Absolute Temperature Research Articles

Minimally invasive measurement of carotid artery and brain temperature in the mouse.

Brain temperature is tightly regulated and reflects a balance between cerebral metabolic heat production and heat transfer between the brain, blood, and external environment. Blood temperature and flow are critical to the regulation of brain temperature. Current methods for measuring in vivo brain and blood temperature are invasive and impractical for use in small animals. This work presents a methodology to measure both brain and arterial blood temperature in anesthetized mice by MRI using a paramagnetic lanthanide complex: thulium tetramethyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (TmDOTMA-). A phase-based imaging approach using a multi-TE gradient echo sequence was used to measure the temperature-dependent chemical shift difference between thulium tetramethyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid methyl protons and water, and from this calculate absolute temperature using calibration data. In a series of mice in which core body temperature was held stable but at different values within the range of 33° to 37°C, brain temperature away from the midline was independent of carotid artery blood temperature. In contrast, midline voxels correlated with carotid artery blood temperature, likely reflecting the preponderance of larger arteries and veins in this region. These results are consistent with brain temperature being actively regulated. A limitation of the present implementation is that the spatial resolution in the brain is coarse relative to the size of the mouse brain, and further optimization is required for this method to be applied for finer spatial scale mapping or to characterize focal pathology.

Electron temperature measurement from neutral atomic tungsten emission line ratio.

A method to determine electron temperature within a plasma by the spectral analysis of atomic tungsten emission has been explored. The technique was applied to a post-discharge region immediately following a high voltage nanosecond pulsed discharge in air with tungsten electrodes. Atomic tungsten lines are readily observed in the weak emission spectrum within the post-discharge region for many microseconds. Intensity ratios were measured at various times after the pulsed discharge for a select pair of neutral tungsten emission lines at 400.88 and 401.52nm, where the upper electronic levels of each transition are at 3.46 and 5.52eV respectively. This significant difference in upper state energy causes their line intensity ratio to vary as the electron temperature changes. In addition to the emission spectra, the absolute electron temperature could be accurately measured in our lab using laser Thomson scattering to calibrate the new tungsten emission line intensity ratio method. An analysis is presented that calculates electron temperature from these tungsten emission data assuming a Maxwellian electron energy distribution contributing to direct electron impact excitation to the upper states of each transition. The results included the derivation of a calibration factor between the two experimental methods representing a previously unreported ratio of Einstein A coefficients for the 400.88-401.52nm transitions. This derivation provides a method for future measurement of absolute electron temperature by the 400.88-401.52nm tungsten line intensity ratio without the need for laser Thomson scattering calibration.

Separation property and asymptotic behavior for a transmission problem of the bulk-surface coupled Cahn–Hilliard system with singular potentials and its Robin approximation

We consider a class of bulk-surface coupled Cahn–Hilliard systems in a smooth, bounded domain [Formula: see text] [Formula: see text], where the bulk phase variable is connected to the surface phase variable via a Dirichlet boundary condition or its Robin approximation. For a general class of singular potentials (including the physically relevant logarithmic potential), we establish the regularity propagation of global weak solutions to the initial boundary value problem. In particular, when the spatial dimension is two, we prove the instantaneous strict separation property, which ensures that every global weak solution remains uniformly away from the pure states [Formula: see text] after any given positive time. In the three-dimensional case, we obtain the eventual strict separation property that holds for sufficiently large time. This strict separation property allows us to prove that every global weak solution converges to a single equilibrium as time goes to infinity using the Łojasiewicz–Simon approach. Finally, we study the double obstacle limit for the problem with logarithmic potentials in the bulk and on the boundary, showing that as the absolute temperature [Formula: see text] tends to zero, the corresponding weak solutions converge (for a suitable subsequence) to a weak solution of the problem with a double obstacle potential.

An off-resonant quantum collision model: Realizing a qubit coupled with an effective negative temperature bath

Abstract Quantum collision model provides a promising tool for investigating system-bath dynamics. Most of the studies on quantum collision models work in the resonant regime. In quantum dynamics, the off-resonant interaction often brings in exciting effects. It is thereby attractive to investigate quantum collision models in the off-resonant regime. On the other hand, a bath with a negative absolute temperature is anticipated to be instrumental in developing thermal devices. The design of an effective bath with negative absolute temperature coupled to a qubit is significant for developing such thermal devices. We establish an effective negative-absolute-temperature bath coupled to a qubit with a quantum collision model in a far-off-resonant regime. We conduct a detailed and systematic investigation on the off-resonant collision model. There is an additional constraint on the collision duration resulting from the far-off resonant collision. The dynamics of the collision model in the far-off-resonant regime are different from the one beyond the far-off-resonant regime. Numerical simulations confirm the validity of the proposed approach.

Testing the validity of the Wiedemann–Franz law for metals and alloys at high pressures

The Wiedemann–Franz (WF) law is a fundamental, empirical law that originally relates the electronic thermal conductivity (Λe) of a metal to its electrical resistivity (ρ) via the Lorenz number L = ρΛe/T, where T is the absolute temperature. Conventionally as ρ is measured or calculated, it has often been used to infer the Λe through the WF law at a wide range of pressure (P)–temperature (T) conditions. However, since the WF law was originally formulated based on a simple electron gas model with L being approximately the Sommerfeld value L0 = 2.44 × 10−8 W Ω K−2, its validity to transition metals involving correlated d-orbital electrons at a variety of P-T conditions has been questioned, not to mention to metallic alloys. Here, we report experimental measurements on the thermal conductivity and electrical resistivity of platinum (Pt), iron (Fe), as well as Fe0.85Si0.15 and FeS alloys at high pressures and room temperature. We demonstrate that the L of Pt and Fe both reasonably agree with L0 from ambient to ∼60 GPa, except for Fe around the pressures where a structural transition (∼12 GPa) and an electronic topological transition (∼30–40 GPa) occur. The L of Fe0.85Si0.15 and FeS alloys, however, both considerably deviate from L0, presumably due to significant inelastic scatterings between carriers and impurities. Our results suggest that using the WF law with ideal L0 to convert ρ of metallic alloys to Λe (and vice versa) at high pressures could lead to a large discrepancy from that obtained by direct measurements.

Measurements of N2+ ions in an inductively coupled plasma using saturated cavity ringdown spectroscopy

Abstract This paper presents a unique study of the bulk plasma characteristics in a low pressure inductively coupled nitrogen plasma. Saturated cavity ringdown spectroscopy (sat-CRDS) has been used to determine the absolute number densities and translational temperatures of N2 +(X, ν = 0). The effect of saturation is readily accounted for by using an effective saturation parameter, Seff , and determined by a simple method employing measurements at two different gain settings of the detection system. The appropriateness of this method is confirmed by comparison with fitting individual ringdown data using a time-dependent saturation parameter, S(t), within the local approximation model for sat-CRDS; the two methods are in excellent agreement in returning absolute number densities and translational temperatures. N2 +(X, ν = 0) number densities are determined across a matrix of pressure (10 − 100 mTorr) and rf power (200 − 400 W) conditions with maximum number densities of ca. 1.3 × 1010 cm−3 while translational temperatures range from 600 − 1500 K.

Eddies driven by eddy currents: Magnetokinetic flow in a conducting drop due to an oscillating magnetic field

An oscillating magnetic field of amplitude H 0 and angular frequency ω is applied across an electrically conducting non-magnetic drop of conductivity κ, viscosity η and radius R. The oscillating magnetic field generates an oscillating electric field due to Faraday's law, , where E and H are the electric and magnetic field, and μ 0 is the magnetic permeability. This generates a current density, . The non-linear interaction between the oscillating current and magnetic field results in a time-independent body force density, due to Ampere's circuital law. This drives a pair of axisymmetric circulation rolls in the two hemispheres of the drop in the viscous limit where inertia is neglected. The characteristic circulation velocity is times a function of the dimensionless parameter , the square root of the ratio of the magnetic field frequency and the eddy current relaxation rate. The velocity increases proportional to for , has a maximum at , and decreases proportional to for . Large strain rates in the range are generated in a metal drop of radius 0.1–1 mm for magnetic flux density as low as , provided relatively high frequencies of oscillation in the range are used. Joule heating could increase the drop temperature by tens of degrees Kelvin in comparison to the ambient.

Absolute Dimensions of the Interferometric Binary HD 174881: A Test of Stellar Evolution Models for Evolved Stars

We report high-resolution spectroscopic monitoring and long-baseline interferometric observations with the Palomar Testbed Interferometer (PTI) of the 215 day binary system HD 174881 (K1 II-III), composed of two giant stars. The system is spatially resolved with the PTI, as well as in archival measurements with the CHARA Array. Our analysis of these observations, along with an analysis of the spectral energy distribution, have allowed us to infer accurate values for the absolute masses ( 3.367−0.041+0.045 and 3.476−0.043+0.043M☉ ), radii (34.0 ± 1.3 and 22.7 ± 1.8 R ☉), effective temperatures (4620 ± 100 and 4880 ± 150 K), and bolometric luminosities of both components, as well as other properties including the orbital parallax (distance). These provide valuable tests of stellar evolution models for evolved stars, which are still relatively uncommon compared to the situation for main-sequence stars. We find generally good agreement of all of these properties of HD 174881 with two sets of recent models (MIST and PARSEC) at compositions near solar, for ages of 255–273 Myr. We also find evidence of an infrared excess, based largely on the flux measurements from IRAS at 60 and 100 μm.

Enhanced Carrier Mobility and Thermoelectric Performance by Nanostructure Engineering of PEDOT Thin Films Fabricated via the OCVD Method Using SbCl5 Oxidant

AbstractAir‐stable, lightweight, and electrically conductive conjugated polymers have attracted significant attention for thermoelectric applications, especially in low‐temperature environments. However, their low carrier mobility has limited broader adoption. This study addresses this challenge by investigating the nanostructure of poly(3,4‐ethylenedioxythiophene) (PEDOT) thin films fabricated via oxidative chemical vapor deposition (oCVD) at various deposition temperatures. Through systematic control of the semi‐crystalline orientation and π–π stacking distance, a substantial enhancement in carrier mobility (23.58 ± 1.71 cm2 V−1 s−1) and electrical conductivity (6345 ± 210 S cm−1) is achieved. The thermoelectric power factor demonstrates a direct correlation with deposition temperature, achieving a maximum value of 112.57 ± 4.33 µW m−1 K−2. PEDOT thin films fabricated at higher deposition temperatures show minimal reductions in electrical conductivity as absolute temperature decreased, reflecting a lower resistivity ratio and extended metallic state, as indicated by the metal–insulator transition in the Zabrodskii plot. Incorporating the Seebeck coefficient into the parabolic energy band diagram revealed strong agreement between theoretical and experimental carrier mobility, while also indicating that the energy barrier for intercrystalline charge transport decreases as deposition temperature increases. The highly face‐on orientation and reduced π–π stacking distance in PEDOT thin films facilitate quasi‐1D conduction, thereby enhancing carrier mobility.

The Preservation of HBV, HCV, HIV Viral Nucleic Acids in Plasma by Dry Spot Method and the Duration of Preservation

To establish a method for preserving viral nucleic acids in plasma using a blood collection card based on the dry spot method, to predict the duration of nucleic acid preservation by establishing the Arrhenius equation, and to demonstrate the feasibility of this preservation method for the re-testing of nucleic acids in blood samples retained by blood banks. Plasma samples positive for HBV, HCV, and HIV nucleic acids were prepared into preservation cards in the form of dry plasma spots for storage. The prepared preservation cards were placed under accelerated storage conditions at 37, 45, 50, and 55 ℃. The preservation cards were periodically retrieved from each temperature condition for nucleic acid extraction, and the nucleic acid samples were purified for subsequent PCR testing, with the recorded CT values. An Arrhenius equation model was established between the expiration time and the storage temperature, thereby predicting the validity period of nucleic acid preservation in blood collection cards under specified storage temperature conditions. For the plasma samples positive for HBV, HCV, and HIV nucleic acids preserved using the dry spot method, the regression equations for the duration with temperature were as follows: y=-11546 x + 31.74 for HBV, y=-12949x + 36.88 for HCV, and y=-12204x + 34.48 for HIV, with the correlation coefficient r greater than 0.98 for all. It was predicted that at a storage temperature of 4 ℃, the preservation periods for HBV, HCV, and HIV viral nucleic acids using the dry spot method would be 20 792 days, 19 289 days, and 14 285 days, respectively. At a storage temperature of 20 ℃, the preservation periods would be 2 135 days 1 502 days, and 1 289 days, respectively. The nucleic acids of the three common viral pathogens in blood samples, when preserved using the dry spot method, conform to a first-order reaction pattern in the accelerated degradation experiment. The relationship between the rate of nucleic acid degradation and the absolute temperature of storage is consistent with the Arrhenius equation. Based on the calculations using this equation, the stability and validity period of plasma nucleic acid samples preserved using the dry spot method can reach a minimum of 3.5 years under storage conditions not exceeding 20 ℃, which essentially meets the requirements for the preservation period of blood samples retained by blood banks.

Perlindungan Sensor Suhu Cu/Ni dengan Nitroselulosa

Coating of Cu/Ni with nitrocellulose (NC) has been carried out with the aim of determining the effect of using NC as a protective film on the sensitivity and activation energy of the sensor. The samples used were Cu/Ni and Cu/Ni/Cu where the NC coating on Cu/Ni was carried out using a spray method with a pressure of 1.2 Mpa. Both sensor samples were used to measure the temperature of liquid nitrogen (liquid N2) which was varied from -160C - 0C. In addition to temperature, voltage and current were also measured. The sensitivity value was obtained from the slope of the resistance curve against temperature, while the activation energy was obtained from the slope of the logarithm of conductivity against one per absolute temperature. From the sensitivity test, it is known that both sensors have a tendency to be more sensitive when the temperature is lowered, but the presence of the NC layer causes a decrease in sensitivity of up to 18.9%, namely from 3.95 /C to 3.18 /C at a temperature of -160C following the equation S(T)=0.10e-0.012T. The use of NC protective layer can also increase the activation energy by 1.3%, namely from (4.29  0.01)x10-9 eV to (4.35  0.01)x10-9 eV. These results can be used as a consideration for temperature sensor manufacturers that the use of NC protective layer is important but can reduce sensor sensitivity.

Effects of ambient temperature on mental and neurological conditions in older adults: A systematic review and meta-analysis

BackgroundEmerging research has suggested a link between ambient temperature and mental and neurological conditions such as depression and dementia. This systematic review aims to summarize the epidemiological evidence on the effects of ambient temperature on mental and neurological conditions in older adults, who may be more vulnerable to temperature-related health effects compared to younger individuals. MethodsA systematic search was conducted in PubMed, Ovid/Embase, Web of Science, and Ovid/PsycINFO on July 17, 2023, and updated on July 31, 2024. We included epidemiological studies investigating the association between ambient temperature exposures and numerous mental and neurological conditions in populations aged 60 years and older. Exclusions were made for studies on indoor or controlled exposure, suicide, substance abuse, those not published as peer-reviewed journal articles, or those not written in English. The risk of bias of included studies was assessed using a tool developed by the World Health Organization (WHO). Qualitative synthesis was performed on all eligible studies, and random-effects meta-analyses were conducted on groups of at least four studies sharing similar study design, exposure metric, and health outcome. The certainty of evidence was assessed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) framework modified by the WHO. ResultsFrom 16,786 screened articles, 76 studies were deemed eligible, primarily from mainland China and North America. There was notable heterogeneity in study variables and methodologies. The most commonly used exposure metrics were daily absolute temperature and heat waves, and time-series and case-crossover analyses were the most frequently employed study designs. Meta-analysis of four studies on the effect of a 1 °C increase in temperature on hospital admissions/visits for mental disorders showed a pooled risk ratio (RR) of 1.014 (95 % Confidence Interval, CI: 1.001, 1.026). Comparing heat wave days to non-heat wave days, pooled effect estimates showed increased risk in hospital admissions/visits (RR: 1.269; 95 % CI: 1.030, 1.564; six studies) and mortality related to mental disorders (RR: 1.266; 95 % CI: 0.956, 1.678; four studies). Despite the limited number of studies on cold exposures, they consistently reported that lower temperatures were associated with an increased risk of various mental and neurological conditions. ConclusionsThis review presents epidemiological evidence of the adverse impacts of ambient temperature exposures, such as high temperatures and heat waves, on mental and neurological conditions among the older adult population, with overall moderate certainty. The findings highlight the need for greater attention to the mental and neurological health of older adults in the context of climate change and population aging.Registration number (PROSPERO ID): CRD42023428137.

Deep learning based heat transfer simulation of the casting process

To avoid the necessity of constitutional models, computational intensity, and the time-consuming nature inherent in numerical simulations, a pioneering approach utilizing deep learning techniques has been adopted to swiftly predict temperature fields during the solidification phase of casting processes. This methodology involves the development of rapid prediction models based on modified U-net network architectures, augmented by the integration of Inception and CBAM (Convolutional Block Attention Module) modules. The construction of the training set involved utilizing 200 diverse geometric models with each containing three kinds of components (casting, mold, and chill), where the temperature fields at a specific time, ti, were input data, while that of the subsequent time point, ti+1, served as the corresponding labels. The geometric models were generated by the erosion of 2D arbitrary shapes through an erosion method, and then their associated temperature fields were obtained via FDM-based numerical simulation. The trained deep learning models exhibit proficiency in promptly forecasting temperature fields during the solidification process for arbitrarily shaped castings at different times. The average accuracy of the predicted outcomes reaches 94.5% as the absolute temperature error set as 7 ℃ and the prediction just takes one second for a time step. Notably, these models are adept at handling multi-component with multi-materials within a geometry model, such as casting, chill, and mold corresponding to the intricate casting process.

(Keynote) Ion Transport across Bilayer Lipid Membranes

Ion transports across cell membranes are related to various important biofunctions such as respiration, metabolism, and signal propagation [1]. Bilayer lipid membranes (BLMs) have been used as base materials to analyze the characteristics of ion transports across biomembranes containing various transporters. Although a BLM, which forms the structural frame of biomembrane, serves as a permeation barrier for hydrophilic ions such as K+, Na+ and Cl‒, it has been reported that electrolyte ions (M+ and X–) slightly transport across a BLM between two aqueous phases (W1 and W2) in the absence of any transporter [2]. In this case, a pair of M+ and X– distributes from aqueous phases to the BLM, and M+ and X– transport oppositely each other by applying the potential difference (membrane potential, E W1-W2). The higher the hydrophobicity of the ion is, the higher the ion transport current flows when the same membrane potential is applied. Based on the Goldman-Hodgkin-Katz equation, the ion transport current density (j W1-W2) is described as Eq. (1) when only MX exists in W1 and W2 [2]. j W1-W2 = - (c 0 F 2 E W1-W2 β)(D M+ + D X-)/(RTd) (1)Here, c 0, F, R, T, d, b and D are the current density for the ion transport, the concentration of the electrolyte (MX), the Faraday constant, the absolute temperature, the thickness of the BLM, the distribution coefficient, and the diffusion coefficient, respectively. Assuming that the effect of ion-pair formation is negligible small, b is described as Eq. (2). ln β = (ΔG ° tr, M+ + ΔG ° tr, X-)/(2RT) (2)ΔG ° tr, M+ and ΔG ° tr, X- are the standard Gibbs energies for the ion transfer of M+ and X–, respectively, from the aqueous phase to the BLM. It is impossible to evaluate and values. Because the standard Gibbs energies for the ion transfer of M+ and X– from the aqueous phase to several organic solution are proportional to hydration energies of M+ and X– ( and ), respectively, and can be expressed as Eq. (3) . ΔG ° tr, M+ = a ΔG ° hyd, M+ + b (ΔG ° tr, X- = a' ΔG ° tr, X- + b') (3)Here, a and b (a' and b') are constant values and depend on the media such as organic solvents. Based on Eqs. (1)-(3), it is clear that the ion permeability depends on the species and concentration of the electrolyte. Accordingly, or can be used as a measure of hydrophobicity of the objective ion.It is well-known that the ion transport is facilitated in the presence of hydrophobic ions, carrier compounds, and/or ion channels [1]. When only 10–7-10–5 mol dm–3 (M) of hydrophobic ions such as tetraphenylborate (TPhB–), dipicrylaminate (DPA–), etc. were added into W1 and/or W2 containing 0.1 M of hydrophilic electrolytes such as KCl, NaCl, etc., a pair of anodic and cathodic peaks symmetrical to 0 V appeared in cyclic voltammograms [3]. The peak currents were found to be related to the adsorption and desorption of hydrophobic ions on the surface of the BLM. Under the steady-state condition, the relationship between E W1-W2 and j W1-W2 indicated a sigmoidal curve. This steady-state current was mainly caused by the transport of the counter ion and hydrophobic ions served as carriers of the counter ion. Similarly, the ion transport was facilitated by an ionophore such as valinomycin (Val) and nonactin (Non). It is thought that these carriers facilitate the transport of alkali ions across the BLM as carriers, because these cations are strongly complexed with these ionophores. The author’s group revealed that the j W1-W2 values depended on not only cation species but also anion species [4]. In the case of the carrier-type transport, it was proved that both the cation and the anion distributed to the BLM and that both two ions simultaneously transported in the opposite direction. We also found that the ion transport through ion channels such as gramicidin A occurs based on the same mechanism [5].

(General Student Poster Award Winner, 3rd Place) Ion Transport across Bilayer Lipid Membranes Formed in the Porous Membrane Filter

Bilayer lipid membranes (BLMs), comprising of lecithin and cholesterol, are useful to analyze ion transport across the BLM in the presence of hydrophobic ions, carrier compounds, and channel proteins. The application of BLMs can prevent the unpredictable influence on other coexisting biological substances such as various enzymes and transporters within biomembranes.However, because the physically fragility of BLMs restricts their application, it is difficult to measure the ion transport phenomena over a wide range of membrane potentials (< 0.15 V) and/or for long time. In this study, a new method for enhancing physical stability of the BLMs was developed using a track-etched membrane (TM). TM is an effective porous sheet to construct the BLMs within the cylindrical pores. BLMs were formed by dropping the n-decane solution containing lecithin and cholesterol, and then the BLMs were automatically formed within the pores of TM. The electrochemical cell employed in this study was composed by two glass chambers. The two chambers (W1 and W2) were filled with aqueous solution containing 0.1 mol dm- 3 (M) of KCl and separated by TM. The formation of BLMs within TM was confirmed by cyclic voltammetry. The capacitance and thickness of the BLMs can be described by the Eq. (1).Here, C m, ε 0, ε m, A, and d are the mean capacitance of membrane, the vacuum permittivity (8.854 pF m-1), the dielectric constant of the BLM (ε m = 2.001), the total area of BLMs (0.057 cm2), and the BLM thickness (nm), respectively. Assuming the BLM as a flat capacitor, d can be expressed by the Eq. (2).Here, v is a potential scanning rate and I W1-W2 is a ion transport current between W1 and W2. The C m and d of BLMs were estimated to be 0.51 ± 0.05 μF cm-2 and 3.5 ± 0.4 nm, respectively. Comparing with those reported by the former researches, the formation of BLMs within TM was confirmed.BLMs formed within TM were stable enough to be applied the membrane potential up to 1.5 V, as shown in Figure 1. The potential range was about 10 times larger than that of the BLM formed by the conventional method. The wide potential range and long lifetime of BLMs within TM provide the ability to measure the transport phenomena happened under high voltage.Ions transport across the BLMs between W1 and W2 containing 0.1 M KCl was discussed. A small amount of KCl was distributed from aqueous phases to the BLM. Applying the potential difference between W1 and W2, K+ and Cl− transported in the opposite direction simultaneously, as shown in Scheme 1. When the concentration of KCl in W1 was different from that in W2, the membrane potential at the zero current (E W1‒W2, i=0) shifted in the positive or negative direction. In the case that the concentration of KCl in W2 was r times higher than that in W1, the relationship between E W1‒W2, i=0 and r was able to be expressed by Eq. (3).Here, α, R, T, and F are the ratio of diffusion coefficient in BLM (D) of K+ to Cl− (α = D K+/D Cl−), the gas coefficient, the absolute temperature, and the Faraday constant, respectively. Based on the high linear relationship between the ln(r) and the measured E W1‒W2, i=0, the α was calculated to be 0.3 ± 0.3. Therefore, the D Cl− was assumed to be 3.2 times higher than D K+.The authors believe that this BLM-forming method can be applied to the studies of various transport phenomena and coupling reactions between electron as well as ion transports. Figure 1

Simultaneous Entropic Coefficient Measurement and Multi-Species, Multi-Reaction Modelling

The multi-species, multi-reaction (MSMR) model is developed through the fitting of pseudo-open circuit voltage (POCV) data acquired by cycling a cell at a sufficiently low rate (C/50).1 By comparing MSMR fitted data taken at various temperatures, both temperature dependence of fitting parameters and thermodynamic data including the state-of-charge (SOC) dependent entropic coefficient (dU/dT), entropy (ΔS), and enthalpy (ΔH) can be gleaned.2 In this presentation, POCV behavior of coal-derived graphite will be discussed and compared to thermodynamic measurements of lithium-intercalation under potentiostatic testing conditions.3 Simultaneously measuring POCV data and determining thermodynamic parameters has the advantages of minimizing testing time and complexity. The MSMR model’s ability to distinguish minute changes in temperature dependent active material behavior will be highlighted through a comparison of coal-derived graphite and commercially available synthetic graphite.4 Implications of thermodynamic parameters and temperature dependent behavior on cell and pack level engineering will also be presented.

Efficient mapping of phase diagrams with conditional Boltzmann Generators

Abstract The accurate prediction of phase diagrams is of central importance for both the fundamental understanding of materials as well as for technological applications in material sciences. However, the computational prediction of the relative stability between phases based on their free energy is a daunting task, as traditional free energy estimators require a large amount of simulation data to obtain uncorrelated equilibrium samples over a grid of thermodynamic states. In this work, we develop deep generative machine learning models based on the Boltzmann Generator approach for entire phase diagrams, employing normalizing flows conditioned on the thermodynamic states, e.g., temperature and pressure, that they map to. By training a single normalizing flow to transform the equilibrium distribution sampled at only one reference thermodynamic state to a wide range of target temperatures and pressures, we can efficiently generate equilibrium samples across the entire phase diagram. Using a permutation-equivariant architecture allows us, thereby, to treat solid and liquid phases on the same footing. We demonstrate our approach by predicting the solid-liquid coexistence line for a Lennard-Jones system in excellent agreement with state-of-the-art free energy methods while significantly reducing the number of energy evaluations needed.

Thermodynamics of solids including anharmonicity through quasiparticle theory

The quasiharmonic approximation (QHA) in combination with density-functional theory is the main computational method used to calculate thermodynamic properties under arbitrary temperature and pressure conditions. QHA can predict thermodynamic phase diagrams, elastic properties and temperature- and pressure-dependent equilibrium geometries, all of which are important in various fields of knowledge. The main drawbacks of QHA are that it makes spurious predictions for the volume and other properties in the high temperature limit due to its approximate treatment of anharmonicity, and that it is unable to model dynamically stabilized structures. In this work, we propose an extension to QHA that fixes these problems. Our approach is based on four ingredients: (i) the calculation of the n-th order force constants using randomly displaced configurations and regularized regression, (ii) the calculation of temperature-dependent effective harmonic frequencies ω(V, T) within the self-consistent harmonic approximation (SCHA), (iii) Allen’s quasiparticle (QP) theory, which allows the calculation of the anharmonic entropy from the effective frequencies, and (iv) a simple Debye-like numerical model that enables the calculation of all other thermodynamic properties from the QP entropies. The proposed method is conceptually simple, with a computational complexity similar to QHA but requiring more supercell calculations. It allows incorporating anharmonic effects to any order. The predictions of the new method coincide with QHA in the low-temperature limit and eliminate the QHA blowout at high temperature, recovering the experimentally observed behavior of all thermodynamic properties tested. The performance of the new method is demonstrated by calculating the thermodynamic properties of geologically relevant minerals MgO and CaO. In addition, using cubic SrTiO3 as an example, we show that, unlike QHA, our method can also predict thermodynamic properties of dynamically stabilized phases. We expect this new method to be an important tool in geochemistry and materials discovery.

On some features of diurnal dynamics of solonchak emissivity in summer

ABSTRACT Widely represented in many arid regions of the world, dry marshes pose a potential threat to the adjacent areas because of soil salinization caused by wind transfer (for long distances) of toxic mineral salts from the dried surface. For environmental monitoring of such soils, remote microwave sensing methods are used. In this work, we study at a 2.3 cm wavelength the summer diurnal dynamics of microwave radiation of sodic solonchak formed on the dried bottom of a hypersaline lake. It has been established that the study indicator (in the centimetre range) depends on the cumulative changes in temperature, moisture and salinity of soils. With rise in soil temperature, intensive evaporation and topsoil drying, a salt crust and the underlying layer with less moisture (accompanied by microwave radiation interference on the layered structure of solonchak) can be formed. In the experiment, a daily variation in the brightness temperature of the study object (a specific object) by 25 K occurred with change in thermodynamic temperature of the skin layer by 10 K.

Nonlinear van't Hoff Behavior in the Interaction of Two Water-Soluble Porphyrins with Bovine Serum Albumin (BSA).

Thermodynamic analysis of the binding process of water-soluble negatively charged meso-tetrakis(p-sulfonatophenyl) (TPPS4) and positively charged meso-tetrakis(4-methylpyridyl) (TMPyP) porphyrins with bovine serum albumin (BSA) at different temperatures was carried out based on the data of BSA quenching fluorescence by porphyrins. The comparison of binding constants (K b) shows that negatively charged TPPS4 possesses higher affinity to BSA than positively charged TMPyP. Thermodynamic characteristics of the binding process were obtained in accordance with the van't Hoff theory by processing nonlinear dependences of ln K b on inverse absolute temperature within the framework of two models: taking into account the dependence or independence of the change in the standard heat capacity (ΔC 0) on temperature. A comparison of thermodynamic characteristics with the data obtained from the Förster fluorescence quenching theory and with literature data leads to the conclusion that TPPS4 is bound to the Sudlow I site (subdomain IIA), while TMPyP is bound to the Heme site (between the subdomains IA and IB). The analysis of ΔC 0 changes with temperature demonstrates that binding of TPPS4 promotes hydration of nonpolar groups in the protein, which increases with the increase of temperature, while binding of TMPyP decreases the hydration of polar groups of the protein, the effect increasing with rising temperature. The obtained information may be useful for elucidating the mechanisms of interaction of porphyrins with albumins and the effect of this interaction upon the effectiveness of porphyrins in photodynamic therapy and in fluorescence diagnostics of cancer.