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The ambient-pressure phase α of C4H2N5Cl transforms under 0.18 GPa to a higher-symmetry phase α′, but its high-pressure recrystallization below 0.20 GPa leads to a stochastic hydrate while above 0.20 GPa recrystallization leads to a new phase, β., Partial hydration of organic compounds can be achieved by high-pressure crystallization. This has been demonstrated for the high-nitro­gen-content compound 6-chloro-1,2,3,4-tetrazolo[1,5-b]pyridazine (C4H2N5Cl), which becomes partly hydrated by isochoric crystallizations below 0.15 GPa. This hydrate, C4H2N5Cl·xH2O, is isostructural with the ambient-pressure phase α of C4H2N5Cl, but the crystal volume is somewhat larger than that of the anhydrate. At 0.20 GPa, the α-C4H2N5Cl anhydrate phase transforms abruptly into a new higher-symmetry phase, α′; the transformation is clearly visible due to a strong contraction of the crystals. The hydrate α-C4H2N5Cl·xH2O can also be isothermally compressed up to 0.30 GPa before transforming to the α′-C4H2N5Cl·xH2O phase. The isochoric recrystallization of C4H2N5Cl above 0.18 GPa yields a new anhydrous phase β, which, on releasing pressure, transforms back to the α phase below 0.15 GPa. The structural transition from the α to the β phase is destructive for the single crystal and involves a large volume drop and significant elongation of all the shortest intermolecular distances which are the CH⋯N and CH⋯Cl hydrogen bonds, as well as the N⋯N contacts. The α-to-α′ phase transition increases the crystal symmetry in the subgroup relation; however, there are no structural nor symmetry relations between phases α and β.

High-pressure polymorphs can be obtained and stabilized at ambient pressure by utilizing dopants with more voluminous molecules, inducing internal strain in the structures. This effect has been confirmed for doped resorcinol and imidazole derivatives by nucleating and stabilizing their high-pressure phases under ambient conditions. The dopant molecular volume and concentration, as well as the bulk modulus of the polymorph in the binary system, are related to the stability region in the single-component phase diagram. High-pressure isothermal and isochoric recrystallizations yielded pure single crystals of resorcinol ε above 0.20 GPa and a new polymorph ζ above 0.70 GPa. These recrystallizations of pure resorcinol revealed within 1 GPa of the p–T phase diagram the boundaries and the stability regions of four resorcinol polymorphs α, β, ε, and ζ, contrary to the compression experiments on ambient-pressure polymorphs α and β, when the high-pressure phases were hidden behind the wide hysteresis extending to nearly 5 GPa. The hysteresis, originating from the H-bonding networks, hinders the formation of polymorphs ε and ζ when polymorphs α and β are compressed without melting or dissolving the crystals. Polymorph ζ is the only known resorcinol structure built of hydrogen-bonded layers.

Methane adsorption on a recuperated activated carbon, AR-V, was studied over the temperature range of 213–393 K and at pressures up to 10 MPa from the perspective of its potential application for adsorption-based storage and separation technologies. The porous structure, phase and chemical compositions of AR-V were examined by nitrogen adsorption at 77 K, x-ray diffraction, and scanning electron microscopy. The amount of adsorbed methane increased with pressure up to 6.3 mmol/g at 243 K and fell dramatically to ~ 1 mmol/g with a temperature rise to 393 K. The molar differential isosteric heat of methane adsorption on AR-V was evaluated from the linear isosteres within the studied P,T-range; the effects from the non-ideality of a gaseous phase and the AR-V non-inertness were considered. The maximal summarized contribution from the AR-V thermal expansion and directly measured adsorption-induced deformation to the molar differential isosteric heat of methane adsorption turned out to be less than that from the gas compressibility. The initial drastic changes in the thermodynamic state functions of the adsorption system were attributed to the binding methane molecules with non-uniformly distributed high-energy adsorption sites. When methane molecules occupied all high-energy adsorption sites, the subsequent variations in the thermodynamic functions were governed by the intensifying attractive forces between methane molecules upon methane adsorption resulting in the formation of adsorption clusters. The temperature dependence of the isosteric heat capacity of the methane/AR-V system varied during adsorption; its value exceeded 2–3 times the isochoric heat capacity of the equilibrium methane gaseous phase.

The determination of the soil-water characteristic curve (SWCC) of compacted bentonites in the isochoric condition is a prerequisite for unsaturated flow simulations in several geoenvironmental applications. The SWCC data are, however, not readily available for many compacted bentonites over a wide suction range due to difficulties associated with the testing. In this work, wetting SWCCs of four Indian bentonites of different plasticity were established experimentally at compaction dry densities of 1.4, 1.6, and 1.8 Mg/m3 in isochoric conditions using two independent laboratory techniques in different suction ranges. The modified Kovács (MK) model was extended to simulate the SWCC data of the Indian bentonites. Empirical relationships between MK model parameters and compaction dry density for these bentonites were established. A theoretical procedure for the estimation of SWCCs of the compacted bentonites based on the basic bentonite properties and proposed correlations was proposed and validated on the available wetting SWCC data of compacted GaoMiaoZi (GMZ), MX80, and FEBEX bentonites from the literature studies. The proposed method predicts the wetting SWCCs of compacted powder bentonites, in volume-restrained condition, from the basic properties satisfactorily. The proposed model is an approximate method for predicting the SWCCs of bentonites in the absence of measured data and in understanding the influence of dry density and plasticity.

This paper analyzes the pressure response to an unsteady heat release source in an unconfined one-dimensional domain. An analytical model based on the acoustic wave equation with an unsteady heat source is derived, and then compared against results from highly-resolved numerical simulations. Two different heat release profiles, a Gaussian spatial distribution with either a step or a Gaussian temporal distribution, are used to model the heat source. The analytical solutions predict two regimes in the pressure response depending on the Helmholtz number, which is defined as the ratio of the acoustic time over the duration of the heat release pulse. A critical Helmholtz number is found to dictate the pressure response regime. For compact cases, in the subcritical regime, the amplitude of the pressure pulse remains constant in space. For noncompact cases, above the critical Helmholtz number, the pressure pulse reaches a maximum at the center of the heat source, and then decays in space converging to a lower far field amplitude. At the limits of very small and very large Helmholtz numbers, the heat release response tends to be a constant pressure process and a constant volume process, respectively. The parameters of the study are chosen to be representative of the extreme conditions in a rocket combustor. The analytical models for both heat source profiles closely match the simulations with a slight overprediction. The differences observed in the analytical solutions are due to neglecting mean flow property variations and the absence of loss mechanisms. The numerical simulations also reveal the presence of nonlinear effects such as weak shocks that cannot be captured by the linear acoustic wave equation.

A new experimental method, i.e., isochoric cooling/heating cycle measurement using differential scanning calorimetry (DSC), is applied to investigate the hysteretic phenomenon of pure components an...

An experimental study has been made of the density and the velocity of sound for liquid decalin and cyclohexane in the range of temperatures 298.15–433.15 K and pressures 0.1–100.1 MPa. Parameters of equations have been obtained that describe the dependences of the specific volume of liquid decalin and cyclohexane on their temperature and pressure and of the isobaric heat of these substances on their temperature at atmospheric pressure. The density, the velocity of sound, the isobaric and isochoric heats, the isobaric expansion coefficient, and the coefficients of isentropic and isothermal compressibilities of liquid decalin and cyclohexane have been determined in the range of temperatures 298.15–433.15 K at pressures to 100 MPa.

Studies on autoignition and combustion wave propagation in a spatial reactivity gradient environment constructed using the shock-converging method were conducted to obtain a new understanding of combustion modes and their mutual transition mechanism. Autoignition induced by the converging cylindrical shock wave and weak detonation can be observed by experiment and numerical simulation. Research indicates that for an appropriate spatial reactivity gradient, the velocity of the weak detonation wave can decrease and adjust to the local sound speed. This leads to the transformation of the weak detonation into the self-propagating Chapman-Jouguet (CJ) detonation. The speed of the spontaneous reaction wave characterizing the end of the chemical reaction is never less than the local sound speed; hence, there is no overdriven phenomenon throughout the weak-to-CJ detonation transition. This conforms to the fact that the overdriven phenomenon is not a necessary condition to initiate the detonation, and the combustion has higher thermal efficiency compared with isochoric combustion. Further research indicates that CJ detonation propagating in the preheated reactant can also transform into weak detonation for an appropriate spatial reactivity gradient. The initial CJ detonation degrades into a shock that decays and finally disappears. The wave-eliminating effect of the CJ-to-weak detonation transition can ensure the flow field quality and thermal efficiency of the combustion. In summary, performing a controllable weak detonation between isochoric combustion and CJ detonation in an engine has significant practical importance for improving combustion thermal efficiency and knock suppression.

The mechanical properties of α-Na3(U0.84(2),Na0.16(2))O4 have been researched using the first-principles calculations combined with the quasi-harmonic Debye model. The obtained lattice parameters agree well with the published experimental data. The results of elastic constants indicate that α-Na3(U0.84(2),Na0.16(2))O4 is mechanically stable. The polycrystalline moduli are predicted. The results show that the α-Na3(U0.84(2),Na0.16(2))O4 exhibits brittleness and possesses obvious elastic anisotropy. The hardness shows that it can be considered a “soft material”. Furthermore, the Debye temperature θD and the minimum thermal conductivity kmin are also discussed, respectively. Finally, the thermal expansion coefficient α , isobaric heat capacity C P and isochoric heat capacity C V are evaluated through the quasi-harmonic Debye model.

The ignition of methane/air and ethylene/air mixtures by nanosecond pulsed discharges (NSPD) is investigated numerically using a zero-dimensional isochoric adiabatic reactor. A combustion kinetics model is coupled with a non-equilibrium plasma mechanism, which features vibrational and electronic excitation, dissociation, and ionization of neutral particles (O2 and N2) via electron impact. A time to ignition metric τ is defined, and ignition simulations encompassing a wide range of pressures (0.5–30 atm) and pulsing conditions for each fuel are executed. For each fuel, it is found that τ depends primarily on initial pressure and energy deposition rate, and scaling laws are derived. In order to quantify the benefit gained from plasma-assisted ignition (PAI), τ is compared with a thermal ignition time. It is found that for both fuels, PAI leads to a faster ignition at low pressures, while at higher pressures (p0 ≥ 5 atm), methane/air ignition becomes inefficient (meaning a longer ignition time for the same input energy compared to thermal ignition). Ethylene/air PAI shows only a modest deterioration. The drop in performance with pressure is found to be due to the mean electron energy achieved during the pulse, which shows an inverse relationship with pressure, leading to fewer excited species and combustion radicals. The poor performance of methane/air mixture ignition at high pressure is explained by an analysis of the reaction pathways. At high pressures (p0 ∼ 30 atm), H is consumed mostly to form hydroperoxyl (HO2), leading to a bottleneck in the formation of formyl (HCO) from formaldehyde (CH2O). Instead, for ethylene/air ignition, at both low and high pressures there exist several bypass pathways that facilitate the formation of HCO and CO directly from various intermediates, explaining the more robust performance of PAI for ethylene at pressure.

The (p, ρ, T) behavior of trifluoroethene (R1123) was investigated with the isochoric method. A total of 87 (p, ρ, T) data were measured along nine isochores (42, 98, 151, 197, 296, 493, 691, 790, and 888 kg · m − 3 ) at temperatures from 300 K to 430 K and pressures up to 6.9 MPa. The uncertainties in temperature are estimated to be within 10 mK below 380 K and 20 mK at higher temperatures, and the uncertainties in pressure are estimated to be within 1 kPa below 380 K and 2 kPa at higher temperatures. The estimated relative uncertainties in the density measurements are 0.15 % or less. A new Helmholtz energy equation of state was formulated based on the (p, ρ, T) data and recently published experimental data for the vapor pressure, liquid and vapor densities including those at saturation, vapor-phase sound speed, and ideal-gas isobaric heat capacity. The equation is applicable at temperatures from the triple-point temperature (195.15 K) to 480 K and pressures up to 20 MPa. Typical uncertainties in calculated properties are 0.1 % for vapor pressures, 0.1 % for liquid densities, and 0.2 % for vapor densities, except in the critical region where larger deviations up to about 1.5 % are sometimes observed in densities. The uncertainties in calculated vapor-phase sound speeds and ideal-gas isobaric heat capacities are 0.03 % and 1 %, respectively. The equation shows reasonable extrapolation behavior at extremely low and high temperatures, and at high pressures.

The class of Double-Double Radio Galaxies (DDRGs) relates to episodic jet outbursts. How various regions and components add to the total intensity in radio images is less well known. In this paper we synthesize synchrotron images for DDRGs based on special relativistic hydrodynamic simulations, making advanced approximations for the magnetic fields. We study the synchrotron images for: Three different radial jet profiles; Ordered, entangled or mixed magnetic fields; Spectral ageing from synchrotron cooling; The contribution from different jet components; The viewing angle and Doppler (de-)boosting; The various epochs of the evolution of the DDRG. To link our results to observational data, we adopt to J1835+6204 as a reference source. In all cases the synthesized synchrotron images show two clear pairs of hotspots, in the inner and outer lobes. The best resemblance is obtained for the piecewise isochoric jet model, for a viewing angle of approximately $\vartheta \sim -71^{\circ}$, i.e. inclined with the lower jet towards the observer, with predominantly entangled ($\gtrsim 70$ per cent of the magnetic pressure) in turbulent, rather than ordered fields. The effects of spectral ageing become significant when the ratio of observation frequencies and cut-off frequency $\nu_{\rm obs}/\nu_{\infty,0} \gtrsim 10^{-3}$, corresponding to $\sim 3 \cdot 10^2$ MHz. For viewing angles $\vartheta \lesssim -30^{\circ}$, a DDRG morphology can no longer be recognized. The second jets must be injected within $\lesssim$ 4 per cent of the lifetime of the first jets for a DDRG structure to emerge, which is relevant for Active Galactic Nuclei feedback constraints., Comment: 24 pages, 8 figures

The enhanced interest in greater convenience foods has recently led to the expansion of minimally processed potato products. This study investigated the effects of isochoric freezing on pre-peeled potato cubes, including quality attributes (microstructure, texture, and color), nutritional value (ascorbic acid (AA) content, total phenolic content, and antioxidant capacity), and polyphenol oxidase activity. Isochoric freezing (-3 °C/30 MPa) was compared with isobaric freezing (-3 °C/0.1 MPa) and individual quick freezing followed by frozen storage at -20 °C for 4 weeks. The isochoric sample had lower drip loss and volume shrinkage as well as better preserved texture and microstructure than the other samples. All freezing methods caused an increase in total phenolic content and antioxidant capacity, but a decrease in AA content. Also, all freezing methods caused browning of the thawed potatoes, but isochoric freezing delayed its onset for more than 1 week. PRACTICAL APPLICATION: Results showed that isochoric freezing of pre-peeled and cut potatoes caused less freeze damage than isobaric and individual quick freezing, which might find application in the commercial preservation of minimally processed food products.

High-intensity short-pulse lasers have made possible the generation of energetic proton beams, unlocking numerous applications in high energy density science. One such application is uniform and isochoric heating of materials to the warm dense matter (WDM) state. We have developed a new experimental platform to simultaneously create and probe WDM at the matter in extreme conditions (MEC) end station at the Linac Coherent Light Source (LCLS). The short pulse optical laser (delivering up to 1 J in 45 fs) and the ultrabright LCLS X-ray laser with tunable frequency, respectively, deliver high power required to heat materials to WDM and precision-timed high-resolution X-rays to probe them. The laser-accelerated proton beam driven from a flat 1.5- $\mu \text{m}$ Cu foil was first measured then directed to a secondary sample of Al or polypropylene (PP), typically 300– $400~\mu \text{m}$ away. The time evolution of the sample electron temperature was measured using streaked optical pyrometry, where we observed a peak temperature of 0.9 ± 0.15 eV on the rear surface of an Al sample heated by the proton beam. Simulations using the hybrid-PIC code LSP and the rad-hydro code HELIOS show that a measured proton beam can heat Al to approximately 4 eV and PP to 1 eV if instead focused by a hemispherical Cu target. Through additional LSP simulations, we anticipate creating hotter WDM states (~20 eV) by increasing the laser energy to 10 J and keeping the other laser parameters fixed.

In this contribution, the phase change of unvulcanized to vulcanized rubber is described by a thermo-mechanical material model within the finite element method (FEM) framework. Before the vulcanization process (curing), rubber exhibits an elasto-visco-plastic behaviour with significant irreversible deformations without a distinct yield surface. After exposing rubber to high temperature, the molecular chains build-up crosslinks among each other and its mechanical behaviour changes to stiffer viscoelastic material. The proposed model assumes, that both phases are present during the vulcanization process. The ratio changes from the uncured phase at the beginning to the cured phase according to the current state of cure. A constitutive curing formulation is introduced into the model, to capture the shape change during the vulcanization and to ensure, that the second law of thermodynamics is fulfilled. A multiplicative split of the deformation gradient is assumed to describe incompressible material. Thermal expansion due to the change of temperature is taken into account in the volumetric part, as well as shrinkage during the vulcanization process. In the isochoric part, the phase change from elasto-visco-plastic to viscoelastic material is described by micro-macro transition based on the micro-sphere model. The consistent formulation of the material model and its tangent are important for a successful implementation into a three-dimensional finite strain FEM framework. The capabilities of the model are shown by the simulation of an axisymmetric tire production process starting at the green tire inserted into the heating press up to a post-cure inflation step.

Elastic tubes can experience surface instabilities when compressed beyond a critical strain, referred to as Wilkes instability herein. Soft materials may undergo the Rayleigh–plateau instability which is driven by surface tension. However, the surface instability of soft elastic tubes can be impeded by the coexistence of axial compression and surface tension. In this paper, we adopted an analytical framework for predicting the surface instability of an incompressible tube accounting for both axial loading and surface tension. A general solution in a mixed cylindrical coordinate is derived for determining isochoric transformations based on energy variational method. A linear perturbation analysis was performed to find out the critical elasto-capillary number and axial stretch for the onset of the instability. Cylindrical tubes with different thickness, i.e., the ratio of outer to inner radii, are investigated. We find that thinner tubes are more likely to experience surface instability than thicker ones, as validated by finite element simulations. We conclude that a compressive strain could prevent the Rayleigh–plateau instability induced by surface tension, while stretching will favor it. Similarly, the surface tension behaves as a barrier to the formation of compression-induced Wilkes instability.

In this contribution, the transition in the thermo-mechanical properties of unvulcanized rubber during the vulcanization (curing) process is modeled by a material model for unvulcanized and vulcanized rubber (two-phase material) in the context of finite strain thermo-mechanics within the finite element method (FEM). For the vulcanization rate, a constitutive approach with few parameters is proposed representing the monotonic increase of the degree of vulcanization as a function of current temperature and the curing history. The material model taking into account the two phases of rubber uses different constitutive approaches for the isochoric part and the volumetric part for which a multiplicative split of the deformation gradient is considered. The isochoric part of the model consists of a hyperelastic spring and a dashpot device in series forming a Maxwell element with properties depending on the degree of vulcanization and temperature. Inelastic isochoric deformations during the forming and vulcanization process of rubber parts can be captured. The volumetric part consists of a hyperelastic spring and takes into account volume changes due to mechanical loads and temperature variations (thermal expansion). The proposed material model is formulated based on the displacement field, the temperature field, the degree of vulcanization and its kinetics. It is implemented into the thermo-mechanically coupled framework of the FEM in 3D for finite strains.

The stability of spherical nanoclusters of methane and carbon dioxide hydrates in the environment of supercooled water has been studied by the molecular dynamics method under the isochoric and isobaric conditions. The process of system melting has been considered within a temperature range of 180–280 K and at pressures of 1, 50, and 100 atm (under isobaric conditions). It has been shown that clusters of CO2 hydrate melt at temperatures lower than clusters of CH4 hydrate do. The difference between the melting temperatures of the hydrates is about 40 K, which is explained by the higher solubility of carbon dioxide in water. The diffusion coefficients calculated for water and the gases attest to different mechanisms of melting their hydrates. The stability of the hydrates under the isochoric conditions appears to be lower than that under the isobaric conditions. For simulation under isobaric conditions, changes in the pressure and the degree of carbon dioxide filling have no effect on the position of the range of melting of hydrate nanoclusters.

The temperature dependence of the crystallographic and thermoelastic properties of BaZrO3 perovskite in the temperature range 4.2 K and 450 K has been investigated using high-resolution time-of-flight neutron powder diffraction and literature values of the isobaric heat capacity. At all measured temperatures, BaZrO3 is cubic, space group $$Pm\overline{3} m$$Pm3¯m, with no clear evidence for diffuse scattering at critical points of the primitive cubic Brillouin zone. Simultaneous fitting of the temperature dependences of the isochoric heat capacity and unit cell volume showed the thermophysical properties of BaZrO3 were consistent with a two-term Debye model in which the cations and anions behave independently of one another with Debye temperatures of 220(2) K and 730(5) K, respectively. This model is further consistent with the temperature variations of the atomic displacement parameters fitted to a modified Debye model in which the vibrational Debye temperatures of the anion are significantly larger than those associated with the cations. The evolution of the crystallographic parameters of BaZrO3 is compared to those of BaCeO3, for barium in the cavity site, and SrZrO3, for zirconium in the octahedral site.

Water expands upon freezing. What happens when water is cooled below 0 °C in an undeformable, constant-volume container? This is a fundamental question in materials thermodynamics, and is also relevant in biological, geological, and technological applications in which ice forms under nano-, meso-, or macroscale confinement. Here, we analyze the phase-equilibria and kinetic behaviors of water and ice-1h in an isochoric (constant-volume) system. By making use of the Helmholtz potential F(temperature, volume), in contrast to the Gibbs potential G(temperature, pressure), we demonstrate significant changes in phase behavior when the specific volume of the container is constrained below that of ice-1h. We construct a T–V (temperature–volume) phase diagram for water and ice that features a broad two-phase equilibrium region, and we further derive an isochoric nucleation theory that reveals the existence of a critical confinement volume, on the order of microns, below which ice-1h is kinetically prohibited from forming. Water expands upon freezing, so what happens when it is brought below 0 °C in an undeformable, constant-volume container? Here, the authors use classical thermodynamics and kinetics to derive the phenomenology of freezing in an isochoric chamber, developing a framework therefrom to study the origin of the limiting effects of confinement on ice formation.

Optimization of protein formulations at subzero temperatures is required for many applications such as storage, transport, and lyophilization. Using isochoric cooling (constant volume) is possible to reach subzero temperatures without freezing aqueous solutions. This accelerates protein damage as protein may unfold by cold denaturation and diffusional and conformational freedom is still present. The use of isochoric cooling to faster protein formulations was first demonstrated for the biomedical relevant protein disulfide isomerase A1. Three osmolytes, sucrose, glycerol, and l-arginine, significantly increased the stability of protein disulfide isomerase A1 at -20°C with all tested under isochoric cooling within the short time frame of 700 h. The redox green fluorescent protein 2 was used to evaluate the applicability of isochoric cooling for stability analysis of highly stable proteins. This derivative of GFP is 2.6-fold more stable than the highly stable GFP β-barrel structure. Nevertheless, it was possible to denature a fraction of roGFP2 at -20°C and to assign a stabilizing effect to sucrose. Isochoric cooling was further applied to insulin. Protein damage was evaluated through a signaling event elicited on human hepatocyte carcinoma cells. Insulin at -20°C under isochoric cooling lost 22% of its function after 15 days and 0.6M sucrose prevented insulin deactivation. Portuguese national funds from FCT - Foundation for Science and Technology UID/Multi/04326/2019;Portugal 2020, CRESC Algarve 2020, Lisboa 2020 European Union (EU) 17653 info:eu-repo/semantics/publishedVersion

This paper presents a novel approach to soil–water retention modelling that is based on the analysis of the material pore network. The approach postulates the existence of a differential coupling function, which relates the variation of water ratio to the variation of void ratio at constant suction. Distinct differential coupling functions have been considered, and the most general option has been integrated in a closed-form relationship between water ratio and void ratio with a suction-dependent integration constant, whose expression describes the isochoric retention behaviour. Four alternative expressions of the suction-dependent integration constant have been proposed resulting in four different, but equivalent, models linking degree of saturation, void ratio and suction. Each model predicts the variation of degree of saturation by means of four parameters, namely two parameters accounting for the effect of void ratio and two parameters accounting for the effect of suction. The models have been calibrated against laboratory data from soils with distinct particle size distributions and have shown accurate predictions of degree of saturation at different levels of suction and void ratio. Validation against additional data has also indicated that the models can extrapolate the soil behaviour to stress paths and suction levels beyond those considered during calibration.

Based on the Mie–Lennard-Jones interatomic pair potential and the Einstein crystal model, the thermal equation of state and the pressure dependences of the thermophysical properties of niobium are obtained. The pressure dependences of the Debye temperature, the first, second, and third Gruneisen parameters, isothermal compression modulus, isochoric and isobaric heat capacity, thermal expansion coefficient, and the pressure derivatives of these parameters along the 300 and 3000 K isotherms are studied. The calculations showed good agreement with experimental data. Based on the results obtained, the pressure dependence of the melting point of niobium and its pressure derivative are calculated.

The density ρ at atmospheric pressure and compression ratios k = Δ V / V o of the {water (1) + acetamide (2)} mixture in the range of temperature from 278.15 K to 323.15 K (278.15, 288.15, 298.15, 308.15, 323.15), pressures from 10 to 100 MPa (10, 25, 50, 75 and 100) and in a wide range of compositions (maximum mole fraction of acetamide (AA) x2 = 0.3875) were measured in the work. The partial molar volumes of both components V ¯ 1 and V ¯ 2 in the mixture, molar isothermal compression K T , m , molar isobaric thermal expansion E P , m , isochoric coefficient of thermal pressure β V , and internal pressure of the mixture P int were calculated. The volume characteristics for an infinitely dilute AA solution in water: limiting partial molar volumes V ¯ 2 ∞ , limiting partial molar isothermal compression K ¯ T ,2 ∞ , and limiting partial molar isobar expansion E ¯ P ,2 ∞ were calculated. The obtained results are discussed from the standpoint of interactions of solute-solvent and solute-solute. The obtained results are discussed in terms of solute-solvent and solute-solute interactions.

We continue in this paper to illustrate the implications of the Dual Model of Liquids (DML) by deriving the expression for the isochoric specific heat as function of the collective degrees of freedom available at a given temperature and analyzing its dependence on temperature. Two main tasks will be accomplished. First, we show that the expression obtained for the isochoric specific heat in the DML is in line with the experimental results. Second, the expression will be compared with the analogous one obtained in another theoretical dual model of the liquid state, the Phonon Theory of Liquid Thermodynamics. This comparison will allow to get interesting insights about the number of collective degrees of freedom available in a liquid and on the value of the isobaric thermal expansion coefficient, two quantities that are related to each other in this framework.

Can CP be less than CV ? This is a fundamental question in physics, chemistry, chemical engineering, and mechanical engineering. This question hangs in the minds of many students, instructors, and researchers. The first instinct is to answer "Yes, for water between 0 and 4 °C" if one knows that water expands as temperature decreases in this temperature range. The same question is asked in several Physical Chemistry and Physics textbooks. Students are supposed to answer that water contracts when heated at below 4 °C in an isobaric process. Because work is done to the contracting water, less heat is required to increase the water temperature in an isobaric process than in an isochoric process. Therefore, CP is less than CV . However, this answer is fundamentally flawed because it assumes, implicitly and incorrectly, that the internal energy change of water depends solely on its temperature change. Neglecting the variation of the internal energy with volume (internal pressure) will invalidate the Clausius inequality and violate the second law of thermodynamics. Once the internal pressure is properly taken into account, it becomes clear that CP cannot be less than CV for any substance at any temperature regardless of the sign of the thermal expansion coefficient of the substance.

In this paper we study a new class of holographic heat engines via charged AdS black hole solutions of Einstein gravity coupled with logarithmic nonlinear $U(1)$ gauge theory. So, Logarithmic $U(1)$ AdS black holes with a horizon of positive, zero and negative constant curvatures are considered as a working substance of a holographic heat engine and the corrections to the usual Maxwell field are controlled by non-linearity parameter $\beta$. The efficiency of an ideal cycle ($\eta$), consisting of a sequence of isobaric $\to$ isochoric $\to$ isobaric $\to$ isochoric processes, is computed using the exact efficiency formula. It is shown that $\eta/\eta_{C}$, with $\eta_{C}$ the Carnot efficiency (the maximum efficiency available between two fixed temperatures), decreases as we move from the strong coupling regime ($\beta \to 0$) to the weak coupling domain ($\beta \to \infty$). We also obtain analytic relations for the efficiency in the weak and strong coupling regimes in both low and high temperature limits. The efficiency for planar and hyperbolic logarithmic $U(1)$ AdS black holes is computed and it is observed that efficiency versus $\beta$ behaves in the same qualitative manner as the spherical black holes., Comment: 23 pages, 20 figures, accepted version

The Taishanmiao granitic batholith, located in the Eastern Qinling Orogen in Henan Province, China, contains numer-ous small (mostly tens of centimeters in maximum dimension) bodies exhibiting textures and mineralogy characteristics of simple quartz and alkali feldspar pegmatites. Analysis of melt inclusions (MI) and fluid inclusions (FI) in pegmatitic quartz, combined with Rhyolite-MELTS modeling of the crystallization of the granite, have been applied to develop a conceptual model of the physical and geochemical processes associated with the formation of the pegmatites. These results allow us to consider the formation of the Taishanmiao pegmatites within the context of varios models that have been proposed for pegmatite formation. Field observations and geochemical data indicate that the pegmatites represent the latest stage in the crystallization of the Taishanmiao granite and occupy

An alternative elastoplastic model based on the Flory’s right Cauchy-Green stretch tensor decomposition is proposed and applied to model soft cores of sandwich panels. It does not follow usual methodologies as the additive decomposition or the Kroner-Lee multiplicative decomposition of strains. It is based on an important hyperelastic relation, Flory’s decomposition, from which the total strain is separated in two isochoric and one volumetric parts. Using this decomposition, the volumetric strain energy continues to be elastic during all elastoplastic analysis and the isochoric parts are managed to produce the plastic evolution. As a consequence of Flory’s decomposition, the plastic flow direction is known and independent of the yielding surfaces. Moreover, it provides the well known deviatoric nature of plastic strains. For validation purposes, the resulting formulation is implemented using a special 3D prismatic element in a geometrical nonlinear positional FEM computational code. The achieved numerical results are compared with literature experimental data of soft core laminated structural elements.

Experimental techniques, such as cryo-electron microscopy, require biological samples to be recovered at cryogenic temperatures (T ≈ 100 K) with water being in an amorphous ice state. However, (bulk) water can exist in two amorphous ices at P < 1 GPa, low-density amorphous (LDA) ice at low pressures and high-density amorphous ice (HDA) at high pressures; HDA is ≈ 20 – 25% denser than LDA. While fast/plunge cooling at 1 bar brings the sample into LDA, high-pressure cooling (HPC), at sufficiently high pressure, produces HDA. HDA can also be produced by isothermal compression of LDA at cryogenic temperatures. Here, we perform classical molecular dynamics simulations to study the effects of LDA, HDA, and the LDA-HDA transformation on the structure and hydration of a small peptide, polyalanine. We follow thermodynamic paths corresponding to (i) fast/plunge cooling at 1 bar, (ii) HPC at P = 400 MPa, and (iii) compression/decompression cycles at T = 80 K. While process (i) produced LDA in the system, path (iii) produces HDA. Interestingly, the amorphous ice produced in process (ii) is an intermediate amorphous ice (IA) with properties that fall in-between those of LDA and HDA. Remarkably, the structural changes in polyalanine are negligible at all conditions studied (0 – 2000 MPa, 80 – 300 K) even when water changes among the low and high-density liquid states as well as the amorphous solids LDA, IA, and HDA. The similarities and differences in the hydration of polyalanine vitrified in LDA, IA, and HDA are described. Since the studied thermodynamic paths are suitable for the cryopreservation of biomolecules, we also study the structure and hydration of polyalanine along isobaric and isochoric heating paths, which can be followed experimentally for the recovery of cryopreserved samples. Upon heating, the structure of polyalanine remains practically unchanged. We conclude with a brief discussion of the practical advantages of (a) using HDA and IA as a cryoprotectant environment (as opposed to LDA), and (b) the use of isochoric heating as a recovery process (as opposed to isobaric heating).

We report the speeds of sound in liquid toluene (methylbenzene) measured using double-path pulse-echo apparatus independently at The University of Western Australia (UWA) and Imperial College London (ICL). The UWA data were measured at temperatures between (306 and 423) K and at pressures up to 65 MPa with standard uncertainties of between (0.02 and 0.04)%. At ICL, measurements were made at temperatures between (283.15 and 473.15) K and at pressures up to 390 MPa with standard uncertainty of 0.06%. By means of thermodynamic integration, the measured sound-speed data were combined with initial density and isobaric heat capacity values obtained from extrapolated experimental data to derive a comprehensive set of thermodynamic properties of liquid toluene over the full measurement range. Extensive uncertainty analysis was performed by studying the response of derived properties to constant and dynamic perturbations of the sound-speed surface, as well as the initial density and heat capacity values. The relative expanded uncertainties at 95% confidence of derived density, isobaric heat capacity, isobaric expansivity, isochoric heat capacity, isothermal compressibility, isentropic compressibility, thermal pressure coefficient and internal pressure were estimated to be (0.2, 2.2, 1.0, 2.6, 0.6, 0.2, 1.0 and 2.7)%, respectively. Due to their low uncertainty, these data and derived properties should be well suited for developing a new and improved fundamental Helmholtz equation of state for toluene.

Unsaturated hydraulic characteristics of compacted smectite clays are essential in many engineering applications. The knowledge of the accurate soil-water characteristic curve (SWCC) and hy...

In a recent experimental campaign, we used laser-accelerated relativistic hot electrons to ensure heating of thin titanium wire targets up to a warm dense matter (WDM) state [EPL 114, 45002 (2016)10.1209/0295-5075/114/45002]. The WDM temperature profiles along several hundred microns of the wire were inferred by using spatially resolved X-ray emission spectroscopy looking at the Ti Kα characteristic lines. A maximum temperature of ∼30 eV was reached. Our study extends this work by discussing the influence of the laser parameters on temperature profiles and the optimisation of WDM wire-based generation. The depth of wire heating may reach several hundreds of microns and it is proven to be strictly dependent on the laser intensity. At the same time, it is quantitatively demonstrated that the maximum WDM temperature doesn’t appear to be sensitive to the laser intensity and mainly depends on the deposited laser energy considering ranges of 6×1018–6×1020 W/cm2 and 50–200 J.

The equation of state P ( v / v o ) and the baric dependences of both the lattice and the surface properties for macro- and nano- crystals germanium were calculated by means of the method with using the Mie-Lennard-Jones pairwise interatomic potential and by of the RP-model of a nanocrystal. It is shown that at a certain value of the relative volume ( v / v o ) 0 , the isothermal dependences P ( v / v o ) for the macro- and nano-crystal intersect. At the intersection point (at ( v / v o ) 0 ), the surface pressure becomes zero. The value ( v / v o ) 0 decreases both with an isomorphic-isomeric rise in temperature, and with an isomorphically-isothermal decrease in the number of atoms in a nanocrystal, or with an isomeric-isothermal deviation of the shape of the nanocrystal from the energy-optimal shape (for the RP-model it is a cube). Based on the obtained equation of state, the change in 23 properties of germanium was studied both at an isochoric ( v / v o = 1) and at an isobaric ( P = 0) decrease in the number of atoms in a nanocrystal at temperatures of 100, 300, and 1000 K. It is shown that at an isobaric ( P = 0) decrease in size, the specific volume of the germanium nanocrystal increases the more, the higher the temperature of the nanocrystal.

In this work phase equilibrium conditions for structure II (sII) gas hydrates in systems containing a mixture of salts (NaCl, KCl, CaCl2, MgCl2) and methanol have been measured using a high-pressure cell. The concentration of salts in aqueous solution (model of reservoir water) was constant in all experiments and equal to 18 wt%. Phase equilibrium conditions were determined by the isochoric method for pressures ranging from 1 to 4.7 MPa and for mass fraction of methanol from 0 to 50 wt%. The experimental data were obtained for water + salts, water + methanol, and water + salts + methanol systems. From the results obtained, it follows that 20 wt% of methanol in distilled water (DW) gives the thermodynamic shift of the hydrate decomposition temperature close to the brine one. Mixtures of 10% methanol + brine and 20% methanol + brine significantly better reduce the equilibrium temperature of hydrate dissociation compared to samples with the similar total mass fraction of inhibitor (methanol) in water (30, 40 wt%). At the pressures of more than 4 MPa combination of 20 wt% methanol + brine provide the same thermodynamic inhibition as 50 wt% of methanol in water. Thus, the synergism of the methanol + salts mixtures in the thermodynamic inhibition of sII gas hydrates has been observed. Synergism manifested itself in a greater shift of equilibrium curves to lower temperatures and higher pressures compared to systems containing only one thermodynamic hydrate inhibitor (THI). The obtained results indicate the possibility of a significant reduction in the consumption of polar organic THI for gas hydrate prevention in deposits with highly mineralized brine. However, it is necessary to take into account the possible complications associated with the precipitation of salts from solutions of water – salt(s) – polar organic THI due to the possible limited mutual solubility of the components.

The phenomenological behavior of the Widom line above the vapor-liquid critical point for the Lennard-Jones (LJ) potential is investigated using four accurate equations of state (EoS) and a comparison with molecular dynamics (MD) simulation data. This involved calculating the supercritical maximum values of the isochoric heat capacity (CV), isobaric heat capacity (Cp), isothermal compressibility (βT), and thermal expansion coefficient (αp). All LJ EoS predict the pressure (p)-temperature (T) Widom line behavior. In contrast, the T-density (ρ) Widom line behavior, observed in MD simulations, is not predicted by any LJ EoS. The calculations highlight the important role of βT in determining the range of p and T for which Widom line behavior is observed. Analysis of MD data for the supercritical maximum/minimum of CV and Cp suggests the extension of a Clausius-Clapeyron-type relationship from the triple point to the supercritical region. This provides a new description of the Widom line as the near critical part of this larger curve for which other thermodynamic functions also have maximum values.

A gauge theory of solids with conformal symmetry is formulated to model various electromechanical and magnetomechanical coupling phenomena. If the pulled back metric of the current configuration (the right Cauchy-Green tensor) is scaled with a constant, the volumetric part of the Lagrange density changes while the isochoric part remains invariant. However, upon a position dependent scaling, the isochoric part also loses invariance. In order to restore the invariance of the isochoric part, a 1-form compensating field is introduced and the notion of a gauge covariant derivative is utilized to minimally replace the Lagrangian. In view of obvious similarities with the Weyl geometry, the Weyl condition is imposed through the Lagrangian and a minimal coupling is employed so the 1-form could evolve. On deriving the Euler-Lagrange equations based on the action functional, we observe a close similarity with the governing equations for flexoelectricity under isochoric deformation if the exact part of 1-form is interpreted as the electric field and the anti-exact part as the polarization vector. Next, we model piezoelectricity and electrostriction phenomena by contracting the Weyl condition in various ways. Applying the Hodge decomposition theorem on the 1-form which leads to the curl of a pseudo-vector field and a vector field, we also model magnetomechanical phenomena. Identifying the pseudo-vector field with magnetic potential and the vector part with magnetization, flexomagnetism, piezomagnetism and magnetostriction phenomena under isochoric deformation are also modeled. Finally, we consider an analytical solution of the equations for piezoelectricity to provide an illustration on the insightful information that the present approach potentially provides., Comment: 46 pages, 1 figure

Phase equilibrium conditions (dissociation data) for clathrate hydrates (gas hydrates) were studied for systems involving fluorinated refrigerants + water + single and mixed electrolytes (NaCl, CaCl2, MgCl2 and Na2SO4) at varying salt concentrations in the absence and presence of cyclopentane (CP). The ternary systems for (R410a or R507) + water + CP were performed in the temperature and pressures ranges of (279.8–294.4) K and (0.158–1.385) MPa, respectively. Measurements for {R410a + water + (NaCl or CaCl2) + CP} were undertaken at salt concentrations of (0.10, 0.15 and 0.20) mass fractions in the temperature and pressure ranges of (278.4–293.7) K and (0.214–1.179) MPa, respectively. The temperature and pressure conditions for the (R410a + water + Na2SO4) system were investigated at salt concentration of 0.10 mass fraction in range of (283.3–291.6) K and (0.483–1.373) MPa respectively. Measurements for {(R410a or R507) + water + mixed electrolytes NaCl, CaCl2, MgCl2} were undertaken at various salt concentrations of (0.002–0.15) mass fractions in the temperature and pressure ranges of (274.5–292.9) K and (0.149–1.119) MPa in the absence and presence of CP, for which there are no published data related to mixed salt and a promoter. The phase equilibrium measurements were performed using a non-visual isochoric equilibrium cell and the pressure-search technique. This study was focused on obtaining equilibrium data that can be utilized to design and optimize for water desalination process and the development of a Hydrate Electrolyte–Cubic Plus Association (HE–CPA) Equation of State based model. The results indicate hydrate dissociation pressure reduction/hydrate dissociation temperature increase up to ambient conditions in the presence of promoter (CP). The experimental results were then modelled. The modelling results are in good agreement with the measured hydrate dissociation data.

In this paper we have studied two non-linear black holes in 2+1 dimensions. They are regular and could have two horizons for chosen values of the parameters in the theory. Thermodynamics of the two black holes are studied in the extended phase space where the pressure P = -{\Lambda}/8{\pi}. In order to satisfy the Smarr formula and the first law of thermodynamics, a renormalization parameter is introduced. Hence there is an additional thermodynamical parameter for the black hole. We have also studied the two black holes in the context of heat engines. A thermodynamical cycle, consisting of two isobaric and two isochoric is considered. Efficiency is computed by varying the non-linear parameter and the electric charge of the black hole. It is observed that when the non-linear parameter and the charge increases, the efficiency increases. When compared to the charged BTZ black hole, the efficiency for the rectangle cycle is smaller for the regular black holes., Comment: 5 figures; to appear in Phys. Lett. B

One- ( C V1 ) and two-phase ( C V2 ) liquid + vapor equilibrium isochoric heat capacities, densities ( ρ S ), and phase-transition temperatures ( T S ) of 2-propanol were measured in the critical region. Measurements were made in the immediate vicinity of the liquid–gas phase transition and critical point in order to accurately determine the locus of phase-transition properties ( T S , ρ S , C V1 , and C V2 ). Additional measurements were made over an extended temperature range from (317 to 525) K for 9 liquid and 3 vapor isochores between (234 and 697) kg⋅m−3 at pressure up to 6.5 MPa. The measurements were performed using a high-temperature, high-pressure, nearly constant-volume adiabatic piezo-calorimeter. The standard uncertainty of the density, temperature, and isochoric heat capacity ( C V ) measurements is estimated to be 0.1%, 0.02 K, and 1.5%, respectively. The measured one- ( C V1 ) and two-phase ( C V2 ) isochoric heat capacities along the critical isochore and the saturated liquid ( ρ S ' ) and vapor ( ρ S '' ) densities near the critical point were used to derive theoretically meaningful asymptotic critical amplitudes ( A 0 ± and B 0 ) and related amplitudes for other properties ( Γ 0 + , D 0 , ξ 0 ) and their universal relations, A 0 + / A 0 - , A 0 + Γ 0 + B 0 2 , α A 0 + Γ 0 + B 0 - 2 , D 0 Γ 0 + B 0 δ - 1 , ξ 0 α A 0 + v C 1 / 3 and the asymmetric parameters a 3 and b 2 of the coexistence curve singular diameter. Experimental two-phase heat capacities C V2 as a function of specific volume V , along various isotherms, were used to calculate second temperature derivatives of vapor pressure d 2 P S d T 2 and chemical potential d 2 μ d T 2 and to estimate the value of the Yang-Yang anomaly strength parameter R μ for 2-propanol. The relative contributions of the vapor pressure, C VP = V C T d 2 P S d T 2 , and the chemical potential, C V μ = - T d 2 μ d T 2 , to the measured total two-phase C V2 were estimated.

Phase behaviour including phase equilibria and dissociation enthalpies and structure of double semiclathrate hydrates formed with tetrabutylammonium fluoride (TBAF) + CH4 were measured to evaluate the performance of TBAF for hydrate based industrial applications. The phase equilibria and the dissociation enthalpies for TBAF + CH4 semiclathrate hydrate (SCH) with (0.02–0.15) salt mass fraction were obtained by employing the isochoric pressure-search method and calculated from the experimental data with Clausius-Clapeyron equation, respectively. A confocal Raman spectrometer was applied to analyze the structure of (TBAF + CH4) SCHs. Data showed that TBAF strongly enhanced the stability of CH4 hydrates by increasing the equilibrium temperature at a given pressure. The Raman spectra revealed that small 512 cages of TBAF hydrates could trap CH4 molecules. In particular, the Raman spectra of double TBAF + CH4 SCHs, as compared with those of pure TBAF SCHs, indicated that the large cages which already trapped the cation of TBAF also had the possibility of encaging CH4 molecules at low salt concentrations (

With the emerging application of near-critical fluid, the subject of equation of state (EoS) covering the critical point is of great significance as the thermodynamic behavior of fluids near the critical point is different. Although many different EoSs are available for fluids at the moment, the ones which can give good quantitative results are still rare. Therefore, it is essential to have a suitable model for proper prediction of fluids behavior and their thermodynamic properties near the critical region. In this study, the crossover translation, which applies the asymptotic behavior of fluids and scaling laws near and far from the critical point, was used. Thermodynamic properties including density, vapor pressure and isochoric heat capacity of fifteen pure components in the saturated state and single-phase region on different isotherms were investigated near the critical point by Soave-Redlich-Kwong (SRK) equation of state and crossover SRK EoS and the results were compared with experimental data. According to the results, crossover SRK EoS predicted all of the mentioned properties with quantitative accuracy. The average absolute percent deviation (AAPD) of the saturated liquid density, saturated vapor density, density on isotherms, vapor pressure and isochoric heat capacity based on crossover SRK EoS were 0.0060,0.1287, 0.0171, 0.057 and 2.53, respectively.

A complete description of fluid-phase thermodynamic properties at cryogenic conditions undoubtedly presents a serious challenge for equations of state (EOSs). This work is focused on comparing the capabilities of two Statistical Associating Fluid Theory-based EoSs, namely PC-SAFT, SAFT + Cubic, and one cubic model, the original PR EOS, in correlating and predicting various thermodynamic properties of 14 main cryogenic fluids (noble gases, light hydrocarbons, nitrogen, oxygen, carbon dioxide, carbon monoxide, and nitrous oxide). Additionally, the available low temperature vapor-liquid equilibrium (VLE) data of their binary and ternary mixtures are also evaluated in this comparative study. It has been found that, apart from the critical and near-critical data, PC-SAFT has a clear advantage in modeling the pure compound properties such the sound velocity and density (with the overall AADs% less than 7%). Nevertheless, the overestimation of the single phase properties in low temperature and high pressure regions and the poor accuracy in modeling the high pressure VLE compositions of binary mixtures are two major drawbacks of PC-SAFT. SAFT + Cubic is less accurate in predicting pure compound properties; however, having small values of binary interaction parameters, it is slightly more accurate than PC-SAFT in modeling various VLE isotherms of mixtures in a predictive manner (with the overall AADs around 3%). At the same time, PR EOS exhibits the most significant deviations from the low temperature experimental data of both pure cryogens and their mixtures. However, it yields particularly accurate predictions of isochoric heat capacities in the liquid phase.

An experimental study of the pressure–volume–temperature-composition ( P V T x ) properties in the gas phase for the R290 + R13I1 system was performed with an isochoric method. The measurements of R290 + R13I1 mixtures were conducted in the range of temperatures from 283.37 K to 353.29 K, pressures from 242.2 kPa to 1065.0 kPa, densities from 0.1091 moldm−3 to 0.4133 moldm−3, and compositions from 0.4502 to 0.8524 mol fraction of propane. The uncertainties in the present work were estimated to be within ±10 mK for temperature, ± 2.4 kPa for pressure, ± 0.1 mol% for mole composition and ±0.16% for density, respectively. On the basis of the experimental P V T x property data, a truncated virial equation of state was developed for the R290 + R13I1 system. This equation reproduces the experimental data in gas phase with relative deviation within ±0.23% in pressure and within ±0.25% in density.

The solubility of hydrogen sulfide (H2S) in N-methylimidazole (NMI) and gamma-butyrolactone (GBL) were experimentally measured. Gas concentrations were systematically measured by isochoric saturation method at temperatures from (303.15 to 353.15) K and pressure from vapour pressure of solvent up to about 1.2 MPa, in all experiments mole fraction of dissolved gas has been measured with uncertainty order of 10−3. In order to construct a GA-artificial neural network (ANN)-based model, the H2S solubility, molality and total pressure were selected for the output. The precision of the GA is compared with experimental data and also with thermodynamic modelling approach in which Peng-Robinson-Stryjek-Vera (PRSV) cubic equation of state with Panagiotopoulos-Reid combining rule has been chosen for this purpose.