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Sample records for verwey transition temperatures

  1. Pressure effect on the low-temperature remanences of multidomain magnetite: Change in the Verwey transition temperature

    Science.gov (United States)

    Sato, M.; Yamamoto, Y.; Nishioka, T.; Kodama, K.; Mochizuki, N.; Tsunakawa, H.

    2011-12-01

    The Verwey transition of magnetite is the basic issues for the rock magnetism, since main magnetic mineral of terrestrial rocks is magnetite and its associates. One of the most important issues concerning the Verwey transition is the change in transition temperature (Tv) due to pressure, which is thought to improve our understanding of its electric and magnetic nature in relation to the phase diagram. Recently, the opposite pressure effects of the transition temperature were reported applying the different experimental method. Measuring the electrical resistivity of single crystalline samples, Môri et al. [2002] reported that Tv becomes lower with increasing pressure by 9 GPa. In contrast, Pasternak et al. [2003] reported from Mössbauer experiment that transition temperature becomes higher with increasing pressure by 30 GPa. Thus the change in transition temperature with pressure has been controversial, and nature of the Verwey transition is still unclear. The magnetic property measurements using low temperature cycle are a powerful tool for identifying the state of magnetic minerals. Carporzen and Gilder [2010] conducted the thermal demagnetization experiment of low-temperature remanences of magnetite, and observed an increase in Tv with increasing pretreated pressure. From this result, they suggested that the Verwey transition of magnetite have the potential of a geobarometer. Modern techniques of high-pressure experiments enable us to measure sample magnetizations under pressure [Gilder et al., 2002; Kodama and Nishioka, 2005; Sadykov et al., 2008]. In the present study, systematic experiments of low-temperature remanences have been conducted for powder samples of stoichiometric magnetite under pressure up to 0.7 GPa using the high-pressure cell specially designed for MPMS, which was made of CuBe and ZrO2 [Kodama and Nishioka, 2005]. Natural magnetite of large single crystals were crushed by hand and sieved in an ultrasonic bath to be ~50 μm in size. For

  2. Magnetic susceptibility studies of the spin-glass and Verwey transitions in magnetite nanoparticles

    OpenAIRE

    Lopez Maldonado, K. L.; Presa Muñoz del Toro, Patricia de la; Flores Tavizon, E.; Farias Mancilla, J: R:; Matutes Aquino, J. A.; Hernando Grande, Antonio; Elizalde Galindo, J. T.

    2013-01-01

    Magnetite nanostructured powder samples were synthesized by aging chemical method. Phase, structural, and magnetic properties were characterized. X-ray diffraction patterns showed cubic magnetite pure phase, with average crystallite size, , equal to 40 nm. Susceptibility measurements showed the well-known Verwey transition at a temperature of 90 K. The decrease of Verwey transition temperature, with respect to the one reported in literature (125 K) was attributed to the low average cryst...

  3. The Verwey transition observed by spin-resolved photoemission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain); Tusche, Christian [Max Planck Institute of Microstructure Physics, Halle D-06120 (Germany); Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-6), D-52425 Jülich (Germany)

    2017-01-01

    Highlights: • First observations of magnetic domains on magnetite (001) by spin-resolved PEEM. • Spin-polarization through the Verwey transitions does not change appreciably. • Shape and distribution of domains has been observed through the Verwey transition. - Abstract: We have imaged the magnetic domains on magnetite (001) through the Verwey transition by means of spin-resolved photoemission electron microscopy. A He laboratory source is used for illumination. The magnetic domains walls above the Verwey transition are aligned with 〈110〉 in-plane directions. Below the Verwey transition, the domain structure is interpreted as arising from a distribution of areas with different monoclinic c-axis, with linear 180° domain walls within each area and ragged edges when the magnetic domain boundaries coincide with structural domain walls. The domains evolve above the Verwey transition, while they are static below.

  4. Anisotropic magnetoresistance across Verwey transition in charge ordered Fe3O4 epitaxial films

    KAUST Repository

    Liu, Xiang

    2017-12-26

    The anisotropic magnetoresistance (AMR) near the Verwey temperature (T-V) is investigated in charge ordered Fe3O4 epitaxial films. When the temperature continuously decreases below T-V, the symmetry of AMR in Fe3O4(100) film evolves from twofold to fourfold at a magnetic field of 50 kOe, where the magnetic field is parallel to the film surface, whereas AMR in Fe3O4(111) film maintains twofold symmetry. By analyzing AMR below T-V, it is found that the Verwey transition contains two steps, including a fast charge ordering process and a continuous formation process of trimeron, which is comfirmed by the temperature-dependent Raman spectra. Just below T-V, the twofold AMR in Fe3O4(100) film originates from uniaxial magnetic anisotropy. The fourfold AMR at a lower temperature can be ascribed to the in-plane trimerons. By comparing the AMR in the films with two orientations, it is found that the trimeron shows a smaller resistivity in a parallel magnetic field. The field-dependent AMR results show that the trimeron-sensitive field has a minimum threshold of about 2 kOe.

  5. Direct observation of magnetic domain evolution in the vicinity of Verwey transition in Fe3O4 thin films

    Science.gov (United States)

    Liu, X. H.; Liu, W.; Dai, Z. M.; Li, S. K.; Wang, T. T.; Cui, W. B.; Li, D.; Komarek, A. C.; Chang, C. F.; Zhang, Z. D.

    2017-11-01

    We report a direct observation of magnetic domain evolution near the Verwey transition (TV) in Fe3O4 films. We found the stripe domains in the Fe3O4/Mg2TiO4 film while the irregular domains in the Fe3O4/MgO film and the similar characters of magnetic domains in the vicinity of TV for both samples: the bigger domain size and the higher contrast of the phase signal below TV and the more disordered domain images at TV. Remarkably, the magnetic behaviors can be well understood and the domain-wall energy and the demagnetizing energy can be calculated from the magnetic domains near TV in the Fe3O4/Mg2TiO4 film. Our work presents a demonstration of the low-temperature magnetic domains and gives a new perspective to understand the Verwey transition in Fe3O4 thin films.

  6. X-ray emission spectroscopy study of the Verwey transition in Fe sub 3 O sub 4

    CERN Document Server

    Moewes, A; Finkelstein, L D; Galakhov, A V; Gota, S; Gautier-Soyer, M; Rueff, J P; Hague, C F

    2003-01-01

    The temperature-dependent Verwey transition in a 500 A (111) thin film of Fe sub 3 O sub 4 (magnetite) has been studied using soft-x-ray emission spectroscopy at room temperature and below the transition temperature T sub V. The Fe L sub 2 sub , sub 3 x-ray emission spectra show an increase in the intensity of the L sub 2 emission relative to the L sub 3 emission below T sub V. This is independent of the excitation energy and is attributed to a metal-insulator transition across T sub V. Comparison of the Fe L sub 3 emission and O K alpha spectra with LDA band structure calculations supports the suggestion of charge ordering in Fe sub 3 O sub 4 at low temperature.

  7. Ferrimagnetic/ferroelastic domain interactions in magnetite below the Verwey transition. Part I: electron holography and Lorentz microscopy

    DEFF Research Database (Denmark)

    Kasama, Takeshi; Harrison, R. J.; Church, N. S.

    2013-01-01

    domain oriented along the monoclinic [001] axis. The nature of the interactions between the magnetic domain walls and the ferroelastic twin walls is investigated. Cooling and warming cycles through the transition temperature are used to show that a memory effect is likely to exist between the magnetic......-related crystal orientations to be distinguished. Off-axis electron holography and Lorentz electron microscopy are used to show that magnetic domains present at room temperature become subdivided into sub-micron-sized magnetic domains below the Verwey transition, with the magnetization direction in each magnetic...... states that form above and below the transition. Our results suggest that ferroelastic twin walls have a strong influence on the low temperature magnetic properties of magnetite....

  8. Ferrimagnetic/ferroelastic domain interactions in magnetite below the Verwey transition: Part II. Micromagnetic and image simulations

    DEFF Research Database (Denmark)

    Bryson, James F.J.; Kasama, Takeshi; Dunin-Borkowski, Rafal E.

    2013-01-01

    Micromagnetic simulations have been used to explore the interaction between ferrimagnetic domain walls (DWs) and ferroelastic twin walls (TWs) below the Verwey transition in magnetite (Fe3O4). Simulations were performed using a thin-foil geometry in order to replicate the domain patterns observed...

  9. Study of the Verwey transition in magnetite by low field and magnetically modulated non-resonant microwave absorption

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, M.P. [Escuela Superior de Fisica y Matematicas del Instituto Politecnico Nacional, Mexico, D.F. 07738 (Mexico)]. E-mail: mpga@servidor.unam.mx; Alvarez, G. [Instituto de Investigaciones en Materiales de la Universidad Nacional Autonoma de Mexico, Mexico, D.F. 04510 (Mexico); Montiel, H. [Centro de Ciencias Aplicadas y Desarrollo Tecnologico de la Universidad Nacional Autonoma de Mexico, Mexico, D.F. 04510 (Mexico); Zamorano, R. [Escuela Superior de Fisica y Matematicas del Instituto Politecnico Nacional, Mexico, D.F. 07738 (Mexico); Valenzuela, R. [Instituto de Investigaciones en Materiales de la Universidad Nacional Autonoma de Mexico, Mexico, D.F. 04510 (Mexico)

    2007-09-15

    We have investigated the Verwey phase transition (VPT) by two novel non-resonant microwave absorption techniques: low-field absorption (LFA) and magnetically modulated microwave absorption spectroscopy (MAMMAS). Measurements were carried out on sintered polycrystalline samples of Fe{sub 3}O{sub 4}, in the 77-300 K temperature range. LFA refers to the microwave absorption around the zero DC field range (-1000temperature, and seem particularly well adapted to detect a wide range of phase transitions. In the magnetite case, a continuous increase in the microwave power absorption level was observed as temperature decreased, reaching a strong maximum at 130 K and a minimum at 100 K. An inflection point at 126 K was found, in very good agreement with LFA measurements. These results are discussed in detail.

  10. Evolution of magnetic properties in the vicinity of the Verwey transition in Fe3O4 thin films

    Science.gov (United States)

    Liu, X. H.; Liu, W.; Zhang, Z. D.

    2017-09-01

    We have systematically studied the evolution of magnetic properties, especially the coercivity and the remanence ratio in the vicinity of the Verwey transition temperature (TV), of high-quality epitaxial Fe3O4 thin films grown on MgO (001), MgAl2O4 (MAO) (001), and SrTiO3 (STO) (001) substrates. We observed rapid change of magnetization, coercivity, and remanence ratio at TV, which are consistent with the behaviors of resistivity versus temperature [ρ (T )] curves for the different thin films. In particular, we found quite different magnetic behaviors for the thin films on MgO from those on MAO and STO, in which the domain size and the strain state play very important roles. The coercivity is mainly determined by the domain size but the demagnetization process is mainly dependent on the strain state. Furthermore, we observed a reversal of remanence ratio at TV with thickness for the thin films grown on MgO: from a rapid enhancement for 40-nm- to a sharp drop for 200-nm-thick film, and the critical thickness is about 80 nm. Finally, we found an obvious hysteretic loop of coercivity (or remanence ratio) with temperature around TV, corresponding to the hysteretic loop of the ρ (T ) curve, in Fe3O4 thin film grown on MgO.

  11. Magneto-resistive coefficient enhancement observed around Verwey-like transition on spinel ferrites XFe{sub 2}O{sub 4} (X = Mn, Zn)

    Energy Technology Data Exchange (ETDEWEB)

    López Maldonado, K. L., E-mail: liliana.lopez.maldonado@gmail.com; Vazquez Zubiate, L.; Elizalde Galindo, J. T. [Instituto de Ingeniería y Tecnología, Universidad Autónoma de Ciudad Juárez, Av. Del Charro 450 norte, 32310 Ciudad Juárez (Mexico); Presa, P. de la [Instituto de Magnetismo Aplicado (UCM-ADIF-CSIC), P.O. Box 155, 28230 Las Rozas (Spain); Departamento de Física de Materiales, Univ. Complutense de Madrid, Madrid (Spain); Matutes Aquino, J. A. [Centro de Investigación en Materiales Avanzados, Miguel de Cervantes 120, 31109 Chihuahua (Mexico)

    2014-05-07

    Manganese and Zinc ferrites were prepared by solid state reaction. The resulting powders were pressed into pellets and heat treated at 1100 °C. The samples were characterized by using X-ray diffraction, pure phases of zinc ferrite (ZnFe{sub 2}O{sub 4}) and manganese ferrite (MnFe{sub 2}O{sub 4}) were obtained. Scanning electron microscopy images showed a good contact between particles. A drop of electrical resistance was found in both samples, MnFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4}, with values going from 2750 to 130 Ω and from 1100 to 55 Ω, respectively. Transition temperatures were determined to be T{sub V} = 225 K for MnFe{sub 2}O{sub 4} and T{sub V} = 130 K for ZnFe{sub 2}O{sub 4}. Magnetoresistance measurements were carried out in the temperature range where R showed the transition, defined as the Verwey-like transition temperature range, ΔT{sub V}. No magnetoresistive effect was observed out of it. The magnetoresistive coefficient (MRC) observed at ΔT{sub V} reached its maximum values of 1.1% for MnFe{sub 2}O{sub 4} and 6.68% for ZnFe{sub 2}O{sub 4}. The differences between MRC values are related to the divalent metal element used. Finally, the magnetoresistive response indicates that the electrical transition observed is strongly influencing the magnetoresistance; where the underlying responsible for this behavior could be a charge reordering occurring at the Verwey-like transition temperature.

  12. Anomalous Hall effect in Zn{sub x}Fe{sub 3-x}O{sub 4}: Universal scaling law and electron localization below the Verwey transition

    Energy Technology Data Exchange (ETDEWEB)

    Jedrecy, N., E-mail: jedrecy@insp.jussieu.fr; Hamieh, M.; Hebert, C.; Escudier, M.; Becerra, L.; Perriere, J. [Institut des Nano Sciences de Paris, UPMC-Sorbonne Universités, CNRS-UMR7588, 4 Place Jussieu, 75252 Paris Cedex 05 (France)

    2016-08-15

    We show that the well-established universal scaling σ{sub xy}{sup AHE} ∼ σ{sub xx}{sup 1.6} between anomalous Hall and longitudinal conductivities in the low conductivity regime (σ{sub xx} < 10{sup 4} Ω{sup −1} cm{sup −1}) transforms into the scaling σ{sub xy}{sup AHE} ∼ σ{sub xx}{sup 2} at the onset of strong electron localization. The crossover between the two relations is observed in magnetite-derived Zn{sub x}Fe{sub 3-x}O{sub 4} thin films where an insulating/hopping regime follows a bad metal/hopping regime below the Verwey transition temperature T{sub v}. Our results demonstrate that electron localization effects come into play in the anomalous Hall effect (AHE) modifying significantly the scaling exponent. In addition, the thermal evolution of the anomalous Hall resistivity suggests the existence of spin polarons whose size would decrease below T{sub v}.

  13. Direct observation of ferrimagnetic/ferroelastic domain interactions in magnetite below the Verwey transition

    DEFF Research Database (Denmark)

    Kasama, Takeshi; Church, Nathan S.; Feinberg, Joshua M.

    2010-01-01

    . This study provides a new understanding of the low-temperature magnetic properties of magnetite that will affect a broad range of rock magnetic studies, from the interpretation of magnetic remanence in terrestrial rocks and sediments to the search for biogenic magnetite in extraterrestrial materials....

  14. Quest for secondary μSR signals for Fe3O4 using MaxEnt: a Verwey phase transition study.

    Science.gov (United States)

    Boekema, C.; Colebaugh, A.; Lee, A.-L.; Lin, I.; Cabot, A.; Morante, C.

    Most muon-spin rotation (μSR) time series for magnetite (Fe3O4) have been interpreted in terms of one μSR frequency signal. Its Fourier transform appears to confirm this internal magnetic field. Yet many time series show a beat pattern, strongly suggesting a second signal with a close-by frequency. We are searching for secondary signals in zero-field Fe3O4 μ SR data using Maximum Entropy, a recently developed technique more sensitive than curve fitting and/or Fourier transformation. There is also another dilemma namely: the upper signal found for Fe3O4 has a local magnetic field larger than the maximum allowable vectorial sum of external and internal contributions. However, the (non)occurrence of secondary signals may shed light on the nature of the Verwey phase transition and its precursors in the Fe3O4 Mott-Wigner glass between Tv (123 K) and twice Tv (247 K). Research supported by LANL-DOE, SETI-NASA, SJSU & AFC.

  15. Low-Temperature Magnetic Anomaly in Magnetite

    OpenAIRE

    Svindrych, Zdenek; Janu, Zdenek; Kozlowski, Andrzej; Honig, Jurgen M.

    2013-01-01

    We have studied experimentally the responses of high quality single crystals of stoichiometric synthetic magnetite to applied weak dc and ac magnetic fields in the range of 6 K to 60 K, far below the Verwey transition. The results can be compared to so called Magnetic After Effects (MAE) measurements, which are the most extensive magnetic measurements of magnetite at these temperatures. We present a novel point of view on the relaxation phenomena encountered at these temperatures - the Low Te...

  16. Sudden transition from finite temperature spin environments

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Zheng-Da; He, Qi-Liang; Xu, Hang-Shi [Zhejiang Institute of Modern Physics and Physics Department, Zhejiang University, Hangzhou 310027 (China); Xu, Jing-Bo, E-mail: xujb@zju.edu.cn [Zhejiang Institute of Modern Physics and Physics Department, Zhejiang University, Hangzhou 310027 (China)

    2012-10-01

    We investigate the phenomenon of sudden transition from finite temperature critical environments in the study of quantum correlations of a two-qubit system coupled to independent thermal Ising baths. The influence of the temperature and external field of bath on the critical time of sudden transition is also explored. It is found that the phenomenon of sudden transition can be used to detect the critical points of thermal spin environments. How to protect quantum correlations of the system is also examined by applying a series of π-phase pulses. -- Highlights: ► The sudden transition phenomenon from thermal critical environments is studied. ► How to detect quantum critical points of thermal Ising baths is explored. ► The quantum discord can be protected against thermal bath by π-phase pulses.

  17. Phase transition in nanomagnetite

    Science.gov (United States)

    Dézsi, I.; Fetzer, Cs.; Gombkötő, Á.; Szűcs, I.; Gubicza, J.; Ungár, T.

    2008-05-01

    Recently, the application of nanosized magnetite particles became an area of growing interest for their potential practical applications. Nanosized magnetite samples of 36 and 9nm sizes were synthesized. Special care was taken on the right stoichiometry of the magnetite particles. Mössbauer spectroscopy measurements were made in 4.2-300K temperature range. The temperature dependence of the intensities of the spectral components indicated size dependent transition taking place in a broad temperature range. For nanosized samples, the hyperfine interaction values and their relative intensities changed above the Verwey transition temperature value of bulk megnetite. The continuous transition indicated the formation of dendritelike granular assemblies formed during the preparation of the samples.

  18. Superconducting transition temperature of aluminum fine particles

    Energy Technology Data Exchange (ETDEWEB)

    Ohshima, K.; Kuroishi, T.; Fujita, T.

    1976-10-01

    The superconducting transition temperature T/sub C/ of films of aluminium fine particles deposited by gas evaporation method was determined by measuring D.C. electrical resistance. The observed values of T/sub C/ were distributed from 1.5 to 2.5K, about 5/4 = 2 times of that of bulk metal, for the samples of average particle diameter 150 = 50 A. The observed enhancement of T/sub C/ was not explained by the surface softening of the particles only.

  19. Concurrent transition of ferroelectric and magnetic ordering near room temperature.

    Science.gov (United States)

    Ko, Kyung-Tae; Jung, Min Hwa; He, Qing; Lee, Jin Hong; Woo, Chang Su; Chu, Kanghyun; Seidel, Jan; Jeon, Byung-Gu; Oh, Yoon Seok; Kim, Kee Hoon; Liang, Wen-I; Chen, Hsiang-Jung; Chu, Ying-Hao; Jeong, Yoon Hee; Ramesh, Ramamoorthy; Park, Jae-Hoon; Yang, Chan-Ho

    2011-11-29

    Strong spin-lattice coupling in condensed matter gives rise to intriguing physical phenomena such as colossal magnetoresistance and giant magnetoelectric effects. The phenomenological hallmark of such a strong spin-lattice coupling is the manifestation of a large anomaly in the crystal structure at the magnetic transition temperature. Here we report that the magnetic Néel temperature of the multiferroic compound BiFeO(3) is suppressed to around room temperature by heteroepitaxial misfit strain. Remarkably, the ferroelectric state undergoes a first-order transition to another ferroelectric state simultaneously with the magnetic transition temperature. Our findings provide a unique example of a concurrent magnetic and ferroelectric transition at the same temperature among proper ferroelectrics, taking a step toward room temperature magnetoelectric applications.

  20. Drift en koers : de levens van Hilda Verwey-Jonker (1908-2004)

    NARCIS (Netherlands)

    Steen, Margaretha Wilhelmina Francisca van der

    2011-01-01

    Drift en koers (Passion and control) is the first scientific biography on the Dutch socialist, sociologist and feminist Hilda Verwey-Jonker (1908-2004). She is best known for the introduction of the word allochtonen (foreigner/alien) in the Dutch discourse and has very been influential in improving

  1. Oscillation phenomenon of transition temperatures of coupled magnetic planes

    Directory of Open Access Journals (Sweden)

    H. Moradi

    2004-06-01

    Full Text Available   Oscillatory behavior of transition temperature in supper lattice, Ni/Au/Ni, has been observed as a function of spacer layer, Au. The observed oscillation period is almost the half period of interlayer exchange coupling. The high temperature susceptibility of a two - dimensional lattice is evaluated within the Bethe-Peierls-Wiess approximation in the presence of a random field with square distribution. This susceptibility is used to evaluate the transition temperature of coupled planes as a function of spacer thickness. The calculated transition temperature of coupled planes oscillates as half period of interlayer exchange coupling and falls below the results of the uncoupled films at some values of the average spacer thickness that were experimentally observed. Additionally, the transition temperature depends on the distribution function of random field at the small thickness of spacer.

  2. Glass transition and heavy oil dynamics at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Abivin, P.; Indo, K.; Cheng, Y.; Freed, D.; Taylor, S. D. [Schlumberger (Canada)], email: PAbivin@slb.com

    2011-07-01

    In the oil industry, the viscosity of crude oils is a key factor as it affects market value, field developments and the design of production strategies. In heavy oils, a glass transition occurs and previous work related this to oil's temperature-viscosity behavior. This study aimed at better characterizing heavy oil dynamics and the temperature dependency of viscosity. Experiments were conducted with differential scanning calorimetry and shear rate sweeps on heavy oils from Asia, South America and North America over a wide range of temperatures to measure their viscosities and characterize their glass transition. The glass transition was observed at around 210K and results showed that the Arrhenius model does not fit the experimental data at low temperatures but the WLF model does. This research provided a better understanding of heavy oil dynamics but further work is required to explain the viscosity-temperature behavior of heavy oils at low temperatures.

  3. Transition temperature of martensitic transformations in hafnia and zirconia

    Science.gov (United States)

    Luo, Xuhui; Demkov, A. A.

    2008-03-01

    Transition metal oxides find applications in ceramics, catalysis and semiconductor technology. In particular, hafnium dioxide or hafnia will succeed silica as a gate dielectric in advanced transistors. However, thermodynamic properties of thin hafnia films are not well understood, despite their technological importance. We use density functional theory to investigate the tetragonal to monoclinic phase transition in hafnia and zirconia. We find that unlike the case of the cubic to tetragonal transition, this phase transition is not driven by a soft mode. We use transition state theory to identify the minimum energy path (MEP) employing first principle calculations for hafnia and zirconia, sow that both transformations are martensitic, and obtain the transition barriers. Martensitic transformations include both the internal coordinate transformation and deformation of the cell lattice vectors (``strain and shuffle''), therefore the potential energy surface and MEP are function not only of the internal atomic coordinates but also of the unit cell lattice vectors. Considering the simplest case of uniform strain the transition temperatures we then relate the barrier height to the transition temperature. As a self-consistency check, assuming the equality of thermodynamics potentials of the tetragonal and monoclinic phases during the transition, and using the difference in the internal energy calculated from first principles we estimate the entropy change associated with the transition which is found in good agreement with that calculated form the phonon spectra.

  4. Luminous transmittance and phase transition temperature of VO 2 ...

    African Journals Online (AJOL)

    The phase transition temperature (τc) of the films was obtained from both the transmittance and sheet resistance against temperature curves. A change in sheet resistance of 2 to 3 orders of magnitude was observed for both undoped and Ce-doped VO2 films. Comparison between undoped and doped VO2 films revealed ...

  5. Critical temperature for shape transitions in excited nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Martin, V. [Analisis Numerico, Facultad de Informatica, Universidad Politecnica de Madrid, E-28660, Madrid (Spain); Egido, J.L.; Robledo, L.M. [Departamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049, Madrid (Spain)

    2004-04-01

    The behavior of shell effects with temperature is studied within the framework of the finite-temperature Hartree-Fock-Bogoliubov theory with the Gogny force. Thermal shape fluctuations in the quadrupole degree of freedom are taken into account in the frame of the Landau theory. Numerical results for the superfluid-to-normal and deformed-to-spherical phase transitions are presented for the nucleus {sup 164}Er. We find that the critical temperature for the deformed-spherical shape transition is much lowered when the thermal shape fluctuations are considered. (orig.)

  6. The Wilson flow and the finite temperature phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Wandelt, M. [Department of Mathematics, School of Mathematics and Natural Sciences,Bergische Universität Wuppertal, Gaußstr. 20, 42119 Wuppertal (Germany); Knechtli, F. [Department of Physics, School of Mathematics and Natural Sciences,Bergische Universität Wuppertal, Gaußstr. 20, 42119 Wuppertal (Germany); Günther, M. [Department of Mathematics, School of Mathematics and Natural Sciences,Bergische Universität Wuppertal, Gaußstr. 20, 42119 Wuppertal (Germany)

    2016-10-12

    We consider the determination of the finite temperature phase transition in the Yang-Mills SU(3) gauge theory. We compute the difference of the spatial and temporal energy density at a physical Wilson flow time. This difference is zero in the confined phase and becomes non zero in the deconfined phase. We locate the phase transition by using a new technique based on an exponential smoothing spline. This method is an alternative to the determination of the phase transition based on the Polyakov loop susceptibility and can also be used with dynamical fermions.

  7. Fluorinated epoxy resins with high glass transition temperatures

    Science.gov (United States)

    Griffith, James R.

    1991-01-01

    Easily processed liquid resins of low dielectric constants and high glass transition temperatures are useful for the manufacture of certain composite electronic boards. That combination of properties is difficult to acquire when dielectric constants are below 2.5, glass transition temperatures are above 200 C and processability is of conventional practicality. A recently issued patent (US 4,981,941 of 1 Jan. 1991) teaches practical materials and is the culmination of 23 years of research and effort and 15 patents owned by the Navy in the field of fluorinated resins of several classes. In addition to high fluorine content, practical utility was emphasized.

  8. Transitions in aqueous solutions of sucrose at subzero temperatures

    Czech Academy of Sciences Publication Activity Database

    Sikora, Antonín; Dupanov, V. O.; Kratochvíl, Jaroslav; Zámečník, J.

    2007-01-01

    Roč. 46, č. 1 (2007), s. 71-85 ISSN 0022-2348 R&D Projects: GA ČR(CZ) GA522/04/0384 Institutional research plan: CEZ:AV0Z40500505 Keywords : aqueous sucrose solutions * subzero temperature * glass transitions Subject RIV: BJ - Thermodynamics Impact factor: 0.809, year: 2007

  9. The Relationships Between Polymers and Glass Transition Temperatures. Part 3.

    Science.gov (United States)

    1967-09-01

    eicosane . A good fit was obtained with C I = 768 cal/mole for the energy difference between trans and gauche states, and gauche rotations of opposite...transition temperatures for the n-alkanes, hexane to eicosane . A good fit was obtained with E1 =768 cal/molf for the energy difference between trans and

  10. Citrate increases glass transition temperature of vitrified sucrose preparations

    NARCIS (Netherlands)

    Kets, E.P.W.; Lipelaar, P.J.; Hoekstra, F.A.; Vromans, H.

    2004-01-01

    The aim of this study was to investigate the effect of sodium citrate on the properties of dried amorphous sucrose glasses. Addition of sodium citrate to a sucrose solution followed by freeze-drying or convective drying resulted in a glass transition temperature (T-g) that was higher than the

  11. luminous transmittance and phase transition temperature of vo2:ce ...

    African Journals Online (AJOL)

    nb

    A two-step increase in transmittance observed in the cooling loop in pure VO2 was found to be suppressed by cerium inclusion. Keywords: vanadium dioxide, luminous transmittance, phase transition temperature. INTRODUCTION. Discovery of novel behavior of vanadium dioxide to undergo a metal-to-insulator phase.

  12. Depression of Glass Transition Temperatures of Polymer Networks by Diluents

    NARCIS (Netherlands)

    Brinke, Gerrit ten; Karasz, Frank E.; Ellis, Thomas S.

    1983-01-01

    A classical thermodynamic theory is used to derive expressions for the depression of the glass transition temperature Tg of a polymer network by a diluent. The enhanced sensitivity of Tg in cross-linked systems to small amounts of diluent is explained. Predictions of the theory are in satisfactory

  13. Glass transition temperature and its relevance in food processing.

    Science.gov (United States)

    Roos, Yrjö H

    2010-01-01

    Amorphous, noncrystalline solids are typical of low water content and frozen foods. Solids in these foods, e.g., confectionary, dehydrated foods, cereal foods, and frozen foods, often form nonequilibrium glass-like structures. The glassy state of the solids forms during food processing in a reversible glass transition. Vitrification can occur in numerous glassy states that exhibit various relaxations around the glass transition. The success of freeze drying, spray drying, and extrusion and the stability of dehydrated foods against flow, collapse, and crystallization is based on the control of the glassy state during the dehydration process and storage. Encapsulation processes often use glass-forming materials to entrap dispersed components or improve retention of volatiles. Plasticization of the noncrystalline structures by temperature or water reduce relaxation times exponentially above the glass transition, which results in rapid deterioration. Critical values for water activity and water content express the level of water plasticization leading to glass transition in food storage.

  14. Understanding the Mossbauer spectrum of magnetite below the Verwey transition: ab initio calculations, simulation, and experiment

    Czech Academy of Sciences Publication Activity Database

    Řezníček, R.; Chlan, V.; Štěpánková, H.; Novák, Pavel; Żukrowski, J.; Kozlowski, A.; Kakol, Z.; Tarnawski, Z.; Honig, J.M.

    2017-01-01

    Roč. 96, č. 19 (2017), s. 1-10, č. článku 195124. ISSN 2469-9950 Institutional support: RVO:68378271 Keywords : magnetite * Mossbauer effect * density functional theory * modelling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016

  15. Taste and Temperature in Swallowing Transit Time after Stroke

    Directory of Open Access Journals (Sweden)

    Paula C. Cola

    2012-09-01

    Full Text Available Background: Oropharyngeal dysphagia is common in individuals after stroke. Taste and temperature are used in dysphagia rehabilitation. The influence of stimuli, such as taste and temperature, on swallowing biomechanics has been investigated in both healthy individuals and in individuals with neurological disease. However, some questions still remain unanswered, such as how the sequence of offered stimuli influences the pharyngeal response. The goal of the present study was to determine the influence of the sequence of stimuli, sour taste and cold temperature, on pharyngeal transit time during deglutition in individuals after stroke. Methods: The study included 60 individuals with unilateral ischemic stroke, 29 males and 31 females, aged 41–88 years (mean age: 66.2 years examined 0–50 days after ictus (median: 6 days, with mild to moderate oropharyngeal dysphagia. Exclusion criteria were hemorrhagic stroke patients, patients with decreased level of consciousness, and clinically unstable patients, as confirmed by medical evaluation. The individuals were divided into two groups of 30 individuals each. Group 1 received a nonrandomized sequence of stimuli (i.e. natural, cold, sour, and sour-cold and group 2 received a randomized sequence of stimuli. A videofluoroscopic swallowing study was performed to analyze the pharyngeal transit time. Four different stimuli (natural, cold, sour, and sour-cold were offered. The images were digitalized and specific software was used to measure the pharyngeal transit time. Since the values did not present regular distribution and uniform variances, nonparametric tests were performed. Results: Individuals in group 1 presented a significantly shorter pharyngeal transit time with the sour-cold stimulus than with the other stimuli. Individuals in group 2 did not show a significant difference in pharyngeal transit time between stimuli. Conclusions: The results showed that the sequence of offered stimuli influences

  16. Elevated transition temperature in Ge doped VO2 thin films

    Science.gov (United States)

    Krammer, Anna; Magrez, Arnaud; Vitale, Wolfgang A.; Mocny, Piotr; Jeanneret, Patrick; Guibert, Edouard; Whitlow, Harry J.; Ionescu, Adrian M.; Schüler, Andreas

    2017-07-01

    Thermochromic GexV1-xO2+y thin films have been deposited on Si (100) substrates by means of reactive magnetron sputtering. The films were then characterized by Rutherford backscattering spectrometry (RBS), four-point probe electrical resistivity measurements, X-ray diffraction, and atomic force microscopy. From the temperature dependent resistivity measurements, the effect of Ge doping on the semiconductor-to-metal phase transition in vanadium oxide thin films was investigated. The transition temperature was shown to increase significantly upon Ge doping (˜95 °C), while the hysteresis width and resistivity contrast gradually decreased. The precise Ge concentration and the film thickness have been determined by RBS. The crystallinity of phase-pure VO2 monoclinic films was confirmed by XRD. These findings make the use of vanadium dioxide thin films in solar and electronic device applications—where higher critical temperatures than 68 °C of pristine VO2 are needed—a viable and promising solution.

  17. Direct investigations of deformation and yield induced structure transitions in polyamide 6 below glass transition temperature with WAXS and SAXS

    DEFF Research Database (Denmark)

    Guo, Huilong; Wang, Jiayi; Zhou, Chengbo

    2015-01-01

    Deformation and yield induced structure transitions of polyamide 6 (PA6) were detected with the combination of the wide- and small-angle X-ray scattering (WAXS and SAXS) at 30 degrees C below glass transition temperature (T-g) of PA6. During deformation, gamma-alpha phase transition was found...

  18. Mean global ocean temperatures during the last glacial transition.

    Science.gov (United States)

    Bereiter, Bernhard; Shackleton, Sarah; Baggenstos, Daniel; Kawamura, Kenji; Severinghaus, Jeff

    2018-01-03

    Little is known about the ocean temperature's long-term response to climate perturbations owing to limited observations and a lack of robust reconstructions. Although most of the anthropogenic heat added to the climate system has been taken up by the ocean up until now, its role in a century and beyond is uncertain. Here, using noble gases trapped in ice cores, we show that the mean global ocean temperature increased by 2.57 ± 0.24 degrees Celsius over the last glacial transition (20,000 to 10,000 years ago). Our reconstruction provides unprecedented precision and temporal resolution for the integrated global ocean, in contrast to the depth-, region-, organism- and season-specific estimates provided by other methods. We find that the mean global ocean temperature is closely correlated with Antarctic temperature and has no lead or lag with atmospheric CO 2 , thereby confirming the important role of Southern Hemisphere climate in global climate trends. We also reveal an enigmatic 700-year warming during the early Younger Dryas period (about 12,000 years ago) that surpasses estimates of modern ocean heat uptake.

  19. Low-temperature transitions in cod and tuna determined by differential scanning calorimetry

    DEFF Research Database (Denmark)

    Jensen, Kristina Nedenskov; Jørgensen, Bo; Nielsen, Jette

    2003-01-01

    Differential scanning calorimetry measurements have revealed different thermal transitions in cod and tuna samples. Transition temperatures detected Lit -11degreesC, -15degreesC and -21degreesC were highly dependent on the annealing temperature. In tuna muscle an additional transition was observed...

  20. Variability in Glycemic Control with Temperature Transitions during Therapeutic Hypothermia

    Directory of Open Access Journals (Sweden)

    Krystal K. Haase

    2017-01-01

    Full Text Available Purpose. Patients treated with therapeutic hypothermia (TH and continuous insulin may be at increased risk of hyperglycemia or hypoglycemia, particularly during temperature transitions. This study aimed to evaluate frequency of glucose excursions during each phase of TH and to characterize glycemic control patterns in relation to survival. Methods. Patients admitted to a tertiary care hospital for circulatory arrest and treated with both therapeutic hypothermia and protocol-based continuous insulin between January 2010 and June 2013 were included. Glucose measures, insulin, and temperatures were collected through 24 hours after rewarming. Results. 24 of 26 patients experienced glycemic excursions. Hyperglycemic excursions were more frequent during initiation versus remaining phases (36.3%, 4.3%, 2.5%, and 4.0%, p=0.002. Hypoglycemia occurred most often during rewarming (0%, 7.7%, 23.1%, and 3.8%, p=0.02. Patients who experienced hypoglycemia had higher insulin doses prior to rewarming (16.2 versus 2.1 units/hr, p=0.03. Glucose variation was highest during hypothermia and trended higher in nonsurvivors compared to survivors (13.38 versus 9.16, p=0.09. Frequency of excursions was also higher in nonsurvivors (32.3% versus 19.8%, p=0.045. Conclusions. Glycemic excursions are common and occur more often in nonsurvivors. Excursions differ by phase but risk of hypoglycemia is increased during rewarming.

  1. Stochasticity of bacterial attachment and its predictability by the extended derjaguin-landau-verwey-overbeek theory.

    Science.gov (United States)

    Chia, Teck Wah R; Nguyen, Vu Tuan; McMeekin, Thomas; Fegan, Narelle; Dykes, Gary A

    2011-06-01

    Bacterial attachment onto materials has been suggested to be stochastic by some authors but nonstochastic and based on surface properties by others. We investigated this by attaching pairwise combinations of two Salmonella enterica serovar Sofia (S. Sofia) strains (with different physicochemical and attachment properties) with one strain each of S. enterica serovar Typhimurium, S. enterica serovar Infantis, or S. enterica serovar Virchow (all with similar physicochemical and attachment abilities) in ratios of 0.428, 1, and 2.333 onto glass, stainless steel, Teflon, and polysulfone. Attached bacterial cells were recovered and counted. If the ratio of attached cells of each Salmonella serovar pair recovered was the same as the initial inoculum ratio, the attachment process was deemed stochastic. Experimental outcomes from the study were compared to those predicted by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. Significant differences (P attached ratios for serovar pairs containing S. Sofia S1296a for all different ratios were apparent for all materials. For S. Sofia S1635-containing pairs, 7 out of 12 combinations of serovar pairs and materials had attachment ratios not significantly different (P > 0.05) from the initial ratio of 0.428. Five out of 12 and 10 out of 12 samples had attachment ratios not significantly different (P > 0.05) from the initial ratios of 1 and 2.333, respectively. These results demonstrate that bacterial attachment to different materials is likely to be nonstochastic only when the key physicochemical properties of the bacteria were significantly different (P theory could successfully predict the attachment of some individual isolates to particular materials but could not be used to predict the likelihood of stochasticity in pairwise attachment experiments.

  2. Photoswitching of glass transition temperatures of azobenzene-containing polymers induces reversible solid-to-liquid transitions

    Science.gov (United States)

    Zhou, Hongwei; Xue, Changguo; Weis, Philipp; Suzuki, Yasuhito; Huang, Shilin; Koynov, Kaloian; Auernhammer, Günter K.; Berger, Rüdiger; Butt, Hans-Jürgen; Wu, Si

    2017-02-01

    The development of polymers with switchable glass transition temperatures (Tg) can address scientific challenges such as the healing of cracks in high-Tg polymers and the processing of hard polymers at room temperature without using plasticizing solvents. Here, we demonstrate that light can switch the Tg of azobenzene-containing polymers (azopolymers) and induce reversible solid-to-liquid transitions of the polymers. The azobenzene groups in the polymers exhibit reversible cis-trans photoisomerization abilities. Trans azopolymers are solids with Tg above room temperature, whereas cis azopolymers are liquids with Tg below room temperature. Because of the photoinduced solid-to-liquid transitions of these polymers, light can reduce the surface roughness of azopolymer films by almost 600%, repeatedly heal cracks in azopolymers, and control the adhesion of azopolymers for transfer printing. The photoswitching of Tg provides a new strategy for designing healable polymers with high Tg and allows for control over the mechanical properties of polymers with high spatiotemporal resolution.

  3. Low temperature magnetic transition and high temperature oxidation in INCONEL alloy 718

    Energy Technology Data Exchange (ETDEWEB)

    Seehra, M.S.; Babu, V.S. [Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

    1996-05-01

    X-ray diffraction and temperature dependent (5 K{endash}380 K) magnetic measurements have been carried out in INCONEL 718 superalloy before and after high temperature aging treatments (INCONEL is a trademark of the INCO family of companies). The nominal composition of this alloy is Ni (52.5{percent}), Cr (19.0{percent}), Fe (18.5{percent}), Nb (5.1{percent}), Mo (3.0{percent}), Ti (0.9{percent}), Al (0.5{percent}), Cu (0.15{percent}) and C (0.08{percent}) and it yields an x-ray diffraction pattern consisting of a fcc phase with {ital a}=3.5987 (3) A and an orthorhombic phase associated with {delta}{minus}Ni{sub 3}Nb. It is concluded that the fcc pattern is due to both the {gamma} austenitic phase and {gamma}{prime} Ni{sub 3}(Al,Ti) phase of alloy 718. The standard annealing and aging treatment carried out in air at temperatures between 621 and 982{degree}C produces surface oxides (Cr,Fe){sub 2}O{sub 3} and FeNbO{sub 4} (which are easily removed by etching and polishing) and contracts the lattice. Magnetic measurements show a distinct phase transition at {ital T}{sub {ital c}}=14 K, which has been attributed to the {gamma}{prime}{minus}Ni{sub 3}(Al,Ti) phase by the process of elimination and by observing that it has most of the characteristics of the weak itinerant ferromagnet Ni{sub 74.5}Al{sub 25.5}. This transition may have some effects on the cryogenic applications of this alloy. {copyright} {ital 1996 Materials Research Society.}

  4. High transition-temperature SQUID magnetometers and practical applications

    Energy Technology Data Exchange (ETDEWEB)

    Dantsker, Eugene [Univ. of California, Berkeley, CA (United States). Dept. of Physics

    1997-05-01

    The design, fabrication and performance of SQUID magnetometers based on thin films of the high-transition temperature superconductor YBa2Cu3O7-x (YBCO) are described. Essential to the achieving high magnetic field resolution at low frequencies is the elimination of 1/f flux noise due to thermally activated hopping of flux vortices between pinning sites in the superconducting films. Through improvements in processing, 1/f noise in single layer YBCO thin films and YBCO-SrTiO3-YBCO trilayers was systematically reduced to allow fabrication of sensitive SQUID magnetometers. Both single-layer directly coupled SQUID magnetometers and multilayer magnetometers were fabricated, based on the dc SQUID with bicrystal grain boundary Josephson junctions. Multilayer magnetometers had a lower magnetic field noise for a given physical size due to greater effective sensing areas. A magnetometer consisting of a SQUID inductively coupled to the multiturn input coil of a flux transformer in a flip-chip arrangement had a field noise of 27 fT Hz-1/2 at 1 Hz and 8.5 fT Hz-1/2 at 1 kHz. A multiloop multilayer SQUID magnetometer had a field noise of 37 fT Hz-1/2 at 1 Hz and 18 fT Hz-1/2 at 1 kHz. A three-axis SQUID magnetometer for geophysical applications was constructed and operated in the field in the presence of 60 Hz and radiofrequency noise. Clinical quality magnetocardiograms were measured using multilayer SQUID magnetometers in a magnetically shielded room.

  5. luminous transmittance and phase transition temperature of vo2:ce ...

    African Journals Online (AJOL)

    nb

    68 oC accompanied by dramatic changes in electrical and optical properties has attracted intensive research in this thermochromic material. The phase transition in VO2 has been tailored to suit various applications in devices such as smart.

  6. Transitions through critical temperatures in nematic liquid crystals

    KAUST Repository

    Majumdar, Apala

    2013-08-06

    We obtain estimates for critical nematic liquid crystal (LC) temperatures under the action of a slowly varying temperature-dependent control variable. We show that biaxiality has a negligible effect within our model and that these delay estimates are well described by a purely uniaxial model. The static theory predicts two critical temperatures: the supercooling temperature below which the isotropic phase loses stability and the superheating temperature above which the ordered nematic states do not exist. In contrast to the static problem, the isotropic phase exhibits a memory effect below the supercooling temperature in the dynamic framework. This delayed loss of stability is independent of the rate of change of temperature and depends purely on the initial value of the temperature. We also show how our results can be used to improve estimates for LC material constants. © 2013 American Physical Society.

  7. Low-temperature structural phase transition in deuterated and protonated lithium acetate dihydrate

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, F., E-mail: schroeder@kristall.uni-frankfurt.d [Goethe-Universitaet Frankfurt am Main, Institut fuer Geowissenschaften, Abt. Kristallographie, Altenhoeferallee 1, 60438 Frankfurt am Main (Germany); Winkler, B.; Haussuehl, E. [Goethe-Universitaet Frankfurt am Main, Institut fuer Geowissenschaften, Abt. Kristallographie, Altenhoeferallee 1, 60438 Frankfurt am Main (Germany); Cong, P.T.; Wolf, B. [Goethe-Universitaet Frankfurt am Main, Physikalisches Institut, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main (Germany); Avalos-Borja, M. [Instituto Potosino de Investigacion Cientifica y Tecnologica, A.C. Camino a la Presa San Jose 2055, Col. Lomas 4 seccion CP 78216, San Luis Potosi (Mexico); Quilichini, M.; Hennion, B. [Laboratoire Leon Brillouin, CEN Saclay, 91191 Gif-sur-Yvette (France)

    2010-08-15

    Heat capacity measurements of protonated lithium acetate dihydrate show a structural phase transition at T = 12 K. This finding is in contrast to earlier work, where it was thought that only the deuterated compound undergoes a low temperature structural phase transition. This finding is confirmed by low temperature ultrasound spectroscopy, where the structural phase transition is associated with a velocity decrease of the ultrasonic waves, i.e. with an elastic softening. We compare the thermodynamic properties of the protonated and deuterated compounds and discuss two alternatives for the mechanism of the phase transition based on the thermal expansion measurements.

  8. Determining magnetic phase transitions temperatures in working magnetocaloric coolers bodies and gas cryorefrigerators regenerators

    Science.gov (United States)

    Karagusov, V. I.; Mayankov, I. V.

    2017-08-01

    Due to magnetic phase transitions rare-earth materials possess unique properties near the Curie and Neel temperatures, such as the magneto-caloric effect, the abnormally high heat capacity, the magnetic susceptibility and permeability extremes. Using rare earth materials in gas cryogenic refrigerators regenerators increases the efficiency, reduces the power consumption and allows reaching helium temperatures. The magneto-caloric effect has also extreme values near the Curie and Neel temperatures. The paper presents theoretical and experimental methods allowing to determine magnetic phase transitions temperatures in a wide range of low temperature materials with a various rare-earth components content and expected thermophysical properties of a certain rare-earth materials composition at the temperatures based on starting pure metals characteristics. The results analysis has shown that magnetic phase transitions temperatures are a linear function of the components concentration. Moreover, heat capacity values and MCE also depend linearly on the starting components concentration, which simplifies calculations significantly.

  9. Differences in pressure and temperature transitions of proteins and polymer gels

    Directory of Open Access Journals (Sweden)

    Kunugi S.

    2005-01-01

    Full Text Available Pressure-driven and temperature-driven transitions of two thermoresponsive polymers, poly(N-isopropylacrylamide (pNIPAM and poly(N-vinylisobutyramide (pNVIBA, in both a soluble linear polymer form and a cross-linked hydro-gel form, were examined by a dynamic light-scattering method and direct microscopic observation, respectively. Their behavior was compared with that of protein systems. Changes in some characteristic parameters in the time-intensity correlation functions of dynamic light-scattering measurement of aqueous solutions of pNIPAM at various pressures and temperatures showed no essential differences during temperature and pressure scanning and, as a whole, the motions of polymers in aqueous solutions were similar in two types of transitions until chain shrinkage occurred. The gels (cross-linked polymer gels prepared from the thermoresponsive polymers also showed similar volume transitions responding to the pressure and temperature increase. In temperature transitions, however, gels showed drastic volume shrinkage with loss of transparency, while pressure-induced transition showed a slow recovery of transparency while keeping the size, after first transient drastic volume shrinkage with loss of transparency. At a temperature slightly higher than the transition under atmospheric temperature, so-called reentry of the volume change and recovery of the transparency were observed during the pressure-increasing process, which implies much smaller aggregation or non-aggregated collapsed polymer chains in the gel at higher pressures, indicating a certain mechanistic difference of the dehydration processes induced by temperature and pressure.

  10. Polymeric nanoparticles - Influence of the glass transition temperature on drug release.

    Science.gov (United States)

    Lappe, Svenja; Mulac, Dennis; Langer, Klaus

    2017-01-30

    The physico-chemical characterisation of nanoparticles is often lacking the determination of the glass transition temperature, a well-known parameter for the pure polymer carrier. In the present study the influence of water on the glass transition temperature of poly (DL-lactic-co-glycolic acid) nanoparticles was assessed. In addition, flurbiprofen and mTHPP as model drugs were incorporated in poly (DL-lactic-co-glycolic acid), poly (DL-lactic acid), and poly (L-lactic acid) nanoparticles. For flurbiprofen-loaded nanoparticles a decrease in the glass transition temperature was observed while mTHPP exerted no influence on this parameter. Based on this observation, the release behaviour of the drug-loaded nanoparticles was investigated at different temperatures. For all preparations an initial burst release was measured that could be attributed to the drug adsorbed to the large nanoparticle surface. At temperatures above the glass transition temperature an instant drug release of the nanoparticles was observed, while at lower temperatures less drug was released. It could be shown that the glass transition temperature of drug loaded nanoparticles in suspension more than the corresponding temperature of the pure polymer is the pivotal parameter when characterising a nanostructured drug delivery system. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Glass Transition Temperature- and Specific Volume- Composition Models for Tellurite Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Brian J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Vienna, John D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-09-01

    This report provides models for predicting composition-properties for tellurite glasses, namely specific gravity and glass transition temperature. Included are the partial specific coefficients for each model, the component validity ranges, and model fit parameters.

  12. 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.

  13. 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)

  14. 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-...

  15. Correlation between defect transition levels and thermoelectric operational temperature of doped CrSi2

    Science.gov (United States)

    Singh, Abhishek; Pandey, Tribhuwan

    2014-03-01

    The performance of a thermoelectric material is quantified by figure of merit ZT. The challenge in achieving high ZT value requires simultaneously high thermopower, high electrical conductivity and low thermal conductivity at optimal carrier concentration. So far doping is the most versatile approach used for modifying thermoelectric properties. Previous studies have shown that doping can significantly improve the thermoelectric performance, however the tuning the operating temperature of a thermoelectric device is a main issue. Using first principles density functional theory, we report for CrSi2, a linear relationship between thermodynamic charge state transition levels of defects and temperature at which thermopower peaks. We show for doped CrSi2 that the peak of thermopower occurs at the temperature Tm, which corresponds to the position of defect transition level. Therefore, by modifying the defect transition level, a thermoelectric material with a given operational temperature can be designed. The authors thankfully acknowledge support from ADA under NpMASS.

  16. On-chip detection of gel transition temperature using a novel micro-thermomechanical method.

    Directory of Open Access Journals (Sweden)

    Tsenguun Byambadorj

    Full Text Available We present a new thermomechanical method and a platform to measure the phase transition temperature at microscale. A thin film metal sensor on a membrane simultaneously measures both temperature and mechanical strain of the sample during heating and cooling cycles. This thermomechanical principle of operation is described in detail. Physical hydrogel samples are prepared as a disc-shaped gels (200 μm thick and 1 mm diameter and placed between an on-chip heater and sensor devices. The sol-gel transition temperature of gelatin solution at various concentrations, used as a model physical hydrogel, shows less than 3% deviation from in-depth rheological results. The developed thermomechanical methodology is promising for precise characterization of phase transition temperature of thermogels at microscale.

  17. Magnetic and Structural Phase Transitions in Thulium under High Pressures and Low Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Vohra, Yogesh K.; Tsoi, Georgiy M.; Samudrala, Gopi K. [UAB

    2017-10-01

    The nature of 4f electrons in many rare earth metals and compounds may be broadly characterized as being either "localized" or "itinerant", and is held responsible for a wide range of physical and chemical properties. The pressure variable has a very dramatic effect on the electronic structure of rare earth metals which in turn drives a sequence of structural and magnetic transitions. We have carried out four-probe electrical resistance measurements on rare earth metal Thulium (Tm) under high pressures to 33 GPa and low temperatures to 10 K to monitor the magnetic ordering transition. These studies are complemented by angle dispersive x-ray diffraction studies to monitor crystallographic phase transitions at high pressures and low temperatures. We observe an abrupt increase in magnetic ordering temperature in Tm at a pressure of 17 GPa on phase transition from ambient pressure hcp-phase to α-Sm phase transition. In addition, measured equation of state (EOS) at low temperatures show anomalously low thermal expansion coefficients likely linked to magnetic transitions.

  18. Magnetic and Structural Phase Transitions in Thulium under High Pressures and Low Temperatures

    Science.gov (United States)

    Vohra, Yogesh K.; Tsoi, Georgiy M.; Samudrala, Gopi K.

    2017-10-01

    The nature of 4f electrons in many rare earth metals and compounds may be broadly characterized as being either “localized” or “itinerant”, and is held responsible for a wide range of physical and chemical properties. The pressure variable has a very dramatic effect on the electronic structure of rare earth metals which in turn drives a sequence of structural and magnetic transitions. We have carried out four-probe electrical resistance measurements on rare earth metal Thulium (Tm) under high pressures to 33 GPa and low temperatures to 10 K to monitor the magnetic ordering transition. These studies are complemented by angle dispersive x-ray diffraction studies to monitor crystallographic phase transitions at high pressures and low temperatures. We observe an abrupt increase in magnetic ordering temperature in Tm at a pressure of 17 GPa on phase transition from ambient pressure hcp-phase to α-Sm phase transition. In addition, measured equation of state (EOS) at low temperatures show anomalously low thermal expansion coefficients likely linked to magnetic transitions.

  19. Large temperature drop across the Eocene-Oligocene transition in central North America.

    Science.gov (United States)

    Zanazzi, Alessandro; Kohn, Matthew J; MacFadden, Bruce J; Terry, Dennis O

    2007-02-08

    The Eocene-Oligocene transition towards a cool climate (approximately 33.5 million years ago) was one of the most pronounced climate events during the Cenozoic era. The marine record of this transition has been extensively studied. However, significantly less research has focused on continental climate change at the time, yielding partly inconsistent results on the magnitude and timing of the changes. Here we use a combination of in vivo stable isotope compositions of fossil tooth enamel with diagenetic stable isotope compositions of fossil bone to derive a high-resolution (about 40,000 years) continental temperature record for the Eocene-Oligocene transition. We find a large drop in mean annual temperature of 8.2 +/- 3.1 degrees C over about 400,000 years, the possibility of a small increase in temperature seasonality, and no resolvable change in aridity across the transition. The large change in mean annual temperature, exceeding changes in sea surface temperatures at comparable latitudes and possibly delayed in time with respect to marine changes by up to 400,000 years, explains the faunal turnover for gastropods, amphibians and reptiles, whereas most mammals in the region were unaffected. Our results are in agreement with modelling studies that attribute the climate cooling at the Eocene-Oligocene transition to a significant drop in atmospheric carbon dioxide concentrations.

  20. Finite temperature spin-dynamics and phase transitions in spin-orbital models

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C.-C.

    2010-04-29

    We study finite temperature properties of a generic spin-orbital model relevant to transition metal compounds, having coupled quantum Heisenberg-spin and Ising-orbital degrees of freedom. The model system undergoes a phase transition, consistent with that of a 2D Ising model, to an orbitally ordered state at a temperature set by short-range magnetic order. At low temperatures the orbital degrees of freedom freeze-out and the model maps onto a quantum Heisenberg model. The onset of orbital excitations causes a rapid scrambling of the spin spectral weight away from coherent spin-waves, which leads to a sharp increase in uniform magnetic susceptibility just below the phase transition, reminiscent of the observed behavior in the Fe-pnictide materials.

  1. The finite temperature phase transition in the lattice SU(2)-Higgs model

    CERN Document Server

    Farakos, K; Rummukainen, K; Shaposhnikov, Mikhail E

    1994-01-01

    We study the finite temperature transition of SU(2)-Higgs model with lattice Monte Carlo techniques. We use dimensional reduction to transform the original 4-dimensional SU(2)-gauge + fundamental Higgs theory to an effective 3-dimensional SU(2) + adjoint Higgs + fundamental Higgs model. The simulations were performed with Higgs masses of 35 and 80 GeV; in both cases we observe a stronger first order transition than the perturbation theory predicts, indicating that the dynamics of the transition strongly depend on non-perturbative effects.

  2. Polymorph transitions in uranium at low temperatures: first-principles investigation

    Science.gov (United States)

    Migdal, K. P.; Yanilkin, A. V.

    2018-02-01

    Polymorph transition from α to {α }1 uranium was considered using the all-electron and pseudopotential approaches of density functional theory. The role of equilibrium lattice parameters of α uranium and the effect of a model for the atomic shift due to the considered transition were subjected to detailed investigation. Quasi-one-dimensional structures were observed by an increase in charge density between pairs of ions in the {α }1 phase. A transition temperature of 39 K was predicted using the Peierls formula. A comparison of the {α }1 structure between experimental and calculation data was discussed with regard to the accuracy of predicted interatomic forces.

  3. The insulating-to-superconducting transition in europium high-temperature superconducting ceramics

    CERN Document Server

    Rosenbaum, R

    1997-01-01

    Experiment resistivity data on high-temperature superconducting ceramics of fully oxygenated EuBa sub 2 Cu sub 3 sub - sub x Co sub x O sub y show that the insulating-to-superconducting transitions take place at liquid-helium temperature, provided that the cobalt fraction x exceeds 0.3. The resistivity follows a simple power-law dependence rho propor to T sup - sup 1 sup / sup 2 , attributed to electron-electron interactions. A model based upon intrinsic Josephson tunnelling junctions is suggested to explain the transition from insulating to superconducting states. (author)

  4. The Present SP Tests for Determining the Transition Temperature TSP on "U" Notch Disc Specimens.

    Science.gov (United States)

    Matocha, Karel; Dorazil, Ondrej; Hurst, Roger

    2017-05-03

    The principal difference between the small punch (SP) testing technique and standardized impact testing lies in the fact that the SP tests carried out in accordance with CWA 15627 Small Punch Test Method for Metallic Materials use disc-shaped test specimens without a notch. Especially in tough materials, the temperature dependence of SP fracture energy ESP in the transition area is very steep and lies close to the temperature of liquid nitrogen. In this case, the determination of SP transition temperature TSP can lead to significant errors in its determination. Efforts to move the transition area of penetration testing closer to the transition area of standardized impact tests led to the proposal of the notched disc specimen 8 mm in diameter and 0.5 mm in thickness with a "U" shaped notch 0.2 mm deep in the axis plane of the disc. The paper summarizes the results obtained to date when determining the transition temperature of SP tests TSP, determined according to CWA 15627 for material of pipes made of P92, P22, and a heat treated 14MoV6-3 steel in the as delivered state. Although the results obtained confirmed the results of other works in that the presence of a notch in a SP disc is insufficient to increase the transition temperature significantly and certainly not to the values obtained by Charpy testing, comparison of the different behaviors of the alloys tested reveals some evidence that the notch reduces the energy for initiation. This implies that the test on a notched disc is more a test of crack growth and would be a useful instrument if included in the forthcoming EU standard for SP testing.

  5. Transition Temperatures of Thermotropic Liquid Crystals from the Local Binary Gray Level Cooccurrence Matrix

    Directory of Open Access Journals (Sweden)

    S. Sreehari Sastry

    2012-01-01

    Full Text Available This paper presents a method which combines the statistical analysis with texture structural analysis called Local Binary Gray Level Cooccurrence Matrix (LBGLCM to investigate the phase transition temperatures of thermotropic p,n-alkyloxy benzoic acid (nOBA, n=4,6,8,10 and 12 liquid crystals. Textures of the homeotropically aligned liquid crystal compounds are recorded as a function of temperature using polarizing optical microscope attached to the hot stage and high resolution camera. In this method, second-order statistical parameters (contrast, energy, homogeneity, and correlation are extracted from the LBGLCM of the textures. The changes associatedwiththe values of extracted parameters as a function of temperature are a helpful process to identify the phases and phase transition temperatures of the samples. Results obtained from this method have validity and are in good agreement with the literature.

  6. Vanadium dioxide thin film with low phase transition temperature deposited on borosilicate glass substrate

    Energy Technology Data Exchange (ETDEWEB)

    Huang Zhangli; Chen Sihai, E-mail: cshai99@mail.hust.edu.cn; Wang Boqing; Huang Ying; Liu Nengfu; Xu Jin; Lai Jianjun

    2011-04-29

    A nanostructured vanadium dioxide (VO{sub 2}) thin film showing a low metal-insulator transition temperature of 30 {sup o}C has been fabricated through reactive ion beam sputtering followed by thermal annealing. The thin film was grown on borosilicate glass substrate at the temperature of 280 {sup o}C with a Si{sub 3}N{sub 4} buffer layer. Both scanning electron microscopy and atomic force microscopy images have been taken to investigate the configuration of VO{sub 2} thin film. The average height of the crystallite is 20 nm and the grain size ranges from 40 nm to 100 nm. The transmittance measured from low to high temperatures also reveals that the film possesses excellent switching property in infrared light at critical transition temperature, with switching efficiency of 52% at 2600 nm. This experiment paves the way of VO{sub 2} thin film's application in smart windows.

  7. Interplay between quantum phase transitions and the behavior of quantum correlations at finite temperatures

    OpenAIRE

    Werlang, T.; Ribeiro, G. A. P.; Rigolin, Gustavo

    2012-01-01

    We review the main results and ideas showing that quantum correlations at finite temperatures (T), in particular quantum discord, are useful tools in characterizing quantum phase transitions that only occur, in principle, at the unattainable absolute zero temperature. We first review some interesting results about the behavior of thermal quantum discord for small spin-1/2 chains and show that they already give us important hints of the infinite chain behavior. We then study in detail and in t...

  8. A phase transition close to room temperature in BiFeO3 thin films.

    Science.gov (United States)

    Kreisel, J; Jadhav, P; Chaix-Pluchery, O; Varela, M; Dix, N; Sánchez, F; Fontcuberta, J

    2011-08-31

    BiFeO3 (BFO) multiferroic oxide has a complex phase diagram that can be mapped by using appropriately substrate-induced strain in epitaxial films. By using Raman spectroscopy, we conclusively show that films of the so-called supertetragonal T-BFO phase, stabilized under compressive strain, display a reversible temperature-induced phase transition at about 100 °C, and thus close to room temperature.

  9. A phase transition close to room temperature in BiFeO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kreisel, J; Jadhav, P; Chaix-Pluchery, O [Laboratoire des Materiaux et du Genie Physique, Grenoble INP, CNRS, Minatec, 3, parvis Louis Neel, 38016 Grenoble (France); Varela, M [Departamento Fisica Aplicada i Optica, Universitat de Barcelona, Carrer MartI i Franques 1. 08028 Campus UAB, Bellaterra 08193 (Spain); Dix, N; Sanchez, F; Fontcuberta, J, E-mail: jens.kreisel@grenoble-inp.fr [Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193 (Spain)

    2011-08-31

    BiFeO{sub 3} (BFO) multiferroic oxide has a complex phase diagram that can be mapped by using appropriately substrate-induced strain in epitaxial films. By using Raman spectroscopy, we conclusively show that films of the so-called supertetragonal T-BFO phase, stabilized under compressive strain, display a reversible temperature-induced phase transition at about 100 deg. C, and thus close to room temperature. (fast track communication)

  10. EHL Transition Temperature Measurements on a Geostationary Operational Environmental Satellite (GOES) Filter Wheel Bearing

    Science.gov (United States)

    Jansen, Mark J.; Jones, William R., Jr.; Pepper, Stephen V.; Predmore, Roamer E.; Shogrin, Bradley A.

    2001-01-01

    The elastohydrodynamic lubrication (EHL) transition temperature was measured for a Geostationary Operational Environmental Satellite (GOES) sounder filter wheel bearing in a vacuum tribometer. Conditions included both an 89 N (20 lb.) hard and soft load, 600 rpm, temperatures between 23 C (73 F) and 85 C (185 F), and a vacuum of approximately 1.3 x 10(exp -5) Pa. Elastohydrodynamic to mixed lubrication started to occur at approximately 70 C (158 F).

  11. Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formation.

    Science.gov (United States)

    Ovsyannikov, Sergey V; Bykov, Maxim; Bykova, Elena; Kozlenko, Denis P; Tsirlin, Alexander A; Karkin, Alexander E; Shchennikov, Vladimir V; Kichanov, Sergey E; Gou, Huiyang; Abakumov, Artem M; Egoavil, Ricardo; Verbeeck, Johan; McCammon, Catherine; Dyadkin, Vadim; Chernyshov, Dmitry; van Smaalen, Sander; Dubrovinsky, Leonid S

    2016-05-01

    Phase transitions that occur in materials, driven, for instance, by changes in temperature or pressure, can dramatically change the materials' properties. Discovering new types of transitions and understanding their mechanisms is important not only from a fundamental perspective, but also for practical applications. Here we investigate a recently discovered Fe4O5 that adopts an orthorhombic CaFe3O5-type crystal structure that features linear chains of Fe ions. On cooling below ∼150 K, Fe4O5 undergoes an unusual charge-ordering transition that involves competing dimeric and trimeric ordering within the chains of Fe ions. This transition is concurrent with a significant increase in electrical resistivity. Magnetic-susceptibility measurements and neutron diffraction establish the formation of a collinear antiferromagnetic order above room temperature and a spin canting at 85 K that gives rise to spontaneous magnetization. We discuss possible mechanisms of this transition and compare it with the trimeronic charge ordering observed in magnetite below the Verwey transition temperature.

  12. Recombinant production and purification of short hydrophobic Elastin-like polypeptides with low transition temperatures.

    Science.gov (United States)

    Bataille, Laure; Dieryck, Wilfrid; Hocquellet, Agnès; Cabanne, Charlotte; Bathany, Katell; Lecommandoux, Sébastien; Garbay, Bertrand; Garanger, Elisabeth

    2016-05-01

    Elastin-like polypeptides (ELPs) are biodegradable polymers with interesting physico-chemical properties for biomedical and biotechnological applications. We report herein the recombinant expression of three hydrophobic ELPs (VPGIG)n with variable lengths (n = 20, 40, 60) and sub-ambient transition temperatures. These ELPs were purified from the cytoplasmic soluble fraction of Escherichia coli by inverse transition cycling, and their exact molecular weight was confirmed by various mass spectrometry techniques. Transition temperatures of ELP20, ELP40, and ELP60 were measured at 18.6 °C, 12.4 °C and 11.7 °C, respectively. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Pressure and temperature effects on optical transitions in cubic GaN

    Science.gov (United States)

    Liu, Z. X.; Goñi, A. R.; Syassen, K.; Siegle, H.; Thomsen, C.; Schöttker, B.; As, D. J.; Schikora, D.

    1999-07-01

    Pressure and temperature effects on optical transitions in cubic GaN grown on a GaAs substrate have been studied by photoluminescence (PL) spectroscopy at hydrostatic pressures up to 9 GPa (10 K) and as a function of temperature (10-300 K) at ambient pressure. The dominant emissions at 10 K and ambient pressure are assigned to the bound-exciton transition (zero-phonon line), the donor-acceptor-pair (DAP) emission, and, tentatively, to the first three LO-phonon replicas of the bound exciton. These PL features shift to higher energy with increasing pressure. The pressure coefficients indicate that the observed recombination processes involve states which are closely related to the band edges. Temperature-induced evolutions from bound to free-exciton (FE) transition and DAP emission to free-to-bound transition are resolved. The binding energies of the FE and donor and acceptor levels in cubic GaN have been determined from the temperature and power-density dependence of the PL emission energies.

  14. TRANSITION TEMPERATURE IN QCD WITH PHYSICAL LIGHT AND STRANGE QUARK MASSES.

    Energy Technology Data Exchange (ETDEWEB)

    KARSCH, F.

    2006-11-14

    We present results from a calculation of the transition temperature in QCD with two light (up, down) and one heavier (strange) quark mass as well as for QCD with three degenerate quark masses. Furthermore, we discuss first results from an ongoing calculation of the QCD equation of state with almost realistic light and strange quark masses.

  15. Pressure-Driven Commensurate-Incommensurate Transition Low-Temperature Submonolayer Krypton on Graphite

    DEFF Research Database (Denmark)

    Nielsen, Mourits; Als-Nielsen, Jens Aage; Bohr, Jakob

    1981-01-01

    By using D2 gas as a source of two-dimensional spreading pressure, we have studied the commensurate-incommensurate (C-I) transition in submonolayer Kr on ZYX graphite at temperatures near 40 K. High-resolution synchrotron x-ray diffraction results show both hysteresis and C-I phase coexistence, c...

  16. Time evolution of chiral phase transition at finite temperature and density in the linear sigma model

    Energy Technology Data Exchange (ETDEWEB)

    Sato, K.; Koide, Tomoi; Maruyama, Masahiro [Tohoku Univ., Faculty of Science, Sendai, Miyagi (Japan)

    1999-08-01

    There are various approaches to nonequilibrium system. We use the projection operator method investigated by F. Shibata and N. Hashitsume on the linear sigma model at finite temperature and density. We derive a differential equation of the time evolution for the order parameter and pion number density in chiral phase transition. (author)

  17. Circulatory osmotic desalination driven by a mild temperature gradient based on lower critical solution temperature (LCST) phase transition materials.

    Science.gov (United States)

    Mok, Yeongbong; Nakayama, Daichi; Noh, Minwoo; Jang, Sangmok; Kim, Taeho; Lee, Yan

    2013-11-28

    Abrupt changes in effective concentration and osmotic pressure of lower critical solution temperature (LCST) mixtures facilitate the design of a continuous desalination method driven by a mild temperature gradient. We propose a prototype desalination system by circulating LCST mixtures between low and high temperature (low T and high T) units. Water molecules could be drawn from a high-salt solution to the LCST mixture through a semipermeable membrane at a temperature lower than the phase transition temperature, at which the effective osmotic pressure of the LCST mixture is higher than the high-salt solution. After transfer of water to the high T unit where the LCST mixture is phase-separated, the water-rich phase could release the drawn water into a well-diluted solution through the second membrane due to the significant decrease in effective concentration. The solute-rich phase could be recovered in the low T unit via a circulation process. The molar mass, phase transition temperature, and aqueous solubility of the LCST solute could be tuneable for the circulatory osmotic desalination system in which drawing, transfer, release of water, and the separation and recovery of the solutes could proceed simultaneously. Development of a practical desalination system that draws water molecules directly from seawater and produces low-salt water with high purity by mild temperature gradients, possibly induced by sunlight or waste heat, could be attainable by a careful design of the molecular structure and combination of the circulatory desalination systems based on low- and high-molar-mass LCST draw solutes.

  18. Mathematical modeling of photoinitiated coating degradation: Effects of coating glass transition temperature and light stabilizers

    DEFF Research Database (Denmark)

    Kiil, Søren; G.de With, R.A.T.M.Van Benthem

    2013-01-01

    A mathematical model, describing coating degradation mechanisms of thermoset coatings exposed to ultraviolet radiation and humidity at constant temperature, was extended to simulate the behavior of a coating with a low glass transition temperature. The effects of adding light stabilizers (a UV......, and simulates the transient development of an oxidation zone. Simulations are in good agreement with experimental data for a fast degrading epoxy-amine coating with a glass transition temperature of −50°C. It was found that the degradation rate of the non-stabilized coating was influenced significantly...... by the diffusion rate of oxygen in the oxidation zone, whereas light absorption by the photoproducts formed was only a secondary effect. On the other hand, the degradation rate of the stabilized coating was mainly influenced by the light absorption capability of the coating and in this case there was no oxygen...

  19. A tool to evaluate local biophysical effects on temperature due to land cover change transitions

    Science.gov (United States)

    Perugini, Lucia; Caporaso, Luca; Duveiller, Gregory; Cescatti, Alessandro; Abad-Viñas, Raul; Grassi, Giacomo; Quesada, Benjamin

    2017-04-01

    Land Cover Changes (LCC) affect local, regional and global climate through biophysical variations of the surface energy budget mediated by albedo, evapotranspiration, and roughness. Assessment of the full climate impacts of anthropogenic LCC are incomplete without considering biophysical effects, but the high level of uncertainties in quantifying their impacts to date have made it impractical to offer clear advice on which policy makers could act. To overcome this barrier, we provide a tool to evaluate the biophysical impact of a matrix of land cover transitions, following a tiered methodological approach similar to the one provided by the IPCC to estimate the biogeochemical effects, i.e. through three levels of methodological complexity, from Tier 1 (i.e. default method and factors) to Tier 3 (i.e. specific methods and factors). In particular, the tool provides guidance for quantitative assessment of changes in temperature following a land cover transition. The tool focuses on temperature for two main reasons (i) it is the main variable of interest for policy makers at local and regional level, and (ii) temperature is able to summarize the impact of radiative and non-radiative processes following LULCC. The potential changes in annual air temperature that can be expected from various land cover transitions are derived from a dedicated dataset constructed by the JRC in the framework of the LUC4C FP7 project. The inputs for the dataset are air temperature values derived from satellite Earth Observation data (MODIS) and land cover characterization from the ESA Climate Change Initiative product reclassified into their IPCC land use category equivalent. This data, originally at 0.05 degree of spatial resolution, is aggregated and analysed at regional level to provide guidance on the expected temperature impact following specific LCC transitions.

  20. Efficiency of Adaptive Temperature-Based Replica Exchange for Sampling Large-Scale Protein Conformational Transitions.

    Science.gov (United States)

    Zhang, Weihong; Chen, Jianhan

    2013-06-11

    Temperature-based replica exchange (RE) is now considered a principal technique for enhanced sampling of protein conformations. It is also recognized that existence of sharp cooperative transitions (such as protein folding/unfolding) can lead to temperature exchange bottlenecks and significantly reduce the sampling efficiency. Here, we revisit two adaptive temperature-based RE protocols, namely, exchange equalization (EE) and current maximization (CM), that were previously examined using atomistic simulations (Lee and Olson, J. Chem. Physics2011, 134, 24111). Both protocols aim to overcome exchange bottlenecks by adaptively adjusting the simulation temperatures, either to achieve uniform exchange rates (in EE) or to maximize temperature diffusion (CM). By designing a realistic yet computationally tractable coarse-grained protein model, one can sample many reversible folding/unfolding transitions using conventional constant temperature molecular dynamics (MD), standard REMD, EE-REMD, and CM-REMD. This allows rigorous evaluation of the sampling efficiency, by directly comparing the rates of folding/unfolding transitions and convergence of various thermodynamic properties of interest. The results demonstrate that both EE and CM can indeed enhance temperature diffusion compared to standard RE, by ∼3- and over 10-fold, respectively. Surprisingly, the rates of reversible folding/unfolding transitions are similar in all three RE protocols. The convergence rates of several key thermodynamic properties, including the folding stability and various 1D and 2D free energy surfaces, are also similar. Therefore, the efficiency of RE protocols does not appear to be limited by temperature diffusion, but by the inherent rates of spontaneous large-scale conformational rearrangements. This is particularly true considering that virtually all RE simulations of proteins in practice involve exchange attempt frequencies (∼ps(-1)) that are several orders of magnitude faster than the

  1. Low temperature electroweak phase transition in the Standard Model with hidden scale invariance

    Directory of Open Access Journals (Sweden)

    Suntharan Arunasalam

    2018-01-01

    Full Text Available We discuss a cosmological phase transition within the Standard Model which incorporates spontaneously broken scale invariance as a low-energy theory. In addition to the Standard Model fields, the minimal model involves a light dilaton, which acquires a large vacuum expectation value (VEV through the mechanism of dimensional transmutation. Under the assumption of the cancellation of the vacuum energy, the dilaton develops a very small mass at 2-loop order. As a result, a flat direction is present in the classical dilaton-Higgs potential at zero temperature while the quantum potential admits two (almost degenerate local minima with unbroken and broken electroweak symmetry. We found that the cosmological electroweak phase transition in this model can only be triggered by a QCD chiral symmetry breaking phase transition at low temperatures, T≲132 MeV. Furthermore, unlike the standard case, the universe settles into the chiral symmetry breaking vacuum via a first-order phase transition which gives rise to a stochastic gravitational background with a peak frequency ∼10−8 Hz as well as triggers the production of approximately solar mass primordial black holes. The observation of these signatures of cosmological phase transitions together with the detection of a light dilaton would provide a strong hint of the fundamental role of scale invariance in particle physics.

  2. Low temperature electroweak phase transition in the Standard Model with hidden scale invariance

    Science.gov (United States)

    Arunasalam, Suntharan; Kobakhidze, Archil; Lagger, Cyril; Liang, Shelley; Zhou, Albert

    2018-01-01

    We discuss a cosmological phase transition within the Standard Model which incorporates spontaneously broken scale invariance as a low-energy theory. In addition to the Standard Model fields, the minimal model involves a light dilaton, which acquires a large vacuum expectation value (VEV) through the mechanism of dimensional transmutation. Under the assumption of the cancellation of the vacuum energy, the dilaton develops a very small mass at 2-loop order. As a result, a flat direction is present in the classical dilaton-Higgs potential at zero temperature while the quantum potential admits two (almost) degenerate local minima with unbroken and broken electroweak symmetry. We found that the cosmological electroweak phase transition in this model can only be triggered by a QCD chiral symmetry breaking phase transition at low temperatures, T ≲ 132 MeV. Furthermore, unlike the standard case, the universe settles into the chiral symmetry breaking vacuum via a first-order phase transition which gives rise to a stochastic gravitational background with a peak frequency ∼10-8 Hz as well as triggers the production of approximately solar mass primordial black holes. The observation of these signatures of cosmological phase transitions together with the detection of a light dilaton would provide a strong hint of the fundamental role of scale invariance in particle physics.

  3. Winding transitions at finite energy and temperature: An O(3) model

    CERN Document Server

    Tinyakov, Peter G; Habib, S

    1996-01-01

    We consider winding number transitions in the two dimensional O(3) non-linear sigma model, modified by a suitable conformal symmetry breaking term. We discuss the general properties of the relevant instanton solutions which dominate the transition amplitudes at finite energy, and find the solutions numerically. The Euclidean period of the solution increases with energy, contrary to the behavior found in the abelian Higgs model or simple one dimensional systems. This indicates that there is a sharp crossover from instanton dominated tunneling to sphaleron dominated thermal activation at a certain critical temperature in this model. We argue that the electroweak theory in four dimensions should exhibit a similar behavior.

  4. A Vesicle-to-Worm Transition Provides a New High-Temperature Oil Thickening Mechanism.

    Science.gov (United States)

    Derry, Matthew J; Mykhaylyk, Oleksandr O; Armes, Steven P

    2017-02-06

    Diblock copolymer vesicles are prepared via RAFT dispersion polymerization directly in mineral oil. Such vesicles undergo a vesicle-to-worm transition on heating to 150 °C, as judged by TEM and SAXS. Variable-temperature 1 H NMR spectroscopy indicates that this transition is the result of surface plasticization of the membrane-forming block by hot solvent, effectively increasing the volume fraction of the stabilizer block and so reducing the packing parameter for the copolymer chains. The rheological behavior of a 10 % w/w copolymer dispersion in mineral oil is strongly temperature-dependent: the storage modulus increases by five orders of magnitude on heating above the critical gelation temperature of 135 °C, as the non-interacting vesicles are converted into weakly interacting worms. SAXS studies indicate that, on average, three worms are formed per vesicle. Such vesicle-to-worm transitions offer an interesting new mechanism for the high-temperature thickening of oils. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Optical nonlinearities of nanostructured VO{sub 2} thin films with low phase transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wang Boqing [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Chen Sihai, E-mail: cshai99@163.com [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Huang Zhangli; Fu Ming [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2012-05-01

    Vanadium dioxides (VO{sub 2}) thin films which change from a monoclinic semiconductor phase to a tetragonal metallic structure at the temperature of 29 Degree-Sign C have been fabricated by reactive ion beam sputtering. Micrograph of scanning electron microscope (SEM) shows that the grain size of VO{sub 2} crystallite ranges from 20 nm to 50 nm. Regeneratively amplified Ti:sapphire laser pulses were applied to induce the phase transition, which was accompanying with the third-order optical nonlinearities in VO{sub 2} thin films. Open-aperture and closed-aperture measurements of Z-scan were used to study the optical absorptive and refractive nonlinearities. Nanostructured VO{sub 2} thin films exhibit two-photon absorption and a negative nonlinear index of refraction when phase transition is induced. The optical nonlinearities are due to excitation of electronic subsystem only and without involving of the structural semiconductor-to-metal phase transition.

  6. Organization versus frustration: low temperature transitions in a gelatine-based gel

    Energy Technology Data Exchange (ETDEWEB)

    Philipp, M; Mueller, U; Sanctuary, R; Baller, J; Krueger, J K [Laboratoire de Physique des Materiaux, Universite du Luxembourg, 162A, avenue de la Faiencerie, L-1511 (Luxembourg)], E-mail: martine.philipp@uni.lu

    2008-09-15

    A commercial physical gel composed of gelatine, water and glycerol shows a sol-gel transition which has been resolved by optical rotation measurements by step-wise heating the gel. This transition is not observable in the longitudinal acoustic mode measured at hypersonic frequencies with Brillouin spectroscopy. Depending on the thermal treatment of the investigated material during the sol-gel transition and within the gel state, Brillouin spectroscopy reflects tremendously different hypersonic dynamics. These distinct dynamics are responsible for the formation of different glassy states at low temperatures including that of a glass-ceramic. The large variety of super-cooled and glassy states is attributed to distinct distributions of the gel's constituents within the samples. Surprisingly, the same gel state can be produced either by annealing the gel over months or by the non-equilibrium effect of thermo-diffusion (Soret effect) in the course of some minutes.

  7. Relaxation theory of spin-3/2 Ising system near phase transition temperatures

    Science.gov (United States)

    Osman, Canko; Mustafa, Keskin

    2010-08-01

    Dynamics of a spin-3/2 Ising system Hamiltonian with bilinear and biquadratic nearest-neighbour exchange interactions is studied by a simple method in which the statistical equilibrium theory is combined with the Onsager's theory of irreversible thermodynamics. First, the equilibrium behaviour of the model in the molecular-field approximation is given briefly in order to obtain the phase transition temperatures, i.e. the first- and second-order and the tricritical points. Then, the Onsager theory is applied to the model and the kinetic or rate equations are obtained. By solving these equations three relaxation times are calculated and their behaviours are examined for temperatures near the phase transition points. Moreover, the z dynamic critical exponent is calculated and compared with the z values obtained for different systems experimentally and theoretically, and they are found to be in good agrement.

  8. Atomically Thin Transition-Metal Dinitrides: High-Temperature Ferromagnetism and Half-Metallicity.

    Science.gov (United States)

    Wu, Fang; Huang, Chengxi; Wu, Haiping; Lee, Changhoon; Deng, Kaiming; Kan, Erjun; Jena, Puru

    2015-12-09

    High-temperature ferromagnetic two-dimensional (2D) materials with flat surfaces have been a long-sought goal due to their potential in spintronics applications. Through comprehensive first-principles calculations, we show that the recently synthesized MoN2 monolayer is such a material; it is ferromagnetic with a Curie temperature of nearly 420 K, which is higher than that of any flat 2D magnetic materials studied to date. This novel property, made possible by the electron-deficient nitrogen ions, render transition-metal dinitrides monolayers with unique electronic properties which can be switched from the ferromagnetic metals in MoN2, ZrN2, and TcN2 to half-metallic ones in YN2. Transition-metal dinitrides monolayers may, therefore, serve as good candidates for spintronics devices.

  9. Transition in Deformation Mechanism of AZ31 Magnesium Alloy during High-Temperature Tensile Deformation

    Directory of Open Access Journals (Sweden)

    Masafumi Noda

    2011-01-01

    Full Text Available Magnesium alloys can be used for reducing the weight of various structural products, because of their high specific strength. They have attracted considerable attention as materials with a reduced environmental load, since they help to save both resources and energy. In order to use Mg alloys for manufacturing vehicles, it is important to investigate the deformation mechanism and transition point for optimizing the material and vehicle design. In this study, we investigated the transition of the deformation mechanism during the high-temperature uniaxial tensile deformation of the AZ31 Mg alloy. At a test temperature of 523 K and an initial strain rate of 3×10−3 s-1, the AZ31 Mg alloy (mean grain size: ~5 μm exhibited stable deformation behavior and the deformation mechanism changed to one dominated by grain boundary sliding.

  10. Quasi-dynamic pressure and temperature initiated βδ solid phase transitions in HMX

    Science.gov (United States)

    Zaug, Joseph M.; Farber, Daniel L.; Craig, Ian M.; Blosch, Laura L.; Shuh, David K.; Hansen, Donald W.; Aracne-Ruddle, Chantel M.

    2000-04-01

    The phase transformation of β-HMX (>0.5% RDX) to δ phase has been studied for over twenty years and more recently with an high-contrast optical second harmonic generation technique. Shock studies of the plastic binder composites of HMX have indicated that the transition is perhaps irreversible, a result that concurs with the static pressure results published by F. Goetz et al. [1] in 1978. However, the stability field favors the β polymorph over δ as pressure is increased (up to 5.4 GPa) along any thermodynamically reasonable isotherm. In this experiment, strict control of pressure and temperature is maintained while x-ray and optical diagnostics are applied to monitor the conformational dynamics of HMX. Unlike the temperature induced β→δ transition, the pressure induced is heterogeneous in nature. The 1 bar 25 °C δ→β transition is not immediate, occuring over tens of hours. Transition points and kinetics are path dependent and consequently this paper describes our work in progress.

  11. Glass-transition temperature gradient in nanocomposites: evidence from nuclear magnetic resonance and differential scanning calorimetry.

    Science.gov (United States)

    Papon, Aurélie; Montes, Hélène; Hanafi, Mohamed; Lequeux, François; Guy, Laurent; Saalwächter, Kay

    2012-02-10

    The slowing-down of the dynamics of a polymer chain near a surface has been observed for many years now. Here we show that the behavior of model nanocomposites can be quantitatively described with a gradient of glass-transition temperature. We describe with a single parameter-the range of this gradient-the temperature and solvent effect on the spin relaxation dynamics. Moreover, this parameter allows a quantitative description of the nanocomposite calorimetric response from the one of the bulk polymer.

  12. Spatially resolved quantitative mapping of thermomechanical properties and phase transition temperatures using scanning probe microscopy

    Science.gov (United States)

    Jesse, Stephen; Kalinin, Sergei V; Nikiforov, Maxim P

    2013-07-09

    An approach for the thermomechanical characterization of phase transitions in polymeric materials (polyethyleneterephthalate) by band excitation acoustic force microscopy is developed. This methodology allows the independent measurement of resonance frequency, Q factor, and oscillation amplitude of a tip-surface contact area as a function of tip temperature, from which the thermal evolution of tip-surface spring constant and mechanical dissipation can be extracted. A heating protocol maintained a constant tip-surface contact area and constant contact force, thereby allowing for reproducible measurements and quantitative extraction of material properties including temperature dependence of indentation-based elastic and loss moduli.

  13. Extraction of aromatic compounds using ionic liquids and low transition temperature mixtures as separation agents

    OpenAIRE

    Fernandez Requejo, Patricia

    2015-01-01

    The main objective of this thesis is the evaluation of the feasibility of two types of designer solvents, ionic liquids (ILs) and low transition temperature mixtures (LTTMs), as extraction agents to improve the efficiency and/or sustainability of the separation of aromatic hydrocarbons from their mixtures with aliphatic hydrocarbons. The research about the applicability of the ionic liquids as entrainers for the separation of aromatic/aliphatic mixtures was developed through the experimental ...

  14. Double sudden transitions of geometric discord at finite-temperature in the framework of stochastic description

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Wei; Luo, Da-Wei; Xu, Jing-Bo, E-mail: xujb@zju.edu.cn [Zhejiang Institute of Modern Physics and Physics Department, Zhejiang University, Hangzhou 310027 (China)

    2014-06-28

    We investigate the phenomenon of double sudden transitions in geometric quantum correlations for a system consisting of a bare qubit and a qubit locally coupled to its finite-temperature heat environment with an Ohmic spectrum in the framework of stochastic description. Moreover, we explore the possibility of protecting the geometric discord between the two qubits and prolonging the time during which the geometric discord remains constant by applying Bang-Bang pulses.

  15. Temperature Measurements in the Solar Transition Region Using N III Line Intensity Ratios

    Science.gov (United States)

    Doron, R.; Doschek, G. A.; Laming, J. M.; Feldman, U.; Bhatia, A. K.

    2003-01-01

    UV emission from B-like N and O ions a rather rare opportunity for recording spectral lines in a narrow wavelength range that can potentially be used to derive temperatures relevant to the solar transition region. In these ions, the line intensity ratios of the type (2s2p(sup 2) - 2p(sup 3)) / (2s(sup 2)2p - 2s2p(sup 2)) are very sensitive to the electron temperature. Additionally, the lines involving the ratios fall within a range of only - 12 A; in N III the lines fall in the 980 - 992 A range and in O IV in the 780 - 791 A range. In this work, we explore the use of these atomic systems, primarily in N III, for temperature diagnostics of the transition region by analyzing UV spectra obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory (SOHO). The N III temperature-sensitive line ratios are measured in more than 60 observations. Most of the measured ratios correspond to temperatures in the range 5.7x10(exp 4) - 6.7x10(exp 4) K. This range is considerably lower than the calculated temperature of maximum abundance of N III, which is approx. 7.6x10(exp 4) K. Detailed analysis of the spectra further indicates that the measured ratios are probably somewhat overestimated due to resonant scattering effects in the 2s(sup 2)2p - 2s2p(sup 2) lines and small blends in the 2s2p(sup 2) - 2p3 lines. Actual lower ratios would only increase the disagreement between the ionization balance calculations and present temperature measurements based on a collisional excitation model. In the case of the O IV spectra, we determined that due to the close proximity in wavelength of the weak line (2s2p(sup 2)-2p3 transitions) to a strong Ne VIII line, sufficiently accurate ratio measurements cannot be obtained. Subject headings: atomic data --- atomic processes --- Sun: transition region --- Sun: U V radiation --- techniques: spectroscopic

  16. Temperature decline thermography for laminar-turbulent transition detection in aerodynamics

    Science.gov (United States)

    von Hoesslin, Stefan; Stadlbauer, Martin; Gruendmayer, Juergen; Kähler, Christian J.

    2017-09-01

    Detailed knowledge about laminar-turbulent transition and heat transfer distribution of flows around complex aerodynamic components are crucial to achieve highest efficiencies in modern aerodynamical systems. Several measurement techniques have been developed to determine those parameters either quantitatively or qualitatively. Most of them require extensive instrumentation or give unreliable results as the boundary conditions are often not known with the required precision. This work introduces the simple and robust temperature decline method to qualitatively detect the laminar-turbulent transition and the respective heat transfer coefficients on a surface exposed to an air flow, according to patent application Stadlbauer et al. (Patentnr. WO2014198251 A1, 2014). This method provides results which are less sensitive to control parameters such as the heat conduction into the blade material and temperature inhomogeneities in the flow or blade. This method was applied to measurements with NACA0018 airfoils exposed to the flow of a calibration-free jet at various Reynolds numbers and angles of attack. For data analysis, a post-processing method was developed and qualified to determine a quantity proportional to the heat transfer coefficient into the flow. By plotting this quantity for each pixel of the surface, a qualitative, two-dimensional heat transfer map was obtained. The results clearly depicted the areas of onset and end of transition over the full span of the model and agreed with the expected behavior based on the respective flow condition. To validate the approach, surface hotfilm measurements were conducted simultaneously on the same NACA profile. Both techniques showed excellent agreement. The temperature decline method allows to visualize laminar-turbulent transitions on static or moving parts and can be applied on a very broad range of scales—from tiny airfoils up to large airplane wings.

  17. Low-temperature structure anomalies in CuNCN. Manifestations of RVB phase transitions?

    Science.gov (United States)

    Tchougréeff, A L; Dronskowski, R

    2013-10-30

    We propose a new frustrated Heisenberg antiferromagnetic model with spatially anisotropic exchange parameters Jc, Ja, and Jac, extending along the c, a, and a ± c (c-a-ca model) lattice directions, and apply it to describe the fascinating physics of copper carbodiimide, CuNCN, assuming the resonating valence bond (RVB) type of its phases. This explains within a unified picture the intriguing absence of magnetic order in CuNCN. We further present a parameters-temperature phase diagram of the c-a-ca-RVB model in the high-temperature approximation. Eight different phases including Curie and Pauli paramagnets (respectively, in disordered and 1D- or Q1D-RVB phases) and (pseudo)gapped (quasi-Arrhenius) paramagnets (2D-RVB phases) are possible. By adding magnetostriction and elastic terms to the model, we derive possible structural manifestations of RVB phase transitions. Assuming a sequence of RVB phase transitions to occur in CuNCN with decreasing temperature, several anomalies observed in the temperature course of the lattice constants are explained.

  18. Temperature dependent electrical transport in single Ge nanowires near insulator-metal transition

    Science.gov (United States)

    Raychaudhuri, Arup Kumar; Seth, Shaili; Das, Kaustuv

    We report low temperature (4K Resolution Transmission Electron Microscope and established their crystalline quality. A single nanowire dispersed on a Si/SiO2 substrate was connected by Cr/Au contacts made by electron beam lithography in 2-probe / 4-probe configurations. The undoped nanowires have a room temperature resistivity (ρ) of 2 ohm.cm or more (estimated carrier concentration ~1015/cm3) and below the 25K (where it shows carrier freeze out) the ρ rises to high value of 35 ohm.cm. For nanowires with ρ <= .01 ohm.cm at 300K , low temperature ρ becomes finite, signaling transition to a metallic state with negative temperature co-efficient of ρ. The critical composition for the insulator-metal transition is more than an order higher than that observed in the bulk. At low T (<25K) resistivity data in this regime can be fitted to weak-localization form ρ =ρ0 - aTp/2 with ρ0 the NW's ~ 0.5-3.5 mohm.cm, with the exponent p ~ 3-4 as expected from theoretical predictions. Acknowldge Financial Support from Department od Science and Technology, Government of India for Sponsored Project.

  19. Temperature-driven topological transition in 1T'-MoTe2

    Science.gov (United States)

    Berger, Ayelet Notis; Andrade, Erick; Kerelsky, Alexander; Edelberg, Drew; Li, Jian; Wang, Zhijun; Zhang, Lunyong; Kim, Jaewook; Zaki, Nader; Avila, Jose; Chen, Chaoyu; Asensio, Maria C.; Cheong, Sang-Wook; Bernevig, Bogdan A.; Pasupathy, Abhay N.

    2018-01-01

    The topology of Weyl semimetals requires the existence of unique surface states. Surface states have been visualized in spectroscopy measurements, but their connection to the topological character of the material remains largely unexplored. 1T'-MoTe2, presents a unique opportunity to study this connection. This material undergoes a phase transition at 240 K that changes the structure from orthorhombic (putative Weyl semimetal) to monoclinic (trivial metal), while largely maintaining its bulk electronic structure. Here, we show from temperature-dependent quasiparticle interference measurements that this structural transition also acts as a topological switch for surface states in 1T'-MoTe2. At low temperature, we observe strong quasiparticle scattering, consistent with theoretical predictions and photoemission measurements for the surface states in this material. In contrast, measurements performed at room temperature show the complete absence of the scattering wavevectors associated with the trivial surface states. These distinct quasiparticle scattering behaviors show that 1T'-MoTe2 is ideal for separating topological and trivial electronic phenomena via temperature-dependent measurements.

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

    Science.gov (United States)

    Davis, Paul M.

    2017-05-01

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

  1. Reproducible technique for fabrication of thin films of high transition temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Mankiewich, P.M.; Scofield, J.H.; Skocpol, W.J.; Howard, R.E.; Dayem, A.H.; Good, E.

    1987-11-23

    We report on a new process to make films of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/ using coevaporation of Y, Cu, and BaF/sub 2/ on SrTiO/sub 3/ substrates. The films have high transition temperatures (up to 91 K for a full resistive transition), high critical current densities (10/sup 6/ A/cm/sup 2/ at 81 K), and a reduced sensitivity to fabrication and environmental conditions. Because of the lower reactivity of the films, we have been able to pattern them in both the pre-annealed and post-annealed states using conventional positive photoresist technology.

  2. Bifurcation Theory of the Transition to Collisionless Ion-temperature-gradient-driven Plasma Turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Kolesnikov, R.A.; Krommes, J.A.

    2005-09-22

    The collisionless limit of the transition to ion-temperature-gradient-driven plasma turbulence is considered with a dynamical-systems approach. The importance of systematic analysis for understanding the differences in the bifurcations and dynamics of linearly damped and undamped systems is emphasized. A model with ten degrees of freedom is studied as a concrete example. A four-dimensional center manifold (CM) is analyzed, and fixed points of its dynamics are identified and used to predict a ''Dimits shift'' of the threshold for turbulence due to the excitation of zonal flows. The exact value of that shift in terms of physical parameters is established for the model; the effects of higher-order truncations on the dynamics are noted. Multiple-scale analysis of the CM equations is used to discuss possible effects of modulational instability on scenarios for the transition to turbulence in both collisional and collisionless cases.

  3. Structural stability and phase transition of Bi 2 Te 3 under high pressure and low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J. L.; Zhang, S. J.; Zhu, J. L.; Liu, Q. Q.; Wang, X. C.; Jin, C. Q.; Yu, J. C.

    2017-09-01

    Structural stability and phase transition of topological insulator Bi2Te3 were studied via angle-dispersive synchrotron radiation X-ray diffraction under high pressure and low temperature condition. The results manifest that the R-3m phase (phase I) is stable at 8 K over the pressure range up to 10 GPa and phase transition occurs between 8 K and 45 K at 8 GPa. According to the Birch-Murnaghan equation of state, the bulk modulus at ambient pressure B0 was estimated to be 45 ± 3 GPa with the assumption of B0' = 4. The structural robustness of phase I at 8 K suggests that the superconductivity below 10 GPa is related to phase I. Topological properties of superconducting Bi2Te3 phase under pressure were discussed.

  4. Impact of caramelization on the glass transition temperature of several caramelized sugars. Part I: Chemical analyses.

    Science.gov (United States)

    Jiang, Bin; Liu, Yeting; Bhandari, Bhesh; Zhou, Weibiao

    2008-07-09

    This study aims to investigate the relationship between caramelization of several sugars including fructose, glucose, and sucrose and their glass transition temperature (Tg). Differential scanning calorimetry (DSC) was used for creating caramelized sugar samples as well as determining their glass transition temperature, which was found to decrease first and then increase as the holding time at the highest temperature increased. The extent of caramelization was quantified by UV-vis absorbance measurement and high-performance liquid chromatography analysis. Results showed that the amount of small molecules from the degradation of sugar increased very fast at the beginning of heating, and this increase slowed down in the later stage of caramelization. On the other hand, there was a lag phase in the formation of large molecules from the degradation of sugar at the beginning of heating, followed by a fast increase in the later stage of caramelization. The obtained results clearly indicate the impact of melting condition on the T g of sugars through formation of intermediates and end products of caramelization. Generally, when the heating condition is relatively mild, small molecules are formed first by decomposition of the sugar, which leads to a decrease of the overall Tg, and as the heating time becomes longer and/or the heating condition becomes more severe, polymerization takes over and more large molecules are formed, which results in an increase of the overall Tg. Mathematical modeling of the relationship will be presented as part II of the study in a separate paper.

  5. Structure and dynamical intra-molecular heterogeneity of star polymer melts above glass transition temperature

    Science.gov (United States)

    Chremos, Alexandros; Glynos, Emmanouil; Green, Peter F.

    2015-01-01

    Structural and dynamical properties of star melts have been investigated with molecular dynamics simulations of a bead-spring model. Star polymers are known to be heterogeneous, but a systematic simulation study of their properties in melt conditions near the glass transition temperature was lacking. To probe their properties, we have expanded from linear to star polymers the applicability of Dobkowski's chain-length dependence correlation function [Z. Dobkowski, Eur. Polym. J. 18, 563 (1982)]. The density and the isokinetic temperature, based on the canonical definition of the laboratory glass-transition, can be described well by the correlation function and a subtle behavior manifests as the architecture becomes more complex. For linear polymer chains and low functionality star polymers, we find that an increase of the arm length would result in an increase of the density and the isokinetic temperature, but high functionality star polymers have the opposite behavior. The effect between low and high functionalities is more pronounced for short arm lengths. Complementary results such as the specific volume and number of neighbors in contact provide further insights on the subtle relation between structure and dynamics. The findings would be valuable to polymer, colloidal, and nanocomposites fields for the design of materials in absence of solution with the desired properties.

  6. Low-temperature thermal transport and thermopower of monolayer transition metal dichalcogenide semiconductors

    Science.gov (United States)

    Sengupta, Parijat; Tan, Yaohua; Klimeck, Gerhard; Shi, Junxia

    2017-10-01

    We study the low temperature thermal conductivity of single-layer transition metal dichalcogenides (TMDCs). In the low temperature regime where heat is carried primarily through transport of electrons, thermal conductivity is linked to electrical conductivity through the Wiedemann-Franz law (WFL). Using a k.p Hamiltonian that describes the K and K{\\prime} valley edges, we compute the zero-frequency electric (Drude) conductivity using the Kubo formula to obtain a numerical estimate for the thermal conductivity. The impurity scattering determined transit time of electrons which enters the Drude expression is evaluated within the self-consistent Born approximation. The analytic expressions derived show that low temperature thermal conductivity (1) is determined by the band gap at the valley edges in monolayer TMDCs and (2) in presence of disorder which can give rise to the variable range hopping regime, there is a distinct reduction. Additionally, we compute the Mott thermopower and demonstrate that under a high frequency light beam, a valley-resolved thermopower can be obtained. A closing summary reviews the implications of results followed by a brief discussion on applicability of the WFL and its breakdown in context of the presented calculations.

  7. THE SEMICONDUCTOR THERMOELECTRIC DEVICE FOR TEMPERATURE CONTROL OF COMPUTER PROCESSOR WITH USE OF MATERIALS IN THE CONDITION OF PHASE TRANSITION

    Directory of Open Access Journals (Sweden)

    H. M. Gadjiyev

    2015-01-01

    Full Text Available The article deals with the cooling system computer processor on the based sublimation phase transitions, allowing to provide temperature control mode in a transient thermal load, which will prevent the failure of the VLSI processor. 

  8. High count-rate study of two TES x-ray microcalorimeters with different transition temperatures

    Science.gov (United States)

    Lee, Sang-Jun; Adams, Joseph S.; Bandler, Simon R.; Betancourt-Martinez, Gabriele L.; Chervenak, James A.; Eckart, Megan E.; Finkbeiner, Fred M.; Kelley, Richard L.; Kilbourne, Caroline A.; Porter, Frederick S.; Sadleir, John E.; Smith, Stephen J.; Wassell, Edward J.

    2017-10-01

    We have developed transition-edge sensor (TES) microcalorimeter arrays with high count-rate capability and high energy resolution to carry out x-ray imaging spectroscopy observations of various astronomical sources and the Sun. We have studied the dependence of the energy resolution and throughput (fraction of processed pulses) on the count rate for such microcalorimeters with two different transition temperatures (T c). Devices with both transition temperatures were fabricated within a single microcalorimeter array directly on top of a solid substrate where the thermal conductance of the microcalorimeter is dependent upon the thermal boundary resistance between the TES sensor and the dielectric substrate beneath. Because the thermal boundary resistance is highly temperature dependent, the two types of device with different T cs had very different thermal decay times, approximately one order of magnitude different. In our earlier report, we achieved energy resolutions of 1.6 and 2.3 eV at 6 keV from lower and higher T c devices, respectively, using a standard analysis method based on optimal filtering in the low flux limit. We have now measured the same devices at elevated x-ray fluxes ranging from 50 Hz to 1000 Hz per pixel. In the high flux limit, however, the standard optimal filtering scheme nearly breaks down because of x-ray pile-up. To achieve the highest possible energy resolution for a fixed throughput, we have developed an analysis scheme based on the so-called event grade method. Using the new analysis scheme, we achieved 5.0 eV FWHM with 96% throughput for 6 keV x-rays of 1025 Hz per pixel with the higher T c (faster) device, and 5.8 eV FWHM with 97% throughput with the lower T c (slower) device at 722 Hz.

  9. West Florida shelf circulation and temperature budget for the 1999 spring transition

    Science.gov (United States)

    He, Ruoying; Weisberg, Robert H.

    2002-01-01

    Mid-latitude continental shelves undergo a spring transition as the net surface heat flux changes from cooling to warming. Using in situ data and a numerical circulation model we investigate the circulation and temperature budget on the West Florida Continental Shelf (WFS) for the spring transition of 1999. The model is a regional adaptation of the primitive equation, Princeton Ocean Model forced by NCEP reanalysis wind and heat flux fields and by river inflows. Based on agreements between the modeled and observed fields we use the model to draw inferences on how the surface momentum and heat fluxes affect the seasonal and synoptic scale variability. We account for a strong southeastward current at mid-shelf by the baroclinic response to combined wind and buoyancy forcing, and we show how this local forcing leads to annually occurring cold and low salinity tongues. Through term-by-term analyses of the temperature budget we describe the WFS temperature evolution in spring. Heat flux largely controls the seasonal transition, whereas ocean circulation largely controls the synoptic scale variability. These two processes, however, are closely linked. Bottom topography and coastline geometry are important in generating regions of convergence and divergence. Rivers contribute to the local hydrography and are important ecologically. Along with upwelling, river inflows facilitate frontal aggregation of nutrients and the spring formation of a high concentration chlorophyll plume near the shelf break (the so-called ‘Green River’) coinciding with the cold, low salinity tongues. These features originate by local, shelf-wide forcing; the Loop Current is not an essential ingredient.

  10. Deformation, Stress Relaxation, and Crystallization of Lithium Silicate Glass Fibers Below the Glass Transition Temperature

    Science.gov (United States)

    Ray, Chandra S.; Brow, Richard K.; Kim, Cheol W.; Reis, Signo T.

    2004-01-01

    The deformation and crystallization of Li(sub 2)O (center dot) 2SiO2 and Li(sub 2)O (center dot) 1.6SiO2 glass fibers subjected to a bending stress were measured as a function of time over the temperature range -50 to -150 C below the glass transition temperature (Tg). The glass fibers can be permanently deformed at temperatures about 100 C below T (sub)g, and they crystallize significantly at temperatures close to, but below T,, about 150 C lower than the onset temperature for crystallization for these glasses in the no-stress condition. The crystallization was found to occur only on the surface of the glass fibers with no detectable difference in the extent of crystallization in tensile and compressive stress regions. The relaxation mechanism for fiber deformation can be best described by a stretched exponential (Kohlrausch-Williams-Watt (KWW) approximation), rather than a single exponential model.The activation energy for stress relaxation, Es, for the glass fibers ranges between 175 and 195 kJ/mol, which is considerably smaller than the activation energy for viscous flow, E, (about 400 kJ/mol) near T, for these glasses at normal, stress-free condition. It is suspected that a viscosity relaxation mechanism could be responsible for permanent deformation and crystallization of the glass fibers below T,

  11. Comparative High Field Magneto-transport Of Rare Earth Oxypnictides With Maximum Transition Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Balakirev, Fedor F [Los Alamos National Laboratory; Migliori, A [MPA-NHMFL; Riggs, S [NHMFL-FSU; Hunte, F [NHMFL-FSU; Gurevich, A [NHMFL-FSU; Larbalestier, D [NHMFL-FSU; Boebinger, G [NHMFL-FSU; Jaroszynski, J [NHMFL-FSU; Ren, Z [CHINA; Lu, W [CHINA; Yang, J [CHINA; Shen, X [CHINA; Dong, X [CHINA; Zhao, Z [CHINA; Jin, R [ORNL; Sefat, A [ORNL; Mcguire, M [ORNL; Sales, B [ORNL; Christen, D [ORNL; Mandrus, D [ORNL

    2008-01-01

    We compare magnetotransport of the three iron-arsenide-based compounds ReFeAsO (Re=La, Sm, Nd) in very high DC and pulsed magnetic fields up to 45 and 54 T, respectively. Each sample studied exhibits a superconducting transition temperature near the maximum reported to date for that particular compound. While high magnetic fields do not suppress the superconducting state appreciably, the resistivity, Hall coefficient, and critical magnetic fields, taken together, suggest that the phenomenology and superconducting parameters of the oxypnictide superconductors bridges the gap between MgB{sub 2} and YBCO.

  12. Trends in low-temperature water–gas shift reactivity on transition metals

    DEFF Research Database (Denmark)

    Schumacher, Nana Maria Pii; Boisen, Astrid; Dahl, Søren

    2005-01-01

    Low-temperature water–gas shift reactivity trends on transition metals were investigated with the use of a microkinetic model based on a redox mechanism. It is established that the adsorption energies for carbon monoxide and oxygen can describe to a large extent changes in the remaining activation...... that the redox mechanism dominates and to the neglect of adsorbate interactions, which play an important role at high coverages. The model predicts that the activity of copper can be improved by increasing the strengths with which carbon monoxide and oxygen are bonded to the surface, thus suggesting possible...

  13. Predicting the glass transition temperature as function of crosslink density and polymer interactions in rubber compounds

    Science.gov (United States)

    D'Escamard, Gabriella; De Rosa, Claudio; Auriemma, Finizia

    2016-05-01

    Crosslink sulfur density in rubber compounds and interactions in polymer blends are two of the composition elements that affect the rubber compound properties and glass transition temperature (Tg), which is a marker of polymer properties related to its applications. Natural rubber (NR), butadiene rubber (BR) and styrene-butadiene rubber (SBR) compounds were investigated using calorimetry (DSC) and dynamic mechanical analysis (DMA). The results indicate that the Di Marzio's and Schneider's Models predict with accuracy the dependence of Tg on crosslink density and composition in miscible blends, respectively, and that the two model may represent the base to study the relevant "in service" properties of real rubber compounds.

  14. Understanding the physical stability of freeze dried dosage forms from the glass transition temperature of the amorphous components.

    Science.gov (United States)

    Fitzpatrick, Shaun; Saklatvala, Robert

    2003-12-01

    Modulated differential scanning calorimetry has been applied to understanding the long-term physical stability of freeze-dried units. It is known that these units are liable to contract on exposure to elevated temperature or humidity. The contraction occurs when the storage temperature is above the glass transition temperature of the amorphous components in the system. The effect of moisture content on the glass transition temperature of the amorphous components in the system has been studied. By combining this information with the moisture sorption isotherm it has been demonstrated that it is possible to predict the temperature and humidity conditions that will induce contraction of the unit. The magnitude of the glass transition temperature is composed of the contribution of each of the amorphous components in the system. It is proposed that it should be possible to develop a more robust system by the rational selection of excipients that increase the glass transition temperature or by modification of the processing conditions to promote crystallization of components that would otherwise depress the glass transition temperature. Copyright 2003 Wiley-Liss, Inc.

  15. Ionic Hamiltonians for transition metal atoms: effective exchange coupling and Kondo temperature

    Science.gov (United States)

    Flores, F.; Goldberg, E. C.

    2017-02-01

    An ionic Hamiltonian for describing the interaction between a metal and a d-shell transition metal atom having an orbital singlet state is introduced and its properties analyzed using the Schrieffer-Wolf transformation (exchange coupling) and the poor man’s scaling method (Kondo temperature). We find that the effective exchange coupling between the metal and the atom has an antiferromagnetic or a ferromagnetic interaction depending on the kind of atomic fluctuations, either S\\to S-1/2 or S\\to S+1/2 , associated with the metal-atom coupling. We present a general scheme for all those processes and calculate, for the antiferromagnetic interaction, the corresponding Kondo-temperature.

  16. Low transition temperature mixtures as innovative and sustainable CO2 capture solvents.

    Science.gov (United States)

    Zubeir, Lawien F; Lacroix, Mark H M; Kroon, Maaike C

    2014-12-11

    The potential of three newly discovered low transition temperature mixtures (LTTMs) is explored as sustainable substituents for the traditional carbon dioxide (CO2) absorbents. LTTMs are mixtures of two solid compounds, a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA), which form liquids upon mixing with melting points far below those of the individual compounds. In this work the HBD is lactic acid and the HBAs are tetramethylammonium chloride, tetraethylammonium chloride, and tetrabutylammonium chloride. These compounds were found to form LTTMs for the first time at molar ratios of HBD:HBA = 2:1. First, the LTTMs were characterized by determining the thermal operating window (e.g., decomposition temperature and glass transition temperature) and the physical properties (e.g., density and viscosity). Thereafter, the phase behavior of CO2 with the LTTMs has been measured using a gravimetric magnetic suspension balance operating in the static mode at 308 and 318 K and pressures up to 2 MPa. The CO2 solubility increased with increasing chain length, increasing pressure, and decreasing temperature. The Peng-Robinson equation of state was applied to correlate the phase equilibria. From the solubility data, thermodynamic parameters were determined (e.g., Henry's law coefficient and enthalpy of absorption). The heat of absorption was found to be similar to that in conventional physical solvents (-11.21 to -14.87 kJ·mol(-1)). Furthermore, the kinetics in terms of the diffusion coefficient of CO2 in all LTTMs were determined (10(-11)-10(-10) m(2)·s(-1)). Even though the CO2 solubilities in the studied LTTMs were found to be slightly lower than those in thoroughly studied conventional physical solvents, LTTMs are a promising new class of absorbents due to their low cost, their environmentally friendly character, and their easy tunability, allowing further optimization for carbon capture.

  17. Substrate effects on photoluminescence and low temperature phase transition of methylammonium lead iodide hybrid perovskite thin films

    Science.gov (United States)

    Shojaee, S. A.; Harriman, T. A.; Han, G. S.; Lee, J.-K.; Lucca, D. A.

    2017-07-01

    We examine the effects of substrates on the low temperature photoluminescence (PL) spectra and phase transition in methylammonium lead iodide hybrid perovskite (CH3NH3PbI3) thin films. Structural characterization at room temperature with X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy indicated that while the chemical structure of films deposited on glass and quartz was similar, the glass substrate induced strain in the perovskite films and suppressed the grain growth. The luminescence response and phase transition of the perovskite thin films were studied by PL spectroscopy. The induced strain was found to affect both the room temperature and low temperature PL spectra of the hybrid perovskite films. In addition, it was found that the effects of the glass substrate inhibited a tetragonal to orthorhombic phase transition such that it occurred at lower temperatures.

  18. Influence of temperature on transit times and microwave noise performances of SiGe HBT

    Science.gov (United States)

    Diaz-Albarran, L. M.; Ramirez-Garcia, E.; Zerounian, N.; Aniel, F.; Rodriguez-Mendez, L. M.; Valdez-Perez, D.; Galaz-Larios, M. C.; Enciso-Aguilar, M. A.

    2016-03-01

    The influence of temperature (300 K and 40 K) on intrinsic transit times and microwave noise performances of silicon germanium (SiGe) heterojunction bipolar transistors (HBTs) is investigated. At 300 K, we compared measured and modelled S-parameters and four noise parameters, and we found a good agreement. At 40 K, we compared measured and modelled S-parameters, and we deduced noise performances from the S-parameter measurements. The electric model includes correlated junction noise sources and a proper extraction of the transit times involved in these sources. Moreover, the microwave noise model considers all the physical phenomena that impact noise performances in SiGe HBTs. We analysed three devices having different Ge content (10%-20%, 10%-25% and 10%-30%). At 40 K, the device with 10%-25% reaches one of the lowest base transit times (τ B), the lowest minimum noise figure (NFmin), and the lowest equivalent noise resistance (R n), for operation frequencies up to the maximum device dynamic performances (f ≈ f T) These results demonstrate the excellent potential to develop cryogenic applications of SiGe HBTs.

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

    Science.gov (United States)

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

    2016-05-01

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

  20. Impact of caramelization on the glass transition temperature of several caramelized sugars. Part II: Mathematical modeling.

    Science.gov (United States)

    Jiang, Bin; Liu, Yeting; Bhandari, Bhesh; Zhou, Weibiao

    2008-07-09

    Further to part I of this study, this paper discusses mathematical modeling of the relationship between caramelization of several sugars including fructose, glucose, and sucrose and their glass transition temperatures ( T g). Differential scanning calorimetry (DSC) was used for creating caramelized sugar samples and determining their glass transition temperatures ( T g). UV-vis absorbance measurement and high-performance liquid chromatography (HPLC) analysis were used for quantifying the extent of caramelization. Specifically, absorbances at 284 and 420 nm were obtained from UV-vis measurement, and the contents of sucrose, glucose, fructose, and 5-hydroxymethyl-furfural (HMF) in the caramelized sugars were obtained from HPLC measurements. Results from the UV and HPLC measurements were correlated with the Tg values measured by DSC. By using both linear and nonlinear regressions, two sets of mathematical models were developed for the prediction of Tg values of sugar caramels. The first set utilized information obtained from both UV-vis measurement and HPLC analysis, while the second set utilized only information from the UV-vis measurement, which is much easier to perform in practice. As a caramelization process is typically characterized by two stages, separate models were developed for each of the stages within a set. Furthermore, a third set of nonlinear equations were developed, serving as criteria to decide at which stage a caramelized sample is. The models were evaluated through a validation process.

  1. Low temperature synthesis of lamellar transition metal oxides containing surfactant ions

    Energy Technology Data Exchange (ETDEWEB)

    Janauer, G.G.; Chen, R.; Dobley, A.D.; Zavalij, P.Y.; Whittingham, M.S. [State Univ. of New York, Binghamton, NY (United States)

    1997-09-01

    Recently there has been much interest in reacting vanadium oxides hydrothermally with cationic surfactants to form novel layered compounds. A series of new transition metal oxides, however, has also been formed at or near room temperature in open containers. Synthesis, characterization, and proposed mechanisms of formation are the focus of this work. Low temperature reactions of vanadium pentoxide and ammonium (DTA) transition metal oxides with long chain amine surfactants, such as dodecyltrimethylammonium bromide yielded interesting new products many of which are layered phases. DTA{sub 4}H{sub 2}V{sub 10}O{sub 28}{center_dot}8H{sub 2}O, a layered highly crystalline phase, is the first such phase for which a single crystal X-ray structure has been determined. The unit cell for this material was found to be triclinic with space group P {bar 1} and dimensions a = 9.895(1){angstrom}, b = 11.596(1){angstrom}, c = 21.924(1){angstrom}, {alpha} = 95.153(2){degree}, {beta} = 93.778(1){degree}, and {gamma} = 101.360(1){degree}. Additionally, the authors synthesized a dichromate phase and a manganese chloride layered phase, with interlayer spacings of 26.8{angstrom}, and 28.7{angstrom} respectively. The structure, composition, and synthesis of the vanadium compound are described, as well as the synthesis and preliminary characterization of the new chromium and manganese materials.

  2. Treatments of intrinsic viscosity and glass transition temperature data of poly(2,6-dimethylphenylmethacrylate)

    Energy Technology Data Exchange (ETDEWEB)

    Hamidi, Nasrollah; Massoudi, Ruhullah

    2003-03-05

    A useful relationship, ln(T{sub g})=ln(T{sub g,{infinity}})-m[{eta}]{sup -{nu}}, between intrinsic viscosity and glass transition temperature for a series of homologous polymers was obtained by combining the Mark-Houwink-Kuhn-Sakurada (MHKS) relation for intrinsic viscosity and molecular mass, and the Fox-Flory equation for glass transition temperature and number-average molecular mass. This relationship was applied to poly(2,6-dimethylphenylmethacrylate) (PDMPh) in a variety of solvents (ideal to good) such as toluene, tetrahydrofuran/water, tetrahydrofuran, and chlorobenzene systems. The parameter {alpha} estimated by this procedure in toluene, tetrahydrofuran/water, tetrahydrofuran, and chlorobenzene systems are 0.50{sub 6}, 0.51{sub 1}, 0.56{sub 7}, and 0.67{sub 3}, respectively which are in agreement with those of Mark-Houwink-Kuhn-Sakurada values by less than 5% differences. The T{sub g,{infinity}} quantity estimated from this equation also is within the standard deviation of that obtained from the Fox-Flory method. The m quantity is increasing as the thermodynamic quality of the solvent improves, therefore, m may be considered as an indicator of coil conformations in a given solvent.

  3. Thermodynamic Properties, Sorption Isotherms and Glass Transition Temperature of Cape Gooseberry (Physalis peruviana L.

    Directory of Open Access Journals (Sweden)

    Jessica López

    2014-01-01

    Full Text Available Adsorption and desorption isotherms of fresh and dried Cape gooseberry (Physalis peruviana L. were determined at three temperatures (20, 40 and 60 °C using a gravimetric technique. The data obtained were fitted to several models including Guggenheim-Anderson- De Boer (GAB, Brunauer-Emmett-Teller (BET, Henderson, Caurie, Smith, Oswin, Halsey and Iglesias-Chirife. A non-linear least square regression analysis was used to evaluate the models. The Iglesias-Chirife model fitted best the experimental data. Isosteric heat of sorption was also determined from the equilibrium sorption data using the Clausius-Clapeyron equation and was found to decrease exponentially with increasing moisture content. The enthalpy-entropy compensation theory was applied to the sorption isotherms and indicated an enthalpy-controlled sorption process. Glass transition temperature (Tg of Cape gooseberry was also determined by differential scanning calorimetry and modelled as a function of moisture content with the Gordon-Taylor, the Roos and the Khalloufi models, which proved to be excellent tools for predicting glass transition of Cape gooseberry.

  4. Transition metal doping of GaSe implemented with low temperature liquid phase growth

    Science.gov (United States)

    Lei, Nuo; Sato, Youhei; Tanabe, Tadao; Maeda, Kensaku; Oyama, Yutaka

    2017-02-01

    Our group works on improving the conversion efficiencies of terahertz (THz) wave generation using GaSe crystals. The operating principle is based on difference frequency generation (DFG) which has the advantages such as high output power, a single tunable frequency, and room temperature operation. In this study, GaSe crystals were grown by the temperature difference method under controlled vapor pressure (TDM-CVP). It is a liquid phase growth method with temperature 300 °C lower than that of the Bridgman method. Using this method, the point defects concentration is decreased and the polytype can be controlled. The transition metal Ti was used to dope the GaSe in order to suppress free carrier absorption in the low frequency THz region. As a result, a deep acceptor level of 38 meV was confirmed as being formed in GaSe with 1.4 at% Ti doping. Compared with undoped GaSe, a decrease in carrier concentration ( 1014 cm-3) at room temperature was also confirmed. THz wave transmittance measurements reveal the tendency for the absorption coefficient to increase as the amount of dopant is increased. It is expected that there is an optimum amount of dopant.

  5. Molecular relaxation behavior and isothermal crystallization above glass transition temperature of amorphous hesperetin.

    Science.gov (United States)

    Shete, Ganesh; Khomane, Kailas S; Bansal, Arvind Kumar

    2014-01-01

    The purpose of this paper was to investigate the relaxation behavior of amorphous hesperetin (HRN), using dielectric spectroscopy, and assessment of its crystallization kinetics above glass transition temperature (Tg ). Amorphous HRN exhibited both local (β-) and global (α-) relaxations. β-Relaxation was observed below Tg , whereas α-relaxation prominently emerged above Tg . β-Relaxation was found to be of Johari-Goldstein type and was correlated with α-process by coupling model. Secondly, isothermal crystallization experiments were performed at 363 K (Tg + 16.5 K), 373 K (Tg + 26.5 K), and 383 K (Tg + 36.5 K). The kinetics of crystallization, obtained from the normalized dielectric strength, was modeled using the Avrami model. Havriliak-Negami (HN) shape parameters, αHN and αHN .βHN , were analyzed during the course of crystallization to understand the dynamics of amorphous phase during the emergence of crystallites. HN shape parameters indicated that long range (α-like) were motions affected to a greater extent than short range (β-like) motions during isothermal crystallization studies at all temperature conditions. The variable behavior of α-like motions at different isothermal crystallization temperatures was attributed to evolving crystallites with time and increase in electrical conductivity with temperature. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

  6. Renormalization group theory for temperature-driven first-order phase transitions in scalar models

    Science.gov (United States)

    Liang, Ning; Zhong, Fan

    2017-12-01

    We study the scaling and universal behavior of temperature-driven first-order phase transitions in scalar models. These transitions are found to exhibit rich phenomena, though they are controlled by a single complex-conjugate pair of imaginary fixed points of ϕ 3 theory. Scaling theories and renormalization group theories are developed to account for the phenomena, and three universality classes with their own hysteresis exponents are found: a field-like thermal class, a partly thermal class, and a purely thermal class, designated, respectively, as Thermal Classes I, II, and III. The first two classes arise from the opposite limits of the scaling forms proposed and may cross over to each other depending on the temperature sweep rate. They are both described by a massless model and a purely massive model, both of which are equivalent and are derived from ϕ 3 theory via symmetry. Thermal Class III characterizes the cooling transitions in the absence of applied external fields and is described by purely thermal models, which include cases in which the order parameters possess different symmetries and thus exhibit different universality classes. For the purely thermal models whose free energies contain odd-symmetry terms, Thermal Class III emerges only at the mean-field level and is identical to Thermal Class II. Fluctuations change the model into the other two models. Using the extant three- and two-loop results for the static and dynamic exponents for the Yang-Lee edge singularity, respectively, which falls into the same universality class as ϕ 3 theory, we estimate the thermal hysteresis exponents of the various classes to the same precision. Comparisons with numerical results and experiments are briefly discussed.

  7. The Effects of Temperature and Birth Weight on the Transition Rate of Hypothermia in Hospitalized Neonates Using Markov Models

    Directory of Open Access Journals (Sweden)

    F Nayeri

    2012-08-01

    Full Text Available Background: Hypothermia is an important determinant of survival in newborns, especially among low-birth-weight ones. Prolonged hypothermia leads to edema, generalized hemorrhage, jaundice and ultimately death. This study was undertaken to examine the factors affecting transition from hypothermic state in neonates.Methods: The study consisted of 439 neonates hospitalized in NICU of Valiasr in Tehran, Iran in 2005. The neonates' rectal temperature was measured immediately after birth and every 30 minutes afterwards, until neonates passed hypothermia stages. In order to estimate the rate of transition from neonatal hypothermic state, we used multi-state Markov models with two covariates, birth weight and environmental temperature. We also used R package to fit the model.Results: Estimated transition rates from severe hypothermia and mild hypothermia were 0.1192 and 0.0549 per minute, respectively. Weight had a significant effect on transition from hypothermia to normal condition (95% CI: 0.1364-0.4165, P<0.001. Environmental temperature significantly affected the transition from hypothermia to normal stage (95% CI: 0.0439-0.4963, P<0.001.Conclusion: The results of this study showed that neonates with normal weight and neonates in an environmental temperature greater than 28 °C had a higher transition rate from hypothermia stages. Since birth weight at the time of delivery is not under the control of medical staff, keeping the environmental temperature in an optimum level could help neonates to pass through the hypothermia stages faster.

  8. High temperature phase transition of mixed (PuO2 + ThO2) investigated by laser melting

    NARCIS (Netherlands)

    Böhler, R.; Cakir, P.; Benes, O.; Hein, H.; Konings, R.J.M.; Manara, D.

    2014-01-01

    A laser heating approach combined with fast pyrometry in a thermal arrest method was used to provide new data for the melting/solidification phase transition in mixed (PuO2 + ThO2) at high temperature. At low concentration of ThO2 in PuO2 a minimum in the solidification temperature in the pseudo

  9. Mechanism of dehydroxylation temperature decrease and high temperature phase transition of coal-bearing strata kaolinite intercalated by potassium acetate.

    Science.gov (United States)

    Cheng, Hongfei; Liu, Qinfu; Cui, Xiaonan; Zhang, Qian; Zhang, Zhiliang; Frost, Ray L

    2012-06-15

    The thermal decomposition and dehydroxylation process of coal-bearing strata kaolinite-potassium acetate intercalation complex (CSKK) has been studied using X-ray diffraction (XRD), infrared spectroscopy (IR), thermal analysis, mass spectrometric analysis and infrared emission spectroscopy. The XRD results showed that the potassium acetate (KAc) have been successfully intercalated into coal-bearing strata kaolinite with an obvious basal distance increase of the first basal peak, and the positive correlation was found between the concentration of intercalation regent KAc and the degree of intercalation. As the temperature of the system is raised, the formation of KHCO(3), KCO(3) and KAlSiO(4), which is derived from the thermal decomposition or phase transition of CSKK, is observed in sequence. The IR results showed that new bands appeared, the position and intensities shift can also be found when the concentration of intercalation agent is raised. The thermal analysis and mass spectrometric analysis results revealed that CSKK is stable below 300°C, and the thermal decomposition products (H(2)O and CO(2)) were further proved by the mass spectrometric analysis. A comparison of thermal analysis results of original coal-bearing strata kaolinite and its intercalation complex gives new discovery that not only a new mass loss peak is observed at 285 °C, but also the temperature of dehydroxylation and dehydration of coal bearing strata kaolinite is decreased about 100 °C. This is explained on the basis of the interlayer space of the kaolinite increased obviously after being intercalated by KAc, which led to the interlayer hydrogen bonds weakened, enables the dehydroxylation from kaolinite surface more easily. Furthermore, the possible structural model for CSKK has been proposed, with further analysis required in order to prove the most possible structures. Copyright © 2012 Elsevier Inc. All rights reserved.

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

    DEFF Research Database (Denmark)

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

    2001-01-01

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

  11. Kinetics of low-temperature transitions and a reaction rate theory from non-equilibrium distributions

    Science.gov (United States)

    Aquilanti, Vincenzo; Coutinho, Nayara Dantas; Carvalho-Silva, Valter Henrique

    2017-03-01

    This article surveys the empirical information which originated both by laboratory experiments and by computational simulations, and expands previous understanding of the rates of chemical processes in the low-temperature range, where deviations from linearity of Arrhenius plots were revealed. The phenomenological two-parameter Arrhenius equation requires improvement for applications where interpolation or extrapolations are demanded in various areas of modern science. Based on Tolman's theorem, the dependence of the reciprocal of the apparent activation energy as a function of reciprocal absolute temperature permits the introduction of a deviation parameter d covering uniformly a variety of rate processes, from those where quantum mechanical tunnelling is significant and d 0, corresponding to the Pareto-Tsallis statistical weights: these generalize the Boltzmann-Gibbs weight, which is recovered for d = 0. It is shown here how the weights arise, relaxing the thermodynamic equilibrium limit, either for a binomial distribution if d > 0 or for a negative binomial distribution if d < 0, formally corresponding to Fermion-like or Boson-like statistics, respectively. The current status of the phenomenology is illustrated emphasizing case studies; specifically (i) the super-Arrhenius kinetics, where transport phenomena accelerate processes as the temperature increases; (ii) the sub-Arrhenius kinetics, where quantum mechanical tunnelling propitiates low-temperature reactivity; (iii) the anti-Arrhenius kinetics, where processes with no energetic obstacles are rate-limited by molecular reorientation requirements. Particular attention is given for case (i) to the treatment of diffusion and viscosity, for case (ii) to formulation of a transition rate theory for chemical kinetics including quantum mechanical tunnelling, and for case (iii) to the stereodirectional specificity of the dynamics of reactions strongly hindered by the increase of temperature. This article is part of

  12. Low Temperature Conductivity in n-Type Noncompensated Silicon below Insulator-Metal Transition

    Directory of Open Access Journals (Sweden)

    A. L. Danilyuk

    2017-01-01

    Full Text Available We investigate the transport properties of n-type noncompensated silicon below the insulator-metal transition by measuring the electrical and magnetoresistances as a function of temperature T for the interval 2–300 K. Experimental data are analyzed taking into account possible simple activation and hopping mechanisms of the conductivity in the presence of two impurity bands, the upper and lower Hubbard bands (UHB and LHB, resp.. We demonstrate that the charge transport develops with decreasing temperature from the band edge activation (110–300 K to the simple activation with much less energy associated with the activation motion in the UHB (28–90 K. Then, the Mott-type variable range hopping (VRH with spin dependent hops occurs (5–20 K. Finally, the VRH in the presence of the hard gap (HG between LHB and UHB (2–4 K takes place. We propose the empiric expression for the low T density of states which involves both the UHB and LHB and takes into account the crossover from the HG regime to the Mott-type VRH with increasing temperature. This allows us to fit the low T experimental data with high accuracy.

  13. Hydrogen detonation and detonation transition data from the High-Temperature Combustion Facility

    Energy Technology Data Exchange (ETDEWEB)

    Ciccarelli, G.; Boccio, J.L.; Ginsberg, T.; Finfrock, C. [Brookhaven National Lab., Upton, NY (United States)] [and others

    1996-03-01

    The BNL High-Temperature Combustion Facility (HTCF) is an experimental research tool capable of investigating the effects of initial thermodynamic state on the high-speed combustion characteristic of reactive gas mixtures. The overall experimental program has been designed to provide data to help characterize the influence of elevated gas-mixture temperature (and pressure) on the inherent sensitivity of hydrogen-air-steam mixtures to undergo detonation, on the potential for flames accelerating in these mixtures to transition into detonations, on the effects of gas venting on the flame-accelerating process, on the phenomena of initiation of detonations in these mixtures by jets of hot reactant products, and on the capability of detonations within a confined space to transmit into another, larger confined space. This paper presents results obtained from the completion of two of the overall test series that was designed to characterize high-speed combustion phenomena in initially high-temperature gas mixtures. These two test series are the intrinsic detonability test series and the deflagration-to-detonation (DDT) test series. A brief description of the facility is provided below.

  14. Chemical Structure And Glass Transition Temperature Of Ricinodendron Heudelotii Wood For Its Pulp Production Potential

    Directory of Open Access Journals (Sweden)

    Bolade M. Ogunleye

    2017-02-01

    Full Text Available The chemical structure and glass transition temperature of Ricinodendron heudelotii wood were studied using Attenuated total reflectance Fourier transform infrared FTIR spectroscopy and dynamic mechanical analysis DMA respectively. The thermal characteristic of R. heudelotii was conducted on N-methyl-2-pyrolidone saturated specimens while submerged under the same solvent at a temperature range from 130 to 0C at 3Cmin multi-frequencies of 0.1-10 Hz using DMA. Ratios of syringyl to guaiacyl associated bands along the longitudinal and radial positions of the wood differ significantly. Higher syringylguaiacyl ratio of the corewood than middlewood correlate well with lowering softening temperature. The findings in this research reveals that more chemical would be required to pulp R. heudelotii wood obtained from the base 10 of the merchantable height and outerwood because of the presence of high lignin content compared to the other longitudinal and radial positions respectively where wood were collected. Also outerwood favour pulp production compared to middlewood and corewood because of the high holocellulose content.

  15. The influence of sour taste and cold temperature in pharyngeal transit duration in patients with stroke

    Directory of Open Access Journals (Sweden)

    Paula Cristina Cola

    2010-03-01

    Full Text Available CONTEXT: The effect of sour taste and food temperature variations in dysphagic patients has not been entirely clarified. OBJECTIVE: To determine the effect of sour and cold food in the pharyngeal transit times of patients with stroke. METHODS: Patients participating in this study were 30 right-handed adults, 16 of which were male and 14 were female, aged 41 to 88 (average age 62.3 years with ictus varying from 1 to 30 days (median of 6 days. To analyze the pharyngeal transit time a videofluoroscopy swallow test was performed. Each patient was observed during swallow of a 5 mL paste bolus given by spoon, totaling four different stimuli (natural, cold, sour and cold sour, one at a time, room temperature (22ºC and cold (8ºC were used. Later, the tests were analyzed using specific software to measure bolus transit time during the pharyngeal phase. RESULTS: The results showed that the pharyngeal transit time was significantly shorter during swallow of cold sour bolus when compared with other stimuli. Conclusion - Sour taste stimuli associated to cold temperature cause significant change in swallowing patterns, by shortening the pharyngeal transit time, which may lead to positive effects in patients with oropharyngeal dysphagia.CONTEXTO: O efeito do sabor azedo e as variações da temperatura dos alimentos em indivíduos disfágicos, ainda não foi totalmente esclarecidos. OBJETIVO: Verificar o efeito do sabor azedo e da temperatura fria no tempo de trânsito faríngeo da deglutição em indivíduos após acidente vascular encefálico hemisférico isquêmico. MÉTODOS: Participaram deste estudo 30 indivíduos adultos, sendo 16 do gênero masculino e 14 do feminino, destros, com faixa etária variando de 41 a 88 anos (média de 62,3 anos e ictus que variou de 1 a 30 dias (mediana de 6 dias. Para analisar o tempo de trânsito faríngeo da deglutição foi realizado o exame de videofluoroscopia da deglutição. Cada indivíduo foi observado durante a

  16. Using the Weak-Temperature Gradient Approximation to Evaluate Parameterizations: An Example of the Transition From Suppressed to Active Convection

    Science.gov (United States)

    Daleu, C. L.; Plant, R. S.; Woolnough, S. J.

    2017-10-01

    Two single-column models are fully coupled via the weak-temperature gradient approach. The coupled-SCM is used to simulate the transition from suppressed to active convection under the influence of an interactive large-scale circulation. The sensitivity of this transition to the value of mixing entrainment within the convective parameterization is explored. The results from these simulations are compared with those from equivalent simulations using coupled cloud-resolving models. Coupled-column simulations over nonuniform surface forcing are used to initialize the simulations of the transition, in which the column with suppressed convection is forced to undergo a transition to active convection by changing the local and/or remote surface forcings. The direct contributions from the changes in surface forcing are to induce a weakening of the large-scale circulation which systematically modulates the transition. In the SCM, the contributions from the large-scale circulation are dominated by the heating effects, while in the CRM the heating and moistening effects are about equally divided. A transition time is defined as the time when the rain rate in the dry column is halfway to the value at equilibrium after the transition. For the control value of entrainment, the order of the transition times is identical to that obtained in the CRM, but the transition times are markedly faster. The locally forced transition is strongly delayed by a higher entrainment. A consequence is that for a 50% higher entrainment the transition times are reordered. The remotely forced transition remains fast while the locally forced transition becomes slow, compared to the CRM.

  17. Low Temperature Phase Transitions in Single Crystal Magnetoelectric GdMnO3

    Science.gov (United States)

    Williamsen, Mark; Ray, Shishir; Sen, Somaditya; Zou, Ying; Guptasarma, Prasenjit

    2009-03-01

    GdMnO3 is proposed to have a magnetic phase transition from paramagnet to incommensurate antiferromagnet at 43K, further ordering to canted antiferromagnetism around 23K, followed by Gd magnetic ordering at 6.5K[1]. We present further studies of a large single crystal of orthorhombic GdMnO3 grown by us from a floating zone, revealing additional features at lower temperature. Dielectric spectroscopy measurements confirm these new features. We also report dc-magnetization, frequency dependent ac-magnetization 2-300K, and specific heat 0.4-300K in a variable magnetic field 0-9T, and propose additional features in the magnetoelectric phase diagram. [1]T. Kimura,Phys.Rev.B 71,224425(2005)

  18. 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.

  19. Holographic s+p insulator/superconductor phase transition at zero temperature

    Directory of Open Access Journals (Sweden)

    Ran Li

    2017-03-01

    Full Text Available We study the holographic s+p insulator/superconductor phase transition at zero temperature by using the model with a scalar triplet charged under an SU(2 gauge field in anti-de Sitter (AdS soliton background. In this model, besides the insulator phase, s-wave condensate phase and p-wave condensate phase, the s+p coexisting condensate phase is found numerically when operator dimension Δ is greater than a critical value Δc. We also construct the complete phase diagram in Δ−μ plane, which shows the s+p coexisting region is very narrow. Furthermore, we calculate the corresponding conductivities for different phases. The delta function support for the real part of conductivity of the spontaneous breaking phases is also revealed numerically as expected for the superconducting phases.

  20. Bifunctional Transition Metal Hydroxysulfides: Room-Temperature Sulfurization and Their Applications in Zn-Air Batteries.

    Science.gov (United States)

    Wang, Hao-Fan; Tang, Cheng; Wang, Bin; Li, Bo-Quan; Zhang, Qiang

    2017-09-01

    Bifunctional electrocatalysis for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) constitutes the bottleneck of various sustainable energy devices and systems like rechargeable metal-air batteries. Emerging catalyst materials are strongly requested toward superior electrocatalytic activities and practical applications. In this study, transition metal hydroxysulfides are presented as bifunctional OER/ORR electrocatalysts for Zn-air batteries. By simply immersing Co-based hydroxide precursor into solution with high-concentration S(2-) , transition metal hydroxides convert to hydroxysulfides with excellent morphology preservation at room temperature. The as-obtained Co-based metal hydroxysulfides are with high intrinsic reactivity and electrical conductivity. The electron structure of the active sites is adjusted by anion modulation. The potential for 10 mA cm(-2) OER current density is 1.588 V versus reversible hydrogen electrode (RHE), and the ORR half-wave potential is 0.721 V versus RHE, with a potential gap of 0.867 V for bifunctional oxygen electrocatalysis. The Co3 FeS1.5 (OH)6 hydroxysulfides are employed in the air electrode for a rechargeable Zn-air battery with a small overpotential of 0.86 V at 20.0 mA cm(-2) , a high specific capacity of 898 mAh g(-1) , and a long cycling life, which is much better than Pt and Ir-based electrocatalyst in Zn-air batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. High-temperature nuclear magnetic resonance study of phase transition kinetics in LiNaSO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Shakhovoy, R. A., E-mail: roman.shakhovoy@cnrs-orleans.fr, E-mail: r.a.shakhovoy@gmail.com; Sarou-Kanian, V.; Rakhmatullin, A.; Véron, E.; Bessada, C. [CNRS, CEMHTI UPR 3079, Univ. Orléans, F-45071 Orléans (France)

    2015-12-28

    A new high-temperature NMR technique for measurements of the phase transition kinetics in solids has been developed. The technique allows measuring the time evolution of the volume of the appearing phase at controlled cooling rates. Developed method was applied to study the phase transition kinetics in the superionic conductor LiNaSO{sub 4}. It was revealed that the phase transition in LiNaSO{sub 4} is governed by the diffusion-controlled growth of nuclei (“germs”). An effect of the crystallite rearrangement in the LiNaSO{sub 4} powder after cooling through the phase transition was also revealed. This effect was studied by means of high-temperature XRD and NMR.

  2. A room temperature reversible phase transition containing dielectric switching of a host-guest supramolecular metal-halide compound.

    Science.gov (United States)

    Lu, Yang; Hua, Xiu-Ni; Liao, Wei-Qiang; Gao, Ji-Xing; Yin, Zi

    2017-10-03

    Following our recent findings on dielectric materials, we synthesized a new host-guest supramolecular metal-halide compound, [(2-AMPD)(18-crown-6)]CuCl4 (1, 2-AMPD = 2-aminomethylpiperidinium). Systematic characterization techniques such as variable-temperature crystal structure analyses, differential scanning calorimetry (DSC) measurements, temperature-dependent dielectric measurements and powder X-ray diffraction (PXRD) measurements demonstrate that 1 undergoes a reversible phase transition at room temperature, accompanied by switchable dielectric responses and remarkable anisotropy along three different crystallographic axes. The structural phase transition mechanism is triggered by the order-disorder transition of the 18-crown-6 molecules. We believe that these findings might further promote the application of a host-guest inclusion compound in the field of switchable dielectric materials.

  3. Size Dependence of a Temperature-Induced Solid-Solid Phase Transition in Copper(I) Sulfide

    Energy Technology Data Exchange (ETDEWEB)

    Rivest, Jessy B; Fong, Lam-Kiu; Jain, Prashant K; Toney, Michael F; Alivisatos, A Paul

    2011-07-24

    Determination of the phase diagrams for the nanocrystalline forms of materials is crucial for our understanding of nanostructures and the design of functional materials using nanoscale building blocks. The ability to study such transformations in nanomaterials with controlled shape offers further insight into transition mechanisms and the influence of particular facets. Here we present an investigation of the size-dependent, temperature-induced solid-solid phase transition in copper sulfide nanorods from low- to high-chalcocite. We find the transition temperature to be substantially reduced, with the high chalcocite phase appearing in the smallest nanocrystals at temperatures so low that they are typical of photovoltaic operation. Size dependence in phase trans- formations suggests the possibility of accessing morphologies that are not found in bulk solids at ambient conditions. These other- wise-inaccessible crystal phases could enable higher-performing materials in a range of applications, including sensing, switching, lighting, and photovoltaics.

  4. Summation of all petal-shaped diagrams in O(N) model near the phase transition temperature

    CERN Document Server

    Bordag, M

    2002-01-01

    The temperature phase transition in the theory of the N-component scalar field is studied. The weak phase transition of the first order is obtained in the approximation of summation of all petal-shaped diagrams. By the N -> infinity it becomes the phase transition of the second order. The comparison with other approaches is carried out. The necessary data on the Legendre transformation of the second order and Schwinger-Dyson equations are presented. The gap equations are solved in the approximation of summation of all petal-shaped diagrams for the arbitrary N

  5. Thickness dependence of Morin transition temperature in iridium-doped hematite layers studied through nuclear resonant scattering

    Science.gov (United States)

    Mibu, Ko; Mikami, Kazuaki; Tanaka, Masaaki; Masuda, Ryo; Yoda, Yoshitaka; Seto, Makoto

    2017-11-01

    The Morin transition of very thin Ir-doped α-Fe2O3 films, which is not detectable with conventional magnetization measurements, was studied by conversion electron Mössbauer spectroscopy using a 57Co source and nuclear resonant scattering using a synchrotron light source. It was found that (i) the Morin transition temperature increases as the Ir ratio increases, (ii) it decreases when the film thickness decreases, and (iii) the transition becomes irreversible when Ir ratio is small and the thickness is thin. These tendencies were found reproducible and systematic, although the mechanisms are to be clarified by further studies.

  6. Epitaxial growth of higher transition-temperature VO2 films on AlN/Si

    Directory of Open Access Journals (Sweden)

    Tetiana Slusar

    2016-02-01

    Full Text Available We report the epitaxial growth and the mechanism of a higher temperature insulator-to-metal-transition (IMT of vanadium dioxide (VO2 thin films synthesized on aluminum nitride (AlN/Si (111 substrates by a pulsed-laser-deposition method; the IMT temperature is TIMT ≈ 350 K. X-ray diffractometer and high resolution transmission electron microscope data show that the epitaxial relationship of VO2 and AlN is VO2 (010 ‖ AlN (0001 with VO2 [101] ‖   AlN   [ 2 1 ̄ 1 ̄ 0 ] zone axes, which results in a substrate-induced tensile strain along the in-plane a and c axes of the insulating monoclinic VO2. This strain stabilizes the insulating phase of VO2 and raises TIMT for 10 K higher than TIMT single crystal ≈ 340 K in a bulk VO2 single crystal. Near TIMT, a resistance change of about four orders is observed in a thick film of ∼130 nm. The VO2/AlN/Si heterostructures are promising for the development of integrated IMT-Si technology, including thermal switchers, transistors, and other applications.

  7. Gas Temperature Demography and the HI-to-H2 Transition in the Magellanic Clouds

    Science.gov (United States)

    Jameson, Katherine; McClure-Griffiths, Naomi; Liu, Boyang; Staveley-Smith, Lister; Miller Dickey, John; Bolatto, Alberto D.; Dawson, Joanne; Dénes, Helga; Li, Di; Stanimirovic, Snezana; Wolfire, Mark G.; Wong, Tony H.

    2017-06-01

    Given their proximity and low metallicity, the Magellanic Clouds provide the ideal laboratory to study the evolution of gas in the interstellar medium. We present first results from a new HI and OH absorption line study using the ATCA to measure the warm-to-cold atomic fraction and the atomic-to-molecular transition in the Large and Small Magellanic Clouds (LMC and SMC, respectively). The survey targets 48 sources in the LMC and 29 sources in the SMC, which covers more sources at higher senstitivity and spectral resolutin than previous absorption line measurement studies. We decompose the emission and absorption spectra using the autonomous gaussian decomposition software GaussPy (Lindner et al. 2015), which allows us to measure the spin temperature and optical depth of the HI gas. These measurements of the optical depth allow us to constrain the amount of "CO-faint" gas that is optically thick HI gas. Initial analysis indicates that we measure higher spin temperatures than the previous studies (Dickey et al. 1994, Marx-Zimmer et al. 2000), and cold atomic gas fractions of ~20%. We currently have no detections of OH absorption and an upper limit on the column density of molecular gas in the targeted lines of sight of ~few x 1022 cm-2, which is consistent with the dust-based molecular gas estimates.

  8. Spin crossover and Mott—Hubbard transition under high pressure and high temperature in the low mantle of the Earth

    Science.gov (United States)

    Ovchinnikov, S. G.; Ovchinnikova, T. M.; Plotkin, V. V.; Dyad'kov, P. G.

    2015-11-01

    Effect of high pressure induced spin crossover on the magnetic, electronic and structural properties of the minerals forming the Earth's low mantle is discussed. The low temperature P, T phase diagram of ferropericlase has the quantum phase transition point Pc = 56 GPa at T = 0 confirmed recently by the synchrotron Mössbauer spectroscopy. The LDA+GTB calculated phase diagram describes the experimental data. Its extension to the high temperature resulted earlier in prediction of the metallic properties of the Earth's mantle at the depth 1400 km insulator transition and compare them with the experimental seismic and geomagnetic field data.

  9. High-temperature phase transitions, spectroscopic properties, and dimensionality reduction in rubidium thorium molybdate family.

    Science.gov (United States)

    Xiao, Bin; Gesing, Thorsten M; Kegler, Philip; Modolo, Giuseppe; Bosbach, Dirk; Schlenz, Hartmut; Suleimanov, Evgeny V; Alekseev, Evgeny V

    2014-03-17

    Four new rubidium thorium molybdates have been synthesized by high-temperature solid-state reactions. The crystal structures of Rb8Th(MoO4)6, Rb2Th(MoO4)3, Rb4Th(MoO4)4, and Rb4Th5(MoO4)12 were determined using single-crystal X-ray diffraction. All these compounds construct from MoO4 tetrahedra and ThO8 square antiprisms. The studied compounds adopt the whole range of possible structure dimensionalities from zero-dimensional (0D) to three-dimensional (3D): finite clusters, chains, sheets, and frameworks. Rb8Th(MoO4)6 crystallizes in 0D containing clusters of [Th(MoO4)6](8-). The crystal structure of Rb2Th(MoO4)3 is based upon one-dimensional chains with configuration units of [Th(MoO4)3](2-). Two-dimensional sheets occur in compound Rb4Th(MoO4)4, and a 3D framework with channels formed by thorium and molybdate polyhedra has been observed in Rb4Th5(MoO4)12. The Raman and IR spectroscopic properties of these compounds are reported. Temperature-depended phase transition effects were observed in Rb2Th(MoO4)3 and Rb4Th(MoO4)4 using thermogravimetry-differential scanning calorimetry analysis and high-temperature powder diffraction methods.

  10. Live cell plasma membranes do not exhibit a miscibility phase transition over a wide range of temperatures.

    Science.gov (United States)

    Lee, Il-Hyung; Saha, Suvrajit; Polley, Anirban; Huang, Hector; Mayor, Satyajit; Rao, Madan; Groves, Jay T

    2015-03-26

    Lipid/cholesterol mixtures derived from cell membranes as well as their synthetic reconstitutions exhibit well-defined miscibility phase transitions and critical phenomena near physiological temperatures. This suggests that lipid/cholesterol-mediated phase separation plays a role in the organization of live cell membranes. However, macroscopic lipid-phase separation is not generally observed in cell membranes, and the degree to which properties of isolated lipid mixtures are preserved in the cell membrane remain unknown. A fundamental property of phase transitions is that the variation of tagged particle diffusion with temperature exhibits an abrupt change as the system passes through the transition, even when the two phases are distributed in a nanometer-scale emulsion. We support this using a variety of Monte Carlo and atomistic simulations on model lipid membrane systems. However, temperature-dependent fluorescence correlation spectroscopy of labeled lipids and membrane-anchored proteins in live cell membranes shows a consistently smooth increase in the diffusion coefficient as a function of temperature. We find no evidence of a discrete miscibility phase transition throughout a wide range of temperatures: 14-37 °C. This contrasts the behavior of giant plasma membrane vesicles (GPMVs) blebbed from the same cells, which do exhibit phase transitions and macroscopic phase separation. Fluorescence lifetime analysis of a DiI probe in both cases reveals a significant environmental difference between the live cell and the GPMV. Taken together, these data suggest the live cell membrane may avoid the miscibility phase transition inherent to its lipid constituents by actively regulating physical parameters, such as tension, in the membrane.

  11. The Present SP Tests for Determining the Transition Temperature TSP on “U” Notch Disc Specimens

    Science.gov (United States)

    Matocha, Karel; Dorazil, Ondrej; Hurst, Roger

    2017-01-01

    The principal difference between the small punch (SP) testing technique and standardized impact testing lies in the fact that the SP tests carried out in accordance with CWA 15627 Small Punch Test Method for Metallic Materials use disc-shaped test specimens without a notch. Especially in tough materials, the temperature dependence of SP fracture energy ESP in the transition area is very steep and lies close to the temperature of liquid nitrogen. In this case, the determination of SP transition temperature TSP can lead to significant errors in its determination. Efforts to move the transition area of penetration testing closer to the transition area of standardized impact tests led to the proposal of the notched disc specimen 8 mm in diameter and 0.5 mm in thickness with a “U” shaped notch 0.2 mm deep in the axis plane of the disc. The paper summarizes the results obtained to date when determining the transition temperature of SP tests TSP, determined according to CWA 15627 for material of pipes made of P92, P22, and a heat treated 14MoV6-3 steel in the as delivered state. Although the results obtained confirmed the results of other works in that the presence of a notch in a SP disc is insufficient to increase the transition temperature significantly and certainly not to the values obtained by Charpy testing, comparison of the different behaviors of the alloys tested reveals some evidence that the notch reduces the energy for initiation. This implies that the test on a notched disc is more a test of crack growth and would be a useful instrument if included in the forthcoming EU standard for SP testing. PMID:28772851

  12. Pentachlorophenol-induced change of zeta-potential and gel-to-fluid transition temperature in model lecithin membranes.

    Science.gov (United States)

    Smejtek, P; Barstad, A W; Wang, S

    1989-01-01

    We have determined zeta-potentials for dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC) membranes by measuring the electrophoretic mobility of multilayered vesicles and the temperatures of the gel-to-ripple-to-fluid phase transitions of sonicated vesicles by a photometric method. Some conclusions are: (1) The zeta-potentials of DMPC and DPPC vesicles become negative due to adsorption of ionized pentachlorophenol (PCP), (2) their magnitude changes, step-like, on gel-to-fluid transition and (3) the temperature of the step-like change in zeta-potential decreases with an increase in PCP concentration. (4) PCP exhibits a large effect on membrane structure: It induces an isothermal phase change from the ordered to disordered state, which is enhanced by monovalent salt in the aqueous phase. (5) Both ionized and unionized PCP decrease the melting phase transition temperature and abolish the pretransition, (6) the unionized species increases the melting transition width and (7) the ionized species is more potent in abolishing the pretransition. (8) The shorter chain lipid (DMPC) is more sensitive to the presence of PCP; the maximum decrease in delta Tt is 13 K (DMPC) and 7 K (DPPC) in the presence of ionized PCP. We have shown experimentally, by comparing the delta Tt from photometric studies with the density of adsorbed PCP derived from zeta-potential isotherms, that (9) the shift of the melting phase transition temperature increases linearly with the density of adsorbed PCP. (10) In contrast to membranes made of negatively charged lipids, the transition temperature of DMPC and DPPC membranes in the presence of PCP further decreases in the presence of monovalent salt. The salt effect is due to screening of the membrane surface leading to enhanced adsorption of ionized PCP and a depression in transition temperature. (11) It is shown that both the adsorption and the changes of gel-to-fluid phase transition temperature can be described in terms

  13. Determination of the Glass Transition Temperature of Freestanding and Supported Azo-Polymer Thin Films by Thermal Assisted Atomic Force Microscopy

    Science.gov (United States)

    Chernykh, Elena; Kharintsev, Sergey; Fishman, Alexandr; Alekseev, Alexander; Salakhov, Myakzuym

    2017-03-01

    In this paper we introduce and apply the method for determination of the glass transition temperature of the sub-100 nm thick freestanding and supported polymer films based on thermally assisted atomic force microscopy (AFM). In proposed approach changes of the phase of an oscillating AFM cantilever are used to determine glass transition temperature. An anomalous decrease of the glass transition temperature for both free-standing and supported azobenzene-functionalized polymer thin films is shown.

  14. Glass-Transition Temperature Profile Measured in a Wood Cell Wall Using Scanning Thermal Expansion Microscope (SThEM)

    Science.gov (United States)

    Antoniow, J. S.; Maigret, J.-E.; Jensen, C.; Trannoy, N.; Chirtoc, M.; Beaugrand, J.

    2012-11-01

    This study aims to assess the in situ spatial distribution of glass-transition temperatures ( T g) of the main lignocellulosic biopolymers of plant cell walls. Studies are conducted using scanning thermal expansion microscopy to analyze the cross-section of the cell wall of poplar. The surface topography is mapped over a range of probe-tip temperatures to capture the change of thermal expansion on the sample surface versus temperature. For different temperature values chosen between 20 °C and 250 °C, several quantitative mappings were made to show the spatial variation of the thermal expansion. As the glass transition affects the thermal expansion coefficient and elastic modulus considerably, the same data line of each topography image was extracted to identify specific thermal events in their topographic evolution as a function of temperature. In particular, it is shown that the thermal expansion of the contact surface is not uniform across the cell wall and a profile of the glass-transition temperature could thus be evidenced and quantified corresponding to the mobility of lignocellulosic polymers having a role in the organization of the cell wall structures.

  15. Neutron Diffraction and Electrical Transport Studies on Magnetic Transition in Terbium at High Pressures and Low Temperatures

    Science.gov (United States)

    Thomas, Sarah; Montgomery, Jeffrey; Tsoi, Georgiy; Vohra, Yogesh; Weir, Samuel; Tulk, Christopher; Moreira Dos Santos, Antonio

    2013-06-01

    Neutron diffraction and electrical transport measurements have been carried out on the heavy rare earth metal terbium at high pressures and low temperatures in order to elucidate its transition from a helical antiferromagnetic to a ferromagnetic ordered phase as a function of pressure. The electrical resistance measurements using designer diamonds show a change in slope as the temperature is lowered through the ferromagnetic Curie temperature. The temperature of the ferromagnetic transition decreases at a rate of -16.7 K/GPa till 3.6 GPa, where terbium undergoes a structural transition from hexagonal close packed (hcp) to an α-Sm phase. Above this pressure, the electrical resistance measurements no longer exhibit a change in slope. In order to confirm the change in magnetic phase suggested by the electrical resistance measurements, neutron diffraction measurements were conducted at the SNAP beamline at the Oak Ridge National Laboratory. Measurements were made at pressures to 5.3 GPa and temperatures as low as 90 K. An abrupt increase in peak intensity in the neutron diffraction spectra signaled the onset of magnetic order below the Curie temperature. A magnetic phase diagram of rare earth metal terbium will be presented to 5.3 GPa and 90 K based on these studies.

  16. Monte Carlo Comparisons to a Cryogenic Dark Matter Search Detector with Low Transition-Edge-Sensor Transition Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Leman, S.W.; McCarthy, K.A.; /MIT, MKI; Brink, P.L.; Cabrera, B.; Cherry, M.; /Stanford U., Phys. Dept.; Silva, E.Do Couto E; /SLAC; Figueroa-Feliciano, E.; /MIT, MKI; Kim, P.; /SLAC; Mirabolfathi, N.; /UC, Berkeley; Pyle, M.; /Stanford U., Phys. Dept.; Resch, R.; /SLAC; Sadoulet, B.; Serfass, B.; Sundqvist, K.M.; /UC, Berkeley; Tomada, A.; /Stanford U., Phys. Dept.; Young, B.A.; /Santa Clara U.

    2012-06-05

    We present results on phonon quasidiffusion and Transition Edge Sensor (TES) studies in a large, 3-inch diameter, 1-inch thick [100] high purity germanium crystal, cooled to 50 mK in the vacuum of a dilution refrigerator, and exposed with 59.5 keV gamma-rays from an Am-241 calibration source. We compare calibration data with results from a Monte Carlo which includes phonon quasidiffusion and the generation of phonons created by charge carriers as they are drifted across the detector by ionization readout channels. The phonon energy is then parsed into TES based phonon readout channels and input into a TES simulator.

  17. Effects of fragility and reduced glass transition temperature on the glass formation ability of amorphous alloys

    Science.gov (United States)

    Xu, Xiao-Jin; Long, Zhi-Lin; Liu, Wei; Liao, Guang-Kai

    2017-11-01

    In this paper, based on the reduced glass transition temperature ({{T}rg} ) proposed by Turnbull and the relation between the glass-forming ability (GFA) and the short-range bond ordering of liquids demonstrated by Tanaka, a detailed analysis on the specific roles of {{T}rg} and fragility of the glass forming liquid (m) in characterizing the GFA has been conducted, and then a novel GFA parameter α [=2/3× (100{{T}rg}{)}-(16/100)× m=67{{T}rg}-0.16m] was put forward. This new GFA parameter α , which increases with a decrease in the critical cooling rate (R c) for glass formation, is a complex function of {{T}rg} and m. The relationship between R c and the parameter α was identified and verified using available literature data for broad range of amorphous alloys with widely varying GFA. The correlation coefficient (R 2) of 0.9 clearly shows an excellent correlation between GFA and the parameter α and that α is a more superior indicator compared to currently reported similar GFA parameters.

  18. Using combined computational techniques to predict the glass transition temperatures of aromatic polybenzoxazines.

    Directory of Open Access Journals (Sweden)

    Phumzile Mhlanga

    Full Text Available The Molecular Operating Environment software (MOE is used to construct a series of benzoxazine monomers for which a variety of parameters relating to the structures (e.g. water accessible surface area, negative van der Waals surface area, hydrophobic volume and the sum of atomic polarizabilities, etc. are obtained and quantitative structure property relationships (QSPR models are formulated. Three QSPR models (formulated using up to 5 descriptors are first used to make predictions for the initiator data set (n = 9 and compared to published thermal data; in all of the QSPR models there is a high level of agreement between the actual data and the predicted data (within 0.63-1.86 K of the entire dataset. The water accessible surface area is found to be the most important descriptor in the prediction of T(g. Molecular modelling simulations of the benzoxazine polymer (minus initiator carried out at the same time using the Materials Studio software suite provide an independent prediction of T(g. Predicted T(g values from molecular modelling fall in the middle of the range of the experimentally determined T(g values, indicating that the structure of the network is influenced by the nature of the initiator used. Hence both techniques can provide predictions of glass transition temperatures and provide complementary data for polymer design.

  19. Terbium-Doped VO2 Thin Films: Reduced Phase Transition Temperature and Largely Enhanced Luminous Transmittance.

    Science.gov (United States)

    Wang, Ning; Duchamp, Martial; Dunin-Borkowski, Rafal E; Liu, Shiyu; Zeng, XianTing; Cao, Xun; Long, Yi

    2016-01-26

    Vanadium dioxide (VO2) is a well-known thermochromic material with large IR modulating ability, promising for energy-saving smart windows. The main drawbacks of VO2 are its high phase transition temperature (τ(c) = 68°C), low luminous transmission (T(lum)), and weak solar modulating ability (ΔT(sol)). In this paper, the terbium cation (Tb(3+)) doping was first reported to reduce τ(c) and increase T(lum) of VO2 thin films. Compared with pristine VO2, 2 at. % doping level gives both enhanced T(lum) and ΔT(sol) from 45.8% to 54.0% and 7.7% to 8.3%, respectively. The T(lum) increases with continuous Tb(3+) doping and reaches 79.4% at 6 at. % doping level, representing ∼73.4% relative increment compared with pure VO2. This has surpassed the best reported doped VO2 thin films. The enhanced thermochromic properties is meaningful for smart window applications of VO2 materials.

  20. Thermal fluctuations in Y-Ba-Cu-O thin films near the transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, S.; Hallemeier, P.; Surya, C. (Northeastern Univ., Boston, MA (United States). Dept. of Electrical and Computer Engineering); Phillips, J.M. (AT and T Bell Labs., Murray Hill, NJ (United States))

    1994-11-01

    Detailed studies on the properties of low frequency noise in Y-Ba-Cu-O thin films in the transition region were conducted. The experimental results showed that the low frequency excess noise exhibited a lower cutoff frequency of about 5 Hz, below which the noise power spectra were independent of frequency. At T close to [Tc] and at small current biases the voltage noise power spectra were proportional to I[sup 2], ([partial derivative]R/[partial derivative]T)[sup 2] and inversely proportional to the volume of the device, [Omega]. In addition, low frequency noise measured from two segments separated by a distance of 300 [mu]m was found to be correlated. The lower cutoff frequencies computed for both the noise power spectra and the frequency dependent correlation function, according to the thermal fluctuation model, were found to be in good agreement with the experimental values. The experimental results provide strong evidence that the low frequency excess noise in the device originates from equilibrium temperature fluctuations for small I and T [approx equal] [Tc].

  1. Application of biopolymers for improving the glass transition temperature of hairtail fish meat.

    Science.gov (United States)

    Yu, Haixia; Yang, Shuibing; Yuan, Chunhong; Hu, Qinglan; Li, Yuan; Chen, Shiguo; Hu, Yaqin

    2017-08-04

    Glass transition temperature (Tg ) and food moisture content are closely related, especially in foods with a high moisture content, such as surimi products. In order to improve storage condition and maintain food quality, the influence of six biopolymers on the Tg of hairtail fish meat paste was investigated by differential scanning colorimetry. Samples were stored at -8 °C (>Tg ), -14 °C (Tg ) and -18 °C (

  2. Strain-tuning of the magnetocaloric transition temperature in model FeRh films

    Science.gov (United States)

    Loving, M. G.; Barua, R.; Le Graët, C.; Kinane, C. J.; Heiman, D.; Langridge, S.; Marrows, C. H.; Lewis, L. H.

    2018-01-01

    The chemically ordered B2 phase of equiatomic FeRh is known to absorb or evolve a significant latent heat as it traverses its first-order phase transition in response to thermal, magnetic, and mechanical drivers. This attribute makes FeRh an ideal magnetocaloric material testbed for investigation of relationships between the crystalline lattice and the magnetic spins, which are especially experimentally accessible in thin films. In this work, epitaxial FeRh films of nominal 30 nm and 50 nm thicknesses with out-of-plane c-axis orientation were sputter-deposited at high temperature onto (0 0 1)-MgO or (0 0 0 1)-Al2O3 substrates and capped with Al, Au, Cr, or W after in situ annealing at 973 K to promote CsCl-type chemical order. In this manner a controlled strain state was invoked. Experimental results derived from laboratory and synchrotron x-ray diffraction combined with magnetometry indicate that the antiferromagnetic (AF)—ferromagnetic (FM) magnetostructural phase transformation in these films may be tuned over an ~50° range (373 K–425 K) through variation in the c/a ratio derived from lattice strain delivered by the substrate and the capping layers. These results supply fundamental information that might be used to engineer the magnetocaloric working material in new system designs by introducing targeted values of passive strain to the system.

  3. Solid-to-fluid DNA transition inside HSV-1 capsid close to the temperature of infection

    Energy Technology Data Exchange (ETDEWEB)

    Sae-Ueng, Udom; Li, Dong; Zuo, Xiaobing; Huffman, Jamie B.; Homa, Fred L.; Rau, Donald; Evilevitch, Alex

    2014-10-01

    DNA in the human Herpes simplex virus type 1 (HSV-1) capsid is packaged to a tight density. This leads to tens of atmospheres of internal pressure responsible for the delivery of the herpes genome into the cell nucleus. In this study we show that, despite its liquid crystalline state inside the capsid, the DNA is fluid-like, which facilitates its ejection into the cell nucleus during infection. We found that the sliding friction between closely packaged DNA strands, caused by interstrand repulsive interactions, is reduced by the ionic environment of epithelial cells and neurons susceptible to herpes infection. However, variations in the ionic conditions corresponding to neuronal activity can restrict DNA mobility in the capsid, making it more solid-like. This can inhibit intranuclear DNA release and interfere with viral replication. In addition, the temperature of the human host (37 °C) induces a disordering transition of the encapsidated herpes genome, which reduces interstrand interactions and provides genome mobility required for infection.

  4. Superconducting transition temperature of MgB_2 H_0.03 is higher than that of MgB_2

    OpenAIRE

    Flambaum, V. V.; Stewart, G. A.; Russell, G J; Horvat, J.; Dou, S.X

    2001-01-01

    Hydrogenation of MgB_2 powder has lead to an increase in the superconducting temperature, as determined by ac susceptibility. Applied dc fields reduce the transition temperature in the same ratio as for the pure powder.

  5. Magnetic surface domain imaging of uncapped epitaxial FeRh(001 thin films across the temperature-induced metamagnetic transition

    Directory of Open Access Journals (Sweden)

    Xianzhong Zhou

    2016-01-01

    Full Text Available The surface magnetic domain structure of uncapped epitaxial FeRh/MgO(001 thin films was imaged by in-situ scanning electron microscopy with polarization analysis (SEMPA at various temperatures between 122 and 450 K. This temperature range covers the temperature-driven antiferromagnetic-to-ferromagnetic phase transition in the body of the films that was observed in-situ by means of the more depth-sensitive magneto-optical Kerr effect. The SEMPA images confirm that the interfacial ferromagnetism coexisting with the antiferromagnetic phase inside the film is an intrinsic property of the FeRh(001 surface. Furthermore, the SEMPA data display a reduction of the in-plane magnetization occuring well above the phase transition temperature which, thus, is not related to the volume expansion at the phase transition. This observation is interpreted as a spin reorientation of the surface magnetization for which we propose a possible mechanism based on temperature-dependent tetragonal distortion due to different thermal expansion coefficients of MgO and FeRh.

  6. Magnetic surface domain imaging of uncapped epitaxial FeRh(001) thin films across the temperature-induced metamagnetic transition

    Science.gov (United States)

    Zhou, Xianzhong; Matthes, Frank; Bürgler, Daniel E.; Schneider, Claus M.

    2016-01-01

    The surface magnetic domain structure of uncapped epitaxial FeRh/MgO(001) thin films was imaged by in-situ scanning electron microscopy with polarization analysis (SEMPA) at various temperatures between 122 and 450 K. This temperature range covers the temperature-driven antiferromagnetic-to-ferromagnetic phase transition in the body of the films that was observed in-situ by means of the more depth-sensitive magneto-optical Kerr effect. The SEMPA images confirm that the interfacial ferromagnetism coexisting with the antiferromagnetic phase inside the film is an intrinsic property of the FeRh(001) surface. Furthermore, the SEMPA data display a reduction of the in-plane magnetization occuring well above the phase transition temperature which, thus, is not related to the volume expansion at the phase transition. This observation is interpreted as a spin reorientation of the surface magnetization for which we propose a possible mechanism based on temperature-dependent tetragonal distortion due to different thermal expansion coefficients of MgO and FeRh.

  7. From a Single-Band Metal to a High-Temperature Superconductor via Two Thermal Phase Transitions

    Energy Technology Data Exchange (ETDEWEB)

    He, R.-H.; Hashimoto, M.; Karapetyan, H.; Koralek, J.D.; Hinton, J.P.; Testaud, J.P.; Nathan, V.; Yoshida, Y.; Yao, H.; Tanaka, K.; Meevasana, W.; Moore, R.G.; Lu, D.H.; Mo, S.-K.; Ishikado, M.; Eisaki, H.; Hussain, Z.; Devereaux, T.P.; Kivelson, S.A.; Orenstein, J.; Kapitulnik, A.

    2011-11-08

    The nature of the pseudogap phase of cuprate high-temperature superconductors is one of the most important unsolved problems in condensed matter physics. We studied the commencement of the pseudogap state at temperature T* using three different techniques (angle-resolved photoemission spectroscopy, polar Kerr effect, and time-resolved reflectivity) on the same optimally-doped Bi2201 crystals. We observe the coincident onset at T* of a particle-hole asymmetric antinodal gap, a non-zero Kerr rotation, and a change in the relaxational dynamics, consistent with a phase transition. Upon further cooling, spectroscopic signatures of superconductivity begin to grow close to the superconducting transition temperature (T{sub c}), entangled in an energy-momentum dependent fashion with the pre-existing pseudogap features.

  8. Theory of relaxation phenomena in a spin-3/2 Ising system near the second-order phase transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)]. E-mail: keskin@erciyes.edu.tr; Canko, Osman [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2005-12-19

    The relaxation behavior of the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic interactions near the second-order phase transition temperature or critical temperature is studied by means of the Onsager's theory of irreversible thermodynamics or the Onsager reciprocity theorem (ORT). First, we give the equilibrium case briefly within the molecular-field approximation in order to study the relaxation behavior by using the ORT. Then, the ORT is applied to the model and the kinetic equations are obtained. By solving these equations, three relaxation times are calculated and examined for temperatures near the second-order phase transition temperature. It is found that one of the relaxation times goes to infinity near the critical temperature on either side, the second relaxation time makes a cusp at the critical temperature and third one behaves very differently in which it terminates at the critical temperature while approaching it, then showing a 'flatness' property and then decreases. We also study the influences of the Onsager rate coefficients on the relaxation times. The behavior of these relaxation times is discussed and compared with the spin-1/2 and spin-1 Ising systems.

  9. Theory of relaxation phenomena in a spin-3/2 Ising system near the second-order phase transition temperature

    Science.gov (United States)

    Keskin, Mustafa; Canko, Osman

    2005-12-01

    The relaxation behavior of the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic interactions near the second-order phase transition temperature or critical temperature is studied by means of the Onsager's theory of irreversible thermodynamics or the Onsager reciprocity theorem (ORT). First, we give the equilibrium case briefly within the molecular-field approximation in order to study the relaxation behavior by using the ORT. Then, the ORT is applied to the model and the kinetic equations are obtained. By solving these equations, three relaxation times are calculated and examined for temperatures near the second-order phase transition temperature. It is found that one of the relaxation times goes to infinity near the critical temperature on either side, the second relaxation time makes a cusp at the critical temperature and third one behaves very differently in which it terminates at the critical temperature while approaching it, then showing a “flatness” property and then decreases. We also study the influences of the Onsager rate coefficients on the relaxation times. The behavior of these relaxation times is discussed and compared with the spin-1/2 and spin-1 Ising systems.

  10. Composition dependence of the phase transition temperature in Sr{sub x}Ba{sub 1-x}Nb{sub 2}O{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    David, C.; Tunyagi, A.; Woehlecke, M.; Betzler, K.; Ulex, M.; Imlau, M.; Pankrath, R. [Fachbereich Physik, Universitaet Osnabrueck, Barbarastr. 7, 49069 Osnabrueck (Germany); Granzow, T.; Woike, Th. [Institut fuer Mineralogie, Zuelpicher Str. 49b, 50674 Koeln (Germany)

    2004-06-01

    The temperature dependence of the spontaneous polarization in strontium-barium-niobate single crystals with varying Sr/Ba ratio is presented. The temperature of the relaxor phase-transition is determined from the inflexion point of the curve of the ferroelectric polarization versus temperature. The influence of the Sr/Ba ratio in the crystal on the transition temperature is discussed within an effective field approach. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. An observed connection between wintertime temperature anomalies over Northwest China and weather regime transitions in North Atlantic

    Science.gov (United States)

    Li, Chao; Zhang, Qingyun

    2015-04-01

    In this study, the association between wintertime temperature anomalies over Northwest China and the weather regime transitions in North Atlantic on synoptic scale is analyzed by using observational surface air temperature (SAT) data and atmospheric reanalysis data. Daily SAT anomaly and duration time are used in order to define SAT anomaly cases. Differences with regard to the circulation anomalies over the Ural Mountains and the upstream North Atlantic area are evident. It is found that the colder than normal SAT is caused by the enhanced Ural high and associated southward flow over Northwest China. Time-lagged composites reveal possible connections between the SAT anomalies and the different development phases of the North Atlantic Oscillation (NAO). The Ural highs tend to be strengthened during the negative phase of NAO (NAO-) to Atlantic ridge transition, which are closely related to the downstream-propagating Rossby wave activity. The opposite circulation patterns are observed in the warm SAT cases. A cyclonic circulation anomaly is distinctly enhanced over the Urals during the positive phase of NAO (NAO+) to Scandinavian blocking transition, which would cause warmer SAT over Northwest China. Further analyses suggest that the intensified zonal wind over North Atlantic would favor the NAO- to Atlantic ridge transition, while the weakened zonal wind may be responsible for the transition between NAO+ and Scandinavian blocking.

  12. Dynamics of phase transitions at finite temperatures in the early universe.

    Science.gov (United States)

    Patzelt, H.

    1991-12-01

    A statistical description of phase transitions on a macroscopic, phenomenological level is used to treat the dynamics of phase transitions and the dynamics of an expanding universe simultaneously. The author considers phase transitions with non-vanishing background densities. The ratio of the typical interaction time to the typical expansion time suggests two scenarios that are discussed concerning their influence on the evolution of the universe.

  13. Effect of sugar addition on glass transition temperatures of cassava starch with low to intermediate moisture contents.

    Science.gov (United States)

    Figueroa, Yetzury; Guevara, Marvilan; Pérez, Adriana; Cova, Aura; Sandoval, Aleida J; Müller, Alejandro J

    2016-08-01

    This work studies how sucrose (S) addition modifies the thermal properties of cassava starch (CS). Neat CS and CS-S blends with 4, 6 and 8% sugar contents (CS-S-4%, CS-S-6% and CS-S-8%) were prepared and analyzed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), in a wide range of moisture levels (2-20%). In equilibrated samples with moisture contents lower than 10%, twoendothermic steps were observed during first DSC heating scans and two corresponding relaxation maxima in tan δ were detected by DMTA. The first transition, detected at around 45-55°C by both DSC and DMTA, is frequently found in starchy foods, while the second observed at higher temperatures is associated to the glass transition temperature of the blends. At higher moisture contents, only one thermal transition was observed. Samples analyzed immediately after cooling from the melt (i.e., after erasing their thermal history), exhibited a single glass transition temperature, regardless of their moisture content. Addition of sugar promotes water plasticization of CS only at high moisture contents. In the low moisture content range, anti-plasticization was observed for both neat and sugar-added CS samples. Addition of sugar decreases the moisture content needed to achieve the maximum value of the glass transition temperature before plasticization starts. The results of this work may be valuable for the study of texture establishment in low moisture content extruded food products. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Transition duct system with arcuate ceramic liner for delivering hot-temperature gases in a combustion turbine engine

    Energy Technology Data Exchange (ETDEWEB)

    Wiebe, David J.

    2017-11-07

    A transition duct system (10) for delivering hot-temperature gases from a plurality of combustors in a combustion turbine engine is provided. The system includes an exit piece (16) for each combustor. The exit piece may include an arcuate connecting segment (36). An arcuate ceramic liner (60) may be inwardly disposed onto a metal outer shell (38) along the arcuate connecting segment of the exit piece. Structural arrangements are provided to securely attach the ceramic liner in the presence of substantial flow path pressurization. Cost-effective serviceability of the transition duct systems is realizable since the liner can be readily removed and replaced as needed.

  15. Bismuth doping strategies in GeTe nanowires to promote high-temperature phase transition from rhombohedral to face-centered cubic structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jie; Huang, Rong; Wei, Fenfen; Cheng, Guosheng, E-mail: gscheng2006@sinano.ac.cn [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, 398 Ruoshui Road, Suzhou Industrial Park, Jiangsu 215123 (China); University of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049 (China); Kong, Tao [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, 398 Ruoshui Road, Suzhou Industrial Park, Jiangsu 215123 (China)

    2014-11-17

    The phase transition of Bi-doped (∼3 at. %) GeTe nanowires from a rhombohedral (R) to a face-centered cubic (C) structure was observed in in situ high-temperature X-ray diffraction. The promotion of high-temperature R-C phase transition by a doping approach was revealed. Ab initio energy calculations of doped GeTe at various Bi doping concentrations were performed to interpret the promoted temperature-induced phase transitions. Those results indicated that the total energy differences between R and C structures of doped GeTe decreased as Bi doping concentrations increased, which facilitated R-C phase transitions.

  16. Observation of reduced phase transition temperature in N-doped thermochromic film of monoclinic VO2

    Science.gov (United States)

    Wan, Meinan; Xiong, Mo; Li, Neng; Liu, Baoshun; Wang, Shuo; Ching, Wai-Yim; Zhao, Xiujian

    2017-07-01

    Research on monoclinic (M1) phase of VO2 has attracted a great of interest for smart coating applications due to its exceptional thermochromic property. Herein, we report the results using a novel approach to synthesize N-doped VO2(M1) thin films with high purity by heat treatment in NH3 atmosphere. The N dopant in the film can be regulated by varying NH3 concentration during the annealing process. We find that the N atoms are located at the interstitial sites or substitute oxygen atoms, and the V-N bonds in the VO2 thin films increase with NH3 concentration. The metal to insulator transition (MIT) temperature (τc,h) of the VO2 thin film is effectively reduced from 80.0 to 62.9 °C, while the solar modulation efficiency (ΔTsol) and the modulation efficiency at 2000 nm (ΔT2000nm) are 7.36% and 55.6% respectively. The band gap of N-doped VO2 thin films related to MIT (Eg1) is estimated to be as low as 0.18-0.25 eV whereas the band gap associated with the visible transparency (Eg2) is about 1.50-1.58 eV. Based on the highly accurate first-principles calculations, the Eg1 of VO2 (M1) is reduced after substituted or interstitial N-doping, while the Eg2 alters with the mode of N-doping, which is excellent agreement with experimental measurement.

  17. Changes in core electron temperature fluctuations across the ohmic energy confinement transition in Alcator C-Mod plasmas

    Science.gov (United States)

    Sung, C.; White, A. E.; Howard, N. T.; Oi, C. Y.; Rice, J. E.; Gao, C.; Ennever, P.; Porkolab, M.; Parra, F.; Mikkelsen, D.; Ernst, D.; Walk, J.; Hughes, J. W.; Irby, J.; Kasten, C.; Hubbard, A. E.; Greenwald, M. J.; the Alcator C-Mod Team

    2013-08-01

    The first measurements of long wavelength (kyρs < 0.3) electron temperature fluctuations in Alcator C-Mod made with a new correlation electron cyclotron emission diagnostic support a long-standing hypothesis regarding the confinement transition from linear ohmic confinement (LOC) to saturated ohmic confinement (SOC). Electron temperature fluctuations decrease significantly (∼40%) crossing from LOC to SOC, consistent with a change from trapped electron mode (TEM) turbulence domination to ion temperature gradient (ITG) turbulence as the density is increased. Linear stability analysis performed with the GYRO code (Candy and Waltz 2003 J. Comput. Phys. 186 545) shows that TEMs are dominant for long wavelength turbulence in the LOC regime and ITG modes are dominant in the SOC regime at the radial location (ρ ∼ 0.8) where the changes in electron temperature fluctuations are measured. In contrast, deeper in the core (ρ < 0.8), linear stability analysis indicates that ITG modes remain dominant across the LOC/SOC transition. This radial variation suggests that the robust global changes in confinement of energy and momentum occurring across the LOC/SOC transition are correlated to local changes in the dominant turbulent mode near the edge.

  18. Fracture Toughness in Transition Temperature Region with Cooling Rate for SA508 Gr. 4N Model Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Park, Sang Gyu; Wee, Dang Moon [KIAST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-05-15

    Materials for reactor pressure vessel (RPV), which is the key component in the determination of the life span and safety margin of reactors, are required to have enough mechanical properties to endure the high pressure inside the reactor. Various studies have focused on improving mechanical properties by the controlling the heat treatment process of commercial RPV steel, SA508 Gr.3 Mn-Mo-Ni low alloy steel. On the other hand, some researches for identifying new material with high strength and toughness for larger capacity and longer lifetime of reactor are being conducted. SA508 Gr.4N Ni-Cr-Mo low alloy steel may be a candidate RPV material due to its excellent mechanical properties from its tempered martensitic microstructure. Wallin observed that the temperature dependency of fracture toughness is not sensitive to the chemical composition, heat treatment, and irradiation for ferritic steels. This result led to the concept of a universal shape in the median toughness-temperature curve for all 'ferritic steels'. Recently, some researches showed that F/M steel composed of the tempered martensitic microstructure has steeper temperature dependency of the measured fracture toughness than the prediction in the master curve. We also focused on the steep transition properties of SA508 Gr.4N low alloy steel with tempered martensitic structure in previous research. However, it has not yet confirmed whether that the transition properties including temperature dependency vary with phase fraction of tempered martensite. In this study, the effect of fraction of tempered martensite on the fracture toughness transition behavior in SA508 Gr.4N was assessed by controlling cooling rate after austenitization. The relationship between phase fraction and the fracture toughness variation with temperature in the transition region was analyzed. Also, the tendencies were compared with the prediction in the sta

  19. Predicting Snow-To-Rain Transitions Across The Western U.S.: When Is Daily Air Temperature Sufficient?

    Science.gov (United States)

    Rajagopal, S.

    2015-12-01

    The phase of precipitation at the land surface is critical for determining the timing and amount of water available for hydrological and ecological systems. Natural variability in precipitation phase due to elevation, micro-climate, and storm characteristics make it a challenge to predict phase. In addition, regional warming is expected to move the snow-rain elevation higher in the future, which has the potential to alter water availability. Despite this, there are few techniques for direct observation of precipitation phase and many predictive techniques apply simple temperature thresholds (i.e. 0 degree Celsius) to determine spatiotemporal patterns. In this paper, we asked two questions: 1) what is the optimum daily temperature for predicting snow-rain transitions in the mountains of the Western U.S.? and 2) what errors in precipitation phase estimation are associated with common temperature thresholds? We use 502 Snow Telemetry (SNOTEL) stations with data from 2004 to 2014 to determine rain versus snow using a combination of precipitation, snow depth, and SWE observations. From the observations, we determined that daily maximum temperature is a better predictor of rain and snow events than average temperature. The optimum temperature varied from -2.0 to 3 C, with an average of 0.3 C across ecoregions. The Northern Basin and Northern Cascades with lower average elevations had higher temperature thresholds and the Southern Rockies with highest elevations had the lowest thresholds. Developing a relationship based on station elevation improved the RMSE by 12%, whereas using an optimum temperature developed for each station improved the RMSE by 34% on average. While using optimum temperature thresholds reduce error in prediction, they do not eliminate misclassification of rain-show transitions. These results highlight a current weakness in our ability to predict the effects of regional warming that could have uneven impacts on water and ecological resource management

  20. Direct measurement of the low-temperature spin-state transition in LaCoO3.

    Science.gov (United States)

    Klie, R F; Zheng, J C; Zhu, Y; Varela, M; Wu, J; Leighton, C

    2007-07-27

    LaCoO3 exhibits an anomaly in its magnetic susceptibility around 80 K associated with a thermally excited transition of the Co3+-ion spin. We show that electron energy-loss spectroscopy is sensitive to this Co3+-ion spin-state transition, and that the O K edge prepeak provides a direct measure of the Co3+ spin state in LaCoO3 as a function of temperature. Our experimental results are confirmed by first-principles calculations, and we conclude that the thermally excited spin-state transition occurs from a low to an intermediate spin state, which can be distinguished from the high-spin state.

  1. Glass transition-related changes in molecular mobility below glass transition temperature of freeze-dried formulations, as measured by dielectric spectroscopy and solid state nuclear magnetic resonance.

    Science.gov (United States)

    Yoshioka, Sumie; Aso, Yukio

    2005-02-01

    The purpose of this study was to explore why changes in the molecular mobility associated with glass transition, the timescale of which is on the order of 100 s, can be detected by measuring the nuclear magnetic resonance relaxation times that reflect molecular motions on the order of 10 kHz and 1 MHz. The molecular motions in freeze-dried dextran 40k, dextran 1k, isomaltotriose (IMT), and alpha-glucose comprising a common unit but with different glass transition temperatures, were investigated by dielectric spectroscopy (DES) in the frequency range of 0.01 Hz to 100 kHz and in the temperature range of -20 degrees to 200 degrees C, in order to compare with the molecular motions reflected in nuclear magnetic resonance relaxation times. The alpha-relaxation process for freeze-dried alpha-glucose was visualized by DES, whereas those for freeze-dried dextran 40k, dextran 1k, and IMT were too slow to be visualized by DES. The latter freeze-dried cakes exhibited quasi-dc polarization because of proton-hopping-like motion rather than alpha-relaxation process. The correlation time (tau(c)) for the backbone carbon of dextran 40k and IMT, calculated from the measured value of spin-lattice relaxation time in the rotating frame, was found to be close to the relaxation time of proton-hopping-like motion determined by DES (tau(DES)) at temperatures around glass transition temperature. The timescales of molecular motions reflected in the tau(c) and tau(DES) were significantly smaller than that of motions leading to molecular rearrangement (molecular rearrangement motions), which correspond to alpha-relaxation. However, the shapes of temperature dependence for the tau(c) and tau(DES) were similar to that of the calorimetrically determined relaxation time of molecular rearrangement motions. Results suggest that the molecular motions reflected in the tau(c) and tau(DES) are linked to molecular rearrangement motions, such that enhancement of molecular rearrangement motions enhances

  2. The question of high- or low-temperature glass transition in frozen fish. Construction of the supplemented state diagram for tuna muscle by differential scanning calorimetry.

    Science.gov (United States)

    Orlien, Vibeke; Risbo, Jens; Andersen, Mogens L; Skibsted, Leif H

    2003-01-01

    The thermal behavior of fresh tuna muscle, rehydrated freeze-dried tuna muscle, and tuna sarcoplasmic protein fraction was studied by three types of differential scanning calorimetry (DSC): conventional DSC, alternating DSC, and sensitive micro-DSC. The relationship between glass transition temperature, T(g), and water content was established. Only a low-temperature glass transition was detected for fresh tuna and freeze-dried tuna rehydrated to high water contents, whereas for sarcoplasmic protein fraction both a low-temperature and an apparent high-temperature glass transition were detected for samples of high water content. Construction of the supplemented state diagrams for whole tuna muscle and for tuna sarcoplasmic protein fraction confirmed the low-temperature transition to be glass transition of the maximally freeze-dehydrated phase. The apparent upper transition of sarcoplasmic protein fraction was shown not to be a glass transition but rather to originate from the onset of melting of ice, and the temperature of this event should be denoted T(m)'. The glass transition temperature and the concentration of the maximally freeze dehydrated tuna muscle are -74 degrees C and 79% (w/w), respectively.

  3. Confinement effects on glass transition temperature, transition breadth, and linear expansivity: an ultraslow X-ray reflectivity study on supported ultrathin polystyrene films.

    Science.gov (United States)

    Yang, Chunming; Onitsuka, Rena; Takahashi, Isao

    2013-06-01

    X-ray reflectivity measurements of the glass transition in thin polystyrene films supported on Si substrates were performed at slow cooling rates ranging from 0.62 to 0.01 (°)C/min. At a cooling rate of 0.14 (°)C/min, a depression in the glass transition temperature Tg was clearly observed with decreasing thickness. However, at a cooling rate of 0.62 (°)C/min, only a slight decrease in Tg for a 12-nm-thick film was observed, while at an ultraslow cooling rate of 0.01 °C/min, a significant reduction in the Tg of ultrathin films (12 and 6 nm) was observed. As the thickness decreased, a broadening in the width of the glass transition, w, was found at higher cooling rates (0.62 °C/min and 0.14 °C/min), while narrowing of w was observed at ultraslow cooling rates of 0.01 °C/min and 0.04 °C/min. A narrow distribution of relaxation time in the ultrathin films indicates that most segments are able to relax under the ultraslow cooling process, thus showing an inherent reduction in the Tg of the confined thin polymer films.

  4. Molecular simulation and mathematical modelling of glass transition temperature depression induced by CO2 plasticization in Polysulfone membranes

    Science.gov (United States)

    Lock, S. S. M.; Lau, K. K.; Lock Sow Mei, Irene; Shariff, A. M.; Yeong, Y. F.; Bustam, A. M.

    2017-08-01

    A sequence of molecular modelling procedure has been proposed to simulate experimentally validated membrane structure characterizing the effect of CO2 plasticization, whereby it can be subsequently employed to elucidate the depression in glass transition temperature (Tg ). Based on the above motivation, unswollen and swollen Polysulfone membrane structures with different CO2 loadings have been constructed, whereby the accuracy has been validated through good compliance with experimentally measured physical properties. It is found that the presence of CO2 constitutes to enhancement in polymeric chain relaxation, which consequently promotes the enlargement of molecular spacing and causes dilation in the membrane matrix. A series of glass transition temperature treatment has been conducted on the verified molecular structure to elucidate the effect of CO2 loadings to the depression in Tg induced by plasticization. Subsequently, a modified Michealis-Menten (M-M) function has been implemented to quantify the effect of CO2 loading attributed to plasticization towards Tg .

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

    Science.gov (United States)

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

    2018-01-05

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

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

    Science.gov (United States)

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

    2018-01-01

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

  7. Freeze-Drying Above the Glass Transition Temperature in Amorphous Protein Formulations While Maintaining Product Quality and Improving Process Efficiency.

    Science.gov (United States)

    Depaz, Roberto A; Pansare, Swapnil; Patel, Sajal Manubhai

    2016-01-01

    This study explored the ability to conduct primary drying during lyophilization at product temperatures above the glass transition temperature of the maximally freeze-concentrated solution (Tg′) in amorphous formulations for four proteins from three different classes. Drying above Tg′ resulted in significant reductions in lyophilization cycle time. At higher protein concentrations, formulations freeze dried above Tg′ but below the collapse temperature yielded pharmaceutically acceptable cakes. However, using an immunoglobulin G type 4 monoclonal antibody as an example, we found that as protein concentration decreased, minor extents of collapse were observed in formulations dried at higher temperatures. No other impacts to product quality, physical stability, or chemical stability were observed in this study among the different drying conditions for the different proteins. Drying amorphous formulations above Tg′, particularly high protein concentration formulations, is a viable means to achieve significant time and cost savings in freeze-drying processes.

  8. An ab initio study of transition metals doped with WSe2 for long-range room temperature ferromagnetism in two-dimensional transition metal dichalcogenide.

    Science.gov (United States)

    Gil, Carmen J; Pham, Anh; Yu, Aibing; Li, Sean

    2014-07-30

    We report a systematic study of the magnetic properties in transition metals doped with WSe2 through the use of first principle calculations. The results demonstrate the possibility of generating long-range room temperature ferromagnetic interaction in WSe2 with the use of Mn and Fe doping. In the case of Fe, a percolation threshold is required for long-range ferromagnetism, whereas the long-range room temperature ferromagnetic interaction in Mn-doped WSe2 persists even at a low concentration (~5.6%). The ferromagnetism is mediated by the delocalized p states in the Se atoms, which couple antiferromagnetically with the spin-down a1 and e1 states in Fe doping through a correlated interaction. In Mn doping, the p states of Se tend to couple ferromagnetically with the 3d state of Mn, which stabilizes the long-range ferromagnetism between the Mn ions, although the short-range interaction is antiferromagnetic. In addition, the calculations indicate that Fe and Mn tend to configure at a high spin state, thus they possess much larger magnetic moments in WSe2 than when they are doped into other transition metal dichalcogenides. We also discovered a strong dependence of the exchange interaction on the dopants' spatial positions, distances, and concentrations, which alters the magnetic coupling from strong ferromagnetism to strong antiferromagnetism. These results can provide useful guidance to engineer the magnetic properties of WSe2 in future experiments.

  9. Phase transitions and steady-state microstructures in a two-temperature lattice-gas model with mobile active impurities

    DEFF Research Database (Denmark)

    Henriksen, Jonas Rosager; Sabra, Mads Christian; Mouritsen, Ole G.

    2000-01-01

    The nonequilibrium, steady-state phase transitions and the structure of the different phases of a two-dimensional system with two thermodynamic temperatures are studied via a simple lattice-gas model with mobile active impurities ("hot/cold spots'') whose activity is controlled by an external drive....... The properties of the model are calculated by Monte Carlo computer-simulation techniques. The two temperatures and the external drive on the system lead to a rich phase diagram including regions of microstructured phases in addition to macroscopically ordered (phase-separated) and disordered phases. Depending...

  10. Bonding at Compatible and Incompatible Amorphous Interfaces of Polystyrene and Poly(Methyl Methacrylate) Below the Glass Transition Temperature

    DEFF Research Database (Denmark)

    Boiko, Yuri M.; Lyngaae-Jørgensen, Jørgen

    2004-01-01

    Films of high-molecular-weight amorphous polystyrene (PS, M-w = 225 kg/mol, M-w/M-n = 3, T-g-bulk = 97degreesC, where T-g-bulk is the glass transition temperature of the bulk sample) and poly(methyl methacrylate) (PMMA, M-w = 87 kg/mol, M-w/M-n = 2, Tg-bulk = 109degreesC) were brought into contact...

  11. DEFLAGRATION-TO-DETONATION TRANSITION IN LX-04 AS A FUNCTION OF LOADING DENSITY, TEMPERATURE, AND CONFINEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Sandusky, H W; Granholm, R H; Bohl, D G; Vandersall, K S; Hare, D E; Garcia, F

    2006-06-20

    The potential for deflagration-to-detonation transition (DDT) in LX-04 (85/15 HMX/Viton) is being evaluated as a function of loading density, temperature, and confinement. In the high confinement arrangement, a matrix of tests is nearly completed with the LX-04 loaded at {approx} 51, 70, 90, and {approx} 99% of theoretical maximum density (TMD); and temperatures of ambient, 160 C, and 190 C at each loading density. A more limited set of tests with {approx}99 %TMD loadings at medium confinement were conducted at temperatures of ambient and 186 C. LX-04 does not undergo DDT at near TMD loadings in both medium and high confinement, although the latter still results in significant fragmentation. Most porous beds in high confinement undergo DDT, with the minimum run distance to detonation (l) for a 70 %TMD loading at ambient temperature. LX-04 does not transit to detonation for a pour density (51.3 %TMD) loading at 160 C, but does at 190 C with a longer l than at ambient. The limited ambient temperature measurements for l in high confinement are similar to previous data for 91/9 HMX/wax, which has nearly the same %volume of HMX as LX-04.

  12. The peculiar behavior of the glass transition temperature of amorphous drug-polymer films coated on inert sugar spheres.

    Science.gov (United States)

    Dereymaker, Aswin; Van Den Mooter, Guy

    2015-05-01

    Fluid bed coating has been proposed in the past as an alternative technology for manufacturing of drug-polymer amorphous solid dispersions, or so-called glass solutions. It has the advantage of being a one-step process, and thus omitting separate drying steps, addition of excipients, or manipulation of the dosage form. In search of an adequate sample preparation method for modulated differential scanning calorimetry analysis of beads coated with glass solutions, glass transition broadening and decrease of the glass transition temperature (Tg ) were observed with increasing particle size of crushed coated beads and crushed isolated films of indomethacin (INDO) and polyvinylpyrrolidone (PVP). Substituting INDO with naproxen gave comparable results. When ketoconazole was probed or the solvent in INDO-PVP films was switched to dichloromethane (DCM) or a methanol-DCM mixture, two distinct Tg regions were observed. Small particle sizes had a glass transition in the high Tg region, and large particle sizes had a glass transition in the low Tg region. This particle size-dependent glass transition was ascribed to different residual solvent amounts in the bulk and at the surface of the particles. A correlation was observed between the deviation of the Tg from that calculated from the Gordon-Taylor equation and the amount of residual solvent at the Tg of particles with different sizes. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  13. Icosahedron-fcc transition size by molecular dynamics simulation of Lennard-Jones clusters at a finite temperature.

    Science.gov (United States)

    Ikeshoji, T; Torchet, G; de Feraudy, M F; Koga, K

    2001-03-01

    We studied finite-temperature ensembles of solid clusters produced by cooling liquid droplets either by evaporation or by a thermostat through a molecular dynamics calculation using the Lennard-Jones potential. The ensembles consist of either single or binary component clusters with 25% of the atoms 8% smaller in diameter than the other 75%. These clusters (380 clusters in total) exhibit various structures in the size range of n=160-2200, where n is the number of atoms in a cluster. For increasing size, the clusters show a gradual transition from icosahedral to a variety of structures: decahedral, face centered cubic, a small amount of hexagonal, and some icosahedral structures. They are asymmetrical or faulted. Electron diffraction patterns calculated with average structure factors of clusters after grouping them into several size regions are very similar to those experimentally observed. The size transition is around n=450 for single component clusters whatever the cooling process, evaporation or thermostat. This size is smaller than the experimental transition size estimated for argon clusters formed in a supersonic expansion. The transition size for binary component clusters is around n=600 for evaporative cooling, and larger for thermostatic cooling. The larger transition size found for the binary component clusters is consistent with the large icosahedral Au-Fe and Au-Cu alloy clusters observed experimentally.

  14. A Physically Based Correlation of Irradiation-Induced Transition Temperature Shifts for RPV Steels

    Energy Technology Data Exchange (ETDEWEB)

    Eason, Ernest D. [Modeling and Computing Services, LLC; Odette, George Robert [UCSB; Nanstad, Randy K [ORNL; Yamamoto, Takuya [ORNL

    2007-11-01

    The reactor pressure vessels (RPVs) of commercial nuclear power plants are subject to embrittlement due to exposure to high-energy neutrons from the core, which causes changes in material toughness properties that increase with radiation exposure and are affected by many variables. Irradiation embrittlement of RPV beltline materials is currently evaluated using Regulatory Guide 1.99 Revision 2 (RG1.99/2), which presents methods for estimating the shift in Charpy transition temperature at 30 ft-lb (TTS) and the drop in Charpy upper shelf energy (ΔUSE). The purpose of the work reported here is to improve on the TTS correlation model in RG1.99/2 using the broader database now available and current understanding of embrittlement mechanisms. The USE database and models have not been updated since the publication of NUREG/CR-6551 and, therefore, are not discussed in this report. The revised embrittlement shift model is calibrated and validated on a substantially larger, better-balanced database compared to prior models, including over five times the amount of data used to develop RG1.99/2. It also contains about 27% more data than the most recent update to the surveillance shift database, in 2000. The key areas expanded in the current database relative to the database available in 2000 are low-flux, low-copper, and long-time, high-fluence exposures, all areas that were previously relatively sparse. All old and new surveillance data were reviewed for completeness, duplicates, and discrepancies in cooperation with the American Society for Testing and Materials (ASTM) Subcommittee E10.02 on Radiation Effects in Structural Materials. In the present modeling effort, a 10% random sample of data was reserved from the fitting process, and most aspects of the model were validated with that sample as well as other data not used in calibration. The model is a hybrid, incorporating both physically motivated features and empirical calibration to the U.S. power reactor surveillance

  15. Transition Metal Coatings for Energy Conversion and Storage; Electrochemical and High Temperature Applications

    Science.gov (United States)

    Falola, Bamidele Daniel

    Energy storage provides sustainability when coupled with renewable but intermittent energy sources such as solar, wave and wind power, and electrochemical supercapacitors represent a new storage technology with high power and energy density. For inclusion in supercapacitors, transition metal oxide and sulfide electrodes such as RuO2, IrO2, TiS2, and MoS2 exhibit rapid faradaic electron-transfer reactions combined with low resistance. The pseudocapacitance of RuO2 is about 720 F/g, and is 100 times greater than double-layer capacitance of activated carbon electrodes. Due to the two-dimensional layered structure of MoS2, it has proven to be an excellent electrode material for electrochemical supercapacitors. Cathodic electrodeposition of MoS2 onto glassy carbon electrodes is obtained from electrolytes containing (NH4)2MoS 4 and KCl. Annealing the as-deposited Mo sulfide deposit improves the capacitance by a factor of 40x, with a maximum value of 360 F/g for 50 nm thick MoS2 films. The effects of different annealing conditions were investigated by XRD, AFM and charge storage measurements. The specific capacitance measured by cyclic voltammetry is highest for MoS2 thin films annealed at 500°C for 3h and much lower for films annealed at 700°C for 1 h. Inclusion of copper as a dopant element into electrodeposited MoS2 thin films for reducing iR drop during film charge/discharge is also studied. Thin films of Cu-doped MoS2 are deposited from aqueous electrolytes containing SCN-, which acts as a complexing agent to shift the cathodic Cu deposition potential, which is much more anodic than that of MoS2. Annealed, Cu-doped MoS2 films exhibit enhanced charge storage capability about 5x higher than undoped MoS2 films. Coal combustion is currently the largest single anthropogenic source of CO2 emissions, and due to the growing concerns about climate change, several new technologies have been developed to mitigate the problem, including oxyfuel coal combustion, which makes CO2

  16. Dynamic approach to finite-temperature magnetic phase transitions in the extended J1-J2 model with vacancy order.

    Science.gov (United States)

    Zhou, N J; Zheng, B; Dai, J H

    2013-02-01

    The recently discovered iron-based superconductors A(y)Fe(2-x)Se(2) (A=K, Rb, Cs, Tl) show a long-range antiferromagnetic order with an unexpectedly high transition temperature T(N)~550 K and a unique √5×√5 vacancy order. Taking the extended J(1)-J(2) model as a minimal model, we investigate the finite-temperature magnetic phase transitions in a square lattice with a √5×√5 vacancy superstructure by using large-scale Monte Carlo simulations. By the parallel tempering technique, the block spin checkerboard and stripe antiferromagnetic states are detected to be the ground states for three representative sets of model parameters. The short-time dynamic approach is applied to accurately determine the critical temperature as well as the static and dynamic exponents. Our results indicate that the dramatic enhancement of the critical temperature as observed in experiments should be mainly due to a combination of the vacancy order and the block lattice contraction.

  17. Direct observation of temperature-driven magnetic symmetry transitions by vectorial resolved MOKE magnetometry

    Science.gov (United States)

    Cuñado, Jose Luis F.; Pedrosa, Javier; Ajejas, Fernando; Perna, Paolo; Miranda, Rodolfo; Camarero, Julio

    2017-10-01

    Angle- and temperature-dependent vectorial magnetometry measurements are necessary to disentangle the effective magnetic symmetry in magnetic nanostructures. Here we present a detailed study on an Fe(1 0 0) thin film system with competing collinear biaxial (four-fold symmetry) and uniaxial (two-fold) magnetic anisotropies, carried out with our recently developed full angular/broad temperature range/vectorial-resolved magneto-optical Kerr effect magnetometer, named TRISTAN. The data give direct views on the angular and temperature dependence of the magnetization reversal pathways, from which characteristic axes, remanences, critical fields, domain wall types, and effective magnetic symmetry are obtained. In particular, although the remanence shows four-fold angular symmetry for all investigated temperatures (15 K-400 K), the critical fields show strong temperature and angular dependencies and the reversal mechanism changes for specific angles at a given (angle-dependent) critical temperature, showing signatures of an additional collinear two-fold symmetry. This symmetry-breaking is more relevant as temperature increases to room temperature. It originates from the competition between two anisotropy contributions with different symmetry and temperature evolution. The results highlight the importance of combining temperature and angular studies, and the need to look at different magnetic parameters to unravel the underlying magnetic symmetries and temperature evolutions of the symmetry-breaking effects in magnetic nanostructures.

  18. Standard Guide for Predicting Radiation-Induced Transition Temperature Shift in Reactor Vessel Materials, E706 (IIF)

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2002-01-01

    1.1 This guide presents a method for predicting reference transition temperature adjustments for irradiated light-water cooled power reactor pressure vessel materials based on Charpy V-notch 30-ftlbf (41-J) data. Radiation damage calculative procedures have been developed from a statistical analysis of an irradiated material database that was available as of May 2000. The embrittlement correlation used in this guide was developed using the following variables: copper and nickel contents, irradiation temperature, and neutron fluence. The form of the model was based on current understanding for two mechanisms of embrittlement: stable matrix damage (SMD) and copper-rich precipitation (CRP); saturation of copper effects (for different weld materials) was included. This guide is applicable for the following specific materials, copper, nickel, and phosphorus contents, range of irradiation temperature, and neutron fluence based on the overall database: 1.1.1 MaterialsA 533 Type B Class 1 and 2, A302 Grade B, A302 G...

  19. Hydrogen-doping induced reduction in the phase transition temperature of VO2: a first-principles study.

    Science.gov (United States)

    Cui, Yuanyuan; Shi, Siqi; Chen, Lanli; Luo, Hongjie; Gao, Yanfeng

    2015-08-28

    VO2 is a promising thermochromic material that can intelligently control the transmittance of sunlight in the near-infrared region in response to temperature change, although the high phase transition temperature (Tc) of 340 K restricts its wide application. Our first-principles calculations show that hydrogen is an efficient dopant which can stabilize the metallic VO2 phase at ambient temperature through reducing Tc by 38 K/at% H. The reduction in Tc is coupled with the changes in atomic and electronic structures, i.e., the V-V chains feature the dimerization characteristics in H-doped VO2(R) and the V-O bonds become less ionic due to the formation of a typical H-O covalent bond. In addition, hydrogen-doped VO2 is more sensitive to external strain as compared with pure VO2, implying that Tc can be further regulated through a combination of H-doping and strain.

  20. Effect of heat-treatment on phase transition temperatures of a superelastic NiTi alloy for medical use

    Energy Technology Data Exchange (ETDEWEB)

    Yeung, K.W.K.; Cheung, K.M.C.; Lu, W.W.; Luk, K.D.K. [Univ. of Hong Kong (China). Dept. of Orthopaedic Surgery; Chung, C.Y. [City Univ. of Hong Kong, Kowloon (China). Dept. of Physics and Materials Science

    2002-07-01

    Surgical correction of scoliosis typically uses stainless steel or titanium alloy spinal instrumentation to straighten the scoliotic spine by 70% only. Our aim is to develop a method to overcome this by using an implantable superelastic (SE) nickel-titanium (NiTi) alloy rod, which will impose a continuous gradual correction force to the spine after the surgery so as to achieve a superior correction. More than 75 specimens made of a Ti-50.0 at% Ni alloy were treated by different heat treatment routes. The Austenitic transition temperature of the NiTi alloy can be adjusted to be available at 37.5 C by altering the heat treatment parameters: time and temperature of heat treatment. The experimental results showed that the heat treatment temperature should set between 400-500 C and the heat treatment time should be less than 60 minutes for the alloy. (orig.)

  1. On the critical temperature discontinuity at the theoretical bcc-fcc phase transition in compressed selenium and tellurium superconductors

    Science.gov (United States)

    Szczęśniak, D.; Wrona, I. A.; Drzazga, E. A.; Kaczmarek, A. Z.; Szewczyk, K. A.

    2017-11-01

    Recent hydrides-driven advent in the high-pressure phonon-mediated superconductivity motivates research on chemical elements which compound with hydrogen. It is desired that such elements should allow chemical pre-compression of hydrogen to assure the induction of the superconducting phase with the high transition temperature (T C). Herein, we present detailed theoretical insight into the properties of the superconducting state induced under pressure (p) in two of such component elements, namely selenium (Se) and tellurium (Te) at p=250 GPa and p=70 GPa, respectively. The assumed external pressure conditions allow us to conduct our analysis just above previously theoretically predicted bcc-fcc structural phase transition of Se and Te, and identify the possible associated discontinuity effect of the critical temperature. In particular, our numerical analysis is conducted within Migdal-Eliashberg formalism, due to the confirmed electron-phonon pairing mechanism and relatively high electron-phonon coupling constant in the materials of interest. We predict that T C values in Se and Te equal 8.13 K and 5.96 K, respectively, and mark the highest critical temperature values for these elements within the postulated fcc phase. Additionally, we supplement these results by the estimated maximum values of the superconducting energy band gap and the effective mass of electrons. We predict that all these parameters can be used as a guidelines for experimental observation of the critical temperature discontinuity and the corresponding bcc-fcc phase transition in Se and Te superconductors. Moreover, we show that the thermodynamics of superconducting phase in both elements may exhibit deviations from the conventional estimates of the Bardeen-Cooper-Schrieffer theory, and suggest existence of the strong-coupling and retardation effects. Finally, we note that our results can be also instructive for future screening of chemical elements for applications in superconducting hydrides.

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

    Science.gov (United States)

    Popova, V A; Surovtsev, N V

    2014-09-01

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

  3. Hydrothermal extraction of antioxidant compounds from mangosteen pericarp with low-transition-temperature mixture and sonication pretreatment

    Science.gov (United States)

    Machmudah, Siti; Widiyastuti, Nurtono, Tantular; Winardi, Sugeng; Wahyudiono, Kanda, Hideki; Goto, Motonobu

    2017-05-01

    Antioxidant compounds from mangosteen pericarps have been extracted with low-transition-temperature mixture (LTTM) assisted hydrothermal method. Extracted antioxidant compounds were determined as xanthone and total phenolic compounds. The effects of temperature, concentration of LTTM, and sonication pretreatment on the recovery of xanthone and total phenolic compounds were investigated. Extraction were carried out in a batch extractor at various temperatures (120 - 160°C), concentrations of LTTM (0.1 - 0.3 mg/mL), and sonication pretreatments (0 - 10 min). LTTM used for extraction was consisted of citric acid as hydrogen bond donor and alanine as hydrogen bond acceptor. Xanthone and total phenolic compounds were analyzed by spectrophotometer. In order to determine the effect of extraction condition on the antioxidant efficiency of the extract, the antioxidant efficiency of extract were analyzed by DPPH assay method. Based on the result, the recovery of xanthone increased as increasing temperature and concentration of LTTM. Inversely, the recovery of total phenolic compounds decreased as increasing temperature. The sonication pretreatment had significantly effect on the recovery of both xanthone and total phenolic compounds, however the optimum condition of sonication pretreatment was at 5 min. The antioxidant efficiency of the extract was affected by the extraction condition, and the highest antioxidant efficiency was 1.395 obtained at temperature of 120°C, LTTM concentration of 0.3 mg/mL, and sonication time of 5 min.

  4. Orientation relations during the α-ω phase transition of zirconium: in situ texture observations at high pressure and temperature.

    Science.gov (United States)

    Wenk, H-R; Kaercher, P; Kanitpanyacharoen, W; Zepeda-Alarcon, E; Wang, Y

    2013-11-08

    Transition metals Ti, Zr, and Hf have a hexagonal close-packed structure (α) at ambient conditions, but undergo phase transformations with increasing temperature and pressure. Of particular significance is the high-pressure hexagonal ω phase which is brittle compared to the α phase. There has been a long debate about transformation mechanisms and orientation relations between the two crystal structures. Here we present the first high pressure experiments with in situ synchrotron x-ray diffraction texture studies on polycrystalline aggregates. We follow crystal orientation changes in Zr, confirming the original suggestion by Silcock for an α→ω martensitic transition for Ti, with (0001)(α)||(1120)(ω), and a remarkable orientation memory when ω reverts back to α.

  5. Hydrogen-bond mediated transitional adlayer of glycine on Si(111)7 x 7 at room temperature.

    Science.gov (United States)

    Zhang, L; Chatterjee, A; Ebrahimi, M; Leung, K T

    2009-03-28

    The growth of glycine film by thermal evaporation on Si(111)7 x 7 at room temperature has been studied by X-ray photoemission. In contrast to common carboxylic acids, glycine is found to adsorb on Si(111)7 x 7 dissociatively through cleavage of a N-H bond instead of O-H bond. The intricate evolution of the observed N 1s features at 399.1, 401.4, and 402.2 eV with increasing film thickness demonstrates the existence of a transitional adlayer between the first adlayer and the zwitterionic multilayer. This transitional adlayer is estimated to be 1-2 adlayer thick and is characterized by the presence of intermolecular N...HO hydrogen bond. An intramolecular proton transfer mechanism is proposed to account for the adsorption process through the amino group.

  6. Mapping of the Resistance of a Superconducting Transition Edge Sensor as a Function of Temperature, Current, and Applied Magnetic Field

    Science.gov (United States)

    Zhang, Shou; Eckart, Megan E.; Jaeckel, Felix; Kripps, Kari L.; McCammon, Dan; Zhou, Yu; Morgan, Kelsey M.

    2017-01-01

    We have measured the resistance R (T, I, B(sub ext) of a superconducting transition edge sensor over the entire transition region on a fine scale, producing a four-dimensional map of the resistance surface. The dimensionless temperature and current sensitivities (alpha equivalence partial derivative log R/partial derivative log T|(sub I) and beta equivalence partial derivative log R/partial derivative log I|(sub T) of the TES resistance have been determined at each point. alpha and beta are closely related to the sensor performance, but show a great deal of complex, large amplitude fine structure over large portions of the surface that is sensitive to the applied magnetic field. We discuss the relation of this structure to the presence of Josephson weak link fringes.

  7. On the Frequency Correction in Temperature-Modulated Differential Scanning Calorimetry of Glass Transition

    DEFF Research Database (Denmark)

    Guo, Xiaoju; Mauro, J.C.; Allan, D.C.

    2012-01-01

    Temperature-modulated differential scanning calorimetry (TMDSC) is based on conventional DSC but with a sinusoidally modulated temperature path. Simulations of TMDSC signals were performed for Corning EAGLE XG® glass over a wide range of modulation frequencies. Our results reveal that the frequency...

  8. Insights into glass transition and relaxation behavior using temperature-modulated differential scanning calorimetry

    DEFF Research Database (Denmark)

    Guo, Xiaoju; Mauro, J.C.; Allan, D.C.

    Temperature-modulated differential scanning calorimetry (TMDSC) is based on conventional DSC but with a sinusoidally modulated temperature path. Our simulations of TMDSC signals prove that the frequency correction of non-reversing heat flow can give a master curve within a certain range of freque...

  9. Magnetic Phase Transition in Rare Earth Metal Holmium at Low Temperatures and High Pressures

    Science.gov (United States)

    Thomas, Sarah; Uhoya, Walter; Wenger, Lowell; Vohra, Yogesh

    2012-02-01

    The heavy rare earth metal Holmium has been studied under high pressures and low temperatures using a designer diamond anvil cell and neutron diffraction using a Paris-Edinburgh Cell at the Spallation Neutrons and Pressure (SNAP) Diffractometer. The electrical resistance measurement using designer diamond shows a change in slope at the Neel temperature as the temperature is lowered at high pressures. At atmospheric pressure TN=120 K and decreases with a slope of -4.7 K/GPa as pressure is increased, until reaching 9 GPa, at which pressure the magnetic ordering is lost. This correlates to the pressure at which there is a structural change from an hcp phase to an α-Sm structure. Neutron diffraction measurements made above and below the Neel temperature at increasing pressures show the reversibility of the change between the paramagnetic and antiferromagnetic states. The parameters of the low temperature incommensurate magnetic phase will be reported at various pressures.

  10. EFFECTS OF TRITIUM GAS EXPOSURE ON THE GLASS TRANSITION TEMPERATURE OF EPDM ELASTOMER AND ON THE CONDUCTIVITY OF POLYANILINE

    Energy Technology Data Exchange (ETDEWEB)

    Clark, E; Marie Kane, M

    2008-12-12

    Four formulations of EPDM (ethylene-propylene diene monomer) elastomer were exposed to tritium gas initially at one atmosphere and ambient temperature for between three and four months in closed containers. Material properties that were characterized include density, volume, mass, appearance, flexibility, and dynamic mechanical properties. The glass transition temperature was determined by analysis of the dynamic mechanical property data per ASTM standards. EPDM samples released significant amounts of gas when exposed to tritium, and the glass transition temperature increased by about 3 C. during the exposure. Effects of ultraviolet and gamma irradiation on the surface electrical conductivity of two types of polyaniline films are also documented as complementary results to planned tritium exposures. Future work will determine the effects of tritium gas exposure on the electrical conductivity of polyaniline films, to demonstrate whether such films can be used as a sensor to detect tritium. Surface conductivity was significantly reduced by irradiation with both gamma rays and ultraviolet light. The results of the gamma and UV experiments will be correlated with the tritium exposure results.

  11. Room-temperature electrically driven phase transition of two-dimensional 1T-TaS2 layers.

    Science.gov (United States)

    Zheng, Shoujun; Liu, Fucai; Zhu, Chao; Liu, Zheng; Fan, Hong Jin

    2017-02-16

    Due to the strong electron-electron and electron-phonon interactions, the transition metal dichalcogenide 1T-TaS2 exhibits temperature dependent as well as electric field driven charge density wave (CDW) phase transitions (PTs). In this work, we investigate the thickness dependence of the electric field driven PT in 1T-TaS2 two-dimensional (2D) flakes. Electrically driven PT between high- and low-resistance states occurs at temperatures in the range of 60-300 K. For a thin 1T-TaS2 (≤8.8 nm) sample, only one PT is triggered, whereas thick films experience double PTs (13-17 nm) and multiple PTs (≥17.5 nm) until reaching the final low-resistance state. The multiple PTs may imply the existence of hidden nearly-commensurate charge density wave (NCCDW) states. In addition, a threshold electric field is observed, in which the low-resistance state is unable to resume the high-resistance state. Finally, we fabricate a 1T-TaS2/graphene hybrid field effect transistor to achieve a gate-tunable PT at room temperature. Such a hybrid device might provide a new avenue for the construction of CDW-based memories based on 2D materials.

  12. Near infrared absorption spectrum of perfluoro- t-butanol/acetonitrile complexes at low temperatures: Fermi resonances and simultaneous transitions

    Science.gov (United States)

    Burneau, André

    1989-01-01

    Interactions between perfluoro- t-butanol (PFTB) and acetonitrile- d3 (AN) in a mixture of freons are studied between 298 and 88 K in liquid or vitreous states. In the conditions of the experiment, a mean 1:2 stoichiometry [PFTB⋯(AN) 2] is inferred from previous matrix measurements. A ν OH shift of about 160 cm -1 is observed in this temperature range: it is mainly ascribed to solvent effects on the complex. In fact, the dν OH/d T coefficient increases at low temperature on account of specific solvation of the complex by the freon Br atoms. The ν OH + τ OH combination wavenumber is little dependent on the state of PFTB, near 3900 cm -1. A comparatively strong simultaneous transition involving the PFTB ν OH mode and a ν CN mode of neighbouring AN molecules is observed. Weaker bands could also be explained by such transitions involving a combination level of PFTB and a ν CN vibration. Strong Fermi resonances are displayed in the 2ν OH region when the ν OH band is located around 3100 cm -1, either in pure AN or in freons at low temperature. The levels interacting with 2ν OH are ternary combinations and quaternary overtones mainly involving the COH bend and the CO stretch. These resonances are favoured by a strong increase of the OH stretching vibration anharmonicity.

  13. Seeded Growth of Ferrite Nanoparticles from Mn oxides : Observation of Anomalies in Magnetic Transitions

    KAUST Repository

    Song, Hyon-Min

    2015-06-17

    A series of magnetically active ferrite nanoparticles (NPs) are prepared by using Mn oxide NPs as seeds. Verwey transition is identified in Fe3O4 NPs with an average diameter of 14.5 nm at 96 K, where a sharp drop of magnetic susceptibility occurs. In MnFe2O4 NPs, spin glass-like state is observed with the decrease of magnetization below the blocking temperature due to the disordered spins during the freezing process. From these MnFe2O4 NPs, MnFe2O4@MnxFe1-xO core-shell NPs are prepared by seeded growth. The structure of core is cubic spinels (Fd-3m), and shell is composed of iron-manganese oxide (MnxFe1-xO) with a rock salt structure (Fm-3m). Moiré fringes appear perpendicular to <110> directions on the cubic shape NPs through the plane-matched epitaxial growth. These fringes are due to the difference in their lattice spacings between MnFe2O4 and MnxFe1-xO. Exchange bias is observed in these MnFe2O4@MnxFe1-xO core-shell NPs with an enhanced coercivity as well as the shift of hysteresis along the field direction.

  14. Synthesis, crystal structure, and high-temperature phase transition of the novel plumbide Na2MgPb.

    Science.gov (United States)

    Yamada, Takahiro; Ikeda, Takuji; Stoffel, Ralf P; Deringer, Volker L; Dronskowski, Richard; Yamane, Hisanori

    2014-05-19

    A hitherto unknown sodium magnesium plumbide, Na2MgPb, was synthesized by heating the constituent elements. Na2MgPb crystallizes in a hexagonal unit cell with the Li2CuAs-type structure (P63/mmc, Z = 2, a = 5.110(2) Å, c = 10.171(4) Å at 293 K). The compound furthermore displays polymorphism: high-temperature powder XRD measurements revealed that hexagonal Na2MgPb (dubbed the "α" phase) transforms to another hexagonal phase (β) which is existent at 493-553 K, and the β phase changes to a cubic structure (γ) at 533-633 K further. The molar volume of γ-Na2MgPb is approximately 9% and 13% smaller than the molar volumes of the α phase and the β phase, respectively (at 543 K). The electrical resistivity of Na2MgPb is 0.39 mΩ at 300 K; it rises with increasing temperature from 300 to 491 K, and then drops at 491 and 523 K. These abrupt changes in resistivity may be attributed to the α → β and β → γ phase transitions, respectively. To gain further insight into the structure of cubic γ-Na2MgPb, putative models with regular Heusler-type (Cu2MnAl-type) and inverse Heusler-type (Li2AgSb-type) arrangements were probed using first-principles computations based on density functional theory (DFT). These computations indicate that, for the cubic γ phase, an inverse Heusler-type structure is distinctly more stable than the alternative regular Heusler type (at 0 K); beyond that, ab initio thermochemistry was successfully used to verify the stability ordering (α-Na2MgPb being favorable at low temperature, γ-Na2MgPb at high temperature), albeit the theoretically predicted transition temperature of 900 K which is higher than observed in experiment.

  15. The influence of temperature induced phase transition on the energy storage density of anti-ferroelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Jinqiao; Zhang, Ling; Xie, Bing; Jiang, Shenglin, E-mail: nanx1013@163.com [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2015-09-28

    Anti-ferroelectric (AFE) composite ceramics of (Pb{sub 0.858}Ba{sub 0.1}La{sub 0.02}Y{sub 0.008})(Zr{sub 0.65}Sn{sub 0.3}Ti{sub 0.05})O{sub 3}-(Pb{sub 0.97}La{sub 0.02})(Zr{sub 0.9}Sn{sub 0.05} Ti{sub 0.05})O{sub 3} (PBLYZST-PLZST) were fabricated by the conventional solid-state sintering process (CS), the glass-aided sintering (GAS), and the spark plasma sintering (SPS), respectively. The influence of the temperature induced phase transition on the phase structure, hysteresis loops, and energy storage properties of the composite ceramics were investigated in detail. The measured results of X-ray diffraction demonstrate that the composite ceramics exhibit the perovskite phases and small amounts of non-functional pyrochlore phases. Compared with the CS process, the GAS and SPS processes are proven more helpful to suppress the diffusion behaviors between the PBLYZST and PLZST phases according to the field emission scanning electron microscopy, thereby being able to improve the contribution of PBLYZST phase to the temperature stability of the orthogonal AFE phase. When the ambient temperature rises from 25 °C to 125 °C, CS and GAS samples have undergone a phase transition from orthorhombic AFE phase to tetragonal AFE phase, which results in a sharp decline in the energy storage density. However, the phase transition temperature of SPS samples is higher than 125 °C, and the energy storage density only slightly decreases due to the disorder of material microstructure caused by the high temperature. As a result, the SPS composite ceramics obtain a recoverable high energy storage density of 6.46 J/cm{sup 3} and the excellent temperature stability of the energy storage density of 1.16 × 10{sup −2} J/°C·cm{sup 3}, which is 1.29 × 10{sup −2} J/°C·cm{sup 3} lower than that of CS samples and about 0.43 times as that of GAS samples.

  16. Kinetics of a bioactive compound (caffeine) mobility at the vicinity of the mechanical glass transition temperature induced by gelling polysaccharide.

    Science.gov (United States)

    Jiang, Bin; Kasapis, Stefan

    2011-11-09

    An investigation of the diffusional mobility of a bioactive compound (caffeine) within the high-solid (80.0% w/w) matrices of glucose syrup and κ-carrageenan plus glucose syrup exhibiting distinct mechanical glass transition properties is reported. The experimental temperature range was from 20 to -60 °C, and the techniques of modulated differential scanning calorimetry, small deformation dynamic oscillation in shear, and UV spectrometry were employed. Calorimetric and mechanical measurements were complementary in recording the relaxation dynamics of high-solid matrices upon controlled heating. Predictions of the reaction rate theory and the combined WLF/free volume framework were further utilized to pinpoint the glass transition temperature (T(g)) of the two matrices in the softening dispersion. Independent of composition, calorimetry yielded similar T(g) predictions for both matrices at this level of solids. Mechanical experimentation, however, was able to detect the effect of adding gelling polysaccharide to glucose syrup as an accelerated pattern of vitrification leading to a higher value of T(g). Kinetic rates of caffeine diffusion within the experimental temperature range were taken with UV spectroscopy. These demonstrated the pronounced effect of the gelling κ-carrageenan/glucose syrup mixture to retard diffusion of the bioactive compound near the mechanical T(g). Modeling of the diffusional mobility of caffeine produced activation energy and fractional free-volume estimates, which were distinct from those of the carbohydrate matrix within the glass transition region. This result emphasizes the importance of molecular interactions between macromolecular matrix and small bioactive compound in glass-related relaxation phenomena.

  17. Temperature-induced transitions in disordered proteins probed by NMR spectroscopy

    DEFF Research Database (Denmark)

    Kjærgaard, Magnus; Poulsen, Flemming Martin; Kragelund, Birthe Brandt

    2012-01-01

    Intrinsically disordered proteins are abundant in nature and perform many important physiological functions. Multidimensional NMR spectroscopy has been crucial for the understanding of the conformational properties of disordered proteins and is increasingly used to probe their conformational...... ensembles. Compared to folded proteins, disordered proteins are more malleable and more easily perturbed by environmental factors. Accordingly, the experimental conditions and especially the temperature modify the structural and functional properties of disordered proteins. NMR spectroscopy allows analysis...... of temperature-induced structural changes at residue resolution using secondary chemical shift analysis, paramagnetic relaxation enhancement, and residual dipolar couplings. This chapter discusses practical aspects of NMR studies of temperature-induced structural changes in disordered proteins....

  18. Temperature effect on first excited state energy and transition frequency of a strong-coupling polaron in a symmetry RbCl quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yong; Ding, Zhao-Hua; Xiao, Jing-Lin, E-mail: xiaojlin@126.com

    2014-07-01

    The first excited state energy, excitation energy and transition frequency of a strong-coupling polaron in a symmetric RbCl quantum dot (SRQD) are obtained by employing the linear combination operator and unitary transformation methods. Effects of temperature and confinement strength are taken into account. It is found that the first excited state energy, excitation energy and transition frequency are increasing functions of temperature and confinement strength.

  19. Temperature effect on first excited state energy and transition frequency of a strong-coupling polaron in a symmetry RbCl quantum dot

    Science.gov (United States)

    Sun, Yong; Ding, Zhao-Hua; Xiao, Jing-Lin

    The first excited state energy, excitation energy and transition frequency of a strong-coupling polaron in a symmetric RbCl quantum dot (SRQD) are obtained by employing the linear combination operator and unitary transformation methods. Effects of temperature and confinement strength are taken into account. It is found that the first excited state energy, excitation energy and transition frequency are increasing functions of temperature and confinement strength.

  20. Room temperature magneto-structural transition in Al for Sn substituted Ni–Mn–Sn melt spun ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Maziarz, W. [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 W. Reymonta Str., 30-059 Kraków (Poland); Czaja, P., E-mail: p.czaja@imim.pl [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 W. Reymonta Str., 30-059 Kraków (Poland); Szczerba, M.J. [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 W. Reymonta Str., 30-059 Kraków (Poland); Przewoźnik, J.; Kapusta, C. [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Department of Solid State Physics, Al. Mickiewicza 30, 30-059 Krakow (Poland); Żywczak, A.; Stobiecki, T. [AGH University of Science and Technology, Department of Electronics, Al. Mickiewicza 30, 30-059 Kraków (Poland); Cesari, E. [Department de Fisica, Universitat de Illes Balears, Ctra. de Valldemossa, km 7.5, Palma de Mallorca E-07071 (Spain); Dutkiewicz, J. [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 W. Reymonta Str., 30-059 Kraków (Poland)

    2013-12-15

    Martensitic and magnetic transformations in Ni{sub 48}Mn{sub 39.5}Sn{sub 12.5−x}Al{sub x} (x=0, 1, 2, 3) Heusler alloy ribbons were investigated. It is demonstrated that both magnetic and structural transformations occur in all of the studied samples. It is also shown that substitution of Sn with Al causes the martensitic transformation (MT) and the reverse martensitic transformation (RMT) temperatures to increase to room temperature (ΔT{sub MT}=49 K; ΔT{sub RMT}=43 K), whereas the Curie temperature of martensite T{sub C}{sup M} decreases (ΔT=36 K) and the Curie temperature of austenite T{sub C}{sup A} remains practically insensitive to Al introduction. This then allows to tune T{sub C}{sup A} and the MT temperature leading to their coincidence at ambient temperature. The austenite phase with the L2{sub 1} type structure has been identified to exist in all the samples regardless of composition. On the other hand the structure of martensite has been shown to be sensitive to composition. It has been determined as the 10 M martensite with (32{sup ¯}) stacking sequence in Al free samples and the 4O martensite with the stacking periodicity (31{sup ¯}) in Al containing samples. In addition, the splitting of the field cooling (FC) and the field heating (FH) thermo-magnetic curves at low (50 Oe) magnetic field and below the T{sub C}{sup M} has been attributed to intermartensitic transition. The application of large magnetic field (50 kOe) has shown the existence of two distinct ferromagnetic states with a considerable hysteresis loop. The properties of these materials make them promising for magnetocaloric applications. - Highlights: • Al for Sn substituted Ni–Mn–Sn based ferromagnetic Heusler alloys were produced by melt spinning. • Martensitic, reverse martensitic and intermartensitic transformations were observed, their temperatures and magnitude changed with Al substitution. • Different types of martensite structures were identified depending on Al

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-10-15

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

  2. Drastic lowering of the order-disorder phase transition temperatures in Zr1-xMxW2O8-y(M=Sc,Y,In) solid solutions

    Science.gov (United States)

    Yamamura, Yasuhisa; Nakajima, Noriyuki; Tsuji, Toshihide; Kojima, Ayumi; Kuroiwa, Yoshihiro; Sawada, Akikatsu; Aoyagi, Shinobu; Kasatani, Hirofumi

    2004-09-01

    ZrW2O8 undergoes an order-disorder phase transition associated with the orientational disordering of the WO4 tetrahedra at 440K . We have showed previously that the phase transition temperatures of Zr1-xMxW2O8-y(M=Sc,Y,In) solid solutions are decreased by a maximum of 80K with only 4% trivalent Sc content. In order to understand the drastic composition dependence on the transition temperature, precise x-ray diffraction experiments on the solid solutions were performed by using a synchrotron radiation. The results provided the evidence of the strong correlation between the phase transition temperature and the number of WO4 units with the ordered orientation. A model was proposed to interpret the drastic composition dependence on the transition temperature, by considering the existence of a local region including the WO4 pairs with the orientational disorder in Zr1-xMxW2O8-y(M=Sc,Y,In) . The local region has the crystal structure of the high-temperature phase in a nonequilibrium state, and spreads out around the substituted trivalent cations. The size of the local region was estimated to be a few unit cells. The local regions play just like nonmagnetic impurities in a site-diluted magnetic system, leading to drastic lowering of the phase transition temperatures in Zr1-xMxW2O8-y solid solutions.

  3. Response of a continuous anaerobic digester to temperature transitions: A critical range for restructuring the microbial community structure and function.

    Science.gov (United States)

    Kim, Jaai; Lee, Changsoo

    2016-02-01

    Temperature is a crucial factor that significantly influences the microbial activity and so the methanation performance of an anaerobic digestion (AD) process. Therefore, how to control the operating temperature for optimal activity of the microbes involved is a key to stable AD. This study examined the response of a continuous anaerobic reactor to a series of temperature shifts over a wide range of 35-65 °C using a dairy-processing byproduct as model wastewater. During the long-term experiment for approximately 16 months, the reactor was subjected to stepwise temperature increases by 5 °C at a fixed HRT of 15 days. The reactor showed stable performance within the temperature range of 35-45 °C, with the methane production rate and yield being maximum at 45 °C (18% and 26% greater, respectively, than at 35 °C). However, the subsequent increase to 50 °C induced a sudden performance deterioration with a complete cessation of methane recovery, indicating that the temperature range between 45 °C and 50 °C had a critical impact on the transition of the reactor's methanogenic activity from mesophilic to thermophilic. This serious process perturbation was associated with a severe restructuring of the reactor microbial community structure, particularly of methanogens, quantitatively as well as qualitatively. Once restored by interrupted feeding for about two months, the reactor maintained fairly stable performance under thermophilic conditions until it was upset again at 65 °C. Interestingly, in contrast to most previous reports, hydrogenotrophs largely dominated the methanogen community at mesophilic temperatures while acetotrophs emerged as a major group at thermophilic temperature. This implies that the primary methanogenesis route of the reactor shifted from hydrogen- to acetate-utilizing pathways with the temperature shifts from mesophilic to thermophilic temperatures. Our observations suggest that a mesophilic digester may not need to be cooled at up

  4. Non-equilibrium phase transitions in the two-temperature Ising model with Kawasaki dynamics. Phase diagram from position space renormalization group transformation

    Science.gov (United States)

    Renklioglu, B.; Yalabik, M. C.

    2012-12-01

    Phase transitions of the two-finite temperature Ising model on a square lattice are investigated by using a position space renormalization group (PSRG) transformation. Different finite temperatures, T x and T y , and also different time-scale constants, α x and α y for spin exchanges in the x and y directions define the dynamics of the non-equilibrium system. The critical surface of the system is determined by RG flows as a function of these exchange parameters. The Onsager critical point (when the two temperatures are equal) and the critical temperature for the limit when the other temperature is infinite, previously studied by the Monte Carlo method, are obtained. In addition, two steady-state fixed points which correspond to the non-equilibrium phase transition are presented. These fixed points yield the different universality class properties of the non-equilibrium phase transitions.

  5. Fast wettability transition from hydrophilic to superhydrophobic laser-textured stainless steel surfaces under low-temperature annealing

    Science.gov (United States)

    Ngo, Chi-Vinh; Chun, Doo-Man

    2017-07-01

    Recently, the fabrication of superhydrophobic metallic surfaces by means of pulsed laser texturing has been developed. After laser texturing, samples are typically chemically coated or aged in ambient air for a relatively long time of several weeks to achieve superhydrophobicity. To accelerate the wettability transition from hydrophilicity to superhydrophobicity without the use of additional chemical treatment, a simple annealing post process has been developed. In the present work, grid patterns were first fabricated on stainless steel by a nanosecond pulsed laser, then an additional low-temperature annealing post process at 100 °C was applied. The effect of 100-500 μm step size of the textured grid upon the wettability transition time was also investigated. The proposed post process reduced the transition time from a couple of months to within several hours. All samples showed superhydrophobicity with contact angles greater than 160° and sliding angles smaller than 10° except samples with 500 μm step size, and could be applied in several potential applications such as self-cleaning and control of water adhesion.

  6. Temperature-mediated transition from Dyakonov-Tamm surface waves to surface-plasmon-polariton waves

    Science.gov (United States)

    Chiadini, Francesco; Fiumara, Vincenzo; Mackay, Tom G.; Scaglione, Antonio; Lakhtakia, Akhlesh

    2017-08-01

    The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov-Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.

  7. Pressure effect of glass transition temperature in Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk metallic glass

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Roseker, W.; Sikorski, M.

    2004-01-01

    Pressure effects on glass transition temperature and supercooled liquid region of a Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass have been investigated by performing in situ high-temperature and high-pressure x-ray powder diffraction measurements using synchrotron radiation. The glass transition was det...... range of 0-2.2 GPa. This method opens a possibility to study the pressure effect of glass transition process in glassy systems under high pressures (>1 GPa). (C) 2004 American Institute of Physics....

  8. Can Holstein-Kondo lattice model be used as a candidate for the theory of high transition temperature superconductors

    Directory of Open Access Journals (Sweden)

    R Nourafkan

    2009-08-01

    Full Text Available   It is a common knowledge that the formation of electron pairs is a necessary ingredient of any theoretical work describing superconductivity. Thus, finding the mechanism of the formation of the electron pairs is of utmost importance. There are some experiments on high transition temperature superconductors which support the electron-phonon (e-ph interactions as the pairing mechanism (ARPES, and there are others which support the spin fluctuations as their pairing mechanism (tunneling spectroscopy. In this paper, we introduce the Holstein-Kondo lattice model (H-KLM which incorporates the e-ph as well as the Kondo exchange interaction. We have used the dynamical mean field theory (DMFT to describe heavy fermion semiconductors and have employed the exact-diagonalization technique to obtain our results. The phase diagram of these systems in the parameter space of the e-ph coupling, g, and the Kondo exchange coupling, J, show that the system can be found in the Kondo insulating phase, metallic phase or the bi-polaronic phase. It is shown that these systems develop both spin gap and a charge gap, which are different and possess energies in the range of 1-100 meV. In view of the fact that both spin excitation energies and phonon energies lie in this range, we expect our work on H-KLM opens a way to formalize the theory of the high transition temperature superconductors .

  9. Comparison of electron temperature fluctuations with gyrokinetic sumulations across the ohmic energy confinement transition in Alcator C-Mod

    Science.gov (United States)

    Sung, C.; White, A.; Howard, N.; Mikkelsen, D.; Rice, J.; Reinke, M.; Gao, C.; Ennever, P.; Porkolab, M.; Churchill, R.; Theiler, C.; Hubbard, A.; Greenwald, M.

    2013-10-01

    Long wavelength electron temperature fluctuations (kyρs < 0 . 3) near the edge (r / a ~ 0 . 85) are reduced across the ohmic confinement transition from Linear Ohmic Confinement(LOC) regime to Saturated Ohmic Confinement(SOC) regime in Alcator C-Mod. Linear stability analysis shows that the dominant mode of long wavelength turbulence near the edge is changed from Trapped Electron Mode(TEM) to Ion Temperature Gradient(ITG) mode while the dominant mode is not changed deeper in the core (r / a ~ 0 . 5). This indicates that local turbulence changes near the edge might be responsible for the change of global energy confinement in ohmic plasmas. Further study using nonlinear gyrokinetic simulations is being performed to clarify the relation between the change of local turbulence and global ohmic energy confinement. Through nonlinear gyrokinetic simulation (GYRO), we will investigate the change of fluctuating quantities (T~ , ñ , ϕ~) and their phase relations across ohmic confinement transitions, and relate them to the change of energy transport. A synthetic CECE diagnostic for C-Mod has been developed, and it will be used to validate the gyrokinetic simulations. Research supported by USDoE awards DE-SC0006419, DE-FC02-99ER54512.

  10. Phase transitions in Cd3P2 at high pressures and high temperatures

    DEFF Research Database (Denmark)

    Yel'kin, F.S.; Sidorov, V.A.; Waskowska, A.

    2008-01-01

    The high-pressure, high-temperature structural behaviour of Cd3P2 has been studied using electrical resistance measurements, differential thermal analysis, thermo baric analysis and X-ray diffraction. At room temperature, a phase transformation is observed at 4.0 GPa in compression....... The experimental zero-pressure bulk modulus of the low-pressure phase is 64.7(7) GPa, which agrees quite well with the calculated value of 66.3 GPa using the tight-binding linear muffin-tin orbital method within the local density approximation. Tentatively, the high-pressure phase has an orthorhombic crystal...

  11. Relationship Between Clumped Isotope and Growth Temperature of Foraminifera: Methodology and Application to the Mid-Pleistocene Transition

    Science.gov (United States)

    Peral, M.; Daëron, M.; Blamart, D.; Bassinot, F. C.; Marino, M.; Nomade, S.; Ciaranfi, N.; Girone, A.; Maiorano, P.; Pereira, A.; Scao, V.

    2016-12-01

    The O-isotope composition (δ18Oc) of marine bio-carbonates alone cannot directly constrain past changes in oceanic temperatures, because δ18Oc also depends on the isotopic composition of seawater, which is often poorly constrained in past environments. The carbonate clumped isotope thermometer, based on the dependence between temperature and statistical over-abundance of 13C-18O bonds in carbonate (Δ47), provides estimates of calcification temperature independent from the isotopic composition of seawater. Past investigation of Δ47 in foraminifera suggests that their clumped isotope composition is consistent with temperature calibration laws obtained from synthetic carbonates [1,2]. Here we report on the early results of our methodological investigations. First, we performed a detailed study, including SEM observations and stable isotope analyses on planktonic foraminifera, aiming to establish optimal cleaning protocols. We subsequently selected three benthic foraminifera in range of 450 to 200μm (sorted in bins of 50μm) to test size and/or species effect. Our "optimal" protocols were then applied to test the relationship between ∆47 and temperature by comparison with synthetic carbonates believed to have formed close to thermodynamic equilibrium. The isotopic values of ∆47 are compared to marine temperature from Mg/Ca and from NOAA database. Modern annual temperatures range from 7 to 25°C between our sites. The results obtained using the temperature from NOAA database are statistically indistinguishable from those derived from the local (LSCE) carbonate calibration law. Finally, we apply this relationship to six benthic foraminifer samples coming from the continental (paleo-marine) section Montalbano Jonico (Italy), corresponding respectively to MIS 34, MIS 31, MIS 22-21, and MIS 20-19, in order to constrain paleo-temperatures for these glacial-interglacial couples and to estimate local seawater temperatures and δ18O during the Mid

  12. Temperature-driven topological quantum phase transitions in a phase-change material Ge2Sb2Te5.

    Science.gov (United States)

    Eremeev, S V; Rusinov, I P; Echenique, P M; Chulkov, E V

    2016-12-13

    The Ge2Sb2Te5 is a phase-change material widely used in optical memory devices and is a leading candidate for next generation non-volatile random access memory devices which are key elements of various electronics and portable systems. Despite the compound is under intense investigation its electronic structure is currently not fully understood. The present work sheds new light on the electronic structure of the Ge2Sb2Te5 crystalline phases. We demonstrate by predicting from first-principles calculations that stable crystal structures of Ge2Sb2Te5 possess different topological quantum phases: a topological insulator phase is realized in low-temperature structure and Weyl semimetal phase is a characteristic of the high-temperature structure. Since the structural phase transitions are caused by the temperature the switching between different topologically non-trivial phases can be driven by variation of the temperature. The obtained results reveal the rich physics of the Ge2Sb2Te5 compound and open previously unexplored possibility for spintronics applications of this material, substantially expanding its application potential.

  13. The effect of temperature and external field on transitions in elements of kagome spin ice

    Science.gov (United States)

    Liashko, Sergei Y.; Jónsson, Hannes; Uzdin, Valery M.

    2017-11-01

    Transitions between magnetic states of one and two ring kagome spin ice elements consisting of 6 and 11 prolate magnetic islands are calculated and the lifetime of the ground states evaluated using harmonic transition state theory and the stationary state approximation. The calculated values are in close agreement with experimental lifetime measurements made by Farhan and co-workers (Farhan et al 2013 Nat. Phys. 9 375) when values of the parameters in the Hamiltonian are chosen to be best estimates for a single island, obtained from measurements and micromagnetic modeling. The effective pre-exponential factor in the Arrhenius rate law for the elementary steps turns out to be quite small, on the order of 109 s‑1, three orders of magnitude smaller than has been assumed in previous analysis of the experimental data, while the effective activation energy is correspondingly lower than the previous estimate. The application of an external magnetic field is found to strongly affect the energy landscape of the system. Even a field of 4 {{mT}} can eliminate states that correspond to ground states in the absence of a field. The theoretical approach presented here and the close agreement found with experimental data demonstrates that the properties of spin ice systems can be calculated using the tools of rate theory and a Hamiltonian parametrized only from the properties of a single island.

  14. Investigations of α-helix↔β-sheet transition pathways in a miniprotein using the finite-temperature string method

    Energy Technology Data Exchange (ETDEWEB)

    Ovchinnikov, Victor, E-mail: ovchinnv@georgetown.edu [Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138 (United States); Karplus, Martin, E-mail: marci@tammy.harvard.edu [Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138 (United States); Laboratoire de Chimie Biophysique, ISIS, Université de Strasbourg, 67000 Strasbourg (France)

    2014-05-07

    A parallel implementation of the finite-temperature string method is described, which takes into account the invariance of coordinates with respect to rigid-body motions. The method is applied to the complex α-helix↔β-sheet transition in a β-hairpin miniprotein in implicit solvent, which exhibits much of the complexity of conformational changes in proteins. Two transition paths are considered, one derived from a linear interpolant between the endpoint structures and the other derived from a targeted dynamics simulation. Two methods for computing the conformational free energy (FE) along the string are compared, a restrained method, and a tessellation method introduced by E. Vanden-Eijnden and M. Venturoli [J. Chem. Phys. 130, 194103 (2009)]. It is found that obtaining meaningful free energy profiles using the present atom-based coordinates requires restricting sampling to a vicinity of the converged path, where the hyperplanar approximation to the isocommittor surface is sufficiently accurate. This sampling restriction can be easily achieved using restraints or constraints. The endpoint FE differences computed from the FE profiles are validated by comparison with previous calculations using a path-independent confinement method. The FE profiles are decomposed into the enthalpic and entropic contributions, and it is shown that the entropy difference contribution can be as large as 10 kcal/mol for intermediate regions along the path, compared to 15–20 kcal/mol for the enthalpy contribution. This result demonstrates that enthalpic barriers for transitions are offset by entropic contributions arising from the existence of different paths across a barrier. The possibility of using systematically coarse-grained representations of amino acids, in the spirit of multiple interaction site residue models, is proposed as a means to avoid ad hoc sampling restrictions to narrow transition tubes.

  15. Field-induced transition from room-temperature ferromagnetism to diamagnetism in proton-irradiated fullerene.

    Science.gov (United States)

    Lee, Kyu Won; Kweon, Hyocheon; Lee, Cheol Eui

    2013-10-18

    Room-temperature ferromagnetism in proton-irradiated C60 fullerene is demonstrated. The ferromagnetism turns into diamagnetism intrinsic to the fullerene as the magnetic field increases above a critical field. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Nuclear ordering in lithium and an upper limit on its ambient pressure superconducting transition temperature.

    Science.gov (United States)

    Juntunen, K I; Tuoriniemi, J T

    2004-10-08

    We have discovered spontaneous ordering of nuclear spins in lithium metal by NMR measurements at very low temperatures. In low magnetic fields, Blithium at normal pressure down to T(e) approximately 100 microK (B<10 nT).

  17. Molecular dynamics simulations to calculate glass transition temperature and elastic constants of novel polyethers.

    Science.gov (United States)

    Sarangapani, Radhakrishnan; Reddy, Sreekantha T; Sikder, Arun K

    2015-04-01

    Molecular dynamics simulations studies are carried out on hydroxyl terminated polyethers that are useful in energetic polymeric binder applications. Energetic polymers derived from oxetanes with heterocyclic side chains with different energetic substituents are designed and simulated under the ensembles of constant particle number, pressure, temperature (NPT) and constant particle number, volume, temperature (NVT). Specific volume of different amorphous polymeric models is predicted using NPT-MD simulations as a function of temperature. Plots of specific volume versus temperature exhibited a characteristic change in slope when amorphous systems change from glassy to rubbery state. Several material properties such as Young's, shear, and bulk modulus, Poisson's ratio, etc. are predicted from equilibrated structures and established the structure-property relations among designed polymers. Energetic performance parameters of these polymers are calculated and results reveal that the performance of the designed polymers is comparable to the benchmark energetic polymers like polyNIMMO, polyAMMO and polyBAMO. Overall, it is worthy remark that this molecular simulations study on novel energetic polyethers provides a good guidance on mastering the design principles and allows us to design novel polymers of tailored properties. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. High-temperature order-disorder phase transition in nacaphite, Na2CaPO4F

    Science.gov (United States)

    Avdontceva, Margarita S.; Krzhizhanovskaya, Maria G.; Krivovichev, Sergey V.; Yakovenchuk, Viktor N.

    2015-09-01

    The thermal behavior of nacaphite, Na2CaPO4F, was studied by the powder high-temperature X-ray diffraction method. A monoclinic-to-orthorhombic phase transition has been observed at 330 °C associated with the appearance of the Ca/Na disorder at one of the two crystallographically inequivalent Na sites. At room temperature, nacaphite is monoclinic, P21 /c, a = 13.3185(14), b = 7.0964(8), c = 10.6490(11) Å, β = 113.526(1)°, V = 922.81(17) Å3. The structure is based upon one-dimensional antiperovskite units consisting of face-sharing [FNa4Ca2]7+ anion-centered octahedra running parallel to the c axis. The structure is fully ordered and contains two Ca and four Na sites. The crystal structure of the high-temperature modification [refined by Rietveld method ( R B 0.025) at 400 °C from the powder X-ray diffraction data] is orthorhombic, Pnma, a = 5.4123(1), b = 7.1196(1), c = 12.3171(1) Å, V = 474.62(1) Å3. The structure has one fully occupied Na1 site and one mixed occupied Na2 site, the latter being equally occupied by Na and Ca. The Na1 and Na2 sites are coordinated by two F- and four O2- anions each. The phase transition has an order-disorder character and is associated with the decrease of structural complexity measured as an information content per unit cell (300.235 bits for the low- and 98.117 bits for the high-temperature modifications). Thermal expansion of both modifications has an anisotropic character with the degree of anisotropy increasing from the low- to the high-temperature phase. The direction of the strongest thermal expansion is parallel to the direction of chains of face-sharing anion-centered octahedra that can be explained by the temperature-induced expansion of the F-Na/Ca bonds.

  19. Soy Sauce Residue Oil Extracted by a Novel Continuous Phase Transition Extraction under Low Temperature and Its Refining Process.

    Science.gov (United States)

    Zhao, Lichao; Zhang, Yong; He, Liping; Dai, Weijie; Lai, Yingyi; Yao, Xueyi; Cao, Yong

    2014-04-09

    On the basis of previous single-factor experiments, extraction parameters of soy sauce residue (SSR) oil extracted using a self-developed continuous phase transition extraction method at low temperature was optimized using the response surface methodology. The established optimal conditions for maximum oil yield were n-butane solvent, 0.5 MPa extraction pressure, 45 °C temperature, 62 min extraction time, and 45 mesh raw material granularity. Under these conditions, the actual yield was 28.43% ± 0.17%, which is relatively close to the predicted yield. Meanwhile, isoflavone was extracted from defatted SSR using the same method, but the parameters and solvent used were altered. The new solvent was 95% (v/v) ethanol, and extraction was performed under 1.0 MPa at 60 °C for 90 min. The extracted isoflavones, with 0.18% ± 0.012% yield, mainly comprised daidzein and genistein, two kinds of aglycones. The novel continuous phase transition extraction under low temperature could provide favorable conditions for the extraction of nonpolar or strongly polar substances. The oil physicochemical properties and fatty acids compositions were analyzed. Results showed that the main drawback of the crude oil was the excess of acid value (AV, 63.9 ± 0.1 mg KOH/g) and peroxide value (POV, 9.05 ± 0.3 mmol/kg), compared with that of normal soybean oil. However, through molecular distillation, AV and POV dropped to 1.78 ± 0.12 mg KOH/g and 5.9 ± 0.08 mmol/kg, respectively. This refined oil may be used as feedstuff oil.

  20. Amorphous to nanocrystalline transition in HWCVD Si:H films by substrate temperature variation

    Energy Technology Data Exchange (ETDEWEB)

    Gogoi, Purabi; Jha, Himanshu S.; Agarwal, Pratima [Department of Physics, IIT Guwahati, Guwahati (India); Deva, Dinesh [Department of Chemical Engineering, IIT Kanpur, Kanpur (India)

    2010-04-15

    Thin films of hydrogenated silicon with band gap ranging from 2.0-2.34 eV are prepared at deposition rate 8-14A/sec in an indigenously fabricated HWCVD system keeping all parameters except substrate temperature fixed. The films grown at T{sub s}{<=}150 C are found to be pure amorphous, whereas the formation of nanocrystalline phase starts at T{sub s} {>=} 200 C. With increase in T{sub s}, crystalline fraction increases along with the increase in the band gap whereas the hydrogen content in the films and the deposition rate decreases. The variation of microstructure by varying substrate temperature without a significant decrease in deposition rate is useful for various device applications. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. High-Glass-Transition-Temperature Polyimides Developed for Reusable Launch Vehicle Applications

    Science.gov (United States)

    Chuang, Kathy; Ardent, Cory P.

    2002-01-01

    Polyimide composites have been traditionally used for high-temperature applications in aircraft engines at temperatures up to 550 F (288 C) for thousands of hours. However, as NASA shifts its focus toward the development of advanced reusable launch vehicles, there is an urgent need for lightweight polymer composites that can sustain 600 to 800 F (315 to 427 C) for short excursions (hundreds of hours). To meet critical vehicle weight targets, it is essential that one use lightweight, high-temperature polymer matrix composites in propulsion components such as turbopump housings, ducts, engine supports, and struts. Composite materials in reusable launch vehicle components will heat quickly during launch and reentry. Conventional composites, consisting of layers of fabric or fiber-reinforced lamina, would either blister or encounter catastrophic delamination under high heating rates above 300 C. This blistering and delamination are the result of a sudden volume expansion within the composite due to the release of absorbed moisture and gases generated by the degradation of the polymer matrix. Researchers at the NASA Glenn Research Center and the Boeing Company (Long Beach, CA) recently demonstrated a successful approach for preventing this delamination--the use of three-dimensional stitched composites fabricated by resin infusion.

  2. Tuning the Transition Temperature of WSix Alloys for Use in Cryogenic Microcalorimeters

    Science.gov (United States)

    Cecil, T.; Gades, L.; Madden, T.; Yan, D.; Miceli, A.

    2016-07-01

    Microwave kinetic inductance detectors (MKID) provide a pathway to highly multiplexed, high-resolution, detectors. Over the past several years we have introduced the concept of the thermal kinetic inductance detector (TKID), which operates as a microcalorimeter. As with other microcalorimeters, the thermal noise of a TKID is reduced when the operating temperature is decreased. However, because the sensitivity of a TKID decreases as the operating temperature drops below 20 % of T_C, the T_C of the resonator material must be tuned to match the desired operating temperature. We have investigated the WSix alloy system as a material for these detectors. By co-sputtering from a Si and W2Si target, we have deposited WSix films with a tunable T_C that ranges from 5 K down to 500 mK. These films provide a large kinetic inductance fraction and relatively low noise levels. We provide results of these studies showing the T_C, resistivity, quality factors, and noise as a function of deposition conditions. These results show that WSix is a good candidate for TKIDs.

  3. Use of glass transition temperature for stabilization of board's cracks of Eucalyptus grandis

    Directory of Open Access Journals (Sweden)

    Fred W. Calonego

    2010-09-01

    Full Text Available The Eucalyptus grandis logs temperatures were determined and correlated with the board's cracks during steaming. Thermocouples were inserted in the logs center, registering their temperatures during steaming at 90"C. The logs were sawed and the board's cracks measured. It was concluded that: (1 the logistic S-shaped curve explains the logs temperature variation; (2 the logs with diameter of 20 to As temperaturas em toras de Eucalyptus grandis, durante a vaporização, foram determinadas e correlacionadas com as rachaduras das tábuas. Nos centros das toras foram inseridos termopares e registradas suas temperaturas durante a vaporização à 90"C. As toras foram desdobradas e as rachaduras das tábuas mensuradas. Concluiu-se que: (1 o modelo estatístico sigmoidal logístico explica a variação da temperatura nas toras; (2 as toras com 20 a <25, 25 a <30 e 30 a <35 cm de diâmetro apresentaram, respectivamente, 84,2"C, 73,1"C e 45,8"C ao final da vaporização; e (3 as rachaduras foramsignificativamente menores nas toras que atingiram a temperatura de transição vítrea.

  4. Techniques for Surface-Temperature Measurements and Transition Detection on Projectiles at Hypersonic Velocities--Status Report No. 2

    Science.gov (United States)

    Bogdanoff, D. W.; Wilder, M. C.

    2006-01-01

    The latest developments in a research effort to advance techniques for measuring surface temperatures and heat fluxes and determining transition locations on projectiles in hypersonic free flight in a ballistic range are described. Spherical and hemispherical titanium projectiles were launched at muzzle velocities of 4.6-5.8 km/sec into air and nitrogen at pressures of 95-380 Torr. Hemisphere models with diameters of 2.22 cm had maximum pitch and yaw angles of 5.5-8 degrees and 4.7-7 degrees, depending on whether they were launched using an evacuated launch tube or not. Hemisphere models with diameters of 2.86 cm had maximum pitch and yaw angles of 2.0-2.5 degrees. Three intensified-charge-coupled-device (ICCD) cameras with wavelength sensitivity ranges of 480-870 nm (as well as one infrared camera with a wavelength sensitivity range of 3 to 5 microns), were used to obtain images of the projectiles in flight. Helium plumes were used to remove the radiating gas cap around the projectiles at the locations where ICCD camera images were taken. ICCD and infrared (IR) camera images of titanium hemisphere projectiles at velocities of 4.0-4.4 km/sec are presented as well as preliminary temperature data for these projectiles. Comparisons were made of normalized temperature data for shots at approx.190 Torr in air and nitrogen and with and without the launch tube evacuated. Shots into nitrogen had temperatures 6% lower than those into air. Evacuation of the launch tube was also found to lower the projectile temperatures by approx.6%.

  5. Mean ocean temperature change over the last glacial transition based on heavy noble gases in the atmosphere

    Science.gov (United States)

    Bereiter, Bernhard; Severinghaus, Jeff; Shackleton, Sarah; Baggenstos, Daniel; Kawamura, Kenji

    2017-04-01

    On paleo-climatic timescales heavy noble gases (krypton and xenon) are conserved in the atmosphere-ocean system and are passively cycled through this system without interaction with any biogeochemical process. Due to the characteristic temperature dependency of the gas solubility factors in sea water, the atmospheric noble gas content is unambiguously linked to mean global ocean temperature (MOT). Here we use this proxy to reconstruct MOT over the course of the last glacial transition based on measurements of trapped air in the WAIS Divide ice core. We analyzed 78 ice samples with a recently developed method that yields the isotopic ratios of N2, Ar, Kr and the elemental ratios of Kr/N2, Xe/N2 and Xe/Kr in the trapped air with the required precision. Based on the isotopic ratios we correct the elemental ratios for the fractionation processes in the firn column to obtain the true atmospheric values. On the basis of a 4-box model that incorporates effects of sea-level change, different saturation states of the water and different temperature distributions in the global ocean, we infer MOT based on the three elemental ratio pairs and assess its uncertainty. On average, the uncertainty of our MOT record is +/- 0.27°C, which is a significant improvement to earlier studies that reached about +/- 1°C uncertainty. This allows an unprecedented assessment of the glacial-interglacial MOT difference, as well as a direct comparison between MOT and climate change for the first time. We find a LGM-Holocene difference of 2.6°C, which is on the lower end of what earlier studies have suggested (3 +/- 1°C) and provides a new constraint on ocean heat uptake over the last glacial transition. Furthermore, we find a very close relation between MOT and Antarctic temperatures which shows for the first time the effect of Atlantic overturning circulation changes on global ocean heat uptake. Finally, our record shows a MOT warming rate during the Younger Dryas that is almost double to

  6. Temperature-, pH- and CO2-Sensitive Poly(N-isopropylacryl amide-co-acrylic acid Copolymers with High Glass Transition Temperatures

    Directory of Open Access Journals (Sweden)

    Yeong-Tarng Shieh

    2016-12-01

    Full Text Available A series of poly(N-isopropylacrylamide-co-acrylic acid (PNIPAAm-co-PAA random copolymers were synthesized through free radical copolymerization in MeOH. The incorporation of the acrylic acid units into PNIPAAm tended to enhance the glass transition temperature (Tg, due to strong intermolecular hydrogen bonding between the amide groups of PNIPAAm and the carboxyl groups of PAA, as observed using 1H nuclear magnetic resonance (NMR and Fourier transform infrared (FTIR spectroscopic analyses. The lower critical solution temperature (LCST increased upon increasing the pH of the aqueous solution containing PNIPAAm-co-PAA because the COOH groups of the PAA segment dissociated into COO− groups, enhancing the solubility of the copolymer. In addition, high-pressure differential scanning calorimetry revealed that the LCSTs of all the aqueous solutions of the copolymers decreased upon increasing the pressure of CO2, suggesting that CO2 molecules had displaced H2O molecules around the polar CONH and COOH groups in PNIPAAm-co-PAA, thereby promoting the hydrophobicity of the copolymers in the aqueous solution. In addition, the values of Tg of a film sample increased upon treatment with supercritical CO2, implying that intermolecular interactions in the copolymer had been enhanced after such treatment.

  7. Medium decoupling of dynamics at temperatures ~100 K above glass-transition temperature: a case study with (acetamide + lithium bromide/nitrate) melts.

    Science.gov (United States)

    Guchhait, Biswajit; Daschakraborty, Snehasis; Biswas, Ranjit

    2012-05-07

    Time-resolved fluorescence Stokes shift and anisotropy measurements using a solvation probe in [0.78CH(3)CONH(2) + 0.22{f LiBr + (1-f) LiNO(3)}] melts reveal a strong decoupling of medium dynamics from viscosity. Interestingly, this decoupling has been found to occur at temperatures ∼50-100 K above the glass transition temperatures of the above melt at various anion concentrations (f(LiBr)). The decoupling is reflected via the following fractional viscosity dependence (η) of the measured average solvation and rotation times ( and , respectively): ∝ (η∕T)(p) (x being solvation or rotation), with p covering the range, 0.20 than for , indicating a sort of translation-rotation decoupling. Multiple probes have been used in steady state fluorescence measurements to explore the extent of static heterogeneity. Estimated experimental dynamic Stokes shift for coumarin 153 in these mixtures lies in the range, 1000 < Δν(t)/cm(-1) < 1700, and is in semi-quantitative agreement with predictions from our semi-molecular theory. The participation of the fluctuating density modes at various length-scales to the observed solvation times has also been investigated.

  8. Dynamic Simulation of Temperature Transition on the Secondary Helium Loop of a VHTR-SI Hydrogen Production System

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Ji Woon; Shin, Young Joon; Lee, Tae Hoon; Lee, Ki Young; Kim, Yong Wan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Youn, Cheong [Chungnam National University, Daejeon (Korea, Republic of)

    2011-10-15

    A sulfur.iodine (SI) cycle coupled to a Very High Temperature Gas Cooled Reactor (VHTR) is one of the leading candidates of thermochemical cycles for hydrogen production. The SI cycle can be divided into three sections based on the chemical reactions: a Bunsen reaction (Section 1), sulfuric acid concentration and decomposition (Section 2), and a hydrogen iodine concentration and decomposition (Section 3). The heat required in the SI cycle can be supplied through an intermediate heat exchanger (IHX) by the VHTR. On the other hand, helium is used as a high-temperature energy carrier gas between the VHTR and the IHX or IHX and the SI cycle. In the SI cycle, the chemical reactors that receive thermal energy from the helium are a sulfuric acid vaporizer, sulfuric acid decomposer, sulfuric trioxide decomposer, and hydriodic acid decomposer including a pre-heating part. To simulate the dynamic behavior of the VHTR-SI cycle, the Korea Atomic Energy Research Institute -Dynamic Simulation Code (KAERI-DySCo) based on the Visual C++ has been prepared by the KAERI research group in 2010. KAERI-DySCo is integration application software, which includes several code modules that can solve the dynamic problem of the seven chemical reactors in the VHTR-SI cycle. In this paper, the dynamic behavior of the temperature transition on the secondary helium loop of the SI cycle has been simulated using KAERI-DySCo

  9. Sorption isotherms, thermodynamic properties and glass transition temperature of mucilage extracted from chia seeds (Salvia hispanica L.).

    Science.gov (United States)

    Velázquez-Gutiérrez, Sandra Karina; Figueira, Ana Cristina; Rodríguez-Huezo, María Eva; Román-Guerrero, Angélica; Carrillo-Navas, Hector; Pérez-Alonso, César

    2015-05-05

    Freeze-dried chia mucilage adsorption isotherms were determined at 25, 35 and 40°C and fitted with the Guggenheim-Anderson-de Boer model. The integral thermodynamic properties (enthalpy and entropy) were estimated with the Clausius-Clapeyron equation. Pore radius of the mucilage, calculated with the Kelvin equation, varied from 0.87 to 6.44 nm in the temperature range studied. The point of maximum stability (minimum integral entropy) ranged between 7.56 and 7.63kg H2O per 100 kg of dry solids (d.s.) (water activity of 0.34-0.53). Enthalpy-entropy compensation for the mucilage showed two isokinetic temperatures: (i) one occurring at low moisture contents (0-7.56 kg H2O per 100 kg d.s.), controlled by changes in water entropy; and (ii) another happening in the moisture interval of 7.56-24 kg H2O per 100 kg d.s. and was enthalpy driven. The glass transition temperature Tg of the mucilage fluctuated between 42.93 and 57.93°C. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Integrated high-transition temperature magnetometer with only two superconducting layers

    DEFF Research Database (Denmark)

    Kromann, R.; Kingston, J.J.; Miklich, A.H.

    1993-01-01

    We describe the fabrication and testing of an integrated YBa2Cu3O7-x thin-film magnetometer consisting of a dc superconducting quantum interference device (SQUID), with biepitaxial grain boundary junctions, integrated with a flux transformer on a single substrate. Only two superconducting layers...... are required, the SQUID body serving as the crossunder that completes the multiturn flux transformer. The highest temperature at which any of the magnetometers functioned was 76 K. At 60 K the magnetic field gain of this device was 63, and the magnetic field noise was 160 fT Hz-1/2 at 2 kHz, increasing to 3...

  11. RR-MR transition of a Type V shock interaction in inviscid double-wedge flow with high-temperature gas effects

    Science.gov (United States)

    Xiong, W.; Li, J.; Zhu, Y.; Luo, X.

    2017-11-01

    The transition between regular reflection (RR) and Mach reflection (MR) of a Type V shock-shock interaction on a double-wedge geometry with non-equilibrium high-temperature gas effects is investigated theoretically and numerically. A modified shock polar method that involves thermochemical non-equilibrium processes is applied to calculate the theoretical critical angles of transition based on the detachment criterion and the von Neumann criterion. Two-dimensional inviscid numerical simulations are performed correspondingly to reveal the interactive wave patterns, the transition processes, and the critical transition angles. The theoretical and numerical results of the critical transition angles are compared, which shows evident disagreement, indicating that the transition mechanism between RR and MR of a Type V shock interaction is beyond the admissible scope of the classical theory. Numerical results show that the collisions of triple points of the Type V interaction cause the transition instead. Compared with the frozen counterpart, it is found that the high-temperature gas effects lead to a larger critical transition angle and a larger hysteresis interval.

  12. Medium decoupling of dynamics at temperatures ˜100 K above glass-transition temperature: A case study with (acetamide + lithium bromide/nitrate) melts

    Science.gov (United States)

    Guchhait, Biswajit; Daschakraborty, Snehasis; Biswas, Ranjit

    2012-05-01

    Time-resolved fluorescence Stokes shift and anisotropy measurements using a solvation probe in [0.78CH3CONH2 + 0.22{f LiBr + (1-f) LiNO3}] melts reveal a strong decoupling of medium dynamics from viscosity. Interestingly, this decoupling has been found to occur at temperatures ˜50-100 K above the glass transition temperatures of the above melt at various anion concentrations (fLiBr). The decoupling is reflected via the following fractional viscosity dependence (η) of the measured average solvation and rotation times (⟨τs⟩ and ⟨τr⟩, respectively): ⟨τx⟩ ∝ (η/T)p (x being solvation or rotation), with p covering the range, 0.20 < p < 0.70. Although this is very similar to what is known for deeply supercooled liquids, it is very surprising because of the temperature range at which the above decoupling occurs for these molten mixtures. The kinship to the supercooled liquids is further exhibited via p which is always larger for ⟨τr⟩ than for ⟨τs⟩, indicating a sort of translation-rotation decoupling. Multiple probes have been used in steady state fluorescence measurements to explore the extent of static heterogeneity. Estimated experimental dynamic Stokes shift for coumarin 153 in these mixtures lies in the range, 1000 < Δνt/cm-1 < 1700, and is in semi-quantitative agreement with predictions from our semi-molecular theory. The participation of the fluctuating density modes at various length-scales to the observed solvation times has also been investigated.

  13. Standard test method for determination of reference temperature, to, for ferritic steels in the transition range

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    1.1 This test method covers the determination of a reference temperature, To, which characterizes the fracture toughness of ferritic steels that experience onset of cleavage cracking at elastic, or elastic-plastic KJc instabilities, or both. The specific types of ferritic steels (3.2.1) covered are those with yield strengths ranging from 275 to 825 MPa (40 to 120 ksi) and weld metals, after stress-relief annealing, that have 10 % or less strength mismatch relative to that of the base metal. 1.2 The specimens covered are fatigue precracked single-edge notched bend bars, SE(B), and standard or disk-shaped compact tension specimens, C(T) or DC(T). A range of specimen sizes with proportional dimensions is recommended. The dimension on which the proportionality is based is specimen thickness. 1.3 Median KJc values tend to vary with the specimen type at a given test temperature, presumably due to constraint differences among the allowable test specimens in 1.2. The degree of KJc variability among specimen types i...

  14. Field-History Dependence of the Superconducting Transition Temperature in Erbium/Niobium Bilayers

    Science.gov (United States)

    Witt, James; Satchell, Nathan; Langridge, Sean; Burnell, Gavin

    Recently, there has been much interest in a new class of superconducting (S) spintronic devices based upon hybrid S/F (ferromagnet) heterostructures. The prototypical super-spintronic device is the superconducting spin valve (SSV), within which the critical temperature (Tc) of an S layer can be controlled by the relative orientation of two or more F layers. Such manipulation of the F layers requires careful engineering of the heterostructure and the rotation of the structure with respect to an applied magnetic field. Here, we show that such control over Tc is also possible in a simple S/F bilayer. By manipulating the remenant magnetic state of a thin Er layer - which is proximity coupled to a Nb S layer - we are able to demonstrate a high level of control over the Tc of the Nb (which is measured in zero field). The shifts in Tc are comparable in size to the largest seen in the SSV and are manipulated using solely the field history. The system can be reset by warming the sample through the Er Curie temperature (approximately 20 K). Our results are of particular interest due to the simplicity of both the bilayer and the measurement geometry in comparison to the SSV.

  15. Cooperative transition of electronic states of antisite As defects in Be-doped low-temperature-grown GaAs layers

    Science.gov (United States)

    Ambri Mohamed, Mohd; Tien Lam, Pham; Bae, K. W.; Otsuka, N.

    2011-12-01

    Magnetic properties resulting from localized spins associated with antisite arsenic ions AsGa+ in Be-doped low-temperature-grown GaAs (LT-GaAs) layers were studied by measuring the magnetization of lift-off samples. With fast cooling, the magnetization of samples at 1.8 K becomes significantly lower than that expected from Curie-type paramagnetism in the range of the applied field to 7 T, and a transition from low magnetization to the magnetization of paramagnetism occurs upon the heating of samples to 4.5 K. With slow cooling, on the other hand, samples have a paramagnetic temperature dependence throughout the measurement-temperature range. The magnetization was found to decrease monotonically when a sample was kept at a fixed low temperature. These observations are explained by the cooperative transition of electron states of AsGa defects, which is closely related to the normal-metastable state transition of EL2 defects in semi-insulating GaAs. The results of the magnetization measurements in the present study suggest that AsGa+ ions are spontaneously displaced at low temperature without photoexcitation in Be-doped LT-GaAs. The similarity of the transition observed in this system to the normal-metastable state transition of the EL2 defect was also suggested by first-principle calculations of the electron state of an AsGa defect with a doped Be atom.

  16. Hydrogen incorporation induced metal-semiconductor transition in ZnO:H thin films sputtered at room temperature

    Science.gov (United States)

    Singh, Anil; Chaudhary, Sujeet; Pandya, D. K.

    2013-04-01

    The room temperature deposited ZnO:H thin films having high conductivity of 500 Ω-1 cm-1 and carrier concentration reaching 1.23 × 1020 cm-3 were reactively sputter deposited on glass substrates in the presence of O2 and 5% H2 in Ar. A metal-semiconductor transition at 165 K is induced by the increasing hydrogen incorporation in the films. Hydrogen forms shallow donor complex with activation energy of ˜10-20 meV at oxygen vacancies (VO) leading to increase in carrier concentration. Hydrogen also passivates VO and VZn causing ˜4 times enhancement of mobility to 25.4 cm2/V s. These films have potential for use in transparent flexible electronics.

  17. Standard test method for conducting drop-weight test to determine nil-ductility transition temperature of ferritic steels

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2006-01-01

    1.1 This test method covers the determination of the nil-ductility transition (NDT) temperature of ferritic steels, 5/8 in. (15.9 mm) and thicker. 1.2 This test method may be used whenever the inquiry, contract, order, or specification states that the steels are subject to fracture toughness requirements as determined by the drop-weight test. 1.3 The values stated in inch-pound units are to be regarded as the standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  18. Hydrogen incorporation induced metal-semiconductor transition in ZnO:H thin films sputtered at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Anil; Chaudhary, Sujeet; Pandya, D. K. [Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

    2013-04-29

    The room temperature deposited ZnO:H thin films having high conductivity of 500 Ohm-Sign {sup -1} cm{sup -1} and carrier concentration reaching 1.23 Multiplication-Sign 10{sup 20} cm{sup -3} were reactively sputter deposited on glass substrates in the presence of O{sub 2} and 5% H{sub 2} in Ar. A metal-semiconductor transition at 165 K is induced by the increasing hydrogen incorporation in the films. Hydrogen forms shallow donor complex with activation energy of {approx}10-20 meV at oxygen vacancies (V{sub O}) leading to increase in carrier concentration. Hydrogen also passivates V{sub O} and V{sub Zn} causing {approx}4 times enhancement of mobility to 25.4 cm{sup 2}/V s. These films have potential for use in transparent flexible electronics.

  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. Temperature and electric field induced metal-insulator transition in atomic layer deposited VO2 thin films

    Science.gov (United States)

    Tadjer, Marko J.; Wheeler, Virginia D.; Downey, Brian P.; Robinson, Zachary R.; Meyer, David J.; Eddy, Charles R.; Kub, Fritz J.

    2017-10-01

    Amorphous vanadium oxide (VO2) films deposited by atomic layer deposition (ALD) were crystallized with an ex situ anneal at 660-670 °C for 1-2 h under a low oxygen pressure (10-4 to 10-5 Torr). Under these conditions the crystalline VO2 phase was maintained, while formation of the V2O5 phase was suppressed. Electrical transition from the insulator to the metallic phase was observed in the 37-60 °C range, with an ROFF/RON ratio of up to about 750 and ΔTC ≅ 7-10 °C. Lateral electric field applied across two-terminal device structures induced a reversible phase change, with a room temperature transition field of about 25 kV/cm in the VO2 sample processed with the 2 h long O2 anneal. Both the width and slope of the field induced MIT I-V hysteresis were dependent upon the VO2 crystalline quality.

  1. Phase transitions and melting on the Hugoniot of Mg2SiO4 forsterite: new diffraction and temperature results

    Science.gov (United States)

    Asimow, P. D.; Akin, M. C.; Homel, M.; Crum, R. S.; Pagan, D.; Lind, J.; Bernier, J.; Mosenfelder, J. L.; Dillman, A. M.; Lavina, B.; Lee, S.; Fat'yanov, O. V.; Newman, M. G.

    2017-06-01

    The phase transitions of forsterite under shock were studied by x-ray diffraction and pyrometry. Samples of 2 mm thick, near-full density (>98% TMD) polycrystalline forsterite were characterized by EBSD and computed tomography and shock compressed to 50 and 75 GPa by two-stage gas gun at the Dynamic Compression Sector, Advanced Photon Source, with diffraction imaged during compression and release. Changes in diffraction confirm a phase transition by 75 GPa. In parallel, single-crystal forsterite shock temperatures were taken from 120 to 210 GPa with improved absolute calibration procedures on the Caltech 6-channel pyrometer and two-stage gun and used to examine the interpretation of superheating and P-T slope of the liquid Hugoniot. This work performed under the auspices of the U.S. Department of Energy (DOE) by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, supported in part by LLNL's LDRD program under Grants 15-ERD-012 and 16-ERD-010. The Dynamic Compression Sector (35) is supported by DOE / National Nuclear Security Administration under Award Number DE-NA0002442. This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Caltech lab supported by NSF EAR-1426526.

  2. TRANSITION AND DECOMPOSITION TEMPERATURES OF CEMENT PHASES - A COLLECTION OF THERMAL ANALYSIS DATA

    Directory of Open Access Journals (Sweden)

    Nick C. Collier

    2016-10-01

    Full Text Available Thermal analysis techniques provide the cement chemist with valuable tools to qualify and quantify the products formed during the hydration of cementitious materials. These techniques are commonly used alongside complimentary techniques such as X-ray diffraction and electron microscopy/energy dispersive spectroscopy to confirm the composition of phases present and identify amorphous material unidentified by other techniques. The most common thermal analysis techniques used by cement chemists are thermogravimetry, differential thermal analysis and differential scanning calorimetry. In order to provide a useful reference tool to the cement chemist, this paper provides a brief summary of the temperatures at which phase changes occur in the most common cement hydrates in the range 0-800°C in order to aid phase identification.

  3. Ferroelectric InMnO{sub 3}: Growth of single crystals, structure and high-temperature phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Bekheet, Maged F., E-mail: maged.bekheet@ceramics.tu-berlin.de [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany); Svoboda, Ingrid; Liu, Na [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Bayarjargal, Lkhamsuren [Institut für Geowissenschaften, Goethe-Universität, Altenhöferallee 1, d-60438 Frankfurt a.M. (Germany); Irran, Elisabeth [Institut für Chemie, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin (Germany); Dietz, Christian; Stark, Robert W.; Riedel, Ralf [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Gurlo, Aleksander [Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany)

    2016-09-15

    To understand the origin of the ferroelectricity in InMnO{sub 3}, single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. The results of single crystal X-ray diffraction, second harmonic generation and piezoresponse force microscopy studies of high-quality InMnO{sub 3} single crystals reveal that the room-temperature state in this material is ferroelectric with P6{sub 3}cm symmetry. The polar InMnO{sub 3} specimen undergoes a reversible phase transition from non-centrosymmetric P6{sub 3}cm structure to a centrosymmetric P6{sub 3}/mmc structure at 700 °C as confirmed by the in situ high-temperature Raman spectroscopic and synchrotron X-ray diffraction experiments. - Graphical abstract: Piezoresponse fore microscopy (PFM) studies of high quality InMnO{sub 3} single crystal revealed that the room-temperature state of this material is ferroelectric with a clear cloverleaf pattern corresponding to six antiphase ferroelectric domains with alternating polarization ±P{sub z}. Display Omitted - Highlights: • InMnO{sub 3} single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. • The room-temperature state of InMnO{sub 3} is ferroelectric with polar P6{sub 3}cm structure. • PolarInMnO{sub 3} reversibly transforms to a centrosymmetric P6{sub 3}/mmc structure above 700 °C.

  4. Analytical Expressions of the Order Parameters Near the Transition Temperatures in the SPIN-3/2 Ising System with Bilinear and Biquadratic Interactions

    Science.gov (United States)

    Canko, Osman; Keskin, Mustafa

    Analytical expressions of the order parameters near the transition temperatures in the spin-3/2 Ising system with bilinear (J) and biquadratic (K) interactions are presented for various values of J/K. First, we obtain the free energy expression and the equations to determine order parameters by using the mean-field approximation. Then, the order parameters are expressed in the vicinity of the transition temperatures in which these expressions are very important to study the dynamics of the system by means of Onsager's theory of irreversible thermodynamics. Hence, we investigate the phase transitions occurring in the system and also obtain two tricritical points analytically. Finally, the specific heat and magnetic susceptibility are calculated and an argument about the critical exponents at the second-order phase transitions and tricritical points is given.

  5. Relationship between Covalence and Displacive Phase Transition Temperature in RAO 4 and Li AO 3 ( R = Rare-Earth Element and A = Nb and Ta)

    Science.gov (United States)

    Tsunekawa, S.; Kamiyama, T.; Asano, H.; Fukuda, T.

    1995-04-01

    Crystal structure analyses by TOF neutron powder diffraction are performed for RTaO4 (R = rare-earth element) and the Ta-O interatomic distances are determined. The relationship between the covalency of A -O bonds (A = Nb and Ta), which show the most shortening upon phase transition, and the transition temperature is discussed for RA O4 and LiAO3, and the parameters of Ta-O covalence are determined.

  6. Finite-temperature phase transition to a Kitaev spin liquid phase on a hyperoctagon lattice: A large-scale quantum Monte Carlo study

    Science.gov (United States)

    Mishchenko, Petr A.; Kato, Yasuyuki; Motome, Yukitoshi

    2017-09-01

    The quantum spin liquid is an enigmatic quantum state in insulating magnets, in which conventional long-range order is suppressed by strong quantum fluctuations. Recently, an unconventional phase transition was reported between the low-temperature quantum spin liquid and the high-temperature paramagnet in the Kitaev model on a three-dimensional hyperhoneycomb lattice. Here, we show that a similar "liquid-gas" transition takes place in another three-dimensional lattice, the hyperoctagon lattice. We investigate the critical phenomena by adopting the Green-function based Monte Carlo technique with the kernel polynomial method, which enables systematic analysis of up to 2048 sites. The critical temperature is lower than that in the hyperhoneycomb case, reflecting the smaller flux gap. We also discuss the transition on the basis of an effective model in the anisotropic limit.

  7. Direct synthesis of chromium perovskite oxyhydride with a high magnetic-transition temperature.

    Science.gov (United States)

    Tassel, Cédric; Goto, Yoshihiro; Kuno, Yoshinori; Hester, James; Green, Mark; Kobayashi, Yoji; Kageyama, Hiroshi

    2014-09-22

    We report a novel oxyhydride SrCrO2H directly synthesized by a high-pressure high-temperature method. Powder neutron and synchrotron X-ray diffraction revealed that this compound adopts the ideal cubic perovskite structure (Pm3̄m) with O(2-)/H(-) disorder. Surprisingly, despite the non-bonding nature between Cr 3d t(2g) orbitals and the H 1s orbital, it exhibits G-type spin ordering at T(N)≈380 K, which is higher than that of RCrO3 (R=rare earth) and any chromium oxides. The enhanced T(N) in SrCrO2H with four Cr-O-Cr bonds in comparison with RCr(3+)O3 with six Cr-O-Cr bonds is reasonably explained by the tolerance factor. The present result offers an effective strategy to tune octahedral tilting in perovskites and to improve physical and chemical properties through mixed anion chemistry. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Polarization induced water molecule dissociation below the first-order electronic-phase transition temperature

    CERN Document Server

    Arulsamy, Andrew Das; Elersic, Kristina; Modic, Martina; Subramani, Uma Shankar

    2011-01-01

    Hydrogen produced from the photocatalytic splitting of water is one of the reliable alternatives to replace the polluting fossil and the radioactive nuclear fuels. Here, we provide unequivocal evidence for the existence of blue- and red-shifting O$-$H covalent bonds within a single water molecule adsorbed on MgO surface as a result of asymmetric displacement polarizabilities. The adsorbed H-O-H on MgO gives rise to one weaker H-O bond, while the other O-H covalent bond from the same adsorbed water molecule compensates this effect with a stronger bond. The weaker bond (nearest to the surface), the interlayer tunneling electrons and the silver substrate are shown to be the causes for the smallest dissociative activation energy on MgO monolayer. The origin that is responsible to initiate the splitting mechanism is proven to be due to the changes in the polarizability of an adsorbed water molecule, which are further supported by the temperature-dependent static dielectric constant measurements for water below the...

  9. Temperature phase transitions associated with local minima of energy in continous unbounded spins

    CERN Document Server

    Dobrovolny, B

    2004-01-01

    {\\footnotesize In this work we develop an alternative version of the theory of contour models adapted to continuous spins, $\\omega_{x}\\in {\\large{\\bf {R}}}$, located in sites, $x$ of a $d\\geq 2$ dimensional lattice ${\\large{\\bf Z^{d}}}$. \\\\ The spins interacting via nearest neighbors ferromagnetic interactions are embedded in a single spin potential $V$ similar to that, already, introduced by Dobrushin and Shlosman.\\\\ The potential $V$, has an ordered sequence $\\left( \\omega_{1}m_{q^{^{\\prime }}}$, $q< q^{^{\\prime }}$. \\item The distance between two successive minima is sufficiently great and the they are separated by a sufficiently heigh energy barrier. \\end{itemize} For all finite reciprocal temperature $\\beta$, satisfying $1\\leq \\beta <\\infty$, and for the mass $m_{n}$ ( corresponding to the $n^{th}$ minimum) large enough, we prove the Peierls condition, and we derive the phase diagram by proving that there exist sequences ($\\beta_{1},... ,\\beta_{N(n)}$) , $N(n)

  10. Accurate electronic free energies of the 3 d ,4 d , and 5 d transition metals at high temperatures

    Science.gov (United States)

    Zhang, Xi; Grabowski, Blazej; Körmann, Fritz; Freysoldt, Christoph; Neugebauer, Jörg

    2017-04-01

    Free energies of bulk materials are nowadays routinely computed by density functional theory. In particular for metals, electronic excitations can significantly contribute to the free energy. For an ideal static lattice, this contribution can be obtained at low computational cost, e.g., from the electronic density of states derived at T =0 K or by utilizing the Sommerfeld approximation. The error introduced by these approximations at elevated temperatures is rarely known. The error arising from the ideal lattice approximation is likewise unexplored but computationally much more challenging to overcome. In order to shed light on these issues we have computed the electronic free energies for all 3 d ,4 d , and 5 d transition elements on the ideal lattices of the bcc, fcc, and hcp structures using finite-temperature density-functional theory. For a subset of elements we have explored the impact of explicit thermal vibrations on the electronic free energies by using ab initio molecular dynamics simulations. We provide an analysis of the observed chemical trends in terms of the electronic density of states and the canonical d band model and quantify the errors in the approximate methods. The electronic contribution to the heat capacities and the corresponding errors due to the different approximations are studied as well.

  11. Protein brownian rotation at the glass transition temperature of a freeze-concentrated buffer probed by superparamagnetic nanoparticles.

    Science.gov (United States)

    Eloi, J-C; Okuda, M; Jones, S E Ward; Schwarzacher, W

    2013-06-18

    For applications from food science to the freeze-thawing of proteins it is important to understand the often complex freezing behavior of solutions of biomolecules. Here we use a magnetic method to monitor the Brownian rotation of a quasi-spherical cage-shaped protein, apoferritin, approaching the glass transition Tg in a freeze-concentrated buffer (Tris-HCl). The protein incorporates a synthetic magnetic nanoparticle (Co-doped Fe3O4 (magnetite)). We use the magnetic signal from the nanoparticles to monitor the protein orientation. As T decreases toward Tg of the buffer solution the protein's rotational relaxation time increases exponentially, taking values in the range from a few seconds up to thousands of seconds, i.e., orders of magnitude greater than usually accessed, e.g., by NMR. The longest relaxation times measured correspond to estimated viscosities >2 MPa s. As well as being a means to study low-temperature, high-viscosity environments, our method provides evidence that, for the cooling protocol used, the following applies: 1), the concentration of the freeze-concentrated buffer at Tg is independent of its initial concentration; 2), little protein adsorption takes place at the interface between ice and buffer; and 3), the protein is free to rotate even at temperatures as low as 207 K. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  12. Physical stability of drugs after storage above and below the glass transition temperature: Relationship to glass-forming ability.

    Science.gov (United States)

    Alhalaweh, Amjad; Alzghoul, Ahmad; Mahlin, Denny; Bergström, Christel A S

    2015-11-10

    Amorphous materials are inherently unstable and tend to crystallize upon storage. In this study, we investigated the extent to which the physical stability and inherent crystallization tendency of drugs are related to their glass-forming ability (GFA), the glass transition temperature (Tg) and thermodynamic factors. Differential scanning calorimetry was used to produce the amorphous state of 52 drugs [18 compounds crystallized upon heating (Class II) and 34 remained in the amorphous state (Class III)] and to perform in situ storage for the amorphous material for 12h at temperatures 20°C above or below the Tg. A computational model based on the support vector machine (SVM) algorithm was developed to predict the structure-property relationships. All drugs maintained their Class when stored at 20°C below the Tg. Fourteen of the Class II compounds crystallized when stored above the Tg whereas all except one of the Class III compounds remained amorphous. These results were only related to the glass-forming ability and no relationship to e.g. thermodynamic factors was found. The experimental data were used for computational modeling and a classification model was developed that correctly predicted the physical stability above the Tg. The use of a large dataset revealed that molecular features related to aromaticity and π-π interactions reduce the inherent physical stability of amorphous drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Size-induced effect upon the Neel temperature of the antiferro/paramagnetic transition in gadolinium oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Mutelet, B.; Martini, M.; Perriat, P. [Universite de Lyon, MATEIS, UMR 5510 CNRS, Villeurbanne (France); Keller, N. [Universite de Versailles-St-Quentin, GEMAC, UMR 8635 CNRS, Versailles (France); Roux, S. [Universite de Franche-Comte, UTINAM, UMR 6213 CNRS, Besanon (France); Flores-Gonzales, M.A.; Lux, F.; Tillement, O.; Billotey, C.; Janier, M. [Universite de Lyon, Universite Claude Bernard, LPCML, Villeurbanne (France); Villiers, C. [Institut Albert Bonniot, INSERM U823, La Tronche (France); Novitchi, Ghenadie; Luneau, Dominique [Universite de Lyon, Universite Claude Bernard, Laboratoire des Multimateriaux et Interfaces, Villeurbanne (France)

    2011-10-15

    In this paper, we demonstrate that cubic gadolinium oxide is paramagnetic and follows the Curie-Weiss law from 20 K to room temperature for particles size comprised between 3.5 and 60 nm. The largest particles (60 nm) possess the macroscopic behaviour of Gd oxide with a Neel temperature, T{sub N}, close to 18 K (Gd oxide is antiferromagnetic below T{sub N}, paramagnetic above). Then size-induced effects can be encountered only for particles smaller than 60 nm. We find that the finite-size scaling model used for describing the size evolution of the antiferro/paramagnetic transition is valid for sizes comprised between 3.5 and 35 nm with parameters in excellent agreement with those usually found for antiferromagnetic materials. The correlation length (3.6 nm) is of the order of magnitude of a few lattice parameters and the critical exponent {lambda} is found equal to 1.3, a value very close to that predicted by the three dimensional Heisenberg model ({lambda}=1.4). (orig.)

  14. Effect of the polymer chain length of poly(N-isopropylacrylamide) on the temperature-responsive phase transition behavior of its conjugates with [60]fullerene.

    Science.gov (United States)

    Uchida, Katsumi; Tamura, Atsushi; Yajima, Hirofumi

    2010-03-01

    In order to develop biomedical materials with specific functionalities, thermoresponsive conjugates [poly(N-isopropylacrylamide)-C(60) (PIPAAm-C(60)) ]of [60]fullerene (C(60)) and PIPAAm with two different polymer chain lengths (4 and 20 kDa) were synthesized by atom transfer radical polymerization. The effects of the polymer chain length on the temperature-responsive phase transition behavior of the synthetic PIPAAm-C(60) conjugates were probed by means of various physicochemical techniques. The coexistence of unimers and molecular assemblies of PIPAAm-C(60) was observed by gel permeation chromatography and dynamic light scattering studies in two PIPAAm-C(60) aqueous solutions below their lower critical solution temperatures (LCSTs). Additionally, below their LCSTs, differences in PIPAAm chain length gave rise to changes in the composition of the unimers and molecular assemblies. In response to temperature, the absorbance of the PIPAAm-C(60) aqueous solution changed according to a two-step behavior profile. Increasing temperature during the primary stage, where a change in the absorbance of the PIPAAm-C(60) aqueous solution took place, did not change the transition temperature, regardless of the solution concentration of PIPAAm-C(60). This absorbance change was associated with the phase transition of the molecular assemblies of PIPAAm-C(60). However, at the second stage, the transition temperature shifted to a higher value with the decrease in the concentration of PIPAAm-C(60), in the same manner as free PIPAAm chains. The second change was associated with the phase transition of the unimeric PIPAAm-C(60). Differences in PIPAAm chain length gave rise to the change in the phase transition behavior of PIPAAm-C(60) aqueous solution. Therefore, the chain length of PIPAAm was found to be a predominant factor involved in the solution characteristics of PIPAAm-C(60). Consequently, the PIPAAm-C(60) is expected to be an intelligent biomaterial possessing heat

  15. Quantifying Ice Volume and Temperature Change for the Greenhouse to Icehouse Transition: A Coupled Palaeoceanographic and Palaeoclimate Modelling Approach

    Science.gov (United States)

    Peck, V. L.; Riesselman, C.; Haywood, A. M.; Valdes, P. J.

    2007-12-01

    The abrupt and widespread glaciation of Antarctica in the earliest Oligocene marked a fundamental change in global climate leading to the Earth's current glaciated state. An increase in benthic δ18O of up to 1.5 ‰ occurred over a 300-400 kyr interval and is widely assumed to document both cooling and ice sheet growth marking the inception of the icehouse world. Resolving the relative contribution of ice volume and temperature changes to this shift is essential to understanding, and accurately modelling, this climate transition. In an attempt to quantify relative ice volume and temperature changes at the Eocene-Oligocene boundary we present the initial results from a coupled paleoceanographic and paleoclimate modelling approach. Coupled δ18O and Mg/Ca records of surface dwelling Turborotalia ampliapertura and thermocline dwelling Subbotina angiporoides have the potential to document upper ocean temperature and δ18O seawater at ODP site 1263, Walvis Ridge in the South Atlantic. %CaCO3 measurements from the suite of sites drilled on ODP Leg 208 place the lyscoline at ~3.8 km in the latest Eocene, prior to deepening in the earliest Oligocene. Collected at a present day water depth of 2717 m, ODP Site 1263 was positioned above the lysocline throughout the Eocene-Oligocene transition. Carbonate concentrations vary between 84 and 96 % (within the studied interval) and planktonic foraminifera appear well preserved. Spanning 33.8 to 32.8 Ma, initial records have a temporal resolution averaging temperature shift of less than 0.5° C in the Mg/Ca records of both the surface and subsurface-dwelling species. This finding matches that of the simulated response of sea surface temperatures (SST) at the paleolatitude associated with ODP Site 1263 to the growth of an Antarctic ice sheet during the earliest Oligocene using the HadCM3L General Circulation Model. Two Early Oligocene experiments are being performed which are identical in all respects expect in their prescribed

  16. Dynamics across the structural transitions at elevated temperatures in Na0.7CoO2

    Directory of Open Access Journals (Sweden)

    Juranyi Fanni

    2015-01-01

    Full Text Available The layered transition-metal oxide Nax CoO2 has been studied extensively both for its correlated electronic properties as well as for potential battery applications. It was discovered that high-temperature Na ion vacancy order and dynamics can be very useful to tailor low-temperature properties of members of this compound family. We have studied the Na-ion dynamics on the atomic length-scale in the Na0.7 CoO2 compound by neutron spectroscopy. The temperature dependence of both the elastic and the inelastic intensities show steps at TA ≈ 290 K and TB ≈ 400 K. At TA the step is shown to be connected to low energy phonons, while at TB the Na ion diffusion suddenly gets fast enough, and the characteristic signal of quasielastic scattering appears. The current results further elucidate the subtle changes in the Na ion dynamics that have been revealed in our previous neutron diffraction studies [1], intimately connecting structural transformations at TA and TB with the opening-up of 1D and 2D Na-ion diffusion paths. Finally, the estimated diffusion coefficient above TB was found to differ from the one measured by muon-spin relaxation (μ+SR [2] by about four orders of magnitude. However it might be that the present QENS data rather describe a fast localized prozess than a long range translational diffusion. Within this model the corresponding time scale (ℏ/E would be in the order of 50 ps.

  17. A High-Temperature Order-Disorder Phase Transition Coupled With Conformational Change in the Hybrid Material [C6 H13 NH]2 ⋅ZnBr4.

    Science.gov (United States)

    Khan, Tariq; Asghar, Muhammad Adnan; Sun, Zhihua; Zeb, Aurang; Li, Lina; Sijie, Liu; Zhao, Sangen; Ji, Chengmin; Luo, Junhua

    2016-10-20

    A new high-temperature, hybrid, phase-transition material, 1-methylpiperidinium tetrabromozincate (1), that shows a reversible transition at 345 K was synthesized. Differential scanning calorimetry and specific heat capacity measurements confirmed this reversible transformation with a large heat hysteresis of 25 K, which describes a typical first-order phase transition in 1. The dielectric constant exhibited a steplike anomaly and showed high and low dielectric states in the high- and room-temperature phases, respectively, and therefore, this hybrid might be considered as a potential switchable dielectric material. The variable-temperature powder X-ray diffraction patterns displayed remarkable shifts between the experimental patterns at the two different phases. Single-crystal X-ray diffraction analyses at various temperatures revealed that the origin of this transformation could be attributed to disordering of the bromine atoms in the anion and the nitrogen atom of the cation. The cation also assumed a conformational change, which was likely induced by the disordered nitrogen atom. The conformational onset of the transformation of the cation from a planar conformer into a relaxed chair also occurred upon decreasing the temperature below transition point; thus, the combined order-disorder and conformational change induced the structural transformation and the change in symmetry. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Directory of Open Access Journals (Sweden)

    Hoong-Kun Fun

    2014-07-01

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

  19. Comparison between experiment and theory in the temperature variation of film tension above the bulk isotropic transition in free-standing liquid-crystal films.

    Science.gov (United States)

    Veum, M; Duelge, L; Droske, J; Nguyen, H T; Huang, C C; Mirantsev, L V

    2009-09-01

    Using differential scanning calorimetry, the transition enthalpies and temperatures for the bulk smectic-isotropic phase transition have been measured for a series of liquid-crystal compounds. For five compounds, those values were used as parameters in a microscopic mean-field model to predict the temperature dependence of the difference in free-energy density between a sample of material in a free-standing smectic film and that in the bulk. The model predicts a weak temperature dependence below the bulk clearing point and a pronounced monotonic increase with temperature above the transition temperature. The compounds used in this study were chosen specifically because they were also the subject of a previous independent experimental study [M. Veum, Phys. Rev. E 74, 011703 (2006)] that demonstrated a sudden monotonic increase in the free-standing film tension with temperature, which is qualitatively consistent with the predictions of the above-mentioned mean-field model. This study presents a direct and quantitative comparison between the predictions of the mean-field model and the results from previous tension experiments.

  20. Enzymatic liquefaction of agarose above the sol-gel transition temperature using a thermostable endo-type β-agarase, Aga16B.

    Science.gov (United States)

    Kim, Jung Hyun; Yun, Eun Ju; Seo, Nari; Yu, Sora; Kim, Dong Hyun; Cho, Kyung Mun; An, Hyun Joo; Kim, Jae-Han; Choi, In-Geol; Kim, Kyoung Heon

    2017-02-01

    The main carbohydrate of red macroalgae is agarose, a heterogeneous polysaccharide composed of D-galactose and 3,6-anhydro-L-galactose. When saccharifying agarose by enzymes, the unique physical properties of agarose, namely the sol-gel transition and the near-insolubility of agarose in water, limit the accessibility of agarose to the enzymes. Due to the lower accessibility of agarose to enzymes in the gel state than to the sol state, it is important to prevent the sol-gel transition by performing the enzymatic liquefaction of agarose at a temperature higher than the sol-gel transition temperature of agarose. In this study, a thermostable endo-type β-agarase, Aga16B, originating from Saccharophagus degradans 2-40(T), was characterized and introduced in the liquefaction process. Aga16B was thermostable up to 50 °C and depolymerized agarose mainly into neoagarooligosaccharides with degrees of polymerization 4 and 6. Aga16B was applied to enzymatic liquefaction of agarose at 45 °C, which was above the sol-gel transition temperature of 1 % (w/v) agarose (∼35 °C) when cooling agarose. This is the first systematic demonstration of enzymatic liquefaction of agarose, enabled by determining the sol-gel temperature of agarose under specific conditions and by characterizing the thermostability of an endo-type β-agarase.

  1. A conformational polymorphic transition in the high-temperature epsilon-form of chlorpropamide on cooling: a new epsilon'-form.

    Science.gov (United States)

    Drebushchak, Tatiana N; Chesalov, Yury A; Boldyreva, Elena V

    2009-12-01

    Structural changes in the high-temperature -polymorph of chlorpropamide, 4-chloro-N-(propylaminocarbonyl)benzenesulfonamide, C(10)H(13)ClN(2)O(3)S, on cooling down to 100 K and on reverse heating were followed by single-crystal X-ray diffraction. At temperatures below 200 K the phase transition into a new polymorph (termed the epsilon'-form) has been observed for the first time. The polymorphic transition preserves the space group Pna2(1), is reversible and is accompanied by discontinuous changes in the cell volume and parameters, resulting from changes in molecular conformation. As shown by IR spectroscopy and X-ray powder diffraction, the phase transition in a powder sample is inhomogeneous throughout the bulk, and the two phases co-exist in a wide temperature range. The cell parameters and the molecular conformation in the new polymorph are close to those in the previously known alpha-polymorph, but the packing of the z-shaped molecular ribbons linked by hydrogen bonds inherits that of the epsilon-form and is different from the packing in the alpha-polymorph. A structural study of the alpha-polymorph in the same temperature range has revealed no phase transitions.

  2. Study of the pressure-time-temperature transformation of amorphous La6Ni5Al89 by the energy dispersive method for phase transition

    DEFF Research Database (Denmark)

    Paci, B.; Rossi-Albertini, V.; Sikorski, M.

    2005-01-01

    was measured and the curves describing the transitions, qualitatively equivalent to a differential scanning calorimetry (DSC) thermogram, could be drawn. Finally, the analysis of such curves allowed calculation of some points of the alloy pressure-time-temperature transformation (PTTT) diagram. More...

  3. Study of negative thermal expansion and shift in phase transition temperature in Ti4+- and Sn4+-substituted ZrW2O8 materials.

    Science.gov (United States)

    Buysser, Klaartje De; Driessche, Isabel Van; Putte, Bart Vande; Vanhee, Paul; Schaubroeck, Joseph; Hoste, Serge

    2008-01-21

    The negative-thermal-expansion material ZrW(2)O(8) is known to undergo an order-disorder phase transition which affects its expansion behavior. In this study, Ti(4+) and Sn(4+) are examined as possible substituting ions for the Zr(4+) position in ZrW(2)O(8). This substitution leads to a decrease in cell parameters, as the ionic radii of the substituents are smaller than the Zr(4+) ionic radius. A remarkable decrease in transition temperature is noticed. DSC is used to quantify the enthalpy and entropy changes during the phase transition in order to reveal the mechanisms behind this decrease. It is shown that the strength of the M-O bond plays an important role, as it is a partner in the rigid unit mode motion and the order-disorder transition mechanism.

  4. Synthesis and Characterization of Fluorescently Labeled Diblock Copolymers for Location-Specific Measurements of The Glass Transition Temperature

    Science.gov (United States)

    Christie, Dane; Register, Richard; Priestley, Rodney

    Interfaces play a determinant role in the size dependence of the glass transition temperature (Tg) of polymers confined to nanometric length scales. Interfaces are intrinsic in diblock copolymers, which, depending on their molecular weight and composition, are periodically nanostructured in the bulk. As a result diblock copolymers are model systems for characterizing the effect of interfaces on Tg in bulk nanostructured materials. Investigating the effect of intrinsic interfaces on Tg in diblock copolymers has remained unexplored due to their small periodic length scale. By selectively incorporating trace amounts of a fluorescent probe into a diblock copolymer, Tg can be characterized relative to the diblock copolymer's intrinsic interface using fluorescence spectroscopy. Here, pyrene is selectively incorporated into the poly(methyl methacrylate) (PMMA) block of lamellar forming diblock copolymers of poly(butyl- b-methyl methacrylate) (PBMA-PMMA). Preliminary results show a correlation of Tg as measured by fluorescence with the onset of Tg as measured by calorimetry in labeled homopolymers of PMMA. This result is consistent with previous characterizations of Tg using fluorescence spectroscopy. In selectively labeled diblock copolymers Tg is found to vary systematically depending on the distance of the probe from the PBMA-PMMA interface. We acknowledge funding from the Princeton Center for Complex Materials, a MRSEC supported by NSF Grant DMR 1420541.

  5. Effect of borojo (Borojoa patinoi Cuatrecasas) three-phase composition and gum arabic on the glass transition temperature.

    Science.gov (United States)

    Rodríguez-Bernal, Jenny M; Tello, Edisson; Flores-Andrade, Enrique; Perea-Flores, Maria de Jesús; Vallejo-Cardona, Alba A; Gutiérrez-López, Gustavo F; Quintanilla-Carvajal, Maria X

    2016-02-01

    The search for natural, novel, high-quality, stable food ingredients is an ongoing practice in the food industry. Pulp of borojo (Borojoa patinoi Cuatrecasas), which is a fruit of the Colombian Pacific region, can be separated into three phases: liquid (LP), medium (MP) and solid (SP) phases. The objective of this work was to evaluate the effect of the three-phase composition and gum arabic on their glass transitions temperatures (T(g)). The best mixture, LP-MP, MP-SP and LP-SP and gum arabic (GA) was identified by response surface methodology. When adding GA to SP borojo phase in a 1:1 proportion, the resulting T(g) of the mixture was 132.27 °C whereas Tg for GA and SP-phase were 154.89 °C and 79.86 °C respectively, which supported this combination as attractive from a processing perspective and supports an industrial advantage of using borojo as food ingredient. Phases were characterized by high-performance liquid chromatography, Fourier transform infrared spectroscopy, confocal laser scanning microscopy and mass spectrometry. Low molecular weight compounds such as fructose for MP lowered T(g) whereas the presence of lignin increased T(g) of the mixtures as with the SP. The addition of GA significantly increased T(g) of borojo phases so leading to propose them as novel food processing materials. © 2015 Society of Chemical Industry.

  6. Observation of exchanging role of gold and silver nanoparticles in bimetallic thin film upon annealing above the glass transition temperature

    Science.gov (United States)

    Htet Kyaw, Htet; Tay Zar Myint, Myo; Hamood Al-Harthi, Salim; Maekawa, Toru; Yanagisawa, Keiichi; Sellai, Azzouz; Dutta, Joydeep

    2017-08-01

    The exchange role of gold (Au) and silver (Ag) in bimetallic films co-evaporated onto soda-lime glass substrates with Au-Ag volume ratios of 1:2, 1:1 and 2:1 have been demonstrated. Annealing of the films above the glass transition temperature in air led to non-alloying nature of the films, silver neutrals (Ag0) and gold nanoparticles (AuNPs) on the surface, along with silver nanoparticles (AgNPs) inside the glass matrix. Moreover, the size distribution and interparticle spacing of the AuNPs on the surface were governed by the Ag content in the deposited film. In contrast, the content of Au in the film played an opposite role leading to the migration of Ag ions (i.e. Ag0 being transformed to Ag ions after annealing in oxygen ambient) to form AgNPs inside the glass matrix. The higher the Au content in the film is, the more likely Ag0 to stay on the surface and impacts on the size distribution of AuNPs and consequently on the refractive index sensitivity measurements. Experimental realisation of this fact was reflected from the best performance for localized surface plasmon resonance (LSPR) sensitivity test achieved with Au-Ag ratio of 1:2. The Au/Ag/glass bimetallic dynamic results of this study can be pertinent to sensor applications integrated with optical devices.

  7. Influence of manufacturing factors on physical stability and solubility of solid dispersions containing a low glass transition temperature drug.

    Science.gov (United States)

    Sakurai, Atsushi; Sako, Kazuhiro; Maitani, Yoshie

    2012-01-01

    In this study, we investigated the effect of manufacturing factors such as particle size, water content and manufacturing method on the physical stability and solubility of solid dispersion formulations of a low-glass-transition-temperature (T(g)) drug. Solid dispersions were prepared from polyvinylpyrrolidone (PVP) and hydroxypropylmethylcellulose (HPMC) by hot melt extrusion or spray drying. Water content of solid dispersions prepared by hot melt extrusion determined by dynamic moisture sorption measurement was increased drastically with relative humidity below a certain level of particle size. The blends with a lower water content (0.8%) prepared by hot melt extrusion during storage were more stable than those with a higher water content (3.5%) prepared by spray drying, which caused rapid recrystallization. Physical stability in the hot melt blends may be attributed to reduced molecular mobility due to a higher T(g). Dissolution study revealed that solid dispersions prepared by hot melt extrusion with the smallest particle size showed decreased solubility, attributed to reduced wetting properties (surface energy), which is not predictable by the Noyes-Whitney equation. Taken together, these results indicate that the control of particle size concerned in water content or wetting properties is critical to ensuring the physical stability or enhancing solubility of low-T(g) drugs. Further, hot melt extrusion, which can reduce water content, is a suitable manufacturing method for solid dispersions of low-T(g) drugs.

  8. High-temperature phase transformations in YBa/sub 2/Cu/sub 3/O(7+delta) and their effect on the superconducting transition

    Energy Technology Data Exchange (ETDEWEB)

    Sukharevskii, B.IA.; Shatalova, G.E.; Khokhlova, S.I.; Mikheenko, P.N.; Ksenofontov, V.G.

    1987-09-01

    Low-temperature (700 K or less), intermediate equilibrium (700-900 K), and hardened metastable phases, as well as a high-temperature (900 K and above) tetragonal phase, have been identified in polycrystalline YBa/sub 2/Cu/sub 3/O(7+delta). The transition between the first two phases is associated with the loss (during heating) or addition (during cooling) of one oxygen ion per formula unit. Superconductivity is realized in the low-temperature phase, in which the copper ions of two middle copper-oxygen planes are octahedrally coordinated by oxygen ions.

  9. Direct measurement of the low temperature spin state transitions in La1-xSrxCoO3 (0.05 < x < 0.3)

    Science.gov (United States)

    Gulec, A.; Klie, R. F.

    2014-12-01

    Sr-doped LaCoO3 has a complex magnetic phase diagram, which is believed to be directly correlated to changes in the crystal structure and ordering of the Co3+ spin states. In this work, we study the low temperature Co3+-ion spin state transitions in Sr-doped LaCoO3 around the critical doping concentration where a metal to insulator transition has been observed using electron energy-loss spectroscopy of the O K-edge combined with the Co L-edge fine structure. We measure the local spin state of the Co3+-ions and we demonstrate that the Co3+ spin-state transition only occurs in La0.95Sr0.05CoO3 single-crystal materials in the temperature range accessible by LN2 in-situ cooling, while no structural symmetry change is observed. The presence of this low-temperature spin-state transition in La1-xSrxCoO3 (x LaCoO3.

  10. Molecular Dynamic Simulations of Glass Transition Temperature and Mechanical Properties in the Amorphous Region of Oil-Immersed Transformer Insulation Paper

    Science.gov (United States)

    Wang, You-Yuan; Yang, Tao; Liao, Rui-Jin

    2012-07-01

    The glass transition temperature (Tg) in the amorphous region of an insulation paper is one of the most important characteristics for thermal stability. Molecular dynamic simulations have been performed on three micro-structural models, namely, amorphous pure cellulose, amorphous cellulose with water and amorphous cellulose with oil, to study the microscopic mechanism of the glass transition process for oil-immersed transformer insulation paper. Using the method of specific volume versus temperature curve, the Tg of amorphous pure cellulose, cellulose with water, and cellulose with oil was determined as 448, 418 and 440 K, respectively. The current study may provide some information for thermal aging. The simulation results show that during the glass transition process, both the chain motion and mechanical properties of cellulose changes significantly. Relative to the oil molecules, water molecules immersed in the amorphous region of insulation paper can disrupt hydrogen bonds between cellulose chains. This phenomenon results in a significant reduction in the glass transition temperature and affects the thermal stability of the insulation paper.

  11. Photoluminescent-dielectric duple switch in a perovskite-type high-temperature phase transition compound: [(CH3)3PCH2OCH3][PbBr3].

    Science.gov (United States)

    Geng, Fu-Juan; Wu, De-Hong; Zhou, Lin; Shi, Ping-Ping; Li, Peng-Fei; Gao, Ji-Xing; Zheng, Xuan; Fu, Da-Wei; Ye, Qiong

    2017-07-25

    A bistable optical-electrical duple switch belongs to a class of highly satisfying intelligent materials that can transform optical and electrical responses simultaneously in one device. A perovskite-type high-temperature phase transition compound with one-dimensional chain-like crystal structure, ([(CH3)3PCH2OCH3][PbBr3], 1), displays remarkable bistable photoluminescent-dielectric duple switching behaviors. The noteworthy order-disorder transition of the phosphonium cation and the motions of anions contribute to the phase transition, leading to the space group P21/c at a low temperature phase to C2/c at a high temperature phase. 1 exhibits a prominent step-like dielectric anomaly at 401.0 K and demonstrates novel optical properties with a band gap of 3.54 eV. The photoluminescence intensity suddenly declines from 398 K to 408 K, which may be attributed to the occurrence of phase transition. The electron cloud distributions of the frontier orbital in compound 1 have been calculated using a DFT program.

  12. Phase transitions in the hard-core Bose-Fermi-Hubbard model at non-zero temperatures in the heavy-fermion limit

    Energy Technology Data Exchange (ETDEWEB)

    Stasyuk, I.V.; Krasnov, V.O., E-mail: krasnoff@icmp.lviv.ua

    2017-04-15

    Phase transitions at non-zero temperatures in ultracold Bose- and Fermi-particles mixture in optical lattices using the Bose-Fermi-Hubbard model in the mean field and hard-core boson approximations are investigated. The case of infinitely small fermion transfer and the repulsive on-site boson-fermion interaction is considered. The possibility of change of order (from the 2nd to the 1st one) of the phase transition to the superfluid phase in the regime of fixed values of the chemical potentials of Bose- and Fermi-particles is established. The relevant phase diagrams determining the conditions at which such a change takes place, are built.

  13. Clumped isotope analyses suggest constant seawater temperatures at the Middle-Late Jurassic transition in the Subboreal realm

    Science.gov (United States)

    Wierzbowski, Hubert; Bajnai, David; Wacker, Ulrike; Fiebig, Jens; Rogov, Mikhail

    2017-04-01

    Clumped isotope analyses were performed on a set of 18 well-preserved belemnite rostra and 4 ammonite shells derived from uppermost Middle-Upper Jurassic strata of the Russian Platform. The aim of the study is to reconstruct palaeoclimatic variations and paleoceanographic changes during and after the Middle-Late Jurassic transition in the Subboreal realm. Previous studies, based on the δ18O values and elemental ratios of belemnite rostra, suggest the presence of a prolonged Late Callovian-Middle Oxfordian cool period with bottom waters at ˜5 °C, followed by a pronounced Late Oxfordian-Late Kimmeridgian warming (by 6.5-9.5 °C) in the epicontinental Middle Russian Sea. The occurrence of cold bottom waters is interpreted as a result of the formation of wide marine connections with the Arctic Sea during a sea-level highstand. As an independent proxy for palaeotemperatures, clumped isotopes could estimate the extent to which the δ18O record is influenced by local salinity variations. Clumped isotope analyses suggest constant bottom water temperatures (˜15 °C) of the Middle Russian Sea during the latest Callovian-earliest Late Kimmeridgian. This questions the previous interpretation of the δ18O record. The Upper Oxfordian-Lower Kimmeridgian decrease in δ18O values, which was previously explained by warming, probably results instead from a decrease in salinity. A decrease in sea level after the Middle-Late Jurassic boundary transgression could have contributed to the enhanced freshwater runoff. Consequently, the limited water exchange in the restricted basin of the Middle Russian Sea probably led to the significant decrease in salinity and water δ18O values.

  14. Ligand partitioning into lipid bilayer membranes under high pressure: Implication of variation in phase-transition temperatures.

    Science.gov (United States)

    Matsuki, Hitoshi; Kato, Kentaro; Okamoto, Hirotsugu; Yoshida, Shuntaro; Goto, Masaki; Tamai, Nobutake; Kaneshina, Shoji

    2017-12-01

    The variation in phase-transition temperatures of dipalmitoylphosphatidylcholine (DPPC) bilayer membrane by adding two membrane-active ligands, a long-chain fatty acid (palmitic acid (PA)) and an inhalation anesthetic (halothane (HAL)), was investigated by light-transmittance measurements and fluorometry. By assuming the thermodynamic colligative property for the bilayer membrane at low ligand concentrations, the partitioning behavior of these ligands into the DPPC bilayer membrane was considered. It was proved from the differential partition coefficients between two phases that PA has strong affinity with the gel (lamellar gel) phase in a micro-molal concentration range and makes the bilayer membrane more ordered, while HAL has strong affinity with the liquid crystalline phase in a milli-molal concentration range and does the bilayer membrane more disordered. The transfer volumes of both ligands from the aqueous solution to each phase of the DPPC bilayer membrane showed that the preferential partitioning of the PA molecule into the gel (lamellar gel) produces about 20% decrease in transfer volume as compared with the liquid crystalline phase, whereas that of the HAL molecule into the liquid crystalline phase does about twice increase in transfer volume as compared with the gel (ripple gel) phase. Furthermore, changes in thermotropic and barotropic phase behavior of the DPPC bilayer membrane by adding the ligand was discussed from the viewpoint of the ligand partitioning. Reflecting the contrastive partitioning of PA and HAL into the pressure-induced interdigitated gel phase among the gel phases, it was revealed that PA suppresses the formation of the interdigitated gel phase under high pressure while HAL promotes it. These results clearly indicate that each phase of the DPPC bilayer membrane has a potential to recognize various ligand molecules. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Selecting polymers for two-phase partitioning bioreactors (TPPBs): Consideration of thermodynamic affinity, crystallinity, and glass transition temperature.

    Science.gov (United States)

    Bacon, Stuart L; Peterson, Eric C; Daugulis, Andrew J; Parent, J Scott

    2015-01-01

    Two-phase partitioning bioreactor technology involves the use of a secondary immiscible phase to lower the concentration of cytotoxic solutes in the fermentation broth to subinhibitory levels. Although polymeric absorbents have attracted recent interest due to their low cost and biocompatibility, material selection requires the consideration of properties beyond those of small molecule absorbents (i.e., immiscible organic solvents). These include a polymer's (1) thermodynamic affinity for the target compound, (2) degree of crystallinity (wc ), and (3) glass transition temperature (Tg ). We have examined the capability of three thermodynamic models to predict the partition coefficient (PC) for n-butyric acid, a fermentation product, in 15 polymers. Whereas PC predictions for amorphous materials had an average absolute deviation (AAD) of ≥16%, predictions for semicrystalline polymers were less accurate (AAD ≥ 30%). Prediction errors were associated with uncertainties in determining the degree of crystallinity within a polymer and the effect of absorbed water on n-butyric acid partitioning. Further complications were found to arise for semicrystalline polymers, wherein strongly interacting solutes increased the polymer's absorptive capacity by actually dissolving the crystalline fraction. Finally, we determined that diffusion limitations may occur for polymers operating near their Tg , and that the Tg can be reduced by plasticization by water and/or solute. This study has demonstrated the impact of basic material properties that affects the performance of polymers as sequestering phases in TPPBs, and reflects the additional complexity of polymers that must be taken into account in material selection. © 2015 American Institute of Chemical Engineers.

  16. Lead(II) coordination polymers based on rigid-flexible 3,5-bis-oxyacetate-benzoic acid: Structural transition driven by temperature control

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yong-Qiang, E-mail: chenjzxy@126.com; Tian, Yuan

    2017-03-15

    Three Pb(II) complexes ([Pb{sub 3}(BOABA){sub 2}(H{sub 2}O)]·H{sub 2}O){sub n} (1), ([Pb{sub 4}(BOABA){sub 2}(µ{sub 4}-O)(H{sub 2}O){sub 2}]·H{sub 2}O){sub n} (2), and [Pb{sub 3}(BOABA){sub 2}(H{sub 2}O)]{sub n} (3) (H{sub 3}BOABA=3,5-bis-oxyacetate-benzoic acid) were obtained under the same reaction systems with different temperatures. Complexes 1 and 2 are two dimensional (2D) networks based on Pb-BOABA chains and Pb{sub 4}(µ{sub 4}-O)(COO){sub 6} SBUs, respectively. Complex 3 presents an interesting three dimensional (3D) framework, was obtained by increasing the reaction temperature. Structural transition of the crystallization products is largely dependent on the reaction temperature. Moreover, the fluorescence properties of complexes 1–3 have been investigated. - Graphical abstract: Three Pb(II) coordination polymers were obtained under the same reaction systems with different temperatures. Both of complexes 1 and 2 are 2D network. 3 presents a 3D framework based on Pb–O–C rods SBUs. The 2D to 3D structures transition between three complexes was achieved successfully by temperature control. - Highlights: • Three Pb(II) complexes were obtained under the same reaction systems with different temperatures. • Structural transition of the crystallization products is largely dependent on the reaction temperature. • The luminescence properties studies reveal that three complexes exhibit yellow fluorescence emission behavior, which might be good candidates for obtaining photoluminescent materials.

  17. Physicochemical processes in embryonic plant tissue during the transition to the state of cold anabiosis and storage at liquid nitrogen temperature

    Science.gov (United States)

    Khodko, A. T.; Lysak, Yu. S.

    2017-10-01

    Critical opalescence phenomenon was observed in the cytoplasm of garlic embryonic tissue—meristem—upon cooling in liquid nitrogen vapor, indicating liquid-liquid phase transition in the system. It was established that cells of the meristem tissue survive the cooling-thawing cycle. We suggest that the transition of meristem tissue to the state of anabiosis is mainly due to a drastic slowing of the diffusion in the cytoplasm caused by the passage of the solution through the critical point, followed by the formation of a dispersed system—a highly concentrated emulsion—as a result of a liquid-liquid phase transition. This macrophase separation is characteristic of polymer-solvent systems. We established the regime of cooling down to liquid nitrogen temperature and subsequent thawing in the cryopreservation cycle for the biological object under study, which ensures the preservation of tissue viability.

  18. Calculation of the Dielectric Constant as a Function of Temperature Close to the Smectic A-Smectic B Transition in B5 Using the Mean Field Model

    Directory of Open Access Journals (Sweden)

    Hamit Yurtseven

    2012-01-01

    Full Text Available The temperature dependence of the static dielectric constant ( is calculated close to the smectic A-smectic B ( transition ( = 71.3°C for the liquid crystal compound B5. By expanding the free energy in terms of the order parameter in the mean field theory, the expression for the dielectric susceptibility (dielectric constant is derived and is fitted to the experimental data for which was obtained at the field strengths of 0 and 67 kV/cm from literature. Coefficients in the free energy expansion are determined from our fit for the transition of B5. Our results show that the observed behaviour of the dielectric constant close to the transition in B5 can be described satisfactorily by our mean field model.

  19. Phase stabilization of magnetite (Fe3O4) nanoparticles with B2O3 addition: A significant enhancement on the phase transition temperature

    Science.gov (United States)

    Topal, Uğur; Aksan, Mehmet Ali

    2016-05-01

    Magnetite nanoparticles (MNPs) are extensively investigated for biomedical applications, particularly as contrast agents for Magnetic Resonance Imaging and as drug delivery agent and heat mediators for cancer therapy. Tuning the magnetic properties of the magnetite nanoparticles with doping of foreign atoms has a crucial importance for determining the application areas of these materials and so attracts much interests. On the other hand the doping with foreign atoms requires high temperature annealing, and it causes a phase transition to the hematite phase above 400 °C. In this work the phase transition temperature from the magnetite to the hematite phase has been increased by 200 °C, which is the highest enhancement reported in literature. It was achieved by addition of the appropriate amounts of B2O3. Our experiments indicates that the 5.0 wt% of B2O3 addition stabilizes and keeps the existence of single phase magnetite up to 600 °C.

  20. Spin-driven pyroelectricity in Ni{sub 3}TeO{sub 6} without ferroelectric signatures of the transition at Neel temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, L.; Komarek, A.C. [Max-Planck-Institute for Chemical Physics of Solids, Dresden (Germany); Du, C.H. [Department of Physics, Tamkang University, Tamsui, Taiwan (China)

    2017-07-15

    Here we report on dielectric studies on Ni{sub 3}TeO{sub 6}. We confirm the spin-driven pyroelectric transition at the Neel temperature (T{sub N}) of ∝52.5 K. The measurement of single crystalline and polycrystalline samples excludes a ferroelectric nature of the transition at T{sub N} in this compound. The excellent pyroelectric properties without any intrinsic ferroelectric hysteresis make Ni{sub 3}TeO{sub 6} appropriate for applications in future devices. Pyroelectric measurements on our Ni{sub 3}TeO{sub 6} single crystals. The polarization that appears on cooling through T{sub N} can not be inverted by opposite poling fields (applied when cooling from above T{sub N} to base temperature). (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Percolation Phase Transition of Surface Air Temperature Networks under Attacks of El Niño/La Niña.

    Science.gov (United States)

    Lu, Zhenghui; Yuan, Naiming; Fu, Zuntao

    2016-05-26

    In this study, sea surface air temperature over the Pacific is constructed as a network, and the influences of sea surface temperature anomaly in the tropical central eastern Pacific (El Niño/La Niña) are regarded as a kind of natural attack on the network. The results show that El Niño/La Niña leads an abrupt percolation phase transition on the climate networks from stable to unstable or metastable phase state, corresponding to the fact that the climate condition changes from normal to abnormal significantly during El Niño/La Niña. By simulating three different forms of attacks on an idealized network, including Most connected Attack (MA), Localized Attack (LA) and Random Attack (RA), we found that both MA and LA lead to stepwise phase transitions, while RA leads to a second-order phase transition. It is found that most attacks due to El Niño/La Niña are close to the combination of MA and LA, and a percolation critical threshold Pc can be estimated to determine whether the percolation phase transition happens. Therefore, the findings in this study may renew our understandings of the influence of El Niño/La Niña on climate, and further help us in better predicting the subsequent events triggered by El Niño/La Niña.

  2. The determination of the phase transition temperatures of a semifluorinated liquid crystalline biphenyl ester by impedance spectroscopy as an alternative method

    Energy Technology Data Exchange (ETDEWEB)

    Yıldız, Alptekin [Istanbul Technical University, Department of Physics Engineering, Maslak, 34469 Istanbul (Turkey); Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Canli, Nimet Yilmaz, E-mail: niyilmaz@yahoo.com [Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Karanlık, Gürkan; Ocak, Hale [Yildiz Technical University, Department of Chemistry, 34220 Istanbul (Turkey); Okutan, Mustafa [Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Eran, Belkız Bilgin [Yildiz Technical University, Department of Chemistry, 34220 Istanbul (Turkey)

    2016-12-15

    Dielectric spectroscopy (DS) is a very powerful and important for better understanding of the molecular dynamics and relaxation phenomena in liquid crystals. The dielectric and impedance characteristics Ethyl 4-(7,7,8,8,9,9,10,10,10-nonafluorodecyloxy)biphenyl-4′-carboxylate (ENBC) liquid crystal have been analyzed over the frequency range of 100 Hz to MHz in the temperature region from room temperature to 180 °C. The compound ENBC shows enantiotropic a smectic mesophase in a wide temperature range. The phase transition temperatures T (°C) of the liquid crystal ENBC, which were characterized by Differential Scanning Calorimetry (DSC), have been verified by the dielectric measurements and conductivity mechanisms of the ENBC. The activation energies for some selected angular frequencies have also been calculated.

  3. Hydration and Hydrogen Bond Network of Water during the Coil-to-Globule Transition in Poly(N-isopropylacrylamide) Aqueous Solution at Cloud Point Temperature.

    Science.gov (United States)

    Shiraga, Keiichiro; Naito, Hirotaka; Suzuki, Tetsuhito; Kondo, Naoshi; Ogawa, Yuichi

    2015-04-30

    Aqueous solutions of poly(N-isopropylacrylamide), P-NIPAAm, exhibit a noticeable temperature responsive change in molecular conformation at a cloud point temperature (Tcp). As the temperature rises above Tcp, the extended coil-like P-NIPAAm structure changes into a swollen globule-like conformation as hydration levels decrease and hydrophobic interactions increase. Though water plays an important role in this coil-to-globule transition of P-NIPAAm, the behavior of water molecules and the associated hydrogen-bond (HB) network of the surrounding bulk water are still veiled in uncertainty. In this study, we elucidate changes in the hydration state and the dynamical structure of the water HB network of P-NIPAAm aqueous solutions during the coil-to-globule transition by analyzing the complex dielectric constant in the terahertz region (0.25-12 THz), where bulk water reorientations and intermolecular vibrations of water can be selectively probed. The structural properties of the water HB network were examined in terms of the population of the non-HB water molecules (not directly engaged in the HB network or hydrated to P-NIPAAm) and the tetrahedral coordination of the water molecules engaged in the HB network. We found the hydration number below Tcp (≈10) was decreased to approximately 6.5 as temperature increased, in line with previous studies. The HB network of bulk water becomes more structured as the coil-to-globule phase transition takes place, via decreases in non-HB water and reduction in the orderliness of the tetrahedral HB architecture. Together these results indicate that the coil-to-globule transition is associated with a shift to hydrophobic-dominated interactions that drive thermoresponsive structural changes in the surrounding water molecules.

  4. The Pre-Onset, Transitional, and Foot Regions in Resistance Versus Temperature Behavior in High-T sub 2 Cuprates: Inferences Regarding Maximum T sub 2

    Science.gov (United States)

    1992-09-01

    linearity region, the transitional regime, and the foot region in the resistance versus temperature behavior of high-Tc oxide superconductors ... superconductor Tl1Ca 1Ba2 Cu207.6 to show commonality of pyramidal building blocks, and also to the well known A2 BX4 related archetype. The structure...The material shows strong levitation , high density, very low porosity, large grain size, and very high electrical conductivity in the normal state. In

  5. Temperature-induced phase transitions for stuffed tridymites SrGa2O4 and CaGa2O4

    Science.gov (United States)

    Jiang, Fuwei; Jiang, Pengfei; Yue, Mufei; Gao, Wenliang; Cong, Rihong; Yang, Tao

    2017-10-01

    Temperature-induced phase transitions for stuffed tridymite AGa2O4 (A = Sr, Ca) were investigated by experimental and theoretical calculations. A simple annealing of SrCO3 and Ga2O3 led to the formation of γ-SrGa2O4 (P21/n) below 1200 °C, and transform to β-SrGa2O4 (P21/c) when heated at 1200 °C. A similar phenomenon was found for CaGa2O4, and the temperature boundary between α-CaGa2O4 (Pna21) and the high temperature polymorph β-CaGa2O4 (P21/c) was about 1350 °C. Rietveld refinements provided detailed structural information for these polymorphs and suggest that the driving force of these phase transitions is the under-bonded nature of the alkaline earth cations. In other words, the need of larger space for Sr2+/Ca2+ in the high temperature β-phase forces the 6-membered-ring channel expand through increasing the Ga-O-Ga angles. Density functional theory calculations proved the formation energies for γ-SrGa2O4 and α-CaGa2O4 were both lower than their high temperature β-polymorphs, in accordance with the experimental observations.

  6. Nonmonotonic Temperature Dependence of the Pressure-Dependent Reaction Rate Constant and Kinetic Isotope Effect of Hydrogen Radical Reaction with Benzene Calculated by Variational Transition-State Theory.

    Science.gov (United States)

    Zhang, Hui; Zhang, Xin; Truhlar, Donald G; Xu, Xuefei

    2017-11-30

    The reaction between H and benzene is a prototype for reactions of radicals with aromatic hydrocarbons. Here we report calculations of the reaction rate constants and the branching ratios of the two channels of the reaction (H addition and H abstraction) over a wide temperature and pressure range. Our calculations, obtained with an accurate potential energy surface, are based on variational transition-state theory for the high-pressure limit of the addition reaction and for the abstraction reaction and on system-specific quantum Rice-Ramsperger-Kassel theory calibrated by variational transition-state theory for pressure effects on the addition reaction. The latter is a very convenient way to include variational effects, corner-cutting tunneling, and anharmonicity in falloff calculations. Our results are in very good agreement with the limited experimental data and show the importance of including pressure effects in the temperature interval where the mechanism changes from addition to abstraction. We found a negative temperature effect of the total reaction rate constants at 1 atm pressure in the temperature region where experimental data are missing and accurate theoretical data were previously missing as well. We also calculated the H + C 6 H 6 /C 6 D 6 and D + C 6 H 6 /C 6 D 6 kinetic isotope effects, and we compared our H + C 6 H 6 results to previous theoretical data for H + toluene. We report a very novel nonmonotonic dependence of the kinetic isotope effect on temperature. A particularly striking effect is the prediction of a negative temperature dependence of the total rate constant over 300-500 K wide temperature ranges, depending on the pressure but generally in the range from 600 to 1700 K, which includes the temperature range of ignition in gasoline engines, which is important because aromatics are important components of common fuels.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-15

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

  8. The Heat Resistance of Microbial Cells Represented by D Values Can be Estimated by the Transition Temperature and the Coefficient of Linear Expansion.

    Science.gov (United States)

    Nakanishi, Koichi; Kogure, Akinori; Deuchi, Keiji; Kuwana, Ritsuko; Takamatsu, Hiromu; Ito, Kiyoshi

    2015-01-01

    We previously developed a method for evaluating the heat resistance of microorganisms by measuring the transition temperature at which the coefficient of linear expansion of a cell changes. Here, we performed heat resistance measurements using a scanning probe microscope with a nano thermal analysis system. The microorganisms studied included six strains of the genus Bacillus or related genera, one strain each of the thermophilic obligate anaerobic bacterial genera Thermoanaerobacter and Moorella, two strains of heat-resistant mold, two strains of non-sporulating bacteria, and one strain of yeast. Both vegetative cells and spores were evaluated. The transition temperature at which the coefficient of linear expansion due to heating changed from a positive value to a negative value correlated strongly with the heat resistance of the microorganism as estimated from the D value. The microorganisms with greater heat resistance exhibited higher transition temperatures. There was also a strong negative correlation between the coefficient of linear expansion and heat resistance in bacteria and yeast, such that microorganisms with greater heat resistance showed lower coefficients of linear expansion. These findings suggest that our method could be useful for evaluating the heat resistance of microorganisms.

  9. Observation of reduced phase transition temperature in N-doped thermochromic film of monoclinic VO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Meinan; Xiong, Mo [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Li, Neng, E-mail: lineng@whut.edu.cn [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Liu, Baoshun; Wang, Shuo [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Ching, Wai-Yim [Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, MO 64110 (United States); Zhao, Xiujian, E-mail: opluse@whut.edu.cn [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China)

    2017-07-15

    Highlights: • N-doped VO{sub 2}(M1) thin films have been synthesized by annealing in NH{sub 3} atmosphere. • The phase purity, microstructure and optical property of VO{sub 2} thin film can be regulated by NH{sub 3} concentration. • First-principles calculations have been carried out to study the mechanism of N-doping on energy band structures of VO{sub 2}(M1). • The energy band gaps of VO{sub 2}(M1) are tuned by substitution N-doping or interstitial N-doping. - Abstract: Research on monoclinic (M1) phase of VO{sub 2} has attracted a great of interest for smart coating applications due to its exceptional thermochromic property. Herein, we report the results using a novel approach to synthesize N-doped VO{sub 2}(M1) thin films with high purity by heat treatment in NH{sub 3} atmosphere. The N dopant in the film can be regulated by varying NH{sub 3} concentration during the annealing process. We find that the N atoms are located at the interstitial sites or substitute oxygen atoms, and the V-N bonds in the VO{sub 2} thin films increase with NH{sub 3} concentration. The metal to insulator transition (MIT) temperature (τ{sub c,h}) of the VO{sub 2} thin film is effectively reduced from 80.0 to 62.9 °C, while the solar modulation efficiency (ΔT{sub sol}) and the modulation efficiency at 2000 nm (ΔT{sub 2000nm}) are 7.36% and 55.6% respectively. The band gap of N-doped VO{sub 2} thin films related to MIT (E{sub g1}) is estimated to be as low as 0.18–0.25 eV whereas the band gap associated with the visible transparency (E{sub g2}) is about 1.50–1.58 eV. Based on the highly accurate first-principles calculations, the E{sub g1} of VO{sub 2} (M1) is reduced after substituted or interstitial N-doping, while the E{sub g2} alters with the mode of N-doping, which is excellent agreement with experimental measurement.

  10. Local glass transition temperature Tg(z) of polystyrene next to different polymers: Hard vs. soft confinement

    Science.gov (United States)

    Baglay, Roman R.; Roth, Connie B.

    2017-05-01

    The depth to which the local glass transition temperature Tg and alpha-relaxations are perturbed near a boundary is believed to be related to the characteristic length scales associated with cooperative dynamics in dynamically heterogeneous glasses. Following our recent work [R. R. Baglay and C. R. Roth, J. Chem. Phys. 143, 111101 (2015)] that measured a very broad 350-400 nm local Tg(z) profile across a glassy-rubbery interface of polystyrene (PS)/poly(n-butyl methacrylate) (PnBMA), we compare here how the Tg(z) profile in PS varies when changing the neighboring polymer from a lower Tg material to a higher Tg material. Here we report local Tg(z) profiles for PS when in contact with polysulfone (PSF), poly(methyl methacrylate) (PMMA), and poly(isobutyl methacrylate) (PiBMA). We find that the distance from the interface before bulk Tg of PS (Tgbulk=101 °C) is recovered depends on whether PS forms the high-Tg glassy component experiencing so-called soft confinement, z ≈ 225-250 nm for PS next to PiBMA (Tgbulk=62°C) and PnBMA (Tgbulk=21 °C), or PS forms the low-Tg rubbery component experiencing hard confinement, z ≈ 100-125 nm for PS next to PSF (Tgbulk=186°C) and PMMA (Tgbulk=120 °C). The depth to which these Tg(z) perturbations persist and the magnitude of the local Tg perturbation at the interface are independent of the difference in Tgbulk between the two polymers, the interaction parameter, and the chemical structure. We demonstrate that these broad, extended Tg(z) length scales appear to be universal across these different systems but show that the strong dynamical coupling across the dissimilar polymer-polymer interface only occurs when this interface has been annealed to equilibrium. We consider why dissimilar polymer-polymer interfaces exhibit continuous local dynamics across the interface in contrast to polymer-free surface, polymer-substrate, or polymer-liquid interfaces that show discontinuous local dynamics.

  11. Long-Range Order and Critical Scattering of Neutrons below the Transition Temperature in β-Brass

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Dietrich, O.W.

    1967-01-01

    The temperature dependence of long-range order langPrang has been determined from the temperature variation of a superlattice Bragg reflection. The results fitted a power law langPrang prop (Tc-T)beta with Tc the critical temperature and beta = 0.305plusmn0.005, in agreement with the theoretical ...

  12. Elimination of bus voltage impact on temperature sensitive electrical parameter during turn-on transition for junction temperature estimation of high-power IGBT modules

    DEFF Research Database (Denmark)

    Luo, Haoze; Iannuzzo, Francesco; Blaabjerg, Frede

    2017-01-01

    Junction temperature is of great importance to safe operating area of IGBT modules. Various information of the IGBT operating state is reflected on electrical characteristics during turn-on transient. A unified extraction method for internal junction temperature via dynamic thermo-sensitive elect......Junction temperature is of great importance to safe operating area of IGBT modules. Various information of the IGBT operating state is reflected on electrical characteristics during turn-on transient. A unified extraction method for internal junction temperature via dynamic thermo......-sensitive electrical parameters (DTSEP) during turn-on transient is proposed. Two DTSEP, turn-on delay time (tdon) and the maximum increasing rate of collector current dic/dt(max), are combined to eliminate the bus voltage impact. Using the inherent emitter-auxiliary inductor LeE in high-power modules, the temperature...

  13. Composite hydrogels with temperature sensitive heterogeneities: influence of gel matrix on the volume phase transition of embedded poly-(N-isopropylacrylamide) microgels.

    Science.gov (United States)

    Meid, Judith; Friedrich, Tatjana; Tieke, Bernd; Lindner, Peter; Richtering, Walter

    2011-02-28

    The thermo-responsive behaviour of poly-(N-isopropylacrylamide) (PNiPAM) microgels embedded in covalently cross-linked non-temperature-sensitive polyacrylamide (PAam) hydrogel matrixes with different compositions was investigated by using small angle neutron scattering (SANS). The composition of the composite hydrogel was varied by (a) increasing the cross-linker and acrylamide concentration leading to strong hydrogel matrixes and (b) by increasing the microgel concentration to obtain composite gels with an internal structure. Additionally we synthesized composite hydrogels by using γ-irradiation as initiation for the polymerisation. This leads to the formation of chemical bonds between the PNiPAM microgels and the surrounding polyacrylamide matrix. Thus it is possible to synthesize hydrogels without an additional cross-linker, as well as pure particle networks. Some samples were prepared at two different temperatures, below and above the volume phase transition temperature of PNiPAM, resulting in highly swollen or totally collapsed microgels during the incorporation step. The volume phase transition of microgels is not influenced by a hydrogel matrix with high acrylamide concentration independent of the preparation temperature. However, an increased cross-linker concentration leads to a corset like constraint on microgel swelling. Microgels, which are embedded in the collapsed state (at 50 °C), are not able to swell upon cooling, whereas microgels embedded in the swollen state can collapse upon heating. For samples with an increased microgel concentration, the close microgel packing was disturbed by the formation of the polyacrylamide matrix. The hydrogel matrix squeezes the microgels together and leads to partial aggregation. The experiments demonstrate how composite hydrogels with stimuli-sensitive heterogeneities can be prepared such that the full responsiveness of the embedded microgels is retained while the macroscopic dimensions of the gel are not affected

  14. Investigation of the Influence of Sucrose and Cholesterol on the Phase Transition Temperature of nanoliposomal formulation besides using particle size Reduction Techniques (Ultrasonication/High Pressure Homogenization

    Directory of Open Access Journals (Sweden)

    Z Malaei-Balasi

    2017-05-01

    Full Text Available Introduction: The successful application of nanoliposoms as an effective drug delivery system depends on their stability in the medium. In this article, influence of additive materials such as cholesterol and sucrose besides two natural and synthesized phospholipids have been investigated. Methods: In the present study, designing and synthesis of nanoliposomal formulations were prepared using thin film method. This liposomal suspension was downsized by two methods, the high-pressure homogenizer and ultrasound to form small unilamellar vesicles. The size distributions, zeta potentials and phase transition temperature of formulations were all determined by a zetasizer and differential scanning calorimetry(DSC. In addition, the contribution of nanoliposomal formulation has been investigated by HPLC and FTIR methods. Results: Results of the DSC measurments indicated that incorporation of unsaturated phospholipid (SOY PC may cause phase separation with partial miscibility in the liposome bilayer containing of DPPG. The optimal nanoliposomal formulation was composed of (DPPC: CHOL: mPEG2000-DSPE with the mole percents equal to (83:15:2, respectively. In addition, sucrose has been used in the formulation with a total amounts six times greater than that of the lipids. The properties of optimized nanoliposome have been shown as the size average 104nm, zeta potential 8.04mv and phase transition temperature of lipid less than 37°C which were stable enough to be utilized for loading and releasing bioactives in body temperature. Conclusion: Finally the produced nanoliposomes were stable vesicles in the proper size, phase transition temperature and surface charge without any aggregation and fusion.

  15. Dielectric response to the low-temperature magnetic defect structure and spin state transition in polycrystalline LaCoO3

    Science.gov (United States)

    Schmidt, Rainer; Wu, J.; Leighton, C.; Terry, I.

    2009-03-01

    The dielectric and magnetic properties and their correlations were investigated in polycrystalline perovskite LaCoO3-δ . The intrinsic bulk and grain-boundary (GB) dielectric relaxation processes were deconvoluted using impedance spectroscopy between 20 and 120 K, and resistivity and capacitance were analyzed separately. A thermally induced magnetic transition from a Co3+ low-spin (LS) (S=0;t2g6eg0) to a higher spin state occurs at Ts1≈80K , which is controversial in nature and has been suggested to be an intermediate-spin (IS) state (S=1;t2g5eg1) or a high-spin (HS) state (S=2;t2g4eg2) transition. This spin state transition was confirmed by magnetic-susceptibility measurements and was reflected in the impedance by a split of the single GB relaxation process into two coexisting contributions. This apparent electronic phase coexistence at T>80K was interpreted as a reflection of the coexistence of magnetic LS and IS/HS states. At lower temperatures (T≤40K) perceptible variation in bulk dielectric permittivity with temperature appeared to be correlated with the magnetic susceptibility associated with a magnetic defect structure. At 40Kdefect-related magnetism.

  16. Origin of cooperative transition of antisite-Arsenic defects in Be-doped low-temperature-grown GaAs layers

    Science.gov (United States)

    Mohamed, Mohd Ambri; Lam, Pham Tien; Otsuka, N.

    2013-09-01

    We investigated the origin of the cooperative transition of AsGa atoms in Be-doped low-temperature-grown GaAs layers by magnetization measurements and first principle calculations. For first principle calculations, a large supercell was used to reproduce the average distance of AsGa atoms and Be atoms in experimental samples. With one AsGa atom and Be atom in each supercell and the periodic boundary condition, the calculated total energy of the AsGa at the substitutional site is lower than that at the interstitial site by 0.87 eV. The magnetization measurements have shown that the transition occurs in a sample with a GaAs substrate similar to that in lift-off samples, indicating that a uniform strain induced by the substrate does not affect the occurrence of the transition. These results suggest that the complex strain field induced by the coexistence of AsGa defects at substitution and interstitial site plays a major role in the cooperative transition.

  17. X-ray diffraction and Raman spectroscopy studies of temperature and composition induced phase transitions in Ba{sub 2-x}Sr{sub x}ZnWO{sub 6} (0 {<=} x {<=} 2) double perovskite oxides

    Energy Technology Data Exchange (ETDEWEB)

    Manoun, Bouchaib, E-mail: manounb@gmail.com [Equipe Materiaux et environnement, Laboratoire des Procedes de Valorisation des Ressources Naturelles, des Materiaux et Environnement, FST Settat, Universite Hassan 1er, (Morocco); Ezzahi, A. [Equipe Materiaux et environnement, Laboratoire des Procedes de Valorisation des Ressources Naturelles, des Materiaux et Environnement, FST Settat, Universite Hassan 1er, (Morocco); Benmokhtar, S. [LRCPGM, Laboratoire de Recherche de Chimie-Physique Generale des Materiaux, Department of Chemistry, Faculty of Sciences Ben M' Sik, Casablanca (Morocco); Ider, A. [Equipe Materiaux et environnement, Laboratoire des Procedes de Valorisation des Ressources Naturelles, des Materiaux et Environnement, FST Settat, Universite Hassan 1er, (Morocco); Lazor, P. [Department of Earth Sciences, Uppsala University, SE-752 36, Uppsala (Sweden); Bih, L. [Laboratoire de Physico-Chimie des Materiaux, Departement de Chimie, FST Errachidia (Morocco); Igartua, J.M. [Fisika Aplikatua II, Zientzia eta Teknologia Fak., UPV/EHU, PB 644, Bilbao 48080 (Spain)

    2012-08-25

    Highlights: Black-Right-Pointing-Pointer Synthesis and characterization of new double perovskites. Black-Right-Pointing-Pointer High temperature studies of double perovskite using Raman spectroscopy. Black-Right-Pointing-Pointer Temperature and compositions induced phase transitions in these materials. Black-Right-Pointing-Pointer Structural determination/refinement of these compounds as a function of composition. - Abstract: X-ray diffraction and Raman spectroscopy studies of Sr doped double perovskites compound Ba{sub 2-x}Sr{sub x}ZnWO{sub 6} with (0 {<=} x {<=} 2) were investigated. As a function of composition while increasing strontium amount, the samples show two phase transitions from cubic to tetragonal phase and from tetragonal to monoclinic structure. Both Rietveld refinements and Raman studies showed that the first phase transition occurs between x = 1 and 1.2; the second phase transition is observed around x = 2. Furthermore, increasing the temperature for the compositions (1.2 {<=} x < 2), manifests the tetragonal to cubic phase transition. For x = 2 two phase transitions were observed as a function of temperature. For this series, the phase transitions are illustrated by considerable changes in the composition and temperature dependence of the modes. All the Raman modes show a linear behavior when the composition or temperature is increased, then the slope change indicating the symmetry change.

  18. Benchmark Transiting Brown Dwarf LHS 6343 C: Spitzer Secondary Eclipse Observations Yield Brightness Temperature and Mid-T Spectral Class

    NARCIS (Netherlands)

    Montet, B.T.; Johnson, J.A.; Fortney, J.J.; Desert, J.-M.

    2016-01-01

    There are no field brown dwarf analogs with measured masses, radii, and luminosities, precluding our ability to connect the population of transiting brown dwarfs with measurable masses and radii and field brown dwarfs with measurable luminosities and atmospheric properties. LHS 6343 C, a weakly

  19. The Transition of High-Resolution NASA MODIS Sea Surface Temperatures into the WRF Environmental Modeling System

    Science.gov (United States)

    Case, Jonathan L.; Jedlove, Gary J.; Santos, Pablo; Medlin, Jeffrey M.; Rozumalski, Robert A.

    2009-01-01

    The NASA Short-term Prediction Research and Transition (SPoRT) Center has developed a Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) composite at 2-km resolution that has been implemented in version 3 of the National Weather Service (NWS) Weather Research and Forecasting (WRF) Environmental Modeling System (EMS). The WRF EMS is a complete, full physics numerical weather prediction package that incorporates dynamical cores from both the Advanced Research WRF (ARW) and the Non-hydrostatic Mesoscale Model (NMM). The installation, configuration, and execution of either the ARW or NMM models is greatly simplified by the WRF EMS to encourage its use by NWS Weather Forecast Offices (WFOs) and the university community. The WRF EMS is easy to run on most Linux workstations and clusters without the need for compilers. Version 3 of the WRF EMS contains the most recent public release of the WRF-NMM and ARW modeling system (version 3 of the ARW is described in Skamarock et al. 2008), the WRF Pre-processing System (WPS) utilities, and the WRF Post-Processing program. The system is developed and maintained by the NWS National Science Operations Officer Science and Training Resource Coordinator. To initialize the WRF EMS with high-resolution MODIS SSTs, SPoRT developed the composite product consisting of MODIS SSTs over oceans and large lakes with the NCEP Real-Time Global (RTG) filling data over land points. Filling the land points is required due to minor inconsistencies between the WRF land-sea mask and that used to generate the MODIS SST composites. This methodology ensures a continuous field that adequately initializes all appropriate arrays in WRF. MODIS composites covering the Gulf of Mexico, western Atlantic Ocean and the Caribbean are generated daily at 0400, 0700, 1600, and 1900 UTC corresponding to overpass times of the NASA Aqua and Terra polar orbiting satellites. The MODIS SST product is output in gridded binary-1 (GRIB-1) data

  20. Lowering of L1{sub 0} phase transition temperature of FePt thin films by single shot H{sup +} ion exposure using plasma focus device

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Z.Y.; Lin, J.J. [NSSE, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore); Zhang, T. [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Karamat, S.; Tan, T.L.; Lee, P.; Springham, S.V. [NSSE, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore); Ramanujan, R.V. [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Rawat, R.S. [NSSE, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore)], E-mail: rajdeep.rawat@nie.edu.sg

    2009-02-27

    FePt thin films are exposed to pulsed energetic H{sup +} ion beam from plasma focus. In irradiated films, the phase transition from the low K{sub u} disordered face-centered-cubic structure to high K{sub u} ordered face-centered-tetragonal phase was achieved at 400 deg. C with the order parameter S ranging from 0.73 to 0.83, high coercivity of about 5356 kA/m, high negative nucleation field of about 7700 kA/m and high squareness ratio ranging from 0.73 to 0.79. The advantage of using plasma focus device is that it can lower phase transition temperature and significantly enhance the magnetic properties by a pulsed single shot exposure.

  1. Controlled reactive HiPIMS—effective technique for low-temperature (300 °C) synthesis of VO2 films with semiconductor-to-metal transition

    Science.gov (United States)

    Vlček, J.; Kolenatý, D.; Houška, J.; Kozák, T.; Čerstvý, R.

    2017-09-01

    Reactive high-power impulse magnetron sputtering with a pulsed O2 flow control and to-substrate O2 injection into a high-density plasma in front of the sputtered vanadium target was used for low-temperature (300 °C) deposition of VO2 films with a pronounced semiconductor-to-metal transition onto conventional soda-lime glass substrates without any substrate bias voltage and without any interlayer. The depositions were performed using an unbalanced magnetron with a planar target of 50.8 mm diameter in argon-oxygen gas mixtures at the argon pressure of 1 Pa. The deposition-averaged target power density was close to 13 W cm-2 at a fixed duty cycle of 1% with a peak target power density up to 5 kW cm-2 during voltage pulses ranged from 40 µs to 100 µs. A high modulation of the transmittance at 2500 nm (between 51% and 8% at the film thickness of 88 nm) and the electrical resistivity (changed 350 times) at the transition temperature of 56-57 °C was achieved for the VO2 films synthesized using 50 µs voltage pulses when the crystallization of the thermochromic VO2(M1) phase was supported by the high-energy (up to 50 eV relative to ground potential) ions. Principles of this effective low-temperature deposition technique with a high application potential are presented.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-04-21

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

  3. Moisture sorption isotherms and glass transition temperature of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) roots at 25°C.

    Science.gov (United States)

    Cervenka, L; Kubínová, J; Juszczak, L; Witczak, M

    2012-02-01

    Sorption isotherms of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) root samples were obtained at 25 °C. Elecampe exhibited hysteresis loop in the range of 0.35-0.90 a(w) , whereas burdock roots showed significant differences between adsorption and desorption isotherms from 0.65 to 0.80 a(w) . Blahovec-Yanniotis was considered to give the best fit over the whole range of a(w) tested. Various parameters describing the properties of sorbed water derived from GAB, Henderson and Blahovec-Yanniotis models have been discussed. Differential scanning calorimetric method was used to measure the glass transition temperature (T (g)) of root samples in relation to water activity. The safe moisture content was determined in 12.01 and 14.96 g/100 g d. b. for burdock and elecampe root samples at 25 °C, respectively. Combining the T (g) line with sorption isotherm in one plot, it was found that the glass transition temperature concept overestimated the temperature stability for both root samples.

  4. Morin transition temperature in (0001)-oriented α-Fe{sub 2}O{sub 3} thin film and effect of Ir doping

    Energy Technology Data Exchange (ETDEWEB)

    Shimomura, Naoki, E-mail: shimomura@ecei.tohoku.ac.jp; Pati, Satya Prakash; Sato, Yuji; Nozaki, Tomohiro; Sahashi, Masashi [Department of Electronic Engineering, Graduate School of Electronic Engineering, Tohoku University, Sendai 980-8579 (Japan); Shibata, Tatsuo [Advanced Technology Development Center, TDK Corporation, Ichikawa 272-0026 (Japan); Mibu, Ko [Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

    2015-05-07

    The structural properties and Morin transition in c-plane-oriented α-Fe{sub 2}O{sub 3} and Ir-doped α-Fe{sub 2}O{sub 3} thin films have been investigated. The enhancement of the Morin transition temperature (T{sub M}) in α-Fe{sub 2}O{sub 3} film by Ir doping has been demonstrated. The T{sub M} in the c-plane-oriented α-Fe{sub 2}O{sub 3} thin film was determined from the temperature-dependent in-plane magnetization and change of coercivity (H{sub c}); this T{sub M} value was found close to that of bulk α-Fe{sub 2}O{sub 3}. The spin directions of non-doped and Ir-doped α-Fe{sub 2}O{sub 3} at room temperature were also estimated from conversion electron Mössbauer spectroscopy measurements. We confirmed that Ir doping dramatically enhances the T{sub M} of α-Fe{sub 2}O{sub 3} thin film.

  5. Numerical analysis of ion temperature effects to the plasma wall transition using a one-dimensional two-fluid model. I. Finite Debye to ionization length ratio.

    Science.gov (United States)

    Gyergyek, T; Kovačič, J

    2017-06-01

    A one-dimensional, two-fluid, steady state model is used for the analysis of ion temperature effects to the plasma-wall transition. In this paper, the model is solved for a finite ratio ε between the Debye and the ionization length, while in Part II [T. Gyergyek and J. Kovačič, Phys Plasmas 24, 063506 (2017)], the solutions for [Formula: see text] are presented. Ion temperature is treated as a given, independent parameter and it is included in the model as a boundary condition. It is shown that when the ion temperature larger than zero is selected, the ion flow velocity and the electric field at the boundary must be consistent with the selected ion temperature. A numerical procedure, how to determine such "consistent boundary conditions," is proposed, and a simple relation between the ion temperature and ion velocity at the boundary of the system is found. The effects of the ion temperature to the pre-sheath length, potential, ion temperature, and ion density drops in the pre-sheath and in the sheath are investigated. It is concluded that larger ion temperature results in a better shielding of the plasma from the wall. An attempt is made to include the ion heat flux q i into the model in its simplest form [Formula: see text], where [Formula: see text] is a constant heat conduction coefficient. It is shown that inclusion of such a term into the energy transfer equation introduces an additional ion heating mechanism into the system and the ion flow then becomes isothermal instead of adiabatic even in the sheath.

  6. Solid-state stability of spray-dried insulin powder for inhalation: chemical kinetics and structural relaxation modeling of Exubera above and below the glass transition temperature.

    Science.gov (United States)

    Sadrzadeh, Negar; Miller, Danforth P; Lechuga-Ballesteros, David; Harper, Nancy J; Stevenson, Cynthia L; Bennett, David B

    2010-09-01

    The effect of temperature on the chemical stability of an amorphous spray-dried insulin powder formulation (Exubera) was evaluated in the solid state at constant moisture content. The chemical stability of the powder was assessed using reversed-phase high-performance liquid chromatography (RP-HPLC) and high-performance-size exclusion chromatography (HP-SEC). The major degradants in spray-dried insulin produced during heat stressing were identified as A21-desamidoinsulin (A21) and high molecular weight protein (HMWP). As expected, the rates of formation of A21 and HMWP were observed to increase with temperature. A stretched-time kinetic model (degradation rate is proportional to the square root of time) was applied to the degradant profiles above and below the glass transition temperature (T(g)) and apparent reaction rate constants were determined. Below T(g), isothermal enthalpy of relaxation measurements were used to assess the effect of temperature on molecular mobility. The formation of A21 and HMWP was found to follow an Arrhenius temperature dependence above and below the T(g). Comparison of reaction rate constants to those estimated from structural relaxation experiments suggests that the reaction pathways to form A21 and HMWP below the T(g) may be coupled with the molecular motions involved in structural relaxation.

  7. Influence of the spin quantum number $s$ on the zero-temperature phase transition in the square lattice $J$-$J'$ model

    OpenAIRE

    Darradi, R.; Richter, J.; Farnell, D. J. J.

    2004-01-01

    We investigate the phase diagram of the Heisenberg antiferromagnet on the square lattice with two different nearest-neighbor bonds $J$ and $J'$ ($J$-$J'$ model) at zero temperature. The model exhibits a quantum phase transition at a critical value $J'_c > J$ between a semi-classically ordered N\\'eel and a magnetically disordered quantum paramagnetic phase of valence-bond type, which is driven by local singlet formation on $J'$ bonds. We study the influence of spin quantum number $s$ on this p...

  8. Transition temperatures and irreversibility-field properties of (Cu1-xCx)Sr2CaCu2O7-δ superconductors with precisely controlled oxygen contents

    Science.gov (United States)

    Shibaoka, Shunki; Aoba, Tomoya; Suzuki, Tsuneo; Nakayama, Tadachika; Suematsu, Hisayuki; Niihara, Koichi

    2014-02-01

    (Cu1-xCx)Sr2CaCu2O7-δ samples with precisely controlled oxygen contents (δ = 0.10-0.35) were successfully synthesized under a pressure of 5.5 GPa and followed by annealing in He gas at various temperatures. The oxygen content of an as-synthesized sample was determined by iodometric titration, and the changes of the oxygen content were estimated by measuring weight-loss during the post-annealing. Superconducting transition temperatures (Tc) decreased from 93.1 to 83.1 K with decreasing the oxygen content from 6.90 to 6.65. Hole-doping level was tuned to be underdoped so that the slope of the irreversibility field (Hirr) increased.

  9. Configurational temperature and local properties of the anisotropic Gay-Berne liquid crystal model: applications to the isotropic liquid/vapor interface and isotropic/nematic transition.

    Science.gov (United States)

    Ghoufi, Aziz; Morineau, Denis; Lefort, Ronan; Malfreyt, Patrice

    2011-01-21

    Molecular simulations in the isothermal statistical ensembles require that the macroscopic thermal and mechanical equilibriums are respected and that the local values of these properties are constant at every point in the system. The thermal equilibrium in Monte Carlo simulations can be checked through the calculation of the configurational temperature, k(B)T(conf)=/, where ∇(r) is the nabla operator of position vector r. As far as we know, T(conf) was never calculated with the anisotropic Gay-Berne potential, whereas the calculation of T(conf) is much more widespread with more common potentials (Lennard Jones, electrostatic, ...). We establish here an operational expression of the macroscopic and local configurational temperatures, and we investigate locally the isotropic liquid phase, the liquid / vapor interface, and the isotropic-nematic transition by Monte Carlo simulations.

  10. Stomach temperature records reveal nursing behaviour and transition to solid food consumption in an unweaned mammal, the harbour seal pup (Phoca vitulina).

    Science.gov (United States)

    Sauvé, Caroline C; Van de Walle, Joanie; Hammill, Mike O; Arnould, John P Y; Beauplet, Gwénaël

    2014-01-01

    Knowledge of milk transfer from mother to offspring and early solid food ingestions in mammals allows for a greater understanding of the factors affecting transition to nutritional independence and pre-weaning growth and survival. Yet studies monitoring suckling behaviour have often relied on visual observations, which might not accurately represent milk intake. We assessed the use of stomach temperature telemetry to monitor suckling and foraging behaviour in free-ranging harbour seal (Phoca vitulina) pups during lactation. Stomach temperature declines were analysed using principal component and cluster analyses, as well as trials using simulated stomachs resulting in a precise classification of stomach temperature drops into milk, seawater and solid food ingestions. Seawater and solid food ingestions represented on average 15.3±1.6% [0-40.0%] and 0.7±0.2% [0-13.0%], respectively, of individual ingestions. Overall, 63.7% of milk ingestions occurred while the pups were in the water, of which 13.9% were preceded by seawater ingestion. The average time between subsequent ingestions was significantly less for seawater than for milk ingestions. These results suggest that seawater ingestion might represent collateral ingestion during aquatic suckling attempts. Alternatively, as solid food ingestions (n = 19) were observed among 7 pups, seawater ingestion could result from missed prey capture attempts. This study shows that some harbour seals start ingesting prey while still being nursed, indicating that weaning occurs more gradually than previously thought in this species. Stomach temperature telemetry represents a promising method to study suckling behaviour in wild mammals and transition to nutritional independence in various endotherm species.

  11. Stomach Temperature Records Reveal Nursing Behaviour and Transition to Solid Food Consumption in an Unweaned Mammal, the Harbour Seal Pup (Phoca vitulina)

    Science.gov (United States)

    Sauvé, Caroline C.; Van de Walle, Joanie; Hammill, Mike O.; Arnould, John P. Y.; Beauplet, Gwénaël

    2014-01-01

    Knowledge of milk transfer from mother to offspring and early solid food ingestions in mammals allows for a greater understanding of the factors affecting transition to nutritional independence and pre-weaning growth and survival. Yet studies monitoring suckling behaviour have often relied on visual observations, which might not accurately represent milk intake. We assessed the use of stomach temperature telemetry to monitor suckling and foraging behaviour in free-ranging harbour seal (Phoca vitulina) pups during lactation. Stomach temperature declines were analysed using principal component and cluster analyses, as well as trials using simulated stomachs resulting in a precise classification of stomach temperature drops into milk, seawater and solid food ingestions. Seawater and solid food ingestions represented on average 15.3±1.6% [0–40.0%] and 0.7±0.2% [0–13.0%], respectively, of individual ingestions. Overall, 63.7% of milk ingestions occurred while the pups were in the water, of which 13.9% were preceded by seawater ingestion. The average time between subsequent ingestions was significantly less for seawater than for milk ingestions. These results suggest that seawater ingestion might represent collateral ingestion during aquatic suckling attempts. Alternatively, as solid food ingestions (n = 19) were observed among 7 pups, seawater ingestion could result from missed prey capture attempts. This study shows that some harbour seals start ingesting prey while still being nursed, indicating that weaning occurs more gradually than previously thought in this species. Stomach temperature telemetry represents a promising method to study suckling behaviour in wild mammals and transition to nutritional independence in various endotherm species. PMID:24587327

  12. Stomach temperature records reveal nursing behaviour and transition to solid food consumption in an unweaned mammal, the harbour seal pup (Phoca vitulina.

    Directory of Open Access Journals (Sweden)

    Caroline C Sauvé

    Full Text Available Knowledge of milk transfer from mother to offspring and early solid food ingestions in mammals allows for a greater understanding of the factors affecting transition to nutritional independence and pre-weaning growth and survival. Yet studies monitoring suckling behaviour have often relied on visual observations, which might not accurately represent milk intake. We assessed the use of stomach temperature telemetry to monitor suckling and foraging behaviour in free-ranging harbour seal (Phoca vitulina pups during lactation. Stomach temperature declines were analysed using principal component and cluster analyses, as well as trials using simulated stomachs resulting in a precise classification of stomach temperature drops into milk, seawater and solid food ingestions. Seawater and solid food ingestions represented on average 15.3±1.6% [0-40.0%] and 0.7±0.2% [0-13.0%], respectively, of individual ingestions. Overall, 63.7% of milk ingestions occurred while the pups were in the water, of which 13.9% were preceded by seawater ingestion. The average time between subsequent ingestions was significantly less for seawater than for milk ingestions. These results suggest that seawater ingestion might represent collateral ingestion during aquatic suckling attempts. Alternatively, as solid food ingestions (n = 19 were observed among 7 pups, seawater ingestion could result from missed prey capture attempts. This study shows that some harbour seals start ingesting prey while still being nursed, indicating that weaning occurs more gradually than previously thought in this species. Stomach temperature telemetry represents a promising method to study suckling behaviour in wild mammals and transition to nutritional independence in various endotherm species.

  13. Percolation Phase Transition of Surface Air Temperature Networks: A new test bed for El Niño/La Niña simulations.

    Science.gov (United States)

    Hua, Lijuan; Lu, Zhenghui; Yuan, Naiming; Chen, Lin; Yu, Yongqiang; Wang, Lu

    2017-08-16

    In this work, we studied the air-sea interaction over the tropical central eastern Pacific from a new perspective, climate network. The surface air temperatures over the tropical Pacific were constructed as a network, and the nodes within this network were linked if they have a similar temporal varying pattern. Using three different reanalysis datasets, we verified the percolation phase transition. That is, when the influences of El Niño/La Niña are strong enough to isolate more than 48% of the nodes, the network may abruptly be divided into many small pieces, indicating a change of the network state. This phenomenon was reproduced successfully by a coupled general circulation model, Flexible Global Ocean-Atmosphere-Land System Model Spectral Version 2, but another model, Flexible Global Ocean-Atmosphere-Land System Model Grid-point Version 2, failed. As both models have the same oceanic component, but are with different atmospheric components, the improperly used atmospheric component should be responsible for the missing of the percolation phase transition. Considering that this new phenomenon is only recently noticed, current state-of-the-art models may ignore this process and induce unrealistic simulations. Accordingly, percolation phase transition is proposed as a new test bed, which deserves more attention in the future.

  14. Silicon nanocrystals at elevated temperatures: retention of photoluminescence and diamond silicon to β-silicon carbide phase transition.

    Science.gov (United States)

    Rowland, Clare E; Hannah, Daniel C; Demortière, Arnaud; Yang, Jihua; Cook, Russell E; Prakapenka, Vitali B; Kortshagen, Uwe; Schaller, Richard D

    2014-09-23

    We report the photoluminescence (PL) properties of colloidal Si nanocrystals (NCs) up to 800 K and observe PL retention on par with core/shell structures of other compositions. These alkane-terminated Si NCs even emit at temperatures well above previously reported melting points for oxide-embedded particles. Using selected area electron diffraction (SAED), powder X-ray diffraction (XRD), liquid drop theory, and molecular dynamics (MD) simulations, we show that melting does not play a role at the temperatures explored experimentally in PL, and we observe a phase change to β-SiC in the presence of an electron beam. Loss of diffraction peaks (melting) with recovery of diamond-phase silicon upon cooling is observed under inert atmosphere by XRD. We further show that surface passivation by covalently bound ligands endures the experimental temperatures. These findings point to covalently bound organic ligands as a route to the development of NCs for use in high temperature applications, including concentrated solar cells and electrical lighting.

  15. The Insulator to Superconductor Transition in Ga-Doped Semiconductor Ge Single Crystal Induced by the Annealing Temperature

    Directory of Open Access Journals (Sweden)

    Y. B. Sun

    2015-01-01

    Full Text Available We have fabricated the heavily Ga-doped layer in Ge single crystal by the implantation and rapid thermal annealing method. The samples show a crossover from the insulating to the superconducting behavior as the annealing temperature increases. Transport measurements suggest that the superconductivity is from the heavily Ga-doped layer in Ge.

  16. The role of electrostatics and temperature on morphological transitions of hydrogel nanostructures self-assembled by peptide amphiphiles via molecular dynamics simulations.

    Science.gov (United States)

    Fu, Iris W; Markegard, Cade B; Chu, Brian K; Nguyen, Hung D

    2013-10-01

    Smart biomaterials that are self-assembled from peptide amphiphiles (PA) are known to undergo morphological transitions in response to specific physiological stimuli. The design of such customizable hydrogels is of significant interest due to their potential applications in tissue engineering, biomedical imaging, and drug delivery. Using a novel coarse-grained peptide/polymer model, which has been validated by comparison of equilibrium conformations from atomistic simulations, large-scale molecular dynamics simulations are performed to examine the spontaneous self-assembly process. Starting from initial random configurations, these simulations result in the formation of nanostructures of various sizes and shapes as a function of the electrostatics and temperature. At optimal conditions, the self-assembly mechanism for the formation of cylindrical nanofibers is deciphered involving a series of steps: (1) PA molecules quickly undergo micellization whose driving force is the hydrophobic interactions between alkyl tails; (2) neighboring peptide residues within a micelle engage in a slow ordering process that leads to the formation of β-sheets exposing the hydrophobic core; (3) spherical micelles merge together through an end-to-end mechanism to form cylindrical nanofibers that exhibit high structural fidelity to the proposed structure based on experimental data. As the temperature and electrostatics vary, PA molecules undergo alternative kinetic mechanisms, resulting in the formation of a wide spectrum of nanostructures. A phase diagram in the electrostatics-temperature plane is constructed delineating regions of morphological transitions in response to external stimuli. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Low temperature vibrational spectroscopy. II. Evidence for order–disorder phase transitions due to weak C–H···Cl hydrogen bonding in tetramethylammonium hexachloroplatinate (IV), -tellurate (IV), and -stannate (IV) and the related perdeuterated compounds

    DEFF Research Database (Denmark)

    Berg, Rolf W.

    1978-01-01

    and it is suggested that the phase transitions are caused by an ordering of rotationally disordered methyl groups via the formation of weak C–H···Cl hydrogen bonds at low temperatures. The transition temperatures and hence the interactions are shown to depend on both the kind of hydrogen isotope and metal present...... torsions and other noncubic features play a role, especially in spectra at low temperatures. Possible site symmetries of the [PtCl6]2− ion, which cannot have strictly Oh symmetry in either phase, have been deduced. The spectra of a mixed Pt : Te compound showed that the hexachlorometallate anions vibrate...

  18. Probing the Mobility of Supercooled Liquid 3-Methylpentane at Temperatures Near the Glass Transition Using Rare Gas Permeation

    Energy Technology Data Exchange (ETDEWEB)

    Matthiesen, Jesper; Smith, R. Scott; Kay, Bruce D.

    2012-08-14

    We study the diffusivity of three-methyl pentane (3MP) using the permeation of inert gases (Ar,Kr, Xe) through the supercooled created when initially amorphous overlayers are heated above Tg. We find that the permeation rates for all of the gases have non-Arrhenius temperature dependences that are well described by the Vogel-Fulcher-Tamman equation. Comparison with the literature viscosity shows that the Stokes-Einstein equation breaks down at temperatures approaching Tg. The fractional Stokes-Einstein, D ∝ (T/η)n, does fit the permeation data, albeit with different values of n for each gas. There is qualitative agreement with the Stokes-Einstein equation in that the permeation rate decreases with increasing radius of the gas probe, but the differences in radii are not quantitatively proportional to the differences in the permeation rates. Instead the permeation rates are better correlated with the gas-3MP interaction energy than with the gas radius.

  19. Low-temperature phase transition in γ-glycine single crystal. Pyroelectric, piezoelectric, dielectric and elastic properties

    Energy Technology Data Exchange (ETDEWEB)

    Tylczyński, Zbigniew, E-mail: zbigtyl@amu.edu.pl [Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Busz, Piotr [Institute of Molecular Physics, Polish Academy of Science, Smoluchowskiego 17, 60-179 Poznań (Poland)

    2016-11-01

    Temperature changes in the pyroelectric, piezoelectric, elastic and dielectric properties of γ-glycine crystals were studied in the range 100 ÷ 385 K. The pyroelectric coefficient increases monotonically in this temperature range and its value at RT was compared with that of other crystals having glycine molecules. A big maximum in the d14 component of piezoelectric tensor compared by maximum in attenuation of the resonant face-shear mode were observed at 189 K. The components of the elastic stiffness tensor and other components of the piezoelectric tensor show anomalies at this temperature. The components of electromechanical coupling coefficient determined indicate that γ-glycine is a weak piezoelectric. The real and imaginary part of the dielectric constant measured in the direction perpendicular to the trigonal axis show the relaxation anomalies much before 198 K and the activation energies were calculated. These anomalies were interpreted as a result of changes in the NH{sub 3}{sup +} vibrations through electron-phonon coupling of the so called “dynamical transition”. The anomalies of dielectric constant ε*{sub 11} and piezoelectric tensor component d{sub 14} taking place at 335 K are associated with an increase in ac conductivity caused by charge transfer of protons. - Graphical abstract: Imaginary part of dielectric constant in [100] direction. - Highlights: • Piezoelectric, elastic and dielectric constants anomalies were discovered at 189 K. • These anomalies were interpreted as a result of so called “dynamical transition”. • Relaxational dielectric anomaly was explained by the dynamics of glycine molecules. • Pyroelectric coefficient of γ-glycine was determined in a wide temperature range. • Complex dielectric & piezoelectric anomalies at 335 K were caused by protons hopping.

  20. Sequential transition of the injury phenotype, temperature-dependent survival and transcriptional response in Listeria monocytogenes following lethal H2O2 exposure.

    Science.gov (United States)

    Ochiai, Yoshitsugu; Yamada, Fumiya; Yoshikawa, Yuko; Mochizuki, Mariko; Takano, Takashi; Hondo, Ryo; Ueda, Fukiko

    2017-10-16

    The food-borne pathogen Listeria monocytogenes is present persistently in food processing environments, where this bacterium is exposed to various stress factors, including oxidative stress. This study aimed to elucidate the temperature-dependent response of L. monocytogenes to H2O2 exposure and the phenotypic changes in colony formation by H2O2-treated bacteria. Survival curves indicated an increase in the resistance to H2O2 in L. monocytogenes as the temperature decreased during the stress exposure procedure. Transcriptional induction of genes with key roles in response to H2O2, including sigB and kat, was observed at 37°C, but not at 20°C, whereas other stress response genes were induced at both temperatures. Following H2O2 exposure, L. monocytogenes produced small colony phenotypes and the colony size decreased in a stress exposure duration-dependent manner. Resuscitated cells with no ability to form colonies in the absence of sodium pyruvate were also found. Our findings show the possibility that a sequential transition in the injury phenotype from small colony phenotype to resuscitated cells occurred during the course of exposure to H2O2. The higher H2O2 resistance at 20°C than 37°C suggests further investigation of the response to H2O2 exposure under the lower temperatures, including refrigeration temperature, which may contribute to elucidation of bacterial survival over extended time periods in food-processing environments. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. 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.

  2. Effect of junction temperature on the large-signal properties of a 94 GHz silicon based double-drift region impact avalanche transit time device

    Science.gov (United States)

    Acharyya, Aritra; Banerjee, Suranjana; Banerjee, J. P.

    2013-02-01

    The authors have developed a large-signal simulation technique extending an in-house small-signal simulation code for analyzing a 94 GHz double-drift region impact avalanche transit time device based on silicon with a non-sinusoidal voltage excitation and studied the effect of junction temperature between 300 and 550 K on the large-signal characteristics of the device for both continuous wave (CW) and pulsed modes of operation. Results show that the large-signal RF power output of the device in both CW and pulsed modes increases with the increase of voltage modulation factor up to 60%, but decreases sharply with further increase of voltage modulation factor for a particular junction temperature; while the same parameter increases with the increase of junction temperature for a particular voltage modulation factor. Heat sinks made of copper and type-IIA diamond are designed to carry out the steady-state and transient thermal analysis of the device operating in CW and pulsed modes respectively. Authors have adopted Olson's method to carry out the transient analysis of the device, which clearly establishes the superiority of type-IIA diamond over copper as the heat sink material of the device from the standpoint of the undesirable effect of frequency chirping due to thermal transients in the pulsed mode.

  3. Detecting phase transitions in a CaCl2-H2O system at low temperatures using a fiber-optic Fresnel reflection sensor.

    Science.gov (United States)

    Priyadarshini, Mani; Machavaram, Venkata Rajanikanth; Sivaramakrishna, Akella; Arulmozhivarman, Pachiyappan

    2017-04-10

    Temperature-induced crystallization events in an aqueous calcium chloride solution in the concentration range of 15-40 mass% are monitored using an optical fiber Fresnel reflection sensor in the temperature range of 30°C to -200°C. The deviation of the phase boundary from equilibrium and the formation of an eutectic mixture followed by its densification during rapid cooling are inferred from the distinct signatures of the optical fiber sensor via the changes in refractive index. During the natural heating at laboratory ambient conditions, the optical signals impart the completion of dissolution of ice and CaCl2·6H2O. The corresponding temperatures have been used in Linke's equations to obtain the salinities, which are in good agreement with the intended solution concentrations. The sensor signal imparts simultaneous melting of the constituents of the eutectic mixture of a 29.7 mass% solution during the natural heating phase. The persistence of the metastable liquid phase at -200°C for tens of minutes followed by solidification is observed at all the concentrations studied. Finally, the feasibility of monitoring phase transitions in a NaCl-CaCl2-H2O system has been demonstrated.

  4. Relationship Between Unusual High-Temperature Fatigue Crack Growth Threshold Behavior in Superalloys and Sudden Failure Mode Transitions

    Science.gov (United States)

    Telesman, Jack; Smith, Timothy M.; Gabb, Timothy P.; Ring, Andrew J.

    2017-01-01

    An investigation of high temperature cyclic fatigue crack growth (FCG) threshold behavior of two advanced nickel disk alloys was conducted. The focus of the study was the unusual crossover effect in the near-threshold region of these type of alloys where conditions which produce higher crack growth rates in the Paris regime, produce higher resistance to crack growth in the near threshold regime. It was shown that this crossover effect is associated with a sudden change in the fatigue failure mode from a predominant transgranular mode in the Paris regime to fully intergranular mode in the threshold fatigue crack growth region. This type of a sudden change in the fracture mechanisms has not been previously reported and is surprising considering that intergranular failure is typically associated with faster crack growth rates and not the slow FCG rates of the near-threshold regime. By characterizing this behavior as a function of test temperature, environment and cyclic frequency, it was determined that both the crossover effect and the onset of intergranular failure are caused by environmentally driven mechanisms which have not as yet been fully identified. A plausible explanation for the observed behavior is proposed.

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

    Directory of Open Access Journals (Sweden)

    Wenhui He

    2014-07-01

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

  6. Transcriptional Regulations on the Low-Temperature-Induced Floral Transition in an Orchidaceae Species, Dendrobium nobile: An Expressed Sequence Tags Analysis.

    Science.gov (United States)

    Liang, Shan; Ye, Qing-Sheng; Li, Rui-Hong; Leng, Jia-Yi; Li, Mei-Ru; Wang, Xiao-Jing; Li, Hong-Qing

    2012-01-01

    Vernalization-induced flowering is a cold-relevant adaptation in many species, but little is known about the genetic basis behind in Orchidaceae species. Here, we reported a collection of 15017 expressed sequence tags (ESTs) from the vernalized axillary buds of an Orchidaceae species, Dendrobium nobile, which were assembled for 9616 unique gene clusters. Functional enrichment analysis showed that genes in relation to the responses to stresses, especially in the form of low temperatures, and those involving in protein biosynthesis and chromatin assembly were significantly overrepresented during 40 days of vernalization. Additionally, a total of 59 putative flowering-relevant genes were recognized, including those homologous to known key players in vernalization pathways in temperate cereals or Arabidopsis, such as cereal VRN1, FT/VRN3, and Arabidopsis AGL19. Results from this study suggest that the networks regulating vernalization-induced floral transition are conserved, but just in a part, in D. nobile, temperate cereals, and Arabidopsis.

  7. Transcriptional Regulations on the Low-Temperature-Induced Floral Transition in an Orchidaceae Species, Dendrobium nobile: An Expressed Sequence Tags Analysis

    Directory of Open Access Journals (Sweden)

    Shan Liang

    2012-01-01

    Full Text Available Vernalization-induced flowering is a cold-relevant adaptation in many species, but little is known about the genetic basis behind in Orchidaceae species. Here, we reported a collection of 15017 expressed sequence tags (ESTs from the vernalized axillary buds of an Orchidaceae species, Dendrobium nobile, which were assembled for 9616 unique gene clusters. Functional enrichment analysis showed that genes in relation to the responses to stresses, especially in the form of low temperatures, and those involving in protein biosynthesis and chromatin assembly were significantly overrepresented during 40 days of vernalization. Additionally, a total of 59 putative flowering-relevant genes were recognized, including those homologous to known key players in vernalization pathways in temperate cereals or Arabidopsis, such as cereal VRN1, FT/VRN3, and Arabidopsis AGL19. Results from this study suggest that the networks regulating vernalization-induced floral transition are conserved, but just in a part, in D. nobile, temperate cereals, and Arabidopsis.

  8. Quantum phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Sachdev, S. [Yale University, New Haven, CT (United States)

    1999-04-01

    Phase transitions are normally associated with changes of temperature but a new type of transition - caused by quantum fluctuations near absolute zero - is possible, and can tell us more about the properties of a wide range of systems in condensed-matter physics. Nature abounds with phase transitions. The boiling and freezing of water are everyday examples of phase transitions, as are more exotic processes such as superconductivity and superfluidity. The universe itself is thought to have passed through several phase transitions as the high-temperature plasma formed by the big bang cooled to form the world as we know it today. Phase transitions are traditionally classified as first or second order. In first-order transitions the two phases co-exist at the transition temperature - e.g. ice and water at 0 deg., or water and steam at 100 deg. In second-order transitions the two phases do not co-exist. In the last decade, attention has focused on phase transitions that are qualitatively different from the examples noted above: these are quantum phase transitions and they occur only at the absolute zero of temperature. The transition takes place atthe ''quantum critical'' value of some other parameter such as pressure, composition or magnetic field strength. A quantum phase transition takes place when co-operative ordering of the system disappears, but this loss of order is driven solely by the quantum fluctuations demanded by Heisenberg's uncertainty principle. The physical properties of these quantum fluctuations are quite distinct from those of the thermal fluctuations responsible for traditional, finite-temperature phase transitions. In particular, the quantum system is described by a complex-valued wavefunction, and the dynamics of its phase near the quantum critical point requires novel theories that have no analogue in the traditional framework of phase transitions. In this article the author describes the history of quantum phase

  9. Cooling Mediterranean Sea surface temperatures during the Late Miocene provide a climate context for evolutionary transitions in Africa and Eurasia

    Science.gov (United States)

    Tzanova, Alexandrina; Herbert, Timothy D.; Peterson, Laura

    2015-06-01

    In the Late Miocene, grasslands proliferated, succulent plants diversified in the mid-latitudes, and the desert-like conditions appeared in the Sahara. Despite this major environmental change on land, the coeval deep-sea oxygen isotope record does not provide evidence for significant high latitude cooling or continental ice growth, making it difficult to relate widespread terrestrial environmental change to global climatic changes. A U37K‧ -derived sea surface temperature (SST) reconstruction spanning 13 to 6 Ma from uplifted hemipelagic sediments in Northern Italy provides the first continuous mid-latitude temperature record with which to compare the evolution of aridity and biotic events at similar latitudes in Northern Africa and Pakistan. Between 13 and 8.8 Ma, Mediterranean SST lay near the upper limit of the alkenone temperature proxy (∼28 °C), exceeding modern SST at the site by as much as 10 °C. Throughout the record, sapropel layers correspond to local SST maxima, suggesting that Late Miocene hydrological conditions in the Mediterranean responded to insolation forcing via mechanisms similar to those documented for the Plio-Pleistocene. Mediterranean SST cooled rapidly beginning at ∼8 Ma, with an episode of intense cooling to ∼19 °C between 7.2 Ma and 6.6 Ma, followed by a rebound to ∼25 °C preceding the Messinian Salinity Crisis at 5.9 Ma. These observations establish, for the first time, a direct relationship between increasing aridity in the Northern hemisphere mid-latitudes and significant cooling. Evidently, this cooling was not accompanied by significant growth in continental ice volume. The extreme warmth and subsequent cooling of the Mediterranean Sea are not well-represented in current Late Miocene climate models, which our results suggest underestimate regional warmth prior to the Late Miocene cooling. Evidence of secular cooling during the Late Miocene gives new support to the much-debated link between a possible decline in

  10. Giant Volume Change and Topological Gaps in Temperature- and Pressure-Induced Phase Transitions: Experimental and Computational Study of ThMo2 O8.

    Science.gov (United States)

    Xiao, Bin; Kegler, Philip; Gesing, Thorsten M; Robben, Lars; Blanca-Romero, Ariadna; Kowalski, Piotr M; Li, Yan; Klepov, Vladislav; Bosbach, Dirk; Alekseev, Evgeny V

    2016-01-18

    By applying high temperature (1270 K) and high pressure (3.5 GPa), significant changes occur in the structural volume and crystal topology of ThMo2 O8 , allowing the formation of an unexpected new ThMo2 O8 polymorph (high-temperature/high-pressure (HT/HP) orthorhombic ThMo2 O8 ). Compared with the other three ThMo2 O8 polymorphs prepared at the ambient pressure (monoclinic, orthorhombic, and hexagonal phases), the molar volume for the quenched HT/HP-orthorhombic ThMo2 O8 is decreased by almost 20 %. As a result of such a dramatic structural transformation, a permanent high-pressure quenchable state is able to be sustained when the pressure is released. The crystal structures of the three ambient ThMo2 O8 phases are based on three-dimensional (3D) frameworks constructed from corner-sharing ThOx (x=6, 8, or 9) polyhedra and MoO4 tetrahedra. The HT/HP-orthorhombic ThMo2 O8 , however, crystallizes in a novel structural topology, exhibiting very dense arrangements of ThO11 and MoO4+1 polyhedra connecting along the crystallographic c axis. The phase transitions among all four of these ThMo2 O8 polymorphs are unveiled and fully characterized with regard to the structural transformation, thermal stability, and vibrational properties. The complementary first principles calculations of Gibbs free energies reveal the underlying energetics of the phase transition, which support the experimental findings. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Structural evolution versus temperature of the β0 phase of the {n- eicosane}/{n- docosane} system: rotator transitions

    Science.gov (United States)

    Dirand, M.; Achour-Boudjema, Z.

    1996-02-01

    The orthorhombic phase {β 0[n- C20H42}/{n- C22H46] } (Fmmm) determined by Gerson and Nyburg is isostructural with the orthorhombic Rotator phase β-RI (Fmmm), observed in n-tricosane( n-C 23H 48) and n-pentacosane( n-C 25H 52) and in the two binary systems: [ {n- C22H46}/{n- C24H50}] and [ {n- C24H50}/{n- C26H54}]. When the temperature increases, its {b}/{a} ratio changes progressively from 1.51 at 293 K to 1.73 at 309 K; it then transforms into the rhombohedral Rotator phase α-RII (R 3¯ m) just below the solidus curve. These observations allow generalization of structural behaviour of two n-alkane mixtures (19 < n < 27), whose difference between carbon numbers is equal to 1 or 2.

  12. A crystalline-to-crystalline phase transition in Ca(OH)2 at 8 GPa and room temperature

    Science.gov (United States)

    Catalli, K.; Shim, S.-H.; Prakapenka, V. B.

    2008-03-01

    X-ray diffraction and Raman spectroscopy measurements reveal that Ca(OH)2-portlandite transforms to a crystalline phase with an ordered OH sublattice between 8 and 14 GPa at room temperature under quasi-hydrostatic stress conditions in an Ar pressure medium. The amorphization previously reported at 11 GPa under no pressure medium was not observed up to 26 GPa. The width and separation of the fluorescence peaks from the ruby chips embedded in Ca(OH)2 without a medium suggest that deviatoric stress is responsible for the previously observed amorphization. Our study demonstrates that the behavior of hydrous phases in the subducting slab could be sensitive to local deviatoric stresses. Together with similar reports on quartz, our observation on Ca(OH)2 indicates that deviatoric stress is an important factor to consider for P-induced amorphization reported in a wide range of materials.

  13. A crystalline-to-crystalline phase transition in Ca(OH)[subscript 2] at 8 GPa and room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Catalli, K.; Shim, S.-H.; Prakapenka, V.B. (MIT); (UC)

    2008-07-02

    X-ray diffraction and Raman spectroscopy measurements reveal that Ca(OH){sub 2}-portlandite transforms to a crystalline phase with an ordered OH sublattice between 8 and 14 GPa at room temperature under quasi-hydrostatic stress conditions in an Ar pressure medium. The amorphization previously reported at 11 GPa under no pressure medium was not observed up to 26 GPa. The width and separation of the fluorescence peaks from the ruby chips embedded in Ca(OH){sub 2} without a medium suggest that deviatoric stress is responsible for the previously observed amorphization. Our study demonstrates that the behavior of hydrous phases in the subducting slab could be sensitive to local deviatoric stresses. Together with similar reports on quartz, our observation on Ca(OH){sub 2} indicates that deviatoric stress is an important factor to consider for P-induced amorphization reported in a wide range of materials.

  14. Reversible change of charge ordering transition temperature in LaCaMnO induced by electric pulses

    Science.gov (United States)

    Wu, Z. H.; Xie, H. Q.

    2010-09-01

    Specific heats and magnetic moments of LaCaMnO polycrystalline ceramics were measured under different resistance states induced by electric pulses. Experimental results revealed that the specific heat associated with ferromagnetic spin waves had a larger value at a low resistance state compared to that at a high state, indicating the growth of ferromagnetic regions as the resistance changed from a high state to a lower one. The charge ordering temperature (T) at a low resistance state was higher than that at a high state, in contrast to the prediction based on the traditional double exchange model. We proposed that the ferromagnetic clusters at a low resistance state would cause a reduction of the collective Jahn-Teller distortion in the ferromagnetic phase, thus leading to an increase in T.

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

    Science.gov (United States)

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

    2017-08-01

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

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

    Science.gov (United States)

    Onasch, Timothy Bruce

    1999-10-01

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

  17. Effect of thermal aging on grain structural characteristic and Ductile-to-Brittle transition temperature of CLAM steel at 550 °C

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); University of Science and Technology of China, Hefei, Anhui, 230031 (China); Chen, Jianwei [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); Xu, Gang, E-mail: gang.xu@fds.org.cn [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China)

    2017-02-15

    Highlights: • The grain boundary length per unit area decreased with the increasing aging time. • The fraction of LABs increased obviously after thermal aging. • Prior austenitic grain refinement is more important to improve low temperature toughness. - Abstract: In this work, electron backscatter diffraction (EBSD) was used to investigate the grain structure evolution of China low activation martensitic (CLAM) steel samples which were aged at 550 °C for 0 h, 2000 h, 4000 h and 10,000 h. The results showed that the prior austenitic grain size increased with the aging time, which led to the decrease of grain boundary length. The fraction of misorientation angle in a range from about 4 to 10° increased obviously after thermal aging for 10,000 h, and it indicated that the fine subgrains formed in the CLAM steel during the long-term thermal exposure. Furthermore, Charpy impact experiments were carried out to analyze the toughness of the CLAM steel before and after aging, particularly the Ductile-to-Brittle Transition Temperature (DBTT). Though amounts of fine subgrians formed in matrix, a substantial increase in DBTT (∼40.1 °C) had been noticed after aging for 10,000 h. The results showed that the high angle boundaries such as prior austenitic grain boundaries are more effective in retarding the propagation of cleavage crack than subgrain boundaries.

  18. A study on the change in the phase transition temperature of TiSi sub 2 by adding the Zr element on different Si substrates

    CERN Document Server

    Yoon, S H

    1999-01-01

    The stabilization of C49 TiSi sub 2 at high temperature was investigated by adding Zr element to Ti-silicide both on single crystalline Si(100) and amorphous Si substrates. This stabilization of the C49 TiSi sub 2 phase, which exhibits lower surface and interface energies than those of the C54 TiSi sub 2 phase, was expected to suppress the problems of Ti-silicide, such as the phase transition and the agglomeration. Ti and Zr films of 40 nm were co-deposited on Si substrates in a dual e-beam evaporation system equipped with an ion pump and at a base pressure of approx 5x10 sup - sup 9 Torr. The amounts of Zr contents added to the Ti-silicide were 5, 10 and 20 atomic %, and the thicknesses were monitored by in-situ quartz-crystal thickness monitors. After the deposition, films were annealed by using an ex-situ vacuum furnace at temperatures between 600 .deg. C and 900 .deg. C in 100 .deg. C increments. The phase identification and the chemical compositions were investigated by X-ray diffraction (XRD) and Auger ...

  19. A geographically-aware multilevel analysis on the association between atmospheric temperature and the “Emergency and transitional shelter population”

    Directory of Open Access Journals (Sweden)

    Carlos Siordia

    2014-11-01

    Full Text Available Understanding the geographical distribution and correlates of special segments of the population has the potential for offering insight into human behavior. Our study examines the Emergency and Transitional Shelter Population (ETSP—which includes what are commonly referred to as “homeless” people. We use 2010 data from two sources: United States (US Census Bureau county-level ETSP estimates; and North America Land Data Assimilation System Phase 2 (NLDAS-2. We investigate the ecological correlates of ETSP concentration by using a geographically-aware multilevel linear model. The specific aim is to investigate if an how atmospheric temperature is related with ETSP concentration by county—after accounting for population density and percent non-Hispanic-White. We use ArcGIS® 10.1 to create a spatial weight matrix of the ten most proximal counties and use SAS® 9.3 to create an algorithm that estimates County Cluster Dyadic Averages (CCDAs. By nesting the 31,090 CCDAs over the 3,109 counties in the continental US, we find a positive and statistically significant relationship between ETSP density and atmospheric temperature. Ecological studies should continue to explore the spatial heterogeneity of the ETSP.

  20. Effect of temperature-driven phase transition on energy-storage and -release properties of Pb0.97La0.02[Zr0.55Sn0.30Ti0.15]O3 ceramics

    Science.gov (United States)

    Xu, Ran; Tian, Jingjing; Zhu, Qingshan; Feng, Yujun; Wei, Xiaoyong; Xu, Zhuo

    2017-07-01

    Temperature-driven phase transition of Pb0.97La0.02[Zr0.55Sn0.30Ti0.15]O3 ceramics was studied, and the consecutive ferroelectric-antiferroelectric-paraelectric (FE-AFE-PE) switching was confirmed. The materials have better dielectric tunability (-82% to 50%) in the AFE state than in the FE state. Also, the phase transition influences the energy-storage and -release performance significantly. A sharp increase in releasable energy density and efficiency was observed due to the temperature-driven FE-AFE transition. Highest releasable energy density, current density, and peak power density were achieved at 130 °C, which was attributed to the highest backward transition field. The stored charge was released completely in AFE and PE states in the microseconds scale, while only a small part of it was released in the FE state. The above results indicate the huge impact of temperature-driven phase transition on dielectrics' performance, which is significant when developing AFE materials working in a wide temperature range.

  1. High temperature investigation of the solid/liquid transition in the PuO2-UO2-ZrO2 system

    Science.gov (United States)

    Quaini, A.; Guéneau, C.; Gossé, S.; Sundman, B.; Manara, D.; Smith, A. L.; Bottomley, D.; Lajarge, P.; Ernstberger, M.; Hodaj, F.

    2015-12-01

    The solid/liquid transitions in the quaternary U-Pu-Zr-O system are of great interest for the analysis of core meltdown accidents in Pressurised Water Reactors (PWR) fuelled with uranium-dioxide and MOX. During a severe accident the Zr-based cladding can become completely oxidised due to the interaction with the oxide fuel and the water coolant. In this framework, the present analysis is focused on the pseudo-ternary system UO2-PuO2-ZrO2. The melting/solidification behaviour of five pseudo-ternary and one pseudo-binary ((PuO2)0.50(ZrO2)0.50) compositions have been investigated experimentally by a laser heating method under pre-set atmospheres. The effects of an oxidising or reducing atmosphere on the observed melting/freezing temperatures, as well as the amount of UO2 in the sample, have been clearly identified for the different compositions. The oxygen-to-metal ratio is a key parameter affecting the melting/freezing temperature because of incongruent vaporisation effects. In parallel, a detailed thermodynamic model for the UO2-PuO2-ZrO2 system has been developed using the CALPHAD method, and thermodynamic calculations have been performed to interpret the present laser heating results, as well as the high temperature behaviour of the cubic (Pu,U,Zr)O2±x-c mixed oxide phase. A good agreement was obtained between the calculated and experimental data points. This work enables an improved understanding of the major factors relevant to severe accident in nuclear reactors.

  2. M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Zhihong [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti5Si3-based alloys was investigated. Oxidation behavior of Ti5Si3-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti5Si3 by nucleation and growth of nitride subscale. Ti5Si3.2and Ti5Si3C0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi2 coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo3Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo3Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nbss (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L {leftrightarrow} NbSS + NbB was determined to occur at 2104 ± 5 C by DTA.

  3. Low temperature vibrational spectra, lattice dynamics, and phase transitions in some potassium hexahalometallates: K2[XY6] with X=Sn or Te and Y=Cl or Br

    DEFF Research Database (Denmark)

    Chodos, Steven L.; Berg, Rolf W.

    1979-01-01

    This paper deals with the observation and identification of phonon frequencies resulting from the low temperature phase transitions in K2XY6 crystals. By means of a simple lattice dynamical model, the vibrational Raman and IR data available in the literature and obtained here have been analyzed. ...

  4. SCK-CEN Contribution to the''Relation between different measures of exposure-induced shifts in ductile-brittle transition temperatures'' (REFEREE). Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    Chaouadi, R.; Van Walle, E.; Fabry, A.; Puzzolante, J.L

    1998-08-01

    The relationship between Charpy-V (CVN) impact, fracture toughness and tensile properties for selected reactor pressure -vessel steels in the transition temperature range are investigated. Data on the testing of unirradiated material are reported. The applied methods include chemical analysis, Charpy-V impact testing, tensile testing and fracture toughness determination.

  5. Infield X-ray diffraction studies of field and temperature driven structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}

    Energy Technology Data Exchange (ETDEWEB)

    Shahee, Aga, E-mail: agashahee@gmail.com [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India); Department of Physics, IIT Bombay, Powai, Mumbai 400076 (India); Sharma, Shivani; Singh, K.; Lalla, N.P. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India)

    2017-07-15

    Highlights: • Temperature and magnetic field driven coupled magneto-structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}. • Microscopic evidence of strong spin-charge-lattice coupling. • Iso-thermal magnetic field driven structure phase transition. • Field-driven structural phase transition origin of observed 1st order type CMR effect. - Abstract: Comprehensive X-ray diffraction (XRD) studies have been performed at different temperature (T) (4.2–300 K) and magnetic field (H) (0–8 T) to understand the evolution of crystal structure of Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ} (NSMO) under non ambient conditions. The T dependent XRD results show the abrupt change in the lattice parameters without any change in lattice symmetry at ∼200 K, which is associated with the first order structural phase transition from ferromagnetic to antiferromagnetic phase. This phase transition is strongly H dependent and shifted to lower temperature (∼150 K) on the application of 8 T field with phase coexistence (high temperature phase ∼18%), even down to 4.2 K. Isothermal XRD results at 150 K under different H clearly illustrate the H induced first order structural phase transition. The critical H at which this phase transformation starts is ∼1 T, with rapid growth above 4 T with hysteretic nature during increasing and decreasing H. These results are supported with the resistivity and magnetoresistance results and affirm the strong spin-lattice coupling in NSMO. Our detail studies reveal the structural correlations to the observed colossal magnetoresistance and magnetocaloric effect in this material.

  6. Temperature-induced reversible first-order single crystal to single crystal phase transition in Boc-γ(4)(R)Val-Val-OH: interplay of enthalpy and entropy.

    Science.gov (United States)

    Pal, Rumpa; Reddy, M B Madhusudana; Dinesh, Bhimareddy; Balaram, Padmanabhan; Guru Row, Tayur N

    2014-10-09

    Crystals of Boc-γ(4)(R)Val-Val-OH undergo a reversible first-order single crystal to single crystal phase transition at Tc ≈ 205 K from the orthorhombic space group P22121 (Z' = 1) to the monoclinic space group P21 (Z' = 2) with a hysteresis of ∼2.1 K. The low-temperature monoclinic form is best described as a nonmerohedral twin with ∼50% contributions from its two components. The thermal behavior of the dipeptide crystals was characterized by differential scanning calorimetry experiments. Visual changes in birefringence of the sample during heating and cooling cycles on a hot-stage microscope with polarized light supported the phase transition. Variable-temperature unit cell check measurements from 300 to 100 K showed discontinuity in the volume and cell parameters near the transition temperature, supporting the first-order behavior. A detailed comparison of the room-temperature orthorhombic form with the low-temperature (100 K) monoclinic form revealed that the strong hydrogen-bonding motif is retained in both crystal systems, whereas the non-covalent interactions involving side chains of the dipeptide differ significantly, leading to a small change in molecular conformation in the monoclinic form as well as a small reorientation of the molecules along the ac plane. A rigid-body thermal motion analysis (translation, libration, screw; correlation of translation and libration) was performed to study the crystal entropy. The reversible nature of the phase transition is probably the result of an interplay between enthalpy and entropy: the low-temperature monoclinic form is enthalpically favored, whereas the room-temperature orthorhombic form is entropically favored.

  7. Chromium–niobium co-doped vanadium dioxide films: Large temperature coefficient of resistance and practically no thermal hysteresis of the metal–insulator transition

    Directory of Open Access Journals (Sweden)

    Kenichi Miyazaki

    2016-05-01

    Full Text Available We investigated the effects of chromium (Cr and niobium (Nb co-doping on the temperature coefficient of resistance (TCR and the thermal hysteresis of the metal–insulator transition of vanadium dioxide (VO2 films. We determined the TCR and thermal-hysteresis-width diagram of the V1−x−yCrxNbyO2 films by electrical-transport measurements and we found that the doping conditions x ≳ y and x + y ≥ 0.1 are appropriate for simultaneously realizing a large TCR value and an absence of thermal hysteresis in the films. By using these findings, we developed a V0.90Cr0.06Nb0.04O2 film grown on a TiO2-buffered SiO2/Si substrate that showed practically no thermal hysteresis while retaining a large TCR of 11.9%/K. This study has potential applications in the development of VO2-based uncooled bolometers.

  8. Chromium–niobium co-doped vanadium dioxide films: Large temperature coefficient of resistance and practically no thermal hysteresis of the metal–insulator transition

    Energy Technology Data Exchange (ETDEWEB)

    Miyazaki, Kenichi, E-mail: kenichi-miyazaki@denso.co.jp, E-mail: k.shibuya@aist.go.jp [Denso Corporation, Aichi 470-0111 (Japan); University of Tsukuba, Tsukuba 305-8571 (Japan); Shibuya, Keisuke, E-mail: kenichi-miyazaki@denso.co.jp, E-mail: k.shibuya@aist.go.jp; Sawa, Akihito [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565 (Japan); Suzuki, Megumi; Sakai, Kenichi [Denso Corporation, Aichi 470-0111 (Japan); Fujita, Jun-ichi [University of Tsukuba, Tsukuba 305-8571 (Japan)

    2016-05-15

    We investigated the effects of chromium (Cr) and niobium (Nb) co-doping on the temperature coefficient of resistance (TCR) and the thermal hysteresis of the metal–insulator transition of vanadium dioxide (VO{sub 2}) films. We determined the TCR and thermal-hysteresis-width diagram of the V{sub 1−x−y}Cr{sub x}Nb{sub y}O{sub 2} films by electrical-transport measurements and we found that the doping conditions x ≳ y and x + y ≥ 0.1 are appropriate for simultaneously realizing a large TCR value and an absence of thermal hysteresis in the films. By using these findings, we developed a V{sub 0.90}Cr{sub 0.06}Nb{sub 0.04}O{sub 2} film grown on a TiO{sub 2}-buffered SiO{sub 2}/Si substrate that showed practically no thermal hysteresis while retaining a large TCR of 11.9%/K. This study has potential applications in the development of VO{sub 2}-based uncooled bolometers.

  9. Polymer combination increased both physical stability and oral absorption of solid dispersions containing a low glass transition temperature drug: physicochemical characterization and in vivo study.

    Science.gov (United States)

    Sakurai, Atsushi; Sakai, Toshiro; Sako, Kazuhiro; Maitani, Yoshie

    2012-01-01

    The purpose of this study was establishing a solid dispersion formulation containing a low glass transition temperature (T(g)) and poorly water-soluble drug. Drug/polymer blends with differing physicochemical stabilities and oral absorption were prepared from copolyvidone (PVP-VA), polyvinylpyrrolidone (PVP) or hydroxypropylmethylcellulose (HPMC) by a hot melt extrusion. HPMC drastically increased the drug oral absorption property, while PVP-VA or PVP stabilized solid dispersions during storage by increasing the T(g) in proportion to polymer concentration. Experimental T(g) values corresponded closely with theoretical T(g) values; indeed, the T(g) values of solid dispersion with HPMC did not increase significantly compared to the T(g) value for the drug alone. A solid dispersion formulation incorporating two different polymers-HPMC and either PVP-VA or PVP-maintained increased T(g), physicochemical stability, solubility, and bioavailability of the solid dispresions owing to each polymer. These findings suggested that both oral absorption and physicochemical stability of low-T(g) drug will be improved using less amount of solid dispersion of combined two polymers than polymer alone.

  10. Comparison of applicability of current transition temperature shift models to SA533B-1 reactor pressure vessel steel of Korean nuclear reactors

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Ji Hyun; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-08-15

    The precise prediction of radiation embrittlement of aged reactor pressure vessels (RPVs) is a prerequisite for the long-term operation of nuclear power plants beyond their original design life. The expiration of the operation licenses for Korean reactors the RPVs of which are made from SA533B-1 plates and welds is imminent. Korean regulatory rules have adopted the US Nuclear Regulatory Commission's transition temperature shift (TTS) models to the prediction of the embrittlement of Korean reactor pressure vessels. The applicability of the TTS model to predict the embrittlement of Korean RPVs made of SA533B-1 plates and welds was investigated in this study. It was concluded that the TTS model of 10 CFR 50.61a matched the trends of the radiation embrittlement in the SA533B-1 plates and welds better than did that of Regulatory Guide (RG) 1.99 Rev. 2. This is attributed to the fact that the prediction performance of 10 CFR 50.61a was enhanced by considering the difference in radiation embrittlement sensitivity among the different types of RPV materials.

  11. Correlations of norbornenyl crosslinked polyimide resin structures with resin thermo-oxidative stability, resin glass transition temperature and composite initial mechanical properties

    Science.gov (United States)

    Alston, William B.

    1988-01-01

    PMR (polymerization of monomeric reactants) methodology was used to prepare 70 different polyimide oligomeric resins and 30 different unidirectional graphite fiber/polyimide composites. Monomeric composition as well as chain length between sites of crosslinks were varied to examine their effects on resin thermo-oxidative stability and glass transition temperature (Tg) of the cured/postcured resins. A linear correlation of decreasing 316 C resin weight loss/surface area versus (1) decreasing aliphatic content, or (2) increasing benzylic/aliphatic content stoichiometry ratio over a wide range of resin compositions was observed. An almost linear correlation of Tg versus molecular distance between the crosslinks was also observed. An attempt was made to correlate Tg with initial composite mechanical properties (flexural strength and interlaminar shear strength). However, the scatter in mechanical strength data prevented obtaining a clear correlation. Instead, only a range of composite mechanical properties was obtained at 25, 288, and 316 C. Perhaps more importantly, what did become apparent during the correlation study was (1) the PMR methodology could be used to prepare composites from resins containing a wide variety of monomer modifications, (2) that these composites almost invariably provided satisfactory initial mechanical properties as long as the resins formulated exhibited satisfactory processing flow, and (3) that PMR resins exhibited predictable rates of 316 C weight loss/surface area based on their benzylic/aliphatic stoichiometery ratio.

  12. Measurement of glass transition temperature, residual heat of reaction and mixing ratio of epoxy resins using near infrared spectroscopy: a preliminary study

    DEFF Research Database (Denmark)

    Houmøller, Lars Plejdrup; Laursen, Peter Clemen

    2003-01-01

    As a measure of the degree of curing of epoxy resins, the glass transition temperature, Tg, and the residual heat of reaction, DeltaHr, are often used. In this study, near infrared spectroscopy and multivariate calibration (partial least squares regression (PLSR)) have been used to monitor the two...... variables, using differential scanning calorimetry (DSC) as the reference method. The epoxy under study was a commercial system consisting of the resin, trimethylolpropanetriglycidylether, and the hardener, 3-aminomethyl-3,5,5,-trimethylcyclohexylamine. Using samples cured under different conditions......, calibrations resulted in root mean square errors of cross-validation (RMSECV) of 18 J/g for DeltaHr (range for Hr: 6.1-231.3 J/g) and 7.2ºC for Tg (range for Tg: 41.5-98.8ºC). Also, a PLSR model for mixing ratio of hardener and resin was obtained, resulting in a RMSECV of 0.0040 (range for mixing ratio: 0.180-0.380)...

  13. Martensitic phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Petry, W.; Neuhaus, J. [Techn. Universitaet Muenchen, Physik Department E13, Munich (Germany)

    1996-11-01

    Many elements transform from a high temperature bcc phase to a more dense packed temperature phase. The great majority of these transitions are of 1st order, displacive and reconstructive. The lattice potentials which govern these martensitic transitions can be probed by inelastic neutron scattering, thereby answering fundamental questions like : Will the transition be announced by dynamical or static fluctuations? What are the trajectories for the displacements needed for the transformation? Does the vibrational entropy stabilize the high temperature phase? Are the unusual transport properties in these materials related to their ability to transform? (author) 17 figs., 1 tab., 46 refs.

  14. High-temperature phase transitions and domain structures of KLiSO{sub 4}. Studied by polarisation-optics, X-ray topography and liquid-crystal surface decoration

    Energy Technology Data Exchange (ETDEWEB)

    Scherf, Christian; Chung, Su Jin; Hahn, Theo; Klapper, Helmut [RWTH Aachen Univ. (Germany). Inst. fuer Kristallographie; Ivanov, Nicolay R. [Russian Academy of Sciences, Moscow (Russian Federation). Shubnikov Inst. of Crystallography

    2017-07-01

    The transitions between the room temperature phase III (space group P6{sub 3}) and the two high-temperature phases II (Pcmn) and I (P6{sub 3}/mmc) of KLiSO{sub 4} and the domain structures generated by them were investigated by high-temperature polarisation optics (birefringence) and room-temperature X-ray topography, optical activity and nematic-liquid-crystal (NLC) surface decoration. The transition from the polar hexagonal phase III into the centrosymmetric orthorhombic phase II at 708 K leads, due to the loss of the trigonal axis and the radial temperature gradient of the optical heating chamber used, to a roughly hexagonal arrangement of three sets of thin orthorhombic {110} lamelleae with angles of 60 (120 ) between them. The associated twin law ''reflection m{110}{sub orth}'' corresponds to the frequent growth twin m{10 anti 10}{sub hex} of phase III. The domains are easily ferroelastically switched. Upon further heating above 949 K into phase I (P6{sub 3}/mmc) all domains vanish. Upon cooling back into phase II the three domain states related by 60 (120 ) reflections m{110}{sub orth} re-appear, however (due to the higher thermal agitation at 949 K) with a completely different domain structure consisting of many small, irregularly arranged {110}{sub orth} domains. Particular attention is paid to the domain structure of the hexagonal room temperature phase III generated during the re-transition from the orthorhombic phase II. Curiously, from the expected three twin laws inversion anti 1, rotation 2 perpendicular to [001]{sub hex} and reflection m{10 anti 10}{sub hex} only the latter, which corresponds to the frequent growth twinning, has been found. Finally a short treatise of the structural relations of the KLiSO{sub 4} high-temperature polymorphs is given.

  15. (Fe3O4) thin films

    Indian Academy of Sciences (India)

    Unknown

    resistance vs temperature measurements. Implantation decreases the change in resistance at 120 K and this effect saturates beyond 3 × 1014 ions/cm2. The Verwey transition temperature, TV, shifts towards lower temperatures with increase in ion dose. Keywords. Implantation; magnetite; thin films; pulsed laser ablation; ...

  16. Effect of 80 keV Ar implantation on the properties of pulse laser ...

    Indian Academy of Sciences (India)

    Ion beam induced modifications in the films were investigated using XRD and resistance vs temperature measurements. Implantation decreases the change in resistance at 120 K and this effect saturates beyond 3 × 1014 ions/cm2. The Verwey transition temperature, , shifts towards lower temperatures with increase in ...

  17. Finite-temperature coupled-cluster, many-body perturbation, and restricted and unrestricted Hartree-Fock study on one-dimensional solids: Luttinger liquids, Peierls transitions, and spin- and charge-density waves

    Science.gov (United States)

    Hermes, Matthew R.; Hirata, So

    2015-09-01

    One-dimensional (1D) solids exhibit a number of striking electronic structures including charge-density wave (CDW) and spin-density wave (SDW). Also, the Peierls theorem states that at zero temperature, a 1D system predicted by simple band theory to be a metal will spontaneously dimerize and open a finite fundamental bandgap, while at higher temperatures, it will assume the equidistant geometry with zero bandgap (a Peierls transition). We computationally study these unique electronic structures and transition in polyyne and all-trans polyacetylene using finite-temperature generalizations of ab initio spin-unrestricted Hartree-Fock (UHF) and spin-restricted coupled-cluster doubles (CCD) theories, extending upon previous work [He et al., J. Chem. Phys. 140, 024702 (2014)] that is based on spin-restricted Hartree-Fock (RHF) and second-order many-body perturbation (MP2) theories. Unlike RHF, UHF can predict SDW as well as CDW and metallic states, and unlike MP2, CCD does not diverge even if the underlying RHF reference wave function is metallic. UHF predicts a gapped SDW state with no dimerization at low temperatures, which gradually becomes metallic as the temperature is raised. CCD, meanwhile, confirms that electron correlation lowers the Peierls transition temperature. Furthermore, we show that the results from all theories for both polymers are subject to a unified interpretation in terms of the UHF solutions to the Hubbard-Peierls model using different values of the electron-electron interaction strength, U/t, in its Hamiltonian. The CCD wave function is shown to encompass the form of the exact solution of the Tomonaga-Luttinger model and is thus expected to describe accurately the electronic structure of Luttinger liquids.

  18. Finite-temperature coupled-cluster, many-body perturbation, and restricted and unrestricted Hartree–Fock study on one-dimensional solids: Luttinger liquids, Peierls transitions, and spin- and charge-density waves

    Energy Technology Data Exchange (ETDEWEB)

    Hermes, Matthew R. [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)

    2015-09-14

    One-dimensional (1D) solids exhibit a number of striking electronic structures including charge-density wave (CDW) and spin-density wave (SDW). Also, the Peierls theorem states that at zero temperature, a 1D system predicted by simple band theory to be a metal will spontaneously dimerize and open a finite fundamental bandgap, while at higher temperatures, it will assume the equidistant geometry with zero bandgap (a Peierls transition). We computationally study these unique electronic structures and transition in polyyne and all-trans polyacetylene using finite-temperature generalizations of ab initio spin-unrestricted Hartree–Fock (UHF) and spin-restricted coupled-cluster doubles (CCD) theories, extending upon previous work [He et al., J. Chem. Phys. 140, 024702 (2014)] that is based on spin-restricted Hartree–Fock (RHF) and second-order many-body perturbation (MP2) theories. Unlike RHF, UHF can predict SDW as well as CDW and metallic states, and unlike MP2, CCD does not diverge even if the underlying RHF reference wave function is metallic. UHF predicts a gapped SDW state with no dimerization at low temperatures, which gradually becomes metallic as the temperature is raised. CCD, meanwhile, confirms that electron correlation lowers the Peierls transition temperature. Furthermore, we show that the results from all theories for both polymers are subject to a unified interpretation in terms of the UHF solutions to the Hubbard–Peierls model using different values of the electron-electron interaction strength, U/t, in its Hamiltonian. The CCD wave function is shown to encompass the form of the exact solution of the Tomonaga–Luttinger model and is thus expected to describe accurately the electronic structure of Luttinger liquids.

  19. Large adiabatic temperature change in magnetoelastic transition in Ni{sub 50}Mn{sub 35}Cr{sub 2}Sn{sub 13} Heusler alloy of granular nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, H. R.; Sharma, S. K.; Ram, S., E-mail: prakashhr73@gmail.com [Materials Science Centre, Indian Institute of Technology, Kharagpur-721302 (India); Chatterjee, S. [High Magnetic Field Lab, UGC-DAE Consortium of Scientific Research, Kolkata-700098 (India)

    2016-05-06

    The Ni-Mn-Sn alloys are a pioneering series of magnetocaloric materials of a huge heat-energy exchanger in the martensite transition. A small additive of nearly 2 at% Cr effectively tunes the valence electron density of 8.090 electrons per atom and a large change in the entropy ΔS{sub M←A} = 4.428 J/kg-K (ΔS{sub M→A} = 3.695 J/kg-K in the recycle) at the martensite ← austenite phase transition as it is useful for the magnetic refrigeration and other cooling devices. The Cr additive tempers the tetragonality with the aspect ratio c/a = 0.903 of the martensite phase and exhibits an adiabatic temperature change of 10 K. At room temperature, a hysteresis loop exhibits 48.91 emu/g saturation magnetization and 82.1 Oe coercivity.

  20. High-temperature structural phase transition coupled with dielectric switching in an organic-inorganic hybrid crystal: [NH3(CH2)2Br]3CdBr5.

    Science.gov (United States)

    Chen, Hai-Peng; Wang, Zhong-Xia; Chen, Cheng; Lu, Yang; Yin, Zi; Sun, Xiao-Fen; Fu, Da-Wei

    2017-04-05

    Molecular bistable switches (electrical switches "ON" and "OFF") represent a class of highly desirable intelligent materials due to their sensitive switchable responses, simple and environmentally friendly processing, light weight, and mechanical flexibility. In particular, these switches above room temperature with potential practical application are rarely reported. In this work, a new zigzag chained organic-inorganic hybrid compound [NH3(CH2)2Br]3CdBr5 (1), which displays rapidly sensitive dielectric switching reversibility and remarkable switching antifatigue, has been successfully synthesized. Systematic characterization including differential scanning calorimetry measurements (DSC), dielectric measurements, and variable-temperature structural analyses was performed to reveal the phase transition of 1. A couple of reversible heat anomaly peaks at 335.6/323.8 K with a large hysteresis (ca. 11.8 K) were observed in the DSC curve, indicating the first-order type of phase transition. 1 exhibits an obvious dielectric switching at around 327 K, which makes 1 a potential switchable dielectric material. Variable-temperature structural analyses show that the cationic order-disorder motion is the main attribution for the phase transition of 1.

  1. Phase stabilization of magnetite (Fe{sub 3}O{sub 4}) nanoparticles with B{sub 2}O{sub 3} addition: A significant enhancement on the phase transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Topal, Uğur, E-mail: ugur.topal@tubitak.gov.tr [TUBITAK-UME, National Metrology Institute, PK 54, 41470 Gebze-Kocaeli (Turkey); Aksan, Mehmet Ali [Inonu Universitesi, Fen Edebiyat Fakultesi, Fizik Bolumu 44280, Malatya (Turkey)

    2016-05-15

    Magnetite nanoparticles (MNPs) are extensively investigated for biomedical applications, particularly as contrast agents for Magnetic Resonance Imaging and as drug delivery agent and heat mediators for cancer therapy. Tuning the magnetic properties of the magnetite nanoparticles with doping of foreign atoms has a crucial importance for determining the application areas of these materials and so attracts much interests. On the other hand the doping with foreign atoms requires high temperature annealing, and it causes a phase transition to the hematite phase above 400 °C. In this work the phase transition temperature from the magnetite to the hematite phase has been increased by 200 °C, which is the highest enhancement reported in literature. It was achieved by addition of the appropriate amounts of B{sub 2}O{sub 3.} Our experiments indicates that the 5.0 wt% of B{sub 2}O{sub 3} addition stabilizes and keeps the existence of single phase magnetite up to 600 °C. - Highlights: • B{sub 2}O{sub 3} addition to magnetite nanoparticles enhances the superparamagnetism. • The phase transition temperature of magnetite to hematite increases by 200 °C. • B{sub 2}O{sub 3} addition increases the activation energy of magnetite.

  2. Ge(001)-(<2 1>, <0 3>)-Pb(<2 1>, <0 6>)↔Pb: Low-temperature two-dimensional phase transition

    DEFF Research Database (Denmark)

    Bunk, Oliver; Nielsen, Martin Meedom; Zeysing, J.H.

    2001-01-01

    configuration. Both the room-temperature and low-temperature phases of this system were investigated by surface x-ray diffraction using synchrotron radiation. The room-temperature Ge(001)-((2 1)(0 3)) phase is best described by a model with dynamically flipping germanium dimers underneath a distorted Pb(111...

  3. Perubahan suhu transisi kaca dan massa resin akrilik heat cured akibat kelembaban dan lama penyimpanan (Changes in glass transition temperature and heat cured acrylic resin mass due to moisture and storage time

    Directory of Open Access Journals (Sweden)

    Sherman Salim

    2014-09-01

    Full Text Available Background: Acrylic resins, especially poly methyl methacrylate (PMMA was introduced in 1937. Acrylic resin has favorable properties, among others, aesthetic, color and texture similar to that of the gingival aesthetic in the mouth, relatively low water absorption and dimensional changes. However, some studies suggest that the duration of storage of acrylic resin will affect the changes in the glass transition temperature and the mass of acrylic resin. Purpose: The objective of this research was to study the effect of humidity and storage time led to changes in the glass transition temperature and the mass of the acrylic resin. Methods: The research method is experimental laboratory. Acrylic resin specimens are kept in conditions of humidity of 90%, 70%, 40% and 30% for 24 hours, one week, one month and two months. In this study used three methods of curing, namely conventional JIs, 24-hour curing at 70 °C and using the microwave. Results: Low humidity causes changes in the glass transition temperature and the mass of acrylic resin. Longer storage of acrylic resins in low humidity, can affect change greater than the glass transition temperature and the mass of acrylic resin. Conclusion: It can be concluded that the humidity and longer storage of acrylic resins can affect the glass transition temperature and a change in mass.Latar belakang: Resin akrilik terutama poli metil metakrilat (PMMA telah diperkenalkan pada tahun 1937. Resin akrilik memiliki sifat yang menguntungkan antara lain estetis, warna dan tekstur mirip dengan gingiva sehingga estetik di dalam mulut baik, daya serap air relatif rendah dan perubahan dimensi kecil. Akan tetapi, dari beberapa penelitian menyatakan bahwa lamanya waktu penyimpanan resin akrilik akan berpengaruh pada perubahan suhu transisi kaca dan massa resin akrilik. Tujuan: Tujuan dari penelitian ini adalah untuk mempelajari pengaruh kelembaban dan waktu penyimpanan yang menyebabkan perubahan suhu transisi kaca dan

  4. Transition metal carbides (WC, Mo2C, TaC, NbC) as potential electrocatalysts for the hydrogen evolution reaction (HER) at medium temperatures

    DEFF Research Database (Denmark)

    Meyer, Simon; Nikiforov, Aleksey V.; Petrushina, Irina M.

    2015-01-01

    used as electrodes and allowed the measurement of the intrinsic catalytic properties of different transition metal carbides in direct comparison to Pt at 260 degrees C. Under these conditions, the activity in the hydrogen evolution reaction (HER) followed the order WC > Pt approximate to MO2C > Nb...

  5. Data set: 31 years of spatially distributed air temperature, humidity, precipitation amount and precipitation phase from a mountain catchment in the rain-snow transition zone

    Science.gov (United States)

    Thirty one years of spatially distributed air temperature, relative humidity, dew point temperature, precipitation amount, and precipitation phase data are presented for the Reynolds Creek Experimental Watershed. The data are spatially distributed over a 10m Lidar-derived digital elevation model at ...

  6. Effects of the embedding kinetics on the surface nano-morphology of nano-grained Au and Ag films on PS and PMMA layers annealed above the glass transition temperature

    Science.gov (United States)

    Ruffino, F.; Torrisi, V.; Marletta, G.; Grimaldi, M. G.

    2012-06-01

    The morphology evolution of nano-grained Ag and Au films deposited on polystyrene (PS) and poly(methyl methacrylate) (PMMA) polymeric layers were studied, using the atomic force microscopy technique, when annealed above the polymers glass transition temperature. The main effects on the morphology changes were identified with those concerning the embedding kinetics of the Ag and Au nanoparticles in the PS or PMMA layers. The embedding process of the nanoparticles follows as a consequence of the long-range mobility of the polymeric chains above the glass transition temperature. In particular, the dependence of the nanoparticles mean height and surface density on the annealing time at various temperatures was quantified. The analyses of these behaviors allowed us: (1) to distinguish the overall embedding process in a first stage in which a thin wetting layer of the polymer coats the nanoparticles followed by a true embedding process of the nanoparticles into the polymer layer; (2) to evaluate the characteristic coating time for the Ag and Au nanoparticles in the PS and PMMA in the first stage; (3) to evaluate the characteristic embedding velocity for the Ag and Au nanoparticles in the PS and PMMA in the second stage; (4) to derive the activation energies for the embedding process of the Ag and Au nanoparticles in PS and PMMA; (5) to identify the embedding statistics of the Ag and Au nanoparticles in PS and PMMA with a "failure" Weibull statistics.

  7. Incipient ferroelectric to a possible ferroelectric transition in Te4+ doped calcium copper titanate (CaCu3Ti4O12 ceramics at low temperature as evidenced by Raman and dielectric spectroscopy

    Directory of Open Access Journals (Sweden)

    Nabadyuti Barman

    2017-03-01

    Full Text Available Partial replacement of Ti4+ by Te4+ ions in calcium copper titanate lattice improved its dielectric behaviour mostly due to cubic-to-tetragonal structural transformation and associated distortion in TiO6 octahedra. The relative permittivity values (23–30 x 103 of Te4+ doped ceramics is more than thrice that of un-doped ceramics (8 x 103 at 1 kHz. A decreasing trend in relative permittivity with increasing temperature (50–300 K is observed for all the samples. Barrett’s formula, as a signature of incipient ferroelectricity, is invoked to rationalize the relative permittivity variation as a function of temperature. A systematic investigation supported by temperature dependent Raman studies reveal a possible ferroelectric transition in Te4+ doped ceramic samples below 120 K. The possible ferroelectric transition is attributed to the interactions between quasi-local vibrations associated with the micro-clusters comprising TiO6 and TeO6 structural units and indirect dipole-dipole interactions of off-center B–cations (Ti4+ and Te4+ in double perovskite lattice.

  8. Low-temperature phase transition in glycine-glutaric acid co-crystals studied by single-crystal X-ray diffraction, Raman spectroscopy and differential scanning calorimetry.

    Science.gov (United States)

    Zakharov, Boris A; Losev, Evgeniy A; Kolesov, Boris A; Drebushchak, Valeri A; Boldyreva, Elena V

    2012-06-01

    The occurrence of a first-order reversible phase transition in glycine-glutaric acid co-crystals at 220-230 K has been confirmed by three different techniques - single-crystal X-ray diffraction, polarized Raman spectroscopy and differential scanning calorimetry. The most interesting feature of this phase transition is that every second glutaric acid molecule changes its conformation, and this fact results in the space-group symmetry change from P2(1)/c to P1. The topology of the hydrogen-bonded motifs remains almost the same and hydrogen bonds do not switch to other atoms, although the hydrogen bond lengths do change and some of the bonds become inequivalent.

  9. Microstructure of the Transitional Area of the Connection of a High-temperature Ni-based Brazing Alloy and Stainless Steel AISI 321 (X6CrNiTi 18–10)

    OpenAIRE

    R. Augustin; R. Koleňák

    2010-01-01

    This paper presents a detailed examination of the structure of the transitional area between a brazing alloy and the parent material, the dimensions of the diffusion zones that are created, and the influence on them of a change in the brazing parameters. Connections between Ni-based brazing alloys (NI 102) with a small content of B and AISI 321 stainless steel (X6CrNiTi 18–10) were created in a vacuum (10−2 Pa) at various brazing temperatures and for various holding times at the brazing tempe...

  10. Room-temperature and transition-metal-free Mizoroki-Heck-type reaction. Synthesis of E-stilbenes by photoinduced C-H functionalization.

    Science.gov (United States)

    Guastavino, Javier F; Budén, María E; Rossi, Roberto A

    2014-10-03

    We report a conceptually different approach toward E-stilbene syntheses by photoinduced direct C-H arylation of alkenes at rt without the addition of transition metals, with a broad range of aryl halides, including ArI, ArBr, and even ArCl. This is the first time that this reaction has been produced without extra solvent but with 18-crown-6 ether and t-BuOK in only 15 min of reaction.

  11. Synthesis, characterisation and phase transition behaviour of temperature-responsive physically crosslinked poly (N-vinylcaprolactam) based polymers for biomedical applications.

    Science.gov (United States)

    Halligan, Shane C; Dalton, Maurice B; Murray, Kieran A; Dong, Yixiao; Wang, Wenxin; Lyons, John G; Geever, Luke M

    2017-10-01

    Poly (N-vinylcaprolactam) (PNVCL) is a polymer which offers superior characteristics for various potential medical device applications. In particular it offers unique thermoresponsive capabilities, which fulfils the material technology constraints required in targeted drug delivery applications. PNVCL phase transitions can be tailored in order to suit the requirements of current and next generation devices, by modifying the contents with regard to the material composition and aqueous polymer concentration. In this study, physically crosslinked Poly (N-vinylcaprolactam)-Vinyl acetate (PNVCL-VAc) copolymers were prepared by photopolymerisation. The structure of the polymers was established by Fourier transform infrared spectroscopy, nuclear magnetic resonance and gel permeation chromatography. The polymers were further characterised using differential scanning calorimetry and swelling studies. Determination of the LCST of the polymers in aqueous solution was achieved by employing four techniques; cloud point, UV-spectrometry, differential scanning calorimetry and rheometry. Sol-gel transition was established using tube inversion method and rheological analysis. This study was conducted to determine the characteristics of PNVCL with the addition of VAc, and to establish the effects on the phase transition. The PNVCL based polymers exhibited a decrease in the LCST as the composition of VAc increased. Sol-gel transition could be controlled by altering the monomeric feed ratio and polymer concentration in aqueous milieu. Importantly all copolymers (10wt% in solution) underwent gelation between 33.6 and 35.9°C, and based on this and the other materials properties recorded in this study, these novel copolymers have potential for use as injectable in situ forming drug delivery systems for targeted drug delivery. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. PENGARUH SORPSI AIR DAN SUHU TRANSISI GELAS TERHADAP LAJU PENCOKLATAN NON-ENZIMATIS PADA PANGAN MODEL [The Effect of Water Sorption and Glass Transition Temperature on Non-Enzymatic Browning Reaction of Food Models

    Directory of Open Access Journals (Sweden)

    Dede R Adawiyah1

    2005-12-01

    Full Text Available This research was aimer/ to study the extend of non enzymatic browning reaction in food models containing the mixture of tapioca starch, casein, sucrose and oh at different moisture contents (2.55%, 5.26%, 7.54%, 15.20%. 15.93% and 23.99% and storage temperatures (30, 55 and 700C. The non-enzymatic browning reaction was detected from brown color intensity measured by spechtrophotometer and colorimetric methods. The non-enzymatic browning reaction or food model follow pseudo-zero order reaction, suggesting that browning reaction occurred at moisture content above monolayer zone. T-Tg (T storage - Tg prediction and reaction rate constant (k plots showed that browning reaction occurred at temperature around glass transition and increased significantly at 150 above Tg of casein. Tapioca starch in the food model was under glassy condition. The mobility of substrate increased and diffused at amorphous matrix.

  13. Intrinsic evolutions of dielectric function and electronic transition in tungsten doping Ge{sub 2}Sb{sub 2}Te{sub 5} phase change films discovered by ellipsometry at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Guo, S.; Ding, X. J.; Zhang, J. Z.; Hu, Z. G., E-mail: zghu@ee.ecnu.edu.cn; Chu, J. H. [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Ji, X. L.; Wu, L. C.; Song, Z. T. [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2015-02-02

    Tungsten (W) doping effects on Ge{sub 2}Sb{sub 2}Te{sub 5} (GSTW) phase change films with different concentrations (3.2, 7.1, and 10.8%) have been investigated by variable-temperature spectroscopic ellipsometry. The dielectric functions from 210 K to 660 K have been evaluated with the aid of Tauc-Lorentz and Drude dispersion models. The analysis of Tauc gap energy (E{sub g}) and partial spectral weight integral reveal the correlation between optical properties and local structural change. The order degree increment and chemical bond change from covalent to resonant should be responsible for band gap narrowing and electronic transition enhancement during the phase change process. It is found that the elevated crystalline temperature for GSTW can be related to improved disorder degree. Furthermore, the shrinkage of E{sub g} for GSTW should be attributed to the enhanced metallicity compared with undoped GST.

  14. Transitional Justice

    DEFF Research Database (Denmark)

    Gissel, Line Engbo

    This presentation builds on an earlier published article, 'Contemporary Transitional Justice: Normalising a Politics of Exception'. It argues that the field of transitional justice has undergone a shift in conceptualisation and hence practice. Transitional justice is presently understood to be th...

  15. A facile approach for the fabrication of 3D flower-like Cu2S nanostructures on brass mesh with temperature-induced wetting transition for efficient oil-water separation

    Science.gov (United States)

    Niu, Lei; Kang, Zhixin

    2017-11-01

    3D flower-like Cu2S nanostructures on brass meshes have been fabricated for the first time, with a reversible wetting transition and excellent durability. In the present work, we demonstrated a simple and environmentally-benign method to fabricate the nanostructures utilizing an electrolyte containing CuSO4·5H2O, EDTA-2Na and CH3CSNH2. The superhydrophobicity was achieved by drying thoroughly at 200 °C, instead of using low surface energy materials. After annealing at 300 °C for 6 min, the superhydrophobic surface was oxidized and became superhydrophilic. However, the superhydrophobicity can be restored by heating at 200 °C for several hours. In simpler terms, the reversible wetting transition is responded to the temperature. Scanning electron microscopy, X-ray diffractometer, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were employed to characterize the surfaces and analyze the wetting transition mechanism. Furthermore, different kinds of oily sewages were separated by as-prepared mesh with high separation efficiency. It is believed that this method should have a promising future in expanding the applications of copper alloys.

  16. A new face of phenalenyl-based radicals in the transition metal-free C-H arylation of heteroarenes at room temperature: trapping the radical initiatorviaC-C σ-bond formation.

    Science.gov (United States)

    Ahmed, Jasimuddin; P, Sreejyothi; Vijaykumar, Gonela; Jose, Anex; Raj, Manthan; Mandal, Swadhin K

    2017-11-01

    The radical-mediated transition metal-free approach for the direct C-H bond functionalization of arenes is considered as a cost effective alternative to transition metal-based catalysis. An organic ligand-based radical plays a key role by generating an aryl radical which undergoes a subsequent functionalization process. The design principle of the present study takes advantage of a relatively stable odd alternant hydrocarbon-based phenalenyl (PLY) radical. In this study, the first transition metal-free catalyzed direct C-H arylation of a variety of heteroarenes such as azoles, furan, thiophene and pyridine at room temperature has been reported using a phenalenyl-based radical without employing any photoactivation step. This protocol has been successfully applied to the gram scale synthesis of core moieties of bioactive molecules. The phenalenyl-based radical initiator has been characterized crystallographically by trapping it via the formation of a C-C σ-bond between the phenalenyl radical and solvent-based radical species.

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

    Science.gov (United States)

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

    2017-07-01

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

  18. Hysteresis and change of transition temperature in thin films of Fe([Me{sub 2}Pyrz]{sub 3}BH){sub 2}, a new sublimable spin-crossover molecule

    Energy Technology Data Exchange (ETDEWEB)

    Davesne, V.; Gruber, M. [Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, 67034 Cedex 2 Strasbourg (France); Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe (Germany); Studniarek, M. [Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, 67034 Cedex 2 Strasbourg (France); Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette (France); Doh, W. H.; Zafeiratos, S. [Institut de Chimie et Procédés pour l’Energie, l’Environnement et la Santé, UMR 7515 CNRS, Université de Strasbourg, 25 rue Becquerel, 67087 Cedex 2 Strasbourg (France); Joly, L.; Schmerber, G.; Bowen, M.; Weber, W.; Boukari, S.; Da Costa, V.; Arabski, J.; Beaurepaire, E. [Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, 67034 Cedex 2 Strasbourg (France); Sirotti, F.; Silly, M. G. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette (France); Gaspar, A. B.; Real, J. A. [Institut de Ciència Molecular (ICMol), Universitat de València, C/Catedrático José Beltrán Martínez 2, 46980 Paterna (València) (Spain); and others

    2015-05-21

    Thin films of the spin-crossover (SCO) molecule Fe([Me{sub 2}Pyrz]{sub 3}BH){sub 2} (Fe-pyrz) were sublimed on Si/SiO{sub 2} and quartz substrates, and their properties investigated by X-ray absorption and photoemission spectroscopies, optical absorption, atomic force microscopy, and superconducting quantum interference device. Contrary to the previously studied Fe(phen){sub 2}(NCS){sub 2}, the films are not smooth but granular. The thin films qualitatively retain the typical SCO properties of the powder sample (SCO, thermal hysteresis, soft X-ray induced excited spin-state trapping, and light induced excited spin-state trapping) but present intriguing variations even in micrometer-thick films: the transition temperature decreases when the thickness is decreased, and the hysteresis is affected. We explain this behavior in the light of recent studies focusing on the role of surface energy in the thermodynamics of the spin transition in nano-structures. In the high-spin state at room temperature, the films have a large optical gap (∼5 eV), decreasing at thickness below 50 nm, possibly due to film morphology.

  19. Effects of calcining temperatures of Eu{sup 2+} and Dy{sup 3+} ion-codoped calcia-alumina binary compounds on their phase transition and luminescence properties

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Chen-Jui, E-mail: cjliang@fcu.edu.tw; Siao, Hao-Yi

    2017-06-01

    In this study, phase evolution as a function of calcining temperature in calcia-alumina binary compound phosphors was examined to interpret their luminescence properties. The binary compounds were prepared through a coprecipitation method employing potassium carbonate as the precipitant to obtain precursors with a high-precision stoichiometric composition for the calcination. The results indicate that the morphology, surface properties, and infrared transmittance of the prepared phosphors were affected by the calcining temperature. X-ray diffraction analysis results enabled identification of Ca{sub 12}Al{sub 14}O{sub 33}, CaAl{sub 2}O{sub 4}, and CaAl{sub 4}O{sub 7} phase transitions at various calcining temperatures. The amount of the CaAl{sub 2}O{sub 4} phase increased with the calcining temperature within the range of 700–1060 °C. The Ca{sub 12}Al{sub 14}O{sub 33} and CaAl{sub 4}O{sub 7} phases exhibited trends opposite to that of the CaAl{sub 2}O{sub 4} phase. When the calcining temperature reached 980 °C, the CaAl{sub 2}O{sub 4} phase (60.5%) was determined to be the main phase in the structure, and excellent emission intensity at an emission band of 449 nm was observed as a result of the complete substitution of Eu{sup 2+} for Ca{sup 2+}. The emission intensity corresponding to Eu{sup 2+} 4f{sup 6}5d{sup 1} → 4f{sup 7} decreased slightly when the temperature reached 1060 °C because of more monoclinic reciprocal CaAl{sub 4}O{sub 7} phase (81.5%) formation, causing the transfer of some Eu{sup 2+} to Eu{sup 3+}, during which strong photoluminescence spectra of Eu{sup 3+5}D{sub 0} → {sup 7}F{sub j} (j = 0, 1, 2, 3, 4) within the wavelength range of 570–720 nm were observed. Because the strong photoluminescence spectra of the Eu{sup 2+} and Eu{sup 3+} emissions were together within the wavelength range of 449–720 nm in this phosphor, the photoluminescence was white light. One moderately intense emission band in the infrared region was observed and

  20. Low temperature vibrational spectroscopy. III. Structural aspects and detection of phase transitions in crystalline alkali metal and tetramethylammonium hexabromotellurates and platinates

    DEFF Research Database (Denmark)

    Berg, Rolf W.

    1979-01-01

    cases sharp, bands were observed at low temperatures. The spectra have been assigned, and in most cases a confirmation of previous results was obtained. The assignment ambiguity in the literature on the nu4 mode of [PtBr6]2− has been solved, placing it at ~ 130 cm−1. The majority of the new low...... of the tetramethylammonium compounds, methyl torsional IR bands were observed with increasing sharpness at lower temperatures. This behavior can be correlated with a gradual ordering of methyl torsional disorder. The potential energy barrier against methyl group rotation was found to be of the order 4–5 kcal/mol, showing...

  1. A high-temperature Raman scattering study of the phase transitions in GaPO{sub 4} and in the AlPO{sub 4}-GaPO{sub 4} system

    Energy Technology Data Exchange (ETDEWEB)

    Angot, E [Laboratoire des Colloides, des Verres et des Nanomateriaux, UMR CNRS 5587, Universite Montpellier II, cc026, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Parc, R Le [Laboratoire des Colloides, des Verres et des Nanomateriaux, UMR CNRS 5587, Universite Montpellier II, cc026, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Levelut, C [Laboratoire des Colloides, des Verres et des Nanomateriaux, UMR CNRS 5587, Universite Montpellier II, cc026, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Beaurain, M [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc003, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Armand, P [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc003, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Cambon, O [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc003, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Haines, J [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc003, Place E Bataillon, F-34095 Montpellier Cedex 5 (France)

    2006-05-03

    Al{sub 1-x}Ga{sub x}PO{sub 4} solid solutions (x = 0.2, 0.3, 0.38, 0.7) and the pure AlPO{sub 4} (x = 0) and GaPO{sub 4} (x = 1) end members with the {alpha}-quartz-type structure were studied by Raman scattering. An investigation as a function of composition enabled the various modes to be assigned, in particular coupled and decoupled vibrations. The tetrahedral tilting modes, which have been linked to high-temperature phase transitions to {beta}-quartz-type forms, were found to be decoupled. In addition, it is shown that Raman spectroscopy is a powerful technique for determining the gallium content of these solid solutions. Single crystals with x = 0.2, 0.38, and 1.0 (GaPO{sub 4}) were investigated at high temperature. The composition Al{sub 0.8}Ga{sub 0.2}PO{sub 4} was found to exhibit sequential transitions upon heating to the {beta}-quartz and {beta}-cristobalite forms at close to 993 K and 1073 K, respectively. Direct {alpha}-quartz-{beta}-cristobalite transitions were observed for the two other compositions at close to 1083 K and 1253 K, respectively, upon heating. The spectra of the {beta}-quartz and {beta}-cristobalite forms indicate the presence of significant disorder. Back transformation to the {alpha}-quartz-type form occurred readily with a hysteresis of less than 100 K for the composition x = 0.38 and for pure GaPO{sub 4}. Rapid cooling was necessary to obtain the metastable {alpha}-cristobalite form. In contrast, for Al{sub 0.80}Ga{sub 0.20}PO{sub 4}, the {alpha}-cristobalite form was obtained even upon slow cooling.

  2. Neutron diffraction and magnetic study of the low-temperature transitions in SrMo{sub 1−x}Fe{sub x}O{sub 3−δ}

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-Coronado, R., E-mail: rmartinez@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, E-28049 Madrid (Spain); Aguadero, A. [CIC Energigune, Albert Einstein 48, 01510 Alava (Spain); Alonso, J.A. [Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, E-28049 Madrid (Spain); Fernández-Díaz, M.T. [Institut Laue Langevin, BP 156X, Grenoble F-38042 (France)

    2012-09-15

    Highlights: ► SrMo{sub 1−x}Fe{sub x}O{sub 3−δ} (x = 0, 0.1, 0.2 and 0.3) were obtained as polycrystalline powders. ► Cooling, two structural transitions are identified, tetragonal and orthorhombic. ► DSC curves exhibit an endothermic peak close to 240 K. ► Magnetic behavior of the samples changes, inducing a ferromagnetic character. ► The tilt angles are appreciably high at low temperatures. -- Abstract: SrMo{sub 1−x}Fe{sub x}O{sub 3−δ} (x = 0, 0.1, 0.2 and 0.3) perovskites have recently been described as performing anode materials in solid-oxide fuel cells. In this work, we describe the structural phase transitions they undergo below room-temperature (RT), studied “in-situ” from neutron powder diffraction data and DSC measurements. At RT all the studied compositions are cubic, space group Pm-3m, with unit-cell parameters that decrease with Fe doping. Upon cooling the samples, two structural phase transitions are identified: one to a tetragonal structure with I4/mcm space group (around T{sub 1} = 240 K), and the second one to an orthorhombic Imma phase below T{sub 2} = 100 K. The magnetic properties have also been evaluated; the Fe substitution drives an evolution from a Pauli-paramagnetic state (x = 0) to a weak ferromagnetic state combined with antiferromagnetic interactions; the susceptibility and the saturation magnetization increases monotonically with increasing the Fe-doping content.

  3. Effect of Reheating Temperature and Cooling Treatment on the Microstructure, Texture, and Impact Transition Behavior of Heat-Treated Naval Grade HSLA Steel

    Science.gov (United States)

    Sk, Md. Basiruddin; Ghosh, A.; Rarhi, N.; Balamuralikrishnan, R.; Chakrabarti, D.

    2017-07-01

    In order to achieve the desired mechanical properties [YS > 390 MPa, total elongation >16 pct and Charpy impact toughness of 78 J at 213 K (-60 °C)] for naval application, samples from a low-carbon microalloyed steel have been subjected to different austenitization (1223 K to 1523 K) (950 °C to 1250 °C) and cooling treatments (furnace, air, or water cooling). The as-rolled steel and the sample air cooled from 1223 K (950 °C) could only achieve the required tensile properties, while the sample furnace cooled from 1223 K (950 °C) showed the best Charpy impact properties. Water quenching from 1223 K (950 °C) certainly contributed to the strength but affected the impact toughness. Overall, predominantly ferrite matrix with fine effective grain size and intense gamma-fiber texture was found to be beneficial for impact toughness as well as impact transition behavior. Small size and fraction of precipitates (like TiN, Nb, and V carbonitrides) eliminated the possibility of particle-controlled crack propagation and grain size-controlled crack propagation led to cleavage fracture. A simplified analytical approach has been used to explain the difference in impact transition behavior of the investigated samples.

  4. Magnetic-Field-Induced Soft-Mode Quantum Phase Transition in the High-Temperature Superconductor La1.855Sr0.145CuO4

    DEFF Research Database (Denmark)

    Chang, J.; Christensen, Niels Bech; Niedermayer, C.

    2009-01-01

    Inelastic neutron-scattering experiments on the high-temperature superconductor La1.855Sr0.145CuO4 reveal a magnetic excitation gap Delta that decreases continuously upon application of a magnetic field perpendicular to the CuO2 planes. The gap vanishes at the critical field required to induce long...

  5. Numerical analysis of ion temperature effects to the plasma wall transition using a one-dimensional two-fluid model. II. Asymptotic two-scale limit

    Science.gov (United States)

    Gyergyek, T.; Kovačič, J.

    2017-06-01

    A one-dimensional, steady state, two fluid model, presented in Part I [T. Gyergyek and J. Kovačič, Phys. Plasmas 24, 063505 (2017)] is extended to the asymptotic two-scale limit. Separate solutions in the pre-sheath and in the sheath region are presented. Ion temperature is treated as an independent parameter, which is included in the model as a boundary condition. For the pre-sheath solutions, it is shown that when the ion temperature is increased, the ion flow velocity at the boundary of the system must also be increased. A simple relationship between ion temperature and ion flow velocity at the boundary is found. This relationship is the same as the corresponding relationship found in Part I. If ion temperature is increased, both the potential drop and the density drop in the pre-sheath decrease. The same is true for the pre-sheath length. As for the solutions in the sheath scale, it is shown that the ion velocity, electron velocity, and electric field at the sheath edge must all be above a certain minimum value in order to obtain physically acceptable monotonic solutions. It is proposed to select the ion velocity at the sheath edge equal to the ion sound velocity. If, at the same time, the zero electron flow velocity at the sheath edge is selected, the electric field at the sheath edge must be larger than roughly 3 × 10-6, in order to obtain monotonic solutions of the model. The selection of the electron velocity at the sheath edge is elaborated extensively. It is concluded that increased ion temperature improves the shielding of the plasma from the electrode.

  6. Phase transitions modern applications

    CERN Document Server

    Gitterman, Moshe

    2014-01-01

    This book provides a comprehensive review of the theory of phase transitions and its modern applications, based on the five pillars of the modern theory of phase transitions i.e. the Ising model, mean field, scaling, renormalization group and universality. This expanded second edition includes, along with a description of vortices and high temperature superconductivity, a discussion of phase transitions in chemical reaction and moving systems. The book covers a close connection between phase transitions and small world phenomena as well as scale-free systems such as the stock market and the Internet. Readership: Scientists working in different fields of physics, chemistry, biology and economics as well as teaching material for undergraduate and graduate courses.

  7. Estimated phase transition and melting temperature of APTES self-assembled monolayer using surface-enhanced anti-stokes and stokes Raman scattering

    Science.gov (United States)

    Sun, Yingying; Yanagisawa, Masahiro; Kunimoto, Masahiro; Nakamura, Masatoshi; Homma, Takayuki

    2016-02-01

    A structure's temperature can be determined from the Raman spectrum using the frequency and the ratio of the intensities of the anti-Stokes and Stokes signals (the Ias/Is ratio). In this study, we apply this approach and an equation relating the temperature, Raman frequency, and Ias/Is ratio to in-situ estimation of the phase change point of a (3-aminopropyl)triethoxysilane self-assembled monolayer (APTES SAM). Ag nanoparticles were deposited on APTES to enhance the Raman signals. A time-resolved measurement mode was used to monitor the variation in the Raman spectra in situ. Moreover, the structural change in APTES SAM (from ordered to disordered structure) under heating was discussed in detail, and the phase change point (around 118 °C) was calculated.

  8. Photochemical transformation of aircraft exhausts at their transition from the plume to the large scale dispersion in the Northern temperature belt

    Energy Technology Data Exchange (ETDEWEB)

    Karol, I.L.; Kiselev, A.A. [Main Geophysical Observatory, St.Petersburg (Russian Federation)

    1997-12-31

    The 2-D diurnally varying photochemical model of the Northern temperate zonal tropospheric belt with fixed (off line) temperature and air transport is used for the description of the formation of aircraft exhaust concentration distribution in the North Atlantic commercial flight corridor, based on actual flights in summer and winter. A strong diurnal and seasonal variation of emitted NO{sub x} oxidation rate is revealed and evaluated. (author) 11 refs.

  9. Evaluation of Arctic land snow cover characteristics, surface albedo and temperature during the transition seasons from regional climate model simulations and satellite data

    OpenAIRE

    Zhou, X.(Wuhan University, Wuhan, 430072, People's Republic of China); Matthes, H.; Rinke, A.; K. Klehmet; B. Heim; Dorn, W.; D. Klaus; K. Dethloff; Rockel, B.

    2014-01-01

    This paper evaluates the simulated Arctic land snow cover duration, snow water equivalent, snow cover fraction, surface albedo and land surface temperature in the regional climate model HIRHAM5 during 2008-2010, compared with various satellite and reanalysis data and one further regional climate model (COSMO-CLM). HIRHAM5 shows a general agreement in the spatial patterns and annual course of these variables, although distinct biases for specific regions and months are obvious. The most promin...

  10. Optoelectronic properties and interband transition of La-doped BaSnO3 transparent conducting films determined by variable temperature spectral transmittance

    Science.gov (United States)

    Xing, S. M.; Shan, C.; Jiang, K.; Zhu, J. J.; Li, Y. W.; Hu, Z. G.; Chu, J. H.

    2015-03-01

    Perovskite-structured Ba1-xLaxSnO3 (x = 0-0.10) films have been directly grown on (0001) sapphire substrates by a sol-gel method. Optical properties and bandgap energy of the films have been investigated by transmittance spectra from 10 K to 450 K. It indicates that these films exhibit a high transmission of more than 80% in the visible region. With increasing temperature, there is a significant bandgap shrinkage of about 0.5 eV for lightly La doping (x ≤ 0.04) films. For heavily La doping concentration (x ≥ 0.06), the bandgap remains nearly stable with the temperature and La composition. This is due to the fact that the lattice expansion caused by La doping is close to the saturation for the film doped with x = 0.06. Moreover, temperature dependent conductivity behavior shows a similar pattern, which suggests that the doping concentration of La-doped BaSnO3 (BLSO) films has a saturated state. The La introduction can modify the Sn 5s-O 2p antibonding state and the nonbonding O 2p orbital, which remarkably affect the electronic bandgap of the BLSO films.

  11. Evaluation of Arctic Land Snow Cover Characteristics, Surface Albedo, and Temperature during the Transition Seasons from Regional Climate Model Simulations and Satellite Data

    Directory of Open Access Journals (Sweden)

    X. Zhou

    2014-01-01

    Full Text Available This paper evaluates the simulated Arctic land snow cover duration, snow water equivalent, snow cover fraction, surface albedo, and land surface temperature in the regional climate model HIRHAM5 during 2008–2010, compared with various satellite and reanalysis data and one further regional climate model (COSMO-CLM. HIRHAM5 shows a general agreement in the spatial patterns and annual course of these variables, although distinct biases for specific regions and months are obvious. The most prominent biases occur for east Siberian deciduous forest albedo, which is overestimated in the simulation for snow covered conditions in spring. This may be caused by the simplified albedo parameterization (e.g., nonconsideration of different forest types and neglecting the effect of fallen leaves and branches on snow for deciduous tree forest. The land surface temperature biases mirror the albedo biases in their spatial and temporal structures. The snow cover fraction and albedo biases can explain the simulated land surface temperature bias of ca. −3°C over the Siberian forest area in spring.

  12. Small angle X-ray scattering study of poly(N-isopropyl acrylamide) based cryogels near the volume-phase transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Chalal, Mohand [Laboratoire d' Electronique Quantique, Faculte de Physique, USTHB Alger, 16111 Alger (Algeria); Ehrburger-Dolle, Francoise; Morfin, Isabelle [Laboratoire de Spectrometrie Physique, UMR 5588 CNRS/UJF, 38402 Saint Martin d' Heres (France); Armas, Maria-Rosa Aguilar de; Lopez, Maria-Luisa [Instituto de Ciencia y TecnologIa de PolImeros, CSIC and CIBER-BBN, 28006 Madrid (Spain); Bley, Francoise, E-mail: francoise.ehrburger-dolle@ujf-grenoble.f [Science et Ingenierie des Materiaux et Procedes, UMR 5266 CNRS/INPG/UJF, 38402 Saint Martin d' Heres (France)

    2010-10-01

    The structural modifications induced by changes in temperature are investigated by Small-Angle X-ray Scattering (SAXS) over a broad range of q-values (3.5x10{sup -2} - 12 nm{sup -1}) in cryogels based on N-isopropylacrylamide (NIPA) and/or 2-Hydroxyethyl methacrylate-L-Lactide-Dextran (HEMA-LLA-D) macromer. Various copolymeric cryogels of these two monomers are prepared by cryopolymerization yielding macroporous gels (cryogels). For the plain pNIPA cryogel, the SAXS curves obtained at each temperature are well fitted by a sum of four equations describing respectively the scattering resulting from the gel surface (power law), from the solid-like (Guinier equation) and liquid-like (Ornstein-Zernike equation) heterogeneities and from the chain-chain correlation yielding a broad peak (pseudo-Voigt equation) in the high-q domain. The temperature dependence of the parameters obtained from the fit is analyzed and discussed. It is shown that the existence of an isoscattering (or isosbestic) point observed in pNIPA gels and in some copolymers is related to features observed by Differential Scanning Calorimetry and swelling ratio measurements.

  13. Monolayer of the 5 d transition metal trichloride OsCl3: A playground for two-dimensional magnetism, room-temperature quantum anomalous Hall effect, and topological phase transitions

    Science.gov (United States)

    Sheng, Xian-Lei; Nikolić, Branislav K.

    2017-05-01

    Based on density functional theory (DFT) calculations, we predict that a monolayer of OsCl3 (which is a layered material whose interlayer coupling is weaker than in graphite) possesses a quantum anomalous Hall (QAH) insulating phase generated by the combination of honeycomb lattice of osmium atoms, their strong spin-orbit coupling (SOC), and ferromagnetic ground state with in-plane easy axis. The band gap opened by SOC is Eg≃67 meV (or ≃191 meV if the easy axis can be tilted out of the plane by an external electric field), and the estimated Curie temperature of such an anisotropic planar rotator ferromagnet is TC≲350 K. The Chern number C =-1 , generated by the manifold of Os t2 g bands crossing the Fermi energy, signifies the presence of a single chiral edge state in nanoribbons of finite width, where we further show that edge states are spatially narrower for zigzag than armchair edges and investigate edge-state transport in the presence of vacancies at Os sites. Since 5 d electrons of Os exhibit both strong SOC and moderate correlation effects, we employ DFT+U calculations to show how increasing on-site Coulomb repulsion U : gradually reduces Eg while maintaining C =-1 for 0 insulating phase with C =0 for U >Uc .

  14. LASER EMISSIONS FROM CO2 VIBRATIONAL TRANSITIONS IN A LOW TEMPERATURE SUPERSONIC FLOW EXCITED BY A PULSED ELECTRON BEAM STABILIZED DISCHARGE

    OpenAIRE

    Fontaine, B.; Forestier, B.; Gross, P.; Koudriavtsev, E.

    1980-01-01

    High power long pulse infrared laser emission has been achieved on CO2 molecule with the high density and very low temperature supersonic flow-electron beam-stabilized discharge excitation device developped at I.M.F.M. ([MATH] [MATH] 2 amagats, T [MATH] 70 - 150 K). Laser emission at [MATH] = 10.6 µ has been achieved for a resonant cavity set at the discharge location and also 3 cm downstream of the discharge location. With Ar/CO2, Ar/CO2/H2, He/CO2, and He/CO2/N2 mixtures, lasing energy and ...

  15. A macroscopic constitutive model of temperature-induced phase transition of polycrystalline Ni{sub 2}MnGa by directional solidification

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Yuping, E-mail: zhuyuping@126.com; Gu, Yunling; Liu, Hongguang

    2015-02-25

    Directional solidification technology has been widely used to improve the properties of polycrystalline Ni{sub 2}MnGa materials. Mechanical training can adjust the internal organizational structures of the materials, reduce the stress of twin boundaries motion, and then result in larger strain at lower outfield levels. In this paper, we test the microscopic structure of Ni{sub 2}MnGa polycrystalline ferromagnetic shape memory alloy produced by directional solidification and compress it along two axes successively for mechanical training. The influences of pre-compressive stresses on the temperature-induced strains are analyzed. The macroscopic mechanical behaviors show anisotropy. According to the generating mechanism of the macroscopic strain, a three-dimensional constitutive model is established. Based on thermodynamic method, the kinetic equations of the martensitic transformation and inverse transformation are presented considering the driving force and energy dissipation. The prediction curves of temperature-induce strains along two different directions are investigated. And the results coincide well with the experiment data. It well explains the macroscopic anisotropy mechanical behaviors and fits for using in engineering.

  16. Transitional Care

    Science.gov (United States)

    Naylor, Mary; Keating, Stacen A.

    2008-01-01

    Transitional care encompasses a broad range of services and environments designed to promote the safe and timely passage of patients between levels of health care and across care settings. High-quality transitional care is especially important for older adults with multiple chronic conditions and complex therapeutic regimens, as well as for their…

  17. An x-ray powder diffraction study of the high temperature phase transitions in {alpha}-quartz-type AlPO{sub 4}-GaPO{sub 4} solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Haines, J [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc 003, Place E Bataillon, F-34095 Montpellier, Cedex 5 (France); Cambon, O [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc 003, Place E Bataillon, F-34095 Montpellier, Cedex 5 (France); Fraysse, G [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc 003, Place E Bataillon, F-34095 Montpellier, Cedex 5 (France); Lee, A van der [Institut Europeen des Membranes de Montpellier, UMR-CNRS 5635, Universite Montpellier II, cc 047, 300 Avenue Prof. E Jeanbrau, F-34095 Montpellier, Cedex 5 (France)

    2005-07-20

    Al{sub 1-x}Ga{sub x}PO{sub 4} solid solutions (x = 0.3, 0.7) with the {alpha}-quartz-type structure were investigated up to 1208 K by x-ray powder diffraction. The composition Al{sub 0.7}Ga{sub 0.3}PO{sub 4} exhibits almost simultaneous transitions to the {beta}-quartz and {beta}-cristobalite forms at close to 1050 K. The tendency towards the {beta}-quartz type structure is found to be much less marked for the Ga-rich composition (x = 0.7) based on the temperature dependence of the cell parameters, molar volume, fractional atomic coordinates and tetrahedral tilt angle. Direct transformation to the {beta}-cristobalite form begins close to 1123 K. The {beta}-quartz form exists as a stable phase only for values below x = 0.3.

  18. Low-temperature transitions in the SrMo{sub 1−x}Cr{sub x}O{sub 3−δ} (x = 0.1 and 0.2) perovskite system

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-Coronado, R., E-mail: rmartinez@icmm.csic.es [Texas Materials Institute and Materials Science and Engineering Program, The University of Texas at Austin, Austin, TX 78712 (United States); Alonso, J.A. [Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, E-28049 Madrid (Spain); Fernández-Díaz, M.T. [Institut Laue Langevin, BP 156X, Grenoble F-38042 (France)

    2014-09-01

    Highlights: • Neutron diffraction study of SrMo{sub 1−x}Cr{sub x}O{sub 3−δ} (x = 0.1 and 0.2) oxides. • Cooling, two structural transitions are identified, tetragonal and orthorhombic. • DSC curves exhibits an endothermic peak close to 240 K. • Magnetic behavior of the samples changes, inducing a ferromagnetic character. • The tilt angles are appreciably high at low temperatures. - Abstract: In this paper we have studied the effect of Cr doping on the structural and electronic transport properties in 4d perovskites SrMo{sub 1−x}Cr{sub x}O{sub 3} (x = 0, 0.1 and 0.2). Polycrystalline samples were prepared by a soft chemistry procedure followed by thermal treatments in a 5%H{sub 2} atmosphere. X-ray and neutron powder diffraction analysis were used to identify the purity of the samples and provide an accurate description of the crystal structure features (GdFeO{sub 3} type). The Cr doping at B position does not change the space group of the samples; they are all cubic, space group Pm-3m, at room temperature. However, upon cooling down the samples two structural phase transitions appear, the first from cubic Pm-3m structure to a tetragonal structure defined in I4/mcm close to 240 K, and the second to an orthorhombic Imma phase below 100 K. Cr substitution drives the SrMo{sub 1−x}Cr{sub x}O{sub 3} system from a Pauli-paramagnetic state to a weak ferromagnetic state combined with predominant antiferromagnetic interactions; the susceptibility and the saturation magnetization increases monotonically with increasing the Cr-doping content.

  19. Temperature dependence of local structural changes around transition metal centers Cr3+ and Mn2+ in RAl3(BO3)4 crystals studied by EMR

    Science.gov (United States)

    Açıkgöz, Muhammed; Rudowicz, Czesław; Gnutek, Paweł

    2017-11-01

    Theoretical investigations are carried out to determine the temperature dependence of the local structural parameters of Cr3+ and Mn2+ ions doped into RAl3(BO3)4 (RAB, R = Y, Eu, Tm) crystals. The zero-field splitting (ZFS) parameters (ZFSPs) obtained from the spin Hamiltonian (SH) analysis of EMR (EPR) spectra serve for fine-tuning the theoretically predicted ZFSPs obtained using the semi-empirical superposition model (SPM). The SPM analysis enables to determine the local structure changes around Cr3+ and Mn2+ centers in RAB crystals and explain the observed temperature dependence of the ZFSPs. The local monoclinic C2 site symmetry of all Al sites in YAB necessitates consideration of one non-zero monoclinic ZFSP (in the Stevens notation, b21) for Cr3+ ions. However, the experimental second-rank ZFSPs (D =b20 , E = 1 / 3b22) were expressed in a nominal principal axis system. To provide additional insight into low symmetry aspects, the distortions (ligand's distances ΔRi and angular distortions Δθi) have been varied while preserving monoclinic site symmetry, in such way as to obtain the calculated values (D, E) close to the experimental ones, while keeping b21 close to zero. This procedure yields good matching of the calculated ZFSPs and the experimental ones, and enables determination of the corresponding local distortions. The present results may be useful in future studies aimed at technological applications of the Huntite-type borates with the formula RM3(BO3)4. The model parameters determined here may be utilized for ZFSP calculations for Cr3+ and Mn2+ ions at octahedral sites in single-molecule magnets and single-chain magnets.

  20. Electroweak phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Gregory W. [Univ. of California, Berkeley, CA (United States)

    1991-09-16

    An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, <Φ>T is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of <Φ>T. In very minimal extensions of the standard model it is quite easy to increase <Φ>T so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value <Φ> = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state <Φ> = 246 GeV unstable. The requirement that the state <Φ> = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.

  1. Structural Transition in Supercritical Fluids

    Directory of Open Access Journals (Sweden)

    Boris I. Sedunov

    2011-01-01

    Full Text Available The extension of the saturation curve ( on the PT diagram in the supercritical region for a number of monocomponent supercritical fluids by peak values for different thermophysical properties, such as heat capacities and and compressibility has been studied. These peaks signal about some sort of fluid structural transition in the supercritical region. Different methods give similar but progressively diverging curves st( for this transition. The zone of temperatures and pressures near these curves can be named as the zone of the fluid structural transition. The outstanding properties of supercritical fluids in this zone help to understand the physical sense of the fluid structural transition.

  2. High temperature spin state transitions in misfit-layered Ca{sub 3}Co{sub 4}O{sub 9}

    Energy Technology Data Exchange (ETDEWEB)

    Altin, S.; Aksan, M.A., E-mail: mehmet.aksan@inonu.edu.tr; Bayri, A.

    2014-02-25

    Highlights: • Ca{sub 3}Co{sub 4}O{sub 9} system has been fabricated using the solid-state technique. • There is an anomaly in magnetic the susceptibility χ between 680 and 920 K. • The anomaly is related to a critical threshold number of the high spin Co-ions. • The anomaly was also observed in the B and Sb-substituted Ca{sub 3}Co{sub 4}O{sub 9}. -- Abstract: This study reports high temperature magnetic properties of the unsubstituted one together with B and Sb-substituted Ca{sub 3}Co{sub 4}O{sub 9} system. The measured data indicated that there is an anomaly in the magnetic susceptibility, χ, between 680 and 920 K. It is believed that this anomaly is related to a critical threshold number of the high spin Co-ions such that when this threshold number is achieved, some exchange interactions between Co{sup 3+} and Co{sup 4+} take place which causes an abrupt increase in the χ–T curve. The anomaly was further investigated with B and Sb-substitutions. It is realized that both dopants promote more Co-ions in the rock salt unit cell to high spin state.

  3. Rate coefficients of the CF3CHFCF3 + H → CF3CFCF3 + H2 reaction at different temperatures calculated by transition state theory with ab initio and DFT reaction paths.

    Science.gov (United States)

    Ng, Maggie; Mok, Daniel K W; Lee, Edmond P F; Dyke, John M

    2013-03-15

    The minimum energy path (MEP) of the reaction, CF(3)CHFCF(3) + H → transition state (TS) → CF(3)CFCF(3) + H(2), has been computed at different ab initio levels and with density functional theory (DFT) using different functionals. The computed B3LYP/6-31++G**, BH&HLYP/cc-pVDZ, BMK/6-31++G**, M05/6-31+G**, M05-2X/6-31+G**, UMP2/6-31++G**, PUMP2/6-31++G**//UMP2/6-31++G**, RCCSD(T)/aug-cc-pVDZ//UMP2/6-31++G**, RCCSD(T)/aug-cc-pVTZ(spd,sp)//UMP2//6-31++G**, RCCSD(T)/CBS//M05/6-31+G**, and RCCSD(T)/CBS//UMP2/6-31++G** MEPs, and associated gradients and Hessians, were used in reaction rate coefficient calculations based on the transition state theory (TST). Reaction rate coefficients were computed between 300 and 1500 K at various levels of TST, which include conventional TST, canonical variational TST (CVT) and improved CVT (ICVT), and with different tunneling corrections, namely, Wigner, zero-curvature, and small-curvature (SCT). The computed rate coefficients obtained at different ab initio, DFT and TST levels are compared with experimental values available in the 1000-1200 K temperature range. Based on the rate coefficients computed at the ICVT/SCT level, the highest TST level used in this study, the BH&HLYP functional performs best among all the functionals used, while the RCCSD(T)/CBS//MP2/6-31++G** level is the best among all the ab initio levels used. Comparing computed reaction rate coefficients obtained at different levels of theory shows that, the computed barrier height has the strongest effect on the computed reaction rate coefficients as expected. Variational effects on the computed rate coefficients are found to be negligibly small. Although tunneling effects are relatively small at high temperatures (~1500 K), SCT corrections are significant at low temperatures (~300 K), and both barrier heights and the magnitudes of the imaginary frequencies affect SCT corrections. Copyright © 2012 Wiley Periodicals, Inc.

  4. Transitional determinacies.

    Science.gov (United States)

    Luelsdorff, P A

    1992-01-01

    In classic generative grammar a distinction is drawn between linguistic 'competence' and linguistic 'performance', the former referring to linguistic knowledge, the latter to how linguistic knowledge is used. However, this controversial differentiation obscures the additional dichotomy between linguistic knowledge for production and linguistic knowledge for recognition. In this article it is shown that production and recognition differ, that recognition is not simply the inverse of production, and that the derivation of production from recognition and recognition from production require a small set of generalizable 'transitional determinacies'. Secondly, it is shown that transitional determinacies explain the difference between 'overt' and 'covert' recognition recently observed in prosopagnosics, patients unable to recognize familiar faces. Prosopagnosics and normals are found to differ in their transitional determinacies, such that prosopagnosics require more binders (precisors) for covert recognition than normals. In general, it is concluded that transitional determinacies are as necessary to the theory of grammar as determinacies themselves.

  5. Effects of helium on ductile brittle transition behavior of reduced activation ferritic steels after high concentration he implantation at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, A.; Ejiri, M.; Nogami, S.; Ishiga, M.; Abe, K. [Tohoku Univ., Dept. of Quantum Science and Energy Engr, Sendai (Japan); Kasada, R.; Kimura, A. [Kyoto Univ., Institute of Advanced Energy (Japan); Jitsukawa, S. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan)

    2007-07-01

    Full text of publication follows: Influence of Helium (He) on fracture behavior of reduced activation ferritic/martensitic steels including Oxide Dispersion Strengthening (ODS) steels and F82H were examined. To study the He effects on fracture behavior of these steels after He bubble formation conditions, higher concentration of He implantation at around 550 C were performed and examined the relationship between microstructure evolution and fracture behavior of the steels. The 1.5CVN mini size Charpy specimens were used to evaluate impact test behavior. Reduced activation ferritic ODS steels, 9Cr-ODS and 12Cr-ODS steels were examine. F82H was also examined as reference material. Helium implantation was performed by a cyclotron of Tohoku University with a beam of 50 MeV {alpha}-particles at temperature around 550 C. A tandem-type energy degrader system was used to implant He into the specimen from the irradiated surface to the range of 50 MeV {alpha}-particles, that was about 380 {mu}m in iron. Implanted He concentration were about 1000 appm. Charpy impact test was performed using a instrumented impact test apparatus in Oarai branch of IMR, Tohoku University. Analyses of absorbed energy change and fracture surface were carried out. Vickers hardness test was also carried out on He implanted area of the 1.5CVN specimen to estimate irradiation hardening. Microstructural observation was performed by TEM. In the case of F82H, DBTT increased by the 1000 appm He implantation condition was about 80 C and grain boundary fracture surface was only observed in the He implanted area of all the ruptured specimens in brittle manner. On the other hand, DBTT shift and fracture mode change of He implanted 9Cr-ODS steel was not observed after He implantation. Microstructural observation showed that He bubble formation on the lath boundaries and grain boundaries were significant in F82H, but the bubble segregation on grain boundary in ODS steel was not apparent. The bubble formation

  6. Understanding quantum phase transitions

    CERN Document Server

    Carr, Lincoln

    2010-01-01

    Quantum phase transitions (QPTs) offer wonderful examples of the radical macroscopic effects inherent in quantum physics: phase changes between different forms of matter driven by quantum rather than thermal fluctuations, typically at very low temperatures. QPTs provide new insight into outstanding problems such as high-temperature superconductivity and display fundamental aspects of quantum theory, such as strong correlations and entanglement. Over the last two decades, our understanding of QPTs has increased tremendously due to a plethora of experimental examples, powerful new numerical meth

  7. Effect of He pressure on the superconducting transition temperatures of Na{sub 2}CsC{sub 60} and (NH{sub 3}){sub 4}Na{sub 2}CsC{sub 60}

    Energy Technology Data Exchange (ETDEWEB)

    Schirber, J.E.; Bayless, W.R. [Sandia National Labs., Albuquerque, NM (United States); Rosseinsky, M.J.; Zhou, O.; Fleming, R.M.; Murphy, D. [AT and T Bell Labs., Murray Hill, NJ (United States); Fischer, J.E. [Pennsylvania Univ., Philadelphia, PA (United States)

    1994-12-31

    The Na based mixed alkali doped C{sub 60} superconductors show anomalous behavior with respect to the ``universal`` superconducting transition temperature {Tc} vs lattice constant a{sub 0} relation followed by most of the fcc A{sub 3}C{sub 60} superconductors. We have measured dt{sub c}/dP for Na{sub 2}CsC{sub 60} and (NH{sub 3}){sub 4}Na{sub 2}CsC{sub 60} using solid He as the pressure medium to {approximately} 6 kbar finding dT{sub c}/dP equal to {minus}0.8{plus_minus}(0.01) K/kbar and {minus}1.0({plus_minus}0.1)K/kbar for Na{sub 2}CsC{sub 60} and Na{sub 2}(NH{sub 3}){sub 4}C{sub 60} respectively. Our value for Na{sub 2}CsC{sub 60} differs markedly from that obtained by Mizuki et al of about {minus}1.3 K/kbar. However, using N{sub 2} or Ar, we obtain values for dT{sub c}/dP in substantial agreement with Mizuki et al who used fluorinert to generate their pressure. This work emphasizes the need for compressibility measurements with the same pressure medium in the appropriate temperature range so that meaningful comparisons can be made between various pressure measurements and models which are based on lattic spacing.

  8. Size reduction effect on the critical behavior near the paramagnetic to ferromagnetic phase transition temperature in La0.9Sr0.1MnO3 nanoparticles

    Science.gov (United States)

    Baaziz, H.; Tozri, A.; Dhahri, E.; Hlil, E. K.

    2015-04-01

    The critical behavior of La0.9Sr0.1MnO3 nanoparticles, annealed at different temperatures (H6, H8, H10 and H12 annealed at 600 °C, 800 °C, 1000 °C, 1200 °C, respectively), has been investigated by magnetization measurements. Indeed, the magnetic data indicate that the compound exhibits a continuous (second-order) paramagnetic (PM) to ferromagnetic (FM) phase transition. The critical exponents are estimated by various techniques such as the Modified Arrott plot, Kouvel-Fisher plot and critical isotherm technique. Compared to standard models, the critical exponent values determined in our work are close to those expected for the mean-field model (with β=0.5, γ=1, and δ=3) (H8, H10, and H12). Concerning the sample having a smaller crystallite size (H6), the obtained values of the critical exponents β and δ are similar to those predicted by the mean-field model. However, the value of γ shows a (3D) Heisenberg model-like. This behavior, which is quite new and surprising, shows that the reduction of grain size strongly influences the universality class. Moreover, the decrease of the critical exponents (β, γ, δ) with the increase of grain size has been explained by crossover phenomenon. This result and the other obtained values are explained taking into account the contribution of uncompensated spins at the surface, strain anisotropies, and noncollinear magnetic ordering.

  9. The Strongly Interacting Electroweak Phase Transition

    OpenAIRE

    Bergerhoff, B.; Wetterich, C

    1994-01-01

    A quantitative discussion of nonperturbative effects for the high temperature electroweak phase transition is presented. We propose a method for the computation of the temperature dependent effective scalar potential that takes into account the running of the effective gauge coupling. Compared to perturbation theory we find a moderate decrease of the critical temperature and an important change in the strength of the first order transition. We conclude that perturbation theory gives a mislead...

  10. Transition metals in superheat melts

    Science.gov (United States)

    Jakes, Petr; Wolfbauer, Michael-Patrick

    1993-01-01

    A series of experiments with silicate melts doped with transition element oxides was carried out at atmospheric pressures of inert gas at temperatures exceeding liquidus. As predicted from the shape of fO2 buffer curves in T-fO2 diagrams the reducing conditions for a particular oxide-metal pair can be achieved through the T increase if the released oxygen is continuously removed. Experimental studies suggest that transition metals such as Cr or V behave as siderophile elements at temperatures exceeding liquidus temperatures if the system is not buffered by the presence of other oxide of more siderophile element. For example the presence of FeO prevents the reduction of Cr2O3. The sequence of decreasing siderophility of transition elements at superheat conditions (Mo, Ni, Fe, Cr) matches the decreasing degree of depletion of siderophile elements in mantle rocks as compared to chondrites.

  11. Electroweak phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, G.W.

    1991-09-16

    An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, {l angle}{phi}{r angle}{sub T} is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of {l angle}{phi}{r angle}{sub T}. In very minimal extensions of the standard model it is quite easy to increase {l angle}{phi}{r angle}{sub T} so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value {l angle}{phi}{r angle} = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state {l angle}{phi}{r angle} = 246 GeV unstable. The requirement that the state {l angle}{phi}{r angle} = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.

  12. Interfacial stick–slip transition in hydroxyapatite filled high density ...

    Indian Academy of Sciences (India)

    Effect of filler addition and temperature on the stick–slip transition in high density polyethylene melt was studied. Results showed that shear stresses corresponding to stick–slip transition increases with the addition of filler. Increase in temperature also increases the shear stresses for stick–slip transition. The features of the ...

  13. Presidential Transitions

    Science.gov (United States)

    2006-06-09

    done to facilitate the transition.52 CRS-12 53 David T. Stanley, Changing Administrations (Washington: Brookings Institution, 1965), p. 6. 54 “Pre...Conference of Mayors; Sharleen Hirsch, an educational administrator; and Jule Sugarman , a public administrator. Staff members were assigned to task forces...Issues,” Washington Post, Nov. 13, 1980, p. Al. 77 David Hoffman, “Bush Names Baker Secretary of State,” Washington Post, Nov. 10, 1988, pp. Al and

  14. Phase transition to QGP matter : confined vs deconfined matter

    CERN Multimedia

    Maire, Antonin

    2015-01-01

    Simplified phase diagram of the nuclear phase transition, from the regular hadronic matter to the QGP phase. The sketch is meant to describe the transition foreseen along the temperature axis, at low baryochemical potential, µB.

  15. Characterization of the insulator barrier and the superconducting transition temperature in GdBa{sub 2}Cu{sub 3}O{sub 7−δ}/BaTiO{sub 3} bilayers for application in tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, H., E-mail: henrynavarro@cab.cnea.gov.ar; Sirena, M.; Haberkorn, N. [Instituto Balseiro, Universidad Nacional de Cuyo and CNEA, 8400 Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica. Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Yang, Ilkyu [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); Kim, Jeehoon [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); CALDES, Institute for Basic Science, Pohang (Korea, Republic of)

    2015-07-28

    The optimization of the superconducting properties in a bottom electrode and the quality of an insulator barrier are the first steps in the development of superconductor/insulator/superconductor tunnel junctions. Here, we study the quality of a BaTiO{sub 3} tunnel barrier deposited on a 16 nm thick GdBa{sub 2}Cu{sub 3}O{sub 7−δ} thin film by using conductive atomic force microscopy. We find that the tunnel current is systematically reduced (for equal applied voltage) by increasing the BaTiO{sub 3} barrier thickness between 1.6 and 4 nm. The BaTiO{sub 3} layers present an energy barrier of ≈1.2 eV and an attenuation length of 0.35–0.5 nm (depending on the applied voltage). The GdBa{sub 2}Cu{sub 3}O{sub 7−δ} electrode is totally covered by a BaTiO{sub 3} thickness above 3 nm. The presence of ferroelectricity was verified by piezoresponse force microscopy for a 4 nm thick BaTiO{sub 3} top layer. The superconducting transition temperature of the bilayers is systematically suppressed by increasing the BaTiO{sub 3} thickness. This fact can be associated with stress at the interface and a reduction of the orthorhombicity of the GdBa{sub 2}Cu{sub 3}O{sub 7−δ}. The reduction in the orthorhombicity is expected by considering the interface mismatch and it can also be affected by reduced oxygen stoichiometry (poor oxygen diffusion across the BaTiO{sub 3} barrier)

  16. Rapid transitions

    Energy Technology Data Exchange (ETDEWEB)

    Hamrin, J.G.

    1980-01-01

    Solar energy programs are entering a critical transitional period as we move from the initial marketing of solar technologies into a phase of widespread commercialization. We face the dual challenge of trying to get enough solar systems in place fast enough to prove solar is a viable alternative, while trying to ensure the systems are designed and installed properly, proving the energy savings as promised. This is a period of both great opportunity and high risk as the field becomes crowded with new solar cheerleaders and supporters but seldom enough competent players. The status of existing and proposed programs for the accelerated commercialization of solar energy in California is described.

  17. Transit space

    DEFF Research Database (Denmark)

    Raahauge, Kirsten Marie

    2008-01-01

    This article deals with representations of one specific city, Århus, Denmark, especially its central district. The analysis is based on anthropological fieldwork conducted in Skåde Bakker and Fedet, two well-off neighborhoods. The overall purpose of the project is to study perceptions of space...... and the interaction of cultural, social, and spatial organizations, as seen from the point of view of people living in Skåde Bakker and Fedet. The focus is on the city dwellers’ representations of the central district of Århus with specific reference to the concept of transit space. When applied to various Århusian...

  18. Symmetry structure and phase transitions

    Indian Academy of Sciences (India)

    ... symmetry structure at finite density and temperature in the presence of external magnetic field and gravity, a situation relevant in the early Universe and in the core of compact stars. We then investigate the dynamical evolution of phase transition in the expanding early Universe and possible formation of quark nuggets and ...

  19. Phase transition in nonlinear viscous cosmology

    Science.gov (United States)

    Novello, M.; Duque, S. L. S.; Triay, R.; Fliche, H. H.

    1993-04-01

    A simple example of a phase transition process describing the isotropization of a universe of Bianchi type is outlined. Such a mechanism is induced by a self-gravitating fluid, and it operates as described by Landau's phase transition. The expansion factor (the Hubble constant) plays the part of the control parameter as the temperature does for ordinary matter.

  20. The Structural Phase Transition in Solid DCN

    DEFF Research Database (Denmark)

    Dietrich, O. W.; Mackenzie, Gordon A.; Pawley, G. S.

    1975-01-01

    Neutron scattering measurements on deuterated hydrogen cyanide have shown that the structural phase change from a tetragonal to an orthorhombic form at 160K is a first-order transition. A transverse acoustic phonon mode, which has the symmetry of the phase change, was observed at very low energies...... and showed 'softening' as the transition temperature was approached from above....

  1. Rheological diagnostic tools for state transitions

    Energy Technology Data Exchange (ETDEWEB)

    McKenzie, Ruel [Institute of Electronic Structure and Laser, Foundation for Research and Technology—Hellas (FORTH), N. Plastira 100, 70013 Heraklion, Crete (Greece); Vlassopoulos, Dimitris, E-mail: dvlasso@iesl.forth.gr [Institute of Electronic Structure and Laser, Foundation for Research and Technology—Hellas (FORTH), N. Plastira 100, 71103 Heraklion, Crete, Greece and Department of Materials Science and Technology, University of Crete, P. O. Box 2208, 70013 Heraklion, Crete (Greece)

    2016-05-15

    Thermodynamic or kinetic state transitions of six polymeric systems were probed using rheology in isothermal and nonisothermal isochronal experiments. The polymeric systems were representative of three different types of transitions: Gelation, macrophase separation, and order-disorder transitions. A phenomenological dimensionless parameter termed the relative elasticity, R, was found to be particularly sensitive to these transitions and was finitely bound by the viscous limit and the elastic limit with values of zero and one, respectively. In addition, the (time or temperature) derivative of R and tan δ (with δ being the phase angle) proved to be more sensitive to transitions as compared to the respective pure values. When compared to other methods found in literature, these new phenomenological protocols are found to be robust while providing a convenient and precise means of detecting transitions. Hence, they may complement existing methods, whereas they are beneficial to industrial or other systems exhibiting multiple transitions due to their high sensitivity.

  2. Point defects in Cu 2 ZnSnSe 4 (CZTSe): Resonant X-ray diffraction study of the low-temperature order/disorder transition: Point defects in Cu 2 ZnSnSe 4 (CZTSe)

    Energy Technology Data Exchange (ETDEWEB)

    Schelhas, L. T. [Applied Energy Programs, SLAC National Accelerator Laboratory, Menlo Park California 94025 USA; Stone, K. H. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park California 94025 USA; Harvey, S. P. [National Renewable Energy Laboratory, Golden Colorado 80401 USA; Zakhidov, D. [Materials Science and Engineering Department, Stanford University, Stanford CA 94305 USA; Salleo, A. [Materials Science and Engineering Department, Stanford University, Stanford CA 94305 USA; Teeter, G. [National Renewable Energy Laboratory, Golden Colorado 80401 USA; Repins, I. L. [National Renewable Energy Laboratory, Golden Colorado 80401 USA; Toney, M. F. [Applied Energy Programs, SLAC National Accelerator Laboratory, Menlo Park California 94025 USA; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park California 94025 USA

    2017-07-25

    The interest in Cu2ZnSn(S,Se)4 (CZTS) for photovoltaic applications is motivated by similarities to Cu(In,Ga)Se2 while being comprised of non-toxic and earth abundant elements. However, CZTS suffers from a Voc deficit, where the Voc is much lower than expected based on the band gap, which may be the result of a high concentration of point-defects in the CZTS lattice. Recently, reports have observed a low-temperature order/disorder transition by Raman and optical spectroscopies in CZTS films and is reported to describe the ordering of Cu and Zn atoms in the CZTS crystal structure. To directly determine the level of Cu/Zn ordering, we have used resonant-XRD, a site, and element specific probe of long range order. We used CZTSe films annealed just below and quenched from just above the transition temperature; based on previous work, the Cu and Zn should be ordered and highly disordered, respectively. Our data show that there is some Cu/Zn ordering near the low temperature transition but significantly less than high chemical order expected from Raman. To understand both our resonant-XRD results and the Raman results, we present a structural model that involves antiphase domain boundaries and accommodates the excess Zn within the CZTS lattice.

  3. Low-temperature high magnetic field powder x-ray diffraction setup for field-induced structural phase transition studies from 2 to 300 K and at 0 to 8-T field

    Science.gov (United States)

    Shahee, Aga; Sharma, Shivani; Kumar, Dhirendra; Yadav, Poonam; Bhardwaj, Preeti; Ghodke, Nandkishor; Singh, Kiran; Lalla, N. P.; Chaddah, P.

    2016-10-01

    A low-temperature and high magnetic field powder x-ray diffractometer (XRD) has been developed at UGC-DAE CSR (UGC: University Grant Commission, DAE: Department of Atomic Energy, and CSR: Consortium for scientific research), Indore, India. The setup has been developed around an 18 kW rotating anode x-ray source delivering Cu-Kα x-rays coming from a vertical line source. It works in a symmetric θ-2θ parallel beam geometry. It consists of a liquid helium cryostat with an 8 T split-pair Nb-Ti superconducting magnet comprising two x-ray windows each covering an angular range of 65°. This is mounted on a non-magnetic type heavy duty goniometer equipped with all necessary motions along with data collection accessories. The incident x-ray beam has been made parallel using a parabolic multilayer mirror. The scattered x-ray is detected using a NaI detector through a 0.1° acceptance solar collimator. To control the motions of the goniometer, a computer programme has been developed. The wide-angle scattering data can be collected in a range of 2°-115° of 2θ with a resolution of ˜0.1°. The whole setup is tightly shielded for the scattered x-rays using a lead hutch. The functioning of the goniometer and the artifacts arising possibly due to the effect of stray magnetic field on the goniometer motions, on the x-ray source, and on the detector have been characterized by collecting powder XRD data of a National Institute of Standards and Technology certified standard reference material LaB6 (SRM-660b) and Si powder in zero-field and in-field conditions. Occurrence of field induced structural-phase transitions has been demonstrated on various samples like Pr0.5Sr0.5MnO3, Nd0.49Sr0.51MnO3-δ and La0.175Pr0.45Ca0.375MnO3 by collecting data in zero field cool and field cool conditions.

  4. Low-temperature high magnetic field powder x-ray diffraction setup for field-induced structural phase transition studies from 2 to 300 K and at 0 to 8-T field.

    Science.gov (United States)

    Shahee, Aga; Sharma, Shivani; Kumar, Dhirendra; Yadav, Poonam; Bhardwaj, Preeti; Ghodke, Nandkishor; Singh, Kiran; Lalla, N P; Chaddah, P

    2016-10-01

    A low-temperature and high magnetic field powder x-ray diffractometer (XRD) has been developed at UGC-DAE CSR (UGC: University Grant Commission, DAE: Department of Atomic Energy, and CSR: Consortium for scientific research), Indore, India. The setup has been developed around an 18 kW rotating anode x-ray source delivering Cu-Kα x-rays coming from a vertical line source. It works in a symmetric θ-2θ parallel beam geometry. It consists of a liquid helium cryostat with an 8 T split-pair Nb-Ti superconducting magnet comprising two x-ray windows each covering an angular range of 65°. This is mounted on a non-magnetic type heavy duty goniometer equipped with all necessary motions along with data collection accessories. The incident x-ray beam has been made parallel using a parabolic multilayer mirror. The scattered x-ray is detected using a NaI detector through a 0.1° acceptance solar collimator. To control the motions of the goniometer, a computer programme has been developed. The wide-angle scattering data can be collected in a range of 2°-115° of 2θ with a resolution of ∼0.1°. The whole setup is tightly shielded for the scattered x-rays using a lead hutch. The functioning of the goniometer and the artifacts arising possibly due to the effect of stray magnetic field on the goniometer motions, on the x-ray source, and on the detector have been characterized by collecting powder XRD data of a National Institute of Standards and Technology certified standard reference material LaB6 (SRM-660b) and Si powder in zero-field and in-field conditions. Occurrence of field induced structural-phase transitions has been demonstrated on various samples like Pr0.5Sr0.5MnO3, Nd0.49Sr0.51MnO3-δ and La0.175Pr0.45Ca0.375MnO3 by collecting data in zero field cool and field cool conditions.

  5. Stimulated coherent transition radiation

    Energy Technology Data Exchange (ETDEWEB)

    Hung-chi Lihn

    1996-03-01

    Coherent radiation emitted from a relativistic electron bunch consists of wavelengths longer than or comparable to the bunch length. The intensity of this radiation out-numbers that of its incoherent counterpart, which extends to wavelengths shorter than the bunch length, by a factor equal to the number of electrons in the bunch. In typical accelerators, this factor is about 8 to 11 orders of magnitude. The spectrum of the coherent radiation is determined by the Fourier transform of the electron bunch distribution and, therefore, contains information of the bunch distribution. Coherent transition radiation emitted from subpicosecond electron bunches at the Stanford SUNSHINE facility is observed in the far-infrared regime through a room-temperature pyroelectric bolometer and characterized through the electron bunch-length study. To measure the bunch length, a new frequency-resolved subpicosecond bunch-length measuring system is developed. This system uses a far-infrared Michelson interferometer to measure the spectrum of coherent transition radiation through optical autocorrelation with resolution far better than existing time-resolved methods. Hence, the radiation spectrum and the bunch length are deduced from the autocorrelation measurement. To study the stimulation of coherent transition radiation, a special cavity named BRAICER is invented. Far-infrared light pulses of coherent transition radiation emitted from electron bunches are delayed and circulated in the cavity to coincide with subsequent incoming electron bunches. This coincidence of light pulses with electron bunches enables the light to do work on electrons, and thus stimulates more radiated energy. The possibilities of extending the bunch-length measuring system to measure the three-dimensional bunch distribution and making the BRAICER cavity a broadband, high-intensity, coherent, far-infrared light source are also discussed.

  6. Temperature, salinity, and sigma-T profiles from WECOMA for the Coastal Transition Zone project in the Coastal Waters of Washington/Oregon from 19870216 to 19870618 (NODC Accession 8800202)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Three Wecoma cruises were conducted from February 1987 to June 1987 as part of the pilot study for the Coastal Transition Zone project. This archival package only...

  7. Phase transitions of ε-HNIW in compound systems

    Directory of Open Access Journals (Sweden)

    Jing-yuan Zhang

    2016-05-01

    Full Text Available The heat-induced phase transitions of ε-HNIW, both neat and coated with various additives used in plastic bonded explosives, were investigated using powder X-ray diffraction and differential scanning calorimetry. It was found that ε-HNIW, after being held at 70°C for 60h, remained in the ε-phase. Applying other conditions, various phase transition parameters were determined, including Tc (the critical phase transition temperature, T50 (the temperature at which 50% of the phase transition is complete and T180 (the percentage of γ-HNIW present in samples heated to 180°C. According to the above three parameters, additives were divided into three categories: those that delay phase transition, those that raise the critical temperature and the transition rate, and those that promote the phase transition. Based on the above data, a phase transition mechanism is proposed.

  8. The temperature dependent shear strain of the (NbSe4)(10)I-3 compound, a quasi-one-dimensional charge density wave system, below the Peierls transition

    NARCIS (Netherlands)

    Vucic, Z; Gladic, J; Haas, C; DeBoer, JL

    An X-ray study of the quasi-one-dimensional charge density wave (CDW) system (NbSe4)(10)I-3 as a function of temperature from room temperature down to 130 K has been performed by taking oscillation and zeroth level Weissenberg photographs. A reversible transformation of the room temperature

  9. Temperature and electric-field induced phase transitions, and full tensor properties of [011] C -poled domain-engineered tetragonal 0.63Pb(Mg1/3Nb2/3)-0.37PbTiO3 single crystals.

    Science.gov (United States)

    Zheng, Limei; Jing, Yujia; Lu, Xiaoyan; Wang, Ruixue; Liu, Gang; Lü, Weiming; Zhang, Rui; Cao, Wenwu

    2016-03-01

    The phase-transition sequence of 0.67Pb(Mg1/3Nb2/3)-0.37PbTiO3 (PMN-0.37PT) single crystals driven by the electric (E) field and temperature is comprehensively studied. Based on the strain-E field loop, polarization-E field loop, and the evolution of domain configurations, the E field along the [011] C induced phase transitions have been confirmed to be as follows: tetragonal (T) → monoclinic (MC ) → single domain orthorhombic (O) phase. As the E field decreases, the induced O phase cannot be maintained and transformed to the MC phase, then to the coexistence state of MC and T phases. In addition, the complete sets of dielectric, piezoelectric, and elastic constants for the [011] C -poled domain-engineered PMN-0.37PT single crystal were measured at room temperature, which show high longitudinal dielectric, piezoelectric, and electromechanical properties ([Formula: see text], d33 = 1052 pC/N, and k33 = 0.766). Our results revealed that the MC phase plays an important role in the high electromechanical properties of this domain-engineered single crystal. The temperature dependence of the domain configuration revealed that the volume fraction of the MC phase decreases with temperature accompanied by the reduction of [Formula: see text], d31, and k31 due to the substantially smaller intrinsic properties of the T phase.

  10. Transitions: A Personal Perspective.

    Science.gov (United States)

    Wood, Ann Stace

    1995-01-01

    Distinguishes between unchosen transitions (children maturing and leaving, parents aging, companies downsizing) and chosen ones (moving, divorce, marriage, career changes). Describes the steps one goes through: uneasiness, renewed energy, complaining, exploration, partial transition, and the completed transition. (JOW)

  11. Studies on magnetic-field-induced first-order transitions

    Indian Academy of Sciences (India)

    We shall discuss magnetization and transport measurements in materials exhibiting a broad first-order transition. The phase transitions would be caused by varying magnetic field as well as temperature, and we concentrate on ferro- to antiferromagnetic transitions in magnetic materials. We distinguish between metastable ...

  12. Critical behavior in the hydrogen insulator-metal transition

    Science.gov (United States)

    Hemley, R. J.; Mao, H. K.

    1990-01-01

    The vibrational Raman spectrum of solid hydrogen has been measured from 77 to 295 K in the vicinity of the recently observed insulator-metal transition and low-temperature phase transition at 150 gigapascals. The measurements provide evidence for a critical point in the pressure-temperature phase boundary of the low-temperature transition. The result suggests that below the critical temperature the insulator-metal transition changes from continuous to discontinuous, consistent with the general criteria originally proposed by Mott (1949) for metallization by band-gap closure. The effect of temperature on hydrogen metallization closely resembles that of the lower-pressure insulator-metal transitions in doped V2O3 alloys.

  13. Flux density distribution and the ac loss near the glass-liquid transition temperature in high-Tc superconductors; Koon chodendo no jisoku gurasu-ekitai sen'i ondo kinbo ni okeru naibu jisoku bunpu to koryu sonshitsu

    Energy Technology Data Exchange (ETDEWEB)

    Ohashi, K.; Fujiyoshi, T. [Kumamoto Univ., Kumamoto (Japan); Kisu, T. [Kyushu Univ., Fukuoka (Japan); Yamafuji, K.

    1999-11-10

    It is possible that the high temperature superconductor keeps the superconductivity at boiling point of cheap liquid nitrogen, and the electric power application is expected. Then, the ac loss in the alternating current utilization becomes a problem. For the reason, analysis of the field distribution in the superconductor is necessary. Using the nonlinear E-J characteristics model in which high temperature superconductor was peculiar, the computer analyzed the field distribution of high temperature superconductor numerically, and the ac loss was evaluated. In addition, the theoretical evaluation of the ac loss was carried out using the model in which Bean model was made to consider the frequency dependence. (NEDO)

  14. Army Leader Transitions Handbook

    Science.gov (United States)

    2008-01-01

    usacac.army.mil/CAC2/CAL. LEADER TRANSITION MODEL Leader Transitions Handbook 1 The Army Leader Transitions Handbook is designed to help leaders plan and...D-1) Managing transitions is a leadership responsibility. Leader transitions within the Army are significant events for any organization due to...current. Administrative skills - Brush up on personnel management , especially leader development. Know UCMJ, promotions, administrative discharge

  15. Crystal lattice and phase transitions in Na4TiP2O9 (NTP) and Na4.5FeP2O8(O,F) (NFP) superionic conductors as a function of high pressures and temperatures.

    Science.gov (United States)

    Maximov; Sirota; Werner; Schulz

    1999-06-01

    The lattice dynamics of Na(4)TiP(2)O(9) (tetrasodium titanium diphosphorus nonaoxide, NTP) and Na(4.5)FeP(2)O(8)(O,F) (nonasodium diiron tetraphosphorus difluoride octadecaoxide, NFP) crystals, which are superionic conductors with Na(+)-ion conductivity, were studied under high pressures. Lattice constants as a function of hydrostatic pressure were measured on a four-circle diffractometer using a high-pressure cell with diamond anvils. At 1.78 +/- 0.15 GPa NTP undergoes a reversible phase transition from the modulated monoclinic (pseudo-orthorhombic) modification which is stable under atmospheric conditions. A similar phase transition in NTP is observed at 523 K. For NFP, it may be assumed that at least three phase transitions occur when the pressure increases from atmospheric to 12 GPa, at 1.39 +/- 0.08, 4.52 +/- 0.32, and 6.02 +/- 0.02 GPa, as concluded from the change in the unit-cell parameters and in the color of the crystals: the color changes from ginger (dark orange) to pink at ~1.5-2.0 GPa pressure and to violet at ~6.0 GPa.

  16. On the Peierls Transition in a Periodic Potential

    DEFF Research Database (Denmark)

    Hansen, Lars Kai; da Costa Carneiro, Kim

    1984-01-01

    The properties of a one-dimensional conductor in the presence of an external periodic potential VQ have been investigated. The low temperature gap is enhanced, the temperature dependence of the gap Δ(T) is smeared at TPF, the Peierls transition temperature in the absence of VQ, and hence there is......The properties of a one-dimensional conductor in the presence of an external periodic potential VQ have been investigated. The low temperature gap is enhanced, the temperature dependence of the gap Δ(T) is smeared at TPF, the Peierls transition temperature in the absence of VQ, and hence...

  17. Echoes of the Glass Transition in Athermal Soft Spheres

    Science.gov (United States)

    Morse, Peter K.; Corwin, Eric I.

    2017-09-01

    Recent theoretical advances have led to the creation of a unified phase diagram for the thermal glass and athermal jamming transitions. This diagram makes clear that, while related, the mode-coupling—or dynamic—glass transition is distinct from the jamming transition, occurring at a finite temperature and significantly lower density than the jamming transition. Nonetheless, we demonstrate a prejamming transition in athermal frictionless spheres which occurs at the same density as the mode-coupling transition and is marked by percolating clusters of locally rigid particles. At this density in both the thermal and athermal systems, individual motions of an extensive number of particles become constrained, such that only collective motion is possible. This transition, which is well below jamming, exactly matches the definition of collective behavior at the dynamical transition of glasses. Thus, we reveal that the genesis of rigidity in both thermal and athermal systems is governed by the same underlying topological transition in their shared configuration space.

  18. High Temperature QCD

    CERN Document Server

    Lombardo, M P

    2012-01-01

    I review recent results on QCD at high temperature on a lattice. Steady progress with staggered fermions and Wilson type fermions allow a quantitative description of hot QCD whose accuracy in many cases parallels that of zero temperature studies. Simulations with chiral quarks are coming of age, and togheter with theoretical developments trigger interesting developments in the analysis of the critical region. Issues related with the universality class of the chiral transition and the fate of the axial symmetry are discussed in the light of new numerical and analytical results. Transport coefficients and analysis of bottomonium spectra compare well with results of heavy ion collisions at RHIC and LHC. Model field theories, lattice simulations and high temperature systematic expansions help building a coherent picture of the high temperature phase of QCD. The (strongly coupled) Quark Gluon Plasma is heavily investigated, and asserts its role as an inspiring theoretical laboratory.

  19. Gas turbine combustor transition

    Science.gov (United States)

    Coslow, Billy Joe; Whidden, Graydon Lane

    1999-01-01

    A method of converting a steam cooled transition to an air cooled transition in a gas turbine having a compressor in fluid communication with a combustor, a turbine section in fluid communication with the combustor, the transition disposed in a combustor shell and having a cooling circuit connecting a steam outlet and a steam inlet and wherein hot gas flows from the combustor through the transition and to the turbine section, includes forming an air outlet in the transition in fluid communication with the cooling circuit and providing for an air inlet in the transition in fluid communication with the cooling circuit.

  20. Calculated Phase Diagram for the γ⇌α Transition in Ce

    DEFF Research Database (Denmark)

    Johansson, Børje; Abrikosov, I. A.; Aldén, Magnus

    1995-01-01

    We have calculated the pressure-temperature phase diagram of the γ⇌α isostructural transition in Ce on the basis of the Mott transition model. The theory correctly describes the linear variation of the transition temperature with pressure and the existence of a critical point. The quantitative ag...

  1. Combined Poisson and soft-particle DLVO analysis of the specific and nonspecific adhesion forces measured between L. monocytogenes grown at various temperatures and silicon nitride.

    Science.gov (United States)

    Gordesli, F Pinar; Abu-Lail, Nehal I

    2012-09-18

    Adhesion forces between pathogenic L. monocytogenes EGDe and silicon nitride (Si(3)N(4)) were measured using atomic force microscopy (AFM) under water and at room temperature for cells grown at five different temperatures (10, 20, 30, 37, and 40 °C). Adhesion forces were then decoupled into specific (hydrogen bonding) and nonspecific (electrostatic and Lifshitz-van der Waals) force components using Poisson statistical analysis. The strongest specific and nonspecific attraction forces were observed for cells grown at 30 °C, compared to those observed for cells grown at higher or lower temperatures, respectively. By combining the results of Poisson analysis with the results obtained through soft-particle Derjaguin-Landau-Verwey-Overbeek (DLVO) analysis, the contributions of the Lifshitz-van der Waals and electrostatic forces to the overall nonspecific interaction forces were determined. Our results showed that the Lifshitz-van der Waals attraction forces dominated the total nonspecific adhesion forces for all investigated thermal conditions. However, irrespective of the temperature of growth investigated, hydrogen bonding forces were always stronger than the nonspecific forces. Finally, by combining Poisson analysis with soft-particle analysis of DLVO forces, the closest separation distances where the irreversible bacterial adhesion takes place can be determined relatively easily. For all investigated thermal conditions, the closest separation distances were <1 nm.

  2. Short-term high temperature growth conditions during vegetative-to-reproductive phase transition irreversibly compromise cell wall invertase-mediated sucrose catalysis and microspore meiosis in grain sorghum

    Science.gov (United States)

    Grain sorghum (Sorghum bicolor L. Moench) crop yield is significantly compromised by high temperature stress-induced male sterility, and is attributed to reduced cell wall invertase (CWI)-mediated sucrose hydrolysis in microspores and anthers leading to altered carbohydrate metabolism and starch def...

  3. Conceptualizing Transitions to Adulthood

    Science.gov (United States)

    Wyn, Johanna

    2014-01-01

    This chapter provides an overview of theories of the transition to young adulthood. It sets out the argument for conceptual renewal and discusses some implications of new patterns of transition for adult education.

  4. Public Transit Stations

    Data.gov (United States)

    Department of Homeland Security — fixed rail transit stations within the Continental United States, Alaska, Hawaii, the District of Columbia, and Puerto Rico. The modes of transit that are serviced...

  5. Biodiesel Mass Transit Demonstration

    Science.gov (United States)

    2010-04-01

    The Biodiesel Mass Transit Demonstration report is intended for mass transit decision makers and fleet managers considering biodiesel use. This is the final report for the demonstration project implemented by the National Biodiesel Board under a gran...

  6. Cosmological phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Kolb, E.W. [Fermi National Accelerator Lab., Batavia, IL (United States)]|[Chicago Univ., IL (United States)

    1993-10-01

    If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions.

  7. Curie and Neel Temperatures of Quantum Magnets

    OpenAIRE

    Oitmaa, J.; Zheng, Weihong

    2004-01-01

    We estimate, using high-temperature series expansions, the transition temperatures of the spin 1/2, 1 and 3/2 Heisenberg ferromagnet and antiferromagnet in 3-dimensions. The manner in which the difference between Curie and Neel temperatures vanishes with increasing spin quantum number is investigated.

  8. Modeling for transition management

    NARCIS (Netherlands)

    Chappin, E.J.L.; Dijkema, G.P.J.

    2015-01-01

    A framework for the modeling and simulation of transitions is presented. A transition, “substantial change in the state of a socio-technical system”, typically unfolds over a long timespan. We therefore suggest to use simulation to inform transition managers on the effect of their decisions.

  9. Origins of evolutionary transitions.

    Science.gov (United States)

    Clarke, Ellen

    2014-04-01

    An 'evolutionary transition in individuality' or 'major transition' is a transformation in the hierarchical level at which natural selection operates on a population. In this article I give an abstract (i.e. level-neutral and substrate-neutral) articulation of the transition process in order to precisely understand how such processes can happen, especially how they can get started.

  10. Modeling for Transition Management

    NARCIS (Netherlands)

    Chappin, Emile J L; Dijkema, Gerard P.J.

    2015-01-01

    A framework for the modeling and simulation of transitions is presented. A transition, “substantial change in the state of a socio-technical system”, typically unfolds over a long timespan. We therefore suggest to use simulation to inform transition managers on the effect of their decisions.

  11. Transition to Adulthood

    Science.gov (United States)

    ... a lot of ground to cover! But it’s essential ground, if the student’s transition to the adult ... of transition planning? Here’s a closer look at writing transition-related IEP goals. Students Get Involved ! Very ...

  12. Origins of evolutionary transitions

    Indian Academy of Sciences (India)

    An `evolutionary transition in individuality' or `major transition' is a transformation in the hierarchical level at which natural selection operates on a population. In this article I give an abstract (i.e. level-neutral and substrate-neutral) articulation of the transition process in order to precisely understand how such processes can ...

  13. Theory of transition-layer emission measures and coronae

    Science.gov (United States)

    Bohm-Vitense, Erika

    1987-01-01

    The basic equations describing the energy equilibria, the conductive heat flux, and the temperature stratifications for stellar transition layers and coronae with 'open' field lines are summarized. The temperature dependence of the emission measures for lines originating in different temperature regions of the transition zone is determined. It is found that the stellar transition regions consist of two basically different parts: the lower part where mechnical energy input is balanced by the radiative losses, and the upper part where the mechanical energy input is balanced by the divergence of the conductive flux and radiative losses. In the lower part, the temperature stratification is determined by an equilibrium between mechanical flux input and radiative energy losses. The coronal temperatures increase with increasing mechanical flux and damping length in the upper transition zone.

  14. Electroweak phase transition recent results

    CERN Document Server

    Csikor, Ferenc

    2000-01-01

    Recent results of four-dimensional (4d) lattice simulations on the finite temperature electroweak phase transition (EWPT) are discussed. The phase transition is of first order in the SU(2)-Higgs model below the end point Higgs mass 66.5$\\pm$1.4 GeV. For larger masses a rapid cross-over appears. This result completely agrees with the results of the dimensional reduction approach. Including the full Standard Model (SM) perturbatively the end point is at 72.1$\\pm$1.4 GeV. Combined with recent LEP Higgs mass lower bounds, this excludes any EWPT in the SM. A one-loop calculation of the static potential makes possible a precise comparison of the lattice and perturbative results. Recent 4d lattice studies of the Minimal Supersymmetric SM (MSSM) are also mentioned.

  15. A methodology of tracking transitioning Cyclones

    Energy Technology Data Exchange (ETDEWEB)

    Garde, L A; Pezza, A B; Simmonds, I [Department of Earth Sciences, University of Melbourne, Victoria 3010 (Australia); Davidson, N E, E-mail: l.garde@pgrad.unimelb.edu.a [Centre for Australian Weather and Climate Research, Bureau of Meteorology, Victoria, 3000 (Australia)

    2010-08-15

    'Cyclone transition' is a process in which either a tropical cyclone or an extratropical cyclone undergoes a fundamental dynamic and thermodynamic transformation. A 'tropical transition' is a process in which a cold-core extratropical cyclone transforms to a warm-core tropical cyclone, while 'extratropical transition' refers to the opposite mechanism. The transition process is gradual, with no sharp defining threshold representing its commencement or completion. This study develops and explores a methodology of identifying tropical transition and extratropical transition events. Using the 1.5{sup 0} ERA-Interim reanalysis dataset over the period from 1989 to present, cyclone tracks are derived using The Melbourne University Tracking Scheme. The average temperature difference between the cyclone core and an environmental ring, set at a distance corresponding to the cyclones size, is then calculated throughout the troposphere during the life cycle of the cyclone. This difference represents the index or phase of the cyclone relative to its immediate environment. The lack of a complete cyclone transition climatology and the uncertainty behind the transition process is the motivation for this research, with the overarching aim of placing these systems in climatic perspective. This methodology seeks to create the foundations for further cyclone research.

  16. Effect of sodium deficiency on the critical behavior near the paramagnetic to ferromagnetic phase transition temperature in La0.8Na0.2-x□xMnO3 oxides

    Science.gov (United States)

    Wali, M.; Khlifi, M.; Dhahri, E.; Hlil, E. K.

    2017-11-01

    The critical behavior associated with the magnetic phase transition has been investigated by in La0.8Na0.2-x□xMnO3 (0.00 ≤ x ≤ 0.15) (□ is the sodium deficiency). The critical exponents are estimated by various techniques such as the modified Arrott plot, Kouvel-Fisher plot and critical isotherm technique. Compared to standard models, the critical exponent values determined in our work are close to those expected by the tricritical model (β = 0.25, γ = 1, and δ = 5) for x = 0.00 and 0.05 samples and by mean field theory (β = 0.5, γ = 1, and δ = 3) for x = 0.10 and 0.15 samples. We conclude that the Na deficiency rate affect the critical exponents.

  17. Transition Theory – Sustainable Transition of Socio-Technical Systems

    DEFF Research Database (Denmark)

    Søndergård, Bent; Holm, Jesper; Stauning, Inger

    2015-01-01

    Theories of transition management, transition studies and social practise theory Applied to studies of hosuing and construction......Theories of transition management, transition studies and social practise theory Applied to studies of hosuing and construction...

  18. Transition path time distributions

    Science.gov (United States)

    Laleman, M.; Carlon, E.; Orland, H.

    2017-12-01

    Biomolecular folding, at least in simple systems, can be described as a two state transition in a free energy landscape with two deep wells separated by a high barrier. Transition paths are the short part of the trajectories that cross the barrier. Average transition path times and, recently, their full probability distribution have been measured for several biomolecular systems, e.g., in the folding of nucleic acids or proteins. Motivated by these experiments, we have calculated the full transition path time distribution for a single stochastic particle crossing a parabolic barrier, including inertial terms which were neglected in previous studies. These terms influence the short time scale dynamics of a stochastic system and can be of experimental relevance in view of the short duration of transition paths. We derive the full transition path time distribution as well as the average transition path times and discuss the similarities and differences with the high friction limit.

  19. PENGARUH SORPSI AIR DAN SUHU TRANSISI GELAS TERHADAP LAJU PENCOKLATAN NON-ENZIMATIS PADA PANGAN MODEL [The Effect of Water Sorption and Glass Transition Temperature on Non-Enzymatic Browning Reaction of Food Models

    OpenAIRE

    Dede R Adawiyah1); S.T. Soekarto; P Hariyadi1); Suyitno

    2005-01-01

    This research was aimer/ to study the extend of non enzymatic browning reaction in food models containing the mixture of tapioca starch, casein, sucrose and oh at different moisture contents (2.55%, 5.26%, 7.54%, 15.20%. 15.93% and 23.99%) and storage temperatures (30, 55 and 700C). The non-enzymatic browning reaction was detected from brown color intensity measured by spechtrophotometer and colorimetric methods. The non-enzymatic browning reaction or food model follow pseudo-zero order react...

  20. Temperature measurement

    Science.gov (United States)

    ... an oral temperature. Other factors to take into account are: In general, rectal temperatures are considered to ... urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows ...

  1. Modeling dynamic beta-gamma polymorphic transition in Tin

    Science.gov (United States)

    Chauvin, Camille; Montheillet, Frank; Petit, Jacques; CEA Gramat Collaboration; EMSE Collaboration

    2015-06-01

    Solid-solid phase transitions in metals have been studied by shock waves techniques for many decades. Recent experiments have investigated the transition during isentropic compression experiments and shock-wave compression and have highlighted the strong influence of the loading rate on the transition. Complementary data obtained with velocity and temperature measurements around the polymorphic transition beta-gamma of Tin on gas gun experiments have displayed the importance of the kinetics of the transition. But, even though this phenomenon is known, modeling the kinetic remains complex and based on empirical formulations. A multiphase EOS is available in our 1D Lagrangian code Unidim. We propose to present the influence of various kinetic laws (either empirical or involving nucleation and growth mechanisms) and their parameters (Gibbs free energy, temperature, pressure) on the transformation rate. We compare experimental and calculated velocities and temperature profiles and we underline the effects of the empirical parameters of these models.

  2. Role of the Pair Correlation Function in the Dynamical Transition Predicted by Mode Coupling Theory.

    Science.gov (United States)

    Nandi, Manoj Kumar; Banerjee, Atreyee; Dasgupta, Chandan; Bhattacharyya, Sarika Maitra

    2017-12-29

    In a recent study, we have found that for a large number of systems the configurational entropy at the pair level S_{c2}, which is primarily determined by the pair correlation function, vanishes at the dynamical transition temperature T_{c}. Thus, it appears that the information of the transition temperature is embedded in the structure of the liquid. In order to investigate this, we describe the dynamics of the system at the mean field level and, using the concepts of the dynamical density functional theory, show that the dynamical transition temperature depends only on the pair correlation function. Thus, this theory is similar in spirit to the microscopic mode coupling theory (MCT). However, unlike microscopic MCT, which predicts a very high transition temperature, the present theory predicts a transition temperature that is similar to T_{c}. This implies that the information of the dynamical transition temperature is embedded in the pair correlation function.

  3. Role of the Pair Correlation Function in the Dynamical Transition Predicted by Mode Coupling Theory

    Science.gov (United States)

    Nandi, Manoj Kumar; Banerjee, Atreyee; Dasgupta, Chandan; Bhattacharyya, Sarika Maitra

    2017-12-01

    In a recent study, we have found that for a large number of systems the configurational entropy at the pair level Sc 2, which is primarily determined by the pair correlation function, vanishes at the dynamical transition temperature Tc. Thus, it appears that the information of the transition temperature is embedded in the structure of the liquid. In order to investigate this, we describe the dynamics of the system at the mean field level and, using the concepts of the dynamical density functional theory, show that the dynamical transition temperature depends only on the pair correlation function. Thus, this theory is similar in spirit to the microscopic mode coupling theory (MCT). However, unlike microscopic MCT, which predicts a very high transition temperature, the present theory predicts a transition temperature that is similar to Tc. This implies that the information of the dynamical transition temperature is embedded in the pair correlation function.

  4. Extracellular ice phase transitions in insects.

    Science.gov (United States)

    Hawes, T C

    2014-01-01

    At temperatures below their temperature of crystallization (Tc), the extracellular body fluids of insects undergo a phase transition from liquid to solid. Insects that survive the transition to equilibrium (complete freezing of the body fluids) are designated as freeze tolerant. Although this phenomenon has been reported and described in many Insecta, current nomenclature and theory does not clearly delineate between the process of transition (freezing) and the final solid phase itself (the frozen state). Thus freeze tolerant insects are currently, by convention, described in terms of the temperature at which the crystallization of their body fluids is initiated, Tc. In fact, the correct descriptor for insects that tolerate freezing is the temperature of equilibrium freezing, Tef. The process of freezing is itself a separate physical event with unique physiological stresses that are associated with ice growth. Correspondingly there are a number of insects whose physiological cryo-limits are very specifically delineated by this transitional envelope. The distinction also has considerable significance for our understanding of insect cryobiology: firstly, because the ability to manage endogenous ice growth is a fundamental segregator of cryotype; and secondly, because our understanding of internal ice management is still largely nascent.

  5. System Geometries and Transit/Eclipse Probabilities

    Directory of Open Access Journals (Sweden)

    Howard A.

    2011-02-01

    Full Text Available Transiting exoplanets provide access to data to study the mass-radius relation and internal structure of extrasolar planets. Long-period transiting planets allow insight into planetary environments similar to the Solar System where, in contrast to hot Jupiters, planets are not constantly exposed to the intense radiation of their parent stars. Observations of secondary eclipses additionally permit studies of exoplanet temperatures and large-scale exo-atmospheric properties. We show how transit and eclipse probabilities are related to planet-star system geometries, particularly for long-period, eccentric orbits. The resulting target selection and observational strategies represent the principal ingredients of our photometric survey of known radial-velocity planets with the aim of detecting transit signatures (TERMS.

  6. Non-equilibrium phase transitions in a liquid crystal.

    Science.gov (United States)

    Dan, K; Roy, M; Datta, A

    2015-09-07

    The present manuscript describes kinetic behaviour of the glass transition and non-equilibrium features of the "Nematic-Isotropic" (N-I) phase transition of a well known liquid crystalline material N-(4-methoxybenzylidene)-4-butylaniline from the effects of heating rate and initial temperature on the transitions, through differential scanning calorimetry (DSC), Fourier transform infrared and fluorescence spectroscopy. Around the vicinity of the glass transition temperature (Tg), while only a change in the baseline of the ΔCp vs T curve is observed for heating rate (β) > 5 K min(-1), consistent with a glass transition, a clear peak for β ≤ 5 K min(-1) and the rapid reduction in the ΔCp value from the former to the latter rate correspond to an order-disorder transition and a transition from ergodic to non-ergodic behaviour. The ln β vs 1000/T curve for the glass transition shows convex Arrhenius behaviour that can be explained very well by a purely entropic activation barrier [Dan et al., Eur. Phys. Lett. 108, 36007 (2014)]. Fourier transform infrared spectroscopy indicates sudden freezing of the out-of-plane distortion vibrations of the benzene rings around the glass transition temperature and a considerable red shift indicating enhanced coplanarity of the benzene rings and, consequently, enhancement in the molecular ordering compared to room temperature. We further provide a direct experimental evidence of the non-equilibrium nature of the N-I transition through the dependence of this transition temperature (TNI) and associated enthalpy change (ΔH) on the initial temperature (at fixed β-values) for the DSC scans. A plausible qualitative explanation based on Mesquita's extension of Landau-deGennes theory [O. N. de Mesquita, Braz. J. Phys. 28, 257 (1998)] has been put forward. The change in the molecular ordering from nematic to isotropic phase has been investigated through fluorescence anisotropy measurements where the order parameter, quantified by the

  7. Optimizing the superconducting transition temperature and upper critical field of Sn 1-x In x Te

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, R. D.; Schneeloch, J. A.; Shi, X. Y.; Xu, Z. J.; Zhang, C.; Tranquada, J. M.; Li, Q.; Gu, G. D.

    2013-07-01

    Sn 1 - x In x Te is a possible candidate for topological superconductivity. Previous work has shown that substitution of In for Sn in the topological crystalline insulator SnTe results in superconductivity, with the transition temperature, T c , growing with In concentration. We have performed a systematic investigation of Sn 1 - x In x Te for a broad range of x , synthesizing single crystals (by a modified floating-zone method) as well as polycrystalline samples. The samples have been characterized by x-ray diffraction, resistivity, and magnetization. For the single crystals, the maximum T c is obtained at x = 0.45 with a value of 4.5 K, as determined by the onset of diamagnetism.

  8. Effect of Potential Range in Pressure-Temperature Behavior in Isotropic-Nematic Transition of 4-4´-Bis(EthyloxyAzoxybenzene (P-Azoxyphenetole, Pap, 4-Pentyl-4´-Cyanobiphenyl (5cb, P-Methoxybenzydidene-P-N-Butylaniline (Mbba and P–Ethoxybenzylidene–P–N-Butylaniline (Ebba

    Directory of Open Access Journals (Sweden)

    García-Sánchez E.

    2011-04-01

    Full Text Available In this work we employed the Density Functional Theory (IPCM model to calculate molecular volume and k, and the perturbation theory proposed by García-Sánchez et al. (2002 to predict phase diagram and experimental behavior pressure-temperature for isotropic-nematic transition of 4-4´-bis(ethyloxyazoxybenzene (p-azoxyphenetole, PAP, 4-pentyl-4´-cyanobiphenyl (5CB, p-methoxybenzydidene-p-n-butylaniline (MBBA and p–ethoxybenzylidene–p–n-butylaniline (EBBA at 1 atm. If during the theoretical prediction bigger potential values of potential range of square well (l > k are considered in the theoretical model, it is possible to get better prediction of the experimental behavior. The above mentioned is according with the theoretical formulation of the Second Order Perturbation Theory since Ponce-Renon approximation is included.

  9. AC hysteresis losses near the glass-liquid transition temperature in high-T{sub c} cuprate superconductors. Handy expression for AC hysteresis loss; Sankabutsu koon chodendotai no jisoku gurasu - ekitai ten'i ondo fukin ni okeru koryu rireki sonshitsu. Koryu rireki sonshitsu ni taisuru kanbenna rironshiki

    Energy Technology Data Exchange (ETDEWEB)

    Fujiyoshi, T.; Ohashi, K.; Hiramatsu, A. [Kumamoto Univ., Kumamoto (Japan); Yamafuji, K.; Nakamura, S. [Ariake National College of Tech., Fukuoka (Japan); Kisu, T. [Kyushu Univ., Fukuoka (Japan). Graduate School of Information Science and Electrical Engineering

    2000-05-25

    The AC loss in high-T{sub c} superconductors near the glass-liquid transition temperature, T{sub g}, is studied numerically and theoretically. It is shown that the AC loss in a slab sample under a DC bias magnetic field depends noticeably on the angular frequency, {omega}, and hence, cannot be described by the usual critical state model using critical current density, J{sub c}, defined with the aid of the electric field criterion. However, the AC loss including the flux flow loss is shown to be describable quantitatively by present handy theoretical expression, which has the same form as the well-known expression based on Bean's critical state model except that J{sub c} is replaced by the effective critical current density, J{sub ce}({omega}). (author)

  10. Phase transitions in the coal-water-methane system

    Directory of Open Access Journals (Sweden)

    A.D.Alexeev

    2006-01-01

    Full Text Available Low temperature phase transitions in water and methane occurring in fossil coals were studied experimentally using Nuclear Magnetic Resonance (NMR techniques. Contributions of constituent fluids into narrow line of 1H NMR wide line spectrum were analyzed.

  11. Melting Phase Transitions and Catalytic Activity of Bilayer Gold Nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Yanting Wang; Sergey N. Rashkeev

    2009-06-01

    Recent experiments in oxidation catalysis indicate that bilayer gold nanostructures exhibit exceptional catalytic activity at ambient temperatures. Here we use molecular dynamics simulations to show that an unsupported bilayer gold nanocluster has a broad and mild second-order melting phase transition. The transition is characterized by an interplay between the intralayer and interlayer diffusion processes, and the transition temperature region ranges from about 300 K to 1200 K. We suggest that surface thermal instabilities of partially melted bilayer gold nanoclusters result in their exceptional catalytic activity at ambient temperatures. For gold nanoclusters with more than two layers, the melting transition temperature range narrows, and the activity of the cluster decreases due to the suppression of surface fluctuations. These results systematically explain experimental observations showing that catalytic ability of gold nanoclusters decreases with size.

  12. The order of the QCD transition with two light flavors

    Energy Technology Data Exchange (ETDEWEB)

    Bonati, Claudio; Cossu, Guido [Dipartimento di Fisica dell' Universita and INFN, Pisa, largo Pontecorvo 3, I-56127, Pisa (Italy); D' Elia, Massimo [Dipartimento di Fisica dell' Universita and INFN, Genova, via Dodecaneso 33, I-16146, Genova (Italy); Di Giacomo, Adriano [Dipartimento di Fisica dell' Universita and INFN, Pisa, largo Pontecorvo 3, I-56127, Pisa (Italy); Pica, Claudio [Physics Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)

    2009-04-01

    We report on the status of our analysis on the order of the finite temperature transition in QCD with two light flavors. Our new simulations on larger lattices give preliminary evidence of the first order nature of the transition also at small non-zero quark masses.

  13. Phase transition in L-alaninium oxalate by photoacoustics

    Indian Academy of Sciences (India)

    Phase transition in L-alaninium oxalate is studied by using TG, DTA and photoacoustic spectroscopy. A sharp transition at 378 K by photoacoustics is observed whereas at the same temperature the endothermic energy change observed by TG and DTA is not very sharp. This is discussed in detail with reference to the other ...

  14. Resolution of conflicting views on thermodynamics of glass transition

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Classical description of thermodynamic properties during glass transition has been questioned by the entropy-loss model. The uncompensated loss of entropy at the glass transition temperature and zero residual entropy is at the heart of the controversy. Both the models are critically reviewed. A unified model is.

  15. Economic Transition and Growth

    OpenAIRE

    Phillips, Peter C.B.; Donggyu Sul

    2005-01-01

    Some extensions of neoclassical growth models are discussed that allow for cross section heterogeneity among economies and evolution in rates of technological progress over time. The models offer a spectrum of transitional behavior among economies that includes convergence to a common steady state path as well as various forms of transitional divergence and convergence. Mechanisms for modeling such transitions and measuring them econometrically are developed in the paper. A new regression tes...

  16. Transitions in Mathematics Education

    National Research Council Canada - National Science Library

    Verschaffel, Ghislaine GueudetMarianna BoschAndrea A. diSessaOh Nam KwonLieven

    2016-01-01

    .... The book focuses on research in the area of mathematics education, and starts out with a literature review, describing the epistemological, cognitive, institutional and sociocultural perspectives on transition...

  17. Transit Benefit Program Data -

    Data.gov (United States)

    Department of Transportation — This data set contains information about any US government agency participating in the transit benefits program, funding agreements, individual participating Federal...

  18. Gluon propagator at finite temperature

    Energy Technology Data Exchange (ETDEWEB)

    Mandula, J.E.; Ogilvie, M.

    1988-01-28

    The Landau gauge gluon propagator at finite temperature above and below the deconfinement transition is measured using lattice Monte Carlo simulation. The color electric and magnetic masses are determined. The most striking result of the calculation is that the time component of the gluon field appears to acquire a vacuum expected value in the deconfined region.

  19. SPECTROSCOPIC DIAGNOSIS IN ELECTRONIC TEMPERATURE ...

    African Journals Online (AJOL)

    ABSTRACT. In this work, we are interested in the diagnostics in electronic temperature of a plasma purely photoionized, based on the intensity ration of lines emitted by ions helium-like, which have an atomic number Z relatively small. We considered the three lines corresponding to the transitions starting from the excited ...

  20. Chiral phase transition from string theory.

    Science.gov (United States)

    Parnachev, Andrei; Sahakyan, David A

    2006-09-15

    The low energy dynamics of a certain D-brane configuration in string theory is described at weak t'Hooft coupling by a nonlocal version of the Nambu-Jona-Lasinio model. We study this system at finite temperature and strong t'Hooft coupling, using the string theory dual. We show that for sufficiently low temperatures chiral symmetry is broken, while for temperatures larger then the critical value, it gets restored. We compute the latent heat and observe that the phase transition is of the first order.