophysics Data System (ADS)

    Zhou, Xinquan; Doup, Benjamin; Sun, Xiaodong

    2013-12-01

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

  3. Pressure-Induced Electronic Phase Transitions Transition Metal Oxides and Rare Earth Metals

    E-print Network

    Islam, M. Saif

    Pressure-Induced Electronic Phase Transitions in Transition Metal Oxides and Rare Earth Metals Metal Oxides and Rare Earth Metals by Brian Ross Maddox Electron correlation can affect profound changes transition in a transition metal monoxide. iv #12;The lanthanides (the 4f metals also known as rare-earths

  4. Pressure induced phase transitions in ceramic compounds containing tetragonal zirconia

    SciTech Connect

    Sparks, R.G.; Pfeiffer, G.; Paesler, M.A.

    1988-12-01

    Stabilized tetragonal zirconia compounds exhibit a transformation toughening process in which stress applied to the material induces a crystallographic phase transition. The phase transition is accompanied by a volume expansion in the stressed region thereby dissipating stress and increasing the fracture strength of the material. The hydrostatic component of the stress required to induce the phase transition can be investigated by the use of a high pressure technique in combination with Micro-Raman spectroscopy. The intensity of Raman lines characteristic for the crystallographic phases can be used to calculate the amount of material that has undergone the transition as a function of pressure. It was found that pressures on the order of 2-5 kBar were sufficient to produce an almost complete transition from the original tetragonal to the less dense monoclinic phase; while a further increase in pressure caused a gradual reversal of the transition back to the original tetragonal structure.

  5. Density-functional theory and Monte Carlo simulations of the phase behavior of a simple model liquid crystal.

    PubMed

    Giura, Stefano; Schoen, Martin

    2014-08-01

    We consider the phase behavior of a simple model of a liquid crystal by means of modified mean-field density-functional theory (MMF DFT) and Monte Carlo simulations in the grand canonical ensemble (GCEMC). The pairwise additive interactions between liquid-crystal molecules are modeled via a Lennard-Jones potential in which the attractive contribution depends on the orientation of the molecules. We derive the form of this orientation dependence through an expansion in terms of rotational invariants. Our MMF DFT predicts two topologically different phase diagrams. At weak to intermediate coupling of the orientation dependent attraction, there is a discontinuous isotropic-nematic liquid-liquid phase transition in addition to the gas-isotropic liquid one. In the limit of strong coupling, the gas-isotropic liquid critical point is suppressed in favor of a fluid- (gas- or isotropic-) nematic phase transition which is always discontinuous. By considering three representative isotherms in parallel GCEMC simulations, we confirm the general topology of the phase diagram predicted by MMF DFT at intermediate coupling strength. From the combined MMF DFT-GCEMC approach, we conclude that the isotropic-nematic phase transition is very weakly first order, thus confirming earlier computer simulation results for the same model [see M. Greschek and M. Schoen, Phys. Rev. E 83, 011704 (2011)]. PMID:25215749

  6. FULLY INTEGRATED ONE PHASE LIQUID COOLING SYSTEM FOR ORGANIC BOARDS

    E-print Network

    Paris-Sud XI, Université de

    into the environment and a pump and pipes to drive and contain the working fluid (most often water). Most presented in designing liquid cooling solu- tions are performance, reliability and price. To that end a one-phase liquid cooling concept is pro- posed, where all pumps, valves and piping are fully integrated on board level

  7. Elastic energy and string configurations in the chiral gauge theory of biaxial uniaxial nematic phase transitions

    E-print Network

    L. V. Elnikova

    2014-10-09

    In nematic liquid crystals (NLCs), topological defects of a chiral origin play a role in phase transitions and lead to phase configurations of nontrivial topology, like those in neutron stars and helium in the A-phase. In the biaxial-uniaxial phase transition, the deformation of the orbit, as the order parameter degeneracy of the NLC, connects together an evolution of topological defects, the surface anchoring energy and elastic Frank modui. In this work we estimate the chiral gauge field presentation of the constrained Ladnau-de Gennes theory of the biaxial nematics, which have to explain their topologically dependent phase transformation, using the description of the transformation of disclinations in the biaxial nematic phase into the surface bojooms of a uniaxial NLC.

  8. Solid + liquid phase equilibria in the hydroxylammonium nitrate + water system

    Microsoft Academic Search

    Johanne I. Artman; J. Bevan Ott

    1989-01-01

    The binary solid + liquid phase diagram has been measured for the water + hydroxylammonium nitrate (HAN) system. The phase diagram is a simple eutectic type with the eutectic at 231.5 K (41.7°C) and a mole fraction HAN of 0.281 (wt fraction HAN - 0.676).The enthalpy of fusion of the HAN was determined from the solid + liquid results to

  9. Cosmological Consequences of QCD Phase Transition(s) in Early Universe

    SciTech Connect

    Tawfik, A. [ECTP, Egyptian Center for Theoretical Physics, MTI Modern University, Mukattam Cairo (Egypt)

    2009-04-17

    We discuss the cosmological consequences of QCD phase transition(s) on the early universe. We argue that our recent knowledge about the transport properties of quark-gluon plasma (QGP) should thraw additional lights on the actual time evolution of our universe. Understanding the nature of QCD phase transition(s), which can be studied in lattice gauge theory and verified in heavy ion experiments, provides an explanation for cosmological phenomenon stem from early universe.

  10. Continuous phases in emulsions of three liquids

    SciTech Connect

    Smith, D.H. (Morgantown Energy Technology Center, WV (United States) Univ. of Oklahoma, Norman (United States)); Johnson, G.K. (Morgantown Energy Technology Center, WV (United States)); Dadyburjor, D.B. (West Virginia Univ., Morgantown (United States))

    1993-08-01

    For three-phase (macro)emulsions formed by the top (T), middle (M), and bottom (B) phases of amphiphile/oil/water systems, it has been variously stated in the literature either (1) that the continuous phase is always M or (2) that the continuous phase is B below the phase inversion temperature (PIT) and T above the PIT. We show by means of isothermal electrical conductivity measurements at various temperatures on emulsions of known phase volume fractions that neither hypothesis is generally correct. For our experimental conditions the [open quotes]choice[close quotes] of continuous phase depends on the phase volume fractions, and at all temperatures - by appropriate choice of phase volume fractions - any of T, M, or B may be made the continuous phase. 21 refs., 6 figs.

  11. Random laser emission in a sphere-phase liquid crystal

    NASA Astrophysics Data System (ADS)

    Zhu, Ji-Liang; Li, Wei-Huan; Sun, Yubao; Lu, Jian-Gang; Song, Xiao-Long; Chen, Chao-Yuan; Zhang, Zhidong; Su, Yikai

    2015-05-01

    We investigated random lasing from a fluid self-assembly sphere-phase liquid crystal, which was composed of three-dimensional twist sphere structures with disclinations among them. The threshold energy of the random lasing from sphere-phase liquid crystal was 32% of that from the chiral nematic phase because of the interference associated with multiple scattering by randomly distributed sphere-phase platelets. Such random lasers composed of self-assembly soft organic materials may be useful for holographic displays, point-of-care biomedical analysis, and optical security coatings.

  12. PIV measurements in a liquid liquid system at volume percentages up to 10% dispersed phase

    NASA Astrophysics Data System (ADS)

    Svensson, Fredrik J. E.; Rasmuson, Anders

    2006-12-01

    In this study the effect of the volume percentage dispersed phase on the flow structure in an immiscible liquid liquid system is investigated. A model system, consisting of two refraction index matched liquids, is presented along with velocity measurements of the continuous phase utilising the particle image velocimetry technique. Velocity fields at three locations have been measured inside a baffled cylindrical tank, stirred with a six-bladed Rushton turbine. The experiments show that this technique is applicable for volume fractions of up to 10% of dispersed phase. The magnitudes of velocity and turbulence are clearly affected by the level of the dispersed volume fraction.

  13. Phase transition induced by a shock wave in hard-sphere and hard-disk systems.

    PubMed

    Zhao, Nanrong; Sugiyama, Masaru; Ruggeri, Tommaso

    2008-08-01

    Dynamic phase transition induced by a shock wave in hard-sphere and hard-disk systems is studied on the basis of the system of Euler equations with caloric and thermal equations of state. First, Rankine-Hugoniot conditions are analyzed. The quantitative classification of Hugoniot types in terms of the thermodynamic quantities of the unperturbed state (the state before a shock wave) and the shock strength is made. Especially Hugoniot in typical two possible cases (P-1 and P-2) of the phase transition is analyzed in detail. In the case P-1 the phase transition occurs between a metastable liquid state and a stable solid state, and in the case P-2 the phase transition occurs through coexistence states, when the shock strength changes. Second, the admissibility of the two cases is discussed from a viewpoint of the recent mathematical theory of shock waves, and a rule with the use of the maximum entropy production rate is proposed as the rule for selecting the most probable one among the possible cases, that is, the most suitable constitutive equation that predicts the most probable shock wave. According to the rule, the constitutive equation in the case P-2 is the most promising one in the dynamic phase transition. It is emphasized that hard-sphere and hard-disk systems are suitable reference systems for studying shock wave phenomena including the shock-induced phase transition in more realistic condensed matters. PMID:18698913

  14. A Simplified Theory of Liquid-Solid Transitions. III HardCore Transitions

    Microsoft Academic Search

    Hazime Mori; Shiro Isa; Hisao Okamoto; Hiroshi Furukawa

    1972-01-01

    The hard-sphere transition predicted by computer experiments is theoretically studied with the aid of the expandable-lattice theory of liquid-solid transitions developed in previous two papers. The freezing and melting points are thus given in the mean energy approximation by P\\/kT_rho_c = 2.3577, rho_f\\/rho_c = 0.6819, rho_m\\/rho_c = 0.9053, where rho_c is the closest-packed density &surd;{2}\\/r_0^3, r_0 being the core diameter.{

  15. Liquid-phase deposition of single-phase alpha-copper-indium-diselenide

    Microsoft Academic Search

    J. Cowen; L. Lucas; F. Ernst; P. Pirouz; A. Hepp; S. Bailey

    2005-01-01

    Based on the first complete Cu–In–Se phase diagram, which was recently established, we propose a new method for making single-phase copper-indium-diselenide (CuInSe2) films for high-specific-power photovoltaic applications: “liquid-phase deposition.” Contrary to established methods, in particular physical vapor deposition, liquid-phase deposition operates close to thermodynamic equilibrium and should therefore yield films with a smaller concentration of defects and better photovoltaic performance.

  16. Method for identifying and probing phase transitions in materials

    DOEpatents

    Asay, Blaine W. (Los Alamos, NM); Henson, Bryan F. (Los Alamos, NM); Sander, Robert K. (Los Alamos, NM); Robinson, Jeanne M. (Los Alamos, NM); Son, Steven F. (Los Alamos, NM); Dickson, Peter M. (Los Alamos, NM)

    2002-01-01

    The present invention includes a method for identifying and probing phase transitions in materials. A polymorphic material capable of existing in at least one non-centrosymmetric phase is interrogated with a beam of laser light at a chosen wavelength and frequency. A phase transition is induced in the material while it is interrogated. The intensity of light scattered by the material and having a wavelength equal to one half the wavelength of the interrogating laser light is detected. If the phase transition results in the production of a non-centrosymmetric phase, the intensity of this scattered light increases; if the phase transition results in the disappearance of a non-centrosymmetric phase, the intensity of this scattered light decreases.

  17. Hydration-Responsive Folding and Unfolding in Graphene Oxide Liquid Crystal Phases

    PubMed Central

    Guo, Fei; Kim, Franklin; Han, Tae Hee; Shenoy, Vivek B.; Huang, Jiaxing; Hurt, Robert H.

    2011-01-01

    Graphene oxide is promising as a plate-like giant molecular building block for the assembly of new carbon materials. Its water dispersibility, liquid crystallinity, and ease of reduction offer advantages over other carbon precursors if its fundamental assembly rules can be identified. This article shows that graphene oxide sheets of known lateral dimension form nematic liquid crystal phases with transition points in agreement with the Onsager hard-plate theory. The liquid crystal phases can be systematic ordered into defined supramolecular patterns using surface anchoring, complex fluid flow, and micro-confinement. Graphene oxide is seen to exhibit homeotropic surface anchoring at interfaces driven by excluded volume entropy and by adsorption enthalpy associated with its partially hydrophobic basal planes. Surprisingly, some of the surface-ordered graphene oxide phases dry into graphene oxide solids that undergo a dramatic anisotropic swelling upon rehydration to recover their initial size and shape. This behavior is shown to be a unique hydration-responsive folding and unfolding transition. During drying, surface tension forces acting parallel to the layer planes cause a buckling instability that stores elastic energy in accordion-folded structures in the dry solid. Subsequent water infiltration reduces interlayer frictional forces and triggers release of the stored elastic energy in the form of dramatic unidirectional expansion. We explain the folding/unfolding phenomena by quantitative nanomechanics, and introduce the potential of liquid crystal-derived graphene oxide phases as new stimuli-response materials. PMID:21877716

  18. Hydration-responsive folding and unfolding in graphene oxide liquid crystal phases.

    PubMed

    Guo, Fei; Kim, Franklin; Han, Tae Hee; Shenoy, Vivek B; Huang, Jiaxing; Hurt, Robert H

    2011-10-25

    Graphene oxide is promising as a plate-like giant molecular building block for the assembly of new carbon materials. Its water dispersibility, liquid crystallinity, and ease of reduction offer advantages over other carbon precursors if its fundamental assembly rules can be identified. This article shows that graphene oxide sheets of known lateral dimension form nematic liquid crystal phases with transition points in agreement with the Onsager hard-plate theory. The liquid crystal phases can be systematically ordered into defined supramolecular patterns using surface anchoring, complex fluid flow, and microconfinement. Graphene oxide is seen to exhibit homeotropic surface anchoring at interfaces driven by excluded volume entropy and by adsorption enthalpy associated with its partially hydrophobic basal planes. Surprisingly, some of the surface-ordered graphene oxide phases dry into graphene oxide solids that undergo a dramatic anisotropic swelling upon rehydration to recover their initial size and shape. This behavior is shown to be a unique hydration-responsive folding and unfolding transition. During drying, surface tension forces acting parallel to the layer planes cause a buckling instability that stores elastic energy in accordion-folded structures in the dry solid. Subsequent water infiltration reduces interlayer frictional forces and triggers release of the stored elastic energy in the form of dramatic unidirectional expansion. We explain the folding/unfolding phenomena by quantitative nanomechanics and introduce the potential of liquid crystal-derived graphene oxide phases as new stimuli-response materials. PMID:21877716

  19. Possible explanations of phase transitions in highway traffic

    Microsoft Academic Search

    C. F. Daganzo; M. J. Cassidy; R. L. Bertini

    1999-01-01

    It is shown that all the phase transitions in and out of freely flowing traffic reported earlier for a German site could be caused by bottlenecks, as are all the transitions observed at two other sites examined here. The evidence suggests that bottlenecks cause these transitions in a predictable way, and does not suggest that stoppages (jams) appear spontaneously in

  20. New Phase transitions of the Ising model on Cayley trees

    E-print Network

    D. Gandolfo; F. H. Haydarov; U. A. Rozikov; J. Ruiz

    2013-06-25

    We show that the nearest neighbors Ising model on the Cayley tree exhibits new temperature driven phase transitions. These transitions holds at various inverse temperatures different from the critical one. They are depicted by a change in the number of Gibbs states as well as by a drastic change of the behavior of free energies at these new transition points.

  1. Studies of structures and phase transitions in pyrrhotite

    SciTech Connect

    Li, F.

    1997-03-31

    This report contains a general introduction, the experimental section, general conclusions, and two appendices: using projection operators to construct the basis functions and the magnetic transition of bulk pyrrhotite samples in the low-temperature range. Four chapters have been removed for separate processing. They are: From pyrrhotite to troilite: An application of the Landau theory of phase transitions; Phase transition in near stoichiometric iron sulfide; A ordering, incommensuration and phase transitions in pyrrhotite. Part 1: A TEM study of Fe{sub 7}S{sub 8}; and Part 2: A high-temperature X-ray powder diffraction and thermomagnetic study.

  2. Phase transitions in a gas of anyons

    SciTech Connect

    MacKenzie, R.; Nebia-Rahal, F.; Paranjape, M. B. [Groupe de physique des particules, Departement de physique, Universite de Montreal, C.P. 6128, Succ. Centre-ville, Montreal, Quebec, H3C 3J7 (Canada); Richer, J. [Reseau quebecois de calcul de haute performance, DGTIC, Universite de Montreal, C.P. 6128, Succ. Centre-ville, Montreal, Quebec, H3C 3J7 (Canada)

    2010-10-01

    We continue our numerical Monte Carlo simulation of a gas of closed loops on a 3 dimensional lattice, however, now in the presence of a topological term added to the action which corresponds to the total linking number between the loops. We compute the linking number using a novel approach employing certain notions from knot theory. Adding the topological term converts the particles into anyons. Interpreting the model as an effective theory that describes the 2+1-dimensional Abelian Higgs model in the asymptotic strong-coupling regime, the topological linking number simply corresponds to the addition to the action of the Chern-Simons term. The system continues to exhibit a phase transition as a function of the vortex mass as it becomes small. We find the following new results. The Chern-Simons term has no effect on the Wilson loop. On the other hand, it does effect the 't Hooft loop of a given configuration, adding the linking number of the 't Hooft loop with all of the dynamical vortex loops. We find the unexpected result that both the Wilson loop and the 't Hooft loop exhibit a perimeter law even though there are no massless particles in the theory, in both phases of the theory. It should be noted that our method suffers from numerical instabilities if the coefficient of the Chern-Simons term is too large; thus, we have restricted our results to small values of this parameter. Furthermore, interpreting the lattice loop gas as an effective theory describing the Abelian Higgs model is only known to be true in the infinite coupling limit; for strong but finite coupling this correspondence is only a conjecture, the validity of which is beyond the scope of this article.

  3. Photonic quantum-corral ring laser: A fermionic phase transition

    Microsoft Academic Search

    O'Dae Kwon; B. H. Park; J. Y. Kim; J. Bae; M. J. Kim; J. C. Ahn; O. H. Kwon

    2002-01-01

    Extensive Bose-Einstein condensation research activities have recently led to studies of fermionic atoms and optical confinements. Here we present a case of micro-optical fermionic electron phase transition. Optically confined ordering and phase transitions of a fermionic cloud in dynamic steady state are associated with Rayleigh emissions from photonic quantum ring manifold which are generated by nature without any ring lithography.

  4. On Landau Theory and Symmetric Energy Landscapes for Phase Transitions

    E-print Network

    Hormann, Kai

    On Landau Theory and Symmetric Energy Landscapes for Phase Transitions Kai Hormann Department of Informatics Clausthal University of Technology Johannes Zimmer Department of Mathematical Sciences University the global complex energy landscapes of phase transitions. For the sake of clarity and brevity the exposition

  5. CLUSTER KINETICS OF PHASE TRANSITIONS: APPLICATIONS TO INNOVATIVE TECHNOLOGIES

    Microsoft Academic Search

    Benjamin J. McCoy; Giridhar Madras

    2008-01-01

    Phase transitions are critical in many of the new technologies of interest to chemical engineers. Applications to materials processing and pharmaceuticals manufacture are among the uses for phase transition dynamics investigated with the methods of population balance modeling for clustering processes. The underlying phenomenon of clustering occurs during condensation processes such as crystallization from solution. Self-assembly of molecules or supramolecules

  6. Effect of pressure on phase transition in DTGS and LADTGS

    Microsoft Academic Search

    Yao Yushu; Li Fenying; Lin Xueshi; Zhao Zhengrong; Wang Min

    1990-01-01

    The effects of pressure on the phase transition in DTGS and LADTGS crystals have been investigated by means of dielectric constant measurements at high hydrostatic pressures up to 10 kbar. The behavior of the phase transition for DTGS under pressure is similar to that of TGS. For LADTGS, however, Tc varies non-monotonously with increase of pressure. The maximum of Tc

  7. First-order liquid crystal orientation transition on inhomogeneous substrates.

    PubMed

    Tsui, Ophelia K C; Lee, Fuk Kay; Zhang, Baoshe; Sheng, Ping

    2004-02-01

    In a recent experiment, we uncovered an unconventional liquid crystal (LC) orientation transition on microtextured substrates consisting of alternating horizontal and vertical corrugations. When the period of alternation was decreased toward approximately 1 microm, the LC alignment underwent an abrupt transition from inhomogeneous planar to a more uniform configuration with a large pretilt angle ( approximately 40 degrees ). With the aid of a model based on the competition between the Frank-Oseen elastic energy and a phenomenological surface potential of the form W(theta,phi)=(1/2)W((2))(theta) sin(2) theta+(1/4)W((4))(theta) sin(4) theta+(1/2)W(phi) cos(2) theta sin(2) phi(x,y) (where theta and phi are, respectively, the pretilt and azimuthal angles of the LC director and W((2))(theta), W((4))(theta), and W(phi) are constants) that demonstrated good agreement with experiment, we investigated the microscopic origin of the observed transition. It was found that this transition comprises two steps. First, the LC director homogenizes toward the phi=45 degrees azimuthal direction in the plane to relax the elastic energy. The resulting rise in azimuthal anchoring energy subsequently drives the LC to adopt a finite pretilt. The values of the W's deduced from the model reveal that the polar anchoring energy is about approximately 1/10 of the typical values, with the sin(4) theta term dominating the sin(2) theta term. We present a possible explanation for this unexpected finding. PMID:14995466

  8. Thermodynamic and conformational insights into the phase transition of a single flexible homopolymer chain using replica exchange Monte Carlo method.

    PubMed

    Wang, Lei; Li, Ningning; Xiao, Shiyan; Liang, Haojun

    2014-07-01

    The phase transition of a single flexible homopolymer chain in the limit condition of dilute solution is systematically investigated using a coarse-grained model. Replica exchange Monte Carlo method is used to enhance the performance of the conformation space exploration, and thus detailed investigation of phase behavior of the system can be provided. With the designed potentials, the coil-globule transition and the liquid-solid-like transition are identified, and the transition temperatures are measured with the conformational and thermodynamic analyses. Additionally, by extrapolating the coil-globule transition temperature, T ? , and the liquid-solid-like transition temperature T(L ? S) to the thermodynamic limit, N????, we found no "tri-critical" point in the current model. PMID:24961896

  9. J. Phys. II France 6 (1996) 1331-1340 SEPTEMBER1996, PAGE 1331 Grafted Rods: A Tilting Phase Transition

    E-print Network

    Boyer, Edmond

    1996-01-01

    director inside a liquid crystal cell with no electric or magnetic field applied is usually determinedJ. Phys. II France 6 (1996) 1331-1340 SEPTEMBER1996, PAGE 1331 Grafted Rods: A Tilting Phase 1996, accepted lo May1996) PACS.64.70.-p Specific phase transitions PACS.68.35.-p Solid suriaces

  10. Membrane phase transitions are responsible for imbibitional damage in dry pollen.

    PubMed

    Crowe, J H; Hoekstra, F A; Crowe, L M

    1989-01-01

    We have found that the most probable cause of the leakage seen when dry cells or organisms such as seeds, pollen, or yeast cells are plunged into water is a gel to liquid crystalline phase transition in membrane phospholipids accompanying rehydration. By using Fourier transform infrared spectroscopy we have recorded infrared spectra of CH(2) stretching vibrations in dry and partially hydrated intact pollen grains of Typha latifolia. The vibrational frequency changes abruptly as phospholipids pass through the gel to liquid crystalline phase transition. Below the apparent transition, viable pollen shows low germination and high leakage when placed in water, but above the transition germination increases and leakage decreases. The apparent transition temperature falls with increasing water content, much as in pure phospholipids. By using this phenomenon, it was possible to construct a hydration-dependent phase diagram for the intact pollen. This phase diagram has immediate applications since it has high predictive value for the viability of the pollen when it is placed in water. PMID:16594011

  11. Novel biaxial nematic phases of side-chain liquid crystalline polymers.

    PubMed

    Matsuyama, Akihiko

    2012-12-14

    We present a mean field theory to describe biaxial nematic phases of side-chain liquid crystalline polymers, in which rigid side-chains (mesogens) and rigid-backbone chains favor mutually perpendicular orientations. Taking into account both excluded volume and attractive interactions between rigid rods, novel biaxial nematic phases are theoretically predicted. We calculate uniaxial and biaxial orientational order parameters as a function of temperature and the length of backbone chains. We find a first-order biaxial-biaxial phase transition and a first (or second)-order uniaxial-biaxial one, depending on the length of mesogens and backbone chains. PMID:23249031

  12. Edward A. Bouchet Award Talk: Nuclear liquid-gas phase diagram - What have learned?

    NASA Astrophysics Data System (ADS)

    Lopez, Jorge

    2015-04-01

    Heavy ion reactions started fragmenting nuclei since the 1980. In the intervening decades the study of such fragmentations taught us that nuclear matter has both liquid and gaseous phases that can undergo phase transitions, can exhibit critical phenomena, and many other rich phenomena. In this talk a summary of experimental and theoretical efforts leading to the understanding of the thermodynamical properties of nuclear matter will be presented, including those recent ones that extend the phase diagram in a new direction: isospin. Work supported by NSF Grant 1066031.

  13. Thermal and Structural Studies of Imidazolium-Based Ionic Liquids with and without Liquid-Crystalline Phases: The Origin of Nanostructure.

    PubMed

    Nemoto, Fumiya; Kofu, Maiko; Yamamuro, Osamu

    2015-04-16

    To clarify the origin of the nanostructure of ionic liquids (ILs), we have investigated two series of ILs 1-alkyl-3-methylimidazolium hexafluorophosphate (CnmimPF6, n = 4-16, n is an alkyl-carbon number) and 1-alkyl-3-methylimidazolium chloride (CnmimCl, n = 4-14) using differential scanning calorimetry and X-ray diffraction techniques. The PF6 samples with n > 13 and the Cl samples with n > 10 exhibited the liquid-crystalline (LC) to liquid (L) phase transitions, as reported before. We found that both samples with smaller n also exhibited the LC to L transitions under supercooled states as far as the ionic motions were not frozen-in at the glass transition temperatures Tg. The Tg of the LC phase was close to that of the L phase, indicating that the characteristic length of the glass transition is shorter than that of the nanostructure. A low-Q peak due to the nanostructure in the L phase and a diffraction peak due to the layer structure in the LC phase appeared at almost the same Q positions in both samples. On the basis of the above results and some thermodynamic analysis, we argue that the nanostructures of ILs are essentially the same as the layer structures in the LC phases. PMID:25790251

  14. Quark-Hadron Phase Transitions in Viscous Early Universe

    E-print Network

    A. Tawfik; T. Harko

    2012-04-15

    Based on hot big bang theory, the cosmological matter is conjectured to undergo QCD phase transition(s) to hadrons, when the universe was about $1-10 \\mu$s old. In the present work, we study the quark-hadron phase transition, by taking into account the effect of the bulk viscosity. We analyze the evolution of the quantities relevant for the physical description of the early universe, namely, the energy density $\\rho$, temperature $T$, Hubble parameter $H$ and scale factor $a$ before, during and after the phase transition. To study the cosmological dynamics and the time evolution we use both analytical and numerical methods. By assuming that the phase transition may be described by an effective nucleation theory (prompt {\\it first-order} phase transition), we also consider the case where the universe evolved through a mixed phase with a small initial supercooling and monotonically growing hadronic bubbles. The numerical estimation of the cosmological parameters, $a$ and $H$ for instance, makes it clear that the time evolution varies from phase to phase. As the QCD era turns to be fairly accessible in the high-energy experiments and the lattice QCD simulations, the QCD equation of state is very well defined. In light of this, we introduce a systematic study of the {\\it cross-over} quark-hadron phase transition and an estimation for the time evolution of Hubble parameter.

  15. Phase transition and correlation effects in vanadium dioxide

    SciTech Connect

    Ilinskiy, A. V. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Kvashenkina, O. E. [St. Petersburg State Polytechnical University (Russian Federation); Shadrin, E. B., E-mail: shardr.solid@mail.ioffe.ru [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2012-04-15

    A complex concept concerning the multistage process of thermal semiconductor-metal phase transition in vanadium dioxide is proposed. According to the concept, the transition proceeds in three stages: two stages occurring in a system of strongly correlated electrons and one stage which reduces to transformation of the crystal lattice symmetry. These stages can be initiated individually by hydrogenating the polycrystalline VO{sub 2} film, since hydrogenation selectively affects different stages of the phase transition.

  16. Effect of enantiomeric excess on the phase behavior of antiferroelectric liquid crystals.

    PubMed

    Pan, LiDong; McCoy, B K; Wang, Shun; Liu, Z Q; Wang, S T; Pindak, R; Huang, C C

    2011-06-01

    Null transmission ellipsometry and resonant x-ray diffraction are employed to study the effect of enantiomeric excess (EE) on the phase behavior of antiferroelectric liquid crystal 10OTBBB1M7. Phase sequence, layer spacing, and pitch of the helical structures of the smectic-C(?)* and smectic-C* phases are studied as a function of temperature and EE. Upon reducing EE, a liquid-gas-type critical point of the smectic-C(?)* to smectic-C* transition is observed, as well as the disappearance of the smectic-C(d4)* and the smectic-C(d3)* phases. Results are analyzed in a mean-field model. PMID:21797292

  17. Crystalline phase transitions and acoustic phonons behaviour of polymorphic ethanol

    NASA Astrophysics Data System (ADS)

    Jiménez Riobóo, R. J.; Kabtoul, B.; Ramos, M. A.

    2009-09-01

    Ethanol shows a complex scenario of different crystalline phases in the temperature range between its glass transition at Tg = 97 K and its melting point at Tm = 159 K. Brillouin spectroscopy has revealed capable of observing and assessing acoustic phonon changes related to these phase transitions between different crystalline phases (either a plastic-crystal phase or different monoclinic phases). By combining this technique and calorimetric experimental data, we are able to corroborate the existence of at least two stable and two metastable (monoclinic) crystalline phases of pure ethanol.

  18. Gamma-ray spectra of hexane in gas phase and liquid phase

    E-print Network

    Xiaoguang Ma; Feng Wang

    2012-11-01

    Theoretical gamma-ray spectra of molecule hexane have been calculated and compared with the experimental results in both gas (Surko et al, 1997) and liquid (Kerr et al, 1965) phases. The present study reveals that in gas phase not all valence electrons of hexane exhibit the same probability to annihilate a positron. Only the positrophilic electrons in the valence space dominate the gamma-ray spectra, which are in good agreement with the gas phase measurement. When hexane is confined in liquid phase, however, the intermolecular interactions ultimately eliminate the free molecular orientation and selectivity for the positrophilic electrons in the gas phase. As a result, the gamma-ray spectra of hexane become an averaged contribution from all valence electrons, which is again in agreement with liquid phase measurement. The roles of the positrophilic electrons in annihilation process for gas and liquid phases of hexane have been recognized for the first time in the present study.

  19. A single-component liquid-phase hydrogen storage material.

    PubMed

    Luo, Wei; Campbell, Patrick G; Zakharov, Lev N; Liu, Shih-Yuan

    2011-12-01

    The current state-of-the-art for hydrogen storage is compressed H(2) at 700 bar. The development of a liquid-phase hydrogen storage material has the potential to take advantage of the existing liquid-based distribution infrastructure. We describe a liquid-phase hydrogen storage material that is a liquid under ambient conditions (i.e., at 20 °C and 1 atm pressure), air- and moisture-stable, and recyclable; releases H(2) controllably and cleanly at temperatures below or at the proton exchange membrane fuel cell waste-heat temperature of 80 °C; utilizes catalysts that are cheap and abundant for H(2) desorption; features reasonable gravimetric and volumetric storage capacity; and does not undergo a phase change upon H(2) desorption. PMID:22070729

  20. Determination of Atmospheric Hydroxyl Radical by Liquid Phase Scrubbing and High Performance Liquid Chromatography

    Microsoft Academic Search

    Xiaohui Chen

    1995-01-01

    A new in situ method for determining atmospheric hydroxyl radical (OH) was developed. This method is based on liquid phase scrubbing technique and high performance liquid chromatography (LPS-HPLC). The sampling system employs glass bubblers to trap atmospheric OH into a buffered solution containing the chemical probe, salicylic acid (o-hydroxybenzoic acid, OHBA). The reaction of OHBA with OH produces a stable

  1. Calculating Partition Coecients of Chain Anchors in Liquid-Ordered and Liquid-Disordered Phases

    Microsoft Academic Search

    Mark J. Uline; Gabriel S. Longo; M. Schick; Igal Szleifer

    We calculate partition coe!cients of various chain anchorsin liquid-ordered and liquid- disordered phases utilizing a theoretical model of a bilayer membrane containing cholesterol, di- palmitoylphophatidylcholine (DPPC), and dioleoylphosphatidylcholine (DOPC). The partition coe!cients are calculated as a function of chain length, degree of saturation, and temperature. Partitioning depends on the di\\

  2. Nematohydrodynamic Effects on the Phase Separation of a Symmetric Mixture of an Isotropic Liquid and a Liquid Crystal

    E-print Network

    Nematohydrodynamic Effects on the Phase Separation of a Symmetric Mixture of an Isotropic Liquid phase-separation dynamics of symmetric mixtures of an isotropic liquid and a liquid crystal- separation of polymers and liquid crystals, are widely applied for electro-optical devices. Theoretically

  3. Technical feasibility of transition phase tests in TREAT. [LMFBR

    SciTech Connect

    Stewart, R.R.; Bauer, T.H.; Hoff, O.I.; Koyama, K.; Stephenson, M.E.; Kraft, T.E.

    1982-01-01

    Understanding the behavior of molten fuel-steel mixtures subjected to fission heating within a HCDA environment is essential to continuing the mechanistic description of the whole-core accident into the transition phase, and further to a permanent subcritical and safe fuel debris configuration. Fundamentally, the RX1 TREAT test will simulte the transition phase of a HCDA (the accident phase in which the fuel in individual subassemblies melts and becomes a heat-generating pool of molten fuel and boiling steel). This assessment of the feasibility of such a test indicates that a transition phase test can be achieved in TREAT, at power levels simulating decay heat.

  4. Dynamic compression experiments on liquid deuterium above the melt boundary to investigate the insulator-to-metal transition

    NASA Astrophysics Data System (ADS)

    Knudson, Marcus

    2014-10-01

    Recently we have been exploring various pulsed power experimental concepts to access off-Hugoniot states in liquids at the Sandia Z Accelerator. One very promising technique utilizes a so-called shock-ramp platform. Here a relatively small gap is introduced between the ramp compression load electrode and a liquid sample cell. The accelerator is configured to deliver a two-step current pulse; the first step accelerates the electrode to a reasonably constant velocity, which upon impact with the sample cell creates a well-defined shock, while the subsequent current rise produces ramp compression from the initially shocked state. This technique makes it possible to achieve relatively cool (~ 1000-2000 K), high pressure (> 300 GPa), high compression states (~ 10-15 fold compression), allowing experimental access to the region of phase space where hydrogen is predicted to undergo a first-order phase transition from an insulating molecular-like liquid to a conducting atomic-like fluid. In this talk we will discuss the development of the liquid shock-ramp platform, survey the various theoretical predictions for the liquid-liquid transition in hydrogen, and present the results of initial experiments performed that access this region of phase space. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  5. The electro-mechanical phase transition of Gent model dielectric elastomer tube with two material constants

    NASA Astrophysics Data System (ADS)

    Liu, Liwu; Luo, Xiaojian; Fei, Fan; Wang, Yixing; Leng, Jinsong; Liu, Yanju

    2013-04-01

    Applied to voltage, a dielectric elastomer membrane may deform into a mixture of two states under certain conditions. One of which is the flat state and the other is the wrinkled state. In the flat state, the membrane is relatively thick with a small area, while on the contrary, in the wrinkled state, the membrane is relatively thin with a large area. The coexistence of these two states may cause the electromechanical phase transition of dielectric elastomer. The phase diagram of idea dielectric elastomer membrane under unidirectional stress and voltage inspired us to think about the liquid-to-vapor phase transition of pure substance. The practical working cycle of a steam engine includes the thermodynamical process of liquid-to-vapor phase transition, the fact is that the steam engine will do the maximum work if undergoing the phase transition process. In this paper, in order to consider the influence of coexistent state of dielectric elastomer, we investigate the homogeneous deformation of the dielectric elastomer tube. The theoretical model is built and the relationship between external loads and stretch are got, we can see that the elastomer tube experiences the coexistent state before reaching the stretching limit from the diagram. We think these results can guide the design and manufacture of energy harvesting equipments.

  6. Insight into Structural Phase Transitions from Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Ruzsinszky, Adrienn

    2014-03-01

    Structural phase transitions caused by high pressure or temperature are very relevant in materials science. The high pressure transitions are essential to understand the interior of planets. Pressure or temperature induced phase transitions can be relevant to understand other phase transitions in strongly correlated systems or molecular crystals.Phase transitions are important also from the aspect of method development. Lower level density functionals, LSDA and GGAs all fail to predict the lattice parameters of different polymorphs and the phase transition parameters at the same time. At this time only nonlocal density functionals like HSE and RPA have been proved to resolve the geometry-energy dilemma to some extent in structural phase transitions. In this talk I will report new results from the MGGA_MS family of meta-GGAs and give an insight why this type of meta-GGAs can give a systematic improvement of the geometry and phase transition parameters together. I will also present results from the RPA and show a possible way to improve beyond RPA.

  7. Gas liquid flow at microgravity conditions - Flow patterns and their transitions

    NASA Technical Reports Server (NTRS)

    Dukler, A. E.; Fabre, J. A.; Mcquillen, J. B.; Vernon, R.

    1987-01-01

    The prediction of flow patterns during gas-liquid flow in conduits is central to the modern approach for modeling two phase flow and heat transfer. The mechanisms of transition are reasonably well understood for flow in pipes on earth where it has been shown that body forces largely control the behavior observed. This work explores the patterns which exist under conditions of microgravity when these body forces are suppressed. Data are presented which were obtained for air-water flow in tubes during drop tower experiments and Learjet trajectories. Preliminary models to explain the observed flow pattern map are evolved.

  8. Reentrant topological phase transitions in a disordered spinless superconducting wire

    NASA Astrophysics Data System (ADS)

    Rieder, Maria-Theresa; Brouwer, Piet W.; Adagideli, ?nanç

    2013-08-01

    In a one-dimensional spinless p-wave superconductor with coherence length ?, disorder induces a phase transition between a topologically nontrivial phase and a trivial insulating phase at the critical mean-free path l=?/2. Here, we show that a multichannel spinless p-wave superconductor goes through an alternation of topologically trivial and nontrivial phases upon increasing the disorder strength, the number of phase transitions being equal to the channel number N. The last phase transition, from a nontrivial phase into the trivial phase, takes place at a mean-free path l=?/(N+1), parametrically smaller than the critical mean-free path in one dimension. Our result is valid in the limit that the wire width W is much smaller than the superconducting coherence length ?.

  9. Two-step nucleation mechanism in solid-solid phase transitions.

    PubMed

    Peng, Yi; Wang, Feng; Wang, Ziren; Alsayed, Ahmed M; Zhang, Zexin; Yodh, Arjun G; Han, Yilong

    2015-01-01

    The microscopic kinetics of ubiquitous solid-solid phase transitions remain poorly understood. Here, by using single-particle-resolution video microscopy of colloidal films of diameter-tunable microspheres, we show that transitions between square and triangular lattices occur via a two-step diffusive nucleation pathway involving liquid nuclei. The nucleation pathway is favoured over the direct one-step nucleation because the energy of the solid/liquid interface is lower than that between solid phases. We also observed that nucleation precursors are particle-swapping loops rather than newly generated structural defects, and that coherent and incoherent facets of the evolving nuclei exhibit different energies and growth rates that can markedly alter the nucleation kinetics. Our findings suggest that an intermediate liquid should exist in the nucleation processes of solid-solid transitions of most metals and alloys, and provide guidance for better control of the kinetics of the transition and for future refinements of solid-solid transition theory. PMID:25218059

  10. Two-step nucleation mechanism in solid–solid phase transitions

    NASA Astrophysics Data System (ADS)

    Peng, Yi; Wang, Feng; Wang, Ziren; Alsayed, Ahmed M.; Zhang, Zexin; Yodh, Arjun G.; Han, Yilong

    2015-01-01

    The microscopic kinetics of ubiquitous solid–solid phase transitions remain poorly understood. Here, by using single-particle-resolution video microscopy of colloidal films of diameter-tunable microspheres, we show that transitions between square and triangular lattices occur via a two-step diffusive nucleation pathway involving liquid nuclei. The nucleation pathway is favoured over the direct one-step nucleation because the energy of the solid/liquid interface is lower than that between solid phases. We also observed that nucleation precursors are particle-swapping loops rather than newly generated structural defects, and that coherent and incoherent facets of the evolving nuclei exhibit different energies and growth rates that can markedly alter the nucleation kinetics. Our findings suggest that an intermediate liquid should exist in the nucleation processes of solid–solid transitions of most metals and alloys, and provide guidance for better control of the kinetics of the transition and for future refinements of solid–solid transition theory.

  11. Possible existence of two amorphous phases of d-mannitol related by a first-order transition

    NASA Astrophysics Data System (ADS)

    Zhu, Men; Wang, Jun-Qiang; Perepezko, John H.; Yu, Lian

    2015-06-01

    We report that the common polyalcohol d-mannitol may have two amorphous phases related by a first-order transition. Slightly above its glass transition temperature Tg (284 K), the supercooled liquid (SCL) of d-mannitol transforms to a low-energy, apparently amorphous phase with stronger hydrogen bonds. The enthalpy of this so-called Phase X is approximately halfway between those of the known amorphous and crystalline phases, a position low for glass aging and high for crystal polymorphs. Similar to the SCL, Phase X is transparent with broad X-ray diffraction and Raman scattering; upon temperature cycling, it exhibits a glass-transition-like change of heat capacity. On fast heating, Phase X transforms back to the SCL near Tg + 50 K, enabling a determination of their equilibrium temperature. The presence of d-sorbitol as a plasticizer enables observation of a first-order transition from the SCL to Phase X entirely in the liquid state (liquid-liquid transition). The transition from d-mannitol's SCL to Phase X has intriguing similarities with the formation of the glacial phase of triphenyl phosphite (TPP) and the conversion from high-density to low-density amorphous ice, both studied intensely in the context of polyamorphism. All three processes occur near Tg with substantial enthalpy decrease toward the crystalline phases; the processes in water and d-mannitol both strengthen the hydrogen bonds. In contrast to TPP, d-mannitol's Phase X forms more rapidly and can transform back to the SCL. These features make d-mannitol a valuable new model for understanding polyamorphism.

  12. Detection of an intermediate biaxial phase in the phase diagram of biaxial liquid crystals: entropic sampling study.

    PubMed

    Kamala Latha, B; Jose, Regina; Murthy, K P N; Sastry, V S S

    2014-05-01

    We investigate the phase sequence of biaxial liquid crystals, based on a general quadratic model Hamiltonian over the relevant parameter space, with a Monte Carlo simulation which constructs equilibrium ensembles of microstates, overcoming possible (free) energy barriers (combining entropic and frontier sampling techniques). The resulting phase diagram qualitatively differs from the universal phase diagram predicted earlier from mean-field theory (MFT), as well as the Monte Carlo simulations with the Metropolis algorithm. The direct isotropic-to-biaxial transition predicted by the MFT is replaced in certain regions of the space by the onset of an additional intermediate biaxial phase of very low order, leading to the sequence N(B)-N(B1)-I. This is due to inherent barriers to fluctuations of the components comprising the total energy, and may explain the difficulties in the experimental realization of these phases. PMID:25353730

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

    Microsoft Academic Search

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

    2003-01-01

    This paper reports on the directed self-assembly of nanoparticles onto charged surface areas with a resolution of 200 nm from the liquid phase and 100 nm from the gas phase. The charged areas required for this type of nanoxerographic printing were fabricated using a parallel method that employs a flexible, electrically conductive, electrode to charge a thin-film electret. As electrodes,

  14. Domain Growth in Chiral Phase Transitions: Inertial Dynamics

    E-print Network

    Awaneesh Singh; Sanjay Puri; Hiranmaya Mishra

    2013-05-25

    We investigate the kinetics of phase transitions for chiral symmetry breaking in heavy-ion collisions. We use a Langevin description for order-parameter kinetics in the chiral transition. The Langevin equation of motion includes {\\it dissipation} and an {\\it inertial term}. We study the ordering dynamics subsequent to a quench from the massless quark phase to the massive quark phase, and discuss the effect of inertia on the growth kinetics.

  15. Domain growth in chiral phase transitions: Role of inertial dynamics

    NASA Astrophysics Data System (ADS)

    Singh, Awaneesh; Puri, Sanjay; Mishra, Hiranmaya

    2013-06-01

    We investigate the kinetics of phase transitions for chiral symmetry breaking in heavy-ion collisions. We use a Langevin description for order-parameter kinetics in the chiral transition. The Langevin equation of motion includes dissipation and an inertial term. We study the ordering dynamics subsequent to a quench from the massless quark phase to the massive quark phase, and discuss the effect of inertia on the growth kinetics.

  16. Pressure-induced phase transition of HgS

    NASA Technical Reports Server (NTRS)

    Huang, T.; Ruoff, A. L.

    1983-01-01

    The high pressure phase transition of cinnabar (alpha-HgS) was studied by energy dispersive X-ray diffraction using a synchrotron X-ray source. The cinnabar crystal structure was found to transform to the sodium-chloride structure at about 130 kbar. The lattice parameter of the new phase was determined to be 5.070 + or - 0.005 A at 300 kbar. No further phase transition was observed up to 400 kbar.

  17. High-pressure isosymmetric phase transition in orthorhombic lead fluoride

    Microsoft Academic Search

    J. Haines; J. M. Léger; O. Schulte

    1998-01-01

    Orthorhombic alpha-PbF2 was investigated at high pressure by angle-dispersive, x-ray powder diffraction. A phase transition between the cotunnite-structured alpha phase (alpha-PbCl2-type, space group Pnam, Z=4) and a second orthorhombic gamma phase (Co2Si-related, space group Pnam, Z=4) was observed beginning at close to 10 GPa. The experimental evidence is consistent with a first-order, isosymmetric transition with a volume change of 2%.

  18. Defects and order in liquid crystal phases

    Microsoft Academic Search

    Shilpa Jain

    1999-01-01

    This thesis investigates the partial destruction of ordering in liquid crystalline systems due to the influence of defects and thermal fluctuations. The systems under consideration are hexagonal columnar crystals with crystalline order perpendicular to the columns, and two-dimensional smectics with order perpendicular to the layers. We first study the possibility of reentrant melting of a hexagonal columnar crystal of flexible

  19. The liquid and vapor phases in particle models with Kac potentials

    E-print Network

    Roma Tor Vergata, Università di

    The liquid and vapor phases in particle models with Kac potentials F. BaÆoni, I. Merola, and E curve #21; = #21;(#12;), #12; > #12; c > 0, where two phases (liquid and vapor) coexist, elsewhere #12; LIQUID AND VAPOR PHASES 2 P T liquid solid gas Figure 1. Phase diagram well understood. Indeed

  20. Decohering the Fermi liquid: A dual approach to the Mott transition

    E-print Network

    Todadri, Senthil

    We present a theoretical approach to describing the Mott transition of electrons on a two-dimensional lattice that begins with the low-energy effective theory of the Fermi liquid. The approach to the Mott transition must ...

  1. Quantum Phase Transitions Induced by the Spin--Orbit Interaction in the N = 1 Landau Level

    NASA Astrophysics Data System (ADS)

    Ito, Toru; Nomura, Kentaro; Shibata, Naokazu

    2012-03-01

    The effect of the spin--orbit interaction on the fractional quantum Hall states at filling factors ? = 7/3, 5/2, and 12/5 is studied by the exact diagonalization method and density-matrix renormalization group (DMRG) method. We calculate the excitation energy gap, ground-state pair-correlation functions, and the topological entanglement entropy to analyze the effect of the spin--orbit interaction. The obtained results show that, at ?=7/3, the spin--orbit interaction destabilizes the parafermion state, leading to the phase transition to the Laughlin state. At ?=5/2 the Pfaffian state is stabilized but the phase transition to the composite fermion liquid state finally occurs. At ?=12/5, the parafermion ground state is destabilized and the phase transition to the Jain state occurs.

  2. Statistical mechanics of bend flexoelectricity and the twist-bend phase in bent-core liquid crystals

    E-print Network

    Shaikh M. Shamid; Subas Dhakal; Jonathan V. Selinger

    2013-05-21

    We develop a Landau theory for bend flexoelectricity in liquid crystals of bent-core molecules. In the nematic phase of the model, the bend flexoelectric coefficient increases as we reduce the temperature toward the nematic to polar phase transition. At this critical point, there is a second order transition from high-temperature uniform nematic phase to low-temperature nonuniform polar phase composed of twist-bend or splay-bend deformations. To test the predictions of Landau theory, we perform Monte Carlo simulations to find the director and polarization configurations as functions of temperature, applied electric field, and interaction parameters.

  3. Statistical mechanics of bend flexoelectricity and the twist-bend phase in bent-core liquid crystals.

    PubMed

    Shamid, Shaikh M; Dhakal, Subas; Selinger, Jonathan V

    2013-05-01

    We develop a Landau theory for bend flexoelectricity in liquid crystals of bent-core molecules. In the nematic phase of the model, the bend flexoelectric coefficient increases as we reduce the temperature toward the nematic to polar phase transition. At this critical point, there is a second-order transition from high-temperature uniform nematic phase to low-temperature nonuniform polar phase composed of twist-bend or splay-bend deformations. To test the predictions of Landau theory, we perform Monte Carlo simulations to find the director and polarization configurations as functions of temperature, applied electric field, and interaction parameters. PMID:23767556

  4. Confinement effects on the glass transition of hydrogen bonded liquids

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; Simon, Sindee L.

    2007-11-01

    The glass transition behavior of glycerol and propylene glycol confined in nanoporous glass is investigated using differential scanning calorimetry. Both silanized and unsilanized porous glasses are used to confine the liquids with nominal pore sizes ranging from 2.5to7.5nm, and the glass transition temperature (Tg) and the limiting fictive temperature (Tf') sare measured on cooling and heating, respectively. The effect of pore fullness is also examined. We find that differences in Tg, ?Cp, and the enthalpy overshoot behavior observed on heating are significant between partially and completely filled pores for the case of the unsilanized controlled pore glasses (CPGs) but that the effect of pore fullness is insignificant for the silanized CPGs. In general, the behavior in the silanized CPGs is similar to the behavior in the completely filled unsilanized pores. For glycerol, this includes a small depression in Tf' on the order of 5K at 2.5nm. For propylene glycol, similar behavior is found except that an additional glass transition is observed in both silanized and unsilanized systems approximately 30K higher than the bulk and a slightly smaller depression on the order of 3K at 2.5nm is observed in the completely filled unsilanized pores and in partially and completely filled silanized pores. The results are compared to those in the literature, and the confinement effects are discussed.

  5. The Electroweak Phase Transition in the Inert Doublet Model

    E-print Network

    Blinov, Nikita; Stefaniak, Tim

    2015-01-01

    We study the strength of a first-order electroweak phase transition in the Inert Doublet Model (IDM), where particle dark matter (DM) is comprised of the lightest neutral inert Higgs boson. We improve over previous studies in the description and treatment of the finite-temperature effective potential and of the electroweak phase transition. We focus on a set of benchmark models inspired by the key mechanisms in the IDM leading to a viable dark matter particle candidate, and illustrate how to enhance the strength of the electroweak phase transition by adjusting the masses of the yet undiscovered IDM Higgs states. We argue that across a variety of DM masses, obtaining a strong enough first-order phase transition is a generic possibility in the IDM. We find that due to direct dark matter searches and collider constraints, a sufficiently strong transition and a thermal relic density matching the universal DM abundance is possible only in the Higgs funnel regime.

  6. New ferroelastic phase transition induced by impurity tunneling with a structural local transition

    NASA Astrophysics Data System (ADS)

    Vikhnin, V. S.; Maksimova, T. I.

    2009-12-01

    We predict a new ferroelastic phase transition in a matrix, which is induced by the tunneling states appearing under the conditions of structural local transitions for impurity ions. This ferroelastic phase transition has been studied in crystals of the proper ferroelastic K3Na(CrO4)2 with impurity molecular ions of MnO{4/2-} and the dielectric KCl with impurity atoms of Cu0. A model of the induced phase transitions of this type is proposed and the related applications are discussed.

  7. Salt-induced phase separation in the liquid crystalline phase of phosphatidylcholines

    Microsoft Academic Search

    Michael Rappolt; Georg Pabst; Heinz Amenitsch; Peter Laggner

    2001-01-01

    The effects of alkali chlorides on multilamellar vesicles of various phosphatidylcholines in the lamellar liquid crystalline L?-phase were investigated by using small-angle X-ray scattering. At alkali chloride concentrations above 70 mM (LiCl) a phase separation in the liquid crystalline phase of POPC is induced. The splitting of the first and second order diffraction peaks into two major discrete components indicates

  8. Clusterization and phase-transitions in atomic nuclei

    SciTech Connect

    Darai, J. [Institute of Experimental Physics, University of Debrecen, Debrecen Pf. 105, 4010 (Hungary); Cseh, J. [Institute of Nuclear Research, Debrecen Pf 51, 4001 (Hungary); Hess, P. O. [Instituto de Sciancias Nucleares, UNAM, A. P. 70-543, 04510 Mexico D. F. (Mexico)

    2011-10-28

    The question of phases and phase-transitions of cluster states is reviewed. First some features of the algebraic models are recalled. Then we address the question, what the experimental spectrum of {sup 20}Ne suggests on the phase of the {sup 16}O+{alpha} system.

  9. Growth and the Phase Transition of Indium Sulfide Ultrafine Particle

    NASA Astrophysics Data System (ADS)

    Ueda, Masahiro; Suzuki, Hitoshi; Kido, Osamu; Shintaku, Masayuki; Kurumada, Mami; Sato, Takeshi; Saito, Yoshio; Kaito, Chihiro

    2005-05-01

    Indium sulfide particles produced in smoke have been analyzed by transmission electron microscopy. Three phases, ?, ? and ?' with the different external shapes were produced. A mixture phase of ? and ?' was found and the lattice relation was elucidated. The phase transition temperatures were assigned to be 400°C (? to ?) and 500°C (?' to ?).

  10. Thermodynamics at the nanoscale: phase diagrams of nickel-carbon nanoclusters and equilibrium constants for phase transitions.

    PubMed

    Engelmann, Yannick; Bogaerts, Annemie; Neyts, Erik C

    2014-10-21

    Using reactive molecular dynamics simulations, the melting behavior of nickel-carbon nanoclusters is examined. The phase diagrams of icosahedral and Wulff polyhedron clusters are determined using both the Lindemann index and the potential energy. Formulae are derived for calculating the equilibrium constants and the solid and liquid fractions during a phase transition, allowing more rational determination of the melting temperature with respect to the arbitrary Lindemann value. These results give more insight into the properties of nickel-carbon nanoclusters in general and can specifically be very useful for a better understanding of the synthesis of carbon nanotubes using the catalytic chemical vapor deposition method. PMID:25177915

  11. A liquid crystalline phase in spermidine-condensed DNA.

    PubMed Central

    Sikorav, J L; Pelta, J; Livolant, F

    1994-01-01

    Over a large range of salt and spermidine concentrations, short DNA fragments precipitated by spermidine (a polyamine) sediment in a pellet from a dilute isotropic supernatant. We report here that the DNA-condensed phase consists of a cholesteric liquid crystal in equilibrium with a more concentrated phase. These results are discussed according to Flory's theory for the ordering of rigid polymers. The liquid crystal described here corresponds to an ordering in the presence of attractive interactions, in contrast with classical liquid crystalline DNA. Polyamines are often used in vitro to study the functional properties of DNA. We suggest that the existence of a liquid crystalline state in spermidine-condensed DNA is relevant to these studies. Images FIGURE 1 PMID:7819480

  12. Continuous phase transition in the region of the vacuum arc cathode spot

    SciTech Connect

    Askari, S.; Minoo, H. [Department of Physics, KNT University, Tehran 19697 (Iran, Islamic Republic of); Moussakhani, K. [Department of Electrical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

    2008-09-15

    A model for the near-cathode region of electric arcs is presented to investigate the liquid-plasma phase transition in the cathode spot region. Due to the high values of pressure and temperature after spot ignition, a 'continuous phase transition' occurs in the liquid-vapor interface. A set of fluid equations with suitable boundary conditions have been solved to obtain diagrams of the spot plasma in the temperature-density plane during the spot evolution for a typical spot. To evaluate the model, the magnitude of some essential quantities such as the mean ion charge state of plasma and current density have been calculated, which are in accordance with experimental results.

  13. Observation of topological phase transitions in photonic quasicrystals.

    PubMed

    Verbin, Mor; Zilberberg, Oded; Kraus, Yaacov E; Lahini, Yoav; Silberberg, Yaron

    2013-02-15

    Topological insulators and topological superconductors are distinguished by their bulk phase transitions and gapless states at a sharp boundary with the vacuum. Quasicrystals have recently been found to be topologically nontrivial. In quasicrystals, the bulk phase transitions occur in the same manner as standard topological materials, but their boundary phenomena are more subtle. In this Letter we directly observe bulk phase transitions, using photonic quasicrystals, by constructing a smooth boundary between topologically distinct one-dimensional quasicrystals. Moreover, we use the same method to experimentally confirm the topological equivalence between the Harper and Fibonacci quasicrystals. PMID:25166388

  14. Observation of Topological Phase Transitions in Photonic Quasicrystals

    E-print Network

    Verbin, Mor; Zilberberg, Oded; Lahini, Yoav; Silberberg, Yaron

    2012-01-01

    Topological insulators and topological superconductors are distinguished by their bulk phase transitions and gapless states at a sharp boundary with the vacuum. Quasicrystals have recently been found to be topologically nontrivial. In quasicrystals, the bulk phase transitions occur in the same manner as standard topological materials, but their boundary phenomena are more subtle. In this work we directly observe bulk phase transitions, using photonic quasicrystals, by constructing a smooth boundary between topologically-distinct one-dimensional quasicrystals. Moreover, we use the same method to experimentally verify the topological equivalence between the Harper and Fibonacci quasicrystals.

  15. Observation of Topological Phase Transitions in Photonic Quasicrystals

    E-print Network

    Mor Verbin; Oded Zilberberg; Yaacov E. Kraus; Yoav Lahini; Yaron Silberberg

    2013-02-15

    Topological insulators and topological superconductors are distinguished by their bulk phase transitions and gapless states at a sharp boundary with the vacuum. Quasicrystals have recently been found to be topologically nontrivial. In quasicrystals, the bulk phase transitions occur in the same manner as standard topological materials, but their boundary phenomena are more subtle. In this Letter we directly observe bulk phase transitions, using photonic quasicrystals, by constructing a smooth boundary between topologically distinct one-dimensional quasicrystals. Moreover, we use the same method to experimentally confirm the topological equivalence between the Harper and Fibonacci quasicrystals.

  16. Heterogeneous ice nucleation on phase-separated organic-sulfate particles: effect of liquid vs. glassy coatings

    NASA Astrophysics Data System (ADS)

    Schill, G. P.; Tolbert, M. A.

    2013-05-01

    Atmospheric ice nucleation on aerosol particles relevant to cirrus clouds remains one of the least understood processes in the atmosphere. Upper tropospheric aerosols as well as sub-visible cirrus residues are known to be enhanced in both sulfates and organics. The hygroscopic phase transitions of organic-sulfate particles can have an impact on both the cirrus cloud formation mechanism and resulting cloud microphysical properties. In addition to deliquescence and efflorescence, organic-sulfate particles are known to undergo another phase transition known as liquid-liquid phase separation. The ice nucleation properties of particles that have undergone liquid-liquid phase separation are unknown. Here, Raman microscopy coupled with an environmental cell was used to study the low temperature deliquescence, efflorescence, and liquid-liquid phase separation behavior of 2 : 1 mixtures of organic polyols (1,2,6-hexanetriol and 1 : 1 1,2,6-hexanetriol + 2,2,6,6-tetrakis(hydroxymethyl)cyclohexanol) and ammonium sulfate from 240-265 K. Further, the ice nucleation efficiency of these organic-sulfate systems after liquid-liquid phase separation and efflorescence was investigated from 210-235 K. Raman mapping and volume-geometry analysis indicate that these particles contain solid ammonium sulfate cores fully engulfed in organic shells. For the ice nucleation experiments, we find that if the organic coatings are liquid, water vapor diffuses through the shell and ice nucleates on the ammonium sulfate core. In this case, the coatings minimally affect the ice nucleation efficiency of ammonium sulfate. In contrast, if the coatings become semi-solid or glassy, ice instead nucleates on the organic shell. Consistent with recent findings that glasses can be efficient ice nuclei, the phase-separated particles are nearly as efficient at ice nucleation as pure crystalline ammonium sulfate.

  17. Heterogeneous ice nucleation on phase-separated organic-sulfate particles: effect of liquid vs. glassy coatings

    NASA Astrophysics Data System (ADS)

    Schill, G. P.; Tolbert, M. A.

    2012-12-01

    Atmospheric ice nucleation on aerosol particles relevant to cirrus clouds remains one of the least understood processes in the atmosphere. Upper tropospheric aerosols as well as sub-visible cirrus residues are known to be enhanced in both sulfates and organics. The hygroscopic phase transitions of organic-sulfate particles can have an impact on both the cirrus cloud formation mechanism and resulting cloud microphysical properties. In addition to deliquescence and efflorescence, organic-sulfate particles are known to undergo another phase transition known as liquid-liquid phase separation. The ice nucleation properties of particles that have undergone liquid-liquid phase separation are unknown. Here, Raman microscopy coupled with an environmental cell was used to study the low temperature deliquescence, efflorescence, and liquid-liquid phase separation behavior of 2:1 mixtures of organic polyols (1,2,6-hexanetriol, and 1:1 1,2,6-hexanetriol +2,2,6,6-tetrakis(hydroxymethyl)cycohexanol) and ammonium sulfate from 240-265 K. Further, the ice nucleation efficiency of these organic-sulfate systems after liquid-liquid phase separation and efflorescence was investigated from 210-235 K. Raman mapping and volume-geometry analysis indicates that these particles contain solid ammonium sulfate cores fully engulfed in organic shells. For the ice nucleation experiments, we find that if the organic coatings are liquid, water vapor diffuses through the shell and ice nucleates on the ammonium sulfate core. In this case, the coatings minimally affect the ice nucleation efficiency of ammonium sulfate. In contrast, if the coatings become semi-solid or glassy, ice instead nucleates on the organic shell. Consistent with recent findings that glasses can be efficient ice nuclei, the phase separated particles are nearly as efficient at ice nucleation as pure crystalline ammonium sulfate.

  18. Containerless Liquid-Phase Processing of Ceramic Materials

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  19. 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.

  20. 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.