Speed Of Sound Measurements Research Articles

Highly Accurate Densities and Isobaric and Isochoric Heat Capacities of Compressed Liquid Water Derived from New Speed of Sound Measurements

Comprehensive and accurate measurements of the speed of sound in liquid water are reported. The measurements were carried out by a double-path-length pulse-echo technique and cover the temperature range from 273.65 K to 368.15 K with pressures up to 100 MPa. The relative expanded (k=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${ k}=2$$\\end{document}) uncertainties are 2.1 mK in temperature, 45 parts-per-million (ppm) in pressure, and between 40 ppm and 70 ppm in speed of sound. Furthermore, values for the density and specific isobaric and isochoric heat capacities were derived from the speed of sound data in the measured temperature range up to 100 MPa by the method of thermodynamic integration. Very accurate values for the derived properties were obtained by using density data of Takenaka and Masui (Metrologia 27:165–171, 1990) and isobaric heat capacity data of Osborne et al. (J Res Natl Bur Stand 23:197, 1939) at ambient pressure as initial values in combination with an accurate correlation of our speed of sound. The relative expanded (k=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${ k}=2$$\\end{document}) uncertainties of the derived properties are 2 ppm in density, 0.11% in isobaric heat capacity, and 0.12% in isochoric heat capacity. The experimental speeds of sound and derived properties are compared with experimental data of other authors from the literature, the IAPWS-95 (International Association of the Properties of Water and Steam) formulation for the thermodynamic properties of water, and a recent equation of state for supercooled water.

Speed of sound measurements and derived thermodynamic properties of bio-jet fuel components at saturation: N-butylcyclohexane

The composition of bio-jet fuels, i.e., the total content of hydrocarbons such as n-alkanes, iso-alkanes, cycloalkanes and aromatics, reached 85 % to 95 %, are mainly defining the thermophysical properties of bio-jet fuels. Short-chain cycloalkanes, such as n-butylcyclohexane, are one of the main components of bio-jet fuel. N-butylcyclohexane is included as one of the components of diesel fuel surrogate mixture. Therefore, more information on n-butylcyclohexane thermophysical properties in surrogate mixtures is required. In the present work the speed of sound in n-butylcyclohexane at saturation in the temperature range from (276 to 456) K has been measured using the pulse method with a constant (acoustic) sounding base. The combined expanded absolute and relative uncertainties (0.95 level of confidence, k = 2) of the temperature and speed of sound measurements are estimated to be 20 mK and 0.2 %, respectively. The measured speed of sound data together with reported density data were used to calculate the derived thermodynamic properties (kS,kT, and CP/CV) of n-butylcyclohexane at saturation.

Ultrasonic Sound Speed Estimation for Liver Fat Quantification: A Review by the AIUM-RSNA QIBA Pulse-Echo Quantitative Ultrasound Initiative.

Non-alcoholic fatty liver disease (NAFLD) is a significant cause of diffuse liver disease, morbidity and mortality worldwide. Early and accurate diagnosis of NALFD is critical to identify patients at risk of disease progression. Liver biopsy is the current gold standard for diagnosis and prognosis. However, a non-invasive diagnostic tool is desired because of the high cost and risk of complications of tissue sampling. Medical ultrasound is a safe, inexpensive and widely available imaging tool for diagnosing NAFLD. Emerging sonographic tools to quantitatively estimate hepatic fat fraction, such as tissue sound speed estimation, are likely to improve diagnostic accuracy, precision and reproducibility compared with existing qualitative and semi-quantitative techniques. Various pulse-echo ultrasound speed of sound estimation methodologies have been investigated, and some have been recently commercialized. We review state-of-the-art in vivo speed of sound estimation techniques, including their advantages, limitations, technical sources of variability, biological confounders and existing commercial implementations. We report the expected range of hepatic speed of sound as a function of liver steatosis and fibrosis that may be encountered in clinical practice. Ongoing efforts seek to quantify sound speed measurement accuracy and precision to inform threshold development around meaningful differences in fat fraction and between sequential measurements.

“Water-in-salt” super concentrated electrolyte clusters are “micelles”

Water-in-salt electrolytes are super concentrated mixtures of salt and water with molal concentration exceeding 20 m. Previous microscopic measurements revealed the presence of clusters. We hypothesize that these clusters are “micelles” because salts contain large “amphiphilic” anions. For verifying this hypothesis, we study bis(trifluoromethanesulfonyl)imide (LiTFSI) within a wide concentration range from 0.1 molal up to 21 molal. We measure conductivity and sound speed. Both methods yield the same value of CMC: 5 m (≈2.9 Molar). Sound speed measurement indicates a decline of the solvating number from 14.2 to below 2 at highest concentration. Assuming micelle diameter as 2 nm, we calculated number of TFSI- anions in a single micelle as 17. Some of them could be neutralized by ion-pairing with Li ions. Nevertheless, the high electric charge causes internal stress that competes with “hydrophobic effect” and shifts the CMC value. Strong DLVO electrostatic repulsion between separate micelles prevents formation of super-micelles and gels at high concentrations, keeping the solution in liquid state.

Ultrasonic Study of Novel Polymer Dextran in Aqueous Media at 12 MHz

Background: The characteristics of matter and the dynamics of molecular processes are examined by acoustic approaches. The primary techniques in molecular acoustics are the measure-ment of sound speed and sound absorption, as well as the relationship between these quantities and different physical variables including pressure, temperature, and wave frequency. Molecular acoustics emerged as a separate field in the 1930s. When it was discovered that many substances disperse the speed of sound during the transmission of sound waves through them and that the classical law, which states that the coefficient of absorption is proportional to the square of the frequency, however, it does not adequately describe how sound is absorbed. Objective: The ultrasonic technique is employed because it is one of the most popular techniques, which is very easy to use, and provides precise velocity results. With careful analysis of the results, the correlation between solute and solvent was discovered. In the pharmaceutical, agricultural, and cosmetics industries, dextran and its derivatives from a few select strains have found a wide range of uses. This is why we have chosen it for our study. For assessing the impact of temperature and con-centration on the aqueous medium containing the polymer dextran, ultrasonic properties are crucial. Pycnometer, Ostwald viscometer, and ultrasonic interferometer were used respectively to measure density (ρ), viscosity (η), and ultrasonic speed (u) at "303 K, 308 K, 313 K, 318 K, and 323 K." The experimental parameters are used to determine the acoustic parameters "adiabatic compressibility, Intermolecular free length, relaxation time, acoustic impedance, and Gibb's free energy". Method: To measure the density, viscosity, and ultrasonic velocity of the solution using a pycnome-ter, an Ostwald's viscometer, and an ultrasonic interferometer, and to calculate the thermo acoustical parameters based on the measured parameters. Result: Applications for examining the physico-chemical behaviour of aqueous dextran using ultra-sound include understanding the nature of molecular interactions. Conclusion: It was investigated how concentration and temperature affected the thermoacoustic char-acteristics of aqueous dextran. Hydrogen bonds, charge transfer complexes, and the dissolution of hy-drogen bonds and complexes are only a few examples of the forces that exist between molecules and how the analysis has interpreted their nature. Weak intermolecular forces exist. Other: Recent developments in ultrasonic techniques have made them an effective tool for evaluating information regarding the physical and chemical behaviour of liquid molecules.

Data Assimilation of Range- and Depth-Averaged Sound Speed from Acoustic Tomography Measurements in Fram Strait

Abstract The 2010–12 Acoustic Technology for Observing the Interior of the Arctic Ocean (ACOBAR) experiment provided acoustic tomography data along three 167–301-km-long sections in Fram Strait between Greenland and Spitsbergen. Ocean sound speed data were assimilated into a regional numerical ocean model using the Massachusetts Institute of Technology General Circulation Model–Estimating the Circulation and Climate of the Ocean four-dimensional variational (MITgcm-ECCO 4DVAR) assimilation system. The resulting state estimate matched the assimilated sound speed time series; the root-mean-squared (RMS) error of the sound speed estimate (∼0.4 m s−1) is smaller than the uncertainty of the measurement (∼0.8 m s−1). Data assimilation improved modeled range- and depth-averaged ocean temperatures at the 78°50′N oceanographic mooring section in Fram Strait. The RMS error of the state estimate (0.21°C) is comparable to the uncertainty of the interpolated mooring section (0.23°C). Lack of depth information in the assimilated ocean sound speed measurements caused an increased temperature bias in the upper ocean (0–500 m). The correlations with the mooring section were not improved as short-term variations in the mooring measurements and the ocean state estimate do not always coincide in time. This is likely due to the small-scale eddying and nonlinearity of the ocean circulation in Fram Strait. Furthermore, the horizontal resolution of the state estimate (4.5 km) is eddy permitting, rather than eddy resolving. Thus, the state estimate cannot represent the full ocean dynamics of the region. This study is the first to demonstrate the usefulness of large-scale acoustic measurements for improving ocean state estimates at high latitudes. Significance Statement Acoustic tomography measurements allow one to observe ocean temperature in large ocean volumes under the Arctic sea ice by measuring sound speed, which is hard to synoptically observe by other methods. This study has established methods for assimilation of depth- and range-averaged ocean sound speed from an acoustic tomography experiment in Fram Strait. For the first time, a 2-yr time series of ocean sound from acoustic tomography has been assimilated into an ocean state estimate. The results highlight the use of ocean tomography in ice-covered regions to improve state estimates of ocean temperature.

Wavelength-dependent elasto-optic tensor elements from acoustic Bragg diffraction

We report measurements of the elasto-optic constants p11 and p21 as a function of wavelength, for a variety of commercial glasses. The measurements were made using an apparatus based on the Dixon–Cohen design, in which the intensity of light diffracted from an acoustic pulse train is used to extract the elasto-optic tensor, using also data on the index of refraction and speed of sound. A variety of glass compositions were studied, and characterized compositionally using electron microprobe analysis; mechanically using speed of sound measurements; optically, via wavelength-dependent index of refraction; and structurally, using Raman and NMR spectroscopies. The final elasto-optic data were fit using the Wemple–DiDomenico model, and the results interpreted in terms of the effective band gap and deformation potentials, which were found to be sensitive to the different chemical bonds found in the glasses.

Extracting relaxational features from measurements of sound speeds for gas sensing

In recent years, gas sensing methods by jointly measuring acoustic relaxation absorption and sound speeds have become a research focus in acoustic fields. However, the existing methods are difficult to be employed in practical gas detection due to complex measurement processes and large measurement errors when measuring the sound relaxational absorption. Furthermore, the acoustic relaxation absorption spectrum's small signal is hard to be measured because of the noise and large classical relaxation in the high-frequency range. In this paper, a gas sensing method is proposed by only measuring the sound speeds at the three frequencies, avoiding the problems of measuring the acoustic absorption spectrum. First, sound speeds are measured at three frequency points; second, the relaxation strength and the relaxation time of the acoustic relaxation features are extracted; finally, the absorption spectral peak is acquired and located for gas detection. The simulation results verify the feasibility of our method, and the detection errors from the measurement errors of sound speeds can be eliminated effectively. Thus, our work provides a high-accurate and simple acoustic method for gas sensing.

Online and noninvasive monitoring of battery health at negative-half cell in all-vanadium redox flow batteries using ultrasound

Hydrogen evolution is one of the major side reactions that is detrimental to the health of all-vanadium redox flow batteries, especially for long-term cycling. Effective, low-cost, and accurate online prediction and detection methods for hydrogen generation are not yet available. In this work, we designed an online, noninvasive ultrasonic probing approach for monitoring the state of charge (SoC), predicting the hydrogen generation, and detecting hydrogen gas bubbles in anolyte solutions. The technique employs a pulse-echo method to measure the sound speed and the acoustic attenuation coefficient of the anolyte solution. Through static offline experiments and online in operando experiments, we have demonstrated that when hydrogen gas is generated in anolyte solutions, large variations are observed in both sound speed and acoustic attenuation coefficient measurements. We found that the variations of acoustic attenuation coefficient are highly correlated (correlation coefficients >0.9) with the gas flow rate. The designed acoustic method can monitor the SoC of anolyte, predict the hydrogen generation, and detect the presence of gas bubbles in an anolyte solution and, thus, provide information about the state of health for operation and management of flow battery systems.

Gaseous speed of sound and virial coefficients for 2,3,3,3-tetrafluoropropene (R1234yf) + 1,1,1,2-tetrafluoroethane (R134a) binary mixture

The binary mixture 2,3,3,3-tetrafluoropropene (R1234yf) + 1,1,1,2-tetrafluoroethane (R134a) is commercially interesting and is widely studied in thermodynamics properties, but except for gaseous speed of sound. In this work, we modified the experimental procedure of the cylindrical fixed-path acoustic resonance method for the sound speed measurement of mixtures. Then we obtained the first two sets of gaseous sound speed data at the molar fraction of about (0.207/0.793) and (0.580/0.420) with a combined relative expanded uncertainty (k = 2) of 0.03%. The accurate molar fractions along each isotherm line were determined by extrapolating the experimental data with the absolute expanded uncertainty (k = 2) of 0.003. The interaction virial coefficients were derived from the experimental sound speed data and were used to establish a hard-core square-well molecular potential model. A previous virial coefficient correlation was modified to predict the virial coefficients for mixtures. The experimental results and model calculations agree well with each other, confirming the correctness of the experimental method. The data could provide references to test and develop the mixing model.

Calcium supplementation and body mass index modify associations between prenatal phthalate exposure and perinatal bone ultrasound measures among pregnant women

Phthalates have endocrine activity that may interfere with bone health, particularly during pregnancy and the early postpartum period, when bone resorption increases. We evaluated associations between prenatal phthalate exposure and perinatal bone health among 289 mothers in the ELEMENT birth cohort in Mexico City who were randomized upon recruitment to receive 1,200 mg daily calcium supplementation or placebo throughout pregnancy. Spot urine samples at up to three timepoints during pregnancy were assayed for 9 phthalate metabolites. Bone integrity was assessed by quantitative ultrasound speed of sound (SOS) measurements of the phalange and distal radius at 3, 6, and 8 months of pregnancy and 1, 3, 7, and 12 months postpartum. Geometric means of specific gravity-corrected phthalate concentrations were used as overall measures of prenatal exposure. Linear mixed effect models estimated associations between phthalate exposure and repeated perinatal bone SOS measures, adjusting for age, pre-pregnancy body mass index (BMI), education, parity, calcium supplementation, and month of pregnancy/postpartum. Effect modification by calcium supplementation and BMI were assessed in sensitivity analyses. An interquartile range increase in MEP and MiBP increased pregnancy phalange z-scores (β: 0.11; 95%CI: 0.003, 0.31 and β: 0.15; 95%CI: 0.00,0.42, respectively). Higher concentrations of several phthalate metabolites resulted in lower SOS measures among women who received calcium supplements (compared to placebo group) but higher SOS measures among women with a BMI≥25 (compared to BMI<25). These results suggest that phthalate exposure may interfere with bone remodeling during pregnancy, and that consideration of effect modifiers is paramount to fully understand the effects of environmental exposures on bone health.

Hugoniot, sound speed, and phase transitions of single-crystal sapphire for pressures 0.2–2.1 TPa

Sapphire (${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$) is a major constituent of the Earth's mantle and has significant contributions to the field of high-pressure physics. Constraining its Hugoniot over a wide pressure range and identifying the location of shock-driven phase transitions allows for development of a multiphase equation of state and enables its use as an impedance-matching standard in shock physics experiments. Here, we present measurements of the principal Hugoniot and sound velocity from direct impact experiments using magnetically launched flyers on the Z machine at Sandia National Laboratories. The Hugoniot was constrained for pressures from 0.2--2.1 TPa and a four-segment piecewise linear shock-velocity--particle-velocity fit was determined. First-principles molecular dynamics simulations were conducted and agree well with the experimental Hugoniot. Sound-speed measurements identified the onset of melt between 450 and 530 GPa, and the Hugoniot fit refined the onset to $525\ifmmode\pm\else\textpm\fi{}13$ GPa. A phase diagram which incorporates literature diamond-anvil cell data and melting measurements is presented.

Speed of Sound Measurement of Hydrogen Isotopologues Containing Tritium for Reference Gas Sample Verification

Accurate gas samples containing tritiated molecules are essential for the development of tritium monitoring tools and to study tritium-induced reaction dynamics. We prepared gas samples that may contain any of the six hydrogen isotopologues by manometrically mixing high-purity homonuclear isotopologues and forming the remaining isotopologues by chemical equilibration. In order to independently verify the relative isotopologue concentrations to the manometrically derived composition and thus validate the accuracy of the produced gas samples, we measured the effective speed of sound (SoS) in the gas mixtures, which are highly sensitive to small deviations in the relative molar fractions due to the large difference in the individual SoSs. We found that deviations between the manometrically derived and measured SoSs are on a 0.1% level, demonstrating the accuracy of the sample production procedure and the suitability of SoS measurements for inline composition monitoring in tritium applications.

Speed of Sound Measurements in Helium at Pressures from 15 to 100 MPa and Temperatures from 273 to 373 K.

The speed of sound in helium was measured along five isotherms in a temperature range from 273 to 373 K at pressures from 15 to 100 MPa with a relative expanded uncertainty (k = 2) from 0.02 to 0.04%. A dual-path pulse-echo system was utilized to conduct these measurements. The data were compared with the reference equation of state developed by Ortiz Vega et al. At pressures up to 50 MPa, relative deviations were within the uncertainty of our measurements, while, at higher pressures, increasing negative deviations were observed up to -0.26%. We also compared the results with predictions based on the virial equation of state correct to the seventh virial coefficient, using the ab initio virial coefficients reported recently by Gokul et al., finding agreement to within the experimental uncertainty at all investigated states.

Accurate mass flow and density of bubbly liquids using speed of sound augmented Coriolis technology

Speed of sound augmented Coriolis technology utilizes a process fluid sound speed measurement to improve the accuracy of Coriolis meters operating on bubbly liquids. This paper presents a theoretical development and experimental validation of speed of sound augmented Coriolis meters. The approach utilizes a process fluid sound speed measurement, based on a beam-forming interpretation of a pair of acoustic pressure transducers installed on either side of a Coriolis meter, to quantify, and mitigate, errors in the mass flow, density, and volumetric flow reported by two modern, dual bent-tube Coriolis meters operating on bubbly mixtures of air and water with gas void fractions ranging from 0% to 5%. By improving accuracy of Coriolis meters operating on bubbly liquids, speed of sound augmented Coriolis meters offer the potential to improve the utility of Coriolis meters on many existing applications and expand the application space of Coriolis meters to address additional multiphase measurement challenges.The sources of measurement errors in Coriolis meters operating on bubbly liquids have been well-characterized in the literature. In general, conventional Coriolis meters interpret the mass flow and density of the process fluid using calibrations developed for single-phase process fluids which are essentially incompressible and homogeneous. While these calibrations typically provide sufficient accuracy for single-phase flow applications, their use on bubbly liquids often results in significant errors in both the reported mass flow, density and volumetric flow. Utilizing a process fluid sound speed measurement and an empirically-informed aeroelastic model of bubbly flows in Coriolis meters, the methodology developed herein compensates the output of conventional Coriolis meters for the effects of entrained gas to provide accurate mass flow, density, volumetric flow, and gas void fraction of bubbly liquids.Data presented are limited to air and water mixtures. However, by influencing the effective bubble size through mixture flow velocity, the bubbly liquids tested exhibit decoupling characteristics which spanned theoretical limits from nearly fully-coupled to nearly fully-decoupled flows. Thus, from a non-dimensional parameter perspective, the data presented is representative of a broad range of bubbly liquids likely to be encountered in practice.

Investigation of surficial sediment acoustic, physical, and biological properties in the New England Mud Patch

Measurements of surficial sediment properties at five locations in the New England Mud Patch (NEMP) were conducted during a coring survey in April 2022. At each location the Acoustic-Multi-Corer (AMC) sampled the upper few decimeters of sediment near the water-seabed interface. The AMC inserted acoustic probes into the sediment to collect in situ measurements of compressional waves (30–140 kHz) and shear waves (0.8–1.2 kHz) at near ambient conditions, after which cores were collected from the inter-probe propagation paths for ex situ analysis of the sediment properties. Onboard the ship, the cores were scanned with a Core and Resonance Logger (CARL), which provided high-frequency sound speed and attenuation measurements (100–1000 kHz) along the lengths of the cores, as well as resonance-based measurements of sound speed at 12–16 kHz. A subset of cores was sieved for infauna onboard the vessel, and the remaining cores were later analyzed in an onshore laboratory for porosity, bulk density, mineral and organic matter composition, and grain size. The frequency dependence of the surficial sediment acoustic properties will be discussed in the context of the mud’s physical and biological properties as well as sediment acoustics models. [Work sponsored by ONR.]

Holography-based measurement of sound speed and attenuation coefficient values for small samples of tissue phantoms

For therapeutic ultrasound applications, design and planning of treatments often involve simulations to predict the in situ acoustic field, and these simulations rely on estimates of the acoustic properties of soft tissues. As defined in simulation models, these properties describe how a plane wave propagates in a homogeneous medium. However, because soft tissues inherently contain inhomogeneities, measurements are most appropriately performed on small, relatively homogeneous samples. In addition, mostly small samples of human tissue, either autopsy or post-surgical, are typically available for characterization. As published in a recent paper [J. Acoust. Soc. Am. 2021, 149(1): 386–404], we have proposed a holography-based technique to extract plane-wave measurements from ultrasound beams passing through small (cm-sized) material samples. Here, we seek to adapt this technique for measuring small samples of deformable materials using an apparatus that holds such samples with two plane, parallel surfaces that can be interrogated by an incident ultrasound beam having a diameter smaller than that of the sample. Initial testing over a range of frequencies from 0.5 to 10MHz is performed utilizing well characterized materials, such as hydrogels and silicone rubber. [Work supported by NIH grant R01EB025187.]

Mid-frequency sound intensity fluctuations on the Washington shelf

A joint Oceanography/Acoustics experiment was conducted 15 July–13 August, 2022 in Washington’s shallow coastal shelf waters to investigate mid-frequency sound intensity fluctuations and the oceanographic mechanisms driving them, including subsurface ducts, internal tides, and internal waves. Acoustic pulses centered at 3.5 kHz and 6 kHz were transmitted up-shelf from a stationary source and recorded by receivers on two moorings at 10 km and 20 km ranges, respectively. A ship-towed Shallow Water Integrated Mapping System (SWIMS) repeatedly sampled the ocean between the source and receiver moorings, providing sound speed measurements as a function of range, depth, and time. In addition, five oceanographic moorings strategically placed around the acoustic path took additional ocean data over time. The sound speed profiles feature a surface mixed layer underneath which a subsurface duct with local sound speed minima of 1–2 m/s is frequently present. Analysis shows that (1) when the sound source is inside the subsurface duct, transmission loss is reduced by 15 dB compared to when the source is outside and (2) the statistics of the acoustic intensity are consistent with strong scattering. [Work supported by the Office of Naval Research.]

Alteration of speed-of-sound by fixatives and tissue processing methods in scanning acoustic microscopy

The elasticity of biological tissues is one of the physical characteristics of tissues and has attracted attention as a clinical diagnostic parameter. The elasticity can be determined on the microscopic scale with speed of sound (SoS) measurements using acoustic microscopy. In SoS measurements, a thin-sliced section is attached to a glass slide in the same manner as a light microscopic specimen. There are two main methods for preparing thin sections: paraffin-embedding and frozen-section. The frozen-section method requires fewer processing steps from sectioning to measurement and is considered to reduce artifacts in the sample compared with the paraffin-embedding method. Both methods need fixatives to keep tissue structures. Many reports of measurements using frozen sections are focused on soft tissues with relatively high protein contents. In this study, we determined the SoS in thin sections of four types of organs (brain, heart, liver, and kidney) prepared using two different methods (paraffin-embedding and frozen-section) and four different chemical fixatives (formalin, Karnovsky fixative (KF) 0.5% and 2.0% glutaraldehyde, and ethanol). The SoS in heart and liver samples prepared using KF showed good agreement with reported values for raw samples. For samples fixed with KF, the SoS increased as the glutaraldehyde concentration increased from 0.5% to 2.0%. A brain tumor sample was processed with KF 0.5%, and the SoS in the tumor was significantly higher than that in the non-tumor area. The results confirmed that it is possible to measure the SoS in brain samples with low protein contents using appropriate fixatives.

Entropy, Heat Capacity, and Thermal Conductivity of trans-1,1,1,4,4,4-Hexafluoro-2-butene [R1336mzz(E)] Derived from the Gaseous Sound Speed Measurement

Thermophysical properties such as entropy, heat capacity, and thermal conductivity of trans-1,1,1,4,4,4-hexafluoro-2-butene, which is designated as R1336mzz(E) for refrigerant use, were derived from the sound speed measurement in the gaseous phase. The gaseous sound speed was measured by using an acoustic-microwave resonator with a cylindrical cavity, which enables simultaneous measurement of the gaseous relative dielectric permittivity. The ideal gas heat capacity was determined from the gaseous sound speed by analyzing the measurement data with the acoustic-virial equation, and the electric dipole moment was additionally determined from the gaseous relative permittivity measurements. In compliance with the fluid-property correlation models that involve parameters associated with the ideal gas heat capacity and the dipole moment under the corresponding states principle, entropies at saturated vapor and liquid, isobaric heat capacities at saturated liquid, and thermal conductivities at vapor and liquid phases were evaluated for R1336mzz(E).