WorldWideScience

Sample records for vfth temperature dependence

  1. 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.

  2. TEMPERATURE DEPENDENCE OF THE THERMAL ...

    African Journals Online (AJOL)

    Thermal conductivity values, in the temperature range 300 – 1200 K, have been measured in air and at atmospheric pressure for a Kenyan kaolinite refractory with 0% - 50% grog proportions. The experimental thermal conductivity values were then compared with those calculated using the Zumbrunnen et al [1] and the ...

  3. 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 ...

  4. 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.

  5. 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 ...

  6. Escherichia coli survival in waters: Temperature dependence

    Science.gov (United States)

    Knowing the survival rates of water-borne Escherichia coli is important in evaluating microbial contamination and making appropriate management decisions. E. coli survival rates are dependent on temperature, a dependency that is routinely expressed using an analogue of the Q10 mo...

  7. Investigations of Low Temperature Time Dependent Cracking

    Energy Technology Data Exchange (ETDEWEB)

    Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J

    2002-09-30

    The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.

  8. 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.

  9. 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.

  10. 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 ...

  11. 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.

  12. Temperature and angular momentum dependence of the ...

    Indian Academy of Sciences (India)

    Temperature and angular momentum dependence of the quadrupole deformation is studied in the middle of the sd-shell for 28Si and 27Si isotopes using the spherical shell model approach. The shell model calculations have been performed using the standard universal sd-shell (USD) interaction and the canonical ...

  13. 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....

  14. 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.

  15. 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.

  16. Escherichia coli survival in waters: temperature dependence.

    Science.gov (United States)

    Blaustein, R A; Pachepsky, Y; Hill, R L; Shelton, D R; Whelan, G

    2013-02-01

    Knowing the survival rates of water-borne Escherichia coli is important in evaluating microbial contamination and making appropriate management decisions. E. coli survival rates are dependent on temperature, a dependency that is routinely expressed using an analogue of the Q₁₀ model. This suggestion was made 34 years ago based on 20 survival curves taken from published literature, but has not been revisited since then. The objective of this study was to re-evaluate the accuracy of the Q₁₀ equation, utilizing data accumulated since 1978. We assembled a database of 450 E. coli survival datasets from 70 peer-reviewed papers. We then focused on the 170 curves taken from experiments that were performed in the laboratory under dark conditions to exclude the effects of sunlight and other field factors that could cause additional variability in results. All datasets were tabulated dependencies "log concentration vs. time." There were three major patterns of inactivation: about half of the datasets had a section of fast log-linear inactivation followed by a section of slow log-linear inactivation; about a quarter of the datasets had a lag period followed by log-linear inactivation; and the remaining quarter were approximately linear throughout. First-order inactivation rate constants were calculated from the linear sections of all survival curves and the data grouped by water sources, including waters of agricultural origin, pristine water sources, groundwater and wells, lakes and reservoirs, rivers and streams, estuaries and seawater, and wastewater. Dependency of E. coli inactivation rates on temperature varied among the water sources. There was a significant difference in inactivation rate values at the reference temperature between rivers and agricultural waters, wastewaters and agricultural waters, rivers and lakes, and wastewater and lakes. At specific sites, the Q₁₀ equation was more accurate in rivers and coastal waters than in lakes making the value of

  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. 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

  2. Temperature Dependent Molecular Dynamic Simulation of Friction

    OpenAIRE

    Dias, R. A.; Rapini, M.; Costa, B. V.; Coura, P. Z.

    2006-01-01

    In this work we present a molecular dynamics simulation of a FFM experiment. The tip-sample interaction is studied by varying the normal force in the tip and the temperature of the surface. The friction force, cA, at zero load and the friction coefficient, $\\mu$, were obtained. Our results strongly support the idea that the effective contact area, A, decreases with increasing temperature and the friction coefficient presents a clear signature of the premelting process of the surface.

  3. Temperature-dependent dielectric function of nickel

    Science.gov (United States)

    Zollner, Stefan; Nathan Nunley, T.; Trujillo, Dennis P.; Pineda, Laura G.; Abdallah, Lina S.

    2017-11-01

    Confirming historical results by Ornstein and Koefoed (1938), the authors found an anomaly in the optical constants at 1.96 eV for bulk nickel near the Curie temperature through careful high-precision spectroscopic ellipsometry measurements from 80 to 800 K. The anomaly is only seen in sweeps with increasing temperature if the sample carries a net magnetization. In decreasing temperature sweeps or for unmagnetized samples, the anomaly is absent. The sign of the anomaly in the optical conductivity at 1.96 eV is in contrast to the sign of the anomaly in the electrical DC conductivity. The anomaly is rather large and therefore explained with changes in the on-diagonal Drude-Lorentz portion of the dielectric tensor. No sign of anisotropy (polar magneto-optical Kerr effect) is found in the data.

  4. Temperature dependence of fission product release rates

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, J.L.; McGown, M.E.; Reynolds, A.B.

    1984-10-01

    Fission product fractional release rates, K, used in the Albrecht-Wild model and measured at Kernforschungszentrum Karlsruhe and Oak Ridge National Laboratory can be fitted well by a single straight line for each fission product over the entire temperature range of the data when in K is plotted as a function of 1/T. Past applications of the Albrecht-Wild model have used plots of ln K versus T, which required three fits over the temperature range. Thus it is suggested that fractional release rates be represented by the Arrhenius form, K = K /SUB o/ exp(-Q/RT).

  5. Parametric dependencies of JET electron temperature profiles

    Energy Technology Data Exchange (ETDEWEB)

    Schunke, B. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Imre, K.; Riedel, K. [New York Univ., NY (United States)

    1994-07-01

    The JET Ohmic, L-Mode and H-Mode electron temperature profiles obtained from the LIDAR Thomson Scattering Diagnostic are parameterized in terms of the normalized flux parameter and a set of the engineering parameters like plasma current, toroidal field, line averages electron density... It is shown that the electron temperature profiles fit a log-additive model well. It is intended to use the same model to predict the profile shape for D-T discharges in JET and in ITER. 2 refs., 5 figs.

  6. The temperature dependence of the magnetoelastic characteristics ...

    Indian Academy of Sciences (India)

    Special cylindrical backing enables application of the uniform compressive stress to the wound ring sample. A resistive furnace heated the experimental set-up. Results presented in the paper indicate a significant influence of the temperature on the magnetoelastic characteristics of Fe70Ni8Si10B12 amorphous alloy.

  7. Temperature and angular momentum dependence of the ...

    Indian Academy of Sciences (India)

    a metallic superconductor, the linear dimension of the system is quite large and the transition from one phase to the ... This has been demonstrated in small metallic grains in which discontinuity is observed with large ... in the above studies critically depends on the inclusion of the quantal and statistical fluctuations [8,11].

  8. Change of MMP dependent on temperature

    DEFF Research Database (Denmark)

    Rudyk, Svetlana Nikolayevna; Søgaard, Erik Gydesen; Akwansa, Eugene

    2008-01-01

       The experiment was conducted with the purpose to investigate how Minimum Miscibility Pressure (MMP) changes at different temperatures. MMP was measured in a high pressure unit. An original oil saturated chalk core plug from the Danish oil field in North Sea was under investigation. The plug...... was divided into three samples. The pure carbon dioxide was injected into a chamber with the sample under pressure gradually increasing from 60 bars to 420 bars. CO2 was injected in a first sample at temperature 50oC , second at 60oC and third at 70oC. The amount of oil extracted was plotted against pressure....... The oil recovery/pressure correlation obtained showed that: -  oil recovery grows rather in steps, - MMP (the point B on the curve), above which the oil recovery increases insignificantly,  is equal for all the temperatures, - but the starting points (A on the graph) from which oil recovery starts growing...

  9. 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

  10. Temperature-Dependent van der Waals Forces

    Science.gov (United States)

    Parsegian, V. A.; Ninham, B. W.

    1970-01-01

    Biological systems can experience a strong van der Waals interaction involving electromagnetic fluctuations at the low frequency limit. In lipid-water mixtures the free energy of this interaction is proportional to temperature, primarily involves an entropy change, and has qualitative features of a “hydrophobic bond.” Protein-protein attraction in dilute solution is due as much to low frequency proton fluctuation (Kirkwood-Shumaker forces) and permanent dipole forces as to high frequency (infrared and UV) van der Waals intreactions. These conclusions are described in terms of numerical calculations via the Lifshitz theory of van der Waals forces. PMID:5449916

  11. A temperature dependent slip factor based thermal model for friction ...

    Indian Academy of Sciences (India)

    This paper proposes a new slip factor based three-dimensional thermal model to predict the temperature distribution during friction stir welding of 304L stainless steel plates. The proposed model employs temperature and radius dependent heat source to study the thermal cycle, temperature distribution, power required, the ...

  12. A temperature dependent slip factor based thermal model for friction ...

    Indian Academy of Sciences (India)

    Abstract. This paper proposes a new slip factor based three-dimensional thermal model to predict the temperature distribution during friction stir welding of 304L stainless steel plates. The proposed model employs temperature and radius dependent heat source to study the thermal cycle, temperature distribution, power ...

  13. Temperature Dependence in Homogeneous and Heterogeneous Nucleation

    Energy Technology Data Exchange (ETDEWEB)

    McGraw R. L.; Winkler, P. M.; Wagner, P. E.

    2017-08-01

    Heterogeneous nucleation on stable (sub-2 nm) nuclei aids the formation of atmospheric cloud condensation nuclei (CCN) by circumventing or reducing vapor pressure barriers that would otherwise limit condensation and new particle growth. Aerosol and cloud formation depend largely on the interaction between a condensing liquid and the nucleating site. A new paper published this year reports the first direct experimental determination of contact angles as well as contact line curvature and other geometric properties of a spherical cap nucleus at nanometer scale using measurements from the Vienna Size Analyzing Nucleus Counter (SANC) (Winkler et al., 2016). For water nucleating heterogeneously on silver oxide nanoparticles we find contact angles around 15 degrees compared to around 90 degrees for the macroscopically measured equilibrium angle for water on bulk silver. The small microscopic contact angles can be attributed via the generalized Young equation to a negative line tension that becomes increasingly dominant with increasing curvature of the contact line. These results enable a consistent theoretical description of heterogeneous nucleation and provide firm insight to the wetting of nanosized objects.

  14. 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.

  15. 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.)

  16. Poiseuille Flow of Fluid Whose Viscosity is Temperature Dependent ...

    African Journals Online (AJOL)

    We discuss a fluid flowing between two parallel plates. We assume a Poiseuille flow. Furthermore, we assume that the viscosity μ, depends on temperature T. We show that the velocity equation has two solutions. Graph features prominently in the presentation.

  17. 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...

  18. 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.

  19. 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...

  20. 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...

  1. 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.

  2. 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.

  3. 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.

  4. 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, ...

  5. Existence of a secondary flow for a temperature dependent viscous ...

    African Journals Online (AJOL)

    We model a viscous fluid flowing between parallel plates. The viscosity depends on temperature. We investigate the properties of the velocity and we show that the temperature and velocity fields have two solutions. The existence of two velocity solutions is new. This means that there exist secondary flows. Journal of the ...

  6. 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 ...

  7. 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 ...

  8. Time dependent temperature distribution in pulsed Ti:sapphire lasers

    Science.gov (United States)

    Buoncristiani, A. Martin; Byvik, Charles E.; Farrukh, Usamah O.

    1988-01-01

    An expression is derived for the time dependent temperature distribution in a finite solid state laser rod for an end-pumped beam of arbitrary shape. The specific case of end pumping by circular (constant) or Gaussian beam is described. The temperature profile for a single pump pulse and for repetitive pulse operation is discussed. The particular case of the temperature distribution in a pulsed titanium:sapphire rod is considered.

  9. 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.

  10. 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.

  11. 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

  12. 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...

  13. 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.

  14. New Insight into Time-Temperature Correlation for Polymer Relaxations Ranging from Secondary Relaxation to Terminal Flow: Application of a Universal and Developed WLF Equation

    Directory of Open Access Journals (Sweden)

    Yonggang Shangguan

    2017-11-01

    Full Text Available The three equations involved in the time-temperature superposition (TTS of a polymer, i.e., Williams–Landel–Ferry (WLF, Vogel–Fulcher–Tammann–Hesse (VFTH and the Arrhenius equation, were re-examined, and the mathematical equivalence of the WLF form to the Arrhenius form was revealed. As a result, a developed WLF (DWLF equation was established to describe the temperature dependence of relaxation property for the polymer ranging from secondary relaxation to terminal flow, and its necessary criteria for universal application were proposed. TTS results of viscoelastic behavior for different polymers including isotactic polypropylene (iPP, high density polyethylene (HDPE, low density polyethylene (LDPE and ethylene-propylene rubber (EPR were well achieved by the DWLF equation at high temperatures. Through investigating the phase-separation behavior of poly(methyl methacrylate/poly(styrene-co-maleic anhydride (PMMA/SMA and iPP/EPR blends, it was found that the DWLF equation can describe the phase separation behavior of the amorphous/amorphous blend well, while the nucleation process leads to a smaller shift factor for the crystalline/amorphous blend in the melting temperature region. Either the TTS of polystyrene (PS and PMMA or the secondary relaxations of PMMA and polyvinyl chloride (PVC confirmed that the Arrhenius equation can be valid only in the high temperature region and invalid in the vicinity of glass transition due to the strong dependence of apparent activation energy on temperature; while the DWLF equation can be employed in the whole temperature region including secondary relaxation and from glass transition to terminal relaxation. The theoretical explanation for the universal application of the DWLF equation was also revealed through discussing the influences of free volume and chemical structure on the activation energy of polymer relaxations.

  15. 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.

  16. 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.

  17. Substrate-dependent temperature sensitivity of soil organic matter decomposition

    Science.gov (United States)

    Myachina, Olga; Blagodatskaya, Evgenia

    2015-04-01

    Activity of extracellular enzymes responsible for decomposition of organics is substrate dependent. Quantity of the substrate is the main limiting factor for enzymatic or microbial heterotrophic activity in soils. Different mechanisms of enzymes response to temperature suggested for low and high substrate availability were never proved for real soil conditions. We compared the temperature responses of enzymes-catalyzed reactions in soils. Basing on Michaelis-Menten kinetics we determined the enzymes affinity to substrate (Km) and mineralization potential of heterotrophic microorganisms (Vmax) 1) for three hydrolytic enzymes: β-1,4-glucosidase, N-acetyl- β -D-glucosaminidase and phosphatase by the application of fluorogenically labeled substrates and 2) for mineralization of 14C-labeled glucose by substrate-dependent respiratory response. Here we show that the amount of available substrate is responsible for temperature sensitivity of hydrolysis of polymers in soil, whereas monomers oxidation to CO2 does not depend on substrate amount and is mainly temperature governed. We also found that substrate affinity of enzymes (which is usually decreases with the temperature) differently responded to warming for the process of depolymerisation versus monomers oxidation. We suggest the mechanism to temperature acclimation based on different temperature sensitivity of enzymes kinetics for hydrolysis of polymers and for monomers oxidation.

  18. A framework for elucidating the temperature dependence of fitness.

    Science.gov (United States)

    Amarasekare, Priyanga; Savage, Van

    2012-02-01

    Climate warming is predicted to cause large-scale extinctions, particularly of ectothermic species. A striking difference between tropical and temperate ectotherms is that tropical species experience a mean habitat temperature that is closer to the temperature at which fitness is maximized (T(opt)) and an upper temperature limit for survival (T(max)) that is closer to T(opt) than do temperate species. Thus, even a small increase in environmental temperature could put tropical ectotherms at high risk of extinction, whereas temperate ectotherms have a wider temperature cushion. Although this pattern is widely observed, the mechanisms that produce it are not well understood. Here we develop a mathematical framework to partition the temperature response of fitness into its components (fecundity, mortality, and development) and test model predictions with data for insects. We find that fitness declines at high temperatures because the temperature responses of fecundity and mortality act in opposite ways: fecundity decreases with temperature when temperatures exceed the optimal range, whereas mortality continues to increase. The proximity of T(opt) to T(max) depends on how the temperature response of development mediates the interaction between fecundity and mortality. When development is highly temperature sensitive, mortality exceeds reproduction only after fecundity has started to decline with temperature, which causes fitness to decline rapidly to zero when temperatures exceed T(opt). The model correctly predicts empirically observed fitness-temperature relationships in insects from different latitudes. It also suggests explanations for the widely reported phenological shifts in many ectotherms and the latitudinal differences in fitness responses.

  19. Temperature dependence of alkali-antimonide photocathodes: Evaluation at cryogenic temperatures

    Science.gov (United States)

    Mamun, M. A.; Hernandez-Flores, M. R.; Morales, E.; Hernandez-Garcia, C.; Poelker, M.

    2017-10-01

    CsxKySb photocathodes were manufactured on a niobium substrate and evaluated over a range of temperatures from 300 to 77 K. Vacuum conditions were identified that minimize surface contamination due to gas adsorption when samples were cooled below room temperature. Measurements of the photocathode spectral response provided a means to evaluate the photocathode band gap dependence on the temperature and to predict the photocathode quantum efficiency at 4 K, a typical temperature at which superconducting radio frequency photoguns operate.

  20. 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...

  1. 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.

  2. Honeybee flight metabolic rate: does it depend upon air temperature?

    Science.gov (United States)

    Woods, William A; Heinrich, Bernd; Stevenson, Robert D

    2005-03-01

    Differing conclusions have been reached as to how or whether varying heat production has a thermoregulatory function in flying honeybees Apis mellifera. We investigated the effects of air temperature on flight metabolic rate, water loss, wingbeat frequency, body segment temperatures and behavior of honeybees flying in transparent containment outdoors. For periods of voluntary, uninterrupted, self-sustaining flight, metabolic rate was independent of air temperature between 19 and 37 degrees C. Thorax temperatures (T(th)) were very stable, with a slope of thorax temperature on air temperature of 0.18. Evaporative heat loss increased from 51 mW g(-1) at 25 degrees C to 158 mW g(-1) at 37 degrees C and appeared to account for head and abdomen temperature excess falling sharply over the same air temperature range. As air temperature increased from 19 to 37 degrees C, wingbeat frequency showed a slight but significant increase, and metabolic expenditure per wingbeat showed a corresponding slight but significant decrease. Bees spent an average of 52% of the measurement period in flight, with 19 of 78 bees sustaining uninterrupted voluntary flight for periods of >1 min. The fraction of time spent flying declined as air temperature increased. As the fraction of time spent flying decreased, the slope of metabolic rate on air temperature became more steeply negative, and was significant for bees flying less than 80% of the time. In a separate experiment, there was a significant inverse relationship of metabolic rate and air temperature for bees requiring frequent or constant agitation to remain airborne, but no dependence for bees that flew with little or no agitation; bees were less likely to require agitation during outdoor than indoor measurements. A recent hypothesis explaining differences between studies in the slope of flight metabolic rate on air temperature in terms of differences in metabolic capacity and thorax temperature is supported for honeybees in voluntary

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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".

  10. 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)

  11. 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

  12. Size-dependent cohesive energy, melting temperature, and Debye temperature of spherical metallic nanoparticles

    Science.gov (United States)

    Qu, Y. D.; Liang, X. L.; Kong, X. Q.; Zhang, W. J.

    2017-06-01

    It is necessary to theoretically evaluate the thermodynamic properties of metallic nanoparticles due to the lack of experimental data. Considering the surface effects and crystal structures, a simple theoretical model is developed to study the size dependence of thermodynamic properties of spherical metallic nanoparticles. Based on the model, we have considered Co and Cu nanoparticles for the study of size dependence of cohesive energy, Au and Cu nanoparticles for size dependence of melting temperature, and Cu, Co and Au nanoparticles for size dependence of Debye temperature, respectively. The results show that the size effects on melting temperature, cohesive energy and Debye temperature of the spherical metallic nanoparticles are predominant in the sizes ranging from about 3 nm to 20 nm. The present theoretical predictions are in agreement with available corresponding experimental and computer simulation results for the spherical metallic nanoparticles. The model could be used to determine the thermodynamic properties of other metallic nanoparticles to some extent.

  13. 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

  14. 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 ...

  15. 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 ...

  16. 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 ...

  17. 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)

  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. 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.

  20. 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.

  1. Effects of Temperature on Time Dependent Rheological Characteristics of Koumiss

    Directory of Open Access Journals (Sweden)

    Serdal Sabancı

    2016-04-01

    Full Text Available The rheological properties of koumiss were investigated at different temperatures (4, 10, and 20°C. Experimental shear stress–shear rate data were fitted to different rheological models. The consistency of koumiss was predicted by using the power-law model since it described the consistency of koumiss best with highest regression coefficient and lowest errors (root mean square error and chi-square. Koumiss exhibited shear thinning behavior (n<1. The flow activation energy for temperature dependency of consistency was 25.532 kJ/mol, and the frequency constant was 2.18×10-7Pa.sn. As the temperature increased the time dependent thixotropic characteristics of koumiss decreased.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Depth Dependent Relationships between Temperature and Ocean Heterotrophic Prokaryotic Production

    KAUST Repository

    Lønborg, Christian

    2016-06-07

    Marine prokaryotes play a key role in cycling of organic matter and nutrients in the ocean. Using a unique dataset (>14,500 samples), we applied a space-for-time substitution analysis to assess the temperature dependence of prokaryotic heterotrophic production (PHP) in epi- (0-200 m), meso- (201-1000 m) and bathypelagic waters (1001-4000 m) of the global ocean. Here, we show that the temperature dependence of PHP is fundamentally different between these major oceanic depth layers, with an estimated ecosystem-level activation energy (E) of 36 ± 7 kJ mol for the epipelagic, 72 ± 15 kJ mol for the mesopelagic and 274 ± 65 kJ mol for the bathypelagic realm. We suggest that the increasing temperature dependence with depth is related to the parallel vertical gradient in the proportion of recalcitrant organic compounds. These Ea predict an increased PHP of about 5, 12, and 55% in the epi-, meso-, and bathypelagic ocean, respectively, in response to a water temperature increase by 1°C. Hence, there is indication that a major thus far underestimated feedback mechanism exists between future bathypelagic ocean warming and heterotrophic prokaryotic activity.

  7. 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.

  8. Temperature Dependence of the Resonant Magnetoelectric Effect in Layered Heterostructures

    Directory of Open Access Journals (Sweden)

    Dmitrii A. Burdin

    2017-10-01

    Full Text Available The dependence of the resonant direct magnetoelectric effect on temperature is studied experimentally in planar composite structures. Samples of rectangular shapes with dimensions of 5 mm × 20 mm employed ferromagnetic layers of either an amorphous (metallic glass alloy or nickel with a thickness of 20–200 μm and piezoelectric layers of single crystalline langatate material or lead zirconate titanate piezoelectric ceramics with a thickness of 500 μm. The temperature of the samples was varied in a range between 120 and 390 K by blowing a gaseous nitrogen stream around them. It is shown that the effective characteristics of the magnetoelectric effect—such as the mechanical resonance frequency fr, the quality factor Q and the magnitude of the magnetoelectric coefficient αE at the resonance frequency—are contingent on temperature. The interrelations between the temperature changes of the characteristics of the magnetoelectric effect and the temperature variations of the following material parameters—Young’s modulus Y, the acoustic quality factor of individual layers, the dielectric constant ε, the piezoelectric modulus d of the piezoelectric layer as well as the piezomagnetic coefficients λ(n of the ferromagnetic layer—are established. The effect of temperature on the characteristics of the nonlinear magnetoelectric effect is observed for the first time. The results can be useful for designing magnetoelectric heterostructures with specified temperature characteristics, in particular, for the development of thermally stabilized magnetoelectric devices.

  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. 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.

  11. Quantitative Temperature Dependence of Longitudinal Spin Seebeck Effect at High Temperatures

    Directory of Open Access Journals (Sweden)

    Ken-ichi Uchida

    2014-11-01

    Full Text Available We report temperature-dependent measurements of longitudinal spin Seebeck effects (LSSEs in Pt/Y_{3}Fe_{5}O_{12} (YIG/Pt systems in a high temperature range from room temperature to above the Curie temperature of YIG. The experimental results show that the magnitude of the LSSE voltage in the Pt/YIG/Pt systems rapidly decreases with increasing the temperature and disappears above the Curie temperature. The critical exponent of the LSSE voltage in the Pt/YIG/Pt systems at the Curie temperature is estimated to be 3, which is much greater than that for the magnetization curve of YIG. This difference highlights the fact that the mechanism of the LSSE cannot be explained in terms of simple static magnetic properties in YIG.

  12. 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...

  13. Temperature and size dependent friction of gold nanoislands on graphene

    Science.gov (United States)

    Dawson, Ben D.; Lodge, Michael S.; Williams, Zachary; Ishigami, Masa

    2013-03-01

    Nanoscale motors and machines require the ability to tune frictional properties at the nanoscale. Yet a fundamental understanding of frictional processes of nanoislands still remains unknown. We have performed a quartz crystal microbalance study to investigate the role of temperature and island size on frictional energy dissipation for gold nanoislands on graphene. Significant frictional dissipation is observed even at room temperature, consistent with activated friction on the graphene surface. We will discuss these results and compare them to previously predicted models for thermally activated and size dependent friction. This work is funded by the Intelligence Community Postdoctoral Research Fellowship program

  14. 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.

  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 Conformations of Model Viscosity Index Improvers

    Energy Technology Data Exchange (ETDEWEB)

    Ramasamy, Uma Shantini; Cosimbescu, Lelia; Martini, Ashlie

    2015-05-01

    Lubricants are comprised of base oils and additives where additives are chemicals that are deliberately added to the oil to enhance properties and inhibit degradation of the base oils. Viscosity index (VI) improvers are an important class of additives that reduce the decline of fluid viscosity with temperature [1], enabling optimum lubricant performance over a wider range of operating temperatures. These additives are typically high molecular weight polymers, such as, but not limited to, polyisobutylenes, olefin copolymer, and polyalkylmethacrylates, that are added in concentrations of 2-5% (w/w). Appropriate polymers, when dissolved in base oil, expand from a coiled to an uncoiled state with increasing temperature [2]. The ability of VI additives to increase their molar volume and improve the temperature-viscosity dependence of lubricants suggests there is a strong relationship between molecular structure and additive functionality [3]. In this work, we aim to quantify the changes in polymer size with temperature for four polyisobutylene (PIB) based molecular structures at the nano-scale using molecular simulation tools. As expected, the results show that the polymers adopt more conformations at higher temperatures, and there is a clear indication that the expandability of a polymer is strongly influenced by molecular structure.

  17. 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 ...

  18. Density of biogas digestate depending on temperature and composition.

    Science.gov (United States)

    Gerber, Mandy; Schneider, Nico

    2015-09-01

    Density is one of the most important physical properties of biogas digestate to ensure an optimal dimensioning and a precise design of biogas plant components like stirring devices, pumps and heat exchangers. In this study the density of biogas digestates with different compositions was measured using pycnometers at ambient pressure in a temperature range from 293.15 to 313.15K. The biogas digestates were taken from semi-continuous experiments, in which the marine microalga Nannochloropsis salina, corn silage and a mixture of both were used as feedstocks. The results show an increase of density with increasing total solid content and a decrease with increasing temperature. Three equations to calculate the density of biogas digestate were set up depending on temperature as well as on the total solid content, organic composition and elemental composition, respectively. All correlations show a relative deviation below 1% compared to experimental data. Copyright © 2015. Published by Elsevier Ltd.

  19. The temperature-dependence of elementary reaction rates: beyond Arrhenius.

    Science.gov (United States)

    Smith, Ian W M

    2008-04-01

    The rates of chemical reactions and the dependence of their rate constants on temperature are of central importance in chemistry. Advances in the temperature-range and accuracy of kinetic measurements, principally inspired by the need to provide data for models of combustion, atmospheric, and astrophysical chemistry, show up the inadequacy of the venerable Arrhenius equation--at least, over wide ranges of temperature. This critical review will address the question of how to reach an understanding of the factors that control the rates of 'non-Arrhenius' reactions. It makes use of a number of recent kinetic measurements and shows how developments in advanced forms of transition state theory provide satisfactory explanations of complex kinetic behaviour (72 references).

  20. Temperature dependent mistranslation in a hyperthermophile adapts proteins to lower temperatures

    Science.gov (United States)

    Schwartz, Michael H.; Pan, Tao

    2016-01-01

    All organisms universally encode, synthesize and utilize proteins that function optimally within a subset of growth conditions. While healthy cells are thought to maintain high translational fidelity within their natural habitats, natural environments can easily fluctuate outside the optimal functional range of genetically encoded proteins. The hyperthermophilic archaeon Aeropyrum pernix (A. pernix) can grow throughout temperature variations ranging from 70 to 100°C, although the specific factors facilitating such adaptability are unknown. Here, we show that A. pernix undergoes constitutive leucine to methionine mistranslation at low growth temperatures. Low-temperature mistranslation is facilitated by the misacylation of tRNALeu with methionine by the methionyl-tRNA synthetase (MetRS). At low growth temperatures, the A. pernix MetRS undergoes a temperature dependent shift in tRNA charging fidelity, allowing the enzyme to conditionally charge tRNALeu with methionine. We demonstrate enhanced low-temperature activity for A. pernix citrate synthase that is synthesized during leucine to methionine mistranslation at low-temperature growth compared to its high-fidelity counterpart synthesized at high-temperature. Our results show that conditional leucine to methionine mistranslation can make protein adjustments capable of improving the low-temperature activity of hyperthermophilic proteins, likely by facilitating the increasing flexibility required for greater protein function at lower physiological temperatures. PMID:26657639

  1. Quantifying the Temperature Dependence of Glycine Betaine RNA Duplex Destabilization

    Science.gov (United States)

    Schwinefus, Jeffrey J.; Menssen, Ryan J.; Kohler, James M.; Schmidt, Elliot C.; Thomas, Alexandra L.

    2013-01-01

    Glycine betaine stabilizes folded protein structure due to its unfavorable thermodynamic interactions with amide oxygen and aliphatic carbon surface area exposed during protein unfolding. However, glycine betaine can attenuate nucleic acid secondary structure stability, although its mechanism of destabilization is not currently understood. In this work we quantify glycine betaine interactions with the surface area exposed during thermal denaturation of nine RNA dodecamer duplexes with guanine-cytosine (GC) contents of 17–100%. Hyperchromicity values indicate increasing glycine betaine molality attenuates stacking. Glycine betaine destabilizes higher GC content RNA duplexes to a greater extent than low GC content duplexes due to greater accumulation at the surface area exposed during unfolding. The accumulation is very sensitive to temperature and displays characteristic entropy-enthalpy compensation. Since the entropic contribution to the m-value (used to quantify GB interaction with the RNA solvent accessible surface area exposed during denaturation) is more dependent on temperature than the enthalpic contribution, higher GC content duplexes with their larger transition temperatures are destabilized to a greater extent than low GC content duplexes. The concentration of glycine betaine at the RNA surface area exposed during unfolding relative to bulk was quantified using the solute partitioning model. Temperature correction predicts a glycine betaine concentration at 25 °C to be nearly independent of GC content, indicating that glycine betaine destabilizes all sequences equally at this temperature. PMID:24219229

  2. Complete FDTD analysis of microwave heating processes in frequency-dependent and temperature dependent media

    Energy Technology Data Exchange (ETDEWEB)

    Torres, F.; Jecko, B. [Univ. de Limoges (France). Inst. de Recherche en Communications Optiques et Microondes

    1997-01-01

    It is well known that the temperature rise in a material modifies its physical properties and, particularly, its dielectric permittivity. The dissipated electromagnetic power involved in microwave heating processes depending on {var_epsilon}({omega}), the electrical characteristics of the heated media must vary with the temperature to achieve realistic simulations. In this paper, the authors present a fast and accurate algorithm allowing, through a combined electromagnetic and thermal procedure, to take into account the influence of the temperature on the electrical properties of materials. First, the temperature dependence of the complex permittivity ruled by a Debye relaxation equation is investigated, and a realistic model is proposed and validated. Then, a frequency-dependent finite-differences time-domain ((FD){sup 2}TD) method is used to assess the instantaneous electromagnetic power lost by dielectric hysteresis. Within the same iteration, a time-scaled form of the heat transfer equation allows one to calculate the temperature distribution in the heated medium and then to correct the dielectric properties of the material using the proposed model. These new characteristics will be taken into account by the EM solver at the next iteration. This combined algorithm allows a significant reduction of computation time. An application to a microwave oven is proposed.

  3. The Temperature Condition of the Plate with Temperature-Dependent Thermal Conductivity and Energy Release

    Directory of Open Access Journals (Sweden)

    V. S. Zarubin

    2016-01-01

    Full Text Available The temperature state of a solid body, in addition to the conditions of its heat exchange with the environment, can greatly depend on the heat release (or heat absorption processes within the body volume. Among the possible causes of these processes should be noted such as a power release in the fuel elements of nuclear reactors, exothermic or endothermic chemical reactions in the solid body material, which respectively involve heat release or absorbtion, heat transfer of a part of the electric power in the current-carrying conductors (so-called Joule’s heat or the energy radiation penetrating into the body of a semitransparent material, etc. The volume power release characterizes an intensity of these processes.The extensive list of references to the theory of heat conductivity of solids offers solutions to problems to determine a stationary (steady over time and non-stationary temperature state of the solids (as a rule, of the canonical form, which act as the sources of volume power release. Thus, in general case, a possibility for changing power release according to the body volume and in solving the nonstationary problems also a possible dependence of this value on the time are taken into consideration.However, in real conditions the volume power release often also depends on the local temperature, and such dependence can be nonlinear. For example, with chemical reactions the intensity of heat release or absorption is in proportion to their rate, which, in turn, is sensitive to the temperature value, and a dependence on the temperature is exponential. A further factor that in such cases makes the analysis of the solid temperature state complicated, is dependence on the temperature and the thermal conductivity of this body material, especially when temperature distribution therein  is significantly non-uniform. Taking into account the influence of these factors requires the mathematical modeling methods, which allow us to build an adequate

  4. Temperature-dependent magnetic EXAFS investigation of Gd

    CERN Document Server

    Wende, H; Poulopoulos, P N; Rogalev, A; Goulon, J; Schlagel, D L; Lograsso, T A; Baberschke, K

    2001-01-01

    Magnetic EXAFS (MEXAFS) is the helicity-dependent counterpart of the well-established EXAFS technique. By means of MEXAFS it is possible not only to analyze the local magnetic structure but also to learn about magnetic fluctuations. Here we present the MEXAFS of a Gd single crystal at the L sub 3 sub , sub 2 -edges in the temperature range of 10-250 K. For the first time MEXAFS was probed over a large range in reduced temperature of 0.04<=T/T sub C<=0.85 with T sub C =293 K. We show that the vibrational damping described by means of a Debye temperature of theta sub D =160 K must be taken into account for the spin-dependent MEXAFS before analyzing magnetic fluctuations. For a detailed analysis of the MEXAFS and the EXAFS, the experimental data are compared to ab initio calculations. This enables us to separate the individual single- from the multiple-scattering contributions. The MEXAFS data have been recorded at the ID 12A beamline of the European Synchrotron Radiation Facility (ESRF). To ensure that th...

  5. 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.)

  6. 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.

  7. 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.

  8. 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.

  9. 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.)

  10. 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.

  11. 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.

  12. Brittle Creep of Tournemire Shale: Orientation, Temperature and Pressure Dependences

    Science.gov (United States)

    Geng, Zhi; Bonnelye, Audrey; Dick, Pierre; David, Christian; Chen, Mian; Schubnel, Alexandre

    2017-04-01

    Time and temperature dependent rock deformation has both scientific and socio-economic implications for natural hazards, the oil and gas industry and nuclear waste disposal. During the past decades, most studies on brittle creep have focused on igneous rocks and porous sedimentary rocks. To our knowledge, only few studies have been carried out on the brittle creep behavior of shale. Here, we conducted a series of creep experiments on shale specimens coming from the French Institute for Nuclear Safety (IRSN) underground research laboratory located in Tournemire, France. Conventional tri-axial experiments were carried under two different temperatures (26˚ C, 75˚ C) and confining pressures (10 MPa, 80 MPa), for three orientations (σ1 along, perpendicular and 45˚ to bedding). Following the methodology developed by Heap et al. [2008], differential stress was first increased to ˜ 60% of the short term peak strength (10-7/s, Bonnelye et al. 2016), and then in steps of 5 to 10 MPa every 24 hours until brittle failure was achieved. In these long-term experiments (approximately 10 days), stress and strains were recorded continuously, while ultrasonic acoustic velocities were recorded every 1˜15 minutes, enabling us to monitor the evolution of elastic wave speed anisotropy. Temporal evolution of anisotropy was illustrated by inverting acoustic velocities to Thomsen parameters. Finally, samples were investigated post-mortem using scanning electron microscopy. Our results seem to contradict our traditional understanding of loading rate dependent brittle failure. Indeed, the brittle creep failure stress of our Tournemire shale samples was systematically observed ˜50% higher than its short-term peak strength, with larger final axial strain accumulated. At higher temperatures, the creep failure strength of our samples was slightly reduced and deformation was characterized with faster 'steady-state' creep axial strain rates at each steps, and larger final axial strain

  13. Temperature dependence of thermal conductivity of biological tissues.

    Science.gov (United States)

    Bhattacharya, A; Mahajan, R L

    2003-08-01

    In this paper, we present our experimental results on the determination of the thermal conductivity of biological tissues using a transient technique based on the principles of the cylindrical hot-wire method. A novel, 1.45 mm diameter, 50 mm long hot-wire probe was deployed. Initial measurements were made on sponge, gelatin and Styrofoam insulation to test the accuracy of the probe. Subsequent experiments conducted on sheep collagen in the range of 25 degrees C thermal conductivity to be a linear function of temperature. Further, these changes in the thermal conductivity were found to be reversible. However, when the tissue was heated beyond 55 degrees C, irreversible changes in thermal conductivity were observed. Similar experiments were also conducted for determining the thermal conductivity of cow liver. In this case, the irreversible effects were found to set in much later at around 90 degrees C. Below this temperature, in the range of 25 degrees C thermal conductivity, as for sheep collagen, varied linearly with temperature. In the second part of our study, in vivo measurements were taken on the different organs of a living pig. Comparison with reported values for dead tissues shows the thermal conductivities of living organs to be higher, indicating thereby the dominant role played by blood perfusion in enhancing the net heat transfer in living tissues. The degree of enhancement is different in different organs and shows a direct dependence on the blood flow rate.

  14. 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

  15. 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.

  16. The Temperature Condition of the Plate with Temperature-Dependent Thermal Conductivity and Energy Release

    OpenAIRE

    V. S. Zarubin; A. V. Kotovich; G. N. Kuvyrkin

    2016-01-01

    The temperature state of a solid body, in addition to the conditions of its heat exchange with the environment, can greatly depend on the heat release (or heat absorption) processes within the body volume. Among the possible causes of these processes should be noted such as a power release in the fuel elements of nuclear reactors, exothermic or endothermic chemical reactions in the solid body material, which respectively involve heat release or absorbtion, heat transfer of a part of the elect...

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Analogy between temperature-dependent and concentration-dependent bacterial killing.

    Science.gov (United States)

    Neef, C; van Gils, S A; IJzerman, W L

    2002-11-01

    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 describe the sterilization process. Total lethality of the process is calculated as the integral of the lethality (a function of the temperature) over time. In the case of concentration-dependent killing-i.e. using antibiotic drugs-the k-value is not necessarily a constant; it is the difference between growth and killing of the microorganism. Equations are derived for the decimal reduction time D and resistance coefficient z. Pharmacodynamic models of tobramycin, ciprofloxacin and ceftazidime are used to demonstrate that there is an optimal concentration for all three drugs: C(opt-tobra)=3.20 MICmg/l, C(opt-cipro)=3.45 MICmg/l and C(opt-cefta)=1.35 MICmg/l.

  2. Time dependent and temperature dependent properties of the forward voltage characteristic of InGaN high power LEDs

    National Research Council Canada - National Science Library

    P. L. Fulmek; P. Haumer; F. P. Wenzl; W. Nemitz; J. Nicolics

    2017-01-01

    Estimating the junction temperature and its dynamic behavior in dependence of various operating conditions is an important issue, since these properties influence the optical characteristics as well...

  3. 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.

  4. Dependence of the brittle ductile transition on strain-rate-dependent critical homologous temperature

    Science.gov (United States)

    Davis, Paul M.

    2017-05-01

    Earthquakes mainly occur in crust or mantle that is below a critical temperature for the tectonic strain-rate, \\dot{e}_t, such that stress builds up to the breaking point before it can relax due to creep. Then long-range stress correlation gives rise to power law seismicity including large events. The limiting temperature depends on pressure, which is taken into account by finding a critical homologous temperature THc = T/TM above which earthquakes are rarely observed (where T, TM are temperature and average melting temperature of constituent minerals). We find that THc for ocean plates is ∼0.55. For California earthquakes, it is also close to 0.55. The uppermost mantle layer of oceanic plates of thickness ∼50 km is composed of harzburgite and depleted peridotite from which basalt has been removed to form ocean crust. Thus it has a higher melting temperature than the peridotite of the surrounding mantle, or the lower halves of plates. Thicknesses of seismicity in deep subduction zones, determined from 2-D polynomial fits to a relocated catalogue, are ∼50 km, which suggests that the earthquake channel is confined to this layer. We construct models to find homologous temperatures in slabs, and find that seismicity thicknesses are also, on average, confined to TH ≤ 0.55 ± 0.05. The associated rheology is compared with that obtained from flexure models of ocean lithosphere. The brittle-ductile transition occurs where viscosity drops from high values in the cold cores of slabs to values of 1022-1023 Pa s, that is, where creep strain-rates become comparable to tectonic rates. The cut-off for deep earthquakes is not sharp. However they appear unlikely to occur if homologous temperature is high TH > 0.55. Exceptions to the rule are anomalously deep earthquakes such as those beneath the Iceland and the Hawaiian hotspots, and the Newport Inglewood Fault. These are smaller events with short-range stress correlation, and can be explained if strain-rates are two to

  5. Honeybee flight metabolic rate: does it depend upon air temperature?

    National Research Council Canada - National Science Library

    Woods, William A; Heinrich, Bernd; Stevenson, Robert D

    2005-01-01

    .... We investigated the effects of air temperature on flight metabolic rate, water loss, wingbeat frequency, body segment temperatures and behavior of honeybees flying in transparent containment outdoors...

  6. 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.

  7. Anomalous dependence of the heat capacity of supercooled water on pressure and temperature

    Directory of Open Access Journals (Sweden)

    I.A. Stepanov

    2014-01-01

    Full Text Available In some papers, dependences of the isobaric heat capacity of water versus pressure and temperature were obtained. It is shown that these dependences contradict both the dependence of heat capacity on temperature for supercooled water, and an important thermodynamic equation for the dependence of heat capacity on pressure. A possible explanation for this contradiction is proposed.

  8. Fracture strength of the particulate-reinforced ultra-high temperature ceramics based on a temperature dependent fracture toughness model

    Science.gov (United States)

    Wang, Ruzhuan; Li, Weiguo; Ji, Baohua; Fang, Daining

    2017-10-01

    The particulate-reinforced ultra-high temperature ceramics (pUHTCs) have been particularly developed for fabricating the leading edge and nose cap of hypersonic vehicles. They have drawn intensive attention of scientific community for their superior fracture strength at high temperatures. However, there is no proper model for predicting the fracture strength of the ceramic composites and its dependency on temperature. In order to account for the effect of temperature on the fracture strength, we proposed a concept called energy storage capacity, by which we derived a new model for depicting the temperature dependent fracture toughness of the composites. This model gives a quantitative relationship between the fracture toughness and temperature. Based on this temperature dependent fracture toughness model and Griffith criterion, we developed a new fracture strength model for predicting the temperature dependent fracture strength of pUHTCs at different temperatures. The model takes into account the effects of temperature, flaw size and residual stress without any fitting parameters. The predictions of the fracture strength of pUHTCs in argon or air agreed well with the experimental measurements. Additionally, our model offers a mechanism of monitoring the strength of materials at different temperatures by testing the change of flaw size. This study provides a quantitative tool for design, evaluation and monitoring of the fracture properties of pUHTCs at high temperatures.

  9. Temperature-dependent macromolecular X-ray crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Weik, Martin, E-mail: martin.weik@ibs.fr; Colletier, Jacques-Philippe [CEA, IBS, Laboratoire de Biophysique Moléculaire, F-38054 Grenoble (France); CNRS, UMR5075, F-38027 Grenoble (France); Université Joseph Fourier, F-38000 Grenoble (France)

    2010-04-01

    The dynamical behaviour of crystalline macromolecules and their surrounding solvent as a function of cryo-temperature is reviewed. X-ray crystallography provides structural details of biological macromolecules. Whereas routine data are collected close to 100 K in order to mitigate radiation damage, more exotic temperature-controlled experiments in a broader temperature range from 15 K to room temperature can provide both dynamical and structural insights. Here, the dynamical behaviour of crystalline macromolecules and their surrounding solvent as a function of cryo-temperature is reviewed. Experimental strategies of kinetic crystallography are discussed that have allowed the generation and trapping of macromolecular intermediate states by combining reaction initiation in the crystalline state with appropriate temperature profiles. A particular focus is on recruiting X-ray-induced changes for reaction initiation, thus unveiling useful aspects of radiation damage, which otherwise has to be minimized in macromolecular crystallography.

  10. 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.

  11. Temperature dependence of a silicon power device switching parameters

    Science.gov (United States)

    Habchi, R.; Salame, C.; Khoury, A.; Mialhe, P.

    2006-04-01

    This study presents measurements of device switching parameters performed on a commercial power metal-oxide-semiconductor field-effect transistor under high-temperature conditions. Measured switching times show that the device response to being turned off becomes faster at high temperatures. The inverse drain-source current rapidly increases above the 300°C limit. I-V curves indicate that the saturation current in the channel increases with temperature.

  12. Temperature-dependent rate models of vascular cambium cell mortality

    Science.gov (United States)

    Matthew B. Dickinson; Edward A. Johnson

    2004-01-01

    We use two rate-process models to describe cell mortality at elevated temperatures as a means of understanding vascular cambium cell death during surface fires. In the models, cell death is caused by irreversible damage to cellular molecules that occurs at rates that increase exponentially with temperature. The models differ in whether cells show cumulative effects of...

  13. Thermal Aware Floorplanning Incorporating Temperature Dependent Wire Delay Estimation

    DEFF Research Database (Denmark)

    Winther, AndreasThor; Liu, Wei; Nannarelli, Alberto

    2015-01-01

    Temperature has a negative impact on metal resistance and thus wire delay. In state-of-the-art VLSI circuits, large thermal gradients usually exist due to the uneven distribution of heat sources. The difference in wire temperature can lead to performance mismatch because wires of the same length ...

  14. 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...

  15. PRELIMINARY STUDIES 'ON TEMPERATURE DEPENDENCE 'Q,F ...

    African Journals Online (AJOL)

    ferromagnetic has characteristic temperature/magnetisation curves. At varying temperatures the magnetic susceptibility of a diamagnet is constant. (Fig.1), while it decreases for paramagnetic materials (Fig.2). The paramagnetic materials obey Curie law,. (eqn.1) in which the magnetic susceptibility varies inversely with.

  16. Substrate bias voltage and deposition temperature dependence on ...

    Indian Academy of Sciences (India)

    ... on Si (100) substrate. Deposition at higher substrate temperature causes the film to react with Si forming silicides at the film/Si substrate interface. Ti film undergoes a microstructural transition from hexagonal plate-like to round-shaped grains as the substrate temperature was raised from 300 to 50 °C during film deposition ...

  17. 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.

  18. 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.

  19. 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.

  20. Temperature Dependence of Dark Current in Quantum Well Infrared Detectors

    National Research Council Canada - National Science Library

    Hickey, Thomas

    2002-01-01

    ...) /cu cm were gathered and analyzed for various temperatures. The device was cooled with a closed cycle refrigerator, and the data were acquired using the Agilent 4155B Semiconductor Parameter Analyzer...

  1. Temperature dependence of the magnetic properties of ferromagnetic amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gaunt, P.

    1979-01-01

    The magnetic hysteresis properties of amorphous alloys have recently been discussed in terms of an exchange-enhanced applied field. This absolute-zero model is here extended to finite temperatures. The modified treatment predicts a remanent magnetization which is unaffected by thermal activation while the coercive force falls (finally to zero) as temperature increases. Comparison with experiment for TbFe/sub 2/ suggests that regions of volume approx. =7500 A/sup 3/ reverse coherently.

  2. 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...

  3. 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

  4. Temperature Dependent Seed Germination of Dalbergia nigra Allem (Leguminosae

    Directory of Open Access Journals (Sweden)

    Fernanda G. A. Ferraz-Grande

    2001-12-01

    Full Text Available The germination of endangered species Dalbergia nigra was studied and 30.5° C was found as optimum temperature, although the species presented a broad temperature range where germination occurs and light had no effect. The analysis of kinetics of seed germination confirmed the asynchronized germination below and above the optimum temperature. The light insensitive seed and germination also at high temperatures indicated that D. nigra could occur both in understories and gaps where the mean temperature was high.A germinação de sementes de Dalbergia nigra Allem, comumente conhecida como jacarandá-da-Bahia, caviúna, jacarandá, uma espécie em extinção, foi estudada e determinamos a temperatura ótima de 30,5° C. A espécie apresenta uma ampla faixa de temperatura onde a germinação ocorre e a luz branca não influenciou o processo. A análise da cinética da germinação de sementes confirma a germinação não sincronizada acima e abaixo da temperatura ótima de germinação. A semente insensível à luz e a germinação também em altas temperaturas indicam que D. nigra pode ocorrer tanto na sombra da vegetação bem como em clareiras.

  5. 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.

  6. Temperature-dependent permittivity of annealed and unannealed gold films

    CERN Document Server

    Shen, Po-Ting; Lin, Cheng-Wei; Liu, Hsiang-Lin; Chang, Chih-Wei; Chu, Shi-Wei

    2016-01-01

    Due to local field enhancement and subwavelength confinements, nano-plasmonics provide numerous novel applications. Simultaneously, as an efficient nanoscale heat generator from inherent absorption, thermo-plasmonics is emerging as an important branch. However, although significant temperature increase is involved in applications, detailed characterization of metal permittivity at different temperatures is lacking. In this work, we extract the permittivity of gold film from 300K to the annealing temperature of 570K. By comparing annealed and unannealed films, more than one-order difference in thermo-derivative of permittivity is revealed, resulting in unexpectedly large variation of plasmonic properties. Our result is valuable not only for characterizing extensively used unannealed nanoparticles, but also for designing future thermo-nano-plasmonic systems.

  7. 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.

  8. Temperature-Dependent Magnetoelectric Effect from First Principles

    NARCIS (Netherlands)

    Mostovoy, Maxim; Scaramucci, Andrea; Spaldin, Nicola A.; Delaney, Kris T.

    2010-01-01

    We show that nonrelativistic exchange interactions and spin fluctuations can give rise to a linear magnetoelectric effect in collinear antiferromagnets at elevated temperatures that can exceed relativistic magnetoelectric responses by more than 1 order of magnitude. We show how symmetry arguments,

  9. Temperature-Dependent Nickel Release from Nickel-Alloys

    DEFF Research Database (Denmark)

    Menne, T.; Solgaard, Per Bent

    1979-01-01

    Ni release from Danish 1 krone coins and metal buttons from jeans was measured at 20.degree. C in distilled water and at 35.degree. C in distilled water and synthetic sweat. The temperature elevation increased the Ni release from the coins and 2 of the 9 metal buttons investigated. The sensitivity...

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

    Indian Academy of Sciences (India)

    Administrator

    agreed that the electro-oxidation of methanol was improved by raising the temperature and ruthenium modification. Keywords. Cyclic voltammetry; electrochemical impedance spectroscopy; activation energy; fuel cell; alcohol. 1. Introduction. The use of hydrogen carrier like alcohol as alterna- tive fuels in the direct alcohol ...

  11. Temperature dependent small-angle neutron scattering of CTABr ...

    Indian Academy of Sciences (India)

    Small-angle neutron scattering studies have been carried out to check the structural integrity of citryltrimethylammonium bromide (CTABr) micelles in a magnetic fluid for different magnetic fluid concentrations at two different temperatures 303 and 333 K. It is found that the CTABr micelles grow with increasing magnetic fluid ...

  12. Temperature dependence of transport coefficients of 'simple liquid ...

    African Journals Online (AJOL)

    ... (MD) simulations has been investigated. The study carried out at two densities, r* = 0.60 and r* = 0.95. Result shows erratic variations of the shear viscosity in the two lattices structures. KeyWords: Temperature effect, face centred, simple cubic, transport properties, simple liquid. [Global Jnl Pure & Appl. Sci. Vol.9(3) 2003: ...

  13. Temperature dependent small-angle neutron scattering of CTABr ...

    Indian Academy of Sciences (India)

    K. It is found that the CTABr micelles grow with increasing magnetic fluid concentration and there is a decrease in the micellar size with increase in temperature. Keywords. Magnetic fluids; micellar solutions; small-angle neutron scattering. .... studies [16] where viscosity increases when the magnetic fluid concentration in the.

  14. Second law analysis of a reacting temperature dependent viscous ...

    African Journals Online (AJOL)

    In this paper, entropy generation during the flow of a reacting viscous fluid through an inclined Channel with isothermal walls are investigated. The coupled energy and momentum equations were solved numerically. Previous results in literature (Adesanya et al 2006 [[17]) showed both velocity and temperature have two ...

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

    Indian Academy of Sciences (India)

    Activation energies for permeation of polymer nanocomposite membrane have not been reported so far. A tradeoff relation between permeability and selectivity shows that as permeability increases, the selectivity decreases. Attempts have been made to see this trade-off relation at relatively higher temperature. It is found ...

  16. Direct method for calculating temperature-dependent transport properties

    NARCIS (Netherlands)

    Liu, Y.; Yuan, Z.; Wesselink, R.J.H.; Starikov, A.A.; van Schilfgaarde, M.; Kelly, Paul J.

    2015-01-01

    We show how temperature-induced disorder can be combined in a direct way with first-principles scattering theory to study diffusive transport in real materials. Excellent (good) agreement with experiment is found for the resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are

  17. Temperature dependent scintillation properties of pure LaCl3

    NARCIS (Netherlands)

    Bizarri, G.; Dorenbos, P.

    2009-01-01

    The scintillation yield, scintillation decay, and x-ray excited emission of pure LaCl3 was studied as a function of temperature between 80 and 600 K. Two broad band emissions centered around 325 nm and 400 nm were identified and correlated to emissions from two localized exciton states named STE1

  18. Temperature dependence of the dielectric properties of rubber wood

    Science.gov (United States)

    Mohammed Firoz Kabir; Wan M. Daud; Kaida B. Khalid; Haji A.A. Sidek

    2001-01-01

    The effect of temperature on the dielectric properties of rubber wood was investigated in three anisotropic directions—longitudinal, radial, and tangential, and at different measurement frequencies. Low frequency measurements were conducted with a dielectric spectrometer, and high frequencies used microwave applied with open-ended coaxial probe sensors. Dielectric...

  19. Temperature Dependence of the Stability of Ion Pair Interactions ...

    Indian Academy of Sciences (India)

    Abstract. An understanding of the determinants of the thermal stability of thermostable proteins is expected to enable design of enzymes that can be employed in industrial biocatalytic processes carried out at high temperatures. A major factor that has been proposed to stabilize thermostable proteins is the high occurrence.

  20. Temperature Dependence of the Stability of Ion Pair Interactions ...

    Indian Academy of Sciences (India)

    An understanding of the determinants of the thermal stability of thermostable proteins is expected to enable design of enzymes that can be employed in industrial biocatalytic processes carried out at high temperatures. A major factor that has been proposed to stabilize thermostable proteins is the high occurrenceof salt ...

  1. The external field dependence of the BCS critical temperature

    DEFF Research Database (Denmark)

    Frank, Rupert L.; Hainzl, Christian; Seiringer, Robert

    2016-01-01

    We consider the Bardeen-Cooper-Schrieffer free energy functional for particles interacting via a two-body potential on a microscopic scale and in the presence of weak external fields varying on a macroscopic scale. We study the influence of the external fields on the critical temperature. We show...

  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. Temperature dependence of planktonic metabolism in the ocean

    Science.gov (United States)

    Regaudie-De-Gioux, A.; Duarte, C. M.

    2012-03-01

    Standard metabolic theory predicts that both respiration and photosynthesis should increase with increasing temperature, albeit at different rates. However, test of this prediction for ocean planktonic communities is limited, despite the broad consequences of this prediction in the present context of global ocean warming. We compiled a large data set on volumetric planktonic metabolism in the open ocean and tested the relationship between specific metabolic rates and water temperature. The relationships derived are consistent with predictions derived from metabolic theory of ecology, yielding activation energy for planktonic metabolism consistent with predictions from the metabolic theory. These relationships can be used to predict the effect of warming on ocean metabolism and, thus, the role of planktonic communities in the flow of carbon in the global ocean.

  4. Temperature dependence of electron impact ionization coefficient in bulk silicon

    Science.gov (United States)

    Ahmed, Mowfaq Jalil

    2017-09-01

    This work exhibits a modified procedure to compute the electron impact ionization coefficient of silicon for temperatures between 77 and 800K and electric fields ranging from 70 to 400 kV/cm. The ionization coefficients are computed from the electron momentum distribution function through solving the Boltzmann transport equation (BTE). The arrangement is acquired by joining Legendre polynomial extension with BTE. The resulting BTE is solved by differences-differential method using MATLAB®. Six (X) equivalent ellipsoidal and non-parabolic valleys of the conduction band of silicon are taken into account. Concerning the scattering mechanisms, the interval acoustic scattering, non-polar optical scattering and II scattering are taken into consideration. This investigation showed that the ionization coefficients decrease with increasing temperature. The overall results are in good agreement with previous experimental and theoretical reported data predominantly at high electric fields.

  5. Temperature dependent transport characteristics of graphene/n-Si diodes

    NARCIS (Netherlands)

    Parui, S.; Ruiter, R.; Zomer, P. J.; Wojtaszek, M.; van Wees, B. J.; Banerjee, T.

    2014-01-01

    Realizing an optimal Schottky interface of graphene on Si is challenging, as the electrical transport strongly depends on the graphene quality and the fabrication processes. Such interfaces are of increasing research interest for integration in diverse electronic devices as they are thermally and

  6. Temperature and concentration dependences of the activity coefficients of electrolytes

    Science.gov (United States)

    Tikhonov, N. A.; Sidel'nikov, G. B.

    2017-10-01

    A model has been suggested that describes the interaction of hydrated ions in electrolytes and allows the calculation of the main physical effects. The model explains the character of the curves of the activity coefficients. Binary solutions of uni-univalent electrolytes at concentrations from zero to several moles per liter and at temperatures from zero to a few dozens of degrees were studied. The results of simulation were verified by comparing them with many literature data.

  7. 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...

  8. Characterization and Temperature Dependence of Arctic Micromonas polaris Viruses.

    Science.gov (United States)

    Maat, Douwe S; Biggs, Tristan; Evans, Claire; van Bleijswijk, Judith D L; van der Wel, Nicole N; Dutilh, Bas E; Brussaard, Corina P D

    2017-06-02

    Global climate change-induced warming of the Artic seas is predicted to shift the phytoplankton community towards dominance of smaller-sized species due to global warming. Yet, little is known about their viral mortality agents despite the ecological importance of viruses regulating phytoplankton host dynamics and diversity. Here we report the isolation and basic characterization of four prasinoviruses infectious to the common Arctic picophytoplankter Micromonas. We furthermore assessed how temperature influenced viral infectivity and production. Phylogenetic analysis indicated that the putative double-stranded DNA (dsDNA) Micromonas polaris viruses (MpoVs) are prasinoviruses (Phycodnaviridae) of approximately 120 nm in particle size. One MpoV showed intrinsic differences to the other three viruses, i.e., larger genome size (205 ± 2 vs. 191 ± 3 Kb), broader host range, and longer latent period (39 vs. 18 h). Temperature increase shortened the latent periods (up to 50%), increased the burst size (up to 40%), and affected viral infectivity. However, the variability in response to temperature was high for the different viruses and host strains assessed, likely affecting the Arctic picoeukaryote community structure both in the short term (seasonal cycles) and long term (global warming).

  9. Characterization and Temperature Dependence of Arctic Micromonas polaris Viruses

    Science.gov (United States)

    Maat, Douwe S.; Biggs, Tristan; Evans, Claire; van Bleijswijk, Judith D. L.; van der Wel, Nicole N.; Dutilh, Bas E.; Brussaard, Corina P. D.

    2017-01-01

    Global climate change-induced warming of the Artic seas is predicted to shift the phytoplankton community towards dominance of smaller-sized species due to global warming. Yet, little is known about their viral mortality agents despite the ecological importance of viruses regulating phytoplankton host dynamics and diversity. Here we report the isolation and basic characterization of four prasinoviruses infectious to the common Arctic picophytoplankter Micromonas. We furthermore assessed how temperature influenced viral infectivity and production. Phylogenetic analysis indicated that the putative double-stranded DNA (dsDNA) Micromonas polaris viruses (MpoVs) are prasinoviruses (Phycodnaviridae) of approximately 120 nm in particle size. One MpoV showed intrinsic differences to the other three viruses, i.e., larger genome size (205 ± 2 vs. 191 ± 3 Kb), broader host range, and longer latent period (39 vs. 18 h). Temperature increase shortened the latent periods (up to 50%), increased the burst size (up to 40%), and affected viral infectivity. However, the variability in response to temperature was high for the different viruses and host strains assessed, likely affecting the Arctic picoeukaryote community structure both in the short term (seasonal cycles) and long term (global warming). PMID:28574420

  10. 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).

  11. Efficiency and temperature dependence of water removal by membrane dryers

    Science.gov (United States)

    Leckrone, K. J.; Hayes, J. M.

    1997-01-01

    The vapor pressure of water in equilibrium with sorption sites within a Nafion membrane is given by log P(WN) = -3580/T + 10.01, where P(WN) is expressed in Torr and T is the membrane temperature, in kelvin. The efficiency of dryers based on selective permeation of water through Nafion can thus be enhanced by cooling the membrane. Residual water in effluents exceeds equilibrium levels if insufficient time is allowed for water to diffuse to the membrane surface as gas passes through the dryer. For tubular configurations, this limitation can be avoided if L > or = Fc(10(3.8)/120 pi D), where L is the length of the tubular membrane, in centimeters, Fc is the gas flow rate, in mL/ min, and D is the diffusion coefficient for water in the carrier gas at the operating temperature of the dryer, in cm2/s. An efficient dryer that at room temperature dries gas to a dew point of -61 degrees C is described; the same dryer maintained at 0 degrees C yields a dew point of -80 degrees C and removes water as effectively as Mg(ClO4)2 or a dry ice/acetone slush. The use of Nafion membranes to construct devices capable of delivering gas streams with low but precisely controlled humidities is discussed.

  12. 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.

  13. Temperature dependent simulation of diamond depleted Schottky PIN diodes

    Science.gov (United States)

    Hathwar, Raghuraj; Dutta, Maitreya; Koeck, Franz A. M.; Nemanich, Robert J.; Chowdhury, Srabanti; Goodnick, Stephen M.

    2016-06-01

    Diamond is considered as an ideal material for high field and high power devices due to its high breakdown field, high lightly doped carrier mobility, and high thermal conductivity. The modeling and simulation of diamond devices are therefore important to predict the performances of diamond based devices. In this context, we use Silvaco® Atlas, a drift-diffusion based commercial software, to model diamond based power devices. The models used in Atlas were modified to account for both variable range and nearest neighbor hopping transport in the impurity bands associated with high activation energies for boron doped and phosphorus doped diamond. The models were fit to experimentally reported resistivity data over a wide range of doping concentrations and temperatures. We compare to recent data on depleted diamond Schottky PIN diodes demonstrating low turn-on voltages and high reverse breakdown voltages, which could be useful for high power rectifying applications due to the low turn-on voltage enabling high forward current densities. Three dimensional simulations of the depleted Schottky PIN diamond devices were performed and the results are verified with experimental data at different operating temperatures

  14. Temperature dependent simulation of diamond depleted Schottky PIN diodes

    Energy Technology Data Exchange (ETDEWEB)

    Hathwar, Raghuraj; Dutta, Maitreya; Chowdhury, Srabanti; Goodnick, Stephen M. [Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287-8806 (United States); Koeck, Franz A. M.; Nemanich, Robert J. [Department of Physics, Arizona State University, Tempe, Arizona 85287-8806 (United States)

    2016-06-14

    Diamond is considered as an ideal material for high field and high power devices due to its high breakdown field, high lightly doped carrier mobility, and high thermal conductivity. The modeling and simulation of diamond devices are therefore important to predict the performances of diamond based devices. In this context, we use Silvaco{sup ®} Atlas, a drift-diffusion based commercial software, to model diamond based power devices. The models used in Atlas were modified to account for both variable range and nearest neighbor hopping transport in the impurity bands associated with high activation energies for boron doped and phosphorus doped diamond. The models were fit to experimentally reported resistivity data over a wide range of doping concentrations and temperatures. We compare to recent data on depleted diamond Schottky PIN diodes demonstrating low turn-on voltages and high reverse breakdown voltages, which could be useful for high power rectifying applications due to the low turn-on voltage enabling high forward current densities. Three dimensional simulations of the depleted Schottky PIN diamond devices were performed and the results are verified with experimental data at different operating temperatures.

  15. Temperature-dependent surface nanomechanical properties of a thermoplastic nanocomposite.

    Science.gov (United States)

    Huang, Hui; Dobryden, Illia; Ihrner, Niklas; Johansson, Mats; Ma, Houyi; Pan, Jinshan; Claesson, Per M

    2017-05-15

    In polymer nanocomposites, particle-polymer interactions influence the properties of the matrix polymer next to the particle surface, providing different physicochemical properties than in the bulk matrix. This region is often referred to as the interphase, but detailed characterization of its properties remains a challenge. Here we employ two atomic force microscopy (AFM) force methods, differing by a factor of about 15 in probing rate, to directly measure the surface nanomechanical properties of the transition region between filler particle and matrix over a controlled temperature range. The nanocomposite consists of poly(ethyl methacrylate) (PEMA) and poly(isobutyl methacrylate) (PiBMA) with a high concentration of hydrophobized silica nanoparticles. Both AFM methods demonstrate that the interphase region around a 40-nm-sized particle located on the surface of the nanocomposite could extend to 55-70nm, and the interphase exhibits a gradient distribution in surface nanomechanical properties. However, the slower probing rate provides somewhat lower numerical values for the surface stiffness. The analysis of the local glass transition temperature (Tg) of the interphase and the polymer matrix provides evidence for reduced stiffness of the polymer matrix at high particle concentration, a feature that we attribute to selective adsorption. These findings provide new insight into understanding the microstructure and mechanical properties of nanocomposites, which is of importance for designing nanomaterials. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Temperature dependences in electron-stimulated desorption of neutral europium

    CERN Document Server

    Ageev, V N; Madey, T E

    2003-01-01

    The electron-stimulated desorption (ESD) yield for neutral europium (Eu) atoms from Eu layers adsorbed on oxygen-covered tungsten surfaces has been measured as a function of electron energy, europium coverage and degree of oxidation of tungsten, with an emphasis on effects of substrate temperature. The measurements have been carried out using a time-of-flight method and surface ionization detector. We expand on an earlier report, and compare ESD of multivalent Eu with ESD of monovalent alkali atoms, studied previously. The Eu atom ESD is a complicated function of Eu coverage, electron energy and substrate temperature. In the coverage range 0.05-0.35 monolayer (ML), overlapping resonant-like Eu atom yield peaks are observed at electron energies E sub e of 36 and 41 eV that might be associated with Eu or W shallow core level excitations. Additional resonant-like peaks are seen at E sub e of 54 and 84 eV that are associated with W 5p and 5s level excitations. The Eu atom yield peaks at 36 and 41 eV are seen only...

  17. 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.

  18. 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.

  19. 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.

  20. Temperature and relative humidity dependence of radiochromic film dosimeter response to gamma electron radiation

    DEFF Research Database (Denmark)

    McLaughlin, W.L.; Puhl, J.M.; Miller, A.

    1995-01-01

    on some earlier studies, their response functions have been reported to be dependent on the temperature and relative humidity during irradiation. The present study investigates differences in response over practical ranges of temperature, relative humidity, dose, and for different recent batches of films...... humidity) and should be calibrated under environmental conditions (temperature) at which they will be used routinely....

  1. Temperature and Humidity Dependence of a Polymer-Based Gas Sensor

    Science.gov (United States)

    Ryan, M. A.; Buehler, M. G.

    1997-01-01

    This paper quantifies the temperature and humidity dependence of a polymer-based gas sensor. The measurement and analysis of three polymers indicates that resistance changes in the polymer films, due to temperature and humidity, can be positive or negative. The temperature sensitivity ranged from +1600 to -320 ppm/nd the relative sensitivity ranged from +1100 to -260 ppm/%.

  2. 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.

  3. 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.

  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. 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.

  6. 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.

  7. 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.

  8. Torque and Drag Friction Model: Implemented Friction Factor Dependency of Temperature

    OpenAIRE

    Brekke, Alexander

    2016-01-01

    Master's thesis in Petroleum engineering We investigated the friction factor dependency of temperature. “Friction factor” is a parameter in the calculations of torque and drag. Increased well reach is dependent on accurate torque and drag modeling. We proposed that the friction factor can be dependent on temperature other than linear approximations as studied by Kaarstad et al. [2009]. The results was implemented in the work of Aadnoy [2006] torque and drag 3D model. The local friction fac...

  9. 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

    The surfaces of the Galilean icy satellites Europa, Ganymede and Callisto, dominated by water ice, also show substantial amounts of non-water-ice compounds. These satellites will be the subject of close exploration by the ESA JUICE mission and the NASA Europa Multiple-Flyby Mission, which will focus on Ganymede and Europa, respectively. Among non-water-ice compounds thought to exist on the surfaces of the Jovian icy satellites, hydrated salt minerals have been proposed to exist as a by-product of endogenic processes. Safe detection of these minerals shall rely on laboratory spectroscopic analysis of these materials carried out under appropriate environmental conditions. Here we report on laboratory measurements, carried out in the framework of a Europlanet Transnational Access (TA) 2020 proposal approved in 2016, on two hydrated sodium carbonates, namely sodium carbonate monohydrate (Na2CO3·1H2O) and sodium carbonate decahydrate (Na2CO3·10H2O). Spectral profiles of these compounds were obtained in the visible and near-infrared (VNIR) spectral domain, taking advantage of the Cold Surfaces spectroscopy facility at the Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), where such compounds can be measured under cryogenic conditions indicative of real planetary surfaces. Carbonates were first sieved so as to separate them in three different grain size ranges: 20-50 μm, 75-100 μm, and 125-150 μm. These grain sizes have been chosen to: (1) be indicative of typical regoliths known or expected to exist on the surface of the icy satellites, and (2) avoid overlapping between ranges, therefore minimizing particles contamination among the dimensional classes. Each grain size was then measured with the Spectro-Gonio-Radiometer facility in the overall 0.5-4.0 μm spectral range, with spectral sampling increasing with increasing wavelength. For each sample, the overall 93-279 K temperature ramp was acquired in 11 steps varying from 10 K to 25 K, imposed by time

  10. Experimental determination of monoethanolamine protonation constant and its temperature dependency

    Directory of Open Access Journals (Sweden)

    Ma’mun Sholeh

    2017-01-01

    Full Text Available Carbon dioxide as one of the major contributors to the global warming problem is produced in large quantities by many important industries and its emission seems to rise from year to year. Aminebased absorption is one of the methods to capture CO2 from its sources. As a reactive system, mass transfer and chemical reaction take place simultaneously. In a vapor-liquid equilibrium model for the CO2-amine-water system, some parameters such as mass transfer coefficients and chemical equilibrium constants need to be known. However, some parameters could be determined experimentally and the rests could be regressed from the model. The protonation constant (pKa, as one of the model parameters, could then be measured experimentally. The purpose of this study is to measure the pKa of monoethanolamine (MEA at a range of temperatures from 303 to 330K by a potentiometric titration method. The experimental data obtained were in a good agreement with the literature data. The pKa data from this work together with those from the literature were then correlated in an empirical correlation to be used for future research.

  11. Monitoring operating temperature and supply voltage in achieving high system dependability

    NARCIS (Netherlands)

    Khan, M.A.; Kerkhoff, Hans G.

    2013-01-01

    System dependability being a set of number of attributes, of which the important reliability, heavily depends on operating temperature and supply voltage. Any change beyond the designed specifications may change the system performance and could result in system reliability and hence dependability

  12. 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...

  13. 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.

  14. 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 ...

  15. 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.

  16. 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.)

  17. The dependence of surface temperature on IGBTs load and ambient temperature

    Directory of Open Access Journals (Sweden)

    Alexander Čaja

    2015-01-01

    Full Text Available Currently, older power electronics and electrotechnics are improvement and at the same time developing new and more efficient devices. These devices produce in their activities a significant part of the heat which, if not effectively drained, causing damage to these elements. In this case, it is important to develop new and more efficient cooling system. The most widespread of modern methods of cooling is the cooling by heat pipe. This contribution is aimed at cooling the insulated-gate bipolar transistor (IGBT elements by loop heat pipe (LHP. IGBTs are very prone to damage due to high temperatures, and therefore is the important that the surface temperature was below 100°C. It was therefore created a model that examined what impact of surface temperature on the IGBT element and heat removal at different load and constant ambient temperature.

  18. 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.

  19. 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...

  20. Tunneling magnetoresistance dependence on the temperature in a ferromagnetic Zener diode

    Energy Technology Data Exchange (ETDEWEB)

    Comesana, E; Aldegunde, M; GarcIa-Loureiro, A, E-mail: enrique.comesana@usc.e [Departamento de Electronica e Computacion, Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain)

    2009-11-15

    In the present work we focus on the study of the temperature dependence of the tunnelling current in a ferromagnetic Zener diode. We predict the tunneling magnetoresistance dependence on the temperature. Large doping concentrations lead to magnetic semiconductors with Curie temperature T{sub C} near or over room temperature and this will facilitate the introduction of new devices that make use of the ferromagnetism effects. According to our calculations the tunneling magnetoresistance has the form TMR {proportional_to} (T{sup n}{sub C}-T{sup n}).

  1. 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.

  2. 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...

  3. 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.

  4. 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.

  5. 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.

  6. Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells.

    Science.gov (United States)

    Foxman, Ellen F; Storer, James A; Fitzgerald, Megan E; Wasik, Bethany R; Hou, Lin; Zhao, Hongyu; Turner, Paul E; Pyle, Anna Marie; Iwasaki, Akiko

    2015-01-20

    Most isolates of human rhinovirus, the common cold virus, replicate more robustly at the cool temperatures found in the nasal cavity (33-35 °C) than at core body temperature (37 °C). To gain insight into the mechanism of temperature-dependent growth, we compared the transcriptional response of primary mouse airway epithelial cells infected with rhinovirus at 33 °C vs. 37 °C. Mouse airway cells infected with mouse-adapted rhinovirus 1B exhibited a striking enrichment in expression of antiviral defense response genes at 37 °C relative to 33 °C, which correlated with significantly higher expression levels of type I and type III IFN genes and IFN-stimulated genes (ISGs) at 37 °C. Temperature-dependent IFN induction in response to rhinovirus was dependent on the MAVS protein, a key signaling adaptor of the RIG-I-like receptors (RLRs). Stimulation of primary airway cells with the synthetic RLR ligand poly I:C led to greater IFN induction at 37 °C relative to 33 °C at early time points poststimulation and to a sustained increase in the induction of ISGs at 37 °C relative to 33 °C. Recombinant type I IFN also stimulated more robust induction of ISGs at 37 °C than at 33 °C. Genetic deficiency of MAVS or the type I IFN receptor in infected airway cells permitted higher levels of viral replication, particularly at 37 °C, and partially rescued the temperature-dependent growth phenotype. These findings demonstrate that in mouse airway cells, rhinovirus replicates preferentially at nasal cavity temperature due, in part, to a less efficient antiviral defense response of infected cells at cool temperature.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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...

  12. Temperature-dependent magnetic properties of individual glass spherules, Apollo 11, 12, and 14 lunar samples.

    Science.gov (United States)

    Thorpe, A. N.; Sullivan, S.; Alexander, C. C.; Senftle, F. E.; Dwornik, E. J.

    1972-01-01

    Magnetic susceptibility of 11 glass spherules from the Apollo 14 lunar fines have been measured from room temperature to 4 K. Data taken at room temperature, 77 K, and 4.2 K, show that the soft saturation magnetization was temperature independent. In the temperature range 300 to 77 K the temperature-dependent component of the magnetic susceptibility obeys the Curie law. Susceptibility measurements on these same specimens and in addition 14 similar spherules from the Apollo 11 and 12 mission show a Curie-Weiss relation at temperatures less than 77 K with a Weiss temperature of 3-7 degrees in contrast to 2-3 degrees found for tektites and synthetic glasses of tektite composition. A proposed model and a theoretical expression closely predict the variation of the susceptibility of the glass spherules with temperature.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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-...

  19. 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

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

    NARCIS (Netherlands)

    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 (?) 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

  1. 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....

  2. 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.

  3. 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.

  4. Temperature dependence of fracture toughness in HT9 steel neutron-irradiated up to 145 dpa

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Jong-Hyuk [KAERI; Byun, Thak Sang [ORNL; Maloy, S [Los Alamos National Laboratory (LANL); Toloczko, M [Pacific Northwest National Laboratory (PNNL)

    2014-01-01

    The temperature dependence of fracture toughness in HT9 steel irradiated to high doses was investigated using miniature three-point bend (TPB) fracture specimens. These specimens were from the ACO-3 fuel duct wall of the Fast Flux Test Facility (FFTF), in which irradiation doses were in the range of 3.2 144.8 dpa and irradiation temperatures in the range of 380.4 502.6 oC. A miniature specimen reuse technique has been established for this investigation: the specimens used were the tested halves of miniature Charpy impact specimens (~13 3 4 mm) with diamond-saw cut in the middle. The fatigue precracking for specimens and fracture resistance (J-R) tests were carried out in a MTS servo-hydraulic testing machine with a vacuum furnace following the standard procedure described in the ASTM Standard E 1820-09. For each of five irradiated and one archive conditions, 7 to 9 J-R tests were performed at selected temperatures ranging from 22 C to 600 C. The fracture toughness of the irradiated HT9 steel was strongly dependent on irradiation temperatures rather than irradiation dose. When the irradiation temperature was below about 430 C, the fracture toughness of irradiated HT9 increased with test temperature, reached an upper shelf of 180 200 MPa m at 350 450 C and then decreased with test temperature. When the irradiation temperature 430 C, the fracture toughness was nearly unchanged until about 450 C and decreased with test temperature in higher temperature range. Similar test temperature dependence was observed for the archive material although the highest toughness values are lower after irradiation. Ductile stable crack growth occurred except for a few cases where both the irradiation temperature and test temperature are relatively low.

  5. Temperature dependence of spin-orbit torques in Cu-Au alloys

    KAUST Repository

    Wen, Yan

    2017-03-07

    We investigated current driven spin-orbit torques in Cu40Au60/Ni80Fe20/Ti layered structures with in-plane magnetization. We have demonstrated a reliable and convenient method to separate dampinglike torque and fieldlike torque by using the second harmonic technique. It is found that the dampinglike torque and fieldlike torque depend on temperature very differently. Dampinglike torque increases with temperature, while fieldlike torque decreases with temperature, which are different from results obtained previously in other material systems. We observed a nearly linear dependence between the spin Hall angle and longitudinal resistivity, suggesting that skew scattering may be the dominant mechanism of spin-orbit torques.

  6. 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 ...

  7. 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.

  8. Equation of states and melting temperatures of diamond cubic and zincblende semiconductors: pressure dependence

    Energy Technology Data Exchange (ETDEWEB)

    Hung, V V; Hanh, P T M [Hanoi National Pedagogic University, Km8 Hanoi-Sontay Highway, Hanoi (Viet Nam); Masuda-Jindo, K [Department of Material Science and Engineering, Tokyo Institute of Technology, Nagasuta, Midori-ku, Yokohama 226-8503 (Japan); Hai, N T [Hanoi University of Technology, 01 Dai Co Viet Road, Hanoi (Viet Nam)], E-mail: kmjindo@issp.u-tokyo.ac.jp

    2008-02-15

    The pressure dependence of the melting temperatures of tetrahedrally coordinated semiconductors are studied using the equation of states derived from the statistical moment method, in comparison with those of the normal metals. Using the general expressions of the limiting temperatures T{sub m}, we calculate the 'melting' temperatures of the semiconductor crystals and normal metals as a function of the hydrostatic pressure. The physical origins for the inverse pressure dependence of T{sub m} observed for tetrahedrally coordinated semiconductors are also discussed.

  9. 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.

  10. 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.

  11. 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.

  12. 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).

  13. Viscosity analysis of the temperature dependence of the solution conformation of ovalbumin.

    Science.gov (United States)

    Monkos, K

    2000-05-31

    The viscosity of ovalbumin aqueous solutions was studied as a function of temperature and of protein concentration. Viscosity-temperature dependence was discussed on the basis of the modified Arrhenius formula at temperatures ranging from 5 to 55 degrees C. The activation energy of viscous flow for hydrated and unhydrated ovalbumin was calculated. Viscosity-concentration dependence, in turn, was discussed on the basis of Mooney equation. It has been shown that the shape parameter S decreases with increasing temperature, and self-crowding factor K does not depend on temperature. At low concentration limit the numerical values of the intrinsic viscosity and of Huggins coefficient were calculated. A master curve relating the specific viscosity etasp to the reduced concentration c[eta], over the whole range of temperature, was obtained and the three ranges of concentrations: diluted, semi-diluted and concentrated, are discussed. It has been proved that the Mark-Houvink-Kuhn-Sakurada (MHKS) exponent for ovalbumin does not depend on temperature.

  14. 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.

  15. 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.

  16. Temperature dependences of the contact resistivity in ohmic contacts to n{sup +}-InN

    Energy Technology Data Exchange (ETDEWEB)

    Sachenko, A. V.; Belyaev, A. E. [National Academy of Sciences, Lashkaryov Institute of Semiconductor Physics (Ukraine); Boltovets, N. S. [“Orion” Research Institute (Ukraine); Brunkov, P. N.; Jmerik, V. N.; Ivanov, S. V. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Kapitanchuk, L. M. [National Academy of Sciences of Ukraine, Paton Electric Welding Institute (Ukraine); Konakova, R. V., E-mail: konakova@isp.kiev.ua; Klad’ko, V. P.; Romanets, P. N.; Saja, P. O.; Safryuk, N. V.; Sheremet, V. N. [National Academy of Sciences, Lashkaryov Institute of Semiconductor Physics (Ukraine)

    2015-04-15

    The temperature dependences of the contact resistivity (ρ{sub c}) of ohmic contacts based on the Au-Ti-Pd-InN system are measured at an InN doping level of 2 × 10{sup 18} cm{sup −3} in the temperature range of 4.2–300 K. At temperatures T > 150 K, linearly increasing dependences ρ{sub c}(T) are obtained. The dependences are explained within the mechanism of thermionic current flow through metal shunts associated with dislocations. Good agreement between theoretical and experimental dependences is achieved assuming that the flowing current is limited by the total resistance of the metal shunts, and the density of conductive dislocations is ∼5 × 10{sup 9} cm{sup −2}. Using the X-ray diffraction method, the density of screw and edge dislocations in the structure under study is measured: their total density exceeds 10{sup 10} cm{sup −2}.

  17. Influence of excitation power density on temperature dependencies of NaYF4: Yb, Er nanoparticles luminescence spectra

    Science.gov (United States)

    Ustalkov, Sergey O.; Kozlova, Ekaterina A.; Savenko, Olga A.; Mohammed, Ammar H. M.; Kochubey, Vyacheslav I.; Skaptsov, Alexander A.

    2017-03-01

    Upconversion nanoparticles are good candidates for nanothermometry. The wavelength of the excitation and luminescence lie in optical window. The influence of the excitation power density on the luminescence temperature dependences is studded. Ratio of luminescence intensities linearly depends on temperature.

  18. Temperature-dependent subsurface growth during atomic layer deposition on polypropylene and cellulose fibers.

    Science.gov (United States)

    Jur, Jesse S; Spagnola, Joseph C; Lee, Kyoungmi; Gong, Bo; Peng, Qing; Parsons, Gregory N

    2010-06-01

    Nucleation and subsequent growth of aluminum oxide by atomic layer deposition (ALD) on polypropylene fiber substrates is strongly dependent on processing temperature and polymer backbone structure. Deposition on cellulose cotton, which contains ample hydroxyl sites for ALD nucleation and growth on the polymer backbone, readily produces a uniform and conformal coating. However, similar ALD processing on polypropylene, which contains no readily available active sites for growth initiation, results in a graded and intermixed polymer/inorganic interface layer. The structure of the polymer/inorganic layer depends strongly on the process temperature, where lower temperature (60 degrees C) produced a more abrupt transition. Cross-sectional transmission electron microscopy images of polypropylene fibers coated at higher temperature (90 degrees C) show that non-coalesced particles form in the near-surface region of the polymer, and the particles grow in size and coalesce into a film as the number of ALD cycles increases. Quartz crystal microbalance analysis on polypropylene films confirms enhanced mass uptake at higher processing temperatures, and X-ray photoelectron spectroscopy data also confirm heterogeneous mixing between the aluminum oxide and the polypropylene during deposition at higher temperatures. The strong temperature dependence of film nucleation and subsurface growth is ascribed to a relatively large increase in bulk species diffusivity that occurs upon the temperature-driven free volume expansion of the polypropylene. These results provide helpful insight into mechanisms for controlled organic/inorganic thin film and fiber materials integration.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Temperature and humidity dependence of secondary organic aerosol yield from the ozonolysis of β-pinene

    Directory of Open Access Journals (Sweden)

    C. von Hessberg

    2009-06-01

    Full Text Available The temperature dependence of secondary organic aerosol (SOA formation from ozonolysis of β-pinene was studied in a flow reactor at 263 K–303 K and 1007 hPa under dry and humid conditions (0% and 26%–68% relative humidity, respectively. The observed SOA yields reached maximum values of 0.18–0.39 at high particle mass concentrations (Mo. Under dry conditions, the measurement data showed an overall increase in SOA yield with inverse temperature, but significant oscillatory deviations from the predicted linear increase with inverse temperature (up to 50% at high Mo was observed. Under humid conditions the SOA yield exhibited a linear decrease with inverse temperature. For the atmospherically relevant concentration level of Mo=10 μg m−3 and temperature range 263 K–293 K, the results from humid experiments in this study indicate that the SOA yield of β-pinene ozonolysis may be well represented by an average value of 0.15 with an uncertainty estimate of ±0.05. When fitting the measurement data with a two-product model, both the partitioning coefficients (Kom,i and the stoichiometric yields (αi of the low-volatile and semi-volatile model species were found to vary with temperature. The results indicate that not only the reaction product vapour pressures but also the relative contributions of different gas-phase or multiphase reaction channels are strongly dependent on temperature and the presence of water vapour. In fact, the oscillatory positive temperature dependence observed under dry conditions and the negative temperature dependence observed under humid conditions indicate that the SOA yield is governed much more by the temperature and humidity dependence of the involved chemical reactions than by vapour pressure temperature dependencies. We suggest that the elucidation and modelling of SOA formation need to take into account the

  9. A space and time scale-dependent nonlinear geostatistical approach for downscaling daily precipitation and temperature

    KAUST Repository

    Jha, Sanjeev Kumar

    2015-07-21

    A geostatistical framework is proposed to downscale daily precipitation and temperature. The methodology is based on multiple-point geostatistics (MPS), where a multivariate training image is used to represent the spatial relationship between daily precipitation and daily temperature over several years. Here, the training image consists of daily rainfall and temperature outputs from the Weather Research and Forecasting (WRF) model at 50 km and 10 km resolution for a twenty year period ranging from 1985 to 2004. The data are used to predict downscaled climate variables for the year 2005. The result, for each downscaled pixel, is daily time series of precipitation and temperature that are spatially dependent. Comparison of predicted precipitation and temperature against a reference dataset indicates that both the seasonal average climate response together with the temporal variability are well reproduced. The explicit inclusion of time dependence is explored by considering the climate properties of the previous day as an additional variable. Comparison of simulations with and without inclusion of time dependence shows that the temporal dependence only slightly improves the daily prediction because the temporal variability is already well represented in the conditioning data. Overall, the study shows that the multiple-point geostatistics approach is an efficient tool to be used for statistical downscaling to obtain local scale estimates of precipitation and temperature from General Circulation Models. This article is protected by copyright. All rights reserved.

  10. Homogeneous broadening effect on temperature dependence of green upconversion luminescence in erbium doped fibers

    Energy Technology Data Exchange (ETDEWEB)

    Egatz-Gómez, A. [Facultad de Óptica y Optometría, Universidad Complutense de Madrid, Arcos de Jalón 118, Madrid 28037 (Spain); Department of Biomedical Engineering, Texas A and M University, College Station, TX 77843 (United States); Calderón, Oscar G., E-mail: oscargc@fis.ucm.es [Facultad de Óptica y Optometría, Universidad Complutense de Madrid, Arcos de Jalón 118, Madrid 28037 (Spain); Melle, Sonia; Carreño, F.; Antón, M.A. [Facultad de Óptica y Optometría, Universidad Complutense de Madrid, Arcos de Jalón 118, Madrid 28037 (Spain); Gort, Elske M. [Facultad de Óptica y Optometría, Universidad Complutense de Madrid, Arcos de Jalón 118, Madrid 28037 (Spain); Department of Biomedical Engineering, University of Groningen, 9700 RB Groningen (Netherlands)

    2013-07-15

    We study the green upconversion luminescence of Er{sup 3+} ions in an aluminosilicate optical fiber upon near infrared excitation at 787 nm. The dependence of the upconversion luminescence on temperature has been determined. As temperature drops from room to cryogenic temperatures, the upconversion green emission reaches a maximum around 40 K, and then decreases. A nearly quadratic dependence of the upconversion luminescence with excitation power is found, which is consistent with a sequential stepwise two-photon absorption process. These results have been explained with a semiclassical model that considers the inhomogeneous broadening of the optical transitions due to glass imperfections, and the dependence of the homogeneous linewidth broadening on temperature. -- Highlights: ► We study green upconversion luminescence of Er{sup 3+} ions in a fiber excited at 787 nm. ► Upconversion luminescence variation from room to cryogenic temperature is analyzed. ► Upconversion emission consists in a sequential two-photon absorption process. ► A semiclassical model considering inhomogeneous broadening explains the results. ► Homogeneous broadening is responsible for the upconversion temperature dependence.

  11. 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.

  12. 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.

  13. 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.

  14. 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 ).

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. Anomalous temperature dependent magneto-conductance in organic light-emitting diodes with multiple emissive states

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Chen-xiao; Jia, Wei-yao; Huang, Ke-Xun; Zhang, Qiao-ming; Yang, Xiao-hui; Xiong, Zu-hong, E-mail: zhxiong@swu.edu.cn [School of Physical Science and Technology, MOE Key Laboratory on Luminescence and Real-Time Analysis, Southwest University, Chongqing 400715 (China)

    2015-07-13

    The temperature dependence of the magneto-conductance (MC) in organic electron donor-acceptor hybrid and layer heterojunction diodes was studied. The MC value increased with temperature in layer heterojunction and in 10 wt. % hybrid devices. An anomalous decrease of the MC with temperature was observed in 25 wt. %–50 wt. % hybrid devices. Further increasing donor concentration to 75 wt. %, the MC again increased with temperature. The endothermic exciplex-exciton energy transfer and the change in electroplex/exciton ratio caused by change in charge transport with temperature may account for these phenomena. Comparative studies of the temperature evolutions of the IV curves and the electroluminescence and photoluminescence spectra back our hypothesis.

  3. 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.

  4. 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.

  5. 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.

  6. Temperature dependence of the magnetization of disc shaped NiO nanoparticles

    DEFF Research Database (Denmark)

    Klausen, Stine Nyborg; Lindgard, P.A.; Lefmann, Kim

    2002-01-01

    We present neutron diffraction data of NiO nanoparticles measuring the total magnetization and the sublattice magnetization at various temperatures. Electron microscopy shows that the particles are disc shaped with average diameter of about 12 nm and a thickness of about 2 nm. The Neel temperature...... as a temperature dependent contribution of a structural peak in contrast to bulk NiO. The two magnetic signals vanish at the same temperature. The data are interpreted on the basis of an extended mean field model on disc shaped NiO particles. This model includes the finite size dependence of the effective field...... (approximate to460 K) is less than for bulk NiO (523 K). The magnetic domain size, as estimated from the width of the neutron diffraction peaks corresponding to the antiferromagnetic reflection is smaller than the particle size estimated from the structural peaks. A ferromagnetic contribution is present...

  7. 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...

  8. 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.

  9. 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...

  10. 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.

  11. 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....

  12. 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...

  13. Microbial interactions with the cyanobacterium Microcystis aeruginosa and their dependence on temperature

    DEFF Research Database (Denmark)

    Dziallas, Claudia; Grossart, Hans-Peter

    2012-01-01

    cultures changed in a temperature-dependent manner, its quality greatly varied under the same environmental conditions, but with different associated bacterial communities. Furthermore, temperature affected quantity and quality of cell-bound microcystins, whereby interactions between M. aeruginosa......’ methanogens contributed to the associated microbial community. This implies so far uncharacterized interactions between Microcystis aeruginosa and its associated prokaryotic community, which has unknown ecological consequences in a climatically changing world....

  14. 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

  15. Temperature and humidity dependence of bulk resistivity of bakelite for resistive plate chambers in CMS

    CERN Document Server

    Ahn, S H; Bahk, S Y; Gapienko, V A; Hong, B; Hong, S J; Jung, S Y; Kim, J Y; Kim, Y J; Kim, Y U; Koo, D G; Lee, K S; Lee, S J; Lee, Y L; Lim, I T; Nam, S K; Pac, M Y; Park, S K; Ra, Y S; Rhee, J T; Seo, S W; Sim, K S

    2000-01-01

    This paper presents data obtained in a systematic study on the bulk resistivity of Korean bakelike as a function of temperature in the range 20-30 degrees C and relative humidity in the range 35-65%. Strong dependence of resistivity on both temperature and humidity was observed. Measurements were carried out in the framework of R&D work on resistive plate chambers which will be used in the CMS detector. (4 refs).

  16. 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.

  17. Temperature dependence of magnetism near defects in SrB sub 6

    CERN Document Server

    Jarlborg, T

    2003-01-01

    The temperature (T) dependence of magnetic moments in SrB sub 6 is studied through spin-polarized band calculations for a supercell of Sr sub 2 sub 7 B sub 1 sub 5 sub 6 containing a B sub 6 vacancy. The magnetic moment decays rather quickly with T despite the fact that only electronic Fermi-Dirac effects are included. This result and the T dependence of moments near an La impurity can hardly explain the reports of a very high Curie temperature in hexaborides, but suggest that the magnetism is caused by some other type of impurity. (letter to the editor)

  18. Thermally Activated Contact Strengthening Explains Nonmonotonic Temperature and Velocity Dependence of Atomic Friction

    Directory of Open Access Journals (Sweden)

    Mykhaylo Evstigneev

    2013-11-01

    Full Text Available While the well-established Prandtl-Tomlinson (PT model of atomic friction predicts that the friction force decreases with temperature and grows with velocity, several recent experiments reported that a nonmonotonic temperature dependence and a decreasing velocity dependence may also occur. We propose a minimal extension of the PT model, incorporating the possibility of thermally activated contact strengthening and providing one common framework to quantitatively explain all those “anomalous” experimental findings, as well as the previously known “normal” (PT-like behavior.

  19. Temperature dependence of nanosecond laser pulse thresholds of melanosome and microsphere microcavitation

    Science.gov (United States)

    Schmidt, Morgan S.; Kennedy, Paul K.; Noojin, Gary D.; Thomas, Robert J.; Rockwell, Benjamin A.

    2016-01-01

    Melanosome microcavitation is the threshold-level retinal pigment epithelium (RPE) damage mechanism for nanosecond (ns) pulse exposures in the visible and near-infrared (NIR). Thresholds for microcavitation of isolated bovine RPE melanosomes were determined as a function of temperature (20 to 85°C) using single ns laser pulses at 532 and 1064 nm. Melanosomes were irradiated using a 1064-nm Q-switched Nd:YAG (doubled for 532-nm irradiation). For comparison to melanosome data, a similar temperature (20 to 65°C) dependence study was also performed for 532 nm, ns pulse exposures of black polystyrene microbeads. Results indicated a decrease in the microcavitation average radiant exposure threshold with increasing sample temperature for both 532- and 1064-nm single pulse exposures of melanosomes and microbeads. Threshold data and extrapolated nucleation temperatures were used to estimate melanosome absorption coefficients in the visible and NIR, and microbead absorption coefficients in the visible, indicating that melanin is a better absorber of visible light than black polystyrene. The NIR melanosome absorption coefficients ranged from 3713 cm-1 at 800 nm to 222 cm-1 at 1319 nm. These data represent the first temperature-dependent melanosome microcavitation study in the NIR and provide additional information for understanding melanosome microcavitation threshold dependence on wavelength and ambient temperature.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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...

  6. 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.

  7. Dependence of the depth distribution of implanted silver ions on the temperature of irradiated glass

    CERN Document Server

    Stepanov, A L

    2001-01-01

    The peculiarities of the glass ion implantation by the silver ions in dependence on the substrate temperature within the interval of 20-100 deg C are studied. Modeling the profiles of the implanted ions distribution in depth with an account of the thermostimulated increase in the admixture diffusion mobility is carried out. It is shown, that increase in the substrate temperature leads to the diffusion wash-out of the introduced admixture ions distribution. The analysis of the modeling results indicates the necessity of strict control of the substrate temperature by the dielectrics implantation for obtaining the conditions for the metal nanoparticles synthesis

  8. 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.

  9. Modelling temperature-dependent heat production over decades in High Arctic coal waste rock piles

    DEFF Research Database (Denmark)

    Hollesen, Jørgen; Elberling, Bo; Jansson, P.E.

    2011-01-01

    Subsurface heat production from oxidation of pyrite is an important process that may increase subsurface temperatures within coal waste rock piles and increase the release of acid mine drainage, AMD. Waste rock piles in the Arctic are especially vulnerable to changes in subsurface temperatures...... as the release of AMD normally is limited by permafrost. Here we show that temperatures within a 20 year old heat-producing waste rock pile in Svalbard (78°N) can be modelled by the one-dimensional heat and water flow model (CoupModel) with a new temperature-dependent heat-production module that includes both...... biological and chemical oxidation processes and heat source depletion over time. Inputs to the model are meteorological measurements, physical properties of the waste rock material and measured subsurface heat-production rates. Measured mean annual subsurface temperatures within the waste rock pile are up...

  10. Temperature dependence of vegetative growth and dark respiration: a mathematical model.

    Science.gov (United States)

    Gent, M P; Enoch, H Z

    1983-03-01

    A mathematical model of the processes involved in carbon metabolism is described that predicts the influence of temperature on the growth of plants. The model assumes that the rate of production of dry matter depends both on the temperature and the level of nonstructural carbohydrate. The level of nonstructural carbohydrate is determined by the rates of photosynthesis, growth, and maintenance respiration. The model describes the rate of growth and dark respiration, and the levels of carbohydrate seen in vegetative growth of carnation and tomato. The model suggests that the growth of plants at low temperatures is limited by a shortage of respiratory energy, whereas at high temperatures growth is limited by the shortage of carbohydrate. Thermoperiodism, wherein a warm day and cool night results in faster growth than does constant temperature, is explained by the model as an increase in the level of nonstructural carbohydrate which promotes the rate of growth relative to the rate of maintenance respiration.

  11. 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.

  12. Temperature dependence of the non-local spin Seebeck effect in YIG/Pt nanostructures

    Directory of Open Access Journals (Sweden)

    Kathrin Ganzhorn

    2017-08-01

    Full Text Available We study the transport of thermally excited non-equilibrium magnons through the ferrimagnetic insulator YIG using two electrically isolated Pt strips as injector and detector. The diffusing magnons induce a non-local inverse spin Hall voltage in the detector corresponding to the so-called non-local spin Seebeck effect (SSE. We measure the non-local SSE as a function of temperature and strip separation. In experiments at room temperature we observe a sign change of the non-local SSE voltage at a characteristic strip separation d0, in agreement with previous investigations. At lower temperatures however, we find a strong temperature dependence of d0. This suggests that both the angular momentum transfer across the YIG/Pt interface as well as the transport mechanism of the magnons in YIG as a function of temperature must be taken into account to describe the non-local SSE.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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 ...

  18. A novel theoretical model for the temperature dependence of band gap energy in semiconductors

    Science.gov (United States)

    Geng, Peiji; Li, Weiguo; Zhang, Xianhe; Zhang, Xuyao; Deng, Yong; Kou, Haibo

    2017-10-01

    We report a novel theoretical model without any fitting parameters for the temperature dependence of band gap energy in semiconductors. This model relates the band gap energy at the elevated temperature to that at the arbitrary reference temperature. As examples, the band gap energies of Si, Ge, AlN, GaN, InP, InAs, ZnO, ZnS, ZnSe and GaAs at temperatures below 400 K are calculated and are in good agreement with the experimental results. Meanwhile, the band gap energies at high temperatures (T  >  400 K) are predicted, which are greater than the experimental results, and the reasonable analysis is carried out as well. Under low temperatures, the effect of lattice expansion on the band gap energy is very small, but it has much influence on the band gap energy at high temperatures. Therefore, it is necessary to consider the effect of lattice expansion at high temperatures, and the method considering the effect of lattice expansion has also been given. The model has distinct advantages compared with the widely quoted Varshni’s semi-empirical equation from the aspect of modeling, physical meaning and application. The study provides a convenient method to determine the band gap energy under different temperatures.

  19. 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.

  20. Temperature dependent structural, vibrational and magnetic properties of K3Gd5(PO4)6.

    Science.gov (United States)

    Bevara, Samatha; Achary, S Nagabhusan; Mishra, Karuna Kara; Ravindran, T R; Sinha, Anil K; Sastry, P U; Tyagi, Avesh Kumar

    2017-02-22

    Herein we report the evolution of the crystal structure of K3Gd5(PO4)6 in the temperature range from 20 K to 1073 K, as observed from variable temperature X-ray diffraction and Raman spectroscopic studies. K3Gd5(PO4)6 has an open tunnel containing a three dimensional structure built by [Gd5(PO4)6]3- ions which in turn are formed of PO4 tetrahedra and GdOn (n = 8 and 9) polyhedra. The empty tunnels in the structure are occupied by K+ ions and maintain charge neutrality in the lattice. Evolution of unit cell parameters with temperature shows a systematic increase with temperature. The average axial thermal expansion coefficients between 20 K and 1073 K are: αa = 10.6 × 10-6 K-1, αb = 5.5 × 10-6 K-1 and αc = 16.4 × 10-6 K-1. The evolution of distortion indices of the various coordination polyhedra with temperature indicates a gradual decrease with increasing temperature, while those of Gd2O9 and K2O8 polyhedra show opposite trends. The overall anisotropy of the lattice thermal expansion is found to be controlled largely by the effect of temperature on GdOn polyhedra and their linkages. Temperature dependent Raman spectroscopic studies indicated that the intensities and wavenumbers of most of the Raman modes decrease continuously with increasing temperature. Anharmonic analyses of Raman modes indicated that the lattice, rigid translation and librational modes have larger contributions towards thermal expansion of K3Gd5(PO4)6 compared to high frequency internal modes. The temperature and field dependent magnetic measurements indicated no long range ordering down to 2 K and the observed effective magnetic moment per Gd3+ ion and the Weiss constant are 7.91 μB and 0.38 K, respectively.

  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. 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

  3. Temperature-dependent photoluminescence of cadmium-free Cu-Zn-In-S quantum dot thin films as temperature probes.

    Science.gov (United States)

    Wang, Lan; Kang, Xiaojiao; Huang, Lijian; Pan, Daocheng

    2015-12-21

    We reported temperature-dependent photoluminescence (PL) studies on Cu-Zn-In-S quantum dot (QD) thin films. In this paper, cadmium-free and luminescent Cu-Zn-In-S quantum dot thin films were in situ formed by thermal decomposition of molecular-based precursors in the open air, without need of the complicated quantum dot synthesis. Molecular-based precursor solutions were prepared by dissolving Cu2O, ZnO, and In(OH)3 in the ethanol solution of butylamine and carbon disulfide. The effects of sintering temperature, sintering time, and the concentration of capping agents on the photoluminescence properties of Cu-Zn-In-S QD thin films have been systematically investigated. It was found that alkali metal ions play an important role in enhancing the PL quantum yield of quantum dot thin films. The as-prepared QD thin films show composition-tunable emission in the range of 535 nm to 677 nm, and the absolute PL quantum yields can reach as high as 22.1%. All of the as-deposited QD thin films show a single-exponential decay to temperature, indicating that these cadmium-free QD thin films have high potential as temperature probes.

  4. The role of electron transport in determining the temperature dependence of the photosynthetic rate in spinach leaves grown at contrasting temperatures.

    Science.gov (United States)

    Yamori, Wataru; Noguchi, Ko; Kashino, Yasuhiro; Terashima, Ichiro

    2008-04-01

    The temperature response of the uncoupled whole-chain electron transport rate (ETR) in thylakoid membranes differs depending on the growth temperature. However, the steps that limit whole-chain ETR are still unclear and the question of whether the temperature dependence of whole-chain ETR reflects that of the photosynthetic rate remains unresolved. Here, we determined the whole-chain, PSI and PSII ETR in thylakoid membranes isolated from spinach leaves grown at 30 degrees C [high temperature (HT)] and 15 degrees C [low temperature (LT)]. We measured temperature dependencies of the light-saturated photosynthetic rate at 360 microl l(-1) CO2 (A360) in HT and LT leaves. Both of the temperature dependences of whole-chain ETR and of A360 were different depending on the growth temperature. Whole-chain ETR was less than the rates of PSI ETR and PSII ETR in the broad temperature range, indicating that the process was limited by diffusion processes between the PSI and PSII. However, at high temperatures, whole-chain ETR appeared to be limited by not only the diffusion processes but also PSII ETR. The C3 photosynthesis model was used to evaluate the limitations of A360 by whole-chain ETR (Pr) and ribulose bisphosphate carboxylation (Pc). In HT leaves, A360 was co-limited by Pc and Pr at low temperatures, whereas at high temperatures, A360 was limited by Pc. On the other hand, in LT leaves, A360 was solely limited by Pc over the entire temperature range. The optimum temperature for A360 was determined by Pc in both HT and LT leaves. Thus, this study showed that, at low temperatures, the limiting step of A360 was different depending on the growth temperature, but was limited by Pc at high temperatures regardless of the growth temperatures.

  5. 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...

  6. Role of heat advection in a channeled lava flow with power law, temperature-dependent rheology

    Science.gov (United States)

    Filippucci, Marilena; Tallarico, Andrea; Dragoni, Michele

    2013-06-01

    The cooling of a lava flow, both in the transient and the steady state, is investigated considering that lava rheology is pseudoplastic and dependent on temperature. Lava exits from the vent with constant velocity and flows down a slope under the effect of gravity force inside a channel of rectangular cross section. We consider that cooling of lava is caused by thermal radiation into the atmosphere and thermal conduction at the channel walls and at the ground. The heat equation is solved numerically in a 3-D computational domain, and the solution is tested to evaluate the numerical errors. We study the steady state and the initial transient period of lava cooling. Results indicate that the advective heat transport significantly modifies the cooling rate of lava, slowing down the cooling process. Since the lava velocity depends on temperature, the cooling rate depends on the effusion temperature. Velocity profiles are modified during cooling showing two marginal static zones where the crust can form and remain stable. The fraction of crust coverage is calculated under the assumption that the solid lava is a plastic body with temperature-dependent yield strength. We numerically confirm that heat advection cannot be neglected in the mechanism of formation of lava tubes.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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...

  12. 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...

  13. 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.

  14. 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

  15. 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

  16. 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…

  17. 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

  18. Temperature- and pressure-dependent lattice behaviour of RbFe(MoO4)(2)

    DEFF Research Database (Denmark)

    Waskowska, A.; Gerward, Leif; Olsen, J. S.

    2010-01-01

    Trigonal RbFe(MoO4)(2) is a quasi-two-dimensional antiferromagnet on a triangular lattice below T-N = 3.8 K, The crystal exhibits also a structural phase transition at T-c = 190 K related to symmetry change from Pm1 to P. We present the temperature-and pressure-dependent characteristics of this m......Trigonal RbFe(MoO4)(2) is a quasi-two-dimensional antiferromagnet on a triangular lattice below T-N = 3.8 K, The crystal exhibits also a structural phase transition at T-c = 190 K related to symmetry change from Pm1 to P. We present the temperature-and pressure-dependent characteristics...... of this material in the context of ambiguous opinions on the symmetry and crystal properties below T-c. A single-crystal x-ray diffraction shows that the temperature-dependent evolution of the unit cell in the range 100-300 K is strongly anisotropic with markedly discontinuous changes at T-c. The transition...... is connected with a spontaneous strain developing in effect of the volume decrease. The structure releases the strain by rotation of corner-sharing rigid MoO4 and FeO6 polyhedra in the (a, b) basal plane. The temperature dependence of the IR vibrational wavenumbers exhibits weak changes near T-c, which...

  19. 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

  20. 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.

  1. 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

  2. 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

  3. 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…

  4. Path dependent models to predict property changes in graphite irradiated at changing irradiation temperatures

    CSIR Research Space (South Africa)

    Kok, S

    2010-10-01

    Full Text Available .co.za ] Path dependent models to predict property changes in graphite irradiated at changing irradiation temperatures S KOK CSIR Advanced Mathematical Modelling, Modelling and Digital Science, PO Box 395, Pretoria, 0001, South Africa E-mail: skok...

  5. 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

  6. 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.

  7. 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

  8. Temperature Dependent Local Atomic Structure of LuFe2O4

    Science.gov (United States)

    Liu, S.; Zhang, H.; Ghose, S.; Cheong, S.-W.; Emge, T.; Chen, Y.-S.; Tyson, T.

    The LuFe2O4 system has be studied intensively as a novel material with charge ordered driven ferroelectricity. However, the existence and origin of electric polarization and it coupling to the magnetic structure are open questions still to be addressed. Distinctly differing experiments yield different results. In this work, structural measurements on multiple length scales have been conducted over a broad range of temperatures. We have studied the correlation between the structural distortion and the electronic/magnetic properties in single-crystalline LuFe2O4 by using X-ray diffraction (XRD), temperature and orientation dependent Raman spectroscopy, temperature dependent X-ray pair distribution function (PDF) measurements and DFT modeling. The nature of the observed local atomic and electronic structural changes will be discussed and compared with previous work. This work is supported by DOE Grant DE-FG02-07ER46402.

  9. 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.

  10. 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.

  11. Viscosity of magnetite–toluene nanofluids: Dependence on temperature and nanoparticle concentration

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Rahul [Department of Mechanical Engineering, Iowa State University, Ames, IA (United States); Sanchez, Oswaldo [Department of Mathematical Sciences, Morningside College, Sioux City, IA (United States); Ghosh, Suvojit [Department of Engineering Physics, McMaster University, Hamilton, ON (Canada); Kadimcherla, Naveen [Department of Mechanical Engineering, Iowa State University, Ames, IA (United States); Sen, Swarnendu [Department of Mechanical Engineering, Jadavpur University, Kolkata, West Bengal (India); Balasubramanian, Ganesh, E-mail: bganesh@iastate.edu [Department of Mechanical Engineering, Iowa State University, Ames, IA (United States)

    2015-10-23

    Highlights: • Viscosity of magnetite in toluene nanofluid increases monotonically with particle concentration. • Clusters formed at higher particle concentration are monodisperse. • With increasing temperature, viscosity decreases due less fraction of immobile fluid molecules. - Abstract: We examine the dependence of the viscosity of nanofluids, comprised of magnetite nanoparticles dispersed in toluene, on particle concentration and temperature. The nanofluid viscosity increases monotonically with particle concentration. We show that although the nanoparticles aggregate to form clusters with increasing concentration, the cluster size is fairly monodisperse and hence the viscosity can be expressed as a function of only the particle concentration. The viscosity of the nanofluid is found to decrease with temperature, similarly to the characteristics of the carrier liquid. We describe these dependencies through an empirical correlation, since the observations are useful to employ such nanofluids in engineering applications.

  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. Thickness- and temperature-dependent magnetodynamic properties of yttrium iron garnet thin films

    Energy Technology Data Exchange (ETDEWEB)

    Haidar, M., E-mail: mohammad.haidar@Physics.gu.se; Ranjbar, M.; Balinsky, M.; Dumas, R. K. [Department of Physics, University of Gothenburg, 41296 Gothenburg (Sweden); Khartsev, S. [Department of Integrated Devices and Circuits, School of ICT, Royal Institute of Technology (KTH), 16440 Kista (Sweden); Åkerman, J. [Department of Physics, University of Gothenburg, 41296 Gothenburg (Sweden); Materials Physics, School of ICT, Royal Institute of Technology (KTH), 16440 Kista (Sweden)

    2015-05-07

    The magnetodynamical properties of nanometer-thick yttrium iron garnet films are studied using ferromagnetic resonance as a function of temperature. The films were grown on gadolinium gallium garnet substrates by pulsed laser deposition. First, we found that the damping coefficient increases as the temperature increases for different film thicknesses. Second, we found two different dependencies of the damping on film thickness: at room temperature, the damping coefficient increases as the film thickness decreases, while at T = 8 K, we find the damping to depend only weakly on the thickness. We attribute this behavior to an enhancement of the relaxation of the magnetization by impurities or defects at the surfaces.

  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. 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.

  17. 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.

  18. Temperature and frequency dependence of AC conductivity and modulus in Cr-Doped ZnO

    Science.gov (United States)

    Junais, P. M.; Govindaraj, G.

    2017-05-01

    A nanocrystalline Cr-doped ZnO has been prepared by refluxing method. The samples were characterized using XRD and impedance spectroscopy. The XRD pattern shows the crystalline nature of the sample and well confirms the successful doping Cr into the host lattice. The conductivity of the sample measured in the temperature range 303-603K and in the frequency range 10Hz-1MHz. The temperature dependent dc conductivity and hopping frequency show Arrhenius behavior. AC conductivity data were analyzed using Jonscher's power law. Modulus data were analyzed using Bergman modified KWW function. Temperature dependent capacitance shows a sharp peak at 540K which may be due to ferroelectric nature of the material.

  19. Diffractometric measurement of the temperature dependence of piezoelectric tensor in GMO monocrystal

    Science.gov (United States)

    Breczko, Teodor; Lempaszek, Andrzej

    2007-04-01

    Functional materials, of which an example is ferroelectric, ferroelastic monocrystal of molybdate (III) gadolinium (VI), are often used in the micro-motor operators (micro-servo motors) working in changeable environment conditions. Most frequently this change refers to temperature. That is why the important practical problem is the precise measurement of the value of piezoelectric tensor elements in dependence on the temperature of a particular monocrystal. In the presented article for this kind of measurements, the use of X-ray diffractometer has been shown. The advantage of the method presented is that, apart from precise dependence measurement between the temperature of a monocrystal and the value of piezoelectric tensor elements, it enables synchronous measurement of the value of thermal expansion tensor elements for a monocrystal.

  20. Stimulus-Dependent Effects of Temperature on Bitter Taste in Humans.

    Science.gov (United States)

    Green, Barry G; Andrew, Kendra

    2017-02-01

    This study investigated the effects of temperature on bitter taste in humans. The experiments were conducted within the context of current understanding of the neurobiology of bitter taste and recent evidence of stimulus-dependent effects of temperature on sweet taste. In the first experiment, the bitterness of caffeine and quinine sampled with the tongue tip was assessed at 4 different temperatures (10°, 21°, 30°, and 37 °C) following pre-exposure to the same solution or to water for 0, 3, or 10 s. The results showed that initial bitterness (0-s pre-exposure) followed an inverted U-shaped function of temperature for both stimuli, but the differences across temperature were statistically significant only for quinine. Conversely, temperature significantly affected adaptation to the bitterness of quinine but not caffeine. A second experiment used the same procedure to test 2 additional stimuli, naringin and denatonium benzoate. Temperature significantly affected the initial bitterness of both stimuli but had no effect on adaptation to either stimulus. These results confirm that like sweet taste, temperature affects bitter taste sensitivity and adaptation in stimulus-dependent ways. However, the thermal effect on quinine adaptation, which increased with warming, was opposite to what had been found previously for adaptation to sweetness. The implications of these results are discussed in relation to findings from prior studies of temperature and bitter taste in humans and the possible neurobiological mechanisms of gustatory thermal sensitivity. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  1. Generalized Magneto-thermo-microstretch Response of a Half-space with Temperature-dependent Properties During Thermal Shock

    Directory of Open Access Journals (Sweden)

    Qi-lin Xiong

    Full Text Available Abstract The generalized magneto-thermoelastic problem of an infinite homogeneous isotropic microstretch half-space with temperature-dependent material properties placed in a transverse magnetic field is investigated in the context of different generalized thermoelastic theories. The upper surface of the half-space is subjected to a zonal time-dependent heat shock. By solving finite element governing equations, the solution to the problem is obtained, from which the transient magneto-thermoelastic responses, including temperature, stresses, displacements, microstretch, microrotation, induced magnetic field and induced electric field are presented graphically. Comparisons are made in the results obtained under different generalized thermoelastic theories to show some unique features of generalized thermoelasticity, and comparisons are made in the results obtained under three forms of temperature dependent material properties (absolute temperature dependent, reference temperature dependent and temperature-independent to show the effects of absolute temperature and reference temperature. Weibull or Log-normal.

  2. Measurement of Wavelength and Temperature-Dependent Optical Properties of Thermochromic Pigments.

    Science.gov (United States)

    Hu, Jianying; Yu, Xiong Bill

    2017-01-01

    Thermochromic material is a substance that is capable of changing reversibly the color as the temperature rises. Therefore, the optical spectrum of thermochromic material is responsive to the environmental temperature. In this study, the temperature-dependent optical constants of thermochromic pigments over the wavelength of 350-1800 nm were investigated. Three kinds of thermochromic pigments featured with black, blue, and red colors at room temperature were suspended in water and the light reflection and transmission of the suspensions at different temperatures were measured by a multifunctional spectrophotometer. It was found that below the transition temperature of thermochromic material, the refractive index was 2.1-2.5, 2.2-2.6, and 2.0-2.4 over the wavelength range of 350-1800 nm for black, blue, and red thermochromic pigment, respectively, while above the transition temperature it reached 2.3-2.7, 2.4-2.9, and 2.4-2.7, respectively. It was also observed that the relationship between refractive index of thermochromic pigment and wavelength follows the cubic polynomial function. Furthermore, the extinction coefficient is in the range of 1 × 10-5-1.2 × 10-4 for all thermochromic pigments and remains approximately stable at different temperatures. The determination of optical constants of thermochromic pigments provides essential parameters in the modeling of light scattering and absorption by pigment particles to further fine-tune the optical properties of thermochromic coating.

  3. The dependence of thermoluminescence sensitivity upon the temperature of irradiation in meteorites and in terrestrial apatites

    Energy Technology Data Exchange (ETDEWEB)

    Durrani, S.A.; Al-Khalifa, I.J.M. (Birmingham Univ. (UK). School of Physics and Space Research)

    1990-01-01

    Measurements are reported on the TL sensitivity (i.e. TL glow output per unit {gamma} ray test dose) of meteoritic specimens as well as terrestrial fluor- and chlor-apatites, as a function of irradiation temperature (T{sub irr}). The irradiation temperatures ranged from liquid nitrogen to room temperature (77 - 293 K). A kilocurie {sup 60}Co {gamma} ray source was used to deliver test doses of 400 Gy (40 krad) and 40 (4 krad) to the various samples. A strong dependence of the TL sensitivity upon the temperature of irradiation was noted in the case of Kirin meteorite: its TL sensitivity (for the 493 K readout peak) decreased by a factor of {similar to} 2 when T{sub irr} rose from liquid nitrogen (77 K) to dry ice in acetone (197 K) temperature, in the case of both 400 Gy and 40 Gy {gamma} ray doses. In the case of the Antarctic meteorite specimen (ALHA 77182.13), there was a smaller effect, viz. a fall of {similar to} 14% in the TL output corresponding to dry ice and higher irradiating temperatures as compared to the 77 K irradiation. For chlorapatite, the TL sensitivity decreased monotonically with increasing temperature for both the 563 K and the 448 K glow peaks. For the fluorapatite, the effect of reduced response was observed only between -17{sup 0}C (256 K) and room temperature (293 K). Both the theoretical and the practical implications of these observations are discussed. (author).

  4. The Dependence of Constitutive Properties on Temperature and Effective Normal Stress in Seismogenic Environments

    Science.gov (United States)

    Kato, Aitaro; Yoshida, Shingo; Ohnaka, Mitiyasu; Mochizuki, Hiromine

    We have evaluated how the parameters prescribing the slip-dependent constitutive law are affected by temperature and effective normal stress, by conducting the triaxial fracture experiments on Tsukuba-granite samples in seismogenic environments, which correspond to a depth range to 15 km. The normalized critical slip displacement Dc almost remains constant below 300oC (insensitive to both temperature and effective normal stress σneff) Dc increases with increasing temperature above 300 °C, and the rate of Dc increase with temperature tends to be largest at higher σneff. The breakdown stress drop Δτb for the granite at constant σneff is roughly 80 MPa below 300 °C, and does not depend on σneff. Above 300 °C, Δτb decreases gradually with increasing temperature, and the rate of Δτb reduction with temperature increases at higher σneff. The peak shear strength τp increases nearly linearly with increasing σneff below 300 °C. However, τp becomes lower above 300 °C, deviating from the linear relation extrapolated from below 300 °C. This is consistent with the onset of crystal plastic deformation mechanisms of Tsukuba granite.

  5. 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.

  6. Temperature dependence of the interfacial magnetic anisotropy in W/CoFeB/MgO

    Directory of Open Access Journals (Sweden)

    Kyoung-Min Lee

    2017-06-01

    Full Text Available The interfacial perpendicular magnetic anisotropy in W/CoFeB (1.2 ∼ 3 nm/MgO thin film structures is strongly dependent on temperature, and is significantly reduced at high temperature. The interfacial magnetic anisotropy is generally proportional to the third power of magnetization, but an additional factor due to thermal expansion is required to explain the temperature dependence of the magnetic anisotropy of ultrathin CoFeB films. The reduction of the magnetic anisotropy is more prominent for the thinner films; as the temperature increases from 300 K to 400 K, the anisotropy is reduced ∼50% for the 1.2-nm-thick CoFeB, whereas the anisotropy is reduced ∼30% for the 1.7-nm-thick CoFeB. Such a substantial reduction of magnetic anisotropy at high temperature is problematic for data retention when incorporating W/CoFeB/MgO thin film structures into magneto-resistive random access memory devices. Alternative magnetic materials and structures are required to maintain large magnetic anisotropy at elevated temperatures.

  7. 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.

  8. 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.

  9. 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.

  10. Temperature-dependent gain compensation of CsI(Tl) detectors using pulse shape analysis

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Joel; Isaak, Johann; Loeher, Bastian; Savran, Deniz; Wamers, Felix [ExtreMe Matter Institute EMMI and Research Division, GSI Helmholtzzentrum, Darmstadt (Germany); Frankfurt Institute for Advanced Studies FIAS, Frankfurt (Germany); Vencelj, Matjaz [Jozef Stefan Institute, Ljubljana (Slovenia)

    2014-07-01

    The scintillation properties of CsI(Tl) crystals and the gain of photo-sensors such as avalanche photodiodes (APDs) and photo-multipliers (PMs) are temperature dependent. Therefore, for accurate measurements in γ-ray spectroscopy using CsI(Tl) detectors temperature variations have to be precisely monitored. Since the decay time constants in the scintillation process of CsI(Tl) crystals also depend on the temperature, these changes can be compensated by analyzing the pulse shape of detector signals. The method uses the correlation between the gain and the pulse-shape to correct the effect of the temperature. The results of the implementation of this method using CsI(Tl) crystals read out by PMs are presented. It shows to improve that the energy resolution of the detectors in a temperature changing environment ranging from -10 {sup circle} C to 40 {sup circle} C is improved. The suitability of the method using CsI(Tl) read out by APDs was investigated in the same temperature range. First results are also presented.

  11. Temperature dependence of the interfacial magnetic anisotropy in W/CoFeB/MgO

    Science.gov (United States)

    Lee, Kyoung-Min; Choi, Jun Woo; Sok, Junghyun; Min, Byoung-Chul

    2017-06-01

    The interfacial perpendicular magnetic anisotropy in W/CoFeB (1.2 ˜ 3 nm)/MgO thin film structures is strongly dependent on temperature, and is significantly reduced at high temperature. The interfacial magnetic anisotropy is generally proportional to the third power of magnetization, but an additional factor due to thermal expansion is required to explain the temperature dependence of the magnetic anisotropy of ultrathin CoFeB films. The reduction of the magnetic anisotropy is more prominent for the thinner films; as the temperature increases from 300 K to 400 K, the anisotropy is reduced ˜50% for the 1.2-nm-thick CoFeB, whereas the anisotropy is reduced ˜30% for the 1.7-nm-thick CoFeB. Such a substantial reduction of magnetic anisotropy at high temperature is problematic for data retention when incorporating W/CoFeB/MgO thin film structures into magneto-resistive random access memory devices. Alternative magnetic materials and structures are required to maintain large magnetic anisotropy at elevated temperatures.

  12. 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

  13. 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

  14. Results of scalp cooling during anthracycline containing chemotherapy depend on scalp skin temperature.

    Science.gov (United States)

    Komen, M M C; Smorenburg, C H; Nortier, J W R; van der Ploeg, T; van den Hurk, C J G; van der Hoeven, J J M

    2016-12-01

    The success of scalp cooling in preventing or reducing chemotherapy induced alopecia (CIA) is highly variable between patients undergoing similar chemotherapy regimens. A decrease of the scalp skin temperature seems to be an important factor, but data on the optimum temperature reached by scalp cooling to prevent CIA are lacking. This study investigated the relation between scalp skin temperature and its efficacy to prevent CIA. In this explorative study, scalp skin temperature was measured during scalp cooling in 62 breast cancer patients undergoing up to six cycles of anthracycline containing chemotherapy. Scalp skin temperature was measured by using two thermocouples at both temporal sides of the head. The primary end-point was the need for a wig or other head covering. Maximal cooling was reached after 45 min and was continued for 90 min after chemotherapy infusion. The scalp skin temperature after 45 min cooling varied from 10 °C to 31 °C, resulting in a mean scalp skin temperature of 19 °C (SEM: 0,4). Intrapersonal scalp skin temperatures during cooling were consistent for each chemotherapy cycle (ANOVA: P = 0,855). Thirteen out of 62 patients (21%) did not require a wig or other head covering. They appeared to have a significantly lower mean scalp skin temperature (18 °C; SEM: 0,7) compared to patients with alopecia (20 °C; SEM: 0,5) (P = 0,01). The efficacy of scalp cooling during chemotherapy is temperature dependent. A precise cut-off point could not be detected, but the best results seem to be obtained when the scalp temperature decreases below 18 °C. TRIALREGISTER. 3082. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Expanded modeling of temperature-dependent dielectric properties for microwave thermal ablation.

    Science.gov (United States)

    Ji, Zhen; Brace, Christopher L

    2011-08-21

    Microwaves are a promising source for thermal tumor ablation due to their ability to rapidly heat dispersive biological tissues, often to temperatures in excess of 100 °C. At these high temperatures, tissue dielectric properties change rapidly and, thus, so do the characteristics of energy delivery. Precise knowledge of how tissue dielectric properties change during microwave heating promises to facilitate more accurate simulation of device performance and helps optimize device geometry and energy delivery parameters. In this study, we measured the dielectric properties of liver tissue during high-temperature microwave heating. The resulting data were compiled into either a sigmoidal function of temperature or an integration of the time-temperature curve for both relative permittivity and effective conductivity. Coupled electromagnetic-thermal simulations of heating produced by a single monopole antenna using the new models were then compared to simulations with existing linear and static models, and experimental temperatures in liver tissue. The new sigmoidal temperature-dependent model more accurately predicted experimental temperatures when compared to temperature-time integrated or existing models. The mean percent differences between simulated and experimental temperatures over all times were 4.2% for sigmoidal, 10.1% for temperature-time integration, 27.0% for linear and 32.8% for static models at the antenna input power of 50 W. Correcting for tissue contraction improved agreement for powers up to 75 W. The sigmoidal model also predicted substantial changes in heating pattern due to dehydration. We can conclude from these studies that a sigmoidal model of tissue dielectric properties improves prediction of experimental results. More work is needed to refine and generalize this model.

  16. 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

  17. 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.

  18. How to apply the dependence structure analysis to extreme temperature and precipitation for disaster risk assessment

    Science.gov (United States)

    Feng, Jieling; Li, Ning; Zhang, Zhengtao; Chen, Xi

    2017-06-01

    IPCC reports that a changing climate can affect the frequency and the intensity of extreme events. However, the extremes appear in the tail of the probability distribution. In order to know the relationship between extreme events in the tail of temperature and precipitation, an important but previously unobserved dependence structure is analyzed in this paper. Here, we examine the dependence structure by building a bivariate joint of Gumbel copula model for temperature and precipitation using monthly average temperature (T) and monthly precipitation (P) data from Beijing station in China covering a period of 1951-2015 and find the dependence structure can be divided into two sections, they are the middle part and the upper tail. We show that T and P have a strong positive correlation in the high tail section (T > 25.85 °C and P > 171.1 mm) (=0.66, p < 0.01) while they do not demonstrate the same relation in the other section, which suggests that the identification of a strong influence of T on extreme P needs help from the dependence structure analysis. We also find that in the high tail section, every 1 °C increase in T is associated with 73.45 mm increase in P. Our results suggested that extreme precipitation fluctuations by changes in temperature will allow the data dependence structure to be included in extreme affect for the disaster risk assessment under future climate change scenarios. Copula bivariate jointed probability distribution is useful to the dependence structure analysis.

  19. Time dependent and temperature dependent properties of the forward voltage characteristic of InGaN high power LEDs

    Science.gov (United States)

    Fulmek, P. L.; Haumer, P.; Wenzl, F. P.; Nemitz, W.; Nicolics, J.

    2017-03-01

    Estimating the junction temperature and its dynamic behavior in dependence of various operating conditions is an important issue, since these properties influence the optical characteristics as well as the aging processes of a light-emitting diode (LED). Particularly for high-power LEDs and pulsed operation, the dynamic behavior and the resulting thermal cycles are of interest. The forward voltage method relies on the existence of a time-independent unique triple of forward-voltage, forward-current, and junction temperature. These three figures should as well uniquely define the optical output power and spectrum, as well as the loss power of the LED, which is responsible for an increase of the junction temperature. From transient FEM-simulations one may expect an increase of the temperature of the active semiconductor layer of some 1/10 K within the first 10 μs. Most of the well-established techniques for junction temperature measurement via forward voltage method evaluate the measurement data several dozens of microseconds after switching on or switching off and estimate the junction temperature by extrapolation towards the time of switching. In contrast, the authors developed a measurement procedure with the focus on the first microseconds after switching. Besides a fast data acquisition system, a precise control of the switching process is required, i.e. a precisely defined current pulse amplitude with fast rise-time and negligible transient by-effects. We start with a short description of the measurement setup and the newly developed control algorithm for the generation of short current pulses. The thermal characterization of the LED chip during the measurement procedures is accomplished by an IR thermography system and transient finite element simulations. The same experimental setup is used to investigate the optical properties of the LED in an Ulbricht-sphere. Our experiments are performed on InGaN LED chips mounted on an Al based insulated metal substrate

  20. Time dependent and temperature dependent properties of the forward voltage characteristic of InGaN high power LEDs

    Directory of Open Access Journals (Sweden)

    P. L. Fulmek

    2017-03-01

    Full Text Available Estimating the junction temperature and its dynamic behavior in dependence of various operating conditions is an important issue, since these properties influence the optical characteristics as well as the aging processes of a light-emitting diode (LED. Particularly for high-power LEDs and pulsed operation, the dynamic behavior and the resulting thermal cycles are of interest. The forward voltage method relies on the existence of a time-independent unique triple of forward-voltage, forward-current, and junction temperature. These three figures should as well uniquely define the optical output power and spectrum, as well as the loss power of the LED, which is responsible for an increase of the junction temperature. From transient FEM-simulations one may expect an increase of the temperature of the active semiconductor layer of some 1/10 K within the first 10 μs. Most of the well-established techniques for junction temperature measurement via forward voltage method evaluate the measurement data several dozens of microseconds after switching on or switching off and estimate the junction temperature by extrapolation towards the time of switching. In contrast, the authors developed a measurement procedure with the focus on the first microseconds after switching. Besides a fast data acquisition system, a precise control of the switching process is required, i.e. a precisely defined current pulse amplitude with fast rise-time and negligible transient by-effects. We start with a short description of the measurement setup and the newly developed control algorithm for the generation of short current pulses. The thermal characterization of the LED chip during the measurement procedures is accomplished by an IR thermography system and transient finite element simulations. The same experimental setup is used to investigate the optical properties of the LED in an Ulbricht-sphere. Our experiments are performed on InGaN LED chips mounted on an Al based

  1. Temperature-dependent thermal properties of ex vivo liver undergoing thermal ablation.

    Science.gov (United States)

    Guntur, Sitaramanjaneya Reddy; Lee, Kang Il; Paeng, Dong-Guk; Coleman, Andrew John; Choi, Min Joo

    2013-10-01

    Thermotherapy uses a heat source that raises temperatures in the target tissue, and the temperature rise depends on the thermal properties of the tissue. Little is known about the temperature-dependent thermal properties of tissue, which prevents us from accurately predicting the temperature distribution of the target tissue undergoing thermotherapy. The present study reports the key thermal parameters (specific heat capacity, thermal conductivity and heat diffusivity) measured in ex vivo porcine liver while being heated from 20 ° C to 90 ° C and then naturally cooled down to 20 ° C. The study indicates that as the tissue was heated, all the thermal parameters resulted in plots with asymmetric quasi-parabolic curves with temperature, being convex downward with their minima at the turning temperature of 35-40 ° C. The largest change was observed for thermal conductivity, which decreased by 9.6% from its initial value (at 20 ° C) at the turning temperature (35 ° C) and rose by 45% at 90 ° C from its minimum (at 35 ° C). The minima were 3.567 mJ/(m(3) ∙ K) for specific heat capacity, 0.520 W/(m.K) for thermal conductivity and 0.141 mm(2)/s for thermal diffusivity. The minimum at the turning temperature was unique, and it is suggested that it be taken as a characteristic value of the thermal parameter of the tissue. On the other hand, the thermal parameters were insensitive to temperature and remained almost unchanged when the tissue cooled down, indicating that their variations with temperature were irreversible. The rate of the irreversible rise at 35 ° C was 18% in specific heat capacity, 40% in thermal conductivity and 38.3% in thermal diffusivity. The study indicates that the key thermal parameters of ex vivo porcine liver vary largely with temperature when heated, as described by asymmetric quasi-parabolic curves of the thermal parameters with temperature, and therefore, substantial influence on the temperature distribution of the tissue undergoing

  2. Universal scaling of the temperature dependence of the strength of crystals governed by the Peierls mechanism

    Science.gov (United States)

    Takeuchi, S.; Suzuki, T.

    2010-07-01

    The temperature dependences of the critical resolved shear stress (CRSS) governed by the Peierls mechanism in pure NaCl type crystals, those in pure bcc transition metals, those by dissociated dislocations in covalent crystals of the diamond and the zinc blende structures and those by perfect dislocations at low temperatures in zinc blende crystals have been demonstrated to be roughly scalable with respect to the non-dimensional normalization of the CRSS by the shear modulus G and the temperature by Gb3/kB, where b is the strength of the Burgers vector and kB the Boltzmann constant. Furthermore, CRSS vs. T relations have been shown to be scaled universally by normalizing respectively the CRSS by the estimated Peierls stress τp and the temperature by the kink-pair energy parameter of (τp/G)1/2(bd)3/2G/kB, where d is the period of the Peierls potential.

  3. Temperature dependence of electromechanical impedance based bond-line integrity monitoring

    Science.gov (United States)

    Bilgunde, Prathamesh; Bond, Leonard J.

    2017-04-01

    Electromechanical impedance (EMI) is an important technique for bond-line integrity monitoring of adhesively bonded joints in automotive and aerospace structures. In the current work, numerical analysis of temperature sensitivity of the EMI technique is performed. The objective is to detect stiffness reduction of the adhesive in the presence of temperature and external mechanical load. Increase in the operating temperature can degrade the bonded piezoelectric material causing misinterpretation of the EMI data. EMI Signal features are numerically investigated to decouple the effect of load and temperature on the piezoelectric material in the mechanically loaded bonded joint. The computational results indicate higher dependence of EM resonance spectrum towards piezoelectric material matrix as compared to the tensile load applied on the bonded sample as the stiffness of adhesive is numerically varied.

  4. Temperature Dependence of Soil Respiration Modulated by Thresholds in Soil Water Availability Across European Shrubland Ecosystems

    DEFF Research Database (Denmark)

    Lellei-Kovács, Eszter; Botta-Dukát, Zoltán; de Dato, Giovanbattista

    2016-01-01

    Soil respiration (SR) is a major component of the global carbon cycle and plays a fundamental role in ecosystem feedback to climate change. Empirical modelling is an essential tool for predicting ecosystem responses to environmental change, and also provides important data for calibrating...... the performance of SR models by including the interaction between soil moisture and soil temperature. We found that the best fit for the temperature functions depended on the site-specific climatic conditions. Including soil moisture, we identified thresholds in the three different response functions...... that improved the model fit in all cases. The direct soil moisture effect on SR, however, was weak at the annual time scale. We conclude that the exponential soil temperature function may only be a good predictor for SR in a narrow temperature range, and that extrapolating predictions for future climate based...

  5. Temperature dependent recombination dynamics in InP/ZnS colloidal nanocrystals

    DEFF Research Database (Denmark)

    Shirazi, Roza; Kopylov, Oleksii; Kovács, András

    2012-01-01

    In this letter, we investigate exciton recombination in InP/ZnS core-shell colloidal nanocrystals over a wide temperature range. Over the entire range between room temperature and liquid helium temperature, multi-exponential exciton decay curves are observed and well explained by the presence...... of bright and dark exciton states, as well as defect states. Two different types of defect are present: one located at the core-shell interface and the other on the surface of the nanocrystal. Based on the temperature dependent contributions of all four states to the total photoluminescence signal, we...... estimate that the four states are distributed within a 20 meV energy band in nanocrystals that emit at 1.82 eV....

  6. Temperature Dependence of NMR Parameters Calculated from Path Integral Molecular Dynamics Simulations.

    Science.gov (United States)

    Dračínský, Martin; Bouř, Petr; Hodgkinson, Paul

    2016-03-08

    The influence of temperature on NMR chemical shifts and quadrupolar couplings in model molecular organic solids is explored using path integral molecular dynamics (PIMD) and density functional theory (DFT) calculations of shielding and electric field gradient (EFG) tensors. An approach based on convoluting calculated shielding or EFG tensor components with probability distributions of selected bond distances and valence angles obtained from DFT-PIMD simulations at several temperatures is used to calculate the temperature effects. The probability distributions obtained from the quantum PIMD simulations, which includes nuclear quantum effects, are significantly broader and less temperature dependent than those obtained with conventional DFT molecular dynamics or with 1D scans through the potential energy surface. Predicted NMR observables for the model systems were in excellent agreement with experimental data.

  7. Unusual temperature dependence of the dissociative electron attachment cross section of 2-thiouracil

    Energy Technology Data Exchange (ETDEWEB)

    Kopyra, Janina [Faculty of Science, Siedlce University, 3 Maja 54, 08-110 Siedlce (Poland); Abdoul-Carime, Hassan [Université de Lyon, F-69003 Lyon (France); Université Lyon 1, Villeurbanne (France); CNRS/IN2P3, UMR5822, Institut de Physique Nucléaire de Lyon, Lyon (France)

    2016-01-21

    At low energies (<3 eV), molecular dissociation is controlled by dissociative electron attachment for which the initial step, i.e., the formation of the transient negative ion, can be initiated by shape resonance or vibrational Feshbach resonance (VFR) mediated by the formation of a dipole bound anion. The temperature dependence for shape-resonances is well established; however, no experimental information is available yet on the second mechanism. Here, we show that the dissociation cross section for VFRs mediated by the formation of a dipole bound anion decreases as a function of a temperature. The change remains, however, relatively small in the temperature range of 370-440 K but it might be more pronounced at the extended temperature range.

  8. Unusually strong temperature dependence of P2X3 receptor traffic to the plasma membrane

    Directory of Open Access Journals (Sweden)

    Evgeny ePryazhnikov

    2011-12-01

    Full Text Available ATP-gated P2X3 receptors are expressed by nociceptive neurons and participate in transduction of pain. Responsiveness of P2X3 receptors is strongly enhanced at high temperatures, suggesting a role for these receptors in temperature detection. Since sustained responsiveness depends on receptor trafficking to the plasma membrane, we employed total-internal reflection fluorescence (TIRF microscopy to highlight perimembrane pool of DsRed-tagged P2X3 receptors and studied the effects of temperature on perimembrane turnover of P2X3-DsRed. Patch clamp recordings confirmed membrane expression of functional, rapidly desensitizing P2X3-DsRed receptors. By combining TIRF microscopy with the technique of fluorescence recovery after photobleaching (FRAP, we measured the rate of perimembrane turnover of P2X3-DsRed receptors expressed in hippocampal neurons. At room temperature, the P2X3-DsRed perimembrane turnover as measured by TIRF-FRAP had a time constant of ~2 min. At 29oC, receptor turnover was strongly accelerated, yielding an extremely high temperature dependence coefficient Q10 ~4.5. In comparison, AMPA receptor turnover measured with TIRF-FRAP was only moderately sensitive to temperature (Q10 ~1.5. The traffic inhibitor Brefeldin A selectively decelerated P2X3-DsRed receptor turnover at 29oC, but had no effect at 21oC (Q10 ~1.5. This indicates that receptor traffic to plasma membrane, rather than endosomal recycling, is the key temperature-sensitive component of P2X3 turnover. The selective inhibitor of the RhoA kinase Y27632 significantly decreased the temperature dependence of P2X3-DsRed receptor turnover (Q10 ~2.0. In summary, the RhoA kinase-dependent membrane trafficking of P2X3 receptors to plasma membrane has an exceptional sensitivity to temperature. These data link two fundamental sensory processes, thermoreception and nociception, which are likely co-involved in hyperthermia-associated pain states.

  9. Global patterns in lake ecosystem responses to warming based on the temperature dependence of metabolism.

    Science.gov (United States)

    Kraemer, Benjamin M; Chandra, Sudeep; Dell, Anthony I; Dix, Margaret; Kuusisto, Esko; Livingstone, David M; Schladow, S Geoffrey; Silow, Eugene; Sitoki, Lewis M; Tamatamah, Rashid; McIntyre, Peter B

    2017-05-01

    Climate warming is expected to have large effects on ecosystems in part due to the temperature dependence of metabolism. The responses of metabolic rates to climate warming may be greatest in the tropics and at low elevations because mean temperatures are warmer there and metabolic rates respond exponentially to temperature (with exponents >1). However, if warming rates are sufficiently fast in higher latitude/elevation lakes, metabolic rate responses to warming may still be greater there even though metabolic rates respond exponentially to temperature. Thus, a wide range of global patterns in the magnitude of metabolic rate responses to warming could emerge depending on global patterns of temperature and warming rates. Here we use the Boltzmann-Arrhenius equation, published estimates of activation energy, and time series of temperature from 271 lakes to estimate long-term (1970-2010) changes in 64 metabolic processes in lakes. The estimated responses of metabolic processes to warming were usually greatest in tropical/low-elevation lakes even though surface temperatures in higher latitude/elevation lakes are warming faster. However, when the thermal sensitivity of a metabolic process is especially weak, higher latitude/elevation lakes had larger responses to warming in parallel with warming rates. Our results show that the sensitivity of a given response to temperature (as described by its activation energy) provides a simple heuristic for predicting whether tropical/low-elevation lakes will have larger or smaller metabolic responses to warming than higher latitude/elevation lakes. Overall, we conclude that the direct metabolic consequences of lake warming are likely to be felt most strongly at low latitudes and low elevations where metabolism-linked ecosystem services may be most affected. © 2016 John Wiley & Sons Ltd.

  10. Monte Carlo method for photon heating using temperature-dependent optical properties.

    Science.gov (United States)

    Slade, Adam Broadbent; Aguilar, Guillermo

    2015-02-01

    The Monte Carlo method for photon transport is often used to predict the volumetric heating that an optical source will induce inside a tissue or material. This method relies on constant (with respect to temperature) optical properties, specifically the coefficients of scattering and absorption. In reality, optical coefficients are typically temperature-dependent, leading to error in simulation results. The purpose of this study is to develop a method that can incorporate variable properties and accurately simulate systems where the temperature will greatly vary, such as in the case of laser-thawing of frozen tissues. A numerical simulation was developed that utilizes the Monte Carlo method for photon transport to simulate the thermal response of a system that allows temperature-dependent optical and thermal properties. This was done by combining traditional Monte Carlo photon transport with a heat transfer simulation to provide a feedback loop that selects local properties based on current temperatures, for each moment in time. Additionally, photon steps are segmented to accurately obtain path lengths within a homogenous (but not isothermal) material. Validation of the simulation was done using comparisons to established Monte Carlo simulations using constant properties, and a comparison to the Beer-Lambert law for temperature-variable properties. The simulation is able to accurately predict the thermal response of a system whose properties can vary with temperature. The difference in results between variable-property and constant property methods for the representative system of laser-heated silicon can become larger than 100K. This simulation will return more accurate results of optical irradiation absorption in a material which undergoes a large change in temperature. This increased accuracy in simulated results leads to better thermal predictions in living tissues and can provide enhanced planning and improved experimental and procedural outcomes. Copyright

  11. Temperature-dependent modulation of regional lymphatic contraction frequency and flow.

    Science.gov (United States)

    Solari, Eleonora; Marcozzi, Cristiana; Negrini, Daniela; Moriondo, Andrea

    2017-11-01

    Lymph drainage and propulsion are sustained by an extrinsic mechanism, based on mechanical forces acting from the surrounding tissues against the wall of lymphatic vessels, and by an intrinsic mechanism attributable to active spontaneous contractions of the lymphatic vessel muscle. Despite being heterogeneous, the mechanisms underlying the generation of spontaneous contractions share a common biochemical nature and are thus modulated by temperature. In this study, we challenged excised tissues from rat diaphragm and hindpaw, endowed with spontaneously contracting lymphatic vessels, to temperatures from 24°C (hindpaw) or 33°C (diaphragmatic vessels) to 40°C while measuring lymphatic contraction frequency (fc) and amplitude. Both vessel populations displayed a sigmoidal relationship between fc and temperature, each centered around the average temperature of surrounding tissue (36.7 diaphragmatic and 32.1 hindpaw lymphatics). Although the slope factor of the sigmoidal fit to the fc change of hindpaw vessels was 2.3°C·cycles-1·min-1, a value within the normal range displayed by simple biochemical reactions, the slope factor of the diaphragmatic lymphatics was 0.62°C·cycles-1·min-1, suggesting the added involvement of temperature-sensing mechanisms. Lymph flow calculated as a function of temperature confirmed the relationship observed on fc data alone and showed that none of the two lymphatic vessel populations would be able to adapt to the optimal working temperature of the other tissue district. This poses a novel question whether lymphatic vessels might not adapt their function to accommodate the change if exposed to a surrounding temperature, which is different from their normal condition.NEW & NOTEWORTHY This study demonstrates to what extent lymphatic vessel intrinsic contractility and lymph flow are modulated by temperature and that this modulation is dependent on the body district that the vessels belong to, suggesting a possible functional misbehavior

  12. Temperature dependent growth, feeding, nutritional condition and aerobic metabolism of juvenile spiny lobster, Sagmariasus verreauxi.

    Science.gov (United States)

    Fitzgibbon, Quinn P; Simon, Cedric J; Smith, Gregory G; Carter, Chris G; Battaglene, Stephen C

    2017-05-01

    We examined the effects of temperature on the growth, feeding, nutritional condition and aerobic metabolism of juvenile spiny lobster, Sagmariasus verreauxi, in order to determine if temperature acclimated aerobic scope correlates with optimum for growth and to establish the thermal tolerance window for this emerging aquaculture species. Juvenile lobsters (initial weight=10.95±0.47g) were reared (n=7) at temperatures from 11.0 to 28.5°C for 145days. All lobsters survived from 14.5 to 25.0°C while survival was reduced at 11.0°C (86%) and all lobsters died at 28.5°C. Lobster specific growth rate and specific feed consumption displayed a unimodal response with temperature, peaking at 21.5°C. Lobster standard, routine and maximum metabolic rates, and aerobic scope all increased exponentially up to maximum non-lethal temperature. Optimum temperature for growth did not correspond to that for maximum aerobic scope suggesting that aerobic scope is not an effective predictor of the thermal optimum of spiny lobsters. Plateauing of specific feed consumption beyond 21.5°C suggests that temperature dependent growth of lobsters is limited by capacity to ingest or digest sufficient food to meet increasing maintenance metabolic demands at high temperatures. The nutritional condition of lobsters was not influenced by temperature and feed conversion ratio was improved at lower temperatures. These findings add to a growing body of evidence questioning the generality of aerobic scope to describe the physiological thermal boundaries of aquatic ectotherms and suggest that feed intake plays a crucial role in regulating performance at thermal extremes. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Temperature and ionization balance dependence of O VII line ratios. [in solar corona

    Science.gov (United States)

    Acton, L. W.; Brown, W. A.

    1978-01-01

    The forbidden-plus-intersystem to resonance line ratio (G) for the heliumlike ion O VII is calculated, taking into account cascades, blended satellite lines, and radiative plus dielectric recombination. It is noted that G is of particular use for investigating radiative-transfer effects and nonequilibrium ionization in the solar corona and that the calculations are applicable to a low-density optically thin Maxwellian plasma. The temperature dependence of G is considered for the case of a steady-state equilibrium plasma, and the effect of departures from ionization equilibrium on G is examined. It is found that G is quite insensitive to temperature over the range from 600,000 to 6 million K for a steady-state plasma, but that recombinations may be suppressed or dominant, depending on the relative abundance of O VIII, for a plasma in which the state of ionization is not in equilibrium with the electron temperature. This latter effect is shown to be capable of causing large variations in G that are dependent on electron temperature.

  14. 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).

  15. 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.

  16. The temperature dependence of the BK channel activity - kinetics, thermodynamics, and long-range correlations.

    Science.gov (United States)

    Wawrzkiewicz-Jałowiecka, Agata; Dworakowska, Beata; Grzywna, Zbigniew J

    2017-10-01

    Large-conductance, voltage dependent, Ca2+-activated potassium channels (BK) are transmembrane proteins that regulate many biological processes by controlling potassium flow across cell membranes. Here, we investigate to what extent temperature (in the range of 17-37°C with ΔT=5°C step) is a regulating parameter of kinetic properties of the channel gating and memory effect in the series of dwell-time series of subsequent channel's states, at membrane depolarization and hyperpolarization. The obtained results indicate that temperature affects strongly the BK channels' gating, but, counterintuitively, it exerts no effect on the long-range correlations, as measured by the Hurst coefficient. Quantitative differences between dependencies of appropriate channel's characteristics on temperature are evident for different regimes of voltage. Examining the characteristics of BK channel activity as a function of temperature allows to estimate the net activation energy (Eact) and changes of thermodynamic parameters (ΔH, ΔS, ΔG) by channel opening. Larger Eact corresponds to the channel activity at membrane hyperpolarization. The analysis of entropy and enthalpy changes of closed to open channel's transition suggest the entropy-driven nature of the increase of open state probability during voltage activation and supports the hypothesis about the voltage-dependent geometry of the channel vestibule. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Time-Dependent Behavior of Shrinkage Strain for Early Age Concrete Affected by Temperature Variation

    Directory of Open Access Journals (Sweden)

    Yu Qin

    2017-01-01

    Full Text Available Shrinkage has been proven to be an important property of early age concrete. The shrinkage strain leads to inherent engineering problems, such as cracking and loss of prestress. Atmospheric temperature is an important factor in shrinkage strain. However, current research does not provide much attention to the effect of atmospheric temperature on shrinkage of early age concrete. In this paper, a laboratory study was undertaken to present the time-dependent shrinkage of early age concrete under temperature variation. A newly developed Material Deformation Tester (MDT, which can simulate consecutive variation of atmospheric temperature, was used to collect the shrinkage strain of specimens and temperature data. A numerical model was established to describe the thermoelastic strain of a specimen. The results show that (1 there are several sharp shrinkages up to 600 μ for early age concrete in the first 3 days; (2 the absolute value of shrinkage strain is larger than thermal strain; and (3 the difference of shrinkage strain under temperature variation or constant temperature is up to 500 μ.

  18. Plasmon resonance enhanced temperature-dependent photoluminescence of Si-V centers in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Shaoheng [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Song, Jie; Wang, Qiliang; Liu, Junsong; Li, Hongdong, E-mail: hdli@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Zhang, Baolin [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China)

    2015-11-23

    Temperature dependent optical property of diamond has been considered as a very important factor for realizing high performance diamond-based optoelectronic devices. The photoluminescence feature of the zero phonon line of silicon-vacancy (Si-V) centers in Si-doped chemical vapor deposited single crystal diamond (SCD) with localized surface plasmon resonance (LSPR) induced by gold nanoparticles has been studied at temperatures ranging from liquid nitrogen temperature to 473 K, as compared with that of the SCD counterpart in absence of the LSPR. It is found that with LSPR the emission intensities of Si-V centers are significantly enhanced by factors of tens and the magnitudes of the redshift (width) of the emissions become smaller (narrower), in comparison with those of normal emissions without plasmon resonance. More interestingly, these strong Si-V emissions appear remarkably at temperatures up to 473 K, while the spectral feature was not reported in previous studies on the intrinsic Si-doped diamonds when temperatures are higher than room temperature. These findings would lead to reaching high performance diamond-based devices, such as single photon emitter, quantum cryptography, biomarker, and so forth, working under high temperature conditions.

  19. 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.

  20. Temperature dependent fracture properties of shape memory alloys: novel findings and a comprehensive model.

    Science.gov (United States)

    Maletta, Carmine; Sgambitterra, Emanuele; Niccoli, Fabrizio

    2016-12-21

    Temperature dependent fracture properties of NiTi-based Shape Memory Alloys (SMAs), within the pseudoelastic regime, were analyzed. In particular, the effective Stress Intensity Factor (SIF) was estimated, at different values of the testing temperature, by a fitting of the William's expansion series, based on Digital Image Correlation (DIC) measurements. It was found that temperature plays an important role on SIF and on critical fast fracture conditions. As a consequence, Linear Elastic Fracture Mechanics (LEFM) approaches are not suitable to predict fracture properties of SMAs, as they do not consider the effects of temperature. On the contrary, good agreements between DIC results and the predictions of an ad-hoc analytical model were observed. In fact, the model takes into account the whole thermo mechanical loading condition, including both mechanical load and temperature. Results revealed that crack tip stress-induced transformations do not represent a toughening effect and this is a completely novel result within the SMA community. Furthremore, it was demonstrated that the analytical model can be actually used to define a temperature independent fracture toughness parameter. Therefore, a new approach is proposed, based on the analytical model, where both mechanical load and temperature are considered as loading parameters in SIF computation.

  1. Temperature dependent lattice misfit in nickel-base superalloys - Simulation and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Neumeier, Steffen; Goeken, Mathias [Lehrstuhl fuer Allgemeine Werkstoffeigenschaften, Universitaet Erlangen-Nuernberg, Erlangen (Germany)

    2011-07-01

    Ni-base superalloys are widely used in high temperature applications like jet engines and land-based turbines, because of their excellent high temperature properties. They derive their excellent high temperature strength and creep resistance from the presence of a high volume fraction of Ni{sub 3}Al {gamma}{sup '} precipitates (L1{sub 2} structure), which are embedded coherently within the face centred cubic (A1) {gamma} matrix. The magnitude and sign of the lattice misfit between {gamma} and {gamma}{sup '} are important parameters affecting the microstructural evolution and high temperature strength of Ni-base superalloys. Therefore the knowledge of the lattice misfit at application temperature is of great importance. In this study the lattice misfit of several 1{sup st}, 2{sup nd} and 4{sup th} generation Ni-base superalloys in dependence of temperature has been measured by means of HRXRD and compared with lattice misfit simulations based on thermodynamic calculations. The influence of the thermal expansion coefficients and the change in the chemical composition of both {gamma} and {gamma}{sup '} due to the {gamma}{sup '} dissolution with increasing temperature has been taking into account. The experimentally measured {gamma} and {gamma}{sup '} lattice parameters could be reproduced by the simulation and the {gamma}/{gamma}{sup '} lattice misfit could be reasonably predicted.

  2. 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.

  3. 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.

  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-Dependent Photoluminescence Emission from Unstrained and Strained GaSe Nanosheets

    Directory of Open Access Journals (Sweden)

    Duan Zhang

    2017-11-01

    Full Text Available Two-dimensional AIIIBVI layered semiconductors have recently attracted great attention due to their potential applications in piezo-phototronics and optoelectronics. Here, we report the temperature-dependent photoluminescence (PL of strained and unstrained GaSe flakes. It is found that, as the temperature increases, the PL from both the strained (wrinkled and unstrained (flat positions show a prominent red-shift to low energies. However, for the flat case, the slope of PL energy versus temperature at the range of 163–283 K is about −0.36 meV/K, which is smaller than that of the wrinkled one (−0.5 meV/K. This is because more strain can be introduced at the freestanding wrinkled position during the temperature increase, thus accelerates the main PL peak (peak I, direct band gap transition shift to lower energy. Additionally, for the wrinkled sheet, three new exciton states (peaks III, IV, and V appear at the red side of peak I, and the emission intensity is highly dependent on the temperature variation. These peaks can be attributed to the bound exciton recombination. These findings demonstrate an interesting route for optical band gap tuning of the layered GaSe sheet, which are important for future optoelectronic device design.

  6. 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.

  7. 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.

  8. Expected changes in future temperature extremes and their elevation dependency over the Yellow River source region

    Directory of Open Access Journals (Sweden)

    Y. Hu

    2013-07-01

    Full Text Available Using the Statistical DownScaling Model (SDSM and the outputs from two global climate models, we investigate possible changes in mean and extreme temperature indices and their elevation dependency over the Yellow River source region for the two future periods 2046–2065 and 2081–2100 under the IPCC SRES A2, A1B and B1 emission scenarios. Changes in interannual variability of mean and extreme temperature indices are also analyzed. The validation results show that SDSM performs better in reproducing the maximum temperature-related indices than the minimum temperature-related indices. The projections show that by the middle and end of the 21st century all parts of the study region may experience increases in both mean and extreme temperature in all seasons, along with an increase in the frequency of hot days and warm nights and with a decrease in frost days. By the end of the 21st century, interannual variability increases in all seasons for the frequency of hot days and warm nights and in spring for frost days while it decreases for frost days in summer. Autumn demonstrates pronounced elevation-dependent changes in which around six out of eight indices show significant increasing changes with elevation.

  9. 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.

  10. 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.

  11. Size dependence study of the ordering temperature in the Fast Monte Carlo method

    Energy Technology Data Exchange (ETDEWEB)

    Velasquez, E. A., E-mail: eavelas@gmail.com [Universidad de San Buenaventura Seccional Medellin, Grupo de Investigacion en Modelamiento y Simulacion Computacional, Facultad de Ingenierias (Colombia); Mazo-Zuluaga, J., E-mail: johanmazo@gmail.com [Universidad de Antioquia, Grupo de Estado Solido, Grupo de Instrumentacion Cientifica y Microelectronica, Instituto de Fisica-FCEN (Colombia); Mejia-Lopez, J., E-mail: jmejia@puc.cl [Universidad de Antioquia, Instituto de Fisica-FCEN (Colombia)

    2013-02-15

    Based on the framework of the Fast Monte Carlo approach, we study the diameter dependence of the ordering temperature in magnetic nanostructures of cylindrical shape. For the purposes of this study, Fe cylindrical-shaped samples of different sizes (20 nm height, 30-100 nm in diameter) have been chosen, and their magnetic properties have been computed as functions of the scaled temperature. Two main set of results are concluded: (a) the ordering temperature of nanostructures follows a linear scaling relationship as a function of the scaling factor x, for all the studied sizes. This finding rules out a scaling relation T Prime {sub c} = x{sup 3{eta}}T{sub c} (where {eta} is a scaling exponent, and T Prime {sub c} and T{sub c} are the scaled and true ordering temperatures) that has been proposed in the literature, and suggests that temperature should scale linearly with the scaling factor x. (b) For the nanostructures, there are three different order-disorder magnetic transition modes depending on the system's size, in very good agreement with previous experimental reports.

  12. 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).

  13. 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

  14. 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

  15. Strong temperature dependence of extraordinary magnetoresistance correlated to mobility in a two-contact device

    KAUST Repository

    Sun, Jian

    2012-02-21

    A two-contact extraordinary magnetoresistance (EMR) device has been fabricated and characterized at various temperatures under magnetic fields applied in different directions. Large performance variations across the temperature range have been found, which are due to the strong dependence of the EMR effect on the mobility. The device shows the highest sensitivity of 562ω/T at 75 K with the field applied perpendicularly. Due to the overlap between the semiconductor and the metal shunt, the device is also sensitive to planar fields but with a lower sensitivity of about 20 to 25% of the one to perpendicular fields. © 2012 The Japan Society of Applied Physics.

  16. Measurements of extreme orientation-dependent temperature increase around an irradiated gold nanorod

    DEFF Research Database (Denmark)

    Ma, Haiyan; Bendix, Pól Martin; Oddershede, Lene Broeng

    2012-01-01

    as nanoscopic heat transducers, it is essential to know how the photothermal efficiency depends on parameters like size and shape. Here we present the measurements of the temperature profile around single irradiated gold nanorods and nanospheres placed on a biologically relevant matrix, a lipid bilayer. [1......] We developed a novel assay based on molecular partitioning between two coexisting phases, the gel and fluid phase, within the bilayer. [2, 3] This assay allows for a direct measurement of local temperature gradients, an assay which does not necessitate any pre-assumptions about...

  17. 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.

  18. 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.

  19. Patterns in new dimensionless quantities containing melting temperature, and their dependence on pressure

    Directory of Open Access Journals (Sweden)

    U. WALZER

    1980-06-01

    Full Text Available The relationships existing between melting temperature and other
    macroscopic physical quantities are investigated. A new dimensionless
    quantity Q(1 not containing the Grtineisen parameter proves to be suited for serving in future studies as a tool for the determination of the melting temperature in the outer core of the Earth. The pressure dependence of more general dimensionless quantities Q„ is determined analytically and, for the chemical elements, numerically, too. The patterns of various interesting dimensionless quantities are shown in the Periodic Table and compared.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Unusual temperature dependence in the low-temperature specific heat of U3Ni5Al19

    Science.gov (United States)

    Kim, J. S.; Stewart, G. R.; Bauer, E. D.; Ronning, F.

    2008-10-01

    Specific heat has been measured down to 0.053 K on a single crystal of the heavy-fermion antiferromagnet U3Ni5Al19 that orders at TN=23K . As has been previously reported, these data can be fitted between 0.4 and 4 K by the spin-fluctuation model of Moriya and Takimoto, which describes the contribution of weakly interacting critical spin fluctuations to the specific heat, C , where, as T→0 , C/T=γ0-a√T . However, below 0.35 K a noticeable divergence in C/ Ttilde logT dependence, consistent with the existence of strongly interacting fluctuations, is observed. This increase in the divergence of C/T at the lowest temperatures—which is contrary to the self-consistent renormalization theory of Moriya and Takimoto, which predicts √T dependence for C/T as T→0 and logT dependence at higher temperatures—has been measured as a function of magnetic field to further understand its origin. The field data in the low-temperature regime, where C/ Ttilde logT exhibit scaling with ΔB/T1.9 , further evidence that there exist strongly interacting fluctuations below 0.35 K in U3Ni5Al19 .

  5. 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.

  6. Channelled flow of lava with temperature dependent pseudoplastic rheology: condition for tube formation

    Science.gov (United States)

    Filippucci, Marilena; Tallarico, Andrea; Dragoni, Michele

    2010-05-01

    Conditions for crust and tube formation are studied assuming for lava a pseudoplastic rheology dependent on temperature (Sonder, pers. Comm.). The pseudoplasticity is the rheological model which, from recent laboratory studies, better describes the behaviour of basaltic lava (e.g. Sonder et al., 2006). The pseudoplastic rheology belongs to the power law rheology and the constitutive equation for a power law fluid is the following: σij = 2kdot en-1dot eij (1) where k is the fluid consistency, n is the power law exponent and e depends on the second invariant of the deformation rate tensor. For a pseudoplastic fluid we have that n

  7. Mechanical properties of NiO/Ni-YSZ composites depending on temperature, porosity and redox cycling

    DEFF Research Database (Denmark)

    Pihlatie, Mikko; Kaiser, Andreas; Mogensen, Mogens Bjerg

    2009-01-01

    %. For all samples a linear relation between Young's modulus and porosity was found. The temperature dependency of the mechanical properties of both as-sintered and reduced composites was investigated by IET up to 1200 degrees C. In the as-sintered state, first an increase and peak of stiffness coinciding...... increased above ca. 600 degrees C and was found to be very dependent on microstructure. Damage caused by redox cycling degraded the elastic properties of the composites. Degradation started linearly from 0.5 to 0.6% redox strain leading to macroscopic sample failures at about 2.5% dL/L-o. A simple continuum...

  8. 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

  9. 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...

  10. 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.

  11. 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.

  12. 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.

  13. Temperature dependence of an abiotic glucose/air alkaline fuel cell

    Science.gov (United States)

    Orton, Dane; Scott, Daniel

    2015-11-01

    The temperature dependence of a previously developed glucose fuel cell is explored. This cell uses a small molecule dye mediator to transport oxidizable electrons from glucose to a carbon felt anode. This reaction is driven by an air breathing MnO2 cathode. This research investigates how the temperature of the system affects the power production of the fuel cell. Cell performance is observed using either methyl viologen, indigo carmine, trypan blue, or hydroquinone as a mediator at temperatures of 15, 19, 27, 32, 37, 42, and 49 °C. Cyclic voltammetry of the cell anode at the given temperatures with the individual dyes is also presented. The highest power production amongst all of the cells occurs at 32 °C. This occurs with the mediator indigo carmine or with the mediator methyl viologen. These sustained powers are 2.31 mW cm-2 and 2.39 mW cm-2, respectively. This is approximately a 350% increase for these cells compared to their power produced at room temperature. This dramatic increase is likely due to increased solubility of the mediator dye at higher temperatures.

  14. Temperature and time dependence of the electro-mechanical properties of flexible active fiber composites

    Science.gov (United States)

    Ben Atitallah, H.; Ounaies, Z.; Muliana, A.

    2016-04-01

    Active fiber composites (AFCs) are comprised of piezoelectric fibers embedded in a polymeric matrix. AFCs use interdigitated electrodes, which produce electric field lines parallel to the fiber direction, thus taking advantage of the larger d 33 piezoelectric coefficient. The polymer volume content of the AFCs is generally more than 50%; since polymers tend to have behaviors affected by their viscoelastic characteristics especially at elevated temperatures, it is necessary to understand the thermo-electro-mechanical behavior of AFCs at different loading rates. In this study, mechanical, electrical and electromechanical properties of AFCs were measured at different isothermal temperatures, namely 25 °C, 50 °C and 75 °C and at different loading rates. The measurements of all the properties of AFCs were done along the fiber direction. It was found that at higher temperatures, the modulus and tensile strength decreased for all strain rates and the strain at failure increased. The remnant polarization increased with decrease in frequency and increase in temperature; however, the coercive field decreased with temperature and was not affected by the frequency. Due to the viscoelastic behavior of the epoxy, the piezoelectric coefficient d 33 increased at higher temperature and lower frequency. It was also noted that this coefficient is dependent on the magnitude of the electric field.

  15. 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.

  16. 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.

  17. Frequency and Temperature Dependence of Electrical Breakdown at 21, 30 and 39 GHz

    CERN Document Server

    Braun, Hans Heinrich; Wilson, Ian H; Wuensch, Walter

    2003-01-01

    A TeV-range e+e- linear collider has emerged as one of the most promising candidates to extend the high energy frontier of experimental elementary particle physics. A high accelerating gradient for such a collider is desirable to limit its overall length. Accelerating gradient is mainly limited by electrical breakdown, and it has been generally assumed that this limit increases with increasing frequency for normal-conducting accelerating structures. Since the choice of frequency has a profound influence on the design of a linear collider, the frequency dependence of breakdown has been measured using six exactly scaled single-cell cavities at 21, 30, and 39 GHz. The influence of temperature on breakdown behavior was also investigated. The maximum obtainable surface fields were found to be in the range of 300 to 400 MV/m for copper, with no significant dependence on either frequency or temperature.

  18. Weak antilocalization effect in exfoliated black phosphorus revealed by temperature- and angle-dependent magnetoconductivity

    KAUST Repository

    Hou, Zhipeng

    2018-01-10

    Recently, there have been increasingly debates on whether there exists a surface resonance state (SRS) in black phosphorus (BP), as suggested by recent angle-resolved photoemission spectroscopy (ARPES) results. To resolve this issue, we have performed temperature- and angle-dependent magnetoconductivity measurements on exfoliated, high-quality BP single crystals. A pronounced weak-antilocalization (WAL) effect was observed within a narrow temperature range of 8 - 16 K, with the electrical current flowing parallel to the cleaved ac-plane (along the a- or c-axis) and the magnetic field along the b-axis. The angle-dependent magnetoconductivity and the Hikami-Larkin-Nagaoka (HLN) model-fitted results have revealed that the observed WAL effect shows surface-bulk coherent features, which supports the existence of SRS in black phosphorus.

  19. 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.

  20. 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.)

  1. 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

  2. Flow properties of oral contrast medium formulations depend on the temperature.

    Science.gov (United States)

    Ekberg, Olle; Stading, Mats; Johansson, Daniel; Bülow, Margareta; Ekman, Susanne; Wendin, Karin

    2010-05-01

    During the therapeutic videofluoroscopic examination of swallowing, gradation of bolus volume, texture, and viscosity can be implemented to determine the optimal bolus characteristics in that particular patient. When a thickened liquid is given to a dysphagic patient it is served at room temperature. However, in these patients with a delayed oral and/or pharyngeal stage of swallow, the bolus is held for a long time in the oral cavity. The temperature of the thickened liquid thereby increases. To study the rheological exploration (variation of viscosity with temperature) of thickened food used for radiologic swallowing examinations in patients with oral and pharyngeal dysfunction, in particular in mixtures of barium sulfate suspensions and in iodine solutions. Deep-frozen mango purée was thawed at room temperature. It was then mixed with barium sulfate contrast medium to a density of 25% w/w. Resorce Thicken Up was mixed at room temperature at two concentrations: 4.3% w/w (4.5 g thickener + 100 g distilled water) and 6.0% w/w (4.5 g thickener + 70 g distilled water). The thickener consisted of modified corn starch. Resorce Thicken Up was also mixed at room temperature with two concentrations of an iodine contrast material, iohexol (Omnipaque, 350 mg I/ml). The two concentrations were: 4.3% w/w (4.5 g thickener + 100 g iohexol) and 6% w/w (6 g thickener + 100 g iohexol). Measurements were carried out from 20 degrees C to 37 degrees C using a Stresstech HR rheometer. The rheometer was equipped with a concentric cylinder measuring system (inner cylinder 15 mm). The samples containing thickener in water as well as in iohexol showed a dependence on thickener concentration and temperature. The mango purée with barium sulfate displayed very small temperature dependence. The thickener solutions in iohexol had significantly higher viscosity compared with the other thickener solutions and the mango purée. The relative decrease shows that mango purée, the 6% thickener

  3. Mechanisms of temperature-dependent swimming: the importance of physics, physiology and body size in determining protist swimming speed.

    Science.gov (United States)

    Beveridge, Oliver S; Petchey, Owen L; Humphries, Stuart

    2010-12-15

    Body temperatures and thus physiological rates of poikilothermic organisms are determined by environmental temperature. The power an organism has available for swimming is largely dependent on physiological rates and thus body temperature. However, retarding forces such as drag are contingent on the temperature-dependent physical properties of water and on an organism's size. Consequently, the swimming ability of poikilotherms is highly temperature dependent. The importance of the temperature-dependent physical properties of water (e.g. viscosity) in determining swimming speed is poorly understood. Here we propose a semi-mechanistic model to describe how biological rates, size and the physics of the environment contribute to the temperature dependency of microbial swimming speed. Data on the swimming speed and size of a predatory protist and its protist prey were collected and used to test our model. Data were collected by manipulating both the temperature and the viscosity (independently of temperature) of the organism's environment. Protists were either cultured in their test environment (for several generations) or rapidly exposed to their test environment to assess their ability to adapt or acclimate to treatments. Both biological rates and the physics of the environment were predicted to and observed to contribute to the swimming speed of protists. Body size was not temperature dependent, and protists expressed some ability to acclimate to changes in either temperature or viscosity. Overall, using our parameter estimates and novel model, we are able to suggest that 30 to 40% (depending on species) of the response in swimming speed associated with a reduction in temperature from 20 to 5°C is due to viscosity. Because encounter rates between protist predators and their prey are determined by swimming speed, temperature- and viscosity-dependent swimming speeds are likely to result in temperature- and viscosity-dependent trophic interactions.

  4. 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

  5. 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...

  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. 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.

  8. Molecular Based Temperature and Strain Rate Dependent Yield Criterion for Anisotropic Elastomeric Thin Films

    Science.gov (United States)

    Bosi, F.; Pellegrino, S.

    2017-01-01

    A molecular formulation of the onset of plasticity is proposed to assess temperature and strain rate effects in anisotropic semi-crystalline rubbery films. The presented plane stress criterion is based on the strain rate-temperature superposition principle and the cooperative theory of yielding, where some parameters are assumed to be material constants, while others are considered to depend on specific modes of deformation. An orthotropic yield function is developed for a linear low density polyethylene thin film. Uniaxial and biaxial inflation experiments were carried out to determine the yield stress of the membrane via a strain recovery method. It is shown that the 3% offset method predicts the uniaxial elastoplastic transition with good accuracy. Both the tensile yield points along the two principal directions of the film and the biaxial yield stresses are found to obey the superposition principle. The proposed yield criterion is compared against experimental measurements, showing excellent agreement over a wide range of deformation rates and temperatures.

  9. Implementation of a method for calculating temperature-dependent resistivities in the KKR formalism

    Science.gov (United States)

    Mahr, Carsten E.; Czerner, Michael; Heiliger, Christian

    2017-10-01

    We present a method to calculate the electron-phonon induced resistivity of metals in scattering-time approximation based on the nonequilibrium Green's function formalism. The general theory as well as its implementation in a density-functional theory based Korringa-Kohn-Rostoker code are described and subsequently verified by studying copper as a test system. We model the thermal expansion by fitting a Debye-Grüneisen curve to experimental data. Both the electronic and vibrational structures are discussed for different temperatures, and employing a Wannier interpolation of these quantities we evaluate the scattering time by integrating the electron linewidth on a triangulation of the Fermi surface. Based thereupon, the temperature-dependent resistivity is calculated and found to be in good agreement with experiment. We show that the effect of thermal expansion has to be considered in the whole calculation regime. Further, for low temperatures, an accurate sampling of the Fermi surface becomes important.

  10. Temperature dependence of the transverse piezoelectric coefficient of thin films and aging effects

    Energy Technology Data Exchange (ETDEWEB)

    Rossel, C., E-mail: rsl@zurich.ibm.com; Sousa, M.; Abel, S.; Caimi, D. [IBM Research—Zurich, CH-8803 Rüschlikon (Switzerland); Suhm, A.; Abergel, J.; Le Rhun, G.; Defay, E. [CEA-LETI, Minatec, 17 rue des Martyrs, F-38054 Grenoble (France)

    2014-01-21

    We present a technique to measure the temperature dependence of the transverse piezoelectric coefficient e{sub 31,f} of thin films of lead zirconate titanate (PZT), aluminum nitride, and BaTiO{sub 3} deposited on Si wafers. It is based on the collection of electric charges induced by the deflection of a Si cantilever coated with the piezoelectric film. The aim of this work is to assess the role of temperature in the decay of the remnant polarization of these materials, in particular, in optimized gradient-free PZT with composition PbZr{sub 0.52}Ti{sub 0.48}O{sub 3}. It is found that in contrast to theoretical predictions, e{sub 31,f} decreases with temperature because of the dominance of relaxation effects. The observation of steps in the logarithmic aging decay law is reminiscent of memory effects seen in frustrated spin glasses.

  11. Temperature dependence of the optical absorption spectra of InP/ZnS quantum dots

    Science.gov (United States)

    Savchenko, S. S.; Vokhmintsev, A. S.; Weinstein, I. A.

    2017-03-01

    The optical-absorption spectra of InP/ZnS (core/shell) quantum dots have been studied in a broad temperature range of T = 6.5-296 K. Using the second-order derivative spectrophotometry technique, the energies of optical transitions at room temperature were found to be E 1 = 2.60 ± 0.02 eV (for the first peak of excitonic absorption in the InP core) and E 2 = 4.70 ± 0.02 eV (for processes in the ZnS shell). The experimental curve of E 1( T) has been approximated for the first time in the framework of a linear model and in terms of the Fan's formula. It is established that the temperature dependence of E 1 is determined by the interaction of excitons and longitudinal acoustic phonons with hω = 15 meV.

  12. Role of temperature-dependent spin model parameters in ultra-fast magnetization dynamics

    Science.gov (United States)

    Deák, A.; Hinzke, D.; Szunyogh, L.; Nowak, U.

    2017-08-01

    In the spirit of multi-scale modelling magnetization dynamics at elevated temperature is often simulated in terms of a spin model where the model parameters are derived from first principles. While these parameters are mostly assumed temperature-independent and thermal properties arise from spin fluctuations only, other scenarios are also possible. Choosing bcc Fe as an example, we investigate the influence of different kinds of model assumptions on ultra-fast spin dynamics, where following a femtosecond laser pulse, a sample is demagnetized due to a sudden rise of the electron temperature. While different model assumptions do not affect the simulational results qualitatively, their details do depend on the nature of the modelling.

  13. Temperature-Dependent Light-Stabilized States in Thin-Film PV Modules

    Energy Technology Data Exchange (ETDEWEB)

    Deceglie, Michael G.; Silverman, Timothy J.; Marion, Bill; Kurtz, Sarah R.

    2015-06-14

    Thin-film photovoltaic modules are known to exhibit light-induced transient behavior which interferes with accurate and repeatable measurements of power. Typically power measurements are made after a light exposure in order to target a 'light state' of the module that is representative of outdoor performance. Here we show that the concept of a unique light state is poorly defined for both CIGS and CdTe modules. Instead we find that their metastable state after a light exposure can depend on the temperature of the module during the exposure. We observe changes in power as large as 5.8% for a 20 degrees C difference in light exposure temperature. These results lead us to conclude that for applications in which reproducibility and repeatability are critical, module temperature should be tightly controlled during light exposure.

  14. Temperature dependence of graphene and N-doped graphene for gas sensor applications

    Science.gov (United States)

    Panyathip, R.; Choopun, S.; Singjai, P.; Sakulsermsuk, S.

    2017-09-01

    We report the response of graphene and N-doped graphene to ethanol vapor as gas sensors with varying the concentration of ethanol and temperature of graphene. Graphene was synthesized by chemical vapor deposition on copper foils and then was transferred to a glass slide by chemical etching. N-doped graphene was produced by annealing graphene in ammonia atmosphere. Results showed the response of both graphene and N-doped graphene are at low level up to 2.4%. The response of graphene increases with temperature up to 1.15%, but that of N-doped graphene decreases down to 0.30%. We proposed that the absorbed oxygen and nitrogen detachment are the key factors for the temperature dependence of the response of graphene and N-doped graphene, respectively.

  15. Temperature dependence of the photoluminescence polarization of ordered III-V semiconductor alloys

    Energy Technology Data Exchange (ETDEWEB)

    Prutskij, T.; Makarov, N. [Instituto de Ciencias, BUAP, Privada 17 Norte, No 3417, col. San Miguel Huyeotlipan, 72050 Puebla, Pue. (Mexico); Attolini, G. [IMEM/CNR, Parco Area delle Scienze 37/A, 43010 Parma (Italy)

    2016-03-21

    We studied the linear polarization of the photoluminescence (PL) emission of atomically ordered GaInAsP and GaInP alloys with different ordering parameters in the temperature range from 10 to 300 K. The epitaxial layers of these alloys were grown on GaAs and Ge (001) substrates by metal organic vapor phase epitaxy. The polarization of the PL emission propagating along different crystallographic axes depends on the value of biaxial strain in the layer and changes with temperature. We calculated the PL polarization patterns for different propagation directions as a function of biaxial strain using an existing model developed for ternary atomically ordered III-V alloys. Comparing the calculated PL polarization patterns with those obtained experimentally, we separated the variation of the PL polarization due to change of biaxial strain with temperature.

  16. Temperature dependence of BGO-CsI(Tl) phoswich detector properties

    Energy Technology Data Exchange (ETDEWEB)

    Piro, L.; Massaro, E.; Fiacconi, S.; Gigante, G.E.; Costa, E.

    1987-06-15

    We have studied the variations of the performances, and particularly the discrimination efficiency, of a BGO-CsI(Tl) phoswich detector in the temperature range 2.5-40/sup 0/C. The scintillation decay time evaluation has been carried out by means of a double constant fraction discriminator and a time to amplitude converter on 1 ..mu..s shaped pulses. Good discrimination between BGO and CsI(Tl) events has been obtained over the whole temperature range, even though small efficiency variations are present because of the relative displacement of the acceptance window of the discriminator due to the decay time dependence on temperature. A criterium to minimize this effect, useful in particular for the BGO-CsI(Tl) phoswhich, has been developed.

  17. Temperature dependence of the cross section for the fragmentation of thymine via dissociative electron attachment

    Energy Technology Data Exchange (ETDEWEB)

    Kopyra, Janina [Faculty of Science, Siedlce University, 3 Maja 54, 08-110 Siedlce (Poland); Abdoul-Carime, Hassan, E-mail: hcarime@ipnl.in2p3.fr [Université de Lyon, Université Claude Bernard Lyon1, Institut de Physique Nucléaire de Lyon, CNRS/IN2P3 UMR 5822, 43 Bd du 11 novembre 1918, 69622 Villeurbanne Cedex (France)

    2015-05-07

    Providing experimental values for absolute Dissociative Electron Attachment (DEA) cross sections for nucleobases at realistic biological conditions is a considerable challenge. In this work, we provide the temperature dependence of the cross section, σ, of the dehydrogenated thymine anion (T − H){sup −} produced via DEA. Within the 393-443 K temperature range, it is observed that σ varies by one order of magnitude. By extrapolating to a temperature of 313 K, the relative DEA cross section for the production of the dehydrogenated thymine anion at an incident energy of 1 eV decreases by 2 orders of magnitude and the absolute value reaches approximately 6 × 10{sup −19} cm{sup 2}. These quantitative measurements provide a benchmark for theoretical prediction and also a contribution to a more accurate description of the effects of ionizing radiation on molecular medium.

  18. Temperature-Dependent Light-Stabilized States in Thin-Film PV Modules: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Deceglie, Michael G.; Silverman, Timothy J.; Marion, Bill; Kurtz, Sarah R.

    2015-09-17

    Thin-film photovoltaic modules are known to exhibit light-induced transient behavior which interferes with accurate and repeatable measurements of power. Typically power measurements are made after a light exposure in order to target a 'light state' of the module that is representative of outdoor performance. Here we show that the concept of a unique light state is poorly defined for both CIGS and CdTe modules. Instead we find that their metastable state after a light exposure can depend on the temperature of the module during the exposure. We observe changes in power as large as 5.8% for a 20 degrees C difference in light exposure temperature. These results lead us to conclude that for applications in which reproducibility and repeatability are critical, module temperature should be tightly controlled during light exposure.

  19. 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.

  20. 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.

  1. Temperature-dependent optical properties of individual vascular wall components measured by optical coherence tomography.

    Science.gov (United States)

    van der Meer, Freek J; Faber, Dirk J; Cilesiz, Inci; van Gemert, Martin J C; van Leeuwen, Ton G

    2006-01-01

    Optical properties of tissues and tissue components are important parameters in biomedical optics. We report measurements of tissue refractive index n and the attenuation coefficient mu(t) using optical coherence tomography (OCT) of individual vascular wall layers and plaque components. Moreover, since the temperature dependence of optical properties is widely known, we compare measurements at room and body temperatures. A decrease of n and mu(t) is observed in all samples, with the most profound effect on samples with high lipid content. The sample temperature is of influence on the quantitative measurements within OCT images. For extrapolation of ex-vivo experimental results, especially for structures with high lipid content, this effect should be taken into account.

  2. Thermal stresses in a spherical pressure vessel having temperature-dependent, transversely isotropic, elastic properties

    Science.gov (United States)

    Tauchert, T. R.

    1976-01-01

    Rayleigh-Ritz and modified Rayleigh-Ritz procedures are used to construct approximate solutions for the response of a thick-walled sphere to uniform pressure loads and an arbitrary radial temperature distribution. The thermoelastic properties of the sphere are assumed to be transversely isotropic and nonhomogeneous; variations in the elastic stiffness and thermal expansion coefficients are taken to be an arbitrary function of the radial coordinate and temperature. Numerical examples are presented which illustrate the effect of the temperature-dependence upon the thermal stress field. A comparison of the approximate solutions with a finite element analysis indicates that Ritz methods offer a simple, efficient, and relatively accurate approach to the problem.

  3. Temperature dependence of the spin Seebeck effect in [Fe3O4/Pt]n multilayers

    Directory of Open Access Journals (Sweden)

    R. Ramos

    2017-05-01

    Full Text Available We report temperature dependent measurements of the spin Seebeck effect (SSE in multilayers formed by repeated growth of a Fe3O4/Pt bilayer junction. The magnitude of the observed enhancement of the SSE, relative to the SSE in the single bilayer, shows a monotonic increase with decreasing the temperature. This result can be understood by an increase of the characteristic length for spin current transport in the system, in qualitative agreement with the recently observed increase in the magnon diffusion length in Fe3O4 at lower temperatures. Our result suggests that the thermoelectric performance of the SSE in multilayer structures can be further improved by careful choice of materials with suitable spin transport properties.

  4. 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.

  5. Weak temperature dependence of ageing of structural properties in atomistic model glassformers

    Science.gov (United States)

    Jenkinson, Thomas; Crowther, Peter; Turci, Francesco; Royall, C. Patrick

    2017-08-01

    Ageing phenomena are investigated from a structural perspective in two binary Lennard-Jones glassformers, the Kob-Andersen and Wahnström mixtures. In both, the geometric motif assumed by the glassformer upon supercooling, the locally favoured structure (LFS), has been established. The Kob-Andersen mixture forms bicapped square antiprisms; the Wahnström model forms icosahedra. Upon ageing, we find that the structural relaxation time has a time-dependence consistent with a power law. However, the LFS population and potential energy increase and decrease, respectively, in a logarithmic fashion. Remarkably, over the time scales investigated, which correspond to a factor of 104 change in relaxation times, the rate at which these quantities age appears almost independent of temperature. Only at temperatures far below the Vogel-Fulcher-Tamman temperature do the ageing dynamics slow.

  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. 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.

  8. 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.

  9. A Differential Temperature-Dependent Dielectric Relaxation Study of Organoclay Cloisite^{TM}

    Science.gov (United States)

    Sharma, Abhimanyu; Kumar, Rohtash; Asokan, K.; Rawat, Kamla; Kanjilal, D.

    2017-01-01

    We report variation in the dielectric relaxation profiles of an important class of commercially available Cloisite ^{TM} organoclays, 25A, 15A, 30B and 10A, which are extensively used as rheology modifiers. A systematic and comprehensive comparison is made of their dielectric permittivity ({{ɛ}^' }}), and loss ({{ɛ}^' ' }}), conductivity ({σ}^' }) and loss tangent (tan δ ) parameters as function of temperature. The dispersion profiles showed relatively higher values for {{ɛ}^' }}, {ɛ}^' ' }}, σ^' } and tan δ for the Cloisite^{TM}30B samples in low-frequency region. A clear temperature-dependent transition in the values of {{ɛ}^' }} and {{ɛ}^' ' }} was noticed for Cloisite^{TM}25A sample at 436 K, which was independent of frequency, ω . The values of {{ɛ}^' }} and {{ɛ }^' ' }} showed 1/ω dependence with temperature. Cloisite^{TM}30B sample showed a marked decrease in the value of tan δ with increase in temperature compared to other samples. Thus, it was concluded that these clays bear signature dielectric properties regardless of the fact that they all belong to the same structural class of clays. Considering the large-scale use of these clays in many industrial products the above-mentioned results are of significant importance.

  10. Temperature dependent electrical transport characteristics of BaTiO3 modified lithium borate glasses

    Directory of Open Access Journals (Sweden)

    Vanita Thakur

    2015-08-01

    Full Text Available The glass samples with composition (70B2O3-29Li2O-1Dy2O3-xBT; x = 0, 10 and 20 weight percent, have been prepared by conventional melt quench technique. The dielectric measurements as a function of temperature have been carried out on these samples in the frequency range 1 Hz-10 MHz. The dielectric relaxation characteristics of these samples have been studied by analyzing dielectric spectroscopy, dielectric loss, electric modulus formulation and electrical conductivity spectroscopy. It is found that the dielectric permittivity of the samples increases with an increase in the temperature and BT content. The frequency dependent ac conductivity has been analyzed using Jonscher’s universal power law whereas non exponential KWW function has been invoked to fit the experimental data of the imaginary part of the electric modulus. The values of the activation energy determined from the electric modulus and that from dc conductivity have been found to be quite close to each other suggesting that the same type of charge barriers are involved in the relaxation and the conduction mechanisms. The stretched exponent (β and the power exponent (n have been found to be temperature and composition dependent. The decrease in n with an increase in temperature further suggested that the ac conduction mechanism of the studied samples follows the correlated barrier hopping (CBH model.

  11. 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.

  12. 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.

  13. Temperature-dependent optical properties of Cd(1-x),Zn(x),Te substitute material

    Science.gov (United States)

    Quijada, Manuel A.; Russell, Anne Marie; Hill, Robert J.

    2005-01-01

    In this study, we report cryogenic optical properties of Cd(l-x), Zn(x), Te wafers that are used as substrate seed layers in the manufacturing of HgCdTe focal-plane array detectors. These studies are motivated by the fact that the substrate optical properties influence the overall detector performance. The studies consist of measuring the substrate frequency dependent transmittance T(W) and reflectance R(W) above and below the optical band-gap in the UV/Visible and infrared frequency ranges, and with temperature variation of the sample from 5 to 300 K. Determination of the optical absorption from these measurements show that the optical absorption energy gap near 1.6 eV shows a substantial increase as the temperature is reduced from 300 to 5 K. Furthermore, we observe the presence of infrared-active optical phonons whose peak frequency shifts as the temperature of the sample is varied over the measured temperature range. The theoretical frequency dependent optical conductivity, with allowance for redistribution of spectral weight among the interband transition charge carriers, will be discussed.

  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. MATERIAL DEPENDENCE OF TEMPERATURE DISTRIBUTION IN MULTI-LAYER MULTI-METAL COOKWARE

    Directory of Open Access Journals (Sweden)

    MOHAMMADREZA SEDIGH

    2017-09-01

    Full Text Available Laminated structure is becoming more popular in cookware markets; however, there seems to be a lack of enough scientific studies to evaluate its pros and cons, and to show that how it functions. A numerical model using a finite element method with temperature-dependent material properties has been performed to investigate material and layer dependence of temperature distribution in multi-layer multi-metal plate exposed to irregular heating. Behavior of two parameters including mean temperature value and uniformity on the inner surface of plate under variations of thermal properties and geometrical conditions have been studied. The results indicate that conductive metals used as first layer in bi-layer plates have better thermal performance than those used in the second layer. In addition, since cookware manufacturers increasingly prefer to use all-clad aluminium plate, recently, this structure is analysed in the present study as well. The results show all-clad copper and aluminum plate possesses lower temperature gradient compared with single layer aluminum and all-clad aluminum core plates.

  16. Temperature dependence of interfacial properties and viscosity of nanofluids for droplet-based microfluidics

    Energy Technology Data Exchange (ETDEWEB)

    Murshed, S M Sohel; Tan, Say-Hwa; Nguyen, Nam-Trung [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)], E-mail: mntnguyen@ntu.edu.sg

    2008-04-21

    Interfacial tension and viscosity of a liquid play an important role in microfluidic systems. In this study, temperature dependence of surface tension, interfacial tension and viscosity of a nanofluid are investigated for its applicability in droplet-based microfluidics. Experimental results show that nanofluids having TiO{sub 2} nanoparticles of 15 nm diameter in deionized water exhibit substantially smaller surface tension and oil-based interfacial tension than those of the base fluid (i.e. deionized water). These surface and interfacial tensions of this nanofluid were found to decrease almost linearly with increasing temperature. The Brownian motion of nanoparticles in the base fluid was identified as a possible mechanism for reduced surface and interfacial tensions of the nanofluid. The measured effective viscosity of the nanofluid was found to be insignificantly higher than that of the base fluid and to decrease with increasing fluid temperature. The dependence on the temperature of the droplet formation at the T-junction of a microfluidic device is also studied and the nanofluid shows larger droplet size compared with its base fluid.

  17. Notes on the temperature dependence of carbon isotope fractionation by aerobic CH(4)-oxidising bacteria.

    Science.gov (United States)

    Nihous, Gerard C

    2010-06-01

    While the importance of environmental analyses based on isotope discrimination has been growing, uncertainties remain about underlying phenomena. Published results on the temperature dependence of carbon isotope fractionation during methane oxidation in various media show different trends. A decrease in fractionation is generally expected with temperature, but some data for methane oxidation in aqueous media show an inverse relationship. This apparent contradiction was probed by representing the first methane oxidation step as three elementary processes: the adsorption of methane on the bacterial cell wall, the desorption of methane from the wall, and the conversion of methane into methanol mediated by methane monooxygenase (MMO) enzymes. Assuming that the proportion of vacant adsorption sites is stationary, a formula for the composite fractionation factor alpha was obtained. It was shown that alpha not only expresses the fractionation that may occur in each elementary process, but that it also depends on the ratio of the kinetic rates for conversion into methanol and desorption. This result and experimental data were used to estimate the activation energy for the desorption of methane from methanotroph cell wall in aqueous medium ( approximately 200 kJ/mol). Simple Rosso models of bacterial maximal-specific growth rate were then used to demonstrate that alpha and the isotope fractionation from the MMO-mediated conversion into methanol alone could vary in opposite ways as temperature changes, but that care must be exercised when using fitted relationships across wide temperature ranges.

  18. Facile catalytic combustion of rice husk and burning temperature dependence of the ashes.

    Science.gov (United States)

    Xiong, Liangming; Sekiya, Edson H; Wada, Shigetaka; Saito, Kazuya

    2009-11-01

    In this work, it was discovered and demonstrated that the combustion of rice husk is a catalytic process by the thermoanalytical technique. The catalyst involves the oxides of such transition metals as Mn, Fe, and Cu, which are mainly formed in the initial stage of rice husk combustion and remain in the rice husk ash as an impurity. Mn(2+) ions of various concentrations were reloaded into the HCl-washed husk for cocombustion. As a result, the complete combustion temperature of the husk was decreased exponentially depending on the Mn(2+) concentration. By the facile Mn loading technique using a 0.5 M solution, the combustion temperature can be decreased by approximately 100 degrees C, and the resulting ashes themselves can be a good catalyst in the complete combustion of many other organic compounds. The physicochemical properties and amorphous structure of the ashes from both the raw and HCl-washed husks were found to be strongly dependent on the burning temperature. A decreased complete rice husk combustion temperature can be beneficial in preparing porous amorphous silica with high surface area, high densification, and small Si-O-Si band angles.

  19. Temperature-dependent physical properties of egg white for HIFU applications

    Science.gov (United States)

    Liu, Yunbo; Maruvada, Subha; Herman, Bruce A.; Harris, Gerald R.

    2012-10-01

    Because egg white denatures at elevated temperature due to its protein content, it has the potential for use as a blood coagulation surrogate in pre-clinical evaluations of thermal therapy procedures such as high intensity focused ultrasound (HIFU) surgery. We therefore have measured the relevant physical properties of egg white, including coagulation temperature, frequency-dependent attenuation, sound speed, viscosity, and thermal properties, as a function of temperature (20 - 95°C). Thermal coagulation and attenuation (5-12 MHz) of cow blood, pig blood, and human blood also were assessed and compared with egg white. For a 30 s thermal exposure, both egg white and blood samples started to denature at 65°C and coagulate into an elastic gel at 85°C. The temperature-dependent parameters were found to be similar to that of the blood samples. For example, the attenuation of egg white ranged from 0.23f1.09 to 2.7f0.5 dB/cm over the 20°C - 95°C range. These results suggest that egg white would make a useful blood mimic for bench testing of therapeutic ultrasound devices.

  20. 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.

  1. Insight into Temperature Dependence of GTPase Activity in Human Guanylate Binding Protein-1

    Science.gov (United States)

    Rahman, Safikur; Deep, Shashank; Sau, Apurba Kumar

    2012-01-01

    Interferon-γ induced human guanylate binding protein-1(hGBP1) belongs to a family of dynamin related large GTPases. Unlike all other GTPases, hGBP1 hydrolyzes GTP to a mixture of GDP and GMP with GMP being the major product at 37°C but GDP became significant when the hydrolysis reaction was carried out at 15°C. The hydrolysis reaction in hGBP1 is believed to involve with a number of catalytic steps. To investigate the effect of temperature in the product formation and on the different catalytic complexes of hGBP1, we carried out temperature dependent GTPase assays, mutational analysis, chemical and thermal denaturation studies. The Arrhenius plot for both GDP and GMP interestingly showed nonlinear behaviour, suggesting that the product formation from the GTP-bound enzyme complex is associated with at least more than one step. The negative activation energy for GDP formation and GTPase assay with external GDP together indicate that GDP formation occurs through the reversible dissociation of GDP-bound enzyme dimer to monomer, which further reversibly dissociates to give the product. Denaturation studies of different catalytic complexes show that unlike other complexes the free energy of GDP-bound hGBP1 decreases significantly at lower temperature. GDP formation is found to be dependent on the free energy of the GDP-bound enzyme complex. The decrease in the free energy of this complex at low temperature compared to at high is the reason for higher GDP formation at low temperature. Thermal denaturation studies also suggest that the difference in the free energy of the GTP-bound enzyme dimer compared to its monomer plays a crucial role in the product formation; higher stability favours GMP but lower favours GDP. Thus, this study provides the first thermodynamic insight into the effect of temperature in the product formation of hGBP1. PMID:22859948

  2. Insight into temperature dependence of GTPase activity in human guanylate binding protein-1.

    Directory of Open Access Journals (Sweden)

    Anjana Rani

    Full Text Available Interferon-γ induced human guanylate binding protein-1(hGBP1 belongs to a family of dynamin related large GTPases. Unlike all other GTPases, hGBP1 hydrolyzes GTP to a mixture of GDP and GMP with GMP being the major product at 37°C but GDP became significant when the hydrolysis reaction was carried out at 15°C. The hydrolysis reaction in hGBP1 is believed to involve with a number of catalytic steps. To investigate the effect of temperature in the product formation and on the different catalytic complexes of hGBP1, we carried out temperature dependent GTPase assays, mutational analysis, chemical and thermal denaturation studies. The Arrhenius plot for both GDP and GMP interestingly showed nonlinear behaviour, suggesting that the product formation from the GTP-bound enzyme complex is associated with at least more than one step. The negative activation energy for GDP formation and GTPase assay with external GDP together indicate that GDP formation occurs through the reversible dissociation of GDP-bound enzyme dimer to monomer, which further reversibly dissociates to give the product. Denaturation studies of different catalytic complexes show that unlike other complexes the free energy of GDP-bound hGBP1 decreases significantly at lower temperature. GDP formation is found to be dependent on the free energy of the GDP-bound enzyme complex. The decrease in the free energy of this complex at low temperature compared to at high is the reason for higher GDP formation at low temperature. Thermal denaturation studies also suggest that the difference in the free energy of the GTP-bound enzyme dimer compared to its monomer plays a crucial role in the product formation; higher stability favours GMP but lower favours GDP. Thus, this study provides the first thermodynamic insight into the effect of temperature in the product formation of hGBP1.

  3. Temperature dependence of stream aeration coefficients and the effect of water turbulence: a critical review.

    Science.gov (United States)

    Demars, B O L; Manson, J R

    2013-01-01

    The gas transfer velocity (K(L)) and related gas transfer coefficient (k(2) = K(L)A/V, with A, area and V, volume) at the air-water interface are critical parameters in all gas flux studies such as green house gas emission, whole stream metabolism or industrial processes. So far, there is no theoretical model able to provide accurate estimation of gas transfer in streams. Hence, reaeration is often estimated with empirical equations. The gas transfer velocity need then to be corrected with a temperature coefficient θ = 1.0241. Yet several studies have long reported variation in θ with temperature and 'turbulence' of water (i.e. θ is not a constant). Here we re-investigate thoroughly a key theoretical model (Dobbins model) in detail after discovering important discrepancies. We then compare it with other theoretical models derived from a wide range of hydraulic behaviours (rigid to free continuous surface water, wave and waterfalls with bubbles). The results of the Dobbins model were found to hold, at least theoretically in the light of recent advances in hydraulics, although the more comprehensive results in this study highlighted a higher degree of complexity in θ's behaviour. According to the Dobbins model, the temperature coefficient θ, could vary from 1.005 to 1.042 within a temperature range of 0-35 °C and wide range of gas transfer velocities, i.e. 'turbulence' condition (0.005 turbulence', and only modest variability in θ with change in temperature. However, the other theoretical models did not have the same temperature coefficient θ (with 1.000 turbulence and bubble mediated gas transfer velocities suggested a lower temperature dependence for bubble (1.013turbulence (1.023turbulence on the temperature dependence of gas transfer at the air-water interface has still to be clarified, although many models simulate different flow conditions which may explain some of the observed discrepancies. We suggest that the temperature dependence curves produced by

  4. Transport lattice models of heat transport in skin with spatially heterogeneous, temperature-dependent perfusion

    Directory of Open Access Journals (Sweden)

    Martin Gregory T

    2004-11-01

    Full Text Available Abstract Background Investigation of bioheat transfer problems requires the evaluation of temporal and spatial distributions of temperature. This class of problems has been traditionally addressed using the Pennes bioheat equation. Transport of heat by conduction, and by temperature-dependent, spatially heterogeneous blood perfusion is modeled here using a transport lattice approach. Methods We represent heat transport processes by using a lattice that represents the Pennes bioheat equation in perfused tissues, and diffusion in nonperfused regions. The three layer skin model has a nonperfused viable epidermis, and deeper regions of dermis and subcutaneous tissue with perfusion that is constant or temperature-dependent. Two cases are considered: (1 surface contact heating and (2 spatially distributed heating. The model is relevant to the prediction of the transient and steady state temperature rise for different methods of power deposition within the skin. Accumulated thermal damage is estimated by using an Arrhenius type rate equation at locations where viable tissue temperature exceeds 42°C. Prediction of spatial temperature distributions is also illustrated with a two-dimensional model of skin created from a histological image. Results The transport lattice approach was validated by comparison with an analytical solution for a slab with homogeneous thermal properties and spatially distributed uniform sink held at constant temperatures at the ends. For typical transcutaneous blood gas sensing conditions the estimated damage is small, even with prolonged skin contact to a 45°C surface. Spatial heterogeneity in skin thermal properties leads to a non-uniform temperature distribution during a 10 GHz electromagnetic field exposure. A realistic two-dimensional model of the skin shows that tissue heterogeneity does not lead to a significant local temperature increase when heated by a hot wire tip. Conclusions The heat transport system model of the

  5. 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.

  6. Peculiar temperature-dependent charge response of frustrated chain cuprates near a critical point

    Energy Technology Data Exchange (ETDEWEB)

    Drechsler, S-L; Malek, J; Nishimoto, S; Nitzsche, U; Kuzian, R; Eschrig, H [Leibniz-Institut fuer Festkoerper- und Werkstoffforschung (IFW) Dresden, PO Box 270116, D-01171 Dresden (Germany); Rosner, H, E-mail: s.l.drechsler@ifw-dresden.d [Max-Planck-Institut fuer Chemische Physik fester Stofie, Dresden (Germany)

    2009-01-01

    The optical conductivity sigma(omega) is calculated at finite temperature T for CuO{sub 2} chain clusters within a pd-Hubbard model. Data at T = 300 K for Li{sub 2}CuO{sub 2} are reanalyzed within this approach. The relative weights of Zhang-Rice singlet and triplet charge excitations near 2.5 and 4 eV, respectively, depend strongly on T, and a dramatic dependence of sigma(omega) on the ratio of the 1st to 2nd neighbor exchange integrals is predicted. Information about exchange interactions for edge-shared cuprates can be obtained from T-dependent optical spectra. A reduced intensity of the ZRS-transition with increasing T is also relevant for unfrustrated cuprates in general.

  7. Shape of the liquid-vapor coexistence curve for temperature and density dependent effective interactions.

    Science.gov (United States)

    Amokrane, S; Bouaskarne, M

    2002-05-01

    The asymmetry of the coexistence curve that is observed in several micellar systems is discussed in relation with the dependence of the effective interaction on temperature and density. Standard results for the diameter of the coexistence curve in the van der Waals theory are generalized so as to deal with this combined dependence. The qualitative trends so deduced are assessed by comparison with coexistence curves of Yukawa fluids computed with integral equation theories. The role of the variables used to plot the coexistence curve and the nonlinear behavior of its diameter beyond the critical region are discussed in relation with the decrease of the interaction strength with density. The possibility of using the asymmetry of the coexistence curve as an indicator of the state dependence of the effective interaction is finally discussed.

  8. Memory-dependent derivatives for photothermal semiconducting medium in generalized thermoelasticity with two-temperature

    Science.gov (United States)

    Lotfy, K.; Sarkar, N.

    2017-11-01

    In this work, a novel generalized model of photothermal theory with two-temperature thermoelasticity theory based on memory-dependent derivative (MDD) theory is performed. A one-dimensional problem for an elastic semiconductor material with isotropic and homogeneous properties has been considered. The problem is solved with a new model (MDD) under the influence of a mechanical force with a photothermal excitation. The Laplace transform technique is used to remove the time-dependent terms in the governing equations. Moreover, the general solutions of some physical fields are obtained. The surface taken into consideration is free of traction and subjected to a time-dependent thermal shock. The numerical Laplace inversion is used to obtain the numerical results of the physical quantities of the problem. Finally, the obtained results are presented and discussed graphically.

  9. Density dependence of spin relaxation in GaAs quantum well at room temperature

    Science.gov (United States)

    Teng, L. H.; Zhang, P.; Lai, T. S.; Wu, M. W.

    2008-10-01

    Carrier density dependence of electron spin relaxation in an intrinsic GaAs quantum well is investigated at room temperature using time-resolved circularly polarized pump-probe spectroscopy. It is revealed that the spin relaxation time first increases with density in the relatively low-density regime where the linear D'yakonov-Perel' spin-orbit coupling terms are dominant, and then tends to decrease when the density is large and the cubic D'yakonov-Perel' spin-orbit coupling terms become important. These features are in good agreement with theoretical predictions on density dependence of spin relaxation by Lüet al. (Phys. Rev. B, 73 (2006) 125314). A fully microscopic calculation based on numerically solving the kinetic spin Bloch equations with both the D'yakonov-Perel' and the Bir-Aronov-Pikus mechanisms included, reproduces the density dependence of spin relaxation very well.

  10. Quantifying Temperature-Dependent T1 Changes in Cortical Bone Using Ultrashort Echo-Time MRI

    Science.gov (United States)

    Han, Misung; Rieke, Viola; Scott, Serena J; Ozhinsky, Eugene; Salgaonkar, Vasant A; Jones, Peter D; Larson, Peder E Z; Diederich, Chris J; Krug, Roland

    2015-01-01

    Purpose To demonstrate the feasibility of using ultrashort echo-time (UTE) MRI to quantify T1 changes in cortical bone due to heating. Methods Variable flip-angle T1 mapping combined with 3D UTE imaging was used to measure T1 in cortical bone. A calibration experiment was performed to detect T1 changes with temperature in ex vivo cortical bone samples from a bovine femur. Ultrasound heating experiments were performed using an interstitial applicator in ex vivo bovine femur specimens, and heat-induced T1 changes were quantified. Results The calibration experiment demonstrated that T1 increases with temperature in cortical bone. We observed a linear relationship between temperature and T1 with a linear coefficient of 0.67–0.84 ms/°C over a range of 25–70°C. The ultrasound heating experiments showed increased T1 changes in the heated regions, and the relationship between the temperature changes and T1 changes was similar to that of the calibration. Conclusion We demonstrated a temperature dependence of T1 in ex vivo cortical bone using a variable flip-angle UTE T1 mapping method. PMID:26390357

  11. Temperature dependent PAC studies with the rare earth '$^{172}$Lu' in ZnO

    CERN Document Server

    Nédélec, R

    2006-01-01

    Wide band-gap semiconductors have become an important base material for applications in optoelectronics and in high power, high temperature electronics. After doping with various rare earths, electroluminescence throughout the whole visible spectrum has been observed. We have studied the implantation behaviour of the rare earth Lu in ZnO. Our samples were implanted at the ISOLDE facility at CERN. In order to recover the sustained implantation damage the samples were treated in a rapid thermal annealing furnace. In a first attempt to measure the temperature dependence of the electric field gradient at the site of 172Lu/172Yb in ZnO a large jump in the quadrupole interaction frequency was observed between measurements at room temperature and 200 °C. Above 200 °C the frequency only changed very little. In order to understand this unusual behaviour we prepared another sample and studied the temperature range between room temperature and 200 °C in more detail. The results obtained previously could be confirmed....

  12. 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.

  13. Finite-temperature time-dependent variation with multiple Davydov states

    Science.gov (United States)

    Wang, Lu; Fujihashi, Yuta; Chen, Lipeng; Zhao, Yang

    2017-03-01

    The Dirac-Frenkel time-dependent variational approach with Davydov Ansätze is a sophisticated, yet efficient technique to obtain an accurate solution to many-body Schrödinger equations for energy and charge transfer dynamics in molecular aggregates and light-harvesting complexes. We extend this variational approach to finite temperature dynamics of the spin-boson model by adopting a Monte Carlo importance sampling method. In order to demonstrate the applicability of this approach, we compare calculated real-time quantum dynamics of the spin-boson model with that from numerically exact iterative quasiadiabatic propagator path integral (QUAPI) technique. The comparison shows that our variational approach with the single Davydov Ansätze is in excellent agreement with the QUAPI method at high temperatures, while the two differ at low temperatures. Accuracy in dynamics calculations employing a multitude of Davydov trial states is found to improve substantially over the single Davydov Ansatz, especially at low temperatures. At a moderate computational cost, our variational approach with the multiple Davydov Ansatz is shown to provide accurate spin-boson dynamics over a wide range of temperatures and bath spectral densities.

  14. Growth-temperature dependence of Er-doped GaN luminescent thin films

    Science.gov (United States)

    Lee, D. S.; Heikenfeld, J.; Steckl, A. J.

    2002-01-01

    Visible photoluminescence (PL) and electroluminescence (EL) emission has been observed from Er-doped GaN thin films grown on (111) Si at various temperatures from 100 to 750 °C in a radio-frequency plasma molecular beam epitaxy system. PL and EL intensities of green emission at 537 nm from GaN:Er films exhibited strong dependence on the growth temperature, with a maximum at 600 °C. Scanning electron and atomic force microscopy showed smooth surfaces at 600 °C and rough surfaces at 100 and 750 °C. X-ray diffraction indicated that the GaN:Er film structure was oriented with the c axis perpendicular to the substrate for all growth temperatures. The crystalline quality initially improves with an increase in growth temperature, and saturates at ˜500 °C. Considering both the luminescence and structural properties of the film, ˜600 °C seems to be the optimal temperature for growth of Er-doped GaN luminescent films on Si substrates.

  15. Quantifying the temperature dependence of glycine-betaine RNA duplex destabilization.

    Science.gov (United States)

    Schwinefus, Jeffrey J; Menssen, Ryan J; Kohler, James M; Schmidt, Elliot C; Thomas, Alexandra L

    2013-12-23

    Glycine-betaine (GB) stabilizes folded protein structure because of its unfavorable thermodynamic interactions with amide oxygen and aliphatic carbon surface area exposed during protein unfolding. However, GB can attenuate nucleic acid secondary structure stability, although its mechanism of destabilization is not currently understood. Here we quantify GB interactions with the surface area exposed during thermal denaturation of nine RNA dodecamer duplexes with guanine-cytosine (GC) contents of 17-100%. Hyperchromicity values indicate increasing GB molality attenuates stacking. GB destabilizes higher-GC-content RNA duplexes to a greater extent than it does low-GC-content duplexes due to greater accumulation at the surface area exposed during unfolding. The accumulation is very sensitive to temperature and displays characteristic entropy-enthalpy compensation. Since the entropic contribution to the m-value (used to quantify GB interaction with the RNA solvent-accessible surface area exposed during denaturation) is more dependent on temperature than is the enthalpic contribution, higher-GC-content duplexes with their larger transition temperatures are destabilized to a greater extent than low-GC-content duplexes. The concentration of GB at the RNA surface area exposed during unfolding relative to bulk was quantified using the solute-partitioning model. Temperature correction predicts a GB concentration at 25 °C to be nearly independent of GC content, indicating that GB destabilizes all sequences equally at this temperature.

  16. 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.

  17. The pressure and temperature dependence of vertical cavity surface emitting semiconductor lasers

    CERN Document Server

    Knowles, G

    2002-01-01

    The factors affecting the performance of GalnP/AIGalnP vertical-cavity surface-emitting lasers (VCSELs) emitting at an attenuation minimum of PMMA plastic optical fibres (650nm) have been investigated. Using wide temperature-range and high pressure measurement techniques on equivalent (i.e the same active region) edge emitting lasers (EELs), emitting at 672nm, the temperature sensitive leakage current into the indirect X-minima is shown to be approx 20% of the total threshold current at room temperature. This is then estimated to rise to approx 70% for 655nm emission, but may be reduced to approx 50% by using a graded-index separate confinement heterostructure (GRINSCH). By making the same measurements on the full VCSEL structures and using a combination of thermal and gain spectrum models the performance modifying effect of the Bragg stacks have then been evaluated. It is found that temperature dependent tuning/detuning of the gain-peak and the cavity mode is significant at low temperature due to the relativ...

  18. Temperature dependence of scintillation properties of SrMoO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Mikhailik, V.B., E-mail: vmikhai@hotmail.com [Diamond Light Source, Harwell Science Campus, Didcot OX11 0DE (United Kingdom); Elyashevskyi, Yu. [Department of Physics, University of Oxford, Keble Rd., Oxford OX1 3RH (United Kingdom); Scientific-technical and Educational Centre of Low Temperature Studies, I. Franko National University of Lviv, 50 Dragomanova Str., 79005 Lviv (Ukraine); Kraus, H. [Department of Physics, University of Oxford, Keble Rd., Oxford OX1 3RH (United Kingdom); Kim, H.J. [Department of Physics of Kyungpook National University, 1370 Sangyeok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of); Kapustianyk, V.; Panasyuk, M. [Scientific-technical and Educational Centre of Low Temperature Studies, I. Franko National University of Lviv, 50 Dragomanova Str., 79005 Lviv (Ukraine)

    2015-08-21

    Studies of the X-ray luminescence and scintillation properties of a SrMoO{sub 4} crystal as function of temperature down to T=10 K have been carried out. The luminescence in SrMoO{sub 4} is quenched at room temperature, but below T<200 K the crystal exhibits a broad emission band with a maximum at a wavelength of 520 nm. The emission is attributed to the radiative decay of self-trapped excitons and defects acting as traps for the exactions at low temperatures. Such complex character of radiative decay is reflected in the kinetics which contains several components plus a contribution from delayed recombination at low temperatures. The temperature dependence of scintillation light output of SrMoO{sub 4} was studied. Comparing with a reference ZnWO{sub 4} crystal measured under the same experimental conditions it was found that the light output of SrMoO{sub 4} is 15±5%. It is suggested, therefore, that there is scope for optimisation of strontium molybdate for application as scintillator in cryogenic rare event searches.

  19. Mechanistic basis of temperature-dependent dwell fatigue in titanium alloys

    Science.gov (United States)

    Zheng, Zebang; Balint, Daniel S.; Dunne, Fionn P. E.

    2017-10-01

    The temperature-dependent dwell sensitivity of Ti-6242 and Ti-6246 alloys has been assessed over a temperature range from - 50∘ C to 390 °C using discrete dislocation plasticity which incorporates both thermal activation of dislocation escape from obstacles and slip transfer across grain boundaries. The worst-case load shedding in Ti-6242 alloy is found to be at or close to 120 °C under dwell fatigue loading, which diminishes and vanishes at temperatures lower than - 50∘ C or higher than 230 °C. Load shedding behaviour is predicted to occur in alloy Ti-6246 also but over a range of higher temperatures which are outside those relevant to in-service conditions. The key controlling dislocation mechanism with respect to load shedding in titanium alloys, and its temperature sensitivity, is shown to be the time constant associated with the thermal activation of dislocation escape from obstacles, with respect to the stress dwell time. The mechanistic basis of load shedding and dwell sensitivity in dwell fatigue loading is presented and discussed in the context of experimental observations.

  20. Febrile temperature facilitates hERG/IKr degradation through an altered K(+) dependence.

    Science.gov (United States)

    Zhao, Yan; Wang, Tingzhong; Guo, Jun; Yang, Tonghua; Li, Wentao; Koichopolos, Jennifer; Lamothe, Shawn M; Kang, Yudi; Ma, Aiqun; Zhang, Shetuan

    2016-10-01

    Dysfunction of the rapidly activating delayed rectifier K(+) channel (IKr) encoded by the human ether-à-go-go-related gene (hERG) is the primary cause of acquired long QT syndrome (LQTS). Fever has been reported to trigger LQTS in various conditions. We aim to clarify the effect and underlying mechanisms of febrile temperature on hERG expressed in HEK cells, IKr in neonatal rat ventricular myocytes, and the QT interval in rabbits. Western blot analysis was used to determine the expression of hERG channel protein in stably transfected HEK 293 cells. Immunocytochemistry was used to visualize the localization of hERG channels. The whole-cell patch clamp technique was used to record hERG K(+) current (IhERG) in hERG expressing HEK 293 cells, as well as IKr, transient outward K(+) current (Ito), and L-type Ca(2+) current (ICa) in neonatal rat ventricular myocytes. Electrocardiographic recordings were performed in an in vivo rabbit model. Compared with culture at 37°C, culture at 40°C reduced the mature hERG expression and IhERG in an extracellular K(+) concentration-dependent manner. Point mutations that remove the K(+) dependence of hERG-S624T and F627Y-also abolished the febrile temperature-induced hERG reduction. In neonatal rat ventricular myocytes, febrile temperature prolonged the action potential duration and selectively reduced IKr in a manner similar to low K(+) culture. In an in vivo rabbit model, fever and hypokalemia synergistically prolonged the QT interval. Febrile temperature facilitates the development of LQTS by expediting hERG degradation through altered K(+) dependence. Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

  1. Temperature and state dependence of dynamic phrenic oscillations in the decerebrate juvenile rat.

    Science.gov (United States)

    Marchenko, Vitaliy; Rogers, Robert F

    2007-12-01

    The aim of the present study was to determine characteristics of fast oscillations in the juvenile rat phrenic nerve (Ph) and to establish their temperature and state dependence. Two different age-matched decerebrate, baro- and chemodenervated rat preparations, in vivo and in situ arterially perfused models, were used to examine three systemic properties: 1) generation and dynamics of fast oscillations in Ph activity (both preparations), 2) responses to anoxia (both preparations), and 3) the effects of temperature on fast oscillations (in situ only). Both juvenile preparations generated power and coherence in two major bands analogous to adult medium- and high-frequency oscillations (HFO) at frequencies that increased with temperature but were lower than in adults. At < 28 degrees C, however, Ph oscillations were confined primarily to one low-frequency band (20-45 Hz). During sustained anoxia, both preparations produced stereotypical state changes from eupnea to hyperpnea to transition bursting (a behavior present only in vivo during incomplete ischemia) to gasping. Thus the juvenile rat produces a sequential pattern of responses to anoxia that are intermediate forms between those produced by neonates and those produced by adults. Time-frequency analysis determined that fast oscillations demonstrated dynamics over the course of the inspiratory burst and a state dependence similar to that of adults in vivo in which hyperpnea (and transition) bursts are associated with increases in HFO, while gasping contains no HFO. Our results confirm that both the fast oscillations in Ph activity and the coherence between Ph pairs produced by the juvenile rat are profoundly state- and temperature-dependent.

  2. Infrared cross-sections and integrated band intensities of propylene: Temperature-dependent studies

    KAUST Repository

    Es-sebbar, Et-touhami

    2014-01-01

    Propylene, a by-product of biomass burning, thermal cracking of hydrocarbons and incomplete combustion of fossil fuels, is a ubiquitous molecule found in the environment and atmosphere. Accurate infrared (IR) cross-sections and integrated band intensities of propylene are essential for quantitative measurements and atmospheric modeling. We measured absolute IR cross-sections of propylene using Fourier Transform Infrared (FTIR) Spectroscopy over the wavenumber range of 400-6500cm-1 and at gas temperatures between 296 and 460K. We recorded these spectra at spectral resolutions ranging from 0.08 to 0.5cm-1 and measured the integrated band intensities for a number of vibrational bands in certain spectral regions. We then compared the integrated band intensities measured at room temperature with values derived from the National Institute of Standards and Technology (NIST) and the Pacific Northwest National Laboratory (PNNL) databases. Our results agreed well with the results reported in the two databases with a maximum deviation of about 4%. The peak cross-sections for the primary bands decreased by about 20-54% when the temperature increased from 296 to 460K. Moreover, we determined the integrated band intensities as a function of temperature for certain features in various spectral regions; we found no significant temperature dependence over the range of temperatures considered here. We also studied the effect of temperature on absorption cross-section using a Difference Frequency Generation (DFG) laser system. We compared the DFG results with those obtained from the FTIR study at certain wavenumbers over the 2850-2975cm-1 range and found a reasonable agreement with less than 10% discrepancy. © 2013 Elsevier Ltd.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Optical tweezers with fluorescence detection for temperature-dependent microrheological measurements

    Science.gov (United States)

    Shundo, Atsuomi; Hori, Koichiro; Penaloza, David P.; Tanaka, Keiji

    2013-01-01

    We introduce a setup of optical tweezers, capable of carrying out temperature-dependent rheological measurements of soft materials. In our setup, the particle displacement is detected by imaging a bright spot due to fluorescence emitted from a dye-labeled particle against a dark background onto a quadrant photodiode. This setup has a relatively wide space around the sample that allows us to further accessorize the optical tweezers by a temperature control unit. The applicability of the setup was examined on the basis of the rheological measurements using a typical viscoelastic system, namely a worm-like micelle solution. The temperature and frequency dependences of the local viscoelastic functions of the worm-like micelle solution obtained by this setup were in good accordance with those obtained by a conventional oscillatory rheometer, confirming the capability of the optical tweezers as a tool for the local rheological measurements of soft materials. Since the optical tweezers measurements only require a tiny amount of sample (˜40 μL), the rheological measurements using our setup should be useful for soft materials of which the available amount is limited.

  12. 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.

  13. 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.

  14. 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.

  15. Circularly polarized photoluminescence from platinum porphyrins in organic hosts: Magnetic field and temperature dependence

    Science.gov (United States)

    Diaconu, C. V.; Batista, E. R.; Martin, R. L.; Smith, D. L.; Crone, B. K.; Crooker, S. A.; Smith's, D. L.

    2011-04-01

    We study the temperature and magnetic field-dependent photoluminescence from the metalorganic molecules octaethyl-porphine platinum (PtOEP) and porphine platinum (PtP) that are doped into organic hosts. We first consider PtOEP in the polymer host poly-dioctylfluorene (PFO), which is characteristic of the phosphorescent dopants and polymers used in organic light-emitting diodes. We observe that the intensity of the PtOEP zero-phonon emission band, which is strongly suppressed at low temperatures to 1.6 K, increases dramatically with applied magnetic field and is accompanied by a marked circular polarization. This "magnetic brightening" effect, similar to that observed in other organic systems such as carbon nanotubes, highlights the interplay between low-energy optically active and optically forbidden excited states of PtOEP, which become mixed in applied magnetic fields. To elucidate these findings, we also investigate (i) dilute PtOEP in n-octane hosts (where emission lines are much sharper), and (ii) dilute PtP in n-octane hosts, for which the emission spectra are simpler and can be directly compared with theory. Detailed electronic structure calculations of PtP were performed, and a model for the magnetic field and temperature dependence of the zero phonon emission lines is developed, which agrees quantitatively with the data for PtP and with the circular polarization of the PtOEP emission.

  16. Mechanism of quasilinear temperature dependence of the surface magnetization in a semi-infinite ferromagnet (abstract)

    Science.gov (United States)

    Rado, George T.

    1990-05-01

    A semiclassical method involving surface spin waves is used to calculate the spontaneous magnetization M near the surface of a semi-infinite ferromagnet. It is assumed as before1 that the magnitude of the surface anisotropy constant Ks introduced by Néel is negligible compared to the surface anisotropy constant Kss introduced by the present author. We now generalize our calculations in two respects. First, we include dipolar interactions to keep the calculated M from diverging even when the value of Kss is relatively large. We find, as in our previous work,1 that under the above conditions any positive value of Kss causes the dependence of M on the temperature T to be quasilinear rather than proportional to T3/2 and the dependence of M on position to be exponential. Alternative predictions2 of a quasilinear T dependence of M apply only to T values near the Curie temperature. Second, we explore the consequences of assuming that the exchange stiffness constant A is weakened at the surface. We show that such a weakening is equivalent to the use of a spatially uniform value of A and an increased value of Kss. This mechanism provides a possible interpretation of recent experimental results3 on MnF2-covered Fe(110) which require a relatively large value of Kss. The full text of the present paper recently appeared4 in Physical Review B.

  17. 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

  18. 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%.

  19. Temperature dependent electrical behaviour of Cu2SnS3 films

    Directory of Open Access Journals (Sweden)

    Sandra Dias

    2014-03-01

    Full Text Available The temperature dependent electrical properties of the dropcasted Cu2SnS3 films have been measured in the temperature range 140 K to 317 K. The log I versus √V plot shows two regions. The region at lower bias is due to electrode limited Schottky emission and the higher bias region is due to bulk limited Poole Frenkel emission. The ideality factor is calculated from the ln I versus V plot for different temperatures fitted with the thermionic emission model and is found to vary from 6.05 eV to 12.23 eV. This large value is attributed to the presence of defects or amorphous layer at the Ag / Cu2SnS3 interface. From the Richardson's plot the Richardson's constant and the barrier height were calculated. Owing to the inhomogeneity in the barrier heights, the Richardson's constant and the barrier height were also calculated from the modified Richardson's plot. The I-V-T curves were also fitted using the thermionic field emission model. The barrier heights were found to be higher than those calculated using thermionic emission model. From the fit of the I-V-T curves to the field emission model, field emission was seen to dominate in the low temperature range of 140 K to 177 K. The temperature dependent current graphs show two regions of different mechanisms. The log I versus 1000/T plot gives activation energies Ea1 = 0.367095 − 0.257682 eV and Ea2 = 0.038416 − 0.042452 eV. The log (I/T2 versus 1000/T graph gives trap depths Φo1 = 0.314159 − 0.204752 eV and Φo2 = 0.007425 − 0.011163 eV. With increasing voltage the activation energy Ea1 and the trap depth Φo1 decrease. From the ln (IT1/2 versus 1/T1/4 graph, the low temperature region is due to variable range hopping mechanism and the high temperature region is due to thermionic emission.

  20. Resolving the dependence of Δ47 thermometers on acid digestion temperature

    Science.gov (United States)

    Colman, A. S.; Olack, G.

    2015-12-01

    Clumped isotope paleothermometry on carbonate minerals has emerged as a leading tool in paleoclimate and paleoaltimetry studies. The utility of Δ47 measurements is especially pronounced when estimating formation temperature of carbonates that precipitated from solutions with unknown water oxygen isotope composition. However, the interpretation of Δ47 values has been hindered by discrepancies among the many published thermometric calibrations. As the number of calibrations grows, it now appears that the slope of the Δ47 vs. inverse temperature relationship clusters into two distinct groupings based on whether the carbonate minerals were digested at low temperature (25°C) vs. high temperature (generally 70 - 90°C). We model the effect that small amounts of oxygen exchange between CO2 liberated to the phosphoric acid solution and trace water in that solution can have on measured Δ47. This can occur with very little shift in δ47 and δ18O of the CO2. The extent and effect of oxygen exchange following CaCO3 dissolution is a complex function of the phosphoric acid's temperature, water content, and viscosity. Conventional approaches to preparation of phosphoric acid (targeting a defined density range at room temperature) are likely inadequate for resolving the details of these dependencies. This stems in part from changes that can occur to the water content and density of phosphoric acid during heating of the acid under vacuum. Secondary effects may also arise that relate to the grain and crystallite size of the carbonate minerals, intercalation of carbonate minerals with siliciclastic matrix in sediments or paleosols, and possibly the reactivity of hydrous components of a siliciclastic rich sample.