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Sample records for temperature-dependent phase behaviors

  1. Temperature-dependent Raman and ultraviolet photoelectron spectroscopy studies on phase transition behavior of VO{sub 2} films with M1 and M2 phases

    Energy Technology Data Exchange (ETDEWEB)

    Okimura, Kunio, E-mail: okifn@keyaki.cc.u-tokai.ac.jp; Hanis Azhan, Nurul [Graduate School of Engineering, Tokai University, Hiratsuka 259-1292 (Japan); Hajiri, Tetsuya [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Kimura, Shin-ichi [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871 (Japan); Zaghrioui, Mustapha; Sakai, Joe [GREMAN, UMR 7347 CNRS, Université François Rabelais de Tours, Parc de Grandmont, 37200 Tours (France)

    2014-04-21

    Structural and electronic phase transitions behavior of two polycrystalline VO{sub 2} films, one with pure M1 phase and the other with pure M2 phase at room temperature, were investigated by temperature-controlled Raman spectroscopy and ultraviolet photoelectron spectroscopy (UPS). We observed characteristic transient dynamics in which the Raman modes at 195 cm{sup −1} (V-V vibration) and 616 cm{sup −1} (V-O vibration) showed remarkable hardening along the temperature in M1 phase film, indicating the rearrangements of V-V pairs and VO{sub 6} octahedra. It was also shown that the M1 Raman mode frequency approached those of invariant M2 peaks before entering rutile phase. In UPS spectra with high energy resolution of 0.03 eV for the M2 phase film, narrower V{sub 3d} band was observed together with smaller gap compared to those of M1 phase film, supporting the nature of Mott insulator of M2 phase even in the polycrystalline film. Cooperative behavior of lattice rearrangements and electronic phase transition was suggested for M1 phase film.

  2. Simulation of phase separation with temperature-dependent viscosity using lattice Boltzmann method.

    Science.gov (United States)

    Wang, Heping; Zang, Duyang; Li, Xiaoguang; Geng, Xingguo

    2017-12-27

    This paper presents an exploration of the phase separation behavior and pattern formation in a binary fluid with temperature-dependent viscosity via a coupled lattice Boltzmann method (LBM). By introducing a viscosity-temperature relation into the LBM, the coupling effects of the viscosity-temperature coefficient [Formula: see text] , initial viscosity [Formula: see text] and thermal diffusion coefficient [Formula: see text] , on the phase separation were successfully described. The calculated results indicated that an increase in initial viscosity and viscosity-temperature coefficient, or a decrease in the thermal diffusion coefficient, can lead to the orientation of isotropic growth fronts over a wide range of viscosity. The results showed that droplet-type phase structures and lamellar phase structures with domain orientation parallel or perpendicular to the walls can be obtained in equilibrium by controlling the initial viscosity, thermal diffusivity, and the viscosity-temperature coefficient. Furthermore, the dataset was rearranged for growth kinetics of domain growth and thermal diffusion fronts in a plot by the spherically averaged structure factor and the ratio of separated and continuous phases. The analysis revealed two different temporal regimes: spinodal decomposition and domain growth stages, which further quantified the coupled effects of temperature and viscosity on the evolution of temperature-dependent phase separation. These numerical results provide guidance for setting optimum temperature ranges to obtain expected phase separation structures for systems with temperature-dependent viscosity.

  3. Temperature-dependent mechanical deformation of silicon at the nanoscale: Phase transformation versus defect propagation

    Energy Technology Data Exchange (ETDEWEB)

    Kiran, M. S. R. N., E-mail: kiran.mangalampalli@anu.edu.au; Tran, T. T.; Smillie, L. A.; Subianto, D.; Williams, J. S.; Bradby, J. E. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Australian Capital Territory, Canberra 2601 (Australia); Haberl, B. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Australian Capital Territory, Canberra 2601 (Australia); Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2015-05-28

    This study uses high-temperature nanoindentation coupled with in situ electrical measurements to investigate the temperature dependence (25–200 °C) of the phase transformation behavior of diamond cubic (dc) silicon at the nanoscale. Along with in situ indentation and electrical data, ex situ characterizations, such as Raman and cross-sectional transmission electron microscopy, have been used to reveal the indentation-induced deformation mechanisms. We find that phase transformation and defect propagation within the crystal lattice are not mutually exclusive deformation processes at elevated temperature. Both can occur at temperatures up to 150 °C but to different extents, depending on the temperature and loading conditions. For nanoindentation, we observe that phase transformation is dominant below 100 °C but that deformation by twinning along (111) planes dominates at 150 °C and 200 °C. This work, therefore, provides clear insight into the temperature dependent deformation mechanisms in dc-Si at the nanoscale and helps to clarify previous inconsistencies in the literature.

  4. COMPENSATION OF OUTPUT SIGNAL TEMPERATURE DEPENDENCE IN HOMODYNE DEMODULATION TECHNIQUE FOR PHASE FIBER-OPTIC SENSORS

    Directory of Open Access Journals (Sweden)

    M. V. Mekhrengin

    2015-03-01

    Full Text Available Modified phase-generated carrier homodyne demodulation technique for fiber-optic sensors is presented. Nowadays phase-generated carrier homodyne demodulation technique is one of the most widespread. One of its drawbacks is the temperature dependence of the output signal because of the modulator scale factor temperature dependence. In order to compensate this dependence an automatic adjustment of the phase modulation depth is necessary. To achieve the result, additional harmonics analysis is used with the help of the Bessel functions. For this purpose the known demodulation scheme is added with the branch, where interferometric signal is multiplied by the third harmonic of the modulation signal. The deviation of optimal ratio of odd harmonics is used as a feedback signal for adjusting the modulation depth. Unwanted emissions arise in the feedback signal, when the third harmonic possesses a value close to zero. To eliminate unwanted emission in the feedback signal, the principle scheme is added with one more branch, where interferometric signal is multiplied by the forth harmonic of the modulation signal. The deviation of optimal ratio of even harmonics is used as a feedback signal alternately with the deviation of optimal ratio of odd harmonics. A mathematical model of the algorithm is designed using the MATLAB package. Results of modeling have confirmed that suggested method gives the possibility for an automatic adjustment of the phase modulation depth and makes it possible to compensate temperature dependence for the modulator scale factor and output signal magnitude.

  5. Temperature dependence of scattering phases and Friedel phase discontinuity in quantum wires

    Science.gov (United States)

    Vargiamidis, Vassilios; Fessatidis, Vassilios

    2011-07-01

    Two important issues concerning the scattering phases in a quantum wire with an attractive scatterer are investigated. We consider the case of two quasibound states which couple to a scattering channel and give rise to two Fano resonances. First, we examine the effects of temperature on the phase of the transmission amplitude and the Friedel phase. It is shown that temperature effects tend to smear sharp features of the transmission phase; namely, the phase drops become less than π, and acquire finite widths which increase linearly in the low-temperature regime. The influence of temperature on the Friedel phase and density of states becomes stronger as the Fano resonance becomes narrower. Second, we examine the behavior of the Friedel phase when the energy of the incident electron crosses an infinitely narrow Fano resonance, forming bound state in the continuum. It is shown that the Friedel phase exhibits abrupt jump of π at this energy. We discuss this odd behavior in relation to the Friedel sum rule and point out its consequences on the charge in the scattering region.

  6. An improved stochastic algorithm for temperature-dependent homogeneous gas phase reactions

    CERN Document Server

    Kraft, M

    2003-01-01

    We propose an improved stochastic algorithm for temperature-dependent homogeneous gas phase reactions. By combining forward and reverse reaction rates, a significant gain in computational efficiency is achieved. Two modifications of modelling the temperature dependence (with and without conservation of enthalpy) are introduced and studied quantitatively. The algorithm is tested for the combustion of n-heptane, which is a reference fuel component for internal combustion engines. The convergence of the algorithm is studied by a series of numerical experiments and the computational cost of the stochastic algorithm is compared with the DAE code DASSL. If less accuracy is needed the stochastic algorithm is faster on short simulation time intervals. The new stochastic algorithm is significantly faster than the original direct simulation algorithm in all cases considered.

  7. Surprising behaviors in the temperature dependent kinetics of diatomic interhalogens with anions and cations

    Science.gov (United States)

    Shuman, Nicholas S.; Martinez, Oscar; Ard, Shaun G.; Wiens, Justin P.; Keyes, Nicholas R.; Guo, Hua; Viggiano, Albert A.

    2017-06-01

    Rate constants and product branching fractions of reactions between diatomic interhalogens (ICl, ClF) and a series of anions (Br-, I-) and cations (Ar+, N2+) are measured using a selected ion flow tube apparatus and reported over the temperature range 200-500 K. The efficiency of both anion reactions with ICl is 2%-3% at 300 K to yield Cl-, increasing with temperature in a manner consistent with the small endothermicities of the reactions. The anion reactions with ClF are 10%-20% efficient at 300 K to yield Cl- and also show a positive temperature dependence despite being highly exothermic. The stationary points along the anion + ClF reaction coordinates were calculated using density functional theory, showing no endothermic barriers inhibiting reaction. The observed temperature dependence can be rationalized by a decreasing dipole attraction with increasing rotational energy, but confirmation requires trajectory calculations of the systems. All four cation reactions are fairly efficient at 300 K with small positive temperature dependences, despite large exothermicities to charge transfer. Three of the four reactions proceed exclusively by dissociative charge transfer to yield Cl+. The N2+ + ClF reaction proceeds by both non-dissociative and dissociative charge transfer, with the non-dissociative channel surprisingly increasing with increasing temperature. The origins of these behaviors are not clear and are discussed within the framework of charge-transfer reactions.

  8. Temperature dependence of the magneto-controllable first-order phase transition in dilute magnetic fluids

    Science.gov (United States)

    Ivanov, A. S.

    2017-11-01

    Experimental study was carried out to investigate the influence of particle size distribution function on the temperature dependent magneto-controllable first-order phase transition of the ;gas-liquid; type in magnetic fluids. The study resolves one crisis situation in ferrohydrodynamic experiment made by several research groups in the 1980-1990s. It is shown that due to polydispersity magnetic fluids exhibit phase diagrams which are divided into three regions by vaporus and liquidus curves. Granulometric data states the primary role of the width of the particle size distribution function in the process of spinodal decomposition. New modified Langevin parameter is introduced for unification of liquidus curves of different ferrofluids despite the significant difference between the curves (one order of magnitude) in (H, T) coordinates.

  9. Bending behavior of thermoplastic composite sheets viscoelasticity and temperature dependency in the draping process

    CERN Document Server

    Ropers, Steffen

    2017-01-01

    Within the scope of this work, Steffen Ropers evaluates the viscoelastic and temperature-dependent nature of the bending behavior of thermoplastic composite sheets in order to further enhance the predictability of the draping simulation. This simulation is a useful tool for the development of robust large scale processes for continuously fiber-reinforced polymers (CFRP). The bending behavior thereby largely influences the size and position of wrinkles, which are one of the most common processing defects for continuously fiber-reinforced parts. Thus, a better understanding of the bending behavior of thermoplastic composite sheets as well as an appropriate testing method along with corresponding material models contribute to a wide-spread application of CFRPs in large scale production. Contents Thermoplastic Prepregs Draping Simulation of Thermoplastic Prepregs Bending Characterization of Textile Composites Modeling of Bending Behavior Target Groups Researchers and students in the field of polymer, lightweight,...

  10. Temperature dependence of the excitonic insulator phase model in 1T-TiSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Monney, C., E-mail: claude.monney@unifr.c [Institut de Physique, Universite de Fribourg, CH-1700 Fribourg (Switzerland); Cercellier, H. [Institut Neel, CNRS, F-38042 Grenoble (France); Battaglia, C.; Schwier, E.F.; Didiot, C.; Garnier, M.G.; Beck, H.; Aebi, P. [Institut de Physique, Universite de Fribourg, CH-1700 Fribourg (Switzerland)

    2009-10-15

    Recently, detailed calculations of the excitonic insulator phase model adapted to the case of 1T-TiSe{sub 2} have been presented. Through the spectral function theoretical photoemission intensity maps can be generated which are in very good agreement with experiment [H. Cercellier, et al., Phys. Rev. Lett. 99 (2007) 146403]. In this model, excitons condensate in a BCS-like manner and give rise to a charge density wave, characterized by an order parameter. Here, we assume an analytical form of the order parameter, allowing to perform temperature dependent calculations. The influence of this order parameter on the electronic spectral function, to be observed in photoemission spectra, is discussed. The resulting chemical potential shift and an estimation of the resistivity are also shown.

  11. Investigation of the temperature dependence of water adsorption on silica-based stationary phases in hydrophilic interaction liquid chromatography.

    Science.gov (United States)

    Bartó, Endre; Felinger, Attila; Jandera, Pavel

    2017-03-17

    In the present work, the adsorption of water was investigated in aqueous normal-phase liquid chromatography on Cogent Silica C and Cogent Phenyl hydride stationary phases at different temperatures by frontal analysis - using coulometric Karl Fischer titration - to compare the temperature dependence of adsorption of water from aqueous acetonitrile. The Cogent Silica-C and Cogent Phenyl Hydride columns have a silicon hydride surface (silica hydride) with less than 2% free silanol group; therefore, they do not have a strong association with water. The adsorption behavior of water on the mentioned stationary phases was modeled by Langmuir isotherm. The preferentially adsorbed water was expressed in terms of a hypothetical monomolecular water layer equivalent in the inner pores. The uptake of water slightly depends on the temperature. The adsorbed water may fill four to eight percent of the pore volume over the studied temperature range, which approximately corresponds to the equivalent of 0.24-0.68 water layer coverage of the adsorbent surface. The phenyl hydride stationary phase shows decreased water uptake in comparison to the Silica C stationary phase. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Structural phase transitions in ionic conductor Bi2O3 by temperature dependent XPD and XAS

    Science.gov (United States)

    Zhu, Yingcai; An, Pengfei; Yu, Meijuan; Marcelli, Augusto; Liu, Yong; Hu, Tiandou; Xu, Wei

    2016-05-01

    The superionic behavior of cubic δ-phase Bi2O3, a metastable phase at high temperature, is of great interests from both scientific and technological perspectives. With the highest ionic conductivity among all known compounds, the δ-phase Bi2O3 possesses promising applications in solid-oxide fuel cells. Previous investigations pointed out the α to δ- phase transition occurs during the heating process, as supported by the X-ray and Neutron diffraction experiments. Through in situ measurements of the long-range order structure and the local structure by X-ray powder diffraction and X-ray absorption spectroscopy, we investigated the evolution of the structures under different temperatures. Both techniques provided ample evidence that the existence of meta-stable β-phase are crucial for forming the defective fluorite cubic δ phase. Our finding suggested that the phase transition from tetragonal β-phase to δ-phase is an influencing factor for the generation of the oxygen-ion pathways.

  13. Estimation of brittle fracture behavior of SA508 carbon steel by considering temperature dependence of damage model

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Shin Beom; Jeong, Jae Uk; Choi, Jae Boong [Sungkyunkwan Univ., Seoul (Korea, Republic of); Chang, Yoon Suk [Kyunghee Univ., Seoul (Korea, Republic of); Kim, Min Chul [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    The aim of this study was to determine the brittle fracture behavior of reactor pressure vessel steel by considering the temperature dependence of a damage model. A multi island genetic algorithm was linked to a Weibull stress model, which is the model typically used for brittle fracture evaluation, to improve the calibration procedure. The improved calibration procedure and fracture toughness test data for SA508 carbon steel at the temperatures -60 .deg. C, -80 .deg. C, and -100 .deg. C were used to decide the damage parameters required for the brittle fracture evaluation. The model was found to show temperature dependence, similar to the case of NUREG/CR 6930. Finally, on the basis of the quantification of the difference between 2- and 3-parameter Weibull stress models, an engineering equation that can help obtain more realistic fracture behavior by using the simpler 2-parameter Weibull stress model was proposed.

  14. Anomalous temperature dependence of gas chromatographic retention indices of polar compounds on non-polar stationary phases.

    Science.gov (United States)

    Pavlovskii, Alexander A; Héberger, Károly; Zenkevich, Igor G

    2016-05-06

    Increasing the reliability of both GC and GC-MS identification requires appropriate interlaboratory reproducibility of gas chromatographic retention indices (I). Known temperature dependence, I(T), is the main source of non-reproducibility of these parameters. It can be approximated with a simple linear function I(T). However, since mid-1990s-beginning of 2000s some examples of anomalous temperature dependence, I(T), preferably for polar analytes on non-polar stationary phases were revealed independently by different authors. The effect implies the variations in the sign of the temperature coefficients β=dI/dT for selected compounds and, hence, the appearance of the I-extrema (usually, minima). The current work provides evidence that the character of the anomalous I(Т) dependences (ascending, descending, or with extrema) is strongly influenced by the amounts of analytes injected into the chromatographic column, but these anomalies appeared not to be connected directly with the mass overloading of separation systems. The physicochemical model is proposed to describe the observed anomalies of I(T) dependence. This model is based on three previously known principles of chromatography, namely: The superposition of these objectives allows understanding both the unusual temperature dependence of retention indices, and the influence of the amounts of polar analytes injected into GC column on the parameters of this dependence. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. [Study on the Temperature Dependent Phase Transformation of Raman Spectra for Cyclobutanol].

    Science.gov (United States)

    Zhang, Huan-jun; Cheng, Xue-rui; Ren, Yu-fen; Zhu, Xiang; Yuan, Chao-sheng

    2016-02-01

    Cyclobutanol (C₄H₈O) is one of the four-membered ring type molecules, which usually adopts a non-planar equilibrium conformation, and the substituent group OH can adopt two positions relative to the puckered ring, the axial or the equatorial, giving rise to an additional degree of freedom and various molecular conformations. Additionally, temperature is one important thermodynamic parameter that greatly influents the structure and induces the possibility of conformational change or crystal change. As a consequence, there may be a number of phase transitions and molecular conformations for cyclobutanol under different temperature. In this paper, Raman and infrared spectroscopic technique were applied to investigate the vibration modes of cyclobutanol. The results indicate that the main component of the liquid cyclobutanol is equatorial-trans (Eq-t) conformer with a few Eq-g conformers at ambient condition. Then differential scanning calorimetry (DSC) and low temperature Raman spectroscopic were applied to study the phase transition of cyclobutanol during the cooling and heating process. It is observed that the Raman spectra and the intensities of these bands are not significantly changed during the cooling process. The results indicate that there is sill no presence of solidification especially cooling to 140K, which indicates that the cyclobutanol still remains the liquid state and supercooled state is observed during the cooling process. And this supercooled liquid is one metastable state, not in thermodynamic equilibrium. Further cooling to 138 K, the super-cooling liquid cyclobutanol will transform into the glassy state, accompanied with a small change of entropy. During the heating process, as the temperature is raised to 180 K, the Raman peaks became sharper and some new characteristic peaks appeared abruptly and a discontinuous change was observed in bandwidths versus temperature. And these new signatures can be maintained upon to 220 K, and then will

  16. Simulation study of temperature-dependent diffusion behaviors of Ag/Ag(001) at low substrate temperature

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Danyun; Mo, Yunjie [State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou, 510275 (China); Feng, Xiaofang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-sen University, Guangzhou, 510275 (China); He, Yingyou [State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou, 510275 (China); Jiang, Shaoji, E-mail: stsjsj@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-sen University, Guangzhou, 510275 (China)

    2017-06-01

    Highlights: • The model of combinations of nearest-neighbor atoms of adatom was built to calculate the diffusion barrier of every configuration for Ag/Ag(001). • The complete potential energy curve of a specific diffusion path on the surface was worked out with the help of elementary diffusion behaviors. • The non-monotonic relation between the surface roughness and the substrate temperature (decreasing from 300 K to 100 K) was demonstrated. • A theoretical explanation of diffusion mechanism for the non-monotonic variation of roughness at low substrate temperature was presented. - Abstract: In this study, a model based on the First Principles calculations and Kinetic Monte Carlo simulation were established to study the growth characteristic of Ag thin film at low substrate temperature. On the basis of the interaction between the adatom and nearest-neighbor atoms, some simplifications and assumptions were made to categorize the diffusion behaviors of Ag adatoms on Ag(001). Then the barriers of all possible diffusion behaviors were calculated using the Climbing Image Nudged Elastic Band method (CI-NEB). Based on the Arrhenius formula, the morphology variation, which is attributed to the surface diffusion behaviors during the growth, was simulated with a temperature-dependent KMC model. With this model, a non-monotonic relation between the surface roughness and the substrate temperature (decreasing from 300 K to 100 K) were discovered. The analysis of the temperature dependence on diffusion behaviors presents a theoretical explanation of diffusion mechanism for the non-monotonic variation of roughness at low substrate temperature.

  17. Phase transition analysis of V-shaped liquid crystal: Combined temperature-dependent FTIR and density functional theory approach.

    Science.gov (United States)

    Singh, Swapnil; Singh, Harshita; Karthick, T; Tandon, Poonam; Prasad, Veena

    2018-01-05

    Temperature-dependent Fourier transform infrared spectroscopy (FTIR) combined with density functional theory (DFT) is employed to study the mechanism of phase transitions of V-shaped bent-core liquid crystal. Since it has a large number of flexible bonds, one-dimensional potential energy scan (PES) was performed on the flexible bonds and predicted the most stable conformer I. A detailed analysis of vibrational normal modes of conformer I have been done on the basis of potential energy distribution. The good agreement between the calculated spectrum of conformer I and observed FTIR spectrum at room temperature validates our theoretical structure model. Furthermore, the prominent changes observed in the stretching vibrational bands of CH3/CH2, CO, ring CC, ring CO, ring CH in-plane bending, and ring CH out-of-plane bending at Iso→nematic phase transition (at 155°C) have been illustrated. However, the minor changes in the spectral features observed for the other phase transitions might be due to the shape or bulkiness of molecules. Combined FTIR and PES study beautifully explained the dynamics of the molecules, molecular realignment, H-bonding, and conformational changes at the phase transitions. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Phase transition analysis of V-shaped liquid crystal: Combined temperature-dependent FTIR and density functional theory approach

    Science.gov (United States)

    Singh, Swapnil; Singh, Harshita; Karthick, T.; Tandon, Poonam; Prasad, Veena

    2018-01-01

    Temperature-dependent Fourier transform infrared spectroscopy (FTIR) combined with density functional theory (DFT) is employed to study the mechanism of phase transitions of V-shaped bent-core liquid crystal. Since it has a large number of flexible bonds, one-dimensional potential energy scan (PES) was performed on the flexible bonds and predicted the most stable conformer I. A detailed analysis of vibrational normal modes of conformer I have been done on the basis of potential energy distribution. The good agreement between the calculated spectrum of conformer I and observed FTIR spectrum at room temperature validates our theoretical structure model. Furthermore, the prominent changes observed in the stretching vibrational bands of CH3/CH2, Cdbnd O, ring CC, ring CO, ring CH in-plane bending, and ring CH out-of-plane bending at Iso → nematic phase transition (at 155 °C) have been illustrated. However, the minor changes in the spectral features observed for the other phase transitions might be due to the shape or bulkiness of molecules. Combined FTIR and PES study beautifully explained the dynamics of the molecules, molecular realignment, H-bonding, and conformational changes at the phase transitions.

  19. Temperature dependence of the deformation behavior of 316 stainless steel after low temperature neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Pawel-Robertson, J.E.; Rowcliffe, A.F.; Grossbeck, M.L. [Oak Ridge National Lab., TN (United States)] [and others

    1996-10-01

    The effects of low temperature neutron irradiation on the tensile behavior of 316 stainless steel have been investigated. A single heat of solution annealed 316 was irradiated to 7 and 18 dpa at 60, 200, 330, and 400{degrees}C. The tensile properties as a function of dose and as a function of temperature were examined. Large changes in yield strength, deformation mode, strain to necking, and strain hardening capacity were seen in this irradiation experiment. The magnitudes of the changes are dependent on both irradiation temperature and neutron dose. Irradiation can more than triple the yield strength over the unirradiated value and decrease the strain to necking (STN) to less than 0.5% under certain conditions. A maximum increase in yield strength and a minimum in the STN occur after irradiation at 330{degrees}C but the failure mode remains ductile.

  20. Modeling of a Two-Phase Jet Pump with Phase Change, Shocks and Temperature-Dependent Properties

    Science.gov (United States)

    Sherif, S. A.

    1998-01-01

    One of the primary motivations behind this work is the attempt to understand the physics of a two-phase jet pump which constitutes part of a flow boiling test facility at NASA-Marshall. The flow boiling apparatus is intended to provide data necessary to design highly efficient two-phase thermal control systems for aerospace applications. The facility will also be capable of testing alternative refrigerants and evaluate their performance using various heat exchangers with enhanced surfaces. The test facility is also intended for use in evaluating single-phase performance of systems currently using CFC refrigerants. Literature dealing with jet pumps is abundant and covers a very wide array of application areas. Example application areas include vacuum pumps which are used in the food industry, power station work, and the chemical industry; ejector systems which have applications in the aircraft industry as cabin ventilators and for purposes of jet thrust augmentation; jet pumps which are used in the oil industry for oil well pumping; and steam-jet ejector refrigeration, to just name a few. Examples of work relevant to this investigation includes those of Fairuzov and Bredikhin (1995). While past researchers have been able to model the two-phase flow jet pump using the one-dimensional assumption with no shock waves and no phase change, there is no research known to the author apart from that of Anand (1992) who was able to account for condensation shocks. Thus, one of the objectives of this work is to model the dynamics of fluid interaction between a two-phase primary fluid and a subcooled liquid secondary fluid which is being injected employing atomizing spray injectors. The model developed accounts for phase transformations due to expansion, compression, and mixing. It also accounts for shock waves developing in the different parts of the jet pump as well as temperature and pressure dependencies of the fluid properties for both the primary two-phase mixture and the

  1. Effects of Phase Fraction on Temperature Dependency of Fracture Toughness in Transition Temperature Region in SA508 Gr. 4N Ni-Mo-Cr Low Alloy Steels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Wee, Dang Moon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    The Reactor Pressure Vessel (RPV) is the main component in determining the lifetime of nuclear power plants because it is subject to the aging phenomenon of irradiation embrittlement and there is no practical method for replacing that component. For materials used for the RPV, sufficient strength and toughness are required to prevent failure against the severe operating conditions and the aging degradation of materials. SA508 Gr.4N Ni-Mo-Cr low alloy steel, in which Ni and Cr contents are higher than in conventional RPV steels, may be a promising RPV material with the improved strength and toughness from its tempered martensitic microstructure. Wallin observed that the temperature dependency of fracture toughness is not sensitive to the chemical composition, heat treatment, and irradiation for ferritic steels. This result led to the concept of a universal shape in the median toughness-temperature curve for all 'ferritic steels'. However, there are some doubts about the universal shape in the ASTM master curve for the tempered martensitic steels, such as Eurofer97. It was also reported that the fracture toughness increased discontinuously when the phase fraction of the tempered martensite was over a critical fraction in the heat affected zones of SA508 Gr.3. Therefore, it may be necessary to evaluate the changes of transition behavior with microstructures of steel. In this study, the effects phase fraction of tempered martensite controlled by a cooling rate on the transition behavior of SA508 Gr.4N low alloy steels was evaluated. Additionally, the relationship between the variations of yield strength with the temperature and fracture stress in a local approach was discussed

  2. Exploring the Origin of the Temperature-Dependent Behavior of PbS Nanocrystal Thin Films and Solar Cells

    NARCIS (Netherlands)

    Szendrei, Krisztina; Speirs, Mark; Gomulya, Widianta; Jarzab, Dorota; Manca, Marianna; Mikhnenko, Oleksandr V.; Yarema, Maksym; Kooi, Bart J.; Heiss, Wolfgang; Loi, Maria A.

    2012-01-01

    Temperature-dependent studies of the electrical and optical properties of cross-linked PbS nanocrystal (NC) solar cells can provide deeper insight into their working mechanisms. It is demonstrated that the overall effect of temperature on the device efficiency originates from the temperature

  3. Infrared studies of temperature-dependent phase transitions in ammonium sulfate aerosol and the development of a visible light scattering technique to measure atmospheric particle compositions

    Science.gov (United States)

    Onasch, Timothy Bruce

    1999-10-01

    Sulfate containing particles exist globally throughout the atmosphere and impact its chemistry and radiative properties. Under the low temperature conditions found in the upper troposphere and lower stratosphere, sulfate particles act as nuclei for cirrus clouds and facilitate heterogeneous reactions which affect ozone chemistry. Both of these processes are dependent upon the chemical composition and phase of the background aerosol, and thus the behavior of these particles at low temperatures. This thesis represents two approaches undertaken to investigate the composition and phase of atmospheric aerosols. First, a flow tube system has been developed to study the low temperature behavior of atmospherically relevant particles within a controlled laboratory environment. Second, a visible light scattering technique has been developed to characterize the physical properties of particles in situ from an aircraft platform. The relative humidities of temperature-dependent phase transitions in ammonium sulfate aerosols were measured within a flow tube system. A chilled-mirror hygrometer measured the relative humidity and Fourier transform infrared spectroscopy was utilized to probe the phase of the particles and to characterize their microphysical properties. The relative humidity of deliquescence changed from 80% to 82% over the temperature range from 294.8 K to 258.0 K, in agreement with thermodynamic theory. The efflorescence relative humidity of submicron ammonium sulfate particles increased slightly from 32% to 39% as the temperature decreased from 294.8 K to 234.3 K. The latter result suggests that salt particles may exist as metastable solution droplets under low relative humidity conditions for significant time periods in the upper troposphere. To measure particle refractive indices in situ, a visible light scattering technique based on NCAR's Multiangle Aerosol Spectrometer Probe (MASP) was developed. The MASP was calibrated with monodisperse particles having

  4. Glycol-Water Interactions and co-existing phases and Temperature Dependent Solubility. An Example Of Carbon-Hydrogen Chemistry In Water

    CERN Document Server

    Michael, Fredrick

    2010-01-01

    Recently there has been great interest in Glycol-Water chemistry and solubility and temperature dependent phase dynamics. The Glycol-Water biochemistry of interactions is present in plant biology and chemistry, is of great interest to chemical engineers and biochemists as it is a paradigm of Carbon-Hydrogen Water organic chemistry. There is an interest moreover in formulating a simpler theory and computation model for the Glycol-Water interaction and phase dynamics, that is not fully quantum mechanical yet has the high accuracy available from a fully quantum mechanical theory of phase transitions of fluids and Fermi systems. Along these lines of research interest we have derived a Lennard-Jones -like theory of interacting molecules-Water in a dissolved adducts of Glycol-Water system interacting by Hydrogen bonds whose validity is supported at the scale of interactions by other independent molecular dynamics investigations that utilize force fields dependent on their experimental fittings to the Lennard-Jones ...

  5. Measurement of the temperature dependence of Young's modulus of cartilage by phase-sensitive optical coherence elastography

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C H; Li, J; Singh, M; Larin, K V [Department of Biomedical Engineering, University of Houston, Houston, Texas (United States); Skryabina, M N [Department of Physics, M.V. Lomonosov Moscow State University (Russian Federation); Sobol, E N [Institute of Laser and Information Technologies, Russian Academy of Sciences, Troitsk, Moscow Region (Russian Federation)

    2014-08-31

    The development of an effective system to monitor the changes in the elastic properties of cartilage tissue with increasing temperature in laser reconstruction is an urgent practical task. In this paper, the use of phase-sensitive optical coherence elastography for detection of elastic waves in the sample has allowed Young's modulus of cartilage tissue to be measured directly during heating. Young's modulus was calculated from the group velocity of propagation of elastic waves excited by means of a system supplying focused air pulses. The measurement results are in agreement with the results of measurements of the modulus of elasticity under mechanical compression. The technique developed allows for noninvasive measurements; its development is promising for the use in vivo. (laser biophotonics)

  6. First Order Temperature Dependent Phase Transition in a Monoclinic Polymorph Crystal of 1,6-Hexanedioic Acid: An Interpretation Based on the Landau Theory Approach

    Directory of Open Access Journals (Sweden)

    Hoong-Kun Fun

    2014-07-01

    Full Text Available Crystals of 1,6-hexanedioic acid (I undergo a temperature-dependent reversible phase transition from monoclinic P21/c at a temperature higher than the critical temperature (Tc 130 K to another monoclinic P21/c at temperature lower than Tc. The phase transition is of first order, involving a discontinuity and a tripling of the b-axis at Tc whereas the other unit cell parameters vary continuously. The transition is described by the phenomenological Landau theory. The crystal structure analyses for data collected at 297(2 K and 120.0(1 K show that there is half of a molecule of (I in the asymmetric unit at 297(2 K whereas there are one and a half molecules of (I in the asymmetric unit at 120.0(1 K. At both temperatures, 297(2 and 120.0(1 K, intermolecular O-H···O hydrogen bonds link the molecules of I into infinite 1D chains along [101] direction. However there are significantly more O-H···O hydrogen bonds presented in the 120.0(1 K polymorph, thereby indicating this phase transition is negotiated via hydrogen bonds. The relationship of the conformational changes and hydrogen bonding for these two polymorphs are explained in detail.

  7. Investigation Of Temperature Dependent Characteristics Of ...

    African Journals Online (AJOL)

    The structure, magnetization and magnetostriction of Laves phase compound TbCo2 were investigated by temperature dependent high resolution neutron powder diffraction. The compound crystallizes in the cubic Laves phase C15 structure above its Curie temperature, TC and exhibits a rhombohedral distortion (space ...

  8. Temperature-dependent Hammond behavior in a protein-folding reaction: analysis of transition-state movement and ground-state effects.

    Science.gov (United States)

    Taskent, Humeyra; Cho, Jae-Hyun; Raleigh, Daniel P

    2008-05-02

    Characterization of the transition-state ensemble and the nature of the free-energy barrier for protein folding are areas of intense activity and some controversy. A key issue that has emerged in recent years is the width of the free-energy barrier and the susceptibility of the transition state to movement. Here we report denaturant-induced and temperature-dependent folding studies of a small mixed alpha-beta protein, the N-terminal domain of L9 (NTL9). The folding of NTL9 was determined using fluorescence-detected stopped-flow fluorescence measurements conducted at seven different temperatures between 11 and 40 degrees C. Plots of the log of the observed first-order rate constant versus denaturant concentration, "chevron plots," displayed the characteristic V shape expected for two-state folding. There was no hint of deviation from linearity even at the lowest denaturant concentrations. The relative position of the transition state, as judged by the Tanford beta parameter, beta(T), shifts towards the native state as the temperature is increased. Analysis of the temperature dependence of the kinetic and equilibrium m values indicates that the effect is due to significant movement of the transition state and also includes a contribution from temperature-dependent ground-state effects. Analysis of the Leffler plots, plots of Delta G versus Delta G degrees, and their cross-interaction parameters confirms the transition-state movement. Since the protein is destabilized at high temperature, the shift represents a temperature-dependent Hammond effect. This provides independent confirmation of a recent theoretical prediction. The magnitude of the temperature-denaturant cross-interaction parameter is larger for NTL9 than has been reported for the few other cases studied. The implications for temperature-dependent studies of protein folding are discussed.

  9. Spectroscopic evidence for Fermi liquid-like energy and temperature dependence of the relaxation rate in the pseudogap phase of the cuprates.

    Science.gov (United States)

    Mirzaei, Seyed Iman; Stricker, Damien; Hancock, Jason N; Berthod, Christophe; Georges, Antoine; van Heumen, Erik; Chan, Mun K; Zhao, Xudong; Li, Yuan; Greven, Martin; Barišić, Neven; van der Marel, Dirk

    2013-04-09

    Cuprate high-Tc superconductors exhibit enigmatic behavior in the nonsuperconducting state. For carrier concentrations near "optimal doping" (with respect to the highest Tcs) the transport and spectroscopic properties are unlike those of a Landau-Fermi liquid. On the Mott-insulating side of the optimal carrier concentration, which corresponds to underdoping, a pseudogap removes quasi-particle spectral weight from parts of the Fermi surface and causes a breakup of the Fermi surface into disconnected nodal and antinodal sectors. Here, we show that the near-nodal excitations of underdoped cuprates obey Fermi liquid behavior. The lifetime τ(ω, T) of a quasi-particle depends on its energy ω as well as on the temperature T. For a Fermi liquid, 1/τ(ω, T) is expected to collapse on a universal function proportional to (ℏω)(2) + (pπk(B)T)(2). Magneto-transport experiments, which probe the properties in the limit ω = 0, have provided indications for the presence of a T(2) dependence of the dc (ω = 0) resistivity of different cuprate materials. However, Fermi liquid behavior is very much about the energy dependence of the lifetime, and this can only be addressed by spectroscopic techniques. Our optical experiments confirm the aforementioned universal ω- and T dependence of 1/τ(ω, T), with p ∼ 1.5. Our data thus provide a piece of evidence in favor of a Fermi liquid-like scenario of the pseudogap phase of the cuprates.

  10. Evaluation of the three-phase equilibrium method for measuring temperature dependence of internally consistent partition coefficients (K(OW), K(OA), and K(AW)) for volatile methylsiloxanes and trimethylsilanol.

    Science.gov (United States)

    Xu, Shihe; Kropscott, Bruce

    2014-12-01

    Partitioning equilibria and their temperature dependence of chemicals between different environmental media are important in determining the fate, transport, and distribution of contaminants. Unfortunately, internally consistent air/water (K(AW)), 1-octanol/air (K(OA)), and 1-octanol/water (K(OW)) partition coefficients, as well as information on their temperature dependence, are scarce for organosilicon compounds because of the reactivity of these compounds in water and octanol and their extreme partition coefficients. A newly published 3-phase equilibrium method was evaluated for simultaneous determination of the temperature dependence of (K(OW), K(OA), and K(AW)) of 5 volatile methylsiloxanes (VMS) and trimethylsilanol (TMS) in a temperature range from 4 °C to 35 °C. The measured partition coefficients at the different temperatures for any given compound, and the enthalpy and entropy changes for the corresponding partition processes, were all internally consistent, suggesting that the 3-phase equilibrium method is suitable for this type of measurement. Compared with common environmental contaminants reported in the literature, VMS have enthalpy and entropy relationships similar to those of alkanes for air/water partitioning and similar to those of polyfluorinated compounds for octanol/air partitioning, but more like those for benzoates and phenolic compounds for octanol/water partitioning. The temperature dependence of the partition coefficients of TMS is different from those of VMS and is more like that of alcohols, phenols, and sulfonamides. © 2014 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc.

  11. Temperature dependence of surface nanobubbles

    NARCIS (Netherlands)

    Berkelaar, R.P.; Seddon, James Richard Thorley; Zandvliet, Henricus J.W.; Lohse, Detlef

    2012-01-01

    The temperature dependence of nanobubbles was investigated experimentally using atomic force microscopy. By scanning the same area of the surface at temperatures from 51 °C to 25 °C it was possible to track geometrical changes of individual nanobubbles as the temperature was decreased.

  12. Modeling temperature dependence of trace element concentrations in groundwater using temperature dependent distribution coefficient

    Science.gov (United States)

    Saito, H.; Saito, T.; Hamamoto, S.; Komatsu, T.

    2015-12-01

    In our previous study, we have observed trace element concentrations in groundwater increased when groundwater temperature was increased with constant thermal loading using a 50-m long vertical heat exchanger installed at Saitama University, Japan. During the field experiment, 38 degree C fluid was circulated in the heat exchanger resulting 2.8 kW thermal loading over 295 days. Groundwater samples were collected regularly from 17-m and 40-m deep aquifers at four observation wells located 1, 2, 5, and 10 m, respectively, from the heat exchange well and were analyzed with ICP-MS. As a result, concentrations of some trace elements such as boron increased with temperature especially at the 17-m deep aquifer that is known as marine sediment. It has been also observed that the increased concentrations have decreased after the thermal loading was terminated indicating that this phenomenon may be reversible. Although the mechanism is not fully understood, changes in the liquid phase concentration should be associated with dissolution and/or desorption from the solid phase. We therefore attempt to model this phenomenon by introducing temperature dependence in equilibrium linear adsorption isotherms. We assumed that distribution coefficients decrease with temperature so that the liquid phase concentration of a given element becomes higher as the temperature increases under the condition that the total mass stays constant. A shape function was developed to model the temperature dependence of the distribution coefficient. By solving the mass balance equation between the liquid phase and the solid phase for a given element, a new term describing changes in the concentration was implemented in a source/sink term of a standard convection dispersion equation (CDE). The CDE was then solved under a constant ground water flow using FlexPDE. By calibrating parameters in the newly developed shape function, the changes in element concentrations observed were quite well predicted. The

  13. Spectroscopic evidence for Fermi liquid-like energy and temperature dependence of the relaxation rate in the pseudogap phase of the cuprates

    NARCIS (Netherlands)

    Mirzaei, S.I.; Stricker, D.; Hancock, J.N.; Berthod, C.; Georges, A.; van Heumen, E.; Chan, M.K.; Zhao, X.; Li, Y.; Greven, M.; Barišić, N.; van der Marel, D.

    2013-01-01

    Cuprate high-Tc superconductors exhibit enigmatic behavior in the nonsuperconducting state. For carrier concentrations near "optimal doping" (with respect to the highest Tcs) the transport and spectroscopic properties are unlike those of a Landau-Fermi liquid. On the Mott-insulating side of the

  14. Temperature-dependent phase transition and comparative investigation on enhanced magnetic and optical properties between sillenite and perovskite bismuth ferrite-rGO nanocomposites

    Science.gov (United States)

    Jalil, M. A.; Chowdhury, Sayeed Shafayet; Alam Sakib, Mashnoon; Enamul Hoque Yousuf, S. M.; Khan Ashik, Emran; Firoz, Shakhawat H.; Basith, M. A.

    2017-08-01

    The manuscript reports the synthesis as well as a comparative investigation of the structural, magnetic, and optical properties between sillenite and perovskite type bismuth ferrite-reduced graphene oxide nanocomposites. Graphite oxide is prepared using the modified Hummers' method, followed by hydrothermal synthesis of bismuth ferrite-reduced graphene oxide nanocomposites at different reaction temperatures. The X-ray diffraction measurements confirm the formation of perovskite type BiFeO3-rGO nanocomposites at a reaction temperature of 200 °C. This is the lowest temperature to obtain perovskite type BiFeO3-rGO nanocomposites under the reaction procedure adopted, however, a structural transition to sillenite type Bi25FeO40-rGO is observed at 180 °C. The FESEM images demonstrate that the particle size of the perovskite nanocomposite is 25-60 nm, and for the sillenite phase nanocomposite it is 10-30 nm. The as-synthesized nanocomposites exhibit significantly enhanced saturation magnetization over pure BiFeO3 nanoparticles, with the sillenite Bi25FeO40-rGO nanocomposite having higher saturation magnetization than perovskite BiFeO3-rGO. The optical characteristics of the as-synthesized nanocomposites demonstrate considerably higher absorbance in the visible range with significantly lower band gap in comparison to undoped BiFeO3. Again, the sillenite Bi25FeO40-rGO nanocomposite is shown to have a lower band gap compared to the perovskite counterpart. Our investigation provides a means of selective phase formation as desired between sillenite Bi25FeO40-rGO and perovskite BiFeO3-rGO by controlling the hydrothermal reaction temperature. The outcome of our investigation suggests that the formation of nanocomposite of sillenite bismuth ferrite with reduced graphene oxide is promising to improve the magnetic and optical properties for potential technological applications.

  15. Second-order structural phase transitions, free energy curvature, and temperature-dependent anharmonic phonons in the self-consistent harmonic approximation: Theory and stochastic implementation

    Science.gov (United States)

    Bianco, Raffaello; Errea, Ion; Paulatto, Lorenzo; Calandra, Matteo; Mauri, Francesco

    2017-07-01

    The self-consistent harmonic approximation is an effective harmonic theory to calculate the free energy of systems with strongly anharmonic atomic vibrations, and its stochastic implementation has proved to be an efficient method to study, from first-principles, the anharmonic properties of solids. The free energy as a function of average atomic positions (centroids) can be used to study quantum or thermal lattice instability. In particular the centroids are order parameters in second-order structural phase transitions such as, e.g., charge-density-waves or ferroelectric instabilities. According to Landau's theory, the knowledge of the second derivative of the free energy (i.e., the curvature) with respect to the centroids in a high-symmetry configuration allows the identification of the phase-transition and of the instability modes. In this work we derive the exact analytic formula for the second derivative of the free energy in the self-consistent harmonic approximation for a generic atomic configuration. The analytic derivative is expressed in terms of the atomic displacements and forces in a form that can be evaluated by a stochastic technique using importance sampling. Our approach is particularly suitable for applications based on first-principles density-functional-theory calculations, where the forces on atoms can be obtained with a negligible computational effort compared to total energy determination. Finally, we propose a dynamical extension of the theory to calculate spectral properties of strongly anharmonic phonons, as probed by inelastic scattering processes. We illustrate our method with a numerical application on a toy model that mimics the ferroelectric transition in rock-salt crystals such as SnTe or GeTe.

  16. Understanding the importance of the temperature dependence of viscosity on the crystallization dynamics in the Ge2Sb2Te5 phase-change material

    Science.gov (United States)

    Aladool, A.; Aziz, M. M.; Wright, C. D.

    2017-06-01

    The crystallization dynamics in the phase-change material Ge2Sb2Te5 is modelled using the more detailed Master equation method over a wide range of heating rates commensurate with published ultrafast calorimetry experiments. Through the attachment and detachment of monomers, the Master rate equation naturally traces nucleation and growth of crystallites with temperature history to calculate the transient distribution of cluster sizes in the material. Both the attachment and detachment rates in this theory are strong functions of viscosity, and thus, the value of viscosity and its dependence on temperature significantly affect the crystallization process. In this paper, we use the physically realistic Mauro-Yue-Ellison-Gupta-Allan viscosity model in the Master equation approach to study the role of the viscosity model parameters on the crystallization dynamics in Ge2Sb2Te5 under ramped annealing conditions with heating rates up to 4 × 104 K/s. Furthermore, due to the relatively low computational cost of the Master equation method compared to atomistic level computations, an iterative numerical approach was developed to fit theoretical Kissinger plots simulated with the Master equation system to experimental Kissinger plots from ultrafast calorimetry measurements at increasing heating rates. This provided a more rigorous method (incorporating both nucleation and growth processes) to extract the viscosity model parameters from the analysis of experimental data. The simulations and analysis revealed the strong coupling between the glass transition temperature and fragility index in the viscosity and crystallization models and highlighted the role of the dependence of the glass transition temperature on the heating rate for the accurate estimation of the fragility index of phase-change materials from the analysis of experimental measurements.

  17. Temperature-Dependent Phase Transition in Orthorhombic [011]c Pb(Mg1/3Nb2/3 O3-0.35PbTiO3 Single Crystal

    Directory of Open Access Journals (Sweden)

    Wenhui He

    2014-07-01

    Full Text Available Relaxor [011]c PMN-0.35PT single crystal phase transition characteristics are investigated through various methods including variable temperature dielectric properties, X-ray diffraction, bipolar ferroelectric hysteresis loops (P-E and electric-field-induced strain (S-E hysteresis loops measurements. The results reveal that two phase transitions exist within the range from room temperature to 250 °C: orthorhombic (O-tetragonal (T-cubic (C. The O-to-T and T-to-C phase transition temperatures have been identified as 84 °C and 152 °C, respectively. Diffuseness degree of the T-to-C phase transition for the unpoled single crystal has been calculated to be 1.56, implying an intermediate state between normal and relaxor ferroelectrics. Temperature-dependent remanent polarization (Pr, coercive field (Ec, saturation polarization (Ps, hysteresis loop squareness (Rsq, and longitudinal piezoelectric constant (d* 33 are also explored to learn the details of the phase transitions. Variable temperature unipolar Suni-E hysteresis loops avail additional evidence for the microstructure change in the as-measured single crystal.

  18. Temperature dependence of magnetotransport behavior and its correlation with inter-particle interaction in Cu{sub 100-x}Co{sub x} granular films

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Dinesh; Chaudhary, Sujeet; Pandya, Dinesh K. [Thin Film Laboratory, Indian Institute of Technology Delhi, New Delhi-110016 (India)

    2013-02-05

    Granular Cu{sub 100-x}Co{sub x} (x=15.1-30.9) films were deposited by magnetron co-sputtering and their magnetotransport properties were investigated as a function of temperature. We observed that with increasing cobalt content the room temperature magnetoresistance (MR) shows a maximum at x=20.9. With decreasing temperature, it is observed that the cobalt concentration at which the maximum MR occurs shifts progressively towards lower Co concentration. This behavior has been discussed in terms of the inter-particle magnetic interactions.

  19. Temperature-dependent differences in the nonlinear acoustic behavior of ultrasound contrast agents revealed by high-speed imaging and bulk acoustics.

    Science.gov (United States)

    Mulvana, Helen; Stride, Eleanor; Tang, Mengxing; Hajnal, Jo V; Eckersley, Robert

    2011-09-01

    Previous work by the authors has established that increasing the temperature of the suspending liquid from 20°C to body temperature has a significant impact on the bulk acoustic properties and stability of an ultrasound contrast agent suspension (SonoVue, Bracco Suisse SA, Manno, Lugano, Switzerland). In this paper the influence of temperature on the nonlinear behavior of microbubbles is investigated, because this is one of the most important parameters in the context of diagnostic imaging. High-speed imaging showed that raising the temperature significantly influences the dynamic behavior of individual microbubbles. At body temperature, microbubbles exhibit greater radial excursion and oscillate less spherically, with a greater incidence of jetting and gas expulsion, and therefore collapse, than they do at room temperature. Bulk acoustics revealed an associated increase in the harmonic content of the scattered signals. These findings emphasize the importance of conducting laboratory studies at body temperature if the results are to be interpreted for in vivo applications. Copyright © 2011 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  20. Temperature-dependent leakage current behavior of epitaxial Bi0.5Na0.5TiO3-based thin films made by pulsed laser deposition

    Science.gov (United States)

    Hejazi, M. M.; Safari, A.

    2011-11-01

    This paper discusses the electrical conduction mechanisms in a 0.88 Bi0.5Na0.5TiO3-0.08 Bi0.5K0.5TiO3-0.04 BaTiO3 thin film in the temperature range of 200-350 K. The film was deposited on a SrRuO3/SrTiO3 substrate by pulsed laser deposition technique. At all measurement temperatures, the leakage current behavior of the film matched well with the Lampert's triangle bounded by three straight lines of different slopes. The relative location of the triangle sides varied with temperature due to its effect on the density of charge carriers and un-filled traps. At low electric fields, the ohmic conduction governed the leakage mechanism. The calculated activation energy of the trap is 0.19 eV implying the presence of shallow traps in the film. With increasing the applied field, an abrupt increase in the leakage current was observed. This was attributed to a trap-filling process by the injected carriers. At sufficiently high electric fields, the leakage current obeyed the Child's trap-free square law suggesting the space charge limited current was the dominant mechanism.

  1. Temperature dependent terahertz properties of Ammonium Nitrate

    Science.gov (United States)

    Rahman, Abdur; Azad, Abul; Moore, David

    Terahertz spectroscopy has been demonstrated as an ideal nondestructive method for identifying hazardous materials such as explosives. Many common explosives exhibit distinct spectral signatures at terahertz range (0.1-6.0 THz) due to the excitations of their low frequency vibrational modes. Ammonium nitrate (AN), an easily accessible oxidizer often used in improvised explosive, exhibits strong temperature dependence. While the room temperature terahertz absorption spectrum of AN is featureless, it reveals distinct spectral features below 240 K due to the polymorphic phase transition. We employed terahertz time domain spectroscopy to measure the effective dielectric properties of AN embedded in polytetrafluoroethylene (PTFE) binder. The dielectric properties of pure AN were extracted using three different effective medium theories (EMT), simple effective medium approach, Maxwell-Garnett (MG) model, and Bruggeman (BR) model. In order to understand the effect of temperature on the dielectric properties, we varied the sample temperature from 5K to 300K. This study indicates presence of additional vibrational modes at low temperature. These results may greatly enhance the detectability of AN and facilitate more accurate theoretical modeling.

  2. Probing Temperature-Dependent Recombination Kinetics in Polymer:Fullerene Solar Cells by Electric Noise Spectroscopy

    Directory of Open Access Journals (Sweden)

    Giovanni Landi

    2017-09-01

    Full Text Available The influence of solvent additives on the temperature behavior of both charge carrier transport and recombination kinetics in bulk heterojunction solar cells has been investigated by electric noise spectroscopy. The observed differences in charge carrier lifetime and mobility are attributed to a different film ordering and donor-acceptor phase segregation in the blend. The measured temperature dependence indicates that bimolecular recombination is the dominant loss mechanism in the active layer, affecting the device performance. Blend devices prepared with a high-boiling-point solvent additive show a decreased recombination rate at the donor-acceptor interface as compared to the ones prepared with the reference solvent. A clear correlation between the device performance and the morphological properties is discussed in terms of the temperature dependence of the mobility-lifetime product.

  3. Temperature dependences of hydrous species in feldspars

    Science.gov (United States)

    Liu, W. D.; Yang, Y.; Zhu, K. Y.; Xia, Q. K.

    2018-01-01

    Feldspars are abundant in the crust of the Earth. Multiple hydrogen species such as OH, H2O and NH4 + can occur in the structure of feldspars. Hydrogen species play a critical role in influencing some properties of the host feldspars and the crust, including mechanical strength, electrical property of the crust, and evolution of the crustal fluids. Knowledge of hydrous species in feldspars to date has been mostly derived from spectroscopic studies at ambient temperature. However, the speciation and sites of hydrous species at high temperatures may not be quenchable. Here, we investigated the temperature dependences of several typical hydrous components (e.g., type IIa OH, type IIb OH and type I H2O) in feldspars by measuring the in situ FTIR spectra at elevated temperatures up to 800 °C. We found that the hydrous species demonstrated different behaviors at elevated temperatures. With increasing temperature, type IIa OH redistributes on the various sites in the anorthoclase structure. Additionally, O-H vibration frequencies increase for types IIa and IIb OH, and they decrease for type I H2O with increasing temperature. In contrast to type I H2O which drastically dehydrates during the heating process, types IIa and IIb OH show negligible loss; however, the bulk integral absorption coefficients drastically decrease with increasing temperature. These results may have implications in understanding the properties of hydrous species and feldspars at non-ambient temperatures, not only under geologic conditions but also at cold planetary surface conditions.

  4. Temperature dependencies of frequency characteristics of HTSC RLC curcuit

    Science.gov (United States)

    Buniatyan, Vahe V.; Aroutiounian, V. M.; Shmavonyan, G. Sh.; Buniatyan, Vaz. V.

    2006-05-01

    Analytical expressions of temperature dependencies of magnitude-frequency and phase-frequency characteristics of a HTSC RLC parallel circuit are obtained, where the resistance and inductance are non-linearly depended on the optical signal modulated by the intensity. It is shown that the magnitude-frequency and phase-frequency characteristics of circuits can be controlled by choosing the parameters of the HTSC thin film and optical "pump".

  5. Controlling block copolymer phase behavior using ionic surfactant

    Energy Technology Data Exchange (ETDEWEB)

    Ray, D.; Aswal, V. K. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India E-mail: debes.phys@gmail.com (India)

    2016-05-23

    The phase behavior of poly(ethylene oxide)-poly(propylene oxide-poly(ethylene oxide) PEO-PPO-PEO triblock copolymer [P85 (EO{sub 26}PO{sub 39}EO{sub 26})] in presence of anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution as a function of temperature has been studied using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations (1 wt%) of block copolymer and surfactants. Each of the individual components (block copolymer and surfactant) and the nanoparticle–surfactant mixed system have been examined at varying temperature. The block copolymer P85 forms spherical micelles at room temperature whereas shows sphere-to-rod like micelle transition at higher temperatures. On the other hand, SDS surfactant forms ellipsoidal micelles over a wide temperature range. Interestingly, it is found that phase behavior of mixed micellar system (P85 + SDS) as a function of temperature is drastically different from that of P85, giving the control over the temperature-dependent phase behavior of block copolymers.

  6. Phase Behavior and Implications for Travel time Observables (PHASE 2)

    Science.gov (United States)

    2015-09-30

    Phase behavior and implications for travel - time observables (PHASE-2) Emmanuel Skarsoulis Foundation for Research and Technology Hellas...perturbation behavior of travel time observables due to sound-speed perturbations. OBJECTIVES The objective is to study the behavior of the wave-theoretic...for this work came from the results of previous studies, supported by ONR, suggesting that the perturbation behavior of different travel - time

  7. Universality in the phase behavior of soft matter: a law of corresponding states.

    Science.gov (United States)

    Malescio, G

    2006-10-01

    We show that the phase diagram of substances whose molecular structure changes upon varying the thermodynamic parameters can be mapped, through state-dependent scaling, onto the phase diagram of systems of molecules having fixed structure. This makes it possible to identify broad universality classes in the complex phase scenario exhibited by soft matter, and enlightens a surprisingly close connection between puzzling phase phenomena and familiar behaviors. The analysis presented provides a straightforward way for deriving the phase diagram of soft substances from that of simpler reference systems. This method is applied here to study the phase behavior exhibited by two significative examples of soft matter with temperature-dependent molecular structure: thermally responsive colloids and polymeric systems. A region of inverse melting, i.e., melting upon isobaric cooling, is predicted at relatively low pressure and temperature in polymeric systems.

  8. Correlation between temperature-dependent permittivity dispersion ...

    Indian Academy of Sciences (India)

    The results indicate that the poling temperature plays a crucial role in the domains' alignment process, as expected. The temperature-dependent permittivity frequency dispersion and depolarization behaviours may have same origin. The aligned domains' break up into random state/nanodomains at depoling temperature ...

  9. Temperature Dependent Models of Semiconductor Devices for ...

    African Journals Online (AJOL)

    The paper presents an investigation of the temperature dependent model of a diode and bipolar transistor built-in to the NAP-2 program and comparison of these models with experimentally measured characteristics of the BA 100 diode and BC 109 transistor. The detail of the modelling technique has been discussed and ...

  10. Measurements of temperature dependence of 'localized susceptibility'

    CERN Document Server

    Shiozawa, H; Ishii, H; Takayama, Y; Obu, K; Muro, T; Saitoh, Y; Matsuda, T D; Sugawara, H; Sato, H

    2003-01-01

    The magnetic susceptibility of some rare-earth compounds is estimated by measuring magnetic circular dichroism (MCD) of rare-earth 3d-4f absorption spectra. The temperature dependence of the magnetic susceptibility obtained by the MCD measurement is remarkably different from the bulk susceptibility in most samples, which is attributed to the strong site selectivity of the core MCD measurement.

  11. Temperature dependence of the MDT gas gain

    CERN Document Server

    Gaudio, G; Treichel, M

    1999-01-01

    This note describes the measurements taken in the Gamma Irradiation Facility (GIF) in the X5 test beam area at CERN to investigate the temperature dependence of the MDT drift gas (Ar/CO2 - 90:10). Spectra were taken with an Americium-241 source during the aging studies. We analysed the effects of temperature changes on the pulse height spectrum.

  12. Temperature dependence of the kinetic isotope effect in β-pinene ozonolysis

    Science.gov (United States)

    Gensch, Iulia; Laumer, Werner; Stein, Olaf; Kammer, Beatrix; Hohaus, Thorsten; Saathoff, Harald; Wegener, Robert; Wahner, Andreas; Kiendler-Scharr, Astrid

    2011-10-01

    The temperature dependence of the kinetic isotope effect (KIE) of β-pinene ozonolysis was investigated experimentally at 258, 273 and 303 K in the AIDA atmospheric simulation chamber. Compound specific carbon isotopic analysis of gas phase samples was performed off-line with a Thermo Desorption-Gas Chromatography-Isotope Ratio Mass Spectrometry (TD-GC-IRMS) system. From the temporal behavior of the δ13C of β-pinene a KIE of 1.00358 ± 0.00013 was derived at 303 K, in agreement with literature data. Furthermore, KIE values of 1.00380 ± 0.00014 at 273 K and 1.00539 ± 0.00012 at 258 K were determined, showing an increasing KIE with decreasing temperature. A parameterization of the observed KIE temperature dependence was deduced and used in a sensitivity study carried out with the global chemistry transport model MOZART-3. Two scenarios were compared, the first neglecting, the second implementing the KIE temperature dependence in the simulations. β-Pinene stable carbon isotope ratio and concentration were computed, with emphasis on boreal zones. For early spring it is shown that when neglecting the temperature dependence of KIE, the calculated average age of β-pinene in the atmosphere can be up to two times over- or underestimated. The evolution of the isotopic composition of the major β-pinene oxidation product, nopinone, was examined using Master Chemical Mechanism (MCM) simulations. The tested hypothesis that formation of nopinone and its associated KIE are the determining factors for the observed δ13C values of nopinone is supported at high β-pinene conversion levels.

  13. Anharmonic behavior and structural phase transition in Yb2O3

    Directory of Open Access Journals (Sweden)

    Sugandha Dogra Pandey

    2013-12-01

    Full Text Available The investigation of structural phase transition and anharmonic behavior of Yb2O3 has been carried out by high-pressure and temperature dependent Raman scattering studies respectively. In situ Raman studies under high pressure were carried out in a diamond anvil cell at room temperature which indicate a structural transition from cubic to hexagonal phase at and above 20.6 GPa. In the decompression cycle, Yb2O3 retained its high pressure phase. We have observed a Stark line in the Raman spectra at 337.5 cm−1 which arises from the electronic transition between 2F5/2 and 2F7/2 multiplates of Yb3+ (4f13 levels. These were followed by temperature dependent Raman studies in the range of 80–440 K, which show an unusual mode hardening with increasing temperature. The hardening of the most dominant mode (Tg + Ag was analyzed in light of the theory of anharmonic phonon-phonon interaction and thermal expansion of the lattice. Using the mode Grüneisen parameter obtained from high pressure Raman measurements; we have calculated total anharmonicity of the Tg + Ag mode from the temperature dependent Raman data.

  14. PHASE BEHAVIOR OF LIGHT GASES IN HYDROCARBON AND AQUEOUS SOLVENTS

    Energy Technology Data Exchange (ETDEWEB)

    KHALED A.M. GASEM; ROBERT L. ROBINSON, JR.

    1998-08-31

    Under previous support from the Department of Energy, an experimental facility has been established and operated to measure valuable vapor-liquid equilibrium data for systems of interest in the production and processing of coal fluids. To facilitate the development and testing of models for prediction of the phase behavior for such systems, we have acquired substantial amounts of data on the equilibrium phase compositions for binary mixtures of heavy hydrocarbon solvents with a variety of supercritical solutes, including hydrogen, methane, ethane, carbon monoxide, and carbon dioxide. The present project focuses on measuring the phase behavior of light gases and water in Fischer-Tropsch (F-T) type solvents at conditions encountered in indirect liquefaction processes and evaluating and developing theoretically-based correlating frameworks to predict the phase behavior of such systems. Specific goals of the proposed work include (a) developing a state-of-the-art experimental facility to permit highly accurate measurements of equilibrium phase compositions (solubilities) of challenging F-T systems, (b) measuring these properties for systematically-selected binary, ternary and molten F-T wax mixtures to provide critically needed input data for correlation development, (c) developing and testing models suitable for describing the phase behavior of such mixtures, and (d) presenting the modeling results in generalized, practical formats suitable for use in process engineering calculations. During the present period, the Park-Gasem-Robinson (PGR) equation of state (EOS) has been modified to improve its volumetric and equilibrium predictions. Specifically, the attractive term of the PGR equation was modified to enhance the flexibility of the model, and a new expression was developed for the temperature dependence of the attractive term in this segment-segment interaction model. The predictive capability of the modified PGR EOS for vapor pressure, and saturated liquid and

  15. Temperature dependence of the elastocaloric effect in natural rubber

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Zhongjian, E-mail: zhongjian.xie521@gmail.com; Sebald, Gael; Guyomar, Daniel

    2017-07-12

    The temperature dependence of the elastocaloric (eC) effect in natural rubber (NR) has been studied. This material exhibits a large eC effect over a broad temperature range from 0 °C to 49 °C. The maximum adiabatic temperature change (ΔT) occurred at 10 °C and the behavior could be predicted by the temperature dependence of the strain-induced crystallization (SIC) and the temperature-induced crystallization (TIC). The eC performance of NR was then compared with that of shape memory alloys (SMAs). This study contributes to the SIC research of NR and also broadens the application of elastomers. - Highlights: • A large elastocaloric effect over a broad temperature range was found in natural rubber (NR). • The caloric performance of NR was compared with that of shape memory alloys. • The temperature dependence of the elastocaloric effect in NR can be prediced by the theory of strain-induced crystallization.

  16. Temperature-dependent structural and functional features of a hyperthermostable enzyme using elastic neutron scattering

    NARCIS (Netherlands)

    Koutsopoulos, S; van der Oost, J; Norde, W

    2005-01-01

    The dynamic behavior of an endoglucanase from the hyperthermophilic microorganism Pyrococcus furiosus was investigated using elastic neutron scattering. The temperature dependence of the atomic motions was correlated with conformational. and functional characteristics of the enzyme. The onset of

  17. Temperature dependent Raman scattering in YCrO3

    Science.gov (United States)

    Mall, A. K.; Mukherjee, S.; Sharma, Y.; Garg, A.; Gupta, R.

    2014-04-01

    High quality polycrystalline YCrO3 samples were synthesized using solid-state-reaction method. The samples were subsequently characterized using X-ray diffraction and magnetometry. Further, temperature dependent Raman spectroscopy over a spectral range from 100 to 800 cm-1 was used to examine the variation of phonons as a function of temperature from 90 to 300 K. In the low temperature ferroelectric phase of YCrO3, the observed phonon spectra showed softening of some Raman modes below the magnetic ordering temperature (TN ˜ 142K), suggesting a coupling between the spin and phonon degrees of freedom.

  18. Temperature dependence of diffusion in model and live cell membranes characterized by imaging fluorescence correlation spectroscopy.

    Science.gov (United States)

    Bag, Nirmalya; Yap, Darilyn Hui Xin; Wohland, Thorsten

    2014-03-01

    The organization of the plasma membrane is regulated by the dynamic equilibrium between the liquid ordered(Lo) and liquid disordered (Ld) phases. The abundance of the Lo phase is assumed to be a consequence of the interaction between cholesterol and the other lipids, which are otherwise in either the Ld or gel (So) phase.The characteristic lipid packing in these phases results in significant differences in their respective lateral dynamics.In this study, imaging total internal reflection fluorescence correlation spectroscopy (ITIR-FCS) is applied to monitor the diffusion within supported lipid bilayers (SLBs) as functions of temperature and composition. We show that the temperature dependence of membrane lateral diffusion,which is parameterized by the Arrhenius activation energy (EArr), can resolve the sub-resolution phase behavior of lipid mixtures. The FCS diffusion law, a novel membrane heterogeneity ruler implemented in ITIR-FCS, is applied to show that the domains in the So–Ldphase are static and large while they are small and dynamic in the Lo–Ld phase. Diffusion measurements and the subsequent FCS diffusion law analyses at different temperatures show that the modulation in membrane dynamics at high temperature (313 K) is a cumulative effect of domain melting and rigidity relaxation. Finally, we extend these studies to the plasma membranes of commonly used neuroblastoma, HeLa and fibroblast cells.The temperature dependence of membrane dynamics for neuroblastoma cells is significantly different from that of HeLa or fibroblast cells as the different cell types exhibit a high level of compositional heterogeneity.

  19. Temperature dependence of optically induced cell deformations

    Science.gov (United States)

    Fritsch, Anatol; Kiessling, Tobias R.; Stange, Roland; Kaes, Josef A.

    2012-02-01

    The mechanical properties of any material change with temperature, hence this must be true for cellular material. In biology many functions are known to undergo modulations with temperature, like myosin motor activity, mechanical properties of actin filament solutions, CO2 uptake of cultured cells or sex determination of several species. As mechanical properties of living cells are considered to play an important role in many cell functions it is surprising that only little is known on how the rheology of single cells is affected by temperature. We report the systematic temperature dependence of single cell deformations in Optical Stretcher (OS) measurements. The temperature is changed on a scale of about 20 minutes up to hours and compared to defined temperature shocks in the range of milliseconds. Thereby, a strong temperature dependence of the mechanics of single suspended cells is revealed. We conclude that the observable differences arise rather from viscosity changes of the cytosol than from structural changes of the cytoskeleton. These findings have implications for the interpretation of many rheological measurements, especially for laser based approaches in biological studies.

  20. Temperature dependence of photovoltaic cells, modules, and systems

    Energy Technology Data Exchange (ETDEWEB)

    Emery, K.; Burdick, J.; Caiyem, Y. [National Renewable Energy Lab., Golden, CO (United States)] [and others

    1996-05-01

    Photovoltaic (PV) cells and modules are often rated in terms of a set of standard reporting conditions defined by a temperature, spectral irradiance, and total irradiance. Because PV devices operates over a wide range of temperatures and irradiances, the temperature and irradiance related behavior must be known. This paper surveys the temperature dependence of crystalline and thin-film, state-of-the-art, research-size cells, modules, and systems measured by a variety of methods. The various error sources and measurement methods that contribute to cause differences in the temperature coefficient for a given cell or module measured with various methods are discussed.

  1. Ultra-capacitor electrical modeling using temperature dependent parameters

    Energy Technology Data Exchange (ETDEWEB)

    Lajnef, W.; Briat, O.; Azzopardi, S.; Woirgard, E.; Vinassa, J.M. [Bordeaux-1 Univ., Lab. IXL CNRS UMR 5818 - ENSEIRB, 33 - Talence (France)

    2004-07-01

    This paper deals with ultra-capacitor electrical modeling. For a proper characterization and identification, a dedicated test bench is designed. First, the ultra-capacitor electric behavior is presented and an electrical model is proposed. The model parameters are identified using a combination of constant currents and frequency response measurements. Then, the temperature dependence of the ultra-capacitor parameters is investigated. Therefore, constant currents and impedance spectroscopy tests are done at different ambient temperatures. Finally, the electrical model parameters are adjusted according to temperature. (authors)

  2. Temperature Dependent Wire Delay Estimation in Floorplanning

    DEFF Research Database (Denmark)

    Winther, Andreas Thor; Liu, Wei; Nannarelli, Alberto

    2011-01-01

    Due to large variations in temperature in VLSI circuits and the linear relationship between metal resistance and temperature, the delay through wires of the same length can be different. Traditional thermal aware floorplanning algorithms use wirelength to estimate delay and routability....... In this work, we show that using wirelength as the evaluation metric does not always produce a floorplan with the shortest delay. We propose a temperature dependent wire delay estimation method for thermal aware floorplanning algorithms, which takes into account the thermal effect on wire delay. The experiment...... results show that a shorter delay can be achieved using the proposed method. In addition, we also discuss the congestion and reliability issues as they are closely related to routing and temperature....

  3. Traders' behavioral coupling and market phase transition

    Science.gov (United States)

    Ma, Rong; Zhang, Yin; Li, Honggang

    2017-11-01

    Traditional economic theory is based on the assumption that traders are completely independent and rational; however, trading behavior in the real market is often coupled by various factors. This paper discusses behavioral coupling based on the stock index in the stock market, focusing on the convergence of traders' behavior, its effect on the correlation of stock returns and market volatility. We find that the behavioral consensus in the stock market, the correlation degree of stock returns, and the market volatility all exhibit significant phase transitions with stronger coupling.

  4. Temperature-dependent gate-swing hysteresis of pentacene thin film transistors

    Directory of Open Access Journals (Sweden)

    Yow-Jon Lin

    2014-10-01

    Full Text Available The temperature-dependent hysteresis-type transfer characteristics of pentacene-based organic thin film transistors (OTFTs were researched. The temperature-dependent transfer characteristics exhibit hopping conduction behavior. The fitting data for the temperature-dependent off-to-on and on-to-off transfer characteristics of OTFTs demonstrate that the hopping distance (ah and the barrier height for hopping (qϕt control the carrier flow, resulting in the hysteresis-type transfer characteristics of OTFTs. The hopping model gives an explanation of the gate-swing hysteresis and the roles played by qϕt and ah.

  5. Temperature dependence of resonant x-ray magnetic scattering in holmium

    Science.gov (United States)

    Helgesen, G.; Hill, J. P.; Thurston, T. R.; Gibbs, Doon; Kwo, J.; Hong, M.

    1994-08-01

    We report the results of resonant x-ray magnetic scattering experiments on bulk and thin-film single crystals of holmium. The scattering at the principal magnetic reflection has been characterized as a function of the temperature in the spiral phases near and below their respective Néel temperatures. The integrated intensity of the principal magnetic peak in both samples shows power-law behavior versus reduced temperature with nearly equal exponents. The exponents for the scattering at the resonant second and third harmonics in the bulk sample are not simple integer multiples of the first, and motivate the consideration of simple scaling corrections to mean-field theory. We also present and compare the results of high-resolution measurements of the temperature dependence of the magnetic wave vectors, c-axis lattice constants, and correlation lengths of the magnetic scattering of the two samples in their spiral phases. Although the qualitative behavior is similar, systematic differences are found, including uniformly larger magnetic wave vectors and the suppression of the 1/6 phase in the film. The spiral magnetic structure of the film forms a domain state at all temperatures in the ordered phase. The magnetic correlation lengths of both samples are greatest near the Néel temperature, where that of the film appears to exceed the translational correlation lengths of the lattice. As the temperature decreases, the magnetic correlation lengths also decrease. These results are discussed in terms of the strain present in the samples.

  6. Temperature dependence of phonons in photosynthesis proteins

    Science.gov (United States)

    Xu, Mengyang; Myles, Dean; Blankenship, Robert; Markelz, Andrea

    Protein long range vibrations are essential to biological function. For many proteins, these vibrations steer functional conformational changes. For photoharvesting proteins, the structural vibrations play an additional critical role in energy transfer to the reaction center by both phonon assisted energy transfer and energy dissipation. The characterization of these vibrations to understand how they are optimized to balance photoharvesting and photoprotection is challenging. To date this characterization has mainly relied on fluorescence line narrowing measurements at cryogenic temperatures. However, protein dynamics has a strong temperature dependence, with an apparent turn on in anharmonicity between 180-220 K. If this transition affects intramolecular vibrations, the low temperature measurements will not represent the phonon spectrum at biological temperatures. Here we use the new technique of anisotropic terahertz microscopy (ATM) to measure the intramolecular vibrations of FMO complex. ATM is uniquely capable of isolating protein vibrations from isotropic background. We find resonances both red and blue shift with temperature above the dynamical transition. The results indicate that the characterization of vibrations must be performed at biologically relevant temperatures to properly understand the energy overlap with the excitation energy transfer. This work was supported by NSF:DBI 1556359, BioXFEL seed Grant funding from NSF:DBI 1231306, DOE: DE-SC0016317, and the Bruce Holm University at Buffalo Research Foundation Grant.

  7. Temperature-dependent vibrational spectroscopic study and DFT calculations of the sorbic acid

    Science.gov (United States)

    Saraiva, G. D.; Nogueira, C. E. S.; Freire, P. T. C.; de Sousa, F. F.; da Silva, J. H.; Teixeira, A. M. R.; Mendes Filho, J.

    2015-02-01

    This work reports a temperature-dependent vibrational spectroscopic study of the sorbic acid (C6H8O2), as well as the mode assignment at ambient conditions, based on the density functional theory. Temperature-dependent vibrational properties have been performed in polycrystalline sorbic acid through both Raman and infrared spectroscopy in the 20-300 K and 80-300 K temperature ranges, respectively. These studies present the occurrence of some modifications in the Raman spectra that could be interpreted as a low temperature phase transition undergone by sorbic acid from the monoclinic phase to an unknown phase with conformational change of the molecules in the unit cell.

  8. Integrated optic current transducers incorporating photonic crystal fiber for reduced temperature dependence.

    Science.gov (United States)

    Chu, Woo-Sung; Kim, Sung-Moon; Oh, Min-Cheol

    2015-08-24

    Optical current transducers (OCT) are indispensable for accurate monitoring of large electrical currents in an environment suffering from severe electromagnetic interference. Temperature dependence of OCTs caused by its components, such as wave plates and optical fibers, should be reduced to allow temperature-independent operation. A photonic crystal fiber with a structural optical birefringence was incorporated instead of a PM fiber, and a spun PM fiber was introduced to overcome the temperature-dependent linear birefringence of sensing fiber coil. Moreover, an integrated optic device that provides higher stability than fiber-optics was employed to control the polarization and detect the phase of the sensed optical signal. The proposed OCT exhibited much lower temperature dependence than that from a previous study. The OCT satisfied the 0.5 accuracy class (IIEC 60044-8) and had a temperature dependence less than ± 1% for a temperature range of 25 to 78 °C.

  9. Temperature Dependent Variations of Phonon Interactions in Nanocrystalline Cerium Oxide

    Directory of Open Access Journals (Sweden)

    Sugandha Dogra Pandey

    2015-01-01

    Full Text Available The temperature dependent anharmonic behavior of the phonon modes of nanocrystalline CeO2 was investigated in the temperature range of 80–440 K. The anharmonic constants have been derived from the shift in phonon modes fitted to account for the anharmonic contributions as well as the thermal expansion contribution using the high pressure parameters derived from our own high pressure experimental data reported previously. The total anharmonicity has also been estimated from the true anharmonicity as well as quasiharmonic component. In the line-width variation analysis, the cubic anharmonic term was found to dominate the quartic term. Finally, the phonon lifetime also reflected the trend so observed.

  10. Temperature dependence of microwave absorption phenomena in single and biphase soft magnetic microwires

    Energy Technology Data Exchange (ETDEWEB)

    El Kammouni, Rhimou, E-mail: elkammounirhimou@gmail.com [Instituto de Ciencia de Materiales de Madrid, CSIC, 28049 Madrid (Spain); Vázquez, Manuel [Instituto de Ciencia de Materiales de Madrid, CSIC, 28049 Madrid (Spain); Lezama, Luis [Depto. Química Inorgánica, Universidad País Vasco, UPV/EHU, Bilbao (Spain); Kurlyandskaya, Galina [Depto. Electricidad y Electrónica, Universidad País Vasco, UPV/EHU, Bilbao (Spain); Dept. Magnetism and Magnetic Nanomaterials, Ural Federal University, Ekaterinburg (Russian Federation); Kraus, Ludek [Institute of Physics, Academy of Sciences of the Czech Republic, Prague (Czech Republic)

    2014-11-15

    The microwave absorption phenomena of single and biphase magnetic microwires with soft magnetic behavior have been investigated as a function of DC applied magnetic field using two alternative techniques: (i) absorption measurements in the temperature range of 4–300 K using a spectrometer operating at X-band frequency, at 9.5 GHz, and (ii) room-temperature, RT, ferromagnetic resonance measurements in a network analyzer in the frequency range up to 20 GHz. Complementary low-frequency magnetic characterization was performed in a Vibrating Sample Magnetometer. Studies have been performed for 8 μm diameter small-magnetostriction amorphous CoFeSiB single-phase microwire, coated by micrometric Pyrex layer, and after electroplating an external shell, 2 µm or 4 µm thick, of FeNi alloys. For single phase CoFeSiB microwire, a single absorption is observed, whose DC field dependence of resonance frequency at RT fits to a Kittel-law behavior for in-plane magnetized thin film. The temperature dependence behavior shows a monotonic increase in the resonance field, H{sub r}, with temperature. A parallel reduction of the circular anisotropy field, H{sub K}, is deduced from the temperature dependence of hysteresis loops. For biphase, CoFeSiB/FeNi, microwires, the absorption phenomena at RT also follow the Kittel condition. The observed opposite evolution with temperature of resonance field, H{sub r}, in 2 and 4 µm thick FeNi samples is interpreted considering the opposite sign of magnetostriction of the respective FeNi layers. The stress-induced magnetic anisotropy field, H{sub K}, in the FeNi shell is deduced to change sign at around 130 K. - Highlights: • A single absorption phenomenon is observed for single phase CoFeSiB. • The T dependence of the microwave behavior shows a monotonic increase of H{sub r} with T. • The absorption at RT follows the Kittel condition for biphase CoFe/FeNi microwires. • The T dependence of resonant field of CoFe/FeNi is interpreted to be

  11. Temperature dependence of the NMR spin-lattice relaxation rate for spin-1/2 chains

    Science.gov (United States)

    Coira, E.; Barmettler, P.; Giamarchi, T.; Kollath, C.

    2016-10-01

    We use recent developments in the framework of a time-dependent matrix product state method to compute the nuclear magnetic resonance relaxation rate 1 /T1 for spin-1/2 chains under magnetic field and for different Hamiltonians (XXX, XXZ, isotropically dimerized). We compute numerically the temperature dependence of the 1 /T1 . We consider both gapped and gapless phases, and also the proximity of quantum critical points. At temperatures much lower than the typical exchange energy scale, our results are in excellent agreement with analytical results, such as the ones derived from the Tomonaga-Luttinger liquid (TLL) theory and bosonization, which are valid in this regime. We also cover the regime for which the temperature T is comparable to the exchange coupling. In this case analytical theories are not appropriate, but this regime is relevant for various new compounds with exchange couplings in the range of tens of Kelvin. For the gapped phases, either the fully polarized phase for spin chains or the low-magnetic-field phase for the dimerized systems, we find an exponential decrease in Δ /(kBT ) of the relaxation time and can compute the gap Δ . Close to the quantum critical point our results are in good agreement with the scaling behavior based on the existence of free excitations.

  12. A Temperature-Dependent Battery Model for Wireless Sensor Networks.

    Science.gov (United States)

    Rodrigues, Leonardo M; Montez, Carlos; Moraes, Ricardo; Portugal, Paulo; Vasques, Francisco

    2017-02-22

    Energy consumption is a major issue in Wireless Sensor Networks (WSNs), as nodes are powered by chemical batteries with an upper bounded lifetime. Estimating the lifetime of batteries is a difficult task, as it depends on several factors, such as operating temperatures and discharge rates. Analytical battery models can be used for estimating both the battery lifetime and the voltage behavior over time. Still, available models usually do not consider the impact of operating temperatures on the battery behavior. The target of this work is to extend the widely-used Kinetic Battery Model (KiBaM) to include the effect of temperature on the battery behavior. The proposed Temperature-Dependent KiBaM (T-KiBaM) is able to handle operating temperatures, providing better estimates for the battery lifetime and voltage behavior. The performed experimental validation shows that T-KiBaM achieves an average accuracy error smaller than 0.33%, when estimating the lifetime of Ni-MH batteries for different temperature conditions. In addition, T-KiBaM significantly improves the original KiBaM voltage model. The proposed model can be easily adapted to handle other battery technologies, enabling the consideration of different WSN deployments.

  13. A Temperature-Dependent Battery Model for Wireless Sensor Networks

    Science.gov (United States)

    Rodrigues, Leonardo M.; Montez, Carlos; Moraes, Ricardo; Portugal, Paulo; Vasques, Francisco

    2017-01-01

    Energy consumption is a major issue in Wireless Sensor Networks (WSNs), as nodes are powered by chemical batteries with an upper bounded lifetime. Estimating the lifetime of batteries is a difficult task, as it depends on several factors, such as operating temperatures and discharge rates. Analytical battery models can be used for estimating both the battery lifetime and the voltage behavior over time. Still, available models usually do not consider the impact of operating temperatures on the battery behavior. The target of this work is to extend the widely-used Kinetic Battery Model (KiBaM) to include the effect of temperature on the battery behavior. The proposed Temperature-Dependent KiBaM (T-KiBaM) is able to handle operating temperatures, providing better estimates for the battery lifetime and voltage behavior. The performed experimental validation shows that T-KiBaM achieves an average accuracy error smaller than 0.33%, when estimating the lifetime of Ni-MH batteries for different temperature conditions. In addition, T-KiBaM significantly improves the original KiBaM voltage model. The proposed model can be easily adapted to handle other battery technologies, enabling the consideration of different WSN deployments. PMID:28241444

  14. Nonuniversal surface behavior of dynamic phase transitions.

    Science.gov (United States)

    Riego, Patricia; Berger, Andreas

    2015-06-01

    We have studied the dynamic phase transition (DPT) of the kinetic Ising model in systems with surfaces within the mean-field approximation. Varying the surface exchange coupling strength J(s), the amplitude of the externally applied oscillating field h(0), and its period P, we explore the dynamic behavior of the layer-dependent magnetization and the associated DPTs. The surface phase diagram shows several features that resemble those of the equilibrium case, with an extraordinary bulk transition and a surface transition for high J(s) values, independent from the value of h(0). For low J(s), however, h(0) is found to be a crucial parameter that leads to nonuniversal surface behavior at the ordinary bulk transition point. Specifically, we observed here a bulk-supported surface DPT for high field amplitudes h(0) and correspondingly short critical periods P(c), whereas this surface transition simultaneous to the bulk one is suppressed for slow critical dynamics occurring for low values of h(0). The suppression of the DPT for low h(0) not only occurs for the topmost surface layer, but also affects a significant number of subsurface layers. We find that the key physical quantity that explains this nonuniversal behavior is the time correlation between the dynamic surface and bulk magnetizations at the bulk critical point. This time correlation has to pass a threshold value to trigger a bulk-induced DPT in the surface layers. Otherwise, dynamic phase transitions are absent at the surface in stark contrast to the equilibrium behavior of the corresponding thermodynamic Ising model. Also, we have analyzed the penetration depth of the dynamically ordered phase for the surface DPT that occurs for large J(s) values. Here we find that the penetration depth depends strongly on J(s) and behaves identically to the corresponding equilibrium Ising model.

  15. Temperature dependence of the electronic structure of semiconductors and insulators

    Energy Technology Data Exchange (ETDEWEB)

    Poncé, S., E-mail: samuel.pon@gmail.com; Gillet, Y.; Laflamme Janssen, J.; Gonze, X. [European Theoretical Spectroscopy Facility and Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des étoiles 8, bte L07.03.01, B-1348 Louvain-la-neuve (Belgium); Marini, A. [Consiglio Nazionale delle Ricerche (CNR), Via Salaria Km 29.3, CP 10, 00016 Monterotondo Stazione (Italy); Verstraete, M. [European Theoretical Spectroscopy Facility and Physique des matériaux et nanostructures, Université de Liège, Allée du 6 Août 17, B-4000 Liège (Belgium)

    2015-09-14

    The renormalization of electronic eigenenergies due to electron-phonon coupling (temperature dependence and zero-point motion effect) is sizable in many materials with light atoms. This effect, often neglected in ab initio calculations, can be computed using the perturbation-based Allen-Heine-Cardona theory in the adiabatic or non-adiabatic harmonic approximation. After a short description of the recent progresses in this field and a brief overview of the theory, we focus on the issue of phonon wavevector sampling convergence, until now poorly understood. Indeed, the renormalization is obtained numerically through a slowly converging q-point integration. For non-zero Born effective charges, we show that a divergence appears in the electron-phonon matrix elements at q → Γ, leading to a divergence of the adiabatic renormalization at band extrema. This problem is exacerbated by the slow convergence of Born effective charges with electronic wavevector sampling, which leaves residual Born effective charges in ab initio calculations on materials that are physically devoid of such charges. Here, we propose a solution that improves this convergence. However, for materials where Born effective charges are physically non-zero, the divergence of the renormalization indicates a breakdown of the adiabatic harmonic approximation, which we assess here by switching to the non-adiabatic harmonic approximation. Also, we study the convergence behavior of the renormalization and develop reliable extrapolation schemes to obtain the converged results. Finally, the adiabatic and non-adiabatic theories, with corrections for the slow Born effective charge convergence problem (and the associated divergence) are applied to the study of five semiconductors and insulators: α-AlN, β-AlN, BN, diamond, and silicon. For these five materials, we present the zero-point renormalization, temperature dependence, phonon-induced lifetime broadening, and the renormalized electronic band structure.

  16. Using extrathermodynamic relationships to model the temperature dependence of Henry's law constants of 209 PCB congeners.

    Science.gov (United States)

    Bamford, Holly A; Poster, Dianne L; Huie, Robert E; Baker, Joel E

    2002-10-15

    Our previous measurements of the temperature dependencies of Henry's law constants of 26 polychlorinated biphenyls (PCBs) showed a well-defined linear relationship between the enthalpy and the entropy of phase change. Within a homologue group, the Henry's law constants converged to a common value at a specific isoequilibrium temperature. We use this relationship to model the temperature dependencies of the Henry's law constants of the remaining PCB congeners. By using experimentally measured Henry's law constants at 11 degrees C for 61 PCB congeners described in this paper combined with the isoequilibrium temperatures from our previous measurements of Henry's law constants of 26 PCB congeners, we have derived an empirical relationship between the enthalpies and the entropies of phase change for these additional PCB congeners. A systematic variation in the enthalpies and entropies of phase change was found to be partially dependent on the chlorine number and substitution patterns on the biphenyl rings, allowing further estimation of the temperature dependence of Henry's law constants for the remaining 122 PCB congeners. The enthalpies of phase change for all 209 PCB congeners ranged between 10 and 169 kJ mol(-1), where the enthalpies of phase change decreased as the number of ortho chlorine substitutions on the biphenyl rings increased within homologue groups. These data are used to predict the temperature dependence of Henry's law constants for all 209 PCB congeners.

  17. Inclusion of temperature dependent shell corrections in Landau ...

    Indian Academy of Sciences (India)

    Abstract. Landau theory used for studying hot rotating nuclei usually uses zero temperature Struti- nsky smoothed total energy for the temperature dependent shell corrections. This is replaced in this work by the temperature dependent Strutinsky smoothed free energy. Our results show that this re- placement has only ...

  18. Inclusion of temperature dependent shell corrections in Landau ...

    Indian Academy of Sciences (India)

    Landau theory used for studying hot rotating nuclei usually uses zero temperature Strutinsky smoothed total energy for the temperature dependent shell corrections. This is replaced in this work by the temperature dependent Strutinsky smoothed free energy. Our results show that this replacement has only marginal effect for ...

  19. Temperature dependence of ferromagnetic resonance measurements in nanostructured line arrays

    Directory of Open Access Journals (Sweden)

    Raposo V.

    2014-07-01

    Full Text Available We report the effect of temperature on the ferromagnetic resonance (FMR spectra of nanostructured line arrays. Different temperature dependences are observed for permalloy an nickel based samples. The qualitative features of the temperature dependence of the resonance field and linewidth can be described by the usual expression of slow relaxing linewidth mechanism and Bloch equation.

  20. Temperature dependence of the magnetization of canted spin structures

    DEFF Research Database (Denmark)

    Jacobsen, Henrik; Lefmann, Kim; Brok, Erik

    2012-01-01

    for the temperature dependence of the magnetization of a simple canted spin structure in which relaxation can take place at finite temperatures between spin configurations with different canting angles. We show that the saturation magnetization may either decrease or increase with decreasing temperature, depending...

  1. Temperature dependent fluorescence in disordered Frenkel chains : Interplay of equilibration and local band-edge level structure

    NARCIS (Netherlands)

    Bednarz, M.; Malyshev, V.; Knoester, J.

    2003-01-01

    We model the optical dynamics in linear Frenkel exciton systems governed by scattering on static disorder and lattice vibrations and calculate the temperature dependent fluorescence spectrum and lifetime. The fluorescence Stokes shift shows a nonmonotonic behavior with temperature, which derives

  2. Temperature Dependence and Magnetic Properties of Injection Molding Tool Materials Used in Induction Heating

    DEFF Research Database (Denmark)

    Guerrier, Patrick; Nielsen, Kaspar Kirstein; Hattel, Jesper Henri

    2015-01-01

    To analyze the heating phase of an induction heated injection molding tool precisely, the temperature-dependent magnetic properties, B–H curves, and the hysteresis loss are necessary for the molding tool materials. Hence, injection molding tool steels, core materials among other materials have...

  3. Temperature dependent behaviour of lead sulfide quantum dot solar cells and films

    NARCIS (Netherlands)

    Speirs, Mark J.; Dirin, Dmitry N.; Abdu-Aguye, Mustapha; Balazs, Daniel M.; Kovalenko, Maksym V.; Loi, Maria Antonietta

    2016-01-01

    Despite increasing greatly in power conversion efficiency in recent times, lead sulfide quantum dot (PbS QD) solar cells still suffer from a low open circuit voltage (V-OC) and fill factor (FF). In this work, we explore the temperature dependent behavior of similar to 9% efficient solar cells. In

  4. Temperature Dependent Fracture Model and its Application to Ultra Heavy Thick Steel Plate Used for Shipbuilding

    Science.gov (United States)

    Jang, Yun Chan; Lee, Youngseog; An, Gyu Baek; Park, Joon Sik; Lee, Jong Bong; Kim, Sung Il

    In this study, experimental and numerical studies were performed to examine the effects of thickness of steel plate on the arrest fracture toughness. The ESSO tests were performed with the steel plates having temperature gradient along the crack propagation direction. A temperature dependent crack initiation criterion was proposed as well. A series of three-dimensional FEA was then carried out to simulate the ESSO test while the thickness of the steel plate varies. Results reveal that a temperature dependent brittle criterion proposed in this study can describe the fracture behavior properly.

  5. Correlation between temperature dependent dielectric and DC resistivity of Cr substituted barium hexaferrite

    Science.gov (United States)

    Kumar, Sunil; Supriya, Sweety; Kar, Manoranjan

    2017-12-01

    The chromium substituted barium hexaferrite (BaFe12O19) crystallize to the hexagonal symmetry (P63/mmc space group), which has been studied by employing the XRD technique. The XRD analysis is supported by the Raman spectra and, microstructural analysis has been carried out by the FESEM (field emission scanning electron microscope) technique. Average particle size is found to be around 85 nm. Two peaks are observed in the temperature versus dielectric constant plots and, these two transition temperatures are identified as T d and T m. The temperature T d is due to dipole relaxation, whereas T m is assigned as dielectric phase transition. Both T d and T m increase with the increase in frequency. However, the former one (i.e. T d) increases more rapidly compare to that of later one (i.e. T m). Both the temperature (T d and T m) are also well identified in the temperature dependent DC resistivity. All the samples exhibit the negative temperature coefficient of resistance (NTCR) behavior, which reveals the semiconducting behavior of the material. The Mott VRH model could explain the DC electrical conductivity. Both dielectric constant and DC resistivity is well correlated with each other to explain the transport properties in Cr3+ substituted barium hexaferrite.

  6. Selecting Temperature for Protein Crystallization Screens Using the Temperature Dependence of the Second Virial Coefficient

    Science.gov (United States)

    Liu, Jun; Yin, Da-Chuan; Guo, Yun-Zhu; Wang, Xi-Kai; Xie, Si-Xiao; Lu, Qin-Qin; Liu, Yong-Ming

    2011-01-01

    Protein crystals usually grow at a preferable temperature which is however not known for a new protein. This paper reports a new approach for determination of favorable crystallization temperature, which can be adopted to facilitate the crystallization screening process. By taking advantage of the correlation between the temperature dependence of the second virial coefficient (B22) and the solubility of protein, we measured the temperature dependence of B22 to predict the temperature dependence of the solubility. Using information about solubility versus temperature, a preferred crystallization temperature can be proposed. If B22 is a positive function of the temperature, a lower crystallization temperature is recommended; if B22 shows opposite behavior with respect to the temperature, a higher crystallization temperature is preferred. Otherwise, any temperature in the tested range can be used. PMID:21479212

  7. Manipulating the temperature dependence of the thermal conductivity of graphene phononic crystal.

    Science.gov (United States)

    Hu, Shiqian; An, Meng; Yang, Nuo; Li, Baowen

    2016-07-01

    By using non-equilibrium molecular dynamics simulations, modulating the temperature dependence of thermal conductivity of graphene phononic crystals (GPnCs) is investigated. It is found that the temperature dependence of thermal conductivity of GPnCs follows ∼T (-α) behavior. The power exponents (α) can be efficiently tuned by changing the characteristic size of GPnCs. The phonon participation ratio spectra and dispersion relation reveal that the long-range phonon modes are more affected in GPnCs with larger holes (L 0). Our results suggest that constructing GPnCs is an effective method to manipulate the temperature dependence of thermal conductivity of graphene, which would be beneficial for developing GPnC-based thermal management and signal processing devices.

  8. Hysteresis and Temperature Dependency of Moisture Sorption – New Measurements

    DEFF Research Database (Denmark)

    Rode, Carsten; Hansen, Kurt Kielsgaard

    2011-01-01

    It is well known that sorption characteristics of building materials exhibit hysteresis in the way the equilibrium curves develop between adsorption and desorption, and that the sorption curves are also somewhat temperature dependent. However, these two facts are most often neglected in models...... measurements of hysteresis and temperature dependency of the moisture sorption characteristics of three different porous building materials: aerated concrete, cement paste and spruce. Scanning curves are measured for all three materials where periods with adsorption and desorption interrupt each other...

  9. Electroneutrality and phase behavior of colloidal suspensions.

    Science.gov (United States)

    Denton, A R

    2007-11-01

    Several statistical mechanical theories predict that colloidal suspensions of highly charged macroions and monovalent microions can exhibit unusual thermodynamic phase behavior when strongly deionized. Density-functional, extended Debye-Hückel, and response theories, within mean-field and linearization approximations, predict a spinodal phase instability of charged colloids below a critical salt concentration. Poisson-Boltzmann cell model studies of suspensions in Donnan equilibrium with a salt reservoir demonstrate that effective interactions and osmotic pressures predicted by such theories can be sensitive to the choice of reference system, e.g., whether the microion density profiles are expanded about the average potential of the suspension or about the reservoir potential. By unifying Poisson-Boltzmann and response theories within a common perturbative framework, it is shown here that the choice of reference system is dictated by the constraint of global electroneutrality. On this basis, bulk suspensions are best modeled by density-dependent effective interactions derived from a closed reference system in which the counterions are confined to the same volume as the macroions. Lower-dimensional systems (e.g., monolayers, clusters), depending on the strength of macroion-counterion correlations, may be governed instead by density-independent effective interactions tied to an open reference system with counterions dispersed throughout the reservoir, possibly explaining the observed structural crossover in colloidal monolayers and anomalous metastability of colloidal crystallites.

  10. Phase Behavior of Carbon Nanotube Suspensions

    Science.gov (United States)

    Poulin, Philippe

    2006-03-01

    We study the phase behavior of nanotube suspensions stabilized by surfactants or amphiphilic polymers. The control of the composition of the solutions allows the interaction potential between the nanotubes to be finely tuned. As a consequence, it is possible to quantitatively analyze important phenomena such as percolation or liquid crystalline phase transitions. In particular, we describe how the percolation of rod-like particles is quantitatively decreased in the presence of attractive interactions (1). We show that rod-like particles respond much more strongly than spheres to attractive interactions; strengthening thereby the technological interest of carbon nanotubes to achieve low percolation thresholds for electrostatic dissipation or electromagnetic shielding. By contrast, carbon nanotubes which experience repulsive interactions can spontaneously order and form liquid crystalline solutions (2). Aligning and packing nanotubes is a major challenge to obtain macroscopic materials with improved properties. We will briefly discuss at the end of the presentation, our latest results concerning the fabrication of fibers aligned nanotubes (3). In particular, we will present new treatments of these fibers which lead to unusual mechanical properties and shape memory effects with giant stress recovery (4). *B. Vigolo, C. Coulon, M. Maugey, C. Zakri, P. Poulin, Science 2005. *S. Badaire, C. Zakri, M. Maugey, A. Derr'e, J. Barisci, G. Wallace, P. Poulin, Adv. Mat. 2005. *P. Miaudet, M. Maugey, A. Derr'e, V. Pichot, P. Launois, P. Poulin, C. Zakri, Nanoletters 2005. *P. Miaudet, A. Derr'e, M. Maugey, C. Zakri, P. Poulin, in preparation.

  11. Phase Behavior of Laundry Surfactants in Polar Solvents

    NARCIS (Netherlands)

    Stuart, Marc C.A.; Pas, John C. van de; Engberts, Jan B.F.N.

    2006-01-01

    Laundry surfactants are usually mixtures of ionic and nonionic detergents that exhibit a complex phase behavior. Here the ternary phase behavior of an isotropic and a liquid crystalline (LC) surfactant mixture has been examined in water/solvent systems. The size of the LC area in the ternary phase

  12. Temperature-Dependent Henry's Law Constants of Atmospheric Amines.

    Science.gov (United States)

    Leng, Chunbo; Kish, J Duncan; Roberts, Jason E; Dwebi, Iman; Chon, Nara; Liu, Yong

    2015-08-20

    There has been growing interest in understanding atmospheric amines in the gas phase and their mass transfer to the aqueous phase because of their potential roles in cloud chemistry, secondary organic aerosol formation, and the fate of atmospheric organics. Temperature-dependent Henry's law constants (KH) of atmospheric amines, a key parameter in atmospheric chemical transport models to account for mass transfer, are mostly unavailable. In this work, we investigated gas-liquid equilibria of five prevalent atmospheric amines, namely 1-propylamine, di-n-propylamine, trimethylamine, allylamine, and 4-methylmorpholine using bubble column technique. We reported effective KH, intrinsic KH, and gas phase diffusion coefficients of these species over a range of temperatures relevant to the lower atmosphere for the first time. The measured KH at 298 K and enthalpy of solution for 1-propylamine, di-n-propylamine, trimethylamine, allylamine, and 4-methylmorpholine are 61.4 ± 4.9 mol L(-1) atm(-1) and -49.0 ± 4.8 kJ mol(-1); 14.5 ± 1.2 mol L(-1) atm(-1) and -72.5 ± 6.8 kJ mol(-1); 8.9 ± 0.7 mol L(-1) atm(-1) and -49.6 ± 4.7 kJ mol(-1); 103.5 ± 10.4 mol L(-1) atm(-1) and -42.7 ± 4.3 kJ mol(-1); and 952.2 ± 114.3 mol L(-1) atm(-1) and -82.7 ± 9.7 kJ mol(-1), respectively. In addition, we evaluated amines' characteristic times to achieve gas-liquid equilibrium for partitioning between gas and aqueous phases. Results show gas-liquid equilibrium can be rapidly established at natural cloud droplets surface, but the characteristic times may be extended substantially at lower temperatures and pHs. Moreover, our findings imply that atmospheric amines are more likely to exist in cloud droplets, and ambient temperature, water content, and pH of aerosols play important roles in their partitioning.

  13. Temperature-Dependent Polarization in Field-Effect Transport and Photovoltaic Measurements of Methylammonium Lead Iodide.

    Science.gov (United States)

    Labram, John G; Fabini, Douglas H; Perry, Erin E; Lehner, Anna J; Wang, Hengbin; Glaudell, Anne M; Wu, Guang; Evans, Hayden; Buck, David; Cotta, Robert; Echegoyen, Luis; Wudl, Fred; Seshadri, Ram; Chabinyc, Michael L

    2015-09-17

    While recent improvements in the reported peak power conversion efficiency (PCE) of hybrid organic-inorganic perovskite solar cells have been truly astonishing, there are many fundamental questions about the electronic behavior of these materials. Here we have studied a set of electronic devices employing methylammonium lead iodide ((MA)PbI3) as the active material and conducted a series of temperature-dependent measurements. Field-effect transistor, capacitor, and photovoltaic cell measurements all reveal behavior consistent with substantial and strongly temperature-dependent polarization susceptibility in (MA)PbI3 at temporal and spatial scales that significantly impact functional behavior. The relative PCE of (MA)PbI3 photovoltaic cells is observed to reduce drastically with decreasing temperature, suggesting that such polarization effects could be a prerequisite for high-performance device operation.

  14. Refined energy-conserving dissipative particle dynamics model with temperature-dependent properties and its application in solidification problem

    Science.gov (United States)

    Ng, K. C.; Sheu, T. W. H.

    2017-10-01

    It has been observed previously that the physical behaviors of Schmidt number (Sc) and Prandtl number (Pr) of an energy-conserving dissipative particle dynamics (eDPD) fluid can be reproduced by the temperature-dependent weight function appearing in the dissipative force term. In this paper, we proposed a simple and systematic method to develop the temperature-dependent weight function in order to better reproduce the physical fluid properties. The method was then used to study a variety of phase-change problems involving solidification. The concept of the "mushy" eDPD particle was introduced in order to better capture the temperature profile in the vicinity of the solid-liquid interface, particularly for the case involving high thermal conductivity ratio. Meanwhile, a way to implement the constant temperature boundary condition at the wall was presented. The numerical solutions of one- and two-dimensional solidification problems were then compared with the analytical solutions and/or experimental results and the agreements were promising.

  15. Characterization of temperature-dependent optical material properties of polymer powders

    Energy Technology Data Exchange (ETDEWEB)

    Laumer, Tobias [Bayerisches Laserzentrum GmbH, 91052 Erlangen (Germany); SAOT Erlangen Graduate School in Advanced Optical Technologies, 91052 Erlangen (Germany); CRC Collaborative Research Center 814 - Additive Manufacturing, 91052 Erlangen (Germany); Stichel, Thomas; Bock, Thomas; Amend, Philipp [Bayerisches Laserzentrum GmbH, 91052 Erlangen (Germany); CRC Collaborative Research Center 814 - Additive Manufacturing, 91052 Erlangen (Germany); Schmidt, Michael [Bayerisches Laserzentrum GmbH, 91052 Erlangen (Germany); University of Erlangen-Nürnberg, Institute of Photonic Technologies, 91052 Erlangen (Germany); SAOT Erlangen Graduate School in Advanced Optical Technologies, 91052 Erlangen (Germany); CRC Collaborative Research Center 814 - Additive Manufacturing, 91052 Erlangen (Germany)

    2015-05-22

    In former works, the optical material properties of different polymer powders used for Laser Beam Melting (LBM) at room temperature have been analyzed. With a measurement setup using two integration spheres, it was shown that the optical material properties of polymer powders differ significantly due to multiple reflections within the powder compared to solid bodies of the same material. Additionally, the absorption behavior of the single particles shows an important influence on the overall optical material properties, especially the reflectance of the powder bed. Now the setup is modified to allow measurements at higher temperatures. Because crystalline areas of semi-crystalline thermoplastics are mainly responsible for the absorption of the laser radiation, the influence of the temperature increase on the overall optical material properties is analyzed. As material, conventional polyamide 12 and polypropylene as new polymer powder material, is used. By comparing results at room temperature and at higher temperatures towards the melting point, the temperature-dependent optical material properties and their influence on the beam-matter interaction during the process are discussed. It is shown that the phase transition during melting leads to significant changes of the optical material properties of the analyzed powders.

  16. Temperature dependence of the HNO3 UV absorption cross sections

    Science.gov (United States)

    Burkholder, James B.; Talukdar, Ranajit K.; Ravishankara, A. R.; Solomon, Susan

    1993-01-01

    The temperature dependence of the HNO3 absorption cross sections between 240 and 360 K over the wavelength range 195 to 350 nm has been measured using a diode array spectrometer. Absorption cross sections were determined using both (1) absolute pressure measurements at 298 K and (2) a dual absorption cell arrangement in which the absorption spectrum at various temperatures is measured relative to the room temperature absorption spectrum. The HNO3 absorption spectrum showed a temperature dependence which is weak at short wavelengths but stronger at longer wavelengths which are important for photolysis in the lower stratosphere. The 298 K absorption cross sections were found to be larger than the values currently recommended for atmospheric modeling (DeMore et al., 1992). Our absorption cross section data are critically compared with the previous measurements of both room temperature and temperature-dependent absorption cross sections. Temperature-dependent absorption cross sections of HNO3 are recommended for use in atmospheric modeling. These temperature dependent HNO3 absorption cross sections were used in a two-dimensional dynamical-photochemical model to demonstrate the effects of the revised absorption cross sections on loss rate of HNO3 and the abundance of NO2 in the stratosphere.

  17. Temperature dependent optical properties of PbS nanocrystals.

    Science.gov (United States)

    Nordin, M N; Li, Juerong; Clowes, S K; Curry, R J

    2012-07-11

    A comprehensive study of the optical properties of PbS nanocrystals (NCs) is reported that includes the temperature dependent absorption, photoluminescence (PL) and PL lifetime in the range of 3-300 K. The absorption and PL are found to display different temperature dependent behaviour though both redshift as temperature is reduced. This results in a temperature dependent Stokes shift which increases from ∼75 meV at 300 K with reducing temperature until saturating at ∼130 meV below ∼150 K prior to a small reduction to 125 meV upon cooling from 25 to 3 K. The PL lifetime is found to be single exponential at 3 K with a lifetime of τ(1) = 6.5 μs. Above 3 K biexponential behaviour is observed with the lifetime for each process displaying a different temperature dependence. The Stokes shift is modelled using a three-level rate equation model incorporating temperature dependent parameter values obtained via fitting phenomenological relationships to the observed absorption and PL behaviour. This results in a predicted energy difference between the two emitting states of ∼6 meV which is close to the excitonic exchange energy splitting predicted theoretically for these systems.

  18. Temperature dependence of Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal

    Directory of Open Access Journals (Sweden)

    Qieni Lu

    2015-08-01

    Full Text Available We measure temperature dependence on Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal simultaneously in this work, based on digital holographic interferometry (DHI. And the spatial distribution of the field-induced refractive index change can also be visualized and estimated by numerically retrieving sequential phase maps of Mn:Fe:KTN crystal from recording digital holograms in different states. The refractive indices decrease with increasing temperature and quadratic polarized optical coefficient is insensitive to temperature. The experimental results suggest that the DHI method presented here is highly applicable in both visualizing the temporal and spatial behavior of the internal electric field and accurately measuring electro-optic coefficient for electrooptical media.

  19. Multiple-phase behavior and memory effect of polymer gel

    CERN Document Server

    Annaka, M; Nakahira, T; Sugiyama, M; Hara, K; Matsuura, T

    2002-01-01

    A poly(4-acrylamidosalicylic acid) gel (PASA gel) exhibits multiple phases as characterized by distinct degrees of swelling; the gel can take one of four different swelling values, but none of the intermediate values. The gel has remarkable memory: the phase behavior of the gel depends on whether the gel has experienced the most swollen phase or the most collapsed phase in the immediate past. The information is stored and reversibly erased in the form of a macroscopic phase transition behavior. The structure factors corresponding to these four phases were obtained by SANS, which indicated the presence of characteristic structures depending on pH and temperature, particularly in the shrunken state. (orig.)

  20. Multiple-phase behavior and memory effect of polymer gel

    Energy Technology Data Exchange (ETDEWEB)

    Annaka, M.; Motokawa, R.; Nakahira, T. [Department of Materials Technology, Chiba University, Chiba 263-8522 (Japan); Sugiyama, M. [Department of Physics, Kyushu University, Fukuoka 812-8581 (Japan); Hara, K. [Institute of Environmental Systems, Kyushu University, Fukuoka 812-8581 (Japan); Matsuura, T. [Department of Ophtalmology, Nava Medical University, Nava 634-8522 (Japan)

    2002-07-01

    A poly(4-acrylamidosalicylic acid) gel (PASA gel) exhibits multiple phases as characterized by distinct degrees of swelling; the gel can take one of four different swelling values, but none of the intermediate values. The gel has remarkable memory: the phase behavior of the gel depends on whether the gel has experienced the most swollen phase or the most collapsed phase in the immediate past. The information is stored and reversibly erased in the form of a macroscopic phase transition behavior. The structure factors corresponding to these four phases were obtained by SANS, which indicated the presence of characteristic structures depending on pH and temperature, particularly in the shrunken state. (orig.)

  1. BUCKLING OF A COLUMN WITH TEMPERATURE DEPENDENT MATERIAL PROPERTIES

    Directory of Open Access Journals (Sweden)

    Ömer SOYKASAP

    2001-01-01

    Full Text Available Buckling of a column with temperature dependent material properties is investigated. Euler-Bernoulli theory of thin beams is used to derive the element matrices by means of the minimum potential energy principle. Temperature dependency of material properties is taken into account in the formulation. The column is divided into finite elements with the axial degrees of freedom defined at the outer fiber of the column. Column elements have simpler derivations and compact element matrices than those of classical beam-bending element. Some illustrative examples are presented to show the convergence of numerical results obtained by the use of new elements. The results are compared with those of the classical beam-bending element and analytical solution. The new element converges to the analytical results as powerful as the classical beam-bending element. The temperature effects on the buckling loads of the column with temperature dependent material properties are also examined.

  2. Temperature dependent climate projection deficiencies in CMIP5 models

    DEFF Research Database (Denmark)

    Christensen, Jens H.; Boberg, Fredrik

    2012-01-01

    Monthly mean temperatures for 34 GCMs available from the CMIP5 project are compared with observations from CRU for 26 different land regions covering all major land areas in the world for the period 1961-2000 by means of quantile-quantile (q-q) diagrams. A warm period positive temperature dependent...... bias is identified for many of the models within many of the chosen climate regions. However, the exact temperature dependence varies considerably between the models. We analyse the role of this difference as a contributing factor for some models to project stronger regional warming than others...... that in general models with a positive temperature dependent bias tend to have a large projected temperature change, and these tendencies increase with increasing global warming level. We argue that this appears to be linked with the ability of models to capture complex feedbacks accurately. In particular land...

  3. On the Temperature Dependence of the UNIQUAC/UNIFAC Models

    DEFF Research Database (Denmark)

    Skjold-Jørgensen, Steen; Rasmussen, Peter; Fredenslund, Aage

    1980-01-01

    Local composition models for the description of the properties of liquid mixtures do not in general give an accurate representation of excess Gibbs energy and excess enthalpy simultaneously. The introduction of temperature dependent interaction parameters leads to considerable improvements...... of the simultaneous correlation. The temperature dependent parameters have, however, little physical meaning and very odd results are frequently obtained when the interaction parameters obtained from excess enthalpy information alone are used for the prediction of vapor-liquid equilibria. The UNIQUAC/UNIFAC models...... are modified in this work by the introduction of a general temperature dependence of the coordination number. The modified UNIQUAC/UNIFAC models are especially suited for the representation of mixtures containing non-associating components. The modified models contain the same number of interaction parameters...

  4. Temperature dependence of the in situ widths of a rotating condensate in one dimensional optical potential

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, Ahmed S., E-mail: ahmedhassan117@yahoo.com; Soliman, Shemi S.M.

    2016-01-08

    In this paper, a conventional method of quantum statistical mechanics is used to study the temperature dependence of the in situ widths of a rotating condensate bosons in 1D optical potential. We trace the experimentally accessible parameters for which the temperature dependence of the in situ widths becomes perceivable. The calculated results showed that the temperature dependence of the in situ widths is completely different from that of a rotating condensate or trapped bosons in the optical lattice separately. The z-width shows distinct behavior from x- and y-widths due to the rotation effect. The obtained results provide useful qualitative theoretical results for future Bose Einstein condensation experiments in such traps. - Highlights: • The temperature dependence of the in situ widths of a rotating condensate boson in 1D optical potential is investigated. • We trace the experimentally accessible parameters for which the in situ widths become perceivable. • The above mentioned parameters exhibit a characteristic rotation rate and optical potential depth dependence. • Characteristic dependence of the effective widths on temperature is investigated. • Our results provide useful qualitatively and quantitative theoretical results for experiments in various traps.

  5. The temperature dependent amide I band of crystalline acetanilide

    Energy Technology Data Exchange (ETDEWEB)

    Cruzeiro, Leonor [CCMAR, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Physics Department, FCT, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Freedman, Holly [CCMAR, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal)

    2013-10-01

    The temperature dependent anomalous peak in the amide I band of crystalline acetanilide is thought to be due to self-trapped states. On the contrary, according to the present model, the anomalous peak comes from the fraction of ACN molecules strongly hydrogen-bonded to a neighboring ACN molecule, and its intensity decreases because, on average, this fraction decreases as temperature increases. This model provides, for the first time, an integrated and theoretically consistent view of the temperature dependence of the full amide I band and a qualitative explanation of some of the features of nonlinear pump–probe experiments.

  6. Thermal dissociation of molten KHSO4: Temperature dependence of Raman spectra and thermodynamics

    DEFF Research Database (Denmark)

    Knudsen, Christian B.; Kalampounias, Angelos G.; Fehrmann, Rasmus

    2008-01-01

    intensities with the stoichiometric coefficients, the equilibrium constant, and the thermodynamics of the reaction equilibrium is derived. The method is used-along with the temperature-dependent features of the Raman spectra-to show that the studied equilibrium 2HSO(4)(-) (1) S2O72-(1) + H2O(g) is the only......Raman spectroscopy is used to study the thermal dissociation of molten KHSO4 at temperatures of 240-450 degrees C under static equilibrium conditions. Raman spectra obtained at 10 different temperatures for the molten phase and for the vapors thereof exhibit vibrational wavenumbers and relative...... band intensities inferring the occurrence of the temperature-dependent dissociation equilibrium 2HSO(4)(-) (1) S2O72-(1) + H2O(g). The Raman data are adequate for determining the partial pressures of H2O in the gas phase above the molten mixtures. A formalism for correlating relative Raman band...

  7. Compact model of power MOSFET with temperature dependent Cauer RC network for more accurate thermal simulations

    Science.gov (United States)

    Marek, Juraj; Chvála, Aleš; Donoval, Daniel; Príbytný, Patrik; Molnár, Marián; Mikolášek, Miroslav

    2014-04-01

    A new, more accurate SPICE-like model of a power MOSFET containing a temperature dependent thermal network is described. The designed electro-thermal MOSFET model consists of several parts which represent different transistor behavior under different conditions such as reverse bias, avalanche breakdown and others. The designed model is able to simulate destruction of the device as thermal runaway and/or overcurrent destruction during the switching process of a wide variety of inductive loads. Modified thermal equivalent circuit diagrams were designed taking into account temperature dependence of thermal resistivity. The potential and limitations of the new models are presented and analyzed. The new model is compared with the standard and empirical models and brings a higher accuracy for rapid heating pulses. An unclamped inductive switching (UIS) test as a stressful condition was used to verify the proper behavior of the designed MOSFET model.

  8. Quark mass density- and temperature- dependent model for bulk strange quark matter

    OpenAIRE

    al, Yun Zhang et.

    2002-01-01

    It is shown that the quark mass density-dependent model can not be used to explain the process of the quark deconfinement phase transition because the quark confinement is permanent in this model. A quark mass density- and temperature-dependent model in which the quark confinement is impermanent has been suggested. We argue that the vacuum energy density B is a function of temperature. The dynamical and thermodynamical properties of bulk strange quark matter for quark mass density- and temper...

  9. Modeling of Circuits with Strongly Temperature Dependent Thermal Conductivities for Cryogenic CMOS

    OpenAIRE

    Hamlet, J.; Eng, K.; Gurrieri, T.; Levy, J; Carroll, M

    2010-01-01

    When designing and studying circuits operating at cryogenic temperatures understanding local heating within the circuits is critical due to the temperature dependence of transistor and noise behavior. We have investigated local heating effects of a CMOS ring oscillator and current comparator at T=4.2K. In two cases, the temperature near the circuit was measured with an integrated thermometer. A lumped element equivalent electrical circuit SPICE model that accounts for the strongly temperature...

  10. Temperature dependence of electromechanical properties of PLZT x ...

    Indian Academy of Sciences (India)

    Administrator

    the temperature dependence of electromechanical proper- ties of PLZT. It has been observed that the compositions of PLZT ceramics with Zr/Ti 57/43 show enhanced piezoelectric response at room temperature and can be used in low power transducer devices (Shukla et al 2004). Keeping the device application in view, ...

  11. Temperature dependence of exciton diffusion in conjugated polymers

    NARCIS (Netherlands)

    Mikhnenko, O.V.; Cordella, F.; Sieval, A.B.; Hummelen, J.C.; Blom, P.W.M.; Loi, M.A.

    2008-01-01

    The temperature dependence of the exciton dynamics in a conjugated polymer is studied using time-resolved spectroscopy. Photoluminescence decays were measured in heterostructured samples containing a sharp polymer-fullerene interface, which acts as an exciton quenching wall. Using a ID diffusion

  12. Temperature dependence of electromechanical properties of PLZT x ...

    Indian Academy of Sciences (India)

    The compositions of lead lanthanum zirconate titanate PLZT [Pb(Zr0.57Ti0.43)O3 + at% of La, where = 3, 5, 6, 10 and 12] have been synthesized using mixed oxide route. The temperature dependent electromechanical parameters have been determined using vector impedance spectroscopy (VIS). The charge constant ...

  13. Temperature-dependent gas transport and its correlation with kinetic ...

    Indian Academy of Sciences (India)

    2017-05-20

    May 20, 2017 ... Temperature-dependent gas transport and its correlation with kinetic diameter in polymer nanocomposite membrane. N K ACHARYA. Applied Physics Department, Faculty of Technology and Engineering, The M S University of Baroda,. Vadodara 390 001, India sarnavee@gmail.com. MS received 18 May ...

  14. Temperature dependence studies on the electro-oxidation of ...

    Indian Academy of Sciences (India)

    Cyclic voltammetry; electrochemical impedance spectroscopy; activation energy; fuel cell; alcohol. Abstract. Temperature dependence on the electro-oxidation of methanol, ethanol and 1-propanol in 0.5 M H2SO4 were investigated with Pt and PtRu electrodes. Tafel slope and apparent activation energy were evaluated ...

  15. Electronically induced nuclear transitions - temperature dependence and Rabi oscillations

    CERN Document Server

    Niez, J J

    2002-01-01

    This paper deals with a nucleus electromagnetically coupled with the bound states of its electronic surroundings. It describes the temperature dependence of its dynamics and the onset of potential Rabi oscillations by means of a Master Equation. The latter is generalized in order to account for possible strong resonances. Throughout the paper the approximation schemes are discussed and tested. (authors)

  16. Temperature dependence of postmortem MR quantification for soft tissue discrimination

    Energy Technology Data Exchange (ETDEWEB)

    Zech, Wolf-Dieter; Schwendener, Nicole; Jackowski, Christian [University of Bern, From the Institute of Forensic Medicine, Bern (Switzerland); Persson, Anders; Warntjes, Marcel J. [University of Linkoeping, The Center for Medical Image Science and Visualization (CMIV), Linkoeping (Sweden)

    2015-08-15

    To investigate and correct the temperature dependence of postmortem MR quantification used for soft tissue characterization and differentiation in thoraco-abdominal organs. Thirty-five postmortem short axis cardiac 3-T MR examinations were quantified using a quantification sequence. Liver, spleen, left ventricular myocardium, pectoralis muscle and subcutaneous fat were analysed in cardiac short axis images to obtain mean T1, T2 and PD tissue values. The core body temperature was measured using a rectally inserted thermometer. The tissue-specific quantitative values were related to the body core temperature. Equations to correct for temperature differences were generated. In a 3D plot comprising the combined data of T1, T2 and PD, different organs/tissues could be well differentiated from each other. The quantitative values were influenced by the temperature. T1 in particular exhibited strong temperature dependence. The correction of quantitative values to a temperature of 37 C resulted in better tissue discrimination. Postmortem MR quantification is feasible for soft tissue discrimination and characterization of thoraco-abdominal organs. This provides a base for computer-aided diagnosis and detection of tissue lesions. The temperature dependence of the T1 values challenges postmortem MR quantification. Equations to correct for the temperature dependence are provided. (orig.)

  17. On the effect of temperature dependent thermal conductivity on ...

    African Journals Online (AJOL)

    We consider the effect of temperature dependent thermal conductivity on temperature rise in biologic tissues during microwave heating. The method of asymptotic expansion is used for finding solution. An appropriate matching procedure was used in our method. Our result reveals the possibility of multiple solutions and it ...

  18. Extraction of temperature dependent interfacial resistance of thermoelectric modules

    DEFF Research Database (Denmark)

    Chen, Min

    2011-01-01

    This article discusses an approach for extracting the temperature dependency of the electrical interfacial resistance associated with thermoelectric devices. The method combines a traditional module-level test rig and a nonlinear numerical model of thermoelectricity to minimize measurement errors...... on the interfacial resistance. The extracted results represent useful data to investigating the characteristics of thermoelectric module resistance and comparing performance of various modules....

  19. Pressure–temperature dependence of thermodynamic properties of ...

    Indian Academy of Sciences (India)

    properties of materials under high pressures and temperatures for microscopic under- standing as well as technological applications. In this paper, we report our theoretical study of both pressure and temperature dependences of the thermal properties of rutile within the Debye and Debye–Grüneisen models with and ...

  20. Arrhenius temperature dependence of in vitro tissue plasminogen activator thrombolysis

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, George J [Department of Emergency Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0769 (United States); Dhamija, Ashima [Department of Emergency Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0769 (United States); Bavani, Nazli [Department of Emergency Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0769 (United States); Wagner, Kenneth R [Department of Neurology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0769 (United States); Holland, Christy K [Department of Biomedical Engineering, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0769 (United States)

    2007-06-07

    Stroke is a devastating disease and a leading cause of death and disability. Currently, the only FDA approved therapy for acute ischemic stroke is the intravenous administration of the thrombolytic medication, recombinant tissue plasminogen activator (tPA). However, this treatment has many contraindications and can have dangerous side effects such as intra-cerebral hemorrhage. These treatment limitations have led to much interest in potential adjunctive therapies, such as therapeutic hypothermia (T {<=} 35 deg. C) and ultrasound enhanced thrombolysis. Such interest may lead to combining these therapies with tPA to treat stroke, however little is known about the effects of temperature on the thrombolytic efficacy of tPA. In this work, we measure the temperature dependence of the fractional clot mass loss {delta}m(T) resulting from tPA exposure in an in vitro human clot model. We find that the temperature dependence is well described by an Arrhenius temperature dependence with an effective activation energy E{sub eff} of 42.0 {+-} 0.9 kJ mole{sup -1}. E{sub eff} approximates the activation energy of the plasminogen-to-plasmin reaction of 48.9 kJ mole{sup -1}. A model to explain this temperature dependence is proposed. These results will be useful in predicting the effects of temperature in future lytic therapies.

  1. Investigation of temperature dependence of development and aging

    Science.gov (United States)

    Sacher, G. A.

    1969-01-01

    Temperature dependence of maturation and metabolic rates in insects, and the failure of vital processes during development were investigated. The paper presented advances the general hypothesis that aging in biological systems is a consequence of the production of entropy concomitant with metabolic activity.

  2. Temperature dependent structural disintegration of delafossite CuFeO2

    Science.gov (United States)

    Shojan, P.; Kumar, Ashok; Katiyar, Ram

    2009-03-01

    Single phase delafossite p-type CuFeO2 (CFO) semiconductor was synthesized by modified solid state reaction technique. X-ray diffraction (XRD) and X-ray photo spectroscopy (XPS) studies suggest pure phase of CFO and Energy dispersive X-ray spectroscopy (EDX) also revealed that the atomic ratio Cu and Fe is 1:1. The XPS spectra showed two intense Cu 2p3/2 and 2p1/2 peaks at 932.5 eV and 952 eV and two Fe 2p3/2 and 2p1/2 peaks at 710 eV and 725 eV suggesting Cu and Fe ions are in +1 and +3 state with high spin S=5/2. The room temperature Raman spectra of CFO displayed two main strong active modes at 351 cm-1 and 692 cm-1 that matched with other delaffosite structure. Temperature dependent Raman spectra indicate that the lowest mode vanished or overdammped at ˜ 400 K where as higher modes shifted to lower frequency side with significantly decreased in intensity. We have also observed a low frequency (E2^low) mode at 79 cm-1 using 532 nm (<5MHz line width) laser line. The line width and intensity of the lowest mode indicates temperature independent behavior. Raman Spectra were carried out from 80 K to 1300 K which revealed structural disintegration in CFO over 800 K in air. The structural degradation is counter confirmed by XPS, XRD, DTA measurements. Around 800 K in air, CFO disintegrates to form CuO and CuFe2O4.

  3. Temperature dependence of low-frequency polarized Raman scattering spectra in TlInS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Paucar, Raul; Wakita, Kazuki [Electronics and Computer Engineering, Chiba Institute of Technology, Chiba (Japan); Shim, YongGu; Mimura, Kojiro [Graduate School of Engineering, Osaka Prefecture University, Osaka (Japan); Alekperov, Oktay; Mamedov, Nazim [Institute of Physics, Azerbaijan National Academy of Sciences, Baku (Azerbaijan)

    2017-06-15

    In this work, we examined phase transitions in the layered ternary thallium chalcogenide TlInS{sub 2} by studying the temperature dependence of polarized Raman spectra with the aid of the Raman confocal microscope system. The Raman spectra were measured over the temperature range of 77-320 K (which includes the range of successive phase transitions) in the low-frequency region of 35-180 cm{sup -1}. The optical phonons that showed strong temperature dependence were identified as interlayer vibrations related to phase transitions, while the phonons that showed weak temperature dependence were identified as intralayer vibrations. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Brominated flame retardants in the urban atmosphere of Northeast China: Concentrations, temperature dependence and gas-particle partitioning

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Hong; Li, Wen-Long; Liu, Li-Yan; Song, Wei-Wei; Ma, Wan-Li, E-mail: mawanli002@163.com; Li, Yi-Fan, E-mail: ijrc_pts_paper@yahoo.com

    2014-09-01

    57 pairs of air samples (gas and particle phases) were collected using a high volume air sampler in a typical city of Northeast China. Brominated flame retardants (BFRs) including 13 polybrominated diphenyl ethers (PBDEs, including BDEs 17, 28, 47, 49, 66, 85, 99, 100, 138, 153, 154, 183, and 209) and 9 alternative BFRs (p-TBX, PBBZ, PBT, PBEB, DPTE, HBBZ, γ-HBCD, BTBPE, and DBDPE) were analyzed. The annual average total concentrations of the 13 PBDEs and the 9 alternative BFRs were 69 pg/m{sup 3} and 180 pg/m{sup 3}, respectively. BDE 209 and γ-HBCD were the dominant congeners, according to the one-year study. The partial pressure of BFRs in the gas phase was significantly correlated with the ambient temperature, except for BDE 85, γ-HBCD and DBDPE, indicating the important influence of ambient temperature on the behavior of BFRs in the atmosphere. It was found that the gas–particle partitioning coefficients (logK{sub p}) for most low molecular weight BFRs were highly temperature dependent as well. Gas–particle partitioning coefficients (logK{sub p}) also correlated with the sub-cooled liquid vapor pressure (logP{sub L}{sup o}). Our results indicated that absorption into organic matter is the main control mechanism for the gas–particle partitioning of atmospheric PBDEs. - Highlights: • Both PBDEs and alternative BFRs were analyzed in the atmosphere of Northeast China. • Partial pressure of BFRs was significantly correlated with the ambient temperature. • A strong temperature dependence of gas-particle partitioning was found. • Absorption into organic matter was the control mechanism for G-P partitioning.

  5. Phase behavior of Au and Pt surfaces

    DEFF Research Database (Denmark)

    Grübel, G.; Gibbs, D.; Zehner, D.M.

    1993-01-01

    We summarize the results of X-ray scattering studies of the Au(001) and Pt(001) surfaces between 300 K and their respective bulk melting temperatures (T(m)). Both surfaces exhibit three distinct structural phases. At high temperatures (0.88T(m) surfaces are disordered. The Pt(001......) surface is rough. At a temperature of T/T(m) almost-equal-to 0.88 there are reversible phase transformations to incommensurate, corrugated-hexagonal phases. Below T/T(m) almost-equal-to 0.8 hexagonal domains rotate with respect to the substrate orientation. In Pt, the rotational transformation...

  6. Molecular modeling of temperature dependence of solubility parameters for amorphous polymers.

    Science.gov (United States)

    Chen, Xianping; Yuan, Cadmus; Wong, Cell K Y; Zhang, Guoqi

    2012-06-01

    A molecular modeling strategy is proposed to describe the temperature (T) dependence of solubility parameter (δ) for the amorphous polymers which exhibit glass-rubber transition behavior. The commercial forcefield "COMPASS" is used to support the atomistic simulations of the polymer. The temperature dependence behavior of δ for the polymer is modeled by running molecular dynamics (MD) simulation at temperatures ranging from 250 up to 650 K. Comparing the MD predicted δ value at 298 K and the glass transition temperature (T(g)) of the polymer determined from δ-T curve with the experimental value confirm the accuracy of our method. The MD modeled relationship between δ and T agrees well with the previous theoretical works. We also observe the specific volume (v), cohesive energy (U(coh)), cohesive energy density (E(CED)) and δ shows a similar temperature dependence characteristics and a drastic change around the T(g). Meanwhile, the applications of δ and its temperature dependence property are addressed and discussed.

  7. Temperature dependence of Young's modulus of titanium dioxide (TIO2) nanotubes: Molecular mechanics modeling

    Science.gov (United States)

    Lukyanov, S. I.; Bandura, A. V.; Evarestov, R. A.

    2015-12-01

    Temperature dependence of the Young's modulus of cylindrical single-wall nanotubes with zigzag and armchair chiralities and consolidated-wall nanotubes has been studied by the molecular mechanics method with the use of the atom-atom potential. The nanotubes have been obtained by rolling up of crystal layers (111) of TiO2 with fluorite structure. Calculations have been performed for isothermal conditions on the basis of calculating the Helmholtz free energy of the system. The dependence of the Helmholtz free energy of nanotubes on the period has been calculated in the quasi-harmonic approximation as a result of calculation of phonon frequencies. It has been shown that the temperature dependence of the stiffness of nanotubes is determined by their chirality, and some nanotubes exibit anomalous behavior of both the Young's modulus and the period of unit cell with variation in temperature.

  8. Temperature dependence of magnetic anisotropies in ultrathin Fe film on vicinal Si(111)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yong-Sheng; He, Wei; Ye, Jun; Hu, Bo; Tang, Jin; Zhang, Xiang-Qun [State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Cheng, Zhao-Hua, E-mail: zhcheng@aphy.iphy.ac.cn [State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190 (China)

    2017-05-01

    The temperature dependence of magnetic anisotropy of ultrathin Fe film with different thickness epitaxially grown on vicinal Si(111) substrate has been quantitatively investigated using the anisotropic magnetoresistance(AMR) measurements. Due to the effect of the vicinal substrate, the magnetic anisotropy is the superposition of a four-fold, a two-fold and a weakly six-fold contribution. It is found that the temperature dependence of the first-order magnetocrystalline anisotropies coefficient follows power laws of the reduced magnetization m(T)(=M(T)/M(0)) being consistent with the Callen and Callen's theory. However the temperature dependence of uniaxial magnetic anisotropy (UMA) shows novel behavior that decreases roughly as a function of temperature with different power law for samples with different thickness. We also found that the six-fold magnetocrystalline anisotropy is almost invariable over a wide temperature range. Possible mechanisms leading to the different exponents are discussed.

  9. Temperature-dependent structure evolution in liquid gallium

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, L. H.; Wang, X. D.; Yu, Q.; Zhang, H.; Zhang, F.; Sun, Y.; Cao, Q. P.; Xie, H. L.; Xiao, T. Q.; Zhang, D. X.; Wang, C. Z.; Ho, K. M.; Ren, Y.; Jiang, J. Z.

    2017-04-01

    Temperature-dependent atomistic structure evolution of liquid gallium (Ga) has been investigated by using in situ high energy X-ray diffraction experiment and ab initio molecular dynamics simulation. Both experimental and theoretical results reveal the existence of a liquid structural change around 1000 K in liquid Ga. Below and above this temperature the liquid exhibits differences in activation energy for selfdiffusion, temperature-dependent heat capacity, coordination numbers, density, viscosity, electric resistivity and thermoelectric power, which are reflected from structural changes of the bond-orientational order parameter Q6, fraction of covalent dimers, averaged string length and local atomic packing. This finding will trigger more studies on the liquid-to-liquid crossover in metallic melts.

  10. Temperature-dependent enthalpy of oxygenation in Antarctic fish hemoglobins

    DEFF Research Database (Denmark)

    Fago, A.; Wells, R.M.G.; Weber, Roy E.

    1997-01-01

    The effect of temperature on the oxygen-binding properties of the hemoglobins of three cold-adapted Antarctic fish species, Dissostichus mawsoni, Pagothenia borchgrevinki and Trematomus, sp., has been investigated under different pH values and buffer conditions. A clear non linear van't Hoff plot...... oxygen binding. The degree of the temperature dependence of the heat of oxygenation observed in these hemoglobins seems to reflect the differences in their allosteric effects rather than a specific molecular adaptation to low temperatures. Moreover, this study indicates that the disagreement between...... (logP(50) vs 1/T) of D. mawsoni hemoglobin indicates that the enthalpy of oxygenation (slope of the plot) is temperature dependent and that at high temperatures oxygen-binding becomes less exothermic. Nearly linear relationships were found in the hemoglobins of the other two species. The data were...

  11. Molecular modeling of temperature dependence of solubility parameters for amorphous polymers

    OpenAIRE

    Chen, X.; Yuan, C.; Wong, C.K.Y.; Zhang, G

    2011-01-01

    A molecular modeling strategy is proposed to describe the temperature (T) dependence of solubility parameter (δ) for the amorphous polymers which exhibit glass-rubber transition behavior. The commercial forcefield “COMPASS” is used to support the atomistic simulations of the polymer. The temperature dependence behavior of δ for the polymer is modeled by running molecular dynamics (MD) simulation at temperatures ranging from 250 up to 650 K. Comparing the MD predicted δ value at 298 K and the ...

  12. AlN Bandgap Temperature Dependence from its Optical Properties

    Science.gov (United States)

    2008-06-07

    AlN bandgap temperature dependence from its optical properties E. Silveira a,, J.A. Freitas b, S.B. Schujman c, L.J. Schowalter c a Depto. de Fisica ...literature could, in part, be lifted in terms of selection rules for the optical transitions [5]. Further experimental investigations corroborated with...CL, transmission/ absorption and OR measurements at different temperatures. 2. Experimental details The high-quality large bulk AlN single crystals

  13. Temperature dependence of the fundamental band gap parameters ...

    Indian Academy of Sciences (India)

    Abstract. Thin films of ternary ZnxCd1 xSe were deposited on GaAs (100) substrate using metal- organic-chemical-vapour-deposition (MOCVD) technique. Temperature dependence of the near- band-edge emission from these Cd-rich ZnxCd1 xSe (for x = 0.025, 0.045) films has been studied using photoluminescence ...

  14. Iron mapping using the temperature dependency of the magnetic susceptibility.

    Science.gov (United States)

    Birkl, Christoph; Langkammer, Christian; Krenn, Heinz; Goessler, Walter; Ernst, Christina; Haybaeck, Johannes; Stollberger, Rudolf; Fazekas, Franz; Ropele, Stefan

    2015-03-01

    The assessment of iron content in brain white matter (WM) is of high importance for studying neurodegenerative diseases. While R2 * mapping and quantitative susceptibility mapping is suitable for iron mapping in gray matter, iron mapping in WM still remains an unsolved problem. We propose a new approach for iron mapping, independent of diamagnetic contributions of myelin by assessing the temperature dependency of the paramagnetic susceptibility. We used unfixed human brain slices for relaxometry and calculated R2 ' as a measure for microscopic susceptibility variations at several temperatures (4°C-37°C) at 3 Tesla. The temperature coefficient of R2 ' (TcR2p) was calculated by linear regression and related to the iron concentration found by subsequent superconducting quantum interference device (SQUID) magnetometry and by inductively coupled plasma mass spectrometry. In line with SQUID measurements, R2 ' mapping showed a linear temperature dependency of the bulk susceptibility with the highest slope in gray matter. Even in WM, TcR2p yielded a high linear correlation with the absolute iron concentration. According to Curie's law, only paramagnetic matter exhibits a temperature dependency while the diamagnetism shows no effect. We have demonstrated that the temperature coefficient (TcR2p) can be used as a measure of the paramagnetic susceptibility despite of an unknown diamagnetic background. © 2014 Wiley Periodicals, Inc.

  15. {open_quotes}Exchange-spring{close_quotes} Nd-Fe-B alloys: Investigations into reversal mechanisms and their temperature dependence

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, L.H.; Welch, D.O. [Brookhaven National Labs., Upton, NY (United States); Panchanathan, V. [Magnequench International, (MQI), Inc., Anderson, IN (United States)

    1996-10-01

    In order to investigate factors affecting coercivity a series of two-phase Nd{sub 2}Fe{sub 14}B-based nanocomposite alloys with different excess iron concentrations were produced by melt-spinning methods. The constituent grain size was estimated by diffraction methods to be in the range of 150 {Angstrom} - 500 {Angstrom}, and room-temperature demagnetization curves verify that the alloys studied exhibit a modest remanence enhancement. Isothermal remanence magnetization (IRM) and dc-demagnetization (DCD) measurements performed at temperatures in the range 275 K {le} T {le} 350 K illustrate that the coercivity and irreversible magnetization develops in a bimodal, incoherent manner from a demagnetized state but upon demagnetization from a saturated state the system evinces collective, exchange-coupled behavior as illustrated by the reversible magnetization M{sub rev}. The temperature dependencies and values of the irreversible susceptibility X{sub irr} (DCD) suggest that a moderating phase with a magnetic anisotropy intermediate to the two constituent main phases may be present in the alloys.

  16. Model analysis of temperature dependence of abnormal resistivity of a multiwalled carbon nanotube interconnection

    Directory of Open Access Journals (Sweden)

    Yi-Chen Yeh

    2010-07-01

    Full Text Available Yi-Chen Yeh1, Lun-Wei Chang2, Hsin-Yuan Miao3, Szu-Po Chen1, Jhu-Tzang Lue11Department of Physics and 2Institute of Electronics Engineering, National Tsing Hua University, Hsinchu, Taiwan; 3Department of Electrical Engineering, Tunghai University, Taichung, TaiwanAbstract: A homemade microwave plasma-enhanced chemical vapor deposition method was used to grow a multiwalled carbon nanotube between two nickel catalyst electrodes. To investigate the transport properties and electron scattering mechanism of this interconnection (of approximately fixed length and fixed diameter, we carried out a model analysis of temperature dependence of resistivity. To explain the abnormal behavior of the negative temperature coefficient of resistivity in our experimental results, we then employed theories, such as hopping conductivity theory and variable range hopping conductivity theory, to describe resistivity in the high- and low-temperature ranges, respectively. Further, the grain boundary scattering model is also provided to fit the entire measured curve of temperature dependence of resistivity.Keywords: multiwalled carbon nanotube, resistivity, hopping conductivity, temperature dependence

  17. Comparing the temperature dependence of photosynthetic electron transfer in Chloroflexus aurantiacus and Rhodobactor sphaeroides reaction centers.

    Science.gov (United States)

    Guo, Zhi; Lin, Su; Xin, Yueyong; Wang, Haiyu; Blankenship, Robert E; Woodbury, Neal W

    2011-09-29

    The process of electron transfer from the special pair, P, to the primary electron donor, H(A), in quinone-depleted reaction centers (RCs) of Chloroflexus (Cf.) aurantiacus has been investigated over the temperature range from 10 to 295 K using time-resolved pump-probe spectroscopic techniques. The kinetics of the electron transfer reaction, P* → P(+)H(A)(-), was found to be nonexponential, and the degree of nonexponentiality increased strongly as temperature decreased. The temperature-dependent behavior of electron transfer in Cf. aurantiacus RCs was compared with that of the purple bacterium Rhodobacter (Rb.) sphaeroides . Distinct transitions were found in the temperature-dependent kinetics of both Cf. aurantiacus and Rb. sphaeroides RCs, at around 220 and 160 K, respectively. Structural differences between these two RCs, which may be associated with those differences, are discussed. It is suggested that weaker protein-cofactor hydrogen bonding, stronger electrostatic interactions at the protein surface, and larger solvent interactions likely contribute to the higher transition temperature in Cf. aurantiacus RCs temperature-dependent kinetics compared with that of Rb. sphaeroides RCs. The reaction-diffusion model provides an accurate description for the room-temperature electron transfer kinetics in Cf. aurantiacus RCs with no free parameters, using coupling and reorganization energy values previously determined for Rb. sphaeroides , along with an experimental measure of protein conformational diffusion dynamics and an experimental literature value of the free energy gap between P* and P(+)H(A)(-). © 2011 American Chemical Society

  18. Temperature-Dependent Ellipsometry Measurements of Partial Coulomb Energy in Superconducting Cuprates

    Science.gov (United States)

    Levallois, J.; Tran, M. K.; Pouliot, D.; Presura, C. N.; Greene, L. H.; Eckstein, J. N.; Uccelli, J.; Giannini, E.; Gu, G. D.; Leggett, A. J.; van der Marel, D.

    2016-07-01

    We performed an experimental study of the temperature and doping dependence of the energy-loss function of the bilayer and trilayer bismuth cuprates family. The primary aim is to obtain information on the energy stored in the Coulomb interaction between the conduction electrons, on the temperature dependence thereof, and on the change of Coulomb interaction when Cooper pairs are formed. We performed temperature-dependent ellipsometry measurements on several Bi2 Sr2 CaCu2 O8 -x single crystals: underdoped with Tc=60 , 70, and 83 K; optimally doped with Tc=91 K ; overdoped with Tc=84 , 81, 70, and 58 K; as well as optimally doped Bi2 Sr2 Ca2 Cu3 O10 +x with Tc=110 K . Our first observation is that, as the temperature drops through Tc, the loss function in the range up to 2 eV displays a change of temperature dependence as compared to the temperature dependence in the normal state. This effect at—or close to—Tc depends strongly on doping, with a sign change for weak overdoping. The size of the observed change in Coulomb energy, using an extrapolation with reasonable assumptions about its q dependence, is about the same size as the condensation energy that has been measured in these compounds. Our results therefore lend support to the notion that the Coulomb energy is an important factor for stabilizing the superconducting phase. Because of the restriction to small momentum, our observations do not exclude a possible significant contribution to the condensation energy of the Coulomb energy associated with the region of q around (π ,π ).

  19. Temperature-Dependent Ellipsometry Measurements of Partial Coulomb Energy in Superconducting Cuprates

    Directory of Open Access Journals (Sweden)

    J. Levallois

    2016-08-01

    Full Text Available We performed an experimental study of the temperature and doping dependence of the energy-loss function of the bilayer and trilayer bismuth cuprates family. The primary aim is to obtain information on the energy stored in the Coulomb interaction between the conduction electrons, on the temperature dependence thereof, and on the change of Coulomb interaction when Cooper pairs are formed. We performed temperature-dependent ellipsometry measurements on several Bi_{2}Sr_{2}CaCu_{2}O_{8-x} single crystals: underdoped with T_{c}=60, 70, and 83 K; optimally doped with T_{c}=91  K; overdoped with T_{c}=84, 81, 70, and 58 K; as well as optimally doped Bi_{2}Sr_{2}Ca_{2}Cu_{3}O_{10+x} with T_{c}=110  K. Our first observation is that, as the temperature drops through T_{c}, the loss function in the range up to 2 eV displays a change of temperature dependence as compared to the temperature dependence in the normal state. This effect at—or close to—T_{c} depends strongly on doping, with a sign change for weak overdoping. The size of the observed change in Coulomb energy, using an extrapolation with reasonable assumptions about its q dependence, is about the same size as the condensation energy that has been measured in these compounds. Our results therefore lend support to the notion that the Coulomb energy is an important factor for stabilizing the superconducting phase. Because of the restriction to small momentum, our observations do not exclude a possible significant contribution to the condensation energy of the Coulomb energy associated with the region of q around (π,π.

  20. Light phase testing of social behaviors: not a problem

    Directory of Open Access Journals (Sweden)

    Mu Yang

    2008-12-01

    Full Text Available The rich repertoire of mouse social behaviors makes it possible to use mouse models to study neurodevelopmental disorders characterized by social deficits. The fact that mice are naturally nocturnal animals raises a critical question of whether behavioral experiments should be strictly conducted in the dark phase and whether light phase testing is a major methodologically mistake. Although mouse social tasks have been performed in both phases in different laboratories, there seems to be no general consensus on whether testing phase is a critical factor or not. A recent study from our group showed remarkably similar social scores obtained from inbred mice tested in the light and the dark phase, providing evidence that light phase testing could yield reliable results as robust as dark phase testing for the sociability test. Here we offer a comprehensive review on mouse social behaviors measured in light and dark phases and explain why it is reasonable to test laboratory mice in experimental social tasks in the light phase.

  1. Phase behavior of coal fluids: Data for correlation development

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, R.L. Jr.

    1990-02-06

    The effective design and operation of processes for conversion of coal to fluid fuels requires accurate knowledge of the phase behavior of the fluid mixtures encountered in the conversion process. Multiple phases are present in essentially all stages of feed preparation, conversion reactions and product separation; thus, knowledge of the behavior of these multiple phases is important in each step. The overall objective of the author's work is to develop accurate predictive methods for representation of vapor-liquid equilibria in systems encountered in coal conversion processes. 59 refs., 6 figs., 7 tabs.

  2. Temperature dependence of photoluminescence from ordered GaInP{sub 2} epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Prutskij, T. [Instituto de Ciencias, BUAP, Apartado Postal 207, 72000 Puebla, Pue. (Mexico); Pelosi, C. [IMEM/CNR, Parco Area delle Scienze 37/A, 43010 Parma (Italy)

    2010-01-15

    The temperature behavior of the integrated intensity of photoluminescence (PL) emission from ordered GaInP{sub 2} epitaxial layer was measured at temperatures of 10 - 300 K. Within this temperature range the PL emission is dominated by band-to-band radiative recombination. The PL intensity temperature dependence has two regions: at low temperatures it quenches rapidly as the temperature increases, and above 100 K it reduces slowly. This temperature behavior is compared with that of disordered GaInP{sub 2} layer. The specter of the PL emission of the disordered layer has two peaks, which are identified as due to donor-accepter (D-A) and band-to-band recombination. The PL intensity quenching of these spectral bands is very different: With increasing temperature, the D-A peak intensity remains almost unchanged at low temperatures and then decreases at a higher rate. The intensity of the band-to-band recombination peak decays gradually, having a higher rate at low temperatures than at higher temperatures. Comparing these temperature dependencies of these PL peaks of ordered and disordered alloys and the temperature behavior of their full width at half maximum (FWHM), we conclude that the different morphology of these alloys causes their different temperature behavior. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Temperature dependence of the Brewer global UV measurements

    Science.gov (United States)

    Fountoulakis, Ilias; Redondas, Alberto; Lakkala, Kaisa; Berjon, Alberto; Bais, Alkiviadis F.; Doppler, Lionel; Feister, Uwe; Heikkila, Anu; Karppinen, Tomi; Karhu, Juha M.; Koskela, Tapani; Garane, Katerina; Fragkos, Konstantinos; Savastiouk, Volodya

    2017-11-01

    Spectral measurements of global UV irradiance recorded by Brewer spectrophotometers can be significantly affected by instrument-specific optical and mechanical features. Thus, proper corrections are needed in order to reduce the associated uncertainties to within acceptable levels. The present study aims to contribute to the reduction of uncertainties originating from changes in the Brewer internal temperature, which affect the performance of the optical and electronic parts, and subsequently the response of the instrument. Until now, measurements of the irradiance from various types of lamps at different temperatures have been used to characterize the instruments' temperature dependence. The use of 50 W lamps was found to induce errors in the characterization due to changes in the transmissivity of the Teflon diffuser as it warms up by the heat of the lamp. In contrast, the use of 200 or 1000 W lamps is considered more appropriate because they are positioned at longer distances from the diffuser so that warming is negligible. Temperature gradients inside the instrument can cause mechanical stresses which can affect the instrument's optical characteristics. Therefore, during the temperature-dependence characterization procedure warming or cooling must be slow enough to minimize these effects. In this study, results of the temperature characterization of eight different Brewer spectrophotometers operating in Greece, Finland, Germany and Spain are presented. It was found that the instruments' response changes differently in different temperature regions due to different responses of the diffusers' transmittance. The temperature correction factors derived for the Brewer spectrophotometers operating at Thessaloniki, Greece, and Sodankylä, Finland, were evaluated and were found to remove the temperature dependence of the instruments' sensitivity.

  4. Gas diffusion and temperature dependence of bubble nucleation during irradiation

    DEFF Research Database (Denmark)

    Foreman, A. J. E.; Singh, Bachu Narain

    1986-01-01

    of the diatomic nucleation of helium bubbles, assuming helium to diffuse substitutionally, with radiation-enhanced diffusion at lower temperatures. The calculated temperature dependence of the bubble density shows excellent agreement with that observed in 600 MeV proton irradiations, including a reduction...... in activation energy below Tm/2. The coalescence of diatomic nuclei due to Brownian motion markedly improves the agreement and also provides a well-defined terminal density. Bubble nucleation by this mechanism is sufficiently fast to inhibit any appreciable initial loss of gas to grain boundaries during...

  5. Phase behavior of Janus colloids determined by sedimentation equilibrium.

    Science.gov (United States)

    Beltran-Villegas, Daniel J; Schultz, Benjamin A; Nguyen, Nguyen H P; Glotzer, Sharon C; Larson, Ronald G

    2014-07-14

    We investigate the phase behavior of short-range interacting isotropic particles and single-patch Janus particles via simulations of sedimentation equilibrium, which allows for a rapid assessment of the equation of state and phase behavior directly from simulation. The methodology is tested against results by traditional methods and is found to yield good agreement for isotropic interactions. The method is then used to study single-patch Janus particles with different interaction strengths and patch sizes with particle area coverage greater than ∼0.63. Our results show an interplay between translational and orientational order. We observe a lamellar phase, a fluid phase and a rotator close-packed structure. The lamellar phase is shown to have a different range of stability than previously observed in simulation studies for systems of similar and longer-ranged interactions.

  6. Temperature-dependent regulation of reproduction in the diving beetle Dytiscus sharpi (Coleoptera: Dytiscidae).

    Science.gov (United States)

    Inoda, Toshio; Tajima, Fumitada; Taniguchi, Hiroshi; Saeki, Motoyuki; Numakura, Kazuki; Hasegawa, Masami; Kamimura, Shinji

    2007-11-01

    The effects of temperature on the mating behavior, gonad development, germ cell maturation, and egg spawning of the predaceous diving beetle Dytiscus sharpi (Coleoptera; Dytiscidae), were investigated. By field observations, we found that mating behavior started in October and occurred more frequently from November to December. Under our laboratory breeding conditions, we observed almost the same seasonal variation in mating behavior. We found that temperatures lower than 20 degrees C were required to trigger mating behavior. We also found the same temperature threshold triggered gonadogenesis as well as spermatogenesis. Furthermore, for females, exposure to lower temperatures (<8 degrees C) during the winter was required for egg maturation and spawning in spring; that is, there was a second threshold for successful female reproduction. We conclude that the termination of summer reproductive diapause of D. sharpi is regulated in a temperature-dependent manner, thus effecting the adaptation of D. sharpi to southern warm habitats.

  7. Temperature dependence of the flux line lattice transition into square symmetry in superconducting LuNi2B2C

    DEFF Research Database (Denmark)

    Eskildsen, M.R.; Abrahamsen, A.B.; Kogan, V.G.

    2001-01-01

    We have investigated the temperature dependence of the H parallel to c flux line lattice structural phase transition from square to hexagonal symmetry, in the tetragonal superconductor LuNi2B2C (T-c = 16.6 K). At temperatures below 10 K the transition onset field, H-2(T), is only weakly temperature...... dependent. Above 10 K, H-2(T) rises sharply, bending away from the upper critical field. This contradicts theoretical predictions of H-2(T) merging with the upper critical field and suggests that just below the H-c2(T) curve the flux line lattice might be hexagonal....

  8. Temperature dependence of NGR Cu(2) line width in YBa sub 2 Cu sub 3 O sub 7 sub - sub y

    CERN Document Server

    Duglav, A V; Sakhratov, Y A; Savinkov, A V

    2001-01-01

    One conducted systematic measurements of sup 6 sup 3 Cu(2) NGR line width using underdoped YBa sub 2 Cu sub 3 O sub 7 sub - sub y specimens within 4.2 K < T < 300 K temperature range. It is shown that as temperature drops below the critical one the width of copper NGR line becomes wider monotonically which temperature dependence resembles behavior of superconducting slit. The observed behavior is associated with energy dependence of condensate of moving current-charge states like waves of charged density on phase of order parameter which according to the calculations occurs at T < T sub c only. The obtained quantitative evaluations of line winding at T< T sub c conform to the measurement results

  9. Temperature-dependent photoluminescence from CdS/Si nanoheterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yue Li; Li, Yong; Ji, Peng Fei; Zhou, Feng Qun; Sun, Xiao Jun; Yuan, Shu Qing; Wan, Ming Li [Pingdingshan University, Department of Physics, Solar New Energy Research Center, Pingdingshan (China); Ling, Hong [North China University of Water Resources and Electric Power, Department of Mathematics and Information Science, Zhengzhou (China)

    2016-12-15

    CdS/Si nanoheterojunctions have been fabricated by growing nanocrystal CdS (nc-CdS) on the silicon nanoporous pillar array (Si-NPA) through using a chemical bath deposition method. The nanoheterojunctions have been constructed by three layers: the upper layer being a nc-CdS thin films, the intermediate layer being the interface region including nc-CdS and nanocrystal silicon (nc-Si), and the bottom layer being nc-Si layer grown on sc-Si substrate. The room temperature and temperature-dependent photoluminescence (PL) have been measured and analyzed to provide some useful information of defect states. Utilizing the Gauss-Newton fitting method, five emission peaks from the temperature-dependent PL spectra can be determined. From the high energy to low energy, these five peaks are ascribed to the some luminescence centers which are formed by the oxygen-related deficiency centers in the silicon oxide layer of Si-NPA, the band gap emission of nc-CdS, the transition from the interstitial cadmium (I{sub Cd}) to the valence band, the recombination from I{sub Cd} to cadmium vacancies (V{sub Cd}), and from sulfur vacancies (V{sub s}) to the valence band, respectively. Understanding of the defect states in the CdS/Si nanoheterojunctions is very meaningful for the performance of devices based on CdS/Si nanoheterojunctions. (orig.)

  10. Temperature Dependent Electrical and Micromechanical Properties of Lanthanum Titanate with Additions of Yttria

    Science.gov (United States)

    Goldsby, Jon C.

    2003-01-01

    Lanthanum titanate (La2Ti2O7) a layered distorted perovskite (1) with space group Pna2(sub 1) has been shown to have potential as a high temperature piezoelectric (2). However this highly refractory oxide compound must be consolidated at relatively high temperatures approximately 1400 C. Commercial La2Ti207 powders were mechanically alloyed with additions of Y2O3 to lower the consolidation temperature by 300 C and to provide post processing mechanical stability. Temperature dependent electrical, elastic and anelastic behavior were selected as nondestructive means of evaluating the effects of yttria on the properties of this ferroceramic material.

  11. Temperature dependence of universal conductance fluctuation due to development of weak localization in graphene

    Science.gov (United States)

    Terasawa, D.; Fukuda, A.; Fujimoto, A.; Ohno, Y.; Matsumoto, K.

    2017-11-01

    The temperature effect of quantum interference on resistivity is examined in monolayer graphene, with experimental results showing that the amplitude of the conductance fluctuation increases as temperature decreases. We find that this behavior can be attributed to the decrease in the inelastic scattering (dephasing) rate, which enhances the weak localization (WL) correction to resistivity. Following a previous report that explained the relationship between the universal conductance fluctuation (UCF) and WL regarding the gate voltage dependence (Terasawa et al., 2017) [19], we propose that the temperature dependence of the UCF in monolayer graphene can be interpreted by the WL theory.

  12. Reversing the temperature dependence of the sensitized Er3+ luminescence intensity

    Science.gov (United States)

    Lenz, F.; Hryciw, A.; DeCorby, R.; Meldrum, A.

    2009-08-01

    The temperature-induced quenching of the Er3+ luminescence is a significant problem in silicon-based materials systems ultimately designed for room-temperature applications. Here, we show that amorphous silicon-rich oxide, moderately annealed in order to avoid growth of Si nanocrystals, exhibits a reversed temperature dependence in which the integrated Er3+ luminescence increases in intensity upon heating from 77 up to 300 K. This behavior is attributed to a unique spectrum of interacting defects that efficiently sensitize the Er3+ levels, even in the absence of nanocrystals. The effect could have ramifications in fiber-optic emitters or amplifiers to be operated at noncryogenic temperatures.

  13. Temperature dependence of Henry's law constant in an extended temperature range.

    Science.gov (United States)

    Görgényi, Miklós; Dewulf, Jo; Van Langenhove, Herman

    2002-08-01

    The Henry's law constants H for chloroform, 1,1-dichloroethane, 1,2-dichloropropane, trichloroethene, chlorobenzene, benzene and toluene were determined by the EPICS-SPME technique (equilibrium partitioning in closed systems--solid phase microextraction) in the temperature range 275-343 K. The curvature observed in the ln H vs. 1/T plot was due to the temperature dependence of the change in enthalpy delta H0 during the transfer of 1 mol solute from the aqueous solution to the gas phase. The nonlinearity of the plot was explained by means of a thermodynamic model which involves the temperature dependence of delta H0 of the compounds and the thermal expansion of water in the three-parameter equation ln (H rho TT) = A2/T + BTB + C2, where rho T is the density of water at temperature T, TB = ln(T/298) + (298-T)/T, A2 = -delta H298(0)/R, delta H298(0) is the delta H0 value at 298 K, B = delta Cp0/R, and C2 is a constant. delta Cp0 is the molar heat capacity change in volatilization from the aqueous solution. A statistical comparison of the two models demonstrates the superiority of the three-parameter equation over the two-parameter one ln H vs. 1/T). The new, three-parameter equation allows a more accurate description of the temperature dependence of H, and of the solubility of volatile organic compounds in water at higher temperatures.

  14. Temperature dependence effect of viscosity on ultrathin lubricant film melting

    Directory of Open Access Journals (Sweden)

    A.V.Khomenko

    2006-01-01

    Full Text Available We study the melting of an ultrathin lubricant film under friction between atomically flat surfaces at temperature dependencies of viscosity described by Vogel-Fulcher relationship and by power expression, which are observed experimentally. It is shown that the critical temperature exists in both cases the exceeding of which leads to the melting of lubricant and, as a result, the sliding mode of friction sets in. The values of characteristic parameters of lubricant are defined, which are needed for friction reduction. In the systems, where the Vogel-Fulcher dependence is fulfilled, it is possible to choose the parameters at which the melting of lubricant takes place even at zero temperature of friction surfaces. The deformational defect of the shear modulus is taken into account in describing the lubricant melting according to the mechanism of the first-order transition.

  15. Temperature Dependence of the Viscosity of Isotropic Liquids

    Science.gov (United States)

    Jadzyn, J.; Czechowski, G.; Lech, T.

    1999-04-01

    Temperature dependence of the shear viscosity measured for isotropic liquids belonging to the three homologous series: 4-(trans-4'-n-alkylcyclohexyl) isothiocyanatobenzenes (Cn H2n+1 CyHx Ph NCS; nCHBT, n=0-12), n-alkylcyanobiphenyls (CnH2n+1 Ph Ph CN; nCB, n=2-12) and 1,n-alkanediols (HO(CH2)nOH; 1,nAD, n=2-10) were analysed with the use of Arrhenius equation and its two modifications: Vogel--Fulcher and proposed in this paper. The extrapolation of the isothermal viscosity of 1,n-alkanediols (n=2-10) to n=1 leads to an interesting conclusion concerning the expected viscosity of methanediol, HOCH2OH, the compound strongly unstable in a pure state.

  16. Temperature-dependent thermal properties of spark plasma sintered alumina

    Directory of Open Access Journals (Sweden)

    Saheb Nouari

    2017-01-01

    Full Text Available In this work, we report temperature-dependent thermal properties of alumina powder and bulk alumina consolidated by spark plasma sintering method. The properties were measured between room temperature and 250ºC using a thermal constants analyzer. Alumina powder had very low thermal properties due to the presence of large pores and absence of bonding between its particles. Fully dense alumina with a relative density of 99.6 % was obtained at a sintering temperature of 1400°C and a holding time of 10 min. Thermal properties were found to mainly dependent on density. Thermal conductivity, thermal diffusivity, and specific heat of the fully dense alumina were 34.44 W/mK, 7.62 mm2s-1, and 1.22 J/gK, respectively, at room temperature. Thermal conductivity and thermal diffusivity decreased while specific heat increased with the increase in temperature from room temperature to 250ºC.

  17. Temperature dependence of contact resistance at metal/MWNT interface

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang-Eui; Moon, Kyoung-Seok; Sohn, Yoonchul, E-mail: yoonchul.son@samsung.com [Materials Research Center, Samsung Advanced Institute of Technology, Samsung Electronics, Suwon 443-803 (Korea, Republic of)

    2016-07-11

    Although contact resistance of carbon nanotube (CNT) is one of the most important factors for practical application of electronic devices, a study regarding temperature dependence on contact resistance of CNTs with metal electrodes has not been found. Here, we report an investigation of contact resistance at multiwalled nanotube (MWNT)/Ag interface as a function of temperature, using MWNT/polydimethylsiloxane (PDMS) composite. Electrical resistance of MWNT/PDMS composite revealed negative temperature coefficient (NTC). Excluding the contact resistance with Ag electrode, the NTC effect became less pronounced, showing lower intrinsic resistivity with the activation energy of 0.019 eV. Activation energy of the contact resistance of MWNT/Ag interface was determined to be 0.04 eV, two times larger than that of MWNT-MWNT network. The increase in the thermal fluctuation assisted electron tunneling is attributed to conductivity enhancement at both MWNT/MWNT and MWNT/Ag interfaces with increasing temperature.

  18. Nonlinear temperature dependent failure analysis of finite width composite laminates

    Science.gov (United States)

    Nagarkar, A. P.; Herakovich, C. T.

    1979-01-01

    A quasi-three dimensional, nonlinear elastic finite element stress analysis of finite width composite laminates including curing stresses is presented. Cross-ply, angle-ply, and two quasi-isotropic graphite/epoxy laminates are studied. Curing stresses are calculated using temperature dependent elastic properties that are input as percent retention curves, and stresses due to mechanical loading in the form of an axial strain are calculated using tangent modulii obtained by Ramberg-Osgood parameters. It is shown that curing stresses and stresses due to tensile loading are significant as edge effects in all types of laminate studies. The tensor polynomial failure criterion is used to predict the initiation of failure. The mode of failure is predicted by examining individual stress contributions to the tensor polynomial.

  19. Measurement system for temperature dependent noise characterization of magnetoresistive sensors

    Science.gov (United States)

    Nording, F.; Weber, S.; Ludwig, F.; Schilling, M.

    2017-03-01

    Magnetoresistive (MR) sensors and sensor systems are used in a large variety of applications in the field of industrial automation, automotive business, aeronautic industries, and instrumentation. Different MR sensor technologies like anisotropic magnetoresistive, giant magnetoresistive, and tunnel magnetoresistive sensors show strongly varying properties in terms of magnetoresistive effect, response to magnetic fields, achievable element miniaturization, manufacturing effort, and signal-to-noise ratio. Very few data have been reported so far on the comparison of noise performance for different sensor models and technologies, especially including the temperature dependence of their characteristics. In this paper, a stand-alone measurement setup is presented that allows a comprehensive characterization of MR sensors including sensitivity and noise over a wide range of temperatures.

  20. Temperature dependence of topological susceptibility using gradient flow

    CERN Document Server

    Taniguchi, Yusuke; Kanaya, Kazuyuki; Kitazawa, Masakiyo; Suzuki, Hiroshi; Umeda, Takashi; Iwami, Ryo; Wakabayashi, Naoki

    2016-01-01

    We study temperature dependence of the topological susceptibility with the $N_{f}=2+1$ flavors Wilson fermion. We have two major interests in this paper. One is a comparison of gluonic and fermionic definitions of the topological susceptibility. Two definitions are related by the chiral Ward-Takahashi identity but their coincidence is highly non-trivial for the Wilson fermion. By applying the gradient flow both for the gauge and quark fields we find a good agreement of these two measurements. The other is a verification of a prediction of the dilute instanton gas approximation at low temperature region $T_{pc}< T<1.5T_{pc}$, for which we confirm the prediction that the topological susceptibility decays with power $\\chi_{t}\\propto(T/T_{pc})^{-8}$ for three flavors QCD.

  1. Temperature dependence of the dielectric constant of acrylic dielectric elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Junjie; Chen, Hualing; Li, Bo; Chang, Longfei [Xi' an Jiaotong University, State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an (China); Xi' an Jiaotong University, School of Mechanical Engineering, Xi' an (China)

    2013-02-15

    The dielectric constant is an essential electrical parameter to the achievable voltage-induced deformation of the dielectric elastomer. This paper primarily focuses on the temperature dependence of the dielectric constant (within the range of 173 K to 373 K) for the most widely used acrylic dielectric elastomer (VHB 4910). First the dielectric constant was investigated experimentally with the broadband dielectric spectrometer (BDS). Results showed that the dielectric constant first increased with temperature up to a peak value and then dropped to a relative small value. Then by analyzing the fitted curves, the Cole-Cole dispersion equation was found better to characterize the rising process before the peak values than the Debye dispersion equation, while the decrease process afterward can be well described by the simple Debye model. Finally, a mathematical model of dielectric constant of VHB 4910 was obtained from the fitted results which can be used to further probe the electromechanical stability of the dielectric elastomers. (orig.)

  2. Temperature dependence of the dielectric constant of acrylic dielectric elastomer

    Science.gov (United States)

    Sheng, Junjie; Chen, Hualing; Li, Bo; Chang, Longfei

    2013-02-01

    The dielectric constant is an essential electrical parameter to the achievable voltage-induced deformation of the dielectric elastomer. This paper primarily focuses on the temperature dependence of the dielectric constant (within the range of 173 K to 373 K) for the most widely used acrylic dielectric elastomer (VHB 4910). First the dielectric constant was investigated experimentally with the broadband dielectric spectrometer (BDS). Results showed that the dielectric constant first increased with temperature up to a peak value and then dropped to a relative small value. Then by analyzing the fitted curves, the Cole-Cole dispersion equation was found better to characterize the rising process before the peak values than the Debye dispersion equation, while the decrease process afterward can be well described by the simple Debye model. Finally, a mathematical model of dielectric constant of VHB 4910 was obtained from the fitted results which can be used to further probe the electromechanical stability of the dielectric elastomers.

  3. Apparatus for temperature-dependent cathodoluminescence characterization of materials

    Science.gov (United States)

    Bok, Jan; Schauer, Petr

    2014-07-01

    An apparatus for characterization of temperature-dependent cathodoluminescence (CL) of solid-state materials is presented. This device excites a specimen using an electron beam and the CL emission is collected from the specimen side opposite the e-beam irradiation. The design of the temperature-controlled specimen holder that enables cooling down to 100 K and heating up to 500 K is described. The desired specimen temperature is automatically stabilized using a PID controller, which is the proportional-integral-derivative control feedback loop. Moreover, the specimen holder provides in situ e-beam current measurement during the specimen excitation. The apparatus allows the measurement of the CL intensity, the CL spectrum, or the CL intensity decay depending on the specimen temperature, or on a variety of excitation conditions, such as excitation energy, electron current (dose), or excitation duration. The apparatus abilities are demonstrated by an example of the CL measurements of the YAG:Ce single-crystal scintillator.

  4. Detailed behavioral modeling of bang-bang phase detectors

    DEFF Research Database (Denmark)

    Jiang, Chenhui; Andreani, Pietro; Keil, U. D.

    2006-01-01

    In this paper, the metastability of current-mode logic (CML) latches and flip-flops is studied in detail. Based on the results of this analysis, a behavioral model of bang-bang phase detectors (BBPDs) is proposed, which is able to reliably capture the critical deadzone effect. The impact of jitter...

  5. Complex phase behavior in solvent-free nonionic surfactants

    DEFF Research Database (Denmark)

    Hillmyer, M.A.; Bates, F.S.; Almdal, K.

    1996-01-01

    was synthesized here. The general phase behavior in these materials resembles that of both higher molecular weight block copolymers and lower molecular weight nonionic surfactant solutions. Two of the block copolymers exhibited thermally induced order-order transitions and were studied in detail by small...

  6. Phase behavior of coal fluids: Data for correlation development

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, R.J. Jr.; Gasem, K.A.M.; Shaver, R.D.

    1990-01-01

    The effective design and operation of processes for conversion of coal to fluid fuels requires accurate knowledge of the phase behavior of the fluid mixtures encountered in the conversion process. The overall objective of the author's work is to develop accurate predictive methods for representation of vapor-liquid equilibria in systems encountered in coal conversion processes. The objectives of the present project include: (1) measurements of binary vapor-liquid phase behavior data for selected solute gases (e.g. CO{sub 2} and C{sub 2}H{sub 6}) in a series of heavy hydrocarbon solvents to permit evaluation of interaction parameters in models for phase behavior, (2) measurements on ternary systems in which high-melting-point solvents are dissolved in more volatile aromatics to provide mixed solvents, (3) evaluation of existing equations-of-state and other models for representation of phase behavior in systems of the type studied experimentally; development of new correlation frameworks as needed, and (4) generalization of the interaction parameters for the solutes studied to a wide spectrum of heavy solvents; presentations of final results in formats useful in the design/optimization of coal liquefaction processes. This quarter, our framework for correlating saturation properties using a scaled-variable-reduced-coordinate'' approach was further developed to provide for generalized vapor pressure predictions. 59 refs., 6 figs., 8 tabs.

  7. 17th International Conference on Petroleum Phase Behavior and Fouling

    DEFF Research Database (Denmark)

    von Solms, Nicolas; Yan, Wei; Andersen, Simon

    2017-01-01

    This special section of Energy & Fuels contains contributedpapers from the 17th International Conference on PetroleumPhase Behavior and Fouling (Petrophase 2016). Petrophase 2016 was organized by the Technical University of Denmark and Schlumberger and took place in Elsinore (Helsingør) Denmark...

  8. Phase behavior of flowerlike micelles in a SCF cell model

    NARCIS (Netherlands)

    Sprakel, J.; Besseling, N.A.M.; Cohen Stuart, M.A.; Leermakers, F.A.M.

    2008-01-01

    We study the interactions between flowerlike micelles, self-assembled from telechelic associative polymers, using a molecular self-consistent field (SCF) theory and discuss the corresponding phase behavior. In these calculations we do not impose properties such as aggregation number, micellar

  9. Measurement of the dynamic behavior of thin poly(N-isopropylacrylamide) hydrogels and their phase transition temperatures measured using reflectometric interference spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Fuminori [Konica Minolta, INC. (Japan); Akiyama, Yoshikatsu, E-mail: akiyama.yoshikatsu@twmu.ac.jp, E-mail: akiyama.yoshikatsu@abmes.twmu.ac.jp; Kobayashi, Jun [Tokyo Women’s Medical University (TWIns), Institute of Advanced Biomedical Engineering and Science (Japan); Ninomiya, Hidetaka [Konica Minolta, INC. (Japan); Kanazawa, Hideko [Keio University, Faculty of Pharmacy (Japan); Yamato, Masayuki; Okano, Teruo [Tokyo Women’s Medical University (TWIns), Institute of Advanced Biomedical Engineering and Science (Japan)

    2015-03-15

    Temperature-responsive cell culture surfaces prepared by modifying tissue-culture polystyrene with nanoscale poly(N-isopropylacrylamide) (PIPAAm) hydrogels are widely used as intelligent surfaces for the fabrication of various cell sheets that change with temperature. In this work, the characteristics of nanoscale PIPAAm hydrogels were phenomenologically elucidated on the basis of time-dependent surface evaluations under conditions of changing temperature. Because the dynamic characteristics of the nanoscale hydrogel did not exhibit good performance, the nanoscale PIPAAm hydrogel was analyzed by monitoring its temperature-dependent dynamic swelling/deswelling changes using reflectometric interference spectroscopy (RIfS) on an instrument equipped with a microfluidic system. RIfS measurements under ambient atmosphere provided the precise physical thickness of the dry PIPAAm hydrogel (6.7 nm), which agreed with the atomic force microscopy results (6.6 nm). Simulations of the reflectance spectra revealed that changes in the wavelength of the minimum reflectance (Δλ) were attributable to the changes in the refractive index of the thin PIPAAm hydrogel induced by a temperature-dependent volume phase transition. The temperature-dependent Δλ change was used to monitor the swelling/deswelling behavior of the nanoscale PIPAAm hydrogel. In addition, the phase transition temperature of the thin PIPAAm hydrogel under aqueous conditions was also determined to be the inflection point of the plot of the change in Δλ as a function of temperature. The dynamic behavior of a thin PIPAAm hydrogel chemically deposited on a surface was readily analyzed using a new analytical system with RIfS and microfluidic devices.

  10. Seeing spots: complex phase behavior in simple membranes.

    Science.gov (United States)

    Veatch, Sarah L; Keller, Sarah L

    2005-12-30

    Liquid domains in model lipid bilayers are frequently studied as models of raft domains in cell plasma membranes. Micron-scale liquid domains are easily produced in vesicles composed of ternary mixtures of a high melting temperature lipid, a low melting temperature lipid, and cholesterol. Here, we describe the rich phase behavior observed in binary and ternary systems. We then discuss experimental challenges inherent in mapping phase diagrams of even simple lipid systems. For example, miscibility behavior varies with lipid type, lipid ratio, lipid oxidation, and level of impurity. Liquid domains are often circular, but can become noncircular when membranes are near critical points. Finally, we reflect on applications of phase diagrams in model systems to rafts in cell membranes.

  11. Frequency doubling in LiNbO3 using temperature dependent QPM

    DEFF Research Database (Denmark)

    Belmonte, Michele; Skettrup, Torben; Pedersen, Christian

    1999-01-01

    We report the application of temperature-dependent quasi-phase matching (QPM) for second harmonic generation of green light using periodically field poled LiNbO3. In contrast to the usual QPM devices, here the fundamental and second harmonic waves are polarized orthogonally so that the second...... harmonic signal corresponds to the extraordinary wave. This requires the utilization of the d31 component of the nonlinear tensor (i.e. the same component as used for ordinary birefringent phase matching). d31 is smaller than the d33 component usually used in QPM devices and therefore yields a lower...... efficiency. However, the use of QPM in our geometry with orthogonally polarized waves results in a greatly enhanced temperature tunability, which increases the versatility of the devices. Moreover, the domain inversion grating period required in this geometry for first-order QPM at the Nd laser wavelength...

  12. Temperature Dependence of the Penetration Depth at Low Temperatures of Zn and Ni Doped YBCO Thin Films at Various Oxygen Concentrations

    Science.gov (United States)

    Turneaure, Stefan J.; Lemberger, T. R.

    1997-03-01

    We have measured the absolute value of the magnetic penetration depth in YBCO films doped with either Zn or Ni at several different oxygen concentrations. The low temperature behavior of λ(T) is nearly quadratic, but there is a small linear term. Several papers have predicted that phase fluctuations would give rise to a linear term in the temperature dependence of λ(T) which is proportional to λ ^3(0) (E. Roddick and D. Stroud, Phys. Rev. Lett. 74, 1430 (1995)) (V.J. Emery and S.A. Kivelson, Phys. Rev. Lett. 74, 3253 (1995)) (M.W. Coffey, Phys. Lett. A 200, 195 (1995)). Second order polynomial fits were made to extract the size of the linear portion of λ(T). The linear coefficients from the fits together with the measured values of λ(0) are used to make a comparison with theory. ohio-state.edu/ trl/group/>Lemberger

  13. Critical behaviors and phase transitions of black holes in higher order gravities and extended phase spaces

    CERN Document Server

    Sherkatghanad, Zeinab; Mirzaeyan, Zahra; Mansoori, Seyed Ali Hosseini

    2014-01-01

    We consider the critical behaviors and phase transitions of Gauss Bonnet-Born Infeld-AdS black holes (GB-BI-AdS) for $d=5,6$ and the extended phase space. We assume the cosmological constant, $\\Lambda$, the coupling coefficient $\\alpha$, and the BI parameter $\\beta$ to be thermodynamic pressures of the system. Having made these assumptions, the critical behaviors are then studied in the two canonical and grand canonical ensembles. We find "reentrant and triple point phase transitions" (RPT-TP) and "multiple reentrant phase transitions" (multiple RPT) with increasing pressure of the system for specific values of the coupling coefficient $\\alpha$ in the canonical ensemble. Also, we observe a reentrant phase transition (RPT) of GB-BI-AdS black holes in the grand canonical ensemble and for $d=6$. These calculations are then expanded to the critical behavior of Born-Infeld-AdS (BI-AdS) black holes in the third order of Lovelock gravity and in the grand canonical ensemble to find a Van der Waals behavior for $d=7$ ...

  14. Competitive interactions modify the temperature dependence of damselfly growth rates.

    Science.gov (United States)

    Nilsson-Ortman, Viktor; Stoks, Robby; Johansson, Frank

    2014-05-01

    Individual growth rates and survival are major determinants of individual fitness, population size structure, and community dynamics. The relationships between growth rate, survival, and temperature may thus be important for predicting biological responses to climate change. Although it is well known that growth rates and survival are affected by competition and predation in addition to temperature, the combined effect of these factors on growth rates, survival, and size structure has rarely been investigated simultaneously in the same ecological system. To address this question, we conducted experiments on the larvae of two species of damselflies and determined the temperature dependence of growth rate, survival, and cohort size structure under three scenarios of increasing ecological complexity: no competition, intraspecific competition, and interspecific competition. In one species, the relationship between growth rate and temperature became steeper in the presence of competitors, whereas that of survival remained unchanged. In the other species, the relationship between growth rate and temperature was unaffected by competitive interactions, but survival was greatly reduced at high temperatures in the presence of interspecific competitors. The combined effect of competitive interactions and temperature on cohort size structure differed from the effects of these factors in isolation. Together, these findings suggest that it will be challenging to scale up information from single-species laboratory studies to the population and community level.

  15. Temperature dependent bacteriophages of a tropical bacterial pathogen

    Directory of Open Access Journals (Sweden)

    Martha Rebecca Jane Clokie

    2014-11-01

    Full Text Available There is an increasing awareness of the multiple ways that bacteriophages (phages influence bacterial evolution, population dynamics, physiology and pathogenicity. By studying a novel group of phages infecting a soil borne pathogen, we revealed a paradigm shifting observation that the phages switch their lifestyle according to temperature. We sampled soil from an endemic area of the serious tropical pathogen Burkholderia pseudomallei, and established that podoviruses infecting the pathogen are frequently present in soil, and many of them are naturally occurring variants of a common virus type. Experiments on one phage in the related model Burkholderia thailandensis demonstrated that temperature defines the outcome of phage-bacteria interactions. At higher temperatures (37°C, the phage predominantly goes through a lytic cycle, but at lower temperatures (25°C, the phage remains temperate. This is the first report of a naturally occurring phage that follows a lytic or temperate lifestyle according to temperature. These observations fundamentally alter the accepted views on the abundance, population biology and virulence of B. pseudomallei. Furthermore, when taken together with previous studies, our findings suggest that the phenomenon of temperature dependency in phages is widespread. Such phages are likely to have a profound effect on bacterial life, and on our ability to culture and correctly enumerate viable bacteria.

  16. Temperature-dependent yield criterion for high strength steel sheets under warm-forming conditions

    Directory of Open Access Journals (Sweden)

    Cai Zhengyang

    2015-01-01

    Full Text Available In this paper, uniaxial and biaxial tensile tests with cruciform specimens were conducted to investigate the deformation behaviour of dual phase steel sheet with a tensile strength of 590 MPa (DP590 under evaluated warm-forming temperatures (20–190 ∘C. Detailed analyses were then carried out to obtain the corresponding experimental yield loci. For the purpose of describing the temperature-dependent yield behaviour of DP590 appropriately, the Yld2000–2d yield function with temperature-dependent exponent was proposed. The identification procedures of the introduced parameters were then proposed based on Levenberg-Marquardt optimization algorithm. Afterwards, the proposed model was implemented into ABAQUS as user subroutine VUMAT with NICE (Next Increment Corrects Error explicit integration scheme. The numerical simulations of biaxial tensile tests were then conducted to confirm the validity of the proposed model. It could be concluded that the flexibility and accuracy of the proposed model guarantee the applicability in warm-forming applications.

  17. Temperature dependent rate coefficients for the reactions of Criegee biradicals with selected alcohols and sulphides

    Science.gov (United States)

    McGillen, Max; McMahon, Laura; Curchod, Basile; Shallcross, Dudley; Orr-Ewing, Andrew

    2017-04-01

    The reactions of Criegee biradicals have received much attention in recent years, yet few reactive systems have undergone direct experimental measurement, and fewer still have been measured as a function of temperature. In this study, absolute temperature-dependent rate coefficients for the gas-phase reactions of a suite of alcohols and sulphides with both formaldehyde oxide (CH2OO) and acetone oxide ((CH3)2COO) are determined experimentally between 254 and 328 K using cavity ringdown spectroscopy for detecting Criegee biradicals. Major differences in reactivity and temperature dependence are observed both in terms of the functionality (between alcohols and sulphides) and also the degree of alkyl substitution about the Criegee biradical. This diverse behaviour represents a uniquely challenging problem for atmospheric chemistry since the atmosphere contains a large variety of both functionalized compounds and Criegee biradicals, leading to a formidable parameter space which may be impossible to cover experimentally. Notwithstanding, new experimental data such as these are vital for understanding the general behaviour of Criegee biradicals in the atmosphere.

  18. Temperature dependent electron paramagnetic resonance study on magnetoelectric YCrO3

    Science.gov (United States)

    Mall, Ashish Kumar; Dixit, Ambesh; Garg, Ashish; Gupta, Rajeev

    2017-12-01

    We report temperature dependent electron paramagnetic resonance (EPR) studies on polycrystalline YCrO3 samples at X-band (9.46 GHz) in the temperature range of 120 K–298 K. The EPR spectra exhibit a single broad line across the whole temperature range, attributed to Cr3+ ions. The variation of EPR spectra parameters (line width, integrated intensity, and g-factor) as a function of temperature was analyzed to understand the nature of spin-dynamics in the paramagnetic region of YCrO3. A peak in the g-factor suggests the presence of a new phase within the paramagnetic state at an intermediate point of temperature T IP ~ 230 K, attributed to the onset of short range canted antiferromagnetic correlations in the material much above 140 K, Néel temperature (T N) of YCrO3. The EPR intensity increases with a decrease in temperature up to T N due to the renormalization of the magnetic moments arising from the appearance of canted antiferromagnetic correlations. Further, temperature dependent dielectric measurements also exhibit an anomaly at ~230 K suggesting the presence of magnetodielectric coupling in YCrO3, with a possibility towards a relatively high temperature magnetodielectric system.

  19. Study of the temperature dependent nitrogen retention in tungsten surfaces by XPS-analysis

    Energy Technology Data Exchange (ETDEWEB)

    Plank, Ulrike [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Fakultaet fuer Physik der Ludwig-Maximilians-Universitaet Muenchen, Schellingstrasse 4, D-80799 Muenchen (Germany); Meisl, Gerd; Hoeschen, Till [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany)

    2016-07-01

    To reduce the power load on the divertor of fusion experiments, nitrogen (N) is puffed into the plasma. As a side effect, nitrogen gets implanted into the tungsten (W) walls of the reactor and forms nitride layers. Their formation and, therefore, the N accumulation in W showed an unexpected temperature dependence in previous experiments. To study the nitrogen retention, we implanted N ions with an energy of 300 eV into W and observed the evolution of the surface composition by X-ray photoelectron spectroscopy (XPS). We find that the N content does not change when the sample is annealed up to 800 K after implantation at lower temperatures. In contrast, the N concentration decreases with increasing implantation temperature. At 800 K implantation temperature, the N saturation level is about 5 times lower compared to 300 K implantation. A possible explanation for this difference is an enhanced diffusion during ion bombardment due to changes in the structure or in the chemical state of the tungsten nitride system. Ongoing tungsten nitride erosion experiments shall help to clarify whether the strong temperature dependence is the result of enhanced diffusion or of phase changes.

  20. The temperature dependence of intermediate range oxygen-oxygen correlations in liquid water.

    Science.gov (United States)

    Schlesinger, Daniel; Wikfeldt, K Thor; Skinner, Lawrie B; Benmore, Chris J; Nilsson, Anders; Pettersson, Lars G M

    2016-08-28

    We analyze the recent temperature dependent oxygen-oxygen pair-distribution functions from experimental high-precision x-ray diffraction data of bulk water by Skinner et al. [J. Chem. Phys. 141, 214507 (2014)] with particular focus on the intermediate range where small, but significant, correlations are found out to 17 Å. The second peak in the pair-distribution function at 4.5 Å is connected to tetrahedral coordination and was shown by Skinner et al. to change behavior with temperature below the temperature of minimum isothermal compressibility. Here we show that this is associated also with a peak growing at 11 Å which strongly indicates a collective character of fluctuations leading to the enhanced compressibility at lower temperatures. We note that the peak at ∼13.2 Å exhibits a temperature dependence similar to that of the density with a maximum close to 277 K or 4 °C. We analyze simulations of the TIP4P/2005 water model in the same manner and find excellent agreement between simulations and experiment albeit with a temperature shift of ∼20 K.

  1. Temperature dependence and GABA modulation of (TH)triazolam binding in the rat brain

    Energy Technology Data Exchange (ETDEWEB)

    Earle, M.E.; Concas, A.; Wamsley, J.K.; Yamamura, H.I.

    1987-07-27

    The hypnotic triazolam (TZ), a triazolobenzodiazepine displays a short physiological half life and has been used for the treatment of insomnia related to anxiety states. The authors major objectives were the direct measurement of the temperature dependence and the gamma-aminobutyric acid (GABA) effect of (TH)TZ binding in the rat brain. Saturation studies showed a shift to lower affinity with increasing temperatures (K/sub d/ = 0.27 +/- 08 nM at 0C; K/sub d/ = 1.96 +/- 0.85 nM at 37C) while the B/sub max/ values remained unchanged (1220 +/- 176 fmoles/mg protein at 0C and 1160 +/- 383 fmoles/mg protein at 37C). Saturation studies of (TH)TZ binding in the presence or absence of GABA (100 M) showed a GABA-shift. At 0C the K/sub d/ values were (K/sub d/ = 0.24 +/- 0.03 nM/-GABA; K/sub d/ = 0.16 +/- 0.04/+GABA) and at 37C the K/sub d/ values were (K/sub d/ = 1.84 +/- 0.44 nM/-GABA; K/sub d/ = 0.95 +/- 0.29 nM/+GABA). In contrast to reported literature, the authors findings show that TZ interacts with benzodiazepine receptors with a temperature dependence and GABA-shift consistent with predicted behavior for benzodiazepine agonists. 20 references, 3 tables.

  2. Temperature dependent diode and photovoltaic characteristics of graphene-GaN heterojunction

    Science.gov (United States)

    Kalita, Golap; Dzulsyahmi Shaarin, Muhammad; Paudel, Balaram; Mahyavanshi, Rakesh; Tanemura, Masaki

    2017-07-01

    Understanding the charge carrier transport characteristics at the graphene-GaN interface is of significant importance for the fabrication of efficient photoresponsive devices. Here, we report on the temperature dependent diode and photovoltaic characteristics of a graphene/n-GaN heterostructure based Schottky junction. The graphene/n-GaN heterojunction showed rectifying diode characteristics and photovoltaic action with photoresponsivity in the ultra-violet wavelength. The current-voltage characteristics of the graphene/n-GaN heterojunction device were investigated under dark and light illumination with changes in temperature. Under dark conditions, an increase in the forward bias current as well as saturation current was observed, and a decrease in the device ideality factor was obtained with an increase in temperature. Under illumination of light, a decrease in the open circuit voltage (Voc) and an increase in the short circuit current density (Jsc) was obtained with an increase in temperature. The increase in saturation current and carrier recombination with the increase in temperature leads to a reduction in Voc, while the photo-generated carrier increases in the heterojunction interface at higher temperatures contributing to the increase in Jsc. The observed temperature dependent device characteristics of the graphene/n-GaN heterojunction can be significant to understand the junction behavior and photovoltaic action.

  3. Efficient Temperature-Dependent Green's Functions Methods for Realistic Systems: Compact Grids for Orthogonal Polynomial Transforms.

    Science.gov (United States)

    Kananenka, Alexei A; Phillips, Jordan J; Zgid, Dominika

    2016-02-09

    The Matsubara Green's function that is used to describe temperature-dependent behavior is expressed on a numerical grid. While such a grid usually has a couple of hundred points for low-energy model systems, for realistic systems with large basis sets the size of an accurate grid can be tens of thousands of points, constituting a severe computational and memory bottleneck. In this paper, we determine efficient imaginary time grids for the temperature-dependent Matsubara Green's function formalism that can be used for calculations on realistic systems. We show that, because of the use of an orthogonal polynomial transform, we can restrict the imaginary time grid to a few hundred points and reach micro-Hartree accuracy in the electronic energy evaluation. Moreover, we show that only a limited number of orthogonal polynomial expansion coefficients are necessary to preserve accuracy when working with a dual representation of the Green's function or self-energy and transforming between the imaginary time and frequency domain.

  4. Sequence- and Temperature-Dependent Properties of Unfolded and Disordered Proteins from Atomistic Simulations.

    Science.gov (United States)

    Zerze, Gül H; Best, Robert B; Mittal, Jeetain

    2015-11-19

    We use all-atom molecular simulation with explicit solvent to study the properties of selected intrinsically disordered proteins and unfolded states of foldable proteins, which include chain dimensions and shape, secondary structure propensity, solvent accessible surface area, and contact formation. We find that the qualitative scaling behavior of the chains matches expectations from theory under ambient conditions. In particular, unfolded globular proteins tend to be more collapsed under the same conditions than charged disordered sequences of the same length. However, inclusion of explicit solvent in addition naturally captures temperature-dependent solvation effects, which results in an initial collapse of the chains as temperature is increased, in qualitative agreement with experiment. There is a universal origin to the collapse, revealed in the change of hydration of individual residues as a function of temperature: namely, that the initial collapse is driven by unfavorable solvation free energy of individual residues, which in turn has a strong temperature dependence. We also observe that in unfolded globular proteins, increased temperature also initially favors formation of native-like (rather than non-native-like) structure. Our results help to establish how sequence encodes the degree of intrinsic disorder or order as well as its response to changes in environmental conditions.

  5. Temperature dependence of positron lifetime in a polymer of intrinsic microporosity

    Energy Technology Data Exchange (ETDEWEB)

    Raetzke, K.; Miranda, R.L. de; Kruse, J.; Faupel, F. [Univ. Kiel, Materialverbunde (Germany); Fritsch, D.; Abetz, V. [Inst. fuer Polymerforschung, GKSS, Geesthacht (Germany); Budd, P.; Selbie, J. [School of Chemistry, The Univ. of Manchester (United Kingdom); McKeown, N.; Ghanem, B. [School of Chemistry, Cardiff Univ. (United Kingdom)

    2007-07-01

    The performance of polymeric membranes for gas separation is mainly determined by the free volume. Polymers of intrinsic microporosity are interesting candidates for state of the art gas separation membranes due to the high abundance of accessible free volume. Positron annihilation lifetime spectroscopy is a generally accepted technique for investigation of free volume in polymers where the orthopositronium lifetime is directly connected to the mean free volume size. We performed measurements of the temperature dependence of the positron lifetime in a polymer of intrinsic microporosity (PIM-7) in the range from 143 to 523 K. The mean value of the free volume calculated from the ortho-positronium life time ({sup {proportional_to}}5 ns) is in the range of typical values for high free volume membrane polymers (V=0.47 nm{sup 3}). However, the temperature dependence of the positronium-lifetime is non-monotonous. Comparison with thermal expansion measurements will be made and a possible explanation of this unexpected behavior given. (orig.)

  6. Equilibrium Phase Behavior of a Continuous-Space Microphase Former.

    Science.gov (United States)

    Zhuang, Yuan; Zhang, Kai; Charbonneau, Patrick

    2016-03-04

    Periodic microphases universally emerge in systems for which short-range interparticle attraction is frustrated by long-range repulsion. The morphological richness of these phases makes them desirable material targets, but our relatively coarse understanding of even simple models hinders controlling their assembly. We report here the solution of the equilibrium phase behavior of a microscopic microphase former through specialized Monte Carlo simulations. The results for cluster crystal, cylindrical, double gyroid, and lamellar ordering qualitatively agree with a Landau-type free energy description and reveal the nontrivial interplay between cluster, gel, and microphase formation.

  7. Temperature-dependent Henry's law constants of atmospheric organics of biogenic origin.

    Science.gov (United States)

    Leng, Chunbo; Kish, J Duncan; Kelley, Judas; Mach, Mindy; Hiltner, Joseph; Zhang, Yunhong; Liu, Yong

    2013-10-10

    There have been growing interests in modeling studies to understand oxidation of volatile organic compounds in the gas phase and their mass transfer to the aqueous phase for their potential roles in cloud chemistry, formation of secondary organic aerosols, and fate of atmospheric organics. Temperature-dependent Henry's law constants, key parameters in the atmospheric models to account for mass transfer, are often unavailable. In the present work, we investigated gas-liquid equilibriums of isoprene, limonene, α-pinene, and linalool using a bubble column technique. These compounds, originating from biogenic sources, were selected for their implications in atmospheric cloud chemistry and secondary organic aerosol formation. We reported Henry's law constants (K(H)), first order loss rates (k), and gas phase diffusion coefficients over a range of temperatures relevant to the lower atmosphere (278-298 K) for the first time. The measurement results of K(H) values for isoprene, limonene, α-pinene, and linalool at 298 K were 0.036 ± 0.003; 0.048 ± 0.004; 0.029 ± 0.004; and 21.20 ± 0.30 mol L(-1) atm(-1), respectively. The fraction for these compounds in stratocumulus and cumulonimbus clouds at 278 K were also estimated in this work (isoprene, 1.0 × 10(-6), 6.8 × 10(-6); limonene, 1.5 × 10(-6), 1.0 × 10(-5); α-pinene, 4.5 × 10(-7), 3.1 × 10(-6); and linalool, 6.2 × 10(-4), 4.2 × 10(-3)). Our measurements in combination with literature results indicated that noncyclic alkenes could have smaller K(H) values than those of cyclic terpenes and that K(H) values may increase with an increasing number of double bonds. It was also shown that estimated Henry's law constants and their temperature dependence based on model prediction can differ from experimental results considerably and that direct measurements of temperature-dependent Henry's law constants of atmospheric organics are necessary for future work.

  8. Human behavioral regularity, fractional Brownian motion, and exotic phase transition

    Science.gov (United States)

    Li, Xiaohui; Yang, Guang; An, Kenan; Huang, Jiping

    2016-08-01

    The mix of competition and cooperation (C&C) is ubiquitous in human society, which, however, remains poorly explored due to the lack of a fundamental method. Here, by developing a Janus game for treating C&C between two sides (suppliers and consumers), we show, for the first time, experimental and simulation evidences for human behavioral regularity. This property is proved to be characterized by fractional Brownian motion associated with an exotic transition between periodic and nonperiodic phases. Furthermore, the periodic phase echoes with business cycles, which are well-known in reality but still far from being well understood. Our results imply that the Janus game could be a fundamental method for studying C&C among humans in society, and it provides guidance for predicting human behavioral activity from the perspective of fractional Brownian motion.

  9. Temperature-dependent dispersion model of float zone crystalline silicon

    Science.gov (United States)

    Franta, Daniel; Dubroka, Adam; Wang, Chennan; Giglia, Angelo; Vohánka, Jirí; Franta, Pavel; Ohlídal, Ivan

    2017-11-01

    In this paper, we present the temperature dependent dispersion model of float zone crystalline silicon. The theoretical background for valence electronic excitations is introduced in the theoretical part of this paper. This model is based on application of sum rules and parametrization of transition strength functions corresponding to the individual elementary phonon and electronic excitations. The parameters of the model are determined by fitting ellipsometric and spectrophotometric experimental data in the spectral range from far infrared (70 cm-1) to extreme ultraviolet (40 eV). The ellipsometric data were measured in the temperature range 5-700 K. The excitations of the valence electrons to the conduction band are divided into the indirect and direct electronic transitions. The indirect transitions are modeled by truncated Lorentzian terms, whereas the direct transitions are modeled using Gaussian broadened piecewise smooth functions representing 3D and 2D van Hove singularities modified by excitonic effects. Since the experimental data up to high energies (40 eV) are available, we are able to determine the value of the effective number of valence electrons. The Tauc-Lorentz dispersion model is used for modeling high energy electron excitations. Two slightly different values of the effective number of valence electrons are obtained for the Jellison-Modine (4.51) and Campi-Coriasso (4.37) parametrization. Our goal is to obtain the model of dielectric response of crystalline silicon which depends only on photon energy, temperature and small number of material parameters, e.g. the concentration of substituted carbon and interstitial oxygen. The model presented in this paper is accurate enough to replace tabulated values of c-Si optical constants used in the optical characterization of thin films diposited on silicon substrates. The spectral dependencies of the optical constants obtained in our work are compared to results obtained by other authors.

  10. Temperature dependent modulation of lobster neuromuscular properties by serotonin.

    Science.gov (United States)

    Hamilton, Jonna L; Edwards, Claire R; Holt, Stephen R; Worden, Mary Kate

    2007-03-01

    In cold-blooded species the efficacy of neuromuscular function depends both on the thermal environmental of the animal's habitat and on the concentrations of modulatory hormones circulating within the animal's body. The goal of this study is to examine how temperature variation within an ecologically relevant range affects neuromuscular function and its modulation by the neurohormone serotonin (5-HT) in Homarus americanus, a lobster species that inhabits a broad thermal range in the wild. The synaptic strength of the excitatory and inhibitory motoneurons innervating the lobster dactyl opener muscle depends on temperature, with the strongest neurally evoked muscle movements being elicited at cold (temperatures. However, whereas neurally evoked contractions can be elicited over the entire temperature range from 2 to >20 degrees C, neurally evoked relaxations of resting muscle tension are effective only at colder temperatures at which the inhibitory junction potentials are hyperpolarizing in polarity. 5-HT has two effects on inhibitory synaptic signals: it potentiates their amplitude and also shifts the temperature at which they reverse polarity by approximately +7 degrees C. Thus 5-HT both potentiates neurally evoked relaxations of the muscle and increases the temperature range over which neurally evoked muscle relaxations can be elicited. Neurally evoked contractions are maximally potentiated by 5-HT at warm (18 degrees C) temperatures; however, 5-HT enhances excitatory junction potentials in a temperature-independent manner. Finally, 5-HT strongly increases resting muscle tension at the coldest extent of the temperature range tested (2 degrees C) but is ineffective at 22 degrees C. These data demonstrate that 5-HT elicits several temperature-dependent physiological changes in the passive and active responses of muscle to neural input. The overall effect of 5-HT is to increase the temperature range over which neurally evoked motor movements can be elicited in this

  11. Phase behavior and interfacial tension studies of surfactant systems

    Energy Technology Data Exchange (ETDEWEB)

    Franses, E.I.

    1979-01-01

    Parallel studies of isomerically pure sodium P(1-heptylnonyl) benzene sulfoante, Texas No. 1, its mixture with sodium dodecyl sulfate (SDS), and the petroleum sulfonate TRS 10-80 were made. Phase behavior in water, in decane, and in water-decane mixtures was studied by spectroturbidimetry, polarizing light microscopy, ultracentrifugation, ultrafiltration, densitometry, conductimetry, low-frequency, 0.2 to 20 kHz, dielectric relaxation, isopiestic vapor pressure, and nuclear magnetic resonance spectroscopy. It was deduced that ultralow tensions (less than 0.01 dyn/cm) arise from the dispersed microcrystallites which form a third, usually liquid crystalline, phase at the decane-brine interfacial region. It appears that neither molecular adsorption from solution for micelles have anything to do with ultralow tensions, which appear to be sensitive to the third phase microstructure. The implications of these results for the mechanism of ultralow tensions in surfactant flooding processes for enhanced petroleum recovery are discussed.

  12. Phase behavior of lipid monolayers containing DPPC and cholesterol analogs.

    Science.gov (United States)

    Stottrup, Benjamin L; Keller, Sarah L

    2006-05-01

    We investigate the miscibility phase behavior of lipid monolayers containing a wide variety of sterols. Six of the sterols satisfy a definition from an earlier study of "membrane-active sterols" in bilayers (cholesterol, epicholesterol, lathosterol, dihydrocholesterol, ergosterol, and desmosterol), and six do not (25-hydroxycholesterol, lanosterol, androstenolone, coprostanol, cholestane, and cholestenone). We find that monolayers containing dipalmitoyl phosphatidylcholine mixed with membrane-active sterols generally produce phase diagrams containing two distinct regions of immiscible liquid phases, whereas those with membrane-inactive sterols generally do not. This observation establishes a correlation between lipid monolayers and bilayers. It also demonstrates that the ability to form two regions of immiscibility in monolayers is not one of the biophysical attributes that explains cholesterol's predominance in animal cell membranes. Furthermore, we find unusual phase behavior for dipalmitoyl phosphatidylcholine monolayers containing 25-hydroxycholesterol, which produce both an upper and a lower miscibility transition. The lower transition correlates with a sharp change of slope in the pressure-area isotherm.

  13. Temperature dependence of the infinite dilution activity coefficient and Henry's law constant of polycyclic aromatic hydrocarbons in water.

    Science.gov (United States)

    Reza, Joel; Trejo, Arturo

    2004-08-01

    The water solubility of 9,10-dihydroanthracene was experimentally determined between 278.12 and 313.17 K. Determinations were carried out by an experimental procedure developed in our laboratory, which is a modification of the dynamic coupled column liquid chromatographic technique. The uncertainty of the experimental determinations ranged from +/- 0.50% to +/- 3.10%. These data, as well as the water solubility data of other five polycyclic aromatic hydrocarbons (PAHs) previously studied, were used to calculate the temperature dependence of the infinite dilution activity coefficient of 9,10-dihydroanthracene, anthracene, pyrene, 9,10-dihydrophenanthrene, m-terphenyl, and guaiazulene in water. Molar excess enthalpies and entropies at infinite dilution, at 298.15 K, were also derived. The temperature dependence of the infinite dilution activity coefficients was used, together with literature values of the vapor pressures of supercooled liquid PAHs (p(B)(sc)), to estimate their Henry's law constants (HLC). Only HLC for anthracene, pyrene, and 9,10-dihydrophenanthrene were calculated, since no p(B)(sc) data were available in the literature for 9,10-dihydroanthracene, m-terphenyl, and guaiazulene. From the observed temperature dependence of the Henry's law constants the enthalpy and entropy of the phase change from the dissolved phase to the gas phase were also derived for anthracene, pyrene, and 9,10-dihydrophenanthrene.

  14. Formation of temperature dependable holographic memory using holographic polymer-dispersed liquid crystal.

    Science.gov (United States)

    Ogiwara, Akifumi; Watanabe, Minoru; Moriwaki, Retsu

    2013-04-01

    Grating devices using photosensitive organic materials play an important role in the development of optical and optoelectronic systems. High diffraction efficiency and polarization dependence achieved in a holographic polymer-dispersed liquid crystal (HPDLC) grating are expected to provide polarization controllable optical devices, such as the holographic memory for optically reconfigurable gate arrays (ORGAs). However, the optical property is affected by the thermal modulation around the transition temperature (T(ni)) that the liquid crystal (LC) changes from nematic to isotropic phases. The temperature dependence of the diffraction efficiency in HPDLC grating is discussed with two types of LC composites comprised of isotropic and LC diacrylate monomers. The holographic memory formed by the LC and LC diacrylate monomer performs precise reconstruction of the context information for ORGAs at high temperatures more than 150°C.

  15. Temperature dependence of anisotropic diffraction in holographic polymer-dispersed liquid crystal memory.

    Science.gov (United States)

    Ogiwara, Akifumi; Watanabe, Minoru; Moriwaki, Retsu

    2013-09-10

    Grating devices using photosensitive organic materials play an important role in the development of optical and optoelectronic systems. High diffraction efficiency and polarization dependence achieved in a holographic polymer-dispersed liquid crystal (HPDLC) grating are expected to provide polarization-controllable optical devices, such as a holographic memory for optically reconfigurable gate arrays (ORGAs). However, the optical property is affected by the thermal modulation around the transition temperature (T(ni)) where the liquid crystal (LC) changes from nematic to isotropic phases. The temperature dependence of the diffraction efficiency in HPDLC grating is investigated using four types of LC composites comprised of LCs and monomers having different physical properties such as T(ni) and anisotropic refractive indices. The holographic memory formed by the LC with low anisotropic refractive index and LC diacrylate monomer implements optical reconfiguration for ORGAs at a high temperature beyond T(ni) of LC.

  16. Simulation of thermal ablation by high-intensity focused ultrasound with temperature-dependent properties.

    Science.gov (United States)

    Huang, C W; Sun, M K; Chen, B T; Shieh, J; Chen, C S; Chen, W S

    2015-11-01

    An integrated computational framework was developed in this study for modeling high-intensity focused ultrasound (HIFU) thermal ablation. The temperature field was obtained by solving the bioheat transfer equation (BHTE) through the finite element method; while, the thermal lesion was considered as a denatured material experiencing phase transformation and modeled with the latent heat. An equivalent attenuation coefficient, which considers the temperature-dependent properties of the target material and the ultrasound diffraction due to bubbles, was proposed in the nonlinear thermal transient analysis. Finally, a modified thermal dose formulation was proposed to predict the lesion size, shape and location. In-vitro thermal ablation experiments on transparent tissue phantoms at different energy levels were carried out to validate this computational framework. The temperature histories and lesion areas from the proposed model show good correlation with those from the in-vitro experiments. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Temperature dependence of the surface plasmon resonance in small electron gas fragments, self consistent field approximation

    Science.gov (United States)

    Fasolato, C.; Sacchetti, F.; Tozzi, P.; Petrillo, C.

    2017-07-01

    The temperature dependence of the surface plasmon resonance in small metal spheres is calculated using an electron gas model within the Random Phase Approximation. The calculation is mainly devoted to the study of spheres with diameters up to at least 10 nm, where quantum effects can still be relevant and a simple plasmon pole approximation for the dielectric function is no more appropriate. We find a possible blue shift of the plasmon resonance position when the temperature is increased while keeping the size of the sphere fixed. The blue shift is appreciable only when the temperature is a large fraction of the Fermi energy. These results provide a guide for pump and probe experiments with a high time resolution, tailored to study the excited electron system before thermalisation with the lattice takes place.

  18. PRESSURE AND TEMPERATURE DEPENDENT DEFLAGRATION RATE MEASUREMENTS OF LLM-105 AND TATB BASED EXPLOSIVES

    Energy Technology Data Exchange (ETDEWEB)

    Glascoe, E A; Tan, N; Koerner, J; Lorenz, K T; Maienschein, J L

    2009-11-10

    The pressure dependent deflagration rates of LLM-105 and TATB based formulations were measured in the LLNL high pressure strand burner. The role of binder amount, explosive type, and thermal damage and their effects on the deflagration rate will be discussed. Two different formulations of LLM-105 and three formulations of TATB were studied and results indicate that binder amount and type play a minor role in the deflagration behavior. This is in sharp contrast to the HMX based formulations which strongly depend on binder amount and type. The effect of preheating these samples was considerably more dramatic. In the case of LLM-105, preheating the sample appears to have little effect on the deflagration rate. In contrast, preheating TATB formulations causes the deflagration rate to accelerate and become erratic. The thermal and mechanical properties of these formulations will be discussed in the context of their pressure and temperature dependent deflagration rates.

  19. Analytical pair correlations in ideal quantum gases: temperature-dependent bunching and antibunching.

    Science.gov (United States)

    Bosse, J; Pathak, K N; Singh, G S

    2011-10-01

    The fluctuation-dissipation theorem together with the exact density response spectrum for ideal quantum gases has been utilized to yield a new expression for the static structure factor, which we use to derive exact analytical expressions for the temperature-dependent pair distribution function g(r) of the ideal gases. The plots of bosonic and fermionic g(r) display "Bose pile" and "Fermi hole" typically akin to bunching and antibunching as observed experimentally for ultracold atomic gases. The behavior of spin-scaled pair correlation for fermions is almost featureless, but bosons show a rich structure including long-range correlations near T(c). The coherent state at T=0 shows no correlation at all, just like single-mode lasers. The depicted decreasing trend in correlation with decrease in temperature for T

  20. Temperature dependence of energy transfer mechanisms in Eu-doped GaN

    Science.gov (United States)

    Lee, Chang-Won; Everitt, Henry O.; Lee, D. S.; Steckl, A. J.; Zavada, J. M.

    2004-06-01

    The temperature dependent behavior of continuous-wave and time-resolved photoluminescence of Eu-doped GaN in the visible region is measured for both the 5D0→7F2 and 5D0→7F3 transitions. The radiative decay of these transitions, following pulsed laser excitation of the GaN host, is monitored by a grating spectrometer and photomultiplier tube detector system. In addition to these two radiative energy transfer pathways within Eu3+, the data reveal two nonradiative energy transfer paths between Eu3+ and the host GaN. Decay constants for the relaxation processes are extracted from the data using a numerically solved rate equation model. Although the dominant radiative relaxation processes decayed with a temperature insensitive decay constant of 166 μs, a prominent role for nonradiative transfer between Eu3+ and impurities within the GaN host was deduced above 180 K.

  1. Temperature-dependent resonance energy transfer from semiconductor quantum wells to graphene.

    Science.gov (United States)

    Yu, Young-Jun; Kim, Keun Soo; Nam, Jungtae; Kwon, Se Ra; Byun, Hyeryoung; Lee, Kwanjae; Ryou, Jae-Hyun; Dupuis, Russell D; Kim, Jeomoh; Ahn, Gwanghyun; Ryu, Sunmin; Ryu, Mee-Yi; Kim, Jin Soo

    2015-02-11

    Resonance energy transfer (RET) has been employed for interpreting the energy interaction of graphene combined with semiconductor materials such as nanoparticles and quantum-well (QW) heterostructures. Especially, for the application of graphene as a transparent electrode for semiconductor light emitting diodes, the mechanism of exciton recombination processes such as RET in graphene-semiconductor QW heterojunctions should be understood clearly. Here, we characterized the temperature-dependent RET behaviors in graphene/semiconductor QW heterostructures. We then observed the tuning of the RET efficiency from 5% to 30% in graphene/QW heterostructures with ∼60 nm dipole-dipole coupled distance at temperatures of 300 to 10 K. This survey allows us to identify the roles of localized and free excitons in the RET process from the QWs to graphene as a function of temperature.

  2. Anomalous optical and magnetic behavior of multi-phase Mn doped Zn2SiO4 nanowires: a new class of dilute magnetic semiconductors

    Science.gov (United States)

    Hafeez, Muhammad; Ali, Awais; Manzoor, Sadia; Bhatti, Arshad S.

    2014-11-01

    We present the synthesis of Mn doped Zn2SiO4 dense nanowire bundles using the VLS mode of growth with unusual optical and magnetic properties. The synthesized Zn2SiO4 nanowires were identified with two phases, α-Zn2SiO4 as the major phase and β-Zn2SiO4 as the minor phase. XPS studies confirmed that Zn2SiO4 nanowires were Zn rich and Mn doped. Temperature dependent photoluminescence (PL) measurements showed three distinct emission bands: green, yellow and red due to Mn doping in the α-phase, β-phase and the substitution of Si with Mn in the α-phase, respectively. The PL analysis showed that these emission bands followed anomalous Berthelot-type behavior. The carrier escape energies were 70 +/- 3 meV, 49 +/- 2 meV and 65 +/- 4 meV for the 530, 570 and 660 nm bands, respectively, while the radiation rates (Er =) were 1.0 +/- 0.4 meV, 3.10 +/- 1.10 meV and 1.4 +/- 0.4 meV corresponding to the three respective bands. Mn doping of Zn2SiO4 nanowires induced ferromagnetism, which was observed above room temperature, with a Curie temperature well above 380 K. The observation of magnetic behavior in this class of semiconductors has potential applications in high temperature spintronics and magneto-optical devices.

  3. Temperature dependence of optical anisotropy of holographic polymer-dispersed liquid crystal transmission gratings.

    Science.gov (United States)

    Drevensek-Olenik, I; Fally, M; Ellabban, M A

    2006-08-01

    We measured the angular dependence of the 0th, +/-1 st, and +/-2 nd optical diffraction orders from a 50 microm thick transmission grating recorded in a UV-curable holographic polymer-dispersed liquid crystal (HPDLC) made from commercially available constituents. The analysis was performed for two orthogonal polarizations of the probe beams. The emphasis was laid on the temperature dependence of the grating anisotropy. Above the nematic-isotropic phase transition, the grating is optically isotropic. At lower temperatures the grating strength for the optical polarization perpendicular to the grating vector decreases with decreasing temperature, while for orthogonal polarization it increases with decreasing temperature. As a consequence, a regime of diffraction with strongly overmodulated gratings is observed. Our investigations indicate that the anisotropy of the refractive-index modulation scales with the optical anisotropy of the liquid crystal medium forming the phase-separated domains. We further demonstrate that light scattering effects, which are profound only in the nematic phase, must not be neglected and can be taken into account via a Lorentzian line-shape broadening of the probing wave vector directions in the framework of the diffraction theory for anisotropic optical phase gratings.

  4. Temperature Dependence of Light Transmittance in Polymer Dispersed Liquid Crystals

    OpenAIRE

    Bloisi, F.; Ruocchio, C.; Vicari, L

    1997-01-01

    Polymer Dispersed Liquid Crystals (PDLC) axe composite materials made of a dispersion of liquid crystal droplets in a polymeric matrix. When the liquid crystal is in the nematic phase, droplets appeax as optically anisotropic spheres and the material is opaque white. Sample transmittance is a function of the temperature. If the liquid crystal refractive index in the isotropic phase is equal to the one of the polymer, after the nematic-isotropic transition the material is transparent. We prese...

  5. Temperature-dependent Henry's law constants of 4-alkyl-branched chain fatty acids and 3-methylindole in an oil-air matrix and analysis of volatiles in lamb fat using selected ion flow tube mass spectrometry (SIFT-MS).

    Science.gov (United States)

    Castada, Hardy Z; Polentz, Victoria; Barringer, Sheryl; Wick, Macdonald

    2017-10-07

    4-Alkyl-branched chain fatty acids and 3-methylindole are characteristic flavor compounds associated with sheep meat. Determining their partitioning behavior between the gas and condensed phase and ultimately developing a correlation between the compound's headspace concentration and sensory descriptive grouping are important for high throughput characterization and grading classification. The headspace concentrations of 3-methylindole, 4-methyloctanoic acid, 4-ethyloctanoic acid, and 4-methylnonanoic acid above corn oil-based standard solutions, and lamb fat samples were measured using selected ion flow tube-mass spectrometry (SIFT-MS). The standard solutions were equilibrated at 80, 100, 110 and 125(o) C while the fat samples were equilibrated at 125(o) C. Statistical evaluation, linear and polynomial regression analyses were performed to establish the compound-specific and temperature-dependent Henry's law constants, enthalpy (∆H) and entropy (∆S) of phase changes. The Henry's law constants (kH(cp) ) were calculated from the regression analysis with a high degree of confidence (p 0.99). The kH(cp) increased with increase in equilibrium temperature. The empirical calculation of the ∆H and ∆S at different temperatures confirmed the temperature-dependence of the Henry's law constants. The headspace concentrations of the lamb-flavor compounds were determined above actual lamb fat samples and the corresponding condensed phase concentrations were successfully derived. The temperature-dependent Henry's law constants, ∆H, and ∆S of phase changes for 3-methylindole, 4-methyloctanoic acid, 4-ethyloctanoic acid, and 4-methylnonanoic acid in an air-oil matrix were empirically derived. The effectiveness of SIFT-MS for the direct, real-time, and rapid determination of key flavor compounds in lamb fat samples was established. This article is protected by copyright. All rights reserved.

  6. Mercury Phase II Study - Mercury Behavior in Salt Processing Flowsheet

    Energy Technology Data Exchange (ETDEWEB)

    Jain, V. [Savannah River Remediation, LLC., Aiken, SC (United States); Shah, H. [Savannah River Remediation, LLC., Aiken, SC (United States). Sludge and Salt Planning; Bannochie, C. J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Wilmarth, W. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-07-25

    Mercury (Hg) in the Savannah River Site Liquid Waste System (LWS) originated from decades of canyon processing where it was used as a catalyst for dissolving the aluminum cladding of reactor fuel. Approximately 60 metric tons of mercury is currently present throughout the LWS. Mercury has long been a consideration in the LWS, from both hazard and processing perspectives. In February 2015, a Mercury Program Team was established at the request of the Department of Energy to develop a comprehensive action plan for long-term management and removal of mercury. Evaluation was focused in two Phases. Phase I activities assessed the Liquid Waste inventory and chemical processing behavior using a system-by-system review methodology, and determined the speciation of the different mercury forms (Hg+, Hg++, elemental Hg, organomercury, and soluble versus insoluble mercury) within the LWS. Phase II activities are building on the Phase I activities, and results of the LWS flowsheet evaluations will be summarized in three reports: Mercury Behavior in the Salt Processing Flowsheet (i.e. this report); Mercury Behavior in the Defense Waste Processing Facility (DWPF) Flowsheet; and Mercury behavior in the Tank Farm Flowsheet (Evaporator Operations). The evaluation of the mercury behavior in the salt processing flowsheet indicates, inter alia, the following: (1) In the assembled Salt Batches 7, 8 and 9 in Tank 21, the total mercury is mostly soluble with methylmercury (MHg) contributing over 50% of the total mercury. Based on the analyses of samples from 2H Evaporator feed and drop tanks (Tanks 38/43), the source of MHg in Salt Batches 7, 8 and 9 can be attributed to the 2H evaporator concentrate used in assembling the salt batches. The 2H Evaporator is used to evaporate DWPF recycle water. (2) Comparison of data between Tank 21/49, Salt Solution Feed Tank (SSFT), Decontaminated Salt Solution Hold Tank (DSSHT), and Tank 50 samples suggests that the total mercury as well as speciated

  7. Phase Behavior of Light Gases in Hydrocarbon and Aqueous Solvents

    Energy Technology Data Exchange (ETDEWEB)

    Gasem, K.A.M.; Robinson, R.L., Jr.; Trvedi, N.J., Gao, W.

    1997-09-01

    Under previous support from the Department of Energy, an experimental facility has been established and operated to measure valuable vapor-liquid equilibrium data for systems of interest in the production and processing of coal fluids. To facilitate the development and testing of models for prediction of the phase behavior for such systems, we have acquired substantial amounts of data on the equilibrium phase compositions for binary mixtures of heavy hydrocarbon solvents with a variety of supercritical solutes, including hydrogen, methane, ethane, carbon monoxide, and carbon dioxide. The present project focuses on measuring the phase behavior of light gases and water in Fischer-Tropsch (F-T) type solvents at conditions encountered in indirect liquefaction processes and evaluating and developing theoretically-based correlating frameworks to predict the phase behavior of such systems. Specific goals of the proposed work include (a) developing a state-of-the-art experimental facility to permit highly accurate measurements of equilibrium phase compositions (solubilities) of challenging F-T systems, (b) measuring these properties for systematically-selected binary, ternary and molten F-T wax mixtures to provide critically needed input data for correlation development, (c) developing and testing models suitable for describing the phase behavior of such mixtures, and (d) presenting the modeling results in generalized, practical formats suitable for use in process engineering calculations. During the present reporting period, our solubility apparatus was refurbished and restored to full service. To test the experimental apparatus and procedures used, measurements were obtained for the solubility Of C0{sub 2} in benzene at 160{degrees}F. Having confirmed the accuracy of the newly acquired data in comparison with our previous measurements and data reported in the literature for this test system, we have begun to measure the solubility of hydrogen in hexane. The measurements

  8. Phase behavior of charged colloids on spherical surfaces

    Science.gov (United States)

    Kelleher, Colm; Guerra, Rodrigo; Chaikin, Paul

    For a broad class of 2D materials, the transition from isotropic fluid to crystalline solid is described by the theory of melting due to Kosterlitz, Thouless, Halperin, Nelson and Young. According to this theory, long-range order is achieved via elimination of the topological defects which proliferate in the fluid phase. However, many natural and man-made 2D systems posses spatial curvature and/or non-trivial topology, which require the presence of defects, even at T = 0 . In principle, the presence of these defects could profoundly affect the phase behavior of such a system. In this presentation, we describe experiments and simulations we have performed on repulsive particles which are bound to the surface of a sphere. We observe spatial structures and inhomogeneous dynamics that cannot be captured by the measures traditionally used to describe flat-space phase behavior. We show that ordering is achieved by a novel mechanism: sequestration of topological defects into freely-terminating grain boundaries (``scars''), and simultaneous spatial organization of the scars themselves on the vertices of an icosahedron. The emergence of icosahedral order coincides with the localization of mobility into isolated ``lakes'' of fluid or glassy particles, situated at the icosahedron vertices.

  9. Phase behavior, rheological and mechanical properties of hydrophilic polymer dispersions.

    Science.gov (United States)

    Bhattarai, Sushila; Bunt, Craig; Rathbone, Michael; Alany, Raid G

    2011-06-01

    Liquid polymeric systems that can undergo phase change (sol to gel) upon administration into the teat canal of cow's mammary gland can serve as a physical barrier to invading pathogens and can also serve as a reservoir for controlled release of therapeutic agents. The aim of the study was to investigate the phase behavior, rheological and mechanical properties of selected in situ gelling systems. Six in situ gelling polymer formulations were identified using phase behavior studies. Rheological studies revealed pseudoplastic flow with thixotropy. All six formulations showed significantly different viscosity, pseudoplasticity and thixotropy values except for CMC1 and HPMC2 which where statistically similar. The gel strength was dependent on the solvent system used and amount of water in the system. These in situ gelling systems have the potential to serve as a platform for development of intramammary formulations intended for administration into the teat canal of the cow's mammary gland. They can serve as a physical barrier or a matrix for controlled drug release.

  10. Temperature Dependence of Single-Event Burnout in N-Channel Power MOSFET’s

    Science.gov (United States)

    1994-03-15

    AD-A277 921 P O Temperature Dependence of Single-Event Burnout in N-Channel Power MOSFETs 15 March 1994 Prepared by G. H. JOHNSON, R. D. SCHRIMPF...Makimunm 200 words) The temperature dependence of single-event burnout (SEB) in n-channel power metal-oxide- semiconductor field effect transistors...power MOSFET is tmned off (blocking a large The temperature dependence of single-event burn drain-source bias) [3]. Previous burnout modeling has beow

  11. The Phase Behavior of γ-Oryzanol and β-Sitosterol in Edible Oil

    NARCIS (Netherlands)

    Sawalha, H.I.M.; Venema, P.; Bot, A.; Flöter, E.; Adel, den R.; Linden, van der E.

    2015-01-01

    The phase behavior of binary mixtures of ¿-oryzanol and ß-sitosterol and ternary mixtures of ¿-oryzanol and ß-sitosterol in sunflower oil was studied. Binary mixtures of ¿-oryzanol and ß-sitosterol show double-eutectic behavior. Complex phase behavior with two intermediate mixed solid phases was

  12. Temperature dependence of the electrical resistivity of amorphous Co 80-xEr xB 20 alloys

    Science.gov (United States)

    Touraghe, O.; Khatami, M.; Menny, A.; Lassri, H.; Nouneh, K.

    2008-06-01

    The temperature dependence of the electrical resistivity of amorphous Co 80-xEr xB 20 alloys with x=0, 3.9, 7.5 and 8.6 prepared by melt spinning in pure argon atmosphere was studied. All amorphous alloys investigated here are found to exhibit a resistivity minimum at low temperature. The electrical resistivity exhibits logarithmic temperature dependence below the temperature of resistivity minimum Tmin. In addition, the resistivity shows quadratic temperature behavior in the interval Tmin< T<77 K. At high temperature, the electrical resistivity was discussed by the extended Ziman theory. For the whole series of alloys, the composition dependence of the temperature coefficient of electrical resistivity α shows a change in structural short range occurring in the composition range 8-9 at%.

  13. Phase behavior of multicomponent membranes: Experimental and computational techniques

    DEFF Research Database (Denmark)

    Bagatolli, Luis; Kumar, P.B. Sunil

    2009-01-01

    , mainly because of their complexity, the precise in-plane organization of lipids and proteins and their stability in biological membranes remain difficult to elucidate. This has reiterated the importance of understanding the equilibrium phase behavior and the kinetics of fluid multicomponent lipid...... of the membrane. Experiments indicate that biomembranes of eukaryotic cells may be laterally organized into small nanoscopic domains. This inplane organization is expected to play an important role in a variety of physiological functions such as signaling, recruitment of specific proteins and endocytosis. However...... membranes. Current increase in interest in the domain formation in multicomponent membranes also stems from the experiments demonstrating liquid ordered-liquid disordered coexistence in mixtures of lipids and cholesterol and the success of several computational models in predicting their behavior...

  14. Temperature dependence of microwave oscillations in magnetic tunnel junctions with a perpendicularly magnetized free layer

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Peng; Feng, Jiafeng, E-mail: hxwei@iphy.ac.cn, E-mail: jiafengfeng@iphy.ac.cn; Wei, Hongxiang, E-mail: hxwei@iphy.ac.cn, E-mail: jiafengfeng@iphy.ac.cn; Han, Xiufeng [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Fang, Bin; Zhang, Baoshun; Zeng, Zhongming [Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Ruoshui Road 398, Suzhou 215123 (China)

    2015-01-05

    We experimentally study the temperature dependence of the spin-transfer-torque-induced microwave oscillations in MgO-based magnetic tunnel junction nanopillars with a perpendicularly magnetized free layer. We demonstrate that the oscillation frequency increases rapidly with decreasing temperature, which is mainly ascribed to the temperature dependence of both the saturation magnetization and the perpendicular magnetic anisotropy. We also find that a strong temperature dependence of the output power while a nonmonotonic temperature dependence of spectral linewidth are maintained for a constant dc bias in measured temperature range. Possible mechanisms leading to the different dependences of oscillation frequency, output power, and linewidth are discussed.

  15. Temperature dependence of poly(lactic acid) mechanical properties

    DEFF Research Database (Denmark)

    Zhou, Chengbo; Guo, Huilong; Li, Jingqing

    2016-01-01

    The mechanical properties of polymers are not only determined by their structures, but also related to the temperature field in which they are located. The yield behaviors, Young's modulus and structures of injection-molded poly(lactic acid) (PLA) samples after annealing at different temperatures...

  16. Temperature dependent current transport of Pd/ZnO nanowire Schottky diodes

    Science.gov (United States)

    Gayen, R. N.; Bhattacharyya, S. R.; Jana, P.

    2014-09-01

    Zinc oxide (ZnO) nanowire based Schottky barrier diodes are fabricated by depositing Pd metal contact on top of vertically well-aligned ZnO nanowire arrays. A vertical array of ZnO nanowires on indium tin oxide (ITO) coated glass substrates is synthesized by hybrid wet chemical route. Scanning electron microscopy (SEM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) measurement confirm the formation of stoichiometric well-aligned hexagonal (h-ZnO) nanowire arrays with wurtzite structure. Temperature dependent current-voltage (I-V) measurements on palladium-ZnO (Pd/ZnO) nanowire Schottky junctions in the temperature range 303-383 K exhibit excellent rectifying character. From these nonlinear I-V plots, different electrical parameters of diode-like reverse saturation current, barrier height and ideality factor are determined as a function of temperature assuming pure thermionic emission model. The ideality factor is found to decrease while the barrier height increases with the increase in temperature. The series resistance values calculated from Cheung’s functions also show temperature dependency. Such behavior can be attributed to the presence of defects that traps carriers, and barrier height inhomogeneity at the interface of the barrier junction. After barrier height inhomogeneity correction, considering a Gaussian distributed barrier height fluctuation across the Pd/ZnO interface, the estimated values of mean barrier height and modified Richardson constant are more closely matched to the theoretically predicted value for Pd/ZnO Schottky barrier diodes. The variation of density of interface states as a function of interface state energy is also calculated.

  17. Irradiation temperature dependence of production efficiency of lattice defects in some neutron-irradiated oxides

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Moritami [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 5900494 (Japan)]. E-mail: okada@rri.kyoto-u.ac.jp; Atobe, Kozo [Faculty of Science, Naruto University of Education, Naruto, Tokushima 7728502 (Japan); Nakagawa, Masuo [Faculty of Education, Kagawa University, Takamatsu, Kagawa 7608522 (Japan)

    2004-11-01

    Temperature dependence of production efficiency of irradiation-induced defects in neutron-irradiated oxides has been investigated. Some oxide single crystals, MgO, {alpha}-Al{sub 2}O{sub 3} (sapphire) and TiO{sub 2} (rutile), were irradiated at several controlled temperatures, 10, 20, 50, 100, 150 and 200 K, using the low-temperature irradiation facility of Kyoto University Reactor (KUR-LTL), and at ambient temperature ({approx}370 K) in the same facility. Irradiation temperature dependence of production efficiency of a 1 {mu}m band in TiO{sub 2} differs greatly from that of anion vacancy (F-type centers) in MgO and {alpha}-Al{sub 2}O{sub 3}. Results for MgO and {alpha}-Al{sub 2}O{sub 3} show steep negative gradients from 10 to 370 K, whereas that for TiO{sub 2} includes a valley between 40 and 60 K and a hump at about 130 K, and then disappear at about 200 K. In MgO and {alpha}-Al{sub 2}O{sub 3}, this behavior can be explained by the recombination of Frenkel pairs, which is activated at higher temperature. In TiO{sub 2}, in addition to the recombination mechanism, a covalent bonding property is thought to be exerted strong influence, and it is suggested that a disappearance of the 1 {mu}m band at above 200 K is due to the recombination process of Frenkel pairs which is caused by the irradiation-induced crystallization.

  18. Temperature-dependent fluorescence characteristics of an ytterbium-sensitized erbium-doped tellurite glass

    Energy Technology Data Exchange (ETDEWEB)

    Li Xujie [College of Computer Science and Engineering, Wenzhou University, Zhejiang 325035 (China); Faculty of Information Science and Engineering, State Key Laboratory, Base of Novel Functional Materials and Preparation Science, Ningbo University, Zhejiang 315211 (China)], E-mail: lixujie101@yahoo.com.cn; Zhang Wenjie [College of Computer Science and Engineering, Wenzhou University, Zhejiang 325035 (China)

    2008-09-01

    In this article, the 1.5 {mu}m emission spectra corresponding to the {sup 4}I{sub 13/2}{yields}{sup 4}I{sub 15/2} transition of Er{sup 3+} in tellurite glass are studied within the temperature from 8 to 300 K. The emission spectra of Er{sup 3+}: {sup 4}I{sub 13/2}{yields}{sup 4}I{sub 15/2} transition are also analyzed using a peak-fit routine, and an equivalent four-level system is proposed to estimate the stark splitting for the {sup 4}I{sub 15/2} and {sup 4}I{sub 13/2} levels of Er{sup 3+} in the tellurite glass. The results indicate that the {sup 4}I{sub 13/2}{yields}{sup 4}I{sub 15/2} emission of Er{sup 3+} can exhibit a considerable broadening due to a significant enhance the peak a', and b' change, respectively, and the peaks of which are located at about 1507 and 1556 nm. A detailed study of temperature-dependent 1.5 {mu}m emission spectra involving the change of the corresponding sub-bands shows that as the temperature decreases from 300 to 8 K, its line-shape becomes sharper and more intense (the full-width at half-maximum decreases from 59 to 38 nm). Temperature-dependent fluorescence intensities and the experimentally determined lifetimes are investigated; the results show that a decrease behavior of fluorescence intensities and lifetimes are observed for temperature from 8 to 300 K.

  19. Temperature Dependence of the Oxygen Reduction Mechanism in Nonaqueous Li–O 2 Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Bin [Energy; Xu, Wu [Energy; Zheng, Jianming [Energy; Yan, Pengfei [Environmental; Walter, Eric D. [Environmental; Isern, Nancy [Environmental; Bowden, Mark E. [Environmental; Engelhard, Mark H. [Environmental; Kim, Sun Tai [Energy; Department; Read, Jeffrey [Power; Adams, Brian D. [Energy; Li, Xiaolin [Energy; Cho, Jaephil [Department; Wang, Chongmin [Environmental; Zhang, Ji-Guang [Energy

    2017-10-11

    The temperature dependence of the oxygen reduction mechanism in Li-O2 batteries was investigated using carbon nanotube-based air electrodes and 1,2-dimethoxyethane-based electrolyte within a temperature range of 20C to 40C. It is found that the discharge capacity of the Li-O2 batteries decreases from 7,492 mAh g-1 at 40C to 2,930 mAh g-1 at 0C. However, a sharp increase in capacity was found when the temperature was further decreased and a very high capacity of 17,716 mAh g-1 was observed at 20C at a current density of 0.1 mA cm-2. When the temperature increases from 20C to 40C, the morphologies of the Li2O2 formed varied from ultra-small spherical particles to small flakes and then to large flake-stacked toroids. The lifetime of superoxide and the solution pathway play a dominate role on the battery capacity in the temperature range of -20C to 0C, but the electrochemical kinetics of oxygen reduction and the surface pathway dominate the discharge behavior in the temperature range of 0C to 40C. These findings provide fundamental understanding on the temperature dependence of oxygen reduction process in a Li-O2 battery and will enable a more rational design of Li-O2 batteries.

  20. Structural phase transformation and hysteresis behavior of Cu-Zn ferrites

    Science.gov (United States)

    Maria, Kazi Hanium; Choudhury, Shamima; Hakim, Mohammad Abdul

    2013-06-01

    A series of Cu1- x Zn x Fe2O4 ferrite (with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) compositions were synthesized using the standard solid-state reaction technique. X-ray diffraction was used to study the structure of the above investigated samples. The theoretical and experimental lattice parameters ( a th and a exp) were calculated for each composition. A significant decrease in density and subsequent increase in porosity were observed with increasing Zn content. Curie temperature, T C, has been determined from the temperature dependence of permeability and found to decrease with increasing Zn content. The anomaly observed in the temperature dependence of permeability was attributed to the existence of two structural phases: cubic phase and tetragonal phase. Low-field hysteresis measurements have been performed using a B- H loop trace from which hysteresis parameters have been determined. Coercivity and hysteresis loss were estimated with different Zn contents.

  1. Temperature-dependent anisotropic resistivity in electron, hole and isoelectron - doped BaFe2As2 superconductors

    Science.gov (United States)

    Tanatar, M. A.

    2012-02-01

    Anisotropic electrical resistivity, ρ(T), was studied in iron-arsenide superconductors, obtained by doping the parent BaFe2As2 compound on three different sites: (1) electron donor transition metal (Co,Ni,Rh,Pd) substitution of Fe [1,2]; (2) hole donor K substitution of Ba [3]; (3) isoelectron P substitution of As. For all three types of dopants a range of T-linear behavior is found at the optimal doping in both the in-plane and the inter-plane ρ(T) above Tc. At some higher temperature this range of T-linear resistivity is capped by a slope-changing anomaly, which, by comparison with NMR, magnetic susceptibility and Hall effect measurements, can be identified with the onset of carrier activation over the pseudogap [1]. The doping-evolution of anisotropic temperature dependent ρ(T) and of the pseudogap are quite different for three types of doping. A three-dimensional T-H phase diagram summarizing our results will be presented. Furthermore, potential correlation of the anisotropic normal state transport and anisotropic superconducting state heat transport will be discussed. [4pt] In collaboration with N. Ni, A. Thaler, S.L.Bud'ko, P.C. Canfield, R. Prozorov, Bing Shen, Hai-Hu Wen, K. Hashimoto, S. Kasahara, T. Terashima, T. Shibauchi and Y. Matsuda. [4pt] [1] M.A.Tanatar et al. PRB 82, 134528 (2010)[0pt] [2] M.A.Tanatar et al. PRB 84, 014519 (2011)[0pt] [3] M.A.Tanatar et al. arXiv:1106.0533

  2. Effect of alpha/gamma phase ratio on corrosion behavior of dual-phase stainless steels.

    Science.gov (United States)

    Lim, Y J; Reyes, M; Thongthammachat, S; Sukchit, K; Panich, M; Oshida, Y

    1999-01-01

    Dual-phase stainless steels have been developed in order to reduce the nickel content, which is potentially responsible to an allergic reaction when these steels are used as medical or dental applications. In this study, two different dual-phase stainless steels (2205 and Z100) were electrochemically tested to evaluate their corrosion resistance in three corrosive solutions (i.e., synthetic saliva, 0.9% NaCl solution, and Ringer solution). Particularly, an attempt was made to correlate the corrosion resistance to a metallographic parameter, which is, in this study, the alpha/gamma phase ratio. It was concluded that (1) type 2205 stainless steel exhibited excellent corrosion resistance in all three corrosion media; however 2205 stainless steel decreases its corrosion resistance by increasing chloride concentration in tested electrolytes from synthetic saliva through 0.9% NaCl solution to Ringer solution. (2) X-ray diffraction analysis indicated that the alpha/gamma phase ratio of 2205 (1.735) was higher than that of Z100 (0.905). As a result, it is suggested that by increasing the alpha/gamma phase ratio the material shows more corrosion-prone behavior when being subjected to a hostile environment containing higher chloride ion concentration.

  3. Freezing in porous media: Phase behavior, dynamics and transport phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Wettlaufer, John S. [Yale Univ., New Haven, CT (United States)

    2012-12-21

    This research was focused on developing the underlying framework for the mechanisms that control the nature of the solidification of a broad range of porous media. To encompass the scope of porous media under consideration we considered material ranging from a dilute colloidal suspension to a highly packed saturated host matrix with a known geometry. The basic physical processes that occur when the interstitial liquid phase solidifies revealed a host of surprises with a broad range of implications from geophysics to materials science and engineering. We now understand that ostensibly microscopic films of unfrozen liquid control both the equilibrium and transport properties of a highly packed saturated host matrix as well as a rather dilute colloidal suspension. However, our description of the effective medium behavior in these settings is rather different and this sets the stage for the future research based on our past results. Once the liquid phase of a saturated relatively densely packed material is frozen, there is a rich dynamical behavior of particles for example due to the directed motion driven by thermomolecular pressure gradients or the confined Brownian motion of the particles. In quite striking contrast, when one freezes a dilute suspension the behavior can be rather more like that of a binary alloy with the particles playing the role of a ``solute''. We probed such systems quantitatively by (i) using X ray photon correlation spectroscopy (XPCS) and Small Angle X-ray Scattering (SAXS) at the Advanced Photon Source at Argonne (ii) studying the Argonne cell in the laboratory using optical microscopy and imagery (because it is not directly visible while in the vacuum can). (3) analyzed the general transport phenomena within the framework of both irreversible thermodynamics and alloy solidification and (4) applied the results to the study of the redistribution of solid particles in a frozen interstitial material. This research has gone a long way

  4. Deformation Behavior across the Zircon-Scheelite Phase Transition

    Science.gov (United States)

    Yue, Binbin; Hong, Fang; Merkel, Sébastien; Tan, Dayong; Yan, Jinyuan; Chen, Bin; Mao, Ho-Kwang

    2016-09-01

    The pressure effects on plastic deformation and phase transformation mechanisms of materials are of great importance to both Earth science and technological applications. Zircon-type materials are abundant in both nature and the industrial field; however, there is still no in situ study of their deformation behavior. Here, by employing radial x-ray diffraction in a diamond anvil cell, we investigate the dislocation-induced texture evolution of zircon-type gadolinium vanadate (GdVO4 ) in situ under pressure and across its phase transitions to its high-pressure polymorphs. Zircon-type GdVO4 develops a (001) compression texture associated with dominant slip along ⟨100 ⟩{001 } starting from 5 GPa. This (001) texture transforms into a (110) texture during the zircon-scheelite phase transition. Our observation demonstrates a martensitic mechanism for the zircon-scheelite transformation. This work will help us understand the local deformation history in the upper mantle and transition zone and provides fundamental guidance on material design and processing for zircon-type materials.

  5. Unusual crystallization behavior in Ga-Sb phase change alloys

    Directory of Open Access Journals (Sweden)

    Magali Putero

    2013-12-01

    Full Text Available Combined in situ X-ray scattering techniques using synchrotron radiation were applied to investigate the crystallization behavior of Sb-rich Ga-Sb alloys. Measurements of the sheet resistance during heating indicated a reduced crystallization temperature with increased Sb content, which was confirmed by in situ X-ray diffraction. The electrical contrast increased with increasing Sb content and the resistivities in both the amorphous and crystalline phases decreased. It was found that by tuning the composition between Ga:Sb = 9:91 (in at.% and Ga:Sb = 45:55, the change in mass density upon crystallization changes from an increase in mass density which is typical for most phase change materials to a decrease in mass density. At the composition of Ga:Sb = 30:70, no mass density change is observed which should be very beneficial for phase change random access memory (PCRAM applications where a change in mass density during cycling is assumed to cause void formation and PCRAM device failure.

  6. Temperature dependence of Henry's law constants of metolachlor and diazinon.

    Science.gov (United States)

    Feigenbrugel, Valérie; Le Calvé, Stéphane; Mirabel, Philippe

    2004-10-01

    A dynamic system based on the water/air equilibrium at the interface within the length of a microporous tube has been used to determine experimentally the Henry's law constants (HLC) of two pesticides: metolachlor and diazinon. The measurements were conducted over the temperature range 283-301 K. At 293 K, HLCs values are (42.6+/-2.8) x 10(3) (in units of M atm(-1)) for metolachlor and (3.0+/-0.3)x10(3) for diazinon. The obtained data were used to derive the following Arrhenius expressions: HLC=(3.0+/-0.4) x 10(-11) exp((10,200+/-1,000)/T) for metolachlor and (7.2+/-0.5) x 10(-15) exp((11,900+/-700)/T) for diazinon. At a cumulus cloud temperature of 283 K, the fractions of metolachlor and diazinon in the atmospheric aqueous phase are about 57% and 11% respectively. In order to evaluate the impact of a cloud on the atmospheric chemistry of both studied pesticides, we compare also their atmospheric lifetimes under clear sky (tau(gas)), and cloudy conditions (tau(multiphase)). The calculated multiphase lifetimes (in units of hours) are significantly lower than those in gas phase at a cumulus temperature of 283 K (in parentheses): metolachlor, 0.4 (2.9); diazinon, 1.9 (5.0).

  7. Fabrication and temperature-dependent field-emission properties of bundlelike VO2 nanostructures.

    Science.gov (United States)

    Yin, Haihong; Luo, Min; Yu, Ke; Gao, Yanfeng; Huang, Rong; Zhang, Zhengli; Zeng, Min; Cao, Chuanxiang; Zhu, Ziqiang

    2011-06-01

    Bundlelike VO(2)(B) nanostructures were synthesized via a hydrothermal method, and VO(2)(M(1)/R) nanobundles were obtained after a heat-treatment process. Structural characterization shows that these nanobundles are self-assembled by VO(2) nanowires, and VO(2)(M(1)/R) nanobundles have better crystallinity. Temperature-dependent field-emission (FE) measurement indicates that FE properties of these two phases of nanobundles can both be improved by increasing the ambient temperature. Moreover, for the VO(2)(M(1)/R) nanobundles, their FE properties are also strongly dependent on the temperature-induced metal-insulator transitions process. Compared with poor FE properties found in the insulating phase, FE properties were significantly improved by increasing the temperature, and about a three-orders-of-magnitude increasing of the emission current density has been observed at a fixed field of 6 V/μm. Work function measurement and density-functional theory calculations indicated that the decrease of work function with temperature is the main reason that caused the improvement of FE properties. These characteristics make VO(2)(M(1)/R) a candidate material for application of new type of temperature-controlled field emitters, whose emission density can be adjusted by ambient temperature. © 2011 American Chemical Society

  8. Universal Scaling Behavior of Non-Equilibrium Phase Transitions

    Science.gov (United States)

    Lübeck, Sven

    Non-equilibrium critical phenomena have attracted a lot of research interest in the recent decades. Similar to equilibrium critical phenomena, the concept of universality remains the major tool to order the great variety of non-equilibrium phase transitions systematically. All systems belonging to a given universality class share the same set of critical exponents, and certain scaling functions become identical near the critical point. It is known that the scaling functions vary more widely between different universality classes than the exponents. Thus, universal scaling functions offer a sensitive and accurate test for a system's universality class. On the other hand, universal scaling functions demonstrate the robustness of a given universality class impressively. Unfortunately, most studies focus on the determination of the critical exponents, neglecting the universal scaling functions. In this work a particular class of non-equilibrium critical phenomena is considered, the so-called absorbing phase transitions. Absorbing phase transitions are expected to occur in physical, chemical as well as biological systems, and a detailed introduction is presented. The universal scaling behavior of two different universality classes is analyzed in detail, namely the directed percolation and the Manna universality class. Especially, directed percolation is the most common universality class of absorbing phase transitions. The presented picture gallery of universal scaling functions includes steady state, dynamical as well as finite size scaling functions. In particular, the effect of an external field conjugated to the order parameter is investigated. Incorporating the conjugated field, it is possible to determine the equation of state, the susceptibility, and to perform a modified finite-size scaling analysis appropriate for absorbing phase transitions. Focusing on these equations, the obtained results can be applied to other non-equilibrium continuous phase transitions

  9. On the Temperature Dependence of the Shear Viscosity and Holography

    CERN Document Server

    Cremonini, Sera; Szepietowski, Phillip

    2012-01-01

    We examine the structure of the shear viscosity to entropy density ratio eta/s in holographic theories of gravity coupled to a scalar field, in the presence of higher derivative corrections. Thanks to a non-trivial scalar field profile, eta/s in this setup generically runs as a function of temperature. In particular, its temperature behavior is dictated by the shape of the scalar potential and of the scalar couplings to the higher derivative terms. We consider a number of dilatonic setups, but focus mostly on phenomenological models that are QCD-like. We determine the geometric conditions needed to identify local and global minima for eta/s as a function of temperature, which translate to restrictions on the signs and ranges of the higher derivative couplings. Finally, such restrictions lead to an holographic argument for the existence of a global minimum for eta/s in these models, at or above the deconfinement transition.

  10. Temperature-dependent Gilbert damping of Co2FeAl thin films with different degree of atomic order

    Science.gov (United States)

    Kumar, Ankit; Pan, Fan; Husain, Sajid; Akansel, Serkan; Brucas, Rimantas; Bergqvist, Lars; Chaudhary, Sujeet; Svedlindh, Peter

    2017-12-01

    Half-metallicity and low magnetic damping are perpetually sought for spintronics materials, and full Heusler compounds in this respect provide outstanding properties. However, it is challenging to obtain the well-ordered half-metallic phase in as-deposited full Heusler compound thin films, and theory has struggled to establish a fundamental understanding of the temperature-dependent Gilbert damping in these systems. Here we present a study of the temperature-dependent Gilbert damping of differently ordered as-deposited Co2FeAl full Heusler compound thin films. The sum of inter- and intraband electron scattering in conjunction with the finite electron lifetime in Bloch states governs the Gilbert damping for the well-ordered phase, in contrast to the damping of partially ordered and disordered phases which is governed by interband electronic scattering alone. These results, especially the ultralow room-temperature intrinsic damping observed for the well-ordered phase, provide fundamental insights into the physical origin of the Gilbert damping in full Heusler compound thin films.

  11. A study of the temperature dependence of the local ferroelectric properties of c-axis oriented Bi6Ti3Fe2O18 Aurivillius phase thin films: Illustrating the potential of a novel lead-free perovskite material for high density memory applications

    Directory of Open Access Journals (Sweden)

    Ahmad Faraz

    2015-08-01

    Full Text Available The ability to control the growth, texture and orientation of self-nanostructured lead-free Aurivillius phase thin films can in principle, greatly improve their ferroelectric properties, since in these materials the polarization direction is dependent on crystallite orientation. Here, we report the growth of c-plane oriented Bi6Ti3Fe2O18 (B6TFO functional oxide Aurivillius phase thin films on c-plane sapphire substrates by liquid injection chemical vapour deposition (LI-CVD. Microstructural analysis reveals that B6TFO thin films annealed at 850°C are highly crystalline, well textured (Lotgering factor of 0.962 and single phase. Typical Aurivillius plate-like morphology with an average film thickness of 110nm and roughness 24nm was observed. The potential of B6TFO for use as a material in lead-free piezoelectric and ferroelectric data storage applications was explored by investigating local electromechanical (piezoelectric and ferroelectric properties at the nano-scale. Vertical and lateral piezoresponse force microscopy (PFM reveals stronger in-plane polarization due to the controlled growth of the a-axis oriented grains lying in the plane of the B6TFO films. Switching spectroscopy PFM (SS-PFM hysteresis loops obtained at higher temperatures (up to 200°C and at room temperature reveal a clear ferroelectric signature with only minor changes in piezoresponse observed with increasing temperature. Ferroelectric domain patterns were written at 200°C using PFM lithography. Hysteresis loops generated inside the poled regions at room and higher temperatures show a significant increase in piezoresponse due to alignment of the c-axis polarization components under the external electric field. No observable change in written domain patterns was observed after 20hrs of PFM scanning at 200°C, confirming that B6TFO retains polarization over this finite period of time. These studies demonstrate the potential of B6TFO thin films for use in piezoelectric

  12. Thermodynamic phase behavior of API/polymer solid dispersions.

    Science.gov (United States)

    Prudic, Anke; Ji, Yuanhui; Sadowski, Gabriele

    2014-07-07

    To improve the bioavailability of poorly soluble active pharmaceutical ingredients (APIs), these materials are often integrated into a polymer matrix that acts as a carrier. The resulting mixture is called a solid dispersion. In this work, the phase behaviors of solid dispersions were investigated as a function of the API as well as of the type and molecular weight of the carrier polymer. Specifically, the solubility of artemisinin and indomethacin was measured in different poly(ethylene glycol)s (PEG 400, PEG 6000, and PEG 35000). The measured solubility data and the solubility of sulfonamides in poly(vinylpyrrolidone) (PVP) K10 and PEG 35000 were modeled using the perturbed-chain statistical associating fluid theory (PC-SAFT). The results show that PC-SAFT predictions are in a good accordance with the experimental data, and PC-SAFT can be used to predict the whole phase diagram of an API/polymer solid dispersion as a function of the kind of API and polymer and of the polymer's molecular weight. This remarkably simplifies the screening process for suitable API/polymer combinations.

  13. Metaphysics, science and the asphaltene phase behavior problem

    Energy Technology Data Exchange (ETDEWEB)

    Lockhart, T.P. [Eniricerche SpA, Milanese (Italy)

    1996-12-31

    Spontaneous phase separation and deposition of the asphaltenic component of crude oils is the source of costly problems in the petroleum industry. Over the past several decades so-called {open_quotes}colloid stabilization{close_quotes} model has dominated attempts to account for the phase behavior of the asphaltene fraction of the crude oil. We will argue that this model is not {open_quotes}scientific{close_quotes} in the sense that is has been applied only for the post-hoc rationalization of experimental results; absent have been serious attempts to experimentally test specific predictions deduced from the model. A critical examination of the colloid stabilization model brings to light several fundamental shortcomings. An alternative thermodynamic, or {open_quotes}solvation{close_quotes} model is shown to make predictions in far better agreement with experiment, and has been the key to developing an analytical model that accurately predicts the conditions under which crude oils become unstable to asphaltene deposition. This example will be used to argue that the defining elements of (good) scientific research - the formulation of explicit hypotheses of high predictive content and their critical evaluation, above all by experimental attempts at falsification - are also effective, indeed necessary, for analyzing the complex problems offered by the {open_quotes}real{close_quotes} world and for achieving technological advancement.

  14. Tethered Nanoparticle -Polymer Composites: Phase behavior and rheology

    Science.gov (United States)

    Mangal, Rahul; Archer, Lynden A.

    2014-03-01

    Polymer nanocomposites with particle radius (a) approaching the radius of gyration (Rg) of entangled host polymer have been reported to exhibit an unusual negative reinforcement effect, which leads to an anomalous reduction in relative an anomalous reduction in relative viscosity at low particle loadings (φ) . This so-called Non-Einsteinian flow behavior is understood to be sensitive to the dispersion state of particles in host polymer. We studied suspensions of SiO2 nanoparticles tethered with polethylene glycol (PEG) in polymethylmethacralate (PMMA) with molecular weights (Mw) from 17 KDa to 280 KDa. Due to strong enthalpic interactions between PEG and PMMA (χ = -0.65), nanoparticles are expected to be well-dispersed, independent of Mw of PMMA. Using small angle x-ray scattering measurements we show that the phase stability of suspensions depends on Mw of the tethered PEG, host PMMA, and φ. Particles functionalized with low molecular weight PEG aggregate at low φ, but disperse at high φ. In contrast, nanoparticles functionalized with higher molecular weight PEG are well dispersed for host chain lengths (P) to tethered chain length (N), (P/N), is as high as 160. The stability boundary of these suspensions extends well beyond expectations for nanocomposites based on tethered PEG chains suspended in PEG. Through in-depth analysis of rheology and x-ray photon correlation spectra we explore the fundamental origins of non-Einsteinian flow behavior. King Abdullah University of Science and Technology (KAUST), Advanced Photon Source (APS).

  15. Phase transition behaviors of the supported DPPC bilayer investigated by sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM).

    Science.gov (United States)

    Wu, Heng-Liang; Tong, Yujin; Peng, Qiling; Li, Na; Ye, Shen

    2016-01-21

    The phase transition behaviors of a supported bilayer of dipalmitoylphosphatidyl-choline (DPPC) have been systematically evaluated by in situ sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). By using an asymmetric bilayer composed of per-deuterated and per-protonated monolayers, i.e., DPPC-d75/DPPC and a symmetric bilayer of DPPC/DPPC, we were able to probe the molecular structural changes during the phase transition process of the lipid bilayer by SFG spectroscopy. It was found that the DPPC bilayer is sequentially melted from the top (adjacent to the solution) to bottom leaflet (adjacent to the substrate) over a wide temperature range. The conformational ordering of the supported bilayer does not decrease (even slightly increases) during the phase transition process. The conformational defects in the bilayer can be removed after the complete melting process. The phase transition enthalpy for the bottom leaflet was found to be approximately three times greater than that for the top leaflet, indicating a strong interaction of the lipids with the substrate. The present SFG and AFM observations revealed similar temperature dependent profiles. Based on these results, the temperature-induced structural changes in the supported lipid bilayer during its phase transition process are discussed in comparison with previous studies.

  16. Temperature-dependent phenotypic variation of Campylobacter jejuni lipooligosaccharides

    LENUS (Irish Health Repository)

    Semchenko, Evgeny A

    2010-11-30

    Abstract Background Campylobacter jejuni is a major bacterial cause of food-borne enteritis, and its lipooligosaccharide (LOS) plays an initiating role in the development of the autoimmune neuropathy, Guillain-Barré syndrome, by induction of anti-neural cross-reactive antibodies through ganglioside molecular mimicry. Results Herein we describe the existence and heterogeneity of multiple LOS forms in C. jejuni strains of human and chicken origin grown at 37°C and 42°C, respectively, as determined on sodium dodecyl sulphate-polyacrylamide electrophoresis gels with carbohydrate-specific silver staining and blotting with anti-ganglioside ligands, and confirmed by nuclear magnetic resonance (NMR) spectroscopy. The C. jejuni NCTC 11168 original isolate (11168-O) was compared to its genome-sequenced variant (11168-GS), and both were found to have a lower-Mr LOS form, which was different in size and structure to the previously characterized higher-Mr form bearing GM1 mimicry. The lower-Mr form production was found to be dependent on the growth temperature as the production of this form increased from ~5%, observed at 37°C to ~35% at 42°C. The structure of the lower-Mr form contained a β-D-Gal-(1→3)-β-D-GalNAc disaccharide moiety which is consistent with the termini of the GM1, asialo-GM1, GD1, GT1 and GQ1 gangliosides, however, it did not display GM1 mimicry as assessed in blotting studies but was shown in NMR to resemble asialo-GM1. The production of multiple LOS forms and lack of GM1 mimicry was not a result of phase variation in the genes tested of NCTC 11168 and was also observed in most of the human and chicken isolates of C. jejuni tested. Conclusion The presence of differing amounts of LOS forms at 37 and 42°C, and the variety of forms observed in different strains, indicate that LOS form variation may play a role in an adaptive mechanism or a stress response of the bacterium during the colonization of different hosts.

  17. Temperature-dependent phenotypic variation of Campylobacter jejuni lipooligosaccharides.

    Science.gov (United States)

    Semchenko, Evgeny A; Day, Christopher J; Wilson, Jennifer C; Grice, I Darren; Moran, Anthony P; Korolik, Victoria

    2010-11-30

    Campylobacter jejuni is a major bacterial cause of food-borne enteritis, and its lipooligosaccharide (LOS) plays an initiating role in the development of the autoimmune neuropathy, Guillain-Barré syndrome, by induction of anti-neural cross-reactive antibodies through ganglioside molecular mimicry. Herein we describe the existence and heterogeneity of multiple LOS forms in C. jejuni strains of human and chicken origin grown at 37 °C and 42 °C, respectively, as determined on sodium dodecyl sulphate-polyacrylamide electrophoresis gels with carbohydrate-specific silver staining and blotting with anti-ganglioside ligands, and confirmed by nuclear magnetic resonance (NMR) spectroscopy. The C. jejuni NCTC 11168 original isolate (11168-O) was compared to its genome-sequenced variant (11168-GS), and both were found to have a lower-M(r) LOS form, which was different in size and structure to the previously characterized higher-M(r) form bearing GM₁ mimicry. The lower-M(r) form production was found to be dependent on the growth temperature as the production of this form increased from ~5%, observed at 37 °C to ~35% at 42 °C. The structure of the lower-M(r) form contained a β-D-Gal-(1→3)-β-D-GalNAc disaccharide moiety which is consistent with the termini of the GM₁, asialo-GM₁, GD₁, GT₁ and GQ₁ gangliosides, however, it did not display GM₁ mimicry as assessed in blotting studies but was shown in NMR to resemble asialo-GM₁. The production of multiple LOS forms and lack of GM1 mimicry was not a result of phase variation in the genes tested of NCTC 11168 and was also observed in most of the human and chicken isolates of C. jejuni tested. The presence of differing amounts of LOS forms at 37 and 42 °C, and the variety of forms observed in different strains, indicate that LOS form variation may play a role in an adaptive mechanism or a stress response of the bacterium during the colonization of different hosts.

  18. Temperature-dependent phenotypic variation of Campylobacter jejuni lipooligosaccharides

    Directory of Open Access Journals (Sweden)

    Moran Anthony P

    2010-11-01

    Full Text Available Abstract Background Campylobacter jejuni is a major bacterial cause of food-borne enteritis, and its lipooligosaccharide (LOS plays an initiating role in the development of the autoimmune neuropathy, Guillain-Barré syndrome, by induction of anti-neural cross-reactive antibodies through ganglioside molecular mimicry. Results Herein we describe the existence and heterogeneity of multiple LOS forms in C. jejuni strains of human and chicken origin grown at 37°C and 42°C, respectively, as determined on sodium dodecyl sulphate-polyacrylamide electrophoresis gels with carbohydrate-specific silver staining and blotting with anti-ganglioside ligands, and confirmed by nuclear magnetic resonance (NMR spectroscopy. The C. jejuni NCTC 11168 original isolate (11168-O was compared to its genome-sequenced variant (11168-GS, and both were found to have a lower-Mr LOS form, which was different in size and structure to the previously characterized higher-Mr form bearing GM1 mimicry. The lower-Mr form production was found to be dependent on the growth temperature as the production of this form increased from ~5%, observed at 37°C to ~35% at 42°C. The structure of the lower-Mr form contained a β-D-Gal-(1→3-β-D-GalNAc disaccharide moiety which is consistent with the termini of the GM1, asialo-GM1, GD1, GT1 and GQ1 gangliosides, however, it did not display GM1 mimicry as assessed in blotting studies but was shown in NMR to resemble asialo-GM1. The production of multiple LOS forms and lack of GM1 mimicry was not a result of phase variation in the genes tested of NCTC 11168 and was also observed in most of the human and chicken isolates of C. jejuni tested. Conclusion The presence of differing amounts of LOS forms at 37 and 42°C, and the variety of forms observed in different strains, indicate that LOS form variation may play a role in an adaptive mechanism or a stress response of the bacterium during the colonization of different hosts.

  19. Temperature dependence of ion irradiation induced amorphization of zirconolite

    Energy Technology Data Exchange (ETDEWEB)

    Smith, K. L.; Blackford, M. G.; Lumpkin, G. R.; Zaluzec, N. J.

    1999-12-22

    Zirconolite is one of the major host phases for actinides in various wasteforms for immobilizing high level radioactive waste (HLW). Over time, zirconolite's crystalline matrix is damaged by {alpha}-particles and energetic recoil nuclei recoil resulting from {alpha}-decay events. The cumulative damage caused by these particles results in amorphization. Data from natural zirconolites suggest that radiation damage anneals over geologic time and is dependant on the thermal history of the material. Proposed HLW containment strategies rely on both a suitable wasteform and geologic isolation. Depending on the waste loading, depth of burial, and the repository-specific geothermal gradient, burial could result in a wasteform being exposed to temperatures of between 100--450 C. Consequently, it is important to assess the effect of temperature on radiation damage in synthetic zirconolite. Zirconolite containing wasteforms are likely to be hot pressed at or below 1,473 K (1,200 C) and/or sintered at or below 1,623 K (1,350 C). Zirconolite fabricated at temperatures below 1,523 K (1,250 C) contains many stacking faults. As there have been various attempts to link radiation resistance to structure, the authors decided it was also pertinent to assess the role of stacking faults in radiation resistance. In this study, they simulate {alpha}-decay damage in two zirconolite samples by irradiating them with 1.5 MeV Kr{sup +} ions using the High Voltage Electron Microscope-Tandem User Facility (HTUF) at Argonne National Laboratory (ANL) and measure the critical dose for amorphization (D{sub c}) at several temperatures between 20 and 773 K. One of the samples has a high degree of crystallographic perfection, the other contains many stacking faults on the unit cell scale. Previous authors proposed a model for estimating the activation energy of self annealing in zirconolite and for predicting the critical dose for amorphization at any temperature. The authors discuss their results

  20. Diamagnetic Torque Signal and Temperature-Dependent Paramagnetism in Bi2Sr2CaCu2O8+δ

    Science.gov (United States)

    Tsuchiya, Satoshi; Mochiku, Takashi; Ooi, Shuichi; Hirata, Kazuto; Sugii, Kaori; Terashima, Taichi; Uji, Shinya

    2017-11-01

    Magnetic torque and resistance measurements for the superconducting cuprate Bi2Sr2CaCu2O8+δ with Tc = 87 K have been performed to determine the phase diagram in a parallel magnetic field fields up to 14 T. The anisotropy of the magnetization, derived from the torque, is found to decrease with decreasing temperature below 125 K, which can be ascribed to the temperature dependent paramagnetic spin susceptibility. The angular dependence of the torque clearly shows small diamagnetism due to fluctuating or inhomogeneous superconductivity at temperatures between Tc and ˜100 K. The results suggest that the pseudogap is not of superconducting origin.

  1. Mantle dynamics with pressure- and temperature-dependent thermal expansivity and conductivity

    Science.gov (United States)

    Tosi, Nicola; Yuen, David A.; de Koker, Nico; Wentzcovitch, Renata M.

    2013-04-01

    In numerical simulations of mantle convection it is commonly assumed that the coefficients of thermal expansion α and thermal conduction k are either constant or pressure-dependent. Pressure changes are generally computed using parametrizations that rely on extrapolations of low-pressure data for a single upper-mantle phase. Here we collect data for both the pressure and temperature dependence of α from a database of first-principles calculations, and of k from recent experimental studies. We use these data-sets to construct analytical parametrizations of α and k for the major upper- and lower-mantle phases that can be easily incorporated into exisiting convection codes. We then analyze the impact of such parametrizations on Earth's mantle dynamics by employing two-dimensional numerical models of thermal convection. When α is the only variable parameter, both its temperature and pressure dependence enhance hot plumes and tend to inhibit the descent of cold downwellings. Taking into account a variable k leads to a strong increase of the bulk mantle temperature, which reduces the buoyancy available to amplify bottom boundary layer instabilities and causes mantle flow to be driven primarily by the instability of cold plates whose surface velocity also tends to rise. When both parameters are considered together, we observe an increased propensity to local layering which favors slab stagnation in the transition zone and subsequent thickening in the lower mantle. Furthermore, the values of k near the core-mantle boundary ultimately control the effect of this physical property on convection, which stresses the importance of determining the thermal conductivity of the post-perovskite phase.

  2. Correction of the temperature dependent error in a correlation based time-of-flight system by measuring the distortion of the correlation signal

    Science.gov (United States)

    Hofbauer, M.; Seiter, J.; Davidovic, M.; Zimmermann, H.

    2013-04-01

    Correlation based time-of-flight systems suffer from a temperature dependent distance measurement error induced by the illumination source of the system. A change of the temperature of the illumination source, results in the change of the bandwidth of the used light emitters, which are light emitting diodes (LEDs) most of the time. For typical illumination sources this can result in a drift of the measured distance in the range of ~20 cm, especially during the heat up phase. Due to the change of the bandwidth of the LEDs the shape of the output signal changes as well. In this paper we propose a method to correct this temperature dependent error by investigating this change of the shape of the output signal. Our measurements show, that the presented approach is capable of correcting the temperature dependent error in a large range of operation without the need for additional hardware.

  3. Temperature-dependent VNIR spectroscopy of hydrated Na-carbonates

    Science.gov (United States)

    Tosi, Federico; Carli, Cristian; De Angelis, Simone; Beck, Pierre; Brissaud, Olivier; Schmitt, Bernard; Capaccioni, Fabrizio; De Sanctis, Maria Cristina; Piccioni, Giuseppe

    2017-04-01

    constraints. In particular, the uppermost temperature, 279 K, has been acquired both at the beginning and at end of the ramp, to check for any macroscopic physico-chemical changes in the sample. In sodium carbonate monohydrate, about ten spectral signatures are revealed in the spectral range 1.0-3.0 µm. These signatures are due in part to combinations and overtones of the fundamental vibration modes of the water molecule, and in part to the carbonate. For comparison, sodium carbonate decahydrate shows fewer diagnostic and generally wider signatures, due to the larger number of water molecules existing in this mineral. We analyzed the spectral behavior of the diagnostic signatures of these two hydrated minerals as a function of both grain size and temperature, deriving trends related to specific spectral parameters such as band center, band depth, band area, and bandwidth. We plan to complete this set of measurements with those obtained for anhydrous sodium carbonate, which serves as a valid comparison for the hydrated carbonates discussed here and may provide a valid support to spectroscopic analysis of bright faculae discovered by the NASA Dawn mission in crater Occator on the dwarf planet Ceres.

  4. Mantle plumes - A boundary layer approach for Newtonian and non-Newtonian temperature-dependent rheologies. [modeling for island chains and oceanic aseismic ridges

    Science.gov (United States)

    Yuen, D. A.; Schubert, G.

    1976-01-01

    Stress is placed on the temperature dependence of both a linear Newtonian rheology and a nonlinear olivine rheology in accounting for narrow mantle flow structures. The boundary-layer theory developed incorporates an arbitrary temperature-dependent power-law rheology for the medium, in order to facilitate the study of mantle plume dynamics under real conditions. Thermal, kinematic, and dynamic structures of mantle plumes are modelled by a two-dimensional natural-convection boundary layer rising in a fluid with a temperature-dependent power-law relationship between shear stress and strain rate. An analytic similarity solution is arrived at for upwelling adjacent to a vertical isothermal stress-free plane. Newtonian creep as a deformation mechanism, thermal anomalies resulting from chemical heterogeneity, the behavior of plumes in non-Newtonian (olivine) mantles, and differences in the dynamics of wet and dry olivine are discussed.

  5. Temperature dependence of electron mobility in N-type organic molecular crystals: Theoretical study

    Science.gov (United States)

    Lin, Lili; Fan, Jianzhong; Jiang, Supu; Wang, Zhongjie; Wang, Chuan-Kui

    2017-11-01

    The temperature dependence of electron mobility in three Fx-TCNQ molecular crystals is studied. The electron mobility calculated based on Marcus charge transfer rate for all three molecules increases, as the temperature becomes high. Nevertheless, the electron mobility calculated based on quantum charge transfer rate shows opposite temperature dependence and indicates bandlike transport mechanism. Similar intrinsic transport properties are obtained for three systems. The different temperature dependence for Fx-TCNQ molecules detected should be induced by different transfer paths or external factors. Our investigation could help one better understand experimental results and provide intuitive view on the transfer mechanism in molecular crystals.

  6. Effect of the temperature dependence of the viscosity of pseudoplastic lubricants on the boundary friction regime

    Science.gov (United States)

    Lyashenko, I. A.

    2013-07-01

    The boundary friction regime appearing between two atomically smooth solid surfaces with an ultrathin lubricating layer between them is considered. The interrupted (stick-slip) regime of motion typical of the boundary lubrication is represented as a first-order phase transition between the structural states of the lubricant. The thermodynamic and shear melting is described. The universal dependence of the viscosity of high-molecular alkanes (lubricants) on the temperature and velocity gradient is taken into account. The dependence of the friction force on the lubricant temperature and the relative shear velocity of the interacting surfaces are analyzed. It is shown that the temperature dependence of the viscosity makes it possible to describe some experimentally observed effects. The possibility of prolonged damped oscillations after lubricant melting prior to the stabilization of the steady-state sliding mode is predicted. In the stick-slip regime in a wide range of parameters, a reversive motion is observed when the upper block moves in both directions after melting.

  7. Temperature dependence of N-phenyl-1-naphthylamine binding in egg lecithin vesicles.

    Science.gov (United States)

    Ting, P; Solomon, A K

    1975-10-17

    The temperature dependence of the binding of PhNapNH2 (N-phenyl-1-naphthylamine) to vesicles of egg phosphatidylcholine has been determined. The Arrhenius plot of the association constant exhibits a discontinuity at 20.9 degrees C, some 30 degrees C above the broad phase transition region of the phospholipid. In the temperature range above 20 degrees C, deltaH0 =--6100 cal-mol-1 and deltaS0 = 9.7 e.u.; in the temperature range below 20 degrees C, deltaH0 = 0 cal-mol-1 and deltaS0 = 30.4 e.u. These values are consistent with the view that there are well ordered lipid-lipid bonds below 20 degrees C which are significantly less important above this temperature. The order in the temperature range of 5 to 20 degrees C, though significantly greater than that above 20 degrees C, is still significiantly less than that in the crystalline state.

  8. Temperature dependences of growth rates and carrying capacities of marine bacteria depart from metabolic theoretical predictions

    KAUST Repository

    Huete-Stauffer, Tamara Megan

    2015-09-11

    Using the metabolic theory of ecology (MTE) framework, we evaluated over a whole annual cycle the monthly responses to temperature of the growth rates (μ) and carrying capacities (K) of heterotrophic bacterioplankton at a temperate coastal site. We used experimental incubations spanning 6oC with bacterial physiological groups identified by flow cytometry according to membrane integrity (live), nucleic acid content (HNA and LNA) and respiratory activity (CTC+). The temperature dependence of μat the exponential phase of growth was summarized by the activation energy (E), which was variable (-0.52 to 0.72 eV) but followed a seasonal pattern, only reaching the hypothesized value for aerobic heterotrophs of 0.65 eV during the spring bloom for the most active bacterial groups (live, HNA, CTC+). K (i.e. maximum experimental abundance) peaked at 4 × 106 cells mL-1 and generally covaried with μbut, contrary to MTE predictions, it did not decrease consistently with temperature. In the case of live cells, the responses of μand K to temperature were positively correlated and related to seasonal changes in substrate availability, indicating that the responses of bacteria to warming are far from homogeneous and poorly explained by MTE at our site. © FEMS 2015.

  9. Temperature-dependent morphology of hybrid nanoflowers from elastin-like polypeptides

    Directory of Open Access Journals (Sweden)

    Koushik Ghosh

    2014-02-01

    Full Text Available We report a method for creating hybrid organic-inorganic “nanoflowers” using calcium or copper ions as the inorganic component and a recombinantly expressed elastin-like polypeptide (ELP as the organic component. Polypeptides provide binding sites for the dynamic coordination with metal ions, and then such noncovalent complexes become nucleation sites for primary crystals of metal phosphates. We have shown that the interaction between the stimuli-responsive ELP and Ca2+ or Cu2+, in the presence of phosphate, leads to the growth of micrometer-sized particles featuring nanoscale patterns shaped like flower petals. The morphology of these flower-like composite structures is dependent upon the temperature of growth and has been characterized by scanning electron microscopy. The composition of nanoflowers has also been analyzed by energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The temperature-dependent morphologies of these hybrid nanostructures, which arise from the controllable phase transition of ELPs, hold potential for morphological control of biomaterials in emerging applications such as tissue engineering and biocatalysis.

  10. Viscous heating in fluids with temperature-dependent viscosity: implications for magma flows

    Directory of Open Access Journals (Sweden)

    A. Costa

    2003-01-01

    Full Text Available Viscous heating plays an important role in the dynamics of fluids with strongly temperature-dependent viscosity because of the coupling between the energy and momentum equations. The heat generated by viscous friction produces a local temperature increase near the tube walls with a consequent decrease of the viscosity which may dramatically change the temperature and velocity profiles. These processes are mainly controlled by the Peclét number, the Nahme number, the flow rate and the thermal boundary conditions. The problem of viscous heating in fluids was investigated in the past for its practical interest in the polymer industry, and was invoked to explain some rheological behaviours of silicate melts, but was not completely applied to study magma flows. In this paper we focus on the thermal and mechanical effects caused by viscous heating in tubes of finite lengths. We find that in magma flows at high Nahme number and typical flow rates, viscous heating is responsible for the evolution from Poiseuille flow, with a uniform temperature distribution at the inlet, to a plug flow with a hotter layer near the walls. When the temperature gradients  induced by viscous heating are very pronounced, local instabilities may occur and the triggering of secondary flows is possible. For completeness, this paper also describes magma flow in infinitely long tubes both at steady state and in transient phase.

  11. Temperature-Dependent Magnetic Response of Antiferromagnetic Doping in Cobalt Ferrite Nanostructures

    Science.gov (United States)

    Nairan, Adeela; Khan, Maaz; Khan, Usman; Iqbal, Munawar; Riaz, Saira; Naseem, Shahzad

    2016-01-01

    In this work MnxCo1−xFe2O4 nanoparticles (NPs) were synthesized using a chemical co-precipitation method. Phase purity and structural analyses of synthesized NPs were performed by X-ray diffractometer (XRD). Transmission electron microscopy (TEM) reveals the presence of highly crystalline and narrowly-dispersed NPs with average diameter of 14 nm. The Fourier transform infrared (FTIR) spectrum was measured in the range of 400–4000 cm−1 which confirmed the formation of vibrational frequency bands associated with the entire spinel structure. Temperature-dependent magnetic properties in anti-ferromagnet (AFM) and ferromagnet (FM) structure were investigated with the aid of a physical property measurement system (PPMS). It was observed that magnetic interactions between the AFM (Mn) and FM (CoFe2O4) material arise below the Neel temperature of the dopant. Furthermore, hysteresis response was clearly pronounced for the enhancement in magnetic parameters by varying temperature towards absolute zero. It is shown that magnetic properties have been tuned as a function of temperature and an externally-applied field. PMID:28335203

  12. Temperature dependences of growth rates and carrying capacities of marine bacteria depart from metabolic theoretical predictions.

    Science.gov (United States)

    Huete-Stauffer, Tamara Megan; Arandia-Gorostidi, Nestor; Díaz-Pérez, Laura; Morán, Xosé Anxelu G

    2015-10-01

    Using the metabolic theory of ecology (MTE) framework, we evaluated over a whole annual cycle the monthly responses to temperature of the growth rates (μ) and carrying capacities (K) of heterotrophic bacterioplankton at a temperate coastal site. We used experimental incubations spanning 6ºC with bacterial physiological groups identified by flow cytometry according to membrane integrity (live), nucleic acid content (HNA and LNA) and respiratory activity (CTC+). The temperature dependence of μ at the exponential phase of growth was summarized by the activation energy (E), which was variable (-0.52 to 0.72 eV) but followed a seasonal pattern, only reaching the hypothesized value for aerobic heterotrophs of 0.65 eV during the spring bloom for the most active bacterial groups (live, HNA, CTC+). K (i.e. maximum experimental abundance) peaked at 4 × 10(6) cells mL(-1) and generally covaried with μ but, contrary to MTE predictions, it did not decrease consistently with temperature. In the case of live cells, the responses of μ and K to temperature were positively correlated and related to seasonal changes in substrate availability, indicating that the responses of bacteria to warming are far from homogeneous and poorly explained by MTE at our site. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  13. Temperature dependent tensile and flexural rigidities of a cross-ply thermoplastic for a forming model

    Science.gov (United States)

    Dangora, L. M.; Sherwood, J. A.; Parker, J. C.; Mitchell, C. J.; White, K. D.

    2016-10-01

    This paper discusses the characterization of temperature dependent tensile and flexural rigidities for Dyneema® HB80, a cross-ply thermoplastic lamina. The low coefficient of friction of this material posed a challenge to securing specimens during tensile testing. Therefore, modification to the standard gripping method was implemented to facilitate the collection of meaningful test data. Furthermore, a long gauge length was selected to mitigate the influence of slippage on the measure of the elastic modulus. An experimental setup is presented to characterize the bending behavior above ambient temperature conditions based on the vertical cantilever method. The material properties derived from the test data were implemented in a finite element model of the cross ply lamina. The finite element model was generated using a hybrid discrete mesoscopic approach, and deep draw forming of the material was simulated to investigate its formability. Simulation results were compared with an experimental forming trial to demonstrate the capabilities of the model to predict the development of out-of-plane waves during preform manufacturing.

  14. Experimental Investigation of Strain Rate and Temperature Dependent Response of an Epoxy Resin Undergoing Large Deformation

    Science.gov (United States)

    Tamrakar, Sandeep; Ganesh, Raja; Sockalingam, Subramani; Haque, Bazle Z.; Gillespie, John W.

    2018-01-01

    Experimental investigation of the effect of strain rate and temperature on large inelastic deformation of an epoxy resin is presented. Uniaxial compression tests were conducted on DER 353 epoxy resin at strain rates ranging from 0.001 to 12,000/s. Experimental results showed significant rate sensitivity in yield stress, which increased from 85 MPa at 0.001/s to 220 MPa at 12,000/s strain rate. Thermal softening became more prominent as the strain rate was increased, resulting in complete absence of strain hardening at high strain rates. Rise in temperature under high strain rate, due to adiabatic heating, was estimated to increase above glass transition temperature (T g ). A series of compression tests carried out at temperatures ranging from ambient to T g + 80 °C showed yield stress vanishing at T g . Above T g , the epoxy became completely rubbery elastic at quasi-static loading rate. Epoxy became less sensitive to strain rate as the temperature was increased further above T g . The strain rate and temperature dependent yield behavior of the epoxy resin is predicted using Ree-Eyring model.

  15. Temperature dependence of ion diffusion coefficients in NaCl electrolyte confined within graphene nanochannels.

    Science.gov (United States)

    Kong, Jing; Bo, Zheng; Yang, Huachao; Yang, Jinyuan; Shuai, Xiaorui; Yan, Jianhua; Cen, Kefa

    2017-03-15

    The behavior of ion diffusion in nano-confined spaces and its temperature dependence provide important fundamental information about electric double-layer capacitors (EDLCs) employing nano-sized active materials. In this work, the ion diffusion coefficients of NaCl electrolyte confined within neutral and charged graphene nanochannels at different temperatures are investigated using molecular dynamics simulations. The results show that ions confined in neutral nanochannels diffuse faster (along the graphene surfaces) than those in bulk solution, which could be attributed to the relatively smaller concentration in confined spaces and the solvophobic nature of graphene surfaces. In charged nanochannels where the electrostatic interactions between counter-ions and charged channel surfaces govern the motion of ions, the diffusion coefficients are found to be lower than those in the neutral counterparts. The increase of temperature will lead to enhanced vibrant thermal motion of ions. Due to the significant role of ion-surface interactions, ion diffusion coefficients in nano-confined spaces are more stable, that is, insensitive to the temperature variation, than those in bulk solution. The electrical conductivity is further estimated using the Nernst-Einstein equation. The findings of the current work could provide basic data and information for research studies on the thermal effects of graphene-based EDLCs.

  16. Temperature-dependent Schottky barrier in high-performance organic solar cells

    Science.gov (United States)

    Li, Hui; He, Dan; Zhou, Qing; Mao, Peng; Cao, Jiamin; Ding, Liming; Wang, Jizheng

    2017-01-01

    Organic solar cells (OSCs) have attracted great attention in the past 30 years, and the power conversion efficiency (PCE) now reaches around 10%, largely owning to the rapid material developments. Meanwhile with the progress in the device performance, more and more interests are turning to understanding the fundamental physics inside the OSCs. In the conventional bulk-heterojunction architecture, only recently it is realized that the blend/cathode Schottky junction serves as the fundamental diode for the photovoltaic function. However, few researches have focused on such junctions, and their physical properties are far from being well-understood. In this paper based on PThBDTP:PC71BM blend, we fabricated OSCs with PCE exceeding 10%, and investigated temperature-dependent behaviors of the junction diodes by various characterization including current-voltage, capacitance-voltage and impedance measurements between 70 to 290 K. We found the Schottky barrier height exhibits large inhomogeneity, which can be described by two sets of Gaussian distributions. PMID:28071700

  17. Embryonic origin of mate choice in a lizard with temperature-dependent sex determination.

    Science.gov (United States)

    Putz, Oliver; Crews, David

    2006-01-01

    Individual differences in the adult sexual behavior of vertebrates are rooted in the fetal environment. In the leopard gecko (Eublepharis macularius), a species with temperature-dependent sex determination (TSD), hatchling sex ratios differ between incubation temperatures, as does sexuality in same-sex animals. This variation can primarily be ascribed to the temperature having direct organizing actions on the brain. Here we demonstrate that embryonic temperature can affect adult mate choice in the leopard gecko. Given the simultaneous choice between two females from different incubation temperatures (30.0 and 34.0 degrees C), males from one incubation temperature (30.0 degrees C) preferred the female from 34.0 degrees C, while males from another incubation temperature (32.5 degrees C) preferred the female from 30.0 degrees C. We suggest that this difference in mate choice is due to an environmental influence on brain development leading to differential perception of opposite-sex individuals. This previously unrecognized modulator of adult mate choice lends further support to the view that mate choice is best understood in the context of an individual's entire life-history. Thus, sexual selection results from a combination of the female's as well as the male's life history. Female attractiveness and male choice therefore are complementary. Copyright 2005 Wiley Periodicals, Inc.

  18. Temperature dependence of carbon kinetic isotope effect for the oxidation reaction of ethane by OH radicals under atmospherically relevant conditions

    Science.gov (United States)

    Piansawan, Tammarat; Saccon, Marina; Laumer, Werner; Gensch, Iulia; Kiendler-Scharr, Astrid

    2015-04-01

    Modeling of the global distribution of atmospheric ethane sources and sinks by using the 13C isotopic composition requires accurate knowledge of the carbon kinetic isotope effect (KIE) of its atmospheric removal reactions. The quantum mechanical prediction implies the necessity to elucidate the temperature dependence of KIE within atmospherically relevant temperature range by experiment. In this study, the KIE and its temperature dependence for ethane oxidation by OH radicals was investigated at ambient pressure in a temperature range of 243 K to 303 K. The chemical reactions were carried out in a 15 L PFE reaction chamber, suspended in a thermally controlled oven. The isotope ratios of the gas phase components during the course of the reactions were measured by Thermal Desorption -- Gas Chromatography -- Isotope Ratio Mass Spectrometry (TD-GC-IRMS). For each temperature, the KIE was derived from the temporal evolution of the concentration and stable carbon isotope ratio (δ13C) of ethane using a method adapted from the relative reaction rate concept. The room temperature KIE of the ethane reaction with OH radicals was found to be 6.85 ± 0.32 ‰. This value is in agreement with the previously reported value of 8.57 ± 1.95 ‰ [Anderson et al. 2004] but has a substantially lower uncertainty. The experimental results will be discussed with the KIE temperature dependence predicted by quantum mechanical calculations. Reference: Rebecca S. Anderson, Lin Huang, Richard Iannone, Alexandra E. Thompson, and Jochen Rudolph (2004), Carbon Kinetic Isotope Effects in the Gas Phase Reactions of Light Alkanes and Ethene with the OH Radical at 296 ± 4 K, J. Phys. Chem. A, 108, 11537--11544

  19. Fracture behavior of single phase iron titanate laminate composites

    Science.gov (United States)

    Baskin, Donald Matthew

    1999-11-01

    The study of single phase iron titanate (Fe2TiO5) laminates was undertaken to explore a novel technique for producing tough ceramics without the use of multiple phases. Iron titanate is an orthorhombic, microcracking ceramic whose single crystals exhibit anisotropie thermal contraction and magnetic behavior. Due to the latter anisotropy, it was possible to produce crystallographically textured material, and thereby transfer the thermal anisotropy of the single crystal to bulk materials. Magnetic-assisted gelcasting was exploited to form laminates of alternating layers of crystallographically textured and nontextured material. Aggregates of non-textured material were discovered within textured layers that lead to a population of "aggregate cracks" in the microstructure. These cracks were always oriented normal to the direction of alignment. By changing the orientation of alignment and textured strength in the textured layers, it was possible to produce a spectrum of residual stresses within the laminates. Many spontaneous types of cracking were observed, ranging from tunnel cracks to complete delamination. Laminates were machined into single-edge notch-beam specimens and tested for toughness. Depending on the stacking sequence chosen, test crack trajectories ranged from penetration of all the layers, to large scale (>4 mm) interlaminar bifurcation. The maximum peak toughness observed in mixed layer laminates was 2.4 +/- 0.4 MPa.m1/2, which was an improvement over the toughnesses measured in laminates consisting of all non-textured layers (1.6 +/- 0.1 MPa.m1/2 ). Maximum toughnesses did not correspond to instances of crack bifurcation. Instead, x-ray tomography results and finite element simulations indicated that the aggregate cracks were responsible for the observed toughness enhancements. As the variety of different cracking behaviors observed during this study corresponded closely with the spectrum of residual stresses produced, it was possible to draw a fracture

  20. A simulation study on the phase behavior of hard rhombic platelets

    NARCIS (Netherlands)

    Tasios, N.; Dijkstra, M.

    2017-01-01

    Using Monte Carlo simulations, we investigate the phase behavior of hard rhombic platelets as a function of the thickness of the platelets, T. The phase diagram displays a columnar phase and a crystal phase in which the platelets are stacked in columns that are arranged in a two-dimensional lattice.

  1. Quantitative Analysis of Temperature Dependence of Raman shift of monolayer WS2

    National Research Council Canada - National Science Library

    Huang, Xiaoting; Gao, Yang; Yang, Tianqi; Ren, Wencai; Cheng, Hui-Ming; Lai, Tianshu

    2016-01-01

    We report the temperature-dependent evolution of Raman spectra of monolayer WS2 directly CVD-grown on a gold foil and then transferred onto quartz substrates over a wide temperature range from 84 to 543 K...

  2. Molecular players involved in temperature-dependent sex determination and sex differentiation in Teleost fish

    Science.gov (United States)

    2014-01-01

    The molecular mechanisms that underlie sex determination and differentiation are conserved and diversified. In fish species, temperature-dependent sex determination and differentiation seem to be ubiquitous and molecular players involved in these mechanisms may be conserved. Although how the ambient temperature transduces signals to the undifferentiated gonads remains to be elucidated, the genes downstream in the sex differentiation pathway are shared between sex-determining mechanisms. In this paper, we review recent advances on the molecular players that participate in the sex determination and differentiation in fish species, by putting emphasis on temperature-dependent sex determination and differentiation, which include temperature-dependent sex determination and genetic sex determination plus temperature effects. Application of temperature-dependent sex differentiation in farmed fish and the consequences of temperature-induced sex reversal are discussed. PMID:24735220

  3. Crystalline-like temperature dependence of the electrical characteristics in amorphous Indium-Gallium-Zinc-Oxide thin film transistors

    Science.gov (United States)

    Estrada, M.; Hernandez-Barrios, Y.; Cerdeira, A.; Ávila-Herrera, F.; Tinoco, J.; Moldovan, O.; Lime, F.; Iñiguez, B.

    2017-09-01

    A crystalline-like temperature dependence of the electrical characteristics of amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) thin film transistors (TFTs) is reported, in which the drain current reduces as the temperature is increased. This behavior appears for values of drain and gate voltages above which a change in the predominant conduction mechanism occurs. After studying the possible conduction mechanisms, it was determined that, for gate and drain voltages below these values, hopping is the predominant mechanism with the current increasing with temperature, while for values above, the predominant conduction mechanism becomes percolation in the conduction band or band conduction and IDS reduces as the temperature increases. It was determined that this behavior appears, when the effect of trapping is reduced, either by varying the density of states, their characteristic energy or both. Simulations were used to further confirm the causes of the observed behavior.

  4. Theory of Gas Injection: Interaction of Phase Behavior and Flow

    Science.gov (United States)

    Dindoruk, B.

    2015-12-01

    The theory of gas injection processes is a central element required to understand how components move and partition in the reservoir as one fluid is displacing another (i.e., gas is displacing oil). There is significant amount of work done in the area of interaction of phase-behavior and flow in multiphase flow conditions. We would like to present how the theory of gas injection is used in the industry to understand/design reservoir processes in various ways. The tools that are developed for the theory of gas injection originates from the fractional flow theory, as the first solution proposed by Buckley-Leveret in 1940's, for water displacing oil in porous media. After 1960's more and more complex/coupled equations were solved using the initial concept(s) developed by Buckley-Leverett, and then Welge et al. and others. However, the systematic use of the fractional flow theory for coupled set of equations that involves phase relationships (EOS) and phase appearance and disappearance was mainly due to the theory developed by Helfferich in early 80's (in petroleum literature) using method of characteristics primarily for gas injection process and later on by the systematic work done by Orr and his co-researchers during the last two decades. In this talk, we will present various cases that use and extend the theory developed by Helfferich and others (Orr et al., Lake et al. etc.). The review of various injection systems reveals that displacement in porous media has commonalities that can be represented with a unified theory for a class of problems originating from the theory of gas injection (which is in a way generalized Buckley-Leverett problem). The outcome of these solutions can be used for (and are not limited to): 1) Benchmark solutions for reservoir simulators (to quantify numerical dispersion, test numerical algorithms) 2) Streamline simulators 3) Design of laboratory experiments and their use (to invert the results) 4) Conceptual learning and to investigate

  5. Temperature dependence of the strain response of chemical composition gratings in optical fibers

    Science.gov (United States)

    Li, Guoyu; Guan, Bai-ou

    2008-11-01

    Chemical composition gratings, used as strain sensing elements at high temperature environments, show a temperature dependence of their strain response. Temperature dependence of the strain response of CCGs over a range of temperatures from 24°C to 900°C has been measured. It is found that the wavelength shift of CCGs is linear with applied tensile strain at a constant temperature, and the strain sensitivity is 0.0011nm/μɛ.

  6. Temperature dependent optical characterization of Ni-TiO2 thin films as potential photocatalytic material

    Directory of Open Access Journals (Sweden)

    Rajnarayan De

    2017-09-01

    Full Text Available Along with other transition metal doped titanium dioxide materials, Ni-TiO2 is considered to be one of the most efficient materials for catalytic applications due to its suitable energy band positions in the electronic structure. The present manuscript explores the possibility of improving the photocatalytic activity of RF magnetron sputtered Ni-TiO2 films upon heat treatment. Optical, structural and morphological and photocatalytic properties of the films have been investigated in detail for as deposited and heat treated samples. Evolution of refractive index (RI and total film thickness as estimated from spectroscopic ellipsometry characterization are found to be in agreement with the trend in density and total film thickness estimated from grazing incidence X-ray reflectivity measurement. Interestingly, the evolution of these macroscopic properties were found to be correlated with the corresponding microstructural modifications realized in terms of anatase to rutile phase transformation and appearance of a secondary phase namely NiTiO3 at high temperature. Corresponding morphological properties of the films were also found to be temperature dependent which leads to modifications in the grain structure. An appreciable reduction of optical band gap from 2.9 to 2.5 eV of Ni-TiO2 thin films was also observed as a result of post deposition heat treatment. Testing of photocatalytic activity of the films performed under UV illumination demonstrates heat treatment under atmospheric ambience to be an effective means to enhance the photocatalytic efficiency of transition metal doped titania samples.

  7. Swelling, Compressibility, and Phase Behavior of Soft Ionic Microgels

    Science.gov (United States)

    Denton, Alan

    Soft colloids have inspired great attention recently for their rich and tunable materials properties. Particular interest has focused on microgels - microscopic cross-linked polymer gel particles that, when dispersed in water, become swollen and can acquire charge through dissociation of counterions. Electrostatic interparticle interactions strongly influence the structure and thermodynamics of ionic microgel suspensions*. Permeability to solvent molecules and small ions creates a competition between elastic and electrostatic forces that determines equilibrium particle sizes. Swelling can be controlled by adjusting temperature, pH, and salt concentration, with applications to chemical/biosensing and targeted drug delivery. By combining molecular dynamics and Monte Carlo simulation with Poisson-Boltzmann theory of electrostatics and Flory-Rehner theory of swollen polymer networks, we investigate swelling and compressibility of ionic microgel particles and implications for thermodynamic phase behavior of bulk suspensions at concentrations approaching and exceeding hard-sphere close packing. Predictions for particle size and osmotic pressure are compared with available experimental data. This work was supported by the National Science Foundation under Grant No. DMR-1106331.

  8. Theoretical Analysis on the Kinetic Isotope Effects of Bimolecular Nucleophilic Substitution (SN2 Reactions and Their Temperature Dependence

    Directory of Open Access Journals (Sweden)

    Wan-Chen Tsai

    2013-04-01

    Full Text Available Factors affecting the kinetic isotope effects (KIEs of the gas-phase SN2 reactions and their temperature dependence have been analyzed using the ion-molecule collision theory and the transition state theory (TST. The quantum-mechanical tunneling effects were also considered using the canonical variational theory with small curvature tunneling (CVT/SCT. We have benchmarked a few ab initio and density functional theory (DFT methods for their performance in predicting the deuterium KIEs against eleven experimental values. The results showed that the MP2/aug-cc-pVDZ method gave the most accurate prediction overall. The slight inverse deuterium KIEs usually observed for the gas-phase SN2 reactions at room temperature were due to the balance of the normal rotational contribution and the significant inverse vibrational contribution. Since the vibrational contribution is a sensitive function of temperature while the rotation contribution is temperature independent, the KIEs are thus also temperature dependent. For SN2 reactions with appreciable barrier heights, the tunneling effects were predicted to contribute significantly both to the rate constants and to the carbon-13, and carbon-14 KIEs, which suggested important carbon atom tunneling at and below room temperature.

  9. Dynamic thermal behavior of building using phase change materials for latent heat storage

    Directory of Open Access Journals (Sweden)

    Selka Ghouti

    2015-01-01

    Full Text Available This study presents a two-dimensional model with a real size home composed of two-storey (ground and first floor spaces separated by a slab, enveloped by a wall with rectangular section containing phase change material (PCM in order to minimize energy consumption in the buildings. The main objective of the PCM-wall system is to decrease the temperature change from outdoor space before it reaches the indoor space during the daytime. The numerical approach uses effective heat capacity Ceff model with realistic outdoor climatic conditions of Tlemcen city, Algeria. The numerical results showed that by using PCM in wall as energy storage components may reduce the room temperature by about 6 to 7°C of temperature depending on the floor level (first floor spaces or ground floor spaces.

  10. Temperature dependencies of Henry's law constants and octanol/water partition coefficients for key plant volatile monoterpenoids.

    Science.gov (United States)

    Copolovici, Lucian O; Niinemets, Ulo

    2005-12-01

    To model the emission dynamics and changes in fractional composition of monoterpenoids from plant leaves, temperature dependencies of equilibrium coefficients must be known. Henry's law constants (H(pc), Pa m3 mol(-1) and octanol/water partition coefficients (K(OW), mol mol(-1)) were determined for 10 important plant monoterpenes at physiological temperature ranges (25-50 degrees C for H(pc) and 20-50 degrees C for K(OW)). A standard EPICS procedure was established to determine H(pc) and a shake flask method was used for the measurements of K(OW). The enthalpy of volatilization (deltaH(vol)) varied from 18.0 to 44.3 kJ mol(-1) among the monoterpenes, corresponding to a range of temperature-dependent increase in H(pc) between 1.3- and 1.8-fold per 10 degrees C rise in temperature. The enthalpy of water-octanol phase change varied from -11.0 to -23.8 kJ mol(-1), corresponding to a decrease of K(OW) between 1.15- and 1.32-fold per 10 degrees C increase in temperature. Correlations among physico-chemical characteristics of a wide range of monoterpenes were analyzed to seek the ways of derivation of H(pc) and K(OW) values from other monoterpene physico-chemical characteristics. H(pc) was strongly correlated with monoterpene saturated vapor pressure (P(v)), and for lipophilic monoterpenes, deltaH(vol) scaled positively with the enthalpy of vaporization that characterizes the temperature dependence of P(v) Thus, P(v) versus temperature relations may be employed to derive the temperature relations of H(pc) for these monoterpenes. These data collectively indicate that monoterpene differences in H(pc) and K(OW) temperature relations can importantly modify monoterpene emissions from and deposition on plant leaves.

  11. Temperature-dependent absorption and gain of ytterbium-doped potassium double tungstates for chip-scale amplifiers and lasers

    Science.gov (United States)

    Yong, Yean-Sheng; Aravazhi, Shanmugam; Vázquez-Córdova, Sergio A.; Herek, Jennifer L.; García-Blanco, Sonia M.; Pollnau, Markus

    2017-02-01

    Ytterbium-doped potassium rare-earth double tungstate thin films are excellent candidates for highly efficient waveguide lasers, as well as high-gain waveguide amplifiers, with a record-high optical gain per unit length of 935 dB/cm recently demonstrated. However, the spectroscopic properties of these highly ytterbium-doped thin films and, in particular, their temperature dependence are not well investigated. These characteristics are required for the understanding of the behavior of the fabricated optical devices and crucial for further device optimization. We experimentally determined the absorption cross-sections for a potassium ytterbium gadolinium double tungstate, KYb0.57Gd0.43(WO4)2, thin film grown lattice matched onto an undoped KY(WO4)2 substrate. At room temperature, the peak cross-section value at 981 nm and the overall absorption spectrum are very similar to those of Yb-doped bulk potassium double tungstate crystals, although Yb is now the dominating rare-earth content. The temperature-dependent study shows a significant decrease of the absorption cross-section values at 933 nm and 981 nm with increasing temperature. We verify theoretically that this is due to the temperature dependence of fractional populations in the individual Stark levels of the absorbing crystal-field multiplet, in combination with the linewidth broadening with increasing temperature. Further investigations suggest that the broadening of absorption linewidth at 981 nm originates in the intra-manifold relaxation between the two lowest Stark levels of the ground state. Finally, the implications of the spectroscopic findings on the operating characteristics of waveguide amplifiers are investigated. Amplifiers operating at 80 °C are expected to exhibit only 67% of the maximum theoretical gain at room temperature.

  12. Phase behavior, formation, and rheology of cubic phase and related gel emulsion in Tween 80/water/oil systems.

    Science.gov (United States)

    Alam, Mohammad Mydul; Ushiyama, Kousuke; Aramaki, Kenji

    2009-01-01

    We investigated the phase behavior, formation, and rheology of the cubic phase (I(1)) and related O/I(1) gel emulsion in water/Tween 80/oil systems using squalane, liquid paraffin (LP), and decane as oil components. In the phase behavior study, the phase sequences were similar for squalane and LP systems, while a lamellar liquid crystal (L(alpha)) was observed for decane system. In all the systems the addition of oil to W(m) or H(1) phase induced the I(1) phase, which can solubilize some amounts of oil followed by the appearance of I(1)+O phase. The formation of the O/I(1) gel emulsion has been studied at a fixed w/s (50/50) and we found that 30 wt% decane, 70 wt% squalane, and 60 wt% LP can form the gel emulsion. The water/Tween 80/squalane system has been taken as a model system to study viscoelastic properties of the I(1) phase and O/I(1) gel emulsion. The I(1) phase shows a typical hard gel cubic structure under the frequency and the values of the complex viscosity, /eta*/ and the elastic modulus, G ' increase with the addition of squalane, which could be due to the neighboring micellar interaction. On the other hand, the decreasing values of the viscoelastic parameters in the O/I(1) gel emulsion simply relate to the volume fraction of the I(1) phase in the system.

  13. Temperature dependence of ac response in diluted half-metallic CrO{sub 2} powder compact

    Energy Technology Data Exchange (ETDEWEB)

    Chen Yajie; Zhang Xiaoyu; Cai Tianyi; Li Zhenya

    2004-10-06

    We present a study on temperature dependence of impedance spectra of the cold-pressed chromium dioxide (CrO{sub 2})-titanic dioxide (TiO{sub 2}) composite over the temperature range of 77-300 K, and over the frequency range of 40 Hz-500 kHz. The microstructure of the sample is analyzed using transmission electron microscopy (TEM), SEM and X-ray diffraction (XRD). The impedance spectra exhibit a strong dependence upon temperature. By evaluating the ac electricity behavior of the composite, we find the experimental data are successfully described by a power-law behavior {sigma}{sub ac}=A(T){omega}{sup s}, in which the frequency exponent s shows slightly greater than a universal value (0{<=}s{<=}1), and rises approximately linearly with temperature over a broad range of low temperature.

  14. Transition from Arrhenius to non-Arrhenius temperature dependence of structural relaxation time in glass-forming liquids: continuous versus discontinuous scenario.

    Science.gov (United States)

    Popova, V A; Surovtsev, N V

    2014-09-01

    The temperature dependences of α relaxation time τ(α)(T) of three glass-forming liquids (salol, o-terphenyl, and α-picoline) were investigated by a depolarized light scattering technique. A detailed description of τ(α)(T) near T(A), the temperature of the transition from the Arrhenius law at high temperatures to a non-Arrhenius behavior of τ(α)(T) at lower temperatures, was done. It was found that this transition is quite sharp. If the transition is described as switching from the Arrhenius law to the Vogel-Fulcher-Tammann law, it occurs within the temperature range of about 15 K or less. Most of the known expressions for τ(α)(T) cannot describe this sharp transition. Our analysis revealed that this transition can be described either as a discontinuous transition in the spirit of the frustration-limited domain theory [D. Kivelson, G. Tarjus, X. Zhao, and S. A. Kivelson, Phys. Rev. E 53, 751 (1996)], implying a phase transition, or by a phenomenological expression recently suggested [B. Schmidtke, N. Petzold, R. Kahlau, M. Hofmann, and E. A. Rössler, Phys. Rev. E 86, 041507 (2012)], where the activation energy includes the term depending exponentially on temperature.

  15. Temperature dependence of the EPR spectra for the Ni{sub 1-x}Co{sub x}Fe{sub 2}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    P, Silva; W, Braemer; F, Torres [Institute Venezolano de Investigaciones Cientificas, Centro de Fisica, Carretera Panamericana Km. 11, Aptdo. 20632 (Venezuela, Bolivarian Republic of); V, Sagredo; E, Perez, E-mail: silva@ivic.v [Universidad de Los Andes, Departamento de Fisica, Laboratorio de Magnetismo, Merida (Venezuela, Bolivarian Republic of)

    2010-01-01

    Electron Paramagnetic Resonance (EPR) was used to study, the temperature dependence, of the magnetic behavior of Ni{sub 1-x}Co{sub x}Fe{sub 2}O{sub 4} with 0.0 < x < 0.5, in the temperature range 80 < T < 700 K. Nanoparticles of sizes between 30 and 40 nm were obtained using the sol-gel method. The results show that the resonance field (H{sub R}) decrease while the linewidth (AH{sub PP}) increase, in the temperature range studied, when x is increased. The H{sub R} values for x = 0 are in agreement with a superparamagnetic phase in the temperature range studied, while for x = 0.2, H{sub R} and {Delta}H{sub PP} are in accordance with a ferri to superparamagnetic transition at T{approx}350 K, where T is related to the EPR blocking temperature of these samples. For sample with x = 0.5 this temperature is T{approx}470 K. These results are in good agreement with the magnetization and MOKE results. MOKE measurements as a function of temperature were made to corroborate EPR results.

  16. Temperature-Dependence of the Rates of Reaction of Trifluoroacetic Acid with Criegee Intermediates.

    Science.gov (United States)

    Chhantyal-Pun, Rabi; McGillen, Max R; Beames, Joseph M; Khan, M Anwar H; Percival, Carl J; Shallcross, Dudley E; Orr-Ewing, Andrew J

    2017-07-24

    The rate coefficients for gas-phase reaction of trifluoroacetic acid (TFA) with two Criegee intermediates, formaldehyde oxide and acetone oxide, decrease with increasing temperature in the range 240-340 K. The rate coefficients k(CH 2 OO + CF 3 COOH)=(3.4±0.3)×10 -10  cm 3  s -1 and k((CH 3 ) 2 COO + CF 3 COOH)=(6.1±0.2)×10 -10  cm 3  s -1 at 294 K exceed estimates for collision-limited values, suggesting rate enhancement by capture mechanisms because of the large permanent dipole moments of the two reactants. The observed temperature dependence is attributed to competitive stabilization of a pre-reactive complex. Fits to a model incorporating this complex formation give k [cm 3  s -1 ]=(3.8±2.6)×10 -18  T 2 exp((1620±180)/T) + 2.5×10 -10 and k [cm 3  s -1 ]=(4.9±4.1)×10 -18  T 2 exp((1620±230)/T) + 5.2×10 -10 for the CH 2 OO + CF 3 COOH and (CH 3 ) 2 COO + CF 3 COOH reactions, respectively. The consequences are explored for removal of TFA from the atmosphere by reaction with biogenic Criegee intermediates. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  17. Temperature Dependence of Laser-Induced Demagnetization in Ni: A Key for Identifying the Underlying Mechanism

    Directory of Open Access Journals (Sweden)

    T. Roth

    2012-05-01

    Full Text Available The microscopic mechanisms responsible for the ultrafast loss of magnetic order triggered in ferromagnetic metals by optical excitation are still under debate. One of the ongoing controversies is about the thermal origin of ultrafast demagnetization. Although different theoretical investigations support a main driving mechanism of thermal origin, alternative descriptions in terms of coherent interaction between the laser and the spin system or superdiffusive spin transport have been proposed. Another important matter of debate originates from the experimental observation of two time scales in the demagnetization dynamics of the 4f ferromagnet gadolinium. Here, it is still unclear whether it is necessary to invoke two distinct microscopic mechanisms to explain such behavior, or if one single mechanism is indeed sufficient. To uncover the physics behind these two unsolved issues, we explore the dependence of ultrafast-demagnetization dynamics in nickel through a survey of different laser intensities and ambient temperatures. Measurements in a large range of these external parameters are performed by means of the time-resolved magneto-optical Kerr effect and display a pronounced change in the maximum loss of magnetization and in the temporal profile of the demagnetization traces. The most striking observation is that the same material system (nickel can show a transition from a one-step (one time scale to a two-step (two time scales demagnetization, occurring on increasing the ambient temperature. We find that the fluence and the temperature dependence of ultrafast demagnetization—including the transition from one-step to two-step dynamics—are reproduced theoretically assuming only a single scattering mechanism coupling the spin system to the temperature of the electronic system. This finding means that the origin of ultrafast demagnetization is thermal and that only a single microscopic channel is sufficient to describe magnetization dynamics

  18. Temperature Dependence of Rheology and Polymer Diffusion in Silica/Polystyrene Nanocomposites

    Science.gov (United States)

    Tung, Wei-Shao; Clarke, Nigel; Composto, Russell; Meth, Jeffrey; Winey, Karen

    2015-03-01

    Time-temperature superposition using the WLF equation is well-established for both the zero shear viscosity and the polymer diffusion coefficient in homopolymer melts. This talk will present the temperature-dependence of polymer dynamics in polymer nanocomposites comprised of polystyrene and phenyl-capped silica nanoparticles (0 - 50 vol%). The WLF equation fits the temperature dependence of the tracer polymer diffusion coefficient and the fitting parameter (B/fo) decreases smoothly with nanoparticle concentration suggesting an increase in the thermal expansion coefficient for the free volume. The WLF equation also fits the temperature dependence of the zero shear viscosity from oscillatory shear experiments, although the fitting parameter (B/fo) increases substantially with nanoparticle concentration. This discrepancy between the diffusion and rheology will be discussed with respect to the reptation model, which predicts that the temperature dependence of polymer diffusion depends predominately on the temperature dependence of local viscosity, and the elastic response in nanocomposites. National Science Foundation DMR-12-10379.

  19. Temperature dependence of 1H NMR chemical shifts and its influence on estimated metabolite concentrations.

    Science.gov (United States)

    Wermter, Felizitas C; Mitschke, Nico; Bock, Christian; Dreher, Wolfgang

    2017-07-06

    Temperature dependent chemical shifts of important brain metabolites measured by localised 1H MRS were investigated to test how the use of incorrect prior knowledge on chemical shifts impairs the quantification of metabolite concentrations. Phantom measurements on solutions containing 11 metabolites were performed on a 7 T scanner between 1 and 43 °C. The temperature dependence of the chemical shift differences was fitted by a linear model. Spectra were simulated for different temperatures and analysed by the AQSES program (jMRUI 5.2) using model functions with chemical shift values for 37 °C. Large differences in the temperature dependence of the chemical shift differences were determined with a maximum slope of about ±7.5 × 10-4 ppm/K. For 32-40 °C, only minor quantification errors resulted from using incorrect chemical shifts, with the exception of Cr and PCr. For 1-10 °C considerable quantification errors occurred if the temperature dependence of the chemical shifts was neglected. If 1H MRS measurements are not performed at 37 °C, for which the published chemical shift values have been determined, the temperature dependence of chemical shifts should be considered to avoid systematic quantification errors, particularly for measurements on animal models at lower temperatures.

  20. Sex reversal triggers the rapid transition from genetic to temperature-dependent sex.

    Science.gov (United States)

    Holleley, Clare E; O'Meally, Denis; Sarre, Stephen D; Marshall Graves, Jennifer A; Ezaz, Tariq; Matsubara, Kazumi; Azad, Bhumika; Zhang, Xiuwen; Georges, Arthur

    2015-07-02

    Sex determination in animals is amazingly plastic. Vertebrates display contrasting strategies ranging from complete genetic control of sex (genotypic sex determination) to environmentally determined sex (for example, temperature-dependent sex determination). Phylogenetic analyses suggest frequent evolutionary transitions between genotypic and temperature-dependent sex determination in environmentally sensitive lineages, including reptiles. These transitions are thought to involve a genotypic system becoming sensitive to temperature, with sex determined by gene-environment interactions. Most mechanistic models of transitions invoke a role for sex reversal. Sex reversal has not yet been demonstrated in nature for any amniote, although it occurs in fish and rarely in amphibians. Here we make the first report of reptile sex reversal in the wild, in the Australian bearded dragon (Pogona vitticeps), and use sex-reversed animals to experimentally induce a rapid transition from genotypic to temperature-dependent sex determination. Controlled mating of normal males to sex-reversed females produces viable and fertile offspring whose phenotypic sex is determined solely by temperature (temperature-dependent sex determination). The W sex chromosome is eliminated from this lineage in the first generation. The instantaneous creation of a lineage of ZZ temperature-sensitive animals reveals a novel, climate-induced pathway for the rapid transition between genetic and temperature-dependent sex determination, and adds to concern about adaptation to rapid global climate change.

  1. A Study of the Temperature Dependence of Bienzyme Systems and Enzymatic Chains

    Directory of Open Access Journals (Sweden)

    N. V. Kotov

    2007-01-01

    Full Text Available It is known that most enzyme-facilitated reactions are highly temperature dependent processes. In general, the temperature coefficient, Q10, of a simple reaction reaches 2.0–3.0. Nevertheless, some enzyme-controlled processes have much lower Q10 (about 1.0, which implies that the process is almost temperature independent, even if individual reactions involved in the process are themselves highly temperature dependent. In this work, we investigate a possible mechanism for this apparent temperature compensation: simple mathematical models are used to study how varying types of enzyme reactions are affected by temperature. We show that some bienzyme-controlled processes may be almost temperature independent if the modules involved in the reaction have similar temperature dependencies, even if individually, these modules are strongly temperature dependent. Further, we show that in non-reversible enzyme chains the stationary concentrations of metabolites are dependent only on the relationship between the temperature dependencies of the first and last modules, whilst in reversible reactions, there is a dependence on every module. Our findings suggest a mechanism by which the metabolic processes taking place within living organisms may be regulated, despite strong variation in temperature.

  2. Behavior of the smectic A phase of colloidal goethite in a magnetic field

    NARCIS (Netherlands)

    van den Pol, E.; Petukhov, A.V.; Byelov, D.; Thies-Weesie, D.M.E.; Snigirev, A.; Snigireva, I.; Vroege, G.J.

    2010-01-01

    The behavior of the smectic A phase of colloidal goethite in a magnetic field has been studied using small-angle X-ray scattering. It was found that in systems with a high polydispersity the smectic phase aligns parallel to a small field and it transforms into a columnar phase in high fields. In

  3. Crystal-Structure-Based Modeling Study of Temperature-Dependent Fracture Toughness for Brittle Coating Deposited on Ductile Substrate

    Science.gov (United States)

    Gu, Yichen; Chen, Kuiying; Liu, Rong; Yao, Matthew X.; Collier, Rachel

    2016-10-01

    The temperature-dependent fracture toughness of a brittle coating/ductile substrate system, WC-10Co4Cr deposited on 1018 low carbon steel, is evaluated at microscopic level using an indentation-based model in terms of the Arrhenius-type equation and rate-controlling theory. The formulation of the model utilizes the parameters of crystal structures of each phase in the coating material. The slip systems of hard hexagonal δ-WC phase and soft FCC α-Co phase are analyzed. The fracture toughness of the two-phase coating is obtained by integrating the fracture toughness of single δ-WC phase coating and that of single α-Co phase coating using either the basic mixture method or the unconstrained mixture method. The results suggest that the fracture toughness of WC-10Co4Cr coating/1018 low carbon steel substrate system may remain constant until the temperature reaches a critical value, about 200 K, and ranges from 2.16 to 10.82 {{MPa}}{{m}}^{1/2} , with temperature increasing from room temperature (298 K) to 1000 K.

  4. The effect of temperature dependent tissue parameters on acoustic radiation force induced displacements

    CERN Document Server

    Suomi, Visa; Konofagou, Elisa; Cleveland, Robin

    2016-01-01

    Multiple ultrasound elastography techniques rely on acoustic radiation force (ARF) in monitoring high-intensity focused ultrasound (HIFU) therapy. However, ARF is dependent on tissue attenuation and sound speed, both of which are also known to change with temperature making the therapy monitoring more challenging. Furthermore, the viscoelastic properties of tissue are also temperature dependent, which affects the displacements induced by ARF. The aim of this study is to quantify the temperature dependent changes in the acoustic and viscoelastic properties of liver and investigate their effect on ARF induced displacements by using both experimental methods and simulations. Furthermore, the temperature dependent viscoelastic properties of liver are experimentally measured over a frequency range of 0.1-200 Hz at temperatures reaching 80 C, and both conventional and fractional Zener models are used to fit the data. The fractional Zener model was found to fit better with the experimental viscoelasticity data with ...

  5. Temperature dependence of a refractive index sensor based on a macrobending micro-plastic optical fiber.

    Science.gov (United States)

    Jing, Ning; Teng, Chuanxin; Zhao, Xiaowei; Zheng, Jie

    2015-03-10

    We investigate the temperature dependence of a refractive index (RI) sensor based on a macrobending micro-plastic optical fiber (m-POF) both theoretically and experimentally. The performance of the RI sensor at different temperatures (10°C-70°C) is measured and simulated over an RI range from 1.33 to 1.45. It is found that the temperature dependent bending loss and RI measurement deviation monotonically change with temperature, and the RI deviation has a higher gradient with temperature variation for a higher measured RI. Because of the linear trend of temperature dependence of the sensor, it is feasible to correct for changes in ambient temperature.

  6. Investigation on the effects of temperature dependency of material parameters on a thermoelastic loading problem

    Science.gov (United States)

    Kumar, Anil; Mukhopadhyay, Santwana

    2017-08-01

    The present work is concerned with the investigation of thermoelastic interactions inside a spherical shell with temperature-dependent material parameters. We employ the heat conduction model with a single delay term. The problem is studied by considering three different kinds of time-dependent temperature and stress distributions applied at the inner and outer surfaces of the shell. The problem is formulated by considering that the thermal properties vary as linear function of temperature that yield nonlinear governing equations. The problem is solved by applying Kirchhoff transformation along with integral transform technique. The numerical results of the field variables are shown in the different graphs to study the influence of temperature-dependent thermal parameters in various cases. It has been shown that the temperature-dependent effect is more prominent in case of stress distribution as compared to other fields and also the effect is significant in case of thermal shock applied at the two boundary surfaces of the spherical shell.

  7. Temperature dependence of the ClONO{sub 2} UV absorption spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Burkholder, J.B.; Talukdar, R.K.; Ravishankara, A.R. [Univ. of Colorado, Boulder, CO (United States)

    1994-04-01

    The temperature dependence of the ClONO{sub 2} absorption spectrum has been measured between 220 and 298 K and between 195 and 430 nm using a diode array spectrometer. The absorption cross sections were determined using both: (1) absolute pressure measurements at 296 K and (2) measurements at various temperatures relative to 296 K using a dual absorption cell arrangement. The temperature dependence of the ClONO{sub 2} absorption spectrum shows very broad structure. The amplitude of the temperature dependence relative to that at 296 K is weak at short wavelengths, < 2% at 215 nm and 220 K, but significant at the wavelengths important in the stratosphere, {approximately} 30% at 325 nm and 220 K. The authors ClONO{sub 2} absorption cross section data are in good general agreement with the previous measurements of Molina and Molina.

  8. Temperature dependence of the ClONO2 UV absorption spectrum

    Science.gov (United States)

    Burkholder, James B.; Talukdar, Ranajit K.; Ravishankara, A. R.

    1994-01-01

    The temperature dependence of the ClONO2 absorption spectrum has been measured between 220 and 298 K and between 195 and 430 nm using a diode array spectrometer. The absorption cross sections were determined using both: (1) absolute pressure measurements at 296 K and (2) measurements at various temperatures relative to 296 K using a dual absorption cell arrangement. The temperature dependence of the ClONO2 absorption spectrum shows very broad structure. The amplitude of the temperature dependence relative to that at 296 K is weak at short wavelengths, less than 2% at 215 nm and 220 K, but significant at the wavelengths important in the stratosphere, about 30% at 325 nm and 220 K. Our ClONO2 absorption cross section data are in good general agreement with the previous measurements of Molina and Molina (1979).

  9. Phase Separation Behavior and System Properties of Aqueous Two-Phase Systems with Polyethylene Glycol and Different Salts: Experiment and Correlation

    OpenAIRE

    Haihua Yuan; Yang Liu; Wanqian Wei; Yongjie Zhao

    2015-01-01

    The phase separation behaviors of PEG1000/sodium citrate, PEG4000/sodium citrate, PEG1000/ammonium sulfate, and PEG4000/ammonium sulfate aqueous two-phase systems were investigated, respectively. There are two distinct situations for the phase separation rate in the investigated aqueous two-phase systems: one state is top-continuous phase with slow phase separation rate and strong bottom-continuous phase with fast phase separation rate and weak volume ratio dependence. The system properties s...

  10. Temperature dependence of the electrical, mechanical and electromechanical properties of high sensitivity novel piezoceramics

    Directory of Open Access Journals (Sweden)

    Algueró, M.

    2004-04-01

    Full Text Available The temperature dependence of the ε33 T dielectric permittivity and losses of piezoelectric Mn doped 0.65Pb(Mg1/3Nb2/3O3-0.35PbTiO3 ceramics has been measured up to 350oC at frequencies between 1 and 100 kHz by impedance spectroscopy. The temperature dependence of the low frequency Young´s modulus and mechanical losses of the ceramics has been measured in the same temperature range by dynamic mechanical analysis in three points bending configuration. Complex ε33 T, s11 E compliance and d31 piezoelectric coefficients have been obtained from radial piezoelectric resonances at temperatures up to 90oC (before depolarisation by an automatic iterative method. All the measurements reflect the occurrence of the ferroelectric rhombohedral to ferroelectric tetragonal phase transition, which is thougth to be responsible of the high electromechanical response of the PMN-PT system, and allow describing some of its characteristics for the investigated ceramics.

    Se ha medido por espectroscopía de impedancias la dependencia con la temperatura hasta 350oC de la permitividad y las pérdidas dieléctricas, ε33 T y tan δ, de cerámicas piezoeléctricas de 0.65Pb(Mg1/3Nb2/3O3-0.35PbTiO3 dopadas con Mn a frecuencias entre 1 y 100 kHz. Se ha medido por análisis mecánico dinámico en la configuración de flexión por tres puntos la dependencia con la temperatura en el mismo rango del módulo de Young y las pérdidas mecánicas de baja frecuencia de las cerámicas. Se han obtenido por un método automático iterativo los coeficientes del material ε33 T, módulo elástico s11 E y coeficiente piezoeléctrico d31 en forma compleja a partir de resonancias radiales piezoeléctricas a temperaturas entre ambiente y 90oC (antes de la despolarización. Todas las medidas reflejan la existencia de la transición de la fase ferroeléctrica con estructura romboédrica a la fase ferroeléctrica con estructura tetragonal, que se cree responsable de la alta respuesta

  11. Temperature dependent properties of InSb and InAs nanowire field-effect transistors

    Science.gov (United States)

    Nilsson, Henrik A.; Caroff, Philippe; Thelander, Claes; Lind, Erik; Karlström, Olov; Wernersson, Lars-Erik

    2010-04-01

    We present temperature dependent electrical measurements on InSb and InAs nanowire field-effect transistors (FETs). The FETs are fabricated from InAs/InSb heterostructure nanowires, where one complete transistor is defined within each of the two segments. Both the InSb and the InAs FETs are n-type with good current saturation and low voltage operation. The off-current for the InSb FET shows a strong temperature dependence, which we attribute to a barrier lowering due to an increased band-to-band tunneling in the drain part of the channel.

  12. DETERMINATION OF TEMPERATURE DISTRIBUTION FOR ANNULAR FINS WITH TEMPERATURE DEPENDENT THERMAL CONDUCTIVITY BY HPM

    Directory of Open Access Journals (Sweden)

    Davood Domairry Ganji

    2011-01-01

    Full Text Available In this paper, homotopy perturbation method has been used to evaluate the temperature distribution of annular fin with temperature-dependent thermal conductivity and to determine the temperature distribution within the fin. This method is useful and practical for solving the nonlinear heat transfer equation, which is associated with variable thermal conductivity condition. The homotopy perturbation method provides an approximate analytical solution in the form of an infinite power series. The annular fin heat transfer rate with temperature-dependent thermal conductivity has been obtained as a function of thermo-geometric fin parameter and the thermal conductivity parameter describing the variation of the thermal conductivity.

  13. Temperature-Dependent Diffusion Coefficients from ab initio Computations: Hydrogen in Nickel

    Energy Technology Data Exchange (ETDEWEB)

    E Wimmer; W Wolf; J Sticht; P Saxe; C Geller; R Najafabadi; G Young

    2006-03-16

    The temperature-dependent mass diffusion coefficient is computed using transition state theory. Ab initio supercell phonon calculations of the entire system provide the attempt frequency, the activation enthalpy, and the activation entropy as a function of temperature. Effects due to thermal lattice expansion are included and found to be significant. Numerical results for the case of hydrogen in nickel demonstrate a strong temperature dependence of the migration enthalpy and entropy. Trapping in local minima along the diffusion path has a pronounced effect especially at low temperatures. The computed diffusion coefficients with and without trapping bracket the available experimental values over the entire temperature range between 0 and 1400 K.

  14. The Temperature Dependence of the Debye-Waller Factor of Magnesium

    DEFF Research Database (Denmark)

    Sledziewska-Blocka, D.; Lebech, Bente

    1976-01-01

    The temperature dependence of the average Debye-Waller factor for magnesium was measured by means of neutron diffraction spectrometry. The experimental results obtained in the temperature range from 5 to 256 K are compared with theoretical calculations, using the harmonic and quasi-harmonic appro......The temperature dependence of the average Debye-Waller factor for magnesium was measured by means of neutron diffraction spectrometry. The experimental results obtained in the temperature range from 5 to 256 K are compared with theoretical calculations, using the harmonic and quasi...

  15. Temperature dependence of photoluminescence from submonolayer deposited InGaAs/GaAs quantum dots

    DEFF Research Database (Denmark)

    Xu, Zhangcheng; Leosson, K.; Birkedal, Dan

    2002-01-01

    The temperature dependence of photoluminescence (PL) from self-assembled InGaAs quantum dots (QD's) grown by submonolayer deposition mode (non-SK mode), is investigated. It is found that the PL spectra are dominated by the ground-state transitions at low temperatures, but increasingly by the exci......The temperature dependence of photoluminescence (PL) from self-assembled InGaAs quantum dots (QD's) grown by submonolayer deposition mode (non-SK mode), is investigated. It is found that the PL spectra are dominated by the ground-state transitions at low temperatures, but increasingly...

  16. Time and Temperature Dependence of Viscoelastic Stress Relaxation in Gold and Gold Alloy Thin Films

    Science.gov (United States)

    Mongkolsuttirat, Kittisun

    Radio frequency (RF) switches based on capacitive MicroElectroMechanical System (MEMS) devices have been proposed as replacements for traditional solid-state field effect transistor (FET) devices. However, one of the limitations of the existing capacitive switch designs is long-term reliability. Failure is generally attributed to electrical charging in the capacitor's dielectric layer that creates an attractive electrostatic force between a moving upper capacitor plate (a metal membrane) and the dielectric. This acts as an attractive stiction force between them that may cause the switch to stay permanently in the closed state. The force that is responsible for opening the switch is the elastic restoring force due to stress in the film membrane. If the restoring force decreases over time due to stress relaxation, the tendency for stiction failure behavior will increase. Au films have been shown to exhibit stress relaxation even at room temperature. The stress relaxation observed is a type of viscoelastic behavior that is more significant in thin metal films than in bulk materials. Metal films with a high relaxation resistance would have a lower probability of device failure due to stress relaxation. It has been shown that solid solution and oxide dispersion can strengthen a material without unacceptable decreases in electrical conductivity. In this study, the viscoelastic behavior of Au, AuV solid solution and AuV2O5 dispersion created by DC magnetron sputtering are investigated using the gas pressure bulge testing technique in the temperature range from 20 to 80°C. The effectiveness of the two strengthening approaches is compared with the pure Au in terms of relaxation modulus and 3 hour modulus decay. The time dependent relaxation curves can be fitted very well with a four-term Prony series model. From the temperature dependence of the terms of the series, activation energies have been deduced to identify the possible dominant relaxation mechanism. The measured

  17. Lamellar Thickness and Stretching Temperature Dependency of Cavitation in Semicrystalline Polymers

    Science.gov (United States)

    Wang, Yaotao; Jiang, Zhiyong; Fu, Lianlian; Lu, Ying; Men, Yongfeng

    2014-01-01

    Polybutene-1 (PB-1), a typical semicrystalline polymer, in its stable form I shows a peculiar temperature dependent strain-whitening behavior when being stretched at temperatures in between room temperature and melting temperature of the crystallites where the extent of strain-whitening weakens with the increasing of stretching temperature reaching a minima value followed by an increase at higher stretching temperatures. Correspondingly, a stronger strain-hardening phenomenon was observed at higher temperatures. The strain-whitening phenomenon in semicrystalline polymers has its origin of cavitation process during stretching. In this work, the effect of crystalline lamellar thickness and stretching temperature on the cavitation process in PB-1 has been investigated by means of combined synchrotron ultrasmall-angle and wide-angle X-ray scattering techniques. Three modes of cavitation during the stretching process can be identified, namely “no cavitation” for the quenched sample with the thinnest lamellae where only shear yielding occurred, “cavitation with reorientation” for the samples stretched at lower temperatures and samples with thicker lamellae, and “cavitation without reorientation” for samples with thinner lamellae stretched at higher temperatures. The mode “cavitation with reorientation” occurs before yield point where the plate-like cavities start to be generated within the lamellar stacks with normal perpendicular to the stretching direction due to the blocky substructure of the crystalline lamellae and reorient gradually to the stretching direction after strain-hardening. The mode of “cavitation without reorientation” appears after yield point where ellipsoidal shaped cavities are generated in those lamellae stacks with normal parallel to the stretching direction followed by an improvement of their orientation at larger strains. X-ray diffraction results reveal a much improved crystalline orientation for samples with thinner lamellae

  18. The Temperature Dependence of the Resistivity the Noble Metals from 0.03 to 9 K.

    Science.gov (United States)

    Steenwyk, Steven Dale

    We present here a thorough investigation of the temperature dependent resistivity (rho)(T) of the noble metals for temperatures from 0.3 K - 9 K. We experimentally determine the magnitude of electron-electron scattering contributions as well as the magnitude and mathematical form of the phonon contribution and its variation with strain and impurity content. We review the basics of the relevant theory including some of the recent calculations of the contribution from various scattering mechanisms, specifically, scattering of electrons by other electrons and by phonons. We consider at length the fundamental effects of the dominant contributors to the residual resistivity, impurity and dislocation scattering, in light of the anisotropy in k-space of the relaxation time determined by these mechanisms. We performed measurements of the resistivity to a precision of one ppm on samples ranging from extremely pure single crystals of Cu and Ag to dilute polycrystalline alloys of Cu with Ag. The techniques required to prepare such samples and to make very high precision measurements are discussed. In particular, treatment is given to some of the unique problems faced in using a SQUID based measuring system on samples of nano-ohm resistance with special attention paid to the use of superconducting chokes and transformers to control the electrical response time of the circuit. The results of our measurements give substantial verification of the calculations of the e-e scattering contribution to (rho)(T). Of special interest is the serendipitious verification of the theory of Bermann, Kaveh and Wiser('(DAG)) explaining the origin of the T('4) behavior we had observed in the earliest work. This theory reproduces a nearly T('4) behavior by a combination of electron-electron and electron-phonon scattering. Our data fit their equations very well. While we expected to find, and indeed did find, the effect of dislocation to be a reduction in the phonon scattering, we did not

  19. Rate- and Temperature-Dependent Material Behavior of a Multilayer Polymer Battery Separator

    Science.gov (United States)

    Avdeev, Ilya; Martinsen, Michael; Francis, Alex

    2014-01-01

    Designing battery packs for safety in automotive applications requires multiscale modeling, as macroscopic deformations due to impact cause the mechanical failure of individual cells on a sub-millimeter level. The separator material plays a critical role in this process, as the thinning or perforating of the separator can lead to thermal runaway and catastrophic failure of an entire battery pack. The electrochemical properties of various polymer separators have been extensively investigated; however, the dependency of mechanical properties of these thin films on various factors, such as high temperature and strain rate, has not been sufficiently characterized. In this study, the macroscopic mechanical properties of a multilayer polymer thin film used as a battery separator are studied experimentally at various temperatures, strain rates, and solvent saturations. Due to the anisotropy of the material, material testing was conducted in two perpendicular directions (machine and transverse directions). Material samples were tested in both dry and saturated conditions at several temperatures, and it was found that temperature and strain rate have a nearly linear effect on the stress experienced by the material. Additionally, saturating the separator material in a common lithium-ion solvent had softened it and had a positive effect on its toughness. The experimental results obtained in this study can be used to develop mathematical constitutive models of the multilayer separator material for subsequent numerical simulations and design.

  20. Universal scaling behavior at the upper critical dimension of non-equilibrium continuous phase transitions

    OpenAIRE

    Lubeck, S.; Heger, P. C.

    2003-01-01

    In this work we analyze the universal scaling functions and the critical exponents at the upper critical dimension of a continuous phase transition. The consideration of the universal scaling behavior yields a decisive check of the value of the upper critical dimension. We apply our method to a non-equilibrium continuous phase transition. But focusing on the equation of state of the phase transition it is easy to extend our analysis to all equilibrium and non-equilibrium phase transitions obs...

  1. Phase Behaviors of Reservoir Fluids with Capillary Eff ect Using Particle Swarm Optimization

    KAUST Repository

    Ma, Zhiwei

    2013-05-06

    The study of phase behavior is important for the oil and gas industry. Many approaches have been proposed and developed for phase behavior calculation. In this thesis, an alternative method is introduced to study the phase behavior by means of minimization of Helmholtz free energy. For a system at fixed volume, constant temperature and constant number of moles, the Helmholtz free energy reaches minimum at the equilibrium state. Based on this theory, a stochastic method called Particle Swarm Optimization (PSO) algorithm, is implemented to compute the phase diagrams for several pure component and mixture systems. After comparing with experimental and the classical PT-ash calculation, we found the phase diagrams obtained by minimization of the Helmholtz Free Energy approach match the experimental and theoretical diagrams very well. Capillary effect is also considered in this thesis because it has a significant influence on the phase behavior of reservoir fluids. In this part, we focus on computing the phase envelopes, which consists of bubble and dew point lines. Both fixed and calculated capillary pressure from the Young-Laplace equation cases are introduced to study their effects on phase envelopes. We found that the existence of capillary pressure will change the phase envelopes. Positive capillary pressure reduces the dew point and bubble point temperatures under the same pressure condition, while the negative capillary pressure increases the dew point and bubble point temperatures. In addition, the change of contact angle and pore radius will affect the phase envelope. The effect of the pore radius on the phase envelope is insignificant when the radius is very large. These results may become reference for future research and study. Keywords: Phase Behavior; Particle Swarm Optimization; Capillary Pressure; Reservoir Fluids; Phase Equilibrium; Phase Envelope.

  2. Comprehensive study of internal quantum efficiency of high-brightness GaN-based light-emitting diodes by temperature-dependent electroluminescence method

    Science.gov (United States)

    Wang, Yaqi; Pan, Mengshu; Li, Ting

    2014-02-01

    We report on the development of a temperature-dependent electroluminescence experimental setup for characterizing the internal quantum efficiency (IQE) of high-brightness GaN-based light-emitting diodes (LEDs). A systematic IQE study of commercial LED chips from major LED manufacturers (including Cree, Nichia, Osram, and Sanan) is presented. The chips show distinctive temperature- and current-dependence in the IQE behavior. Analysis to correlate the onset of droop with the onset of high injection is also presented.

  3. Temperature dependence of structural and optical properties of GeSbTe alloy thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chabli, A. E-mail: achabli@cea.fr; Vergnaud, C.; Bertin, F.; Gehanno, V.; Valon, B.; Hyot, B.; Bechevet, B.; Burdin, M.; Muyard, D

    2002-09-01

    Ge{sub 2}Sb{sub 2}Te{sub 5} films sandwiched by ZnS-SiO{sub 2} layers were studied by spectroscopic ellipsometry from room temperature up to 800 deg. C. An irreversible modification of both materials is pointed out. ZnS cubic phase precipitation occurs after heating at 650 deg. C, shown by grazing incidence X-ray diffraction. Chemical modification in phase change material is observed above 300 deg. C, revealed by a typical behavior of a transparent layer.

  4. Re-entrant phase behavior of a concentrated anionic surfactant system with strongly binding counterions.

    Science.gov (United States)

    Ghosh, Sajal Kumar; Rathee, Vikram; Krishnaswamy, Rema; Raghunathan, V A; Sood, A K

    2009-08-04

    The phase behavior of the anionic surfactant sodium dodecyl sulfate (SDS) in the presence of the strongly binding counterion p-toluidine hydrochloride (PTHC) has been examined using small-angle X-ray diffraction and polarizing microscopy. A hexagonal-to-lamellar transition on varying the PTHC to SDS molar ratio (alpha) occurs through a nematic phase of rodlike micelles (Nc) --> isotropic (I) --> nematic of disklike micelles (N(D)) at a fixed surfactant concentration (phi). The lamellar phase is found to coexist with an isotropic phase (I') over a large region of the phase diagram. Deuterium nuclear magnetic resonance investigations of the phase behavior at phi = 0.4 confirm the transition from N(C) to N(D) on varying alpha. The viscoelastic and flow behaviors of the different phases were examined. A decrease in the steady shear viscosity across the different phases with increasing alpha suggests a decrease in the aspect ratio of the micellar aggregates. From the transient shear stress response of the N() and N(D) nematic phases in step shear experiments, they were characterized to be tumbling and flow aligning, respectively. Our studies reveal that by tuning the morphology of the surfactant micelles strongly binding counterions modify the phase behavior and rheological properties of concentrated surfactant solutions.

  5. Thermal behavior variations in coating thickness using pulse phase thermography

    Energy Technology Data Exchange (ETDEWEB)

    Ranjit, Shrestha; Chung, Yoonjae; Kim, Won Tae [Kongju National University, Cheonan (Korea, Republic of)

    2016-08-15

    This paper presents a study on the use of pulsed phase thermography in the measurement of thermal barrier coating thickness with a numerical simulation. A multilayer heat transfer model was used to analyze the surface temperature response acquired from one-sided pulsed thermal imaging. The test sample comprised four layers: the metal substrate, bond coat, thermally grown oxide and the top coat. The finite element software, ANSYS, was used to model and predict the temperature distribution in the test sample under an imposed heat flux on the exterior of the TBC. The phase image was computed with the use of the software MATLAB and Thermofit Pro using a Fourier transform. The relationship between the coating thickness and the corresponding phase angle was then established with the coating thickness being expressed as a function of the phase angle. The method is successfully applied to measure the coating thickness that varied from 0.25 mm to 1.5 mm.

  6. Lattice dynamics and dielectric functions of multiferroic BiFeO{sub 3}/c-sapphire films determined by infrared reflectance spectra and temperature-dependent Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Zhihua; Yu, Qian [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Wu, Jiada; Sun, Jian [Key Laboratory for Advanced Photonic Materials and Devices, Ministry of Education, Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Hu, Zhigao, E-mail: zghu@ee.ecnu.edu.cn [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Chu, Junhao [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China)

    2012-12-15

    Multiferroic BiFeO{sub 3} (BFO) films have been grown on c-sapphire substrates by pulsed laser deposition under different laser energies (E{sub L}). The X-ray diffraction and Raman spectra indicate that the films are polycrystalline and exhibit the single rhombohedral (R) phase. The crystal distortion becomes weaker with decreasing the E{sub L}, which is described by the ratio of c/a. It was found that different E{sub L} values also lead to the variation of the Bi/Fe ratio. Temperature-dependent Raman spectra were carried out to study the phonon mode evolution behaviors. The three A{sub 1} transverse optical (TO) phonon modes located at 219, 172, and 142 cm{sup -1} shift towards a lower energy side with the temperature due to thermal expansion, thermal disorder and the anharmonic effects of lattice. The E(TO) and three A{sub 1}(TO) phonon frequencies slightly increase with increasing the E{sub L} of the growth condition, which results from the Bi vacancies, the changes of the length and intensity of Bi-O bonds and the local structure distortion in the FeO{sub 6} octahedra. The dielectric functions of the BFO films in the frequency range of 50-8000 cm{sup -1} have been extracted by fitting infrared reflectance spectra with the Lorentz multi-oscillator dispersion model. The variation trend of the dielectric functions with different E{sub L} can be observed and related to the packing density, surface roughness, and defect states. It was concluded that the E{sub L} corresponding to changing the c/a ratio has an obvious influence on the lattice vibrations and intraband transitions of the BFO films. - Highlights: Black-Right-Pointing-Pointer The c/a and Bi/Fe ratios of BiFeO{sub 3} films at different laser energy (E{sub L}). Black-Right-Pointing-Pointer The temperature-dependent evolution of phonon modes. Black-Right-Pointing-Pointer The crystal distortion and Bi vacancies influence the lattice vibration. Black-Right-Pointing-Pointer The E{sub L} effect on the dielectric

  7. NMR and computational studies of the configurational properties of spirodioxyselenuranes. Are dynamic exchange processes or temperature-dependent chemical shifts involved?

    Science.gov (United States)

    Press, David J; McNeil, Nicole M R; Rauk, Arvi; Back, Thomas G

    2012-10-19

    Spirodioxyselenurane 4a and several substituted analogs revealed unexpected (1)H NMR behavior. The diastereotopic methylene hydrogens of 4a appeared as an AB quartet at low temperature that coalesced to a singlet upon warming to 267 K, suggesting a dynamic exchange process with a relatively low activation energy. However, DFT computational investigations indicated high activation energies for exchange via inversion through the selenium center and for various pseudorotation processes. Moreover, the NMR behavior was unaffected by the presence of water or acid catalysts, thereby ruling out reversible Se-O or benzylic C-O cleavage as possible stereomutation pathways. Remarkably, when 4a was heated beyond 342 K, the singlet was transformed into a new AB quartet. Further computations indicated that a temperature dependence of the chemical shifts of the diastereotopic protons results in convergence upon heating, followed by crossover and divergence at still higher temperatures. The NMR behavior is therefore not due to dynamic exchange processes, but rather to temperature dependence of the chemical shifts of the diastereotopic hydrogens, which are coincidentally equivalent at intermediate temperatures. These results suggest the general need for caution in ascribing the coalescence of variable-temperature NMR signals of diastereotopic protons to dynamic exchange processes that could instead be due to temperature-dependent chemical shifts and highlight the importance of corroborating postulated exchange processes through additional computations or experiments wherever possible.

  8. A simple equation for describing the temperature dependent growth of free-floating macrophytes

    NARCIS (Netherlands)

    Heide, van Tj.; Roijackers, R.M.M.; Nes, van E.H.; Peeters, E.T.H.M.

    2006-01-01

    Temperature is one of the most important factors determining growth rates of free-floating macrophytes in the field. To analyse and predict temperature dependent growth rates of these pleustophytes, modelling may play an important role. Several equations have been published for describing

  9. The importance of temperature dependent energy gap in the understanding of high temperature thermoelectric properties

    Science.gov (United States)

    Singh, Saurabh; Pandey, Sudhir K.

    2016-10-01

    In this work, we show the importance of temperature dependent energy band gap, E g (T), in understanding the high temperature thermoelectric (TE) properties of material by considering LaCoO3 (LCO) and ZnV2O4 (ZVO) compounds as a case study. For the fix value of band gap, E g , deviation in the values of α has been observed above 360 K and 400 K for LCO and ZVO compounds, respectively. These deviation can be overcomed by consideration of temperature dependent band gap. The change in used value of E g with respect to temperature is ∼4 times larger than that of In As. This large temperature dependence variation in E g can be attributed to decrement in the effective on-site Coulomb interaction due to lattice expansion. At 600 K, the value of ZT for n and p-doped, LCO is ∼0.35 which suggest that it can be used as a potential material for TE device. This work clearly suggest that one should consider the temperature dependent band gap in predicting the high temperature TE properties of insulating materials.

  10. Temperature dependence of single-event burnout in n-channel power MOSFETs

    Science.gov (United States)

    Johnson, Gregory H.; Schrimpf, Ronald D.; Galloway, Kenneth F.; Koga, Rocky

    1992-12-01

    The temperature dependence of single-event burnout (SEB) in n-channel power MOSFETs is investigated experimentally and analytically. Experimental data are presented which indicate that the SEB susceptibility of the power MOSFET decreases with increasing temperature. A previously reported analytical model that describes the SEB mechanism is updated to include temperature variations. This model is shown to agree with the experimental trends.

  11. Observed and simulated temperature dependence of the liquid water path of low clouds

    Energy Technology Data Exchange (ETDEWEB)

    Del Genio, A.D.; Wolf, A.B. [NASA Goddard Institute for Space Studies, New York, NY (United States)

    1996-04-01

    Data being acquired at the Atmospheric Radiation Measurement (ARM) Southern great Plains (SGP) Cloud and Radiation Testbed (CART) site can be used to examine the factors determining the temperature dependence of cloud optical thickness. We focus on cloud liquid water and physical thickness variations which can be derived from existing ARM measurements.

  12. Temperature-dependent dynamic mechanical properties of magnetorheological elastomers under magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ju, Benxiang, E-mail: jubenxiang@qq.com [National Instrument Functional Materials Engineering Technology Research Center, Chongqing 400707 (China); Tang, Rui; Zhang, Dengyou; Yang, Bailian [National Instrument Functional Materials Engineering Technology Research Center, Chongqing 400707 (China); Yu, Miao; Liao, Changrong [College of Optoelectronic Engineering, Chongqing University, Chongqing 400044 (China)

    2015-01-15

    Both anisotropic and isotropic magnetorheological elastomer (MRE) samples were fabricated by using as-prepared polyurethane (PU) matrix and carbonyl iron particles. Temperature-dependent dynamic mechanical properties of MRE were investigated and analyzed. Due to the unique structural features of as-prepared matrix, temperature has a greater impact on the properties of as-prepared MRE, especially isotropic MRE. With increasing of temperature and magnetic field, MR effect of isotropic MRE can reach up to as high as 4176.5% at temperature of 80 °C, and the mechanism of the temperature-dependent in presence of magnetic field was discussed. These results indicated that MRE is a kind of temperature-dependent material, and can be cycled between MRE and MR plastomer (MRP) by varying temperature. - Highlights: • Both anisotropic and isotropic MRE were fabricated by using as-prepared matrix. • Temperature-dependent properties of MRE under magnetic field were investigated. • As-prepared MRE can transform MRE to MRP by adjusting temperature.

  13. Temperature dependence of UV radiation effects in Arctic and temperate isolates of three red macrophytes

    NARCIS (Netherlands)

    van de Poll, W.H.; Eggert, A.; Buma, A.G.J.; Breeman, Arno

    The temperature dependence of UV effects was studied for Arctic and temperate isolates of the red macrophytes Palmaria palmata, Coccotylus truncatus and Phycodrys rubens. The effects of daily repeated artificial ultraviolet B and A radiation (UVBR: 280-320 nm, UVAR: 320-400 nm) treatments were

  14. The Heated Laminar Vertical Jet in a Liquid with Power-law Temperature Dependence of Density

    OpenAIRE

    Sharifulin, V. A.

    2009-01-01

    The analytical solution of heated laminar vertical jet in a liquid with power-law temperature dependence of density was obtained in the skin-layer approximation for certain values of Prandtl number. Cases of point and linear sources were considered.

  15. Temperature-dependent infrared and calorimetric studies on arsenicals adsorption from solution to hematite nanoparticles

    Science.gov (United States)

    To address the lack of systematic and surface sensitive studies on the adsorption energetics of arsenic compounds on metal (oxyhydr)oxides, we conducted temperature-dependent ATR-FTIR studies for the adsorption of arsenate, monomethylarsonic acid, and dimethylarsinic acid on hematite nanoparticles a...

  16. Temperature Dependence of the Polariton Linewidth in a GaAs Quantum Well Microcavity

    DEFF Research Database (Denmark)

    Borri, P.; Jensen, Jacob Riis; Langbein, W.

    2000-01-01

    The temperature dependent linewidths of the polariton resonances in a GaAs/AlGaAs single quantum well microcavity are measured. Due to the dominant homogeneous broadening of the investigated resonances, a direct linewidth analysis of the reflectivity spectra allows us to investigate the role of s...

  17. Theory of Temperature Dependence of the Magnetization in Rare-Earth-Transition-Metal Alloys

    DEFF Research Database (Denmark)

    Szpunar, B.; Lindgård, Per-Anker

    1977-01-01

    It is shown that the temperature dependence of the magnetic moments and Curie and ferrimagnetic compensation temperatures for Gdl-xTx (T = Co, Ni, and Fe) and Y1-xCox can be accounted for by a simple model assuming a RKKY interaction between the rare-earth moments and the transition-metal pseudo-...

  18. PRELIMINARY s'T'u_D|Es" on TEMPERATURE DEPENDENCE 'QF ...

    African Journals Online (AJOL)

    Bartington MS2B sensor operating at low frequency. The temperature dependence of magnetic.susceptibility experiment was carried out on representative samples using the. Bartington MS2X/T system (Fig.2). The samples' were frozen in the refrigerator to nearly 0°C and then quickly transferred to the water (MS2W) sensor.

  19. Temperature dependence of the superconducting proximity effect quantified by scanning tunneling spectroscopy

    Directory of Open Access Journals (Sweden)

    A. Stępniak

    2015-01-01

    Full Text Available Here, we present the first systematic study on the temperature dependence of the extension of the superconducting proximity effect in a 1–2 atomic layer thin metallic film, surrounding a superconducting Pb island. Scanning tunneling microscopy/spectroscopy (STM/STS measurements reveal the spatial variation of the local density of state on the film from 0.38 up to 1.8 K. In this temperature range the superconductivity of the island is almost unaffected and shows a constant gap of a 1.20 ± 0.03 meV. Using a superconducting Nb-tip a constant value of the proximity length of 17 ± 3 nm at 0.38 and 1.8 K is found. In contrast, experiments with a normal conductive W-tip indicate an apparent decrease of the proximity length with increasing temperature. This result is ascribed to the thermal broadening of the occupation of states of the tip, and it does not reflect an intrinsic temperature dependence of the proximity length. Our tunneling spectroscopy experiments shed fresh light on the fundamental issue of the temperature dependence of the proximity effect for atomic monolayers, where the intrinsic temperature dependence of the proximity effect is comparably weak.

  20. Dissecting the frog inner ear with Gaussian noise .2. Temperature dependence of inner ear function

    NARCIS (Netherlands)

    vanDijk, P; Wit, HP; Segenhout, JM

    1997-01-01

    The temperature dependence of the response of single primary auditory nerve fibers (n = 31) was investigated in the European edible frog, Rana esculenta (seven ears). Nerve fiber responses were analyzed with Wiener kernel analysis and polynomial correlation. The responses were described with a

  1. Temperature dependence of electronic heat capacity in Holstein model of DNA

    Science.gov (United States)

    Fialko, N.; Sobolev, E.; Lakhno, V.

    2016-04-01

    The dynamics of charge migration was modeled to calculate temperature dependencies of its thermodynamic equilibrium values such as energy and electronic heat capacity in homogeneous adenine fragments. The energy varies from nearly polaron one at T ∼ 0 to midpoint of the conductivity band at high temperatures. The peak on the graph of electronic heat capacity is observed at the polaron decay temperature.

  2. Demonstrating the Temperature Dependence of Density via Construction of a Galilean Thermometer

    Science.gov (United States)

    Priest, Marie A.; Padgett, Lea W.; Padgett, Clifford W.

    2011-01-01

    A method for the construction of a Galilean thermometer out of common chemistry glassware is described. Students in a first-semester physical chemistry (thermodynamics) class can construct the Galilean thermometer as an investigation of the thermal expansivity of liquids and the temperature dependence of density. This is an excellent first…

  3. Indications for a changing electricity demand pattern : The temperature dependence of electricity demand in the Netherlands

    NARCIS (Netherlands)

    Hekkenberg, M.; Benders, R. M. J.; Moll, H. C.; Uiterkamp, A. J. M. Schoot

    This study assesses the electricity demand pattern in the relatively temperate climate of the Netherlands (latitude 52 degrees 30'N). Daily electricity demand and average temperature during the period from 1970 until 2007 are investigated for possible trends in the temperature dependence of

  4. The temperature dependence of Cr3+ : YAG zero-phonon lines

    NARCIS (Netherlands)

    Marceddu, Marco; Manca, Marianna; Ricci, Pier Carlo; Anedda, Alberto

    2012-01-01

    This paper deals with the photoluminescence temperature dependence of the zero-phonon lines of Cr3+ ions in an yttrium aluminium garnet (YAG) matrix. Experimental data were analysed in the framework of electron-phonon coupling in the quadratic approximation and it was found that Cr3+ ions in the YAG

  5. Analogy between temperature-dependent and concentration-dependent bacterial killing

    NARCIS (Netherlands)

    Neef, C.; van Gils, Stephanus A.; Ijzerman, W.L.

    2002-01-01

    In this article an analogy between temperature-dependent and concentration-dependent bacterial killing is described. The validation process of autoclaves uses parameters such as reduction rate constant k, decimal reduction time D and resistance coefficient z from an imaginary microorganism to

  6. Temperature dependence of CIE-x,y color coordinates in YAG:Ce single crystal phosphor

    Czech Academy of Sciences Publication Activity Database

    Rejman, M.; Babin, Vladimir; Kučerková, Romana; Nikl, Martin

    2017-01-01

    Roč. 187, Jul (2017), s. 20-25 ISSN 0022-2313 R&D Projects: GA TA ČR TA04010135 Institutional support: RVO:68378271 Keywords : YAG:Ce * single-crystal * simulation * energy level lifetime * white LED * CIE * temperature dependence Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.686, year: 2016

  7. A theoretical analysis for temperature dependences of laser-induced damage threshold

    Science.gov (United States)

    Mikami, K.; Motokoshi, S.; Somekawa, T.; Jitsuno, T.; Fujita, M.; Tanaka, K. A.

    2013-11-01

    The temperature dependence of the laser-induced damage threshold on optical coatings was studied in detail for laser pulses from 123 K to 473 K at different temperature using Nd:YAG laser (wavelength 1064 nm and pulse width 4 ns) and Ti:Sapphire laser (wavelength 800 nm and pulse width 100 fs, 2 ps, and 200 ps). The six kinds of optical monolayer coatings were prepared by electron beam evaporation and the coating materials were SiO2, Al2O3, HfO2, ZrO2, Ta2O5, and MgF2. For pulses longer than a few picoseconds, the laser-induced damage threshold of single-layer coatings increased with decreasing temperature. This temperature dependence was reversed for pulses shorter than a few picoseconds. We describe the physics models to explain the observed scaling. The electron avalanche is essential to explain the differences in the temperature dependence. In other words, the balance between linear process such as electron avalanche etc. and nonlinear process such as multiphoton ionization etc. will be able to decide the tendency of the temperature dependence. The proposed model also gives one of possibility for an extremely high LIDT optics.

  8. Temperature dependence of the electrical conductivity of amorphous V sub x Si sub 1 minus x

    Energy Technology Data Exchange (ETDEWEB)

    Boghosian, H.H.; Howson, M.A. (Department of Physics, The University of Leeds, Leeds LS2 9JT, United Kingdom (GB))

    1990-04-15

    We present results for the temperature dependence of electrical conductivity for amorphous V{sub {ital x}}Si{sub 1{minus}{ital x}} alloys. The alloys investigated span the composition range from {ital x}=0.5 to 0.1. For the alloys with more than 20 at. % V, the temperature dependence could be successfully fitted with use of the theories of quantum interference effects, and values for the spin-orbit and inelastic scattering rates are extracted from the fits. As the concentration of V is decreased, there is evidence for a metal-insulator transition seen at around 15 to 13 at. % V. The temperature dependence of the conductivity is surprisingly similar for all the alloys on the metallic side of the transition, showing a clear {ital T}{sup 1/2} dependence at the lowest temperatures while the insulating V{sub 0.1}Si{sub 0.9} alloy shows evidence for variable-range-hopping conduction. The V{sub 0.13}Si{sub 0.87} alloy, which is right at the transition, exhibits an unusual temperature dependence. The sample is metallic and seems to follow a {ital T}{sup 1/3} dependence at low temperatures.

  9. Hartmann flow with temperature-dependent physical properties. [magnetohydrodynamics of liquid metal

    Science.gov (United States)

    Linn, G. T.; Walker, J. S.

    1978-01-01

    Attention is given to the steady, fully developed, one-dimensional flow of a liquid metal in which thermal conductivity, electrical conductivity, and viscosity are functions of temperature. It is found that the properties are decreasing functions of temperature and the first differences between temperature-dependent and constant properties are discussed.

  10. Transient energy growth modulation by temperature dependent transport properties in a stratified plane Poiseuille flow

    NARCIS (Netherlands)

    Rinaldi, E.; Boersma, B.J.; Pecnik, R.

    2015-01-01

    We investigate the effect of temperature dependent thermal conductivity ? and isobaric specific heat c_P on the transient amplification of perturbations in a thermally stratified laminar plane Poiseuille flow. It is shown that for decreasing thermal conductivity the maximum transient energy growth

  11. THE TEMPERATURE DEPENDENCE OF THE EMISSION OF PERCHLORO- ETHYLENE FROM DRY CLEANED FABRICS

    Science.gov (United States)

    A study was conducted to evaluate the emission of perchloroethylene (tetrachloroethylene) from freshly dry cleaned fabrics using small environmental test chambers. The temperature dependence of the release of perchloroethylene was evaluated over a temperature range of 20 to 45°C....

  12. Habitat related variation in UV tolerance of tropical marine red macrophytes is not temperature dependent

    NARCIS (Netherlands)

    van de Poll, W.H.; Bischof, K.; Buma, A.G.J.; Breeman, Arno

    Because tropical marine macrophytes experience high ultraviolet-B radiation (UVBR: 280-320 nm) it is assumed that they have high UV tolerance. This was investigated by examining the relative UV sensitivity of five Caribbean red macrophytes. Furthermore, the possibility of temperature dependence of

  13. A Simple Method to Calculate the Temperature Dependence of the Gibbs Energy and Chemical Equilibrium Constants

    Science.gov (United States)

    Vargas, Francisco M.

    2014-01-01

    The temperature dependence of the Gibbs energy and important quantities such as Henry's law constants, activity coefficients, and chemical equilibrium constants is usually calculated by using the Gibbs-Helmholtz equation. Although, this is a well-known approach and traditionally covered as part of any physical chemistry course, the required…

  14. Temperature-dependent remineralization of organic matter - small impacts on the carbon cycle

    Science.gov (United States)

    Laufkötter, Charlotte; John, Jasmin; Stock, Charles; Dunne, John

    2017-04-01

    The temperature dependence of remineralization of organic matter is regularly mentioned as important but unconstrained factor, with the potential to cause considerable uncertainty in projections of marine export production, carbon sequestration and oceanic carbon uptake. We have recently presented evidence for a temperature dependence of the particulate organic matter (POC) flux to depth, based on a compilation of observations. Here, we explore the impacts of the new temperature dependence on net primary production, POC flux and oceanic carbon uptake in the ecosystem model COBALT coupled to GFDL's ESM2M Coupled Climate-Carbon Earth System Model. We have implemented two remineralization schemes: COBALT-R1 includes a temperature dependence using parameter values according to our data analysis. COBALT-R1 shows very high remineralization in warm surface waters. The data used to constrain it, however, comes from colder water below 150m. Colonization of sinking material occurs throughout the euphotic zone, potentially reducing remineralization in the immediate vicinity of the ocean surface relative to R1 rates [Mislan et al., 2014]. We thus considered a second model version (COBALT-R2) that decreases remineralization towards the surface but ramped up remineralization rates to R1 values below 150m. After 1300 years of spin-up, the effects of the temperature dependence are most visible in the intermediate part of the water column (150 - 1500m), with stronger remineralization in the warmer upper water but weaker remineralization below, such that the carbon flux at 2000m is barely affected. Also, both COBALT-R1 and COBALT-R2 simulate lower POC flux in the low latitudes and higher POC flux in high latitudes compared to the original model version. In terms of future changes, COBALT-R1 projects an increase in NPP while COBALT-R2 projects a moderate decrease. However, the percentaged decrease in POC flux at 100m is identical in both model versions and the original COBALT

  15. Natural convection with evaporation in a vertical cylindrical cavity under the effect of temperature-dependent surface tension

    Science.gov (United States)

    Kozhevnikov, Danil A.; Sheremet, Mikhail A.

    2018-01-01

    The effect of surface tension on laminar natural convection in a vertical cylindrical cavity filled with a weak evaporating liquid has been analyzed numerically. The cylindrical enclosure is insulated at the bottom, heated by a constant heat flux from the side, and cooled by a non-uniform evaporative heat flux from the top free surface having temperature-dependent surface tension. Governing equations with corresponding boundary conditions formulated in dimensionless stream function, vorticity, and temperature have been solved by finite difference method of the second-order accuracy. The influence of Rayleigh number, Marangoni number, and aspect ratio on the liquid flow and heat transfer has been studied. Obtained results have revealed that the heat transfer rate at free surface decreases with Marangoni number and increases with Rayleigh number, while the average temperature inside the cavity has an opposite behavior; namely, it growths with Marangoni number and reduces with Rayleigh number.

  16. Temperature dependent electrical characteristics of an organic-inorganic heterojunction obtained from a novel organometal Mn complex

    Energy Technology Data Exchange (ETDEWEB)

    Ocak, Y.S., E-mail: yusufselim@gmail.co [Department of Science, Faculty of Education, University of Dicle, Diyarbakir (Turkey); Ebeoglu, M.A. [Department of Electrical and Electronics Engineering, Faculty of Engineering, University of Dumlupinar, Kutahya (Turkey); Topal, G. [Department of Chemistry, Faculty of Education, University of Dicle, Diyarbakir (Turkey); Kilicoglu, T., E-mail: tahsin@dicle.edu.t [Department of Physics, Faculty of Art and Science, University of Dicle, Diyarbakir (Turkey); Department of Physics, Faculty of Art and Science, University of Batman, Batman (Turkey)

    2010-05-01

    This study includes synthesizing a Mn hexaamide (MnHA) organometal compound (C{sub 27}H{sub 21}N{sub 9}O{sub 6}MnCl{sub 2}).(1/2H{sub 2}O), fabrication of MnHA/n-Si organic-inorganic heterojunction and analysis of conduction mechanism of the device over the room temperature. After synthesizing the molecule, the structure of the compound was determined using spectroscopic methods. The Sn/MnHA/n-Si structure was constructed by forming a thin MnHA layer on n-Si inorganic semiconductor and evaporating Sn metal on organic complex. The structure has shown good rectifying behavior and obeys the thermionic emission theory. The current-voltage (I-V) characteristics of the diode have been measured at temperatures ranging from 300 to 380 K at 10 K intervals to determine the temperature dependent electrical characteristics of the device.

  17. Natural convection with evaporation in a vertical cylindrical cavity under the effect of temperature-dependent surface tension

    Science.gov (United States)

    Kozhevnikov, Danil A.; Sheremet, Mikhail A.

    2017-07-01

    The effect of surface tension on laminar natural convection in a vertical cylindrical cavity filled with a weak evaporating liquid has been analyzed numerically. The cylindrical enclosure is insulated at the bottom, heated by a constant heat flux from the side, and cooled by a non-uniform evaporative heat flux from the top free surface having temperature-dependent surface tension. Governing equations with corresponding boundary conditions formulated in dimensionless stream function, vorticity, and temperature have been solved by finite difference method of the second-order accuracy. The influence of Rayleigh number, Marangoni number, and aspect ratio on the liquid flow and heat transfer has been studied. Obtained results have revealed that the heat transfer rate at free surface decreases with Marangoni number and increases with Rayleigh number, while the average temperature inside the cavity has an opposite behavior; namely, it growths with Marangoni number and reduces with Rayleigh number.

  18. Role of temperature-dependent viscosity and surface plates in spherical shell models of mantle convection

    Science.gov (United States)

    Zhong, Shijie; Zuber, Maria T.; Moresi, Louis; Gurnis, Michael

    2000-05-01

    Layered viscosity, temperature-dependent viscosity, and surface plates have an important effect on the scale and morphology of structure in spherical models of mantle convection. We find that long-wavelength structures can be produced either by a layered viscosity with a weak upper mantle or temperature-dependent viscosity even in the absence of surface plates, corroborating earlier studies. However, combining the layered viscosity structure with a temperature-dependent viscosity results in structure with significantly shorter wavelengths. Our models show that the scale of convection is mainly controlled by the surface plates, supporting the previous two-dimensional studies. Our models with surface plates, layered and temperature-dependent viscosity, and internal heating explain mantle structures inferred from seismic tomography. The models show that hot upwellings initiate at the core-mantle boundary (CMB) with linear structures, and as they depart from CMB, the linear upwellings quickly change into quasi-cylindrical plumes that dynamically interact with the ambient mantle and surface plates while ascending through the mantle. A linear up welling structure is generated again at shallow depths (maintained throughout the mantle. The tendency for linear upwelling and downwelling structures to break into plume-like structures is stronger at higher Rayleigh numbers. Our models also show that downwellings to first-order control surface plate motions and the locations and horizontal motion of upwellings. Upwellings tend to form at stagnation points predicted solely from the buoyancy forces of downwellings. Temperature-dependent viscosity greatly enhances the ascending velocity of developed upwelling plumes, and this may reduce the influence of global mantle flow on the motion of plumes. Our results can explain the anticorrelation between hotspot distribution and fast seismic wave speed anomalies in the lower mantle and may also have significant implications to the

  19. Np Behavior in Synthesized Uranyl Phases: Results of Initial Tests

    Energy Technology Data Exchange (ETDEWEB)

    Friese, Judah I.; Douglas, Matthew; McNamara, Bruce K.; Clark, Sue B.; Hanson, Brady D.

    2004-09-28

    Initial tests were completed at Pacific Northwest National Laboratory for developing a potential mechanism to retard the mobility of neptunium at the Yucca Mountain repository. Neptunium is of concern because of its mobility in the environment and long half life, contributing a large percentage of the potential dose over extended times at the perimeter of the site. The mobility of neptunium could be retarded by associating with uranium mineral phases. The following four uranium mineral phases were examined and are potential secondary phases expected to form as a result of interactions of spent nuclear fuel with the local environment: meta-schoepite, studtite, uranophane, and sodium boltwoodite. The fate of the neptunium was examined in these synthetic experiments.

  20. Au(111) and Pt(111) surface phase behavior

    DEFF Research Database (Denmark)

    Sandy, A.R.; Mochrie, S.G.J.; Zehner, D.M.

    1993-01-01

    We describe our recent X-ray scattering studies of the structure and phases of the clean Au(111) and Pt(111) surfaces. Below 0.65 of their respective bulk melting temperatures, the Au(111) surface has a well-ordered chevron reconstruction and the Pt(111) surface is unreconstructed. Above...... these temperatures, both surfaces reconstruct to form layers that are isotropically compresses and have only short-range order. Throughout their reconstructed phases, the densities of the Au and Pt(111) surfaces increase with increasing temperature....

  1. Phase Behavior of Polymer Nanocomposites from Gravity-based Combinatorial Simulations

    Science.gov (United States)

    Meng, Dong; Kumar, Sanat

    2012-02-01

    The phase behavior of polymers mixed with nanoparticles, termed nanocomposites, has been of great current interest. Holding the promise of improved engineering properties, the property improvement is critically dependent on the spatial dispersion of nanoparticles, which is controlled by polymer-nanoparticle phase behavior. Enumerating the appropriate phase diagrams, however, still remain outside the realm of most simulation-based methods. The difficulty arises since inserting a large particle into a dense sea of small particles, critically for establishing phase equilibrium, is prohibitively difficult. Here we extend a gravity-based combinatorial method, first devise by Biben et al., and used primarily in the context of pure fluids to circumvent this insertion issue. Our results are validated against available simulations for colloid mixtures, but provide new insight into the phase behavior of polymers and nanoparticles.

  2. Feasibility analysis of phase transition signals based on e-bike rider behavior

    OpenAIRE

    Sheng Dong; Jibiao Zhou; Li Zhao; Keshuang Tang; Renfa Yang

    2015-01-01

    This article evaluates the feasibility of two scenarios of phase transition signals, that is, the flashing green together with red–yellow light and the green countdown together with red countdown, at signalized intersections in terms of e-bike rider behavior. An evaluation framework is first proposed. During the phase transition, the stop-go and start-up behavioral parameters are collected at four intersections in Shanghai, China. Sensitivity analysis is then performed to identify the most si...

  3. Structure and phase behavior of colloidal rod suspensions

    NARCIS (Netherlands)

    Savenko, S.V.

    2006-01-01

    The first chapter of the thesis provides the general background on the subject. Overview of experimental results and some key theoretical developments is given and the simulational methods are briefly discussed. In the Chapter 2 sedimentation and multi-phase equilibria in a suspension of hard

  4. Phase behavior of polylactides in solvent-nonsolvent mixtures

    NARCIS (Netherlands)

    van de Witte, P.; van de Witte, P.; Dijkstra, Pieter J.; van den Berg, J.W.A.; Feijen, Jan

    1996-01-01

    Isothermal phase diagrams for the semicrystalline poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA) in combination with several solvent-nonsolvent combinations (dioxane/water, dioxane/methanol, chloroform/methanol, and NMP/water) have been determined. The locations of the liquid-liquid

  5. Coupled Interfacial Tension and Phase Behavior Model Based on Micellar Curvatures

    KAUST Repository

    Torrealba, V. A.

    2017-11-08

    This article introduces a consistent and robust model that predicts interfacial tensions for all microemulsion Winsor types and overall compositions. The model incorporates film bending arguments and Huh\\'s equation and is coupled to phase behavior so that simultaneous tuning of both interfacial tension (IFT) and phase behavior is possible. The oil-water interfacial tension and characteristic length are shown to be related to each other through the hydrophilic-lipophilic deviation (HLD). The phase behavior is tied to the micelle curvatures, without the need for using the net average curvature (NAC). The interfacial tension model is related to solubilization ratios in order to introduce a coupled interfacial tension-phase behavior model for all phase environments. The approach predicts two- and three-phase interfacial tensions and phase behavior (i.e., tie lines and tie triangles) for changes in composition and HLD input parameters, such as temperature, pressure, surfactant structure, and oil equivalent alkane carbon number. Comparisons to experimental data show excellent fits and predictive capability.

  6. Characterization of Bitumen Micro-Mechanical Behaviors Using AFM, Phase Dynamics Theory and MD Simulation

    Directory of Open Access Journals (Sweden)

    Yue Hou

    2017-02-01

    Full Text Available Fundamental understanding of micro-mechanical behaviors in bitumen, including phase separation, micro-friction, micro-abrasion, etc., can help the pavement engineers better understand the bitumen mechanical performances at macroscale. Recent researches show that the microstructure evolution in bitumen will directly affect its surface structure and micro-mechanical performance. In this study, the bitumen microstructure and micro-mechanical behaviors are studied using Atomic Force Microscopy (AFM experiments, Phase Dynamics Theory and Molecular Dynamics (MD Simulation. The AFM experiment results show that different phase-structure will occur at the surface of the bitumen samples under certain thermodynamic conditions at microscale. The phenomenon can be explained using the phase dynamics theory, where the effects of stability parameter and temperature on bitumen microstructure and micro-mechanical behavior are studied combined with MD Simulation. Simulation results show that the saturates phase, in contrast to the naphthene aromatics phase, plays a major role in bitumen micro-mechanical behavior. A high stress zone occurs at the interface between the saturates phase and the naphthene aromatics phase, which may form discontinuities that further affect the bitumen frictional performance.

  7. Phase Transition Behavior of HPMC-AA and Preparation of HPMC-PAA Nanogels

    Directory of Open Access Journals (Sweden)

    Risheng Yao

    2011-01-01

     nm diameters characterized by transmission electron microscope and dynamic light scattering. The HPMC-PAA nanogels exhibit the temperature phase transition behaviors, and these nanogels' volume phase transition temperature is close to the LCST of HPMC/AA system.

  8. A comparative study of monoclonal antibodies. 1. Phase behavior and protein-protein interactions.

    Science.gov (United States)

    Lewus, Rachael A; Levy, Nicholas E; Lenhoff, Abraham M; Sandler, Stanley I

    2015-01-01

    Protein phase behavior is involved in numerous aspects of downstream processing, either by design as in crystallization or precipitation processes, or as an undesired effect, such as aggregation. This work explores the phase behavior of eight monoclonal antibodies (mAbs) that exhibit liquid-liquid separation, aggregation, gelation, and crystallization. The phase behavior has been studied systematically as a function of a number of factors, including solution composition and pH, in order to explore the degree of variability among different antibodies. Comparisons of the locations of phase boundaries show consistent trends as a function of solution composition; however, changing the solution pH has different effects on each of the antibodies studied. Furthermore, the types of dense phases formed varied among the antibodies. Protein-protein interactions, as reflected by values of the osmotic second virial coefficient, are used to correlate the phase behavior. The primary findings are that values of the osmotic second virial coefficient are useful for correlating phase boundary locations, though there is appreciable variability among the antibodies in the apparent strengths of the intrinsic protein-protein attraction manifested. However, the osmotic second virial coefficient does not provide a clear basis to predict the type of dense phase likely to result under a given set of solution conditions. © 2014 American Institute of Chemical Engineers.

  9. The phase behavior of a hard sphere chain model of a binary n-alkane mixture

    Energy Technology Data Exchange (ETDEWEB)

    Malanoski, A. P. [Department of Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Monson, P. A. [Department of Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003 (United States)

    2000-02-08

    Monte Carlo computer simulations have been used to study the solid and fluid phase properties as well as phase equilibrium in a flexible, united atom, hard sphere chain model of n-heptane/n-octane mixtures. We describe a methodology for calculating the chemical potentials for the components in the mixture based on a technique used previously for atomic mixtures. The mixture was found to conform accurately to ideal solution behavior in the fluid phase. However, much greater nonidealities were seen in the solid phase. Phase equilibrium calculations indicate a phase diagram with solid-fluid phase equilibrium and a eutectic point. The components are only miscible in the solid phase for dilute solutions of the shorter chains in the longer chains. (c) 2000 American Institute of Physics.

  10. Plastic behavior of quasicrystals and related intermetallic phases

    Energy Technology Data Exchange (ETDEWEB)

    Heggen, M.

    2003-07-01

    In the present work, the plasticity of quasicrystals, metallic glasses and structurally complex alloy phases was investigated. The concepts of plasticity for simple crystalline materials cannot be applied to these materials without substational modification. Plastic deformation experiments and subsequent microstructural investigations by means of transmission electron microscopy (TEM) were performed on icosahedral Zn-Mg-Dy and Al-Pd-Mn single quasicrystals. A constitutive model approach describing the plasticity of icosahedral quasicrystals was applied to a wide range of experimental deformation parameters. In both materials plastic deformation depends on the interaction of dislocation storage and recovery and the strain driven disordering and diffusion driven reordering of the material. The plastic deformation behaviour of Pd-Ni-Cu-P bulk metallic glass was studied in creep experiments at three different temperatures and in a wide range of creep stresses. The transition between steady-state creep and accelerating creep was studied. Based on the free-volume description a constitutive model was developed, which comprehensively describes the salient features of metallic-glass plasticity for various deformation conditions. Furthermore dislocation-like defects in the structurally complex alloy phases {xi}'-Al-Pd-Mn and c{sub 2}-Al-Pd-Fe were investigated. New types of defects, which are present in the materials after plastic deformation, were found and characterized by means of TEM. It was shown that the basic concepts of dislocation-like defects show clear similarities in both structurally complex phases. (orig.)

  11. Temperature dependence of the electrical resistivity of amorphous Co{sub 80-x}Er{sub x}B{sub 20} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Touraghe, O.; Khatami, M. [LPMMAT, Universite Hassan II, Faculte des Sciences Ain Chock, B.P. 5366, Route d' EL Jadida km-8, Casablanca (Morocco); Menny, A. [LPMMAT, Universite Hassan II, Faculte des Sciences Ain Chock, B.P. 5366, Route d' EL Jadida km-8, Casablanca (Morocco); Departement de Physique, Faculte des Sciences et Technique de Nouakchott (Mauritania); Lassri, H. [LPMMAT, Universite Hassan II, Faculte des Sciences Ain Chock, B.P. 5366, Route d' EL Jadida km-8, Casablanca (Morocco)], E-mail: lassrih@hotmail.com; Nouneh, K. [CENM/CNESTEN, Maamora Rabat (Morocco)

    2008-06-01

    The temperature dependence of the electrical resistivity of amorphous Co{sub 80-x}Er{sub x}B{sub 20} alloys with x=0, 3.9, 7.5 and 8.6 prepared by melt spinning in pure argon atmosphere was studied. All amorphous alloys investigated here are found to exhibit a resistivity minimum at low temperature. The electrical resistivity exhibits logarithmic temperature dependence below the temperature of resistivity minimum T{sub min}. In addition, the resistivity shows quadratic temperature behavior in the interval T{sub min}

  12. Perturbation Solutions for Hagen-Poiseuille Flow and Heat Transfer of Third-Grade Fluid with Temperature-Dependent Viscosities and Internal Heat Generation

    Directory of Open Access Journals (Sweden)

    B. Y. Ogunmola

    2016-01-01

    Full Text Available Regular perturbation technique is applied to analyze the fluid flow and heat transfer in a pipe containing third-grade fluid with temperature-dependent viscosities and heat generation under slip and no slip conditions. The obtained approximate solutions were used to investigate the effects of slip on the heat transfer characteristics of the laminar flow in a pipe under Reynolds’s and Vogel’s temperature-dependent viscosities. Also, the effects of parameters such as variable viscosity, non-Newtonian parameter, viscous dissipation, and pressure gradient at various values were established. The results of this work were compared with the numerical results found in literature and good agreements were established. The results can be used to advance the analysis and study of the behavior of third-grade fluid flow and steady state heat transfer processes such as those found in coal slurries, polymer solutions, textiles, ceramics, catalytic reactors, and oil recovery applications.

  13. Temperature dependence of electron magnetic resonance spectra of iron oxide nanoparticles mineralized in Listeria innocua protein cages

    Science.gov (United States)

    Usselman, Robert J.; Russek, Stephen E.; Klem, Michael T.; Allen, Mark A.; Douglas, Trevor; Young, Mark; Idzerda, Yves U.; Singel, David J.

    2012-10-01

    Electron magnetic resonance (EMR) spectroscopy was used to determine the magnetic properties of maghemite (γ-Fe2O3) nanoparticles formed within size-constraining Listeria innocua (LDps)-(DNA-binding protein from starved cells) protein cages that have an inner diameter of 5 nm. Variable-temperature X-band EMR spectra exhibited broad asymmetric resonances with a superimposed narrow peak at a gyromagnetic factor of g ≈ 2. The resonance structure, which depends on both superparamagnetic fluctuations and inhomogeneous broadening, changes dramatically as a function of temperature, and the overall linewidth becomes narrower with increasing temperature. Here, we compare two different models to simulate temperature-dependent lineshape trends. The temperature dependence for both models is derived from a Langevin behavior of the linewidth resulting from "anisotropy melting." The first uses either a truncated log-normal distribution of particle sizes or a bi-modal distribution and then a Landau-Liftshitz lineshape to describe the nanoparticle resonances. The essential feature of this model is that small particles have narrow linewidths and account for the g ≈ 2 feature with a constant resonance field, whereas larger particles have broad linewidths and undergo a shift in resonance field. The second model assumes uniform particles with a diameter around 4 nm and a random distribution of uniaxial anisotropy axes. This model uses a more precise calculation of the linewidth due to superparamagnetic fluctuations and a random distribution of anisotropies. Sharp features in the spectrum near g ≈ 2 are qualitatively predicted at high temperatures. Both models can account for many features of the observed spectra, although each has deficiencies. The first model leads to a nonphysical increase in magnetic moment as the temperature is increased if a log normal distribution of particles sizes is used. Introducing a bi-modal distribution of particle sizes resolves the unphysical

  14. Designing stable finite state machine behaviors using phase plane analysis and variable structure control

    Energy Technology Data Exchange (ETDEWEB)

    Feddema, J.T.; Robinett, R.D.; Driessen, B.J.

    1998-03-10

    This paper discusses how phase plane analysis can be used to describe the overall behavior of single and multiple autonomous robotic vehicles with finite state machine rules. The importance of this result is that one can begin to design provably asymptotically stable group behaviors from a set of simple control laws and appropriate switching points with decentralized variable structure control. The ability to prove asymptotically stable group behavior is especially important for applications such as locating military targets or land mines.

  15. Phase behavior of chromonic liquid crystal mixtures of Sunset Yellow and Disodium Cromoglycate

    Science.gov (United States)

    Yamaguchi, Akihiro; Smith, Gregory; Yi, Youngwoo; Xu, Charles; Biffi, Silvia; Serra, Francesca; Bellini, Tommaso; Clark, Noel

    2014-03-01

    Chromonic liquid crystals (CLCs) are formed when planar molecules dissolved in water stack into rod-like aggregates that can order as liquid crystals. Isotropic, nematic, and M-phases can be observed depending on the degree of molecular orientational and positional order by variation of the CLC concentration. We focused on mixtures of two well-known CLCs, Sunset Yellow, a food dye, and disodium cromoglycate (DSCG), an asthma medication. In order to study the phase behaviors of these mixtures, we observed their textures in glass cells and capillaries using polarized light microscopy. We report here a ternary phase diagram describing the complete phase behavior of the CLC mixtures. We observed a variety of phase behaviors depending on species ratio and concentration. In the isotropic phase, no clear phase separation of the two dyes was observed, while separation did occur in many nematic and M-phase combinations. We will also describe phase observations made using a light spectroscopy and bulk centrifugal partitioning. Grant support: NSF DMR 1207606 and NSF MRSEC DMR-0820579.

  16. Effects of attractive colloids on the phase separation behaviors of binary polymer blends

    Science.gov (United States)

    Zhang, Xinghua; Chen, Yunlin; Qu, Lijian; Yan, Dadong

    2013-08-01

    The attractive colloids are added as fillers to control the phase behaviors of binary polymer blends. Because the colloids attract both components in the blends, aggregates are formed by the colloids coated with both kinds of polymer brushes. The aggregation results in two contradictory effects on the phase separation. First, the formation of aggregate decreases the translational entropy, which promotes the phase separation. On the other hand, the phase separation causes the extra free energy penalty due to the stretch of the chains attaching on the colloids, which prevents the phase separation. Furthermore, as the concentration or adsorbability of the colloids increases the local fluctuations within the aggregates become important. This results in a transition from the macro-phase separation to the micro-phase separation and the existence of the Lifshitz point. All of these effects lead to diverse phase behaviors in the polymer nanocomposites system. In present work, these behaviors are studied theoretically by the random phase approximation in a model system.

  17. miR-124 Regulates the Phase of Drosophila Circadian Locomotor Behavior.

    Science.gov (United States)

    Zhang, Yong; Lamba, Pallavi; Guo, Peiyi; Emery, Patrick

    2016-02-10

    Animals use circadian rhythms to anticipate daily environmental changes. Circadian clocks have a profound effect on behavior. In Drosophila, for example, brain pacemaker neurons dictate that flies are mostly active at dawn and dusk. miRNAs are small, regulatory RNAs (≈22 nt) that play important roles in posttranscriptional regulation. Here, we identify miR-124 as an important regulator of Drosophila circadian locomotor rhythms. Under constant darkness, flies lacking miR-124 (miR-124(KO)) have a dramatically advanced circadian behavior phase. However, whereas a phase defect is usually caused by a change in the period of the circadian pacemaker, this is not the case in miR-124(KO) flies. Moreover, the phase of the circadian pacemaker in the clock neurons that control rhythmic locomotion is not altered either. Therefore, miR-124 modulates the output of circadian clock neurons rather than controlling their molecular pacemaker. Circadian phase is also advanced under temperature cycles, but a light/dark cycle partially corrects the defects in miR-124(KO) flies. Indeed, miR-124(KO) shows a normal evening phase under the latter conditions, but morning behavioral activity is suppressed. In summary, miR-124 controls diurnal activity and determines the phase of circadian locomotor behavior without affecting circadian pacemaker function. It thus provides a potent entry point to elucidate the mechanisms by which the phase of circadian behavior is determined. In animals, molecular circadian clocks control the timing of behavioral activities to optimize them with the day/night cycle. This is critical for their fitness and survival. The mechanisms by which the phase of circadian behaviors is determined downstream of the molecular pacemakers are not yet well understood. Recent studies indicate that miRNAs are important regulators of circadian outputs. We found that miR-124 shapes diurnal behavioral activity and has a striking impact on the phase of circadian locomotor behavior

  18. Temperature Dependence of Fraction of Frozen Water in Solutions of Glucose and its Oligomers, Dextrans, and Potato Starch

    National Research Council Canada - National Science Library

    PRADIPASENA, Pasawadee; TATTIAKUL, Jirarat; NAKAMURA, Keiko; MIYAWAKI, Osato

    2007-01-01

    Initial freezing point and freezable water fraction, as the two parameters to determine the temperature dependence of fraction of frozen water, were measured systematically for solutions of glucose...

  19. TiO2 films annealing temperature-dependent properties in terms of the Amlouk-Boubaker opto-thermal expansivity ψAB

    Science.gov (United States)

    Amlouk, A.; Boubaker, K.; El Mir, L.; Amlouk, M.

    2011-02-01

    In this study, TiO2 films were grown at room temperature by sol-gel process using titanium (IV)-isopropylat as precursor. XRD, EDS and MEB analyses proved that an eventual annealing treatment caused the TiO2 amorphous phase to shift to a crystalline anatase phase. Optical measurements were carried out via absorbance spectra in 500-2500 nm wavelength domain. From these optical measurements, the temperature-dependent conjoint optical and thermal properties were deduced using the Amlouk-Boubaker opto-thermal expansivity ψAB.

  20. HLB (hydrophilic lipophilic balance), CMC (critical micelle concentration) and phase behavior as related to hydrophobe branching

    Energy Technology Data Exchange (ETDEWEB)

    Graciaa, A.; Barakat, Y.; El-Eary, M.; Fortney, L.; Schechter, R.S.

    1982-09-01

    Increased hydrophobe branching is employed to increase water solubility of surfactants. This is often considered synonymous with increasing surfactant HLB. When HLB is viewed in the context of the phase behavior of oil/water/surfactant systems, it is seen that increased branching favors partitioning into the oil phase, thus lowering surfactant HLB despite an experimentally observed increase in CMC. An alternative to HLB is proposed which defines a surfactant's properties based on the optimal alkane needed for the appropriate surfactant phase behavior. 23 references.

  1. Elevated temperature dependent transport properties of phosphorus and arsenic doped zinc oxide thin films

    Science.gov (United States)

    Cai, B.; Nakarmi, M. L.; Oder, T. N.; McMaster, M.; Velpukonda, N.; Smith, A.

    2013-12-01

    Elevated temperature dependent Hall effect measurements were performed in a wide temperature range from 80 to 800 K to study transport properties of zinc oxide (ZnO) thin films heavily doped with phosphorus (P) and arsenic (As), and grown on sapphire substrates by RF magnetron sputtering. Double thermal activation processes in both P- and As-doped ZnO thin films with small activation energy of ˜0.04 eV and large activation energy of ˜0.8 eV were observed from variable temperature Hall effect measurements. The samples exhibited n-type conductivities throughout the temperature range. Based on photoluminescence measurements at 11 K and theoretical results, the large activation energy observed in the temperature dependent Hall effect measurement has been assigned to a deep donor level, which could be related to oxygen vacancy (VO) in the doped ZnO thin films.

  2. Temperature dependence of magnetically dead layers in ferromagnetic thin-films

    Directory of Open Access Journals (Sweden)

    M. Tokaç

    2017-11-01

    Full Text Available Polarized neutron reflectometry has been used to study interface magnetism and magnetic dead layers in model amorphous CoFeB:Ta alloy thin-film multilayers with Curie temperatures tuned to be below room-temperature. This allows temperature dependent variations in the effective magnetic thickness of the film to be determined at temperatures that are a significant fraction of the Curie temperature, which cannot be achieved in the material systems used for spintronic devices. In addition to variation in the effective magnetic thickness due to compositional grading at the interface with the tantalum capping layer, the key finding is that at the interface between ferromagnetic film and GaAs(001 substrate local interfacial alloying creates an additional magnetic dead-layer. The thickness of this magnetic dead-layer is temperature dependent, which may have significant implications for elevated-temperature operation of hybrid ferromagnetic metal-semiconductor spintronic devices.

  3. Study of frequency- and temperature-dependent electrical transport in heavy fermion systems

    Science.gov (United States)

    Baral, P. C.

    2017-05-01

    This paper focuses on the frequency- and temperature-dependent electrical transport properties of heavy fermion (HF) systems. For this, Kondo lattice model (KLM) with Coulomb correlation between f-f electrons at the same site is considered. The Hamiltonian is treated in mean-field approximation (MFA) for the Kondo hybridization and Heisenberg-type interaction to get mean-field Hamiltonian and it is written after the Fourier transformation. The Hartree-Fock-type approximation is considered for the Coulomb repulsion between f-f electrons, the perturbed part of the Hamiltonian. The two Green’s functions for the conduction and f-electrons are calculated to define the self-energy. Then the frequency- and temperature-dependent optical conductivity and resistivity are calculated by using the Kubo’s formula within the linear dynamical response approach. They are studied by varying the model parameters. The anomalies and results obtained are compared with experimental data.

  4. Temperature Dependence of Faraday Effect-Induced Bias Error in a Fiber Optic Gyroscope.

    Science.gov (United States)

    Li, Xuyou; Liu, Pan; Guang, Xingxing; Xu, Zhenlong; Guan, Lianwu; Li, Guangchun

    2017-09-07

    Improving the performance of interferometric fiber optic gyroscope (IFOG) in harsh environments, such as magnetic field and temperature field variation, is necessary for its practical applications. This paper presents an investigation of Faraday effect-induced bias error of IFOG under varying temperature. Jones matrix method is utilized to formulize the temperature dependence of Faraday effect-induced bias error. Theoretical results show that the Faraday effect-induced bias error changes with the temperature in the non-skeleton polarization maintaining (PM) fiber coil. This phenomenon is caused by the temperature dependence of linear birefringence and Verdet constant of PM fiber. Particularly, Faraday effect-induced bias errors of two polarizations always have opposite signs that can be compensated optically regardless of the changes of the temperature. Two experiments with a 1000 m non-skeleton PM fiber coil are performed, and the experimental results support these theoretical predictions. This study is promising for improving the bias stability of IFOG.

  5. Determination of the built-in voltage of BHJ solar cells by temperature dependent photocurrent measurements

    Energy Technology Data Exchange (ETDEWEB)

    Mingebach, Markus; Deibel, Carsten [Experimental Physics VI, Physical Institute, Julius-Maximilians-University of Wuerzburg (Germany); Dyakonov, Vladimir [Experimental Physics VI, Physical Institute, Julius-Maximilians-University of Wuerzburg (Germany); Bavarian Center of Applied Energy Research (ZAE Bayern e.V.), Wuerzburg (Germany)

    2011-07-01

    Despite all progresses in the performance of organic BHJ solar cells (up to 8% power conversion efficiency) some very important properties such as the voltage dependent photocurrent or the built-in potential are not fully understood yet. We investigate poly(3-hexyl thiophene) (P3HT): [6,6]-phenyl-C{sub 61} butyric acid methyl ester (PCBM) solar cells by means of temperature dependent pulsed photocurrent measurements and impedance spectroscopy. We find a point of optimal symmetry (POS) that represents the case of quasi flat bands (QFB) in the bulk of the cell, which is lower than the built-in voltage. This difference is due to band bending at the contacts, which is reduced at lower temperatures. Therefore we can identify the built-in voltage by measuring the POS (confirmed by temperature dependent current voltage measurements). This leads to the conclusion that the potential determined by Mott-Schottky analysis is not the built-in potential.

  6. Temperature dependent thermoelectric properties of chemically derived gallium zinc oxide thin films

    KAUST Repository

    Barasheed, Abeer Z.

    2013-01-01

    In this study, the temperature dependent thermoelectric properties of sol-gel prepared ZnO and 3% Ga-doped ZnO (GZO) thin films have been explored. The power factor of GZO films, as compared to ZnO, is improved by nearly 17% at high temperature. A stabilization anneal, prior to thermoelectric measurements, in a strongly reducing Ar/H2 (95/5) atmosphere at 500°C was found to effectively stabilize the chemically derived films, practically eliminating hysteresis during thermoelectric measurements. Subtle changes in the thermoelectric properties of stabilized films have been correlated to oxygen vacancies and excitonic levels that are known to exist in ZnO-based thin films. The role of Ga dopants and defects, formed upon annealing, in driving the observed complex temperature dependence of the thermoelectric properties is discussed. © The Royal Society of Chemistry 2013.

  7. Temperature-dependent piezoresistivity in an MWCNT/epoxy nanocomposite temperature sensor with ultrahigh performance

    Science.gov (United States)

    Alamusi; Li, Yuan; Hu, Ning; Wu, Liangke; Yuan, Weifeng; Peng, Xianghe; Gu, Bin; Chang, Christiana; Liu, Yaolu; Ning, Huiming; Li, Jinhua; Surina; Atobe, Satoshi; Fukunaga, Hisao

    2013-11-01

    A temperature sensor was fabricated from a polymer nanocomposite with multi-walled carbon nanotube (MWCNT) as nanofiller (i.e., MWCNT/epoxy). The electrical resistance and temperature coefficient of resistance (TCR) of the temperature sensor were characterized experimentally. The effects of temperature (within the range 333-373 K) and MWCNT content (within the range 1-5 wt%) were investigated thoroughly. It was found that the resistance increases with increasing temperature and decreasing MWCNT content. However, the resistance change ratio related to the TCR increases with increasing temperature and MWCNT content. The highest value of TCR (0.021 K-1), which was observed in the case of 5 wt% MWCNT, is much higher than those of traditional metals and MWCNT-based temperature sensors. Moreover, the corresponding numerical simulation—conducted to explain the above temperature-dependent piezoresistivity of the nanocomposite temperature sensor—indicated the key role of a temperature-dependent tunneling effect.

  8. Temperature Dependence of Sound Velocity in High-Strength Fiber-Reinforced Plastics

    Science.gov (United States)

    Nomura, Ryuji; Yoneyama, Keiichi; Ogasawara, Futoshi; Ueno, Masashi; Okuda, Yuichi; Yamanaka, Atsuhiko

    2003-08-01

    Longitudinal sound velocity in unidirectional hybrid composites or high-strength fiber-reinforced plastics (FRPs) was measured along the fiber axis over a wide temperature range (from 77 K to 420 K). We investigated two kinds of high-strength crystalline polymer fibers, polyethylene (Dyneema) and polybenzobisoxazole (Zylon), which are known to have negative thermal expansion coefficients and high thermal conductivities along the fiber axis. Both FRPs had very high sound velocities of about 9000 m/s at low temperatures and their temperature dependences were very strong. Sound velocity monotonically decreased with increasing temperature. The temperature dependence of sound velocity was much stronger in Dyneema-FRP than in Zylon-FRP.

  9. Temperature dependence of magnetically dead layers in ferromagnetic thin-films

    Science.gov (United States)

    Tokaç, M.; Kinane, C. J.; Atkinson, D.; Hindmarch, A. T.

    2017-11-01

    Polarized neutron reflectometry has been used to study interface magnetism and magnetic dead layers in model amorphous CoFeB:Ta alloy thin-film multilayers with Curie temperatures tuned to be below room-temperature. This allows temperature dependent variations in the effective magnetic thickness of the film to be determined at temperatures that are a significant fraction of the Curie temperature, which cannot be achieved in the material systems used for spintronic devices. In addition to variation in the effective magnetic thickness due to compositional grading at the interface with the tantalum capping layer, the key finding is that at the interface between ferromagnetic film and GaAs(001) substrate local interfacial alloying creates an additional magnetic dead-layer. The thickness of this magnetic dead-layer is temperature dependent, which may have significant implications for elevated-temperature operation of hybrid ferromagnetic metal-semiconductor spintronic devices.

  10. Temperature dependence of direct current conductivity in Ag-ED20 nanocomposite films

    Science.gov (United States)

    Novikov, G. F.; Rabenok, E. V.; Bogdanova, L. M.; Irzhak, V. I.

    2017-10-01

    The effect of silver nanoparticles (NPs) in the concentration range of ≤0.8 wt % have on direct current conductivity σdc of Ag-ED20 nanocomposite is studied by method of broadband dielectric spectroscopy (10-2-105 Hz) method of broadband dielectric spectroscopy. It is found that temperature dependence σdc consists of two sections: above the glass transition temperature ( T g), the dependence corresponds to the empirical Vogel-Fulcher-Tammann law (Vogel temperature T 0 does not depend on the NP concentration); below T g, the dependence is Arrhenius with activation energy E a ≈ 1.2 eV. In the region where T > T g, the σdc value grows along with NP concentration. It is concluded that the observed broken form of the temperature dependence is apparently due to a change in the conduction mechanism after the freezing of ion mobility at temperatures below T g.

  11. Temperature dependence of stress in CVD diamond films studied by Raman spectroscopy

    Directory of Open Access Journals (Sweden)

    Dychalska Anna

    2015-09-01

    Full Text Available Evolution of residual stress and its components with increasing temperature in chemical vapor deposited (CVD diamond films has a crucial impact on their high temperature applications. In this work we investigated temperature dependence of stress in CVD diamond film deposited on Si(100 substrate in the temperature range of 30 °C to 480 °C by Raman mapping measurement. Raman shift of the characteristic diamond band peaked at 1332 cm-1 was studied to evaluate the residual stress distribution at the diamond surface. A new approach was applied to calculate thermal stress evolution with increasing tempera­ture by using two commonly known equations. Comparison of the residts obtained from the two methods was presented. The intrinsic stress component was calculated from the difference between average values of residual and thermal stress and then its temperature dependence was discussed.

  12. EXACT SOLUTION FOR TEMPERATURE-DEPENDENT BUCKLING ANALYSIS OF FG-CNT-REINFORCED MINDLIN PLATES

    Directory of Open Access Journals (Sweden)

    Seyed Mohammad Mousavi

    2016-03-01

    Full Text Available This research deals with the buckling analysis of nanocomposite polymeric temperature-dependent plates reinforced by single-walled carbon nanotubes (SWCNTs. For the carbon-nanotube reinforced composite (CNTRC plate, uniform distribution (UD and three types of functionally graded (FG distribution patterns of SWCNT reinforcements are assumed. The material properties of FG-CNTRC plate are graded in the thickness direction and estimated based on the rule of mixture. The CNTRC is located in a elastic medium which is simulated with temperature-dependent Pasternak medium. Based on orthotropic Mindlin plate theory, the governing equations are derived using Hamilton’s principle and solved by Navier method. The influences of the volume fractions of carbon nanotubes, elastic medium, temperature and distribution type of CNTs are considered on the buckling of the plate. Results indicate that CNT distribution close to top and bottom are more efficient than those distributed nearby the mid-plane for increasing the stiffness of plates.

  13. A finite element technique for non-deterministic thermal deformation analyses including temperature dependent material properties

    Science.gov (United States)

    Case, W. R., Jr.; Walston, W. H., Jr.

    1977-01-01

    A technique utilizing the finite element displacement method is developed for the static analysis of structures subjected to non-deterministic thermal loading in which the material properties, assumed isotropic, are temperature dependent. Matrix equations are developed for the first two statistical moments of the displacements using a third order series expansion for the displacements in terms of the random temperatures. Sample problems are included to demonstrate the range of applicability of the third order series solutions. These solutions are compared with results from Monte Carlo analyses and also, for some problems, with solutions obtained by numerically integrating equations for the statistical properties of the displacements. In general, it is shown that the effect of temperature dependent material properties can have a significant effect on the covariances of the displacements.

  14. A Model of Temperature-Dependent Young's Modulus for Ultrahigh Temperature Ceramics

    Directory of Open Access Journals (Sweden)

    Weiguo Li

    2011-01-01

    Full Text Available Based on the different sensitivities of material properties to temperature between ultrahigh temperature ceramics (UHTCs and traditional ceramics, the original empirical formula of temperature-dependent Young's modulus of ceramic materials is unable to describe the temperature dependence of Young's modulus of UHTCs which are used as thermal protection materials. In this paper, a characterization applied to Young's modulus of UHTC materials under high temperature which is revised from the original empirical formula is established. The applicable temperature range of the characterization extends to the higher temperature zone. This study will provide a basis for the characterization for strength and fracture toughness of UHTC materials and provide theoretical bases and technical reserves for the UHTC materials' design and application in the field of spacecraft.

  15. Temperature dependence of the photoluminescence of MnS/ZnS core—shell quantum dots

    Science.gov (United States)

    Fang, Dai-Feng; Ding, Xing; Dai, Ru-Cheng; Zhao, Zhi; Wang, Zhong-Ping; Zhang, Zeng-Ming

    2014-12-01

    The temperature dependence of the photoluminescence (PL) from MnS/ZnS core—shell quantum dots is investigated in a temperature range of 8 K-300 K. The orange emission from the 4T1 → 6A1 transition of Mn2+ ions and the blue emission related to the trapped surface state are observed in the MnS/ZnS core—shell quantum dots. As the temperature increases, the orange emission is shifted toward a shorter wavelength while the blue emission is shifted towards the longer wavelength. Both the orange and blue emissions reduce their intensities with the increase of temperature but the blue emission is quenched faster. The temperature-dependent luminescence intensities of the two emissions are well explained by the thermal quenching theory.

  16. Competitive adsorption equilibrium model with continuous temperature dependent parameters for naringenin enantiomers on Chiralpak AD column.

    Science.gov (United States)

    Xu, Jin; Jiang, Xiaoxiao; Guo, Jinghua; Chen, Yongtao; Yu, Weifang

    2015-11-27

    Determination of competitive adsorption equilibrium model with continuous temperature dependent parameters is important for the design and optimization of a chromatographic separation process operated under non-isothermal conditions. In this study, linear pulse experiments were first carried to determine the parameters of transport-dispersive model and their temperature dependences in the range of 283–313 K. Overloaded band profiles of naringenin enantiomers on a Chiralpak AD column were acquired under various temperatures. Three of them were first separately fitted using Langmuir, linear-Langmuir and bi-Langmuir isotherm models substituted into the transport-dispersive column model. The comparison showed that bi-Langmuir model captures more details of the experimental results. This model was then extended with three extra parameters accounting for adsorption heat effects and used to simultaneously fit the band profiles at three temperatures.

  17. A Temperature-Dependent Thermal Model of IGBT Modules Suitable for Circuit-Level Simulations

    DEFF Research Database (Denmark)

    Wu, Rui; Wang, Huai; Ma, Ke

    2014-01-01

    Thermal impedance of IGBT modules may vary with operating conditions due to that the thermal conductivity and heat capacity of materials are temperature dependent. This paper proposes a Cauer thermal model for a 1700 V/1000 A IGBT module with temperature-dependent thermal resistances and thermal...... relevant reliability aspect performance. A test bench is built up with an ultra-fast infrared (IR) camera to validate the proposed thermal impedance model....... capacitances. The temperature effect is investigated by Finite Element Method (FEM) simulation based on the geometry and material information of the IGBT module. The developed model is ready for circuit-level simulation to achieve an improved accuracy of the estimation on IGBT junction temperature and its...

  18. Unusual temperature dependence of the positron lifetime in a polymer of intrinsic microporosity

    Energy Technology Data Exchange (ETDEWEB)

    Lima de Miranda, Rodrigo; Kruse, Jan; Raetzke, Klaus; Faupel, Franz [Technische Fakultaet der Christian-Albrechts-Universitaet, Lehrstuhl fuer Materialverbunde, Kaiserstr. 2, 24143 Kiel (Germany); Fritsch, Detlev; Abetz, Volker [Institut fuer Polymerforschung, GKSS-Forschungszentrum Geesthacht GmbH, Max-Planck-Strasse 1, 21502 Geesthacht (Germany); Budd, Peter M.; Selbie, James D. [School of Chemistry, The University of Manchester, Manchester M13 9PL (United Kingdom); McKeown, Neil B.; Ghanem, Bader S. [School of Chemistry, Cardiff University, Cardiff CF10 3AT (United Kingdom)

    2007-10-15

    The performance of polymeric membranes for gas separation is mainly determined by the free volume. Polymers of intrinsic microporosity are interesting due to the high abundance of accessible free volume. We performed measurements of the temperature dependence of the positron lifetime, generally accepted for investigation of free volume, in two polymers of intrinsic microporosity (PIM-1 and PIM-7) in the range from 143 to 523 K. The mean value of the free volume calculated from the ortho-positronium lifetime is in the range of typical values for high free volume polymers. However, the temperature dependence of the local free volume is non-monotonous in contrast to the macroscopic thermal expansion. The explanation is linked to the spirocenters in the polymer. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Identification of microscopic domain wall motion from temperature dependence of nonlinear dielectric response.

    Czech Academy of Sciences Publication Activity Database

    Mokrý, Pavel; Sluka, T.

    2017-01-01

    Roč. 110, č. 16 (2017), č. článku 162906. ISSN 0003-6951 R&D Projects: GA ČR(CZ) GA14-32228S Institutional support: RVO:61389021 Keywords : microscopic domain wall * electric fields * temperature dependence Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.411, year: 2016 http://dx.doi.org/10.1063/1.4981874

  20. Temperature dependence of single-event burnout in n-channel power MOSFET's

    Science.gov (United States)

    Johnson, G. H.; Schrimpf, R. D.; Galloway, K. F.; Koga, R.

    1994-03-01

    The temperature dependence of single-event burnout (SEB) in n-channel power metal-oxide-semiconductor field effect transistors (MOSFET's) is investigated experimentally and analytically. Experimental data are presented which indicate that the SEB susceptibility of the power MOSFET decreases with increasing temperature. A previously reported analytical model that describes the SEB mechanism is updated to include temperature variations. This model is shown to agree with the experimental trends.

  1. Temperature-dependent photoluminescence and Raman investigation of Cu-incorporated ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Yu, J.L. [Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou (China); Jiangsu Collaborative Innovation Center of Photovolatic Science and Engineering, Changzhou University, Changzhou 213164, Jiangsu (China); Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Lai, Y.F., E-mail: laiyunfeng@gmail.com [Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou (China); Cheng, S.Y.; Zheng, Q. [Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou (China); Chen, Y.H. [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

    2015-05-15

    Temperature-dependent Raman and photoluminescence (PL) investigation of Cu-incorporated ZnO nanorods prepared by hydrothermal method have been investigated. A strong broad violet–blue emission has been observed in the PL spectra of Cu-incorporated ZnO nanorods, which decreases dramatically with increasing temperature. By Gaussian fitting, this peak can be resolved into two peaks centered at around 393 and 405 nm, respectively, under a temperature of 8 K. The origins of these two peaks are discussed. Temperature-dependent energies of neutral donor bound exciton (D{sup 0}X) are analyzed, and the Einstein temperature is deduced to be around 343±44 K, which do not show significant change compared with that without Cu incorporation. An activation energy of about 14±1 meV is determined from the quenching of D{sup 0}X as a function of temperature in the Cu-incorporated ZnO nanorods, which is much smaller than that deduced in the undoped ZnO nanorods (about 22±2 meV). The small activation energy can be attributed to the additional nonradiative centers introduced by Cu incorporation. The high concentration of defects and impurities in the Cu-incorporated ZnO nanorods are also confirmed by the larger value of the line width of the Raman spectra and its temperature-dependent relationship. - Highlights: • A strong violet–blue emission is observed in the PL spectra of ZnO:Cu nanorods. • This emission can be resolved into two peaks by Gaussian fitting. • Activation energy of the nonradiative centers and Einstein temperature is deduced. • The small activation energy indicates the additional nonradiative centers. • The temperature-dependent Raman spectra indicates more defects in the doping sample.

  2. Inverse temperature dependence of reverse gate leakage current in AlGaN/GaN HEMT

    Science.gov (United States)

    Kaushik, J. K.; Balakrishnan, V. R.; Panwar, B. S.; Muralidharan, R.

    2013-01-01

    The experimentally observed inverse temperature dependence of the reverse gate leakage current in AlGaN/GaN HEMT is explained using a virtual gate trap-assisted tunneling model. The virtual gate is formed due to the capture of electrons by surface states in the vicinity of actual gate. The increase and decrease in the length of the virtual gate with temperature due to trap kinetics are used to explain this unusual effect. The simulation results have been validated experimentally.

  3. Temperature dependency of the hysteresis behaviour of PZT actuators using Preisach model

    DEFF Research Database (Denmark)

    Mangeot, Charles; Zsurzsan, Tiberiu-Gabriel

    2016-01-01

    The Preisach model is a powerful tool for modelling the hysteresis phenomenon on multilayer piezo actuators under large signal excitation. In this paper, measurements at different temperatures are presented, showing the effect on the density of the Preisach matrix. An energy-based approach...... is presented, aiming at defining a temperature-dependent phenomenological model of hysteresis for a better understanding of the non-linear effects in piezo actuators....

  4. Modeling of Temperature-Dependent Noise in Silicon Nanowire FETs including Self-Heating Effects

    OpenAIRE

    Anandan, P.; Malathi, N.; Mohankumar, N.

    2014-01-01

    Silicon nanowires are leading the CMOS era towards the downsizing limit and its nature will be effectively suppress the short channel effects. Accurate modeling of thermal noise in nanowires is crucial for RF applications of nano-CMOS emerging technologies. In this work, a perfect temperature-dependent model for silicon nanowires including the self-heating effects has been derived and its effects on device parameters have been observed. The power spectral density as a function of thermal resi...

  5. Temperature dependence and mechanism of the reaction between O(3P) and chlorine dioxide

    Science.gov (United States)

    Colussi, A. J.; Sander, S. P.; Fiedl, R. R.

    1992-01-01

    Second-order rate constants for the decay of O(3P) in excess chlorine dioxide, k(II), were measured as a function of total pressure (20-600 Torr argon) and temperature (248-312 K), using flash photolysis-atomic resonance fluorescence. Results indicate that k(II) is pressure dependent with a value, K(b), that is nonzero at zero pressure, and both the third-order rate constant and k(b) have negative temperature dependences.

  6. Adomian Decomposition Method for a Nonlinear Heat Equation with Temperature Dependent Thermal Properties

    Directory of Open Access Journals (Sweden)

    Ashfaque H. Bokhari

    2009-01-01

    Full Text Available The solutions of nonlinear heat equation with temperature dependent diffusivity are investigated using the modified Adomian decomposition method. Analysis of the method and examples are given to show that the Adomian series solution gives an excellent approximation to the exact solution. This accuracy can be increased by increasing the number of terms in the series expansion. The Adomian solutions are presented in some situations of interest.

  7. Temperature-dependent respiration-growth relations in ancestral maize cultivars

    Science.gov (United States)

    Bruce N. Smith; Jillian L. Walker; Rebekka L. Stone; Angela R. Jones; Lee D. Hansen

    2001-01-01

    Shoots from 4- to 6-day old seedlings of seven ancestral or old cultivars of Zea mays L. were placed in a calorimeter. Dark metabolic heat rate (q) and CO2 production rate (RCO2) were measured at nine temperatures (5, 10, 15, 20, 25, 30, 35, 40, and 45 °C). Temperature dependencies of q and RCO2 were used to model response of both growth and substrate carbon conversion...

  8. Inferring the temperature dependence of population parameters: the effects of experimental design and inference algorithm.

    Science.gov (United States)

    Palamara, Gian Marco; Childs, Dylan Z; Clements, Christopher F; Petchey, Owen L; Plebani, Marco; Smith, Matthew J

    2014-12-01

    Understanding and quantifying the temperature dependence of population parameters, such as intrinsic growth rate and carrying capacity, is critical for predicting the ecological responses to environmental change. Many studies provide empirical estimates of such temperature dependencies, but a thorough investigation of the methods used to infer them has not been performed yet. We created artificial population time series using a stochastic logistic model parameterized with the Arrhenius equation, so that activation energy drives the temperature dependence of population parameters. We simulated different experimental designs and used different inference methods, varying the likelihood functions and other aspects of the parameter estimation methods. Finally, we applied the best performing inference methods to real data for the species Paramecium caudatum. The relative error of the estimates of activation energy varied between 5% and 30%. The fraction of habitat sampled played the most important role in determining the relative error; sampling at least 1% of the habitat kept it below 50%. We found that methods that simultaneously use all time series data (direct methods) and methods that estimate population parameters separately for each temperature (indirect methods) are complementary. Indirect methods provide a clearer insight into the shape of the functional form describing the temperature dependence of population parameters; direct methods enable a more accurate estimation of the parameters of such functional forms. Using both methods, we found that growth rate and carrying capacity of Paramecium caudatum scale with temperature according to different activation energies. Our study shows how careful choice of experimental design and inference methods can increase the accuracy of the inferred relationships between temperature and population parameters. The comparison of estimation methods provided here can increase the accuracy of model predictions, with important

  9. Temperature dependency of mechanical properties for crystalline cellulose added to silicone elastomer

    Science.gov (United States)

    Kameda, Takao; Sugino, Naoto; Takei, Satoshi; Hanabata, Makoto

    2017-08-01

    A chemical cross-linked transparent film was got by a silicon compound to crystalline cellulose. Temperature dependency for the elasticity modulus of a provided film was measured. The shear elastic modulus was obtained the value of 2 x 106 [Pa] at room temperature. The sample decreases in 190 [deg. C] for the elasticity modulus at the room temperature as 60%, but approximately 10% recover when temperature rises up to 200 [deg. C] or more.

  10. Does N2 fixation amplify the temperature dependence of ecosystem metabolism?

    Science.gov (United States)

    Welter, Jill R; Benstead, Jonathan P; Cross, Wyatt F; Hood, James M; Huryn, Alexander D; Johnson, Philip W; Williamson, Tanner J

    2015-03-01

    Variation in resource supply can cause variation in temperature dependences of metabolic processes (e.g., photosynthesis and respiration). Understanding such divergence is particularly important when using metabolic theory to predict ecosystem responses to climate warming. Few studies, however, have assessed the effect of temperature-resource interactions on metabolic processes, particularly in cases where the supply of limiting resources exhibits temperature dependence. We investigated the responses of biomass accrual, gross primary production (GPP), community respiration (CR), and N2 fixation to warming during biofilm development in a streamside channel experiment. Areal rates of GPP, CR, biomass accrual, and N2 fixation scaled positively with temperature, showing a 32- to 71-fold range across the temperature gradient (approximately 7 degrees-24 degrees C). Areal N2-fixation rates exhibited apparent activation energies (1.5-2.0 eV; 1 eV = approximately 1.6 x 10(-19) J) approximating the activation energy of the nitrogenase reaction. In contrast, mean apparent activation energies for areal rates of GPP (2.1-2.2 eV) and CR (1.6-1.9 eV) were 6.5- and 2.7-fold higher than estimates based on metabolic theory predictions (i.e., 0.32 and 0.65 eV, respectively) and did not significantly differ from the apparent activation energy observed for N2 fixation. Mass-specific activation energies for N2 fixation (1.4-1.6 eV), GPP (0.3-0.5 eV), and CR (no observed temperature relationship) were near or lower than theoretical predictions. We attribute the divergence of areal activation energies from those predicted by metabolic theory to increases in N2 fixation with temperature, leading to amplified temperature dependences of biomass accrual and areal rates of GPP and R. Such interactions between temperature dependences must be incorporated into metabolic models to improve predictions of ecosystem responses to climate change.

  11. EFFECT OF TEMPERATURE-DEPENDENCY OF SURFACE EMISSIVITY ON HEAT TRANSFER USING THE PARAMETERIZED PERTURBATION METHOD

    Directory of Open Access Journals (Sweden)

    Maziar Jalaal

    2011-01-01

    Full Text Available Knowledge of the temperature dependence of the physical properties such surface emissivity, which controls the radiative problem, is fundamental for determining the thermal balance of many scientific and industrial processes. The current work studies the ability of a strong analytical method called parameterized perturbation method (PPM, which unlike classic perturbation method do not need small parameter, for nonlinear heat transfer equations. The results are compared with the numerical Runge-Kutta method showed good agreement.

  12. Unconventional Surface Critical Behavior Induced by a Quantum Phase Transition from the Two-Dimensional Affleck-Kennedy-Lieb-Tasaki Phase to a Néel-Ordered Phase.

    Science.gov (United States)

    Zhang, Long; Wang, Fa

    2017-02-24

    A symmetry-protected topological phase has nontrivial surface states in the presence of certain symmetries, which can either be gapless or be degenerate. In this work, we study the physical consequence of such gapless surface states at the bulk quantum phase transition (QPT) that spontaneously breaks these symmetries. The two-dimensional Affleck-Kennedy-Lieb-Tasaki phase on a square lattice and its QPTs to Néel ordered phases are realized with the spin-1/2 Heisenberg model on a decorated square lattice. With large-scale quantum Monte Carlo simulations, we show that even though the bulk QPTs are governed by the conventional Landau phase transition theory, the gapless surface states induce unconventional universality classes of the surface critical behavior.

  13. Temperature dependence of current-and capacitance-voltage characteristics of an Au/4H-SiC Schottky diode

    Science.gov (United States)

    Gülnahar, Murat

    2014-12-01

    In this study, the current-voltage (I-V) and capacitance-voltage (C-V) measurements of an Au/4H-SiC Schottky diode are characterized as a function of the temperature in 50-300 K temperature range. The experimental parameters such as ideality factor and apparent barrier height presents to be strongly temperature dependent, that is, the ideality factor increases and the apparent barrier height decreases with decreasing temperature, whereas the barrier height values increase with the temperature for C-V data. Likewise, the Richardson plot deviates at low temperatures. These anomaly behaviors observed for Au/4H-SiC are attributed to Schottky barrier inhomogeneities. The barrier anomaly which relates to interface of Au/4H-SiC is also confirmed by the C-V measurements versus the frequency measured in 300 K and it is interpreted by both Tung's lateral inhomogeneity model and multi-Gaussian distribution approach. The values of the weighting coefficients, standard deviations and mean barrier height are calculated for each distribution region of Au/4H-SiC using the multi-Gaussian distribution approach. In addition, the total effective area of the patches NAe is obtained at separate temperatures and as a result, it is expressed that the low barrier regions influence meaningfully to the current transport at the junction. The homogeneous barrier height value is calculated from the correlation between the ideality factor and barrier height and it is noted that the values of standard deviation from ideality factor versus q/3kT curve are in close agreement with the values obtained from the barrier height versus q/2kT variation. As a result, it can be concluded that the temperature dependent electrical characteristics of Au/4H-SiC can be successfully commented on the basis of the thermionic emission theory with both models.

  14. Tuning of electrostatic vs. depletion interaction in deciding the phase behavior of nanoparticle-polymer system

    Science.gov (United States)

    Kumar, Sugam; Aswal, V. K.; Kohlbrecher, J.

    2015-06-01

    Nanoparticle-polymer system interestingly show a re-entrant phase behavior where charge stabilized silica nanoparticles (phase I) undergo particle clustering (phase II) and then back to individual particles (phase I) as a function of polymer concentration. Such phase behavior arises as a result of dominance of various interactions (i) nanoparticle-nanoparticle electrostatic repulsion (ii) polymer induced attractive depletion between nanoparticles and (iii) polymer-polymer repulsion, at different concentration regimes. Small-angle neutron scattering (SANS) has been used to study the evolution of interaction during this re-entrant phase behavior of nanoparticles by contrast-marching the polymer. The SANS data have been modeled using a two-Yukawa potential accounting for both attractive and repulsive parts of the interaction between nanoparticles. The degree of both of these parts has been separately tuned by varying the polymer concentration and ionic strength of the solution. Both of these parts are found to have long-range nature. At low polymer concentrations, the electrostatic repulsion dominates over the depletion attraction. The magnitude and the range of the depletion interaction increase with the polymer concentration leading to nanoparticle clustering. At higher polymer concentrations, the increased polymer-polymer repulsion reduces the strength of depletion leading to re-entrant phase behavior. The clusters formed under depletion attraction are found to have surface fractal morphology.

  15. Tuning of electrostatic vs. depletion interaction in deciding the phase behavior of nanoparticle-polymer system

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sugam, E-mail: sugam@barc.gov.in; Aswal, V. K. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kohlbrecher, J. [Laboratory for Neutron Scattering, Paul Scherrer Institut, H-5232 PSI Villigen (Switzerland)

    2015-06-24

    Nanoparticle-polymer system interestingly show a re-entrant phase behavior where charge stabilized silica nanoparticles (phase I) undergo particle clustering (phase II) and then back to individual particles (phase I) as a function of polymer concentration. Such phase behavior arises as a result of dominance of various interactions (i) nanoparticle-nanoparticle electrostatic repulsion (ii) polymer induced attractive depletion between nanoparticles and (iii) polymer-polymer repulsion, at different concentration regimes. Small-angle neutron scattering (SANS) has been used to study the evolution of interaction during this re-entrant phase behavior of nanoparticles by contrast-marching the polymer. The SANS data have been modeled using a two-Yukawa potential accounting for both attractive and repulsive parts of the interaction between nanoparticles. The degree of both of these parts has been separately tuned by varying the polymer concentration and ionic strength of the solution. Both of these parts are found to have long-range nature. At low polymer concentrations, the electrostatic repulsion dominates over the depletion attraction. The magnitude and the range of the depletion interaction increase with the polymer concentration leading to nanoparticle clustering. At higher polymer concentrations, the increased polymer-polymer repulsion reduces the strength of depletion leading to re-entrant phase behavior. The clusters formed under depletion attraction are found to have surface fractal morphology.

  16. Thermal rectification in restructured graphene with locally modulated temperature dependence of thermal conductivity

    Science.gov (United States)

    Arora, Anuj; Hori, Takuma; Shiga, Takuma; Shiomi, Junichiro

    2017-10-01

    We study thermal rectification (TR) in a selectively restructured graphene by performing deviational phonon Monte Carlo (MC) simulations with frequency-dependent phonon transport properties obtained from first principles. The restructuring is achieved by introducing vacancy defects in a portion of graphene. The defects significantly change phonon transport properties, resulting in a modulation of temperature dependence of thermal conductivity. With this modulated temperature dependence, we predict TR ratio through a Fourier's-law-based iterative scheme (FIS), where heat flow through the system is analyzed by solving the Fourier's law of heat conduction with spatially varying temperature-dependent thermal conductivity. To identify structure parameters for maximal TR ratio, we investigate the influence of defect size, volume percentage of defects, and system (consisting of defective and nondefective regions) length through FIS analysis. As a result, we find that the TR ratio is mainly a function of length of defective and nondefective regions and volume percentage of defect, and it is mostly independent of defect size. A longer (of the order of 10 μm) nondefective side, coupled to a shorter (of the order of 100 nm) defective side, can lead to large TR ratios. Finally, MC simulation for the restructured graphene (full system) is performed to verify the predictions from FIS analysis. The full system calculations give similar trends but with enhanced TR ratios up to 70% for the temperature range of 200-500 K.

  17. Modeling and Compensating Temperature-Dependent Non-Uniformity Noise in IR Microbolometer Cameras

    Science.gov (United States)

    Wolf, Alejandro; Pezoa, Jorge E.; Figueroa, Miguel

    2016-01-01

    Images rendered by uncooled microbolometer-based infrared (IR) cameras are severely degraded by the spatial non-uniformity (NU) noise. The NU noise imposes a fixed-pattern over the true images, and the intensity of the pattern changes with time due to the temperature instability of such cameras. In this paper, we present a novel model and a compensation algorithm for the spatial NU noise and its temperature-dependent variations. The model separates the NU noise into two components: a constant term, which corresponds to a set of NU parameters determining the spatial structure of the noise, and a dynamic term, which scales linearly with the fluctuations of the temperature surrounding the array of microbolometers. We use a black-body radiator and samples of the temperature surrounding the IR array to offline characterize both the constant and the temperature-dependent NU noise parameters. Next, the temperature-dependent variations are estimated online using both a spatially uniform Hammerstein-Wiener estimator and a pixelwise least mean squares (LMS) estimator. We compensate for the NU noise in IR images from two long-wave IR cameras. Results show an excellent NU correction performance and a root mean square error of less than 0.25 ∘C, when the array’s temperature varies by approximately 15 ∘C. PMID:27447637

  18. Temperature dependence of amino acid side chain IR absorptions in the amide I' region.

    Science.gov (United States)

    Anderson, Benjamin A; Literati, Alex; Ball, Borden; Kubelka, Jan

    2014-05-01

    Amide I' IR spectra are widely used for studies of structural changes in peptides and proteins as a function of temperature. Temperature dependent absorptions of amino acid side-chains that overlap the amide I' may significantly complicate the structural analyses. While the side-chain IR spectra have been investigated previously, thus far their dependence on temperature has not been reported. Here we present the study of the changes in the IR spectra with temperature for side-chain groups of aspartate, glutamate, asparagine, glutamine, arginine, and tyrosine in the amide I' region (in D2O). Band fitting analysis was employed to extract the temperature dependence of the individual spectral parameters, such as peak frequency, integrated intensity, band width, and shape. As expected, the side-chain IR bands exhibit significant changes with temperature. The majority of the spectral parameters, particularly the frequency and intensity, show linear dependence on temperature, but the direction and magnitude vary depending on the particular side-chain group. The exception is arginine, which exhibits a distinctly nonlinear frequency shift with temperature for its asymmetric CN3H5(+) bending signal, although a linear fit can account for this change to within ~1/3 cm(-1). The applicability of the determined spectral parameters for estimations of temperature-dependent side-chain absorptions in peptides and proteins are discussed. Copyright © 2013 Wiley Periodicals, Inc.

  19. Investigation of temperature-dependent small-signal performances of TB SOI MOSFETs

    Science.gov (United States)

    Huang, Yuping; Liu, Jun; Lü, Kai; Chen, Jing

    2017-04-01

    This paper investigated the temperature dependence of the cryogenic small-signal ac performances of multi-finger partially depleted (PD) silicon-on-insulator (SOI) metal oxide semiconductor field effect transistors (MOSFETs), with T-gate body contact (TB) structure. The measurement results show that the cut-off frequency increases from 78 GHz at 300 K to 120 GHz at 77 K and the maximum oscillation frequency increases from 54 GHz at 300 K to 80 GHz at 77 K, and these are mainly due to the effect of negative temperature dependence of threshold voltage and transconductance. By using a simple equivalent circuit model, the temperature-dependent small-signal parameters are discussed in detail. The understanding of cryogenic small-signal performance is beneficial to develop the PD SOI MOSFETs integrated circuits for ultra-low temperature applications. Project supported by the National Natural Science Foundation of China (No. 61331006) and the National Defense Pre-Research Foundation of China (No. 9140A11040114DZ04152).

  20. Modeling and Compensating Temperature-Dependent Non-Uniformity Noise in IR Microbolometer Cameras

    Directory of Open Access Journals (Sweden)

    Alejandro Wolf

    2016-07-01

    Full Text Available Images rendered by uncooled microbolometer-based infrared (IR cameras are severely degraded by the spatial non-uniformity (NU noise. The NU noise imposes a fixed-pattern over the true images, and the intensity of the pattern changes with time due to the temperature instability of such cameras. In this paper, we present a novel model and a compensation algorithm for the spatial NU noise and its temperature-dependent variations. The model separates the NU noise into two components: a constant term, which corresponds to a set of NU parameters determining the spatial structure of the noise, and a dynamic term, which scales linearly with the fluctuations of the temperature surrounding the array of microbolometers. We use a black-body radiator and samples of the temperature surrounding the IR array to offline characterize both the constant and the temperature-dependent NU noise parameters. Next, the temperature-dependent variations are estimated online using both a spatially uniform Hammerstein-Wiener estimator and a pixelwise least mean squares (LMS estimator. We compensate for the NU noise in IR images from two long-wave IR cameras. Results show an excellent NU correction performance and a root mean square error of less than 0.25 ∘ C, when the array’s temperature varies by approximately 15 ∘ C.

  1. Estimation of the temperature dependent interaction between uncharged point defects in Si

    Energy Technology Data Exchange (ETDEWEB)

    Kamiyama, Eiji [Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja-shi, Okayama-ken 719-1197 (Japan); GlobalWafers Japan Co., Ltd., 30 Soya, Hadano, Kanagawa, 257-8566 (Japan); Vanhellemont, Jan [Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, Ghent B-9000 (Belgium); Sueoka, Koji [Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja-shi, Okayama-ken 719-1197 (Japan)

    2015-01-15

    A method is described to estimate the temperature dependent interaction between two uncharged point defects in Si based on DFT calculations. As an illustration, the formation of the uncharged di-vacancy V{sub 2} is discussed, based on the temperature dependent attractive field between both vacancies. For that purpose, all irreducible configurations of two uncharged vacancies are determined, each with their weight given by the number of equivalent configurations. Using a standard 216-atoms supercell, nineteen irreducible configurations of two vacancies are obtained. The binding energies of all these configurations are calculated. Each vacancy is surrounded by several attractive sites for another vacancy. The obtained temperature dependent of total volume of these attractive sites has a radius that is closely related with the capture radius for the formation of a di-vacancy that is used in continuum theory. The presented methodology can in principle also be applied to estimate the capture radius for pair formation of any type of point defects.

  2. Temperature dependence of critical currents in REBCO thin films with artificial pinning centers

    Science.gov (United States)

    Matsumoto, Kaname; Nishihara, Masaya; Kimoto, Takamasa; Horide, Tomoya; Jha, Alok Kumar; Yoshida, Yutaka; Awaji, Satoshi; Ichinose, Ataru

    2017-10-01

    Conventionally, δT c type (order parameter modulation) and δl type (mean free path modulation) pinning mechanisms have been proposed to explain the temperature dependence of the flux pinning of superconducting materials. According to previous studies, it is assumed that the temperature dependence of J c of REBa2Cu3O7 (REBCO, RE = Y, Gd, Sm, etc) films without artificial pinning centers (APCs) is δl type, but it is unidentified when APCs are introduced into the films. In this paper, GdBCO thin films doped with BaHfO3 (BHO) deposited on LaAlO3 substrates by pulsed laser deposition were studied. A target exchange method was used to alternately ablate two targets of pure GdBCO and BHO for introducing nanorods as APCs into GdBCO films. Since the insulative BHO acts as a strong pinning center, the δT c pinning mechanism is expected for the temperature dependence of J c of these thin films. However, the experimental results showed that the J c of the films with BHO nanorods was determined by the δl pinning mechanism over a wide temperature range. In order to explain these unexpected results, we examined the pinning mechanism by nanorods based on a resultant pinning force model.

  3. Methane fluxes show consistent temperature dependence across microbial to ecosystem scales.

    Science.gov (United States)

    Yvon-Durocher, Gabriel; Allen, Andrew P; Bastviken, David; Conrad, Ralf; Gudasz, Cristian; St-Pierre, Annick; Thanh-Duc, Nguyen; del Giorgio, Paul A

    2014-03-27

    Methane (CH4) is an important greenhouse gas because it has 25 times the global warming potential of carbon dioxide (CO2) by mass over a century. Recent calculations suggest that atmospheric CH4 emissions have been responsible for approximately 20% of Earth's warming since pre-industrial times. Understanding how CH4 emissions from ecosystems will respond to expected increases in global temperature is therefore fundamental to predicting whether the carbon cycle will mitigate or accelerate climate change. Methanogenesis is the terminal step in the remineralization of organic matter and is carried out by strictly anaerobic Archaea. Like most other forms of metabolism, methanogenesis is temperature-dependent. However, it is not yet known how this physiological response combines with other biotic processes (for example, methanotrophy, substrate supply, microbial community composition) and abiotic processes (for example, water-table depth) to determine the temperature dependence of ecosystem-level CH4 emissions. It is also not known whether CH4 emissions at the ecosystem level have a fundamentally different temperature dependence than other key fluxes in the carbon cycle, such as photosynthesis and respiration. Here we use meta-analyses to show that seasonal variations in CH4 emissions from a wide range of ecosystems exhibit an average temperature dependence similar to that of CH4 production derived from pure cultures of methanogens and anaerobic microbial communities. This average temperature dependence (0.96 electron volts (eV)), which corresponds to a 57-fold increase between 0 and 30°C, is considerably higher than previously observed for respiration (approximately 0.65 eV) and photosynthesis (approximately 0.3 eV). As a result, we show that both the emission of CH4 and the ratio of CH4 to CO2 emissions increase markedly with seasonal increases in temperature. Our findings suggest that global warming may have a large impact on the relative contributions of CO2 and CH

  4. Phase behavior of coal fluids: Data for correlation development

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, R.L. Jr.; Gasem, K.A.M.; Shaver, R.D.

    1989-10-15

    During the present report period, our framework for correlating saturation properties using the scaled-variable-reduced coordinate approach was used to develop a correlation for saturated liquid densities of pure fluids at temperatures from the triple point to the critical point. The new correlation results in precise representation of liquid densities of diverse chemical species with average errors of 0.12% when two adjustable parameters are used to characterize each substance. In addition, the proposed model compares favorably with the modified Rackett and the Hankinson-Thomson correlations with the added advantages of covering the full saturation range and obeying scaling-law behavior in the near-critical region. Although the approach is essentially empirical, the results obtained suggest an underlying physical significance for the model parameters and show an excellent potential for generalized predictions. This is demonstrated by the results given here for saturated liquid densities where fully generalized predictions yield average errors of less than 1.0%.

  5. Extracting Constitutive Stress-Strain Behavior of Microscopic Phases by Micropillar Compression

    Science.gov (United States)

    Williams, J. J.; Walters, J. L.; Wang, M. Y.; Chawla, N.; Rohatgi, A.

    2013-02-01

    The macroscopic behavior of metallic materials is a complex function of microstructure. The size, morphology, volume fraction, crystallography, and distribution of a 2nd phase within a surrounding matrix all control the mechanical properties. Understanding the contributions of the individual microconstituents to the mechanical behavior of multiphase materials has proven difficult due to the inability to obtain accurate constitutive relationships of each individual constituent. In dual-phase steels, for example, the properties of martensite or ferrite in bulk form are not representative of their behavior at the microscale. In this study, micropillar compression was employed to determine the mechanical properties of individual microconstituents in metallic materials with "composite" microstructures, consisting of two distinct microconstituents: (I) a Mg-Al alloy with pure Mg dendrites and eutectic regions and (II) a powder metallurgy steel with ferrite and martensite constituents. The approach is first demonstrated in a Mg-Al directionally solidified alloy where the representative stress-strain behavior of the matrix and eutectic phases was obtained. The work is then extended to a dual-phase steel where the constitutive behavior of the ferrite and martensite were obtained. Here, the results were also incorporated into a modified rule-of-mixtures approach to predict the composite behavior of the steel. The constitutive behavior of the ferrite and martensite phases developed from micropillar compression was coupled with existing strength-porosity models from the literature to predict the ultimate tensile strength of the steel. Direct comparisons of the predictions with tensile tests of the bulk dual-phase steel were conducted and the correlations were quite good.

  6. Understanding phase-change behaviors of carbon-doped Ge₂Sb₂Te₅ for phase-change memory application.

    Science.gov (United States)

    Zhou, Xilin; Xia, Mengjiao; Rao, Feng; Wu, Liangcai; Li, Xianbin; Song, Zhitang; Feng, Songlin; Sun, Hongbo

    2014-08-27

    Phase-change materials are highly promising for next-generation nonvolatile data storage technology. The pronounced effects of C doping on structural and electrical phase-change behaviors of Ge2Sb2Te5 material are investigated at the atomic level by combining experiments and ab initio molecular dynamics. C dopants are found to fundamentally affect the amorphous structure of Ge2Sb2Te5 by altering the local environments of Ge-Te tetrahedral units with stable C-C chains. The incorporated C increases the amorphous stability due to the enhanced covalent nature of the material with larger tetrahedral Ge sites. The four-membered rings with alternating atoms are reduced greatly with carbon addition, leading to sluggish phase transition and confined crystal grains. The lower RESET power is presented in the PCM cells with carbon-doped material, benefiting from its high resistivity and low thermal conductivity.

  7. Synthesis of delafossite-derived phases, RCuO{sub 2+{delta}} with R=Y, La, Pr, Nd, Sm, and Eu, and observation of spin-gap-like behavior

    Energy Technology Data Exchange (ETDEWEB)

    Isawa, K.; Yaegashi, Y.; Komatsu, M.; Nagano, M.; Sudo, S. [Research and Development Center, Tohoku Electric Power Company, Incorporated, 2-1 Nakayama 7-chome, Aoba-ku, Sendai 981 (Japan); Karppinen, M.; Yamauchi, H. [Materials and Structures Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226 (Japan)

    1997-08-01

    The structural and physical properties of layered cuprates of a RCuO{sub 2} delafossite structure have been investigated for various rare-earth elements R: Y, La, Pr, Nd, Sm, and Eu. An oxygen-rich delafossite-derived phase, RCuO{sub 2+{delta}} ({delta}{ge}0.5), as previously reported by Cava {ital et al.} for R=Y and La was found for all the other R presently studied. Each as-sintered RCuO{sub 2} sample appeared to have a nearly stoichiometric oxygen content, but by thermal oxidation excess oxygen atoms corresponding to {delta}{ge}0.5 per formula unit could be loaded into the lattices. Although electrical resistivity ({rho}) of the oxygen-rich RCuO{sub 2+{delta}} samples exhibited semiconducting behavior at temperatures below 325 K a couple of samples showed anomalous temperature dependences in {rho} at low temperatures. Unusual temperature dependence of magnetic susceptibility ({chi}), was observed for Ca-doped YCuO{sub 2+{delta}} samples, but not for the other RCuO{sub 2+{delta}} phases. If the Curie term was subtracted from the susceptibility of (Y,Ca)CuO{sub 2+{delta}}, the remaining part of {chi} decreased monotonically with decreasing temperature down to {approximately}100K, and then leveled off with a finite value. Assuming that this finite value could be attributed to the Pauli paramagnetism of free carriers, the {chi} vs T characteristics were compared with those of other layered cuprates, such as SrCu{sub 2}O{sub 3}, (Sr,Ca){sub 14}Cu{sub 24}O{sub 41}, and (La,Sr)CuO{sub 2.5}, which have been reported to exhibit spin-gap behavior. {copyright} {ital 1997} {ital The American Physical Society}

  8. Room-temperature and temperature-dependent QSRR modelling for predicting the nitrate radical reaction rate constants of organic chemicals using ensemble learning methods.

    Science.gov (United States)

    Gupta, S; Basant, N; Mohan, D; Singh, K P

    2016-07-01

    Experimental determinations of the rate constants of the reaction of NO3 with a large number of organic chemicals are tedious, and time and resource intensive; and the development of computational methods has widely been advocated. In this study, we have developed room-temperature (298 K) and temperature-dependent quantitative structure-reactivity relationship (QSRR) models based on the ensemble learning approaches (decision tree forest (DTF) and decision treeboost (DTB)) for predicting the rate constant of the reaction of NO3 radicals with diverse organic chemicals, under OECD guidelines. Predictive powers of the developed models were established in terms of statistical coefficients. In the test phase, the QSRR models yielded a correlation (r(2)) of >0.94 between experimental and predicted rate constants. The applicability domains of the constructed models were determined. An attempt has been made to provide the mechanistic interpretation of the selected features for QSRR development. The proposed QSRR models outperformed the previous reports, and the temperature-dependent models offered a much wider applicability domain. This is the first report presenting a temperature-dependent QSRR model for predicting the nitrate radical reaction rate constant at different temperatures. The proposed models can be useful tools in predicting the reactivities of chemicals towards NO3 radicals in the atmosphere, hence, their persistence and exposure risk assessment.

  9. Study of thermal-field emission properties and investigation of temperature dependent noise in the field emission current from vertical carbon nanotube emitters

    Science.gov (United States)

    Kolekar, Sadhu; Patole, S. P.; Patil, Sumati; Yoo, J. B.; Dharmadhikari, C. V.

    2017-10-01

    We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well-defined cathode surface is given by Millikan and Lauritsen [1] for the combination of temperature and electric field effect. The same expression has been used to explain the electron emission characteristics from vertical CNT emitters. Furthermore, this has been applied to explain the electron emission for different temperatures ranging from room temperature to 1500 K. The real-time field electron emission images at room temperature and 1500 K are recorded by using Charge Coupled Device (CCD) in order to understand the effect of temperature on distribution of electron emission spots and ring like structures in Field Emission Microscope (FEM) image. The FEM images could be used to calculate the total number of emitters per cm2 for electron emission. The calculated number of emitters per cm2 from FEM image is typically, 4.5 × 107 and the actual number emitters per cm2 present as per Atomic Force Microscopy (AFM) data is 1.2 × 1012. The measured Current-Voltage (I-V) characteristics exhibit non linear Folwer-Nordheim (F-N) type behavior. The fluctuations in the emission current were recorded at different temperatures and Fast Fourier transformed into temperature dependent power spectral density. The latter was found to obey power law relation S(f) = A(Iδ/fξ), where δ and ξ are temperature dependent current and frequency exponents respectively.

  10. Investigating the Effect of Particle Size on Pulmonary Surfactant Phase Behavior

    Science.gov (United States)

    Kodama, Akihisa T.; Kuo, Chin-Chang; Boatwright, Thomas; Dennin, Michael

    2014-01-01

    We study the impact of the addition of particles of a range of sizes on the phase transition behavior of lung surfactant under compression. Charged particles ranging from micro- to nanoscale are deposited on lung surfactant films in a Langmuir trough. Surface area versus surface pressure isotherms and fluorescent microscope observations are utilized to determine changes in the phase transition behavior. We find that the deposition of particles close to 20 nm in diameter significantly impacts the coexistence of the liquid-condensed phase and liquid-expanded phase. This includes morphological changes of the liquid-condensed domains and the elimination of the squeeze-out phase in isotherms. Finally, a drastic increase of the domain fraction of the liquid-condensed phase can be observed for the deposition of 20-nm particles. As the particle size is increased, we observe a return to normal phase behavior. The net result is the observation of a critical particle size that may impact the functionality of the lung surfactant during respiration. PMID:25296309

  11. Structure and interaction in the polymer-dependent reentrant phase behavior of a charged nanoparticle solution

    Science.gov (United States)

    Kumar, Sugam; Ray, D.; Aswal, V. K.; Kohlbrecher, J.

    2014-10-01

    Small-angle neutron scattering (SANS) studies have been carried out to examine the evolution of interaction and structure in a nanoparticle (silica)-polymer (polyethylene glycol) system. The nanoparticle-polymer solution interestingly shows a reentrant phase behavior where the one-phase charged stabilized nanoparticles go through a two-phase system (nanoparticle aggregation) and back to one-phase as a function of polymer concentration. Such phase behavior arises because of the nonadsorption of polymer on nanoparticles and is governed by the interplay of polymer-induced attractive depletion with repulsive nanoparticle-nanoparticle electrostatic and polymer-polymer interactions in different polymer concentration regimes. At low polymer concentrations, the electrostatic repulsion dominates over the depletion attraction. However, the increase in polymer concentration enhances the depletion attraction to give rise to the nanoparticle aggregation in the two-phase system. Further, the polymer-polymer repulsion at high polymer concentrations is believed to be responsible for the reentrance to one-phase behavior. The SANS data in polymer contrast-matched conditions have been modeled by a two-Yukawa potential accounting for both repulsive and attractive parts of total interaction potential between nanoparticles. Both of these interactions (repulsive and attractive) are found to be long range. The magnitude and the range of the depletion interaction increase with the polymer concentration leading to nanoparticle clustering. At higher polymer concentrations, the increased polymer-polymer repulsion reduces the depletion interaction leading to reentrant phase behavior. The nanoparticle clusters in the two-phase system are characterized by the surface fractal with simple cubic packing of nanoparticles within the clusters. The effect of varying ionic strength and polymer size in tuning the interaction has also been examined.

  12. Investigation of the relationships between the thermodynamic phase behavior and gelation behavior of a series of tripodal trisamide compounds

    Science.gov (United States)

    Feng, Li

    Low molecular weight organic gelators(LMOGs) are important due to potential applications in many fields. Currently, most of the major studies focus on the empirical explanation of the crystallization for gelator assembly formation and morphologies, few efforts have been devoted to the thermodynamic phase behaviors and the effect of the non-ideal solution behavior on the structure of the resultant gels. In this research, tripodal trisamide compounds, synthesized from tris(2-aminoethyl)amine (TREN) by condensation with different acid chlorides, were studied as model LMOGs due to the simple one-step reaction and the commercially available chemical reactants. Gelation of organic solvents was investigated as a function of concentration and solvent solubility parameter.It has been found that the introduction of branches or cyclic units have dramatically improves the gelation ability compared to linear alkyl peripheral units. Fitting the liquidus lines using the regular solution model and calculation of the trisamide solubility parameter using solubility parameter theory gave good agreement with the trisamide solubility parameter calculated by group contribution methods. These results demonstrate that non-ideal solution behavior is an important factor in the gelation behavior of low molecular mass organic gelators. Understanding and controlling the thermodynamics and phase behaviors of the gel systems will provide effective ways to produce new efficient LMOGs in the future.

  13. The behavior of commensurate-incommensurate transitions using the phase field crystal model

    Science.gov (United States)

    Zhang, Tinghui; Lu, Yanli; Chen, Zheng

    2018-02-01

    We study the behavior of the commensurate-incommensurate (CI) transitions by using a phase field crystal model. The model is capable of modeling both elastic and plastic deformation and can simulate the evolution of the microstructure of the material at the atomic scale and the diffusive time scale, such as for adsorbed monolayer. Specifically, we study the behavior of the CI transitions as a function of lattice mismatch and the amplitude of substrate pinning potential. The behavior of CI phase transitions is revealed with the increase of the amplitude of pinning potential in some certain lattice mismatches. We find that for the negative lattice mismatch absorbed monolayer undergoes division, reorganization and displacement as increasing the amplitude of substrate pinning potential. In addition, for the positive mismatch absorbed monolayer undergoes a progress of phase transformation after a complete grain is split. Our results accord with simulations for atomic models of absorbed monolayer on a substrate surface.

  14. Chromatographic behavior of new antiepileptic active compounds on different reversed-phase materials.

    Science.gov (United States)

    Flieger, J; Pizoń, M; Plech, T

    2014-04-18

    A chromatographic and thermodynamic study of the derivatives of 4,5-disubstituted-2,4-dihydro-3H-1,2,4-triazole-3-thiones (and their Mannich bases) was undertaken. Three reversed-phase materials: a Zorbax Extend-C18, Cogent UDC Cholesterol and Regis IAM. PC. DD. 2 were studied. Plots of logk vs. the volume fraction of organic solvent in the mobile phase (φ) and the van't Hoff relationships were constructed. The van't Hoff plots revealed at least one phase transition on Cogent UDC Cholesterol and Regis IAM. PC. DD. 2. Obtained results indicated that adsorption was enthalpy-entropy driven. Cholesterol phase and Regis IAM. PC. DD. 2 in contrast to conventional octadecyl silica phase at aqueous-organic mobile phase demonstrated some liquid crystals behavior at defined conditions. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Effect of Secondary Phase Precipitation on the Corrosion Behavior of Duplex Stainless Steels

    Directory of Open Access Journals (Sweden)

    Kai Wang Chan

    2014-07-01

    Full Text Available Duplex stainless steels (DSSs with austenitic and ferritic phases have been increasingly used for many industrial applications due to their good mechanical properties and corrosion resistance in acidic, caustic and marine environments. However, DSSs are susceptible to intergranular, pitting and stress corrosion in corrosive environments due to the formation of secondary phases. Such phases are induced in DSSs during the fabrication, improper heat treatment, welding process and prolonged exposure to high temperatures during their service lives. These include the precipitation of sigma and chi phases at 700–900 °C and spinodal decomposition of ferritic grains into Cr-rich and Cr-poor phases at 350–550 °C, respectively. This article gives the state-of the-art review on the microstructural evolution of secondary phase formation and their effects on the corrosion behavior of DSSs.

  16. Effect of Secondary Phase Precipitation on the Corrosion Behavior of Duplex Stainless Steels

    Science.gov (United States)

    Chan, Kai Wang; Tjong, Sie Chin

    2014-01-01

    Duplex stainless steels (DSSs) with austenitic and ferritic phases have been increasingly used for many industrial applications due to their good mechanical properties and corrosion resistance in acidic, caustic and marine environments. However, DSSs are susceptible to intergranular, pitting and stress corrosion in corrosive environments due to the formation of secondary phases. Such phases are induced in DSSs during the fabrication, improper heat treatment, welding process and prolonged exposure to high temperatures during their service lives. These include the precipitation of sigma and chi phases at 700–900 °C and spinodal decomposition of ferritic grains into Cr-rich and Cr-poor phases at 350–550 °C, respectively. This article gives the state-of the-art review on the microstructural evolution of secondary phase formation and their effects on the corrosion behavior of DSSs. PMID:28788129

  17. Direct NMR Monitoring of Phase Separation Behavior of Highly Supersaturated Nifedipine Solution Stabilized with Hypromellose Derivatives.

    Science.gov (United States)

    Ueda, Keisuke; Higashi, Kenjirou; Moribe, Kunikazu

    2017-07-03

    We investigated the phase separation behavior and maintenance mechanism of the supersaturated state of poorly water-soluble nifedipine (NIF) in hypromellose (HPMC) derivative solutions. Highly supersaturated NIF formed NIF-rich nanodroplets through phase separation from aqueous solution containing HPMC derivative. Dissolvable NIF concentration in the bulk water phase was limited by the phase separation of NIF from the aqueous solution. HPMC derivatives stabilized the NIF-rich nanodroplets and maintained the NIF supersaturation with phase-separated NIF for several hours. The size of the NIF-rich phase was different depending on the HPMC derivatives dissolved in aqueous solution, although the droplet size had no correlation with the time for which NIF supersaturation was maintained without NIF crystallization. HPMC acetate and HPMC acetate succinate (HPMC-AS) effectively maintained the NIF supersaturation containing phase-separated NIF compared with HPMC. Furthermore, HPMC-AS stabilized NIF supersaturation more effectively in acidic conditions. Solution 1 H NMR measurements of NIF-supersaturated solution revealed that HPMC derivatives distributed into the NIF-rich phase during the phase separation of NIF from the aqueous solution. The hydrophobicity of HPMC derivative strongly affected its distribution into the NIF-rich phase. Moreover, the distribution of HPMC-AS into the NIF-rich phase was promoted at lower pH due to the lower aqueous solubility of HPMC-AS. The distribution of a large amount of HPMC derivatives into NIF-rich phase induced the strong inhibition of NIF crystallization from the NIF-rich phase. Polymer distribution into the drug-rich phase directly monitored by solution NMR technique can be a useful index for the stabilization efficiency of drug-supersaturated solution containing a drug-rich phase.

  18. Reversed-phase thin-layer chromatography behavior of aldopentose derivatives

    Directory of Open Access Journals (Sweden)

    Malbaša Radomir V.

    2012-01-01

    Full Text Available Quantitative structure-retention relationships (QSRR have been used to study the chromatographic behavior of some aldopentose. The behavior of aldopentose derivatives was investigated by means of the reversed-phase thin-layer chromatography (RP TLC on the silica gel impregnated with paraffin oil stationary phases. Binary mixtures of methanol-water, acetone-water and dioxane-water were used as mobile phases. Retention factors, RM0, corresponding to zero percent organic modifier in the aqueous mobile phase was determined. Lipophilicity C0 was calculated as the ratio of the intercept and slope values. There was satisfactory correlation between them and log P values calculated using different theoretical procedures. Some of these correlations offer very good predicting models, which are important for a better understanding of the relationships between chemical structure and retention. The study showed that the hydrophobic parameters RM0 and C0 can be used as a measures of lipophilicity of investigated compounds.

  19. Temperature dependent dynamics of DegP-trimer: A molecular dynamics study

    Directory of Open Access Journals (Sweden)

    Nivedita Rai

    2015-01-01

    Full Text Available DegP is a heat shock protein from high temperature requirement protease A family, which reacts to the environmental stress conditions in an ATP independent way. The objective of the present analysis emerged from the temperature dependent functional diversity of DegP between chaperonic and protease activities at temperatures below and above 28 °C, respectively. DegP is a multimeric protein and the minimal functional unit, DegP-trimer, is of great importance in understanding the DegP pathway. The structural aspects of DegP-trimer with respect to temperature variation have been studied using molecular dynamics simulations (for 100 ns and principal component analysis to highlight the temperature dependent dynamics facilitating its functional diversity. The DegP-trimer revealed a pronounced dynamics at both 280 and 320 K, when compared to the dynamics observed at 300 K. The LA loop is identified as the highly flexible region during dynamics and at extreme temperatures, the residues 46–80 of LA loop express a flip towards right (at 280 and left ( at 320 K with respect to the fixed β-sheet connecting the LA loop of protease for which Phe46 acts as one of the key residues. Such dynamics of LA loop facilitates inter-monomeric interaction with the PDZ1 domain of the neighbouring monomer and explains its active participation when DegP exists as trimer. Hence, the LA loop mediated dynamics of DegP-trimer is expected to provide further insight into the temperature dependent dynamics of DegP towards the understanding of its assembly and functional diversity in the presence of substrate.

  20. A Temperature-Dependent Phenology Model for Liriomyza huidobrensis (Diptera: Agromyzidae)

    Science.gov (United States)

    Sporleder, Marc; Carhuapoma, Pablo; Kroschel, Jürgen

    2017-01-01

    Abstract Liriomyza huidobrensis (Blanchard) is an economically important and highly polyphagous worldwide pest. To establish a temperature-dependent phenology model, essential for understanding the development and growth of the pest population under a variety of climates and as part of a pest risk analysis, L. huidobrensis life-table data were collected under laboratory conditions at seven constant temperatures on its host faba bean (Vicia faba L.). Several nonlinear equations were fitted to each life stage to model the temperature-dependent population growth and species life history and finally compile an overall temperature-dependent pest phenology model using the Insect Life Cycle Modeling (ILCYM) software. Liriomyza huidobrensis completed development from egg to adult in all temperatures evaluated, except at 32 °C, which was lethal to pupae. Eggs did not develop at 35 °C. Mean development time of all immature stages decreased with increasing temperature. Nonlinear models predicted optimal temperature for immature survival between 20–25 °C (32–38% mortality of all immature stages). Life-table parameters simulated at constant temperatures indicated that L. huidobrensis develops within the range of 12–28 °C. Simulated life-table for predicting the population dynamics of L. huidobrensis under two contrasting environments showed that lowland temperatures at the coast of Peru (250 m.a.s.l.) presented better conditions for a potential population increase than highland (3,400 m.a.s.l.) conditions. The presented model linked with Geographic Information Systems will allow pest risk assessments in different environmental regions to support the regulation of pest movement to prevent pest entry into not-yet invaded regions as well as to implement effective management strategies. PMID:28334271

  1. The effect of temperature dependent tissue parameters on acoustic radiation force induced displacements

    Science.gov (United States)

    Suomi, Visa; Han, Yang; Konofagou, Elisa; Cleveland, Robin O.

    2016-10-01

    Multiple ultrasound elastography techniques rely on acoustic radiation force (ARF) in monitoring high-intensity focused ultrasound (HIFU) therapy. However, ARF is dependent on tissue attenuation and sound speed, both of which are also known to change with temperature making the therapy monitoring more challenging. Furthermore, the viscoelastic properties of tissue are also temperature dependent, which affects the displacements induced by ARF. The aim of this study is to quantify the temperature dependent changes in the acoustic and viscoelastic properties of liver and investigate their effect on ARF induced displacements by using both experimental methods and simulations. Furthermore, the temperature dependent viscoelastic properties of liver are experimentally measured over a frequency range of 0.1-200 Hz at temperatures reaching 80 °C, and both conventional and fractional Zener models are used to fit the data. The fractional Zener model was found to fit better with the experimental viscoelasticity data with respect to the conventional model with up to two orders of magnitude lower sum of squared errors (SSE). The characteristics of experimental displacement data were also seen in the simulations due to the changes in attenuation coefficient and lesion development. At low temperatures before thermal ablation, attenuation was found to affect the displacement amplitude. At higher temperature, the decrease in displacement amplitude occurs approximately at 60-70 °C due to the combined effect of viscoelasticity changes and lesion growth overpowering the effect of attenuation. The results suggest that it is necessary to monitor displacement continuously during HIFU therapy in order to ascertain when ablation occurs.

  2. Temperature-Dependent Modeling and Crosstalk Analysis in Mixed Carbon Nanotube Bundle Interconnects

    Science.gov (United States)

    Rai, Mayank Kumar; Garg, Harsh; Kaushik, B. K.

    2017-08-01

    The temperature-dependent circuit modeling and performance analysis in terms of crosstalk in capacitively coupled mixed carbon nanotube bundle (MCB) interconnects, at the far end of the victim line, have been analyzed with four different structures of MCBs (MCB-1, MCB-2, MCB-3 and MCB-4) constituted under case 1 and case 2 at the 22-nm technology node. The impact of tunneling and intershell coupling between adjacent shells on temperature-dependent equivalent circuit parameters of a multi-walled carbon nanotube bundle are also critically analyzed and employed for different MCB structures under case 1. A similar analysis is performed for copper interconnects and comparisons are made between results obtained through these analyses over temperatures ranging from 300 K to 500 K. The simulation program with integrated circuit emphasis simulation results reveals that, compared with all MCB structures under case 1 and case 2, with rise in temperature from 300 K to 500 K, crosstalk-induced noise voltage levels at the far end of the victim line are found to be significantly large in copper. It is also observed that due to the dominance of larger temperature-dependent resistance and ground capacitance in case 1, the MCB-2 is of lower crosstalk-induced noise voltage levels than other structures of MCBs. On the other hand, the MCB-1 has smaller time duration of victim output. Results further reveal that, compared with case 2 of MCB, with rise in temperatures, the victim line gets less prone to crosstalk-induced noise in MCB interconnects constituted under case 1, due to tunneling effects and intershell coupling between adjacent shells. Based on these comparative results, a promising MCB structure (MCB-2) has been proposed among other structures under the consideration of tunneling effects and intershell coupling (case 1).

  3. Effect of Charge Patterning on the Phase Behavior of Polymer Coacervates for Charge Driven Self Assembly

    Science.gov (United States)

    Radhakrishna, Mithun; Sing, Charles E.

    Oppositely charged polymers can undergo associative liquid-liquid phase separation when mixed under suitable conditions of ionic strength, temperature and pH to form what are known as `polymeric complex coacervates'. Polymer coacervates find use in diverse array of applications like microencapsulation, drug delivery, membrane filtration and underwater adhesives. The similarity between complex coacervate environments and those in biological systems has also found relevance in areas of bio-mimicry. Our previous works have demonstrated how local charge correlations and molecular connectivity can drastically affect the phase behavior of coacervates. The precise location of charges along the chain therefore dramatically influences the local charge correlations, which consequently influences the phase behavior of coacervates. We investigate the effect of charge patterning along the polymer chain on the phase behavior of coacervates in the framework of the Restricted Primitive Model using Gibbs Ensemble Monte Carlo simulations. Our results show that charge patterning dramatically changes the phase behavior of polymer coacervates, which contrasts with the predictions of the classical Voorn-Overbeek theory. This provides the basis for designing new materials through charge driven self assembly by controlling the positioning of the charged monomers along the chain.

  4. The temperature-dependent expression of the desaturase gene desA in Synechocystis PCC6803.

    Science.gov (United States)

    Los, D; Horvath, I; Vigh, L; Murata, N

    1993-02-22

    We examined the temperature-dependent regulation of the expression of the desA gene, which encodes delta 12 desaturase of Synechocystis PCC6803. The level of desA transcript increased 10-fold within 1 h upon a decrease in temperature from 36 degrees C to 22 degrees C. This suggests that the low-temperature-induced desaturation of membrane lipid fatty acids is regulated at the level of the expression of the desaturase genes. The accumulation of the desA transcript depended on the extent of temperature change over a certain threshold level, but not on the absolute temperature.

  5. Calculation of the Effect of Random Superfluid Density on the Temperature Dependence of the Penetration Depth

    Energy Technology Data Exchange (ETDEWEB)

    Lippman, Thomas; Moler, Kathryn A.

    2012-07-20

    Microscopic variations in composition or structure can lead to nanoscale inhomogeneity in superconducting properties such as the magnetic penetration depth, but measurements of these properties are usually made on longer length scales. We solve a generalized London equation with a non-uniform penetration depth {lambda}(r), obtaining an approximate solution for the disorder-averaged Meissner screening. We find that the effective penetration depth is different from the average penetration depth and is sensitive to the details of the disorder. These results indicate the need for caution when interpreting measurements of the penetration depth and its temperature dependence in systems which may be inhomogeneous.

  6. Intensity and temperature-dependent photoluminescence of tris (8-hydroxyquinoline) aluminum films

    Energy Technology Data Exchange (ETDEWEB)

    Ajward, A. M.; Wang, X.; Wagner, H. P. [Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221 (United States)

    2013-12-04

    We investigate the recombination of excitons in tris (8-hydroxyquinoline) aluminum films by intensity and temperature dependent time-resolved photoluminescence (PL). At low temperature (15 K) and elevated excitation intensity the radiative emission is quenched by singlet-singlet annihilation processes. With rising temperature the PL quenching is strongly reduced resulting in a PL efficiency maximum at ∼170 K. The reduced exciton annihilation is attributed to thermally activated occupation of non-quenchable trapped exciton states. Above 170 K the PL efficiency decreases due to thermal de-trapping of radiative states and subsequent migration to non-radiative centers.

  7. Thin film flow in MHD third grade fluid on a vertical belt with temperature dependent viscosity.

    Science.gov (United States)

    Gul, Taza; Islam, Saed; Shah, Rehan Ali; Khan, Ilyas; Shafie, Sharidan

    2014-01-01

    In this work, we have carried out the influence of temperature dependent viscosity on thin film flow of a magnetohydrodynamic (MHD) third grade fluid past a vertical belt. The governing coupled non-linear differential equations with appropriate boundary conditions are solved analytically by using Adomian Decomposition Method (ADM). In order to make comparison, the governing problem has also been solved by using Optimal Homotopy Asymptotic Method (OHAM). The physical characteristics of the problem have been well discussed in graphs for several parameter of interest.

  8. Physico-chemical characterization of the temperature dependent hydration kinetics of Gleditsia sinensis gum.

    Science.gov (United States)

    Jian, Hong-Lei; Lin, Xue-Jiao; Zhang, Wei-Ming; Sun, Da-Feng; Jiang, Jian-Xin

    2013-11-01

    The physico-chemical properties and hydration kinetics of Gleditsia sinensis gum were investigated to evaluate its temperature dependence. The increase of temperature resulted in improved solubility of G. sinensis gum, and the dissolved galactomannan showed decreased degree of galactose substitution (DSGal) and increased molecular weight (p0.96), and the hydration index t0.8 at different temperatures varied in the range of 51-302 min. It was found that galactomannan with low DSGal and high molecular weight exhibited slow hydration rate and poor solubility. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Analysis of the temperature dependence of the thermal conductivity of insulating single crystal oxides

    Directory of Open Access Journals (Sweden)

    E. Langenberg

    2016-10-01

    Full Text Available The temperature dependence of the thermal conductivity of 27 different single crystal oxides is reported from ≈20 K to 350 K. These crystals have been selected among the most common substrates for growing epitaxial thin-film oxides, spanning over a range of lattice parameters from ≈3.7 Å to ≈12.5 Å. Different contributions to the phonon relaxation time are discussed on the basis of the Debye model. This work provides a database for the selection of appropriate substrates for thin-film growth according to their desired thermal properties, for applications in which heat management is important.

  10. A Temperature-Dependent Thermal Model of IGBT Modules Suitable for Circuit-Level Simulations

    DEFF Research Database (Denmark)

    Wu, Rui; Wang, Huai; Pedersen, Kristian Bonderup

    2016-01-01

    A basic challenge in the IGBT transient simulation study is to obtain the realistic junction temperature, which demands not only accurate electrical simulations but also precise thermal impedance. This paper proposed a transient thermal model for IGBT junction temperature simulations during short...... circuits or overloads. The updated Cauer thermal model with varying thermal parameters is obtained by means of FEM thermal simulations with temperature-dependent physical parameters. The proposed method is applied to a case study of a 1700 V/1000 A IGBT module. Furthermore, a testing setup is built up...

  11. Computational modeling of 915 MHz microwave ablation: Comparative assessment of temperature-dependent tissue dielectric models.

    Science.gov (United States)

    Deshazer, Garron; Hagmann, Mark; Merck, Derek; Sebek, Jan; Moore, Kent B; Prakash, Punit

    2017-09-01

    The objective of this study is to develop a computational model for simulating 915 MHz microwave ablation (MWA), and verify the simulation predictions of transient temperature profiles against experimental measurements. Due to the limited experimental data characterizing temperature-dependent changes of tissue dielectric properties at 915 MHz, we comparatively assess two temperature-dependent approaches of modeling of dielectric properties: model A- piecewise linear temperature dependencies based on existing, but limited, experimental data, and model B- similar to model A, but augmented with linear decrease in electrical conductivity above 95 °C, as guided by our experimental measurements. The finite element method was used to simulate MWA procedures in liver with a clinical 915 MHz ablation applicator. A coupled electromagnetic-thermal solver incorporating temperature-dependent tissue biophysical properties of liver was implemented. Predictions of the transient temperature profiles and ablation zone dimensions for both model A and model B were compared against experimental measurements in ex vivo bovine liver tissue. Broadband dielectric properties of tissue within different regions of the ablation zone were measured and reported at 915 MHz and 2.45 GHz. Model B yielded peak tissue temperatures in closer agreement with experimental measurements, attributed to the inclusion of decrease in electrical conductivity at elevated temperature. The simulated transverse diameters of the ablation zone predicted by both models were greater than experimental measurements, which may be in part due to the lack of a tissue shrinkage model. At both considered power levels, predictions of transverse ablation zone diameters were in closer agreement with measurements for model B (max. discrepancy of 5 mm at 60 W, and 3 mm at 30 W), compared to model A (max. discrepancy of 9 mm at 60 W, and 6 mm at 30 W). Ablation zone lengths with both models were within 2 mm at 30 W, but

  12. Defect-induced change of temperature-dependent elastic constants in BCC iron

    Energy Technology Data Exchange (ETDEWEB)

    Gao, N.; Setyawan, W.; Zhang, S. H.; Wang, Z. G.

    2017-07-01

    The effects of radiation-induced defects (randomly distributed vacancies, voids, and interstitial dislocation loops) on temperature-dependent elastic constants, C11, C12, and C44 in BCC iron, are studied with molecular dynamics method. The elastic constants are found to decrease with increasing temperatures for all cases containing different defects. The presence of vacancies, voids, or interstitial loops further decreases the elastic constants. For a given number of point defects, the randomly distributed vacancies show the strongest effect compared to voids or interstitial loops. All these results are expected to provide useful information to combine with experimental results for further understanding of radiation damage.

  13. Temperature dependence of the single photon emission from interface-fluctuation GaN quantum dots.

    Science.gov (United States)

    Le Roux, F; Gao, K; Holmes, M; Kako, S; Arita, M; Arakawa, Y

    2017-11-23

    The temperature dependent single photon emission statistics of interface-fluctuation GaN quantum dots are reported. Quantum light emission is confirmed at temperatures up to ~77 K, by which point the background emission degrades the emission purity and results in a measured g(2) (0) in excess of 0.5. A discussion on the extent of the background contamination is also given through comparison to extensive data taken under various ambient and experimental conditions, revealing that the quantum dots themselves are emitting single photons with high purity.

  14. Unraveling the Transcriptional Basis of Temperature-Dependent Pinoxaden Resistance in Brachypodium hybridum.

    Science.gov (United States)

    Matzrafi, Maor; Shaar-Moshe, Lidor; Rubin, Baruch; Peleg, Zvi

    2017-01-01

    Climate change endangers food security and our ability to feed the ever-increasing human population. Weeds are the most important biotic stress, reducing crop-plant productivity worldwide. Chemical control, the main approach for weed management, can be strongly affected by temperature. Previously, we have shown that temperature-dependent non-target site (NTS) resistance of Brachypodium hybridum is due to enhanced detoxification of acetyl-CoA carboxylase inhibitors. Here, we explored the transcriptional basis of this phenomenon. Plants were characterized for the transcriptional response to herbicide application, high-temperature and their combination, in an attempt to uncover the genetic basis of temperature-dependent pinoxaden resistance. Even though most of the variance among treatments was due to pinoxaden application (61%), plants were able to survive pinoxaden application only when grown under high-temperatures. Biological pathways and expression patterns of members of specific gene families, previously shown to be involved in NTS metabolic resistance to different herbicides, were examined. Cytochrome P450, glucosyl transferase and glutathione-S-transferase genes were found to be up-regulated in response to pinoxaden application under both control and high-temperature conditions. However, biological pathways related to oxidation and glucose conjugation were found to be significantly enriched only under the combination of pinoxaden application and high-temperature. Analysis of reactive oxygen species (ROS) was conducted at several time points after treatment using a probe detecting H2O2/peroxides. Comparison of ROS accumulation among treatments revealed a significant reduction in ROS quantities 24 h after pinoxaden application only under high-temperature conditions. These results may indicate significant activity of enzymatic ROS scavengers that can be correlated with the activation of herbicide-resistance mechanisms. This study shows that up-regulation of genes

  15. Scaling of temperature dependence of charge mobility in molecular Holstein chains

    Science.gov (United States)

    Tikhonov, D. A.; Fialko, N. S.; Sobolev, E. V.; Lakhno, V. D.

    2014-03-01

    The temperature dependence of a charge mobility in a model DNA based on a Holstein Hamiltonian is calculated for four types of homogeneous sequences It has turned out that upon rescaling all four types are quite similar. Two types of rescaling, i.e., those for low and intermediate temperatures, are found. The curves obtained are approximated on a logarithmic scale by cubic polynomials. We believe that for model homogeneous biopolymers with parameters close to the designed ones, one can assess the value of the charge mobility without carrying out resource-intensive direct simulation, just by using a suitable approximating function.

  16. Temperature dependence of large positive magnetoresistance in hybrid ferromagnetic/semiconductor devices

    Science.gov (United States)

    Overend, N.; Nogaret, A.; Gallagher, B. L.; Main, P. C.; Henini, M.; Marrows, C. H.; Howson, M. A.; Beaumont, S. P.

    1998-04-01

    We investigate a new type of magnetoresistance (MR) in which the resistivity of a near-surface two-dimensional electron gas is controlled by the magnetization of a submicron ferromagnetic grating defined on the surface of the device. We observe an increase in resistance of up to ˜1500% at a temperature of 4 K and ˜1% at 300 K. The magnitude and temperature dependence of the MR are well accounted for by a semiclassical theory. Optimization of device parameters is expected to increase considerably the magnitude of the room temperature MR.

  17. Temperature dependence of unitary properties of an ATP-dependent potassium channel in cardiac myocytes.

    OpenAIRE

    McLarnon, J G; Hamman, B.N.; Tibbits, G.F.

    1993-01-01

    The temperature dependence of the properties of unitary currents in cultured rat ventricular myocytes has been studied. Currents flowing through an ATP-dependent K+ channel were recorded from inside-out patches with the bath temperature varied from 10 degrees to 30 degrees C. The channel conductance was 56 pS at room temperature (22 degrees C), and the amplitudes of unitary currents and the channel conductance exhibited a relatively weak (Q10 from 1.4 to 1.6) dependence on temperature. The te...

  18. Temperature-Dependent Electrical and Micromechanical Properties of Lanthanum Titanate with Additions of Yttria

    Science.gov (United States)

    Goldsby, Jon C.

    2010-01-01

    Temperature-dependent elastic properties were determined by establishing continuous flexural vibrations in the material at its lowest resonance frequency of 31tHz. The imaginary part of the complex impedance plotted as a function of frequency and temperature reveals a thermally activated peak, which decreases in magnitude as the temperature increases. Additions of yttria do not degrade the electromechanical in particularly the elastic and anelastic properties of lanthanum titanate. Y2O3/La2Ti2O7 exhibits extremely low internal friction and hence may be more mechanical fatigue-resistant at low strains.

  19. Temperature dependent electrical properties of polyaniline film grown on paper through aniline vapor polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Deb, K.; Bera, A.; Saha, B., E-mail: biswajit.physics@gmail.com [Department of Physics, National Institute of Technology Agartala, Jirania, West Tripura 799046 (India); Bhowmik, K. L. [Department of Physics, National Institute of Technology Agartala, Jirania, West Tripura 799046 (India); Department of Chemistry, Bir Bikram Memorial College, Agartala, West Tripura 799004 (India); Chattopadhyay, K. K. [Department of Physics, Jadavpur University, Kolkata 700 032 (India)

    2016-05-23

    Polyaniline thin film has been prepared on paper by aniline vapor deposition technique. Ferric chloride has been used as polymerizing agent in this approach. The prepared films were studied through electrical resistivity and optical properties measurements. The electrical resistivity of the polyaniline film shows significant temperature dependence. The resistance sharply falls with the increase in temperature. The optical absorbance measurements shows characteristics absorbance peak indicating the formation of conducting emeraldine salt form of polyaniline. The optical energy band gap of the film was calculated from the transmittance spectra. The optical energy band gap and electrical conductivity of the polyaniline film is well suited for their applications in electronic devices.

  20. Effects of Temperature Dependence of Energy Bandgap on I-V Characteristics in CNTFETs Models

    Science.gov (United States)

    Marani, R.; Perri, A. G.

    In this paper, we analyze the effects of temperature dependence of energy bandgap on I-V characteristics in some carbon nanotube field effect transistors (CNTFETs) models proposed in literature in order to identify the one more suitable for computer aided design (CAD) applications. At first we consider a compact, semi-empirical model, already proposed by us, performing I-V characteristic simulations at different temperatures. Our results are compared with those obtained with the Stanford-Source virtual carbon nanotube field-effect transistor model (VS-CNFET), obtaining I-V characteristics comparable, but with lower CPU calculation time.

  1. Unraveling the Transcriptional Basis of Temperature-Dependent Pinoxaden Resistance in Brachypodium hybridum

    Science.gov (United States)

    Matzrafi, Maor; Shaar-Moshe, Lidor; Rubin, Baruch; Peleg, Zvi

    2017-01-01

    Climate change endangers food security and our ability to feed the ever-increasing human population. Weeds are the most important biotic stress, reducing crop-plant productivity worldwide. Chemical control, the main approach for weed management, can be strongly affected by temperature. Previously, we have shown that temperature-dependent non-target site (NTS) resistance of Brachypodium hybridum is due to enhanced detoxification of acetyl-CoA carboxylase inhibitors. Here, we explored the transcriptional basis of this phenomenon. Plants were characterized for the transcriptional response to herbicide application, high-temperature and their combination, in an attempt to uncover the genetic basis of temperature-dependent pinoxaden resistance. Even though most of the variance among treatments was due to pinoxaden application (61%), plants were able to survive pinoxaden application only when grown under high-temperatures. Biological pathways and expression patterns of members of specific gene families, previously shown to be involved in NTS metabolic resistance to different herbicides, were examined. Cytochrome P450, glucosyl transferase and glutathione-S-transferase genes were found to be up-regulated in response to pinoxaden application under both control and high-temperature conditions. However, biological pathways related to oxidation and glucose conjugation were found to be significantly enriched only under the combination of pinoxaden application and high-temperature. Analysis of reactive oxygen species (ROS) was conducted at several time points after treatment using a probe detecting H2O2/peroxides. Comparison of ROS accumulation among treatments revealed a significant reduction in ROS quantities 24 h after pinoxaden application only under high-temperature conditions. These results may indicate significant activity of enzymatic ROS scavengers that can be correlated with the activation of herbicide-resistance mechanisms. This study shows that up-regulation of genes

  2. Temperature-dependent transport mechanisms through PE-CVD coatings: comparison of oxygen and water vapour

    Science.gov (United States)

    Kirchheim, D.; Wilski, S.; Jaritz, M.; Mitschker, F.; Gebhard, M.; Brochhagen, M.; Böke, M.; Benedikt, Jan; Awakowicz, P.; Devi, A.; Hopmann, Ch; Dahlmann, R.

    2017-10-01

    When it comes to thin coatings such as plasma-enhanced chemical vapour deposition or plasma-enhanced atomic layer deposition coatings on substrates of polymeric material, existing models often describe transport through these thin coatings as mainly driven by transport through defects of different sizes. However, temperature-dependent measurements of permeation could not confirm this hypothesis and instead gaseous transport through these thin coatings was found to more likely to occur through the molecular structure. This paper correlates existing transport models with data from oxygen transmission experiments and puts recent investigations for water vapour transmission mechanisms into context for a better understanding of gaseous transport through thin coatings.

  3. Temperature dependence of dislocation-related luminescence in silicon-germanium heterostructure

    CERN Document Server

    Lee, H S

    1998-01-01

    We measured the photoluminescence spectra of very thin and partially strained Si sub 0 sub . sub 6 Ge sub 0 sub . sub 4 alloys grown on silicon substrate with varying degrees of strain relaxation. We observed photoluminescence lines, so called D-lines, which arose from dislocations in the SiGe/Si alloys. We identified the origin of the D-lines as the dislocations in Si substrate extending from the SiGe/Si interface. We also studied the temperature dependence of the Si D-lines and determined the dissociation energy of the defect energy levels.

  4. Strained silicon on SiGe: Temperature dependence of carrier effective masses

    Science.gov (United States)

    Richard, Soline; Cavassilas, Nicolas; Aniel, Frédéric; Fishman, Guy

    2003-10-01

    A strain Bir-Pikus Hamiltonian Hst, based on a 20 band sps* kṡp Hamiltonian Hkp, is used to describe the valence band and the first two conduction bands over the entire Brillouin zone. This full-band kṡp computation of the carrier dispersion relation is used to calculate electron and hole effective masses in strained silicon. Hole density of states masses are found to be very temperature dependent whereas electron effective masses can be considered temperature independent to first order.

  5. Experimental data showing the thermal behavior of a flat roof with phase change material.

    Science.gov (United States)

    Tokuç, Ayça; Başaran, Tahsin; Yesügey, S Cengiz

    2015-12-01

    The selection and configuration of building materials for optimal energy efficiency in a building require some assumptions and models for the thermal behavior of the utilized materials. Although the models for many materials can be considered acceptable for simulation and calculation purposes, the work for modeling the real time behavior of phase change materials is still under development. The data given in this article shows the thermal behavior of a flat roof element with a phase change material (PCM) layer. The temperature and energy given to and taken from the building element are reported. In addition the solid-liquid behavior of the PCM is tracked through images. The resulting thermal behavior of the phase change material is discussed and simulated in [1] A. Tokuç, T. Başaran, S.C. Yesügey, An experimental and numerical investigation on the use of phase change materials in building elements: the case of a flat roof in Istanbul, Build. Energy, vol. 102, 2015, pp. 91-104.

  6. Experimental data showing the thermal behavior of a flat roof with phase change material

    Directory of Open Access Journals (Sweden)

    Ayça Tokuç

    2015-12-01

    Full Text Available The selection and configuration of building materials for optimal energy efficiency in a building require some assumptions and models for the thermal behavior of the utilized materials. Although the models for many materials can be considered acceptable for simulation and calculation purposes, the work for modeling the real time behavior of phase change materials is still under development. The data given in this article shows the thermal behavior of a flat roof element with a phase change material (PCM layer. The temperature and energy given to and taken from the building element are reported. In addition the solid–liquid behavior of the PCM is tracked through images. The resulting thermal behavior of the phase change material is discussed and simulated in [1] A. Tokuç, T. Başaran, S.C. Yesügey, An experimental and numerical investigation on the use of phase change materials in building elements: the case of a flat roof in Istanbul, Build. Energy, vol. 102, 2015, pp. 91–104.

  7. Equilibrium Phase Behavior of the Square-Well Linear Microphase-Forming Model.

    Science.gov (United States)

    Zhuang, Yuan; Charbonneau, Patrick

    2016-07-07

    We have recently developed a simulation approach to calculate the equilibrium phase diagram of particle-based microphase formers. Here, this approach is used to calculate the phase behavior of the square-well linear model for different strengths and ranges of the linear long-range repulsive component. The results are compared with various theoretical predictions for microphase formation. The analysis further allows us to better understand the mechanism for microphase formation in colloidal suspensions.

  8. Phase behavior and nanoscale structure of phospholipid membranes incorporated with acylated C-14-peptides

    DEFF Research Database (Denmark)

    Pedersen, T.B.; Kaasgaard, Thomas; Jensen, M.O.

    2005-01-01

    The thermotropic phase behavior and lateral structure of dipalmitoylphosphatidylcholine (DPPC) lipid bilayers containing an acylated peptide has been characterized by differential scanning calorimetry (DSC) on vesicles and atomic force microscopy (AFM) on mica-supported bilayers. The acylated...... gel phase DPPC bilayers, inserts preferentially into preexisting defect regions and has a noticeable influence on the organization of the surrounding lipids. The presence of the C-14-peptide gives rise to a laterally heterogeneous bilayer structure with coexisting lipid domains characterized by a 10...

  9. Enthalpy and phase behavior of coal derived liquid mixtures. Technical progress report, July-September 1984

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1984-10-30

    Work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. Calorimetric measurements were made on pure quinoline. These measurements extended the range of previous measurements which had been made on quinoline, and improved the accuracy of previously measured results in the vapor phase when the quinoline sample used was believed to contain considerable quantities of water. 5 figures, 4 tables.

  10. Interplay between quantum phase transitions and the behavior of quantum correlations at finite temperatures

    OpenAIRE

    Werlang, T.; Ribeiro, G. A. P.; Rigolin, Gustavo

    2012-01-01

    We review the main results and ideas showing that quantum correlations at finite temperatures (T), in particular quantum discord, are useful tools in characterizing quantum phase transitions that only occur, in principle, at the unattainable absolute zero temperature. We first review some interesting results about the behavior of thermal quantum discord for small spin-1/2 chains and show that they already give us important hints of the infinite chain behavior. We then study in detail and in t...

  11. The effect of pressure on the phase behavior of surfactant systems: An experimental study

    DEFF Research Database (Denmark)

    Sandersen, Sara Bülow; Stenby, Erling Halfdan; von Solms, Nicolas

    2012-01-01

    Enhanced oil recovery is employed in many mature oil reservoirs to maintain or increase the reservoir recovery factor. In this context, surfactant flooding has recently gained interest again. Surfactant flooding is the injection of surfactants (and co-surfactants) into the reservoir, in order...... is influenced to an even greater extent. It was concluded that at certain compositions of the surfactant system (near to the phase boundary found at atmospheric pressure) the increase in pressure changed the phase behavior (for example causing the system to move from two phases to three or vice versa...

  12. Enthalpy and phase behavior of coal derived liquid mixtures. Technical progress report, January-March 1985

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1985-04-30

    On July 15, 1984, work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. During the third quarter modifications to both the calorimeter and the phase equilibria system were completed. The phase equilibria system was checked out against literature data for methanol/ethanol. Results of these tests are included in this report. The calorimeter was evaluated using previously confirmed heptane data and published data by Thinh, et al. These results are also reported. Initial calorimetry data have been obtained for tetralin and the data will be reported when the data set has been completed. 5 refs., 5 figs., 3 tabs.

  13. Cooling-induced shape memory effect and inverse temperature dependence of superelastic stress in Co2Cr(Ga,Si) ferromagnetic Heusler alloys

    Science.gov (United States)

    Xu, Xiao; Omori, Toshihiro; Nagasako, Makoto; Okubo, Akinari; Umetsu, Rie Y.; Kanomata, Takeshi; Ishida, Kiyohito; Kainuma, Ryosuke

    2013-10-01

    Normally, shape memory effect (SME) is obtained by the reverse martensitic transformation, therefore only induced by heating a sample from the deformed martensite phase. In this study, we report a phenomenon of cooling-induced SME, observed in a Co2Cr(Ga,Si) Heusler alloy, where the normal heating-induced SME can be obtained at the same time. The cooling-induced SME is attributed to an abnormal martensitic transformation in Co2Cr(Ga,Si) Heusler alloy. Moreover, an inverse temperature dependence of superelastic stress was also observed. The discoveries of these phenomena provide application possibilities for shape memory alloys, especially at low temperatures.

  14. Temperature dependence of the current in Schottky-barrier source-gated transistors

    Science.gov (United States)

    Sporea, R. A.; Overy, M.; Shannon, J. M.; Silva, S. R. P.

    2015-05-01

    The temperature dependence of the drain current is an important parameter in thin-film transistors. In this paper, we propose that in source-gated transistors (SGTs), this temperature dependence can be controlled and tuned by varying the length of the source electrode. SGTs comprise a reverse biased potential barrier at the source which controls the current. As a result, a large activation energy for the drain current may be present which, although useful in specific temperature sensing applications, is in general deleterious in many circuit functions. With support from numerical simulations with Silvaco Atlas, we describe how increasing the length of the source electrode can be used to reduce the activation energy of SGT drain current, while maintaining the defining characteristics of SGTs: low saturation voltage, high output impedance in saturation, and tolerance to geometry variations. In this study, we apply the dual current injection modes to obtain drain currents with high and low activation energies and propose mechanisms for their exploitation in future large-area integrated circuit designs.

  15. On the temperature dependence of H-U{sub iso} in the riding hydrogen model

    Energy Technology Data Exchange (ETDEWEB)

    Lübben, Jens; Volkmann, Christian [Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, D-37077 Göttingen (Germany); Grabowsky, Simon [School of Chemistry and Biochemistry, Stirling Highway 35, WA-6009 Crawley (Australia); Edwards, Alison [Bragg Institute, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Morgenroth, Wolfgang [Institut für Geowissenschaften, Abteilung Kristallographie, Goethe-Universität, Altenhöferallee 1, 60438 Frankfurt am Main (Germany); Fabbiani, Francesca P. A. [GZG, Abteilung Kristallographie, Georg-August Universität, Goldschmidtstrasse 1, 37077 Göttingen (Germany); Sheldrick, George M. [Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, D-37077 Göttingen (Germany); Dittrich, Birger, E-mail: birger.dittrich@chemie.uni-hamburg.de [Institut für Anorganische und Angewandte Chemie, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany); Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, D-37077 Göttingen (Germany)

    2014-07-01

    The temperature dependence of hydrogen U{sub iso} and parent U{sub eq} in the riding hydrogen model is investigated by neutron diffraction, aspherical-atom refinements and QM/MM and MO/MO cluster calculations. Fixed values of 1.2 or 1.5 appear to be underestimated, especially at temperatures below 100 K. The temperature dependence of H-U{sub iso} in N-acetyl-l-4-hydroxyproline monohydrate is investigated. Imposing a constant temperature-independent multiplier of 1.2 or 1.5 for the riding hydrogen model is found to be inaccurate, and severely underestimates H-U{sub iso} below 100 K. Neutron diffraction data at temperatures of 9, 150, 200 and 250 K provide benchmark results for this study. X-ray diffraction data to high resolution, collected at temperatures of 9, 30, 50, 75, 100, 150, 200 and 250 K (synchrotron and home source), reproduce neutron results only when evaluated by aspherical-atom refinement models, since these take into account bonding and lone-pair electron density; both invariom and Hirshfeld-atom refinement models enable a more precise determination of the magnitude of H-atom displacements than independent-atom model refinements. Experimental efforts are complemented by computing displacement parameters following the TLS+ONIOM approach. A satisfactory agreement between all approaches is found.

  16. Temperature-Dependent Rate Coefficients for the Reaction of CH2OO with Hydrogen Sulfide.

    Science.gov (United States)

    Smith, Mica C; Chao, Wen; Kumar, Manoj; Francisco, Joseph S; Takahashi, Kaito; Lin, Jim Jr-Min

    2017-02-09

    The reaction of the simplest Criegee intermediate CH 2 OO with hydrogen sulfide was measured with transient UV absorption spectroscopy in a temperature-controlled flow reactor, and bimolecular rate coefficients were obtained from 278 to 318 K and from 100 to 500 Torr. The average rate coefficient at 298 K and 100 Torr was (1.7 ± 0.2) × 10 -13 cm 3 s -1 . The reaction was found to be independent of pressure and exhibited a weak negative temperature dependence. Ab initio quantum chemistry calculations of the temperature-dependent reaction rate coefficient at the QCISD(T)/CBS level are in reasonable agreement with the experiment. The reaction of CH 2 OO with H 2 S is 2-3 orders of magnitude faster than the reaction with H 2 O monomer. Though rates of CH 2 OO scavenging by water vapor under atmospheric conditions are primarily controlled by the reaction with water dimer, the H 2 S loss pathway will be dominated by the reaction with monomer. The agreement between experiment and theory for the CH 2 OO + H 2 S reaction lends credence to theoretical descriptions of other Criegee intermediate reactions that cannot easily be probed experimentally.

  17. Dimorphic DNA methylation during temperature-dependent sex determination in the sea turtle Lepidochelys olivacea.

    Science.gov (United States)

    Venegas, Daniela; Marmolejo-Valencia, Alejandro; Valdes-Quezada, Christian; Govenzensky, Tzipe; Recillas-Targa, Félix; Merchant-Larios, Horacio

    2016-09-15

    Sex determination in vertebrates depends on the expression of a conserved network of genes. Sea turtles such as Lepidochelys olivacea have temperature-dependent sex determination. The present work analyses some of the epigenetic processes involved in this. We describe sexual dimorphism in global DNA methylation patterns between ovaries and testes of L. olivacea and show that the differences may arise from a combination of DNA methylation and demethylation events that occur during sex determination. Irrespective of incubation temperature, 5-hydroxymethylcytosine was abundant in the bipotential gonad; however, following sex determination, this modification was no longer found in pre-Sertoli cells in the testes. These changes correlate with the establishment of the sexually dimorphic DNA methylation patterns, down regulation of Sox9 gene expression in ovaries and irreversible gonadal commitment towards a male or female differentiation pathway. Thus, DNA methylation changes may be necessary for the stabilization of the gene expression networks that drive the differentiation of the bipotential gonad to form either an ovary or a testis in L. olivacea and probably among other species that manifest temperature-dependent sex determination. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Temperature dependence of the heterogeneous uptake of acrylic acid on Arizona test dust.

    Science.gov (United States)

    Liu, Qifan; Wang, Yidan; Wu, Lingyan; Jing, Bo; Tong, Shengrui; Wang, Weigang; Ge, Maofa

    2017-03-01

    In this study, the temperature dependence of the heterogeneous uptake of acrylic acid on Arizona test dust (ATD) has been investigated within a temperature range of 255-315K using a Knudsen cell reactor. Combined with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiment, it was found that acrylic acid could adsorb on ATD via surface OH groups and convert to carboxylate on the particle surface. The kinetics study suggests that the initial true uptake coefficient (γt) of acrylic acid on ATD decreases from (4.02±0.12)×10(-5) to (1.73±0.05)×10(-5) with a temperature increase from 255 to 315K. According to the temperature dependence of uptake coefficients, the enthalpy (ΔHobs) and entropy (ΔSobs) of uptake processes were determined to be -(9.60±0.38) KJ/mol and -(121.55±1.33) J·K/mol, respectively. The activation energy for desorption (Edes) was calculated to be (14.57±0.60) KJ/mol. These results indicated that the heterogeneous uptake of acrylic acid on ATD surface was sensitive to temperature. The heterogeneous uptake on ATD could affect the concentration of acrylic acid in the atmosphere, especially at low temperature. Copyright © 2016. Published by Elsevier B.V.

  19. Improved Regression Analysis of Temperature-Dependent Strain-Gage Balance Calibration Data

    Science.gov (United States)

    Ulbrich, N.

    2015-01-01

    An improved approach is discussed that may be used to directly include first and second order temperature effects in the load prediction algorithm of a wind tunnel strain-gage balance. The improved approach was designed for the Iterative Method that fits strain-gage outputs as a function of calibration loads and uses a load iteration scheme during the wind tunnel test to predict loads from measured gage outputs. The improved approach assumes that the strain-gage balance is at a constant uniform temperature when it is calibrated and used. First, the method introduces a new independent variable for the regression analysis of the balance calibration data. The new variable is designed as the difference between the uniform temperature of the balance and a global reference temperature. This reference temperature should be the primary calibration temperature of the balance so that, if needed, a tare load iteration can be performed. Then, two temperature{dependent terms are included in the regression models of the gage outputs. They are the temperature difference itself and the square of the temperature difference. Simulated temperature{dependent data obtained from Triumph Aerospace's 2013 calibration of NASA's ARC-30K five component semi{span balance is used to illustrate the application of the improved approach.

  20. Temperature dependence of relaxation times and temperature mapping in ultra-low-field MRI.

    Science.gov (United States)

    Vesanen, Panu T; Zevenhoven, Koos C J; Nieminen, Jaakko O; Dabek, Juhani; Parkkonen, Lauri T; Ilmoniemi, Risto J

    2013-10-01

    Ultra-low-field MRI is an emerging technology that allows MRI and NMR measurements in microtesla-range fields. In this work, the possibilities of relaxation-based temperature measurements with ultra-low-field MRI were investigated by measuring T1 and T2 relaxation times of agarose gel at 50 μT-52 mT and at temperatures 5-45°C. Measurements with a 3T scanner were made for comparison. The Bloembergen-Purcell-Pound relaxation theory was combined with a two-state model to explain the field-strength and temperature dependence of the data. The results show that the temperature dependencies of agarose gel T1 and T2 in the microtesla range differ drastically from those at 3T; the effect of temperature on T1 is reversed at approximately 5 mT. The obtained results were used to reconstruct temperature maps from ultra-low-field scans. These time-dependent temperature maps measured from an agarose gel phantom at 50 μT reproduced the temperature gradient with good contrast. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. Temperature dependence of a microstructured SiC coherent thermal source

    Science.gov (United States)

    Hervé, Armande; Drévillon, Jérémie; Ezzahri, Younès; Joulain, Karl; De Sousa Meneses, Domingos; Hugonin, Jean-Paul

    2016-09-01

    By ruling a grating on a polar material that supports surface phonon-polaritons such as silicon carbide (SiC), it is possible to create directional and monochromatic thermal sources. So far, most of the studies have considered only materials with room temperature properties as the ones tabulated in Palik's handbooks. Recently, measurements have provided experimental data of the SiC dielectric function at different temperatures. Here we study, numerically, the effect of the temperature dependence of the dielectric function on the thermal emission of SiC gratings (1D grating, in a first approach), heated at different temperatures. When materials are heated, the position of the grating emissivity peak shifts towards higher wavelength values. A second consequence of the temperature dependence of optical properties is that room temperature designed gratings are not optimal for higher temperatures. However, by modifying the grating parameters, it is possible to find an emission peak, with a maximum of emissivity near 1, for each temperature. We tried first to catch some patterns in the emissivity variation. Then, we obtained a grating, which leads to an optimum emissivity for all available temperature data for SiC.

  2. Mapping the temperature-dependent conformational landscapes of the dynamic enzymes cyclophilin A and urease

    Science.gov (United States)

    Thorne, Robert; Keedy, Daniel; Warkentin, Matthew; Fraser, James; Moreau, David; Atakisi, Hakan; Rau, Peter

    Proteins populate complex, temperature-dependent ensembles of conformations that enable their function. Yet in X-ray crystallographic studies, roughly 98% of structures have been determined at 100 K, and most refined to only a single conformation. A combination of experimental methods enabled by studies of ice formation and computational methods for mining low-density features in electron density maps have been applied to determine the evolution of the conformational landscapes of the enzymes cyclophilin A and urease between 300 K and 100 K. Minority conformations of most side chains depopulate on cooling from 300 to ~200 K, below which subsequent conformational evolution is quenched. The characteristic temperatures for this depopulation are highly heterogeneous throughout each enzyme. The temperature-dependent ensemble of the active site flap in urease has also been mapped. These all-atom, site-resolved measurements and analyses rule out one interpretation of the protein-solvent glass transition, and give an alternative interpretation of a dynamical transition identified in site-averaged experiments. They demonstrate a powerful approach to structural characterization of the dynamic underpinnings of protein function. Supported by NSF MCB-1330685.

  3. Temperature dependence of hydroxyl radical reactions with chloramine species in aqueous solution.

    Science.gov (United States)

    Gleason, Jamie M; McKay, Garrett; Ishida, Kenneth P; Mezyk, Stephen P

    2017-11-01

    The absolute temperature-dependent kinetics for the reaction between hydroxyl radicals and the chloramine water disinfectant species monochloramine (NH2Cl), as well as dichloramine (NHCl2) and trichloramine (NCl3), have been determined using electron pulse radiolysis and transient absorption spectroscopy. These radical reaction rate constants were fast, with values of 6.06 × 108, 2.57 × 108, and 1.67 × 108 M-1 s-1 at 25 °C for NH2Cl, NHCl2, and NCl3, respectively. The corresponding temperature dependence of these reaction rate constants, measured over the range 10-40 °C, is well-described by the transformed Arrhenius equations:giving activation energies of 8.57 ± 0.58, 6.11 ± 0.40, and 5.77 ± 0.72 kJ mol-1 for these three chloramines, respectively. These data will aid water utilities in predicting hydroxyl radical partitioning and chemical contaminant removal efficiencies under real-world advanced oxidation process treatment conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Temperature-dependent transformation thermotics for unsteady states: Switchable concentrator for transient heat flow

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ying, E-mail: 13110290008@fudan.edu.cn [Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433 (China); Shen, Xiangying, E-mail: 13110190068@fudan.edu.cn [Department of Physics, State Key Laboratory of Surface Physics, and Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433 (China); Huang, Jiping, E-mail: jphuang@fudan.edu.cn [Department of Physics, State Key Laboratory of Surface Physics, and Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433 (China); Ni, Yushan, E-mail: niyushan@fudan.edu.cn [Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433 (China)

    2016-04-22

    For manipulating heat flow efficiently, recently we established a theory of temperature-dependent transformation thermotics which holds for steady-state cases. Here, we develop the theory to unsteady-state cases by considering the generalized Fourier's law for transient thermal conduction. As a result, we are allowed to propose a new class of intelligent thermal metamaterial — switchable concentrator, which is made of inhomogeneous anisotropic materials. When environmental temperature is below or above a critical value, the concentrator is automatically switched on, namely, it helps to focus heat flux in a specific region. However, the focusing does not affect the distribution pattern of temperature outside the concentrator. We also perform finite-element simulations to confirm the switching effect according to the effective medium theory by assembling homogeneous isotropic materials, which bring more convenience for experimental fabrication than inhomogeneous anisotropic materials. This work may help to figure out new intelligent thermal devices, which provide more flexibility in controlling heat flow, and it may also be useful in other fields that are sensitive to temperature gradient, such as the Seebeck effect. - Highlights: • Established the unsteady-state temperature dependent transformation thermotics. • A thermal concentrator with switchable functionality. • An effective-medium design for experimental realization.

  5. DEVELOPMENT OF GREEN’S FUNCTION APPROACH CONSIDERING TEMPERATURE-DEPENDENT MATERIAL PROPERTIES AND ITS APPLICATION

    Directory of Open Access Journals (Sweden)

    HAN-OK KO

    2014-02-01

    Full Text Available About 40% of reactors in the world are being operated beyond design life or are approaching the end of their life cycle. During long-term operation, various degradation mechanisms occur. Fatigue caused by alternating operational stresses in terms of temperature or pressure change is an important damage mechanism in continued operation of nuclear power plants. To monitor the fatigue damage of components, Fatigue Monitoring System (FMS has been installed. Most FMSs have used Green's Function Approach (GFA to calculate the thermal stresses rapidly. However, if temperature-dependent material properties are used in a detailed FEM, there is a maximum peak stress discrepancy between a conventional GFA and a detailed FEM because constant material properties are used in a conventional method. Therefore, if a conventional method is used in the fatigue evaluation, thermal stresses for various operating cycles may be calculated incorrectly and it may lead to an unreliable estimation. So, in this paper, the modified GFA which can consider temperature-dependent material properties is proposed by using an artificial neural network and weight factor. To verify the proposed method, thermal stresses by the new method are compared with those by FEM. Finally, pros and cons of the new method as well as technical findings from the assessment are discussed.

  6. Temperature-dependent electronic decay profiles in CZT: probe of bulk and surface properties

    Science.gov (United States)

    Kessick, Royal; Maupin, Hugh; Tepper, Gary C.; Szeles, Csaba

    2003-01-01

    The electronic performance of CZT-based gamma radiation spectrometers is governed by a synergism of bulk and surface properties. Compensation is used to increase the bulk resistivity of Cd1-xZnxTe (x~0.1), but the same electronic states that are introduced to increase the material resistivity can also trap charge and reduce the carrier lifetime. Electrical and mechanical surface defects introduced during or subsequent to crystal harvesting are also known to interfere with device performance. Using a contactless, pulsed laser microwave cavity perturbation technique, electronic decay profiles were studied in high pressure Bridgman CZT as a function of temperature. The electronic decay profile was found to depend very strongly on temperature and was modeled using a function consisting of two exponential terms with temperature-dependent amplitudes and time constants. The model was used to relate the observed temperature dependent decay kinetics in CZT to specific trap energies. It was found that, at low temperatures, the electronic decay process is dominated by a deep trap with an energy of approximately 0.69 +/- 0.1 eV from the band edge. As the temperature is increased, the charge trapping becomes dominated by a second trap with an energy of approximately 0.60 +/- 0.1 eV from the band edge. Surface damage introduces additional charge traps that significantly alter the decay kinetics particularly at low temperatures.

  7. Temperature dependence of CO2-enhanced primary production in the European Arctic Ocean

    KAUST Repository

    Holding, J. M.

    2015-08-31

    The Arctic Ocean is warming at two to three times the global rate1 and is perceived to be a bellwether for ocean acidification2, 3. Increased CO2 concentrations are expected to have a fertilization effect on marine autotrophs4, and higher temperatures should lead to increased rates of planktonic primary production5. Yet, simultaneous assessment of warming and increased CO2 on primary production in the Arctic has not been conducted. Here we test the expectation that CO2-enhanced gross primary production (GPP) may be temperature dependent, using data from several oceanographic cruises and experiments from both spring and summer in the European sector of the Arctic Ocean. Results confirm that CO2 enhances GPP (by a factor of up to ten) over a range of 145–2,099 μatm; however, the greatest effects are observed only at lower temperatures and are constrained by nutrient and light availability to the spring period. The temperature dependence of CO2-enhanced primary production has significant implications for metabolic balance in a warmer, CO2-enriched Arctic Ocean in the future. In particular, it indicates that a twofold increase in primary production during the spring is likely in the Arctic.

  8. Shutter-Less Temperature-Dependent Correction for Uncooled Thermal Camera Under Fast Changing FPA Temperature

    Science.gov (United States)

    Lin, D.; Westfeld, P.; Maas, H.-G.

    2017-05-01

    Conventional temperature-dependant correction methods for uncooled cameras are not so valid for images under the condition of fast changing FPA temperature as usual, therefore, a shutter-less temperature-dependant correction method is proposed here to compensate for these errors and stabilize camera's response only related to the object surface temperature. Firstly, sequential images are divided into the following three categories according to the changing speed of FPA temperature: stable (0°C/min), relatively stable (0.5°C/min). Then all of the images are projected into the same level using a second order polynomial relation between FPA temperatures and gray values from stable images. Next, a third order polynomial relation between temporal differences of FPA temperatures and the above corrected images is implemented to eliminate the deviation caused by fast changing FPA temperature. Finally, radiometric calibration is applied to convert image gray values into object temperature values. Experiment results show that our method is more effective for fast changing FPA temperature data than FLIR GEV.

  9. Temperature dependence of conductivity measurement for PEDOT:PSS and corresponding solar cell performance

    Science.gov (United States)

    Duarte, Fernanda; Myers, Brooke; Lucas, Tyler; Barnes, Brandon; Wang, Weining

    Conducting polymers have been studied and used widely; applications include light-emitting diodes, solar cells, and sensors. In our previous work, we have shown that conducting polymers can be used as the back contact of CdTe solar cells. Our results show that the efficiency of the CdTe solar cell increases as the conductivity of the polymer increases. For this reason, it is of interest to study the polymer conductivity's temperature dependence, and how it affects the solar cell. In this work, we show our studies on temperature dependence of conductivity measurement for poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), and its effect on the CdTe/PEDOT:PSS solar cells. A series of PEDOT:PSS with different conductivities were studied, and a temperature-varying apparatus built in house, using a thermoelectric cooler module, was used to vary the temperature of the polymer films. The activation energy of PEDOT:PSS with different conductivity will be reported. The effect of the temperature on the short-circuit current, open-circuit voltage and efficiency of the solar cells will also be discussed. Clare Boothe Luce Foundation, Cottrell College Science Award from Research Corporation for Science Advancement.

  10. Temperature dependence of the calibration factor of radon and radium determination in water samples by SSNTD

    CERN Document Server

    Hunyadi, I; Hakl, J; Baradacs, E; Dezso, Z

    1999-01-01

    The sensitivity of a sup 2 sup 2 sup 6 Ra determination method of water samples by SSNTD was measured as a function of storage temperature during exposure. The method is based on an etched track type radon monitor, which is closed into a gas permeable foil and is immersed in the water sample. The sample is sealed in a glass vessel and stored for an exposure time of 10-30 days. The sensitivity increased more than a factor of two when the storage temperature was raised from 2 deg. C to 30 deg. C. Temperature dependence of the partition coefficient of radon between water and air provides explanation for this dependence. For practical radio- analytical application the temperature dependence of the calibration factor is given by fitting the sensitivity data obtained by measuring sup 2 sup 2 sup 6 Ra standard solutions (in the activity concentration range of 0.1-48.5 kBq m sup - sup 3) at different storage temperatures.

  11. On the temperature dependence of the optical spectral weight in correlated electron systems

    Energy Technology Data Exchange (ETDEWEB)

    Millis, A.J. [AT& T Bell Laboratories, Murray Hill, NJ (United States)

    1994-12-31

    A temperature dependence of the low frequency optical spectral weight has recently been observed in several strongly correlated insulating or nearly insulating systems including FeSi, Ce{sub 3}Bi{sub 4}Pt{sub 3} and V{sub 2}O{sub 3{minus}y}, and Bi{sub 2}Te{sub 3}. This temperature dependence is at first sight surprising because one is accustomed to thinking of optical spectral weigth in terms of the f-sum rule, which in its most general form states that the integral of any of the diagonal components of the optical conductivity {sigma}{sub ii}({omega}) is {pi}ne{sup 2}/2m. This is not very useful in most condensed matter physics contexts because the quantity n is the total number of electrons, including e.g. those in core levels, and because one must extend the integral to energies greater than the binding energy of the 1s shell to exhaust the sum rule. In condensed matter problems one typically focuses on a small number of bands close to the chemical potential. One may then ask what is the restricted sum rule governing optical transitions involving only these bands. Of course, the answer to this question is useful only if optical transitions involving bands retained in the model can be separated from those involving bands not retained.

  12. Temperature dependence of optical properties in Nd/Cr:YAG materials

    Energy Technology Data Exchange (ETDEWEB)

    Honda, Yoshiyuki, E-mail: honda-y@ile.osaka-u.ac.jp [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Motokoshi, Shinji [Institute for Laser Technology, 1-8-4 Utsubo-honmachi, Nishi-ku, Osaka 550-0004 (Japan); Jitsuno, Takahisa; Miyanaga, Noriaki; Fujioka, Kana [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Nakatsuka, Masahiro [Institute for Laser Technology, 1-8-4 Utsubo-honmachi, Nishi-ku, Osaka 550-0004 (Japan); Yoshida, Minoru [Kinki University, 3-4-1 Kowakae, Higashi-osaka, Osaka 577-8052 (Japan)

    2014-04-15

    The energy transfer from Cr{sup 3+} to Nd{sup 3+} for Nd/Cr:YAG (Nd: 1.0%, Cr: 2.0%) materials was investigated by measuring the temperature dependences of fluorescence characteristics. The fluorescence intensity of Nd{sup 3+} increased with temperature owing to enhancement of the absorption coefficient of Cr{sup 3+}. The energy transfer efficiency was constant from 77 to 450 K. The energy transfer time decreased with increasing temperature. -- Highlights: • We investigate the energy transfer from Cr{sup 3+} to Nd{sup 3+} in Nd/Cr:YAG materials by measuring the temperature dependence of fluorescence characteristics. • The fluorescence intensity of Nd{sup 3+} increased with temperature owing to enhancement of the absorption coefficient of Cr{sup 3+}. • The energy transfer efficiency was constant from 77 to 450 K. • The energy transfer time decreased with increasing temperature. • Nd/Cr:YAG ceramics pumped by a flash lamp would not only provide high conversion efficiency, but can also be expected to function as an effective laser operating at high temperature.

  13. Challenges in Modelling of Lightning-Induced Delamination; Effect of Temperature-Dependent Interfacial Properties

    Science.gov (United States)

    Naghipour, P.; Pineda, E. J.; Arnold, S.

    2014-01-01

    Lightning is a major cause of damage in laminated composite aerospace structures during flight. Due to the dielectric nature of Carbon fiber reinforced polymers (CFRPs), the high energy induced by lightning strike transforms into extreme, localized surface temperature accompanied with a high-pressure shockwave resulting in extensive damage. It is crucial to develop a numerical tool capable of predicting the damage induced from a lightning strike to supplement extremely expensive lightning experiments. Delamination is one of the most significant failure modes resulting from a lightning strike. It can be extended well beyond the visible damage zone, and requires sophisticated techniques and equipment to detect. A popular technique used to model delamination is the cohesive zone approach. Since the loading induced from a lightning strike event is assumed to consist of extreme localized heating, the cohesive zone formulation should additionally account for temperature effects. However, the sensitivity to this dependency remains unknown. Therefore, the major focus point of this work is to investigate the importance of this dependency via defining various temperature dependency profiles for the cohesive zone properties, and analyzing the corresponding delamination area. Thus, a detailed numerical model consisting of multidirectional composite plies with temperature-dependent cohesive elements in between is subjected to lightning (excessive amount of heat and pressure) and delamination/damage expansion is studied under specified conditions.

  14. Analysis of convective longitudinal fin with temperature-dependent thermal conductivity and internal heat generation

    Directory of Open Access Journals (Sweden)

    M.G. Sobamowo

    2017-03-01

    Full Text Available In this study, analysis of heat transfer in a longitudinal rectangular fin with temperature-dependent thermal conductivity and internal heat generation was carried out using finite difference method. The developed systems of non-linear equations that resulted from the discretization using finite difference scheme were solved with the aid of MATLAB using fsolve. The numerical solution was validated with the exact solution for the linear problem. The developed heat transfer models were used to investigate the effects of thermo-geometric parameters, coefficient of heat transfer and thermal conductivity (non-linear parameters on the temperature distribution, heat transfer and thermal performance of the longitudinal rectangular fin. From the results, it shows that the fin temperature distribution, the total heat transfer, and the fin efficiency are significantly affected by the thermo-geometric parameters of the fin. Also, for the solution to be thermally stable, the fin thermo-geometric parameter must not exceed a specific value. However, it was established that the increase in temperature-dependent properties and internal heat generation values increases the thermal stability range of the thermo-geometric parameter. The results obtained in this analysis serve as basis for comparison of any other method of analysis of the problem.

  15. Temperature-dependent elastic properties of brain tissues measured with the shear wave elastography method.

    Science.gov (United States)

    Liu, Yan-Lin; Li, Guo-Yang; He, Ping; Mao, Ze-Qi; Cao, Yanping

    2017-01-01

    Determining the mechanical properties of brain tissues is essential in such cases as the surgery planning and surgical training using virtual reality based simulators, trauma research and the diagnosis of some diseases that alter the elastic properties of brain tissues. Here, we suggest a protocol to measure the temperature-dependent elastic properties of brain tissues in physiological saline using the shear wave elastography method. Experiments have been conducted on six porcine brains. Our results show that the shear moduli of brain tissues decrease approximately linearly with a slope of -0.041±0.006kPa/°C when the temperature T increases from room temperature (~23°C) to body temperature (~37°C). A case study has been further conducted which shows that the shear moduli are insensitive to the temperature variation when T is in the range of 37 to 43°C and will increase when T is higher than 43°C. With the present experimental setup, temperature-dependent elastic properties of brain tissues can be measured in a simulated physiological environment and a non-destructive manner. Thus the method suggested here offers a unique tool for the mechanical characterization of brain tissues with potential applications in brain biomechanics research. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Temperature dependence of band gaps in semiconductors: electron-phonon interaction

    Energy Technology Data Exchange (ETDEWEB)

    Kremer, Reinhard K.; Cardona, M.; Lauck, R. [MPI for Solid State Research, Stuttgart (Germany); Bhosale, J.; Ramdas, A.K. [Physics Dept., Purdue University, West Lafayette, IN (United States); Burger, A. [Fisk University, Dept. of Life and Physical Sciences, Nashville, TN (United States); Munoz, A. [MALTA Consolider Team, Dept. de Fisica Fundamental II, Universidad de La Laguna, Tenerife (Spain); Instituto de Materiales y Nanotecnologia, Universidad de La Laguna, Tenerife (Spain); Romero, A.H. [CINVESTAV, Dept. de Materiales, Unidad Queretaro, Mexico (Mexico); MPI fuer Mikrostrukturphysik, Halle an der Saale (Germany)

    2013-07-01

    We investigate the temperature dependence of the energy gap of several semiconductors with chalcopyrite structure and re-examine literature data and analyze own high-resolution reflectivity spectra in view of our new ab initio calculations of their phonon properties. This analysis leads us to distinguish between materials with d-electrons in the valence band (e.g. CuGaS{sub 2}, AgGaS{sub 2}) and those without d-electrons (e.g. ZnSnAs{sub 2}). The former exhibit a rather peculiar non-monotonic temperature dependence of the energy gap which, so far, has resisted cogent theoretical description. We demonstrate it can well be fitted by including two Bose-Einstein oscillators with weights of opposite sign leading to an increase at low-T and a decrease at higher T's. We find that the energy of the former correlates well with characteristic peaks in the phonon density of states associated with low-energy vibrations of the d-electron constituents.

  17. Similar temperature dependencies of glycolytic enzymes: an evolutionary adaptation to temperature dynamics?

    Directory of Open Access Journals (Sweden)

    Cruz Luisa Ana B

    2012-12-01

    Full Text Available Abstract Background Temperature strongly affects microbial growth, and many microorganisms have to deal with temperature fluctuations in their natural environment. To understand regulation strategies that underlie microbial temperature responses and adaptation, we studied glycolytic pathway kinetics in Saccharomyces cerevisiae during temperature changes. Results Saccharomyces cerevisiae was grown under different temperature regimes and glucose availability conditions. These included glucose-excess batch cultures at different temperatures and glucose-limited chemostat cultures, subjected to fast linear temperature shifts and circadian sinoidal temperature cycles. An observed temperature-independent relation between intracellular levels of glycolytic metabolites and residual glucose concentration for all experimental conditions revealed that it is the substrate availability rather than temperature that determines intracellular metabolite profiles. This observation corresponded with predictions generated in silico with a kinetic model of yeast glycolysis, when the catalytic capacities of all glycolytic enzymes were set to share the same normalized temperature dependency. Conclusions From an evolutionary perspective, such similar temperature dependencies allow cells to adapt more rapidly to temperature changes, because they result in minimal perturbations of intracellular metabolite levels, thus circumventing the need for extensive modification of enzyme levels.

  18. Temperature-Dependent Development Modeling of the Phorid Fly Megaselia halterata (Wood) (Diptera: Phoridae).

    Science.gov (United States)

    Barzegar, S; Zamani, A A; Abbasi, S; Vafaei Shooshtari, R; Shirvani Farsani, N

    2016-10-01

    The effect of temperature on the development of Megaselia halterata (Wood) (Diptera: Phoridae) on A15 variety of button mushroom in the stages of casing and spawn-running was investigated at eight constant temperatures (10, 12.5, 15, 18, 20, 22.5, 25, and 27°C) and developmental rates were modeled as a function of temperature. At 25 and 27°C, an average of 22.2 ± 0.14 and 20.0 ± 0.10 days was needed for M. halterata to complete its development from oviposition to adult eclosion in the stages of casing and spawn-running, respectively. The developmental times of males or females at various constant temperatures were significantly different. Among the linear models, the Ikemoto and Takai linear model in the absence of 12.5 and 25°C showed the best statistical goodness-of-fit and based on this model, the lower developmental threshold and the thermal constant were estimated as 10.4°C and 526.3 degree-days, respectively. Twelve nonlinear temperature-dependent models were examined to find the best model to describe the relationship between temperature and development rate of M. halterata. The Logan 10 nonlinear model provided the best estimation for T opt and T max and is strongly recommended for the description of temperature-dependent development of M. halterata.

  19. The temperature dependence of luminescence from a long-lasting phosphor exposed to ionizing radiation

    CERN Document Server

    Kowatari, M; Satoh, Y; Iinuma, K; Uchida, S I

    2002-01-01

    The temperature dependence of luminescence from a long-lasting phosphor (LLP), SrAl sub 2 O sub 4 : Eu sup 2 sup + ,Dy sup 3 sup + , exposed to ionizing radiation has been measured to understand the LLP luminescence mechanism. Evaluation of the decay constants of the LLP exposed to alpha-, beta- or gamma-rays at temperatures from 200 to 390 K showed that the decay constant is divided into four components ranging from 10 sup - sup 4 to 10 sup - sup 1 s sup - sup 1 with activation energies of 0.02-0.35 eV. Total luminous intensity from the LLP with changing irradiation temperature has its maximum value around the room temperature. Irradiation at elevated temperature (390 K) has the total luminescence pattern with monotonous decrease as temperature rises. As a result of evaluating the temperature dependence of luminescence, the luminescence mechanism is considered as follows: (1.) holes generated by irradiation are stored at Dy sup 3 sup + sites (hole traps) and then released to recombine with electrons trapped ...

  20. Novel phase diagram behavior and materials design in heterostructural semiconductor alloys.

    Science.gov (United States)

    Holder, Aaron M; Siol, Sebastian; Ndione, Paul F; Peng, Haowei; Deml, Ann M; Matthews, Bethany E; Schelhas, Laura T; Toney, Michael F; Gordon, Roy G; Tumas, William; Perkins, John D; Ginley, David S; Gorman, Brian P; Tate, Janet; Zakutayev, Andriy; Lany, Stephan

    2017-06-01

    Structure and composition control the behavior of materials. Isostructural alloying is historically an extremely successful approach for tuning materials properties, but it is often limited by binodal and spinodal decomposition, which correspond to the thermodynamic solubility limit and the stability against composition fluctuations, respectively. We show that heterostructural alloys can exhibit a markedly increased range of metastable alloy compositions between the binodal and spinodal lines, thereby opening up a vast phase space for novel homogeneous single-phase alloys. We distinguish two types of heterostructural alloys, that is, those between commensurate and incommensurate phases. Because of the structural transition around the critical composition, the properties change in a highly nonlinear or even discontinuous fashion, providing a mechanism for materials design that does not exist in conventional isostructural alloys. The novel phase diagram behavior follows from standard alloy models using mixing enthalpies from first-principles calculations. Thin-film deposition demonstrates the viability of the synthesis of these metastable single-phase domains and validates the computationally predicted phase separation mechanism above the upper temperature bound of the nonequilibrium single-phase region.

  1. Phase behavior of olive and soybean oils in compressed propane and n-butane

    Directory of Open Access Journals (Sweden)

    P. M. Ndiaye

    2006-09-01

    Full Text Available The aim of this work is to report the experimental data and thermodynamic modeling of phase equilibrium of binary systems containing soybean and olive oils with propane and n-butane. Phase equilibrium experiments were carried out using the static synthetic method in a high-pressure variable-volume view cell in the temperature range from 30 to 70ºC and varying the solvent overall composition from 5 to 98 wt%. Vapor-liquid, liquid-liquid and vapor-liquid-liquid phase transitions were observed at relatively low pressures. The Peng-Robinson and the SAFT equations of state without any binary interaction parameters were employed in an attempt at representing the phase behavior of the systems. Results show the satisfactory performance of SAFT-EoS in predicting qualitatively all phase transitions reported in this work.

  2. Improved AIOMFAC model parameterisation of the temperature dependence of activity coefficients for aqueous organic mixtures

    Science.gov (United States)

    Ganbavale, G.; Zuend, A.; Marcolli, C.; Peter, T.

    2015-01-01

    This study presents a new, improved parameterisation of the temperature dependence of activity coefficients in the AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) model applicable for aqueous as well as water-free organic solutions. For electrolyte-free organic and organic-water mixtures the AIOMFAC model uses a group-contribution approach based on UNIFAC (UNIversal quasi-chemical Functional-group Activity Coefficients). This group-contribution approach explicitly accounts for interactions among organic functional groups and between organic functional groups and water. The previous AIOMFAC version uses a simple parameterisation of the temperature dependence of activity coefficients, aimed to be applicable in the temperature range from ~ 275 to ~ 400 K. With the goal to improve the description of a wide variety of organic compounds found in atmospheric aerosols, we extend the AIOMFAC parameterisation for the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon to atmospherically relevant low temperatures. To this end we introduce a new parameterisation for the temperature dependence. The improved temperature dependence parameterisation is derived from classical thermodynamic theory by describing effects from changes in molar enthalpy and heat capacity of a multi-component system. Thermodynamic equilibrium data of aqueous organic and water-free organic mixtures from the literature are carefully assessed and complemented with new measurements to establish a comprehensive database, covering a wide temperature range (~ 190 to ~ 440 K) for many of the functional group combinations considered. Different experimental data types and their processing for the estimation of AIOMFAC model parameters are discussed. The new AIOMFAC parameterisation for the temperature dependence of activity coefficients from low to high temperatures shows an overall improvement of 28% in

  3. Mechanistic investigation of non-ideal sorption behavior in natural organic matter. 1. Vapor phase equilibrium.

    Science.gov (United States)

    Bell, Katherine Young; Leboeuf, Eugene J

    2012-06-19

    Results from an experimental and modeling investigation of the influence of thermodynamic properties of highly purified natural organic matter (NOM) on observed equilibrium sorption/desorption behaviors of vapor phase trichloroethylene (TCE) is presented. Identification of glass transition (T(g)) behavior in Leonardite humic acid and Organosolv lignin enabled evaluation of equilibrium and nonequilibrium sorption behavior in glassy and rubbery NOM. Specific differences in vapor phase equilibrium behavior in NOM above and below their T(g) were identified. In the glassy state (below T(g)), sorption of TCE is well-described by micropore models, with enthalpies of sorption characteristic of microporous, glassy macromolecules. Above T(g), sorptive behavior was well-described by Flory-Huggins theory, indicating that the mobility and structural configuration of rubbery NOM materials may be analogous to the characteristic sorption behavior observed in more mobile, rubbery macromolecules, including strong entropic changes during sorption. Results from this work provide further support that, at least for the samples employed in this study, NOM possesses macromolecular characteristics which display sorption behavior similar to synthetic macromolecules-an important assumption in conceptual sorption equilibrium models used in the analysis of the fate and transport of VOCs in the environment.

  4. Fabrication of Colloidal Laves Phases via Hard Tetramers and Hard Spheres: Bulk Phase Diagram and Sedimentation Behavior

    Science.gov (United States)

    2017-01-01

    Colloidal photonic crystals display peculiar optical properties that make them particularly suitable for application in different fields. However, the low packing fraction of the targeted structures usually poses a real challenge in the fabrication stage. Here, we propose a route to colloidal photonic crystals via a binary mixture of hard tetramers and hard spheres. By combining theory and computer simulations, we calculate the phase diagram as well as the stacking diagram of the mixture and show that a colloidal analogue of the MgCu2 Laves phase—which can serve as a precursor of a photonic band-gap structure—is a thermodynamically stable phase in a large region of the phase diagram. Our findings show a relatively large coexistence region between the fluid and the Laves phase, which is potentially accessible by experiments. Furthermore, we determine the sedimentation behavior of the suggested mixture, by identifying several stacking sequences in the sediment. Our work uncovers a self-assembly path toward a photonic structure with a band gap in the visible region. PMID:28787126

  5. Temperature dependent dielectric and conductivity studies of polyvinyl alcohol-ZnO nanocomposite films by impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hemalatha, K. S.; Damle, R.; Rukmani, K., E-mail: rukmani9909@yahoo.co.in [Department of Physics, Bangalore University, Bangalore 560056 (India); Sriprakash, G. [Department of Physics, Maharani' s Science College for Women, Bangalore 560001 (India); Ambika Prasad, M. V. N. [Department of Physics, Gulbarga University, Gulbarga 585106 (India)

    2015-10-21

    Dielectric and conductivity behaviors of nano ZnO doped polyvinyl alcohol (PVA) composites for various concentrations of dopant were investigated using impedance spectroscopy for a wide range of temperatures (303 K–423 K) and frequencies (5 Hz–30 MHZ). The dielectric properties of host polymer matrix have been improved by the addition of nano ZnO and are found to be highly temperature dependent. Anomalous dielectric behavior was observed in the frequency range of 2.5 MHz–5 MHz. Increase in dielectric permittivity and dielectric loss was observed with respect to temperature. The Cole-Cole plot could be modeled by low resistance regions in a high resistance matrix and the lowest resistance was observed for the 10 mol. % films. The imaginary part of the electric modulus showed asymmetric peaks with the relaxation following Debye nature below and non-Debye nature above the peaks. The ac conductivity is found to obey Jonscher's power law, whereas the variation of dc conductivity with temperature was found to follow Arrhenius behavior. Two different activation energy values were obtained from Arrhenius plot indicating that two conduction mechanisms are involved in the composite films. Fitting the ac conductivity data to Jonscher's law indicates that large polaron assisted tunneling is the most likely conduction mechanism in the composites. Maximum conductivity is observed at 423 K for all the samples and it is optimum for 10 mol. % ZnO doped PVA composite film. Significant increase in dc and ac conductivities in these composite films makes them a potential candidate for application in electronic devices.

  6. Off-lattice model for the phase behavior of lipid-cholesterol bilayers

    DEFF Research Database (Denmark)

    Nielsen, Morten; Miao, Ling; Ipsen, John Hjorth

    1999-01-01

    Lipid bilayers exhibit a phase behavior that involves two distinct, but coupled, order-disorder processes, one in terms of lipid-chain crystalline packing (translational degrees of freedom) and the other in terms of lipid-chain conformational ordering (internal degrees of freedom). Experiments an...

  7. Synthesis and phase behavior of dendrons derived from 3, 4, 5-tris ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 127; Issue 10. Synthesis and phase behavior of dendrons derived from 3,4,5-tris(tetradecyloxy)benzoic acid with different functional groups in focal point. Matvey Gruzdev Ulyana Chervonova Olga Akopova Arkadiy Kolker. Volume 127 Issue 10 October 2015 pp 1801- ...

  8. Chaotic behavior in Casimir oscillators : A case study for phase-change materials

    NARCIS (Netherlands)

    Tajik, Fatemeh; Sedighi, Mehdi; Khorrami, Mohammad; Masoudi, Amir Ali; Palasantzas, George

    2017-01-01

    Casimir forces between material surfaces at close proximity of less than 200 nm can lead to increased chaotic behavior of actuating devices depending on the strength of the Casimir interaction. We investigate these phenomena for phase-change materials in torsional oscillators, where the amorphous to

  9. Synthesis and phase behavior of dendrons derived from 3,4,5-tris ...

    Indian Academy of Sciences (India)

    derived from 3,4,5-tris(tetradecyloxy)benzoic acid, and determination of the dependence of phase behavior on molecular structure. Thus prepared dendrons are used as precursor to Schiff bases in complexation reaction of spin-cross over metal containing systems.20 Recent- ly, magnetic properties of a new dendrimeric ...

  10. The phase behavior of polydisperse multiblock copolymer melts : (a theoretical study)

    NARCIS (Netherlands)

    Angerman, Hindrik Jan

    1998-01-01

    Summary The main theme of this thesis is the influence of polydispersity on the phase behavior of copolymer melts. With “polydispersity” we do not only refer to polydispersity in overall chain length, but also to polydispersity in the composition and the monomer sequence of the chains. Study of the

  11. Modeling the Phase Behavior in Mixtures of Pharmaceuticals with Liquid or Supercritical Solvents

    DEFF Research Database (Denmark)

    Tsivintzelis, Ioannis; Economou, Ioannis; Kontogeorgis, Georgios

    2009-01-01

    the phase behavior of mixtures of six pharmaceuticals (i.e., ibuprofen, ketoprofen, naproxen, benzoic acid, methyl paraben, and ethyl paraben). The pure fluid parameters of the studied pharmaceuticals were estimated using limited available experimental (or predicted) data on sublimation pressures, liquid...

  12. Phase behavior of polymer-diluent systems characterized by temperature modulated differential scanning calorimetry

    NARCIS (Netherlands)

    van der Heijden, P.C.; Mulder, M.H.V.; Wessling, Matthias

    2001-01-01

    The thermodynamic phase behavior of a polymer–diluent system (atactic polystyrene–1-dodecanol) forms the fundamental basis of the description of thermally-induced demixing processes. In this paper, we demonstrate that temperature modulated differential scanning calorimetry (TMDSC) can accurately

  13. Temperature Dependence of Near-Infrared CO_2 Line Shapes Measured by Cavity Ring-Down Spectroscopy

    Science.gov (United States)

    Ghysels, Mélanie; Fleisher, Adam J.; Liu, Qingnan; Hodges, Joseph T.

    2017-06-01

    We present high signal-to-noise ratio, mode-by-mode cavity ring-down spectroscopy (CRDS) line shape measurements of air-broadened transitions in the 30013 → 0001 band of ^{12}C^{16}O_2 located near λ = 1.6 μm. Absorption spectra were acquired from (230-290) K with a variable-temperature spectrometer developed in the framework of the NASA Orbiting Carbon Observatory-2 Mission to improve our understanding of carbon dioxide and oxygen line shape parameters. This system comprises a monolithic, thermally stabilized two-mirror, optical resonator exhibiting a mode stability of 200 kHz and a minimum detectable absorption coefficient of 10^{-11} cm^{-1}. Observed spectra were modeled the using the recently recommended Hartmann-Tran line profile (HTP) (and several of its limiting cases) which includes the effects of Dicke narrowing, speed dependent broadening, correlation between velocity- and phase-changing collisions and first-order line mixing effects. At fixed temperature, line shape parameters were determined by constrained multispectrum fitting of spectra acquired over the pressure range (30 - 300) Torr. For each transition considered, analysis of the temperature dependence of the fitted line shape parameters yielded the pressure-broadening temperature exponent and speed dependence parameter, where the latter quantity was found to be in good agreement with theoretical values consistent with the HTP model. Tennyson, et al., Pure Appl. Chem. 86, (2014) 1931

  14. Investigating Size- and Temperature-Dependent Coercivity and Saturation Magnetization in PEG Coated Fe3O4 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Chiranjib Nayek

    2017-05-01

    Full Text Available Polyethylene glycol (PEG coated magnetic Fe3O4 nanoparticles with diameters of 12 nm, 15 nm, and 16 nm were synthesized by the usual co-precipitation method. The structure and morphology of the samples were characterized using X-ray diffraction (XRD and high resolution transmission electron microscopy (HRTEM. The ac magnetic susceptibility measurements were carried out using a vibrating sample magnetometer (VSM. The dc magnetic measurements were carried out using a commercial Quantum Design superconducting quantum interference device (SQUID. The XRD patterns indicated the sole existence of the inverse cubic spinel phase of Fe3O4 in all the samples. The histograms extracted from the TEM images show narrow size distributions with average sizes that are very similar to those obtained from the XRD images using the Scherrer’s formula. The temperature dependence of both coercivity and saturation magnetization, which were determined from the magnetic hysteresis loops, were found to have considerable deviations from the Bloch’s and Kneller’s laws. The size-dependent coercivity and saturation magnetization were found to be non-monotonic at nearly all temperatures. These results are discussed and attributed mainly to the finite size effects in addition to the existence of inter-particle interactions and of spin-glass structures that resulted from frozen canted surface spins at low temperatures.

  15. Natural convection in square enclosures differentially heated at sides using alumina-water nanofluids with temperature-dependent physical properties

    Directory of Open Access Journals (Sweden)

    Cianfrini Marta

    2015-01-01

    Full Text Available Laminar natural convection of Al2O3 + H2O nanofluids inside square cavities differentially heated at sides is studied numerically. A computational code based on the SIMPLE-C algorithm is used for the solution of the system of the mass, momentum and energy transfer governing equations. Assuming that the nanofluid behaves like a single-phase fluid, these equations are the same as those valid for a pure fluid, provided that the thermophysical properties appearing in them are the nanofluid effective properties. The thermal conductivity and dynamic viscosity of the nanofluid are calculated by means of a couple of empirical equations based on a wide variety of experimental data reported in the literature. The other effective properties are evaluated by the conventional mixing theory. Simulations are performed for different values of the nanoparticle volume fraction in the range 0-0.06, the diameter of the suspended nanoparticles in the range 25-100 nm, the temperature of the cooled sidewall in the range 293-313 K, the temperature of the heated sidewall in the range 298-343 K, and the Rayleigh number of the base fluid in the range 103-107. All computations are executed in the hypothesis of temperature-dependent effective properties. The main result obtained is the existence of an optimal particle loading for maximum heat transfer, that is found to increase as the size of the suspended nanoparticles is decreased, and the nanofluid average temperature is increased.

  16. A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

    Science.gov (United States)

    Burnell, E. Elliott; Weber, Adrian C. J.; Dong, Ronald Y.; Meerts, W. Leo; de Lange, Cornelis A.

    2015-01-01

    The proton NMR spectra of n-pentane orientationally ordered in two nematic liquid-crystal solvents are studied over a wide temperature range and analysed using covariance matrix adaptation evolutionary strategy. Since alkanes possess small electrostatic moments, their anisotropic intermolecular interactions are dominated by short-range size-and-shape effects. As we assumed for n-butane, the anisotropic energy parameters of each n-pentane conformer are taken to be proportional to those of ethane and propane, independent of temperature. The observed temperature dependence of the n-pentane dipolar couplings allows a model-free separation between conformer degrees of order and conformer probabilities, which cannot be achieved at a single temperature. In this way for n-pentane 13 anisotropic energy parameters (two for trans trans, tt, five for trans gauche, tg, and three for each of gauche+ gauche+, pp, and gauche+ gauche-, pm), the isotropic trans-gauche energy difference Etg and its temperature coefficient Etg ' are obtained. The value obtained for the extra energy associated with the proximity of the two methyl groups in the gauche+ gauche- conformers (the pentane effect) is sensitive to minute details of other assumptions and is thus fixed in the calculations. Conformer populations are affected by the environment. In particular, anisotropic interactions increase the trans probability in the ordered phase.

  17. Thermodynamics and Phase Behavior of Phosphonated Block Copolymers Containing Ionic Liquids

    Science.gov (United States)

    Jung, Ha Young; Park, Moon Jeong

    Charge-containing copolymers have drawn intensive attention in recent years for their uses in wide range of electrochemical devices such as fuel cells, lithium batteries and actuators. Particularly, the creation of microphase-separated morphologies in such materials by designing them in block and graft configurations has been the subject of extensive studies, in order to establish a synergistic means of optimizing ion transport properties and mechanical integrity. Interest in this topic has been further stimulated by intriguing phase behavior from charge-containing polymers, which was not projected from conventional phase diagrams of non-ionic polymers. Herein, we investigate thermodynamics and phase behavior of a set of phosphonated block copolymers. By synthesizing low-molecular weight samples with degree of polymerization (N) random phase approximation. We further examined the systems by adding various ionic liquids, where noticeable increases in χ values and modulated microphase separation behavior were observed. The morphology-conductivity relationship has been elucidated by taking into account the segmental motion of polymer chains, volume of conducting phases, and the molecular interactions between phosphonated polymer chains and cations of ionic liquids.

  18. Thermal Response and Stability Characteristics of Bistable Composite Laminates by Considering Temperature Dependent Material Properties and Resin Layers

    Science.gov (United States)

    Moore, M.; Ziaei-Rad, S.; Salehi, H.

    2013-02-01

    In this study, the stability characteristics and thermal response of a bistable composite plate with different asymmetric composition were considered. The non-linear finite element method (FEM) was utilized to determine the response of the laminate. Attention was focused on the temperature dependency of laminate mechanical properties, especially on the thermal expansion coefficients of the composite graphite-epoxy plate. Also the effect of including the resin layers on the stability characteristics of the laminate was investigated. The effect of the temperature on the laminate cured configurations in the range of 25°C to 180°C and -60°C to 40°C was examined. The results indicate that the coefficient of thermal expansions has a major effect on the cured shapes. Next, optical microscopy was used to characterize the laminate composition and for the first time the effect of including the resin layers on the actuation loads that causes snapping behavior between two stable shapes was studied. The results obtained from the finite element simulations were compared with experimental results and a good correlation was obtained. Finally, the stability characteristics of a tapered composite panel were investigated for using in a sample winglet as a candidate application of bistable structures.

  19. Fabrication and Characterization of n-ZnO Hexagonal Nanorods/p-Si Heterojunction Diodes: Temperature-Dependant Electrical Characteristics.

    Science.gov (United States)

    Umar, Ahmad; Badran, R I; Al-Hajry, A; Al-Heniti, S

    2015-07-01

    This paper reports the temperature-dependant electrical characteristics of n-ZnO hexagonal nanorods/p-Si heterojunction diodes. The n-ZnO hexagonal nanorods were grown on p-Si substrate by a simple thermal evaporation process using metallic zinc powder in the presence of oxygen. The spectroscopic characterization revealed well-crystalline nanorods, quasi-aligned to the substrate and possessing hexagonal shape. The as-grown nanorods exhibited a strong near-band-edge emis- sion with very weak deep-level emission in the room-temperature photoluminescence spectrum, confirming good optical properties. Furthermore, the electrical properties of as-grown ZnO nanorods were examined by fabricating n-ZnO/p-Si heterojunction assembly and the I-V characteristics of the fabricated heterojunction assembly were investigated at different temperatures. The fabricated n-ZnO/p-Si heterojunction diodes exhibited a turn-on voltage of ~5 V at different temperatures with a mean built-in-potential barrier of 1.12 eV. Moreover, the high values of quality factor obtained from I-V analysis suggested a non-ideal behavior of Schottky junction.

  20. Temperature dependence of o-Ps annihilation lifetime in non-uniform cylindrical pores in comparison with ETE model

    Energy Technology Data Exchange (ETDEWEB)

    Khaghani, Morteza, E-mail: m.khaghani@pgs.usb.ac.ir; Mehmandoost-Khajeh-Dad, Ali Akbar, E-mail: mehmandoost@phys.usb.ac.ir

    2017-04-01

    Highlights: • Using the well known multi-physics program COMSOL calculating o-Ps annihilation lifetime in complex geometries. • Investigation of shape non-uniformity of cylindrical pores on o-Ps annihilation lifetime. • Verifying temperature dependency of o-Ps lifetime in non-uniform cylindrical pores. • Suggesting PALS at low temperature as a method to verify pore uniformity in porous material. - Abstract: Ortho-positronium (o-Ps) annihilation lifetime was calculated in non-uniform cylinder-shaped pores by solving Schrodinger equation using a well-known multi-physics program called COMSOL. The o-Ps annihilation lifetime variation in terms of temperature was calculated on the basis of ETE model via a numerical method. The COMSOL simulations indicate that as long as the pore is uniform cylinder-shaped, the results agree with those of two-dimensional ETE model, whereas deformations in the cylinder shape (indentation or protrusion) change the temperature behavior of ETE model and, thereby, higher values are predicted for o-Ps lifetime in the pore at lower temperatures. The geometry of the non-uniform cylinder-shaped pores, which is accompanied by empirical evidence, can be used for the analysis of empirical results obtained from positron lifetime spectroscopy in different temperatures.