Isobaric Conditions Research Articles

Medium-Range Structural Order as the Driver of Activated Dynamics and Complexity Reduction in Glass-Forming Liquids.

We analyze in depth the Elastically Collective Nonlinear Langevin Equation theory of activated dynamics in metastable liquids to establish that the predicted inter-relationships between the alpha relaxation time, local cage and collective elastic barriers, dynamic localization length, and shear modulus are causally related within the theory to the medium range order (MRO) static correlation length. The latter grows exponentially with density for metastable hard sphere fluids and as a nonuniversal inverse power law with temperature for supercooled liquids under isobaric conditions. The physical origin of predicted connections between the alpha time and other metrics of cage order and the thermodynamic inverse dimensionless compressibility is fully established. It is discovered that although kinetic constraints from the real space first coordination shell are important for the alpha time, they are of secondary importance compared to the consequences of the more universal MRO correlations in both the modestly and deeply metastable regimes. This understanding sheds new light on the theoretical basis for, and prior successes of, the predictive mapping of chemically complex thermal liquids to effective hard sphere fluids based on matching their dimensionless compressibilities, a scheme we call "complexity reduction". In essence, the latter is equivalent to the physical requirement that the thermal liquid MRO correlation equals that of its effective hard sphere analog. The mapping alone is shown to provide a remarkable level of quantitative predictive power for the glass transition temperature Tg of 21 molecular and polymer liquids. Predictions for the chemically specific absolute magnitude and growth with cooling of the MRO correlation length are obtained and lie in the window of 2-6 nm at Tg. Dynamic heterogeneity, elastic facilitation, and beyond pair structure issues are briefly discussed. Future opportunities to theoretically analyze the equilibrated deep glass regime are outlined.

Hydrodynamic theory of premixed flames propagating in closed vessels: flame speed and Markstein lengths

A hydrodynamic theory of premixed flame propagation within closed vessels is developed assuming the flame is much thinner than all other fluid dynamic lengths. In this limit, the flame is confined to a surface separating the unburned mixture from burned combustion products, and propagates at a speed determined from the analysis of its internal structure. Unlike freely propagating flames that propagate under nearly isobaric conditions, combustion in a closed vessel results in continuous increases in pressure, burning rate and flame temperature, and a progressive decrease in flame thickness. The flame speed is shown to depend on the voluminal stretch rate, which measures the deformation of a volume element of the flame zone, and on the rate of pressure rise. Both effects are modulated by pressure-dependent Markstein numbers that depend on heat release and mixture properties while capturing the effects of temperature-dependent transport and stoichiometry. The model applies to flames of arbitrary shape propagating in general flows, laminar or turbulent, within vessels of general configurations. The main limitation of hydrodynamic flame theories is the assumption that variations inside the flame zone due to chemistry or turbulence, which could potentially alter its internal structure, are physically unresolved. Nonetheless, the theory, deduced from physical first principles, identifies the various mechanisms involved in the combustion process as demonstrated in detailed discussions of planar flames propagating in rectangular channels and spherically expanding flames in spherical vessels. It also enables the construction of instructive models to numerically simulate the evolution of multi-dimensional and corrugated flames under confinement.

Enlarged Curvature, Torsion and Torque in Helical Conformations and the Stability and Growth of α-Peptide under the Isochoric and Isobaric Conditions: Variatonal Optimization

The torsional deformation behavior of an elastic bar with a circular cross-section was investigated by applying invariant dyadic analysis, where the small finite displacement functions advocated by Saint-Venant (1855) were fully employed. It was found that the previously overlooked circumferential shear force field generated by pure torsion on the side walls of a bar produces an unusual torque term induced by the skew-symmetric part of the deformation tensor and exhibits quadratic length dependence along the z-axis of the bar. The adaptation of this torque term for a helical conformation of α-peptides creates moments acting on the circular cross-sections and is directed along the surface normal of circular cross-sections, which coincides with the tangent vector of the helix. The projection of this torque along the z-axis of the helix varies quadratically with the azimuthal angle. The radial component of the unusual torque, which also lies along the principal normal vector of the helix, starts to perform a precession motion by tracking a spiral orbit around the z-axis, whereas its apex angle decreases asymptotically with the azimuthal angle and finally reaches a finite value depending on the height of the helix along the z-axis. The ordinary torque terms, which are also deduced from the self- and anti-self-conjugate parts of the deformation tensor, have magnitudes half that of the full torque term reported in the literature. The present results were applied to the helical conformation of α-peptides designated by {3.611} to show that the mechanical stability of strained open-ended helical conformations can be successfully achieved by spontaneous readjustments of the surface and bulk Helmholtz free energies under isothermal isochoric conditions. It has been demonstrated that the main contribution to the mechanical stability of α-peptide 3.611 cannot come alone from the electrostatic dipole-dipole interaction potential of the anti-align excess dipole pairs but also from the surface Helmholtz free energy, which is characterized by a binding free energy of -15.5 eV/molecule (-32.56 Kcal/mole) for an alpha-peptide composed of 11 amino acid residues with a critical arc length of approximately 10 nm, assuming that the shear modulus is G = 1GPa and the surface Helmholtz specific free energy density is fs = 800 erg/cm2. This result was in excellent agreement with the experimental observations of the AH-1 conformation of (Glu)n Cys at pH 8. The present theory indicates that only two excess permanent anti-align dipole pairs for one α-Helical peptide molecule is requirement to stabilize the whole secondary structure of the protein that is exposed to heavy torsional deformation during the folding processes which amounts to 7.75 eV/molecule stored electrostatic energy compared to the interfacial Helmholtz free energy of -23.25 eV/molecule, which is exposed to hydrophobic environments.

Comparison of methods for calculating the enthalpy of vaporization of binary azeotropic mixtures

Objectives. To calculate the molar enthalpy of vaporization of binary homogeneous mixtures based on isothermal and isobaric vapor–liquid equilibrium data, and to compare the results of calculation of molar enthalpy of vaporization by different methods with experimental data.Methods. Simulation of the vapor–liquid equilibrium of binary systems according to the Non-Random Two Liquid “local compositions” equation and thermodynamic calculations of molar vaporization enthalpies of binary mixtures at different conditions of vapor–liquid equilibrium were used.Results. Arrays of calculated data were obtained with regard to molar enthalpies of vaporization for 25 compositions of binary azeotropes (isothermal, isobaric conditions of phase equilibrium), and the full range of compositions of the benzene–ethanol system at atmospheric pressure.Conclusions. The accuracy of thermodynamic methods for calculating the vaporization enthalpy of binary azeotropic mixtures according to vapor–liquid equilibrium data is higher in 85% of cases for isothermal, and in 75% of cases for isobaric conditions. By taking into account the influence of temperature on the activity coefficients of components in the liquid phase, the values of excess molar enthalpy both for azeotrope compositions and for the full concentration range of the benzene–ethanol system under isobaric conditions of liquid–vapor phase equilibrium can be accurately reproduced.

An experimental and modeling study of propane oxidation kinetics in low temperature supercritical water

Propane oxidation in supercritical water was investigated at iso-thermal iso-baric conditions using a batch reactor facility. Mixtures were comprised of 0.014 % propane by volume with an equivalence ratio of 0.8 and a total density of 222 mg/mL or 610 mg/mL. Reaction times ranged from 8 to 30 min for a temperature of 375ºC at 220 or 400 bar, or 400ºC at 220 bar. Major reaction products were CO and CO2 and minor products were propene, acetone, ethene, ethanol, methane, methanol and hydrogen. New detailed chemical kinetic models were developed by combining and refining existing models using genetic optimization. Model predictions exhibited excellent agreement with experimental observations, and indicated that rates of H-abstraction and OH addition reactions involving alkanes and alkenes are affected by the supercritical water environment. Model accuracy was highly sensitive to the rates of CH3O2H = CH3O + OH and CH3 + H2O2 = CH4 + HO2.

Experimental determination and theoretical modeling of isobaric vapor–liquid equilibria, liquid mass density, surface tension and dynamic viscosity for the methyl butyrate and tert-butanol binary mixture

The purpose of this work is to provide consistent experimental measurements on the vapor–liquid equilibria (VLE) at the isobaric conditions of 50.00, 75.00 and 94.00kPa, as well as experimental determinations of the liquid mass densities, the surface tensions and the dynamic viscosities at 298.15K and 101.3kPa of the methyl butyrate + tert-butanol binary system within the whole composition range. For these goals, a Gillespie-type cell is used to carry out the VLE measurements, whereas an oscillating densimeter, a maximum differential bubble pressure tensiometer, and a rotating viscometer are used to quantify the remaining physical properties. The thermodynamical quality of the reported VLE data is validated by Fredenslund’s consistency test. Based on the VLE results, this zeotropic binary mixture exhibits a positive deviation from Raoult’s law. Furthermore, the validated data are correlated with three activity coefficient models (i.e., Wilson, NRTL, and UNIQUAC), with the Wilson equation being the most accurate one. Excess volumes, surface tensions, and liquid viscosities data are correlated by Redlich–Kister-type expansions, and the Grunberg–Nissan equation is also applied to viscosity modeling. The calculated excess volumes display a positive deviation from the ideal solution model. Regarding surface tensions, this system showcases both negative and positive deviation, althouhg slight, from the linear behavior while exhibiting the linear trend at a molar fraction of methyl butyrate of 0.758. In addition, this bimodal deviation is adequately predicted by the Chunxi model with the Wilson parameters determined from the VLE data. Finally, the dynamic viscosities data obey a strictly monotonic mole dependence predicted by Eyring’s theory, although without high accuracy. These results also reflect some interesting phenomena related to competitive association effects, which are discussed.

Development of a Meshless Kernel-Based Scheme for Particle-Field Brownian Dynamics Simulations.

We develop a meshless discretization scheme for particle-field Brownian dynamics simulations. The density is assigned on the particle level using a weighting kernel with finite support. The system's free energy density is derived from an equation of state (EoS) and includes a square gradient term. The numerical stability of the scheme is evaluated in terms of reproducing the thermodynamics (equilibrium density and compressibility) and dynamics (diffusion coefficient) of homogeneous samples. Using a reduced description to simplify our analysis, we find that numerical stability depends strictly on reduced reference compressibility, kernel range, time step in relation to the friction factor, and reduced external pressure, the latter being relevant under isobaric conditions. Appropriate parametrization yields precise thermodynamics, further improved through a simple renormalization protocol. The dynamics can be restored exactly through a trivial manipulation of the time step and friction coefficient. A semiempirical formula for the upper bound on the time step is derived, which takes into account variations in compressibility, friction factor, and kernel range. We test the scheme on realistic mesoscopic models of fluids, involving both simple (Helfand) and more sophisticated (Sanchez-Lacombe) equations of state.

Diffusion in multicomponent mixed solvent electrolyte systems

Thermodynamic ideality is often assumed in diffusion calculation, implying concentrations are assumed equal to the activities with activity coefficients of one. A general set of diffusion flux and molar flux equations are developed, incorporating equilibrium thermodynamic models for non-ideal conditions in well-known non-equilibrium diffusion theory. Derivations are based on the Maxwell-Stefan friction theory with the chemical potential as the driving force. Isothermal and isobaric conditions are assumed, and the theory does not include the Soret coefficient or the Onsager formalism.In this work, Fick's law is derived from the general diffusion theory, also as a function of activity gradients. The results illustrate that concentration cannot just be substituted by activity. Using a similar approach demonstrates that the Nernst-Planck (NP) equation may be derived from the general theory incorporating terms for migration and convection. An extended NP equation is derived including the thermodynamic correction factors (TCF) to account for the non-ideality of the liquid. The derived equation shows the improvement of the self-diffusion terms and friction coefficients in the NP equation and that the TCF enhances the observed effective diffusivities.Examples of TCF are presented using the extended UNIQUAC thermodynamic model. This is done for the CO2-NaOH-monoethyleneglycol-water system, which is typically found in wet natural gas pipeline CO2 corrosion systems. pH-stabilization is classically used in the prevention of corrosion, but the results show that glycol has a noticeable effect of the diffusion on key components in the corrosion mechanism. A TCF of 0.4 to 1.3 may be expected. This indicates that the flux calculation deviates up to 60 % from the real-life scenario if ideality is assumed. The thermodynamic model may therefore improve the diffusion calculations considerably.

Pressure studies of rod-like liquid crystals – experimental facts and theoretical deficiencies

ABSTRACT In the years 1990–2015, many liquid crystalline (LC) substances were studied under elevated pressure. The main aims of studies were to determine the P vs. T phase diagrams, the equation of state V(P,T) for isotropic and LC phases, measuring the dynamical properties of molecules (mainly the flip-flop motions) and analysing them at the isobaric, isothermal and isochoric conditions. The observed phenomena were discussed using existing theoretical models of LC state or – in the absence of them – models adopted from the field of glass-forming liquids. In the present review, the attention will be paid to a comparative data analysis for two rings compounds with the strongly polar terminal group (CN or NCS) at one site and the n-alkyl or n-alkoxy group at the other. Such molecules may well mimic the rod-like molecules commonly used in theoretical models of LC state.

Phase diagram of a rigid rod system with attractive end groups

We present a molecular dynamics study into the thermotropic liquid crystalline phase behaviour of a coarse-grained model of a rigid bolaamphiphilic molecule. The model consists of 11 spherical beads held in a fixed linear arrangement, where the two opposing terminal beads are self-attracting, mimicking hydrophilic segments and the remaining internal beads, as well as cross-bead interactions, are softly repulsive, mimicking hydrophobic organic segments. The effect of the model’s end bead self-attraction strength on liquid crystalline phase behaviour is studied. Coexistence points between the smectic A, nematic and isotropic phases exhibited by the model are determined following a thermodynamic integration pathway, using equations of state constructed by multiple histogram reweighting of simulation data. Variants of Gibbs–Duhem integration are used to trace pressure–temperature coexistence curves. Under isobaric conditions, the effect of increasing the end-group self-attraction on the nematic–isotropic coexistence temperature is relatively small; however, the nematic phase stability is reduced at the expense of a significant increase in the smectic A–nematic coexistence temperature. Lower temperature simulations show the approximate smectic A–crystalline transition temperature to be only weakly dependent on the strength of the end-group self-attraction.

Textures and Chemistry of Crystal Cargo of the Pleiades Volcanic Field, Antarctica: Potential Influence of Ice Load in Modulating the Plumbing System

Abstract The Pleiades Volcanic Field (PVF) of northern Victoria Land (Antarctica) is made up of a dozen scoria cones whose erupted products present an unusually complete evolutionary trend from alkali-basalt to trachyte. With the aim of reconstructing the evolution of the PVF plumbing system, we have investigated the petrography and chemistry of main mineral phases using scanning electron microscopy (SEM-EDS) coupled with major element analyses using an electron probe microanalyser (EPMA-WDS). We further focussed on clinopyroxene phenocrysts obtaining a more detailed characterization by means of trace laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) element analyses coupled with machine learning thermobarometry. The results indicate that fractional crystallization and magma mixing are the major processes determining the development of the complete evolution trend. While fractional crystallization is a persistently active process in all parts of the plumbing system, mixing among differently evolved magma batches pertaining to the same association is responsible for the formation of intermediate compositions in the differentiation lineage at a specific pressure range (0.4–0.5 GPa). These processes are compatible with significant residence time of magmas at depth, resulting in multiple episodes of magma mixing, as testified by resorption and overgrowth textures in phenocryst assemblage occurring under isobaric conditions. The prolonged residence time likely increased the efficiency of the mixing process, leading to the formation of magmas with intermediate composition. In turn, the build-up of volatiles during the magma differentiation at depth could have favoured the eruption of these (variably differentiated) magmas. Considering that the PVF is situated in a glacial region, a process forcing long magma residence time can be envisaged associated with increased ice loading during glacial stages. This study specifically considers the ice fluctuations in the last 100 ka, theorizing the possibility of a climate-controlled volcano plumbing system.

Hydrate Formation with the Memory Effect Using Classical Nucleation Theory

Methane hydrate formation is analytically studied in the presence of the water memory effect using the classical nucleation theory. The memory effect is introduced as a change in nucleation site from a three-dimensional heterogenous nucleation on a solid surface with cap-shaped hydrate clusters (3D-HEN) to a two-dimensional nucleation on the solid hydrate residue surface with monolayer disk-shaped hydrate clusters (2D-NOH). The analysis on the stationary nucleation of methane hydrate under isobaric conditions shows that the memory effect caused an average decrease of 4.4 K in metastable zone width, or subcooling. This decrease can be erased at higher dissociation temperatures (ΔT > 17.2 K) due to a decrease in the concentration of 2D-NOH nucleation sites. Moreover, the probability of hydrate formation is estimated for the purpose of quantifying risk associated with methane hydrate formation in the presence of the memory effect.

Navigating energy landscapes for materials discovery: Integrating modeling, simulation, and machine learning

AbstractThe energy landscape represents a high‐dimensional mapping of the configurational states of an atomic system with their respective energies. Under isobaric conditions, enthalpy landscapes can be used to account for volumetric changes of the system. Understanding the energy or enthalpy landscape holds the key for discovering materials with targeted properties, since the landscape encapsulates the complete thermodynamic and kinetic behavior of a system, including relaxation, metastable phases, and reactivity. However, the curse of dimensionality prohibits one from enumerating and visualizing the energy landscape—the energy landscape of an N‐atom system has 3N dimensions. Here, we outline the emerging computational techniques that allow the exploration of complex energy landscapes of materials in three distinct categories: the classical, metaheuristic, and machine learning approaches. We discuss the advantages and disadvantages associated with each of these methods, with a focus on the nature of problems where they can provide excellent solutions (and vice versa). Altogether, in addition to giving an overview of existing approaches, we hope the review provides an impetus to develop novel methods to explore the energy landscapes that can, in turn, provide both a fundamental understanding of the physics of materials and accelerate the discovery of novel materials.

Transient and Steady‐State Friction in Non‐Isobaric Conditions

AbstractThe frictional properties of faults control the initiation and propagation of earthquakes and the associated hazards. Although the ambient temperature and instantaneous slip velocity controls on friction in isobaric conditions are increasingly well understood, the role of normal stress on steady‐state and transient frictional behaviors remains elusive. The friction coefficient of rocks exhibits a strong dependence on normal stress at typical crustal depths. Furthermore, rapid changes in normal stress cause a direct effect on friction followed by an evolutionary response. Here, we derive a constitutive friction law that consistently explains the yield strength of rocks from atmospheric pressure to gigapascals while capturing the transient behavior following perturbations in normal stress. The model explains the frictional strength of a variety of sedimentary, metamorphic, and igneous rocks and the slip‐dependent response upon normal stress steps of Westerly granite bare contact and synthetic gouges made of quartz and a mixture of quartz and smectite. The nonlinear normal stress dependence of the frictional resistance may originate from the distribution of asperities that control the real area of contact. The direct and transient effects may be important for induced seismicity by hydraulic fracturing or for naturally occurring normal stress perturbations within fault zones in the brittle crust.

Highlighting the interdependence between volumetric contribution of fragility and cooperativity for polymeric segmental relaxation.

The blurring around the link between the isobaric fragility and the characteristic size of cooperative rearranging region for glass-forming liquids has been cleared up by considering volumetric and thermal contributions of the structural relaxation. The measurement of these contributions is carried out for three amorphous thermoplastic polymers using broadband dielectric spectroscopy under pressure, providing an understanding of the link between isobaric fragilities, glass transition temperatures, and microstructures. The cooperative rearranging region (CRR) volume is calculated as a function of pressure using the extended Donth's approach, and the values are compared with the activation volume at the glass transition under different isobaric conditions. By combining these different results, a link between the chemical structure and the influence of pressure/temperature on the molecular mobility can be established. Furthermore, this study shows also a strong correlation between the activation volume, leading to the volumetric contribution of the isobaric fragility, and the CRR volume. Finally, this work highlights the influence of inter- and intra-molecular interactions on thermal and volumetric contributions of the isobaric fragility as a function of pressure.

Desorbent swing adsorption process using ethylene to separate propane and propylene under isobaric conditions

The separation of olefin and paraffin using adsorption technology remains a significant challenge. This study proposes a novel desorbent swing adsorption (DSA) process using an olefin desorbent with a weaker adsorption affinity (C2: ethylene) to separate a paraffin/olefin mixture with a higher adsorption affinity (C3s: propane and propylene) under isobaric conditions, which is the reverse concept of using a desorbent with a stronger affinity in conventional DSA systems. The proposed DSA process effectively separates the C3 mixture because the deteriorating effects caused by the desorbent is minimized. Based on sequential breakthrough experiments with zeolite 13X DSA using ethylene, the efficient separation of a propylene dehydrogenation product (propane:propylene = 60:40 vol%) to produce polymer-grade propylene is achieved. It is confirmed that ethylene desorbent stream pushes out the adsorbed propylene and regenerates the adsorption bed without changing the pressure. The desorption step plays a key role in the separation performance of the proposed DSA process because the regenerated bed offers favorable conditions when filled with the weaker desorbent after the desorption step. The flowrate of the desorbent strongly affects the efficiency of propylene desorption. After validating the dynamic mathematical model using the experimental results, a two-bed DSA process using a six-step sequence that includes rinse export/import and idle steps is shown to achieve a propylene purity above 99.999 % (desorbent-free basis) with a recovery of 99.39 %, a productivity of 4.21 mol∙kg−1∙hr−1, and an ethylene usage of 7.59 mol∙kg−1∙hr−1. This study offers important insights into the development of adsorptive separation designs for olefin/paraffin separation.

Harvesting Water from Air with High-Capacity, Stable Furan-Based Metal-Organic Frameworks.

We synthesized two isoreticular furan-based metal-organic frameworks (MOFs), MOF-LA2-1(furan) and MOF-LA2-2(furan) with rod-like secondary building units (SBUs) featuring 1D channels, as sorbents for atmospheric water harvesting (LA = long arm). These aluminum-based MOFs demonstrated a combination of high water uptake and stability, exhibiting working capacities of 0.41 and 0.48 gwater/gMOF (under isobaric conditions of 1.70 kPa), respectively. Remarkably, both MOFs showed a negligible loss in water uptake after 165 adsorption-desorption cycles. These working capacities rival that of MOF-LA2-1(pyrazole), which has a working capacity of 0.55 gwater/gMOF. The current MOFs stand out for their high water stability, as evidenced by 165 cycles of water uptake and release. MOF-LA2-2(furan) is the first aluminum MOF to employ a double 'long arm' extension strategy, which is confirmed through single-crystal X-ray diffraction (SCXRD). The MOFs were synthesized by using a straightforward synthesis route. This study offers valuable insights into the design of durable, water-stable MOFs and underscores their potential for efficient water harvesting.

A comparison of raspberry freezing-damage during preservation in isochoric and isobaric conditions.

Fruits are perishable, thus it's crucial to have an efficient preservation technique that can increase storage time while keeping physical quality and nutritional attributes in order to avoid wastage. The majority of methods for long-term storage require refrigeration. In this investigation, we assess the viability of isochoric freezing as a different technique of raspberry (Rubus idaeus L.) preservation. Raspberries were subjected to different storage conditions: isochoric freezing at -4°C, conventional isobaric settings at +3°C (refrigerator), -21°C (freezer), and -4°C with a trehalose solution in a plastic bag. The study assessed changes in weight loss, visual appearance, color, hardness, °Brix values, and pH over a seven-day period. Key findings reveal that raspberries subjected to isochoric freezing below the freezing point of water experienced minimal weight loss after seven days. Visual appearance, color, hardness, °Brix values, and pH were comparable to fresh raspberries, indicating minimal alteration. These results suggest that isochoric freezing shows potential as a preservation method that maintains the physical and chemical properties of raspberries similar to fresh fruit. Implementing diverse preservation techniques tailored to raspberries may contribute to environmental sustainability by reducing food wastage and the associated environmental impact.

Isobaric Vapor-Liquid Equilibrium of Methyl Salicylate + Ethyl Salicylate and Methyl Salicylate + α-Pinene Binary Systems at 20.0 and 50.0 kPa

Gandapura oil, also called wintergreen oil in international trade, is evaluated based on the purity of its methyl salicylate content. Gandapura oil has several impurities including mainly ethyl salicylate and α-pinene, which can lower its quality and price. Indonesian local farmer’s gandapura oil has a low methyl salicylate content of only 82.23%, and appears in a dark red colour instead of clear. The low grade product may have been caused by thermal degradation of compounds within gandapura oil by constant heating during atmospheric distillation at temperature above its thermal threshold. The determination of their vapor-liquid equilibrium data can provide basic data for the separation and purification of methyl salicylate towards its two main impurities in gandapura oil. The vacuum pressure condition was selected to lower the distillation temperature, aiming to reduce the chance of thermal decomposition. The vapor-liquid equilibrium under isobaric conditions in the binary systems of methyl salicylate + ethyl salicylate and methyl salicylate + α-Pinene at 20.0 and 50.0 kPa were measured experimentally using modified Glass Othmer-Still. Gas Chromatography (GC) was utilized to analyze the composition of both the liquid and vapor phases in the samples. The thermodynamic consistency of experimental data was confirmed through the L-W Wisniak method. The experimental results were successfully correlated with Wilson, NRTL, and UNIQUAC models. The average absolute deviations of temperature (AAD T) and vapor phase composition (AAD y) between experimental data and models are less than 0.8058 and 0.0196, respectively for all systems. In terms of quality, all samples collected post-experiment maintained a clear color, suggesting that vacuum pressure distillation effectively prevents the thermal decomposition of compounds in gandapura oil.

Direct comparison of isobaric and isochoric vitrification of two aqueous solutions with photon counting X-ray computed tomography

Vitrification is a promising approach for ice-free cryopreservation of biological material, but progress is hindered by the limited set of experimental tools for studying processes in the interior of the vitrified matter. Isochoric cryopreservation chambers are often metallic, and their opacity prevents direct visual observation. In this study, we introduce photon counting X-ray computed tomography (CT) to compare the effects of rigid isochoric and unconfined isobaric conditions on vitrification and ice formation during cooling of two aqueous solutions: 50 wt% DMSO and a coral vitrification solution, CVS1. Previous studies have only compared vitrification in isochoric systems with isobaric systems that have an exposed air-liquid interface. We use a movable piston to replicate the surface and thermal boundary conditions of the isochoric system yet maintain isobaric conditions. When controlling for the boundary conditions we find that similar ice and vapor volume fractions form during cooling in isochoric and isobaric conditions. Interestingly, we observe distinct ice and vapor cavity morphology in the isochoric systems, possibly due to vapor outgassing or cavitation as rapid cooling causes the pressure to drop in the confined systems. These observations highlight the array of thermal-fluid processes that occur during vitrification in confined aqueous systems and motivate the further application of imaging techniques such as photon counting X-ray CT in fundamental studies of vitrification.