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1

Generic mechanism for generating a liquid-liquid phase transition.

Recent experimental results indicate that phosphorus--a single-component system--can have a high-density liquid (HDL) and a low-density liquid (LDL) phase. A first-order transition between two liquids of different densities is consistent with experimental data for a variety of materials, including single-component systems such as water, silica and carbon. Molecular dynamics simulations of very specific models for supercooled water, liquid carbon and supercooled silica predict a LDL-HDL critical point, but a coherent and general interpretation of the LDL-HDL transition is lacking. Here we show that the presence of a LDL and a HDL can be directly related to an interaction potential with an attractive part and two characteristic short-range repulsive distances. This kind of interaction is common to other single-component materials in the liquid state (in particular, liquid metals), and such potentials are often used to describe systems that exhibit a density anomaly. However, our results show that the LDL and HDL phases can occur in systems with no density anomaly. Our results therefore present an experimental challenge to uncover a liquid-liquid transition in systems like liquid metals, regardless of the presence of a density anomaly. PMID:11217853

Franzese, G; Malescio, G; Skibinsky, A; Buldyrev, S V; Stanley, H E

2001-02-01

2

MODELLING AND SIMULATION OF LIQUID-VAPOR PHASE TRANSITION

, (,) div(q) heat transfert. (,) P pressure law. G. Faccanoni DNS OF LIQUIDE-VAPOR PHASE TRANSITION 5 / 20, (,) div(q) heat transfert. (,) P pressure law. G. Faccanoni DNS OF LIQUIDE-VAPOR PHASE TRANSITION 5 / 20 =T s > 0 pressure, g def = +P -T s free enthalpy (Gibbs potential). G. Faccanoni DNS OF LIQUIDE-VAPOR

Helluy, Philippe

3

Existence of a liquid-liquid phase transition in methanol

NASA Astrophysics Data System (ADS)

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.

Huš, Matej; Urbic, Tomaz

2014-12-01

4

Phase Transition in Dimer Liquids Danh-Tai Hoang

crystals. We recall that liquid crystals are somewhere between solid and liquid states where molecules havePhase Transition in Dimer Liquids Danh-Tai Hoang Asia Pacific Center for Theoretical Physics of first order for large enough D, for both polarized and non polarized dimers. This transition has

Boyer, Edmond

5

of protein-rich liquid droplets for bovine serum albumin and chicken egg lysozyme at 25 Â°C. These dropletsLiquid-Liquid Phase Transition of Protein Aqueous Solutions Isothermally Induced by Protein Cross that liquid-liquid phase separation (LLPS) of protein aqueous solutions can be induced by isothermal protein

Annunziata, Onofrio

6

The liquid to vapor phase transition in excited nuclei

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

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

2001-05-08

7

Interpenetration as a mechanism for liquid-liquid phase transitions

NASA Astrophysics Data System (ADS)

We study simple lattice systems to demonstrate the influence of interpenetrating bond networks on phase behavior. We promote interpenetration by using a Hamiltonian with a weakly repulsive interaction with nearest neighbors and an attractive interaction with second-nearest neighbors. In this way, bond networks will form between second-nearest neighbors, allowing for two (locally) distinct networks to form. We obtain the phase behavior from analytic solution in the mean-field approximation and exact solution on the Bethe lattice. We compare these results with exact numerical results for the phase behavior from grand canonical Monte Carlo simulations on square, cubic, and tetrahedral lattices. All results show that these simple systems exhibit rich phase diagrams with two fluid-fluid critical points and three thermodynamically distinct phases. We also consider including third-nearest-neighbor interactions, which give rise to a phase diagram with four critical points and five thermodynamically distinct phases. Thus the interpenetration mechanism provides a simple route to generate multiple liquid phases in single-component systems, such as hypothesized in water and observed in several model and experimental systems. Additionally, interpenetration of many such networks appears plausible in a recently considered material made from nanoparticles functionalized by single-strands of DNA.

Hsu, Chia Wei; Starr, Francis W.

2009-04-01

8

Synthesis and Liquid Crystal Phase Transitions of Zirconium Phosphate Disks

-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...

Shuai, Min

2013-05-07

9

Suppression of phase transitions in a confined rodlike liquid crystal.

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

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

2011-11-22

10

Effect of dimensionality on vapor-liquid phase transition

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

Singh, Sudhir Kumar, E-mail: sksingh@thapar.edu [Department Chemical Engineering, Thapar University, Patiala-147004 Punjab (India)

2014-04-24

11

Effect of dimensionality on vapor-liquid phase transition

NASA Astrophysics Data System (ADS)

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

Singh, Sudhir Kumar

2014-04-01

12

Modeling the solid-liquid phase transition in saturated triglycerides

NASA Astrophysics Data System (ADS)

We investigated theoretically two competing published scenarios for the melting transition of the triglyceride trilaurin (TL): those of (1) Corkery et al. [Langmuir 23, 7241 (2007)], in which the average state of each TL molecule in the liquid phase is a discotic "Y" conformer whose three chains are dynamically twisted, with an average angle of ˜120° between them, and those of (2) Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid-state conformation of the TL molecule in the liquid phase is a nematic h?-conformer whose three chains are in a modified "chair" conformation. We developed two competing models for the two scenarios, in which TL molecules are in a nematic compact-chair (or "h") conformation, with extended, possibly all-trans, chains at low-temperatures, and in either a Y conformation or an h? conformation in the liquid state at temperatures higher than the phase-transition temperature, T?=319 K. We defined an h-Y model as a realization of the proposal of Corkery et al. [Langmuir 23, 7241 (2007)], and explored its predictions by mapping it onto an Ising model in a temperature-dependent field, performing a mean-field approximation, and calculating the transition enthalpy ?H. We found that the most plausible realization of the h-Y model, as applied to the solid-liquid phase transition in TL, and likely to all saturated triglycerides, gave a value of ?H in reasonable agreement with the experiment. We then defined an alternative h-h? model as a realization of the proposal of Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid phase exhibits an average symmetry breaking similar to an h conformation, but with twisted chains, to see whether it could describe the TL phase transition. The h-h? model gave a value of ?H that was too small by a factor of ˜3-4. We also predicted the temperature dependence of the 1132 cm-1 Raman band for both models, and performed measurements of the ratios of three TL Raman bands in the temperature range of -20 °C?T ?90 °C. The experimental results were in accord with the predictions of the h-Y model and support the proposal of Corkery et al. [Langmuir 23, 7241 (2007)] that the liquid state is made up of molecules that are each, on average, in a Y conformation. Finally, we carried out computer simulations of minimal-model TLs in the liquid phase, and concluded that although the individual TL molecules are, on average, Y conformers, long-range discotic order is unlikely to exist.

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

2010-02-01

13

Quantum phase transitions in semilocal quantum liquids

NASA Astrophysics Data System (ADS)

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 point, for which the order parameter remains gapped at the critical point, and thus is not driven by soft order parameter fluctuations. Rather it appears to be driven by "confinement" which arises when two fixed points annihilate and lose conformality. On the condensed side, there is an infinite tower of condensed states and the nonlinear response of the tower exhibits an infinite spiral structure; (ii) a "hybridized" critical point which can be described by a standard Landau-Ginsburg sector of order parameter fluctuations hybridized with a strongly coupled sector; (iii) a "marginal" critical point which is obtained by tuning the above two critical points to occur together and whose bosonic fluctuation spectrum coincides with that postulated to underly the "Marginal Fermi Liquid" description of the optimally doped cuprates.

Iqbal, Nabil; Liu, Hong; Mezei, Márk

2015-01-01

14

Liquid-liquid phase transition of water in hydrophobic and hydrophilic pores

Effect of confinement on the liquid-liquid transition of water are studied by simulations in the Gibbs ensemble. Upon cooling along the liquid-vapor coexistence curve, confined water undergoes transition from normal to strongly tetrahedral water via a first order phase transition (as in the bulk) or in a continuous way in dependence on pore hydrophilicity. In all cases, transition temperature is only slightly shifted by the confinement. This agrees with the experimentally observed weak effect of confinement on the temperature of the fragile-to-strong transition of water.

Ivan Brovchenko; Alla Oleinikova

2006-06-08

15

Liquid-liquid transition without macroscopic phase separation in a water-glycerol mixture.

The existence of more than two liquid states in a single-component substance and the ensuing liquid-liquid transitions (LLTs) has attracted considerable attention because of its counterintuitive nature and its importance in the fundamental understanding of the liquid state. Here we report direct experimental evidence for a genuine (isocompositional) LLT without macroscopic phase separation in an aqueous solution of glycerol. We show that liquid I transforms into liquid II by way of two types of kinetics: nucleation and growth, and spinodal decomposition. Although liquid II is metastable against crystallization, we could access both its static and dynamical properties experimentally. We find that liquids I and II differ in density, refractive index, structure, hydrogen bonding state, glass transition temperature and fragility, and that the transition between the two liquids is mainly driven by the local structuring of water rather than of glycerol, suggesting a link to a plausible LLT in pure water. PMID:22426459

Murata, Ken-ichiro; Tanaka, Hajime

2012-05-01

16

Critical fluctuations in electrolytes with a liquid-liquid phase transition

Near-critical fluctuations of ionic solutions with a liquid-liquid phase transition are investigated by measurements of turbidity and static and dynamic light scattering. Phase diagrams are also presented. The systems are substituted ammonium salts (picrate, nitrate, iodide) dissolved in higher alcohols and water. The correlation lengths, determined from the time correlation functions using the Kawasaki mode coupling theory, also describe the

W. Schroer; S. Wiegand; M. Kleemeier; H. Weingartner

1994-01-01

17

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

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

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

2010-01-01

18

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

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

Cubrovi?, Mihailo; Zaanen, Jan; Schalm, Koenraad

2009-07-24

19

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

Turbidity measurements showing crossover from mean-field to Ising criticality have been reported by Narayanan and Pitzer for the liquid - liquid phase transition in ionic solutions of alkyl-ammonium picrates in higher alcohols. The Ising region was found to increase with the dielectric permittivity D for solvents with 4 < D < 8. It was conjectured that the Ising region becomes

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

1996-01-01

20

Synthesis and liquid crystal phase transitions of zirconium phosphate disks

NASA Astrophysics Data System (ADS)

Solvent-mediated self-assembly of nanoparticles is an effective and efficient way for the bottom-up organization of functional structures. The primary object of this work is to build up a model system for the study of suspensions of disk-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. Systematic experiments revealed that regular-shaped alpha-zirconium phosphate crystalline disks with a size-to-thickness ratio from 1 to 50 and size polydispersity as low as 0.2 can be obtained through hydrothermal treatment in 3 M to 15 M phosphoric acid solutions. Transmission and scanning electron micrographs revealed that the growth of the disks is mediated by oriented attachment, which happened continuously throughout the hydrothermal treatment between various sized disks. Ostwald ripening is effective in improving the regularity of the shape of the disks, especially under prolonged hydrothermal treatment. Under the microwave assisted hydrothermal conditions, the rate of attachment on the flat surfaces of the disks is accelerated, which leads to the formation of the column-shaped crystals. With the ability to adjust the size, aspect ratio, and polydispersity of ZrP disks, the study on self-assembly behavior and the discotic liquid crystal phases was enabled. Firstly, liquid crystal phases of aqueous suspensions of ZrP disks were investigated. Iridescent smectic phase and the critical points of phase transitions were found. Moreover, monolayer ZrP nanosheets with extremely high aspect ratio, which were achieved by exfoliating the ZrP crystals, were also used in this study. The high aspect ratio of nanosheets produces a laminar phase at low nanosheet concentration. Chiral liquid crystal phases were demonstrated when increased the concentration of the nanosheets. The competition between the chirality and layering leads to twisted and layered structures. For the final part, solvent-mediated self-assembly of disks and nanosheets via undulation of liquid crystal phases showed an interesting approach for bottom-up design of functional nano-structures.

Shuai, Min

21

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

Ultrafast dynamics of the laser-induced solid-to-liquid phase transition in aluminum A thesis dynamics of the laser-induced solid-to-liquid phase transition in aluminum Eric Mazur Maria Kandyla Abstract This dissertation reports the ultrafast dynamics of aluminum during the solid-to- liquid phase

Mazur, Eric

22

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

23

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

NASA Technical Reports Server (NTRS)

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.

Clark, Noel A.

2000-01-01

24

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

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

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

2014-09-01

25

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

NASA Astrophysics Data System (ADS)

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 indicative of liquid unmixing on the nanoscale, combined with an abrupt realignment in WAXS features related to reversible shifts in polyhedral packing on the atomic scale. We also observed a rotary action in the suspended supercooled drop driven by repetitive transitions (a polyamorphic rotor) from which the reversible changes in molar volume (1.2 ± 0.2 cubic centimeters) and entropy (19 ± 4 joules mole 1 kelvin 1) can be estimated.

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

2008-10-01

26

Liquid-liquid phase transitions for soft-core attractive potentials.

Using event-driven molecular dynamics simulations, we study a three-dimensional one-component system of spherical particles interacting via a discontinuous potential combining a repulsive square soft core and an attractive square well. In the case of a narrow attractive well, it has been shown that this potential has two metastable gas-liquid critical points. Here we systematically investigate how the changes of the parameters of this potential affect the phase diagram of the system. We find a broad range of potential parameters for which the system has both a gas-liquid critical point C1 and a liquid-liquid critical point C2. For the liquid-gas critical point we find that the derivatives of the critical temperature and pressure, with respect to the parameters of the potential, have the same signs: they are positive for increasing width of the attractive well and negative for increasing width and repulsive energy of the soft core. This result resembles the behavior of the liquid-gas critical point for standard liquids. In contrast, for the liquid-liquid critical point the critical pressure decreases as the critical temperature increases. As a consequence, the liquid-liquid critical point exists at positive pressures only in a finite range of parameters. We present a modified van der Waals equation which qualitatively reproduces the behavior of both critical points within some range of parameters, and gives us insight on the mechanisms ruling the dependence of the two critical points on the potential's parameters. The soft-core potential studied here resembles model potentials used for colloids, proteins, and potentials that have been related to liquid metals, raising an interesting possibility that a liquid-liquid phase transition may be present in some systems where it has not yet been observed. PMID:15244553

Skibinsky, A; Buldyrev, S V; Franzese, G; Malescio, G; Stanley, H E

2004-06-01

27

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

28

NASA Astrophysics Data System (ADS)

Using molecular dynamics simulations we analyze the dynamics of two atomic liquids that display a liquid-liquid phase transition (LLPT): Si described by the Stillinger-Weber potential and Ga as modeled by the modified embedded-atom model. In particular, our objective is to investigate the extent to which the presence of a dip in the self-intermediate scattering function is a manifestation of an excess of vibrational states at low frequencies and may be associated with a fragile-to-strong transition (FTST) across the LLPT, as suggested recently. Our results suggest a somewhat different picture. First, in the case of Ga we observe the appearance of an excess of vibrational states at low frequencies, even in the absence of the appearance of a dip in the self-intermediate scattering function across the LLPT. Second, studying the behavior of the shear viscosities traversing the LLPTs we find that both substances are fragile in character above and below their respective LLPT temperatures. Instead of a FTST in an absolute sense these findings are more in line with a view in which the LLPTs are accompanied by a transition from a more fragile to a less fragile liquid. Furthermore, we do not find this transition to correlate with the presence of a dip in the intermediate scattering function.

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

2013-12-01

29

Using molecular dynamics simulations we analyze the dynamics of two atomic liquids that display a liquid-liquid phase transition (LLPT): Si described by the Stillinger-Weber potential and Ga as modeled by the modified embedded-atom model. In particular, our objective is to investigate the extent to which the presence of a dip in the self-intermediate scattering function is a manifestation of an excess of vibrational states at low frequencies and may be associated with a fragile-to-strong transition (FTST) across the LLPT, as suggested recently. Our results suggest a somewhat different picture. First, in the case of Ga we observe the appearance of an excess of vibrational states at low frequencies, even in the absence of the appearance of a dip in the self-intermediate scattering function across the LLPT. Second, studying the behavior of the shear viscosities traversing the LLPTs we find that both substances are fragile in character above and below their respective LLPT temperatures. Instead of a FTST in an absolute sense these findings are more in line with a view in which the LLPTs are accompanied by a transition from a more fragile to a less fragile liquid. Furthermore, we do not find this transition to correlate with the presence of a dip in the intermediate scattering function.

Cajahuaringa, Samuel; Koning, Maurice de, E-mail: dekoning@ifi.unicamp.br; Antonelli, Alex, E-mail: aantone@ifi.unicamp.br [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, UNICAMP, 13083-859 Campinas, São Paulo (Brazil)] [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, UNICAMP, 13083-859 Campinas, São Paulo (Brazil)

2013-12-14

30

Liquid-liquid phase transition for an attractive isotropic potential with wide repulsive range.

We investigate how the phase diagram of a repulsive soft-core attractive potential, with a liquid-liquid phase transition in addition to the standard gas-liquid phase transition, changes by varying the parameters of the potential. We extend our previous work on short soft-core ranges to the case of large soft-core ranges, by using an integral equation approach in the hypernetted-chain approximation. We show, using a modified van der Waals equation we recently introduced, that if there is a balance between the attractive and repulsive part of the potential this potential has two fluid-fluid critical points well separated in temperature and in density. This implies that for the repulsive (attractive) energy U(R)(U(A)) and the repulsive (attractive) range w(R)(w(A)) the relation U(R)/U(A) proportional to w(R)/w(A) holds for short soft-core ranges, while U(R)/U(A) proportional to 3w(R)/w(A) holds for large soft-core ranges. PMID:16089740

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

2005-06-01

31

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

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.

Bharat K. Sharma; Subrata Pal

2010-01-14

32

NASA Astrophysics Data System (ADS)

We propose a new formulation of the statistical multifragmentation model based on the analysis of the virial expansion for a system of the nuclear fragments of all sizes. The developed model not only allows us to account for short-range repulsion, but also to calculate the surface free energy which is induced by the interaction between the fragments. Also we propose a new parameterization for the liquid phase pressure which allows us to introduce a compressible nuclear liquid into the statistical multifragmentation model. The resulting model is exactly solvable and has no irregular behavior of the isotherms in the mixed phase region that is typical for mean-field models. The general conditions for the 1-st and 2-nd (or higher) order phase transitions are formulated. It is shown that all endpoints of the present model phase diagram are the tricritical points, if the Fisher exponent ? is in the range 32???2. The treatment of nuclear liquid compressibility allows us to reduce the tricritical endpoint density of the statistical multifragmentation model to one third of the normal nuclear density. A specific attention is paid to the fragment size distributions in the region of a negative surface tension at supercritical temperatures.

Sagun, V. V.; Ivanytskyi, A. I.; Bugaev, K. A.; Mishustin, I. N.

2014-04-01

33

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

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.

Tian Ma; Shouhong Wang

2008-05-31

34

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

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 ...

Grover, Tarun

35

Probability analysis of contact forces in quasi-solid-liquid phase transition of granular shear flow

NASA Astrophysics Data System (ADS)

The quasi-solid-liquid phase transition exists widely in different fields, and attracts more attention due to its instinctive mechanism. The structure of force chains is an important factor to describe the phase transition properties. In this study, the discrete element model (DEM) is adopted to simulate a simple granular shear flow with period boundary condition on micro scale. The quasi-solid-liquid phase transition is obtained under various volume fractions and shear rates. Based on the DEM results, the probability distribution functions of the inter-particle contact force are obtained in different shear flow phases. The normal, tangential and total contact forces have the same distributions. The distribution can be fitted as the exponential function for the liquid-like phase, and as the Weibull function for the solid-like phase. To describe the progressive evolution of the force distribution in phase transition, we use the Weibull function and Corwin-Ngan function, respectively. Both of them can determine the probability distributions in different phases and the Weibull function shows more reasonable results. Finally, the force distributions are discussed to explain the characteristics of the force chain in the phase transition of granular shear flow. The distribution of the contact force is an indicator to determine the flow phase of granular materials. With the discussions on the statistical properties of the force chain, the phase transition of granular matter can be well understood.

Ji, ShunYing

2013-02-01

36

Using molecular dynamics simulations we analyze the dynamics of two atomic liquids that display a liquid-liquid phase transition (LLPT): Si described by the Stillinger-Weber potential and Ga as modeled by the modified embedded-atom model (MEAM). In particular, our objective is to investigate the extent to which the presence of a dip in the self-intermediate scattering function is a manifestation of an excess of vibrational states at low frequencies and may be associated with a fragile-to-strong transition (FTST) across the LLPT, as suggested recently. Our results do not lend support to these suggestions. Specifically, in the case of Ga we observe the appearance of an excess of vibrational states at low frequencies, even in the absence of the appearance of a dip in the self-intermediate scattering function across the LLPT. Furthermore, studying the behavior of the shear viscosities traversing the LLPTs we find that, despite the development of a dip in the self-intermediate scattering function for the case of Si and its absence in Ga, both substances are fragile in character above and below their respective LLPT temperatures.

Samuel Cajahuaringa; Maurice de Koning; Alex Antonelli

2013-11-05

37

The thermal conductivity, lambda, is one of the few transport coefficients which shows a relatively small change at the solid-liquid phase transition, and hence it is a property that can be used in comparing dynamic properties of both ordered and disordered systems. Although the discontinuity in lambda can be accounted for largely by the difference in density, /rho/, of solid and liquid at the phase transition, its volume dependence is examined more closely. The thermal diffusivity, which is known to dominate the dynamic structure factor of liquid argon, has been determined around the phase transition also; the sound velocity has been considered in addition. The results are discussed and a comparison is made with these properties in solid and liquid benzene and cyclohexane.

Van Loef, J.J.; Hauley, H.J.M.; Cezairliyan, A.

1986-01-01

38

Solid-liquid phase coexistence and structural transitions in palladium clusters

We use molecular dynamics with an embedded atom potential to study the behavior of palladium nanoclusters near the melting point in the microcanonical ensemble. We see transitions from both fcc and decahedral ground-state structures to icosahedral structures prior to melting over a range of cluster sizes. In all cases this transition occurs during solid-liquid phase coexistence and the mechanism for

D. Schebarchov; S. C. Hendy

2006-01-01

39

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

Lavrentovich, Oleg D.

40

NASA Astrophysics Data System (ADS)

The electrostatic screening of a medium disordered quantum Hall liquid was investigated using an electric field penetration (EFP) technique. At sufficiently low temperatures and at magnetic fields corresponding to the integral quantum Hall regime with even filling factors, two topologically different phases of the bulk electron liquid have been identified. By means of elementary analysis of experimental data it has further been shown that the transition between these phases reveals features typical of a Kosterlitz-Thouless type phase transition. Finally, the validity of the presented physical picture has been supported by means of numerical simulations of local filling factor topography.

Mareš, Ji?í J.; Siddiki, Afif; Kindl, Dobroslav; Hubík, Pavel; Krištofik, Jozef

2009-08-01

41

On the existence of vapor-liquid phase transition in dusty plasmas

The phenomenon of phase transition in a dusty-plasma system (DPS) has attracted some attention in the past. Earlier Farouki and Hamaguchi [J. Chem. Phys. 101, 9876 (1994)] have demonstrated the existence of a liquid to solid transition in DPS where the dust particles interact through a Yukawa potential. However, the question of the existence of a vapor-liquid (VL) transition in such a system remains unanswered and relatively unexplored so far. We have investigated this problem by performing extensive molecular dynamics simulations which show that the VL transition does not have a critical curve in the pressure versus volume diagram for a large range of the Yukawa screening parameter ? and the Coulomb coupling parameter ?. Thus, the VL phase transition is found to be super-critical, meaning that this transition is continuous in the dusty plasma model given by Farouki and Hamaguchi. We provide an approximate analytic explanation of this finding by means of a simple model calculation.

Kundu, M.; Sen, A.; Ganesh, R. [Institute for Plasma Research, Bhat, Gandhinagar 382 428, Gujarat (India); Avinash, K. [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

2014-10-15

42

On the existence of vapor-liquid phase transition in dusty plasmas

NASA Astrophysics Data System (ADS)

The phenomenon of phase transition in a dusty-plasma system (DPS) has attracted some attention in the past. Earlier Farouki and Hamaguchi [J. Chem. Phys. 101, 9876 (1994)] have demonstrated the existence of a liquid to solid transition in DPS where the dust particles interact through a Yukawa potential. However, the question of the existence of a vapor-liquid (VL) transition in such a system remains unanswered and relatively unexplored so far. We have investigated this problem by performing extensive molecular dynamics simulations which show that the VL transition does not have a critical curve in the pressure versus volume diagram for a large range of the Yukawa screening parameter ? and the Coulomb coupling parameter ?. Thus, the VL phase transition is found to be super-critical, meaning that this transition is continuous in the dusty plasma model given by Farouki and Hamaguchi. We provide an approximate analytic explanation of this finding by means of a simple model calculation.

Kundu, M.; Avinash, K.; Sen, A.; Ganesh, R.

2014-10-01

43

Detection of first-order liquid/liquid phase transitions in yttrium oxide-aluminum oxide melts.

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 indicative of liquid unmixing on the nanoscale, combined with an abrupt realignment in WAXS features related to reversible shifts in polyhedral packing on the atomic scale. We also observed a rotary action in the suspended supercooled drop driven by repetitive transitions (a polyamorphic rotor) from which the reversible changes in molar volume (1.2 +/- 0.2 cubic centimeters) and entropy (19 +/- 4 joules mole(-1) kelvin(-1)) can be estimated. PMID:18948535

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

2008-10-24

44

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

NASA Astrophysics Data System (ADS)

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.

Mirgorod, Yu. A.

2010-10-01

45

MODELLING AND SIMULATION OF LIQUID-VAPOR PHASE TRANSITION

Generator Turbine Generator Cooling Tower Condenser Cooling Water Pump Reactor Core Reactor Vessel Control Condenser Cooling Water Pump Reactor Core Reactor Vessel Control Rods G. Faccanoni DNS OF LIQUIDE, (x,t) u velocity; (,) Vvf volumic forces, (,) Ssf surface forces, (,) div(q) heat transfert

Faccanoni, Gloria

46

MODELLING AND SIMULATION OF LIQUID-VAPOR PHASE TRANSITION

Generator Turbine Generator Cooling Tower Condenser Cooling Water Pump Reactor Core Reactor Vessel Control Condenser Cooling Water Pump Reactor Core Reactor Vessel Control Rods G. Faccanoni DNS OF LIQUIDE, (x,t) specific internal energy, (x,t) u velocity; (,) Vvf volumic forces, (,) Ssf surface forces

Faccanoni, Gloria

47

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.

Peter O. Fedichev; Leonid I. Menshikov

2012-01-30

48

Phase transition in the vortex liquid and the critical endpoint in YBa2Cu3Oy

NASA Astrophysics Data System (ADS)

The vortex phase diagram of optimally doped untwinned YBa2Cu3Oy is studied. We find a first-order transition TL(H) in the vortex liquid above the terminal point Hmcp (?7 T) of both the vortex glass line Tg(H) and the field-driven disordering transition line H*(T). The obtained small entropy change (˜0.02 kB/vortex/layer) and the critical endpoint Hcep (?11 T) of the TL(H) line indicate that the vortex liquid undergoes the vortex slush regime before the solidification into the vortex glass phase. Below Hmcp, the vortex liquid phase shows the first-order melting transition into the Bragg glass phase. We also study the oxygen content y dependence of the vortex phase diagram and find that the vortex slush regime is located in the borderline (i.e., 6.90?y?6.92) below which the vortex lattice melting transition disappears. The result indicates that the point disorder with the intermediate strength plays an important role in the vortex slush regime.

Shibata, Kenji; Nishizaki, Terukazu; Sasaki, Takahiko; Kobayashi, Norio

2002-12-01

49

We studied dielectric properties of nano-sized liquid water samples confined in polymerized silicates MCM-41 characterized by the porous sizes \\sim 3-10nm. We report the direct measurements of the dielectric constant by the dielectric spectroscopy method at frequencies 25Hz-1MHz and demonstrate clear signatures of the second-order phase transition of ferroelectric nature at temperatures next to the \\lambda- point in the bulk supercooled water. The presented results support the previously developed polar liquid phenomenology and hence establish its applicability to model actual phenomena in liquid water.

Fedichev, P O; Bordonskiy, G S; Orlov, A O

2011-01-01

50

On a phase field model for solid-liquid phase transitions

solidification) or for liquid-vapor mix- tures (e.g. boiling water), but also for elastic materials subject distinct phases. This is the case for solid-liquid mix- tures (e.g. ice-water or alloys during telling how much the interface temperature differs from the equilibrium temperature when the interface

51

Ab-initio MD simulation on the Liquid-liquid Phase Transition in AlSi Alloy

NASA Astrophysics Data System (ADS)

Motivated by the recent experimental paper [X.F.Bian et al. Mater. Lett. 44, 54 (2000); F.Q.Zu et al. Phy s. Rev. lett 89, 125505,(2001)], we use ab-initio molecular-dynamics method to study the phase transitions in binary alloy liquid at high temperature. Our calculations are based on the density functional theory with local density approximation, the interaction between core and valence electrons is modeled by ultrasoft pseudopotential. The simulation cell contains 54 Al atoms and 10 Si atoms, which are simulated from 900K-2400K in the liquid phase. We have calculated the temperature-dependent energy, volume, pair-correlation function. But we did not see the expected phase transition as observed in experiment. The possible reason of the inconsistence between simulation and experimental results are discussed.

Ji, M.; Gong, X. G.

2003-03-01

52

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. PMID:25399190

Lu, Qing; Kim, Jaegil; Farrell, James D; Wales, David J; Straub, John E

2014-11-14

53

NASA Astrophysics Data System (ADS)

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.

Lu, Qing; Kim, Jaegil; Farrell, James D.; Wales, David J.; Straub, John E.

2014-11-01

54

NASA Astrophysics Data System (ADS)

Water is an anomalous liquid because its properties are different from those of the majority of liquids. Here, we first review what is anomalous about water. Then we study a many-body model for a water monolayer confined between hydrophobic plates in order to answer fundamental questions related to the origin of its anomalies and to predict new testable futures. In particular, we study by Monte Carlo simulations the low temperature phase diagram of the model. By finite size scaling, we find a liquid-liquid first order phase transition ending in a critical point (LLCP) in the region in which bulk water would be supercooled. We show that the LLCP belongs to the universality class of the two-dimensional (2D) Ising model in the limit of infinite walls. Next, we study the limit of stability of the liquid phase with respect to the crystal phases. To this goal we modify the model in order to characterize the crystal formation and find that the model has a crystal-crystal phase transition and that the LLCP is stable with respect to the liquid-crystal phase transition depending on the relative strength of the three-body interaction with respect to the rest of many-body interactions.

Bianco, Valentino; Vilanova, Oriol; Franzese, Giancarlo

2014-03-01

55

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

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.

X. Wang; X. Sun; H. Zhao

2011-09-01

56

Quantum Hall liquid to Charge density wave phase transitions in ABC-trilayer graphene

NASA Astrophysics Data System (ADS)

We study interaction driven states within ABC-stacked trilayer graphene's 12-fold degenerate Landau level which appear near the neutral system Fermi level. The 12-fold degeneracy of the zero-energy LL is due to spin and valley degeneracy along with a degenerate set of triplet (n=0,1,2) LL orbitals. We predict that at filling factors ?= - 5,-2, 1,4 a quantum phase transition from a quantum Hall liquid state to a triangular charge density wave occurs as a function of the single-particle induced LL orbital splitting. This transition is preceded by a softening of the magneto-roton minima of the quantum Hall liquid which appears at qlB˜2.4. The charge density wave is a manifestation of the LL orbital pseudospin textures with nonzero winding numbers. The phase diagrams at other filling factors along with the experimental consequences of our theoretical predictions will also be addressed.

Barlas, Yafis; Cote, Rene; Rondeau, Maxine

2012-02-01

57

NASA Astrophysics Data System (ADS)

Current theories describing the phase diagrams of nematic-nematic mixtures and polymer-nematic liquid crystal mixtures are based on the combination of classical Flory-Huggins (FH) theory of isotropic mixing and the Maier-Saupe (MS) free energy of nematic ordering. This combined FH-MS theory was extended by Kyu and Chiu to polymer-smectic-A systems by incorporating McMillan free energy of the nematic-smectic-A transition. We have developed a generalized model for an LC system undergoing crystallization, extending the Maier-Saupe-McMillan theory in conjunction with the Landau-Brazowiskii model of weak first order phase transition such as solidification. The generalized FH-extended MSM free energy is then minimized with respect to all order parameters and the phase diagram is constructed by balancing the chemical potentials of corresponding phases. This form of the free energy could be valuable in the time evolution studies of phase transitions in polymer/liquid crystal mixtures.

Dayal, P.; Matkar, R.; Ginzburg, V.; Kyu, T.

2006-03-01

58

Water in nanopores. II. Liquid-vapour phase transition near hydrophobic surfaces

The liquid-vapour phase transition near a weakly attractive surface is studied by simulations of the coexistence curves of water in hydrophobic pores. There is a pronounced gradual density depletion of the liquid phase near the surface without any trend to the formation of a vapour layer below the bulk critical temperature Tc. The temperature dependence of the order parameter in the surface layer follows the power law (rol - rov) ~ (1 - T/Tc)^beta1 with a value of the exponent beta1 close to the critical exponent beta1 = 0.82 of the ordinary transition in the Ising model. The order parameter profiles in the subcritical region are consistent with the behaviour of an ordinary transition and their temperature evolution is governed by the bulk correlation length. Density profiles of water at supercritical temperatures are consistent with the behaviour of the normal transition caused by the preferential adsorption of voids. The relation between normal and ordinary transitions in the Ising model and in fluids is discussed.

I. Brovchenko; A. Geiger; A. Oleinikova

2004-02-02

59

Quantum phase transition and Fermi liquid behavior in Pd1 -xNix nanoalloys

NASA Astrophysics Data System (ADS)

The Pd1 -xNix alloy system is an established ideal transition-metal system possessing a composition-induced paramagnetic-to-ferromagnetic quantum phase transition (QPT) at the critical concentration xc˜0.026 in bulk. A low-temperature non-Fermi liquid (NFL) behavior around xc usually indicates the presence of quantum criticality (QC) in this system. In this work, we explore the existence of such a QPT in nanoparticles of this alloy system. We synthesized single-phase, polydispersed and 40-50 nm mean diameter crystalline nanoparticles of Pd1 -xNix alloys, with x near xc and beyond, by a chemical reflux method. In addition to the determination of the size, composition, phase, and crystallinity of the alloys by microscopic and spectroscopic techniques, the existence of a possible QPT was explored by resistivity and dc magnetization measurements. A dip in the value of the exponent n near xc, and a concomitant peak in the constant A of the A Tn dependence of the low-temperature (T ) resistivity indicate the presence of a quantum-like phase transition in the system. The minimum value of n , however, remains within the Fermi liquid regime (n >2 ). The dc magnetization results suggest an anticipatory presence of a superparamagnetic-to-ferromagnetic QPT in the mean-sized nanoparticles. The observation of a possible quantum critical NFL behavior (n <2 ) through resistivity is argued to be inhibited by the electron-magnon scatterings present in the smaller nanoparticles.

Swain, P.; Srivastava, Suneel K.; Srivastava, Sanjeev K.

2015-01-01

60

We investigate the phase behavior of a single-component system in three dimensions with spherically-symmetric, pairwise-additive, soft-core interactions with an attractive well at a long distance, a repulsive soft-core shoulder at an intermediate distance, and a hard-core repulsion at a short distance, similar to potentials used to describe liquid systems such as colloids, protein solutions, or liquid metals. We showed [Nature (London) 409, 692 (2001)] that, even with no evidence of the density anomaly, the phase diagram has two first-order fluid-fluid phase transitions, one ending in a gas-low-density-liquid (LDL) critical point, and the other in a gas-high-density-liquid (HDL) critical point, with a LDL-HDL phase transition at low temperatures. Here we use integral equation calculations to explore the three-parameter space of the soft-core potential and perform molecular dynamics simulations in the interesting region of parameters. For the equilibrium phase diagram, we analyze the structure of the crystal phase and find that, within the considered range of densities, the structure is independent of the density. Then, we analyze in detail the fluid metastable phases and, by explicit thermodynamic calculation in the supercooled phase, we show the absence of the density anomaly. We suggest that this absence is related to the presence of only one stable crystal structure. PMID:12513478

Franzese, G; Malescio, G; Skibinsky, A; Buldyrev, S V; Stanley, H E

2002-11-01

61

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

62

The FTIR spectra were measured for liquid crystal molecules in CaF2 cell over a temperature range of 40-150 degrees C. The alkyl chain transformed from ordered zigzag-dominated conformation to disordered gaucheness-dominated conformation with increasing temperature. Meanwhile, the degree of freedom of the rotation of the carbonyl group increased, the co-plane interaction between the carbonyl group and the phenyl ring broke, and the conjugation between the C=O bond and the phenyl ring was reduced at the S(CA)* --> S(A) phase transition point, followed by the increase of the plane angle between the two phenyl rings. Due to the surface stability effect of the LC cell, there existed on the cell surface a layer whose structure was independent of the temperature and LC phase. Therefore, the molecules still retained its originally phase property even at temperatures near and above the transition point. PMID:17763759

Cheng, Yu-Chuan; Sun, Li; Zhao, Chun; Wang, Xu; Xu, Wei-Qing; Zhao, Bing

2007-06-01

63

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

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.

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

2007-12-01

64

NASA Astrophysics Data System (ADS)

Detailed dielectric, polarization current, electro-optical, and textural observations are reported on an asymmetric banana-shaped compound 1,3-biphenylene-bis[4-(3-fluoro-4-octyloxyphenyliminomethyl)benzoate]. The material possesses a chiral-ferroelectric-racemic-antiferroelectric phase transition. Our studies reveal that the higher temperature ferroelectric phase has a polar double-tilted smectic structure, where both the molecular plane and the long axis are tilted with respect to the layer normal. Accordingly, it has a chiral triclinic structure with an out-of-plane polarization component. The lower temperature phase has a monoclinic symmetry, which is higher than that of the higher temperature phase. To our knowledge, among liquid crystals such situations were previously observed only in reentrant phases.

Rauch, S.; Bault, P.; Sawade, H.; Heppke, G.; Nair, G. G.; Jákli, A.

2002-08-01

65

Liquid-Solid Phase Transition Alloy as Reversible and Rapid Molding Bone Cement

Bone cement has been demonstrated as an essential restorative material in the orthopedic surgery. However current materials often imply unavoidable drawbacks, such as tissue-cement reaction induced thermal injuries and troublesome revision procedure. Here we proposed an injectable alloy cement to address such problems through its liquid-solid phase transition mechanism. The cement is made of a unique alloy BiInSnZn with a specifically designed low melting point 57.5{\\deg}C. This property enables its rapid molding into various shapes with high plasticity. Some fundamental characteristics including mechanical strength behaviors and phase transition-induced thermal features have been measured to demonstrate the competence of alloy as unconventional cement with favorable merits. Further biocompatible tests showed that this material could be safely employed in vivo. In addition, experiments also found the alloy cement capability as an excellent contrast agent for radiation imaging. Particularly, the proposed alloy...

Yi, Liting; Liu, Jing

2013-01-01

66

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

NASA Astrophysics Data System (ADS)

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.

Xu, Xinpeng; Qian, Tiezheng

2010-11-01

67

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

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. PMID:21133449

Xu, Xinpeng; Qian, Tiezheng

2010-11-28

68

Dynamic Modeling Strategy for Flow Regime Transition in Gas-Liquid Two-Phase Flows

In modeling gas-liquid two-phase flows, the concept of flow regimes has been widely 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 flow regime dependent. Current nuclear reactor safety analysis codes, such as RELAP5, classify flow regimes using flow regime maps or transition criteria that were developed for steady-state, fully-developed flows. As twophase flows are dynamic in nature, it is important to model the flow regime transitions dynamically to more accurately predict the two-phase flows. The present work aims to develop a dynamic modeling strategy to determine flow regimes in gas-liquid two-phase flows through 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 of the interfacial area, fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation, and the destruction of the interfacial area, fluid particle coalescence and condensation. For 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 shapes, namely group-1 and group-2 bubbles. A preliminary approach to dynamically identify the flow regimes is discussed, in which discriminator s are based on the predicted information, such as the void fraction and interfacial area concentration. The flow regime predicted with this method shows good agreement with the experimental observations.

Xia Wang; Xiaodong Sun; Benjamin Doup; Haihua Zhao

2012-12-01

69

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

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.

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

70

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

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

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

2014-12-01

71

Chain-length dependence of lipid bilayer properties near the liquid crystal to gel phase transition.

The temperature dependence of the mean orientational order parameter in the vicinity of the liquid crystal to gel phase transition is obtained from the first moment M1 of deuterium nuclear magnetic resonance spectra for bilayers of chain perdeuterated phosphatidylcholines with acyl chains of 12, 14, 16, and 18 carbons. The data clearly show an increasing temperature dependence of the orientational order parameter in the vicinity of the transition, with the effect becoming more pronounced with decreasing chain length. Assuming a linear relationship between the mean orientational order parameter and the extension of the acyl chain, estimates of the change in area of the membrane at the transition are shown to be consistent with those obtained from other measurements. It is shown that the transition may be modeled in terms of a Landau expansion of the free energy involving a small number of phenomenological parameters. From this it is shown that the behavior of these systems in the temperature range of interest is, in large part, controlled by the close proximity of a spinodal to the transition temperature. PMID:1420865

Morrow, M R; Whitehead, J P; Lu, D

1992-01-01

72

NASA Astrophysics Data System (ADS)

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.

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

2002-03-01

73

(1)H, (7)Li, (14)N, and (23)Na high resolution nuclear magnetic resonance (NMR) measurements are reported for fluid solutions of lithium and sodium in anhydrous liquid ammonia across the metal-to-nonmetal transition (MNM transition), paying particular attention to the phenomenon of liquid-liquid phase separation which occurs in the composition/temperature region close to the MNM transition. Our results are discussed in terms of the electronic structure of fluid metal-ammonia solutions at low temperatures (ca. 240 K). We find that the electronic phase transition to the metallic state in these solutions, especially at temperatures close to the liquid-liquid critical consolute temperature, occurs from a nonmetallic, electrolytic solution containing a predominance of electron spin-paired, (diamagnetic) charged bosonic states. The possible implications of these observations to the nature of the liquid-liquid phase separation are discussed, both from the views of N. F. Mott, regarding the MNM transition in sodium-ammonia solutions, and those of R. A. Ogg, regarding the possibility of high-temperature superconductivity in these solutions. Similarities between the electronic structure of metal-ammonia solutions and the high-temperature cuprate superconductors are also briefly emphasized. PMID:23947596

Lodge, Matthew T J H; Cullen, P; Rees, Nicholas H; Spencer, Neil; Maeda, Kiminori; Harmer, Jeffrey R; Jones, Martin O; Edwards, Peter P

2013-10-24

74

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.

Robert Felix Tournier

2014-04-25

75

Universality and criticality of a second-order granular solid-liquid-like phase transition

NASA Astrophysics Data System (ADS)

We experimentally study the critical properties of the nonequilibrium solid-liquid-like transition that takes place in vibrated granular matter. The critical dynamics is characterized by the coupling of the density field with the bond-orientational order parameter Q4, which measures the degree of local crystallization. Two setups are compared, which present the transition at different critical accelerations as a result of modifying the energy dissipation parameters. In both setups five independent critical exponents are measured, associated to different properties of Q4: the correlation length, relaxation time, vanishing wavenumber limit (static susceptibility), the hydrodynamic regime of the pair correlation function, and the amplitude of the order parameter. The respective critical exponents agree in both setups and are given by ??=1 ,??=2 ,? =1 ,? ?0.6 -0.67 , and ? =1 /2 , whereas the dynamical critical exponent is z =??/??=2 . The agreement on five exponents is an exigent test for the universality of the transition. Thus, while dissipation is strictly necessary to form the crystal, the path the system undergoes toward the phase separation is part of a well-defined universality class. In fact, the local order shows critical properties while density does not. Being the later conserved, the appropriate model that couples both is model C in the Hohenberg and Halperin classification. The measured exponents are in accord with the nonequilibrium extension to model C if we assume that ? , the exponent associated in equilibrium to the specific heat divergence but with no counterpart in this nonequilibrium experiment, vanishes.

Castillo, Gustavo; Mujica, Nicolás; Soto, Rodrigo

2015-01-01

76

Kinetics of liquid-solid phase transition in large nickel clusters

NASA Astrophysics Data System (ADS)

In this paper, we have explored computationally the solidification process of a nickel cluster consisting of 2057 atoms. This process has the characteristic features of the first-order phase transition occurring in a finite system. The focus of our research is placed on the elucidation of correlated dynamics of a large ensemble of particles in the course of the nanoscale liquid-solid phase transition through the computation and analysis of the results of molecular dynamics (MD) simulations with the corresponding theoretical model. This problem is of significant interest and importance because the controlled dynamics of systems on the nanoscale is one of the central topics in the development of modern nanotechnologies. MD simulations in large molecular systems are rather computer power demanding. Therefore, in order to advance with MD simulations, we have used modern computational methods based on the graphics processing units (GPUs). The advantages of the use of GPUs for MD simulations in comparison with the CPUs are demonstrated and benchmarked. The reported speedup reaches factors greater than 400. This work opens a path towards exploration with the use of MD of a larger number of scientific problems inaccessible earlier with the CPU-based computational technology.

Yakubovich, Alexander V.; Sushko, Gennady; Schramm, Stefan; Solov'yov, Andrey V.

2013-07-01

77

Effect of CNTs and Induced Chirality on Smectic- Smectic Liquid Crystal Phase Transitions

NASA Astrophysics Data System (ADS)

High-resolution calorimetry results are presented of carbon nanotubes (CNTs) and the liquid crystal (LC) 9OO4 nano-colloidal dispersions as a function of temperature, scan rate, and CNT concentration (0, 0.025, 0.05, 0.20 wt/%). The CNT used have an enantiomeric excess that has been shown to induce chirality into this LC. The pure LC exhibits the phase sequence I-N-SmA-SmC-SmB-Cr on cooling with the expected heat capacity Cp signatures, except for the SmA-SmC transition, manifesting a double-Cp peak ˜2 K apart at low effective scan rates (< 0.5 K min-1). The introduction of CNTs results in the I-N, N-SmA, and SmA-SmC double Cp features shifting to higher temperatures by ˜1 K and remain sharp. However, the SmC-SmB and SmB-Cr transitions shift to lower temperatures by ˜3-4 K and broaden dramatically with increasing CNT content. We interpret these observations as a consequence of the ?-? interactions between the phenyl rings of 9OO4 and the graphene surfaces that induces bulk chirality, and the pinning of the director parallel to the CNT long-axis far from the surface. The balance of these two mechanisms may stabilize phases that lack any in-smectic-plane ordering.

Kalakonda, P.; Iannacchione, G. S.; Basu, R.; Rosenblatt, C.; Lemieux, R. P.

2012-02-01

78

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

Rout, Alok; Binnemans, Koen

2014-02-28

79

Liquid-to-gas phase transitions in two-dimensional quantum systems at zero temperature

Two-dimensional systems of bosons and fermions are studied at zero temperature by means of variational calculations. When viewed as a function of the quantum parameter? = ?2\\/m?S in the variational context, bosons are found to undergo a second-order liquid-to-gas transition, whereas, contrary to expectations, fermions are found to undergo a first-order transition with a region in which liquid and gaseous

M. D. Miller; L. H. Nosanow

1978-01-01

80

Degenerate Fermi and non-Fermi liquids near a quantum critical phase transition

NASA Astrophysics Data System (ADS)

Recently there is renewed interest in quantum critical phase transitions (QCPT) at T = 0 K in metallic strongly correlated electron systems. From early experimental results, the QCPT in the Kondo-lattice compound YbRh2Si2 is not a case of the ordinary spin density wave (SDW) instability observed in Ce-based Kondo lattices, but a candidate for a novel locally critical case. Here, we observe that coexisting, static Fermi liquid (FL) and non-Fermi liquid (NFL) states are a key feature of the QCPT in YbRh2Si2. By means of nuclear magnetic resonance (NMR) spin-lattice relaxation time (T1) measurements on a single-crystalline sample, we find that the FL and NFL states are invariant, whereas their ratio in a crossover is field dependent near the QCPT. Such a pair of states has remained hidden in Ce compounds, owing presumably to the short lifetimes of the two states. We derive a scaling law for the occupation ratio of the two states, which could be widely applicable to Kondo-lattice systems.

Kambe, S.; Sakai, H.; Tokunaga, Y.; Lapertot, G.; Matsuda, T. D.; Knebel, G.; Flouquet, J.; Walstedt, R. E.

2014-11-01

81

We investigate, for two water models displaying a liquid-liquid critical point, the relation between changes in dynamic and thermodynamic anomalies arising from the presence of the liquid-liquid critical point. We find a correlation between the dynamic fragility transition and the locus of specific heat maxima $C_P^{\\rm max}$ (``Widom line'') emanating from the critical point. Our findings are consistent with a possible relation between the previously hypothesized liquid-liquid phase transition and the transition in the dynamics recently observed in neutron scattering experiments on confined water. More generally, we argue that this connection between $C_P^{\\rm max}$ and dynamic crossover is not limited to the case of water, a hydrogen bond network forming liquid, but is a more general feature of crossing the Widom line. Specifically, we also study the Jagla potential, a spherically-symmetric two-scale potential known to possess a liquid-liquid critical point, in which the competition between two liquid structures is generated by repulsive and attractive ramp interactions.

L. Xu; P. Kumar; S. V. Buldyrev; S. -H. Chen; P. H. Poole; F. Sciortino; H. E. Stanley

2005-10-06

82

On a phase field model for solid-liquid phase transitions

during solidification) or for liquid-vapor mix- tures (e.g. boiling water), but also for elastic temperature differs from the equilib- rium temperature when the interface is moving or/and is curved des martyrs, F-38054 Grenoble cedex 9, didier.jamet@cea.fr 1 #12;tures (e.g. ice-water or alloys

Sart, Remi

83

Phase transitions of hydroxypropylcellulose liquid-crystalline solutions in magnetic field

The phase transitions and the phase state of hydroxypropylcellulose-DMAc and hydroxypropylcellulose-ethanol solutions both\\u000a under an applied magnetic field and in its absence have been studied via the cloud-point method, polarization microscopy,\\u000a and polarization-photoelectric measurements. The magnetic field changes the structure of solutions and increases the phase\\u000a transition temperature. The higher the field strength, the more pronounced this effect. As the

S. A. Vshivkov; E. V. Rusinova; N. V. Kudrevatykh; A. G. Galyas; M. S. Alekseeva; D. K. Kuznetsov

2006-01-01

84

NASA Astrophysics Data System (ADS)

Photoisomerization-induced phase transition of neat liquid-crystalline azobenzene chromophore (LCAC) and its effect on phase diagrams of its mixtures with reactive mesogenic diacrylate monomer (RM257) have been investigated experimentally and theoretically. Upon irradiation with ultraviolet light, the nematic phase of LCAC transformed to isotropic, while the crystal phase showed corrugated textures on the surface (i.e., ripples). The phase-transition temperatures and corresponding morphologies of the blends have been investigated by means of differential scanning calorimetry and optical microscopy. A theoretical phase diagram of a binary nematic and crystalline system was constructed by self-consistently solving the combined free energies of Flory-Huggins, Maier-Saupe, and phase-field theory. The calculation revealed various coexistence regions such as nematic + liquid (N1 + L2), crystal + liquid (Cr1 + L2), crystal + nematic (Cr1 + N2), and crystal + crystal (Cr1 + Cr2) over a broad range of compositions including the single-phase nematic (N1, N2) of the corresponding constituents. The calculated liquidus lines were in good accord with the depressed mesophase-isotropic transition points. The present paper demonstrates the effect of trans-cis photoisomerization on the mesophase transitions of neat LCAC and the phase diagram of LCAC-RM257 as well as on the ripple formation (i.e., periodic undulation) on the azobenzene crystals.

Kim, Namil; Li, Quan; Kyu, Thein

2011-03-01

85

NASA Astrophysics Data System (ADS)

Liquid sulfur is a well-known liquid which exhibits a polymerization transition at T_p=159 °C. Recently, it was found from our experiments that such a transition can be induced below Tp through laser illumination and that an iridescent pattern appears under strong illumination with a pulsed laser of more than 60 mJ/cm2 pulse. It is proposed that the visible change in iridescence is due to a macroscopic reconstruction of laser-generated polymers and that a laser-induced phase transition takes place from a freely expanded polymer phase to an ordered polymer phase when increasing the laser illumination. To further examine this possibility, the time variation of the iridescent pattern has been fully investigated using a macro lens, a polarized microscope and an optical microscope. In an analysis of the iridescent pattern, a rapid decrease in the area was observed after an initial slow decrease, suggesting a type of phase transition. Results from the observation of a quenched sulfur sample with a polarized microscope gave evidence that the iridescent region consists of polymers. Through observation of the liquid with a microscope, a striped pattern with micrometer sized spacing was noted in the iridescent pattern. A drastic color change was observed in the pattern from its generation to its disappearance. Sample thickness dependence of the pattern was also observed. These results were well explained by assuming the self-arrangement of laser-generated colloidal polymers.

Sakaguchi, Y.; Tamura, K.

2007-04-01

86

The direct and reversible transformation of matter between the solid and liquid phases by light at constant temperature is of great interest because of its potential applications in various manufacturing settings. We report a simple molecular design strategy for the phase transitions: azobenzenes having para-dialkoxy groups with a methyl group at the meta-position. The photolithography processes were demonstrated using the azobenzene as a photoresist in a single process combining development and etching of a copper substrate. PMID:25216186

Norikane, Yasuo; Uchida, Emi; Tanaka, Satoko; Fujiwara, Kyoko; Koyama, Emiko; Azumi, Reiko; Akiyama, Haruhisa; Kihara, Hideyuki; Yoshida, Masaru

2014-10-01

87

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

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

2014-07-14

88

We investigate light-induced patterning of a monodomain side-chain liquid crystal elastomer (SC-LCE) doped with light-sensitive azobenzene moiety in the temperature region close to the nematic-paranematic phase transition. We show that a strongly nonlinear relationship between the concentration of the cis isomers of the azomesogens and the refractive index modification of the material, which is characteristic for the phase transition region, results in nonmonotonous time dependence of the diffraction efficiency of a probe beam. From this effect we determine the sensitivity of the nematic transition temperature on the molar fraction of the cis isomers. The relation between the cis isomer molar fraction and nematic order also provides a possibility for recording hidden holograms, which can be made visible by cooling the sample from the paranematic to the nematic phase. PMID:23496535

Gregorc, Marko; Li, Hui; Domenici, Valentina; Ambroži?, Gabriela; ?opi?, Martin; Drevenšek-Olenik, Irena

2013-02-01

89

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

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

2011-01-01

90

Dimensional Phase Transition from an Array of 1D Luttinger Liquids to a 3D Bose-Einstein Condensate

NASA Astrophysics Data System (ADS)

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. Because of 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.

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

2014-11-01

91

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

92

NASA Astrophysics Data System (ADS)

We study smectic-liquid-crystal order in a cell with a heterogeneous substrate imposing surface random positional and orientational pinnings. Proposing a minimal random elastic model, we demonstrate that, for a thick cell, the smectic state without a rubbed substrate is always unstable at long scales and, for weak random pinning, is replaced by a smectic glass state. We compute the statistics of the associated substrate-driven distortions and the characteristic smectic domain size on the heterogeneous substrate and in the bulk. We find that for weak disorder, the system exhibits a three-dimensional temperature-controlled phase transition between a weakly and strongly pinned smectic glass states akin to the Cardy-Ostlund phase transition. We explore experimental implications of the predicted phenomenology and suggest that it provides a plausible explanation for the experimental observations on polarized light microscopy and x-ray scattering.

Zhang, Quan; Radzihovsky, Leo

2013-02-01

93

NASA Astrophysics Data System (ADS)

Isentropic ramp-wave loading of materials is a novel method to study the kinetics of phase transitions, particularly in regimes that are overdriven by shock-loading techniques or that cannot be accessed using shock-loading techniques. In our experiments, the Sandia Saturn accelerator produces magnetically driven planar ramp waves of 200-300 ns rise time in aluminum, which then propagate into a material sample. To study the kinetics of the liquid-solid transition in tin under dynamic loading, molten tin initially at 600-800 K is isentropically loaded up to 300 kbar, driving it across the liquid-solid phase boundary. Experiments currently under way to obtain VISAR measurements at a lithium flouride window interface should show evidence of nonequilibrium freezing in tin if the characteristic transition time is in the range of 10-400 ns. *Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

Davis, Jean-Paul; Hayes, Dennis B.; Asay, James R.; Flores, Paul A.; Watts, Phillip W.; Reisman, David B.

2001-10-01

94

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

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

2013-10-01

95

The orientational order and rotational dynamics of 2-[3-(diphenyl-hexatrienyl) propanoyl]-3-palmitoyl-L-alpha- phosphatidylcholine (DPH-PC) embedded in dioleoylphosphatidyl-ethanolamine (DOPE) were studied by fluorescence depolarization technique. Upon increasing the temperature, the calculated wobbling diffusion constant D perpendicular of the fluorescent probe was found to decrease at the lamellar (L alpha) to inverted cylindrical (H II) phase transition (10 degrees C). This suggested that the increased gauche rotamers of the alkene chains in the HII phase imposes a constraint in the wobbling motion of the fluorophore. The calculated ratio of order parameter in the L alpha phase to that in the HII phase was 1.7 and different from the theoretical value of 2.0 as predicted from the change in packing symmetry. This result can be explained by a slightly higher local order parameter of the fluorophore or by the fast rotational diffusion motion of the fluorophore around the symmetry axis of the cylindrical tubes in the HII phase. PMID:2765643

Cheng, K H

1989-01-01

96

Fluorescence lifetime and fluorescence quantum yield measurements have been made on acetone and acetone-d6 in the gas phase, in solution, and in the neat liquid. The variation of the radiative and nonradiative transition probabilities with deuteration, and the effect of solvent environment are discussed. Radiative transition probabilities are compared with those calculated from the equation of Strickler and Berg. The

Arthur M. Halpern; William R. Ware

1971-01-01

97

Faraday waves on nematic liquid crystals: effect of Marangoni flow and thermal phase transition.

The parametric instability in nematic liquid crystal layers has been studied using linear stability theory. Using material parameters of typical nematics, the neutral stability curve and dispersion relation of a system that presents critical subharmonic waves is obtained. The critical acceleration and wave number of the unstable stationary waves are discontinuous at the nematic-isotropic transition temperature and conform to similar sharp changes experienced by the viscosities and surface tension as a function of temperature. Due to Marangoni flow the curve of the critical acceleration as a function of excitation frequency exhibits a minimum. If the Marangoni flow is neglected and the dynamical viscosity is increased, a monotonously increasing dependence of the acceleration in terms of oscillation frequency is observed. A bicritical instability is reached for a layer thickness of a few millimeters. A well-defined subharmonic wave is attained when the thickness of the layer is further increased. The dispersion relation of these waves displays a discontinuous shift at high frequencies due to alternating secondary thresholds of Faraday waves. At negligible external forcing we determined the dispersion relationship of thermal surface waves. PMID:24483448

Hernández-Contreras, M

2013-12-01

98

The liquid-liquid phase transition (LLPT) in aqueous salt solutions of lysozyme protein has been studied by small-angle neutron scattering. Measurements have been carried out on fixed protein concentration with varying salt concentration approaching LLPT. The data are fitted considering protein interaction by the two Yukawa (2Y) potential which combines short-range attraction and long-range repulsion. We show that LLPT arises because of enhancement of non-DLVO (Derjaguin-Landau-Verwey-Overbeek) short-range attraction without any conformational structural change of the protein. The salt concentration required for LLPT as well as corresponding short-range attraction decreases significantly with increase in protein concentration. PMID:23848716

Chinchalikar, A J; Aswal, V K; Kohlbrecher, J; Wagh, A G

2013-06-01

99

NASA Astrophysics Data System (ADS)

Magnetic-birefringence measurements were performed in the nematic phase of the binary lyotropic liquid crystal cesium perfluoro-octanoate and water within 75 mK of the superheating limit. Several results were obtained: (1) The induced birefringence was linear in H for small H, but showed significant deviations from linearity for H>5 T; (2) the elastic constant was found to be very small near the transition, indicating that director fluctuations may contribute a significant multiplicative factor to the average order parameter; and (3) the order-parameter exponent ?=0.34+/-0.06. This last result is examined in the context of a mean-field theory with higher-order terms in the free-energy expansion and in the context of the d=3, N=5 N-vector model.

Rosenblatt, Charles

1985-08-01

100

Investigations of the phase transitions in cholesteryl oleyl carbonate, cholesteryl stearate and their mixtures have been made by measuring dielectric parameters, (??) and (??), percentage optical transmittance and density in the temperature range of 15–85°C. The study of all these parameters clearly indicates sharp discontinuities at transition temperatures exhibiting solid–cholesteric and cholesteric–isotropic phase transitions. Also the transition temperatures for both

R. Manohar; M. Gupta; J. P Shukla

2000-01-01

101

NASA Astrophysics Data System (ADS)

The thermal conductivity of liquid CHCl3, C6H6, and CCl4 is measured by a steady-state method under saturated vapor pressure in the temperature regions corresponding to pre-crystallization temperatures. The experimental results obtained are used to investigate the isobaric thermal conductivity jump ??p at the crystal-liquid phase transition in CHCl3, C6H6, and CCl4. The contributions of the phonon-phonon and phonon-rotational interaction to the total thermal resistance in solid and liquid state are specified using a modified method of reduced coordinates. The decrease in the thermal conductivity at the crystal-liquid phase transition, ??p, is explained by a combined effect of variations in positional distribution of molecules and in the form of rotational molecular motion.

Pursky, I. O.; Konstantinov, V. A.; Bulakh, V. V.

2009-04-01

102

Quite recently, we reported a semianalytical equation of state (EOS) for the Ga-Pb alloy [Phys. Rev. B 78, 024205 (2008)], which was based on the first-order perturbation theory of fluid mixtures, within the simplified random phase approximation, in conjunction with the Grosdidier et al. model pair potentials for Ga-Ga and Pb-Pb with a suitable nonadditive pair potential between Ga-Pb unlike pairs. In the present work, we employ the present EOS to calculate the Ga-Pb phase diagram along the immiscibility gap region. The accuracy of the EOS is tested by consulting the empirical binodal curve. A statistical-mechanical-based theory for the surface tension is employed to obtain an analytical expression for the alloy surface tension. We calculated the surface tension along the bimodal curve and at extreme conditions of temperatures and pressures. The surface tension exhibits reasonably well the prewetting transition of Pb atoms at the surface of the Ga-rich liquid alloy and could qualitatively explain the prewetting phenomena occurring in the Ga-rich side of the phase diagram. The predicted prewetting line and wetting temperature qualitatively agree with the empirical measurements. PMID:23848623

Osman, S M; Grosdidier, B; Ali, I; Abdellah, A Ben

2013-06-01

103

The frequency and temperature dependence of the complex dielectric constant was measured near the smectic-C*-smectic-A liquid-crystal phase (Sm-C*-Sm-A) transition for two ferroelectric liquid crystals with a very large spontaneous polarization. The dielectric strengths as well as the corresponding relaxation frequencies of the dielectric modes were determined. Due to the large polarization we were able to resolve the contributions from the

C. Filipic; T. Carlsson; A. Levstik; B. Zeks; R. Blinc; F. Gouda; S. T. Lagerwall; K. Skarp

1988-01-01

104

The spin-liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3 has been studied by measuring the uniaxial expansion coefficients alphai, the specific heat, and magnetic susceptibility. Special emphasis was placed on the mysterious anomaly around 6 K---a potential spin-liquid instability. Distinct and strongly anisotropic lattice effects have been observed at 6 K, clearly identifying this feature as a second-order phase transition. Owing to the large anomalies

R. S. Manna; M. de Souza; A. Brühl; J. A. Schlueter; M. Lang

2010-01-01

105

LIGHT NONAQUEOUS PHASE LIQUIDS

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

106

Theoretical approaches and experimental evidence for liquid-vapor phase transitions in nuclei

The leptodermous approximation is applied to nuclear systems for T > 0. The introduction of surface corrections leads to anomalous caloric curves and to negative heat capacities in the liquid-gas coexistence region. Clusterization in the vapor is described by associating surface energy to clusters according to Fisher's formula. The three-dimensional Ising model, a leptodermous system par excellence, does obey rigorously Fisher's scaling up to the critical point. Multifragmentation data from several experiments including the ISiS and EOS Collaborations, as well as compound nucleus fragment emission at much lower energy follow the same scaling, thus providing the strongest evidence yet of liquid-vapor coexistence.

Moretto, L.G.; Elliott, J.B.; Phair, L.; Wozniak, G.J.; Mader, C.M.; Chappars, A.

2001-01-01

107

ERIC Educational Resources Information Center

The aim of this study was to explore pre-service primary teachers' understandings of the effect of temperature and pressure on the solid-liquid phase transition of water. In the study a survey approach was used, and the sample consisted of one-hundred and three, third year pre-service primary science teachers. As a tool for data collection, a test…

Yalcin, Fatma Aggul

2012-01-01

108

Quantum Phase Transitions Subir Sachdev

lives, with hardly a second thought. When we boil water for a cup of tea, we observe that the water and liquid water cross each other at 0 C, accounting for the phase transition at this temperature. So far we is quiescent until it reaches a certain temperature (100 C), and then bub- bles appear vigorously until all

109

NASA Astrophysics Data System (ADS)

In this Letter, a new approach to distinguish liquid water and ice based on dual spectrum neutron radiography is presented. The distinction is based on arising differences between the cross section of water and ice in the cold energy range. As a significant portion of the energy spectrum of the ICON beam line at Paul Scherrer Institut is in the thermal energy range, no differences can be observed with the entire beam. Introducing a polycrystalline neutron filter (beryllium) inside the beam, neutrons above its cutoff energy are filtered out and the cold energy region is emphasized. Finally, a contrast of about 1.6% is obtained with our imaging setup between liquid water and ice. Based on this measurement concept, the temporal evolution of the aggregate state of water can be investigated without any prior knowledge of its thickness. Using this technique, we could unambiguously prove the production of supercooled water inside fuel cells with a direct measurement method.

Biesdorf, J.; Oberholzer, P.; Bernauer, F.; Kaestner, A.; Vontobel, P.; Lehmann, E. H.; Schmidt, T. J.; Boillat, P.

2014-06-01

110

In this Letter, a new approach to distinguish liquid water and ice based on dual spectrum neutron radiography is presented. The distinction is based on arising differences between the cross section of water and ice in the cold energy range. As a significant portion of the energy spectrum of the ICON beam line at Paul Scherrer Institut is in the thermal energy range, no differences can be observed with the entire beam. Introducing a polycrystalline neutron filter (beryllium) inside the beam, neutrons above its cutoff energy are filtered out and the cold energy region is emphasized. Finally, a contrast of about 1.6% is obtained with our imaging setup between liquid water and ice. Based on this measurement concept, the temporal evolution of the aggregate state of water can be investigated without any prior knowledge of its thickness. Using this technique, we could unambiguously prove the production of supercooled water inside fuel cells with a direct measurement method. PMID:24996112

Biesdorf, J; Oberholzer, P; Bernauer, F; Kaestner, A; Vontobel, P; Lehmann, E H; Schmidt, T J; Boillat, P

2014-06-20

111

NASA Astrophysics Data System (ADS)

High temperature resolution measurements of thermal conductivity, thermal diffusivity, and specific heat, with simultaneous polarized light visual inspection of the sample, have been performed at two different liquid crystal phase transitions: the SmA-SmC (Smectic-A Smectic-C) and the SmA-HexB (Smectic-A hexatic-B) in racemic A7 [4-(3-methyl-2-chlorobutanoyloxy)-4'-heptyloxybiphenyl] and 65OBC (n-hexyl-4'-n-pentyloxybiphenyl-4-carboxylate) compounds, respectively. In the past, anomalies in the thermal conductivity at the transitions have been reported. Our results indicate a nonsingular behavior of the thermal conductivity at both transitions, similarly to what has been previously reported for the smectic-A nematic phase transition. It is also shown how, in several cases, the nature of the transition can be affected by the sample thermal history due to the presence of strain annealing phenomena.

Mercuri, F.; Marinelli, M.; Zammit, U.; Huang, C. C.; Finotello, D.

2003-11-01

112

NASA Astrophysics Data System (ADS)

A variety of phase transitions controlled by pressure are addressed, in which anharmonicity plays a central role. After a brief discussion of the melting temperature of some transition metals as a function of pressure, the brittle-to-ductile transition is treated. Finally, quantum critical points are briefly referred to, in relation to singular behaviour of the Grüneisen ratio.

Angilella, G. G. N.; March, N. H.; Matthai, C. C.; Pucci, R.

2008-07-01

113

Liquid crystalline phase transitions in virus and virus/polymer suspensions A Dissertation

diagrams. As a model system of rod-like particles we use bacteriophage fd, which is a charge stabilized . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3 Bacteriophage fd as a versatile model system of rod like colloids 24 3.1 Introduction with covalently attached polymer . . . . . . . . . . . . . . . . 29 4 Cholesteric phase in bacteriophage fd 34 4

Fraden, Seth

114

The earliest phase transition?

NASA Astrophysics Data System (ADS)

The question of a phase transition in exiting the Planck epoch of the early universe is addressed. An order parameter is proposed to help decide the issue, and estimates are made concerning its behavior. Our analysis is suggestive that a phase transition occurred.

Samuel, Stuart

2000-10-01

115

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

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.

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

2005-07-08

116

NASA Astrophysics Data System (ADS)

We have studied the in-plane (parallel to the magnetic field) alignment of 8CB mixed with FeCo nanoparticles covered with different funtionalization compounds. The functionalization compounds are Polyethelene glycol (PEG (3000)), hydroxyl succinimide (NHS), aminopropyl tri-ethoxy silane (APTS) and mercapto hexa-decanoic acid (MHDA). We have studied them using X-ray scattering. We have found that the inverse integrated intensity of the X-ray scans in the plane of the magnetic field is a good measure of how much energy the system (liquid crystal, nanoparticles, functionalization compound) will need to reorient the liquid crystal in the magnetic field. In addition, we have observed that the orientation the liquid crystal adopts with respect to the nanoparticles can result in a phase transition that takes the liquid crystal to a more disordered and symmetric phase that favors the rotation, as happens in the smectic-nematic transition, observed in the sample with APTS. We relate the disordering to the changes observed in the transition for the liquid crystal and this termination to recent heat capacity measurements by Cordoyiannis et al. [1]. References [1] Cordoyiannis, G., Kurihara, L.K., Martinez-Miranda, L. J, Glorieux, C., Thoen, J., submitted to PRE (2008).

Martinez-Miranda, Luz J.; Kurihara, Lynn K.

2009-03-01

117

Liquid-liquid transition in a strong bulk metallic glass-forming liquid

NASA Astrophysics Data System (ADS)

Polymorphic phase transitions are common in crystalline solids. Recent studies suggest that phase transitions may also exist between two liquid forms with different entropy and structure. Such a liquid-liquid transition has been investigated in various substances including water, Al2O3-Y2O3 and network glass formers. However, the nature of liquid-liquid transition is debated due to experimental difficulties in avoiding crystallization and/or measuring at high temperatures/pressures. Here we report the thermodynamic and structural evidence of a temperature-induced weak first-order liquid-liquid transition in a bulk metallic glass-forming system Zr41.2Ti13.8Cu12.5Ni10Be22.5 characterized by non- (or weak) directional bonds. Our experimental results suggest that the local structural changes during the transition induce the drastic viscosity changes without a detectable density anomaly. These changes are correlated with a heat capacity maximum in the liquid. Our findings support the hypothesis that the ‘strong’ kinetics (low fragility) of a liquid may arise from an underlying lambda transition above its glass transition.

Wei, Shuai; Yang, Fan; Bednarcik, Jozef; Kaban, Ivan; Shuleshova, Olga; Meyer, Andreas; Busch, Ralf

2013-07-01

118

The present work is devoted to the study of the thermo-optical properties of liquid crystals doped with traces of fullerene C(60) at the vicinity of the nematic-smectic-A phase transition. By using the time-resolved Z-scan technique, we measure the temperature dependence of the thermo-optical coefficient and the thermal diffusivity. Our results reveal that the critical behavior of the thermal diffusivity is strongly affected by the fullerene addition. We provide a detailed discussion under the light of the distinct mechanisms behind the thermal transport in liquid-crystal samples. PMID:25353819

Omena, Lidiane; de Melo, Pedro B; Pereira, Maria S S; de Oliveira, Italo N

2014-05-01

119

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

120

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.

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

121

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

Annunziata, Onofrio

122

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

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

2013-09-01

123

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

124

Single crystalline metal oxide nanowires formed via a vapor-liquid-solid (VLS) route provide a platform not only for studying fundamental nanoscale properties but also for exploring novel device applications. Although the crystal phase variation of metal oxides, which exhibits a variety of physical properties, is an interesting feature compared with conventional semiconductors, it has been difficult to control the crystal phase of metal oxides during the VLS nanowire growth. Here we show that a material flux critically determines the crystal phase of indium-tin oxide nanowires grown via the VLS route, although thermodynamical parameters, such as temperature and pressure, were previously believed to determine the crystal phase. The crystal phases of indium-tin oxide nanowires varied from the rutile structures (SnO2), the metastable fluorite structures (InxSnyO3.5) and the bixbyite structures (Sn-doped In2O3) when only the material flux was varied within an order of magnitude. This trend can be interpreted in terms of the material flux dependence of crystal phases (rutile SnO2 and bixbyite In2O3) on the critical nucleation at the liquid-solid (LS) interface. Thus, precisely controlling the material flux, which has been underestimated for VLS nanowire growths, allows us to design the crystal phase and properties in the VLS nanowire growth of multicomponent metal oxides. PMID:24842296

Meng, Gang; Yanagida, Takeshi; Yoshida, Hideto; Nagashima, Kazuki; Kanai, Masaki; Zhuge, Fuwei; He, Yong; Klamchuen, Annop; Rahong, Sakon; Fang, Xiaodong; Takeda, Seiji; Kawai, Tomoji

2014-06-21

125

NASA Astrophysics Data System (ADS)

The equilibrium density distribution and thermodynamic properties of a Lennard-Jones fluid confined to nanosized spherical cavities at a constant chemical potential was determined using Monte Carlo simulations. The results describe both a single cavity with semi-permeable walls as well as a collection of closed cavities formed at the constant chemical potential. The results are compared to calculations using classical density functional theory (DFT). It is found that the DFT calculations give a quantitatively accurate description of the pressure and structure of the fluid. Both theory and simulation show the presence of a 'reverse' liquid-vapor transition whereby the equilibrium state is a liquid at large volumes but becomes a vapor at small volumes.

Lutsko, James F.; Laidet, Julien; Grosfils, Patrick

2010-01-01

126

The equilibrium density distribution and thermodynamic properties of a Lennard-Jones fluid confined to nanosized spherical cavities at a constant chemical potential was determined using Monte Carlo simulations. The results describe both a single cavity with semi-permeable walls as well as a collection of closed cavities formed at the constant chemical potential. The results are compared to calculations using classical density functional theory (DFT). It is found that the DFT calculations give a quantitatively accurate description of the pressure and structure of the fluid. Both theory and simulation show the presence of a 'reverse' liquid-vapor transition whereby the equilibrium state is a liquid at large volumes but becomes a vapor at small volumes. PMID:21386277

Lutsko, James F; Laidet, Julien; Grosfils, Patrick

2010-01-27

127

NASA Astrophysics Data System (ADS)

Single crystalline metal oxide nanowires formed via a vapor-liquid-solid (VLS) route provide a platform not only for studying fundamental nanoscale properties but also for exploring novel device applications. Although the crystal phase variation of metal oxides, which exhibits a variety of physical properties, is an interesting feature compared with conventional semiconductors, it has been difficult to control the crystal phase of metal oxides during the VLS nanowire growth. Here we show that a material flux critically determines the crystal phase of indium-tin oxide nanowires grown via the VLS route, although thermodynamical parameters, such as temperature and pressure, were previously believed to determine the crystal phase. The crystal phases of indium-tin oxide nanowires varied from the rutile structures (SnO2), the metastable fluorite structures (InxSnyO3.5) and the bixbyite structures (Sn-doped In2O3) when only the material flux was varied within an order of magnitude. This trend can be interpreted in terms of the material flux dependence of crystal phases (rutile SnO2 and bixbyite In2O3) on the critical nucleation at the liquid-solid (LS) interface. Thus, precisely controlling the material flux, which has been underestimated for VLS nanowire growths, allows us to design the crystal phase and properties in the VLS nanowire growth of multicomponent metal oxides.Single crystalline metal oxide nanowires formed via a vapor-liquid-solid (VLS) route provide a platform not only for studying fundamental nanoscale properties but also for exploring novel device applications. Although the crystal phase variation of metal oxides, which exhibits a variety of physical properties, is an interesting feature compared with conventional semiconductors, it has been difficult to control the crystal phase of metal oxides during the VLS nanowire growth. Here we show that a material flux critically determines the crystal phase of indium-tin oxide nanowires grown via the VLS route, although thermodynamical parameters, such as temperature and pressure, were previously believed to determine the crystal phase. The crystal phases of indium-tin oxide nanowires varied from the rutile structures (SnO2), the metastable fluorite structures (InxSnyO3.5) and the bixbyite structures (Sn-doped In2O3) when only the material flux was varied within an order of magnitude. This trend can be interpreted in terms of the material flux dependence of crystal phases (rutile SnO2 and bixbyite In2O3) on the critical nucleation at the liquid-solid (LS) interface. Thus, precisely controlling the material flux, which has been underestimated for VLS nanowire growths, allows us to design the crystal phase and properties in the VLS nanowire growth of multicomponent metal oxides. Electronic supplementary information (ESI) available: STEM mapping of In and Sn in an ISO nanowire (Fig. S1) and homogeneity of a fluorite ISO phase at the full length of a nanowire (Fig. S2). See DOI: 10.1039/c4nr01016g

Meng, Gang; Yanagida, Takeshi; Yoshida, Hideto; Nagashima, Kazuki; Kanai, Masaki; Zhuge, Fuwei; He, Yong; Klamchuen, Annop; Rahong, Sakon; Fang, Xiaodong; Takeda, Seiji; Kawai, Tomoji

2014-05-01

128

Viscosity near phase transitions

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.

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

2010-09-30

129

String mediated phase transitions

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

130

Solitosynthesis induced phase transitions

NASA Astrophysics Data System (ADS)

We consider a phase transition induced by the growth of Q-balls in a false vacuum. Such a transition could occur in the early universe in the case of broken supersymmetry with a metastable false vacuum. Small Q-balls with a negative potential energy can grow in a false vacuum by accretion of global charge until they reach critical size, expand, and cause a phase transition. We consider the growth of Q-balls from small to large, using the Bethe-Salpeter equation to describe small charge solitons and connecting to the growth of larger solitons for which the semiclassical approximation is reliable. We thus test the scenario in a simplified example inspired by supersymmetric extensions of the standard model.

Pearce, Lauren

2012-06-01

131

Metastable liquid-liquid transition in a molecular model of water

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

132

Kerr-Effect in the Isotropic Liquid Phase of Nematogens

The existence of strong fluctuations of the orientational order in the isotropic phase of nematics determines the nature of electro-optical effects near to Tc the temperature of the phase transition of the isotropic liquid into the liquid crystalline state. Electric birefringence in the isotropic phase of liquid crystals differing in the value and direction of the dipole moment of the

V. N. Tsvetkov; E. I. Rjumtsev

1986-01-01

133

Late-time Phase transition and the Galactic halo as a Bose Liquid: (II) the Effect of Visible Matter

In the previous work, we investigated the rotation curves of galaxies assuming that the dark matter consists of ultra light boson appearing in $'$late time phase transition' theory. Generalizing this work, we consider the effect of visible matter and classify the types of rotation curves as we vary the fraction of the mass and extention of visible matter. We show that visible matter, in galaxies with flat rotation curves, has mass fraction $ 2\\% \\sim 10\\% $ and it is confined within the distance fraction $ 10\\% \\sim 20\\%$.

S. U. Ji; S. J. Sin

1994-09-10

134

NASA Astrophysics Data System (ADS)

Absorption spectra of liquid water H2O are investigated in the region 4500-5600 cm-1 at temperatures from -53.0 to +20.3°C. The absorption band is decomposed into component modes at (I) 4700, (II) 4890, (III) 5080, and (IV) 5200 cm-1 whose centers are shifted slightly with temperature. Modes (II), (III), and (IV) are present in the spectrum of liquid water, whereas modes (I), (II), and (III) are registered in the spectrum of ice. The appearance of the ordered crystalline lattice is characterized by the occurrence of low-frequency mode (I) and by the disappearance of high-frequency component (IV) of the water absorption band in the region 4500-5600 cm-1. The spectral regions and temperature ranges in which the structure is changed during phase transition are determined.

Sinitsa, L. N.; Lugovskoy, A. A.; Sukhov, A. B.; Poplavskii, Yu. A.

2015-01-01

135

The interaction of surfactants with the vesicle membrane of the negatively charged lipid, dilauroylphosphatidic acid, was investigated through their effect on the gel-to-liquid-crystalline phase transition of the lipid bilayer. Three types of surfactants (anionic, cationic and non-ionic) with different hydrocarbon chain length were examined. (i) Anionic sodium alkylsulfates affected the phase transition temperature, Tm, only weakly. (ii) Non-ionic alkanoyl-N-methylglucamides decreased Tm monotonously with increasing concentration. The depression of Tm induced by these surfactants was analyzed by applying the van't Hoff model for the freezing-point depression, and the partition coefficients of the surfactants between bulk water and lipid membrane were estimated. (iii) Cationic alkyltrimethylammonium bromides affected Tm in a complex manner depending on the hydrocarbon chain length of the surfactants. Octyl-/tetradecyl-trimethylammonium bromide depressed/elevated Tm monotonously with increasing concentration, whereas the change in Tm induced by decyl- and dodecyltrimethylammonium bromides was not monotonous but biphasic. This complex behavior of the phase transition temperature was well explained, based on the statistical mechanical theory presented by Suezaki et al. (Biochim. Biophys. Acta, 818 (1985) 31-37), which takes into account the interaction between surfactant molecules incorporated in the lipid membrane. PMID:3242947

Inoue, T; Iwanaga, T; Fukushima, K; Shimozawa, R; Suezaki, Y

1988-10-01

136

NASA Astrophysics Data System (ADS)

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.

Tournier, Robert F.

2014-12-01

137

NASA Astrophysics Data System (ADS)

The quantum spin liquid is an enigmatic entity that is often hard to characterize within the conventional framework of condensed matter physics. We here present theoretical and numerical evidence for the characterization of a quantum spin liquid phase extending from the exact ground state to a finite critical temperature. We investigate a three-dimensional variant of the Kitaev model on a hyperhoneycomb lattice in the limit of strong anisotropy; the model is mapped onto an effective Ising-type model, where elementary excitations consist of closed loops of flipped Ising-type variables on a diamond lattice. Analyzing this effective model by Monte Carlo simulation, we find a phase transition from the quantum spin liquid to a paramagnet at a finite critical temperature Tc, accompanied by a divergent singularity of the specific heat. We also compute the magnetic properties in terms of the original quantum spins. We find that the magnetic susceptibility exhibits a broad hump above Tc, while it obeys the Curie law at high temperature and approaches a nonzero Van Vleck-type constant at low temperature. Although the susceptibility changes continuously at Tc, its temperature derivative shows a critical divergence at Tc. We also clarify that the dynamical spin correlation function is momentum independent but shows quantized peaks corresponding to discretized excitations. Although the phase transition accompanies no apparent symmetry breaking in terms of the Ising-type variables or of the original quantum spins, we characterize it from a topological viewpoint. We find that, by defining the flux density for loops of the Ising-type variables, the transition can be interpreted as one occurring from the zero-flux quantum spin liquid to the nonzero-flux paramagnet; the latter has a Coulombic nature due to the local constraints. The role of global constraints on the Ising-type variables is examined in comparison with the results in the two-dimensional loop model. The correspondence of our model to the Ising model on a diamond lattice is also discussed. A possible relevance of our results to the recently discovered hyperhoneycomb compound ?-Li2IrO3 is mentioned.

Nasu, J.; Kaji, T.; Matsuura, K.; Udagawa, M.; Motome, Y.

2014-03-01

138

Quantum phase transitions in disordered magnets

NASA Astrophysics Data System (ADS)

We study the effects of quenched weak disorder on quantum phase transitions in disordered magnets. The presence of disorder in the system can lead to a variety of exotic phenomena, e.g., the smearing of transitions or quantum Griffiths singularities. Phase transitions are smeared if individual spatial regions can order independently of the bulk system. In paper I, we study smeared quantum phase transitions in binary alloys A1-xBx that are tuned by changing the composition x. We show that in this case the ordered phase is extended over all compositions x < 1. We also study the composition dependence of observables. In paper II, we investigate the influence of spatial disorder correlations on smeared phase transitions. As an experimental example, we demonstrate in paper III, that the composition-driven ferromagnetic-toparamagnetic quantum phase transition in Sr1-xCaxRuO3 is smeared. When individual spatial regions cannot order but fluctuate slowly, the phase transition is characterized by strong singularities in the quantum Griffiths phase. In paper IV, we develop a theory of the quantum Griffiths phases in disordered ferromagnetic metals. We show that the quantum Griffiths singularities are stronger than the usual power-law quantum Griffiths singularities in insulating magnets. In paper V, we present an efficient numerical method for studying quantum phase transitions in disordered systems with O(N) order parameter symmetry in the large-N limit. Our algorithm solves iteratively the large-N self-consistent equations for the renormalized distances from criticality. Paper VI is devoted to the study of transport properties in the quantum Griffiths phase associated with the antiferromagnetic quantum phase transition in a metal. We find unusual behavior of transport properties which is in contrast to the normal Fermi-liquid behavior.

Nozadze, David

139

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.

Pruess, K.

2011-05-15

140

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

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

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

2012-01-01

141

NASA Technical Reports Server (NTRS)

Industry spends billions of dollars each year on machine tools to manufacture products out of metal. This includes tools for cutting every kind of metal part from engine blocks to Shuttle main engine components. Cutting tool tips often break because of weak spots or defects in their composition. Based on a new concept called defect trapping, space offers a novel environment to study defect formation in molten metal materials as they solidify. After the return of these materials from space, researchers can evaluate the source of the defect and seek ways to eliminate them in products prepared on Earth. A widely used process for cutting tip manufacturing is liquid phase sintering. Compared to Earth-sintered samples which slump due to buoyancy induced by gravity, space samples are uniformly shaped and defects remain where they are formed. By studying metals sintered in space the US tool industry can potentially enhance its worldwide competitiveness. The Consortium for Materials Development in Space along with Wyle Labs, Teledyne Advanced Materials, and McDornell Douglas have conducted experiments in space.

2004-01-01

142

The isotropic phase of nematogenic liquid crystals has nanometer length scale domains with pseudonematic ordering. As the isotropic to nematic phase transition temperature (TNI) is approached from above, the orientational correlation length, ?, of the pseudonematic domains grows as (T - T(*))(-1/2), where T(*) is 0.5-1 K below TNI. The orientational relaxation, which is a collective property of the pseudonematic domains, was measured with optical heterodyne detected-optical Kerr effect (OHD-OKE). The orientational relaxation obeys Landau-de Gennes theory, as has been shown previously. To examine the environmental evolution experienced by molecules in the pseudonematic domains, two-dimensional infrared (2D IR) vibrational echo experiments on the CN stretching mode of the non-perturbative vibrational probes 4-pentyl-4(')-selenocyanobiphenyl (5SeCB) and 4-pentyl-4(')-thiocyanobiphenyl (5SCB) in the nematogen 4-cyano-4(')-pentylbiphenyl (5CB) were performed. The 2D IR experiments measure spectral diffusion, which is caused by structural fluctuations that couple to the CN vibrational frequency. Temperature dependent studies were performed just above TNI, where the correlation length of pseudonematic domains is large and changing rapidly with temperature. These studies were compared to 2D IR experiments on 4-pentylbiphenyl (5B), a non-mesogenic liquid that is very similar in structure to 5CB. The time constants of spectral diffusion in 5CB and 5B are practically identical at temperatures ?5 K above TNI. As the temperature is lowered, spectral diffusion in 5B slows gradually. However, the time constants for spectral diffusion in 5CB slow dramatically and diverge as T(*) is approached. This divergence has temperature dependence proportional to (T - T(*))(-1/2), precisely the same as seen for the correlation length of pseudonematic domains, but different from the observed orientational relaxation times, which are given by the Landau-de Gennes theory. The data and previous results show that spectral diffusion in 5CB has no contributions from orientational relaxation, and the structural dynamics responsible for the spectral diffusion are likely a result of density fluctuations. The results suggest that the correlation length of the density fluctuations is diverging with the same temperature dependence as the pseudonematic domain correlation length, ?. The isotropic-nematic phase transition in liquid crystals is described in the context of the slowing of orientational relaxation associated with divergent growth of the orientational correlation length. The results presented here show that there is another divergent dynamical process, likely associated with density fluctuations. PMID:25416893

Sokolowsky, Kathleen P; Bailey, Heather E; Fayer, Michael D

2014-11-21

143

Quantum phase transition in space

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}.

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

2008-01-01

144

Diffusion phase transitions in alloys

NASA Astrophysics Data System (ADS)

We present a critical analysis of research on the thermodynamics, kinetics, and morphology of diffusion phase transitions in alloys. We show that diffusion phase transitions are mainly driven by the chemical potential difference due to a change in the sign of the chemical interaction among the component atoms. We explain how the sign of the chemical interaction energy can be obtained from experimental measurements. Examples are given to illustrate the kinetics and morphology of the ordering-separation phase transition in Ni- and Co-based alloys. We show how introducing the concept of the ordering-separation phase transition may affect our thinking in this area.

Ustinovshchikov, Yu I.

2014-07-01

145

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

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

146

NASA Astrophysics Data System (ADS)

The phase field theory (PFT) has been applied to predict equilibrium interfacial properties and nucleation barrier in the binary eutectic system Ag-Cu using double well and interpolation functions deduced from a Ginzburg-Landau expansion that considers fcc (face centered cubic) crystal symmetries. The temperature and composition dependent free energies of the liquid and solid phases are taken from CALculation of PHAse Diagrams-type calculations. The model parameters of PFT are fixed so as to recover an interface thickness of ˜1nm from molecular dynamics simulations and the interfacial free energies from the experimental dihedral angles available for the pure components. A nontrivial temperature and composition dependence for the equilibrium interfacial free energy is observed. Mapping the possible nucleation pathways, we find that the Ag and Cu rich critical fluctuations compete against each other in the neighborhood of the eutectic composition. The Tolman length is positive and shows a maximum as a function of undercooling. The PFT predictions for the critical undercooling are found to be consistent with experimental results. These results support the view that heterogeneous nucleation took place in the undercooling experiments available at present. We also present calculations using the classical droplet model [classical nucleation theory (CNT)] and a phenomenological diffuse interface theory (DIT). While the predictions of the CNT with a purely entropic interfacial free energy underestimate the critical undercooling, the DIT results appear to be in a reasonable agreement with the PFT predictions.

Tóth, Gyula I.; Gránásy, László

2007-08-01

147

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

Susan S. Sorini; John F. Schabron

2006-03-01

148

Phase transitions in disordered systems

NASA Astrophysics Data System (ADS)

Disorder can have a wide variety of consequences for the physics of phase transitions. Some transitions remain unchanged in the presence of disorder while others are completely destroyed. In this thesis we study the effects of disorder on several classical and quantum phase transitions in condensed matter systems. After a brief introduction, we study the ferromagnetic phase transition in a randomly layered Heisenberg magnet using large-scale Monte-Carlo simulations. Our results provide numerical evidence for the exotic infinite-randomness scenario. We study classical and quantum smeared phase transitions in substitutional alloys A1-xBx. Our results show that the disorder completely destroys the phase transition with a pronounced tail of the ordered phase developing for all compositions x < 1. In addition, we find that short-ranged disorder correlations can have a dramatic effect on the transition. Moreover, we show an experimental realization of the composition-tuned ferromagnetic-to-paramagnetic quantum phase transition in Sr1-xCa xRuO3. We investigate the effects of disorder on first-order quantum phase transitions on the example of the N-color quantum Ashkin-Teller model. By means of a strong disorder renormalization group, we demonstrate that disorder rounds the first-order transition to a continuous one for both weak and strong coupling between the colors. Finally, we investigate the superfluid-insulator quantum phase transition of one-dimensional bosons with off-diagonal disorder by means of large-scale Monte-Carlo simulations. Beyond a critical disorder strength, we find nonuniversal, disorder dependent critical behavior.

Hrahsheh, Fawaz Y.

149

Fluctuation driven electroweak phase transition

NASA Technical Reports Server (NTRS)

We examine the dynamics of the electroweak phase transition in the early Universe. For Higgs masses in the range 46 less than or = M sub H less than or = 150 GeV and top quark masses less than 200 GeV, regions of symmetric and asymmetric vacuum coexist to below the critical temperature, with thermal equilibrium between the two phases maintained by fluctuations of both phases. We propose that the transition to the asymmetric vacuum is completed by percolation of these subcritical fluctuations. Our results are relevant to scenarios of baryogenesis that invoke a weakly first-order phase transition at the electroweak scale.

Gleiser, Marcelo; Kolb, Edward W.

1991-01-01

150

Liquid-liquid transition in ST2 water

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

151

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

We model the intercolloidal interaction by a hard-sphere Yukawa repulsion to which is added the long-range van der Waals attraction. In comparison with the Derjaguin-Landau-Verwey-Overbeek repulsion, the Yukawa repulsion explicitly incorporates the spatial correlations between colloids and small ions. As a result, the repulsive part can be expressed analytically and has a coupling strength depending on the colloidal volume fraction. By use of this two-body potential of mean force and in conjunction with a second-order thermodynamic perturbation theory, we construct the colloidal Helmholtz free energy and use it to calculate the thermodynamic quantities, pressure and chemical potential, needed in the determination of the liquid-liquid and liquid-solid phase diagrams. We examine, in an aqueous charged colloidal dispersion, the effects of the Hamaker constant and particle size on the conformation of a stable liquid-liquid phase transition calculated with respect to the liquid-solid coexistence phases. We find that there exists a threshold Hamaker constant or particle size whose value demarcates the stable liquid-liquid coexistence phases from their metastable counterparts. Applying the same technique and using the energetic criterion, we extend our calculations to study the flocculation phenomenon in aqueous charged colloids. Here, we pay due attention to determining the loci of a stability curve stipulated for a given temperature T0, and obtain the parametric phase diagram of the Hamaker constant vs the coupling strength or, at given surface potential, the particle size. By imposing T0 to be the critical temperature T(c), i.e., setting k(B)T0 (=k(B)T(c)) equal to a reasonable potential barrier, we arrive at the stability curve that marks the irreversible/reversible phase transition. The interesting result is that there occurs a minimum size for the colloidal particles below (above) which the colloidal dispersion is driven to an irreversible (reversible) phase transition. PMID:12443203

Lai, S K; Wu, K L

2002-10-01

152

This report on the solid-to-liquid transition region of an Ag-Pd bimetallic nanocluster is based on a constant energy microcanonical ensemble molecular dynamics simulation combined with a collision method. By varying the size and composition of an Ag-Pd bimetallic cluster, we obtained a complete solid-solution type of binary phase diagram of the Ag-Pd system. Irrespective of the size and composition of the cluster, the melting temperature of Ag-Pd bimetallic clusters is lower than that of the bulk state and rises as the cluster size and the Pd composition increase. Additionally, the slope of the phase boundaries (even though not exactly linear) is lowered when the cluster size is reduced on account of the complex relations of the surface tension, the bulk melting temperature, and the heat of fusion. The melting of the cluster initially starts at the surface layer. The initiation and propagation of a five-fold icosahedron symmetry is related to the sequential melting of the cluster. PMID:19562138

Kim, Da Hye; Kim, Hyun You; Ryu, Ji Hoon; Lee, Hyuck Mo

2009-07-01

153

Phase transition and lattice distortion in the proposed spin-liquid system kappa-(BEDT-TTF)Cu2(CN)3

We report measurements of the uniaxial coefficients of thermal expansion alphai and the specific heat C on the spin-liquid candidate kappa-(BEDT-TTF)Cu2(CN)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'\\/t upon cooling into the low-temperature regime. Most importantly, the alphai data reveal

M. Lang; R. S. Manna; M. de Souza; A. Brühl; J. A. Schlueter

2010-01-01

154

Liquid-Vapour Phase Change Rates and Interfacial Entropy Production

Measurements have recently been made of the thermodynamic conditions at the interface during steady state, liquid-vapour phase transitions. In these stationary, nonequilibrium states discontinuities were recorded in the temperature and other intensive properties. Independently of whether evaporation or condensation was taking place, it was found that the interfacial temperature was higher in the vapour phase than that in the liquid.

C. A. Ward

2002-01-01

155

Isotropic to cholesteric phase transition of DNA solutions

NASA Astrophysics Data System (ADS)

Experimental studies have shown that both long and short complementary B-form DNA oligomers exhibit liquid crystals phases. We study the isotropic to cholesteric (I-Ch) phase transition of DNA solutions using Landau theory. We define relevant order parameters for this transition. It is shown that the I-Ch transition temperature is depressed and a two phase region is formed due to the presence of the DNA concentration. The concentration and oligomers length dependent transition temperature is calculated and compared with experimental results. The Kerr effect and Cotton-Mouton coefficient are calculated in the isotropic phase above the I-Ch transition.

Mukherjee, Prabir K.

2014-01-01

156

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

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

2014-09-24

157

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

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

2012-12-27

158

The transition from the annular to the slug flow regime in two-phase flow

Experiments were conducted to determine the transition from annular to semiannular flow regimes for two-phase, gas-liquid upflow in vertical tubes. The influencesof liquid flow rate, tube diameter, liquid viscosity, surface ...

Haberstroh, Robert D.

1964-01-01

159

Simulations of phase transitions in ionic systems

NASA Astrophysics Data System (ADS)

A review of recent simulation work in the area of phase transitions in ionic systems is presented. The vapour-liquid transition for the restricted primitive model has been studied extensively in the past decade. The critical temperature is now known to excellent accuracy and the critical density to moderate accuracy. There is also strong simulation-based evidence that the model is in the Ising universality class. Discretized lattice versions of the model are reviewed. Other systems covered are size- and charge-asymmetric electrolytes, colloid-salt mixtures, realistic salt models and charged chains. Areas of future research needs are briefly discussed.

Panagiotopoulos, A. Z.

2005-11-01

160

Liquid-Phase Combinatorial Synthesis

A concept termed liquid-phase combinatorial synthesis (LPCS) is described. The central feature of this methodology is that it combines the advantages that classic organic synthesis in solution offers with those that solid-phase synthesis can provide, through the application of a linear homogeneous polymer. To validate this concept two libraries were prepared, one of peptide and the second of non-peptide origin.

Hyunsoo Han; Mary M. Wolfe; Sydney Brenner; Kim D. Janda

1995-01-01

161

Fragility Control Using the Liquid-Liquid Transition in Molecular Liquid

Liquids, whose viscosity obeys the Arrhenius law, are called ``strong,'' while ``fragile'' liquids have the super-Arrhenius behavior. Here we report the first continuous control of the fragility of liquid of the same material over a wide range of fragility, using a continuous liquid-liquid transition. Our study clearly demonstrates that the fragility is not a material specific quantity, but is controlled

Rei Kurita; Hajime Tanaka

2006-01-01

162

Polymer-stabilized blue phase liquid crystals: a tutorial [Invited

. Cheng, S. Gauza, Y. Li, M. Jiao, L. Rao, and S. T. Wu, "Extended Kerr effect of polymer-stabilized blue crystal `blue phases' with a wide temperature range," Nature 436(7053), 997Â1000 (2005). 14. H. Kikuchi. Porsch, "Electric field effect on phase transitions in liquid-crystalline blue-phase systems," Phys. Rev

Wu, Shin-Tson

163

Texture transitions in the liquid crystalline alkyloxybenzoic acid 6OBAC

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.

A. Sparavigna; A. Mello; B. Montrucchio

2006-09-01

164

Phase Transitions in Two-Dimensional Superconductors

NASA Astrophysics Data System (ADS)

In this thesis, we describe a number of experiments which are designed to explore the theoretically predicted phase transitions for two-dimensional superconductors. We first examine the behavior of a two-dimensional superconductor in the absence of a magnetic field, where the fluctuations in the phase of the superconducting order parameter results in the reduction of the superconducting transition temperature for a two-dimensional superconductor below the mean field transition temperature. The experimental results presented show the importance of the vortex unbinding mechanism; however they challenge some of the predictions of the current theoretical model for the normal/superconducting transition. We then turn our attention to the behavior of two-dimensional superconductors in the presence of a magnetic field. In this case, our experimental results show that vortices in weakly disordered two-dimensional superconducting films freeze into locally correlated areas at temperatures below the mean field transition temperature. The experimentally measured phase boundary between the liquid phase and the locally ordered solid phase for the vortices in our samples shows good agreement with that predicted by the dislocation unbinding melting mechanism for the two-dimensional vortex lattice. For this transition, we have also done a detailed study of the correlations in the vortex lattices as a function of the strength of pinning in our samples and established a connection between the melting theory and collective pinning theory for vortices in two dimensions. To fully examine the phase diagram of a two-dimensional superconductor we have extended our studies of the properties of this system to the limit of strong disorder, where superconductivity is weak. In this limit, we report experimental evidence for a zero temperature field-tuned superconducting-insulating phase transition driven by quantum fluctuation of the phase of the superconducting order parameter. Overall, the results of this thesis provide an experimental bases for a number of phase transitions in two-dimensional superconductors, thereby establishing a rich phase diagram for this system as a function of the temperature, the magnetic field, and the amount of disorder.

Yazdani, Ali

1995-01-01

165

ERIC Educational Resources Information Center

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…

Johnson, Michael R.

2006-01-01

166

761 Lyotropic effects of alkanes and headgroup composition on the L03B1 -HII lipid liquid crystal of mixed phospholipid headgroup composition and the addition of small amounts of alkane were examined relieved, for instance, by the addition of alkane. Without alkane, the L03B1 phase extended to high

Boyer, Edmond

167

Phase transition in black holes

The present thesis is devoted towards the study of various aspects of the phase transition phenomena occurring in black holes defined in an Anti-de-Sitter (AdS) space. Based on the fundamental principles of thermodynamics and considering a grand canonical framework we examine various aspects of the phase transition phenomena occurring in AdS black holes. We analytically check that this phase transition between the smaller and larger mass black holes obey Ehrenfest relations defined at the critical point and hence confirm a second order phase transition. This include both the rotating and charged black holes in Einstein gravity. Apart from studying these issues, based on a canonical framework, we also investigate the critical behavior in charged AdS black holes. The scaling laws for these black holes are found to be compatible with the static scaling hypothesis. Finally, based on the usual framework of AdS/CFT duality, we investigate the phase transition phenomena occurring in charged hairy black holes defined in an asymptotically AdS space. Based on analytic calculations, and using the AdS/CFT dictionary, we explicitly compute the order-parameter for the dual CFT close to the critical point of the phase transition and found that the critical exponent associated with the condensation is $\\frac{1}{2}$, which is the universal result of the mean field theory. Moreover, we also find that in the presence of an external magnetic field, the dual CFT exhibit a perfect diamagnetism at low temperatures, which may be regarded as the reminiscent of the so called Meissner effect.

Dibakar Roychowdhury

2014-03-18

168

Two Phase Flow Mapping and Transition Under Microgravity Conditions

NASA Technical Reports Server (NTRS)

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.

Parang, Masood; Chao, David F.

1998-01-01

169

THEORY OF MAGNETIC PHASE TRANSITIONS

The existence of magnetic order (also termed collective magnetism) that is the orderly arrangement of the magnetic spins appearing in materials below an ordering temperature (e.g., the Curie temperature, TC, of a ferromagnet or the Neel temperature, T N, of an antiferromagnet; see Magnetic Moment and Magnetization) points to a class of physical phenomena that can be described as magnetic phase transitions. The thermodynamics of these phase transitions can be described by energy functions (expressed in terms of intensive or extensive variables), in terms of magnetization–temperature (M–T) phase diagrams, or in terms of critical exponents that describe the variation of thermodynamic properties (as a function of the order parameter) as the ordering temperature is approached. In this article, we describe the thermodynamics of magnetic ordering transitions, the order of the transitions, critical exponents, and thermodynamic variables. We further describe magnetic phase transitions within the framework of the mean field Landau theory of phase transitions with discussion of several magnetic equations of state. The discussion of thermodynamic properties begins with the definition of thermodynamic potential functions and their derivatives. For simplicity, we can take pressure and volume as being held constant and consider only magnetic work terms. In this case the entropy (S) and magnetization (M) are extensive variables, the temperature (T) and field (H) are intensive variables, and the different energy functions are the internal energy (U(S, M)), the enthalpy (E(S, H)) (many texts express enthalpy as H, but E is used here to avoid confusion with applied magnetic fields, H), the Helmholtz free

Michael E. Mchenry; David; E. Laughlin; De Tds Mdh; Df Sdtþhdm; Dg Sdt Mdh

170

Phase transitions in nuclear matter

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.

Glendenning, N.K.

1984-11-01

171

Liquid-phase chromatography detector

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

Voigtman, Edward G. (Gainesville, FL); Winefordner, James D. (Gainesville, FL); Jurgensen, Arthur R. (Gainesville, FL)

1983-01-01

172

Liquid-phase chromatography detector

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

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

1983-11-08

173

Phase transition in colloidal dispersions

NASA Astrophysics Data System (ADS)

Dynamic light scattering (DLS) is applied to the glass transition of concentrated N-isopropylacrylamde (NIPA) gel nanoparticle dispersions. These dispersions are treated as simple superatomic systems. Intermediate scattering functions are obtained as the function of temperature and scattering angle. The observed phase behavior is consistent with an essentially hard-sphere interaction between the particles.

Li, Jianyou; Gao, Jun; Hu, Zhibing

2000-10-01

174

Interplay between micelle formation and waterlike phase transitions

NASA Astrophysics Data System (ADS)

A lattice model for amphiphilic aggregation in the presence of a structured waterlike solvent is studied through Monte Carlo simulations. We investigate the interplay between the micelle formation and the solvent phase transition in two different regions of temperature-density phase diagram of pure water. A second order phase transition between the gaseous (G) and high density liquid (HDL) phases that occurs at very high temperatures, and a first order phase transition between the low density liquid (LDL) and (HDL) phases that takes place at lower temperatures. In both cases, we find the aggregate size distribution curve and the critical micellar concentration as a function of the solvent density across the transitions. We show that micelle formation drives the LDL-HDL first order phase transition to lower solvent densities, while the transition G-HDL is driven to higher densities, which can be explained by the markedly different degrees of micellization in both cases. The diffusion coefficient of surfactants was also calculated in the LDL and HDL phases, changing abruptly its behavior due to the restructuring of waterlike solvent when we cross the first order LDL-HDL phase transition. To understand such behavior, we calculate the solvent density and the number of hydrogen bonds per water molecule close to micelles. The curves of the interfacial solvent density and the number of hydrogen bonds per water molecule in the first hydration signal a local phase change of the interfacial water, clarifying the diffusion mechanism of free surfactants in the solvent.

Heinzelmann, G.; Figueiredo, W.; Girardi, M.

2010-02-01

175

Images reveal that atmospheric particles can undergo liquid–liquid phase separations

A large fraction of submicron atmospheric aerosol particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere and the water content of the particles correspondingly changes, these mixed particles can undergo a range of phase transitions, possibly including liquid–liquid phase separation. If liquid–liquid phase separation occurs, the gas-particle partitioning of atmospheric semivolatile organic compounds, the scattering and absorption of solar radiation, and the reactive uptake of gas species on atmospheric particles may be affected, with important implications for climate predictions. The actual occurrence of liquid–liquid phase separation within individual atmospheric particles has been considered uncertain, in large part because of the absence of observations for real-world samples. Here, using optical and fluorescence microscopy, we present images that show the coexistence of two noncrystalline phases for real-world samples collected on multiple days in Atlanta, GA as well as for laboratory-generated samples under simulated atmospheric conditions. These results reveal that atmospheric particles can undergo liquid–liquid phase separations. To explore the implications of these findings, we carried out simulations of the Atlanta urban environment and found that liquid–liquid phase separation can result in increased concentrations of gas-phase NO3 and N2O5 due to decreased particle uptake of N2O5. PMID:22847443

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

2012-01-01

176

Exothermic Supercooled Liquid—Liquid Transition in Amorphous Sulfur

NASA Astrophysics Data System (ADS)

Amorphous sulfur (a-S) is prepared by rapidly compressing molten sulfur to high pressure. From differential scanning calorimeter measurements, a large exothermic peak has been observed around 396 K. Online wide-angled x-ray scattering spectra indicate that no crystallization occurs in the temperature range 295-453 K, suggesting that the exothermal process corresponds to an amorphous-to-amorphous transition. The transition from amorphous sulfur to liquid sulfur is further verified by the direct observation of sulfur melt at the temperature of the associated transition. This is the first time of reporting that a-S transforms to liquid sulfur directly, which has avoided a crystallization process. What is more, the transition is an exothermic and a volume expansion process.

Zhang, Dou-Dou; Liu, Xiu-Ru; Hong, Shi-Ming; Li, Liang-Bin; Cui, Kun-Peng; Shao, Chun-Guang; He, Zhu; Xu, Ji-An

2014-06-01

177

Critical Point and Metal-Nonmetal Transition in Expanded Liquid Metals

For most metals the two phases of the liquid-gas transition are metallic in a region around the critical point. A method for determining the critical data of expanded liquid metals under such conditions has been published recently. Mercury, however, is a well-known exception with the metal-nonmetal transition inside the liquid phase. Mercury is no longer a metal at the critical

Helmut Hess; Hartmut Schneidenbach; Andreas Kloss

1999-01-01

178

Entropy Calculations for a Supercooled Liquid Crystalline Blue Phase

ERIC Educational Resources Information Center

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

Singh, U.

2007-01-01

179

Mixed Stationary Liquid Phases for Gas-Liquid Chromatography.

ERIC Educational Resources Information Center

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)

Koury, Albert M.; Parcher, Jon F.

1979-01-01

180

Phase transition theory of sprite halo

NASA Astrophysics Data System (ADS)

We present the phase transition theory for sprite halo using measurable lightning parameters (charge moment and discharge time) on the basis of steady state thermodynamics. A halo is located at the upper part of the tree-like structure of a sprite and is produced through electron impact excitation of neutral species under the lightning-induced electric field. We proposed in our previous studies that the occurrence criteria for halos and sprites are characterized by the above lightning parameters, and additionally, the intensity of a halo weakens rapidly with an increase in the discharge time T. We assume that this phenomenon is quite similar to the phase transition between the vapor and the liquid states of water; here the analogy is between the accelerated electrons and the water molecules. We demonstrate analytically a phase transition for a simply modeled halo based on the quasistatic theory of lightning-induced electric field. Choosing the luminosity of a halo as an order parameter, we show that it has a dependence of T-0.25 - Tc-0.25 near the critical point Tc, which is characteristic of the phase transition. Furthermore, the critical time scale Tc ? 5.5 ms is provided naturally from our modeling and is somewhat larger than the typical time scale of the halo luminosity in observations. We consider that this kind of formalism is useful in understanding the detailed relationship between lightning activity and occurrence of halos. We discuss this point for future observations along with the possibilities of the transition model of column and carrot structures.

Hiraki, Yasutaka

2010-04-01

181

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

2277 Coexistence of an ordered anisotropic phase and a liquid expanded phase in an amphiphilic. - Nous prÃ©sentons une Ã©tude expÃ©rimentale d'une transition de phase d'une monocouche d'amphiphiles amphiphiles. We have combined measurement of surface tension isotherms, ellipsometry and observations

Paris-Sud XI, UniversitÃ© de

182

In the present study, we employ quantum cluster equilibrium calculations on a small water cluster set in order to derive thermochemical equilibrium properties of the liquid phase as well as the liquid-vapor phase transition. The focus is set on the calculation of liquid phase entropies, from which entropies of vaporization at the normal boiling point of water are derived. Different

Christian Spickermann; Sebastian B. C. Lehmann; Barbara Kirchner

2008-01-01

183

Phase Transitions on Quasicrystalline Surfaces

The sputtering of the surfaces of quasicrystals with Ar^+ changes their chemical composition by preferential removal of particular atomic species. At room temperature, this produces a phase transition at the surface of the icosahedral Al_70Pd_20Mn_10 to a cubic structure. Using secondary-electron imaging (SEI), which reveals the atomic symmetry of surfaces and shallow interfaces in real space, we have investigated the

Bernhard Bolliger

2000-01-01

184

Non-equilibrium phase transitions

This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Non-equilibrium phase transitions play a central role in a very broad range of scientific areas, ranging from nuclear, particle, and astrophysics to condensed matter physics and the material and biological sciences. The aim of this project was to explore the path to a deeper and more fundamental understanding of the common physical principles underlying the complex real time dynamics of phase transitions. The main emphasis was on the development of general theoretical tools to deal with non-equilibrium processes, and of numerical methods robust enough to capture the time-evolving structures that occur in actual experimental situations. Specific applications to Laboratory multidivisional efforts in relativistic heavy-ion physics (transition to a new phase of nuclear matter consisting of a quark-gluon plasma) and layered high-temperature superconductors (critical currents and flux flow at the National High Magnetic Field Laboratory) were undertaken.

Mottola, E.; Cooper, F.M.; Bishop, A.R.; Habib, S.; Kluger, Y.; Jensen, N.G.

1998-12-31

185

Transient liquid phase ceramic bonding

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.

Glaeser, Andreas M. (Berkeley, CA)

1994-01-01

186

Phase transition dynamics and gravitational waves

During a first-order phase transition, gravitational radiation is generated either by bubble collisions or by turbulence. For phase transitions which took place at the electroweak scale and beyond, the signal is expected to be within the sensitivity range of planned interferometers such as LISA or BBO. We review the generation of gravitational waves in a first-order phase transition and discuss the dependence of the spectrum on the dynamics of the phase transition.

Megevand, Ariel [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales Universidad Nacional de Mar del Plata, Dean Funes 3350 (7600) Mar del Plata (Argentina)

2009-04-20

187

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

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

Hejazi, Vahid; Nosonovsky, Michael

2012-01-31

188

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

189

LIQUID-LIQUID EXTRACTION OF TRANSITION METAL CATIONS BY CALIXARENE-BASED CYCLIC LIGANDS

The selective liquid-liquid extraction of various alkali and transition metal cations from the aqueous phase to the organic phase was carried out by using p-tert-butylcalix[4]arene (L1), p-tert-butylcalix[6]arene (L2), tetra-ethyl p-tert-butylcalix[4]arene-tetra-acetate (L3), tetra-methyl-p-tert-butyl-calix[4]arene-tetra-ketone (L4), calix[n]arenes (n=4 and 6) bearing oxime groups on the lower rim (L5, L6 ) and a polymeric calix[4]arene. It was found that compounds L5 and L6, showed

Hasalettin Deligöz; Mustafa Yilmaz

1995-01-01

190

Liquid-like phases of ?^+?^- matter

To give a common theoretical description of liquid phases of the charged pion matter in a wide temperature interval, the relativistic quantum $\\phi^6$ type model is considered. The liquid states of pion condensate and hot pion matter are investigated.

D. V. Anchishkin; A. V. Nazarenko

2006-11-11

191

Phases and phase transitions in disordered quantum systems

NASA Astrophysics Data System (ADS)

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.

Vojta, Thomas

2013-08-01

192

Phase transitions for the Lifshitz black holes

We study possibility of phase transitions between Lifshitz black holes and other configurations by using free energies explicitly. A phase transition between Lifshitz soliton and Lifshitz black hole might not occur in three dimensions. We find that a phase transition between Lifshitz and BTZ black holes unlikely occurs because they have different asymptotes. Similarly, we point out that any phase transition between Lifshitz and black branes unlikely occurs in four dimensions since they have different asymptotes. This is consistent with a necessary condition for taking a phase transition in the gravitational system, which requires the same asymptote.

Yun Soo Myung

2012-07-02

193

Liquid phase sintering of silicon carbide

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

Cutler, Raymond A. (Bountiful, UT); Virkar, Anil V. (Salt Lake City, UT); Hurford, Andrew C. (Salt Lake City, UT)

1989-01-01

194

Liquid phase sintering of silicon carbide

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.

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

1989-05-09

195

NASA Astrophysics Data System (ADS)

Using a semiempirical many-body potential based on the second-moment approximation to the tight-binding method, we performed molecular-dynamics simulations to compute the diffusion constants and shear viscosities of the fcc transition metals Ni, Pd, Pt, Cu, Ag, and Au and the simple fcc metals Al and Pb in the liquid phase; in the case of Ni and Pb, we also computed the dynamic structure factors. Comparison of the molecular-dynamics results with available experimental data shows that the tight-binding potentials give a reasonable description of the dynamic properties of the liquid metals considered, in spite of having been parametrized on the basis of solid-state data.

Alemany, M. M. G.; Diéguez, O.; Rey, C.; Gallego, L. J.

1999-10-01

196

Application of ionic liquid in liquid phase microextraction technology.

Ionic liquids (ILs) are novel nonmolecular solvents. Their unique properties, such as high thermal stability, tunable viscosity, negligible vapor pressure, nonflammability, and good solubility for inorganic and organic compounds, make them excellent candidates as extraction media for a range of microextraction techniques. Many physical properties of ILs can be varied, and the structural design can be tuned to impart the desired functionality and enhance the analyte extraction selectivity, efficiency, and sensitivity. This paper provides an overview of the applications of ILs in liquid phase microextraction technology, such as single-drop microextraction, hollow fiber based liquid phase microextraction, and dispersive liquid-liquid microextraction. The sensitivity, linear calibration range, and detection limits for a range of target analytes in the methods were analyzed to determine the advantages of ILs in liquid phase microextraction. PMID:23002004

Han, Dandan; Tang, Baokun; Lee, Yu Ri; Row, Kyung Ho

2012-11-01

197

Phase Transition to Exact Susy

The anthropic principle is based on the observation that, within narrow bounds, the laws of physics are such as to have allowed the evolution of life. The string theoretic approach to understanding this observation is based on the expectation that the effective potential has an enormous number of local minima with different particle masses and perhaps totally different fundamental couplings and space time topology. The vast majority of these alternative universes are totally inhospitable to life, having, for example, vacuum energies near the natural (Planck) scale. The statistics, however, are assumed to be such that a few of these local minima (and not more) have a low enough vacuum energy and suitable other properties to support life. In the inflationary era, the "multiverse" made successive transitions between the available minima until arriving at our current state of low vacuum energy. String theory, however, also suggests that the absolute minimum of the effective potential is exactly supersymmetric. Questions then arise as to why the inflationary era did not end by a transition to one of these, when will the universe make the phase transition to the exactly supersymmetric ground state, and what will be the properties of this final state.

L. Clavelli

2007-03-20

198

Phase transitions in the assembly of multivalent signalling proteins

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.

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

199

Microphase Segregation and Twisting Transitions in Liquid Crystal Polymers

NASA Astrophysics Data System (ADS)

This dissertation is a collection of five related journal articles, each exploring some aspect of the theory of polymers and liquid crystal polymers. In the first article, Lamellar Ordering in Symmetric Diblock Copolymers, the lamellar period and interphase thickness of an incompressible melt of symmetric diblock copolymers are calculated numerically, from the weak segregation limit to the strong segregation limit. An analytic expression for the lamellar period, valid in the neighborhood of the weak segregation limit, is also derived. In the second article, Nematic Ordering and Microphase Segregation in a Diblock Polymer-Liquid Crystal Polymer, a theory of nematic ordering and microphase segregation in an incompressible melt of AB diblock copolymers is developed, for the case when the A block is a polymer composed of isotropic monomers, and the B block is a main chain liquid crystal polymer composed of freely-jointed rod-like nematogens. Various segregation morphologies are considered, and a phase diagram--revealing both morphological and isotropic-nematic transitions--is presented. In the third article, Twisting Transition in a Capillary Filled with Chiral Smectic-C Liquid Crystal Polymer, a capillary filled with the chiral smectic-C phase of a main chain liquid crystal polymer is considered. Due to steric constraints, a line disclination appears along the capillary axis. The tendency for chiral twisting competes with boundary conditions at the capillary wall, and the disclination line can shift away from the axis and twist into a helix. The fourth article, Twisting Transition in a Fiber Composed of Chiral Smectic-C Liquid Crystal Polymer, is similar to the third, but considers the transformation of a free-standing fiber from a cylinder to a helix. In the fifth article, Fluctuations and Light Scattering in a Liquid Crystal Polymer Fiber, the spatial correlation function is calculated for thermal fluctuations of the liquid crystal director field in the core of an optical fiber composed of main chain liquid crystal polymer in the smectic-C phase. The correlation function is used to estimate the scattering distribution and attenuation of the fiber.

Sones, Richard Allen

200

NASA Astrophysics Data System (ADS)

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.

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

2010-10-01

201

QCD Phase Transitions, Volume 15

The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.

Schaefer, T.; Shuryak, E.

1999-03-20

202

The Quantum Hall Liquid to Insulator Transitions

NASA Astrophysics Data System (ADS)

We have conducted a systematic study of the quantum phase transitions between insulating and quantum Hall effect (QHE) phases of two dimensional electron system (2DES) at high magnetic fields (B<15.5 T) and low temperatures (T>20 mK). More than 100 samples were studied, with mobilities and densities (? =1.2\\cdot 10^4-5\\cdot 10^6 cm^2/Vsec and n=8\\cdot 10^9-2.26\\cdot 10^11 cm-2, respectively) that effectively cover the whole range of 2DES samples that are currently available. We observed a remarkable similarity among the various transitions which transcends not only the vast differences in the parameters of our samples, but also the differences between the integer and the fractional QHE states. This similarity can be quantitatively expressed in terms of two parameters describing the transitions, the T scaling parameter, 1/? z =0.45± 0.05 and the the critical resistivity at the transition, ?_xxc=25.3± 6 k?, both of which are independent of sample parameters and transitions, within the errors specified. In the vicinity of the transitions, the I-V_xx traces are strongly non-linear, and exhibit a marked reflection symmetry between the traces in the QHE and those in the insulator, which we take as evidence for the existence of charge-flux duality symmetry near the transitions. These results support the predictions of the bosonic Chern-Simons theory recently developed by Kivelson, Lee and Zhang (KLZ),^1 to describe the interplay between the various phases of 2DES at high B. Finally, our study included ultra-high mobility samples that exhibit reentrant insulating phases near 1/5 and 1/3 fractional QHE state, which are explicitly forbidden in the framework developed by KLZ. Transitions involving these insulating phases show surprising similarities, and intriguing differences, to the allowed transitions. ^*In collaboration with D. C. Tsui, M. Shayegan, J. E. Cunningham, R. N. Bhatt, E. Shimshoni, S. L. Sondhi. [1] S. A. Kivelson, D. H. Lee, and S. C. Zhang, Phys. Rev. B 46, 2223 (1992).

Shahar, Dan

1996-03-01

203

Structural phase transitions in the systems with isotropic repulsive potentials

NASA Astrophysics Data System (ADS)

A simple analytical approach for the calculation of the phase diagram for polymorphic fcc-bcc transition in systems with isotropic repulsive potentials is proposed. A comparison of the proposed approach with the existing numerical and theoretical data is presented for Yukawa and inverse-power potentials: the emphasis is on the Yukawa model. The influence of the non-linearity (of anharmonic corrections) of the pair interaction forces on the phase-equilibrium curves for fcc-bcc and solid-liquid phase transitions is considered.

Vaulina, O. S.; Vasilieva, E. V.

2011-09-01

204

Transitions de phase dans les agrégats

NASA Astrophysics Data System (ADS)

The solid to liquid transition of clusters is discussed, mainly from an experimental point of view. An experiment is sketched which allows to measure the caloric curve of size selected sodium clusters. Melting temperatures, latent heats, and entropies of melting are determined in the size range between 55 and 357 atoms per cluster. The melting temperatures are about 30% less than the bulk value and fluctuate strongly, one additional atom can change it by ±10 K. Latent heats and entropies show a similar behaviour. From the change in entropy one can deduce the increase of phase space upon melting, which is about twelve orders of magnitude already for Na +55 and increases exponentially for larger clusters. The theoretical prediction that a finite particle can have a negative heat capacity is verified experimentally, showing that their are differences between a canonical and a microcanonical description. Finally the analogue of the boiling phase transition is shown for a finite system. To cite this article: M. Schmidt, H. Haberland, C. R. Physique 3 (2002) 327-340.

Schmidt, Martin; Haberland, Hellmut

2002-04-01

205

The Electroweak Phase Transition - Standard and ``Beyond''

We first review why a strongly first-order phase transition needed for baryogenesis is excluded in the electroweak standard model. We also comment on some intriguing effects in the strongly interacting hot phase. In the MSSM with a light stop a strongly first-order phase transition can be achieved. It possibly proceeds in two stages.

Michael G. Schmidt

1997-08-12

206

Competition between glass transition and liquid-gas separation in attracting colloids

We present simulation results addressing the phenomena of colloidal gelation induced by attractive interactions. The liquid-gas transition is prevented by the glass arrest at high enough attraction strength, resulting in a colloidal gel. The dynamics of the system is controlled by the glass, with little effect of the liquid-gas transition. When the system separates in a liquid and vapor phases, even if the denser phase enters the non-ergodic region, the vapor phase enables the structural relaxation of the system as a whole.

A. M. Puertas; M. Fuchs; M. E. Cates

2006-10-19

207

Diamagnetic phase transition by helicon resonance

NASA Astrophysics Data System (ADS)

The onset of the diamagnetic phase transition in aluminum is shown by analyzing the temperature dependence of the helicon resonance frequency and damping and by comparing between the theory and the experiment. Softening of the helicon mode due to the domain appearance is calculated. The critical growth of the helicon damping is connected with the phase transition nature of the domain occurrence, i.e. with the critical dynamics of diamagnetic phase transitions related to critical slowing down of the electron relaxation time.

Gordon, A.; Joss, W.; Logoboy, N.; Vagner, I. D.

2003-09-01

208

Phase behavior and dynamics of a cholesteric liquid crystal

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

Roy, D.; Fragiadakis, D.; Roland, C. M. [Naval Research Laboratory, Chemistry Division, Code 6120, Washington DC 20375-5342 (United States)] [Naval Research Laboratory, Chemistry Division, Code 6120, Washington DC 20375-5342 (United States); Dabrowski, R.; Dziaduszek, J. [Institute of Chemistry, Military University of Technology, 00-908 Warsaw (Poland)] [Institute of Chemistry, Military University of Technology, 00-908 Warsaw (Poland); Urban, S. [Institute of Physics, Jagiellonian University, Krakow (Poland)] [Institute of Physics, Jagiellonian University, Krakow (Poland)

2014-02-21

209

Interfacial Wave Transitions in Liquid-Liquid Flows and Insight into Flow Regime

Interfacial Wave Transitions in Liquid-Liquid Flows and Insight into Flow Regime Transition M. J://www.nd.edu/~mjm/ #12;http://www.nd.edu/~mjm Flow geometry of interest liquid gas Two-fluid stratified flow Transition://www.nd.edu/~mjm Flow regime importance Â· Why do we care which regime it is? Â Pressure drop varies by an order

McCready, Mark J.

210

Bonding and phase transitions in transition metal dichalcogenide layer compounds

The electronic structure of the transition metal dichalcogenide layer compounds is studied using hybridised orbitals appropriate to the transition metal atom coordination. Non-bonding orbitals on the transition metal atoms give the conduction electron bands which are responsible for the charge-density-wave phase transitions in the VB compounds, and the band structure of 1T- and 2H-TaS2 is found using tight binding. The

J. E. Inglesfield

1980-01-01

211

Efimov-driven phase transitions of the unitary Bose gas

NASA Astrophysics Data System (ADS)

Initially predicted in nuclear physics, Efimov trimers are bound configurations of three quantum particles that fall apart when any one of them is removed. They open a window into a rich quantum world that has become the focus of intense experimental and theoretical research, as the region of ‘unitary’ interactions, where Efimov trimers form, is now accessible in cold-atom experiments. Here we use a path-integral Monte Carlo algorithm backed up by theoretical arguments to show that unitary bosons undergo a first-order phase transition from a normal gas to a superfluid Efimov liquid, bound by the same effects as Efimov trimers. A triple point separates these two phases and another superfluid phase, the conventional Bose-Einstein condensate, whose coexistence line with the Efimov liquid ends in a critical point. We discuss the prospects of observing the proposed phase transitions in cold-atom systems.

Piatecki, Swann; Krauth, Werner

2014-03-01

212

On critical anomalies at diamagnetic phase transitions

NASA Astrophysics Data System (ADS)

Calculations of the thermal expansion coefficient and magnetic field susceptibility jumps at second-order diamagnetic phase transitions are performed. The temperature and size dependence of the susceptibility, of the thermal expansion coefficient and of the sound velocity is presented near the diamagnetic phase transition. The compressibility growth observed in beryllium and occurring as a result of the Condon domain formation confirms indirectly the presence of a thermal expansion jump at the phase transition point. A possibility of a first-order diamagnetic phase transition occurrence is considered as a result of the magneto-elastic coupling.

Gordon, A.; Wyder, P.

2002-11-01

213

Hot electron injection driven phase transitions

NASA Astrophysics Data System (ADS)

We report on a general mechanism for photo-induced phase transitions. The process relies on the photo-injection of hot electrons from an adjacent metallic layer to trigger the structural dynamics of the materials of interest. This mechanism is demonstrated for the semiconductor-to-metal phase transition of VO2 using a 20 nm Au injection layer. The nature of the phase transition is demonstrated by time-resolved optical transmission measurements, as well as a well defined bias dependence that illustrates that the Au film is the source of nonequilibrium electrons driving the phase transition.

Hada, Masaki; Zhang, Dongfang; Casandruc, Albert; Miller, R. J. Dwayne; Hontani, Yusaku; Matsuo, Jiro; Marvel, Robert E.; Haglund, Richard F., Jr.

2012-10-01

214

Quantum phase transitions in disordered antiferromagnets

NASA Astrophysics Data System (ADS)

Recently quantum phase transitions have attracted the interest of both theorists and experimentalists in condensed matter physics. Quantum magnets provide a perfect playground for studying these phase transitions since they can be triggered by many control parameters such as frustration, lattice dimerization, and magnetic field. Most previous studies have focused on the magnetic properties in pure systems. In these systems, responses to the triggering parameters are found to be uniform, leading to homogeneous phases. However little progress has been made so far on the phase transitions and properties in disordered quantum magnets because they are more complicated systems, and few theoretical tools can be applied. In this thesis we use the stochastic series expansion quantum Monte Carlo method to study quantum phase transitions in disordered magnets. We find that disordered magnets can behave quite differently from pure systems. The system inhomogeneity can strongly affect phase transitions by changing their universality class. We also find order-disorder transitions are often accompanied by the appearance of novel quantum disordered phases, in which magnetic properties behave highly nontrivial, even singular. In this thesis two examples are studied in great detail. The first one is the phase diagram of an inhomogeneous, bond-diluted two-dimensional antiferromagnet near the percolation threshold. We show that the magnetic transition can be tuned by the inhomogeneity of the dilution from a classical percolation to a quantum phase transition. Interestingly the quantum transition still takes the nature of a renormalized percolative transition, with continuously varying critical exponents. A gapless quantum disordered phase with no magnetic long-range order but geometric percolation is found. The low-temperature uniform susceptibility diverges as a non-universal power-law of the temperature in this phase, indicating that this is a quantum Griffiths phase. In the second example, we study field-induced quantum phase transitions in two-dimensional site-diluted coupled dimers. We find that an extremely small field drives the order-by-disordered phase into a quantum disordered disordered-free-moment phase. The magnetization curve in this phase shows a series of pseudo-plateaus, which can be explained by the highly inhomogeneous field response of the free moments. A spin-boson mapping reveals that the disordered-free-moment phase can be understood as a low-field Bose glass phase, and hence the associated phase transition is a realization of a two-dimensional Bose-glass-to-disordered-free-moment transition. This is confirmed by the entire phase diagram and the study of the scaling behavior of correlation length, order parameter, and spin stiffness in the critical regime.

Yu, Rong

215

Phenomenological theories of ferroelectric phase transitions

Phenomenological theories of ferroelectric phase transitions W. Cao parameter in the free energy expansion, phenomenological theory can also describe inhomogeneous structures appear-Phenomenological parent and product phases. phenomenological theories in multidimensions for describ-Phenomenological

Cao, Wenwu

216

Phase Transitions on Quasicrystalline Surfaces.

NASA Astrophysics Data System (ADS)

The sputtering of the surfaces of quasicrystals with Ar^+ changes their chemical composition by preferential removal of particular atomic species. At room temperature, this produces a phase transition at the surface of the icosahedral Al_70Pd_20Mn_10 to a cubic structure. Using secondary-electron imaging (SEI), which reveals the atomic symmetry of surfaces and shallow interfaces in real space, we have investigated the structural registry of the cubic surface layers grown on the pentagonal face of the quasicrystal. The bulk effectively acts as a thermodynamic and structural template for the quasicrystalline state. Annealing at 700 K restores the stoichiometry near the surface and the quasicrystalline structure is recovered. SEI helps us establish the relationship between the body-centered cubic and the quasicrystalline structures. Sputtering the same quasicrystal near 500 K shifts the chemical equilibrium at the surface in favor of a decagonal structure. This surface layer is structurally commensurate with the bulk pentagonal symmetry. Upon annealing, the chemical composition is recovered and the decagonal symmetry reverts back to pentagonal. Real time observations of this transition at elevated temperatures with SEI shows the structural coherence between the icosahedral and the decagonal quasicrystals. These studies have motivated a model for icosahedral quasicrystals: we start with an icosahedron as a seed and lay planes parallel to its faces. The atoms sit at the intersections of the planes. If the interplanar distances follow the Fibonacci sequence, the resulting solid successfully reproduces in quantum mechanical simulations the experimental secondary-electron patterns. Thus, this investigation reveals the long-range properties of Al_70Pd_20Mn_10.

Bolliger, Bernhard

2000-03-01

217

Modeling the liquid-solid transition in saturated triglycerides

NASA Astrophysics Data System (ADS)

Corkery et al. have proposed that the high-temperature state of the triglyceride trilaurin (TL) is a Y-conformer, in which the three hydrocarbon chains are dynamically twisted with an average angle of ˜120 between them. Using computer simulations, we first show that the high-temperature state is indeed the Y conformation. We then develop a theory of the liquid-solid transition of this system, in which TL molecules are in a chair (h) conformation, with extended, possibly all-trans, chains at low-temperatures, and are in a Y conformation in the liquid phase at temperatures higher than the transition temperature, T* 319K. We map this ``h-Y model'' onto an Ising model in a temperature-dependent field, perform a mean-field approximation, and calculate the transition enthalpy, which is in good agreement with experiment. We also predict the temperature-dependence of the 1132 cm-1 Raman band. Our results support the proposal that the liquid state is made up of molecules in the Y conformation.

Hanna, C. B.; Pink, D. A.; MacDonald, A. J.; Thillainadarajah, K.; Corkery, R.; Rousseau, D.

2007-03-01

218

Phase behavior of ionic liquid crystals

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

219

More is the Same; Phase Transitions and Mean Field Theories

This paper looks at the early theory of phase transitions. It considers a group of related concepts derived from condensed matter and statistical physics. The key technical ideas here go under the names of "singularity", "order parameter", "mean field theory", and "variational method". In a less technical vein, the question here is how can matter, ordinary matter, support a diversity of forms. We see this diversity each time we observe ice in contact with liquid water or see water vapor, "steam", come up from a pot of heated water. Different phases can be qualitatively different in that walking on ice is well within human capacity, but walking on liquid water is proverbially forbidden to ordinary humans. These differences have been apparent to humankind for millennia, but only brought within the domain of scientific understanding since the 1880s. A phase transition is a change from one behavior to another. A first order phase transition involves a discontinuous jump in a some statistical variable of the system. The discontinuous property is called the order parameter. Each phase transitions has its own order parameter that range over a tremendous variety of physical properties. These properties include the density of a liquid gas transition, the magnetization in a ferromagnet, the size of a connected cluster in a percolation transition, and a condensate wave function in a superfluid or superconductor. A continuous transition occurs when that jump approaches zero. This note is about statistical mechanics and the development of mean field theory as a basis for a partial understanding of this phenomenon.

Leo P. Kadanoff

2009-09-14

220

Game Theory and Topological Phase Transition

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.

Tieyan Si

2006-01-02

221

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

ERIC Educational Resources Information Center

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…

Torzo, Giacomo; Soletta, Isabella; Branca, Mario

2007-01-01

222

Phase Transitions in Two-Dimensional Superconductors

In this thesis, we describe a number of experiments which are designed to explore the theoretically predicted phase transitions for two-dimensional superconductors. We first examine the behavior of a two-dimensional superconductor in the absence of a magnetic field, where the fluctuations in the phase of the superconducting order parameter results in the reduction of the superconducting transition temperature for a

Ali Yazdani

1995-01-01

223

Phase Diagram of Glass Forming Liquids with Randomly Pinned Particles

Extensive molecular dynamics simulations are performed to determine the phase diagram of two model glass forming liquids in the presence of external quenched disorder. The quenched disorder is introduced in the system by randomly choosing a fraction $\\rho_{pin}$ of particles from an equilibrium configuration of the supercooled liquids at temperature $T$ and freezing them in space. The study of the dynamics of supercooled liquids with this type of quenched disorder has drawn a lot of attention in recent years due to theoretical predictions of the possibility of observing the ideal thermodynamic glass transition in such systems. In this Letter, we numerically examine this possibility by determining the phase diagram of the systems in the $\\rho_{pin}-T$ plane. We find that the phase diagram differs considerably from existing theoretical predictions and show that a rapid decrease in the kinetic fragility of the system with increasing pin concentration is a probable reason for this difference.

Saurish Chakrabarty; Smarajit Karmakar; Chandan Dasgupta

2014-05-14

224

Analysis of Nuclear Quantum Phase Transitions

A microscopic analysis, based on nuclear energy density functionals, is presented for shape phase transitions in Nd isotopes. Low-lying excitation spectra and transition probabilities are calculated starting from a five-dimensional Hamiltonian, with parameters determined by constrained relativistic mean-field calculations for triaxial shapes. The results reproduce available data, and show that there is an abrupt change of structure at N = 90, that corresponds to a first-order quantum phase transition between spherical and axially deformed shapes.

Li, Z. P.; Meng, J. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Niksic, T.; Vretenar, D. [Physics Department, Faculty of Science, University of Zagreb (Croatia); Lalazissis, G. A. [Department of Theoretical Physics, Aristotle University of Thessaloniki, GR-54124 (Greece); Ring, P. [Physik-Department der Technischen Universitaet Muenchen, D-85748 Garching (Germany)

2009-08-26

225

First-order dynamical phase transitions.

Recently, dynamical phase transitions have been identified based on the nonanalytic behavior of the Loschmidt echo in the thermodynamic limit [Heyl et al., Phys. Rev. Lett. 110, 135704 (2013)]. By introducing conditional probability amplitudes, we show how dynamical phase transitions can be further classified, both mathematically, and potentially in experiment. This leads to the definition of first-order dynamical phase transitions. Furthermore, we develop a generalized Keldysh formalism which allows us to use nonequilibrium dynamical mean-field theory to study the Loschmidt echo and dynamical phase transitions in high-dimensional, nonintegrable models. We find dynamical phase transitions of first order in the Falicov-Kimball model and in the Hubbard model. PMID:25615356

Canovi, Elena; Werner, Philipp; Eckstein, Martin

2014-12-31

226

First-Order Dynamical Phase Transitions

NASA Astrophysics Data System (ADS)

Recently, dynamical phase transitions have been identified based on the nonanalytic behavior of the Loschmidt echo in the thermodynamic limit [Heyl et al., Phys. Rev. Lett. 110, 135704 (2013)]. By introducing conditional probability amplitudes, we show how dynamical phase transitions can be further classified, both mathematically, and potentially in experiment. This leads to the definition of first-order dynamical phase transitions. Furthermore, we develop a generalized Keldysh formalism which allows us to use nonequilibrium dynamical mean-field theory to study the Loschmidt echo and dynamical phase transitions in high-dimensional, nonintegrable models. We find dynamical phase transitions of first order in the Falicov-Kimball model and in the Hubbard model.

Canovi, Elena; Werner, Philipp; Eckstein, Martin

2014-12-01

227

Phase transitions in human IgG solutions

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

228

78 FR 30951 - SBIR/STTR Phase I to Phase II Transition Benchmarks

Federal Register 2010, 2011, 2012, 2013, 2014

...ADMINISTRATION SBIR/STTR Phase I to Phase II Transition Benchmarks AGENCY: U...Innovation Research Program Phase I to Phase II Transition Benchmarks; Amended...amendments to the SBIR/STTR Phase I to Phase II transition rate benchmark...

2013-05-23

229

77 FR 63410 - SBIR/STTR Phase I to Phase II Transition Benchmarks

Federal Register 2010, 2011, 2012, 2013, 2014

...ADMINISTRATION SBIR/STTR Phase I to Phase II Transition Benchmarks AGENCY: U...Technology Transfer Programs Phase I to Phase II Transition Benchmarks...Technology Transfer (STTR) Phase I to Phase II transition rate benchmarks for...

2012-10-16

230

Order Parameter for a Diamagnetic Phase Transition

NASA Astrophysics Data System (ADS)

A theory of the magnetic induction bifurcation at a diamagnetic phase transition in normal metals is developed. Our results are in good agreement with the recent observation of the muon spin rotation resonance splitting in beryllium due to Condon domains, Solt et al. [Phys. Rev. Lett. 76, 2575 (1996); Hyperfine Interact. 104, 257 (1997)], being the first measurement of the onset of a diamagnetic phase transition. Temperature dependence of the order parameter, the magnetization in each Condon domain, is explained and reproduced quantitatively. A new kind of phase diagram for diamagnetic phase transitions is constructed.

Gordon, A.; Itskovsky, M. A.; Vagner, I. D.; Wyder, P.

1998-09-01

231

Coupled phase transitions under periodic perturbation

NASA Astrophysics Data System (ADS)

The influence of periodic perturbation on the system of two nonlinear stochastic equations, which model low-frequency pulsations in crisis and transient modes of heat-and-mass transfer with phase transitions, has been investigated by numerical methods. When studying the influence of the periodic perturbation on the system, a researcher should largely take into account the phase diagram. It is shown that nonequilibrium phase transitions from asymmetric cycles of phase trajectories to centrally symmetric ones occur in the absence of noise. These transitions are accompanied by the stochastic resonance response, which enhances as the frequency of the external periodic force decreases.

Koverda, V. P.; Skokov, V. N.

2014-07-01

232

Microscopic Description of Nuclear Quantum Phase Transitions

The relativistic mean-field framework, extended to include correlations related to restoration of broken symmetries and to fluctuations of the quadrupole deformation, is applied to a study of shape transitions in Nd isotopes. It is demonstrated that the microscopic self-consistent approach, based on global effective interactions, can describe not only general features of transitions between spherical and deformed nuclei, but also the singular properties of excitation spectra and transition rates at the critical point of quantum shape phase transition.

Niksic, T.; Vretenar, D.; Lalazissis, G. A.; Ring, P. [Physics Department, University of Zagreb, Bijenicka 32, Zagreb (Croatia); Department of Theoretical Physics, Aristotle University of Thessaloniki, GR-54124 (Greece); Physik-Department der Technischen Universitaet Muenchen, D-85748 Garching (Germany)

2007-08-31

233

Vapor-liquid phase separator studies

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

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

1983-10-01

234

The Nonequilibrium Phase and Glass Transition Behavior of ?-Lactoglobulin

Concentrated solutions of bovine ?-lactoglobulin were studied using osmotic stress and rheological techniques. At pH 6.0 and 8.0, the osmotic pressure was largely independent of NaCl concentration and could be described by a hard sphere equation of state. At pH 5.1, close to the isoelectric point, the osmotic pressure was lower at the lower NaCl concentrations (0 mM, 100 mM) and was fitted by an adhesive hard sphere model. Liquid-liquid phase separation was observed at pH 5.1 at ionic strengths of 13 mM and below. Comparison of the liquid-liquid and literature solid-liquid coexistence curves showed these solutions to be supersaturated and the phase separation to be nonequilibrium in nature. In steady shear, the zero shear viscosity of concentrated solutions at pH 5.1 was observed at shear rates above 50 s?1. With increasing concentration, the solution viscosity showed a progressive increase, a behavior interpreted as the approach to a colloidlike glass transition at ?60% w/w. In oscillatory shear experiments, the storage modulus crossed the loss modulus at concentrations of 54% w/w, an indication of the approaching glass transition. Comparison of the viscous behavior with predictions from the Krieger-Dougherty equation indicates the hydrodynamic size of the protein decreases with increasing concentration, resulting in a slower approach to the glass transition than a hard sphere system. PMID:15923230

Parker, Roger; Noel, Timothy R.; Brownsey, Geoffrey J.; Laos, Katrin; Ring, Stephen G.

2005-01-01

235

Critical phenomena at diamagnetic phase transitions

NASA Astrophysics Data System (ADS)

The critical phenomena near diamagnetic phase transitions and in the domain phase are considered. Possibilities of the soft-mode existence and the static critical effect in susceptibility related to the appearance of Condon domains in aluminium are discussed. The constructed phase diagram and the temperature behaviour of the susceptibility give the value of the phase-transition temperature observed in aluminium. We present the temperature dependence of the magnetisation in each domain being the order parameter of the diamagnetic phase transition and confirming the softening of the orbital magnon-mode in aluminium. Calculations of the spectral density of excitations at diamagnetic phase transitions are made in order to explain the critical growth of the helicon damping observed in aluminium. The temperature dependence of the damping coincides with that measured in aluminium. The calculated magnetic-induction splitting due to Condon domains turns out to be close to that estimated in muon rotation spectroscopy experiment.

Gordon, A.; Logoboy, N.; Joss, W.

2004-12-01

236

Thermodynamic properties of three organic solute families in 4,4-bis(heptyloxyl)azoxybenzene (BHOAB) at infinite dilution were determined from gas–liquid chromatographic retention data. The reduced free energies of transfer of solutes between liquid crystal phases at transition temperatures were determined and related to the “disorder parameter” of Flory's liquid crystal theory. Reduced free energies of transfer between phases were functions of solute solubility

Jan-Chan Huang; Jose Coca; Stanley H. Langer

2007-01-01

237

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

NASA Astrophysics Data System (ADS)

Yagasaki et al. [Phys. Rev. E 89, 020301 (2014), 10.1103/PhysRevE.89.020301] 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.

Limmer, David T.; Chandler, David

2015-01-01

238

In this paper, the concept of the molecular free path is introduced to derive a criterion distinguishing active molecules from inactive molecules in liquid phase. A concept of the critical aggregation concentration (CAC) of active molecules is proposed to describe the physical configuration before the formation of a nucleus during vapor–liquid phase transition. All active molecules exist as monomers when

Xiao-Dong Wang; Xiao-Feng Peng; Yong Tian; Bu-Xuan Wang

2005-01-01

239

Ionic liquid stationary phases for gas chromatography.

This article provides a summary of the development of ionic liquids as stationary phases for gas chromatography beginning with early work on packed columns that established details of the retention mechanism and established working methods to characterize selectivity differences compared with molecular stationary phases through the modern development of multi-centered cation and cross-linked ionic liquids for high-temperature applications in capillary gas chromatography. Since there are many reviews on ionic liquids dealing with all aspects of their chemical and physical properties, the emphasis in this article is placed on the role of gas chromatography played in the design of ionic liquids of low melting point, high thermal stability, high viscosity, and variable selectivity for separations. Ionic liquids provide unprecedented opportunities for extending the selectivity range and temperature-operating range of columns for gas chromatography, an area of separation science that has otherwise been almost stagnant for over a decade. PMID:21290604

Poole, Colin F; Poole, Salwa K

2011-04-01

240

Electroweak phase transition in ultraminimal technicolor

We unveil the temperature-dependent electroweak phase transition in new extensions of the standard model in which the electroweak symmetry is spontaneously broken via strongly coupled, nearly conformal dynamics achieved by the means of multiple matter representations. In particular, we focus on the low energy effective theory introduced to describe ultra minimal walking technicolor at the phase transition. Using the one-loop effective potential with ring improvement, we identify regions of parameter space, which yield a strong first-order transition. A striking feature of the model is the existence of a second phase transition associated to the electroweak-singlet sector. The interplay between these two transitions leads to an extremely rich phase diagram.

Jaervinen, Matti; Sannino, Francesco [University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark); Ryttov, Thomas A. [Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen O (Denmark)

2009-05-01

241

Phase Transitions in Hexane Monolayers Physisorbed onto Graphite

We report the results of molecular dynamics (MD) simulations of a complete monolayer of hexane physisorbed onto the basal plane of graphite. At low temperatures the system forms a herringbone solid. With increasing temperature, a solid to nematic liquid crystal transition takes place at $T_1 = 138 \\pm 2$K followed by another transition at $T_2 = 176 \\pm 3$K into an isotropic fluid. We characterize the different phases by calculating various order parameters, coordinate distributions, energetics, spreading pressure and correlation functions, most of which are in reasonable agreement with available experimental evidence. In addition, we perform simulations where the Lennard-Jones interaction strength, corrugation potential strength and dihedral rigidity are varied in order to better characterize the nature of the two transitions through. We find that both phase transitions are facilitated by a ``footprint reduction'' of the molecules via tilting, and to a lesser degree via creation of gauche defects in the molecules.

M. W. Roth; C. L. Pint; Carlos Wexler

2004-11-16

242

Phase transitions in the early universe

NASA Astrophysics Data System (ADS)

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.

Wainwright, Carroll L.

243

Liquid-phase compositions from vapor-phase analyses

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

Davis, W. Jr. (Oak Ridge Gaseous Diffusion Plant, TN (USA)); Cochran, H.D. (Oak Ridge National Lab., TN (USA))

1990-02-01

244

Defects and order in liquid crystal phases

NASA Astrophysics Data System (ADS)

This thesis investigates the partial destruction of ordering in liquid crystalline systems due to the influence of defects and thermal fluctuations. The systems under consideration are hexagonal columnar crystals with crystalline order perpendicular to the columns, and two-dimensional smectics with order perpendicular to the layers. We first study the possibility of reentrant melting of a hexagonal columnar crystal of flexible charged polymers at high enough densities. The Lindemann criterion is employed in determining the melting point. Lattice fluctuations are calculated in the Debye model, and an analogy with the Abrikosov vortex lattice in superconductors is exploited in estimating both the elastic constants of the hexagonal lattice, and the appropriate Lindemann constant. We also discuss the unusual functional integral describing the statistical mechanics of a single polymer in an Einstein cage model using the path-integral formulation. A crossover as a function of an external field along the column axis is discussed as well. Next, we study defects in a columnar crystal in the form of vacancy/interstitial loops or strings of vacancies and interstitials bounded by column "heads" and "tails". These defect strings are oriented by the columnar lattice and can change size and shape by movement of the ends and forming kinks along the length. Hence an analysis in terms of directed living polymers is appropriate to study their size and shape distribution, volume fraction, etc. If the entropy of transverse fluctuations overcomes the string line tension in the crystalline phase, a string proliferation transition occurs, leading to a "supersolid" phase with infinitely long vacancy or interstitial strings. We estimate the wandering entropy and examine the behaviour in the transition regime. We also calculate numerically the line tension of various species of vacancies and interstitials in a triangular lattice for power-law potentials as well as for a modified Bessel function interaction between columns as occurs in the case of flux lines in type-II superconductors or long polyelectrolytes in an ionic solution. We find that the centered interstitial is the lowest energy defect for a very wide range of interactions; the symmetric vacancy is preferred only for extremely short interaction ranges. Finally, we take a look at the hydrodynamics of smectic films at an air-water interface, with particular focus on the viscous response of the film under flow normal to the layers. The corrections to the response functions of the smectic phase, arising from the coupling between the flow and the smectic order parameter, are calculated. The results for the effective viscosity are illustrated by analysing smectic film flow in a channel geometry. The limiting cases of the flow, namely, motion dominated by dislocation-induced shear-softening or motion dominated by the permeation mode of mass transfer, are studied. The effect of drag from a finite depth liquid subphase is considered. The results are compared to those for hexatic and liquid films.

Jain, Shilpa

245

Multiple liquid crystal phases of DNA at high concentrations.

DNA packaging in vivo is very tight, with volume concentrations approaching 70% w/v in sperm heads, virus capsids and bacterial nucleoids. The packaging mechanisms adopted may be related to the natural tendency of semi-rigid polymers to form liquid crystalline phases in concentrated solutions. We find that DNA forms at least three distinct liquid crystalline phases at concentrations comparable to those in vivo, with phase transitions occurring over relatively narrow ranges of DNA concentration. A weakly birefringent, dynamic, 'precholesteric' mesophase with microscopic textures intermediate between those of a nematic and a true cholesteric phase forms at the lowest concentrations required for phase separation. At slightly higher DNA concentrations, a second mesophase forms which is a strongly birefringent, well-ordered cholesteric phase with a concentration-dependent pitch varying from 2 to 10 micron. At the highest DNA concentrations, a phase forms which is two-dimensionally ordered and resembles smectic phases of thermotropic liquid crystals observed with small molecules. PMID:3340191

Strzelecka, T E; Davidson, M W; Rill, R L

1988-02-01

246

Multiple liquid crystal phases of DNA at high concentrations

NASA Astrophysics Data System (ADS)

DNA packaging in vivo is very tight, with volume concentrations approaching 70% w/v in sperm heads, virus capsids and bacterial nucleoids1-3. The packaging mechanisms adopted may be related to the natural tendency of semi-rigid polymers to form liquid crystalline phases in concentrated solutions4-8. We find that DNA forms at least three distinct liquid crystalline phases at concentrations comparable to those in vivo, with phase transitions occurring over relatively narrow ranges of DNA concentration. A weakly birefringent, dynamic, 'precholesteric' mesophase with microscopic textures intermediate between those of a nematic and a true cholesteric phase forms at the lowest concentrations required for phase separation. At slightly higher DNA concentrations, a second mesophase forms which is a strongly birefringent, well-ordered cholesteric phase with a concentration-dependent pitch varying from 2 to lO?m. At the highest DNA concentrations, a phase forms which is two-dimensionally ordered and resembles smectic phases of thermotropic liquid crystals observed with small molecules.

Strzelecka, Teresa E.; Davidson, Michael W.; Rill, Randolph L.

1988-02-01

247

Gas–liquid two-phase flow in microchannels Part I: two-phase flow patterns

Capillary gas–liquid two-phase flow occurs in increasingly more modern industrial applications. The existing relevant data are limited and are inconsistent with respect to the reported flow patterns and their transition boundaries. A systematic experimental investigation of two-phase flow patterns in microchannels was the objective of this study.Using air and water, experiments were conducted in circular microchannels with 1.1 and 1.45mm

K. A. Triplett; S. M. Ghiaasiaan; S. I. Abdel-Khalik; D. L. Sadowski

1999-01-01

248

Stability of the Liquid Phase in Colloidal Electrolytes

The equilibrium phase diagram of a 1:1 symmetrical mixture composed of oppositely charged colloids is calculated using Monte Carlo simulations. We model the system by the DLVO effective interaction potential. The phase diagram is similar to that of its atomic analog (the ionic fluid), where a liquid-gas first order transition emerges in the low $T-\\rho$ regions being stable with respect to crystallization. As in the ionic fluids, we have found two different crystals: at high $T$ the fluid crystallizes in a FCC lattice, whereas at low $T$, the liquid coexists with a BCC crystal. The region of gas-liquid stability is observed to be narrower as the interaction range is diminished.

José B. Caballero; Antonio M. Puertas

2005-11-28

249

Synthetic gauge fields stabilize a chiral spin liquid phase

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.

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

2015-01-16

250

The Influence of Disorder on Thermotropic Nematic Liquid Crystals Phase Behavior

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

Popa-Nita, Vlad; Gerli?, Ivan; Kralj, Samo

2009-01-01

251

Enhancement of the superfluid transition temperature in liquid 3He due to transient polarization

NASA Astrophysics Data System (ADS)

We have produced polarized liquid 3He by rapid melting of polarized solid 3He grown from the superfluid phase. The superfluid transition temperature of transiently polarized 3He is shown to be above the equilibrium transition tempearture in the external field of 9.2 T. The quadratic term in the increase of the transition temperature with polarization seems lower than is predicted recently.

Wiegers, S. A. J.; Hata, T.; Van de Haar, P. G.; Roobol, L. P.; Van Woerkens, C. M. C. M.; Jochemsen, R.; Frossati, G.

1990-08-01

252

Critical behaviours of contact near phase transitions

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

253

Locally critical quantum phase transitions in strongly correlated metals

When a metal undergoes a continuous quantum phase transition, non-Fermi liquid behavior arises near the critical point. It is standard to assume that all low-energy degrees of freedom induced by quantum criticality are spatially extended, corresponding to long-wavelength fluctuations of the order parameter. However, this picture has been contradicted by recent experiments on a prototype system: heavy fermion metals at

Qimiao Si; Silvio Rabello; Kevin Ingersent; Lleweilun Smith

2001-01-01

254

Lattice dynamics and structural phase transitions

NASA Astrophysics Data System (ADS)

Results of lattice dynamics, or atomic motions in a solid, explain many of the thermodynamic properties of solids. Inelastic neutron scattering conveniently explores the atomic motions, quantized as phonons. Of particular interest are materials that undergo structural phase transitions. The soft mode theory has been successful in relating anomalous phonon behavior to structural changes in solids. One such example is the ferromagnetic shape memory alloy, Ni2MnGa, which undergoes a sequence of phase transitions leading to a magnetic, incommensurate modulated, tetragonal phase as the ground state. The experiments, coupled with first principles calculations, provide evidence that strong electron-phonon coupling is the driving mechanism of the phase transformation.

Shapiro, S. M.

2010-06-01

255

Is there a third order phase transition for supercritical fluids?

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.

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

256

Electrically driven phase transition in magnetite nanostructures.

Magnetite (Fe3O4), an archetypal transition-metal oxide, has been used for thousands of years, from lodestones in primitive compasses to a candidate material for magnetoelectronic devices. In 1939, Verwey found that bulk magnetite undergoes a transition at TV approximately 120 K from a high-temperature 'bad metal' conducting phase to a low-temperature insulating phase. He suggested that high-temperature conduction is through the fluctuating and correlated valences of the octahedral iron atoms, and that the transition is the onset of charge ordering on cooling. The Verwey transition mechanism and the question of charge ordering remain highly controversial. Here, we show that magnetite nanocrystals and single-crystal thin films exhibit an electrically driven phase transition below the Verwey temperature. The signature of this transition is the onset of sharp conductance switching in high electric fields, hysteretic in voltage. We demonstrate that this transition is not due to local heating, but instead is due to the breakdown of the correlated insulating state when driven out of equilibrium by electrical bias. We anticipate that further studies of this newly observed transition and its low-temperature conducting phase will shed light on how charge ordering and vibrational degrees of freedom determine the ground state of this important compound. PMID:18084295

Lee, Sungbae; Fursina, Alexandra; Mayo, John T; Yavuz, Cafer T; Colvin, Vicki L; Sofin, R G Sumesh; Shvets, Igor V; Natelson, Douglas

2008-02-01

257

Electrically driven phase transition in magnetite nanostructures

NASA Astrophysics Data System (ADS)

Magnetite (Fe3O4), an archetypal transition-metal oxide, has been used for thousands of years, from lodestones in primitive compasses to a candidate material for magnetoelectronic devices. In 1939, Verwey found that bulk magnetite undergoes a transition at TV~120K from a high-temperature `bad metal' conducting phase to a low-temperature insulating phase. He suggested that high-temperature conduction is through the fluctuating and correlated valences of the octahedral iron atoms, and that the transition is the onset of charge ordering on cooling. The Verwey transition mechanism and the question of charge ordering remain highly controversial. Here, we show that magnetite nanocrystals and single-crystal thin films exhibit an electrically driven phase transition below the Verwey temperature. The signature of this transition is the onset of sharp conductance switching in high electric fields, hysteretic in voltage. We demonstrate that this transition is not due to local heating, but instead is due to the breakdown of the correlated insulating state when driven out of equilibrium by electrical bias. We anticipate that further studies of this newly observed transition and its low-temperature conducting phase will shed light on how charge ordering and vibrational degrees of freedom determine the ground state of this important compound.

Lee, Sungbae; Fursina, Alexandra; Mayo, John T.; Yavuz, Cafer T.; Colvin, Vicki L.; Sumesh Sofin, R. G.; Shvets, Igor V.; Natelson, Douglas

2008-02-01

258

Using the generalized Landau model [Phys. Rev. A 36, 1484 (1987)], the temperature and frequency dependence of the complex dielectric constant of the ferroelectric smectic-C* (Sm-C*) phase and the corresponding smectic-A (Sm-A) phase is calculated. It is demonstrated how the dielectric response of the Sm-C* phase generally consists of four modes-two high-frequency polarization modes and two modes of lower frequency

T. Carlsson; B. Zeks; C. Filipic; A. Levstik

1990-01-01

259

Consistent lattice Boltzmann equations for phase transitions

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

260

Consistent lattice Boltzmann equations for phase transitions.

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. PMID:25493907

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

2014-11-01

261

Valence fluctuation driven quantum phase transition

NASA Astrophysics Data System (ADS)

In recent years quantum critical phenomenon have acquired a great interest in the condensed matter community. Many rare earth intermetallic compounds, which are also heavy fermions can be tuned easily to quantum critical point by application of external perturbations like magnetic field and pressure. YbRh2Si2 and CeCu2Si2 are a few examples. The periodic Anderson model (PAM) is a paradigm for studying these kind of systems. We investigate the extended periodic anderson model (EPAM), which includes Coulomb interaction of conduction and localised electrons using local moment approach (LMA) within dynamical mean field theory (DMFT) with the objective of developing an understanding of quantum phase transitions due to valence fluctuations. We show that tuning c-f interaction and on-site energy of localised electron (which can be achieved by varying external perturbation like pressure) leads to some exotic phenomena like vanishing of Fermi liquid scale. We study transport properties near quantum critical point and highlight the anomalies due to the proximity of QCP.

Kumar, Pramod; Vidhyadhiraja, N. S.

2012-02-01

262

First Order Phase Transitions in Gravitational Collapse

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.

P. Bizo?; T. Chmaj

1998-01-31

263

Quantum phase transitions in rotating nuclei

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.

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

264

Electrically driven phase transition in magnetite nanostructures

Magnetite (Fe3O4), an archetypal transition-metal oxide, has been used for thousands of years, from lodestones in primitive compasses to a candidate material for magnetoelectronic devices. In 1939, Verwey found that bulk magnetite undergoes a transition at TV~120K from a high-temperature `bad metal' conducting phase to a low-temperature insulating phase. He suggested that high-temperature conduction is through the fluctuating and correlated

Sungbae Lee; Alexandra Fursina; John T. Mayo; Cafer T. Yavuz; Vicki L. Colvin; R. G. Sumesh Sofin; Igor V. Shvets; Douglas Natelson

2008-01-01

265

Phase separation kinetics in immiscible liquids

NASA Technical Reports Server (NTRS)

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.

Sadoway, D. R.

1986-01-01

266

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

737 EPR investigation of phase transitions in amphiphilic systems D.D. Lasi010D Institute J. Stefan amphiphiles utilisant de l'acide palmitique marquÃ©. Deux des systÃ¨mes ne prÃ©sentent pas de changement-cristal liquide. Une transition supplÃ©mentaire est observÃ©e dans la phase cristal liquide du systÃ¨me amphiphile

Paris-Sud XI, UniversitÃ© de

267

Higgs Couplings and Electroweak Phase Transition

We argue that extensions of the Standard Model (SM) with a strongly first-order electroweak phase transition generically predict significant deviations of the Higgs couplings to gluons, photons, and Z bosons from their SM values. Precise experimental measurements of the Higgs couplings at the LHC and at the proposed next-generation facilities will allow for a robust test of the phase transition dynamics. To illustrate this point, in this paper we focus on the scenario in which loops of a new scalar field are responsible for the first-order phase transition, and study a selection of benchmark models with various SM gauge quantum numbers of the new scalar. We find that the current LHC measurement of the Higgs coupling to gluons already excludes the possibility of a first-order phase transition induced by a scalar in a sextet, or larger, representation of the SU(3)_c. Future LHC experiments (including HL-LHC) will be able to definitively probe the case when the new scalar is a color triplet. If the new scalar is not colored, an electron-positron Higgs factory, such as the proposed ILC or TLEP, would be required to test the nature of the phase transition. The extremely precise measurement of the Higgsstrahlung cross section possible at such machines will allow for a comprehensive and definitive probe of the possibility of a first-order electroweak phase transition in all models we considered, including the case when the new scalar is a pure gauge singlet.

Andrey Katz; Maxim Perelstein

2014-07-14

268

Closure Phase Signatures of Planet Transit Events

Planet transit events present as attractive targets for the ultra-high-resolution capabilities afforded by optical interferometers. Herein is presented an evaluation of the possibility of detection of such events through measurement of high-precision closure phases with the MIRC instrument on the CHARA Array. Recovery of the transit position angle upon the sky appears readily achievable with the existing capabilities of the instrument, along with characterization of other system parameters, such as stellar radius, planet radius, and other parameters of the transit event. This technique is the only one presently available that can provide a transiting planet's orbital plane position angle, and can directly determine the planet's radius independent of any outside observations, appearing able to improve substantially upon other determinations of that radius. Additional directly observed parameters - also not dependent upon transit photometry or spectroscopy - include impact parameter, transit ingress time, transit velocity and stellar radius.

G. T. van Belle

2008-04-16

269

Liquid-liquid coexistence in the phase diagram of a fluid confined in fractal porous materials

Multicanonical ensemble sampling simulations have been performed to calculate the phase diagram of a Lennard-Jones fluid embedded in a fractal random matrix generated through diffusion-limited cluster aggregation. The study of the system at increasing size and constant porosity shows that the results are independent of the matrix realization but not of the size effects. A gas-liquid transition shifted with respect

V. DeGrandis; P. Gallo; M. Rovere

2006-01-01

270

After some introductory remarks about the prospects of first order phase transitions in the early universe, we discuss in some detail the electroweak phase transition. In the standard model case a clear picture is arising including perturbative and nonperturbative effects. Since in this case the phase transition is not strongly first order as needed for baryogenesis, we discuss supersymmetric variants of the standard model, the MSSM with a light stop$_R$ and a NMSSM model where this can be achieved. We conclude with some remarks about the technical procedure and about possible effects of a strongly first order electroweak phase transition including baryogenesis.

M. G. Schmidt

1998-11-30

271

Magnetic phase transitions in layered intermetallic compounds

NASA Astrophysics Data System (ADS)

Magnetic, magnetoelastic, and magnetotransport properties have been studied for the RMn2Si2 and RMn6Sn6 (R is a rare earth metal) intermetallic compounds with natural layered structure. The compounds exhibit wide variety of magnetic structures and magnetic phase transitions. Substitution of different R atoms allows us to modify the interatomic distances and interlayer exchange interactions thus providing the transition from antiferromagnetic to ferromagnetic state. Near the boundary of this transition the magnetic structures are very sensitive to the external field, temperature and pressure. The field-induced transitions are accompanied by considerable change in the sample size and resistivity. It has been shown that various magnetic structures and magnetic phase transitions observed in the layered compounds arise as a result of competition of the Mn-Mn and Mn-R exchange interactions.

Mushnikov, N. V.; Gerasimov, E. G.; Rosenfeld, E. V.; Terent'ev, P. B.; Gaviko, V. S.

2012-10-01

272

Dynamic Phase Transition, Enhanced Reaction Rate, and

reactions, biological populations, growth- deposition, economics, etc. Catalytic processes have many-reaction model that describes kinetics aspects of the gas- phase catalytic oxidation of carbon monoxide arriving to the surface is CO. Proportional to partial pressure of CO. #12;Two kinetic phase transitions

Rikvold, Per Arne

273

Fidelity at Berezinskii-Kosterlitz-Thouless quantum phase transitions

NASA Astrophysics Data System (ADS)

We clarify the long-standing controversy concerning the behavior of the ground-state fidelity in the vicinity of a quantum phase transition of the Berezinskii-Kosterlitz-Thouless type in one-dimensional systems. Contrary to the prediction based on the Gaussian approximation of the Luttinger-liquid approach, it is shown that the fidelity susceptibility does not diverge at the transition but has a cusplike peak ?c-? (? ) ˜?{| ?c-? | } , where ? is a parameter driving the transition and ?c is the peak value at the transition point ? =?c . Numerical claims of the logarithmic divergence of fidelity susceptibility with the system size (or temperature) are explained by logarithmic corrections due to marginal operators, which is supported by numerical calculations for large systems.

Sun, G.; Kolezhuk, A. K.; Vekua, T.

2015-01-01

274

QGP phase transition and multiplicity fluctuations

The scaled factorial moments in QGP phase transitions are studied analytically by the extended Ginzburg-Landau model. The\\u000a dependence of lnF\\u000a q on phase space interval is different for the first- and second-order QGP phase transitions. When lnF\\u000a q, are fitted to polynomials ofX??1\\/3, the relative sign between the fitted coefficients ofX andb\\u000a q,1 calculated theoretically can be used to judge

Chunbin Yang; Xiaorong Wang; Xu Cai

1997-01-01

275

Heavy Fermions and Quantum Phase Transitions

Quantum phase transitions arise in many-body systems due to competing interactions that promote rivaling ground states. Recent years have seen the identification of continuous quantum phase transitions, or quantum critical points, in a host of antiferromagnetic heavy-fermion compounds. Studies of the interplay between the various effects have revealed new classes of quantum critical points, and are uncovering a plethora of new quantum phases. At the same time, quantum criticality has provided fresh insights into the electronic, magnetic, and superconducting properties of the heavy-fermion metals. We review these developments, discuss the open issues, and outline some directions for future research.

Qimiao Si; Frank Steglich

2011-02-24

276

Theory of smeared quantum phase transitions.

We present an analytical strong-disorder renormalization group theory of the quantum phase transition in the dissipative random transverse-field Ising chain. For Ohmic dissipation, we solve the renormalization flow equations analytically, yielding asymptotically exact results for the low-temperature properties of the system. We find that the interplay between quantum fluctuations and Ohmic dissipation destroys the quantum critical point by smearing. We also determine the phase diagram and the behavior of observables in the vicinity of the smeared quantum phase transition. PMID:18643562

Hoyos, José A; Vojta, Thomas

2008-06-20

277

Random Fields at a Nonequilibrium Phase Transition

NASA Astrophysics Data System (ADS)

We study nonequilibrium phase transitions in the presence of disorder that locally breaks the symmetry between two equivalent macroscopic states. In low-dimensional equilibrium systems, such random-field disorder is known to have dramatic effects: it prevents spontaneous symmetry breaking and completely destroys the phase transition. In contrast, we show that the phase transition of the one-dimensional generalized contact process persists in the presence of random-field disorder. The ultraslow dynamics in the symmetry-broken phase is described by a Sinai walk of the domain walls between two different absorbing states. We discuss the generality and limitations of our theory, and we illustrate our results by large-scale Monte Carlo simulations.

Barghathi, Hatem; Vojta, Thomas

2013-03-01

278

Random fields at a nonequilibrium phase transition.

We study nonequilibrium phase transitions in the presence of disorder that locally breaks the symmetry between two equivalent macroscopic states. In low-dimensional equilibrium systems, such random-field disorder is known to have dramatic effects: it prevents spontaneous symmetry breaking and completely destroys the phase transition. In contrast, we show that the phase transition of the one-dimensional generalized contact process persists in the presence of random-field disorder. The ultraslow dynamics in the symmetry-broken phase is described by a Sinai walk of the domain walls between two different absorbing states. We discuss the generality and limitations of our theory, and we illustrate our results by large-scale Monte Carlo simulations. PMID:23215170

Barghathi, Hatem; Vojta, Thomas

2012-10-26

279

NASA Astrophysics Data System (ADS)

Subject to forces and voltage, a dielectric elastomer may undergo electromechanical phase transition. A phase diagram is constructed for an ideal dielectric elastomer membrane under uniaxial force and voltage, reminiscent of the phase diagram for liquid-vapor transition of a pure substance. We identify a critical point for the electromechanical phase transition. Two states of deformation (thick and thin) may coexist during the phase transition, with the mismatch in lateral stretch accommodated by wrinkling of the membrane in the thin state. The processes of electromechanical phase transition under various conditions are discussed. A reversible cycle is suggested for electromechanical energy conversion using the dielectric elastomer membrane, analogous to the classical Carnot cycle for a heat engine. The amount of energy conversion, however, is limited by failure of the dielectric elastomer due to electrical breakdown. With a particular combination of material properties, the electromechanical energy conversion can be significantly extended by taking advantage of the phase transition without electrical breakdown.

Huang, Rui; Suo, Zhigang

2012-02-01

280

Phase transition and properties of compact star

We investigate the phase transition to a deconfined phase and the consequences in the formation of neutron stars. We use the recently proposed effective field theory motivated relativistic mean field theory for hadron and the MIT Bag model and color-flavor locked (CFL) phase for the quark matter in order to get the appropriate equation of state. The properties of star are then calculated. The differences between unpaired and CFL quark matter are discussed.

B. K. Sharma; P. K. Panda; S. K. Patra

2006-11-13

281

Ternary cubic phases containing ionic liquid

The phase diagram of 1-butyl-3-methylimidazolium tetrafluoroborate (bmim-BF4) in aqueous solutions of oleyl polyoxyethylene (20) ether (C18:1E20) was determined at 25?°C by a combination of visual inspection and small-angle X-ray scattering (SAXS). The micellar cubic Im3m liquid crystalline phase found in the ternary system was investigated by means of SAXS and rheological techniques. The cubic samples show highly elastic gel-like properties

Zhongni Wang; Wu Zhou; Ganzuo Li

2008-01-01

282

Size dependence of phase transitions in aerosol nanoparticles

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

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

2015-01-01

283

Size dependence of phase transitions in aerosol nanoparticles

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

284

Size dependence of phase transitions in aerosol nanoparticles.

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

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

2015-01-01

285

Quantum Phase Transition in an Interacting Fermionic Chain

We rigorously analyze the quantum phase transition between a metallic and an insulating phase in (non solvable) interacting spin chains or one dimensional fermionic systems. In particular, we prove the persistence of Luttinger liquid behavior in the presence of an interaction even arbitrarily close to the critical point, where the Fermi velocity vanishes and the two Fermi points coalesce. The analysis is based on two different multiscale analysis; the analysis of the first regime provides gain factors which compensate exactly the small divisors due to the vanishing Fermi velocity.

F. Bonetto; V. Mastropietro

2014-06-13

286

PT phase transition in multidimensional quantum systems

Non-Hermitian PT-symmetric quantum-mechanical Hamiltonians generally exhibit a phase transition that separates two parametric regions, (i) a region of unbroken PT symmetry in which the eigenvalues are all real, and (ii) a region of broken PT symmetry in which some of the eigenvalues are complex. This transition has recently been observed experimentally in a variety of physical systems. Until now, theoretical studies of the PT phase transition have generally been limited to one-dimensional models. Here, four nontrivial coupled PT-symmetric Hamiltonians, $H=p^2/2+x^2/2+q^2/2+y^2/2+igx^2y$, $H=p^2/2+x^2/2+q^2/2+y^2+igx^2y$, $H=p^2/2+x^2/2+q^2/2+y^2/2+r^2/2+z^2/2+igxyz$, and $H=p^2/2+x^2/2+q^2/2+y^2+r^2/2+3z^2/2+igxyz$ are examined. Based on extensive numerical studies, this paper conjectures that all four models exhibit a phase transition. The transitions are found to occur at $g\\approx 0.1$, $g\\approx 0.04$, $g\\approx 0.1$, and $g\\approx 0.05$. These results suggest that the PT phase transition is a robust phenomenon not limited to systems having one degree of freedom.

Carl M. Bender; David J. Weir

2012-06-22

287

Vapor-liquid phase separator permeability results

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

288

Liquid phase sintered compacts in space

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

289

Diffraction Studies of Ordered Phases and Phase Transitions

^.,. 6 OD RisÃ¸-R-506 X'n Diffraction Studies of Ordered Phases and Phase Transitions K. KjÃ¦r RisÃ¸ National Laboratory, DK-4000 Roskilde, Denmark August 1984 #12;RISÃ?-R-506 DIFFRACTION STUDIES OF ORDERED physisorbed on the (001) face of graphite have been studied by means of x-ray diffraction experiments carried

290

Solute effects on the thermodynamic and kinetic behavior of water and liquid-liquid transition

NASA Astrophysics Data System (ADS)

Water is known to be an exceptionally poor glass former, which is one of the characteristic features of water, but its link to the thermodynamic and kinetic anomalies of water remains elusive. Recently we showed that the glass-forming ability and the fragility of a water/salt mixture are closely related to its equilibrium phase diagram.footnotetextM. Kobayashi and H. Tanaka, Phys. Rev. Lett. 106, 125703 (2011);J. Phys. Chem. B 115, 14077 (2011) We proposed that frustration between local and global orderings controls both the glass-forming ability and fragility on the basis of experimental evidence. Relying on the same role of salt and pressure, which commonly breaks tetrahedral order, we apply this idea to pure water under pressure. This scenario not only explains unusual behavior of water-type liquids such as water, Si and Ge, but also provides a general explanation on the link between the equilibrium phase diagram, the glass-forming ability, and the fragility of various materials including oxides, chalcogenides, and metallic glasses.footnotetextH. Tanaka, Eur. Phys. J. E 35, 113 (2012) We also discuss liquid-liquid transition found in mixtures of water with glycerolfootnotetextK. Murata and H. Tanaka, Nature Mater. 11, 436 (2012) and other molecules and its implications.

Tanaka, Hajime

2013-03-01

291

Mechanics and chemical thermodynamics of phase transition in temperature-sensitive hydrogels

separates into two liquid phases with different concentrations of the polymer. Covalently crosslinked PNIPAM associated with the phase transition of the PNIPAM hydrogel. We analyze free swelling, uniaxially and biaxially constrained swelling of a hydrogel, swelling of a coreÂshell structure, and coexistent phases

Suo, Zhigang

292

NASA Astrophysics Data System (ADS)

Polymer phases can be described in the same way as phases in other condensed matter using a number density operator and its correlation functions. This description requires the understanding of symmetry operations and order at different atomic and molecular levels. Statistical mechanics provides a link between the microscopic description of the structure and motion and the macroscopic thermodynamic properties. Within the limits of the laws of thermodynamics, polymers exhibit a rich variety of phase transition behaviors. By definition, a first-order phase transition describes a transformation that involves a sudden change of thermodynamic properties at its transition temperature, whereas higher-order phase transitions are classified as critical phenomena. Of special interest is the role of metastability in phase and phase transition behaviors. Although a metastable state possesses a local free energy minimum, it is not at the global equilibrium. Furthermore, metastable states can also be associated with phase sizes. Metastable behavior is also observed in phase transformations that are impeded by kinetic limitations along the pathway to thermodynamic equilibrium. This is illustrated in structural and morphological investigations of crystallization and mesophase transitions, liquid-liquid phase separation, vitrification, and gel formation, as well as combinations of transformation processes. In these cases, the metastable state often becomes the dominant state for the entire system and is observed over a range of time and size scales. This review describes the general principles of metastability in polymer phases and phase transitions and provides illustrations from current experimental works in selected areas.

Cheng, Stephen Z. D.; Keller, Andrew

1998-08-01

293

Liquid Layer Characteristics in Stratified Gas-Liquid Downflow: A Study of Transition to Wavy Flow

The purpose of this work was to study the transition from the smooth to the wavy stratified flow regime for various pipe inclination angles and liquid physical properties. The accurate characterization of both the structure of the gas-liquid interface and the flow field inside the liquid layer can improve our physical understanding of the mechanisms involved in the evolution of

J. S. Lioumbas; A. A. Mouza; S. V. Paras; A. J. Karabelas

2007-01-01

294

Gravitational Role in Liquid Phase Sintering

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

295

Phase transitions in multiplicative competitive processes

We introduce a discrete multiplicative process as a generic model of competition. Players with different abilities successively join the game and compete for finite resources. Emergence of dominant players and evolutionary development occur as a phase transition. The competitive dynamics underlying this transition is understood from a formal analogy to statistical mechanics. The theory is applicable to bacterial competition, predicting novel population dynamics near criticality.

Shimazaki, Hideaki; Niebur, Ernst [Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Department of Neuroscience, Zanvyl Krieger Mind/Brain Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21218 (United States)

2005-07-01

296

Friction forces on phase transition fronts

In cosmological first-order phase transitions, the microscopic interaction of the phase transition fronts with non-equilibrium plasma particles manifests itself macroscopically as friction forces. In general, it is a nontrivial problem to compute these forces, and only two limits have been studied, namely, that of very slow walls and, more recently, ultra-relativistic walls which run away. In this paper we consider ultra-relativistic velocities and show that stationary solutions still exist when the parameters allow the existence of runaway walls. Hence, we discuss the necessary and sufficient conditions for the fronts to actually run away. We also propose a phenomenological model for the friction, which interpolates between the non-relativistic and ultra-relativistic values. Thus, the friction depends on two friction coefficients which can be calculated for specific models. We then study the velocity of phase transition fronts as a function of the friction parameters, the thermodynamic parameters, and the amount of supercooling.

Mégevand, Ariel, E-mail: megevand@mdp.edu.ar [IFIMAR (CONICET–UNMdP), Departamento de Física, Facultad de Ciencias Exactas y Naturales, UNMdP, Deán Funes 3350, (7600) Mar del Plata (Argentina)

2013-07-01

297

Phase transitions in nanoscale ferroelectric structures.

Over decades of effort, investigations of the intrinsic phase transition behavior of nanoscale ferroelectric structures have been greatly complicated by materials processing variations and by the common and uncontrolled occurrence of spacecharge, which interacts directly with the polarization and can obscure fundamental behavior. These challenges have largely been overcome, and great progress in understanding the details of this class of phase transitions has been made, largely based on advances in the growth of high-quality, epitaxial ferroelectric films and in the theory and simulation of ferroelectricity. Here we will discuss recent progress in understanding the ferroelectric phase transition in a particular class of model systems: nanoscale perovskite thin-film heterostructures. The outlook for ferroelectric technology based on these results is promising, and extensions to laterally confined nanostructures will be described.

Streiffer, S. K.; Fong, D. D. (Center for Nanoscale Materials); ( MSD)

2009-01-01

298

Elementary excitations and phase transitions in crystals

The unique method of measuring elementary excitations in solids over a wide range of energy and momentum transfers is inelastic scattering of neutrons. Elementary excitations are defined as a correlated motion of atoms or spins in a solid which include phonons, magnons, rotons, or crystal field excitations. These excitations play a fundamental role in a wide variety of structural and magnetic phase transitions and provide the information in understanding the underlying microscopic mechanism of the transformation. Below, I shall review some of the relevant aspects of neutron scattering formalism related to inelastic neutron scattering and demonstrate how it has been applied to the study of phase transitions in crystals. I shall give two examples of structural phase transitions where the phonons are the elementary excitations and studies in a conventional superconductor where the phonon linewidths are a measure of the electron-phonon coupling responsible for the pairing.

Shapiro, S.M.

1993-12-31

299

Magnetic Phase Transitions in One-Dimensional Strongly Attractive Three-Component Ultracold Fermions

We investigate the nature of trions, pairing, and quantum phase transitions in one-dimensional strongly attractive three-component ultracold fermions in external fields. Exact results for the ground-state energy, critical fields, magnetization and phase diagrams are obtained analytically from the Bethe ansatz solutions. Driven by Zeeman splitting, the system shows exotic phases of trions, bound pairs, a normal Fermi liquid, and four mixtures of these states. Particularly, a smooth phase transition from a trionic phase into a pairing phase occurs as the highest hyperfine level separates from the two lower energy levels. In contrast, there is a smooth phase transition from the trionic phase into a normal Fermi liquid as the lowest level separates from the two higher levels.

Guan, X. W. [Department of Theoretical Physics, Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200 (Australia); Batchelor, M. T. [Department of Theoretical Physics, Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200 (Australia); Mathematical Sciences Institute, Australian National University, Canberra ACT 0200 (Australia); Lee, C. [Nonlinear Physics Centre and ARC Centre of Excellence for Quantum-Atom Optics, Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200 (Australia); Zhou, H.-Q. [Centre for Modern Physics, Chongqing University, Chongqing 400044 (China)

2008-05-23

300

Microrheology close to an equilibrium phase transition

We investigate the microstructural and microrheological response to a tracer particle of a two-dimensional colloidal suspension under thermodynamic conditions close to a liquid-gas phase boundary. On the liquid side of the binodal, increasing the velocity of the (repulsive) tracer leads to the development of a pronounced cavitation bubble, within which the concentration of colloidal particles is strongly depleted. The tendency of the liquid to cavitate is characterized by a dimensionless “colloidal cavitation” number. On the gas side of the binodal, a pulled (attractive) tracer leaves behind it an extended trail of colloidal liquid, arising from downstream advection of a wetting layer on its surface. For both situations the velocity dependent friction is calculated.

Reinhardt, J.; Scacchi, A.; Brader, J. M., E-mail: joseph.brader@unifr.ch [Department of Physics, University of Fribourg, CH-1700 Fribourg (Switzerland)

2014-04-14

301

Reconstructive structural phase transitions in dense Mg.

The question raised recently about whether the high-pressure phase transitions of Mg follow a hexagonal close-packed (hcp) ? body centered cubic (bcc) or hcp ? double hexagonal close-packed (dhcp) ? bcc sequence at room temperature is examined by the use of first principles density functional methods. Enthalpy calculations show that the bcc structure replaces the hcp structure to become the most stable structure near 48 GPa, whereas the dhcp structure is never the most stable structure in the pressure range of interest. The characterized phase-transition mechanisms indicate that the hcp ? dhcp transition is also associated with a higher enthalpy barrier. At room temperature, the structural sequence hcp ? bcc is therefore more energetically favorable for Mg. The same conclusion is also reached from the simulations of the phase transitions using metadynamics methods. At room temperature, the metadynamics simulations predict the onset of a hcp ? bcc transition at 40 GPa and the transition becomes more prominent upon further compression. At high temperatures, the metadynamics simulations reveal a structural fluctuation among the hcp, dhcp, and bcc structures at 15 GPa. With increasing pressure, the structural evolution at high temperatures becomes more unambiguous and eventually settles to a bcc structure once sufficient pressure is applied. PMID:22692144

Yao, Yansun; Klug, Dennis D

2012-07-01

302

Late-time cosmological phase transitions

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.

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

1990-11-01

303

The ?–? phase transition in volcanic cristobalite

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

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

2014-01-01

304

Second-order symmetric-asymmetric phase transition of randomly connected membranes

NASA Astrophysics Data System (ADS)

Static light-scattering experiments on pseudoternary systems of salted water, pentanol, and salium dodecyl sulfate are presented. The results show evidence for a second-order phase transition between two isotropic phases which is not a classical liquid-liquid phase separation. We discuss these results in the frame of the sponge-asymmetric phase transition which has been described for systems of self-avoiding connected membranes. Both the correlation function and the critical behavior of the scattered intensity are analyzed and are shown to be in agreement with theory.

Coulon, C.; Roux, D.; Bellocq, A. M.

1991-04-01

305

Shape phase transitions and critical points

We investigate different aspects connected with shape phase transitions in nuclei and the possible occurrence of dynamical symmetries at the critical points. We discuss in particular the behaviour of the neighbour odd nuclei at the vicinity of the critical points in the even nuclei. We consider both the case of the transition from the vibrational behaviour to the gamma-unstable deformation (characterized within the collective Bohr hamiltonian by the E(5) critical point symmetry) and the case of the transition from the vibrational behaviour to the stable axial deformation (characterized by the X(5) symmetry). The odd particle is assumed to be moving in the three single particle orbitals j = 1/2,3/2,5/2, a set of orbitals that is known to lead to possible supersymmetric cases. The coupling of the odd particle to the Bohr hamiltonian does lead in fact in the former case at the critical point to the E(5/12) boson-fermion dynamical symmetry. An alternative approach to the two shape transitions is based on the Interacting Boson Fermion Model. In this case suitably parametrized boson-fermion hamiltonians can describe the evolution of the odd system along the shape transitions. At the critical points both energy spectra and electromagnetic transitions were found to display characteristic patterns similar to those displayed by the even nuclei at the corresponding critical point. The behaviour of the odd nuclei can therefore be seen as necessary complementary signatures of the occurrence of the phase transitions.

Alonso, C. E.; Arias, J. M. [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Fisica Universidad de Sevilla, Apartado 1065, 41080 Sevilla (Spain); Fortunato, L.; Vitturi, A. [Dipartimento di Fisica Galileo Galilei and INFN, Via Marzolo 8, 35131 Padova (Italy)

2009-05-04

306

Particle dynamics in colloidal suspensions above and below the glass-liquid re-entrance transition

We study colloidal particle dynamics of a model glass system using confocal and fluorescence microscopy as the sample evolves from a hard-sphere glass to a liquid with attractive interparticle interactions. The transition from hard-sphere glass to attractive liquid is induced by short-range depletion forces. The development of liquid-like structure is indicated by particle dynamics. We identify particles which exhibit substantial motional events and characterize the transition using the properties of these motional events. As samples enter the attractive liquid region, particle speed during these motional events increases by about one order of magnitude, and the particles move more cooperatively. Interestingly, colloidal particles in the attractive liquid phase do not exhibit significantly larger displacements than particles in the hard-sphere glass.

Andrzej Latka; Yilong Han; Ahmed M. Alsayed; Andrew B. Schofield; A. G. Yodh; Piotr Habdas

2009-02-17

307

On transit time instability in liquid jets

NASA Technical Reports Server (NTRS)

A basic transit time instability in flows with disturbances of speed is found. It was shown that the mass distribution is established by and large by the described transit time effects. These transit time effects may also be involved for gas jets.

Grabitz, G.; Meier, G.

1982-01-01

308

Phase transition in sarcosine phosphite single crystals

NASA Astrophysics Data System (ADS)

Single crystals of sarcosine phosphite (SarcH3PO3) have been grown. The amino acid sarcosine is an isomer of the protein amino acid alanine. Both amino acids are described by the same chemical formula but have different structures; or, more specifically, in contrast to the alanine molecule, the sarcosine molecule has a symmetric structure. It has been found that the sarcosine phosphite compound undergoes a structural phase transition at a temperature of approximately 200 K. This result has demonstrated that compounds of achiral amino acids are more susceptible to structural phase transitions.

Lemanov, V. V.; Popov, S. N.; Pankova, G. A.

2011-06-01

309

Dimension changing phase transitions in instanton crystals

NASA Astrophysics Data System (ADS)

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.

Kaplunovsky, Vadim; Sonnenschein, Jacob

2014-04-01

310

Dissociative phase transitions from hypervelocity impacts

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations are used to study hypervelocity impacts of an ultrathin flyer plate with a semi-infinite two-dimensional model diatomic molecular solid. These hypervelocity impacts are shown to produce a dissociative phase transition from a molecular to a close-packed solid in the target material. Although this close-packed phase persists for less than 10 picoseconds and is confined to a domain less than 10 nanometers wide it nevertheless behaves in a manner consistent with continuum theory.

White, C. T.; Robertson, D. H.; Brenner, D. W.

1992-09-01

311

Liquid-phase compositions from vapor-phase analyses

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

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

1989-09-01

312

Phase change in liquid face seals

NASA Technical Reports Server (NTRS)

A study is made of boiling (or phase change) in liquid face seals. An appropriate model is set up and approximate solutions obtained. Some practical illustrative examples are given. Major conclusions are that (1) boiling may occur more often than has been suspected particularly when the sealed liquid is near saturation conditions, (2) the temperature variation in a seal clearance region may not be very great and the main reason for boiling is the flashing which occurs as the pressure decreases through the seal clearance, and (3) there are two separate values of the parameter film-thickness/angular-velocity-squared (and associated radii where phase change takes place) which provide the same separating force under a given set of operating conditions. For a given speed seal face excursions about the larger spacing are stable, but excursions about the smaller spacing are unstable, leading to a growth to the larger spacing or a catastrophic collapse.

Hughes, W. F.; Winowich, N. S.; Birchak, M. J.; Kennedy, W. C.

1978-01-01

313

Phase transition dynamics in QGP hadronization

Our aim is to study qualitatively the process of QGP cooling and hadronization. Following the statistical theory of the first order phase transitions we have to operate with such categories as nucleation rate, pre-exponential factor, surface free energy of bubbles and velocity of bubble growth. We compute the temperature, average bubble size, bubble density and fraction of space converted to

E. E. Zabrodin; L. P. Csernai; J. I. Kapusta; Gy. Kluge

1994-01-01

314

Caloric materials near ferroic phase transitions

NASA Astrophysics Data System (ADS)

A magnetically, electrically or mechanically responsive material can undergo significant thermal changes near a ferroic phase transition when its order parameter is modified by the conjugate applied field. The resulting magnetocaloric, electrocaloric and mechanocaloric (elastocaloric or barocaloric) effects are compared here in terms of history, experimental method, performance and prospective cooling applications.

Moya, X.; Kar-Narayan, S.; Mathur, N. D.

2014-05-01

315

Dual condensate and QCD phase transition

The dual condensate is a new QCD phase transition order parameter, which connnects confinement and chiral symmetry breaking as different mass limits. We discuss the relation between the fermion spectrum at general boundary conditions and the dual condensate and show numerical results for the latter from unquenched SU(3) lattice configurations.

Zhang Bo; Bruckmann, Falk [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany); Fodor, Zoltan; Szabo, Kalman K. [Department of Physics, University of Wuppertal, Gaussstr. 20, D-42119 (Germany); Gattringer, Christof [Institut fuer Physik, Universitaet Graz, Universitaetsplatz 5, A-8010 Graz (Austria)

2011-05-23

316

Chiral Phase Transitions around Black Holes

In this paper we discuss the possibility that chiral phase transitions, analogous to those of QCD, occur in the vicinity of a black hole. If the black hole is surrounded by a gas of strongly interacting particles, an inhomogeneous condensate will form. We demonstrate this by explicitly constructing self-consistent solutions.

Antonino Flachi; Takahiro Tanaka

2011-06-20

317

Large N Phase Transitions in Low Dimensions

NASA Astrophysics Data System (ADS)

Quantum models with fields in matrix representations of classical groups exhibit a high order phase transition in the limit of large order of the group. In zero dimension of space-time the Green functions of the newly found branch are those of a Gaussian model; in one dimension, the physical mass vanishes at the critical point.

Cicuta, G. M.; Molinari, L.; Montaldi, E.

318

Passive Supporters of Terrorism and Phase Transitions

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.

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

2010-01-01

319

Quantum Plasma Model with Hydrodynamical Phase Transition

Quantum Plasma Model with Hydrodynamical Phase Transition By Geoffrey L. Sewell* DepartmentÂhydrodynamics of the Jellium plasma model from its manyÂparticle SchrÂ¨odinger equation, subject to certain general initial Introduction The quantum Jellium model is a system of electrons, interacting via Coulomb forces both with one

320

Phase Transitions in Gravitational Allocation Sourav Chatterjee

to individual stars dominate). In dimension 4 we find a double phase transi- tion, where the transition betweenÂ§ March 10, 2010 (revised version) Abstract Given a Poisson point process of unit masses ("stars to individual stars dominate). When d 5, the large deviation is due to a thin tube (a "wormhole") along which

Romik, Dan

321

NASA Technical Reports Server (NTRS)

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.

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

1978-01-01

322

Generalized phase transitions in Lovelock gravity

We investigate a novel mechanism for phase transitions that is a distinctive feature of higher-curvature gravity theories. For definiteness, we bound ourselves to the case of Lovelock gravities. These theories are known to have several branches of asymptotically AdS solutions. Here, extending our previous work, we show that phase transitions among some of these branches are driven by a thermalon configuration: a bubble separating two regions of different effective cosmological constants, generically hosting a black hole in the interior. Above some critical temperature, this thermalon configuration is preferred with respect to the finite-temperature AdS space, triggering a sophisticated version of the Hawking-Page transition. After being created, the unstable bubble configuration can in general dynamically change the asymptotic cosmological constant. While this phenomenon already occurs in the case of a gravity action with square curvature terms, we point out that in the case of Lovelock theory with cubic (and...

Camanho, Xian O; Giribet, Gaston; Gomberoff, Andres

2013-01-01

323

Homogeneous phases of polar active liquids

We study the spatially homogeneous phases of polar active particles in the low density limit, and specifically the transition from the isotropic to the polar phase. We identify the forward component of the change of momentum induced by collisions as a fundamental quantity of interest. We propose an ansatz for the angular distribution of velocities and obtain a close equation for the order parameter. This equation provides a very intuitive and physically meaningful criterion for the destabilization of the isotropic phase, where the ansatz is exact. The criterion also predicts whether the transition is supercritical or subcritical. The theoretical predictions for the polar state are in excellent agreement with numerical simulations of a mean-field Vicsek-like model, even far from the transition. Finally, we show how the intuition gained by this criterion allows to anticipate that polar active hard discs aligning through Vicsek-like rules shall display a continuous transition, while polar active hard discs aligning inelastically shall display a discontinuous one. These predictions are confirmed numerically.

Khanh-Dang Nguyen Thu Lam; Michael Schindler; Olivier Dauchot

2014-10-16

324

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

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 \

Voskresensky, D N

2010-01-01

325

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

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 \

D. N. Voskresensky; V. V. Skokov

2010-12-22

326

Vapor-liquid phase separator studies

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

327

Transient liquid phase bonding of intermetallics

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

Yimin Guan

1998-01-01

328

Does Sex Induce a Phase Transition?

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...

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

2009-01-01

329

Liquid-phase electroepitaxy - Dopant segregation

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

330

Hexagonal and nematic phases of chains. I - Correlation functions. II - Phase transitions

NASA Technical Reports Server (NTRS)

The statistical mechanics of a system of semiflexible chains, which can represent polymer liquid crystals, long-chain biomolecules, stiff wormlike micelles, or columns of discotic liquid crystals, are examined. A continuum theory is used to calculate static correlation functions in the hexagonal and nematic phases. Two correlation functions are considered: (1) the structure factor which describes fluctuations in the density; and (2) the director fluctuation spectrum, which describes fluctuations in the local optical axis. In addition, a model is developed for the phase transitions of a system of infinitely long, semiflexible chains which interact through a steric, excluded-volume repulsion. The model yields generic phase diagrams in terms of pressure or density vs. persistence length or temperature.

Selinger, Jonathan V.; Bruinsma, Robijn F.

1991-01-01

331

General nature of liquid-liquid transition in aqueous organic solutions

NASA Astrophysics Data System (ADS)

The presence or absence of a liquid-liquid transition in water is one of the hot topics in liquid science, and while a liquid-liquid transition in water/glycerol mixtures is known, its generality in aqueous solutions has remained elusive. Here we reveal that 14 aqueous solutions of sugar and polyol molecules, which have an ability to form hydrogen bonding with water molecules, exhibit liquid-liquid transitions. We find evidence that both melting of ice and liquid-liquid transitions in all these aqueous solutions are controlled solely by water activity, which is related to the difference in the chemical potential between an aqueous solution and pure water at the same temperature and pressure. Our theory shows that water activity is determined by the degree of local tetrahedral ordering, indicating that both phenomena are driven by structural ordering towards ice-like local structures. This has a significant implication on our understanding of the low-temperature behaviour of water.

Murata, Ken-Ichiro; Tanaka, Hajime

2013-11-01

332

Phase Transition of DNA Coated Nanogold Networks

NASA Astrophysics Data System (ADS)

Melting and hybridization of DNA-coated gold nanoparticle networks are investigated with optical absorption spectroscopy and tansmission electron microscopy. Single-stranded DNA-coated nanogold are linked with complementary, single-stranded linker DNA to form particle networks. Network formation results in a solution color change, which can be used for DNA detection. Compared to free DNA, networked DNA-nanoparticle systems result in a sharp melting transition. Melting curves calculated from percolation theory agree with our experimental results(1). (1) C.-H. Kiang, ``Phase Transition of DNA-Linked Gold Nanoparticles,'' Physica A, 321 (2003) 164--169.

Kiang, Ching-Hwa; Sun, Young; Harris, Nolan; Wickremasinghe, Nissanka

2004-03-01

333

Phase Transitions in Paradigm Shift Models

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

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

2013-01-01

334

Liquid-vapor phase boundaries determination by dynamic experimental method

NASA Astrophysics Data System (ADS)

Shock-induced vaporization of matter under expansion from high-energy states is of interest as an experimental method to determine two-phase region boundaries and position of critical point of liquid- vapor transition. Fast pyrometry technique was used to determine velocity of expansion, pressure and temperature nearby metal - gas boundary. Heating of material under research on the boundary with hot shocked gas at a constant final pressure of material expansion is another source of high temperature states. Optically transparent or translucent shocked helium and neon give the possibility to achieve temperatures and pressures exceeding critical parameters of tungsten- one of the most refractory metals. Intensive heat and mass transfer on the boundary give the opportunity to investigate states not only near binodal but also liquid spinodal. Experimental results and issues of such investigation with lead, tin, nickel, and tungsten is analyzed in the proposed paper.

Ternovoi, Vladimir; Filimonov, Aleksandr; Fortov, Vladimir; Gordon, Yulyi; Nikolaev, Dmitry; Pyalling, Alexei

1999-06-01

335

Dynamic Phase Transitions of Active Gels

NASA Astrophysics Data System (ADS)

Spreading of fibroblasts on matrix-coated glass proceeds via extension of thin lamellipodia sheets driven by actin polymerization and contraction of the actin in those lamellipodia that generates force on the substrate. Quantitative analysis of motility patterns seen with differential interference as well as total internal reflection fluorescence microscopy shows sequential well-defined cell states or phases of spreading: In a common form of spreading, an early homogenous spreading phase precedes a periodic contractile phase and then the fully spread cell transitions to a phase of polarized migration. Fourier power spectra of membrane velocity and the scaling behavior of adhesion area growth both indicate dynamic phase transitions between these different cell states reflecting activity variations in the molecular motor myosin. Based on these observations, we propose a basic phase model of cell motility. We believe cell spreading can be described as a sequence of different dynamic states of an active gel (actin & myosin) controlled by a fairly small set of essential regulatory proteins.

Doebereiner, Hans-Guenther; Dubin-Thaler, Benjamin J.; Giannone, Gregory; Xenias, Harry; Sheetz, Michael P.

2004-03-01

336

Dimensional phase transition in small Yukawa clusters.

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

Sheridan, T E; Wells, K D

2010-01-01

337

Dimensional phase transition in small Yukawa clusters

NASA Astrophysics Data System (ADS)

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.

Sheridan, T. E.; Wells, K. D.

2010-01-01

338

One of the most controversial hypotheses for explaining the origin of the thermodynamic anomalies characterizing liquid water postulates the presence of a metastable second-order liquid-liquid critical point [1] located in the "no-man's land" [2]. In this scenario, two liquids with distinct local structure emerge near the critical temperature. Unfortunately, since spontaneous crystallization is rapid in this region, experimental support for this hypothesis relies on significant extrapolations, either from the metastable liquid or from amorphous solid water [3, 4]. Although the liquid-liquid transition is expected to feature in many tetrahedrally coordinated liquids, including silicon [5], carbon [6] and silica, even numerical studies of atomic and molecular models have been unable to conclusively prove the existence of this transition. Here we provide such evidence for a model in which it is possible to continuously tune the softness of the interparticle interaction and the flexibility of the bonds, the key ingredients controlling the existence of the critical point. We show that conditions exist where the full coexistence is thermodynamically stable with respect to crystallization. Our work offers a basis for designing colloidal analogues of water exhibiting liquid-liquid transitions in equilibrium, opening the way for experimental confirmation of the original hypothesis. PMID:25264453

Smallenburg, Frank; Filion, Laura; Sciortino, Francesco

2014-09-01

339

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

NASA Astrophysics Data System (ADS)

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.

Matsuyama, Akihiko

2014-11-01

340

Analysis Of Phase Transitions In Quasi-Two-Dimensional Dusty Systems In RF-Discharge Plasma

In this work, we investigate the phase transitions in quasi-two-dimensional systems of dusty plasma in RF discharge. The quasi-2D systems are considered, where the areas with different phase states (dusty liquid and dusty crystal) coexist. The parameters of these areas of dusty subsystem are estimated, the obtained results are analysed and compared with theoretical predictions.

Adamovich, X. G.; Vaulina, O. S.; Khrustalev, Yu. V.; Nekhaevsky, Yu. Yu.; Petrov, O. F.; Fortov, V. E. [Joint Institute for High Temperatures, RAS, Izhorskaya 13/19, Moscow, 125412 (Russian Federation)

2008-09-07

341

Phase transitions: An overview with a view

The dynamics of phase transitions plays a crucial role in the so- called interface between high energy particle physics and cosmology. Many of the interesting results generated during the last fifteen years or so rely on simplified assumptions concerning the complex mechanisms typical of nonequilibrium field theories. After reviewing well-known results concerning the dynamics of first and second order phase transitions, I argue that much is yet to be understood, in particular in situations where homogeneous nucleation theory does not apply. I present a method to deal with departures from homogeneous nucleation, and compare its efficacy with numerical simulations. Finally, I discuss the interesting problem of matching numerical simulations of stochastic field theories with continuum models.

Gleiser, M. [Dartmouth Coll., Hanover, NH (United States)

1997-10-01

342

Evolution of structure during phase transitions

Nanostructured materials can be synthesized by utilizing the domain growth that accompanies first-order phase separation. Structural control can be achieved by appropriately selecting the quench depth and the quench time, but in order to do this in a mindful fashion one must understand the kinetics of domain growth. The authors have completed detailed light scattering studies of the evolution of structure in both temperature- and field-quenched phase transitions in two and three dimensional systems. They have studied these systems in the quiescent state and in shear and have developed theoretical models that account for the experimental results.

Martin, J.E.; Wilcoxon, J.P.; Anderson, R.A.

1996-03-01

343

If crystallization can be avoided when a liquid is cooled, it will typically form a glass. Near the glass transition temperature the viscosity increases continuously but rapidly with cooling. As the glass forms, the molecular relaxation time increases with an Arrhenius-like (simple activated) form in some liquids, but shows highly non-Arrhenius behaviour in others. The former are said to be

Kaori Ito; Cornelius T. Moynihan; C. Austen Angell

1999-01-01

344

Finite Temperature Phase Transition in $?^6$ potential

The temperature dependance of the action in the thin-wall and thick-wall limits is obtained analytically for the $\\phi^6$ scalar potential. The nature of the phase transition is investigated from the quantum tunnelling regime at low temperatures to the thermal hopping regime at high temperatures. It is first-order for the case of a thin wall while for the thick wall it is second- order.

Hatem Widyan

2008-12-29

345

Phase transitions in models with discrete symmetry

NASA Astrophysics Data System (ADS)

We investigate a class of models with a massless fermion and a self-interacting scalar field with the Yukawa interaction between these two fields. The models considered are formulated in two and four spacetime dimensions and possess a discrete symmetry. We calculate the chiral condensates which are calculated in the one-loop approximation. We show that the models have phase transitions as a function of the coupling constants.

Ksenzov, V. G.; Romanov, A. I.

2014-12-01

346

Phase transitions in Nowak Sznajd opinion dynamics

NASA Astrophysics Data System (ADS)

The Nowak modification of the Sznajd opinion dynamics model on the square lattice assumes that with probability ? the opinions flip due to mass-media advertising from down to up, and vice versa. Besides, with probability ? the Sznajd rule applies that a neighbour pair agreeing in its two opinions convinces all its six neighbours of that opinion. Our Monte Carlo simulations and mean-field theory find sharp phase transitions in the parameter space.

Wo?oszyn, Maciej; Stauffer, Dietrich; Ku?akowski, Krzysztof

2007-05-01

347

Empty liquid phase of colloidal ellipsoids: the role of shape and interaction anisotropy.

We study the effect of anisotropic excluded volume and attractive interactions on the vapor-liquid phase transition of colloidal ellipsoids. In our model, the hard ellipsoid is embedded into an ellipsoidal well, where both the shape of the hard ellipsoid and that of the added enclosing ellipsoidal well can be varied independently. The bulk properties of these particles are examined by means of a van der Waals type perturbation theory and validated with replica exchange Monte Carlo simulations. It is shown that both the critical volume fraction (?c) and the critical temperature (Tc) of the vapor-liquid phase transition vanish with increasing shape anisotropy for oblate shapes, while ?c ? 0 and Tc ? 0 are obtained for very elongated prolate shapes. These results suggest that the chance to stabilize empty liquids (a liquid phase with vanishing density) is higher in suspensions of rod-like colloidal ellipsoids than in those of plate-like ones. PMID:24712814

Varga, Szabolcs; Meneses-Júarez, Efrain; Odriozola, Gerardo

2014-04-01

348

Generalized phase transitions in Lovelock gravity

NASA Astrophysics Data System (ADS)

We investigate a novel mechanism for phase transitions that is a distinctive feature of higher-curvature gravity theories. For definiteness, we bound ourselves to the case of Lovelock gravities. These theories are known to have several branches of asymptotically anti-de Sitter solutions. Here, extending our previous work, we show that phase transitions among some of these branches are driven by a thermalon configuration: a bubble separating two regions of different effective cosmological constants, generically hosting a black hole in the interior. Above some critical temperature, this thermalon configuration is preferred with respect to the finite-temperature anti-de Sitter space, triggering a sophisticated version of the Hawking-Page transition. After being created, the unstable bubble configuration can in general dynamically change the asymptotic cosmological constant. While this phenomenon already occurs in the case of a gravity action with square curvature terms, we point out that in the case of Lovelock theory with cubic (and higher) terms new effects appear. For instance, the theory may admit more than one type of bubble and branches that are in principle free of pathologies may also decay through the thermalon mechanism. We also find ranges of the gravitational couplings for which the theory becomes sick. These add up to previously found restrictions to impose tighter constraints on higher-curvature gravities. The results of this paper point to an intricate phase diagram which might accommodate similarly rich behavior in the dual conformal field theory side.

Camanho, Xián O.; Edelstein, José D.; Giribet, Gastón; Gomberoff, Andrés

2014-09-01

349

The glass-liquid transition of water on hydrophobic surfaces

Interactions of thin water films with surfaces of graphite and vitrified room-temperature ionic liquid [1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6])] were investigated using time-of-flight secondary ion mass spectrometry as a function of temperature and annealing time to elucidate the glass-liquid transition of water at the molecular level. Surface diffusion of water occurs at temperatures higher than 120 K, thereby forming three-dimensional clusters (a

Ryutaro Souda

2008-01-01

350

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.

351

NASA Astrophysics Data System (ADS)

We investigate nonperturbative features of a three-dimensional Abelian Higgs model with singly and doubly charged scalar fields coupled to a single compact Abelian gauge field. The model is pretending to describe various planar systems of strongly correlated electrons such as high- Tc superconductivity in the overdoped regime and exotic materials possessing excitations with fractionalized quantum numbers. The complicated phase structure of the model is studied thoroughly using numerical tools and analytical arguments. In the three-dimensional space of coupling parameters we identify the Fermi liquid, the spin gap, the superconductor and the strange metallic phases. The behavior of three kinds of topological defects—holon, spinon vortices, and monopoles—is explored in various phases. We also observe an effect, the strong enhancement of the phase transition strength reflected in a lower order of the transition: at sufficiently strong gauge coupling the two second-order phase transitions—corresponding to spinon pair and holon condensation lines—join partially in the phase diagram and become a first-order phase transition in that region. The last observation may have an analog in quantum chromodynamics at nonzero temperature and finite baryon density. We argue that at sufficiently large baryon density the finite-temperature transition between the (three-flavor paired) color superconducting phase and the quark-gluon plasma phases should be much stronger compared with the transition between two-flavor paired and three-flavor paired superconducting phases.

Bock, M.; Chernodub, M. N.; Ilgenfritz, E.-M.; Schiller, A.

2007-11-01

352

Phase field modeling of liquid metal embrittlement

NASA Astrophysics Data System (ADS)

Liquid metal embrittlement (LME) is a phenomenon whereby a liquid metal in contact with another, higher-melting-point polycrystalline metal, rapidly penetrates from the surface along grain boundaries. This phenomenon is known to be greatly accelerated by the application of tensile stress, resulting in the rapid propagation of intergranular cracks in normally ductile materials. Although this phenomenon has been known for a long time, it still lacks a convincing physical explanation. In particular, the relationship of LME to conventional fracture mechanics remains unclear. We investigate LME using a phenomenological three-order-parameter phase field model that describes both the short scale physics of crystal decohesion and macroscopic linear elasticity. The model reproduces expected macroscopic properties for well separated crack surfaces and additionally introduces short scale modifications for liquid layer thicknesses in the nanometric range, which depend on the interfacial and grain boundary energy as well as elastic effects. The results shed light on the relative importance of capillary phenomena and stress in the kinetics of LME.

Spatschek, Robert; Wang, Nan; Karma, Alain

2008-03-01

353

Phase transitions in complex network dynamics

NASA Astrophysics Data System (ADS)

Two phase transitions in complex networks are analyzed. The first of these is a percolation transition, in which the network develops a macroscopic connected component as edges are added to it. Recent work has shown that if edges are added "competitively" to an undirected network, the onset of percolation is abrupt or "explosive." A new variant of explosive percolation is introduced here for directed networks, whose critical behavior is explored using numerical simulations and finite-size scaling theory. This process is also characterized by a very rapid percolation transition, but it is not as sudden as in undirected networks. The second phase transition considered here is the emergence of instability in Boolean networks, a class of dynamical systems that are widely used to model gene regulation. The dynamics, which are determined by the network topology and a set of update rules, may be either stable or unstable, meaning that small perturbations to the state of the network either die out or grow to become macroscopic. Here, this transition is analytically mapped onto a well-studied percolation problem, which can be used to predict the average steady-state distance between perturbed and unperturbed trajectories. This map applies to specific Boolean networks with few restrictions on network topology, but can only be applied to two commonly used types of update rules. Finally, a method is introduced for predicting the stability of Boolean networks with a much broader range of update rules. The network is assumed to have a given complex topology, subject only to a locally tree-like condition, and the update rules may be correlated with topological features of the network. While past work has addressed the separate effects of topology and update rules on stability, the present results are the first widely applicable approach to studying how these effects interact. Numerical simulations agree with the theory and show that such correlations between topology and update rules can have profound effects on the qualitative behavior of these systems.

Squires, Shane

354

Deliquescence phase transition measurements by quartz crystal microbalance frequency shifts.

Measurements of the hygroscopic properties of aerosols are needed to better understand the role of aerosols as cloud condensation nuclei. Several techniques have been used to measure deliquescence (solid to liquid) phase transitions in particular. In this study, we have measured the deliquescence relative humidity (DRH) of organic and inorganic salts, organic acids (glutaric and succinic acid), and mixtures of organic acids with ammonium sulfate using a quartz crystal microbalance (QCM). The QCM allows for measurement of the deliquescence phase transition due to inherent measurement differences between solids and liquids in the oscillation frequency of a quartz crystal. The relative humidity dependent frequency measurements can be used to identify compounds that adsorb monolayer amounts of water or form hydrates prior to deliquescence (e.g., lithium chloride, potassium and sodium acetate). Although the amount of water uptake by a deliquescing material cannot be quantified with this technique, deliquescence measurements of mixtures of hygroscopic and nonhygroscopic components (e.g., ammonium sulfate and succinic acid (DRH > 95%)) show that the mass fraction of the deliquescing portion of the sample can be quantitatively determined from the relative change in oscillation frequency at deliquescence. The results demonstrate the use of this technique as an alternative method for phase transition measurements and as a direct measurement of the mass fraction of a sample that undergoes deliquescence. Further, deliquescence measurements by the QCM may provide improved understanding of discrepancies in atmospheric particle mass measurements between filter samples and the tapered element oscillating microbalance given the similar measurement principle employed by the QCM. PMID:22742475

Arenas, Kathleen Jane L; Schill, Steven R; Malla, Ammaji; Hudson, Paula K

2012-07-26

355

Liquid crystalline growth within a phase-field crystal model

By using a phase-field crystal (PFC) model, the liquid-crystal growth of the plastic triangular phase is simulated with emphasis on crystal shape and topological defect formation. The equilibrium shape of a plastic triangular crystal (PTC) grown from a isotropic phase is compared with that grown from a columnar/smectic A (CSA) phase. While the shape of a PTC nucleus in the isotropic phase is almost identical to that of a classical PFC model, the shape of a PTC nucleus in CSA is affected by the orientation of stripes in the CSA phase, and irregular hexagonal, elliptical, octagonal, and rectangular shapes are obtained. Concerning the dynamics of the growth process we analyse the topological structure of the nematic-order, which starts from nucleation of $+\\frac{1}{2}$ and $-\\frac{1}{2}$ disclination pairs at the PTC growth front and evolves into hexagonal cells consisting of $+1$ vortices surrounded by six satellite $-\\frac{1}{2}$ disclinations. It is found that the orientational and the positional order do not evolve simultaneously, the orientational order evolves behind the positional order, leading to a large transition zone, which can span over several lattice spacings.

Sai Tang; Simon Praetorius; Rainer Backofen; Axel Voigt; Yan-Mei Yu; Jincheng Wang

2015-01-09

356

The Phase Transition of Dark Energy

Considering that the universe is filled with the nonrelativistic matter and dark energy and each component is respectively satisfied with its conservation condition in the absence of their interaction, we give the change rate of the fractional density and the density of dark energy from the conservation condition. It is clear that the fractional density of dark energy will monotonously increase and gradually become the dominating contribution to the universe as the redshift becomes low. Combining the evolutional trend of the state equation of dark energy and the change rate of the density of dark energy we find that the density of dark energy will decrease up to a minimum and whereafter it will increase again as the redshift becomes low. This can be regarded as the phase transition of dark energy from the quintessence phase to the phantom phase.

Wei Wang; Yuanxing Gui; Ying Shao

2006-12-05

357

NASA Astrophysics Data System (ADS)

We study the extent of the spin liquid phases in the Kitaev-Heisenberg model using infinite projected entangled-pair states tensor network ansatz wave functions directly in the thermodynamic limit. To assess the accuracy of the ansatz wave functions, we perform benchmarks against exact results for the Kitaev model and find very good agreement for various observables. In the case of the Kitaev-Heisenberg model, we confirm the existence of six different phases: Néel, stripy, ferromagnetic, zigzag, and two spin liquid phases. We find finite extents for both spin liquid phases and discontinuous phase transitions connecting them to symmetry-broken phases.

Osorio Iregui, Juan; Corboz, Philippe; Troyer, Matthias

2014-11-01

358

Phase transitions of nuclear matter beyond mean field theory

The Cornwall-Jackiw-Tomboulis (CJT) effective action approach is applied to study the phase transition of nuclear matter modeled by the four-nucleon interaction. It is shown that in the Hartree-Fock approximation (HFA) a first-order phase transition takes place at low temperature, whereas the phase transition is of second order at higher temperature.

Tran Huu Phat [Vietnam Atomic Energy Commission, 59 Ly Thuong Kiet, Hanoi (Viet Nam) and Dong Do University, 8 Nguyen Cong Hoan, Hanoi (Viet Nam); Nguyen Tuan Anh [Institute for Nuclear Science and Technique, 5T-160 Hoang Quoc Viet, Hanoi (Viet Nam); Nguyen Van Long [Gialai Teacher College, 126 Le Thanh Ton, Pleiku, Gialai (Viet Nam); Le Viet Hoa [Hanoi National University of Education, 136 Xuan Thuy, Cau Giay, Hanoi (Viet Nam)

2007-10-15

359

An improved model for the transit entropy of monatomic liquids

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.

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

2009-01-01

360

PHASE TRANSITIONS, CRITICAL PHENOMENA AND EXACTLY SOLVABLE LATTICE MODELS

of common everyday expe- rience. If we boil a kettle of water we observe a change of phase from a liquid this point the liquid and gas phases are indistinguishable. The melting (0C) and boiling points (100C the liquid density L to the gas density G as the temperature passes through the boiling point at atmospheric

Pearce, Paul A.

361

Quantum Phase Transitions in Antiferromagnets and Superfluids

NASA Astrophysics Data System (ADS)

A general introduction to the non-zero temperature dynamic and transport properties of low-dimensional systems near a quantum phase transition shall be presented. Basic results will be reviewed in the context of experiments on the spin-ladder compounds. Recent large N computations (M. Vojta and S. Sachdev, Phys. Rev. Lett. 83), 3916 (1999) on an extended t-J model motivate a global scenario of the quantum phases and transitions in the high temperature superconductors, and connections will be made to numerous experiments. A universal theory (S. Sachdev, C. Buragohain, and M. Vojta, Science, in press M. Vojta, C. Buragohain, and S. Sachdev, cond- mat/9912020) of quantum impurities in spin-gap antiferromagnets near a magnetic ordering transition will be compared quantitatively to experiments on Zn doped Y Ba2 Cu3 O7 (Fong et al.), Phys. Rev. Lett. 82, 1939 (1999)

Sachdev, Subir

2000-03-01

362

Study of cerium phase transitions in shock wave experiments

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.

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

363

Vibrational Fredericksz transition in liquid crystals V. A. Vladimirov*

Vibrational FrÃ©edericksz transition in liquid crystals V. A. Vladimirov* Department of Mathematics received 8 August 2007; published 27 September 2007 Our aim is to show the possibility of a "vibrational-frequency vibrations imposed on LCs by employing the rigorous two-timing asymptotic averaging method to the governing

364

Phase Transitions of MgO Along the Hugoniot (Invited)

NASA Astrophysics Data System (ADS)

The formation of terrestrial planets and planetary structure has become of great interest because of recent exoplanet discoveries of super earths. MgO is a major constituent of Earth's mantle, the rocky cores of gas giants such as Jupiter, and likely constitutes the interiors of many exoplanets. The high pressure - high temperature behavior of MgO directly affects equation of state models for planetary structure and formation. In this work, we examine single crystal MgO under shock compression utilizing experimental and density functional theory (DFT) methods to determine phase transformations along the Hugoniot. We perform plate impact experiments using Sandia's Z - facility on MgO up to 11.6 Mbar. The plate impact experiments generate highly accurate Hugoniot state data. The experimental results show the B1 - B2 solid - solid phase transition occurs near 4 Mbar on the Hugoniot. The solid - liquid transition is determined to be near 7 Mbar with a large region of B2-liquid coexistence. Using DFT methods, we also determine melt along the B1 and B2 solid phase boundaries as well as along the Hugoniot. The combined experimental and DFT results have determined the phase boundaries along the Hugoniot, which can be implemented into new planetary and EOS models. 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 Securities Administration under Contract No. DE-AC04-94AL85000.

Root, S.; Shulenburger, L.; Lemke, R. W.; Cochrane, K. R.; Mattsson, T. R.

2013-12-01

365

Liquid crystalline phases in concentrated aqueous solutions of Na/sup +/ DNA

Concentrated aqueous saline solutions of short (146-base-pair) DNA fragments suddenly become turbid and iridescent when the DNA concentration is slightly increased or the temperature is decreased. Microscopic examination through crossed polarizing filters shows that turbidity and iridescence is due to formation of a liquid crystalline DNA phase similar to cholesteric liquid crystals formed by other semirigid, but nonelectrolyte, chiral polymers. Several distinct textures of the liquid crystalline phase or phases are observed depending on DNA concentration, temperature, and method of sample preparation. Textures observed include spherulites with Maltese crosses, striated and highly colored ribbons, whorls of periodic interference fringes, and colored flakes. The liquid crystalline DNA phase coexists in metastable equilibrium with the isotropic phase over a relatively narrow temperature/ concentration range - approximately 175-250 mg/ml and 25-62/sup 0/C (limit of measurements). At higher concentrations and temperatures above approx.25/sup 0/C, the solutions appear fully liquid crystalline. When concentrated solutions are cooled below room temperature, crystals form due to precipitation of supporting electrolyte. A partial phase diagram is reported for the isotropic ..-->.. liquid crystal ..-->.. crystal transitions of solutions of DNA in buffered saline (2 M Na/sup +/). The general features of this phase diagram and the critical DNA volume fraction for formation of the anisotropic phase are consistent with the observed and theoretically predicted phase behavior of rodlike or semirigid nonelectrolyte polymers.

Rill, R.L.

1986-01-01

366

Topological Phase Transition without Gap Closing

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

Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

2013-01-01

367

Magnetoelastic effects on antiferromagnetic phase transitions (invited)

NASA Astrophysics Data System (ADS)

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 CoF2, FeF2, MnF2, and ?Fe2O3, as well as in mixed crystals with the same structures. Strain gradients may produce similar effects in other antiferromagnets which are magnetoelectric, including DyPO4, DyAlO3, and Cr2O3.

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

1988-04-01

368

Condensation of lattice defects and melting transitions in quantum Hall phases

NASA Astrophysics Data System (ADS)

Motivated by recent progress in understanding the interplay between lattice and electronic topological phases, we consider quantum-melting transitions of weak quantum liquid crystals, a crystal and a nematic phase, in which electrons form a quantum Hall state. In certain classes of Chern band insulators and quantum Hall phases, it has been previously demonstrated that there are topological Chern-Simons terms such as a Hall viscosity term and a gravitational Chern-Simons term for local lattice deformations. The Chern-Simons terms can induce anyonic statistics for the topological lattice defects and, furthermore, dress the defects with certain symmetry quantum numbers. On the other hand, the melting transitions of such liquid-crystalline orders are driven by the condensation of lattice defects. Based on these observations, we show how the topological terms can change the nature of the proximate disordered phases of the quantum liquid-crystalline phases. We derive and study the effective dual field theories for the liquid-crystalline phases with the geometric Chern-Simons terms, and carefully examine the symmetry quantum numbers and statistics of defects. We show that a crystal may go through a continuous phase transition into another crystal with the different discrete translational symmetries because the dislocation, the topological defect in the crystal, carries nonzero crystal momentum due to the Hall viscosity term. For the nematic phase, the disclination will condense at the phase transition to the isotropic phase, and we show that the isotropic phase may support a deconfined fractionally charged excitation due to the Wen-Zee term, and thus the isotropic phase and the nematic phase have different electromagnetic Hall responses.

Cho, Gil Young; Parrikar, Onkar; You, Yizhi; Leigh, Robert G.; Hughes, Taylor L.

2015-01-01

369

Phase transition in strongly stretched polymer gels

NASA Astrophysics Data System (ADS)

We will present the volume phase transition of cylindrical poly N-isopropylacrylamide (NIPA) gels under large distortion along the uniaxial direction. The neutral and slightly ionized NIPA gels were synthesized in submillimeter diameter. The gel was stretched along the uniaxial direction with the longitudinal deformation ratio, ?? (the ratio of the stretched length to the equilibrium length in the swollen state at 30 °C). By keeping the longitudinal length constant, we have simultaneously measured the equilibrium diameter and the force as functions of temperature. The swelling curves of the neutral NIPA gels including the volume phase transition temperature were obtained for several deformations in the range between ??=1 and ??=6. With increasing ??, the transition temperature increased up to 1 °C in the small deformation below ??˜3.5, and it saturated and slightly decreased in the large ?? above ??˜4. At the transition temperature on heating, the force to keep the length constant increased discontinuously in the smaller region below ??˜3.5. The magnitude of this steplike change in the force began to decrease in the vicinity of ??˜3.5, and hereafter exhibited negative change above ??˜4. In the case of the slightly ionized NIPA gels, these effects came into play at an earlier stage, that is, at smaller ??, because of the prestretching due to the ionic pressure. The present observations, especially for the strong deformation above ??˜4, were discussed by the equation of states of strongly stretched hydrophobic gels on the basis of the extended Flory-type free energy taken into account the non-Gaussian effect.

Suzuki, A.; Sanda, K.; Omori, Y.

1997-10-01

370

Ionic liquid-modified stationary phases are an important class of stationary phase. They have been shown a capability of separating various classes of compounds in HPLC. In this review, we focus on the preparation and application of ionic liquid-modified stationary phases in HPLC. First, two common theories of retention mechanism in the ionic liquid-modified stationary phases in HPLC were discussed. Then,

Jun Zhou; Wentao Bi; Kyung-Ho Row

2011-01-01

371

Ionic liquid-modified stationary phases are an important class of stationary phase. They have been shown to have a capability of separating various classes of compounds in HPLC. In this review, we focus on the preparation and application of ionic liquid-modified stationary phases in HPLC. First, two common theories of retention mechanism in the ionic liquid-modified stationary phases in HPLC were

Wentao Bi; Jun Zhou; Kyung-Ho Row

2012-01-01

372

Swarms, phase transitions, and collective intelligence

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.

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

1992-12-31

373

Swarms, phase transitions, and collective intelligence

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.

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

1992-01-01

374

Colloidal gas-liquid transition: tuning nucleation and growth by Critical Casimir forces

NASA Astrophysics Data System (ADS)

The nucleation and growth of the liquid phase has been well studied in simulations, but direct experimental observations remain challenging. Here we present a detailed study of the colloidal gas-liquid transition induced by Critical Casimir forces that allow direct control over particle interactions via temperature-dependent solvent fluctuations. We show that with the direct control over particle interactions we can ``freeze'' a dilute colloidal gas into a dense colloidal liquid. By using dynamic light scattering to follow the evolution of liquid aggregates we observe three clearly distinct regimes: nucleation, interface limited- and diffusion limited growth. We elucidate these regimes directly in real space by using confocal microscopy. In the nucleation regime, we determine the Gibbs free energy, interfacial tension and chemical potential of the liquid aggregates directly from their size distribution. In the growth regime, we can directly follow the attachment of particles, and the collapse of liquid aggregates to large drops. Our critical Casimir colloidal system allows us to control all stages of nucleation and growth with temperature, thereby providing unprecedented insight into this gas-liquid transition.

Nguyen, Duc; Schall, Peter

2012-02-01

375

Chiral Phase Transition from String Theory

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.

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

2006-09-15

376

Black Hole Instabilities and Phase Transitions

NASA Astrophysics Data System (ADS)

Generalised black holes have a horizon given by an arbitrary Einstein manifold. I review a criterion for the classical stability of these black holes. Roughly, spherical horizons are stable but lemon-shaped horizons can be unstable. In Anti-de Sitter space these black holes are dual to gauge theory on a curved background given by the same Einstein manifold. The dual thermal field theory effect is a novel phase transition induced by inhomogeneous Casimir pressures and characterised by a "condensation of pressure".

Hartnoll, Sean

377

Chiral phase transition from string theory.

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

Parnachev, Andrei; Sahakyan, David A

2006-09-15

378

Transient liquid phase bonding of intermetallics

NASA Astrophysics Data System (ADS)

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.

Guan, Yimin

379

Prediction of Orientational Phase Transition in Boron , W. P. Huhna

Prediction of Orientational Phase Transition in Boron Carbide M. Widoma, , W. P. Huhna a-268-7645 Abstract The assessed binary phase diagram of boron-carbon exhibits a single intrinsi- cally disordered on carbon content. Keywords: Boron carbide, B4C, B13C2, phase diagram, orientational phase transition

Widom, Michael

380

Topological phase transitions in superradiance lattices

The discovery of the quantum Hall effect (QHE) reveals a new class of matter phases, topological insulators (TI's), which have been extensively studied in solid-state materials and recently in photonic structures, time-periodic systems and optical lattices of cold atoms. All these topological systems are lattices in real space. Our recent study shows that Scully's timed Dicke states (TDS) can form a superradiance lattice (SL) in momentum space. Here we report the discovery of topological phase transitions in a two-dimensional SL in electromagnetically induced transparency (EIT). By periodically modulating the three EIT coupling fields, we can create a Haldane model with in-situ tunable topological properties. The Chern numbers of the energy bands and hence the topological properties of the SL manifest themselves in the contrast between diffraction signals emitted by superradiant TDS. The topological superradiance lattices (TSL) provide a controllable platform for simulating exotic phenomena in condensed matte...

Wang, Da-Wei; Yuan, Luqi; Liu, Ren-Bao; Zhu, Shi-Yao

2015-01-01

381

Miscellaneous results on the electroweak phase transition

NASA Astrophysics Data System (ADS)

We present new 4 — D Monte Carlo results characterizing the strength of the finite temperature phase transition for Higgs/W mass ratios 1.0 and 0.6, obtained on isotropic lattices mainly with Ns= 16, Nt = 2. We discuss the distribution of an gauge invariant block spin order parameter, estimating the Higgs condensate c at T c. We use the Potvin/Rebbi method in order to find the interface tension ?/ T 3c. We demonstrate how the multi-histogram method (giving free energy differences) can be used to avoid the limiting procedure ??? 0. From pure-phase histograms at ?c, extrapolated with the help of this method, we estimate the latent heat ? ?/ T c4. Actual time series at lower Higgs mass require blocking in order to determine the jump of the lattice observables.

Ilgenfritz, E.-M.; Schiller, A.

1995-04-01

382

Phase equilibria and modeling of ammonium ionic liquid, C2NTf2, solutions.

Novel quaternary ammonium ionic liquid, ethyl(2-hydroxyethyl)dimethylammonium bis(trifluomethylsulfonyl)imide (C2NTf2), has been prepared from N,N-dimethylethanolamine as a substrate. The paper includes a specific basic characterization of the synthesized compound by NMR and the basic thermophysical properties: the melting point, enthalpy of fusion, enthalpy of solid-solid phase transition, glass transition determined by the differential scanning calorimetry (DSC), temperature of decomposition, and water content. The density of the new compound was measured. The solid-liquid or liquid-liquid phase equilibria of binary mixtures containing {C2NTf2+water or an alcohol (propan-1-ol, butan-1-ol, hexan-1-ol, octan-1-ol, decan-1-ol), aromatic hydrocarbons (benzene, toluene), aliphatic hydrocarbons (n-hexane, n-octane), dimethylsulfoxide (DMSO), or tetrahydrofuran (THF)} have been measured by a dynamic method in a wide range of temperatures from 230 to 430 K. These data were correlated by means of the nonrandom two-liquid (NRTL) equation utilizing temperature-dependent parameters derived from the solid-liquid or liquid-liquid equilibrium. From the solubility results, the negative value of the partition coefficient of ionic liquid in binary system octan-1-ol/water (log P) at 298.15 K has been calculated. PMID:18179194

Doma?ska, Urszula; Marciniak, Andrzej; Królikowski, Marek

2008-01-31

383

NASA Astrophysics Data System (ADS)

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.

Dahms, Rainer N.; Oefelein, Joseph C.

2013-09-01

384

CARBON DIOXIDE SEPARATION BY PHASE ENHANCED GAS-LIQUID ABSORPTION

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.

Liang Hu

2004-09-30

385

CARBON DIOXIDE SEPARATION BY PHASE ENHANCED GAS-LIQUID ABSORPTION

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.

Liang Hu; Adeyinka A. Adeyiga

2004-05-01

386

Mechanics and chemical thermodynamics of phase transition in temperature-sensitive hydrogels

NASA Astrophysics Data System (ADS)

This paper uses the thermodynamic data of aqueous solutions of uncrosslinked poly( N-isopropylacrylamide) (PNIPAM) to study the phase transition of PNIPAM hydrogels. At a low temperature, uncrosslinked PNIPAM can be dissolved in water and form a homogenous liquid solution. When the temperature is increased, the solution separates into two liquid phases with different concentrations of the polymer. Covalently crosslinked PNIPAM, however, does not dissolve in water, but can imbibe water and form a hydrogel. When the temperature is changed, the hydrogel undergoes a phase transition: the amount of water in the hydrogel in equilibrium changes with temperature discontinuously. While the aqueous solution is a liquid and cannot sustain any nonhydrostatic stress in equilibrium, the hydrogel is a solid and can sustain nonhydrostatic stress in equilibrium. The nonhydrostatic stress can markedly affect various aspects of the phase transition in the hydrogel. We adopt the Flory-Rehner model, and show that the interaction parameter as a function of temperature and concentration obtained from the PNIPAM-water solution can be used to analyze diverse phenomena associated with the phase transition of the PNIPAM hydrogel. We analyze free swelling, uniaxially and biaxially constrained swelling of a hydrogel, swelling of a core-shell structure, and coexistent phases in a rod. The analysis is related to available experimental observations. Also outlined is a general theory of coexistent phases undergoing inhomogeneous deformation.

Cai, Shengqiang; Suo, Zhigang

2011-11-01

387

Gravitational waves from the electroweak phase transition

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{sup ?4} Hz, and give intensities as high as h{sup 2}?{sub GW} ? 10{sup ?8}.

Leitao, Leonardo; Mégevand, Ariel; Sánchez, Alejandro D., E-mail: lleitao@mdp.edu.ar, E-mail: megevand@mdp.edu.ar, E-mail: sanchez@mdp.edu.ar [IFIMAR (CONICET-UNMdP) Departamento de Física, Facultad de Ciencias Exactas y Naturales, UNMdP, Deán Funes 3350, (7600) Mar del Plata (Argentina)

2012-10-01

388

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

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

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

2014-11-26

389

Phase Transitions in the Assembly of Multi-Valent Signaling Proteins

Cells are organized on length scales ranging from Angstroms to microns. However, the mechanisms by which Angstrom-scale molecular properties are translated to micron-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 micron-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 valency of the interacting species. In the case of the actin regulatory protein, neuronal 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 toward the actin nucleation factor, 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 are likely used to spatially organize and biochemically regulate information throughout biology. PMID:22398450

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.

2012-01-01

390

Liquid-gas transition of neon in quasi-one-dimensional environments

NASA Astrophysics Data System (ADS)

We characterize the behavior of a system of Ne20 atoms in a pure one-dimensional environment between 12 and 30 K by means of path integral Monte Carlo calculations. This is a reasonable model to describe neon absorbed inside a narrow carbon nanotube. When embedded in a bundle of those tubes, this quasi-one-dimensional system can undergo a liquid-gas phase transition if nanotubes are narrow and close enough.

Brualla, L.; Gordillo, M. C.

2003-08-01

391

PHYSICAL REVIEW E 85, 051503 (2012) Fragile-to-strong crossover coupled to the liquid-liquid to the liquid-liquid critical point of the solvent. We find that the fragile-to-strong dynamic transition in the diffusive behavior is always coupled to the low-densityÂhigh-density liquid transition. Above the liquid-liquid

Stanley, H. Eugene

392

Theory of the viscosity of supercooled liquids and the glass transition: Fragile liquids

A statistical mechanical theory is presented for viscosity of relatively low molecular weight organic liquids which are supercooled down to the glass transition temperature. In this theory a relation resembling the Stokes-Einstein relation between the viscosity and self-diffusion coefficient of supercooled liquids and an expression for the self-diffusion coefficient are augmented by a suitably constructed semiempirical generic van der Waals

Kyunil Rah; Byung Chan Eu

2003-01-01

393

A continuous tri-phase transition effect for HIFU-mediated intravenous drug delivery.

Aiming at substantially enhanced efficacy and biosafety of clinical HIFU therapy, a natural solid medium, L-menthol (LM), characteristic of mild and controllable "solid-liquid-gas" (SLG) tri-phase transition, was adopted, instead of those conventional explosive liquid-gas (LG) bi-phase transitional media, in constructing a multifunctional theranostic system. Owing to the continuous and controllable characteristics of SLG tri-phase transition, such a novel tri-phase transition-based theranostic system has been demonstrated of the repeatedly enhanced HIFU efficacy ex vivo and in vivo under once intravenous injection and the significantly improved treatment precision, controllability and biosafety when comparing to the traditional bi-phase transition medium, perfluorohexane (PFH), thus promising great application potential in clinical HIFU treatment. Moreover, this theranostic system has been demonstrated a long blood-circulation lifetime and continuous accumulation in tumor in 24 h, which is very beneficial for the enhanced tumor ablation in vivo along with SLG tri-phase transition. More importantly, after loading multiple model drugs and real drug, such a theranostic system presents a HIFU-mediated temperature-responsive drug release property, and depending on the versatile miscibility of LM, co-loadings with hydrophobic and hydrophilic drugs are also achieved, which provides the possibility of synergistic treatment combining HIFU therapy and chemotherapy. PMID:24746229

Zhang, Kun; Chen, Hangrong; Li, Faqi; Wang, Qi; Zheng, Shuguang; Xu, Huixiong; Ma, Ming; Jia, Xiaoqing; Chen, Yu; Mou, Juan; Wang, Xia; Shi, Jianlin

2014-07-01

394

Understanding the problem of glass transition on the basis of elastic waves in a liquid

We propose that the properties of glass transition can be understood on the basis of elastic waves. Elastic waves originating from atomic jumps in a liquid propagate local expansion due to the anharmonicity of interatomic potential. This creates dynamic compressive stress, which increases the activation barrier for other events in a liquid. The non-trivial point is that the range of propagation of high-frequency elastic waves, $d_{\\rm el}$, increases with liquid relaxation time $\\tau$. A self-consistent calculation shows that this increase gives the Vogel-Fulcher-Tammann (VFT) law. In the proposed theory, we discuss the origin of two dynamic crossovers in a liquid: 1) the crossover from exponential to non-exponential and from Arrhenius to VFT relaxation at high temperature and 2) the crossover from the VFT to a more Arrhenius-like relaxation at low temperature. The corresponding values of $\\tau$ at the two crossovers are in quantitative parameter-free agreement with experiments. The origin of the second crossover allows us to reconcile the ongoing controversy surrounding the possible divergence of $\\tau$. The crossover to Arrhenius relaxation universally takes place when $d_{\\rm el}$ reaches system size, thus avoiding divergence and associated theoretical complications such as identifying the nature of the phase transition and the second phase itself. Finally, we discuss the effect of volume on $\\tau$ and the origin of liquid fragility.

Kostya Trachenko; V. V. Brazhkin

2009-08-27

395

Predictions of Phase Distribution in Liquid–Liquid Two-Component Flow

Ground-based liquid–liquid two-component flow can be used to study reduced-gravity gas-liquid two-phase flows provided that\\u000a the two liquids are immiscible with similar densities. In this paper, we present a numerical study of phase distribution in\\u000a liquid–liquid two-component flows using the Eulerian two-fluid model in FLUENT, together with a one-group interfacial area\\u000a transport equation (IATE) that takes into account fluid particle

Xia Wang; Xiaodong Sun; Walter M. Duval

2011-01-01

396

Glass transition in biomolecules and the liquid-liquid critical point of water

Using molecular dynamics simulations, we investigate the relation between the dynamic transitions of biomolecules (lysozyme and DNA) and the dynamic and thermodynamic properties of hydration water. We find that the dynamic transition of the macromolecules, sometimes called a ``protein glass transition'', occurs at the temperature of dynamic crossover in the diffusivity of hydration water, and also coincides with the maxima of the isobaric specific heat $C_P$ and the temperature derivative of the orientational order parameter. We relate these findings to the hypothesis of a liquid-liquid critical point in water. Our simulations are consistent with the possibility that the protein glass transition results from crossing the Widom line, which is defined as the locus of correlation length maxima emanating from the hypothesized second critical point of water.

P. Kumar; Z. Yan; L. Xu; M. G. Mazza; S. V. Buldyrev; S. -H. Chen; S. Sastry; H. E. Stanley

2006-08-28

397

Size and phase control of cubic lyotropic liquid crystal nanoparticles.

The effective use of lyotropic liquid crystalline dispersions, such as cubosomes, as drug delivery vehicles requires that they have tailored physical characteristics that suit specific therapeutics and external conditions. Here, we have developed phytantriol-based cubosomes from a dispersion of unilamellar vesicles and show that we can control their size as well as the critical packing parameter (CPP) of the amphiphilic bilayer through regulation of temperature and salt concentration, respectively. Using the anionic biological lipid 1,2-dipalmi-toylphosphatidylserine (DPPS) to prevent the cubic phase from forming, we show that the addition of phosphate buffered saline (PBS) results in a transition from small unilamellar vesicles to the cubic phase due to charge-shielding of the anionic lipid. Using dynamic light scattering, we show that the cubosomes formed following the addition of PBS are as small as 30 nm; however, we can increase the average size of the cubsosomes to create an almost monodisperse dispersion of cubosomes through cooling. We propose that this phenomenon is brought about through the phase separation of the Pluronic F-127 used to stabilize the cubosomes. To complement previous work using the salt-induced method of cubosome production, we show, using synchrotron small-angle X-ray scattering (SAXS), that we can control the CPP of the amphiphile bilayer which grants us phase and lattice parameter control of the cubosomes. PMID:24915497

Hartnett, Terence E; Ladewig, Katharina; O'Connor, Andrea J; Hartley, Patrick G; McLean, Keith M

2014-07-01

398

Magnetic Quantum Phase Transition in an Anisotropic Kondo Lattice

The quantum phase transition between paramagnetic and antiferromagnetic phases of the Kondo lattice model with Ising anisotropy in the intersite exchange is studied within extended dynamical mean-field theory. Nonperturbative numerical solutions at zero temperature point to a continuous transition for both two- and three-dimensional magnetism. In the former case, the transition is associated with critical local physics, characterized by a

Matthew T. Glossop; Kevin Ingersent

2007-01-01

399

Coal-Face Fracture With A Two-Phase Liquid

NASA Technical Reports Server (NTRS)

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

Collins, E. R., Jr.

1985-01-01

400

In this paper, liquid phase selective hydrogenation of furfural on Raney nickel which has been modified by impregnation of salts (including alkali metals, alkaline earth metals, and transition metals) of heteropolyacids (HPAs) having Keggin type structure was studied. Effects of reaction conditions on catalytic activity and selectivity were examined. It has been found that all Raney nickel catalysts modified with

Liu Baijun; Lu Lianhai; Wang Bingchun; Cai Tianxi; Katsuyoshi Iwatani

1998-01-01

401

Continuous or catastrophic solid-liquid transition in jammed systems

NASA Astrophysics Data System (ADS)

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.

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

2005-01-01

402

New type of two-dimensional phase transition

NASA Astrophysics Data System (ADS)

A first-order phase transition in a Cu double layer on a Mo(110) surface in which the orientation of the interfacial misfit dislocations changes by 90° is reported. The transition shows considerable hysteresis. The analysis of the transition and of an irreversible transition preceding it suggests that the core of the misfit dislocations is partially empty.

Tikhov, M.; Stolzenberg, M.; Bauer, E.

1987-12-01

403

The process of conversion of large multilamellar vesicles (MLVs) of dimyristoylphosphatidylcholine (DMPC) into the final state of small unilamellar vesicles (SUVs) with an increase in time length of ultrasonic irradiation was investigated by calorimetry and negative-stain electron microscopy. The process was found out to be composed of two stages depending on the primary (near 24 degrees C) and secondary (near 19 degrees C) peaks due to the gel-to-liquid crystal phase (Tm) transition, respectively; a new transition peak for the secondary Tm appears after a maximum broadening of the primary Tm peak is attained. Sonicated vesicles characterized by the primary peak of the broadest shape were observed to be about 200 nm in mean diameter and mostly four or so lamellae, and have an internal aqueous space, in contrast to sonicated SUVs (approx. 40 nm in diameter) characterized by the limiting secondary Tm peak. Thermal data associated with the Tm transition for these two sonicated vesicles were compared with that of the MLV. The enthalpy and entropy changes and cooperative units increased in the order sonicated SUV < sonicated large vesicle < MLV. Furthermore, the enthalpy changes were revealed to fairly differ between the sonicated large vesicle and SUV. Based on the effect of the annealing treatment at -5 degrees C on these vesicles the present result suggested a large contribution of the aggregation state of DMPC molecules to the enthalpy possessed by the vesicles of a gel phase temperature, which is related to the mode of the Tm transitions, primary and secondary. PMID:8334155

Kodama, M; Miyata, T; Takaichi, Y

1993-07-21

404

Experimental liquid–liquid phase diagrams are presented for the multicomponent systems isooctane–benzene–(80mass% methanol+20mass% water)–5mass% isobutyl alcohol (2-methyl-1-propanol) and isooctane–benzene–(80mass% methanol+20mass% water)–15mass% isobutyl alcohol, at 298.15K. The density and interfacial tension of conjugate phases of concentration located in the isothermal binodal have been determined at 298.15K for the partially miscible systems: isooctane–benzene–methanol, isooctane–benzene–(80mass% methanol+20mass% water), isooctane–benzene–(80mass% methanol+20mass% water)–5mass% isobutyl alcohol, and isooctane–benzene–(80mass%

Blanca Estela García-Flores; Arturo Trejo; Jacinto Águila-Hernández

2007-01-01

405

Phase Separation in Tungsten Transition Edge Sensors

NASA Astrophysics Data System (ADS)

To optimize the signal efficiency in detectors utilizing Transition Edge Sensor (TES) technology we have fabricated and characterized test devices which approximate the electrical and thermal properties of the tungsten TES parallel arrays used for the Cryogenic Dark Matter Search (CDMS) phonon sensors. We measure the equilibrium power as a function of bias voltage by sweeping the bias current through the TES array and measuring the resulting current through the sensor. Our results are in agreement with previous estimates of the critical length for a TES to separate into superconducting and normal phases. However, we found that the presence of the tungsten sections, which connect the TES to the aluminum fins, significantly shortens the critical length for the onset of phase separation, and indicate that many CDMS phonon sensors have operated with phase separated TESs. We have also improved the determination of the electron-phonon coupling in our tungsten films to be (0.32±0.02)×109W/m3K5. Finally, we also found that the thermal conductance between the tungsten electron and phonon systems does not scale linearly with added fin connector volume, instead ˜75% of added volume contributes.

Hart, S. J.; Pyle, M.; Yen, J. J.; Young, B. A.; Brink, P. L.; Cabrera, B.; Cherry, M.; Mirabolfathi, N.; Sadoulet, B.; Seitz, D.; Sundqvist, K.; Tomada, A.

2009-12-01

406

Phase transitions in biogenic amorphous calcium carbonate

NASA Astrophysics Data System (ADS)

Geological calcium carbonate exists in both crystalline phases and amorphous phases. Compared with crystalline calcium carbonate, such as calcite, aragonite and vaterite, the amorphous calcium carbonate (ACC) is unstable. Unlike geological calcium carbonate crystals, crystalline sea urchin spicules (99.9 wt % calcium carbonate and 0.1 wt % proteins) do not present facets. To explain this property, crystal formation via amorphous precursors was proposed in theory. And previous research reported experimental evidence of ACC on the surface of forming sea urchin spicules. By using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), we studied cross-sections of fresh sea urchin spicules at different stages (36h, 48h and 72h after fertilization) and observed the transition sequence of three mineral phases: hydrated ACC ? dehydrated ACC ? biogenic calcite. In addition, we unexpectedly found hydrated ACC nanoparticles that are surrounded by biogenic calcite. This observation indicates the dehydration from hydrated ACC to dehydrated ACC is inhibited, resulting in stabilization of hydrated ACC nanoparticles. We thought that the dehydration was inhibited by protein matrix components occluded within the biomineral, and we designed an in vitro assay to test the hypothesis. By utilizing XANES-PEEM, we found that SM50, the most abundant occluded matrix protein in sea urchin spicules, has the function to stabilize hydrated ACC in vitro.

Gong, Yutao

407

QCD PHASE TRANSITIONS-VOLUME 15.

The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some. efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.

SCHAFER,T.

1998-11-04

408

Smooth phase transitions in the early universe

We apply a quadratic teleparallel torsion scalar of the $f(T)=T+\\alpha T^{2}$ field equations to the flat FRW model. We assume two perfect fluid components, the matter component has a fixed equation of state (EoS), while the torsion component has a dynamical EoS. We obtain an effective scale factor allowing an early stage of an inflationary vacuum, while it pushes the inflation to end naturally at later stage turning the universe to a matter dominant phase. The model represents an alternative to inflation models. However, it does not require slow roll conditions to end the inflation phase. We perform a standard cosmological study to examine the cosmic evolution. In addition, we study the effective EoS. The study shows consistent results confirming a smooth phase transition from inflation to matter dominant universe. We consider the case when the torsion is made of a scalar field. This treatment enables us to study the quadratic effect of $f(T)$ on the potential patterns of the scalar field. At the limit $\\alpha \\rightarrow 0$ the potential is dominated by the kinetic term and coincides with the quadratic inflation. Both cosmological and scalar field analysis show consistent results.

G. G. L. Nashed; W. El Hanafy; Sh. Kh. Ibrahim

2014-11-09

409

Fragile to strong crossover coupled to liquid-liquid transition in hydrophobic solutions

Using discrete molecular dynamics simulations we study the relation between the thermodynamic and diffusive behaviors of a primitive model of aqueous solutions of hydrophobic solutes consisting of hard spheres in the Jagla particles solvent, close to the liquid-liquid critical point of the solvent. We find that the fragile-to-strong dynamic transition in the diffusive behavior is always coupled to the low-density/high-density liquid transition. Above the liquid-liquid critical pressure, the diffusivity crossover occurs at the Widom line, the line along which the thermodynamic response functions show maxima. Below the liquid-liquid critical pressure, the diffusivity crossover occurs when the limit of mechanical stability lines are crossed, as indicated by the hysteresis observed when going from high to low temperature and vice versa. These findings show that the strong connection between dynamics and thermodynamics found in bulk water persists in hydrophobic solutions for concentrations from low to moderate, indicating that experiments measuring the relaxation time in aqueous solutions represent a viable route for solving the open questions in the field of supercooled water.

D. Corradini; P. Gallo; S. V. Buldyrev; H. E. Stanley

2012-05-07

410

Metastable phase formation in undercooled liquid lead alloys

NASA Technical Reports Server (NTRS)

During non-equilibrium processes metastable phases are formed instead of stable phases due to the operation of various kinetic or structural constraints. By removing the most effective nucleation sites for the stable phase using emulsified droplet samples, stable phase formation can be prohibited in a broad range of undercooling and the phase space available in the metastable regime can be mapped out. With this method the thermodynamic properties of the undercooled liquid and the metastable phase boundaries corresponding to reversible metastable (solid + liquid) phase equilibria are examined from experimental data. The analysis reveals important implications for the nucleation kinetics and the choice of the kinetically most favored solidification path.

Fecht, Hans J.

1991-01-01

411

Role of liquid crystal in the emulsification of a gel emulsion with high internal phase fraction.

A gel emulsion with high internal oil phase volume fraction was formed via an inversion process induced by a water-oil ratio change. The process involved the formation of intermediate multiple emulsions prior to inversion. The multiple emulsions contain a liquid crystal formed by the surfactant with water; this was both predicted by the equilibrium phase diagram as well as observed using polarization microscopy. These multiple emulsions were more stable compared to alternative multiple emulsions prepared in the same way with a surfactant that does not form liquid crystals. While the formation of a stable intermediate multiple emulsion may not be a necessary condition for the inversion to occur, the transitional presence of a liquid crystal proved to be a significant factor in the stabilization of the intermediate multiple emulsions. The resulting gel emulsion contained a small fraction of the liquid crystal according to the phase diagram, and it exhibited excellent stability. PMID:19781712

Liu, Yihan; Friberg, Stig E

2009-12-15

412

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

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

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

2012-10-14

413

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

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.

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

414

Quantum Phase Transitions and the Breakdown of Classical General Relativity

It is proposed that the event horizon of a black hole is a quantum phase transition of the vacuum of space-time analogous to the liquid-vapor critical point of a bose fluid. The equations of classical general relativity remain valid arbitrarily close to the horizon yet fail there through the divergence of a characteristic coherence length. The integrity of global time, required for conventional quantum mechanics to be defined, is maintained. The metric inside the event horizon is different from that predicted by classical general relativity and may be de Sitter space. The deviations from classical behavior lead to distinct spectroscopic and bolometric signatures that can, in principle, be observed at large distances from the black hole.

G. Chapline; E. Hohlfeld; R. B. Laughlin; D. I. Santiago

2000-12-25

415

A Susy Phase Transition as Central Engine

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.

L. Clavelli

2005-01-10

416

A transition index for rock failure due to liquid impact

Impingement of rocks by liquid projectiles causes the erosion of structures, but is also the principal process for non-traditional drilling and cutting methods, such as hydrodemolition, hydrodynamic fragmentation, and cavitating drilling. Based on loading and failure analyses, an elastic–plastic transition condition is proposed which is characterised by a toughness-strength-index, KIc2\\/(?C3cM); here KIc is the fracture toughness, ?c is the compressive

A. W. Momber

2006-01-01

417

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

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

2014-12-01

418

Topological and geometrical aspects of phase transitions

NASA Astrophysics Data System (ADS)

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.

Santos, F. A. N.; Rehn, J. A.; Coutinho-Filho, M. D.

2014-03-01

419

Liquid Crystals: The Phase of the Future.

ERIC Educational Resources Information Center

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.…

Ondris-Crawford, Renate; And Others

1992-01-01

420

Gravitational waves from global second order phase transitions

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.

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

421

Quantum phase transitions beyond the Landau paradigm in a Sp(4) spin system

NASA Astrophysics Data System (ADS)

We propose quantum phase transitions beyond the Landau’s paradigm of Sp(4) spin Heisenberg models on the triangular and square lattices motivated by the exact Sp(4)?SO(5) symmetry of spin-3/2 fermionic cold atomic system with only s -wave scattering. On the triangular lattice, we study a phase transition between the 3×3 spin ordered phase and a Z2 spin liquid phase; this phase transition is described by an O(8) sigma model in terms of fractionalized spinon fields, with significant anomalous scaling dimensions of spin order parameters. On the square lattice, we propose a deconfined critical point between the Neel order and the valence bond solid (VBS) order, which is described by the CP(3) model, and the monopole effect of the compact U(1) gauge field is expected to be suppressed at the critical point.

Qi, Yang; Xu, Cenke

2008-07-01

422

Crystal templating through liquid-liquid phase separation.

Controlled induction of crystal nucleation is a highly desirable but elusive goal. Attempts to speed up crystallization, such as high super saturation or working near a liquid-liquid critical point, always led to irregular and uncontrollable crystal growth. Here, we show that under highly nonequilibrium conditions of spinodal decomposition, water crystals grow as thin wires in a template-less formation of "Haareis". This suggests that such nonequilibrium conditions may be employed more widely as mechanisms for crystal growth control. PMID:25466237

Mosses, Joanna; Turton, David A; Lue, Leo; Sefcik, Jan; Wynne, Klaas

2015-01-21

423

In chiral smectic-A (Sm-A) liquid crystals, an applied electric field induces a tilt of the optic axis from the layer normal. When these materials are of the de Vries type, the electroclinic tilt susceptibility is unusually large, with the field-induced director reorientation accompanied by a substantial increase in optical birefringence with essentially no change in the smectic layer spacing. In order to account for the observed electro-optic behavior, we assume that the molecular orientation distribution in the Sm-A has two degrees of freedom: azimuthal orientation and tilt of the molecular long axis from the layer normal, with the tilt confined to a narrow range of angles. We present a generalized Langevin-Debye model of the response of this orientational distribution to applied field that gives a field-induced optic axis tilt, birefringence, and polarization dependence that agrees well with experimental measurements and reproduces the double-peaked polarization current response characteristic of a first-order Sm-A(*)-Sm-C(*) transition. Additionally, we find that the measured field-induced polarization and the Langevin-Debye model predictions can be quantitatively described as pre-transitional behavior near the tricritical point of a recently published generalized 3D XY model of interacting hard rods confined to reorient on a cone in the presence of an applied field. PMID:24483465

Shen, Yongqiang; Wang, Lixing; Shao, Renfan; Gong, Tao; Zhu, Chenhui; Yang, Hong; Maclennan, Joseph E; Walba, David M; Clark, Noel A

2013-12-01

424

Cluster-liquid transition in finite saturated fermionic systems

The role of saturation for cluster formation in finite systems such as atomic nuclei is analyzed by considering three length-scale ratios, and performing deformation-constrained self-consistent mean-field calculations. The effect of clusterisation in deformed light systems is related to the saturation property of the inter-nucleon interaction. The formation of clusters at low nucleon density is illustrated by expanding the radius of $^{16}$O. A phase diagram shows that the formation of clusters can be interpreted as a hybrid state between the crystal and the liquid phases. In the hybrid cluster phase the confining potential attenuates the delocalization generated by the effective nuclear interaction.

Jean-Paul Ebran; Elias Khan; Tamara Niksic; Dario Vretenar

2014-02-20

425

Pressure-Induced Electronic Phase Transitions Transition Metal Oxides and Rare Earth Metals

Pressure-Induced Electronic Phase