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1

Models for a liquid-liquid phase transition  

NASA Astrophysics Data System (ADS)

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

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

2002-02-01

2

Modeling liquid-liquid phase transitions and quasicrystal formation  

NASA Astrophysics Data System (ADS)

In this thesis, studies which concern two different subjects related to phase transitions in fluids and crystalline solids are presented. Condensed matter formation, structure, and phase transitions are modeled using molecular dynamics simulations of simple discontinuous potentials with attractive and repulsive interactions. Novel phase diagrams are proposed for quasicrystals, crystals, and liquids. In the first part of the thesis, the formation of a quasicrystal in a two dimensional monodisperse system is investigated using molecular dynamics simulations of hard sphere particles interacting via a two-dimensional square-well potential. It is found that for certain values of the square-well parameters more than one stable crystalline phase can form. By quenching the liquid phase at a very low temperature, an amorphous phase is obtained. When this the amorphous phase is heated, a quasicrystalline structure with five-fold symmetry forms. From estimations of the Helmholtz potentials of the stable crystalline phases and of the quasicrystal, it is concluded that within a specific temperature range, the observed quasicrystal phase can be the stable phase. The second part of the thesis concerns a study of the liquid-liquid phase transition for a single-component system in three dimensions, interacting via an isotropic potential with a repulsive soft-core shoulder at short distance and an attractive well at an intermediate distance. The potential is similar to potentials used to describe such liquid systems as colloids, protein solutions, or liquid metals. It is shown that the phase diagram for such a potential can have two lines of first-order fluid-fluid phase transitions: one separating a gas and a low-density liquid (LDL), and another between the LDL and a high-density liquid (HDL). Both phase transition lines end in a critical point, a gas-LDL critical point and, depending on the potential parameters, either a gas-HDL critical point or a LDL-HDL critical point. A systematic study through varying potential parameters is carried out to determine the influence of attractive and repulsive interactions on the formation and stability of the liquid-liquid phase transitions and the two fluid critical points. No hints of the density anomaly are found, suggesting that the absence of the density anomaly, such as the one found in water, is independent of the choice of the parameters and that the liquid-liquid phase transition and density anomaly are not directly related.

Skibinsky, Anna

3

Nonextensive nuclear liquid-gas phase transition  

NASA Astrophysics Data System (ADS)

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

Lavagno, A.; Pigato, D.

2013-10-01

4

Liquid-Liquid phase transition in a single component system  

NASA Astrophysics Data System (ADS)

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

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

2001-06-01

5

Phase transition in liquid drop fragmentation  

SciTech Connect

A liquid droplet is fragmented by a sudden pressurized-gas blow, and the resulting droplets, adhered to the window of a flatbed scanner, are counted and sized by computerized means. The use of a scanner plus image recognition software enables us to automatically count and size up to tens of thousands of tiny droplets with a smallest detectable volume of approximately 0.02 nl. Upon varying the gas pressure, a critical value is found where the size distribution becomes a pure power law, a fact that is indicative of a phase transition. Away from this transition, the resulting size distributions are well described by Fisher's model at coexistence. It is found that the sign of the surface correction term changes sign, and the apparent power-law exponent {tau} has a steep minimum, at criticality, as previously reported in nuclear multifragmentation studies. We argue that the observed transition is not percolative, and introduce the concept of dominance in order to characterize it. The dominance probability is found to go to zero sharply at the transition. Simple arguments suggest that the correlation length exponent is {nu}=1/2. The sizes of the largest and average fragments, on the other hand, do not go to zero abruptly but behave in a way that appears to be consistent with recent predictions of Ashurst and Holian.

Moukarzel, Cristian F.; Fernandez-Sabido, Silvia F.; Ruiz-Suarez, J. C. [CINVESTAV del IPN Unidad Merida, Departamento de Fisica Aplicada, 97310 Merida, Yucatan (Mexico)

2007-06-15

6

Investigation of Dielectric Properties of Liquid Crystals near Phase Transitions  

Microsoft Academic Search

Precise capacitance measurement has been performed near the phase transitions of scientifically important liquid crystals such as 8-CB. The details of the measurements to get high precision data on dielectric constant and its temperature dependence will be presented. The results show significant changes of the dielectric properties of the liquid crystal near the smectic-to-nematic and nematic-to-liquid phase transitions attributed to

Michael Kordell; Tracy Lawson; Chandra Prayaga; Laszlo Ujj

2010-01-01

7

Liquid plasmonics: manipulating surface plasmon polaritons via phase transitions.  

PubMed

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

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

2012-07-31

8

Phase Transitions and recent advances in liquid-crystals research  

Microsoft Academic Search

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

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

2009-01-01

9

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

10

Communication: Protein dynamical transition vs. liquid-liquid phase transition in protein hydration water  

NASA Astrophysics Data System (ADS)

In this work, we compare experimental data on myoglobin hydrated powders from elastic neutron scattering, broadband dielectric spectroscopy, and differential scanning calorimetry. Our aim is to obtain new insights on the connection between the protein dynamical transition, a fundamental phenomenon observed in proteins whose physical origin is highly debated, and the liquid-liquid phase transition (LLPT) possibly occurring in protein hydration water and related to the existence of a low temperature critical point in supercooled water. Our results provide a consistent thermodynamic/dynamic description which gives experimental support to the LLPT hypothesis and further reveals how fundamental properties of water and proteins are tightly related.

Schirò, Giorgio; Fomina, Margarita; Cupane, Antonio

2013-09-01

11

On the Phase Transition of SmCA* Liquid Crystals  

NASA Astrophysics Data System (ADS)

A simple microscopic model of the antiferroelectric SmCA* liquid crystals is proposed so as to analyse a few possible phase transitions between smectic subphases with various macroscopic dipole moments. It is theoretically implied that SmCA* liquid crystals show a universal phase sequence SmCA* (Antiferroelectric), SmC?* (Ferrielectric), and SmC* (Ferroelectric) with increasing temperature in general. This is considered as a consequence of a competition between an attractive dipolar interaction and an excluded volume effect which results in a packing entropy related to the steric hindrance between the biaxial molecules. Also the effect of an external electric field on the phase transition is investigated.

Nakagawa, Masahiro

1993-07-01

12

Liquid-Crystal Phase Transition Probed by Fluorescent Molecules  

NASA Astrophysics Data System (ADS)

Phase transition of four liquid crystal materials have been studied by measuring the decay times of time-resolved intensity of fluorescence from two kind of dyes, malachite green and cryptocyanine, doped in these materials. It was found that the observed fluorescence lifetimes observed depend strongly on the doped molecules and that they change depending on the phase transition of the liquid-crystal materials. These results show that the fluorescence lifetime measurements are effective molecular probes for estimating the microscopic dynamics in these materials.

Hattori, Toshiaki; Hanai, Nobuhiko; Inouye, Hideyuki; Nakatsuka, Hiroki

2001-08-01

13

Adiabatic nucleation in the liquid-vapor phase transition  

NASA Astrophysics Data System (ADS)

The fundamental difference between classical (isothermal) nucleation theory (CNT) and adiabatic nucleation theory (ANT) is discussed. CNT uses the concept of isothermal heterophase fluctuations, while ANT depends on common fluctuations of the thermodynamic variables. Applications to the nonequilibrium liquid to vapor transition are shown. However, we cannot yet calculate nucleation frequencies. At present, we can only indicate at what temperatures and pressures copious homogeneous nucleation is expected in the liquid to vapor phase transition. It is also explained why a similar general indication cannot be made for the inverse vapor to liquid transition. Simultaneously, the validity of Peng-Robinson's equation of state [D.-Y. Peng and D. B. Robinson, Ind. Eng. Chem. Fundam. 15, 59 (1976)] is confirmed for highly supersaturated liquids.

de Sá, Elon M.; Meyer, Erich; Soares, Vitorvani

2001-05-01

14

Phase transitions for a collective coordinate coupled to luttinger liquids.  

PubMed

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

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

2013-09-09

15

Lattice Boltzmann model for anisotropic liquid-solid phase transition.  

PubMed

We develop a simple reaction model for the liquid-solid phase transition in the context of the lattice Boltzmann method with enhanced collisions. Calculations for a two-dimensional test problem of Ga melting and for a two-dimensional anisotropic growth of dendrites are presented and commented on. PMID:11328027

Miller, W; Succi, S; Mansutti, D

2001-04-16

16

Interpenetration as a mechanism for liquid-liquid phase transitions  

NASA Astrophysics Data System (ADS)

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

Hsu, Chia Wei; Starr, Francis W.

2009-04-01

17

Suppression of phase transitions in a confined rodlike liquid crystal.  

PubMed

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

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

2011-10-11

18

Ferroelectric phase transitions near ionic liquid/vacuum interfaces.  

PubMed

A simple theoretical model is developed describing ionic liquids as regular solutions. The separation of these ionic mixtures is studied on the base of the Cahn-Hilliard theory coupled with electrostatics. It is shown that the ionic liquids decompose to thin layers of oppositely charged liquids at low temperatures. At larger temperatures the separation occurs only near the ionic liquid/vacuum surface, thus explaining the oscillatory-decaying structure of the electric double layer observed via computer simulations. In contrast to noncharged liquids the ionic ones exhibit two critical temperatures, where the temperature coefficients of all characteristic lengths possess singularities. These second order ferroelectric phase transitions are possible explanations of the experimentally measured via light scattering peculiar temperature dependence of the interfacial dipole moment density on several ionic liquid/vacuum interfaces. PMID:17523790

Tsekov, Roumen

2007-05-21

19

Nuclear liquid-gas phase transition with finite range force  

NASA Astrophysics Data System (ADS)

The possibilities of the occurrence of liquid-gas phase transition in nuclear matter and finite nuclei are investigated in the framework of temperature-dependent Hartree-Fock theory employing the finite-range Brink-Boeker effective interaction. The equation of state at subnuclear density is obtained. It is found that for infinite nuclear matter critical temperature for the phase transition is substantially reduced because of the finite-range nature of the force as compared to those obtained using zero-range forces. When finite-size effect and Coulomb force are taken into account, critical temperature is found to be around 8 MeV.

Satpathy, L.; Mishra, M.; Nayak, R.

1989-01-01

20

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.

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

2012-01-01

21

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

PubMed

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

Murata, Ken-ichiro; Tanaka, Hajime

2012-03-18

22

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

NASA Astrophysics Data System (ADS)

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

Murata, Ken-Ichiro; Tanaka, Hajime

2012-05-01

23

Vapor-liquid phase transition and multifragmentation of nuclei  

Microsoft Academic Search

Nucleation theory based on the steady-state solution of Fokker-Plank kinetic equation is applied to study of the liquid-gas phase transition in nuclear matter. Theoretical predictions are compared with the parameters extracted from the analysis of the charge distributions of fragments in heavy ion collisions at intermediate energies. The phenomenological droplet model is shown to be able to explain both the

Eugene E. Zabrodin

1995-01-01

24

Solitary wave and nonequilibrium phase transition in liquid crystals  

NASA Astrophysics Data System (ADS)

The solitary-wave character of the Brochard-Leger wall in liquid crystals is analytically revealed. Such a solitary wave has precisely described the behavior of the phase transition. The results obtained are in good quantitative agreement with experiment. A useful formula to determine the viscosity coefficient ?1 is proposed. The equation describing the motion of the wall is similar to the Huxley equation, which describes nerve-signal propagation in biology. This similarity is very impressive.

Xin-Yi, Wang

1985-11-01

25

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

2009-06-25

26

Electrostatic Effects in Phase Transitions of Biomembranes between Cubic Phases and Lamellar Liquid-Crystalline (Lalpha) phase  

Microsoft Academic Search

Elucidation of the mechanisms of transitions between cubic phase and liquid-crystalline (Lalpha) phase, and between different IPMS cubic phases, are essential for understanding of dynamics of biomembranes and topological transformation of lipid membranes. Recently, we found that electrostatic interactions due to surface charges of lipid membranes induce transition between cubic phase and Lalpha phase, and between different IPMS cubic phases.

Shu Jie Li; Yukihiro Tamba; Yuko Yamashita; Masahito Yamazaki

2004-01-01

27

In-situ isothermal phase transitions in photochromic liquid crystals  

NASA Astrophysics Data System (ADS)

This study examines the optical response and physical properties of the homologous series 4-n-butyl-4'-n-alkoxyazobenzene. The members of this series all exhibit liquid crystalline phase behavior, and have also been used as dopants in 4-cyano-4'- n'pentylbiphenyl (5CB), a room temperature nematic liquid crystal. The guest-host system and the azobenzene series have been characterized using optical microscopy and UV-vis spectrophotometry. Illumination of these systems with light of a suitable wavelength induces a trans-cis isomerization of the azo- dye molecules which results in a reorientation of the liquid crystal director, often to such an extent that the liquid crystal phase is disrupted, causing an in situ isothermal phase transition. The response of the liquid crystal system to a linearly polarized beam of exciting radiation is examined with the use of a probe He:Ne laser. Changes in light transmission are then detected with a photodiode. Responses are discussed in terms of homologue, cell thickness and temperature.

Watson, Samantha J.; Gleeson, Helen F.; D'Emanuele, A.; Serak, Svetlana V.; Grozhik, Vladimir A.

1998-06-01

28

Modeling the solid-liquid phase transition in saturated triglycerides.  

PubMed

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 approximately 120 degrees 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 DeltaH. 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 DeltaH 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 DeltaH that was too small by a factor of approximately 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 degrees C < or = T < or = 90 degrees 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. PMID:20136317

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

2010-02-01

29

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

Microsoft Academic Search

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; rho = 1\\/V) or the entropy (S(T)) rather than by gradients in the chemical potential (mu(X), where X is the chemical composition). Experiments and liquid simulation studies now show that such transitions are likely to exist within

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

2007-01-01

30

High-resolution calorimetric study of phase transitions in chiral smectic-C liquid crystalline phases  

NASA Astrophysics Data System (ADS)

We carried out an improved characterization of phase transitions among chiral smectic-C subphases observed for various antiferroelectric liquid crystals by precise heat capacity measurements. It was found that the phase transitions are intrinsically first order exhibiting a remarkable heat anomaly which involves little pretransitional thermal fluctuation and a finite thermal hysteresis. On the other hand, we also noticed that the critical point of the smectic-C?*-smectic-C* transition is induced by the destabilization of the smectic-C?* phase which couples with the fluctuation associated with the smectic-A-smectic-C?* phase transition.

Sasaki, Y.; Le, K. V.; Aya, S.; Isobe, M.; Yao, H.; Huang, C. C.; Takezoe, H.; Ema, K.

2012-12-01

31

High-resolution calorimetric study of phase transitions in chiral smectic-C liquid crystalline phases.  

PubMed

We carried out an improved characterization of phase transitions among chiral smectic-C subphases observed for various antiferroelectric liquid crystals by precise heat capacity measurements. It was found that the phase transitions are intrinsically first order exhibiting a remarkable heat anomaly which involves little pretransitional thermal fluctuation and a finite thermal hysteresis. On the other hand, we also noticed that the critical point of the smectic-C(?)(*)-smectic-C* transition is induced by the destabilization of the smectic-C(?)(*) phase which couples with the fluctuation associated with the smectic-A-smectic-C(?)(*) phase transition. PMID:23367966

Sasaki, Y; Le, K V; Aya, S; Isobe, M; Yao, H; Huang, C C; Takezoe, H; Ema, K

2012-12-28

32

Vapor-liquid phase transition and multifragmentation of nuclei  

SciTech Connect

Nucleation theory based on the steady-state solution of Fokker-Plank kinetic equation is applied to study of the liquid-gas phase transition in nuclear matter. Theoretical predictions are compared with the parameters extracted from the analysis of the charge distributions of fragments in heavy ion collisions at intermediate energies. The phenomenological droplet model is shown to be able to explain both the characteristic power-law falloff and the long tail of the yields of light and heavy nuclear fragments correspondingly. It is shown that the traditional equilibrium approach to the analysis of the multifragmentation data leads to significant overestimation of the parameters of nuclear equation of state.

Zabrodin, E.E. [Department of Physics, University of Bergen, Allegaten 55, N-5007 Bergen (Norway)]|[Institute for Nuclear Physics, Moscow State University, 119899 Moscow (Russian Federation)

1995-11-01

33

Theory of bent-core liquid-crystal phases and phase transitions  

NASA Astrophysics Data System (ADS)

We study phases and phase transitions that can take place in the recently discovered bow-shaped or bent-core liquid-crystal molecules. We show that to completely characterize phases exhibited by such bent-core molecules a third-rank tensor Tijk order parameter is necessary in addition to the vector and the nematic (second-rank) tensor order parameters. We present an exhaustive list of possible liquid phases, characterizing them by their space-symmetry group and order parameters, and catalog the universality classes of the corresponding phase transitions that we expect to take place in such bent-core molecular liquid crystals. In addition to the conventional liquid-crystal phases such as the nematic phase, we predict the existence of other liquid phases, including the spontaneously chiral nematic (NT+2)* and chiral polar (VT+2)* phases, the orientationally ordered but optically isotropic tetrahedratic T phase, and a nematic NT phase with D2d symmetry that is neither uniaxial nor biaxial. Interestingly, the isotropic-tetrahedratic transition is continuous in mean-field theory, but is likely driven first order by thermal fluctuations. We conclude with a discussion of smectic analogs of these phases and their experimental signatures.

Lubensky, T. C.; Radzihovsky, Leo

2002-09-01

34

Theory of bent-core liquid-crystal phases and phase transitions.  

PubMed

We study phases and phase transitions that can take place in the recently discovered bow-shaped or bent-core liquid-crystal molecules. We show that to completely characterize phases exhibited by such bent-core molecules a third-rank tensor T(ijk) order parameter is necessary in addition to the vector and the nematic (second-rank) tensor order parameters. We present an exhaustive list of possible liquid phases, characterizing them by their space-symmetry group and order parameters, and catalog the universality classes of the corresponding phase transitions that we expect to take place in such bent-core molecular liquid crystals. In addition to the conventional liquid-crystal phases such as the nematic phase, we predict the existence of other liquid phases, including the spontaneously chiral nematic (N(T)+2)(*) and chiral polar (V(T)+2)(*) phases, the orientationally ordered but optically isotropic tetrahedratic T phase, and a nematic N(T) phase with D(2d) symmetry that is neither uniaxial nor biaxial. Interestingly, the isotropic-tetrahedratic transition is continuous in mean-field theory, but is likely driven first order by thermal fluctuations. We conclude with a discussion of smectic analogs of these phases and their experimental signatures. PMID:12366133

Lubensky, T C; Radzihovsky, Leo

2002-09-11

35

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

2013-04-29

36

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

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

37

Dynamical behavior near a liquid-liquid phase transition in simulations of supercooled water.  

PubMed

We examine the behavior of the diffusion coefficient of the ST2 model of water over a broad region of the phase diagram via molecular dynamics simulations. The ST2 model has an accessible liquid-liquid transition between low-density and high-density phases, making the model an ideal candidate to explore the impacts of the liquid-liquid transition on dynamics. We locate characteristic dynamical loci in the phase diagram and compare them with the previously investigated thermodynamic loci. The low-density liquid phase shows a crossover from non-Arrhenius to Arrhenius behavior, signaling the onset of a crossover from fragile-to-strong behavior. We explain this crossover in terms of the asymptotic approach of the low-density liquid to a random tetrahedral network and show that the temperature dependence of the diffusion coefficient over a wide temperature range can be simply related to the concentration of defects in the network. Our findings thus confirm that the low-density phase of ST2 water is a well-defined metastable liquid. PMID:21866981

Poole, Peter H; Becker, Stephen R; Sciortino, Francesco; Starr, Francis W

2011-08-26

38

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

39

Mixturelike behavior near a liquid-liquid phase transition in simulations of supercooled water.  

PubMed

In simulations of a waterlike model (ST2) that exhibits a liquid-liquid phase transition, we test for the occurrence of a thermodynamic region in which the liquid can be modeled as a two-component mixture. We assign each molecule to one of two species based on the distance to its fifth-nearest neighbor, and evaluate the concentration of each species over a wide range of temperature and density. Our concentration data compare well with mixture-model predictions in a region between the liquid-liquid critical temperature and the temperature of maximum density. Fits of the model to the data in this region yield accurate estimates for the location of the critical point. We also show that the liquid outside the region of density anomalies is poorly modeled as a simple mixture. PMID:21469883

Cuthbertson, Megan J; Poole, Peter H

2011-03-17

40

Micellar structures in lyotropic liquid crystals and phase transitions  

Microsoft Academic Search

The formation of micellar nematics is discussed with emphasis on the transitions between nematic phases and nematic-smectic transitions. Phase diagrams for MTAB\\/l-decanol\\/D,O systems show a direct transition between uniaxial nematics. Electrical conductivity and birefringence measurements on a mixture of sodium decylsulfate. 1-decanol, D,O demonstrate, on the other hand, the existence of a biaxial nemantic range that separates the Uniaxial nematics.

A. Saupe; S. Y. Xu; Sulakshana Plumley; Y. K. Zhu; P. Photinos

1991-01-01

41

Changes in adsorption and optical properties of liquid crystal langmuir films at structural phase transition  

NASA Astrophysics Data System (ADS)

The adsorption isotherms of water molecules, absorption spectra, and spectra of diffuse scattering and polarization of reflected light are studied for ultrathin Langmuir films prepared based on liquid crystals. A structural phase transition near 70°C is detected. Some specific features of the reflection spectra at the phase transition temperature are found. Suggestions are made regarding the nature of the phase transition.

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

2012-12-01

42

Accurate Method for the Determination of Phase Transitions in Liquid Crystals with Photoacoustic Technique  

Microsoft Academic Search

A compact Photoacoustic spectrometer (PAS) was fabricated, for the determination of phase transitions in liquid crystals (LCs). Photoacoustic (PA) technique is a powerful tool for the determination of phase transitions in solids, liquids and gasses compared to other techniques like Raman spectroscopy, Newton scattering, NMR & ultrasound studies and DSC. PA signal information is used to investigate the variations in

S. Lakshminarayana; K. Gouthami; V. G. K. M. Pisipati; N. V. S. Rao; G. Venkata Rao

2009-01-01

43

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

National Technical Information Service (NTIS)

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...

N. A. Clark

2000-01-01

44

Phase transitions induced by nanoconfinement in liquid water.  

PubMed

We present results from molecular dynamics simulations of water confined by two parallel atomically detailed hydrophobic walls. Simulations are performed at T = 300 K and wall-wall separation d = 0.6-1.6 nm. At 0.7 < or = d < or = 0.9 nm, a first order transition occurs between a bilayer liquid (BL) and a trilayer heterogeneous fluid (THF) as water density increases. The THF is characterized by a liquid (central) layer and two crystal-like layers next to the walls. The BL-THF transition involves freezing of the two surface layers in contact with the walls. At d = 0.6 nm, the THF transforms into a bilayer ice (BI) upon decompression. Both the BL-THF and BI-THF transitions are induced by the surface regular atomic-scale structure. PMID:19257497

Giovambattista, Nicolas; Rossky, Peter J; Debenedetti, Pablo G

2009-02-06

45

Phase Transitions Induced by Nanoconfinement in Liquid Water  

NASA Astrophysics Data System (ADS)

We present results from molecular dynamics simulations of water confined by two parallel atomically detailed hydrophobic walls. Simulations are performed at T=300K and wall-wall separation d=0.6-1.6nm. At 0.7?d?0.9nm, a first order transition occurs between a bilayer liquid (BL) and a trilayer heterogeneous fluid (THF) as water density increases. The THF is characterized by a liquid (central) layer and two crystal-like layers next to the walls. The BL-THF transition involves freezing of the two surface layers in contact with the walls. At d=0.6nm, the THF transforms into a bilayer ice (BI) upon decompression. Both the BL-THF and BI-THF transitions are induced by the surface regular atomic-scale structure.

Giovambattista, Nicolas; Rossky, Peter J.; Debenedetti, Pablo G.

2009-02-01

46

First-order liquid-liquid phase transition in dense hydrogen  

SciTech Connect

We use ab initio molecular-dynamics simulations to study the nonmetal-to-metal transition in dense liquid hydrogen. By calculating the equation of state of hydrogen at high pressures up to several megabars and temperatures above the melting line up to 1500 K we confirm the first-order nature of this transition at these temperatures. We characterize both phases based on equation of state data, the electrical conductivity, and the pair-correlation functions, which are all derived self-consistently from these simulations. We locate the respective transition line in the phase diagram and give an estimate for its critical point. We compare with available experimental data and other theoretical predictions.

Lorenzen, Winfried; Holst, Bastian; Redmer, Ronald [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany)

2010-11-15

47

In-situ isothermal phase transitions in photochromic liquid crystals  

Microsoft Academic Search

This study examines the optical response and physical properties of the homologous series 4-n-butyl-4'-n-alkoxyazobenzene. The members of this series all exhibit liquid crystalline phase behavior, and have also been used as dopants in 4-cyano-4'- n'pentylbiphenyl (5CB), a room temperature nematic liquid crystal. The guest-host system and the azobenzene series have been characterized using optical microscopy and UV-vis spectrophotometry. Illumination of

Samantha J. Watson; Helen F. Gleeson; A. D'Emanuele; Svetlana V. Serak; Vladimir A. Grozhik

1998-01-01

48

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

Microsoft Academic Search

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

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

2005-01-01

49

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

NASA Astrophysics Data System (ADS)

Liquid-liquid phase transitions (LLPT) have been proposed in order to explain the thermodynamic anomalies exhibited by some liquids. Recently, it was found, through molecular dynamics simulations, that liquid elemental gallium, described by a modified embedded-atom model, exhibits a LLPT between a high-density liquid (HDL) and a low-density liquid (LDL), about 60 K below the melting temperature. In this work [1], we studied the dynamics of supercooled liquid gallium close to the LLPT. Our results show a large increase in the plateau of the self-intermediate scattering function (?-relaxation process) and in the non-Gaussian parameter, indicating a pronounced dynamical heterogeneity upon the onset of the LLPT. The dynamical heterogeneity of the LDL is closely correlated to its structural heterogeneity, since the fast diffusing atoms belong to high-density domains of predominantly 9-fold coordinated atoms, whereas the slow diffusing ones are mostly in low-density domains of 8-fold coordinated atoms. The energetics suggests that the reason for the sluggish dynamics of LDL is due to its larger cohesive energy as compared to that of the HDL. [1] S. Cajahuaringa, M. de Koning, and A. Antonelli, J. Chem. Phys. 136, 064513 (2012).

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

2013-03-01

50

A superconductor to superfluid phase transition in liquid metallic hydrogen  

Microsoft Academic Search

Although hydrogen is the simplest of atoms, it does not form the simplest of solids or liquids. Quantum effects in these phases are considerable (a consequence of the light proton mass) and they have a demonstrable and often puzzling influence on many physical properties, including spatial order. To date, the structure of dense hydrogen remains experimentally elusive. Recent studies of

Egor Babaev; Asle Sudbø; N. W. Ashcroft

2004-01-01

51

Effect of carbon nanotube on phase transitions of nematic liquid crystals  

Microsoft Academic Search

Phase diagrams of multiwall carbon nanotube (MWNT)\\/nematic liquid crystal (E7) and bucky ball (C60)\\/nematic liquid crystal binary systems were investigated by means of optical microscopy and differential scanning calorimetry (DSC). It was found that the isotropic-nematic phase transition temperature of liquid crystal component is enhanced by MWNT. A chimney type phase diagram occur over a narrow range of 0.1-0.2ball\\/E7 system

Hatice Duran; Bruce Gazdecki; Liming Dai; Thein Kyu

2004-01-01

52

Water in nanopores: II. The liquid vapour phase transition near hydrophobic surfaces  

Microsoft Academic Search

The liquid-vapour phase transition near a weakly attractive surface is studied by simulations of the coexistence curves of water in hydrophobic pores. There is a pronounced gradual density depletion of the liquid phase near the surface without any trend to the formation of a vapour layer below the bulk critical temperature TC. The temperature dependence of the order parameter in

Ivan Brovchenko; Alfons Geiger; Alla Oleinikova

2004-01-01

53

Influence of the Coulomb Interaction on the Liquid-Gas Phase Transition and Nuclear Multifragmentation  

Microsoft Academic Search

The liquid-gas phase transition is analyzed from the topologic properties of the event distribution in the observables space. A multicanonical formalism allows one to directly relate the standard phase transition with neutral particles to the case where the nonsaturating Coulomb interaction is present, and to interpret the Coulomb effect as a deformation of the probability distributions and a rotation of

F. Gulminelli; Ph. Chomaz; Al. H. Raduta; Ad. R. Raduta

2003-01-01

54

Quasi-liquid layer theory based on the bulk first-order phase transition  

SciTech Connect

The theory of the superionic phase transition (bulk first-order transition) proposed in [1] is used to explain the existence of a quasi-liquid layer at an ice surface below its melting point. An analytical expression is derived for the quasi-liquid layer thickness. Numerical estimates are made and compared with experiment. Distinction is made between the present model and other quasi-liquid layer theories.

Ryzhkin, I. A. [Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation)], E-mail: i.a.ryzhkin@list.ru; Petrenko, V. F. [Dartmouth College, Thayer School of Engineering (United States)

2009-01-15

55

Evidence of a Liquid-Liquid Phase Transition Hot Dense Hydrogen  

NASA Astrophysics Data System (ADS)

We use pulsed laser heating of hydrogen at static pressures in the megabar pressure region generated in a diamond anvil cell to search for the plasma phase transition (PPT) to liquid atomic metallic hydrogen. Heating the sample substantially above the melting line we observe a plateau in a temperature vs laser power curve that otherwise increases with power. This anomaly in the heating curve is closely correlated with theoretical predictions for the PPT, falling within the theoretically predicted range and having a negative slope with increasing pressure. Details will be presented.

Silvera, Isaac; Dzyabura, Vasily; Zaghoo, Mohamed

2013-03-01

56

Information geometry, phase transitions, and the Widom line: Magnetic and liquid systems  

NASA Astrophysics Data System (ADS)

We study information geometry of the thermodynamics of first and second order phase transitions, and beyond criticality, in magnetic and liquid systems. We establish a universal microscopic characterization of such phase transitions via a conjectured equality of the correlation lengths ? in co-existing phases, where ? is related to the scalar curvature of the equilibrium thermodynamic state space. The 1-D Ising model, and the mean-field Curie-Weiss model are discussed, and we show that information geometry correctly describes the phase behavior for the latter. The Widom lines for these systems are also established. We further study a toy model for the thermodynamics of liquid-liquid phase co-existence, and show that our method provides a simple and direct way to obtain its phase behavior and the location of the Widom line. Our analysis points towards the possibility of multiple Widom lines in liquid systems.

Dey, Anshuman; Roy, Pratim; Sarkar, Tapobrata

2013-12-01

57

Dynamics near a liquid-liquid phase transition in a non-tetrahedral liquid: The case of gallium  

NASA Astrophysics Data System (ADS)

We use molecular simulation to analyze liquid dynamics in the vicinity of the liquid-liquid phase transition (LLPT) recently discovered in the modified embedded-atom model for elemental gallium. For this purpose we analyze the diffusive behavior in terms of the mean-squared displacement and self-intermediate scattering functions for two systems obtained by cooling the stable liquid through the LLPT at different cooling rates. The results show a pronounced heterogeneity of the dynamics upon the onset of the LLPT. Furthermore, it is found that this heterogeneity is closely correlated to the structural properties of the 9-fold coordinated high-density and 8-fold coordinated low-density liquid forms involved in the transition, showing a mixture of domains with very different diffusion time scales. The dynamics of the low-density liquid is found to be much more sluggish than that of the high-density form. Analysis of the energetics suggests that the origin of this difference is rooted in the fact that the cohesion in the former is significantly stronger than that in the latter.

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

2012-02-01

58

Effect of carbon nanotube on phase transitions of nematic liquid crystals  

NASA Astrophysics Data System (ADS)

Phase diagrams of multiwall carbon nanotube (MWNT)/nematic liquid crystal (E7) and bucky ball (C60)/nematic liquid crystal binary systems were investigated by means of optical microscopy and differential scanning calorimetry (DSC). It was found that the isotropic-nematic phase transition temperature of liquid crystal component is enhanced by MWNT. A chimney type phase diagram occur over a narrow range of 0.1-0.2ball/E7 system did not showed any changes of TNI in the same concentration range. This behavior has been attributed to anisotropic alignment of carbon nanotubes and liquid crystal molecules, which is entropic in origin.

Duran, Hatice; Gazdecki, Bruce; Dai, Liming; Kyu, Thein

2004-03-01

59

Liquid-gas phase transition in nuclear matter: Mean-field and beyond  

NASA Astrophysics Data System (ADS)

The liquid-gas phase transition in nuclear systems is a unique phenomenon, at the frontier of nuclear, many-body and statistical physics. We study this phase transition theoretically at the Hartree-Fock level and explore the available parameter space for the critical point by using several mean-field parametrizations. We find the latent heat of the transition and describe its temperature dependence from first principles. Using tools from many-body physics, we also describe the phase transition beyond the mean-field approximation and find a marked dependence on both the microscopic interaction and the many-body approximation scheme.

Rios, A.; Carbone, A.; Polls, A.; Vidaña, I.

2012-07-01

60

Photo-induced phase transitions in azobenzene-doped liquid crystals  

Microsoft Academic Search

The effect of irradiation (UV-visible light) on a nematic liquid crystal doped with a photoactive azobenzene derivative was investigated. The selective irradiation results in either an E implies Z or Z implies E isomerization of the azobenzene unit. The effect of the isomerization is to cause a reversible depression of the liquid crystal to isotropic (LC implies l) phase transition

C. H. Legge; G. R. Mitchell

1992-01-01

61

The Complement: A Solution to Liquid Drop Finite Size Effects in Phase Transitions  

SciTech Connect

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

Moretto, L.G.; Bugaev, K.A.; Elliott, J.B.; Phair, L. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Ghetti, R. [Department of Physics, Lund University (Sweden); Helgesson, J. [School of Technology and Society, Malmoe University (Sweden)

2005-05-27

62

The Complement: A Solution to Liquid Drop Finite Size Effects in Phase Transitions  

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

63

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

2008-01-31

64

Liquid-gas phase transition in nuclear matter in the mean-field approximation  

NASA Astrophysics Data System (ADS)

The liquid gas phase transition in nuclear systems is a unique phenomenon, at the frontier of nuclear, many-body and statistical physics. We use self-consistent mean-field calculations to quantify the properties of the transition in symmetric nuclear matter. We explore the available parameter space of critical properties by analyzing the mean-field dependence of the phase transition. The latent heat of the transition is computed and we find that it exhibits a model independent temperature dependence due to basic physical principles.

Rios, A.; Carbone, A.; Polls, A.; Vidaña, I.

2011-09-01

65

Low Frequency Raman Spectra in Ester Liquid Crystals Near Phase Transitions  

Microsoft Academic Search

Phase transitions of the ferroelectric liquid crystal were studied by recording low-frequency Raman spectra and three Raman lines at 15, 49 and 93 cm-1 were observed. The intensities of the 15 and 49 cm-1 modes reduce to zero at smectic C* transition temperature, and in the isotropic phase the 93 cm-1 Raman line with partial frequency shift totally disappears. Bibtex

Mingsheng Zhang; Gongjian Hu; Qiang Chen; Zhengmin Sun; Zhen Yin

1991-01-01

66

The influence of Coulomb on the liquid-gas phase transition and nuclear multifragmentation  

Microsoft Academic Search

The liquid-gas phase transition is analyzed from the topologic properties of\\u000athe event distribution in the obervables space. A multi-canonical formalism\\u000aallows to directly relate the standard phase transition with neutral particles\\u000ato the case where the non saturating Coulomb interaction is present, and to\\u000ainterpret the effect of Coulomb as a deformation of the probability\\u000adistributions and a rotation

F. Gulminelli; Ph. Chomaz; Al. H. Raduta; Ad. R. Raduta

2003-01-01

67

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

SciTech Connect

The liquid-gas phase transition in hot asymmetric nuclear matter is investigated within the 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.

Sharma, Bharat K.; Pal, Subrata [Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

2010-06-15

68

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

NASA Astrophysics Data System (ADS)

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

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

1996-11-01

69

Liquid crystalline phase behavior and sol-gel transition in aqueous halloysite nanotube dispersions.  

PubMed

The liquid crystalline phase behavior and sol-gel transition in halloysite nanotubes (HNTs) aqueous dispersions have been investigated by applying polarized optical microscopy (POM), macroscopic observation, rheometer, small-angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy. The liquid crystalline phase starts to form at the HNT concentration of 1 wt %, and a full liquid crystalline phase forms at the HNT concentration of 25 wt % as observed by POM and macroscopic observation. Rheological measurements indicate a typical shear flow behavior for the HNT aqueous dispersions with concentrations above 20 wt % and further confirm that the sol-gel transition occurs at the HNT concentration of 37 wt %. Furthermore, the HNT aqueous dispersions exhibit pH-induced gelation with more intense birefringence when hydrochloric acid (HCl) is added. The above findings shed light on the phase behaviors of diversely topological HNTs and lay the foundation for fabrication of the long-range ordered nano-objects. PMID:24070131

Luo, Zhiqiang; Song, Hongzan; Feng, Xiaorui; Run, Mingtao; Cui, Huanhuan; Wu, Licun; Gao, Jungang; Wang, Zhigang

2013-09-26

70

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

NASA Astrophysics Data System (ADS)

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

Mirgorod, Yu. A.

2010-10-01

71

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

PubMed

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. PMID:16383397

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

2005-10-05

72

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

Microsoft Academic Search

We conduct extensive molecular dynamics computer simulations of two models for liquid silica [the model of Woodcock, Angell and Cheeseman, J. Phys. Chem. 65, 1565 (1976); and that of van Beest, Kramer, and van Santen, Phys. Rev. Lett. 64, 1955 (1990)] to determine their thermodynamic properties at low temperature T across a wide density range. We find for both models

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

2001-01-01

73

Effects of magnetic nanoparticles with different surface coating on the phase transitions of octylcyanobiphenyl liquid crystal  

Microsoft Academic Search

The impact of magnetic nanoparticles with different surface coating upon the isotropic-to-nematic and nematic-to-smectic- A phase transitions of the liquid crystal octylcyanobiphenyl is explored by means of high-resolution adiabatic scanning calorimetry. A shrinkage of the nematic range is observed, which is strongly dependent on the surface coating of the nanoparticles. The isotropic-to-nematic transition remains weakly first order while the nematic-to-smectic-

George Cordoyiannis; Lynn K. Kurihara; Luz J. Martinez-Miranda; Christ Glorieux; Jan Thoen

2009-01-01

74

Relation between the Widom line and the dynamic crossover in systems with a liquid-liquid phase transition  

PubMed Central

We investigate, for two water models displaying a liquid–liquid critical point, the relation between changes in dynamic and thermodynamic anomalies arising from the presence of the liquid–liquid critical point. We find a correlation between the dynamic crossover and the locus of specific heat maxima \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}C_{P}^{{\\mathrm{max}}}\\end{equation*}\\end{document} (“Widom line”) emanating from the critical point. Our findings are consistent with a possible relation between the previously hypothesized liquid–liquid phase transition and the transition in the dynamics recently observed in neutron scattering experiments on confined water. More generally, we argue that this connection between \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}C_{P}^{{\\mathrm{max}}}\\end{equation*}\\end{document} and dynamic crossover is not limited to the case of water, a hydrogen bond network-forming liquid, but is a more general feature of crossing the Widom line. Specifically, we also study the Jagla potential, a spherically symmetric two-scale potential known to possess a liquid–liquid critical point, in which the competition between two liquid structures is generated by repulsive and attractive ramp interactions.

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

2005-01-01

75

High pressure effects on liquid viscosity and glass transition behaviour, polyamorphic phase transitions and structural properties of glasses and liquids  

Microsoft Academic Search

Since the pioneering work of Bridgman it has been known that pressure affects the glass transition of polymers and liquid state viscosities. Usually the Tg and viscosity both increase as a function of pressure as expected from ‘free volume’ theories. However, H2O provided a notable exception in that the viscosity passes through a minimum at low temperature. It was thought

Paul F. McMillan; Martin C. Wilding

2009-01-01

76

Entanglement entropy and quantum phase transitions in quantum dots coupled to Luttinger liquid wires  

NASA Astrophysics Data System (ADS)

We study a quantum phase transition that occurs in a system composed of two impurities (or quantum dots), each coupled to a different interacting (Luttinger liquid) lead. While the impurities are coupled electrostatically, there is no tunneling between them. Using a mapping of this system onto a Kondo model, we show analytically that the system undergoes a Berezinskii-Kosterlitz-Thouless quantum phase transition as a function of the Luttinger liquid parameter in the leads and the dot-lead interaction. The phase with low values of the Luttinger liquid parameter is characterized by an abrupt switch of the population between the impurities as a function of a common applied gate voltage. However, this behavior is hard to verify numerically since one would have to study extremely long systems. Interestingly, though, at the transition the entanglement entropy drops from a finite value of ln(2) to zero. The drop becomes sharp for infinite systems. One can employ finite-size scaling to extrapolate the transition point and the behavior in its vicinity from the behavior of the entanglement entropy in moderate size samples. We employ the density matrix renormalization-group numerical procedure to calculate the entanglement entropy of systems with lead lengths of up to 480 sites. Using finite-size scaling, we extract the transition value and show it to be in good agreement with the analytical prediction.

Goldstein, Moshe; Gefen, Yuval; Berkovits, Richard

2011-06-01

77

Liquid-gas phase transition in nuclear matter from realistic many-body approaches  

NASA Astrophysics Data System (ADS)

The existence of a liquid-gas phase transition for hot nuclear systems at subsaturation densities is a well-established prediction of finite-temperature nuclear many-body theory. In this paper, we discuss for the first time the properties of such a phase transition for homogeneous nuclear matter within the self-consistent Green's function approach. We find a substantial decrease of the critical temperature with respect to the Brueckner-Hartree-Fock approximation. Even within the same approximation, the use of two different realistic nucleon-nucleon interactions gives rise to large differences in the properties of the critical point.

Rios, A.; Polls, A.; Ramos, A.; Müther, H.

2008-10-01

78

Free energy surface of ST2 water near the liquid-liquid phase transition.  

PubMed

We carry out umbrella sampling Monte Carlo simulations to evaluate the free energy surface of the ST2 model of water as a function of two order parameters, the density and a bond-orientational order parameter. We approximate the long-range electrostatic interactions of the ST2 model using the reaction-field method. We focus on state points in the vicinity of the liquid-liquid critical point proposed for this model in earlier work. At temperatures below the predicted critical temperature we find two basins in the free energy surface, both of which have liquid-like bond orientational order, but differing in density. The pressure and temperature dependence of the shape of the free energy surface is consistent with the assignment of these two basins to the distinct low density and high density liquid phases previously predicted to occur in ST2 water. PMID:23343283

Poole, Peter H; Bowles, Richard K; Saika-Voivod, Ivan; Sciortino, Francesco

2013-01-21

79

Energy landscape view of phase transitions and slow dynamics in thermotropic liquid crystals  

PubMed Central

Thermotropic liquid crystals are known to display rich phase behavior on temperature variation. Although the nematic phase is orientationally ordered but translationally disordered, a smectic phase is characterized by the appearance of a partial translational order in addition to a further increase in orientational order. In an attempt to understand the interplay between orientational and translational order in the mesophases that thermotropic liquid crystals typically exhibit upon cooling from the high-temperature isotropic phase, we investigate the potential energy landscapes of a family of model liquid crystalline systems. The configurations of the system corresponding to the local potential energy minima, known as the inherent structures, are determined from computer simulations across the mesophases. We find that the depth of the potential energy minima explored by the system along an isochor grows through the nematic phase as temperature drops in contrast to its insensitivity to temperature in the isotropic and smectic phases. The onset of the growth of the orientational order in the parent phase is found to induce a translational order, resulting in a smectic-like layer in the underlying inherent structures; the inherent structures, surprisingly, never seem to sustain orientational order alone if the parent nematic phase is sandwiched between the high-temperature isotropic phase and the low-temperature smectic phase. The Arrhenius temperature dependence of the orientational relaxation time breaks down near the isotropic–nematic transition. We find that this breakdown occurs at a temperature below which the system explores increasingly deeper potential energy minima.

Chakrabarti, Dwaipayan; Bagchi, Biman

2006-01-01

80

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

81

Liquid-Gas Phase Transition in Nuclear Matter Within a Correlated Approach  

NASA Astrophysics Data System (ADS)

The existence of a liquid-gas phase transition for hot nuclear systems close to saturation densities is an interesting prediction of finite temperature nuclear many-body theory. We have applied the realistic Self-Consistent Green's Function's (SCGF) method together with the Luttinger-Ward (LW) formalism to the study of the thermodynamical (TD) properties of infinite symmetric nuclear matter. We compare our results with those obtained within the Brueckner-Hartree-Fock (BHF) theory and find substantial differences.

Rios, A.; Polls, A.; Ramos, A.; Müther, H.

2008-06-01

82

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

83

Surface phase transitions in liquid Ga-Bi alloys studied by optical second harmonic generation  

NASA Astrophysics Data System (ADS)

Optical second harmonic generation (SHG) as a particularly surface sensitive technique was employed for the first time to investigate the surface phase behaviour of a liquid alloy, BixGa1-x, in different heating and cooling cycles up to 280 °C. The aim of these experiments is to establish a relatively simple experimental access to the surface phase diagrams of liquid alloys. Measurements of the characteristic changes of the SH signal have been performed on pure Bi and different Ga-rich alloys (xBi?0.367). In pure bismuth the melting and freezing of the surface is indicated by a distinct polarization dependent variation of the SH intensities. Of particular interest is the characterization of the wetting transition found in Ga-Bi recently at the monotectic phase transition (xm = 0.085, Tm = 222 °C). Surprisingly, on first heating of the Ga-rich alloys up to 280 °C the SHG signals give no indication of the dramatic compositional change at the surface induced by the wetting transition. From these observations we conclude that the main source for the nonlinear polarization is the outermost layer of the alloy which in the wet and the non-wet state consists of an adsorbed Bi-rich monolayer. It is shown that SHG is very sensitive to structural changes at the surface. Most interestingly, on cooling of the Ga-rich alloys a Bi-rich film crystallizes on top of the bulk liquid alloy.

Wang, Cong; Nattland, Detlef; Freyland, Werner

2000-07-01

84

Field-induced transitions between multilayer phases of polar smectic liquid crystals.  

PubMed

Recently Wang et al. [Phys. Rev. Lett. 104, 027801 (2010)] reported the discovery of a novel multilayer phase in polar liquid crystals. The phase was unambiguously assigned to a six-layer antiferroelectric structure (Sm-C(d6)(*)) by resonant x-ray diffraction. This discovery lead to essential progress in understanding the nature of polar phases. However, more recently, Chandani et al. [Liq. Cryst. 38, 663 (2011)] in the same material clearly identified the novel phase as a ferrielectric five-layer structure (Sm-C(d5)(*)) by the electric-field-induced birefringence. This contradiction seemed to be a mystery. In this paper we show that the two experiments are in agreement. Phenomenological Landau theory of the phase transitions shows that both phases (Sm-C(d6)(*) and Sm-C(d5)(*)) exist and transform into each other in a relatively low electric field. PMID:23005711

Dolganov, P V; Zhilin, V M; Dolganov, V K; Kats, E I

2012-08-15

85

Surface Specularity as AN Indicator of Shock-Induced Solid-Liquid Phase Transitions in Tin  

NASA Astrophysics Data System (ADS)

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 usually occurs at pressures high enough to melt the free surface. Unlike many other potential material phase-sensitive diagnostics (e.g., reflectometery, 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.

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

2007-12-01

86

Surface Specularity as an Indicator of Shock-Induced Solid-Liquid Phase Transitions  

NASA Astrophysics Data System (ADS)

When highly polished metal surfaces melt upon release after shock loading, they exhibit a number of features that suggest that 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 velocimetric measurements typically observed above pressures high enough to melt the free-surface. Unlike many other potential material phase-sensitive diagnostics (e.g., reflectometery, conductivity), changes in the specularity of reflection provide a dramatic, sensitive indicator of the solid-liquid phase transition. Data will be presented from multiple diagnostics that support the hypothesis that specularity changes indicate melt. These diagnostics include shadowgraphy, infrared imagery, high-magnification surface images, interferometric velocimetry, and most recently scattering angle measurements.

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

2007-06-01

87

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

88

Surface Specularity as an Indicator of Shock-Induced Solid-Liquid Phase Transitions  

SciTech Connect

When highly polished metal surfaces melt upon release after shock loading, they exhibit a number of features that suggest that 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 velocimetric measurements typically observed above pressures high enough to melt the free-surface. Unlike many other potential material phase-sensitive diagnostics (e.g., reflectometery, conductivity), changes in the specularity of reflection provide a dramatic, sensitive indicator of the solid-liquid phase transition. Data will be presented from multiple diagnostics that support the hypothesis that specularity changes indicate melt. These diagnostics include shadowgraphy, infrared imagery, high-magnification surface images, interferometric velocimetry, and most recently scattering angle measurements.

Gerald Stevens, Stephen Lutz, William Turley, Lynn Veeser

2007-06-29

89

Phonon-Roton Excitations and Quantum Phase Transitions in Liquid 4HE in Nanoporous Media  

NASA Astrophysics Data System (ADS)

We present measurements of the elementary phonon-roton and other excitations of liquid 4He confined in nanoporous media using inelastic neutron scattering methods. The aim is to compare phonon-roton (P-R) and superfluid density measurements and to explore the interdependence of Bose-Einstein Condensation (BEC), P-R modes and superfluidity in helium at nanoscales and in disorder. Specifically a goal is to determine the region of temperature and pressure in which well defined phonon-roton modes exist and compare this with the superfluid phase diagram. In porous media the liquid phase is extended up to 35-40 bars. A second goal is to investigate helium at higher pressures. At low temperature and at saturated vapor pressure (SVP) (p ? 0) liquid 4He supports well defined P-R modes in all porous media investigated to date (aerogel, xerogel, Vycor, MCM-41 and gelsil of several pore diameters). As temperature is increased at SVP, the P-R modes broaden but well defined modes exist above Tc in the normal phase, up to T?. The superfluid to normal transition temperature, Tc, in porous media always lies below the corresponding temperature, T?, in bulk helium. In liquid 4He in 25 Å and 34 Å mean pore diameter gelsil under pressure and at low temperature, we observe loss of all well defined P-R modes at p = 36.3 - 36.8 bars. Yamamoto et al. have observed a possible Quantum Phase Transition (QPT) (T?0 K) from the superfluid to normal liquid at p = 34 bars in superfluid density measurements. The existence of P-R modes under pressure up to 36.3 bars and their subsequent loss supports the finding of a QPT. We discuss the implications of these results for the basic concepts of BEC and superfluidity in helium at nanoscales and in disorder.

Glyde, Henry R.; Pearce, Jonathan V.; Bossy, Jacques; Schober, Helmut

2008-06-01

90

Epitaxial growth of graphene on transition metal surfaces: chemical vapor deposition versus liquid phase deposition  

NASA Astrophysics Data System (ADS)

The epitaxial growth of graphene on transition metal surfaces by ex situ deposition of liquid precursors (LPD, liquid phase deposition) is compared to the standard method of chemical vapor deposition (CVD). The performance of LPD strongly depends on the particular transition metal surface. For Pt(111), Ir(111) and Rh(111), the formation of a graphene monolayer is hardly affected by the way the precursor is provided. In the case of Ni(111), the growth of graphene strongly depends on the applied synthesis method. For CVD of propene on Ni(111), a 1 × 1 structure as expected from the vanishing lattice mismatch is observed. However, in spite of the nearly perfect lattice match, a multi-domain structure with 1 × 1 and two additional rotated domains is obtained when an oxygen-containing precursor (acetone) is provided ex situ.

Grandthyll, Samuel; Gsell, Stefan; Weinl, Michael; Schreck, Matthias; Hüfner, Stefan; Müller, Frank

2012-08-01

91

Metastable liquid-liquid phase transition in a single-component system with only one crystal phase and no density anomaly  

NASA Astrophysics Data System (ADS)

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

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

2002-11-01

92

Caloric curve for nuclear liquid-gas phase transition in relativistic mean-field hadronic model  

NASA Astrophysics Data System (ADS)

The main thermodynamical properties of the first order phase transition of the relativistic mean-field (RMF) hadronic model were explored in the isobaric, the canonical and the grand canonical ensembles on the basis of the method of the thermodynamical potentials and their first derivatives. It was proved that the first order phase transition of the RMF model is the liquid-gas type one associated with the Gibbs free energy G. The thermodynamical potential G is the piecewise smooth function and its first order partial derivatives with respect to variables of state are the piecewise continuous functions. We have found that the energy in the caloric curve is discontinuous in the isobaric and the grand canonical ensembles at fixed values of the pressure and the chemical potential, respectively, and it is continuous, i.e. it has no plateau, in the canonical and microcanonical ensembles at fixed values of baryon density, while the baryon density in the isotherms is discontinuous in the isobaric and the canonical ensembles at fixed values of the temperature. The general criterion for the nuclear liquid-gas phase transition in the canonical ensemble was identified.

Parvan, A. S.

2012-08-01

93

A calorimetric study of liquid crystalline phase transitions in confined geometries  

NASA Astrophysics Data System (ADS)

The behavior of the mesophase to isotropic transitions of liquid crystals in confined geometries has been studied using differential scanning calorimetry in an effort to understand the effects of finite size on the transition temperature and the latent heat. Liquid crystals 4-5-alkyl-4sp'-cyanobiphenyl, 4-10-alkyl-4sp '-cyanobiphenyl, 4-5-alkoxy-4sp'-cyanobiphenyl, and 4-10-alkoxy-4sp'-cyanobiphenyl were confined in a series of porous silica glasses with mean pore radii between 6.4 and 146 nm. For each liquid crystalline material and for each pore radius, one completely filled and two partially filled samples were prepared by varying the ratio of the volume of liquid crystals to the available pore volume. The first order nematic to isotropic phase transition was studied using 4-5-alkyl-4sp'-cyanobiphenyl and 4-5-alkoxy-4sp '-cyanobiphenyl while 4-10-alkyl-4sp'-cyanobiphenyl and 4-10-alkoxy-4sp'-cyanobiphenyl were used in studying the smectic A to isotropic transition. In completely filled pores, the transition temperatures and latent heats were found to be increasingly depressed from their corresponding bulk values with decreasing pore radii. In each of the liquid crystals studied, the reduction in the transition temperature and latent heat with pore radii showed stronger dependence than the expected inverse radii behavior. In partially filled pores, the transition temperatures showed a linear decrease with inverse liquid crystal layer thickness. The latent heat of the smectic A to isotropic transition showed similar behavior to that of the transition temperature. The latent heat of the nematic to isotropic transition was found to decrease with decreasing layer thickness and reach a plateau at smaller thicknesses. The data were fit to a modified version of a nucleation based model for first order phase transitions. Using the best fit parameters, a lower and an upper bound for the surface free energy of the nematic/isotropic and smectic A/isotropic interfaces was estimated. The estimated lower bounds for the interfacial free energy of 4-5-alkyl-4sp'-cyanobiphenyl, 4-5-alkoxy-4sp'-cyanobiphenyl, 4-10-alkyl-4sp '-cyanobiphenyl and 4-10-alkoxy-4sp'-cyanobiphenyl were 0.06 ± 0.04, 0.04 ± 0.02, 0.307 ± 0.001, and 0.316 ± 0.001 mJ/msp2, respectively. The corresponding estimated upperbounds for 4-5-alkyl-4sp'-cyanobiphenyl, 4-5-alkoxy-4sp'-cyanobiphenyl,4-10-alkyl-4sp '-cyanobiphenyl and 4-10-alkoxy-4sp '-cyanobiphenyl were 0.12 ± 0.08, 0.09 ± 0.04, 0.614 ± 0.002, and 0.632 ± 0.002 mJ/msp2, respectively. Finally the temperature dependence of the interfacial free energy was also estimated.

Weerasekera, Indira Amarangani

94

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

NASA Astrophysics Data System (ADS)

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

Dai, Song

1995-01-01

95

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

96

Macroscopic description of the isotropic to antiferroelectric B(2) phase transition in banana-shaped liquid crystals.  

PubMed

We present a mean-field description of the phase transitions, which are obtained when cooling from the isotropic liquid to the first liquid crystalline phase in compounds composed of achiral banana-shaped molecules. We put special emphasis on the isotropic to antiferroelectric B(2) phase transition. The free energy is written in terms of the coupled order parameters including the antiferroelectric polarization. We present a detailed analysis of the different phases that can occur and analyze the question under which conditions a direct isotropic to antiferroelectric B(2) phase transition is possible when compared with other phase transitions. The theoretical results are found to be in qualitative agreement with all published experimental results. PMID:20095705

Mukherjee, Prabir K

2010-01-14

97

Phase transitions and reentrant phenomena in liquid crystals having both rigid and flexible intramolecular joints  

NASA Astrophysics Data System (ADS)

Two series of liquid-crystalline compounds having three phenyl rings separated by flexible spacer —CH(CH{3})CH{2}—COO— and by rigid azo and azoxy group, were studied by DSC, optical and X-ray methods. For esters of dl-3-(4^{prime}-nitro)-phenylbutyric acid with 4^{prime}-alkoxy-phenylazo-phenol-4 having dodecyloxy or longer terminal chains, as well as for related azoxy compounds, a narrow (even below 5 K) reentrant or inverted nematic phase appearing between partly bilayer and monolayer smectics A was observed. For higher homologues of the azoxy series additional smectic phases appear, leading to the occurrence of new multicritical points, e.g. the critical end point Ad Cd N^re. On each of the lines, which separate nematic from smectic A phases, transitions are of weakly first or second-order and more than one tricritical point can occur. On the A{1} N/A{1} N^re line, a simple N A{1} tricritical point is observed at T_NI/T_AN = 0.834. The presence of further critical points depends on the components of the binary system involved. Four of the azoxy compounds studied undergo a second order phase transition between partly bilayer smectics, Ad and Cd. Such a transition is accompanied by a jumb in the specific heat, varying linearly with the length of the molecular tails. Various temperature dependences of the layer spacing in the Ad phase are observed for subsequent homologues from the azoxy series. Plusieurs cristaux liquides composés de trois groupements phényl séparés par un groupement —CH(CH{3})CH{2}—COO—, ainsi que par des groupements azo et azoxy, ont été examinés par AED, méthodes optiques et par rayons X. Pour des esters de l'acide dl-3-(4^{prime}-nitro)phénylbutyrique et de 4^{prime}-alkoxy-phénylazo-phénol-4 ayant comme terminaison une chaîne dodecyloxy ou bien plus longue, ainsi que pour des composés azoxy relatif, on observe (même au-dessous de 5 K) une étroite phase nématique réentrante ou inverse entre les phases smectiques : monocouche et partiellement bicouche. Pour des homologues plus longs dans la série des composés azoxy, on a constaté l'existence d'autres phases smectiques ce qui implique l'apparition, sur les diagrammes des phases, de nouveau points multicritiques, par exemple le point Ad Cd N^re. Sur chaque ligne séparant les phases smectiques A de la phase nématique les transitions sont faiblement du premier ordre ou du deuxième ordre ce qui mène dans certain cas à plus qu'un point tricritique. Sur la ligne A{1} N/A{1} N^re on observe à T_NI/T_AN = 0,834 un simple point tricritique N A{1} — l'apparition des autres dépend du choix des constituants du système binaire. Dans le cas de quatre composés azoxy on a constaté une transition du deuxième ordre entre les phases smectiques partiellement bicouches, Ad et Cd. La transition est accompagnée d'un brusque changement de la chaleur spécifique qui varie linéairement avec la longueur de la queue de la molécule. Pour des homologues suivants de la série des composés azoxy on observe différentes dépendances en température de la distance entre les couches de la phase Ad.

Py?uk, W.; Górecka, E.; Mieczkowski, J.; Przedmojski, J.

1992-07-01

98

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

DOEpatents

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

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

1993-01-01

99

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

DOEpatents

A method and apparatus for sensing a liquid-solid phase transition event is provided which comprises an acoustic plate mode detecting element placed in contact with a liquid or solid material which generates a high-frequency acoustic wave that is attenuated to an extent based on the physical state of the material in contact with the detecting element. The attenuation caused by the material in contact with the acoustic plate mode detecting element is used to determine the physical state of the material being detected. The method and device are particularly suited for detecting conditions such as the icing and deicing of wings of an aircraft. In another aspect of the present invention, a method is provided wherein the adhesion of a solid material to the detecting element can be measured using the apparatus of the invention. 3 figs.

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

1990-01-01

100

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

DOEpatents

A method and apparatus for sensing a liquid-solid phase transition event is provided which comprises an acoustic plate mode detecting element placed in contact with a liquid or solid material which generates a high-frequency acoustic wave that is attenuated to an extent based on the physical state of the material in contact with the detecting element. The attenuation caused by the material in contact with the acoustic plate mode detecting element is used to determine the physical state of the material being detected. The method and device are particularly suited for detecting conditions such as the icing and deicing of wings of an aircraft. In another aspect of the present invention, a method is provided wherein the adhesion of a solid material to the detecting element can be measured using the apparatus of the invention. 3 figs.

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

1990-12-31

101

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

SciTech Connect

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

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

1993-02-23

102

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

NASA Astrophysics Data System (ADS)

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

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

1990-05-01

103

Effects of magnetic nanoparticles with different surface coating on the phase transitions of octylcyanobiphenyl liquid crystal  

NASA Astrophysics Data System (ADS)

The impact of magnetic nanoparticles with different surface coating upon the isotropic-to-nematic and nematic-to-smectic- A phase transitions of the liquid crystal octylcyanobiphenyl is explored by means of high-resolution adiabatic scanning calorimetry. A shrinkage of the nematic range is observed, which is strongly dependent on the surface coating of the nanoparticles. The isotropic-to-nematic transition remains weakly first order while the nematic-to-smectic- A is continuous with the effective critical exponent ? values (0.35 and 0.39, depending on the coating) between the pure octylcyanobiphenyl value of 0.31±0.03 and the theoretical tricritical value of 0.5.

Cordoyiannis, George; Kurihara, Lynn K.; Martinez-Miranda, Luz J.; Glorieux, Christ; Thoen, Jan

2009-01-01

104

First-order transition in confined water between high-density liquid and low-density amorphous phases  

Microsoft Academic Search

Supercooled water and amorphous ice have a rich metastable phase behaviour. In addition to transitions between high- and low-density amorphous solids, and between high- and low-density liquids, a fragile-to-strong liquid transition has recently been proposed, and supported by evidence from the behaviour of deeply supercooled bilayer water confined in hydrophilic slit pores. Here we report evidence from molecular dynamics simulations

Kenichiro Koga; Hideki Tanaka; X. C. Zeng

2000-01-01

105

Phase-separation transition in liquid mixtures near curved charged objects.  

PubMed

We study the thermodynamic behavior of nonpolar liquid mixtures in the vicinity of curved charged objects, such as electrodes or charged colloids. There is a critical value of charge (or potential), above which a phase-separation transition occurs, and the interface between high- and low-dielectric constant components becomes sharp. Analytical and numerical composition profiles are given, and the equilibrium front location as a function of charge or voltage is found. We further employ a simple Cahn-Hilliard type equation to study the dynamics of phase separation in spatially nonuniform electric fields. We find an exponential temporal relaxation of the demixing front location. We give the dependence of the steady-state location and characteristic time on the charge, mixture composition and ambient temperature. PMID:18715044

Marcus, Gilad; Samin, Sela; Tsori, Yoav

2008-08-14

106

Evidence for a simple monatomic ideal glass former: The thermodynamic glass transition from a stable liquid phase  

NASA Astrophysics Data System (ADS)

Under cooling, a liquid can undergo a transition to the 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 in a metastable liquid domain below the melting point where crystalline nucleation interfered with the glass formation. We report the first observation of the liquid-glass transition by a first-order polyamorphous phase transition from the equilibrium stable liquid phase. The observation was made in a molecular dynamics simulation of a one-component system with a model metallic pair potential. In this way, the model, demonstrating the thermodynamic glass transition from a stable liquid phase, may be regarded as a candidate for a simple monatomic ideal glass former. This observation is of conceptual importance in the context of continuing attempts to resolve the long-standing Kauzmann paradox. The possibility of a thermodynamic glass transition from an equilibrium melt in a metallic system also indicates a new strategy for the development of bulk metallic glass-forming alloys.

Elenius, Ma?Ns; Oppelstrup, Tomas; Dzugutov, Mikhail

2010-11-01

107

Evidence for a simple monatomic ideal glass former: the thermodynamic glass transition from a stable liquid phase.  

PubMed

Under cooling, a liquid can undergo a transition to the 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 in a metastable liquid domain below the melting point where crystalline nucleation interfered with the glass formation. We report the first observation of the liquid-glass transition by a first-order polyamorphous phase transition from the equilibrium stable liquid phase. The observation was made in a molecular dynamics simulation of a one-component system with a model metallic pair potential. In this way, the model, demonstrating the thermodynamic glass transition from a stable liquid phase, may be regarded as a candidate for a simple monatomic ideal glass former. This observation is of conceptual importance in the context of continuing attempts to resolve the long-standing Kauzmann paradox. The possibility of a thermodynamic glass transition from an equilibrium melt in a metallic system also indicates a new strategy for the development of bulk metallic glass-forming alloys. PMID:21054046

Elenius, Måns; Oppelstrup, Tomas; Dzugutov, Mikhail

2010-11-01

108

Rapid heating of a strongly coupled plasma at the solid-liquid phase transition  

NASA Astrophysics Data System (ADS)

Between 10^4 and 10^6 ^9Be^+ ions are trapped in a 4.5 Tesla Penning trap and laser-cooled to ˜1 mK, where the ions form a crystalline plasma with an interparticle spacing of ˜20 ?m. This system is a realization of a strongly coupled one-component plasma. Using Doppler laser spectroscopy on a single-photon transition, we measured the temperature and heating rate of this plasma when not being laser-cooled. We measured a slow heating rate of ? 100 mK/s due to residual gas collisions for the first 100-200 ms after turning off the cooling laser. This slow heating is followed by a rapid heating to 1-2 K in 100 ms as the plasma undergoes the solid-liquid phase transition at T=10 mK (? ˜ 170). We will present evidence that this rapid heating is due to a sudden release of energy from weakly cooled degrees of freedom involving the cyclotron motion of trapped impurity ions. We will also discuss the prospects for observing the latent heat associated with the phase transition.

Jensen, M. J.; Hasegawa, T.; Bollinger, J. J.; Dubin, D. H. E.

2004-11-01

109

Dynamical Behavior of Liquid Crystals Containing Dispersed Silica Particles Near Sm A - N and N - I Phase Transitions  

Microsoft Academic Search

The dynamical behavior of liquid crystal 8CB containing 2% of dispersed silica particles was investigated using photon correlation spectroscopy. The behavior differs from the one observed in the bulk. Near the phase transition from the nematic to the smectic A phase the orientational fluctuations of nematic director are drastically slower than in the bulk and this strongly resembles the observations

A. Mertelj; A. Jákli; M. ?opi?

1999-01-01

110

Multielement NMR Studies of the Liquid-Liquid Phase Separation and the Metal-to-Nonmetal Transition in Fluid Lithium- and Sodium-Ammonia Solutions.  

PubMed

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

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

2013-09-13

111

Kinetics of liquid-solid phase transition in large nickel clusters  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

112

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

PubMed Central

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

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

2008-01-01

113

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

114

Bubbles in liquids with phase transition—part 2: on balance laws for mixture theories of disperse vapor bubbles in liquid with phase change  

NASA Astrophysics Data System (ADS)

We study averaging methods for the derivation of mixture equations for disperse vapor bubbles in liquids. The carrier liquid is modeled as a continuum, whereas simplified assumptions are made for the disperse bubble phase. An approach due to Petrov and Voinov is extended to derive mixture equations for the case that there is a phase transition between the carrier liquid and the vapor bubbles in water. We end up with a system of balance laws for a multi-phase mixture, which is completely in divergence form. Additional non-differential source terms describe the exchange of mass, momentum and energy between the phases. The sources depend explicitly on evolution laws for the total mass, the radius and the temperature of single bubbles. These evolution laws are derived in a prior article (Dreyer et al. in Cont Mech Thermodyn. doi: 10.1007/s00161-0225-6 , 2011) and are used to close the system. Finally, numerical examples are presented.

Dreyer, Wolfgang; Hantke, Maren; Warnecke, Gerald

2013-08-01

115

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

2011-04-25

116

Molecular studies of the gel to liquid-crystalline phase transition for fully hydrated DPPC and DPPE bilayers  

Microsoft Academic Search

Molecular dynamics simulations were used for a comprehensive study of the structural properties of saturated lipid bilayers, DPPC and DPPE, near the main phase transition. Though the chemical structure of DPPC and DPPE are largely similar (they only differ in the choline and ethanolamine groups), their transformation process from a gel to a liquid-crystalline state is contrasting. For DPPC, three

Sukit Leekumjorn; Amadeu K. Sum

2007-01-01

117

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

118

Laurdan fluorescence spectroscopy reveals a single liquid-crystalline lipid phase and lack of thermotropic phase transitions in the plasma membrane of living human sperm  

Microsoft Academic Search

Membrane lipid phase(s), phase coexistence, and thermotropic phase transitions have been investigated in viable human spermatozoa using Laurdan fluorescence spectroscopy. Generalized polarization (GP) values derived from Laurdan excitation and emission spectra confirm that the sperm plasma membrane is a low polar, highly rigid (liquid-ordered) structure, and give evidence that, in the range from 10°C to 42°C, membrane lipids are in

Simonetta Palleschi; Leopoldo Silvestroni

1996-01-01

119

Liquid crystal phase transitions in suspensions of mineral colloids: new life from old roots.  

PubMed

A review is given of the field of mineral colloidal liquid crystals: liquid crystal phases formed by individual mineral particles within colloidal suspensions. Starting from their discovery in the 1920s, we discuss developments on the levels of both fundamentals and applications. We conclude by highlighting some promising results from recent years, which may point the way towards future developments. PMID:23459965

Lekkerkerker, H N W; Vroege, G J

2013-03-04

120

A Phenomenological Theory of the Antiferroelectric Phase Transition in Smectic Liquid Crystals  

Microsoft Academic Search

By applying the Landau theory, the appearance of the antiferroelectric phase in smectic liquid crystals and the double hysteresis loop are interpreted. Several types of phase sequences including the antiferroelectric, ferroelectric and\\/or ferrielectric phase are obtained phenomenologically. The D-E curves in the antiferroelectric phase are classified into three types depending on temperature and the coefficients of the fourth-order terms in

Hiroshi Orihara; Yoshihiro Ishibashi

1990-01-01

121

Effect of Hydrostatic Pressure on the Phase Transition Temperatures of a Nematic Liquid Crystal.  

National Technical Information Service (NTIS)

The note reports the effect of hydrostatic pressure on the mesomorphic phase transition temperatures of p-(p-ethoxyphenylazo)-phenyl undecylenate (PPU), which exhibits a nematic range between 65 and 110C at one atmospheric pressure. Pressure up to approxi...

J. D. Boyd C. H. Wang

1973-01-01

122

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

123

Study of the isotropic to smectic-A phase transition in liquid crystal and acetone binary mixtures  

NASA Astrophysics Data System (ADS)

The first-order transition from the isotropic (I) to smectic-A (Sm A) phase in the liquid crystal 4-cyano-4'-decylbiphenyl (10CB) doped with the polar solvent acetone (ace) has been studied as a function of solvent concentration by high-resolution ac-calorimetry. Heating and cooling scans were performed for miscible 10CB+ace samples having acetone mole fractions from xace=0.05 (1 wt %) to 0.36 (10%) over a wide temperature range from 310 to 327 K. Two distinct first-order phase transition features are observed in the mixture whereas there is only one transition (I-Sm A) in the pure 10CB for that particular temperature range. Both calorimetric features reproduce on repeated heating and cooling scans and evolve with increasing xace with the high-temperature feature relatively stable in temperature but reduced in size while the low-temperature feature shifts dramatically to lower temperature and exhibits increased dispersion. The coexistence region increases for the low-temperature feature but remains fairly constant for the high-temperature feature as a function of xace. Polarizing optical microscopy supports the identification of a smectic phase below the high-temperature heat capacity signature indicating that the low-temperature feature represents an injected smectic-smectic phase transition. These effects may be the consequence of screening the intermolecular potential of the liquid crystals by the solvent that stabilizes a weak smectic phase intermediate of the isotropic and pure smectic-A.

Sigdel, Krishna P.; Iannacchione, Germano S.

2010-11-01

124

Evolution of the isotropic to smectic-A phase transition in liquid crystal and acetone binary mixtures  

NASA Astrophysics Data System (ADS)

The first-order transition from the isotropic (I) to smectic- A(SmA) phase in the liquid crystal 4-cyano-4'-decylbiphenyl (10CB) doped with the polar solvent acetone (ace) has been studied as a function of solvent concentration by high- resolution ac-calorimetry. Heating and cooling scans were performed for miscible 10CB+ace samples having acetone mole fractions from xace = 0.05 (1 wt.%) to 0.36 (10%) over a wide temperature range from 310 to 327 K. Two distinct first-order phase transition features are observed in the mixture whereas there is only one transition (I-SmA) in the pure 10CB for that particular temperature range. Both calorimetric features reproduce on repeated heating and cooling scans and evolve with increasing xace with the high temperature feature relatively stable in temperature but reduced in size while the low temperature feature shifts dramatically to lower temperature and exhibits increased dispersion. Polarizing optical microscopy supports the identification of a smectic phase below the high-temperature heat capacity signature indicating that the low-temperature feature represents an injected smectic-smectic phase transition. These effects may be the consequence of screening the intermolecular potential of the liquid crystals by the solvent that stabilizes a weak smectic phase intermediate of the isotropic and pure smectic-A.

Sigdel, Krishna; Iannacchione, Germano

2011-03-01

125

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

2008-08-28

126

Liquid-crystal phase transitions of thin layers: A photothermal analysis  

NASA Astrophysics Data System (ADS)

A numerical analysis of the photothermal probe-beam signal generated at first- and second-order phase transitions in 4-n-octyl-4'-cyanobiphenyl (8CB) is proposed. A criterion for photothermal signal sensitivity in detection of phase transitions is given. The influences of probe-beam transverse offset and modulation frequency, as well as thermal parameters of the probed medium, on this sensitivity are investigated experimentally and theoretically. It is shown that the photothermal signal may be insensitive to the phase transitions for certain values of the modulation frequency and the probe-beam transverse offset, while a maximum of sensitivity is obtained for a range of values of these parameters. It is also shown that this sensitivity is improved if we use a probed medium with an effusivity smaller than the sample effusivity. A comparison of some of the results of the theory with experimental results is given.

Hadj-Sahraoui, A.; Louis, G.; Mangeot, B.; Peretti, P.; Billard, J.

1991-10-01

127

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.

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

2011-01-01

128

Effect of phase transitions in Fe-Cr-Al alloys on their corrosion resistance in gases and liquid metals  

Microsoft Academic Search

We investigate the process of oxidation of Fe-Cr-Al alloys in argon and liquid sodium at a temperature of 650°C for 1000 h, analyze distinctive features of the process of formation of surface oxide and sub-oxide layers, and demonstrate the effect of phase transitions in alloys on the corrosion losses in these media. The process of oxidation of ferrochrome alloys in

O. I. Eliseeva; S. B. Prima

1996-01-01

129

Characterization Several Novel Phase Transitions in a Unique Lower Dimension System of Free-Standing Liquid-Crystal Films  

Microsoft Academic Search

Motivated by the defect-mediated two-stage melting theory, extensive experiments have been concluded on free-standing films of a liquid-crystal sample which exhibits the isotropic-smectic-A-hexatic B-crystal-B bulk phase sequence. For a two-layer film, which is virtually two-dimensional, our calorimetric measurement shows an apparently divergent anomaly near the smectic-A-hexatic-B transition. Its anomaly has a dominant fluctuation contribution and can be fitted to a

A. J. Jin; M. Veum; C. F. Chou; J. T. Ho; V. Surendranath; T. Stoebe; S. W. Hui; C. C. Huang

1996-01-01

130

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

131

Experimental Investigation of Solid--Solid and Liquid--Solid Phase Transition Kinetics Using Isentropic Compression Experiments (ICE)  

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. In our experiments, the Sandia Z accelerator produces magnetically driven planar ramp waves of 200-300 ns rise time in copper, which then propagate into a material sample. Two different materials are investigated; iron and molten tin. The two-wave structure in iron due to the ? arrow ? transition disappears under shock loading above 300 kbar, preventing observation of phase change kinetics. Unsteady ramp-wave loading can resolve this behavior over some propagation distance. Isentropic compression of pure iron to 300-400 kbar therefore elucidates the kinetics of the ? arrow ? transition. In-situ (sapphire window interface) VISAR measurements extend earlier free-surface measurements of iron under isentropic and shock loading. Molten tin initially at 600-800 K will be isentropically loaded to 100 kbar, driving it across the liquid-solid phase boundary. VISAR measurements at a sapphire window interface should show evidence of nonequilibrium freezing in tin if the characteristic transition time is in the range of of 10-1000 ns. Computational analysis of both sets of experiments using a rate-dependent phase transition model relates observed wave structure to the underlying material response.

Davis, Jean-Paul; Hayes, Dennis; Hall, Clint; Asay, James; Watts, Phillip; Reisman, David

2001-06-01

132

Pretransitional behavior above the nematic-isotropic phase transition of an auxetic trimer liquid crystal.  

PubMed

Static light scattering and electric field-induced Kerr measurements were performed above the nematic-isotropic phase transition of a terminal-lateral-lateral-terminal negative Poisson ratio trimer. For both measurements the inverse susceptibility was observed to be nearly linear with temperature, a result inconsistent with our previously reported Kerr data [Phys. Rev. E 58, 2041 (1998)]. PMID:11970370

Kang, D; Mahajan, M P; Zhang, S; Petschek, R G; Rosenblatt, C; He, C; Liu, P; Griffin, A C

1999-10-01

133

Fluctuations and criticality of a granular solid-liquid-like phase transition.  

PubMed

We present an experimental study of density and order fluctuations in the vicinity of the solid-liquid-like transition that occurs in a vibrated quasi-two-dimensional granular system. The two-dimensional projected static and dynamic correlation functions are studied. We show that density fluctuations, characterized through the structure factor, increase in size and intensity as the transition is approached, but they do not change significantly at the transition itself. The dense, metastable clusters, which present square symmetry, also increase their local order in the vicinity of the transition. This is characterized through the bond-orientational order parameter Q4, which in Fourier space shows an Ornstein-Zernike-like behavior. Depending on the filling density and vertical height, the transition can be of first- or second-order type. In the latter case, the associated correlation length ?4, the relaxation time ?4, the zero k limit of Q4 fluctuations (static susceptibility), the pair correlation function of Q4, and the amplitude of the order parameter obey critical power laws, with saturations due to finite size effects. Their respective critical exponents are ?(perpendicular))=1, ?(parallel)=2, ?=1, ?=0.67, and ?=1/2, whereas the dynamical critical exponent z=?(parallel)/?(perpendicular)=2. These results are consistent with model C of dynamical critical phenomena, valid for a nonconserved critical order parameter (bond-orientation order) coupled to a conserved field (density). PMID:23002853

Castillo, Gustavo; Mujica, Nicolás; Soto, Rodrigo

2012-08-27

134

Free-surface optical scattering as an indicator of the shock-induced solid-liquid phase transition in tin  

NASA Astrophysics Data System (ADS)

When highly polished metal surfaces melt upon release after shock loading, they exhibit features that suggest that significant surface changes accompany the phase transition. The reflection of light from such surfaces changes from specular (preshock) to diffuse upon melting. A familiar manifestation of this phenomenon is the loss of signal light observed with a velocity interferometer system for any reflector, which occurs at pressures high enough to melt the free surface. Unlike many other potential material phase-sensitive diagnostics (e.g., reflectometry and conductivity) that show relatively small changes, the specularity of reflection provides a more sensitive and definitive indication of the solid-liquid phase transition. Data are 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

135

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

136

Search for the first-order liquid-to-liquid phase transition in low-temperature confined water by neutron scattering  

NASA Astrophysics Data System (ADS)

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 ?-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; Wang, Zhe; Kolesnikov, Alexander I.; Zhang, Yang; Liu, Kao-Hsiang

2013-02-01

137

Quantum Phase Transition Between a Luttinger Liquid and a Gas of Cold Molecules  

SciTech Connect

We consider cold polar molecules confined in a helical optical lattice similar to those used in holographic microfabrication. An external electric field polarizes molecules along the axis of the helix. The large-distance intermolecular dipolar interaction is attractive but the short-scale interaction is repulsive due to geometric constraints and thus prevents collapse. The interaction strength depends on the electric field. We show that a zero-temperature second-order liquid-gas transition occurs at a critical field. It can be observed under experimentally accessible conditions.

Law, K. T.; Feldman, D. E. [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States)

2008-08-29

138

Phase transitions of capillary-held liquids in a slit-like pore.  

PubMed

Dynamics of capillary held liquids plays important roles in a wide range of systems including adhesion, printing of paints and inks, the behavior of wet granular materials, and the mass transfer through porous media. Recent study suggested the presence of two distinct modes for the disappearance of capillary-held liquids in a slit-like pore of adjustable slit width that depended on the slit-opening rates. In contrast to the first mode that is well-documented in terms of the Young-Laplace equation, a novel and unexpected mode was observed when the liquid bridge was held in the vicinity of the thermodynamic phase boundary (equilibrium Kelvin length). Here we extended the study to three new compounds that have a wide range of vapor pressures. An evaporating liquid bridge developed large refractive index gradients that extended over a few micrometers from the edge of the meniscus once the slit width was increased beyond the equilibrium Kelvin length. This interfacial region with depleted refractive index retreated inward as the meniscus shrank with time, and the refractive index of the entire bridge subsequently fell from that of the liquid once the interfacial regions from the opposite sides of the shrinking bridge met at the center. The refractive index recovered to that of the liquid when the slit width was closed to below the Kelvin length and the vapor was allowed to recondense. The time scale of the evaporation and condensation depended on the size of the surface gap, and, when the surfaces were placed at a separation very close to the Kelvin length, it was possible to detect a stage in which the system was in an apparent kinetic equilibrium between two physical states--with and without the liquid connecting the two surfaces. PMID:17181248

Maeda, Nobuo

2006-12-28

139

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

140

Polyamorphic transitions in yttria–alumina liquids  

Microsoft Academic Search

There has been much recent discussion given to the phenomenon of polyamorphism where distinct, different states of amorphous liquids and solids are observed as a function of density. Underlying this phenomenon is the possibility of a first order liquid–liquid phase transition driven by the density and entropy differences between the two amorphous phases. Differential scanning calorimetry (DSC) of aluminate glasses

Martin C Wilding; Paul F McMillan

2001-01-01

141

Application of a quartz-crystal microbalance for detection of phase transitions in liquid crystals and lipid multibilayers  

SciTech Connect

Resonance frequency increased abruptly at the phase transition temperature (T{sub c}) from solid to liquid crystalline state of liquid crystals (LCs) or lipid multibilayer films cast on a quartz-crystal microbalance (QCM) electrode when the ambient temperature increased gradually. The large frequency enhancement at the T{sub c} was observed in the case of smectic LC-coated QCM compared with those of nematic and cholesteric LC-coated QCM. Although the frequency enhancement at the T{sub c} of the LC-coated QCM was observed independent of media such as water and air phases, the frequency of the lipid multibilayer-coated QCM increased abruptly at the T{sub c} only in a water phase, but not in an air phase. Frequency enhancements at T{sub c} can be explained by slipping between layered structures of smectic LC and lipid multibilayer in the fluid liquid crystalline state above the T{sub c}. In the case of lipid multibilayers, the penetration of water into interlayers (swelling) occurs at the T{sub c} and then the frequency increase is observed due to slipping between hydrated and fluid layers only in aqueous phases.

Okahata, Yoshio; Ebato, Hiroshi (Tokyo Institute of Technology (Japan))

1989-10-01

142

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

143

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

NASA Astrophysics Data System (ADS)

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 xBi=0.0032, 0.0023, 0.000 37, and 0.000 037. The monolayer coverage of the alloys with xBi=0.0023, and xBi=0.000 37 is about 0.85 and only very slightly temperature dependent. The monolayer coverage in the lowest-concentration alloy, with xBi=0.000 037, 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 xBi=0.000 037 suggest that near 80 °C there is a disordered phase-to-disordered phase transition.

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

2005-06-01

144

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

145

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

146

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

147

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

2013-09-11

148

Raman study of the molecular motions of pivalic acid: the liquid—plastic phase transition  

NASA Astrophysics Data System (ADS)

Raman spectra of pivalic acid in the plastic and liquid phase have been measured. The reorientational correlation times have been evaluated from the ? asCH, ?C?O and ?C?C bands as a function of temperature. The reorientational correlation time corresponding to ? as CH and ?C?C bands is ? < 10 -11 s whilst for the ?C?O band ? = 4ps ( T = 20°C). The calculated activation energy is 26 KJ mol -1. The reorientation of the carboxylic groups which may be assisted by the proton transfer along the hydrogen bonds in dimers is discussed.

Balevi?ius, V.; Orel, B.; Hadži, D.

149

Long-chain alcohol induced phase transition in lyotropic mixed polyoxyethylene-type surfactant liquid-crystals  

Microsoft Academic Search

The structural change and phase transition in the mixed surfactant liquid crystalline (LC) system of nonaethyleneglycol dodecylether (C12EO9), polyoxyethylene (20) sorbitan monostearate (Tween 60) and water has been studied on addition of primary alcohols CnH2n+1OH (CnOH, n=10, 12, and 14) or replacement of C12EO9 with CnOH. In the alcohol-added systems, the C12EO9\\/Tween 60\\/CnOH\\/H2O mixture at a 1:1:x:60 molar ratio for

Tsuyoshi Kijima; Yuki Nishida; Daisuke Fujikawa; Masafumi Uota; Takumi Yoshimura; Go Sakai

2007-01-01

150

Anomaly of pretransitional behavior at the nematic-smectic-A phase transition of amphiphilic liquid crystals with a hydrophilic group.  

PubMed

In order to clarify the origin of the X-ray diffraction peak corresponding to the smectic-like layer ordering appearing even in the nematic phase over a wide temperature range above the nematic-smectic A (NA) phase transition in liquid crystal (LC) molecules with a hydroxy group, we investigated the critical behavior of bend elastic constants and the correlation length of the smectic-like ordering in the N phase. It is found that cybotactic clusters with the transient layer ordering grow up extremely even far above the NA phase transition, and the critical exponent of the correlation length of the cybotactic clusters is estimated anomalously larger than that of conventional LC materials. Furthermore, we measured diffusion constants parallel and perpendicular to the director in the N phase, and concluded that cybotactic clusters with the smectic layer ordering create a finite potential barrier to prevent diffusion of the molecules parallel to the director as well as the true smectic A layer structure. PMID:23668232

Kimoto, Yasuhiro; Nishizawa, Ayumi; Takanishi, Yoichi; Yoshizawa, Atsushi; Yamamoto, Jun

2013-05-13

151

Visualizing a dilute vortex liquid to solid phase transition in a Bi2Sr2CaCu2O8 single crystal  

NASA Astrophysics Data System (ADS)

Using high-sensitivity magneto-optical imaging, we find evidence for a jump in local vortex density associated with a vortex liquid to vortex solid phase transition just above the lower critical field in a single crystal of Bi2Sr2CaCu2O8. We find that the regions of the sample where the jump in vortex density occurs are associated with low screening currents. In the field-temperature vortex phase diagram, we identify phase boundaries demarcating a dilute vortex liquid phase and the vortex solid phase. The phase diagram also identifies a coexistence regime of the dilute vortex liquid and solid phases and shows the effect of pinning on the vortex liquid to vortex solid phase transition line. We find that the phase boundary lines can be fitted to the theoretically predicted expression for the low-field portion of the phase boundary delineating a dilute vortex solid from a vortex liquid phase. We show that the same theoretical fit can be used to describe the pinning dependence of the low-field phase boundary lines provided that the dependence of the Lindemann number on pinning strength is considered.

Shaw, Gorky; Mandal, Pabitra; Banerjee, S. S.; Tamegai, T.

2012-08-01

152

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

PubMed

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

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

2013-06-18

153

Two-dimensional infrared spectroscopy study on phase transition and structural variations of a hydrogen-bonded liquid crystal.  

PubMed

Infrared (IR) spectra have been measured for a liquid crystal (LC) consisting of one trans-butene diacid (BD) molecule as a proton donor and two 4-(2,3,4-tridecyloxybenzoyloxy)-4'-stilbazoles (DBS) molecules as a proton acceptor (DBS:BD:DBS) linked together with each other by inter-molecular hydrogen bonds over a temperature range from 20 to 120 degrees C to explore its phase transition and heat-induced structural variations. The temperature-dependent IR spectra have shown that the inter-molecular hydrogen bonds are stable in the liquid crystalline phase but become slightly decoupled with temperature increasing. Two kinds of two-dimensional (2D) correlation spectroscopy, variable-variable (VV) and sample-sample (SS) 2D spectroscopy, have been employed to analyze the observed temperature-dependent spectral variations more efficiently. The SS 2D correlation analysis in the spectral range of 2700-1800 cm(-1) has demonstrated that a change in hydrogen bonds in the LC starts from 40 degrees C, which is not clarified by differential scanning calorimetry (DSC) and conventional IR and Raman spectroscopic analyses. On the other hand, the phase transition of LC revealed by SS 2D spectroscopy in the specific spectral regions of 1750-1650 and 3000-2700 cm(-1) is in a good agreement with that revealed by DSC for the heating process. The VV 2D correlation spectroscopy analysis has provided information about the structural variations of inter-molecular hydrogen bonds. The different species of hydrogen-bonded and free -COOH and -COO- groups in the LC have been clarified by the VV 2D correlation analysis. It has also elucidated the specific order of the temperature-induced structural changes in the intra- and inter-molecular hydrogen bonds concerning with the -COOH and/or -COO- groups in the LC. PMID:15248970

Wu, Yuqing; Jiang, Shimei; Ozaki, Yukihiro

2004-07-01

154

Orientational Fluctuations Near the Smectic A to Smectic C Phase Transition in Two "de Vries"-Type Liquid Crystals.  

PubMed

On the basis of thorough analysis of 2D X-ray diffraction patterns from smectic monodomains, we examine the influence of orientational fluctuations on the weakly first-order smectic A (SmA) to smectic C (SmC) transitions in two nonchiral organosiloxane "de Vries"-type liquid crystals. We find that these materials exhibit very large molecular tilt fluctuations with magnitudes of up to 35°-thus larger than the average tilt itself. This is essential to understand the underlying molecular mechanism behind the practical absence of smectic layer contraction in these materials: in the SmA phase, the nematic order parameter is very low (molecular fluctuations correspondingly high), and the expected layer shrinkage at the SmA to SmC transition is almost fully compensated by the increase in orientational order, as the fluctuations diminish with decreasing temperature. In addition to the general tilt fluctuations, we observe intrinsic soft-mode fluctuations. They have a ?-shaped temperature dependence that peaks at the SmA-SmC transition with a maximum amplitude of about 2°. PMID:23877994

Nonnenmacher, Dorothee; Jagiella, Stefan; Song, Qingxiang; Lemieux, Robert P; Giesselmann, Frank

2013-07-22

155

BEC-BCS crossover and the liquid-gas phase transition in hot and dense nuclear matter  

NASA Astrophysics Data System (ADS)

The effect of nucleon-nucleon correlations in symmetric nuclear matter at finite temperature is studied beyond BCS theory. Starting from a Hartree-Fock description of nuclear matter with the Gogny effective interaction, we add correlations corresponding to the formation of preformed pairs and scattering states above the superfluid critical temperature within the in-medium T-matrix approach, which is analogous to the Nozières-Schmitt-Rink theory. We calculate the critical temperature for a BEC superfluid of deuterons, of a BCS superfluid of nucleons, and in the crossover between these limits. The effect of the correlations on thermodynamic properties (equation of state, energy, entropy) and the liquid-gas phase transition is discussed. Our results show that nucleon-nucleon correlations beyond BCS play an important role for the properties of nuclear matter, especially in the low-density region.

Jin, Meng; Urban, Michael; Schuck, Peter

2010-08-01

156

Small-Angle X-Ray Scattering Studies of Phase Transitions in Liquids.  

NASA Astrophysics Data System (ADS)

New advances in synchrotron radiation small-angle x-ray scattering were used to investigate phase transitions in supercooled water and in polymer solutions. Supercooled water exhibits a number of unusual characteristics which have been conjectured to be associated with a spinodal point at {-46}^ circC. Experiments performed down to {-34}^circC show that the correlation lengths of density fluctuations are small and change very little with temperature, suggesting that supercooled water is not approaching the proposed spinodal point. Instead, the increasing density fluctuations with supercooling appear to be due to an increased fraction of water molecules which participate in clusters. A comprehensive study of the equilibrium structure factors and kinetics of spinodal decomposition in semidilute solutions of polystyrene in cyclohexane (PS-CH) and a semidilute solution of polystyrene in dioctyl phthalate (PS-DOP) has been performed. In equilibrium, mean-field behavior was observed near the spinodal point. Scaling theory was found to be valid near the Theta-temperature, at which the excluded volume effect disappears, and to break down as the spinodal temperature is approached. The well-known excess low-angle scattering is best described by the Debye-Bueche random heterogeneity model, rather than the attractive potential model of Medjahdi and co -workers. Time-resolved small-angle x-ray scattering, which utilized the high viscosity Theta -solvent DOP and a high concentration solution, allowed the kinetics of the phase separation process at an early stage to be examined. Although strong nonlinearities in the kinetics were observed, linear theory could describe the process at short times and low wavenumbers. The experimental results also indicate that nonlinearities become significant earlier at higher wavenumbers, which is consistent with recent computer simulation studies. From a linear theory analysis, the exponential relaxation rate of the structure factor R(q) was found to be linear in q^2 in the low-wavenumber region of the experiments, in agreement with Binder's theory for spinodal decomposition in polymer solutions. The wavenumber-dependent Onsager coefficient Lambda(q), which is the Fourier transform of the nonlocal mobility in a polymer system, was determined to scale as q^{ -4}. This stronger q-dependence than that predicted by Binder's theory is suggested to be directly related to the observed, and unexplained, equilibrium excess low -angle scattering.

Xie, Yonglin

1995-01-01

157

Fluorescence of CdSe nanoparticles in the Liquid Crystal 8CB near the Phase Transitions  

Microsoft Academic Search

The liquid crystal 4'octyl---4-cyanobiphenyl (8CB) doped with cadmium selenide nanoparticles was injected into a commercially available liquid crystal cell (INSTEC, Inc). The cell was housed in a temperature controlled environment constructed in the lab and exposed to light from a frequency doubled Nd: YAG laser. Fluorescence from the sample was filtered from the incident light and detected using a photodiode

Jodie Gray; Shane Drye; Darren North; Samuel Beck; Tim Royappa; Laszlo Ujj; Chandra Prayaga

2011-01-01

158

Spectral Measurements of Fluorescence of CdSe nanoparticles in Liquid Crystals near Phase Transitions  

Microsoft Academic Search

The liquid crystal 4'octyl-4-cyanobiphenyl (8CB) doped with cadmium selenide nanoparticles was injected into a commercially available liquid crystal cell (INSTEC, Inc). The cell was housed in a temperature controlled environment constructed in the lab and exposed to light from a frequency doubled Nd: YAG laser. The spectrum of fluorescence from the sample was measured at several temperatures over the range

Samuel Beck; Jodie Gray; Shane Drye; Darren North; Tim Royappa; Chandra Prayaga; Laszlo Ujj

2011-01-01

159

Liquid manipulation via morphological transitions  

Microsoft Academic Search

Liquid deposited on rectangular grooves, has a variety of possible liquid morphologies determined by the contact angle, theta, and the exact channel geometry. In our experiments, electrowetting is used to tune theta reversibly from 100 to 50 ^o, leading to a reversible transition between a drop- like morphology at large theta and extended liquid filaments for small theta. The transition

Ralf Seemann; Martin Brinkmann; Evgeny Gurevich; Stephan Herminghaus; Jean-Christophe Baret; Michel Decre

2006-01-01

160

Fluorescence decay of CdSe nanoparticles in Liquid Crystals near Phase Transitions  

Microsoft Academic Search

The liquid crystal 4'octyl-4-cyanobiphenyl (8CB) doped with cadmium selenide nanoparticles (Sigma-Aldrich) was injected into a commercially available liquid crystal cell (INSTEC, Inc). The cell was housed in a temperature controlled environment constructed in the lab and exposed to light from a frequency doubled pulsed Nd: YAG laser. The decay of fluorescence from the sample was measured at several temperatures over

Darren North; Samuel Beck; Jodie Gray; Shane Drye; Chandra Prayaga; Laszlo Ujj; Tim Royappa

2011-01-01

161

Liquid gallium-lead mixture phase diagram, surface tension near the critical mixing point, and prewetting transition.  

PubMed

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

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

2013-06-03

162

Ultrafast spectroscopy of electron transfer dynamics in liquids; excitation transfer studies of phase transitions  

Microsoft Academic Search

The transfer of an electron from a donor to an acceptor is the fundamental step in a wide range of chemical and biological processes. As a result, electron-transfer reactions have been the focus of numerous theoretical and experimental efforts aimed at understanding the kinetics and mechanism of the transfer event. Liquid solvents are an important medium for electron-transfer processes. The

Alexei A. Goun

2008-01-01

163

Pre-Service Primary Science Teachers' Understandings of the Effect of Temperature and Pressure on Solid-Liquid Phase Transition of Water  

ERIC Educational Resources Information Center

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

Yalcin, Fatma Aggul

2012-01-01

164

Pre-Service Primary Science Teachers' Understandings of the Effect of Temperature and Pressure on Solid-Liquid Phase Transition of Water  

ERIC Educational Resources Information Center

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

Yalcin, Fatma Aggul

2012-01-01

165

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

166

Phonon-Roton Excitations and Quantum Phase Transitions in Liquid 4HE in Nanoporous Media  

Microsoft Academic Search

We present measurements of the elementary phonon-roton and other excitations of liquid 4He confined in nanoporous media using inelastic neutron scattering methods. The aim is to compare phonon-roton (P-R) and superfluid density measurements and to explore the interdependence of Bose-Einstein Condensation (BEC), P-R modes and superfluidity in helium at nanoscales and in disorder. Specifically a goal is to determine the

Henry R. Glyde; Jonathan V. Pearce; Jacques Bossy; Helmut Schober

2008-01-01

167

?5?1 Integrin-Fibronectin Interactions Specify Liquid to Solid Phase Transition of 3D Cellular Aggregates  

PubMed Central

Background Tissue organization during embryonic development and wound healing depends on the ability of cells on the one hand to exchange adhesive bonds during active rearrangement and on the other to become fixed in place as tissue homeostasis is reached. Cells achieve these contradictory tasks by regulating either cell-cell adhesive bonds, mediated by cadherins, or cell-extracellular matrix (ECM) connections, regulated by integrins. Integrin ?5?1 and soluble fibronectin (sFN) are key players in cell-ECM force generation and in ECM polymerization. Here, we explore the interplay between integrin ?5?1 and sFN and its influence on tissue mechanical properties and cell sorting behavior. Methodology/Principal Findings We generated a series of cell lines varying in ?5?1 receptor density. We then systematically explored the effects of different sFN concentrations on aggregate biomechanical properties using tissue surface tensiometry. We found previously unreported complex behaviors including the observation that interactions between fibronectin and integrin ?5?1 generates biphasic tissue cohesion profiles. Specifically, we show that at constant sFn concentration, aggregate cohesion increases linearly as ?5?1 receptor density is increased from low to moderate levels, producing a transition from viscoelastic-liquid to pseudo viscoelastic-solid behavior. However, further increase in receptor density causes an abrupt drop in tissue cohesion and a transition back to viscoelastic-liquid properties. We propose that this may be due to depletion of sFn below a critical value in the aggregate microenvironment at high ?5?1 levels. We also show that differential expression of ?5?1 integrin can promote phase-separation between cells. Conclusions/Significance The interplay between ?5-integrin and sFn contributes significantly to tissue cohesion and, depending on their level of expression, can mediate a shift from liquid to elastic behavior. This interplay represents a tunable level of control between integrins and the ECM that can influence tissue cohesion and other mechanical properties, which may translate to the specification of tissue structure and function. These studies provide insights into important biological processes such as embryonic development, wound healing, and for tissue engineering applications.

Caicedo-Carvajal, Carlos E.; Shinbrot, Troy; Foty, Ramsey A.

2010-01-01

168

Kinetics of the gel-to-liquid phase transition of binary lipid bilayers using volume perturbation calorimetry  

Microsoft Academic Search

The relaxation kinetics of the gel-liquid crystalline transition of multilamellar vesicles (MLV) made of binary mixtures of\\u000a dimyristoylphosphatidylcholine (DMPC), diapalmitoylphosphatidylcholine (DPPC) and distearoyl-phosphatidylcholine (DSPC) have\\u000a been studied with volume perturbation calorimetry. The temperature and pressure relaxations following a volume perturbation\\u000a were used to monitor the transition time-course. Data collected in the time domain were converted into and analyzed in the

R. L. Biltonen; Q. Ye

169

Liquid-liquid transitions: Silicon in silico  

NASA Astrophysics Data System (ADS)

Extensive numerical simulations provide evidence that the thermodynamic behaviour of supercooled silicon is similar to that proposed for supercooled water: a line of liquid-liquid transitions that ends at a critical point. In the case of silicon, however, the critical point occurs at negative pressures.

Sciortino, Francesco

2011-07-01

170

Molecular modeling of liquid crystalline self-organization of fullerodendrimers: columnar to lamellar phase transitions driven by temperature and/or concentration changes.  

PubMed

The molecular cubic-block model [ J. Chem. Phys. 2005, 123, 164904 ] is used to study a class of poly(benzyl ether) fullerodendrimers that have recently been reported to form columnar liquid crystal phases. In agreement with experiment, the model-molecules are found to self-assemble into columns which form hexagonal or rectangular lattices. The columnar cross sections are elongated in the rectangular phase. Transitions to the isotropic phase, either directly or through the intermediate formation of smectic phases, have been found. The effects of dissolving small amounts of nonbonded fullerene molecules have been explored. The results predict that the fullerene solutes restrict the range of stability of the columnar phase and may induce transitions from the columnar to the smectic or the isotropic phase. PMID:18795770

Peroukidis, Stavros D; Vanakaras, Alexandros G; Photinos, Demetri J

2008-09-17

171

Energy landscapes for cooperative processes: nearly ideal glass transitions, liquid-liquid transitions and folding transitions.  

PubMed

We describe basic phenomenology in the physics of supercooling liquids at constant volume (most simulations), and at constant pressure (most laboratory experiments) before focusing attention on the exceptional cases that exhibit liquid-liquid phase transitions on constant-pressure cooling. We give evidence for point defects in glasses and liquids near T(g). Models based on defects predict transitions with density gaps in constant-pressure systems. We describe the energy landscape representation of such systems. Water, in these terms, is post-critical, and its nearly ideal glass formation can be related to nucleation-free protein 'funnel-folding'. For nucleated folding of proteins, a pseudo-gap should be present. Experimental methods of distinguishing between alternative folding scenarios are described. PMID:15664891

Angell, C Austen

2005-02-15

172

Effect of ZnO nanoparticles on the SmC*-SmA* phase transition temperature in electroclinic liquid crystals  

NASA Astrophysics Data System (ADS)

ZnO nanoparticles (NPs), synthesized in an alcoholic medium at room temperature, were added to electroclinic liquid crystal (ELC) materials. The addition of ZnO NPs in ELCs, caused a remarkable shift in SmC*-SmA* phase transition which was investigated from the dielectric and electro-optical measurements. The anchoring of ELC molecules around ZnO NPs creates orientational distortions near the surface, which may give additional ordering to the ELC molecular arrangement. After analyzing collective dielectric relaxation processes of ZnO NP doped ELCs, three distinct loss peaks were observed. The different behavior of ZnO NP doped ELC from pure ELC has been explained by determining the dielectric strength, the distribution parameter and the corresponding relaxation frequency, and so on, and then these results have been compared with the data calculated by using the theoretical model. The effect of ZnO NPs addition on physical parameters, such as spontaneous polarization (Ps) and rotational viscosity (?) has also been observed.

Malik, A.; Choudhary, A.; Silotia, P.; Biradar, A. M.

2011-09-01

173

Effect of long range order on sheared liquid crystalline materials: flow regimes, transitions, and rheological phase diagrams  

PubMed

A generalized theory that includes short-range elasticity, long-range elasticity, and flow effects is used to simulate and characterize the shear flow of liquid crystalline materials as a function of the Deborah (De) and Ericksen (Er) numbers in the presence of fixed planar director boundary conditions; the results are also interpreted as a function of the ratio R between short-range and long-range elasticity. The results are effectively summarized into rheological phase diagrams spanned by De and Er, and also by R and Er, where the stability region of four distinct flow regimes are indicated. The four regimes for planar (two-dimensional orientation) shear flow are (1) the elastic-driven steady state, (2) the composite tumbling-wagging periodic state, (3) the wagging periodic state, and (4) the viscous-driven steady state. The coexistence of the four regimes at a quacritical point is shown to be due to the emergence of a defect structure. The origin, the significant steady and dynamical features, and the transitions between these regimes are thoroughly characterized and analyzed. Quantitative and qualitative comparisons between the present complete model predictions and those obtained from the classical theories of nematodynamics (Leslie-Ericksen and Doi theories) are presented and the main physical mechanisms that drive the observed deviations between the predictions of these models are identified. The presented results fill the previously existing gap between the classical Leslie-Ericksen theory and the Doi theory, and present a unified description of nematodynamics. PMID:11138099

Tsuji; Rey

2000-12-01

174

Temperature-tunable scattering strength based on the phase transition of liquid crystal infiltrated in well-defined macroporous random media  

NASA Astrophysics Data System (ADS)

Temperature dependence of scattering strength for the visible light (488 nm) has been investigated for a siloxane-based macroporous monolith infiltrated with liquid crystal molecules. A macroporous gel with interconnected pores and organosiloxane skeletons is prepared via a sol gel route by inducing the phase separation parallel to the hydrolysis and condensation of silicon alkoxide. The interconnected macropores of the dried gel are infiltrated with liquid crystal 4-cyano-4?-n-pentylbiphenyl (5CB) which undergoes the phase transition between nematic and isotropic at 35 °C. Temperature variation of the scattering strength for 5CB-filled gel is measured by means of coherent backscattering and total transmission, both of which exhibit a significant change in transport mean free path at around the phase transition temperature of 5CB. The results indicate that the scattering strength of 5CB-filled monolith gel can be tuned externally via temperature.

Murai, Shunsuke; Fujita, Koji; Hirao, Takayuki; Nakanishi, Kazuki; Hirao, Kazuyuki

2007-04-01

175

Activated Kinetics of Nematic and Smectic Phase Transitions in an Aligned Matrix of Nano-colloidal Liquid Crystalline Gel  

NASA Astrophysics Data System (ADS)

This study investigates an interesting thermal behavior of an aligned aerosil nano-colloidal system in the aligned matrix of octyl-cyanobiphenyl liquid crystal. This system was prepared by solvent dispersion method (SDM) where different densities of aerosil nanoparticles were added into octyl-cyanobiphenyl liquid crystal. Then samples were cycled into magnetic field during SmA-I transition to get an aligned matrix of nanocolloids. Heating scans were performed at various heating rates from 20 to 1 K min-1 using DSC. Aligned samples follow Arrhenius behavior and showed a decrease in transitions temperature for SmA--N and N--I transitions when compared with the unaligned samples. The activation energy of the aligned system increases and its respective enthalpy decreases for the lowest density of aerosils 0.05 g cm-3, then for the further increase of aerosil density, the activation energy decreases and its respective enthalpy increases. The second order transition SmA--N shows a higher activated kinetics than the weak first order N--I transition. This can be explained in terms of molecular interaction in between aerosil nanoparticles and aligned liquid crystal molecules, and developed strain in the matrix of the aligned system.

Sharma, Dipti

2009-03-01

176

Interaction and Response of a Smectic-A liquid crystal to a 2 nm Nanometer Particle: Phase transition due to the Functionalization Compound  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

177

Study of the smecticA-hexaticB phase transition in homeotropic single domain samples of 65OBC liquid crystal by photopyroelectric calorimetry.  

PubMed

The smecticA-hexaticB phase transition was studied in a homeotropic single domain sample and in a non-aligned sample of n-hexyl-4'-n-pentyloxybiphenyl-4-carboxylate liquid crystal compound to probe the effect of different amount of defects on the phase transition. The specific heat, the thermal diffusivity and the enthalpy exchange were monitored over the transition and, at the same time, polarization microscopy observations could be carried out. The transition during the first cooling run was found to be accompanied by a considerably larger defect annealing in the non-aligned sample than in the homeotropic one, but the critical behaviour of the specific heat remained substantially the same. PMID:23445031

Mercuri, F; Paoloni, S; Marinelli, M; Pizzoferrato, R; Zammit, U

2013-02-21

178

Slow relaxation effects at the second-order nematic to lamellar smectic phase transition in micellar liquid crystals  

Microsoft Academic Search

The second-order nematic to lamellar-smectic phase transition is studied in the micellar systems decylammonium chloride-NH4Cl-water and cesium perfluoro-octanoate-D2O, by measuring the electric conductivity of aligned samples and the density as functions of temperature. In the nematic range, for temperatures higher than about 1 °C above the transition, the data on cooling and heating coincide within experimental error. Closer to the

Panos Photinos; Alfred Saupe

1990-01-01

179

Lattice effects and entropy release at the low-temperature phase transition in the spin-liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3.  

PubMed

The spin-liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3 has been studied by measuring the uniaxial expansion coefficients alpha(i), the specific heat, and magnetic susceptibility. Special emphasis was placed on the mysterious anomaly around 6 K--a potential spin-liquid instability. Distinct and strongly anisotropic lattice effects have been observed at 6 K, clearly identifying this feature as a second-order phase transition. Owing to the large anomalies in alpha(i), the application of Grüneisen scaling has enabled us to determine the corresponding specific heat contribution and the entropy release. Comparison of the latter with available spin models suggests that spin degrees of freedom alone cannot account for the phase transition. Scenarios involving charge degrees of freedom are discussed. PMID:20366375

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

2010-01-07

180

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

181

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

182

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

183

Extended transition-state theory and constant-energy chemical-reaction molecular-dynamics method for liquid-phase chemical reactions  

Microsoft Academic Search

An extension of transition-state theory for liquid-phase chemical reactions is presented. The effect of adding a second solvent water molecule on the proton-transfer reaction in a formamidine–water (FW) cluster was studied. Abinitio molecular-orbital calculations were performed for the formamidine–water–water (FWW) system to obtain the adiabatic potential-energy surface. It was expressed in two coordinate systems: (i) the total normal-coordinate system of

Masataka Nagaoka; Yoshishige Okuno; Tokio Yamabe

1992-01-01

184

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.

Zubelewicz, Aleksander

2013-01-01

185

Phase Transition Taylor Test  

Microsoft Academic Search

In this article, the Taylor impact test is applied to investigate the dynamic phase transformation behavior of NiTi alloy, which we call it the phase transition Taylor test (PTTT). The symmetry impact configuration is applied in the study at impact velocity range from 47m\\/s to 175m\\/s by using a light gas gun facility in this lab. The NiTi alloy is

Xinghua Zhang

2005-01-01

186

The Electroweak Phase Transition  

Microsoft Academic Search

The electroweak phase transition is investigated by means of the perturbatively calculated high temperature effective potential. An analytic result to order $g^4,\\\\lambda^2$ is presented for the Abelian Higgs model, the SU(2)-Higgs model and the standard model and a complete on-shell renormalization at zero temperature is performed. Higher order corrections are found to increase the strength of the first order phase

A. Hebecker

1995-01-01

187

In situ observation of multiple phase transitions in low-melting ionic liquid [BMIM][BF4] under high pressure up to 30 GPa.  

PubMed

In situ characterization of phase transitions and direct microscopic observations of a low-melting ionic liquid, 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF(4)]), has been performed in detail by Raman spectroscopy. Compression of [BMIM][BF(4)] was measured under hydrostatic pressure up to ~30.0 GPa at room temperature by using a high-pressure diamond anvil cell. With pressure increasing, the characteristic bands of [BMIM][BF(4)] displayed nonmonotonic pressure-induced frequency shifts, and it is found to undergo four successive phase transitions at around 2.25, 6.10, 14.00, and 21.26 GPa. Especially, above a pressure of 21.26 GPa, luminescence of the sample occurs, which is connected with the most significant phase transition at around this pressure. It was indicated that the structure change under high pressure might be associated with a conformational change in the butyl chain. Upon releasing pressure, the spectrum was not recovered under a pressure up to 1.16 GPa, thereby indicating that this high-pressure phase remains stable over a large pressure range between 30 and 1.16 GPa in low-melting ionic liquid [BMIM][BF(4)]. Although the sample was kept under the normal pressure for 24 h, the spectrum was recovered, and it showed that the phase transition of [BMIM][BF(4)] was reversible. In other words, such a low-melting ionic liquid [BMIM][BF(4)] remains stable even after being treated under so a high pressure of up to 30 GPa. PMID:22239600

Su, Lei; Zhu, Xiang; Wang, Zheng; Cheng, Xuerui; Wang, Yongqiang; Yuan, Chaosheng; Chen, Zhenping; Ma, Chunli; Li, Fangfei; Zhou, Qiang; Cui, Qiliang

2012-02-08

188

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

189

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

2012-02-21

190

X-ray cross-correlation analysis of liquid crystal membranes in the vicinity of the hexatic-smectic phase transition  

NASA Astrophysics Data System (ADS)

We present an x-ray study of liquid crystal membranes in the vicinity of the hexatic-smectic phase transition by means of angular x-ray cross-correlation analysis. By applying two-point angular-intensity cross-correlation functions to the measured series of diffraction patterns the parameters of bond-orientational (BO) order in hexatic phase were directly determined. The temperature dependence of the positional correlation lengths was analyzed as well. The obtained correlation lengths show larger values for the higher-order Fourier components of BO order. These findings indicate a strong coupling between BO and positional order.

Kurta, R. P.; Ostrovskii, B. I.; Singer, A.; Gorobtsov, O. Y.; Shabalin, A.; Dzhigaev, D.; Yefanov, O. M.; Zozulya, A. V.; Sprung, M.; Vartanyants, I. A.

2013-10-01

191

Interaction and response of a smectic-A liquid crystal to a nanometer particle: Phase transition due to the combined effect of the functionalization compound and particle size  

NASA Astrophysics Data System (ADS)

The interaction of nanometer particles with organic materials is important because of their increased use in many applications and their potential use in biosystems. We found that liquid crystals respond to nanometer particles differently depending on the surface functionalization of the nanoparticles using x rays and developed a phenomenological model to explain the differences that we observed. We found from the analysis of the peaks close to 0.199 A?-1 that the inverse integrated intensity serves as a measure of how well the liquid crystal has reoriented and compared the graph obtained from the phenomenological theory to the graph obtained with the inverse integrated intensity. An analysis of the widths of these peaks (inverse correlation length) shows that the reorientation under the magnetic field can lead to a phase transition of the portion of the liquid crystal that is reorienting.

Martínez-Miranda, L. J.; Kurihara, Lynn K.

2009-04-01

192

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

2011-12-08

193

Unraveling the Solid-Liquid-Vapor Phase Transition Dynamics at the Atomic Level with Ultrafast X-Ray Absorption Near-Edge Spectroscopy  

NASA Astrophysics Data System (ADS)

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 (˜3ps) 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.

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

194

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

195

Propagation of the polyamorphic transition of ice and the liquid-liquid critical point  

Microsoft Academic Search

Water has a rich metastable phase behaviour that includes transitions between high- and low-density amorphous ices, and between high- and low-density supercooled liquids. Because the transitions occur under conditions where crystalline ice is the stable phase, they are challenging to probe directly. In the case of the liquids, it remains unclear whether their mutual transformation at low temperatures is continuous,

Osamu Mishima; Yoshiharu Suzuki

2002-01-01

196

[The effect of pressure on binary solution phase transition and fermi resonance--comparing pressure effect for binary solution and pure liquid].  

PubMed

The Raman spectra of binary solution (CCl4 and C6 H6) and pure liquid were measured up to pressures of 11 GPa. The results show that pressure effect on binary solution is different from that on pure liquid: When mixing two liquids, owing to the changes in the density of the solution, intermolecular distance decreases and interaction energy increases, the frequency shift (blue shift) of spectral bands increases, and the frequency shift of binary liquid is faster than pure liquid frequency shift. Phase transitions (spectral bands splitting) change earlier and natural frequency difference delta0 increases with increasing pressure, while the Fermi resonance bands nu1 + nu6 and nu8 of benzene and nu1 + nu4 and nu3 of CCl4 disappear as the pressure decreases gradually, the spectral bands with different compressibility have different speed, whereas CCl4 has smaller density, longer bond, smaller force constant and larger compressibility and is easy to compress, C6H6 has larger density, smaller bond, larger force constant, smaller compressibility and is hard to compress. The frequency shift of CCl4 is faster than benzene. In this paper we provide good reference on Raman bands assignment and certification under high pressure, and also provide methods and ideas for study of the different environment of high pressure effect, intermolecular interaction and solvent effect. PMID:20939325

Yang, Guang; Zhou, Mi; Jiang, Xiu-lan; Zhang, Peng; Liu, Tie-cheng; Xu, Da-peng; Li, Zuo-wei; Gao, Shu-qin; Yang, Jian-ge

2010-08-01

197

Sudden switchover between the polyamorphic phase separation and the glass-to-liquid transition in glassy LiCl aqueous solutions  

NASA Astrophysics Data System (ADS)

Lithium chloride aqueous solutions (LiClaq solutions) below 10 mol.% are vitrified by cooling from room temperature to 77 K at 0.3 GPa. We examine the solvent state of the glassy sample and its transformation by heating at 1 atm using low-temperature differential scanning calorimetry and Raman spectroscopy. This experimental study suggests strongly that the solvent state of the glassy LiClaq solution closely relates to the state of high-density amorphous ice. Moreover, we reconfirm that the separation into the low-density amorphous ice and the glassy highly concentrated LiClaq solution occurs in the glassy dilute LiClaq solution at ~130 K, not the glass-to-liquid transition which is commonly observed in the glassy LiClaq solution above ~10 mol.%. In order to interpret the sudden switchover between the glass-to-liquid transition and the phase separation at ~10 mol.%, we propose a state diagram of LiClaq solution which connects with a polyamorphic state diagram of pure water and discuss a possibility that the electric field induces a polyamorphic transition of water.

Suzuki, Yoshiharu; Mishima, Osamu

2013-02-01

198

Sudden switchover between the polyamorphic phase separation and the glass-to-liquid transition in glassy LiCl aqueous solutions.  

PubMed

Lithium chloride aqueous solutions (LiClaq solutions) below 10 mol.% are vitrified by cooling from room temperature to 77 K at 0.3 GPa. We examine the solvent state of the glassy sample and its transformation by heating at 1 atm using low-temperature differential scanning calorimetry and Raman spectroscopy. This experimental study suggests strongly that the solvent state of the glassy LiClaq solution closely relates to the state of high-density amorphous ice. Moreover, we reconfirm that the separation into the low-density amorphous ice and the glassy highly concentrated LiClaq solution occurs in the glassy dilute LiClaq solution at ?130 K, not the glass-to-liquid transition which is commonly observed in the glassy LiClaq solution above ?10 mol.%. In order to interpret the sudden switchover between the glass-to-liquid transition and the phase separation at ?10 mol.%, we propose a state diagram of LiClaq solution which connects with a polyamorphic state diagram of pure water and discuss a possibility that the electric field induces a polyamorphic transition of water. PMID:23464160

Suzuki, Yoshiharu; Mishima, Osamu

2013-02-28

199

Phase transitions in DNA  

NASA Astrophysics Data System (ADS)

Experiments on light absorption in DNA solutions in the region of 260 nm demonstrate specific multiple sharp oscillations of dAdT vs temperature T, A being the optical density. A one-dimensional Ising model with a long-range polyspin interaction in an inhomogeneous "magnetic field" is used to present a quantitative description of these oscillations. An explicit analytical formula, derived in the paper, provides a surprisingly good agreement between the theory and experiments. It also alows one to obtain from these experiments important information about the sequence of the "magnetic fields," which represents the DNA component sequence. This is demonstrated by an example of a particular DNA. The long-range interaction in the Ising model implies a phase transition. Its nature is shown to depend crucially on well-defined properties of the DNA sequence.

Azbel, M. Ya.

1979-10-01

200

Anleasticity of Phase Interfaces and Phase Transitions  

NASA Astrophysics Data System (ADS)

Any first-order phase transition involves the formation of a phase interface between the two phases involved, whether for reconstructive transitions or other displacive (e.g. martensitic) phase transitions. We have investigated the response of such interfaces to applied stress. A number of model systems have been employed in these investigations, including gallate perovskites, ortho-phosphate structures, as well as silicates. Using mechanical spectroscopic methods, including dynamic mechanical analysis (DMA) we have measured the mechanical loss (inverse qualiity factor, Q) as a function of applied stress at a number of frequencies of dynamic stress and as a function of temperature through the phase transitions that occur in the model compounds. We find that there is significant anelastic loss very close to the phase transition in each case, and that this loss can be associated with the rapid and rather easy movement of the phase interface that exists between the co-existing phases in the two-phase regions of the pertinent phase diagrams. The results indicate that large increases in inverse quality factor would be expected at first-order phase transitions in mantle materials, and provide a further route to identifying potential phase boundaries as and where they occur in the deep Earth.

Redfern, S.; Daraktchiev, M.; Harrison, R.; Jakeways, C.; Walsh, J.

2006-12-01

201

Nonequilibrium Phase Transitions Associated with DNA Replication  

NASA Astrophysics Data System (ADS)

Thermodynamics governing the synthesis of DNA and RNA strands under a template is considered analytically and applied to the population dynamics of competing replicators. We find a nonequilibrium phase transition for high values of polymerase fidelity in a single replicator, where the two phases correspond to stationary states with higher elongation velocity and lower error rate than the other. At the critical point, the susceptibility linking velocity to thermodynamic force diverges. The overall behavior closely resembles the liquid-vapor phase transition in equilibrium. For a population of self-replicating macromolecules, Eigen’s error catastrophe transition precedes this thermodynamic phase transition during starvation. For a given thermodynamic force, the fitness of replicators increases with increasing polymerase fidelity above a threshold.

Woo, Hyung-June; Wallqvist, Anders

2011-02-01

202

Quantum phase transition in space  

SciTech Connect

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

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

2008-01-01

203

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

204

Study of Phase Transitions.  

National Technical Information Service (NTIS)

The diamagnetic transition in CuCl has been verified, and materials studies have been carried out to determine the conditions under which this transition, which may per precursive to high temperature superconductivity, may be found. A photoactivated, defe...

I. Lefkowitz

1983-01-01

205

Phase diagrams and kinetics of phase transitions in protein solutions  

NASA Astrophysics Data System (ADS)

The phase behavior of proteins is of interest for fundamental and practical reasons. The nucleation of new phases is one of the last major unresolved problems of nature. The formation of protein condensed phases (crystals, polymers, and other solid aggregates, as well as dense liquids and gels) underlies pathological conditions, plays a crucial role in the biological function of the respective protein, or is an essential part of laboratory and industrial processes. In this review, we focus on phase transitions of proteins in their properly folded state. We first summarize the recently acquired understanding of physical processes underlying the phase diagrams of the protein solutions and the thermodynamics of protein phase transitions. Then we review recent findings on the kinetics of nucleation of dense liquid droplets and crystals. We explore the transition from nucleation to spinodal decomposition for liquid-liquid separation and introduce the new concept of solution-to-crystal spinodal. We review the two-step mechanism of protein crystal nucleation, in which mesoscopic metastable protein clusters serve as precursors to the ordered crystal nuclei. The concepts and mechanisms reviewed here provide powerful tools for control of the nucleation process by varying the solution thermodynamic parameters.

Vekilov, Peter G.

2012-05-01

206

Phase diagrams and kinetics of phase transitions in protein solutions.  

PubMed

The phase behavior of proteins is of interest for fundamental and practical reasons. The nucleation of new phases is one of the last major unresolved problems of nature. The formation of protein condensed phases (crystals, polymers, and other solid aggregates, as well as dense liquids and gels) underlies pathological conditions, plays a crucial role in the biological function of the respective protein, or is an essential part of laboratory and industrial processes. In this review, we focus on phase transitions of proteins in their properly folded state. We first summarize the recently acquired understanding of physical processes underlying the phase diagrams of the protein solutions and the thermodynamics of protein phase transitions. Then we review recent findings on the kinetics of nucleation of dense liquid droplets and crystals. We explore the transition from nucleation to spinodal decomposition for liquid-liquid separation and introduce the new concept of solution-to-crystal spinodal. We review the two-step mechanism of protein crystal nucleation, in which mesoscopic metastable protein clusters serve as precursors to the ordered crystal nuclei. The concepts and mechanisms reviewed here provide powerful tools for control of the nucleation process by varying the solution thermodynamic parameters. PMID:22495288

Vekilov, Peter G

2012-04-11

207

Nonequilibrium dynamics of phase transitions  

NASA Astrophysics Data System (ADS)

Phase transitions occur in such diverse and important systems as ferromagnets, liquid crystals and the early Universe. The dynamics of phase transitions such as these have been studied for decades, but the analytical models still need a great deal of improvement before they can adequately describe all time stages and regions under the coexistence curve. Numerical studies can supplement these analytical theories, but they need to accurately describe the continuum equations that they are intended to solve. This thesis describes a method for removing the lattice- spacing and renormalization-mass dependence of Langevin simulations of phase mixing in (2 + 1)-dimensional asymmetric Ginzburg-Landau models with short-ranged interactions. Also, the spread in the order parameter near the critical value of the control parameter due to critical slowing down is used to more accurately determine this value of the control parameter in these simulations. In addition, a new method is proposed for quantifying the departure from equilibrium. The method explores the behavior of the rate of change of the momentum-integrated structure function, ?Stot( t), as it evolves in time. As an illustration, we examine a (1 + 1)-dimensional model of a stochastic Ginzburg-Landau model at varying cooling rates. We show that ?Stot(t) displays a peak which scales with cooling time-scale as t1/2q in the over-damped limit and t1/3q in the underdamped limit. The peak amplitude was found to scale with cooling time-scale as t6/5q in all viscosities studied.

Gagne, Carmen Jeanne

2001-11-01

208

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

SciTech Connect

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

Pruess, K.

2011-05-15

209

Chimie douce and phase transitions  

Microsoft Academic Search

New oxides have been prepared in the WO3-MoO3 system, the structure of which can be described by corner-sharing (MO6) octahedra forming structures of hexagonal tungsten bronze-type, ReO3-type and pyrochlore-type. These oxides are metastable phases which transform irreversibly above 400°C into the stable phases. These monotropic, reconstructive and first-order transitions present special features compared with classical phase transitions. Indeed, they are

M. Figlarz; B. Gerand; B. Dumont; A. Delahaye-Vidal; F. Portemer

1991-01-01

210

Phase Transitions in Ionic Gels  

Microsoft Academic Search

The polymer network of a gel, under certain conditions, undergoes a discrete transition in equilibrium volume with changes in solvent composition or temperature. This Letter demonstrates that ionization of the gel network plays an essential role in the phase transition. The volume collapse is also observed when the pH within the gel is varied.

Toyoichi Tanaka; David Fillmore; Shao-Tang Sun; Izumi Nishio; Gerald Swislow; Arati Shah

1980-01-01

211

Phase transitions in ionic gels  

Microsoft Academic Search

It has been reported that under certain conditions the polymer network of acrylamide gels immersed in acetone—water mixtures undergoes a discrete transition in equilibrium volume with changes in acetone concentration or temperature. In the present work, the physical and chemical basis of this phase transition is identified. The magnitude of the collapse can increase substantially when a small percentage of

Toyoichi Tanaka; Shao-Tang Sun; Izumi Nishio; Gerald Swislow; Arati Shah

1980-01-01

212

Theory of a dye laser in a mesogenic matrix near a transition to the liquid crystal phase  

SciTech Connect

A stochastic distributed feedback mechanism is proposed to account for the experimental results (blue shift of the wavelength, reduction of the threshold) on the lasing of a dye in a liquid crystal matrix. It is shown that this mechanism involves scattering by inhomogeneous fluctuations of the order and provides a correct quantitative description of the experimental data.

Lyakhov, G.A.; Svirko, Y.P.

1985-10-01

213

Phase Transitions in Thin Block Copolymer Films  

SciTech Connect

David Turnbull's experiments and theoretical insights paved the way for much of our modern understanding of phase transitions in materials. In recognition of his contributions, this lecture will concentrate on phase transitions in a material system not considered by Turnbull, thin diblock copolymer films. Well-ordered block copolymer films are attracting increasing interest as we attempt to extend photolithography to smaller dimensions. In the case of diblock copolymer spheres, an ordered monolayer is hexagonal, but the ordered bulk is body-centered cubic (bcc). There is no hexagonal plane in the bcc structure, so a phase transition must occur as n, the number of layers of spheres in the film, increases. How this phase transition occurs with n and how it can be manipulated is the subject of the first part of my presentation. In the second part of the talk, I show that monolayers of diblock copolymer spheres and cylinders undergo order-to-disorder transitions that differ greatly from those of the bulk. These ordered 2D monolayers are susceptible to phonon-generated disorder as well as to thermal generation of defects, such as dislocations, which, while they are line defects in 3D, are point defects in 2D. The results are compared to the theories of melting of 2D crystals (spheres) and of 2D smectic liquid crystals (cylinders), a comparison that will allow us to understand most, but not all, of the features of these order-disorder transitions that occur as the temperature is increased.

Kramer, Edward J. (UCSB)

2010-10-08

214

Phase diagram of Ag-Pd bimetallic nanoclusters by molecular dynamics simulations: solid-to-liquid transition and size-dependent behavior.  

PubMed

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

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

2009-04-03

215

Holographic approach to phase transitions  

SciTech Connect

We provide a description of phase transitions at finite temperature in strongly coupled field theories using holography. For this purpose, we introduce a general class of gravity duals to superconducting theories that exhibit various types of phase transitions (first or second order with both mean and non-mean field behavior) as parameters in their Lagrangian are changed. Moreover the size and strength of the conductivity coherence peak can also be controlled. Our results suggest that certain parameters in the gravitational dual control the interactions responsible for binding the condensate and the magnitude of its fluctuations close to the transition.

Franco, Sebastian; Garcia-Garcia, Antonio M.; Rodriguez-Gomez, Diego [KITP, University of California, Santa Barbara, CA93106-4030 (United States); CFIF, IST, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal) and Physics Department, Princeton University, Princeton, New Jersey 08544 (United States); Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom)

2010-02-15

216

Structural features of the liquid/plastic crystal phase transition for cyclohexane in bulk and confined geometry  

NASA Astrophysics Data System (ADS)

Neutron diffraction measurements have been made for cyclohexane, C6D12 as a function of temperature for bulk samples and also in porous silica with characteristic pore dimensions of ~90Å. The results show that the simplifying assumption of cyclohexane as an unhindered rotator are not valid and that complex spatial correlations exist in all phases. The nucleation of the plastic crystal phase is displaced to low temperature for the confined material and the diffraction pattern of the plastic crystal phase is found to depend on thermal history as well as temperature. The results may be interpreted in terms of defect properties which influence the orientational correlations between neighbouring molecules.

Farman, H.; Coveney, F. M.; Dore, J. C.

1992-06-01

217

Alternating-Current-Field Induced Cholesteric-Nematic Phase Transitions  

Microsoft Academic Search

In order to determine whether interaction between the permanent or the induced molecular dipole moments of a cholesteric liquid crystal and an applied electric field is responsible for inducing a transition to a nematic phase, ac-field measurements were performed. In a mixture of cholesteryl chloride and cholesteryl myristate, phase transitions can be induced by an ac field of a frequency

H. Baessler; M. M. Labes

1969-01-01

218

Liquid-liquid transition in ST2 water  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

219

Liquid-liquid transition in ST2 water.  

PubMed

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

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

2012-12-01

220

QCD Phase Transitions, Volume 15.  

National Technical Information Service (NTIS)

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 discuss...

E. Shuryak T. Schaefer

1999-01-01

221

PHASE CHANGE LIQUIDS  

SciTech Connect

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

Susan S. Sorini; John F. Schabron

2006-03-01

222

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

2012-12-13

223

Phase Transitions in Two-Dimensional Superconductors  

NASA Astrophysics Data System (ADS)

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

Yazdani, Ali

1995-01-01

224

Determination of sialyl and neutral oligosaccharide levels in transition and mature milks of Samoan women, using anthranilic derivatization followed by reverse phase high performance liquid chromatography.  

PubMed

An improved analytical method using reverse-phase high performance liquid chromatography following anthranilic acid derivatization for the measurement of each oligosaccharide level in transition (5 to 10 d lactation) and mature (21 to 155 d lactation) milks of sixteen Samoan women is described. The method was applied for the measurement of sialyl as well as neutral oligosaccharide levels. We found that disialyllacto-N-tetraose (DSLNT), sialylacto-N-tetraose c (LSTc), and 6'-sialyllactose (6'-SL) were the most abundant of the sialyl oligosaccharides. In the neutral oligosaccharide fraction, lacto-N-fucopentaose II and III combined (LNFP II+III) were the most dominant, followed by lacto-N-tetraose (LNT) and 3-fucosyllactose (3-FL). 2'-Fucosyllactose (2'-FL) and lacto-N-fucopentaose I (LNFP I) were absent in some and found at low levels in most of the Samoan women. Our study indicates that the milk oligosaccharide composition in Samoan women is similar to that of Japanese women with respect to sialyl but not to neutral oligosaccharides. The differences in neutral oligosaccharides might have a genetic origin. PMID:20139617

Leo, Fiame; Asakuma, Sadaki; Fukuda, Kenji; Senda, Akitsugu; Urashima, Tadasu

2010-02-07

225

Quantum phase transitions of magnetic rotons.  

PubMed

Because of weak spin-orbit coupling and broken inversion symmetry the paramagnons of an itinerant, almost ferromagnetic system become magnetic rotons. Using self-consistent Hartree and renormalization group calculations, we study weak fluctuation-driven first-order quantum phase transitions, a quantum tricritical point controlled by anisotropy, and non-Fermi liquid behavior associated with the large phase volume of magnetic rotons. We propose that magnetic rotons are essential for the description of the anomalous high-pressure behavior of the itinerant helical ferromagnet MnSi. PMID:15323847

Schmalian, Jörg; Turlakov, Misha

2004-07-16

226

Liquid-Vapour Phase Change Rates and Interfacial Entropy Production  

Microsoft Academic Search

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

C. A. Ward

2002-01-01

227

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

PubMed

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

Lai, S K; Wu, K L

2002-10-21

228

Energy landscapes for cooperative processes: nearly ideal glass transitions, liquid-liquid transitions and folding transitions: One contribution of 17 to a Discussion Meeting 'Configurational energy landscapes and structural transitions in clusters, fluids and biomolecules'  

Microsoft Academic Search

We describe basic phenomenology in the physics of supercooling liquids at constant volume (most simulations), and at constant pressure (most laboratory experiments) before focusing attention on the exceptional cases that exhibit liquid-liquid phase transitions on constant-pressure cooling. We give evidence for point defects in glasses and liquids near Tg. Models based on defects predict transitions with density gaps in constant-pressure

C. Austen Angell

2005-01-01

229

Phase transitions in nuclear matter  

SciTech Connect

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

Glendenning, N.K.

1984-11-01

230

Phase transitions in potassium nitrate  

Microsoft Academic Search

It is shown that the heat of transition of the phase change II ? I at 129° on heating KNO3 is dependent on the thermal history of the sample, since it involves two steps, viz., II? III and III? I at 2° interval. During cooling, the latter step is fast and truly reversible, though with a temperature hysteresis. The former

V. V. DESI-IPAVa; M. D. Karkhanavala; U. R. K. Rao

1974-01-01

231

Order of phase transitions and tricriticality in mixtures of octyloxycyanobiphenyl and nonyloxycyanobiphenyl liquid crystals: a high-resolution study by adiabatic scanning calorimetry.  

PubMed

A detailed study has been performed for mixtures of octyloxycyanobiphenyl (8OCB) and nonyloxycyanobiphenyl (9OCB) liquid crystals and nine of their mixtures by means of high-resolution adiabatic scanning calorimetry. The isotropic to nematic transitions are weakly first order with latent heat values in the range usually encountered for this transition in other liquid crystals. With the exception of pure 8OCB, for which only an upper limit of 1.8?J? kg(-1) for the latent heat could be established, finite latent heats have been obtained for the nematic to smectic-A transition of all the mixtures and of pure 9OCB. The concentration dependence of their latent heats could be well fitted with a crossover function consistent with a mean-field free-energy expression that has a nonzero cubic term induced by the Halperin-Lubensky-Ma (HLM) coupling between the smectic-A order parameter and the orientational director fluctuations. Clearly first-order transitions with measurable latent heats are found for mole fractions of 9OCB in the mixtures where the effective critical exponent for the specific-heat capacity has substantially lower values than the tricritical one (0.5). This is qualitatively different from what has been observed so far in other liquid-crystal systems and yields strong experimental evidence from a calorimetric experiment for the HLM coupling between the smectic-A order parameter and the director orientation fluctuations. PMID:21230091

Cordoyiannis, George; Tripathi, Chandra Shekhar Pati; Glorieux, Christ; Thoen, Jan

2010-09-22

232

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

SciTech Connect

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

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

2010-01-08

233

Interplay between micelle formation and waterlike phase transitions  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

234

Dynamics of Layering Transitions in Confined Liquids  

SciTech Connect

Multiple beam interferometry and video microscopy were used to investigate the layering transition of thin liquid films of 1-undecanol confined between atomically smooth mica surfaces. The expulsion of a molecularly thin lubricant layer was followed directly in two dimensions. Overall, the dynamics of the transition follows theoretical predictions based on two-dimensional hydrodynamics. Frequently, pockets of liquid remain trapped inside the contact area at the end of the transition. The trapped pockets undergo shape transformations to minimize elastic and interfacial energy. (c) 2000 The American Physical Society.

Mugele, F.; Salmeron, M.

2000-06-19

235

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

2013-08-28

236

Formation of liquid marbles and wetting transitions.  

PubMed

The formation of liquid marbles was studied in the situation where hydrophobic particles coating the marbles "come from air". Droplets of water/ethanol solutions of various concentrations were coated with three kinds of powders: polytetrafluoroethylene, polyvinylidene fluoride and polyethylene. We established that there exists a critical concentration of ethanol, and correspondingly a critical surface tension of the water/ethanol solution allowing formation of liquid marbles. A critical surface tension depends on the kind of the powder. In parallel, wetting transitions of water/ethanol solutions were studied on the layers of the same polymer powders. The onset of wetting transitions on the powders took place at the concentrations of ethanol coinciding with those enabling the formation of liquid marbles. Wetting transitions stipulate the formation of liquid marbles when a droplet is deposited on a layer of hydrophobic powder. This assumption was validated by the experiments performed with di-iodomethane and glycerol. PMID:22832095

Bormashenko, Edward; Balter, Revital; Aurbach, Doron

2012-06-27

237

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

238

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

Microsoft Academic Search

Storage of COâ in saline aquifers is intended to be at supercritical pressure and temperature conditions, but COâ leaking from a geologic storage reservoir and migrating toward the land surface (through faults, fractures, or improperly abandoned wells) would reach subcritical conditions at depths shallower than 500-750 m. At these and shallower depths, subcritical COâ can form two-phase mixtures of liquid

Pruess

2011-01-01

239

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

240

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

241

CP Symmetry and Phase Transitions  

NASA Astrophysics Data System (ADS)

The analytic behaviour of ?-vacuum energy at ? = 0 and ? = ? in QCD is related to the existence of phase transitions which might involve CP symmetry breaking. The appearance of cusp singularities is a signal of CP symmetry breaking by non-perturbative effects. The only cusp singularities that could arise in the vacuum energy density are due to the presence of Lee-Yang zeros but these singularities are always ? cusp singularities and never ? cusps, which in the case ? = 0 is incompatible with the Vafa-Witten diamagnetic inequality. The argument is very similar to that used in the derivation of Bank-Casher formula. In this case the topological charge condensate is proportional to the density of Lee-Yang zeros at the CP invariant points. The fact that this density is always positive provides a key missing link in the Vafa-Witten proof of parity symmetry conservation in vector-like gauge theories like QCD. However, this property does not exclude the existence of a first phase transition at ? = ? with a ? cusp singularity, or a second order phase transition at ? = 0, which might be very relevant for interpretation of the anomalous behavior of the topological susceptibility in the CP1 sigma model.

Aguado, M.; Asorey, M.

2011-04-01

242

Convective instability of solidification with a phase transition zone  

SciTech Connect

The morphological instability of solidification is analytically studied in the presence of an anisotropic and heterogeneous phase transition zone with allowance for a liquid flow and convective heat-andmass transfer in this two-phase zone. The mechanism of breaking the stability of solidification is considered; it consists in a convective heat and impurity transfer during a liquid flow along channels in the phase transition zone. The morphological instability is subjected to linear analysis with allowance for a liquid flow in the liquid phase of the system, impurity diffusion in the two-phase zone, and the dependence of the transfer coefficients on the phase composition. The perturbation evolution parameter is determined for an anisotropic and heterogeneous two-phase zone, and neutral stability curves of the process are obtained. It is shown that taking into account impurity diffusion and an increase in the heterogeneity of the phase transition zone broaden the instability region and that a decrease in the anisotropy narrows this region. A new criterion of convective morphological instability of solidification with a two-phase zone is found, and it substantially broadens the instability region when the liquid flow velocity increases.

Alexandrov, D. V.; Malygin, A. P., E-mail: Alexey.Malygin@usu.ru [Gorkiy Ural State University (Russian Federation)

2011-04-15

243

Phase Transition in a Phosphatidylcholine Membrane Induced by Halogenated Alcohol  

NASA Astrophysics Data System (ADS)

The effects of halogenated alcohol on the phase transitions of dipalmitoylphosphatidylcholine (DPPC) were investigated. Differential scanning calorimetry (DSC) was used to study the gel-to-liquid-crystalline phase transitions. A biphasic behavior takes place in DPPC with halogenated alcohol. The transition temperature from the gel to a liquid-crystalline phase (T m) decreases with increasing concentration of halogenated alcohol in aqueous solution. Above the threshold concentration, T m increases with increasing the concentration in the solution. Except for bromopropanol, the transition temperature decreases again at a much higher concentration and a third-phase region is formed. The biphasic or triphasic behavior of DPPC with halogenated alcohol is as follows: bromoalcohol gives rise to a larger shift of T m at the threshold concentration than chloroalcohol. The curvature of T m at the threshold concentration was larger in the case of longer-chain halogenated alcohol.

Adachi, Tomohiro; Hatta, Ichiro; Ikeda, Hironobu

1998-09-01

244

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

245

Conformational Phase Transitions and ReEntrance Phenomena in Dendromesogens  

Microsoft Academic Search

We investigate theoretically the liquid crystalline phase behaviour of globular dendrimers consisting of a soft inner scaffold and peripheral mesogenic units attached to the scaffold by means of flexible chains. We use a generalised Onsager molecular theory to analyse model systems exhibiting conformational rod-sphere and rod-disc interconversions. Phase transitions normally not encountered in low molar mass mesogens are reported. For

A. F. Terzis; A. G. Vanakaras; D. J. Photinos

2000-01-01

246

Phase transitions in condensed systems - experiments and theory  

SciTech Connect

These proceedings collect papers on phase transitions. Topics include: nucleation theory, neutron-induced vaporization of superheated liquids, kinetics of nucleation, glass formation, Co-Zr glasses, uranium-based metallic glasses, x-ray scattering technique, phase formation in thin-film lateral-diffusion couples, and solute trapping.

Cargill, G.S. III; Spaepen, F.; Tu, K.N.

1987-01-01

247

Quantum Phase Transition for {gamma} -Soft Nuclei  

SciTech Connect

We examine a quantum phase transition in {gamma} -soft nuclei, where the O(6) limit is simultaneously a dynamical symmetry of the U(6) group of the interacting boson model and a critical point of a prolate-oblate phase transition. This is the only example of phase transitional behavior that can be described analytically for a finite s,d boson system.

Jolie, J.; Casten, R. F.; von Brentano, P.; Werner, V.

2001-10-15

248

Experimental indication for liquid-liquid transition in aqueous solutions  

NASA Astrophysics Data System (ADS)

Contrary to the conventional wisdom that there exists only one unique liquid state for any material, there are growing experimental and numerical evidence for the existence of more than two liquid states in a single component substance. The transition between them is called liquid-liquid transition (LLT). LLT has attracted considerable attention because of its counterintuitive nature and its importance in the fundamental understanding of the liquid state. However, the physical nature of the transition has remained elusive. Particularly for water, the possible existence of LLT has special implications not only on its fundamental understanding, but also on a link of various thermodynamic and transport anomalies with critical anomaly associated with LLT. In this paper, we show experimental indications for a LLT in aqueous solutions of glycerol. We demonstrated that LLT proceeds through two types of kinetics characteristic of the first order transition: nucleation-growth (NG) and spinodal-decomposition (SD) type transformation. We also reveal that local tetrahedral ordering of water molecules play a key role, which is suggestive of the presence of LLT in pure water.

Murata, Ken-ichiro; Tanaka, Hajime

2013-02-01

249

Dissociation and dissociative phase transition in dense hydrogen  

SciTech Connect

A simple physical model is proposed for dissociating dense fluid hydrogen. We propose that free dissociated atoms interact via quantum electron-electron exchange analogously to the interaction in the liquid-metal phase of alkali metals. The density dependence of a hydrogen atom's binding energy in such a quasi-liquid is calculated. It is shown that the transition from the molecular fluid to liquid hydrogen is a first-order phase transition. The critical parameters of the transition are determined: P{sub c} = 72 GPa, T{sub c} = 10500 K, and {rho}{sub c} = 0.5 g/cm{sup 3}. The possibility of the metastable existence of atomic liquid hydrogen in a dissociated molecular fluid under decreased pressure is established.

Khomkin, A. L., E-mail: alhomkin@mail.ru; Shumikhin, A. S., E-mail: shum_ac@mail.ru [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2012-01-15

250

Coyote series data report LLNL/NWC 1981 LNG spill tests dispersion, vapor burn, and rapid-phase-transition. Volume 1. [7 experiments with liquefied natural gas, 2 with liquid methane, and one with liquid nitrogen  

SciTech Connect

The Coyote series of liquefied natural gas (LNG) spill experiments was performed at the Naval Weapons Center (NWC), China Lake, California, during the summer and fall of 1981. These tests were a joint effort of the Lawrence Livermore National Laboratory (LLNL) and the NWC and were sponsored by the US Department of Energy (DOE) and the Gas Research Institute. There were ten Coyote experiments, five primarily for the study of vapor dispersion and burning vapor clouds, and five for investigating the occurrence of rapid-phase-transition (RPT) explosions. Each of the last four of the five RPT tests consisted of a series of three spills. Seven experiments were with LNG, two were with liquid methane (LCH/sub 4/), and one was with liquid nitrogen (LN/sub 2/). Three arrays of instrumentation were deployed. An array of RPT diagnostic instruments was concentrated at the spill pond and was operated during all of the tests, vapor burn as well as RPT. The wind-field array was operated during the last nine experiments to define the wind direction and speed in the area upwind and downwind of the spill pond. The gas-dispersion array was deployed mostly downwind of the spill pond to measure gas concentration, humidity, temperature, ground heat flux, infrared (IR) radiation, and flame-front passage during three of the vapor dispersion and burn experiments (Coyotes 3, 5, and 6). High-speed color motion pictures were taken during every test, and IR imagery (side and overhead) was obtained during some vapor-burn experiments. Data was obtained by radiometers during Coyotes 3, 6, and 7. This report presents a comprehensive selection of the data obtained. It does not include any data analysis except that required to determine the test conditions and the reliability of the data. Data analysis is to be reported in other publications. 19 references, 76 figures, 13 tables.

Goldwire, H.C. Jr.; Rodean, H.C.; Cederwall, R.T.; Kansa, E.J.; Koopman, R.P.; McClure, J.W.; McRae, T.G.; Morris, L.K.; Kamppinen, L.; Kiefer, R.D.

1983-10-01

251

On the role of frustration on the glass transition and polyamorphism of mesoscopically heterophase liquids  

NASA Astrophysics Data System (ADS)

The model of heterophase fluctuations is developed accounting frustration of the mesoscopic solidlike fluctuons. Within the framework of this model, the glass transition and polyamorphous transformations are considered. It is shown that the frustration increases the temperature range in which the heterophase liquid state exists. the upper and lower boundaries of this temperature range are determined. These boundaries separate different phase states-amorphous solid, heterophase liquid, and fluid phases. Polyamorphous liquid-liquid transitions in the liquid are investigated. Frustration can call forth continuous fluid-solid phase transformation avoiding the first- or second-order phase transition. Conditions under which the first-order phase transition fraction takes place are formulated. Two scenarios of the first-order liquid-liquid polyamorphous transformation are described. As an example the glacial phase formation and the first-order liquid-liquid phase transition in triphenyl phosphate are considered and discussed. Impact of frustration on the liquid crystallization and crystallinity of the glassy state is studied.

Bakai, A. S.

2006-08-01

252

On the role of frustration on the glass transition and polyamorphism of mesoscopically heterophase liquids.  

PubMed

The model of heterophase fluctuations is developed accounting frustration of the mesoscopic solidlike fluctuons. Within the framework of this model, the glass transition and polyamorphous transformations are considered. It is shown that the frustration increases the temperature range in which the heterophase liquid state exists. the upper and lower boundaries of this temperature range are determined. These boundaries separate different phase states-amorphous solid, heterophase liquid, and fluid phases. Polyamorphous liquid-liquid transitions in the liquid are investigated. Frustration can call forth continuous fluid-solid phase transformation avoiding the first- or second-order phase transition. Conditions under which the first-order phase transition fraction takes place are formulated. Two scenarios of the first-order liquid-liquid polyamorphous transformation are described. As an example the glacial phase formation and the first-order liquid-liquid phase transition in triphenyl phosphate are considered and discussed. Impact of frustration on the liquid crystallization and crystallinity of the glassy state is studied. PMID:16942294

Bakai, A S

2006-08-14

253

Surface-functionalized ionic liquid crystal-supported ionic liquid phase materials: ionic liquid crystals in mesopores.  

PubMed

The influence of confinement on the ionic liquid crystal (ILC) [C(18)C(1)Im][OTf] is studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The ILC studied is supported on Si-based powders and glasses with pore sizes ranging from 11 to 50 nm. The temperature of the solid-to-liquid-crystalline phase transition seems mostly unaffected by the confinement, whereas the temperature of the liquid-crystalline-to-liquid phase transition is depressed for smaller pore sizes. A contact layer with a thickness in the order of 2 nm is identified. The contact layer exhibits a phase transition at a temperature 30 K lower than the solid-to-liquid-crystalline phase transition observed for the neat ILC. For applications within the "supported ionic liquid phase (SILP)" concept, the experiments show that in pores of diameter 50 nm a pore filling of ?>0.4 is sufficient to reproduce the phase transitions of the neat ILC. PMID:22069236

Kohler, Florian T U; Morain, Bruno; Weiss, Alexander; Laurin, Mathias; Libuda, Jörg; Wagner, Valentin; Melcher, Berthold U; Wang, Xinjiao; Meyer, Karsten; Wasserscheid, Peter

2011-11-08

254

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

PubMed

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

Hejazi, Vahid; Nosonovsky, Michael

2011-11-22

255

Fingerprints of quantum phase transitions  

NASA Astrophysics Data System (ADS)

Phase transitions that occur at the absolute zero of temperature are driven entirely by quantum fluctuations. When such a transition is continuous, the characteristic length scale for these fluctuations diverges at a quantum critical point (QCP). Although QCPs exist only at zero temperature, they can leave fingerprints on, the finite-temperature properties of a system---effects known as quantum critical scaling. For this reason, QCPs have become prime suspects in the ongoing experimental investigation of strongly correlated systems like heavy fermions and cuprate superconductors. Before considering experimental results, it is important to identify the range in temperature over which quantum criticality can be observed. We have addressed this question by calculating the free energy exactly for two models of QCPs. In both cases we find that quantum critical scaling can persist up to a temperature on the order of the microscopic energy scale of the model; however, when we include irrelevant operators in the Hamiltonian, it is possible for the scaling regime to shrink drastically. We have also used quantum criticality to make specific predictions for the hole-doped copper oxide superconductors. If we assume that both sides of the superconducting dome terminate in a QCP, then the transition temperature Tc and the zero-temperature superfluid density rhos(0) should be related by Tc ? rhos(0) y in the vicinity of each QCP. We predict different values of y on the underdoped and overdoped sides of the phase diagram. The value y = 1/2 agrees with recent experiments on underdoped YBa2Cu3O6+delta; existing data on overdoped materials appear to support our conjecture that y > 1/2. The current understanding of quantum phase transitions relies almost entirely on analogies with classical critical phenomena. While these analogies are adequate in many cases, there are other models for which they certainly do not apply. For instance, Anderson localization in three dimensions features a metal-insulator transition accompanied by a diverging localization length, yet the ground state energy density is analytic at the QCP. We propose that the concept of quantum entanglement is very useful in studying QCPs that have no classical analog. In particular, we show that the von Neumann entropy (which measures ground state entanglement) is non-analytic at the QCP in a number of different models, including Anderson localization in three dimensions.

Kopp, Angela Jean

256

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

NASA Astrophysics Data System (ADS)

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

Jakse, N.; Pasturel, A.

2007-11-01

257

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

258

Phases and phase transitions in disordered quantum systems  

NASA Astrophysics Data System (ADS)

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

Vojta, Thomas

2013-08-01

259

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

260

Mott physics and topological phase transition in correlated dirac fermions.  

PubMed

We investigate the interplay between the strong correlation and the spin-orbit coupling in the Kane-Mele-Hubbard model and obtain the qualitative phase diagram via the variational cluster approach. We identify, through an increase of the Hubbard U, the transition from the topological band insulator to either the spin liquid phase or the easy-plane antiferromagnetic insulating phase, depending on the strength of the spin-orbit coupling. A nontrivial evolution of the bulk bands in the topological quantum phase transition is also demonstrated. PMID:21797524

Yu, Shun-Li; Xie, X C; Li, Jian-Xin

2011-06-29

261

Thermodynamic and structural aspects of the polyamorphic transition in yttrium and other rare-earth aluminate liquids  

Microsoft Academic Search

A first-order transition between two liquids has been reported in yttrium–aluminate liquids close to Y3Al5O12 (YAG) composition. This transition is seen as the nucleation and growth of a low-density phase in a matrix of a higher density liquid when Y2O3–Al2O3 liquids are cooled below the liquidus. Both liquids are quenched to glass before the transition is complete. Analysis of the

Martin C. Wilding; Paul F. McMillan; Alexandra Navrotsky

2002-01-01

262

Quantum Phase Transitions in the Kane-Mele-Hubbard Model  

NASA Astrophysics Data System (ADS)

We study the ground state phase diagram of the Kane-Mele-Hubbard model on the two-dimensional honeycomb lattice. At half-filling the phase diagram is mapped out using projective auxiliary field quantum Monte Carlo simulations. We present a refined phase boundary for the quantum spin liquid. The topological (quantum spin-Hall) insulator at finite Hubbard interaction strength is adiabatically connected to the ground state of the Kane-Mele model. For the magnetic phase at large Hubbard interaction strength, we show that the magnetic order is restricted to the transverse direction. The transition from the topological band insulator to the antiferromagnetic Mott insulator is in the universality class of the three-dimensional XY model. The numerical data also suggest that the spin liquid to topological insulator and spin liquid to Mott insulator transitions are both continuous.

Meng, Zi Yang; Hohenadler, Martin; Lang, Thomas C.; Wessel, Stefan; Muramatsu, Alejandro; Assaad, Fakher F.

2012-02-01

263

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

264

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

265

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

266

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

267

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.

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

268

Scaling Effects in the CSP Phase Transition  

Microsoft Academic Search

Phase transitions in constraint satisfaction problems (CSP's) are the subject ofintense study. We identify an order parameter for random binary CSP's. There isa rapid transition in the probability of a CSP having a solution at a critical valueof this parameter. The order parameter allows different phase transition behaviourto be compared in an uniform manner, for example CSP's generated under differentregimes.

Ian P. Gent; Ewan Macintyre; Patrick Prosser; Toby Walsh

1995-01-01

269

Peculiarities of biphasic regions at phase transitions in oriented textures of 4-cyano-4?- n-pentylbiphenyl  

Microsoft Academic Search

Peculiarities of the biphasic regions at the direct and reverse phase transitions between homeotropic oriented nematic mesophase and isotropic liquid have been investigated in detail in this work. The shift of phase transition temperatures to the low temperatures by the reverse phase transitions have been observed for this mesophase. Nonlinearity of thermotropic and thermo-optical properties at the phase transitions between

Arif Nesrullajev; Nejmettin Avci; ?ener Oktik

2007-01-01

270

Effect of electric field on the rheological and dielectric properties of a liquid crystal exhibiting nematic-to-smectic-A phase transition.  

PubMed

We report simultaneous measurements of shear viscosity (?) and dielectric constant (?) of octyloxy cyanobiphenyl (8OCB) in the nematic (N) and smectic-A (SmA) phases as functions of temperature and electric field. With increasing electric field ? increases in the N phase whereas it decreases in the SmA phase and saturates beyond a particular field in both the phases. The flow curves in the intermediate-field range show two Newtonian regimes in the N phase. The temperature-dependent behavior of ? and ? at zero or at small electric field suggests the occurrence of several structures that results from precessional motion of the director along the neutral direction as reported in similar other system. We show that the precessional motions are gradually suppressed with increasing electric field and the effective viscosity resembles with the Miesowicz viscosity ?1 at high enough electric field. In the intermediate field range the temperature-dependent ? exhibits anomalous behavior across the N-SmA phase transition which is attributed to the large contribution of Leslie coefficient ?1. PMID:21805394

Ananthaiah, J; Rajeswari, M; Sastry, V S S; Dabrowski, R; Dhara, S

2011-08-03

271

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.

Andersson, Ove

2011-01-01

272

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

PubMed Central

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

Caffrey, M; Hogan, J; Mencke, A

1991-01-01

273

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

274

Phase Transitions in Two Dimensions: a Correlation Spectroscopy Investigation of Amphiphilic Monolayers.  

NASA Astrophysics Data System (ADS)

Phase transitions in monolayer films of amphiphilic molecules are studied using correlation spectroscopy. The phase transition models for such monolayers are discussed and compared. The technique of light scattering from thermodynamically driven capillary waves at a film covered liquid-liquid interface is developed in detail. Light beating heterodyne spectroscopy, used for detection of the scattered light, is discussed. Data for lecithin monolayers is presented in the context of recent theoretical phase transition models.

Bergstrom, Neil Gerald

275

Aspects of the electroweak phase transition.  

National Technical Information Service (NTIS)

The electroweak phase transition is reviewed in light of some recent developments. Emphasis is on the issue whether the transition is first or second order and its possible role in the generation of the baryon asymmetry of the universe.

P. Huet

1992-01-01

276

Phase transitions in experimental systems  

NASA Astrophysics Data System (ADS)

Scaling functions of the support and of the measure have been used to characterize the scaling behavior of a dynamical system. While scaling functions for the scaling of the measure, ƒ;(?), have been calculated for a number of experimental systems, examples of scaling functions ?(?) for the scaling of the support are difficult to obtain. In this contribution, we report on a phase-transition-like effect of an experimental p-doped germanium semiconductor sample. It is found that the results obtained from the dynamical scaling function agree with those obtained by Horita et al. from model maps, indicating that scaling functions for the scaling of the support are a powerful method of characterizing experimental dynamical systems.

Stoop, Ruedi; Peinke, Joachim; Parisi, Jürgen

1991-07-01

277

Comments on the electroweak phase transition  

Microsoft Academic Search

We report on an investigation of various problems related to the theory of the electroweak phase transition. This includes a determination of the nature of the phase transition, a discussion of the possible role of higher order radiative corrections and the theory of the formation and evolution of the bubbles of the new phase. We find in particular that no

Michael Dine; Robert G. Leigh; Patrick Huet; Andrei Linde; Dmitri Linde

1992-01-01

278

Bonding and phase transitions in transition metal dichalcogenide layer compounds  

Microsoft Academic Search

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

J. E. Inglesfield

1980-01-01

279

RESEARCH NOTE The absence of a liquid phase in van der Waals fluids at high dimensionality  

NASA Astrophysics Data System (ADS)

It is demonstrated that a model van der Waals fluid does not possess a liquid phase at high dimensionality. The model is hard hypercubes with a long-range attraction. The gas-liquid and fluid-solid transitions cross as the dimensionality is increased, and at high dimensionality the gas-liquid transition is pre-empted by the transition to a solid phase.

Sear Bela, Richard P.; Mulder, M.

280

Disclination Unbinding Transition in Quantum Hall Liquid Crystals  

NASA Astrophysics Data System (ADS)

Recent experiments [1] in the transitional region between plateaus of the quantum Hall effect have revealed a plæthora of unusual behavior in the low-temperature magnetotransport: in particular large anisotropies of the longitudinal resistivities are observed at temperatures lower than ca. 150 mK for near half filling of high (N>= 2) Landau levels (LL). the long-wavelength elastic theory for the quantum Hall smectic state starting from the Hartree-Fock approximation. Dislocations and phonons lead to an effective nematic model for T>0. This model undergoes a Kosterlitz-Thouless disclination unbinding transition from a phase with algebraic orientational order into an isotropic phase. Without the use of any fitting parameter, we obtain transition temperatures which are in qualitative agreement with recent experiments which have observed large anisotropies of the longitudinal resistivities in half-filled Landau levels, lending credence to the liquid crystal interpretation [3] of experiments. [[1

Wexler, Carlos

2002-03-01

281

Quantum phase transitions in the Kitaev model on decorated lattices  

NASA Astrophysics Data System (ADS)

We have proposed an exactly solvable \\text{spin-}\\frac{1}{2} model defined on 2D decorated lattices of two types. The ground-state phase diagram of the system includes different topological phases with gapless chiral edge states. We show that two types of chiral spin liquid with gapless edge modes are realized on lattices with different symmetry. The phase transition between the topological phase with chiral gapped (Chern number zero) and the topological phase with chiral gapless edge modes (Chern number +/- 1 ) occurs in the model on the square (symmetric) decorated lattice. On the rectangular (asymmetric) decorated lattice the topological phase is defined by a chiral gapless (gapped) edge mode in the x (y) direction and a chiral gapped (gapless) edge mode in another y (x) direction. We show that a \\text{spin-}\\frac{1}{2} Kitaev model on a decorated asymmetric square lattice exhibits the quantum phase transition between topological phases with equal Chern numbers.

Karnaukhov, Igor N.

2013-06-01

282

When is the Deconfinement Phase Transition Universal?  

NASA Astrophysics Data System (ADS)

Pure Yang-Mills theory has a finite-temperature phase transition, separating the confined and deconfined bulk phases. Svetitsky and Yaffe conjectured that if this phase transition is of second order, it belongs to the universality class of transitions for particular scalar field theories in one lower dimension. We examine Yang-Mills theory with the symplectic gauge groups Sp(N). We find new evidence supporting the Svetitsky-Yaffe conjecture and make our own conjecture as to which gauge theories have a universal second order deconfinement phase transition.

Holland, K.; Pepe, M.; Wiese, U.-J.

2004-04-01

283

Two-liquid-phase bioreactors.  

PubMed

The application of two liquid phases that are poorly miscible is a fascinating research topic for biocatalytical conversions because of the promising results. Motives for application include an increase of productivity and achievement of continuous processing, but new limitations arise, e.g., interfacial effects such as biocatalyst accumulation and loss of activity, medium component accumulation, and slow coalescence. Centrifuges, membranes, and immobilization are tools that can overcome part of the problems, but more fundamental knowledge about interfaces and coalescence is still necessary for successful application. For scaleup and further development of processes based on the obtained results, a choice must be made for the configuration of the experimental setup of a bioreactor. Aspects like aeration, shear stress, batch or continuous processing, and immobilization can play an important role. This review article describes these aspects and the proposals that have been made in recent years concerning two-liquid-phase bioreactors. It shows some adaptations to existing bioreactors, such as loop reactors and stirred-tank reactors. PMID:7764006

Van Sonsbeek, H M; Beeftink, H H; Tramper, J

1993-09-01

284

Liquid phase sintered superconducting cermet  

SciTech Connect

This patent describes a method of making a superconducting cermet having superconducting properties with improved bulk density, low porosity and in situ stabilization. It comprises: forming a structure of a superconducting ceramic material having the formula RM{sub 2}Cu{sub 3}O{sub (6.5 + x)}wherein R is one or more rare earth elements capable of reacting to form a superconducting ceramic, M is one or more alkaline earth metal elements selected from barium and strontium capable of reacting to form a superconducting ceramic, x is greater than 0 and less than 0.5; and a precious metal compound in solid form selected from the class consisting of oxides, sulfides and halides of silver; and liquid phase sintering the mixture at a temperature wherein the precious metal of the precious metal compound is molten and below the melting point of the ceramic material. The liquid phase sintering is carried out for a time less than 36 hours but sufficient to improve the bulk density of the cermet.

Ray, S.P.

1990-01-09

285

Peculiarities of biphasic regions at phase transitions in oriented textures of 4-cyano-4?-n-pentylbiphenyl  

NASA Astrophysics Data System (ADS)

Peculiarities of the biphasic regions at the direct and reverse phase transitions between homeotropic oriented nematic mesophase and isotropic liquid have been investigated in detail in this work. The shift of phase transition temperatures to the low temperatures by the reverse phase transitions have been observed for this mesophase. Nonlinearity of thermotropic and thermo-optical properties at the phase transitions between nematic mesophase and isotropic liquid have been found.

Nesrullajev, Arif; Avc?, Nejmettin; Oktik, ?ener

2007-05-01

286

Phase transitions in physiologic coupling  

PubMed Central

Integrated physiological systems, such as the cardiac and the respiratory system, exhibit complex dynamics that are further influenced by intrinsic feedback mechanisms controlling their interaction. To probe how the cardiac and the respiratory system adjust their rhythms, despite continuous fluctuations in their dynamics, we study the phase synchronization of heartbeat intervals and respiratory cycles. The nature of this interaction, its physiological and clinical relevance, and its relation to mechanisms of neural control is not well understood. We investigate whether and how cardiorespiratory phase synchronization (CRPS) responds to changes in physiological states and conditions. We find that the degree of CRPS in healthy subjects dramatically changes with sleep-stage transitions and exhibits a pronounced stratification pattern with a 400% increase from rapid eye movement sleep and wake, to light and deep sleep, indicating that sympatho-vagal balance strongly influences CRPS. For elderly subjects, we find that the overall degree of CRPS is reduced by approximately 40%, which has important clinical implications. However, the sleep-stage stratification pattern we uncover in CRPS does not break down with advanced age, and surprisingly, remains stable across subjects. Our results show that the difference in CRPS between sleep stages exceeds the difference between young and elderly, suggesting that sleep regulation has a significantly stronger effect on cardiorespiratory coupling than healthy aging. We demonstrate that CRPS and the traditionally studied respiratory sinus arrhythmia represent different aspects of the cardiorespiratory interaction, and that key physiologic variables, related to regulatory mechanisms of the cardiac and respiratory systems, which influence respiratory sinus arrhythmia, do not affect CRPS.

Bartsch, Ronny P.; Schumann, Aicko Y.; Kantelhardt, Jan W.; Penzel, Thomas; Ivanov, Plamen Ch.

2012-01-01

287

Symmetry and Phase Transitions in Nuclei  

SciTech Connect

The role of symmetry in (shape) quantum phase transitions (QPT) in nuclei is briefly reviewed. Finite size scaling is discussed. The concepts of excited state quantum phase transitions (ESQPT) and of critical matter are introduced. The ab initio theory of QPT is mentioned.

Iachello, Francesco [Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, CT 06520-8120 (United States)

2009-08-26

288

Theory for photoinduced structural phase transitions  

Microsoft Academic Search

For the photoinduced ionic-->neutral structural phase transition in the organic charge transfer crystal TTF-CA, we, at first, theoretically show the adiabatic path of this transition, which starts from a single charge transfer (CT) exciton in the ionic phase, but finally results in a macroscopic neutral domain. In the next, using a more simplified model, we theoretically study nonlinear nonequilibrium quantum

H. Mizouchi; H. Ping; K. Nasu

2001-01-01

289

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

290

Phase transition in a super superspin glass  

NASA Astrophysics Data System (ADS)

We here confirm the occurrence of spin glass phase transition and extract estimates of associated critical exponents of a highly monodisperse and densely compacted system of bare maghemite nanoparticles. This system has earlier been found to behave like an archetypal spin glass, with, e.g., a sharp transition from paramagnetic to non-equilibrium behavior, suggesting that this system undergoes a spin glass phase transition at a relatively high temperature, Tg ? 140 K.

Mathieu, R.; De Toro, J. A.; Salazar, D.; Lee, S. S.; Cheong, J. L.; Nordblad, P.

2013-06-01

291

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.

2011-01-01

292

Continuous phase transition and negative specific heat in finite nuclei  

SciTech Connect

The liquid-gas phase transition in finite nuclei is studied in a heated liquid-drop model where the nuclear drop is assumed to be in thermodynamic equilibrium with its own evaporated nucleonic vapor, conserving the total baryon number and isospin of the system. It is found that in the liquid-vapor coexistence region the pressure is not a constant on an isotherm, indicating that the transition is continuous. At constant pressure, the caloric curve shows some anomalies; namely, the systems studied exhibit negative heat capacity in a small temperature domain. The dependence of this specific feature on the mass and isospin of the nucleus, Coulomb interaction, and the chosen pressure is studied. The effects of the presence of clusters in the vapor phase on specific heat have also been explored.

De, J.N. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States); Samaddar, S.K. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Shlomo, S.; Natowitz, J.B. [Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States)

2006-03-15

293

Bilayer ice and alternate liquid phases of confined water  

NASA Astrophysics Data System (ADS)

We report results from molecular dynamics simulations of the freezing and melting, at ambient temperature (T=300 K), of a bilayer of liquid water induced by either changing the distance between two confining parallel walls at constant lateral pressure or by lateral compression at constant plate separation. Both transitions are found to be first order. The system studied consisted of 1200 water molecules that were described by the TIP5P model. The in-plane symmetry of the oxygen atoms in the ice bilayer was found to be rhombic with a distorted in-registry arrangement. Above and below the stability region of the ice bilayer we observed two bilayer phases of liquid water that differ in the local ordering at the level of the second shell of nearest neighbors and in the density profile normal to the plane, yielding two liquid phases with different densities. These results suggest the intriguing possibility of a liquid-liquid transition of water, confined to a bilayer, at regions where the ice bilayer is unstable with respect to either of the liquid phases. In addition, we find that under the same conditions, water confined to 3-8 layers remains in the liquid phase (albeit stratification of the transverse density profile) with values of the lateral diffusion coefficient comparable to that of the bulk.

Zangi, Ronen; Mark, Alan E.

2003-07-01

294

Transit Switch Design Analysis (Phase 1). Transit Cooperative Research Program.  

National Technical Information Service (NTIS)

This report presents the results of a research task carried out under TCRP Project D7, Joint Rail Transit-Related Research with the Association of American Railroads/Transportation Technology Center, inc., Transit Switch Design Analysis (Phase 1). Under t...

S. P. Singh D. D. Davis S. Kalay

2003-01-01

295

A dynamical test of phase transition order: New things in old places or old wine in new bottles  

Microsoft Academic Search

We first discuss nonlinear aspects of phase transition theory applied to a particular liquid crystal phase transition. A simple derivation is given to show how two coupled Goldstone modes (one appearing as gauge fluctuations of the ordered phase) can force a phase transition, against all expectations, to take place discontinuously (theory of Halperin, Lubensky, and Ma)-but the discontinuity may be

P. E. Cladis

1991-01-01

296

Phase transitions of monoglyceride emulsifier systems and pearlescent effects in cosmetic creams studied by 13C NMR spectroscopy and DSC  

Microsoft Academic Search

The present work investigates the phase transitions of monoglyceride emulsifier systems and pearlescent effects in cosmetic creams using 13C-NMR spectroscopy and DSC. The four phases of monoglyceride emulsifier systems – the coagel, gel phase, liquid-crystalline lamellar phase, and cubic phase – can be characterized in creams at appropriate temperatures by NMR spectroscopy. The phase transition temperatures were determined by DSC.

Cécile Alberola; Bernhard Blümich; Detlef Emeis; Klaus-Peter Wittern

2006-01-01

297

Mode transitions in an oscillating liquid sheet  

NASA Astrophysics Data System (ADS)

Longitudinal oscillations in air-blasted or air-assisted liquid sheets have been the subject of a large number of papers in the last 30 years. Frequency and sometimes amplitude are the main parameters used to characterize these oscillations. Attending to them, and also in dependence on the surface topology (e.g., the presence of perforations or ligaments), several oscillation modes have been described. In most works, two or at most three regimes are considered. Following these previous descriptions, this experimental work has found that some submodes can also be discerned. Based on visual observations, frequency measurements, and spray angle calculations, for some liquid and air flow rates up to six modes have been observed with defined transitions among them. The different modes are analyzed and characterized, and their presence is related to the flow conditions.

Lozano, A.; Calvo, E.; García, J. A.; Barreras, F.

2011-04-01

298

Force oscillation and phase transition of simple fluids under confinement  

NASA Astrophysics Data System (ADS)

We use molecular dynamics simulations to explore the force oscillation mechanism of a simple fluid confined between two surfaces. Force profiles obtained through simulations are qualitatively similar to those in surface force measurements. Our results demonstrate that the layering transition is an abrupt, liquid-to-solid phase transition. The nucleation of solid phase starts at the central region of the confined film that can sustain a finite shear stress. The packing structure of the solid film is a hexagonal close-packed (hcp) crystalline structure, whose mechanical property is highly asymmetric. The elastic modulus and repulsive peaks of oscillatory forces during normal approach are always larger than those during retraction.

Lei, Yajie; Leng, Yongsheng

2010-10-01

299

Vibrational Fréedericksz transition in liquid crystals.  

PubMed

Our aim is to show the possibility of a "vibrational Fréedericksz's transition" in nematic liquid crystals (LCs) consisting of asymmetric molecules (in the absence of the reflectional symmetry for the director field). For this purpose we study the effects of the external high-frequency vibrations imposed on LCs by employing the rigorous two-timing asymptotic averaging method to the governing LC equations in their most general form. We restrict our attention only to translational mechanical vibrations of an incompressible LC medium as a whole, so our vibrations are not related to acoustical waves. We show that the averaged "vibrogenic" torque acted on the director field is mathematically equivalent to the torque caused by an external magnetic field. This equivalence leads us to the key conclusion that the high-frequency mechanical vibrations can cause the vibrational Fréedericksz's transition. Our evaluation of the relevant physical parameters shows that this phenomenon can be observed in laboratory experiments. PMID:17930262

Vladimirov, V A; Zhukov, M Yu

2007-09-27

300

Vibrational Fréedericksz transition in liquid crystals  

NASA Astrophysics Data System (ADS)

Our aim is to show the possibility of a “vibrational Fréedericksz’s transition” in nematic liquid crystals (LCs) consisting of asymmetric molecules (in the absence of the reflectional symmetry for the director field). For this purpose we study the effects of the external high-frequency vibrations imposed on LCs by employing the rigorous two-timing asymptotic averaging method to the governing LC equations in their most general form. We restrict our attention only to translational mechanical vibrations of an incompressible LC medium as a whole, so our vibrations are not related to acoustical waves. We show that the averaged “vibrogenic” torque acted on the director field is mathematically equivalent to the torque caused by an external magnetic field. This equivalence leads us to the key conclusion that the high-frequency mechanical vibrations can cause the vibrational Fréedericksz’s transition. Our evaluation of the relevant physical parameters shows that this phenomenon can be observed in laboratory experiments.

Vladimirov, V. A.; Zhukov, M. Yu.

2007-09-01

301

On the Phase Transition in Cuprous Iodide  

Microsoft Academic Search

The phase transition and the crystal structures of cuprous iodide (CuI) have been studied by the X-ray and calorimetric measurement Two phase transitions at 369°C and 407°C were found and the corresponding energy and entropy changes were estimated from the specific heat-temperature curve. The crystal lattice of gamma, beta and alpha-phases were determined to be the cubic (ZnS type), hexagonal

Shizuo Miyake; Sadao Hoshino; Toshio Takenaka

1952-01-01

302

The chiral and deconfinement phase transitions  

NASA Astrophysics Data System (ADS)

By introducing the dressed Polayakov loop or dual chiral condensate as a candidate order parameter to describe the deconfinement phase transition for light flavors, we discuss the interplay between the chiral and deconfinement phase transitions, and propose the possible QCD phase diagram at finite temperature and density. We also introduce a dynamical gluodynamic model with dimension-2 gluon condensate, which can describe the color electric deconfinement as well as the color magnetic confinement.

Xu, Fukun; Huang, Mei

2012-12-01

303

Electroweak phase transition in ultraminimal technicolor  

SciTech Connect

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

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

2009-05-01

304

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

305

Application of ionic liquid in liquid phase microextraction technology.  

PubMed

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

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

2012-09-24

306

Liquid-Phase Epitaxy of Advanced Materials  

NASA Astrophysics Data System (ADS)

The performance of many electronic and optoelectronic devices critically depends on the structural quality and homogeneity of the base material, which is often an epitaxial film grown by either vapor-phase epitaxy (VPE) or liquid-phase epitaxy (LPE).

Klemenz Rivenbark, Christine F.

307

Phase transitions in human IgG solutions.  

PubMed

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

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

2013-09-28

308

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

309

Lifshitz phase transition in nuclear matter  

NASA Astrophysics Data System (ADS)

Starting from the extended Nambu-Jona-Lasinio (ENJL) model, we show that in nuclear matter the Lifshitz phase transition (LPT) takes place at suprasaturation density and zero temperature, while it is subsaturation transition in neutron matter. At finite temperature T and nucleon chemical potential ? the phase diagram in the (T,?) plane for nuclear and neutron matters is established with the existence of corresponding tricritical points (TCP) which separate the first- and half-order from the second-order phase transitions. Many properties of the LPT are cleared up throughout the investigation of equations of state and other thermodynamic quantities. How to experimentally identify the LPT in nuclear matter is discussed.

Phat, Tran Huu; Thu, Nguyen Van

2013-02-01

310

QCD Phase Transition in Dgp Brane Cosmology  

NASA Astrophysics Data System (ADS)

In the standard picture of cosmology it is predicted that a phase transition, associated with chiral symmetry breaking after the electroweak transition, has occurred at approximately 10? seconds after the Big Bang to convert a plasma of free quarks and gluons into hadrons. We consider the quark-hadron phase transition in a Dvali, Gabadadze and Porrati (DGP) brane world scenario within an effective model of QCD. We study the evolution of the physical quantities useful for the study of the early universe, namely, the energy density, temperature and the scale factor before, during and after the phase transition. Also, due to the high energy density in the early universe, we consider the quadratic energy density term that appears in the Friedmann equation. In DGP brane models such a term corresponds to the negative branch (? = -1) of the Friedmann equation when the Hubble radius is much smaller than the crossover length in 4D and 5D regimes. We show that for different values of the cosmological constant on a brane, ?, phase transition occurs and results in decreasing the effective temperature of the quark-gluon plasma and of the hadronic fluid. We then consider the quark-hadron transition in the smooth crossover regime at high and low temperatures and show that such a transition occurs along with decreasing the effective temperature of the quark-gluon plasma during the process of the phase transition.

Atazadeh, K.; Ghezelbash, A. M.; Sepangi, H. R.

2012-08-01

311

REVIEWS OF TOPICAL PROBLEMS: Phase transitions in various kinds of clusters  

NASA Astrophysics Data System (ADS)

This discussion examines cluster phase transitions and properties related to those phase transitions. Interpreted in terms of their potential energy surfaces, phase transitions in clusters of dielectric and metal atoms differ. Properties of aggregate states of dielectric clusters vary weakly as functions of temperature, and phase coexistence takes place in a range of conditions around the traditional melting point, where the solid and liquid phases have equal chemical potentials. On contrary, the configurational state of a solid metal cluster may well vary as it is heated, and the phase transition results, at least in part, from electronic coupling, as well as from changes in atomic configuration.

Berry, R. S.; Smirnov, Boris M.

2009-02-01

312

Polymerization and phase separation studies in liquids  

NASA Astrophysics Data System (ADS)

In technology, a thermosetting polymer's electrical, thermal and mechanical properties are modified by incorporating an elastomer phase in its matrix. This is achieved by phase separation of the dissolved elastomer during the course of polymerization until the liquid vitrifies. The phase separation mechanism and nature of interface formed determine the negative effect of phase separation on polymerization and the transition of mass-controlled kinetics to diffusion-controlled kinetics. This thesis provides an experimental study of polymerization, phase separation and vitrification processes by using real time measurements of dielectric relaxation, calorimetric changes, elastic constants and thermal conductivity of diepoxide-amine mixtures with and without the phase separating amine-terminated butadiene acrylonitrile elastomer. The results are discussed in general terms of mutual slowing of molecular diffusion and polymerization, and of the development of diffused interfaces between regions of elastomer and polymer matrix, that form as a result of, (i) high degree of spatial heterogeneity in the intermingled regions of non-stoichiometric amounts of polymer and elastomer, (ii) high degree of compatibility between the elastomer and polymer matrix and (iii) large size of the elastomer and polymer molecules. The consequence of molecular diffusional constraints and manifestation of spatial heterogeneity is confirmed by the appearance of Johari-Goldstein relaxation which acts as the precursor for the significantly broadened alpha-relaxation and higher values of dielectric permittivity in the frequency range of 1 kHz and greater. Spatial heterogeneity in the intermingled regions of non-stoichiometric amounts of polymer and elastomer is also confirmed by calorimetry studies. With increasing diffusional limitation, the total heat of polymerization varies from values obtained for stoichiometric amounts of reactants with no change in calorimetric peak temperature. Furthermore, the relaxation region of reversible heat capacity broadens. Diffusional constraints are also confirmed by the corresponding broadening of measured thermal conductivity values. Part of the thesis has been published in papers listed in Chapter I.

Venkateshan, Karthik

313

Physical gels made of liquid crystalline B4 phase.  

PubMed

The achiral liquid crystalline materials showing two B4 (HN) phases have been found to exhibit strong gelation ability for various organic solvents with reversible sol-gel phase transition. The gel is formed by helical tubules, which build entangled 3D network, encapsulating the solvent. The equilibrium of left- and right-handed tubules is preserved in the gel, even if the chiral solvent is used. PMID:23471159

Zep, Anna; Salamonczyk, Miroslaw; Vaupoti?, Nataša; Pociecha, Damian; Gorecka, Ewa

2013-03-08

314

Phase Transitions and Elementary-Particle Physics.  

National Technical Information Service (NTIS)

The reason physicists have recently taken an intense interest in the statistical mechanics of certain lattice models is reviewed. Phase transitions in these systems are of direct relevance to whether the gauge theory of interacting quarks and gluons can p...

M. Creutz

1981-01-01

315

Laves Phases of Uranium and Transition Metals.  

National Technical Information Service (NTIS)

Pauling's valence-bond theory of metals was used to calculate bond numbers of uranium-transition metal Laves phase compounds. Hybridization was determined from Pauling's relationships between single bond radii and d orbital participation in bonding. The a...

E. C. Beahm

1975-01-01

316

About the Dynamics of Structural Phase Transitions.  

National Technical Information Service (NTIS)

The dynamics of structural phase transitions with a fourth order interaction between the soft phonon fields is studied in the 1/n approximation, using many body methods at finite temperatures. Two limits are considered: high transition temperature T sub(c...

J. T. N. Medeiros

1975-01-01

317

Electrically driven phase transition in magnetite nanostructures  

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

318

Phase Transitions in Ferroelectric and Antiferroelectric Crystals  

Microsoft Academic Search

Group theory is applied to phase transitions in ferroelectric and antiferroelectric crystals. The procedure is given to derive for a paraelectric crystal with a given space group all possible ferroelectric states which can exist for arbitrarily small values of the polarization. A knowledge of the space groups of the crystal above and below the transition point makes it possible to

C. Haas

1965-01-01

319

Phase Transition of N-Component Superconductors  

Microsoft Academic Search

We investigate the phase transition in the three-dimensional Abelian Higgs model for N complex scalar fields, using the gauge-invariant average action Gammak. The dependence of Gammak. on the effective infrared cutoff k is described by a nonperturbative flow equation. The transition turns out to be first or second order, depending on the ratio between the scalar and gauge coupling. We

B. Bergerhoff; D. F. Litim; S. Lola; C. Wetterich

1996-01-01

320

Athermal Character of Structural Phase Transitions  

Microsoft Academic Search

The significance of thermal fluctuations in nucleation in structural first-order phase transitions has been examined. The prototypical case of martensitic transitions has been experimentally investigated by means of acoustic emission techniques. We propose a model based on the mean first-passage time to account for the experimental observations. Our study provides a unified framework to establish the conditions for isothermal and

Francisco J. Pérez-Reche; Eduard Vives; Lluís Mañosa; Antoni Planes

2001-01-01

321

Quantum phase transitions for excited states  

SciTech Connect

The impact of the ground-state quantum phase transitions on the evolution of excited levels in the critical parameter region is discussed. The analysis is focused on systems with first- and second-order transitions and is illustrated by the cusp and nuclear collective Hamiltonians.

Cejnar, P.; Stransky, P. [Inst., of Particle and Nuclear Physics, Charles University, V Holesovickach 2, Prague, CZ-18000 (Czech Republic)

2009-01-28

322

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

323

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

324

Using Peltier cells to study solid liquid vapour transitions and supercooling  

Microsoft Academic Search

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

Giacomo Torzo; Isabella Soletta; Mario Branca

2007-01-01

325

Condensation phase transition in nonlinear fitness networks  

NASA Astrophysics Data System (ADS)

We analyze the condensation phase transitions in out-of-equilibrium complex networks in a unifying framework which includes the nonlinear model and the fitness model as its appropriate limits. We show a novel phase structure which depends on both the fitness parameter and the nonlinear exponent. The occurrence of the condensation phase transitions in the dynamical evolution of the network is demonstrated by using Bianconi-Barabási method. We find that the nonlinear and the fitness preferential-attachment mechanisms play important roles in the formation of an interesting phase structure.

Su, Guifeng; Zhang, Xiaobing; Zhang, Yi

2012-11-01

326

Phase Transitions with Nonstandard Critical Behavior  

NASA Astrophysics Data System (ADS)

We discuss phase transitions and critical behavior deviating from the standard scheme based on a mean-field theory renormalizing only the mass of the critical excitations completed with a perturbative scaling renormalization of the interaction strength. On examples of mean-field theories for spin glasses and for quantum phase transitions we show that coupling constants are relevant variables in these systems and are to be renormalized already within the mean-field approximations.

Janis, Vaclav

2001-10-01

327

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

NASA Astrophysics Data System (ADS)

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

Feng, Xunda; Bahr, Christian

2011-03-01

328

Liquid-phase compositions from vapor-phase analyses  

Microsoft Academic Search

In the safe handling and processing of uranium hexafluoride (UFâ), it is often desirable to calculate vapor composition and pressure from known liquid composition and temperature. Furthermore, the ability to use analyses of equilibrium vapor-phase samples to calculate liquid-phase compositions would be economically advantageous to the International Atomic Energy Agency (IAEA) in its international safeguards program and to uranium enrichment

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

1989-01-01

329

Phase structure and phase transitions in semicrystalline isotactic polystyrene  

Microsoft Academic Search

Semicrystalline polymers have been recognized as being in a non-equilibrium, metastable state. A single molecule can participate in several phase regimes. Thus, interpretation of the phase structure of semicrystalline polymers, and an understanding of their correspondent phase transitions are essential aspects in today's polymer physics research. The ultimate goal of this thesis is to provide general descriptions regarding understanding the

Hui Xu

2005-01-01

330

Negativity and quantum phase transition in the anisotropic XXZ model  

NASA Astrophysics Data System (ADS)

In this paper, the dynamical behavior of the renormalization of negativity in the quantum phase transition has been studied by exploiting the quantum renormalization group method. The results show that the negativity develops two saturated values after several iterations of the renormalization. These values are associated with two different phases, that is, spin-liquid and Néel phases. Furthermore, we not only investigate the performance of the first derivative of the negativity, but explicitly discuss the nonanalytic and scaling behavior which comes from the divergence of the first derivative of negativity as the system becomes large.

Song, Xue-ke; Wu, Tao; Ye, Liu

2013-05-01

331

SIMMER-II analysis of transition-phase experiments  

SciTech Connect

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

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

1985-01-01

332

Time Resolved Electronic Phase Transitions in Manganites  

SciTech Connect

At the critical point of a first-order electronic phase transition, fluctuations between the competing phases are often a dominant phenomenon. The direct observation of these fluctuations in electronic phases is vital to revealing the microscopic details of the phase transition. This is especially true in strongly correlated transition metal oxides, in which a diversity of electronic phases coexist and are closely connected to several remarkable properties such as high-Tc superconductivity and colossal magnetoresistance. Here we report a novel and generic approach that directly records the fluctuations of the electronic phases at the critical point of the metal-insulator transition, using a manganite system as example. In our approach, we reduce a single crystal thin film of La5/8-xPrxCa3/8MnO3 to the scale of its inherent electronic charge ordered insulating (COI) and ferromagnetic metal (FMM) phase domains and conduct high resolution resistance vs. time measurements within a critical regime of temperature and magnetic field at the metal insulator transition (MIT). Within this window, we are able to observe individual domains as they fluctuate between COI and FMM.

Ward, Thomas Z [ORNL; Shen, Jian [ORNL; Zhang, Xiaoguang [ORNL; Yin, Lifeng [ORNL; Zhang, X. Q. [State Key Laboratory of Magnetism and Beijing National Laboratory, Chinese Acade; Liu, Ming [Chinese Academy of Sciences; Snijders, Paul C [ORNL; Jesse, Stephen [ORNL; Plummer, E Ward [ORNL; Cheng, Z. H. [State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed; Dagotto, Elbio R [ORNL

2009-01-01

333

Thermal transistor utilizing gas-liquid transition.  

PubMed

We propose a simple thermal transistor, a device to control heat current. In order to effectively change the current, we utilize the gas-liquid transition of the heat-conducting medium (fluid) because the gas region can act as a good thermal insulator. The three terminals of the transistor are located at both ends and the center of the system, and are put into contact with distinct heat baths. The key idea is a special arrangement of the three terminals. The temperature at one end (the gate temperature) is used as an input signal to control the heat current between the center (source, hot) and another end (drain, cold). Simulating the nanoscale systems of this transistor, control of heat current is demonstrated. The heat current is effectively cut off when the gate temperature is cold and it flows normally when it is hot. By using an extended version of this transistor, we also simulate a primitive application for an inverter. PMID:21405731

Komatsu, Teruhisa S; Ito, Nobuyasu

2011-01-25

334

Thermal transistor utilizing gas-liquid transition  

NASA Astrophysics Data System (ADS)

We propose a simple thermal transistor, a device to control heat current. In order to effectively change the current, we utilize the gas-liquid transition of the heat-conducting medium (fluid) because the gas region can act as a good thermal insulator. The three terminals of the transistor are located at both ends and the center of the system, and are put into contact with distinct heat baths. The key idea is a special arrangement of the three terminals. The temperature at one end (the gate temperature) is used as an input signal to control the heat current between the center (source, hot) and another end (drain, cold). Simulating the nanoscale systems of this transistor, control of heat current is demonstrated. The heat current is effectively cut off when the gate temperature is cold and it flows normally when it is hot. By using an extended version of this transistor, we also simulate a primitive application for an inverter.

Komatsu, Teruhisa S.; Ito, Nobuyasu

2011-01-01

335

Nonequilibrium liquid crystalline layered phase stabilized by light.  

PubMed

The ability of light to alter/stabilize a particular thermodynamic phase is a power tool to investigate condensed matter from a new dimension. This field of photoinduced phase transitions is currently an important area of research. Being elastically soft and having subtle changes between its many phases a liquid crystal material is an attractive medium to investigate such light-driven phase transitions. The attraction is partly due to the large birefringence changes accompanying these transitions that are useful in developing photonic devices. In all of the cases reported to date, the photoinduced transition always leads to a phase that in any case exists in the thermal cycle. Recently we reported the first exception to such an established phenomenon (Adv. Mater. 2005, 17, 2086). The guest-host ternary mixture consisting of the photoactive azobenzene guest molecules does not exhibit smectic A phase in the absence of UV radiation. However, the smectic A phase is induced and stabilized only in the presence of UV light. In this paper, we map out hitherto unexplored temperature versus UV intensity phase diagrams for various mixtures, which illustrate that light mimics, in a limited sense, the role of a thermodynamic parameter such as, for example, pressure. The threshold UV intensity required to photodrive the appearance of the smectic A phase is seen to have a strong concentration dependence. Our studies also suggest the possibility of observing a double critical point by employing the UV intensity as a fine-tuning parameter. PMID:17214484

Prasad, S Krishna; Nair, Geetha G; Hegde, Gurumurthy

2007-01-18

336

Isotropic to biaxial nematic phase transition in an external magnetic field  

NASA Astrophysics Data System (ADS)

The first theoretical observation of the tricritical point for the isotropic to biaxial nematic phase transition of biaxial nematic liquid crystals in the presence of an external field is reported. The influence of an external magnetic field on the isotropic to biaxial nematic phase transition have been studied using Landau phenomenological theory. Topological classification of phase diagrams in the field – temperature coordinates is performed. It is shown that for a particular value of the magnetic field, the first order isotropic to biaxial nematic phase transition becomes second order phase transition at a tricritical point.

Mukherjee, Prabir K.; Rahman, Muklesur

2013-09-01

337

Magnetic phase transitions in layered intermetallic compounds  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

338

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

339

Electroweak phase transition in nearly conformal technicolor  

SciTech Connect

We examine the temperature-dependent electroweak phase transition in extensions of the standard model in which the electroweak symmetry is spontaneously broken via strongly coupled, nearly conformal dynamics. In particular, we focus on the low energy effective theory used to describe minimal walking technicolor at the phase transition. Using the one-loop effective potential with ring improvement, we identify significant regions of parameter space which yield a sufficiently strong first-order transition for electroweak baryogenesis. The composite particle spectrum corresponding to these regions can be produced and studied at the Large Hadron Collider experiment. We note the possible emergence of a second phase transition at lower temperatures. This occurs when the underlying technicolor theory possesses a nontrivial center symmetry.

Cline, James M.; Jaervinen, Matti; Sannino, Francesco [McGill University, Montreal, Quebec H3A 2T8 (Canada); High Energy Center, University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark)

2008-10-01

340

Phase Transitions in Disordered Quantum Hamiltonians  

NASA Astrophysics Data System (ADS)

The problem of the interplay between disorder and interactions in quantum systems is challenging and has a long history. Disorder can, by itself, cause localization and the vanishing of the conductivity, the Anderson transition. At appropriate densities, interactions can drive insulating states, the Mott transition, as well as ordered magnetic phases. In this talk I will describe the application of Quantum Monte Carlo techniques to the fermion Hubbard model, including calculations of the conductivity and density of states at the superconductor--insulator phase transition in the attractive model, and the effect of randomness on the Mott and magnetic phase transitions in the repulsive model.(N. Trivedi, R.T. Scalettar, and M. Randeria, Phys. Rev. B54), 3756 (1996); C. Huscroft and R.T. Scalettar, Phys. Rev. B55, 1185 (1997); M. Ulmke and R.T. Scalettar, Phys. Rev. B55, 4149 (1997); M. Ulmke, P. J. H. Denteneer, R. T. Scalettar, and G. T. Zimanyi, preprint.

Scalettar, Richard T.

1998-03-01

341

Supercooling and phase coexistence in cosmological phase transitions  

SciTech Connect

Cosmological phase transitions are predicted by particle physics models, and have a variety of important cosmological consequences, which depend strongly on the dynamics of the transition. In this work we investigate in detail the general features of the development of a first-order phase transition. We find thermodynamical constraints on some quantities that determine the dynamics, namely, the latent heat, the radiation energy density, and the false-vacuum energy density. Using a simple model with a Higgs field, we study numerically the amount and duration of supercooling and the subsequent reheating and phase coexistence. We analyze the dependence of the dynamics on the different parameters of the model, namely, the energy scale, the number of degrees of freedom, and the couplings of the scalar field with bosons and fermions. We also inspect the implications for the cosmological outcomes of the phase transition.

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

2008-03-15

342

Qcd phase transitions-volume 15.  

National Technical Information Service (NTIS)

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 discuss...

Schafer

1998-01-01

343

Cell Plasma Membranes and Phase Transitions  

Microsoft Academic Search

Cell plasma membrane phaseplays a large role in membrane trafficking and signaling. The rolethat membrane phase plays in cell\\u000a function, current hypothesesconcerning the size and time duration of the phase transitions, andthe role in disease are discussed.

Mark M. Banaszak Holl

344

QGP phase transition and multiplicity fluctuations  

Microsoft Academic Search

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

Chunbin Yang; Xiaorong Wang; Xu Cai

1997-01-01

345

Phase transitions in layered superconductors  

Microsoft Academic Search

A system of superconducting layers with Josephson coupling J between them is studied. When the in-layer penetration depth lambdae is larger than the spacing d between layers, as in CuO2-based superconductors, there is a single three-dimensional transition temperature Tc. The ratio Tc\\/tau, where tau=phi20\\/4pi2lambdae, is found to vary from ~1\\/8 to ~1, being near 1\\/8 when J\\/Tc is exponentially small.

Baruch Horovitz

1992-01-01

346

Paclitaxel-loaded Pluronic nanoparticles formed by a temperature-induced phase transition for cancer therapy  

Microsoft Academic Search

We prepared nanoparticles by a temperature-induced phase transition in a mixture of Pluronic F-68 and liquid PEG (polyethylene glycol, molecular weight: 400) containing paclitaxel (PTX) with a fast, simple, continuous and solvent-free process. The liquid PEG is used as solubilizer of PTX and the polymer for the encapsulation of PTX is composed of Pluronic F-68. At the phase transition temperature,

Keun Sang Oh; Ji Yung Song; Sun Hang Cho; Bum Suk Lee; Sang Yoon Kim; Kwangmeyung Kim; Hyesung Jeon; Ick Chan Kwon; Soon Hong Yuk

2010-01-01

347

Mesoscopic aspects of phase transitions in a solvent extraction system.  

PubMed

In liquid-liquid extraction, organic phase splitting arises when high concentrations of polar solutes (acids/metal ions) are extracted. Herein, we investigate the mesoscopic roots that underpin phase splitting in alkane phases containing mixed amphiphiles, of contemporary interest in solvent extraction separation systems, by extracting various oxoacids. The oxoacids exhibited individual macroscopic (extractive and physical) behaviors, inducing phase splitting into heavy and light domains under markedly different conditions. Using small-angle X-ray scattering (SAXS) data analyzed using the generalized indirect Fourier transform (GIFT) method, we showed that, in all cases, acid extraction drove the self-assembly of reverse micelles into rods. These grew with increased acid extraction until reaching a critical length of 20 nm, at which point interactions produced interconnected cylinders or lamellar sheets that prelude phase splitting into heavy and light domains. In all cases, the heavy phase contained the same surfactant ratio-TBP (tri-n-butyl phosphate) and CMPO (octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide)-even though the concentrations of acid, water, and amphiphiles were markedly different. The remarkable similarities in structure and amphiphile stoichiometries underpinning phase splitting across the macroscopically different acid extraction series allude to the mesoscopic roots of organic phase behavior in solvent extraction. Our studies show that the structures underpinning phase splitting in solvent extraction systems are more complex than previously thought and are reminiscent of phase transitions in soft matter. PMID:23062174

Ellis, Ross J; Audras, Matthieu; Antonio, Mark R

2012-10-25

348

Ionic liquid-derived charged polymers to show highly thermoresponsive LCST-type transition with water at desired temperatures.  

PubMed

A polymerised ionic liquid (poly(IL)) having suitable hydrophobicity undergoes a strongly temperature-sensitive LCST-type phase transition with pure water and also with aqueous salt solution, and the resulting hydrated poly(IL) further undergoes a sharp and reversible liquid-to-gel transition at ambient temperatures. PMID:23123678

Kohno, Yuki; Deguchi, Yuki; Ohno, Hiroyuki

2012-12-18

349

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

350

Phase transition in ultrathin Bi films  

NASA Astrophysics Data System (ADS)

Dynamical studies of Bi ultrathin films prepared on carbon at 100 K exhibit a phase transition from nanocrystalline to amorphouslike clusters. Evidence for the transition at a thickness of ~8 Å is provided by the form, intensity, and polarization dependence of in situ Raman-scattering measurements in ultrahigh vacuum. A substantial increase in frequency of the opticlike band with decreasing thickness indicates increased covalent interactions. This contrasts with superconducting Bi films, suggesting a semiconducting amorphous state in clusters.

Mitch, M. G.; Chase, S. J.; Fortner, J.; Yu, R. Q.; Lannin, J. S.

1991-08-01

351

Liquid Crystal Phases of Colloidal Platelets and their Use as Nanocomposite Templates  

Microsoft Academic Search

This thesis explores the gelation and liquid crystal phase behavior of colloidal dispersions of platelike particles as well as the use of such dispersions for the generation of nanocomposites. We report on the sol-gel, sol-glass and liquid crystal phase transitions of positively charged colloidal gibbsite platelets in water over a wide range of particle concentrations and salt concentrations. The natures

M. C. D. Mourad

2009-01-01

352

Topological and spin-liquid phases in strongly correlated iridates  

NASA Astrophysics Data System (ADS)

Recently, the emergence of topological phases in interacting electron systems such as topological insulators and spin liquid phases, has been a subject of intensive research. In particular, much attention has been given to 5d transition metal oxides where the strong spin-orbit coupling and intermediate strength of the electron interaction provide an ideal playground for the emergence of a number of interesting topological phases. We summarize recent theoretical efforts in this direction in the context of Iridates, or iridium oxides. We make connections to the existing and future experiments on a variety of iridates materials including pyrochlore iridates, honeycomb-lattice iridates, and hyperkagome-lattice systems.

Kim, Yong Baek

2012-02-01

353

Chemical reaction models for non-equilibrium phase transitions  

Microsoft Academic Search

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

F. Schlögl

1972-01-01

354

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

355

Phase transitions in models of ion-specific protein solutions  

NASA Astrophysics Data System (ADS)

Protein crystallization is an ongoing area of research. Much theoretical work exists in this field, however currently there is no universal theory that predicts the conditions at which proteins crystallize. A better understanding of protein behavior in different solutions well help create high quality crystals suitable for crystallography and will also allow us to prevent and understand the onset of certain diseases. In this thesis, we examine many interesting models of protein self-assembly in the presence of aqueous electrolyte solutions to extend the understanding of phase transitions taking place in such systems. It is well known experimentally that salts play an important role in phase transitions of protein solutions, among other things. We analyze a salt specific model of lysozyme based on ion-dispersion interactions in order to determine where the liquid-liquid and liquid-solid phase transitions occur. Using Monte Carlo simulations, we show that the system has a metastable fluid-fluid transition, which is consistent with experimental observations of this system at similar salt concentrations. We also examine the role of salts on the metastable fluid-fluid curve in a model of aluminum oxide nanoparticles. The methods we employ include finite-size scaling, multicanonical histogram reweighting and Gibbs ensemble Monte Carlo. We show that, as expected, this interaction potential belongs to the Ising universality class. The scaling fields and critical point parameters are obtained in the thermodynamic limit of infinite system size by extrapolation of our finite size scaling results. We also quantitatively demonstrate how different salts have an effect on the critical point of the metastable fluid-fluid curve. Ion-specific interactions may manifest themselves in many ways. In our most recent study, we examine another model of lysozyme at different salt concentrations which includes interactions due to ion-specific and hydrophobic surface effects. We use a potential of mean force along with Monte Carlo simulations to determine the liquid-liquid and liquid-solid phase diagrams for different salt concentrations of NaCl. In one case, we observe a stable liquid-solid phase transition while for the higher salt concentration, we observe that the system is just slightly metastable. We attribute this to the fact that the potential for the higher salt concentration has a repulsive maximum, which effectively shortens the range of the attraction. Lastly, we present preliminary results on gelation for a simple model of globular proteins in which the liquid-liquid and liquid-solid phase diagram is already known. In this model, we use canonical ensemble Monte Carlo simulations to investigate the gel region below the critical point where we observe that the arrested gel state is preceded by spinodal decomposition. In some cases, we also observe local crystallization within the gel state.

Lettieri, Steven A.

356

Phase Transitions with Subnucleonic Degrees of Freedom  

SciTech Connect

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

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

2008-01-24

357

Absorbing phase transition in energy exchange models  

NASA Astrophysics Data System (ADS)

We study energy exchange models with dissipation (?) and noise (of amplitude ?) and show that in presence of a threshold these models undergo an absorbing phase transition when either dissipation or noise strength or both are varied. Using Monte Carlo simulations we find that the behaviour along the critical line, which separates the active phase from the absorbing one, belongs to directed percolation (DP) universality class. We claim that the conserved version with ? = 1 and ? = 0 also shows a DP transition; the apparent non-DP behaviour observed earlier is an artifact of undershooting in the decay of activity density starting from a random initial condition.

Basu, U.; Basu, M.; Mohanty, P. K.

2013-05-01

358

Structural phase transitions in titanium oxide  

NASA Astrophysics Data System (ADS)

In the present paper, we have analyzed the pressure induced structural phase transition in TiO with great accuracy by three body force potential (TBFP) model modified calculation approach. The more accurate description of the inter ionic spacing (r0) confirms that the interactions considered in the present computation are capable of correctly predicting the minimum cohesive energy (U) for TiO. The computed inter ionic spacing (r0), cohesive energy (U) and phase transition pressure (PT) are in reasonable agreement with the other reported data. It is observed that the relative volume change is 0.103 for TiO which is close to the ab an initio result.

Diwan, Bhoopendra Dhar; Singh, Surendra Kumar

2013-06-01

359

Phase transitions in phosphatidylcholine multibilayers  

PubMed Central

The 2H NMR spectrum of a multilamellar dispersion of 1-myristoyl-2-[14,14,14-2H3]myristoyl-sn-glycero-3-phosphocholine with 1 mol% cholesterol in excess water has been recorded at temperatures between -15°C and 36°C. Motionally averaged quadrupole coupling constants ??Q? and motionally induced asymmetry parameters ? are obtained by spectral analysis. Values of these quantities indicate that, at temperatures below -4°C, any rotational motion of the molecules about their molecular long axis is slow on the NMR time scale. At temperatures immediately above the pretransition these same parameters show that a fast-rotational motion is occurring about the molecular long axis. This rotational motion is hindered in that the molecules flip about a twofold symmetry axis. Between -4°C and the pretransition, spectra appear as the superposition of two powder patterns, one corresponding to the pattern observed below -4°C and the other to the pattern above the pretransition. The relative contribution of the latter increases with temperature until the pretransition is reached. These data have been interpreted in two ways: either the sample between -4°C and the pretransition contains two populations of rapidly and slowly rotating molecules, or there is only a single population of molecules undergoing a 180° flipping motion on the time scale of the NMR measurement. The latter interpretation is more consistent with other experimental findings. At the temperature of the main transition the hydrocarbon chains melt. In the absence of cholesterol, spectra are more complex in that the line shape is reproduced by the superposition of three spectral powder patterns between -4°C and the pretransition and by the superposition of two spectral patterns above the pretransition. It is postulated that these two patterns observed above the pretransition are in direct correspondence to the two ripple structures observed by freeze-fracture electron microscopy in the absence of cholesterol.

Westerman, Philip W.; Vaz, Maria Joao; Strenk, Lawrence M.; Doane, J. William

1982-01-01

360

Liquid–Liquid and SolidPhase Extraction Techniques  

Microsoft Academic Search

\\u000a Liquid–liquid extraction and solid-phase extraction are classical sample preparation techniques that have been used with various\\u000a types of samples. The fundamentals of these two techniques, as well as several microextraction techniques based on the same\\u000a principles, are described in this chapter. Application of these techniques to the sample preparation of pharmaceutical dosage\\u000a forms for analysis is also discussed.

Beverly Nickerson; Ivelisse Colón

361

Analyzing phase diagrams and phase transitions in networked competing populations  

NASA Astrophysics Data System (ADS)

Phase diagrams exhibiting the extent of cooperation in an evolutionary snowdrift game implemented in different networks are studied in detail. We invoke two independent payoff parameters, unlike a single payoff often used in most previous works that restricts the two payoffs to vary in a correlated way. In addition to the phase transition points when a single payoff parameter is used, phase boundaries separating homogeneous phases consisting of agents using the same strategy and a mixed phase consisting of agents using different strategies are found. Analytic expressions of the phase boundaries are obtained by invoking the ideas of the last surviving patterns and the relative alignments of the spectra of payoff values to agents using different strategies. In a Watts-Strogatz regular network, there exists a re-entrant phenomenon in which the system goes from a homogeneous phase into a mixed phase and re-enters the homogeneous phase as one of the two payoff parameters is varied. The non-trivial phase diagram accompanying this re-entrant phenomenon is quantitatively analyzed. The effects of noise and cooperation in randomly rewired Watts-Strogatz networks are also studied. The transition between a mixed phase and a homogeneous phase is identify to belong to the directed percolation universality class. The methods used in the present work are applicable to a wide range of problems in competing populations of networked agents.

Ni, Y.-C.; Yin, H. P.; Xu, C.; Hui, P. M.

2011-03-01

362

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

Microsoft Academic Search

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

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

1999-01-01

363

Liquid-phase compositions from vapor-phase analyses  

SciTech Connect

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

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

1990-02-01

364

Holographic endpoint of spatially modulated phase transition  

NASA Astrophysics Data System (ADS)

In a previous paper [S. Nakamura, H. Ooguri, and C. S. Park, Phys. Rev. DPRVDAQ1550-7998 81, 044018 (2010)10.1103/PhysRevD.81.044018], we showed that the Reissner-Nordström black hole in the five-dimensional anti-de Sitter space coupled to the Maxwell theory with the Chern-Simons term is unstable when the Chern-Simons coupling is sufficiently large. In the dual conformal field theory, the instability suggests a spatially modulated phase transition. In this paper, we construct and analyze nonlinear solutions which describe the endpoint of this phase transition. In the limit where the Chern-Simons coupling is large, we find that the phase transition is of the second order with the mean field critical exponent. However, the dispersion relation with the Van Hove singularity enhances quantum corrections in the bulk, and we argue that this changes the order of the phase transition from the second to the first. We compute linear response functions in the nonlinear solution and find an infinite off-diagonal DC conductivity in the new phase.

Ooguri, Hirosi; Park, Chang-Soon

2010-12-01

365

Correlated effects in topological phase transitions  

NASA Astrophysics Data System (ADS)

Correlation effects in topological phases have been a central topic of interest, yet elusive in experiment. In this talk, we present the results of a numerical study beyond mean-field theory of a phase transition between a two-dimensional Z2 topological insulator phase and a trivial insulator that is driven by correlation effects. In addition to the Z2 invariant, we find that certain features of the single-particle Green's functions (simpler to compute than the full Z2 invariant) carry important information that are strongly indicative of a non-trivial Z2 topological character. We observe that the fluctuations originating from correlations tend to move the topological phase transition boundary to larger values of interactions.

Hung, Hsiang-Hsuan; Wang, Lei; Gu, Zheng-Cheng; Fiete, Gregory A.

2013-03-01

366

Ultrasonic velocity measurements as a method for investigating phase transitions of monoglyceride emulsifier systems in pearlescent cosmetic creams  

Microsoft Academic Search

The phase transitions of monoglyceride emulsifier systems and pearlescent effects in cosmetic creams are investigated using ultrasonic velocity measurements. The transitions between the different phases of monoglyceride emulsifier systems—the coagel, liquid–crystalline lamellar phase, and gel phase—are detected in creams by changes in the ultrasonic velocity with variation of the temperature. The phase transition temperatures correspond to DSC results. Furthermore, the

Cécile Alberola; Thomas Dederichs; Detlef Emeis; Martin Möller; Tobias Sokolowski; Klaus-Peter Wittern

2007-01-01

367

Survey of CRISM Transition Phase Observations  

Microsoft Academic Search

The Mars Reconnaissance Orbiter (MRO) transition phase extends from the end of aerobraking (08\\/30\\/06) to the start of the Primary Science Phase (PSP) (11\\/08\\/2006). Within this timeframe, the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) will acquire Mars scene observations in association with the deployment of the telescope cover (09\\/27\\/06) and during the operational checkout of the full science payload

F. P. Seelos; S. L. Murchie; T. H. Choo; J. A. McGovern

2006-01-01

368

Fragmentation phase transitions in atomic clusters III  

Microsoft Academic Search

We discuss the role and the treatment of polarization effects in many-body systems of charged conducting clusters and apply this to the statistical fragmentation of Na-clusters. We see a first order microcanonical phase transition in the fragmentation of $Na^{Z+}_{70}$ for $Z=$ 0 to 8. We can distinguish two fragmentation phases, namely evaporation of large particles from a large residue and

O. Schapiro; P. J. Kuntz; K. Möhring; P. A. Hervieux; D. H. E. Gross; M. E. Madjet

1997-01-01

369

30 GHz liquid crystal phased array  

Microsoft Academic Search

This paper describes the design and measurement of a phased array antenna at 30 GHz. The objective of this work is to build an antenna demonstrator to examine the feasibility of liquid crystal based phase shifters for scanning arrays. A wideband antenna concept is presented and the proper feeding network is designed. The final design comprises of a 4??4 array,

Bahram Sanadgol; Sybille Holzwarth; Jürgen Kassner

2009-01-01

370

Search for Electronic Phase Separation at Quantum Phase Transitions  

NASA Astrophysics Data System (ADS)

Phase separation and extreme sensitivity to disorder and defects are key features of electronic order near quantum phase transitions. Neutron depolarization imaging and neutron Larmor diffraction are new experimental techniques capable of providing detailed real-space and reciprocal-space information, respectively, on the existence and nature of phase separations. Proof-of-principle depolarization imaging in Pd1- x Ni x , CePd1- x Rh x and NbFe2 suggests distinct differences of the real-space distribution of ferromagnetic moments and Curie temperatures in materials at ferromagnetic quantum phase transitions. This compares with neutron Larmor diffraction which provides high-resolution reciprocal-space information of phase separation and the absence of quantum criticality in the itinerant helimagnet MnSi or the parasitic nature of small moment antiferromagnetism in URu2Si2.

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

2010-10-01

371

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

SciTech Connect

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

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

1995-07-10

372

Deformation phase transition in vanadium under high pressure  

NASA Astrophysics Data System (ADS)

Within the framework of the Landau theory of phase transitions and the density functional method, it is shown that the structural transformation from a body-centered cubic phase to a rhombohedral phase revealed in vanadium at 69 GPa is a first-order deformation phase transition close to a second-order phase transition.

Bondarenko, N. G.; Vekilov, Yu. Kh.; Isaev, E. I.; Krasil'Nikov, O. M.

2010-06-01

373

Random lasing in blue phase liquid crystals.  

PubMed

Random lasing actions have been observed in optically isotropic pure blue-phase and polymer-stabilized blue-phase liquid crystals containing laser dyes. Scattering, interferences and recurrent multiple scatterings arising from disordered platelet texture as well as index mismatch between polymer and mesogen in these materials provide the optical feedbacks for lasing action. In polymer stabilized blue-phase liquid crystals, coherent random lasing could occur in the ordered blue phase with an extended temperature interval as well as in the isotropic liquid state. The dependence of lasing wavelength range, mode characteristics, excitation threshold and other pertinent properties on temperature and detailed make-up of the crystals platelets were obtained. Specifically, lasing wavelengths and mode-stability were found to be determined by platelet size, which can be set by controlling the cooling rate; lasing thresholds and emission spectrum are highly dependent on, and therefore can be tuned by temperature. PMID:23188364

Chen, Chun-Wei; Jau, Hung-Chang; Wang, Chun-Ta; Lee, Chun-Hong; Khoo, I C; Lin, Tsung-Hsien

2012-10-01

374

Phase transition dynamics in QGP hadronization  

Microsoft Academic Search

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

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

1994-01-01

375

A Note on Holography and Phase Transitions  

Microsoft Academic Search

Focusing on the connection between the Landau theory of second order phase transitions and the holographic approach to critical phenomena, we study diverse field theories in an anti-de Sitter black hole background. Through simple analytical approximations, solutions to the equations of motion can be obtained in closed form which give rather good approximations of the results obtained using more involved

Marc Bellon; Enrique F. Moreno; Fidel A. Schaposnik

2010-01-01

376

Critical Computation, Phase Transitions, and Hierarchical Learning  

Microsoft Academic Search

A study of the various routes to chaos in dynamical systems reveals that significant computation occurs at the onset of chaos. At first blush this is not surprising since statistical mechanics views these as phase transitions with infinite temporal correlations. In computational terms processes that are in a critical state, like those at the onset of chaos considered here, have

James P. Crutchfield

1994-01-01

377

Thermal phase transitions in antimony (III) oxides  

SciTech Connect

Previous reports of the thermal behaviour of antimony trioxide show significant disagreement on the values for the temperatures associated with specific thermal events. In this reappraisal, samples of both polymorphs of Sb{sub 2}O{sub 3} (senarmontite and valentinite) have been analysed using X-ray diffraction and simultaneous differential thermal/thermogravimetric analysis techniques. The senarmontite-valentinite phase transition has been observed to occur as a multi-stage event commencing at temperatures as low as 615{+-}3 deg. C-evidence of oxidation to Sb{sub 2}O{sub 4} under inert atmosphere may indicate that the depression is related to surface- or bulk-bound water. Valentinite produced by mechanical milling of senarmontite exhibits the reverse phase transition to senarmontite at a lower than normal temperature (445{+-}3 deg. C). Oxidation temperatures of 531{+-}4 deg. C for senarmontite and 410{+-}3 deg. C for mechanically derived valentinite were also recorded. - Graphical abstract: The phase transitions of Sb{sub 2}O{sub 3} have been re-examined using XRD and simultaneous TG/DTA, clarifying apparent disagreements in previous works. The thermal events have been detailed, and the {alpha}-{beta} phase transition has been observed to occur as a multi-stage event-possibly relating to the presence of surface- or bulk-bound water.

Orman, R.G. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Holland, D. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)], E-mail: d.holland@warwick.ac.uk

2007-09-15

378

Quantum Phase Transitions in Random Spin Systems  

Microsoft Academic Search

We report a systematic numerical study of quantum critical phenomena in random spin systems. At zero temperature, quantum phase transitions in these systems are caused by the interplay of quantum fluctuations and ordering interactions with built-in quenched randomness. As demonstrated in the one dimensional case, random quantum spin systems show unusual critical behavior as compared to classical systems. In this

Muyu Guo

1995-01-01

379

Geometry-induced phase transition in fluids: Capillary prewetting  

NASA Astrophysics Data System (ADS)

We report a new first-order phase transition preceding capillary condensation and corresponding to the discontinuous formation of a curved liquid meniscus. Using a mean-field microscopic approach based on the density functional theory we compute the complete phase diagram of a prototypical two-dimensional system exhibiting capillary condensation, namely that of a fluid with long-ranged dispersion intermolecular forces which is spatially confined by a substrate forming a semi-infinite rectangular pore exerting long-ranged dispersion forces on the fluid. In the T-? plane the phase line of the new transition is tangential to the capillary condensation line at the capillary wetting temperature Tcw. The surface phase behavior of the system maps to planar wetting with the phase line of the new transition, termed capillary prewetting, mapping to the planar prewetting line. If capillary condensation is approached isothermally with T>Tcw, the meniscus forms at the capping wall and unbinds continuously, making capillary condensation a second-order phenomenon. We compute the corresponding critical exponent for the divergence of adsorption.

Yatsyshin, Petr; Savva, Nikos; Kalliadasis, Serafim

2013-02-01

380

Signatures in the Conductance for Phase Transitions in Excitonic Systems  

NASA Astrophysics Data System (ADS)

In this paper, we analyze two phase transitions in exciton bilayer systems: a topological phase transition to a phase which hosts Majorana fermions and a phase transition to a Wigner crystal. Using generic simple models for different phases, we discuss the conductance properties of the latter when contacted to metallic leads and demonstrate the possibility to observe the different phase transitions by simple conductance measurements.

Soller, H.; Breyel, D.

2013-10-01

381

Modeling CO 2 leakage scenarios, including transitions between super- and sub-critical conditions, and phase change between liquid and gaseous CO 2  

Microsoft Academic Search

Storage of CO2 in saline aquifers would be made at supercritical pressure and temperature conditions, but CO2 leaking from a geologic storage reservoir and migrating towards the land surface (through faults, fractures, or improperly abandoned wells) would reach sub-critical conditions above 500-750 m depth for typical temperature and pressure conditions in terrestrial crust. At shallower horizons, subcritical CO2 can form two-phase

Karsten Pruess

2011-01-01

382

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

Microsoft Academic Search

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

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

2009-01-01

383

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

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

384

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.

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

1978-01-01

385

Phase transitions in nucleonic matter and neutron-star cooling.  

PubMed

A new scenario for neutron-star cooling is suggested by the correspondence between pion condensation, induced by critical spin-isospin fluctuations, and the metal-insulator phase transition in a 2D electron gas. Above the threshold density for pion condensation, the neutron single-particle spectrum acquires an insulating gap that quenches neutron contributions to neutrino production. In the liquid phase just below the transition, the fluctuations play dual roles by (i) creating a multisheeted neutron Fermi surface that extends to low momenta and activates the normally forbidden direct Urca cooling mechanism, and (ii) amplifying the nodeless P-wave neutron superfluid gap while suppressing S-wave pairing. Lighter stars without a pion-condensed core undergo slow cooling, whereas enhanced cooling occurs in heavier stars via direct Urca emission from a thin shell of the interior. PMID:15524862

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

2004-10-05

386

New signatures of phase transitional behavior in nuclei  

SciTech Connect

The phase/shape transitional behavior of different observables is discussed, with emphasis on the 2{sub {gamma}}{sup +}{yields}0{sub 2}{sup +} transition rate. The existing data on transitional Sm isotopes show that the vibrator-rotor shape transition behaves as a critical phase transition despite the finite-body nature of the nuclear environment.

Zamfir, N. V. [WNSL Yale University, New Haven, Connecticut 06520 (United States); Clark University, Worcester, Massachusetts 01610 (United States); Institute of Atomic Physics, Bucharest (Romania); Casten, R. F.; Kruecken, R.; Beausang, C. W.; Cooper, J. R.; Liu Benyuan; Novak, J. R. [WNSL Yale University, New Haven, Connecticut 06520 (United States); Cata-Danil, G. [WNSL Yale University, New Haven, Connecticut 06520 (United States); Institute of Atomic Physics, Bucharest (Romania); Barton, C. J. [Clark University, Worcester, Massachusetts 01610 (United States)

1998-12-21

387

Two phase flow and isopycnic liquid-liquid two phase fluid in reduced gravity field  

Microsoft Academic Search

The possibility of applying the existent gas-liquid two phase flow behavior diagrams in the earth gravity to those in reduced gravity are described. Outlines of the results of free drop tower experiments, airplane experiments, free drop tower experiment and airplane experiment are reviewed. The result of the isopycnic two phase liquid flow experiments on the ground simulating the reduced gravity

Terushige Fujii; Junichi Oota

1993-01-01

388

Quadrupolar phase transitions in UPd3  

NASA Astrophysics Data System (ADS)

Quadrupolar order in a 5f electron system has been observed directly for the first time, using x-ray scattering techniques [1]. In UPd3, 2 sets of satellite peaks appear at low temperatures, and show resonant enhancement at the uranium MIV edge. X-ray and neutron scattering, and bulk property measurements, reveal a total of 4 phase transitions in UPd3 below 8K, which we associate with different quadrupolar order parameters. We have now developed a new model for the crystal field states of UPd3 that enables us to explain not only the order parameters of the 4 phase transitions, but also the excitations in the ordered phases, as observed in our inelastic neutron scattering studies of UPd3. [1] D.F.McMorrow, K.A.McEwen, U.Steigenberger, H.M.Ronnow, F.Yakhou, Phys. Rev. Lett. 87 (2001) 057201

McEwen, Keith

2003-03-01

389

Glass Transitions and Low-Frequency Dynamics of Room-Temperature Ionic Liquids  

NASA Astrophysics Data System (ADS)

We have measured the heat capacity and neutrion quasi- and inelastic scattering spectra of some salts of 1-butyl-3-methylimidazolium ion bmim+, which is a typical cation of room-temperature ionic liquids, and its derivatives. The heat capacity measurements revealed that the room-temperature ionic liquids have glass transitions as molecular liquids. The temperature dependence of configurational entropy demonstrated that the room-temperature ionic liquids are ``fragile liquids''. Both heat capacity and inelastic neutron scattering data revealed that the glassy phases exhibit large low-energy excitations usually called ``boson peak''. The quasielastic neutron scattering data showed that so-called ``fast process'' appears around Tg as in molecular and polymer glasses. The temperature dependence of the self-diffusion coefficient derived from the neutron scattering data indicated that the orientation of bmim+ ions and/or butyl-groups of bmim+ ions is highly disordered and very flexible in an ionic liquid phase.

Yamamuro, O.; Inamura, Y.; Hayashi, S.; Hamaguchi, H.

2006-05-01

390

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

SciTech Connect

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

Ross, M

2008-08-15

391

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 .

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

2013-01-01

392

Phase transitions in NM-TM spinglasses  

NASA Astrophysics Data System (ADS)

The co-operative spin-freezing caused by RKKY and DM-interactions leads to finite discontinuities in the EA-order parameter because of the co-existence of an effective single impurity effect and a spinglass effect. Derived expressions for specific heat and susceptibility yield a multiple order (first and third) phase transition. This third order transition may be reconciled with the observed ``knees'' in the specific heat and discontinuities in the susceptibility slope at Tf. Science Faculty, Garyounis University, Benghazi, Libya.

Sheikh, A. W.

1988-10-01

393

Phase transitions near the ``game of Life''  

NASA Astrophysics Data System (ADS)

Whether or not the cellular automaton (CA) ``game of Life'' is an example of self-organized criticality has been a controversial question. Here we view the problem from a different perspective by introducing probabilities into the rules. Thereby we extend the discrete space of deterministic CA to a hypercubic space of stochastic CA, where each corner represents a deterministic CA. We examine the scaling structure near the ``game of Life'' corner and identify a phase-transition line separating ``Life'' and ``Death.'' The transition line ends very close to but not in the ``game of Life.''

Nordfalk, Jacob; Alstrøm, Preben

1996-08-01

394

Phase transitions in lattice gauge theories  

NASA Astrophysics Data System (ADS)

Topological excitations in lattice gauge theories are studied with an aim towards understanding the role of such excitations in the Abelian Higgs model. First, the topological excitations of the compact U(1) lattice Higgs model are reviewed. The phases of the system are discussed in terms of these excitations and the results of Monte Carlo studies summarized. New results are then presented clarifying the role of topological excitations in the non-compact lattice version of the Abelian Higgs model. The Villain form of the non-compact model's partition function is represented as a sum over world- sheets of gauge-invariant 'vortex' sheets. The phase transition of the system is then related to the condensation of these excitations via standard energy- entropy arguments. Results of Monte Carlo simulations are then presented. The density of the vortex sheets is shown to be a good disorder parameter for the system. The vortex density essentially vanishes in the Higgs phase, and the Coulomb phase consists of a single vortex condensate. The critical line derived in the vortex representation of the theory is in good agreement with the Monte Carlo results. In part II Quantum Chromodynamics (QCD) is studied at non-zero baryon density. The essential properties of QCD are reviewed, including the broken chiral symmetry of the QCD vacuum state. The current understanding of the deconfining and chiral symmetry restoring transitions at non-zero temperature and density is then summarized. The use of a four-fermion coupling as an improved extrapolation parameter over the bare quark mass in Monte Carlo simulations is discussed. A mean field analysis of finite density QCD is then presented, including the effects of additional chiral invariant four-fermion interactions. A lattice regularization is used with Nf = 4 flavors of staggered fermions. Particular attention is given to the structure of the phase diagram and the order of the chiral phase transition. At zero gauge coupling the model reduces to a Nambu-Jona-Lasinio model. In this limit the chiral phase transition is found to be second-order near the zero-density critical point and otherwise first-order. In the strong gauge coupling limit a first-order chiral phase transition is found. In this limit the additional four-fermion interactions do not qualitatively change the physics. The results agree with previous studies of QCD as the four-fermion coupling vanishes.

Chavel, Michael Van

395

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

396

Characterization of micellar mobile phases for reversed phase liquid chromatography  

SciTech Connect

The use of micellar mobile phases for reversed phase liquid chromatography with emphasis on efficiency optimization, physical studies, selectivity, and gradient elution capabilities is examined, and whenever relevant, compared to traditional hydroorganic mobile phases. Surfactants self-aggregate into larger units called micelles, which provide a hydrophobic site for interaction with the solute in the mobile phase and can be used in place of an organic modifier. Certain advantages exist for micellar mobile phases including unique selectivities, economic considerations, purity, and safety. Purely aqueous micellar mobile phases can provide unique selectivities in liquid chromatography, however they are very inefficient in comparison to traditional hydroorganic mobile phases. This inefficiency is shown to arise from slow mass transfer, which comes from poor wetting of the stationary phase. Low concentrations of organic modifiers are useful for modifying the surface of the stationary phase and providing the wetting needed for good mass transfer. Elevated temperatures are also shown to be useful in overcoming the higher viscosity of micellar mobile phases and thereby serving to improve peak shape. The capacity factor and selectivity were chosen to express the retention behavior of four non-polar solutes for each surfactant studied. The combined mechanisms of ion-pairing band partitioning into micelles describes the electrostatic effects of ionic solutes with ionic surfactants above the CMC (critical micelle concentration). Gradient elution for micellar mobile phases is shown to be feasible and much improved as compared to traditional hydroorganic mobile phases due to fast reequilibration times.

Landy, J.S.

1983-01-01

397

Dimensional phase transition in small Yukawa clusters  

SciTech Connect

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

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

2010-01-15

398

Phase transition into the metallic state in hypothetical (without molecules) dense atomic hydrogen  

NASA Astrophysics Data System (ADS)

A simple physical model of the metal-dielectric (vapor-liquid) phase transition in hypothetical (without molecules) atomic hydrogen is proposed. The reason for such a transition is the quantum collective cohesive energy occurring due to quantum electron-electron exchange similar to the cohesive energy in the liquid-metal phase of alkali metals. It is found that the critical parameters of the transition are P c ˜ 41000 atm, ? c ˜ 0.1 g/cm3, and T c ˜ 9750 K.

Khomkin, A. L.; Shumikhin, A. S.

2013-10-01

399

Phase Behavior of Block Copolymer Solutions in an Ionic Liquid  

NASA Astrophysics Data System (ADS)

Incorporation of ionic liquids into block copolymers is of interest for applications such as high temperature fuel cell membranes. We investigate the lyotropic and thermotropic phase behavior of solutions of poly(styrene-b-2-vinyl pyridine) (S2VP) block copolymers in an ionic liquid consisting of imidazole and bis(trifluoromethane)sulfonamide (HTFSI). Using small angle X-ray scattering (SAXS) and static birefringence, we demonstrate that the ionic liquid behaves as a selective solvent, preferentially solvating the poly(2-vinyl pyridine) segment of the block copolymer. At moderate to high concentrations (>= 40 wt%) of copolymer, we observe lyotropic phase transitions to lamellar and cylindrical (hcp) nanostructures. At low concentrations of S2VP copolymer (<= 30 wt%), we observe poorly-ordered, microphase-separated structures, which do not resemble the face-centered cubic or body-centered cubic spherical micelles observed in block copolymer solutions in molecular solvents. We observe that the order-disorder transition temperature of the series of SVP copolymers does not depend strongly on the concentration of the block copolymer solution in ionic liquid.

Virgili, J. M.; Hoarfrost, M. L.; Balsara, N. P.; Segalman, R. A.

2009-03-01

400

Ultrasonic atomization: effect of liquid phase properties.  

PubMed

Experiments have been conducted to understand the mechanism by which the ultrasonic vibration at the gas liquid interface causes the atomization of liquid. For this purpose, aqueous solutions having different viscosities and liquids showing Newtonian (aqueous solution of glycerin) and non-Newtonian behavior (aqueous solution of sodium salt of carboxy methyl cellulose) were employed. It has been found that the average droplet size produced by the pseudo-plastic liquid is less than that produced by the viscous Newtonian liquid having viscosity equal to zero-shear rate viscosity of the shear thinning liquid. The droplet size was found to increase initially with an increase in the viscosity up to a certain threshold viscosity after which the droplet size was found to decrease again. Also droplet size distribution is found to be more compact (uniform sizes) with an increasing viscosity of the atomizing liquid. The presence of the cavitation and its effect on the atomization has been semi quantitatively confirmed using energy balance and by the measurement of the droplet ejection velocities and validated on the basis of the decomposition of the aqueous KI solution. A correlation has been proposed for the prediction of droplet size for aqueous Newtonian fluids and fluids showing non-Newtonian behavior based on the dimensionless numbers incorporating the operating parameters of the ultrasonic atomizer and the liquid phase physico-chemical properties. PMID:16321416

Avvaru, Balasubrahmanyam; Patil, Mohan N; Gogate, Parag R; Pandit, Aniruddha B

2005-11-07

401

The Ultrasonic Investigation of Phase Transition in Olive Oil up to 0.7 GPa.  

PubMed

This paper presents measurements of sound velocity and attenuation in olive oil, with known chemical composition, as a function of pressure, within the range of pressure up to 0.7 GPa. Dependencies of sound velocity, relative ultrasonic wave attenuation, volume, and adiabatic compressibility on pressure show discontinuities. This proves the existence of the first order phase transition in olive oil (liquid to solid-like phase transition). Rapid and large changes in relative attenuation testify to the existence of a phase transition in olive oil. Moreover, the kinetics of phase transition was also investigated. Measurement of acoustic wave velocity and relative attenuation in olive oil during the phase transition and in the high-pressure phase is a novelty. The results obtained can be useful in the development of new methods in food (edible oils) control, processing, and preservation. PMID:23710073

Rostocki, A J; Tarakowski, R; Kie?czy?ski, P; Szalewski, M; Balcerzak, A; Ptasznik, S

2013-03-12

402

Phase transition in lithium yttrium oxide  

SciTech Connect

Ferroelectricity was studied in LiYO/sub 2/ with the aid of measurements of the dielectric constant, the electrical conductivity, and the polarizability as functions of the temperature. The investigation of polycrystalline lithium yttrium oxide revealed that under room conditions LiYO/sub 2/ is a dielectric. The temperature investigations carried out showed that the structural transformation is accompanied by a clearly expressed anomaly in the dielectric properties. It was established that the structural transformations in lithium yttrium oxide are accompanied by an antiferroelectric phase transition of the first kind. The temperature of the Curie-Weiss transition is 1130 K, the temperature of the Curie transition is 1170 K, and the dielectric constant at the Curie point equals 36,000.

Shuster, N.S.; Kuli-zade, E.S.

1988-08-01

403

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

SciTech Connect

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

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

1982-11-01

404

Phase transitions and phase equilibria in spherical confinement  

NASA Astrophysics Data System (ADS)

Phase transitions in finite systems are rounded and shifted and affected by boundary effects due to the surface of the system. This interplay of finite size and surface effects for fluids confined inside of a sphere of radius R is studied by a phenomenological theory and Monte Carlo simulations of a model for colloid-polymer mixtures. For this system the phase separation in a colloid-rich phase and a polymer-rich phase has been previously studied extensively in the bulk. It is shown that spherical confinement can strongly enhance the miscibility of the mixture. Depending on the wall potentials at the confining surface, the wetting properties of the wall can be controlled, and this interplay between preferential adsorption of one species to the confining surface and bulk unmixing leads to very special shapes of the loops observed for the chemical potential of the colloids as a function of their packing fraction. We also discuss the extent to which concepts used for phase transitions in macroscopic systems, such as critical exponents of the order parameter distinguishing the phases, or the Kelvin equation describing the shift of the chemical potential at phase coexistence with the radius R, are applicable.

Winkler, Alexander; Statt, Antonia; Virnau, Peter; Binder, Kurt

2013-03-01

405

Supercooled liquids and the glass transition  

Microsoft Academic Search

Glasses are disordered materials that lack the periodicity of crystals but behave mechanically like solids. The most common way of making a glass is by cooling a viscous liquid fast enough to avoid crystallization. Although this route to the vitreous state — supercooling — has been known for millennia, the molecular processes by which liquids acquire amorphous rigidity upon cooling

Pablo G. Debenedetti; Frank H. Stillinger

2001-01-01

406

Evolution of structure during phase transitions  

SciTech Connect

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

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

1996-03-01

407

Shock Induced Phase Transitions in Polymeric Nitrogen  

NASA Astrophysics Data System (ADS)

The reported density functional molecular dynamics simulations are of a shock travelling through ˜4,000 atoms arranged in the equilibrium cg-N configuration equilibrated at T = 250K, P = 1 atm. Atoms within a small segment of the material given an extra velocity consistent with various desired flyer plate impact velocity. The resulting atomic trajectories show a number of complex behaviors including a phase transition to a previously unseen phase, spontaneous defect formation, and chemical reactions. The stability of the shock and the unusual properties of the above phenomena will be discussed.

Mattson, William

2010-03-01

408

Shock Induced Phase Transitions in Polymeric Nitrogen  

NASA Astrophysics Data System (ADS)

The reported density functional molecular dynamics simulations are of a shock travelling through ˜4,000 atoms arranged in the equilibrium cg-N configuration equilibrated at T = 250K, P = 1 atm. Atoms within a small segment of the material given an extra velocity consistent with various desired flyer plate impact velocity. The resulting atomic trajectories show a number of complex behaviors including a phase transition to a previously unseen phase, spontaneous defect formation, and chemical reactions. The stability of the shock and the unusual properties of the above phenomena will be discussed.

Mattson, William; Balu, Radhakrishnan

2011-06-01

409

Chiral phase transition in effective models  

NASA Astrophysics Data System (ADS)

Incorporating its most relevant global symmetry, chiral effective models are aimed at investigat- ing, in a simplified framework, important aspects of the yet unsolved QCD. We review some recent results obtained in these models on the restoration of chiral and axial symmetries, on the boundary of the first order phase transition region in the m? mK -plane at vanishing baryonic ¡ chemical potential µB , and on the µB T phase diagram. ¡ PACS: 11.10.Wx, 11.30.Rd, 12.39.Fe

Szép, Zsolt

2006-09-01

410

Determination of transition and rare earth elements in low-alloy steels as chelates with 4-(2-Thiazolylazo)resorcinol by reversed-phase high performance liquid chromatography  

Microsoft Academic Search

4-(2-Thiazolylazo)resorcinol (TAR) is used as a chelating reagent in the reversed-phase HPLC separation and determination of transition and rare earth elements in low-alloy steels. A precolumn derivatization method is used, followed by separation on an octadecyl-bonded silica stationary phase with a sodium octane-1-sulphonate-tartaric acid mobile phase. The eluted metal chelates are detected by uv-visible spectrophotometry. The requirements for sample preparation,

Rajananda Saraswati; N. R. Desikan; T. H. Rao

1992-01-01

411

Gravitational effects upon cosmological phase transitions  

Microsoft Academic Search

The effects of spacetime curvature upon phase transitions in an expanding universe are investigated. We consider a Robertson-Walker model which is a radiation-dominated universe at early times and becomes de Sitter space at later times. In this universe the stability of a field theory containing a pair of interacting scalar fields is studied in first-order perturbation theory. It is noted

Alexander Vilenkin; L. H. Ford

1982-01-01

412

Phase transitions in AgI  

Microsoft Academic Search

The ordering of silver ions in the superionic conductor alpha-AgI has been studied using a discrete version of density-functional theory. We obtained a transition to a low-temperature phase different from that found by Madden et al. using computer simulations [Phys. Rev. B 45, 10 206 (1992)]. We suggest that the difference originates from the fact that the I- lattice is

Chaok Seok; David W. Oxtoby

1997-01-01

413

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

414

On Phase Transitions in Coupled Map Lattices  

Microsoft Academic Search

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

W. Just; F. Schmüser

2005-01-01

415

Topological phase transitions in frustrated magnets  

NASA Astrophysics Data System (ADS)

The role of topological excitations in frustrated Heisenberg antiferromagnets between two and three spatial dimensions is considered. In particular, the antiferromagnetic Heisenberg model on a stacked triangular geometry with a finite number of layers is studied using Monte Carlo methods. A phase transition that is purely topological in nature occurs at a finite temperature for all film thicknesses. The results indicate that topological excitations are important for a complete understanding of the critical properties of the model between two and three dimensions.

Southern, B. W.; Peles, A.

2006-06-01

416

Conserved quantities and electroweak phase transitions  

NASA Astrophysics Data System (ADS)

Some cosmological consequences of including the adequate conserved quantities in the density matrix of the electroweak theory are investigated. Several arguments against including the charges associated to the spontaneously broken symmetry are presented. Special attention is focused on the phenomenon of W-boson condensation and its interplay with the phase transition for the symmetry restoration is considered. The emerging cosmological implications, such as on the baryon and lepton number densities, are of interest.

Chaichian, M.; Felipe, R. Gonzalez; Rojas, H. Perez

1995-02-01

417

Recent theoretical advances on superradiant phase transitions  

NASA Astrophysics Data System (ADS)

The Dicke model describing a single-mode boson field coupled to two-level systems is an important paradigm in quantum optics. In particular, the physics of ``superradiant phase transitions'' in the ultrastrong coupling regime is the subject of a vigorous research activity in both cavity and circuit QED. Recently, we explored the rich physics of two interesting generalizations of the Dicke model: (i) A model describing the coupling of a boson mode to two independent chains A and B of two-level systems [1], where chain A is coupled to one quadrature of the boson field and chain B to the orthogonal quadrature. This original model leads to a quantum phase transition with a double symmetry breaking and a fourfold ground state degeneracy. (ii) A generalized Dicke model with three-level systems [2,3] including the diamagnetic term. In contrast to the case of two-level atoms for which no-go theorems exist, in the case of three-level system we prove that the Thomas-Reich-Kuhn sum rule does not always prevent a superradiant phase transition.[4pt] [1] P. Nataf, A. Baksic and C. Ciuti, Phys. Rev. A 86, 013832 (2012).[0pt] [2] C. Ciuti and P. Nataf, Phys. Rev. Lett. 109, 179301 (2012).[0pt] [3] A. Baksic, P. Nataf, and C. Ciuti, arXiv:1206.3213 (2012).

Baksic, Alexandre; Nataf, Pierre; Ciuti, Cristiano

2013-03-01

418

Liquid phase separator with chromatographic column.  

PubMed

Presented liquid phase separator with integrated chromatographic column enables the separation and treatment of a solvent extract layer after the extraction of organic compounds from water in one simple run in a single piece of glassware. The separator has been successfully applied for the determination of hydrocarbon oil index in waters. PMID:15628145

Mikita, Martin; Tölgyessy, Peter; Hrivnák, Peter

2004-12-01

419

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...

420

FAST TRACK COMMUNICATION: Microscopic structural evolution during the liquid liquid transition in triphenyl phosphite  

Microsoft Academic Search

Recently the liquid-liquid transition (LLT) was found in a molecular liquid, triphenyl phosphite, which allows us to follow the kinetics of the transformation of one liquid to another. Here we investigate the microscopic structural change during the LLT by means of time-resolved synchrotron x-ray scattering measurements. We confirm that during spinodal-decomposition-type transformation a new peak corresponding to a particular intermolecular

Rei Kurita; Yuya Shinohara; Yoshiyuki Amemiya; Hajime Tanaka

2007-01-01

421

Ion induced lamellar-lamellar phase transition in charged surfactant systems  

NASA Astrophysics Data System (ADS)

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

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

2006-06-01

422

Supercooled liquids and the glass transition.  

PubMed

Glasses are disordered materials that lack the periodicity of crystals but behave mechanically like solids. The most common way of making a glass is by cooling a viscous liquid fast enough to avoid crystallization. Although this route to the vitreous state-supercooling-has been known for millennia, the molecular processes by which liquids acquire amorphous rigidity upon cooling are not fully understood. Here we discuss current theoretical knowledge of the manner in which intermolecular forces give rise to complex behaviour in supercooled liquids and glasses. An intriguing aspect of this behaviour is the apparent connection between dynamics and thermodynamics. The multidimensional potential energy surface as a function of particle coordinates (the energy landscape) offers a convenient viewpoint for the analysis and interpretation of supercooling and glass-formation phenomena. That much of this analysis is at present largely qualitative reflects the fact that precise computations of how viscous liquids sample their landscape have become possible only recently. PMID:11258381

Debenedetti, P G; Stillinger, F H

2001-03-01

423

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

SciTech Connect

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

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

2008-09-07

424

Magnetic-Field Induced Isotropic to Nematic Phase Transition in Ferronematics  

Microsoft Academic Search

In this work the thermotropic liquid crystal 4-(trans-4 -n-hexylcyclohexyl)-isothiocyanato-benzene (6CHBT) was doped with differently shaped magnetic nanoparticles with the aim to increase the sensitivity of the liquid crystal on the external magnetic field. The volume concentration of the magnetic particles was . The phase transition temperature from isotropic to nematic phase in external magnetic fields up to 12 T was

Peter Kopcansky; Natália Tomasovicova; Martina Koneracka; Vlasta Zavisova; Milan Timko; Michal Hnatic; Nándor Eber; Tibor Toth-Katona; Jan Jadzyn; Juha Honkonen; Eric Beaugnon; Xavier Chaud

2011-01-01