Full Temperature Range Research Articles

Intrinsic and extrinsic pinning in NdFeAs(O,F): vortex trapping and lock-in by the layered structure.

Fe-based superconductors (FBS) present a large variety of compounds whose properties are affected to different extents by their crystal structures. Amongst them, the REFeAs(O,F) (RE1111, RE being a rare-earth element) is the family with the highest critical temperature Tc but also with a large anisotropy and Josephson vortices as demonstrated in the flux-flow regime in Sm1111 (Tc ∼ 55 K). Here we focus on the pinning properties of the lower-Tc Nd1111 in the flux-creep regime. We demonstrate that for H//c critical current density Jc at high temperatures is dominated by point-defect pinning centres, whereas at low temperatures surface pinning by planar defects parallel to the c-axis and vortex shearing prevail. When the field approaches the ab-planes, two different regimes are observed at low temperatures as a consequence of the transition between 3D Abrikosov and 2D Josephson vortices: one is determined by the formation of a vortex-staircase structure and one by lock-in of vortices parallel to the layers. This is the first study on FBS showing this behaviour in the full temperature, field, and angular range and demonstrating that, despite the lower Tc and anisotropy of Nd1111 with respect to Sm1111, this compound is substantially affected by intrinsic pinning generating a strong ab-peak in Jc.

Atmospheric Chemistry of Criegee Intermediates: Unimolecular Reactions and Reactions with Water.

Criegee intermediates are produced in the ozonolysis of unsaturated hydrocarbons in the troposphere, and understanding their fate is a prerequisite to modeling climate-controlling atmospheric aerosol formation. Although some experimental and theoretical rate data are available, they are incomplete and partially inconsistent, and they do not cover the tropospheric temperature range. Here, we report quantum chemical rate constants for the reactions of stabilized formaldehyde oxide (CH2OO) and acetaldehyde oxide (syn-CH3CHOO and anti-CH3CHOO) with H2O and for their unimolecular reactions. Our results are obtained by combining post-CCSD(T) electronic structure benchmarks, validated density functional theory potential energy surfaces, and multipath variational transition state theory with multidimensional tunneling, coupled-torsions anharmonicity, and high-frequency anharmonicity. We consider two different types of reaction mechanisms for the bimolecular reactions, namely, (i) addition-coupled hydrogen transfer and (ii) double hydrogen atom transfer (DHAT). First, we show that the MN15-L exchange-correlation functional has kJ/mol accuracy for the CH2OO + H2O and syn-CH3CHOO + H2O reactions. Then we show that, due to tunneling, the DHAT mechanism is especially important in the syn-CH3CHOO + H2O reaction. We show that the dominant pathways for reactions of Criegee intermediates depend on altitude. The results we obtain eliminate the discrepancy between experiment and theory under those conditions where experimental results are available, and we make predictions for the full range of temperatures and pressures encountered in the troposphere and stratosphere. The present results are an important cog in clarifying the atmospheric fate and oxidation processes of Criegee intermediates, and they also show how theoretical methods can provide reliable rate data for complex atmospheric processes.

A Physically Constrained Calibration Database for Land Surface Temperature Using Infrared Retrieval Algorithms

Land surface temperature (LST) is routinely retrieved from remote sensing instruments using semi-empirical relationships between top of atmosphere (TOA) radiances and LST, using ancillary data such as total column water vapor or emissivity. These algorithms are calibrated using a set of forward radiative transfer simulations that return the TOA radiances given the LST and the thermodynamic profiles. The simulations are done in order to cover a wide range of surface and atmospheric conditions and viewing geometries. This study analyzes calibration strategies while considering some of the most critical factors that need to be taken into account when building a calibration dataset, covering the full dynamic range of relevant variables. A sensitivity analysis of split-windows and single channel algorithms revealed that selecting a set of atmospheric profiles that spans the full range of surface temperatures and total column water vapor combinations that are physically possible seems beneficial for the quality of the regression model. However, the calibration is extremely sensitive to the low-level structure of the atmosphere, indicating that the presence of atmospheric boundary layer features such as temperature inversions or strong vertical gradients of thermodynamic properties may affect LST retrievals in a non-trivial way. This article describes the criteria established in the EUMETSAT Land Surface Analysis—Satellite Application Facility to calibrate its LST algorithms, applied both for current and forthcoming sensors.

Understanding the Effect of Temperature on the Sulfur Tolerance of a Ca Rich Ferrite SOFC Electrode

Previously, we have shown that a symmetrical La0.3Ca0.7Fe0.7Cr0.3O3-δ (LCFCr) SOFC full cell (LCFCr used at both electrodes) exhibits very good electrochemical performance in H2 and CO at the fuel cell and also has good sulfur tolerance in wet H2 with a low ppm H2S content at 800 oC [1]. In fact, a somewhat enhanced performance of the LCFCr anode towards the hydrogen oxidation reaction was observed under these conditions [1]. However, the effect of temperature, which is known to have a significant impact on the sulfur tolerance of conventional Ni-based anodes [2-6], has not yet been studied. Therefore, in this work, both a symmetrical full cell and a three electrode half cell configuration, using LCFCr for all of the electrodes, were constructed and tested to better understand the sulfur tolerance of this Ca rich ferrite based perovskite in humidified H2 at temperatures ranging from 600-800 oC. Our preliminary potentiostatic data have shown that, in both the full and half-cell mode in low ppm H2S, the LCFCr electrode exhibits an enhancement in the hydrogen oxidation reaction (HOR) kinetics at 750-800 oC, while between 600 and 700 oC, the LCFCr electrode shows some form of deactivation. For instance, in the three electrode half-cell study at a constant anodic overpotential of 100 mV, the current density of the LCFCr electrode increased by 7-10% with the addition of 9 ppm H2S to 50% humidified H2 in the higher temperature range, while at 600 oC and 650 oC, the current density decreased by 2% and 15%, respectively. This deactivation was found to be fully reversible when H2S was removed from the gas stream, however, indicating that there was no permanent damage to either the electrodes, the interfaces, or the current collectors. Similarly, open circuit impedance data for the symmetrical full cell study showed that the polarization resistance (Rp) decreased from 1.0 to 0.95 Ωcm2 with the addition of 9 ppm H2S to 30% humidified H2 at 800 oC, while at 650 oC, Rp increased from 15.3 to 17.6 Ωcm2. To better understand these results, we are employing various surface characterization techniques, such as X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), to better understand the interaction between H2S and LCFCr, as well as the type of S species formed, over the full temperature range in low ppm H2S.

Evaluation of a novel in-line point-of-care blood gas analyser.

Point-of-care testing is becoming increasingly relevant to the practice of anaesthesia and critical care medicine, especially in terms of minimisation of sample volumes and decreased time to decision making. We performed a prospective observational study to evaluate a novel, in-line blood gas analysis device against a conventional benchtop model, and assessed it while placing the enrolled patients under extreme physiological conditions, specifically deep hypothermic circulatory arrest. Eight patients were studied, and had between seven and 11 samples analysed for seven variables (pH, pCO2 , pO2 , HCO3 (-) , base excess [BE], K(+) and haematocrit [Hct]), using the device during the process of cooling to 20°C on cardiopulmonary bypass, and subsequent rewarming to normothermia. After Passing-Bablok analysis, the variables were evaluated for bias, limits of agreement and percentage error at above and below 30°C. Of the measured variables, only pH (percentage error 2.4%) and potassium (19.8%) demonstrated acceptable (<30%) percentage error over the full range of temperatures measured. Carbon dioxide, when stratified by temperature, was acceptable (<30°C percentage error 24.6%, >30°C percentage error 9.9%), but the overall percentage error of the dataset (45.8%) was excessively high. Bicarbonate and haematocrit both had an acceptable percentage error above 30°C (25.2% and 18.5%, respectively), but similar to carbon dioxide, percentage error for the full range of temperatures exceeded 30%. These data differ from previous work examining this device, and highlights the difference between derived measures using different apparatuses when exposed to extreme physiological conditions.

Micro-Tomographic Investigation of Ice and Clathrate Formation and Decomposition under Thermodynamic Monitoring.

Clathrate hydrates are inclusion compounds in which guest molecules are trapped in a host lattice formed by water molecules. They are considered an interesting option for future energy supply and storage technologies. In the current paper, time lapse 3D micro computed tomographic (µCT) imaging with ice and tetrahydrofuran (THF) clathrate hydrate particles is carried out in conjunction with an accurate temperature control and pressure monitoring. µCT imaging reveals similar behavior of the ice and the THF clathrate hydrate at low temperatures while at higher temperatures (3 K below the melting point), significant differences can be observed. Strong indications for micropores are found in the ice as well as the THF clathrate hydrate. They are stable in the ice while unstable in the clathrate hydrate at temperatures slightly below the melting point. Significant transformations in surface and bulk structure can be observed within the full temperature range investigated in both the ice and the THF clathrate hydrate. Additionally, our results point towards an uptake of molecular nitrogen in the THF clathrate hydrate at ambient pressures and temperatures from 230 K to 271 K.

Probing firing-induced changes in non-carbonate clay through 55Mn EPR techniques

Non-carbonate clay samples, fired in steps of 50°C between 600°C and 1000°C, were examined through electron paramagnetic resonance (EPR) techniques (X- and Q-Band pulsed- and cw-EPR). X-band pulsed EPR and Q-Band pulsed- and cw-EPR techniques were able to spot 55Mn(II) signals out of the large iron background in the full range of firing temperatures, allowing one to follow the phase transformations through the evolution of the manganese signal. Q-Band pulsed EPR turned out to be particularly suitable to detect even small amounts of this ion in calcite, while the 55Mn hyperfine coupling constant, determined through Q-Band cw-EPR, could be used to detect transitions to the glassy phase.

Thermophysical properties validation for soy methyl ester biodiesel through experimental spray data

ABSTRACTThe scarcity of experimental data for soy biodiesel fuel properties covering the full temperature range from injection to critical temperature reduces the reliability and accuracy of fuel property estimation techniques, and hence engine simulations. This study reviews and validates soy biodiesel fuel property estimation techniques indirectly using experimental spray data utilizing a modified version of KIVA-3V computer code. The effect of each estimation technique on spray penetration was investigated through several runs, and one set of fuel property models capable of predicting accurate liquid length for soy biodiesel is presented. The results showed in some cases a significant difference in estimation techniques available in literature with the highest discrepancy found in enthalpy calculations. The results also showed that a higher average fuel particle temperature will result in smaller spray penetration and that estimation techniques can be compared using their effect on average particle temperature. Comparing calculated spray penetration results with experimental values showed that almost all cases tend to overestimate the liquid length with some extreme cases predicting wall impingement.

Localization model description of diffusion and structural relaxation in glass-forming Cu–Zr alloys

We test the localization model (LM) prediction of a parameter-free relationship between the α-structural relaxation time τ α and the Debye–Waller factor 〈u 2 〉 for a series of simulated glass-forming Cu–Zr metallic liquids having a range of alloy compositions. After validating this relationship between the picosecond (‘fast’) and long-time relaxation dynamics over the full range of temperatures and alloy compositions investigated in our simulations, we show that it is also possible to estimate the self-diffusion coefficients of the individual atomic species (D Cu, D Zr) and the average diffusion coefficient D using the LM, in conjunction with the empirical fractional Stokes–Einstein (FSE) relation linking these diffusion coefficients to τ α . We further observe that the fragility and extent of decoupling between D and τ α strongly correlate with 〈u 2 〉 at the onset temperature of glass-formation T A where particle caging and the breakdown of Arrhenius relaxation first emerge.

A double differential torsional accelerometer with improved temperature robustness

This paper reports the design, realization and characterization of a novel double differential torsional MEMS accelerometer with improved temperature robustness. Based on the structure of conventional torsional accelerometers, normally composed of two unbalanced proof masses and an identical torsional beam, this work explores a torsional accelerometer with two structural optimizations aiming to improve the temperature robustness: a double differential configuration and an on-chip integrated reference capacitor configuration. The double differential configuration realizes the temperature self-calibration by making the two pairs of unbalanced masses have the same sensitivity to temperature but opposite sensitivity to acceleration. And the on-chip integrated reference capacitor realizes the temperature self-calibration by transferring the temperature dependent reference capacitor from ASIC or PCB into the MEMS structure. Totally ten accelerometer prototypes are fabricated with the pre-buried mask wet-etching method and tested. Comparison tests show that, for most of the accelerometers, by taking the double differential configuration and the on-chip integrated reference capacitor configuration, the temperature sensitivity of the scale factor, the bias stability and the output drift of in the full temperature range are greatly improved. The testing results experimentally demonstrate the effectivity of the optimization for improving temperature robustness.

Consistent bosonization-debosonization. II. The two-lead Kondo problem and the fate of its nonequilibrium Toulouse point

Following the development of a scheme to bosonize and debosonize consistently [N. Shah and C.J. Bolech, Phys. Rev B 93, 085440 (2016); arXiv:1508.03078], we present in detail the Toulouse-point analytic solution of the two-lead Kondo junction model. The existence and location of the solvable point is not modified, but the calculational methodology and the final expressions for observable quantities change markedly as compared to the existent results. This solvable point is one of the remarkably few exact results for non-equilibrium transport in correlated systems. It yields relatively simple analytical expressions for the current in the full range of temperature, magnetic field and voltage. It also shows precisely, within the limitations of the Toulouse fine-tuning, how the transport evolves depending on the relative strengths of inter-lead and intra-lead Kondo exchange couplings ranging from weak to strong. Thus its improved understanding is an important stepping stone for future research.

Lattice specific heat for the RMIn5 (R=Gd, La, Y; M=Co, Rh) compounds: Non-magnetic contribution subtraction

We analyze theoretically a common experimental process used to obtain the magnetic contribution to the specific heat of a given magnetic material. In the procedure, the specific heat of a non-magnetic analog is measured and used to subtract the non-magnetic contributions, which are generally dominated by the lattice degrees of freedom in a wide range of temperatures.We calculate the lattice contribution to the specific heat for the magnetic compounds GdMIn5 (M=Co, Rh) and for the non-magnetic YMIn5 and LaMIn5 (M=Co, Rh), using density functional theory based methods. We find that the best non-magnetic analog for the subtraction depends on the magnetic material and on the range of temperatures. While the phonon specific heat contribution of YRhIn5 is an excellent approximation to the one of GdCoIn5 in the full temperature range, for GdRhIn5 we find a better agreement with LaCoIn5, in both cases, as a result of an optimum compensation effect between masses and volumes. We present measurements of the specific heat of the compounds GdMIn5 (M=Co, Rh) up to room temperature where it surpasses the value expected from the Dulong–Petit law. We obtain a good agreement between theory and experiment when we include anharmonic effects in the calculations.

Effects of gas bubbles in protection gel on performance of MEMS pressure sensor

The process of dispensing gel above the silicon chip aimed at protecting chip surface and bonding wire is one of the most critical steps in the production of highly accurate low-pressure sensor modules. Numerous research efforts focused on the influences of dispensing process parameters, configuration and mechanical behavior of cured gel on the performance of sensors, while few concerns were taken on the air bubbles formed in protection gel that adversely influence the sensitivity and zero-drift in full temperature range. In this research, a series of hydrostatic fluid-element based 3D models in consideration of different positions and various diameters of gas bubble were conducted to explore this phenomenon. Results show that the existence of gas bubble brings in an extra load and changes the pressure distribution on the sensing membrane of the chip, which will result in zero-drift and sensitivity variation of packaged sensors. The influence degree is closely correlated with the position and size of gas bubble in protection gel. An experiment was conducted to verify the simulation, the results fit well. Due to the random distribution of bubble it is almost impossible to design signal modulation circuits to compensate for voltage drift in mass production. Therefore, in practical production, the gas bubble should be avoided especially in the region close to the sensing membrane of sensor chip.

Optimization and Experimentation of Dual-Mass MEMS Gyroscope Quadrature Error Correction Methods.

This paper focuses on an optimal quadrature error correction method for the dual-mass MEMS gyroscope, in order to reduce the long term bias drift. It is known that the coupling stiffness and demodulation error are important elements causing bias drift. The coupling stiffness in dual-mass structures is analyzed. The experiment proves that the left and right masses’ quadrature errors are different, and the quadrature correction system should be arranged independently. The process leading to quadrature error is proposed, and the Charge Injecting Correction (CIC), Quadrature Force Correction (QFC) and Coupling Stiffness Correction (CSC) methods are introduced. The correction objects of these three methods are the quadrature error signal, force and the coupling stiffness, respectively. The three methods are investigated through control theory analysis, model simulation and circuit experiments, and the results support the theoretical analysis. The bias stability results based on CIC, QFC and CSC are 48 °/h, 9.9 °/h and 3.7 °/h, respectively, and this value is 38 °/h before quadrature error correction. The CSC method is proved to be the better method for quadrature correction, and it improves the Angle Random Walking (ARW) value, increasing it from 0.66 °/√h to 0.21 °/√h. The CSC system general test results show that it works well across the full temperature range, and the bias stabilities of the six groups’ output data are 3.8 °/h, 3.6 °/h, 3.4 °/h, 3.1 °/h, 3.0 °/h and 4.2 °/h, respectively, which proves the system has excellent repeatability.

New explicit correlation for the compressibility factor of natural gas: linearized z-factor isotherms

The compressibility factor (z-factor) of gases is a thermodynamic property used to account for the deviation of real gas behavior from that of an ideal gas. Correlations based on the equation of state are often implicit, because they require iteration and are computationally expensive. A number of explicit correlations have been derived to enhance simplicity; however, no single explicit correlation has been developed for the full range of pseudo-reduced temperatures $$\left( {1.05 \le T_{pr} \le 3} \right)$$ and pseudo-reduced pressures $$\left( {0.2 \le P_{pr} \le 15} \right)$$ , which represents a significant research gap. This work presents a new z-factor correlation that can be expressed in linear form. On the basis of Hall and Yarborough’s implicit correlation, we developed the new correlation from 5346 experimental data points extracted from 5940 data points published in the SPE natural gas reservoir engineering textbook and created a linear z-factor chart for a full range of pseudo-reduced temperatures $$(1.15 \le T_{pr} \le 3)$$ and pseudo-reduced pressures $$(0.2 \le P_{pr} \le 15)$$ .

Mesoscopic transport in thin films of La0.67Sr0.33MnO3

We investigate thin films of La0.7Sr0.3MnO3 grown on SrTiO3 in which bridges of 100μm long and 1μm or 300nm wide (distance between voltage contacts was 25μm) were defined lithographically. In bridges of 1μm, we find the current–voltage characteristics to be perfectly linear (ohmic) over the full temperature range between 400K and 10K. Strong non-linearities however are observed for a 300nm wide bridge in the temperature regime below the transition temperature. The non-linearities are present even when applying a high magnetic field of 9T.

Kinematics and energetics of swimming performance during acute warming in brown trout Salmo trutta.

This study examined how acute warming of water temperature affects the mechanical efficiency of swimming and aerobic capabilities of the brown trout Salmo trutta. Swimming efficiency was assessed using the relationship between swimming kinematics and forward speed (U), which is thought to converge upon an optimum range of a dimensionless parameter, the Strouhal number (St ). Swim-tunnel intermittent stopped-flow respirometry was used to record kinematics and measure oxygen consumption (ṀO2) of S. trutta during warming and swimming challenges. Salmo trutta maintained St between 0·2 and 0·3 at any given U over a range of temperatures, irrespective of body size. The maintenance of St within the range for maximum efficiency for oscillatory propulsion was achieved through an increase in tail-beat frequency (ftail) and a decrease in tail-beat amplitude (A) as temperature increased. Maintenance of efficient steady-state swimming was fuelled by aerobic metabolism, which increased as temperature increased up to 18° C but declined above this temperature, decreasing the apparent metabolic scope. As St was maintained over the full range of temperatures whilst metabolic scope was not, the results may suggest energetic trade-offs at any given U at temperatures above thermal optima.

Structurally Restricted Phase Transitions in VO2(B) and Their Impact on Transport Properties

Despite the relatively simple composition and numerous applications of layered VO2(B), several issues such as effect of electron correlations and the nature of its metal–insulator transition remain unresolved due to the low irreversible phase transition temperature. We have overcome this challenge by using spark plasma sintering and reporting its reliable electronic transport properties. All our transport, magnetic and thermal data, converge in favor of an interesting multiphase nature of VO2(B): low temperature phase (insulating and magnetically ordered), an intermediate temperature phase (insulating), and a high temperature phase (presumably metallic with strong electron correlations) coexist. The coexistence domain for these three phases is broad and extends over about 60 K around 235 K. The low temperature phase with spin singlets is always associated with, at least one another phase and becomes dominant below 200 K. The high temperature phase is present over the full temperature range and exists alon...

Convergence of Clock Processes and Aging in Metropolis Dynamics of a Truncated REM

We study the aging behavior of a truncated version of the Random Energy Model evolving under Metropolis dynamics. We prove that the natural time-time correlation function defined through the overlap function converges to an arcsine law distribution function, almost surely in the random environment and in the full range of time scales and temperatures for which such a result can be expected to hold. This establishes that the dynamics ages in the same way as Bouchaud’s REM-like trap model, thus extending the universality class of the latter model. The proof relies on a clock process convergence result of a new type where the number of summands is itself a clock process. This reflects the fact that the exploration process of Metropolis dynamics is itself an aging process, governed by its own clock. Both clock processes are shown to converge to stable subordinators below certain critical lines in their time-scale and temperature domains, almost surely in the random environment.

Thermal diffusivity and 3D-XY critical behavior of ferroelectric semiconductors (PbxSn1−x)2P2Se6

An ac photopyroelectric calorimeter has been used to study the thermal diffusivity of the ferroelectric semiconductors family (PbxSn1−x)2P2Se6 (x=0–1) from 30K to room temperature. Phase transitions have been found for x=0, 0.05, 0.2, 0.47 but not for x=1 in the full temperature range. A continuous phase transition has been found for x=0, 0.05, 0.2 and 0.47 which corresponds to the paraelectric commensurate to incommensurate phase. It has been possible to study the critical behavior of this transition for x=0, 0.05 and the critical parameters obtained have been α=−0.019, A+/A−=1.00 and α=−0.026, A+/A−=1.03, respectively, having fitted at the same time both the low and high temperature branches of the transition as rigorous critical theory indicates; these results agree with the theoretical prediction from renormalization group theory that this kind of transition complies with the 3D-XY universality class (αtheor=−0.014, A+/A−=1.06), which has been experimentally confirmed only in a few materials. A first order incommensurate to ferroelectric phase transition has been characterized in x=0, 0.05 at lower temperature.