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1

Phase transitions in superconductor liquid crystals  

E-print Network

We study properties of phase transitions of 2D superconductor liquid crystal phases, and analyze the competition between the recently proposed Pair Density Wave (PDW) and nematic $4e$ superconductor ($4e$SC). Nematic fluctuations enhance the $4e$SC and suppress the PDW phase. In the absence of lattice effects, the PDW state exists only at T=0 and the low temperature phase is a nematic $4e$SC with short ranged PDW order. A geometric description of the $4e$ SC is presented.

Daniel G. Barci; Eduardo Fradkin

2010-05-11

2

Spin liquids, exotic phases and phase transitions  

E-print Network

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

Ran, Ying

2007-01-01

3

Phase transitions of liquid water at nanoscale  

NASA Astrophysics Data System (ADS)

The behaviour of fluids confined within nanometric pores significantly differs from that of the bulk. The effect of confinement, surface forces, and reduced dimension is to shift the phase transitions of the confined fluid (condensation, freezing and crystallisation). By postponing or avoiding the inconvenient crystallization process it is often suggested that confinement allows a deeper penetration into the supercooled regime and helps in the understanding the glass formation; in the case of water, confinement might helps to extend the liquid state into the so-called ``no-man's land.'' However below confining conditions of about 10?, ? being the size of the molecule, water or van der Waals liquids are strongly perturbed by the presence of a surface. Thus a question always remains whether the confined liquid, water or any other fluid, is an extension of the ``bulk'' supercooled regime or refers to specific behavior controlled by external parameters such as the size and the surface interactions imposed to the system. Despite the obvious fundamental interest in understanding bulk water, this situation corresponds to most of the cases in biological and geological systems and deserves particular attention per se. However a prerequisite is to understand and quantify how pores are filled and how much; so we studied the processes of entrance and saturation to a pore (adsorption, imbibition and intrusion) in connection with the structure and the local dynamics of liquid water. Then, we will present new experimental results on the thermodynamic, structural and vibrational properties of water confined within nanometric pores (size of a few molecular diameters).

Alba-Simionesco, Christiane

2013-03-01

4

Fission and Nuclear Liquid-Gas Phase Transition  

E-print Network

The temperature dependence of the liquid-drop fission barrier is considered, the critical temperature for the liquid-gas phase transition in nuclear matter being a parameter. Experimental and calculated data on the fission probability are compared for highly excited $^{188}$Os. The calculations have been made in the framework of the statistical model. It is concluded that the critical temperature for the nuclear liquid--gas phase transition is higher than 16 MeV.

E. A. Cherepanov; V. A. Karnaukhov

2007-03-30

5

Liquid crystal phase transition in large grown micelles  

SciTech Connect

Various theories of the phase transition from isotropic fluid to nematic liquid crystalline phase in systems of anisotropic particles in solution are reviewed. It is found that a knowledge of the flexibility of the ordering objects is critical to determining the concentration at which this phase transition occurs. Measurements of the persistence length, a measure of flexibility, are also discussed. These two results are used to predict where such a phase transition should occur. Finally, preliminary experimental results indicating this phase transition are presented.

Mishic, J.R.; Nash, R.J.; Fisch, M.R. (John Carroll Univ., Cleveland, OH (USA))

1990-05-01

6

The liquid to vapor phase transition in excited nuclei  

SciTech Connect

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

Ultrafast phase transitions in metastable water near liquid interfaces.  

PubMed

Electron spectroscopy for chemical analysis (ESCA) is a powerful tool for the quantitative analysis of the composition and the chemical environment of molecular systems. Due to the lack of compatibility of liquids and vacuum, liquid-phase ESCA is much less well established. The chemical shift in the static ESCA approach is a particularly powerful observable quantity for probing electron orbital energies in molecules in different molecular environments. Employing high harmonics of 800 nm (40 eV), near-infrared femtosecond pulses, and liquid-water microbeams in vacuum we were able to add the dimension of time to the liquid interface ESCA technique. Tracing time-dependent chemical shifts and energies of valence electrons in liquid interfacial water in time, we have investigated the timescale and molecular signatures of laser-induced liquid-gas phase transitions on a picosecond timescale. PMID:19227352

Link, Oliver; Vöhringer-Martinez, Esteban; Lugovoj, Eugen; Liu, Yaxing; Siefermann, Katrin; Faubel, Manfred; Grubmüller, Helmut; Gerber, R Benny; Miller, Yifat; Abel, Bernd

2009-01-01

8

MODELLING AND SIMULATION OF LIQUID-VAPOR PHASE TRANSITION  

E-print Network

by a wall at a fixed temperature Twall (pool boiling). When Twall increases, we switch from a nucleate boiling to a film boiling. Nucleate Boiling Film Boiling source: http://www.spaceflight.esa.int/users/fluids/TT_boilingMODELLING AND SIMULATION OF LIQUID-VAPOR PHASE TRANSITION A Boiling Crisis Study Contribution

Helluy, Philippe

9

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

10

Liquid-gas phase transition in nuclear matter including strangeness  

SciTech Connect

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

Wang, P.; Leinweber, D.B.; Williams, A.G. [Special Research Center for the Subatomic Structure of Matter (CSSM) and Department of Physics, University of Adelaide, Adelaide 5005 (Australia); Thomas, A.W. [Special Research Center for the Subatomic Structure of Matter (CSSM) and Department of Physics, University of Adelaide, Adelaide 5005 (Australia); Jefferson Laboratory, 12000 Jefferson Avenue, Newport News, Virginia 23606 (United States)

2004-11-01

11

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

PubMed Central

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

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

2012-01-01

12

Electrical properties of ferroelectric liquid crystals during thermal phase transition  

NASA Astrophysics Data System (ADS)

The ferroelectric properties of ferroelectric liquid crystals (FLCs) during thermal phase transition in the surface-stabilized ferroelectric liquid crystal (SSFLC) cells were examined. The coercive electric field (Ec) and remanent polarization (Pr) changed with increasing temperature. These temperature-dependent variations of Ec and Pr were in agreement with the differential scanning calorimetry results. Moreover, the fatigue characteristic of the SSFLC cells was examined. No polarized fatigue was observed after 1 × 106 cycles of polarization switching, because FLCs may have the self-repair property for structural and interfacial defects.

Morimoto, Masahiro; Sakaki, Yosuke; Koshiba, Yasuko; Misaki, Masahiro; Ueda, Yasukiyo; Ishida, Kenji

2014-01-01

13

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

PubMed

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

14

Multifragmentation and nuclear phase transitions (liquid-fog and liquid-gas)  

E-print Network

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid-fog phase transition. The charge distributions of the intermediate mass fragments produced in p(3.6 GeV) + Au and p(8.1 GeV) + Au collisions are analyzed within the statistical multifragmentation model with the critical temperature for the nuclear liquid-gas phase transition Tc as a free parameter. The analysis presented here provides strong support for a value of Tc > 15 MeV.

V. A. Karnaukhov; H. Oeschler; S. P. Avdeyev; V. K. Rodionov; A. V. Simomenko; V. V. Kirakosyan; A. Budzanowski; W. Karcz; I. Skwirczynska; E. A. Kuzmin; E. Norbeck; A. S. Botvina

2003-10-10

15

Phase transitions of semiflexible hard-sphere chain liquids Hanif Bayat Movahed,1,2  

E-print Network

liquid and solid phases 1,3­7 . Studies of liquid-crystalline ordering in this model using densityPhase transitions of semiflexible hard-sphere chain liquids Hanif Bayat Movahed,1,2 Raul Cruz liquid-crystalline phase transitions in a fluid of semi- flexible hard-sphere chain molecules based

Sullivan, Donald E.

16

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

17

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

Microsoft Academic Search

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

18

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

19

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

PubMed

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

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

2013-05-14

20

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

PubMed Central

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

Scandolo, Sandro

2003-01-01

21

Isotropic to smectic-C phase transition in liquid-crystalline elastomers.  

PubMed

A phenomenological model is developed to describe the isotropic-smectic-C phase transition in liquid-crystalline side-chain elastomers. We analyze the influence of external mechanical stress on the isotropic-smectic-C phase transition. While this phase transition is first order in low-molecular-weight materials, we show here that the order of this transition does not change in liquid-crystalline elastomers. The temperature dependence of the heat capacity and the nonlinear dielectric effect in the isotropic phase above the isotropic-smectic-C phase transition in liquid crystalline elastomers are calculated. The theoretical results are found to be in good agreement with experiment. PMID:22502545

Mukherjee, Prabir K

2012-04-14

22

Polyamorphism and liquid liquid phase transitions: challenges for experiment and theory  

NASA Astrophysics Data System (ADS)

Phase transitions in the liquid state can be related to pressure-driven fluctuations developed in the density (i.e., the inverse of the molar volume; ? = 1/V) or the entropy (S(T)) rather than by gradients in the chemical potential (?(X), where X is the chemical composition). Experiments and liquid simulation studies now show that such transitions are likely to exist within systems with a wide range of chemical bonding types. The observations permit us to complete the trilogy of expected liquid state responses to changes in P and T as well as ?(X), as is the case among crystalline solids. Large structure-property changes occurring within non-ergodic amorphous solids as a function of P and T are also observed, that are generally termed 'polyamorphism'. The polyamorphic changes can map on to underlying density- or entropy-driven L-L transitions. Studying these phenomena poses challenges to experimental studies and liquid simulations. Experiments must be carried out over a wide P-T range for in situ structure-property determinations, often in a highly metastable regime. It is expected that L-L transitions often occur below the melting line, so that studies encounter competing crystallization phenomena. Simulation studies of liquid state polyamorphism must involve large system sizes, and examine system behaviour at low T into the deeply supercooled regime, with distance and timescales long enough to sample characteristic density/entropy fluctuations. These conditions must be achieved for systems with different bonding environments, that can change abruptly across the polyamorphic transitions. Here we discuss opportunities for future work using simulations combined with neutron and x-ray amorphous scattering techniques, with special reference to the behaviour of two polyamorphic systems: amorphous Si and supercooled Y2O3-Al2O3 liquids. This paper is presented as a contribution to the conference on 'Current Challenges in Liquid and Glass Science' held in Abingdon, UK, January 10-12, 2007 in honour of Spencer Howells.

McMillan, Paul F.; Wilson, Mark; Wilding, Martin C.; Daisenberger, Dominik; Mezouar, Mohamed; Neville Greaves, G.

2007-10-01

23

ccsd-00001067(version2):11Mar2004 Nuclear liquid-gas phase transition and  

E-print Network

ccsd-00001067(version2):11Mar2004 Nuclear liquid-gas phase transition and supernovae evolution J appearing at the onset of the first order nuclear liquid-gas phase transition can play an important role of matter near the proto-neutron star surface. The resulting increase of pressure may induce strong particle

Boyer, Edmond

24

Observation of molecular reorientation at a two-dimensional-liquid phase transition  

SciTech Connect

The structure of a monolayer of pentadecanoic acid near the liquid-expanded--liquid-condensed phase transition at a water-air interface is studied by optical second-harmonic generation. The results show that this transition is accompanied by a reorientation of the molecules and that the two phases are separated by an inhomogeneous coexistence region on the isotherms.

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

1985-12-23

25

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

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

26

Synthesis and Liquid Crystal Phase Transitions of Zirconium Phosphate Disks  

E-print Network

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...

Shuai, Min

2013-05-07

27

Revisiting dynamics near a liquid-liquid phase transition in Si and Ga: The fragile-to-strong transition  

SciTech Connect

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

28

Universality of Holographic Phase Transitions and Holographic Quantum Liquids  

E-print Network

We explore the phase structure for defect theories in full generality using the gauge/gravity correspondence. On the gravity side, the systems are constructed by introducing M (probe) D(p+4-2k)-branes in a background generated by N Dp-branes to obtain a codimension-k intersection. The dual gauge theory is a U(N) Supersymmetric Yang-Mills theory on a (1+p-k)-dimensional defect with both adjoint and fundamental degrees of freedom. We focus on the phase structure in the chemical potential versus temperature plane. We observe the existence of two universality classes for holographic gauge theories, which are identified by the order of the phase transition in the interior of the chemical potential/temperature plane. Specifically, all the sensible systems with no defect show a third order phase transition. Gauge theories on a defect with (p-1)-spatial directions are instead characterised by a second order phase transition. One can therefore state that the order of this phase transition is intimately related to the codimensionality of the defect. We also discuss the massless hypermultiplet at low temperature, where a thermodynamical instability seems to appear for $p<3$. Finally, we comment on such an instability.

Paolo Benincasa

2009-10-31

29

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

E-print Network

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

30

Experimental observation of a transition between two uniaxial nematic liquid-crystal phases  

Microsoft Academic Search

The experimental observation of a phase transition between two uniaxial nematic liquid-crystalline phases is reported. High-resolution x-ray scattering and ac calorimetric studies in binary mixtures of octyl- and decyloxyphenyl-nitrobenzoyloxy benzoates show evidence of a first-order transition between two nematic phases with different types of short-range smectic order. This transition is observed in the vicinity of the termination of the smectic-Ad-smectic-A1

G. Nounesis; Satyendra Kumar; S. Pfeiffer; R. Shashidhar; C. W. Garland

1994-01-01

31

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

E-print Network

Liquid-crystal-anchoring transitions at surfaces created by polymerization-induced phase separation surfaces created by polymerization-induced phase separation is presented. This transition is unusual by considerating enthalpic and entropic contributions to surface energy. Interesting behavior of some polymer-dispersed

Srinivasarao, Mohan

32

Phase diagram and layer-thinning transitions in free-standing liquid crystal films  

NASA Astrophysics Data System (ADS)

In free-standing smectic liquid crystal films, the simultaneous action of finite-size, surface and field effects leads to a very unique scenario concerning a diversity of phase transitions and critical phenomena. Here, we review the main characteristic of this special liquid crystal system, with particular attention to the changes on the bulk phase diagram as the film thins. In particular, we stress the emergence of new phases and special critical points. Further, we discuss the phenomenon of layer-thinning transitions under the light of an extended mean-field theory, emphasizing the similarities and differences between temperature and field induced thinning transitions.

Pereira, Maria S. S.; de Oliveira, Italo N.; Lyra, Marcelo L.

2014-03-01

33

Photo-stimulated phase and anchoring transitions of chiral azo-dye doped nematic liquid crystals.  

PubMed

We report concurring phase and anchoring transitions of chiral azo-dye doped nematic liquid crystals. The transitions are induced by photo-stimulation and stable against light and thermal treatments. Photochromic trans- to cis-isomerization of azo-dye induces an augmented dipole moment and strong dipole-dipole interaction of the cis-isomers, resulting in the formation of nano-sized dye-aggregates. Consequent phase separation of the aggregates of a chiral azo-dye induces phase transition from a chiral to nonchiral nematic phase. In addition, the deposition of dye-aggregates at the surfaces brings about anchoring transition of LC molecules. The stability and irreversibility of the transition, together with no need of pretreatments for LC alignment, provide fascinating opportunity for liquid crystal device applications. PMID:24514707

Kundu, Sudarshan; Kang, Shin-Woong

2013-12-16

34

Liquid-solid phase transition in a heterogeneous system of solid spheres  

Microsoft Academic Search

A molecular dynamics method is used to study the influence of a heavy dispersed particle on a liquid-solid phase transition\\u000a in a molecular system of solid spheres. It is shown that the presence of a dispersed particle shifts the transition toward\\u000a higher densities and pressures. In addition, in the liquid state the heterogeneous system has a lower pressure, whereas in

V. Ya. Rudnyak; A. A. Belkin

1999-01-01

35

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

36

Unexpected field-induced phase transitions between ferrielectric and antiferroelectric liquid crystal structures.  

PubMed

Liquid crystals are intriguing electrically responsive soft matter systems. We report previously unexplored field-induced changes in the structures of some frustrated liquid crystal phases and describe them theoretically. Specifically, we have discovered using resonant x-ray scattering that the four-layer intermediate smectic phase can undergo either a transition to the ferrielectric (three-layer) phase or to the ferroelectric phase, depending on temperature. Our studies of intermediate phases using electric fields offer a way to test theories that describe ferroelectricity in self-assembling fluids. PMID:18351811

Jaradat, S; Brimicombe, P D; Southern, C; Siemianowski, S D; DiMasi, E; Osipov, M; Pindak, R; Gleeson, H F

2008-01-01

37

Organosiloxane supramolecular liquids--surface-energy-driven phase transitions.  

PubMed

Autocondensation of organoalkoxysilanes and subsequent anion exchange produces organosiloxane supramolecular liquids which are core-free and solvent-free nanoparticle nanofluids. This hybrid supramolecular liquid, [C(81)H(156)NO(3)S(SiO([2>x>3/2]))](y), exhibits (see TEM image; 200 nm width) interparticle menisci and softness (from imputed deformations) of interparticle potential. PMID:23341098

Texter, John; Bian, Kejian; Chojnowski, Dan; Byrom, Joe

2013-02-25

38

Relaxations, Fluctuations, Phase Transitions and Chemical Reactions in Liquid Water  

Microsoft Academic Search

Fluctuations and collective motions in liquid water and their effects on chemical reactions dynamics are analyzed. Liquid water is a `frustrated' system with multiple random hydrogen bond network structures, and has anomalous microscopic and macroscopic properties. Rearrangement dynamics of the hydrogen bond network induces collective motions of water molecules and energy fluctuations. Vibrational motions of photoexcited molecules strongly resonate to

Iwao Ohmine; Masaki Sasai

1991-01-01

39

Liquid-gas Phase Transition in Strange Hadronic Matter with Weak Y-Y Interaction  

E-print Network

The liquid-gas phase transition in strange hadronic matter is reexamined by using the new parameters about the $\\Lambda - \\Lambda$ interaction deduced from recent observation of $^{6}_{\\Lambda\\Lambda}He$ double hypernucleus. The extended Furnstahl-Serot-Tang model with nucleons and hyperons is utilized. The binodal surface, the limit pressure, the entropy, the specific heat capacity and the Caloric curves are addressed. We find that the liquid-gas phase transition can occur more easily in strange hadronic matter with weak Y-Y interaction than that of the strong Y-Y interaction.

Li Yang; Shao Yu Yin; Wei Liang Qian; Ru-keng Su

2005-06-19

40

Weakly first-order character of the nematic-isotropic phase transition in liquid crystals  

NASA Astrophysics Data System (ADS)

The classification of phase transitions in first-order and second-order (or continuous) ones is widely used. The nematic-to-isotropic (NI) transition in liquid crystals is a weakly first-order transition, with only small discontinuities in enthalpy and specific volume at the transition which are not always easy to measure. On the other hand, fluctuation effects near the transition, typical for a continuous transition, are present because of the only weakly first-order character. In a recent paper [Phys. Rev. E 69, 022701 (2004)], it was concluded from the static dielectric permittivity in the isotropic phase near the NI transition that less polar mesogens (with little or no pretransitional effects) are characteristic for a first-order NI phase transition, whereas in the case of strongly polar ones (with large pretransitional effects) the NI transition is close to second order. In this paper, we address the question whether it is, indeed, possible to use these fluctuation effects in the isotropic phase to quantify the “strength” of a weakly first-order transition, i.e., how far it is from second order. Therefore, we measured the temperature dependence of the enthalpy near the NI transition of seven liquid crystals with adiabatic scanning calorimetry and compared the measured values of the latent heat with pretransitional effects in the dielectric constant and the specific heat capacity. The compounds used in the comparison are MBBA, 5CB, 8CB, 5NCS, 5CN, 8CHBT, and D7AB. From our analysis we find, contrary to the assertion in the above reference, no correlation between the strength of the NI transition of a given compound and the pretransitional effects observed, neither dielectrically, nor thermally.

van Roie, B.; Leys, J.; Denolf, K.; Glorieux, C.; Pitsi, G.; Thoen, J.

2005-10-01

41

O the Nature of the Smectic-A Phase Transition of Liquid Crystals  

Microsoft Academic Search

An ac calorimeter technique has been employed to carry out high resolution heat capacity and thermal conductivity measurements on liquid crystal compounds which exhibit the smectic-A-hexatic-B phase transition. Heat capacity measurements on compounds members of the homologous series n-alkyl-4^'-n-alkoxybiphenyl -4-carboxylate (nmOBC) reveal that the transition is continuous and characterized by large positive heat capacity critical exponents (alpha ~eq 0.60). Measurements

George Fidias Nounesis

1990-01-01

42

Phase-transitions in Langmuir-Blodgett and cast films of a ferroelectric liquid crystal.  

PubMed

Langmuir-Blodgett films and cast films of a ferroelectric liquid crystal of sec-butyl-6-(4-(nonyloxy)benzoyloxy)-2-naphthoate have been fabricated. Their thermal behavior was investigated using infrared spectroscopy at elevated temperature combined with principal component analysis. The result shows a new phase transition from smectic A to nematic phase, compared to the phase sequence obtained by polarizing optical microscopy. Another solid transition of different isomeric crystals was also found, which was confirmed by calorimetric measurement. PMID:17625316

Wen, Zi; Jiang, Qing; DU, Yiping; Ozaki, Yukihiro

2007-07-01

43

Calorimetric study of phase transitions in a liquid-crystal-based microemulsion  

Microsoft Academic Search

A lyotropic inverse micelle phase composed of water, thermotropic liquid-crystal octylcyanobiphenyl (8CB), and surfactant (DDAB) was studied by using high-resolution calorimetry on several mixtures with 3%, 8%, and 15% micelle concentration. Calorimetric results show strong depression of the isotropic to nematic (I-N) phase-transition temperature. Broad heat-capacity anomalies show the existence of a wide coexistence range of isotropic, nematic, and smectic-A

Zdravko Kutnjak; George Cordoyiannis; George Nounesis; Andrija Lebar; Slobodan Zumer

2005-01-01

44

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

E-print Network

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

45

Experimental evidence of the ferroelectric phase transition near the $\\lambda-$point in liquid water  

E-print Network

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

46

In situ transmission electron microscopy of solid-liquid phase transition of silica encapsulated bismuth nanoparticles.  

PubMed

The solid-liquid phase transition of silica encapsulated bismuth nanoparticles was studied by in situ transmission electron microscopy (TEM). The nanoparticles were prepared by a two-step chemical synthesis process involving thermal decomposition of organometallic precursors for nucleating bismuth and a sol-gel process for growing silica. The microstructural and chemical analyses of the nanoparticles were performed using high-resolution TEM, Z-contrast imaging, focused ion beam milling, and X-ray energy dispersive spectroscopy. Solid-liquid-solid phase transitions of the nanoparticles were directly recorded by electron diffractions and TEM images. The silica encapsulation of the nanoparticles prevented agglomeration and allowed particles to preserve their original volume upon melting, which is desirable for applications of phase change nanoparticles with consistently repeatable thermal properties. PMID:21796304

Hu, Jianjun; Hong, Yan; Muratore, Chris; Su, Ming; Voevodin, Andrey A

2011-09-01

47

Changes in the optical properties of ultrathin films of liquid crystals during phase transitions  

NASA Astrophysics Data System (ADS)

The temperature dependences of diffuse reflection spectra and the polarization of light reflected from ultrathin Langmuir films based on liquid crystals are studied. The results are compared to the experimental data obtained on thicker liquid films. The dependences of the electric capacity of metal-film-metal structures on temperature are measured. The maximum for ultrathin films lies near 75°C, indicating the occurrence of a ferroelectric phase transition. Features in the intensity and polarization of the reflected light are registered at the phase transition temperature. It is concluded that the generality of the results obtained using samples of both types indicates the existence of a mesomorphic phase in Langmuir films. The observed differences could be associated with either dimensional effects or differences in the structures of the films.

Zaitsev, V. B.; Levshin, N. L.; Khlybov, S. V.; Yudin, S. G.

2013-06-01

48

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

PubMed

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

49

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

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

50

Two-channel pseudogap Kondo and Anderson models: Quantum phase transitions and non-Fermi liquids  

NASA Astrophysics Data System (ADS)

We discuss the two-channel Kondo problem with a pseudogap density of states ?(?)?|?|r of the bath fermions. Combining both analytical and numerical renormalization group techniques, we characterize the impurity phases and quantum phase transitions of the relevant Kondo and Anderson models. The line of stable points, corresponding to the overscreened non-Fermi-liquid behavior of the metallic r=0 case, is replaced by a stable particle-hole-symmetric intermediate-coupling fixed point for 0rmax, this non-Fermi-liquid phase disappears, and instead a critical fixed point with an emergent spin-channel symmetry appears, controlling the quantum phase transition between two phases with stable spin and channel moments, respectively. We propose low-energy field theories to describe the quantum phase transitions, all being formulated in fermionic variables. We employ ? expansion techniques to calculate critical properties near the critical dimensions r=0 and 1, the latter being potentially relevant for two-channel Kondo impurities in neutral graphene. We find the analytical results to be in excellent agreement with those obtained from applying Wilson’s numerical renormalization group technique.

Schneider, Imke; Fritz, Lars; Anders, Frithjof B.; Benlagra, Adel; Vojta, Matthias

2011-09-01

51

Phase transition studies in polar and nonpolar liquids at microwave frequencies  

Microsoft Academic Search

A resonant microwave cavity technique was employed to study the dielectric behavior of polar and nonpolar liquids near the phase transition temperatures at microwave frequencies of 7.2, 9.2, and 10.8 GHz. The Slater perturbation equations for a resonant microwave cavity are briefly discussed to show that the above technique can be used to determine both the real and imaginary parts

J. N. Dahiya; S. K. Jani; J. A. Roberts

1981-01-01

52

Structure and phase transitions into ionic adsorption layers on liquid interfaces  

E-print Network

The structure of ionic adsorption layers is studied via a proper thermodynamic treatment of the electrostatic and non-electrostatic interactions between the surfactant ions as well as of the effect of thermodynamic non-locality. The analysis is also applied to phase transitions into the ionic adsorption layer, which interfere further with the oscillatory-diffusive structure of the electric double layer and hydrodynamic stability of squeezing waves in thin liquid films.

R. Tsekov

2014-03-02

53

Transition liquid phase bonding of a Hastelloy X and the bond strength at 1173 K  

Microsoft Academic Search

Transition liquid phase (TLP) bonding has been conducted on a Hastelloy X using amorphous foil filler metals. The inserted fillers were made by rapid solidification of a Ni-15% Cr alloy containing 3 to 5 mass% boron as a melting point depressant. The microstructural change with isothermal bonding time from 2.4 to 38.4 ks was examined in the bond regions by

Tetsuro Toyoda; Taka O Endo

1996-01-01

54

Isotropic to nematic liquid crystalline phase transition of F-actin  

NASA Astrophysics Data System (ADS)

The cytoskeletal protein actin self-assembles to form long and stiff filaments, F-actin, which serve essential cell functions, such as control of cell shape, division, and motility. Suspensions of F-actin form either entangled isotropic networks or a nematic liquid crystalline phase. In vitro, suspensions of F-actin form entangled networks, and as predicted by the Onsager theory, undergo the isotropic-nematic (I-N) liquid crystalline transition at less than 1% wt protein content. In this thesis we show that the isotropic to nematic liquid crystalline phase transition of F-actin can be either continuous or discontinuous, depending critically on the filament length. For F-actin with average filament length ?3mum, the transition is continuous in both filament alignment and local concentration. In contrast, for filament length ?2mum the F-actin solution undergoes a first order transition. Tactoidal droplets of co-existing isotropic and nematic domains are observed. Phenomena of nucleation-and-growth and spinodal decomposition both occur, depending sensitively on the exact concentration and average filament length of F-actin. In the late stage, the tactoidal droplets continually grow and occasionally coalesce to form larger granules. We performed a systematic study of the orientational order parameter and filament motions of F-actin traversing the isotropic-nematic phase transition using a combination of techniques, including fluorescence imaging, local birefringence measurements, and x-ray scattering. The order parameter approaches a saturated value of 0.75 at actin concentrations above the region of the isotropic-nematic phase transition, which implies a significant extent of misalignment and consequently, entanglement among long actin filaments even in the nematic phase. At concentrations slightly below the isotropic-nematic transition, non-zero values of the order parameter are detected within a time window on the order of hours following an initial alignment, indicating extremely slow rotational kinetics of F-actin in the entangled networks. We detect the Brownian motions of F-actin to be confined within a virtual tube along the filament axis. The frictional coefficient increases non-monotonically as a function of the protein concentration. Surprisingly, the longitudinal diffusion coefficient decreases sharply in the concentration range of the I-N transition, and then becomes nearly constant in the nematic phase.

Viamontes, Jorge

55

Liquid natural gas rapid phase transitions. Topical report September 79-September 80  

SciTech Connect

An apparatus was constructed to test the concept of initiating a rapid phase transition (RPT) in methane-rich LNG on water by collapsing the vapor film with a shock wave. Helium overpressures were achieved by breaking a diaphragm in a high-pressure helium chamber. Pressure transducers recorded subsequent events. NO RPT were noted for liquid nitrogen, liquid ethane, liquid methane or methane-rich LNG even with helium driver pressures up to 62 bar. The helium did, however, greatly enhance the boiling rate of the cryogen on water. On the basis of analytical modelling, it was concluded that a RPT would be very improbable for a methane-rich LNG contacting ambient water in a mode where the surface pressures were high. In the course of the project, a new thermodynamic model was developed as a possible explanation for a RPT in cases where the hot liquid temperature would exceed the critical temperature of the cryogen.

Corbin, G.A.; Reid, R.C.

1981-01-01

56

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

SciTech Connect

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

57

Smectic-smectic phase transitions in binary liquid-crystalline mixtures of DB5-T8  

Microsoft Academic Search

We have used high-resolution x-ray diffraction and ac calorimetry to study the liquid–crystalline smectic-A-smectic-A phase transitions in binary mixtures of polar mesogenic compounds DB5 [benzoic acid, (4-cyano)-4-[(4-pentylphenoxy) carbonyl] phenyl ester] and T8 [(E)-benzoic acid, 4-octyloxy-4-[2-(4-cyanophenyl) ethenyl] phenyl ester]. A detailed synthesis for each of these compounds is presented. The smectic A1 phase in this system shows two collinear diffuse x-ray

Ernest Fontes; Wah Keat Lee; Paul A. Heiney; George Nounesis; Carl W. Garland; Antoni Riera; John P. McCauley Jr.; Amos B. Smith III

1990-01-01

58

Liquid-solid phase transition of hydrogen and deuterium in silica aerogel  

NASA Astrophysics Data System (ADS)

Behavior of hydrogen isotopes confined in disordered low-density nanoporous solids remains essentially unknown. Here, we use relaxation calorimetry to study freezing and melting of H2 and D2 in an ˜85%-porous base-catalyzed silica aerogel. We find that liquid-solid transition temperatures of both isotopes inside the aerogel are depressed. The phase transition takes place over a wide temperature range of ˜4 K and non-trivially depends on the liquid filling fraction, reflecting the broad pore size distribution in the aerogel. Undercooling is observed for both H2 and D2 confined inside the aerogel monolith. Results for H2 and D2 are extrapolated to tritium-containing hydrogens with the quantum law of corresponding states.

Van Cleve, E.; Worsley, M. A.; Kucheyev, S. O.

2014-10-01

59

Tricritical behavior of the nematic to smectic-A phase transition in the binary mixture of liquid crystal  

NASA Astrophysics Data System (ADS)

We propose a phenomenological model to describe the tricritical behavior of the nematic to smectic-A (N-SmA) phase transition in liquid crystal mixture. To describe the mesophase transitions in binary mixture, nematic and smectic order parameters have been coupled with the concentration. We show that a tricritical point on the N-SmA phase transition line can be achieved under certain conditions. The predictive capability of the present model for determining the tricritical point of a binary mixture displaying the N-SmA transition has been demonstrated by testing with reported phase diagrams sharing both phases.

Mukherjee, Prabir K.; Tamarit, Josep Ll.

2013-03-01

60

Critical temperature for the nuclear liquid-gas phase transition (from multifragmentation and fission)  

E-print Network

Critical temperature Tc for the nuclear liquid-gas phase transition is stimated both from the multifragmentation and fission data. In the first case,the critical temperature is obtained by analysis of the IMF yields in p(8.1 GeV)+Au collisions within the statistical model of multifragmentation (SMM). In the second case, the experimental fission probability for excited 188Os is compared with the calculated one with Tc as a free parameter. It is concluded for both cases that the critical temperature is higher than 16 MeV.

V. A. Karnaukhov; H. Oeschler; A. Budzanowski; S. P. Avdeyev; A. S. Botvina; E. A. Cherepanov; W. Karcz; V. V. Kirakosyan; P. A. Rukoyatkin; I. Skwirczynska; E. Norbeck

2008-01-29

61

Critical temperature for the nuclear liquid-gas phase transition (from multifragmentation and fission)  

SciTech Connect

Critical temperature T{sub c} for the nuclear liquid-gas phase transition is estimated from both the multifragmentation and fission data. In the first case, the critical temperature is obtained by analysis of the intermediate-mass-fragment yields in p(8.1 GeV) + Au collisions within the statistical model of multifragmentation. In the second case, the experimental fission probability for excited {sup 188}Os is compared with the calculated one with T{sub c} as a free parameter. It is concluded for both cases that the critical temperature is higher than 15 MeV.

Karnaukhov, V. A. [Joint Institute for Nuclear Research (Russian Federation); Oeschler, H. [Darmstadt University of Technology, Institut fuer Kernphysik (Germany); Budzanowski, A. [H. Niewodniczanski Institute of Nuclear Physics (Poland); Avdeyev, S. P. [Joint Institute for Nuclear Research (Russian Federation); Botvina, A. S. [Institute for Nuclear Research (Russian Federation); Cherepanov, E. A. [Joint Institute for Nuclear Research (Russian Federation); Karcz, W. [H. Niewodniczanski Institute of Nuclear Physics (Poland); Kirakosyan, V. V.; Rukoyatkin, P. A. [Joint Institute for Nuclear Research (Russian Federation); Skwirczynska, I. [H. Niewodniczanski Institute of Nuclear Physics (Poland); Norbeck, E. [University of Iowa (United States)

2008-12-15

62

Unusual stacking variations in liquid-phase exfoliated transition metal dichalcogenides.  

PubMed

Liquid-phase exfoliation of layered materials offers a large-scale approach toward the synthesis of 2D nanostructures. Structural properties of materials can however change during transition from bulk to the 2D state. Any such changes must be examined and understood for successful implementation of 2D nanostructures. In this work, we demonstrate nonbulk stacking sequences in the few-layer MoS2 and WS2 nanoflakes produced by liquid-phase exfoliation. Our analysis shows that nonbulk stacking sequences can be derived from its bulk counterparts by translational shifts of the layers. No structural changes within the layers were observed. Twenty-seven MoS2 and five WS2 nanoflakes were imaged and analyzed. Nine MoS2 and four WS2 nanoflakes displayed nonbulk stacking. Such dominance of the nonbulk stacking suggests high possibility of unusual stacking sequences in other 2D nanostructures. Notably, the electronic structure of some non bulk stacked bilayers presents characteristics which are uncommon to either the bulk phase or the single monolayer, for instance, a spin-split conduction band bottom. Our main characterization technique was annular dark-field scanning transmission electron microscopy, which offers direct and reliable imaging of atomic columns. The stacking characterization approach employed here can be readily applied toward other few-layer transition metal chalcogenides and oxides. PMID:24588696

Shmeliov, Aleksey; Shannon, Mervyn; Wang, Peng; Kim, Judy S; Okunishi, Eiji; Nellist, Peter D; Dolui, Kapildeb; Sanvito, Stefano; Nicolosi, Valeria

2014-04-22

63

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

PubMed

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

64

Synthesis and phase transitional behavior of dimer-like optically active liquid crystals.  

PubMed

The results of our detailed studies pertaining to a relatively new class of low molar mass mesogens are presented. Four homologous series of optically active dimer-like mesogens, comprising cholesterol as the conventional pro-mesogenic core covalently tethered to a nonmesogenic salicylaldimine segment through a flexible spacer of varying length and parity, have been synthesized and evaluated for their thermal, electrical switching, electrochemical, and gelation properties. The thermal behavior, being the prime focus of this study, has been characterized by optical, calorimetric, X-ray diffraction, and electrical switching studies. In each series, the length of the even/odd-parity spacer is held constant, while the length of the terminal N-alkyl tail attached to nonmesogenic salicylaldimine core has been varied to gain insight into the fundamental correlation between structure and phase transitional properties. These compounds, with a few exceptions, exhibit liquid crystal phase(s); the identified phases are chiral nematic (N*), twist grain boundary (TGB), chiral smectic A (SmA), and chiral smectic C (SmC*) phases. The selective reflection property of the N* phase and ferroelectric behavior of the SmC* phase have been ascertained for some selected members. In general, the phase behavior shows a dependence on the length and parity of the central spacer as well as the length of the terminal tail. The odd-even effect has been prominently found in the clearing temperatures; the even-parity dimer-like compounds belonging to three different series exhibit higher values when compared to members of an odd-parity series. Thus, our study demonstrates that these new class of low molar mass materials behave analogous to liquid crystal dimers. Electrochemical behavior and gelation ability have been demonstrated for some selected materials. PMID:21830781

Shanker, Govindaswamy; Yelamaggad, Channabasaveshwar V

2011-09-22

65

Impact of Surface-Functionalized CdSe Nanoparticles on Phase Transitions of 8CB And CE8 Liquid Crystals  

Microsoft Academic Search

The impact of the surface–functionalised CdSe nanoparticles on various phase transitions of the two liquid crystals, 8CB and CE8, has been examined by means of high-resolution calorimetry. The addition of nanoparticles results in suppression of phase transitions and change in heat capacity anomalies. In contrast to silica aerosils CdSe nanoparticles do not form a rigid network. As a consequence, the

B. Roži?; E. Karatairi; G. Nounesis; V. Tzitzios; G. Cordoyiannis; S. Kralj; Z. Kutnjak

2012-01-01

66

Photoinduced phase transitions.  

PubMed

Optically induced ultrafast electronic excitations with sufficiently long lifetimes may cause strong effects on phase transitions like structural and nonmetal?metal ones and on supercooling, supersaturation, etc. Examples are the transitions diamond?graphite, graphite?graphene, non-metal?metal, solid?liquid and vapor?liquid, solid. Photoinduced formation of graphene and water condensation of saturated or supersaturated vapor due to increased bonding amongst water molecules are of particular interest. These nonequilibrium transitions are an ultrafast response, on a few hundred fs time scale, to the fast low to large energy electronic excitations. The energy of the photons is converted into electronic energy via electronic excitations changing the cohesive energy. This changes the chemical potential controlling the phase transition. In view of the advances in laser optics photon induced transitions are expected to become an active area in nonequilibrium physics and phase transition dynamics. Conservation laws like energy or angular momentum conservation control the time during which the transitions occur. Since the photon induced effects result from weakening or strengthening of the bonding between the atoms or molecules transitions like solid/liquid, etc can be shifted in both directions. Photoinduced transitions will be discussed from a unified point of view. PMID:21411879

Bennemann, K H

2011-02-23

67

Liquid-Liquid Transition at Tg and Stable-Glass Phase Nucleation Rate Maximum at the Kauzmann Temperature TK  

E-print Network

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

2014-04-10

68

Effects of the liquid-gas phase transition and cluster formation on the symmetry energy  

NASA Astrophysics Data System (ADS)

Various definitions of the symmetry energy are introduced for nuclei, dilute nuclear matter below saturation density and stellar matter, which is found in compact stars or core-collapse supernovae. The resulting differences are exemplified by calculations in a theoretical approach based on a generalized relativistic density functional for dense matter. It contains nucleonic clusters as explicit degrees of freedom with medium-dependent properties that are derived for light clusters from a quantum statistical approach. With such a model the dissolution of clusters at high densities can be described. The effects of the liquid-gas phase transition in nuclear matter and of cluster formation in stellar matter on the density dependence of the symmetry energy are studied for different temperatures. It is observed that correlations and the formation of inhomogeneous matter at low densities and temperatures causes an increase of the symmetry energy as compared to calculations assuming a uniform uncorrelated spatial distribution of constituent baryons and leptons.

Typel, S.; Wolter, H. H.; Röpke, G.; Blaschke, D.

2014-02-01

69

Probing the material properties and phase transitions of ferroelectric liquid crystals by determination of the Landau potential.  

PubMed

The full Landau potential of several, widely varying ferroelectric liquid-crystalline materials has been experimentally determined. Tilt angle and polarisation data is analysed across the SmA to SmC transition for varying applied electric-field amplitudes, allowing the determination of all the coefficients of the generalised Landau model of ferroelectric liquid crystals. The materials investigated encompass different materials, including low-polarisation mixtures to high-polarisation single-component materials. The materials also possess a variation in the order of the SmA to SmC phase transition from strongly first order to strongly second order. The effects of both the polarisation and order of phase transition of the system are discussed with respect to the various terms of the generalised Landau model. Further, the mechanisms behind the difference between a first- and second-order phase transition are discussed with respect to the Landau potential and the second Landau coefficient b . PMID:18425407

Archer, P; Dierking, I; Görtz, V; Goodby, J W

2008-04-01

70

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

PubMed

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

71

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

SciTech Connect

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

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

1985-06-01

72

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

73

Phase-field model of solid-liquid phase transition with density difference and latent heat in velocity and elastic fields.  

PubMed

We present a phase-field model of solid-liquid transitions with inhomogeneous temperature in one-component systems, including hydrodynamics and elasticity. Our model can describe plastic deformations at large elastic strains. We use it to investigate the melting of a solid domain, accounting for the latent heat effect, where there appears a velocity field in liquid and an elastic field in solid. We present simulation results in two dimensions for three cases of melting. First, a solid domain is placed on a heated wall, which melts mostly near the solid-liquid-wall contact region. Second, a solid domain is suspended in a warmer liquid under shear flow, which rotates as a whole because of elasticity and melts gradually. Cooling of the surrounding liquid is accelerated by convection. Third, a solid rod is under high compression in liquid, where slips appear from the solid-liquid interface, leading to a plastic deformation. Subsequently, melting starts in the plastically deformed areas, eventually resulting in the fracture of the rod into pieces. In these phase-transition processes, the interface temperature is kept nearly equal to the coexisting temperature T(cs)(p) away from the heated wall, but this local equilibrium is not attained near the the contact region. We also examine a first-order liquid-liquid phase transition under heating from a boundary in one-component liquids. PMID:21599166

Takae, Kyohei; Onuki, Akira

2011-04-01

74

Nature of smectic A*-C* phase transitions in a series of ferroelectric liquid crystals with little smectic layer shrinkage.  

PubMed

The smectic layer spacing of two homologous series of ferroelectric liquid crystal compounds was characterized by small-angle x-ray diffraction and different degrees of smectic layer shrinkage on cooling from the SmA* into the SmC* phase were observed. The smectic A*-smectic C* phase transition was further studied by measuring the thermal and electric field effects on the optical tilt angle and the electric polarization. With decreasing length of the alkyl terminal chain the phase transition changes from tricritical exhibiting high layer shrinkage to a pure second-order transition with almost no layer shrinkage. This is explained by the increased one-dimensional translational order of the smectic layers, which seems to promote the "de Vries"-type [Mol. Cryst. Liq. Cryst. 41, 27 (1977)] smectic A*-C* phase transition with no or little layer shrinkage. PMID:17302502

Bezner, Samuel; Krueger, Michael; Hamplová, Vera; Glogarová, Milada; Giesselmann, Frank

2007-02-01

75

Freeze-out temperature and density in heavy-ion collisions at liquid-gas phase transition  

SciTech Connect

The study of properties of hot nuclei and the search for liquid-gas phase transition in nuclei have been the subjects of many investigations in recent decades. We present a short and limited review of the theoretical and experimental status of determining the temperature and density of the disassembling nucleus from ratios of the yields of emitted fragments.

Shlomo, Shalom [Cyclotron Institute, Texas A and M University, College Station, TX 77843 (United States)

2010-08-04

76

Gas-Liquid-Solid Phase Transition Model for Two-Dimensional Nanocrystal Self-Assembly on Graphite  

E-print Network

Gas-Liquid-Solid Phase Transition Model for Two-Dimensional Nanocrystal Self-Assembly on Graphite. Introduction The assembly of nanocrystals from solution into ordered arrays is a promising approach toward of alkane hair which lubricates the interface between the nanocrystal and the graphite; high mobility

77

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

78

Quantum Phase Transitions  

NASA Astrophysics Data System (ADS)

Part I. Introduction: 1. Basic concepts; 2. Overview; Part II. A First Course: 3. Classical phase transitions; 4. The renormalization group; 5. The quantum Ising model; 6. The quantum rotor model; 7. Correlations, susceptibilities, and the quantum critical point; 8. Broken symmetries; 9. Boson Hubbard model; Part III. Non-zero Temperatures: 10. The Ising chain in a transverse field; 11. Quantum rotor models: large-N limit; 12. The d = 1, O(N ? 3) rotor models; 13. The d = 2, O(N ? 3) rotor models; 14. Physics close to and above the upper-critical dimension; 15. Transport in d = 2; Part IV. Other Models: 16. Dilute Fermi and Bose gases; 17. Phase transitions of Dirac fermions; 18. Fermi liquids, and their phase transitions; 19. Heisenberg spins: ferromagnets and antiferromagnets; 20. Spin chains: bosonization; 21. Magnetic ordering transitions of disordered systems; 22. Quantum spin glasses; References; Index.

Sachdev, Subir

2011-04-01

79

The nuclear liquid-vapor phase transition: Equilibrium between phases or free decay in vacuum?  

SciTech Connect

Recent analyses of multifragmentation in terms of Fisher's model and the related construction of a phase diagram brings forth the problem of the true existence of the vapor phase and the meaning of its associated pressure. Our analysis shows that a thermal emission picture is equivalent to a Fisher-like equilibrium description which avoids the problem of the vapor and explains the recently observed Boltzmann-like distribution of the emission times. In this picture a simple Fermi gas thermometric relation is naturally justified. Low energy compound nucleus emission of intermediate mass fragments is shown to scale according to Fisher's formula and can be simultaneously fit with the much higher energy ISiS multifragmentation data.

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

2002-11-14

80

Three stage-volume phase transitions of a side-chain liquid crystalline elastomer immersed in nematic solvents  

NASA Astrophysics Data System (ADS)

We theoretically study volume phase transitions of a side-chain liquid crystalline elastomer (LCE) immersed in nematic solvents. Six different uniaxial nematic phases (N1?, N1?, N2?, N2?, N3?, and N3?) are defined by using orientational order parameter Sm of a side-chain mesogen, Sb of a backbone chain, and S0 of a nematic solvent inside the gel. We derive the free energy of a side-chain LCE dissolved in nematic solvents and calculate the swelling behavior of the LCE, the order parameters, and the deformations of the LCE as a function of temperature. We find various phase transitions of the LCE, such as the isotropic (I)-N1?-N3? and the I-N2?-N3?, etc., accompanied by volume phase transitions. These results present new concepts in the structure of a side-chain LCE dispersed in nematic solvent molecules.

Matsuyama, Akihiko; Kushibe, Yoshinari

2010-03-01

81

Meta-stable nematic pre-ordering in smectic liquid crystalline phase transitions  

E-print Network

Modeling and simulation studies using a high-order Landau-de Gennes type model for the direct isotropic/smectic-A liquid crystal transition are presented showing the existence of meta-stable nematic pre-ordering under certain conditions, in agreement with experimental observations (Tokita, M. et al. Macromolecules 2006, 39, 2021-2023)

Nasser Mohieddin Abukhdeir; Alejandro D. Rey

2009-04-11

82

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

NASA Astrophysics Data System (ADS)

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 ? = ?e2n1/3 (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 \\varepsilon _{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.

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

2014-07-01

83

Photoinduced Crystal-to-Liquid Phase Transitions of Azobenzene Derivatives and Their Application in Photolithography Processes through a Solid-Liquid Patterning.  

PubMed

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

84

Dynamic mechanism of the ferroelectric to antiferroelectric phase transition in chiral smectic liquid crystals.  

PubMed

The temperature-induced phase transition between the chiral smectic phases, antiferroelectric (smectic-C(A)*) and ferroelectric (smectic-C*), is found to occur through solitary wave propagation. We measure the free energy, which shows a double well shape in the entire SmC(A)* temperature range and the global minimum is found to shift from the antiferroelectric order to the ferroelectric order at the transition temperature. However, any significant supercooling is not observed and the transition cannot be described by the first order Landau-de Gennes theory, where the double well potential exists only in a narrow range of temperatures. This implies that the SmC(A)*-SmC* transition can occur only nonhomogeneously through the solitary wave propagation which overcomes the high energy barrier between the two minima. PMID:18851661

Song, Jang-Kun; Fukuda, Atsuo; Vij, J K

2008-08-29

85

Observation of Lyotropic Liquid Crystalline Phases in Some Transition Metal Salt Dispersed Soft Non-Aqueous Systems  

NASA Astrophysics Data System (ADS)

Present studies demonstrate the nucleation and stabilization of soft lyotropic liquid crystalline (LLC) phases, derived via transition metal salt (ZnCl2 = 1,3,5,10 wt %) dispersion in a binary mixture (40:60 wt %) of cationic surfactant (cetyl pyridinium chloride) and protic polar solvent (ethylene glycol). Textural and structural investigations reveal the formation of mixed (hexagonal and lamellar) LLC phase at 1, 3, 5 wt % ZnCl2 concentration, although, system show neat lamellar phase at higher metal salt content ( 10 wt %). Our textural and structural investigations were found in agreement with each other and hint at the origin, stability and diversity of these complex materials.

Shukla, Ravi K.; Raina, K. K.

2011-12-01

86

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

PubMed Central

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

87

The study of phase transition in some irradiated cholesteric liquid crystalline mixtures  

NASA Astrophysics Data System (ADS)

We present the study of binary and multicomponent cholesteric mixtures undertaken with the aim of forming a system with the temperature of the phase transition close to the room temperature, which could be suitable for the detection of ionizing radiation. The phase diagrams were established on the basis of data from the optical microscopy and differential scanning calorimetry (DSC). The mixtures were exposed to the continual spectrum of X-Ray radiation in the period of 30/60 min. The mixtures react by changing the color of the mesophase, and a shift of the mesophase transition towards lower temperatures. The duration of the effects exceeds six months.

Obadovi?, D. Ž.; Stojanovi?, M.; Cvetinov, M.; Vajda, A.; Éber, N.; Lazar, D.

2011-12-01

88

The nuclear liquid-gas phase transition at large $N_c$ in the Van der Waals approximation  

E-print Network

We examine the nuclear liquid-gas phase transition at large number of colors ($N_c$) within the framework of the Van Der Waals (VdW) model. We argue that the VdW equation is appropriate at describing inter-nucleon forces, and discuss how each parameter scales with $N_c$. We demonstrate that $N_c=3$ (our world) is not large with respect to the other dimensionless scale relevant to baryonic matter, the number of neighbors in a dense system $N_N$. Consequently, we show that the liquid-gas phase transition looks dramatically different at $N_c \\to \\infty$ with respect of our world: The critical point temperature becomes of the order of $\\lqcd$ rather than below it. The critical point density becomes of the order of the baryonic density, rather than an order of magnitude below it. These are precisely the characteristics usually associated with the "Quarkyonic phase". We therefore conjecture that quarkyonic matter is simply the large $N_c$ limit of the nuclear liquid, and the interplay between $N_c$ and $N_N$ is the reason why the nuclear liquid in our world is so different from quarkyonic matter. We conclude by suggesting ways our conjecture can be tested in future lattice measurements.

Giorgio Torrieri; Igor Mishustin

2010-06-12

89

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

SciTech Connect

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

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

2010-11-15

90

pH dependent isotropic to nematic phase transitions in graphene oxide dispersions reveal droplet liquid crystalline phases.  

PubMed

Size fractionation, amplified by the surface charge density of graphene oxide (GO) sheets, broadens the pH dependent isotropic (I) to nematic (N) phase transition in aqueous dispersions of graphene oxide (GO). In this biphasic region, a highly organized droplet nematic phase of uniform size (20 ± 2.8 ?m diameter) with an isotropic interior is observed. PMID:24828948

Tkacz, Rachel; Oldenbourg, Rudolf; Mehta, Shalin B; Miansari, Morteza; Verma, Amitabh; Majumder, Mainak

2014-06-25

91

Investigating the Solid-Liquid Phase Transition of Water Nanofilms Using the Generalized Replica Exchange Method  

E-print Network

be calculated as in Eq. (7) and (8). As shown in Fig. 3 (a), the internal energy increases with temperature mono- tonically across the phase transition region, as a result of reweighting gREM derived caloric curve into the canonical ensemble. The heat capacity...

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

2014-01-01

92

Free-Surface Optical Scattering as an Indicator of the Shock-Induced Solid-Liquid Phase Transition in Tin  

SciTech Connect

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. A familiar manifestation of this phenomenon is the loss of signal light in VISAR measurements, which 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 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.

Stevens, G. D.; Lutz, S. S.; Marshall, B. R.; Turley, W. D.; Veeser, L. R.; Furlanetto, M. R.; Hixson, R. S.; Holtkamp, D. B.; Jensen, B. J.; Rigg, P. A.; Wilke, M. D.

2008-07-01

93

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

SciTech Connect

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

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

2013-01-01

94

Small-angle neutron scattering study of structure and interaction during salt-induced liquid-liquid phase transition in protein solutions  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

95

Phase behavior and mixing-demixing transitions in binary liquid mixtures with spherical and non-spherical interactions  

NASA Astrophysics Data System (ADS)

We have carried out extensive equilibrium molecular dynamics simulations to study the temperature versus density phase diagrams and the mixing-demixing transition line in fluid equimolar binary mixtures modeled by: (i) Lennard-Jones, (ii) Stock-Mayer, and (iii) Gay- Berne molecular interactions. These studies are performed as function of miscibility parameter, ?= ?AB/ ?AA, where ?AA= ?BB and ?AB stand for the parameters related to the attractive part of the intermolecular interactions for similar and dissimilar particles, respectively. When the miscibility of the Lennard-Jones mixture varies in the range 0 < ?< 1, a continuous critical line of consolute points Tcons(?), appears. This line intersects the liquid-vapor coexistence curve at different positions depending on the values of ?, yielding mainly three different topologies for the phase diagrams. These results are in qualitative agreement to those found previously for square well and hard-core Yukawa binary mixtures. We also carry out a detailed study of the liquid-liquid interfacial and liquid-vapor surface tensions, as function of temperature and miscibility as well as its relationship to the topologies of the phase diagrams. Similar studies and analysis are also performed for Stock-Mayer and Gay-Berne binary mixtures.

Diaz-Herrera, Enrique; Ramirez-Santiago, Guillermo; Moreno-Razo, J. Antonio

2006-03-01

96

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

PubMed

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

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

2014-05-14

97

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

98

Effect of the ionic liquid 1-ethyl-3-methylimidazolium acetate on the phase transition of starch: dissolution or gelatinization?  

PubMed

This work revealed that the interactions between starch, the ionic liquid 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]), and water might contribute to the phase transition (gelatinization, dissolution, or both) of native starch at reduced temperature. Using mixtures of water and [Emim][OAc] at certain ratios (7.2/1 and 10.8/1 mol/mol), both the gelatinization and dissolution of the starch occur competitively, but also in a synergistic manner. At lower [Emim][OAc] concentration (water/[Emim][OAc] molar ratio?25.0/1), mainly gelatinization occurs which is slightly impeded by the strong interaction between water and [Emim][OAc]; while at higher [Emim][OAc] concentration (water/[Emim][OAc] molar ratio?2.8/1), the dissolution of starch is the major form of phase transition, possibly restricted by the difficulty of [Emim][OAc] to interact with starch. PMID:23544570

Mateyawa, Sainimili; Xie, David Fengwei; Truss, Rowan W; Halley, Peter J; Nicholson, Timothy M; Shamshina, Julia L; Rogers, Robin D; Boehm, Michael W; McNally, Tony

2013-04-15

99

Smectic order, pinning, and phase transition in a smectic-liquid-crystal cell with a random substrate  

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

100

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

NASA Astrophysics Data System (ADS)

We report measurements of the uniaxial coefficients of thermal expansion ?i and the specific heat C on the spin-liquid candidate ?-(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 ?i data reveal clear evidence for a second-order phase transition around 6 K, accompanied by distinct lattice effects. By using a Grüneisen-scaling Ansatz, we are able to extract the corresponding anomaly to the specific heat. Estimates of the entropy indicate that spin degrees of freedom alone cannot account for the phase transition anomaly, suggesting that charge degrees of freedom are involved.

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

101

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

NASA Astrophysics Data System (ADS)

We report measurements of the uniaxial coefficients of thermal expansion ?i and the specific heat C on the spin-liquid candidate ?-(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 ?i data reveal clear evidence for a second-order phase transition around 6 K, accompanied by distinct lattice effects. By using a Grüneisen-scaling Ansatz, we are able to extract the corresponding anomaly to the specific heat. Estimates of the entropy indicate that spin degrees of freedom alone cannot account for the phase transition anomaly, suggesting that charge degrees of freedom are involved.

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

2010-06-01

102

Phase transitions in the liquid-vapor interface of dilute alloys of Bi in Ga: New experimental studies  

SciTech Connect

We report the results of measurements of x-ray reflectivity and grazing incidence x-ray diffraction from the liquid-vapor interfaces of four dilute alloys of Bi in Ga with mole fractions x{sub Bi} = 0.0032, 0.0023, 0.00037, and 0.000037. The monolayer coverage of the alloys with x{sub Bi} = 0.0023, and x{sub Bi} = 0.00037 is about 0.85 and only very slightly temperature dependent. The monolayer coverage in the lowest-concentration alloy, with x{sub Bi} = 0.000037, ranged from 0.82 at 29 C to 0.58 at 110 C. In none of these alloys, down to the lowest temperature used, 29 C, can we find any evidence for crystallization of the Bi monolayer that segregates as the outermost stratum of the liquid-vapor interface. Drawing on theoretical arguments we propose that the transitions inferred from the second-harmonic generation and plasma generation studies of dilute Bi in Ga alloys are from the liquid state to the hexatic state of the Bi monolayer. The data for the alloy with x{sub Bi} = 0.000037 suggest that near 80 C there is a disordered phase-to-disordered phase transition.

Li, Dongxu; Jiang, Xu; Yang, Bin; Rice, Stuart A. (UC)

2010-07-19

103

Experimental Data on Liquid-Solid Phase Transition in Tin Using Pulsed Magnetic Loading on the Saturn Accelerator  

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

104

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

PubMed

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

105

Photopolymerization-Induced Mesophase Transition in Relation to Phase Diagram of Reactive Nematic Mesogen and Hexagonal Columnar Liquid Crystal Mixture  

NASA Astrophysics Data System (ADS)

The phase diagram of columnar liquid crystal, 2,3,6,7,10,11-hexakispentyloxy triphenylene (HPTP), and nematic monomer, 4-(3-Acryloyloxypropyloxy)-benzoic acid 2-methyl-1,4-phenylene ester (RM257) mixtures has been investigated experimentally. Phase transition temperatures are determined by using polarized optical microscopy (POM), and differential scanning calorimetry (DSC). The phase diagram shows a eutectic phase behavior and consists of isotropic, nematic, order hexagonal, crystalline, and an induced mesophase which is not existed in the neat components. Wide-angle x-ray diffraction (WAXD) result shows this induced mesophase is the disordered hexagonal phase. By virtue of photocurable capability of RM257, the evolution of phase morphology of the LC mixtures subjected to photopolymerization has been also studied under UV illumination. Depending on reaction temperature and composition, the morphology of the cured mixtures can be fixed in the isotropic or anisotropic states. The existence of columnar phase of HPTP after reaction can be identified in some compositions by WAXD that undergoes reaction-driven phase transformation.

Huang, Tsang-Min; Kyu, Thein

2010-03-01

106

Fluctuations and phase transitions in Larkin-Ovchinnikov liquid-crystal states of a population-imbalanced resonant Fermi gas  

SciTech Connect

Motivated by a realization of imbalanced Feshbach-resonant atomic Fermi gases, we formulate a low-energy theory of the Fulde-Ferrell and the Larkin-Ovchinnikov (LO) states and use it to analyze fluctuations, stability, and phase transitions in these enigmatic finite momentum-paired superfluids. Focusing on the unidirectional LO pair-density-wave state, which spontaneously breaks the continuous rotational and translational symmetries, we show that it is characterized by two Goldstone modes, corresponding to a superfluid phase and a smectic phonon. Because of the liquid-crystalline ''softness'' of the latter, at finite temperature the three-dimensional state is characterized by a vanishing LO order parameter, quasi-Bragg peaks in the structure and momentum distribution functions, and a ''charge''-4, paired-Cooper-pairs, off-diagonal long-range order, with a superfluid-stiffness anisotropy that diverges near a transition into a nonsuperfluid state. In addition to conventional integer vortices and dislocations, the LO superfluid smectic exhibits composite half-integer vortex-dislocation defects. A proliferation of defects leads to a rich variety of descendant states, such as the charge-4 superfluid and Fermi-liquid nematics and topologically ordered nonsuperfluid states, that generically intervene between the LO state and the conventional superfluid and the polarized Fermi liquid at low and high imbalance, respectively. The fermionic sector of the LO gapless superconductor is also quite unique, exhibiting a Fermi surface of Bogoliubov quasiparticles associated with the Andreev band of states, localized on the array of the LO domain walls.

Radzihovsky, Leo [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)

2011-08-15

107

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

E-print Network

vibrations in the discotic liquid crystal nematogen hexakis 6-hexyloxy triphenylene are shown to be sensitive. Optical spectroscopy has always played a central role in the understanding of LC's in view of the stunning variety of effects they display 6 . In particular, Raman spectroscopy has been used in the past to study

Nollmann, Marcelo

108

Quantum Phase Transitions  

Microsoft Academic Search

Quantum Phase Transitions details the fundamental changes that can occur in the macroscopic nature of matter at zero temperature due to small variations in a given external parameter. The author develops the theory of quantum phase transitions in the simplest possible class of nondisordered, interacting systems--the quantum Ising and rotor models. He pays particular attention to their non-zero temperature dynamic

Subir Sachdev; Matthew P. A. Fisher

2001-01-01

109

Pretransitional effects near the smectic- A smectic C* phase transition of hydrophilic and hydrophobic aerosil networks dispersed in ferroelectric liquid crystals  

Microsoft Academic Search

A detailed x-ray scattering and high-resolution ac calorimetric study has been carried out near the smectic- A to chiral smectic- C phase transition of liquid-crystal compounds 4-(2-methyl butyl) phenyl 4- n -octylbiphenyl-4-carboxylate (CE8) and p -( n -decyloxy) benzylidene- p -amino-(2-methylbutyl) cinnamate (DOBAMBC) confined in hydrophilic and hydrophobic aerosil nanoparticle networks. The character of the transition, which is mean field

George Cordoyiannis; Samo Kralj; George Nounesis; Zdravko Kutnjak; Slobodan Zumer

2007-01-01

110

Is there evidence for a liquid-gas phase transition in nuclear matter?  

SciTech Connect

The multifragmentation of gold nuclei at 1 GeV/nucleon has been studied using reverse kinematics. The moments of the resulting charged fragment distribution have been analyzed using methods borrowed from percolation theory. These moments provide clear evidence for critical behavior occurring in a system of about 200 nucleons. The critical exponents extracted from the data are close to those of liquid-gas systems.

Hirsch, A.S. [Purdue Univ., West Lafayette, IN (United States). Dept. of Physics; EOS Collaboration

1994-09-01

111

Quantum phase transitions  

Microsoft Academic Search

In recent years, quantum phase transitions have attracted the interest of\\u000aboth theorists and experimentalists in condensed matter physics. These\\u000atransitions, which are accessed at zero temperature by variation of a\\u000anon-thermal control parameter, can influence the behavior of electronic systems\\u000aover a wide range of the phase diagram. Quantum phase transitions occur as a\\u000aresult of competing ground state

Thomas Vojta

2003-01-01

112

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

113

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

E-print Network

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

Garland, Carl W.

114

Critical-Like Phenomena Associated with Liquid-Liquid Transition in a Molecular Liquid  

NASA Astrophysics Data System (ADS)

Contrary to the conventional wisdom that there is only one unique liquid state for any material, recent evidence suggests that there can be more than two liquid states even for a single-component substance. The transition between these liquid states is called a liquid-liquid phase transition. We report the detailed experimental investigation on the kinetics of the continuous spinodal-decomposition-type transformation of one liquid into another for triphenyl phosphite. From the analysis of the linear regime, we found that the correlation length, ?, of fluctuations of the relevant order parameter diverges as ? = ?0[(TSD - T)/TSD]-? (where ?0 = 60 nm and ? = 0.5) while approaching the spinodal temperature, TSD. This is an indication of a critical-like anomaly associated with the liquid-liquid transition. We also revealed that the order parameter governing the liquid-liquid transition must be of a nonconserved nature.

Kurita, Rei; Tanaka, Hajime

2004-10-01

115

Electrolyte effects on a nearly second order nematic-isotropic phase transition in a micellar liquid crystal  

E-print Network

susceptibilité magnétique de la phase isotrope observés pour le crystal liquide lyotrope de cesium perfluoro liquid crystal cesium perfluoro octanoate + water in the presence of an added salt CsCl. Based upon mixture cesium perfluoro octanoate (CsPFO) + water, which forms disk-like micelles with a positive net

Paris-Sud XI, Université de

116

LIGHT NONAQUEOUS PHASE LIQUIDS  

EPA Science Inventory

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

117

"Crystal-clear" liquid-liquid transition in a tetrahedral fluid.  

PubMed

For a model known to exhibit liquid-liquid transitions, we examine how varying the bond orientational flexibility affects the stability of the liquid-liquid transition relative to that of the crystal phases. For very rigidly oriented bonds, the crystal is favored over all amorphous phase transitions. We find that increasing the bond flexibility decreases both the critical temperature Tc for liquid-liquid phase separation and the melting temperature Tm. The effect of increasing flexibility is much stronger for melting, so that the distance between Tc and Tm progressively reduces and inverts sign. Under these conditions, a "naked" liquid-liquid critical point bulges out in the liquid phase and becomes accessible, without the possibility of crystallization. These results confirm that a crystal-clear, liquid-liquid transition can occur as a genuine, thermodynamically stable phenomenon for tetrahedral coordinated particles with flexible bond orientation, but that such a transition is hidden by crystallization when bonds are highly directional. PMID:25349962

Starr, Francis W; Sciortino, Francesco

2014-12-21

118

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

E-print Network

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

119

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

PubMed Central

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

Bitler, A; Stavrov, SS

1999-01-01

120

Kinetics and Control of Liquid-Liquid Transition  

NASA Astrophysics Data System (ADS)

Recently it was revealed that even a single-component liquid can have more than two liquid states. The transition between these liquid states is called "liquid-liquid transition". This phenomenon has attracted a considerable attention because of its counter-intuitive character and the fundamental importance for our understanding of the liquid state of matter. The connection between the liquid-liquid transition and polyamorphism is also an interesting issue. In many cases, liquid-liquid transitions exist in a region which is difficult to access experimentally. Because of this experimental difficulty, the physical nature and kinetics of the transition remains elusive. However, a recent finding of liquid-liquid transition in molecular liquids opens up a possibility to study the kinetics in detail. Here we report the first detailed comparison between experiments and a phenomenological theory for the liquid-liquid transition of a molecular liquid, triphenyl phosphite. Both nucleation-growth-type and spinodal-decomposition-type liquid-liquid transformation are remarkably well reproduced by a two-order-parameter model of liquid that regards the liquid-liquid transition as the cooperative formation of locally favored structures. This may shed new light on the nature and the dynamics of the liquid-liquid transition. We also show evidence that this second order parameter controls the fragility of the liquid. We also discuss a possibility of controlling liquid-liquid transition by spatial confinement. Remaining open questions on the nature of the transition are also discussed.

Tanaka, Hajime; Kurita, Rei; Murata, Ken-ichiro

2008-02-01

121

Liquid Phase Heating Systems  

E-print Network

Liquid phase heating systems involve sensible heat transfer in a closed loop wherein a pumped fluid's temperature is raised in a heater, then lowered in a heat user and returned for reheating. No formation and condensation of vapor occurs. High...

Mordt, E. H.

1979-01-01

122

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

PubMed

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

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

2014-06-01

123

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

124

Critical behavior at nematic-smectic-A1 phase transitions. I. High-resolution x-ray-scattering and calorimetric study of the liquid-crystal octyloxyphenylnitrobenzoyloxy benzoate  

Microsoft Academic Search

High-resolution x-ray scattering and ac-calorimetric measurements have been carried out near the nematic-smectic-A1 phase transition of the pure liquid-crystal compound octyloxyphenylnitrobenzoyl- oxy benzoate (DB8ONO2). Several forms of the structure factor S(q) for fitting the x-ray line shape have been tested. The critical temperature dependences of the resulting longitudinal and transverse correlation lengths xi|| and xi? and the smectic susceptibility sigma

G. Nounesis; K. I. Blum; M. J. Young; C. W. Garland; R. J. Birgeneau

1993-01-01

125

Electroweak phase transitions  

SciTech Connect

An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, {l_angle}{phi}{r_angle}{sub T} is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of {l_angle}{phi}{r_angle}{sub T}. In very minimal extensions of the standard model it is quite easy to increase {l_angle}{phi}{r_angle}{sub T} so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value {l_angle}{phi}{r_angle} = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state {l_angle}{phi}{r_angle} = 246 GeV unstable. The requirement that the state {l_angle}{phi}{r_angle} = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.

Anderson, G.W.

1991-09-16

126

Electroweak phase transitions  

SciTech Connect

An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, {l angle}{phi}{r angle}{sub T} is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of {l angle}{phi}{r angle}{sub T}. In very minimal extensions of the standard model it is quite easy to increase {l angle}{phi}{r angle}{sub T} so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value {l angle}{phi}{r angle} = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state {l angle}{phi}{r angle} = 246 GeV unstable. The requirement that the state {l angle}{phi}{r angle} = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.

Anderson, G.W.

1991-09-16

127

Effects of fullerene addition on the thermo-optical properties of smectic liquid crystals at the vicinity of the nematic-smectic-A phase transition  

NASA Astrophysics Data System (ADS)

The present work is devoted to the study of the thermo-optical properties of liquid crystals doped with traces of fullerene C60 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.

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

2014-05-01

128

Pretransitional effects near the smectic-A-smectic-C* phase transition of hydrophilic and hydrophobic aerosil networks dispersed in ferroelectric liquid crystals  

Microsoft Academic Search

A detailed x-ray scattering and high-resolution ac calorimetric study has been carried out near the smectic-A to chiral smectic-C phase transition of liquid-crystal compounds 4-(2-methyl butyl) phenyl 4-n-octylbiphenyl-4-carboxylate (CE8) and p-(n-decyloxy) benzylidene-p-amino-(2-methylbutyl) cinnamate (DOBAMBC) confined in hydrophilic and hydrophobic aerosil nanoparticle networks. The character of the transition, which is mean field near a tricritical point in bulk, is changed dramatically

George Cordoyiannis; Samo Kralj; George Nounesis; Zdravko Kutnjak; Slobodan Zumer

2007-01-01

129

Liquid-liquid-solid transition in viscoelastic liquids  

PubMed Central

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

Zubelewicz, Aleksander

2013-01-01

130

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

PubMed

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

131

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

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

132

A flux induced crystal phase transition in the vapor-liquid-solid growth of indium-tin oxide nanowires.  

PubMed

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

133

Critical behavior of director fluctuations in suspensions of ferroelectric nanoparticles in liquid crystals at the nematic to smectic-A phase transition.  

PubMed

By dynamic light scattering we studied the temperature dependence of scattered intensities and relaxation rates for pure twist and pure bend modes in a colloidal system of BaTiO(3) single domain nanoparticles and liquid crystal octylcyanobiphenyl (8CB) close to the nematic to smectic-A phase transition. From the experiments we obtained the critical exponents for the smectic correlation lengths, which in suspensions differ from the values for pure 8CB. The phase transition temperatures from isotropic to nematic phase (T(NI)) and from nematic to smectic-A phase (T(NA)) are both affected by the presence of the particles in two ways. The electric field around the ferroelectric particles increases the transition temperatures, whereas the disorder and probably also the excess of the surfactant cause a decrease of the transition temperatures compared to pure 8CB. The net effect is lower T(NI) and almost unchanged T(NA) in suspensions. After prolonged exposure to the external field the ferroelectric particles irreversibly aggregate, which results in the decrease of the internal electric field and, consequently, in the decrease of both transition temperatures. PMID:22463229

Mertelj, Alenka; Cmok, Luka; ?opi?, Martin; Cook, Gary; Evans, Dean R

2012-02-01

134

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

135

String Mediated Phase Transitions.  

National Technical Information Service (NTIS)

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 e...

E. Copeland, D. Haws, R. Rivers, S. Holbraad

1988-01-01

136

Pretransitional effects near the smectic-A -smectic-C* phase transition of hydrophilic and hydrophobic aerosil networks dispersed in ferroelectric liquid crystals.  

PubMed

A detailed x-ray scattering and high-resolution ac calorimetric study has been carried out near the smectic-A to chiral smectic-C phase transition of liquid-crystal compounds 4-(2-methyl butyl) phenyl 4-n-octylbiphenyl-4-carboxylate (CE8) and p-( n-decyloxy) benzylidene-p-amino-(2-methylbutyl) cinnamate (DOBAMBC) confined in hydrophilic and hydrophobic aerosil nanoparticle networks. The character of the transition, which is mean field near a tricritical point in bulk, is changed dramatically with an increase of aerosil-induced disorder. X-ray measurements revealed pretransitional behavior and compression of the smectic layers, phenomena that are strongly pronounced in high aerosil concentrations. A theoretical model that takes into account the interplay of relevant mechanisms is proposed to explain the observed phenomena. The effect of chirality on the interaction of liquid crystals with aerosils is discussed. PMID:17358355

Cordoyiannis, George; Kralj, Samo; Nounesis, George; Kutnjak, Zdravko; Zumer, Slobodan

2007-02-01

137

Volume phase transitions of smectic gels  

NASA Astrophysics Data System (ADS)

We present a mean-field theory to describe volume phase transitions of side-chain liquid crystalline (LC) gels, accompanied by isotropic-nematic-smectic- A phase transitions. Three different uniaxial nematic phases ( N1 , N2 , and N3 ) and smectic- A phases ( S1 , S2 , and S3 ) are defined by using orientational order parameter Sm of side-chain liquid crystals (mesogens), Sb of semiflexible backbone chains, and a translational order parameter ? for a smectic- A phase. We derive the free energy for smectic- A phases of side-chain LC gels dissolved in an isotropic solvent and examine the swelling curve of the LC gel, the orientational order parameters, and the deformation of the LC gel as a function of temperature. We find that the LC gel discontinuously changes the volume at an isotropic-nematic, an isotropic-smectic- A , and a nematic-smectic- A phase transition.

Matsuyama, Akihiko

2009-05-01

138

Emergence and Phase Transitions  

NASA Astrophysics Data System (ADS)

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

Sikkema, Arnold

2006-05-01

139

Control of fluidity and miscibility of a binary liquid mixture by the liquid-liquid transition  

NASA Astrophysics Data System (ADS)

Matter in its liquid state is convenient for processing and controlling chemical reactions, owing to its fluidity. Recently much evidence has been accumulated for the existence of a liquid-liquid transition (LLT) in single-component liquids. Here, we report that we can control, by the LLT of a molecular liquid, triphenyl phosphite (TPP), the fluidity and miscibility of its mixture with another molecular liquid. For a mixture of TPP with toluene or aniline, we find that both liquid I and II mix well and liquid II remains in a `liquid' state, in contrast to pure TPP, where liquid II is a non-ergodic amorphous state. This is the first example of a `true' LLT in a molecular liquid. Furthermore, we find demixing induced by the LLT for a mixture of TPP with diethyl ether or ethanol. These findings will open a new phase of research towards various applications of the LLT.

Kurita, Rei; Murata, Ken-Ichiro; Tanaka, Hajime

2008-08-01

140

Unraveling the solid-liquid-vapor phase transition dynamics at the atomic level with ultrafast x-ray absorption near-edge spectroscopy.  

PubMed

X-ray absorption near-edge spectroscopy (XANES) is a powerful probe of electronic and atomic structures in various media, ranging from molecules to condensed matter. We show how ultrafast time resolution opens new possibilities to investigate highly nonequilibrium states of matter including phase transitions. Based on a tabletop laser-plasma ultrafast x-ray source, we have performed a time-resolved (?3??ps) XANES experiment that reveals the evolution of an aluminum foil at the atomic level, when undergoing ultrafast laser heating and ablation. X-ray absorption spectra highlight an ultrafast transition from the crystalline solid to the disordered liquid followed by a progressive transition of the delocalized valence electronic structure (metal) down to localized atomic orbitals (nonmetal-vapor), as the average distance between atoms increases. PMID:22243009

Dorchies, F; Lévy, A; Goyon, C; Combis, P; Descamps, D; Fourment, C; Harmand, M; Hulin, S; Leguay, P M; Petit, S; Peyrusse, O; Santos, J J

2011-12-01

141

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

SciTech Connect

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

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

2010-01-01

142

Liquid-liquid and liquid-solid phase separation and flocculation for a charged colloidal dispersion S. K. Lai and K. L. Wu  

E-print Network

Liquid-liquid and liquid-solid phase separation and flocculation for a charged colloidal dispersion of the liquid-liquid and liquid-solid phase diagrams. We examine, in an aqueous charged colloidal dispersion transition calculated with respect to the liquid-solid coexistence phases. We find that there exists

143

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

144

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

PubMed

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

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

2014-06-19

145

The Putative Liquid-Liquid Transition is a Liquid-Solid Transition in Atomistic Models of Water  

E-print Network

We use numerical simulation to examine the possibility of a reversible liquid-liquid transition in supercooled water and related systems. In particular, for two atomistic models of water, we have computed free energies as functions of multiple order parameters, where one is density and another distinguishes crystal from liquid. For a range of temperatures and pressures, separate free energy basins for liquid and crystal are found, conditions of phase coexistence between these phases are demonstrated, and time scales for equilibration are determined. We find that at no range of temperatures and pressures is there more than a single liquid basin, even at conditions where amorphous behavior is unstable with respect to the crystal. We find a similar result for a related model of silicon. This result excludes the possibility of the proposed liquid-liquid critical point for the models we have studied. Further, we argue that behaviors others have attributed to a liquid-liquid transition in water and related systems are in fact reflections of transitions between liquid and crystal.

David T. Limmer; David Chandler

2011-07-01

146

Phase transition thermodynamics of bisphenols.  

PubMed

Herein we have studied, presented, and analyzed the phase equilibria thermodynamics of a bisphenols (BP-A, BP-E, BP-F, BP-AP, and BP-S) series. In particular, the heat capacities, melting temperatures, and vapor pressures at different temperatures as well as the standard enthalpies, entropies, and Gibbs energies of phase transition (fusion and sublimation) were experimentally determined. Also, we have presented the phase diagrams of each bisphenol derivative and investigated the key parameters related to the thermodynamic stability of the condensed phases. When all the bisphenol derivatives are compared at the same conditions, solids BP-AP and BP-S present lower volatilities (higher Gibbs energy of sublimation) and high melting temperatures due to the higher stability of their solid phases. Solids BP-A and BP-F present similar stabilities, whereas BP-E is more volatile. The introduction of -CH3 groups in BP-F (giving BP-E and BP-A) leads an entropic differentiation in the solid phase, whereas in the isotropic liquids the enthalpic and entropic differentiations are negligible. PMID:25244127

Costa, José C S; Dávalos, Juan Z; Santos, Luís M N B F

2014-10-16

147

Phase equilibria of a polymer discotic liquid crystal mixture.  

NASA Astrophysics Data System (ADS)

Thermodynamic phase diagrams of a polymer dispersed liquid crystal (PDLC) containing a monomeric discotic liquid crystal (DLC) and a polymer have been established theoretically by combing Flory-Huggins theory for the free energy of mixing of isotropic phase and Chandrasekhar-Clark theory for the phase transition of hexagonal crystalline ordering of discotic liquid crystals. By varying interaction parameter of hexagonal columnar phase, columnar-isotropic and columnar-nematic-isotropic phase transitions can be predicted. The spinodal line of the columnar DLC/polymer will be calculated in conjunction with the conventional liquid-liquid spinodal. Effects of various molecular parameters on the columnar LC phase diagram will be discussed.

Huang, Tsang-Min; Kyu, Thein

2009-03-01

148

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

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

149

Finite-temperature phase transition to a quantum spin liquid in a three-dimensional Kitaev model on a hyperhoneycomb lattice  

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

150

Phase transition in multiprocessor scheduling.  

PubMed

An "easy-hard" phase transition is shown to characterize the multiprocessor scheduling problem in which one has to distribute the workload on a parallel computer such as to minimize the overall run time. The transition can be analyzed in detail by mapping it on a mean-field antiferromagnetic Potts model. The static phase transition, characterized by a vanishing ground state entropy, corresponds to a transition in the performance of practical scheduling algorithms. PMID:12732079

Bauke, Heiko; Mertens, Stephan; Engel, Andreas

2003-04-18

151

Phase Transition in Multiprocessor Scheduling  

NASA Astrophysics Data System (ADS)

An “easy-hard” phase transition is shown to characterize the multiprocessor scheduling problem in which one has to distribute the workload on a parallel computer such as to minimize the overall run time. The transition can be analyzed in detail by mapping it on a mean-field antiferromagnetic Potts model. The static phase transition, characterized by a vanishing ground state entropy, corresponds to a transition in the performance of practical scheduling algorithms.

Bauke, Heiko; Mertens, Stephan; Engel, Andreas

2003-04-01

152

Phase transitions in layered crystals  

E-print Network

It is demonstrated by analyzing real examples that phase transitions in layered crystals occur like all other solid-state phase transitions by nucleation and crystal growth, but have a specific morphology. There the nucleation is epitaxial, resulting in the rigorous orientation relationship between the polymorphs, such that the direction of molecular layers are preserved. The detailed molecular mechanism of these phase transitions and formation of the laminar domain structures are described and related to the nature of ferroelectrics.

Yuri Mnyukh

2011-05-22

153

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

154

Quantum Nature of a Nuclear Phase Transition  

SciTech Connect

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

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

2008-09-19

155

Liquid-liquid phase separation in biology.  

PubMed

Cells organize many of their biochemical reactions in non-membrane compartments. Recent evidence has shown that many of these compartments are liquids that form by phase separation from the cytoplasm. Here we discuss the basic physical concepts necessary to understand the consequences of liquid-like states for biological functions. PMID:25288112

Hyman, Anthony A; Weber, Christoph A; Jülicher, Frank

2014-10-11

156

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

PubMed

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

Tanaka, Hajime

2012-10-01

157

Modeling phase transition and metastable phases  

E-print Network

We propose a model that describes phase transition including metastable phases present in the van der Waals Equation of State (EoS). We introduce a dynamical system that is able to depict the mass transfer between two phases, for which equilibrium states are both metastable and stable states, including mixtures. The dynamical system is then used as a relaxation source term in a isothermal two-phase model. We use a Finite volume scheme (FV) that treats the convective part and the source term in a fractional step way. Numerical results illustrate the ability of the model to capture phase transition and metastable states.

James, François

2014-01-01

158

Novelties of liquid–liquid–liquid phase transfer catalysis  

Microsoft Academic Search

Liquid–liquid–liquid phase transfer catalysis (L–L–L PTC) offers orders of magnitude intensification of rates of reaction and better selectivities than the biphasic PTC. The catalyst-rich middle phase is the main reaction phase. The etherification or alkoxylation of p-chloronitrobenzene (PCNB) was conducted by using alkanol and alkali instead of the metal alkoxide. A kinetic model is presented and validated.

G. D Yadav; Suguna S Naik

2001-01-01

159

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

160

Liquid to quasicrystal transition in bilayer water.  

PubMed

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

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

2010-10-21

161

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

PubMed

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

162

Liquid Phase Sintering  

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

163

Liquid–liquid transition in supercooled water suggested by microsecond simulations  

PubMed Central

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

Li, Yaping; Li, Jicun; Wang, Feng

2013-01-01

164

The Putative Liquid-Liquid Transition is a Liquid-Solid Transition in Atomistic Models of Water, Part II  

E-print Network

This paper extends our earlier studies of free energy functions of density and crystalline order parameters for models of supercooled water, which allows us to examine the possibility of two distinct metastable liquid phases [J. Chem. Phys. 135, 134503 (2011) and arXiv:1107.0337v2]. Low-temperature reversible free energy surfaces of several different atomistic models are computed: mW water, TIP4P/2005 water, SW silicon and ST2 water, the last of these comparing three different treatments of long-ranged forces. In each case, we show that there is one stable or metastable liquid phase, and there is an ice-like crystal phase. The time scales for crystallization in these systems far exceed those of structural relaxation in the supercooled metastable liquid. We show how this wide separation in time scales produces an illusion of a low-temperature liquid-liquid transition. The phenomenon suggesting metastability of two distinct liquid phases is actually coarsening of the ordered ice-like phase, which we elucidate u...

Limmer, David T

2013-01-01

165

Nanostructures of Liquid Crystal Phases  

NASA Astrophysics Data System (ADS)

Bent-core liquid crystals have attracted intense interest in recent years, exhibiting a wide variety of novel structural phenomena involving the interplay of chirality, molecular bend and molecular tilt. Freeze-fracture transmission electron microscopy together with other experimental methods has been used to characterize the nanostructures of bent-core liquid crystal phases in which the molecules undergo complex self-assembly, forming, for example, helical nanofilaments (the B4 phase), disordered focal conics (the DC phase), and layer undulations (the B7 phase) in the bulk. These studies have helped us better understand the complex nature of these and other liquid crystal phases. For example, the investigation of the chirality-preserving growth of the helical nanofilaments in the B4 phase will allow better control of its growth for applications, the discovery of the quasi-ordered toric focal conics of the DC phase at the air/liquid crystal interface opens the way for the development of two-dimensional or even three-dimensional periodic dielectric media for photonic crystal applications, the study of layer undulation defects reveals the detailed molecular arrangement in the B7 phase, and the discovery and characterization of the randomized twist grain boundary phase broads the understanding of chiral liquid crystal phases.

Chen, Dong

166

Disappearance of the Gas-Liquid Phase Transition for Highly Charged Colloids A.-P. Hynninen and A. Z. Panagiotopoulos  

E-print Network

using the primitive model, consisting of explicit hard-sphere colloids and point counterions. In our model, the colloids are modeled as hard spheres with diameter and point charge Qq at the center to a gas-solid phase separation at colloid charges Q 20 times the counterion charge. Approximate free

167

Dielectric pre-transitional behavior in the vicinity of isotropic–blue phase III transition  

Microsoft Academic Search

Pre-transitional effects have been observed from the study of static dielectric permittivity () and its temperature derivatives () near the isotropic to blue phase-III (I–BPIII) transition in a highly polar T-shaped liquid crystalline material having a stable BPIII phase which persists over a comparatively wide range of temperature (?8°C). The pre-transitional behavior near I–BPIII transition is found to be very

Manoj Marik; M. Rahman; B. K. Chaudhuri; A. Yoshizawa

2011-01-01

168

Dielectric pre-transitional behavior in the vicinity of isotropic–blue phase III transition  

Microsoft Academic Search

Pre-transitional effects have been observed from the study of static dielectric permittivity () and its temperature derivatives () near the isotropic to blue phase-III (I–BPIII) transition in a highly polar T-shaped liquid crystalline material having a stable BPIII phase which persists over a comparatively wide range of temperature (?8°C). The pre-transitional behavior near I–BPIII transition is found to be very

Manoj Marik; M. Rahman; B. K. Chaudhuri; A. Yoshizawa

2012-01-01

169

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

PubMed

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

170

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

E-print Network

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

171

Phase transition in black holes  

E-print Network

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

172

Phase transition in porous electrodes.  

PubMed

It is shown by Monte Carlo simulation that electrochemical thermodynamics of electrolytes in a porous electrode is qualitatively different from that in the bulk with a planar electrode. In particular, first order phase transitions occur in porous electrodes when the pore size is comparable to the ion size of the electrolytes: as the voltage is increased from zero, the surface charge density and the ion density in the porous electrodes discontinuously change at a specific voltage. The critical points for those phase transitions are identified. PMID:21513411

Kiyohara, Kenji; Sugino, Takushi; Asaka, Kinji

2011-04-21

173

Transitions between paraelectric and ferroelectric phases of bent-core smectic liquid crystals in the bulk and in thin freely suspended films.  

PubMed

We report on the contrasting phase behavior of a bent-core liquid crystal with a large opening angle between the mesogenic units in the bulk and in freely suspended films. Second-harmonic generation experiments and direct observation of director inversion walls in films in an applied electric field reveal that the nonpolar smectic C phase observed in bulk samples becomes a ferroelectric "banana" phase in films, showing that a mesogen with a small steric moment can give a phase with polar order in freely suspended films even when the corresponding bulk phase is paraelectric. PMID:23214799

Eremin, Alexey; Floegel, Martin; Kornek, Ulrike; Stern, Stephan; Stannarius, Ralf; Nádasi, Hajnalka; Weissflog, Wolfgang; Zhu, Chenhui; Shen, Yongqiang; Park, Cheol Soo; Maclennan, Joseph; Clark, Noel

2012-11-01

174

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

PubMed Central

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

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

1994-01-01

175

The Ehrenfest Classification of Phase Transitions: Introduction and Evolution  

Microsoft Academic Search

The first classification of general types of transition between phases of matter, introduced by Paul Ehrenfest in 1933,\\u000a lies at a crossroads in the thermodynamical study of critical phenomena. It arose following the discovery in 1932 of a suprising\\u000a new phase transition in liquid helium, the “lambda transition,” when W. H. Keesom and coworkers in Leiden, Holland observed\\u000a a ?haped

Gregg Jaeger; H. STUEWER

1998-01-01

176

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

E-print Network

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

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

2014-04-09

177

Phase transitions in quantum chromodynamics  

SciTech Connect

The current understanding of finite-temperature phase transitions in QCD is reviewed. A critical discussion of refined phase-transition criteria in numerical lattice simulations and of analytical tools going beyond the mean-field level in effective continuum models for QCD is presented. Theoretical predictions about the order of the transitions are compared with possible experimental manifestations in heavy-ion collisions. Various places in phenomenological descriptions are pointed out where more reliable data for QCD{close_quote}s equation of state would help in selecting the most realistic scenario among those proposed. Unanswered questions are raised about the relevance of calculations that assume thermodynamic equilibrium. Promising new approaches for implementing nonequilibrium aspects of the thermodynamics of heavy-ion collisions are described. {copyright} {ital 1996 The American Physical Society.}

Meyer-Ortmanns, H. [Institut fuer Theoretische Physik, Universitaet Heidelberg, D-69120 Heidelberg (Germany)] [Institut fuer Theoretische Physik, Universitaet Heidelberg, D-69120 Heidelberg (Germany)

1996-04-01

178

Non-equilibrium phase transitions  

Microsoft Academic Search

These lecture notes give a basic introduction to the physics of phase transitions under non-equilibrium conditions. The notes start with a general introduction to non-equilibrium statistical mechanics followed by four parts. The first one discusses the universality class of directed percolation, which plays a similar role as the Ising model in equilibrium statistical physics. The second one gives an overview

Haye Hinrichsen

2006-01-01

179

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

180

Liquid-Liquid Phase Equilibria in Binary Mixtures Under Negative Pressure  

Microsoft Academic Search

\\u000a Several binary or multicomponent solutions exhibit liquid-liquid phase transition; i.e. changing the temperature and\\/or pressure\\u000a and\\/or concentration etc., the initially homogeneous liquid can split into two or more liquid phases. In this paper we would\\u000a like to give examples where the extension of liquid-liquid solubility branches below p=0 gives us new information about the\\u000a studied binary and quasi-binary mixtures.

Attila R. Imre

181

Texture transitions in the liquid crystalline alkyloxybenzoic acid 6OBAC  

E-print Network

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

182

FT-IR and two-dimensional correlation analysis of the liquid crystalline phase transitions in the 4-Bromobenzylidene-4'-alkyloxyanilines.  

PubMed

The FT-IR spectra of the 4-bromobenzylidene-4'-alkyloxyanilines (nBBAA, for n = 4-12) were studied as a function of temperature. The molten state of the alkyloxy chain in smectic B (SmB), smectic A (SmA), and isotropic phases was analyzed. Generalized two-dimensional (2D) correlation spectroscopy has been applied to study changes in the conformational structure and specific interactions of molecules at phase transition in homologous series of nBBAA. A windowed autocorrelation analysis enabled us to locate transition points basing on the spectroscopic data. PMID:23931048

Osiecka, Natalia; Czarnecki, Miros?aw A; Galewski, Zbigniew; Massalska-Arod?, Maria

2013-09-12

183

Lyotropic effects of alkanes and headgroup composition on the L03B1 -HII lipid liquid crystal phase transition : hydrocarbon packing versus intrinsic curvature  

E-print Network

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

184

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

ERIC Educational Resources Information Center

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

185

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

Microsoft Academic Search

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

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

1975-01-01

186

Liquid-Phase Adsorption Fundamentals.  

ERIC Educational Resources Information Center

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

Cooney, David O.

1987-01-01

187

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

188

Non-equilibrium phase transitions  

SciTech Connect

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

189

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

NASA Astrophysics Data System (ADS)

One of the most successful theories of a non-Fermi-liquid metallic state is the composite Fermi-liquid (CFL) theory of the half-filled Landau level. In this paper, we study continuous quantum phase transitions out of the CFL state and into a Landau Fermi liquid, in the limit of no disorder and fixed particle number. This transition can be induced by tuning the bandwidth of the Landau level relative to the interaction energy, for instance through an externally applied periodic potential. We find a transition to the Landau Fermi liquid through a gapless Mott insulator with a Fermi surface of neutral fermionic excitations. In the presence of spatial symmetries, we also find a direct continuous transition between the CFL and the Landau Fermi liquid. The transitions have a number of characteristic observable signatures, including the presence of two crossover temperature scales, resistivity jumps, and vanishing compressibility. When the composite fermions are paired instead, our results imply quantum critical points between various non-Abelian topological states, including the ?=1/2 Moore-Read Pfaffian [Ising × U(1) topological order], a version of the Kitaev B phase (Ising topological order), and paired electronic superconductors. To study such transitions, we use a projective construction of the CFL, which goes beyond the conventional framework of flux attachment to include a broader set of quantum fluctuations. These considerations suggest a possible route to fractionalized Mott insulators by starting with fractional quantum Hall states and tuning the Landau-level bandwidth.

Barkeshli, Maissam; McGreevy, John

2012-08-01

190

An enthalpy-based hybrid lattice-Boltzmann method for modelling solid?liquid phase transition in the presence of convective transport  

NASA Astrophysics Data System (ADS)

An extended lattice Boltzmann model is developed for simulating the convectionliquid phase transition processes. Macroscopic hydrodynamic variables are obtained through the solution of an evolution equation of a single-particle density distribution function, whereas, the macroscopic temperature field is obtained by solving auxiliary scalar transport equations. The novelty of the present methodology lies in the formulation of an enthalpy-based approach for phase-change modelling within a lattice-Boltzmann framework, in a thermodynamically consistent manner. Thermofluidic aspects of phase transition are handled by means of a modified enthalpyBénard convection in the presence of directional solidification in a top-cooled cavity, and crystal growth during solidification of an undercooled melt agree well with the numerical and experimental results available in the literature, and provide substantial evidence regarding the upscaled computational economy provided by the present methodology.

Chakraborty, Suman; Chatterjee, Dipankar

191

Dynamical signature of two ``ideal glass transitions'' in nematic liquid crystals  

E-print Network

Dynamical signature of two ``ideal glass transitions'' in nematic liquid crystals Hu Cang, Jie Li heterodyne detected optical Kerr effect data for four liquid crystals. The data cover a range of times from 1G theory for the isotropic phase of liquid crystals. However, it is also found that the liquid crystal data

Fayer, Michael D.

192

Phase transition dynamics and gravitational waves  

SciTech Connect

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

193

Phase transitions in surface layers of polycrystalline solids  

Microsoft Academic Search

The fundamental equations of the thermodynamics of films were applied to describe the properties of polycrystalline solids,\\u000a namely, first-order phase transitions of grain boundaries with the formation of two-dimensional liquids. The generalized equation\\u000a obtained was used to calculate the temperature of this phase transition (the premelting temperature) for metals; it was found\\u000a to lie between 0.55 and 0.86 of the

Yu. A. Minaev

2007-01-01

194

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

NASA Astrophysics Data System (ADS)

A large fraction of submicron atmospheric particles contain both organic material and inorganic salts. As the relative humidity cycles in the atmosphere, these mixed particles can undergo a range of phase transitions, possibly including liquid-liquid phase separation. If liquid-liquid phase separation occurs, the gas-particle partitioning of atmospheric semi-volatile organic compounds, the scattering and absorption of solar radiation, and the uptake of reactive gas species on atmospheric particles may be affected. Here, using optical and fluorescence microscopy, we present images that show the coexistence of two non-crystalline phases in particles generated from samples collected on multiple days in Atlanta, Georgia, and in particles generated in the laboratory using simulated atmospheric conditions. These results show that atmospheric particles can undergo liquid-liquid phase separations.

Bertram, A. K.; You, Y.; Renbaum-Wolff, L.; Carreras-Sospedra, M.; Hiranuma, N.; Smith, M.; Zhang, X.; Weber, R.; Shilling, J. E.; Dabdub, D.; Martin, S. T.

2012-12-01

195

Liquid-phase chromatography detector  

DOEpatents

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

196

Liquid-phase chromatography detector  

DOEpatents

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

197

Observation of equilibrium liquid-liquid transition in triphenyl phosphite  

NASA Astrophysics Data System (ADS)

The thermal signature of an equilibrium liquid-liquid transition (LLT) in triphenyl phosphite was detected by differential scanning calorimetry measurements at a fast heating rate reaching 500 K min-1. The estimated temperature, enthalpy, and entropy of the LLT were 241.7 K, 12.0 kJ mol-1, and 49.5 J K-1 mol-1, respectively. The estimated residual entropy for a glacial sample prepared at 224.7 K was 6 J K-1 mol-1; this value is much smaller than that for the normal glassy liquid. This glacial state was found to be a highly ordered liquid compared with the normal glassy liquid in terms of entropy.

Terashima, Y.; Tsuchie, M.; Takeda, K.; Honda, M.

2013-10-01

198

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

SciTech Connect

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

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

2012-07-30

199

Work and quantum phase transitions: quantum latency.  

PubMed

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

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

2014-06-01

200

Dynamic Phase Transitions in PVT Systems  

E-print Network

The main objective of this article are two-fold. First, we introduce some general principles on phase transition dynamics, including a new dynamic transition classification scheme, and a Ginzburg-Landau theory for modeling equilibrium phase transitions. Second, apply the general principles and the recently developed dynamic transition theory to study dynamic phase transitions of PVT systems. In particular, we establish a new time-dependent Ginzburg-Landau model, whose dynamic transition analysis is carried out. It is worth pointing out that the new dynamic transition theory, along with the dynamic classification scheme and new time-dependent Ginzburg Landau models for equilibrium phase transitions can be used in other phase transition problems, including e.g. the ferromagnetism and superfluidity, which will be reported elsewhere. In addition, the analysis for the PVT system in this article leads to a few physical predications, which are otherwise unclear from the physical point of view.

Tian Ma; Shouhong Wang

2007-12-21

201

Nanoscale Dynamics of Phase Flipping in Water near its Hypothesized Liquid-Liquid Critical Point  

PubMed Central

One hypothesized explanation for water's anomalies imagines the existence of a liquid-liquid (LL) phase transition line separating two liquid phases and terminating at a LL critical point. We simulate the classic ST2 model of water for times up to 1000?ns and system size up to N = 729. We find that for state points near the LL transition line, the entire system flips rapidly between liquid states of high and low density. Our finite-size scaling analysis accurately locates both the LL transition line and its associated LL critical point. We test the stability of the two liquids with respect to the crystal and find that of the 350 systems simulated, only 3 of them crystallize and these 3 for the relatively small system size N = 343 while for all other simulations the incipient crystallites vanish on a time scales smaller than ? 100?ns. PMID:22761987

Kesselring, T. A.; Franzese, G.; Buldyrev, S. V.; Herrmann, H. J.; Stanley, H. E.

2012-01-01

202

Low Frequency Acoustic Resonance Studies of the Liquid-Vapor Transition in Silica Aerogel  

E-print Network

Fluid phase transitions in porous media are a powerful probe of the effect of confinement and disorder on phase transitions. Aerogel may provide a model system in which to study the effect of dilute impurities on a variety of phase transitions. In this paper we present a series of low frequency acoustic experiments on the effect of aerogel on the liquid-vapor phase transition. Acoustic resonators were used to study the liquid-vapor transition in two fluids (helium and neon) and in two different porosity aerogels (95% and 98%). While effective coexistence curves could be mapped out, the transition was sometimes difficult to pinpoint, leading to doubt as to whether this transition can be treated as an equilibrium macroscopic phase transition at all.

Tobias Herman; John Beamish

2005-06-30

203

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

PubMed Central

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

204

Phase Inversion in a Batch Liquid - Liquid Stirred System  

Microsoft Academic Search

Phase inversion phenomenon occurs in many industrial processes including liquid- liquid dispersions. Some parameters such as energy input or the presence of mineral compounds in the system affect this phenomenon. The aim of this research is to study the speed of rotation or energy input at a range of 400 to 800 rpm in a batch liquid-liquid system containing toluene

M. Amouei; P. Khadiv-Parsi; M. M. Moosavian; N. Hedayat; A. A. Davoodi

205

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

206

Physica A 354 (2005) 19 The reversible phase transition of DNA-linked  

E-print Network

online 23 March 2005 Abstract We present direct evidence for a reversible phase transition of DNA evidence of a liquid­gel phase transition of DNA-linked gold colloid assemblies via diPhysica A 354 (2005) 1­9 The reversible phase transition of DNA-linked colloidal gold assemblies

Kiang, Ching-Hwa

207

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

E-print Network

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

Paris-Sud XI, Université de

208

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

209

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

E-print Network

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

Wu, Shin-Tson

210

Glass–liquid transition of water at high pressure  

PubMed Central

The knowledge of the existence of liquid water under extreme conditions and its concomitant properties are important in many fields of science. Glassy water has previously been prepared by hyperquenching micron-sized droplets of liquid water and vapor deposition on a cold substrate (ASW), and its transformation to an ultraviscous liquid form has been reported on heating. A densified amorphous solid form of water, high-density amorphous ice (HDA), has also been made by collapsing the structure of ice at pressures above 1 GPa and temperatures below approximately 140 K, but a corresponding liquid phase has not been detected. Here we report results of heat capacity Cp and thermal conductivity, in situ, measurements, which are consistent with a reversible transition from annealed HDA to ultraviscous high-density liquid water at 1 GPa and 140 K. On heating of HDA, the Cp increases abruptly by (3.4 ± 0.2) J mol-1 K-1 before crystallization starts at (153 ± 1) K. This is larger than the Cp rise at the glass to liquid transition of annealed ASW at 1 atm, which suggests the existence of liquid water under these extreme conditions. PMID:21690361

Andersson, Ove

2011-01-01

211

Notes on Black Hole Phase Transitions  

Microsoft Academic Search

In these notes we present a summary of existing ideas about phase transitions of black hole spacetimes in semiclassical gravity and offer some thoughts on three possible scenarios or mechanisms by which these transitions could take place. We begin with a review of the thermodynamics of a black hole system and emphasize that the phase transition is driven by the

G. J. Stephens; B. L. Hu

2001-01-01

212

Phase transitions of superconducting wire network  

E-print Network

Phase transitions of superconducting wire network under field modulation Institute for Solid State;Normal ( = 0) R = 0 Phase transition of superconducting wire network (SWN) 1. Mean field transition o 14 o 12 o 10 o 8 o 6 o 4 o 2 o 0 o Offset:30 mK Pick up one period Compare with calculation (black

Katsumoto, Shingo

213

Structural study of supercooled liquid transition metals  

NASA Astrophysics Data System (ADS)

Local structural models for supercooled liquid transition metals (Ti, Ni, and Zr) are proposed based on a reverse Monte Carlo analysis of high-energy x-ray diffraction data taken from the electrostatically levitated liquids. The resulting structures are characterized by their bond angle distributions, Honeycutt and Andersen indices [J. Phys. Chem. 91, 4950 (1987)], and bond orientational order parameters. All analyses suggest that an icosahedral short-range order is present in these supercooled liquids, but it is distorted in liquid Ti. These results are in agreement with the observed evolution of the high-q shoulder on the second peak in the structure factor S(q ) and with an earlier analysis based on a local cluster model.

Kim, T. H.; Kelton, K. F.

2007-02-01

214

QCD Phase Transitions, Volume 15  

SciTech Connect

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

215

Spontaneous liquid-liquid phase separation of water  

NASA Astrophysics Data System (ADS)

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

Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

2014-02-01

216

Thermodynamics and phase relationships of transition metal-sulfur systems: Part V. A reevaluation of the Fe-S system using an associated solution model for the liquid phase  

Microsoft Academic Search

The relevant thermodynamic and phase equilibrium data for the Fe-S binary system have been reevaluated in light of more recent\\u000a data. An associated solution model is used to describe the thermodynamic properties of the liquid phase as a function of composition\\u000a and temperature. For the pyrrhotite phase, a statistical thermodynamic model based on the formation of Frenkel defects in\\u000a the

Y. AUSTIN CHANG; K. C. Hsieh

1985-01-01

217

Phase Transitions in Nonlinear Filtering  

E-print Network

It has been established under very general conditions that the ergodic properties of Markov processes are inherited by their conditional distributions given partial information. While the existing theory provides a rather complete picture of classical filtering models, many infinite-dimensional problems are outside its scope. Far from being a technical issue, the infinite-dimensional setting gives rise to surprising phenomena and new questions in filtering theory. The aim of this paper is to discuss some elementary examples, conjectures, and general theory that arise in this setting, and to highlight connections with problems in statistical mechanics and ergodic theory. In particular, we exhibit a simple example of a uniformly ergodic model in which ergodicity of the filter undergoes a phase transition, and we develop some qualitative understanding as to when such phenomena can and cannot occur. We also discuss closely related problems in the setting of conditional Markov random fields.

Patrick Rebeschini; Ramon van Handel

2014-01-24

218

Size-dependent phase transition temperatures of dispersed systems  

NASA Astrophysics Data System (ADS)

A phase transition equation on the basis of the additional pressure on the curved surfaces of dispersed systems has been proposed, and the specific differential equations for various kinds of phase transitions of dispersed systems have been derived by the phase transition equation. Applying the fusion transition equations, the melting temperatures of Au and Sn nanoparticles have been calculated, and the predicted melting temperatures are in good agreement with the available experimental data. The results show that the phase transition equations can be used to predict the temperatures of phase transitions of dispersed systems and to explain the phenomenon of metastable states; the size of the dispersed phase has noticeable effect on the phase transition temperature; all temperatures of fusion, solidification, condensation, vaporization, sublimation and desublimation decrease with decreasing radius of the dispersed phase, but the bubble point temperature of a planar liquid increases with decreasing absolute value of radius of the bubbles; the depression of melting temperature for a nanowire is approximately half of that for a spherical nanoparticle with identical radius.

Xue, Yong-Qiang; Zhao, Miao-Zhi; Lai, Wei-Peng

2013-01-01

219

Liquid Phase Miscibility Gap Materials  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

220

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

221

Transient liquid phase ceramic bonding  

DOEpatents

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

222

Large-scale rapid phase-transition explosions  

Microsoft Academic Search

When a cryogenic liquid such as liquefied natural gas (LNG) is suddenly heated, one of the results is a kind of explosive boiling that occurs with the rapid-phase-transition (RPT) from liquid to gas. Such RPT explosions can produce damaging energy releases. RPT explosions with detonation energy equivalents of several kilograms of TNT have occurred in the large-scale spill tests of

McRae

1983-01-01

223

Liquid-like phases of ?^+?^- matter  

E-print Network

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

224

Chiral strain and reentrancy in blue-phase transitions  

NASA Astrophysics Data System (ADS)

We have studied the effect of chiral strain on phase transitions in a chiral material by examining the cholesteric (Ch) blue-phase (BP) liquid-crystal system in the Cano-wedge configuration. We observe both Ch and BP Cano rings whose positions are explained by Ch elastic theory. In the phase-transition region, chiral strain causes the positions of the Ch-BP coexistence rings to be temperature dependent and to exhibit reentrancy with respect to chiral strain. A free-energy model is presented which explains the gross features of the positions of the coexistence rings.

Feldman, A. I.; Crooker, P. P.; Goh, L. M.

1987-01-01

225

Topological Phase Transitions in Strongly Correlated Fermi Systems  

Microsoft Academic Search

Opportunities for topological phase transitions in strongly correlated Fermi systems near a quantum critical point are explored as an alternative to collective scenarios for experimentally observed departures from standard Fermi-liquid behavior. Attention is focused on a quantum critical point at which the effective mass is divergent due to vanishing of the quasiparticle group velocity at the Fermi surface. Working within

J. W. Clark; V. A. Khodel; M. V. Zverev

2010-01-01

226

Topological Phase Transitions in Strongly Correlated Fermi Systems  

Microsoft Academic Search

Opportunities for topological phase transitions in strongly correlated Fermi systems near a quantum critical point are explored as an alternative to collective scenarios for experimentally observed departures from standard Fermi-liquid behavior. Attention is focused on a quantum critical point at which the effective mass is divergent due to vanishing of the quasiparticle group velocity at the Fermi surface. Working within

J. W. Clark; V. A. Khodel; M. V. Zverev

2009-01-01

227

Liquid phase sintering in microgravity  

NASA Astrophysics Data System (ADS)

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

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

228

Remarks on the Electroweak Phase Transition  

E-print Network

In the standard scenario, the electroweak phase transition is a first order phase transition which completes by the nucleation of critical bubbles. Recently, there has been speculation that the standard picture of the electroweak phase transition is incorrect. Instead, it has been proposed that throughout the phase transition appreciable amounts of both broken and unbroken phases of $SU(2)$ coexist in equilibrium. I argue that this can not be the case. General principles insure that the universe will remain in a homogenous state of unbroken $SU(2)$ until the onset of critical bubble production. In addition, an analytic treatment of the one Higgs doublet, electroweak phase transition in the standard model and minimal extensions is reviewed. Results from the thin wall approximation are compared to results obtained using the Lindes' action. Perhaps the most important quantitative result we can get from an analysis of the phase transition is determination of $\\vevphi$ when the phase transition completes. For Higgs boson masses above the current experimental limit, the thin wall approximation determines the value of $\\vevphi$ at the end of the phase transition to an accuracy of better than three percent.

Greg W. Anderson

1992-06-23

229

Experimental (solid + liquid) or (liquid + liquid) phase equilibria of (amine + nitrile) binary mixtures  

Microsoft Academic Search

(Solid+liquid) phase diagrams have been determined for (hexylamine, or octylamine, or 1,3-diaminopropane+acetonitrile) mixtures. Simple eutectic systems have been observed in these mixtures. (Liquid+liquid) phase diagrams have been determined for (octylamine, or decylamine+propanenitrile, or +butanenitrile) mixtures. Mixtures with propanenitrile and butanenitrile show immiscibility in the liquid phase with an upper critical solution temperature, UCST. (Solid+liquid) phase diagrams have been correlated using

Urszula Doma?ska; Ma?gorzata Marciniak

2007-01-01

230

Liquid phase sintering of silicon carbide  

DOEpatents

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

231

Liquid phase sintering of silicon carbide  

DOEpatents

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

232

Game Theory and Topological Phase Transition  

E-print Network

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

233

Liquid-vapor transition driven by bond disorder.  

PubMed

We report grand-canonical Monte Carlo simulations of an equimolar mixture of hard colloids coated with long polymers that have a complementary functionalization. Such systems have the potential to function as self-healing materials. Under conditions where the complementary polymer ends are strongly associated, we observe a first-order vapor-liquid transition from a dilute gas of colloidal dimers to a dense, liquid-like phase. This transition is driven exclusively by the increase in entropy associated with bond disorder-an effect that was predicted theoretically by Zilman et al. [Phys. Rev. Lett. 91, 015901 (2003)10.1103/PhysRevLett.91.015901]. Our simulations rationalize experimental observations by Schmatko et al. [Soft Matter 03 (2007) 703.]. PMID:18764339

Bozorgui, Behnaz; Frenkel, Daan

2008-07-25

234

Phase transitions in rocks under shock compression  

Microsoft Academic Search

The zero-pressure densities of some rock Hugoniots in their high-pressure phases are determined. Comparison of these densities with experimental results on phase transitions of a number of rock-forming minerals suggests that the predominant transition in Stillwater bronzitite and Bushveld bronzitite is pyroxene --> spinel + stipoverite (stishovite). Pyroxene in Healdsburg diabase and Centreville diabase is likely to transform in the

Wang Chi-Yuen

1967-01-01

235

FRACTIONAL LAPLACIAN PHASE TRANSITIONS AND BOUNDARY REACTIONS  

E-print Network

FRACTIONAL LAPLACIAN PHASE TRANSITIONS AND BOUNDARY REACTIONS: A GEOMETRIC INEQUALITY-called fractional Laplacian. The study of this nonlocal equation is made via a careful analysis of the following: Boundary reactions, Allen-Cahn phase transitions, frac- tional operators, Poincar´e-type inequality. 2000

236

Magnetic field generation from nonequilibrium phase transitions  

Microsoft Academic Search

We study the generation of magnetic fields during the stage of particle production resulting from spinodal instabilities during phase transitions out of equilibrium. The main premise is that long-wavelength instabilities that drive the phase transition lead to strong nonequilibrium charge and current fluctuations which generate electromagnetic fields. We present a formulation based on the nonequilibrium Schwinger-Dyson equations that leads to

D. Boyanovsky; H. J. de Vega; M. Simionato

2003-01-01

237

Quantum Phase Transitions in a Finite System  

E-print Network

A general procedure for studying finite-N effects in quantum phase transitions of finite systems is presented and applied to the critical-point dynamics of nuclei undergoing a shape-phase transition of second-order (continuous), and of first-order with an arbitrary barrier.

A. Leviatan

2006-12-05

238

Environmentally Friendly Renormalization Group and Phase Transitions  

E-print Network

We discuss an environmentally friendly renormalization group approach to analyze phase transitions. We intend to apply this method to the Electroweak Phase Transition. This work is in progress. We present some previously obtained results concerning a scalar theory, where the main features of this algorithm are introduced.

F. Astorga

2002-02-01

239

Environmentally Friendly Renormalization Group and Phase Transitions  

E-print Network

We discuss an environmentally friendly renormalization group approach to analyze phase transitions. We intend to apply this method to the Electroweak Phase Transition. This work is in progress. We present some previously obtained results concerning a scalar theory, where the main features of this algorithm are introduced.

Astorga, F

2002-01-01

240

PHASE TRANSITION BEHAVIOR IN COMBINATORICS AND  

E-print Network

PHASE TRANSITION BEHAVIOR IN COMBINATORICS AND COMPUTATION Thesis submitted in partial fulfillment-Gurion University of the Negev April 2009 Beer-Sheva #12;#12;PHASE TRANSITION BEHAVIOR IN COMBINATORICS Beimel, who put their hearts into my education as a researcher and into the completion of my thesis. I

Beimel, Amos

241

Phase transitions of superconducting wire network  

E-print Network

POS44 Phase transitions of superconducting wire network under field modulation Institute for Solid-13(2006)@KyotoResearchPark #12;Normal ( = 0) R = 0 Phase transition of superconducting wire network (SWN) 1. MeanK Pick up one period Compare with calculation (black dotted line) Result 8 mT = 1 0o = 0 16o = 1

Katsumoto, Shingo

242

General analysis of the chiral phase transition  

SciTech Connect

The universality classes applicable to the chiral phase transition are studied. The epsilon-expansion predicts that the chiral transition should always be of first order for three or more flavors. If fluctuations with topological charge evaporate at temperatures well below the chiral transition point, a new phase of hadronic matter could occur, one in which there would be massive violations of isospin. 20 refs., 5 figs.

Pisarski, R.D.

1985-06-01

243

Finite-temperature phase transitions in the ionic Hubbard model  

NASA Astrophysics Data System (ADS)

We investigate paramagnetic metal-insulator transitions in the infinite-dimensional ionic Hubbard model at finite temperatures. By means of the dynamical mean-field theory with an impurity solver of the continuous-time quantum Monte Carlo method, we show that an increase in the interaction strength brings about a crossover from a band insulating phase to a metallic one, followed by a first-order transition to a Mott insulating phase. The first-order transition turns into a crossover above a certain critical temperature, which becomes higher as the staggered lattice potential is increased. Further, analysis of the temperature dependence of the energy density discloses that the intermediate metallic phase is a Fermi liquid. It is also found that the metallic phase is stable against strong staggered potentials even at very low temperatures.

Kim, Aaram J.; Choi, M. Y.; Jeon, Gun Sang

2014-04-01

244

Phase transitions in supported lipid bilayers studied by AFM.  

PubMed

We review the capabilities of Atomic Force Microscopy (AFM) in the study of phase transitions in Supported Lipid Bilayers (SLBs). AFM represents a powerful technique to cover the resolution range not available to fluorescence imaging techniques and where spectroscopic data suggest what the relevant lateral scale for domain formation might be. Phase transitions of lipid bilayers involve the formation of domains characterized by different heights with respect to the surrounding phase and are therefore easily identified by AFM in liquid solution once the bilayer is confined to a flat surface. Even if not endowed with high time resolution, AFM allows light to be shed on some aspects related to lipid phase transitions in the case of both a single lipid component and lipid mixtures containing sterols also. We discuss here the obtained results in light of the peculiarities of supported lipid bilayer model systems. PMID:25090108

Alessandrini, Andrea; Facci, Paolo

2014-10-01

245

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

E-print Network

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 · Why do we care which regime it is? ­ Pressure drop varies by an order

McCready, Mark J.

246

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

247

More is the Same; Phase Transitions and Mean Field Theories  

NASA Astrophysics Data System (ADS)

This paper is the first in a series that will look at the theory of phase transitions from the perspectives of physics and the philosophy of science. The series will consider a group of related concepts derived from condensed matter and statistical physics. The key technical ideas go under the names of "singularity", "order parameter", "mean field theory", "variational method", "correlation length", "universality class", "scale changes", and "renormalization". The first four of these will be considered here. 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 some statistical variable. The discontinuous property is called the order parameter. Each phase transition has its own order parameter. The possible order parameters 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 the discontinuity in the jump approaches zero. This article is about statistical mechanics and the development of mean field theory as a basis for a partial understanding of phase transition phenomena. Much of the material in this review was first prepared for the Royal Netherlands Academy of Arts and Sciences in 2006. It has appeared in draft form on the authors' web site (http://jfi.uchicago.edu/~leop/) since then. The title of this article is a hommage to Philip Anderson and his essay "More is Different" (Sci. New Ser. 177(4047):393-396, 1972; N.-P. Ong and R. Bhatt (eds.) More is Different: Fifty Years of Condensed Matter Physics, Princeton Series in Physics, Princeton University Press, 2001) which describes how new concepts, not applicable in ordinary classical or quantum mechanics, can arise from the consideration of aggregates of large numbers of particles. Since phase transitions only occur in systems with an infinite number of degrees of freedom, such transitions are a prime example of Anderson's thesis.

Kadanoff, Leo P.

2009-12-01

248

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

249

Phase transitions in QCD and string theory  

NASA Astrophysics Data System (ADS)

We develop a unified effective field theory approach to the high-temperature phase transitions in QCD and string theory, incorporating winding modes (time-like Polyakov loops, vortices) as well as low-mass states (pseudoscalar mesons and glueballs, matter and dilaton supermultiplets). Anomalous scale invariance and the Z3 structure of the centre of SU(3) decree a first-order phase transition with simultaneous deconfinement and Polyakov loop condensation in QCD, whereas string vortex condensation is a second-order phase transition breaking a Z2 symmetry. We argue that vortex condensation is accompanied by a dilaton phase transition to a strong coupling regime, and comment on the possible role of soliton degrees of freedom in the high-temperature string phase. On leave of absence from the School of Physics & Astronomy, University of Minnesota, Minneapolis, Minnesota, USA.

Campell, Bruce A.; Ellis, John; Kalara, S.; Nanopoulos, D. V.; Olive, Keith A.

1991-02-01

250

How generic scale invariance influences quantum and classical phase transitions  

SciTech Connect

This review discusses a paradigm that has become of increasing importance in the theory of quantum phase transitions, namely, the coupling of the order-parameter fluctuations to other soft modes and the resulting impossibility of constructing a simple Landau-Ginzburg-Wilson theory in terms of the order parameter only. The soft modes in question are manifestations of generic scale invariance, i.e., the appearance of long-range order in whole regions in the phase diagram. The concept of generic scale invariance and its influence on critical behavior is explained using various examples, both classical and quantum mechanical. The peculiarities of quantum phase transitions are discussed, with emphasis on the fact that they are more susceptible to the effects of generic scale invariance than their classical counterparts. Explicit examples include the quantum ferromagnetic transition in metals, with or without quenched disorder; the metal-superconductor transition at zero temperature; and the quantum antiferromagnetic transition. Analogies with classical phase transitions in liquid crystals and classical fluids are pointed out, and a unifying conceptual framework is developed for all transitions that are influenced by generic scale invariance.

Belitz, D.; Kirkpatrick, T.R.; Vojta, Thomas [Department of Physics and Materials Science Institute, University of Oregon, Eugene, Oregon 97403 (United States); Institute for Physical Science and Technology, and Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Department of Physics, University of Missouri-Rolla, Rolla, Missouri 65409 (United States)

2005-04-01

251

Phase transition from nuclear to quark matter  

SciTech Connect

We use the flavor SU(2) NJL model to describe both nuclear and quark matter, and construct phase diagrams to illustrate the phase transitions to normal quark matter (NQM) and color superconducting quark matter (SQM). We calculate the corresponding charge neutral equations of state using the Gibbs conditions to generate the mixed phases.

S. Lawley; W. Bentz; T. Horikawa; A. W. Thomas

2005-04-01

252

Phase behavior and dynamics of a cholesteric liquid crystal  

NASA Astrophysics Data System (ADS)

The synthesis, equation of state, phase diagram, and dielectric relaxation properties are reported for a new liquid crystal, 4'-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.; Dabrowski, R.; Dziaduszek, J.; Urban, S.

2014-02-01

253

Phase behavior and dynamics of a cholesteric liquid crystal.  

PubMed

The synthesis, equation of state, phase diagram, and dielectric relaxation properties are reported for a new liquid crystal, 4(')-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. PMID:24559352

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

2014-02-21

254

Optical sensor for characterizing the phase transition in salted solutions.  

PubMed

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

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

2010-01-01

255

Randomized Grain Boundary Liquid Crystal Phase  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

256

Critical behaviours of contact near phase transitions  

PubMed Central

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

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

2014-01-01

257

Critical behaviours of contact near phase transitions.  

PubMed

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

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

2014-01-01

258

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

259

Sharp phase transition and critical behaviour in  

E-print Network

of the classical RSW theorem. Keywords: dependent percolation, sharp phase transition, critical behaviour, duality, DaC model, RSW theorem, pc = 1/2. AMS 2000 Subject Classification: 60K35, 82B43, 82B20 E

Meester, Ronald

260

Notes on Black Hole Phase Transitions  

Microsoft Academic Search

In these notes we present a summary of existing ideas about phase transitions of black hole spacetimes in semiclassical gravity and offer some thoughts on three possible scenarios by which these transitions could take place. Our first theme is ilustrated by a quantum atomic black hole system, generalizing to finite-temperature a model originally offered by Bekenstein. In this equilibrium atomic

G. J. Stephens; B. L. Hu

2001-01-01

261

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

262

Electrically driven phase transition in magnetite nanostructures  

Microsoft Academic Search

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

263

Phase behavior of ionic liquid crystals  

E-print Network

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.

S. Kondrat; M. Bier; L. Harnau

2010-04-15

264

Higgs couplings and electroweak phase transition  

NASA Astrophysics Data System (ADS)

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.

Katz, Andrey; Perelstein, Maxim

2014-07-01

265

Higgs Couplings and Electroweak Phase Transition  

E-print Network

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

2014-01-08

266

Phase Transitions, Domain Walls, and Dark Matter  

NASA Astrophysics Data System (ADS)

We discuss possible roles in the Early Universe of the electroweak (EW) phase transition, which endows masses to the various particles, and the QCD phase transition, which gives rise to quark confinement and chiral symmetry breaking. Both phase transitions are well-established phenomena in the standard model of particle physics. Presumably, the EW phase transition would have taken place in the early universe at around 10-11sec, or at the temperature of about 300 GeV while QCD phase transition occurred between 10-5sec and 10-4sec, or at about 150 MeV. In this article, I wish to model the EW or QCD phase transition in the early universe as driven by a complex scalar field with spontaneous symmetry breaking such that the continuous degeneracy of the true ground states can be well represented. Specific interest has been directed to nucleation of domains, production of domain walls, and subsequent re-organization of domain walls resulting in "domain-wall nuggets". It is suggested that the domain-wall nuggets contribute to dark matter in the present Universe.

Hwang, W.-Y. P.

267

Formation of liquid and solid products from liquid phase pyrolysis.  

PubMed

The aim of the present work was to improve the C:O ratio in biomass by preserving the lignin macrostructure of lignocellulosic feed. The intention of liquid phase pyrolysis is to liquefy biomass and prepare biomass for further upgrading steps like hydrogenation and deoxygenation. Pyrolysis was carried out in a non-aqueous liquid phase heat carrier. The process was carried out in a semi-batch reaction vessel under isothermal conditions at T=350°C, supported by a quench to stop reactions instantaneously in order to observe formation of solid intermediates. This pyrolysis system enables the observation of liquid and solid product formation. Transformation of biomass into biochar was analyzed by infrared spectroscopy and elemental analysis. Stable lignin structure throughout the whole transformation was confirmed. It was shown that the lignin frame in wood remains without substantial loss, while the major amount of carbohydrates is pyrolyzed during liquid phase pyrolysis at T=350°C. PMID:22989638

Schwaiger, N; Witek, V; Feiner, R; Pucher, H; Zahel, K; Pieber, A; Pucher, P; Ahn, E; Chernev, B; Schroettner, H; Wilhelm, P; Siebenhofer, M

2012-11-01

268

Cancer as a dynamical phase transition  

PubMed Central

This paper discusses the properties of cancer cells from a new perspective based on an analogy with phase transitions in physical systems. Similarities in terms of instabilities and attractor states are outlined and differences discussed. While physical phase transitions typically occur at or near thermodynamic equilibrium, a normal-to-cancer (NTC) transition is a dynamical non-equilibrium phenomenon, which depends on both metabolic energy supply and local physiological conditions. A number of implications for preventative and therapeutic strategies are outlined. PMID:21867509

2011-01-01

269

Microscopic description of nuclear quantum phase transitions.  

PubMed

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. PMID:17931001

Niksi?, T; Vretenar, D; Lalazissis, G A; Ring, P

2007-08-31

270

Liquid-Vapor Transition Driven by Bond Disorder  

NASA Astrophysics Data System (ADS)

We report grand-canonical Monte Carlo simulations of an equimolar mixture of hard colloids coated with long polymers that have a complementary functionalization. Such systems have the potential to function as self-healing materials. Under conditions where the complementary polymer ends are strongly associated, we observe a first-order vapor-liquid transition from a dilute gas of colloidal dimers to a dense, liquidlike phase. This transition is driven exclusively by the increase in entropy associated with bond disorder—an effect that was predicted theoretically by Zilman et al. [Phys. Rev. Lett. 91, 015901 (2003)PRLTAO0031-900710.1103/PhysRevLett.91.015901]. Our simulations rationalize experimental observations by Schmatko et al. [Soft Matter 03 (2007) 703.

Bozorgui, Behnaz; Frenkel, Daan

2008-07-01

271

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

E-print Network

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

Buddhapriya Chakrabarti; Yashodhan Hatwalne; N. V. Madhusudana

2005-01-29

272

Tracing dynamic biological processes during phase transition  

PubMed Central

Background Phase transition widely exists in the biological world, such as transformation of cell cycle phases, cell differentiation stages, disease development, and so on. Such a nonlinear phenomenon is considered as the conversion of a biological system from one phenotype/state to another. Studies on the molecular mechanisms of biological phase transition have attracted much attention, in particular, on different genotypes (or expression variations) in a specific phase, but with less of focus on cascade changes of genes' functions (or system state) during the phase shift or transition process. However, it is a fundamental but important mission to trace the temporal characteristics of a biological system during a specific phase transition process, which can offer clues for understanding dynamic behaviors of living organisms. Results By overcoming the hurdles of traditional time segmentation and temporal biclustering methods, a causal process model (CPM) in the present work is proposed to study the biological phase transition in a systematic manner, i.e. first, we make gene-specific segmentation on time-course expression data by developing a new boundary gene estimation scheme, and then infer functional cascade dynamics by constructing a temporal block network. After the computational validation on synthetic data, CPM was used to analyze the well-known Yeast cell cycle data. It was found that the dynamics of the boundary genes are periodic and consistent with the phases of the cell cycle, and the temporal block network indeed demonstrates a meaningful cascade structure of the enriched biological functions. In addition, we further studied protein modules based on the temporal block network, which reflect temporal features in different cycles. Conclusions All of these results demonstrate that CPM is effective and efficient comparing to traditional methods, and is able to elucidate essential regulatory mechanism of a biological system even with complicated nonlinear phase transitions. PMID:23046764

2012-01-01

273

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

E-print Network

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

Paris-Sud XI, Université de

274

Phase-transition driven memristive system  

NASA Astrophysics Data System (ADS)

Memristors are passive circuit elements which behave as resistors with memory. The recent experimental realization of a memristor has triggered interest in this concept and its possible applications. Here, we demonstrate memristive response in a thin film of vanadium dioxide. This behavior is driven by the insulator-to-metal phase transition typical of this oxide. We discuss details of this form of phase-change memristance and potential applications of our device. Most importantly, our results demonstrate the potential for a realization of memristive systems based on phase-transition phenomena.

Driscoll, T.; Kim, H.-T.; Chae, B.-G.; Di Ventra, M.; Basov, D. N.

2009-07-01

275

Surface criticality at a dynamic phase transition.  

PubMed

In order to elucidate the role of surfaces at nonequilibrium phase transitions, we consider kinetic Ising models with surfaces subjected to a periodic oscillating magnetic field. Whereas, the corresponding bulk system undergoes a continuous nonequilibrium phase transition characterized by the exponents of the equilibrium Ising model, we find that the nonequilibrium surface exponents do not coincide with those of the equilibrium critical surface. In addition, in three space dimensions, the surface phase diagram of the nonequilibrium system differs markedly from that of the equilibrium system. PMID:23215204

Park, Hyunhang; Pleimling, Michel

2012-10-26

276

Glass transition dynamics in water and other tetrahedral liquids: 'order disorder' transitions versus 'normal' glass transitions  

NASA Astrophysics Data System (ADS)

We review some aspects of the confusion concerning the glass transition in water, and then show that it must be of a quite different character from that in other molecular liquids, and in fact is the kinetically controlled part of a classical order-disorder transition. (This is the conclusion reached in a review of the low temperature phenomenology of amorphous water currently being published in Science by the present author. Material that would normally appear in the present abbreviated paper will appear in the Science article to which the interested reader is referred.) We do this using a combination of (i) thermodynamic reasoning for 'bulk' water (based on known properties of supercooled water and nearly glassy water), and (ii) direct measurements on nanoscopic (non-crystallizing) water. Both require the heat capacity to be sharply peaked near 220 K and thus to imply the existence of a 'strong-to-fragile' transition during heating. Both require the excess heat capacity to drop to near-vanishing values in the vicinity of 130-150 K. The similarity to order-disorder transitions in crystalline solids is noted, the relation to the second critical point scenario for water is discussed, and the modelling of the anomaly by current theories is considered. Finally we argue that water, with its fragile-to-strong liquid transition below the melting point, links (lies in between) the extremes of classical network liquids (where this transition occurs only above the experimentally accessible range) and fragile molecular liquids, where the fragile-to-strong transition is pushed beneath the glass temperature.

Angell, C. Austen

2007-05-01

277

Dynamics of a discotic liquid crystal in the isotropic phase  

NASA Astrophysics Data System (ADS)

Optically heterodyne-detected optical Kerr effect (OHD-OKE) experiments are conducted to study the orientational dynamics of a discotic liquid crystal 2,3,6,7,10,11-hexakis(pentyloxy)triphenylene (HPT) in the isotropic phase near the columnar-isotropic (C-I) phase transition. The OHD-OKE signal of HPT is characterized by an intermediate power law t-0.76±0.02 at short times (a few picoseconds), a von Schweidler power law t-0.26±0.01 at intermediate times (hundreds of picoseconds), and an exponential decay at long times (tens of nanoseconds). The exponential decay has Arrhenius temperature dependence. The functional form of the total time dependent decay is identical to the one observed previously for a large number of molecular supercooled liquids. The mode coupling theory schematic model based on the Sjögren [Phys. Rev. A 33, 1254 (1986)] model is able to reproduce the HPT data over a wide range of times from <1ps to tens of nanoseconds. The studies indicate that the HPT C-I phase transition is a strong first order transition, and the dynamics in the isotropic phase display a complex time dependent profile that is common to other molecular liquids that lack mesoscopic structure.

Li, Jie; Fruchey, Kendall; Fayer, M. D.

2006-11-01

278

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

E-print Network

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

Alessia Berti; Valeria Berti

2012-11-15

279

Phase transition and properties of compact star  

E-print Network

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

280

Microgravity Two-Phase Flow Transition  

NASA Technical Reports Server (NTRS)

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

Parang, M.; Chao, D.

1999-01-01

281

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

E-print Network

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

Paris-Sud XI, Université de

282

Evidence of Liquid-Liquid Transition in Triphenyl Phosphite from Time-Resolved Light Scattering Experiments  

NASA Astrophysics Data System (ADS)

Here, we study the phase transition kinetics in a supercooled liquid state of triphenyl phosphite by means of time-resolved polarized and depolarized light scattering to address a long-standing controversy on its mechanism, i.e., whether the phenomenon is primarily induced by liquid-liquid transition (LLT) or by nanocrystal formation. We find that the polarized scattering intensity exhibits a peak as a function of time, and its low wave number limit is nonzero for any annealing temperatures, both of which strongly indicate the nonconserved nature of an order parameter governing the transition. We also observe evolution of depolarized scattering. Above the spinodal temperature TSD, the depolarized scattering intensity monotonically increases with time since it is dominated by scattering from nanocrystallites, which are continuously formed during the process. Below TSD, on the other hand, it exhibits a distinct peak as a function of time as the polarized scattering intensity does. This appearance of the peak suggests that dielectric tensor fluctuations responsible for the depolarized scattering mainly come from isotropic density fluctuations and not from nanocrystallites, supporting the occurrence of LLT.

Shimizu, Ryotaro; Kobayashi, Mika; Tanaka, Hajime

2014-03-01

283

Evidence of liquid-liquid transition in triphenyl phosphite from time-resolved light scattering experiments.  

PubMed

Here, we study the phase transition kinetics in a supercooled liquid state of triphenyl phosphite by means of time-resolved polarized and depolarized light scattering to address a long-standing controversy on its mechanism, i.e., whether the phenomenon is primarily induced by liquid-liquid transition (LLT) or by nanocrystal formation. We find that the polarized scattering intensity exhibits a peak as a function of time, and its low wave number limit is nonzero for any annealing temperatures, both of which strongly indicate the nonconserved nature of an order parameter governing the transition. We also observe evolution of depolarized scattering. Above the spinodal temperature TSD, the depolarized scattering intensity monotonically increases with time since it is dominated by scattering from nanocrystallites, which are continuously formed during the process. Below TSD, on the other hand, it exhibits a distinct peak as a function of time as the polarized scattering intensity does. This appearance of the peak suggests that dielectric tensor fluctuations responsible for the depolarized scattering mainly come from isotropic density fluctuations and not from nanocrystallites, supporting the occurrence of LLT. PMID:24724660

Shimizu, Ryotaro; Kobayashi, Mika; Tanaka, Hajime

2014-03-28

284

More is the Same; Phase Transitions and Mean Field Theories  

E-print Network

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 syste...

Kadanoff, Leo P

2009-01-01

285

Phase transitions in a complex network  

E-print Network

We study a mean field model of a complex network, focusing on edge and triangle densities. Our first result is the derivation of a variational characterization of the entropy density, compatible with the infinite node limit. We then determine the optimizing graphs for small triangle density and a range of edge density, though we can only prove they are local, not global, maxima of the entropy density. With this assumption we then prove that the resulting entropy density must lose its analyticity in various regimes. In particular this implies the existence of a phase transition between distinct heterogeneous multipartite phases at low triangle density, and a phase transition between these phases and the disordered phase at high triangle density.

Charles Radin; Lorenzo Sadun

2013-01-07

286

Phase Transitions in Coarse-Grained Lipid Bilayers Containing Cholesterol by Molecular Dynamics Simulations  

PubMed Central

Coarse-grained simulations of model membranes containing mixtures of phospholipid and cholesterol molecules at different concentrations and temperatures have been performed. A random mixing without tendencies for segregation or formation of domains was observed on spatial scales corresponding to a few thousand lipids and timescales up to several microseconds. The gel-to-liquid crystalline phase transition is successively weakened with increasing amounts of cholesterol without disappearing completely even at a concentration of cholesterol as high as 60%. The phase transition temperature increases slightly depending on the cholesterol concentration. The gel phase system undergoes a transition with increasing amounts of cholesterol from a solid-ordered phase into a liquid-ordered one. In the solid phase, the amplitude of the oscillations in the radial distribution function decays algebraically with a prefactor that goes to zero at the solid-liquid transition. PMID:23200046

Waheed, Qaiser; Tjornhammar, Richard; Edholm, Olle

2012-01-01

287

Binary Solid-Liquid Phase Equilibria  

ERIC Educational Resources Information Center

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

Ellison, Herbert R.

1978-01-01

288

Phase transitions in multiplicative competitive processes  

SciTech Connect

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

289

Notes on Black Hole Phase Transitions  

Microsoft Academic Search

In these notes we present a summary of existing ideas about phase transitions\\u000aof black hole spacetimes in semiclassical gravity and offer some thoughts on\\u000athree possible scenarios by which these transitions could take place. Our first\\u000atheme is ilustrated by a quantum atomic black hole system, generalizing to\\u000afinite-temperature a model originally offered by Bekenstein. In this\\u000aequilibrium atomic

G. J. Stephens; B. L. Hu

2001-01-01

290

Photopyroelectric Calorimetry for the Thermal and Optical Study Over Phase Transitions  

NASA Astrophysics Data System (ADS)

The capabilities of an upgraded photopyroelectric calorimetric setup to perform simultaneous evaluations of thermal and optical parameters for a more comprehensive evaluation of several phase transition studies are reported. It has been applied to the study of the nematic-isotropic phase transition of an 8CB liquid crystal hosted in a network of silica nanoparticles, of the sol-gel transition in hydrated parchment fibers and of the nematic-isotropic and the smecticA-nematic transitions of 8CB liquid crystal with inclusions of photochromic molecules.

Zammit, U.; Mercuri, F.; Paoloni, S.; Marinelli, M.

2014-06-01

291

Holographic Phase Transitions with Fundamental Matter  

SciTech Connect

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

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

2006-09-01

292

The ?-? phase transition in volcanic cristobalite  

PubMed Central

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.

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

2014-01-01

293

Stability of the Liquid Phase in Colloidal Electrolytes  

E-print Network

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

294

Shape phase transitions and critical points  

SciTech Connect

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

295

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

296

Isentropic curves at magnetic phase transitions  

NASA Astrophysics Data System (ADS)

Experiments on cold atom systems in which a lattice potential is ramped up on a confined cloud have raised intriguing questions about how the temperature varies along isentropic curves, and how these curves intersect features in the phase diagram. In this paper, we study the isentropic curves of two models of magnetic phase transitions—the classical Blume-Capel model (BCM) and the Fermi Hubbard model (FHM). Both mean field theory and Monte Carlo methods are used. The isentropic curves of the BCM generally run parallel to the phase boundary in the Ising regime of low vacancy density, but intersect the phase boundary when the magnetic transition is mainly driven by a proliferation of vacancies. Adiabatic heating occurs in moving away from the phase boundary. The isentropes of the half-filled FHM have a relatively simple structure, running parallel to the temperature axis in the paramagnetic phase, and then curving upward as the antiferromagnetic transition occurs. However, in the doped case, where two magnetic phase boundaries are crossed, the isentrope topology is considerably more complex.

Cone, J. D.; Zujev, A.; Scalettar, R. T.

2011-01-01

297

Phase transition and thermal expansion of hexafluoroethane  

NASA Astrophysics Data System (ADS)

X-ray studies of the lattice parameters of polycrystalline hexafluoroethane provide data on the linear and volume coefficients of thermal expansion in the low- and high-temperature phases for temperatures of 5-130K. The thermal expansion of the low-temperature monoclinic phase is found to be highly anisotropic. The expansion anisotropy is similar to that usually observed in laminar crystals. Strong damping of the diffraction pattern is observed in the high-temperature phase. It is proposed that this effect may be related to peculiarities in the lattice dynamics of C2F6 owing to a strong rotational-translational interaction. In this case, increased disorder associated with rising temperature, in both the orientational and translational subsystems of the crystal, becomes probable, as does the formation of a "dynamic glass" state at a certain time. A previously observed shift of the temperature of the orientational phase transition to 70K is explained. The contributions of the translational and rotational subsystems to the specific heat are analyzed thermodynamically. Indications of extremely strong disinhibition of torsional rotation of C2F6 are obtained, which ultimately leads to a structural phase transition. The temperature variation in the Grüneisen coefficient for the low-temperature phase of hexafluoroethane is found to be qualitatively similar to that observed for ethane and other simple molecular substances. This suggests that the lattice dynamics and scenarios for orientational disorder in the region of the phase transition are similar for these substances.

Klymenko, N. A.; Galtsov, N. N.; Prokhvatilov, A. I.

2011-02-01

298

Beyond Nuclear Pasta: Phase Transitions and Neutrino Opacity of Non-Traditional Pasta  

E-print Network

In this work, we focus on different length scales within the dynamics of nucleons in conditions according to the neutron star crust, with a semiclassical molecular dynamics model, studying isospin symmetric matter at subsaturation densities. While varying the temperature, we find that a solid-liquid phase transition exists, that can be also characterized with a morphology transition. For higher temperatures, above this phase transition, we study the neutrino opacity, and find that in the liquid phase, the scattering of low momenta neutrinos remain high, even though the morphology of the structures differ significatively from those of the traditional nuclear pasta.

Pablo N. Alcain; Pedro A. Giménez Molinelli; Claudio O. Dorso

2014-06-05

299

Microrheology close to an equilibrium phase transition.  

PubMed

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. PMID:24735312

Reinhardt, J; Scacchi, A; Brader, J M

2014-04-14

300

Fermi-liquid, non-Fermi-liquid, and Mott phases in iron pnictides and cuprates  

NASA Astrophysics Data System (ADS)

The role of Coulomb correlations in the iron pnictide LaFeAsO is studied by generalizing exact diagonalization dynamical mean-field theory to five orbitals. For rotationally invariant Hund’s rule coupling a transition from a paramagnetic Fermi-liquid phase to a non-Fermi-liquid metallic phase exhibiting frozen moments is found at moderate Coulomb energies. For Ising-like exchange, this transition occurs at a considerably lower critical Coulomb energy. The correlation-induced scattering rate as a function of doping relative to half filling, i.e., ?=n/5-1 , where n=6 for the undoped material, is shown to be qualitatively similar to the one in the two-dimensional single-band Hubbard model which is commonly used to study strong correlations in high- Tc cuprates. In this scenario, the parent Mott insulator of LaFeAsO is the half-filled n=5 limit, while the undoped n=6 material corresponds to the critical doping region ?c?0.2 in the cuprates, on the verge between the Fermi-liquid phase of the overdoped region and the non-Fermi-liquid pseudogap phase in the underdoped region.

Ishida, Hiroshi; Liebsch, Ansgar

2010-02-01

301

Elastic anomalies at phase transitions in multiferroics  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

302

The Influence of Disorder on Thermotropic Nematic Liquid Crystals Phase Behavior  

PubMed Central

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

303

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

304

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 iamging of the resultant microstructure as it evolves with time. Refractive index differences allow documentation of the changing microstructures by noninvasive optical techniques without the need to quench the liquid structures for analysis.

Ng, Lee H.; Sadoway, Donald R.

1987-01-01

305

THE ROLE OF METASTABLE STATES IN POLYMER PHASE TRANSITIONS: Concepts, Principles, and Experimental Observations  

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

306

Chiral Phase Transitions around Black Holes  

E-print Network

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

307

Passive Supporters of Terrorism and Phase Transitions  

E-print Network

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

308

Dynamic Phase Transition, Enhanced Reaction Rate, and  

E-print Network

-reaction model that describes kinetics aspects of the gas- phase catalytic oxidation of carbon monoxide: continuous at y1; discontinuous at y2. y poisoned state y > y2 : CO poisoned state Real systems do not posses an oxygen-poisoned state. Transitions between states of low and high CO coverage have

Rikvold, Per Arne

309

Solid-liquid transition in polydisperse Lennard-Jones systems  

NASA Astrophysics Data System (ADS)

We study melting of a face-centered crystalline solid consisting of polydisperse Lennard-Jones spheres with Gaussian polydispersity in size. The phase diagram reproduces the existence of a nearly temperature invariant terminal polydispersity (?t ? 0.11), with no signature of reentrant melting. The absence of reentrant melting can be attributed to the influence of the attractive part of the potential upon melting. We find that at terminal polydispersity the fractional density change approaches zero, which seems to arise from vanishingly small compressibility of the disordered phase. At constant temperature and volume fraction the system undergoes a sharp transition from crystalline solid to the disordered amorphous or fluid state with increasing polydispersity. This has been quantified by second- and third-order rotational invariant bond orientational order, as well as by the average inherent structure energy. The translational order parameter also indicates a similar sharp structural change at ? ? 0.09 in case of T* = 1.0, ? = 0.58. The free energy calculation further supports the sharp nature of the transition. The third-order rotationally invariant bond order shows that with increasing polydispersity, the local cluster favors a more icosahedral arrangement and the system loses its local crystalline symmetry. Interestingly, the value of structure factor S(k) of the amorphous phase at ? ? 0.10 (just beyond the solid-liquid transition density at T* = 1) becomes 2.75, which is below the value of 2.85 required for freezing given by the empirical Hansen-Verlet rule of crystallization, well known in the theory of freezing.

Sarkar, Sarmistha; Biswas, Rajib; Santra, Mantu; Bagchi, Biman

2013-08-01

310

Simulating liquid-liquid phase separation and lipid transport on the Anton special purpose machine  

NASA Astrophysics Data System (ADS)

We present simulation data for a bilayer composed of a ternary mixture of cholesterol, dioloeoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine. The composition is chosen to be in the two-phase region and the temperature in the vicinity of the miscibility transition. Using the Anton special purpose computer to generate continuous trajectories longer the ten microseconds---which admits complete mixing of the lipids---we observe robust liquid-liquid phase coexistence. The time-and ensemble-averaged mean squared displacement (MSD) displays anomalous scaling on timescales less than 50 nsec and normal diffusion on longer timescales. The short-time anomalous scaling is explained by a mode-coupling argument[Flenner et al Phys Rev E 79:011907(2009)]. The per-lipid MSD's suggest that a few lipids remain associated with the liquid ordered domain for the duration of the simulation, suggesting a possible mechanism for anomalous transport on experimentally accessible timescales.

Lyman, Edward; Sandar, Logan; Sodt, Alexader; Pastor, Richard W.

2013-03-01

311

Phase transitions in phosphatidylcholine dispersion observed with an interference refractometer.  

PubMed Central

An interferometer is used to measure the refractive index change accompanying the crystal-to-liquid-crystal phase transition in the dispersion of phosphatidylcholines. Two separate methods of obtaining the refractive index change are employed: the first method analyzes the intensity transmitted through a spatial filter and the second method utilizes a piezoeletric crystal-based electronic compensator. The results of the two methods agree well. The accuracy of the apparatus (6 X 10(-6)) permitted us to use a very dilute sample to detect the phase change. Only a fraction of a milligram of dry lecithin is needed to observe the change. The result confirms conclusively that the major reason for the turbidity change at the transition temperature is the alteration in the refractive index of the lipid membranes. The fractional change in the refractive index does not agree well with the fractional change in the density of lipid molecules in vesicles. PMID:638225

Behof, A F; Koza, R A; Lach, L E; Yi, P N

1978-01-01

312

Detecting Quantum Phase Transitions using Classical Noises  

NASA Astrophysics Data System (ADS)

We theoretically propose that the classical noise spectra provide an efficient and straightforward way to detect the quantum phase transition points in low-dimensional quantum spin systems. By using Ornstein-Uhlenbeck noise, we employ both a quadratic response theory and time-dependent density matrix renormalization group method to study the quantum system. In the non-Markovian region, the time evolutions of physical observables exhibit distinct behaviors for different quantum phases. In addition, we have the freedom to choose various noises to detect peculiar quantum phases. This method can be used to measure the three body correlation function directly. We demonstrate that the method can determine faithfully the quantum transition points of the transverse Ising model as well as spin-1 bilinear-biquadratic Heisenberrg model. The possible experimental realizations of noise detection are discussed.

Chen, Yan; He, Yinchen

2012-02-01

313

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

314

Glass Transition in Biomolecules and the Liquid-Liquid Critical Point of Water Pradeep Kumar,1  

E-print Network

, sometimes called a ``protein glass transition,'' occurs at the temperature of dynamic crossoverGlass Transition in Biomolecules and the Liquid-Liquid Critical Point of Water Pradeep Kumar,1 Z and the temperature derivative of the orientational order parameter. We relate these findings to the hypothesis

Stanley, H. Eugene

315

A reactive force field simulation of liquidliquid phase transitions in phosphorus  

E-print Network

A reactive force field simulation of liquid­liquid phase transitions in phosphorus P. Ballone 2004; accepted 6 August 2004 A force field model of phosphorus has been developed based on density T of the black P to arsenic A17 structure observed in the solid state, and also corresponds to a semiconductor

316

Phase Transitions in Paradigm Shift Models  

PubMed Central

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

317

Deconfinement phase transition and the quark condensate  

E-print Network

We study the dual quark condensate as a signal for the confinement-deconfinement phase transition of QCD. This order parameter for center symmetry has been defined recently by Bilgici et al. within the framework of lattice QCD. In this work we determine the ordinary and the dual quark condensate with functional methods using a formulation of the Dyson-Schwinger equations for the quark propagator on a torus. The temperature dependence of these condensates serves to investigate the interplay between the chiral and deconfinement transitions of quenched QCD.

Christian S. Fischer

2009-04-17

318

Heat-capacity study of phase transitions in the liquid-crystal racemic 4-(2'-methylbutyl)phenyl-4'-n-nonyloxybiphenyl-4-carboxylate (2M4P9OBC)  

SciTech Connect

The heat capacity of racemic 4-(2'-methylbutyl)phenyl-4'-n-nonyloxybiphenyl-4-carboxylate (2M4P9OBC) has been measured in the vicinity of SmC-SmI, SmI-SmG, and SmG-SmH phase transitions. The nature of the SmC-SmI transition will be discussed in the context of known microscopic pictures of each phase. In contrast to the continuous SmA-hexatic-B phase transition found in n-hexyl-4'-n-pentyloxybiphenyl-4-carboxylate, an asymmetric heat-capacity anomaly is identified in the SmC-SmI transition of 2M4P9OBC.

Viner, J.M.; Huang, C.C.

1983-05-01

319

DENSE NONAQUEOUS PHASE LIQUIDS -- A WORKSHOP SUMMARY  

EPA Science Inventory

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

320

A simple monatomic ideal glass former: the glass transition by a first-order phase transition above the melting point  

E-print Network

A liquid can form under cooling a glassy state either as a result of a continuous slowing down or by a first order polyamorphous phase transition. The second scenario has so far always been observed below the melting point where it interfered with crystalline nucleation. We report the first observation of the liquid-glass transition by a first order phase transition above the melting point. The observation was made in a molecular dynamics simulation of a one-component system with a model metallic pair potential. This is also the first observation of a simple monatomic ideal glass former -- a liquid that avoids crystallization at any cooling rate. Besides its conceptual importance, this result indicates a possibility of existence of metallic ideal glass formers.

Måns Elenius; Tomas Oppelstrup; Mikhail Dzugutov

2010-04-15

321

Liquid as a required catalyst phase for carbon single-walled nanotube growth  

NASA Astrophysics Data System (ADS)

The evolution of the iron catalyst during carbon single-walled nanotube growth is studied using calorimetry, temperature-programmed oxidation and Raman measurements. Carbon-induced solid-liquid, and solid-liquid-solid phase transitions of the nanocatalyst during the synthesis were observed. We found that liquid phase is favored for the growth of nanotubes, while the solidification of the catalyst nearly terminates the growth. No growth was observed below the eutectic point, when the catalyst is in solid phase. Our results support a growth mechanism of single-walled carbon nanotubes on liquid catalyst particles.

Harutyunyan, A. R.; Tokune, T.; Mora, E.

2005-08-01

322

Two-phase slug-to-annular flow pattern transition in microgravity  

NASA Astrophysics Data System (ADS)

It has been established through the identification and evaluation of characteristic forces dominant in two-phase gas-liquid flow field that Suratman number is the key dimensionless group in slug-annular flow pattern transition under microgravity. Furthermore, the intrinsic physical mechanism underlying the transition has been explored with the aid of experimental results. It is revealed that slug-annular flow pattern transition depends on Suratman number and the ratio of superficial gas to liquid Reynolds numbers. This result provides a physical basis to the existing empirical transition equation which is based on the same two dimensionless groups.

Sen, Nilava

2010-05-01

323

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

Federal Register 2010, 2011, 2012, 2013

[Federal Register Volume 78, Number 100 (Thursday, May 23...BUSINESS ADMINISTRATION SBIR/STTR Phase I to Phase II Transition Benchmarks AGENCY: U...Business Innovation Research Program Phase I to Phase II Transition...

2013-05-23

324

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

Federal Register 2010, 2011, 2012, 2013

[Federal Register Volume 77, Number 200 (Tuesday, October...BUSINESS ADMINISTRATION SBIR/STTR Phase I to Phase II Transition Benchmarks AGENCY: U...Business Technology Transfer Programs Phase I to Phase II Transition...

2012-10-16

325

Phase transition in the countdown problem  

NASA Astrophysics Data System (ADS)

We present a combinatorial decision problem, inspired by the celebrated quiz show called Countdown, that involves the computation of a given target number T from a set of k randomly chosen integers along with a set of arithmetic operations. We find that the probability of winning the game evidences a threshold phenomenon that can be understood in the terms of an algorithmic phase transition as a function of the set size k. Numerical simulations show that such probability sharply transitions from zero to one at some critical value of the control parameter, hence separating the algorithm's parameter space in different phases. We also find that the system is maximally efficient close to the critical point. We derive analytical expressions that match the numerical results for finite size and permit us to extrapolate the behavior in the thermodynamic limit.

Lacasa, Lucas; Luque, Bartolo

2012-07-01

326

Nonequilibrium phase transitions in biomolecular signal transduction  

NASA Astrophysics Data System (ADS)

We study a mechanism for reliable switching in biomolecular signal-transduction cascades. Steady bistable states are created by system-size cooperative effects in populations of proteins, in spite of the fact that the phosphorylation-state transitions of any molecule, by means of which the switch is implemented, are highly stochastic. The emergence of switching is a nonequilibrium phase transition in an energetically driven, dissipative system described by a master equation. We use operator and functional integral methods from reaction-diffusion theory to solve for the phase structure, noise spectrum, and escape trajectories and first-passage times of a class of minimal models of switches, showing how all critical properties for switch behavior can be computed within a unified framework.

Smith, Eric; Krishnamurthy, Supriya; Fontana, Walter; Krakauer, David

2011-11-01

327

Rethinking Renormalization for Quantum Phase Transitions  

E-print Network

This is a conceptual paper that re-examines the principles underlying the application of renormalization theory to quantum phase transitions in the light of quantum information theory. We start by describing the intuitive argument known as the Kadanoff ``block-spin'' construction for spins fixed on a lattice and then outline some subsequent ideas by Wilson and White. We then reconstruct these concepts for quantum phase transitions from first principles. This new perspective offers some very natural explanations for some features of renormalization theory that had previously seemed rather mysterious, even contrived. It also offers some suggestions as to how we might modify renormalization methods to make them more successful. We then discuss some possible order parameters and a class of functionals that are analogues of the correlation length in such systems.

Hilary A. Carteret

2004-05-28

328

Nonequilibrium phase transitions in biomolecular signal transduction.  

PubMed

We study a mechanism for reliable switching in biomolecular signal-transduction cascades. Steady bistable states are created by system-size cooperative effects in populations of proteins, in spite of the fact that the phosphorylation-state transitions of any molecule, by means of which the switch is implemented, are highly stochastic. The emergence of switching is a nonequilibrium phase transition in an energetically driven, dissipative system described by a master equation. We use operator and functional integral methods from reaction-diffusion theory to solve for the phase structure, noise spectrum, and escape trajectories and first-passage times of a class of minimal models of switches, showing how all critical properties for switch behavior can be computed within a unified framework. PMID:22181454

Smith, Eric; Krishnamurthy, Supriya; Fontana, Walter; Krakauer, David

2011-11-01

329

Phase transitions: An overview with a view  

SciTech Connect

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

330

A compressible mixture model with phase transition  

NASA Astrophysics Data System (ADS)

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

Dreyer, Wolfgang; Giesselmann, Jan; Kraus, Christiane

2014-04-01

331

Gravitational phase transition of fermionic matter  

NASA Astrophysics Data System (ADS)

We study the phase transition of a system of self-gravitating weakly interacting massive fermions in the presence of a large radiation-density background in the framework of the Thomas-Fermi model. We show that by cooling a nondegenerate gas of weakly interacting massive fermions below some critical temperature, a condensed phase emerges, consisting of quasidegenerate supermassive fermion stars. These compact dark objects could play an important role in structure formation in the early universe, as they might in fact provide seeds for galactic nuclei and quasistellar objects.

Bili?, Neven; Viollier, Raoul D.

1997-02-01

332

Topological phase transition in a discrete quasicrystal  

NASA Astrophysics Data System (ADS)

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

Sagi, Eran; Eisenberg, Eli

2014-07-01

333

Topological phase transition in a discrete quasicrystal.  

PubMed

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

Sagi, Eran; Eisenberg, Eli

2014-07-01

334

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

335

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

336

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

337

Phase Equilibrium Model for Nanoparticle-Filled Nematic Liquid Crystals  

NASA Astrophysics Data System (ADS)

This work presents an integrated characterization of phase transitions and structure formation in mixtures of nanoparticles (NP) and liquid crystals (LC), by means of a model for phase equilibrium and an experimental study on the system composed by 5CB and gold NPs. The model takes into account mixing, nematic ordering of the LC, crystalline ordering (self-assembly) of NPs, and LC-NP interactions. Generic features of phase diagrams for NP-LC mixtures are discussed. The model can explain some experimental observations, like the formation of NP aggregates and distinctive nematic textures, as a function of experimental parameters like NP concentration and the nature of the NP surface are changed. The parameters that produce these changes in phase behaviours can be directly correlated with experimental variables.

Soule, Ezequiel; Milette, Jonathan; Reven, Linda; Rey, Alejandro

2011-03-01

338

Hydrated/Dehydrated lipid phase transitions measured using nanocalorimetry.  

PubMed

The phase transition evolution with hydration of a model system, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), was investigated with a fast nanocalorimetry system. Using nanocalorimetry, it is possible to measure the gel to liquid phase transitions that occur on millisecond to second time scales and quantify the time to recover the hydrated state. The results show the phase transition occurring in a few milliseconds and the relaxation or recovery time from the dehydrated state back to original hydrated state occurring with times dependent on the local humidity. With relative humidity (RH) of 43% or higher, the recovery time can be less than a few seconds. With RH of 11% or lower, the recovery time is extended to greater than a minute. The recovery process is controlled by mechanisms that depend on the lipid molecular repacking and water transport from the environment. Nanocalorimetry provides a powerful method to investigate the kinetics of such transformations in lipids and other biological and pharmaceutical moieties. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:3442-3447, 2014. PMID:25256917

Yi, Feng; Kim, Il Kyoon; Li, Song; Lavan, David A

2014-11-01

339

Ionic phase transitions in non-ideal systems  

E-print Network

We construct an explicitly solvable Landau mean-field theory for volume phase transitions of confined or fixed ions driven by relative concentrations of divalent and monovalent counterions. Such phase transitions have been widely studied in ionic gels, where the mechanism relies on self-attraction or elasticity of a network. We find here that non-ideal behavior of ions in aqueous solution can in theory drive phase transitions without a self-attracting or elastic network. We represent non-ideality by a Debye-H\\"uckel-like power-law activity, or correlation free energy, and retain a mechanical self-repulsion to avoid runaway collapse due to the non-ideal term. Within this model we find a continuous line of gas-liquid-type critical points, connecting a purely monovalent, divalent-sensitive critical point at one extreme with a divalent, monovalent-sensitive critical point at the other. An alternative representation of the Landau functional handles the second case. We include a formula for electrical potential, which may be a convenient proxy for critically varying volume. Our relatively simple mean-field formulation may facilitate explorations of tunable critical sensitivity in areas such as ion detection technology and biological osmotic control.

Kyle J. Welch; Fred Gittes

2011-02-16

340

Chiral smectic transition phases appearing near the electric-field-induced phase transition observed by resonant microbeam x-ray scattering  

NASA Astrophysics Data System (ADS)

The electric-field-induced phase transition of a chiral liquid crystal containing Br revealed a transition phase between the three-layer periodicity ferrielectric phase and the synclinic ferroelectric phase in the electric field versus temperature phase diagram. Resonant x-ray scattering from the transition phase showed a diffuse streak or spotty weak reflections, which were composed of strong m/3-order (where m = 1 and 2) reflections and other weak peaks. The spotty reflections were found to be related to a 12-layer periodicity phase with a weak contribution from the 15-layer periodicity. An x-ray intensity analysis based on the Ising model suggested that the 12-layer periodicity phase was composed of two three-layer ferrielectric blocks and six synclinic layers. This model indicated that, in the transition phase, the three-layer ferrielectric molecular configuration gradually changed to the synclinic configuration. The diffuse streak appearing around m/3-order reflections near the field-induced transition from the four-layer periodicity phase to the synclinic ferroelectric phase is also discussed.

Iida, Atsuo; Nishiyama, Isa; Takanishi, Yoichi

2014-03-01

341

Chiral smectic transition phases appearing near the electric-field-induced phase transition observed by resonant microbeam x-ray scattering.  

PubMed

The electric-field-induced phase transition of a chiral liquid crystal containing Br revealed a transition phase between the three-layer periodicity ferrielectric phase and the synclinic ferroelectric phase in the electric field versus temperature phase diagram. Resonant x-ray scattering from the transition phase showed a diffuse streak or spotty weak reflections, which were composed of strong m/3-order (where m = 1 and 2) reflections and other weak peaks. The spotty reflections were found to be related to a 12-layer periodicity phase with a weak contribution from the 15-layer periodicity. An x-ray intensity analysis based on the Ising model suggested that the 12-layer periodicity phase was composed of two three-layer ferrielectric blocks and six synclinic layers. This model indicated that, in the transition phase, the three-layer ferrielectric molecular configuration gradually changed to the synclinic configuration. The diffuse streak appearing around m/3-order reflections near the field-induced transition from the four-layer periodicity phase to the synclinic ferroelectric phase is also discussed. PMID:24730860

Iida, Atsuo; Nishiyama, Isa; Takanishi, Yoichi

2014-03-01

342

Thermal phase diagrams of columnar liquid crystals  

E-print Network

In order to understand the possible sequence of transitions from the disordered columnar phase to the helical phase in hexa(hexylthio)triphenylene (HHTT), we study a three-dimensional planar model with octupolar interactions inscribed on a triangular lattice of columns. We obtain thermal phase diagrams using a mean-field approximation and Monte Carlo simulations. These two approaches give similar results, namely, in the quasi one-dimensional regime, as the temperature is lowered, the columns order with a linear polarization, whereas helical phases develop at lower temperatures. The helicity patterns of the helical phases are determined by the exact nature of the frustration in the system, itself related to the octupolar nature of the molecules.

G. Lamoureux; A. Caillé; D. Sénéchal

1998-01-07

343

Homogeneous phases of polar active liquids  

E-print Network

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

344

The Phase Transition of Dark Energy  

E-print Network

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

345

Phase Transition of High Carbon Steel Demonstration  

NSDL National Science Digital Library

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

2012-07-09

346

Mixing and Phase Separation in Liquid Crystal/matrix Systems  

NASA Astrophysics Data System (ADS)

We review mixing and phase separation (demixing) in mixtures of low molecular weight liquid crystals (LCs) and organic matrices, with emphasis on aspects relevant to the formation of polymer-dispersed liquid crystal films. These films, which contain a myriad of micron-sized LC droplets, are of interest because of their electro-optic properties. Film formation is simple: A liquid crystal and a liquid polymer precursor are initially mixed to form a single phase. Subsequently the polymer is hardened, and LC microdroplets phase-separate from the matrix. Although matrix hardening can be achieved in several ways, this review focuses on curing, during which cross-linking reactions lead to an increased matrix molecular weight. Topics discussed include: phase behavior of the binary system before, during, and after cure and LC/matrix solubilities. The Flory-Huggins model for phase separation (as modified by several workers) has provided a theoretical basis for the studies. Principal experimental tools have been calorimetry and light scattering. Uncured LC/matrix binaries possess phase diagrams with an upper critical solution temperature. Such systems, when heated through the mixing temperature, exhibit a decrease in specific heat, the (negative) excess specific heat of mixing, °Cmix. A plot of °Cmix vs. LC concentration exhibits a minimum, from which we can estimate LC and uncured-matrix solubilities. Matrix cure plays a major role in the phase separation process: In partially-cured samples, °Cmix transitions persist until cure is nearly complete, at which time a fraction of the LC is permanently phase-separated, with the rest remaining dissolved in the matrix. The kinetics of phase separation can be determined by calorimetry or light scattering. Cure rates have been shown to control LC microdroplet size, with fast cures leading to small droplets. Calorimetry of the fully cured system also allows us to determine the solubility of liquid crystal in the polymer matrix, as well as the fraction of phase-separated LC. An approximation based on the lever rule and the Flory-Huggins spinodal curve provides an upper bound for the solubilities and also describes their temperature dependence.

Smith, George W.

347

Phase transitions in copper(3)gold, silver iodide, and n-alkanes  

Microsoft Academic Search

We have studied phase transitions in two lattice systems, Cu3Au and AgI, using a discrete version of density functional theory and gas-liquid nucleation in n-alkanes using a density functional theory for a polyatomic system. First, the order-disorder transition and bulk and surface nucleation in Cu3Au have been investigated. A continuous surface transition occurs due to a smaller number of surface

Chaok Seok

1998-01-01

348

Cryocrystal phase transitions applied as temperature standards  

NASA Astrophysics Data System (ADS)

International temperature scales define several fixed points, the temperature values of which are determined with a very high precision. Some of them, which lie in a low-temperature range, are called gaseous fixed points because the reference substances under normal conditions—in a room-temperature range—are in a gaseous state. When occurring in a solid state at low temperature these reference substances are called cryocrystals or quantum crystals by physicists. These substances play an important role in a standard thermometry. The triple point of argon, oxygen, neon, and hydrogen are primary fixed points of the International Temperature Scale of 1990 (ITS-90) [H. Preston-Thomas, Metrologia 27, 3 (1990)].1 The triple points of nitrogen, methane, and carbon dioxide are secondary fixed points of the scale [R. E. Bedford, G. Bonnier, H. Maas, and F. Pavese, Metrologia 33, 133 (1996)].2 Also, the solid-solid phase transitions in the cryocrystals are secondary fixed points of the scale. The highest-accuracy methods of measurements applied in standard thermometry can be used to determine, with a very small uncertainty, the phase transition temperatures and their reproducibility and stability. The reproducibility and stability of the transition temperature are the most important factors deciding about usefulness of these points in thermometry. Using the highest-accuracy methods, better than 1mK, which at present are used only in metrology, can give new information about the nature and properties of the investigated substances, also of importance for physicists.

Szmyrka-Grzebyk, A.; Kowal, A.

2009-04-01

349

Thin film phase transition materials development program  

NASA Astrophysics Data System (ADS)

A number of application concepts have emerged based on the idea that a phase transition thin film such as vanadium dioxide provides a high resolution, two-dimensional format for switching, recording, and processing optical signals. These applications range from high density optical disk recording systems and optical data processing to laser protection devices, infrared FLIRS and seekers, laser radar systems and IR scene simulators. All application candidates have a potential for providing either a totally new capability, an improved performance, a lower cost, or combinations of the three. Probably of greatest significance is the emergence of agile sensor concepts arising out of some of the film's special properties. These are represented by the above FLIRs, seekers and laser radar systems. A three year research program has been completed to advance the state-of-the-art in the preparation and characterization of selected thin film phase transition materials. The objectives of the program were: (1) to expand the data base and improve operational characteristics of Vought prepared vanadium dioxide thin films, (2) to evolve process chemistry and subsequently characterize several new program materials, including rare-earth chalcogenides, organic semiconductor charge complexes, alloys of transition metal oxides, and metal-insulator cermets, and (3) to spin-off new applications and concepts.

Case, W. E.

1985-04-01

350

The Effect of Interface Deformation on the Orientation Transition of Ellipsoidal Particles at Liquid-Liquid Interfaces  

E-print Network

Manufacturing new soft materials with specific optical, mechanical and magnetic properties is a significant challenge. Assembling and manipulating colloidal particles at fluid interfaces is a promising way to make such materials. We use lattice-Boltzmann simulations to investigate the response of magnetic ellipsoidal particles adsorbed at liquid-liquid interfaces to external magnetic fields. We provide further evidence for the first-order orientation phase transition predicted by Bresme and Faraudo [Journal of Physics: Condensed Matter 19 (2007), 375110]. We show that capillary interface deformations around the ellipsoidal particle significantly affect the tilt-angle of the particle for a given dipole-field strength, altering the properties of the orientation transition. We propose scaling laws governing this transition, and suggest how to use these deformations to facilitate particle assembly at fluid-fluid interfaces.

Gary B. Davies; Timm Krüger; Peter V. Coveney; Jens Harting; Fernando Bresme

2014-05-23

351

The Transition Between Symmetry Phases in Nuclei  

NASA Astrophysics Data System (ADS)

The understanding of collective nuclear structure often relies upon a set of benchmarks or symmetries which describe idealized limits. The three standard benchmarks of nuclear structure, the vibrator, rotor, and ?-soft structure have been known for decades. Few nuclei actually manifest these symmetries, however, and the range of structures between them is extensive. Until recently, transitional nuclei were traditionally described by numerical diagonalization of a multi-parameter Hamiltonian. However, newly proposed critical point symmetries, X(5) and E (5), can now describe nuclei at the point of a phase transition from spherical to deformed shapes. The success of these analytic models has generated considerable interest in developing other simple models to describe a wider class of transitional nuclei. These models in fact, now provide analytic solutions to describe the entire range of nuclei between spherical and deformed shapes. The predictions of these models, along with traditional descriptions, will be presented. They show both excellent agreement and striking discrepancies with the data on most transitional nuclei. This work was supported by the U.S. DOE Grant No. DE-F602-91-ER-40609.

McCutchan, E. A.

2006-10-01

352

Thermodynamic Model of Liquid-Liquid Phase Equilibrium in Solutions of Alkanethiol-Coated Nanoparticles  

E-print Network

A thermodynamic model for a mixture of alkanethiol-coated nanoparticles (NPs) and low molecular weight (non-polymeric) solvent is developed, and calculations of liquid-liquid phase equilibrium for different values of NP core radius, alkanethiol chain length, solvent molar volume and alkanethiol-solvent interaction parameter, are presented. The model takes into account the swelling of the organic coronas and the dispersion of particles with swollen coronas in the solvent. The energetic interaction between alkyl chains and solvent is considered, both within the corona and between the outer alkyl segments and free solvent. Swelling involves mixing of alkanethiol chains and solvent in the corona and stretching of the organic chains. Dispersion considers an entropic contribution based on Carnahan Starling equation of state and an enthalpic term calculated considering the surface contacts between alkyl segments placed in the external boundary of the corona and the molecules of free solvent. Two different kinds of phase equilibrium are found. One of them, observed at high values of the interaction parameter, is the typical liquid-liquid equilibrium for compact NPs in a poor solvent where a complete phase separation is observed when cooling (increasing the interaction parameter). The second liquid-liquid equilibrium is observed at low values of the interaction parameter, where swelling of coronas is favored. In this region two different phases co-exist, one more concentrated in NPs that exhibit relatively compact coronas and the other one more diluted in NPs with extended coronas. In diluted solutions of NPs the deswelling of the fully extended coronas takes place abruptly in a very small temperature range, leading to a solution of compact NPs. This critical transition might find practical applications similar to those found for the abrupt shrinkage of hydrogels at a critical temperature.

Ezequiel R. Soule; Cristina E. Hoppe; Julio Borrajo; Roberto J. J. Williams

2013-11-21

353

VISUALISATION OF TRANSITION ON AN AXISYMMETRIC BODY USING SHEAR SENSITIVE LIQUID CRYSTALS  

E-print Network

VISUALISATION OF TRANSITION ON AN AXISYMMETRIC BODY USING SHEAR SENSITIVE LIQUID CRYSTALS Savory E1 Keywords: Liquid crystals, shear stress, transition, axisymmetric body Abstract The present work crystals for measuring surface skin friction under laminar, transitional and turbulent flow conditions

Savory, Eric

354

Room-Temperature Liquid Crystal Blue Phases  

NASA Astrophysics Data System (ADS)

The ``blue phases'' of a highly chiral liquid crystal are defect-studded structures of double-twist cylinders that are laced together. The three phases, BPI*, BPII* and BPIII* differ only in the packing of the double-twist cylinders. Until recently, blue phases were of limited practical use because they appeared for only a very narrow temperature range. Mixtures that show BPI* and BPII* phases for wide temperature ranges at or around room temperature are now available [1]. Relatively wide temperature BPIII (the blue fog) phase so far was available only at very high temperatures [2]. Here we present mixtures with room-temperature wide range BPIII* phase and compare the ability of chiral dopants to form the different blue phases in a base nematic mixture. PDLC films cast with blue-phase material are also examined.[3pt] [1] H. Coles and M. Pivnenko, Nature 2005 436-18 997-1000 [0pt] [2] C. V. Yelamaggad, I. S. Shashikala, G. Liao, D.S. Shankar Rao, S. K. Prasad , Q. Li A. Jakli, Chem. Mater Comm, 2006, 18, 6100-6102

Taushanoff, Stefanie; van Le, Khoa; Twieg, Robert; Jakli, Antal

2009-03-01

355

Magnetic-phase transitions and magnetocaloric effects  

Microsoft Academic Search

We have studied the magnetocaloric properties of a variety of compounds, like Gd5(Si1?xGex)4 with x=0.576 and 0.5875, MnFeP1?xAsx with x between 0.25 and 0.65, RTiGe with R=Tb, Dy, Ho, Er and Tm, Ni53Mn22Ga25, Mn5Si3, and Mn1.95Cr0.05Sb. These compounds have in common that they exhibit either temperature- or field-induced first-order magnetic-phase transitions. Gd5(Si1?xGex)4 exhibits simultaneously a magnetic and a structural transition,

O. Tegus; E. H. Bruck; L. Zhang; W. Dagula; K. H. J. Buschow; F. R de Boer

2002-01-01

356

Topological Phase Transition without Gap Closing  

PubMed Central

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

357

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

358

General nature of liquid-liquid transition in aqueous organic solutions.  

PubMed

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. PMID:24281303

Murata, Ken-ichiro; Tanaka, Hajime

2013-01-01

359

Kinetics of phase transitions in polymers  

NASA Astrophysics Data System (ADS)

I used time-resolved small angle light scattering (SALS), small angle X-ray scattering (SAXS), and computer simulation techniques to study the kinetics of phase transitions in polymer networks and as an application, a membrane forming polymer mixture. Phase separation in these systems is of technological as well as fundamental interest. I studied microphase separation in two polymer networks: (i) a covalently crosslinked N-isopropylacrylamide gel which is known to exhibit a volume collapse upon heating, and (ii) polystyrene-poly (hydrogenated butadiene)-polystyrene triblock copolymer solutions in selective solvents, good for either middle or outer blocks. This system is known to form a network of micelles at low temperatures. For system (i), SALS was used to probe the growth of large scale structures, i.e., phase separated domains, whereas SAXS was used to probe the growth of fluctuations on length scales comparable to the correlation length and mesh-size of the gel. At early times of spinodal decomposition the linear Cahn-Hilliard-Cook (CHC) theory was used to analyze the time evolution of the scattered intensity. Both SALS and SAXS results indicate that the linear CHC theory breaks down earlier at higher wave-numbers and deeper quenches. The exponential growth rate of the scattering intensity, R(q), was found to be positive at all wavenumbers studied here which, though inconsistent with the linear CHC theory, agrees with my numerical study based on the non-linear Cahn Hilliard model using a modified Flory-Huggins free energy which includes network elasticity terms. For system (ii), SAXS was used to study the structure of micelles and the ordering phase transition. In the disordered phase, the scattering function of micelles was analyzed using the Percus-Yevick hard sphere model. The core radius, the hard sphere interaction radius, and the volume fraction of hard spheres were found to increase and eventually saturate as the temperature decreases. At high concentrations, micelles form a simple cubic ordered structure and the kinetics of the ordering process is well described by a nucleation and growth theory due to Cahn. As a potential application of this work, SALS was used to study the kinetics of phase separation in a polyethersulfone solution, which is used commercially to prepare controlled pore size membranes. The transition between nucleation and spinodal decomposition mechanisms was clearly observed as the quench temperature was changed. The time evolution of the droplet size was found to scale as tsp{1/2}. The data in the spinodal region was described by the linear CHC theory. The results suggest that by varying the quench temperature it is feasible to control the size and morphology of the pore structure.

Liao, Guangdong

360

Swarms, phase transitions, and collective intelligence  

SciTech Connect

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

361

Swarms, phase transitions, and collective intelligence  

SciTech Connect

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

362

On a third-order phase transition  

NASA Astrophysics Data System (ADS)

The asymptotic behaviour of random variables of the general form 220_2005_Article_BF01209390_TeX2GIFE1.gif ln sumlimits_{i = 1}^{kappa ^N } {exp (N^{1/p} ? ? _i )} with independent identically distributed random variables ? i is studied. This generalizes the random energy model of Derrida. In the limit N??, there occurs a particular kind of phase transition, which does not incorporate a bifurcation phenomenon or symmetry breaking. The hypergeometric character of the problem (see definitions of Sect. 4), its ?-function, and its entropy function are discussed.

Eisele, Theodor

1983-03-01

363

Quantum phase transitions and bipartite entanglement.  

PubMed

We develop a general theory of the relation between quantum phase transitions (QPTs) characterized by nonanalyticities in the energy and bipartite entanglement. We derive a functional relation between the matrix elements of two-particle reduced density matrices and the eigenvalues of general two-body Hamiltonians of d-level systems. The ground state energy eigenvalue and its derivatives, whose nonanalyticity characterizes a QPT, are directly tied to bipartite entanglement measures. We show that first-order QPTs are signaled by density matrix elements themselves and second-order QPTs by the first derivative of density matrix elements. Our general conclusions are illustrated via several quantum spin models. PMID:15697878

Wu, L-A; Sarandy, M S; Lidar, D A

2004-12-17

364

Gravitational phase transition of heavy neutrino matter.  

NASA Astrophysics Data System (ADS)

In the framework of the Thomas-Fermi model at finite temperature, the authors show that a cooling nondegenerate gas of massive neutrinos will, at a certain temperature, undergo a phase transition in which quasi-degenerate supermassive neutrino stars are formed through gravitational collapse. For neutrinos in the mass range of 10 to 25 keV/c2, these compact dark objects could mimic the role of supermassive black holes that are usually assumed to exist at the centres of galaxies and quasi-stellar objects. Astrophysical implications and constraints on the neutrino mass are discussed for this scenario.

Bilic, N.; Tsiklauri, D.; Viollier, R. D.

365

Gravitational phase transition of heavy neutrino matter  

NASA Astrophysics Data System (ADS)

In the framework of the Thomas-Fermi model at finite temperature, we show that a cooling nondegenerate gas of massive neutrinos will, at a certain temperature, undergo a phase transition in which quasi-degenerate supermassive neutrino stars are formed through gravitational collapse. For neutrinos in the mass range of 10 to 25 keV/c 2, these compact dark objects could mimic the role of supermassive black holes that are usually assumed to exist at the centres of galaxies and quasistellar objects. Astrophysical implications and constraints on the neutrino mass are discussed for this scenario.

Bili?, N.; Tsiklauri, D.; Viollier, R. D.

366

Phase transitions and polymorphism of cocoa butter  

Microsoft Academic Search

The polymorphism and phase transitions of cocoa butter (CB) have been reexamined separately by differential scanning calorimetry\\u000a (DSC) and X-ray diffraction as a function of temperature (XRDT) at scanning rates between 0.1 to 5C\\/min and 0.1 to 2C\\/min,\\u000a respectively. A new instrument, which allowed simultaneous DSC and XRDT recordings from the same sample by taking advantage\\u000a of the high-energy flux

C. Loisel; G. Keller; G. Lecq; C. Bourgaux; M. Ollivon

1998-01-01

367

Bound entanglement in quantum phase transitions  

SciTech Connect

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

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

2010-04-15

368

Dependence of phase transitions on small changes  

NASA Astrophysics Data System (ADS)

In this contribution, the generalized thermodynamic formalism is applied to a nonhyperbolic dynamical system in two comparable situations. The change from one situation to the other is small in the sense that the grammar and the singularities of the system are preserved. For the discussion of the effects generated by this change, the generalized entropy functions are calculated and the sets of the specific scaling functions which reflect the phase transition of the system are investigated. It is found that even under mild variations, this set is not invariant.

Stoop, R.

1993-06-01

369

Chiral phase transition from string theory.  

PubMed

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

370

Chiral Phase Transition from String Theory  

SciTech Connect

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

371

Polymerization transition in liquid AsS under pressure: An ab initio molecular dynamics study  

NASA Astrophysics Data System (ADS)

We study the pressure dependence of the structural and electronic properties of liquid AsS by ab initio molecular dynamics simulations. We confirm that liquid AsS consists of As4S4 molecules at ambient pressure, as in the crystalline state. With increasing pressure, a structural transition from molecular to polymeric liquid occurs near 2 GPa, which is eventually followed by metallization. The pressure dependence of the density and diffusion coefficients changes qualitatively with this transition. We find that, during metallization in the polymeric phase at higher pressures, the remnants of covalent interactions between atoms play an important role in the dynamics, i.e., the As-S bond length becomes longer with increasing pressure and the diffusion coefficients have a local maximum near 5 GPa. When the pressure approaches about 15 GPa, the covalent nature of the liquid becomes quite weak. These results explain recent experiments on the pressure dependence of the viscosity.

Ohmura, Satoshi; Shimojo, Fuyuki

2011-12-01

372

A universal reduced glass transition temperature for liquids  

NASA Technical Reports Server (NTRS)

Data on the dependence of the glass transition temperature on the molecular structure for low-molecular-weight liquids are analyzed in order to determine whether Boyer's reduced glass transition temperature (1952) is a universal constant as proposed. It is shown that the Boyer ratio varies widely depending on the chemical nature of the molecule. It is pointed out that a characteristic temperature ratio, defined by the ratio of the sum of the melting temperature and the boiling temperature to the sum of the glass transition temperature and the boiling temperature, is a universal constant independent of the molecular structure of the liquid. The average value of the ratio obtained from data for 65 liquids is 1.15.

Fedors, R. F.

1979-01-01

373

Phase transitions and size scaling of membrane-less organelles  

PubMed Central

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

2013-01-01

374

Study of cerium phase transitions in shock wave experiments  

SciTech Connect

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

375

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

PubMed Central

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

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

2009-01-01

376

Pool boilup analysis using the TRANSIT-HYDRO code with improved vapor/liquid drag models. [LMFBR  

SciTech Connect

The TRANSIT-HYDRO computer code is being developed to provide a tool for assessing the consequences of transition phase events in a hypothetical core disruptive accident in an LMFBR. The TRANSIT-HYDRO code incorporates detailed geometric modeling on a subassembly-by-subassembly basis and detailed modeling of reactor material behavior and thermal and hydrodynamic phenomena. The purpose of this summary is to demonstrate the validity of the improved vapor/liquid momentum exchange models in the TRANSIT-HYDRO code for a prototypic experiment and describe some implications for transition phase scenarios.

Wigeland, R.A.; Graff, D.L.

1984-01-01

377

Phase transitions in fluids and biological systems  

NASA Astrophysics Data System (ADS)

In this thesis, I consider systems from two seemingly different fields: fluid dynamics and microbial ecology. In these systems, the unifying features are the existences of global non-equilibrium steady states. I consider generic and statistical models for transitions between these global states, and I relate the model results with experimental data. A theme of this thesis is that these rather simple, minimal models are able to capture a lot of functional detail about complex dynamical systems. In Part I, I consider the transition between laminar and turbulent flow. I find that quantitative and qualitative features of pipe flow experiments, the superexponential lifetime and the splitting of turbulent puffs, and the growth rate of turbulent slugs, can all be explained by a coarse-grained, phenomenological model in the directed percolation universality class. To relate this critical phenomena approach closer to the fluid dynamics, I consider the transition to turbulence in the Burgers equation, a simplified model for Navier-Stokes equations. Via a transformation to a model of directed polymers in a random medium, I find that the transition to Burgers turbulence may also be in the directed percolation universality class. This evidence implies that the turbulent-to-laminar transition is statistical in nature and does not depend on details of the Navier-Stokes equations describing the fluid flow. In Part II, I consider the disparate subject of microbial ecology where the complex interactions within microbial ecosystems produce observable patterns in microbe abundance, diversity and genotype. In order to be able to study these patterns, I develop a bioinformatics pipeline to multiply align and quickly cluster large microbial metagenomics datasets. I also develop a novel metric that quantifies the degree of interactions underlying the assembly of a microbial ecosystem, particularly the transition between neutral (random) and niche (deterministic) assembly. I apply this metric to 16S rRNA metagenomic studies of 6 vertebrate gastrointestinal microbiomes and find that they assembled through a highly non-neutral process. I then consider a phase transition that may occur in nutrient-poor environments such as ocean surface waters. In these systems, I find that the experimentally observed genome streamlining, specialization and opportunism may well be generic statistical phenomena.

Sipos, Maksim

378

Glass and liquid phase diagram of a polyamorphic monatomic system  

NASA Astrophysics Data System (ADS)

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

Reisman, Shaina; Giovambattista, Nicolas

2013-02-01

379

Scaling analysis of gas-liquid two-phase flow pattern in microgravity  

NASA Technical Reports Server (NTRS)

A scaling analysis of gas-liquid two-phase flow pattern in microgravity, based on the dominant physical mechanism, was carried out with the goal of predicting the gas-liquid two-phase flow regime in a pipe under conditions of microgravity. The results demonstrated the effect of inlet geometry on the flow regime transition. A comparison of the predictions with existing experimental data showed good agreement.

Lee, Jinho

1993-01-01

380

Phase equilibria of binary liquid crystal mixtures involving induced ordered phases  

NASA Astrophysics Data System (ADS)

A phenomenological model for elucidating phase diagrams of hexagonal columnar/nematic liquid crystal mixtures has been developed on the basis of the combination of the Flory-Huggins (FH) free energy of isotropic mixing, Maier-Saupe (MS) free energy for nematic ordering, and Chandrasekhar-Clark free energy for hexagonal ordering. Self-consistent calculations show the theory is capable of predicting the various phase diagrams, covering nematic, hexagonal columnar, and isotropic phases. The model has been tested with the eutectic phase diagram of hexagonal columnar liquid crystal, 2, 3, 6, 7, 10, 11-hexapentyloxy triphenylene (HPTP)/reactive nematic mesogens, 4-(3-acryloyloxypropyloxy)-benzoic acid 2-methyl-1, 4-phenylene ester (RM257) mixtures determined by using DSC, polarized optical microscope (POM), and wide-angle X-ray diffraction (WAXD). The self-consistent calculation displays isotropic (I), nematic (N), hexagonal columnar (Colh), N + I, and Colh + I, and Colh + N coexistence regions. These phase regions has been confirmed by thermal quenching various compositions from the isotropic melt to different phase regions. Guided by the established phase diagram of HPTP/RM257 mixtures, photo-polymerization of the mixture has been carried out in different phase regions. The as-cured HPTP/p-(RM257) composites fabricated at isotropic phase (130 °C) remains single isotropic phase under optical microscope, whereas the SEM and TEM results show the bead-like microstructure with sub-micrometer scale. Polymerization-induced mesophase transition experiments have been carried out at isotropic temperatures slightly above the clearing point of the mixtures. Of particular interest is the development of liquid crystalline spherulites. Moreover, the fixation of the morphology is observed when the photopolymerization is carried out in the N, N + I, and N + Colh region. A generalized thermodynamic model for describing smectic A and smectic B ordering has been developed based on Chandrasekhar-Clark and Maier-Saupe-McMillan theories by introducing hexagonal and layered order parameters. By combining the proposed model with Flory-Huggings theory, the total free energy for induced smectic phase in binary nematic liquid crystal mixtures has been obtained. The calculated phase diagram has been tested with the induced smectic B phase diagram of binary nematic liquid crystal mixtures of 4'-n-pentyl-4-cyanobiphenyl (5CB)/4'-methoxy-benzylidene-4-butylaniline (MBBA) and the induced smectic A phase diagram of 4-cyano-4'-pentyloxy biphenyl (5OCB) and 4-pentylphenyl-4'-heptyloxybenzoate (7O5) mixtures. Our calculation results show the remarkable agreement with the experimental data in the reported literature.

Huang, Tsang-Min

381

Dark Matter and Cosmological QCD Phase Transition  

NASA Astrophysics Data System (ADS)

In this talk, we take the wisdom that the cosmological QCD phase transition, which happened at a time between 10-5 sec and 10-4 sec or at the temperature of about 150 MeV and accounts for confinement of quarks and gluons to within hadrons, would be of first order, i.e., would release latent "heat" or latent energy. I wish to base on two important points, i.e. (1) that we have 25% dark matter in the present Universe, and (2) that when the early universe underwent the cosmological QCD phase transition it released 1.02 × 10gm/cm3 in latent energy huge compared to 5.88 × 109 gm/cm3 radiation (photon) energy, to deduce that the two numbers are in fact closely related. It is sufficient to approximate the true QCD vacuum as one of degenerate ?-vacua and can be modelled effectively via a complex scalar field with spontaneous symmetry breaking. We examine how "pasted" or "patched" domain walls are formed, how such walls evolve in the long run, and we believe that the majority of dark matter could be accounted for in terms of such domain-wall structure and its remnants. The latent energy released due to the conversion of the false vacua to the true vacua, in the form of "pasted" or "patched" domain walls at first and their evolved objects, make it obsolete the "radiation-dominated" epoch or later on the "matter-dominated" epoch.

Hwang, W.-Y. P.

382

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

PubMed

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

Matsuyama, Akihiko

2014-11-14

383

Surface-wetting effects on the liquid-liquid transition of a single-component molecular liquid  

PubMed Central

Even a single-component liquid may have more than two liquid states. The transition between them is called a 'liquid–liquid transition' (LLT). Such LLTs have recently attracted considerable attention mainly because of the fundamental interest in the physical origin of this counter-intuitive phenomenon. In this study, we report the first observation of wetting effects on LLT for a molecular liquid, triphenyl phosphite. We find a transition from partial to complete wetting for nucleation-growth-type LLT when approaching the spinodal temperature of LLT. Some features unique to LLT are also revealed, reflecting for example the non-conserved nature of its order parameter. We also find that the wetting behaviour is not induced by dispersion forces, but by weak hydrogen bonding to a solid substrate, implying its important role in the LLT itself. Using wetting effects may open a new possibility to control kinetics and spatial patterns of nucleation-growth-type LLT. PMID:20975680

Murata, Ken-ichiro; Tanaka, Hajime

2010-01-01

384

Gastrointestinal transit of liquids in unfed cynomolgus monkeys.  

PubMed

In this study, the gastric emptying rate and oro-caecal transit time of two liquid volumes (20 and 60 ml) were compared in unfed cynomolgus monkeys. First, the acetaminophen method was used to determine the gastric half-emptying time (t(50%)). The mean t(50%) from seven monkeys was 21.2 min for the 20-ml volume and 27.8 min for the 60-ml volume. This mean t(50%) in monkeys is similar to that reported previously in fasting humans. Next, the sulfasalazine-sulfapyridine method was used to determine median oro-caecal transit times for the 2 liquid volumes; these times were 2.5 h for the 20-ml volume and 2.3 h for the 60-ml volume, which are about 1.5 h shorter than previously reported transit times in humans. An increase in volume administered did not significantly change either the t(50%) or oro-caecal transit time. The data also show that variability in both t(50%) and oro-caecal transit time within each monkey is not as great as the large variability between monkeys. Consequently, cynomolgus monkeys are good model animals to use for studies on the gastric emptying of drug-containing liquids after fasting; however, analysis of results from bioavailability studies must compensate for differences in the oro-caecal transit time between monkeys and humans. PMID:12673671

Kondo, Hiromu; Takahashi, Yutaka; Watanabe, Takashi; Yokohama, Shigeharu; Watanabe, Jun

2003-04-01

385

Determination of size effects during the phase transition of a nanoscale Au-Si eutectic.  

PubMed

The phase diagram of a nanoscale system can be substantially different than in the bulk, but quantitative measurements have proven elusive. Here we use in situ microscopy to observe a phase transition in a nanoscale system, together with a simple quantitative model to extract the size effects from these measurements. We expose a Au particle to disilane gas, and observe the transition from a two-phase Au + AuSi system to single-phase AuSi. Size effects are evident in the nonlinear disappearance of the solid Au. Our analysis shows a substantial shift in the liquidus line, and a discontinuous change in the liquid composition at the transition. It also lets us estimate the liquid-solid interfacial free energy. PMID:19905650

Kim, B J; Tersoff, J; Wen, C-Y; Reuter, M C; Stach, E A; Ross, F M

2009-10-01

386

Thermodynamics of rotating black holes and black rings: phase transitions and thermodynamic volume  

E-print Network

In this review we summarize, expand, and set in context recent developments on the thermodynamics of black holes in extended phase space, where the cosmological constant is interpreted as thermodynamic pressure and treated as a thermodynamic variable in its own right. We specifically consider the thermodynamics of higher-dimensional rotating asymptotically flat and AdS black holes and black rings in a canonical (fixed angular momentum) ensemble. We plot the associated thermodynamic potential-the Gibbs free energy-and study its behaviour to uncover possible thermodynamic phase transitions in these black hole spacetimes. We show that the multiply-rotating Kerr-AdS black holes exhibit a rich set of interesting thermodynamic phenomena analogous to the "every day thermodynamics" of simple substances, such as reentrant phase transitions of multicomponent liquids, multiple first-order solid/liquid/gas phase transitions, and liquid/gas phase transitions of the Van der Waals type. Furthermore, the reentrant phase transitions also occur for multiply-spinning asymptotically flat Myers-Perry black holes. The thermodynamic volume, a quantity conjugate to the thermodynamic pressure, is studied for AdS black rings and demonstrated to satisfy the reverse isoperimetric inequality; this provides a first example of calculation confirming the validity of isoperimetric inequality conjecture for a black hole with non-spherical horizon topology. The equation of state P=P(V,T) is studied for various black holes both numerically and analytically-in the ultraspinning and slow rotation regimes.

Natacha Altamirano; David Kubiznak; Robert B. Mann; Zeinab Sherkatghanad

2014-01-12

387

Wide Angle Liquid Crystal Optical Phased Array  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

388

Observation of FSS for a First Order Phase Transition  

E-print Network

We present the results of a multicanonical simulation of the q=20 2-d Potts model in the transition region. This is a very strong first order phase transition. We observe, for the first time, the asymptotic finite size scaling behavior predicted by Borgs and Koteck\\'y close to a first order phase transition point.

A. Billoire; T. Neuhaus; B. Berg

1992-11-05

389

Observation of FSS for a first-order phase transition  

Microsoft Academic Search

We present the results of a multicanonical simulation of the q = 20 two-dimensional Potts model in the transition region. This is a very strong first-order phase transition. We observe, for the first time, the asymptotic finite size scaling behavior predicted by Borgs and Kotecký close to a first-order phase transition point. On sabbatical from the Florida State University.

A. Billoire; T. Neuhaus; B. Berg

1993-01-01

390

QCD PHASE TRANSITIONS-VOLUME 15.  

SciTech Connect

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

391

Quarantine generated phase transition in epidemic spreading  

NASA Astrophysics Data System (ADS)

We study the critical effect of quarantine on the propagation of epidemics on an adaptive network of social contacts. For this purpose, we analyze the susceptible-infected-recovered (SIR) model in the presence of quarantine, where susceptible individuals protect themselves by disconnecting their links to infected neighbors with probability w, and reconnecting them to other susceptible individuals chosen at random. Starting from a single infected individual, we show by an analytical approach and simulations that there is a phase transition at a critical rewiring (quarantine) threshold wc separating a phase (wphase (w >= wc) where the disease does not spread out. We find that in our model the topology of the network strongly affects the size of the propagation, and that wc increases with the mean degree and heterogeneity of the network. We also find that wc is reduced if we perform a preferential rewiring, in which the rewiring probability is proportional to the degree of infected nodes.

Dicksion, Mark; Lagorio, Cecilia; Vazquez, F.; Braunstein, L.; Macri, P. A.; Migueles, M. V.; Havlin, S.; Stanley, H. E.

2011-03-01

392

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

393

Electronic and Sturctural Transitions in Dense Liquid Sodium  

SciTech Connect

At ambient conditions, the light alkali metals are free-electron like crystals with a highly symmetric structure. However, they were shown recently to exhibit unexpected complexity under pressure. It was predicted from theory and later confirmed by experiment that Li and Na undergo a sequence of symmetry breaking transitions driven by a Peierls mechanism. Most recently, measurements of the Na melting curve revealed an unprecedented and still unexplained drop in the melting temperature from 1000 K at 30 GPa to room temperature at 120 GPa. Here we report results from ab initio calculations that explain the unusual melting behavior in dense Na. We show that molten Na undergoes a series of pressure-induced structural and electronic transitions analogous to that observed in solid Na, but commencing at much lower pressure in the presence of disorder. With increasing pressure, liquid Na initially evolves by assuming a more compact local structure. However, a transition to a lower coordinated liquid takes place at a pressure around 65 GPa, accompanied by a threefold drop in electrical conductivity. A pseudogap opening at the Fermi level, an effect previously not observed in a liquid metal, drives this transition. Remarkably, the lower coordinated liquid emerges at rather elevated temperatures and above the stability region of a closed packed free electron-like metal. We predict that similar exotic behavior is possible in other materials as well.

Raty, J Y; Schwegler, E R; Bonev, S A

2007-08-06

394

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

395

Covalent-to-ionic transition in liquid zinc dichloride  

NASA Astrophysics Data System (ADS)

We report molecular-dynamics simulations of self-diffusion and structure in a pseudoclassical model of liquid and crystalline ZnCl 2 over a wide region of the pressure-temperature plane. The model parameters are adjusted to reproduce a liquid structure of corner-sharing ZnCl 4 tetrahedra at the standard freezing point and the measured diffusion coefficients as functions of temperature on the sfp isobar. We find that compression first weakens the intermediate-range order of the melt near freezing into a fourfold-coordinated crystal structure, and then drives at higher temperatures a novel liquid-liquid transition consisting of two broad steps: (i) a transition in which the Zn atoms start to leave their tetrahedral cages, followed by (ii) a structural transition from a covalent network of Cl atoms to a dissociated ionic liquid which then freezes into a sixfold-coordinated crystal. Good agreement is found with data from X-ray diffraction experiments under pressure.

Ruberto, R.; Pastore, G.; Tosi, M. P.

2009-03-01

396

Global quantum discord and quantum phase transition in XY model  

E-print Network

We study the relationship between the behavior of global quantum correlations and quantum phase transitions in XY model. We find that the two kinds of phase transitions in the studied model can be characterized by the features of global quantum discord (GQD) and the corresponding quantum correlations. We demonstrate that the maximum of the sum of all the nearest neighbor bipartite GQDs is effective and accurate for signaling the Ising quantum phase transition, in contrast, the sudden change of GQD is very suitable for characterizing another phase transition in the XY model. This may shed lights on the study of properties of quantum correlations in different quantum phases.

Si-Yuan Liu; Yu-Ran Zhang; Wen-Li Yang; Heng Fan

2014-05-20

397

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

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

398

A Susy Phase Transition as Central Engine  

E-print Network

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

399

Some demographic crashes seen as phase transitions  

NASA Astrophysics Data System (ADS)

The purpose of this paper is the application of a usual method of statistical mechanics-the renormalization based on Wilson's recursive relations-in order to study the critical behavior of a social index, namely the live births per 1000 population. The drastic decreases of this index on certain periods have the specific features of the phase transitions as they follow approximately power laws and also, they lead to the complete change of the population age structure. The values of the critical exponents that are obtained by fitting the experimental data referring to some East European countries are in agreement with the value resulting from the theoretical approach, thus showing the universality of the power law behavior in the vicinity of the critical points, for complex social systems.

Gligor, Mircea; Ignat, Margareta

2001-12-01

400

MAGNETIC FIELDS FROM QCD PHASE TRANSITIONS  

SciTech Connect

We study the evolution of QCD phase transition-generated magnetic fields (MFs) in freely decaying MHD turbulence of the expanding universe. We consider an MF generation model that starts from basic non-perturbative QCD theory and predicts stochastic MFs with an amplitude of the order of 0.02 {mu}G and small magnetic helicity. We employ direct numerical simulations to model the MHD turbulence decay and identify two different regimes: a 'weakly helical' turbulence regime, when magnetic helicity increases during decay, and 'fully helical' turbulence, when maximal magnetic helicity is reached and an inverse cascade develops. The results of our analysis show that in the most optimistic scenario the magnetic correlation length in the comoving frame can reach 10 kpc with the amplitude of the effective MF being 0.007 nG. We demonstrate that the considered model of magnetogenesis can provide the seed MF for galaxies and clusters.

Tevzadze, Alexander G. [Faculty of Exact and Natural Sciences, Javakhishvili Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi 0128 (Georgia); Kisslinger, Leonard; Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Brandenburg, Axel, E-mail: aleko@tevza.org [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

2012-11-01

401

Miniaturized sample preparation combined with liquid phase separations  

Microsoft Academic Search

Miniaturized sample preparation methods designed as the sample pretreatment for liquid phase separations, such as liquid chromatography, capillary electrophoresis and capillary electrochromatography, have been reviewed especially for the on-line coupling of the sample preparation process and the separation process. The development of the desorption interfaces for the effective combining of the sample preparation and subsequent liquid phase separations is briefly

Yoshihiro Saito; Kiyokatsu Jinno

2003-01-01

402

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

403

Thermal analysis of phase transition behaviour in liposomes  

Microsoft Academic Search

Liposomes are small vesicles having one or more concentric phospholipid bilayers, interspersed with aqueous phase. Thermal analysis, particularly differential scanning calorimetry (DSC) has been used extensively to study the behaviour of hydrated phospholipids within bilayers. On heating, and dependent on the state of hydration, phospholipids undergo a series of phase transitions. This paper reviews investigations of the phase transition behaviour

Kevin M. G. Taylor; Rita M. Morris

1995-01-01

404

Magnetic successive phase transitions of CuB2O4 probed by B11-NMR technique  

NASA Astrophysics Data System (ADS)

We have performed B11-NMR experiments of CuB2O4 using a single crystal with an operating frequency 6.8 MHz down to liquid He3 temperatures in order to investigate the properties of the successive phase transitions. In addition to the two-step successive magnetic phase transitions at TN=21 K and T*˜10 K, we have found clear evidence of the first-order phase transition at around 0.8 K under 0.5 T. This phase boundary corresponds to the third transition at T˜1.8 K for zero magnetic field whose detail has been unclear so far.

Yasuda, Y.; Nakamura, H.; Fujii, Y.; Kikuchi, H.; Chiba, M.; Yamamoto, Y.; Hori, H.; Petrakovskii, G.; Popov, M.; Bezmaternikh, L.

2007-03-01

405

Probing the stability of the spin-liquid phases in the Kitaev-Heisenberg model using tensor network algorithms  

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

406

Ferroelectric phase transitions in cubic perovskites  

NASA Astrophysics Data System (ADS)

In low-temperature phase, due to the pseudo Jahn-Teller effect in unit cells, atoms are coherently localized in one of eight trigonal wells of the adiabatic potential energy surface. With temperature, nuclear motion delocalizes over symmetry-equivalent wells. Depending on the size of potential barriers, the two limiting cases are considered: (a) shallow wells, and (b) deep wells. They correspond to two different mechanisms of delocalization. When potential barriers are shallow compared to kTC, the delocalization is due to over-the-barrier activation of Arrhenius type. Alternatively, when the over-the-barrier activation is thermally inaccessible, the delocalization is due to tunnelling. Temperature dependence of spontaneous polarization is treated in terms of the mean-field approximation. Using experimental data for BaTiO3, numerical values of the corresponding parameters are estimated. The qualitative description is followed by a numeric evaluation of the temperature sequence of ferroelectric phase transitions for the two cases of shallow and deep wells. The theory agrees with the experimental data.

Polinger, Victor

2013-04-01

407

Phase Transitions in Nucleonic Matter and Neutron-Star Cooling  

E-print Network

A new scenario for neutron-star cooling is proposed, based on the correspondence between pion condensation, occurring in neutron matter due to critical spin-isospin fluctuations, and the metal-insulator phase transition in a two-dimensional electron gas. Beyond the threshold density for pion condensation, where neutron-star matter loses its spatial homogeneity, the neutron single-particle spectrum acquires an insulating gap that quenches neutron contributions to neutrino-production reactions and to the star's specific heat. In the liquid phase at densities below the transition point, spin-isospin fluctuations are found to play dual roles. On the one hand, they lead to a multi-sheeted neutron Fermi surface that extends to low momenta, thereby activating the normally forbidden direct-Urca cooling mechanism; on the other, they amplify the nodeless $P$-wave neutron superfluid gap while suppressing $S$-wave pairing. In this picture, lighter stars without a pion-condensed core experience slow cooling, while enhanced cooling occurs in heavier stars through direct-Urca emission from a narrow shell of the interior.

V. A. Khodel; J. W. Clark; M. Takano; M. V. Zverev

2004-02-22

408

Analysis of fragment yield ratios in the nuclear phase transition  

E-print Network

The critical phenomena of the liquid-gas phase transition has been investigated in the reactions 78,86Kr+58,64Ni at beam energy of 35 MeV/nucleon using the Landau free energy approach with isospin asymmetry as an order parameter. Fits to the free energy of fragments showed three minima suggesting the system to be in the regime of a first order phase transition. The relation m =-{\\partial}F/{\\partial}H, which defines the order parameter and its conjugate field H, has been experimentally verified from the linear dependence of the mirror nuclei yield ratio data, on the isospin asymmetry of the source. The slope parameter, which is a measure of the distance from a critical temperature, showed a systematic decrease with increasing excitation energy of the source. Within the framework of the Landau free energy approach, isoscaling provided similar results as obtained from the analysis of mirror nuclei yield ratio data. We show that the external field is primarily related to the minimum of the free energy, which implies a modification of the source concentration \\Delta used in isospin studies.

R. Tripathi; A. Bonasera; S. Wuenschel; L. W. May; Z. Kohley; G. A. Souliotis; S. Galanopoulos; K. Hagel; D. V. Shetty; K. Huseman; S. N. Soisson; B. C. Stein; S. J. Yennello

2010-10-11

409

Phase Transitions of Nanoemulsions Using Ultrasound: Experimental Observations  

PubMed Central

The ultrasound-induced transformation of perfluorocarbon liquids to gases is of interest in the area of drug and gene delivery. In this study, three independent parameters (temperature, size, and perfluorocarbon species) were selected to investigate the effects of 476-kHz and 20-kHz ultrasound on nanoemulsion phase transition. Two levels of each factor (low and high) were considered at each frequency. The acoustic intensities at gas bubble formation and at the onset of inertial cavitation were recorded and subsequently correlated with the acoustic parameters. Experimental data showed that low frequencies are more effective in forming and collapsing a bubble. Additionally, as the size of the emulsion droplet increased, the intensity required for bubble formation decreased. As expected, perfluorohexane emulsions require greater intensity to form cavitating bubbles than perfluoropentane emulsions. PMID:22444691

Singh, Ram; Husseini, Ghaleb A.; Pitt, William G.

2012-01-01

410

Liquid phase stability under an extreme temperature gradient.  

PubMed

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

Liang, Zhi; Sasikumar, Kiran; Keblinski, Pawel

2013-11-27

411

Chiral phase transition in lattice QCD as a metal-insulator transition  

E-print Network

We investigate the lattice QCD Dirac operator with staggered fermions at temperatures around the chiral phase transition. We present evidence of a metal-insulator transition in the low lying modes of the Dirac operator around the same temperature as the chiral phase transition. This strongly suggests the phenomenon of Anderson localization drives the QCD vacuum to the chirally symmetric phase in a way similar to a metal-insulator transition in a disordered conductor. We also discuss how Anderson localization affects the usual phenomenological treatment of phase transitions a la Ginzburg-Landau.

Antonio M. Garcia-Garcia; James C. Osborn

2006-11-17

412

On liquid phases in cometary nuclei  

NASA Astrophysics Data System (ADS)

In this paper we review the relevant literature and investigate conditions likely to lead to melting of H2O ice, methanol (CH3OH) ice, ethane (C2H6) ice and other volatile ices in cometary nuclei. On the basis of a heat balance model which takes account of volatiles loss, we predict the formation of occasional aqueous and hydrocarbon liquid phases in subsurface regions at heliocentric distances, rh of 1-3 AU, and 5-12 AU, respectively. Low triple-point temperatures and low vapour pressures of C2H6, C3H8, and some higher-order alkanes and alkenes, favour liquid phase formation in cometary bodies at high rh. Microporosity and the formation of a stabilization crust occluding the escape of volatiles facilitate liquid-phase formation. Characteristics of the near-surface which favour subsurface melting include; low effective surface emissivity (at low rh), high amorphous carbon content, average pore sizes of ˜10 ?m or less, presence of solutes (e.g. CH3OH), mixtures of C2-C6 hydrocarbons (for melting at high rh), diurnal thermal cycling, and slow rotation rate. Applying the principles of soil mechanics, capillary forces are shown to initiate pre-melting phenomena and subsequent melting, which is expected to impart considerable strength of ˜104 Pa in partially saturated layers, reducing porosity and permeability, enhancing thermal conductivity and heat transfer. Diurnal thermal cycling is expected to have a marked effect on the composition and distribution of H2O ice in the near-surface leading to frost heave-type phenomena even where little if any true melting occurs. Where melting does take place, capillary suction in the wetted zone has the potential to enhance heat transfer via capillary wetting in a low-gravity environment, and to modify surface topography creating relatively smooth flat-bottomed features, which have a tendency to be located within small depressions. An important aspect of the "wetted layer" model is the prediction that diurnal melt-freeze cycles alter the mixing ratio vs. depth of solutes present, or of other miscible components, largely through a process of fractional crystallization, but also potentially involving frost heave. Wetted layers are potentially durable and can involve significant mass transport of volatile materials in the near-surface, increasing in extent over many rotations of the nucleus prior to and just after perihelion passage, and causing stratification and trapping of the lowest-melting mixtures at depths of several metres. A possible mechanism for cometary outbursts is proposed involving a heat pulse reaching the liquid phase in the deepest wetted zone, leading to supersaturation and triggering the sudden release under pressure of dissolved gases, in particular CO2, CO, CH4 or N2, contained beneath a consolidated near-surface layer. This study indicates that liquid water can persist for long periods of time in the near-surface of some intermediate-sized bodies (102-103 km radius) within protoplanetary discs.

Miles, Richard; Faillace, George A.

2012-06-01

413

Electrostatically Driven Granular Media: Phase Transitions, Patterns and Vortices  

NASA Astrophysics Data System (ADS)

Large ensembles of small particles display fascinating collective behavior when they acquire an electric charge and respond to competing long-range electromagnetic and short-range contact forces. Many industrial technologies face the challenge of assembling and separating such single- or multi-component micro and nano- size ensembles. The dynamics of conducting microparticles in strong electric field in the air or in deep vacuum was studied in Refs. [1,2]. Phase transitions and clustering instability of the electrostatically driven granular gas were found. A continuum model for the phase separation and coarsening in was formulated in terms of a Ginzburg-Landau equation subject to conservation of the total number of grains. In the regime of well-developed clusters, the continuum model is used to derive "sharp-interface" equations that govern the dynamics of the interphase boundary. The situation is remarkably different when the cell is filled with poorly conducting liquid (toluene-ethanol mixute). We have found that metallic particles form a rich variety of phases not observed in the air-filled cell. These phases include static precipitates: honeycombs lattices and Wigner crystals; and novel dynamic condensates: toroidal vortices and pulsating rings. The observed phenomena are attributed to interaction between particles and electro-hydrodynamic flows produced by the action of the electric field on ionic charges in the bulk of liquid. 1. I.S. Aranson, D. Blair, V.A. Kalatsky, G.W. Crabtree, W.-K. Kwok, V.M. Vinokur, and U.Welp, Phys. Rev. Lett. 84, 3306 (2000) 2. I.S. Aranson, B. Meerson, P.V. Sasorov, and V.M. Vinokur, Phys. Rev. Lett. 88, 204301 (2002)

Aranson, Igor

2003-03-01

414

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

E-print Network

be dissolved in water and form a homogenous liquid solution. When the temperature is increased, the solution, 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

Suo, Zhigang

415

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

416

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

Microsoft Academic Search

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

L. Brualla; M. C. Gordillo

2003-01-01

417

Deconfinement transition and Luttinger to Fermi liquid crossover in quasi-one-dimensional systems.  

PubMed

We investigate a system of one-dimensional Hubbard chains of interacting fermions coupled by interchain hopping. Using a generalization of the dynamical mean-field theory we study the deconfinement transition from a Mott insulator to a metal and the crossover between Luttinger and Fermi liquid phases. One-particle properties, local spin response, and interchain optical conductivity are calculated. Possible applications to organic conductors are discussed. PMID:11800903

Biermann, S; Georges, A; Lichtenstein, A; Giamarchi, T

2001-12-31

418

INTERFACIAL WAVE TRANSITIONS IN LIQUID-LIQUID FLOWS AND INSIGHT INTO FLOW REGIME TRANSITION  

E-print Network

multifluid flow on small scales, their defining characteristic, in channels, pipes and even packed beds - liquid packed bed flows, the corresponding region is the pulsing flow regime[3], for which the large, heat exchangers, gas-liquid reactors with solid catalyst and various other process piping and vessels

McCready, Mark J.

419

Pressure induced phase transitions in ceramic compounds containing tetragonal zirconia  

SciTech Connect

Stabilized tetragonal zirconia compounds exhibit a transformation toughening process in which stress applied to the material induces a crystallographic phase transition. The phase transition is accompanied by a volume expansion in the stressed region thereby dissipating stress and increasing the fracture strength of the material. The hydrostatic component of the stress required to induce the phase transition can be investigated by the use of a high pressure technique in combination with Micro-Raman spectroscopy. The intensity of Raman lines characteristic for the crystallographic phases can be used to calculate the amount of material that has undergone the transition as a function of pressure. It was found that pressures on the order of 2-5 kBar were sufficient to produce an almost complete transition from the original tetragonal to the less dense monoclinic phase; while a further increase in pressure caused a gradual reversal of the transition back to the original tetragonal structure.

Sparks, R.G.; Pfeiffer, G.; Paesler, M.A.

1988-12-01

420

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

E-print Network

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

2006-03-21

421

Phase transitions in a gas of anyons  

SciTech Connect

We continue our numerical Monte Carlo simulation of a gas of closed loops on a 3 dimensional lattice, however, now in the presence of a topological term added to the action which corresponds to the total linking number between the loops. We compute the linking number using a novel approach employing certain notions from knot theory. Adding the topological term converts the particles into anyons. Interpreting the model as an effective theory that describes the 2+1-dimensional Abelian Higgs model in the asymptotic strong-coupling regime, the topological linking number simply corresponds to the addition to the action of the Chern-Simons term. The system continues to exhibit a phase transition as a function of the vortex mass as it becomes small. We find the following new results. The Chern-Simons term has no effect on the Wilson loop. On the other hand, it does effect the 't Hooft loop of a given configuration, adding the linking number of the 't Hooft loop with all of the dynamical vortex loops. We find the unexpected result that both the Wilson loop and the 't Hooft loop exhibit a perimeter law even though there are no massless particles in the theory, in both phases of the theory. It should be noted that our method suffers from numerical instabilities if the coefficient of the Chern-Simons term is too large; thus, we have restricted our results to small values of this parameter. Furthermore, interpreting the lattice loop gas as an effective theory describing the Abelian Higgs model is only known to be true in the infinite coupling limit; for strong but finite coupling this correspondence is only a conjecture, the validity of which is beyond the scope of this article.

MacKenzie, R.; Nebia-Rahal, F.; Paranjape, M. B. [Groupe de physique des part