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1

Liquid-liquid phase transition in water  

NASA Astrophysics Data System (ADS)

Water shows anomalies different from most of other materials. Different sceniaros have been proposed to explain water anomalies, among which the liquid-liquid phase transition (LLPT) is the most discussed one. It attributes water anomalies to the existence of a hypothesized liquid-liquid critical point (LLCP) buried deep in the supercooled region. We briefly review the recent experimental and theoretical progresses on the study of the LLPT in water. These studies include the discussion on the existence of the first order LLPT in supercooled water and the detection of liquid-liquid critical point. Simulational results of different water models for LLPT and the experimental evidence in confined water are also discussed.

Sun, ZhaoRu; Sun, Gang; Chen, YiXuan; Xu, LiMei

2014-05-01

2

First-Order Liquid-Liquid Phase Transition in Cerium  

NASA Astrophysics Data System (ADS)

We report the first experimental observation of a liquid-liquid phase transition in the monatomic liquid metal cerium, by means of in situ high-pressure high-temperature x-ray diffraction experiments. At 13 GPa, upon increasing temperature from 1550 to 1900 K high-density liquid transforms to a low-density liquid, with a density difference of 14%. Theoretic models based on ab initio calculations are built to investigate the observed phase behavior of the liquids at various pressures. The results suggest that the transition primarily originates from the delocalization of f electrons and is deemed to be of the first order that terminates at a critical point.

Cadien, A.; Hu, Q. Y.; Meng, Y.; Cheng, Y. Q.; Chen, M. W.; Shu, J. F.; Mao, H. K.; Sheng, H. W.

2013-03-01

3

Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model System  

PubMed Central

We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses. PMID:21614201

Xu, Limei; Buldyrev, Sergey V.; Giovambattista, Nicolas; Stanley, H. Eugene

2010-01-01

4

Liquid-liquid phase transition in a two-dimensional system with anomalous liquid properties.  

PubMed

The phase diagram of the two-dimensional particles interacting through a smooth version of Stell-Hemmer interaction was studied using Monte Carlo computer simulations. By evaluating the pressure-volume isotherms, we observed liquid-liquid, liquid-gas phase transitions and three stable crystal phases. The model shows the liquid-liquid critical point in stable liquid phase and is confirmed by observing properties of other thermodynamic functions such as heat capacity and isothermal compressibility, for example. The liquid-gas and the liquid-liquid critical points were estimated within the thermodynamic limit. PMID:24483440

Urbic, Tomaz

2013-12-01

5

Liquid-liquid phase transition in a two-dimensional system with anomalous liquid properties  

NASA Astrophysics Data System (ADS)

The phase diagram of the two-dimensional particles interacting through a smooth version of Stell-Hemmer interaction was studied using Monte Carlo computer simulations. By evaluating the pressure-volume isotherms, we observed liquid-liquid, liquid-gas phase transitions and three stable crystal phases. The model shows the liquid-liquid critical point in stable liquid phase and is confirmed by observing properties of other thermodynamic functions such as heat capacity and isothermal compressibility, for example. The liquid-gas and the liquid-liquid critical points were estimated within the thermodynamic limit.

Urbic, Tomaz

2013-12-01

6

Existence of a liquid-liquid phase transition in methanol  

NASA Astrophysics Data System (ADS)

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

Huš, Matej; Urbic, Tomaz

2014-12-01

7

Fission and Nuclear Liquid-Gas Phase Transition  

E-print Network

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

E. A. Cherepanov; V. A. Karnaukhov

2007-03-30

8

Phase Transitions In Liquid Crystal Droplets  

NASA Astrophysics Data System (ADS)

Basic studies of a liquid crystal confined to a small droplet have been motivated by the use of polymer dispersed liquid crystals' for a new generation of light shutters and displays.2 The structure of such a droplet is characterized by a specific director configuration and the spatial dependence of the orientational order parameter. Depending on temperature, droplet size, surface interaction, type of liquid crystal and external field, the phase of the material enclosed in the droplet can be either the isotropic (paranematic), nematic or boundary layer nematic phase.3 Director configurations in droplets have been studied extensi% ely,4-7 but the spatial dependence of the order parameter has been treated only for the case of a liquid crystal in contact with a solid planar surface.3.8-10 Lsing the Landaude Gennes approach," the order parameter profile was evaluated, showing how the orientational order varies with distance from the planar surface. In addition, for some values of the surface-liquid crystal coupling, the existence of the boundary layer nematic phase was predicted in a narrow tem-perature range between the isotropic (paranematic) and nematic phases.3

Allender, David W.; Zumer, Slobodan

1989-07-01

9

Influence of chirality on phase transitions in ferroelectric liquid crystals  

Microsoft Academic Search

The transition temperatures between various smectic liquid crystal phases are determined as a function of the enantiomeric excess for three different chiralracemic systems (i.e. binary mixtures consisting of a chiral enantiomer and its racemate). It is shown that transitions involving a ferroelectric phase occur in the chiral compounds at higher temperatures compared to their racemates, the temperature shift being proportional

Ch. Bahr; G. Heppke; B. Sabaschus

1991-01-01

10

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

PubMed Central

Combining molecular dynamics (MD) simulation and Voronoi polyhedral analyses, we discussed the microstructure evolution in liquid and glassy silicon during cooling by focusing on the fraction of various clusters. Liquid-liquid phase transition (LLPT) is detected in supercooled liquid silicon However, freezing the high-density liquid (HDL) to the glassy state is not achieved as the quenching rate goes up to 1014?K/s. The polyamorphism in glassy silicon is found to be mainly associated with low-density liquid (LDL). PMID:25716054

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

2015-01-01

11

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

12

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

2012-08-01

13

Liquid-liquid phase transition in a family of simple models of tetrahedral liquid  

NASA Astrophysics Data System (ADS)

Liquids with tetrahedral symmetry of the first coordination shell often display anomalous thermodynamic and dynamic behavior. Sometimes, these anomalies are associated with the liquid-liquid phase transition at high pressures and low temperatures. We study a family of simple models with few parameters and investigate the conditions for the existence of the liquid-liquid phase transition. A molecule in these models consists of a hard sphere with a square well and four point particles attached to the center of the hard sphere by directional bonds arranged in tetrahedral geometry. We also impose a condition which does not allow a point particle in one molecule to include in its attractive well more than one point particle belonging to different molecules. We find an optimal range of flexibility of the bonds created by the point particles for which the model displays a clear liquid-liquid critical point in the accessible region of the phase diagram: too flexible bonds weaken the anomalies and destroy the critical point, while too rigid bonds slow down the diffusion and shift the critical point beyond the glass transition. We also investigate how minor changes in the model parameters influence crystallization which might make liquid-liquid unobservable.

Buldyrev, Sergey; Franzese, Giancarlo; Giovambattista, Nicolas

2013-03-01

14

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

PubMed

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. PMID:24089711

Schirò, Giorgio; Fomina, Margarita; Cupane, Antonio

2013-09-28

15

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

16

On the possibility of two phase transitions in liquid helium  

NASA Astrophysics Data System (ADS)

An explanation is proposed for the maxima in the dielectric constant and density observed in liquid helium slightly above the superfluid transition temperature. It is shown that they may be caused by a phase transition that results in spontaneous polarization of the helium. This kind of transition is possible in the liquid because when an atom is polarized its energy levels are lowered, so that the polarization is energetically favorable, especially for light atoms. In addition, the development of a dipole moment in an atom leads to the appearance of an additional electric field and, therefore, to an increase in the energy. The possible spontaneous polarization of the system of atoms is determined by the competition among these factors. In accordance with this concept, as the temperature of liquid helium is lowered there is an initial phase transition into a polarized normal phase, followed by one from this nonzero polarization state into the superfluid state. The transition of the normal fluid into the polarized phase is described in terms of a phenomenological theory of phase transitions. The transition can be of first or second order.

Poluektov, Yu. M.; Rybalko, A. S.

2013-09-01

17

Synthesis and Liquid Crystal Phase Transitions of Zirconium Phosphate Disks  

E-print Network

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

Shuai, Min

2013-05-07

18

Liquid-liquid phase transitions and water-like anomalies in liquids  

NASA Astrophysics Data System (ADS)

In this thesis we employ computer simulations and statistical physics to understand the origin of liquid-liquid phase transitions and their relationship with anomalies typical of liquid water. Compared with other liquids, water has many anomalies. For example the density anomaly: when water is cooled below 4 °C the density decreases rather than increases. This and other anomalies have also been found to occur in a few other one-component liquids, sometimes in conjunction with the existence of a liquid-liquid phase transition (LLPT) between a low-density liquid (LDL) and a high-density liquid (HDL). Using simple models we explain how these anomalies arise from the presence of two competing length scales. As a specific example we investigate the cut ramp potential, where we show the importance of "competition" in this context, and how one length scale can sometimes be zero. When there is a clear energetic preference for either LDL or HDL for all pressures and temperatures, then there is insufficient competition between the two liquid structures and no anomalies occur. From the simple models it also follows that anomalies can occur without the presence of a LLPT and vice versa. It remains therefore unclear if water has a LLPT that ends in a liquid-liquid critical point (LLCP), a hypothesis that was first proposed based on simulations of the ST2 water model. We confirm the existence of a LLCP in this model using finite size scaling and the Challa-Landau-Binder parameter, and show that the LLPT is not a liquid-crystal transition, as has recently been suggested. Previous research has indicated the possible existence of a LLCP in liquid silica. We perform a detailed analysis of two different silica models (WAC and BKS) at temperatures much lower than was previously simulated. Within the accessible temperature range we find no LLCP in either model, although in the case of WAC potential it is closely approached. We compare our results with those obtained for other tetrahedral liquids and conclude that insufficient "stiffness" in the Si-O-Si bond angle might be responsible for the absence of a LLCP.

Lascaris, Erik

19

Effect of dimensionality on vapor-liquid phase transition  

SciTech Connect

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

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

2014-04-24

20

Modeling the solid-liquid phase transition in saturated triglycerides  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

21

Quantum phase transitions in semilocal quantum liquids  

NASA Astrophysics Data System (ADS)

We consider several types of quantum critical phenomena from finite-density gauge-gravity duality which to different degrees lie outside the Landau-Ginsburg-Wilson paradigm. These include: (i) a "bifurcating" critical point, for which the order parameter remains gapped at the critical point, and thus is not driven by soft order parameter fluctuations. Rather it appears to be driven by "confinement" which arises when two fixed points annihilate and lose conformality. On the condensed side, there is an infinite tower of condensed states and the nonlinear response of the tower exhibits an infinite spiral structure; (ii) a "hybridized" critical point which can be described by a standard Landau-Ginsburg sector of order parameter fluctuations hybridized with a strongly coupled sector; (iii) a "marginal" critical point which is obtained by tuning the above two critical points to occur together and whose bosonic fluctuation spectrum coincides with that postulated to underly the "Marginal Fermi Liquid" description of the optimally doped cuprates.

Iqbal, Nabil; Liu, Hong; Mezei, Márk

2015-01-01

22

The spatial stochastization of optical radiation scattered by liquid crystal in the process of phase transition  

NASA Astrophysics Data System (ADS)

This paper represents the investigation results of spatial chaotization of optical field scattered by liquid crystals during phase transition liquid - liquid crystal under electric field. Two stochastic parameters of the field, namely, Lyapunov's maximal index and correlation exponent was chosen for this study. It has been established that maximum variances of phase inhomogeneities of the nematic liquid crystal corresponds to maximum fluctuations of order parameter under temperature of phase transition liquid - liquid crystal. Was found that analysis of the radiation field scattered during the phase transition process the liquid-liquid crystal allows to accurately determine the phase transition temperature and voltage of forming Williams's domains.

Gavrylyak, M. S.; Maksimyak, P. P.

2014-09-01

23

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

2012-05-01

24

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

PubMed

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

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

2010-09-28

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

2009-07-24

26

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

NASA Astrophysics Data System (ADS)

Most liquids can form a single glass or amorphous state when cooled sufficiently fast (in order to prevent crystallization). However, there are a few substances that are relevant to scientific and technological applications which can exist in at least two different amorphous states, a property known as polyamorphism. Examples include silicon, silica, and in particular, water. In the case of water, experiments show the existence of a low-density (LDA) and high-density (HDA) amorphous ice that are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation evolves into a first-order liquid-liquid phase transition (LLPT) at temperatures above the glass transition temperature Tg. However, obtaining direct experimental evidence of the LLPT has been challenging since the LLPT occurs at conditions where water rapidly crystallizes. In this talk, I will (i) discuss the general phenomenology of polyamorphism in water and its implications, and (ii) explore the effects of a LLPT on the pressure dependence of Tg(P) for LDA and HDA. Our study is based on computer simulations of two water models -- one with a LLPT (ST2 model), and one without (SPC/E model). In the absence of a LLPT, Tg(P) for all glasses nearly coincide. Instead, when there is a LLPT, different glasses exhibit dramatically different Tg(P) loci which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario that includes a LLPT (ST2 model) and hence, our results support the view that a LLPT may exist for the case of water.

Giovambattista, Nicolas

2013-03-01

27

Liquid-Liquid Phase Transitions in Tetrahedrally Coordinated Fluids via Wertheim Theory.  

PubMed

Network interpenetration has been proposed as a mechanism for generating liquid-liquid phase transitions in one component systems. We introduce a model of four coordinated particles, which explicitly treats the system as a mixture of two interacting interpenetrating networks that can freely exchange particles. This model can be solved within Wertheim's theory for associating fluids and shows liquid-liquid phase separations (in addition to the gas-liquid) for a wide range of model parameters. We find that originating a liquid-liquid transition requires a small degree of interpenetrability and a preference for intranetwork bonding. Physically, these requirements can be seen as controlling the softness of the particle-particle interaction and the bond flexibility, in full agreement with recent findings [Smallenburg, F.; Filion, L.; Sciortino, F. Nat. Phys. 2014, 10, 653]. PMID:25384011

Smallenburg, Frank; Filion, Laura; Sciortino, Francesco

2014-11-10

28

Synthesis and liquid crystal phase transitions of zirconium phosphate disks  

NASA Astrophysics Data System (ADS)

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

Shuai, Min

29

Liquid-liquid phase transition and structure inheritance in carbon films  

PubMed Central

Molecular dynamics simulations are performed to study the cooling process of quasi-2D liquid carbon. Our results show an obvious liquid-liquid phase transition (LLPT) from the twofold coordinated liquid to the threefold coordinated liquid with the decrease of temperature, followed by a liquid-solid phase transition (LSPT). The LLPT can be regarded as the preparation stage of LSPT. During the cooling process, the chain structures firstly self-assemble into some ring structures and then aggregate into some stable islands which can further connect together to form a complete polycrystalline film. The threefold coordinated structures play an important role in the formation of atomic rings. The inheritance of the threefold coordinated structures provides essential condition to form rings and islands. PMID:24407276

He, Yezeng; Li, Hui; Jiang, Yanyan; Li, Xiongying; Bian, Xiufang

2014-01-01

30

Liquid-liquid phase transition and structure inheritance in carbon films  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations are performed to study the cooling process of quasi-2D liquid carbon. Our results show an obvious liquid-liquid phase transition (LLPT) from the twofold coordinated liquid to the threefold coordinated liquid with the decrease of temperature, followed by a liquid-solid phase transition (LSPT). The LLPT can be regarded as the preparation stage of LSPT. During the cooling process, the chain structures firstly self-assemble into some ring structures and then aggregate into some stable islands which can further connect together to form a complete polycrystalline film. The threefold coordinated structures play an important role in the formation of atomic rings. The inheritance of the threefold coordinated structures provides essential condition to form rings and islands.

He, Yezeng; Li, Hui; Jiang, Yanyan; Li, Xiongying; Bian, Xiufang

2014-01-01

31

Cluster Monte Carlo and numerical mean field analysis for the water liquid--liquid phase transition  

E-print Network

By the Wolff's cluster Monte Carlo simulations and numerical minimization within a mean field approach, we study the low temperature phase diagram of water, adopting a cell model that reproduces the known properties of water in its fluid phases. Both methods allows us to study the water thermodynamic behavior at temperatures where other numerical approaches --both Monte Carlo and molecular dynamics-- are seriously hampered by the large increase of the correlation times. The cluster algorithm also allows us to emphasize that the liquid--liquid phase transition corresponds to the percolation transition of tetrahedrally ordered water molecules.

Marco G. Mazza; Kevin Stokely; Elena Strekalova; H. Eugene Stanley; Giancarlo Franzese

2009-01-20

32

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

E-print Network

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

Mazur, Eric

33

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

34

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

NASA Technical Reports Server (NTRS)

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

Clark, Noel A.

2000-01-01

35

Evidence of a liquid–liquid phase transition in hot dense hydrogen  

PubMed Central

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.

2013-01-01

36

Experimental signals of a nuclear liquid-gas phase transition  

NASA Astrophysics Data System (ADS)

The critical phenomenon of the nuclear liquid-gas phase transition has been investigated in the reactions 64Zn+64Zn, 64Ni+64Ni and 70Zn+70Zn at beam energy of 35 MeV/nucleon. Yields of fragments arising from fragmenting quasi-projectiles (QPs) with different neutron-proton asymmetries were analyzed within the framework of the Landau free energy approach. Fits to the free energy of fragments as a function of fragment asymmetry showed three minima, indicating the system to be in a regime of a first-order phase transition. The QP temperature estimates were extracted from the analysis of N=Z fragment data. Additionally, we make use of a recent method based on quantum fluctuations of fermions to derive temperatures and densities of selected QPs. Critical scaling of these observables is found for systems which differ in neutron to proton asymmetry. The derived critical exponent ? = 0.35 ± 0.01, belongs to the liquid-gas universality class.

Mabiala, J.; Bonasera, A.; Zheng, H.; McIntosh, A. B.; Kohley, Z.; Cammarata, P.; Hagel, K.; Heilborn, L.; May, L. W.; Raphelt, A.; Souliotis, G. A.; Zarrella, A.; Yennello, S. J.

2013-03-01

37

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

PubMed

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

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

2014-09-01

38

Indication of liquid-liquid phase transition in CuZr-based melts  

NASA Astrophysics Data System (ADS)

We study the dynamic behavior of CuZr-based melts well above the liquidus temperature. The results show a discontinuous change in viscosity during cooling, which is attributed to an underlying liquid-liquid phase transition (LLPT) in these melts. The LLPT is further verified by thermodynamic response in the same temperature region. We find that the LLPT in the Cu46Zr46Al8 melt is reversible above 1350 K upon repeated heating and cooling. Based on the concept of fluid cluster in metallic melts, the reversible LLPT is attributed to the structural transition from the strongly ordered high-density liquids to the weak-local low-density liquids upon cooling.

Zhou, Chao; Hu, Lina; Sun, Qijing; Qin, Jingyu; Bian, Xiufang; Yue, Yuanzheng

2013-10-01

39

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

SciTech Connect

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

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

1985-12-23

40

Successive Phase Transitions in Antiferroelectric Liquid Crystal Systems  

E-print Network

An axial next-nearest-neighbor XY model is studied as a model of chiral liquid crystals which exhibit many ferro-, ferri- and antiferroelectric tilted smectic phases. Depending on the values of interaction parameters, this model exhibits Ising symmetric (i.e., the tilt directions of directors are parallel or anti parallel) phases or XY symmetric phases. Phases with each type-of-symmetry show the character of devil's staircase, which has been observed in experiments.

Masaya Koroishi; Masashi Torikai; Mamoru Yamashita

2005-10-03

41

Phase transitions and transient liquid-phase sintering in calcium-substituted lanthanum chromite  

SciTech Connect

This paper investigates sintering and phase transitions of La{sub 0.7}Ca{sub x}CrO{sub 3} (0.25 {le} x {le} 0.35), a material useful as electrical interconnections in solid oxide fuel cells. Heating of the quenched, metastable single-phase chromite resulted in exsolution of CaCrO{sub 4} due to Ca solubility limitations below 1,200 C. A transient liquid phase formed between 850 and 1,000 C as the CaCrO{sub 4} melted, causing partial densification in materials having 0.25 < x < 0.30. A slight increase in Ca content induced an additional liquid-phase sintering event, likely due to melting of Ca{sub 3}(CrO{sub 4}){sub 2}, which facilitated near-complete densification by 1,250 C. After enhancing sintering, the secondary phases redissolved into the chromite.

Chick, L.A.; Liu, J.; Stevenson, J.W.; Armstrong, T.R.; McCready, D.E.; Maupin, G.D.; Coffey, G.W.; Coyle, C.A. [Pacific Northwest National Lab., Richland, WA (United States). Materials and Chemical Sciences Dept.

1997-08-01

42

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

43

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

44

Possible links between the liquid-gas and deconfinement-hadronization phase transitions  

E-print Network

It is commonly accepted that strongly interacting matter has several phase transitions in different domains of temperature and baryon density. In this contribution I discuss two most popular phase transitions which in principle can be accessed in nuclear collisions. One of them, the liquid-gas phase transition, is well established theoretically and studied experimentally in nuclear multifragmentation reactions at intermediate energies. The other one, the deconfinement-hadronization phase transition, is at the focus of present and future experimental studies with relativistic heavy-ion beams at SPS, RHIC and LHC. Pssible links between these two phase transitions are identified from the viewpoint of their manifestation in violent nuclear collisions.

I. N. Mishustin

2006-09-19

45

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

E-print Network

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

Bharat K. Sharma; Subrata Pal

2010-01-14

46

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

E-print Network

into surface anchoring. Over the past decade, a variety of polymer/liquid-crystal dispersions have beenLiquid-crystal-anchoring transitions at surfaces created by polymerization-induced phase separation-dispersed liquid-crystal films is explained, and observations provide a pathway to control properties. S1063-651X

Srinivasarao, Mohan

47

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

48

On the Maximal Deviation from the Mirror Image Approximation due to Solid Liquid Phase Transition  

NASA Astrophysics Data System (ADS)

We extend the Walsh and Christian (1955) analysis in a manner which allows a reasonable estimation of the expected deviation from the mirror image approximation due to solid liquid phase transition. This estimate is limited to a phase transition that occurs at shock unloading. This analysis provides a good estimate to metals with low melting pressure such as Tin and Lead.

Pistinner, S. L.; Pecker, S.; Werdiger, M.; Eliezer, S.

2007-12-01

49

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

E-print Network

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

Grover, Tarun

50

Multicanonical Markov chain Monte Carlo simulation of nematic-isotropic phase transition in liquid crystals  

NASA Astrophysics Data System (ADS)

Temperature driven first order transition from isotropic to nematic phase in liquid crystals with and without random and quenched orientational disorder is investigated employing multicanonical Monte Carlo simulation. A lattice model with periodic boundary conditions is employed with the pair wise interaction of two nearest neighbor liquid crystal molecules given by the Lebwohl-Lasher potential. The transition temperature decreases with increase of disorder; also the transition appears to soften under strong disorder.

Chakravarthy, A. K.; Venu, K.; Sastry, V. S. S.; Murthy, K. P.

2004-09-01

51

Ab initio investigation of a possible liquid-liquid phase transition in MgSiO3 at megabar pressures  

NASA Astrophysics Data System (ADS)

We perform density functional molecular dynamics simulations of liquid and solid MgSiO3 in the pressure range of 120-1600 GPa and for temperatures up to 20,000 K in order to provide new insight into the nature of the liquid-liquid phase transition that was recently predicted on the basis of decaying laser shock wave experiments [Phys. Rev. Lett. 108 (2012) 065701]. However, our simulations did not show any signature of a phase transition in the liquid phase. We derive the equation of state for the liquid and solid phases and compute the shock Hugoniot curves. We discuss different thermodynamic functions and by explore alternative interpretations of the experimental findings.

Militzer, Burkhard

2013-03-01

52

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

53

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

54

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

E-print Network

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

Lavrentovich, Oleg D.

55

Crossover from a Kosterlitz-Thouless phase transition to a discontinuous phase transition in two-dimensional liquid crystals.  

PubMed

Liquid crystals in two dimensions do not support long-range nematic order, but a quasinematic phase where the orientational correlations decay algebraically is possible. The transition from the isotropic to the quasinematic phase can be continuous and of the Kosterlitz-Thouless type, or it can be first order. We report here on a liquid-crystal model where the nature of the isotropic to quasinematic transition can be tuned via a single parameter p in the pair potential. For ptransition is of the Kosterlitz-Thouless type, while for p>p(t), it is first order. Precisely at p=p(t), there is a tricritical point where, in addition to the orientational correlations, also the positional correlations decay algebraically. The tricritical behavior is analyzed in detail, including an accurate estimate of p(t). The results follow from extensive Monte Carlo simulations combined with a finite-size scaling analysis. Paramount in the analysis is a scheme to facilitate the extrapolation of simulation data in parameters that are not necessarily field variables (in this case, the parameter p), the details of which are also provided. This scheme provides a simple and powerful alternative for situations where standard histogram reweighting cannot be applied. PMID:25615069

Vink, Richard L C

2014-12-01

56

Crossover from a Kosterlitz-Thouless phase transition to a discontinuous phase transition in two-dimensional liquid crystals  

NASA Astrophysics Data System (ADS)

Liquid crystals in two dimensions do not support long-range nematic order, but a quasinematic phase where the orientational correlations decay algebraically is possible. The transition from the isotropic to the quasinematic phase can be continuous and of the Kosterlitz-Thouless type, or it can be first order. We report here on a liquid-crystal model where the nature of the isotropic to quasinematic transition can be tuned via a single parameter p in the pair potential. For p transition is of the Kosterlitz-Thouless type, while for p >pt , it is first order. Precisely at p =pt , there is a tricritical point where, in addition to the orientational correlations, also the positional correlations decay algebraically. The tricritical behavior is analyzed in detail, including an accurate estimate of pt. The results follow from extensive Monte Carlo simulations combined with a finite-size scaling analysis. Paramount in the analysis is a scheme to facilitate the extrapolation of simulation data in parameters that are not necessarily field variables (in this case, the parameter p ), the details of which are also provided. This scheme provides a simple and powerful alternative for situations where standard histogram reweighting cannot be applied.

Vink, Richard L. C.

2014-12-01

57

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

SciTech Connect

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

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

2014-10-15

58

Liquid-Liquid Phase Transition of Protein Aqueous Solutions Isothermally Induced by Protein Cross-Linking  

E-print Network

-induced phase transitions have been extensively studied to understand and control phase morphologies.1-8 Polymerization reactions also involve large molecules such as proteins. For example, actin9 and sickle

Annunziata, Onofrio

59

Study on liquid-liquid phase transitions of gallium at high pressure and temperature with x-ray microtomography  

NASA Astrophysics Data System (ADS)

There are three crystalline structures for a solid state under ambient condition for gallium. Local structures in melts trend to show short range ordering within a few tenths of a nanometer, which are often considered to be correlated with the atomic arrangements of their solid counterparts. For non-crystalline samples, such as amorphous materials and melts, Due to their lack of periodicity, diffraction patterns from amorphous and liquid phases are very broad; therefore, it is challenging to obtain density information under high-pressure conditions. On the other hand, x-ray microtomography can provide density and geometry information on samples regardless of their crystallinity. Synchrotron x-ray microtomography enables us to carry out in situ density measurements on liquids at high pressures. Thus, we can address whether there are liquid-liquid phase transitions of gallium and better understand the physical processes of phase transitions.

li, R.; li, L.; Rivers, M. L.; Liu, H.

2013-12-01

60

The liquid?amorphous transition and the high pressure phase diagram of carbon  

NASA Astrophysics Data System (ADS)

The phase diagram of carbon is mapped to high pressure using a computationally-tractable potential model. The use of a relatively simple (Tersoff-II) potential model allows a large range of phase space to be explored. The coexistence (melting) curve for the diamond crystal/liquid dyad is mapped directly by modelling the solid/liquid interfaces. The melting curve is found to be re-entrant and belongs to a conformal class of diamond/liquid coexistence curves. On supercooling the liquid a phase transition to a tetrahedral amorphous form (ta-C) is observed. The liquid ? amorphous coexistence curve is mapped onto the pT plane and is found to also be re-entrant. The entropy changes for both melting and the amorphous ? liquid transitions are obtained from the respective coexistence curves and the associated changes in molar volume. The structural change on amorphization is analysed at different points on the coexistence curve including for transitions that are both isochoric and isocoordinate (no change in nearest-neighbour coordination number). The conformal nature of the melting curve is highlighted with respect to the known behaviour of Si. The relationship of the observed liquid/amorphous coexistence curve to the Si low- and high-density amorphous (LDA/HDA) transition is discussed.

Robinson, David R.; Wilson, Mark

2013-04-01

61

Dynamic Transition Theory and its Application to Gas-Liquid Phase Transitions  

E-print Network

for the complete set of transition states. With this philosophy, a dynamic transition theory is developed under, then the steady state equation reduces to the van der Waals equation. 8 #12;III. Phase Transition Dynamics for PVT of equations = 0 critical parameter eq a2 = 0 -(bp + RT)0 + a2 0 - ab3 0 + p = 0 steady state eq (van der

Wang, Shouhong

62

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

E-print Network

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

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

2005-06-19

63

Tactoids and Defects in Nematic-Isotropic Phase Transition in Lyotropic Chromonic Liquid Crystal  

NASA Astrophysics Data System (ADS)

We explore the structure of nuclei (tactoids) and topological defects (disclinations) in the first-order nematic-isotropic phase transition in self-assembled lyotropic chromonic liquid crystals. The shape of tactoids is determined by orientational elasticity of the liquid crystal, surface tension, and surface anchoring of the director. The positive tactoids (nuclei of the nematic phase) show two pointed ends (cusps). The negative tactoids (nuclei of the isotropic phase) show a variety of shapes, with one, two, or three cusps, depending on whether they nucleate at the core of disclinations of strength 1/2, in a homogeneous nematic, or at the core of a (-1/2) disclination, respectively. Zero-cusp and four-cusp formations are also possible at the core of stabilized disclinations of strength 1 and -1, respectively. The results demonstrate a profound role of surface tension and its anisotropy in the morphological dynamics of phase transitions in liquid crystals.

Kim, Young-Ki; Lavrentovich, Oleg D.

2013-03-01

64

A pressure-induced phase-transition from liquid to solid in Water  

Microsoft Academic Search

In connection with recent isentropic experiments on water where a functionally graded impactor in a light-gas gun is used to systematically probe the high-pressure meltline for water, hydrodynamic simulations of water undergoing a pressure-induced phase transition into its ice phase are presented. From a well defined set of initial conditions, the liquid system is isentropically compressed into its solid phase,

Daniel Orlikowski

2005-01-01

65

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

66

Fragmentation Phase Transition in Atomic Clusters IV -- Liquid-gas transition in finite metal clusters and in the bulk --  

E-print Network

Within the micro-canonical ensemble phase transitions of first order can be identified without invoking the thermodynamic limit. We show for the liquid-gas transition of sodium, potassium, and iron at normal pressure that the transition temperature, the latent heat as well as the interface surface tension approach for some 1000 atoms the experimental bulk values. No excursion to the thermodynamic limit is neccessary. It is often easier to identify the transition in mesoscopic systems than in the infinite system. It is shown that the microcanonical T(E) contains important information about the transition which becomes suppressed in the canonical ensemble. The implications for our understanding of phase transitions in general are discussed. For these finite metallic systems it is essential to allow for a fragmentation of the system. Our result demonstrates further that microcanonical Metropolis Monte Carlo sampling (MMMC) is well suited to establish the link between the fragmentation phase transition in small systems like nuclei and atomic clusters and the liquid-gas transition of infinite matter.

D. H. E. Gross; M. E. Madjet

1997-07-25

67

Liquid Crystal Phase Transitions in Systems of Colloidal Platelets with Bimodal Shape Distribution  

E-print Network

ARTICLES Liquid Crystal Phase Transitions in Systems of Colloidal Platelets with Bimodal Shape 17, 2009 We have studied a system of polydisperse, charged colloidal gibbsite platelets of thick and thin hard platelets for various thickness ratios. The predictions are based on the Onsager

Utrecht, Universiteit

68

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

E-print Network

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

Peter O. Fedichev; Leonid I. Menshikov

2012-01-30

69

Isospin and momentum dependence of liquid-gas phase transition in hot asymmetric nuclear matter  

E-print Network

The liquid-gas phase transition in hot neutron-rich nuclear matter is investigated within a self-consistent thermal model using different interactions with or without isospin and/or momentum dependence. The boundary of the phase-coexistence region is shown to be sensitive to the density dependence of the nuclear symmetry energy as well as the isospin and momentum dependence of the nuclear interaction.

Jun Xu; Lie-Wen Chen; Bao-An Li; Hong-Ru Ma

2007-11-12

70

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

E-print Network

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

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

2011-01-01

71

Electric field effect on phase transitions in liquid-crystalline blue-phase systems  

Microsoft Academic Search

The influence of an electric field on the phase-transition temperatures of cholesterogenic mixtures CB 15\\/M 18 exhibiting blue phases (BP) has been investigated. From temperature-voltage phase diagrams it can be seen that the transition temperature BP I\\/cholesteric depends on the field strength E, whereas that of BP II\\/cholesteric does not. The effect DeltaT(E) can be understood by means of the

H. Stegemeyer; F. Porsch

1984-01-01

72

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

73

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

SciTech Connect

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

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

2014-11-14

74

Phases and Phase Transitions  

NASA Astrophysics Data System (ADS)

In discussing phase transitions, the first thing that we have to do is to define a phase. This is a concept from thermodynamics and statistical mechanics, where a phase is defined as a homogeneous system. As a simple example, let us consider instant coffee. This consists of coffee powder dissolved in water, and after stirring it we have a homogeneous mixture, i.e., a single phase. If we add to a cup of coffee a spoonful of sugar and stir it well, we still have a single phase -- sweet coffee. However, if we add ten spoonfuls of sugar, then the contents of the cup will no longer be homogeneous, but rather a mixture of two homogeneous systems or phases, sweet liquid coffee on top and coffee-flavored wet sugar at the bottom...

Gitterman, Moshe

2014-09-01

75

Polyamorphism and polymorphism of a confined water monolayer: liquid-liquid critical point, liquid-crystal and crystal-crystal phase transitions  

NASA Astrophysics Data System (ADS)

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

Bianco, Valentino; Vilanova, Oriol; Franzese, Giancarlo

2014-03-01

76

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

SciTech Connect

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

X. Wang; X. Sun; H. Zhao

2011-09-01

77

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

78

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

2014-03-01

79

Critical behavior at the isotropic to nematic phase transition in a bent-core liquid crystal  

NASA Astrophysics Data System (ADS)

Magnetic birefringence and dynamic light scattering measurements of orientational order parameter fluctuations at the isotropic- nematic phase transition of a bent-core liquid crystal reveal a pretransitional temperature dependence consistent with the standard Landau-deGennes mean field theory. However, the transition in the bent-core compound is more weakly first-order (TNI-T^* 0.4^oC), the leading Landau coefficient is ˜10 times lower, and the viscosity associated with nematic order fluctuations is ˜50 times higher, than typically observed in calamitic (rod- shaped) liquid crystals. These anomalies can be explained by an unconventional optically isotropic phase composed of complexes of bent-core molecules. Also, we will present preliminary magnetic birefringence and density measurements at temperatures above the nematic-isotropic transistion which support the existence of an optically isotropic state.

Wiant, David; Stojadinovic, Strahinja; Neupane, Krishna; Sharma, Sunil; Fodor-Csorba, Katalin; Jakli, Antal; Gleeson, James; Sprunt, Samuel

2006-03-01

80

Structure and phase transitions into ionic adsorption layers on liquid interfaces  

E-print Network

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

R. Tsekov

2014-10-25

81

Thermally enhanced optical nonlinearity in nematic liquid crystal close to phase transition temperature  

NASA Astrophysics Data System (ADS)

This study investigates the beam profile and the liquid crystal (LC) arrangement affected by an optical field on LC thin films at a temperature close to nematic-isotropic phase transition temperature ( TNI). A combined microscopic and conoscopic technique was used in experiments as a convenient way to analyze the optical nonlinearity that is associated with the molecular configuration of nematic liquid crystal (NLC). An optical field combined with thermal enhancement enhances molecular reorientation and causes additional molecular excitation along the axis of propagation of the beam. The reorientational nonlinearity yields an undulating structure with multi-foci; the length between each pair of foci increases with time, as described.

Shih, Chia-Chi; Chen, Yu-Jen; Hung, Wen-Chi; Jiang, I.-Min; Tsai, Ming-Shan

2010-09-01

82

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

83

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

84

Vibrational spectra of OC?HCl complex in Kr solutions at liquid to solid phase transition  

NASA Astrophysics Data System (ADS)

Fundamental and first overtone bands of HCl, CO molecules and OC⋯HCl complex were studied in liquid and solid Kr solution near the phase transition. Triplet to doublet shape transformations were observed for both fundamental ?(HCl) and first overtone 2 ?(HCl) bands at liquid to crystal state transition. Self-association processes of HCl in Kr solutions have resulted in the registration of two to several new sharp peaks on the low frequency P branch of the ?(HCl) band, whereas they only gave an additional diffuse absorption on the P branch of the 2 ?(HCl) band. Evolution of the ?(CO) and 2 ?(CO) bands, observed at temperature lowering of liquid Kr solution, has shown an increased restriction of the rotational motion of CO in an orienting field of the nearest neighbors. Triplet to singlet shape transformation was found for both the CO bands at liquid to crystal state transition. Asymmetry of the central parts of the bands and high frequency shoulder, which are increased at temperature lowering of the solids, suggest the consecutive transformation of orientational motion of CO into libration and growth of vibrational-translational coupling in CO doped low temperature Kr crystal. OC⋯HCl complex formation with a weak intermolecular H-bond were studied by observation of the red shifted ?c(HCl) band and of the blue shifted ?c(CO) and 2 ?c(CO) sharp bands in the solid state. Spectral parameters of dimer bands were estimated.

Rutkowski, K. S.; Melikova, S. M.

1999-11-01

85

Dynamical phase transitions in supercooled liquids: Interpreting measurements of dynamical activity  

NASA Astrophysics Data System (ADS)

We study dynamical phase transitions in a model supercooled liquid. These transitions occur in ensembles of trajectories that are biased towards low (or high) dynamical activity. We compare two different measures of activity that were introduced in recent papers and we find that they are anti-correlated with each other. To interpret this result, we show that the two measures couple to motion on different length and time scales. We find that "inactive" states with very slow structural relaxation nevertheless have increased molecular motion on very short scales. We discuss these results in terms of the potential energy landscape of the system and in terms of the liquid structure in active/inactive states.

Fullerton, Christopher J.; Jack, Robert L.

2013-06-01

86

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

2014-07-01

87

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

E-print Network

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

Yi, Liting; Liu, Jing

2013-01-01

88

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

PubMed

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

Zhao, Tongyang; Wang, Xiaogong

2013-01-14

89

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

E-print Network

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

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

2008-01-29

90

Noncongruence of the nuclear liquid-gas and deconfinement phase transitions  

NASA Astrophysics Data System (ADS)

First-order phase transitions (PTs) with more than one globally conserved charge, so-called noncongruent PTs, have characteristic differences compared to congruent PTs (e.g., dimensionality of phase diagrams and location and properties of critical points and end points). In the present article we investigate the noncongruence of the nuclear liquid-gas PT at subsaturation densities and the deconfinement PT at high densities and/or temperatures in Coulombless models, relevant for heavy-ion collisions and neutron stars. For the first PT, we use the FSUgold relativistic mean-field model and for the second one the relativistic chiral SU(3) model. The chiral SU(3) model is one of the few models for the deconfinement PT, which contains quarks and hadrons in arbitrary proportions (i.e., a “solution”) and gives a continuous transition from pure hadronic to pure quark matter above a critical point. The study shows the universality of the applied concept of noncongruence for the two PTs with an upper critical point and illustrates the different typical scales involved. In addition, we find a principle difference between the liquid-gas and the deconfinement PTs: in contrast to the ordinary Van-der-Waals-like PT, the phase coexistence line of the deconfinement PT has a negative slope in the pressure-temperature plane. As another qualitative difference we find that the noncongruent features of the deconfinement PT become vanishingly small around the critical point.

Hempel, Matthias; Dexheimer, Veronica; Schramm, Stefan; Iosilevskiy, Igor

2013-07-01

91

Liquid crystal phase transitions of monodisperse and bidisperse suspensions of rodlike colloidal virus  

NASA Astrophysics Data System (ADS)

We experimentally study the role of steric and electrostatic interparticle interactions in monodisperse and bidisperse suspensions of rodlike colloids. For our model system we used aqueous suspensions of the charged semiflexible filamentous bacteriophages fd and M13. In solution, these particles undergo entropically driven liquid crystal phase transitions from isotropic to cholesteric (or chiral-nematic) to smectic phases with increasing concentration. For the monodisperse suspensions, we present as a function of ionic strength, measurements of the role of flexibility and surface charge on the transitions between these phases. We also present the evolution of the helical pitch of the cholesteric phase with concentration as a function of solution ionic strength and particle surface charge in order to understand the coupling between ionic strength and surface charge in the expression of chirality in the nematic phase. Unwinding and aligning the chiral-nematic phase in a magnetic field allowed us to measure the nematic ordering of fd as a function of rod concentration and solution ionic strength. The nematic orientational distribution function was measured using x-ray diffraction and birefringence techniques. Results were compared with available theoretical predictions for charged flexible rods. Measurements of the phase behavior consistently show unexpected behavior at low ionic strengths, where electrostatic repulsion is poorly screened, and good agreement with theoretical predictions at high ionic strength, where electrostatic interactions are well screened. For the bidisperse suspensions we measured the phase behavior mixtures of fd and fd coated with poly (ethylene-glycol): two particles of identical length and different diameter. When the diameters differ significantly these mixtures exhibit isotropic-cholesteric, cholesteric-cholesteric and isotropic-cholesteric-cholesteric coexistence. Measured phase diagrams were compared to predictions for binary rod phase behavior.

Purdy, Kirstin Rachael

92

Phase transitions in nuclear physics  

SciTech Connect

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

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

1997-08-01

93

Liquid-Solid Phase Transition of Benzene under Shock Compression Stuided by Time-Resolved Nonlinear Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

The liquid-solid phase transition of benzene has been studied under laser-shock compression up to 4.2 GPa by using nanosecond time-resolved nonlinear Raman spectroscopy. A shock wave is generated by irradiation of 10-ns pulsed laser beam on the plasma confinement target and its pressure is estimated from the particle velocity, which is measured by a velocity interferometer. The ring-breathing mode shows blue shift under shock compression. Nanosecond time-resolved nonlinear Raman spectra show a rapid phase transition from liquid phase to solid phase under shock compression.

Nakamura, K. G.; Matsuda, A.; Kondo, K.

2006-07-01

94

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

SciTech Connect

In modeling gas-liquid two-phase flows, the concept of flow regimes has been widely used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are flow regime dependent. Current nuclear reactor safety analysis codes, such as RELAP5, classify flow regimes using flow regime maps or transition criteria that were developed for steady-state, fully-developed flows. As twophase flows are dynamic in nature, it is important to model the flow regime transitions dynamically to more accurately predict the two-phase flows. The present work aims to develop a dynamic modeling strategy to determine flow regimes in gas-liquid two-phase flows through introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation of the interfacial area, fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation, and the destruction of the interfacial area, fluid particle coalescence and condensation. For flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shapes, namely group-1 and group-2 bubbles. A preliminary approach to dynamically identify the flow regimes is discussed, in which discriminator s are based on the predicted information, such as the void fraction and interfacial area concentration. The flow regime predicted with this method shows good agreement with the experimental observations.

Xia Wang; Xiaodong Sun; Benjamin Doup; Haihua Zhao

2012-12-01

95

Multifragmentation and the liquid-gas phase transition: an experimental overview  

NASA Astrophysics Data System (ADS)

Two roads are presently being followed in order to establish the existence of a liquid- gas phase transition in finite nuclear systems from nuclear reactions at high energy. The clean experiment of observing the thermodynamic properties of a finite number of nucleons in a container is presently only possible with the computer. Performed with advanced nuclear transport models, it has revealed the first-order character of the transition and allowed the extraction of the pertinent thermodynamic parameters. The validity of the applied theory is being confirmed by comparing its predictions for heavy-ion reactions with exclusive experiments. The second approach is experimentally more direct. Signals of the transition are searched for by analysing reaction data within the framework of thermodynamics of small systems. A variety of potential signals has been investigated and found to be qualitatively consistent with the expectations for the phase transition. Many of them are well reproduced with percolation models which places the nuclear fragmentation into the more general context of partitioning phenomena in finite systems. A wealth of new data on this subject has been obtained in recent experiments, some of them with a new generation of multi-detector devices aiming at higher resolutions, isotopic identification of the fragments, and the coincident detection of neutrons. Isotopic effects in multifragmentation were addressed quite intensively, with particular attention being given to their relation to the symmetry energy and its dependence on density.

Trautmann, W.

2005-04-01

96

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

97

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

98

An Estimate for the Deviation from the Mirros Image Due to Solid Liquid Phase Transition of Metals at Shock Unloading.  

NASA Astrophysics Data System (ADS)

We extend the underlying physical reasoning of Walsh and Christian (1955) in a manner which allows a reasonable estimation for the excepted deviation from the mirror image approximation due to solid liquid phase transition. This estimated is limited to a phase transition that occurs at the unloading phase in metals such as Tin and Lead. The idea underlying this estimate is the accumulation of various contributions to the entropy and an estimation of the expected expansion at atmospheric pressure. These estimates combined with the Lindmann melting law and the Clausius Clyperon equation are used to estimate the expansion at the phase transition and the resulting change in free surface velocity.

Pistinner, Shlomi; Peker, Sharon; Werdiger, Meir; Eliezer, Shalom

2007-06-01

99

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

E-print Network

, the polymer may display the liquid crystallinity with the azobenzene groups forming the mesophases. Liquid wavelengths.20,21 Since the confinement may have profound effects on liquid crystal ordering and phase of Liquid Crystalline Azobenzene-Containing Diblock Copolymers Xia Tong, Li Cui, and Yue Zhao* De

Zhao, Yue

100

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

101

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

102

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

E-print Network

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

Sciortino, Francesco

103

Reentrant nematic and tricritical behavior of the nematic to smectic-A phase transition in liquid crystal mixture  

NASA Astrophysics Data System (ADS)

We present an improved analysis of the reentrant nematic and tricritical behavior of the nematic to smectic A phase transition in liquid crystal mixture within phenomenological theory. To describe the nematic-smectic A-reentrant nematic phase sequence in binary mixture, nematic and smectic order parameters have been coupled with the concentration. We show that reentrant nematic and the tricritical point on the N-SmA phase transition line can be achieved in the same phase diagram under certain conditions. We predict two tricritical points. One corresponds to nematic to smectic A phase transition and other corresponds to reentrant nematic to smectic A phase transition. A comparison of the results with experimental phase diagrams is described in great details. The predictions of the theory are in good agreement with available experimental data.

Mukherjee, Prabir K.

2014-08-01

104

Phase Transitions in Liquid Crystal Doped with Magnetic Particles of Different Shapes in Combined Electric and Magnetic Fields  

NASA Astrophysics Data System (ADS)

We have studied the influence of electric and magnetic fields on the orientational structure of ferronematics based on a thermotropic nematic 4- trans-4- n-hexylcyclohexyl-isothiocyanato-benzene (6CHBT). The 6CHBT liquid crystal has been dissolved in phenyl isothiocyanate and doped with rod-like or chain-like magnetic particles. In such a mixture, the phase transition from an isotropic to a nematic phase is via a droplet state, i.e., coexistence of nematic and isotropic phases. The obtained results showed that a combination of the electric and magnetic fields can change the character of a phase transition from the isotropic to the nematic phase via the droplet state in such systems. Moreover, magneto-dielectric measurements of structural transitions showed the magnetic field induced a shift of the phase transition temperature from the isotropic to the droplet state.

Tomašovi?ová, Natália; Timko, Milan; Závišová, Vlasta; Hashim, Anežka; Jadzyn, Jan; Chaud, Xavier; Beaugnon, Eric; Kop?anský, Peter

2014-11-01

105

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. PMID:17571876

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

2008-01-01

106

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

NASA Astrophysics Data System (ADS)

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

Castillo, Gustavo; Mujica, Nicolás; Soto, Rodrigo

2015-01-01

107

Liquid-gas phase transition in hot asymmetric nuclear matter with density-dependent relativistic mean-field models  

E-print Network

The liquid-gas phase transition in hot asymmetric nuclear matter is studied within density-dependent relativistic mean-field models where the density dependence is introduced according to the Brown-Rho scaling and constrained by available data at low densities and empirical properties of nuclear matter. The critical temperature of the liquid-gas phase transition is obtained to be 15.7 MeV in symmetric nuclear matter falling on the lower edge of the small experimental error bars. In hot asymmetric matter, the boundary of the phase-coexistence region is found to be sensitive to the density dependence of the symmetry energy. The critical pressure and the area of phase-coexistence region increases clearly with the softening of the symmetry energy. The critical temperature of hot asymmetric matter separating the gas phase from the LG coexistence phase is found to be higher for the softer symmetry energy.

Guang-Hua Zhang; Wei-Zhou Jiang

2013-02-14

108

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

PubMed

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

Rout, Alok; Binnemans, Koen

2014-02-28

109

Continuous phase transition from Néel state to Z2 spin-liquid state on a square lattice  

NASA Astrophysics Data System (ADS)

Recent numerical studies of the J1-J2 model on a square lattice suggest a possible continuous phase transition between the Néel state and a gapped spin-liquid state with Z2 topological order. We show that such a phase transition can be realized through two steps: First bring the Néel state to the U(1) deconfined quantum critical point, which has been studied in the context of Néel-valence bond solid (VBS) state phase transition. Then condense the spinon pair-skyrmion/antiskyrmion bound state, which carries both gauge charge and flux of the U(1) gauge field emerging at the deconfined quantum critical point. We also propose a Schwinger boson projective wave function to realize such a Z2 spin liquid state and find that it has a relatively low variational energy (-0.4893J1/site) for the J1-J2 model at J2=0.5J1. The spin liquid state we obtain breaks the fourfold rotational symmetry of the square lattice and therefore is a nematic spin liquid state. This direct continuous phase transition from the Néel state to a spin liquid state may be realized in the J1-J2 model, or the anisotropic J1x-J1y-J2 model.

Qi, Yang; Gu, Zheng-Cheng

2014-06-01

110

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

111

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

PubMed

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

Takae, Kyohei; Onuki, Akira

2011-04-01

112

Nematic-to-isotropic photo-induced phase transition in azobenzene-doped low-molar liquid crystals.  

PubMed

The photo-induced phase transition generated by several 4,4'-disubstituted azobenzenes in host nematic low-molar mass liquid crystals was quantified by means of the efficiency, DeltaT(N-I), using polarized optical microscopy (POM) at variable temperature. Non-covalent interactions established between mesogen and azobenzene were the main determinants of the photo-induced phase transition behaviour. The correct design of the chemical structure of the system components allows controlling the temperature range in which the photo-induced mesophase transition occurs. Therefore, more efficient systems were obtained when azobenzenes with an extended aromatic core were used. PMID:19458826

Garcia-Amorós, Jaume; Szymczyk, Anna; Velasco, Dolores

2009-06-01

113

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

114

Phase Transitions of Liquid-Crystal Films at the Air-Water Interface Detected by Surface Potential Measurements  

Microsoft Academic Search

The surface potential of a liquid-crystal 4'-n-octyl-4-cyanobiphenyl (8CB) film at the air-water interface has been measured by a vibrating plate condenser. Phase transitions during multilayer formation could be observed by this method, which were inaccessible by other methods before.

P. Schmitz; H. Gruler

1995-01-01

115

Influence of cross-linking density on volume phase transition of liquid crystalline gels in a nematogenic solvent  

Microsoft Academic Search

The effect of cross-linking density (Cx) on volume phase transition of two liquid crystalline (LC) networks comprising dissimilar mesogens in a low molar mass LC has been investigated. Cross-linking density alters the modulus and nematicity of LC network each of which directly influence one of the three governing forces (elastic force, nematic interaction, isotropic mixing interaction) for the equilibrium swelling:

Yuko Okuno; Kenji Urayama; Shinzo Kohjiya

2003-01-01

116

democrite-00025179,version2-16Mar2006 Role of isospin in the nuclear liquid-gas phase transition  

E-print Network

democrite-00025179,version2-16Mar2006 Role of isospin in the nuclear liquid-gas phase transition C the thermodynamics of asymmetric nuclear matter using a mean-field approximation with a Skyrme effective interaction is first order except at the two ending points where it becomes second order. This result

Boyer, Edmond

117

Formulations of two phase liquid gas compositional Darcy flows with phase transitions  

E-print Network

, and the third is an extension to general compositional two phase flows of the pressure pressure formulation, Sg, and the molar fractions of the components c = (c i )iC in each phase Q where Q is the set the component molar fractions c are expressed as functions of the component fugacities f and of the phase

Paris-Sud XI, Université de

118

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

NASA Astrophysics Data System (ADS)

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 influences of the distance dependence, diffusion, the radial distribution function, and the hydrodynamic effect have been incorporated into the theory of electron transfer in solution, as well as into the theory of electron transfer between donors and acceptors in the head group regions of micelles. The development of new laser system with a pulse duration of tens of femtoseconds, with tunable wavelength allowed us to study these processes on a considerably shorter time scale than previous studies. This allowed us to observe not only the diffusion controlled but also the kinetics of electron transfer for donor/acceptor pairs that are in close proximity. In one set of experiments we have studied the kinetics of electron transfer in electron accepting molecule (rhodamine 3B) dissolved in electron donating solvent (N,N-dimethylaniline). The data for the forward electron transfer and geminate recombination are approximated by the statistical theory of the electron transfer. Optical anisotropy observed in the experiment demonstrates the orientation dependence of the electron transfer rate. In further experiments we investigated the electron transfer in non-hydrogen bonding liquids of increasing viscosity. The effective value of the donor/acceptor electronic coupling was found to decrease with viscosity. Electron transfer experiments were also carried out on the surface of micelles. The systems studied are the hole donor octadecyl-rhodamine B (ODRB) and the hole acceptor N,N-dimethyl-aniline (DMA) in micelles made of dodecyltrimethylammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB). It was found that the effective coupling is reduced compared to donor/acceptor pairs dissolved in simple liquids. In the 2nd half of thesis we have addressed the question of the dynamics of phase transitions. We have demonstrated the ability to use the fluorescent excitation-transfer technique to study the demixing of liquids specifically, kinetics of demixing water and 2,6-dimethylpyridine. These two liquids possess a low critical temperature point, which allowed us to use a temperature jump from a laser pulse to initiate the process of phase separation. It was found that Coumarin480 laser dye and HPTS (8-Hydroxypyrene-1,3,6-trisulfonic acid) fluorescent dye have significantly different solubilities in the components of the mixture. These dyes undergo excitation transfer from Coumarin480 to HPTS in the uniform state, but not in the phase-separated state. A system with a temperature jump pump and an excitation transfer probe measured the time scale of the initial step of the phase separation.

Goun, Alexei A.

119

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

120

Spontaneous formation of liquid crystalline phases and phase transitions in highly concentrated plasmid DNA  

Microsoft Academic Search

The liquid crystalline (LC) properties of two supercoiled plasmid DNA samples, pBSK (2958 bp) and pGEM (3000 bp), have been studied using polarised light microscopy (PLM), circular dichroism (CD) and UV–Vis spectroscopy. The influence of methods of isolation on plasmid LC behaviour is described, and using PLM we have demonstrated the spontaneous formation of cholesteric fingerprint-like textures. Preliminary studies of

Piotr Hanczyc; Katarzyna Matczyszyn; Krzysztof Pawlik; Joanna Olesiak; Herve Leh; Malcolm Buckle

2011-01-01

121

Liquid-solid phase transition of benzene under shock compression studied by nanosecond time-resolved nonlinear Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Phase transition of benzene has been studied under laser-shock compression up to 4.2 GPa by using nanosecond time-resolved nonlinear Raman spectroscopy. The shock wave is generated by irradiation of 10-ns pulsed laser beam on the plasma confinement target and its pressure is estimated from a particle velocity, which is measured by a velocity interferometer system. Higher frequency shifts in the ring- breathing mode of benzene are observed under shock compression. The shift at pressures below 3.0 GPa agrees well with that of liquid benzene under static compression. A metastable supercooled state and a liquid-solid phase transition are observed at shock pressures above 3.0 GPa. Time-resolved Raman spectra reveal that the liquid state is initially a metastable state and rapidly transforms to the solid state under shock compression at 4.2 GPa. Rapid nucleation and growth occurs within 20 ns.

Nakamura, Kazutaka

2005-07-01

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

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

PubMed

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

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

2014-07-14

124

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

NASA Astrophysics Data System (ADS)

A two-component plasma model, which we called a "shelf Coulomb" model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The "shelf Coulomb" model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ? parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ? and ? = ?e2n1/3 (where ? = 1/kBT, n is the particle's density, kB is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ? and ? parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of \\varepsilon _{crit} ? 13( {T_{crit}^* ? 0.076} ),? _{crit} ? 1.8( {v_{crit}^* ? 0.17} ),P_{crit}^* ? 0.39, where specific volume v* = 1/?3 and reduced temperature T* = ?-1.

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

2014-07-01

125

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

SciTech Connect

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

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

2014-07-14

126

An electro-optic experimental study of an unusual liquid crystal phase transition  

NASA Astrophysics Data System (ADS)

Liquid crystal phases are highly sensitive to their surroundings and they interact with light in unusual ways: the index of refraction is different depending on the polarization of the incident light. This combination of properties makes them ideal for low-power liquid crystal displays (LCD's), ubiquitous in today's portable electronic devices. They are also beautiful: optical textures of liquid crystals show bright colors, with the color corresponding to the amount of retardation in the light polarized along different axes. These phases are fluid, but can nevertheless be highly ordered. We have developed a novel experimental analysis using a photometric calculation of microscopy images to perform a series of experiments on several liquid crystal materials, called ``de Vries'' smectics. Using this system, we examined how the structure of these phases changed under the influence of different boundary conditions, temperature, and applied electric fields. These unusual materials show the bizarre behavior of appearing to become less ordered with decreasing temperature. This phase, which is not fully understood, has advantageous optical properties that could lead to the next generation of liquid crystal displays.

Staines, Daniel; Wicks, Derek; Havens, Austin; Fernsler, Jonathan

2009-11-01

127

Critical behavior at the isotropic-to-nematic phase transition in a bent-core liquid crystal  

NASA Astrophysics Data System (ADS)

Magnetic birefringence and dynamic light scattering measurements of orientational order parameter fluctuations at the isotropic-nematic phase transition of a bent-core liquid crystal reveal a pretransitional temperature dependence consistent with the standard Landau-deGennes mean field theory. However, as follows: the transition in the bent-core compound is more weakly first order (TNI-T*?0.4°C) , the leading Landau coefficient is ˜30 times lower, the viscosity associated with nematic order fluctuations is ˜10 times higher, and the density change is ˜10 times lower, than typically observed in calamitic (rod-shaped) liquid crystals. One consistent explanation for these anomalies is an optically isotropic phase composed of microscopic complexes or “clusters” of bent-core molecules.

Wiant, D.; Stojadinovic, S.; Neupane, K.; Sharma, S.; Fodor-Csorba, K.; Jákli, A.; Gleeson, J. T.; Sprunt, S.

2006-03-01

128

The phase transition temperatures of a liquid crystal determined from FT-IR spectra explored by principal component analysis  

NASA Astrophysics Data System (ADS)

The FT-IR spectra of a thin layer of pure 4-chloro-2'-hydroxy-4'-pentyloxyazobenzene (CHPAB) were studied as a function of temperature. A detailed analysis of the intensity variations was performed by a method based on principal component analysis (PCA). It was shown that the phase transition temperatures obtained by means of PCA and those determined by differential scanning calorimetry (DSC), the most widely used technique in the field, were nearly identical. The PCA results revealed that the transition from solid to a liquid crystalline (LC) phase (smectic A) is more drastic phase transition in terms of infrared absorption changes. The nematic to isotropic phase transition is much less infrared sensitive. Very much smaller absorption changes are associated with the transition between the smectic and nematic mesophases. The pattern of the intensity changes strictly is correlated with the orientation of the CHPAB molecules towards the surface windows due to the surface-induced homeotropic alignment of LC molecules. The important role of hydrogen bonding interaction on the observed transition is disclosed.

Czarnik-Matusewicz, B.; Paj?k, J.; Rospenk, M.

2005-11-01

129

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

PubMed

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

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

2011-01-01

130

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

PubMed Central

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

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

2011-01-01

131

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

132

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

133

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

SciTech Connect

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

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

2013-01-01

134

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

135

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

136

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

NASA Astrophysics Data System (ADS)

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

Castillo, Gustavo; Mujica, Nicolás; Soto, Rodrigo

2012-08-01

137

Dimensional crossover in a spin liquid to helimagnet quantum phase transition.  

SciTech Connect

Neutron scattering is used to study magnetic field induced ordering in the quasi-1D quantum spin-tube compound Sul-Cu2Cl4 that in zero field has a non-magnetic spin-liquid ground state. The experiments reveal an incommensurate chiral high-field phase stabilized by a geometric frustration of the magnetic interactions. The measured critical exponents \\beta= 0.235 and \

Garlea, Vasile O [ORNL; Zheludev, Andrey I [ORNL; Habicht, Klaus [Hahn-Meitner Institut, Berlin, Germany; Meissner, Michael [Hahn-Meitner Institut, Berlin, Germany; Grenier, B. [CEA, Grenoble, France; Regnault, L.-P. [CEA, Grenoble, France; Ressouche, E. [CEA, Grenoble, France

2009-01-01

138

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

NASA Astrophysics Data System (ADS)

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

Özgen, Soner; Kuzucu, Veysel; Adigüzel, Osman

1997-10-01

139

Micellar aggregates near the isotropic-cubic liquid crystal phase transition  

NASA Astrophysics Data System (ADS)

Micellar solutions of the palmitoyl-lyso-phosphatidyl choline (PLPC)/water system are studied by small angle x-ray scattering (SAXS) from the diluted isotropic (I) phase up to the concentrated I phase near the I?cubic (Q223) phase transition, for concentrations C in the range 5?C?37.5 wt % of PLPC. The particle distance distribution function p(r) is calculated for the less concentrated solution. A model for the product P(q)S(q), where P(q) is the micellar form factor and S(q) is the intermicellar interference function calculated using a hard sphere interaction potential, is fitted to the SAXS curves. It is found that PLPC micelles remain with a prolate ellipsoidal shape of constant anisometry ?=(1.80±0.05) in the whole concentration range. Such finding contrasts whit that found for systems that show I?hexagonal (H) phase transitions. In the latter, similar SAXS curves revealed that micelles grow to slightly higher anisometry (?˜2.4). Results are analysed in terms of a recent model based on the micellar elastic bending energy, through the surfactant parameter p0=vpar/alc(vpar and lc are the volume and the critical length of the paraffin chain, a the polar head surface area). It is concluded that the formation of the Q223 phase requires that micelles remain spheroidal and avoid the spherocylindrical shape.

Castelletto, Valeria; Itri, Rosangela; Amaral, Lia Q.

1997-07-01

140

Equation of state measurements by radiography provide evidence for a liquid-liquid phase transition in cerium  

NASA Astrophysics Data System (ADS)

A pressure-volume isotherm in cerium metal at 1100 K was measured in a large volume press of the Paris-Edinburgh type up to 6 GPa. The volume was determined by imaging a rectangular shape of the sample via white X-ray radiography. Energy dispersive x-ray diffraction spectra were recorded to ensure that the highly reactive cerium in the cell assembly remained pure at this temperature. Even at 1100 K the p-V equation of state of liquid cerium shows a pronounced decrease of the bulk modulus above the y-phase region similar to the 775 K isotherm in the solid that also shows an inflection point between y- and a-type cerium. The inflection point in the 1100 K isotherm indicating the minimum in the bulk modulus separating the ?- from the ?-type liquid is located at approximately 3.5 GPa.

Lipp, M. J.; Jenei, Zs; Ruddle, D.; Aracne-Ruddle, C.; Cynn, H.; Evans, W. J.; Kono, Y.; Kenney-Benson, C.; Park, C.

2014-05-01

141

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

142

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

E-print Network

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 mechanism 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 non-trivial topology of the director field and also multiply connected tactoids-in-tactoids 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 pi. 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 the function of I-N interfacial tension anisotropy in the 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.

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

2013-03-25

143

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

PubMed

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

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

2013-10-01

144

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

SciTech Connect

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

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

2007-03-21

145

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

NASA Astrophysics Data System (ADS)

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

Hernández-Contreras, M.

2013-12-01

146

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

E-print Network

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 mechanism 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 non-trivial topology of the director field and also multiply connected tactoids-in-tactoids 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 p...

Kim, Young-Ki; Lavrentovich, Oleg D

2013-01-01

147

Structural transitions in liquid cesium  

NASA Astrophysics Data System (ADS)

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

Belashchenko, D. K.

2014-09-01

148

Bimodality: a possible experimental signature of the liquid-gas phase transition of nuclear matter  

E-print Network

We have observed a bimodal behaviour of the distribution of the asymmetry between the charges of the two heaviest products resulting from the decay of the quasi-projectile released in binary Xe+Sn and Au+Au collisions from 60 to 100 MeV/u. Event sorting has been achieved through the transverse energy of light charged particles emitted on the quasi-target side, thus avoiding artificial correlations between the bimodality signal and the sorting variable. Bimodality is observed for intermediate impact parameters for which the quasi-projectile is identified. A simulation shows that the deexcitation step rather than the geometry of the collision appears responsible for the bimodal behaviour. The influence of mid-rapidity emission has been verified. The two bumps of the bimodal distribution correspond to different excitation energies and similar temperatures. It is also shown that it is possible to correlate the bimodality signal with a change in the distribution of the heaviest fragment charge and a peak in potential energy fluctuations. All together, this set of data is coherent with what would be expected in a finite system if the corresponding system in the thermodynamic limit exhibits a first order phase transition.

M. Pichon; B. Tamain; R. Bougault; F. Gulminelli; O. Lopez

2006-02-03

149

Entropy-driven liquid-liquid transitions in supercooled water  

NASA Astrophysics Data System (ADS)

Twenty years ago it was suggested that the anomalous properties of supercooled water may be caused by a critical point that terminates a line of metastable liquid-liquid separation of lower-density and higher-density water. I describe a phenomenological model in which liquid water at low temperatures is viewed as an athermal solution of two hydrogen-bond network structures with different entropies and densities. Alternatively to the lattice-gas/regular solution model, in which fluid phase separation is driven by energy, the phase transition in the athermal two-state water is driven by entropy upon increasing the pressure, while the critical temperature is defined by the reaction equilibrium constant. The order parameter is associated with the entropy, while the ordering field is a combination of temperature and pressure. The model predicts the location of density maxima at the locus of a near-constant fraction of the lower-density structure. Another example of entropy-driven liquid polyamorphism is the transition between the structurally ordered ``Blue Phase III'' and disordered liquid in some chiral materials; this transition is experimentally accessible. I also discuss the application of the two-state model to binary solutions of supercooled water in which liquid-liquid transition may also become accessible to direct observation. Some atomistic ``water-like'' models such as mW, do not show liquid-liquid separation in the metastable liquid domain. However, even without actual liquid-liquid separation, the anomalies observed in MD simulations of mW can be accurately described by the entropy-driven nonideality of two molecular configurations, the same physics that presumably drives the liquid-liquid transition in real water.

Anisimov, Mikhail

2013-03-01

150

Cosmological phase transitions  

SciTech Connect

If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions.

Kolb, E.W. [Fermi National Accelerator Lab., Batavia, IL (United States)]|[Chicago Univ., IL (United States)

1993-10-01

151

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

NASA Astrophysics Data System (ADS)

Quite recently, we reported a semianalytical equation of state (EOS) for the Ga-Pb alloy [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.78.024205 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 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.

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

2013-06-01

152

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

153

LIGHT NONAQUEOUS PHASE LIQUIDS  

EPA Science Inventory

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

154

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

PubMed

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

Starr, Francis W; Sciortino, Francesco

2014-12-21

155

A shock pressure induced phase transition from liquid to solid of cyclohexane using time-resolved coherent anti-Stokes Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The liquid-solid phase transition of cyclohexane has been studied under laser shock compression up to 3.8 GPa by using nanosecond time-resolved Coherent Anti-stokes Raman Spectroscopy (CARS) and laser shock compression. The shock wave is generated by irradiation of 10 ns pulsed laser beam on the plasma confinement target and its pressure is estimated from a particle velocity, which is measured by optically recording velocity interferometer system (ORVIS). Higher frequency shift of the Raman peaks (ring-breathing, C-C stretching, and CH2 twist modes) was observed at high pressure. At 3.8 GPa, splitting of the peak (CH2 twist mode) due to change in symmetry of surrounding molecules, which corresponds to phase transition to solid IV, was observed at delay time of 20 ns. Rapid liquid-solid phase transition has been directly observed to occur within 20 ns.

Oguchi, Shiro; Sato, Akira; Kondo, Ken-Ichi; Nakamura, Kazutaka

2007-06-01

156

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

SciTech Connect

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

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

2001-01-01

157

Tailored Phase Transitions via Mixed-Mesogen Liquid Crystalline Polymers with Silicon-Based Spacers  

E-print Network

-chain liquid crystalline polymers (LCPs) is desired for a variety of applications, including soft actuation composition. Two mesogenic groups, namely, 1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone (M1) and 2-tert reaction techniques. These mesogens and flexible spacers were chosen so that both copolymerization

Mather, Patrick T.

158

Phase transitions in ?  

Microsoft Academic Search

Phase transitions in sintered (0022-3727\\/31\\/4\\/005\\/img2 were investigated by means of a differential scanning calorimeter (DSC) in combination with magnetization measurement. Below 300 K, three phase transitions were identified: charge disorder-order, paramagnetism-antiferromagnetism and antiferromagnetism-canted spin structure transitions. In contrast to the reported single-crystal sample, no field-induced metamagnetic transition occurred in the sintered sample at an applied magnetic field up to 6.5

Y. L. Zhang; G. H. Rao; J. R. Sun; J. K. Liang

1998-01-01

159

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

Microsoft Academic Search

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

Soner Özgen; Veysel Kuzucu; Osman Adigüzel

1997-01-01

160

Dual spectrum neutron radiography: identification of phase transitions between frozen and liquid water.  

PubMed

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

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

2014-06-20

161

Dual Spectrum Neutron Radiography: Identification of Phase Transitions between Frozen and Liquid Water  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

162

Entropically driven reentrant SmC-SmA-SmC phase transition in composite polymer--liquid crystal systems  

E-print Network

I consider the effects of polymers on the smectic phase of a host liquid crystal matrix. Focusing on the regime in which the polymers are predominately confined between the smectic layers, I find that the presence of the polymers can lead to a reentrant phase diagram with the smectic-C sandwiching the smectic-A phase from both the high and low temperature sides. Simple entropy-energy arguments predict the shape of the reentrant phase boundary.

Leo Radzihovsky

1996-11-11

163

The liquid-glass transition of silica  

NASA Astrophysics Data System (ADS)

We studied the liquid-glass transition of SiO2 by means of replica theory, utilizing an effective pair potential which was proved to reproduce a few experimental features of silica. We found a finite critical temperature T0, where the system undergoes a phase transition related to replica symmetry breaking, in a region where experiments do not show any transition. The possible sources of this discrepancy are discussed.

Coluzzi, Barbara; Verrocchio, Paolo

2002-03-01

164

Nature of the liquid crystalline phase transitions in the cesium pentadecafluorooctanoate-water system: The nematic-to-smectic-A transition  

NASA Astrophysics Data System (ADS)

Measurements of the diamagnetic susceptibility ?a, the rotational viscosity coefficient ?1, and the micellar orientational order parameter S have been made as a function of temperature across the entire nematic phases of cesium pentadecafluorooctanoate (CsPFO)-D2O samples over the concentration range weight fraction CsPFO w from 0.350 to 0.500. This has been chosen so as to embrace the pseudo-nematic phase-lamellar tricritical point that has been purported to occur at w=0.43 (volume fraction ?=0.26). The values of ?1 vary from about 0.1 kg m-1 s-1 to 1000 kg m-1 s-1 as the temperature decreases across the nematic phase, covering a much larger range than those reported for thermotropic liquid crystals. Measurements of ?1 have been made much closer to the critical temperature TLN than have previously been reported [(T-TLN)/TLN=2×10-5 for the w=0.350 sample]. The rotational viscosity critical exponents x calculated from the divergence of ?1 on approaching the nematic-phase-to-lamellar transition are found to be constant at 2/3 independent of the concentration. These values differ from those of 1/3 and 1/2, respectively, predicted by the He-like three-dimensional XY and mean-field models, in combination with mean-field dynamical relaxation. However, the former would be supported if complete Fisher renormalization (at ?=1/2) was appropriate over an extended concentration range. Alternatively, this could be an indication of the importance of coupling between the micellar rotational dynamics and critical fluctuations since the latter are seen to be predominant across the entire temperature range of the nematic phase as revealed in the temperature dependence of ?1.

Jolley, K. W.; Boden, N.; Parker, D.; Henderson, J. R.

2002-04-01

165

Quantum Phase Transitions  

Microsoft Academic Search

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

Subir Sachdev; Matthew P. A. Fisher

2001-01-01

166

Transient and stationary flow behaviour of side chain liquid-crystalline polymers: Evidence of a shear-induced isotropic-to-nematic phase transition  

NASA Astrophysics Data System (ADS)

This letter describes the non-linear rheology of the isotropic phase of a thermotropic side chain liquid-crystal polymer (SCLCP), from which we infer a flow-induced iso- tropic-to-nematic (IN) phase transition above a critical shear stress and construct non-equilib- rium phase diagrams. In contrast to the well-studied wormlike-micellar solutions and predictions for simple liquid-crystalline systems, the critical stress does not vanish as the equilibrium transition temperature is approached from the above. We postulate that this is due to: i) the coupling between mesogens and the polymer backbone, whose equilibrium oblate nematic backbone conformation contrasts with the prolate non-equilibrium conformation; and ii) the peculiar topological constraints in SCLCP melts, which have been previously postulated as leading to long-lived clusters.

Pujolle-Robic, C.; Olmsted, P. D.; Noirez, L.

2002-08-01

167

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

PubMed Central

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

Bitler, A; Stavrov, SS

1999-01-01

168

The liquid-glass and liquid-liquid transitions of TPP at elevated pressure.  

PubMed

We studied the polyamorphism of the liquid triphenyl phosphite by means of broadband dielectric spectroscopy at ambient and elevated (p=500 MPa) pressures. The effect of pressure on fragility, liquid-liquid phase transition, and its kinetics is discussed in relation to the two-order-parameter model proposed by Tanaka. The experimental evidence in support of this model is presented. PMID:18671360

Mierzwa, Micha?; Paluch, Marian; Rzoska, Sylwester J; Zio?o, Jerzy

2008-08-28

169

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

170

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

E-print Network

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

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

2005-07-08

171

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

172

Quantum phase transitions  

Microsoft Academic Search

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

Thomas Vojta

2003-01-01

173

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

174

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

PubMed

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 Zr(41.2)Ti(13.8)Cu(12.5)Ni10Be(22.5) 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. PMID:23817404

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

2013-01-01

175

Liquid-liquid-solid transition in viscoelastic liquids  

PubMed Central

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

Zubelewicz, Aleksander

2013-01-01

176

Liquid-liquid-solid transition in viscoelastic liquids.  

PubMed

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

Zubelewicz, Aleksander

2013-01-01

177

Phase Transitions in Materials  

NASA Astrophysics Data System (ADS)

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

Fultz, Brent

2014-08-01

178

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

SciTech Connect

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

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

2014-06-07

179

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

180

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

PubMed

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

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

2013-09-01

181

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

NASA Astrophysics Data System (ADS)

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 BaTiO3 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 (TNI) and from nematic to smectic-A phase (TNA) 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 TNI and almost unchanged TNA 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.

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

2012-02-01

182

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

E-print Network

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

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

2014-10-07

183

Latent heat and nonlinear vortex liquid in the vicinity of the first-order phase transition in layered high-Tc superconductors  

NASA Astrophysics Data System (ADS)

In this work we revisit the vortex matter phase diagram in layered superconductors solving still open questions by means of ac and dc local magnetic measurements in the paradigmatic Bi2Sr2CaCu2O8 compound. We show that measuring with ac magnetic techniques is mandatory in order to probe the bulk response of vortex matter, particularly at high temperatures where surface barriers for vortex entrance dominate. From the TFOT evolution of the enthalpy and latent heat at the transition we find that, contrary to previous reports, the nature of the dominant interlayer coupling is electromagnetic in the whole temperature range. By studying the dynamic properties of the phase located at T ?TFOT, we reveal spanning in a considerable fraction of the phase diagram of a nonlinear vortex phase suggesting that bulk pinning might play a role even in the liquid vortex phase.

Dolz, M. I.; Fasano, Y.; Pastoriza, H.; Mosser, V.; Li, M.; Konczykowski, M.

2014-10-01

184

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

E-print Network

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

185

Viscosity near phase transitions  

E-print Network

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

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

2010-09-30

186

The phase transition temperatures of a liquid crystal determined from FT-IR spectra explored by principal component analysis  

Microsoft Academic Search

The FT-IR spectra of a thin layer of pure 4-chloro-2?-hydroxy-4?-pentyloxyazobenzene (CHPAB) were studied as a function of temperature. A detailed analysis of the intensity variations was performed by a method based on principal component analysis (PCA). It was shown that the phase transition temperatures obtained by means of PCA and those determined by differential scanning calorimetry (DSC), the most widely

B. Czarnik-Matusewicz; J. Pajak; M. Rospenk

2005-01-01

187

Metastable liquid-liquid transition in a molecular model of water  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

188

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

PubMed

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

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

2014-06-19

189

Two melts phase separation in the liquid Sb-Sb2S3 system: critical sound wave propagation and metal-non-metal transition  

NASA Astrophysics Data System (ADS)

The sound velocity and magnetic susceptibility as a function of temperature and composition were measured to investigate critical sound wave propagation and metal-non-metal transition in the liquid Sb-Sb2S3 system. The sound velocity in a homogeneous alloy around 60 at.% of Sb decreases very rapidly and the rate of decrease increases as the two melts phase is approached, which is the typical temperature dependence of the sound velocity in a liquid with a miscibility gap. Below the critical point, the sound velocity was measured along the phase boundary. Using those data, the phase boundary was precisely determined. The critical point is located at 901±2°C and 41.5 ±0.5 at.% S, and the critical exponent of the phase boundary is about 1/3. On the other hand, the magnetic susceptibility as a function of temperature and composition indicates that the electronic state is metallic in liquid Sb and non-metallic in molten Sb2Se3, and crossover form the metallic to non-metallic state occurs around the critical composition.

Endoh, H.; Hisakabe, M.; Kojima, Y.; Kakimuma, F.; Tsuchiya, Y.

2011-05-01

190

String mediated phase transitions  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

191

Solitosynthesis induced phase transitions  

E-print Network

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

Lauren Pearce

2012-04-24

192

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

193

Temperature-dependent Raman study of the smectic to nematic phase transition and vibrational analysis using density functional theory of the liquid crystalline system 4-decyloxy benzoic acid.  

PubMed

Room-temperature Raman spectra of the thermotropic liquid crystalline system, 4-decyloxy benzoic acid (4DBA) have been recorded and the experimentally observed bands are assigned by density functional theory (DFT) for the first time. The C-O and C-C stretching and C-H in-plane bending modes of the phenyl ring and C=O stretching modes of the -COOH group are the marker bands for the smectic (S) --> nematic (N) and nematic (N) --> isotropic (I) transitions for this system. The temperature-dependent Raman spectra for these bands in the heating cycle clearly characterize the S-->N and the N-->I transition over a range <1 degree C, which is much better than the earlier range of 23 degrees C for S-->N and 26 degrees C for the N-->I transition. The approximately 773, approximately 807, approximately 881, and approximately 1146 cm(-1) bands disappear, whereas a band at approximately 830 cm(-1) appears at the S-->N transition. The relative intensity of the approximately 1257 and approximately 1280 cm(-1) bands distinguishes the three phases, namely smectic, nematic, and isotropic, in 4DBA. The variation of line width and peak wavenumber of the approximately 1128 and approximately 1168 cm(-1) bands also clearly shows the two transitions. The molecular reorientation at the transition and the effect of local fields present in the liquid crystalline mesophases are also briefly discussed on the basis of changes in intensity, linewidth and peak wavenumber with temperature. PMID:20149280

Vikram, K; Tarcea, Nicolae; Popp, J; Singh, Ranjan K

2010-02-01

194

First-Order Phase Transition in Liquid Water in Terms of the Mode Structure of Absorption Spectrum in the Near-IR Range  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

195

Emergence and Phase Transitions  

NASA Astrophysics Data System (ADS)

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

Sikkema, Arnold

2006-05-01

196

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

NASA Astrophysics Data System (ADS)

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

Tournier, Robert F.

2014-12-01

197

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

E-print Network

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

Robert Felix Tournier

2015-02-23

198

Mean-field glass transition in a model liquid.  

PubMed

We investigate the liquid-glass phase transition in a system of pointlike particles interacting via a finite-range attractive potential in D -dimensional space. The phase transition is driven by an "entropy crisis" where the available phase space volume collapses dramatically at the transition. We describe the general strategy underlying the first-principles replica calculation for this type of transition; its application to our model system then allows for an analytic description of the liquid-glass phase transition within a mean-field approximation, provided the parameters are chosen suitably. We find a transition exhibiting all the features associated with an entropy crisis, including the characteristic finite jump of the order parameter at the transition while the free energy and its first derivative remain continuous. PMID:16196568

Dotsenko, V S; Blatter, G

2005-08-01

199

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

PubMed

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

Tanaka, Hajime

2012-10-01

200

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

201

Dynamic Phase Transitions.  

NASA Astrophysics Data System (ADS)

For fluids with non-anomalous equations of state. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). one can decide whether a given shock is physically realizable by using either the Lax or viscosity admissibility criterion. However, for fluids with anomalous equations of state. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). these criteria are too restrictive. For example, they rule out static phase transitions. In this thesis an admissibility criterion based on Korteweg's theory of capillarity (and heat conduction for non-isothermal motions) is used. It is shown that this admissibility criterion is equivalent to the preceding criteria for an ideal gas. For anomalous fluids, the new admissibility criterion is used to find the isothermal shocks which connect equilibrium states belonging to distinct phases. As a particular example, the case of a van der Waals fluid is treated. Then the new admissibility criterion is used to find nearly isothermal traveling waves that connect equilibrium states in different phases of a van der Waals fluid.

Hagan, Robert Michael, Jr.

202

Liquid Phase Sintering  

NASA Technical Reports Server (NTRS)

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

2004-01-01

203

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

2012-05-16

204

Pressure-Induced Phase Transitions of n-Tridecane  

NASA Astrophysics Data System (ADS)

Pressure-induced phase transition behavior of n-tridecane from the ordered phase through the rotator phase into the liquid phase has been investigated by using Fourier transform infrared spectroscopy at 25 °C. The transition between the ordered and rotator phases has been observed in the pressure range of 270-220 MPa and the transition between the rotator and liquid phases has been observed in the pressure range of 171-112 MPa, within the experimental error of ±50 MPa. The populations of the -gtg- + -gtg'-, -gg- and gt- defects determined from the methylene wagging mode are smaller in the rotator phase than in the liquid phase and are smaller under higher pressure in both of the rotator and liquid phases. A relationship has been found between the conformation and the intensity of the 890 cm-1 band, which has been assigned as the methyl rocking mode and has been considered as insensitive to conformation.

Yamashita, Motoi

205

Electroweak phase transition and baryogenesis  

Microsoft Academic Search

We give an analytic treatment of the one-Higgs-doublet, electroweak phase transition which demonstrates that the phase transition is first order. The phase transition occurs by the nucleation of thin-walled bubbles and completes as a temperature where the order parameter {l angle}Ï{r angle}{sub {ital T}} is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous

Greg Anderson; Lawrence Hall

1992-01-01

206

New divergent dynamics in the isotropic to nematic phase transition of liquid crystals measured with 2D IR vibrational echo spectroscopy.  

PubMed

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

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

2014-11-21

207

Diffusion phase transitions in alloys  

NASA Astrophysics Data System (ADS)

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

Ustinovshchikov, Yu I.

2014-07-01

208

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

209

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

210

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

NASA Astrophysics Data System (ADS)

This paper extends our earlier studies of free energy functions of density and crystalline order parameters for models of supercooled water, which allows us to examine the possibility of two distinct metastable liquid phases [D. T. Limmer and D. Chandler, J. Chem. Phys. 135, 134503 (2011), 10.1063/1.3643333 and preprint arXiv:1107.0337 (2011)]. Low-temperature reversible free energy surfaces of several different atomistic models are computed: mW water, TIP4P/2005 water, Stillinger-Weber silicon, and ST2 water, the last of these comparing three different treatments of long-ranged forces. In each case, we show that there is one stable or metastable liquid phase, and there is an ice-like crystal phase. The time scales for crystallization in these systems far exceed those of structural relaxation in the supercooled metastable liquid. We show how this wide separation in time scales produces an illusion of a low-temperature liquid-liquid transition. The phenomenon suggesting metastability of two distinct liquid phases is actually coarsening of the ordered ice-like phase, which we elucidate using both analytical theory and computer simulation. For the latter, we describe robust methods for computing reversible free energy surfaces, and we consider effects of electrostatic boundary conditions. We show that sensible alterations of models and boundary conditions produce no qualitative changes in low-temperature phase behaviors of these systems, only marginal changes in equations of state. On the other hand, we show that altering sampling time scales can produce large and qualitative non-equilibrium effects. Recent reports of evidence of a liquid-liquid critical point in computer simulations of supercooled water are considered in this light.

Limmer, David T.; Chandler, David

2013-06-01

211

Spontaneous phase transitions in ferrite garnet films  

NASA Astrophysics Data System (ADS)

Spontaneous phase transitions in ferrite garnet films have been studied. It has been shown that, with variations in the temperature, domain walls undergo phase transitions which cause spontaneous phase transitions in the lattice of cylindrical magnetic domains. The phase transition in a domain wall causes a spin-reorientation phase transition over the whole sample near the magnetic compensation point. The character of the phase transition in the domain wall determines the mechanism of the spin-reorientation phase transition.

Siryuk, Yu. A.; Bezus, A. V.

2013-03-01

212

A continuous Mott transition between a metal and a quantum spin liquid Ryan V. Mishmash,1  

E-print Network

A continuous Mott transition between a metal and a quantum spin liquid Ryan V. Mishmash,1 Iv-Thouless-like) quantum phase transition between a metal and a gapless spin liquid characterized by a spinon Fermi sea, i transitions to metallic phases have a long history reaching back into the pioneering work of Mott1,2 . However

213

Fluctuation driven electroweak phase transition  

NASA Technical Reports Server (NTRS)

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

Gleiser, Marcelo; Kolb, Edward W.

1991-01-01

214

Liquid-liquid transition in ST2 water  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

215

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

E-print Network

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 ...

Barkeshli, Maissam

216

Phase transitions in metastable phases of silicon  

NASA Astrophysics Data System (ADS)

Phase transitions in indentation induced Si-III/XII phases were investigated using a diamond anvil cell and nanoindentation combined with micro-Raman spectroscopy. The in situ high pressure Raman results demonstrate that the Si-III and Si-XII phases have very similar Raman spectra, indicating their relative amount cannot be determined if they are both present in a sample. The Si-III and Si-XII phases coexist in the indentations produced by a nanoindenter on a single crystalline silicon wafer as a result of the local residual compressive stresses near 1 GPa. High power laser annealing on the indentations can initiate a rapid Si-III/XII ? Si-I phase transition. The newly formed polycrystalline Si-I phase initially has very small grain size, and the grains grow when the annealing time is extended. Si-IV phase was not observed in our experiment.

Zeng, Zhidan; Zeng, Qiaoshi; Mao, Wendy L.; Qu, Shaoxing

2014-03-01

217

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

E-print Network

Modelling and Control of Two-Phase Phenomena: Liquid-Liquid Two-Phase Flow Systems Neima Brauner-Newtonian rheological behavior. Therefore, the various concepts and results related to gas-liquid two-phase flows cannot be readily applied to liquid-liquid systems. Diverse flow patterns were observed in liquid-liquid systems

Brauner, Neima

218

Quantum Phase Transitions in Dense QCD  

E-print Network

Quantum chromodynamics (QCD) at finite temperature, $T$, and quark chemical potential, $\\mu$, has a rich phase structure: at low $T$ and low $\\mu$, the Nambu-Goldstone (NG) phase with nearly massless pions is realized by the dynamical breaking of chiral symmetry through condensation of quark-anti-quark pairs, while, at low $T$ and high $\\mu$, a Fermi liquid of deconfined quarks is expected to appear as a consequence of asymptotic freedom. Furthermore, in such a cold quark matter, condensation of quark-quark pairs leads to the color superconductivity (CSC). At high $T$ for arbitrary $\\mu$, all the condensates melt away and a quark-gluon plasma (QGP) is realized. The experimental exploration of thermal phase transition from the NG phase to QGP is being actively pursued in ultrarelativistic heavy ion collisions at RHIC (Relativistic Heavy Ion Collider), and will be continued in the future at LHC (Large Hadron Collider). The quantum phase transition from the NG phase to the CSC at low $T$ is also relevant to heavy-ion collisions at moderate energies, and is of interest in the interiors of neutron stars and possible quark stars. In this Chapter, after a brief introduction to the basic properties of QCD, the current status of the QCD phase structure and associated quantum phase transitions will be summarized with particular emphasis on the symmetry realization of each phase. Possible connection between the physics of QCD and that of ultracold atoms is also discussed.

Tetsuo Hatsuda; Kenji Maeda

2009-12-08

219

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

E-print Network

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

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

2014-08-21

220

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

E-print Network

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

Haberstroh, Robert D.

1964-01-01

221

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

PubMed

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

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

2014-09-24

222

Effects of terminal chain length in hydrogen-bonded chiral switches on phototunable behavior of chiral nematic liquid crystals: helicity inversion and phase transition.  

PubMed

A novel series of photoresponsive chiral switches are fabricated by a facile hydrogen-bonded (H-bonded) assembly method, in which the binaphthyl azobenzene molecule is used as the proton acceptor, and binaphthyl acids with opposite chiral configuration are proton donors. We find that the helical twisted power of H-bonded chiral switches and the helical handedness of induced chiral nematic liquid crystals (N*-LCs) are mainly determined by the terminal flexible chain length in proton donors of binaphthyl acids. Controlling the lengths of the terminal flexible chain leads to different photoswitching behaviors by light irradiation, such as a helical inversion in the N*-LCs and a phase transition from N*-LCs to nematic LCs. This is mainly because of chiral counteraction and intensity attenuation of opposite chiral configurations between the proton acceptor and proton donor during UV-vis irradiation. Additionally, the thermal switching behavior of N*-LCs doped with H-bonded chiral switches is also demonstrated, and the related tuning mechanism may be attributed to the H-bonded effect and the changes in a dihedral angle of the binaphthyl rings. This facile assembly approach provides a new way for the fabrication of functional chiral switches for photonic applications. PMID:25743076

Fu, Dengwei; Li, Juntao; Wei, Jie; Guo, Jinbao

2015-04-01

223

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

2010-01-01

224

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

PubMed

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

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

2012-12-27

225

Phase Transitions without Thermodynamic Limit  

Microsoft Academic Search

Microcanonical statistics can be well applied to non-extensive systems like\\u000anuclei, atomic clusters and systems at phase transitions of first order with\\u000ainhomogeneous configurations like phase separation. No thermodynamic limit has\\u000ato be invoked. It allows to determine the transition temperature, latent heat\\u000aand surface entropy. In the present paper this is demonstrated for systems of\\u000a200 - 3000 Na-,

D. H. E. Gross; Bereich Theoretische Physik; Fachbereich Physik

1998-01-01

226

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

PubMed

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

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

2012-11-01

227

Distinct Metallization and Atomization Transitions in Dense Liquid Hydrogen  

NASA Astrophysics Data System (ADS)

We perform molecular dynamics simulations driven by accurate quantum Monte Carlo forces on dense liquid hydrogen. There is a recent report of a complete atomization transition between a mixed molecular-atomic liquid and a completely dissociated fluid in an almost unaccessible pressure range [Nat. Commun. 5, 3487 (2014)]. Here, instead, we identify a different transition between the fully molecular liquid and the mixed-atomic fluid at ˜400 GPa , i.e., in a much more interesting pressure range. We provide numerical evidence supporting the metallic behavior of this intermediate phase. Therefore, we predict that the metallization at finite temperature occurs in this partially dissociated molecular fluid, well before the complete atomization of the liquid. At high temperature this first-order transition becomes a crossover, in very good agreement with the experimental observation. Several systematic tests supporting the quality of our large scale calculations are also reported.

Mazzola, Guglielmo; Sorella, Sandro

2015-03-01

228

Distinct metallization and atomization transitions in dense liquid hydrogen.  

PubMed

We perform molecular dynamics simulations driven by accurate quantum Monte Carlo forces on dense liquid hydrogen. There is a recent report of a complete atomization transition between a mixed molecular-atomic liquid and a completely dissociated fluid in an almost unaccessible pressure range [Nat. Commun. 5, 3487 (2014)]. Here, instead, we identify a different transition between the fully molecular liquid and the mixed-atomic fluid at ?400??GPa, i.e., in a much more interesting pressure range. We provide numerical evidence supporting the metallic behavior of this intermediate phase. Therefore, we predict that the metallization at finite temperature occurs in this partially dissociated molecular fluid, well before the complete atomization of the liquid. At high temperature this first-order transition becomes a crossover, in very good agreement with the experimental observation. Several systematic tests supporting the quality of our large scale calculations are also reported. PMID:25815949

Mazzola, Guglielmo; Sorella, Sandro

2015-03-13

229

Rheology of liquid crystalline phases of alkyloxybenzylidene toluidines  

NASA Astrophysics Data System (ADS)

A unique viscometer of the CS rheometer viscometer class designed at the Kazan State University of Technology is used to measure viscosities of two p-n-alkyloxybenzylidene- p-toluidines in the entire temperature range of the liquid crystalline state and transition into an isotropic liquid. The measured shear stresses and flow rates are used to calculate shear rates and plot flow and viscosity curves. The liquid crystalline phase and isotropic liquid are demonstrated to possess Newtonian viscosity, whose viscous flow activation parameters are calculated in the temperature range under study. The results are discussed from the standpoint of intermolecular interactions and structural details of the liquid crystalline phase.

Samigullin, F. M.; Malatsion, S. F.; Rodnikova, M. N.; Syrbu, A. A.; Kucherepa, N. S.

2010-01-01

230

Liquid phase methanol synthesis catalyst  

Microsoft Academic Search

This work focuses on the investigation of the stability of catalyst activity in the liquid phase methanol synthesis process. The effects of various kinds of metfhods to inhibit the deactivation of catalyst have been experimentally examined. The activity of catalyst was stabilized without lowering of activity by a suitable hydrothermal treatment, although the activity of the untreated catalyst decreased gradually

H Mabuse; K Hagihara; T Watanabe; M Saito

1997-01-01

231

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

232

Gauge theory of the liquid-glass transition in static and dynamical approaches  

NASA Astrophysics Data System (ADS)

We propose static and dynamical formulations of the liquid-glass transition theory based on the glass gauge theory and the fluctuation theory of phase transitions. In accordance with the proposed theory, the liquid-glass transition is an unattainable second-order phase transition blocked by a premature critical slowing of the gauge field relaxation caused by the system frustration. We show that the proposed theory qualitatively agrees well with experimental data.

Vasin, M. G.

2013-03-01

233

Phase Behaviour and Structure of Weakly Perturbed Liquid Crystals  

Microsoft Academic Search

We study influence of a weak disorder on 1st and 2nd order phase transitions in which a continuous symmetry is broken. As illustrative cases we choose the isotropic-nematic (I-N) and nematic-smectic A (N-SmA) liquid crystal phase transitions. We yield an explanation for the established domain pattern and estimate the phase behaviour as a function of the disorder strength.

Ivan Gerli?; Samo Kralj; Vlad Popa-Nita

2006-01-01

234

Probing a Liquid to Glass Transition in Equilibrium  

NASA Astrophysics Data System (ADS)

We use computer simulations to investigate the static properties of a simple glass-forming fluid in which the positions of a finite fraction of the particles have been frozen. By probing the equilibrium statistics of the overlap between independent configurations of the liquid, we find strong evidence that this random pinning induces a glass transition. At low temperatures, our numerical findings are consistent with the existence of a random first-order phase transition rounded by finite size effects.

Kob, Walter; Berthier, Ludovic

2013-06-01

235

Equilibrium study of a liquid-glass transition  

NASA Astrophysics Data System (ADS)

The liquid-glass transition in dense fluids is characterized by several crossover temperatures, but glasses are obtained without crossing any sharp singularity. The existence of an underlying phase transition, predicted theoretically in some limiting cases, is therefore only supported by uncontrolled extrapolations of macroscopic observables. Here we use a specific random pinning field to induce a liquid-glass transition in a simulated fluid. We discover a range of control parameters for which the transition can be crossed at thermal equilibrium, which allows us to probe for the first time the microscopic nature of an equilibrium glass. Our results, obtained for a range of modest system sizes, suggest that the glass transition is of the random first order type.

Berthier, Ludovic

2013-03-01

236

Solid liquid phase changes with different densities  

E-print Network

In this paper we present a new thermodynamically consistent phase transition model describing the evolution of a liquid substance, e.g., water, in a rigid container $\\Omega$ when we freeze the container. Since the density $\\varrho_{2}$ of ice with volume fraction $\\beta_{2}$, is lower than the density $\\varrho_{1}$ of water with volume fraction $\\beta_{1}$, experiments - for instance the freezing of a glass bottle filled with water - show that the water pressure increases up to the rupture of the bottle. When the container is not impermeable, freezing may produce a non-homogeneous material, for instance water ice or sorbet. Here we describe a general class of phase transition processes including this example as particular case. Moreover, we study the resulting nonlinear and singular PDE system from the analytical viewpoint recovering existence of a global (in time) weak solution and also uniqueness for some particular choices of the nonlinear functions involved.

Fremond, Michel

2008-01-01

237

Solid liquid phase changes with different densities  

E-print Network

In this paper we present a new thermodynamically consistent phase transition model describing the evolution of a liquid substance, e.g., water, in a rigid container $\\Omega$ when we freeze the container. Since the density $\\varrho_{2}$ of ice with volume fraction $\\beta_{2}$, is lower than the density $\\varrho_{1}$ of water with volume fraction $\\beta_{1}$, experiments - for instance the freezing of a glass bottle filled with water - show that the water pressure increases up to the rupture of the bottle. When the container is not impermeable, freezing may produce a non-homogeneous material, for instance water ice or sorbet. Here we describe a general class of phase transition processes including this example as particular case. Moreover, we study the resulting nonlinear and singular PDE system from the analytical viewpoint recovering existence of a global (in time) weak solution and also uniqueness for some particular choices of the nonlinear functions involved.

Michel Fremond; Elisabetta Rocca

2008-06-18

238

Influence of cis double bonds in the sn-2 acyl chain of phosphatidylethanolamine on the gel-to-liquid crystalline phase transition.  

PubMed Central

We have semisynthesized 19 species of mixed-chain phosphatidylethanolamines (PEs) in which the sn-1 acyl chain is derived from saturated fatty acids with varying chain lengths and the sn-2 acyl chain has different chain lengths but contains 0, 1, and 2 cis double bond(s). The gel-to-liquid crystalline phase transition temperatures (Tm) of lipid bilayers prepared from these 19 mixed-chain PEs were determined calorimetrically. When the Tm values are compared with those of saturated and monounsaturated counterparts, a common Tm profile is observed in the plot of Tm versus the number of cis double bonds. Specifically, a marked stepwise decrease in Tm is detected as the number of cis double bonds in the sn-2 acyl chain of the mixed-chain PE is successively increased from 0 to 1 and then to 2. The large Tm-lowering effect of the acyl chain unsaturation can be attributed to the increase in Gibbs free energy of the gel-state bilayer as a result of weaker lateral chain-chain interactions. In addition, we have applied molecular mechanics calculations to simulate the molecular structure of dienoic mixed-chain C(X):C(Y:2 delta n,n+3)PE in the gel-state bilayer, thus enabling the three independent structural parameters (N, delta C, and LS) to be calculated in terms of X, Y, and n, which are intrinsic quantities of C(X):C(Y:2 delta n,n+3)PE. When the Tm values and the corresponding N and delta C values of all dienoic mixed-chain PEs under study are first codified and then analyzed statistically by multiple regressions, the dependence of Tm on the structural parameters can be described quantitatively by a simple and general equation. The physical meaning and the usefulness of this simple and general equation are explained. PMID:9199793

Wang, G; Li, S; Lin, H N; Huang, C

1997-01-01

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

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

241

Dynamics in supercooled liquids and in the isotropic phase of liquid crystals: A comparison  

E-print Network

, the temperatures range from well above the isotropic-to-nematic phase transition temperature TNI down to TNI supercooled liquids and TNI liquid crystals are approached from above, the time range over which the ``intermediate'' power law can be observed increases, until near Tc and TNI , the power law can be observed from

Fayer, Michael D.

242

Cholesteric pitch divergence near smectic phase transitions  

NASA Astrophysics Data System (ADS)

The critical behavior of the pitch divergence of cholesteric liquid crystals in the vicinity to smectic- A? (SmA?) and smectic- C? (SmC?) phases is studied experimentally and compared with conflicting theoretical interpretations. Members of two homologous series were studied with varying polymorphism from N?-SmC? to N?-SmA? . A modified functionality of the temperature dependence of the pitch is introduced to determine the critical exponent, and it is shown that the latter is independent of sample geometry. In contrast to several earlier investigations aiming to determine the critical exponent, which were inconclusive, the results of our critical exponents for the pitch divergence provide evidence for the model by Chen and Lubensky which predicts a critical exponent of ?=1/2 for the N?-SmA? and ?=1 for the N?-SmC? transition. This specifically implies that fluctuations cannot be neglected in the consideration of the nature of the phase transition.

Yoon, H. G.; Dierking, I.; Gleeson, H. F.

2010-07-01

243

On Asymmetric Diffusional Solidification During Transient Liquid Phase Bonding  

NASA Astrophysics Data System (ADS)

The underlying cause of asymmetric diffusion solidification which alters microstructure during transient liquid phase bonding under low temperature gradient was studied. A new solute-conserving asymmetric numerical model coupled with experimental verification showed that a transition from bi-directional to unidirectional solidification, under a constant temperature gradient, is controlled by competition between liquid and solid-state diffusion at one of the two liquid-solid interfaces. This mechanistic understanding would aid a more effective use of the process.

Ghobadi Bigvand, A.; Ojo, Olanrewaju A.

2014-04-01

244

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

PubMed Central

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

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

2012-01-01

245

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

246

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

247

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

248

Interplay between micelle formation and waterlike phase transitions.  

PubMed

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. PMID:20151756

Heinzelmann, G; Figueiredo, W; Girardi, M

2010-02-14

249

Electrical Dissipation Measurement of Polymer Phase Transitions  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

250

Phase Inversion in a Batch Liquid - Liquid Stirred System  

Microsoft Academic Search

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

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

251

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

252

Absence of thermodynamic phase transition in a model glass former  

PubMed

The glass transition can be viewed simply as the point at which the viscosity of a structurally disordered liquid reaches a universal threshold value. But this is an operational definition that circumvents fundamental issues, such as whether the glass transition is a purely dynamical phenomenon. If so, ergodicity gets broken (the system becomes confined to some part of its phase space), but the thermodynamic properties of the liquid remain unchanged across the transition, provided they are determined as thermodynamic equilibrium averages over the whole phase space. The opposite view claims that an underlying thermodynamic phase transition is responsible for the pronounced slow-down in the dynamics at the liquid-glass boundary. Such a phase transition would trigger the dynamic standstill, and then be masked by it. Here we perform Monte Carlo simulations of a two-dimensional system of polydisperse hard disks far within its glassy phase. The approach allows for non-local moves in a way that preserves micro-reversibility. We find no evidence for a thermodynamic phase transition up to very high densities; the glass is thus indistinguishable from the liquid on purely thermodynamic grounds. PMID:10850709

Santen; Krauth

2000-06-01

253

Effect of polyethylene glycol on the liquidliquid phase transition in aqueous protein solutions  

E-print Network

Effect of polyethylene glycol on the liquid­liquid phase transition in aqueous protein solutions, 2002 We have studied the effect of polyethylene glycol (PEG) on the liquid­liquid phase separation. PEG ternary mixtures solubility partitioning Polyethylene glycol (PEG) is a hydrophilic nonionic

Annunziata, Onofrio

254

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

255

Mixed Stationary Liquid Phases for Gas-Liquid Chromatography.  

ERIC Educational Resources Information Center

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

Koury, Albert M.; Parcher, Jon F.

1979-01-01

256

Spontaneous liquid-liquid phase separation of water  

NASA Astrophysics Data System (ADS)

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

Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

2014-02-01

257

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

E-print Network

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

Paris-Sud XI, Université de

258

Phase transition during uniaxial compression  

NASA Astrophysics Data System (ADS)

An experimental study was conducted to investigate the possibility of a first-order isostructural phase transition during the uniaxial compression of single crystals of Sm(1-x)Gd(x)S solid solutions (x = 0.15). The compression of the samples was carried out along the longest dimension corresponding to the 100 crystallographic direction. A change in the color of samples from black to golden yellow and a discontinuity in electrical conductivity were observed. When the pressure was removed the inverse transition did not occur.

Kaminskii, V. V.; Vinogradov, A. A.; Stepanov, N. N.; Smirnov, I. A.

1983-05-01

259

Heat transfer in gas-liquid and liquid-liquid two phase plug flow systems  

Microsoft Academic Search

Liquid-gas and liquid-liquid two phase flows are examined. It has been recently documented that gas-liquid segmented flows offer a thermal enhancement advantage over single phase flows, since the plug flow (Taylor flow) regime produces internal circulations which enhance radial transport. Additional strategies in liquid-gas and liquid-liquid cooling are being pursued with liquid cooled heat sinks. Proper heat transfer and pressure

N. Janes; Y. S. Muzychka; B. Guy; E. J. Walsh; P. Walsh

2010-01-01

260

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

E-print Network

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

Tobias Herman; John Beamish

2005-06-30

261

Ferromagnetic state and phase transitions  

E-print Network

Evidence is summarized attesting that the standard exchange field theory of ferromagnetism by Heisenberg has not been successful. It is replaced by the crystal field and a simple assumption that spin orientation is inexorably associated with the orientation of its carrier. It follows at once that both ferromagnetic phase transitions and magnetization must involve a structural rearrangement. The mechanism of structural rearrangements in solids is nucleation and interface propagation. The new approach accounts coherently for ferromagnetic state and its manifestations.

Yuri Mnyukh

2011-06-20

262

Structured fiber supports for ionic liquid-phase catalysis used in gas-phase continuous hydrogenation  

Microsoft Academic Search

Structured supported ionic liquid-phase (SSILP) catalysis is a new concept with the advantages of ionic liquids (ILs) used as solvents for homogeneous catalyst and the further benefits of structured heterogeneous catalysts. This is achieved by confining the IL with the transition metal complex to the surface of a structured support consisting of sintered metal fibers (SMFs). In an attempt to

Marina Ruta; Igor Yuranov; Paul J. Dyson; Gabor Laurenczy; Lioubov Kiwi-Minsker

2007-01-01

263

Non-equilibrium phase transitions  

SciTech Connect

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

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

1998-12-31

264

Glass–liquid transition of water at high pressure  

PubMed Central

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

Andersson, Ove

2011-01-01

265

Transient liquid phase ceramic bonding  

DOEpatents

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

Glaeser, Andreas M. (Berkeley, CA)

1994-01-01

266

Effect of size polydispersity on liquid-glass crossover, liquid-crystal transition, and gas-liquid transition of Lennard-Jones fluids  

NASA Astrophysics Data System (ADS)

Generalized replica exchange method (gREM) computer simulations are performed on model glass formers, polydisperse Lennard-Jones (LJ) systems at constant pressure, and discuss the effect of size polydispersity on the gas-liquid and liquid-crystal transitions, and on the liquid-glass crossover. At high temperatures in the gas phase, there are no polydispersity effects on the observables. With decreasing temperature, the enthalpy, internal energy and volume decrease with increasing polydispersity, and the gas-liquid transition point shifts to higher temperature. At low temperature, sufficient polydispersity causes the liquid-crystal transition to disappear; the threshold for this phenomenon lies in a polydispersity range of s = 0.15-0.20. Enthalpy and internal energy show the similar behavior over the whole temperature region with changing polydispersity. On the other hand, volume shows a different polydispersity dependence in the liquid, crystal, and glass states. The pressure dependence of polydispersity effects are also discussed, and a preliminary gas-liquid-crystal-glass phase diagram of polydisperse LJ systems is obtained.

Terada, Yayoi; Keyes, Thomas; Kim, Jaegil; Tokuyama, Michio

2013-02-01

267

Advances in liquid phase technology  

SciTech Connect

The liquid phase methanol (LPMEOH) process uses a slurry reactor to convert synthesis gas (primarily a mixture of hydrogen and carbon monoxide) to methanol. Through its superior heat management, the process is ultimately suitable to handle synthesis gas generated through gasification of natural gas and other materials, such as coal, petroleum coke, residual oil, wastes and other environmentally disadvantaged hydrocarbon feedstocks. Apart from production of chemical grade methanol, the process provides economic advantages in the Integrated Gasification Combined Cycle (IGCC) power generation application. Coproduction of power and methanol via the IGCC and the LPMEOH process provides opportunities for energy storage for peak-shaving of electrical demand and/or clean fuel for export. The LPMEOH technology has been developed since the 1980`s, extensively proven in a process development unit in LaPorte, Texas and elected for demonstration under The Clean Coal Technology Program. The slurry reactor being demonstrated is also suitable for other exothermic synthesis gas conversion reactions, like synthesis of Dimethyl Ether and other alcohols/oxygenates. This paper presents an overview of LPMEOH and other liquid phase technology aspects and highlights the demonstration project at Eastman Chemical Company`s coal gasification facility in Kingsport, Tennessee. Commercial aspects of the LPMEOH process are also discussed.

Jijin, P.J.A. [Air Products and Chemicals, Inc., Allentown, PA (United States)

1997-12-31

268

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

269

Liquid-glass transition in equilibrium  

NASA Astrophysics Data System (ADS)

We show in numerical simulations that a system of two coupled replicas of a binary mixture of hard spheres undergoes a phase transition in equilibrium at a density slightly smaller than the glass transition density for an unreplicated system. This result is in agreement with the theories that predict that such a transition is a precursor of the standard ideal glass transition. The critical properties are compatible with those of an Ising system. The relations of this approach to the conventional approach based on configurational entropy are briefly discussed.

Parisi, G.; Seoane, B.

2014-02-01

270

Liquid-glass transition in equilibrium.  

PubMed

We show in numerical simulations that a system of two coupled replicas of a binary mixture of hard spheres undergoes a phase transition in equilibrium at a density slightly smaller than the glass transition density for an unreplicated system. This result is in agreement with the theories that predict that such a transition is a precursor of the standard ideal glass transition. The critical properties are compatible with those of an Ising system. The relations of this approach to the conventional approach based on configurational entropy are briefly discussed. PMID:25353474

Parisi, G; Seoane, B

2014-02-01

271

Phase transition for dielectric breakdown model  

Microsoft Academic Search

In this paper, the phase transition for DBM when ? varies is investigated by using real-space renormalization-group method. The result demonstrates that there are phase transitions for almost all the value of ?, and we find a new result that the larger ? is, the larger the value of phase transition point qc is.

Fuxuan Chang; Houqiang Li; De Liu; Libin Lin

1997-01-01

272

Phase transitions in KIO(3).  

PubMed

The high-pressure behavior of KIO(3) was studied up to 30 GPa using single crystal and powder x-ray diffraction, Raman spectroscopy, second harmonic generation (SHG) experiments and density functional theory (DFT)-based calculations. Triclinic KIO(3) shows two pressure-induced structural phase transitions at 7 GPa and at 14 GPa. Single crystal x-ray diffraction at 8.7(1) GPa was employed to solve the structure of the first high-pressure phase (space group R3, a = 5.89(1) ?, ? = 62.4(1)°). The bulk modulus, B, of this phase was obtained by fitting a second order Birch-Murnaghan equation of state (eos) to synchrotron x-ray powder diffraction data resulting in B(exp,second) = 67(3) GPa. The DFT model gave B(DFT,second) = 70.9 GPa, and, for a third order Birch-Murnaghan eos, B(DFT,third) = 67.9 GPa with a pressure derivative of [Formula: see text]. Both high-pressure transformations were detectable by Raman spectroscopy and the observation of second harmonic signals. The presence of strong SHG signals shows that all high-pressure phases are acentric. By using different pressure media, we showed that the transition pressures are very strongly influenced by shear stresses. Earlier work on low- and high-temperature transitions was complemented by low-temperature heat capacity measurements. We found no evidence for the presence of an orientational glass, in contrast to earlier dielectric studies, but consistent with earlier low-temperature diffraction studies. PMID:22787136

Bayarjargal, Lkhamsuren; Wiehl, Leonore; Friedrich, Alexandra; Winkler, Björn; Juarez-Arellano, Erick A; Morgenroth, Wolfgang; Haussühl, Eiken

2012-08-15

273

Liquid phase sintering of silicon carbide  

DOEpatents

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

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

1989-01-01

274

Liquid phase sintering of silicon carbide  

DOEpatents

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

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

1989-05-09

275

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

Microsoft Academic Search

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

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

2003-01-01

276

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

E-print Network

temperature TNI down to TNI . The slowest exponential component of the data obeys the Landau­de Gennes Ld the isotropic to nematic phase transition temperature, TNI , but is 30­50 K higher than TCL . The liquid crystal but near the nematic­isotropic N­I phase transition tempera- ture, TNI , (TNI T TNI 50 K), orientational

Fayer, Michael D.

277

Liquid-liquid transition in the ST2 model of water  

NASA Astrophysics Data System (ADS)

We present clear evidence of the existence of a metastable liquid-liquid phase transition in the ST2 model of water. Using four different techniques (the weighted histogram analysis method with single-particle moves, well-tempered metadynamics with single-particle moves, weighted histograms with parallel tempering and collective particle moves, and conventional molecular dynamics), we calculate the free energy surface over a range of thermodynamic conditions, we perform a finite size scaling analysis for the free energy barrier between the coexisting liquid phases, we demonstrate the attainment of diffusive behavior, and we perform stringent thermodynamic consistency checks. The results provide conclusive evidence of a first-order liquid-liquid transition. We also show that structural equilibration in the sluggish low-density phase is attained over the time scale of our simulations, and that crystallization times are significantly longer than structural equilibration, even under deeply supercooled conditions. We place our results in the context of the theory of metastability.

Debenedetti, Pablo

2013-03-01

278

Phase Transition to Exact Susy  

NASA Astrophysics Data System (ADS)

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

Clavelli, L.

2007-04-01

279

Phase transitions in the assembly of multivalent signalling proteins  

SciTech Connect

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

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

2013-04-08

280

Microphase Segregation and Twisting Transitions in Liquid Crystal Polymers  

NASA Astrophysics Data System (ADS)

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

Sones, Richard Allen

281

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

282

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

283

Phase transitions and morphologies of aerosol particles  

NASA Astrophysics Data System (ADS)

Tropospheric aerosol particles consisting of complex mixtures of organic compounds, ammonium sulfate (AS) and water undergo phase transitions such as liquid-liquid phase separation (LLPS), efflorescence and deliquescence as a consequence of changes in ambient relative humidity (RH). These phase transitions in the mixed aerosol particles may lead to different particle configurations such as core-shell or partially engulfed structures. However, the physical states and morphologies of these aerosol particles are still poorly understood. In this study, we investigate the phase transitions and morphological changes of various internally mixed organics/AS/water particles with different organic-to-inorganic ratios (OIR), namely OIR = 6:1, 2:1, 1:2 and 1:6 during humidity cycles using optical microscopy and Raman spectroscopy. Particularly, we explore how the properties of different organic functional groups and the compositional complexity of the organic aerosol fraction influence the occurrence of LLPS in the relationship with the organic oxygen-to-carbon (O:C) ratios. We found that LLPS occurred for all mixtures with O:C < 0.56, for none of the mixtures with O:C > 0.80, and depended on the specific types and compositions of organic functional groups for 0.56 < O:C < 0.80. Moreover, the number of mixture components and the spread of the O:C range did not notably influence the conditions for LLPS to occur. Since in ambient aerosols O:C and OIR range typically between 0.2 and 1.0, and between 4:1 and 1:5, respectively, LLPS is expected to be a common feature of tropospheric aerosols. AS in the mixed particles effloresced between 0 and 47 %RH and deliquesced between 71 and 80 %RH during humidity cycles. Compared to a deliquescence relative humidity (DRH) of 80 % for pure AS, the DRH in the mixed particles showed slightly lower values. A strong reduction or complete inhibition of efflorescence occurred for mixtures with high OIR that did not exhibit LLPS. Both core-shell and partially engulfed morphologies were observed. To obtain definitive conclusions whether the core-shell or the partially engulfed configuration is prevalent, we perform supplementary experiments on levitated particles in an electrodynamic balance and also compare surface and interfacial tensions of the investigated mixtures. The detailed results will be presented.

Song, M.; Marcolli, C.; Krieger, U.; Zuend, A.; Peter, T.

2012-12-01

284

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

E-print Network

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

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

2006-10-19

285

Phase behavior of liquid crystals with CO2.  

PubMed

Liquid crystals are being considered as novel process solvents for CO(2) capture. The solubility of CO(2) is higher in the isotropic phase than in the structured (e.g., nematic) phase. CO(2) can be captured in the isotropic phase, and regeneration of the solvent is achieved by cooling down the mixture a few degrees until a phase transition to the structured phase occurs. This CO(2) capture process has the potential to consume less energy than the conventional amine-based processes. To address the potential of liquid crystals to efficiently capture CO(2), experimentally obtained P,T-phase diagrams of five liquid crystals with 5 mass % CO(2) are reported. The liquid crystals used in this study are 4'-(pentyloxy)-4-biphenylcarbonitrile, 4'-pentyl-4-biphenylcarbonitrile, 4-ethyl-4'-propyl-bicyclohexyl, 4-propyl-4'-butyl-bicyclohexyl, and 4'-(octyloxy)-4-biphenylcarbonitrile. It is found that a weakly polar liquid crystal had a higher CO(2) solubility than apolar and more polar liquid crystals. PMID:22731661

de Groen, Mariëtte; Vlugt, Thijs J H; de Loos, Theo W

2012-08-01

286

BNL-65424-AB LIQUID TO LIQUID AND CRITICAL NUCLEUS TO CRITICAL NUCLEUS PHASE  

E-print Network

11973 Key words: Ammonium sulfate; single particle; phase transitions; critical nucleus I. LIQUID the properties of super-cooled/super-saturated electrolyte solutions of ammonium sulfate and ammonium bisulfate changes its role from the solvent to the solute by tightly binding to the ammonium sulfate ions

287

Phase behavior and dynamics of a cholesteric liquid crystal  

SciTech Connect

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

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

2014-02-21

288

Symmetry systematics of pressure - induced phase transitions  

Microsoft Academic Search

Most pressure induced phase transitions are diffusionless. Because of this, there exists a one-to-one correspondence between the positions of atoms in the parent and the product phases, which, therefore, show interesting symmetry relationships. In this paper, we have used these for discussing a symmetry classification of pressure induced phase transitions into four categories: iso-symmetric, group-subgroup, intersection group, and order-disorder transitions.

Satish C. Gupta; R. Chidambaram

1994-01-01

289

Influence of the Anisometry of Magnetic Particles on the Isotropic-Nematic Phase Transition  

E-print Network

The influence of the shape anisotropy of magnetic particles on the isotropic-nematic phase transition was studied in ferronematics based on the nematic liquid crystal 4-(trans-4-n-hexylcyclohexyl)-isothiocyanato-benzene (6CHBT). The liquid crystal was doped with spherical or rod-like magnetic particles of different size and volume concentrations. The phase transition from isotropic to nematic phase was observed by polarizing microscope as well as by capacitance measurements. The influence of the concentration and the shape anisotropy of the magnetic particles on the isotropic-nematic phase transition in liquid crystal is demonstrated. The results are in a good agreement with recent theoretical predictions.

V. Gdovinová; N. Tomašovi?ová; N. Éber; T. Tóth-Katona; V. Závišová; M. Timko; P. Kop?anský

2014-09-05

290

Is the chiral phase transition induced by a metal-insulator transition?  

E-print Network

We investigate the QCD Dirac operator with gauge configurations given by a liquid of instantons in the region of temperatures about the chiral phase transition. Both the quenched and unquenched cases are examined in detail. We present evidence of a localization transition in the low lying modes of the Dirac operator around the same temperature as the chiral phase transition. Thus both level statistics and eigenvectors of the QCD Dirac operator at the chiral phase transition have similar properties than those of a disordered conductor at the metal-insulator transition. This strongly suggests the phenomenon of Anderson localization (localization by destructive quantum interference) is the leading physical mechanism in the restoration of the chiral symmetry. Finally we argue that our findings are not in principle restricted to the ILM approximation and may also be found in lattice simulations.

Antonio M. Garcia-Garcia; James C. Osborn

2007-11-18

291

Liquid Crystalline Polymer Vesicles: Thermotropic Phases in Lyotropic Structures  

E-print Network

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

Lin Jia; Min-Hui Li

2015-03-04

292

Manifestations de la transition solide-liquide dans les agrégats  

NASA Astrophysics Data System (ADS)

The thermodynamics of clusters is a subject of increasing interest, both from the theoretical and experimental points of view. We present a set of theoretical and numerical methods for studying phase transitions, especially the solid-liquid transition, in atomic or molecular clusters. Several means of characterization (thermodynamical, geometrical and dynamical) are introduced, and the differences between the finite-size behaviour and the bulk behaviour are described. The phenomenon of "dynamical coexistence", which can be seen as the cluster spontaneously going back and forth between the solid and liquid states across the time, is illustrated. Its thermodynamical consequences are also emphasized. Finally, we present some typical thermodynamical phenomena due to the finite-size character, and strongly dependent on the physical chemistry of the matter at the microscopic level. We study these phenomena with Monte Carlo and molecular dynamics simulations: surface melting observed on rare gas clusters, multistage melting observed on ionic clusters, the special behaviours of molecular clusters, and the more intricate problem of free or solvated metallic clusters. La thermodynamique des agrégats est un sujet en développement croissant, tant sur le plan théorique qu'expérimental. Nous présentons un ensemble de méthodes théoriques et numériques destinées à l'étude des transitions de phase, en particulier de la transition solide-liquide, dans les agrégats atomiques et moléculaires. Divers moyens de caractérisation (thermodynamiques, géométriques et dynamiques) sont introduits, et les différences entre les comportements à taille finie et à taille macroscopique sont précisées. Le phénomène de "coexistence dynamique", qui voit l'agrégat passer spontanément de l'état solide à l'état liquide (et réciproquement) au cours du temps, est illustré, et ses conséquences thermodynamiques sont soulignées. Enfin, nous présentons un certain nombre de phénomènes thermodynamiques liés à la taille finie, et dépendant fortement de la nature physico-chimique de la matière à ces échelles. Ces phénomènes sont étudiés à l'aide de simulations Monte Carlo ou de dynamique moléculaire, et sont, successivement: la fusion de surface observée sur des agrégats de gaz rares, la transition solide-liquide par étapes successives observée sur des agrégats ioniques, les spécificités de cette transition pour des agrégats moléculaires, et enfin le problème plus complexe des agrégats métalliques libres ou solvatés.

Calvo, F.

293

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

294

Thermodynamics and phase relationships of transition metal-sulfur systems: Part III. Thermodynamic properties of the Fe-S liquid phase and the calculation of the Fe-S phase diagram  

Microsoft Academic Search

An associated solution model is applied to describe the thermodynamic behavior of Fe-S liquid. This model assumes the existence\\u000a of ‘FeS’ species in addition to Fe and S in the liquid. With two solution parameters for each of the binaries Fe-‘FeS’ and\\u000a ‘FeS’-S, this model accounts for the compositional dependence of the thermodynamic properties of Fe-S liquid from pure Fe

R. C. Sharma; Y. A. Chang

1979-01-01

295

Continuous phase transition and negative specific heat in finite nuclei  

E-print Network

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.

J. N. De; S. K. Samaddar; S. Shlomo; J. B. Natowitz

2006-01-30

296

Formation of liquid and solid products from liquid phase pyrolysis.  

PubMed

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

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

2012-11-01

297

Phase behavior of ionic liquid crystals  

E-print Network

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

S. Kondrat; M. Bier; L. Harnau

2010-04-15

298

Phase behavior of ionic liquid crystals  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

299

Modeling the liquid-solid transition in saturated triglycerides  

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

300

More is the Same; Phase Transitions and Mean Field Theories  

E-print Network

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

Leo P. Kadanoff

2009-09-14

301

Gas-liquid chromatography with a volatile "stationary" liquid phase.  

PubMed

A unique type of gas-liquid chromatography is described in which both mobile and "stationary" phases are composed of synthetic mixtures of helium and carbon dioxide. At temperatures below the critical point of the binary mixture and pressures above the vapor pressure of pure liquid carbon dioxide, helium and carbon dioxide can form two immiscible phases over extended composition ranges. A binary vapor phase enriched in helium can act as the mobile phase for chromatographic separations, whereas a CO2-rich liquid in equilibrium with the vapor phase, but condensed on the column wall, can act as a pseudostationary phase. Several examples of chromatographic separations obtained in "empty" capillary columns with no ordinary stationary liquid phase illustrate the range of conditions that produce such separations. In addition, several experiments are reported that confirm the proposed two-phase hypothesis. The possible consequences of the observed chromatographic phenomenon in the field of supercritical fluid chromatography with helium headspace carbon dioxide are discussed. PMID:12033313

Wells, P S; Zhou, S; Parcher, J F

2002-05-01

302

Game Theory and Topological Phase Transition  

E-print Network

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

Tieyan Si

2008-03-29

303

Quantum Phase Transitions in a Finite System  

E-print Network

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

A. Leviatan

2006-12-05

304

Phase transition to an opaque plasma in a sonoluminescing bubble.  

PubMed

Time-resolved spectrum measurements of a sonoluminescing Xe bubble reveal a transition from transparency to an opaque Planck blackbody. As the temperature is <10?000??K and the density is below liquid density, the photon scattering length is 10?000 times too large to explain its opacity. We resolve this issue with a model that reduces the ionization potential. According to this model, sonoluminescence originates in a new phase of matter with high ionization. Analysis of line emission from Xe* also yields evidence of phase segregation for this first-order transition inside a bubble. PMID:21770508

Kappus, Brian; Khalid, Shahzad; Chakravarty, Avik; Putterman, Seth

2011-06-10

305

Phase Transition to an Opaque Plasma in a Sonoluminescing Bubble  

NASA Astrophysics Data System (ADS)

Time-resolved spectrum measurements of a sonoluminescing Xe bubble reveal a transition from transparency to an opaque Planck blackbody. As the temperature is <10000K and the density is below liquid density, the photon scattering length is 10 000 times too large to explain its opacity. We resolve this issue with a model that reduces the ionization potential. According to this model, sonoluminescence originates in a new phase of matter with high ionization. Analysis of line emission from Xe* also yields evidence of phase segregation for this first-order transition inside a bubble.

Kappus, Brian; Khalid, Shahzad; Chakravarty, Avik; Putterman, Seth

2011-06-01

306

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

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

Analysis of Nuclear Quantum Phase Transitions  

SciTech Connect

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

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

2009-08-26

309

First-Order Dynamical Phase Transitions  

NASA Astrophysics Data System (ADS)

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

Canovi, Elena; Werner, Philipp; Eckstein, Martin

2014-12-01

310

Vapor-liquid phase separator studies  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

311

Phase-separation of miscible liquids in a centrifuge  

E-print Network

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

Yoav Tsori; Ludwik Leibler

2007-12-18

312

Switchable thermal antenna by phase transition  

E-print Network

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

Ben-Abdallah, Philippe; Besbes, Mondher

2013-01-01

313

Microscopic Description of Nuclear Quantum Phase Transitions  

SciTech Connect

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

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

2007-08-31

314

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

315

Thermodynamic and transport anomalies near isotropic-nematic phase transition  

E-print Network

A theoretical study of the variation of thermodynamic and transport properties of calamitic liquid crystals across the isotropic-nematic phase transition is carried out by calculating the {\\it wavenumber (k) and time (t)} dependent intermediate scattering function of the liquid, via computer simulations of model nematogens. The objective is to understand the experimentally observed anomalies and sharp variation in many thermodynamic and transport properties, namely specific heat $C$, sound attenuation coefficient $\\Gamma$, thermal diffusivity $D_T$ and sound velocity $c_s$ are as the I-N transition is approached from the isotropic side. The small wavelength limit of the calculated intermediate scattering function $F(k,t)$ is used to obtain the ratio of specific heats $\\gamma$ and other properties mentioned above. We find that all of them show non-monotonic variations near the I-N transition, with $\\Gamma$ showing a cusp-like behavior. We suggest that the observed anomalous features are a direct consequence of the existence of pseudo-nematic domains in the system near the phase boundary and the melting and formation of such domains give rise to sound attenuation and also to the observed specific heat anomaly. A theoretical description of these anomalies should invoke translation-rotation coupling at molecular level. While the heterogeneous dynamics observed here bear resemblance to that in deeply supercooled liquids near glass transition, the thermodynamic anomalies articulated here are largely absent in supercooled liquids.

Prasanth P. Jose; Biman Bagchi

2008-02-15

316

The Nonequilibrium Phase and Glass Transition Behavior of ?-Lactoglobulin  

PubMed Central

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

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

2005-01-01

317

Magnetic correlations and quantum criticality in the insulating antiferromagnetic, insulating spin liquid, renormalized Fermi liquid, and metallic antiferromagnetic phases  

E-print Network

are common among transition-metal oxides and are an important group of materials which cannot be accounted liquid, renormalized Fermi liquid, and metallic antiferromagnetic phases of the Mott system V2O3 Wei Bao* Physics Department, Brookhaven National Laboratory, Upton, New York 11973 C. Broholm Department of Physics

Broholm, Collin Leslie

318

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

319

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

NASA Astrophysics Data System (ADS)

Yagasaki et al. [Phys. Rev. E 89, 020301 (2014), 10.1103/PhysRevE.89.020301] present results from a molecular dynamics trajectory illustrating coarsening of ice, which they interpret as evidence of transient coexistence between two distinct supercooled phases of liquid water. We point out that neither two distinct liquids nor criticality are demonstrated in this simulation study. Instead, the illustrated trajectory is consistent with coarsening behaviors analyzed and predicted in earlier work by others.

Limmer, David T.; Chandler, David

2015-01-01

320

Detection of lipid phase transitions by surface tensiometry.  

PubMed

A technique for the detection of lipid phase transitions is described, which involves measurement of the surface tension as a function of temperature. In the case of insoluble lipids, such as dipalmitoylphosphatidylcholine (DPPC) the lipid is spread as a multibilayer film on an aqueous substrate, while in the case of water-soluble lipids such as lysophosphatidylcholine (LPC) the surface tension of aqueous sols is measured. Surface tension at the interface, is monitored using a Wilhelmy plate while the temperature is continuously varied. Discontinuities or changes in slope in the surface tension-temperature (gamma-T) curve reflect phase transitions in the lipid. In the case of DPPC, the technique has been used to demonstrate the well-known gel-liquid crystalline thermal transition. This occurs at 36-38 degrees C in the multibilayer films; in bulk DPPC-water dispersions the transition is at 41 degrees. Cholesterol has the effect of lowering the thermal transition and broadening the temperature range. In films containing DPPC-cholesterol at a molar ratio of 2:1 or less, the transition is not present. These results are in agreement with a large number of previous studies of this system. In the case of LPC sols, a phase transition at about 70 degrees was detected when the concentration of SPC was close to the critical micelle concentration (CMC) at 70 degrees. This transition appears to reflect an increase in the equilibrium constant for micelle formation at this temperature. At higher concentrations of LPC a transition at 30 degrees, corresponding to a gel-liquid crystalline transition, was also detected. A complete description of gamma as a function of concentration and temperature in the range 10(-7) to 10(-3) g cm-3 and 20 degrees to 80 degrees has been obtained for LPC sols. The CMC varies from 6 X 10(-6) g cm-3 at 20 degrees to 10(-5) g cm-3 at 80 degrees. PMID:991386

Purdon, A D; Tinker, D O; Neumann, A W

1976-10-01

321

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

322

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

323

The inquiry of liquids and glass transition by heat capacity  

NASA Astrophysics Data System (ADS)

Reconsidering the intrinsic connection between simple liquids and the glass transition, we attempt to understand them with an explicit liquid model. Liquids are defined to the mixture composed of tiny particles restricted in non-identical potential energy wells, where translational motions of tiny particles in statistical equilibrium, as well as vibrations and rotations, are distinguished. The liquid model offers an opportunity to build up a quantitative correlation between heat capacity and the basic motions appearing in liquids. Agreements between theoretical prediction and experimental data on heat capacities of typical simple liquids are reached. A serial of experimental data confirm that the glass transition originates from the falling out-of-equilibrium of the translational motions in liquids. The work might provide a novel and intuitive way to uncover a shady corner of the mysterious liquids and the glass transition.

Ke, Hai Bo; Wen, Ping; Wang, Wei Hua

2012-12-01

324

Viscous fingering in liquid crystals: Anisotropy and morphological transitions  

E-print Network

We show that a minimal model for viscous fingering with a nematic liquid crystal in which anisotropy is considered to enter through two different viscosities in two perpendicular directions can be mapped to a two-fold anisotropy in the surface tension. We numerically integrate the dynamics of the resulting problem with the phase-field approach to find and characterize a transition between tip-splitting and side-branching as a function of both anisotropy and dimensionless surface tension. This anisotropy dependence could explain the experimentally observed (reentrant) transition as temperature and applied pressure are varied. Our observations are also consistent with previous experimental evidence in viscous fingering within an etched cell and simulations of solidification.

R. Folch; J. Casademunt; A. Hernandez-Machado

1999-12-16

325

Quantum Phase Transition Induced by Geometrical Changes in Spin–Phonon Interaction  

NASA Astrophysics Data System (ADS)

Spin–phonon interaction effects in a spin-1/2 antiferromagnetic Heisenberg chain coupled to phonons are investigated in systems with variable crystal structures. By performing a unitary transformation to a Hamiltonian of the system, we derive effective Hamiltonians expanded in powers of spin–phonon and spin–spin couplings. Ground-state phase transitions between a spin-liquid phase and a spin-gapped phase are investigated by a level spectroscopy analysis of numerical diagonalization data of effective systems. Our results depend on whether the ground state of the Heisenberg chain is in the spin-liquid phase or the spin-gapped phase. In the system where the ground state is in the spin-liquid phase, the spin–phonon interaction causes the usual phase transition to the spin-gapped phase. On the other hand, in the system where the ground state is in the spin-gapped phase, the spin–phonon interaction causes the novel phase transition to the spin-liquid phase for some geometrical structures. The phase transition from the spin-gapped phase to the spin-liquid phase is observed by changing a parameter to control the change in a geometrical structure.

Yasuda, Chitoshi; Akiyama, Satoru

2015-01-01

326

Binary Solid-Liquid Phase Equilibria  

ERIC Educational Resources Information Center

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

Ellison, Herbert R.

1978-01-01

327

Pressure-induced phase transition in pentacene  

Microsoft Academic Search

We have recently studied two solid phases of bulk pentacene (polymorphs H and C) by means of lattice phonon Raman spectroscopy. The assignment, previously based on lattice dynamics calculations alone, is now verified by X-ray diffraction measurements, conclusively confirming the existence of both polymorphs. Furthermore, Raman phonon spectra indicate a pressure-induced phase transition where the polymorph C (lower density phase)

L. Farina; A. Brillante; R. G. Della Valle; E. Venuti; M. Amboage; K. Syassen

2003-01-01

328

Stability of the Liquid Phase in Colloidal Electrolytes  

E-print Network

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

José B. Caballero; Antonio M. Puertas

2005-11-28

329

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

NASA Astrophysics Data System (ADS)

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

Shimizu, Ryotaro; Kobayashi, Mika; Tanaka, Hajime

2014-03-01

330

Building of Equations of State with Numerous Phase Transitions - Application to Bismuth  

Microsoft Academic Search

We propose an algorithm to build complete equation of state EOS including several solid\\/solid or solid\\/liquid phase transitions. Each phase has its own EOS and independent parameters. The phase diagram is deduced from the thermodynamic equilibrium assumption. Until now, such an approach was used in simple cases and limited to 2 or 3 phases. We have applied it in the

Olivier Heuzé

2006-01-01

331

The Influence of Disorder on Thermotropic Nematic Liquid Crystals Phase Behavior  

PubMed Central

We review the theoretical research on the influence of disorder on structure and phase behavior of condensed matter system exhibiting continuous symmetry breaking focusing on liquid crystal phase transitions. We discuss the main properties of liquid crystals as adequate systems in which several open questions with respect to the impact of disorder on universal phase and structural behavior could be explored. Main advantages of liquid crystalline materials and different experimental realizations of random field-type disorder imposed on liquid crystal phases are described. PMID:19865529

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

2009-01-01

332

Isotropic-nematic phase transition in aqueous sepiolite suspensions.  

PubMed

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

Woolston, Phillip; van Duijneveldt, Jeroen S

2015-01-01

333

Phase Transition in VO2  

Microsoft Academic Search

The thermal dilatation of VO2 has been measured on ceramic samples from room temperature to 95°C, in connection with Mott's consideration which interpretes the non-metal to metal transition observed in some transition metal oxides as an effect of contraction of lattice spacings. A discontinuous volume expansion was unexpectedly observed at 65°C with increasing temperature. The magnetic susceptibility has also been

Tatsuyuki Kawakubo; Takehiko Nakagawa

1964-01-01

334

Dynamics in supercooled liquids and in the isotropic phase of liquid crystals: A comparison  

NASA Astrophysics Data System (ADS)

A comparison is made of the dynamics observed over wide ranges of time and temperature between five supercooled liquids and four isotropic phase liquid crystals that have been previously studied separately. Optical-heterodyne-detected optical Kerr effect (OHD-OKE) measurements were employed to obtain the orientational relaxation dynamics over time scales from sub-ps to tens of ns. For the supercooled liquids, the temperatures range from above the melting point down to ˜Tc, the mode coupling theory critical temperature. For the liquid crystals, the temperatures range from well above the isotropic-to-nematic phase transition temperature TNI down to ˜TNI. For time scales longer than those dominated by intramolecular vibrational dynamics (?1 ps), the fundamental details of the dynamics are identical. All nine liquids exhibit decays of the OHD-OKE signal that begin (>1 ps) with a temperature-independent power law t-z, where z is somewhat less than or equal to 1. The power law decay is followed in both the supercooled liquids and liquid crystals by a crossover region, modeled as a second power law. The longest time scale decay for all nine liquids is exponential. In supercooled liquids, the exponential decay is the ? relaxation (complete structural relaxation). In liquid crystals, the exponential decay is the Landau-de Gennes decay (relaxation of pseudonematic domains). As Tc (supercooled liquids) and TNI (liquid crystals) are approached from above, the time range over which the "intermediate" power law can be observed increases, until near Tc and TNI, the power law can be observed from >1 ps to many ns. The data for all nine liquids are described accurately by the same functional form and exhibit a scaling relation in common. The nature of the dynamics in the liquid crystals is understood in terms of pseudonematic domains that have a correlation length ?, which increases as TNI is approached. It is conjectured that the similarities between the liquid crystal data and supercooled liquid data are produced by the same underlying physical features: that is, like liquid crystals, supercooled liquid dynamics is a result of structural domains even at relatively high temperature.

Cang, Hu; Li, Jie; Novikov, V. N.; Fayer, M. D.

2003-05-01

335

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

E-print Network

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

Paris-Sud XI, Université de

336

Ten remarks on nonconvex minimisation for phase transition simulations  

Microsoft Academic Search

Nonconvex minimisation problems are encountered in many applications such as phase transitions in solids or liquids but also in optimal design tasks or micromagnetism. In contrast to rubber-type elastic materials and many other variational problems in continuum mechanics, the minimal energy may be not attained. In the sense of (Sobolev) functions, the nonrank-1-convex minimisation problem (M) is ill-posed: The gradients

Carsten Carstensen

2005-01-01

337

Critical behaviours of contact near phase transitions  

PubMed Central

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

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

2014-01-01

338

Critical behaviours of contact near phase transitions.  

PubMed

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

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

2014-01-01

339

Phase transition mechanisms in lanthanide elemental crystals  

NASA Astrophysics Data System (ADS)

A unifying theoretical description is given of the phase transition mechanisms occurring in lanthanide elemental crystals. The hcp-9R-dhcp-fcc sequence of reconstructive phase transitions is interpreted in terms of crossover between displacive and reordering mechanisms. The distorted fcc, monoclinic, ?-U-type and bct high-pressure phases can be depicted by purely displacive mechanisms, the low symmetry of these phases resulting from the non-spherical shape of the electronic shells induced by the delocalization of the f-electrons.

Dmitriev, V. P.; Kuznetsov, A. Yu.; Machon, D.; Weber, H.-P.; Tolédano, P.

2003-03-01

340

Phase separation kinetics in immiscible liquids  

NASA Technical Reports Server (NTRS)

The kinetics of phase separation in the succinonitrile-water system are being investigated. Experiments involve initial physical mixing of the two immiscible liquids at a temperature above the consolute, decreasing the temperature into the miscibility gap, followed by imaging of the resultant microstructure as it evolves with time. Refractive index differences allow documentation of the changing microstructures by noninvasive optical techniques without the need to quench the liquid structures for analysis.

Sadoway, D. R.

1986-01-01

341

Electrically driven phase transition in magnetite nanostructures.  

PubMed

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

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

2008-02-01

342

Pressure induced phase transitions in semimagnetic semiconductors  

Microsoft Academic Search

We have investigated the pressure induced phase transitions from zincblende (B3) to rocksalt (Bl) structures in semimagnetic semiconductors (SMS) Cd1?x, Mnx Z(Z=S, Se, Te) for (0 ? x ? 0.6). Besides, we have predicted the volume collapses (??V(P1)\\/V\\/(O)) associated with the phase transitions in these materials. These predictions have been carried out by means of the three. body potential (TBP)

R. K. Singh; Yasin K. Abdalla

1997-01-01

343

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

E-print Network

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

Paris-Sud XI, Université de

344

Higgs Couplings and Electroweak Phase Transition  

E-print Network

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

Andrey Katz; Maxim Perelstein

2014-07-14

345

Higgs couplings and electroweak phase transition  

NASA Astrophysics Data System (ADS)

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

Katz, Andrey; Perelstein, Maxim

2014-07-01

346

Thermodynamical liquid-glass transition in a lennard-jones binary mixture  

PubMed

We use results derived in the framework of the replica approach to study the liquid-glass thermodynamic transition. The main results are derived without using replicas and applied to the study of the Lennard-Jones binary mixture introduced by Kob and Andersen. We find that there is a phase transition due to the entropy crisis. We compute both analytically and numerically the value of the phase transition point T(K) and the specific heat in the low temperature phase. PMID:11015897

Coluzzi; Parisi; Verrocchio

2000-01-10

347

Closure Phase Signatures of Planet Transit Events  

E-print Network

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

G. T. van Belle

2008-04-16

348

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

349

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

350

Fidelity at Berezinskii-Kosterlitz-Thouless quantum phase transitions  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

351

Phase Transition Patterns of Nuclear Matter Based on Extended Linear Sigma Model  

NASA Astrophysics Data System (ADS)

We study systematically various types of phase transitions in nuclear matter at finite temperature T and baryon chemical potential ? based on the extended linear sigma model with nucleon degrees of freedom. It is shown that there are three types of phase transitions in nuclear matter: the chiral symmetry nonrestoration (SNR) at high temperature, the well-known liquid-gas (LG) phase transition at sub-saturation density and the Lifshitz phase transition (LPT) from the fully-gapped state to the state with Fermi surface. Their phase diagrams are established in the (T, ?)-plane and their physical properties are investigated in detail. The relationship between the chiral phase transition and the LG phase transition in nuclear matter is discussed.

Phat, Tran Huu; Anh, Nguyen Tuan; Ha, Phung Thi Thu

2013-11-01

352

A new evidence of first-order phase transition for hydrogen at 3000 K  

NASA Astrophysics Data System (ADS)

The molecular-dynamics simulations based on density functional theory have been explored to study the properties of warm dense hydrogen in the density range 0.3\\text-1.1 \\text{g/cm}3 and temperature between 1000 and 3000 K. We find clear evidence of pressure discontinuity at the isotherm of 3000 K by large-scale simulations, which also confirm the first-order nature of this transition. It indicates that the molecular liquid phase is unexpectedly stable, and the temperature of transition towards an atomic liquid phase is much higher than previously predicted. A new transition line has been located in the phase diagram.

Yang, J.; Tian, Ch. L.; Liu, F. Sh.; Cai, L. C.; Yuan, H. K.; Zhong, M. M.; Xiao, F.

2015-02-01

353

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

NASA Astrophysics Data System (ADS)

Our detailed and controlled studies of free energy surfaces for models of water find no evidence for reversible polyamorphism, and a general theoretical analysis of the phase behavior of cold water in nano pores shows that measured behaviors of these systems reflect surface modulation and dynamics of ice, not a liquid-liquid critical point. A few workers reach different conclusions, reporting evidence of a liquid-liquid critical point in computer simulations of supercooled water. In some cases, it appears that these contrary results are based upon simulation algorithms that are inconsistent with principles of statistical mechanics, such as using barostats that do not reproduce the correct distribution of volume fluctuations. In other cases, the results appear to be associated with difficulty equilibrating the supercooled material and mistaking metastability for coarsening of the ordered ice phase. In this case, sufficient information is available for us to reproduce the contrary results and to establish that they are artifacts of finite time sampling. This finding leads us to the conclusion that two distinct, reversible liquid phases do not exist in models of supercooled water.

Chandler, David; Limmer, David

2013-03-01

354

AdS Phase Transitions at finite ?  

E-print Network

We investigate the effect of adding a Chern-Simons term coupled to an axion field to SU(2) Einstein-Yang-Mills in a fixed $AdS_4$/Schwarzschild background. We show that, when the axion has no potential, there is a phase transition between a Reissner-Nordstrom black-hole and one with a non-abelian condensate as per the vanishing Chern-Simons case. Furthermore, by giving the axion field a mass, one observes a phase transition between a Reissner-Nordstrom black-hole with axion hair to a "superconducting" phase which also has a non-trivial axion profile. We are able to perform a preliminary analysis for this interesting case and observe that we can shift the critical temperature at which the phase transition occurs and observe interesting features of the order parameter scaling form.

Gianni Tallarita

2011-08-17

355

Liquid-vapor phase equilibrium in a tin-selenium system  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

356

Size dependence of phase transitions in aerosol nanoparticles  

PubMed Central

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

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

2015-01-01

357

Size dependence of phase transitions in aerosol nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

358

Phase transition and properties of compact star  

E-print Network

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

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

2006-11-13

359

Liquid phase sintered compacts in space  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

360

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...

361

A Liquid-Phase Diffusion Experiment.  

ERIC Educational Resources Information Center

Describes an experiment that measures the diffusion of ions in the liquid phase and shows that the relative distances of diffusion are related qualitatively to the inverse of the mass of the solvated ion. Involves soluble salts on opposite sides of a Petri dish diffusing through a layer of water and meeting to form an insoluble salt. (JRH)

Nemetz, Thomas M.; Ball, David W.

1995-01-01

362

Quantum Phase Transition in a Clean Two-Dimensional Electron System  

NASA Astrophysics Data System (ADS)

A quantum phase transition that was recently observed in a high-mobility silicon metal-oxide-semiconductor field-effect transistor is analyzed in terms of a scaling theory. The most striking characteristic of the transition is a divergence of the thermopower, according to an inverse linear law, as a critical value of the electron density is approached. A scaling description of this transition yields predictions about the critical behavior of other observables, e.g., the specific heat. We also explore the possibility that this transition realizes a recently predicted transition from a Fermi liquid to a non-Fermi-liquid state.

Kirkpatrick, T. R.; Belitz, D.

2013-01-01

363

Diffraction Studies of Ordered Phases and Phase Transitions  

E-print Network

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

364

Disorder driven quantum phase transitions in transition metal oxides  

Microsoft Academic Search

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

Kohjiro Kobayashi; Nandini Trivedi

2007-01-01

365

Solid-liquid transition in polydisperse Lennard-Jones systems  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

366

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

NASA Astrophysics Data System (ADS)

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

Tanaka, Hajime

2013-03-01

367

Gravitational Role in Liquid Phase Sintering  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

368

Critical Behavior at the L-L Phase Transition of Lysozyme Protein Solutions  

NASA Technical Reports Server (NTRS)

Recent efforts suggest the possibility that crystallization, and liquid-liquid (L-L) phase transitions and critical phenomena are characteristics universal to all macromolecular solutions. Of particular interest to protein crystallographers are the predictions of a critical slowing of crystal growth and subsequent formation of nascent crystals at the L-L phase boundary. Herein, the effects of the L-L phase transition on both crystal growth rates and microcrystal formation are experimentally determined. In general, it was determined that critical slowing down of protein crystal growth rates occurred, as predicted. The L-L phase transition, however, had a net negative influence in the formation of nascent protein crystals. Although crystal nucleation was not induced by the L-L phase transition, it is considered that the phase behavior of macromolecular solutions can be universally defined.

Gorti, Sridhar; Forsythe, Elizabeth; Laxson, Nicole; Pusey, Marc

2003-01-01

369

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

370

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

371

Friction forces on phase transition fronts  

SciTech Connect

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

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

2013-07-01

372

Friction forces on phase transition fronts  

E-print Network

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

Ariel Megevand

2013-03-31

373

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

NASA Astrophysics Data System (ADS)

A temperature scaling analysis using the same mode coupling theory (MCT) scaling relationships employed for supercooled liquids is applied to optical heterodyne detected optical Kerr effect data for four liquid crystals. The data cover a range of times from ˜1 ps to 100 ns and a range of temperatures from ˜50 K above the isotropic to nematic phase transition temperature TNI down to ˜TNI. The slowest exponential component of the data obeys the Landau-de Gennes (LdG) theory for the isotropic phase of liquid crystals. However, it is also found that the liquid crystal data obey MCT scaling relationships, but, instead of a single scaling temperature TC as found for supercooled liquids, in the liquid crystals there are two scaling temperatures TCL (L for low temperature) and TCH (H for high temperature). TCH is very close to T*, which results from LdG scaling, just below the isotropic to nematic phase transition temperature, TNI, but is 30-50 K higher than TCL. The liquid crystal time dependent data have the identical functional form as supercooled liquid data, that is, a fast power law decay with temperature independent exponent, followed by a slower power law decay with temperature independent exponent, and on the longest time scales, an exponential decay with highly temperature dependent decay constant. For each liquid crystal, the amplitudes of the two power laws scale with expressions that involve TCL, but the exponential decay time constant (long time dynamics) scales with an expression that involves TCH. The existence of two scaling temperatures can be interpreted as a signature of two "glass transitions" in liquid crystals. In ideal MCT developed for spheres, TC is the "ideal glass transition temperature," although it is found experimentally to be ˜20%-30% above the experimental glass transition temperature, Tg. The transition in nematic liquid crystals at TCL corresponds to the conventional ideal MCT glass transition, while the transition at TCH can occur for nonspherical molecules, and may correspond to the freezing in of local nematic order.

Cang, Hu; Li, Jie; Novikov, V. N.; Fayer, M. D.

2003-11-01

374

Microrheology close to an equilibrium phase transition  

SciTech Connect

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

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

2014-04-14

375

Late-time cosmological phase transitions  

SciTech Connect

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

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

1990-11-01

376

Reconstructive structural phase transitions in dense Mg  

NASA Astrophysics Data System (ADS)

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

Yao, Yansun; Klug, Dennis D.

2012-07-01

377

Reconstructive structural phase transitions in dense Mg.  

PubMed

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

Yao, Yansun; Klug, Dennis D

2012-07-01

378

The ?–? phase transition in volcanic cristobalite  

PubMed Central

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

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

2014-01-01

379

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

380

Queueing phase transition: theory of translation  

PubMed Central

We study the current of particles on a lattice, where to each site a different hopping probability has been associated and the particles can move only in one direction. We show that the queueing of the particles behind a slow site can lead to a first-order phase transition, and derive analytical expressions for the configuration of slow sites for this to happen. We apply this stochastic model to describe the translation of mRNAs. We show that the first-order phase transition, uncovered in this work, is the process responsible for the classification of the proteins having different biological functions. PMID:19519001

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

2013-01-01

381

Queueing phase transition: theory of translation.  

PubMed

We study the current of particles on a lattice, where to each site a different hopping probability has been associated and the particles can move only in one direction. We show that the queueing of the particles behind a slow site can lead to a first-order phase transition, and derive analytical expressions for the configuration of slow sites for this to happen. We apply this stochastic model to describe the translation of mRNAs. We show that the first-order phase transition, uncovered in this work, is the process responsible for the classification of the proteins having different biological functions. PMID:19519001

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

2009-05-15

382

Observation of shear-induced nematic-isotropic transition in side-chain liquid crystal polymers  

Microsoft Academic Search

Flow-induced phase transitions are a fundamental (but poorly understood) property of non-equilibrium systems, and are also of practical importance for tuning the processing conditions for plastics, petroleum products, and other related materials. Recognition that polymers may exhibit liquid crystal properties has led to the discovery of the first tailored side-chain liquid crystal polymers (SCLCPs), which are formed by inserting a

Caroline Pujolle-Robic; Laurence Noirez

2001-01-01

383

Dimension changing phase transitions in instanton crystals  

NASA Astrophysics Data System (ADS)

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

Kaplunovsky, Vadim; Sonnenschein, Jacob

2014-04-01

384

On transit time instability in liquid jets  

NASA Technical Reports Server (NTRS)

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

Grabitz, G.; Meier, G.

1982-01-01

385

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

Microsoft Academic Search

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

J. J. Brandner; S. Maikowske

2012-01-01

386

Molecular order and thermodynamics of the solid-liquid transition in triglycerides via Raman spectroscopy.  

PubMed

The conformational and thermodynamic behavior of five monoacid saturated triglycerides (TGs) before, during, and above the beta polymorph --> liquid phase transition was studied using Raman spectroscopy. The Raman ratio I[upsilon(s)(CH(2))]/I[upsilon(as)(CH(2))], used to identify intramolecular order about TG hydrocarbon chains, demonstrated that a single conformation, geometry and symmetry existed in liquid-state TGs. The Raman ratio I(1080)/I(1130), used to determine the intermolecular order/disorder about the hydrocarbon chains and relative trans/gauche content, remained constant for TGs in the crystalline state, but steadily increased as a function of temperature in the liquid state. Use of the van't Hoff relation and the spectroscopically-determined trans/gauche content indicated the presence of distinctive pre- and post-transition enthalpies/entropies indicating that the beta --> liquid phase transition is "soft", with possible intermediate conformations. The liquid-state ester carbonyl stretching region, which gave rise to a broad peak between 1780-1700 cm(-1), was decomposed into multiple components. It demonstrated solid-like character 2-3 degrees C above the TG beta-polymorph melting point, above which no further change in spectral character was observed. These results indicate that the solid-liquid transition in TGs is of the "soft" type with non-lamellar conformations likely present in the melt. PMID:18665310

Da Silva, Eric; Rousseau, Dérick

2008-08-21

387

FULLY INTEGRATED ONE PHASE LIQUID COOLING SYSTEM FOR ORGANIC BOARDS  

E-print Network

FULLY INTEGRATED ONE PHASE LIQUID COOLING SYSTEM FOR ORGANIC BOARDS D. May1 , B. Wunderle1 , F in designing liquid cooling solu- tions are performance, reliability and price. To that end a one-phase liquid to keep doing so [1, 2], liquid cooling solutions remain an interesting but challenging al- ternative

Paris-Sud XI, Université de

388

Geometry-induced phase transition in fluids: capillary prewetting  

E-print Network

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-mu 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.

Petr Yatsyshin; Nikos Savva; Serafim Kalliadasis

2013-03-01

389

Convex Arrhenius behaviour in a nematic-isotropic phase transition  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

390

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

2004-10-01

391

Delocalization and phase transitions in Pr: Theory  

NASA Astrophysics Data System (ADS)

Density-functional electronic structure calculations have been used to investigate the high pressure behavior of Pr at low temperature. Several phase transitions are suggested by these calculations and they agree well with available experimental data. At low pressure, a dhcp (Pr-I)-->fcc (Pr-II) transition is calculated to occur at 60 kbar. Not considering the Pr-III phase, which is computationally too demanding, Pr-II transforms to the ?-U (Pr-IV) phase at 165 kbar. This latter transition is accompanied by a volume collapse of about 10% and is driven by delocalization of the 4f electrons in Pr. The axial ratios (b/a and c/a) and the internal parameter y of Pr-IV were calculated as a function of compression. y and c/a are rather insensitive to the compression whereas b/a decreases significantly with increasing pressure. At about 1 Mbar a new phase is predicted, namely a body-centered-tetragonal (bct) structure with a c/a axial ratio of 1.78. This new phase is stable up to very high pressures but at a sixfold compression an ultimate hexagonal close-packed (hcp) structure is predicted. The calculated high pressure behavior of Pr is similar to that of the early actinide Pa. Pressure induced increase in 4f-orbital overlap, occupation and band width together with an increased electrostatic Coulomb interaction with pressure are the key components in stabilizing the high pressure phases of Pr.

Söderlind, Per

2002-03-01

392

Delocalization and phase transitions in Pr: theory  

NASA Astrophysics Data System (ADS)

Density-functional electronic structure calculations have been used to investigate the high pressure behavior of Pr at low temperature. Several phase transitions are suggested by these calculations and they agree well with available experimental data. At low pressure, a dhcp (Pr-I) ? fcc (Pr-II) transition is calculated to occur at 60 kbar. Not considering the Pr-III phase, which is computationally too demanding, Pr-II transforms to the ?-U (Pr-IV) phase at 165 kbar. This latter transition is accompanied by a volume collapse of about 10% and is driven by delocalization of the 4f electrons in Pr. The axial ratios (b/a and c/a) and the internal parameter y of Pr-IV were calculated as a function of compression. y and c/a are rather insensitive to the compression whereas b/a decreases significantly with increasing pressure. At about 1 Mbar a new phase is predicted, namely a body-centered-tetragonal (bct) structure with a c/a axial ratio of 1.78. This new phase is stable up to very high pressures but at a sixfold compression an ultimate hexagonal close-packed (hcp) structure is predicted. The calculated high pressure behavior of Pr is similar to that of the early actinide Pa. Pressure induced increase in 4f-orbital overlap, occupation and band width together with an increased electrostatic Coulomb interaction with pressure are the key components in stabilizing the high pressure phases of Pr.

Soderlind, Per

2002-03-01

393

Phase change in liquid face seals  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

394

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

395

Transient liquid phase bonding of intermetallics  

Microsoft Academic Search

The present work was undertaken to examine the applicability of transient liquid phase bonding to structural intermetallics. This research was based on an investigation of the mechanisms governing microstructural development in the joint and adjacent substrates during the joining process. The bonding systems investigated included polycrystalline NiAl\\/Cu\\/Ni, polycrystalline NiAl\\/Cu\\/superalloys (Martin-Marietta (MM)-247, Inconel (IN) 718 and Nimonic 90), single-crystal NiAl (with

Yimin Guan

1998-01-01

396

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

SciTech Connect

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{sub c} ? 41000 atm, ?{sub c} ? 0.1 g/cm{sup 3}, and T{sub c} ? 9750 K.

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

2013-10-15

397

Phase transitions from preheating in gauge theories  

PubMed

We show by studying the Abelian Higgs model with numerical lattice simulations that nonthermal phase transitions arising out of preheating after inflation are possible in gauge-Higgs models under rather general circumstances. This may lead to the formation of gauged topological defects and, if the scale at which inflation ends is low enough, to electroweak baryogenesis after preheating. PMID:10991438

Rajantie; Copeland

2000-07-31

398

Large N Phase Transitions in Low Dimensions  

NASA Astrophysics Data System (ADS)

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

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

399

Structure and phase transitions in Langmuir monolayers  

Microsoft Academic Search

Lipid monolayers on the surface of water have been studied for over a hundred years, but in the last decade there has been a dramatic evolution in our understanding of the structures and phase transitions of these systems, driven by new experimental techniques and theoretical advances. In this review, dense monolayers of simple lipids are described in detail, including structures

Vladimir M. Kaganer; Helmuth Möhwald; Pulak Dutta

1999-01-01

400

Universal scaling behavior of nonequilibrium phase transitions  

E-print Network

. The presented picture gallery of universal scaling functions includes steady state, dynamical as well as finite.3 Universality 10 1.4 Remarks on renormalization group theory 16 2 Absorbing phase transitions 25 2.1 Definitions and the contact process at first glance 25 2.2 Numerical simulation methods 32 2.2.1 Steady state scaling behavior

Lübeck, Sven

401

Chiral Phase Transitions around Black Holes  

E-print Network

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

Antonino Flachi; Takahiro Tanaka

2011-06-20

402

Discovery of phase transitions in photosynthetic systems  

NASA Astrophysics Data System (ADS)

The temperature dependence of Stokes Raman scattering from green monocellular algae ( Chlorella pyrenoidosa) indicates that phase transitions which involve the photoactive pigment molecules occur during warming up at 230 K and 261 K. It is shown that these collective structural rearrangements lead to a spectral shape which is known from Raman experiments with living cells.

Drissler, F.

1980-05-01

403

Caloric materials near ferroic phase transitions  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

404

Caloric materials near ferroic phase transitions.  

PubMed

A magnetically, electrically or mechanically responsive material can undergo significant thermal changes near a ferroic phase transition when its order parameter is modified by the conjugate applied field. The resulting magnetocaloric, electrocaloric and mechanocaloric (elastocaloric or barocaloric) effects are compared here in terms of history, experimental method, performance and prospective cooling applications. PMID:24751772

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

2014-05-01

405

Polymorphic phase transition mechanism of compressed coesite.  

PubMed

Silicon dioxide is one of the most abundant natural compounds. Polymorphs of SiO2 and their phase transitions have long been a focus of great interest and intense theoretical and experimental pursuits. Here, compressing single-crystal coesite SiO2 under hydrostatic pressures of 26-53?GPa at room temperature, we discover a new polymorphic phase transition mechanism of coesite to post-stishovite, by means of single-crystal synchrotron X-ray diffraction experiment and first-principles computational modelling. The transition features the formation of multiple previously unknown triclinic phases of SiO2 on the transition pathway as structural intermediates. Coexistence of the low-symmetry phases results in extensive splitting of the original coesite X-ray diffraction peaks that appear as dramatic peak broadening and weakening, resembling an amorphous material. This work sheds light on the long-debated pressure-induced amorphization phenomenon of SiO2, but also provides new insights into the densification mechanism of tetrahedrally bonded structures common in nature. PMID:25791830

Hu, Q Y; Shu, J-F; Cadien, A; Meng, Y; Yang, W G; Sheng, H W; Mao, H-K

2015-01-01

406

Does Sex Induce a Phase Transition?  

E-print Network

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

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

2009-01-01

407

The comfortable driving model revisited: traffic phases and phase transitions  

NASA Astrophysics Data System (ADS)

We study the spatiotemporal patterns resulting from different boundary conditions for a microscopic traffic model and contrast them with empirical results. By evaluating the time series of local measurements, the local traffic states are assigned to the different traffic phases of Kerner’s three-phase traffic theory. For this classification we use the rule-based FOTO-method, which provides ‘hard’ rules for this assignment. Using this approach, our analysis shows that the model is indeed able to reproduce three qualitatively different traffic phases: free flow (F), synchronized traffic (S), and wide moving jams (J). In addition, we investigate the likelihood of transitions between the three traffic phases. We show that a transition from free flow to a wide moving jam often involves an intermediate transition: first from free flow to synchronized flow and then from synchronized flow to a wide moving jam. This is supported by the fact that the so-called F ? S transition (from free flow to synchronized traffic) is much more likely than a direct F ? J transition. The model under consideration has a functional relationship between traffic flow and traffic density. The fundamental hypothesis of the three-phase traffic theory, however, postulates that the steady states of synchronized flow occupy a two-dimensional region in the flow-density plane. Due to the obvious discrepancy between the model investigated here and the postulate of the three-phase traffic theory, the good agreement that we found could not be expected. For a more detailed analysis, we also studied vehicle dynamics at a microscopic level and provide a comparison of real detector data with simulated data of the identical highway segment.

Knorr, Florian; Schreckenberg, Michael

2013-07-01

408

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

NASA Technical Reports Server (NTRS)

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

Lee, Jinho

1993-01-01

409

Magnetic fluctuations and correlations in MnSi: Evidence for a chiral skyrmion spin liquid phase  

SciTech Connect

We present a comprehensive analysis of high-resolution neutron scattering data involving neutron spin echo spectroscopy and spherical polarimetry, which confirm the first-order nature of the helical transition in MnSi. The experiments reveal the existence of a totally chiral dynamic phase in a very narrow temperature range above T{sub C}. This unconventional magnetic short-range order has a topology similar to that of a skyrmion liquid or the blue phases of liquid crystals.

Pappas, C. [Delft University of Technology, Faculty of Applied Sciences, Mekelweg 15, NL-2629JB Delft (Netherlands); Helmholtz Center Berlin for Materials and Energy, Glienickerstr. 100, DE-14109 Berlin (Germany); Lelievre-Berna, E.; Bentley, P.; Falus, P.; Fouquet, P.; Farago, B. [Institut Laue Langevin, 6, Rue Jules Horowitz, FR-38042 Grenoble (France)

2011-06-01

410

Glass and liquid phase diagram of a polyamorphic monatomic system.  

PubMed

We perform out-of-equilibrium molecular dynamics (MD) simulations of a monatomic system with Fermi-Jagla (FJ) pair potential interactions. This model system exhibits polyamorphism both in the liquid and glass state. The two liquids, low-density (LDL) and high-density liquid (HDL), are accessible in equilibrium MD simulations and can form two glasses, low-density (LDA) and high-density amorphous (HDA) solid, upon isobaric cooling. The FJ model exhibits many of the anomalous properties observed in water and other polyamorphic liquids and thus, it is an excellent model system to explore qualitatively the thermodynamic properties of such substances. The liquid phase behavior of the FJ model system has been previously characterized. In this work, we focus on the glass behavior of the FJ system. Specifically, we perform systematic isothermal compression and decompression simulations of LDA and HDA at different temperatures and determine "phase diagrams" for the glass state; these phase diagrams varying with the compression/decompression rate used. We obtain the LDA-to-HDA and HDA-to-LDA transition pressure loci, P(LDA-HDA)(T) and P(HDA-LDA)(T), respectively. In addition, the compression-induced amorphization line, at which the low-pressure crystal (LPC) transforms to HDA, P(LPC-HDA)(T), is determined. As originally proposed by Poole et al. [Phys. Rev. E 48, 4605 (1993)] simulations suggest that the P(LDA-HDA)(T) and P(HDA-LDA)(T) loci are extensions of the LDL-to-HDL and HDL-to-LDL spinodal lines into the glass domain. Interestingly, our simulations indicate that the P(LPC-HDA)(T) locus is an extension, into the glass domain, of the LPC metastability limit relative to the liquid. We discuss the effects of compression/decompression rates on the behavior of the P(LDA-HDA)(T), P(HDA-LDA)(T), P(LPC-HDA)(T) loci. The competition between glass polyamorphism and crystallization is also addressed. At our "fast rate," crystallization can be partially suppressed and the glass phase diagram can be related directly with the liquid phase diagram. However, at our "slow rate," crystallization cannot be prevented at intermediate temperatures, within the glass region. In these cases, multiple crystal-crystal transformations are found upon compression/decompression (polymorphism). PMID:23425481

Reisman, Shaina; Giovambattista, Nicolas

2013-02-14

411

Glass and liquid phase diagram of a polyamorphic monatomic system  

NASA Astrophysics Data System (ADS)

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

Reisman, Shaina; Giovambattista, Nicolas

2013-02-01

412

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

413

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

NASA Technical Reports Server (NTRS)

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

Selinger, Jonathan V.; Bruinsma, Robijn F.

1991-01-01

414

Dynamic light scattering study of the N* to NL* transition in a chiral liquid crystal  

NASA Astrophysics Data System (ADS)

The NL* phase, occurring between cholesteric and twist grain boundary (TGB) phases in chiral liquid crystals, has been conjectured to be a “chiral line liquid” [1] characterized by short-range smectic layering and melted grain boundaries. The resulting “fluid” of screw dislocations is the proposed liquid crystal analog of the Abrikosov flux liquid phase. X-ray scattering and heat capacity studies indicate, however, that the NL* phase has fairly well developed smectic order [2], and that there is only a rounded thermal signature of the transition to the higher temperature (cholesteric) structure [3]. Our dynamic light scattering experiments on the homologous series nF2 Mxxxx reveal a very fast (MHz) non-hydrodynamic fluctuation mode throughout the NL* phase, which is consistent with the presence of smectic layering. In addition, in a narrow temperature range just above the reported NL*/N* transition, we observe anomalous director dynamics and a metastable “square lattice” optical diffraction pattern that implies a destabilization of the cholesteric layers. We will discuss the possible connections among these observations, incipient grain boundary formation, and a chiral line liquid structure. Supported by NSF grant no. DMR-9904321 [1] R. D. Kamien and T. C. Lubensky, J. Phys. I (Fr) 3, 2131 (1993). [2] L. Navailles et al, Phys. Rev. Lett. 81, 4168 (1998). [3] L. Navailles, C. W. Garland, and H. Nguyen, J. Phys. II (Fr) 6, 1243 (1996).

Adorjan, Anthony; Stojadinovic, Strahinja; Sukhomlinova, Lucy; Twieg, Robert; Sprunt, Samuel

2002-03-01

415

The comfortable driving model revisited: Traffic phases and phase transitions  

E-print Network

We study the spatiotemporal patterns resulting from different boundary conditions for a microscopic traffic model and contrast it with empirical results. By evaluating the time series of local measurements, the local traffic states are assigned to the different traffic phases of Kerner's three-phase traffic theory. For this classification we use the rule-based FOTO-method, which provides `hard' rules for this assignment. Using this approach, our analysis shows that the model is indeed able to reproduce three qualitatively different traffic phases: free flow (F), synchronized traffic (S), and wide moving jams (J). In addition, we investigate the likelihood of transitions between the three traffic phases. We show that a transition from free flow (F) to a wide moving jam (J) often involves an intermediate transition; first from free flow F to synchronized flow S and then from synchronized flow to a wide moving jam. This is supported by the fact that the so called F->S transition (from free flow to synchronized t...

Knorr, Florian

2013-01-01

416

Phase Separation Kinetics of a Liquid Crystal-Polymer Mixture  

Microsoft Academic Search

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

J. Y. Kim; P. Palffy-muhoray

1991-01-01

417

General nature of liquid-liquid transition in aqueous organic solutions  

NASA Astrophysics Data System (ADS)

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

Murata, Ken-Ichiro; Tanaka, Hajime

2013-11-01

418

Manipulating topological phase transition by strain.  

PubMed

First-principles calculations show that strain-induced topological phase transition is a universal phenomenon in those narrow-gap semiconductors for which the valence band maximum (VBM) and conduction band minimum (CBM) have different parities. The transition originates from the opposite responses of the VBM and CBM, whose magnitudes depend critically on the direction of the applied strain. Our work suggests that strain can play a unique role in tuning the electronic properties of topological insulators for device applications, as well as in the achievement of new topological insulators. PMID:24508956

Liu, Junwei; Xu, Yong; Wu, Jian; Gu, Bing-Lin; Zhang, S B; Duan, Wenhui

2014-02-01

419

Phase Transitions in Paradigm Shift Models  

PubMed Central

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

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

2013-01-01

420

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

421

Twisting transition in a fiber composed of chiral smectic-C liquid crystal polymer  

NASA Astrophysics Data System (ADS)

We consider a cylindrical fiber composed of main-chain liquid crystal polymer in the chiral smectic-C phase. Due to steric constraints on the liquid crystal polymer, the smectic layers orient perpendicular to the fiber axis, the liquid crystal director lies flat against the fiber wall, and a line disclination appears along the fiber axis. Using a Landau-de Gennes expression for the elastic free energy, we show that the fiber may undergo a transition from a cylinder to a helix. The transition is favored by large chirality, large fiber radius, and low surface tension, but is probably not experimentally accessible. However, a related transition involving only the disclination should be observable.

Sones, R. A.; Petschek, R. G.; Cronin, D. W.; Terentjev, E. M.

1996-04-01

422

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

PubMed

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

Matsuyama, Akihiko

2014-11-14

423

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

NASA Astrophysics Data System (ADS)

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

Matsuyama, Akihiko

2014-11-01

424

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

NASA Astrophysics Data System (ADS)

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

Ohmura, Satoshi; Shimojo, Fuyuki

2011-12-01