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At the liquid-gas phase transition in water, the density has a discontinuity at atmospheric pressure; however, the line of these first-order transitions defined by increasing the applied pressure terminates at the critical point.sup.1, a concept ubiquitous in statistical thermodynamics.sup.2. In correlated quantum materials, it was predicted.sup.3 and then confirmed experimentally.sup.4,5 that a critical point terminates the line of Mott metal-insulator transitions, which are also first-order with a discontinuous charge carrier density. In quantum spin systems, continuous quantum phase transitions.sup.6 have been controlled by pressure.sup.7,8, applied magnetic field.sup.9,10 and disorder.sup.11, but discontinuous quantum phase transitions have received less attention. The geometrically frustrated quantum antiferromagnet SrCu.sub.2(BO.sub.3).sub.2 constitutes a near-exact realization of the paradigmatic Shastry-Sutherland model.sup.12-14 and displays exotic phenomena including magnetization plateaus.sup.15, low-lying bound-state excitations.sup.16, anomalous thermodynamics.sup.17 and discontinuous quantum phase transitions.sup.18,19. Here we control both the pressure and the magnetic field applied to SrCu.sub.2(BO.sub.3).sub.2 to provide evidence of critical-point physics in a pure spin system. We use high-precision specific-heat measurements to demonstrate that, as in water, the pressure-temperature phase diagram has a first-order transition line that separates phases with different local magnetic energy densities, and that terminates at an Ising critical point. We provide a quantitative explanation of our data using recently developed finite-temperature tensor-network methods.sup.17,20-22. These results further our understanding of first-order quantum phase transitions in quantum magnetism, with potential applications in materials where anisotropic spin interactions produce the topological properties.sup.23,24 that are useful for spintronic applications. The pressure dependence and magnetic field dependence of the specific heat of a quantum magnet, SrCu.sub.2(BO.sub.3).sub.2, demonstrate that its phase diagram contains a line of first-order transitions terminating at a critical point, in analogy with water., Author(s): J. Larrea Jiménez [sup.1] [sup.2] , S. P. G. Crone [sup.3] [sup.4] , E. Fogh [sup.2] , M. E. Zayed [sup.5] , R. Lortz [sup.6] , E. Pomjakushina [sup.7] [...]

This paper is aimed at the application of a model for simulating the dispersed turbulent flows. The presented model proceeds from a kinetic equation for the probability density function of the particle velocity distribution in turbulent flow. This approach is called the diffusion-inertia model (DIM). Applications of the model to droplet and bubble flows are presented. In the case of vaporized liquid, the interphase heat and mass transfer is introduced by adding the corresponding governing equations. This extended version of the DIM was applied to simulating the boiling water flow in a heated pipe. [DOI: 10.1115/1.4000890]

Supercritical water (SCW) has excellent heat transfer characteristics as a coolant for nuclear reactors. Besides it results in high thermal efficiency of the plant. However, the flow can experience instabilities in supercritical water cooled reactors, as the density change is very large for the supercritical fluids. A computer code SUCLIN has been developed employing supercritical water properties to carry out the steady-state and linear stability analysis of a SCW natural circulation loop (SCWNCL). The conservation equations of mass, momentum, and energy have been linearized by imposing small perturbation inflow rate, enthalpy, pressure, and specific volume. The equations have been solved analytically to generate the characteristic equation. The roots of the equation determine the stability of the system. The code has been benchmarked against published results. Then the code has been extensively used for studying the effect of diameter, heater inlet temperature, and pressure on steady-state and stability behavior of a SCWNCL. A separate computer code, NOLSTA, has been developed, which investigates stability characteristics of supercritical natural circulation loop using nonlinear analysis. The conservation equations of mass, momentum, and energy in transient form were solved numerically using finite volume method. The stable, unstable, and neutrally stable points were identified by examining the amplitude of flow and temperature oscillations with time for a given set of operating conditions. The stability behavior of loop, predicted using nonlinear analysis has been compared with that obtained from linear analysis. The results show that the stability maps obtained by the two methods agree qualitatively. The present paper describes the linear and nonlinear stability analysis models and the results obtained in detail. [DOI: 10.1115/1.4000342] Keywords: supercritical, linear, nonlinear, stability, natural circulation

The dynamic nature of the first water adlayers on solid surfaces at room temperature has made the direct detection of their microscopic structure challenging. We used graphene as an atomically flat coating for atomic force microscopy to determine the structure of the water adlayers on mica at room temperature as a function of relative humidity. Water adlayers grew epitaxially on the mica substrate in a layer-by-layer fashion. Submonolayers form atomically flat, faceted islands of height 0.37 [+ or -] 0.02 nanometers, in agreement with the height of a monolayer of ice. The second adlayers, observed at higher relative humidity, also appear icelike, and thicker layers appear liquidlike. Our results also indicate nanometer-scale surface defects serve as nucleation centers for the formation of both the first and the second adlayers. 10.1126/science.1192907

Thermal modulation voltammetry (TMV) using laser heating at a liquid/liquid microinterface is a useful technique for determining the standard entropy change of ion transfer. In this work, for achieving TMV using a visible laser as a heating source at a 1,2-dichloroethane (DCE)/ water microinterface, we used an optically absorbing supporting electrolyte, i.e., crystalviolet tetrakis(4-chlorophenyl)borate (CTTC1PB). CVTC1PB served well not only as a supporting electrolyte but also as an optical absorber in the DCE solution, and thereby, well-defined linear sweep (LS) and TM voltammograms could be obtained. On the basis of LS and thermal modulation (TM) voltammograms obtained with CVTC1PB, the standard entropy changes of ion transfer for six model ions were successfully determined. 10.1021/ac100927y

Although ice melts and water freezes under equilibrium conditions at 0[degrees]C, water can be supercooled under homogeneous conditions in a dean environment down to -40[degrees]C without freezing. The influence of the electric field on the freezing temperature of supercooled water (electrofreezing) is of topical importance in the living and inanimate worlds. We report that positively charged surfaces of pyroelectric LiTa[O.sub.3] crystals and SrTi[O.sub.3] thin films promote ice nucleation, whereas the same surfaces when negatively charged reduce the freezing temperature. Accordingly, droplets of water cooled down on a negatively charged LiTa[O.sub.3] surface and remaining liquid at -11[degrees]C freeze immediately when this surface is heated to -8[degrees]C, as a result of the replacement of the negative surface charge by a positive one. Furthermore, powder x-ray diffraction studies demonstrated that the freezing on the positively charged surface starts at the solid/water interface, whereas on a negatively charged surface, ice nucleation starts at the air/water interface. 10.1126/science.1178085

The thermodynamic effect on a cavitating inducer is investigated from joint experiments in cold water and Refrigerant 114. The analysis is focused on leading edge cavitation and cavitation instabilities, especially on alternate blade cavitation and supersynchronous rotating cavitation. The cavity length along cylindrical cuts at different radii between the hub and casing is analyzed with respect to the local cavitation number and angle of attack. The similarity in shape of the cavity closure line between water and R114 is examined and deviation caused by thermodynamic effect is clarified. The influence of rotation speed on cavity length is investigated in both fluids and analyzed on the basis of a comparison of characteristic times, namely, the transit time and a thermal time. Thermodynamic delay in the development of leading edge cavities is determined and temperature depressions within the cavities are estimated. Thresholds for the onset of cavitation instabilities are determined for both fluids. The occurrence of cavitation instabilities is discussed with respect to the extent of leading edge cavitation. The thermodynamic delay affecting the occurrence of cavitation instabilities is estimated and compared with the delay on cavity development. [DOI: 10.1115/1.4001006]

Four scenarios have been proposed for the low-temperature phase behavior of liquid water, each predicting different thermodynamics. The physical mechanism that leads to each is debated. Moreover, it is still unclear which of the scenarios best describes water, because there is no definitive experimental test. Here we address both open issues within the framework of a microscopic cell model by performing a study combining mean-field calculations and Monte Carlo simulations. We show that a common physical mechanism underlies each of the four scenarios, and that two key physical quantities determine which of the four scenarios describes water: (i) the strength of the directional component of the hydrogen bond and (ii) the strength of the cooperative component of the hydrogen bond. The four scenarios may be mapped in the space of these two quantities. We argue that our conclusions are model independent. Using estimates from experimental data for H-bond properties the model predicts that the low-temperature phase diagram of water exhibits a liquid-liquid critical point at positive pressure. anomalous liquids | liquid-liquid transition | liquid water | mean field | Monte Carlo simulations doi/ 10.1073/pnas.0912756107

Studying heat transfer problems of supercritical water, the pressure dependency of thermophysical parameters (density, specific heat, viscosity, and thermal conductivity) and the work done by pressure are often neglected. Here we show that the variations of some physical parameters as functions of pressure have the same order of magnitude than their variations as functions of temperature in supercritical water. Therefore, pressure dependency of physical parameters should be taken into account in heat transfer calculations of supercritical water It is also pointed out that the work done by pressure should not be neglected in supercritical water since the pressure work term has the same order of magnitude than the convective term near the pseudocritical temperature. [DOI: 10.1115/1.2983135]

I suggest that the origin of the Mpemba effect (the freezing of hot water before cold) is due to freezing-point depression by solutes, either gaseous or solid, whose solubility decreases with increasing temperature so that they are removed when water is heated. The solutes are concentrated ahead of the freezing front by zone refining in water that has not been heated, reducing the temperature of the freezing front, and thereby reducing the temperature gradient and heat flux, slowing the progress of the freezing front. I present a simple calculation of this effect, and suggest experiments to test this hypothesis. [DOI: 10.1119/1.2996187]

A thermochemical two-step water-splitting cycle using a redox metal oxide was examined for Ni(II) ferrites or [Ni.sub.x][Fe.sub.3-x] [O.sub.4] (0 [less than or equal to] x [less than or equal to] 1) for the purpose of converting solar high-temperature heat to hydrogen. The Ni(II) ferrite was decomposed to Ni-doped wustite ([Ni.sub.y][Fe.sub.l-y]O) at 1400 [degrees]C under an inert atmosphere in the first thermal-reduction step of the cycle; it was then reoxidized with steam to generate hydrogen at 1000 [degrees]C in the second water-decomposition step. Although nondoped [Fe.sub.3][O.sub.4] powders formed a nonporous, dense mass of iron oxide by the fusion of FeO and its subsequent solidification after the thermal-reduction step, Ni(II)-ferrite powders were converted into a porous, soft mass after the step. This was probably because Ni doping in the FeO phase raised the melting point of wustite above 1400 [degrees]C. Supporting the Ni(II) ferrites on m-Zr[O.sub.2] (monoclinic zirconia) alleviated the high-temperature sintering of iron oxide; as a result, the supported ferrites exhibited greater reactivity and assisted the repeatability of the cyclic water splitting process as compared to the unsupported ferrites. The reactivity increased with the doping value x, and was maximum at x = 1.0 in the NixFe3-xO4/m-Zr[O.sub.2] system. Keywords: Solar heat; Energy conversion; Hydrogen production; Thermochemical water splitting; Ni(II) ferrite

When steam power cycles are modeled, thermodynamic properties as functions of enthalpy and entropy are required in the critical and supercritical regions (region 3 of IAPWS-IF97). With IAPWS-IF97, these calculations require cumbersome two-dimensional literation of temperature T and specific volume v from specific enthalpy h and specific entropy s. While these calculations are not frequently required, the computing time can be significant. Therefore, the International Association for the Properties of Water and Steam (IAPWS) adopted backward equations for p(h,s) in region 3. For calculating properties as a function of h and s in the part of the two-phase region that is important for steam-turbine calculations, a backward equation [T.sub.sat](h,s) is provided. In order to avoid time-consuming iteration in determining the region for given values of h and s, equations for the region boundaries were developed. The numerical consistency of the equations documented here is sufficient for most applications in heat-cycle, boiler, and steam-turbine calculations. [DOI: 10.1115/1.2719267]

The article presents a comprehensive analysis of the thermodynamics of the transfer of the metastable water clusters in the nonpolar cavities of the thermostable protein tetrabrachion from the bulk phase into the largest cavity. It is hence seen that the largest nonpolar cavity in tetrabrachion functionally serves as the binding element for the nonpolar anchors of its proteases.

The time-of-flight secondary ion mass spectrometry and reflection absorption infrared spectroscopy were used to determine the properties of supercooled liquid water and the mechanism of crystallization. The supercooled water is found to contain two phases and undergoes immediate crystallization and dissolution of LiCl.

Fluorescence correlation spectroscopy (FCS) is applied to the quantitative evaluation of the local temperature in solutions under the laser trapping condition in the presence of a near-infrared (NIR) laser beam at 1064 nm. The results are described in view of the balance between the extinction coefficient and the thermal conductivity of the solvents.

The thermodynamic analysis of water molecules in the binding sites of six proteins, where each is complexed with a number of inhibitors, is described. Bayesian statistic has allowed the numerical assessment of whether or not a given water molecule should be targeted for displacement as part of a rational drug design strategy.

A study presents the temperature (T) dependence of hole growth kinetics data for aluminium-phthalocyanine-tetrasulfonate (APT) in fresh and annealed hyperquenched glassy water (HGW) at different temperatures. The results show that the hole growth model should also consider the thermal hole filling (THF) processes, as it can help in overcoming the discrepancies existing at extrinsic multiple level systems.

The study employs a steady-state method to perform certain tests for the determination of the effects of particle size on the effective thermal conductivity of [Al.sub2.][O.sub.3] or distilled water nanoparticles and nanofluids. The results demonstrate that an increase in the volume fraction, temperature and particle size results in an increase in the conductivity as well, which leads to the need of an optimum sized particle of different combinations.

The boiling experiments are conducted with 2-propanol/water mixtures in confined gap geometry under various levels of gravity. The results have shown that heat transfer reduces with increase in the gravity level and the gap size can be optimized for a specific condition in order to reach the best heat transfer performance in the system.

An investigation on the phase behaviors of the binary mixture of an anionic surfactant aerosol OT (AOT) and water is conducted on a mesoscopic level using dissipative particle dynamics (DPD) computer simulations. It is proposed that the anomalous lamellar phenomena at intermediate AOT concentration are due to the formation of a defective structure, pseudoreversed hexagonal phase, which evidently decreases the water diffusivity.

The three-dimensional coupled map lattice (CML) method is used for reproducing the characteristic atmospheric pool boiling curve for water on a temperature controlled thin copper having comparable length and breadth. The CML method is qualitative in nature and it is able to predict the critical heat flux (CHF) of saturated pool boiling of water at 1 bar very close to the actual value.

An effective computational procedure for predicting the aqueous acid equilibrium constants of protonated benzimidazoles at 298.15 K is developed. Results reveal that from 50% water-ethanol p[K.sub.a] values of protonated benzimidazoles, aqueous equilibrium constants could be estimated with reasonable accuracy in most cases.

The evaporative cooling rates of a droplet train of liquid water injected into vacuum was studied using Raman thermometry to test the hypothesis that states that on average, molecules in the higher-energy tail of the Boltzmann distribution are more readily transferred into the vapor during evaporation. The value of the evaporation coefficient of liquid water was determined to be 0.62 plusmn 0.09, confirming that a rate-liming barrier impedes the evaporation rate.

Rhodium(III) tetra(p-sulfonato phenyl) porphyrin [(TSPP)Rh] aquo and hydroxo complexes reacting with a series of olefins in water in to form [beta]-hydroxyalkyl complexes is presented. Comparisons of the regiostomers and thermodynamics for addition reactions of olefins with Rh-H and Rh-OH units in water are presented and discussed.

Microwave and ab initio studies of the Xe-[H.sub.2]O van der Waals dimers are presented and the rotational transitions within two internal rotor states are measured using a Fourier transform microwave spectrometer. The obtained effective [H.sub.2]O orientations have supported the contribution to the wave functions in each state from the anti-hydrogen bonded orientations and nonplananr configurations and agreed with the structural parameters and force constants obtained from the rotational and centrifugal distortion constants.

The thermal diffusion behavior of hexaethylene glycol monododecyl ether [[C.sub.12][E.sub.6]] in water is studied by using thermal diffusion forced Rayleigh scattering (TDFRS) and Soret coefficients, thermal diffusion coefficients and diffusion constants are determined at different temperatures and concentrations. The origin of the slow mode of the TDFRS signal is interpreted in terms of a ternary mixture of neutral micelles, dye-charged micelles and water.

A primary focus on the investigation of Earth's stratosphere and mesosphere is made, where vibrational energy transfer from oxygen molecules to water molecules helps control the local temperature through infrared radiative cooling and must be quantitatively understood to retrieve the water altitude profile from infrared radiance. Additional information is available for combustion chemistry, where [O.sub.2] is a primary reagent and [H.sub.2]O is a primary product.

The temperature and density dependence of the molecular and thermodynamic properties of water was investigated theoretically by means of the ab initio electronic structure theory combined with the reference interaction site model method (RISM-SCF). The results for (delta)pK(sub w) obtained from the theory show a monotonic increase with increasing density at all the temperatures investigated in good accord with the experimental observation.

The semi-ideal solution theory is presented to describe the changes in thermodynamic properties accompanying the process of mixing non ideal electrolyte solutions at constant activities of NY and H(sub 2)O. The theory is proposed on the basis of the Debye-Huckel theory and the concept of stepwise hydration equilibrium, from which the novel concentration relations for multicomponent saturated electrolyte solutions are established and the Zdanovskii's rule is theoretically derived.

A sensitivity analysis of bulk water thermodynamics is presented in an effort to understand the relation between qualitative features of molecular potentials and properties they predict. The analysis indicate that all investigated properties are most sensitive to van der Waals repulsive, the short range Coulomb and the polarization components of the potentials.

The dependence of the properties of the water-benzene system on the thermodynamic conditions in a broad range of temperatures and pressures is studied using Monte Carlo simulations at twenty three different thermodynamic states, ranging from ambient to supercritical conditions. It is seen that the nearest water neighbors of the benzene molecules are located above and below the benzene ring.

The effects of varying the relative weights of the Lennard-Jones and Coulombic contributions to the energy of the SPC/E model on its water like structural, dynamic, and thermodynamic anomalies are investigated. The results suggest that for a liquid to show negative thermal expansion and anomalous density dependence in its transport properties, it must have a local structure that differs from and is inconsistent with simple Lennard-Jones type spherical symmetry.

The energetic interactions of water molecules with no polar liquids have to be stronger than predicted by considering only van der Waals contributions. The occurrence of nontraditional hydrogen bonds in an isotropic liquid phase between an inserted water molecule and the surrounding aliphatic or aromatic molecules emerged from the analysis of the solvation thermodynamics of water in nonpolar organic solvents.

A classical molecular dynamics (MD) simulation of the flexible simple point charge (SPC) and extended SPC (SPC/E) water models to determine the temperature dependence of the bulk water vibrational spectrum is presented. MD simulations were performed at -4 and 80 degree Celsius to compare the calculated vibrational spectra, in particular the band associated with the bending mode.

Ground-state potential energy surface of the CO-H2O system is explored using ab initio calculations at the CCSD(T)/6-311++G//MP2/6-311++G level. The results reveal that providing energy of about 74 kcal/mol, the initial bimolecular complex CO-H2O can associate into formic acid (HCOOH) or dihydroxycarbene (HOCOH).

The study was conducted to find out whether 0 K theoretical results are meaningful relative to experiments carried out at 150 K. It is concluded that at 150 K, where periodic adlayers on metals are observed, residual entropy reduces their free energies relative to a 3-D ice crystal by 4.5 meV/molecule, or ~3 percent of the cost of the adlayers' broken H-bonds.

AMOEBA is an atomic multippole-based model that treats dipole polarization explicitly. The parameters in this water model were derived from gas-phase and room temperature liquid properties, mainly the density and heat of vaporization. By comparing AMOEBA and a variant parameterization, AMOEBA-v, it is demonstrated that much of the anomalous behavior of water is closely related to its hydrogen bonding properties.

A thermodynamic study of one component liquid-vapor planar interfaces and the temperature dependence of some relevant thermodynamic quantities is presented. A critical review of data for the surface tension of water found in some textbooks is given. More accurate measurements show a qualitative change in the temperature dependence of the surface tension, from the almost linear dependence of the old data to nonlinear behavior and the occurrence of an inflection point in the more accurate, more recent data. [DOI: 10.1119/1.1477431]

Experiments that measure the specific and latent heat of water are described which teach students important principles of thermodynamics. The experiments proved to be imprecise but this shows students that sometimes experiments fail to work.

The review focuses on the products of the reactions between organic compounds and superheated water and the mechanisms governing their formation. The the dissociation constant of water increases with increasing temperature rendering it a stronger acid and a stronger base. Furthermore, heterocyclic rings of the organic compounds react readily in superheated water.

The focus of the review is the transformations of organic compounds in pure superheated water and elevated temperatures. Discussion on the relevance of aqueous chemistry to high temperature petroleum generation, kerogen formation leading to petroleum by depolymerization, and solvent properties of water at 250-350 C is presented.

Monte Carlo simulation is used to study the impact of an external magnetic field on the heat capacity and internal energy of pure water.

The measured failure diameter and a detonation speed for the liquid explosive mixture 90.5/9.5 wt % H2O2/H2O confined in thick seamless 304 stainless steel tubing and fired at ca. 30 degree Celsius is reported. A general analytical expression is given for the primary shock Hugoniot of any H2O2/H20 mixture at 22.6 degree Celsius.

TOPEX satellite El Nino altimetry data can be used effectively to introduce heat capacity and thermal expansion concepts to chemistry students. The TOPEX altimetry data give an average height over an area 6km-12km in diameter accurate to within 3cm-5cm. In the equatorial Pacific basin a quite large bump was seen in 1997 and into 1998 related to El Nino phenomena. A Jet Propulsion Laboratory (of California Inst. of Technology) colored map of the Pacific Ocean as seen from TOPEX data is useful for teaching.

Liquid desiccant cooling can provide control of temperature and humidity, while at the same time lowering the electrical energy requirement for air conditioning. Since the largest energy requirement associated with desiccant cooling is low temperature heat for desiccant regeneration, the regeneration process greatly influences the overall system performance. Therefore, the effects of variables such as air and desiccant flow rates, air temperature and humidity, desiccant temperature and concentration, and the area available for heat and mass transfer on the regeneration process are of great interest. Due to the complexity of the regeneration process, which involves simultaneous heat and mass transfer, theoretical modeling must be verified by experimental studies. However, a limited number of experimental studies are reported in the literature. This paper presents results from a detailed experimental investigation of the heat and mass transfer between a liquid desiccant (triethylene glycol) and air in a packed bed regenerator using high liquid flow rates. To regenerate the desiccant, it is heated to temperatures readily obtainable from flat-plate solar collectors. A high performance packing that combines good heat and mass transfer characteristics with low pressure drop is used. The rate of water evaporation, as well as the effectiveness of the regeneration process is assessed based on the variables listed above. Good agreement is shown to exist between the experimental findings and predictions from finite difference modeling. In addition, the findings in the present study are compared to findings previously reported in the literature. Also, the results presented here characterize the important variables that impact the system design.

Research was conducted to model and analyze the microwave heating of water slabs bound with a gel without any restriction to the Biot number regime. The mechanism of thermal runaway was caused by resonance of the electromagnetic waves within the object combined with the heat loss even if there was an uneven distribution of temperature over the slab. Results indicate that the almost constant absorption of energy over the whole slab plays a dominant role in the calculations of the temperature profiles.

The temperature-dependent viscosities of liquid H2O, D2O and T2O have been determined by using the thermal offset concept. This method can be used as a validity check using more accurate data obtained from H2O measurements. It has been observed that the thermal offset viscosities become smaller than the experimental viscosities as the temperature increases. This is due to the breakdown of the mixture model, the further softening of the structure and the normal lowering effects on the viscosity with higher temperatures.

Cold dense water from the Denmark Strait sill overflows and descends to keep the deep ocean ventilated and is important in global thermohaline circulation. Important changes in the characteristics of the overflow during winter 1996-97 are reported, using measurements from current-meter moorings and an inverted echo sounder. The overflow was found to warm to its highest monthly value, and exhibited slowing and thinning of the lower margin. The extreme warmth may be a lagged response to early warming upstream in the Fram Strait.

The pure water-vapor equilibrium has been calculated over a temperature range of 300-600 degrees K. The Gibbs ensemble Monte Carlo simulation method with simple two-body molecular models was used to calculate the vapor pressure and saturated liquid and vapor densities. The Ewald summation method was employed to account for the long-range Coulombic interactions. The critical constants, second virial coefficient and the heat of vaporization were also calculated.