Two-phase regime in the magnetic field-temperature phase diagram of a type-II superconductor

International Nuclear Information System (INIS)

Adams, L.L.A.; Halterman, Klaus; Valls, Oriol T.; Goldman, A.M.

2004-01-01

The magnetic field and temperature dependencies of the magnetic moments of superconducting crystals of V 3 Si have been studied. In a constant magnetic field and at temperatures somewhat below the superconducting transition temperature, the moments are hysteretic in temperature. However, the magnetic moment-magnetic field isotherms are reversible and exhibit features that formally resemble the pressure-volume isotherms of the liquid-gas transition. This suggests the existence of a first-order phase transition, a two-phase regime, and a critical point in the superconducting phase diagram. The two phases are disordered vortex configurations with the same magnetization, but with different vortex densities. The entropy change, determined from the data using the Clausius-Clapeyron equation, is consistent with estimates based on the difference in the vortex densities of the two phases

Two-phase regime in the magnetic field-temperature phase diagram of a type-II superconductor

Energy Technology Data Exchange (ETDEWEB)

Adams, L.L.A.; Halterman, Klaus; Valls, Oriol T.; Goldman, A.M

2004-01-01

The magnetic field and temperature dependencies of the magnetic moments of superconducting crystals of V{sub 3}Si have been studied. In a constant magnetic field and at temperatures somewhat below the superconducting transition temperature, the moments are hysteretic in temperature. However, the magnetic moment-magnetic field isotherms are reversible and exhibit features that formally resemble the pressure-volume isotherms of the liquid-gas transition. This suggests the existence of a first-order phase transition, a two-phase regime, and a critical point in the superconducting phase diagram. The two phases are disordered vortex configurations with the same magnetization, but with different vortex densities. The entropy change, determined from the data using the Clausius-Clapeyron equation, is consistent with estimates based on the difference in the vortex densities of the two phases.

Inducing phase decomposition and superconductivity of Bi2Sr2CaCu2Oy single crystals treated in sulphur atmosphere at low temperature

International Nuclear Information System (INIS)

Chen, Q.W.; China Univ. of Science and Technology, Hefei, AH; Wu, W.B.; Qian, Y.T.; China Univ. of Science and Technology, Hefei, AH; Wang, L.B.; Li, F.Q.; Zhou, G.E.; Chen, Z.Y.; Zhang, Y.H.

1995-01-01

As it has been pointed out, phase decomposition which may be hard to be detected in a polycrystalline system and is likely to correlate with changes in both oxygen content and microstructure, has been observed frequently in annealed single crystals especially at higher temperatures (> 500 C). This is still an open question to some degree because the mechanism of phase decomposition is very complex and is dominated by the composition of the Bi-2212 phase, the condition of heat treatment, and the atmosphere. Hence, inducing oxygen loss at low temperature to avoid the evaporation of Bi atoms and other undetected structure changes which would occur at higher temperature annealing undoubtedly provides important information about the relationship between oxygen loss and phase decomposition, as well as the relationship between oxygen content and superconductivity. In this note, we report on the results of treatments of Bi 2 Sr 2 CaCu 2 O y single crystals in sulphur atmosphere at 160 C. (orig.)

Brane-antibrane systems at finite temperature and phase transition near the Hagedorn temperature

International Nuclear Information System (INIS)

Hotta, Kenji

2002-01-01

In order to study the thermodynamic properties of brane-antibrane systems, we compute the finite temperature effective potential of tachyon T in this system on the basis of boundary string field theory. At low temperature, the minimum of the potential shifts towards T=0 as the temperature increases. In the D9-anti-D9 case, the sign of the coefficient of vertical bar T vertical bar 2 term of the potential changes slightly below the Hagedorn temperature. This means that a phase transition occurs near the Hagedorn temperature. On the other hand, the coefficient is kept negative in the Dp-anti-Dp case with p≤8, and thus a phase transition does not occur. This leads us to the conclusion that only a D9-anti-D9 pair and no other (lower dimensional) brane-antibrane pairs are created near the Hagedorn temperature. We also discuss a phase transition in NS9B-anti-NS9B case as a model of the Hagedorn transition of closed strings. (author)

Low-temperature phase diagram of YbBiPt

International Nuclear Information System (INIS)

Movshovich, R.; Lacerda, A.; Canfield, P.C.; Thompson, J.D.; Fisk, Z.

1994-01-01

Resistivity measurements are reported on the cubic heavy-fermion compound YbBiPt at ambient and hydrostatic pressures to ∼19 kbar and in magnetic fields to 1 T. The phase transition at T c =0.4 K is identified by a sharp rise in resistivity. That feature is used to build low-temperature H-T and P-T phase diagrams. The phase boundary in the H-T plane follows the weak-coupling BCS expression remarkably well from T c to T c /4, while small hydrostatic pressure of ∼1 kbar suppresses the low-temperature phase entirely. These effects of hydrostatic pressure and magnetic field on the phase transition are consistent with an spin-density-wave (SDW) formation in a very heavy electron band at T=0.4 K. Outside of the SDW phase at low temperature, hydrostatic pressure increases the T 2 coefficient of resistivity, signaling an increase in heavy-fermion correlations with hydrostatic pressure. The residual resistivity decreases with pressure, contrary to trends in other Yb heavy-fermion compounds

Chromatographic behavior of small organic compounds in low-temperature high-performance liquid chromatography using liquid carbon dioxide as the mobile phase.

Science.gov (United States)

Motono, Tomohiro; Nagai, Takashi; Kitagawa, Shinya; Ohtani, Hajime

2015-07-01

Low-temperature high-performance liquid chromatography, in which a loop injector, column, and detection cell were refrigerated at -35ºC, using liquid carbon dioxide as the mobile phase was developed. Small organic compounds (polyaromatic hydrocarbons, alkylbenzenes, and quinones) were separated by low-temperature high-performance liquid chromatography at temperatures from -35 to -5ºC. The combination of liquid carbon dioxide mobile phase with an octadecyl-silica (C18 ) column provided reversed phase mode separation, and a bare silica-gel column resulted in normal phase mode separation. In both the cases, nonlinear behavior at approximately -15ºC was found in the relationship between the temperature and the retention factors of the analytes (van't Hoff plots). In contrast to general trends in high-performance liquid chromatography, the decrease in temperature enhanced the separation efficiency of both the columns. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two-phase materials for high-temperature service

CSIR Research Space (South Africa)

Nabarro, FRN

2000-09-01

Full Text Available load is carried by the g phase, which is a ductile material; at high temperatures the g phase is weak, and 0966-9795/00/$ - see front matter #2000 Elsevier Science Ltd. All rights reserved. PII: S0966-9795(00)00030-3 Intermetallics 8 (2000) 979?985 www...-temperature phase of ZrO2 containing 4.5 mol% per cent Y2O3 has the cubic ?uorite structure. A 980 F.R.N. Nabarro / Intermetallics 8 (2000) 979?985 face-centred cube of Zr atoms, with 4 Zr atoms in the unit cell, contains a simple cube of 8 O-atoms. On cooling...

Relationship between Acute Phase of Chronic Periodontitis and Meteorological Factors in the Maintenance Phase of Periodontal Treatment: A Pilot Study.

Science.gov (United States)

Takeuchi, Noriko; Ekuni, Daisuke; Tomofuji, Takaaki; Morita, Manabu

2015-08-05

The acute phase of chronic periodontitis may occur even in patients during supportive periodontal therapy. However, the details are not fully understood. Since the natural environment, including meteorology affects human health, we hypothesized that weather conditions may affect occurrence of acute phase of chronic periodontitis. The aim of this study was to investigate the relationship between weather conditions and acute phase of chronic periodontitis in patients under supportive periodontal therapy. Patients who were diagnosed with acute phase of chronic periodontitis under supportive periodontal therapy during 2011-2013 were selected for this study. We performed oral examinations and collected questionnaires and meteorological data. Of 369 patients who experienced acute phase of chronic periodontitis, 153 had acute phase of chronic periodontitis without direct-triggered episodes. When using the autoregressive integrated moving average model of time-series analysis, the independent covariant of maximum hourly range of barometric pressure, maximum hourly range of temperature, and maximum daily wind speed were significantly associated with occurrence of acute phase of chronic periodontitis (p chronic periodontitis.

Neutron diffraction study of phase relationship of Ti-C-H system

International Nuclear Information System (INIS)

Khidirov, I.; Mukhtarova, N.N.; Mirzaev, B.B.; Serikbaev, B.T.; Zaginaichenko, S.Yu.; Schur, D.V.; Pishuk, V.K.; Kuzmenko, L.V.; Garbuz, V.V.; Nuzhda, S.V.; Pishuk, O.V.

2006-01-01

Full text: Due to such properties as high temperature of melting, solidity, stability in aggressive environments, etc., titanium carbide is widely used in modern techniques. It is necessary to know the phase relationships in Ti-C system for scientifically proved using. According to the phase diagram of Ti-C system, there are three phases in it: the solid solutions of carbon in the hexagonal lattice of α-Ti and in the body-centered cubic (BCC) lattice of β-Ti with rather limited solubility and also the face-centered cubic (FCC) titanium carbide TiC x with wide homogeneity range (TiC 0,32 / TiC 1,00 ). A number of the ordered phases was observed on the basis of FCC-phase. It is known, that even insignificant hydrogen impurity strongly influences at the phase relations in Ti-C system. At the same time because of specificity of some technologies of titanium carbide reception, it contains an impurity of hydrogen in its composition. However influence of hydrogen on phase relations of Ti-C system is not investigated enough. The aim of the work is to study hydrogen influence on the phase relations in Ti-C system by neutron (λ =1.085 A) and X-ray ( λ =1.5418 A) diffraction methods. Samples of TiC x H y (x = C/Ti, y H/Ti) were synthesized in the wide interval of carbon and hydrogen concentrations by sintering method from the powder of titanium of PTS trade-mark containing 0,35 mass % of hydrogen, by addition both of given quantity of TiH 2 and of soot of the trade-mark 'very pure'; the samples were studied by neutron and X-ray diffraction methods. Quartz ampoules with briquettes of the samples were pumped out up to vacuum of 1.33 10'-'4 Pa at the room temperature and were sintered in the furnace using the special regime selected by us. The briquettes were annealed from the temperature of 600 deg. C. As our experiments show, at this temperature the formation of Ti 2 C 1-x H 2-x solid solution and rapid absorption of hydrogen by this solution were observed. Also at this

Improving the spectral measurement accuracy based on temperature distribution and spectra-temperature relationship

Science.gov (United States)

Li, Zhe; Feng, Jinchao; Liu, Pengyu; Sun, Zhonghua; Li, Gang; Jia, Kebin

2018-05-01

Temperature is usually considered as a fluctuation in near-infrared spectral measurement. Chemometric methods were extensively studied to correct the effect of temperature variations. However, temperature can be considered as a constructive parameter that provides detailed chemical information when systematically changed during the measurement. Our group has researched the relationship between temperature-induced spectral variation (TSVC) and normalized squared temperature. In this study, we focused on the influence of temperature distribution in calibration set. Multi-temperature calibration set selection (MTCS) method was proposed to improve the prediction accuracy by considering the temperature distribution of calibration samples. Furthermore, double-temperature calibration set selection (DTCS) method was proposed based on MTCS method and the relationship between TSVC and normalized squared temperature. We compare the prediction performance of PLS models based on random sampling method and proposed methods. The results from experimental studies showed that the prediction performance was improved by using proposed methods. Therefore, MTCS method and DTCS method will be the alternative methods to improve prediction accuracy in near-infrared spectral measurement.

Orientational relationships between phases in the γ→α transformations for uranium-molybdenum alloys

International Nuclear Information System (INIS)

Brun, G.

1966-04-01

A crystallographic study has been made of the γ → α + γ transformation in the alloy containing 3 per cent by weight of molybdenum using electronic micro-diffraction; it has been possible to establish the orientational relationships governing the germination of the α phase in the γ phase. One finds: (111)γ // (100) α, (112-bar)γ // (010) α, (11-bar 0)γ // (001)α. By choosing a monoclinic lattice containing the same number of atoms as the orthorhombic lattice for defining the γ mother phase, the change in structure has been explained by adding a homogeneous (112-bar)γ [111]γ shearing deformation to a heterogeneous deformation brought about by slipping of the atoms which are not situated at the nodes of this lattice. The identity of the orientation relationships γ/α and γ/α''b and the loss of coherence γ /α as a function of temperature or of time lead to the conclusion that, in the range studied, the γ → α transformation begins with a martensitic process and continues by germination and growth. (author) [fr

High temperature interdiffusion and phase equilibria in U-Mo

International Nuclear Information System (INIS)

Lundberg, L.B.

1988-01-01

Experimental data for interdiffusion and phase equilibria in the U-Mo system have been obtained over the temperature range 1400 to 1525 K as a fallout from compatibility experiments in which UO 2 was decomposed by lithium in closed molybdenum capsules. Composition-position, x-ray diffraction and microstructural data from the interdiffusion zones indicate that the intermediate phase U 2 Mo is found in this temperature range, contrary to the currently accepted equilibrium U-Mo phase diagram. The U-Mo interdiffusion data are in good agreement with published values. Inclusion of the U 2 Mo phase in a theoretical correlation of interdiffusion and phase equilibria data using Darken's equation indicate that high temperature interdiffusion of uranium and molybdenum follows the usual thermodynamic rules. Significant changes in the value of the thermodynamic based Darken factor near the U 2 Mo phase boundary on the high uranium side are indicated from both the new and published interdiffusion data. 9 refs., 10 figs., 3 tabs

A description of phases with induced hybridisation at finite temperatures

Science.gov (United States)

Golosov, D. I.

2018-05-01

In an extended Falicov-Kimball model, an excitonic insulator phase can be stabilised at zero temperature. With increasing temperature, the excitonic order parameter (interaction-induced hybridisation on-site, characterised by the absolute value and phase) eventually becomes disordered, which involves fluctuations of both its phase and (at higher T) its absolute value. In order to build an adequate mean field description, it is important to clarify the nature of degrees of freedom associated with the phase and absolute value of the induced hybridisation, and the corresponding phase space volume. We show that a possible description is provided by the SU(4) parametrisation on-site. In principle, this allows to describe both the lower-temperature regime where phase fluctuations destroy the long-range order, and the higher temperature crossover corresponding to a decrease of absolute value of the hybridisation relative to the fluctuations level. This picture is also expected to be relevant in other contexts, including the Kondo lattice model.

Room Temperature Monoclinic Phase in BaTiO3 Single Crystals

Science.gov (United States)

Denev, Sava; Kumar, Amit; Barnes, Andrew; Vlahos, Eftihia; Shepard, Gabriella; Gopalan, Venkatraman

2010-03-01

BaTiO3 is a well studied ferroelectric material for the last half century. It is well known to show phase transitions to tetragonal, orthorhombic and rhombohedral phases upon cooling. Yet, some old and some recent studies have argued that all these phases co-exist with a second phase with monoclinic distortion. Using optical second harmonic generation (SHG) at room temperature we directly present evidence for such monoclininc phase co-existing with tetragonal phase at room temperature. We observe domains with the expected tetragonal symmetry exhibiting 90^o and 180^o domain walls. However, at points of higher stress at the tips of the interpenetrating tetragonal domains we observe a well pronounced metastable ``staircase pattern'' with a micron-scale fine structure. Polarization studies show that this phase can be explained only by monoclinic symmetry. This phase is very sensitive to external perturbations such as temperature and fields, hence stabilizing this phase at room temperature could lead to large properties' tunability.

Microstructures and phase relationships in the Ti3Al + Nb system

International Nuclear Information System (INIS)

Kestner-Weykamp, H.T.; Kaufman, M.J.

1989-01-01

Alloys based on the α 2 -Ti 3 Al compound (hexagonal) DO 19 are currently experiencing limited use as advanced aerospace materials. To date, the alloys with the most desirable properties contain additions of β stabilizers, such as Nb, Mo and V, which promote the formation of a two-phase mixture of α 2 +β or α 2 +B2 (where B2 refers to the ordered CsCl structure). Unfortunately, the phase relationships in these systems have not been established in sufficient detail to allow their more widespread application. Recently, there has been a series of investigations aimed at alleviating this deficiency in the ternary Ti-Al-Nb system. These studies have clearly indicated the existence of the ordered B2 phase, which, in the higher Nb alloys, can be retained at room temperature by rapid cooling from the liquid or solid state. The authors describe (TiNb) 3 Al alloys (from 0 to 30 at. pct. Nb) were studies after conventional and nonequilibrium (i.e., rapid solidification) processing with an emphasis on providing further insight into the transformation sequences and phase equilibria in these alloys

Phase behavior of polystyrene-block-poly(n-alkyl methacrylate) copolymers investigated by SANS, SAXS, and temperature-dependent FTIR spectroscopy

International Nuclear Information System (INIS)

Ryu, Du Yeol; Lee, Dong Hyun; Kim, Hye Jeong; Kim, Jin Kon; Jung, Y. M.; Kim, S. B.

2005-01-01

The phase behavior of polystyrene-block -poly(n-alkyl methacrylate) (PS-PnAMA) copolymer were investigated by Small-Angle Neutron Scattering (SANS), Small-Angle X-ray Scattering (SAXS), and temperature-dependent Fourier Transform Infrared (FTIR) spectroscopy. Also, the effect of hydrostatic pressure on the transition temperatures was studied by using SANS with pressure controller. Phase behavior was changed significantly with the change of alkyl number (n). For n = 2∼4, only Lower Disordered-to-Order Tansition (LDOT) was observed, whereas the Ordered-to-Disorder (ODT) was found for n =1 and n =6. Finally, a closed-loop phase behavior was found for n =5. Using incompressible random phase approximation, the segmental interactions (χ) between PS and PnAMA for all n values were obtained. The standard expression of χ = a + b/T (where T is the absolute temperature) was valid only for n =1 and n =6. But, this relationship was not valid any more for n = 2∼4. For n =5, a more complex behavior of χ upon temperature was observed. We investigated, by using temperature-dependent FTIR, the mechanism why as closed loop phase behavior was observed for n =5. Interestingly, the conformation of C-C-O stretching band of the PnPMA chain (n=5) (and thus the directional enthapic gain) was different in the two disordered states, and, therefore, the driving force to induce the disordered state at lower temperatures was different from that at higher temperatures

The relationship between phase and heart rate

International Nuclear Information System (INIS)

Underwood, S.R.; Walton, S.; Brown, N.J.G.; Laming, P.J.; Ell, P.J.; Emanuel, R.W.; Swanton, R.H.

1984-01-01

The Fourier phase image is used in rest and stress radionuclide angiocardiography to assess the timing of ventricular wall motion in a regional fashion, and areas of high phase are taken to reprensent areas of delayed contraction. However, phase increases with heart rate and this can make interpretation difficult. This study investigates the relationship between phase and heart rate. A heterogenous group of 43 subjects was studied by ECG-gated equilibrium radionuclide angiocardiography, all of the subjects having normal extent of left ventricular wall motion as judged by normal ejection fraction and normal amplitude image. Mean left ventricular phase correlated well with mean time of end systole (r=0.92), but there was no correlation with time of end diastole.Thus phase reflects the time of end systole as a proportion of cycle length and should be linearly related to heart rate provided the duration of systole is unchanged. In 28 normal subjects mean left ventricular phase correlated linearly with resting rate (r=0.91), and when exercised the relationship was maintained up to 90 beats per minute. Above this rate the increases were less marked as the duration of systole shortened. The same was true in 4 subjects paced at different rates. Mean resting heart rate in the normal subjects was 70 beats per minute and correcting phase linearly to rate 70 did not change mean left ventricular phase but did decrease the standard deviation from 18 degree to 12 degree. It is concluded that correcting phase for heart rate below 90 beats per minute will increase the sensitivity of the phase image to abnormalities of the timing of ventricular contraction. This correction should be appropriate in resting, isometric exercise, and cold pressor studies but because of the higher heart rates involved will not be appropriate for bicycle exercise. (Author)

Summary of workshop on high temperature materials based on Laves phases

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-08-01

The Offices of Fossil Energy and Basic Energy Sciences of the Department of Energy jointly sponsored the Workshop on High Temperature Materials Based on Laves Phases in conjunction with the Tenth Annual Conference on Fossil Energy Materials held at the Radisson Summit Hill Hotel in Knoxville, Tennessee on May 14-16, 1996. The objective of this workshop was to review the current status and to address critical issues in the development of new-generation high-temperature structural materials based on Laves phases. The one-day workshop included two sessions of overview presentations and a session of discussion on critical scientific and technological issues. The Laves phases represent an abundant class of intermetallic alloys with possible high-temperature structural applications. Laves phases form at or near the AB{sub 2} composition, and there are over 360 binary Laves phases. The ability of these alloys to dissolve considerable amounts of ternary alloying additions provides over 900 combined binary and ternary Laves phases. Many Laves phases have unique properties which make them attractive for high-temperature structural use. At half their homologous temperature, they retain >0.85 of their ambient yield strength, which is higher than all other intermetallics. Many of the Laves phases also have high melting temperatures, excellent creep properties, reasonably low densities, and for alloys containing Cr, Al, Si or Be, good oxidation resistance. Despite these useful properties, the tendency for low-temperature brittleness has limited the potential application of this large class of alloys.

Structural evolution of calcite at high temperatures: Phase V unveiled

Science.gov (United States)

Ishizawa, Nobuo; Setoguchi, Hayato; Yanagisawa, Kazumichi

2013-01-01

The calcite form of calcium carbonate CaCO3 undergoes a reversible phase transition between Rc and Rm at ~1240 K under a CO2 atmosphere of ~0.4 MPa. The joint probability density function obtained from the single-crystal X-ray diffraction data revealed that the oxygen triangles of the CO3 group in the high temperature form (Phase V) do not sit still at specified positions in the space group Rm, but migrate along the undulated circular orbital about carbon. The present study also shows how the room temperature form (Phase I) develops into Phase V through an intermediate form (Phase IV) in the temperature range between ~985 K and ~1240 K. PMID:24084871

Low-temperature thermal expansion of metastable intermetallic Fe-Cr phases

International Nuclear Information System (INIS)

Gorbunoff, A.; Levin, A.A.; Meyer, D.C.

2009-01-01

The thermal expansion coefficients (TEC) of metastable disordered intermetallic Fe-Cr phases formed in thin Fe-Cr alloy films prepared by an extremely non-equilibrium method of the pulsed laser deposition are studied. The lattice parameters of the alloys calculated from the low-temperature wide-angle X-ray diffraction (WAXRD) patterns show linear temperature dependencies in the temperature range 143-293 K and a deviation from the linearity at lower temperatures. The linear thermal expansion coefficients determined from the slopes of the linear portions of the temperature-lattice parameter dependencies differ significantly from phase to phase and from the values expected for the body-centered cubic (b.c.c.) Fe 1-x Cr x solid solutions. Strain-crystallite size analysis of the samples is performed. Predictions about the Debye temperature and the mechanical properties of the alloys are made.

Phase-relationships between scales in the perturbed turbulent boundary layer

Science.gov (United States)

Jacobi, I.; McKeon, B. J.

2017-12-01

The phase-relationship between large-scale motions and small-scale fluctuations in a non-equilibrium turbulent boundary layer was investigated. A zero-pressure-gradient flat plate turbulent boundary layer was perturbed by a short array of two-dimensional roughness elements, both statically, and under dynamic actuation. Within the compound, dynamic perturbation, the forcing generated a synthetic very-large-scale motion (VLSM) within the flow. The flow was decomposed by phase-locking the flow measurements to the roughness forcing, and the phase-relationship between the synthetic VLSM and remaining fluctuating scales was explored by correlation techniques. The general relationship between large- and small-scale motions in the perturbed flow, without phase-locking, was also examined. The synthetic large scale cohered with smaller scales in the flow via a phase-relationship that is similar to that of natural large scales in an unperturbed flow, but with a much stronger organizing effect. Cospectral techniques were employed to describe the physical implications of the perturbation on the relative orientation of large- and small-scale structures in the flow. The correlation and cospectral techniques provide tools for designing more efficient control strategies that can indirectly control small-scale motions via the large scales.

Reduced temperature phase diagrams of the silver-rare earths binary systems

International Nuclear Information System (INIS)

Ferro, R.; Delfino, S.; Capelli, R.; Borsese, A.

1975-01-01

Phase equilibria of the silver-rare earth binary systems have been reported in ''reduced temperature'' diagrams (the ''reduced temperature'' being defined as the ratio between a characteristic temperature of the Agsub(x)R.E. phase and the melting temperature of the corresponding R.E. metal, both in 0 K). The smooth trends of the various characteristic reduced temperatures, when plotted against the R.E. atomic number, have been demonstrated. On passing from the light- to the heavy-rare-earths, a correlation has been found between the crossing of these curves and other phenomena, such as the disappearing of the Ag 5 R.E. phases from incongruently, to congruently melting compounds. The trends of the reduced-temperature curves have been briefly discussed in terms of the treatment suggested by Gschneidner together with the volumetric data known for the different Agsub(x)R.E. phases. In addition, the characteristic data of the 1:1 AgR.E. compounds have been compared with those of the analogous AuR.E. phases. (Auth.)

Phase equilibrium condition of marine carbon dioxide hydrate

International Nuclear Information System (INIS)

Sun, Shi-Cai; Liu, Chang-Ling; Ye, Yu-Guang

2013-01-01

Highlights: ► CO 2 hydrate phase equilibrium was studied in simulated marine sediments. ► CO 2 hydrate equilibrium temperature in NaCl and submarine pore water was depressed. ► Coarse-grained silica sand does not affect CO 2 hydrate phase equilibrium. ► The relationship between equilibrium temperature and freezing point was discussed. - Abstract: The phase equilibrium of ocean carbon dioxide hydrate should be understood for ocean storage of carbon dioxide. In this paper, the isochoric multi-step heating dissociation method was employed to investigate the phase equilibrium of carbon dioxide hydrate in a variety of systems (NaCl solution, submarine pore water, silica sand + NaCl solution mixture). The experimental results show that the depression in the phase equilibrium temperature of carbon dioxide hydrate in NaCl solution is caused mainly by Cl − ion. The relationship between the equilibrium temperature and freezing point in NaCl solution was discussed. The phase equilibrium temperature of carbon dioxide hydrate in submarine pore water is shifted by −1.1 K to lower temperature region than that in pure water. However, the phase equilibrium temperature of carbon dioxide hydrate in mixture samples of coarsed-grained silica sand and NaCl solution is in agreement with that in NaCl solution with corresponding concentrations. The relationship between the equilibrium temperature and freezing point in mixture samples was also discussed.

Temperature-Controlled High-Speed AFM: Real-Time Observation of Ripple Phase Transitions.

Science.gov (United States)

Takahashi, Hirohide; Miyagi, Atsushi; Redondo-Morata, Lorena; Scheuring, Simon

2016-11-01

With nanometer lateral and Angstrom vertical resolution, atomic force microscopy (AFM) has contributed unique data improving the understanding of lipid bilayers. Lipid bilayers are found in several different temperature-dependent states, termed phases; the main phases are solid and fluid phases. The transition temperature between solid and fluid phases is lipid composition specific. Under certain conditions some lipid bilayers adopt a so-called ripple phase, a structure where solid and fluid phase domains alternate with constant periodicity. Because of its narrow regime of existence and heterogeneity ripple phase and its transition dynamics remain poorly understood. Here, a temperature control device to high-speed atomic force microscopy (HS-AFM) to observe dynamics of phase transition from ripple phase to fluid phase reversibly in real time is developed and integrated. Based on HS-AFM imaging, the phase transition processes from ripple phase to fluid phase and from ripple phase to metastable ripple phase to fluid phase could be reversibly, phenomenologically, and quantitatively studied. The results here show phase transition hysteresis in fast cooling and heating processes, while both melting and condensation occur at 24.15 °C in quasi-steady state situation. A second metastable ripple phase with larger periodicity is formed at the ripple phase to fluid phase transition when the buffer contains Ca 2+ . The presented temperature-controlled HS-AFM is a new unique experimental system to observe dynamics of temperature-sensitive processes at the nanoscopic level. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The high temperature phase transition for the φ4 theory

International Nuclear Information System (INIS)

Tetradis, N.

1994-01-01

The use of the perturbative temperature dependent effective potential for the study of second order or weakly first order phase transitions is problematic, due to the appearance of infrared divergences. These divergences can be controlled through the method of the effective average action which employs renormalization group ideas. I review work done with C. Wetterich on the study of the high temperature phase transition for the N-component Φ 4 theory. A detailed quantitative picture of the second order phase transition is presented, including the critical exponents for the behaviour in the vicinity of the critical temperature. (orig.)

Temperature and phase dependence of positron lifetimes in solid cyclohexane

DEFF Research Database (Denmark)

Eldrup, Morten Mostgaard

1985-01-01

The temperature dependence of position lifetimes in both the brittle and plastic phases of cyclohaxane has been examined. Long-lived components in both phases are associated with the formation of positronium (Ps). Two long lifetimes attributable to ortho-Ps are resolvable in the plastic phase....... The longer of these (≈ 2.5 ns), which is temperature dependent, is ascribed to ortho-Ps trapped at vacancies. The shorter lifetime (≈ 0.9 ns), shows little temperature dependence. In contrast to most other plastic crystals, no sigmoidal behaviour of the average ortho-Ps lifetime is observed. A possibility...

Finite temperature susy GUT phase transitions determined by radiative corrections

International Nuclear Information System (INIS)

Kripfganz, J.; Perlt, H.

1983-02-01

Studying the 2-loop perturbative contribution to the free energy of grand unified theories a sequence of phase transitions is found, with SU(3)xSU(2)xU(1) being the prefered low temperature phase. The transition temperatures are still within the weak coupling regime. (author)

Stability of Phase Relationships While Coordinating Arm Reaches with Whole Body Motion.

Directory of Open Access Journals (Sweden)

Romy S Bakker

Full Text Available The human movement repertoire is characterized by the smooth coordination of several body parts, including arm movements and whole body motion. The neural control of this coordination is quite complex because the various body parts have their own kinematic and dynamic properties. Behavioral inferences about the neural solution to the coordination problem could be obtained by examining the emerging phase relationship and its stability. Here, we studied the phase relationships that characterize the coordination of arm-reaching movements with passively-induced whole-body motion. Participants were laterally translated using a vestibular chair that oscillated at a fixed frequency of 0.83 Hz. They were instructed to reach between two targets that were aligned either parallel or orthogonal to the whole body motion. During the first cycles of body motion, a metronome entrained either an in-phase or an anti-phase relationship between hand and body motion, which was released at later cycles to test phase stability. Results suggest that inertial forces play an important role when coordinating reaches with cyclic whole-body motion. For parallel reaches, we found a stable in-phase and an unstable anti-phase relationship. When the latter was imposed, it readily transitioned or drifted back toward an in-phase relationship at cycles without metronomic entrainment. For orthogonal reaches, we did not find a clear difference in stability between in-phase and anti-phase relationships. Computer simulations further show that cost models that minimize energy expenditure (i.e. net torques or endpoint variance of the reach cannot fully explain the observed coordination patterns. We discuss how predictive control and impedance control processes could be considered important mechanisms underlying the rhythmic coordination of arm reaches and body motion.

Effect of temperature gradient on liquid-liquid phase separation in a polyolefin blend.

Science.gov (United States)

Jiang, Hua; Dou, Nannan; Fan, Guoqiang; Yang, Zhaohui; Zhang, Xiaohua

2013-09-28

We have investigated experimentally the structure formation processes during phase separation via spinodal decomposition above and below the spinodal line in a binary polymer blend system exposed to in-plane stationary thermal gradients using phase contrast optical microscopy and temperature gradient hot stage. Below the spinodal line there is a coupling of concentration fluctuations and thermal gradient imposed by the temperature gradient hot stage. Also under the thermal gradient annealing phase-separated domains grow faster compared with the system under homogeneous temperature annealing on a zero-gradient or a conventional hot stage. We suggest that the in-plane thermal gradient accelerates phase separation through the enhancement in concentration fluctuations in the early and intermediate stages of spinodal decomposition. In a thermal gradient field, the strength of concentration fluctuation close to the critical point (above the spinodal line) is strong enough to induce phase separation even in one-phase regime of the phase diagram. In the presence of a temperature gradient the equilibrium phase diagrams are no longer valid, and the systems with an upper critical solution temperature can be quenched into phase separation by applying the stationary temperature gradient. The in-plane temperature gradient drives enhanced concentration fluctuations in a binary polymer blend system above and below the spinodal line.

High temperature resistive phase transition in A15 high temperature superconductors

International Nuclear Information System (INIS)

Chu, C.W.; Huang, C.Y.; Schmidt, P.H.; Sugawara, K.

1976-01-01

Resistive measurements were made on A15 high temperature superconductors. Anomalies indicative of a phase transition were observed at 433 0 K in a single crystal Nb 3 Sn and at 485 0 K in an unbacked Nb 3 Ge sputtered thin film. Results are compared with the high temperature transmission electron diffraction studies of Nb 3 Ge films by Schmidt et al. A possible instability in the electron energy spectrum is discussed

Finescale Structure of the Temperature-Salinity Relationship

National Research Council Canada - National Science Library

Polzin, Kurt L; Ferrari, Raffaele

2005-01-01

The long term goal of this project is to understand the processes that establish the temperature-salinity relationship in the ocean, with emphasis on the interplay between advection at the large scale...

Macroscopic phase separation in high-temperature superconductors

Science.gov (United States)

Wen, Hai-Hu

2000-01-01

High-temperature superconductivity is recovered by introducing extra holes to the Cu-O planes, which initially are insulating with antiferromagnetism. In this paper I present data to show the macroscopic electronic phase separation that is caused by either mobile doping or electronic instability in the overdoped region. My results clearly demonstrate that the electronic inhomogeneity is probably a general feature of high-temperature superconductors. PMID:11027323

Insight into the Am-O Phase Equilibria: A Thermodynamic Study Coupling High-Temperature XRD and CALPHAD Modeling.

Science.gov (United States)

Epifano, Enrica; Guéneau, Christine; Belin, Renaud C; Vauchy, Romain; Lebreton, Florent; Richaud, Jean-Christophe; Joly, Alexis; Valot, Christophe; Martin, Philippe M

2017-07-03

In the frame of minor actinide transmutation, americium can be diluted in UO 2 and (U, Pu)O 2 fuels burned in fast neutron reactors. The first mandatory step to foresee the influence of Am on the in-reactor behavior of transmutation targets or fuel is to have fundamental knowledge of the Am-O binary system and, in particular, of the AmO 2-x phase. In this study, we coupled HT-XRD (high-temperature X-ray diffraction) experiments with CALPHAD thermodynamic modeling to provide new insights into the structural properties and phase equilibria in the AmO 2-x -AmO 1.61+x -Am 2 O 3 domain. Because of this approach, we were able for the first time to assess the relationships between temperature, lattice parameter, and hypostoichiometry for fcc AmO 2-x . We showed the presence of a hyperstoichiometric existence domain for the bcc AmO 1.61+x phase and the absence of a miscibility gap in the fcc AmO 2-x phase, contrary to previous representations of the phase diagram. Finally, with the new experimental data, a new CALPHAD thermodynamic model of the Am-O system was developed, and an improved version of the phase diagram is presented.

High temperature creep behavior in the (α + β) phase temperature range of M5 alloy

International Nuclear Information System (INIS)

Trego, G.

2011-01-01

The isothermal steady-state creep behavior of a M5 thin sheet alloy in a vacuum environment was investigated in the (α + β) temperature, low-stress (1-10 MPa) range. To this aim, the simplest approach consists in identifying α and β creep flow rules in their respective single-phase temperature ranges and extrapolating them in the two-phase domain. However, the (α + β) experimental behavior may fall outside any bounds calculated using such creep flow data. Here, the model was improved for each phase by considering two microstructural effects: (i) Grain size: Thermo-mechanical treatments applied on the material yielded various controlled grain size distributions. Creep tests in near-α and near-β ranges evidenced a strong grain-size effect, especially in the diffusional creep regime. (ii) Chemical contrast between the two phases in the (α + β) range: From thermodynamic calculations and microstructural investigations, the β phase is enriched in Nb and depleted in O (the reverse being true for the α phase). Thus, creep tests were performed on model Zr-Nb-O thin sheets with Nb and O concentrations representative of each phase in the considered temperature range. New α and β creep flow equations were developed from this extended experimental database and used to compute, via a finite element model, the creep rates of the two-phase material. The 3D morphology of phases (β grains nucleated at α grain boundaries) was explicitly introduced in the computations. The effect of phase morphology on the macroscopic creep flow was shown using this specific morphology, compared to other typical morphologies and to experimental data. (author) [fr

Possibility of high temperature superconducting phases in PdH

Science.gov (United States)

Tripodi, Paolo; Di Gioacchino, Daniele; Borelli, Rodolfo; Vinko, Jenny Darja

2003-05-01

Possible new superconducting phases with a high critical transition temperature (Tc) have been found in stable palladium-hydrogen (PdHx) samples for stoichiometric ratio x=H/Pd⩾1, in addition to the well-known low critical transition temperature (0⩽Tc⩽9) when x is in the range (0.75⩽x⩽1.00). Possible new measured superconducting phases with critical temperature in the range 51⩽Tc⩽295 K occur. This Tc varies considerably with every milli part of x when x exceeds unit. A superconducting critical current density Jc⩾6.1×104 A cm-2 has been measured at 77 K with HDC=0 T.

Characterization of phase change materials for thermal control of photovoltaics using Differential Scanning Calorimetry and Temperature History Method

International Nuclear Information System (INIS)

Hasan, A.; McCormack, S.J.; Huang, M.J.; Norton, B.

2014-01-01

Highlights: • Five PCM are characterized using tow techniques for PV temperature regulation. • Thermophysical properties of interest are determined and compared with literature. • Determined PCM properties are discussed as criteria for PV temperature regulation. • One PCM identified as potential candidate for PV temperature regulation. - Abstract: Five solid–liquid phase change materials comprising three basic classes, paraffin waxes, salt hydrates and mixtures of fatty acids were thermophysically characterized for thermal regulation applications in photovoltaics. The PCM were investigated using Differential Scanning Calorimetry and Temperature History Method to find their thermophysical properties of interest. The relationship between thermophysical properties of the PCM and their choice as temperature regulators in photovoltaics is discussed in relation to the ambient conditions under which PV systems operate

Phase stability of TiH{sub 2} under high pressure and temperatures

Energy Technology Data Exchange (ETDEWEB)

Selva Vennila, R.; Durygin, A.; Saxena, S.K. [Center for Study of Matter at Extreme Conditions (CeSMEC), Florida International University, VH-150, University Park, Miami, FL 33199 (United States); Merlini, Marco [European Synchrotron Radiation Facility (ESRF), Grenoble 38043 (France); Wang, Zhongwu [Cornell High Energy Synchrotron Source (CHESS), Wilson Laboratory, Cornell University, Ithaca, NY 14853 (United States)

2008-11-15

Phase stability of titanium hydride (TiH{sub 2}) was studied at high pressure-high temperature conditions using synchrotron radiation under non-hydrostatic conditions. Resistive heating method was used to heat the sample to a maximum temperature of 873 K in a diamond anvil cell (DAC) under pressure up to 12 GPa. Pressure-temperature behavior was studied by varying the temperature upto 823 K in steps of 50 K with pressure variations within 3 GPa. Structural phase transformation from tetragonal (I4/mmm) to cubic (Fm-3 m) was observed with increase in temperature. Tetragonal phase was found to be stabilized when the sample was subjected to pressure and temperature cycle. (author)

Electrical transport and temperature coefficient of resistance in polycrystalline La0.7−xAgxCa0.3MnO3 pellets: Analysis in terms of a phase coexistence transport model and phase separation model

International Nuclear Information System (INIS)

Phong, P.T.; Nguyen, L.H.; Manh, D.H.; Phuc, N.X.; Lee, I.-J.

2013-01-01

The temperature dependent resistivity and temperature coefficient of resistance of Ag doped La 0.7−x Ag x Ca 0.3 MnO 3 polycrystalline pellets (x=0, 0.05, 0.10, 0.15, and 0.20) are investigated. Ag substitution enhances the conductivity of this system. The Curie temperature also increases from 260 to 283 K with increasing Ag content. Using phase-coexistence transport model and phase separation model, we calculated the resistivity as a function of temperature and the temperature coefficient of resistivity (TCR) behavior. Comparing the calculated maximum TCR, we found that it is related to activation energy, transition temperature, and disorder in doped manganites. The relationship between the proposed TCR behavior and the transport parameters can suggest conditions improving TCR max of doped manganites for the use of the bolometric infrared detectors

Phase structure of (φ4)3 field theory at finite temperature

International Nuclear Information System (INIS)

Efimov, G.V.

1992-01-01

Phase structure of φ 4 field theory in the space-time R 3 is investigated at arbitrary coupling constant and temperature. The critical values of the coupling constant and temperature, corresponding to the phase transitions in the system, are calculated by the canonical transformation method within formalism of thermo field dynamics. The Hamiltonians describing the system in each phase are obtained straightforwardly. Comparison with the two-dimensional case shows a crucial influence of higher order renormalization on the phase structure of the model. 13 refs.; 5 figs

Temperature and Violent Crime in Dallas, Texas: Relationships and Implications of Climate Change

Directory of Open Access Journals (Sweden)

Janet L. Gamble

2012-08-01

Full Text Available Introduction: To investigate relationships between ambient temperatures and violent crimes to determine whether those relationships are consistent across different crime categories and whether they are best described as increasing linear functions, or as curvilinear functions that decrease beyond some temperature threshold. A secondary objective was to consider the implications of the observed relationships for injuries and deaths from violent crimes in the context of a warming climate. To address these questions, we examined the relationship between daily ambient temperatures and daily incidents of violent crime in Dallas, Texas from 1993–1999.Methods: We analyzed the relationships between daily fluctuations in ambient temperature, other meteorological and temporal variables, and rates of daily violent crime using time series piece-wise regression and plots of daily data. Violent crimes, including aggravated assault, homicide, and sexualassault, were analyzed.Results: We found that daily mean ambient temperature is related in a curvilinear fashion to daily rates of violent crime with a positive and increasing relationship between temperature and aggravated crime that moderates beyond temperatures of 80 F and then turns negative beyond 90 F.Conclusion: While some have characterized the relationship between temperature and violent crime as a continually increasing linear function, leaving open the possibility that aggravated crime will increase in a warmer climate, we conclude that the relationship in Dallas is not linear, but moderatesand turns negative at high ambient temperatures. We posit that higher temperatures may encourage people to seek shelter in cooler indoor spaces, and that street crime and other crimes of opportunity are subsequently decreased. This finding suggests that the higher ambient temperatures expected with climate change may result in marginal shifts in violent crime in the short term, but are not likely to be

Phase change material for temperature control and material storage

Science.gov (United States)

Wessling, Jr., Francis C. (Inventor); Blackwood, James M. (Inventor)

2011-01-01

A phase change material comprising a mixture of water and deuterium oxide is described, wherein the mole fraction of deuterium oxide is selected so that the mixture has a selected phase change temperature within a range between 0.degree. C. and 4.degree. C. The mixture is placed in a container and used for passive storage and transport of biomaterials and other temperature sensitive materials. Gels, nucleating agents, freezing point depression materials and colorants may be added to enhance the characteristics of the mixture.

Stability of low-temperature Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} cubic phase: The role of temperature and atmosphere

Energy Technology Data Exchange (ETDEWEB)

Quinzeni, Irene; Capsoni, Doretta; Berbenni, Vittorio; Mustarelli, Piercarlo [Chemistry Department, Physical-Chemistry Section, University of Pavia, Viale Taramelli 16, 27100 Pavia (Italy); Sturini, Michela [Chemistry Department, Analytical Section, University of Pavia, Viale Taramelli 12, 27100 Pavia (Italy); Bini, Marcella, E-mail: bini@unipv.it [Chemistry Department, Physical-Chemistry Section, University of Pavia, Viale Taramelli 16, 27100 Pavia (Italy)

2017-01-01

Rechargeable all solid-state lithium batteries are a promising technology for the next generation of safer batteries. In this context, strict requirements are placed on the electrolytes, among which is emerging the Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} garnet, chiefly for the relationships among synthesis conditions and phase stability. Here, the structural modifications of the low temperature (LT) Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} cubic form were investigated by using in situ X-Rays diffraction analysis. In particular, we studied the role of both temperature and atmosphere (air or argon) on phase stabilization. In argon flow, the LT phase is stable under 750 °C, and it transforms into the tetragonal one at lower temperature. In air, it partially decomposes to La{sub 2}Zr{sub 2}O{sub 7} due to Li loss above 250 °C. ICP-OES analysis confirmed that garnet stoichiometry was maintained in argon, whereas in air lithium loss occurred. The structural transformations are driven by the CO{sub 2} absorbed in the LT structure that can form Li{sub 2}CO{sub 3} and/or La{sub 2}(CO{sub 3}){sub 3} so causing stoichiometry changes responsible of the structural evolution. - Highlights: • Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} is a promising electrolyte for rechargeable all solid state batteries. • The stability of low temperature cubic phase of garnet in argon and air was determined. • The garnet stoichiometry was maintained in argon while in air lithium loss occurred. • The influence of CO{sub 2} adsorption on the structural modifications of garnet was proved.

High-pressure high-temperature phase diagram of organic crystal paracetamol

Science.gov (United States)

Smith, Spencer J.; Montgomery, Jeffrey M.; Vohra, Yogesh K.

2016-01-01

High-pressure high-temperature (HPHT) Raman spectroscopy studies have been performed on the organic crystal paracetamol in a diamond anvil cell utilizing boron-doped heating diamond anvil. Isobaric measurements were conducted at pressures up to 8.5 GPa and temperature up to 520 K in five different experiments. Solid state phase transitions from monoclinic Form I  →  orthorhombic Form II were observed at various pressures and temperatures as well as transitions from Form II  →  unknown Form IV. The melting temperature for paracetamol was observed to increase with increasing pressures to 8.5 GPa. This new data is combined with previous ambient temperature high-pressure Raman and x-ray diffraction data to create the first HPHT phase diagram of paracetamol.

High-pressure high-temperature phase diagram of organic crystal paracetamol

International Nuclear Information System (INIS)

Smith, Spencer J; Montgomery, Jeffrey M; Vohra, Yogesh K

2016-01-01

High-pressure high-temperature (HPHT) Raman spectroscopy studies have been performed on the organic crystal paracetamol in a diamond anvil cell utilizing boron-doped heating diamond anvil. Isobaric measurements were conducted at pressures up to 8.5 GPa and temperature up to 520 K in five different experiments. Solid state phase transitions from monoclinic Form I  →  orthorhombic Form II were observed at various pressures and temperatures as well as transitions from Form II  →  unknown Form IV. The melting temperature for paracetamol was observed to increase with increasing pressures to 8.5 GPa. This new data is combined with previous ambient temperature high-pressure Raman and x-ray diffraction data to create the first HPHT phase diagram of paracetamol. (paper)

High-temperature phase transition in hadron matter

International Nuclear Information System (INIS)

Bugrij, A.I.; Trushevsky, A.A.

1976-01-01

A possible phase transition in hadronic systems at temperatures of few of GeV is shown in the framework of the S-matrix formulation of statistical mechanics given by Dashen, Ma, Bernstein by using Regge pole model for the scattering amplitude

Core body temperature, skin temperature, and interface pressure. Relationship to skin integrity in nursing home residents.

Science.gov (United States)

Knox, D M

1999-06-01

To ascertain the effects of 1-, 1 1/2-, and 2-hour turning intervals on nursing home residents' skin over the sacrum and trochanters. (1) the higher the core body temperature, the higher the skin surface temperature; (2) the 2-hour turning interval would have significantly higher skin surface temperature; (3) there would be no relationship between skin surface temperature and interface pressure; and (4) the sacrum would have the lowest skin surface temperature. Modified Latin-square. For-profit nursing home. Convenience sample of 26 residents who scored bedridden. First Temp measured core temperature; a disposable thermistor temperature probe, skin temperature; and a digital interface pressure evaluator, the interface pressure. Negative correlation (r = -.33, P = .003) occurred between core body temperature and skin surface temperature. Skin surface temperature rose at the end of the 2-hour turning interval but was not significant (F = (2.68) = .73, P = .49). Weak negative relationship (r = -12, P = .29) occurred between skin surface temperature and interface pressure, and sacral skin surface temperature was significantly lower for the left trochanter only (F = (8.68) = 7.05, P = .002). Although hypotheses were not supported, more research is needed to understand how time in position and multiple chronic illnesses interact to affect skin pressure tolerance.

Possibility of high temperature superconducting phases in PdH

Energy Technology Data Exchange (ETDEWEB)

Tripodi, Paolo; Di Gioacchino, Daniele; Borelli, Rodolfo; Vinko, Jenny Darja

2003-05-15

Possible new superconducting phases with a high critical transition temperature (T{sub c}) have been found in stable palladium-hydrogen (PdH{sub x}) samples for stoichiometric ratio x=H/Pd{>=}1, in addition to the well-known low critical transition temperature (0{<=}T{sub c}{<=}9) when x is in the range (0.75{<=}x{<=}1.00). Possible new measured superconducting phases with critical temperature in the range 51{<=}T{sub c}{<=}295 K occur. This T{sub c} varies considerably with every milli part of x when x exceeds unit. A superconducting critical current density J{sub c}{>=}6.1x10{sup 4} A cm{sup -2} has been measured at 77 K with H{sub DC}=0 T.

Battery Internal Temperature Estimation for LiFePO4 Battery Based on Impedance Phase Shift under Operating Conditions

Directory of Open Access Journals (Sweden)

Jiangong Zhu

2017-01-01

Full Text Available An impedance-based temperature estimation method is investigated considering the electrochemical non-equilibrium with short-term relaxation time for facilitating the vehicular application. Generally, sufficient relaxation time is required for battery electrochemical equilibrium before the impedance measurement. A detailed experiment is performed to investigate the regularity of the battery impedance in short-term relaxation time after switch-off current excitation, which indicates that the impedance can be measured and also has systematical decrement with the relaxation time growth. Based on the discussion of impedance variation in electrochemical perspective, as well as the monotonic relationship between impedance phase shift and battery internal temperature in the electrochemical equilibrium state, an exponential equation that accounts for both measured phase shift and relaxation time is established to correct the measuring deviation caused by electrochemical non-equilibrium. Then, a multivariate linear equation coupled with ambient temperature is derived considering the temperature gradients between the active part and battery surface. Equations stated above are all identified with the embedded thermocouple experimentally. In conclusion, the temperature estimation method can be a valuable alternative for temperature monitoring during cell operating, and serve the functionality as an efficient implementation in battery thermal management system for electric vehicles (EVs and hybrid electric vehicles (HEVs.

New lipid family that forms inverted cubic phases in equilibrium with excess water: molecular structure-aqueous phase structure relationship for lipids with 5,9,13,17-tetramethyloctadecyl and 5,9,13,17-tetramethyloctadecanoyl chains.

Science.gov (United States)

Yamashita, Jun; Shiono, Manzo; Hato, Masakatsu

2008-10-02

With a view to discovering a new family of lipids that form inverted cubic phases, the aqueous phase behavior of a series of lipids with isoprenoid-type hydrophobic chains has been examined over a temperature range from -40 to 65 degrees C by using optical microscopy, DSC (differential scanning calorimetry), and SAXS (small-angle X-ray scattering) techniques. The lipids examined are those with 5,9,13,17-tetramethyloctadecyl and 5,9,13,17-tetramethyloctadecanoyl chains linked to a series of headgroups, that is, erythritol, pentaerythritol, xylose, and glucose. All of the lipid/water systems displayed a "water + liquid crystalline phase" two-phase coexistence state when sufficiently diluted. The aqueous phase structures of the most diluted liquid crystalline phases in equilibrium with excess water depend both on the lipid molecular structure and on the temperature. Given an isoprenoid chain, the preferred phase consistently follows a phase sequence of an H II (an inverted hexagonal phase) to a Q II (an inverted bicontinuous cubic phase) to an L alpha (a lamellar phase) as A* (cross-section area of the headgroup) increases. For a given lipid/water system, the phase sequence observed as the temperature increases is L alpha to Q II to H II. The present study allowed us to find four cubic phase-forming lipid species, PEOC 18+4 [mono- O-(5,9,13,17-tetramethyloctadecyl)pentaerythritol], beta-XylOC 18+4 [1- O-(5,9,13,17-tetramethyloctadecyl)-beta- d-xylopyranoside], EROCOC 17+4 [1- O-(5,9,13,17-tetramethyloctadecanoyl)erythritol], and PEOCOC 17+4 [mono- O-(5,9,13,17-tetramethyloctadecanoyl)pentaerythritol]. The values of T K (hydrated solid-liquid crystalline phase transition temperature) of the cubic phase-forming lipids are all below 0 degrees C. Quantitative analyses of the lipid molecular structure-aqueous phase structure relationship in terms of the experimentally evaluated "surfactant parameter" allow us to rationally select an optimum combination of hydrophilic

Two-phase exchangers with small temperature differences

International Nuclear Information System (INIS)

Moracchioli, R.; Marie, G.; Lallee, J. de.

1976-01-01

The possibility in using heat available at low temperature level is shown (industrial wastes, solar energy, geothermal energy, heat power from seas). Special emphasis is put on the importance of heat exchangers that commonly should be evaporators and condensors working with small temperature differences (20 to 100 deg C). The expansion of the so-called ''new'' energies or recovery processes will depend on the physical performance of exchangers (Rankine two-phase cycles) and cost of the elementary exchange interfaces and assembling technics [fr

Electronic phase separation and high temperature superconductors

International Nuclear Information System (INIS)

Kivelson, S.A.

1994-01-01

The authors review the extensive evidence from model calculations that neutral holes in an antiferromagnet separate into hole-rich and hole-poor phases. All known solvable limits of models of holes in a Heisenberg antiferromagnet exhibit this behavior. The authors show that when the phase separation is frustrated by the introduction of long-range Coulomb interactions, the typical consequence is either a modulated (charge density wave) state or a superconducting phase. The authors then review some of the strong experimental evidence supporting an electronically-driven phase separation of the holes in the cuprate superconductors and the related Ni oxides. Finally, the authors argue that frustrated phase separation in these materials can account for many of the anomalous normal state properties of the high temperature superconductors and provide the mechanism of superconductivity. In particular, it is shown that the T-linear resistivity of the normal state is a paraconductivity associated with a novel composite pairing, although the ordered superconducting state is more conventional

Inorganic Nanostructured High-Temperature Magnet Wires, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This project will develop a high-temperature tolerant electrically-insulating coating for magnet wires. The Phase I program will result in a flexible, inorganic...

Temperature gradient method for lipid phase diagram construction using time-resolved x-ray diffraction

International Nuclear Information System (INIS)

Caffrey, M.; Hing, F.S.

1987-01-01

A method that enables temperature-composition phase diagram construction at unprecedented rates is described and evaluated. The method involves establishing a known temperature gradient along the length of a metal rod. Samples of different compositions contained in long, thin-walled capillaries are positioned lengthwise on the rod and equilibrated such that the temperature gradient is communicated into the sample. The sample is then moved through a focused, monochromatic synchrotron-derived x-ray beam and the image-intensified diffraction pattern from the sample is recorded on videotape continuously in live-time as a function of position and, thus, temperature. The temperature at which the diffraction pattern changes corresponds to a phase boundary, and the phase(s) existing (coexisting) on either side of the boundary can be identified on the basis of the diffraction pattern. Repeating the measurement on samples covering the entire composition range completes the phase diagram. These additional samples can be conveniently placed at different locations around the perimeter of the cylindrical rod and rotated into position for diffraction measurement. Temperature-composition phase diagrams for the fully hydrated binary mixtures, dimyristoylphosphatidylcholine (DMPC)/dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine (DPPE)/DPPC, have been constructed using the new temperature gradient method. They agree well with and extend the results obtained by other techniques. In the DPPE/DPPC system structural parameters as a function of temperature in the various phases including the subgel phase are reported. The potential limitations of this steady-state method are discussed

Low temperature phase of the trigonal RbIn(MoO4)2 crystal

Science.gov (United States)

Zapart, W.; Zapart, M. B.; Schranz, W.; Reinecker, M.

2013-02-01

The present article is devoted to a new low-temperature phase transition found at about T pt = 84 K in the layered RbIn(MoO4)2 crystal. This phase transition is well proved by dynamical mechanical analysis through anomalies in the temperature behaviour of both real and imaginary parts of the Young's modulus. From the polarizing microscope observations it was found that below T pt the ferroelastic phase disappears. This transition has also been seen through strong changes in the shape of the electron paramagnetic resonance lines. EPR studies, performed in the liquid nitrogen temperature, yield evidence of strong rebuilding of the crystal unit cell in comparison with that of the high temperature paraelastic phase.

Uranium peroxide precipitate drying temperature relationships

Energy Technology Data Exchange (ETDEWEB)

Rodgers, C.; Dyck, B., E-mail: chick_rodgers@cameco.com [Cameco Corp., Saskatoon, SK (Canada)

2010-07-01

Cameco Corporation is in the process of revitalizing the mill at its Key Lake operation in northern Saskatchewan. The current Key Lake process employs ammonia stripping and ammonia precipitation. As part of the revitalization, the company is considering installing strong acid stripping in solvent extraction as used at its Rabbit Lake operation. This change would lead to using hydrogen peroxide for uranium precipitation. As part of the process evaluation, tests were carried out to study how changes in the temperature of an indirect fired dryer affected the properties of uranium peroxide [yellowcake] precipitate. This paper discusses the results of the test work, including the relationships between drying temperature and the following: (author)

Snow cover and temperature relationships in North America and Eurasia

Science.gov (United States)

Foster, J.; Owe, M.; Rango, A.

1983-01-01

In this study the snow cover extent during the autumn months in both North America and Eurasia has been related to the ensuing winter temperature as measured at several locations near the center of each continent. The relationship between autumn snow cover and the ensuing winter temperatures was found to be much better for Eurasia than for North America. For Eurasia the average snow cover extent during the autumn explained as much as 52 percent of the variance in the winter (December-February) temperatures compared to only 12 percent for North America. However, when the average winter snow cover was correlated with the average winter temperature it was found that the relationship was better for North America than for Eurasia. As much as 46 percent of the variance in the winter temperature was explained by the winter snow cover in North America compared to only 12 percent in Eurasia.

The relationship of long term global temperature change and human fertility.

Science.gov (United States)

Fisch, Harry; Andrews, Howard F; Fisch, Karen S; Golden, Robert; Liberson, Gary; Olsson, Carl A

2003-07-01

According to the United Nations, global fertility has declined in the last century as reflected by a decline in birth rates. The earth's surface air temperature has increased considerably and is referred to as global warming. Since changes in temperature are well known to influence fertility we sought to determine if a statistical relationship exists between long-term changes in global air temperatures and birth rates. The most complete and reliable birth rate data in the 20th century was available in 19 industrialized countries. Using bivariate and multiple regression analysis, we compared yearly birth rates from these countries to global air temperatures from 1900 to 1994.A common pattern of change in birth rates was noted for the 19 industrialized countries studied. In general, birth rates declined markedly throughout the century except during the baby boom period of approximately 1940 to 1964. An inverse relationship was found between changes in global temperatures and birth rates in all 19 countries. Controlling for the linear yearly decline in birth rates over time, this relationship remained statistically significant for all the 19 countries in aggregate and in seven countries individually (phuman fertility may have been influenced by change in environmental temperatures.

High Temperature Fiberoptic Thermal Imaging System, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The proposed Phase 1 program will fabricate and demonstrate a small diameter single fiber endoscope that can perform high temperature thermal imaging in a jet engine...

Relationship between prostate-specific antigen levels and ambient temperature

Science.gov (United States)

Ohwaki, Kazuhiro; Endo, Fumiyasu; Hattori, Kazunori; Muraishi, Osamu

2014-07-01

We examined the association between prostate-specific antigen (PSA) and daily mean ambient temperature on the day of the test in healthy men who had three annual checkups. We investigated 9,694 men who visited a hospital for routine health checkups in 2007, 2008, and 2009. Although the means and medians of ambient temperature for the three years were similar, the mode in 2008 (15.8 °C) was very different from those in 2007 and 2009 (22.4 °C and 23.2 °C). After controlling for age, body mass index, and hematocrit, a multiple regression analysis revealed a U-shaped relationship between ambient temperature and PSA in 2007 and 2009 ( P 2.5 ng/mL) by ambient temperature, with the lowest likelihood of having a high PSA at 17.8 °C in 2007 ( P = 0.038) and 15.5 °C in 2009 ( P = 0.033). When tested at 30 °C, there was a 57 % excess risk of having a high PSA in 2007 and a 61 % higher risk in 2009 compared with those at each nadir temperature. We found a U-shaped relationship between PSA and ambient temperature with the lowest level of PSA at 15-20 °C.

Defect-induced local variation of crystal phase transition temperature in metal-halide perovskites.

Science.gov (United States)

Dobrovolsky, Alexander; Merdasa, Aboma; Unger, Eva L; Yartsev, Arkady; Scheblykin, Ivan G

2017-06-26

Solution-processed organometal halide perovskites are hybrid crystalline semiconductors highly interesting for low-cost and efficient optoelectronics. Their properties are dependent on the crystal structure. Literature shows a variety of crystal phase transition temperatures and often a spread of the transition over tens of degrees Kelvin. We explain this inconsistency by demonstrating that the temperature of the tetragonal-to-orthorhombic phase transition in methylammonium lead triiodide depends on the concentration and nature of local defects. Phase transition in individual nanowires was studied by photoluminescence microspectroscopy and super-resolution imaging. We propose that upon cooling from 160 to 140 K, domains of the crystal containing fewer defects stay in the tetragonal phase longer than highly defected domains that readily transform to the high bandgap orthorhombic phase at higher temperatures. The existence of relatively pure tetragonal domains during the phase transition leads to drastic photoluminescence enhancement, which is inhomogeneously distributed across perovskite microcrystals.Understanding crystal phase transition in materials is of fundamental importance. Using luminescence spectroscopy and super-resolution imaging, Dobrovolsky et al. study the transition from the tetragonal to orthorhombic crystal phase in methylammonium lead triiodide nanowires at low temperature.

Phase relationships of the system Fe-Ni-S and structure of the high-pressure phase of (Fe1-xNix)3S2

Science.gov (United States)

Urakawa, Satoru; Kamuro, Ryota; Suzuki, Akio; Kikegawa, Takumi

2018-04-01

The phase relationships of the Fe-Ni-S system at 15 GPa were studied by high pressure quench experiments. The stability fields of (Fe,Ni)3S and (Fe,Ni)3S2 and the melting relationships of the Fe-Ni-S system were determined as a function of Ni content. The (Fe,Ni)3S solid solution is stable in the composition of Ni/(Fe + Ni) > 0.7 and melts incongruently into an Fe-Ni alloy + liquid. The (Fe,Ni)3S2 makes a complete solid solution and melts incongruently into (Fe,Ni)S + liquid, whose structure was determined to show Cmcm-orthorhombic symmetry by in situ synchrotron X-ray diffraction experiments. The eutectic contains about 30 at.% of S, and its temperature decreases with increasing Ni content with a rate of ∼5 K/at.% from 1175 K. The density of the Fe-FeS eutectic composition (Fe70S30) liquid is evaluated to be 6.93 ± 0.08 g/cm3 at 15 GPa and 1200 K based on the Clausius-Clapeyron relations and densities of subsolidus phases. The Fe-Ni-S liquids are a primary sulfur-bearing phase in the deep mantle with a reducing condition (250-660 km depth), and they would play a significant role in the carbon cycle as a carbon host as well as in the generation of diamond.

Phase relationship, vaporization, and thermodynamic properties of the lanthanum--boron system

International Nuclear Information System (INIS)

Storms, E.; Mueller, B.

1978-01-01

The La-B system was studied between LaB/sub 4.24/ and LaB/sub 29.2/, and between 1400 and 2100 K to determine the phase relationship, the chemical activity of the components, the vaporization rate, and the vapor composition. A blue colored phase near LaB 9 was found to exist between purple colored LaB 6 and elemental boron. Diffusion is so much slower than vaporization that large composition differences can exist between the surface and the interior which, nevertheless, produce a steady state loss rate from freely vaporizing material. The flux at 1700 K is 6 x 10 -10 g/cm 2 s for LaB 4 +LaB 6 and 7 x 10 -11 g/cm 2 s for LaB 6 + LaB 9 . There is an activation energy which lowers the vaporization rate of boron from LaB 6 . Freely vaporizing material will have a steady state surface composition between LaB/sub 6.04/ and LaB/sub 6.07/, depending on temperature, purity, and interior composition. The free energy of formation of LaB 6 is (0.07lT - 351)kJ/mol between 1700 and 2100 K

Detection of the relationship between peak temperature and extreme precipitation

Science.gov (United States)

Yu, Y.; Liu, J.; Zhiyong, Y.

2017-12-01

Under the background of climate change and human activities, the characteristics and pattern of precipitation have changed significantly in many regions. As the political and cultural center of China, the structure and character of precipitation in Jingjinji District has varied dramatically in recent years. In this paper, the daily precipitation data throughout the period 1960-2013 are selected for analyzing the spatial-temporal variability of precipitation. The results indicate that the frequency and intensity of precipitation presents an increasing trend. Based on the precipitation data, the maximum, minimum and mean precipitation in different temporal and spatial scales is calculated respectively. The temporal and spatial variation of temperature is obtained by using statistical methods. The relationship between temperature and precipitation in different range is analyzed. The curve relates daily precipitation extremes with local temperatures has a peak structure, increasing at the low-medium range of temperature variations but decreasing at high temperatures. The relationship between extreme precipitation is stronger in downtown than that in suburbs.

The responses of microbial temperature relationships to seasonal change and winter warming in a temperate grassland.

Science.gov (United States)

Birgander, Johanna; Olsson, Pål Axel; Rousk, Johannes

2018-01-18

Microorganisms dominate the decomposition of organic matter and their activities are strongly influenced by temperature. As the carbon (C) flux from soil to the atmosphere due to microbial activity is substantial, understanding temperature relationships of microbial processes is critical. It has been shown that microbial temperature relationships in soil correlate with the climate, and microorganisms in field experiments become more warm-tolerant in response to chronic warming. It is also known that microbial temperature relationships reflect the seasons in aquatic ecosystems, but to date this has not been investigated in soil. Although climate change predictions suggest that temperatures will be mostly affected during winter in temperate ecosystems, no assessments exist of the responses of microbial temperature relationships to winter warming. We investigated the responses of the temperature relationships of bacterial growth, fungal growth, and respiration in a temperate grassland to seasonal change, and to 2 years' winter warming. The warming treatments increased winter soil temperatures by 5-6°C, corresponding to 3°C warming of the mean annual temperature. Microbial temperature relationships and temperature sensitivities (Q 10 ) could be accurately established, but did not respond to winter warming or to seasonal temperature change, despite significant shifts in the microbial community structure. The lack of response to winter warming that we demonstrate, and the strong response to chronic warming treatments previously shown, together suggest that it is the peak annual soil temperature that influences the microbial temperature relationships, and that temperatures during colder seasons will have little impact. Thus, mean annual temperatures are poor predictors for microbial temperature relationships. Instead, the intensity of summer heat-spells in temperate systems is likely to shape the microbial temperature relationships that govern the soil-atmosphere C

FEM Modeling of the Relationship between the High-Temperature Hardness and High-Temperature, Quasi-Static Compression Experiment.

Science.gov (United States)

Zhang, Tao; Jiang, Feng; Yan, Lan; Xu, Xipeng

2017-12-26

The high-temperature hardness test has a wide range of applications, but lacks test standards. The purpose of this study is to develop a finite element method (FEM) model of the relationship between the high-temperature hardness and high-temperature, quasi-static compression experiment, which is a mature test technology with test standards. A high-temperature, quasi-static compression test and a high-temperature hardness test were carried out. The relationship between the high-temperature, quasi-static compression test results and the high-temperature hardness test results was built by the development of a high-temperature indentation finite element (FE) simulation. The simulated and experimental results of high-temperature hardness have been compared, verifying the accuracy of the high-temperature indentation FE simulation.The simulated results show that the high temperature hardness basically does not change with the change of load when the pile-up of material during indentation is ignored. The simulated and experimental results show that the decrease in hardness and thermal softening are consistent. The strain and stress of indentation were analyzed from the simulated contour. It was found that the strain increases with the increase of the test temperature, and the stress decreases with the increase of the test temperature.

FEM Modeling of the Relationship between the High-Temperature Hardness and High-Temperature, Quasi-Static Compression Experiment

Directory of Open Access Journals (Sweden)

Tao Zhang

2017-12-01

Full Text Available The high-temperature hardness test has a wide range of applications, but lacks test standards. The purpose of this study is to develop a finite element method (FEM model of the relationship between the high-temperature hardness and high-temperature, quasi-static compression experiment, which is a mature test technology with test standards. A high-temperature, quasi-static compression test and a high-temperature hardness test were carried out. The relationship between the high-temperature, quasi-static compression test results and the high-temperature hardness test results was built by the development of a high-temperature indentation finite element (FE simulation. The simulated and experimental results of high-temperature hardness have been compared, verifying the accuracy of the high-temperature indentation FE simulation.The simulated results show that the high temperature hardness basically does not change with the change of load when the pile-up of material during indentation is ignored. The simulated and experimental results show that the decrease in hardness and thermal softening are consistent. The strain and stress of indentation were analyzed from the simulated contour. It was found that the strain increases with the increase of the test temperature, and the stress decreases with the increase of the test temperature.

Temporal and radial variation of the solar wind temperature-speed relationship

Science.gov (United States)

Elliott, H. A.; Henney, C. J.; McComas, D. J.; Smith, C. W.; Vasquez, B. J.

2012-09-01

The solar wind temperature (T) and speed (V) are generally well correlated at ˜1 AU, except in Interplanetary Coronal Mass Ejections where this correlation breaks down. We perform a comprehensive analysis of both the temporal and radial variation in the temperature-speed (T-V) relationship of the non-transient wind, and our analysis provides insight into both the causes of the T-V relationship and the sources of the temperature variability. Often at 1 AU the speed-temperature relationship is well represented by a single linear fit over a speed range spanning both the slow and fast wind. However, at times the fast wind from coronal holes can have a different T-V relationship than the slow wind. A good example of this was in 2003 when there was a very large and long-lived outward magnetic polarity coronal hole at low latitudes that emitted wind with speeds as fast as a polar coronal hole. The long-lived nature of the hole made it possible to clearly distinguish that some holes can have a different T-V relationship. In an earlier ACE study, we found that both the compressions and rarefactions T-V curves are linear, but the compression curve is shifted to higher temperatures. By separating compressions and rarefactions prior to determining the radial profiles of the solar wind parameters, the importance of dynamic interactions on the radial evolution of the solar wind parameters is revealed. Although the T-V relationship at 1 AU is often well described by a single linear curve, we find that the T-V relationship continually evolves with distance. Beyond ˜2.5 AU the differences between the compressions and rarefactions are quite significant and affect the shape of the overall T-V distribution to the point that a simple linear fit no longer describes the distribution well. Since additional heating of the ambient solar wind outside of interaction regions can be associated with Alfvénic fluctuations and the turbulent energy cascade, we also estimate the heating rate

Geometric relationships for homogenization in single-phase binary alloy systems

Science.gov (United States)

Unnam, J.; Tenney, D. R.; Stein, B. A.

1978-01-01

A semiempirical relationship is presented which describes the extent of interaction between constituents in single-phase binary alloy systems having planar, cylindrical, or spherical interfaces. This relationship makes possible a quick estimate of the extent of interaction without lengthy numerical calculations. It includes two parameters which are functions of mean concentration and interface geometry. Experimental data for the copper-nickel system are included to demonstrate the usefulness of this relationship.

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 ...

Structural and phase transformations in the low-temperature annealed amorphous “finemet”-type microwires

Energy Technology Data Exchange (ETDEWEB)

Tcherdyntsev, V.V., E-mail: vvch08@yandex.ru [National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation); Aleev, A.A. [SSC RF Institute for Theoretical and Experimental Physics, Moscow 117218 (Russian Federation); Churyukanova, M.N.; Kaloshkin, S.D. [National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation); Medvedeva, E.V. [Institute of Electrophysics, Ural Branch, Russian Academy of Sciences, Yekaterinburg 620016 (Russian Federation); Korchuganova, O.A. [SSC RF Institute for Theoretical and Experimental Physics, Moscow 117218 (Russian Federation); Zhukova, V. [Dpto. de Fns. Mater., UPV/EHU, San Sebastian 20018 (Spain); Zhukov, A.P. [Dpto. de Fns. Mater., UPV/EHU, San Sebastian 20018 (Spain); IKERBASQUE, Basque Foundation for Science, 48011 Bilbao (Spain)

2014-02-15

Highlights: • Structure and magnetic properties evolution at heating of amorphous microwires was studied. • Relaxation processes in the amorphous phase correlate with an increase in Curie temperature. • Curie temperature change can not be stabilized by a prolonged exposure at pre-crystallization temperatures. • Tomographic atom probe microscopy supports the formation of α-Fe phase precipitations enriched in Si. -- Abstract: Finemet-type glass-coated microwires with amorphous and nanocrystalline structure have been investigated. The relaxation and crystallization processes at heating of amorphous alloy have been studied by DSC method. We observed that the relaxation processes in the amorphous phase correlate with an increasing of the Curie temperature. Additionally a prolonged exposure of the samples below the crystallization temperatures does not stabilize the Curie temperature change. An investigation by the tomographic atom probe microscopy supports the formation of precipitations, probably α-Fe phase, as a result of low-temperature annealing (400 °C, 5 min). We found that the observed nano-sized areas were enriched in silicon.

Structural and phase transformations in the low-temperature annealed amorphous “finemet”-type microwires

International Nuclear Information System (INIS)

Tcherdyntsev, V.V.; Aleev, A.A.; Churyukanova, M.N.; Kaloshkin, S.D.; Medvedeva, E.V.; Korchuganova, O.A.; Zhukova, V.; Zhukov, A.P.

2014-01-01

Highlights: • Structure and magnetic properties evolution at heating of amorphous microwires was studied. • Relaxation processes in the amorphous phase correlate with an increase in Curie temperature. • Curie temperature change can not be stabilized by a prolonged exposure at pre-crystallization temperatures. • Tomographic atom probe microscopy supports the formation of α-Fe phase precipitations enriched in Si. -- Abstract: Finemet-type glass-coated microwires with amorphous and nanocrystalline structure have been investigated. The relaxation and crystallization processes at heating of amorphous alloy have been studied by DSC method. We observed that the relaxation processes in the amorphous phase correlate with an increasing of the Curie temperature. Additionally a prolonged exposure of the samples below the crystallization temperatures does not stabilize the Curie temperature change. An investigation by the tomographic atom probe microscopy supports the formation of precipitations, probably α-Fe phase, as a result of low-temperature annealing (400 °C, 5 min). We found that the observed nano-sized areas were enriched in silicon

High-Pressure High-Temperature Phase Diagram of the Organic Crystal Paracetamol

Science.gov (United States)

Smith, Spencer; Montgomery, Jeffrey; Vohra, Yogesh

High-pressure high-temperature (HPHT) Raman spectroscopy studies have been performed on the organic crystal paracetamol in a diamond anvil cell utilizing boron-doped diamond as heating anvil. The HPHT data obtained from boron-doped diamond heater is cross-checked with data obtained using a standard block heater diamond anvil cell. Isobaric measurements were conducted at pressures up to 8.5 GPa and temperature up to 520 K in a number of different experiments. Solid state phase transitions from monoclinic Form I --> orthorhombic Form II were observed at various pressures and temperatures as well as transitions from Form II --> unknown Form IV. The melting temperature for paracetamol was observed to increase with increasing pressures to 8.5 GPa. Our previous angle dispersive x-ray diffraction studies at the Advanced Photon Source has confirmed the existence of two unknown crystal structures Form IV and Form V of paracetamol at high pressure and ambient temperature. The phase transformation from Form II to Form IV occurs at ~8.5 GPa and from Form IV to Form V occurs at ~11 GPa at ambient temperature. Our new data is combined with the previous ambient temperature high-pressure Raman and X- ray diffraction data to create the first HPHT phase diagram of paracetamol. Doe-NNSA Carnegie DOE Alliance Center (CDAC) under Grant Number DE-NA0002006.

Rapid Separation of Copper Phase and Iron-Rich Phase From Copper Slag at Low Temperature in a Super-Gravity Field

Science.gov (United States)

Lan, Xi; Gao, Jintao; Huang, Zili; Guo, Zhancheng

2018-06-01

A novel approach for quickly separating a metal copper phase and iron-rich phase from copper slag at low temperature is proposed based on a super-gravity method. The morphology and mineral evolution of the copper slag with increasing temperature were studied using in situ high-temperature confocal laser scanning microscopy and ex situ scanning electron microscopy and X-ray diffraction methods. Fe3O4 particles dispersed among the copper slag were transformed into FeO by adding an appropriate amount of carbon as a reducing agent, forming the slag melt with SiO2 at low temperature and assisting separation of the copper phase from the slag. Consequently, in a super-gravity field, the metallic copper and copper matte were concentrated as the copper phase along the super-gravity direction, whereas the iron-rich slag migrated in the opposite direction and was quickly separated from the copper phase. Increasing the gravity coefficient (G) significantly enhanced the separation efficiency. After super-gravity separation at G = 1000 and 1473 K (1200 °C) for 3 minutes, the mass fraction of Cu in the separated copper phase reached 86.11 wt pct, while that in the separated iron-rich phase was reduced to 0.105 wt pct. The recovery ratio of Cu in the copper phase was as high as up to 97.47 pct.

Phase diagram and equation of state of TiH2 at high pressures and high temperatures

International Nuclear Information System (INIS)

Endo, Naruki; Saitoh, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori; Aoki, Katsutoshi

2013-01-01

Highlights: ► We determined the phase diagram of TiH 2 at high pressures and high temperatures. ► Compression induced stain inhibited the phase transition from the bct to fcc phase. ► The phase boundary was appropriately determined using a sample with heat treatment. ► The high temperature Birch–Murnaghan equation of state of fcc TiH 2 was firstly determined. - Abstract: We determined the phase diagram and the equation of state (EoS) of TiH 2 at high pressures up to 8.7 GPa and high temperatures up to 600 °C by in situ synchrotron radiation X-ray diffraction measurements. Compression induced strain inhibited the phase transition from the low-temperature bct phase to the high-temperature fcc phase, making the phase diagram difficult to determine. However, heating around 600 °C relieved the strain, and the phase boundary between the bct and fcc phases was elucidated. The phase transition temperature at ambient pressure increased from around room temperature to 200 °C at 8.7 GPa. The high temperature Birch–Murnaghan EoS was determined for the fcc phase. With the pressure derivative of the bulk modulus K′ 0 = 4.0, the following parameters were obtained: ambient bulk modulus K 0 = 97.7 ± 0.2 GPa, ambient unit cell of the fcc phase V 0 = 88.57 ± 0.02 Å 3 , temperature derivative of the bulk modulus at constant pressure (∂K/∂T) P = −0.01 ± 0.02, and volumetric thermal expansivity α = a + bT with a = 2.62 ± 1.4 × 10 −5 and b = 5.5 ± 4.5 × 10 −8 . K 0 of fcc TiH 2 was close to those for pure Ti and bct TiH 2 reported in previous studies.

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.

Finite temperature susy GUT phase transitions determined by radiative corrections

International Nuclear Information System (INIS)

Kripfganz, J.; Perlt, H.

1983-01-01

Studying the 2-loop perturbative contribution to the free energy of supersymmetric grand unified theories, SU(3)xSU(2)xU(1) is found to be the prefered low temperature phase. The transition temperature is still within the weak coupling regime. (author)

Dynamic phases of low-temperature low-current driven vortex matter in superconductors

International Nuclear Information System (INIS)

Benkraouda, M; Obaidat, I M; Khawaja, U Al; Mulaa, N M J

2006-01-01

Using molecular dynamics simulations of vortices in a high-temperature superconductor with square periodic arrays of pinning sites, dynamic phases of the low-current driven vortices are studied at low temperatures. A rough vortex phase diagram of three distinct regimes of vortex flow is proposed. At zero temperature, we obtain a coupled-channel regime where rows of vortices flow coherently in the direction of the driving force. As the temperature is increased, a smooth crossover into an uncoupled-channel regime occurs where the coherence between the flowing rows of vortices becomes weaker. Increasing the temperature further leads to a plastic vortex regime, where the channels of flowing vortices completely disappear. The temperatures of the crossovers between these regimes were found to decrease with the driving force

Temperature anomalies of shock and isentropic waves of quark-hadron phase transition

Science.gov (United States)

Konyukhov, A. V.; Iosilevskiy, I. L.; Levashov, P. R.; Likhachev, A. P.

2018-01-01

In this work, we consider a phenomenological equation of state, which combinesstatistical description for hadron gas and a bag-model-based approach for the quark-gluon plasma. The equation of state is based on the excluded volume method in its thermodynamically consistent variant from Satarov et al [2009 Phys. At. Nucl. 72 1390]. The characteristic shape of the Taub adiabats and isentropes in the phase diagram is affected by the anomalous pressure-temperature dependence along the curve of phase equilibrium. The adiabats have kink points at the boundary of the two-phase region, inside which the temperature decreases with compression. Thermodynamic properties of matter observed in the quark-hadron phase transition region lead to hydrodynamic anomalies (in particular, to the appearance of composite compression and rarefaction waves). On the basis of relativistic hydrodynamics equations we investigate and discuss the structure and anomalous temperature behavior in these waves.

Evaluation of empirical relationships between extreme rainfall and daily maximum temperature in Australia

Science.gov (United States)

Herath, Sujeewa Malwila; Sarukkalige, Ranjan; Nguyen, Van Thanh Van

2018-01-01

Understanding the relationships between extreme daily and sub-daily rainfall events and their governing factors is important in order to analyse the properties of extreme rainfall events in a changing climate. Atmospheric temperature is one of the dominant climate variables which has a strong relationship with extreme rainfall events. In this study, a temperature-rainfall binning technique is used to evaluate the dependency of extreme rainfall on daily maximum temperature. The Clausius-Clapeyron (C-C) relation was found to describe the relationship between daily maximum temperature and a range of rainfall durations from 6 min up to 24 h for seven Australian weather stations, the stations being located in Adelaide, Brisbane, Canberra, Darwin, Melbourne, Perth and Sydney. The analysis shows that the rainfall - temperature scaling varies with location, temperature and rainfall duration. The Darwin Airport station shows a negative scaling relationship, while the other six stations show a positive relationship. To identify the trend in scaling relationship over time the same analysis is conducted using data covering 10 year periods. Results indicate that the dependency of extreme rainfall on temperature also varies with the analysis period. Further, this dependency shows an increasing trend for more extreme short duration rainfall and a decreasing trend for average long duration rainfall events at most stations. Seasonal variations of the scale changing trends were analysed by categorizing the summer and autumn seasons in one group and the winter and spring seasons in another group. Most of 99th percentile of 6 min, 1 h and 24 h rain durations at Perth, Melbourne and Sydney stations show increasing trend for both groups while Adelaide and Darwin show decreasing trend. Furthermore, majority of scaling trend of 50th percentile are decreasing for both groups.

Improvements in X-band transmitter phase stability through Klystron body temperature regulation

Science.gov (United States)

Perez, R. M.

1992-01-01

This article describes the techniques used and experimental results obtained in improving transmitter stability by control of the klystron body temperature. Related work in the measurement of klystron phase control parameters (pushing factors) is also discussed. The contribution of wave guide temperature excursions to uplink phase stability is presented. Suggestions are made as to the direction of future work in this area.

Changes in photosynthesis and soil moisture drive the seasonal soil respiration-temperature hysteresis relationship

Science.gov (United States)

Quan Zhang; Richard P. Phillips; Stefano Manzoni; Russell L. Scott; A. Christopher Oishi; Adrien Finzi; Edoardo Daly; Rodrigo Vargas; Kimberly A. Novick

2018-01-01

In nearly all large-scale terrestrial ecosystem models, soil respiration is represented as a function of soil temperature. However, the relationship between soil respiration and soil temperature is highly variable across sites and there is often a pronounced hysteresis in the soil respiration-temperature relationship over the course of the growing season. This...

Structure-property relationships in flavour-barrier membranes with reduced high-temperature diffusivity

International Nuclear Information System (INIS)

Heitfeld, Kevin A.; Schaefer, Dale W.

2009-01-01

Encapsulation is used to decrease the premature release of volatile flavour ingredients while offering protection against environmental damage such as oxidation, light-induced reactions, etc. Hydroxypropyl cellulose (HPC) is investigated here as a 'smart,' temperature responsive membrane for flavour encapsulation and delivery. Gel films were synthesized and characterized by diffusion and small-angle neutron and X-ray scattering techniques. Increasing temperature typically increases the diffusion rate across a membrane; HPC, however, can be tailored to give substantially improved elevated temperature properties. Scattering results indicate processing conditions have a significant impact on membrane morphology (micro phase separation). Under certain synthetic conditions, micro phase separation is mitigated and the membranes show temperature-independent diffusivity between 25 C and 60 C.

Relationship of core exit-temperature noise to thermal-hydraulic conditions in PWRs

International Nuclear Information System (INIS)

Sweeney, F.J.; Upadhyaya, B.R.

1983-01-01

Core exit thermocouple temperature noise and neutron detector noise measurements were performed at the Loss of Fluid Test Facility (LOFT) reactor and a Westinghouse, 1148 MW(e) PWR to relate temperature noise to core thermal-hydraulic conditions. The noise analysis results show that the RMS of the temperature noise increases linearly with increasing core δT at LOFT and the commercial PWR. Out-of-core test loop temperature noise has shown similar behavior. The phase angle between core exit temperature noise and in-core or ex-core neutron noise is directly related to the core coolant flow velocity. However, if the thermocouple response time is slow, compared to the coolant transit time between the sensors, velocities inferred from the phase angle are lower than measured coolant flow velocities

Relationship between skin temperature and muscle activation during incremental cycle exercise.

Science.gov (United States)

Priego Quesada, Jose I; Carpes, Felipe P; Bini, Rodrigo R; Salvador Palmer, Rosario; Pérez-Soriano, Pedro; Cibrián Ortiz de Anda, Rosa M

2015-02-01

While different studies showed that better fitness level adds to the efficiency of the thermoregulatory system, the relationship between muscular effort and skin temperature is still unknown. Therefore, the present study assessed the relationship between neuromuscular activation and skin temperature during cycle exercise. Ten physically active participants performed an incremental workload cycling test to exhaustion while neuromuscular activations were recorded (via surface electromyography - EMG) from rectus femoris, vastus lateralis, biceps femoris and gastrocnemius medialis. Thermographic images were recorded before, immediately after and 10 min after finishing the cycling test, at four body regions of interest corresponding to the muscles where neuromuscular activations were monitored. Frequency band analysis was conducted to assess spectral properties of EMG signals in order to infer on priority in recruitment of motor units. Significant inverse relationship between changes in skin temperature and changes in overall neuromuscular activation for vastus lateralis was observed (r0.7 and p<0.01). Participants with larger overall activation and reduced low frequency component for vastus lateralis activation presented a better adaptive response of their thermoregulatory system by showing fewer changes in skin temperature after incremental cycling test. Copyright © 2014 Elsevier Ltd. All rights reserved.

Micromachined High-Temperature Sensors for Planet Exploration, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — In phase I of the SBIR program, LEEOAT Company will develop, simulate, fabricate and test high-temperature piezoelectric miniature sensors (up to 800oC), for...

Solid-state phase relationships in the calcia-titania-zirconia system at 1200 C

International Nuclear Information System (INIS)

Swenson, D.; Nieh, T.G.; Fournelle, J.H.

1998-01-01

Phase relationships were investigated in the CaO-TiO 2 -ZrO 2 system at 1200 C for compositions containing 2 O 7 ) and calzirtite (Ca 2 Zr 5 Ti 2 O 16 ), was confirmed. Each of these phases exhibited a significant range of homogeneity between TiO 2 and ZrO 2 , while maintaining a nearly constant concentration of CaO. The ternary solubilities of the constituent binary phases were found to be small (typically 3 and CaZrO 3 ). These latter phases displayed mutual solubilities of at least 22 mol% but exhibited significant variations in composition from grain to grain. Thermodynamic equilibrium was clearly not established in several samples, although most of the phase relationship information obtained was self-consistent

Thermal characteristics of shape-stabilized phase change material wallboard with periodical outside temperature waves

International Nuclear Information System (INIS)

Zhou, Guobing; Yang, Yongping; Wang, Xin; Cheng, Jinming

2010-01-01

Thermal characteristics of shape-stabilized phase change material (SSPCM) wallboard with sinusoidal temperature wave on the outer surface were investigated numerically and compared with traditional building materials such as brick, foam concrete and expanded polystyrene (EPS). One-dimensional enthalpy equation under convective boundary conditions was solved using fully implicit finite-difference scheme. The simulation results showed that the SSPCM wallboard presents distinct characteristics from other ordinary building materials. Phase transition keeping time of inner surface and decrement factor were applied to analyze the effects of PCM thermophysical properties (melting temperature, heat of fusion, phase transition zone and thermal conductivity), inner surface convective heat transfer coefficient and thickness of SSPCM wallboard. It was found that melting temperature is one important factor which influences both the phase transition keeping time and the decrement factor; for a certain outside temperature wave, there exist critical values of latent heat of fusion and thickness of SSPCM above which the phase transition keeping time or the decrement factor are scarcely influenced; thermal conductivity of PCM and inner surface convective coefficient have little effect on the phase transition keeping time but significantly influence the decrement factor; and the phase transition zone leads to small fluctuations of the original flat segment of inner surface temperature line. The results aim to be useful for the selection of SSPCMs and their applications in passive solar buildings.

Low temperature phase transition of the stoichiometric Ln2NiO4 oxides

International Nuclear Information System (INIS)

Fernandez, F.; Saez-Puche, R.; Botto, I.L.; Baran, E.J.

1991-01-01

In this paper we will present a comparative study of the structural phase transition in Ln 2 NiO 4 oxides, by means of neutron diffraction and infrared(IR) spectroscopy. In the Ln 2 NiO 4 oxides (Ln=La, Pr and Nd), there is a low temperature structural phase transition from the orthorhombic symmetry to a tetragonal phase, of first order character. The IR spectra show, at low temperature, a splitting of the bands related with the stretching Ni-O, strongly correlated with the phase transformation. From the neutron data, the phase transition can be visualized as a sudden tilt of the nickel octahedra

Lower critical solution temperature (LCST) phase separation of glycol ethers for forward osmotic control.

Science.gov (United States)

Nakayama, Daichi; Mok, Yeongbong; Noh, Minwoo; Park, Jeongseon; Kang, Sunyoung; Lee, Yan

2014-03-21

Lower critical solution temperature (LCST) phase transition of glycol ether (GE)-water mixtures induces an abrupt change in osmotic pressure driven by a mild temperature change. The temperature-controlled osmotic change was applied for the forward osmosis (FO) desalination. Among three GEs evaluated, di(ethylene glycol) n-hexyl ether (DEH) was selected as a potential FO draw solute. A DEH-water mixture with a high osmotic pressure could draw fresh water from a high-salt feed solution such as seawater through a semipermeable membrane at around 10 °C. The water-drawn DEH-water mixture was phase-separated into a water-rich phase and a DEH-rich phase at around 30 °C. The water-rich phase with a much reduced osmotic pressure released water into a low-salt solution, and the DEH-rich phase was recovered into the initial DEH-water mixture. The phase separation behaviour, the residual GE concentration in the water-rich phase, the osmotic pressure of the DEH-water mixture, and the osmotic flux between the DEH-water mixture and salt solutions were carefully analysed for FO desalination. The liquid-liquid phase separation of the GE-water mixture driven by the mild temperature change between 10 °C and 30 °C is very attractive for the development of an ideal draw solute for future practical FO desalination.

Molecular dynamics simulation of ZnO wurtzite phase under high and low pressures and temperatures

Science.gov (United States)

Chergui, Y.; Aouaroun, T.; Hadley, M. J.; Belkada, R.; Chemam, R.; Mekki, D. E.

2017-11-01

Isothermal and isobaric ensembles behaviours of ZnO wurtzite phase have been investigated, by parallel molecular dynamics method and using Buckingham potential, which contains long-range Coulomb, repulsive exponential, and attractive dispersion terms. To conduct our calculations, we have used dl_poly 4 software, under which the method is implemented. We have examined the influence of the temperature and pressure on molar volume in the ranges of 300-3000 K and 0-200 GPa. Isothermal-isobaric relationships, fluctuations, standard error, equilibrium time, molar volume and its variation versus time are predicted and analyzed. Our results are close to available experimental data and theoretical results.

Dual Phase Membrane for High Temperature CO2 Separation

Energy Technology Data Exchange (ETDEWEB)

Jerry Lin

2007-06-30

This project aimed at synthesis of a new inorganic dual-phase carbonate membrane for high temperature CO{sub 2} separation. Metal-carbonate dual-phase membranes were prepared by the direct infiltration method and the synthesis conditions were optimized. Permeation tests for CO{sub 2} and N{sub 2} from 450-750 C showed very low permeances of those two gases through the dual-phase membrane, which was expected due to the lack of ionization of those two particular gases. Permeance of the CO{sub 2} and O{sub 2} mixture was much higher, indicating that the gases do form an ionic species, CO{sub 3}{sup 2-}, enhancing transport through the membrane. However, at temperatures in excess of 650 C, the permeance of CO{sub 3}{sup 2-} decreased rapidly, while predictions showed that permeance should have continued to increase with temperature. XRD data obtained from used membrane indicated that lithium iron oxides formed on the support surface. This lithium iron oxide layer has a very low conductivity, which drastically reduces the flow of electrons to the CO{sub 2}/O{sub 2} gas mixture; thus limiting the formation of the ionic species required for transport through the membrane. These results indicated that the use of stainless steel supports in a high temperature oxidative environment can lead to decreased performance of the membranes. This revelation created the need for an oxidation resistant support, which could be gained by the use of a ceramic-type membrane. Work was extended to synthesize a new inorganic dual-phase carbonate membrane for high temperature CO{sub 2} separation. Helium permeance of the support before and after infiltration of molten carbonate are on the order of 10{sup -6} and 10{sup -10} moles/m{sup 2} {center_dot} Pa {center_dot} s respectively, indicating that the molten carbonate is able to sufficiently infiltrate the membrane. It was found that La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (LSCF) was a suitable candidate for the support

Heat capacity characterization at phase transition temperature of Agl superionic

International Nuclear Information System (INIS)

Widowati, Arie

2000-01-01

The phase transition of Agl superionic conductor was investigated by calorometric. A single phase transition was found at (153±5) o C which corresponds to the α - β transition. Calorimetric measurement showed an anomalously high heat capacity with a large discontinues change in the Arrhenius plot, was found above the transition temperature of β - α phase. The maximum heat capacity was found to be ±19.7 cal/gmol. Key words : superionic conductor, thermal capacity

Pressure-temperature phase behavior of mixtures of natural sphingomyelin and ceramide extracts.

Science.gov (United States)

Barriga, Hanna M G; Parsons, Edward S; McCarthy, Nicola L C; Ces, Oscar; Seddon, John M; Law, Robert V; Brooks, Nicholas J

2015-03-31

Ceramides are a group of sphingolipids that act as highly important signaling molecules in a variety of cellular processes including differentiation and apoptosis. The predominant in vivo synthetic pathway for ceramide formation is via sphingomyelinase catalyzed hydrolysis of sphingomyelin. The biochemistry of this essential pathway has been studied in detail; however, there is currently a lack of information on the structural behavior of sphingomyelin- and ceramide-rich model membrane systems, which is essential for developing a bottom-up understanding of ceramide signaling and platform formation. We have studied the lyotropic phase behavior of sphingomyelin-ceramide mixtures in excess water as a function of temperature (30-70 °C) and pressure (1-200 MPa) by small- and wide-angle X-ray scattering. At low ceramide concentrations the mixtures form the ripple gel phase (P(β)') below the gel transition temperature for sphingomyelin, and this observation has been confirmed by atomic force microscopy. Formation of the ripple gel phase can also be induced at higher temperatures via the application of hydrostatic pressure. At high ceramide concentration an inverse hexagonal phase (HII) is formed coexisting with a cubic phase.

Temperature induced reversible polymorphic phase transformations in a bis-hydrazone compound

Science.gov (United States)

Jayant, Vikrant; Das, Dinabandhu

2018-03-01

Two reversible polymorphic phase transformation of 2,3-butanedione, 2,3- bis[4,4‧-bis(diethylamino)benzophenone hydrazone] (DEBH) have been identified in DSC experiment. Topotactic phase transformation of three polymorphs has been observed in variable temperature Single Crystal X-ray Diffraction experiment. The reversible phase transformation of bulk material has been confirmed by Powder X-ray diffraction study.

The pion quasiparticle in the low-temperature phase of QCD

Directory of Open Access Journals (Sweden)

Brandt Bastian B.

2018-01-01

Full Text Available We extend our previous studies [PhysRevD.90.054509, PhysRevD.92.094510] of the pion quasiparticle in the low-temperature phase of two-flavor QCD with support from chiral effective theory. This includes the analysis performed on a finite temperature ensemble of size 20 × 643 at T ≈ 151MeV and a lighter zero-temperature pion mass mπ ≈ 185 MeV. Furthermore, we investigate the Gell-Mann–Oakes-Renner relation at finite temperature and the Dey-Eletsky-Ioffe mixing theorem at finite quark mass.

InGaN High Temperature Photovoltaic Cells, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — The objectives of this Phase II project are to develop InGaN photovoltaic cells for high temperature and/or high radiation environments to TRL 4 and to define the...

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.

Phase Transformations in Nickel base Superalloy Inconel 718 during Cyclic Loading at High Temperature

Directory of Open Access Journals (Sweden)

Michal Jambor

2017-06-01

Full Text Available Nickel base superalloys are hi-tech materials intended for high temperature applications. This property owns a complex microstructure formed by matrix of Ni and variety of precipitates. The type, form and the amount of these phases significantly affect the resulting properties of these alloys. At sufficiently long exposure to high temperatures, the transformation phase can occur, which can lead to degradation of properties of these alloys. A cyclic plastic deformation can accelerate these changes, and they could occur at significantly lower temperatures or in shorter time of exposure. The aim of this study is to describe phase transformation, which can occur by a cyclic plastic deformation at high temperatures in nickel base superalloy Inconel 718.

Temperature-Dependent Change of Packing Structure of Condensed-Phase in a Micro-Phase Separated Langmuir Monolayer Studied by Grazing-Incidence X-ray Diffraction

Energy Technology Data Exchange (ETDEWEB)

Iimura, Ken-ichi [Department of Applied Chemisty, Faculty of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585, Utsunomiya (Japan); Kato, Teiji [Department of Applied Chemisty, Faculty of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585, Utsunomiya (Japan); Brezesinski, Gerald [Max-Planck Instutite of Colloids and Interfaces, Research Campus Golm, D-14476 Potsdam (Germany)

2007-10-15

Packing structure of condensed-phase in a binary mixed Langmuir monolayer of behenic acid (C22) and perfluoro-2,5,8-trimethyl-3,6,9-trioxadodecanoic acid (PFPE) on a cadmium acetate aqueous solution was studied by grazing incidence X-ray diffraction (GIXD) as a function of the subphase temperature. The measurements were made during temperature scan at a fixed molecular area to explain the morphological change of the condensed-phase domains due to a thermal treatment reported previously. Analysis of GIXD data implies that the condensed-phase domains are composed of only the C22 molecules perpendicularly oriented and very closely packed in a centered rectangular unit cell with orthorhombic distortion at low temperatures. As the temperature increases the area occupied by molecule increases, and above 25 deg. C the lattice becomes disordered, which would allow morphological transformation of the condensed-phase domains. The process of packing structure change is almost reversible except for non-equilibrium phases observed for the monolayer spread at a low temperature, 5.5 deg. C.

Temperature-Dependent Change of Packing Structure of Condensed-Phase in a Micro-Phase Separated Langmuir Monolayer Studied by Grazing-Incidence X-ray Diffraction

International Nuclear Information System (INIS)

Iimura, Ken-ichi; Kato, Teiji; Brezesinski, Gerald

2007-01-01

Packing structure of condensed-phase in a binary mixed Langmuir monolayer of behenic acid (C22) and perfluoro-2,5,8-trimethyl-3,6,9-trioxadodecanoic acid (PFPE) on a cadmium acetate aqueous solution was studied by grazing incidence X-ray diffraction (GIXD) as a function of the subphase temperature. The measurements were made during temperature scan at a fixed molecular area to explain the morphological change of the condensed-phase domains due to a thermal treatment reported previously. Analysis of GIXD data implies that the condensed-phase domains are composed of only the C22 molecules perpendicularly oriented and very closely packed in a centered rectangular unit cell with orthorhombic distortion at low temperatures. As the temperature increases the area occupied by molecule increases, and above 25 deg. C the lattice becomes disordered, which would allow morphological transformation of the condensed-phase domains. The process of packing structure change is almost reversible except for non-equilibrium phases observed for the monolayer spread at a low temperature, 5.5 deg. C

A Mixed Enthalpy-Temperature Finite Element Method For Generalized Phase-Change Problems

DEFF Research Database (Denmark)

krabbenhøft, Kristian; Damkilde, Lars

2003-01-01

In a large number of problems of engineering interest the transition of the material from one phase to another is of vital importance in describing the overall physical behaviour. Common applications include metal casting, freezing and thawing of foodstuffs and other biological materials, ground ...... freezing and solar energy storage. The phase-change problem is characterized by an abrupt change in enthalpy per unit temperature in a narrow temperature range around the freezing point....

A Mixed Enthalpy-Temperature Finite Element Method For Generalized Phase-Change Problems

DEFF Research Database (Denmark)

krabbenhøft, Kristian; Damkilde, Lars

2003-01-01

In a large number of problems of engineering interest the transition of the material from one phase to another is of vital importance in describing the overall physical behaviour. Common applications include metal casting, freezing and thawing of foodstuffs and other biological materials, ground...... freezing and solar energy storage. The phase-change problem is characterized by an abrupt change in enthalpy per unit temperature in a narrow temperature range around the freezing point....

Low temperature spin-glass-like phases in magnetic nano-granular composites

KAUST Repository

Zhang, Bei

2012-09-01

It is a common understanding that the dipole-dipole interaction among the magnetic nanoparticles may result in a low-temperature spin-glass phase, which has been evidenced by observation of aging effect and memory effect. However, several studies on the nano-particles systems showed that some of the observed spin-glass-like phenomena could be due to the existence of spin-glasslike shells surrounding the ferrimagnetic cores. Therefore, it is very important to understand that how the dipole-dipole interaction induce the spin-glass phase. In order to address this issue, we have fabricated Co-SiO 2 and Fe-SiO 2 nano-granular thin films and measured the memory effect for them. Spin-glass-like phase has been observed at low temperatures. We found that, after annealing, the size of the clusters increased significantly. Based on a simple model, the dipole-dipole interaction between the clusters must be increased accordingly for the annealed samples. Interestingly, the memory effect is greatly weakened in the annealed films, which strongly suggested that the dipole-dipole interaction may not be the major factor for the formation of the low-temperature spin-glass-like phase. Copyright © 2012 American Scientific Publishers All rights reserved.

Dynamic phase transition in the kinetic spin-32 Blume-Capel model: Phase diagrams in the temperature and crystal-field interaction plane

International Nuclear Information System (INIS)

Keskin, Mustafa; Canko, Osman; Deviren, Bayram

2007-01-01

We analyze, within a mean-field approach, the stationary states of the kinetic spin-32 Blume-Capel (BC) model by the Glauber-type stochastic dynamics and subject to a time-dependent oscillating external magnetic field. The dynamic phase transition (DPT) points are obtained by investigating the behavior of the dynamic magnetization as a function of temperature and as well as calculating the Liapunov exponent. Phase diagrams are constructed in the temperature and crystal-field interaction plane. We find five fundamental types of phase diagrams for the different values of the reduced magnetic field amplitude parameter (h) in which they present a disordered, two ordered phases and the coexistences phase regions. The phase diagrams also exhibit a dynamic double-critical end point for 0 5.06

Infrared properties of the organic semiconductor MEM(TCNQ)2 in its high-temperature phase

DEFF Research Database (Denmark)

Yartsev, V. M.; Jacobsen, Claus Schelde

1981-01-01

The infrared spectrum of N-methyl-N-ethylmorpholinium tetra-cyanoquinodimethane, MEM(TCNQ)2, at temperatures above the phase transition at T=335 K is reported. The oscillator strength associated with chargetransfer processes is shifted down in frequency as compared to the room-temperature phase. ...

The Radial Variation of the Solar Wind Temperature-Speed Relationship

Science.gov (United States)

Elliott, H. A.; McComas, D. J.

2010-12-01

Generally, the solar wind temperature (T) and speed (V) are well correlated except in Interplanetary Coronal Mass Ejections where this correlation breaks down. We have shown that at 1 AU the speed-temperature relationship is often well represented by a linear fit for a speed range spanning both the slow and fast wind. By examining all of the ACE and OMNI measurements, we found that when coronal holes are large the fast wind can have a different T-V relationship than the slow wind. The best example of this was in 2003 when there was a very large and long-lived outward polarity coronal hole at low latitudes. The long-lived nature of the hole made it possible to clearly distinguish that large holes can have a different T-V relationship. We found it to be rare that holes are large enough and last long enough to have enough data points to clearly demonstrate this effect. In this study we compare the 2003 coronal hole observations from ACE with the Ulysses polar coronal hole measurements. In an even earlier ACE study we found that both the compressions and rarefactions curves are linear, but the compression curve is shifted to higher temperatures. In this presentation we use Helios, Ulysses, and ACE measurements to examine how the T-V relationship varies with distance. The dynamic evolution of the solar wind parameters is revealed when we first separate compressions and rarefactions and then determine the radial profiles of the solar wind parameters. We find that T-V relationship varies with distance and in particular beyond 3 AU the differences between the compressions and rarefactions are quite important and at such distances a simple linear fit does not represent the T-V distribution very well.

Equation of state, phase stability, and phase transformations of uranium-6 wt. % niobium under high pressure and temperature

Science.gov (United States)

Zhang, Jianzhong; Vogel, Sven; Brown, Donald; Clausen, Bjorn; Hackenberg, Robert

2018-05-01

In-situ time-of-flight neutron diffraction experiments were conducted on the uranium-niobium alloy with 6 wt. % Nb (U-6Nb) at pressures up to 4.7 GPa and temperatures up to 1073 K. Upon static compression at room temperature, the monoclinic structure of U-6Nb (α″ U-6Nb) remains stable up to the highest experimental pressure. Based on the pressure-volume measurements at room temperature, the least-squares fit using the finite-strain equation of state (EOS) yields an isothermal bulk modulus of B0 = 127 ± 2 GPa for the α″-phase of U-6Nb. The calculated zero-pressure bulk sound speed from this EOS is 2.706 ± 0.022 km/s, which is in good agreement with the linear extrapolation of the previous Hugoniot data above 12 GPa for α″ U-6Nb, indicating that the dynamic response under those shock-loading conditions is consistent with the stabilization of the initial monoclinic phase of U-6Nb. Upon heating at ambient and high pressures, the metastable α″ U-6Nb exhibits complex transformation paths leading to the diffusional phase decomposition, which are sensitive to applied pressure, stress state, and temperature-time path. These findings provide new insight into the behavior of atypical systems such as U-Nb and suggest that the different U-Nb phases are separated by rather small energies and hence highly sensitive to compositional, thermal, and mechanical perturbations.

The relationship between brightness temperature and soil moisture. Selection of frequency range for microwave remote sensing

International Nuclear Information System (INIS)

Rao, K.S.; Chandra, G.; Rao, P.V.N.

1987-01-01

The analysis of brightness temperature data acquired from field and aircraft experiments demonstrates a linear relationship between soil moisture and brightness temperature. However, the analysis of brightness temperature data acquired by the Skylab radiometer demonstrates a non-linear relationship between soil moisture and brightness temperature. In view of the above and also because of recent theoretical developments for the calculation of the dielectric constant and brightness temperature under varying soil moisture profile conditions, an attempt is made to study the theoretical relationship between brightness temperature and soil moisture as a function of frequency. Through the above analysis, the appropriate microwave frequency range for soil moisture studies is recommended

Classification of Arctic, midlatitude and tropical clouds in the mixed-phase temperature regime

Science.gov (United States)

Costa, Anja; Meyer, Jessica; Afchine, Armin; Luebke, Anna; Günther, Gebhard; Dorsey, James R.; Gallagher, Martin W.; Ehrlich, Andre; Wendisch, Manfred; Baumgardner, Darrel; Wex, Heike; Krämer, Martina

2017-10-01

The degree of glaciation of mixed-phase clouds constitutes one of the largest uncertainties in climate prediction. In order to better understand cloud glaciation, cloud spectrometer observations are presented in this paper, which were made in the mixed-phase temperature regime between 0 and -38 °C (273 to 235 K), where cloud particles can either be frozen or liquid. The extensive data set covers four airborne field campaigns providing a total of 139 000 1 Hz data points (38.6 h within clouds) over Arctic, midlatitude and tropical regions. We develop algorithms, combining the information on number concentration, size and asphericity of the observed cloud particles to classify four cloud types: liquid clouds, clouds in which liquid droplets and ice crystals coexist, fully glaciated clouds after the Wegener-Bergeron-Findeisen process and clouds where secondary ice formation occurred. We quantify the occurrence of these cloud groups depending on the geographical region and temperature and find that liquid clouds dominate our measurements during the Arctic spring, while clouds dominated by the Wegener-Bergeron-Findeisen process are most common in midlatitude spring. The coexistence of liquid water and ice crystals is found over the whole mixed-phase temperature range in tropical convective towers in the dry season. Secondary ice is found at midlatitudes at -5 to -10 °C (268 to 263 K) and at higher altitudes, i.e. lower temperatures in the tropics. The distribution of the cloud types with decreasing temperature is shown to be consistent with the theory of evolution of mixed-phase clouds. With this study, we aim to contribute to a large statistical database on cloud types in the mixed-phase temperature regime.

Temperature-dependent phase transitions in zeptoliter volumes of a complex biological membrane

International Nuclear Information System (INIS)

Nikiforov, Maxim P; Jesse, Stephen; Kalinin, Sergei V; Hohlbauch, Sophia; Proksch, Roger; King, William P; Voitchovsky, Kislon; Contera, Sonia Antoranz

2011-01-01

Phase transitions in purple membrane have been a topic of debate for the past two decades. In this work we present studies of a reversible transition of purple membrane in the 50-60 deg. C range in zeptoliter volumes under different heating regimes (global heating and local heating). The temperature of the reversible phase transition is 52 ± 5 deg. C for both local and global heating, supporting the hypothesis that this transition is mainly due to a structural rearrangement of bR molecules and trimers. To achieve high resolution measurements of temperature-dependent phase transitions, a new scanning probe microscopy-based method was developed. We believe that our new technique can be extended to other biological systems and can contribute to the understanding of inhomogeneous phase transitions in complex systems.

Coal ash fusion temperatures -- New characterization techniques, and associations with phase equilibria

Energy Technology Data Exchange (ETDEWEB)

Wall, T.F.; Gupta, R.P.; Gupta, S. [Univ. of Newcastle, New South Wales (Australia). Dept. of Chemical Engineering; Creelman, R.A. [R.A. Creelman and Associates, Epping, New South Wales (Australia); Coin, C. [ACIRL Ipswich, Booval, Queensland (Australia); Lowe, A. [Pacific Power, Sydney, New South Wales (Australia)

1996-12-31

The well-documented shortcomings of the standard technique for estimating the fusion temperature of coal ash are its subjective nature and poor accuracy. Alternative measurements based on the shrinkage and electrical conductivity of heating samples are therefore examined with laboratory ash prepared at about 800 C in crucibles, as well as combustion ash sampled from power stations. Sensitive shrinkage measurements indicate temperatures of rapid change which correspond to the formation of liquid phases that can be identified on ternary phase diagrams. The existence and extent of formation of these phases, as quantified by the magnitude of peaks in the test, provide alternative ash fusion temperatures. The peaks from laboratory ashes and corresponding combustion ashes derived from the same coals show clear differences which may be related to the evaporation of potassium during combustion and the reactions of the mineral residues to form combustion ash.

Reversible temperature regulation of electrical and thermal conductivity using liquid–solid phase transitions

Science.gov (United States)

Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

2011-01-01

Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions. PMID:21505445

Reversible temperature regulation of electrical and thermal conductivity using liquid-solid phase transitions.

Science.gov (United States)

Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

2011-01-01

Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions.

Structural relationships in high temperature superconductors

International Nuclear Information System (INIS)

Schuller, I.K.; Segre, C.U.; Hinks, D.G.; Jorgensen, J.D.; Soderholm, L.; Beno, M.; Zhang, K.

1987-09-01

The recent discovery of two types of metallic copper oxide compounds which are superconducting to above 90 0 K has renewed interest in the search for new high temperature superconducting materials. It is significant that both classes of compounds, La/sub 2-x/Sr/sub x/CuO/sub 4-y/ and YBa 2 Cu 3 O/sub 7-δ/ are intimately related to the extensively studied perovskite family. Both compounds contain highly oxidized, covalently bonded Cu-O sublattices, however, they differ in geometry. In this paper we discuss the relationship of these features to the superconducting properties. 30 refs., 6 figs

Importance of granulometry on phase evolution and phase-to-phase relationships of experimentally burned impure limestones intended for production of hydraulic lime and/or natural cement

Science.gov (United States)

Kozlovcev, Petr; Přikryl, Richard; Přikrylová, Jiřina

2015-04-01

In contrast to modern ordinary Portland cement production from finely ground raw material blends, ancient burning of hydraulic lime was conducted by burning larger pieces of natural raw material. Due to natural variability of raw material composition, exploitation of different beds from even one formation can result the product with significantly different composition and/or properties. Prague basin (Neoproterozoic to pre-Variscan Palaeozoic of the central part of the Bohemian Massif - the so-called Barrandian area, Czech Republic) represents a classical example of the limestone-rich region with long-term history of limestone burning for quick lime and/or various types of hydraulic binders. Due to the fact that burning of natural hydraulic lime has been abandoned in this region at the turn of 19th/20th c., significant gap in knowledge on the behavior of various limestone types and on the influence of minor variance in composition on the quality of burned product is encountered. Moreover, the importance of employment of larger pieces of raw material for burning for the development of proper phase-to-phase relationships (i.e. development of hydraulic phases below sintering temperature at mutual contacts of minerals) has not been examined before. To fill this gap, a representative specimens of major limestone types from the Prague basin have been selected for experimental study: Upper Silurian limestone types (Přídolí and Kopanina Lms.), and Lower Devonian limestones (Radotín, Kotýs, Řeporyje, Dvorce-Prokop, and Zlíchov Lms.). Petrographic character of the experimental material was examined by polarizing microscopy, cathodoluminescence, scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS), and X-ray diffraction (XRD) of insoluble residue. Based on the data from wet silicate analyses, modal composition of studied impure limestones was computed. Experimental raw material was burned in laboratory electric furnace at 1000 and 1200°C for 3

Relationship between coal and coke microstructure and the high temperature properties of coke. [Temperature dependence

Energy Technology Data Exchange (ETDEWEB)

Tsuyuguchi, K; Yamaji, M; Sugimoto, Y

1980-02-01

This paper considers the relationship of the properties of coke and parent coal with the high temperature properties, including reactivity, of coke. Aspects considered include coke texture and grade, and the optical reflectivity of coal and coke. (8 refs.) (In Japanese)

TEMPERATURE INFLUENCE ON PHASE STABILITY OF ETHANOL-GASOLINE MIXTURES

Directory of Open Access Journals (Sweden)

Valerian Cerempei

2011-06-01

Full Text Available The article investigates phase stability of ethanol-gasoline mixtures depending on their composition, water concentration in ethanol and ethanol-gasoline mixture and temperature. There have been determined the perfect functioning conditions of spark ignition engines fueled with ethanol-gasoline mixtures.

Temperature-precipitation relationship of the Common Era in northern Europe

Science.gov (United States)

Luoto, Tomi P.; Nevalainen, Liisa

2018-05-01

Due to the lack of knowledge on dynamics of the North Atlantic Oscillation (NAO) prior to the last millennium, synchronized records of air temperature and precipitation variability are needed to understand large-scale drivers of the hydroclimate. Here, we use completely synchronized paleolimnological proxy-based records of air temperature and effective precipitation from two Scandinavian lakes with ˜2000-year sediment profiles. We show that the relationship between air temperature and precipitation (T/P ratio) is synchronous in both study sites throughout the records suggesting warm and dry conditions at ˜300-1100 CE and cold and wet conditions at ˜1200-1900 CE. Owing to the significantly increased air temperatures, the most recent T/P ratio has again turned positive. During the first millennium of the Common Era, the T/P mimics patterns in Southern Oscillation index, whereas the second millennium shows response to the NAO index but is also concurrent with solar irradiance shifts. Since our T/P reconstruction is mostly linked with the NAO, we propose the T/P ratio as an indicator of the NAO. Our results from the coherent records provide first-time knowledge on the long-term temperature-precipitation relationship in Northern Europe that increase understanding of the comprehensive hydroclimate system in the region and the NAO dynamics also further back in time.

Possible higher order phase transition in large-N gauge theory at finite temperature

Energy Technology Data Exchange (ETDEWEB)

Nishimura, Hiromichi

2017-08-07

We analyze the phase structure of SU(¥) gauge theory at finite temperature using matrix models. Our basic assumption is that the effective potential is dominated by double-trace terms for the Polyakov loops. As a function of the temperature, a background field for the Polyakov loop, and a quartic coupling, it exhibits a universal structure: in the large portion of the parameter space, there is a continuous phase transition analogous to the third-order phase transition of Gross,Witten and Wadia, but the order of phase transition can be higher than third. We show that different confining potentials give rise to drastically different behavior of the eigenvalue density and the free energy. Therefore lattice simulations at large N could probe the order of phase transition and test our results. Critical

Temperature and baryon-chemical-potential-dependent bag pressure for a deconfining phase transition

International Nuclear Information System (INIS)

Patra, B.K.; Singh, C.P.

1996-01-01

We explore the consequences of a bag model developed by Leonidov et al. for the deconfining phase transition in which the bag pressure is made to depend on the temperature and baryon chemical potential in order to ensure the entropy and baryon number conservation at the phase boundary together with the Gibbs construction for an equilibrium phase transition. We show that the bag pressure thus obtained yields an anomalous increasing behavior with the increasing baryon chemical potential at a fixed temperature which defies a physical interpretation. We demonstrate that the inclusion of the perturbative interactions in the QGP phase removes this difficulty. Further consequences of the modified bag pressure are discussed. copyright 1996 The American Physical Society

Phase competition and anomalous thermal evolution in high-temperature superconductors

Science.gov (United States)

Yu, Zuo-Dong; Zhou, Yuan; Yin, Wei-Guo; Lin, Hai-Qing; Gong, Chang-De

2017-07-01

The interplay of competing orders is relevant to high-temperature superconductivity known to emerge upon suppression of a parent antiferromagnetic order typically via charge doping. How such interplay evolves at low temperature—in particular at what doping level the zero-temperature quantum critical point (QCP) is located—is still elusive because it is masked by the superconducting state. The QCP had long been believed to follow a smooth extrapolation of the characteristic temperature T* for the strange normal state well above the superconducting transition temperature. However, recently the T* within the superconducting dome was reported to unexpectedly exhibit back-bending likely in the cuprate Bi2Sr2CaCu2O8 +δ . Here we show that the original and revised phase diagrams can be understood in terms of weak and moderate competitions, respectively, between superconductivity and a pseudogap state such as d -density or spin-density wave, based on both Ginzburg-Landau theory and the realistic t -t'-t''-J -V model for the cuprates. We further found that the calculated temperature and doping-level dependence of the quasiparticle spectral gap and Raman response qualitatively agrees with the experiments. In particular, the T* back-bending can provide a simple explanation of the observed anomalous two-step thermal evolution dominated by the superconducting gap and the pseudogap, respectively. Our results imply that the revised phase diagram is likely to take place in high-temperature superconductors.

Classification of Arctic, midlatitude and tropical clouds in the mixed-phase temperature regime

Directory of Open Access Journals (Sweden)

A. Costa

2017-10-01

Full Text Available The degree of glaciation of mixed-phase clouds constitutes one of the largest uncertainties in climate prediction. In order to better understand cloud glaciation, cloud spectrometer observations are presented in this paper, which were made in the mixed-phase temperature regime between 0 and −38 °C (273 to 235 K, where cloud particles can either be frozen or liquid. The extensive data set covers four airborne field campaigns providing a total of 139 000 1 Hz data points (38.6 h within clouds over Arctic, midlatitude and tropical regions. We develop algorithms, combining the information on number concentration, size and asphericity of the observed cloud particles to classify four cloud types: liquid clouds, clouds in which liquid droplets and ice crystals coexist, fully glaciated clouds after the Wegener–Bergeron–Findeisen process and clouds where secondary ice formation occurred. We quantify the occurrence of these cloud groups depending on the geographical region and temperature and find that liquid clouds dominate our measurements during the Arctic spring, while clouds dominated by the Wegener–Bergeron–Findeisen process are most common in midlatitude spring. The coexistence of liquid water and ice crystals is found over the whole mixed-phase temperature range in tropical convective towers in the dry season. Secondary ice is found at midlatitudes at −5 to −10 °C (268 to 263 K and at higher altitudes, i.e. lower temperatures in the tropics. The distribution of the cloud types with decreasing temperature is shown to be consistent with the theory of evolution of mixed-phase clouds. With this study, we aim to contribute to a large statistical database on cloud types in the mixed-phase temperature regime.

Liquid-gas phase transition in asymmetric nuclear matter at finite temperature

Science.gov (United States)

Maruyama, Toshiki; Tatsumi, Toshitaka; Chiba, Satoshi

2010-03-01

Liquid-gas phase transition is discussed in warm asymmetric nuclear matter. Some peculiar features are figured out from the viewpoint of the basic thermodynamics about the phase equilibrium. We treat the mixed phase of the binary system based on the Gibbs conditions. When the Coulomb interaction is included, the mixed phase is no more uniform and the sequence of the pasta structures appears. Comparing the results with those given by the simple bulk calculation without the Coulomb interaction, we extract specific features of the pasta structures at finite temperature.

Liquid-gas phase transition in asymmetric nuclear matter at finite temperature

International Nuclear Information System (INIS)

Maruyama, Toshiki; Tatsumi, Toshitaka; Chiba, Satoshi

2010-01-01

Liquid-gas phase transition is discussed in warm asymmetric nuclear matter. Some peculiar features are figured out from the viewpoint of the basic thermodynamics about the phase equilibrium. We treat the mixed phase of the binary system based on the Gibbs conditions. When the Coulomb interaction is included, the mixed phase is no more uniform and the sequence of the pasta structures appears. Comparing the results with those given by the simple bulk calculation without the Coulomb interaction, we extract specific features of the pasta structures at finite temperature.

Unexpected Relationships and Inbreeding in HapMap Phase III Populations

Science.gov (United States)

Stevens, Eric L.; Baugher, Joseph D.; Shirley, Matthew D.; Frelin, Laurence P.; Pevsner, Jonathan

2012-01-01

Correct annotation of the genetic relationships between samples is essential for population genomic studies, which could be biased by errors or omissions. To this end, we used identity-by-state (IBS) and identity-by-descent (IBD) methods to assess genetic relatedness of individuals within HapMap phase III data. We analyzed data from 1,397 individuals across 11 ethnic populations. Our results support previous studies (Pemberton et al., 2010; Kyriazopoulou-Panagiotopoulou et al., 2011) assessing unknown relatedness present within this population. Additionally, we present evidence for 1,657 novel pairwise relationships across 9 populations. Surprisingly, significant Cotterman's coefficients of relatedness K1 (IBD1) values were detected between pairs of known parents. Furthermore, significant K2 (IBD2) values were detected in 32 previously annotated parent-child relationships. Consistent with a hypothesis of inbreeding, regions of homozygosity (ROH) were identified in the offspring of related parents, of which a subset overlapped those reported in previous studies (Gibson et al. 2010; Johnson et al. 2011). In total, we inferred 28 inbred individuals with ROH that overlapped areas of relatedness between the parents and/or IBD2 sharing at a different genomic locus between a child and a parent. Finally, 8 previously annotated parent-child relationships had unexpected K0 (IBD0) values (resulting from a chromosomal abnormality or genotype error), and 10 previously annotated second-degree relationships along with 38 other novel pairwise relationships had unexpected IBD2 (indicating two separate paths of recent ancestry). These newly described types of relatedness may impact the outcome of previous studies and should inform the design of future studies relying on the HapMap Phase III resource. PMID:23185369

Thermotolerance in preirradiated intestine and its influence on time-temperature relationships

International Nuclear Information System (INIS)

Hume, S.P.; Marigold, J.C.; Manjil, L.G.

1988-01-01

The crypt compartment of mouse jejunum showed a transient increase in thermal susceptibility approximately 10 days after moderate X-ray doses to the abdomen (9-10 Gy). The increase in response was manifest as an increase in slope of the crypt dose-response curve but was limited to temperatures below 43 0 C. As a result, the 43 0 C inflexion in the Arrhenius plot (the relationship between treatment time and temperature) for thermal sensitivity of crypts was eliminated in preirradiated tissue, and the curve became monophasic over the range 42.0-44.5 0 C. At temperatures below 42 0 C, the curve again deviated. At supranormal temperatures of 42 0 C and below, the durations of hyperthermia needed for measurable effect were sufficient to allow thermotolerance to be expressed within the heating period. Neither the threshold heating times nor this thermotolerance were affected by prior irradiation. In the temperature range 42-43 0 C, an earlier development of thermotolerance could be demonstrated in control tissue by challenging with an acute high-temperature heat treatment. This thermotolerance was eliminated in preirradiated tissue, resulting in the apparent increase in sensitivity. The findings support the view that the complex nature of the time-temperature relationship seen in normal tissue in vivo is a manifestation of the ability of the tissue to progressively acquire a thermotolerant state during treatment at temperatures below approximately 43 0 C, so that the intrinsic sensitivity is modulated while being assessed

Phase Stability Diagrams for High Temperature Corrosion Processes

Directory of Open Access Journals (Sweden)

J. J. Ramos-Hernandez

2013-01-01

Full Text Available Corrosion phenomena of metals by fused salts depend on chemical composition of the melt and environmental conditions of the system. Detail knowledge of chemistry and thermodynamic of aggressive species formed during the corrosion process is essential for a better understanding of materials degradation exposed to high temperature. When there is a lack of kinetic data for the corrosion processes, an alternative to understand the thermodynamic behavior of chemical species is to utilize phase stability diagrams. Nowadays, there are several specialized software programs to calculate phase stability diagrams. These programs are based on thermodynamics of chemical reactions. Using a thermodynamic data base allows the calculation of different types of phase diagrams. However, sometimes it is difficult to have access to such data bases. In this work, an alternative way to calculate phase stability diagrams is presented. The work is exemplified in the Na-V-S-O and Al-Na-V-S-O systems. This system was chosen because vanadium salts is one of the more aggressive system for all engineering alloys, especially in those processes where fossil fuels are used.

Temperature stabilisation in Fischer–Tropsch reactors using phase change material (PCM)

International Nuclear Information System (INIS)

Odunsi, Ademola O.; O'Donovan, Tadhg S.; Reay, David A.

2016-01-01

The Fischer–Tropsch (FT) reaction is highly exothermic. The exothermicity combined with a high sensitivity of product selectivity to temperature constitute the main challenges in the design of FT reactors. Temperature control is particularly critical to the process in order to ensure longevity of the catalyst, optimise the product distribution, and to ensure thermo-mechanical reliability of the entire process. The use of encapsulated, Phase Change Material (PCM), in conjunction with a supervisory temperature control mechanism, could help mitigate these challenges and intensify the heat transport from the reactor. A 2D-axisymmetric, pseudo-homogeneous, steady-state model, with the dissipation of the enthalpy of reaction into an isothermal PCM sink, in a wall-cooled, single-tube fixed bed reactor is presented. Effective temperature control shows a shift in thermodynamic equilibrium, favouring the selectivity of longer chain hydrocarbons (C_5_+) to the disadvantage of CH_4 selectivity-a much desired outcome in the hydrocarbon Gas-to-Liquid (GTL) industry. - Highlights: • Phase change material is used to control temperature in a Fischer–Tropsch reactor. • Effective temperature control favours the production of C_5_+ over CH_4. • A 2D-axisymmetric, steady-state model is presented. • The model is verified against similar experimental work done in literature.

Thermal buffering performance of composite phase change materials applied in low-temperature protective garments

Science.gov (United States)

Yang, Kai; Jiao, Mingli; Yu, Yuanyuan; Zhu, Xueying; Liu, Rangtong; Cao, Jian

2017-07-01

Phase change material (PCM) is increasingly being applied in the manufacturing of functional thermo-regulated textiles and garments. This paper investigated the thermal buffering performance of different composite PCMs which are suitable for the application in functional low-temperature protective garments. First, according to the criteria selecting PCM for functional textiles/garments, three kinds of pure PCM were selected as samples, which were n-hexadecane, n-octadecane and n-eicosane. To get the adjustable phase change temperature range and higher phase change enthalpy, three kinds of composite PCM were prepared using the above pure PCM. To evaluate the thermal buffering performance of different composite PCM samples, the simulated low-temperature experiments were performed in the climate chamber, and the skin temperature variation curves in three different low temperature conditions were obtained. Finally composite PCM samples’ thermal buffering time, thermal buffering capacity and thermal buffering efficiency were calculated. Results show that the comprehensive thermal buffering performance of n-octadecane and n-eicosane composite PCM is the best.

Phase Transformation and Shape Memory Effect of Ti-Pd-Pt-Zr High-Temperature Shape Memory Alloys

Science.gov (United States)

Yamabe-Mitarai, Yoko; Takebe, Wataru; Shimojo, Masayuki

2017-12-01

To understand the potential of high-temperature shape memory alloys, we have investigated the phase transformation and shape memory effect of Ti-(50 - x)Pt- xPd-5Zr alloys ( x = 0, 5, and 15 at.%), which present the B2 structure in the austenite phase and B19 structure in the martensite phase. Their phase transformation temperatures are very high; A f and M f of Ti-50Pt are 1066 and 1012 °C, respectively. By adding Zr and Pd, the phase transition temperatures decrease, ranging between 804 and 994 °C for A f and 590 and 865 °C for M f. Even at the high phase transformation temperature, a maximum recovery ratio of 70% was obtained for one cycle in a thermal cyclic test. A work output of 1.2 J/cm3 was also obtained. The recovery ratio obtained by the thermal cyclic test was less than 70% because the recovery strain was training effect was also investigated.

Determination of thermal diffusivity at low temperature using the two-beam phase-lag photoacoustic method with observation of phase-transitions

International Nuclear Information System (INIS)

Jorge, M.P.P.

1992-01-01

This study consists of the determination of thermal diffusivity int he temperature range from 77 K to 300 K by the two-beam phase-lag photoacoustic method. Room temperature measurements of NTD (neutron transmutation doping) silicon suggest that the doping process does not affect its thermal properties. For the superconductor Y Ba 2 Cu 3 O 7 - x it has been verified that the sample density affects its thermal diffusivity. The validity of the experimental method on the Li K SO 4 crystal has been examined by using the thermal diffusivity of a Li F crystal and an Y 2 O 3 ceramic, at room temperature. The behavior of the thermal diffusivity as a function of the temperature for the Li K SO 4 crystal shows two anomalies which correspond at phase-transitions of this crystal in the studied temperature range. (author)

Effects of calcium impurity on phase relationship, ionic conductivity ...

Indian Academy of Sciences (India)

Home; Journals; Bulletin of Materials Science; Volume 39; Issue 3. Effects of calcium impurity on phase relationship, ionic conductivity and microstructure of Na + - β / b e t a " -alumina solid electrolyte. SUNG-TAE LEE DAE-HAN LEE SANG-MIN LEE SANG-SOO HAN SANG-HYUNG LEE SUNG-KI LIM. Volume 39 Issue 3 ...

Experiments on Quantum Hall Topological Phases in Ultra Low Temperatures

International Nuclear Information System (INIS)

Du, Rui-Rui

2015-01-01

This project is to cool electrons in semiconductors to extremely low temperatures and to study new states of matter formed by low-dimensional electrons (or holes). At such low temperatures (and with an intense magnetic field), electronic behavior differs completely from ordinary ones observed at room temperatures or regular low temperature. Studies of electrons at such low temperatures would open the door for fundamental discoveries in condensed matter physics. Present studies have been focused on topological phases in the fractional quantum Hall effect in GaAs/AlGaAs semiconductor heterostructures, and the newly discovered (by this group) quantum spin Hall effect in InAs/GaSb materials. This project consists of the following components: 1) Development of efficient sample cooling techniques and electron thermometry: Our goal is to reach 1 mK electron temperature and reasonable determination of electron temperature; 2) Experiments at ultra-low temperatures: Our goal is to understand the energy scale of competing quantum phases, by measuring the temperature-dependence of transport features. Focus will be placed on such issues as the energy gap of the 5/2 state, and those of 12/5 (and possible 13/5); resistive signature of instability near 1/2 at ultra-low temperatures; 3) Measurement of the 5/2 gaps in the limit of small or large Zeeman energies: Our goal is to gain physics insight of 5/2 state at limiting experimental parameters, especially those properties concerning the spin polarization; 4) Experiments on tuning the electron-electron interaction in a screened quantum Hall system: Our goal is to gain understanding of the formation of paired fractional quantum Hall state as the interaction pseudo-potential is being modified by a nearby screening electron layer; 5) Experiments on the quantized helical edge states under a strong magnetic field and ultralow temperatures: our goal is to investigate both the bulk and edge states in a quantum spin Hall insulator under

Scaling and constitutive relationships in downcomer modeling

International Nuclear Information System (INIS)

Daly, B.J.; Harlow, F.H.

1978-12-01

Constitutive relationships to describe mass and momentum exchange in multiphase flow in a pressurized water reactor downcomer are presented. Momentum exchange between the phases is described by the product of the flux of momentum available for exchange and the effective area for interaction. The exchange of mass through condensation is assumed to occur along a distinct condensation boundary separating steam at saturation temperature from water in which the temperature falls off roughly linearly with distance from the boundary. Because of the abundance of nucleation sites in a typical churning flow in a downcomer, we propose an equilibrium evaporation process that produces sufficient steam per unit time to keep the water perpetually cooled to the saturation temperature. The transport equations, constitutive models, and boundary conditions used in the K-TIF numerical method are nondimensionalized to obtain scaling relationships for two-phase flow in the downcomer. The results indicate that, subject to idealized thermodynamic and hydraulic constraints, exact mathematical scaling can be achieved. Experiments are proposed to isolate the effects of parameters that contribute to mass, momentum, and energy exchange between the phases

Temperature and phase-space density of a cold atom cloud in a quadrupole magnetic trap

Energy Technology Data Exchange (ETDEWEB)

Ram, S. P.; Mishra, S. R.; Tiwari, S. K.; Rawat, H. S. [Raja Ramanna Centre for Advanced Technology, Indore (India)

2014-08-15

We present studies on modifications in the temperature, number density and phase-space density when a laser-cooled atom cloud from optical molasses is trapped in a quadrupole magnetic trap. Theoretically, for a given temperature and size of the cloud from the molasses, the phase-space density in the magnetic trap is shown first to increase with increasing magnetic field gradient and then to decrease with it after attaining a maximum value at an optimum value of the magnetic-field gradient. The experimentally-measured variation in the phase-space density in the magnetic trap with changing magnetic field gradient is shown to exhibit a similar trend. However, the experimentally-measured values of the number density and the phase-space density are much lower than the theoretically-predicted values. This is attributed to the experimentally-observed temperature in the magnetic trap being higher than the theoretically-predicted temperature. Nevertheless, these studies can be useful for setting a higher phase-space density in the trap by establishing an optimal value of the field gradient for a quadrupole magnetic trap.

Pressure, temperature, and electric field dependence of phase transformations in niobium modified 95/5 lead zirconate titanate

Energy Technology Data Exchange (ETDEWEB)

Dong, Wen D.; Carlos Valadez, J.; Gallagher, John A.; Jo, Hwan R.; Lynch, Christopher S., E-mail: cslynch@seas.ucla.edu [Department of Mechanical and Aerospace Engineering, The University of California, Los Angeles, 420 Westwood Plaza, Los Angeles, California 90095 (United States); Sahul, Raffi; Hackenberger, Wes [TRS Technologies, 2820 East College Avenue, State College, Pennsylvania 16801 (United States)

2015-06-28

Ceramic niobium modified 95/5 lead zirconate-lead titanate (PZT) undergoes a pressure induced ferroelectric to antiferroelectric phase transformation accompanied by an elimination of polarization and a volume reduction. Electric field and temperature drive the reverse transformation from the antiferroelectric to ferroelectric phase. The phase transformation was monitored under pressure, temperature, and electric field loading. Pressures and temperatures were varied in discrete steps from 0 MPa to 500 MPa and 25 °C to 125 °C, respectively. Cyclic bipolar electric fields were applied with peak amplitudes of up to 6 MV m{sup −1} at each pressure and temperature combination. The resulting electric displacement–electric field hysteresis loops were open “D” shaped at low pressure, characteristic of soft ferroelectric PZT. Just below the phase transformation pressure, the hysteresis loops took on an “S” shape, which split into a double hysteresis loop just above the phase transformation pressure. Far above the phase transformation pressure, when the applied electric field is insufficient to drive an antiferroelectric to ferroelectric phase transformation, the hysteresis loops collapse to linear dielectric behavior. Phase stability maps were generated from the experimental data at each of the temperature steps and used to form a three dimensional pressure–temperature–electric field phase diagram.

Phase transition temperatures of Sn-Zn-Al system and their comparison with calculated phase diagrams

Czech Academy of Sciences Publication Activity Database

Smetana, B.; Zlá, S.; Kroupa, Aleš; Žaludová, M.; Drápala, J.; Burkovič, R.; Petlák, D.

2012-01-01

Roč. 110, č. 1 (2012), s. 369-378 ISSN 1388-6150 R&D Projects: GA MŠk(CZ) OC08053 Institutional support: RVO:68081723 Keywords : Sn-Zn-Al system * DTA * phase transition temperatures Subject RIV: BJ - Thermodynamics Impact factor: 1.982, year: 2012

Dynamic phase transition in the kinetic spin-32 Blume-Capel model: Phase diagrams in the temperature and crystal-field interaction plane

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); Deviren, Bayram [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

2007-06-15

We analyze, within a mean-field approach, the stationary states of the kinetic spin-32 Blume-Capel (BC) model by the Glauber-type stochastic dynamics and subject to a time-dependent oscillating external magnetic field. The dynamic phase transition (DPT) points are obtained by investigating the behavior of the dynamic magnetization as a function of temperature and as well as calculating the Liapunov exponent. Phase diagrams are constructed in the temperature and crystal-field interaction plane. We find five fundamental types of phase diagrams for the different values of the reduced magnetic field amplitude parameter (h) in which they present a disordered, two ordered phases and the coexistences phase regions. The phase diagrams also exhibit a dynamic double-critical end point for 05.06.

Seasonality in mortality and its relationship to temperature among the older population in Hanoi, Vietnam

Directory of Open Access Journals (Sweden)

Le Thi Thanh Xuan

2014-12-01

Full Text Available Background: Several studies have established a relationship between temperature and mortality. In particular, older populations have been shown to be vulnerable to temperature effects. However, little information exists on the temperature–mortality relationship in Vietnam. Objectives: This article aims to examine the monthly temperature–mortality relationship among older people in Hanoi, Vietnam, over the period between 2005 and 2010, and estimate seasonal patterns in mortality. Methods: We employed Generalized Additive Models, including smooth functions, to model the temperature–mortality relationships. A quasi-Poisson distribution was used to model overdispersion of death counts. Temporal trends, seasonality, and population size were adjusted for while estimating changes in monthly mortality over the study period. A cold month was defined as a month with a mean temperature below 19°C. Results: This study found that the high peak of mortality coincided with low temperatures in the month of February 2008, during which the mean temperature was the lowest in the whole study period. There was a significant relationship between mean monthly temperature and mortality among the older people (p<0.01. Overall, there was a significant decrease in the number of deaths in the year 2009 during the study period. There was a 21% increase in the number of deaths during the cold season compared to the warm season. The increase in mortality during the cold period was higher among females compared to males (female: IRR [incidence relative risk] =1.23; male: IRR=1.18. Conclusions: Cold temperatures substantially increased mortality among the older population in Hanoi, Vietnam, and there were gender differences. Necessary preventive measures are required to mitigate temperature effects with greater attention to vulnerable groups.

Effect of annealing temperature on the crystalline quality and phase transformation of chemically deposited CdSe films

International Nuclear Information System (INIS)

Zapata-Torres, M.; Chale-Lara, F.; Caballero-Briones, F.; Calzadilla, O.

2005-01-01

Polycrystalline CdSe thin films were grown on glass substrates by chemical bath deposition at 50 C. The samples were annealed in air atmosphere at different temperatures and characterized by X-ray diffraction and Raman spectroscopy. It was found that the as-grown films have cubic structure. These samples maintain their cubic structure for annealing temperatures between 60 C and 300 C. For annealing temperatures higher than 300 C we obtain a mixture of cubic and hexagonal phases. The analysis made by X-ray diffraction and Raman dispersion show that the samples annealed at temperatures under the phase-transition temperature increase their crystalline quality. In order to determinate the temperature for the complete transition of the cubic phase, we used the precipitated material obtained during the grown of the CdSe films. This material was annealed on air atmosphere between 300 C and 500 C with 50 intervals. The samples were measured by X-ray diffraction. The samples maintained the cubic structure if the annealing temperature is under 300 C. For temperatures between 300 C and 450 C we found a mixture of cubic and hexagonal phase. For an annealing temperature of 500 C we obtain only the hexagonal phase. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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.

Time-temperature relationships for hyperthermal radiosensitisation in mouse intestine: influence of thermotolerance

International Nuclear Information System (INIS)

Hume, S.P.; Marigold, J.C.L.

1985-01-01

Thermal enhancement of radiation injury to the crypt compartment of mouse small intestinal mucosa has been measured as a function of heating time for temperatures in the range 41.0-44.0 0 C. All the hyperthermal treatments used were themselves subthreshold for gross tissue injury. With this limitation, thermoradiosensitisation increased linearly with duration of hyperthermia for temperatures in the range 42.3-44.0 0 C. Using temperatures below 42.0 0 C, there was a saturation in effect for treatments longer than approximately 40-90 min. For temperatures above the transition, a 1 0 C change was equivalent to a factor of 2.6 in heating time; below the transition, a 1 0 C change was equivalent to a factor of 5.4. Time-temperature relationships for thermoradiosensitisation in other rodent tissues are reviewed and compared with the general relationships for direct thermal injury, previously derived from experimental studies. The results are discussed with relevance to the interpretation of in vivo thermal enhancement of radiation injury. (Auth.)

Modified random phase approximation for multipole excitations at finite temperature

International Nuclear Information System (INIS)

Nguyen Dinh Dang

1991-01-01

The modified finite temperature random phase approximation (modified FT-RPA) has been constructed with taking the influence of thermostat on the structure of quansiparticles into account. The modified FT-RPA linear response for electric quadrupole (λ π = 2 + ) and octupole (λ π = 3 - ) excitations in 5 8Ni has been calculated as a function of the nuclear temperature. As compared to the conventional FT-RPA the modified FT-RPA has given a stronger spreading for the strength distribution of quandrupole excitations at finite temperature T ≤ 3MeV. (author). 22 refs; 4 figs; 2 tabs

Topological Phase Transitions in Zinc-Blende Semimetals Driven Exclusively by Electronic Temperature

Science.gov (United States)

Trushin, Egor; Görling, Andreas

2018-04-01

We show that electronic phase transitions in zinc-blende semimetals with quadratic band touching (QBT) at the center of the Brillouin zone, like GaBi, InBi, or HgTe, can occur exclusively due to a change of the electronic temperature without the need to involve structural transformations or electron-phonon coupling. The commonly used Kohn-Sham density-functional methods based on local and semilocal density functionals employing the local density approximation (LDA) or generalized gradient approximations (GGAs), however, are not capable of describing such phenomena because they lack an intrinsic temperature dependence and account for temperature only via the occupation of bands, which essentially leads only to a shift of the Fermi level without changing the shape or topology of bands. Kohn-Sham methods using the exact temperature-dependent exchange potential, not to be confused with the Hartree-Fock exchange potential, on the other hand, describe such phase transitions. A simple modeling of correlation effects can be achieved by screening of the exchange. In the considered zinc-blende compounds the QBT is unstable at low temperatures and a transition to electronic states without QBT takes place. In the case of HgTe and GaBi Weyl points of type I and type II, respectively, emerge during the transitions. This demonstrates that Kohn-Sham methods can describe such topological phase transitions provided they are based on functionals more accurate than those within the LDA or GGA. Moreover, the electronic temperature is identified as a handle to tune topological materials.

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)

On the Relationship of Rainfall and Temperature across Amazonia

Science.gov (United States)

Ribeiro Lima, C. H.; AghaKouchak, A.

2017-12-01

Extreme droughts in Amazonia seem to become more frequent and have been associated with local and global impacts on society and the ecosystem. The understanding of the dynamics and causes of Amazonia droughts have attracted some attention in the last years and pose several challenges for the scientific community. For instance, in previous work we have identified, based on empirical data, a compounding effect during Amazonia droughts: periods of low rainfall are always associated with positive anomalies of near surface air temperature. This inverse relationship of temperature and rainfall appears at multiple time scales and its intensity varies across Amazonia. To our knowledge, these findings have not been properly addressed in the literature, being not clear whether there is a causal relationship between these two variables, and in this case, which one leads the other one, or they are just responding to the same causal factor. Here we investigate the hypothesis that high temperatures during drought periods are a major response to an increase in the shortwave radiation (due to the lack of clouds) not compensating by an expected increase in the evapotranspiration from the rainforest. Our empirical analysis is based on observed series of daily temperature and rainfall over the Brazilian Amazonia and reanalysis data of cloud cover, outgoing longwave radiation (OLR) and moisture fluxes. The ability of Global Circulation Models (GCMs) to reproduce such compounding effect is also investigated for the historical period and for future RCP scenarios of global climate change. Preliminary results show that this is a plausible hypothesis, despite the complexity of land-atmosphere processes of mass and energy fluxes in Amazonia. This work is a step forward in better understanding the compounding effects of rainfall and temperature on Amazonia droughts, and what changes one might expect in a future warming climate.

Competing magnetic interactions and low temperature magnetic phase transitions in composite multiferroics

International Nuclear Information System (INIS)

Borkar, Hitesh; Singh, V N; Kumar, Ashok; Choudhary, R J; Tomar, M; Gupta, Vinay

2015-01-01

Novel magnetic properties and magnetic interactions in composite multiferroic oxides Pb[(Zr 0.52 Ti 0.48 ) 0.60 (Fe 0.67 W 0.33 ) .40 ]O 3 ] 0.80 –[CoFe 2 O 4 ] 0.20 (PZTFW–CFO) have been studied from 50 to 1000 Oe field cooled (FC) and zero field cooled (ZFC) probing conditions, and over a wide range of temperatures (4–350 K). Crystal structure analysis, surface morphology, and high resolution transmission electron microscopy images revealed the presence of two distinct phases, where micro- and nano-size spinel CFO were embedded in tetragonal PZTFW matrix and applied a significant built-in compressive strain (∼0.4–0.8%). Three distinct magnetic phase transitions were observed with the subtle effect of CFO magnetic phase on PZTFW magnetic phase transitions below the blocking temperature (T B ). Temperature dependence magnetic property m(T) shows a clear evidence of spin freezing in magnetic order with lowering in thermal vibration. Chemical inhomogeneity and confinement of nanoscale ferrimagnetic phase in paramagnetic/antiferromagnetic matrix restrict the long range interaction of spin which in turn develop a giant spin frustration. A large divergence in the FC and ZFC data and broad hump in ZFC data near 200 (±10) K were observed which suggests that large magnetic anisotropy and short range order magnetic dipoles lead to the development of superparamagnetic states in composite. (paper)

Thermal analysis of high temperature phase transformations of steel

Directory of Open Access Journals (Sweden)

K. Gryc

2013-10-01

Full Text Available The series of thermal analysis measurements of high temperature phase transformations of real grain oriented electrical steel grade under conditions of two analytical devices (Netzsch STA 449 F3 Jupiter; Setaram SETSYS 18TM were carried out. Two thermo analytical methods were used (DTA and Direct thermal analysis. The different weight of samples was used (200 mg, 23 g. The stability/reproducibility of results obtained by used methodologies was verified. The liquidus and solidus temperatures for close to equilibrium conditions and during cooling (20 °C/min; 80 °C/min were determined. It has been shown that the higher cooling rate lead to lower temperatures for start and end of solidification process of studied steel grade.

The low-temperature phase of morpholinium tetrafluoroborate

Directory of Open Access Journals (Sweden)

Tadeusz Lis

2008-04-01

Full Text Available The crystal structure of the low-temperature form of the title compound, C4H10NO+·BF4−, was determined at 80 K. Two reversible phase transitions, at 158/158 and 124/126 K (heating/cooling, were detected by differential scanning calorimetry for this compound, and the sequence of phase transitions was subsequently confirmed by single-crystal X-ray diffraction experiments. The asymmetric unit at 80 K consists of three BF4− tetrahedral anions and three morpholinium cations (Z′ = 3. Hydrogen-bonded morpholinium cations form chains along the [100] direction. The BF4− anions are connected to these chains by N—H...F hydrogen bonds. In the crystal structure, two different layers perpendicular to the [001] direction can be distinguished, which differ in the geometry of the hydrogen bonds between cationic and anionic species.

The relationship between gut hormone secretion and gastric emptying in different phases of the migrating motor complex

DEFF Research Database (Denmark)

Rasmussen, L; Oster-Jørgensen, E; Qvist, N

1996-01-01

BACKGROUND: No studies are available on the relationship between the response of gut hormones and gastric emptying in different phases of the migrating motor complex. This study examined whether basal gut hormone concentrations in plasma before food ingestion are predictors of emptying characteri......BACKGROUND: No studies are available on the relationship between the response of gut hormones and gastric emptying in different phases of the migrating motor complex. This study examined whether basal gut hormone concentrations in plasma before food ingestion are predictors of emptying...... a higher incremental integrated postprandial motilin response in phase I than in phase II (998 pmol/l*30 min (495 to 2010) versus 210 pmol/l*30 min (-270 to 2323), p linear relationship between median total integrated motilin response and solid emptying at 120 min in phase I (Rs = 0.58; p...... linear relationship between total integrated area of cholecystokinin and solid emptying at 120 min was demonstrated (Rs = 0.62; p

Temperature mapping using proton phase shift on a 0.3 T permanent magnet open MRI system

International Nuclear Information System (INIS)

Komura, Kazumi; Takahashi, Tetsuhiko; Dohi, Michiko; Harada, Junta

2000-01-01

Temperature mapping using proton phase shift (PPS) was evaluated for ex vivo objects. The evaluation was done on a 0.3 T permanent magnet open magnetic resonance imaging (MRI) machine, like those widely used for clinical diagnosis. Temperature maps were acquired using a gradient echo sequence (TR/TE =80/30 ms, flip angle =60 degrees, field of view =200 x 200 mm, slice thickness =8 mm, matrix size =128 x 128, data acquisition number =1, and imaging time =10.2 s). Specific first order data correction was performed to eliminate calculated temperature fluctuation due to magnetic field instability. A ham, 10 cm in diameter, was heated with a Nd: YAG laser with a wavelength of 1064 nm. The laser fiber was inserted into the ham to a depth of 3 cm. The laser power was 5, 8, or 10 W. Magnetic resonance images were taken continually during and after irradiation. Temperature maps were taken every 15 s. The maps taken during laser ablation showed color changes for the heated areas. Temperatures measured by the MRI and thermocouple had a linear relationship of r 2 =0.80. The inter-image standard deviation of the temperature maps of a non-heated object was 2.07 degrees for a 4.68 x 4.68 x 8 mm volume. This value is negligible for a monitored laser heating process since temperature rise is typically larger than 30 degrees. These results show that temperature mapping based on PPS is feasible for a 0.3 T permanent magnet open MRI system. (author)

Study of cements silicate phases hydrated under high pressure and high temperature; Etude des phases silicatees du ciment hydrate sous haute pression et haute temperature

Energy Technology Data Exchange (ETDEWEB)

Meducin, F.

2001-10-01

This study concerns the durability of oil-well cementing. Indeed, in oil well cementing a cement slurry is pumped down the steel casing of the well up the annular space between it and the surrounding rock to support and protect the casing. The setting conditions of pressure and temperature may be very high (up to 1000 bar and 250 deg C at the bottom of the oil-well). In this research, the hydration of the main constituent of cement, synthetic tri-calcium silicate Ca{sub 3}SiO{sub 2}, often called C{sub 3}S (C = CaO; S = SiO{sub 2} and H H{sub 2}O), is studied. Calcium Silicate hydrates are prepared in high-pressure cells to complete their phase diagram (P,T) and obtain the stability conditions for each species. Indeed, the phases formed in these conditions are unknown and the study consists in the hydration of C{sub 3}S at different temperatures, pressures, and during different times to simulate the oil-well conditions. In a first step (until 120 deg C at ambient pressure) the C-S-H, a not well crystallized and non-stoichiometric phase, is synthesized: it brings adhesion and mechanical properties., Then, when pressure and temperature increase, crystallized phases appear such as jaffeite (Ca{sub 6}(Si{sub 2}O{sub 7})(OH){sub 6}) and hillebrandite (Ca{sub 2}(SiO{sub 3})(OH){sub 2}). Silicon {sup 29}Si Nuclear Magnetic Resonance (using standard sequences MAS, CPMAS) allow us to identify all the silicates hydrates formed. Indeed, {sup 29}Si NMR is a valuable tool to determine the structure of crystallized or not-well crystallized phases of cement. The characterization of the hydrated samples is completed by other techniques: X- Ray Diffraction and Scanning Electron Microscopy. The following results are found: jaffeite is the most stable phase at C/S=3. To simulate the hydration of real cement, hydration of C{sub 3}S with ground quartz and with or without super-plasticizers is done. In those cases, new phases appear: kilchoanite mainly, and xonotlite. A large amount of

Resistive switching characteristics of interfacial phase-change memory at elevated temperature

Science.gov (United States)

Mitrofanov, Kirill V.; Saito, Yuta; Miyata, Noriyuki; Fons, Paul; Kolobov, Alexander V.; Tominaga, Junji

2018-04-01

Interfacial phase-change memory (iPCM) devices were fabricated using W and TiN for the bottom and top contacts, respectively, and the effect of operation temperature on the resistive switching was examined over the range between room temperature and 200 °C. It was found that the high-resistance (RESET) state in an iPCM device drops sharply at around 150 °C to a low-resistance (SET) state, which differs by ˜400 Ω from the SET state obtained by electric-field-induced switching. The iPCM device SET state resistance recovered during the cooling process and remained at nearly the same value for the RESET state. These resistance characteristics greatly differ from those of the conventional Ge-Sb-Te (GST) alloy phase-change memory device, underscoring the fundamentally different switching nature of iPCM devices. From the thermal stability measurements of iPCM devices, their optimal temperature operation was concluded to be less than 100 °C.

INVESTIGATION OF THE FREQUENCY-TEMPERATURE RELATIONSHIP OF THE DIELECTRIC PERMITTIVITY OF THE PZT PIEZOCERAMICS IN THE LOW FREQUENCY RANGE

Directory of Open Access Journals (Sweden)

A. I. ZOLOTAREVSKIY

2018-05-01

Full Text Available Purpose. To investigate the frequency-temperature relationship of the dielectric permittivity of PZT piezoceramics in the low frequency range. Methodology. To obtain the frequency-temperature relationship of the dielectric permittivity of the PZT piezoceramics, a technique was used to determine the capacitance of the capacitor, between which plates the sample was placed. The value of the dielectric permittivity of the sample was calculated from the capacitor capacitance obtained. Findings. The frequency-temperature relationship of the dielectric permittivity of the PZT piezoceramics in the low frequency range has been obtained by the authors. The dielectric permittivity is not practically related to the frequency of the alternating voltage at a low temperature, with increasing in temperature its value increases and frequency relationship is observed. The temperature relationship of the dielectric permittivity of the PZT piezoceramics is satisfactorily described by the exponential functional dependence in the low-temperature range. The activation energy of the PZT piezoceramics polarization is determined from the graph of the dependence of the logarithm of the dielectric permittivity upon the inverse temperature. Different values of the activation energy for the two temperature regions prove on the existence of different mechanisms of the PZT piezoceramics polarization in the temperature range being investigated. Originality. The authors investigated the frequency-temperature relationship of the dielectric permittivity of the PZT piezoceramics in the low-frequency range. It is established that the temperature relationship of the dielectric permittivity of the PZT piezoceramics is satisfactorily described by an exponential functional relationship in the lowtemperature range. The activation energy of polarization is determined for two temperature sections. Practical value. The research results can be used to study the mechanism of polarization of

Thermodynamic Studies of the Phase Relationships of Nonstoichiometric Cerium Oxides at Higher Temperatures

DEFF Research Database (Denmark)

Sørensen, Ole Toft

1976-01-01

Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in CO/CO2 mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range 2.00 greater-or-equal, slanted O/M greater-or-equal, slan......Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in CO/CO2 mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range 2.00 greater-or-equal, slanted O/M greater...

Relationship between the Wigner function and the probability density function in quantum phase space representation

International Nuclear Information System (INIS)

Li Qianshu; Lue Liqiang; Wei Gongmin

2004-01-01

This paper discusses the relationship between the Wigner function, along with other related quasiprobability distribution functions, and the probability density distribution function constructed from the wave function of the Schroedinger equation in quantum phase space, as formulated by Torres-Vega and Frederick (TF). At the same time, a general approach in solving the wave function of the Schroedinger equation of TF quantum phase space theory is proposed. The relationship of the wave functions between the TF quantum phase space representation and the coordinate or momentum representation is thus revealed

Low temperature phase transition and crystal structure of CsMgPO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Orlova, Maria, E-mail: maria.p.orlova@gmail.com [Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Khainakov, Sergey [Departamento de Química Física y Analítica, Universidad de Oviedo—CINN, 33006 Oviedo (Spain); Servicios Científico Técnicos, Universidad de Oviedo, 33006 Oviedo (Spain); Michailov, Dmitriy [Department of Chemistry, University of Nizhny Novgorod, 23 Gagarin av., Nizhny Novgorod 603950 (Russian Federation); Perfler, Lukas [Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Langes, Christoph [Institute of Pharmacy, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Kahlenberg, Volker [Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Orlova, Albina [Department of Chemistry, University of Nizhny Novgorod, 23 Gagarin av., Nizhny Novgorod 603950 (Russian Federation)

2015-01-15

CsMgPO{sub 4} doped with radioisotopes is a promising compound for usage as a radioactive medical source. However, a low temperature phase transition at temperatures close to ambient conditions (∼−40 °C) was observed. Information about such kind of structural changes is important in order to understand whether it can cause any problem for medical use of this compound. The phase transition has been investigated in detail using synchrotron powder diffraction, Raman spectroscopy and DFT calculations. The structure undergoes a transformation from an orthorhombic modification, space group Pnma (RT phase) to a monoclinic polymorph, space group P2{sub 1}/n (LT phase). New LT modification adopts similar to RT but slightly distorted unit cell: a=9.58199(2) Å, b=8.95501(1) Å, c=5.50344(2) Å, β=90.68583(1)°, V=472.198(3) Å{sup 3}. CsMgPO{sub 4} belongs to the group of framework compounds and is made up of strictly alternating MgO{sub 4}- and PO{sub 4}-tetrahedra sharing vertices. The cesium counter cations are located in the resulting channel-like cavities. Upon the transformation a combined tilting of the tetrahedra is observed. A comparison with other phase transitions in ABW-type framework compounds is given. - Graphical abstract: Structural behavior of β-tridymite-type phosphate CsMgPO{sub 4}, considered as potential chemical form for radioactive Cs-source has been studied at near ambient temperatures. A phase transition at (∼−40 °C) has been found and investigated. It has been established that the known orthorhombic RT modification, space group Pnma, adopts a monoclinic cell with space group P2{sub 1}/n at low temperatures. In this paper, we present results of structural analysis of changes accompanying this phase transition and discuss its possible impact on the application properties. - Highlights: • β-Tridymite type phosphate CsMgPO{sub 4} undergoes so called translationengleiche phase transition of index 2 at −40 °C. • The structure

Solution-phase synthesis of nanomaterials at low temperature

Science.gov (United States)

Zhu, Yongchun; Qian, Yitai

2009-01-01

This paper reviews the solution-phase synthesis of nanoparticles via some routes at low temperatures, such as room temperature route, wave-assisted synthesis (γ-irradiation route and sonochemical route), directly heating at low temperatures, and hydrothermal/solvothermal methods. A number of strategies were developed to control the shape, the size, as well as the dispersion of nanostructures. Using diethylamine or n-butylamine as solvent, semiconductor nanorods were yielded. By the hydrothermal treatment of amorphous colloids, Bi2S3 nanorods and Se nanowires were obtained. CdS nanowires were prepared in the presence of polyacrylamide. ZnS nanowires were obtained using liquid crystal. The polymer poly (vinyl acetate) tubule acted as both nanoreactor and template for the CdSe nanowire growth. Assisted by the surfactant of sodium dodecyl benzenesulfonate (SDBS), nickel nanobelts were synthesized. In addition, Ag nanowires, Te nanotubes and ZnO nanorod arrays could be prepared without adding any additives or templates.

Simulated body temperature rhythms reveal the phase-shifting behavior and plasticity of mammalian circadian oscillators

Science.gov (United States)

Saini, Camille; Morf, Jörg; Stratmann, Markus; Gos, Pascal; Schibler, Ueli

2012-01-01

The circadian pacemaker in the suprachiasmatic nuclei (SCN) of the hypothalamus maintains phase coherence in peripheral cells through metabolic, neuronal, and humoral signaling pathways. Here, we investigated the role of daily body temperature fluctuations as possible systemic cues in the resetting of peripheral oscillators. Using precise temperature devices in conjunction with real-time monitoring of the bioluminescence produced by circadian luciferase reporter genes, we showed that simulated body temperature cycles of mice and even humans, with daily temperature differences of only 3°C and 1°C, respectively, could gradually synchronize circadian gene expression in cultured fibroblasts. The time required for establishing the new steady-state phase depended on the reporter gene, but after a few days, the expression of each gene oscillated with a precise phase relative to that of the temperature cycles. Smooth temperature oscillations with a very small amplitude could synchronize fibroblast clocks over a wide temperature range, and such temperature rhythms were also capable of entraining gene expression cycles to periods significantly longer or shorter than 24 h. As revealed by genetic loss-of-function experiments, heat-shock factor 1 (HSF1), but not HSF2, was required for the efficient synchronization of fibroblast oscillators to simulated body temperature cycles. PMID:22379191

Simulated body temperature rhythms reveal the phase-shifting behavior and plasticity of mammalian circadian oscillators.

Science.gov (United States)

Saini, Camille; Morf, Jörg; Stratmann, Markus; Gos, Pascal; Schibler, Ueli

2012-03-15

The circadian pacemaker in the suprachiasmatic nuclei (SCN) of the hypothalamus maintains phase coherence in peripheral cells through metabolic, neuronal, and humoral signaling pathways. Here, we investigated the role of daily body temperature fluctuations as possible systemic cues in the resetting of peripheral oscillators. Using precise temperature devices in conjunction with real-time monitoring of the bioluminescence produced by circadian luciferase reporter genes, we showed that simulated body temperature cycles of mice and even humans, with daily temperature differences of only 3°C and 1°C, respectively, could gradually synchronize circadian gene expression in cultured fibroblasts. The time required for establishing the new steady-state phase depended on the reporter gene, but after a few days, the expression of each gene oscillated with a precise phase relative to that of the temperature cycles. Smooth temperature oscillations with a very small amplitude could synchronize fibroblast clocks over a wide temperature range, and such temperature rhythms were also capable of entraining gene expression cycles to periods significantly longer or shorter than 24 h. As revealed by genetic loss-of-function experiments, heat-shock factor 1 (HSF1), but not HSF2, was required for the efficient synchronization of fibroblast oscillators to simulated body temperature cycles.

High temperature phase transitions in nuclear fuels of the fourth generation

International Nuclear Information System (INIS)

De Bruycker, F.

2010-01-01

Understanding the behaviour of nuclear materials in extreme conditions is of prime importance for the analysis of the operation limits of nuclear fuels, and prediction of possible nuclear reactor accidents, relevant to the general objectives of nuclear safety research. The main purpose of this thesis is the study of high temperature phase transitions in nuclear materials, with special attention to the candidate fuel materials for the reactors of the 4. Generation. In this framework, material properties need to be investigated at temperatures higher than 2500 K, where equilibrium conditions are difficult to obtain. Laser heating combined with fast pyrometer is the method used at the European Institute for Transuranium Elements (JRC - ITU). It is associated to a novel process used to determine phase transitions, based on the detection, via a suited low-power (mW) probe laser, of changes in surface reflectivity that may accompany solid/liquid phase transitions. Fast thermal cycles, from a few ms up to the second, under almost container-free conditions and control atmosphere narrow the problem of vaporisation and sample interactions usually meet with traditional method. This new experimental approach has led to very interesting results. It confirmed earlier research for material systems known to be stable at high temperature (such as U-C) and allowed a refinement of the corresponding phase diagrams. But it was also feasible to apply this method to materials highly reactive, thus original results are presented on PuO 2 , NpO 2 , UO 2 -PuO 2 and Pu-C systems. (author)

Nonequilibrium phase formation in oxides prepared at low temperature: Fergusonite-related phases

International Nuclear Information System (INIS)

Mather, S.A.; Davies, P.K.

1995-01-01

Sol-gel methods have been developed to prepare YNbO 4 , YTaO 4 , and other rare-earth niobates and tantalates with fergusonite-related crystal structures. At low temperatures, all of the fergusonites, with the exception of SmTaO 4 , crystallize in a metastable tetragonal (T') structure similar to that of tetragonal zirconia. Although all of the equilibrium forms of these oxides adopt a crystal structure containing an ordered distribution of the trivalent and pentavalent cations, a random cation distribution is obtained in the metastable T' phase. Metastable phase formation is often ascribed solely to kinetically limited topotactic crystallization. However, the changes in the grain size and unit-cell volumes that accompany the metastable-to-equilibrium fergusonite conversions imply that other physical phenomena induced by small-particle synthesis, namely the Gibbs-Thompson pressure effect and the increased contribution of surface energy, cannot be ignored

Dynamic phase transition in the kinetic spin-1 Blume-Capel model: Phase diagrams in the temperature and crystal-field interaction plane

International Nuclear Information System (INIS)

Keskin, M.; Canko, O.; Temizer, U.

2007-01-01

Within a mean-field approach, the stationary states of the kinetic spin-1 Blume-Capel model in the presence of a time-dependent oscillating external magnetic field is studied. The Glauber-type stochastic dynamics is used to describe the time evolution of the system and obtain the mean-field dynamic equation of motion. The dynamic phase-transition points are calculated and phase diagrams are presented in the temperature and crystal-field interaction plane. According to the values of the magnetic field amplitude, three fundamental types of phase diagrams are found: One exhibits a dynamic tricritical point, while the other two exhibit a dynamic zero-temperature critical point

Phase separation temperatures of a liquid mixture: Dynamic light scattering technique

International Nuclear Information System (INIS)

Dangudom, K.; Wongtawatnugool, C.; Lacharojana, S.

2010-01-01

Light scattering intensity measurements and photon correlation spectroscopy (PCS) techniques were employed in an investigation of liquid-liquid phase separation behaviour of a mixture of cyclohexane and methanol at seven different compositions. It was found that, except for one composition (29% methanol), the temperature at which the scattering intensity was a maximum did not coincide with the one where the diffusion coefficient was a minimum, as would be for the case of a vapour-liquid system. The difference may be explained in terms of the local density fluctuation and the random walk problem responsible for the peak intensity and the minimum in the diffusion coefficient, respectively. The definition of phase separation temperature, as determined from diffusion process, was also proposed in this work.

Thermal conductivity of an organic phase change material/expanded graphite composite across the phase change temperature range and a novel thermal conductivity model

International Nuclear Information System (INIS)

Ling, Ziye; Chen, Jiajie; Xu, Tao; Fang, Xiaoming; Gao, Xuenong; Zhang, Zhengguo

2015-01-01

Highlights: • Expanded graphite can improve thermal conductivity of RT44HC by 20–60 times. • Thermal conductivity of PCM/EG composites keeps constant before/after melting. • Thermal conductivity of PCMs nearly doubled during phase changing. • Thermal conductivity of composite PCM increases with density and percentage of EG. • The simple model predicts thermal conductivity of EG-based composites accurately. - Abstract: This work studies factors that affect the thermal conductivity of an organic phase change material (PCM), RT44HC/expanded graphite (EG) composite, which include: EG mass fraction, composite PCM density and temperature. The increase of EG mass fraction and bulk density will both enhance thermal conductivity of composite PCMs, by up to 60 times. Thermal conductivity of RT44HC/EG composites remains independent on temperature outside the phase change range (40–45 °C), but nearly doubles during the phase change. The narrow temperature change during the phase change allows the maximum heat flux or minimum temperature for heat source if attaching PCMs to a first (constant temperature) or second (constant heat flux) thermal boundary. At last, a simple thermal conductivity model for EG-based composites is put forward, based on only two parameters: mass fraction of EG and bulk density of the composite. This model is validated with experiment data presented in this paper and in literature, showing this model has general applicability to any composite of EG and poor thermal conductive materials

Phonon renormalization at small q values in the high-temperature phase of CsCuCl sub 3

CERN Document Server

Foerster, U; Schotte, U; Stuhr, U

1997-01-01

The hexagonal perovskite CsCuCl sub 3 exhibits a structural phase transition from a dynamically disordered high-temperature phase to an ordered low-temperature phase due to the cooperative Jahn-Teller effect. The lattice dynamics of the high-temperature phase has been studied by inelastic neutron scattering experiments. The investigations concentrated on small wave vectors q, where for the first time renormalized phonons at q=0.02-0.05 A sup - sup 1 could be observed. The measurements confirm the predictions of a theoretical approach based on the coupling between dynamic reorientation processes and acoustic lattice waves (pseudo-spin phonon coupling). (author)

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...... on the temperatures, microstructured phases of both lamellar and droplet symmetry arise, described by a length scale that is determined by the characteristic temperature controlling the diffusive motion of the active impurities....

Discriminating the precipitation phase based on different temperature thresholds in the Songhua River Basin, China

Science.gov (United States)

Zhong, Keyuan; Zheng, Fenli; Xu, Ximeng; Qin, Chao

2018-06-01

Different precipitation phases (rain, snow or sleet) differ greatly in their hydrological and erosional processes. Therefore, accurate discrimination of the precipitation phase is highly important when researching hydrologic processes and climate change at high latitudes and mountainous regions. The objective of this study was to identify suitable temperature thresholds for discriminating the precipitation phase in the Songhua River Basin (SRB) based on 20-year daily precipitation collected from 60 meteorological stations located in and around the basin. Two methods, the air temperature method (AT method) and the wet bulb temperature method (WBT method), were used to discriminate the precipitation phase. Thirteen temperature thresholds were used to discriminate snowfall in the SRB. These thresholds included air temperatures from 0 to 5.5 °C at intervals of 0.5 °C and the wet bulb temperature (WBT). Three evaluation indices, the error percentage of discriminated snowfall days (Ep), the relative error of discriminated snowfall (Re) and the determination coefficient (R2), were applied to assess the discrimination accuracy. The results showed that 2.5 °C was the optimum threshold temperature for discriminating snowfall at the scale of the entire basin. Due to differences in the landscape conditions at the different stations, the optimum threshold varied by station. The optimal threshold ranged 1.5-4.0 °C, and 19 stations, 17 stations and 18 stations had optimal thresholds of 2.5 °C, 3.0 °C, and 3.5 °C respectively, occupying 90% of all stations. Compared with using a single suitable temperature threshold to discriminate snowfall throughout the basin, it was more accurate to use the optimum threshold at each station to estimate snowfall in the basin. In addition, snowfall was underestimated when the temperature threshold was the WBT and when the temperature threshold was below 2.5 °C, whereas snowfall was overestimated when the temperature threshold exceeded 4

Rare earth permanent-magnet alloys’ high temperature phase transformation in situ and dynamic observation and its application in material design

CERN Document Server

Pan, Shuming

2013-01-01

The process of high temperature phase transition of rare earth permanent-magnet alloys is revealed by photographs taken by high voltage TEM. The relationship between the formation of nanocrystal and magnetic properties is discussed in detail, which effects alloys composition and preparation process. The experiment results verified some presumptions, and were valuable for subsequent scientific research and creating new permanent-magnet alloys. The publication is intended for researchers, engineers and managers in the field of material science, metallurgy, and physics. Prof. Shuming Pan is senior engineer of Beijing General Research Institute of Non-ferrous Metal.

Temperature-dependent pitch and phase diagram for incommensurate XY spins in a slab geometry

International Nuclear Information System (INIS)

Collins, M.; Saslow, W.M.

1996-01-01

Strain-engineered Heisenberg antiferromagnets recently have been produced by controlling the layer thickness of MnSe/ZnTe superlattices. Neutron-scattering studies reveal a spiral that tends to untwist with increasing temperature. To simulate this system, we employ an XY model with nearest- and second-nearest neighbor antiferromagnetic interactions. The bulk mean-field phase diagram has four possible phases, for the full range of the exchange constants. Monte Carlo calculations are performed for a slab geometry, using an algorithm that allows the system to choose incommensurate boundary conditions. The phase diagram is constructed by monitoring the spiral pitch as a function of temperature for a range of exchange constants. For appropriate exchange constants, good agreement is obtained with experiment. From the mean-field phase diagram it appears that strain engineering an NaCl structure in a superlattice configuration might produce a type of spiral phase, and an associated antiferromagnetic-to-spiral phase transition. copyright 1996 The American Physical Society

Demonstration of a Variable Phase Turbine Power System for Low Temperature Geothermal Resources

Energy Technology Data Exchange (ETDEWEB)

Hays, Lance G

2014-07-07

A variable phase turbine assembly will be designed and manufactured having a turbine, operable with transcritical, two-phase or vapor flow, and a generator – on the same shaft supported by process lubricated bearings. The assembly will be hermetically sealed and the generator cooled by the refrigerant. A compact plate-fin heat exchanger or tube and shell heat exchanger will be used to transfer heat from the geothermal fluid to the refrigerant. The demonstration turbine will be operated separately with two-phase flow and with vapor flow to demonstrate performance and applicability to the entire range of low temperature geothermal resources. The vapor leaving the turbine is condensed in a plate-fin refrigerant condenser. The heat exchanger, variable phase turbine assembly and condenser are all mounted on single skids to enable factory assembly and checkout and minimize installation costs. The system will be demonstrated using low temperature (237F) well flow from an existing large geothermal field. The net power generated, 1 megawatt, will be fed into the existing power system at the demonstration site. The system will demonstrate reliable generation of inexpensive power from low temperature resources. The system will be designed for mass manufacturing and factory assembly and should cost less than $1,200/kWe installed, when manufactured in large quantities. The estimated cost of power for 300F resources is predicted to be less than 5 cents/kWh. This should enable a substantial increase in power generated from low temperature geothermal resources.

High temperature vapors science and technology

CERN Document Server

Hastie, John

2012-01-01

High Temperature Vapors: Science and Technology focuses on the relationship of the basic science of high-temperature vapors to some areas of discernible practical importance in modern science and technology. The major high-temperature problem areas selected for discussion include chemical vapor transport and deposition; the vapor phase aspects of corrosion, combustion, and energy systems; and extraterrestrial high-temperature species. This book is comprised of seven chapters and begins with an introduction to the nature of the high-temperature vapor state, the scope and literature of high-temp

Is there a relationship between fledge age and nest temperature in Western Bluebirds (Sialia mexicana)?

Energy Technology Data Exchange (ETDEWEB)

Phillips, Emily Marie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Thompson, Brent E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hathcock, Charles Dean [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-11-30

Extensive research has been done on temperature during bird incubation periods, but little has been done during nestling development, and to our knowledge, no studies have been done on Western Bluebird (Sialia mexicana) nestling development. In this study, dataloggers were used to monitor nest temperatures during the nestling development phase of Western Bluebirds to determine if there was a relationship between fledge age and temperature. The study was conducted in an existing nestbox network at Los Alamos National Laboratory and the surrounding area in north-central New Mexico. Based on the age of the nestlings at fledging, the nestboxes (n=65) were split into three groups: early (16 and 17 days old, n=13), average (fledged at or between 18 and 20 days old, n=32), and late (21 days or older, n=20). The temperatures of the early and average (n=45) groups were not significantly different (p=0.32, W=3831000). There was a significant difference in the temperatures between the early and late groups (p=0.000, W=2965600). The early and average groups were then combined, tested against the late group, and were found to be significantly different (p=0.000, W=11315000). Analysis showed a difference within the first seven days post-hatch of 1.42°C between the early/average and late groupings. The results suggest that warmer nest temperatures during the nestling stage may influence the fledge date and may lead to faster fledging. There may be numerous explanations for this, such as a correlation with nestling development, and higher temperatures may allow for faster development. Brood size was non-significant and was not factored into the analysis. Future work should be directed in this area.

Relationships Between Temperature, pH, and Crusting on Mg/Ca Ratios in Laboratory-Grown Neogloboquadrina Foraminifera

Science.gov (United States)

Davis, Catherine V.; Fehrenbacher, Jennifer S.; Hill, Tessa M.; Russell, Ann D.; Spero, Howard J.

2017-11-01

Mg/Ca ratio paleothermometry in foraminifera is an important tool for the reconstruction and interpretation of past environments. However, existing Mg/Ca:temperature relationships for planktic species inhabiting middle- and high-latitude environments are limited by a lack of information about the development and impact of low-Mg/Ca ratio "crusts" and the influence of the carbonate system on Mg/Ca ratios in these groups. To address this, we cultured individual specimens of Neogloboquadrina incompta and Neogloboquadrina pachyderma in seawater across a range of temperature (6°-12°C) and pH (7.4-8.2). We found by laser ablation inductively couple mass spectrometry analyses of shells that culture-grown crust calcite in N. incompta had a lower Mg/Ca ratio than ontogenetic calcite formed at the same temperature, suggesting that temperature is not responsible for the low-Mg/Ca ratio of neogloboquadrinid crusts. The Mg/Ca:temperature relationship for ontogenetic calcite in N. incompta was consistent with the previously published culture-based relationship, and no significant relationship was found between Mg/Ca ratios and pH in this species. However, the Mg/Ca ratio in laboratory-cultured N. pachyderma was much higher than that reported in previous core top and sediment trap samples, due to lack of crust formation in culture. Application of our ontogenetic calcite-specific Mg/Ca:temperature relationships to fossil N. pachyderma and N. incompta from five intervals in cores from the Santa Barbara Basin and the Bering Sea shows that excluding crust calcite in fossil specimens may improve Mg/Ca-based temperature estimates.

CosmoTransitions: Computing cosmological phase transition temperatures and bubble profiles with multiple fields

Science.gov (United States)

Wainwright, Carroll L.

2012-09-01

I present a numerical package (CosmoTransitions) for analyzing finite-temperature cosmological phase transitions driven by single or multiple scalar fields. The package analyzes the different vacua of a theory to determine their critical temperatures (where the vacuum energy levels are degenerate), their supercooling temperatures, and the bubble wall profiles which separate the phases and describe their tunneling dynamics. I introduce a new method of path deformation to find the profiles of both thin- and thick-walled bubbles. CosmoTransitions is freely available for public use.Program summaryProgram Title: CosmoTransitionsCatalogue identifier: AEML_v1_0Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEML_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 8775No. of bytes in distributed program, including test data, etc.: 621096Distribution format: tar.gzProgramming language: Python.Computer: Developed on a 2009 MacBook Pro. No computer-specific optimization was performed.Operating system: Designed and tested on Mac OS X 10.6.8. Compatible with any OS with Python installed.RAM: Approximately 50 MB, mostly for loading plotting packages.Classification: 1.9, 11.1.External routines: SciPy, NumPy, matplotLibNature of problem: I describe a program to analyze early-Universe finite-temperature phase transitions with multiple scalar fields. The goal is to analyze the phase structure of an input theory, determine the amount of supercooling at each phase transition, and find the bubble-wall profiles of the nucleated bubbles that drive the transitions.Solution method: To find the bubble-wall profile, the program assumes that tunneling happens along a fixed path in field space. This reduces the equations of motion to one dimension, which can then be solved using the overshoot

The relationship between ionospheric temperature, electron density and solar activity

International Nuclear Information System (INIS)

McDonald, J.N.; Williams, P.J.S.

1980-01-01

In studying the F-region of the ionosphere several authors have concluded that the difference between the electron temperature Tsub(e) and the ion temperature Tsub(i) is related to the electron density N. It was later noted that solar activity (S) was involved and an empirical relationship of the following form was established: Tsub(e)-Tsub(i) = A-BN+CS. The present paper extends this work using day-time data over a four year period. The results are given and discussed. A modified form of the empirical relation is proposed. (U.K.)

Thermodynamic and experimental study on phase stability in nanocrystalline alloys

International Nuclear Information System (INIS)

Xu Wenwu; Song Xiaoyan; Lu Nianduan; Huang Chuan

2010-01-01

Nanocrystalline alloys exhibit apparently different phase transformation characteristics in comparison to the conventional polycrystalline alloys. The special phase stability and phase transformation behavior, as well as the essential mechanisms of the nanocrystalline alloys, were described quantitatively in a nanothermodynamic point of view. By introducing the relationship between the excess volume at the grain boundary and the nanograin size, the Gibbs free energy was determined distinctly as a function of temperature and the nanograin size. Accordingly, the grain-size-dependence of the phase stability and phase transformation characteristics of the nanocrystalline alloy were calculated systematically, and the correlations between the phase constitution, the phase transformation temperature and the critical nanograin size were predicted. A series of experiments was performed to investigate the phase transformations at room temperature and high temperatures using the nanocrystalline Sm 2 Co 17 alloy as an example. The phase constitution and phase transformation sequence found in nanocrystalline Sm 2 Co 17 alloys with various grain-size levels agree well with the calculations by the nanothermodynamic model.

Robustness of a rhythmic circuit to short- and long-term temperature changes.

Science.gov (United States)

Tang, Lamont S; Taylor, Adam L; Rinberg, Anatoly; Marder, Eve

2012-07-18

Recent computational and experimental work has shown that similar network performance can result from variable sets of synaptic and intrinsic properties. Because temperature is a global perturbation that differentially influences every biological process within the nervous system, one might therefore expect that individual animals would respond differently to temperature. Nonetheless, the phase relationships of the pyloric rhythm of the stomatogastric ganglion (STG) of the crab, Cancer borealis, are remarkably invariant between 7 and 23°C (Tang et al., 2010). Here, we report that, when isolated STG preparations were exposed to more extreme temperature ranges, their networks became nonrhythmic, or "crashed", in a reversible fashion. Animals were acclimated for at least 3 weeks at 7, 11, or 19°C. When networks from the acclimated animals were perturbed by acute physiologically relevant temperature ramps (11-23°C), the network frequency and phase relationships were independent of the acclimation group. At high acute temperatures (>23°C), circuits from the cold-acclimated animals produced less-regular pyloric rhythms than those from warm-acclimated animals. At high acute temperatures, phase relationships between pyloric neurons were more variable from animal to animal than at moderate acute temperatures, suggesting that individual differences across animals in intrinsic circuit parameters are revealed at high temperatures. This shows that individual and variable neuronal circuits can behave similarly in normal conditions, but their behavior may diverge when confronted with extreme external perturbations.

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.

Phase Transformations and Phase Equilibria in the Fe-N System at Temperatures below 573 K

DEFF Research Database (Denmark)

Malinov, S.; Böttger, A.J.; Mittemeijer, E.J.

2001-01-01

The phase transformations of homogeneous Fe-N alloys of nitrogen contents from 10 to 26 at. pct were investigated by means of X-ray diffraction analysis upon aging in the temperature range from 373 to 473 K. It was found that precipitation of alpha double prime-Fe16N2 below 443 K does not only oc...

Pb solubility of the high-temperature superconducting phase Bi2Sr2Ca2Cu3O10+d

International Nuclear Information System (INIS)

Kaesche, S.; Majewski, P.; Aldinger, F.

1994-01-01

For the nominal composition of Bi 2.27x Pb x Sr 2 Ca 2 Cu 3 O 10+d the lead content was varied from x=0.05 to 0.45. The compositions were examined between 830 degrees C and 890 degrees C which is supposed to be the temperature range over which the so-called 2223 phase (Bi 2 Sr 2 Ca 2 Cu 3 O 10+d ) is stable. Only compositions between x=0.18 to 0.36 could be synthesized in a single phase state. For x>0.36 a lead containing phase with a stoichiometry of Pb 4 (Sr,Ca) 5 CuO d is formed, for x 2 Sr 2 CaCu 2 O 8+d and cuprates are the equilibrium phases. The temperature range for the 2223 phase was found to be 830 degrees C to 890 degrees C but the 2223 phase has extremely varying cation ratios over this temperature range. Former single phase 2223 samples turn to multi phase samples when annealed at slightly higher or lower temperatures. A decrease in the Pb solubility with increasing temperature was found for the 2223 phase

Low temperature thermodynamic investigation of the phase diagram of Sr3Ru2O7

Science.gov (United States)

Sun, D.; Rost, A. W.; Perry, R. S.; Mackenzie, A. P.; Brando, M.

2018-03-01

We studied the phase diagram of Sr3Ru2O7 by means of heat capacity and magnetocaloric effect measurements at temperatures as low as 0.06 K and fields up to 12 T. We confirm the presence of a new quantum critical point at 7.5 T which is characterized by a strong non-Fermi-liquid behavior of the electronic specific heat coefficient Δ C /T ˜-logT over more than a decade in temperature, placing strong constraints on theories of its criticality. In particular logarithmic corrections are found when the dimension d is equal to the dynamic critical exponent z , in contrast to the conclusion of a two-dimensional metamagnetic quantum critical end point, recently proposed. Moreover, we achieved a clear determination of the new second thermodynamic phase adjoining the first one at lower temperatures. Its thermodynamic features differ significantly from those of the dominant phase and characteristics expected of classical equilibrium phase transitions are not observed, indicating fundamental differences in the phase formation.

Phase transformation in {delta} Pu alloys at low temperature: In situ dilatometric study

Energy Technology Data Exchange (ETDEWEB)

Texier, G; Oudot, B; Platteau, C; Ravat, B; Delaunay, F, E-mail: gwenael.texier@cea.fr, E-mail: benoit.oudot@cea.fr [CEA, DAM, Valduc, Is sur Tille 21120 (France)

2010-03-15

The purpose of this work is to precisely study the martensitic transformation in a plutonium-gallium alloy. Thus, the thermodynamics and kinetics of the {delta}{yields}{alpha}'+{delta} phase transformation in a Pu-Ga alloy were studied under isochronal and isothermal conditions. The activation energy of the {delta}{yields}{alpha}'+{delta} phase transformation at a constant cooling rate (0.5 K.min{sup -1}) was determined by using Kissinger and Ozawa models. The average value of the activation energy was found to be at -56 kJ.mol{sup -1}. Dilatometry measurement was also used to trace 'in situ' the entire transformation for several temperatures. The kinetics of the {delta}{yields}{alpha}'+{delta} transformation were modelled under isothermal conditions in the theoretical frame of the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory. It is proposed that the transformation consists of three stages. The {alpha}' transformation begins with a nucleation of pre-existing embryos. Then, both nucleation and rapid growth of {alpha}' occurs simultaneously and finally, the plates width expend. Apparent activation energies for nucleation and growth transformation were determined from the temperature dependence of the constant K at respectively -34 kJ.mol{sup -1} and -60 kJ.mol{sup -1}. Adler et al. [1] investigated also the thermodynamics and the kinetics of the martensitic transformation in Pu alloys. These nucleation energies were found by modelling of heterogeneous martensitic nucleation via strain interaction with observed superdislocation-like nucleation sites in PuGa alloys. The values obtain by this model was very close to those we find. Investigations in steels alloys indicate that these energies are of the same order for nucleation near dislocation. Then, it could be indicating a strong relationship between these dislocations and martensitic nucleation sites.

Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases.

Science.gov (United States)

Nakatani, Tomotaka; Yoshiasa, Akira; Nakatsuka, Akihiko; Hiratoko, Tatsuya; Mashimo, Tsutomu; Okube, Maki; Sasaki, Satoshi

2016-02-01

A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298-778 K. A transition from a tetragonal (P4mm) to a cubic (Pm3m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti(4+) and Ba(2+) cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.

High temperature-induced phase transitions in Sr2GdRuO6 complex perovskite

International Nuclear Information System (INIS)

Triana, C.A.; Corredor, L.T.; Landínez Téllez, D.A.; Roa-Rojas, J.

2011-01-01

Highlights: ► Crystal structure, thermal expansion and phase transitions at high-temperature of Sr 2 GdRuO 6 perovskite has been investigated. ► X-ray diffraction pattern at 298 K of Sr 2 GdRuO 6 corresponds to monoclinic perovskite-type structure with P2 1 /n space group. ► Evolution of X-ray diffraction patterns at high-temperature shows that the Sr 2 GdRuO 6 perovskite suffers two-phase transitions. ► At 573 K the X-ray diffraction pattern of Sr 2 GdRuO 6 corresponds to monoclinic perovskite-type structure with I2/m space group. ► At 1273 K the Sr 2 GdRuO 6 perovskite suffers a complete phase-transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87). -- Abstract: The crystal structure behavior of the Sr 2 GdRuO 6 complex perovskite at high-temperature has been investigated over a wide temperature range between 298 K ≤ T ≤ 1273 K. Measurements of X-ray diffraction at room-temperature and Rietveld analysis of the experimental patterns show that this compound crystallizes in a monoclinic perovskite-like structure, which belongs to the P2 1 /n (no. 14) space group and 1:1 ordered arrangement of Ru 5+ and Gd 3+ cations over the six-coordinate M sites. Experimental lattice parameters were obtained to be a =5.8103(5) Å, b =5.8234(1) Å, c =8.2193(9) Å, V = 278.11(2) Å 3 and angle β = 90.310(5)°. The high-temperature analysis shows the occurrence of two-phase transitions on this material. First, at 573 K it adopts a monoclinic perovskite-type structure with I2/m (no. 12) space group with lattice parameters a = 5.8275(6) Å, b = 5.8326(3) Å, c = 8.2449(2) Å, V = 280.31(3) Å 3 and angle β = 90.251(3)°. Close to 1273 K it undergoes a complete phase-transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87), with lattice parameters a = 5.8726(1) Å, c = 8.3051(4) Å, V = 286.39(8) Å 3 and angle β = 90.0°. The high-temperature phase transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87) is characterized

PHASE CHANGES ON 4H AND 6H SIC AT HIGH TEMPERATURE OXIDATION

Directory of Open Access Journals (Sweden)

Jan Setiawan

2016-10-01

Full Text Available ABSTRACT PHASE CHANGES ON 4H AND 6H SIC AT HIGH TEMPERATURE OXIDATION. The oxidation on two silicon carbide contain 6H phase and contains 6H and 4H phases has been done.  Silicon carbide is ceramic non-oxide with excellent properties that potentially used in industry.  Silicon carbide is used in nuclear industry as structure material that developed as light water reactor (LWR fuel cladding and as a coating layer in the high temperature gas-cooled reactor (HTGR fuel.  In this study silicon carbide oxidation simulation take place in case the accident in primary cooling pipe is ruptured.  Sample silicon carbide made of powder that pressed into pellet with diameter 12.7 mm and thickness 1.0 mm, then oxidized at temperature 1000 oC, 1200 oC dan 1400 oC for 1 hour.  The samples were weighted before and after oxidized.  X-ray diffraction con-ducted to the samples using Panalytical Empyrean diffractometer with Cu as X-ray source.  Diffraction pattern analysis has been done using General Structure Analysis System (GSAS software. This software was resulting the lattice parameter changes and content of SiC phases.  The result showed all of the oxidation samples undergoes weight gain.  The 6S samples showed the highest weight change at oxidation temperature 1200 oC, for the 46S samples showed increasing tendency with the oxidation temperature.  X-ray diffraction pattern analysis showed the 6S samples contain dominan phase 6H-SiC that matched to ICSD 98-001-5325 card.  Diffraction pattern on 6S showed lattice parameter, composition and crystallite size changes.  Lattice parameters changes had smaller tendency from the model and before oxidation.  However, the lowest silicon carbide composition or the highest converted into other phases up to 66.85 %, occurred at oxidation temperature 1200 oC.  The 46S samples contains two polytypes silicon car-bide.  The 6H-SiC phases matched by ICSD 98-016-4972 card and 4H-SiC phase matched by ICSD 98

TEM Study of High-Temperature Precipitation of Delta Phase in Inconel 718 Alloy

Directory of Open Access Journals (Sweden)

Moukrane Dehmas

2011-01-01

Full Text Available Inconel 718 is widely used because of its ability to retain strength at up to 650∘C for long periods of time through coherent metastable  Ni3Nb precipitation associated with a smaller volume fraction of  Ni3Al precipitates. At very long ageing times at service temperature,  decomposes to the stable Ni3Nb phase. This latter phase is also present above the  solvus and is used for grain control during forging of alloy 718. While most works available on precipitation have been performed at temperatures below the  solvus, it appeared of interest to also investigate the case where phase precipitates directly from the fcc matrix free of  precipitates. This was studied by X-ray diffraction and transmission electron microscopy (TEM. TEM observations confirmed the presence of rotation-ordered domains in plates, and some unexpected contrast could be explained by double diffraction due to overlapping phases.

Influence of Gas-Liquid Interface on Temperature Wave of Pulsating Heat Pipe

Directory of Open Access Journals (Sweden)

Ying Zhang

2018-01-01

Full Text Available The influence of the interface on the amplitude and phase of the temperature wave and the relationship between the attenuation of the temperature wave and the gas-liquid two-phase physical parameters are studied during the operation of the pulsating heat pipe. The numerical simulation shows that the existence of the phase interface changes the direction of the temperature gradient during the propagation of the temperature wave, which increases the additional “thermal resistance.” The relative size of the gas-liquid two-phase thermal conductivity affects the propagation direction of heat flow at phase interface directly. The blockage of the gas plug causes hysteresis in the phase of the temperature wave, the relative size of the gas-liquid two-phase temperature coefficient will gradually increase the phase of the temperature wave, and the time when the heat flow reaches the peak value is also advanced. The attenuation of the temperature wave is almost irrelevant to the absolute value of the density, heat capacity, and thermal conductivity of the gas-liquid two phases, and the ratio of the thermal conductivity of the gas-liquid two phases is related. When the temperature of the heat pipe was changed, the difference of heat storage ability between gas and liquid will lead to the phenomenon of heat reflux and becomes more pronounced with the increases of the temperature wave.

Enantioseparation of angiotensin II receptor type 1 blockers: evaluation of 6-substituted carbamoyl benzimidazoles on immobilized polysaccharide-based chiral stationary phases. Unusual temperature behavior.

Science.gov (United States)

Su, Ran; Hou, Zhun; Sang, Lihong; Zhou, Zhi-Ming; Fang, Hao; Yang, Xinying

2017-09-15

Enantioseparation of thirteen 6-substituted carbamoyl benzimidazoles by high-performance liquid chromatography (HPLC) was investigated using two immobilized polysaccharide-based chiral stationary phases (CSPs), Chiralpak IC and Chiralpak IA, in normal-phase mode. Most of the examined compounds were completely resolved. The effects of a polar alcohol modifier, analyte structure, and column temperature on the chiral recognition were investigated. Furthermore, the structure-retention relationship was evaluated, and thermodynamic parameters were calculated from plots of ln k' or ln α versus 1/T. The thermodynamic parameters indicated that the separations were enthalpy-driven. Moreover, nonlinear van't Hoff plots were obtained on Chiralpak IA. However, two unusual phenomena were observed: (1) an unusual increase in retention with increasing temperature with linear van't Hoff plots on Chiralpak IC and (2) an extremely high T iso value (i.e., several thousand degrees centigrade). Copyright © 2017 Elsevier B.V. All rights reserved.

A reactor/receiver-concept for liquid-phase high-temperature processes

Energy Technology Data Exchange (ETDEWEB)

Schmidt-Traub, H.; Hahm, T. [Dortmund Univ. (Germany). Dept. of Chemical Engineering

1997-12-31

Besides the conversion of solar light to electricity solar energy can be used directly in photo- and thermochemistry. In the temperature range from 1000 to 2000 K there is a high demand for industrial process heat offering a variety of possibilities for solar thermal applications. Especially in the field of liquid-phase high-temperature processes there are hardly no solar thermal applications which exceed the stage of laboratory experiments. It was therefore the aim of two projects financed by the AG Solar of North Rhine-Westphalia, Germany, to develop concepts for commercial scale solar thermal plants and to judge them economically and ecologically. Some general problems have to be overcome to realize a commercial scale solar thermal plant for liquid-phase processes. The concept developed consists of a heliostat field, a tower reflector and an open receiver with a closed reaction chamber. The feasibility of a solar thermal plant for high-temperature liquid-phase processes has been shown in principle. The projected plant consists of a 4400 m{sup 2} heliostat field, a tower plus reflecting mirrors with a total area of 220 m{sup 2} and an open receiver with a closed annular reaction zone. For temperatures below 1700 K the overall efficiency is high enough to yield energetic amortization times of less than 1 year. For a further improvement and a verification of the calculation a closer look at the reactor/receiver and its heat transfer processes is necessary. This is done by using a mixed strategy of experiments and simulation. First experiments were carried out with a semitransparent salt and an opaque metal. The first stage of the experiments will end during the next weeks and their results have to be compared with the simulation. The simulation will then be extended to transparent melts. The second stage of the experiments which include the reaction chamber will start in 1997. An improvement of the reactor might be achieved using nonimaging concentrators to further

The relationship between experimental geometry, heat rate, and ultrasound wave speed measurement while observing phase changes in highly attenuative materials

Science.gov (United States)

Moore, David G.; Stair, Sarah L.; Jack, David A.

2018-04-01

Ultrasound techniques are capable of monitoring changes in the time-of-flight as a material is exposed to different thermal environments. The focus of the present study is to identify the phase of a material via ultrasound compression wave measurements in a through transmission experimental setup as the material is heated from a solid to a liquid and then allowed to re-solidify. The present work seeks to expand upon the authors' previous research, which proved this through transmission phase monitoring technique was possible, by considering different experimental geometries. The relationship between geometry, the measured speed of sound, and the temperature profile is presented. The use of different volumes helps in establishing a baseline understanding of which aspects of the experiment are geometry dependent and which are independent. The present study also investigates the relationship between the heating rate observed in the experiment and the measured speed of sound. The trends identified between the experimental geometry, heat rate and ultrasound wave speed measurement assist in providing a baseline understanding of the applicability of this technique to various industries, including the polymer industry and the oil industry.

Orientational relationships between phases in the {gamma}{yields}{alpha} transformations for uranium-molybdenum alloys; Relations d'orientation entre phases dans les transformations {gamma}{yields}{alpha} des alliages uranium-molybdene

Energy Technology Data Exchange (ETDEWEB)

Brun, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1966-04-01

A crystallographic study has been made of the {gamma} {yields} {alpha} + {gamma} transformation in the alloy containing 3 per cent by weight of molybdenum using electronic micro-diffraction; it has been possible to establish the orientational relationships governing the germination of the {alpha} phase in the {gamma} phase. One finds: (111){gamma} // (100) {alpha}, (112-bar){gamma} // (010) {alpha}, (11-bar 0){gamma} // (001){alpha}. By choosing a monoclinic lattice containing the same number of atoms as the orthorhombic lattice for defining the {gamma} mother phase, the change in structure has been explained by adding a homogeneous (112-bar){gamma} [111]{gamma} shearing deformation to a heterogeneous deformation brought about by slipping of the atoms which are not situated at the nodes of this lattice. The identity of the orientation relationships {gamma}/{alpha} and {gamma}/{alpha}''b and the loss of coherence {gamma} /{alpha} as a function of temperature or of time lead to the conclusion that, in the range studied, the {gamma} {yields} {alpha} transformation begins with a martensitic process and continues by germination and growth. (author) [French] Une etude cristallographique de la transformation {gamma} {yields} {alpha} + {gamma} dans l'alliage {alpha} 3 pour cent en poids de Mo, effectuee par microdiffraction electronique a permis d'etablir les relations d'orientation regissant la germination de {alpha} dans {gamma}. On a: (111){gamma} // (100){alpha}, (112-bar){gamma} // (010){alpha}, (11-bar 0){gamma} // (001){alpha}. En choisissant pour decrire la phase mere {gamma} une maille monoclinique contenant le meme nombre d'atomes que la maille orthorhombique {alpha}, le changement de structure a ete explique en superposant a une deformation homogene par cisaillement (112-bar){gamma} [111]{gamma} une deformation heterogene par glissement des atomes non situes aux noeuds de cette maille. L identite des relations d'orientation {gamma}/{alpha} et {gamma} /{alpha

Brillouin suppression in a fiber optical parametric amplifier by combining temperature distribution and phase modulation

DEFF Research Database (Denmark)

Lorenzen, Michael Rodas; Noordegraaf, Danny; Nielsen, Carsten Vandel

2008-01-01

We demonstrate an increased gain in optical parametric amplier through suppression of stimulated Brillouin scattering by applying a temperature distribution along the fiber resulting in a reduction of the required phase modulation.......We demonstrate an increased gain in optical parametric amplier through suppression of stimulated Brillouin scattering by applying a temperature distribution along the fiber resulting in a reduction of the required phase modulation....

Synthesis of indium nanoparticles at ambient temperature; simultaneous phase transfer and ripening

Energy Technology Data Exchange (ETDEWEB)

Aghazadeh Meshgi, Mohammad; Kriechbaum, Manfred [Graz University of Technology, Institute of Inorganic Chemistry (Austria); Biswas, Subhajit; Holmes, Justin D., E-mail: j.holmes@ucc.ie [University College Cork, Materials Chemistry and Analysis Group, Department of Chemistry and the Tyndall National Institute (Ireland); Marschner, Christoph, E-mail: christoph.marschner@tugraz.at [Graz University of Technology, Institute of Inorganic Chemistry (Austria)

2016-12-15

The synthesis of size-monodispersed indium nanoparticles via an innovative simultaneous phase transfer and ripening method is reported. The formation of nanoparticles occurs in a one-step process instead of well-known two-step phase transfer approaches. The synthesis involves the reduction of InCl{sub 3} with LiBH{sub 4} at ambient temperature and although the reduction occurs at room temperature, fine indium nanoparticles, with a mean diameter of 6.4 ± 0.4 nm, were obtained directly in non-polar n-dodecane. The direct synthesis of indium nanoparticles in n-dodecane facilitates their fast formation and enhances their size-monodispersity. In addition, the nanoparticles were highly stable for more than 2 months. The nanoparticles were characterised by dynamic light scattering (DLS), small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared (FT-IR) spectroscopy to determine their morphology, structure and phase purity.

Theoretical predictions for latent heats and phase-change temperatures of polycrystalline PCMs

Science.gov (United States)

Medved', Igor; Trník, Anton

2017-07-01

We had previously developed a microscopic approach from which it is possible to fit enthalpy jumps and heat capacity peaks of polycrystalline phase-change materials that consists of a large number of grains. It is also possible to determine the corresponding latent heat and phase-change temperature. These results are given in a form of sums over grain diameters that can be evaluated numerically. Therefore, their behavior and dependence on physical parameters are not susceptible to straightforward interpretations. Here we use the results to derive simple formulas for the maximum position (Tmax), height (H), and an asymmetry factor (α) of those heat capacity peaks that are very asymmetric. In addition, we express the phase-change temperature as a simple combination of Tmax, H, α, and the peak's area. We apply our formulas to Rhubitherm 27 as an example PCM for which the heat capacity peak is so asymmetric that it has about 80 % of its total area below its maximum position.

Temperature-field phase diagram of extreme magnetoresistance.

Science.gov (United States)

Fallah Tafti, Fazel; Gibson, Quinn; Kushwaha, Satya; Krizan, Jason W; Haldolaarachchige, Neel; Cava, Robert Joseph

2016-06-21

The recent discovery of extreme magnetoresistance (XMR) in LaSb introduced lanthanum monopnictides as a new platform to study this effect in the absence of broken inversion symmetry or protected linear band crossing. In this work, we report XMR in LaBi. Through a comparative study of magnetotransport effects in LaBi and LaSb, we construct a temperature-field phase diagram with triangular shape that illustrates how a magnetic field tunes the electronic behavior in these materials. We show that the triangular phase diagram can be generalized to other topological semimetals with different crystal structures and different chemical compositions. By comparing our experimental results to band structure calculations, we suggest that XMR in LaBi and LaSb originates from a combination of compensated electron-hole pockets and a particular orbital texture on the electron pocket. Such orbital texture is likely to be a generic feature of various topological semimetals, giving rise to their small residual resistivity at zero field and subject to strong scattering induced by a magnetic field.

Magnetic phase diagram of MnSi near critical temperature studied by neutron small angle scattering

International Nuclear Information System (INIS)

Ishikawa, Yoshikazu; Arai, Masatoshi

1984-01-01

The magnetic phase diagram of MnSi near the critical temperature T sub(N)=29.5K has been studied by neutron small angle scattering at KENS. It has been found that the anomalous new phase predicted by various methods to exist around at 28 K and 2 kOe is the paramagnetic phase where the magnetic correlations exhibit the same characteristics as those found at 29.5 K and zero magnetic field. This phenomenon, together with the sharp decrease of the magnetic phase boundary at T sub(N) and the substantial increase of the satellite Q vector at this temperature, has been found not to be interpreted by the current theories. (author)

Relationship between vibrations of tubular elements of power equipment and dynamic characteristics of longitudinal two-phase flow

International Nuclear Information System (INIS)

Fokin, B.S.; Gol'dberg, E.N.

1979-01-01

Analytical results of statistical nature of forces exciting vibrations of tubular elements, which are flown around with two-phase flows, are given. Relationships for the calculation of a mean-square amplitude and vibration frequency of a tubular element flown around with a two-phase mixture have been obtained. The relationships are confirmed experimentally

The relationship of sleep with temperature and metabolic rate in a hibernating primate.

Directory of Open Access Journals (Sweden)

Andrew D Krystal

Full Text Available STUDY OBJECTIVES: It has long been suspected that sleep is important for regulating body temperature and metabolic-rate. Hibernation, a state of acute hypothermia and reduced metabolic-rate, offers a promising system for investigating those relationships. Prior studies in hibernating ground squirrels report that, although sleep occurs during hibernation, it manifests only as non-REM sleep, and only at relatively high temperatures. In our study, we report data on sleep during hibernation in a lemuriform primate, Cheirogaleus medius. As the only primate known to experience prolonged periods of hibernation and as an inhabitant of more temperate climates than ground squirrels, this animal serves as an alternative model for exploring sleep temperature/metabolism relationships that may be uniquely relevant to understanding human physiology. MEASUREMENTS AND RESULTS: We find that during hibernation, non-REM sleep is absent in Cheirogaleus. Rather, periods of REM sleep occur during periods of relatively high ambient temperature, a pattern opposite of that observed in ground squirrels. Like ground squirrels, however, EEG is marked by ultra-low voltage activity at relatively low metabolic-rates. CONCLUSIONS: These findings confirm a sleep-temperature/metabolism link, though they also suggest that the relationship of sleep stage with temperature/metabolism is flexible and may differ across species or mammalian orders. The absence of non-REM sleep suggests that during hibernation in Cheirogaleus, like in the ground squirrel, the otherwise universal non-REM sleep homeostatic response is greatly curtailed or absent. Lastly, ultra-low voltage EEG appears to be a cross-species marker for extremely low metabolic-rate, and, as such, may be an attractive target for research on hibernation induction.

Portable system for temperature monitoring in all phases of wine production.

Science.gov (United States)

Boquete, Luciano; Cambralla, Rafael; Rodríguez-Ascariz, J M; Miguel-Jiménez, J M; Cantos-Frontela, J J; Dongil, J

2010-07-01

This paper presents a low-cost and highly versatile temperature-monitoring system applicable to all phases of wine production, from grape cultivation through to delivery of bottled wine to the end customer. Monitoring is performed by a purpose-built electronic system comprising a digital memory that stores temperature data and a ZigBee communication system that transmits it to a Control Centre for processing and display. The system has been tested under laboratory conditions and in real-world operational applications. One of the system's advantages is that it can be applied to every phase of wine production. Moreover, with minimum modification, other variables of interest (pH, humidity, etc.) could also be monitored and the system could be applied to other similar sectors, such as olive-oil production. 2010 ISA. Published by Elsevier Ltd. All rights reserved.

First principles process-product models for vitrification of nuclear waste: Relationship of glass composition to glass viscosity, resistivity, liquidus temperature, and durability

International Nuclear Information System (INIS)

Jantzen, C.M.

1991-01-01

Borosilicate glasses will be used in the USA and in Europe to immobilize radioactive high level liquid wastes (HLLW) for ultimate geologic disposal. Process and product quality models based on glass composition simplify the fabrication of the borosilicate glass while ensuring glass processability and quality. The process model for glass viscosity is based on a relationship between the glass composition and its structural polymerization. The relationship between glass viscosity and electrical resistivity is also shown to relate to glass polymerization. The process model for glass liquidus temperature calculates the solubility of the liquidus phases based on the free energies of formation of the precipitating species. The durability product quality model is based on the calculation of the thermodynamic hydration free energy from the glass composition

Non-linear temperature-dependent curvature of a phase change composite bimorph beam

Science.gov (United States)

Blonder, Greg

2017-06-01

Bimorph films curl in response to temperature. The degree of curvature typically varies in proportion to the difference in thermal expansion of the individual layers, and linearly with temperature. In many applications, such as controlling a thermostat, this gentle linear behavior is acceptable. In other cases, such as opening or closing a valve or latching a deployable column into place, an abrupt motion at a fixed temperature is preferred. To achieve this non-linear motion, we describe the fabrication and performance of a new bilayer structure we call a ‘phase change composite bimorph (PCBM)’. In a PCBM, one layer in the bimorph is a composite containing small inclusions of phase change materials. When the inclusions melt, their large (generally positive and  >1%) expansion coefficient induces a strong, reversible step function jump in bimorph curvature. The measured jump amplitude and thermal response is consistent with theory, and can be harnessed by a new class of actuators and sensors.

High-temperature phase transformation in Cr added TiAl base alloy

Energy Technology Data Exchange (ETDEWEB)

Abe, E.; Niinobe, K.; Nobuki, M.; Nakamura, M.; Tsujimoto, T.

1999-07-01

The authors have investigated a microstructure evolution of a Ti-48Al-3.5Cr (in at.%) alloy at high-temperatures ({gt} 1,473K). In the alloy annealed at 1673K for 1.8ks, followed by air-cooling, a characteristic microstructure with a feathery fashion was uniformly formed. From a cooling-rate-controlling study, it was found that formation of the feathery structure is accomplished during continuous cooling from 1673K to 1573K, within the {alpha} + {gamma} two-phase region. Transmission electron microscopy revealed that the feathery structure is composed of lamellar colonies (5--10{micro}m) which are crystallographically tilted slightly (a few degree) with their neighbors. A surprising fact is that lamellae in each colony are mostly the {gamma} phase with few {alpha}{sub 2} phase less than 5% in volume. This suggests that the feathery structure is a metastable product and has not resulted from the {alpha} {r{underscore}arrow} {alpha} + {gamma} transformation above 1,573 K. Instead, the feathery structure formation should be attributed to the non-equilibrium {alpha} {r{underscore}arrow} {gamma} transformation which occurs at high-temperatures with a small degree of supercooling. The authors discuss this interesting phase transformation in terms of the {alpha} {r{underscore}arrow} {gamma} massive transformation, based on the continuous-cooling-transformation (CCT) diagram constructed for the present alloy.

Reduction in L10 phase transition temperature of PLD grown FePt thin by pre-annealing pulse laser exposure

International Nuclear Information System (INIS)

Wang, Y.; Rawat, R.S.; Bisht, A.

2013-01-01

A pre-annealing atmospheric pulsed laser exposure was applied to decrease the phase transition (from chemically disordered A1 phase to chemically ordered L1 0 phase) temperature of FePt nano-particles on a Si (100) substrate. Different pre-annealing laser energy densities of 0.024 and 0.079 J/cm2 were utilized to expose the pulsed laser deposition (PLD) FePt thin film samples under atmospheric conditions. Subsequently, FePt thin film samples were annealed at different temperatures of 300 and 400 ºC to observe the influence of laser exposure on the phase transition temperature. The phase transition temperature was decreased from conventional 600 ºC to 400 ºC by one shot pre-annealing atmospheric pulsed laser exposure. (author)

Influence of Ti in the β-Zr(Fe) phase stability at ambient temperature

International Nuclear Information System (INIS)

Coelho, J.S.

1980-12-01

Investigations of the Fe-Ti-Zr alloy system with concentrations ranging from 1 at.% Ti to 20 at.% Ti and with a fixed concentration of 4 at.% Fe were performed using X-Ray diffraction, Mossbauer Spectroscopy and Optical and Electronic Metallographies. The alloys were melted in arc furnace in argon atmosphere and after being homogenized, they were quenched from the beta field into cold water in order to retain the high temperature β-Zr(Fe)-Ti phase. The obtained results show that the beta phase was partially retained until the concentration of 7 at.% Ti and was completely retained at the concentration equal to or higher than 8 at.% Ti. It is assumed in Moessbauer Spectroscopy a doublet for the beta phase and a singlet for the supersatured α'-Zr(Fe)-Ti phase resulting from the martensitic transformation. The relative amount of each phase detected by Moessbauer Spectroscopy was measured by the relative area of the each spectral line. The stability of the beta phase at room temperature was discussed in terms of short-range ordering caused by the Fe-Ti bonds. Some related properties were discussed through the changing of the lattice parameter, isomer shift and quadrupole splitting. (Author) [pt

Phase Transformation and Lattice Parameter Changes of Non-trivalent Rare Earth-Doped YSZ as a Function of Temperature

Science.gov (United States)

Jiang, Shengli; Huang, Xiao; He, Zhang; Buyers, Andrew

2018-05-01

To examine the effect of doping/co-doping on high-temperature phase compositions of YSZ, stand-alone YSZ and CeO2 and Nb2O5 co-doped YSZ samples were prepared using mechanical alloy and high-temperature sintering. XRD analysis was performed on these samples from room temperature to 1100 °C. The results show that the structure for the co-doped samples tends to be thermally stable when the test temperature is higher than a critical value. Monoclinic phase was dominant in Nb2O5 co-doped YSZ at temperatures lower than 600 °C, while for the YSZ and CeO2 co-doped YSZ, cubic/tetragonal phase was dominant in the whole test temperature range. The lattice parameters for all the samples increase with increasing test temperature generally. The lattice parameters for the two non-trivalent rare earth oxides co-doped YSZ show that the lattice parameter a for the cubic phase of the Ce4+ co-doped YSZ is consistently greater than that of 7YSZ which is related to the presence of larger radius of Ce4+ in the matrix. The lattice parameters a, b, c for the monoclinic phase of Ce4+ co-doped YSZ are much closer to each other than that of the Nb5+ co-doped YSZ, indicating the former has better tendency to form cubic/tetragonal phase, which is desired for vast engineering applications.

Grain alignment in bulk YBa2Cu3Ox superconductor by a low temperature phase transformation method

International Nuclear Information System (INIS)

Selvamanickam, V.; Goyal, A.; Kroeger, D.M.

1994-01-01

A quench and directional phase transformation process has been developed to achieve grain alignment in bulk YBa 2 Cu 3 O x superconductors at temperatures about 100 degree C below the peritectic temperature. Isothermal phase transformation of quenched precursors at 890 degree C for 3 min is found to result in the formation of more than 75% of YBa 2 Cu 3 O x phase without any formation of Y 2 BaCuO 5 . Phase transformation at higher temperatures leads to rapid formation of Y 2 BaCuO 5 in addition to YBa 2 Cu 3 O x . A well-aligned microstructure is achieved by directional phase transformation of the quenched compacts as a rate of 10 mm/h. The magnetic field dependence of the critical current density at 77 K of the directionally phase transformed material compares well with that of melt-textured YBCO and is superior to that of magnetically aligned and sintered YBCO

PRECIPITATION BEHAVIOR OF Co PHASES IN B2-ORDERED(Ni,Co)Al COMPOUND

Institute of Scientific and Technical Information of China (English)

W.H. Tian; A.L. Fan; M. Nemoto

2002-01-01

The precipitation behavior of Co phases in B2-ordered (Ni, Co)Al has been investigatedin terms of transmission electron microscopy. Fine precipitation off cc-Co occurs in(Ni, Co)Al by aging at temperature over 973K. The orientation relationship betweenthe fcc-Co precipitates and the B2-(Ni, Co)Al matrix follows the Kurdjumow-Sachs(K-S) orientation relation. But when the aging temperature is under 873K the Coprecipitates have a hcp crystal structure. The orientation relationship between thehcp-Co precipitates and the B2-(Ni, Co)Al matrix follows the Burgers orientation re-lation. (Ni, Co)Al is hardened appreciably by the fine precipitation of both the fcc-Coand hcp-Co phases. The temperature dependence of the yield strength of precipitate-containing B2-ordered (Ni, Co)Al was investigated by compression tests over the rangeof 298-1273K. The fine precipitation of Co phases enhances greatly the low and in-termediate temperature yield strength. When the deformation temperature was over873K, the strength of precipitate-containing (Ni, Co)Al is comparable to ternary dual-phase (Ni, Co)Al+Ni3Al alloy.

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.

Preparation of 147Pm metal and the determination of the melting point and phase transformation temperatures

International Nuclear Information System (INIS)

Angelini, P.; Adair, H.L.

1976-07-01

The promethium metal used in the determination of the melting point and phase transformation temperatures was prepared by reduction of promethium oxide with thorium metal at 1600 0 C and distilling the promethium metal into a quartz dome. The melting point and phase transformation temperatures of promethium metal were found to be 1042 +- 5 0 C and 890 +- 5 0 C, respectively. The ratio for the heat of the high-temperature transformation to the heat of fusion was determined to be 0.415

Thermal decomposition of agardites (REE) - relationship between dehydroxylation temperature and electronegativity

International Nuclear Information System (INIS)

Frost, Ray L.; Erickson, Kristy L.; Weier, Matt L.; McKinnon, Adam R.; Williams, Peter A.; Leverett, Peter

2005-01-01

The thermal decomposition of a suite of synthetic agardites of formula ACu 6 (AsO 4 ) 2 (OH) 6 ·3H 2 O where A is given by a rare earth element has been studied using thermogravimetric analysis techniques. Dehydration of the agardites occurs at low temperatures and over an extended temperature range from ambient to around 60 deg. C. This loss of water is attributed to the loss of zeolitic water. The mass loss of water indicates 3 mol of zeolitic water in the structure. Dehydroxylation occurs in steps over a wide range of temperatures from 235 to 456 deg. C. The mass loss during dehydroxylation shows the number of moles of hydroxyl units is six. There is a linear relationship between the first dehydroxylation temperature and the electronegativity of the agardites (REE)

Global land carbon sink response to temperature and precipitation varies with ENSO phase

Energy Technology Data Exchange (ETDEWEB)

Fang, Yuanyuan; Michalak, Anna M.; Schwalm, Christopher R.; Huntzinger, Deborah N.; Berry, Joseph A.; Ciais, Philippe; Piao, Shilong; Poulter, Benjamin; Fisher, Joshua B.; Cook, Robert B.; Hayes, Daniel; Huang, Maoyi; Ito, Akihiko; Jain, Atul; Lei, Huimin; Lu, Chaoqun; Mao, Jiafu; Parazoo, Nicholas C.; Peng, Shushi; Ricciuto, Daniel M.; Shi, Xiaoying; Tao, Bo; Tian, Hanqin; Wang, Weile; Wei, Yaxing; Yang, Jia

2017-05-01

Climate variability associated with the El Niño-Southern Oscillation (ENSO) and its consequent impacts on land carbon sink interannual variability have been used as a basis for investigating carbon cycle responses to climate variability more broadly, and to inform the sensitivity of the tropical carbon budget to climate change. Past studies have presented opposing views about whether temperature or precipitation is the primary factor driving the response of the land carbon sink to ENSO. Here, we show that the dominant driver varies with ENSO phase. Whereas tropical temperature explains sink dynamics following El Niño conditions (r_TG,P=0.59, p<0.01), the post La Niña sink is driven largely by tropical precipitation (r_PG,T=-0.46, p=0.04). This finding points to an ENSO-phase-dependent interplay between water availability and temperature in controlling the carbon uptake response to climate variations in tropical ecosystems. We further find that none of a suite of ten contemporary terrestrial biosphere models captures these ENSO-phase-dependent responses, highlighting a key uncertainty in modeling climate impacts on the future of the global land carbon sink.

High temperature phase transition in SOFC anodes based on Sr2MgMoO6-δ

International Nuclear Information System (INIS)

Marrero-Lopez, D.; Pena-Martinez, J.; Ruiz-Morales, J.C.; Martin-Sedeno, M.C.; Nunez, P.

2009-01-01

The double perovskite Sr 2 MgMoO 6-δ has been recently reported as an efficient anode material for solid oxide fuel cells (SOFCs). In the present work, this material have been investigated by high temperature X-ray diffraction (XRD), differential scanning calorimetry (DSC) and impedance spectroscopy to further characterise its properties as SOFC anode. DSC and XRD measurements indicate that Sr 2 MgMoO 6-δ exhibits a reversible phase transition around 275 deg. C from triclinic (I1-bar) with an octahedral tilting distortion to cubic (Fm3-barm) without octahedral distortion. This phase transition is continuous with increasing temperature without any sudden cell volume change during the phase transformation. The main effect of the phase transformation is observed in the electrical conductivity with a change in the activation energy at low temperature. La 3+ and Fe-substituted Sr 2 MgMoO 6-δ phases were also investigated, however these materials are unstable under oxidising conditions due to phase segregations above 600 deg. C. - Graphical abstract: The double perovskite Sr 2 MgMoO 6 , recently proposed as an efficient SOFC anode for direct hydrocarbon oxidation, exhibits a reversible structural phase transition from triclinic to cubic at 275 deg. C.

Possible mechanism for the room-temperature stabilization of the Ge(111) T > 300 deg.C phase by Ga

DEFF Research Database (Denmark)

Böhringer, M.; Molinás-Mata, P.; Zegenhagen, J.

1995-01-01

At low coverages, Ga on Ge(111) induces a hexagonal, domain wall modulated (2 x 2) adatom phase, stable at room temperature, that is characterized in low energy electron diffraction (LEED) by split 1/2-order reflections. This pattern closely resembles the one observed for a phase of clean Ge(111......) appearing at temperatures above 300 degrees C (T > 300 degrees C phase). We report scanning tunneling microscopy, LEED, as well. as surface x-ray diffraction measurements on the Ga-induced room-temperature (RT) phase and compare it with a model for the T > 300 OC phase of clean Ge(111). RT deposition of Ga...... yields a metastable c(2 x 8) structure which upon annealing transforms to the hexagonal (2 x 2) one. The transition occurs at considerably lower temperatures compared to clean Ge(111) and is irreversible due to pinning of adatom domains at Ga-induced defects, preventing the reordering of the adatoms...

Phase relationships in the Er-Mn-Ti ternary system at 773 K

International Nuclear Information System (INIS)

Liu Jingqi; Wang Xina; Tang Mengqi; Su Kunpeng; Yang Xiaomao; Li Chunhui; Li Xueqiang

2009-01-01

The Phase relationship in the Er-Mn-Ti ternary system at 773 K has been investigated by X-ray powder diffraction analysis with the aid of differential thermal analysis and optical microanalysis techniques in this work. The existence of eight binary compounds Mn 15 Ti 85, αMnTi, βMnTi, Mn 2 Ti, Mn 5 Ti, ErMn 12, Er 6 Mn 23 and ErMn 2 has been confirmed at 773 K in this system. The maximum solid solubility of Ti in Mn is about 8 at%Ti. The homogeneity range of Mn 2 Ti extends from about 31 at% to 39 at% Ti. The maximum solid solubility of Er in Mn 2 Ti phase is about less than 1 at% Er. No ternary compounds were found in this ternary system at 773K. At 773 K, the isothermal section of phase diagram of Er-Mn-Ti ternary system consists of 11 single-phase regions, 19 two-phase regions and 9 three-phase regions.

Assessing phase stability and element distribution in Co-base superalloys at elevated temperatures by in situ TEM heating experiments

Energy Technology Data Exchange (ETDEWEB)

Eggeler, Yolita; Mueller, Julian; Spiecker, Erdmann [Lehrstuhl fuer Mikro- und Nanostrukturforschung and Center for Nanoanalysis and Electron Microscopy (CENEM), Department Werkstoffwissenschaften, Universitaet Erlangen-Nuernberg, Erlangen (Germany)

2016-07-01

Co-based alloys, of a composition of Co-12Al-9W, form a stable two phase γ/γ{sup '} microstructure at 900 C. γ{sup '} cubes, consisting of the L12 crystal structure are coherently embedded in a solid solution fcc (A1) γ matrix. To ensure precipitate hardening at temperatures, which are relevant to practical applications, 700-1100 C, as experienced in gas turbine applications, the stability of the γ/γ{sup '} phases is of fundamental importance. In this analysis in situ TEM studies with chip-based heating systems (by DENS solution) are applied on new Co-based superalloys. After in situ heating at apr. 900 C and controlled quenching with different quenching rates the elemental distribution at the γ/γ{sup '} interface is measured using ChemiSTEM EDX. Exploiting the driving force for interface movement resulting from temperature-dependent volume fraction of γ and γ{sup '} insight into the diffusion of individual alloying elements and the relationship between local chemistry and ordering can be gained from transient phenomena. The experimental results will be compared with theoretical calculations. This work has been carried out within the framework of the SFB-TR 103 ''Single Crystal Superalloys''.

Two cloud-point phenomena in tetrabutylammonium perfluorooctanoate aqueous solutions: anomalous temperature-induced phase and structure transitions.

Science.gov (United States)

Yan, Peng; Huang, Jin; Lu, Run-Chao; Jin, Chen; Xiao, Jin-Xin; Chen, Yong-Ming

2005-03-24

This paper reported the phase behavior and aggregate structure of tetrabutylammonium perfluorooctanoate (TBPFO), determined by differential scanning calorimeter, electrical conductivity, static/dynamic light scattering, and rheology methods. We found that above a certain concentration the TBPFO solution showed anomalous temperature-dependent phase behavior and structure transitions. Such an ionic surfactant solution exhibits two cloud points. When the temperature was increased, the solution turned from a homogeneous-phase to a liquid-liquid two-phase system, then to another homogeneous-phase, and finally to another liquid-liquid two-phase system. In the first homogeneous-phase region, the aggregates of TBPFO were rodlike micelles and the solution was Newtonian fluid. While in the second homogeneous-phase region, the aggregates of TBPFO were large wormlike micelles, and the solution behaved as pseudoplastic fluid that also exhibited viscoelastic behavior. We thought that the first cloud point might be caused by the "bridge" effect of the tetrabutylammonium counterion between the micelles and the second one by the formation of the micellar network.

Deformation and Phase Transformation Processes in Polycrystalline NiTi and NiTiHf High Temperature Shape Memory Alloys

Science.gov (United States)

Benafan, Othmane

2012-01-01

The deformation and transformation mechanisms of polycrystalline Ni49.9Ti50.1 and Ni50.3Ti29.7Hf20 (in at.%) shape memory alloys were investigated by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The thermomechanical response of the low temperature martensite, the high temperature austenite phases, and changes between these two states during thermomechanical cycling were probed and reported. In the cubic austenite phase, stress-induced martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were compared to the bulk macroscopic response. When cycling between these two phases, the evolution of inelastic strains, along with the shape setting procedures were examined and used for the optimization of the transformation properties as a function of deformation levels and temperatures. Finally, this work was extended to the development of multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory.

Method for calculating solid-solid phase transitions at high temperature: An application to N2O

International Nuclear Information System (INIS)

Kuchta, B.; Etters, R.D.

1992-01-01

Two similar techniques for calculating solid-solid phase transitions at high temperatures are developed, where the contribution of the entropy may be a decisive factor. They utilize an artificial reversible path from one phase to another by application of a control parameter. Thermodynamic averages are calculated using constant-volume and constant-pressure Monte Carlo techniques. An application to N 2 O at room temperature shows that the cubic Pa3 to orthorhombic Cmca transition occurs near 4.9-GPa pressure, very close to the value calculated at very low temperatures. These results support experimental evidence that the transition pressure is virtually independent of temperature

The Cu-Te-Sb phase system at temperatures between 300 and 1000 degree C

DEFF Research Database (Denmark)

Karup-Møller, Sven

1997-01-01

Phase relations were determined in the Cu-Te-Sb phase system at 300, 350, 400, 500, 600, 700, 800, 900 and 1000 degree C. At temperatures between 400 and 900 degree C a cubic primitive ternary phase A exists. It has the empirical formula Cu(10.32-0.97x)Te(x)Sb(4-x) (Z=2, a=7.682 Å). A small liquid...

Relationship between alpine tourism demand and hot summer air temperatures associated with climate change

Science.gov (United States)

Rebetez, M.; Serquet, G.

2010-09-01

We quantified the impacts of hot summer air temperatures on tourism in the Swiss Alps by analyzing the relationship between temperature and overnight stays in 40 Alpine resorts. Several temperature and insolation thresholds were tested to detect their relationship to summer tourism. Our results reveal significant correlations between the number of nights spent in mountain resorts and hot temperatures at lower elevations. Alpine resorts nearest to cities are most sensitive to hot temperatures. This is probably because reactions to hot episodes take place on a short-term basis as heat waves remain relatively rare. The correlation in June is stronger compared to the other months, probably because school holidays and the peak domestic tourist demand in summer usually takes place in July and August. Our results suggest that alpine tourist resorts could benefit from hotter temperatures at lower elevations under future climates. Tourists already react on a short-term basis to hot days and spend more nights in hotels in mountain resorts. If heat waves become more regular, it seems likely that tourists choose to stay at alpine resorts more frequently and for longer periods.

Air - water temperature relationships in the trout streams of southeastern Minnesota’s carbonate - sandstone landscape

Science.gov (United States)

Krider, Lori A.; Magner, Joseph A.; Perry, Jim; Vondracek, Bruce C.; Ferrington, Leonard C.

2013-01-01

Carbonate-sandstone geology in southeastern Minnesota creates a heterogeneous landscape of springs, seeps, and sinkholes that supply groundwater into streams. Air temperatures are effective predictors of water temperature in surface-water dominated streams. However, no published work investigates the relationship between air and water temperatures in groundwater-fed streams (GWFS) across watersheds. We used simple linear regressions to examine weekly air-water temperature relationships for 40 GWFS in southeastern Minnesota. A 40-stream, composite linear regression model has a slope of 0.38, an intercept of 6.63, and R2 of 0.83. The regression models for GWFS have lower slopes and higher intercepts in comparison to surface-water dominated streams. Regression models for streams with high R2 values offer promise for use as predictive tools for future climate conditions. Climate change is expected to alter the thermal regime of groundwater-fed systems, but will do so at a slower rate than surface-water dominated systems. A regression model of intercept vs. slope can be used to identify streams for which water temperatures are more meteorologically than groundwater controlled, and thus more vulnerable to climate change. Such relationships can be used to guide restoration vs. management strategies to protect trout streams.

Melting temperature and enthalpy variations of phase change materials (PCMs): a differential scanning calorimetry (DSC) analysis

Science.gov (United States)

Sun, Xiaoqin; Lee, Kyoung Ok; Medina, Mario A.; Chu, Youhong; Li, Chuanchang

2018-06-01

Differential scanning calorimetry (DSC) analysis is a standard thermal analysis technique used to determine the phase transition temperature, enthalpy, heat of fusion, specific heat and activation energy of phase change materials (PCMs). To determine the appropriate heating rate and sample mass, various DSC measurements were carried out using two kinds of PCMs, namely N-octadecane paraffin and calcium chloride hexahydrate. The variations in phase transition temperature, enthalpy, heat of fusion, specific heat and activation energy were observed within applicable heating rates and sample masses. It was found that the phase transition temperature range increased with increasing heating rate and sample mass; while the heat of fusion varied without any established pattern. The specific heat decreased with the increase of heating rate and sample mass. For accuracy purpose, it is recommended that for PCMs with high thermal conductivity (e.g. hydrated salt) the focus will be on heating rate rather than sample mass.

Relationship between body temperature and air temperature in ...

African Journals Online (AJOL)

Body temperatures of singing male Gryllus bimaculatus were measured for the first time. Body temperatures were strongly correlated with ambient temperature. This indicates that, unlike some other orthopterans, larger crickets are not dependent on an elevated body temperature for efficient calling. Our results confirm that it ...

Nucleation and temperature-driven phase transitions of silicene superstructures on Ag(1 1 1)

International Nuclear Information System (INIS)

Grazianetti, C; Chiappe, D; Cinquanta, E; Fanciulli, M; Molle, A

2015-01-01

Silicene grown on Ag(1 1 1) is characterized by several critical parameters. Among them, the substrate temperature plays a key role in determining the morphology during growth. However, an unexpected important role is also equally played by the post-deposition annealing temperature which determines the self-organization of silicene domains even in the submonolayer coverage regime and consecutive transitions between silicene with different periodicity. These temperature-driven phase transitions can be exploited to select the desired majority silicene phase, thus allowing for the manipulation of silicene properties. (paper)

The relationship between gut hormone secretion and gastric emptying in different phases of the migrating motor complex

Energy Technology Data Exchange (ETDEWEB)

Rasmussen, L.; Oester-Joergensen, E.; Quist, N. [Odense University Hospital, Odense (Denmark); and others

1996-05-01

No studies are available on the relationship between the response of gut hormones and gastric emptying in different phases of the migrating motor complex. This study examined whether basal gut hormone concentrations in plasma before food ingestion are predictors of emptying characteristics and whether different hormone secretion patterns are associated with specific alteration in emptying rate. 12 healthy men were examined on two occasion: one with meal ingestion in phase I and the other with meal ingestion in phase II. The meal consisted of an omelette labelled with {sup 99m}Tc followed by 150 ml water labelled with {sup 111}In. Plasma concentrations of gastrin, cholecystokinin, motilin, and peptide YY were measured in the fasting state, immediately after food ingestion, and at 15 min-min intervals in the postprandial period. New findings from the present study include a higher incremental integrated postprandial motilin response in phase I than in phase II, and a linear relationship between median total integrated motilin response and solid emptying at 120 min in phase I. Furthermore, in phase I a linear relationship between total integrated area of cholecystokinin and solid emptying at 120 min was demonstrated. The findings from the present investigation have to be considered in the future design of studies that focus on postprandial release of gastrointestinal hormones. The transition from phase III to phase I is a reproducible and easily recognized pressure event. Therefore, the authors recommend the use of food ingestion immediately after termination of duodenal phase III. 14 refs.

Evaluation of calcination temperature and phase composition ratio for new hyroxyapatite

Science.gov (United States)

Salimi, M. N. Ahmad; Chin, H. S.

2017-10-01

The demand of production of hydroxyapatite (HA) has been increasing for the purpose of medical and dental application. HA possesses the excellent properties leads to the priority choice for ceramic bone replacement. Synthesis route by wet chemical precipitation is commonly practised in industrial scale. Calcium hydroxide and Orthophosphoric acid are the precursors for production scale. The synthesis of HA is conducted by varying the synthetic condition: stirring rate, calcium-phosphate and calcination temperature. This paper is focused on the properties of HA produced by regulating the synthetic condition so that the qualities of HA can be well performed. Characterization studies were also carried out by Fourier Transform Infrared Spectroscopy (FT-IR) for functional group identification, Scanning Electron Microscope (SEM) for surface morphology analysis and X-Ray Diffraction (XRD) for phase composition and crystallinity respectively. Narrow particle size distribution contributed to better quality of hydroxyapatite for bone replacement. Both calcium-phosphate ratio and calcination temperature would affect the phase composition of calcium phosphate.

Characterizing Arctic mixed-phase cloud structure and its relationship with humidity and temperature inversion using ARM NSA observations

Science.gov (United States)

Qiu, Shaoyue; Dong, Xiquan; Xi, Baike; Li, J.-L. F.

2015-08-01

In this study, the characteristics of the Arctic mixed-phase cloud (AMC) have been investigated using data collected at the Atmospheric Radiation Measurement North Slope Alaska site from October 2006 to September 2009. AMC has an annual occurrence frequency of 42.3%, which includes 18.7% of single-layered AMCs and 23.6% for multiple layers. Two cloud base heights (CBHs) are defined from ceilometer and micropulse lidar (MPL) measurements. For single-layered AMC, the ceilometer-derived CBH represents the base of the liquid-dominant layer near the cloud top, while MPL-derived CBH represents base of the lower ice-dominant layer. The annual mean CBHs from ceilometer and MPL measurements are 1.0 km and 0.6 km, respectively, with the largest difference ( 1.0 km) occurring from December to March and the smallest difference in September. The humidity inversion occurrence decreases with increasing humidity inversion intensity (stronger in summer than in winter). During the winter months, AMC occurrences increase from 15% to 35% when the inversion intensity increases from 0.1 to 0.9 g/kg. On the contrary, despite a higher frequency of strong humidity inversion in summer, AMC occurrences are nearly invariant for different inversion intensities. On average, humidity and temperature inversion frequencies of occurrence above an AMC are 5 and 8 times, respectively, as high as those below an AMC. The strong inversion occurrences for both humidity and temperature above an AMC provide the moisture sources from above for the formation and maintenance of AMCs. This result helps to reconcile the persistency of AMCs even when the Arctic surface is covered by snow and ice.

Quenching ilmenite with a high-temperature and high-pressure phase using super-high-energy ball milling.

Science.gov (United States)

Hashishin, Takeshi; Tan, Zhenquan; Yamamoto, Kazuhiro; Qiu, Nan; Kim, Jungeum; Numako, Chiya; Naka, Takashi; Valmalette, Jean Christophe; Ohara, Satoshi

2014-04-25

The mass production of highly dense oxides with high-temperature and high-pressure phases allows us to discover functional properties that have never been developed. To date, the quenching of highly dense materials at the gramme-level at ambient atmosphere has never been achieved. Here, we provide evidence of the formation of orthorhombic Fe2TiO4 from trigonal FeTiO3 as a result of the high-temperature (>1250 K) and high-pressure (>23 GPa) condition induced by the high collision energy of 150 gravity generated between steel balls. Ilmenite was steeply quenched by the surrounding atmosphere, when iron-rich ilmenite (Fe2TiO4) with a high-temperature and high-pressure phase was formed by planetary collisions and was released from the collision points between the balls. Our finding allows us to infer that such intense planetary collisions induced by high-energy ball milling contribute to the mass production of a high-temperature and high-pressure phase.

γ-U phase in U-Pt system retained to low temperatures by means of rapid cooling

Energy Technology Data Exchange (ETDEWEB)

Kim-Ngan, N.-T.H., E-mail: tarnawsk@up.krakow.pl [Institute of Physics, Pedagogical University, Podchorazych 2, 30 084 Kraków (Poland); Paukov, M. [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Prague (Czech Republic); Tarasenko, R. [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Prague (Czech Republic); Institute of Physics, Faculty of Science, P.J. Šafárik University, Park Angelinum 9, 04154 Košice (Slovakia); Tkáč, V.; Minarik, P.; Drozdenko, D.; Havela, L. [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Prague (Czech Republic)

2016-10-15

Splat-cooling technique with a cooling rate better than 10{sup 6} K/s helps to increase the Pt solubility in the (cubic) γ-U phase and retain such γ-U phase in U-15 at.% Pt splat down to low temperatures. The splat-cooled U-Pt alloys are very stable in exposing to air. The γ-U phase (U-15 at.% Pt splat) is characterized by a negative temperature coefficient of the resistivity (dρ/dT < 0). The splats become superconducting below 1.1 K. - Highlights: • γ-U phase stabilization in U-15 at.% Pt splat-cooled alloys. • Splat-cooling helps to increase the Pt solubility in cubic γ-U phase. • All U-Pt alloys (0–15 at.% Pt) become superconducting below 1.1 K.

Low-temperature phase MnBi compound: A potential candidate for rare-earth free permanent magnets

International Nuclear Information System (INIS)

Ly, V.; Wu, X.; Smillie, L.; Shoji, T.; Kato, A.; Manabe, A.; Suzuki, K.

2014-01-01

Highlights: • The spin reorientation temperature of MnBi is suppressed by nanoscale grain refinement. • Hardness parameter of MnBi reaches as large as 2.8 at 580 K. • MnBi has a great potential as a hard phase in rare-earth free nanocomposite magnets. • Improving the surface passivity is a remaining task for MnBi-based permanent magnets. - Abstract: The low-temperature phase (LTP) MnBi is one of the few rare-earth free compounds that exhibit a large magnetocrystalline anisotropy energy in the order of 10 6 J/m 3 . A large coercive field (μ 0 H cj ) above 1 T can be obtained readily by reducing the crystallite size (D) through mechanical grinding (MG). The room-temperature H cj values follow a phenomenological expression μ 0 H cj = μ 0 H a (δ/D) n where the anisotropy field (μ 0 H a ) is ∼4 T, the Bloch wall width (δ) is 7 nm and the exponent (n) is about 0.7 in our study. The grain refinement upon MG is accompanied by suppression of the spin reorientation transition temperature (T SR ) from 110 K to below 50 K. The coercive field starts to exhibit positive temperature dependence approximately 50 K above T SR and the room-temperature magnetic hardening induced by MG could partially be brought about by the lowered onset of this positive temperature dependence. The suppression of T SR by MG is likely to be induced by the surface anisotropy with which the 2nd order crystal field term is enhanced. One of the shortcomings of LTP-MnBi is its poor phase stability under the ambient atmosphere. The spontaneous magnetization decreases considerably after room-temperature aging for 1 week. This is due to oxidation of Mn which leads to decomposition of the MnBi phase. Hence, the surface passivity needs to be established before this material is considered for a permanent magnet in practical uses. Another shortcoming is the limited spontaneous magnetization. The theoretical upper limit of the maximum energy product in LTP-MnBi remains only a quarter of that in Nd 2

Low-temperature phase MnBi compound: A potential candidate for rare-earth free permanent magnets

Energy Technology Data Exchange (ETDEWEB)

Ly, V.; Wu, X.; Smillie, L. [Department of Materials Engineering, Monash University, Clayton, VIC 3800 (Australia); Shoji, T.; Kato, A.; Manabe, A. [Toyota Motor Corporation, Mishuku, Susono, Shizuoka 410-1193 (Japan); Suzuki, K., E-mail: kiyonori.suzuki@monash.edu [Department of Materials Engineering, Monash University, Clayton, VIC 3800 (Australia)

2014-12-05

Highlights: • The spin reorientation temperature of MnBi is suppressed by nanoscale grain refinement. • Hardness parameter of MnBi reaches as large as 2.8 at 580 K. • MnBi has a great potential as a hard phase in rare-earth free nanocomposite magnets. • Improving the surface passivity is a remaining task for MnBi-based permanent magnets. - Abstract: The low-temperature phase (LTP) MnBi is one of the few rare-earth free compounds that exhibit a large magnetocrystalline anisotropy energy in the order of 10{sup 6} J/m{sup 3}. A large coercive field (μ{sub 0}H{sub cj}) above 1 T can be obtained readily by reducing the crystallite size (D) through mechanical grinding (MG). The room-temperature H{sub cj} values follow a phenomenological expression μ{sub 0}H{sub cj} = μ{sub 0}H{sub a}(δ/D){sup n} where the anisotropy field (μ{sub 0}H{sub a}) is ∼4 T, the Bloch wall width (δ) is 7 nm and the exponent (n) is about 0.7 in our study. The grain refinement upon MG is accompanied by suppression of the spin reorientation transition temperature (T{sub SR}) from 110 K to below 50 K. The coercive field starts to exhibit positive temperature dependence approximately 50 K above T{sub SR} and the room-temperature magnetic hardening induced by MG could partially be brought about by the lowered onset of this positive temperature dependence. The suppression of T{sub SR} by MG is likely to be induced by the surface anisotropy with which the 2nd order crystal field term is enhanced. One of the shortcomings of LTP-MnBi is its poor phase stability under the ambient atmosphere. The spontaneous magnetization decreases considerably after room-temperature aging for 1 week. This is due to oxidation of Mn which leads to decomposition of the MnBi phase. Hence, the surface passivity needs to be established before this material is considered for a permanent magnet in practical uses. Another shortcoming is the limited spontaneous magnetization. The theoretical upper limit of the maximum

Urea-temperature phase diagrams capture the thermodynamics of denatured state expansion that accompany protein unfolding

Science.gov (United States)

Tischer, Alexander; Auton, Matthew

2013-01-01

We have analyzed the thermodynamic properties of the von Willebrand factor (VWF) A3 domain using urea-induced unfolding at variable temperature and thermal unfolding at variable urea concentrations to generate a phase diagram that quantitatively describes the equilibrium between native and denatured states. From this analysis, we were able to determine consistent thermodynamic parameters with various spectroscopic and calorimetric methods that define the urea–temperature parameter plane from cold denaturation to heat denaturation. Urea and thermal denaturation are experimentally reversible and independent of the thermal scan rate indicating that all transitions are at equilibrium and the van't Hoff and calorimetric enthalpies obtained from analysis of individual thermal transitions are equivalent demonstrating two-state character. Global analysis of the urea–temperature phase diagram results in a significantly higher enthalpy of unfolding than obtained from analysis of individual thermal transitions and significant cross correlations describing the urea dependence of and that define a complex temperature dependence of the m-value. Circular dichroism (CD) spectroscopy illustrates a large increase in secondary structure content of the urea-denatured state as temperature increases and a loss of secondary structure in the thermally denatured state upon addition of urea. These structural changes in the denatured ensemble make up ∼40% of the total ellipticity change indicating a highly compact thermally denatured state. The difference between the thermodynamic parameters obtained from phase diagram analysis and those obtained from analysis of individual thermal transitions illustrates that phase diagrams capture both contributions to unfolding and denatured state expansion and by comparison are able to decipher these contributions. PMID:23813497

Raman studies of pressure and temperature induced phase transformations in calcite

International Nuclear Information System (INIS)

Exarhos, G.J.; Hess, N.J.

1992-01-01

This patent describes phase stability in the calcium carbonate system investigated as a simultaneous function of pressure and temperature up to 40 kbar and several hundred degrees Kelvin. Micro-Raman techniques were used to interrogate samples constrained within a resistively heated diamond anvil cell. Measured spectra allow unequivocal identification of crystalline phases and are used to refine the P,T phase diagram. Calcium carbonate was found to exhibit both reversible and irreversible transformation phenomena among the four known phases which exist under these conditions. Time-dependent Raman intensity variations as the material is perturbed from its equilibrium state allow real-time kinetics measurements to be performed. Evidence suggests that the order of certain observed transformations may be pressure dependent. The utility of Raman spectroscopy to follow transformation phenomena and to estimate fundamental thermophysical properties from the stress dependence of vibrational mode frequencies is demonstrated

Phase transition temperature in the Zr-rich corner of Zr-Nb-Sn-Fe alloys

Science.gov (United States)

Canay, M.; Danón, C. A.; Arias, D.

2000-08-01

The influence of small composition changes on the phase transformation temperature of Zr-1Nb-1Sn-0.2(0.7)Fe alloys was studied in the present work, by electrical resistivity measurements and metallographic techniques. For the alloy with 0.2 at.% Fe we have determined Tα↔α+β=741°C and Tα+β↔β=973°C, and for the 0.7 at.% Fe the transformation temperatures were T α↔α+β=712°C and T α+β↔β=961°C. We have verified that the addition of Sn stabilized the β phase.

Stress-induced phase transformation and room temperature aging in Ti-Nb-Fe alloys

Energy Technology Data Exchange (ETDEWEB)

Cai, S.; Schaffer, J.E. [Fort Wayne Metals Research Products Corp, 9609 Ardmore Ave., Fort Wayne, IN 46809 (United States); Ren, Y. [Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439 (United States)

2017-01-05

Room temperature deformation behavior of Ti-17Nb-1Fe and Ti-17Nb-2Fe alloys was studied by synchrotron X-ray diffraction and tensile testing. It was found that, after proper heat treatment, both alloys were able to recover a deformation strain of above 3.5% due to the Stress-induced Martensite (SIM) phase transformation. Higher Fe content increased the beta phase stability and onset stress for SIM transformation. A strong {110}{sub β} texture was produced in Ti-17Nb-2Fe compared to the {210}{sub β} texture that was observed in Ti-17Nb-1Fe. Room temperature aging was observed in both alloys, where the formation of the omega phase increased the yield strength (also SIM onset stress), and decreased the ductility and strain recovery. Other metastable beta Ti alloys may show a similar aging response and this should draw the attention of materials design engineers.

Fatigue Damage Evaluation of Short Carbon Fiber Reinforced Plastics Based on Phase Information of Thermoelastic Temperature Change.

Science.gov (United States)

Shiozawa, Daiki; Sakagami, Takahide; Nakamura, Yu; Nonaka, Shinichi; Hamada, Kenichi

2017-12-06

Carbon fiber-reinforced plastic (CFRP) is widely used for structural members of transportation vehicles such as automobile, aircraft, or spacecraft, utilizing its excellent specific strength and specific rigidity in contrast with the metal. Short carbon fiber composite materials are receiving a lot of attentions because of their excellent moldability and productivity, however they show complicated behaviors in fatigue fracture due to the random fibers orientation. In this study, thermoelastic stress analysis (TSA) using an infrared thermography was applied to evaluate fatigue damage in short carbon fiber composites. The distribution of the thermoelastic temperature change was measured during the fatigue test, as well as the phase difference between the thermoelastic temperature change and applied loading signal. Evolution of fatigue damage was detected from the distribution of thermoelastic temperature change according to the thermoelastic damage analysis (TDA) procedure. It was also found that fatigue damage evolution was more clearly detected than before by the newly developed thermoelastic phase damage analysis (TPDA) in which damaged area was emphasized in the differential phase delay images utilizing the property that carbon fiber shows opposite phase thermoelastic temperature change.

X-ray diffraction study of low-temperature phase transformations in nickel-titanium orthodontic wires.

Science.gov (United States)

Iijima, M; Brantley, W A; Guo, W H; Clark, W A T; Yuasa, T; Mizoguchi, I

2008-11-01

Employ conventional X-ray diffraction (XRD) to analyze three clinically important nickel-titanium orthodontic wire alloys over a range of temperatures between 25 and -110 degrees C, for comparison with previous results from temperature-modulated differential scanning calorimetry (TMDSC) studies. The archwires selected were 35 degrees C Copper Ni-Ti (Ormco), Neo Sentalloy (GAC International), and Nitinol SE (3M Unitek). Neo Sentalloy, which exhibits superelastic behavior, is marketed as having shape memory in the oral environment, and Nitinol SE and 35 degrees C Copper Ni-Ti also exhibit superelastic behavior. All archwires had dimensions of 0.016in.x0.022in. (0.41 mm x 0.56 mm). Straight segments cut with a water-cooled diamond saw were placed side-by-side to yield a 1 cm x 1cm test sample of each wire product for XRD analysis (Rint-Ultima(+), Rigaku) over a 2theta range from 30 degrees to 130 degrees and at successive temperatures of 25, -110, -60, -20, 0 and 25 degrees C. The phases revealed by XRD at the different analysis temperatures were in good agreement with those found in previous TMDSC studies of transformations in these alloys, in particular verifying the presence of R-phase at 25 degrees C. Precise comparisons are not possible because of the approximate nature of the transformation temperatures determined by TMDSC and the preferred crystallographic orientation present in the wires. New XRD peaks appear to result from low-temperature transformation in martensite, which a recent transmission electron microscopy (TEM) study has shown to arise from twinning. While XRD is a useful technique to study phases in nickel-titanium orthodontic wires and their transformations as a function of temperature, optimum insight is obtained when XRD analyses are combined with complementary TMDSC and TEM study of the wires.

Simultaneous measurement of temperature and strain using a phase-shifted fiber Bragg grating inscribed by femtosecond laser

Science.gov (United States)

Jiang, Yajun; Liu, Chi; Li, Dong; Yang, Dexing; Zhao, Jianlin

2018-04-01

A novel method for simultaneous measurement of temperature and strain using a single phase-shifted fiber Bragg grating (PS-FBG) is proposed. The PS-FBG is produced by exposing the fusion-spliced fiber with a femtosecond laser and uniform phase mask. Due to the non-uniform structure and strain distribution in the fusion-spliced region, the phase-shift changes with different responses during increases to the temperature and strain; by measuring the central wavelengths and the loss difference of two transmission dips, temperature and strain can be determined simultaneously. The resolutions of this particular sensor in measuring temperature and strain are estimated to be  ±1.5 °C and  ±12.2 µɛ in a range from  -50 °C to 150 °C and from 0 µɛ to 2070 µɛ.

Temperature-dependent high energy-resolution EELS of ferroelectric and paraelectric BaTiO3 phases

Science.gov (United States)

Bugnet, Matthieu; Radtke, Guillaume; Woo, Steffi Y.; Zhu, Guo-zhen; Botton, Gianluigi A.

2016-01-01

Probing the ferroelectricity at the nanometer scale is of particular interest for a wide range of applications. In this Rapid Communication, the structural distortion of BaTiO3 (BTO) is studied in its ferroelectric (rhombohedral and tetragonal), and paraelectric phases from the O K near edge structures in electron energy loss spectroscopy. Modifications of the electronic structure are detected in the lowest energy fine structure (FS) of the O K edge in the ferroelectric phases, and are interpreted by core-hole valence-electron screening geometry. For the paraelectric phase, the lowest energy FS of the O K edge is comparable to the one obtained at room temperature, which is inconsistent with an expected cubic structure. The variations observed in the O K near edge structures, such as a broader and more asymmetric lowest energy FS at low temperature, suggest that the magnitude of the Ti+4 off-centering along increases in lower-temperature phases. These findings demonstrate the sensitivity of the O K near edge structures to the structural distortions of BTO polymorphs, and form a basis for further investigations on defective or strained BTO at the nanoscale.

Evaluation of ODS-AQ stationary phase for use in capillary electrochromatography.

Science.gov (United States)

Djordjevic, N M; Fitzpatrick, F; Houdiere, F

2001-04-01

The aim of this study was to evaluate the applicability of ODS-AQ packing material as a stationary phase in capillary electrochromatography (CEC). The electroosmotic flow created on an ODS-AQ stationary phase was measured at different mobile phase compositions and at different column temperatures. It was observed that the electroosmotic flow generated in the column increased by 50% when the temperature of the system was raised from 20 degrees C to 60 degrees C, while all other conditions were kept constant. The electroosmotic flow produced by the ODS-AQ stationary phase was found to be comparable to the flow generated in a column packed with Nucleosil bare-silica material. In addition, a set of polar compounds (D-lysergic acid diethylamide derivatives) was utilized to determine the influence of temperature and mobile phase composition on their chromatographic behavior on an ODS-AQ stationary phase in a CEC mode. A linear relationship between the solute retention factor and column temperatures was seen over the temperature range studied (20 degrees C to 60 degrees C). A quadratic function was used to describe the changes in the solute retention factors with variation of acetonitrile concentration in the mobile phase.

The influence of temperature on σ-phase formation and the resulting hardening of Fe-Cr-Mo-alloys

International Nuclear Information System (INIS)

Waanders, F.B.; Vorster, S.W.; Pollak, H.

1999-01-01

Hardening in Fe-Cr-Mo-alloys due to the formation of σ-phase, has been the subject of theoretical and experimental interest. In the present investigation Fe-Cr-alloys containing 0, 2, 4 and 6% Mo were prepared and were fully transformed to the σ-phase by isothermally annealing the samples for various periods at temperatures of 600-800 deg. C. After each annealing cycle room temperature CEMS-spectra were recorded and micro-hardness tests were performed. The micro-hardness increases with annealing time and temperature, in accordance with the fraction of σ-phase present, and ranged from about 140 HV to 200 HV. From the measurements, activation energies were also deduced

Liquid-liquid phase separation in dilute solutions of poly(styrene sulfonate) with multivalent cations: Phase diagrams, chain morphology, and impact of temperature

Science.gov (United States)

Hansch, Markus; Hämisch, Benjamin; Schweins, Ralf; Prévost, Sylvain; Huber, Klaus

2018-01-01

The dilute solution behavior of sodium poly(styrene sulfonate) is studied in the presence of trivalent Al3+ and bivalent Ba2+ cations at various levels of excess NaCl. The study evaluates the phase behavior and the morphology of the polyelectrolyte chains with increasing extent of decoration with the Al3+ and Ba2+ cations and analyses the effect of temperature on these decorated chains. The phase behavior is presented in the form of the cation concentration versus the respective poly(styrene sulfonate) concentration, recorded at the onset of precipitation. Whereas poly(styrene sulfonate) with Al3+ exhibits a linear phase boundary, denoted as the "threshold line," which increases with increasing poly(styrene sulfonate) concentration, Ba2+ cations show a threshold line which is independent of the poly(styrene sulfonate) concentration. An additional re-entrant phase, at considerably higher cation content than those of the threshold lines, is observed with Al3+ cations but not with Ba2+ cations. The threshold line and the re-entrant phase boundary form parts of the liquid-liquid phase boundary observed at the limit of low polymer concentration. The dimensions of the polyelectrolyte chains shrink considerably while approaching the respective threshold lines on increase of the Al3+ and Ba2+ cation content. However, subtle differences occur between the morphological transformation induced by Al3+ and Ba2+. Most strikingly, coils decorated with Al3+ respond very differently to temperature variations than coils decorated with Ba2+ do. As the temperature increases, the poly(styrene sulfonate) chains decrease their size in the presence of Al3+ cations but increase in size in the presence of Ba2+ cations.

The relationship between collisional phase defect distribution and cascade collapse efficiency

International Nuclear Information System (INIS)

Morishita, K.; Heinisch, H.L.; Ishino, S.; Sekimura, N.

1994-01-01

Defect distributions after the collisional phase of cascade damage processes were calculated using the computer simulation code MARLOWE, which is based on the binary collision approximation. The densities of vacant sites were evaluated in defect-dense regions at the end of the collisional phase in simulated ion irradiations of several pure metals (Au, Ag, Cu, Ni, Fe, Mo and W). The vacancy density distributions were compared to the measured cascade collapse efficiencies obtained from low-dose ion irradiations of thin foils reported in the literature to identify the minimum or ''critical'' values of the vacancy densities during the collisional phase corresponding to cascade collapse. The critical densities are generally independent of the cascade energy in the same metal. The relationships between physical properties of the target elements and the critical densities are discussed within the framework of the cascade thermal spike model. ((orig.))

Finite element modeling for integrated solid-solid PCM-building material with varying phase change temperatures

Energy Technology Data Exchange (ETDEWEB)

Zhang, D.; Fung, A.S.; Siddiqui, O. [Ryerson Polytechnic Univ., Toronto, ON (Canada). Dept. of Mechanical and Industrial Engineering

2008-08-15

Solid-solid phase change materials (SSPCMs) are used to enhance thermal storage performance and reduce indoor temperature fluctuations in buildings. In this study, a finite element model (FEM) was used to investigate the thermal properties of different types of SSPCMs. An effective heat capacity method was used to develop the model. An integrated PCM-building material was analyzed in relation to temperature and heat flux profiles. Governing equations for the heat transfer process were composed of Navier-Stokes momentum equations; a mass conservation equation; and an energy conservation equation. Effective heat capacity was described as a linear function of the latent heat of fusion on both the heating and cooling processes. Data from the simulation were then compared with an experiment suing drywall, concrete and gypcrete samples. Heat flux across the surfaces and temperatures on the surfaces of the materials were measured. Data were used to validate the finite element model (FEM). Results of the study suggested that heat flux profiles are an effective means of understanding phase change processes. It was concluded that PCMs with lower phase change temperatures lengthened energy releases and improved thermal comfort in the building. 12 refs., 2 tabs., 14 figs.

Changes in photosynthesis and soil moisture drive the seasonal soil respiration-temperature hysteresis relationship

Science.gov (United States)

In nearly all large-scale models, CO2 efflux from soil (i.e., soil respiration) is represented as a function of soil temperature. However, the relationship between soil respiration and soil temperature is highly variable at the local scale, and there is often a pronounced hysteresis in the soil resp...

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

International Nuclear Information System (INIS)

Canko, Osman; Keskin, Mustafa

2010-01-01

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. (general)

Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

Directory of Open Access Journals (Sweden)

Matthias Augustin

2015-01-01

Full Text Available Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mnx+ oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous α-Mn2O3 particles were synthesized by calcination of Mn(II glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure–property relationships. The oxidation process related to the different MnOx species was observed by in situ X-ray diffraction (XRD measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II glycolate precursor to α-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnOx species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnOx species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous α-Mn2O3 species.

Inter-Relationship Between Subtropical Pacific Sea Surface Temperature, Arctic Sea Ice Concentration, and the North Atlantic Oscillation in Recent Summers and Winters

Science.gov (United States)

Lim, Young-Kwon; Cullather, Richard I.; Nowicki, Sophie M.; Kim, Kyu-Myong

2017-01-01

The inter-relationship between subtropical western-central Pacific sea surface temperatures (STWCPSST), sea ice concentration in the Beaufort Sea (SICBS), and the North Atlantic Oscillation (NAO) are investigated for the last 37 summers and winters (1980-2016). Lag-correlation of the STWCPSST×(-1) in spring with the NAO phase and SICBS in summer increases over the last two decades, reaching r = 0.4-0.5 with significance at 5 percent, while winter has strong correlations in approximately 1985-2005. Observational analysis and the atmospheric general circulation model experiments both suggest that STWCPSST warming acts to increase the Arctic geopotential height and temperature in the following season. This atmospheric response extends to Greenland, providing favorable conditions for developing the negative phase of the NAO. SIC and surface albedo tend to decrease over the Beaufort Sea in summer, linked to the positive surface net shortwave flux. Energy balance considering radiative and turbulent fluxes reveal that available energy that can heat surface is larger over the Arctic and Greenland and smaller over the south of Greenland, in response to the STWCPSST warming in spring. XXXX Arctic & Atlantic: Positive upper-level height/T anomaly over the Arctic and Greenland, and a negative anomaly over the central-eastern Atlantic, resembling the (-) phase of the NAO. Pacific: The negative height/T anomaly over the mid-latitudes, along with the positive anomaly over the STWCP, where 1degC warming above climatology is prescribed. Discussion: It is likely that the Arctic gets warm and the NAO is in the negative phase in response to the STWCP warming. But, there are other factors (e.g., internal variability) that contribute to determination of the NAO phase: not always the negative phase of the NAO in the event of STWCP warming (e.g.: recent winters and near neutral NAO in 2017 summer).

Two-phase flow patterns and their relationship to two-phase heat transfer

International Nuclear Information System (INIS)

Hewitt, G.F.

1977-01-01

The objective of this lecture was to discuss the general nature of two phase flows, to define the various regimes of flow and to discuss the influence of these regimes on the heat transfer processes taking place. The methods of regime delineation are briefly described and regime descriptions introduced for both vertical and horizontal flows in tubes. ''Flow regime maps'' have been widely used as an aid to determination of the regime which occurs in a given situation. Some of the more widely used maps are described and the limitations of this approach discussed. There have been many attempts to obtain a better phenomenological description of two phase flow patterns. In this lecture, these attempts will be reviewed in the context of the bubble/plug, plug/churn and churn/annular flow transitions in vertical flow. The latter two transitions are related to the flooding/flow reversal phenomena. For horizontal flows, recent work on the onset of slugging will be reviewed. In flows with evaporation or condensation, the situation is influenced by departures from thermodynamic equilibrium and the types of departure observed are discuss briefly. Flow patterns and their relationships with heat transfer regimes are then reviewed for the case of condensation in horizontal tubes and evaporation in vertical tubes

Size Class Dependent Relationships between Temperature and Phytoplankton Photosynthesis-Irradiance Parameters in the Atlantic Ocean

Directory of Open Access Journals (Sweden)

Alex Robinson

2018-01-01

Full Text Available Over the past decade, a number of methods have been developed to estimate size-class primary production from either in situ phytoplankton pigment data or remotely-sensed data. In this context, the first objective of this study was to compare two methods of estimating size class specific (micro-, nano-, and pico-phytoplankton photosynthesis-irradiance (PE parameters from pigment data. The second objective was to analyse the relationship between environmental variables (temperature, nitrate and PAR and PE parameters in the different size-classes. A large dataset was used of simultaneous measurements of the PE parameters (n = 1,260 and phytoplankton pigment markers (n = 2,326, from 3 different institutes. There were no significant differences in mean PE parameters of the different size classes between the chemotaxonomic method of Uitz et al. (2008 and the pigment markers and carbon-to-Chl a ratios method of Sathyendranath et al. (2009. For both methods, mean maximum photosynthetic rates (PmB for micro-phytoplankton were significantly lower than those for pico-phytoplankton and nano-phytoplankton. The mean light limited slope (αB for nano-phytoplankton were significantly higher than for the other size taxa. For micro-phytoplankton dominated samples identified using the Sathyendranath et al. (2009 method, both PmB and αB exhibited a significant, positive linear relationship with temperature, whereas for pico-phytoplankton the correlation with temperature was negative. Nano-phytoplankton dominated samples showed a positive correlation between PmB and temperature, whereas for αB and the light saturation parameter (Ek the correlations were not significant. For the Uitz et al. (2008 method, only micro-phytoplankton PmB, pico-phytoplankton αB, nano- and pico-phytoplankton Ek exhibited significant relationships with temperature. The temperature ranges occupied by the size classes derived using these methods differed. The Uitz et al. (2008 method

Forest canopy temperatures: dynamics, controls, and relationships with ecosystem fluxes

Science.gov (United States)

Still, C. J.; Griffith, D.; Kim, Y.; Law, B. E.; Hanson, C. V.; Kwon, H.; Schulze, M.; Detto, M.; Pau, S.

2017-12-01

Temperature strongly affects enzymatic reactions, ecosystem biogeochemistry, and species distributions. Although most focus is on air temperature, the radiative or skin temperature of plants is more relevant. Canopy skin temperature dynamics reflect biophysical, physiological, and anatomical characteristics and interactions with the environment, and can be used to examine forest responses to stresses like droughts and heat waves. Thermal infrared (TIR) imaging allows for extensive temporal and spatial sampling of canopy temperatures, particularly compared to spot measurements using thermocouples. We present results of TIR imaging of forest canopies at eddy covariance flux tower sites in the US Pacific Northwest and in Panama. These forests range from an old-growth temperate rainforest to a second growth semi-arid pine forest to a semi-deciduous tropical forest. Canopy temperature regimes at these sites are highly variable. Canopy temperatures at all forest sites displayed frequent departures from air temperature, particularly during clear sky conditions, with elevated canopy temperatures during the day and depressed canopy temperatures at night compared to air temperature. Comparison of canopy temperatures to fluxes of carbon dioxide, water vapor, and energy reveals stronger relationships than those found with air temperature. Daytime growing season net ecosystem exchange at the pine forest site is better explained by canopy temperature (r2 = 0.61) than air temperature (r2 = 0.52). At the semi-deciduous tropical forest, canopy photosynthesis is highly correlated with canopy temperature (r2 = 0.51), with a distinct optimum temperature for photosynthesis ( 31 °C) that agrees with leaf-level measurements. During the peak of one heat wave at an old-growth temperate rainforest, hourly averaged air temperature exceeded 35 °C, 10 °C above average. Peak hourly canopy temperature approached 40 °C, and leaf-to-air vapor pressure deficit exceeded 6 kPa. These extreme

Temperature feedback control for long-term carrier-envelope phase locking

Science.gov (United States)

Chang, Zenghu [Manhattan, KS; Yun, Chenxia [Manhattan, KS; Chen, Shouyuan [Manhattan, KS; Wang, He [Manhattan, KS; Chini, Michael [Manhattan, KS

2012-07-24

A feedback control module for stabilizing a carrier-envelope phase of an output of a laser oscillator system comprises a first photodetector, a second photodetector, a phase stabilizer, an optical modulator, and a thermal control element. The first photodetector may generate a first feedback signal corresponding to a first portion of a laser beam from an oscillator. The second photodetector may generate a second feedback signal corresponding to a second portion of the laser beam filtered by a low-pass filter. The phase stabilizer may divide the frequency of the first feedback signal by a factor and generate an error signal corresponding to the difference between the frequency-divided first feedback signal and the second feedback signal. The optical modulator may modulate the laser beam within the oscillator corresponding to the error signal. The thermal control unit may change the temperature of the oscillator corresponding to a signal operable to control the optical modulator.

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.

Relationship of magnetic field strength and brightness of fine-structure elements in the solar temperature minimum region

Science.gov (United States)

Cook, J. W.; Ewing, J. A.

1990-01-01

A quantitative relationship was determined between magnetic field strength (or magnetic flux) from photospheric magnetograph observations and the brightness temperature of solar fine-structure elements observed at 1600 A, where the predominant flux source is continuum emission from the solar temperature minimum region. A Kitt Peak magnetogram and spectroheliograph observations at 1600 A taken during a sounding rocket flight of the High Resolution Telescope and Spectrograph from December 11, 1987 were used. The statistical distributions of brightness temperature in the quiet sun at 1600 A, and absolute value of magnetic field strength in the same area were determined from these observations. Using a technique which obtains the best-fit relationship of a given functional form between these two histogram distributions, a quantitative relationship was determined between absolute value of magnetic field strength B and brightness temperature which is essentially linear from 10 to 150 G. An interpretation is suggested, in which a basal heating occurs generally, while brighter elements are produced in magnetic regions with temperature enhancements proportional to B.

Numerical Model and Analysis of Peak Temperature Reduction in LiFePO4 Battery Packs Using Phase Change Materials

DEFF Research Database (Denmark)

Coman, Paul Tiberiu; Veje, Christian

2013-01-01

Numerical model and analysis of peak temperature reduction in LiFePO4 battery packs using phase change materials......Numerical model and analysis of peak temperature reduction in LiFePO4 battery packs using phase change materials...

Charge carrier recombination channels in the low-temperature phase of organic-inorganic lead halide perovskite thin films

Science.gov (United States)

Wehrenfennig, Christian; Liu, Mingzhen; Snaith, Henry J.; Johnston, Michael B.; Herz, Laura M.

2014-08-01

The optoelectronic properties of the mixed hybrid lead halide perovskite CH3NH3PbI3-xClx have been subject to numerous recent studies related to its extraordinary capabilities as an absorber material in thin film solar cells. While the greatest part of the current research concentrates on the behavior of the perovskite at room temperature, the observed influence of phonon-coupling and excitonic effects on charge carrier dynamics suggests that low-temperature phenomena can give valuable additional insights into the underlying physics. Here, we present a temperature-dependent study of optical absorption and photoluminescence (PL) emission of vapor-deposited CH3NH3PbI3-xClx exploring the nature of recombination channels in the room- and the low-temperature phase of the material. On cooling, we identify an up-shift of the absorption onset by about 0.1 eV at about 100 K, which is likely to correspond to the known tetragonal-to-orthorhombic transition of the pure halide CH3NH3PbI3. With further decreasing temperature, a second PL emission peak emerges in addition to the peak from the room-temperature phase. The transition on heating is found to occur at about 140 K, i.e., revealing significant hysteresis in the system. While PL decay lifetimes are found to be independent of temperature above the transition, significantly accelerated recombination is observed in the low-temperature phase. Our data suggest that small inclusions of domains adopting the room-temperature phase are responsible for this behavior rather than a spontaneous increase in the intrinsic rate constants. These observations show that even sparse lower-energy sites can have a strong impact on material performance, acting as charge recombination centres that may detrimentally affect photovoltaic performance but that may also prove useful for optoelectronic applications such as lasing by enhancing population inversion.

High-Temperature Phase Equilibria of Duplex Stainless Steels Assessed with a Novel In-Situ Neutron Scattering Approach

Science.gov (United States)

Pettersson, Niklas; Wessman, Sten; Hertzman, Staffan; Studer, Andrew

2017-04-01

Duplex stainless steels are designed to solidify with ferrite as the parent phase, with subsequent austenite formation occurring in the solid state, implying that, thermodynamically, a fully ferritic range should exist at high temperatures. However, computational thermodynamic tools appear currently to overestimate the austenite stability of these systems, and contradictory data exist in the literature. In the present work, the high-temperature phase equilibria of four commercial duplex stainless steel grades, denoted 2304, 2101, 2507, and 3207, with varying alloying levels were assessed by measurements of the austenite-to-ferrite transformation at temperatures approaching 1673 K (1400 °C) using a novel in-situ neutron scattering approach. All grades became fully ferritic at some point during progressive heating. Higher austenite dissolution temperatures were measured for the higher alloyed grades, and for 3207, the temperature range for a single-phase ferritic structure approached zero. The influence of temperatures in the region of austenite dissolution was further evaluated by microstructural characterization using electron backscattered diffraction of isothermally heat-treated and quenched samples. The new experimental data are compared to thermodynamic calculations, and the precision of databases is discussed.

Omega phase in materials

International Nuclear Information System (INIS)

Sikka, S.K.; Vohra, Y.K.; Chidambaram, R.

1982-01-01

The subject is covered in sections, entitled: introduction; occurrence and some systematics of omega phase (omega phase in Ti, Zr and Hf under high pressures; omega phase in Group IV transition metal alloys; omega in other systems; omega embryos at high temperatures); crystallography (omega structure; relationship of ω-structure to bcc (β) and hcp (α) structures); physical properties; kinetics of formation, synthesis and metastability of omega phase (kinetics of α-ω transformation under high pressures; kinetics of β-ω transformation; synthesis and metastability studies); electronic structure of omega phase (electronic structure models; band structure calculations; theoretical results and experimental studies); electronic basis for omega phase stability (unified phase diagram; stability of omega phase); omega phase formation under combined thermal and pressure treatment in alloys (Ti-V alloys under pressure - a prototype case study; P-X phase diagrams for alloys; transformation mechanisms and models for diffuse omega phase (is omega structure a charge density distortion of the bcc phase; nature of incommensurate ω-structure and models for diffuse scattering); conclusion. (U.K.)

The influence of temperature on the polymerization of ethyl cyanoacrylate from the vapor phase

Energy Technology Data Exchange (ETDEWEB)

Dadmun, Mark D [ORNL; Algaier, Dana [University of Tennessee, Knoxville (UTK); Baskaran, Durairaj [University of Tennessee, Knoxville (UTK)

2011-01-01

The polymerization of ethyl cyanoacrylate fumes from surface bound initiators is an important step in many novel and mature technologies. Understanding the effect of temperature on the rate of poly(ethyl cyanoacrylate) (PECA) growth and its molecular weight during its polymerization from the vapor phase from surface bound initiators provides insight into the important mechanistic aspects that impact the polymerizations success. In these studies, it is shown that the amount of PECA formed during the polymerization of ECA from a latent fingerprint increases with decreasing temperature, while the polymer molecular weight varies little. This is interpreted to be the result of the loosening of the ion pair that initiates the polymer chain growth and resides on the end of the growing polymer chain with decreasing temperature. Comparison of temperature effects and counter-ion studies show that in both cases loosening the ion pair results in the formation of more polymer with similar molecular weight, verifying this interpretation. These results further suggest that lowering the temperature may be an effective method to optimize anionic vapor phase polymerizations, including the improvement of the quality of aged latent prints and preliminary results are presented that substantiate this prediction.

Phase relationship in AL-Cu-Sc alloys at 450-500 deg C

International Nuclear Information System (INIS)

Kharakterova, M.L.

1991-01-01

Al-Cu-Sc alloys containing up to 40% Cu and up to 6% Sc at 450 deg C and 500 deg C are studied using light microscopy, X-ray-spectral microanalysis, X-ray diffraction analysis, scanning electron microscopy, measurement of microhardness and electric resistance. It is determined, that in equilibrium with aluminium solid solution under the given temperature ther are Al 3 Sc, CuAl 2 phases of the respective binary systems and W (ScCu 6.6-4 Al 5.4-8 ) ternary phase. Isothermal cross sections of Al-Cu-Sc system at 450 and 500 deg C are plotted. Microhardness of equilibrium phases is measured. Combined solubility of copper and scandium in aluminium is determined

Finite-temperature random-phase approximation for spectroscopic properties of neon plasmas

International Nuclear Information System (INIS)

Colgan, J.; Collins, L. A.; Fontes, C. J.; Csanak, G.

2007-01-01

A finite-temperature random-phase approximation (FTRPA) is applied to calculate oscillator strengths for excitations in hot and dense plasmas. Application of the FTRPA provides a convenient, self-consistent method with which to explore coupled-channel effects of excited electrons in a dense plasma. We present FTRPA calculations that include coupled-channel effects. The inclusion of these effects is shown to cause significant differences in the oscillator strength for a prototypical case of 1 P excitation in neon when compared with single-channel and with average-atom calculations. Trends as a function of temperature and density are also discussed

Maintaining warm, trusting relationships with brands: increased temperature perceptions after thinking of communal brands.

Directory of Open Access Journals (Sweden)

Hans IJzerman

Full Text Available Classical theories on interpersonal relations have long suggested that social interactions are influenced by sensation, such as the experience of warmth. Past empirical work now confirms that perceived differences in temperature impact how people form thoughts about relationships. The present work first integrates our knowledge database on brand research with this idea of "grounded social cognition". It then leverages a large sample (total N = 2,552 toward elucidating links between estimates of temperature and positive versus negative evaluations of communal brands. In five studies, the authors have found that thinking about positively (vs. negatively perceived communal brands leads to heightened temperature estimates. A meta-analysis of the five studies shows a small but consistent effect in this noisy environment, r = .11, 95% CI, .05, .18. Exploratory analyses in Studies 1a and b further suggest that temperature perceptions mediate the (significant relationship between perceived communality and willingness to purchase from the brand. The authors discuss implications for theory and practice and consider the effects from a Social Baseline Perspective.

Maintaining warm, trusting relationships with brands: increased temperature perceptions after thinking of communal brands.

Science.gov (United States)

IJzerman, Hans; Janssen, Janneke A; Coan, James A

2015-01-01

Classical theories on interpersonal relations have long suggested that social interactions are influenced by sensation, such as the experience of warmth. Past empirical work now confirms that perceived differences in temperature impact how people form thoughts about relationships. The present work first integrates our knowledge database on brand research with this idea of "grounded social cognition". It then leverages a large sample (total N = 2,552) toward elucidating links between estimates of temperature and positive versus negative evaluations of communal brands. In five studies, the authors have found that thinking about positively (vs. negatively) perceived communal brands leads to heightened temperature estimates. A meta-analysis of the five studies shows a small but consistent effect in this noisy environment, r = .11, 95% CI, .05, .18. Exploratory analyses in Studies 1a and b further suggest that temperature perceptions mediate the (significant) relationship between perceived communality and willingness to purchase from the brand. The authors discuss implications for theory and practice and consider the effects from a Social Baseline Perspective.

Concurrence of dynamical phase transitions at finite temperature in the fully connected transverse-field Ising model

Science.gov (United States)

Lang, Johannes; Frank, Bernhard; Halimeh, Jad C.

2018-05-01

We construct the finite-temperature dynamical phase diagram of the fully connected transverse-field Ising model from the vantage point of two disparate concepts of dynamical criticality. An analytical derivation of the classical dynamics and exact diagonalization simulations are used to study the dynamics after a quantum quench in the system prepared in a thermal equilibrium state. The different dynamical phases characterized by the type of nonanalyticities that emerge in an appropriately defined Loschmidt-echo return rate directly correspond to the dynamical phases determined by the spontaneous breaking of Z2 symmetry in the long-time steady state. The dynamical phase diagram is qualitatively different depending on whether the initial thermal state is ferromagnetic or paramagnetic. Whereas the former leads to a dynamical phase diagram that can be directly related to its equilibrium counterpart, the latter gives rise to a divergent dynamical critical temperature at vanishing final transverse-field strength.

In Situ Synchrotron Radiation X-ray Diffraction Study on Phase and Oxide Growth during a High Temperature Cycle of a NiTi-20 at.% Zr High Temperature Shape Memory Alloy

Science.gov (United States)

Carl, Matthew; Van Doren, Brian; Young, Marcus L.

2018-02-01

Ternary additions to binary NiTi shape memory alloys are known to significantly affect the characteristic martensite-to-austenite phase transformation, i.e., decrease or increase transformation temperatures. High temperature shape memory alloys can be created by adding Au, Pt, Pd, Hf, or Zr to binary NiTi in appropriate amounts; however, the majority of these ternary additions are exceedingly expensive, unfortunately making them impractical for most commercial applications. Zr is the exception of the group, but it is often disregarded because of its poor workability and thermal stability. In an effort to find a temperature range that allows for the potential workability of NiTiZr alloys in normal atmosphere environments and to gain understanding as to the cause of failure during processing, a NiTi-20 at.% Zr was subjected to a thermal cycle ranging from RT to 1000 °C with short 15 min holds at select temperatures during both heating and cooling while simultaneously collecting high-energy synchrotron radiation X-ray diffraction measurements. This study provides valuable insight into the kinetics of precipitation and oxide formation and its relationship to processing. In addition, scanning electron microscopy was performed on five samples, each isothermally held to examine precipitation and oxide structure and growth.

The high temperature orthorhombic ⇄ hexagonal phase transformation of FeMnP

Science.gov (United States)

Chenevier, B.; Soubeyroux, J. L.; Bacmann, M.; Fruchart, D.; Fruchart, R.

1987-10-01

The compound FeMnP has the hexagonal Fe 2P structure above 1473K. The metal atoms are disordered. The disorder rate decreases with temperature and at 1413K a transition Hex → Orth. takes place. The low temperature phase is of Co 2P type. A simple transition model is proposed based on the displacement of phosphorus chains along the shortest axis of the structure. The thermal evolution of the orthorhombic cell parameters evidences the strong anisotropy of the bondings.

Effect of temperature on two-phase anaerobic reactors treating slaughterhouse wastewater

Directory of Open Access Journals (Sweden)

Simone Beux

2007-11-01

Full Text Available The effectiveness of the anaerobic treatment of effluent from a swine and bovine slaughterhouse was assessed in two sets of two-phase anaerobic digesters, operated with or without temperature control. Set A, consisting of an acidogenic reactor with recirculation and an upflow biological filter as the methanogenic phase, was operated at room temperature, while set B, consisting of an acidogenic reactor without recirculation and an upflow biological filter as the methanogenic phase, was maintained at 32°C. The methanogenic reactors showed COD (Chemical Demand of Oxygen removal above 60% for HRT (Hydraulic Retention Time values of 20, 15, 10, 8, 6, 4, and 2 days. When the HRT value in those reactors was changed to 1 day, the COD percentage removal decreased to 50%. The temperature variations did not have harmful effects on the performance of reactors in set A.Avaliou-se a eficiência do tratamento anaeróbio de efluente de matadouro de suínos e bovinos em dois conjuntos de biodigestores anaeróbios de duas fases, operados com e sem controle de temperatura. O conjunto A, formado por um reator acidogênico com recirculação e um filtro biológico de fluxo ascendente, foi operado a temperatura ambiente e o conjunto B, formado por um reator de fluxo ascendente e um filtro biológico de fluxo ascendente, foi mantido a 32°C. Os reatores metanogênicos apresentaram remoção de DQO acima de 60 % para os TRHs de 20, 15, 10, oito, seis, quatro e dois dias. Quando o TRH destes reatores foi mudado para um dia observou-se uma queda da porcentagem de remoção de DQO para 50 %. As variações de temperatura parecem não ter prejudicado o desempenho dos reatores do conjunto A.

A Three-dimensional Topological Model of Ternary Phase Diagram

International Nuclear Information System (INIS)

Mu, Yingxue; Bao, Hong

2017-01-01

In order to obtain a visualization of the complex internal structure of ternary phase diagram, the paper realized a three-dimensional topology model of ternary phase diagram with the designed data structure and improved algorithm, under the guidance of relevant theories of computer graphics. The purpose of the model is mainly to analyze the relationship between each phase region of a ternary phase diagram. The model not only obtain isothermal section graph at any temperature, but also extract a particular phase region in which users are interested. (paper)

Influence of temperature on growth rate and lag phase of fungi isolated from Argentine corn.

Science.gov (United States)

González, H H; Resnik, S L; Vaamonde, G

1988-03-01

The influence of temperature on the growth of nine strains of fungi belonging to the genera Eurotium, Aspergillus, Penicillium and Fusarium has been investigated for the temperature range 15-35 degrees C. The lag phase and the growth rate were evaluated by using a laboratory medium. The maximum growth rate for E. repens, A. wentii and P. chrysogenum was observed at about 25 degrees C, for P. citrinum near 30 degrees C and for F. semitectum and F. moniliforme between 20 and 25 degrees C. The growth rate of A. niger, A. flavus and A. parasiticus increased with increasing temperatures in the range studied. For all strains studied it appeared that the higher the growth rate the lower the lag phase was.

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.

Chiral ward-Takahashi identities at finite temperature and chiral phase transition in (2+1) dimensional chiral Gross-Neveu model

International Nuclear Information System (INIS)

Shen Kun; Qiu Zhongping

1993-01-01

Chiral Ward-Takahashi identities at finite temperature are derived in (2+1) dimensional chiral Gross-Neveu model. In terms of these identities, fermion mass generation and the mass spectra of bound states are investigate at finite temperature. Taking the fermion mass as an order parameter, the authors discuss the phase structure and chiral phase transition and obtain the critical temperature

A novel perovskite oxide chemically designed to show multiferroic phase boundary with room-temperature magnetoelectricity

Science.gov (United States)

Fernández-Posada, Carmen M.; Castro, Alicia; Kiat, Jean-Michel; Porcher, Florence; Peña, Octavio; Algueró, Miguel; Amorín, Harvey

2016-09-01

There is a growing activity in the search of novel single-phase multiferroics that could finally provide distinctive magnetoelectric responses at room temperature, for they would enable a range of potentially disruptive technologies, making use of the ability of controlling polarization with a magnetic field or magnetism with an electric one (for example, voltage-tunable spintronic devices, uncooled magnetic sensors and the long-searched magnetoelectric memory). A very promising novel material concept could be to make use of phase-change phenomena at structural instabilities of a multiferroic state. Indeed, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of the perovskite BiFeO3-BiCoO3 solid solution, specifically at its morphotropic phase boundary between multiferroic polymorphs of rhombohedral and tetragonal symmetries. Here, we report a novel perovskite oxide that belongs to the BiFeO3-BiMnO3-PbTiO3 ternary system, chemically designed to present such multiferroic phase boundary with enhanced ferroelectricity and canted ferromagnetism, which shows distinctive room-temperature magnetoelectric responses.

Primary collector wall local temperature fluctuations in the area of water-steam phase boundary

Energy Technology Data Exchange (ETDEWEB)

Matal, O.; Klinga, J.; Simo, T. [Energovyzkum Ltd., Brno (Switzerland)

1995-12-31

A limited number of temperature sensors could be installed at the primary collector surface in the area of water - steam phase boundary. The surface temperatures as well WWER 440 steam generator process data were measured and stored for a long time and off-line evaluated. Selected results are presented in the paper. (orig.). 2 refs.

Primary collector wall local temperature fluctuations in the area of water-steam phase boundary

Energy Technology Data Exchange (ETDEWEB)

Matal, O; Klinga, J; Simo, T [Energovyzkum Ltd., Brno (Switzerland)

1996-12-31

A limited number of temperature sensors could be installed at the primary collector surface in the area of water - steam phase boundary. The surface temperatures as well WWER 440 steam generator process data were measured and stored for a long time and off-line evaluated. Selected results are presented in the paper. (orig.). 2 refs.

Anomalous temperature dependence of the superelastic behavior of Ti-Nb-Mo alloys

International Nuclear Information System (INIS)

Al-Zain, Y.; Kim, H.Y.; Koyano, T.; Hosoda, H.; Nam, T.H.; Miyazaki, S.

2011-01-01

The effect of test temperature on the superelasticity of Ti-27Nb and various Ti-Nb-Mo alloys is investigated. A deviation in the stress at which martensitic transformation starts (σ β-α'' ) from the behavior expected from the Clausius-Clapeyron relationship is confirmed in all alloys. The degree of deviation is found to be in inverse proportion to the electron-to-atom ratio. However, no deviation is observed in the stress at which the reverse transformation finishes (σ α''-β ). All alloys exhibit anomalous electrical resistivity during cooling. X-ray diffraction (XRD) and transmission electron microscopy investigations show that the volume fraction of the athermal ω (ω ath ) phase increases with a decrease in temperature. An in situ XRD experiment obtained during a loading-unloading cycle shows that the β and ω ath phases transform into the α'' phase during loading. The annihilation of the ω ath phase within the α'' phase allows σ α''-β to obey the Clausius-Clapeyron relationship. As a result, a large hysteresis loop is produced.

Modified T-history method for measuring thermophysical properties of phase change materials at high temperature

Science.gov (United States)

Omaraa, Ehsan; Saman, Wasim; Bruno, Frank; Liu, Ming

2017-06-01

Latent heat storage using phase change materials (PCMs) can be used to store large amounts of energy in a narrow temperature difference during phase transition. The thermophysical properties of PCMs such as latent heat, specific heat and melting and solidification temperature need to be defined at high precision for the design and estimating the cost of latent heat storage systems. The existing laboratory standard methods, such as differential thermal analysis (DTA) and differential scanning calorimetry (DSC), use a small sample size (1-10 mg) to measure thermophysical properties, which makes these methods suitable for homogeneous elements. In addition, this small amount of sample has different thermophysical properties when compared with the bulk sample and may have limitations for evaluating the properties of mixtures. To avoid the drawbacks in existing methods, the temperature - history (T-history) method can be used with bulk quantities of PCM salt mixtures to characterize PCMs. This paper presents a modified T-history setup, which was designed and built at the University of South Australia to measure the melting point, heat of fusion, specific heat, degree of supercooling and phase separation of salt mixtures for a temperature range between 200 °C and 400 °C. Sodium Nitrate (NaNO3) was used to verify the accuracy of the new setup.

Stress-temperature phase diagram of a ferromagnetic Ni-Mn-Ga shape memory alloy

International Nuclear Information System (INIS)

Chernenko, V.A.; Pons, J.; Cesari, E.; Ishikawa, K.

2005-01-01

A sequence of thermally and stress-induced intermartensitic transformations has been found in a Ni 52.0 Mn 24.4 Ga 23.6 single crystal, which have been confirmed by transmission electron microscopy through in situ cooling experiments. The stress-strain-temperature behavior under compression along the P and P crystallographic directions has also been studied for this compound and a stress-temperature phase diagram has been established

Temperature dependence of the magnetic anisotropy of metallic Y-Ba-Cu-O single crystals in the normal phase

International Nuclear Information System (INIS)

Miljak, M.; Zlatic, V.; Kos, I.; Aviani, I.; Hamzic, A.; Collin, G.

1990-01-01

The magnetic anisotropy measurements of metallic Y-Ba-Cu-O compounds in the normal phase reveal a temperature-dependent diamagnetic component of the susceptibility that increases with decreasing temperature. The temperature variation of the susceptibility anisotropy and its total change do not seem to be much affected by the presence of the superconductivity at some lower temperature and could not be accounted for by superconducting fluctuations. Rather, the data remind one of the behavior of some quasi-two-dimensional metals with anisotropic Fermi surfaces, reflecting the properties of the low-energy excitations in the normal phase. The anisotropy measurements above the bulk superconducting transition temperature T c reveal the nonlinear effects, which are due to the onset of superconductivity in disconnected grains. The existence of a two-step transition, typical for granular superconductors, should be taken into consideration if the normal-phase susceptibility data are compared with the theoretical predictions in the vicinity of T c

Temporal and spatial dispersion of human body temperature during deep hypothermia.

Science.gov (United States)

Opatz, O; Trippel, T; Lochner, A; Werner, A; Stahn, A; Steinach, M; Lenk, J; Kuppe, H; Gunga, H C

2013-11-01

Clinical temperature management remains challenging. Choosing the right sensor location to determine the core body temperature is a particular matter of academic and clinical debate. This study aimed to investigate the relationship of measured temperatures at different sites during surgery in deep hypothermic patients. In this prospective single-centre study, we studied 24 patients undergoing cardiothoracic surgery: 12 in normothermia, 3 in mild, and 9 in deep hypothermia. Temperature recordings of a non-invasive heat flux sensor at the forehead were compared with the arterial outlet temperature of a heart-lung machine, with the temperature on a conventional vesical bladder thermistor and, for patients undergoing deep hypothermia, with oesophageal temperature. Using a linear model for sensor comparison, the arterial outlet sensor showed a difference among the other sensor positions between -0.54 and -1.12°C. The 95% confidence interval ranged between 7.06 and 8.82°C for the upper limit and -8.14 and -10.62°C for the lower limit. Because of the hysteretic shape, the curves were divided into phases and fitted into a non-linear model according to time and placement of the sensors. During cooling and warming phases, a quadratic relationship could be observed among arterial, oesophageal, vesical, and cranial temperature recordings, with coefficients of determination ranging between 0.95 and 0.98 (standard errors of the estimate 0.69-1.12°C). We suggest that measured surrogate temperatures as indices of the cerebral temperature (e.g. vesical bladder temperature) should be interpreted with respect to the temporal and spatial dispersion during cooling and rewarming phases.

Summary of Research through Phase II/Year 2 of Initially Approved 3 Phase/3 Year Project - Establishing the Relationship between Fracture-Related Dolomite and Primary Rock Fabric on the Distribution of Reservoirs in the Michigan Basin

Energy Technology Data Exchange (ETDEWEB)

G. Grammer

2007-09-30

This final scientific/technical report covers the first 2 years (Phases I and II of an originally planned 3 Year/3 Phase program). The project was focused on evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin. The characterization of select dolomite reservoirs was the major focus of our efforts in Phases I and II of the project. Structural mapping and log analysis in the Dundee (Devonian) and Trenton/Black River (Ordovician) suggest a close spatial relationship among gross dolomite distribution and regional-scale, wrench fault-related NW-SE and NE-SW structural trends. A high temperature origin for much of the dolomite in these 2 studied intervals (based upon fluid inclusion homogenization temperatures and stable isotopic analyses,) coupled with persistent association of this dolomite in reservoirs coincident with wrench fault-related features, is strong evidence for these reservoirs being influenced by hydrothermal dolomitization. In the Niagaran (Silurian), there is a general trend of increasing dolomitization shelfward, with limestone predominant in more basinward positions. A major finding is that facies types, when analyzed at a detailed level, are directly related to reservoir porosity and permeability in these dolomites which increases the predictability of reservoir quality in these units. This pattern is consistent with our original hypothesis of primary facies control on dolomitization and resulting reservoir quality at some level. The identification of distinct and predictable vertical stacking patterns within a hierarchical sequence and cycle framework provides a high degree of confidence at this point that the results should be exportable throughout the basin. Much of the data synthesis and modeling for the project was scheduled to be part of Year 3/Phase III, but the discontinuation of funding after Year 2 precluded those efforts

Phase transition in SO(3) gauge theory

International Nuclear Information System (INIS)

Datta, Saumen; Gavai, Rajiv V.

1998-01-01

The phase transition in SO(3) lattice gauge theory is investigated by Monte Carlo techniques with a view (i) to understand the relationship between the bulk transition and the deconfinement transition, and (ii) to resolve the current ambiguity about the nature of the high temperature phase. By introduction of a magnetic field, it was shown that the +ve and -ve values of a > correspond to the same phase. Studies on different sized lattices lead to the conclusion that in SO(3), there is only one transition, which is deconfining in nature. (author)

Search for the first-order liquid-to-liquid phase transition in low-temperature confined water by neutron scattering

Science.gov (United States)

Chen, Sow-Hsin; Wang, Zhe; Kolesnikov, Alexander I.; Zhang, Yang; Liu, Kao-Hsiang

2013-02-01

It has been conjectured that a 1st order liquid-to-liquid (L-L) phase transition (LLPT) between high density liquid (HDL) and low density liquid (LDL) in supercooled water may exist, as a thermodynamic extension to the liquid phase of the 1st order transition established between the two bulk solid phases of amorphous ice, the high density amorphous ice (HDA) and the low density amorphous ice (LDA). In this paper, we first recall our previous attempts to establish the existence of the 1st order L-L phase transition through the use of two neutron scattering techniques: a constant Q elastic diffraction study of isobaric temperature scan of the D2O density, namely, the equation of state (EOS) measurements. A pronounced density hysteresis phenomenon in the temperature scan of the density above P = 1500 bar is observed which gives a plausible evidence of crossing the 1st order L-L phase transition line above this pressure; an incoherent quasi-elastic scattering measurements of temperature-dependence of the α-relaxation time of H2O at a series of pressures, namely, the study of the Fragile-to-Strong dynamic crossover (FSC) phenomenon as a function of pressure which we interpreted as the results of crossing the Widom line in the one-phase region. In this new experiment, we used incoherent inelastic neutron scattering (INS) to measure the density of states (DOS) of H atoms in H2O molecules in confined water as function of temperature and pressure, through which we may be able to follow the emergence of the LDL and HDL phases at supercooled temperature and high pressures. We here report for the first time the differences of librational and translational DOSs between the hypothetical HDL and LDL phases, which are similar to the corresponding differences between the well-established HDA and LDA ices. This is plausible evidence that the HDL and LDL phases are the thermodynamic extensions of the corresponding amorphous solid water HDA and LDA ices.

The Effects of Temperature and Growth Phase on the Lipidomes of Sulfolobus islandicus and Sulfolobus tokodaii

DEFF Research Database (Denmark)

Jensen, Sara Munk; Neesgaard, Vinnie Lund; Skjoldbjerg, Sandra Landbo Nedergaard

2015-01-01

at three different temperatures, with samples withdrawn during lag, exponential, and stationary phases. Three abundant tetraether lipid classes and one diether lipid class were monitored. Beside the expected increase in the number of cyclopentane moieties with higher temperature in both archaea, we......The functionality of the plasma membrane is essential for all organisms. Adaption to high growth temperatures imposes challenges and Bacteria, Eukarya, and Archaea have developed several mechanisms to cope with these. Hyperthermophilic archaea have earlier been shown to synthesize tetraether...... membrane lipids with an increased number of cyclopentane moieties at higher growth temperatures. Here we used shotgun lipidomics to study this effect as well as the influence of growth phase on the lipidomes of Sulfolobus islandicus and Sulfolobus tokodaii for the first time. Both species were cultivated...

Self-Healing Phase Change Salogels with Tunable Gelation Temperature.

Science.gov (United States)

Karimineghlani, Parvin; Palanisamy, Anbazhagan; Sukhishvili, Svetlana A

2018-04-19

Chemically cross-linked polymer matrices have demonstrated strong potential for shape stabilization of molten phase change materials (PCM). However, they are not designed to be fillable and removable from a heat exchange module for an easy replacement with new PCM matrices and lack self-healing capability. Here, a new category of shapeable, self-healing gels, "salogels", is introduced. The salogels reversibly disassemble in a high-salinity environment of a fluid inorganic PCM [lithium nitrate trihydrate (LNH)], at a preprogrammed temperature. LNH was employed as a high latent heat PCM and simultaneously as a solvent, which supported the formation of a network of polyvinyl alcohol (PVA) chains via physical cross-linking through poly(amidoamine) dendrimers of various generations. The existence of hydrogen bonding and the importance of low-hydration state of PVA for the efficient gelation were experimentally confirmed. The thermal behavior of PCM salogels was highly reversible and repeatable during multiple heating/cooling cycles. Importantly, the gel-sol transition temperature could be precisely controlled within a range of temperature above LNH's melting point by the choice of dendrimer generation and their concentration. Shape stabilization and self-healing properties of the salogels, taken together with tunability of their temperature-induced fluidization make these materials attractive for thermal energy storage applications that require on-demand removal and replacement of used inorganic PCM salt hydrates.

Protein synthesis during the initial phase of the temperature-induced bleaching response in Euglena gracilis

International Nuclear Information System (INIS)

Ortiz, W.

1990-01-01

Growing cultures of photoheterotrophic Euglena gracilis experience an increase in chlorophyll accumulation during the initial phase of the temperature-induced bleaching response suggesting an increase in the synthesis of plastid components at the bleaching temperature of 33 degree C. A primary goal of this work was to establish whether an increase in the synthesis of plastid proteins accompanies the observed increase in chlorophyll accumulation. In vivo pulse-labeling experiments with [ 35 S]sodium sulfate were carried out with cells grown at room temperature or at 33 degree C. The synthesis of a number of plastid polypeptides of nucleocytoplasmic origin, including some presumably novel polypeptides, increased in cultures treated for 15 hours at 33 degree C. In contrast, while synthesis of thylakoid proteins by the plastid protein synthesis machinery decreased modestly, synthesis of the large subunit of the enzyme ribulosebisphosphate carboxylase was strongly affected at the elevated temperature. Synthesis of novel plastid-encoded polypeptides was not induced at the bleaching temperature. It is concluded that protein synthesis in plastids declines during the initial phase of the temperature response in Euglena despite an overall increase in cellular protein synthesis and an increase in chlorophyll accumulation per cell

Magnetic phase diagrams of UNiGe

International Nuclear Information System (INIS)

Nakotte, H.; Hagmusa, I.H.; Klaasse, J.C.P.; Hagmusa, I.H.; Klaasse, J.C.P.

1997-01-01

UNiGe undergoes two magnetic transitions in zero field. Here, the magnetic diagrams of UNiGe for B parallel b and B parallel c are reported. We performed temperatures scans of the magnetization in static magnetic fields up to 19.5T applied along the b and c axes. For both orientations 3 magnetic phases have been identified in the B-T diagrams. We confirmed the previously reported phase boundaries for B parallel c, and in addition we determined the location of the phase boundaries for B parallel b. We discuss a possible relationship of the two zero-field antiferromagnetic phases (commensurate: T<42K; incommensurate: 42K< T<50K) and the field-induced phase, which, at low temperatures, occurs between 18 and 25T or 4 and 10T for B parallel b or B parallel c, respectively. Finally, we discuss the field dependence of the electronic contribution γ to the specific heat for B parallel c up to 17.5T, and we find that its field dependence is similar to the one found in more itinerant uranium compounds

Photoluminescence at room temperature of liquid-phase crystallized silicon on glass

Directory of Open Access Journals (Sweden)

Michael Vetter

2016-12-01

Full Text Available The room temperature photoluminescence (PL spectrum due band-to-band recombination in an only 8 μm thick liquid-phase crystallized silicon on glass solar cell absorber is measured over 3 orders of magnitude with a thin 400 μm thick optical fiber directly coupled to the spectrometer. High PL signal is achieved by the possibility to capture the PL spectrum very near to the silicon surface. The spectra measured within microcrystals of the absorber present the same features as spectra of crystalline silicon wafers without showing defect luminescence indicating the high electronic material quality of the liquid-phase multi-crystalline layer after hydrogen plasma treatment.

Phase composition of Al-Ti-Nb-Mo γ alloys in the heat-treatment temperature range: Calculation and experiment

Science.gov (United States)

Belov, N. A.; Dashkevich, N. I.; Bel'tyukova, S. O.

2015-07-01

The phase composition of TNM-type Al-Ti-Nb-Mo γ alloys at heat-treatment temperatures is quantitatively studied using the Thermo-Calc program package and experimental methods. Isothermal cross sections are calculated and the joint influence of two alloying elements on the phase composition of the alloy is determined at the mean concentration of a third component. Based on the calculations of vertical cross sections, the boundaries of the four-phase eutectoid reaction α → α2 + β + γ are found. The temperature is shown to significantly influence the phase compositions of the γ alloys, among them the mass fractions of various phases (α, β, γ,α2) and the element concentration in them.

Relativistic Random-Phase Approximation with Density-dependent Meson-nucleon Couplings at Finite Temperature

International Nuclear Information System (INIS)

Niu, Y.; Paar, N.; Vretenar, D.; Meng, J.

2009-01-01

The fully self-consistent relativistic random-phase approximation (RRPA) framework based on effective interactions with a phenomenological density dependence is extended to finite temperatures. The RRPA configuration space is built from the spectrum of single-nucleon states at finite temperature obtained by the temperature dependent relativistic mean field (RMF-T) theory based on effective Lagrangian with density dependent meson-nucleon vertex functions. As an illustration, the dependence of binding energy, radius, entropy and single particle levels on temperature for spherical nucleus 2 08P b is investigated in RMF-T theory. The finite temperature RRPA has been employed in studies of giant monopole and dipole resonances, and the evolution of resonance properties has been studied as a function of temperature. In addition, exotic modes of excitation have been systematically explored at finite temperatures, with an emphasis on the case of pygmy dipole resonances.(author)

Room temperature chemically oxidized La2CuO4+y: Phase separation induced by thermal treatment

DEFF Research Database (Denmark)

Rial,C.; Moran, E.; Alario-Franco, M.A.

1997-01-01

The structure of roam temperature chemically oxidized La2CuO4+y [y = 0.103(4)] has been refined from powder neutron diffraction data using the space group Bmab. The modifications induced in the CuO2 and the LaO planes by the insertion of oxygen are consistent with the high T-c measured for this m......The structure of roam temperature chemically oxidized La2CuO4+y [y = 0.103(4)] has been refined from powder neutron diffraction data using the space group Bmab. The modifications induced in the CuO2 and the LaO planes by the insertion of oxygen are consistent with the high T-c measured...... a short treatment at 433 K, La2CuO4.103(4) undergoes a phase separation into two phases: phase 1, with estimated y(1) = 0.086(4) and T-cl = 30 K, and phase 2, with estimated y(2) = 0.12(1) and T-c2 = 17 K. By increasing the annealing times, phase 2 transforms to phase I and finally disappears. Therefore...

Effect of high temperature deposition on CoSi2 phase formation

International Nuclear Information System (INIS)

Comrie, C. M.; Ahmed, H.; Smeets, D.; Demeulemeester, J.; Vantomme, A.; Turner, S.; Van Tendeloo, G.; Detavernier, C.

2013-01-01

This paper discusses the nucleation behaviour of the CoSi to CoSi 2 transformation from cobalt silicide thin films grown by deposition at elevated substrate temperatures ranging from 375 °C to 600 °C. A combination of channelling, real-time Rutherford backscattering spectrometry, real-time x-ray diffraction, and transmission electron microscopy was used to investigate the effect of the deposition temperature on the subsequent formation temperature of CoSi 2 , its growth behaviour, and the epitaxial quality of the CoSi 2 thus formed. The temperature at which deposition took place was observed to exert a significant and systematic influence on both the formation temperature of CoSi 2 and its growth mechanism. CoSi films grown at the lowest temperatures were found to increase the CoSi 2 nucleation temperature above that of CoSi 2 grown by conventional solid phase reaction, whereas the higher deposition temperatures reduced the nucleation temperature significantly. In addition, a systematic change in growth mechanism of the subsequent CoSi 2 growth occurs as a function of deposition temperature. First, the CoSi 2 growth rate from films grown at the lower reactive deposition temperatures is substantially lower than that grown at higher reactive deposition temperatures, even though the onset of growth occurs at a higher temperature, Second, for deposition temperatures below 450 °C, the growth appears columnar, indicating nucleation controlled growth. Elevated deposition temperatures, on the other hand, render the CoSi 2 formation process layer-by-layer which indicates enhanced nucleation of the CoSi 2 and diffusion controlled growth. Our results further indicate that this observed trend is most likely related to stress and changes in microstructure introduced during reactive deposition of the CoSi film. The deposition temperature therefore provides a handle to tune the CoSi 2 growth mechanism.

Phase structure of 3DZ(N) lattice gauge theories at finite temperature

International Nuclear Information System (INIS)

Borisenko, O.; Chelnokov, V.; Cortese, G.; Gravina, M.; Papa, A.; Surzhikov, I.

2013-01-01

We perform a numerical study of the phase transitions in three-dimensional Z(N) lattice gauge theories at finite temperature for N>4. Using the dual formulation of the models and a cluster algorithm we locate the position of the critical points and study the critical behavior across both phase transitions in details. In particular, we determine various critical indices, compute the average action and the specific heat. Our results are consistent with the two transitions being of infinite order. Furthermore, they belong to the universality class of two-dimensional Z(N) vector spin models

Phase changes induced by guest orientational ordering of filled ice Ih methane hydrate under high pressure and low temperature

International Nuclear Information System (INIS)

Hirai, H; Tanaka, T; Yagi, T; Matsuoka, T; Ohishi, Y; Ohtake, M; Yamamoto, Y

2014-01-01

Low-temperature and high-pressure experiments were performed with filled ice Ih structure of methane hydrate under pressure and temperature conditions of 2.0 to 77.0 GPa and 30 to 300 K, respectively, using diamond anvil cells and a helium-refrigeration cryostat. Distinct changes in the axial ratios of the host framework were revealed by In-situ X-ray diffractometry. Splitting in the CH vibration modes of the guest methane molecules, which was previously explained by the orientational ordering of the guest molecules, was observed by Raman spectroscopy. The pressure and temperature conditions at the split of the vibration modes agreed well with those of the axial ratio changes. The results indicated that orientational ordering of the guest methane molecules from orientational disordered-state occurred at high pressures and low temperatures, and that this guest ordering led to the axial ratio changes in the host framework. Existing regions of the guest disordered-phase and the guest ordered-phase were roughly estimated by the X-ray data. In addition, above the pressure of the guest-ordered phase, another high pressure phase was developed at a low-temperature region. The deuterated-water host samples were also examined and isotopic effects on the guest ordering and phase changes were observed.

Phase transformation and precipitation in aged Ti-Ni-Hf high-temperature shape memory alloys

International Nuclear Information System (INIS)

Meng, X.L.; Cai, W.; Zheng, Y.F.; Zhao, L.C.

2006-01-01

More attention has been paid to ternary Ti-Ni-Hf high-temperature shape memory alloys (SMAs) due to their high phase transformation temperatures, good thermal stability and low cost. However, the Ti-Ni-Hf alloys have been found to have low ductility and only about 3% shape memory effect and these have hampered their applications. It is well known that there are three methods to improve the shape memory properties of high-temperature SMAs: (a) cold rolling + annealing; (b) adding another element to the alloy; (c) aging. These methods are not suitable to improve the properties of Ti-Ni-Hf alloys. In this paper, a method of conditioning Ni-rich Ti-Ni-Hf alloys as high-temperature SMAs by aging is presented. For Ni-rich Ti 80-x Ni x Hf 20 alloys (numbers indicate at.%) the phase transformation temperatures are on average increased by more than 100 K by aging at 823 K for 2 h. Especially for those alloys with Ni contents less than 50.6 at.%, the martensitic transformation start temperatures (M s ) are higher than 473 K after aging. Transmission electron microscopy shows the presence of (Ti + Hf) 3 Ni 4 precipitates after aging. Compared with the precipitation of Ti 3 Ni 4 particles in Ni-rich Ti-Ni alloys, the precipitation of (Ti + Hf) 3 Ni 4 particles in Ni-rich Ti-Ni-Hf alloys needs higher temperatures and longer times

Novel solid – solid phase change material based on polyethylene glycol and cellulose used for temperature stabilisation

Directory of Open Access Journals (Sweden)

Wojda Marta

2014-01-01

Full Text Available Thermal management is one of crucial issues in the development of modern electronic devices. In the recent years interest in phase change materials (PCMs as alternative cooling possibility has increased significantly. Preliminary results concerning the research into possibility of the use of solid-solid phase change materials (S-S PCMs for stabilisation temperature of electronic devices has been presented in the paper. Novel solid-solid phase change material based on polyethylene glycol and cellulose has been synthesized. Attempt to improve its thermal conductivity has been taken. Material has been synthesized for the purpose of stabilisation of temperature of electronic devices.

Ionothermal synthesis of β-NH4AlF4 and the determination by single crystal X-ray diffraction of its room temperature and low temperature phases

International Nuclear Information System (INIS)

Parnham, Emily R.; Slawin, Alex M.Z.; Morris, Russell E.

2007-01-01

β-NH 4 AlF 4 has been synthesised ionothermally using 1-ethyl-3-methylimidazolium hexafluorophosphate as solvent and template provider. β-NH 4 AlF 4 crystals were produced which were suitable for single crystal X-ray diffraction analysis. A phase transition occurs between room temperature (298 K) and low temperature (93 K) data collections. At 298 K the space group=I4/mcm (no. 140), α=11.642(5), c=12.661(5) A, Z=2 (10NH 4 AlF 4 ), wR(F 2 )=0.1278, R(F)=0.0453. At 93 K the space group=P4 2 /ncm (no. 138), α=11.616(3), c=12.677(3) A, Z=2 (10NH 4 AlF 4 ), wR(F 2 )=0.1387, R(F)=0.0443. The single crystal X-ray diffraction study of β-NH 4 AlF 4 shows the presence of two different polymorphs at low and room temperature, indicative of a phase transition. The [AlF 4/2 F 2 ] - layers are undisturbed except for a small tilting of the AlF 6 octahedra in the c-axis direction. -Ionothermal synthesis, the use of an ionic liquid as the solvent in materials preparation, has been used to prepare β-NH 4 AlF 4 , and structural characterisation indicates that there are two versions of the structure, a low temperature primitive phase at 93 K and a high temperature body-centered phase at 298 K

High temperature phase transition of Tm2Ti2O7

International Nuclear Information System (INIS)

Shlyakhtina, A.V.; Shcherbakova, L.G.; Knot'ko, A.V.; Larina, L.L.; Borichev, S.A.

2004-01-01

A high temperature phase transition type order-disorder is investigated in Tm 2 Ti 2 O 7 at t>1600 Deg C. It is shown that this transformation is irreversible. Ion conductivity of synthesized at 1670 Deg C nanocrystalline Tm 2 Ti 2 O 7 constitutes 2x10 -3 S/cm at 740 Deg C and remains constant after heat treatment at 860 Deg C for 240 h in the air. It is revealed that the conductivity of specimens (grain size of 20-30 nm) on the basis of Tm 2 Ti 2 O 7 high temperature modification with a structure of disordered pyrochlore is independent of grain size [ru

Size and temperature dependent stability and phase transformation in single-crystal zirconium nanowire

International Nuclear Information System (INIS)

Sutrakar, Vijay Kumar; Roy Mahapatra, D.

2011-01-01

A novel size dependent FCC (face-centered-cubic) → HCP (hexagonally-closed-pack) phase transformation and stability of an initial FCC zirconium nanowire are studied. FCC zirconium nanowires with cross-sectional dimensions 20 Å, in which surface stresses are not enough to drive the phase transformation, show meta-stability. In such a case, an external kinetic energy in the form of thermal heating is required to overcome the energy barrier and achieve FCC → HCP phase transformation. The FCC-HCP transition pathway is also studied using Nudged Elastic Band (NEB) method, to further confirm the size dependent stability/metastability of Zr nanowires. We also show size dependent critical temperature, which is required for complete phase transformation of a metastable-FCC nanowire.

A stable algorithm for calculating phase equilibria with capillarity at specified moles, volume and temperature using a dynamic model

KAUST Repository

Kou, Jisheng

2017-09-30

Capillary pressure can significantly affect the phase properties and flow of liquid-gas fluids in porous media, and thus, the phase equilibrium calculation incorporating capillary pressure is crucial to simulate such problems accurately. Recently, the phase equilibrium calculation at specified moles, volume and temperature (NVT-flash) becomes an attractive issue. In this paper, capillarity is incorporated into the phase equilibrium calculation at specified moles, volume and temperature. A dynamical model for such problem is developed for the first time by using the laws of thermodynamics and Onsager\\'s reciprocal principle. This model consists of the evolutionary equations for moles and volume, and it can characterize the evolutionary process from a non-equilibrium state to an equilibrium state in the presence of capillarity effect at specified moles, volume and temperature. The phase equilibrium equations are naturally derived. To simulate the proposed dynamical model efficiently, we adopt the convex-concave splitting of the total Helmholtz energy, and propose a thermodynamically stable numerical algorithm, which is proved to preserve the second law of thermodynamics at the discrete level. Using the thermodynamical relations, we derive a phase stability condition with capillarity effect at specified moles, volume and temperature. Moreover, we propose a stable numerical algorithm for the phase stability testing, which can provide the feasible initial conditions. The performance of the proposed methods in predicting phase properties under capillarity effect is demonstrated on various cases of pure substance and mixture systems.

Is the Freeze Drying Method Effect on the Phase Transition Temperature ofβ/β́́ Lithium Zirconium Phosphate?

Directory of Open Access Journals (Sweden)

S. M. Seyedahmadian

2014-07-01

Full Text Available Spherical granules of the superionic conductor β/β́ LiZr2(PO43 in the range of sub 100 nm sizewere synthesizedvia freeze drying methodand fully reviewed in all aspects. Samples were characterized by the X-ray diffractometry (XRD, the Thermal analysis (TG, DSC, theFourier Transform Infra-Red Spectroscopy (FTIR and the Scanning Electron Microscopy (SEM.Their structuredepends largely on the method of synthesis, thermaltreatment, and conditions of storing samples. Degree of Crystallinity and phase purity in different annealing time were tested. The synthesize temperature does not exceed 873 K in any step of the synthesis.The low temperature phases (β with the Pbna space group and β́ with the P21/n space group were preparedat optimum condition. By the Differential Scanning Calorimetry it was shown the phase transition from β↔β́ occurred at about 567-597 K. The temperature of annealing the phosphate and calcination time is not very effective to phase transition temperature.

Temporal Changes in the Observed Relationship between Cloud Cover and Surface Air Temperature.

Science.gov (United States)

Sun, Bomin; Groisman, Pavel Ya.; Bradley, Raymond S.; Keimig, Frank T.

2000-12-01

The relationship between cloud cover and near-surface air temperature and its decadal changes are examined using the hourly synoptic data for the past four to six decades from five regions of the Northern Hemisphere: Canada, the United States, the former Soviet Union, China, and tropical islands of the western Pacific. The authors define the normalized cloud cover-surface air temperature relationship, NOCET or dT/dCL, as a temperature anomaly with a unit (one-tenth) deviation of total cloud cover from its average value. Then mean monthly NOCET time series (night- and daytime, separately) are area-averaged and parameterized as functions of surface air humidity and snow cover. The day- and nighttime NOCET variations are strongly anticorrelated with changes in surface humidity. Furthermore, the daytime NOCET changes are positively correlated to changes in snow cover extent. The regionally averaged nighttime NOCET varies from 0.05 K tenth1 in the wet Tropics to 1.0 K tenth1 at midlatitudes in winter. The daytime regional NOCET ranges from 0.4 K tenth1 in the Tropics to 0.7 K tenth1 at midlatitudes in winter.The authors found a general strengthening of a daytime surface cooling during the post-World War II period associated with cloud cover over the United States and China, but a minor reduction of this cooling in higher latitudes. Furthermore, since the 1970s, a prominent increase in atmospheric humidity has significantly weakened the effectiveness of the surface warming (best seen at nighttime) associated with cloud cover.The authors apportion the spatiotemporal field of interactions between total cloud cover and surface air temperature into a bivariate relationship (described by two equations, one for daytime and one for nighttime) with surface air humidity and snow cover and two constant factors. These factors are invariant in space and time domains. It is speculated that they may represent empirical estimates of the overall cloud cover effect on the surface air

Phenophases alter the soil respiration-temperature relationship in an oak-dominated forest

Science.gov (United States)

Jared L. DeForest; Askoo Noormets; Steve G. McNulty; Ge Sun; Gwen Teeney; Jiquan Chen

2006-01-01

Soil respiration (SR) represents a major component of forest ecosystem respiration and is influenced seasonally by environmental factors such as temperature, soil moisture, root respiration, and litter fall. Changes in these environmental factors correspond with shifts in plant phenology. In this study, we examined the relationship between canopy phenophases @re-growth...

Room and high temperature deformation behaviour of a forged Fe–15Al–5Nb alloy with a reinforcing dispersion of equiaxed Laves phase particles

International Nuclear Information System (INIS)

Morris, D.G.; Muñoz-Morris, M.A.

2012-01-01

Highlights: ► Forged Fe–15%Al–5%Nb has a composite structure of soft matrix with equiaxed Laves phase particles. ► The material shows good strength with excellent ductility at room temperature. ► Good creep strength is maintained to 700 °C. ► The coarse composite microstructure ensures good long term stability at high temperatures. ► High temperature strength depends on load sharing between phases and microstructural refinement. - Abstract: The cast-in network of continuous Laves phase in a Fe–15%Al–5%Nb alloy has been converted to a dispersion of coarse Laves phase particles by high temperature forging, and the room temperature and high temperature deformation behaviour examined. The material shows good room temperature tensile ductility and good creep strength at temperatures up to 700 °C. The good high temperature strength is explained by the refinement of substructure by the dispersion of Laves phase particles and load and strain partitioning between the stiff and hard phase and the softer matrix. The relatively coarse microstructure is expected to be highly stable against coarsening at high temperatures, which should allow retention of creep properties even for long exposure times.

An Introduction to the Gas Phase

Science.gov (United States)

Vallance, Claire

2017-11-01

'An Introduction to the Gas Phase' is adapted from a set of lecture notes for a core first year lecture course in physical chemistry taught at the University of Oxford. The book is intended to give a relatively concise introduction to the gas phase at a level suitable for any undergraduate scientist. After defining the gas phase, properties of gases such as temperature, pressure, and volume are discussed. The relationships between these properties are explained at a molecular level, and simple models are introduced that allow the various gas laws to be derived from first principles. Finally, the collisional behaviour of gases is used to explain a number of gas-phase phenomena, such as effusion, diffusion, and thermal conductivity.

Magnetic properties of Gd5(Si1.5Ge2.5) near the temperature and magnetic field induced first order phase transition

International Nuclear Information System (INIS)

Levin, E.M.; Gschneidner, K.A.; Pecharsky, V.K.

2001-01-01

The temperature (from 5 to 300 K) and DC magnetic field (from 0 to 90 kOe) dependencies of the DC magnetization and magnetic susceptibility, and the temperature (from 5 to 350 K) dependency of the AC magnetic susceptibility of Gd 5 (Si 1.5 Ge 2.5 ) have been studied. The temperature and/or magnetic field induced magnetic phase transition in Gd 5 (Si 1.5 Ge 2.5 ) is a first order ferromagnet-paramagnet transition. The temperature of the magnetic transition in low AC magnetic field is 206 and 217 K for cooling and heating, respectively. The DC magnetic field increases the transition temperature by ∼0.36 K/kOe indicating that the paramagnetic phase can be reversibly transformed into the ferromagnetic phase. When the magnetic field is removed, the ferromagnetic phase transforms into the paramagnetic phase showing a large remanence-free hysteresis. The magnetic phase diagram based on the isothermal magnetic field dependence of the DC magnetization at various temperatures for Gd 5 (Si 1.5 Ge 2.5 ) is proposed. The magnetic field dependence of the magnetization in the vicinity of the first order phase transition shows evidence for the formation of a magnetically heterogeneous system in the volume of Gd 5 (Si 1.5 Ge 2.5 ) specimen where the magnetically ordered (ferromagnetic) and disordered (paramagnetic) phases co-exist

Charge carrier recombination channels in the low-temperature phase of organic-inorganic lead halide perovskite thin films

Directory of Open Access Journals (Sweden)

Christian Wehrenfennig

2014-08-01

Full Text Available The optoelectronic properties of the mixed hybrid lead halide perovskite CH3NH3PbI3−xClx have been subject to numerous recent studies related to its extraordinary capabilities as an absorber material in thin film solar cells. While the greatest part of the current research concentrates on the behavior of the perovskite at room temperature, the observed influence of phonon-coupling and excitonic effects on charge carrier dynamics suggests that low-temperature phenomena can give valuable additional insights into the underlying physics. Here, we present a temperature-dependent study of optical absorption and photoluminescence (PL emission of vapor-deposited CH3NH3PbI3−xClx exploring the nature of recombination channels in the room- and the low-temperature phase of the material. On cooling, we identify an up-shift of the absorption onset by about 0.1 eV at about 100 K, which is likely to correspond to the known tetragonal-to-orthorhombic transition of the pure halide CH3NH3PbI3. With further decreasing temperature, a second PL emission peak emerges in addition to the peak from the room-temperature phase. The transition on heating is found to occur at about 140 K, i.e., revealing significant hysteresis in the system. While PL decay lifetimes are found to be independent of temperature above the transition, significantly accelerated recombination is observed in the low-temperature phase. Our data suggest that small inclusions of domains adopting the room-temperature phase are responsible for this behavior rather than a spontaneous increase in the intrinsic rate constants. These observations show that even sparse lower-energy sites can have a strong impact on material performance, acting as charge recombination centres that may detrimentally affect photovoltaic performance but that may also prove useful for optoelectronic applications such as lasing by enhancing population inversion.

Neutron diffraction study of high temperature phase of K2SeO4

International Nuclear Information System (INIS)

Iwata, Yutaka; Koyano, Nobumitsu; Shibuya, Iwao; Hidaka, Masanori; Okazaki, Atsushi.

1984-01-01

The crystal structure of high-temperature phase of K 2 SeO 4 has been determined by means of single crystal neutron diffraction. The space group is P6 3 /mmc of hexagonal system with two formula units per unit cell. The structure is characterized by an averaged dispositions of SeO 4 tetrahedra with one of its Se-O bonds pointing parallel and antiparallel to the hexagonal c-axis in addition to the split distribution of potassium atoms. Heavily distorted distribution of oxygen atoms in SeO 4 is observed in Fourier maps corrersponding to split positions and reorientational motion of tetrahedra. This disordered arrangement is found to have close relation with the room temperature orthorhombic structure. The hexagonal-orthorhombic phase transition of K 2 SeO 4 at 472 0 C is grouped to an order-disorder type. (author)

Diatomite: A promising natural candidate as carrier material for low, middle and high temperature phase change material

International Nuclear Information System (INIS)

Qian, Tingting; Li, Jinhong; Min, Xin; Deng, Yong; Guan, Weimin; Ning, Lei

2015-01-01

Graphical abstract: Low-temperature PCMs are always the objects of prime investigations, however, the field of PCMs’ applications is not limited to low temperatures only. In the present study, three kinds of PCMs: polyethylene glycol (PEG), lithium nitrate, and sodium sulfate were respectively employed as the low-, middle- and high-temperature storage medium. A series of novel form-stable phase change materials (fs-PCMs) were tailor-made by blending diatomite and the three kinds of PCMs via a vacuum impregnation method or a facile mixing and sintering method. Various techniques were employed to characterize their structural and thermal properties. - Highlights: • Low-temperature PEG/diatomite was prepared. • Middle-temperature LiNO 3 /diatomite was prepared. • High-temperature Na 2 SO 4 /diatomite was prepared. - Abstract: Low-temperature PCMs are always the objects of prime investigations, however, the field of PCM’s application is not only limited to low temperatures. In this study, polyethylene glycol (PEG), lithium nitrate (LiNO 3 ), and sodium sulfate (Na 2 SO 4 ) were respectively employed as the low-, middle- and high-temperature storage medium. A series of novel form-stable phase change materials (fs-PCMs) were tailor-made by blending diatomite and the three PCMs via a vacuum impregnation method or a facile mixing and sintering method. Various techniques were employed to characterize their structural and thermal properties. The maximum loads of PEG, LiNO 3 , and Na 2 SO 4 in diatomite powder could respectively reach 58%, 60%, and 65%, while PCM melts during the solid–liquid phase transformation. SEM, XRD, and FT-IR results indicated that PCMs were well dispersed into diatomite pores and no chemical changes took place during the heating and cooling process. The prepared fs-PCMs were quite stable in terms of thermal and chemical manner even after a 200-cycle of melting and freezing. The resulting composite fs-PCMs were promising candidates to

Consequences of metallic fuel-cladding liquid phase attack during over-temperature transient on fuel element lifetime

International Nuclear Information System (INIS)

Lahm, C.E.; Koenig, J.F.; Seidel, B.R.

1990-01-01

Metallic fuel elements irradiated in EBR-II at temperatures significantly higher than design, causing liquid phase attack of the cladding, were subsequently irradiated at normal operating temperatures to first breach. The fuel element lifetime was compared to that for elements not subjected to the over-temperature transient and found to be equivalent. 1 ref., 3 figs

How to estimate exposure when studying the temperature-mortality relationship? A case study of the Paris area.

Science.gov (United States)

Schaeffer, Laura; de Crouy-Chanel, Perrine; Wagner, Vérène; Desplat, Julien; Pascal, Mathilde

2016-01-01

Time series studies assessing the effect of temperature on mortality generally use temperatures measured by a single weather station. In the Paris region, there is a substantial measurement network, and a variety of exposure indicators created from multiple stations can be tested. The aim of this study is to test the influence of exposure indicators on the temperature-mortality relationship in the Paris region. The relationship between temperature and non-accidental mortality was assessed based on a time series analysis using Poisson regression and a generalised additive model. Twenty-five stations in Paris and its three neighbouring departments were used to create four exposure indicators. These indicators were (1) the temperature recorded by one reference station, (2) a simple average of the temperatures of all stations, (3) an average weighted on the departmental population and (4) a classification of the stations based on land use and an average weighted on the population in each class. The relative risks and the Akaike criteria were similar for all the exposure indicators. The estimated temperature-mortality relationship therefore did not appear to be significantly affected by the indicator used, regardless of study zone (departments or region) or age group. The increase in temperatures from the 90(th) to the 99(th) percentile of the temperature distribution led to a significant increase in mortality over 75 years (RR = 1.10 [95% CI, 1.07; 1.14]). Conversely, the decrease in temperature between the 10(th) and 1(st) percentile had a significant effect on the mortality under 75 years (RR = 1.04 [95% CI, 1.01; 1.06]). In the Paris area, there is no added value in taking multiple climatic stations into account when estimating exposure in time series studies. Methods to better represent the subtle temperature variations in densely populated areas in epidemiological studies are needed.

[Soil Microbial Respiration Under Different Soil Temperature Conditions and Its Relationship to Soil Dissolved Organic Carbon and Invertase].

Science.gov (United States)

Wu, Jing; Chen, Shu-tao; Hu, Zheng-hua; Zhang, Xu

2015-04-01

In order to investigate the soil microbial respiration under different temperature conditions and its relationship to soil dissolved organic carbon ( DOC) and invertase, an indoor incubation experiment was performed. The soil samples used for the experiment were taken from Laoshan, Zijinshan, and Baohuashan. The responses of soil microbial respiration to the increasing temperature were studied. The soil DOC content and invertase activity were also measured at the end of incubation. Results showed that relationships between cumulative microbial respiration of different soils and soil temperature could be explained by exponential functions, which had P values lower than 0.001. The coefficient of temperature sensitivity (Q10 value) varied from 1.762 to 1.895. The Q10 value of cumulative microbial respiration decreased with the increase of soil temperature for all soils. The Q10 value of microbial respiration on 27 days after incubation was close to that of 1 day after incubation, indicating that the temperature sensitivity of recalcitrant organic carbon may be similar to that of labile organic carbon. For all soils, a highly significant ( P = 0.003 ) linear relationship between cumulative soil microbial respiration and soil DOC content could be observed. Soil DOC content could explain 31.6% variances of cumulative soil microbial respiration. For the individual soil and all soils, the relationship between cumulative soil microbial respiration and invertase activity could be explained by a highly significant (P soil microbial respiration.

Dynamics of the Josephson multi-junction system with junctions characterized by non-sinusoidal current - phase relationship

International Nuclear Information System (INIS)

Abal'osheva, I.; Lewandowski, S.J.

2004-01-01

It is shown that the inclusion of junctions characterized by non-sinusoidal current - phase relationship in the systems composed of multiple Josephson junctions - results in the appearance of additional system phase states. Numerical simulations and stability considerations confirm that those phase states can be realized in practice. Moreover, spontaneous formation of the grain boundary junctions in high-T c superconductors with non-trivial current-phase relations due to the d-wave symmetry of the order parameter is probable. Switching between the phase states of multiple grain boundary junction systems can lead to additional 1/f noise in high-T c superconductors. (author)

Suppression of Brillouin scattering in fibre-optical parametric amplifier by applying temperature control and phase modulation

DEFF Research Database (Denmark)

Lorenzen, Michael Rodas; Noordegraaf, Danny; Nielsen, Carsten Vandel

2009-01-01

An increased gain in a fibre-optical parametric amplifier through suppression of stimulated Brillouin scattering is demonstrated by applying a temperature distribution along the fibre for a fixed phase modulation of the pump. The temperature distribution slightly impacts the gain spectrum....

Theoretical and Experimental Investigation on the Low Temperature Properties of the NbCr{sub 2} Laves Phase

Energy Technology Data Exchange (ETDEWEB)

Thoma, D.J.; Chu, F.; Chen, K.C.; Kotula, P.G.; Mitchell, T.E.; Wills, J.M.; Ormeci, A.; Chen, S.P.; Albers, R.C.

1999-06-03

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The goal of the project was to develop methodologies in which to define and improve the properties of NbCr{sub 2} so that the high temperature structural applications of alloys based upon this would not be limited by the low-temperature brittle behavior of the intermetallic. We accomplished this task by (1) understanding the defect structure and deformation mechanisms in Laves phases, (2) electronic and geometric contributions to phase stability and alloying behavior, and (3) novel processing of dual phase (Laves/bcc) structures. As a result alloys with properties that in many cases surpass superalloys were developed. For example, we have tailored alloy design strategies and processing routes in a metal alloy to achieve ambient temperature ultimate strengths of 2.35 GPa as well as ultimate strengths of 1.5 GPa at 1000 C. This results i n one of the strongest metal alloys that currently exist, while still having deformability at room temperature.

Different Diversity and Distribution of Archaeal Community in the Aqueous and Oil Phases of Production Fluid From High-Temperature Petroleum Reservoirs

Directory of Open Access Journals (Sweden)

Bo Liang

2018-04-01

Full Text Available To get a better knowledge on how archaeal communities differ between the oil and aqueous phases and whether environmental factors promote substantial differences on microbial distributions among production wells, we analyzed archaeal communities in oil and aqueous phases from four high-temperature petroleum reservoirs (55–65°C by using 16S rRNA gene based 454 pyrosequencing. Obvious dissimilarity of the archaeal composition between aqueous and oil phases in each independent production wells was observed, especially in production wells with higher water cut, and diversity in the oil phase was much higher than that in the corresponding aqueous phase. Statistical analysis further showed that archaeal communities in oil phases from different petroleum reservoirs tended to be more similar, but those in aqueous phases were the opposite. In the high-temperature ecosystems, temperature as an environmental factor could have significantly affected archaeal distribution, and archaeal diversity raised with the increase of temperature (p < 0.05. Our results suggest that to get a comprehensive understanding of petroleum reservoirs microbial information both in aqueous and oil phases should be taken into consideration. The microscopic habitats of oil phase, technically the dispersed minuscule water droplets in the oil could be a better habitat that containing the indigenous microorganisms.

High temperature diffusion induced liquid phase joining of a heat resistant alloy

International Nuclear Information System (INIS)

Wikstrom, N.P.; Egbewande, A.T.; Ojo, O.A.

2008-01-01

Transient liquid phase bonding (TLP) of a nickel base superalloy, Waspaloy, was performed to study the influence of holding time and temperature on the joint microstructure. Insufficient holding time for complete isothermal solidification of liquated insert caused formation of eutectic-type microconstituent along the joint centerline region in the alloy. In agreement with prediction by conventional TLP diffusion models, an increase in bonding temperature for a constant gap size, resulted in decrease in the time, t f, required to form a eutectic-free joint by complete isothermal solidification. However, a significant deviation from these models was observed in specimens bonded at and above 1175 deg. C. A reduction in isothermal solidification rate with increased temperature was observed in these specimens, such that a eutectic-free joint could not be achieved by holding for a time period that produced complete isothermal solidification at lower temperatures. Boron-rich particles were observed within the eutectic that formed in the joints prepared at the higher temperatures. An overriding effect of decrease in boron solubility relative to increase in its diffusivity with increase in temperature, is a plausible important factor responsible for the reduction in isothermal solidification rate at the higher bonding temperatures

Room-temperature solid phase ionic liquid (RTSPIL) coated Ω-transaminases: Development and application in organic solvents

DEFF Research Database (Denmark)

Grabner, B.; Nazario, M. A.; Gundersen, M. T.

2018-01-01

ω-Transaminases ATA-40, ATA-47 and ATA-82P were coated with room-temperature solid phase ionic liquids (RTSPILs) by means of three methods, melt coating, precipitation coating, and co‐lyophilization, and showed increased stability in all of the five tested organic solvents. Co‐lyophilization and ......ω-Transaminases ATA-40, ATA-47 and ATA-82P were coated with room-temperature solid phase ionic liquids (RTSPILs) by means of three methods, melt coating, precipitation coating, and co‐lyophilization, and showed increased stability in all of the five tested organic solvents. Co...

The phase transition in the SU(5) model at high temperatures

International Nuclear Information System (INIS)

Daniel, M.; Vayonakis, C.E.

1981-01-01

Within the minimum GUT model we have studied the nature of the fluctuation-induced transition between the SU(5) and the SU(3)sub(c) x SU(2) x U(1) phase which occurs at high temperatures. Our analysis is limited to the case when the phase transition occurs outside the critical (fluctuation-dominated) region. For this to happen the SU(5) model has to be in a mode analogous to the type I superconductor. This corresponds to having the scalar quartic couplings in the Higgs sector less than the squared gauge coupling. For generic values of the coupling constants the phase transition is found to be weakly first order. As we approach the boundaries for the region of the SU(3)sub(c) x SU(2) x U(1) phase, however, a strong first-order transition occurs. The SU(5) mode (analogous to the type II superconductor) when the phase transition occurs inside the fluctuation-dominated region has been recently studied by Ginsparg. His results together with ours show that there is a continuous merging of the type I mode into the type II mode. Finally our analysis elucidates some aspects of the monopole problem in grand unified theories. (orig.)

Dynamical relationship between wind speed magnitude and meridional temperature contrast: Application to an interannual oscillation in Venusian middle atmosphere GCM

Science.gov (United States)

Yamamoto, Masaru; Takahashi, Masaaki

2018-03-01

We derive simple dynamical relationships between wind speed magnitude and meridional temperature contrast. The relationship explains scatter plot distributions of time series of three variables (maximum zonal wind speed UMAX, meridional wind speed VMAX, and equator-pole temperature contrast dTMAX), which are obtained from a Venus general circulation model with equatorial Kelvin-wave forcing. Along with VMAX and dTMAX, UMAX likely increases with the phase velocity and amplitude of a forced wave. In the scatter diagram of UMAX versus dTMAX, points are plotted along a linear equation obtained from a thermal-wind relationship in the cloud layer. In the scatter diagram of VMAX versus UMAX, the apparent slope is somewhat steep in the high UMAX regime, compared with the low UMAX regime. The scatter plot distributions are qualitatively consistent with a quadratic equation obtained from a diagnostic equation of the stream function above the cloud top. The plotted points in the scatter diagrams form a linear cluster for weak wave forcing, whereas they form a small cluster for strong wave forcing. An interannual oscillation of the general circulation forming the linear cluster in the scatter diagram is apparent in the experiment of weak 5.5-day wave forcing. Although a pair of equatorial Kelvin and high-latitude Rossby waves with a same period (Kelvin-Rossby wave) produces equatorward heat and momentum fluxes in the region below 60 km, the equatorial wave does not contribute to the long-period oscillation. The interannual fluctuation of the high-latitude jet core leading to the time variation of UMAX is produced by growth and decay of a polar mixed Rossby-gravity wave with a 14-day period.

Phase diagram of Ti-B-C system in the temperature range of 300-3500 K

International Nuclear Information System (INIS)

Gusev, A.I.

1996-01-01

Calculation of phase equilibrium in the ternary system Ti-B-C in the areas of the TiC y -TiB 2 and B 4 C y -TiB 2 cross sections as well as partial construction of three-dimensional (spatial)diagram of the Ti-B-C system within the temperature range of 300-3500 K is carried out. The form of the isothermal cross section of the ternary system remains almost unchanged up to 1900 K. The most essential change is related to disordering of the low-temperature ordered phases Ti 2 C, Ti 3 C and Ti 6 C 5 of the titanium carbide at T > 950 K [ru

Classification of Arctic, Mid-Latitude and Tropical Clouds in the Mixed-Phase Temperature Regime

Science.gov (United States)

Costa, Anja; Afchine, Armin; Luebke, Anna; Meyer, Jessica; Dorsey, James R.; Gallagher, Martin W.; Ehrlich, André; Wendisch, Manfred; Krämer, Martina

2016-04-01

The degree of glaciation and the sizes and habits of ice particles formed in mixed-phase clouds remain not fully understood. However, these properties define the mixed clouds' radiative impact on the Earth's climate and thus a correct representation of this cloud type in global climate models is of importance for an improved certainty of climate predictions. This study focuses on the occurrence and characteristics of two types of clouds in the mixed-phase temperature regime (238-275K): coexistence clouds (Coex), in which both liquid drops and ice crystals exist, and fully glaciated clouds that develop in the Wegener-Bergeron-Findeisen regime (WBF clouds). We present an extensive dataset obtained by the Cloud and Aerosol Particle Spectrometer NIXE-CAPS, covering Arctic, mid-latitude and tropical regions. In total, we spent 45.2 hours within clouds in the mixed-phase temperature regime during five field campaigns (Arctic: VERDI, 2012 and RACEPAC, 2014 - Northern Canada; mid-latitude: COALESC, 2011 - UK and ML-Cirrus, 2014 - central Europe; tropics: ACRIDICON, 2014 - Brazil). We show that WBF and Coex clouds can be identified via cloud particle size distributions. The classified datasets are used to analyse temperature dependences of both cloud types as well as range and frequencies of cloud particle concentrations and sizes. One result is that Coex clouds containing supercooled liquid drops are found down to temperatures of -40 deg C only in tropical mixed clouds, while in the Arctic and mid-latitudes no liquid drops are observed below about -20 deg C. In addition, we show that the cloud particles' aspherical fractions - derived from polarization signatures of particles with diameters between 20 and 50 micrometers - differ significantly between WBF and Coex clouds. In Coex clouds, the aspherical fraction of cloud particles is generally very low, but increases with decreasing temperature. In WBF clouds, where all cloud particles are ice, about 20-40% of the cloud

Significant effect of substrate temperature on the phase structure, optical and electrical properties of RF sputtered CIGS films

Energy Technology Data Exchange (ETDEWEB)

Yu Zhou; Yan Yong; Li Shasha; Zhang Yanxia; Yan Chuanpeng; Liu Lian; Zhang Yong [Key Laboratory of Magnetic Suspension Technology and Maglev Vehicle, Ministry of Education, Superconductivity and New energy R and D Center (SNERDC), Mail Stop 165, Southwest Jiaotong University, Chengdu 610031 (China); Zhao Yong, E-mail: yzhao@swjtu.edu.cn [Key Laboratory of Magnetic Suspension Technology and Maglev Vehicle, Ministry of Education, Superconductivity and New energy R and D Center (SNERDC), Mail Stop 165, Southwest Jiaotong University, Chengdu 610031 (China); School of Materials Science and Engineering, University of New South Wales, Sydney 2052, NSW (Australia)

2013-01-01

Highlights: Black-Right-Pointing-Pointer Secondary phase exist in the RF sputtered CIGS films as it deposited at 150 Degree-Sign C and 500 Degree-Sign C. Black-Right-Pointing-Pointer CIGS films deposited beyond 350 Degree-Sign C show (1 1 2) prefer orientation. Black-Right-Pointing-Pointer E{sub g} of the CIGS films increased with the increase of substrate temperature. Black-Right-Pointing-Pointer Conductivity of the films is affected by 'variable range hopping' mechanism. - Abstract: This work studied the effect of substrate temperature on the phase structure, optical and electrical properties of the one-step radio frequency sputtered Cu(In,Ga)Se{sub 2} (CIGS) thin films. X-ray diffraction (XRD) analysis revealed that all the deposited CIGS films are chalcopyrite phase with polycrystalline structure. The films deposited beyond the substrate temperature of 350 Degree-Sign C show (1 1 2) prefer orientation. Raman spectra reveal that the 150 Degree-Sign C deposited CIGS film coexists with Cu{sub 2-x}Se phase and the 500 Degree-Sign C deposited film contains ordered defect compound (ODC) phase. With the increase of substrate temperature, energy band gap of the CIGS film increase from 0.99 to 1.27 eV. Films deposited at higher temperature exhibit larger electrical conductivity. Conductivity of the CIGS films is dominated by 'variable range hopping' mechanism. The disorder in our CIGS the films is associated with the formation of intrinsic defects such as V{sub Se} and In{sub Cu} for their low formation energy.

Critical temperature transitions in laser-mediated cartilage reshaping

Science.gov (United States)

Wong, Brian J.; Milner, Thomas E.; Kim, Hong H.; Telenkov, Sergey A.; Chew, Clifford; Kuo, Timothy C.; Smithies, Derek J.; Sobol, Emil N.; Nelson, J. Stuart

1998-07-01

In this study, we attempted to determine the critical temperature [Tc] at which accelerated stress relaxation occurred during laser mediated cartilage reshaping. During laser irradiation, mechanically deformed cartilage tissue undergoes a temperature dependent phase transformation which results in accelerated stress relaxation. When a critical temperature is attained, cartilage becomes malleable and may be molded into complex new shapes that harden as the tissue cools. Clinically, reshaped cartilage tissue can be used to recreate the underlying cartilaginous framework of structures such as the ear, larynx, trachea, and nose. The principal advantages of using laser radiation for the generation of thermal energy in tissue are precise control of both the space-time temperature distribution and time- dependent thermal denaturation kinetics. Optimization of the reshaping process requires identification of the temperature dependence of this phase transformation and its relationship to observed changes in cartilage optical, mechanical, and thermodynamic properties. Light scattering, infrared radiometry, and modulated differential scanning calorimetry (MDSC) were used to measure temperature dependent changes in the biophysical properties of cartilage tissue during fast (laser mediated) and slow (conventional calorimetric) heating. Our studies using MDSC and laser probe techniques have identified changes in cartilage thermodynamic and optical properties suggestive of a phase transformation occurring near 60 degrees Celsius.

Instrument-free exothermic heating with phase change temperature control for paper microfluidic devices

Science.gov (United States)

Singleton, Jered; Zentner, Chris; Buser, Josh; Yager, Paul; LaBarre, Paul; Weigl, Bernhard H.

2013-03-01

Many infectious diseases, as well as some cancers, that affect global health are most accurately diagnosed through nucleic acid amplification and detection. There is a great need to simplify nucleic acid-based assay systems for use in global health in low-resource settings as well as in settings that do not have convenient access to laboratory staff and equipment such as doctors' offices and home care settings. In developing countries, unreliable electric power, inadequate supply chains, and lack of maintenance for complex diagnostic instruments are all common infrastructure shortfalls. Many elements of instrument-free, disposable, nucleic acid amplification assays have been demonstrated in recent years. However, the problem of instrument-free,1 low-cost, temperature-controlled chemical heating remains unsolved. In this paper we present the current status and results of work towards developing disposable, low-cost, temperature-controlled heaters designed to support isothermal nucleic acid amplification assays that are integrated with a two-dimensional paper network. Our approach utilizes the heat generated through exothermic chemical reactions and controls the heat through use of engineered phase change materials to enable sustained temperatures required for nucleic acid amplification. By selecting appropriate exothermic and phase change materials, temperatures can be controlled over a wide range, suitable for various isothermal amplification methods, and maintained for over an hour at an accuracy of +/- 1°C.

Relationship between the Amplitude and Phase of a Signal Scattered by a Point-Like Acoustic Inhomogeneity

Science.gov (United States)

Burov, V. A.; Morozov, S. A.

2001-11-01

Wave scattering by a point-like inhomogeneity, i.e., a strong inhomogeneity with infinitesimal dimensions, is described. This type of inhomogeneity model is used in investigating the point-spread functions of different algorithms and systems. Two approaches are used to derive the rigorous relationship between the amplitude and phase of a signal scattered by a point-like acoustic inhomogeneity. The first approach is based on a Marchenko-type equation. The second approach uses the scattering by a scatterer whose size decreases simultaneously with an increase in its contrast. It is shown that the retarded and advanced waves are scattered differently despite the relationship between the phases of the corresponding scattered waves.

Relationship of activity in ascending paths with phase encoding in the lumbar spinal cord

Directory of Open Access Journals (Sweden)

O. O. Shugurov

2012-02-01

Full Text Available We studied the relationship of discharges phase characteristics in ascending column of spinal cord (SC and specificity of activation of neurones, which generate negative components of evoked potentials of SC. The discharges was recorded from SC at a level of a presence of dorsal column (DC, spinocervical and dorsal spinocerebellar tract in upper lumbar and thoracic segments at a stimulation of a nerve or DC. It is shown, that the phase of the discharges depends on the quantity of synaptic delays in generating chain of such signals. Thus, the phase of a signal can carry the additional information on specificity of activation of the sensory elements in CNS.

Spatial interpolation of hourly precipitation and dew point temperature for the identification of precipitation phase and hydrologic response in a mountainous catchment

Science.gov (United States)

Garen, D. C.; Kahl, A.; Marks, D. G.; Winstral, A. H.

2012-12-01

In mountainous catchments, it is well known that meteorological inputs, such as precipitation, air temperature, humidity, etc. vary greatly with elevation, spatial location, and time. Understanding and monitoring catchment inputs is necessary in characterizing and predicting hydrologic response to these inputs. This is true all of the time, but it is the most dramatically critical during large storms, when the input to the stream system due to rain and snowmelt creates the potential for flooding. Besides such crisis events, however, proper estimation of catchment inputs and their spatial distribution is also needed in more prosaic but no less important water and related resource management activities. The first objective of this study is to apply a geostatistical spatial interpolation technique (elevationally detrended kriging) to precipitation and dew point temperature on an hourly basis and explore its characteristics, accuracy, and other issues. The second objective is to use these spatial fields to determine precipitation phase (rain or snow) during a large, dynamic winter storm. The catchment studied is the data-rich Reynolds Creek Experimental Watershed near Boise, Idaho. As part of this analysis, precipitation-elevation lapse rates are examined for spatial and temporal consistency. A clear dependence of lapse rate on precipitation amount exists. Certain stations, however, are outliers from these relationships, showing that significant local effects can be present and raising the question of whether such stations should be used for spatial interpolation. Experiments with selecting subsets of stations demonstrate the importance of elevation range and spatial placement on the interpolated fields. Hourly spatial fields of precipitation and dew point temperature are used to distinguish precipitation phase during a large rain-on-snow storm in December 2005. This application demonstrates the feasibility of producing hourly spatial fields and the importance of doing

Crystal growth and electronic structure of low-temperature phase SrMgF{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Atuchin, Victor V. [Laboratory of Optical Materials and Structures, Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Functional Electronics Laboratory, Tomsk State University, Tomsk 634050 (Russian Federation); Laboratory of Semiconductor and Dielectric Materials, Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Goloshumova, Alina A. [Laboratory of Crystal Growth, Institute of Geology and Mineralogy, SB RAS, Novosibirsk 630090 (Russian Federation); Isaenko, Ludmila I. [Laboratory of Semiconductor and Dielectric Materials, Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Laboratory of Crystal Growth, Institute of Geology and Mineralogy, SB RAS, Novosibirsk 630090 (Russian Federation); Jiang, Xingxing [BCCRD, Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Lobanov, Sergey I. [Laboratory of Crystal Growth, Institute of Geology and Mineralogy, SB RAS, Novosibirsk 630090 (Russian Federation); Zhang, Zhaoming [Australian Nuclear Science & Technology Organisation, Lucas Heights, NSW 2234 (Australia); Lin, Zheshuai, E-mail: zslin@mail.ipc.ac.cn [BCCRD, Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

2016-04-15

Using the vertical Bridgman method, the single crystal of low temperature phase SrMgF{sub 4} is obtained. The crystal is in a very good optical quality with the size of 10×7×5 mm{sup 3}. Detailed photoemission spectra of the element core levels are determined by a monochromatic AlKa (1486.6 eV) X-ray source. Moreover, the first-principles calculations are performed to investigate the electronic structure of SrMgF{sub 4}. A good agreement between experimental and calculated results is achieved. It is demonstrated that almost all the electronic orbitals are strongly localized and the hybridization with the others is very small, but the Mg–F bonds covalency is relatively stronger than that of Sr–F bonds. - Graphical abstract: Large size of low-temperature phase SrMgF{sub 4} crystal was obtained (right) and its electronic structure was investigated by X-ray photoelectron spectroscopy and first-principles calculation (left). - Highlights: • Large size single crystal of low-temperature phase SrMgF{sub 4} is obtained. • Electronic structure of SrMgF{sub 4} is measured by X-ray photoelectron spectroscopy. • Partial densities of states are determined by first-principles calculation. • Good agreement between experimental and calculated results is achieved. • Strong ionic characteristics of chemical bonds are exhibited in SrMgF{sub 4}.

Why get big in the cold? Size-fecundity relationships explain the temperature-size rule in a pulmonate snail (Physa).

Science.gov (United States)

Arendt, J

2015-01-01

Most ectotherms follow a pattern of size plasticity known as the temperature-size rule where individuals reared in cold environments are larger at maturation than those reared in warm environments. This pattern seems maladaptive because growth is slower in the cold so it takes longer to reach a large size. However, it may be adaptive if reaching a large size has a greater benefit in a cold than in a warm environment such as when size-dependent mortality or size-dependent fecundity depends on temperature. I present a theoretical model showing how a correlation between temperature and the size-fecundity relationship affects optimal size at maturation. I parameterize the model using data from a freshwater pulmonate snail from the genus Physa. Nine families were reared from hatching in one of three temperature regimes (daytime temperature of 22, 25 or 28 °C, night-time temperature of 22 °C, under a 12L:12D light cycle). Eight of the nine families followed the temperature-size rule indicating genetic variation for this plasticity. As predicted, the size-fecundity relationship depended upon temperature; fecundity increases steeply with size in the coldest treatment, less steeply in the intermediate treatment, and shows no relationship with size in the warmest treatment. Thus, following the temperature-size rule is adaptive for this species. Although rarely measured under multiple conditions, size-fecundity relationships seem to be sensitive to a number of environmental conditions in addition to temperature including local productivity, competition and predation. If this form of plasticity is as widespread as it appears to be, this model shows that such plasticity has the potential to greatly modify current life-history theory. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Neutron powder investigation of the tetragonal to monoclinic phase transformation in undoped zirconia

International Nuclear Information System (INIS)

Boysen, H.; Frey, F.

1991-01-01

The tetragonal (t) to monoclinic (m) transformation in pure ZrO 2 was investigated by neutron powder diffraction at temperatures between 1900 K and room temperature. The results of a Rietveld analysis are compared with a previous investigation of the m → t transformation. The t → m transformation takes place near 1200 K (implaying a hysteresis of 300 K) and in a much smaller interval (about 150 K compared with about 600 K in the m → t case). There are no indications of a two-stage process as found for the m → t transformation. The structural parameters of the m phase depend only on temperature while those of the t phase differ at the same temperatures for the forward and reverse transformation. The temperature dependence of the lattice constants suggests an orientational relationship a t parallela m * and c t parallelb m . There are no macrostrains whereas the overall microstrain behaviour is similar in both cases, viz. the large microstrains present in both phases are released within the transformation regime. An analysis of temperature factors and diffuse background suggest dynamical disorder in the t phase and static disorder in the m phase. (orig.)

Determining solid-fluid interface temperature distribution during phase change of cryogenic propellants using transient thermal modeling

Science.gov (United States)

Bellur, K.; Médici, E. F.; Hermanson, J. C.; Choi, C. K.; Allen, J. S.

2018-04-01

Control of boil-off of cryogenic propellants is a continuing technical challenge for long duration space missions. Predicting phase change rates of cryogenic liquids requires an accurate estimation of solid-fluid interface temperature distributions in regions where a contact line or a thin liquid film exists. This paper described a methodology to predict inner wall temperature gradients with and without evaporation using discrete temperature measurements on the outer wall of a container. Phase change experiments with liquid hydrogen and methane in cylindrical test cells of various materials and sizes were conducted at the Neutron Imaging Facility at the National Institute of Standards and Technology. Two types of tests were conducted. The first type of testing involved thermal cycling of an evacuated cell (dry) and the second involved controlled phase change with cryogenic liquids (wet). During both types of tests, temperatures were measured using Si-diode sensors mounted on the exterior surface of the test cells. Heat is transferred to the test cell by conduction through a helium exchange gas and through the cryostat sample holder. Thermal conduction through the sample holder is shown to be the dominant mode with the rate of heat transfer limited by six independent contact resistances. An iterative methodology is employed to determine contact resistances between the various components of the cryostat stick insert, test cell and lid using the dry test data. After the contact resistances are established, inner wall temperature distributions during wet tests are calculated.

Substrate Integrated Waveguide Based Phase Shifter and Phased Array in a Ferrite Low Temperature Co-fired Ceramic Package

KAUST Repository

Nafe, Ahmed A.

2014-03-01

Phased array antennas, capable of controlling the direction of their radiated beam, are demanded by many conventional as well as modern systems. Applications such as automotive collision avoidance radar, inter-satellite communication links and future man-portable satellite communication on move services require reconfigurable beam systems with stress on mobility and cost effectiveness. Microwave phase shifters are key components of phased antenna arrays. A phase shifter is a device that controls the phase of the signal passing through it. Among the technologies used to realize this device, traditional ferrite waveguide phase shifters offer the best performance. However, they are bulky and difficult to integrate with other system components. Recently, ferrite material has been introduced in Low Temperature Co-fired Ceramic (LTCC) multilayer packaging technology. This enables the integration of ferrite based components with other microwave circuitry in a compact, light-weight and mass producible package. Additionally, the recent concept of Substrate Integrated Waveguide (SIW) allowed realization of synthesized rectangular waveguide-like structures in planar and multilayer substrates. These SIW structures have been shown to maintain the merits of conventional rectangular waveguides such as low loss and high power handling capabilities while being planar and easily integrable with other components. Implementing SIW structures inside a multilayer ferrite LTCC package enables monolithic integration of phase shifters and phased arrays representing a true System on Package (SoP) solution. It is the objective of this thesis to pursue realizing efficient integrated phase shifters and phased arrays combining the above mentioned technologies, namely Ferrite LTCC and SIW. In this work, a novel SIW phase shifter in ferrite LTCC package is designed, fabricated and tested. The device is able to operate reciprocally as well as non-reciprocally. Demonstrating a measured maximum

Influence of grain size and ordering degree of the parent phase on M/sub s/ in a CuZnAl alloy containing boron

International Nuclear Information System (INIS)

Jianxin, W.; Bohong, J.; Hsu, T.Y.

1988-01-01

In this paper, the influence of the average grain size and ordering degree of the parent phase on the starting temperature of thermoelastic martensitic transformation in a Cu-25.62 Zn-3.97 Al-0.0018 B (wt%) shape memory alloy is studied. Based on the thermodynamics of phase transformation, a linear relationship between the starting temperature of martensitic transformation and the reciprocal of the square root of grain size is obtained, i.e. M/sub s/ temperature decreases with increasing grain size. Application of Landau's theory gives a quantitative relationship between M/sub s/ temperature and the ordering parameter of the parent phase, which is confirmed by the results of X-ray diffraction and electric resistance measurement. The activation energy of the ordering process is calculated to be 46 kJ/mol

Instantaneous measurement of the internal temperature in lithium-ion rechargeable cells

International Nuclear Information System (INIS)

Srinivasan, Rengaswamy; Carkhuff, Bliss G.; Butler, Michael H.; Baisden, Andrew C.

2011-01-01

We demonstrate, in three different rechargeable lithium-ion cells, the existence of an intrinsic relationship between a cell's internal temperature and a readily measurable electrical parameter, namely the phase shift between an applied sinusoidal current and the resulting voltage. The temperature range examined spanned from -20 to 66 deg. C. The optimum single frequency for the phase measurement is in the 40-100 Hz range, allowing for a measurement time of much less than a second; the phase shift in this range depends predominantly on temperature, and is almost completely independent of the state-of-charge. Literature reports suggest that the observed dependence of the phase shift on temperature arises from the ionic conduction of the so-called solid-electrolyte-interphase layer between the graphite anode and the electrolyte. A meter measuring the phase shift across this interphase is analogous to a thermometer reporting the temperature, thereby providing feedback for rapid corrections of any operating conditions that might lead to the catastrophic destruction of the cell. This level of monitoring and control is distinctly different from the present safety-enabling mechanisms: typically positive thermal coefficient ceramics/plastics, or 'shutdown' separators based on polyethylene that act to often permanently shut down current flow through the cell.

High temperature-induced phase transitions in Sr{sub 2}GdRuO{sub 6} complex perovskite

Energy Technology Data Exchange (ETDEWEB)

Triana, C.A.; Corredor, L.T.; Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Bogota D.C. A.A. 14490 (Colombia); Roa-Rojas, J., E-mail: jroar@unal.edu.co [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Bogota D.C. A.A. 14490 (Colombia)

2011-12-15

Highlights: Black-Right-Pointing-Pointer Crystal structure, thermal expansion and phase transitions at high-temperature of Sr{sub 2}GdRuO{sub 6} perovskite has been investigated. Black-Right-Pointing-Pointer X-ray diffraction pattern at 298 K of Sr{sub 2}GdRuO{sub 6} corresponds to monoclinic perovskite-type structure with P2{sub 1}/n space group. Black-Right-Pointing-Pointer Evolution of X-ray diffraction patterns at high-temperature shows that the Sr{sub 2}GdRuO{sub 6} perovskite suffers two-phase transitions. Black-Right-Pointing-Pointer At 573 K the X-ray diffraction pattern of Sr{sub 2}GdRuO{sub 6} corresponds to monoclinic perovskite-type structure with I2/m space group. Black-Right-Pointing-Pointer At 1273 K the Sr{sub 2}GdRuO{sub 6} perovskite suffers a complete phase-transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87). -- Abstract: The crystal structure behavior of the Sr{sub 2}GdRuO{sub 6} complex perovskite at high-temperature has been investigated over a wide temperature range between 298 K {<=} T {<=} 1273 K. Measurements of X-ray diffraction at room-temperature and Rietveld analysis of the experimental patterns show that this compound crystallizes in a monoclinic perovskite-like structure, which belongs to the P2{sub 1}/n (no. 14) space group and 1:1 ordered arrangement of Ru{sup 5+} and Gd{sup 3+} cations over the six-coordinate M sites. Experimental lattice parameters were obtained to be a =5.8103(5) Angstrom-Sign , b =5.8234(1) Angstrom-Sign , c =8.2193(9) Angstrom-Sign , V = 278.11(2) Angstrom-Sign {sup 3} and angle {beta} = 90.310(5) Degree-Sign . The high-temperature analysis shows the occurrence of two-phase transitions on this material. First, at 573 K it adopts a monoclinic perovskite-type structure with I2/m (no. 12) space group with lattice parameters a = 5.8275(6) Angstrom-Sign , b = 5.8326(3) Angstrom-Sign , c = 8.2449(2) Angstrom-Sign , V = 280.31(3) Angstrom-Sign {sup 3} and angle {beta} = 90.251(3) Degree-Sign . Close

Thermal Stability Test of Sugar Alcohols as Phase Change Materials for Medium Temperature Energy Storage Application

OpenAIRE

Solé, Aran; Neumann, Hannah; Niedermaier, Sophia; Cabeza, Luisa F.; Palomo, Elena

2014-01-01

Sugar alcohols are potential phase change materials candidates as they present high phase change enthalpy values, are non-toxic and low cost products. Three promising sugar-alcohols were selected: D-mannitol, myo-inositol and dulcitol under high melting enthalpy and temperature criterion. Thermal cycling tests were performed to study its cycling stability which can be determining when selecting the suitable phase change material. D-mannitol and dulcitol present poor thermal stability...

Pressure-temperature stability, Ca2+ binding, and pressure-temperature phase diagram of cod parvalbumin: Gad m 1.

Science.gov (United States)

Somkuti, Judit; Bublin, Merima; Breiteneder, Heimo; Smeller, László

2012-07-31

Fish allergy is associated with IgE-mediated hypersensitivity reactions to parvalbumins, which are small calcium-binding muscle proteins and represent the major and sole allergens for 95% of fish-allergic patients. We performed Fourier transform infrared and tryptophan fluorescence spectroscopy to explore the pressure-temperature (p-T) phase diagram of cod parvalbumin (Gad m 1) and to elucidate possible new ways of pressure-temperature inactivation of this food allergen. Besides the secondary structure of the protein, the Ca(2+) binding to aspartic and glutamic acid residues was detected. The phase diagram was found to be quite complex, containing partially unfolded and molten globule states. The Ca(2+) ions were essential for the formation of the native structure. A molten globule conformation appears at 50 °C and atmospheric pressure, which converts into an unordered aggregated state at 75 °C. At >200 MPa, only heat unfolding, but no aggregation, was observed. A pressure of 500 MPa leads to a partially unfolded state at 27 °C. The complete pressure unfolding could only be reached at an elevated temperature (40 °C) and pressure (1.14 GPa). A strong correlation was found between Ca(2+) binding and the protein conformation. The partially unfolded state was reversibly refolded. The completely unfolded molecule, however, from which Ca(2+) was released, could not refold. The heat-unfolded protein was trapped either in the aggregated state or in the molten globule state without aggregation at elevated pressures. The heat-treated and the combined heat- and pressure-treated protein samples were tested with sera of allergic patients, but no change in allergenicity was found.

Phase transformation in sol-gel prepared zirconia using in-situ high temperature X-ray diffraction

International Nuclear Information System (INIS)

Srinivasan, R.; Davis, B.H.; Hubbard, C.R.; Cavin, O.B.; Porter, W.D.

1991-01-01

Zirconia was precipitated at a pH of 10.5 by admixing a solution of ZrCl 4 and NH 4 OH both rapidly (∼ 1 min) and slowly (∼ 8 hr). The precipitate was calcined at 500C for 5 hours and then furnace cooled. The former exhibited monoclinic phase while the latter yielded tetragonal phase. The pathway from amorphous to crystalline form was followed by in-situ high temperature X-ray diffraction in flowing air and in He. The data showed the evolution of the tetragonal crystalline phase on heating. On rapid cooling the tetragonal phase is retained at R.T., and on slow cooling the transformation to monoclinic phase occurs in air

Low-temperature structural phase transition in synthetic libethenite Cu2PO4OH

International Nuclear Information System (INIS)

Belik, Alexei A.; Naumov, Pance; Kim, Jungeun; Tsuda, Shunsuke

2011-01-01

Low-temperature structural properties of the synthetic mineral libethenite Cu 2 PO 4 OH were investigated by single-crystal X-ray diffraction, synchrotron X-ray powder diffraction, specific heat measurements, and Raman spectroscopy. A second-order structural phase transition from the Pnnm symmetry (a=8.0553(8) A, b=8.3750(9) A, c=5.8818(6) A at 180 K) to the P2 1 /n symmetry (a=8.0545(8) A, b=8.3622(9) A, c=5.8755(6) A, β=90.0012(15) at 120 K) was found at 160 K during cooling. At 120 K, the monoclinic angle is 90.0012(15) from single crystal X-ray data vs 90.083(1) from powder X-ray diffraction data. The P2 1 /n-to-Pnnm transition may be a general feature of the adamite-type compounds, M 2 XO 4 OH. - Graphical Abstract: Fragments of experimental synchrotron X-ray powder diffraction patterns of Cu 2 PO 4 OH between 100 and 280 K. Arrows show additional reflections that appear below 160 K in the monoclinic P2 1 /n phase. Highlights: → A low-temperature phase transition was found in the mineral libethenite Cu 2 PO 4 OH. → No magnetic anomalies and weak specific heat anomalies are detected. → Phase transition is of the second order. → Libethenite may exemplify a general feature of the adamite-type compounds.

Phase transition of a cobalt-free perovskite as a high-performance cathode for intermediate-temperature solid oxide fuel cells.

Science.gov (United States)

Jiang, Shanshan; Zhou, Wei; Niu, Yingjie; Zhu, Zhonghua; Shao, Zongping

2012-10-01

It is generally recognized that the phase transition of a perovskite may be detrimental to the connection between cathode and electrolyte. Moreover, certain phase transitions may induce the formation of poor electronic and ionic conducting phase(s), thereby lowering the electrochemical performance of the cathode. Here, we present a study on the phase transition of a cobalt-free perovskite (SrNb(0.1)Fe(0.9)O(3-δ), SNF) and evaluate its effect on the electrochemical performance of the fuel cell. SNF exists as a primitive perovskite structure with space group P4mm (99) at room temperature. As evidenced by in situ high-temperature X-ray diffraction measurements over the temperature range of 600 to 1000 °C, SNF undergoes a transformation to a tetragonal structure with a space group I4/m (87). This phase transition is accompanied by a moderate change in the volume, allowing a good cathode/electrolyte interface on thermal cycling. According to the electrochemical impedance spectroscopy evaluation, the I4/m phase exhibits positive effects on the cathode's performance, showing the highest oxygen reduction reaction activity of cobalt-free cathodes reported so far. This activity improvement is attributed to enhanced oxygen surface processes. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ synchrotron XRD analysis of the kinetics of spodumene phase transitions.

Science.gov (United States)

L Moore, Radhika; Mann, Jason P; Montoya, Alejandro; Haynes, Brian S

2018-04-25

The phase transition by thermal activation of natural α-spodumene was followed by in situ synchrotron XRD in the temperature range 896 to 940 °C. We observed both β- and γ-spodumene as primary products in approximately equal proportions. The rate of the α-spodumene inversion is first order and highly sensitive to temperature (apparent activation energy ∼800 kJ mol-1). The γ-spodumene product is itself metastable, forming β-spodumene, with the total product mass fraction ratio fγ/fβ decreasing as the conversion of α-spodumene continues. We found the relationship between the product yields and the degree of conversion of α-spodumene to be the same at all temperatures in the range studied. A model incorporating first order kinetics of the α- and γ-phase inversions with invariant rate constant ratio describes the results accurately. Theoretical phonon analysis of the three phases indicates that the γ phase contains crystallographic instabilities, whilst the α and β phases do not.

On the high temperature phase transition in Ba(Zr0.20Ti0.80O3 ceramic

Directory of Open Access Journals (Sweden)

K. P. Chandra

2017-08-01

Full Text Available Temperature dependent X-ray diffraction (XRD and dielectric properties of perovskite Ba(Zr0.2Ti0.8O3 ceramic prepared using a standard solid-state reaction process is presented. Along with phase transitions at low temperature, a new phase transition at high temperature (873∘C at 20Hz, diffusive in character has been found where the lattice structure changes from monoclinic (space group: P2∕m to hexagonal (space group: P6∕mmm. This result places present ceramic in the list of potential candidate for intended high temperature applications. The AC conductivity data followed hopping type charge conduction and supports jump relaxation model. The experimental value of d33=98pC/N was found. The dependence of polarization and strain on electric field at room temperature suggested that lead-free Ba(Zr0.2Ti0.8O3 is a promising material for electrostrictive applications.

Raman scattering temperature measurements for water vapor in nonequilibrium dispersed two-phase flow

International Nuclear Information System (INIS)

Anastasia, C.M.; Neti, S.; Smith, W.R.; Chen, J.C.

1982-09-01

The objective of this investigation was to determine the feasibility of using Raman scattering as a nonintrusive technique to measure vapor temperatures in dispersed two-phase flow. The Raman system developed for this investigation is described, including alignment of optics and optimization of the photodetector for photon pulse counting. Experimentally obtained Raman spectra are presented for the following single- and two-phase samples: liquid water, atmospheric nitrogen, superheated steam, nitrogen and water droplets in a high void fraction air/water mist, and superheated water vapor in nonequilibrium dispersed flow

Simulation and Experimental Study on Effect of Phase Change Material Thickness to Reduce Temperature of Photovoltaic Panel

Science.gov (United States)

Indartono, Y. S.; Prakoso, S. D.; Suwono, A.; Zaini, I. N.; Fernaldi, B.

2015-09-01

Solar energy is promising renewable energy which can be applied in Indonesia. Average solar radiation in the country is 4.8 kWh/day/m2. Weakness of silicon-based photovoltaic (PV) is efficiency reduction caused by temperature increase. Many attempts have been done to reduce PV temperature. In previous study, palm oil, which is widely available in Indonesia, is suitable to be used as phase change material (PCM) to reduce PV temperature. In this study, thickness of aluminium rectangular-tube containing phase change material oil is varied. The tube is placed at back part of PV. Numerical and experimental study was done to evaluate the effect of tube thickness to the temperature reduction of the PV. Variation of tube thickness used in the experiment is 50.8mm, 76.2 mm, 101.6 mm. Both studies show that increase of PCM thickness reduces PV temperature. Higher PCM thickness cause large reduction on PV temperature. Simulation result shows there is an optimum thickness of the PCM which is applied to the PV.

Simulation and Experimental Study on Effect of Phase Change Material Thickness to Reduce Temperature of Photovoltaic Panel

International Nuclear Information System (INIS)

Indartono, Y S; Prakoso, S D; Suwono, A; Zaini, I N; Fernaldi, B

2015-01-01

Solar energy is promising renewable energy which can be applied in Indonesia. Average solar radiation in the country is 4.8 kWh/day/m2. Weakness of silicon-based photovoltaic (PV) is efficiency reduction caused by temperature increase. Many attempts have been done to reduce PV temperature. In previous study, palm oil, which is widely available in Indonesia, is suitable to be used as phase change material (PCM) to reduce PV temperature. In this study, thickness of aluminium rectangular-tube containing phase change material oil is varied. The tube is placed at back part of PV. Numerical and experimental study was done to evaluate the effect of tube thickness to the temperature reduction of the PV. Variation of tube thickness used in the experiment is 50.8mm, 76.2 mm, 101.6 mm. Both studies show that increase of PCM thickness reduces PV temperature. Higher PCM thickness cause large reduction on PV temperature. Simulation result shows there is an optimum thickness of the PCM which is applied to the PV. (paper)

Microstructures and mechanical properties of two-phase alloys based on NbCr{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Chen, K.C.; Kotula, P.G.; Cady, C.M.; Mauro, M.E.; Thoma, D.J.

1999-07-01

A two-phase, NbCrTi alloy (bcc + C15 Laves phase) has been developed using several alloy design methodologies. In efforts to understand processing-microstructure-property relationships, different processing routes were employed. The resulting microstructures and mechanical properties are discussed and compared. Plasma arc melted (PAM) samples served to establish baseline, as-cast properties. In addition, a novel processing technique, involving decomposition of a supersaturated and metastable precursor phase during hot isostatic pressing (HIP), was used to produce a refined, equilibrium two-phase microstructure. Quasi-static compression tests as a function of temperature were performed on both alloy types. Different deformation mechanisms were encountered based upon temperature and microstructure.

Relationships between individual behaviour and morphometry under different experimental conditions of temperature and feeding in glass eels (Anguilla anguilla

Directory of Open Access Journals (Sweden)

A. Bardonnet

2008-01-01

Full Text Available After Anguilla anguilla larvae reach the European coast, metamorphosing glass eels exhibit an estuarine migration phase and can potentially colonize the continental area. Associated behaviours to upstream movement in estuary and river basin differ strongly: passive tidal transport in estuary, active swimming beyond the upstream tidal limit. Moreover, the migratory behaviour may shift towards a density-dependent dispersal beyond this limit. A positive relationship has previously been established between glass eels’ body condition and migratory behaviour in estuary and also higher in the river basin. An experiment was settled to test for the density-dependent versus migratory behaviour under controlled conditions. The relationships between some behaviours (swimming, grouping, feeding, and aggressiveness and body condition was investigated at the individual level. Two controlled factors were crossed, leading to four combinations of high and low levels of food and temperature. The high level of food led to a lesser loss in body condition. Swimming activity was positively related to initial body condition and loss in body condition, but these two variables were not related to aggressiveness. We conclude that the density-dependent dispersal hypothesis was not reinforced by these present results.

Relationships between individual behaviour and morphometry under different experimental conditions of temperature and feeding in glass eels (Anguilla anguilla

Directory of Open Access Journals (Sweden)

Bardonnet A.

2009-02-01

Full Text Available After Anguilla anguilla larvae reach the European coast, metamorphosing glass eels exhibit an estuarine migration phase and can potentially colonize the continental area. Associated behaviours to upstream movement in estuary and river basin differ strongly: passive tidal transport in estuary, active swimming beyond the upstream tidal limit. Moreover, the migratory behaviour may shift towards a density-dependent dispersal beyond this limit. A positive relationship has previously been established between glass eels’ body condition and migratory behaviour in estuary and also higher in the river basin. An experiment was settled to test for the density-dependent versus migratory behaviour under controlled conditions. The relationships between some behaviours (swimming, grouping, feeding, and aggressiveness and body condition was investigated at the individual level. Two controlled factors were crossed, leading to four combinations of high and low levels of food and temperature. The high level of food led to a lesser loss in body condition. Swimming activity was positively related to initial body condition and loss in body condition, but these two variables were not related to aggressiveness. We conclude that the density-dependent dispersal hypothesis was not reinforced by these present results.

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

CERN Document Server

Kraft, M

2003-01-01

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

Phase changing nanocomposites for low temperature thermal energy storage and release

Directory of Open Access Journals (Sweden)

A. Dorigato

2017-09-01

Full Text Available The aim of this paper is to develop new elastomeric phase change materials (PCM for the thermal energy storage/release below room temperature. In particular, poly(cyclooctene (PCO/paraffin blends filled with various concentrations of carbon nanotubes (CNTs, were prepared by a melt compounding process. The microstructural, thermo-mechanical and electrical properties of the resulting materials were investigated. The microstructure of these materials was characterized by the presence of paraffin domains inside the PCO, and CNTs were located only inside the paraffin domains in forms of aggregated clusters. DSC tests evidenced the existence of two distinct crystallization peaks at –10 and at 6 °C, respectively associated to the paraffin and the PCO phases, indicating that both the polymeric constituents are thermally active below room temperature. Moreover, CNT addition did not substantially alter the melting/crystallization properties of the material. Noticeable improvements of the mechanical properties and of the electrical conductivity with respect to the neat PCO/paraffin blend could be obtained upon CNT addition, and also thermal conductivity/diffusivity values were considerably enhanced above the percolation threshold. Finite element modeling demonstrated the efficacy of the prepared nanocomposites for applications in the thermal range from –30 to 6 °C.

Temperature-dependent thermal properties of a paraffin phase change material embedded with herringbone style graphite nanofibers

International Nuclear Information System (INIS)

Warzoha, Ronald J.; Weigand, Rebecca M.; Fleischer, Amy S.

2015-01-01

Highlights: • The thermal properties of a PCM with nanofibers are determined. • The solid-phase thermal conductivity scales exponentially with volume fraction. • The liquid-phase thermal conductivity is only enhanced beyond a critical percolation threshold. • The nanoscale interface resistance depends on the nanoparticle’s dimensionality. • The thermal diffusivity and volumetric heat capacity of the nanoenhanced PCMs are found. - Abstract: In many studies, carbon nanoparticles with high values of thermal conductivity (10–3000 W/m K) have been embedded into phase change thermal energy storage materials (PCMs) in order to enhance their bulk thermal properties. While a great deal of work to date has focused on determining the effect of these nanoparticles on a PCM’s solid phase thermal properties, little is known about their effect on its liquid phase thermal properties. Thus, in this study, the effect of implanting randomly oriented herringbone style graphite nanofibers (HGNF, average diameter = 100 nm, average length = 20 μm) on the bulk thermal properties of an organic paraffin PCM (IGI 1230A, T melt = 329.15 K) in both the solid and liquid phase is quantified. The bulk thermal conductivity, volumetric heat capacity and thermal diffusivity of HGNF/PCM nanocomposites are obtained as a function of temperature and HGNF volume loading level. It is found that the property enhancement varies significantly depending on the material phase. In order to explain the difference between solid and liquid phase thermal properties, heat flow at the nanoparticle–PCM and nanoparticle–nanoparticle interfaces is examined as a function of HGNF loading level and temperature. To do this, the solid and liquid phase thermal boundary resistances (TBRs) between the nanoparticles and the surrounding PCM and/or between contacting nanoparticles are found. Results suggest that the TBR at the HGNF–PCM interface is nearly double the TBR across the HGNF–HGNF interface in

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.

In situ Raman spectroscopy of phase transformation in CrOx-Y2O3 system at elevated temperatures

International Nuclear Information System (INIS)

Xing Liqiong; Lu Jiqing; Bi Qingyuan; Pu Zhiying; Guo Ming; Wang Yuejuan; Luo Mengfei

2010-01-01

A CrO x -Y 2 O 3 sample was prepared by a deposition-precipitation method and phase transformation of the sample under N 2 and air atmospheres was characterized by in situ Raman spectroscopy and X-ray diffraction (XRD) techniques. It was found that when the CrO x -Y 2 O 3 sample was heated, CrO 3 transformed to YCrO 4 and then to YCrO 3 and Cr 2 O 3 . Also, the transformation started from the surface region of the sample and then extended to the bulk, due to the fact that the phase transformation was detected by Raman spectroscopy at lower temperature compared to that by XRD. In addition, both atmosphere and temperature had influence on the phase transformation in the surface region, while the phase transformation in the bulk was merely dependent on the temperature. It was also found that low oxidation state Cr(III) species on the surface could be re-oxidized to high oxidation state Cr(V) or Cr(VI) species when the thermal treated sample was exposed to ambient air.

Evaluating the Coda Phase Delay Method for Determining Temperature Ratios in Windy Environments

Energy Technology Data Exchange (ETDEWEB)

Albert, Sarah [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bowman, Daniel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Rodgers, Arthur [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Seastrand, Douglas [National Security Technologies, LLC. (NSTec), Las Vegas, NV (United States)

2017-07-01

We evaluate the acoustic coda phase delay method for estimating changes in atmospheric phenomena in realistic environments. Previous studies verifying the method took place in an environment with negligible wind. The equation for effective sound speed, which the method is based upon, shows that the influence of wind is equal to the square of temperature. Under normal conditions, wind is significant and therefore cannot be ignored. Results from this study con rm the previous statement. The acoustic coda phase delay method breaks down in non-ideal environments, namely those where wind speed and direction varies across small distances. We suggest that future studies make use of gradiometry to better understand the effect of wind on the acoustic coda and subsequent phase delays.

Transmitted wavefront error of a volume phase holographic grating at cryogenic temperature.

Science.gov (United States)

Lee, David; Taylor, Gordon D; Baillie, Thomas E C; Montgomery, David

2012-06-01

This paper describes the results of transmitted wavefront error (WFE) measurements on a volume phase holographic (VPH) grating operating at a temperature of 120 K. The VPH grating was mounted in a cryogenically compatible optical mount and tested in situ in a cryostat. The nominal root mean square (RMS) wavefront error at room temperature was 19 nm measured over a 50 mm diameter test aperture. The WFE remained at 18 nm RMS when the grating was cooled. This important result demonstrates that excellent WFE performance can be obtained with cooled VPH gratings, as required for use in future cryogenic infrared astronomical spectrometers planned for the European Extremely Large Telescope.

PVA assisted low temperature anatase to rutile phase transformation (ART) and properties of titania nanoparticles

International Nuclear Information System (INIS)

Mondal, Shrabani; Madhuri, Rashmi; Sharma, Prashant K.

2015-01-01

Anatase to rutile phase transformation (ART) of titania nanoparticles is observed at very low temperature (180 °C) just by introducing polyvinyl alcohol (PVA) during co-precipitation followed by hydrothermal synthesis. The detailed investigations pertaining to the structural, optical and electrochemical properties of the nanosized titania and titania/PVA nanohybrid has been carried out. The crystallite size and crystal structure is confirmed using X-ray diffraction (XRD). Transmission electron microscopic (TEM) image reveals formation of spherical NPs in both the cases. Identification of functional groups is done using Fourier transform infrared spectroscopy (FTIR). The photoluminescence studies showed that emission slightly shifts towards higher wavelength side with remarkable decrease in intensity for TiO 2 /PVA nanocomposite (rutile samples). The remarkable decrease in PL intensity in TiO 2 /PVA nanocomposite (rutile samples) is explained considering the surface passivation during growth process. Ion transportation is monitored via Cyclic voltammetric (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements. A significant enhancement of peak cathodic current in case of nanocomposite modified electrode is observed. It is assumed that TiO 2 /PVA (rutile) nanoparticles provided the conducting path for the electrons and hence enhanced the electrochemical reaction. - Graphical abstract: Present work reports anatase to rutile phase transformation (ART) of titania nanoparticles at very low temperature (180 °C) just by introducing polyvinyl alcohol (PVA) during co-precipitation followed by hydrothermal synthesis. - Highlights: • Low temperature phase transformation of TiO 2 nanoparticles from anatase to rutile. • Role of PVA in phase transformation. • Synthesis of spherical shaped uniformly distributed PVA capped TiO 2 NPs. • Explained the charge transfer process among anatase to rutile phase transformation via luminescence studies. • Enhanced

Stability of operation versus temperature of a three-phase clock-driven chaotic circuit

International Nuclear Information System (INIS)

Zhou Ji-Chao; Son Hyunsik; Song Han Jung; Kim Namtae

2013-01-01

We evaluate the influence of temperature on the behavior of a three-phase clock-driven metal—oxide—semiconductor (MOS) chaotic circuit. The chaotic circuit consists of two nonlinear functions, a level shifter, and three sample and hold blocks. It is necessary to analyze a CMOS-based chaotic circuit with respect to variation in temperature for stability because the circuit is sensitive to the behavior of the circuit design parameters. The temperature dependence of the proposed chaotic circuit is investigated via the simulation program with integrated circuit emphasis (SPICE) using 0.6-μm CMOS process technology with a 5-V power supply and a 20-kHz clock frequency. The simulation results demonstrate the effects of temperature on the chaotic dynamics of the proposed chaotic circuit. The time series, frequency spectra, bifurcation phenomena, and Lyapunov exponent results are provided. (general)

Experiment study about phase transition characteristics of CO{sub 2} in low-permeable porous media

Energy Technology Data Exchange (ETDEWEB)

Guo, P.; Wang, J.; Luo, Y. [State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu (China); Southwest Petroleum Univ., Chengdu (China); Fan, J.M. [PetroChina, Xian (China). Ultra-low Permeability Reservoir Research Inst.

2009-07-01

This paper described an experimental study conducted to characterize phase changes in carbon dioxide (CO{sub 2}) that occur during CO{sub 2} sequestration and enhanced oil recovery (EOR) processes. An ultrasonic testing method was used to determine the influence of pressure and temperature on core fluids. Phase transitions were characterized by collecting time series of ultrasonic signals in a data acquisition system and calculating the correlation dimension of the phase space. A correlation dimension analysis method was used with a fractal theory to develop correlation curves for the phase transition characteristics of CO{sub 2} in porous media. The study demonstrated that below a critical temperature, the existence of porous media can increase the phase transition point of CO{sub 2}. Above the critical temperature, the existence of porous media decreased the inflection point in the pressure-volume relationship curve for CO{sub 2}. Time difference changes were also more apparent above the critical temperature. 11 refs., 2 tabs., 11 figs.

High temperature series expansions with a multiple-exchange Hamiltonian for the bcc and hcp phases of solid 3He

International Nuclear Information System (INIS)

Roger, M.; Suaudeau, E.; Bernier, M.E.R.

1987-08-01

High temperature series expansions with a multiple-exchange Hamiltonian are performed to fourth order in arbitrary magnetic field for both phases of solid 3 He. The susceptibility series are analysed with Pade approximants and compared with recent experimental results. For the hcp phase we estimate the ferromagnetic ordering temperature from susceptibility series and discuss the influence of four-particle exchange in lowering the transition