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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.

Functionalized porous materials could play a key role in improving the efficiency of gas separation processes as required by applications such as carbon capture and storage (CCS) and across the hydrogen value chain. Due to the large number of different functionalizations, new experimental approaches are needed to determine if an adsorbent is suitable for a specific separation task. Here, it is shown for the first time that Raman spectroscopy is an efficient tool to characterize the adsorption capacity and selectivity of translucent functionalized porous materials at high pressures, whereby translucence is the precondition to study mass transport inside of a material. As a proof of function, the performance of three silica ionogels to separate an equimolar (hydrogen + carbon dioxide) gas mixture is determined by both accurate gravimetric sorption measurements and Raman spectroscopy, with the observed consistency establishing the latter as a novel measurement technique for the determination of adsorption capacity. These results encourage the use of the spectroscopic approach as a rapid screening method for translucent porous materials, particularly since only very small amounts of sample are required. For the first time, Raman spectroscopy is applied to characterize the adsorption capacity and selectivity of translucent functionalized porous materials. Results for the adsorption of an equimolar (hydrogen + carbon dioxide) gas mixture on three silica ionogels are presented. Validation is carried out by comparison with accurate gravimetric adsorption measurements.

Knowledge of thermodynamic properties of aqueous solutions of CO 2 is crucial for various applications including climate science, carbon capture, utilisation and storage (CCUS), and seawater desalination. However, there is a lack of reliable experimental data, and the equation of state (EOS) predictions are not reliable, particularly for sound speeds in low CO 2 concentrations typical of water resources. For this reason, we have measured speeds of sound in three different aqueous solutions containing CO 2 . We report speeds of sound in the single-phase liquid region for binary mixtures of water and CO 2 for mole fractions of CO 2 of 0.0118, 0.0066 and 0.0015 at temperatures from 273.15 K to 313.15 K and at pressures up to 50 MPa, measured using a dual-path pulse-echo apparatus. The relative standard uncertainties of the sound speeds are 0.05 %, 0.03 % and 0.01 % at 0.0118, 0.0066 and 0.0015 CO 2 mole fractions, respectively. The change in sound speeds as functions of composition, pressure and temperature are analysed in this study. We find that dissolution of CO 2 in water increases its sound speeds at all conditions, with the greatest increase occurring at the highest mole fractions of CO 2 . Our sound speed data agree well with the limited available experimental data in the literature but deviate from the EOS-CG of Gernert and Span by up to 7 % at the lowest temperatures, highest pressures, and highest CO 2 mole fraction. The new low-uncertainty sound speed data presented in this work could provide a basis for development of an improved EOS and in establishing reliable predictions of the change in thermodynamic properties of seawater-like mixtures due to absorption of CO 2 gas.

Lorentz symmetry is a foundational property of modern physics, underlying the standard model of particles and general relativity. It is anticipated that these two theories are low-energy approximations of a single theory that is unified and consistent at the Planck scale. Many unifying proposals allow Lorentz symmetry to be broken, with observable effects appearing at Planck-suppressed levels; thus, precision tests of Lorentz invariance are needed to assess and guide theoretical efforts. Here we use ultrastable oscillator frequency sources to perform a modern Michelson-Morley experiment and make the most precise direct terrestrial test to date of Lorentz symmetry for the photon, constraining Lorentz violating orientation-dependent relative frequency changes Δν/ν to 9.2±10.7 × 10(-19) (95% confidence interval). This order of magnitude improvement over previous Michelson-Morley experiments allows us to set comprehensive simultaneous bounds on nine boost and rotation anisotropies of the speed of light, finding no significant violations of Lorentz symmetry.

Microwave resonators are a technology with the potential to automate the rapid acquisition of vapour-liquid equilibrium data in multicomponent mixtures. However, the re-entrant resonators commonly used for fluid characterization have limited ability to mix or drain adequately due to the bulbs and narrow gaps used within the sample volume to spatially distribute the sensing regions with intense electric fields. This work describes a novel composite cavity combining two toroidal split-ring resonators and a cylindrical resonator, each sealed and partially filled with the polymer PEEK, to spatially separate sensing regions whilst maintaining an unobstructed sample volume. This unique design also allows for the total sample volume to be an order-of-magnitude smaller than conventional microwave cavities, without significantly increasing the resonant frequencies. Mass transfer between phases is facilitated by mechanical agitation, reducing equilibration time. Finite element analysis (FEA) is used to model how the dielectric interfaces within the cavity perturb electric field distributions. This model is used to interpret measurements of two-phase propane to quantify liquid volume fraction and phase dielectric permittivities.

The ( p, ρ, T ) behaviour of liquid 3,3,3-trifluoropropene (R-1243zf) was investigated in the temperature range from T  = (203.23 to 293.72) K at pressures from p  = (1.04 to 15.22) MPa utilizing a vibrating-tube densimeter. This work extends measurements of the refrigerant R-1243zf by 109 data points into the low-temperature and high-density region. A physically based and a polynomial model were used to calculate density from the measured values (temperature, pressure and oscillation period). The physically based model was used to present the densities while the polynomial model contributes to the estimate of their uncertainty. The combined expanded uncertainty ( k  = 2) of the experimental densities was estimated to be 1.7 kg·m −3 . The reference equation of state of R-1243zf as implemented in NIST’s REFPROP 10.0 database deviates from the experimental data up to 2.0 %. To improve upon this representation, a genetic programming based symbolic regression approach was used to correlate data reported in the literature and measured in this work for liquid R-1243zf in the density range between (700 and 1240) kg·m −3 . The new density correlation agrees with the experimental data within 0.2 %.

The ability to accurately predict the behavior of multiphase fluid mixtures underpins a broad range of industrial and scientific activity. Expanding the scope and improving the performance of predictive thermodynamic models relies on the availability of accurate experimental data for the complete phase behavior of the corresponding fluid mixtures. Here, we present a novel approach to in situ measurements of heterogeneous two-phase behavior in binary fluid mixtures using a single apparatus. A modified microwave re-entrant cavity apparatus is employed to simultaneously measure the dielectric properties of the liquid and vapor as well as the quality of each phase, based on the frequency shifts caused by a heterogeneous fluid for three independent resonant modes. We report a so far unique mathematical framework to further characterize the thermophysical properties of each phase along tie lines, determining the compositions of the coexisting vapor and liquid phase as well as the vapor and liquid phase densities within the two-phase region based on the Clausius–Mossotti relation between phase dielectric properties, density, and molar polarizability. The framework was validated by comparison of the measured and predicted properties of a (0.35 propane + 0.65 carbon dioxide) mixture throughout the two-phase region along an isothermal pathway at T  = 280 K. These proof-of-concept results demonstrate for the first time that thermophysical properties of a binary mixture with a known overall composition can be determined from experiments with a microwave cavity using a synthetic approach.

Monitoring of skin scar thickness and structural properties is desirable when assessing the efficacy of the healing process. In this work, we report the use of single-sided, low-field nuclear magnetic resonance (NMR) for the analysis of the thickness and collagen structure of healthy and scarred skin. Acquisition of T 2 relaxation profiles was proven to provide quantification of porcine skin thickness as accurate as standard histological techniques. Subsequent analysis of human participants highlighted the utility of this technique for identifying different types of scar and in identifying differences between the thickness of moderate hypertrophic scars and healthy skin. Using bead packings as a model system, determination of the surface-to-volume ( S / V ) ratio and tortuosity ( k ) was successfully measured on the single-sided apparatus based on time-resolved diffusion analysis. Application of this method to human skin was able to detect regional differences in collagen structures, consistent with qualitative expectations. It was also able to differentiate between healthy and scarred skin tissue. Preliminary results indicated that scarred tissue exhibited decreased S / V ratios and tortuosities, which is coherent with the formation of less-aligned collagen within scar tissue and indicated the potential for this technique to differentiate scar types. This novel application of single-sided low-field NMR has the potential to be deployed in clinical settings for the differentiation of scar types and for the assessment and monitoring of skin scarring and healing.

Accurate phase equilibrium data for mixtures of eco-friendly but mildly-flammable refrigerants with inert components like CO 2 will help the refrigeration industry safely employ working fluids with 80 % less global warming potential than those of many widely-used refrigerants. In this work, a visual high-pressure measurement setup was used to measure solid–fluid equilibrium (SFE) of HFC-32 + CO 2 binary systems at temperatures between (132 and 217) K. The experimental data show a eutectic composition of around 11 mol % CO 2 with a eutectic temperature of 131.9 K at solid–liquid–vapour (SLVE) condition. Measured SLVE and solid–liquid equilibrium data were used to tune a thermodynamic model implemented in the ThermoFAST software package by adjusting the binary interaction parameter (BIP) in the Peng–Robinson equation of state. The tuned model represents the measured melting points for binary mixtures with a root mean square deviation (RMSD) of 3.2 K, which is 60 % less than achieved with the default BIP. An RMSD of 0.5 K was obtained using the tuned model for the mixtures with CO 2 fractions over 28 mol % relative to an RMSD of 3.4 K obtained with the default model. The new property data and improved model presented in this work will help avoid solid deposition risk in cryogenic applications of the HFC-32 + CO 2 binary system and promote wider applications of more environmentally-friendly refrigerant mixtures.

Lorentz symmetry is a foundational property of modern physics, underlying the standard model of particles and general relativity. It is anticipated that these two theories are low-energy approximations of a single theory that is unified and consistent at the Planck scale. Many unifying proposals allow Lorentz symmetry to be broken, with observable effects appearing at Planck-suppressed levels; thus, precision tests of Lorentz invariance are needed to assess and guide theoretical efforts. Here we use ultrastable oscillator frequency sources to perform a modern Michelson–Morley experiment and make the most precise direct terrestrial test to date of Lorentz symmetry for the photon, constraining Lorentz violating orientation-dependent relative frequency changes Δ ν / ν to 9.2±10.7 × 10 −19 (95% confidence interval). This order of magnitude improvement over previous Michelson–Morley experiments allows us to set comprehensive simultaneous bounds on nine boost and rotation anisotropies of the speed of light, finding no significant violations of Lorentz symmetry. Lorentz invariance, tested more than a century ago by Michelson and Morley, is a foundational property of modern physics within the standard model and general relativity. Here, the authors report the most precise terrestrial test to date, bounding the lack of violations of Lorentz symmetry in photons to 10 –18 .