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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

Phase transition in dimer liquids  

NASA Astrophysics Data System (ADS)

We study the phase transition in a system composed of dimers interacting with each other via a nearest-neighbor (NN) exchange J and competing interactions taken from a truncated dipolar coupling. Each dimer occupies a link between two nearest sites of a simple cubic lattice. We suppose that dimers are self-avoiding and can have only three orientations, which coincide with the x, y or z direction. The interaction J is attractive if the two dimers are parallel to each other at the NN distance, zero otherwise. The truncated dipolar interaction is characterized by two parameters: its amplitude D and the cutoff distance rc. Using the steepest descent method, we determine the ground-state (GS) configuration as functions of D and rc. We then use Monte Carlo simulations to investigate the nature of the low-temperature phase and to determine characteristics of the phase transition from the ordered phase to the disordered phase at high temperatures at a given dimer concentration. We show that as the temperature increases, dimers remain in the compact state and the transition from the low-T compact phase to the disordered phase where dimers occupy the whole space is of second order when D is small, but becomes of first order for large enough D, for both polarized and nonpolarized dimers. This transition has a resemblance to the unfolding polymer transition. The effect of rc is discussed.

Hoang, Danh-Tai; Diep, H. T.

2014-01-01

3

Solid-liquid phase transition in argon  

NASA Technical Reports Server (NTRS)

Starting from the Lennard-Jones interatomic potential, a modified cell theory has been used to describe the solid-liquid phase transition in argon. The cell-size variations may be evaluated by a self-consistent condition. With the inclusion of cell-size variations, the transition temperature, the solid and liquid densities, and the liquid-phase radial-distribution functions have been calculated. These ab initio results are in satisfactory agreement with molecular-dynamics calculations as well as experimental data on argon.

Tsang, T.; Tang, H. T.

1978-01-01

4

Nuclear liquid-gas phase transition  

SciTech Connect

Calculations of the equation of state of nuclear matter strongly suggest the existence of a liquid-gas phase transition. However, how sharp the transition will appear in finite nuclei, and what the experimental signatures will be are questions which evoke considerable debate. The current status of these issues, particularly the experimental signature ambiguities, is reviewed here.

Boal, D.H.

1984-11-15

5

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

6

Phase transitions in liquid crystal + aerosil gels  

NASA Astrophysics Data System (ADS)

Liquid Crystals (LCs) are found in many different phases, the most well-known, basic ones being Isotropic (I), Nematic (N), and Smectic-A (SmA). LCs show a rich variety of phase transitions between these phases. This makes them very interesting materials in which to study the basics of phase transitions and related topics. In the low symmetry phases, LCs show both positional and directional orders. X-ray scattering is an important tool to study these phase transitions as it probes the instantaneous positional correlations in these phases. Random forces have a nontrivial effect on ordering in nature, and the problem of phase transitions in the presence of a random field is a current and not well-understood topic. It has been found that aerosils posses a quenched randomness in the mixture of LC+aerosil samples, forming a gel random network which destroys long-range order (LRO) in the SmA phase. This can be modeled as a random field problem. In the N to SmA phase transition in 4O.8 LC (butyloxybenzlidene octylaniline), orientational order (N ) is modified by a 1-D density wave describing 2-D fluid layer spacing structure (SmA). Likewise the I to Sm A phase transition in 10CB LC (decylcyanobiphenyl), a transitional ordered phase develops without going through an orientational ordered phase. To study these phase transitions with aerosil dispersion carries the opportunity to probe the effect of induced quenched random disorder on phase transitions, which are 2nd order in the first case and 1st order in the second case. A two-component line-shape analysis is developed to define the phases in all temperature ranges. It consists of the thermal and the static structure factors. The reentered nematic (RN) phase of the [6:8]OCB+aerosil gels ([6:8]OCB is a mixture of hexyloxycyanobiphenyl and octyloxcyanobiphenyl) is another interesting case in which to study the quenched random disorder effects. The weak SmA phase of [6:8]OCB+aerosil gels is followed by a RN phase at low temperatures. The results of the studies of this thesis provide models for random filed systems. Particularly, the developed line-shape analysis can be used to analyze all random field problems in general.

Ramazanoglu, Mehmet Kerim

7

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.

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

2010-01-01

8

Phase transition in liquid drop fragmentation  

SciTech Connect

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

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

2007-06-15

9

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

10

Liquid crystal phase transition in large grown micelles  

SciTech Connect

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

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

1990-05-01

11

Phase Transitions and recent advances in liquid-crystals research  

Microsoft Academic Search

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

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

2009-01-01

12

The liquid to vapor phase transition in excited nuclei  

SciTech Connect

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

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

2001-05-08

13

FBG application in monitoring the liquid-solid and gas-liquid phase transitions of water  

NASA Astrophysics Data System (ADS)

We propose to monitor the liquid-solid and gas-liquid phase transition of water based on FBG sensors. The naked FBGs and the packaged FBG temperature sensors are used to monitoring the liquid-solid phase transition of water at the same time in order to find its characteristics, including the supercooling state and the strain and pressure change introduced by the phase transition. Fourteen FBGs are packaged and arranged in a steam boiler in order to monitor the gas-liquid phase transition, including the temperature and pressure change inside the steam boiler and the strain of the boiler wall. The preliminary experimental results are demonstrated here.

Quan, Chai; Later, Khalil; Yang, Lijie; Peng, Shijun; Zhang, Anna; Hao, Qianqian; Zhang, Jianzhong; Sun, Weimin; Yuan, Libo; Peng, G. D.

2012-01-01

14

Adiabatic nucleation in the liquid-vapor phase transition  

NASA Astrophysics Data System (ADS)

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

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

2001-05-01

15

Fragment production and the liquid-gas phase transition  

SciTech Connect

An inclusive experiment in which isotopically resolved fragments, 3less than or equal toZless than or equal to13, were produced in high energy proton-nucleus collisions has provided evidence for a liquid-gas phase transition in nuclei. We review briefly the data and its description in terms of a critical phenomenon.

Hirsch, A.S.

1984-11-15

16

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

17

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

PubMed Central

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

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

2012-01-01

18

Solitary wave and nonequilibrium phase transition in liquid crystals  

NASA Astrophysics Data System (ADS)

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

Xin-Yi, Wang

1985-11-01

19

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

20

Synthesis and liquid crystal phase transitions of zirconium phosphate disks  

NASA Astrophysics Data System (ADS)

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

Shuai, Min

21

Phosphorus: First principle simulation of a liquid-liquid phase transition  

NASA Astrophysics Data System (ADS)

We report a Car-Parrinello molecular dynamics study of the liquid-liquid phase transition in phosphorus. We employed a gradient corrected density functional (B-LYP) to describe the electronic structure and performed simulations at constant pressure. Upon increasing pressure we observed, along the 1500 K isotherm, a structural transition converting the molecular P4 liquid into an atomic liquid with a network structure. Our calculations suggest this transition to be first order with a discontinuous density increase accompanied by an insulator into metal transition. The transition pressure is significantly higher than obtained by employing the less accurate local density functional (LDA) [Morishita, Phys. Rev. Lett. 87, 105701 (2001)], which matches the experimental value for the pressure. We argue why the LDA result should be considered fortuitous. The change of the calculated structure factor upon the transition shows the same trend as experimentally observed. Analysis of the structural changes during the phase transition revealed that a chain of linked and opened up (``butterfly'') P4 molecules may serve as a seed triggering the transition from the molecular to the network phase.

Ghiringhelli, Luca M.; Meijer, Evert Jan

2005-05-01

22

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

23

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.

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

2013-01-01

24

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

25

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

NASA Astrophysics Data System (ADS)

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

Mukherjee, Prabir K.

2012-04-01

26

Phase Transitions of Side Chain Liquid Crystal Polyamines  

Microsoft Academic Search

Novel side-chain liquid crystalline polyamines (SCLCPs) were synthesized by ring-opening polymerization of aziridine monomers. Their thermal and liquid crystalline properties were examined with a polarizing microscope and a differential scanning calorimeter. Aziridine monomers showed no liquid crystalline phases. SCLCPs with nitro or 2-hydroxyethyl terminal groups in the side chains exhibited a smectic A phase with a fan-shaped texture. However, SCLCP

Yumi Yano; Seiji Ujiie; Akira Mori

2001-01-01

27

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

28

Nonlinear vibrational spectroscopy of water structures utilizing laser-induced phase transition phenomena in liquid water  

Microsoft Academic Search

Anomalous enhancement of the stimulated Raman scattering (SRS) of water molecules in the OH stretching vibrational region is observed when a laser-induced phase transition from liquid to plasma takes place in liquid water. The SRS is emitted before the phase transition and has a duration of several tens of picoseconds full width at half maximum. From the spectroscopic analysis of

Hiroharu Yui; Tsuguo Sawada

2003-01-01

29

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

30

Paraelectric-antiferroelectric phase transition in achiral liquid crystals  

NASA Astrophysics Data System (ADS)

Critical freezing of molecular rotation in an achiral smectic phase, which leads to polar ordering through the second order paraelectric-antiferroelectric (Sm-A?Sm-APA) phase transition is studied theoretically and experimentally. Strong softening of the polar mode in the Sm-A phase and highly intensive dielectric mode in the Sm-APA phase are observed due to weak antiferroelectric interactions in the system. In the Sm-APA phase the dielectric response behaves critically upon biasing by a dc electric field. Such a behavior is found general for the antiferroelectric smectic phase with significant quadrupolar interlayer coupling.

Pociecha, Damian; Gorecka, Ewa; ?epi?, Mojca; Vaupoti?, Nataša; Gomola, Kinga; Mieczkowski, Jozef

2005-12-01

31

Going full circle: phase-transition thermodynamics of ionic liquids.  

PubMed

We present the full enthalpic phase transition cycle for ionic liquids (ILs) as examples of non-classical salts. The cycle was closed for the lattice, solvation, dissociation, and vaporization enthalpies of 30 different ILs, relying on as much experimental data as was available. High-quality dissociation enthalpies were calculated at the G3 MP2 level. From the cycle, we could establish, for the first time, the lattice and solvation enthalpies of ILs with imidazolium ions. For vaporization, lattice, and dissociation enthalpies, we also developed new prediction methods in the course of our investigations. Here, as only single-ion values need to be calculated and the tedious optimization of an ion pair can be circumvented, the computational time is short. For the vaporization enthalpy, a very simple approach was found, using a surface term and the calculated enthalpic correction to the total gas-phase energy. For the lattice enthalpy, the most important constituent proved to be the calculated conductor-like screening model (COSMO) solvation enthalpy in the ideal electric conductor. A similar model was developed for the dissociation enthalpy. According to our assessment, the typical error of the lattice enthalpy would be 9.4 kJ mol(-1), which is less than half the deviation we get when using the (optimized) Kapustinskii equation or the recent volume-based thermodynamics (VBT) theory. In contrast, the non-optimized VBT formula gives lattice enthalpies 20 to 140?kJ?mol(-1) lower than the ones we assessed in the cycle, because of the insufficient description of dispersive interactions. Our findings show that quantum-chemical calculations can greatly improve the VBT approaches, which were parameterized for simple, inorganic salts with ideally point-shaped charges. In conclusion, we suggest the term "augmented VBT", or "aVBT", to describe this kind of theoretical approach. PMID:21538602

Preiss, Ulrich; Verevkin, Sergey P; Koslowski, Thorsten; Krossing, Ingo

2011-05-27

32

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

33

Low electric field induced phase transition of the B1 bent-core liquid crystal phase to a switching phase  

NASA Astrophysics Data System (ADS)

Liquid crystal materials that have ferroelectric and antiferroelectric phases are useful in applications due to their switching properties. The B1 bent-core liquid crystal phase is a columnar phase that does not exhibit switching. A transition from the B1 liquid crystal phase to a switching phase has been seen at an electric field of 10 V/?m, which is much lower than previously seen fields of greater than 25 V/?m [1]. This transition is irreversible upon reduction of the applied field and switching continues almost threshold-less down to an applied field of 40 mV/?m, which has not been previously reported. Any amount of a chiral rod-like dopant increases the field required to transition from the B1 to the switching phase, and the transition becomes reversible with the mixture relaxing back to the B1 phase after a decrease in the electric field. A small concentration of the rod-like dopant also induces a change from the B1 phase to a new liquid crystal phase. These effects were studied using polarized optical microscopy, calorimetry (DSC), and x-ray measurements. [1] J. Ortega et. al., Phys. Rev. E, 69, 011703 (2004)

Kirchhoff, J.; Hirst, L. S.

2008-03-01

34

Computer Simulation Evidence for a Liquid-Liquid Phase Transition in Gallium: Bulk and Nanodroplets  

NASA Astrophysics Data System (ADS)

Over the last decade, there has been an increasing interest in the first-order liquid-liquid phase transition (LLPT) between liquids of the same chemical composition. While LLPT has been speculated to occur in several liquids that exhibit anomalies in their thermodynamic properties, so far in only two cases it has been experimentally verified. This lack of evidence stems from difficult experimental conditions, since in many cases the LLPT is expected to occur in the metastable supercooled regime. Gallium is a very promising substance for the study of LLPT, since it has low melting point (303 K), displays anomalous behavior, and can be kept liquid about 100 K below its melting temperature. In this work, we report on molecular dynamics simulations of liquid Ga that provide theoretical evidence of a LLPT from a high density to a low density liquid in bulk [1] and nanodroplets. Our results indicate a reduction in the temperature and latent heat of the LLPT as the size of the system decreases. [1] D. A. C. Jara, M. F. MIchelon, A. Antonelli, and M. de Koning, Journal of Chemical Physics 130, 221101 (2009).

Antonelli, Alex; Jara, Diego; Michelon, Mateus; de Koning, Maurice

2010-03-01

35

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

36

Theory of volume phase transitions of side-chain liquid crystalline gels  

Microsoft Academic Search

We present a mean field theory to describe volume phase transitions of side-chain liquid crystalline gels. Three different uniaxial nematic phases (N1, N2, and N3) are defined by using orientational order parameter Sm of side-chain liquid crystals (mesogens) and Sb of backbone chains. We derive the free energy for the three nematic phases of side-chain liquid crystalline gels dissolved in

Akihiko Matsuyama

2007-01-01

37

Exotic continuous quantum phase transition between Z2 topological spin liquid and Néel order  

NASA Astrophysics Data System (ADS)

Recent numerical simulations with different techniques have all suggested the existence of a continuous quantum phase transition between the Z2 topological spin-liquid phase and a conventional Néel order. Motivated by this numerical progress, we propose a candidate theory for such Z2-Néel transition. We first argue on general grounds that, for a SU(2)-invariant system, this transition can not be interpreted as the condensation of spinons in the Z2 spin-liquid phase. Then, we propose that such Z2-Néel transition is driven by proliferating the bound state of the bosonic spinon and vison excitation of the Z2 spin liquid, i.e., the so-called (e,m)-type excitation. Universal critical exponents associated with this exotic transition are computed using 1/N expansion. This theory predicts that at the Z2-Néel transition, there is an emergent quasi-long-range power-law correlation of columnar valence bond solid order parameter.

Moon, Eun-Gook; Xu, Cenke

2012-12-01

38

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

39

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

PubMed

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

Kundu, Sudarshan; Kang, Shin-Woong

2013-12-16

40

Study on the thermodynamics of liquid-gas phase transition for asymmetric polarized nuclear matter.  

National Technical Information Service (NTIS)

The equation of state, developed before, for asymmetric polarized nuclear matter revealed a liquid-gas phase transition behaviour. Such transition is typical to that described by Van der Waal equation of real gas. In the present work, the analogy between ...

M. Abd-Alla

1990-01-01

41

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

Microsoft Academic Search

An apparatus was constructed to test the concept of initiating a rapid phase transition (RPT) in methane-rich LNG on water by collapsing the vapor film with a shock wave. Helium overpressures were achieved by breaking a diaphragm in a high-pressure helium chamber. Pressure transducers recorded subsequent events. NO RPT were noted for liquid nitrogen, liquid ethane, liquid methane or methane-rich

G. A. Corbin; R. C. Reid

1981-01-01

42

Dynamics at the Nematic-Isotropic Phase Transition in Aerosil Dispersed Liquid Crystal  

NASA Astrophysics Data System (ADS)

Photopyroelectric high resolution ac calorimetry has been used to study the nematic-isotropic phase transition in octylcyanobiphenyl liquid crystal incorporating an aerosil soft gel. We have found that the sample is not in thermodynamic equilibrium in the two phase coexistence region, as shown by the frequency dependence of the double peak in the specific heat and by its thermal hysteresis. The results suggest that the dynamics of the system becomes slower as it is cooled over the transition temperature. An explanation for the formation of a nematic glassy phase in liquid crystals with quenched disorder based on the similarity of these results with the ones obtained in other disordered materials is attempted.

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

2005-06-01

43

Isospin lattice gas model and liquid-gas phase transition in asymmetric nuclear matter  

Microsoft Academic Search

Liquid-gas phase transition in asymmetric nuclear matter is investigated with an isospin lattice gas model. Nuclear matter is considered as a lattice with each lattice site either empty or occupied by a proton or a neutron, with a nearest-neighbor interaction between the nucleons. The Bragg-Williams mean field approximation is employed to evaluate the thermodynamic potential. Our model exhibits liquid-gas phase

S. Ray; J. Shamanna; T. T. S. Kuo

1997-01-01

44

Molecular packing and phase transitions of side-chain liquid crystalline polymethacrylates based on pmethoxyazobenzene  

Microsoft Academic Search

The phase structures and transition behaviors of a series of side-chain liquid crystalline (LC) polymethacrylates based on p-methoxyazobenzene (PMnAzs, n=6, 8, 10, 12) were studied using differential scanning calorimetry, one- and two-dimensional (1D and 2D) wide-angle X-ray diffraction, and Fourier transform infrared spectroscopic experiments. The LC phase transition of PMnAz follows the sequence of smectic A (SmA)?nematic (N)?isotropic (I). For

Xing-Qi Zhu; Jia-Hao Liu; Yi-Xin Liu; Er-Qiang Chen

2008-01-01

45

Effect of Structure of Photoresponsive Molecules on Photochemical Phase Transition of Liquid Crystals IV. Photochemical Phase Transition Behaviors of Photochromic Azobenzene Guest\\/ Polymer Liquid Crystal Host Mixtures  

Microsoft Academic Search

Sixteen azobenzene derivatives were used as guests in a polymer liquid crystal (PLC) host with side- chain mesogenic phenyl benzoate groups, poly(4?-methoxyphenyl 4-(acryloyloxy)propoxybenzoate (PAPB3), and were examined on their ability to induce the photochemical isothermal phase transition of the guest\\/host mixtures. Although the rates of photoisomerization of the azobenzene guests were found to be similar to those of the mixtures

T. Ikeda; T. Miyamoto; S. Kurihara; S. Tazuke

1990-01-01

46

Nonlinear vibrational spectroscopy of water structures utilizing laser-induced phase transition phenomena in liquid water  

NASA Astrophysics Data System (ADS)

Anomalous enhancement of the stimulated Raman scattering (SRS) of water molecules in the OH stretching vibrational region is observed when a laser-induced phase transition from liquid to plasma takes place in liquid water. The SRS is emitted before the phase transition and has a duration of several tens of picoseconds full width at half maximum. From the spectroscopic analysis of the SRS, it is suggested that the excess electrons, which are generated in a few picoseconds before the phase transition, play an important role in the transient SRS enhancement through the change of the nonlinear polarizability induced around the electrons in liquid water. Several applications of the enhanced vibrational spectra in the OH stretching vibrational region to the spectroscopic analyses of local water structures in various environments are also described.

Yui, Hiroharu; Sawada, Tsuguo

2003-01-01

47

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

NASA Astrophysics Data System (ADS)

Elucidation of the mechanisms of transitions between cubic phase and liquid-crystalline (L?) phase, and between different IPMS cubic phases, are essential for understanding of dynamics of biomembranes and topological transformation of lipid membranes. Recently, we found that electrostatic interactions due to surface charges of lipid membranes induce transition between cubic phase and L? phase, and between different IPMS cubic phases. As electrostatic interactions increase, the most stable phase of a monoolein (MO) membrane changes: Q224 ==> Q229 ==> L?. We also found that a de novo designed peptide partitioning into electrically neutral lipid membrane changed the phase stability of the MO membranes. As peptide-1 concentration increased, the most stable phase of a MO membrane changes: Q224 ==> Q229 ==>L?. In both cases, the increase in the electrostatic repulsive interaction greatly reduced the absolute value of spontaneous curvature of the MO monolayer membrane. We also investigated factors such as poly (L-lysine) and osmotic stress to control structure and phase stability of DOPA/MO membranes. Based on these results, we discuss the mechanism of the effect of electrostatic interactions on the stability of cubic phase.

Masum, Shah Md.; Li, Shu Jie; Tamba, Yukihiro; Yamashita, Yuko; Yamazaki, Masahito

2004-04-01

48

Control of the Fragility of a Glass-Forming Liquid Using the Liquid-Liquid Phase Transition  

Microsoft Academic Search

When a liquid approaches its glass-transition temperatures Tg, the structural relaxation time tau dramatically increases. This basic feature is ubiquitous, but this increase of tau can be classified between strong and fragile extremes using Tg as a scaling parameter. Liquids, whose tau obeys the Arrhenius law, are called ``strong,'' while ``fragile'' liquids have the super-Arrhenius behavior. Here we report the

Rei Kurita; Hajime Tanaka

2005-01-01

49

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

50

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

NASA Astrophysics Data System (ADS)

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

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

2005-10-01

51

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

PubMed

The classification of phase transitions in first-order and second-order (or continuous) ones is widely used. The nematic-to-isotropic (NI) transition in liquid crystals is a weakly first-order transition, with only small discontinuities in enthalpy and specific volume at the transition which are not always easy to measure. On the other hand, fluctuation effects near the transition, typical for a continuous transition, are present because of the only weakly first-order character. In a recent paper [Phys. Rev. E 69, 022701 (2004)], it was concluded from the static dielectric permittivity in the isotropic phase near the NI transition that less polar mesogens (with little or no pretransitional effects) are characteristic for a first-order NI phase transition, whereas in the case of strongly polar ones (with large pretransitional effects) the NI transition is close to second order. In this paper, we address the question whether it is, indeed, possible to use these fluctuation effects in the isotropic phase to quantify the "strength" of a weakly first-order transition, i.e., how far it is from second order. Therefore, we measured the temperature dependence of the enthalpy near the NI transition of seven liquid crystals with adiabatic scanning calorimetry and compared the measured values of the latent heat with pretransitional effects in the dielectric constant and the specific heat capacity. The compounds used in the comparison are MBBA, 5CB, 8CB, 5NCS, 5CN, 8CHBT, and D7AB. From our analysis we find, contrary to the assertion in the above reference, no correlation between the strength of the NI transition of a given compound and the pretransitional effects observed, neither dielectrically, nor thermally. PMID:16383397

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

2005-10-01

52

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

NASA Astrophysics Data System (ADS)

The liquid crystal 4'octyl-4-cyanobiphenyl (8CB) doped with cadmium selenide nanoparticles was injected into a commercially available liquid crystal cell (INSTEC, Inc). The cell was housed in a temperature controlled environment constructed in the lab and exposed to light from a frequency doubled Nd: YAG laser. The spectrum of fluorescence from the sample was measured at several temperatures over the range 250 to 450C, covering the smectic-nematic and nematic-isotropic phase transitions. The sample was held at each temperature with a precision and resolution of 1mK before taking the spectrum. It was therefore possible to approach very close to the phase transitions. The results show a significant change in the fluorescence spectrum near the nematic-isotropic phase transition.

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

2011-03-01

53

Thermal transport behavior of van der Waals solids and liquids in the neighborhood of the solid-liquid phase transition  

Microsoft Academic Search

The thermal conductivity, ?, is one of the few transport coefficients which shows a relatively small change at the solid-liquid phase transition, and hence it is a property that can be used in comparing dynamic properties of both ordered and disordered systems. Although the discontinuity in ? can be accounted for largely by the difference in density, ?, of solid

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

1986-01-01

54

Morphology, crystal structure, phase transitions and blend compatibility of thermotropic liquid crystal terpolyesters  

Microsoft Academic Search

The morphology, crystal structure, phase transitions and blend compatibility of a series of semiflexible thermotropic liquid crystal terpolyesters (LCPs) were studied to understand their crystallization behavior and establish relationships between their microstructure and physical properties. Main characterization methods were electron microscopy and diffraction, and differential scanning calorimetry. The LCPs were composed of equimolar amounts of p-oxybenzoate, p-dioxyphenyl, and aliphatic segments,

Clara Lena Gonzalez-Costoso

1997-01-01

55

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

PubMed Central

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

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

2005-01-01

56

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

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

57

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

NASA Astrophysics Data System (ADS)

A lyotropic inverse micelle phase composed of water, thermotropic liquid-crystal octylcyanobiphenyl (8CB), and surfactant (DDAB) was studied by using high-resolution calorimetry on several mixtures with 3%, 8%, and 15% micelle concentration. Calorimetric results show strong depression of the isotropic to nematic (I-N) phase-transition temperature. Broad heat-capacity anomalies show the existence of a wide coexistence range of isotropic, nematic, and smectic-A phases, which mimics the behavior of a new nearly stable thermodynamic phase. An observation of the rather sharp almost bulklike nematic to smectic-A (N-A) transition at low-temperatures indicates that our heat capacity results are consistent with the phase separation scenario in which significant number of micelles is expelled during I-N conversion leaving almost pure nematic phase at lower temperatures. It was found that micelles get almost completely remixed on heating the mixture back to the isotropic phase.

Kutnjak, Zdravko; Cordoyiannis, George; Nounesis, George; Lebar, Andrija; Zalar, Boštjan; Žumer, Slobodan

2005-06-01

58

Field-induced phase transitions in an antiferroelectric liquid crystal using the pyroelectric effect  

NASA Astrophysics Data System (ADS)

The antiferroelectric liquid crystal (AFLC) under investigation possesses different helical polar phases. Measurements of pyroelectric response of these phases as a function of temperature and bias field have elucidated the ability of this method for investigating the nature of antiferroelectric phases and phase transitions under the bias field. The pyroelectric signal as a function of the bias field at fixed temperatures and as a function of temperature for fixed bias fields was measured for different phases of the investigated AFLC material. A theoretical model describing the pyroelectric response in different phases of AFLC is given, and the experimental results are interpreted. The threshold fields for field induced phase transitions are determined. The type of field induced phase transition from the AF phase in particular is found to be dependent on the temperature within its range. The properties of an unusual ferrielectric phase existing between ferrielectric chiral smectic-C (SmC*) and antiferroelectric AF phases are studied in a great detail. The results confirm that this phase is one of the incommensurate phases, predicted by the axial next-nearest neighbor Ising model and Landau model for this temperature region.

Shtykov, N. M.; Vij, J. K.; Lewis, R. A.; Hird, M.; Goodby, J. W.

2000-08-01

59

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

NASA Astrophysics Data System (ADS)

High-resolution x-ray scattering studies of the nonpolar thermotropic liquid crystal 4-n-pentylphenylthiol-4'-n-octyloxybenzoate (8¯S5) in aerosil gel nanonetworks reveal that the aerosil-induced disorder significantly alters both the nematic to smectic-A and smectic-A to smectic-C phase transitions. The limiting 8¯S5 smectic-A correlation length follows a power-law dependence on the aerosil density in quantitative agreement with the limiting lengths measured previously in other smectic-A liquid crystal gels. The smectic-A to smectic-C liquid crystalline phase transition is altered fundamentally by the presence of the aerosil gel. The onset of the smectic-C phase remains relatively sharp but there is an extended coexistence region where smectic-A and smectic-C domains can exist.

Freelon, B.; Ramazanoglu, M.; Chung, P. J.; Page, R. N.; Lo, Yuan-Tse; Valdivia, P.; Garland, C. W.; Birgeneau, R. J.

2011-09-01

60

The Effect of Aerosil Network on Liquid Crystal (4O.8) Phase Transition  

NASA Astrophysics Data System (ADS)

We report a high resolution x-ray diffraction study of the nematic (N) to smectic-A (SmA) transition in the single-layer smectic (SmAm) liquid crystal butyloxybenzylidene octylaniline (4O.8) within aerosil dispersion. Aerosils are dispersed in liquid crystal material with a broad range concentration. They dramatically affect the phase transition properties in different liquid crystals [1]. These effects were studied in the view of random field theory introduced by quenched randomness of the silica gel network. The second order N-SmA phase transition and strong first order SmA-CrB freezing transitions are shifted to lower temperatures. SmA line-shape is broadened indicating a short-range order. Correlation lengths and power-law fits show behavior similar to bilayer SmAd liquid crystals. The present work enables us to test our understanding of random field effects introduced by dispersed aerosils forming a network in SmAm material. [1] S. Park, R.L. Leheny, R.J. Birgeneau, J.-L. Gallani, C.W. Garland and G.S. Iannacchione, Phys. Rev. E 65 050703(R) (2002)

Ramazanoglu, Mehmet; Larochelle, Simon; Birgeneau, Robert J.

2005-03-01

61

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

NASA Astrophysics Data System (ADS)

This dissertation reports the ultrafast dynamics of aluminum during the solid-to-liquid phase transition of melting after excitation by an intense femtosecond laser pulse. Photoexcitation with intense femtosecond laser pulses is known to create a novel melting mechanism called non-thermal melting. This mechanism has been observed repeatedly in semiconductors, but not yet in metals. We investigate the melting mechanism of aluminum by monitoring the reflectivity response following excitation by an intense laser pulse. We employ an optical pump-probe technique designed to measure broadband reflectivity across the visible spectrum with femtosecond time resolution. A non-thermal melting mechanism was proposed for aluminum by optical experiments that demonstrated transition of the optical properties from solid to liquid values within 500 fs after phototexcitation. This result was later challenged by electron diffraction experiments, which showed that the lattice loses long range order within 3.5 ps during photoinduced melting. This time scale implies conventional thermal melting. We find that the broadband optical properties during the solid-to-liquid phase transition in aluminum agree with the results obtained by the electron diffraction experiments. The transition of the broadband reflectivity from solid to liquid values is complete within 1.5--2 ps in our experiments, which is compatible with thermal melting. We don't observe time scales on the order of 500 fs. All the experimental evidence in this dissertation lead to the conclusion that the laser-induced, solid-to-liquid phase transition in aluminum is a thermal process.

Kandyla, Maria

62

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

SciTech Connect

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 ..delta..T(E) can be understood by means of the Kirkwood-Helfrich equation considering the nonlinear field dependence of the BP I permittivity.

Stegemeyer, H.; Porsch, F.

1984-12-01

63

Kinetics of the Crystalline-Liquid Crystalline Phase Transition of Dimyristoyl L-?-Lecithin Bilayers  

PubMed Central

Aqueous dispersions of synthetic dimyristoyl L-?-lecithin undergo a sharp decrease in turbidity in the temperature range where the crystalline-liquid crystalline phase transition occurs. Equilibrium transition curves, monitored by the absorbancy change at 300 nm, reproduce all the important features of a calorimetric melting curve [Hinz & Sturtevant (1972) J. Biol. Chem. 247, 6071]. A rapid temperature-jump of the dispersion, measured by the same absorbancy change, has detected several different molecular processes depending on the magnitude of the perturbation. These processes include a phase transition, permeation of ions and water across the membrane, and repture, annealing, or fusion of the bilayer structures. When the temperature-jump is limited to 1 degree, only reactions associated with the phase transition are detectable and no signal is generated after a temperature-jump except for those which end within or extend beyond the transition zones. At least two relaxation times are resolved for the phase transition reactions. The faster one in the millisecond time range is strongly temperature-dependent and has an activation energy close to one million calories per mole. The second one, in the 100-msec time range, appears to have a much smaller activation energy. These observations indicate that strongly cooperative nucleation processes and energy-dependent fast propagation steps occur during the phase transition. Since the kinetics of the transition are complex, intermediate state or transient structures must exist in the transition regions of the bilayer dispersions. These thermal fluctuations of the bilayer structures may have important effects on the lateral diffusion and permeation of molecules and ions in the membrane structure. Images

Tsong, Tian Yow

1974-01-01

64

Photocontrolled phase transitions and reflection behaviors of smectic liquid crystals by a chiral azobenzene.  

PubMed

The photocontrolled phase transitions and reflection behaviors of a smectic liquid crystal, 4-octyl-4'-cyanobiphenyl (8CB), tuned by a chiral azobenzene, are systematically investigated. For the smectic 8CB doped with the chiral azobenzene (1R)-(-)-4-n-hexyl-4'-menthylazobenzene (ABE), the initial smectic phase can be switched to cholesteric and then to isotropic upon UV irradiation due to the trans-to-cis photoisomerization of ABE; however, no reflection band is observed. For the smectic 8CB doped with ABE and the chiral agent (S)-(-)-1,1'-binaphthyl-2,2'-diol (BN), a reflection band located in the short-wavelength infrared region is observed, which disappears after further UV irradiation. For the smectic 8CB doped with ABE and a chiral agent with higher helical twisting power, (S)-2,2'-methylendioxy-1,1'-binaphthalene (DBN), a phototunable system with cholesteric pitch short enough to reflect visible light is demonstrated. With a given concentration of the chiral dopant DBN, a reversible reflection color transition is realized tuned by the isomerization of azobenzene. The reverse phase transition from isotropic to cholesteric and then to smectic can be recovered upon visible irradiation. The photocontrolled phase transitions in smectic liquid crystals and the corresponding changes in reflection band switched by photoisomerization of azobenzene may provide impetus for their practical application in optical memories, displays, and switches. PMID:23065840

Guan, Jingjing; Zhang, Mingzhi; Li, Birong; Yang, Huai; Wang, Guojie

2012-12-01

65

Phase transitions and structural parameters of HIQ-40 liquid crystalline co-polyester  

Microsoft Academic Search

We describe the impact of thermal treatment on the structure and phase transitions of the liquid crystalline aromatic co-polyester, HIQ-40, comprising 40mol% p-hydroxybenzoic acid (H), 30mol% isophthalic acid (I), and 30mol% p-hydroquinone (Q). Simultaneous, real-time wide and small angle X-ray scattering (WAXS, SAXS), differential scanning calorimetry, and optical ellipsometry were used to study initially isotropic, amorphous films of HIQ-40. Films

Georgi Georgiev; Nathan Gilfoy; Peggy Cebe; Malcolm Capel

2004-01-01

66

The Phase Transition Behavior of Side Chain Liquid Crystalline Polymers Containing Sulfone Group  

Microsoft Academic Search

The phase transition behavior in side chain liquid crystalline polymers (SCLCPs) based on a hydrophilic poly(ethylene oxide) (PEO) main chain and a hydrophobic alkyl side chain containing sulfone groups was investigated by using DSC, POM, synchrotron X- ray scattering, FT-IR and rheological measurements. In the case of poly[oxy(octylsulfonylhexylthiomethyl) ethylene] (8S6EO) containing sulfone groups located at the intermediate position in the

Daewon Lee

2005-01-01

67

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

NASA Astrophysics Data System (ADS)

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

Magomedov, M. N.

2014-05-01

68

Interfacial Phase Transitions at Solid-Fluid and Liquid-Vapor Interfaces  

NASA Astrophysics Data System (ADS)

To study the interface between a solid surface and nitrogen vapor, the theory of Cahn was applied. The Peng-Robinson equation of state (PREOS) was incorporated in the theory of Cahn to model the thermodynamic functions of the fluid. In this study the wetting transition, as earlier reported by Cahn, was shown. In addition, wetting transitions occurring at a liquid-vapor interface of the three-phase LLV equilibrium of the binary mixtures hexane/water and benzene/water were examined. It was found that by making use of the gradient theory of van der Waals, in which the PREOS was incorporated, the transitions seem to be of third order. For the case where the PREOS was replaced by the Associated-Perturbed-Anisotropic-Chain-Theory, no wetting region was found. It was argued that, in principle, it should he possible to model first-order wetting transitions with the square gradient theory.

Cornelisse, P. M. W.; Peters, C. J.; de Swaan Arons, J.

1998-11-01

69

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

70

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

SciTech Connect

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

Gerald Stevens, Stephen Lutz, William Turley, Lynn Veeser

2007-06-29

71

Phase diagrams and kinetics of solid-liquid phase transitions in crystalline polymer blends  

NASA Astrophysics Data System (ADS)

A free energy functional has been formulated based on an order parameter approach to describe the competition between liquid-liquid phase separation and solid-liquid phase separation. In the free energy description, the assumption of complete solvent rejection from the crystalline phase that is inherent in the Flory diluent theory was removed as solvent has been found to reside in the crystalline phase in the form of intercalates. Using this approach, we have calculated various phase diagrams in binary blends of crystalline and amorphous polymers that show upper or lower critical solution temperature. Also, the discrepancy in the chi values obtained from different experimental methods reported in the literature for the polymer blend of poly(vinylidenefluoride) and poly(methylmethacrylate) has been discussed in the context of the present model. Experimental phase diagram for the polymer blend of poly(caprolactone) and polystyrene has also been calculated. Of particular importance is that the crystalline phase concentration as a function of temperature has been calculated using free energy minimization methods instead of assuming it to be pure. In the limit of complete immiscibility of the solvent in the crystalline phase, the Flory diluent theory is recovered. The model is extended to binary crystalline blends and the formation of eutectic, peritectic and azeotrope phase diagrams has been explained on the basis of departure from ideal solid solution behavior. Experimental eutectic phase diagram from literature of a binary blend of crystalline polymer poly(caprolactone) and trioxane were recalculated using the aforementioned approach. Furthermore, simulations on the spatio temporal dynamics of crystallization in blends of crystalline and amorphous polymers were carried out using the Ginzburg-Landau approach. These simulations have provided insight into the distribution of the amorphous polymer in the blends during the crystallization process. The simulated results are in close accordance with the experimentally observed concentration profiles of atactic polypropylene during the crystallization of isotactic polypropylene in a blend of these polymers. Finally described are the unique thermodynamics and kinetics that occur in thermoplastic elastomer blends of polypropylene and synthetic rubber, leading to the unique biphasic crystalline morphology imparting these blends with their characteristic high toughness and high impact strength. Phase diagrams in such blends exhibit a combined upper and lower critical solution temperature. These phase diagrams have been calculated based on the present model developed, and simulated results explain the structural development in these blends.

Matkar, Rushikesh A.

72

Fluorescence decay of CdSe nanoparticles in Liquid Crystals near Phase Transitions  

NASA Astrophysics Data System (ADS)

The liquid crystal 4'octyl-4-cyanobiphenyl (8CB) doped with cadmium selenide nanoparticles (Sigma-Aldrich) was injected into a commercially available liquid crystal cell (INSTEC, Inc). The cell was housed in a temperature controlled environment constructed in the lab and exposed to light from a frequency doubled pulsed Nd: YAG laser. The decay of fluorescence from the sample was measured at several temperatures over the range 25^o to 45^oC, covering the smectic-nematic and nematic-isotropic phase transitions. The sample was held at each temperature with a stability and resolution of 1mK before taking the measurement. The fluorescence was detected using a high-speed detector and the decay was measured using a boxcar averager. With the temperature control available, it was possible to approach very close to the phase transitions, with milliKelvin resolution. The results show a significant change in the decay of fluorescence near the nematic-isotropic phase transition.

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

2011-03-01

73

Simulating the phosphorus fluid liquid phase transition up to the critical point  

NASA Astrophysics Data System (ADS)

We report a Car-Parrinello molecular dynamics study of the temperature dependence of the fluid-liquid phase transition in phosphorous, involving the transformation of a molecular fluid phase into a network-like phase. We employed density-functional theory (DFT) with a gradient-corrected functional (B-LYP) to describe the electronic structure and interatomic interactions and performed simulations in a constant pressure ensemble. We spanned a temperature interval ranging from 2500 to 3500 K. With increasing temperature, we found that the structural conversion from the molecular P4 fluid into the network liquid occurs at decreasing pressures, consistent with experimental observations. At lower temperatures the transition is characterized by a sudden increase of density in the sample. The magnitude of the density change decreases with increasing temperature and vanishes at 3500 K. In the temperature range 3100-3500 K we found signals of near- and super-criticality. We identified local structural changes that serve as seeds triggering the overall structural transition.

Ghiringhelli, Luca M.; Meijer, Evert Jan

2007-10-01

74

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

NASA Astrophysics Data System (ADS)

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.

Zhao, Tongyang; Wang, Xiaogong

2013-01-01

75

Reversible optical control of transmittance in polymer/liquid crystal composite films by photoinduced phase transition  

NASA Astrophysics Data System (ADS)

We have demonstrated reversible change in transmittance of composite films, which are composed of an isotropic (I) polymer matrix and a host nematic (N) liquid crystal (LC) containing donor-acceptor type azobenzene LCs (AzoLCs) as photoresponsive molecules, by means of reversible phase transition in the LC domain. The composite films were prepared by in situ thermal polymerization-induced phase separation (PIPS) method from their homogeneous mixtures. Photoisomerization of AzoLCs was induced within the polymer network, and the resultant effect brought about isothermal change in transmittance. The photoinduced reversible and repeatable changes between opaque light scattering and clear transparent states were achieved effectively by irradiation with a monochromatic light at 366 nm. These changes are attributed to photochemical N-I phase transition and rapid thermal I-N phase transition in the host LC domain based on reversible change in molecular sharp of the guest AzoLCs. The optical effects were influenced by such factors as temperature of the composite films in the initial state and photoisomerization ability of the guest AzoLCs. The composite films acted as an optical switching material without polarizers.

Lee, Hyoung-Kwan; Kanazawa, Akihiko; Shiono, Takeshi; Ikeda, Tomiki; Fujisawa, Toru; Aizawa, Masao; Lee, Bong

1999-12-01

76

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

PubMed

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

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

2014-04-22

77

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

78

Liquid crystalline phase and gel-sol transitions for concentrated microcrystalline cellulose (MCC)/1-ethyl-3-methylimidazolium acetate (EMIMAc) solutions.  

PubMed

Liquid crystalline (LC) phase transition and gel-sol transition in the solutions of microcrystalline cellulose (MCC) and ionic liquid (1-ethyl-3-methylimidazolium acetate, EMIMAc) have been investigated through a combination of polarized optical microscope (POM) observation and rheological measurements. Molecular LC phase forms at the 10 wt % cellulose concentration, as observed by POM, whereas the critical gel point is 12.5 wt % by rheological measurements according to the Winter and Chambon theory, for which the loss tangent, tan ?, shows frequency independence. Dramatic decreases of G' and G'' in the phase transition temperature range during temperature sweep are observed due to disassembling of the LC domain junctions. The phase diagram describing the LC phase and gel-sol transitions is obtained and the associated mechanisms are elucidated. A significant feature shown in the phase diagram is the presence of a narrow lyotropic LC solution region, which potentially has a great importance for the cellulose fiber wet spinning. PMID:21361275

Song, Hongzan; Niu, Yanhua; Wang, Zhigang; Zhang, Jun

2011-04-11

79

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

NASA Astrophysics Data System (ADS)

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

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

1992-07-01

80

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

PubMed

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

Shanker, Govindaswamy; Yelamaggad, Channabasaveshwar V

2011-09-22

81

Statistical temperature molecular dynamics simulations applied to phase transitions in liquid crystalline systems.  

PubMed

The recently developed statistical temperature molecular dynamics (STMD) method [Kim et al., Phys. Rev. Lett. 97, 050601 (2006)] is applied to the simulation of liquid crystalline soft matter systems. Results are presented demonstrating how, in combination with anisotropic soft core potentials, STMD simulation is able to sample efficiently across a large temperature window; and thus bridge across isotropic-liquid crystal phase transitions. Data is presented for two separate systems, namely, a single-site interaction model and an AB rod-coil block copolymer. The results are in excellent agreement with phase diagrams calculated by a series of traditional canonical molecular dynamics simulations bridging similar temperature/energy windows. In addition to the usual energetic and structural information, the STMD technique provides the temperature dependence of the entropy, free energy and heat capacity of the system as by-products of the single simulation. The combined soft-core/STMD strategy is presented as an effective means of scanning the phase diagram of a simple molecular interaction model to understand the relationship between molecular structure and phase behavior. PMID:20550414

Lintuvuori, Juho S; Wilson, Mark R

2010-06-14

82

Quantum phase transition between the Z2 spin liquid and valence bond crystals on a triangular lattice  

NASA Astrophysics Data System (ADS)

We study the quantum phase transition between the Z2 spin liquid and valence bond solid (VBS) orders on a triangular lattice. With a fully isotropic triangular lattice, the transition from a columnar or resonating-plaquette VBS order can either be first order or there could be two transitions with an intermediate phase. If the transition splits into two, then the Z2 spin liquid will first experience a first-order q =3 Potts transition to a new nematic Z2 spin liquid that breaks the 2?/3 lattice rotation symmetry (but retain translation symmetry, unlike the VBS states). The second transition will then take this new nematic Z2 spin liquid to a columnar or resonating-plaquette VBS state through a second-orderthree-dimensional (3D) XY* transition. On a distorted triangular lattice, the degeneracy between some of the different columnar VBS orders is lifted, and the phase transition can reduce to a single 3D XY * transition.

Slagle, Kevin; Xu, Cenke

2014-03-01

83

Topological quantum phase transition in an exactly solvable model of a chiral spin liquid at finite temperature  

NASA Astrophysics Data System (ADS)

We study the finite-temperature nature of a quantum phase transition between an Abelian and a non-Abelian topological phase in an exactly solvable model of the chiral spin liquid of Yao and Kivelson [Phys. Rev. Lett. 99, 247203 (2007)]. As it is exactly solvable, this model can serve as a testbed for developing better measures for describing topological quantum phase transitions. We use the global flux and entanglement entropy to characterize this phase transition, and we discuss to what extent the existence of a topologically ordered ground state with non-Abelian excitations is revealed at finite temperature.

Chung, Suk Bum; Yao, Hong; Hughes, Taylor L.; Kim, Eun-Ah

2010-02-01

84

Molecular dynamics and phase transitions in phospholipid monolayers at liquid-liquid interfaces  

Microsoft Academic Search

Stablen-hexadecane\\/water andn-tetradecane\\/water macroemulsions containing monolayers of natural (egg yolk lecithin, EY) and synthetic (dimyristoylphosphatidylcholine,\\u000a DMPC) phospholipids at liquid-liquid interfaces were prepared. The existence of the monolayers was proved by studying the\\u000a reduction kinetics of a surface-active spin probe with ascorbate anions. Spin labeled derivatives of stearic acid in which\\u000a the nitroxide group is locared at different distances from the polar

B. G. Dzikovskii; V. A. Livshits

1998-01-01

85

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

NASA Astrophysics Data System (ADS)

The liquid crystal 4'octyl---4-cyanobiphenyl (8CB) doped with cadmium selenide nanoparticles was injected into a commercially available liquid crystal cell (INSTEC, Inc). The cell was housed in a temperature controlled environment constructed in the lab and exposed to light from a frequency doubled Nd: YAG laser. Fluorescence from the sample was filtered from the incident light and detected using a photodiode and measured with a lock-in amplifier. Measurements have been made over the temperature range 25^o to 45^oC. The sample was stabilized at each temperature, and the fluorescence intensity was measured at several temperatures. The results show a significant change in fluorescence near the nematic-isotropic phase transition. The temperature control and precision allowed more than 1000 data points to be taken between 25-50^oC, with most of these clustered in the transition region between 38.5-- 39.5^oC, where the change in intensity was observed.

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

2011-03-01

86

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

2014-05-01

87

Multielement NMR studies of the liquid-liquid phase separation and the metal-to-nonmetal transition in fluid lithium- and sodium-ammonia solutions.  

PubMed

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

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

2013-10-24

88

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

89

Bubble-slug transition in two-phase, liquid-gas flow under microgravity conditions - A preliminary study  

Microsoft Academic Search

Existing microgravity flow-pattern observations in two-phase, gas-liquid flow, when compared against ground-based data, indicate a significant shift in the transition boundaries when gravity is reduced. Under those conditions of minimum or no gravitational forces acting on the flow, and a pronounced influence of surface tension forces; the transition from bubble to slug flow was repeatedly shown to be shifted during

K. S. Rezkallah

1990-01-01

90

Confinement Effects on Photoalignment, Photochemical Phase Transition, and Thermochromic Behavior of Liquid Crystalline Azobenzene-Containing Diblock Copolymers  

Microsoft Academic Search

Two diblock copolymers composed of polystyrene and a liquid crystalline azobenzene- containing polymethacrylate were used as model systems to investigate the confinement effects on the photoalignment, photochemical phase transition, and thermochromic behavior of the azobenzene polymer. The study finds that when confined in the microphase-separated domains in the diblock copolymers, the azobenzene polymer behaves differently with respect to the homopolymer

Xia Tong; Li Cui; Yue Zhao

2004-01-01

91

High pressure effect on the main transition from the ripple gel P'beta phase to the liquid crystal (Lalpha) phase in dipalmitoylphosphatidylcholine. Microcalorimetric study.  

PubMed

Scanning microcalorimetry has been used to study the high pressure effect on the main transition from the ripple gel P'(beta) phase to the liquid crystal (L(alpha)) phase in DPPC (dipalmitoylphosphatidylcholine). It has been demonstrated that an increase of the pressure by 200 MPa shifts the transition to higher temperatures by 36.4 degrees. The pressure increase does not affect the cooperativity of transition but reduces noticeably its enthalpy. The changes of the molar partial volume, isothermal compressibility as well as volume thermal expansibility during transition in DPPC suspension have been estimated. It has been shown that monovalent ions (Na(+), Cl(-)) in solution slightly affect the main thermodynamic parameters of the transition. Calcium ions significantly decrease distinction in compressibility and thermal expansibility between liquid-crystal and ripple gel phases of lipid suspension, which in its turn reflects less difference in their volume fluctuations. PMID:18760993

Potekhin, S A; Senin, A A; Abdurakhmanov, N N; Khusainova, R S

2008-11-01

92

?/s and phase transitions  

NASA Astrophysics Data System (ADS)

We present a calculation of ?/s for the meson gas (zero baryon number), with the viscosity computed within unitarized next-to-leading-order chiral perturbation theory, and confirm the observation that ?/s decreases towards the possible phase transition to a quark-gluon plasma/liquid. The value is somewhat higher than previously estimated in leading-order ?PT. We also examine the case of atomic Argon gas to check the discontinuity of ?/s across a first-order phase transition. Our results suggest employing this dimensionless number, sometimes called KSS number (in analogy with other ratios in fluid mechanics such as Reynolds number or Prandtl number) to pin down the phase transition and critical end point to a crossover in strongly interacting nuclear matter between the hadron gas and quark and gluon plasma/liquid.

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

2009-01-01

93

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

94

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.

95

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

Microsoft Academic Search

We theoretically study volume phase transitions of a side-chain liquid crystalline elastomer (LCE) immersed in nematic solvents. Six different uniaxial nematic phases (N1||, N1?, N2||, N2?, N3||, and N3?) are defined by using orientational order parameter Sm of a side-chain mesogen, Sb of a backbone chain, and S0 of a nematic solvent inside the gel. We derive the free energy

Akihiko Matsuyama; Yoshinari Kushibe

2010-01-01

96

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

97

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 [Formula: see text], 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

98

Morphology, crystal structure, phase transitions and blend compatibility of thermotropic liquid crystal terpolyesters  

NASA Astrophysics Data System (ADS)

The morphology, crystal structure, phase transitions and blend compatibility of a series of semiflexible thermotropic liquid crystal terpolyesters (LCPs) were studied to understand their crystallization behavior and establish relationships between their microstructure and physical properties. Main characterization methods were electron microscopy and diffraction, and differential scanning calorimetry. The LCPs were composed of equimolar amounts of p-oxybenzoate, p-dioxyphenyl, and aliphatic segments, containing variable number, n, of methylenes. Most work was done with P7, n = 7, which has been reported to exhibit chain folding in thin films, with 100 A thick lamellae and unit cell dimensions of a = 8.3 A and b = 5.1 A. An analogue terpolyester, P7-X, with a chlorine pendant group was also investigated; although exhibiting mostly glassy behavior, crystallized samples had unit cell dimensions of a = 7.6 A and b = 5.0 A. Effects of crystallization conditions such as cooling rate, state from which crystallized, and annealing, in the melt and in solution, were analyzed using bulk samples, and quiescent and sheared films. The morphology was observed to be more sensitive to small changes in cooling rate as well as to the type of solvent, while crystal structure and phase transitions depended mostly on the state from which the sample was crystallized. Attempts to produce polymer single crystals, by a method called Confined Thin Film Melt Polymerization, resulted in the formation of oligomers with an average number of six repeat units. These samples produced macrocrystals with lateral dimensions of up to 0.65 mm, and diffraction measurements and thermal behavior similar to those of their corresponding bulk versions. Deviations from the typical p-oxybenzoate homopolymer crystal structures were observed for n = 3. Compatibility of P7 and P7-X in binary blends with polyethylene (PE), polyethylene terephthalate (PET), and nylon 6 (Ny6), was examined to evaluate the effect of the aliphatic segment in promoting good adhesion at the interphase. Partial compatibility was observed for PE blends, while miscibility was obtained in PET and Ny6 blends mixed at high temperatures due to the occurrence of transreactions.

Gonzalez-Costoso, Clara Lena

99

Optical properties of light-sensitive liquid-crystal elastomers in the vicinity of the nematic-paranematic phase transition  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

100

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

101

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

102

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

PubMed Central

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

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

2011-01-01

103

Field controlled nematic-to-isotropic phase transition in liquid crystal–carbon nanotube composites  

Microsoft Academic Search

A nematic-to-isotropic transition has been observed in suspensions of carbon nanotubes (CNTs) and a cyanobiphenyl-based liquid crystal (LC) confined within an indium tin oxide glass sandwich cell. Upon the application of electric field, CNTs rotate out of plane short-circuiting the electrodes and producing a current flow through the CNTs. The resulting Joule heating leads to a local increase in temperature

Hemang J. Shah; Adam K. Fontecchio; Davide Mattia; Yury Gogotsi

2008-01-01

104

Thermal study of the Isotropic to Smectic C phase transition in main-chain liquid-crystalline elastomers  

Microsoft Academic Search

High-resolution calorimetry has been used in order to investigate the nature of the Isotropic to Smectic C phase transition of main-chain liquid-crystalline elastomers. Two polydomain elastomers with a conical distribution of the layer normal with respect to the director and different compositions and crosslinking concentrations were synthesised. The heat capacity temperature profiles were measured over a broad temperature range, using

G. Cordoyiannis; A. Sánchez-Ferrer; H. Finkelmann; B. Roži?; S. Žumer; Z. Kutnjak

2010-01-01

105

Magnetic Observations of the Superfluid-Superfluid Phase Transition in Liquid Helium Three  

NASA Astrophysics Data System (ADS)

We report observations of the first-order phase transition between the two superfluid phases of ^3He. We supercool a long cylindrical sample of the higher-temperature A phase in a magnetic field in a simple dc magnetometer. We then introduce B phase at one end of the sample and observe its growth into the supercooled A phase via the magnetometer signal. For temperatures above a certain value, rm T_{nom }, the phase interface travels up the tube at a fairly constant velocity, in reasonable agreement with the theory of Leggett and Yip. For temperatures below rm T_{nom} there arises a new interaction between the rapidly moving phase interface and the magnetization of the sample. Our observations allow some characterization of this new interaction.

Boyd, Stephen Thomas

106

Free volume and phase transitions of 1-butyl-3-methylimidazolium based ionic liquids from positron lifetime spectroscopy.  

PubMed

Positron annihilation lifetime spectroscopy (PALS) was used to study a series of ionic liquids (ILs) with the 1-butyl-3-methylimidazolium cation ([C(4)MIM](+)) but different anions [Cl](-), [BF(4)](-), [PF(6)](-), [OTf](-), [NTf(2)](-), and [B(hfip)(4)](-) with increasing anion volumes. Changes of the ortho-positronium (o-Ps) lifetime parameters with temperature were observed for crystalline and amorphous (glass, supercooled, and normal liquid) states. Evidence for distinct phase transitions, e.g. melting, crystallization and solid-solid transitions, was observed in several PALS experiments. The o-Ps mean lifetime ??(3)? showed smaller values in the crystalline phase due to dense packing of the material compared to the amorphous phase. The o-Ps lifetime intensity I(3) in the liquid state is clearly smaller than in the crystallized state. This behaviour can be attributed to a solvation of e(+) by the anions, which reduces the Ps formation probability in the normal and supercooled liquid. These phenomena were observed for the first time when applying the PALS technique to ionic liquids by us in one preliminary and in this work. Four of the ionic liquids investigated in this work ([BF(4)](-), [NTf(2)](-), [PF(6)](-) and [Cl](-) ILs) exhibit supercooled phases. The specific hole densities and occupied volumes of those ILs were obtained by comparing the local free volume with the specific volume from pressure-volume-temperature (PVT) experiments. From the o-Ps lifetime, the mean size ?v(h)? of free volume holes of the four samples was calculated and compared with that calculated according to Fürth's hole theory. The hole volumes from both methods agree well. From the Cohen-Turnbull fitting of viscosity and conductivity against PALS/PVT results, the influence of the free volume on molecular transport properties was investigated. PMID:22472912

Yu, Yang; Beichel, Witali; Dlubek, Günter; Krause-Rehberg, Reinhard; Paluch, Marian; Pionteck, Jürgen; Pfefferkorn, Dirk; Bulut, Safak; Friedrich, Christian; Pogodina, Natalia; Krossing, Ingo

2012-04-01

107

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

PubMed

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

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

2014-05-27

108

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

109

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

NASA Astrophysics Data System (ADS)

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 single-phase region from the two-phase region is analyzed to have a moderate sensitivity to the symmetry energy and is higher for the model possessing the softer symmetry energy.

Zhang, Guang-Hua; Jiang, Wei-Zhou

2013-03-01

110

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

111

Experimental evidence for a liquid-gas phase transition in nuclear systems  

Microsoft Academic Search

At certain combinations of temperature and density, nuclear matter may exist as a liquid-gas mixture exhibiting phase instabilities, a characteristic signature of which may be found in the emission of intermediate-mass fragments in nuclear collisions. The present analysis of fragment distributions from proton-- and heavy-ion--induced reactions, in the framework of a theory of condensation, is suggestive of the occurrence of

A. D. Panagiotou; M. W. Curtin; H. Toki; D. K. Scott; P. J. Siemens

1984-01-01

112

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

Microsoft Academic Search

Two series of liquid-crystalline compounds having three phenyl rings separated by flexible spacer ---CH(CH{3})CH{2}---COO--- and by rigid azo and azoxy group, were studied by DSC, optical and X-ray methods. For esters of dl-3-(4^{prime}-nitro)-phenylbutyric acid with 4^{prime}-alkoxy-phenylazo-phenol-4 having dodecyloxy or longer terminal chains, as well as for related azoxy compounds, a narrow (even below 5 K) reentrant or inverted nematic phase

W. Pyzuk; E. Górecka; J. Mieczkowski; J. Przedmojski

1992-01-01

113

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

114

Mean-field theory of phase transitions in liquid-crystalline polymers  

Microsoft Academic Search

We present a self-consistent-field structure for the thermodynamic description of concentrated solutions of liquid-crystal polymers. The polymers are assumed to be locally stiff but capable of curvature over large distances. The formulation of the chain geometry is that of a wormlike polymer, but the final analysis is simpler than the Kratky–Porod form. The phase behavior is analyzed for a cylindrically

Anshu M. Gupta; Sam F. Edwards

1993-01-01

115

Saturated ElastoPlastic Porous Media under Consideration of Gaseous and Liquid Phase Transitions  

Microsoft Academic Search

Taking a closer look on, e.g., storage processes of greenhouse gases in deep geological aquifers or pressure changes in shear\\u000a bands, the observation can be made that pressure and temperature changes in porous materials can induce phase transition processes\\u000a of the respective pore fluids. For a numerical simulation of this behaviour, a continuum mechanical model based on a multiphasic\\u000a formulation

Wolfgang Ehlers; Tobias Graf

116

Critical behavior at transitions from uniaxial to biaxial phases in a smectic liquid-crystal mixture.  

PubMed

We report results of calorimetric and optical investigations of binary mixtures of rodlike and bent-shaped molecules. We find that the observed critical heat anomaly associated with the smectic-A2 to biaxial smectic-A2b transition is well described with a Fisher-renormalized form of the usual scaling expression. The effect of renormalization is large in this system in part because of the moderately steep slope of the phase boundary (dT(c)/ dX?100 K, where X is the mole fraction of the bent-core molecules) and in part because of the proximity to the tricritical point. The magnitude of heat anomaly at the smectic-A2-smectic-A2b transition showed a drastic decrease as X becomes smaller. Moreover, the nematic-smectic-A2 transitions investigated turned out to be always first order and the transition enthalpy showed only weak dependence on the concentration X. The results imply that the energy fluctuations around the smectic-A2-smectic-A2b transition are very sensitive to the underlying ordering of the smectic-A2 background. PMID:20866637

Sasaki, Y; Ema, K; Le, K V; Takezoe, H; Dhara, S; Sadashiva, B K

2010-07-01

117

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

SciTech Connect

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

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

1989-10-01

118

Fluctuations of Imbalanced Fermionic Superfluids in Two Dimensions Induce Continuous Quantum Phase Transitions and Non-Fermi-Liquid Behavior  

NASA Astrophysics Data System (ADS)

We study the nature of superfluid pairing in imbalanced Fermi mixtures in two spatial dimensions. We present evidence that the combined effect of Fermi surface mismatch and order parameter fluctuations of the superfluid condensate can lead to continuous quantum phase transitions from a normal Fermi mixture to an intermediate Sarma-Liu-Wilczek superfluid with two gapless Fermi surfaces—even when mean-field theory (incorrectly) predicts a first-order transition to a phase-separated "Bardeen-Cooper-Schrieffer plus excess fermions" ground state. We propose a mechanism for non-Fermi-liquid behavior from repeated scattering processes between the two Fermi surfaces and fluctuating Cooper pairs. Prospects for experimental observation with ultracold atoms are discussed.

Strack, Philipp; Jakubczyk, Pawel

2014-04-01

119

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

PubMed

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

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

2014-05-14

120

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

PubMed

We study smectic-liquid-crystal order in a cell with a heterogeneous substrate imposing surface random positional and orientational pinnings. Proposing a minimal random elastic model, we demonstrate that, for a thick cell, the smectic state without a rubbed substrate is always unstable at long scales and, for weak random pinning, is replaced by a smectic glass state. We compute the statistics of the associated substrate-driven distortions and the characteristic smectic domain size on the heterogeneous substrate and in the bulk. We find that for weak disorder, the system exhibits a three-dimensional temperature-controlled phase transition between a weakly and strongly pinned smectic glass states akin to the Cardy-Ostlund phase transition. We explore experimental implications of the predicted phenomenology and suggest that it provides a plausible explanation for the experimental observations on polarized light microscopy and x-ray scattering. PMID:23496537

Zhang, Quan; Radzihovsky, Leo

2013-02-01

121

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

122

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

123

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

NASA Astrophysics Data System (ADS)

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

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

2001-10-01

124

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

NASA Astrophysics Data System (ADS)

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

Balevi?ius, V.; Orel, B.; Hadži, D.

125

Precise Measurements of the Density and Critical Phenomena Near Phase Transitions in Liquid Helium  

NASA Technical Reports Server (NTRS)

The first-year progress for the project of precise measurements of the density and critical phenomena of helium near phase transitions is summarized below: (1) completion of a cryogenic sample probe for the proposed measurements, and the rehabilitation of a designated laboratory at Caltech for this project; (2) construction and testing of a superconducting niobium cavity; (3) acquisition of one phase-locked-loop system for high-resolution frequency control and read- out; (4) setting up high-resolution thermometry (HRT) for temperature readout and control; (5) developing new approaches for calibrating the coefficient between the resonant frequency shift (delta f) and the helium density (rho), as well as for measuring the effect of gravity on T(sub lambda) to a much better precision; (6) programming of the interface control of all instruments for automatic data acquisition; and (7) improving data analyses and fitting procedures.

Yeh, Nai-Chang

1997-01-01

126

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

PubMed

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

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

2013-05-23

127

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

NASA Astrophysics Data System (ADS)

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

Huang, Tsang-Min; Kyu, Thein

2010-03-01

128

Liquid-state theory and the renormalization group reconciled: a theory of phase transitions in fluids  

NASA Astrophysics Data System (ADS)

The hierarchical reference theory (HRT) is a unified theory of fluids: in the dense regime it has the accuracy typical of a good theory of the liquid state. At the same time, close to a critical point, it develops the structure of a renormalization group theory in which all non-universal quantities can be deduced from knowledge of the interatomic interaction. The HRT can be applied above as well as below the critical temperature so that the phase diagram, thermodynamic properties and distribution functions are obtained in a unified way. Similar information can be extracted also from models of binary mixtures. In this case, the HRT allows for the determination of the order parameter along lines of critical points and provides an explanation of the strange crossover phenomena found in mixtures.

Reatto, L.; Parola, A.

1996-11-01

129

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

PubMed

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

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

2014-02-18

130

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

131

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

PubMed

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

Hernández-Contreras, M

2013-12-01

132

Temperature-induced conformational transition of bovine serum albumin in neutral aqueous solution by reversed-phase liquid chromatography.  

PubMed

The temperature-induced conformational transition of bovine serum albumin (BSA) in neutral aqueous solution was studied using intrinsic fluorescence emission spectrum, reversed-phase liquid chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the conformation transition thermodynamic parameters were determined in the temperature range 12-50 °C. The results showed that, in the temperature range 12-20 °C, BSA only existed in a single conformation state A, while in the temperature range 22-50 °C, it existed in two different conformation states: A and B. The percentage of conformation state A decreased while that of conformation state B increased with the increase in temperatures, and when temperature approached 50 °C conformation state B accounted for approximately 25% of all conformation states of BSA. In the conformational transition of BSA from conformation state A to conformation state B, the positive enthalpy change, entropy change and free energy changes demonstrated that the conformational transition was endothermic, nonspontaneous and mainly entropy-driven. PMID:24037907

Bian, Liujiao; Wu, Dan; Hu, Wei

2014-02-01

133

On the theory of the shear-induced isotropic-to-nematic phase transition of side chain liquid-crystalline polymers  

Microsoft Academic Search

The shear-induced isotropic-to-nematic phase transition of side chain liquid-crystalline polymers is studied theoretically. A modification of the previous models of main-chain liquid crystals to the case of side chain liquid-crystalline polymers is proposed. Orientational and rheological properties of the model are studied in plane-shear flow. Predictions of the present model agree qualitatively with experimental results (Pujolle-Robic, Noirez in Nature 409:167,

Siegfried Hess; Patrick Ilg

2005-01-01

134

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

135

Orientational fluctuations near the smectic A to smectic C phase transition in two "de Vries"-type liquid crystals.  

PubMed

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

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

2013-09-16

136

Phase transition and decomposition temperatures, heat capacities and viscosities of pyridinium ionic liquids  

Microsoft Academic Search

Ionic liquids are organic salts with low melting points. Many of these compounds are liquid at room temperature in their pure state. Since they have negligible vapor pressure and would not contribute to air pollution, they are being intensively investigated for a variety of applications, including as solvents for reactions and separations, as non-volatile electrolytes, and as heat transfer fluids.

Jacob M. Crosthwaite; Mark J. Muldoon; JaNeille K. Dixon; Jessica L. Anderson; Joan F. Brennecke

2005-01-01

137

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

Microsoft Academic Search

Contrary to the conventional wisdom that there is only one unique liquid state for any material, recent evidence suggests that there can be more than two liquid states even for a single-component substance. The transition between these liquid states is called a liquid-liquid phase transition. We report the detailed experimental investigation on the kinetics of the continuous spinodal-decomposition-type transformation of

Rei Kurita; Hajime Tanaka

2004-01-01

138

Fluctuation-induced first-order quantum phase transition of the U (1) spin liquid in a pyrochlore quantum spin ice  

NASA Astrophysics Data System (ADS)

We predict, using a free-energy calculation, that the quantum phase transition between the U (1) quantum spin liquid (QSL) and antiferromagnet (AFM) phases in certain pyrochlore quantum spin ice is first order rather than second order. This change in order from second to first order is induced by gauge fluctuations, which are explicitly taken into account at gauge theory level in our effective low-energy theory. We therefore have identified a fluctuation-induced first-order quantum phase transition in pyrochlore quantum spin ice. We explicitly derive the quantum free-energy description of this QSL-to-AFM phase transition and predict that it is a weakly first-order phase transition. We also briefly discuss the experimental relevance of this result.

Makhfudz, Imam

2014-01-01

139

Quantum phase transitions  

NASA Astrophysics Data System (ADS)

In recent years, quantum phase transitions have attracted the interest of both theorists and experimentalists in condensed matter physics. These transitions, which are accessed at zero temperature by variation of a non-thermal control parameter, can influence the behaviour of electronic systems over a wide range of the phase diagram. Quantum phase transitions occur as a result of competing ground state phases. The cuprate superconductors which can be tuned from a Mott insulating to a d-wave superconducting phase by carrier doping are a paradigmatic example. This review introduces important concepts of phase transitions and discusses the interplay of quantum and classical fluctuations near criticality. The main part of the article is devoted to bulk quantum phase transitions in condensed matter systems. Several classes of transitions will be briefly reviewed, pointing out, e.g., conceptual differences between ordering transitions in metallic and insulating systems. An interesting separate class of transitions is boundary phase transitions where only degrees of freedom of a subsystem become critical; this will be illustrated in a few examples. The article is aimed at bridging the gap between high-level theoretical presentations and research papers specialized in certain classes of materials. It will give an overview on a variety of different quantum transitions, critically discuss open theoretical questions, and frequently make contact with recent experiments in condensed matter physics.

Vojta, Matthias

2003-12-01

140

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

141

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

142

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

143

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

144

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

145

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

ERIC Educational Resources Information Center

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

Yalcin, Fatma Aggul

2012-01-01

146

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

147

Calorimetric study of the nematic to smectic- A and smectic- A to smectic- C phase transitions in liquid-crystal-aerosil dispersions  

NASA Astrophysics Data System (ADS)

A high-resolution calorimetric study has been carried out on nanocolloidal dispersions of aerosils in the liquid crystal 4-n -pentylphenylthiol- 4'-n -octyloxybenzoate (8¯S5) as a function of aerosil concentration and temperature spanning the smectic- C to nematic phases. Over this temperature range, this liquid crystal possesses two continuous XY phase transitions: a fluctuation-dominated nematic to smectic- A transition with ???XY=-0.013 and a mean-field smectic- A to smectic- C transition. The effective critical character of the N-SmA transition remains unchanged over the entire range of the introduced quenched random disorder while the peak height and enthalpy can be well described by considering a cutoff length scale to the quasicritical fluctuations. The robust nature of the N-SmA transition in this system contrasts with cyanobiphenyl-aerosil systems and may be due to the mesogens being nonpolar and having a long nematic range. The character of the SmA-SmC transition changes gradually with increasing disorder but remains mean field like. The heat capacity maximum at the SmA-SmC transition scales as ?S-0.5 with an apparent evolution from tricritical to a simple mean-field step behavior. These results may be generally understood as a stiffening of the liquid crystal (both the nematic elasticity as well as the smectic layer compression modulus B ) with silica density.

Roshi, A.; Iannacchione, G. S.; Clegg, P. S.; Birgeneau, R. J.; Neubert, M. E.

2005-11-01

148

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

149

Light-scattering-mode optical switching and image storage in polymer\\/liquid crystal composite films by means of photochemical phase transition  

Microsoft Academic Search

Photochemical phase transition behavior triggered by photoisomerization of a guest azobenzene doped in nematic (N) liquid-crystalline (LC) domains was investigated in isotropic (I) acrylate polymers with alkyl side chains on their surfaces. These polymer\\/LC composite films were prepared by in situ thermal polymerization-induced phase separation method (thermal PIPS) from their starting mixtures containing a di- and a mono-functional acrylate monomer.

H.-K. Lee; K. Doi; A. Kanazawa; T. Shiono; T. Ikeda; T. Fujisawa; M. Aizawa; B. Lee

2000-01-01

150

Volume phase transitions of biaxial nematic elastomers  

NASA Astrophysics Data System (ADS)

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

Matsuyama, Akihiko

2012-01-01

151

Gelation versus liquid crystal phase transitions in suspensions of plate-like particles  

Microsoft Academic Search

Gelation is a common effect in aqueous suspensions of charged colloidal clay platelets at\\u000aconcentrations as low as 1 wt%. However, in systems of charged gibbsite [Al(OH)3]\\u000aplatelets, gelation can be delayed to concentrations as high as 50 wt% depending on the\\u000aionic strength. We investigated the phase behaviour of this system approaching the state\\u000aof gelation in the delicate

M. C. D. Mourad; J. E. G. J. Wijnhoven; D. D. van't Zand; David van der Beek; H. N. W. Lekkerkerker

2006-01-01

152

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

NASA Astrophysics Data System (ADS)

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

Sharma, Dipti

2009-03-01

153

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

154

Pairing phase transitions in nuclear wave functions  

SciTech Connect

The exact solution of the nuclear shell model is used for studying the phase transition from superfluid to normal Fermi-liquid as a function of the pairing strength, excitation energy (or temperature), nuclear spin and the presence of other types of residual interactions. The phase transition in a finite system is seen through the change of properties of individual wave functions.

Horoi, Mihai [Department of Physics, Central Michigan University, Mount Pleasant, Michigan 48859 (United States); Zelevinsky, Vladimir [Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824-1321 (United States)

2007-05-15

155

Statistical thermodynamics of the cluster solid-liquid transition  

Microsoft Academic Search

A direct connection between the solid-liquid transition in atomic clusters and the macroscopic phase transition is established through analysis of the size scaling of the latent heat and transition rounding. The transition occurs without phase separation, leading to remarkable consequences in caloric experiments. These features are all quantified through the characteristic shape of the classical state density, computed by a

Pierre Labastie; Robert L. Whetten

1990-01-01

156

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

157

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

PubMed

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

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

2010-01-01

158

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

159

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

PubMed

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

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

2014-06-01

160

Liquid-liquid-solid transition in viscoelastic liquids  

PubMed Central

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

Zubelewicz, Aleksander

2013-01-01

161

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

162

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

NASA Astrophysics Data System (ADS)

The present work is devoted to the study of the thermo-optical properties of liquid crystals doped with traces of fullerene C60 at the vicinity of the nematic-smectic-A phase transition. By using the time-resolved Z-scan technique, we measure the temperature dependence of the thermo-optical coefficient and the thermal diffusivity. Our results reveal that the critical behavior of the thermal diffusivity is strongly affected by the fullerene addition. We provide a detailed discussion under the light of the distinct mechanisms behind the thermal transport in liquid-crystal samples.

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

2014-05-01

163

Electroweak phase transitions  

SciTech Connect

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

Anderson, G.W.

1991-09-16

164

Electroweak phase transitions  

SciTech Connect

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

Anderson, G.W.

1991-09-16

165

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

PubMed

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

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

2012-02-23

166

Topological phase transition in asymmetric nuclear matter  

NASA Astrophysics Data System (ADS)

Starting from an effective model of asymmetric nuclear matter we show that at finite temperature T and baryon chemical potential ?B there exists a topological phase transition from state of non-Fermi liquid to that of Fermi liquid which is protected by winding numbers. At low ?B the transition is first-order, then extends to a second-order phase transition at larger ?B through a tri-critical point. The isospin dependences of the tri-critical point and the phase diagram in the (T, ?B)-plane are established. The distinction between this type of phase transition and the similar phenomenon caused by the Silver Blaze property (SBP) at T = 0 is confirmed for isospin varying from 0 to 1. We reveal that the topological phase transition could emerge in a large class of nuclear theories.

Phat, Tran Huu; Thu, Nguyen Van

2014-05-01

167

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

Microsoft Academic Search

Isentropic ramp-wave loading of materials is a novel method to study the kinetics of phase transitions, particularly in regimes that are overdriven by shock loading techniques. In our experiments, the Sandia Z accelerator produces magnetically driven planar ramp waves of 200-300 ns rise time in copper, which then propagate into a material sample. Two different materials are investigated; iron and

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

2001-01-01

168

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

PubMed

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

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

2014-05-29

169

String Mediated Phase Transitions.  

National Technical Information Service (NTIS)

It is demonstrated from first principles how the existence of string-like structures can cause a system to undergo a phase transition. In particular, the role of topologically stable cosmic string in the restoration of spontaneously broken symmetries is e...

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

1988-01-01

170

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

171

Insights into phase transition kinetics from colloid science  

Microsoft Academic Search

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

Valerie J. Anderson; Henk N. W. Lekkerkerker

2002-01-01

172

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

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

173

Electrophysical properties of silicon near the crystal-melt phase transition in the solid and liquid states  

SciTech Connect

The temperature dependence of the thermo-emf is measured for silicon in the range of melting and liquid state. The nature of the change in the thermo-emf correlates with the changes in other electrophysical properties and confirms that silicon is among those substances that melt by a semiconductor-metal-type transition. The experimental value of the thermo-emf of molten silicon is equal to 14 ..mu..V/K at T/sub m/, which agrees fairly well with calculations using the weakly bound electron approximation.

Glazov, V.M.; Kol'tsov, V.B.; Kurbatov, V.A.

1988-05-01

174

Nucleation and hysteresis of vapor-liquid phase transitions in confined spaces: Effects of fluid-wall interaction  

NASA Astrophysics Data System (ADS)

In this work, we propose a method to stabilize a nucleus in the framework of lattice density-functional theory (LDFT) by imposing a suitable constraint. Using this method, the shape of critical nucleus and height of the nucleation barrier can be determined without using a predefined nucleus as input. As an application of this method, we study the nucleation behavior of vapor-liquid transition in nanosquare pores with infinite length and relate the observed hysteresis loop on an adsorption isotherm to the nucleation mechanism. According to the dependence of hysteresis and the nucleation mechanism on the fluid-wall interaction, w , in this work, we have classified w into three regions ( w>0.9 , 0.1?w?0.9 , and w<0.1 ), which are denoted as strongly, moderately, and weakly attractive fluid-wall interaction, respectively. The dependence of hysteresis on the fluid-wall interaction is interpreted by the different nucleation mechanisms. Our constrained LDFT calculations also show that the different transition paths may induce different nucleation behaviors. The transition path dependence should be considered if morphological transition of nuclei exists during a nucleation process.

Men, Yumei; Yan, Qingzhao; Jiang, Guangfeng; Zhang, Xianren; Wang, Wenchuan

2009-05-01

175

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

176

Nonmaximality and phase transitions  

NASA Astrophysics Data System (ADS)

Detailed analysis of an infinite class of mean-field, Ginzburg-Landau models of continuous phase transitions which violate the twenty-year old Ascher-Michel maximality conjecture is presented. In all previous counterexamples to the conjecture, fluctuations were found to drive the transitions discontinuous, thus restoring the validity of the conjecture. Our renormalization-group ?-expansion calculations for this infinite class of models uncover the first counterexamples also to the restored conjecture. In contrast to the mean-field behavior, direction of the order parameter near the transition is determined by a stable fixed point and depends only on thermodynamic variables perpendicular to the critical surface, showing a characteristic power-law singularity. Analogous models for the Higgs problem are not known.

Jari?, Marko V.; Mukamel, David

1990-06-01

177

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

SciTech Connect

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

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

2010-01-01

178

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

179

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

180

Specific features of the freedericksz transition in nematic-cholesteric droplets: The effect of the liquid crystal-isotropic phase boundary  

NASA Astrophysics Data System (ADS)

Quasi-static orientation transitions in nematic-cholesteric liquid crystal (LC) droplets occurring in an isotropic environment in a constant electric field have been studied. It is shown that transformation of the initial homeotropic orientation of the director field in these LC droplets has a non-threshold character, which is related to the presence of a small cholesteric additive. As the field increases, this dopant leads to continuous growth in the effective size of a deformation field from the LC-isotropic phase interface.

Timirov, Yu. I.; Skaldin, O. A.; Gareeva, E. R.; Kayumov, I. R.

2013-12-01

181

A model for self-sustained potential oscillation of lipid bilayer membranes induced by the gel-liquid crystal phase transitions.  

PubMed Central

To clarify the mechanism of self-sustained oscillation of the electric potential between the two solutions divided by a lipid bilayer membrane, a microscopic model of the membrane system is presented. It is assumed, on the basis of the observed results (Yoshikawa, K., T. Omachi, T. Ishii, Y. Kuroda, and K. liyama. 1985. Biochem. Biophys. Res. Commun. 133:740-744; Ishii, T., Y. Kuroda, T. Omochi, and K. Yoshikawa. 1986. Langmuir. 2:319-321; Toko, K., N. Nagashima, S. liyama, K. Yamafuji, and T. Kunitake. Chem. Lett. 1986:1375-1378), that the gel-liquid crystal phase transition of the membrane drives the potential oscillation. It is studied, by using the model, how and under what condition the repetitive phase transition may occur and induce the potential oscillation. The transitions are driven by the repetitive adsorption and desorption of proton by the membrane surface, actions that are induced the periodic reversal of the direction of protonic current. The essential conditions for the periodic reversal are (a) at least one kind of cations such as Na+ or K+ are included in the system except for proton, and the variation of their permeability across the membrane due to the phase transition is noticeably larger than that of proton permeability; and (b) the phase transition has a hysteresis. When these conditions are fulfilled, the self-sustained potential oscillation may be brought about by adjusting temperature, pH, and the cation concentration in the solutions on both sides of the membrane. Application of electric current across the membrane also induces or modifies the potential oscillation. Periodic, quasiperiodic, and chaotic oscillations appear especially, depending on the value of frequency of the applied alternating current.

Yagisawa, K; Naito, M; Gondaira, K I; Kambara, T

1993-01-01

182

Ultra-stable temperature control in EPR experiments: Thermodynamics of gel-to-liquid phase transition in spin-labeled phospholipid bilayers and bilayer perturbations by spin labels  

NASA Astrophysics Data System (ADS)

An ultra-stable variable temperature accessory for EPR experiments with biological samples has been designed and tested. The accessory is comprised from a digitally controlled circulator bath that pumps fluid through high-efficiency aluminum radiators attached to an EPR resonator of a commercial X-band EPR spectrometer. Temperature stability of this new accessory after a 15 min re-equilibration is at least ±0.007 K. For a standard 1-cm-long capillary sample arranged inside an EPR tube filled with silicon oil, the temperature variations do not exceed ±0.033 K over the sample temperature range from 283 to 333 K. This new accessory has been tested by carrying out a comparative spin-labeling EPR and differential scanning calorimetry (DSC) study of the gel-to-liquid phase transition in multilamellar vesicles (MLV) composed of a synthetic phospholipid 1,2-dimyristoyl- sn-glycero-3-phosphatidylcholine (DMPC). We demonstrate that the gel-to-liquid phase transition temperatures of MLV DMPC measured by EPR and DSC agree within ±0.02 K experimental error even though the sample for EPR study was labeled with 1 mol% of 5PC (1-palmitoyl-2-stearoyl-(5-doxyl)- sn-glycero-3 phosphocholine). Cooperative unit number measured by EPR, N = 676 ± 36, was almost 50% higher than that obtained from DSC ( N = 458 ± 18). These high values of N indicate that (i) the lipid domains should include at least several spin-labeled lipid molecules and (ii) the spin-probe 5PC molecules are not excluded into domains that are different from the bulk lipid phase as was speculated earlier. Overall, our data provide DSC and EPR evidence that in studies of the gel-to-liquid phase transition, the effect of bilayer perturbation by spin-labeled lipids is negligible and therefore thermodynamic parameters of the phase transition can be accurately measured by spin-labeling EPR. This might serve as an indication when spin-labeled molecules with structures similar to those of lipids are introduced at low concentrations, they are easily accommodated by fluid phospholipid bilayers without significant losses of the lipid cooperativity.

Alaouie, Ali M.; Smirnov, Alex I.

2006-10-01

183

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

184

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

185

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

186

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

187

Liquid to quasicrystal transition in bilayer water.  

PubMed

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

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

2010-10-21

188

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

189

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

PubMed

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

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

2014-05-01

190

Liquid-liquid transition in supercooled water suggested by microsecond simulations  

PubMed Central

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

Li, Yaping; Li, Jicun; Wang, Feng

2013-01-01

191

Sensing of phase transition in medium with terahertz pulsed spectroscopy  

NASA Astrophysics Data System (ADS)

Phase state identification and phase transition registration in condensed matter are significant applications of terahertz spectroscopy. A set of fundamental and applied problems are associated with the phase state problem. Our report is devoted to the experimental analysis of the spectral characteristics of water and water solution during the phase transition from the solid state to the liquid state via the method of terahertz pulsed spectroscopy. In this work transformation of the sample spectral characteristics during the phase transition were observed and discussed. Possible application of terahertz pulsed spectroscopy as an effective instrument for phase transition sensing was considered.

Zaytsev, Kirill I.; Fokina, Irina N.; Fedorov, Aleksey K.; Yurchenko, Stanislav O.

2014-03-01

192

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

193

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

PubMed

This paper extends our earlier studies of free energy functions of density and crystalline order parameters for models of supercooled water, which allows us to examine the possibility of two distinct metastable liquid phases [D. T. Limmer and D. Chandler, J. Chem. Phys. 135, 134503 (2011) and preprint 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. PMID:23758385

Limmer, David T; Chandler, David

2013-06-01

194

Phase transitions in ionic gels  

Microsoft Academic Search

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

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

1980-01-01

195

Phase Transitions in Ionic Gels  

Microsoft Academic Search

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

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

1980-01-01

196

Quantum phase transitions in electronic systems  

Microsoft Academic Search

Zero-temperature or quantum phase transitions in itinerant electronic systems both with and without quenched disordered are discussed. Phase transitions considered include, the ferromagnetic transition, the antiferromagnetic transition, the superconductor-metal transition, and various metal-insulator transitions. Emphasis is placed on how to determine the universal properties that characterize these quantum phase transitions. For the first three of the phase transitions listed above,

T. R. Kirkpatrick; D. Belitz

1997-01-01

197

Isotropic to cholesteric phase transition of DNA solutions  

NASA Astrophysics Data System (ADS)

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

Mukherjee, Prabir K.

2014-01-01

198

Phase Transitions in Thin Block Copolymer Films  

SciTech Connect

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

Kramer, Edward J. (UCSB)

2010-10-08

199

Spin transition induced by crystal - liquid crystal transition  

NASA Astrophysics Data System (ADS)

Cobalt(II) compounds [Co(C10C8C2-terpy)2](BF4)2 (1) and [Co(C12C10C2-terpy)2](BF4)2 (2) (CxCyCz-terpy = 4'-5'''-Alkyl-1'''-alkoxy-2,2':6',2''-terpyridine) with branched alkyl chains, based on a terpyridine frame, were synthesized. The cobalt(II) compounds 1 and 2 exhibit the spin transition between low-spin and high-spin with thermal hysteresis loop at the liquid crystal transition temperature (T1/2? = 275 K and T1/2? = 250 K for 1 and T1/2? = 307 K and T1/2? = 296 K for 2), and the spin transition is induced by crystal - liquid crystal transition. The bifunctional materials show synchronizing both spin transition and liquid crystal transition.

Hayami, Shinya; Yamamoto, Yuuki; Kojima, Yoshihiro; Inoue, Katsuya

2010-01-01

200

Nanostructures of Liquid Crystal Phases  

NASA Astrophysics Data System (ADS)

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

Chen, Dong

201

QCD Phase Transitions, Volume 15.  

National Technical Information Service (NTIS)

The title of the workshop, 'The QCD Phase Transitions' in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discuss...

E. Shuryak T. Schaefer

1999-01-01

202

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

203

Phase Transitions in Brownian Pumps  

NASA Astrophysics Data System (ADS)

We study stochastic particle transport between two reservoirs along a channel, where the particles are pumped against a bias by a traveling wave potential. It is shown that phase transitions of period-averaged densities or currents occur inside the channel when exclusion interactions between the particles are taken into account. These transitions reflect those known for the asymmetric simple exclusion process. We argue that their occurrence is a generic feature of Brownian motors operating in open systems.

Dierl, Marcel; Dieterich, Wolfgang; Einax, Mario; Maass, Philipp

2014-04-01

204

Cosmological phase transitions and baryogenesis  

SciTech Connect

We review various aspects of field theory at finite temperature related to the theory of phase transitions. In particular, the real and imaginary time formalisms are discussed, showing their equivalence in simple examples. Bubble nucleation by thermal tunneling, and the subsequent development of the phase transition is described in some detail. Some attention is also devoted to the breakdown of the perturbative expansion and the infrared problem in the finite temperature field theory. Finally the application to baryogenesis at the electroweak phase transition is done in the Standard Model and in the Minimal Supersymmetric Standard Model. In all cases we have translated the condition of not washing out any previously generated baryon asymmetry by upper bounds on the Higgs mass.

Quiros, Mariano [Instituto de Estructura de la Materia (CSIC), Serrano 123, E-28006 Madrid (Spain)

1998-10-05

205

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

NASA Astrophysics Data System (ADS)

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.

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

206

Study of Gas-Liquid Two-Phase Flow Pattern Transitions in Horizontal Pipe, Annulus and Nuclear Fuel Type Rod Bundle Flow Systems  

Microsoft Academic Search

The ability to predict the flow patterns and flow pattern transitions in a two-phase flow process is useful for an accurate prediction of the pressure drop, heat and mass transfer rates, and also for the choice of appropriate two-phase flow design parameters for the system. During a loss of coolant accident (LOCA) in a nuclear reactor, two-phase flow may exist

Sylvester Ifanyi Osamusali

1988-01-01

207

Phase transitions in potassium nitrate  

Microsoft Academic Search

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

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

1974-01-01

208

Zipf's law and phase transition  

NASA Astrophysics Data System (ADS)

In this paper, we describe the link between the Zipf law and statistical distributions for the Fortuin-Kasteleyn clusters in Ising as well as Potts models. From these results, it is seen that Zipf's law can be a criterion of a phase transition, but it does not determine its order. We present the corresponding histograms for fixed domain configurations.

Lukierska-Walasek, K.; Topolski, K.

2014-04-01

209

Liquid-gas transition and multifragmentation in expanding nuclei  

Microsoft Academic Search

In this talk I present results showing that there are two distinct regimes of nuclear multifragmentation. When nuclei are heated up without compression the multifragment disintegration goes like a liquid-gas phase transition in a finite system, similar to the boiling of ordinary fluids. This process is well described by the statistical model assuming a thermal equilibrium at the break-up stage.

I. N. Mishustin

1998-01-01

210

Two Phase Flow Mapping and Transition Under Microgravity Conditions  

NASA Technical Reports Server (NTRS)

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

Parang, Masood; Chao, David F.

1998-01-01

211

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

SciTech Connect

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

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

2010-01-08

212

Fragility Control Using the Liquid-Liquid Transition in Molecular Liquid  

Microsoft Academic Search

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

Rei Kurita; Hajime Tanaka

2006-01-01

213

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

PubMed

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

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

2013-09-12

214

The influence of the polymer backbone flexibility on the phase transitions of side chain liquid crystal polymers containing 6-[4-(4-methoxy-?-methylstyryl)phenoxy]hexyl side groups  

Microsoft Academic Search

The influence of the polymer backbone flexibility on the phase transition temperatures of side chain liquid crystalline polymethacrylate, polyacrylate, polymethylsiloxane, and polyphosphazene containing 6-[4-(4-methoxy- ß- methylstyryl)phenoxy]hexyl side groups is discussed. Flexible backbones enhance the decoupling of the motions of the side chain and main chain and therefore, increase the rate of side-chain crystallization. Subsequently, the kinetically controlled crystallization process may

Virgil Percec; Dimitris Tomazos; Reginald A. Willingham

1989-01-01

215

Liquid-Vapor Flow Regime Transitions for Use in Design of Heat Transfer Loops in Spacecraft - An Investigation of Two-Phase Flow in Zero Gravity Conditions.  

National Technical Information Service (NTIS)

The behavior of viscous (or low velocity) two-phase vapor-liquid flow under zero gravity was simulated in the laboratory by using two immiscible fluids of equal density flowing together in a one inch diameter glass tube. The fluids used wer Polypropylene ...

T. W. Lovell

1985-01-01

216

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

217

Liquid-vapor flow regime transitions for use in design of heat transfer loops in spacecraft: An investigation of two-phase flow in zero gravity conditions  

NASA Astrophysics Data System (ADS)

The behavior of viscous (or low velocity) two-phase vapor-liquid flow under zero gravity was simulated in the laboratory by using two immiscible fluids of equal density flowing together in a one inch diameter glass tube. The fluids used were Polypropylene Glycol (PPG) which simulated the liquid phase and water which simulated the vapor phase. Various tests were conducted varying flow rates and entrance conditions. Four existing flow regime models were analyzed, modeled on a computer, and extrapolated to predict zero-gravity conditions. The flow regimes were the Horizontal Dukler-Taitel, Vertical Dukler-Taitel, Vertical Weisman and Horizontal Weisman. None of these models when extrapolated to zero-g conditions agreed well with the lab data, and some of the observed flow regimes were not predicted at all.

Lovell, T. W.

1985-05-01

218

The Effects of Spontaneous Strains at the Dhd-Drd Phase Transition in HAT Series  

Microsoft Academic Search

Spontaneous strain effects at the Dhd-Drd phase transition in HAT columnar liquid crystal systems are taken into account. The transition is then treated as a paraelasticferroelastic transition, which is known in some crystal systems, but has never been discussed in liquid crystal systems. The anomaly of the elastic compliance near the transition is discussed. The critical exponents remain the same

Y. F. Sun; J. Swift

1985-01-01

219

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

220

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

221

Convective instability of solidification with a phase transition zone  

SciTech Connect

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

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

2011-04-15

222

Alternative View of Cosmological Phase Transitions.  

National Technical Information Service (NTIS)

A description of cosmological phase transitions, which differs from the one based on the effective potential approach is presented. In this scheme, the phase transition is driven by the spontaneous generation of domain walls (solitons), and below the crit...

G. C. Marques I. Ventura

1982-01-01

223

Nonisomorphic nucleation pathways arising from morphological transitions of liquid channels.  

PubMed

Motivated by unexpected morphologies of the emerging liquid phase (channels, bulges, droplets) at the edge of thin, melting alkane terraces, we propose a new heterogeneous nucleation pathway. The competition between bulk and interfacial energies and the boundary conditions determine the growth and shape of the liquid phase at the edge of the solid alkane terraces. Calculations and experiments reveal a "precritical" shape transition (channel-to-bulges) of the liquid before reaching its critical volume along a putative shape-conserving path. Bulk liquid emerges from the new shape, and, depending on the degree of supersaturation, the new pathway may have two, one, or zero energy barriers. The findings are broadly relevant for many heterogeneous nucleation processes because the novel pathway is induced by common, widespread surface topologies (scratches, steps, etc.). PMID:22540599

Kusumaatmaja, H; Lipowsky, R; Jin, C; Mutihac, R-C; Riegler, H

2012-03-23

224

Nonisomorphic Nucleation Pathways Arising from Morphological Transitions of Liquid Channels  

NASA Astrophysics Data System (ADS)

Motivated by unexpected morphologies of the emerging liquid phase (channels, bulges, droplets) at the edge of thin, melting alkane terraces, we propose a new heterogeneous nucleation pathway. The competition between bulk and interfacial energies and the boundary conditions determine the growth and shape of the liquid phase at the edge of the solid alkane terraces. Calculations and experiments reveal a “precritical” shape transition (channel-to-bulges) of the liquid before reaching its critical volume along a putative shape-conserving path. Bulk liquid emerges from the new shape, and, depending on the degree of supersaturation, the new pathway may have two, one, or zero energy barriers. The findings are broadly relevant for many heterogeneous nucleation processes because the novel pathway is induced by common, widespread surface topologies (scratches, steps, etc.).

Kusumaatmaja, H.; Lipowsky, R.; Jin, C.; Mutihac, R.-C.; Riegler, H.

2012-03-01

225

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

PubMed

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

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

2011-12-23

226

Salt-induced transition from a micellar to a lamellar liquid crystalline phase in dilute mixtures of anionic and nonionic surfactants in aqueous solution  

SciTech Connect

In dilute mixtures of anionic surfactant, sodium dodecylbenzenesulfonate (NaDoBS), and nonionic poly(ethylene oxide) alkylmonoether (C[sub 13-15]E[sub <7>]) a transition from a micellar to a lamellar phase is found at high salting-out electrolyte (NaCit) concentrations. With an increase of the salt concentration, different types of lamellar aggregates are formed. The existence of different types of aggregates is reflected by changes of the turbidity of the solutions. Light and fluorescence microscopy, freeze-fractured electron microscopy, confocal scanning laser microscopy (CSLM), and fluorescence depolarization were employed to characterize the aggregates and to induce a mechanism for the transition from a micellar to a lamellar phase. Surfactant aggregation is important in view of possible applications in enhanced oil recovery. 39 refs., 10 figs.

Sein, A.; Engberts, J.B.F.N. (Univ. of Groningen (Netherlands)); Linden, E. van der; Pas, J.C. van de (Unilever Research Lab., Vlaardingen (Netherlands))

1993-07-01

227

Mechanism of the transition to two-phase flow and flow regimes in the boiling of liquid metals in a once-through steam boiler  

Microsoft Academic Search

Results are presented from an experimental study of the stability of drop boiling in forced flow in channels. It is shown that the transition from one- to two-phase flow for the steady-state regime consists of the generation of vapor bubbles with the occurrence of plug flow. It was hypothesized and confirmed experimentally that a heat-transfer crisis of the second type

Y. D. Morozov; A. N. Privalov; V. F. Prisnyakov; S. A. Belogurov

1988-01-01

228

Disentangling dynamical phase transitions from equilibrium phase transitions  

NASA Astrophysics Data System (ADS)

Dynamical phase transitions (DPTs) occur after quenching some global parameters in quantum systems, and are signalled by the nonanalytical time evolution of the dynamical free energy, which is calculated from the Loschmidt overlap between the initial and time evolved states. In a recent Letter [M. Heyl et al., Phys. Rev. Lett. 110, 135704 (2013), 10.1103/PhysRevLett.110.135704], it was suggested that DPTs are closely related to equilibrium phase transitions (EPTs) for the transverse field Ising model. By studying a minimal model, the XY chain in a transverse magnetic field, we show analytically that this connection does not hold generally. We present examples where DPT occurs without crossing any equilibrium critical lines by the quench, and a nontrivial example with no DPT but crossing a critical line by the quench. Although the nonanalyticities of the dynamical free energy on the real time axis do not indicate the presence or absence of an EPT, the structure of Fisher lines for complex times reveals a qualitative difference.

Vajna, Szabolcs; Dóra, Balázs

2014-04-01

229

Simulation of quantum phase transitions  

NASA Astrophysics Data System (ADS)

The accurate simulation of phase transitions in quantum systems has become possible with the development of cluster Monte Carlo algorithms for quantum systems. The first such algorithm, the loop algorithm [H.G. Evertz et al., Phys. Rev. Lett. 70, 875 (1993)], turned out to be as efficient as its classical counterpart, the Swendsen-Wang algorithm, but suffered from an exponential slow down in an external magnetic field. This problems was solved by the worm algorithm [N.V. Prokof'ev et al., Phys. Lett. A 238, 253 (1998)], which was recently combined with the stochastic series expansion (SSE) algorithm [A.W. Sandvik, Phys. Rev. B 59, R14157 (1999)]. I will review applications of these new algorithms to quantum magnets and bosonic systems and show that they allow high precision simulations of large quantum systems. Examples will include the low-temperature asymptotic scaling behavior of two-dimensional quantum Heisenberg antiferromagnets, the critical behavior at quantum phase transitions in these systems, and quantitatve modeling of antiferromagnetic materials. In bosonic systems I will address some long standing problems, such as the existence of supersolids, and the melting of stripe phases. These examples show that today we can simulate quantum statistical systems with the same accuracy as classical systems, which enables the investigation of new universal behavior that has never been observed in classical systems.

Troyer, Matthias

2001-06-01

230

Diffusionless ??? Phase Transition in Polycrystalline and Single-Crystal Cerium  

NASA Astrophysics Data System (ADS)

The cerium ??? transition was investigated using high-pressure, high-temperature angle-dispersive x-ray diffraction measurements on both poly- and single-crystalline samples, explicitly addressing symmetry change and transformation paths. The isomorphic hypothesis of the transition is confirmed, with a transition line ending at a solid-solid critical point. The critical exponent is determined, showing a universal behavior that can be pictured as a liquid-gas transition. We further report an isomorphic transition between two single crystals (with more than 14% of volume difference), an unparalleled observation in solid-state matter interpreted in terms of dislocation-induced diffusionless first-order phase transformation.

Decremps, F.; Belhadi, L.; Farber, D. L.; Moore, K. T.; Occelli, F.; Gauthier, M.; Polian, A.; Antonangeli, D.; Aracne-Ruddle, C. M.; Amadon, B.

2011-02-01

231

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

232

Generalized Hawking Page phase transition  

NASA Astrophysics Data System (ADS)

The issue of radiant spherical black holes being in stable thermal equilibrium with their radiation bath is reconsidered. Using a simple equilibrium statistical mechanical analysis incorporating Gaussian thermal fluctuations in a canonical ensemble of isolated horizons, the heat capacity is shown to diverge at a critical value of the classical mass of the isolated horizon, given (in Planckian units) by the microcanonical entropy calculated using loop quantum gravity. The analysis reproduces the Hawking Page phase transition discerned for anti-de Sitter black holes and generalizes it in the sense that nowhere is any classical metric made use of.

Majumdar, Parthasarathi

2007-04-01

233

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

234

Work and quantum phase transitions: Quantum latency  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

235

Polymer-stabilized liquid crystal blue phases  

Microsoft Academic Search

Blue phases are types of liquid crystal phases that appear in a temperature range between a chiral nematic phase and an isotropic liquid phase. Because blue phases have a three-dimensional cubic structure with lattice periods of several hundred nanometres, they exhibit selective Bragg reflections in the range of visible light corresponding to the cubic lattice. From the viewpoint of applications,

Hirotsugu Kikuchi; Masayuki Yokota; Yoshiaki Hisakado; Huai Yang; Tisato Kajiyama

2002-01-01

236

Glass-liquid transition of water at high pressure.  

PubMed

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 C(p) 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 C(p) increases abruptly by (3.4 ± 0.2) J mol(-1) K(-1) before crystallization starts at (153 ± 1) K. This is larger than the C(p) 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

2011-07-01

237

Glass-liquid transition of water at high pressure  

PubMed Central

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

Andersson, Ove

2011-01-01

238

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

PubMed Central

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

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

2012-01-01

239

Phase transitions and spin waves in cerium  

NASA Astrophysics Data System (ADS)

In the Gamma-Alpha phase transition in Cerium, the magnetic properties change from a temperature-dependent Curie-Weiss susceptibility in the high temperature gamma phase to a temperature-independent paramagnetic susceptibility in the low temperature alpha phase. In this thesis the B-T phase diagram is considered. Taking into account the crystal-field split Hamiltonian, the energy eigenvalues and eigenfunctions are calculated for the doublet and the quartet ground states in Chapter 2, which are then used to determine the Kondo temperature for different crystal field splittings. The susceptibility and B-T phase diagrams are obtained for both the ground states and it is concluded that the doublet ground state is in better agreement with the experimental results. The other phase diagram of importance is the P-T phase diagram obtained in Chapter 3 using the Anderson model and the Non-Crossing Approximation. This numerical method determines the free energy for a given hybridization and subsequently the susceptibility, specific heat and the Fermi-liquid temperature. Using these, the P-V phase diagram is first obtained and then the P-T phase diagram derived from it using Maxwell's equal area construction. CePdSb is one of the few ternary compounds which exhibit Kondo lattice behavior along with a ferromagnetic ground state and is studied in Chapter 4. The competitions between the RKKY interaction and the Kondo interactions are consistent with expectations based on the Doniach phase diagram. The susceptibility in the high temperature regime calculated using the linear response theory concurs well with the experimental results. At low temperatures, the exchange interaction dominates the magnetic behavior of the system. Taking into consideration the single-ion anisotropy and the Heisenberg interaction, the spin-wave dispersion spectrum is obtained using the Holstein-Primakoff transformation and renormalized Stevens coefficients. The spin-spin correlation function is obtained and found to agree very well with the inelastic neutron scattering data.

Basu, Sukalpa

240

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

241

Criterion for Tricritical Points in Liquid Crystal Phases  

Microsoft Academic Search

We propose a criterion to find the symmetric tricritical points of an ordering phase transition in liquid crystals described by more than one scalar order parameter. Our criterion extends the one already put forward in the literature, which is based on the classical Griffiths’s criterion valid when all phases are described by a single order parameter. When applied to a

Giovanni De Matteis; Epifanio G. Virga

242

Macroscopic dynamics near the isotropic micellar to lamellar phase transition  

NASA Astrophysics Data System (ADS)

We present the hydrodynamic equations for the lamellar phase in lyotropic liquid crystals. The hydrodynamic equations are investigated to the vicinity of the isotropic micellar to lamellar phase transition. To derive the hydrodynamic equations we make use of symmetry arguments and irreversible thermodynamics. Besides the usual order parameters to describe the lamellar phase we also keep the concentration of the surfactant molecules which are aggregated in micelles as a variable in order to describe the correct macroscopic behavior of the lamellar phase. The macroscopic dynamic equations are presented on both sides of the transition. We discuss possible experiment were our theory can be tested.

Mukherjee, Prabir K.

2014-02-01

243

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

PubMed Central

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

Caffrey, M; Hogan, J; Mencke, A

1991-01-01

244

Dynamics of a Quantum Phase Transition  

SciTech Connect

We present two approaches to the dynamics of a quench-induced phase transition in the quantum Ising model. One follows the standard treatment of thermodynamic second order phase transitions but applies it to the quantum phase transitions. The other approach is quantum, and uses Landau-Zener formula for transition probabilities in avoided level crossings. We show that predictions of the two approaches of how the density of defects scales with the quench rate are compatible, and discuss the ensuing insights into the dynamics of quantum phase transitions.

Zurek, Wojciech H. [Theory Division, LANL, MS-B213, Los Alamos, New Mexico 87545 (United States); Dorner, Uwe [Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Zoller, Peter [Institute for Theoretical Physics, University of Innsbruck, and Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria)

2005-09-02

245

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

246

Adsorption Induced Anchoring Transition in Confined Liquid Crystal Aerosil Dispersions  

NASA Astrophysics Data System (ADS)

An adsorption induced anchoring transition is seen in liquid crystal-hydrophobic aerosil dispersions imbedded in submicron pores, a doubly-confined system. The aerosil effects on the director configurations and on the orientational order wetting at the pore walls are determined by DNMR. The aerosil hinders the planar anchoring at the pore walls and an axial to radial structural transition is induced with increasing aerosil density. The orientational order wetting in the isotropic phase is modified by the aerosil-introduced disorder from quasi-complete to partial to non-wetting. Supported by NSF Grant 03-06851

Jin, Tao; Finotello, Daniele

2004-03-01

247

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

248

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

PubMed

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

Shreif, Z; Pankavich, S; Ortoleva, P

2009-09-01

249

Size-dependent phase transition temperatures of dispersed systems  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

250

Observation of Ultrasonic Anomaly near a Smectic-A-Smectic-C Phase Transition  

Microsoft Academic Search

The first observation is reported of an anomalous attenuation and velocity dispersion near a smectic-A-smectic-C phase transition in a liquid crystal. The anomaly is found to be strongly anisotropic and dominated by the Landau-Khalatnikov relaxation of the order parameter in contrast with other liquid-crystalline phase transitions.

S. Bhattacharya; B. Y. Cheng; Bimal K. Sarma; J. B. Ketterson

1982-01-01

251

Effects of disorder on a smectic- A nematic phase transition  

NASA Astrophysics Data System (ADS)

Using x-ray scattering, we have studied the nematic to smectic- A phase transition of the liquid crystal butyloxybenzilidene-octylaniline confined in an aerosil network. We find that the disorder introduced by the aerosil network destroys the long-range nature of the phase transition, and that the transition becomes similar to that observed in a finite-size system, with finite low-temperature correlation lengths of the ordered moments and a power-law behavior of the order parameter with respect to the reduced temperature observable in a limited temperature range. We also show evidence for a systematic evolution of the effective order parameter critical exponent ? with increasing disorder.

Larochelle, S.; Ramazanoglu, M.; Birgeneau, R. J.

2006-06-01

252

Aspects of the electroweak phase transition  

SciTech Connect

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

Huet, P.

1992-11-01

253

On the Phase Transition in Solid Hydrogen.  

National Technical Information Service (NTIS)

The phase transition in solid hydrogen is examined with a simple Ising-type model used for the intermolecular interactions. A statistical treatment based on Bethe's method is used. For pure ortho-hydrogen, no abrupt transition between the orientationally ...

J. C. Raich R. D. Etters

1968-01-01

254

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

255

Phase transitions in lattices of magnetic dipoles  

NASA Astrophysics Data System (ADS)

Hexagonal magnetic-dipole lattices containing three to six rows are investigated. Conditions of the excitation of phase transitions that change the orientation configuration of the system are revealed on the basis of a numerical analysis. The changes in the magnetic moment of the system and in the energy of dipole-dipole interaction upon the emergence of phase transitions are found. Both symmetric phase transitions propagating identically on the two sides of the lattice away from the excitation region and asymmetric phase transitions such in which the configurations of the system to the left and to the right of the excitation region are different are considered. Conditions under which there occur unidirectional phase transitions in which either the left-or the right-hand front of the phase transition propagates along the lattice are found.

Shutyi, A. M.

2014-03-01

256

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

257

Detecteur optique de phase liquide dans un disjoncteur au SF6 sous pression  

NASA Astrophysics Data System (ADS)

In this paper, we present a device allowing us to detect gas-liquid or liquid-gas transition in an pressurized cell. This phase detector can be implemented in high voltage system. Dans cet article, on présente un dispositif permettant de détecter localement la transition liquide-gaz ou gaz-liquide dans une enceinte sous pression. Ce détecteur de phase peut etre installé dans des systèmes portés à potentiel élevé.

Buret, F.; Beroual, A.

1991-04-01

258

The Quantum Hall Liquid to Insulator Transitions  

NASA Astrophysics Data System (ADS)

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

Shahar, Dan

1996-03-01

259

Fragmentation phase transition in atomic clusters IV  

Microsoft Academic Search

Within the micro-canonical ensemble it is well possible to identify phase-transitions in small systems. The consequences for the understanding of phase transitions in general are discussed by studying three realistic examples. We present micro-canonical calculations of the fragmentation phase transition in Na-, K-, and Fe- clusters of $N=$ 200 to 3000 atoms at a constant pressure of 1 atm. The

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

1997-01-01

260

Liquid phase sintering in microgravity  

NASA Astrophysics Data System (ADS)

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

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

261

Liquid Crystal Phases of Semiflexible Polymers  

NASA Astrophysics Data System (ADS)

Liquid crystal polymers exhibit orientational order (nematic phase) and position order (smectic phase). Previous work on semiflexible polymers using self consistent field theory studied the isotropic-nematic and nematic-smectic transition for homogenous and diblock copolymers. The nematic phase is stabilized by excluded-volume effects between wormlike cylindrical segments. The smectic phase is further stabilized by excluded-volume effects between terminal end segments. Because models of semiflexible polymers include orientational degrees of freedom, in addition to the usual positional degrees of freedom, they are computationally more demanding to study. Spectral decomposition applied to segment orientations has previously been used to make computation feasible. However this method does not converge well for strongly ordered states, which arise in many real systems. I describe a Crank-Nicolson finite difference method applied to the orientations which is expected to converge well for highly ordered systems. This method also exhibits better numerical stability and accuracy and may thus serve as a better foundation for further studies of highly ordered systems. I also describe a modification to the spectral method which can compute the tilted Smectic C phase.

Mackay, Ian; Sullivan, Don

2012-02-01

262

Efimov-driven phase transitions of the unitary Bose gas  

NASA Astrophysics Data System (ADS)

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

Piatecki, Swann; Krauth, Werner

2014-03-01

263

Liquid phase chromatography on microchips.  

PubMed

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

Kutter, Jörg P

2012-01-20

264

Topology and Phase Transitions I. Preliminary Results  

Microsoft Academic Search

In this first paper, we demonstrate a theorem that establishes a first step toward proving a necessary topological condition for the occurrence of first or second order phase transitions: we prove that the topology of certain submanifolds of configuration space must necessarily change at the phase transition point. The theorem applies to smooth, finite-range and confining potentials V bounded below,

Roberto Franzosi; Marco Pettini; Lionel Spinelli

2005-01-01

265

Electroweak phase transition in nearly conformal technicolor  

Microsoft Academic Search

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

James M. Cline; Matti Järvinen; Francesco Sannino

2008-01-01

266

Phase Transitions in Thin Block Copolymer Films  

Microsoft Academic Search

David Turnbull's experiments and theoretical insights paved the way for much of our modern understanding of phase transitions in materials. In recognition of his contributions, this lecture will concentrate on phase transitions in a material system not considered by Turnbull, thin diblock copolymer films. Well-ordered block copolymer films are attracting increasing interest as we attempt to extend photolithography to smaller

Edward J

2010-01-01

267

Phase transition in continuum Potts models  

Microsoft Academic Search

We establish phase transitions for a class of continuum multi-type particle systems with finite range repulsive pair interaction between particles of different type. This proves an old conjecture of Lebowitz and Lieb. A phase transition still occurs when we allow a background pair interaction (between all particles) which is superstable and has sufficiently short range of repulsion. Our approach involves

H.-O. Georgii; O. Häggström

1996-01-01

268

A comparison of liquid crystal techniques for transition detection  

Microsoft Academic Search

Two techniques for detection of boundary layer transition which employs liquid crystal coatings are compared for incompressible flow over a flat plate. Temperature sensitive liquid crystals are used to measure the characteristic increase in heat transfer coefficient through the transitional region on a uniformly heated surface. Shear sensitive liquid crystals are used to detect the high surface shear stress at

D. J. Mee; T. W. Walton; S. B. Harrison; T. V. Jones

1991-01-01

269

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

270

Isotropic to Nematic Transition of Aerosil-Disordered Liquid Crystals  

NASA Astrophysics Data System (ADS)

We present a high-resolution study of the isotropic to nematic phase transition of a low birefringence liquid-crystal compound incorporating an aerosil gel. Calorimetry, light scattering, and microscopy data coherently combine to allow for an accurate determination of the temperature dependence of the onset of the nematic state. The nematic order develops on cooling through two distinct processes while the nematic correlation length mildly decreases. We understand the doubling of the phase transition as due to a crossover from a random-dilution regime, where the silica gel couples to the scalar part of the nematic order parameter, to a low-T random-field regime, where the coupling induces distortions in the director field.

Caggioni, M.; Roshi, A.; Barjami, S.; Mantegazza, F.; Iannacchione, G. S.; Bellini, T.

2004-09-01

271

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

272

Thermal acoustic radiation from multilamellar vesicles in lipid phase transition.  

PubMed

A new acoustical method for the investigation of lipid phase transition is introduced based on the measurement of the thermal acoustic radiation (TAR) inherent in lipids. The TAR of multilamellar vesicles from dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) was measured in the megahertz range and the variations in the radiation intensity during the lipid phase transition were recorded. Two types of variations are possible: if the temperature of the vesicles decreases (in the process of transition from the liquid crystalline state to the gel state) then the TAR intensity increases, and if the temperature increases (in the reverse transition) then the TAR intensity decreases. These effects are connected with an increase in the ultrasonic absorption in the vesicles under lipid phase transition. Basing on the results of the TAR investigation, a new theoretical estimate has been developed of the variation in the absorption coefficient during the lipid phase transition. In this estimate, the variation is equated to the ratio of the phase transition entropy to the gas constant. PMID:18381070

Anosov, Andrej A; Barabanenkov, Yurij N; Kazanskij, Alexander S; Less, Yulij A; Sharakshane, Anton S

2008-06-01

273

Application of ionic liquid in liquid phase microextraction technology.  

PubMed

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

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

2012-11-01

274

Quantum phase transitions in the two-dimensional J1-J2 model  

Microsoft Academic Search

We analyze the phase diagram of the frustrated Heisenberg antiferromagnet, the J1-J2 model, in two dimensions. Two quantum phase transitions in the model are already known: the second-order transition from the Néel state to the spin liquid state at (J2\\/J1)c2~0.38, and the first-order transition from the spin liquid state to the collinear state at (J2\\/J1)c4~0.60. We have found evidence for

O. P. Sushkov; J. Oitmaa; Zheng Weihong

2001-01-01

275

Finite-temperature phase transitions in the ionic Hubbard model  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

276

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

277

Shape phase transition and phase coexistence in odd Sm nuclei  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

278

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

279

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

280

Phase transitions in one-dimensional steady state hydrothermal flows  

NASA Astrophysics Data System (ADS)

The paper sets out necessary conditions for the existence of a phase transition in a steady state one-dimensional vertical hydrothermal flow. The entropy inequality (reflecting the presence of capillarity) and a thermodynamical inequality at the phase boundary are combined to delineate the region of permissible flow states in the mass-energy flow plane. In particular, it is shown that for small mass flow/permeability ratios the configuration consisting of single-phase liquid lying over a vapor-dominated two-phase fluid is not stable. These and other results are discussed in the context of several field examples, including Kawah Kamojang (Indonesia) and Wairakei (New Zealand).

Young, R. M.

1996-08-01

281

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

Federal Register 2010, 2011, 2012, 2013

...STTR Phase I to Phase II Transition Benchmarks AGENCY: U.S. Small Business Administration...Program Phase I to Phase II Transition Benchmarks; Amended...Phase I to Phase II transition rate benchmark Table, which was originally...

2013-05-23

282

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

Federal Register 2010, 2011, 2012, 2013

...STTR Phase I to Phase II Transition Benchmarks AGENCY: U.S. Small Business Administration...Programs Phase I to Phase II Transition Benchmarks...Phase I to Phase II transition rate benchmarks for the 11 participating agencies...

2012-10-16

283

Electroweak phase transition in ultraminimal technicolor  

SciTech Connect

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

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

2009-05-01

284

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

285

Effective liquid-phase methanol synthesis utilizing liquid-liquid separation  

Microsoft Academic Search

New liquid phase methanol synthesis process is proposed in that methanol is ejected with hydrocarbon solvent exclusively as a liquid phase, while gaseous components are not practically discharged from the reactor. Methanol is obtained in 95% yield with trace amount of feed gas by liquid-liquid separation from hydrophobic solvent. The advantage of the present process is that the gas recycle

K. Hagihara; H. Mabuse; T. Watanabe; M. Kawai; M. Saito

1995-01-01

286

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

287

Phase transitions in the early universe  

NASA Astrophysics Data System (ADS)

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

Wainwright, Carroll L.

288

Developments in liquid-phase microextraction  

Microsoft Academic Search

The development of faster, simpler, inexpensive and more environmentally friendly sample-preparation techniques is an important issue in chemical analysis. Recent research trends involve miniaturisation of the traditional liquid-liquid extraction (LLE) principle by greatly reducing the acceptor-to-donor phase ratio. One of the emerging techniques in this area is liquid-phase microextraction (LPME), where a hollow fibre impregnated with an organic solvent is

E. Psillakis; N. Kalogerakis

2003-01-01

289

Transition pathways between solid and liquid state in suspensions.  

PubMed

Suspensions containing rigid monodisperse spherical particles in a Newtonian carrier liquid are investigated experimentally, providing evidence for solid and liquid states in a transient shear rate from rest. Between these two states a transition takes place; the transition pathways from solid to liquid and from liquid to solid being different. The dynamics of the transition are shown, with the material in this regime reacting as a highly nonlinear system. This involves inverting the input to output and vice versa and comparing them. A key feature of the transition regime is a material instability caused by the collapse of the particle network structure. PMID:17358346

Heymann, Lutz; Aksel, Nuri

2007-02-01

290

Multicomponent phase transitions of diacylphosphatidylethanolamine dispersions.  

PubMed Central

The phase transition properties of aqueous suspensions of a series of nonhydrated (not heated above room temperature) and hydrated 1,2 diacylphosphatidylethanolamines (PE's) have been examined by high sensitivity differential scanning calorimetry at scan rates of 0.02-1.0 K min-1. At all scan rates nonhydrated PE's show a single asymmetric transition curve of excess heat capacity as a function of temperature. Multilamellar dispersions of hydrated PE's, however, exhibit transitions with fine structure, which can be fitted as the sum of three two-state component transitions, at scan rates of 0.02-0.1 K min-1, but give only a single asymmetric transition at 1.0 K min-1. At all scan rates the transition(s) of hydrated samples occur at lower temperatures than those of nonhydrated samples. One of the component transitions of hydrated PE's may be analogous to the pretransition that occurs in 1,2 diacylphosphatidylcholines.

Chowdhry, B Z; Lipka, G; Dalziel, A W; Sturtevant, J M

1984-01-01

291

QCD Phase Transition in Dgp Brane Cosmology  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

292

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

ERIC Educational Resources Information Center

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

Torzo, Giacomo; Soletta, Isabella; Branca, Mario

2007-01-01

293

Phase behavior and dynamics of a cholesteric liquid crystal  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

294

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

NASA Astrophysics Data System (ADS)

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

Feng, Xunda; Bahr, Christian

2011-03-01

295

Optical Sensor for Characterizing the Phase Transition in Salted Solutions  

PubMed Central

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

Claverie, Remy; Fontana, Marc D.; Durickovic, Ivana; Bourson, Patrice; Marchetti, Mario; Chassot, Jean-Marie

2010-01-01

296

Universality in fluid domain coarsening: The case of vapor-liquid transition  

NASA Astrophysics Data System (ADS)

Domain growth during the kinetics of phase separation is studied following vapor-liquid transition in a single component Lennard-Jones fluid. Results are analyzed after appropriately mapping the continuum snapshots obtained from extensive molecular-dynamics simulations to a simple cubic lattice. For near-critical quench interconnected domain morphology is observed. A brief period of slow diffusive growth is followed by a linear viscous hydrodynamic growth that lasts for an extended period of time. This result is in contradiction with earlier reports of late-time growth exponent 1/2 that questions the uniqueness of the non-equilibrium universality for liquid-liquid and vapor-liquid transitions.

Majumder, Suman; Das, Subir K.

2011-08-01

297

Preemptive phase-transitions in multicomponent BECs  

NASA Astrophysics Data System (ADS)

We use analytical arguments and large-scale Monte-Carlo simulations to investigate phase transitions between various complex superfluid phases in a two-component Bose-Einstein condensate with varying non- dissipative drag between the two components. We focus on establishing the phase- diagram and investigate in detail the individual and composite superfluid densities that the system features, using a representation in terms of the phases of the superfluid ordering fields. In particular, we describe a novel preemptive scenario, whereby drag induces a first-order phase transition from the interplay between two phase-transitions that individually would have been in the 3DXY-universality class. Our results may shed light on similar phenomena occuring in certain multicomponent superconductors and in scenarios of deconfined quantum criticality in certain quantum antiferromagnetic systems.

Kragset, Steinar; Kulset Dahl, Eskil; Babaev, Egor; Sudbo, Asle

2008-03-01

298

Liquid-Vapor Transitions in Mercury and Sodium Gas-Controlled Heat-Pipes  

Microsoft Academic Search

The liquid-vapor transitions have been studied of pure mercury between 240 °C and 400 °C and of pure sodium between 660 °C and 960 °C. The phase transitions are realized at IMGC by means of gas controlled heat-pipes, all connected to the same, very accurate, pressure control system. This control uses an SPRT as the sensor and allows the study

A. Merlon; P. Marcarino; R. Dematteis; E. Renaot; M. Elgourdou; G. Bonnier

2003-01-01

299

Critical Line of the Deconfinement Phase Transitions  

NASA Astrophysics Data System (ADS)

Phase diagram of strongly interacting matter is discussed within the exactly solvable statistical model of the quark-gluon bags. The model predicts two phases of matter: the hadron gas at a low temperature T and baryonic chemical potential ? B , and the quark-gluon gas at a high T and/or ? B . The nature of the phase transition depends on a form of the bag massvolume spectrum (its pre-exponential factor), which is expected to change with the ? B /T ratio. It is therefore likely that the line of the 1 st order transition at a high ? B/T ratio is followed by the line of the 2 nd order phase transition at an intermediate ? B/T, and then by the lines of "higher order transitions" at a low ? B /T. This talk is based on a recent paper (Gorenstein, Ga?dzicki, and Greiner, 2005).

Gorenstein, Mark I.

300

Brief Review of Transition Phase Technology.  

National Technical Information Service (NTIS)

A brief review of important phenomena pertaining to the transition phase is given. Special emphasis is laid on the recriticality issue as this process has the potential for energetic disassemblies of the already disrupted core configuration. Questions rel...

W. Maschek

1982-01-01

301

Phase transitions in systems possessing shock solutions  

NASA Astrophysics Data System (ADS)

Recently it has been shown that there are three families of stochastic one-dimensional nonequilibrium lattice models for which the single-shock measures form an invariant subspace of the states of these models. Here, both the stationary states and dynamics of single-shocks on a one-dimensional lattice are studied. This is done for both an infinite lattice and a finite lattice with boundaries. It is seen that these models possess both static and dynamical phase transitions. The static phase transition is the well-known low-high density phase transition for the asymmetric simple exclusion process. The branching-coalescing random walk and asymmetric Kawasaki-Glauber process models also show the same phase transition. Double-shocks on a one-dimensional lattice are also investigated. It is shown that at the stationary state the contribution of double-shocks with higher width becomes small, and the main contribution comes from thin double-shocks.

Arabsalmani, Maryam; Aghamohammadi, Amir

2006-07-01

302

Phase transition kinetics in loaded solids  

Microsoft Academic Search

A study is undertaken into the kinetics of phase transitions in solids under a load at a fixed temperature. The critical size\\u000a of the micropores forming at a given load in the course of a phase transition in a material is found. The steady-state flux\\u000a of pores in size space and the time required to reach this state, which depend

A. A. Vakulenko; S. A. Kukushkin

2000-01-01

303

Quantum phase transitions in rotating nuclei  

SciTech Connect

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

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

2009-01-28

304

Liquid-Vapor Transition Driven by Bond Disorder  

NASA Astrophysics Data System (ADS)

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

Bozorgui, Behnaz; Frenkel, Daan

2008-07-01

305

Randomized Grain Boundary Liquid Crystal Phase  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

306

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

307

Isotropic-nematic transition at the surface of a liquid crystal embedded in an aerosil network  

NASA Astrophysics Data System (ADS)

We reexamined the isotropic-nematic (Iso-N) phase transitions of 4-n-heptyl cyanobiphenyl (7CB) embedded in aerosils of silica nanoparticle dispersions using highly sensitive differential scanning calorimetry (HS-DSC), polarizing optical microscopy (POM), and retardation measurements. We found a simple and very profound relationship between the calorimetric and optical measurements; in addition to double DSC peaks, which have been observed previously, a two-step change of the retardation was clearly observed by varying temperature. From our analysis, there is no doubt that the Iso-N liquid-crystal phase transition certainly occurs in two steps, i.e., the bulk transition takes place at first and then the surface transition takes place upon cooling. We should note that the surface transition takes place below the bulk transition temperature, the opposite of what was recently observed in a polymer-dispersed liquid-crystal system.

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

2011-06-01

308

Decoherence in a dynamical quantum phase transition  

NASA Astrophysics Data System (ADS)

Motivated by the similarity between adiabatic quantum algorithms and quantum phase transitions, we study the impact of decoherence on the sweep through a second-order quantum phase transition for the prototypical example of the Ising chain in a transverse field and compare it to the adiabatic version of Grover’s search algorithm, which displays a first-order quantum phase transition. For site-independent and site-dependent coupling strengths as well as different operator couplings, the results show (in contrast to first-order transitions) that the impact of decoherence caused by a weak coupling to a rather general environment increases with system size (i.e., number of spins or qubits). This might limit the scalability of the corresponding adiabatic quantum algorithm.

Mostame, Sarah; Schaller, Gernot; Schützhold, Ralf

2010-03-01

309

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

310

Differential Scanning Calorimetric Study of Bilayer Membrane Phase Transitions. A Biophysical Chemistry Experiment  

Microsoft Academic Search

In a series of experiments designed for a biologically-oriented physical chemistry lab, the gel to liquid-crystalline phase transition of phospholipid bilayers is examined by differential scanning calorimetry. The four interrelated experiments examine the effect of altering lipid bilayer composition on the thermodynamic properties of the phase transition. Bilayer composition is modified by (i) varying the length of the phospholipid acyl

Shane M. Ohline; Mary L. Campbell; Marilyn T. Turnbull; Susan J. Kohler

2001-01-01

311

Quantum phase transition from a spin-liquid state to a spin-glass state in the quasi-one-dimensional spin-1 system Sr1-xCaxNi2V2O8  

NASA Astrophysics Data System (ADS)

We report a quantum phase transition from a spin-liquid state to a spin-glass state in the quasi-one-dimensional (1D) spin-1 system Sr1-xCaxNi2V2O8, induced by a small amount of Ca substitution at the Sr site. The ground state of the parent compound (x = 0) is found to be a spin-liquid type with a finite energy gap of 26.6 K between the singlet ground state and the triplet excited state. Both dc-magnetization and ac-susceptibility studies on the highest Ca-substituted compound (x = 0.05) indicate a spin-glass-type magnetic ground state. With increasing Ca concentration, the spin-glass ordering temperature increases from 4.5 K (for the x = 0.015 compound) to 6.25 K (for the x = 0.05 compound). The observed results are discussed in the light of earlier experimental reports and theoretical predictions for a quasi-1D spin-1 system.

Bera, A. K.; Yusuf, S. M.

2012-07-01

312

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

PubMed

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

Shimizu, Ryotaro; Kobayashi, Mika; Tanaka, Hajime

2014-03-28

313

Qcd phase transitions-volume 15.  

National Technical Information Service (NTIS)

The title of the workshop, 'The QCD Phase Transitions' in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discuss...

Schafer

1998-01-01

314

Desynchronization transitions in nonlinearly coupled phase oscillators  

Microsoft Academic Search

We consider the nonlinear extension of the Kuramoto model of globally coupled phase oscillators where the phase shift in the coupling function depends on the order parameter. A bifurcation analysis of the transition from fully synchronous state to partial synchrony is performed. We demonstrate that for small ensembles it is typically mediated by stable cluster states, that disappear with creation

Oleksandr Burylko; Arkady Pikovsky

2011-01-01

315

Liquid phase microextraction applications in food analysis  

Microsoft Academic Search

Over the last years, liquid-phase microextraction (LPME) in its different application modes (single drop microextraction, dispersive liquid–liquid microextraction and hollow fiber-LPME) has been increasingly applied for the extraction of both inorganic and organic analytes from different matrices. Its advantages over conventional extraction procedures (simplicity, effectiveness, rapidity and low consumption of organic solvents) has also attracted its application in the complex

María Asensio-Ramos; Lidia M. Ravelo-Pérez; Miguel Ángel González-Curbelo; Javier Hernández-Borges

2011-01-01

316

Polymorphic phase transition in Superhydrous Phase B  

NASA Astrophysics Data System (ADS)

We synthesized superhydrous phase B (shy-B) at 22 GPa and two different temperatures: 1200°C (LT) and 1400°C (HT) using a multi-anvil apparatus. The samples were investigated by transmission electron microscopy (TEM), single crystal X-ray diffraction, Raman and IR spectroscopy. The IR spectra were collected on polycrystalline thin-films and single crystals using synchrotron radiation, as well as a conventional IR source at ambient conditions and in situ at various pressures (up to 15 GPa) and temperatures (down to -180°C). Our studies show that shy-B exists in two polymorphic forms. As expected from crystal chemistry, the LT polymorph crystallizes in a lower symmetry space group ( Pnn2), whereas the HT polymorph assumes a higher symmetry space group ( Pnnm). TEM shows that both modifications consist of nearly perfect crystals with almost no lattice defects or inclusions of additional phases. IR spectra taken on polycrystalline thin films exhibit just one symmetric OH band and 29 lattice modes for the HT polymorph in contrast to two intense but asymmetric OH stretching bands and at least 48 lattice modes for the LT sample. The IR spectra differ not only in the number of bands, but also in the response of the bands to changes in pressure. The pressure derivatives for the IR bands are higher for the HT polymorph indicating that the high symmetry form is more compressible than the low symmetry form. Polarized, low-temperature single-crystal IR spectra indicate that in the LT-polymorph extensive ordering occurs not only at the Mg sites but also at the hydrogen sites.

Koch-Müller, M.; Dera, P.; Fei, Y.; Hellwig, H.; Liu, Z.; Orman, J. Van; Wirth, R.

2005-09-01

317

Polymorphic Phase Transition in Superhydrous Phase B  

SciTech Connect

We synthesized superhydrous phase B (shy-B) at 22 GPa and two different temperatures: 1200 C (LT) and 1400 C (HT) using a multi-anvil apparatus. The samples were investigated by transmission electron microscopy (TEM), single crystal X-ray diffraction, Raman and IR spectroscopy. The IR spectra were collected on polycrystalline thin-films and single crystals using synchrotron radiation, as well as a conventional IR source at ambient conditions and in situ at various pressures (up to 15 GPa) and temperatures (down to -180 C). Our studies show that shy-B exists in two polymorphic forms. As expected from crystal chemistry, the LT polymorph crystallizes in a lower symmetry space group (Pnn2), whereas the HT polymorph assumes a higher symmetry space group (Pnnm). TEM shows that both modifications consist of nearly perfect crystals with almost no lattice defects or inclusions of additional phases. IR spectra taken on polycrystalline thin films exhibit just one symmetric OH band and 29 lattice modes for the HT polymorph in contrast to two intense but asymmetric OH stretching bands and at least 48 lattice modes for the LT sample. The IR spectra differ not only in the number of bands, but also in the response of the bands to changes in pressure. The pressure derivatives for the IR bands are higher for the HT polymorph indicating that the high symmetry form is more compressible than the low symmetry form. Polarized, low-temperature single-crystal IR spectra indicate that in the LT-polymorph extensive ordering occurs not only at the Mg sites but also at the hydrogen sites.

Koch-Muller,M.; Dera, P.; Fei, Y.; Hellwig, H.; Liu, Z.; Van Orman, J.; Wirth, R.

2005-01-01

318

A light scattering study of phase transitions in monolayers of n-pentadecanoic acid  

Microsoft Academic Search

The phase transitions of monolayers of carefully purified n-pentadecanoic acid at the air\\/water interface have been investigated using both classical and laser scattering methods. The equilibrium pi -A isotherms showed flat coexistence regions between the liquid-expanded and liquid-condensed states. Such clear first-order transitions appear only to be observable for pure pentadecanoic acid. In transitions at temperatures above the triple point

P. J. Winch; J. C. Earnshaw

1989-01-01

319

Liquid phase effects on benzene UV spectra  

NASA Astrophysics Data System (ADS)

Some results for the benzene molecular properties in liquid phase are shown, stressing the interest on the electronic spectra properties. The way we follow to perform calculations is a Semi-classical one. taking into account the structural information of the benzene pure liquid and the electronic structure of the benzene molecule at the CNDO level.

Se?e, L. M.; Botella, V.; Gómez, P. C.; Fernández, M.

1986-03-01

320

Lasing effect in blue phase liquid crystal  

NASA Astrophysics Data System (ADS)

We report on the investigation of random lasing in blue phase liquid crystals. Multiple scattering and interference effects arising from disordered platelet texture as well as index mismatch between polymer and mesogen contribute the optical feedbacks towards laser action. In pure blue phase liquid crystals, the random laser can be switched between the coherent and incoherent types by executing distinct heating/cooling cycles; and, the randomness of lasing wavelengths can be determined by the platelet size, which can be set by controlling the cooling rate. After the blue phase liquid crystals are polymer-stabilized, coherent random lasing may occur in both the blue phase with an extended temperature interval and the isotropic liquid state; also, the selected modes are constant from one pulse to another. Additionally, if the laser dye is sensitive to temperature, the excitation threshold and the emission spectrum could be altered via thermal control.

Lin, Tsung-Hsien; Chen, Chun-Wei; Jau, Hung-Chang; Lee, Chun-Hong; Wang, Chun-Ta; Wu, Chih-Wei; Huang, Huai-Ping; Khoo, I. C.

2013-09-01

321

Liquid-Phase Oxidations of Cyclic Alkenes.  

National Technical Information Service (NTIS)

The work was undertaken to relate the initial products of liquid-phase oxidations of unsaturated hydrocarbons under mild conditions (and thus their mechanisms of oxidation) to the structures of the hydrocarbons. Results with cyclopentene, cyclohexene, cyc...

D. E. Van Sickle F. R. Mayo R. M. Arluck

1965-01-01

322

Phase shifting phase contrast interferometer using a dye-doped liquid-crystal self-aligning phase modulator  

NASA Astrophysics Data System (ADS)

A new phase contrast imaging system that permits a quantitative observation of phase distribution of a general object is proposed and experimentally demonstrated. This is realized by implementing the phase shifting technique in the phase contrast imaging system. A dye-doped nematic liquid-crystal (NLC) is newly employed for this purpose as a variable phase filter in contrast to the constant phase plate employed in the conventional phase contrast microscope (PCM). The dye-doped NLC provides a practical advantage to the system that realizes an alignment-free optical system for the phase plate. The self-alignment property of the phase filter is realized by utilizing the local phase transition from the liquid-crystal to liquid, which is induced by the relatively strong incident light of the specular component of the object. In the experiment, the fundamental phase modulation property and the response of phase modulation ability were measured as a function of incident power of light. Next, the phase measurements were performed with several phase gratings and composite objects having different phase amplitudes and absorption. As an experimental result, the usefulness of the proposed method was confirmed, and the accuracy of the phase measurement was estimated to be ?/40. In addition, it was also demonstrated that the phase information could be obtained independently from the absorption component of the object.

Kadono, Hirofumi; Ohno, Kazunori; Toyooka, Satoru

2005-09-01

323

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

324

Mesoscopic aspects of phase transitions in a solvent extraction system.  

PubMed

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

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

2012-11-01

325

Microgravity Two-Phase Flow Transition  

NASA Technical Reports Server (NTRS)

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

Parang, M.; Chao, D.

1999-01-01

326

Ionic liquid expedites partition of curcumin into solid gel phase but discourages partition into liquid crystalline phase of 1,2-dimyristoyl-sn-glycero-3-phosphocholine liposomes.  

PubMed

The hydrolysis of curcumin in alkaline and neutral buffer conditions is of interest because of the therapeutic applicability of curcumin. We show that hydrolysis of curcumin can be remarkably suppressed in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes. The fluorescence of curcumin sensitively detects the phase transition temperature of liposomes. However, at greater concentrations, curcumin affects the phase transition temperature, encouraging fusion of two membrane phases. The interaction of curcumin with DMPC is found to be strong, with a partition coefficient value of Kp = 2.78 × 10(5) in the solid gel phase, which dramatically increases in the liquid crystalline phase to Kp = 1.15 × 10(6). The importance of ionic liquids as green solvents has drawn interest because of their toxicological effect on human health; however, the impact of ionic liquids (ILs) on liposomes is not yet understood. The present study establishes that ILs such as 1-methyl-3-octylimidazolium chloride (moic) affect the permeability and fluidity of liposomes and thus influence parition of curcumin into DMPC liposomes, helping in the solid gel phase but diminishing in the liquid crystalline phase. The Kp value of curcumin does not change appreciably with moic concentration in the solid gel state but decreases with moic concentration in the liquid crystalline phase. Curcumin, a rotor sensitive to detect phase transition temperature, is applied to investigate the influence of ionic liquids such as 1-methyl-3-octylimidazolium chloride, 1-buytl-3-methyl imadazolium tetrafluoroborate, and 1-benzyl-3-methyl imidazolium tetrafluoroborate on DMPC liposome properties. 1-Methyl-3-octylimidazolium chloride lowers the phase transition temperature, but 1-buytl-3-methyl imidazolium tetrafluoroborate and 1-benzyl-3-methyl imidazolium tetrafluoroborate do not perceptibly modify the phase transition temperature; rather, they broaden the phase transition. PMID:23895644

El Khoury, Elsy D; Patra, Digambara

2013-08-22

327

Liquid–Liquid and SolidPhase Extraction Techniques  

Microsoft Academic Search

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

Beverly Nickerson; Ivelisse Colón

328

Formation, structure, and evolution of boiling nucleus and interfacial tension between bulk liquid phase and nucleus  

Microsoft Academic Search

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

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

2005-01-01

329

Quantum phase transition of cold atoms trapped in optical lattices  

NASA Astrophysics Data System (ADS)

We review our recent theoretical advances in phase transition of cold atoms in optical lattices, such as triangular lattice, honeycomb lattice, and Kagomé lattice. By employing the new developed numerical methods called dynamical cluster approximation and cellular dynamical mean-field theory, the properties in different phases of cold atoms in optical lattices are studied, such as density of states, Fermi surface and double occupancy. On triangular lattice, a reentrant behavior of phase translation line between Fermi liquid state and pseudogap state is found due to the Kondo effect. We find the system undergoes a second order Mott transition from a metallic state into a Mott insulator state on honeycomb lattice and triangular Kagomé lattice. The stability of quantum spin Hall phase towards interaction on honeycomb lattice with spin-orbital coupling is systematically discussed. And we investigate the transition from quantum spin Hall insulator to normal insulator in Kagomé lattice which includes a nearest-neighbor intrinsic spin-orbit coupling and a trimerized Hamiltonian. In addition, we propose the experimental protocols to observe these phase transition of cold atoms in optical lattices.

Chen, Yao-hua; Wu, Wei; Liu, Guo-cai; Tao, Hong-shuai; Liu, Wu-ming

2012-04-01

330

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

PubMed Central

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

Waheed, Qaiser; Tjornhammar, Richard; Edholm, Olle

2012-01-01

331

Ionic liquid stationary phases for gas chromatography.  

PubMed

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

Poole, Colin F; Poole, Salwa K

2011-04-01

332

Extended ensemble theory, spontaneous symmetry breaking, and phase transitions  

NASA Astrophysics Data System (ADS)

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

Xiao, Ming-wen

2006-09-01

333

Defects and order in liquid crystal phases  

NASA Astrophysics Data System (ADS)

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

Jain, Shilpa

334

Phase transitions at high pressure in tetracyanoethylene  

NASA Astrophysics Data System (ADS)

We report in situ x-ray diffraction studies in tetracyanoethylene (TCNE) at high pressure using diamond anvil cell (DAC) at Elettra synchrotron source, Trieste, Italy. Experiments were performed with both the polymorphic phases (monoclinic and cubic) of TCNE as the starting phase. While starting with monoclinic (the high temperature stable) TCNE, it was found that the Bragg peaks get broadened with increase of pressure and above 5 GPa only few broad peaks remained to be observed. On release of pressure from 6.4 GPa, when the sample started turning black, the diffraction pattern at ambient pressure corresponds to cubic, the other crystalline phase of TCNE. Results reconfirm the monoclinic to cubic transition at high pressure but via an intermediate 'disordered' phase. This settles a number of conflicting issues. TCNE represents only system, which undergoes transition from one crystalline to another crystalline phase via a 'disordered' metastable phase at high pressure. When the starting phase was cubic (the low temperature stable) no apparent phase transition was observed up to 10.8 GPa.

Mukhopadhyay, R.; Deb, S. K.; Das, Amitabh; Chaplot, S. L.

2009-11-01

335

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

336

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

337

Phase Transitions in Simulation of Hypervelocity Impact Experiments  

NASA Astrophysics Data System (ADS)

Hypervelocity impact experiments can give us additional information about thermodynamical properties of matter in extreme state. In this work we simulate shock--induced melting, fragmentation and vaporization in aluminum and zinc targets. A tantalum impactor strikes zinc and aluminum targets at a velocity of 10 km/s and causes melting of these materials in a shock wave. Then under intensive rarefaction the thermodynamic path crosses the liquid--vapor coexistence boundary and enters into a metastable liquid state. Liquid in a metastable state undergoes either liquid--vapor phase separation or mechanical spallation. The theory of homogeneous nucleation as well as mechanical fragmentation criterion are used to control the kinetics of these processes in our model. The first effect dominates in the vicinity of the critical point, the second one at lower temperatures and negative pressure. Phase transitions and kinetics of phase separations are taken into account using a thermodynamically complete equation of state in tabular form with stable and metastable states for all materials under consideration. It is shown that liquid--vapor properties are very important for adequate description of experiment.

Povarnitsyn, Mikhail; Zakharenkov, Alexey; Khishchenko, Konstantin; Levashov, Pavel

2009-06-01

338

Noisy quantum phase transitions: an intuitive approach  

NASA Astrophysics Data System (ADS)

Equilibrium thermal noise is known to destroy any quantum phase transition. What are the effects of non-equilibrium noise? In two recent papers, we have considered the specific case of a resistively shunted Josephson junction driven by 1/f charge noise. At equilibrium, this system undergoes a sharp quantum phase transition at a critical value of the shunt resistance. By applying a real-time renormalization group approach, we found that the noise has three main effects: it shifts the phase transition, renormalizes the resistance and generates an effective temperature. In this paper, we explain how to understand these effects using simpler arguments based on Kirchhoff laws and time-dependent perturbation theory. We also show how these effects modify physical observables and especially the current-voltage characteristic of the junction. In the appendix, we describe two possible realizations of the model with ultracold atoms confined to one dimension.

Dalla Torre, Emanuele G.; Demler, Eugene; Giamarchi, Thierry; Altman, Ehud

2012-11-01

339

Elementary excitations and phase transitions in crystals  

SciTech Connect

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

Shapiro, S.M.

1993-12-31

340

Holographic Phase Transitions with Fundamental Matter  

SciTech Connect

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

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

2006-09-01

341

Columnar Phases in Liquid Crystal Dendrimers: Variable Pressure X-Ray Diffraction  

Microsoft Academic Search

The structures of the third and fifth generation of a liquid crystal dendrimer have been studied as a function of temperature and pressure using X-ray diffraction. The third generation LC dendrimer showed a crystal to smectic transition and increasing pressure simply increased the transition temperature. The fifth generation showed two different rectangular columnar phases and one hexagonal columnar phase. The

R. M. Richardson; S. Hanna; N. J. Brooks; B. L. L. E. Gauthe; C. Pizzey; E. Agina; N. Boiko; V. P. Shibaev

2011-01-01

342

Phase transitions and size scaling of membrane-less organelles  

PubMed Central

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

2013-01-01

343

Phase transitions in models of ion-specific protein solutions  

NASA Astrophysics Data System (ADS)

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

Lettieri, Steven A.

344

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

345

Liquid-vapor flow regime transitions for spacecraft heat transfer loops  

NASA Astrophysics Data System (ADS)

The major objective of this contract was to develop prediction criteria for microgravity vapor-liquid flow regime transitions. Extensive simulation experiments were conducted using equal density, immiscible liquids. Criteria were established for bubble to slug, slug to annular, and bubble to annular flow regime transitions. These criteria were based on minimum pressure drop considerations and a new analytical model for slug flow. Tentative pressure drop and heat transfer equations are recommended for flow conditions in two phase vapor liquid spacecraft based heating or cooling loops.

Lovell, Thomas W.

1988-12-01

346

Dynamics of the QCD phase transition  

NASA Astrophysics Data System (ADS)

We apply a recently computed nucleation rate to a first-order deconfinement/chiral-symmetry restoring phase transition in a set of rate equations to study the time evolution of expanding quark-gluon plasma as it converts to hadronic matter. At energies of the BNL Relativistic Heavy Ion Colliders, the system must supercool about 20% below Tc before nucleation of hadronic bubbles is sufficiently rapid to overcome the expansion rate. The system reheats to near Tc, nucleation turns off, and the transition is completed by the growth of previously nucleated bubbles. Based on Bjorken hydrodynamics and on current parameter values, we estimate that the transition generates 30% extra entropy.

Csernai, László P.; Kapusta, Joseph I.

1992-08-01

347

Phase transitions in phosphatidylcholine multibilayers  

PubMed Central

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

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

1982-01-01

348

Orientational phase transitions in alloys  

SciTech Connect

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

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

1992-09-22

349

Structural phase transition in epitaxial perovskite films  

NASA Astrophysics Data System (ADS)

Three different film systems have been systematically investigated to understand the effects of strain and substrate constraint on the phase transitions of perovskite films. In SrTiO3 films, the phase transition temperature Tc was determined by monitoring the superlattice peaks associated with rotations of TiO6 octahedra. It is found that Tc depends on both SrTiO3 film thickness and SrRuO3 buffer layer thickness. However, lattice parameter measurements showed no sign of the phase transitions, indicating that the tetragonality of the SrTiO3 unit cells was no longer a good order parameter. This signals a change in the nature of this phase transition, the internal degree of freedom is decoupled from the external degree of freedom. The phase transitions occur even without lattice relaxation through domain formation. In NdNiO3 thin films, it is found that the in-plane lattice parameters were clamped by the substrate, while the out-of-plane lattice constant varied to accommodate the volume change across the phase transition. This shows that substrate constraint is an important parameter for epitaxial film systems, and is responsible for the suppression of external structural change in SrTiO3 and NdNiO3 films. However, in SrRuO3 films we observed domain formation at elevated temperature through x-ray reciprocal space mapping. This indicated that internal strain energy within films also played an important role, and may dominate in some film systems. The final strain states within epitaxial films were the result of competition between multiple mechanisms and may not be described by a single parameter.

He, Feizhou; Wells, B. O.; Ban, Z.-G.; Alpay, S. P.; Grenier, S.; Shapiro, S. M.; Si, Weidong; Clark, A.; Xi, X. X.

2004-12-01

350

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

Microsoft Academic Search

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

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

1999-01-01

351

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.

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

2013-01-01

352

Norm Breaking in Crowd — Athermal Phase Transition  

NASA Astrophysics Data System (ADS)

Standard order-disorder phase transition in the Ising model is described in terms of rates of processes of spin flips. This formulation allows to extend numerous results on phase transition for sciences other than physics of magnetism. We apply it to the problem of norm breaking. Two strategies: to cooperate or to defect, form an analogy to two spin orientations. An example is a crowd at an exit, where to defect means to push others, and to cooperate is to move slowly together.

Malarz, Krzysztof; Korff, Ruediger; Ku?akowski, Krzysztof

353

Quantum correlations in topological quantum phase transitions  

SciTech Connect

We study the quantum correlations in a two-dimensional system that possesses a topological quantum phase transition. The quantumness of two-body correlations is measured by quantum discord. We calculate both the correlation of two local spins and that between an arbitrary spin and the rest of the lattice. It is notable that local spins are classically correlated, while the quantum correlation is hidden in the global lattice. This is different from other systems which are not topologically ordered. Moreover, the mutual information and global quantum discord show critical behavior in the topological quantum phase transition.

Chen Yixin; Li Shengwen [Zhejiang Institute of Modern Physics, Zhejiang University, Hangzhou 310027 (China)

2010-03-15

354

Desynchronization transitions in nonlinearly coupled phase oscillators  

NASA Astrophysics Data System (ADS)

We consider the nonlinear extension of the Kuramoto model of globally coupled phase oscillators where the phase shift in the coupling function depends on the order parameter. A bifurcation analysis of the transition from fully synchronous state to partial synchrony is performed. We demonstrate that for small ensembles it is typically mediated by stable cluster states, that disappear with creation of heteroclinic cycles, while for a larger number of oscillators a direct transition from full synchrony to a periodic or a quasiperiodic regime occurs.

Burylko, Oleksandr; Pikovsky, Arkady

2011-08-01

355

Phase transition in sarcosine phosphite single crystals  

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

356

Phase transition behaviours of a single dendritic polymer.  

PubMed

Dendritic polymers with highly branching structures exhibit many unique properties. In this paper, a computational study using the Wang-Landau sampling technique is carried out to reveal the phase transition behaviours of dendritic homopolymers with various branching structures. Two types of dendritic homopolymers, dendrimers/dendrigrafts (D/D) and hyperbranched (HB) polymers are studied. It is found that with increasing degree of branching in the dendritic polymer, the liquid-solid (LS) transition temperature increases and the coil-globule (CG) transition becomes weak. Additionally, under similar degrees of branching and polymerization, D/D polymers have a higher LS transition temperature than HB polymers. The reason is that the D/D polymers have greater regularity in the radial distribution of the branching units, which facilitates monomer packing during the LS transition. The distinctive internal unit distribution at various temperatures is quantitatively analysed. Our results show the importance of dendritic polymer structure regularity in phase transition behaviours and are valuable in guiding the structural design of dendritic macromolecules for functionalization applications. PMID:24752714

Wang, Zilu; Wang, Long; Chen, Yu; He, Xuehao

2014-05-21

357

Solid-liquid transition in polydisperse Lennard-Jones systems.  

PubMed

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. PMID:24032772

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

2013-08-01

358

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

359

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

NASA Astrophysics Data System (ADS)

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

Foltz, M. Frances; Maienschein, Jon L.

1996-05-01

360

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.

Popa-Nita, Vlad; Gerlic, Ivan; Kralj, Samo

2009-01-01

361

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

NASA Astrophysics Data System (ADS)

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

Cheng, Stephen Z. D.; Keller, Andrew

1998-08-01

362

Aqueous two-phase microdroplets with reversible phase transitions.  

PubMed

Aqueous two-phase systems contained within microdroplets enable a bottom-up approach to mimicking the dynamic microcompartmentation of biomaterial that naturally occurs within the cytoplasm of cells. Here, we demonstrate the generation of femtolitre aqueous two-phase droplets within a microfluidic oil channel. Gated pressure pulses were used to generate individual, stationary two-phase microdroplets with a well-defined time zero for carrying out controlled and sequential phase transformations over time. Reversible phase transitions between single-phase, two-phase, and core-shell microbead states were obtained via evaporation-induced dehydration and water rehydration. In contrast to other microfluidic aqueous two-phase droplets, which require continuous flows and high-frequency droplet formation, our system enables the controlled isolation and reversible transformation of a single microdroplet and is expected to be useful for future studies in dynamic microcompartmentation and affinity partitioning. PMID:23381219

Boreyko, Jonathan B; Mruetusatorn, Prachya; Retterer, Scott T; Collier, C Patrick

2013-04-01

363

Orientational phase transitions in the hexagonal cylinder phase and kinetic pathways of lamellar phase to hexagonal phase transition of asymmetric diblock copolymers under steady shear flow  

Microsoft Academic Search

For asymmetric diblock copolymers under steady shear flow, the orientational phase transitions in the hexagonal cylinder phase and the kinetics of lamellar to hexagonal phase transition were studied based on the time-dependent Ginzburg–Landau approach. As to orientational phase transitions in the hexagonal cylinder phase, the simulation results show that the parallel orientation is stable at low shear rate and the

Kaifu Luo; Yuliang Yang

2004-01-01

364

Defect-driven phase transitions out of the Coulomb phase  

NASA Astrophysics Data System (ADS)

Lattice models constrained by a local "conservation law," such as close-packed dimer models on 3D bipartite lattices, exhibit an emergent "Coulomb phase" with characteristic power-law correlations. We have studied, by Monte Carlo simulations, phase transitions out of the Coulomb phase induced by introducing a finite fugacity of defect excitations in dimer models. We report two cases. (1) In the simple cubic dimer covering, we admit non- bipartite dimers (connecting sites in the same sublattice), which appear as effective charges with Coulomb-like interactions. Non- bipartite defects induce a transition immediately out of the Coulomb phase, exponentially damping the critical correlations via Debye screening. We characterize this transition by extracting the screening length from our numerical calculation of the dimer structure factor.(2) In the diamond lattice, we initially restrict the dimers to a 2D layer forming a (bipartite) honeycomb lattice, and then admit interlayer dimers. These bipartite dimers appear as dipoles and do not destroy the Coulomb phase, but induce an immediate transition from a 2D to 3D Coulomb phase.

Ju, Hyejin; Trebst, Simon; Henley, Christopher

2011-03-01

365

Heat and Momentum Transfer on the Rapid Phase Change of Liquid Induced by Nanosecond-Pulsed Laser Irradiation  

Microsoft Academic Search

This study examines the physics of the liquid -vapor phase transition phenomenon induced by nanosecond -pulsed ultraviolet laser irradiation. This work is concerned with the science and technological applications of the phenomenon of rapid nucleation and explosive vaporization of a liquid in contact with a pulsed-laser heated solid surface. The thermodynamics of the phase transition, the kinetics of collective bubble

Hee Kuwon Park

1994-01-01

366

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

Microsoft Academic Search

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

Terushige Fujii; Junichi Oota

1993-01-01

367

First order Isotropic to Smectic A transition in liquid crystal-aerosil gels  

NASA Astrophysics Data System (ADS)

The effects of dispersed aerosils, which introduce quenched disorder in the decylcyanobiphenyl (10CB) liquid crystal, are studied. 10CB shows a strongly first-order phase transition from the isotropic (I) to smectic A (SmA) phase. Dispersed aerosils randomly pin the phase of smectic density modulation, destroying the long-range smectic ordering. Since there is no nematic (N) phase in 10CB, the phase transition is from I to SmA directly, yielding different results from equivalent studies carried out on materials with continuous N-SmA transition. Random field effects are determined by detailed analysis of the temperature and gel density dependence of the smectic structure factor. The finite smectic correlation length develops discontinuously in the vicinity of an effective I to SmA transition temperature. The correlation lengths saturate rapidly, decreasing with increasing gel density (random field variance). However, the temperature dependence of the peak intensity becomes increasingly gradual as gel density increases.

Ramazanoglu, Mehmet; Clegg, Paul; Birgeneau, Robert J.; Garland, Carl W.; Neubert, M. E.; Kim, J. M.

2004-03-01

368

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

369

Phase transitions and dark matter problems  

Microsoft Academic Search

The possible relationships between phase transitions in the early universe and dark matter problems are discussed. It is shown that there are at least 3 distinct cosmological dark matter problems 1) halos; 2) galaxy formation and clustering; and 3) Omega = 1, each emphasizing different attributes for the dark matter. At least some of the dark matter must be baryonic

David N. Schramm

1985-01-01

370

Femtoscopic search for the phase transition  

NASA Astrophysics Data System (ADS)

It is argued that the femtoscopic signals of the 1st order phase transition in relativistic heavy ion collisions can be obtained only in precise high statistics 3rd generation experiments like those planned in future NICA (JINR) and FAIR (GSI) facilities.

Lednicky, R.

2010-01-01

371

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

372

Phase transitions in marine fish recruitment processes  

Microsoft Academic Search

There has been a recent resurgence of interest in fisheries recruitment as a dynamic and complex process that is integrated over several life stages, with a variety of factors acting across scales to initiate, modulate, and constrain population abundance and variability. In this paper, we review the theory of recruitment phase transitions using a marine fisheries perspective. We propose that

Janet T. Duffy-Anderson; Kevin Bailey; Lorenzo Ciannelli; Philippe Cury; Andrea Belgrano; Nils Chr. Stenseth

2005-01-01

373

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

2014-04-22

374

Phase transition theory of sprite halo  

Microsoft Academic Search

We present the phase transition theory for sprite halo using measurable lightning parameters (charge moment and discharge time) on the basis of steady state thermodynamics. A halo is located at the upper part of the tree-like structure of a sprite and is produced through electron impact excitation of neutral species under the lightning-induced electric field. We proposed in our previous

Yasutaka Hiraki

2010-01-01

375

Phase separation kinetics in immiscible liquids  

NASA Technical Reports Server (NTRS)

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

Ng, Lee H.; Sadoway, Donald R.

1987-01-01

376

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

377

Experimental evidence of the ferroelectric nature of the ?-point transition in liquid water  

NASA Astrophysics Data System (ADS)

We studied the dielectric properties of nano-sized liquid water samples confined in polymerized silicates MCM-41 characterized by pore sizes 3-10 nm. Freezing temperature suppression in nanopores helps keep the water samples in liquid form at temperatures well below 0°C and thus effectively study the properties of supercooled liquid water. We report the first direct measurements of the dielectric constant by the dielectric spectroscopy method and demonstrate very clear signatures of the second-order phase transition of ferroelectric nature at temperatures next to the ?-point in the supercooled bulk water in full agreement with the recently developed model of the polar liquid.

Fedichev, P. O.; Menshikov, L. I.; Bordonskiy, G. S.; Orlov, A. O.

2011-11-01

378

Joint Campaign Glass Ceiling - Successfully Breaking the Transition Phase Barrier.  

National Technical Information Service (NTIS)

The military has created four phases to an operational campaign - Deter/Engage, Seize Initiative, Decisive Operations and Transition. The first three phases work remarkably well to achieve the desired military end state, however the Transition Phase - bri...

S. P. Apland

2002-01-01

379

Geometry-induced phase transition in fluids: capillary prewetting.  

PubMed

We report a new first-order phase transition preceding capillary condensation and corresponding to the discontinuous formation of a curved liquid meniscus. Using a mean-field microscopic approach based on the density functional theory we compute the complete phase diagram of a prototypical two-dimensional system exhibiting capillary condensation, namely that of a fluid with long-ranged dispersion intermolecular forces which is spatially confined by a substrate forming a semi-infinite rectangular pore exerting long-ranged dispersion forces on the fluid. In the T-? plane the phase line of the new transition is tangential to the capillary condensation line at the capillary wetting temperature T(cw). 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>T(cw), 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. PMID:23496446

Yatsyshin, Petr; Savva, Nikos; Kalliadasis, Serafim

2013-02-01

380

Quantum phase transitions around the staggered valence-bond solid  

NASA Astrophysics Data System (ADS)

Motivated by recent numerical results, we study the quantum phase transitions between Z2 spin-liquid, Néel-ordered, and various valence-bond solid (VBS) states on the honeycomb and square lattices, with emphasis on the staggered VBS. In contrast to the well-understood columnar VBS order, the staggered VBS is not described by an XY-order parameter with ZN anisotropy close to these quantum phase transitions. Instead, we demonstrate that on the honeycomb lattice, the staggered VBS is more appropriately described as an O(3)- or CP(2)-order parameter with cubic anisotropy, while on the square lattice it is described by an O(4)- or CP(3)-order parameter.

Xu, Cenke; Balents, Leon

2011-07-01

381

Terraces in the cholesteric phase of DNA liquid crystals  

SciTech Connect

Near the transition to the columnar phase, the cholesteric liquid crystal phase in an aqueous solution of DNA fragments with contour lengths approximating the persistence length undergoes an unwinding of the cholesteric pitch. Unwinding of the cholesteric with planar alignment of the fragments was studied by polarized light microscopy. Terraces or Grandjean planes'' of cholesteric are seen as uniformly birefringent fields of distinct hues (typically blue), bounded by lines which moved as the local concentration of DNA increased. These lines are interpreted as disclination lines, bounding regions of different total twist, which move as the intrinsic pitch of the cholesteric varies with concentration.

Van Winkle, D.H. (Department of Physics and Center for Materials Research and Technology, The Florida State University, Tallahassee, Florida 32306-3016 (United States)); Davidson, M.W. (Center for Materials Research and Technology and Institute of Molecular Biophysics, The Florida State University, Tallahassee, Florida 32306-3006 (United States)); Rill, R.L. (Department of Chemistry and Institute of Molecular Biophysics, The Florida State University, Tallahassee, Florida 32306-3006 (United States))

1992-10-15

382

Characterization of micellar mobile phases for reversed phase liquid chromatography  

SciTech Connect

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

Landy, J.S.

1983-01-01

383

Supercooled liquids and the glass transition  

Microsoft Academic Search

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

Pablo G. Debenedetti; Frank H. Stillinger

2001-01-01

384

Determination of clenbuterol in urine using headspace solid phase microextraction or liquid–liquid–liquid microextraction  

Microsoft Academic Search

Headspace solid phase microextraction (HS-SPME) and liquid–liquid–liquid microextraction with automated movement of the acceptor phase (LLLME\\/AMAP) techniques are described for the extraction of clenbuterol (CB) in urine. HS-SPME technique involves the extraction of the drug by SPME fibre in a headspace mode with a cooling device at the upper part of the vial to cool the headspace of the vial

Mahaveer B. Melwanki; Wei-Hsun Hsu; Shang-Da Huang

2005-01-01

385

Quantitative measurements of phase transitions in nano- and glassy materials  

NASA Astrophysics Data System (ADS)

Novel approaches to the collection and treatment of total x-ray scattering using high energy (> 65 keV) x-ray beams and area detectors allow in situ studies of unprecedented precision to be performed on nano-crystalline (n) and glassy materials at extremes of pressure (p) and temperature (T). Gradual structural transitions in glasses, liquids and nano-materials occurring via continuous changes in density, or involving phases related by pseudo symmetry are inherently difficult to identify due to their disordered nature. In such cases supplementary physical measurements along with modeling of the pair distribution function (PDF) provide powerful constraints on the possible models for the transition. Examples include transitions from n-FeS with a mackinawite-like structure to high p forms with structures related to NiAs structure-type. The distinction between the various high p models - MnP-type, troilite, FeS-III related or mixtures of these phases - is subtle; great care needs to be exercised in refining structure models to fit the observed data. Acoustic techniques are particularly valuable in identifying high p phase transitions in glasses, since measured changes in compressional velocities relate to density changes in the glass while shear waves provide an insight into network rigidity.

Parise, J. B.; Ehm, L.; Benmore, C. J.; Antao, S. M.; Michel, F. M.

2010-03-01

386

Imma phase of Si: phase transitions and stability  

Microsoft Academic Search

First principles calculations of the total energy of Imma states have found instabilities in states near the beta-Sn phase and in states near the simple hexagonal (sh) phase of Si crystal. In agreement with experiment the two instability ranges narrow the stable range between them and also in agreement with experiment the instabilities force first-order transitions to both the beta-Sn

S. L. Qiu; P. M. Marcus

2011-01-01

387

Imma phase of Si: phase transitions and stability  

Microsoft Academic Search

First principles calculations of the total energy of Imma states have found instabilities in states near the ?-Sn phase and in states near the simple hexagonal (sh) phase of Si crystal. In agreement with experiment the two instability\\u000a ranges narrow the stable range between them and also in\\u000a agreement with experiment the instabilities force first-order transitions to both the ?–Sn

S. L. Qiu; P. M. Marcus

2011-01-01

388

Erythrocyte morphological states, phases, transitions and trajectories.  

PubMed

Morphological response (MR) of red blood cells represents a triphasic sequence of spontaneously occurring shape transformation between different shape states upon transfer the cells into isotonic sucrose solution in the order: S(0) (initial discoid shape in physiological saline)-->S(1) (echinocytic shape at the beginning of MR, phase 1)-->S(2) (intermediate discoid shape, phase 2)-->S(3) (final stomatocytic shape, phase 3). In this paper, the dynamics of cell shape changes was investigated by non-invasive light fluctuation method and optical microscopy. Among 12 possible transitions between four main shape states, we experimentally demonstrate here an existence of nine transitions between neighbour or remote states in this sequence. Based on these findings and data from the literature, we may conclude that red blood cells are able to change their shape through direct transitions between four main states except transition S(1)-->S(0), which has not been identified yet. Some shape transitions and their temporal sequence are in accord with predictions of bilayer couple concept, whereas others for example transitions between remote states S(3)-->S(1), S(1)-->S(3) and S(3)-->S(0) are difficult to explain based solely on the difference in relative surface areas of both leaflets of membrane suggesting more complex mechanisms involved. Our data show that MR could represents a phenomenon in which the major role can play pH and chloride-sensitive sensor and switching mechanisms coupled with transmembrane signaling thus involving both cytoskeleton and membrane in coordinated shape response on changes in cell ionic environment. PMID:20538541

Rudenko, Sergey V

2010-09-01

389

Phase Transitions in Paradigm Shift Models  

PubMed Central

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

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

2013-01-01

390

A study of the size dependence of self diffusivity across the solid-liquid transition  

Microsoft Academic Search

The present study investigates the effect of temperature-induced change of phase from face centred cubic solid to liquid on the size dependence of self diffusivity of solutes through detailed molecular dynamics simulations on binary mixtures consisting of a larger solvent and a smaller solute interacting via Lennard-Jones potential. The effect of change in density during the solid-liquid transition as well

Manju Sharma; S. Yashonath

2008-01-01

391

Reexamination of the Synthesis of Liquid Crystalline Side-Chain Polyacrylates Via Liquid-Liquid Phase-Transfer Catalysis,  

National Technical Information Service (NTIS)

We have reexamined the synthesis of liquid crystalline side-chain polyacrylates under liquid liquid phase transfer conditions as first reported by Keller. Instead of the polymeric liquid crystals, the hydrolysis of the mesogen and a subsequent nucleophili...

S. H. Chen Y. F. Maa

1988-01-01

392

Bubble to slug flow transition in vertical upward two-phase flow of cryogenic fluids  

Microsoft Academic Search

An experimental study on the dispersed bubble to slug flow transition in a cryogenic gas-liquid two-phase flow is reported in this work. The transition is detected based on an analysis of the probability distribution function of pulse widths produced by a multivibrator in response to the temporal variation of local void fraction in the flow. An analytical model is also

R. Das; S. Pattanayak

1995-01-01

393

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

394

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

PubMed

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

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

2012-07-01

395

Hidden solidlike properties in the isotropic phase of the 8CB liquid crystal  

NASA Astrophysics Data System (ADS)

Novel dynamic experiments have enabled the identification of a macroscopic solidlike response in the isotropic phase of a low molecular weight liquid crystal, 4,4'-n-octylcyanobiphenyl (8CB). This unknown property indicates that the low frequency shear elasticity identified in the isotropic phase of liquid crystal polymers is not reminiscent from the glass transition but reveals likely a generic property of the liquid state. The comparison to high molecular weight liquid crystals indicates, however, that the shear modulus is much enhanced when the liquid crystal moieties are attached to a polymer chain. The macroscopic length scales probed (0.050-0.100 mm) exclude wall-induced effects.

Kahl, P.; Baroni, P.; Noirez, L.

2013-11-01

396

Gas-Controlled Heat Pipes for Accurate Liquid-Vapor Transition Measurements  

Microsoft Academic Search

At IMGC several gas-controlled heat pipes have been used to realize liquid-vapor transitions of pure fluids, such as water, potassium, mercury, and sodium. A very uniform and stable temperature zone has been realized in all cases, at the millikelvin level. Therefore, very accurate measurements of the phase-transition temperature are possible, using platinum resistance thermometers. Water and potassium heat pipes have

A. Merlone; R. Dematteis; P. Marcarino

2003-01-01

397

Phase transition kinetics in iron and steel during heating  

Microsoft Academic Search

Similarity theory is used to analyze phase transformations in iron and steel during heating. A kinetic equation is obtained by assumption of self-similarity of the phase transition. Experimental data are processed and effective kinetic parameters determined. It is concluded from the results obtained that the elementary act of phase transition consists of a cooperate transition into the new phase of

S. I. Mednikov; D. M. Gureev

1991-01-01

398

Phase transition kinetics in iron and steel during heating  

Microsoft Academic Search

Similarity theory is used to analyze phase transformations in iron and steel during heating. A kinetic equation is obtained by assumption of self-similarity of the phase transition. Experimental data are processed and effective kinetic parameters determined. It is concluded from the results obtained that the elementary act of phase transition consists of a cooperate transition into the new phase of

S. I. Mednikov; D. M. Gureev

1992-01-01

399

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...

400

Improved Boat For Liquid-Phase Epitaxy  

NASA Technical Reports Server (NTRS)

Liquid-phase epitaxial (LPE) growth boat redesigned. Still fabricated from ultra-high-purity graphite, but modified to permit easy disassembly and cleaning, along with improved wiping action for more complete removal of melt to reduce carry-over of gallium. Larger substrates and more uniform composition obtained.

Connolly, John C.

1991-01-01

401

Vapor-liquid phase separator permeability results  

NASA Technical Reports Server (NTRS)

Continued studies are described in the area of vapor-liquid phase separator work with emphasis on permeabilities of porous sintered plugs (stainless steel, nominal pore size 2 micrometer). The temperature dependence of the permeability has been evaluated in classical fluid using He-4 gas at atmospheric pressure and in He-2 on the basis of a modified, thermosmotic permeability of the normal fluid.

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

1981-01-01

402

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

403

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

404

Extremely flat surfaces by liquid phase epitaxy  

Microsoft Academic Search

By analysis of liquid phase epitaxial (LPE) growth experiments of GaAs multilayer structures, the incorporation rates at elementary growth steps (kinetic coefficients) are estimated. Conditions are presented to prepare large singular surfaces with several micrometers distances between regular elementary steps. Such quasi atomically flat surfaces may become important for applications in semiconductor and superconductor technologies, in surface physics and catalysis,

A. A. Chernov; H. J. Scheel

1995-01-01

405

Dynamics of the QCD phase transition  

SciTech Connect

We apply a recently computed nucleation rate to a first-order deconfinement/chiral-symmetry restoring phase transition in a set of rate equations to study the time evolution of expanding quark-gluon plasma as it converts to hadronic matter. At energies of the BNL Relativistic Heavy Ion Colliders, the system must supercool about 20% below {ital T}{sub {ital c}} before nucleation of hadronic bubbles is sufficiently rapid to overcome the expansion rate. The system reheats to near {ital T}{sub {ital c}}, nucleation turns off, and the transition is completed by the growth of previously nucleated bubbles. Based on Bjorken hydrodynamics and on current parameter values, we estimate that the transition generates 30% extra entropy.

Csernai, L.P. (Department of Physics, University of Bergen, N-5007 Bergen (Norway)); Kapusta, J.I. (School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States))

1992-08-03

406

Magnetic phase transitions in spin glasses  

NASA Astrophysics Data System (ADS)

The nature of a phase transition in spin glasses remains unsettled. Its characterization lies in experimentation on materials which closely mimic the theoretical models. Here I consider the "ideal" (2D-Ising) spin glass Rb 2Cu 1- xCo xF 4. The complex ac-susceptibility is measured as a function of temperature and frequency. The results are analyzed to determine the median relaxation time which diverges towards Tc = 0K according to activated dynamics. Far above Tc the relaxation time leaves the experimentally available window. Consequently an equilibrium phase transition cannot be studied as T? Tc+. A similar situation is expected for model 3D spin glasses where Tc is finite.

Mydosh, J. A.

1990-12-01

407

Nonequilibrium phase transitions in biomolecular signal transduction.  

PubMed

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

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

2011-11-01

408

Phase transitions: An overview with a view  

SciTech Connect

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

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

1997-10-01

409

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

PubMed

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

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

2013-06-01

410

Evolution of structure during phase transitions  

SciTech Connect

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

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

1996-03-01

411

Thermal Phase Transitions in Artificial Spin Ice  

NASA Astrophysics Data System (ADS)

We use the sixteen-vertex model to describe bidimensional artificial spin ice. We find excellent agreement between vertex densities in 15 differently grown samples and the predictions of the model. Our results demonstrate that the samples are in usual thermal equilibrium away from a critical point separating a disordered and an antiferromagnetic phase in the model. The second-order phase transition that we predict suggests that the spatial arrangement of vertices in near-critical artificial spin ice should be studied in more detail in order to verify whether they show the expected space and time long-range correlations.

Levis, Demian; Cugliandolo, Leticia F.; Foini, Laura; Tarzia, Marco

2013-05-01

412

Phase transitions and elementary-particle physics  

SciTech Connect

The reason physicists have recently taken an intense interest in the statistical mechanics of certain lattice models is reviewed. Phase transitions in these systems are of direct relevance to whether the gauge theory of interacting quarks and gluons can prevent the quark as appearing as a free isolated object. Monte Carlo simulation techniques have given the strongest evidence for the confinement phenomenon and are beginning to make numerical predictions in strong interaction physics.

Creutz, M.

1981-01-01

413

Topological phase transitions in frustrated magnets  

NASA Astrophysics Data System (ADS)

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

Southern, B. W.; Peles, A.

2006-06-01

414

Thermal Phase Transition of Dense QCD  

Microsoft Academic Search

Using the Ginzburg-Landau (GL) free energy, we study the effects of thermal fluctuations of gluons and the diquark pairing field on the superconducting-to-normal state phase transition in a three-flavor color superconductor. At high baryon densities, the system becomes a Type I superconductor and the gluonic fluctuations dominate over diquark fluctuations. The thermal gluons induce a cubic term in the GL

T. Matsuura; T. Hatsuda; K. Iida; G. Baym

2004-01-01

415

Nanoscale phase transitions within single ion tracks  

Microsoft Academic Search

The dynamics of track development due to the passage of energetic ions through solids is a long-standing issue relevant to nuclear materials, age-dating of minerals, space exploration, and nanoscale fabrication of novel devices. We have integrated computer simulation and experimental approaches to investigate nanoscale phase transitions under the extreme conditions created within single tracks of energetic ions in the Gd2Zr2-xTixO7

William Weber; Ram Devanathan; Pedro Moreira

2011-01-01

416

Recent theoretical advances on superradiant phase transitions  

NASA Astrophysics Data System (ADS)

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

Baksic, Alexandre; Nataf, Pierre; Ciuti, Cristiano

2013-03-01

417

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.