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Sample records for temperature-dependent fission barriers

  1. 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).

  2. Temperature dependence of nuclear fission time in heavy-ion fusion-fission reactions

    Science.gov (United States)

    Eccles, Chris; Roy, Sanil; Gray, Thomas H.; Zaccone, Alessio

    2017-11-01

    Accounting for viscous damping within Fokker-Planck equations led to various improvements in the understanding and analysis of nuclear fission of heavy nuclei. Analytical expressions for the fission time are typically provided by Kramers' theory, which improves on the Bohr-Wheeler estimate by including the time scale related to many-particle dissipative processes along the deformation coordinate. However, Kramers' formula breaks down for sufficiently high excitation energies where Kramers' assumption of a large barrier no longer holds. Focusing on the overdamped regime for energies T >1 MeV, Kramers' theory should be replaced by a new analytical theory derived from the Ornstein-Uhlenbeck first-passage time method that is proposed here. The theory is applied to fission time data from fusion-fission experiments on 16O+208Pb→224Th . The proposed model provides an internally consistent one-parameter fitting of fission data with a constant nuclear friction as the fitting parameter, whereas Kramers' fitting requires a value of friction which falls out of the allowed range. The theory provides also an analytical formula that in future work can be easily implemented in numerical codes such as cascade or joanne4.

  3. Superheavy nuclei and fission barriers

    Science.gov (United States)

    Lu, Bing-Nan; Zhao, Jie; Zhao, En-Guang; Zhou, Shan-Gui

    In this chapter, we will present relativistic mean field (RMF) description of heavy and superheavy nuclei (SHN). We will discuss the shell structure and magic numbers in the mass region of SHN, binding energies and α decay Q values, shapes of ground states and potential energy surfaces and fission barriers. We particularly focus on the multidimensionally-constrained covariant density functional theories (CDFT) and the applications of CDFT to the study of exotic nuclear shapes and fission barriers.

  4. Specific fission J-window and angular momentum dependence of the fission barrier

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Hiroshi; Saito, Tadashi; Takahashi, Naruto; Yokoyama, Akihiko [Osaka Univ., Suita (Japan); Shinohara, Atsushi

    1997-04-01

    A method to determine a unique J-window in the fission process was devised and the fissioning nuclide associated with thus extracted J-window was identified for each of the heavy-ion reaction systems. Obtained fission barriers at the resulting J-window were compared with the calculated values by the rotating finite range model (RFRM). The deduced barriers for individual nuclides were compared with the RFRM barriers to reproduce more or less the angular momentum dependence the RFRM prediction. The deduced systematic behavior of the fission barrier indicates no even-odd and shell corrections are necessary. The nuclear dissipation effect based on Kramer`s model revealed substantial reduction of the statistically deduced barrier heights and brought a fairly large scattering from the RFRM J-dependence. However, introduction of the temperature-dependent friction coefficient ({gamma} = 2 for T {>=} 1.0 MeV and 0.5 for T < 1.0 MeV) was found to bring about satisfactory agreement with both RFRM fission barriers and the pre-fission neutron multiplicity systematics. (author). 81 refs.

  5. Fission barrier heights in the A∼ 200 mass region

    Indian Academy of Sciences (India)

    2015-07-19

    Jul 19, 2015 ... Statistical model analysis is carried out for - and -induced fission reactions using a consistent description for fission barrier and level density in A ∼ 200 mass region. A continuous damping of shell correction with excitation energy is considered. Extracted fission barriers agree well with the recent ...

  6. 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.

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

    Science.gov (United States)

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

    2017-01-01

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

  8. Determination of the fission barrier height in fission of heavy radioactive beams induced by the (d,p)-transfer

    CERN Multimedia

    A theoretical framework is described, allowing to determine the fission barrier height using the observed cross sections of fission induced by the (d,p)-transfer with accuracy, which is not achievable in another type of low-energy fission of neutron-deficient nuclei, the $\\beta$-delayed fission. The primary goal is to directly determine the fission barrier height of proton-rich fissile nuclei, preferably using the radio-active beams of isotopes of odd elements, and thus confirm or exclude the low values of fission barrier heights, typically extracted using statistical calculations in the compound nucleus reactions at higher excitation energies. Calculated fission cross sections in transfer reactions of the radioactive beams show sufficient sensitivity to fission barrier height. In the probable case that fission rates will be high enough, mass asymmetry of fission fragments can be determined. Results will be relevant for nuclear astrophysics and for production of super-heavy nuclei. Transfer induced fission of...

  9. Fission barrier heights in the A ∼ 200 mass region

    Indian Academy of Sciences (India)

    not only to understand the heavy-ion-induced fusion–fission dynamics and prediction of superheavy elements, but also other areas, such as stellar nucleosynthesis and nuclear energy applications. In the actinide region, the fission barrier heights are comparable to the neutron separation energies and could be determined ...

  10. Modelling with uncertainties: The role of the fission barrier

    Directory of Open Access Journals (Sweden)

    Lü Hongliang

    2013-12-01

    Full Text Available Fission is the dominant decay channel of super-heavy elements formed in heavy ions collisions. The probability of synthesizing heavy or super-heavy nuclei in fusion-evaporation reactions is then very sensitive to the height of their fission barriers. This contribution will firstly address the influence of theoretical uncertainty on excitation functions. Our second aim is to investigate the inverse problem, i.e., what information about the fission barriers can be extracted from excitation functions? For this purpose, Bayesian methods have been used with a simplified toy model.

  11. Assessing theoretical uncertainties in fission barriers of superheavy nuclei

    Science.gov (United States)

    Agbemava, S. E.; Afanasjev, A. V.; Ray, D.; Ring, P.

    2017-05-01

    Theoretical uncertainties in the predictions of inner fission barrier heights in superheavy elements have been investigated in a systematic way for a set of state-of-the-art covariant energy density functionals which represent major classes of the functionals used in covariant density functional theory. They differ in basic model assumptions and fitting protocols. Both systematic and statistical uncertainties have been quantified where the former turn out to be larger. Systematic uncertainties are substantial in superheavy elements and their behavior as a function of proton and neutron numbers contains a large random component. The benchmarking of the functionals to the experimental data on fission barriers in the actinides allows reduction of the systematic theoretical uncertainties for the inner fission barriers of unknown superheavy elements. However, even then, on average they increase on moving away from the region where benchmarking has been performed. In addition, a comparison with the results of nonrelativistic approaches is performed in order to define full systematic theoretical uncertainties over the state-of-the-art models. Even for the models benchmarked in the actinides, the difference in the inner fission barrier height of some superheavy elements reaches 5 -6 MeV. This uncertainty in the fission barrier heights will translate into huge (many tens of the orders of magnitude) uncertainties in the spontaneous fission half-lives.

  12. Remarks on the fission barriers of super-heavy nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, S.; Heinz, S.; Mann, R.; Maurer, J.; Münzenberg, G.; Antalic, S.; Barth, W.; Dahl, L.; Eberhardt, K.; Grzywacz, R.; Hamilton, J. H.; Henderson, R. A.; Kenneally, J. M.; Kindler, B.; Kojouharov, I.; Lang, R.; Lommel, B.; Miernik, K.; Miller, D.; Moody, K. J.; Morita, K.; Nishio, K.; Popeko, A. G.; Roberto, J. B.; Runke, J.; Rykaczewski, K. P.; Scheidenberger, C.; Shaughnessy, D. A.; Stoyer, M. A.; Thörle-Pospiech, P.; Tinschert, K.; Trautmann, N.; Uusitalo, J.; Yeremin, A. V.

    2016-04-01

    Shell-correction energies of super-heavy nuclei are approximated by using QαQα values of measured decay chains. Five decay chains were analyzed, which start at the isotopes 285Fl, 294118, 291Lv, 292Lv and 293Lv. The data are compared with predictions of macroscopic-microscopic models. Fission barriers are estimated that can be used to eliminate uncertainties in partial fission half-lives and in calculations of evaporation-residue cross-sections. In that calculations, fission probability of the compound nucleus is a major factor contributing to the total cross-section. The data also provide constraints on the cross-sections of capture and quasi-fission in the entrance channel of the fusion reaction. Arguments are presented that fusion reactions for synthesis of isotopes of elements 118 and 120 may have higher cross-sections than assumed so far.

  13. Temperature dependence of drain-induced barrier lowering in deep submicrometre MOSFETs

    Science.gov (United States)

    Fikry, W.; Ghibaudo, G.; Dutoit, M.

    1994-05-01

    A new method for extracting the drain-induced barrier lowering (DIBL) parameter in an MOS transistor is proposed. This method is used to study the influence of temperature on the DIBL effect. It is found that the DIBL parameter is almost independent of temperature between 50 and 300 K. This method also makes it possible to recalculate the intrinsic output characteristics that the device would have in the absence of DIBL, and, in turn, to evaluate the intrinsic device saturation parameters.

  14. Rupturing the hemi-fission intermediate in membrane fission under tension: Reaction coordinates, kinetic pathways, and free-energy barriers

    Science.gov (United States)

    Zhang, Guojie; Müller, Marcus

    2017-08-01

    Membrane fission is a fundamental process in cells, involved inter alia in endocytosis, intracellular trafficking, and virus infection. Its underlying molecular mechanism, however, is only incompletely understood. Recently, experiments and computer simulation studies have revealed that dynamin-mediated membrane fission is a two-step process that proceeds via a metastable hemi-fission intermediate (or wormlike micelle) formed by dynamin's constriction. Importantly, this hemi-fission intermediate is remarkably metastable, i.e., its subsequent rupture that completes the fission process does not occur spontaneously but requires additional, external effects, e.g., dynamin's (unknown) conformational changes or membrane tension. Using simulations of a coarse-grained, implicit-solvent model of lipid membranes, we investigate the molecular mechanism of rupturing the hemi-fission intermediate, such as its pathway, the concomitant transition states, and barriers, as well as the role of membrane tension. The membrane tension is controlled by the chemical potential of the lipids, and the free-energy landscape as a function of two reaction coordinates is obtained by grand canonical Wang-Landau sampling. Our results show that, in the course of rupturing, the hemi-fission intermediate undergoes a "thinning → local pinching → rupture/fission" pathway, with a bottle-neck-shaped cylindrical micelle as a transition state. Although an increase of membrane tension facilitates the fission process by reducing the corresponding free-energy barrier, for biologically relevant tensions, the free-energy barriers still significantly exceed the thermal energy scale kBT.

  15. I. Fission Probabilities, Fission Barriers, and Shell Effects. II. Particle Structure Functions

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Kexing [Univ. of California, Berkeley, CA (United States)

    1999-05-01

    In Part I, fission excitation functions of osmium isotopes 185,186, 187, 189 Os produced in 3He +182,183, 184, 186W reactions, and of polonium isotopes 209,210, 211, 212Po produced in 3He/4He + 206, 207, 208Pb reactions, were measured with high precision. These excitation functions have been analyzed in detail based upon the transition state formalism. The fission barriers, and shell effects for the corresponding nuclei are extracted from the detailed analyses. A novel approach has been developed to determine upper limits of the transient time of the fission process. The upper limits are constrained by the fission probabilities of neighboring isotopes. The upper limits for the transient time set with this new method are 15x 10–21 sec and 25x 10–21 sec for 0s and Po compound nuclei, respectively. In Part II, we report on a search for evidence of the optical modulations in the energy spectra of alpha particles emitted from hot compound nuclei. The optical modulations are expected to arise from the ~-particle interaction with the rest of the nucleus as the particle prepares to exit. Some evidence for the modulations has been observed in the alpha spectra measured in the 3He-induced reactions, 3He + natAg in particular. The identification of the modulations involves a technique that subtracts the bulk statistical background from the measured alpha spectra, in order for the modulations to become visible in the residuals. Due to insufficient knowledge of the background spectra, however, the presented evidence should only be regarded as preliminary and tentative.

  16. Temperature dependent current-voltage characteristics of Au/n-Si Schottky barrier diodes and the effect of transition metal oxides as an interface layer

    Science.gov (United States)

    Mahato, Somnath; Puigdollers, Joaquim

    2018-02-01

    Temperature dependent current-voltage (I‒V) characteristics of Au/n-type silicon (n-Si) Schottky barrier diodes have been investigated. Three transition metal oxides (TMO) are used as an interface layer between gold and silicon. The basic Schottky diode parameters such as ideality factor (n), barrier height (ϕb 0) and series resistance (Rs) are calculated and successfully explained by the thermionic emission (TE) theory. It has been found that ideality factor decreased and barrier height increased with increased of temperature. The conventional Richardson plot of ln(I0/T2) vs. 1000/T is determined the activation energy (Ea) and Richardson constant (A*). Whereas value of 'A*' is much smaller than the known theoretical value of n-type Si. The temperature dependent I-V characteristics obtained the mean value of barrier height (ϕb 0 bar) and standard deviation (σs) from the linear plot of ϕap vs. 1000/T. From the modified Richardson plot of ln(I0/T2) ˗ (qσ)2/2(kT)2 vs. 1000/T gives Richardson constant and homogeneous barrier height of Schottky diodes. Main observation in this present work is the barrier height and ideality factor shows a considerable change but the series resistance value exhibits negligible change due to TMO as an interface layer.

  17. Fission of heavy nuclei: microscopic study of fission barriers and fragments angular momentum; Fission des noyaux lourds: etude microscopique des barrieres de fission et du moment angulaire des fragments

    Energy Technology Data Exchange (ETDEWEB)

    Bonneau, L

    2003-11-01

    A lot of experimental data on nuclear fission has been being collected for the last 65 years, allowing theoreticians to confront their models with reality. The first part of this work is dedicated to the computation of fission barriers. We have extended the HF + BCS (Hartree Fock + Bandeen-Cooper-Schrieffer) method in order to include a new set of polynomials on which wave functions can be broken to, more accurately than on Hermite's polynomials in the 2 fragment configuration. The fission barriers of 26 heavy nuclei from Thorium-230 to Nobelium-256 have been assessed and compared to experimental data, it appears that differences are no greater than 1 MeV. We have discovered a neat correlation between the variation of the experimental fission lifetimes of even Fermium isotopes and the computed heights of second barriers. Moreover our model reproduces the hyper-deformed well of Thorium-230 with a good agreement on the well depth. The second part deals with the scission region. We have performed Hartree-Fock calculations in order to explore different ways of fragmentation. We have shown that the harmonic oscillator gives a valid description of such ways. In order to compute the mean value of J{sup 2} in the fragments we have been driven to propose an adequate definition of that quantity consistent with the non-locality property of the J{sup 2} operator. (A.C.)

  18. Temperature dependence of friction from pre- and post-scission neutron emission 24.75.+i; 25.70.Jj; Fission dynamics; Nuclear friction; Neutron multiplicities

    CERN Document Server

    Rudolf, G

    2001-01-01

    The magnitude of nuclear friction has been investigated in recent years by measuring pre- and post-scission neutron multiplicities. These data have been analysed mostly in the frame of the statistical model by introducing ad-hoc delays to go from equilibrium to saddle and then to scission. We present here a more simple approach based on remaining excitation energies at saddle. This leads to analytical formulae which reproduce almost all the published data. The temperature at which one observes transition from pre-scission to post-scission emission is the only parameter in the calculation. Its values show no significant variation with the total mass nor with bombarding energy, supporting the concept of temperature dependent friction. The mean value averaged over all published data is 1.11+-0.05 MeV.

  19. A new approach to barrier-top fission dynamics

    Directory of Open Access Journals (Sweden)

    Bertsch G.F.

    2016-01-01

    Full Text Available We proposed a calculational framework for describing induced fission that avoids the Bohr-Wheeler assumption of well-defined fission channels. The building blocks of our approach are configurations that form a discrete, orthogonal basis and can be characterized by both energy and shape. The dynamics is to be determined by interaction matrix elements between the states rather than by a Hill-Wheeler construction of a collective coordinate. Within our approach, several simple limits can be seen: diffusion; quantized conductance; and ordinary decay through channels. The specific proposal for the discrete basis is to use the Kπ quantum numbers of the axially symmetric Hartree-Fock approximation to generate the configurations. Fission paths would be determined by hopping from configuration to configuration via the residual interaction. We show as an example the configurations needed to describe a fictitious fission decay 32S → 16 O + 16 O. We also examine the geometry of the path for fission of 236U, measuring distances by the number of jumps needed to go to a new Kπ partition.

  20. Schottky barrier diode based on β-Ga2O3 (100) single crystal substrate and its temperature-dependent electrical characteristics

    Science.gov (United States)

    He, Qiming; Mu, Wenxiang; Dong, Hang; Long, Shibing; Jia, Zhitai; Lv, Hangbing; Liu, Qi; Tang, Minghua; Tao, Xutang; Liu, Ming

    2017-02-01

    The Pt/β-Ga2O3 Schottky barrier diode and its temperature-dependent current-voltage characteristics were investigated for power device application. The edge-defined film-fed growth (EFG) technique was utilized to grow the (100)-oriented β-Ga2O3 single crystal substrate that shows good crystal quality characterized by X-ray diffraction and high resolution transmission electron microscope. Ohmic and Schottky electrodes were fabricated by depositing Ti and Pt metals on the two surfaces, respectively. Through the current-voltage (I-V) measurement under different temperature and the thermionic emission modeling, the fabricated Pt/β-Ga2O3 Schottky diode was found to show good performances at room temperature, including rectification ratio of 1010, ideality factor (n) of 1.1, Schottky barrier height (ΦB) of 1.39 eV, threshold voltage (Vbi) of 1.07 V, ON-resistance (RON) of 12.5 mΩ.cm2, forward current density at 2 V (J@2V) of 56 A/cm2, and saturation current density (J0) of 2 × 10-16 A/cm2. The effective donor concentration Nd - Na was calculated to be about 2.3 × 1014 cm3. Good temperature dependent performance was also found in the device. The Schottky barrier height was estimated to be about 1.3 eV-1.39 eV at temperatures ranging from room temperature to 150 °C. With increasing temperature, parameters such as RON and J@2V become better, proving that the diode can work well at high temperature. The EFG grown β-Ga2O3 single crystal is a promising material to be used in the power devices.

  1. Temperature dependence of internal motions of protein side-chain NH3(+) groups: insight into energy barriers for transient breakage of hydrogen bonds.

    Science.gov (United States)

    Zandarashvili, Levani; Iwahara, Junji

    2015-01-20

    Although charged side chains play important roles in protein function, their dynamic properties are not well understood. Nuclear magnetic resonance methods for investigating the dynamics of lysine side-chain NH3(+) groups were established recently. Using this methodology, we have studied the temperature dependence of the internal motions of the lysine side-chain NH3(+) groups that form ion pairs with DNA phosphate groups in the HoxD9 homeodomain-DNA complex. For these NH3(+) groups, we determined order parameters and correlation times for bond rotations and reorientations at 15, 22, 28, and 35 °C. The order parameters were found to be virtually constant in this temperature range. In contrast, the bond-rotation correlation times of the NH3(+) groups were found to depend strongly on temperature. On the basis of transition state theory, the energy barriers for NH3(+) rotations were analyzed and compared to those for CH3 rotations. Enthalpies of activation for NH3(+) rotations were found to be significantly higher than those for CH3 rotations, which can be attributed to the requirement of hydrogen bond breakage. However, entropies of activation substantially reduce the overall free energies of activation for NH3(+) rotations to a level comparable to those for CH3 rotations. This entropic reduction in energy barriers may accelerate molecular processes requiring hydrogen bond breakage and play a kinetically important role in protein function.

  2. Fission barriers of super-heavy nuclei produced in cold-fusion reactions

    Energy Technology Data Exchange (ETDEWEB)

    Peter, J. [LPC Caen, ENSICAEN, Caen cedex (France)

    2004-11-01

    Excitation functions of super-heavy evaporation residues formed in cold-fusion reactions were analyzed with the aim of getting information on the fission barrier height of these nuclei. The method uses the location of the maximum of 1n and 2n excitation functions. The results obtained on nuclei from Z=104 to 112 are compared to three theoretical predictions. (orig.)

  3. Challenging fission dynamics around the barrier: The case of {sup 34}S + {sup 186}W

    Energy Technology Data Exchange (ETDEWEB)

    Kozulin, E.M.; Itkis, I.; Knyazheva, G.; Novikov, K.; Bogachev, A.; Dmitriev, S.; Loktev, T. [Joint Institute for Nuclear Research, Flerov Laboratory of Nuclear Reactions, Dubna (Russian Federation); Vardaci, E. [Dipartamento di Scienze Fisiche, Napoli (Italy); INFN, Napoli (Italy); Harca, I.M. [Joint Institute for Nuclear Research, Flerov Laboratory of Nuclear Reactions, Dubna (Russian Federation); Horia Hulubei National Institute for R and D in Physics and Nuclear Engineering (IFIN-HH), Bucharest - Magurele (Romania); Universitatea din Bucuresti, Facultatea de Fizica, Bucharest (Romania); Schmitt, C.; Piot, J. [GANIL, CEA/DSM-CNRS/IN2P3, Bd Henri Becquerel, BP 55027, Caen (France); Azaiez, F.; Matea, I.; Verney, D.; Gottardo, A. [Universite Paris-Saclay, IPN, CNRS/IN2P3, Orsay (France); Dorvaux, O. [Universite de Strasbourg, IPHC, CNRS/IN2P3, Strasbourg (France); Chubarian, G. [Texas A and M University, Cyclotron Institute, College Station, TX (United States); Trzaska, W.H. [Accelerator Laboratory of University of Jyvaskyla (JYFL), Jyvaskyla (Finland); Hanappe, F. [Universite Libre de Bruxelles (ULB), Bruxelles (Belgium); Borcea, C.; Calinescu, S.; Petrone, C. [Horia Hulubei National Institute for R and D in Physics and Nuclear Engineering (IFIN-HH), Bucharest - Magurele (Romania)

    2016-09-15

    The current status of fission dynamics studies in heavy-ion collisions around the Coulomb barrier is illustrated with the {sup 34}S + {sup 186}W reaction. The fission-fragment mass and total kinetic energy were measured at the ALTO facility at IPN Orsay, France, with a dedicated set-up using the (v, E) approach. The measurement reveals the presence of an asymmetric fission component on top of a predominantly symmetric distribution. The asymmetric structure, pointed out for the first time, is discussed along with results of previous experiments studying the same reaction. While these analyses suggested the contribution from either quasi-fission or pre-equilibrium fission, we offer an alternative interpretation, in terms of shell-driven compound-nucleus fission. The present measurement demonstrates the critical influence of resolution when addressing puzzling cases, situated at the crossroads of the various channels opened in a heavy-ion collision. Current status in the field clearly calls for innovative measurements involving manifold correlations and new observables. The outcome of the attempt done in this work in this direction, based on the coincident measurement of prompt γ-rays is reported, and encouraging perspectives are discussed. (orig.)

  4. Mass distributions in nucleon-induced fission at intermediate energies

    CERN Document Server

    Duijvestijn, M C; Hambsch, F J

    2001-01-01

    Temperature-dependent fission barriers and fission-fragment mass distributions are calculated in the framework of the multimodal random neck-rupture model (MM-RNRM). It is shown how the distinction between the different fission modes disappears at higher excitation energies, due to the melting of shell effects. The fission-fragment mass yield calculations are coupled to the nuclear reaction code ALICE-91, which takes into account the competition between the other reaction channels and fission. With the combination of the temperature-dependent MM-RNRM and ALICE-91 nucleon-induced fission is investigated at energies between 10 and 200 MeV for nuclei varying from Au to Am. (72 refs).

  5. Fission Meter Information Barrier Attribute Measurement System: Task 1 Report: Document existing Fission Meter neutron IB system

    Energy Technology Data Exchange (ETDEWEB)

    Kerr, P. L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-02-28

    An SNM attribute Information Barrier (IB) system was developed for a 2011 US/UK Exercise. The system was modified and extensively tested in a 2013-2014 US-UK Measurement Campaign. This work demonstrated rapid deployment of an IB system for potential treaty use. The system utilizes an Ortec Fission Meter neutron multiplicity counter and custom computer code. The system demonstrates a proof-of-principle automated Pu-240 mass determination with an information barrier. After a software start command is issued, the system automatically acquires and downloads data, performs an analysis, and displays the results. This system conveys the results of a Pu mass threshold measurements in a way the does not reveal sensitive information. In full IB mode, only red/green ‘lights’ are displayed in the software. In test mode, more detailed information is displayed. The code can also read in, analyze, and display results from previously acquired or simulated data. Because the equipment is commercial-off-the-shelf (COTS), the system demonstrates a low-cost short-lead-time technology for treaty SNM attribute measurements. A deployed system will likely require integration of additional authentication and tamper-indicating technologies. This will be discussed for the project in this and future progress reports.

  6. Triaxial quadrupole dynamics and the inner fission barrier of some heavy even-even nuclei

    Science.gov (United States)

    Benrabia, K.; Medjadi, D. E.; Imadalou, M.; Quentin, P.

    2017-09-01

    Background: Inner fission barriers of actinide nuclei have been known for a long time to be unstable with respect to the axial symmetry. On the other hand, taking into account the effect of the relevant adiabatic mass parameter reduces or even may wash out this instability. A proper treatment of the dynamics for both axial and triaxial modes is thus crucial to accurately determine the corresponding fission barriers. This entails in particular an accurate description of pairing correlations. Purpose: We evaluate the potential energies, moments of inertia, and vibrational mass parameters in a two-dimensional relevant deformation space (corresponding to the usual β and γ quadrupole deformation parameters) for four actinide nuclei (236U, 240Pu, 248Cm, and 252Cf). We assess the relevance of our approach to describe the dynamics for a triaxial mode by computing the low energy spectra (exploring thus mainly the equilibrium deformation region). We evaluate the inner fission barrier heights releasing the axial symmetry constraint. Method: Calculations within the Hartree-Fock plus BCS approach are performed using the SkM* Skyrme effective interaction in the particle-hole channel and a seniority force in the particle-particle channel. The intensity of this residual interaction has been fixed to allow a good reproduction of some odd-even mass differences in the actinide region. Adiabatic mass parameters for the rotational and vibrational modes are calculated using the Inglis-Belyaev formula supplemented by a global renormalization factor taking into account the so-called Thouless-Valatin corrections. Spectra are obtained through the diagonalization of the corresponding Bohr collective Hamiltonian. Results: The experimental low energy spectra are qualitatively well reproduced by our calculations for the considered nuclei. Inner fission barrier heights are calculated and compared with available estimates from various experimental data. The reproduction of the data is better

  7. Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. V. Extension to fission barriers

    Science.gov (United States)

    Samyn, M.; Goriely, S.; Pearson, J. M.

    2005-10-01

    Large-scale fission barrier calculations have been performed in the framework of the Skyrme-Hartree-Fock model. Our Hartree-Fock-Bogoliubov calculations restore broken symmetries such as translational invariance, particle-number conservation, parity, and, in a more approximate way, rotational invariance. Axial symmetry is imposed, but reflection asymmetry is allowed. The energy surface properties are analyzed with the flooding method. A large set of Skyrme interactions, which were fitted to all known masses under different specific constraints, is used to study the main effects influencing the energy surface and the barrier heights. The principal interaction used in the comparison with experimental barriers is BSk8, the force on which the HFB-8 mass table is based. We found that for nuclei with 92≤Z≤98 the agreement of our calculations with experimental data is excellent; the rms deviation on the primary barriers is 0.722 MeV. For lighter nuclei, however, the calculated primary barriers are always too high because of the existence of a third barrier at very high deformations. However, our calculated superheavy barriers appear to be too low, although they are consistent with previous calculations.

  8. An RNA polymerase III-dependent heterochromatin barrier at fission yeast centromere 1.

    Directory of Open Access Journals (Sweden)

    Kristin C Scott

    Full Text Available Heterochromatin formation involves the nucleation and spreading of structural and epigenetic features along the chromatin fiber. Chromatin barriers and associated proteins counteract the spreading of heterochromatin, thereby restricting it to specific regions of the genome. We have performed gene expression studies and chromatin immunoprecipitation on strains in which native centromere sequences have been mutated to study the mechanism by which a tRNA(Alanine gene barrier (cen1 tDNA(Ala blocks the spread of pericentromeric heterochromatin at the centromere of chromosome 1 (cen1 in the fission yeast, Schizosaccharomyces pombe. Within the centromere, barrier activity is a general property of tDNAs and, unlike previously characterized barriers, requires the association of both transcription factor IIIC and RNA Polymerase III. Although the cen1 tDNA(Ala gene is actively transcribed, barrier activity is independent of transcriptional orientation. These findings provide experimental evidence for the involvement of a fully assembled RNA polymerase III transcription complex in defining independent structural and functional domains at a eukaryotic centromere.

  9. Estimates of fission barrier heights for neutron-deficient Po to Ra nuclei produced in fusion reactions

    Science.gov (United States)

    Sagaidak, Roman

    2017-09-01

    The cross section data for fission and evaporation residue production in fusion reactions leading to nuclei from Po to Ra have been considered in a systematic way in the framework of the conventional barrier-passing (fusion) model coupled with the statistical model. The cross section data obtained in very asymmetric projectile-target combinations can be described within these models rather well with the adjusted model parameters. In particular, one can scale and fix the macroscopic (liquid-drop) fission barrier heights (FBHs) for nuclei involved in the de-excitation of compound nuclei produced in the reactions. The macroscopic FBHs for nuclei from Po to Ra have been derived in the framework of such analysis and compared with the predictions of various theoretical models.

  10. Estimates of fission barrier heights for neutron-deficient Po to Ra nuclei produced in fusion reactions

    Directory of Open Access Journals (Sweden)

    Sagaidak Roman

    2017-01-01

    Full Text Available The cross section data for fission and evaporation residue production in fusion reactions leading to nuclei from Po to Ra have been considered in a systematic way in the framework of the conventional barrier-passing (fusion model coupled with the statistical model. The cross section data obtained in very asymmetric projectile-target combinations can be described within these models rather well with the adjusted model parameters. In particular, one can scale and fix the macroscopic (liquid-drop fission barrier heights (FBHs for nuclei involved in the de-excitation of compound nuclei produced in the reactions. The macroscopic FBHs for nuclei from Po to Ra have been derived in the framework of such analysis and compared with the predictions of various theoretical models.

  11. Fission barriers and asymmetric ground states in the relativistic mean-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Rutz, K. [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Maruhn, J.A. [Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, TN 87831 (United States); Reinhard, P.G. [Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, TN 87831 (United States); Greiner, W. [Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, TN 87831 (United States)

    1995-07-31

    The symmetric and asymmetric fission path for {sup 240}Pu, {sup 232}Th and {sup 226}Ra is investigated within the relativistic mean-field model. Standard parametrizations which are well fitted to nuclear ground-state properties are found to deliver reasonable qualitative and quantitative features of fission, comparable to similar nonrelativistic calculations. Furthermore, stable octupole deformations in the ground states of radium isotopes are investigated. They are found in a series of isotopes, qualitatively in agreement with nonrelativistic models. But the quantitative details differ amongst the models and between the various relativistic parametrizations. (orig.).

  12. 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.

  13. 1: Mass asymmetric fission barriers for {sup 98}Mo; 2: Synthesis and characterization of actinide-specific chelating agents

    Energy Technology Data Exchange (ETDEWEB)

    Veeck, A.C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Livermore National Lab., CA (United States). Glenn T. Seaborg Inst. for Transactinium Science]|[Lawrence Berkeley National Lab., CA (United States). Nuclear Science Div.

    1996-08-01

    Excitation functions have been measured for complex fragment emission from the compound nucleus {sup 98}Mo, produced by the reaction of {sup 86}Kr with {sup 12}C. Mass asymmetric fission barriers have been obtained by fitting the excitation functions with a transition state formalism. The extracted barriers are {approximately} 5.7 MeV higher, on average, than the calculations of the Rotating Finite Range Model (RFRM). These data clearly show an isospin dependence of the conditional barriers when compared with the extracted barriers from {sup 90}Mo and {sup 94}Mo. Eleven different liquid/liquid extractants were synthesized based upon the chelating moieties 3,2-HOPO and 3,4-HOPO; additionally, two liquid/liquid extractants based upon the 1,2-HOPO chelating moiety were obtained for extraction studies. The Pu(IV) extractions, quite surprisingly, yielded results that were very different from the Fe(III) extractions. The first trend remained the same: the 1,2-HOPOs were the best extractants, followed closely by the 3,2-HOPOs, followed by the 3,4-HOPOs; but in these Pu(IV) extractions the 3,4-HOPOs performed much better than in the Fe(III) extractions. 129 refs.

  14. Fission Meter Information Barrier Attribute Measurement System - NA-243 FNI/UKC FY2017 Task 1-2 Report

    Energy Technology Data Exchange (ETDEWEB)

    Kerr, P. L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Decman, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Prasad, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Castro, P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2018-01-03

    An SNM attribute Information Barrier (IB) system was developed for a 2011 US/UK Exercise. The system was modified and extensively tested in a 2013-2014 US-UK Measurement Campaign. This work demonstrated rapid deployment of an IB system for potential treaty use. The system utilizes an Ortec Fission Meter neutron multiplicity counter and custom computer code. The system demonstrates a proof-of-principle automated Pu-240 mass determination with an information barrier. After a software start command is issued, the system automatically acquires and downloads data, performs an analysis, and displays the results. This system conveys the results of a Pu mass threshold measurements in a way the does not reveal sensitive information. In full IB mode, only the pass/fail result is displayed as a “Mass <= Threshold Amount” or “Mass >= Threshold Amount” as shown in Figure 4. This can easily be adapted to a red/green “lights” display similar to the Detective IB system for Pu isotopics as shown in Figure 6. In test mode, more detailed information is displayed. The code can also read in, analyze, and display results from previously acquired or simulated data. Because the equipment is commercial-off-the-shelf (COTS), the system demonstrates a low-cost short-lead-time technology for treaty SNM attribute measurements. A deployed system will likely require integration of additional authentication and tamper-indicating technologies. This will be discussed for the project in this and future progress reports.

  15. Excitation functions and mass asymmetric fission barriers for compound nuclei sup 7 sup 0 sup , sup 7 sup 6 Se 24.60.Dr; 25.85.Ge; 24.75.+i; Nuclear reactions 12C(58,64Ni,X); E=6-14A MeV; Measured sigma(Z) vs E; Deduced mass asymmetric fission barriers for 70,76Se; Transition state fission rates

    CERN Document Server

    Fan, T S; Phair, L; Tso, K; McMahan, M; Hanold, K A; Wozniak, G J; Moretto, L G

    2000-01-01

    Excitation functions were measured for complex fragments with atomic number Z=5-20 emitted from the compound nuclei sup 7 sup 0 sup , sup 7 sup 6 Se produced in the reactions sup 5 sup 8 sup , sup 6 sup 4 Ni+ sup 1 sup 2 C. Mass asymmetric fission barriers were extracted by fitting the excitation functions with a transition state formalism. The extracted barriers were compared with those calculated from macroscopic nuclear models. The measured barriers for symmetric fission seem to support the hypothesis of a shape-dependent congruence energy, which doubles for fission of strongly indented saddle-point shapes. All of the measured excitation functions can be scaled onto a single straight line according to the transition state prediction.

  16. Transition state rates and mass asymmetric fission barriers of compound nuclei sup 9 sup 0 sup , sup 9 sup 4 sup , sup 9 sup 8 Mo

    CERN Document Server

    Jing, K X; Veeck, A C; Colonna, N; Lhenry, I; Tso, K; Hanold, K A; Skulski, W; Sui, Q; Wozniak, G J

    1999-01-01

    Excitation functions were measured for complex fragments with atomic number Z = 5-25 emitted from the compound nuclei sup 9 sup 0 sup , sup 9 sup 4 sup , sup 9 sup 8 Mo produced in the reactions sup 7 sup 8 sup , sup 8 sup 2 sup , sup 8 sup 6 Kr + sup 1 sup 2 C. Mass-asymmetric fission barriers were extracted by fitting the excitation functions with a transition state formalism. The extracted barriers are several MeV higher on average than the calculations of the Rotating Finite-Range Model and substantially lower than predicted by the Rotating Liquid Drop Model. The symmetric fission barriers measured support the hypothesis of a congruence term that doubles for the fission of strongly indented saddle-point shapes. The excitation functions were analyzed to search for atomic number Z- and energy E-dependent deviations from transition-state-method predictions. All of the measured excitation functions can be scaled onto a single universal straight line according to the transition-state predictions. No Z- and/or ...

  17. The fusion-fission process in the reaction {sup 34}S+{sup 186}W near the interaction barrier

    Energy Technology Data Exchange (ETDEWEB)

    Harca, I. M. [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, (FLNR JINR) Dubna, Russia and Faculty of Physics, University of Bucharest - P.O. Box MG 11, RO 77125, Bucharest-Magurele (Romania); Dmitriev, S.; Itkis, J.; Kozulin, E. M.; Knyazheva, G.; Loktev, T.; Novikov, K. [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, (FLNR JINR) Dubna (Russian Federation); Azaiez, F.; Gottardo, A.; Matea, I.; Verney, D. [IPN, CNRS/IN2P3, Univ. Paris-Sud, 91405 Orsay (France); Chubarian, G. [Cyclotron Institute, Texas A and M University, College Station, TX 77843-3366 (United States); Hanappe, F. [Universite Libre de Bruxelles (ULB), Bruxelles (Belgium); Piot, J.; Schmitt, C. [GANIL, CEA/DSM-CNRS/IN2P3, Bd Henri Becquerel, BP 55027, F-14076 Caen Cedex 5 (France); Trzaska, W. H. [Accelerator Laboratory of University of Jyväskylä (JYFL), Jyväskylä (Finland); Vardaci, E. [Dipartamento di Scienze Fisiche and INFN (INFN-Na), Napoli (Italy)

    2015-02-24

    The reaction {sup 34}S+{sup 186}W at E{sub lab}=160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The coupling of the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fission process and gives information regarding production of neutron-rich heavy nuclei. The FF–γ coincidence method is of better use then the γ – γ coincidence method when dealing with low statistic measurements and also offers the opportunity to precisely correct the Dopler shift for in-flight emitted gamma rays. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting a specific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented.

  18. 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 ...

  19. 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 ...

  20. 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.

  1. 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.

  2. 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 ...

  3. 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.

  4. (d,p)-transfer induced fission of heavy radioactive beams

    CERN Document Server

    Veselsky, Martin

    2012-01-01

    (d,p)-transfer induced fission is proposed as a tool to study low energy fission of exotic heavy nuclei. Primary goal is to directly determine the fission barrier height of proton-rich fissile nuclei, preferably using the radio-active beams of isotopes of odd elements, and thus confirm or exclude the low values of fission barrier heights, typically extracted using statistical calculations in the compound nucleus reactions at higher excitation energies. Calculated fission cross sections in transfer reactions of the radioactive beams show sufficient sensitivity to fission barrier height. In the probable case that fission rates will be high enough, mass asymmetry of fission fragments can be determined. Results will be relevant for nuclear astrophysics and for production of super-heavy nuclei. Transfer induced fission offers a possibility for systematic study the low energy fission of heavy exotic nuclei at the ISOLDE.

  5. Fusion-fission studies on 19F+206,208Pb and 11B,19F+238U reactions around barrier energies at IUAC facility

    Science.gov (United States)

    Pullanhiotan, Sugathan; Dubey, Rakesh; Yadav, Chandrabhan; Jhingan, Akhil; Komalan Satheedas, Golda; Nedumbally, Saneesh; Kumar, Mohit

    2017-11-01

    Fission process is strongly influenced by entrance channel dynamical variables. Among these, the nuclear charge product, mass asymmetry and deformation play important role in fission dynamics. Reaction characteristics are distinguished by investigating the properties of fission mass and angular distributions. Experiments using actinide targets are challenging due to many conflicting results making unambiguous identification of quasi-fission difficult. At IUAC accelerator facility many experiments have been performed to make a systematic study of fission mechanism and role of entrance channel parameters and deformation. Fragment mass distribution, angular distribution and neutron multiplicity measurements are performed to study reactions using spherical and deformed targets.

  6. 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.

  7. 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....

  8. 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.

  9. 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.

  10. 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.

  11. Hidden systematics of fission channels

    Directory of Open Access Journals (Sweden)

    Schmidt Karl-Heinz

    2013-12-01

    of the fissioning system obey a hidden systematics that can be explained by the number of states in the vicinity of the outer fission barrier as a function of mass asymmetry, if the potential is constructed as the sum of the macroscopic contribution of the compound nucleus and empirically determined fragment shells. This hidden systematics also explains the transition from asymmetric to symmetric fission around 226Th and around 258Fm.

  12. 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.

  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. Ternary fission

    Indian Academy of Sciences (India)

    2015-08-05

    Aug 5, 2015 ... We present the ternary fission of 252Cf and 236U within a three-cluster model as well as in a level density approach. The competition between collinear and equatorial geometry is studied by calculating the ternary fragmentation potential as a function of the angle between the lines joining the stationary ...

  15. Ternary fission

    Indian Academy of Sciences (India)

    Recently, we have studied the various aspects associated with the ternary fission process. A model, called the three-cluster model (TCM) [1–6] has been put forth. This accounts for the energy minimization of all possible ternary breakups of a heavy radioactive nucleus. Further, within the TCM we have analysed the ...

  16. Theoretical Description of the Fission Process

    Energy Technology Data Exchange (ETDEWEB)

    Witold Nazarewicz

    2003-07-01

    The main goals of the project can be summarized as follows: Development of effective energy functionals that are appropriate for the description of heavy nuclei. Our goal is to improve the existing energy density (Skyrme) functionals to develop a force that will be used in calculations of fission dynamics. Systematic self-consistent calculations of binding energies and fission barriers of actinide and trans-actinide nuclei using modern density functionals. This will be followed by calculations of spontaneous fission lifetimes and mass and charge divisions using dynamic adiabatic approaches based on the WKB approximation. Investigate novel microscopic (non-adiabatic) methods to study the fission process.

  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 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.

  3. Dynamics of fission and Coulomb explosion of multicharged large finite systems

    Science.gov (United States)

    Levy, Y.; Last, I.; Jortner, J.

    This paper reports on studies of the fragmentation dynamics of multicharged (A+)55 Morse clusters, where the variation of the range of the Morse potential parameters induces cluster fission for a long-range potential and Coulomb explosion for a short-range potential. The multidimensional energy landscapes for these fragmentation processes were explored by constructing reduced coordinates utilizing the principal component analysis (PCA), which was previously applied for the energy landscapes and folding dynamics of biomolecules. The distance-matrix based PCA was applied to study the effects of the potential on the fragmentation dynamics and to explore the structural diversity of the fragmentation processes. The first principal coordinate (which captures 95% of the dynamic information content for each trajectory) constitutes an appropriate reaction coordinate for both fission and Coulomb explosion and was used to determine the temperature-dependent fragmentation rates. These obey the Arrhenius law, with the barrier for fission (0.36 eV) being higher than for Coulomb explosion (0.22 eV). Structural and energetic information on the radius of gyration and on the potential energy for small values of the reaction coordinate manifest considerably larger fluctuations for fission than for Coulomb explosion, indicating that in the former case the cluster shrinks and swells prior to dissociation. The joint projection of multiple trajectories for each fragmentation process allows for the description of the energy landscapes and fragmentation pathways in terms of two principal coordinates, which manifest a form of 'ski slopes'. Different collective coordinates describe the spatially isotropic Coulomb explosion and the spatially unisotropic fission.

  4. 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...

  5. 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.

  6. 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.

  7. Above-threshold structure in {sup 244}Cm neutron-induced fission cross section

    Energy Technology Data Exchange (ETDEWEB)

    Maslov, V.M. [Radiation Physics and Chemistry Problems Inst., Minsk-Sosny (Belarus)

    1997-03-01

    The quasi-resonance structure appearing above the fission threshold in neutron-induced fission cross section of {sup 244}Cm(n,f) is interpreted. It is shown to be due to excitation of few-quasiparticle states in fissioning {sup 245}Cm and residual {sup 244}Cm nuclides. The estimate of quasiparticle excitation thresholds in fissioning nuclide {sup 245}Cm is consistent with pairing gap and fission barrier parameters. (author)

  8. 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.

  9. 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...

  10. 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...

  11. 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.

  12. Fission of ionized alkali metal clusters

    Energy Technology Data Exchange (ETDEWEB)

    Lipparini, E.; Vitturi, A. (Trento Univ. (Italy). Dipartimento di Fisica Istituto Nazionale di Fisica Nucleare, Povo (Italy))

    1990-09-01

    We study the symmetric fragmentation of ionized alkali clusters within a liquid-drop type model. The interplay of surface and Coulomb interactions leads to a stability condition against small deformations which depends on the ratio Z{sup 2}/N. For systems which are stable small-amplitude oscillations we consider the possibility of large-amplitude modes eventually leading to fission and give, in terms of the same quantity, an estimate of the potential barrier for this fission channel. (orig.).

  13. Theoretical Description of the Fission Process

    Energy Technology Data Exchange (ETDEWEB)

    Witold Nazarewicz

    2009-10-25

    Advanced theoretical methods and high-performance computers may finally unlock the secrets of nuclear fission, a fundamental nuclear decay that is of great relevance to society. In this work, we studied the phenomenon of spontaneous fission using the symmetry-unrestricted nuclear density functional theory (DFT). Our results show that many observed properties of fissioning nuclei can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. From the calculated collective potential and collective mass, we estimated spontaneous fission half-lives, and good agreement with experimental data was found. We also predicted a new phenomenon of trimodal spontaneous fission for some transfermium isotopes. Our calculations demonstrate that fission barriers of excited superheavy nuclei vary rapidly with particle number, pointing to the importance of shell effects even at large excitation energies. The results are consistent with recent experiments where superheavy elements were created by bombarding an actinide target with 48-calcium; yet even at high excitation energies, sizable fission barriers remained. Not only does this reveal clues about the conditions for creating new elements, it also provides a wider context for understanding other types of fission. Understanding of the fission process is crucial for many areas of science and technology. Fission governs existence of many transuranium elements, including the predicted long-lived superheavy species. In nuclear astrophysics, fission influences the formation of heavy elements on the final stages of the r-process in a very high neutron density environment. Fission applications are numerous. Improved understanding of the fission process will enable scientists to enhance the safety and reliability of the nation’s nuclear stockpile and nuclear reactors. The deployment of a fleet of safe and efficient advanced reactors, which will also minimize radiotoxic

  14. 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.

  15. 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, ...

  16. 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

  17. 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 ...

  18. 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 ...

  19. 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 ...

  20. 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)

  1. 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.)

  2. 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 ...

  3. 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....

  4. 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 ...

  5. 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.

  6. 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.

  7. Fifty years of nuclear fission: Nuclear data and measurements series

    Energy Technology Data Exchange (ETDEWEB)

    Lynn, J.E.

    1989-06-01

    This report is the written version of a colloquium first presented at Argonne National Laboratory in January 1989. The paper begins with an historical preamble about the events leading to the discovery of nuclear fission. This leads naturally to an account of early results and understanding of the fission phenomena. Some of the key concepts in the development of fission theory are then discussed. The main theme of this discussion is the topography of the fission barrier, in which the interplay of the liquid-drop model and nucleon shell effects lead to a wide range of fascinating phenomena encompassing metastable isomers, intermediate-structure effects in fission cross-sections, and large changes in fission product properties. It is shown how study of these changing effects and theoretical calculations of the potential energy of the deformed nucleus have led to broad qualitative understanding of the nature of the fission process. 54 refs., 35 figs.

  8. 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.

  9. 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...

  10. 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".

  11. 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

  12. 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 ...

  13. 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.

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

    Science.gov (United States)

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

    2015-03-01

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

  15. Application of pulse shape discrimination in Si detector for fission ...

    Indian Academy of Sciences (India)

    Pulse shape discrimination (PSD) with totally depleted transmission type Si surface barrier detector in reverse mount has been investigated to identify fission fragments in the presence of elastic background in heavy ion-induced fission reactions by both numerical simulation and experimental studies. The PSD method is ...

  16. Molecular dynamics simulations of cluster fission and fusion processes

    DEFF Research Database (Denmark)

    Lyalin, Andrey G.; Obolensky, Oleg I.; Solov'yov, Ilia

    2004-01-01

    Results of molecular dynamics simulations of fission reactions Na_10^2+ --> Na_7^+ +Na_3^+ and Na_18^2+ --> 2Na_9^+ are presented. The dependence of the fission barriers on the isomer structure of the parent cluster is analyzed. It is demonstrated that the energy necessary for removing homothetic...

  17. Activation Energy for Fission

    Energy Technology Data Exchange (ETDEWEB)

    Seaborg, Glenn T.

    1952-08-29

    The experimentally determined exponential dependence of spontaneous fission rate on Z{sup 2}/A has been used to derive an expression for the dependence of the fission activation energy on Z{sup 2}/A. This expression has been used to calculate the activation energy for slow neutron induced fission and photofission. The correlation with the experimental data on these types of fission seems to be quite good.

  18. Temperature dependence of current-and capacitance-voltage characteristics of an Au/4H-SiC Schottky diode

    Science.gov (United States)

    Gülnahar, Murat

    2014-12-01

    In this study, the current-voltage (I-V) and capacitance-voltage (C-V) measurements of an Au/4H-SiC Schottky diode are characterized as a function of the temperature in 50-300 K temperature range. The experimental parameters such as ideality factor and apparent barrier height presents to be strongly temperature dependent, that is, the ideality factor increases and the apparent barrier height decreases with decreasing temperature, whereas the barrier height values increase with the temperature for C-V data. Likewise, the Richardson plot deviates at low temperatures. These anomaly behaviors observed for Au/4H-SiC are attributed to Schottky barrier inhomogeneities. The barrier anomaly which relates to interface of Au/4H-SiC is also confirmed by the C-V measurements versus the frequency measured in 300 K and it is interpreted by both Tung's lateral inhomogeneity model and multi-Gaussian distribution approach. The values of the weighting coefficients, standard deviations and mean barrier height are calculated for each distribution region of Au/4H-SiC using the multi-Gaussian distribution approach. In addition, the total effective area of the patches NAe is obtained at separate temperatures and as a result, it is expressed that the low barrier regions influence meaningfully to the current transport at the junction. The homogeneous barrier height value is calculated from the correlation between the ideality factor and barrier height and it is noted that the values of standard deviation from ideality factor versus q/3kT curve are in close agreement with the values obtained from the barrier height versus q/2kT variation. As a result, it can be concluded that the temperature dependent electrical characteristics of Au/4H-SiC can be successfully commented on the basis of the thermionic emission theory with both models.

  19. 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.

  20. 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...

  1. 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.

  2. 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.

  3. 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)

  4. 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.)

  5. Single particle fluorescence burst analysis of epsin induced membrane fission.

    Directory of Open Access Journals (Sweden)

    Arielle Brooks

    Full Text Available Vital cellular processes, from cell growth to synaptic transmission, rely on membrane-bounded carriers and vesicles to transport molecular cargo to and from specific intracellular compartments throughout the cell. Compartment-specific proteins are required for the final step, membrane fission, which releases the transport carrier from the intracellular compartment. The role of fission proteins, especially at intracellular locations and in non-neuronal cells, while informed by the dynamin-1 paradigm, remains to be resolved. In this study, we introduce a highly sensitive approach for the identification and analysis of membrane fission machinery, called burst analysis spectroscopy (BAS. BAS is a single particle, free-solution approach, well suited for quantitative measurements of membrane dynamics. Here, we use BAS to analyze membrane fission induced by the potent, fission-active ENTH domain of epsin. Using this method, we obtained temperature-dependent, time-resolved measurements of liposome size and concentration changes, even at sub-micromolar concentration of the epsin ENTH domain. We also uncovered, at 37°C, fission activity for the full-length epsin protein, supporting the argument that the membrane-fission activity observed with the ENTH domain represents a native function of the full-length epsin protein.

  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. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.)

  15. 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.

  16. 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.

  17. 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.

  18. Membrane shape at the edge of the dynamin helix sets location and duration of the fission reaction.

    Science.gov (United States)

    Morlot, Sandrine; Galli, Valentina; Klein, Marius; Chiaruttini, Nicolas; Manzi, John; Humbert, Frédéric; Dinis, Luis; Lenz, Martin; Cappello, Giovanni; Roux, Aurélien

    2012-10-26

    The GTPase dynamin polymerizes into a helical coat that constricts membrane necks of endocytic pits to promote their fission. However, the dynamin mechanism is still debated because constriction is necessary but not sufficient for fission. Here, we show that fission occurs at the interface between the dynamin coat and the uncoated membrane. At this location, the considerable change in membrane curvature increases the local membrane elastic energy, reducing the energy barrier for fission. Fission kinetics depends on tension, bending rigidity, and the dynamin constriction torque. Indeed, we experimentally find that the fission rate depends on membrane tension in vitro and during endocytosis in vivo. By estimating the energy barrier from the increased elastic energy at the edge of dynamin and measuring the dynamin torque, we show that the mechanical energy spent on dynamin constriction can reduce the energy barrier for fission sufficiently to promote spontaneous fission. : Copyright © 2012 Elsevier Inc. All rights reserved.

  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. Comparison of fission modes in 252Cf, 257Fm, and 260Md

    Science.gov (United States)

    van Aarle, J.; Siemon, K.; Wild, J. F.; Lougheed, R. W.; Westmeier, W.; Patzelt, P.

    1998-10-01

    Although the spontaneous-fission properties of heavy actinides have been studied for well over 35 years, many interesting and informative details continue to come into light. During the last decade, the spontaneous fission of 252Cf, 257Fm and 260Md has been extensively investigated at the Philipps University of Marburg (1-4), by means of a gadolinium-doped liquid scintillation tank for neutron counting and surface barrier detectors for fission fragment detection. The three nuclides represent the transition from the well-known asymmetric fission yield distribution, as it is characteristic for 252Cf, to a much more symmetrical one, found in the fission of 260Md. Therefore, trends in the dynamical changes of fission properties have been derived from these studies. For the spontaneous fission of 252Cf and 260Md, it was already shown that different fission modes, as proposed by theoretical calculations of Brosa et al. (5), could be separated, using the correlation between the neutrons emitted in a fission event and both the observed fission-fragment mass and the total kinetic energy (1, 2). In the case of 257Fm, no theoretical calculations for fission modes exist. However, from the fission properties of the two surrounding actinides, one can expect at least three different fission modes, namely two "standard" and the "supershort" mode. In this paper, results from the recent 257Fm experiment will be presented and compared to systematics extracted from the fission properties of other heavy actinides.

  1. Parity nonconservation and Brosa modes in nuclear fission

    Science.gov (United States)

    Graf, U.; Gönnenwein, F.; Geltenbort, P.; Schreckenbach, K.

    1995-09-01

    The parity nonconserving (PNC) asymmetry coefficient α for the angular distribution of fragment emission from binary fission of233U irradiated by polarized thermal neutrons has been measured. Complementary fragments were detected by a double ionization chamber with high resolving power. The experiment was carried out at the high flux reactor of the ILL, Grenoble. Integrated over all masses and energies of light fragments from asymmetric fission of234Uh, the PNC asymmetry coefficient is found to be α=(3.29±0.31) × 10-4.The positive sign of α indicates a preferential emission of light fragments parallel to the spin of neutrons inducing fission. Theory claims that PNC effects are sensitive to the properties of the fission barrier. On the other hand, one may wonder whether characteristics of eventual fragments are already specified at the barrier. The measurement of PNC asymmetries for distinct mass-energy ranges of fragments has been utilized to answer this question. Mass-energy distributions of fragments were analyzed along the lines of the Brosa model of fission as a superposition of individual modes. Within experimental uncertainty no mode dependence of asymmetric fission could be disclosed. The result is in keeping with the Brosa model where asymmetric modes bifurcate only once the standard fission barrier has been passed.

  2. Relativistic Coulomb fission

    Science.gov (United States)

    Norbury, John W.

    Nuclear fission reactions induced by the electromagnetic field of relativistic nuclei are studied for energies relevant to present and future relativistic heavy ion accelerators. Cross sections are calculated for U-238 and Pu-239 fission induced by C-12, Si-28, Au-197, and U-238 projectiles. It is found that some of the cross sections can exceed 10 b.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. A DFT study of temperature dependent dissociation mechanism of ...

    Indian Academy of Sciences (India)

    study also reveals that HF is a stronger acid in water cluster than in bulk water. Further, the ... of H2O are needed to stabilize the acid-water cluster system. .... models. Those molecules which are involved in dissoci- ation process are represented in ball-stick model. Dur- ing the dissociation, barrier height of reaction was esti-.

  8. Tunneling process in heavy-ion fusion and fission

    Energy Technology Data Exchange (ETDEWEB)

    Iwamoto, Akira [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Kondratyev, V.; Bonasera, A.

    1998-10-01

    We present a model towards the many-body description of sub-barrier fusion and spontaneous fission based on the semiclassical Vlasov equation and the Feynman path integral method. We define suitable collective variables from the Vlasov solution and use the imaginary time technique for the dynamics below the Coulomb barrier. (author)

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

    Science.gov (United States)

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

    2017-11-01

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

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

    Science.gov (United States)

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

    2007-03-01

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

  11. 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.

  12. Fission in a Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Younes, W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-10-26

    A three-year theory project was undertaken to study the fission process in extreme astrophysical environments, such as the crust of neutron stars. In the first part of the project, the effect of electron screening on the fission process was explored using a microscopic approach. For the first time, these calculations were carried out to the breaking point of the nucleus. In the second part of the project, the population of the fissioning nucleus was calculated within the same microscopic framework. These types of calculations are extremely computer-intensive and have seldom been applied to heavy deformed nuclei, such as fissioning actinides. The results, tools and methodologies produced in this work will be of interest to both the basic-science and nuclear-data communities.

  13. 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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-01-05

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

  15. Temperature-dependent bias-stress-induced electrical instability of amorphous indium-gallium-zinc-oxide thin-film transistors

    Science.gov (United States)

    Qian, Hui-Min; Yu, Guang; Lu, Hai; Wu, Chen-Fei; Tang, Lan-Feng; Zhou, Dong; Ren, Fang-Fang; Zhang, Rong; Zheng, You-Liao; Huang, Xiao-Ming

    2015-07-01

    The time and temperature dependence of threshold voltage shift under positive-bias stress (PBS) and the following recovery process are investigated in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. It is found that the time dependence of threshold voltage shift can be well described by a stretched exponential equation in which the time constant τ is found to be temperature dependent. Based on Arrhenius plots, an average effective energy barrier Eτstress = 0.72 eV for the PBS process and an average effective energy barrier Eτrecovery = 0.58 eV for the recovery process are extracted respectively. A charge trapping/detrapping model is used to explain the threshold voltage shift in both the PBS and the recovery process. The influence of gate bias stress on transistor performance is one of the most critical issues for practical device development. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB301900 and 2011CB922100) and the Priority Academic Program Development of Jiangsu Higher Education Institutions, China

  16. Fission Product Library and Resource

    Energy Technology Data Exchange (ETDEWEB)

    Burke, J. T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Padgett, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-09-29

    Fission product yields can be extracted from an irradiated sample by performing gamma ray spectroscopy on the whole sample post irradiation. There are several pitfalls to avoid when trying to determine a specific isotope's fission product yield.

  17. Fission gas measuring technology

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyung Kwon; Kim, Eun Ka; Hwang, Yong Hwa; Lee, Eun Pyo; Chun, Yong Bum; Seo, Ki Seog; Park, Dea Gyu; Chu, Yong Sun; Ahn, Sang Bok

    1998-02-01

    Safety and economy of nuclear plant are greatly affected by the integrity of nuclear fuels during irradiation reactor core. A series of post-irradiation examination (PIE) including non-destructive and destructive test is to be conducted to evaluate and characterize the nuclear performance. In this report, a principle of the examination equipment to measure and analyse fission gases existing nuclear fuels were described and features of the component and device consisting the fission gas measuring equipment are investigated. (author). 4 refs., 2 tabs., 6 figs.

  18. Temperature-dependent electrical characteristics of CBD/CBD grown n-ZnO nanowire/p-Si heterojunction diodes

    Science.gov (United States)

    Das, Avishek; Kushwaha, Ajay; Kajen Sivasayan, Rasanayagam; Chakraborty, Sandipan; Sekhar Dutta, Himadri; Karmakar, Anupam; Chattopadhyay, Sanatan; Chi, Dongzhi; Dalapati, Goutam Kumar

    2016-04-01

    Heterojunction diodes are fabricated using a low-temperature chemical bath deposition of oriented and crystalline ZnO nanowires on a    p-silicon substrate. The electrical transport properties of the heterojunction are investigated at various temperatures by measuring current-voltage (I-V) characteristics in the range of 90-390 K. A thermionic emission (TE) model is used to analyze the transport behavior. The deviation in the experimental value of Richardson’s constant for ZnO nanowires is obtained from I-V-T measurement. The temperature dependence of the effective barrier height and ideality factor is attributed to the inhomogeneous barrier height distribution at the n-ZnO NW/p-Si hetero-interface. The TE and barrier inhomogeneity model are simultaneously used to extract the appropriate value of the Richardson’s constants in three different temperature regions. Linear fittings for three different temperature regions suggest multiple Gaussian distributions of barrier heights at the junction.

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

    Science.gov (United States)

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

    2008-05-02

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

  20. Story of Fission

    Indian Academy of Sciences (India)

    IAS Admin

    tained efforts involving many scientists led by Hahn and. Meitner to ... world. Nuclear energy is one of the clean sources of energy and contributes very little to global warming. The discovery of fission of uranium in 1939 changed forever the way society at ... nuclear world with the discovery of neutron by Rutherford's student ...

  1. Story of Fission

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 21; Issue 3. Story of Fission: Unlocking Power of the Nucleus. Amit Roy. General Article Volume 21 Issue 3 March 2016 pp 247-258. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/021/03/0247-0258 ...

  2. Interaction of three fission fragments and yields of various ternary fragments

    Science.gov (United States)

    Denisov, V. Yu.; Pilipenko, N. A.; Sedykh, I. Yu.

    2017-01-01

    The interaction potential energy of the three deformed fragments formed in fission of 252Cf is studied for various combinations of three-fragment fission. The lowest height of the potential energy ridge between three touching and separated deformed fragments is sought. The excitation energies of various three-deformed-fragment configurations, at the lowest barrier heights related to the yield of the corresponding configuration, are considered in detail. The most probable three-fragment fission configurations are discussed. The yields of various ternary fragments in fission of 250Cf agree well with available experimental data.

  3. 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.

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

    Directory of Open Access Journals (Sweden)

    Wan-Chen Tsai

    2013-04-01

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

  5. Investigating fusion dynamics at high angular momentum via fission cross sections

    Science.gov (United States)

    Palshetkar, C. S.; Hinde, D. J.; Williams, E.; Ramachandran, K.; Dasgupta, M.; Cook, K. J.; Wakhle, A.; Jeung, D. Y.; Rafferty, D. C.; McNeil, S. D.; Carter, I. P.; Luong, D. H.

    2017-11-01

    A quantitative understanding of fusion dynamics at high angular momentum is attempted employing experimental fission cross sections as a probe and carrying out a simultaneous description of the fusion and fission cross sections at above barrier energies. For this, experimental fission fragment angular distributions for three systems: 16O+148Sm, 28Si+136Ba and 40Ca+124Sn, all forming the same compound nucleus 164Yb at similar excitation energies, have been measured at four beam energies above their respective capture barriers. A simultaneous description of the angle integrated fission cross sections and evaporation residue/fusion cross sections available in literature for the systems is carried out using coupled-channels and statistical model calculations. Fission cross sections, which are most sensitive to the changes in angular momentum, provide very stringent constraints for model calculations thus indicating the need of precision evaporation residue as well as fission cross sections in such studies. A large diffuseness (ao>0.65 fm) of the nuclear potential gives the best reproduction of the experimental data. In addition, different coupling schemes give very different angular momentum distributions, which, in turn, give very different fission cross section predictions. Both these observations hint at the explanation that depending on energy dissipation of the interacting nuclei occurring inside or outside the fusion pocket, very different fission cross sections can result due to heavily altered angular momentum and thus justifies the sensitivity of fission cross sections used as probes in the present work.

  6. Fission fragment mass and angular distributions: Probes to study ...

    Indian Academy of Sciences (India)

    trajectories bypass the saddle point (fission barrier) when the charge product of the col- liding nuclei exceeds a ... projectile combination, mass asymmetry of the entrance channel, static deformation of the colliding partners ... et al [8], we have considered the charge-to-mass ratio of the target and the projectile to lie along the ...

  7. Application of pulse shape discrimination in Si detector for fission ...

    Indian Academy of Sciences (India)

    Pulse shape discrimination; solid-state surface barrier detector; heavy ion- induced fission reaction studies. PACS Nos 29.40.Wk; 25.70.Jj, 25.85.Ge. 1. Introduction. It has been known for more than 40 years that the shape of the pulse collection in a solid-state detector following the interaction of charged particles can be ...

  8. Comparison of fission modes in {sup 252}Cf, {sup 257}Fm, and {sup 260}Md

    Energy Technology Data Exchange (ETDEWEB)

    van Aarle, J. [Laboratory for Materials Behaviour, Paul Scherrer Institute, CH-5232 Villigen-PSI (Switzerland); Siemon, K.; Patzelt, P. [Philipps University, FB 15---Kernchemie, D-35032 Marburg an der Lahn (Germany); Wild, J.F.; Lougheed, R.W. [University of California, Lawrence Livermore National Lab., Livermore, California 94551 (United States); Westmeier, W. [Dr. Westmeier GmbH, Moellnerweg 32, 35085 Ebsdorfergrund-Moelln (Germany)

    1998-10-01

    Although the spontaneous-fission properties of heavy actinides have been studied for well over 35 years, many interesting and informative details continue to come into light. During the last decade, the spontaneous fission of {sup 252}Cf, {sup 257}Fm and {sup 260}Md has been extensively investigated at the Philipps University of Marburg (1{endash}4), by means of a gadolinium-doped liquid scintillation tank for neutron counting and surface barrier detectors for fission fragment detection. The three nuclides represent the transition from the well-known asymmetric fission yield distribution, as it is characteristic for {sup 252}Cf, to a much more symmetrical one, found in the fission of {sup 260}Md. Therefore, trends in the dynamical changes of fission properties have been derived from these studies. For the spontaneous fission of {sup 252}Cf and {sup 260}Md, it was already shown that different fission modes, as proposed by theoretical calculations of Brosa et al. (5), could be separated, using the correlation between the neutrons emitted in a fission event and both the observed fission-fragment mass and the total kinetic energy (1, 2). In the case of {sup 257}Fm, no theoretical calculations for fission modes exist. However, from the fission properties of the two surrounding actinides, one can expect at least three different fission modes, namely two {open_quotes}standard{close_quotes} and the {open_quotes}supershort{close_quotes} mode. In this paper, results from the recent {sup 257}Fm experiment will be presented and compared to systematics extracted from the fission properties of other heavy actinides. {copyright} {ital 1998 American Institute of Physics.}

  9. 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...

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. Temperature-dependent electrical parameters and current transport mechanisms of Ru/Ti/ n-InP Schottky diodes

    Science.gov (United States)

    Munikrishna Reddy, Y.; Padmasuvarna, R.; Lakshmi Narasappa, T.; Padma, R.; Rajagopal Reddy, V.

    2015-11-01

    The temperature-dependent electrical properties of Ru/Ti/ n-InP Schottky diodes have been investigated in the temperature range of 120 to 400 K. The estimated barrier heights for the Ru/Ti/ n-InP Schottky barrier diode from the I- V and C- V characteristics vary from 0.24 to 0.73 eV ( I- V) and 0.94 to 0.74 eV ( C- V) and the ideality factor ( n) from 4.65 to 1.80 in the temperature range of 120-400 K. It has been observed that the ideality factor decreases while the barrier height increases with the increase in temperature. The barrier height ( Φ b), ideality factor ( n) and series resistance ( R s) of the Ru/Ti/ n-InP Schottky diode have been also determined using Cheung's and Norde methods. The discrepancy between the barrier heights obtained from the I- V and C- V characteristics is discussed. The interface state densities ( N ss) extracted for the Ru/Ti/ n-InP Schottky diode are in the range of 6.75 × 1013 eV-1 cm-2 ( E c —0.23 eV)-1.09 × 1014 eV-1 cm-2 ( E c —0.17 eV) at 120 K and 1.67 × 1013 eV-1 cm-2 ( E c —0.75 eV)-5.02 × 1013 eV-1 cm-2 ( E c —0.59 eV) at 400 K. It is observed that the interface state density ( N ss) decreases with increase in temperature. Results reveal that the conduction current is dominated by Poole-Frenkel emission in the temperature range from 120 to 320 K and by Schottky emission above 360 K.

  16. Fission of heavy and superheavy nuclei at low excitation energies

    CERN Document Server

    Itkis, M G; Hanappe, F; Itkis, Y M; Kelic, A; Kondratev, N A; Kozulin, E M; Oganessian, Yu T; Pokrovsky, I V; Prokhorova, E V; Rudolf, G; Rusanov, A Ya; Stuttgé, L

    1999-01-01

    The talk presents the results of an investigation of the main characteristics (mass and energy distributions of fission fragments and multiplicity of neutrons) of the fission of the nuclei of sup 2 sup 2 sup 0 Ra, sup 2 sup 2 sup 6 Th, sup 2 sup 5 sup 6 No, sup 2 sup 7 sup 0 Sg, sup 2 sup 8 sup 6 112 produced in reactions with ions of sup 1 sup 8 O, sup 2 sup 2 Ne and sup 4 sup 8 Ca at energies close to and essentially below the Coulomb barrier. The data obtained show that the form of the mass and energy distributions of the fission fragments of sup 2 sup 2 sup 6 Th and sup 2 sup 7 sup 0 Sg is accounted for by the multimodal nature of the fission. In addition, for sup 2 sup 2 sup 6 Th, a new phenomenon was established: there is a significant difference between the numbers of prescission neutrons for symmetric and asymmetric fission modes. It was found that, for the low-energy fission of the nucleus of sup 2 sup 8 sup 6 112, the mass distribution of the fragments is of a clear-cut asymmetric form, contrary to ...

  17. Fission yield measurements at IGISOL

    Science.gov (United States)

    Lantz, M.; Al-Adili, A.; Gorelov, D.; Jokinen, A.; Kolhinen, V. S.; Mattera, A.; Moore, I.; Penttilä, H.; Pomp, S.; Prokofiev, A. V.; Rakopoulos, V.; Rinta-Antila, S.; Simutkin, V.; Solders, A.

    2016-06-01

    The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL) technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyväskylä, fission products can be isobarically separated, making it possible to measure relative independent fission yields. In some cases it is even possible to resolve isomeric states from the ground state, permitting measurements of isomeric yield ratios. So far the reactions U(p,f) and Th(p,f) have been studied using the IGISOL-JYFLTRAP facility. Recently, a neutron converter target has been developed utilizing the Be(p,xn) reaction. We here present the IGISOL-technique for fission yield measurements and some of the results from the measurements on proton induced fission. We also present the development of the neutron converter target, the characterization of the neutron field and the first tests with neutron-induced fission.

  18. Fission yield measurements at IGISOL

    Directory of Open Access Journals (Sweden)

    Lantz M.

    2016-01-01

    Full Text Available The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyväskylä, fission products can be isobarically separated, making it possible to measure relative independent fission yields. In some cases it is even possible to resolve isomeric states from the ground state, permitting measurements of isomeric yield ratios. So far the reactions U(p,f and Th(p,f have been studied using the IGISOL-JYFLTRAP facility. Recently, a neutron converter target has been developed utilizing the Be(p,xn reaction. We here present the IGISOL-technique for fission yield measurements and some of the results from the measurements on proton induced fission. We also present the development of the neutron converter target, the characterization of the neutron field and the first tests with neutron-induced fission.

  19. Nuclear Forensics and Radiochemistry: Fission

    Energy Technology Data Exchange (ETDEWEB)

    Rundberg, Robert S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-11-07

    Radiochemistry has been used to study fission since it’ discovery. Radiochemical methods are used to determine cumulative mass yields. These measurements have led to the two-mode fission hypothesis to model the neutron energy dependence of fission product yields. Fission product yields can be used for the nuclear forensics of nuclear explosions. The mass yield curve depends on both the fuel and the neutron spectrum of a device. Recent studies have shown that the nuclear structure of the compound nucleus can affect the mass yield distribution.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Study of temperature-dependent charge conduction in silicon-nanocrystal/SiO{sub 2} multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Mavilla, Narasimha Rao; Chavan, Vinayak [National Centre for Photovoltaic Research and Education (NCPRE), Powai, Mumbai 400 076 (India); Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India); Solanki, Chetan Singh [National Centre for Photovoltaic Research and Education (NCPRE), Powai, Mumbai 400 076 (India); Department of Energy Science and Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India); Vasi, Juzer [National Centre for Photovoltaic Research and Education (NCPRE), Powai, Mumbai 400 076 (India); Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India)

    2016-08-01

    Silicon-nanocrystals (Si-NCs) realized by SiO{sub x} {sub <} {sub 2}/SiO{sub 2} multilayer (ML) approach have shown promise for realizing tightly-controlled dimensions, thus efficiently exploiting the size-dependent quantum effects for device applications. Unfortunately, the confining insulating barriers (SiO{sub 2} sublayers), instrumental for realizing quantum size effects in Si-NC MLs, can also hinder the charge conduction which is crucial for device applications including Si-NC based tandem solar cells and multi-exciton solar cells. Owing to this, a comprehensive study of conduction mechanisms has been carried out using a thorough analysis of temperature-dependent dark I-V measurements of SiO{sub 2} thin film and Si-NC multilayer samples fabricated by Inductively Coupled Plasma CVD (ICPCVD). As the ML samples consisted of interleaved SiO{sub 2} sublayers, current in SiO{sub 2} thin film has initially been studied to understand the conduction properties of bulk ICPCVD SiO{sub 2}. For 21 nm thick SiO{sub 2} film, conduction is observed to be dominated by Fowler–Nordheim (FN) tunneling for higher electric fields (> 8 MV/cm; independent of temperature), while for lower electric fields (5–8 MV/cm) at higher temperatures, the trap-related Generalized Poole–Frenkel (GPF) is dominant. This signified the role of traps in modifying the conduction in bulk ICPCVD SiO{sub 2} films. We then present the conduction in ML samples. For multilayer samples with SiO{sub 2} sublayer thickness of 1.5 nm and 2.5 nm, Direct Tunneling (DT) is observed to be dominant, while for SiO{sub 2} sublayer thickness of 3.5 nm, Space Charge Limited Conduction (SCLC) with exponential trap distribution is found to be the dominant conduction mechanism. This signifies the role of traps in modifying the conduction in Si-NC multilayer samples and SiO{sub 2} sublayer thickness dependence. - Highlights: • Electrical conduction in SiO{sub 2} film & Si-nanocrystal layers (Si-NCs) is reported. • Si

  5. Energy from nuclear fission(*

    Directory of Open Access Journals (Sweden)

    Ripani M.

    2015-01-01

    Full Text Available The main features of nuclear fission as physical phenomenon will be revisited, emphasizing its peculiarities with respect to other nuclear reactions. Some basic concepts underlying the operation of nuclear reactors and the main types of reactors will be illustrated, including fast reactors, showing the most important differences among them. The nuclear cycle and radioactive-nuclear-waste production will be also discussed, along with the perspectives offered by next generation nuclear assemblies being proposed. The current situation of nuclear power in the world, its role in reducing carbon emission and the available resources will be briefly illustrated.

  6. 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 ...

  7. 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

  8. 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.

  9. 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.

  10. 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.

  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. Dynamical features of nuclear fission

    Indian Academy of Sciences (India)

    nuclear decay using the Bohr–Wheeler fission width is usually found to underpredict the pre-scission multiplicities beyond a certain threshold energy [5]. We first briefly re-visit the transition-state model to examine its underlying assumptions which may not be valid for fission at high excitation energies. Pramana – J. Phys.

  14. Fission approach to cluster radioactivity

    Indian Academy of Sciences (India)

    Abstract. Fission theory is used to explain α decay. Also, the analytical superasymmetric fission. (ASAF) model is successfully employed to make a systematic search and to predict, with other mod- els, cluster radioactivity. The macroscopic–microscopic method is illustrated for the superheavy nucleus 286Fl. Then a few ...

  15. Fission approach to cluster radioactivity

    Indian Academy of Sciences (India)

    2015-08-04

    Aug 4, 2015 ... Fission theory is used to explain decay. Also, the analytical superasymmetric fission (ASAF) model is successfully employed to make a systematic search and to predict, with other models, cluster radioactivity. The macroscopic–microscopic method is illustrated for the superheavy nucleus 286Fl. Then a ...

  16. Spontaneous fission of superheavy nuclei

    Indian Academy of Sciences (India)

    and penetrability for binary nuclear configurations typical for fission processes. The deformed two- ... Finally, the WKB method is used to calculate penetrabilities and spontaneous fission half-lives. Calculations ... the mass tensor components contain binary character of the process, because the pairing. Pramana – J. Phys.

  17. Dynamical features of nuclear fission

    Indian Academy of Sciences (India)

    2015-07-24

    Jul 24, 2015 ... Here, we first present the physical picture underlying the dissipative fission dynamics. We mainly concentrate upon the Kramers' prescription for including dissipation in fission dynamics. We discuss, in some detail, the results of a statistical model analysis of the pre-scission neutron multiplicity data from the ...

  18. Fission hindrance and nuclear viscosity

    Indian Academy of Sciences (India)

    2015-07-29

    Jul 29, 2015 ... We discuss the role of nuclear viscosity in hindering the fission of heavy nuclei as observed in the experimental measurements of GDR -ray spectra from the fissioning nuclei. We review a set of experiments carried out and reported by us previously [see Dioszegi et al, Phys. Rev. C 61, 024613 (2000); ...

  19. 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.

  20. 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.

  1. 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...

  2. 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.

  3. 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.

  4. 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...

  5. Cystic fibrosis transmembrane conductance regulator: temperature-dependent cysteine reactivity suggests different stable conformers of the conduction pathway.

    Science.gov (United States)

    Liu, Xuehong; Dawson, David C

    2011-11-29

    Cysteine scanning has been widely used to identify pore-lining residues in mammalian ion channels, including the cystic fibrosis transmembrane conductance regulator (CFTR). These studies, however, have been typically conducted at room temperature rather than human body temperature. Reports of substantial effects of temperature on gating and anion conduction in CFTR channels as well as an unexpected pattern of cysteine reactivity in the sixth transmembrane segment (TM6) prompted us to investigate the effect of temperature on the reactivity of cysteines engineered into TM6 of CFTR. We compared reaction rates at temperatures ranging from 22 to 37 °C for cysteines placed on either side of an apparent size-selective accessibility barrier previously defined by comparing reactivity toward channel-permeant and channel-impermeant, thiol-directed reagents. The results indicate that the reactivity of cysteines at three positions extracellular to the position of the accessibility barrier, 334, 336, and 337, is highly temperature-dependent. At 37 °C, cysteines at these positions were highly reactive toward MTSES(-), whereas at 22 °C, the reaction rates were 2-6-fold slower to undetectable. An activation energy of 157 kJ/mol for the reaction at position 337 is consistent with the hypothesis that, at physiological temperature, the extracellular portion of the CFTR pore can adopt conformations that differ significantly from those that can be accessed at room temperature. However, the position of the accessibility barrier defined empirically by applying channel-permeant and channel-impermeant reagents to the extracellular aspect of the pore is not altered. The results illuminate previous scanning results and indicate that the assay temperature is a critical variable in studies designed to use chemical modification to test structural models for the CFTR anion conduction pathway.

  6. 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

  7. 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.

  8. 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.

  9. 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...

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

    Science.gov (United States)

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

    1992-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-04-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-01-15

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

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

    NARCIS (Netherlands)

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

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

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

    OpenAIRE

    Sharifulin, V. A.

    2009-01-01

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

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

    Science.gov (United States)

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

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

    DEFF Research Database (Denmark)

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

    2000-01-01

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

  17. 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.

  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. 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.

  20. 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.

  1. 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

  2. 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

  3. 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.

  4. 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…

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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....

  14. 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

  15. 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…

  16. The nuclear charge distribution of fission products of thermal neutron induced fission of /sup 235/U

    CERN Document Server

    Wollnik, H; Greif, J; Siegert, G

    1976-01-01

    Nuclear charge distributions of mass separated light fission products, 79barrier Delta E-silicon detector. After averaging over all energies and ionic charges a very pronounced proton odd-even effect and a smaller neutron odd-even effect is found which results in periodical variations of the average nuclear charge, the variance, the skewness, and the excess. The principles of the variations of the nuclear charge distributions due to varying kinetic energies are discussed. (20 refs).

  17. 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

  18. Fission cross section calculations for 209Bi target nucleus based on fission reaction models in high energy regions

    Directory of Open Access Journals (Sweden)

    Kaplan Abdullah

    2015-01-01

    Full Text Available Implementation of projects of new generation nuclear power plants requires the solving of material science and technological issues in developing of reactor materials. Melts of heavy metals (Pb, Bi and Pb-Bi due to their nuclear and thermophysical properties, are the candidate coolants for fast reactors and accelerator-driven systems (ADS. In this study, α, γ, p, n and 3He induced fission cross section calculations for 209Bi target nucleus at high-energy regions for (α,f, (γ,f, (p,f, (n,f and (3He,f reactions have been investigated using different fission reaction models. Mamdouh Table, Sierk, Rotating Liquid Drop and Fission Path models of theoretical fission barriers of TALYS 1.6 code have been used for the fission cross section calculations. The calculated results have been compared with the experimental data taken from the EXFOR database. TALYS 1.6 Sierk model calculations exhibit generally good agreement with the experimental measurements for all reactions used in this study.

  19. 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

  20. Fission product studies at WAIT

    Energy Technology Data Exchange (ETDEWEB)

    De Laeter, J.R.; Rosman, K.J.R.; Loss, R.D. (Western Australian Inst. of Tech., South Bentley)

    1985-07-01

    A general review of fission yields is presented. The Mass Spectrometry Laboratory in the Department of Applied Physics at WAIT has been involved in a continuing programme of measuring the cumulative fission yields of the elements palladium, silver, cadmium, tin and tellurium for a variety of fissile materials (/sup 233/U, /sup 235/U, /sup 238/U and /sup 239/Pu) over a range of neutron energies. Results of studies into the isotopic composition and fission yields of samples from the Oklo natural reactor in Gabon, West Africa are summarised.

  1. The spectroscopy of fission fragments

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, W.R. [Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL (United Kingdom); Collaboration: La Direction des Sciences de la Matiere du CEA (FR); Le Fonds National de la Recherche Scientifique de Belgique (BE)

    1998-12-31

    High-resolution measurements on {gamma} rays from fission fragments have provided a rich source of information, unobtainable at the moment in any other way, on the spectroscopy of neutron-rich nuclei. In recent years important data have been obtained on the yrast- and near yrast-structure of neutron-rich fission fragments. We discuss the scope of measurements which can be made on prompt gamma rays from secondary fission fragments, the techniques used in the experiments and some results recently obtained. (author) 24 refs., 8 figs., 1 tab.

  2. Study of the fission process of deformed Na clusters in liquid-drop stabilized jellium model

    Directory of Open Access Journals (Sweden)

    M Payami

    2008-07-01

    Full Text Available   In this work, using the liquid drop model in the context of the stabilized jellium model, we have studied the fission of charged Na clusters. In this study we have assumed a deformed non-spherical shape for the cluster. The ground state energies, critical sizes, fission barrier height, and the evaporation energies have been calculated. The results show a better agreement to the experimental results compared to our earlier work.

  3. Radiochemistry and the Study of Fission

    Energy Technology Data Exchange (ETDEWEB)

    Rundberg, Robert S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-14

    These are slides from a lecture given at UC Berkeley. Radiochemistry has been used to study fission since its discovery. Radiochemical methods are used to determine cumulative mass yields. These measurements have led to the two-mode fission hypothesis to model the neutron energy dependence of fission product yields. Fission product yields can be used for the nuclear forensics of nuclear explosions. The mass yield curve depends on both the fuel and the neutron spectrum of a device. Recent studies have shown that the nuclear structure of the compound nucleus can affect the mass yield distribution. The following topics are covered: In the beginning: the discovery of fission; forensics using fission products: what can be learned from fission products, definitions of R-values and Q-values, fission bases, K-factors and fission chambers, limitations; the neutron energy dependence of the mass yield distribution (the two mode fission hypothesis); the influence of nuclear structure on the mass yield distribution. In summary: Radiochemistry has been used to study fission since its discovery. Radiochemical measurement of fission product yields have provided the highest precision data for developing fission models and for nuclear forensics. The two-mode fission hypothesis provides a description of the neutron energy dependence of the mass yield curve. However, data is still rather sparse and more work is needed near second and third chance fission. Radiochemical measurements have provided evidence for the importance of nuclear states in the compound nucleus in predicting the mass yield curve in the resonance region.

  4. 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...

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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...

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

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

    Science.gov (United States)

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

    2014-04-01

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

  8. 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...

  9. 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.)

  10. Fabrication and Characterization of n-ZnO Hexagonal Nanorods/p-Si Heterojunction Diodes: Temperature-Dependant Electrical Characteristics.

    Science.gov (United States)

    Umar, Ahmad; Badran, R I; Al-Hajry, A; Al-Heniti, S

    2015-07-01

    This paper reports the temperature-dependant electrical characteristics of n-ZnO hexagonal nanorods/p-Si heterojunction diodes. The n-ZnO hexagonal nanorods were grown on p-Si substrate by a simple thermal evaporation process using metallic zinc powder in the presence of oxygen. The spectroscopic characterization revealed well-crystalline nanorods, quasi-aligned to the substrate and possessing hexagonal shape. The as-grown nanorods exhibited a strong near-band-edge emis- sion with very weak deep-level emission in the room-temperature photoluminescence spectrum, confirming good optical properties. Furthermore, the electrical properties of as-grown ZnO nanorods were examined by fabricating n-ZnO/p-Si heterojunction assembly and the I-V characteristics of the fabricated heterojunction assembly were investigated at different temperatures. The fabricated n-ZnO/p-Si heterojunction diodes exhibited a turn-on voltage of ~5 V at different temperatures with a mean built-in-potential barrier of 1.12 eV. Moreover, the high values of quality factor obtained from I-V analysis suggested a non-ideal behavior of Schottky junction.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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....

  17. 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...

  18. 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.

  19. 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.

  20. 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...

  1. 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

  2. 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...

  3. 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...

  4. 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 ).

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  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. 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.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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).

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Report on simulation of fission gas and fission product diffusion in UO2

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Anders David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Perriot, Romain Thibault [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Pastore, Giovanni [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Tonks, Michael R. [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Cooper, Michael William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Liu, Xiang-Yang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Goyal, Anuj [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Uberuaga, Blas P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Stanek, Christopher Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division

    2016-07-22

    concentration of the XeU3O cluster for intrinsic conditions than under irradiation. We speculate that differences in the irradiation conditions and their impact on the XeU3O cluster can explain the wide range of diffusivities reported in experimental studies. However, all vacancy-­mediated mechanisms underestimate the Xe diffusivity compared to the empirical radiation-­enhanced rate used in most fission gas release models. We investigate the possibility that diffusion of small fission gas bubbles or extended Xe-­vacancy clusters may give rise to the observed radiation-­enhanced diffusion coefficient. These studies highlight the importance of U divacancies and an octahedron coordination of uranium vacancies encompassing a Xe fission gas atom. The latter cluster can migrate via a multistep mechanism with a rather low effective barrier, which together with irradiation-induced clusters of uranium vacancies, gives rise to the irradiation-enhanced diffusion coefficient observed in experiments.

  3. Determination of Temperature-Dependent Stress State in Thin AlGaN Layer of AlGaN/GaN HEMT Heterostructures by Near-Resonant Raman Scattering

    Directory of Open Access Journals (Sweden)

    Yanli Liu

    2015-01-01

    Full Text Available The temperature-dependent stress state in the AlGaN barrier layer of AlGaN/GaN heterostructure grown on sapphire substrate was investigated by ultraviolet (UV near-resonant Raman scattering. Strong scattering peak resulting from the A1(LO phonon mode of AlGaN is observed under near-resonance condition, which allows for the accurate measurement of Raman shifts with temperature. The temperature-dependent stress in the AlGaN layer determined by the resonance Raman spectra is consistent with the theoretical calculation result, taking lattice mismatch and thermal mismatch into account together. This good agreement indicates that the UV near-resonant Raman scattering can be a direct and effective method to characterize the stress state in thin AlGaN barrier layer of AlGaN/GaN HEMT heterostructures.

  4. Fission product solvent extraction

    Energy Technology Data Exchange (ETDEWEB)

    Moyer, B.A.; Bonnesen, P.V.; Sachleben, R.A. [and others

    1998-02-01

    Two main objectives concerning removal of fission products from high-level tank wastes will be accomplished in this project. The first objective entails the development of an acid-side Cs solvent-extraction (SX) process applicable to remediation of the sodium-bearing waste (SBW) and dissolved calcine waste (DCW) at INEEL. The second objective is to develop alkaline-side SX processes for the combined removal of Tc, Cs, and possibly Sr and for individual separation of Tc (alone or together with Sr) and Cs. These alkaline-side processes apply to tank wastes stored at Hanford, Savannah River, and Oak Ridge. This work exploits the useful properties of crown ethers and calixarenes and has shown that such compounds may be economically adapted to practical processing conditions. Potential benefits for both acid- and alkaline-side processing include order-of-magnitude concentration factors, high rejection of bulk sodium and potassium salts, and stripping with dilute (typically 10 mM) nitric acid. These benefits minimize the subsequent burden on the very expensive vitrification and storage of the high-activity waste. In the case of the SRTALK process for Tc extraction as pertechnetate anion from alkaline waste, such benefits have now been proven at the scale of a 12-stage flowsheet tested in 2-cm centrifugal contactors with a Hanford supernatant waste simulant. SRTALK employs a crown ether in a TBP-modified aliphatic kerosene diluent, is economically competitive with other applicable separation processes being considered, and has been successfully tested in batch extraction of actual Hanford double-shell slurry feed (DSSF).

  5. Role of effective distance in the fission mechanism study by the double-energy measurement for uranium isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Hiroshi; Saito, Tadashi; Takahashi, Naruto [Osaka Univ., Suita (Japan)] [and others

    1997-09-01

    Fission product kinetic energies were measured by the double-energy method for thermal-neutron fission of {sup 235,233}U and proton-induced fission of {sup 238}U at the 15.8-MeV excitation. From the obtained energy-mass correlation data, the kinetic-energy distribution was constructed from each mass bin to evaluate the first moment of the kinetic energy for a given fragment mass. The resulting kinetic energy was then converted to the effective distance between the charge centers at the moment of scission. The effective distances deduced for the proton-induced fission was concluded to be classified into two constant values, one for asymmetric and the other for symmetric mode, irrespective of the mass though an additional component was further extracted in the asymmetric mass region. This indicates that the fission takes place via two well-defined saddles, followed by the random neck rupture. On the contrary, the effective distances obtained for thermal-neutron induced fission turned out to lie along the contour line at the same level as the equilibrium deformation in the two-dimensional potential map. This strongly suggests that it is essentially a barrier-penetrating type of fission rather than the over-barrier fission. (author). 73 refs.

  6. Compact fission counter for DANCE

    Energy Technology Data Exchange (ETDEWEB)

    Wu, C Y; Chyzh, A; Kwan, E; Henderson, R; Gostic, J; Carter, D; Bredeweg, T; Couture, A; Jandel, M; Ullmann, J

    2010-11-06

    The Detector for Advanced Neutron Capture Experiments (DANCE) consists of 160 BF{sub 2} crystals with equal solid-angle coverage. DANCE is a 4{pi} {gamma}-ray calorimeter and designed to study the neutron-capture reactions on small quantities of radioactive and rare stable nuclei. These reactions are important for the radiochemistry applications and modeling the element production in stars. The recognition of capture event is made by the summed {gamma}-ray energy which is equivalent of the reaction Q-value and unique for a given capture reaction. For a selective group of actinides, where the neutron-induced fission reaction competes favorably with the neutron capture reaction, additional signature is needed to distinguish between fission and capture {gamma} rays for the DANCE measurement. This can be accomplished by introducing a detector system to tag fission fragments and thus establish a unique signature for the fission event. Once this system is implemented, one has the opportunity to study not only the capture but also fission reactions. A parallel-plate avalanche counter (PPAC) has many advantages for the detection of heavy charged particles such as fission fragments. These include fast timing, resistance to radiation damage, and tolerance of high counting rate. A PPAC also can be tuned to be insensitive to {alpha} particles, which is important for experiments with {alpha}-emitting actinides. Therefore, a PPAC is an ideal detector for experiments requiring a fast and clean trigger for fission. A PPAC with an ingenious design was fabricated in 2006 by integrating amplifiers into the target assembly. However, this counter was proved to be unsuitable for this application because of issues related to the stability of amplifiers and the ability to separate fission fragments from {alpha}'s. Therefore, a new design is needed. A LLNL proposal to develop a new PPAC for DANCE was funded by NA22 in FY09. The design goal is to minimize the mass for the proposed

  7. Thorium-uranium fission radiography

    Science.gov (United States)

    Haines, E. L.; Weiss, J. R.; Burnett, D. S.; Woolum, D. S.

    1976-01-01

    Results are described for studies designed to develop routine methods for in-situ measurement of the abundance of Th and U on a microscale in heterogeneous samples, especially rocks, using the secondary high-energy neutron flux developed when the 650 MeV proton beam of an accelerator is stopped in a 42 x 42 cm diam Cu cylinder. Irradiations were performed at three different locations in a rabbit tube in the beam stop area, and thick metal foils of Bi, Th, and natural U as well as polished silicate glasses of known U and Th contents were used as targets and were placed in contact with mica which served as a fission track detector. In many cases both bare and Cd-covered detectors were exposed. The exposed mica samples were etched in 48% HF and the fission tracks counted by conventional transmitted light microscopy. Relative fission cross sections are examined, along with absolute Th track production rates, interaction tracks, and a comparison of measured and calculated fission rates. The practicality of fast neutron radiography revealed by experiments to data is discussed primarily for Th/U measurements, and mixtures of other fissionable nuclei are briefly considered.

  8. Fission product retention in the Oklo natural fission reactors

    Energy Technology Data Exchange (ETDEWEB)

    Curtis, D.; Benjamin, T.; Gancarz, A.; Loss, E.; Rosman, K.; DeLaeter, J.; Delmore, J.E.; Maeck, W.J.

    We present in this paper the abundances and isotopic composition of U and eight fission product elements in samples from well-defined locations in a cross section of one of the fossil reactors. These are unique data with regard to the chemical diversity represented by the elements measured in each of the samples. We will characterize the degree of retention of the fission products in the samples of the reactor zone and attempt to rationalize our observations by analogy with anthropogenic irradiated reactor fuel.

  9. Identification and systematical studies of the electron-capture delayed fission (ECDF) in the lead region

    CERN Multimedia

    Pauwels, D B; Lane, J

    2008-01-01

    In our recent experiment (March 2007) at the velocity filter SHIP(GSI) we observed the electron-capture delayed fission of the odd-odd isotope $^{194}$At. This is the first unambiguous identification of this phenomenon in the very neutron-deficient nuclei in the vicinity of the proton shell closure at Z=82. In addition, the total kinetic energy (TKE) for the daughter nuclide $^{194}$Po was measured, despite the fact that this isotope does not decay via spontaneous fission. Semi-empirical analysis of the electron-capture Q$_{EC}$ values and fission barriers B$_{f}$ shows that a relatively broad island of ECDF must exist in this region of the Nuclide Chart, with some of the nuclei having unusually high ECDF probabilities. Therefore, this Proposal is intended to initiate the systematic identification and study of $\\beta$-delayed fission at ISOLDE in the very neutron-deficient lead region. Our aim is to provide unique low-energy fission data (e.g. probabilities, TKE release, fission barriers and their isospin dep...

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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).

  15. 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.

  16. Calculation of the Effect of Random Superfluid Density on the Temperature Dependence of the Penetration Depth

    Energy Technology Data Exchange (ETDEWEB)

    Lippman, Thomas; Moler, Kathryn A.

    2012-07-20

    Microscopic variations in composition or structure can lead to nanoscale inhomogeneity in superconducting properties such as the magnetic penetration depth, but measurements of these properties are usually made on longer length scales. We solve a generalized London equation with a non-uniform penetration depth {lambda}(r), obtaining an approximate solution for the disorder-averaged Meissner screening. We find that the effective penetration depth is different from the average penetration depth and is sensitive to the details of the disorder. These results indicate the need for caution when interpreting measurements of the penetration depth and its temperature dependence in systems which may be inhomogeneous.

  17. 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.

  18. Thin film flow in MHD third grade fluid on a vertical belt with temperature dependent viscosity.

    Science.gov (United States)

    Gul, Taza; Islam, Saed; Shah, Rehan Ali; Khan, Ilyas; Shafie, Sharidan

    2014-01-01

    In this work, we have carried out the influence of temperature dependent viscosity on thin film flow of a magnetohydrodynamic (MHD) third grade fluid past a vertical belt. The governing coupled non-linear differential equations with appropriate boundary conditions are solved analytically by using Adomian Decomposition Method (ADM). In order to make comparison, the governing problem has also been solved by using Optimal Homotopy Asymptotic Method (OHAM). The physical characteristics of the problem have been well discussed in graphs for several parameter of interest.

  19. 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.

  20. Analysis of the temperature dependence of the thermal conductivity of insulating single crystal oxides

    Directory of Open Access Journals (Sweden)

    E. Langenberg

    2016-10-01

    Full Text Available The temperature dependence of the thermal conductivity of 27 different single crystal oxides is reported from ≈20 K to 350 K. These crystals have been selected among the most common substrates for growing epitaxial thin-film oxides, spanning over a range of lattice parameters from ≈3.7 Å to ≈12.5 Å. Different contributions to the phonon relaxation time are discussed on the basis of the Debye model. This work provides a database for the selection of appropriate substrates for thin-film growth according to their desired thermal properties, for applications in which heat management is important.

  1. 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...

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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 ...

  8. 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.

  9. 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...

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

    Science.gov (United States)

    Goldsby, Jon C.

    2003-01-01

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

  11. Temperature-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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Temperature-dependent transport mechanisms through PE-CVD coatings: comparison of oxygen and water vapour

    Science.gov (United States)

    Kirchheim, D.; Wilski, S.; Jaritz, M.; Mitschker, F.; Gebhard, M.; Brochhagen, M.; Böke, M.; Benedikt, Jan; Awakowicz, P.; Devi, A.; Hopmann, Ch; Dahlmann, R.

    2017-10-01

    When it comes to thin coatings such as plasma-enhanced chemical vapour deposition or plasma-enhanced atomic layer deposition coatings on substrates of polymeric material, existing models often describe transport through these thin coatings as mainly driven by transport through defects of different sizes. However, temperature-dependent measurements of permeation could not confirm this hypothesis and instead gaseous transport through these thin coatings was found to more likely to occur through the molecular structure. This paper correlates existing transport models with data from oxygen transmission experiments and puts recent investigations for water vapour transmission mechanisms into context for a better understanding of gaseous transport through thin coatings.

  18. Temperature dependence of dislocation-related luminescence in silicon-germanium heterostructure

    CERN Document Server

    Lee, H S

    1998-01-01

    We measured the photoluminescence spectra of very thin and partially strained Si sub 0 sub . sub 6 Ge sub 0 sub . sub 4 alloys grown on silicon substrate with varying degrees of strain relaxation. We observed photoluminescence lines, so called D-lines, which arose from dislocations in the SiGe/Si alloys. We identified the origin of the D-lines as the dislocations in Si substrate extending from the SiGe/Si interface. We also studied the temperature dependence of the Si D-lines and determined the dissociation energy of the defect energy levels.

  19. 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.

  20. Heavy neutron-deficient radioactive beams: fission studies and fragment distributions

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, K.H.; Benlliure, J.; Heinz, A.; Voss, B. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Boeckstiegel, C.; Grewe, A.; Steinhaeuser, S.; Clerc, H.G.; Jong, M. de; Junghans, A.R.; Mueller, J. [Technische Hochschule Darmstadt (Germany). Inst. fuer Kernphysik; Pfuetzner, M. [Warsaw Univ. (Poland). Inst. of Experimental Physics

    1998-02-01

    The secondary-beam facility of GSI Darmstadt was used to study the fission process of short-lived radioactive nuclei. Relativistic secondary projectiles were produced by fragmentation of a 1 A GeV {sup 238}U primary beam and identified in nuclear charge and mass number. Their production cross sections were determined, and the fission competition in the statistical deexcitation was deduced for long isotopical chains. New results on the enhancement of the nuclear level density in spherical and deformed nuclei due to collective rotational and vibrational excitations were obtained. Using these reaction products as secondary beams, the dipole giant resonance was excited by electromagnetic interactions in a secondary lead target, and fission from excitation energies around 11 MeV was induced. The fission fragments were identified in nuclear charge, and their velocity vectors were determined. Elemental yields and total kinetic energies have been determined for a number of neutron-deficient actinides and preactinides which were not accessible with conventional techniques. The characteristics of multimodal fission of nuclei around {sup 226}Th were systematically investigated and related to the influence of shell effects on the potential energy and on the level density between fission barrier and scission. A systematic view on the large number of elemental yields measured gave rise to a new interpretation of the enhanced production of even elements in nuclear fission and allowed for a new understanding of pair breaking in large-scale collective motion. (orig.)

  1. Microscopic description of fission in neutron-rich radium isotopes with the Gogny energy density functional

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Guzman, R. [Kuwait University, Physics Department, Kuwait (Kuwait); Robledo, L.M. [Universidad Autonoma de Madrid, Departamento de Fisica Teorica, Madrid (Spain)

    2016-01-15

    Mean-field calculations, based on the D1S, D1N and D1M parametrizations of the Gogny energy density functional, have been carried out to obtain the potential energy surfaces relevant to fission in several Ra isotopes with the neutron number 144 ≤ N ≤ 176. Inner and outer barrier heights as well as first and second isomer excitation energies are given. The existence of a well-developed third minimum along the fission paths of Ra nuclei is analyzed in terms of the energetics of the ''fragments'' defining such elongated configuration. The masses and charges of the fission fragments are studied as functions of the neutron number in the parent Ra isotope. The comparison between fission and α-decay half-lives, reveals that the former becomes faster for increasing neutron numbers. Though there exists a strong variance of the results with respect to the parameters used in the computation of the spontaneous fission rate, a change in tendency is observed at N = 164 with a steady increase that makes heavier neutron-rich Ra isotopes stable against fission, diminishing the importance of fission recycling in the r-process. (orig.)

  2. Measurement of Angular-Momentum-Dependent Fission Probabilities of 240Pu

    Science.gov (United States)

    Koglin, Johnathon; Burke, Jason; Jovanovic, Igor

    2016-09-01

    An experimental technique using the surrogate reaction method has been developed to measure fission probabilities of actinides as a function of angular momentum state of the fissioning nucleus near the fission barrier. In this work, the 240Pu (α ,α' f) reaction was used as a surrogate for 239Pu (n , f) . An array of 12 silicon telescopes positioned at 10 degree intervals from 40 to 140 degrees detect the outgoing reaction particle for identification and measurement of the excitation energy. The angular momentum state is determined by measuring the angular distribution of fission fragments. The expected distributions are predicted from the Wigner d function. An array of 50 photovoltaic (solar) cells detects fission fragments with 10-degree granularity. The solar cells are sensitive to fission fragments but have no response to light ions. Relative contributions from different angular momentum states are extracted from the measured distributions and compared across all α particle scattering angles to determine fission probability at a specific angular momentum state. The first experiment using this technique was recently completed using 37 MeV α particles incident on 240Pu. First results will be discussed. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This material is based upon work supported by the U.S. Department of Homeland Security under Grant Award Nu.

  3. Fission fragment distributions within dynamical approach

    Science.gov (United States)

    Mazurek, K.; Nadtochy, P. N.; Ryabov, E. G.; Adeev, G. D.

    2017-04-01

    The review covers recent developments and achievements in the dynamical description of fission process at high excitation energy. It is shown that the dynamical approach based on multidimensional Langevin equations combined with the statistical description of nuclear decay by particles evaporation is capable of fairly well describing the formation of fission fragment mass-energy, charge, and angular distributions of fission fragments in coincidence with the pre- and post-scission particle emission. The final yields of fission and evaporation residues channels products could be obtained. The detailed description of fission dynamics allows studying different stages of fission process, indicating the most important ingredients governing fission process and studying in detail such fundamental nuclear properties as nuclear viscosity and fission timescale. The tasks and perspectives of multidimensional dynamical approach are also discussed.

  4. PRODUCING ENERGY AND RADIOACTIVE FISSION PRODUCTS

    Science.gov (United States)

    Segre, E.; Kennedy, J.W.; Seaborg, G.T.

    1959-10-13

    This patent broadly discloses the production of plutonium by the neutron bombardment of uranium to produce neptunium which decays to plutonium, and the fissionability of plutonium by neutrons, both fast and thermal, to produce energy and fission products.

  5. Search for Singlet Fission Chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Havlas, Z.; Akdag, A.; Smith, M. B.; Dron, P.; Johnson, J. C.; Nozik, A. J.; Michl, J.

    2012-01-01

    Singlet fission, in which a singlet excited chromophore shares its energy with a ground-state neighbor and both end up in their triplet states, is of potential interest for solar cells. Only a handful of compounds, mostly alternant hydrocarbons, are known to perform efficiently. In view of the large number of conditions that a successful candidate for a practical cell has to meet, it appears desirable to extend the present list of high performers to additional classes of compounds. We have (i) identified design rules for new singlet fission chromophores and for their coupling to covalent dimers, (ii) synthesized them, and (iii) evaluated their performance as neat solids or covalent dimers.

  6. Fission hindrance and nuclear viscosity

    Indian Academy of Sciences (India)

    is in exact conformity with all the previous measurements [7,10–13]. The CASCADE calculations (solid lines in figure 1) used in this first level of analysis do not include any viscosity or temperature-dependent nuclear level density parameter a. The γ and particle decay are calculated using the standard prescriptions as ...

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  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 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.

  16. 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.

  17. 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.

  18. 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.

  19. Temperature dependence of hydroxyl radical reactions with chloramine species in aqueous solution.

    Science.gov (United States)

    Gleason, Jamie M; McKay, Garrett; Ishida, Kenneth P; Mezyk, Stephen P

    2017-11-01

    The absolute temperature-dependent kinetics for the reaction between hydroxyl radicals and the chloramine water disinfectant species monochloramine (NH2Cl), as well as dichloramine (NHCl2) and trichloramine (NCl3), have been determined using electron pulse radiolysis and transient absorption spectroscopy. These radical reaction rate constants were fast, with values of 6.06 × 108, 2.57 × 108, and 1.67 × 108 M-1 s-1 at 25 °C for NH2Cl, NHCl2, and NCl3, respectively. The corresponding temperature dependence of these reaction rate constants, measured over the range 10-40 °C, is well-described by the transformed Arrhenius equations:giving activation energies of 8.57 ± 0.58, 6.11 ± 0.40, and 5.77 ± 0.72 kJ mol-1 for these three chloramines, respectively. These data will aid water utilities in predicting hydroxyl radical partitioning and chemical contaminant removal efficiencies under real-world advanced oxidation process treatment conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

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

    Science.gov (United States)

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

    2016-02-09

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

  8. 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.

  9. 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.

  10. 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.

  11. On the temperature dependence of the optical spectral weight in correlated electron systems

    Energy Technology Data Exchange (ETDEWEB)

    Millis, A.J. [AT& T Bell Laboratories, Murray Hill, NJ (United States)

    1994-12-31

    A temperature dependence of the low frequency optical spectral weight has recently been observed in several strongly correlated insulating or nearly insulating systems including FeSi, Ce{sub 3}Bi{sub 4}Pt{sub 3} and V{sub 2}O{sub 3{minus}y}, and Bi{sub 2}Te{sub 3}. This temperature dependence is at first sight surprising because one is accustomed to thinking of optical spectral weigth in terms of the f-sum rule, which in its most general form states that the integral of any of the diagonal components of the optical conductivity {sigma}{sub ii}({omega}) is {pi}ne{sup 2}/2m. This is not very useful in most condensed matter physics contexts because the quantity n is the total number of electrons, including e.g. those in core levels, and because one must extend the integral to energies greater than the binding energy of the 1s shell to exhaust the sum rule. In condensed matter problems one typically focuses on a small number of bands close to the chemical potential. One may then ask what is the restricted sum rule governing optical transitions involving only these bands. Of course, the answer to this question is useful only if optical transitions involving bands retained in the model can be separated from those involving bands not retained.

  12. Temperature dependence of optical properties in Nd/Cr:YAG materials

    Energy Technology Data Exchange (ETDEWEB)

    Honda, Yoshiyuki, E-mail: honda-y@ile.osaka-u.ac.jp [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Motokoshi, Shinji [Institute for Laser Technology, 1-8-4 Utsubo-honmachi, Nishi-ku, Osaka 550-0004 (Japan); Jitsuno, Takahisa; Miyanaga, Noriaki; Fujioka, Kana [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Nakatsuka, Masahiro [Institute for Laser Technology, 1-8-4 Utsubo-honmachi, Nishi-ku, Osaka 550-0004 (Japan); Yoshida, Minoru [Kinki University, 3-4-1 Kowakae, Higashi-osaka, Osaka 577-8052 (Japan)

    2014-04-15

    The energy transfer from Cr{sup 3+} to Nd{sup 3+} for Nd/Cr:YAG (Nd: 1.0%, Cr: 2.0%) materials was investigated by measuring the temperature dependences of fluorescence characteristics. The fluorescence intensity of Nd{sup 3+} increased with temperature owing to enhancement of the absorption coefficient of Cr{sup 3+}. The energy transfer efficiency was constant from 77 to 450 K. The energy transfer time decreased with increasing temperature. -- Highlights: • We investigate the energy transfer from Cr{sup 3+} to Nd{sup 3+} in Nd/Cr:YAG materials by measuring the temperature dependence of fluorescence characteristics. • The fluorescence intensity of Nd{sup 3+} increased with temperature owing to enhancement of the absorption coefficient of Cr{sup 3+}. • The energy transfer efficiency was constant from 77 to 450 K. • The energy transfer time decreased with increasing temperature. • Nd/Cr:YAG ceramics pumped by a flash lamp would not only provide high conversion efficiency, but can also be expected to function as an effective laser operating at high temperature.

  13. Challenges in Modelling of Lightning-Induced Delamination; Effect of Temperature-Dependent Interfacial Properties

    Science.gov (United States)

    Naghipour, P.; Pineda, E. J.; Arnold, S.

    2014-01-01

    Lightning is a major cause of damage in laminated composite aerospace structures during flight. Due to the dielectric nature of Carbon fiber reinforced polymers (CFRPs), the high energy induced by lightning strike transforms into extreme, localized surface temperature accompanied with a high-pressure shockwave resulting in extensive damage. It is crucial to develop a numerical tool capable of predicting the damage induced from a lightning strike to supplement extremely expensive lightning experiments. Delamination is one of the most significant failure modes resulting from a lightning strike. It can be extended well beyond the visible damage zone, and requires sophisticated techniques and equipment to detect. A popular technique used to model delamination is the cohesive zone approach. Since the loading induced from a lightning strike event is assumed to consist of extreme localized heating, the cohesive zone formulation should additionally account for temperature effects. However, the sensitivity to this dependency remains unknown. Therefore, the major focus point of this work is to investigate the importance of this dependency via defining various temperature dependency profiles for the cohesive zone properties, and analyzing the corresponding delamination area. Thus, a detailed numerical model consisting of multidirectional composite plies with temperature-dependent cohesive elements in between is subjected to lightning (excessive amount of heat and pressure) and delamination/damage expansion is studied under specified conditions.

  14. Analysis of convective longitudinal fin with temperature-dependent thermal conductivity and internal heat generation

    Directory of Open Access Journals (Sweden)

    M.G. Sobamowo

    2017-03-01

    Full Text Available In this study, analysis of heat transfer in a longitudinal rectangular fin with temperature-dependent thermal conductivity and internal heat generation was carried out using finite difference method. The developed systems of non-linear equations that resulted from the discretization using finite difference scheme were solved with the aid of MATLAB using fsolve. The numerical solution was validated with the exact solution for the linear problem. The developed heat transfer models were used to investigate the effects of thermo-geometric parameters, coefficient of heat transfer and thermal conductivity (non-linear parameters on the temperature distribution, heat transfer and thermal performance of the longitudinal rectangular fin. From the results, it shows that the fin temperature distribution, the total heat transfer, and the fin efficiency are significantly affected by the thermo-geometric parameters of the fin. Also, for the solution to be thermally stable, the fin thermo-geometric parameter must not exceed a specific value. However, it was established that the increase in temperature-dependent properties and internal heat generation values increases the thermal stability range of the thermo-geometric parameter. The results obtained in this analysis serve as basis for comparison of any other method of analysis of the problem.

  15. Temperature-dependent elastic properties of brain tissues measured with the shear wave elastography method.

    Science.gov (United States)

    Liu, Yan-Lin; Li, Guo-Yang; He, Ping; Mao, Ze-Qi; Cao, Yanping

    2017-01-01

    Determining the mechanical properties of brain tissues is essential in such cases as the surgery planning and surgical training using virtual reality based simulators, trauma research and the diagnosis of some diseases that alter the elastic properties of brain tissues. Here, we suggest a protocol to measure the temperature-dependent elastic properties of brain tissues in physiological saline using the shear wave elastography method. Experiments have been conducted on six porcine brains. Our results show that the shear moduli of brain tissues decrease approximately linearly with a slope of -0.041±0.006kPa/°C when the temperature T increases from room temperature (~23°C) to body temperature (~37°C). A case study has been further conducted which shows that the shear moduli are insensitive to the temperature variation when T is in the range of 37 to 43°C and will increase when T is higher than 43°C. With the present experimental setup, temperature-dependent elastic properties of brain tissues can be measured in a simulated physiological environment and a non-destructive manner. Thus the method suggested here offers a unique tool for the mechanical characterization of brain tissues with potential applications in brain biomechanics research. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. 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.

  17. Temperature dependence of band gaps in semiconductors: electron-phonon interaction

    Energy Technology Data Exchange (ETDEWEB)

    Kremer, Reinhard K.; Cardona, M.; Lauck, R. [MPI for Solid State Research, Stuttgart (Germany); Bhosale, J.; Ramdas, A.K. [Physics Dept., Purdue University, West Lafayette, IN (United States); Burger, A. [Fisk University, Dept. of Life and Physical Sciences, Nashville, TN (United States); Munoz, A. [MALTA Consolider Team, Dept. de Fisica Fundamental II, Universidad de La Laguna, Tenerife (Spain); Instituto de Materiales y Nanotecnologia, Universidad de La Laguna, Tenerife (Spain); Romero, A.H. [CINVESTAV, Dept. de Materiales, Unidad Queretaro, Mexico (Mexico); MPI fuer Mikrostrukturphysik, Halle an der Saale (Germany)

    2013-07-01

    We investigate the temperature dependence of the energy gap of several semiconductors with chalcopyrite structure and re-examine literature data and analyze own high-resolution reflectivity spectra in view of our new ab initio calculations of their phonon properties. This analysis leads us to distinguish between materials with d-electrons in the valence band (e.g. CuGaS{sub 2}, AgGaS{sub 2}) and those without d-electrons (e.g. ZnSnAs{sub 2}). The former exhibit a rather peculiar non-monotonic temperature dependence of the energy gap which, so far, has resisted cogent theoretical description. We demonstrate it can well be fitted by including two Bose-Einstein oscillators with weights of opposite sign leading to an increase at low-T and a decrease at higher T's. We find that the energy of the former correlates well with characteristic peaks in the phonon density of states associated with low-energy vibrations of the d-electron constituents.

  18. 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.

  19. 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.

  20. 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.

  1. 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.)

  2. 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 ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-07-01

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

  4. 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

  5. Population Dynamics and Temperature-Dependent Development of Chrysomphalus aonidum (L.) to Aid Sustainable Pest Management Decisions.

    Science.gov (United States)

    Campolo, O; Malacrinò, A; Laudani, F; Maione, V; Zappalà, L; Palmeri, V

    2014-10-01

    The increasing worldwide trades progressively led to decreased impact of natural barriers on wild species movement. The exotic scale Chrysomphalus aonidum (L.) (Hemiptera: Diaspididae), recently reported on citrus in southern Italy, may represent a new threat to Mediterranean citriculture. We studied C. aonidum population dynamics under field conditions and documented its development under various temperatures. To enable describing temperature-dependent development through the use of linear and non-linear models, low temperature thresholds and thermal constants for each developmental stage were estimated. Chrysomphalus aonidum was able to perform four generations on green parts (leaves, sprouts) of citrus trees and three on fruits. In addition, an overall higher population density was observed on samples collected in the southern part of the tree canopy. Temperature had a significant effect on the developmental rate; female needed 625 degree days (DD) to complete its development, while male needed 833 DD. The low threshold temperatures, together with data from population dynamics, demonstrated that C. aonidum is able to overwinter as second instar and as an adult. The results obtained, validated by those collected in the field, revealed few differences between predicted and observed dates of first occurrence of each C. aonidum instar in citrus orchards. Data on C. aonidum phenology and the definition of the thermal parameters (lower and upper threshold temperatures, optimum temperature, and the thermal constant) by non-linear models could allow the estimation of the occurrence in the field of each life stage and would be helpful in developing effective integrated control strategies.

  6. Formation and distribution of fragments in the spontaneous fission of 240Pu

    Science.gov (United States)

    Sadhukhan, Jhilam; Zhang, Chunli; Nazarewicz, Witold; Schunck, Nicolas

    2017-12-01

    Background: Fission is a fundamental decay mode of heavy atomic nuclei. The prevalent theoretical approach is based on mean-field theory and its extensions where fission is modeled as a large amplitude motion of a nucleus in a multidimensional collective space. One of the important observables characterizing fission is the charge and mass distribution of fission fragments. Purpose: The goal of this Rapid Communication is to better understand the structure of fission fragment distributions by investigating the competition between the static structure of the collective manifold and the stochastic dynamics. In particular, we study the characteristics of the tails of yield distributions, which correspond to very asymmetric fission into a very heavy and a very light fragment. Methods: We use the stochastic Langevin framework to simulate the nuclear evolution after the system tunnels through the multidimensional potential barrier. For a representative sample of different initial configurations along the outer turning-point line, we define effective fission paths by computing a large number of Langevin trajectories. We extract the relative contribution of each such path to the fragment distribution. We then use nucleon localization functions along effective fission pathways to analyze the characteristics of prefragments at prescission configurations. Results: We find that non-Newtonian Langevin trajectories, strongly impacted by the random force, produce the tails of the fission fragment distribution of 240Pu. The prefragments deduced from nucleon localizations are formed early and change little as the nucleus evolves towards scission. On the other hand, the system contains many nucleons that are not localized in the prefragments even near the scission point. Such nucleons are distributed rapidly at scission to form the final fragments. Fission prefragments extracted from direct integration of the density and from the localization functions typically differ by more than

  7. Spontaneous fission of superheavy nuclei

    Indian Academy of Sciences (India)

    2015-08-02

    Aug 2, 2015 ... The macroscopic–microscopic method is extended to calculate the deformation energy and penetrability for binary nuclear configurations typical for fission processes. The deformed two-centre shell model is used to obtain single-particle energy levels for the transition region of two partially overlapped ...

  8. Spectroscopy of heavy fissionable nuclei

    Indian Academy of Sciences (India)

    2015-08-05

    Aug 5, 2015 ... Structural studies of heavy nuclei are quite challenging due to increased competition from fission, particularly at high spins. Nuclei in the actinide region exhibit a variety of interesting phenomena. Recent advances in instrumentation and analysis techniques have made feasible sensitive measurements of ...

  9. Nuclear fission with inertial confinement

    CERN Document Server

    Koshkarev, D G

    2002-01-01

    The possibility of initiating the explosive fission reaction in a small quantity of fissile material through the heavy ions beam from the powerful accelerator-driver, developed for realization of the thermonuclear synthesis in the deuterium-tritium cylindrical targets with the direct ignition, is considered. The consequences of applying this method in the nuclear engineering are discussed

  10. Discoveries of isotopes by fission

    Indian Academy of Sciences (India)

    About 3000 different isotopes have been discovered until now. A recent compilation sum- marized details of the discovery of all isotopes [1–4] including the year, laboratory and country of discovery as well as the production mechanism used to produce the isotopes. Fission, one of the largest contributing production ...

  11. Fusion-fission and quasifission of superheavy systems in heavy-ion induced reactions

    Energy Technology Data Exchange (ETDEWEB)

    Itkis, M.G.; Itkis, I.M.; Knyazheva, G.N.; Kozulin, E.M. [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, 141980 Dubna, Moscow reg. (Russian Federation)

    2010-03-01

    Mass and energy distributions of fission-like fragments obtained in the reactions with {sup 26}Mg, {sup 36}S and {sup 58}Fe ions leading to the formation of the Z=108 composite nucleus are reported. From the analysis of TKE distributions for symmetric fragment it was found that at energies below the Coulomb barrier the bimodal fission of {sup 274}Hs, formed in the reaction {sup 26}Mg+{sup 248}Cm, is observed, while in the reaction {sup 36}S+{sup 238}U at these energies the main part of the symmetric fragments arises from the quasifission process. At energies above the Coulomb barrier the fusion-fission is a main process leading to the formation of symmetric fragment for the both reactions.

  12. Characterization of temperature dependent operation of a GaInNAs-based RCEPD designed for 1.3 μm

    Science.gov (United States)

    Sarcan, F.; Nordin, M. S.; Kuruoğlu, F.; Erol, A.; Vickers, A. J.

    2017-02-01

    We report the characteristics of the temperature dependent operation of a GaInNAs-based resonant-cavity-enhanced photodetector (RCEPD), designed to be operated at the dispersion minimum optical communication window of 1.3 μm. A Transfer-Matrix Method (TMM) was used to design the structure of the device. The absorption layer of the photodetector is comprised of nine 7 nm-thick Ga0.733In0.267N0.025As0.975 (Sb)/GaN0.035As0.965 quantum wells, and 15 and 10 pairs of GaAs/AlAs distributed Bragg reflectors (DBRs) grown as the bottom and top mirrors, to form the cavity of the device. All electrical and optical measurements were carried out over a temperature range from 10 to 40 °C in order to investigate the characteristic of the device. The quantum efficiency is determined to be in the range of 16% (at 10 °C) and 31% (at 40 °C). An excellent wavelength selectivity is observed which changed from 3.7 nm (at 10 °C) to 5.4 nm (at 40 °C). The dark current of the device is measured as 11 nA at 10 °C and 19 nA at 40 °C without bias. The photocurrent at -0.5 V is measured to be 1.5 mA at 25 °C. The high dark current of the device is attributed to weak confinement of the electrons in GaInNAs QW surrounded by the strain-compensator GaNAs barrier layers. The temperature dependent cavity wavelength was analytically calculated and compared with that of experimental results. The temperature dependent linear shifts of the resonance wavelength (dλ / dT) is calculated as 0.077 nm/°C, which is in good agreement with the experimental result, 0.080 nm/°C. Our results reveal that the characteristics of a RCEPD, such as quantum efficiency, FWHM etc., are quite sensitive to temperature changes due to the temperature dependence of the refractive index of the DBRs.

  13. Effects of microstructural constraints on the transport of fission products in uranium dioxide at low burnups

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Harn Chyi; Rudman, Karin; Krishnan, Kapil; McDonald, Robert [Arizona State University, Tempe, AZ (United States); Dickerson, Patricia [Los Alamos National Lab, Los Alamos, NM (United States); Gong, Bowen [Arizona State University, Tempe, AZ (United States); Peralta, Pedro, E-mail: pperalta@asu.edu [Arizona State University, Tempe, AZ (United States)

    2016-08-15

    Diffusion of fission gases in UO{sub 2} is studied at low burnups, before bubble growth and coalescence along grain boundaries (GBs) become dominant, using a 3-D finite element model that incorporates actual UO{sub 2} microstructures. Grain boundary diffusivities are assigned based on crystallography with lattice and GB diffusion coupled with temperature to account for temperature gradients. Heterogeneity of GB properties and connectivity can induce regions where concentration is locally higher than without GB diffusion. These regions are produced by “bottlenecks” in the GB network because of lack of connectivity among high diffusivity GBs due to crystallographic constraints, and they can lead to localized swelling. Effective diffusivities were calculated assuming a uniform distribution of high diffusivity among GBs. Results indicate an increase over the bulk diffusivity with a clear grain size effect and that connectivity and properties of different GBs become important factors on the variability of fission product concentration at the microscale. - Highlights: • Microstructure models are developed to study fission gas transport in oxide fuels. • Crystallographic and temperature dependent material properties are applied. • Fission product concentration is affected by grain boundary distribution. • High concentration regions can form as controlled by the grain boundary connectivity.

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

    Science.gov (United States)

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

    2013-10-10

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

  15. Temperature Dependent Electrical Transport in Al/Poly(4-vinyl phenol/p-GaAs Metal-Oxide-Semiconductor by Sol-Gel Spin Coating Method

    Directory of Open Access Journals (Sweden)

    Şadan Özden

    2016-01-01

    Full Text Available Deposition of poly(4-vinyl phenol insulator layer is carried out by applying the spin coating technique onto p-type GaAs substrate so as to create Al/poly(4-vinyl phenol/p-GaAs metal-oxide-semiconductor (MOS structure. Temperature was set to 80–320 K while the current-voltage (I-V characteristics of the structure were examined in the study. Ideality factor (n and barrier height (ϕb values found in the experiment ranged from 3.13 and 0.616 eV (320 K to 11.56 and 0.147 eV (80 K. Comparing the thermionic field emission theory and thermionic emission theory, the temperature dependent ideality factor behavior displayed that thermionic field emission theory is more valid than the latter. The calculated tunneling energy was 96 meV.

  16. 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

  17. Temperature dependence of the 1.06-microm stimulated emission cross section of neodymium in YAG and in GSGG.

    Science.gov (United States)

    Rapaport, Alexandra; Zhao, Shengzhi; Xiao, Guohua; Howard, Andrew; Bass, Michael

    2002-11-20

    A linear temperature dependence between -70 degrees C and +70 degrees C is reported for the peak stimulated emission cross section of Nd3+ ions in both yttrium aluminum garnet (YAG) and gadolinium scandium gallium garnet (GSGG).

  18. 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.

  19. 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.

  20. Temperature dependent forward current-voltage characteristics of Ni/Au Schottky contacts on AlGaN/GaN heterostructures described by a two diodes model

    Science.gov (United States)

    Greco, Giuseppe; Giannazzo, Filippo; Roccaforte, Fabrizio

    2017-01-01

    This paper reports on the temperature dependence of Ni/Au Schottky contacts on AlGaN/GaN heterostructures. The electrical properties of the Schottky barrier were monitored by means of forward current-voltage (I-V) measurements, while capacitance-voltage measurements were used to determine the properties of the two dimensional electron gas. The forward I-V characteristics of Schottky diodes revealed a strong deviation from the ideal behavior, which could not be explained by a standard thermionic emission model. Thus, the Ni/AlGaN/GaN system has been described by a "two diode model," considering the presence of a second barrier height at the AlGaN/GaN heterojunction. Following this approach, the anomalous I-V curves could be explained and the value of the flat-band barrier height (at zero-electric field) could be correctly determined, thus resulting in good agreement with literature data based on photoemission measurements.

  1. Fission anisotropy of 197 Tl produced in fusion reactions in the ...

    Indian Academy of Sciences (India)

    It was shown that in the framework of the modified statistical model, by choosing appropriate values for the temperature coefficient of the effective potential, , and scaling factor of the fission-barrier height, s, one can satisfactorily reproduce the above-mentioned experimental data. It was also shown that the appropriate ...

  2. 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...

  3. 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.

  4. 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.

  5. 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.

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

    Science.gov (United States)

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

    2011-10-01

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

  7. 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.

  8. 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.

  9. Frequency doubling in LiNbO3 using temperature dependent QPM

    DEFF Research Database (Denmark)

    Belmonte, Michele; Skettrup, Torben; Pedersen, Christian

    1999-01-01

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

  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. Modeling of Temperature-Dependent Noise in Silicon Nanowire FETs including Self-Heating Effects

    Directory of Open Access Journals (Sweden)

    P. Anandan

    2014-01-01

    Full Text Available 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 resistance shows significant improvement as the channel length decreases. The effects of thermal noise including self-heating of the device are explored. Moreover, significant reduction in noise with respect to channel thermal resistance, gate length, and biasing is analyzed.

  13. 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...

  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. Receding horizon H∞ guaranteed cost tracking control for microwave heating medium with temperature-dependent permittivity.

    Science.gov (United States)

    Zhong, Jiaqi; Liang, Shan; Xiong, Qingyu

    2018-01-10

    This paper considers the temperature spectrum tracking control of microwave heating model, in the presence of asymmetrical input saturation, nonhomogeneous Neumann boundary condition and temperature-dependent permittivity. The sufficient condition for the existence of receding horizon H∞ guaranteed cost control is proposed based on the derived finite-dimensional ordinary differential equation (ODE) error model. Furthermore, by on-line updating and solving linear matrix inequalities (LMIs) optimization problem, the constrained tracking controller can be obtained in the sense of minimizing H∞ norm and satisfying the quadratic cost performance. The proposed control strategy is implemented on a one-dimensional cavity heating model and its performance is evaluated through the simulation. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

  16. Prediction of the temperature dependency of Henry's law constant from chemical structure.

    Science.gov (United States)

    Kühne, Ralph; Ebert, Ralf-Uwe; Schüürmann, Gerrit

    2005-09-01

    A new model to estimate the temperature dependency of Henry's law constant in water for organic compounds from the two-dimensional structure is presented. Air/water partition enthalpies of 456 chemicals were fitted to 46 substructural parameters with a squared correlation coefficient r2 of 0.81 and a standard error of 7.1 kJ/mol. The compound set covers various organic compound classes with the atom types C, H, N, O, F, Cl, Br, I, and S. Application of the model together with experimental data for 25 degrees C to a set of 462 compounds with 2119 experimental Henry's law constants at temperatures below 20 degrees C yields a predictive squared correlation coefficient q2 of 0.99 and a standard error of 0.21 logarithmic units. The prediction capability is further evaluated using cross validation and permutation.

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

    CERN Document Server

    Ropers, Steffen

    2017-01-01

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

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

    Science.gov (United States)

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

    2004-06-01

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

  19. 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.

  20. 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....

  1. 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.

  2. 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.

  3. 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.

  4. A temperature-dependent coarse-grained model for the thermoresponsive polymer poly(N-isopropylacrylamide)

    Energy Technology Data Exchange (ETDEWEB)

    Abbott, Lauren J.; Stevens, Mark J., E-mail: msteve@sandia.gov [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    2015-12-28

    A coarse-grained (CG) model is developed for the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAM), using a hybrid top-down and bottom-up approach. Nonbonded parameters are fit to experimental thermodynamic data following the procedures of the SDK (Shinoda, DeVane, and Klein) CG force field, with minor adjustments to provide better agreement with radial distribution functions from atomistic simulations. Bonded parameters are fit to probability distributions from atomistic simulations using multi-centered Gaussian-based potentials. The temperature-dependent potentials derived for the PNIPAM CG model in this work properly capture the coil–globule transition of PNIPAM single chains and yield a chain-length dependence consistent with atomistic simulations.

  5. 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}.

  6. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-10-15

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

  8. 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.

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

    Science.gov (United States)

    Ivanov, A. S.

    2017-11-01

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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Simulating Damage Due to a Lightning Strike Event: Effects of Temperature Dependent Properties on Interlaminar Damage

    Science.gov (United States)

    Ghezeljeh, Paria Naghipour; Pineda, Evan Jorge

    2014-01-01

    A multidirectional, carbon fiber-epoxy, composite panel is subjected to a simulated lightning strike, within a finite element method framework, and the effect of material properties on the failure (delamination) response is investigated through a detailed numerical study. The numerical model of the composite panel consists of individual homogenized plies with user-defined, cohesive interface elements between them. Lightning strikes are simulated as an assumed combination of excessive heat and high pressure loadings. It is observed that the initiation and propagation of lightning-induced delamination is a significant function of the temperature dependency of interfacial fracture toughness. This dependency must be defined properly in order to achieve reliable predictions of the present lightning-induced delamination in the composite panel.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Temperature dependence of photoluminescence properties in a thermally activated delayed fluorescence emitter

    Energy Technology Data Exchange (ETDEWEB)

    Niwa, Akitsugu [Department of Physics and Electronics, Osaka Prefecture University, 1-1 Gakuencho, Nakaku, Sakai 599-8531 (Japan); Kobayashi, Takashi, E-mail: tkobaya@pe.osakafu-u.ac.jp; Nagase, Takashi; Naito, Hiroyoshi, E-mail: naito@pe.osakafu-u.ac.jp [Department of Physics and Electronics, Osaka Prefecture University, 1-1 Gakuencho, Nakaku, Sakai 599-8531 (Japan); The Research Institute for Molecular Electronic Devices, Osaka Prefecture University, Sakai 599-8531 (Japan); Goushi, Kenichi; Adachi, Chihaya [Center for Organic Photonics and Electronics Research, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan)

    2014-05-26

    Using steady-state and time-resolved photoluminescence (PL) spectroscopy, we have investigated the temperature dependence of PL properties of 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyano-benzene (4CzIPN), which have a small energy gap between its singlet and triplet excited states and thus exhibits efficient thermally activated delayed fluorescence [H. Uoyama et al., Nature 492, 235 (2012)]. Below around 100 K, PL quantum efficiency of 4CzIPN thin films is largely suppressed and strong photoexcitation intensity dependence appears. These features can be explained by using rate equations for the densities of singlet and triplet excited states considering a triplet-triplet annihilation process.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Temperature dependence of plankton community metabolism in the subtropical and tropical oceans

    KAUST Repository

    Garcia-Corral, Lara S.

    2017-06-22

    Here we assess the temperature dependence of the metabolic rates (gross primary production (GPP), community respiration (CR), and the ratio GPP/CR) of oceanic plankton communities. We compile data from 133 stations of the Malaspina 2010 Expedition, distributed among the subtropical and tropical Atlantic, Pacific, and Indian oceans. We used the in vitro technique to measured metabolic rates during 24 h incubations at three different sampled depths: surface, 20%, and 1% of the photosynthetically active radiation measured at surface. We also measured the % of ultraviolet B radiation (UVB) penetrating at surface waters. GPP and CR rates increased with warming, albeit different responses were observed for each sampled depth. The overall GPP/CR ratio declined with warming. Higher activation energies (E-a) were derived for both processes (GPP(Chla) = 0.97; CRChla = 1.26; CRHPA = 0.95 eV) compared to those previously reported. The Indian Ocean showed the highest E-a (GPP(Chla) = 1.70; CRChla = 1.48; CRHPA = 0.57 eV), while the Atlantic Ocean showed the lowest (GPP(Chla) = 0.86; CRChla = 0.77; CRHPA = -0.13 eV). We believe that the difference between previous assessments and the ones presented here can be explained by the overrepresentation of Atlantic communities in the previous data sets. We found that UVB radiation also affects the temperature dependence of surface GPP, which decreased rather than increased under high levels of UVB. Ocean warming, which causes stratification and oligotrophication of the subtropical and tropical oceans, may lead to reduced surface GPP as a result of increased penetration of UVB radiation.

  6. 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

  7. 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.

  8. Prompt fission γ-ray data from spontaneous fission and the mechanism of fission-fragment de-excitation

    Directory of Open Access Journals (Sweden)

    Oberstedt Stephan

    2017-01-01

    Full Text Available The investigation of prompt γ-ray emission in nuclear fission has a great relevance for the assessment of prompt heat generation in a reactor core and for the better understanding of the de-excitation mechanism of fission fragments. Some years ago experimental data was scarce and available only from a few fission reactions, 233,235U(nth, f, 239Pu(nth, f, and 252Cf(sf. Initiated by a high priority data request published by the OECD/NEA a dedicated prompt fission γ-ray measurement program is being conducted at the Joint Research Centre Geel. In recent years we obtained new and accurate prompt fission γ-ray spectrum (PFGS characteristics (average number of photons per fission, average total energy per fission and mean photon energy from 252Cf(sf, 235U(nth, f and 239,241Pu(nth, f within 2% of uncertainty. In order to understand the dependence of prompt fission γ-ray emission on the compound nuclear mass and excitation energy, we started a first measurement campaign on spontaneously fissioning plutonium and curium isotopes. Results on PFGS characteristics from 240,242Pu(sf show a dependence on the fragment mass distribution rather than on the average prompt neutron multiplicity, pointing to a more complex competition between prompt fission γ-ray and neutron emission.

  9. Prompt fission γ-ray data from spontaneous fission and the mechanism of fission-fragment de-excitation

    Science.gov (United States)

    Oberstedt, Stephan; Dragic, Aleksandar; Gatera, Angelique; Göök, Alf; Hambsch, Franz-Josef; Oberstedt, Andreas

    2017-09-01

    The investigation of prompt γ-ray emission in nuclear fission has a great relevance for the assessment of prompt heat generation in a reactor core and for the better understanding of the de-excitation mechanism of fission fragments. Some years ago experimental data was scarce and available only from a few fission reactions, 233,235U(nth, f), 239Pu(nth, f), and 252Cf(sf). Initiated by a high priority data request published by the OECD/NEA a dedicated prompt fission γ-ray measurement program is being conducted at the Joint Research Centre Geel. In recent years we obtained new and accurate prompt fission γ-ray spectrum (PFGS) characteristics (average number of photons per fission, average total energy per fission and mean photon energy) from 252Cf(sf), 235U(nth, f) and 239,241Pu(nth, f) within 2% of uncertainty. In order to understand the dependence of prompt fission γ-ray emission on the compound nuclear mass and excitation energy, we started a first measurement campaign on spontaneously fissioning plutonium and curium isotopes. Results on PFGS characteristics from 240,242Pu(sf) show a dependence on the fragment mass distribution rather than on the average prompt neutron multiplicity, pointing to a more complex competition between prompt fission γ-ray and neutron emission.

  10. A fission fragment detector for correlated fission output studies

    Energy Technology Data Exchange (ETDEWEB)

    Mosby, S., E-mail: smosby@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Tovesson, F.; Couture, A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Duke, D.L. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Colorado School of Mines, Golden, CO 80401 (United States); Kleinrath, V. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Idaho State University, Pocatello, ID 83201 (United States); Meharchand, R.; Meierbachtol, K.; O' Donnell, J.M.; Perdue, B.; Richman, D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Shields, D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Colorado School of Mines, Golden, CO 80401 (United States)

    2014-09-01

    A digital data acquisition system has been combined with a double Frisch gridded ionization chamber for use at both moderated and unmoderated neutron sources at the Los Alamos Neutron Science (LANSCE) facility. The high efficiency of the instrument combined with intense LANSCE beams and new acquisition system permits fission output measurements across 11 orders of magnitude incident neutron energy. The acquisition and analysis system is presented along with the first in-beam performance tests of the setup.

  11. Multi-modal fission in collinear ternary cluster decay of 252Cf(sf, fff

    Directory of Open Access Journals (Sweden)

    W. von Oertzen

    2015-06-01

    Full Text Available We discuss the multiple decay modes of collinear fission in 252Cf(sf, fff, with three fragments as suggested by the potential energy surface (PES. Fission as a statistical decay is governed by the phase space of the different decay channels, which are suggested in the PES-landscape. The population of the fission modes is determined by the minima in the PES at the scission points and on the internal potential barriers. The ternary collinear decay proceeds as a sequential process, in two steps. The originally observed ternary decay of 252Cf(sf into three different masses (e.g. 132–140Sn, 52–48Ca, 68–72Ni, observed by the FOBOS group in the FLNR (Flerov Laboratory for Nuclear Reactions of the JINR (Dubna the collinear cluster tripartition (CCT, is one of the ternary fission modes. This kind of “true ternary fission” of heavy nuclei has often been predicted in theoretical works during the last decades. In the present note we discuss different ternary fission modes in the same system. The PES shows pronounced minima, which correspond to several modes of ternary fragmentations. These decays have very similar dynamical features as the previously observed CCT-decays. The data obtained in the experiments on CCT allow us to extract the yields for different decay modes using specific gates on the measured parameters, and to establish multiple modes of the ternary fission decay.

  12. The VERDI fission fragment spectrometer

    Directory of Open Access Journals (Sweden)

    Frégeau M.O.

    2013-12-01

    Full Text Available The VERDI time-of-flight spectrometer is dedicated to measurements of fission product yields and of prompt neutron emission data. Pre-neutron fission-fragment masses will be determined by the double time-of-flight (TOF technique. For this purpose an excellent time resolution is required. The time of flight of the fragments will be measured by electrostatic mirrors located near the target and the time signal coming from silicon detectors located at 50 cm on both sides of the target. This configuration, where the stop detector will provide us simultaneously with the kinetic energy of the fragment and timing information, significantly limits energy straggling in comparison to legacy experimental setup where a thin foil was usually used as a stop detector. In order to improve timing resolution, neutron transmutation doped silicon will be used. The high resistivity homogeneity of this material should significantly improve resolution in comparison to standard silicon detectors. Post-neutron fission fragment masses are obtained form the time-of-flight and the energy signal in the silicon detector. As an intermediary step a diamond detector will also be used as start detector located very close to the target. Previous tests have shown that poly-crystalline chemical vapour deposition (pCVD diamonds provides a coincidence time resolution of 150 ps not allowing complete separation between very low-energy fission fragments, alpha particles and noise. New results from using artificial single-crystal diamonds (sCVD show similar time resolution as from pCVD diamonds but also sufficiently good energy resolution.

  13. Technical Application of Nuclear Fission

    Science.gov (United States)

    Denschlag, J. O.

    The chapter is devoted to the practical application of the fission process, mainly in nuclear reactors. After a historical discussion covering the natural reactors at Oklo and the first attempts to build artificial reactors, the fundamental principles of chain reactions are discussed. In this context chain reactions with fast and thermal neutrons are covered as well as the process of neutron moderation. Criticality concepts (fission factor η, criticality factor k) are discussed as well as reactor kinetics and the role of delayed neutrons. Examples of specific nuclear reactor types are presented briefly: research reactors (TRIGA and ILL High Flux Reactor), and some reactor types used to drive nuclear power stations (pressurized water reactor [PWR], boiling water reactor [BWR], Reaktor Bolshoi Moshchnosti Kanalny [RBMK], fast breeder reactor [FBR]). The new concept of the accelerator-driven systems (ADS) is presented. The principle of fission weapons is outlined. Finally, the nuclear fuel cycle is briefly covered from mining, chemical isolation of the fuel and preparation of the fuel elements to reprocessing the spent fuel and conditioning for deposit in a final repository.

  14. 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

  15. Target conception for the Munich fission fragment accelerator

    CERN Document Server

    Maier, H J; Gross, M L; Grossmann, R; Kester, O; Thirolf, P

    1999-01-01

    For the new high-flux reactor FRM II, the fission fragment accelerator MAFF is under design. MAFF will supply intense mass-separated radioactive ion beams of very neutron-rich nuclei with energies around the Coulomb barrier. A central part of this accelerator is the ion source with the fission target, which is operated at a neutron flux of 1.5x10 sup 1 sup 4 cm sup - sup 2 s sup - sup 1. The target consists of typically 1 g of sup 2 sup 3 sup 5 U dispersed in a cylindrical graphite matrix, which is encapsulated in a Re container. To enable diffusion and extraction of the fission products, the target has to be maintained at a temperature of up to 2400 deg. C during operation. It has to stand this temperature for at least one reactor cycle of 1250 h. Comprehensive tests are required to study the long-term behaviour of the involved materials at these conditions prior to operation in the reactor. The present paper gives details of the target conception and the projected tests.

  16. Probing fusion-fission dynamics in Bi203

    Science.gov (United States)

    Mukul, Ish; Nath, S.; Golda, K. S.; Jhingan, A.; Gehlot, J.; Prasad, E.; Kalkal, Sunil; Naik, M. B.; Banerjee, Tathagata; Varughese, T.; Sugathan, P.; Madhavan, N.; Pal, Santanu

    2015-11-01

    Background: Complete fusion between two massive nuclei after capture inside the potential barrier is inhibited by competing fission-like processes. The target-projectile composite system may reseparate after capture without proceeding towards formation of the compound nucleus (CN), which is equilibrated in all degrees of freedom. The nature of these non-CN fission (NCNF) processes and factors that affect them are not completely known yet. Purpose: The nuclear mass regions from where NCNF processes begin to manifest themselves are not clearly demarcated. This work aims to study the onset of NCNF, if any, in the mass region ˜200 . Methods: Fission fragment (FF) mass and angular distribution (MAD) and pre-scission and post-scission neutron multiplicities were measured for the reaction +W184F19 at a laboratory energy (Elab) range of 84-125 MeV. The measurements were carried out using two multiwire proportional counters (MWPC) to detect the FFs in coincidence and four neutron detectors to measure neutron time of flight (TOF). Statistical model (SM) calculation was performed. Results: No significant mass-angle correlation was observed in the MAD plots. Extracted mass ratio distributions were single-peaked and of Gaussian shape. Measured pre-scission neutron multiplicity values indicated dissipative nature of CN decay for this reaction. Conclusions: No clear signatures of NCNF were observed in the studied reaction, indicating that the target-projectile composite system predominantly proceeds towards formation of the CN after capture.

  17. A humidity shock leads to rapid, temperature dependent changes in coffee leaf physiology and gene expression.

    Science.gov (United States)

    Thioune, El-Hadji; McCarthy, James; Gallagher, Thomas; Osborne, Bruce

    2017-03-01

    Climate change is expected to increase the frequency of above-normal atmospheric water deficits contemporaneous with periods of high temperatures. Here we explore alterations in physiology and gene expression in leaves of Coffea canephora Pierre ex A. Froehner caused by a sharp drop in relative humidity (RH) at three different temperatures. Both stomatal conductance (gs) and CO2 assimilation (A) measurements showed that gs and A values fell quickly at all temperatures after the transfer to low RH.  However, leaf relative water content measurements indicated that leaves nonetheless experienced substantial water losses, implying that stomatal closure and/or resupply of water was not fast enough to stop excessive evaporative losses.  At 27 and 35 °C, upper leaves showed significant decreases in Fv/Fm compared with lower leaves, suggesting a stronger impact on photosystem II for upper leaves, while at 42 °C, both upper and lower leaves were equally affected. Quantitative gene expression analysis of transcription factors associated with conventional dehydration stress, and genes involved with abscisic acid signalling, such as CcNCED3, indicated temperature-dependent, transcriptional changes during the Humidity Shock ('HuS') treatments.  No expression was seen at 27 °C for the heat-shock gene CcHSP90-7, but it was strongly induced during the 42 °C 'HuS' treatment. Consistent with a proposal that important cellular damage occurred during the 42 °C 'HuS' treatment, two genes implicated in senescence were induced by this treatment. Overall, the data show that C. canephora plants subjected to a sharp drop in RH exhibit major, temperature-dependent alterations in leaf physiology and important changes in the expression of genes associated with abiotic stress and senescence. The results presented suggest that more detailed studies on the combined effects of low RH and high temperature are warranted. © The Author 2017. Published by Oxford University Press. All rights

  18. 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

  19. 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

  20. 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.

  1. The resonance neutron fission on heavy nuclei

    CERN Document Server

    Kopach, Yu N; Furman, V I; Alfimenkov, V P; Lason', L; Pikelner, L B; Gonin, N N; Kozlovskij, L K; Tambovtsev, D I; Gagarskij, A M; Petrov, G A; Sokolov, V E

    2001-01-01

    A new approach to the description of the fission, similar to the well-known reaction theory and based on the helicity representation for the exit fission channels, is briefly summarized. This approach allows one to connect the multimodal fission representation with A. Bohr's concept of the fission transition states and to obtain formulae for the partial and differential fission cross sections. The formulae are used for analysis of the angular anisotropy of fragments in the neutron resonance induced fission of aligned sup 2 sup 3 sup 5 U nuclei and of the P-even angular forward-backward and right-left correlations of fragments oe the P-odd correlations caused by the interference of s- and p-wave neutron resonances

  2. Comparative evaluation of solar, fission, fusion, and fossil energy resources. Part 2: Power from nuclear fission

    Science.gov (United States)

    Clement, J. D.

    1973-01-01

    Different types of nuclear fission reactors and fissionable materials are compared. Special emphasis is placed upon the environmental impact of such reactors. Graphs and charts comparing reactor facilities in the U. S. are presented.

  3. Describing Temperature-Dependent Self-Diffusion Coefficients and Fluidity of 1- and 3-Alcohols with the Compensated Arrhenius Formalism.

    Science.gov (United States)

    Fleshman, Allison M; Forsythe, Grant E; Petrowsky, Matt; Frech, Roger

    2016-09-22

    The location of the hydroxyl group in monohydroxy alcohols greatly affects the temperature dependence of the liquid structure due to hydrogen bonding. Temperature-dependent self-diffusion coefficients, fluidity (the inverse of viscosity), dielectric constant, and density have been measured for several 1-alcohols and 3-alcohols with varying alkyl chain lengths. The data are modeled using the compensated Arrhenius formalism (CAF). The CAF follows a modified transition state theory using an Arrhenius-like expression to describe the transport property, which consists of a Boltzmann factor containing an energy of activation, Ea, and an exponential prefactor containing the temperature-dependent solution dielectric constant, εs(T). Both 1- and 3-alcohols show the Ea of diffusion coefficients (approximately 43 kJ mol(-1)) is higher than the Ea of fluidity (approximately 35 kJ mol(-1)). The temperature dependence of the exponential prefactor in these associated liquids is explained using the dielectric constant and the Kirkwood-Frölich correlation factor, gk. It is argued that the dielectric constant must be used to account for the additional temperature dependence due to variations in the liquid structure (e.g., hydrogen bonding) for the CAF to accurately model the transport property.

  4. Measurements of Fission Cross Sections of Actinides

    CERN Multimedia

    Wiescher, M; Cox, J; Dahlfors, M

    2002-01-01

    A measurement of the neutron induced fission cross sections of $^{237}$Np, $^{241},{243}$Am and of $^{245}$Cm is proposed for the n_TOF neutron beam. Two sets of fission detectors will be used: one based on PPAC counters and another based on a fast ionization chamber (FIC). A total of 5x10$^{18}$ protons are requested for the entire fission measurement campaign.

  5. Temperature-dependent regulation of rDNA condensation in Saccharomyces cerevisiae.

    Science.gov (United States)

    Shen, Donglai; Skibbens, Robert V

    2017-06-03

    Chromatin condensation during mitosis produces detangled and discrete DNA entities required for high fidelity sister chromatid segregation during mitosis and positions DNA away from the cleavage furrow during cytokinesis. Regional condensation during G1 also establishes a nuclear architecture through which gene transcription is regulated but remains plastic so that cells can respond to changes in nutrient levels, temperature and signaling molecules. To date, however, the potential impact of this plasticity on mitotic chromosome condensation remains unknown. Here, we report results obtained from a new condensation assay that wildtype budding yeast cells exhibit dramatic changes in rDNA conformation in response to temperature. rDNA hypercondenses in wildtype cells maintained at 37°C, compared with cells maintained at 23°C. This hypercondensation machinery can be activated during preanaphase but readily inactivated upon exposure to lower temperatures. Extended mitotic arrest at 23°C does not result in hypercondensation, negating a kinetic-based argument in which condensation that typically proceeds slowly is accelerated when cells are placed at 37°C. Neither elevated recombination nor reduced transcription appear to promote this hypercondensation. This heretofore undetected temperature-dependent hypercondensation pathway impacts current views of chromatin structure based on conditional mutant gene analyses and significantly extends our understanding of physiologic changes in chromatin architecture in response to hypothermia.

  6. 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.

  7. Temperature dependence of the shear modulus of soft tissues assessed by ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    Sapin-de Brosses, E; Gennisson, J-L; Pernot, M; Fink, M; Tanter, M [Langevin Institute (CNRS UMR 7587), INSERM ERL U979, ESPCI ParisTech, 10 rue Vauquelin, 75 005 Paris (France)], E-mail: emilie.sapin@espci.fr

    2010-03-21

    Soft tissue stiffness was shown to significantly change after thermal ablation. To better understand this phenomenon, the study aims (1) to quantify and explain the temperature dependence of soft tissue stiffness for different organs, (2) to investigate the potential relationship between stiffness changes and thermal dose and (3) to study the reversibility or irreversibility of stiffness changes. Ex vivo bovine liver and muscle samples (N = 3 and N = 20, respectively) were slowly heated and cooled down into a thermally controlled saline bath. Temperatures were assessed by thermocouples. Sample stiffness (shear modulus) was provided by the quantitative supersonic shear imaging technique. Changes in liver stiffness are observed only after 45 deg. C. In contrast, between 25 deg. C and 65 deg. C, muscle stiffness varies in four successive steps that are consistent with the thermally induced proteins denaturation reported in the literature. After a 6 h long heating and cooling process, the final muscle stiffness can be either smaller or bigger than the initial one, depending on the stiffness at the end of the heating. Another important result is that stiffness changes are linked to thermal dose. Given the high sensitivity of ultrasound to protein denaturation, this study gives promising prospects for the development of ultrasound-guided HIFU systems.

  8. 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.

  9. Emergence of coherent localized structures in shear deformations of temperature dependent fluids

    KAUST Repository

    Katsaounis, Theodoros

    2016-11-25

    Shear localization occurs in various instances of material instability in solid mechanics and is typically associated with Hadamard-instability for an underlying model. While Hadamard instability indicates the catastrophic growth of oscillations around a mean state, it does not by itself explain the formation of coherent structures typically observed in localization. The latter is a nonlinear effect and its analysis is the main objective of this article. We consider a model that captures the main mechanisms observed in high strain-rate deformation of metals, and describes shear motions of temperature dependent non-Newtonian fluids. For a special dependence of the viscosity on the temperature, we carry out a linearized stability analysis around a base state of uniform shearing solutions, and quantitatively assess the effects of the various mechanisms affecting the problem: thermal softening, momentum diffusion and thermal diffusion. Then, we turn to the nonlinear model, and construct localized states - in the form of similarity solutions - that emerge as coherent structures in the localization process. This justifies a scenario for localization that is proposed on the basis of asymptotic analysis in \\\\cite{KT}.

  10. Electrochemical properties and temperature dependence of a recombinant laccase from Thermus thermophilus.

    Science.gov (United States)

    Liu, Xin; Gillespie, Megan; Ozel, Ayca Demirel; Dikici, Emre; Daunert, Sylvia; Bachas, Leonidas G

    2011-01-01

    The electrochemical properties of a laccase from Thermus thermophilus HB27 (Tth-laccase) were characterized. The gene encoding the laccase was cloned and overexpressed in Escherichia coli. One-step purification of the corresponding apo-enzyme was achieved by nickel-affinity chromatography. Copper was incorporated into the apo-laccase as the cofactor to yield the holo-enzyme. The temperature-dependent catalytic activity of the laccase was investigated by spectrophotometric as well as electrochemical methods. Specifically, the catalytic properties of the enzyme were characterized by employing a photometric assay based on the oxidation of the substrate 2,2-azino-bis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS). The electroactive substrate ABTS can be also monitored by cyclic voltammetry, thus allowing for determination of the enzymatic activity electrochemically. It was found that the recombinant laccase exhibited higher activity as the temperature increased up to 65 °C. Spectroscopic studies of Tth-laccase based on circular dichroism and fluorescence measurements are consistent with a thermally stable secondary structure of the protein.

  11. 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

  12. Oxygen isotope fractionation in the vacuum ultraviolet photodissociation of carbon monoxide: Wavelength, pressure and temperature dependency.

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Subrata; Davis, Ryan; Ahmed, Musahid; Jackson, Teresa L.; Thiemens, Mark H.

    2012-01-03

    Several absorption bands exist in the VUV region of Carbon monoxide (CO). Emission spectra indicate that these bands are all predissociative. An experimental investigation of CO photodissociation by vacuum ultraviolet photons (90 to 108 nm; ~13 to 11 eV) from the Advanced Light Source Synchrotron and direct measurement of the associated oxygen isotopic composition of the products are presented here. A wavelength dependency of the oxygen isotopic composition in the photodissociation product was observed. Slope values (δ'{sup 18}O/ δ'{sup 17}O) ranging from 0.76 to 1.32 were observed in oxygen three-isotope space (δ'{sup 18}O vs. δ'{sup 17}O) which correlated with increasing synchrotron photon energy, and indicate a dependency of the upper electronic state specific dissociation dynamics (e.g., perturbation and coupling associated with a particular state). An unprecedented magnitude in isotope separation was observed for photodissociation at the 105 and 107 nm synchrotron bands and are found to be associated with accidental predissociation of the vibrational states ({nu} = 0 and 1) of the upper electronic state E{sup 1}Π. For each synchrotron band, a large (few hundred per mil) extent of isotopic fractionation was observed and the range of fractionation is a combination of column density and exposure time. A significant temperature dependency in oxygen isotopic fractionation was observed, indicating a rotational level dependency in the predissociation process.

  13. 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.

  14. 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....

  15. 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.

  16. 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.

  17. Population viability at extreme sex-ratio skews produced by temperature-dependent sex determination.

    Science.gov (United States)

    Hays, Graeme C; Mazaris, Antonios D; Schofield, Gail; Laloë, Jacques-Olivier

    2017-02-08

    For species with temperature-dependent sex determination (TSD) there is the fear that rising temperatures may lead to single-sex populations and population extinction. We show that for sea turtles, a major group exhibiting TSD, these concerns are currently unfounded but may become important under extreme climate warming scenarios. We show how highly female-biased sex ratios in developing eggs translate into much more balanced operational sex ratios so that adult male numbers in populations around the world are unlikely to be limiting. Rather than reducing population viability, female-biased offspring sex ratios may, to some extent, help population growth by increasing the number of breeding females and hence egg production. For rookeries across the world (n = 75 sites for seven species), we show that extreme female-biased hatchling sex ratios do not compromise population size and are the norm, with a tendency for populations to maximize the number of female hatchlings. Only at extremely high incubation temperature does high mortality within developing clutches threaten sea turtles. Our work shows how TSD itself is a robust strategy up to a point, but eventually high mortality and female-only hatchling production will cause extinction if incubation conditions warm considerably in the future. © 2017 The Author(s).

  18. Analysis of Radiative Radial Fin with Temperature-Dependent Thermal Conductivity Using Nonlinear Differential Transformation Methods

    Directory of Open Access Journals (Sweden)

    Mohsen Torabi

    2013-01-01

    Full Text Available Radiative radial fin with temperature-dependent thermal conductivity is analyzed. The calculations are carried out by using differential transformation method (DTM, which is a seminumerical-analytical solution technique that can be applied to various types of differential equations, as well as the Boubaker polynomials expansion scheme (BPES. By using DTM, the nonlinear constrained governing equations are reduced to recurrence relations and related boundary conditions are transformed into a set of algebraic equations. The principle of differential transformation is briefly introduced and then applied to the aforementioned equations. Solutions are subsequently obtained by a process of inverse transformation. The current results are then compared with previously obtained results using variational iteration method (VIM, Adomian decomposition method (ADM, homotopy analysis method (HAM, and numerical solution (NS in order to verify the accuracy of the proposed method. The findings reveal that both BPES and DTM can achieve suitable results in predicting the solution of such problems. After these verifications, we analyze fin efficiency and the effects of some physically applicable parameters in this problem such as radiation-conduction fin parameter, radiation sink temperature, heat generation, and thermal conductivity parameters.

  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. 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.

  1. 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.

  2. 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.

  3. Temperature-dependent conduction mechanism of vertically aligned graphene nanoflakes incorporated with nitrogen in situ

    Science.gov (United States)

    Kumar, Pawan

    2017-07-01

    Carbon nanostructured materials have been widely investigated and explored all over the world. However, the frontiers of applications and basic examinations related to these materials have yet to be opened in terms of their stability and robustness in the required environment. I report the temperature-dependent transport properties of vertically aligned graphene nanoflakes (GNFs) at room temperature to 800 K. Investigation of GNFs incorporated with nitrogen (N2) of varying concentration in situ and their possible conduction mechanism has been carried out over the entire range of temperatures mentioned above. N-type conductivity, carrier concentration, mobility and modulation at various temperatures are observed by means of Hall-effect measurements. The film of GNFs incorporated with nitrogen in situ persists in a linear trend, satisfying conduction behaviour expectations for all measured transport parameters with only a small discrete-point anomaly. Supporting evidence of N2 incorporation and structural modifications is studied by scanning electron microscopy, Raman spectroscopy and x-ray photoemission spectroscopy. The observation findings also provide the thermal stability of N2 incorporated into two-dimensional vertically standing GNFs.

  4. Geometry and temperature dependence of low-frequency flux noise in dc SQUIDs

    Science.gov (United States)

    Anton, S. M.; Birenbaum, J. S.; O'Kelley, S. R.; Golubev, D. S.; Hilton, G. C.; Cho, H.-M.; Irwin, K. D.; Bolkhovsky, V.; Braje, D. A.; Fitch, G.; Neeley, M.; Johnson, R. C.; Oliver, W. D.; Wellstood, F. C.; Clarke, John

    2013-03-01

    Measurements on dc SQUIDs reveal a flux noise spectral density SΦ (f) =A2 /(f / 1 Hz) α . An analytic model assuming non-interacting spins localized at the surface of the SQUID loop predicts that the mean square noise scales as R/W--the radius and width of the loop, respectively. However, there are no established theories for the scaling of α with geometry or the dependences of A and α on temperature T. To test the predicted geometric scaling of this model experimentally, we measured flux noise in ten SQUIDs with systematically varying geometries. We find that, at fixed T, A2 scales approximately as R. From the measured values of A and α, we estimate the mean square flux noise, which does not scale with R. As T is lowered, α increases significantly and in such a way that the spectra ``pivot'' about an approximately fixed frequency. This phenomenon implies that the mean square noise is temperature-dependent, an effect not predicted by the analytic model. We discuss our attempts to reconcile these discrepancies by considering the locking together of spins to form clusters. This work was supported by ARO, IARPA, and the US Government.

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

    KAUST Repository

    Huete-Stauffer, Tamara Megan

    2015-09-11

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

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

    Science.gov (United States)

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

    2016-10-01

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

  7. 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.

  8. Temperature Dependence of the Seebeck Coefficient in Zinc Oxide Thin Films

    Science.gov (United States)

    Noori, Amirreza; Masoumi, Saeed; Hashemi, Najmeh

    2017-12-01

    Thermoelectric devices are reliable tools for converting waste heat into electricity as they last long, produce no noise or vibration, have no moving elements, and their light weight makes them suitable for the outer space usage. Materials with high thermoelectric figure of merit (zT) have the most important role in the fabrication of efficient thermoelectric devices. Metal oxide semiconductors, specially zinc oxide has recently received attention as a material suitable for sensor, optoelectronic and thermoelectric device applications because of their wide direct bandgap, chemical stability, high-energy radiation endurance, transparency and acceptable zT. Understanding the thermoelectric properties of the undoped ZnO thin films can help design better ZnO-based devices. Here, we report the results of our experimental work on the thermoelectric properties of the undoped polycrystalline ZnO thin films. These films are deposited on alumina substrates by thermal evaporation of zinc in vacuum followed by a controlled oxidation process in air carried out at the 350-500 °C temperature range. The experimental setup including gradient heaters, thermometry system and Seebeck voltage measurement equipment for high resistance samples is described. Seebeck voltage and electrical resistivity of the samples are measured at different conditions. The observed temperature dependence of the Seebeck coefficient is discussed.

  9. Nanostructures study of CNT nanofluids transport with temperature-dependent variable viscosity in a muscular tube

    Science.gov (United States)

    Akbar, Noreen Sher; Abid, Syed Ali; Tripathi, Dharmendra; Mir, Nazir Ahmed

    2017-03-01

    The transport of single-wall carbon nanotube (CNT) nanofluids with temperature-dependent variable viscosity is analyzed by peristaltically driven flow. The main flow problem has been modeled using cylindrical coordinates and flow equations are simplified to ordinary differential equations using long wavelength and low Reynolds' number approximation. Analytical solutions have been obtained for axial velocity, pressure gradient and temperature. Results acquired are discussed graphically for better understanding. It is observed that with an increment in the Grashof number the velocity of the governing fluids starts to decrease significantly and the pressure gradient is higher for pure water as compared to single-walled carbon nanotubes due to low density. As the specific heat is very high for pure water as compared to the multi-wall carbon nanotubes, it raises temperature of the muscles, in the case of pure water, as compared to the multi-walled carbon nanotubes. Furthermore, it is noticed that the trapped bolus starts decreasing in size as the buoyancy forces are dominant as compared to viscous forces. This model may be applicable in biomedical engineering and nanotechnology to design the biomedical devices.

  10. Temperature-Dependent X-ray Diffraction Measurements of Infrared Superlattices Grown by MBE

    Directory of Open Access Journals (Sweden)

    Charles J. Reyner

    2016-11-01

    Full Text Available Strained-layer superlattices (SLSs are an active research topic in the molecular beam epitaxy (MBE and infrared focal plane array communities. These structures undergo a >500 K temperature change between deposition and operation. As a result, the lattice constants of the substrate and superlattice are expected to change by approximately 0.3%, and at approximately the same rate. However, we present the first temperature-dependent X-ray diffraction (XRD measurements of SLS material on GaSb and show that the superlattice does not contract in the same manner as the substrate. In both InAs/InAs0.65Sb0.35 and In0.8Ga0.2As/InAs0.65Sb0.35 SLS structures, the apparent out-of-plane strain states of the superlattices switch from tensile at deposition to compressive at operation. These changes have ramifications for material characterization, defect generation, carrier lifetime, and overall device performance of superlattices grown by MBE.

  11. Kinetic study of the reactions between chloramine disinfectants and hydrogen peroxide: temperature dependence and reaction mechanism.

    Science.gov (United States)

    McKay, Garrett; Sjelin, Brittney; Chagnon, Matthew; Ishida, Kenneth P; Mezyk, Stephen P

    2013-09-01

    The temperature-dependent kinetics for the reaction between hydrogen peroxide and chloramine water disinfectants (NH2Cl, NHCl2, and NCl3) have been determined using stopped flow-UV/Vis spectrophotometry. Rate constants for the mono- and dichloramine-peroxide reaction were on the order of 10(-2)M(-1)s(-1) and 10(-5)M(-1)s(-1), respectively. The reaction of trichloramine with peroxide was negligibly slow compared to its thermal and photolytically-induced decomposition. Arrhenius expressions of ln(kH2O2-NH2Cl)=(17.3±1.5)-(51500±3700)/RT and ln(kH2O2-NHCl2)=(18.2±1.9)-(75800±5100)/RT were obtained for the mono- and dichloramine peroxide reaction over the temperature ranges 11.4-37.9 and 35.0-55.0°C, respectively. Both monochloramine and hydrogen peroxide were first-order in the rate-limiting kinetic step and concomitant measurements made using a chloride ion selective electrode showed that the chloride was produced quantitatively. These data will aid water utilities in predicting chloramine concentrations (and thus disinfection potential) throughout the water distribution system. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. On the Pressure and Temperature Dependence of the Absorption Coefficient of NH3

    Directory of Open Access Journals (Sweden)

    F. Aousgi

    2011-01-01

    Full Text Available The effects of pressure and temperature on the absorption coefficient of ammonia (NH3 gas self-perturbed and perturbed by nitrogen (N2 gas have been measured. We varied the gas pressure from 10 to 160 Torr and the temperature from 235 to 296 K in order to study the absorption coefficient at the center and the wings of lines in the ν4 band of NH3. These measurements were made using a high resolution (0.0038 cm-1 Bruker Fourier-transform spectrometer. These spectra have been analyzed using the method of multipressure technique permitting to succeed to an evolution of the absorption coefficient with the pressure and the quantum numbers J and K of the NH3 molecule. The results show that the absorption coefficient varies as a quadratic function of the pressure at the center of a given line. However, it has a linear evolution in the wings of the line. Moreover, the absorption coefficients are inversely proportional to temperature in the wings when NH3 lines are broadened by N2. The retrieved values of these coefficients were used to derive the temperature dependence of N2 broadening NH3 lines. The absorption coefficients were shown to fit closely the well-known exponential law.

  13. Theoretical study of temperature dependence and Rayleigh scattering properties of chloride hydration clusters.

    Science.gov (United States)

    Jiang, Shuai; Huang, Teng; Liu, Yi-Rong; Xu, Kang-Ming; Zhang, Yang; Lv, Yu-Zhou; Huang, Wei

    2014-09-28

    Cl(-)(H2O)n (n = 5-6) clusters were investigated using a basin hopping (BH) method coupled with density functional theory (DFT). Structures, energetics, thermodynamics, and vibrational frequencies were obtained using high level ab initio calculations. DF-LMP2 (second-order Møller-Plesset perturbation theory using local and density fitting approximations) with an appropriate basis set were employed for final optimization and frequency calculation, which has been benchmarked in a recent study. The global minimum of Cl(-)(H2O)5 was verified and the new competitive local minimum of Cl(-)(H2O)6 was offered. Considering the increasing complexity of the large system and the high flexibility of the hydrogen bonding environment, Boltzmann averaged Gibbs free energy was provided taking into account the contributions of local minima on the potential energy surface. Finally, the temperature dependence of the conformational population for isomers of Cl(-)(H2O)n (n = 5-6) and Rayleigh scattering properties of Cl(-)(H2O)n (n = 1-6) have been investigated systematically for the first time.

  14. Temperature-Dependent Thermal Conductivity of High Strength Lightweight Raw Perlite Aggregate Concrete

    Science.gov (United States)

    Tandiroglu, Ahmet

    2010-06-01

    Twenty-four types of high strength lightweight concrete have been designed with raw perlite aggregate (PA) from the Erzincan Mollaköy region as new low-temperature insulation material. The effects of the water/cement ratio, the amount of raw PA, and the temperature on high strength lightweight raw perlite aggregate concrete (HSLWPAC) have been investigated. Three empirical equations were derived to correlate the thermal conductivity of HSLWPAC as a function of PA percentage and temperature depending on the water/cement ratio. Experimentally observed thermal conductivities of concrete samples were predicted 92 % of the time for each set of concrete matrices within 97 % accuracy and over the range from 1.457 W · m-1 · K-1 to 1.777 W · m-1 · K-1. The experimental investigation revealed that the usage of raw PA from the Erzincan Mollaköy region in concrete production reduces the concrete unit mass, increases the concrete strength, and furthermore, the thermal conductivity of the concrete has been improved. The proposed empirical correlations of thermal conductivity were considered to be applicable within the range of temperatures 203.15 K ≤ T ≤ 303.15 K in the form of λ = a( PAP b ) + c( T d ).

  15. 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.

  16. Temperature dependence of magnetic order in Fe/(Ga,Mn)As studied by Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Polesya, Svitlana; Minar, Jan; Ebert, Hubert [LMU Muenchen, Dept. Chemie und Biochemie/Phys. Chemie, Butenandtstrasse 11, D-81377 Muenchen (Germany); Back, Christian [Institut fuer Experimentelle Physik, Univ. Regensburg (Germany)

    2008-07-01

    The magnetic order of the heterogeneous interface system (GaMn)As/Fe at finite temperatures has been studied by Monte Carlo simulations. The ground state magnetic properties were determined within ab initio electronic structure calculations using the SPR-TB-KKR Green's function method. All calculations have been performed for the semi-infinite system of (GaMn)As with 5 % Mn covered by a 7 ML Fe film. The temperature dependent properties of this system (with and without external magnetic field) have been studied using MC simulation. The exchange coupling within the Fe and (GaMn)As subsystems were found to be dominantly long-range ferromagnetic whereas the coupling of Fe and Mn moments close to the interface is strongly antiferromagnetic. The Monte Carlo simulations lead to a Curie temperature of about 1000 K for the Fe film. Within the (GaMn)As subsystem due to the polarisation induced by the Fe film the average magnetisation at room temperature is still about 70 % of its T=0 value for several layers close to the interface. These results are in full agreement with recent experimental findings.

  17. 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.

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

    Science.gov (United States)

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

    2017-03-15

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

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

    Directory of Open Access Journals (Sweden)

    Koushik Ghosh

    2014-02-01

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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. Temperature dependence of Fe/++/ crystal field spectra - Implications to mineralogical mapping of planetary surfaces

    Science.gov (United States)

    Sung, C.-M.; Singer, R. B.; Parkin, K. M.; Burns, R. G.; Osborne, M.

    1977-01-01

    Results are reported of Fe(++) crystal field spectral measurements for olivines and pyroxenes up to 400 C. The results are correlated with crystal structure data at elevated temperatures, and the validity of remote-sensed identifications of minerals on hot surfaces of the moon and Mercury is assessed. Two techniques were used to obtain spectra of minerals at elevated temperatures using a spectrophotometer. One employed a diamond cell assembly or a specially designed sample holder to measure polarized absorption spectra of heated single crystals. For the other technique, a sample holder was designed to attach to a diffuse reflectance accessory to produce reflectance spectra of heated powdered samples. Polarized absorption spectra of forsterite at 20-400 C are shown in a graph. Other graphs show the temperature dependence of Fe(++) crystal field bands in olivines, the diffuse reflectance spectra of olivine at 40-400 C, the polarization absorption spectra of orthopyroxene at 30-400 C, the diffuse reflectance spectra of pigeonite at 40-400 C, and unpolarized absorption spectra of lunar pyroxene from Apollo 15 rock 15058.

  6. 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.

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

    Science.gov (United States)

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

    2016-01-01

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

  8. 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.

  9. Baroreflex control of heart rate in the broad-nosed caiman Caiman latirostris is temperature dependent

    DEFF Research Database (Denmark)

    Hagensen, Mette K; Abe, Augusto S; Wang, Tobias

    2010-01-01

    in systemic blood pressure (Psys). At 30 °C the baroreflex was more pronounced at a blood pressure lower than control value (52.3 cmH2O) with a maximal baroreflex gain of 1.97 beats min-1 cmH2O- 1 at a Psys of 41.9 cmH2O, and therefore seems to counteract hypotension. In contrast, the maximal baroreflex at 15......It has been suggested that ectothermic vertebrates primarily control blood pressure to protect the pulmonary vasculature from oedema caused by high pressure, while endothermic vertebrates control blood pressure to maintain adequate oxygen delivery to the tissues. In the present study we have...... °C was found at a Psys almost equal to the control value. The highest baroreflex gain in response to change in blood pressure was measured at the highest temperature. Thus, C. latirostris exhibit a temperature dependent barostatic response....

  10. Uniform Temperature Dependency in the Phenology of a Keystone Herbivore in Lakes of the Northern Hemisphere

    Science.gov (United States)

    Straile, Dietmar; Adrian, Rita; Schindler, Daniel E.

    2012-01-01

    Spring phenologies are advancing in many ecosystems associated with climate warming causing unpredictable changes in ecosystem functioning. Here we establish a phenological model for Daphnia, an aquatic keystone herbivore based on decadal data on water temperatures and the timing of Daphnia population maxima from Lake Constance, a large European lake. We tested this model with long-term time-series data from two lakes (Müggelsee, Germany; Lake Washington, USA), and with observations from a diverse set of 49 lakes/sites distributed widely across the Northern Hemisphere (NH). The model successfully captured the observed temporal variation of Daphnia phenology in the two case study sites (r2 = 0.25 and 0.39 for Müggelsee and Lake Washington, respectively) and large-scale spatial variation in the NH (R2 = 0.57). These results suggest that Daphnia phenology follows a uniform temperature dependency in NH lakes. Our approach – based on temperature phenologies – has large potential to study and predict phenologies of animal and plant populations across large latitudinal gradients in other ecosystems. PMID:23071520

  11. Temperature dependence and the dispersion of nonlinear optical properties of chromophore-containing polyimide thin films

    Science.gov (United States)

    Gorkovenko, A. I.; Plekhanov, A. I.; Simanchuk, A. E.; Yakimanskiy, A. V.; Nosova, G. I.; Solovskaya, N. A.; Smirnov, N. N.

    2014-12-01

    Detailed investigations of the quadratic nonlinear response of a series of new polyimides with covalently attached chromophore DR13 are performed by the Maker fringes method in the range of fundamental wavelength from 850 to 1450 nm. Polymer films with thickness of 100-400 nm were spin-coated on glass substrates and corona poled. For these materials, the maximum values of the second harmonic generation coefficients d33 are 80-120 pm/V. A red shift of the nonlinear response dispersion with respect to the linear absorption spectrum was observed for the DR13 chromophore. The temperature dependences of linear absorption and nonlinear coefficients d33 for studied structures are observed. It was found that the temperature changes of the absorption spectra lead to appreciable contribution to the value of the nonlinear coefficient d33. The demonstrated high temperature stability (up to 120 °C) of chromophore-containing polyimide thin films makes it possible to eliminate the degradation of their nonlinear optical properties in the future applications of such structures.

  12. 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...

  13. 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.

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

    Science.gov (United States)

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

    2015-10-01

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

  15. 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.

  16. 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.

  17. 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

  18. Temperature-dependent frictional properties of ultra-thin boron nitride nanosheets

    Science.gov (United States)

    Qu, Wenyang; Chen, Xiaoming; Ke, Changhong

    2017-04-01

    We investigate the temperature-dependent frictional properties of mono- and few-layer hexagonal boron nitride nanosheets (BNNSs) by using atomic force microscopy (AFM). The measurements reveal that a modest increase in sample temperature results in a substantial decrease of the frictional force between a silicon AFM tip and a BNNS, and the frictional force change is modulated by the scan velocity of the AFM tip and the number of layers in the BNNS. The activation energy of the contact rupture for the examined BNNSs is found to be around 0.35 eV, which is substantially higher than the reported values for graphene. The observed high activation energy for the BNNS is ascribed to its electronically and topographically corrugated surface, which originates from the polarized nature of B-N bonds and the size difference of B and N atoms. The findings are useful to better understand the physical properties of hexagonal BNNS materials and in the pursuit of their applications, such as substrate materials in nano electronic devices.

  19. 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.

  20. 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.