The High Temperature Resistivity of Ba2YCu3O7-x

Science.gov (United States)

Xingkui, Zhang; Shining, Zhu; Hao, Wang; Shiyuan, Zhang; Su, Ye; Ningshen, Zhou; Ziran, Xu

The high temperature resistivity (ρ), thermogravimetry (TG) and derivative thermogravimetry (DTG) have been used to characterize superconductor Ba2YCu3O7-x (BYCO) in O2, air and N2. The resistivity is linear from room temperature to 350°C and then deviate from linearity with oxygen evolution, the derivative of resistivity dρ/dT increases abruptly near orthorhombic to tetragonal phase transition. These phenomena can give good explanations for a two-band Drude model.

Transition conductivity study of high temperature superconductor compounds: the role of fluctuations; Etude de la transition resistive sur des composes supraconducteurs a haute temperature critique le role des fluctuations

Energy Technology Data Exchange (ETDEWEB)

Pagnon, V

1991-04-01

This memory subject is the transition conductivity study of high temperature superconductors in corelation with their anisotropy. Systematic conductivity measurements were made on YBaCuO and BaSrCaCuO in relation with temperature from 4.2 K to 1200 K, and with a magnetic field up to 8 T in several directions. Oxygen order has an effect on the characteristics at YBaCuO transition conductivity. The activation energy for oxygen absorption is about 0.5eV. One method of analysis of the conductivity fluctuations about the transition temperature is proposed. Two separate rates are noticeable in YBaCuO compound. The 3 D fluctuations rate in the immediate neighbourghood of the transition lets place to the 2 D fluctuations rate at high temperature. Transitions temperatures governing each rate are different, that`s incompatible with the formula proposed by Lawrence and Doniach. On the other hand, the analogy with quasi-2 D magnetic systems seems more relevant. A magnetic field application or a lowering of oxygen concentration removes the 3 D fluctuations rate. Non ohmic effects observed at the transition conductivity foot are analysis as a non-linear 2 D excitation manifestation of the supraconductive phase. Finally, by measurements on strontium doped YBaCuO crystals, we confirm a metal-insulator transition along the C-Axe when oxygen concentration reduces. This is connected with the specific heat jump. All these results uplighten the fundamental bidimensional character of high transition temperature superconductivity.

Online junction temperature measurement via internal gate resistance during turn-on

DEFF Research Database (Denmark)

Baker, Nick; Munk-Nielsen, Stig; Liserre, Marco

2014-01-01

A new method for junction temperature measurement of power semiconductor switches is presented. The measurement exploits the temperature dependent resistance of the temperature sensitive electrical parameter (TSEP): the internal gate resistance. This dependence can be observed during the normal...... switching transitions of an IGBT or MOSFET, and as a result the presented method uses the integral of the gate voltage during the turn-on delay. A measurement circuit can be integrated into a gate driver with no modification to converter or gate driver operation and holds significant advantages over other...

Temperature effect on crack resistance and fracture micromechanisms in tungsten-copper pseudoalloy

International Nuclear Information System (INIS)

Babak, A.V.; Gopkalo, E.E.; Krasovskij, A.Ya.; Nadezhdin, G.N.; Uskov, E.I.

1988-01-01

Results of the mechanical- and-physical study of peculiarities of the tungsten-copper pseudoalloy fracture in the temperature range of 293-2273 K are presented. It is shown that the studied material possesses maximum crack resistance in the vicinity of the upper temperature range boundary of the ductile-brittle transition and minimum resistance to cracks propagation when it contains melted copper. It is established that the peculiarities of changes in crack-resistance correspond to peculiarities of fracture micromechanisms for tungsten-copper pseudoalloy in the studied tempearture range

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.

Depression of the Superfluid Transition Temperature in 4He by a Heat Flow

International Nuclear Information System (INIS)

Yin Liang; Qi Xin; Lin Peng

2014-01-01

The depression of the superfluid transition temperature T λ in 4 He by a heat flow Q is studied. A small sealed cell with a capillary is introduced and a stable and flat superfluid transition temperature plateau is easily obtained by controlling the temperature of the variable-temperature platform and the bottom chamber of the sealed cell. Owing to the depression effect of the superfluid transition temperature by the heat flow, the heat flow through the capillary is changed by the temperature control to obtain multiple temperature plateaus of different heat flows. The thermometer self-heating effect, the residual heat leak of the 4.2 K environment, the temperature difference on the He II liquid column, the Kapiza thermal resistance between the liquid helium and the copper surface of the sealed cell, the temperature gradient of the sealed cell, the static pressure of the He II liquid column and other factors have influence on the depression effect and the influence is analyzed in detail. Twenty experiments of the depression of the superfluid transition temperature in 4 He by heat flow are made with four sealed cells in one year. The formula of the superfluid transition temperature pressured by the heat flow is T λ (Q) = −0.00000103Q + 2.1769108, and covers the range 229 ≤ Q ≤ 6462 μW/cm 2

Fatigue Resistance of the Grain Size Transition Zone in a Dual Microstructure Superalloy Disk

Science.gov (United States)

Gabb, T. P.; Kantzos, P. T.; Telesman, J.; Gayda, J.; Sudbrack, C. K.; Palsa, B. S.

2010-01-01

Mechanical property requirements vary with location in nickel-based superalloy disks. To maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored microstructures. In this study, a specialized heat treatment method was applied to produce varying grain microstructures from the bore to the rim portions of a powder metallurgy processed nickel-based superalloy disk. The bore of the contoured disk consisted of fine grains to maximize strength and fatigue resistance at lower temperatures. The rim microstructure of the disk consisted of coarse grains for maximum resistance to creep and dwell crack growth at high temperatures up to 704 C. However, the fatigue resistance of the grain size transition zone was unclear, and needed to be evaluated. This zone was located as a band in the disk web between the bore and rim. Specimens were extracted parallel and transverse to the transition zone, and multiple fatigue tests were performed at 427 and 704 C. Mean fatigue lives were lower at 427 C than for 704 C. Specimen failures often initiated at relatively large grains, which failed on crystallographic facets. Grain size distributions were characterized in the specimens, and related to the grains initiating failures as well as location within the transition zone. Fatigue life decreased with increasing maximum grain size. Correspondingly, mean fatigue resistance of the transition zone was slightly higher than that of the rim, but lower than that of the bore. The scatter in limited tests of replicates was comparable for all transition zone locations examined.

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 disorder and its effect on the superconducting transition temperature in the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br

International Nuclear Information System (INIS)

Su, X.; Zuo, F.; Schlueter, J.A.; Kelly, M.E.; Williams, J.M.

1998-01-01

In this paper, we report direct evidence of a structural transition in the organic superconductor κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br near 80 K and the effect of disorder on the superconducting transition temperature. By cooling the sample from above 80 K, the interlayer magnetoresistance displays a bumplike feature, which increases sharply with increasing cooling rate. The rapidly cooled sample has a much larger resistivity and a lower transition temperature, which decreases linearly with increasing resistivity near the transition temperature. We propose that rapid cooling quenches the sample into a disordered state. Localized moments in the disordered state reduce the superconducting transition temperature. copyright 1998 The American Physical Society

Organizational Transition and Change Resistance

Directory of Open Access Journals (Sweden)

Ciprian Nicolescu

2006-09-01

Full Text Available The paper focuses on the very important atopic of organizational transition and change resistance. It is divided in four parts. The first part deals with transition inevitability and its content in the change process. The second part of the paper refers to the change resistance. After a short presentation of a recent approach of this topic, elaborated by Rick Maurer, the authors present their point of view, identifying 14 main causes refering to the main factors involved in the organizational transition. In the third part, authors have formulated a set of key elements which should be taken into consideration in order to achieve a rapid and succesful organizational changes. These key elements are valable for any type of organization – entreprise, institution, locality, region, country a.s.a. The last part of the study deals with conflicts approach, which appear almost always during organizational transition. The conflicts are separated in three categories and for whom are presented the methodes recommended in order to solve them with good results.

Organizational Transition and Change Resistance

Directory of Open Access Journals (Sweden)

Ovidiu Nicolescu

2006-07-01

Full Text Available The paper focuses on the very important atopic of organizational transition and change resistance. It is divided in four parts. The first part deals with transition inevitability and its content in the change process. The second part of the paper refers to the change resistance. After a short presentation of a recent approach of this topic, elaborated by Rick Maurer, the authors present their point of view, identifying 14 main causes refering to the main factors involved in the organizational transition. In the third part, authors have formulated a set of key elements which should be taken into consideration in order to achieve a rapid and succesful organizational changes. These key elements are valable for any type of organization – entreprise, institution, locality, region, country a.s.a. The last part of the study deals with conflicts approach, which appear almost always during organizational transition. The conflicts are separated in three categories and for whom are presented the methodes recommended in order to solve them with good results.

A study on heat resistance of high temperature resistant coating

Energy Technology Data Exchange (ETDEWEB)

Zhang, Liping; Wang, Xueying; Zhang, Qibin; Qin, Yanlong; Lin, Zhu [Research Institute of Engineering Technology of CNPC, Tianjin (China)

2005-04-15

A high temperature resistant coating has been developed, which is mainly for heavy oil production pipes deserved the serious corrosion. The coating has excellent physical and mechanical performance and corrosion resistance at room and high temperature. In order to simulate the underground working condition of heavy oil pipes,the heat resistance of the high temperature resistant coating has been studied. The development and a study on the heat resistance of the DHT high temperature resistance coating have been introduced in this paper

A study on heat resistance of high temperature resistant coating

International Nuclear Information System (INIS)

Zhang, Liping; Wang, Xueying; Zhang, Qibin; Qin, Yanlong; Lin, Zhu

2005-01-01

A high temperature resistant coating has been developed, which is mainly for heavy oil production pipes deserved the serious corrosion. The coating has excellent physical and mechanical performance and corrosion resistance at room and high temperature. In order to simulate the underground working condition of heavy oil pipes,the heat resistance of the high temperature resistant coating has been studied. The development and a study on the heat resistance of the DHT high temperature resistance coating have been introduced in this paper

Low temperature resistivity plateau and non-saturating magnetoresistance in Type-II Weyl semimetal WP2

Science.gov (United States)

Nagpal, V.; Kumar, P.; Sudesh, Patnaik, S.

2018-04-01

We have studied the resistivity and magnetoresistance (MR) properties of the recently predicted type-II Weyl semimetal WP2. Polycrystalline WP2 is synthesized using solid state reaction and crystallizes in an orthorhombic structure with the Cmc21 spacegroup. The temperature dependent resistivity is enhanced with the application of magnetic field and a resistivity plateau is observed at low temperatures. We find a small dip in resistivity around 30K at 5T field suggesting that there might be a metal-insulator-like transition at higher magnetic fields. A non-saturating magnetoresistance is observed at low temperatures with maximum MR ˜ 94% at 2K and 6T. The value of MR decreases with the increase in temperature. We see a deviation from Kohler's power law which implies that the system comprises of two types of charge carriers.

Thermophysical data for various transition metals at high temperatures obtained by a submicrosecond-pulse-heating method

International Nuclear Information System (INIS)

Seydel, U.; Bauhof, H.; Fucke, W.; Wadle, H.

1979-01-01

Thermophysical data for several transition metals are reported including enthalpies, electric resistivities, and specific volumes at the melting transition, and volume expansion coefficients and heat capacities in the liquid phase. Values for the critical temperatures, pressures, and volumes are given for molybdenum and tungsten. All data have been obtained by a submicrosecond-pulse-heating method. (author)

Critical-temperature inhomogeneities and resistivity rounding in copper oxide superconductors

International Nuclear Information System (INIS)

Maza, J.; Vidal, F.

1991-01-01

By using effective-medium approaches, we obtain the onset of the electrical-resistivity rounding, above the normal-superconducting transition, associated with inhomogeneities of the mean-field critical temperature T c0 at scales larger than the superconducting correlation length. These results are compared with available data in single-crystal and single-phase (to within 4%) polycrystalline YBa 2 Cu 3 O 7-δ samples. This comparison shows that the measured resistivity rounding cannot be explained by these types of local T c0 inhomogeneities. Complementarily, our calculations allow us to check some proposals on T c0 inhomogeneities associated with local sample strains or oxygen-content variations. The interplay between T c0 inhomogeneities and superconducting order-parameter fluctuations (SCOPF) leads to the conclusion that in the mean-field-like region (MFR) above the superconducting transition, the T c0 inhomogeneity contribution to the measured resistivity rounding in high-quality (single-phase) cuprate oxide superconductors is negligible. In contrast, our analysis confirms that in the MFR these effects may be explained quantitatively on the grounds of the Lawrence-Doniach theory for SCOPF

Room temperature resistive state switching with hysteresis in GdMnO3 thin film with low threshold voltage

International Nuclear Information System (INIS)

Nath, Rajib; Raychaudhuri, A. K.; Mukovskii, Ya. M.; Andreev, N.; Chichkov, Vladimir

2014-01-01

In this paper, we report a room temperature resistive state switching with hysteresis, in a thin film of GdMnO 3 grown on NdGaO 3 substrate. The switched states have a resistance ratio ≈10 3 . The switching is unipolar in nature, with a low set voltage <3 V, while the reset voltage <0.3 V. The switching occurs between a high resistance polaronic insulating state and a low resistance metallic state. The resistance state transition has been ascribed to an electronic mechanism that originates from co-existing phases (created by charge disproportionation) that can undergo a percolative transition enabled by the applied bias

Upper critical fields and superconducting transition temperatures of some zirconium-base amorphous transition-metal alloys

International Nuclear Information System (INIS)

Karkut, M.G.; Hake, R.R.

1983-01-01

Superconducting upper critical fields H/sub c/2(T), transition temperatures T/sub c/, and normal-state electrical resistivities rho/sub n/ have been measured in the amorphous transition-metal alloy series Zr/sub 1-z/Co/sub x/, Zr/sub 1-x/Ni/sub x/, (Zr/sub 1-x/Ti/sub x/)/sub 0.78/Ni/sub 0.22/, and (Zr/sub 1-x/Nb/sub x/)/sub 0.78/Ni/sub 0.22/. Structural integrity of these melt-spun alloys is indicated by x-ray, density, bend-ductility, normal-state electrical resistivity, superconducting transition width, and mixed-state flux-pinning measurements. The specimens display T/sub c/ = 2.1--3.8 K, rho/sub n/ = 159--190 μΩ cm, and Vertical Bar(dH/sub c/2/dT)cVertical Bar = 28--36 kG/K. These imply electron mean free paths lroughly-equal2--6 A, zero-temperature Ginzburg-Landau coherence distances xi/sub G/0roughly-equal50--70 A, penetration depths lambda/sub G/0roughly-equal(7--10) x 10 3 A, and extremely high dirtiness parameters xi 0 /lroughly-equal300--1300. All alloys display H/sub c/2(T) curves with negative curvature and (with two exceptions) fair agreement with the standard dirty-limit theory of Werthamer, Helfand, Hohenberg, and Maki (WHHM) for physically reasonable values of spin-orbit-coupling induced, electron-spin-flip scattering time tau/sub so/. This is in contrast to the anomalously elevated H/sub c/2(T) behavior which is nearly linear in T that is observed by some, and the unphysically low-tau/sub so/ fits to WHHM theory obtained by others, for various amorphous alloys

Electric field-triggered metal-insulator transition resistive switching of bilayered multiphasic VOx

Science.gov (United States)

Won, Seokjae; Lee, Sang Yeon; Hwang, Jungyeon; Park, Jucheol; Seo, Hyungtak

2018-01-01

Electric field-triggered Mott transition of VO2 for next-generation memory devices with sharp and fast resistance-switching response is considered to be ideal but the formation of single-phase VO2 by common deposition techniques is very challenging. Here, VOx films with a VO2-dominant phase for a Mott transition-based metal-insulator transition (MIT) switching device were successfully fabricated by the combined process of RF magnetron sputtering of V metal and subsequent O2 annealing to form. By performing various material characterizations, including scanning transmission electron microscopy-electron energy loss spectroscopy, the film is determined to have a bilayer structure consisting of a VO2-rich bottom layer acting as the Mott transition switching layer and a V2O5/V2O3 mixed top layer acting as a control layer that suppresses any stray leakage current and improves cyclic performance. This bilayer structure enables excellent electric field-triggered Mott transition-based resistive switching of Pt-VOx-Pt metal-insulator-metal devices with a set/reset current ratio reaching 200, set/reset voltage of less than 2.5 V, and very stable DC cyclic switching upto 120 cycles with a great set/reset current and voltage distribution less than 5% of standard deviation at room temperature, which are specifications applicable for neuromorphic or memory device applications. [Figure not available: see fulltext.

Dielectric determination of the glass transition temperature (T sub g)

Science.gov (United States)

Ries, Heidi R.

1990-01-01

The objective is to determine the glass transition temperature of a polymer using a dielectric dissipation technique. A peak in the dissipation factor versus temperature curve is expected near the glass transition temperature T sub g. It should be noted that the glass transition is gradual rather than abrupt, so that the glass transition temperature T sub g is not clearly identifiable. In this case, the glass transition temperature is defined to be the temperature at the intersection point of the tangent lines to the dissipation factor versus temperature curve above and below the transition region, as illustrated.

High temperature phase transitions without infrared divergences

International Nuclear Information System (INIS)

Tetradis, N.; Wetterich, C.

1993-09-01

The most commonly used method for the study of high temperature phase transitions is based on the perturbative evaluation of the temperature dependent effective potential. This method becomes unreliable in the case of a second order or weakly first order phase transition, 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. We report 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. An independent check of the results is obtained in the large N limit, and contact with the perturbative approach is established through the study of the Schwinger-Dyson equations. (orig.)

Antibiotic resistance increases with local temperature

Science.gov (United States)

MacFadden, Derek R.; McGough, Sarah F.; Fisman, David; Santillana, Mauricio; Brownstein, John S.

2018-06-01

Bacteria that cause infections in humans can develop or acquire resistance to antibiotics commonly used against them1,2. Antimicrobial resistance (in bacteria and other microbes) causes significant morbidity worldwide, and some estimates indicate the attributable mortality could reach up to 10 million by 20502-4. Antibiotic resistance in bacteria is believed to develop largely under the selective pressure of antibiotic use; however, other factors may contribute to population level increases in antibiotic resistance1,2. We explored the role of climate (temperature) and additional factors on the distribution of antibiotic resistance across the United States, and here we show that increasing local temperature as well as population density are associated with increasing antibiotic resistance (percent resistant) in common pathogens. We found that an increase in temperature of 10 °C across regions was associated with an increases in antibiotic resistance of 4.2%, 2.2%, and 2.7% for the common pathogens Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus. The associations between temperature and antibiotic resistance in this ecological study are consistent across most classes of antibiotics and pathogens and may be strengthening over time. These findings suggest that current forecasts of the burden of antibiotic resistance could be significant underestimates in the face of a growing population and climate change4.

A universal reduced glass transition temperature for liquids

Science.gov (United States)

Fedors, R. F.

1979-01-01

Data on the dependence of the glass transition temperature on the molecular structure for low-molecular-weight liquids are analyzed in order to determine whether Boyer's reduced glass transition temperature (1952) is a universal constant as proposed. It is shown that the Boyer ratio varies widely depending on the chemical nature of the molecule. It is pointed out that a characteristic temperature ratio, defined by the ratio of the sum of the melting temperature and the boiling temperature to the sum of the glass transition temperature and the boiling temperature, is a universal constant independent of the molecular structure of the liquid. The average value of the ratio obtained from data for 65 liquids is 1.15.

Resistive transition of two-dimensional arrays of proximity-effect Josephson junctions

International Nuclear Information System (INIS)

Abraham, D.W.

1983-01-01

Results of measurements on large arrays of PbBi/Cu proximity-effect junctions are presented. Extrapolation of the critical current measured at low temperature to the region at and above T/sub c/ allows us to describe the initial drop in resistance by a simple model of the proximity effect, and also to define an effective temperature T' = E/sub J/(T/sub c/)T/E/sub J/(T) for describing the vortex-unbinding transition. This extrapolation has also allowed comparison of the magnitude of the universal jump in the renormalized coupling strength E/sub J/(T) with prediction, after allowance for renormalization effects. A simple decomposition of the vortex population above T/sub c/ into a sum of thermally-generated and currents-split components allows us to compare data taken at finite voltage sensitivity with theory. This idea is used to understand the broadened universal scaling of this data in a form consistent with the theory of Halperin and Nelson, suitably modified for array samples. Except for temperatures very near the transition temperature, these results can differ significantly from the continuum results of Halperin and Nelson and may be more appropriate for description of junction arrays and some granular films. New experimental data are also presented which show a periodic variation of the resistance of these arrays with the magnetic flux per cell in units of the flux quantum, including a secondary minimum at the half-quantum points. A simple model is presented which accounts for the existence, shape, and magnitude of this periodic variation in terms of vortex core energies. Observations of the current dependence of this periodic variation are presented, and a qualitative model of this effect is discussed

Equivalent network for resistance and temperature coefficient of resistance versus temperature and composition of thick resistive films

International Nuclear Information System (INIS)

Kusy, A.

1987-01-01

Two types of elementary resistances in thick resistive films have been considered: (i) constriction resistance R/sub C/ determined by the bulk properties of conducting material and by the geometry of constriction, and (ii) barrier resistance R/sub B/ determined by the parameters of a thermally activated type of tunneling process and by the geometry of the metal-insulator-metal unit. On this basis a resistance network composed of a large number of the two types of resistances has been defined. The network has been considered as being equivalent to thick resistive film (TRF) from the point of view of the resistance and temperature coefficient of resistance (TCR). The parameters of this network have been evaluated by the computer-aided approximation of the experimental data found for RuO 2 -based TRFs. On the basis of the equations derived for the network as well as the results of the approximation process, it can be concluded that the small values of the network TCR result from the superposition of the TCR of the conducting component β/sub C/ and of the temperature coefficient of barrier resistance α/sub B/. In this superposition β/sub C/ is attenuated (by 1--2 orders of magnitude), while α/sub B/ is attenuated by only few percentages. The network has been found to be strongly barrier dominated

Electric field dependence of excess electrical conductivity below transition temperature in thin superconducting lead films

Energy Technology Data Exchange (ETDEWEB)

Ashwini Kumar, P K; Duggal, V P [Delhi Univ. (India). Dept. of Physics and Astrophysics

1976-01-26

Results of measurements of the electric field dependence of the excess electrical conductivity are reported in thin superconducting lead films below the transition temperature. It is observed that the normal state sheet resistance has some effect on the nonlinearity but the theory of Yamaji still fits well to the experimental data.

Dependence of temperature-dependent electrical resistivity of SrIrO3 on hydrostatic pressure to 9.1 kbar

International Nuclear Information System (INIS)

Foroozani, N.; Lim, J.; Li, L.; Cao, G.; Schilling, J.S.

2013-01-01

Non-Fermi-liquid behavior and close proximity to a quantum critical point in the 5d transition metal iridate SrIrO 3 at ambient pressure motivate our search for possible anomalous behavior in its transport properties under pressure. The electrical resistivity in the ab-plane of a single crystal of SrIrO 3 has been measured over the temperature range 1.35–285 K at both ambient and 9.1 kbar hydrostatic pressure. The resistivity decreases slightly over the entire temperature range, but no superconducting transition or changes in the non-Fermi-liquid behavior are observed under pressure. It is estimated that significantly higher pressures are likely required before sizable changes in the properties of SrIrO 3 will occur.

Effect of the Temperature, External Magnetic Field, and Transport Current on Electrical Properties, Vortex Structure Evolution Processes, and Phase Transitions in Subsystems of Superconducting Grains and "Weak Links" of Granular Two-Level High-Temperature Superconductor YBa2Cu3O7-δ

Science.gov (United States)

Derevyanko, V. V.; Sukhareva, T. V.; Finkel', V. A.

2018-03-01

The temperature dependences of the resistivity of granular high-temperature superconductor YBa2Cu3O7-δ ρ( T) are measured at various transverse external magnetic fields 0 ≤ H ext ≤ 100 Oe in the temperature range from the resistivity onset temperature T ρ = 0 to the superconducting transition critical temperature T c at the transport current density from 50 to 2000 mA/cm2. The effect of the external magnetic field and transport current density on the kinetics of phase transitions in both subsystems of granular two-level HTSC ( T = T c2J, T c1g, T c ) is determined. The feasibility of the topological phase transition, i.e., the Berezinsky-Kosterlitz-Thouless transition, in the Josephson medium at T c2J < T BKT < T c1g "in transport current" is established, and its feasibility conditions are studied.

Characterization of the microwave properties of superconducting films with high transition temperature

International Nuclear Information System (INIS)

Richter, W.; Klinger, M.; Daginnus, M.

1989-01-01

In the meantime high quality Y-Ba-Cu-O thin films were produced. The latest results show, that its surface resistances are clearly lower than the values of copper, measured at a temperature of 77 K and up to frequencies of 86 GHz. This examination had the aim to produce high-T c films with a simple and low cost method, to use them as transmission lines at frequencies up to 30 GHz and above. A screen printing process was investigated, and high-T c thick films were fabricated on several substrates. Superconducting transition temperatures up to 80 K (dc zero resistance) were obtained. The films showed no complete magnetic shielding, and its microwave surface resistances were clearly higher than that ones for copper. The a. c. Josephson effect was proved with granular structures of bulk Y-Ba-Cu-O material and with screen printed thick films. Because of its high surface resistances, these thick films are unsuitable for the use as transmission lines at high frequencies. However, the a.c. Josephson effect can be used to manufacture microwave sensors in bulk Y-Ba-Cu-O and screen printed films of Y-Ba-Cu-O, which have a favourable geometric structure. (orig.) With 16 refs., 2 tabs., 24 figs [de

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)

Temperature and concentration dependences of the electrical resistivity for alloys of plutonium with americium under normal conditions

Science.gov (United States)

Tsiovkin, Yu. Yu.; Povzner, A. A.; Tsiovkina, L. Yu.; Dremov, V. V.; Kabirova, L. R.; Dyachenko, A. A.; Bystrushkin, V. B.; Ryabukhina, M. V.; Lukoyanov, A. V.; Shorikov, A. O.

2010-01-01

The temperature and concentration dependences of the electrical resistivity for alloys of americium with plutonium are analyzed in terms of the multiband conductivity model for binary disordered substitution-type alloys. For the case of high temperatures ( T > ΘD, ΘD is the Debye temperature), a system of self-consistent equations of the coherent potential approximation has been derived for the scattering of conduction electrons by impurities and phonons without any constraints on the interaction intensity. The definitions of the shift and broadening operator for a single-electron level are used to show qualitatively and quantitatively that the pattern of the temperature dependence of the electrical resistivity for alloys is determined by the balance between the coherent and incoherent contributions to the electron-phonon scattering and that the interference conduction electron scattering mechanism can be the main cause of the negative temperature coefficient of resistivity observed in some alloys involving actinides. It is shown that the great values of the observed resistivity may be attributable to interband transitions of charge carriers and renormalization of their effective mass through strong s-d band hybridization. The concentration and temperature dependences of the resistivity for alloys of plutonium and americium calculated in terms of the derived conductivity model are compared with the available experimental data.

Practical Considerations for Determination of Glass Transition Temperature of a Maximally Freeze Concentrated Solution.

Science.gov (United States)

Pansare, Swapnil K; Patel, Sajal Manubhai

2016-08-01

Glass transition temperature is a unique thermal characteristic of amorphous systems and is associated with changes in physical properties such as heat capacity, viscosity, electrical resistance, and molecular mobility. Glass transition temperature for amorphous solids is referred as (T g), whereas for maximally freeze concentrated solution, the notation is (T g'). This article is focused on the factors affecting determination of T g' for application to lyophilization process design and frozen storage stability. Also, this review provides a perspective on use of various types of solutes in protein formulation and their effect on T g'. Although various analytical techniques are used for determination of T g' based on the changes in physical properties associated with glass transition, the differential scanning calorimetry (DSC) is the most commonly used technique. In this article, an overview of DSC technique is provided along with brief discussion on the alternate analytical techniques for T g' determination. Additionally, challenges associated with T g' determination, using DSC for protein formulations, are discussed. The purpose of this review is to provide a practical industry perspective on determination of T g' for protein formulations as it relates to design and development of lyophilization process and/or for frozen storage; however, a comprehensive review of glass transition temperature (T g, T g'), in general, is outside the scope of this work.

Theory of the transition temperature of superconducting amorphous transition metals

International Nuclear Information System (INIS)

Zwicknagel, G.

1979-11-01

In the present paper first the transition temperature Tsub(c) is shown to be a local quantity, which depends on the (average) short range order, and second it is demonstrated how to calculate local electronic properties in the framework of a short range order model and the transition temperature of amorphous systems based on accepted structure models of the amorphous state. In chapter I the theoretical basis of this work is presented in brief. The model used to study the role of short range order (in periodically ordered as well as in disordered system) is described in chapter II. The results of this model for the periodically ordered case are compared in chapter III with band structure calculations. In chapter IV it is shown how to establish short range order models for disordered systems and what kind of information can be obtained with respect to the electronic properties. Finally in chapter V it is discussed to what extend the interpretation of the transition temperature Tsub(c) as being determined by short range order effects can be supported by the electronic properties, which are calculated in the chapters III and IV. (orig.) [de

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

DEFF Research Database (Denmark)

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

2003-01-01

Differential scanning calorimetry measurements have revealed different thermal transitions in cod and tuna samples. Transition temperatures detected Lit -11degreesC, -15degreesC and -21degreesC were highly dependent on the annealing temperature. In tuna muscle an additional transition was observed...... at -72degreesC. This transition appeared differently than the thermal events observed at higher temperatures, as it spanned a broad temperature interval of 25degreesC. The transition was comparable to low-temperature glass transitions reported in protein-rich systems. No transition at this low...... temperature was detected in cod samples. The transitions observed at higher temperatures (-11degreesC to -21degreesC) may possibly stein from a glassy matrix containing muscle proteins. However, the presence of a glass transition at - 11degreesC was in disagreement with the low storage stability at -18degrees...

Model for the resistive critical current transition in composite superconductors

International Nuclear Information System (INIS)

Warnes, W.H.

1988-01-01

Much of the research investigating technological type-II superconducting composites relies on the measurement of the resistive critical current transition. We have developed a model for the resistive transition which improves on older models by allowing for the very different nature of monofilamentary and multifilamentary composite structures. The monofilamentary model allows for axial current flow around critical current weak links in the superconducting filament. The multifilamentary model incorporates an additional radial current transfer between neighboring filaments. The development of both models is presented. It is shown that the models are useful for extracting more information from the experimental data than was formerly possible. Specific information obtainable from the experimental voltage-current characteristic includes the distribution of critical currents in the composite, the average critical current of the distribution, the range of critical currents in the composite, the field and temperature dependence of the distribution, and the fraction of the composite dissipating energy in flux flow at any current. This additional information about the distribution of critical currents may be helpful in leading toward a better understanding of flux pinning in technological superconductors. Comparison of the models with several experiments is given and shown to be in reasonable agreement. Implications of the models for the measurement of critical currents in technological composites is presented and discussed with reference to basic flux pinning studies in such composites

Concurrent transition of ferroelectric and magnetic ordering near room temperature.

Science.gov (United States)

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

2011-11-29

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

The influence of the statistical distributed parameters of the shape of the magneto-resistive transition of a HTc superconductor

International Nuclear Information System (INIS)

Grobnic, D.; Popescu, I.M.

1993-01-01

As a result of their granular structure the conductance of ceramic high temperature superconductors depends strongly on the characteristics of the parameter distribution. To study the influence of these distributions of the magneto-resistive transition from normal to superconductive state, a mathematical model was used. This model simulates the superconductor sample, considered as large three-dimensional collection of Josephson tunnel junctions. Each individual junction, according to the values of the parameters that define it, in a given environment (temperature, magnetic field and current density) allows or not the supercurrent to flow with a given probability. The bond percolation problem was solved using a Monte Carlo procedure. To solve the random resistor network formed, a sparse matrix package was used. As parameters that defined Josephson junction which choose the resistance of the normal junction state and the critical temperature of the grain. We considered the normal junction resistance as obeying a log normal distribution and the critical temperature, a Gaussian one. The influences of the relative dispersion of the first distribution and the dispersion of the critical temperature distribution on the shape of the resistivity versus magnetic field was studied. (Author)

High temperature resistant cermet and ceramic compositions

Science.gov (United States)

Phillips, W. M. (Inventor)

1978-01-01

Cermet compositions having high temperature oxidation resistance, high hardness and high abrasion and wear resistance, and particularly adapted for production of high temperature resistant cermet insulator bodies are presented. The compositions are comprised of a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Also disclosed are novel ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride.

Evolution of low-temperature phases in a low-temperature structural transition of a La cuprate

International Nuclear Information System (INIS)

Inoue, Y.; Horibe, Y.; Koyama, Y.

1997-01-01

The microstructure produced by a low-temperature structural phase transition in La 1.5 Nd 0.4 Sr 0.1 CuO 4 has been examined by transmission electron microscopy with the help of imaging plates. The low-temperature transition was found to be proceeded not only by the growth of the Pccn/low-temperature-tetragonal phases nucleated along the twin boundary but also by the nucleation and growth of the phases in the interior of the low-temperature-orthorhombic domain. In addition, because the map of the octahedron tilt as an order parameter is not identical to that of the spontaneous strain accompanied by the transition, the microstructure below the transition is understood to be a very complex mixture of the low-temperature phases. copyright 1997 The American Physical Society

Unexpected Nonlinear Effects in Superconducting Transition-Edge Sensors

Science.gov (United States)

Sadleir, John

2016-01-01

When a normal metal transitions into the superconducting state the DC resistance drops from a finite value to zero over some finite transition width in temperature, current, and magnetic field. Superconducting transition-edge sensors (TESs) operate within this transition region and uses resistive changes to measure deposited thermal energy. This resistive transition is not perfectly smooth and a wide range of TES designs and materials show sub-structure in the resistive transition (as seen in smooth nonmonotonic behavior, jump discontinuities, and hysteresis in the devices current-voltage relation and derivatives of the resistance with respect to temperature, bias current, and magnetic field). TES technology has advanced to the point where for many applications this structure is the limiting factor in performance and optimization consists of finding operating points away from these structures. For example, operating at or near this structure can lead to nonlinearity in the detectors response and gain scale, limit the spectral range of the detector by limiting the usable resistive range, and degrade energy resolution. The origin of much of this substructure is unknown. This presentation investigates a number of possible sources in turn. First we model the TES as a superconducting weak-link and solve for the characteristic differential equations current and voltage time dependence. We find:(1) measured DC biased current-voltage relationship is the time-average of a much higher frequency limit cycle solution.(2) We calculate the fundamental frequency and estimate the power radiated from the TES treating the bias leads as an antennae.(3) The solution for a set of circuit parameters becomes multivalued leading to current transitions between levels.(4)The circuit parameters can change the measure resistance and mask the true critical current. As a consequence the TES resistance surface is not just a function of temperature, current, and magnetic field but is also a

Using electrical resistance tomography to map subsurface temperatures

Science.gov (United States)

Ramirez, Abelardo L.; Chesnut, Dwayne A.; Daily, William D.

1994-01-01

A method is provided for measuring subsurface soil or rock temperatures remotely using electrical resistivity tomography (ERT). Electrical resistivity measurements are made using electrodes implanted in boreholes driven into the soil and/or at the ground surface. The measurements are repeated as some process changes the temperatures of the soil mass/rock mass. Tomographs of electrical resistivity are calculated based on the measurements using Poisson's equation. Changes in the soil/rock resistivity can be related to changes in soil/rock temperatures when: (1) the electrical conductivity of the fluid trapped in the soil's pore space is low, (2) the soil/rock has a high cation exchange capacity and (3) the temperature changes are sufficiently high. When these three conditions exist the resistivity changes observed in the ERT tomographs can be directly attributed to changes in soil/rock temperatures. This method provides a way of mapping temperature changes in subsurface soils remotely. Distances over which the ERT method can be used to monitor changes in soil temperature range from tens to hundreds of meters from the electrode locations.

Using electrical resistance tomography to map subsurface temperatures

Science.gov (United States)

Ramirez, A.L.; Chesnut, D.A.; Daily, W.D.

1994-09-13

A method is provided for measuring subsurface soil or rock temperatures remotely using electrical resistivity tomography (ERT). Electrical resistivity measurements are made using electrodes implanted in boreholes driven into the soil and/or at the ground surface. The measurements are repeated as some process changes the temperatures of the soil mass/rock mass. Tomographs of electrical resistivity are calculated based on the measurements using Poisson's equation. Changes in the soil/rock resistivity can be related to changes in soil/rock temperatures when: (1) the electrical conductivity of the fluid trapped in the soil's pore space is low, (2) the soil/rock has a high cation exchange capacity and (3) the temperature changes are sufficiently high. When these three conditions exist the resistivity changes observed in the ERT tomographs can be directly attributed to changes in soil/rock temperatures. This method provides a way of mapping temperature changes in subsurface soils remotely. Distances over which the ERT method can be used to monitor changes in soil temperature range from tens to hundreds of meters from the electrode locations. 1 fig.

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

Science.gov (United States)

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

2017-10-01

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

Investigation of size-temperature effects in thin f;.lms of transition metals

International Nuclear Information System (INIS)

Loboda, V.B.; Protsenko, I.E.; Smolin, M.D.; Yaremenko, A.V.

1985-01-01

The temperature and size dependences are studied for specific rho and temperature coeficients of resistance of transition metal films obtained and annealed in the 10 -6 - 5x10 -7 Pa vacuum. The size dependence of lambda sub(g)(1-p), rho sub(db), R, r and rhosub(db)sup(v) parameters was calculated using the Tellier, Tosser and Pichard theory. The temperature dependence of the conductivity was investigated in the 80-700 K range. A conclusion is made that all differences between dependences rho(T) for thin and bulk samples may be explained by effects specific for films but presenting no class of new physical effects. The size dependence of the electron-phonon interaction near T>THETAsub(D) and proportionality factors in the approximating equation rho approximately Asub(1.2)xTsup(2) is obtained for Ni films

A low membrane lipid phase transition temperature is associated with a high cryotolerance of Lactobacillus delbrueckii subspecies bulgaricus CFL1.

Science.gov (United States)

Gautier, J; Passot, S; Pénicaud, C; Guillemin, H; Cenard, S; Lieben, P; Fonseca, F

2013-09-01

The mechanisms of cellular damage that lactic acid bacteria incur during freeze-thaw processes have not been elucidated to date. Fourier transform infrared spectroscopy was used to investigate in situ the lipid phase transition behavior of the membrane of Lactobacillus delbrueckii ssp. bulgaricus CFL1 cells during the freeze-thaw process. Our objective was to relate the lipid membrane behavior to membrane integrity losses during freezing and to cell-freezing resistance. Cells were produced by using 2 different culture media: de Man, Rogosa, and Sharpe (MRS) broth (complex medium) or mild whey-based medium (minimal medium commonly used in the dairy industry), to obtain different membrane lipid compositions corresponding to different recovery rates of cell viability and functionality after freezing. The lipid membrane behavior studied by Fourier transform infrared spectroscopy was found to be different according to the cell lipid composition and cryotolerance. Freeze-resistant cells, exhibiting a higher content of unsaturated and cyclic fatty acids, presented a lower lipid phase transition temperature (Ts) during freezing (Ts=-8°C), occurring within the same temperature range as the ice nucleation, than freeze-sensitive cells (Ts=+22°C). A subzero value of lipid phase transition allowed the maintenance of the cell membrane in a relatively fluid state during freezing, thus facilitating water flux from the cell and the concomitant volume reduction following ice formation in the extracellular medium. In addition, the lipid phase transition of freeze-resistant cells occurred within a short temperature range, which could be ascribed to a reduced number of fatty acids, representing more than 80% of the total. This short lipid phase transition could be associated with a limited phenomenon of lateral phase separation and membrane permeabilization. This work highlights that membrane phase transitions occurring during freeze-thawing play a fundamental role in the

Mechanism of high-temperature resistant water-base mud

Energy Technology Data Exchange (ETDEWEB)

Luo, P

1981-01-01

Based on experiments, the causes and laws governing the changes in the performance of water-base mud under high temperature are analyzed, and the requisites and mechanism of treating agents resisting high temperature are discussed. Ways and means are sought for inhibiting, delaying and making use of the effect of high temperature on the performance of mud, while new ideas and systematic views have been expressed on the preparation of treating agents and set-up of a high temperature resistant water-base mud system. High temperature dispersion and high temperature surface inactivation of clay in the mud, as well as their effect and method of utilization are reviewed. Subjects also touched upon include degradation and cross-linking of the high-temperature resistant treating agents, their use and effect. Based on the above, the preparation of a water-base and system capable of resisting 180 to 250/sup 0/C is recommended.

Phase transitions in K-doped MoO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Alves, L. M. S., E-mail: leandro-fisico@hotmail.com; Lima, B. S. de; Santos, C. A. M. dos [Departamento de Engenharia de Materiais, Escola de Engenharia de Lorena-USP, Lorena, São Paulo 12602-810 (Brazil); Rebello, A.; Masunaga, S. H.; Neumeier, J. J. [Department of Physics, Montana State University, P.O. Box 173840, Bozeman, Montana 59717-3840 (United States); Leão, J. B. [NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Dr. MS 6102, Gaithersburg, Maryland 20899-6102 (United States)

2014-05-28

K{sub 0.05}MoO{sub 2} has been studied by x-ray and neutron diffractometry, electrical resistivity, magnetization, heat capacity, and thermal expansion measurements. The compound displays two phase transitions, a first-order phase transition near room temperature and a second-order transition near 54 K. Below the transition at 54 K, a weak magnetic anomaly is observed and the electrical resistivity is well described by a power-law temperature dependence with exponent near 0.5. The phase transitions in the K-doped MoO{sub 2} compound have been discussed for the first time using neutron diffraction, high resolution thermal expansion, and heat capacity measurements as a function of temperature.

Topological transitions at finite temperatures: A real-time numerical approach

International Nuclear Information System (INIS)

Grigoriev, D.Yu.; Rubakov, V.A.; Shaposhnikov, M.E.

1989-01-01

We study topological transitions at finite temperatures within the (1+1)-dimensional abelian Higgs model by a numerical simulation in real time. Basic ideas of the real-time approach are presented and some peculiarities of the Metropolis technique are discussed. It is argued that the processes leading to topological transitions are of classical origin; the transitions can be observed by solving the classical field equations in real time. We show that the topological transitions actually pass via the sphaleron configuration. The transition rate as a function of temperature is found to be in good agreement with the analytical predictions. No extra suppression of the rate is observed. The conditions of applicability of our approach are discussed. The temperature interval where the low-temperature broken phase persists is estimated. (orig.)

Studies of the transition temperature and normal state resistivity of Nb3Ge and Nb films

International Nuclear Information System (INIS)

Lutz, H.; Weismann, H.; Gurvitch, M.; Goland, A.N.; Kammerer, O.F.; Strongin, M.

1976-01-01

Correlations between T/sub c/ and specific features of the normal state resistance vs temperature curves are discussed for both Nb 3 Ge and ion damaged Nb films. Of particular interest is the correlation between T/sub c/ and rho 0 in Nb 3 Ge films

Ultra-sonic testing for brittle-ductile transition temperature of ferritic steels

International Nuclear Information System (INIS)

Nomakuchi, Michiyoshi

1979-01-01

The ultra-sonic testing for the brittle-ductile transition temperature, the USTB test for short, of ferritic steels is proposed in the present paper. And also the application of the USTB test into the nuclear pressure vessel surveillance is discussed. The USTB test is based upon the experimental results in the present work that the ultrasonic pressure attenuation coefficient of a ferritic steel has the evident transition property with its temperature due to the nature from which the brittle-ductile fracture transition property of the steel come and for four ferritic steels the upper boundary temperatute of the region in which the transition of the attenuation coefficient of a steel takes place is 4 to 5 0 C higher than the sub(D)T sub(E), i.e. the transition temperature of the fracture absorption energy of the steel by the DWTT test. The USTB test estimates the crack arrest temperature which is defined to be the fracture transition elastic temperature by the upper boundary temperature. (author)

High temperature resistant nanofiber by bubbfil-spinning

Directory of Open Access Journals (Sweden)

Li Ya

2015-01-01

Full Text Available Heat-resisting nanofibers have many potential applications in various industries, and the bubbfil spinning is the best candidate for mass-production of such materials. Polyether sulfone/zirconia solution with a bi-solvent system is used in the experiment. Experimental result reveals that polyether sulfone/zirconia nanofibers have higher resistance to high temperature than pure polyether sulfone fibers, and can be used as high-temperature-resistant filtration materials.

Room temperature negative differential resistance in terahertz quantum cascade laser structures

Energy Technology Data Exchange (ETDEWEB)

Albo, Asaf, E-mail: asafalbo@gmail.com; Hu, Qing [Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Reno, John L. [Center for Integrated Nanotechnologies, Sandia National Laboratories, MS 1303, Albuquerque, New Mexico 87185-1303 (United States)

2016-08-22

The mechanisms that limit the temperature performance of GaAs/Al{sub 0.15}GaAs-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated LO-phonon scattering and leakage of charge carriers into the continuum. Consequently, the combination of highly diagonal optical transition and higher barriers should significantly reduce the adverse effects of both mechanisms and lead to improved temperature performance. Here, we study the temperature performance of highly diagonal THz-QCLs with high barriers. Our analysis uncovers an additional leakage channel which is the thermal excitation of carriers into bounded higher energy levels, rather than the escape into the continuum. Based on this understanding, we have designed a structure with an increased intersubband spacing between the upper lasing level and excited states in a highly diagonal THz-QCL, which exhibits negative differential resistance even at room temperature. This result is a strong evidence for the effective suppression of the aforementioned leakage channel.

Resistivity features in intercalated graphite compounds with bromine and iodine chloride in the region of structural phase transitions in the layer of intercalate

International Nuclear Information System (INIS)

Ovsyijenko, Yi.V.; Lazarenko, O.A.; Matsuj, L.Yu.; Prokopov, O.Yi.

2013-01-01

In the paper anomalous changes of resistivity in graphite intercalated compounds with iodine chloride and bromine are investigated in the phase transition temperature interval. It is shown that these anomalies are caused by the change of carriers mobility in the phase transitional interval as well as by the origin of ''mobile ions liquids''

Effect of In-situ Cure on Measurement of Glass Transition Temperatures in High-temperature Thermosetting Polymers

Science.gov (United States)

2015-01-01

TEMPERATURES IN HIGH-TEMPERATURE THERMOSETTING POLYMERS 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...illustrated the difficulties inherent in measurement of the glass transition temperature of this high-temperature thermosetting polymer via dynamic...copyright protection in the United States. EFFECT OF IN-SITU CURE ON MEASUREMENT OF GLASS TRANSITION TEMPERATURES IN HIGH-TEMPERATURE THERMOSETTING

Stability of High Temperature Standard Platinum Resistance Thermometers at High Temperatures

OpenAIRE

Y. A. ABDELAZIZ; F. M. MEGAHED

2010-01-01

An investigation of the stability of high temperature standard platinum resistance thermometers HTSPRTs has been carried out for two different designs thermometers (with nominal resistance 0.25 Ω and 2.5 Ω) from two different suppliers. The thermometers were heated for more than 160 hours at temperatures above 960 0C using a vertical furnace with a ceramic block. A study was made of the influence of the heat treatment on the stability of the resistance at the triple point of water, and on the...

Possibility of the vortex-antivortex transition temperature of a thin-film superconductor being renormalized by disorder

International Nuclear Information System (INIS)

Hebard, A.F.; Kotliar, G.

1989-01-01

The universal relation between the Kosterlitz-Thouless transition temperature T/sub c/ and the superfluid sheet density of thin-film superconductors with mean-field transition temperature T/sub c/ 0 results in a monotonically decreasing dependence of the ratio T/sub c//T/sub c0/ on the normal-state sheet resistance R/sub n/. Ambiguity in the experimental definition of R/sub n/ in highly disordered thin-film superconductors is addressed by reexamining previously published data on amorphous composite In/InO/sub x/ films. Arguments are presented in favor of using the zero-temperature value of R/sub n/, a quantity obtained by extrapolation. The dependence of T/sub c//T/sub c0/ on R/sub n/ that results from such a choice is in agreement with theory for dirty superconductors and thus suggests that additional corrections to T/sub c/ in the presence of extreme disorder are not required

Recovery Temperature, Transition, and Heat Transfer Measurements at Mach 5

Science.gov (United States)

Brinich, Paul F.

1961-01-01

Schlieren, recovery temperature, and heat-transfer measurements were made on a hollow cylinder and a cone with axes alined parallel to the stream. Both the cone and cylinder were equipped with various bluntnesses, and the tests covered a Reynolds number range up to 20 x 10(exp 6) at a free-stream Mach number of 4.95 and wall to free-stream temperature ratios from 1.8 to 5.2 (adiabatic). A substantial transition delay due to bluntness was found for both the cylinder and the cone. For the present tests (Mach 4.95), transition was delayed by a factor of 3 on the cylinder and about 2 on the cone, these delays being somewhat larger than those observed in earlier tests at Mach 3.1. Heat-transfer tests on the cylinder showed only slight effects of wall temperature level on transition location; this is to be contrasted to the large transition delays observed on conical-type bodies at low surface temperatures at Mach 3.1. The schlieren and the peak-recovery-temperature methods of detecting transition were compared with the heat-transfer results. The comparison showed that the first two methods identified a transition point which occurred just beyond the end of the laminar run as seen in the heat-transfer data.

Creep resistant high temperature martensitic steel

Energy Technology Data Exchange (ETDEWEB)

Hawk, Jeffrey A.; Jablonski, Paul D.; Cowen, Christopher J.

2017-01-31

The disclosure provides a creep resistant alloy having an overall composition comprised of iron, chromium, molybdenum, carbon, manganese, silicon, nickel, vanadium, niobium, nitrogen, tungsten, cobalt, tantalum, boron, copper, and potentially additional elements. In an embodiment, the creep resistant alloy has a molybdenum equivalent Mo(eq) from 1.475 to 1.700 wt. % and a quantity (C+N) from 0.145 to 0.205. The overall composition ameliorates sources of microstructural instability such as coarsening of M.sub.23C.sub.6carbides and MX precipitates, and mitigates or eliminates Laves and Z-phase formation. A creep resistant martensitic steel may be fabricated by preparing a melt comprised of the overall composition followed by at least austenizing and tempering. The creep resistant alloy exhibits improved high-temperature creep strength in the temperature environment of around 650.degree. C.

Creep resistant high temperature martensitic steel

Science.gov (United States)

Hawk, Jeffrey A.; Jablonski, Paul D.; Cowen, Christopher J.

2015-11-13

The disclosure provides a creep resistant alloy having an overall composition comprised of iron, chromium, molybdenum, carbon, manganese, silicon, nickel, vanadium, niobium, nitrogen, tungsten, cobalt, tantalum, boron, and potentially additional elements. In an embodiment, the creep resistant alloy has a molybdenum equivalent Mo(eq) from 1.475 to 1.700 wt. % and a quantity (C+N) from 0.145 to 0.205. The overall composition ameliorates sources of microstructural instability such as coarsening of M.sub.23C.sub.6 carbides and MX precipitates, and mitigates or eliminates Laves and Z-phase formation. A creep resistant martensitic steel may be fabricated by preparing a melt comprised of the overall composition followed by at least austenizing and tempering. The creep resistant alloy exhibits improved high-temperature creep strength in the temperature environment of around 650.degree. C.

Graphene/phase change material nanocomposites: light-driven, reversible electrical resistivity regulation via form-stable phase transitions.

Science.gov (United States)

Wang, Yunming; Mi, Hongyi; Zheng, Qifeng; Ma, Zhenqiang; Gong, Shaoqin

2015-02-04

Innovative photoresponsive materials are needed to address the complexity of optical control systems. Here, we report a new type of photoresponsive nanomaterial composed of graphene and a form-stable phase change material (PCM) that exhibited a 3 orders of magnitude change in electrical resistivity upon light illumination while retaining its overall original solid form at the macroscopic level. This dramatic change in electrical resistivity also occurred reversibly through the on/off control of light illumination. This was attributed to the reversible phase transition (i.e., melting/recrystallization) behavior of the microscopic crystalline domains present in the form-stable PCM. The reversible phase transition observed in the graphene/PCM nanocomposite was induced by a reversible temperature change through the on/off control of light illumination because graphene can effectively absorb light energy and convert it to thermal energy. In addition, this graphene/PCM nanocomposite also possessed excellent mechanical properties. Such photoresponsive materials have many potential applications, including flexible electronics.

Temperature dependence of contact resistance at metal/MWNT interface

Energy Technology Data Exchange (ETDEWEB)

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

2016-07-11

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

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

Science.gov (United States)

Lappe, Svenja; Mulac, Dennis; Langer, Klaus

2017-01-30

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

Resistive current limiter with high-temperature superconductors. Final report

International Nuclear Information System (INIS)

Schubert, M.

1995-12-01

Fundamental results of the possibility of using high temperature superconductors (HTSC) in resistive fault current limiters are discussed. Measurement of the homogeneity of BSCCO-powder-in-tube materials were made. In addition, investigations of the transition from superconducting to normalconducting state under AC-current conditions were carried out. Based on these results, simulations of HTSC-materials on ceramic substrate were made and recent results are presented. Important results of the investigations are: 1. Current-limiting without external trigger only possible when the critical current density of HTSC exceeds 10 4 A/cm 2 . 2. Inhomogeneities sometimes cause problems with local destruction. This can be solved by parallel-elements or external trigger. 3. Fast current-limiting causes overvoltages which can be reduced by using parallel-elements. (orig.) [de

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

Contribution to the study of superconducting magnets using high transition temperature superconducting materials

International Nuclear Information System (INIS)

Lecrevisse, Thibault

2012-01-01

The new industrial superconductors using high critical temperature compounds offer new possibilities for superconducting magnetism. Indeed they allow higher magnetic field with the same classical cryogenics at 4.2 K on one hand, and on the other hand they also pave the way for superconducting magnets working between 10 K and 30 K. The high temperature superconductors are then needed in order to produce magnetic fields higher than 16 T (case of HTS dipole insert for Large Hadron Collider at CERN) or to increase the specific density stored in one SMES (Superconducting Magnetic Energy Storage, in the case of the SuperSMES ANR Project).Nevertheless the indisputable assets (critical temperature, critical magnetic field, mechanical stresses) brought by the use of High critical temperature superconductors like YBCO, used in superconducting magnets, require to solve some challenges. Their behavior is still badly understood, especially during the resistive transitions. To succeed in protecting these conductors we need a new reflection on protection schemes designed to avoid the thermal and mechanical damages. The answer to the question: 'Can we use those materials in the long run inside superconducting magnets?' is now inescapable.Some answers are given here. The use of the conductors is approached through various experimental studies to understand the material (electrical characterization and modeling of the critical surface) and to define the key stages of high critical temperature superconducting magnets manufacturing (work on the junctions between conductors and pancakes). This study led to the creation of two coils in order to identify the issues related to the use of YBCO tapes. A numerical thermo-electrical model of the high critical temperature superconductor has been developed and a numerical code based on the CEA software CASTEM (Finish Elements Model) allowed to study the resistive transition (or quench) behavior of those conductor and coil. The code has been

Method of determination of temperature and heat resistance of the points on the integrated circuit crystal surface

Directory of Open Access Journals (Sweden)

Popov V. M.

2011-12-01

Full Text Available Method for visualization of integrated circuit (IC surface temperature by means of the liquid crystal film deposited from solution on its surface is proposed. The boundaries of local regions represent isotherms with corresponding phase transitions. On the base of isotherms positions and consumed by IC power thermal resistances between crystal and environment are determined.

Chromium–niobium co-doped vanadium dioxide films: Large temperature coefficient of resistance and practically no thermal hysteresis of the metal–insulator transition

Directory of Open Access Journals (Sweden)

Kenichi Miyazaki

2016-05-01

Full Text Available We investigated the effects of chromium (Cr and niobium (Nb co-doping on the temperature coefficient of resistance (TCR and the thermal hysteresis of the metal–insulator transition of vanadium dioxide (VO2 films. We determined the TCR and thermal-hysteresis-width diagram of the V1−x−yCrxNbyO2 films by electrical-transport measurements and we found that the doping conditions x ≳ y and x + y ≥ 0.1 are appropriate for simultaneously realizing a large TCR value and an absence of thermal hysteresis in the films. By using these findings, we developed a V0.90Cr0.06Nb0.04O2 film grown on a TiO2-buffered SiO2/Si substrate that showed practically no thermal hysteresis while retaining a large TCR of 11.9%/K. This study has potential applications in the development of VO2-based uncooled bolometers.

Direct-reading dial for noise temperature and noise resistance

DEFF Research Database (Denmark)

Diamond, J.M.

1967-01-01

An attenuator arrangement for a noise generator is described. The scheme permits direct reading of both noise resistance and noise temperature¿the latter with a choice of source resistance.......An attenuator arrangement for a noise generator is described. The scheme permits direct reading of both noise resistance and noise temperature¿the latter with a choice of source resistance....

High temperature resistant cermet and ceramic compositions. [for thermal resistant insulators and refractory coatings

Science.gov (United States)

Phillips, W. M. (Inventor)

1978-01-01

High temperature oxidation resistance, high hardness and high abrasion and wear resistance are properties of cermet compositions particularly to provide high temperature resistant refractory coatings on metal substrates, for use as electrical insulation seals for thermionic converters. The compositions comprise a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride are also described.

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.)

Optical study of phase transitions in single-crystalline RuP

Science.gov (United States)

Chen, R. Y.; Shi, Y. G.; Zheng, P.; Wang, L.; Dong, T.; Wang, N. L.

2015-03-01

RuP single crystals of MnP-type orthorhombic structure were synthesized by the Sn flux method. Temperature-dependent x-ray diffraction measurements reveal that the compound experiences two structural phase transitions, which are further confirmed by enormous anomalies shown in temperature-dependent resistivity and magnetic susceptibility. Particularly, the resistivity drops monotonically upon temperature cooling below the second transition, indicating that the material shows metallic behavior, in sharp contrast with the insulating ground state of polycrystalline samples. Optical conductivity measurements were also performed in order to unravel the mechanism of these two transitions. The measurement revealed a sudden reconstruction of band structure over a broad energy scale and a significant removal of conducting carriers below the first phase transition, while a charge-density-wave-like energy gap opens below the second phase transition.

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)

High temperature oxidation resistant cermet compositions

Science.gov (United States)

Phillips, W. M. (Inventor)

1976-01-01

Cermet compositions are designed to provide high temperature resistant refractory coatings on stainless steel or molybdenum substrates. A ceramic mixture of chromium oxide and aluminum oxide form a coating of chromium oxide as an oxidation barrier around the metal particles, to provide oxidation resistance for the metal particles.

Electrochemical determination of the glass transition temperature of thin polyelectrolyte brushes at solid-liquid interfaces by impedance spectroscopy.

Science.gov (United States)

Alonso-García, Teodoro; Rodríguez-Presa, María José; Gervasi, Claudio; Moya, Sergio; Azzaroni, Omar

2013-07-16

Devising strategies to assess the glass transition temperature (Tg) of polyelectrolyte assemblies at solid-electrolyte interfaces is very important to understand and rationalize the temperature-dependent behavior of polyelectrolyte films in a wide range of settings. Despite the evolving perception of the importance of measuring Tg under aqueous conditions in thin film configurations, its straightforward measurement poses a challenging situation that still remains elusive in polymer and materials science. Here, we describe a new method based on electrochemical impedance spectroscopy (EIS) to estimate the glass transition temperature of planar polyelectrolyte brushes at solid-liquid interfaces. To measure Tg, the charge transfer resistance (Rct) of a redox probe diffusing through the polyelectrolyte brush was measured, and the temperature corresponding to the discontinuous change in Rct was identified as Tg. Furthermore, we demonstrate that impedance measurements not only facilitate the estimation of Tg but also enable a reliable evaluation of the transport properties of the polymeric interface, i.e., determination of diffusion coefficients, close to the thermal transition. We consider that this approach bridges the gap between electrochemistry and the traditional tools used in polymer science and offers new opportunities to characterize the thermal behavior of complex polymeric interfaces and macromolecular assemblies.

Flux lattice commensurability and the resistive transition of wire networks

International Nuclear Information System (INIS)

Wilks, C.W.

1992-01-01

The commensurability of one structure with one length scale with that of another with a different length scale is a familiar problem. For a superconducting wire network in a magnetic field the two competing length scales are that of the network and that of the magnetic flux lattice. The superconducting to normal state phase boundary, Tc(H), of a periodic network shows periodic oscillations with a period of H 0 = Φ 0 /A where Φ 0 = hc/2e and A is the area of the elementary tile. These oscillations are due to flux quantization around the individual tiles of the network. In addition, within each period, there is structure at H = (p/q)H 0 (p,q integers) which is due to the vortices forming energetically favorable commensurate arrangements on top of the underlying lattice. The authors have studied the broadening of the zero field resistive transition with the application of a magnetic field for networks of various geometries. This was done by either directly measuring the resistive transitions at the commensurate fields or by using a technique that utilizes phase boundary measurements and yields the field induced width of the resistive transition as a continued function of the field. There is a striking dependence of the field induced width on whether or not the field is commensurate with the network. The broadening at the commensurate flux filling is well described by thermally activated vortex motion using the formalism of Ambegoakar and Halperin which allows us to extract numbers for the pinning potentials at the various commensurate states. The authors have found that the size of the discontinuity in the slope of the phase boundary at a commensurate filling is related to the strength of the lattice and therefore to the broadening of the transition at that filling so that by just looking at the phase boundary of a network one can gauge the relative broadening of the resistive transitions at the commensurate flux fillings

Multi-Electrode Resistivity Probe for Investigation of Local Temperature Inside Metal Shell Battery Cells via Resistivity: Experiments and Evaluation of Electrical Resistance Tomography

Directory of Open Access Journals (Sweden)

Xiaobin Hong

2015-01-01

Full Text Available Direct Current (DC electrical resistivity is a material property that is sensitive to temperature changes. In this paper, the relationship between resistivity and local temperature inside steel shell battery cells (two commercial 10 Ah and 4.5 Ah lithium-ion cells is innovatively studied by Electrical Resistance Tomography (ERT. The Schlumberger configuration in ERT is applied to divide the cell body into several blocks distributed in different levels, where the apparent resistivities are measured by multi-electrode surface probes. The investigated temperature ranges from −20 to 80 °C. Experimental results have shown that the resistivities mainly depend on temperature changes in each block of the two cells used and the function of the resistivity and temperature can be fitted to the ERT-measurement results in the logistical-plot. Subsequently, the dependence of resistivity on the state of charge (SOC is investigated, and the SOC range of 70%–100% has a remarkable impact on the resistivity at low temperatures. The proposed approach under a thermal cool down regime is demonstrated to monitor the local transient temperature.

Influence of Temperature and Humidity on Bakelite Resistivity

CERN Document Server

Arnaldi, R; Barret, V; Bastid, N; Blanchard, G; Chiavassa, E; Cortese, P; Crochet, Philippe; Dellacasa, G; De Marco, N; Dupieux, P; Espagnon, B; Fargeix, J; Ferretti, A; Gallio, M; Lamoine, L; Luquin, Lionel; Manso, F; Mereu, P; Métivier, V; Musso, A; Oppedisano, C; Piccotti, A; Rahmani, A; Royer, L; Roig, O; Scalas, E; Scomparin, E; Vercellin, Ermanno

1999-01-01

Presentation made at RPC99 and submitted to Elsevier PreprintThe use of phenolic or melaminic bakelite as RPC electrodes is widespread. The electrode resistivity is an important parameter for the RPC performance. As recent studies have pointed out, the bakelite resistivity changes with temperature and is influenced by humidity. In order to gain a quantitative understanding on the influence of temperature and humidity on RPC electrodes, we assembled an apparatus to measure resistivity in well-controlled conditions. A detailed description of the experimental set-up as well as the first resistivity measurements for various laminates in different environmental conditions are presented.

Role of temperature-dependent O-p-Fe-d hybridization parameter in the metal-insulator transition of Fe3O4: a theoretical study

Science.gov (United States)

Fauzi, A. D.; Majidi, M. A.; Rusydi, A.

2017-04-01

We propose a simple tight-binding based model for Fe3O4 that captures the preference of ferrimagnetic over ferromagnetic spin configuration of the system. Our model is consistent with previous theoretical and experimental studies suggesting that the system is half metallic, in which spin polarized electrons hop only among the Fe B sites. To address the metal-insulator transition (MIT) we propose that the strong correlation among electrons, which may also be influenced by the electron-phonon interactions, manifest as the temperature-dependence of the O-p-Fe-d hybridization parameter, particularly Fe-d belonging to one of the Fe B sites (denoted as {t}{{FeB}-{{O}}}(2)). By proposing that this parameter increases as the temperature decreases, our density-of-states calculation successfully captures a gap opening at the Fermi level, transforming the system from half metal to insulator. Within this model along with the corresponding choice of parameters and a certain profile of the temperature dependence of {t}{{FeB}-{{O}}}(2), we calculate the resistivity of the system as a function of temperature. Our calculation result reveals the drastic uprising trend of the resistivity profile as the temperature decreases, with the MIT transition temperature located around 100 K, which is in agreement with experimental data.

High-temperature fracture and fatigue resistance of a ductile β-TiNb reinforced γ-TiAl intermetallic composite

International Nuclear Information System (INIS)

Rao, K.T.V.; Ritchie, R.O.

1998-01-01

The high-temperature fatigue-crack propagation and fracture resistance of a model γ-TiAl intermetallic composite reinforced with 20 vol. % ductile β-TiNb particles is examined at elevated temperatures of 650 and 800 C and compared with behavior at room temperature. TiNb reinforcements are found to enhance the fracture toughness of γ-TiAl, even at high temperatures, from about 123 to ∼40 MPa m 1/2 , although their effectiveness is lower compared to room temperature due to the reduction in strength of TiNb particles. Under monotonic loading, crack-growth response in the composite is characterized by resistance-curve behavior arising from crack trapping, renucleation and resultant crack bridging effects attributable to the presence of TiNb particles. In addition, crack-tip blunting associated with plasticity increases the crack-initiation (matrix) toughness of the composite, particularly at 800 C, above the ductile-to-brittle transition temperature (DBTT) for γ-TiAl. High-temperature fatigue-crack growth resistance, however, is marginally degraded by the addition of TiNb particles in the C-R (edge) orientation, similar to observations made at room temperature; premature fatigue failure of TiNb ligaments in the crack wake diminishes the role of bridging under cyclic loading. Both fatigue and fracture resistance of the composite are slightly lower at 650 C (just below the DBTT for TiAl) compared to the behavior at ambient and 800 C. Overall, the beneficial effect of adding ductile TiNb reinforcements to enhance the room-temperature fracture and fatigue resistance of γ-TiAl alloys is retained up to 800 C, in air environments. There is concern, however, regarding the long-term environmental stability of these composite microstructures in unprotected atmospheres

Stability of High Temperature Standard Platinum Resistance Thermometers at High Temperatures

Directory of Open Access Journals (Sweden)

Y. A. ABDELAZIZ

2010-05-01

Full Text Available An investigation of the stability of high temperature standard platinum resistance thermometers HTSPRTs has been carried out for two different designs thermometers (with nominal resistance 0.25 Ω and 2.5 Ω from two different suppliers. The thermometers were heated for more than 160 hours at temperatures above 960 0C using a vertical furnace with a ceramic block. A study was made of the influence of the heat treatment on the stability of the resistance at the triple point of water, and on the relative resistance W(Ga at the melting point of gallium. The thermometers showed a correlation between the drift note and the values of W(Ga. It was found also that the HTSPRT which has a sensor with strip shaped support and low nominal resistance is more stable than the HTSPRT which has a sensor in the form of a coil wound on silica cross. The 0.25 Ω thermometer has better stability @ 7x10-6 0C (at TPW after 40 hour. Factors affecting the stability and accuracy of HTSPRT also will be discussed.

Pressure-induced transition-temperature reduction in ZnS nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Yang Cuizhuo; Liu Yanguo; Sun Hongyu; Guo Defeng; Li Xiaohong; Li Wei; Zhang Xiangyi [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, 066004 Qinhuangdao (China); Liu Baoting [College of Physics Science and Technology, Hebei University, 071002 Baoding (China)], E-mail: xyzh66@ysu.edu.cn

2008-03-05

The study of the structural transition in nanoscale materials is of particular interest for their potential applications. In the present study, we have observed a lower temperature T = 250 deg. C for the phase transition from the sphalerite structure to the wurtzite structure in ZnS nanoparticles under a pressure of 1 GPa, as compared to those, T = 400 and 1020 deg. C, for ZnS nanoparticles and bulk ZnS under normal pressure, respectively. The reduced transition temperature is attributed to the applied pressure leading to tight particle-particle contacts, which change the surface (or interfacial) environment of the nanoparticles and thus their surface (or interfacial) energy.

Pressure-induced transition-temperature reduction in ZnS nanoparticles

International Nuclear Information System (INIS)

Yang Cuizhuo; Liu Yanguo; Sun Hongyu; Guo Defeng; Li Xiaohong; Li Wei; Zhang Xiangyi; Liu Baoting

2008-01-01

The study of the structural transition in nanoscale materials is of particular interest for their potential applications. In the present study, we have observed a lower temperature T = 250 deg. C for the phase transition from the sphalerite structure to the wurtzite structure in ZnS nanoparticles under a pressure of 1 GPa, as compared to those, T = 400 and 1020 deg. C, for ZnS nanoparticles and bulk ZnS under normal pressure, respectively. The reduced transition temperature is attributed to the applied pressure leading to tight particle-particle contacts, which change the surface (or interfacial) environment of the nanoparticles and thus their surface (or interfacial) energy

Transition conductivity study of high temperature superconductor compounds: the role of fluctuations

International Nuclear Information System (INIS)

Pagnon, V.

1991-04-01

This memory subject is the transition conductivity study of high temperature superconductors in corelation with their anisotropy. Systematic conductivity measurements were made on YBaCuO and BaSrCaCuO in relation with temperature from 4.2 K to 1200 K, and with a magnetic field up to 8 T in several directions. Oxygen order has an effect on the characteristics at YBaCuO transition conductivity. The activation energy for oxygen absorption is about 0.5eV. One method of analysis of the conductivity fluctuations about the transition temperature is proposed. Two separate rates are noticeable in YBaCuO compound. The 3 D fluctuations rate in the immediate neighbourghood of the transition lets place to the 2 D fluctuations rate at high temperature. Transitions temperatures governing each rate are different, that's incompatible with the formula proposed by Lawrence and Doniach. On the other hand, the analogy with quasi-2 D magnetic systems seems more relevant. A magnetic field application or a lowering of oxygen concentration removes the 3 D fluctuations rate. Non ohmic effects observed at the transition conductivity foot are analysis as a non-linear 2 D excitation manifestation of the supraconductive phase. Finally, by measurements on strontium doped YBaCuO crystals, we confirm a metal-insulator transition along the C-Axe when oxygen concentration reduces. This is connected with the specific heat jump. All these results uplighten the fundamental bidimensional character of high transition temperature superconductivity [fr

Transit through the flea vector induces a pretransmission innate immunity resistance phenotype in Yersinia pestis.

Directory of Open Access Journals (Sweden)

Viveka Vadyvaloo

2010-02-01

Full Text Available Yersinia pestis, the agent of plague, is transmitted to mammals by infected fleas. Y. pestis exhibits a distinct life stage in the flea, where it grows in the form of a cohesive biofilm that promotes transmission. After transmission, the temperature shift to 37 degrees C induces many known virulence factors of Y. pestis that confer resistance to innate immunity. These factors are not produced in the low-temperature environment of the flea, however, suggesting that Y. pestis is vulnerable to the initial encounter with innate immune cells at the flea bite site. In this study, we used whole-genome microarrays to compare the Y. pestis in vivo transcriptome in infective fleas to in vitro transcriptomes in temperature-matched biofilm and planktonic cultures, and to the previously characterized in vivo gene expression profile in the rat bubo. In addition to genes involved in metabolic adaptation to the flea gut and biofilm formation, several genes with known or predicted roles in resistance to innate immunity and pathogenicity in the mammal were upregulated in the flea. Y. pestis from infected fleas were more resistant to phagocytosis by macrophages than in vitro-grown bacteria, in part attributable to a cluster of insecticidal-like toxin genes that were highly expressed only in the flea. Our results suggest that transit through the flea vector induces a phenotype that enhances survival and dissemination of Y. pestis after transmission to the mammalian host.

Investigation of low glass transition temperature on COTS PEMs reliability

Science.gov (United States)

Sandor, M.; Agarwal, S.

2002-01-01

Many factors influence PEM component reliability.One of the factors that can affect PEM performance and reliability is the glass transition temperature (Tg) and the coefficient of thermal expansion (CTE) of the encapsulant or underfill. JPL/NASA is investigating how the Tg and CTE for PEMs affect device reliability under different temperature and aging conditions. Other issues with Tg are also being investigated. Some preliminary data will be presented on glass transition temperature test results conducted at JPL.

Resistance transition assisted geometry enhanced magnetoresistance in semiconductors

International Nuclear Information System (INIS)

Luo, Zhaochu; Zhang, Xiaozhong

2015-01-01

Magnetoresistance (MR) reported in some non-magnetic semiconductors (particularly silicon) has triggered considerable interest owing to the large magnitude of the effect. Here, we showed that MR in lightly doped n-Si can be significantly enhanced by introducing two diodes and proper design of the carrier path [Wan, Nature 477, 304 (2011)]. We designed a geometrical enhanced magnetoresistance (GEMR) device whose room-temperature MR ratio reaching 30% at 0.065 T and 20 000% at 1.2 T, respectively, approaching the performance of commercial MR devices. The mechanism of this GEMR is: the diodes help to define a high resistive state (HRS) and a low resistive state (LRS) in device by their openness and closeness, respectively. The ratio of apparent resistance between HRS and LRS is determined by geometry of silicon wafer and electrodes. Magnetic field could induce a transition from LRS to HRS by reshaping potential and current distribution among silicon wafer, resulting in a giant enhancement of intrinsic MR. We expect that this GEMR could be also realized in other semiconductors. The combination of high sensitivity to low magnetic fields and large high-field response should make this device concept attractive to the magnetic field sensing industry. Moreover, because this MR device is based on a conventional silicon/semiconductor platform, it should be possible to integrate this MR device with existing silicon/semiconductor devices and so aid the development of silicon/semiconductor-based magnetoelectronics. Also combining MR devices and semiconducting devices in a single Si/semiconductor chip may lead to some novel devices with hybrid function, such as electric-magnetic-photonic properties. Our work demonstrates that the charge property of semiconductor can be used in the magnetic sensing industry, where the spin properties of magnetic materials play a role traditionally

Transition temperature and fracture mode of as-castand austempered ductile iron.

Science.gov (United States)

Rajnovic, D; Eric, O; Sidjanin, L

2008-12-01

The ductile to brittle transition temperature is a very important criterion that is used for selection of materials in some applications, especially in low-temperature conditions. For that reason, in this paper transition temperature of as-cast and austempered copper and copper-nickel alloyed ductile iron (DI) in the temperature interval from -196 to +150 degrees C have been investigated. The microstructures of DIs and ADIs were examined by light microscope, whereas the fractured surfaces were observed by scanning electron microscope. The ADI materials have higher impact energies compared with DIs in an as-cast condition. In addition, the transition curves for ADIs are shifted towards lower temperatures. The fracture mode of Dls is influenced by a dominantly pearlitic matrix, exhibiting mostly brittle fracture through all temperatures of testing. By contrast, with decrease of temperature, the fracture mode for ADI materials changes gradually from fully ductile to fully brittle.

Fluorinated epoxy resins with high glass transition temperatures

Science.gov (United States)

Griffith, James R.

1991-01-01

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

The Magnetically-Tuned Transition-Edge Sensor

Science.gov (United States)

Sadleir, John E.; Lee, Sang-Jun; Smith, Stephen J.; Busch, Sarah E.; Bandler, Simon R.; Adams, Joseph S.; Eckart, Megan E.; Chevenak, James A.; Kelley, Richard L.; Kilbourne, Caroline A.;

Variation of microchannel plate resistance with temperature and applied voltage

International Nuclear Information System (INIS)

Pearson, J.F.; Fraser, G.W.; Whiteley, M.J.

1987-01-01

The resistance of microchannel plate electron multiplier is well known to be a function of both applied voltage and detector temperature. We show that the apparent variation of resistance with bias voltage is simply due to plate temperature increases resulting from resistive heating. (orig.)

Successful Treatment of Nivolumab-Resistant Multiple In-Transit Melanomas with Ipilimumab and Topical Imiquimod

Directory of Open Access Journals (Sweden)

Taku Fujimura

2018-01-01

Full Text Available Simultaneous or sequential, planned administration of ipilimumab could significantly enhance the antitumor effects of nivolumab in advanced melanoma patients. On the other hand, the efficacy of ipilimumab for nivolumab-resistant advanced melanoma is extremely poor. Therefore, additional supportive therapy for anti-PD-1 antibody therapy-resistant advanced melanoma has been widely investigated. In this report, we describe a case of multiple in-transit melanomas developing in a nivolumab-resistant patient successfully treated with ipilimumab in combination with imiquimod. Our present case suggested a possible therapy for nivolumab-resistant multiple in-transit melanomas using ipilimumab in combination with topical imiquimod.

High transition temperature superconductor/insulator bilayers for the development of ultra-fast electronics

International Nuclear Information System (INIS)

Sirena, M.; Félix, L. Avilés; Haberkorn, N.

2013-01-01

High transition temperature superconductor (HTc)/SrTiO 3 (STO) bilayers were fabricated by sputtering deposition on (100) STO substrates. Their transport and morphological properties were characterized using conductive atomic force microscopy. The STO barriers present good insulating properties, with long attenuation lengths (λ ∼ 1 nm) which reduce the junction resistance and increase the operating critical current. The samples present roughness values smaller than 1 nm, with an extremely low density of surface defects (∼5 × 10 −5 defects/μm 2 ). The high control of the barrier quality over large defect free surfaces is encouraging for the development of microelectronics devices based in HTc Josephson junctions

Temperature-induced transitions between domain structures of ultrathin magnetic films

International Nuclear Information System (INIS)

Polyakova, T.; Zablotskii, V.

2005-01-01

Full text: Understanding of the influence of temperature on behavior of domain patterns of ultrathin magnetic films is of high significance for the fundamental physics of nanomagnetism as well as for technological applications. A thickness-dependent Curie temperature of ultrathin films may cause many interesting phenomena in the thermal evolution of domain structures (DS): i) nontrivial changes of the anisotropy constants as a function of the film thickness; ii) so-called inverse melting of DSs (processes where a more symmetric domain phase is found at lower temperatures than at higher temperatures - the inverse phase sequence) [1]; iii) temperature-induced transitions between domain structures. The possibility of such transitions is determined by lowering of the potential barriers separating different magnetization states as the film temperature approaches the Curie point. In this case with an increase of temperature, due to a significant decrease of the anisotropy constant, the domain wall energy is low enough and allows the system to reach equilibrium by a change of the domain wall number in the sample. This manifests itself in a transition from a metastable DS to a more stable DS which corresponds to new values of the anisotropy constant and magnetizations saturation. Thus, the temperature-induced transitions are driven by temperature changes of the magnetic parameters of the film. The key parameters controlling the DS geometry and period are the characteristic length, l c =σ/4πM S 2 (the ratio between the domain wall and demagnetization energies), and the quality factor Q =K/2πM S 2 (K is the first anisotropy constant). We show that for films with a pronounced nonmonotonic temperature dependence of l c one can expect a counter thermodynamic behavior: the inverse phase sequence and cooling-induced disordering. On changing temperature the existing domain structure should accommodate itself under new magnitudes of l c and Q. There are the two possible

Problems of tungsten crack resistance optimization

International Nuclear Information System (INIS)

Babak, A.V.; Uskov, E.I.

1986-01-01

Technically pure and precipitation-hardening tungsten is studied for its crack resistance in the initial and hardened states at the temperatures of 20...2000 deg C. Results of the study are presented. It is shown that hardening of tungsten base alloys in oil from the temperature corresponding to the upper boundary of the temperature region of ductile-brittle transition increases a crack propagation resistance of the studied materias at elevated and high temperatures

Critical temperature for shape transition in hot nuclei within covariant density functional theory

Science.gov (United States)

Zhang, W.; Niu, Y. F.

2018-05-01

Prompted by the simple proportional relation between critical temperature for pairing transition and pairing gap at zero temperature, we investigate the relation between critical temperature for shape transition and ground-state deformation by taking even-even Cm-304286 isotopes as examples. The finite-temperature axially deformed covariant density functional theory with BCS pairing correlation is used. Since the Cm isotopes are the newly proposed nuclei with octupole correlations, we studied in detail the free energy surface, the Nilsson single-particle (s.p.) levels, and the components of s.p. levels near the Fermi level in 292Cm. Through this study, the formation of octupole equilibrium is understood by the contribution coming from the octupole driving pairs with Ω [N ,nz,ml] and Ω [N +1 ,nz±3 ,ml] for single-particle levels near the Fermi surfaces as it provides a good manifestation of the octupole correlation. Furthermore, the systematics of deformations, pairing gaps, and the specific heat as functions of temperature for even-even Cm-304286 isotopes are discussed. Similar to the relation between the critical pairing transition temperature and the pairing gap at zero temperature Tc=0.6 Δ (0 ) , a proportional relation between the critical shape transition temperature and the deformation at zero temperature Tc=6.6 β (0 ) is found for both octupole shape transition and quadrupole shape transition for the isotopes considered.

Temperature, transitivity, and the zeroth law

DEFF Research Database (Denmark)

Bergthorsson, Bjørn

1977-01-01

Different statements of the zeroth law are examined. Two types of statements—which characterize two aspects of temperature—are found. A new formulation of the zeroth law is given and a corollary is stated. By means of this corollary it is shown how temperature and transitivity are used to disclose...

In-plane dissipation maxima and vortex-line distortions in the resistive transitions of oxygen-doped Bi2Sr2CaCu2O(8+delta) single crystals

Science.gov (United States)

Hsu, J. W. P.; Mitzi, D. B.; Kapitulnik, A.; Lee, Mark

1991-10-01

Measurements of the in-plane resistive transition of Bi2Sr2CaCu2O(8+delta) single crystals in perpendicular magnetic fields reveal that in oxygen-reduced samples a giant resistance maximum evolves with field. This is not seen in oxygenated samples with similar metallic normal resistivities. As the peak resistivity may exceed the normal resistivity, it cannot arise from ordinary vortex-motion dissipation. A model is proposed where the excess resistance results from nonrigid vortex motion coupling the out-of-plane dissipation to the in-plane resistance at temperatures where pinning effects are negligible.

Metal-insulator transition upon heating and negative-differential-resistive-switching induced by self-heating in BaCo0.9Ni0.1S1.8

International Nuclear Information System (INIS)

Fisher, B.; Genossar, J.; Chashka, K. B.; Patlagan, L.; Reisner, G. M.

2014-01-01

The layered compound BaCo 1−x Ni x S 2−y (0.05  1−x Ni x S 2−y (nominal x = 0.1 and y = 0.2). These were due to the steep metal to insulator transition upon heating followed by the activated behavior of the resistivity above the transition. The major role of Joule heating in switching is supported by the absence of nonlinearity in the current as function of voltage, I(V), obtained in pulsed measurements, in the range of electric fields relevant to d.c. measurements. The voltage-controlled negative differential resistance around the threshold for switching was explained by a simple model of self-heating. The main difficulty in modeling I(V) from the samples resistance as function of temperature R(T) was the progressive increase of R(T), and to a lesser extend the decrease of the resistance jumps at the transitions, caused by the damage induced by cycling through the transitions by heating or self-heating. This was dealt with by following systematically R(T) over many cycles and by using the data of R(T) in the heating cycle closest to that of the self-heating one

Preparation of Nb thin films with bulk transition temperatures

Energy Technology Data Exchange (ETDEWEB)

Peirce, L H [Florida State Univ., Tallahassee (USA). Dept. of Physics

1984-08-01

Thin films (1000-2000 A) of Nb were prepared with bulk transition temperatures (9.25 K) by evaporation from an electron gun. Necessary substrate temperatures, evaporation rates and H/sub 2/O pressures were determined.

Pairing transition, coherence transition, and the irreversibility line in granular GdBa2Cu3O7-δ

Science.gov (United States)

Roa-Rojas, J.; Menegotto Costa, R.; Pureur, P.; Prieto, P.

2000-05-01

We report on electrical magnetoconductivity experiments near the superconducting transition of a granular sample of GdBa2Cu3O7-δ. The measurements were performed in magnetic fields ranging from 0 to 500 Oe applied parallel to the current orientation. The results show that the transition proceeds in two steps. When the temperature is decreased we first observe the pairing transition, which stabilizes superconductivity within the grains at a temperature practically coincident with the bulk critical temperature Tc. Analysis of the fluctuation contributions to the conductivity shows that the universality class for this transition is that of the three dimensional (3D)-XY model in the ordered case, with dynamic critical exponent z=3/2. Close to the zero-resistance state, the measurements reveal the occurrence of a coherence transition, where the phases of the order parameter in individual grains become long-range ordered. The critical temperature Tco for this transition is close to the point where the resistivity vanishes. A strong enlargement of the fluctuation interval preceding the coherence transition is caused by the applied magnetic field. In this region, a 3D-Gaussian regime and an asymptotic critical regime were clearly identified. The critical conductivity behavior for the coherence transition is interpreted within a 3D-XY model where disorder and frustration are relevant. The irreversibility line is determined from magnetoconductivity measurements performed according to the zero-field-cooled (ZFC) and field-cooled data collected on cooling (FCC) recipes. The locus of this line coincides with the upper temperature limit for the fluctuation region above the coherence transition. The irreversibility line is interpreted as an effect of the formation of small clusters with closed loops of Josephson-coupled grains.

Isotope effect in glass-transition temperature and ionic conductivity of lithium-borate glasses

International Nuclear Information System (INIS)

Nagasaki, Takanori; Morishima, Ryuta; Matsui, Tsuneo

2002-01-01

The glass-transition temperature and the electrical conductivity of lithium borate (0.33Li 2 O-0.67B 2 O 3 ) glasses with various isotopic compositions were determined by differential thermal analysis and by impedance spectroscopy, respectively. The obtained glass-transition temperature as well as the vibrational frequency of B-O network structure was independent of lithium isotopic composition. This result indicates that lithium ions, which exist as network modifier, only weakly interact with B-O network structure. In addition, the glass-transition temperature increased with 10 B content although the reason has not been understood. The electrical conductivity, on the other hand, increased with 6 Li content. The ratio of the conductivity of 6 Li glass to that of 7 Li glass was found to be 2, being larger than the value (7/6) 1/2 calculated with the simple classical diffusion theory. This strong mass dependence could be explained by the dynamic structure model, which assumes local structural relaxation even far below the glass-transition temperature. Besides, the conductivity appeared to increase with the glass-transition temperature. Possible correlations between the glass-transition temperature and the electrical conductivity were discussed. (author)

The transition-edge microbolometer (TREMBOL)

International Nuclear Information System (INIS)

Wentworth, S.M.; Neikirk, D.P.

1990-01-01

The TREMBOL (transition-edge microbolometer) and the composite TREMBOL are introduced as detectors for FIR imaging arrays. The TREMBOL uses a superconductor's sharp change in resistance at the normal conduction to superconduction transition. The structure of the composite TREMBOL enables heating of the individual detectors in an array up to their transition temperature, and can thus be used in multiplexing, which would be very advantageous for two-dimensional arrays. 23 refs

Ab initio computation of the transition temperature of the charge density wave transition in TiS e2

Science.gov (United States)

Duong, Dinh Loc; Burghard, Marko; Schön, J. Christian

2015-12-01

We present a density functional perturbation theory approach to estimate the transition temperature of the charge density wave transition of TiS e2 . The softening of the phonon mode at the L point where in TiS e2 a giant Kohn anomaly occurs, and the energy difference between the normal and distorted phase are analyzed. Both features are studied as functions of the electronic temperature, which corresponds to the Fermi-Dirac distribution smearing value in the calculation. The transition temperature is found to be 500 and 600 K by phonon and energy analysis, respectively, in reasonable agreement with the experimental value of 200 K.

Noise measurements of YBa2Cu3O7 thin film high-temperature superconductors

International Nuclear Information System (INIS)

Hall, J.J.

1992-01-01

The characteristics of thin-film YBa2Cu3O7 superconductors were studied from the superconducting region through the transition region and into the normal region. The properties studied included the resistance-temperature, current-voltage, and electrical noise with concentration of measurements in the transition region. The resistance vs. temperature measurements show a zero resistance followed by a small rise in magnitude at the onset of resistance followed by a sharp increase until the resistance tapers off in the fully normal region. The a-axis films had a larger normal resistivity, a lower critical temperature, and a broader transition than the similar c-axis films. The current(I) - voltage(V) measurements were concentrated in the transition region. A power relation between I and V was found to be V varies as I a(T) where a(T) is temperature dependent starting high the onset of vortex formation, approaches 3 at the vortex unbinding temperature, and goes to 1 when fully normal. This behavior was predicted by the Kosterlitz-Thouless theory and was found experimentally in all four films measured. The current-induced electrical noise characteristics were measured for four samples varying in thickness and axis orientation. Each film exhibited a widely varying magnitude of the noise voltage spectral density (S V ) in the transition region with a leveling off when fully normal. The normalized noise (S V /V squared) showed a sharp decrease in magnitude from the onset of measurable noise continually decreasing until flattening out when fully normal. The a-axis films exhibited S V /V squared over 3 order of magnitude larger than the c-axis films in the transition and normal regions. The normalized temperature coefficient of resistance (beta) was plotted against S V /V squared on a log-log scale to see if the noise generated was due to temperature fluctuations (slope = 2)

Temperature-dependent electrical property transition of graphene oxide paper

International Nuclear Information System (INIS)

Huang Xingyi; Jiang Pingkai; Zhi Chunyi; Golberg, Dmitri; Bando, Yoshio; Tanaka, Toshikatsu

2012-01-01

Reduction of graphene oxide is primarily important because different reduction methods may result in graphene with totally different properties. For systematically exploring the reduction of graphene oxide, studies of the temperature-dependent electrical properties of graphene oxide (GO) are urgently required. In this work, for the first time, broadband dielectric spectroscopy was used to carry out an in situ investigation on the transition of the electrical properties of GO paper from −40 to 150 °C. The results clearly reveal a very interesting four-stage transition of electrical properties of GO paper with increasing temperature: insulator below 10 °C (stage 1), semiconductor at between 10 and 90 °C (stage 2), insulator at between 90 and 100 °C (stage 3), and semiconductor again at above 100 °C (stage 4). Subsequently, the transition mechanism was discussed in combination with detailed dielectric properties, microstructure and thermogravimetric analyses. It is suggested that the temperature-dependent transition of electronic properties of GO is closely associated with the ion mobility, water molecules removal and the reduction of GO in the GO paper. Most importantly, the present work clearly demonstrates the reduction of GO paper starts at above 100 °C. (paper)

Bipolar resistive switching in room temperature grown disordered vanadium oxide thin-film devices

Science.gov (United States)

Wong, Franklin J.; Sriram, Tirunelveli S.; Smith, Brian R.; Ramanathan, Shriram

2013-09-01

We demonstrate bipolar switching with high OFF/ON resistance ratios (>104) in Pt/vanadium oxide/Cu structures deposited entirely at room temperature. The SET (RESET) process occurs when negative (positive) bias is applied to the top Cu electrode. The vanadium oxide (VOx) films are amorphous and close to the vanadium pentoxide stoichiometry. We also investigated Cu/VOx/W structures, reversing the position of the Cu electrode, and found the same polarity dependence with respect to the top and bottom electrodes, which suggests that the bipolar nature is linked to the VOx layer itself. Bipolar switching can be observed at 100 °C, indicating that it not due to a temperature-induced metal-insulator transition of a vanadium dioxide second phase. We discuss how ionic drift can lead to the bipolar electrical behavior of our junctions, similar to those observed in devices based on several other defective oxides. Such low-temperature processed oxide switches could be of relevance to back-end or package integration processing schemes.

Absence of low temperature phase transitions and enhancement of ferroelectric transition temperature in highly strained BaTiO{sub 3} epitaxial films grown on MgO Substrates

Energy Technology Data Exchange (ETDEWEB)

Kumar, Satish; Kumar, Dhirendra; Sathe, V. G., E-mail: vasant@csr.res.in [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India); Kumar, Ravi; Sharma, T. K. [Semiconductor Physics and Devices Lab, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)

2015-04-07

Recently, a large enhancement in the ferroelectric transition temperature of several oxides is reported by growing the respective thin films on appropriate substrates. This phenomenon is correlated with high residual strain in thin films often leading to large increase in the tetragonality of their crystal structure. However, such an enhancement of transition temperature is usually limited to very thin films of ∼10 nm thickness. Here, we report growth of fully strained epitaxial thin films of BaTiO{sub 3} of 400 nm thickness, which are coherently grown on MgO substrates by pulsed laser deposition technique. Conventional high resolution x-ray diffraction and also the reciprocal space map measurements confirm that the film is fully strained with in-plane tensile strain of 5.5% that dramatically increases the tetragonality to 1.05. Raman measurements reveal that the tetragonal to cubic structural phase transition is observed at 583 K, which results in an enhancement of ∼200 K. Furthermore, temperature dependent Raman studies on these films corroborate absence of all the low temperature phase transitions. Numerical calculations based on thermodynamical model predict a value of the transition temperature that is greater than 1500 °C. Our experimental results are therefore in clear deviation from the existing strain dependent phase diagrams.

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

Temperature rise of the mask-resist assembly during LIGA exposure

International Nuclear Information System (INIS)

Ting, Aili

2004-01-01

Deep X-ray lithography on PMMA resist is used in the LIGA process. The resist is exposed to synchrotron X-rays through a patterned mask and then is developed in a liquid developer to make high aspect ratio microstructures. The limitations in dimensional accuracies of the LIGA generated microstructure originate from many sources, including synchrotron and X-ray physics, thermal and mechanical properties of mask and resist, and from the kinetics of the developer. This work addresses the thermal analysis and temperature rise of the mask-resist assembly during exposure in air at the Advanced Light Source (ALS) synchrotron. The concern is that dimensional errors generated at the mask and the resist due to thermal expansion will lower the accuracy of the lithography. We have developed a three-dimensional finite-element model of the mask and resist assembly that includes a mask with absorber, a resist with substrate, three metal holders, and a water-cooling block. We employed the LIGA exposure-development software LEX-D to calculate volumetric heat sources generated in the assembly by X-ray absorption and the commercial software ABAQUS to calculate heat transfer including thermal conduction inside the assembly, natural and forced convection, and thermal radiation. at assembly outer and/or inner surfaces. The calculations of assembly maximum temperature. have been compared with temperature measurements conducted at ALS. In some of these experiments, additional cooling of the assembly was produced by forced nitrogen flow ('nitrogen jets') directed at the mask surface. The temperature rise in the silicon mask and the mask holder comes directly from the X-ray absorption, but nitrogen jets carry away a significant portion of heat energy from the mask surface, while natural convection carries away negligibly small amounts energy from the holder. The temperature rise in PMMA resist is mainly from heat conducted from the silicon substrate backward to the resist and from the inner

High transition temperature superconductor/insulator bilayers for the development of ultra-fast electronics

Energy Technology Data Exchange (ETDEWEB)

Sirena, M.; Félix, L. Avilés [Consejo Nacional de Investigaciones Científicas y Técnicas, Centro Atómico Bariloche, CNEA, Bustillo 9500, 8400 Bariloche (Argentina); Instituto Balseiro, Universidad Nacional de Cuyo and CNEA, 8400 Bariloche (Argentina); Haberkorn, N. [Consejo Nacional de Investigaciones Científicas y Técnicas, Centro Atómico Bariloche, CNEA, Bustillo 9500, 8400 Bariloche (Argentina)

2013-07-29

High transition temperature superconductor (HTc)/SrTiO{sub 3} (STO) bilayers were fabricated by sputtering deposition on (100) STO substrates. Their transport and morphological properties were characterized using conductive atomic force microscopy. The STO barriers present good insulating properties, with long attenuation lengths (λ ∼ 1 nm) which reduce the junction resistance and increase the operating critical current. The samples present roughness values smaller than 1 nm, with an extremely low density of surface defects (∼5 × 10{sup −5} defects/μm{sup 2}). The high control of the barrier quality over large defect free surfaces is encouraging for the development of microelectronics devices based in HTc Josephson junctions.

Temperature Dependence of Arn+ Cluster Backscattering from Polymer Surfaces: a New Method to Determine the Surface Glass Transition Temperature.

Science.gov (United States)

Poleunis, Claude; Cristaudo, Vanina; Delcorte, Arnaud

2018-01-01

In this work, time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to study the intensity variations of the backscattered Ar n + clusters as a function of temperature for several amorphous polymer surfaces (polyolefins, polystyrene, and polymethyl methacrylate). For all these investigated polymers, our results show a transition of the ratio Ar 2 + /(Ar 2 + + Ar 3 + ) when the temperature is scanned from -120 °C to +125 °C (the exact limits depend on the studied polymer). This transition generally spans over a few tens of degrees and the temperature of the inflection point of each curve is always lower than the bulk glass transition temperature (T g ) reported for the considered polymer. Due to the surface sensitivity of the cluster backscattering process (several nanometers), the presented analysis could provide a new method to specifically evaluate a surface transition temperature of polymers, with the same lateral resolution as the gas cluster beam. Graphical abstract ᅟ.

Temperature-dependent resistance switching in SrTiO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Li, Jian-kun [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Ma, Chao; Ge, Chen, E-mail: kjjin@iphy.ac.cn, E-mail: gechen@iphy.ac.cn; Gu, Lin; He, Xu; Zhou, Wen-jia; Lu, Hui-bin [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Jin, Kui-juan, E-mail: kjjin@iphy.ac.cn, E-mail: gechen@iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100190 (China); Zhang, Qing-hua [School of Materials Science and Engineering, State Key Lab of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084 (China); Yang, Guo-zhen [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100190 (China)

2016-06-13

Resistance switching phenomena were studied by varying temperature in SrTiO{sub 3} single crystal. The resistance hysteresis loops appear at a certain temperature ranging from 340 K to 520 K. With the assistance of 375 nm ultraviolet continuous laser, the sample resistance is greatly reduced, leading to a stable effect than that in dark. These resistance switching phenomena only exist in samples with enough oxygen vacancies, which is confirmed by spherical aberration-corrected scanning transmission electron microscopy measurements, demonstrating an important role played by oxygen vacancies. At temperatures above 340 K, positively charged oxygen vacancies become mobile triggered by external electric field, and the resistance switching effect emerges. Our theoretical results based on drift-diffusion model reveal that the built-in field caused by oxygen vacancies can be altered under external electric field. Therefore, two resistance states are produced under the cooperative effect of built-in field and external field. However, the increasing mobility of oxygen vacancies caused by higher temperature promotes internal electric field to reach equilibrium states quickly, and suppresses the hysteresis loops above 420 K.

Low-temperature technique for thick film resist stabilization and curing

Science.gov (United States)

Minter, Jason P.; Wong, Selmer S.; Marlowe, Trey; Ross, Matthew F.; Narcy, Mark E.; Livesay, William R.

1999-06-01

For a range of thick film photoresist applications, including MeV ion implant processing, thin film head manufacturing, and microelectromechanical systems processing, there is a need for a low-temperature method for resist stabilization and curing. Traditional methods of stabilizing or curing resist films have relied on thermal cycling, which may not be desirable due to device temperature limitations or thermally-induced distortion of the resist features.

Possible observation of the Berezinskii-Kosterlitz-Thouless transition in boron-doped diamond films

Science.gov (United States)

Coleman, Christopher; Bhattacharyya, Somnath

2017-11-01

The occurrence of the Berezinskii-Kosterlitz-Thouless (BKT) transition is investigated in heavily boron-doped nanocrystalline diamond films through a combination of current-voltage and resistance measurements. We observe transport features suggesting a robust BKT transition along with transport features related to vortex pinning in nanocrystalline diamond films with smaller grain size. The vortex core energy determined through analysis of the resistance temperature curves was found to be anti-correlated to the BKT transition temperatures. It is also observed that the higher BKT temperature is related to an increased vortex-antivortex binding energy derived from the activated transport regions. Further, the magnetic field induced superconductor insulator transition shows the possibility of the charge glass state. The consequences of granularity such as localization and vortex pinning can lead to tuneable BKT temperatures and strongly affects the field induced insulating state.

Crack resistance of tungsten strengthened by dispersed refractory oxides

International Nuclear Information System (INIS)

Babak, A.V.; Uskov, E.I.

1984-01-01

Investigation results are presented for crack resistance of commercial tungsten, obtained during specimen testing at temperatures of 20 deg C to Tsub(cr) (upper boundary of temperature range of ductile-brittle transition). Comparison of s-n diagrams and temperature dependences of crack resistance are conducted for commercial tungsten and tungsten strengthened by refractory oxides. It is shown that dispersion hardening increases crack resistance in the temperature range of 20 to 2000 deg C but the upper boundary of ductile-brittle shifts to the side of higher temperatures

Temperature dependence of non-Debye disorder in doped manganites

International Nuclear Information System (INIS)

Meneghini, C.; Cimino, R.; Pascarelli, S.; Mobilio, S.; Raghu, C.; Sarma, D.D.

1997-01-01

Ca-doped manganite La 1-x Ca x MnO 3 samples with x=0.2 and 0.4 were investigated by extended x-ray absorption fine structure (EXAFS) as a function of temperature and preparation method. The samples exhibit characteristic resistivity change across the metal-insulator (MI) transition temperature whose shape and position depend on Ca-doping concentration and sample thermal treatment. EXAFS results evidenced an increase of nonthermal disorder at the MI transition temperature which is significantly correlated with the resistivity behavior. copyright 1997 The American Physical Society

On the temperature dependence of the excess resistivity in dilute volatile alloys

International Nuclear Information System (INIS)

Uray, L.; Vicsek, T.

1978-01-01

In recrystallized wires of many important refractory alloys, an appreciable part of the temperature dependence of the measured excess resistivity is related to the radial distribution of the volatile solutes (extrinsic temperature dependence). Both the extrinsic and the intrinsic part of the temperature dependence of the excess resistivity have been determined for dilute WFe, WCo and WRe alloys, by measuring the resistance as a function of temperature and the thickness of layers removed by electrothinning. In this way the parameters of the evaporation profiles were also determined. In the surface region at low temperatures the length scale of the inhomogeneity is comparable to the mean-free path. Therefore, the observed extrinsic temperature dependence of the excess resistivity was calculated directly from the Boltzmann equation. The WCo alloy is a Kondo system, since its resistivity shows a minimum a 20 K. (author)

Determination of the glass-transition temperature of proteins from a viscometric approach.

Science.gov (United States)

Monkos, Karol

2015-03-01

All fully hydrated proteins undergo a distinct change in their dynamical properties at glass-transition temperature Tg. To determine indirectly this temperature for dry albumins, the viscosity measurements of aqueous solutions of human, equine, ovine, porcine and rabbit serum albumin have been conducted at a wide range of concentrations and at temperatures ranging from 278 K to 318 K. Viscosity-temperature dependence of the solutions is discussed on the basis of the three parameters equation resulting from Avramov's model. One of the parameter in the Avramov's equation is the glass-transition temperature. For all studied albumins, Tg of a solution monotonically increases with increasing concentration. The glass-transition temperature of a solution depends both on Tg for a dissolved dry protein Tg,p and water Tg,w. To obtain Tg,p for each studied albumin the modified Gordon-Taylor equation was applied. This equation describes the dependence of Tg of a solution on concentration, and Tg,p and a parameter depending on the strength of the protein-solvent interaction are the fitting parameters. Thus determined the glass-transition temperature for the studied dry albumins is in the range (215.4-245.5)K. Copyright © 2014 Elsevier B.V. All rights reserved.

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.

Pressure-induced metal-insulator transition in spinel compound CuV2S4

International Nuclear Information System (INIS)

Okada, H.; Koyama, K.; Hedo, M.; Uwatoko, Y.; Watanabe, K.

2008-01-01

In order to investigate the pressure effect on electrical properties of CuV 2 S 4 , we performed the electrical resistivity measurements under high pressures up to 8 GPa for a high-quality polycrystalline sample. The charge density wave (CDW) transition temperatures increase with increasing pressure. The residual resistivity rapidly increases with increasing pressure over 4 GPa, and the temperature dependence of the electrical resistivity at 8 GPa exhibits a semiconducting behavior below about 150 K, indicating that a pressure-induced metal-insulator transition occurs in CuV 2 S 4 at 8 GPa

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

Glass Transition Temperature of Saccharide Aqueous Solutions Estimated with the Free Volume/Percolation Model.

Science.gov (United States)

Constantin, Julian Gelman; Schneider, Matthias; Corti, Horacio R

2016-06-09

The glass transition temperature of trehalose, sucrose, glucose, and fructose aqueous solutions has been predicted as a function of the water content by using the free volume/percolation model (FVPM). This model only requires the molar volume of water in the liquid and supercooled regimes, the molar volumes of the hypothetical pure liquid sugars at temperatures below their pure glass transition temperatures, and the molar volumes of the mixtures at the glass transition temperature. The model is simplified by assuming that the excess thermal expansion coefficient is negligible for saccharide-water mixtures, and this ideal FVPM becomes identical to the Gordon-Taylor model. It was found that the behavior of the water molar volume in trehalose-water mixtures at low temperatures can be obtained by assuming that the FVPM holds for this mixture. The temperature dependence of the water molar volume in the supercooled region of interest seems to be compatible with the recent hypothesis on the existence of two structure of liquid water, being the high density liquid water the state of water in the sugar solutions. The idealized FVPM describes the measured glass transition temperature of sucrose, glucose, and fructose aqueous solutions, with much better accuracy than both the Gordon-Taylor model based on an empirical kGT constant dependent on the saccharide glass transition temperature and the Couchman-Karasz model using experimental heat capacity changes of the components at the glass transition temperature. Thus, FVPM seems to be an excellent tool to predict the glass transition temperature of other aqueous saccharides and polyols solutions by resorting to volumetric information easily available.

Electrical resistivity of ferrimagnetic magnetite thin film

International Nuclear Information System (INIS)

Varshney, Dinesh; Yogi, A.; Kaurav, N.; Gupta, R.P.; Phase, D.M.

2006-01-01

We have grown Fe 3 O 4 (III) epitaxial film on Al 2 O 3 (0001) substrate by pulsed laser deposition, with thickness of 130 nm. X-ray diffraction studies of magnetite show the spinel cubic structure of film with preferential (III) orientation. The electrical resistivity measurement demonstrates that the properties of thin film of magnetite are basically similar to those of bulk magnetite and clearly shows semiconductor-insulator transition at Verwey transition temperature (≅140 K). We have found higher Verwey transition temperature when compared with earlier reports on similar type of system. Possible causes for increase in transition temperature are discussed. (author)

Temperature-induced viral resistance in Emiliania huxleyi (Prymnesiophyceae).

Science.gov (United States)

Kendrick, B Jacob; DiTullio, Giacomo R; Cyronak, Tyler J; Fulton, James M; Van Mooy, Benjamin A S; Bidle, Kay D

2014-01-01

Annual Emiliania huxleyi blooms (along with other coccolithophorid species) play important roles in the global carbon and sulfur cycles. E. huxleyi blooms are routinely terminated by large, host-specific dsDNA viruses, (Emiliania huxleyi Viruses; EhVs), making these host-virus interactions a driving force behind their potential impact on global biogeochemical cycles. Given projected increases in sea surface temperature due to climate change, it is imperative to understand the effects of temperature on E. huxleyi's susceptibility to viral infection and its production of climatically active dimethylated sulfur species (DSS). Here we demonstrate that a 3°C increase in temperature induces EhV-resistant phenotypes in three E. huxleyi strains and that successful virus infection impacts DSS pool sizes. We also examined cellular polar lipids, given their documented roles in regulating host-virus interactions in this system, and propose that alterations to membrane-bound surface receptors are responsible for the observed temperature-induced resistance. Our findings have potential implications for global biogeochemical cycles in a warming climate and for deciphering the particular mechanism(s) by which some E. huxleyi strains exhibit viral resistance.

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.

Sharp superconductor-insulator transition in short wires

International Nuclear Information System (INIS)

Meidan, Dganit; Oreg, Yuval; Refael, Gil; Smith, Robert A.

2008-01-01

Recent experiments on short MoGe nanowires show a sharp superconductor-insulator transition tuned by the normal state resistance of the wire, with a critical resistance of R c ∼ R Q = h/(4e 2 ). These results are at odds with a broad range of theoretical work on Josephson-like systems that predicts a smooth transition, tuned by the value of the resistance that shunts the junction. We develop a self-consistent renormalization group treatment of interacting phase-slips and their dual counterparts, correlated cooper pair tunneling, beyond the dilute approximation. This analysis leads to a very sharp transition with a critical resistance of R Q . The addition of the quasi-particles' resistance at finite temperature leads to a quantitative agreement with the experimental results. This self-consistent renormalization group method should also be applicable to other physical systems that can be mapped onto similar sine-Gordon models, in the previously inaccessible intermediate-coupling 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.

Relaxation dynamics of glass transition in PMMA + SWCNT composites by temperature-modulated DSC

Science.gov (United States)

Pradhan, N. R.; Iannacchione, G. S.

2010-03-01

The experimental technique offered by temperature-modulated differential scanning calorimeter (TMDSC) used to investigate the thermal relaxation dynamics through the glass transition as a function of frequency was studied for pure PMMA and PMMA-single wall carbon nanotubes (SWCNTs) composites. A strong dependence of the temperature dependence peak in the imaginary part of complex heat capacity (Tmax) is found during the transition from the glass-like to the liquid-like region. The frequency dependence of Tmax of the imaginary part of heat capacity (Cp) is described by Arrhenius law. The activation energy obtained from the fitting shows increases while the characteristic relaxation time decreases with increasing mass fraction (phim) of SWCNTs. The dynamics of the composites during glass transition, at slow and high scan rates, are also the main focus of this experimental study. The change in enthalpy during heating and cooling is also reported as a function of scan rate and frequency of temperature modulation. The glass transition temperature (Tg) shows increases with increasing frequency of temperature modulation and phim of SWCNTs inside the polymer host. Experimental results show that Tg is higher at higher scan rates but as the frequency of temperature modulation increases, the Tg values of different scan rates coincide with each other and alter the scan rate dependence. From the imaginary part of heat capacity, it is obvious that Tmax is not the actual glass transition temperature of pure polymer but Tmax and Tg values can be superimposed when phim increases in the polymer host or when the sample undergoes a transition with a certain frequency of temperature modulation.

Variation of transition temperatures from upper to lower bainites in plain carbon steels

International Nuclear Information System (INIS)

Oka, M.; Okamoto, H.

1995-01-01

Experimental results and explanations for the transition temperature from upper to lower bainites in carbon steels containing from 0.20 to 1.80 wt%C were presented metallographically and kinematically. The experimental results are summarized as follows: (1) Lower bainite is not formed in steels with less than 0.35 wt%C and no transition from upper to lower bainite occurs. (2) The transition temperature of steels containing from 0.54 to 1.10 %C indicates a constant temperature of 350 C and does not depend on the carbon content. It is important to note that a transition temperature of 350 C corresponds to the Ms temperature of a 0.55%C steel being the boundary of the martensite morphology between a lath and a plate. (3) Transition temperatures of steels with more than 1.10%C decrease along the a line below about 65 C from T 0 -composition line. The bainitic transformation is essentially a kind of the martensitic one and its nucleation site is considered to be a carbon depleted zone in austenite by the thermal fluctuation of carbon atom at an isothermal holding temperature. The supercooling of about 65 C below the T 0 -composition line at the carbon range more than 1.10 wt%C is attributed to the non-chemical free energy for the displacive growth of lower bainite. (orig.)

Two-step superconducting transition in Cu-V-Si alloys

International Nuclear Information System (INIS)

Sharma, R.G.; Krishna, M.M.; Narlikar, A.V.

1980-01-01

Copper ternary alloys containing small amounts of vanadium and silicon exhibit a two-step superconducting resistive transition. The first transition occurs around 17 K, the transition temperature of β-W V 3 Si, followed by a plateau and a second transition around 10 K. The resistivity, however, does not drop to zero down to 2.5 K. Reduction of the wire diameter causes the two transitions to shift to lower temperatures. Complete superconductivity in these specimens is absent for two reasons. Firstly, the superconducting volume fraction present in these alloy-wires is below the threshold given by either the effective-medium theory or the site percolation theory. Secondly, the superconducting phase V 3 Si does not precipitate in copper matrix in a fine structure and the proximity effect does not operate strongly. Annealing causes the superconducting particles to coalesce and grow in size and suppresses the proximity effect and superconductivity further in these alloy wires. (author)

Size and pressure effects on glass transition temperature of poly (methyl methacrylate) thin films

International Nuclear Information System (INIS)

Lang, X.Y.; Zhang, G.H.; Lian, J.S.; Jiang, Q.

2006-01-01

A simple and unified model, without any adjustable parameter, is developed for size and pressure effects on glass transition temperatures of nanopolymers. The model is based on a model for size dependent glass transition temperature of nanopolymer glasses under ambient pressure, and a pressure-dependent function of the root of mean-square displacement of atom vibration. It is found that the size- and pressure-dependent glass transition temperatures of free-standing films or supported films having weak interaction with substrates decreases with decreasing of pressure and size. However, the glass transition temperature of supported films having strong interaction with substrates increases with the increase of pressure and the decrease of size. The predicted results correspond with available experimental evidences for atactic-Poly (methyl methacrylate) thin films under hydrostatic pressure or under the pressure induced by supercritical fluid CO 2 . In addition, the predicted glass transition temperature of isotactic-Poly (methyl methacrylate) thin films under ambient pressure is consistent with available experimental evidences

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.

Intermartensitic transitions in Ni-Mn-Fe-Cu-Ga Heusler alloys

International Nuclear Information System (INIS)

Khan, Mahmud; Gautam, Bhoj; Pathak, Arjun; Dubenko, Igor; Stadler, Shane; Ali, Naushad

2008-01-01

A series of Fe doped Ni 2 Mn 0.75-x Fe x Cu 0.25 Ga Heusler alloys have been investigated by means of x-ray diffraction, magnetizations, thermal expansion, and electrical resistivity measurements. In Ni 2 Mn 0.75 Cu 0.25 Ga, martensitic and ferromagnetic transitions occur at the same temperature. Partial substitution of Mn by Fe results in a decrease of the martensitic transition temperature, T M , and an increase of the ferromagnetic transition temperature, T C , resulting in separation of the two transitions. In addition to the martensitic transition, complete thermoelastic intermartensitic transformations have been observed in the Fe doped Ni 2 Mn 0.75-x Fe x Cu 0.25 Ga samples with x>0.04. An unusual transition is observed in the alloy with x = 0.04. The magnetization curve as a function of increasing temperature shows only one first-order transition in the temperature range 5-400 K, which is identified as a typical coupled magnetostructural martensitic transformation. The magnetization curve as a function of decreasing temperature shows three different transitions, which are characterized as the ferromagnetic transition, the martensitic transition and the intermartensitic transition.

The anomalous low temperature resistivity of thermally evaporated α-Mn thin film

International Nuclear Information System (INIS)

Ampong, F.K.; Boakye, F.; Nkum, R.K.

2010-01-01

Electrical resistivity measurements have been carried out on thermally evaporated α-Mn thin film between 300 and 1.4 K using the van der Pauw four probe technique. The film was grown on a glass substrate held at a temperature of 373 K, in an ambient pressure of 5x10 -6 Torr. The results show a resistance minimum, a notable characteristic of α-Mn but at a (rather high) temperature of 194±1 K. Below the resistivity maximum which corresponds to 70 K, the resistivity drops by only 0.02 μΩm indicating a rather short range magnetic ordering. The low temperature results show a tendency towards saturation of the resistivity as the temperature approaches zero suggesting a Kondo scattering.

The anomalous low temperature resistivity of thermally evaporated alpha-Mn thin film

Energy Technology Data Exchange (ETDEWEB)

Ampong, F.K., E-mail: kampxx@yahoo.co [Department of Physics, Kwame Nkrumah University of Science and Technology, Kumasi (Ghana); Boakye, F.; Nkum, R.K. [Department of Physics, Kwame Nkrumah University of Science and Technology, Kumasi (Ghana)

2010-08-15

Electrical resistivity measurements have been carried out on thermally evaporated alpha-Mn thin film between 300 and 1.4 K using the van der Pauw four probe technique. The film was grown on a glass substrate held at a temperature of 373 K, in an ambient pressure of 5x10{sup -6} Torr. The results show a resistance minimum, a notable characteristic of alpha-Mn but at a (rather high) temperature of 194+-1 K. Below the resistivity maximum which corresponds to 70 K, the resistivity drops by only 0.02 muOMEGAm indicating a rather short range magnetic ordering. The low temperature results show a tendency towards saturation of the resistivity as the temperature approaches zero suggesting a Kondo scattering.

Iron-niobium-aluminum alloy having high-temperature corrosion resistance

Science.gov (United States)

Hsu, Huey S.

1988-04-14

An alloy for use in high temperature sulfur and oxygen containing environments, having aluminum for oxygen resistance, niobium for sulfur resistance and the balance iron, is discussed. 4 figs., 2 tabs.

Investigation of low glass transition temperature on COTS PEM's reliability for space applications

Science.gov (United States)

Sandor, M.; Agarwal, S.; Peters, D.; Cooper, M. S.

2003-01-01

Plastic Encapsulated Microelectronics (PEM) reliability is affected by many factors. Glass transition temperature (Tg) is one such factor. In this presentation issues relating to PEM reliability and the effect of low glass transition temperature epoxy mold compounds are presented.

Impacts of land cover transitions on surface temperature in China based on satellite observations

Science.gov (United States)

Zhang, Yuzhen; Liang, Shunlin

2018-02-01

China has experienced intense land use and land cover changes during the past several decades, which have exerted significant influences on climate change. Previous studies exploring related climatic effects have focused mainly on one or two specific land use changes, or have considered all land use and land cover change types together without distinguishing their individual impacts, and few have examined the physical processes of the mechanism through which land use changes affect surface temperature. However, in this study, we considered satellite-derived data of multiple land cover changes and transitions in China. The objective was to obtain observational evidence of the climatic effects of land cover transitions in China by exploring how they affect surface temperature and to what degree they influence it through the modification of biophysical processes, with an emphasis on changes in surface albedo and evapotranspiration (ET). To achieve this goal, we quantified the changes in albedo, ET, and surface temperature in the transition areas, examined their correlations with temperature change, and calculated the contributions of different land use transitions to surface temperature change via changes in albedo and ET. Results suggested that land cover transitions from cropland to urban land increased land surface temperature (LST) during both daytime and nighttime by 0.18 and 0.01 K, respectively. Conversely, the transition of forest to cropland tended to decrease surface temperature by 0.53 K during the day and by 0.07 K at night, mainly through changes in surface albedo. Decreases in both daytime and nighttime LST were observed over regions of grassland to forest transition, corresponding to average values of 0.44 and 0.20 K, respectively, predominantly controlled by changes in ET. These results highlight the necessity to consider the individual climatic effects of different land cover transitions or conversions in climate research studies. This short

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.

Heater rod temperature change at boiling transition under flow oscillation

International Nuclear Information System (INIS)

Kasai, Shigeru; Toba, Akio; Takigawa, Yukio; Ebata, Shigeo; Morooka, Shin-ichi; Shirakawa, Ken-etsu; Utsuno, Hideaki.

1986-01-01

The experiments were performed to investigate the boiling transition phenomenon under flow oscillation (OSBT) during thermal hydraulic instability. It was found, from the experimental results, that the thermal hydraulic instability did not immediately lead to the boiling transition (BT) and, even when the BT occurred due to a power increase, the change in the heater rod temperature was periodically up and down with a saw-toothed shape and no excursion occurred. To investigate the temperature change characteristics, an analysis was also performed using the transient thermal hydraulics code. The analytical results showed that the shape of the heater rod temperature change was well simulated by presuming a repeat of alternate BT and rewetting. Based on these results, further analysis has been performed with the lumped parameter model to investigate the temperature profile characteristics as well as the effects of the post-BT heat transfer coefficient and the flow oscillation period on the maximum temperature. (author)

Structure evolution of multilayer materials of heat-resistant intermetallic compounds under the influence of temperature in the process of diffusion welding under pressure and their mechanical properties

Energy Technology Data Exchange (ETDEWEB)

Korzhov, Valeriy P.; Karpov, Michael I.; Prokhorov, Dmitriy V. [Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka (Russian Federation)

2013-07-01

Multilayer materials of high-resistant intermetallic compounds of some transition metals with aluminum and silicon were obtained by diffusion welding of packages, collected from a large number of the respective foils, such as niobium and aluminum. Materials of intermetallics with silicon were obtained by the welding of packages built from metal foils with Si-coating. The change in the structure according to the temperature of the welding was studied, and the high-temperature bending strength was determined. Key words: multilayer composite, high-resistant material, intermetallic compound, diffusion welding, package rolling, layered structure, bending strength.

Effects of pressure and temperature on thermal contact resistance between different materials

Directory of Open Access Journals (Sweden)

Zhao Zhe

2015-01-01

Full Text Available To explore whether pressure and temperature can affect thermal contact resistance, we have proposed a new experimental approach for measurement of the thermal contact resistance. Taking the thermal contact resistance between phenolic resin and carbon-carbon composites, cuprum, and aluminum as the examples, the influence of the thermal contact resistance between specimens under pressure is tested by experiment. Two groups of experiments are performed and then an analysis on influencing factors of the thermal contact resistance is presented in this paper. The experimental results reveal that the thermal contact resistance depends not only on the thermal conductivity coefficient of materials, but on the interfacial temperature and pressure. Furthermore, the thermal contact resistance between cuprum and aluminum is more sensitive to pressure and temperature than that between phenolic resin and carbon-carbon composites.

Polymorphic crystallization of metal-metalloid-glasses above the glass transition temperature

International Nuclear Information System (INIS)

Koster, U.; Schunemann, U.; Stephenson, G.B.; Brauer, S.; Sutton, M.

1992-01-01

Crystallization of metal-metalloid glasses is known to proceed by nucleation and growth processes. Using crystallization statistics in partially crystallized glasses, at temperatures below the glass transition temperature, time-dependent heterogeneous nucleation has been found to occur at a number of quenched-in nucleation sites. Close to the glass transition temperature crystallization proceeds so rapidly that partially crystallized microstructures could not be obtained. Initial results form fully crystallized glasses exhibit evidence for a transient homogeneous nucleation process at higher temperatures. These conclusions are derived post mortem. At there may be some change of the microstructure after crystallization is finished or during he subsequent quenching, it is desirable to directly obtain information during the early stages of crystallization. Recently reported work by Sutton et al. showed that structural changes can be observed in situ during crystallization by time-resolved x-ray diffraction on time scales as short as milliseconds. The aim o the paper is to present the authors study of the crystallization behavior at temperatures near the glass transition by in-situ x-ray diffraction studies and by microstructural analysis after rapid heating experiments. The results are compared to those derived from a computer model of the crystallization process

Mechanistic insights into the room temperature transitions of polytetrafluoroethylene during electron-beam irradiation

Science.gov (United States)

Fu, Congli; Yu, Xianwei; Zhao, Xiaofeng; Wang, Xiuli; Gu, Aiqun; Xie, Meiju; Chen, Chen; Yu, Zili

2017-11-01

In order to recognize the characteristic thermal transitions of polytetrafluoroethylene (PTFE) occurring at 19 °C and 30 °C, PTFE is irradiated on electron beam accelerator at room temperature and analyzed by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results suggest that the two transition temperatures decrease considerably with increasing irradiation doses. Based on the results of structural analysis, the decrease of the two transition temperatures is supposed to be highly relevant to the structural changes. In particular, the content and structure of the side groups generated in PTFE are responsible for the variations of the two thermal transitions after irradiation, offering fundamental insights into the reaction mechanisms of PTFE during irradiation.

Electrical resistivity and thermopower of ErCo3 under hydrostatic pressure

International Nuclear Information System (INIS)

Nakama, T; Niki, H; Nakamura, D; Takaesu, Y; Hedo, M; Yagasaki, K; Uchima, K; Gratz, E; Burkov, A T

2009-01-01

The magnetic state of the Co 3d-electron subsystem of RCo 3 compounds (R=rare-earth elements) with the rhombohedral PuNi 3 -type structure strongly depends on external parameters. In order to clarify the effect of pressure on the magnetic state of the itinerant Co 3d-electrons, we have measured the electrical resistivity and thermopower at temperatures from 2 K to 300 K under hydrostatic pressures up to 2 GPa. Both, ρ and S show anomalies at critical temperature of metamagnetic transition T m . With increasing pressure T m , determined from the temperature-dependent resistivity and thermopower, decreases and apparently vanishes at P ∼ 0.7 GPa. The electrical resistivity and thermopower at low temperatures show abrupt changes at P ∼ 0.7 GPa, indicating a pressure-induced phase transition.

Pristine carbon nanotubes based resistive temperature sensor

International Nuclear Information System (INIS)

Alam, Md Bayazeed; Saini, Sudhir Kumar; Sharma, Daya Shankar; Agarwal, Pankaj B.

2016-01-01

A good sensor must be highly sensitive, faster in response, of low cost cum easily producible, and highly reliable. Incorporation of nano-dimensional particles/ wires makes conventional sensors more effective in terms of fulfilling the above requirements. For example, Carbon Nanotubes (CNTs) are promising sensing element because of its large aspect ratio, unique electronic and thermal properties. In addition to their use for widely reported chemical sensing, it has also been explored for temperature sensing. This paper presents the fabrication of CNTs based temperature sensor, prepared on silicon substrate using low cost spray coating method, which is reliable and reproducible method to prepare uniform CNTs thin films on any substrate. Besides this, simple and inexpensive method of preparation of dispersion of single walled CNTs (SWNTs) in 1,2 dichlorobenzene by using probe type ultrasonicator for debundling the CNTs for improving sensor response were used. The electrical contacts over the dispersed SWNTs were taken using silver paste electrodes. Fabricated sensors clearly show immediate change in resistance as a response to change in temperature of SWNTs. The measured sensitivity (change in resistance with temperature) of the sensor was found ∼ 0.29%/°C in the 25°C to 60°C temperature range.

Pristine carbon nanotubes based resistive temperature sensor

Energy Technology Data Exchange (ETDEWEB)

Alam, Md Bayazeed, E-mail: bayazeed786@gmail.com [CSIR-Central Electronics Engineering Research Institute (CEERI, Pilani, India) (India); Jamia Millia Islamia (New Delhi, India) (India); Saini, Sudhir Kumar, E-mail: sudhirsaini1310@gmail.com [CSIR-Central Electronics Engineering Research Institute (CEERI, Pilani, India) (India); Sharma, Daya Shankar, E-mail: dssharmanit15@gmail.com [CSIR-Central Electronics Engineering Research Institute (CEERI, Pilani, India) (India); Maulana Azad National Institute of Technology (MANIT, Bhopal, India) (India); Agarwal, Pankaj B., E-mail: agarwalbpankj@gmail.com [CSIR-Central Electronics Engineering Research Institute (CEERI, Pilani, India) (India); Academy for Scientific and Innovative Research (AcSIR, Delhi, India) (India)

2016-04-13

A good sensor must be highly sensitive, faster in response, of low cost cum easily producible, and highly reliable. Incorporation of nano-dimensional particles/ wires makes conventional sensors more effective in terms of fulfilling the above requirements. For example, Carbon Nanotubes (CNTs) are promising sensing element because of its large aspect ratio, unique electronic and thermal properties. In addition to their use for widely reported chemical sensing, it has also been explored for temperature sensing. This paper presents the fabrication of CNTs based temperature sensor, prepared on silicon substrate using low cost spray coating method, which is reliable and reproducible method to prepare uniform CNTs thin films on any substrate. Besides this, simple and inexpensive method of preparation of dispersion of single walled CNTs (SWNTs) in 1,2 dichlorobenzene by using probe type ultrasonicator for debundling the CNTs for improving sensor response were used. The electrical contacts over the dispersed SWNTs were taken using silver paste electrodes. Fabricated sensors clearly show immediate change in resistance as a response to change in temperature of SWNTs. The measured sensitivity (change in resistance with temperature) of the sensor was found ∼ 0.29%/°C in the 25°C to 60°C temperature range.

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-05-07

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

Temperature and mixing effects on electrical resistivity of carbon fiber enhanced concrete

International Nuclear Information System (INIS)

Chang, Christiana; Song, Gangbing; Gao, Di; Mo, Y L

2013-01-01

In this paper, the effect of temperature and mixing procedure on the electrical resistivity of carbon fiber enhanced concrete is investigated. Different compositions of concrete containing varying concentrations of carbon fiber into normal and self-consolidating concrete (SCC) were tested under DC electrical loading over the temperature range −10 to 20 °C. The electrical resistivity of the bulk samples was calculated and compared against temperature. It was observed that there is an inverse exponential relationship between resistivity and temperature which follows the Arrhenius relationship. The bulk resistivity decreased with increasing fiber concentration, though data from SCC indicates a saturation limit beyond which electrical resistivity begins to drop. The activation energy of the bulk electrically conductive concrete was calculated and compared. While SCC exhibited the lowest observed electrical resistance, the activation energy was similar amongst SCC and surfactant enhanced concrete, both of which were lower than fiber dispersed in normal concrete. (paper)

High temperature creep strength of Advanced Radiation Resistant Oxide Dispersion Strengthened Steels

Energy Technology Data Exchange (ETDEWEB)

Noh, Sanghoon; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-05-15

Austenitic stainless steel may be one of the candidates because of good strength and corrosion resistance at the high temperatures, however irradiation swelling well occurred to 120dpa at high temperatures and this leads the decrease of the mechanical properties and dimensional stability. Compared to this, ferritic/martensitic steel is a good solution because of excellent thermal conductivity and good swelling resistance. Unfortunately, the available temperature range of ferritic/martensitic steel is limited up to 650 .deg. C. ODS steel is the most promising structural material because of excellent creep and irradiation resistance by uniformly distributed nano-oxide particles with a high density which is extremely stable at the high temperature in ferritic/martensitic matrix. In this study, high temperature strength of advanced radiation resistance ODS steel was investigated for the core structural material of next generation nuclear systems. ODS martensitic steel was designed to have high homogeneity, productivity and reproducibility. Mechanical alloying, hot isostactic pressing and hot rolling processes were employed to fabricate the ODS steels, and creep rupture test as well as tensile test were examined to investigate the behavior at high temperatures. ODS steels were fabricated by a mechanical alloying and hot consolidation processes. Mechanical properties at high temperatures were investigated. The creep resistance of advanced radiation resistant ODS steels was more superior than those of ferritic/ martensitic steel, austenitic stainless steel and even a conventional ODS steel.

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)

Detection of Resistive Transitions in LHC Superconducting Components

OpenAIRE

Denz, R; Rodríguez-Mateos, F

2001-01-01

The LHC has entered the construction phase. It will incorporate a large number of superconducting components like magnets, current leads and busbars. All these components require protection means in case of a transition from the superconducting to the resistive state, the so-called quench. Key elements in the protection system are electronic quench detectors, which have to be able to identify a quench in any state of the powering cycle of the accelerator. According to the different properties...

Study on the high temperature crack resistance of tungsten

International Nuclear Information System (INIS)

Uskov, E.I.; Babak, A.V.

1983-01-01

The possibility of a multiple use of tungsten specimens in crack resistance tests in the temperature range of 600-2000 deg C is studied. It is established experimentally that the minimum length of growth of a main crack is 1x10 -4 m for the most effective repeated use of specimens. A flow diagram of mechanical tests is suggested for investigating high temperature tungsten crack resistance and estimating the degree of weakening the grain-boundary bond

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

Directory of Open Access Journals (Sweden)

Tsenguun Byambadorj

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

Giant magneto resistance and temperature coefficient of resistance in Sm0.55Sr0.30Ag0.15MnO3 perovskite

Directory of Open Access Journals (Sweden)

Masroor Ahmad Bhat

2016-12-01

Full Text Available Silver ions substituted samarium strontium manganite (Sm0.55Sr0.30Ag0.15MnO3 pervoskite was synthesized by using respective oxides in stoichiometric ratio through solid state reaction. The as-prepared sample was characterized by various analytical techniques to confirm its formation and understand the effect of monovalent silver ions in pervoskite lattice. X-ray diffraction pattern confirms the single phase formation while grain morphology in SEM image indicates good connectivity among the grains. The enhancement in metal to insulator transition temperature shows quenched disorder and magnetoresistance phenomena. The magnetoresistance (MR and temperature coefficient of resistance (TCR emerge from grain growth factor and homogeneity induced by Ag+ ions in the lattice. The reduction in hysteresis loss resulted from antiferromagnetic - ferromagnetic (TN and ferromagnetic - paramagnetic (Tc transitions reveals the removal of disorder in perovskite lattice by Ag+ ions substitution. This increases the magnetic moment across distinct ions on the applying magnetic field. The rise in MR% (~99% with silver doping emerging from smooth spin tunneling of the grains across the boundary and suppression of the disordered magnetic fluctuations with increase in magnetic field has been reported. The present compound exhibits the first order nature of magnetism and observed first time the highest value of TCR ~ 95%.

Theory of quantum metal to superconductor transitions in highly conducting systems

Energy Technology Data Exchange (ETDEWEB)

Spivak, B.

2010-04-06

We derive the theory of the quantum (zero temperature) superconductor to metal transition in disordered materials when the resistance of the normal metal near criticality is small compared to the quantum of resistivity. This can occur most readily in situations in which 'Anderson's theorem' does not apply. We explicitly study the transition in superconductor-metal composites, in an swave superconducting film in the presence of a magnetic field, and in a low temperature disordered d-wave superconductor. Near the point of the transition, the distribution of the superconducting order parameter is highly inhomogeneous. To describe this situation we employ a procedure which is similar to that introduced by Mott for description of the temperature dependence of the variable range hopping conduction. As the system approaches the point of the transition from the metal to the superconductor, the conductivity of the system diverges, and the Wiedemann-Franz law is violated. In the case of d-wave (or other exotic) superconductors we predict the existence of (at least) two sequential transitions as a function of increasing disorder: a d-wave to s-wave, and then an s-wave to metal transition.

Temperature dependence of the electrical resistivity of amorphous Co80-xErxB20 alloys

International Nuclear Information System (INIS)

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

2008-01-01

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

The Interface Structure of High-Temperature Oxidation-Resistant Aluminum-Based Coatings on Titanium Billet Surface

Science.gov (United States)

Xu, Zhefeng; Rong, Ju; Yu, Xiaohua; Kun, Meng; Zhan, Zhaolin; Wang, Xiao; Zhang, Yannan

2017-10-01

A new type of high-temperature oxidation-resistant aluminum-based coating, on a titanium billet surface, was fabricated by the cold spray method, at a high temperature of 1050°C, for 8 h, under atmospheric pressure. The microstructure of the exposed surface was analyzed via optical microscopy, the microstructure of the coating and elemental diffusion was analyzed via field emission scanning electron microscopy, and the interfacial phases were identified via x-ray diffraction. The Ti-Al binary phase diagram and Gibbs free energy of the stable phase were calculated by Thermo-calc. The results revealed that good oxidation resistant 50-μm-thick coatings were successfully obtained after 8 h at 1050°C. Two layers were obtained after the coating process: an Al2O3 oxidation layer and a TiAl3 transition layer on the Ti-based substrate. The large and brittle Al2O3 grains on the surface, which can be easily spalled off from the surface after thermal processing, protected the substrate against oxidation during processing. In addition, the thermodynamic calculation results were in good agreement with the experimental data.

Experimental study of the magnetic phase transition in the MnSi itinerant helimagnet

International Nuclear Information System (INIS)

Stishov, S. M.; Petrova, A. E.; Khasanov, S.; Panova, G. Kh.; Shikov, A. A.; Lashley, J. C.; Wu, D.; Lograsso, T. A.

2008-01-01

Magnetic susceptibility, heat capacity, thermal expansion, and resistivity of a high-quality single crystal of MnSi were carefully studied at ambient pressure. The calculated change in magnetic entropy in the temperature range 0-30 K is less than 0.1R, a low value that emphasizes the itinerant nature of magnetism in MnSi. A linear temperature term dominates the behavior of the thermal expansion coefficient in the range 30-150 K, which correlates to a large enhancement of the linear electronic term in the heat capacity. A surprising similarity between variation of the heat capacity, the thermal expansion coefficient, and the temperature derivative of resistivity through the phase transition in MnSi is observed. Specific forms of the heat capacity, thermal expansion coefficient, and temperature derivative of resistivity at the phase transition to a helical magnetic state near 29 K are interpreted as a combination of sharp first-order features and broad peaks or shallow valleys of yet unknown origin. The appearance of these broad satellites probably hints at a frustrated magnetic state in MnSi slightly above the transition temperature. Present experimental findings bring the current views on the phase diagram of MnSi into question

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

Theory of high-T{sub C} superconductivity: transition temperature

Energy Technology Data Exchange (ETDEWEB)

Harshman, Dale R [Physikon Research Corporation, Lynden, WA 98264 (United States); Fiory, Anthony T [Department of Physics, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Dow, John D, E-mail: drh@physikon.net [Department of Physics, Arizona State University, Tempe, AZ 85287 (United States)

2011-07-27

It is demonstrated that the transition temperature (T{sub C}) of high-T{sub C} superconductors is determined by their layered crystal structure, bond lengths, valency properties of the ions, and Coulomb coupling between electronic bands in adjacent, spatially separated layers. Analysis of 31 high-T{sub C} materials (cuprates, ruthenates, ruthenocuprates, iron pnictides, organics) yields the universal relationship for optimal compounds, k{sub B}T{sub C0} ={beta}/{iota}{zeta}, where {iota} is related to the mean spacing between interacting charges in the layers, {zeta} is the distance between interacting electronic layers, {beta} is a universal constant and T{sub C0} is the optimal transition temperature (determined to within an uncertainty of {+-} 1.4 K by this relationship). Non-optimum compounds, in which sample degradation is evident, e.g. by broadened superconducting transitions and diminished Meissner fractions, typically exhibit reduced T{sub C} < T{sub C0}. It is shown that T{sub C0} may be obtained from an average of the Coulomb interaction forces between the two layers.

Polymer brushes: a controllable system with adjustable glass transition temperature of fragile glass formers.

Science.gov (United States)

Xie, Shi-Jie; Qian, Hu-Jun; Lu, Zhong-Yuan

2014-01-28

We present results of molecular dynamics simulations for coarse-grained polymer brushes in a wide temperature range to investigate the factors that affect the glass transition in these systems. We focus on the influences of free surface, polymer-substrate interaction strength, grafting density, and chain length not only on the change of glass transition temperature Tg, but also the fragility D of the glass former. It is found that the confinement can enhance the dependence of the Tg on the cooling rate as compared to the bulk melt. Our layer-resolved analysis demonstrates that it is possible to control the glass transition temperature Tg of polymer brushes by tuning the polymer-substrate interaction strength, the grafting density, and the chain length. Moreover, we find quantitative differences in the influence range of the substrate and the free surface on the density and dynamics. This stresses the importance of long range cooperative motion in glass formers near the glass transition temperature. Furthermore, the string-like cooperative motion analysis demonstrates that there exists a close relation among glass transition temperature Tg, fragility D, and string length ⟨S⟩. The polymer brushes that possess larger string length ⟨S⟩ tend to have relatively higher Tg and smaller D. Our results suggest that confining a fragile glass former through forming polymer brushes changes not only the glass transition temperature Tg, but also the very nature of relaxation process.

Remote calibration of Resistance Temperature Devices (RTDs): Final report

International Nuclear Information System (INIS)

Blalock, T.V.; Roberts, M.J.

1988-02-01

Johnson noise power measuring techniques have been used to calibrate platinum resistance temperature detectors (RTDs) installed in an operating nuclear plant - Connecticut Yankee Atomic Power Company's Haddam Neck Nuclear Plant - achieving agreement with the dc calibration from better than 0.1% to as much as 1% (0.54 to 9.7 0 F) at the normal operating temperature of 585 0 F. Tests were also conducted at plant shutdown conditions. In this application, RTDs with an ice point resistance of 200 Ω were connected with four-wire extension cables approximately 100-ft long to a test station in containment. Methods were developed for in situ characterization of the extension cables and for quantitative measurement of and correction for nonthermal induced noise. Analysis of dc calibration methods showed that resistance-temperature tables used with industrial PRTs may be in error by 0.2 0 F or 0.02% A (expressed as a percentage of absolute temperature in either Kelvin or degrees Rankine) at 540 0 F. Recalibration of the RTDs measured in the plant tests showed differences of about 2.5 0 F or 0.2% A at 540 0 F from calibration tables used in the plant

Metal-insulator transition upon heating and negative-differential-resistive-switching induced by self-heating in BaCo{sub 0.9}Ni{sub 0.1}S{sub 1.8}

Energy Technology Data Exchange (ETDEWEB)

Fisher, B.; Genossar, J.; Chashka, K. B.; Patlagan, L.; Reisner, G. M. [Physics Department, Technion-Israel Institute of Technology, Haifa 32000 (Israel)

2014-04-14

The layered compound BaCo{sub 1−x}Ni{sub x}S{sub 2−y} (0.05 < x < 0.2 and 0.05 < y < 0.2) exhibits an unusual first-order structural and electronic phase transition from a low-T monoclinic paramagnetic metal to a high-T tetragonal antiferromagnetic insulator around 200 K with huge hysteresis (∼40 K) and large volume change (∼0.01). Here, we report on unusual voltage-controlled resistive switching followed by current-controlled resistive switching induced by self-heating in polycrystalline BaCo{sub 1−x}Ni{sub x}S{sub 2−y} (nominal x = 0.1 and y = 0.2). These were due to the steep metal to insulator transition upon heating followed by the activated behavior of the resistivity above the transition. The major role of Joule heating in switching is supported by the absence of nonlinearity in the current as function of voltage, I(V), obtained in pulsed measurements, in the range of electric fields relevant to d.c. measurements. The voltage-controlled negative differential resistance around the threshold for switching was explained by a simple model of self-heating. The main difficulty in modeling I(V) from the samples resistance as function of temperature R(T) was the progressive increase of R(T), and to a lesser extend the decrease of the resistance jumps at the transitions, caused by the damage induced by cycling through the transitions by heating or self-heating. This was dealt with by following systematically R(T) over many cycles and by using the data of R(T) in the heating cycle closest to that of the self-heating one.

Open volume defects and magnetic phase transition in Fe{sub 60}Al{sub 40} transition metal aluminide

Energy Technology Data Exchange (ETDEWEB)

Liedke, M. O., E-mail: m.liedke@hzdr.de; Anwand, W.; Butterling, M.; Wagner, A. [Institute of Radiation Physics, Helmholtz-Zentrum Dresden - Rossendorf, Bautzner Landstraße 400, 01328 Dresden (Germany); Bali, R.; Cornelius, S.; Potzger, K. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden - Rossendorf, Bautzner Landstraße 400, 01328 Dresden (Germany); Trinh, T. T. [Institute of Radiation Physics, Helmholtz-Zentrum Dresden - Rossendorf, Bautzner Landstraße 400, 01328 Dresden (Germany); Technical University Dresden, Helmholtzstr. 10, 01609 Dresden (Germany); Salamon, S.; Walecki, D.; Smekhova, A.; Wende, H. [Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Lotharstraße 1, 47048 Duisburg (Germany)

2015-04-28

Magnetic phase transition in the Fe{sub 60}Al{sub 40} transition metal aluminide from the ferromagnetic disordered A2-phase to the paramagnetic ordered B2-phase as a function of annealing up to 1000 °C has been investigated by means of magneto-optical and spectroscopy techniques, i.e., Kerr effect, positron annihilation, and Mössbauer spectroscopy. The positron annihilation spectroscopy has been performed in-situ sequentially after each annealing step at the Apparatus for In-situ Defect Analysis that is a unique tool combining positron annihilation spectroscopy with temperature treatment, material evaporation, ion irradiation, and sheet resistance measurement techniques. The overall goal was to investigate the importance of the open volume defects onto the magnetic phase transition. No evidence of variation in the vacancy concentration in matching the magnetic phase transition temperature range (400–600 °C) has been found, whereas higher temperatures showed an increase in the vacancy concentration.

Taste and Temperature in Swallowing Transit Time after Stroke

Directory of Open Access Journals (Sweden)

Paula C. Cola

2012-09-01

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

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.

Studies of the Superconducting Transition in the Mo/Au-Bilayer Thin Films

Science.gov (United States)

Sadleir, John; Smith, Stephen; Iyomoto, naoko; Bandler, Simon; Chervenak, Jay; Brown, Ari; Brekowsky, Regis; Kilbourne, Caroline; Robinson, Ian

2007-01-01

At NASA Goddard, microcalorimeter arrays using superconducting transition edge sensor thermometers (TESs) are under development for high energy resolution X-ray astrophysics applications. We report on our studies of the superconducting transition in our Mo/Au-bilayer TES films including: low current measurements of the superconducting bilayer's resistance transition versus temperature on pixels with different normal metal absorber attachment designs and measured temperature scaling of the critical current and critical magnetic field.

Effect of some structural parameters on high-temperature crack resistance of tungsten

International Nuclear Information System (INIS)

Babak, A.V.; Uskov, E.I.

1984-01-01

The paper presents results of physicomechanical studied in high-temperature crack resistance of tungsten produced by powder metallurgy methods. It is shown that at high temperatures (>2000 deg C) a structure is formed in the material and fails at stresses independent of temperature. It is found that high-temperature tungsten crack resistance is affected neighter by changes in the effictive grain size, nor by appearance of grain-boundary microcraks in the material under high-temperature action

Specific heat and electric conductivity of zirconium alloy with 2,5 mass% niobium in the range of phase transitions

International Nuclear Information System (INIS)

Roshchupkin, V.V.; Pokrasin, M.A.; Chernov, A.I.; Semashko, N.A.

1996-01-01

Experimental investigation of specific heat and electric resistance of zirconium alloy with 2.5 mass% niobium in the range of phase transitions was conducted, using adiabatic calorimeter of original design, characterized by high sensitivity, efficiency and high accuracy. It was revealed that temperature dependence of specific heat was characterized by anomalous growth at 590 deg C, related with (α+β Nb )→(α+β Zr )-transition, and at 810 deg -related with (α+β Zr )→β Zr - transition. Temperature dependence of electric resistance was specific in the region of α+β Zr →β Zr phase transition. It was established that revealed anomalies were connected with high oxygen absorption at high temperatures. 11 refs., 1 fig., 1 tab

Temperature dependence of collapse of quantized hall resistance

International Nuclear Information System (INIS)

Tanaka, Hiroyasu; Kawashima, Hironori; Iizuka, Hisamitsu; Fukuda, Hideaki; Kawaji, Shinji

2006-01-01

Similarity is observed in the deviation of Hall resistance from the quantized value with the increase in the source-drain current I SD in our butterfly-type Hall bars and in the Hall bars used by Jeanneret et al., while changes in the diagonal resistivity ρ xx with I SD are significantly different between these Hall bars. The temperature dependence of the critical Hall electric field F cr (T) for the collapse of R H (4) measured in these Hall bars is approximated using F cr (T) = F cr (0)(1 - (T/T cr ) 2 ). Here, the critical Hall electric field at zero temperature depends on the magnetic field B as F cr (0) ∝ B 3/2 . Theoretical considerations are given on F cr (T) on the basis of a temperature-dependent mobility edge model and a schema of temperature-dependent inter-Landau level tunneling probability arising from the Fermi distribution function. The former does not fit in with the I SD dependence of activation energy in ρ xx . (author)

Investigation on low room-temperature resistivity Cr/(Ba0.85Pb0.15)TiO3 positive temperature coefficient composites

DEFF Research Database (Denmark)

He, Zeming; Ma, J.; Qu, Yuanfang

2009-01-01

discussed. Using these special processes, the prepared composite with 20 wt% Cr possessed low room-temperature resistivity (2.96 Ω cm at 25 °C) and exhibited PTC effect (resistivity jump of 10), which is considered as a promising candidate for over-current protector when working at low voltage. The grain......Low room-temperature resistivity positive temperature coefficient (PTC) Cr/(Ba0.85Pb0.15)TiO3 composites were produced via a reducing sintering and a subsequent oxidation treatment. The effects of metallic content and processing conditions on materials resistivity–temperature properties were...

Relaxation Dynamics of the Glass Transition in PMMA+SWCNT Composites by Temperature-Modulated DSC

Science.gov (United States)

Pradhan, Nihar; Iannacchione, Germano

2010-03-01

Temperature Modulated Differential Scanning Calorimeter (TMDSC) used to investigate the thermal relaxation dynamics of PMMA-Single wall carbon nanotubes (SWCNTs) through the glass transition as a function of frequency. A strong dependence of the temperature dependence peak in imaginary part of complex heat capacity (Tmax) was found during the transition from glass like to liquid like region and can be described by Arhenius law. The activation energy shows increases while the charactersistic time decreases with increasing mass fraction (φm) of SWCNTs. Decreasing of enthalpy, while heating and slowly increasing while cooling at 2.0 K/min scan rate was observed and as frequency of temperature modulation increases. There is no relative change of enthalpy in heating and cooling observed at sufficiently slow scan rate. The glass transition temperature (Tg) shows increases as a function of frequency of temperature modulation, φm of SWCNTs and with increasing scan rate. From imaginary part of heat capacity, it obvious that Tmax is not the actual glass transition temperature of pure polymer but Tmax and Tg values can be superimpose when φm of SWCNT increases in polymer.

Influence of temperature and heat treatment on crack resistance of ceramic tungsten

International Nuclear Information System (INIS)

Uskov, E.I.; Babak, A.V.; Bega, N.D.

1983-01-01

The effect of testing temperature in the range from 20 to 2000 deg C, and recrystallization annealing at 2200 deg C on crack resistance of ceramic tungsten in vacuum, is investigated. The extension diagrams thus obtained have been treated in accordance with the standard technique. The value of the critical crack loading and the stress intensity coefficient have been determined. Structural changes have been controlled with X-ray structural methods. Crack resistance of tungsten increases in the test temperature range from 20 deg C to Tsub(x) which is connected with the increase of mobility of screw components of dislocation loops. At the temperature more than Tsub(x) the plasticity growth of ceramic tungsten takes place simultaneously with grain boundary embrittlement. Recrystallization annealing at 2200 deg C creates the structure resistant to temperature effect; crack resistance being minimum

Temperature dependence of residual electrical resistivity of Cu-Au in pseudopotential approximation

International Nuclear Information System (INIS)

Khwaja, F.A.; Ahmed, I.; Shaukat, A.

1986-08-01

The problem of temperature dependence of residual electrical resistivity of Cu-Au system is re-examined in the light of static distortion and thermal vibration of the lattice along with the short-range-order of atoms above critical temperature. The extended version of Ziman's formula for resistivity obtained yields a unified version for the calculation of resistivity in pseudopotential approximation. The temperature dependence of the quantity Δρ/ρ in this framework for Cu-Au system is found to be in better agreement with the experimental data as compared to previous calculation. (author)

Superconducting terahertz mixer using a transition-edge microbolometer

Science.gov (United States)

Prober, D. E.

1993-01-01

We present a new device concept for a mixer element for THz frequencies. This uses a superconducting transition-edge microbridge biased at the center of its superconducting transition near 4.2 K. It is fed from an antenna or waveguide structure. Power from a local oscillator and an RF signal produce a temperature and resulting resistance variation at the difference frequency. The new aspect is the use of a very short bridge in which rapid (less than 0.1 ns) outdiffusion of hot electrons occurs. This gives large intermediate frequency (IF) response. The mixer offers about 4 GHz IF bandwidth, about 80 ohm RF resistive impedance, good match to the IF amplifier, and requires only 1-20 nW of local oscillator power. The upper RF frequency is determined by antenna or waveguide properties. Predicted mixer conversion efficiency is 1/8, and predicted double-sideband receiver noise temperatures are 260 and 90 K for transition widths of 0.1 and 0.5 Tc, respectively.

Electroforming and Switching in Oxides of Transition Metals: The Role of Metal Insulator Transition in the Switching Mechanism

Science.gov (United States)

Chudnovskii, F. A.; Odynets, L. L.; Pergament, A. L.; Stefanovich, G. B.

1996-02-01

Electroforming and switching effects in sandwich structures based on anodic films of transition metal oxides (V, Nb, Ti, Fe, Ta, W, Zr, Hf, Mo) have been studied. After being electroformed, some materials exhibited current-controlled negative resistance with S-shapedV-Icharacteristics. For V, Fe, Ti, and Nb oxides, the temperature dependences of the threshold voltage have been measured. As the temperature increased,Vthdecreased to zero at a critical temperatureT0, which depended on the film material. Comparison of theT0values with the temperatures of metal-insulator phase transition for some compounds (Tt= 120 K for Fe3O4, 340 K for VO2, ∼500 K for Ti2O3, and 1070 K for NbO2) showed that switching was related to the transition in the applied electric field. Channels consisting of the above-mentioned lower oxides were formed in the initial anodic films during the electroforming. The possibility of formation of these oxides with a metal-insulator transition was confirmed by thermodynamic calculations.

Semiconductor resistance thermometer for the temperature range 300-0.3 K

International Nuclear Information System (INIS)

Zinov'eva, K.N.; Zarubin, L.I.; Nemish, I.Yu.; Vorobkalo, F.M.; Boldarev, S.T.; AN Ukrainskoj SSR, Kiev. Inst. Poluprovodnikov)

1979-01-01

Thermometric characteristics of semiconductor resistor thermometers for the temperature range from 300 to 0.3 K and from 77 to 0.3 K are given. Temperature dependence of thermometer resistances in the 300-1.3 K range was measured in cryostats with pumping-out of N 2 , H 2 and 4 He. For measurements below 1.3 K use was made of a 3 H- 4 He dissolving cryostat. The accuracy of measuring temperatures in the 1.3-0.3 K range is not below +-0.003 K, the error in determining thermometer resistances does not exceed 1%. The analysis of obtained thermometric characteristics of several series of semiconductor resistance thermometers showed that observed insignificant spread of resistances of thermometers in one series and identity of characteristics allows them to be used without preliminary calibration for relatively coarse measurements in the range from 3O0 to 0.3 K. Besides, it has been found that in the 4.2-0.3 K range the thermometric characteristics represent a straight line in the lgR-Tsup(-n) coordinates, where R is the thermometer resistance, T is the temperature and n=0.5. Thus, the thermometers of the same series can be calibrated only in 2 or 3 reference point measurements

Glass transition in thin supported polystyrene films probed by temperature-modulated ellipsometry in vacuum.

Science.gov (United States)

Efremov, Mikhail Yu; Kiyanova, Anna V; Last, Julie; Soofi, Shauheen S; Thode, Christopher; Nealey, Paul F

2012-08-01

Glass transition in thin (1-200 nm thick) spin-cast polystyrene films on silicon surfaces is probed by ellipsometry in a controlled vacuum environment. A temperature-modulated modification of the method is used alongside a traditional linear temperature scan. A clear glass transition is detected in films with thicknesses as low as 1-2 nm. The glass transition temperature (T(g)) shows no substantial dependence on thickness for coatings greater than 20 nm. Thinner films demonstrate moderate T(g) depression achieving 18 K for thicknesses 4-7 nm. Less than 4 nm thick samples are excluded from the T(g) comparison due to significant thickness nonuniformity (surface roughness). The transition in 10-20 nm thick films demonstrates excessive broadening. For some samples, the broadened transition is clearly resolved into two separate transitions. The thickness dependence of the glass transition can be well described by a simple 2-layer model. It is also shown that T(g) depression in 5 nm thick films is not sensitive to a wide range of experimental factors including molecular weight characteristics of the polymer, specifications of solvent used for spin casting, substrate composition, and pretreatment of the substrate surface.

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

Phytoclimatic assessment of air temperatures transition across important Bbundary values

International Nuclear Information System (INIS)

Kazandjiev, Valentin; Slavov, Nicola

2004-01-01

Thermal regime investigation in global and regional scale is the problem permanently in field of vision of climatologists in the world. Many of investigations abroad and in our country are devoted to discover long time variation, cycles and their periodicity and especially on the registration of air temperatures changes and averages per year, per six months, seasons and months. Great interest is assessment of change of terms for strong air temperatures transition across 0, 5, 10 and 15 o C during spring and autumn seasons, because they have important scientific and practical application i.e. they are the limit between cold and warm part of the year and trace out duration of the vegetative and non vegetative for different bio ecosystems such as phyto ecosystems and zoo ecosystems. For this reason, the interest on the investigation of agro climatic and forest climatic peculiarity of these indicators increase for last few years. This increase is connected with big importance part of nature season's dynamics connected with human economic activity. Increase of air temperature up to 0 o C an transition by this limit certify for change of cold with warm period and beginning of spring; Contrariwise, decrease the temperatures down the 0 o C shows the end of autumn and beginning of winter. In the moderate continental climatic regions, where is classified most big part of Bulgaria territory is observed for seasons - winter, spring, summer and autumn. Climatologists usually accept these seasons with equal duration - three months. This duration of the seasons, do not permit to provide clear assessment of meteorological conditions in connection with development of plant ecosystems and production in different country regions. By this reason, seasons differentiation by agro climatic and forest-climatic point of view is other use the annual course of the air temperatures. As a strong and most suitable way for beginning and end of seasons are air temperatures transitions up and down

Influence of deposition temperature and amorphous carbon on microstructure and oxidation resistance of magnetron sputtered nanocomposite Crsbnd C films

Science.gov (United States)

Nygren, Kristian; Andersson, Matilda; Högström, Jonas; Fredriksson, Wendy; Edström, Kristina; Nyholm, Leif; Jansson, Ulf

2014-06-01

It is known that mechanical and tribological properties of transition metal carbide films can be tailored by adding an amorphous carbon (a-C) phase, thus making them nanocomposites. This paper addresses deposition, microstructure, and for the first time oxidation resistance of magnetron sputtered nanocomposite Crsbnd C/a-C films with emphasis on studies of both phases. By varying the deposition temperature between 20 and 700 °C and alternating the film composition, it was possible to deposit amorphous, nanocomposite, and crystalline Crsbnd C films containing about 70% C and 30% Cr, or 40% C and 60% Cr. The films deposited at temperatures below 300 °C were X-ray amorphous and 500 °C was required to grow crystalline phases. Chronoamperometric polarization at +0.6 V vs. Ag/AgCl (sat. KCl) in hot 1 mM H2SO4 resulted in oxidation of Crsbnd C, yielding Cr2O3 and C, as well as oxidation of C. The oxidation resistance is shown to depend on the deposition temperature and the presence of the a-C phase. Physical characterization of film surfaces show that very thin C/Cr2O3/Crsbnd C layers develop on the present material, which can be used to improve the oxidation resistance of, e.g. stainless steel electrodes.

Phase transition temperatures of 405-725 K in superfluid ultra-dense hydrogen clusters on metal surfaces

International Nuclear Information System (INIS)

Holmlid, Leif; Kotzias, Bernhard

2016-01-01

Ultra-dense hydrogen H(0) with its typical H-H bond distance of 2.3 pm is superfluid at room temperature as expected for quantum fluids. It also shows a Meissner effect at room temperature, which indicates that a transition point to a non-superfluid state should exist above room temperature. This transition point is given by a disappearance of the superfluid long-chain clusters H_2_N(0). This transition point is now measured for several metal carrier surfaces at 405 - 725 K, using both ultra-dense protium p(0) and deuterium D(0). Clusters of ordinary Rydberg matter H(l) as well as small symmetric clusters H_4(0) and H_3(0) (which do not give a superfluid or superconductive phase) all still exist on the surface at high temperature. This shows directly that desorption or diffusion processes do not remove the long superfluid H_2_N(0) clusters. The two ultra-dense forms p(0) and D(0) have different transition temperatures under otherwise identical conditions. The transition point for p(0) is higher in temperature, which is unexpected.

Magnetic field and pressure dependant resistivity behaviour of MnAs

Science.gov (United States)

Satya, A. T.; Amaladass, E. P.; Mani, Awadhesh

2018-04-01

The studies on the effect of magnetic field and external pressure on temperature dependant electrical resistivity behaviour of polycrystalline MnAs have been reported. At ambient pressure, ρ(T) shows a first order magnetic transition associated with change in sign of the temperature coefficient of resistivity from positive in the ferromagnetic (FM) phase to negative in the paramagnetic (PM) phase. The magneto resistance is negative and shows a peak at the FM transition temperature (T C ). The first order hysteresis width decreases with increase in magnetic field and the intersection of extrapolated linear variations of T C with field for the cooling and warming cycles enabled determination of the tricritical point. At high pressures, ρ(T) displays non monotonic variation exhibiting a low temperature minimum ({T}\\min L) and a high temperature maximum ({T}\\max H) accompanying broad thermal hysteresis above {T}\\min L. It is surmised that spin disorder scattering is responsible for the resistivity behaviour above {T}\\min L and the essential features of ρ(T) are qualitatively explained using Kasuya theoretical model. Below the {T}\\min L, ρ(T) follows linear logarithmic temperature dependence similar to the effect occurring due to Kondo type of scattering of conduction electrons with localised moments.

Note on the glass transition temperature of poly(vinylphenol)

Czech Academy of Sciences Publication Activity Database

Kratochvíl, Jaroslav; Šturcová, Adriana; Sikora, Antonín; Dybal, Jiří

2009-01-01

Roč. 45, č. 6 (2009), s. 1851-1856 ISSN 0014-3057 Institutional research plan: CEZ:AV0Z40500505 Keywords : Poly(4-vinylphenol) * glass transition temperature * differential scanning calorimetry Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.310, year: 2009

Probability based high temperature engineering creep and structural fire resistance

CERN Document Server

Razdolsky, Leo

2017-01-01

This volume on structural fire resistance is for aerospace, structural, and fire prevention engineers; architects, and educators. It bridges the gap between prescriptive- and performance-based methods and simplifies very complex and comprehensive computer analyses to the point that the structural fire resistance and high temperature creep deformations will have a simple, approximate analytical expression that can be used in structural analysis and design. The book emphasizes methods of the theory of engineering creep (stress-strain diagrams) and mathematical operations quite distinct from those of solid mechanics absent high-temperature creep deformations, in particular the classical theory of elasticity and structural engineering. Dr. Razdolsky’s previous books focused on methods of computing the ultimate structural design load to the different fire scenarios. The current work is devoted to the computing of the estimated ultimate resistance of the structure taking into account the effect of high temperatur...

Temperature-dependent vibrational spectroscopy to study order-disorder transitions in charge transfer complexes

Science.gov (United States)

Isaac, Rohan; Goetz, Katelyn P.; Roberts, Drew; Jurchescu, Oana D.; McNeil, L. E.

2018-02-01

Charge-transfer (CT) complexes are a promising class of materials for the semiconductor industry because of their versatile properties. This class of compounds shows a variety of phase transitions, which are of interest because of their potential impact on the electronic characteristics. Here temperature-dependent vibrational spectroscopy is used to study structural phase transitions in a set of organic CT complexes. Splitting and broadening of infrared-active phonons in the complex formed between pyrene and pyromellitic dianhydride (PMDA) confirm the structural transition is of the order-disorder type and complement previous x-ray diffraction (XRD) results. We show that this technique is a powerful tool to characterize transitions, and apply it to a range of binary CT complexes composed of polyaromatic hyrdocarbons (anthracene, perylene, phenanthrene, pyrene, and stilbene) and PMDA. We extend the understanding of transitions in perylene-PMDA and pyrene-PMDA, and show that there are no order-disorder transitions present in anthracene-PMDA, stilbene-PMDA and phenanthrene-PMDA in the temperature range investigated here.

Relationship between thermal expansion coefficient and glass transition temperature in metallic glasses

International Nuclear Information System (INIS)

Kato, H.; Chen, H.-S.; Inoue, A.

2008-01-01

The thermal expansion coefficients of 13 metallic glasses were measured using a thermo-mechanical analyser. A unique correlation was found between the linear thermal expansion coefficient and the glass transition temperature-their product is nearly constant ∼8.24 x 10 -3 . If one assumes the Debye expression for thermal activation, the total linear thermal expansion up to glass transition temperature (T g ) is reduced to 6 x 10 -3 , nearly 25% of that at the fusion of pure metals

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

Directory of Open Access Journals (Sweden)

Tetiana Slusar

2016-02-01

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

In Situ Observation of Gypsum-Anhydrite Transition at High Pressure and High Temperature

Institute of Scientific and Technical Information of China (English)

LIU Chuan-Jiang; ZHENG Hai-Fei

2012-01-01

An in-situ Raman spectroscopic study of gypsum-anhydrite transition under a saturated water condition at high pressure and high temperature is performed using a hydrothermal diamond anvil cell (HDAC).The experimental results show that gypsum dissolvs in water at ambient temperature and above 496 MPa.With increasing temperature,the anhydrite (CaSO4) phase precipitates at 250 320℃ in the pressure range of 1.0 1.5 GPa,indicating that under a saturated water condition,both stable conditions of pressure and temperature and high levels of Ca and SO4 ion concentrations in aqueous solution are essential for the formation of anhydrite.A linear relationship between the pressure and temperature for the precipitation of anhydrite is established as P(GPa) =0.0068T - 0.7126 (250℃≤T≤320℃).Anhydrite remained stable during rapid cooling of the sample chamber,showing that the gypsum-anhydrite transition involving both dissolution and precipitation processes is irreversible at high pressure and high temperature.%An in-situ Raman spectroscopic study of gypsum-anhydrite transition under a saturated water condition at high pressure and high temperature is performed using a hydrothermal diamond anvil cell (HDAC). The experimental results show that gypsum dissolvs in water at ambient temperature and above 496 Mpa. With increasing temperature, the anhydrite (CaSO4) phase precipitates at 250-320℃ in the pressure range of 1.0-1.5 Gpa, indicating that under a saturated water condition, both stable conditions of pressure and temperature and high levels of Ca and SO4 ion concentrations in aqueous solution are essential for the formation of anhydrite. A linear relationship between the pressure and temperature for the precipitation of anhydrite is established as P(Gpa) = 0.0068T - 0.7126 (250℃≤T≤320℃). Anhydrite remained stable during rapid cooling of the sample chamber, showing that the gypsum-anhydrite transition involving both dissolution and precipitation processes is

Effect of In-Situ Cure on Measurement of Glass Transition Temperatures in High-Temperature Thermosetting Polymers (Briefing Charts)

Science.gov (United States)

2015-05-20

TEMPERATURES IN HIGH-TEMPERATURE THERMOSETTING POLYMERS 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...temperature thermosetting polymer via dynamic mechanical analysis alone. These difficulties result from the residual cure of samples heated beyond their...98) Prescribed by ANSI Std. 239.18 Effect of In-Situ Cure on Measurement of Glass Transition Temperatures in High-Temperature Thermosetting

On temperature dependence of deformation mechanism and the brittle - ductile transition in semiconductors

International Nuclear Information System (INIS)

Pirouz, P.; Samant, A.V.; Hong, M.H.; Moulin, A.; Kubin, L.P.

1999-01-01

Recent deformation experiments on semiconductors have shown the occurrence of a break in the variation of the critical resolved shear stress of the crystal as a function of temperature. These and many other examples in the literature evidence a critical temperature at which a transition occurs in the deformation mechanism of the crystal. In this paper, the occurrence of a similar transition in two polytypes of SiC is reported and correlated to the microstructure of the deformed crystals investigated by transmission electron microscopy, which shows evidence for partial dislocations carrying the deformation at high stresses and low temperatures. Based on these results and data in the literature, the explanation is generalized to other semiconductors and a possible relationship to their brittle-ductile transition is proposed. copyright 1999 Materials Research Society

Development of Creep-Resistant and Oxidation-Resistant Austenitic Stainless Steels for High Temperature Applications

Science.gov (United States)

Maziasz, Philip J.

2018-01-01

Austenitic stainless steels are cost-effective materials for high-temperature applications if they have the oxidation and creep resistance to withstand prolonged exposure at such conditions. Since 1990, Oak Ridge National Laboratory (ORNL) has developed advanced austenitic stainless steels with creep resistance comparable to Ni-based superalloy 617 at 800-900°C based on specially designed "engineered microstructures" utilizing a microstructure/composition database derived from about 20 years of radiation effect data on steels. The wrought high temperature-ultrafine precipitate strengthened (HT-UPS) steels with outstanding creep resistance at 700-800°C were developed for supercritical boiler and superheater tubing for fossil power plants in the early 1990s, the cast CF8C-Plus steels were developed in 1999-2001 for land-based gas turbine casing and diesel engine exhaust manifold and turbocharger applications at 700-900°C, and, in 2015-2017, new Al-modified cast stainless steels with oxidation and creep resistance capabilities up to 950-1000°C were developed for automotive exhaust manifold and turbocharger applications. This article reviews and summarizes their development and their properties and applications.

Multiple phase transitions and magnetoresistance of HoFe{sub 4}Ge{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Liu, J., E-mail: liujing@iastate.edu; Pecharsky, V.K.; Gschneidner, K.A.

2015-05-15

Highlights: • Three magnetic transitions at T{sub N} = 51 K, T{sub f1} = 42 K, and T{sub f2} = 15 K. • Kinetically arrested phase below a freezing point of ∼11 K. • First-order metamagnetic transition at critical field ∼22 kOe below 35 K. • A large magnetoresistance of ∼30% at a field change of 30 kOe near 15 K. - Abstract: A systematic study of the structural, magnetic, heat capacity, electrical resistivity and magnetoresistance properties of HoFe{sub 4}Ge{sub 2} has been performed. The temperature dependencies of the magnetization and heat capacity show three magnetic transitions at T{sub N} = 51 K, T{sub f1} = 42 K, and T{sub f2} = 15 K. The high temperature transition is antiferromagnetic ordering and the two low temperature phase transitions are due to rearrangements of the magnetic structure. A kinetically arrested phase is observed below a freezing point of ∼11 K. Below 35 K, the behavior of the isothermal magnetization reflects a first-order metamagnetic phase transition. Multiple phase transitions are also manifested in the electrical resistivity behavior. For a field change of 30 kOe, a large magnetoresistance of ∼30% is observed near T{sub f2} (15 K)

Jamming transition in a two-dimensional open granular pile with rolling resistance

Directory of Open Access Journals (Sweden)

Caio F. M. Magalhães

2014-10-01

Full Text Available We present a molecular dynamics study of the jamming/unjamming transition in two-dimensional granular piles with open boundaries. The grains are modeled by viscoelastic forces, Coulomb friction and resistance to rolling. Two models for the rolling resistance interaction were assessed: one considers a constant rolling friction coefficient, and the other one a strain dependent coefficient. The piles are grown on a finite size substrate and subsequently discharged through an orifice opened at the center of the substrate. Varying the orifice width and taking the final height of the pile after the discharge as the order parameter, one can devise a transition from a jammed regime (when the grain flux is always clogged by an arch to a catastrophic regime, in which the pile is completely destroyed by an avalanche as large as the system size. A finite size analysis shows that there is a finite orifice width associated with the threshold for the unjamming transition, no matter the model used for the microscopic interactions. As expected, the value of this threshold width increases when rolling resistance is considered, and it depends on the model used for the rolling friction. Received: 14 June 2014, Accepted: 7 October 2014; Reviewed by: R. Arévalo, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore; Edited by: L. A. Pugnaloni; DOI: http://dx.doi.org/10.4279/PIP.060007 Cite as: C F M. Magalhaes, A P F Atman, G Combe, J G Moreira, Papers in Physics 6, 060007 (2014

Evaluation of the local temperature of conductive filaments in resistive switching materials

International Nuclear Information System (INIS)

Yalon, E; Cohen, S; Gavrilov, A; Ritter, D

2012-01-01

The resistive switching effect in metal oxides and other dielectric materials is among the leading future non-volatile memory technologies. Resistive switching is widely ascribed to the formation and rupture of conductive filaments in the oxide, which are generated by temperature-enhanced nano-scale ion migration or other thermal effects. In spite of the central role of the local filament temperature on the switching effect, as well as on the conduction and reliability physics, no measurement methods of the filament temperature are yet available. In this work, we report on a method for evaluating the conducting filament temperature, using a metal–insulator–semiconductor bipolar transistor structure. The filament temperature is obtained by analyzing the thermal excitation rate of electrons from the filament Fermi level into the conduction band of a p-type semiconductor electrode. Measurements were carried out to obtain the conductive filament temperature in hafnia at varying ambient temperatures in the range of 3–300 K. Significant Joule heating of the filament was observed across the entire measured ambient temperature range. The extracted temperatures provide physical insight into the resistive switching effect. (paper)

Phase transition temperatures of 405-725 K in superfluid ultra-dense hydrogen clusters on metal surfaces

Energy Technology Data Exchange (ETDEWEB)

Holmlid, Leif, E-mail: holmlid@chem.gu.se [Atmospheric Science, Department of Chemistry, University of Gothenburg, SE-412 96 Göteborg (Sweden); Kotzias, Bernhard [Airbus DS, Department Mechanical Engineering, D28199 Bremen (Germany)

2016-04-15

Ultra-dense hydrogen H(0) with its typical H-H bond distance of 2.3 pm is superfluid at room temperature as expected for quantum fluids. It also shows a Meissner effect at room temperature, which indicates that a transition point to a non-superfluid state should exist above room temperature. This transition point is given by a disappearance of the superfluid long-chain clusters H{sub 2N}(0). This transition point is now measured for several metal carrier surfaces at 405 - 725 K, using both ultra-dense protium p(0) and deuterium D(0). Clusters of ordinary Rydberg matter H(l) as well as small symmetric clusters H{sub 4}(0) and H{sub 3}(0) (which do not give a superfluid or superconductive phase) all still exist on the surface at high temperature. This shows directly that desorption or diffusion processes do not remove the long superfluid H{sub 2N}(0) clusters. The two ultra-dense forms p(0) and D(0) have different transition temperatures under otherwise identical conditions. The transition point for p(0) is higher in temperature, which is unexpected.

Detection of Resistive Transitions in LHC Superconducting Components

CERN Document Server

Denz, R

2001-01-01

The LHC has entered the construction phase. It will incorporate a large number of superconducting components like magnets, current leads and busbars. All these components require protection means in case of a transition from the superconducting to the resistive state, the so-called quench. Key elements in the protection system are electronic quench detectors, which have to be able to identify a quench in any state of the powering cycle of the accelerator. According to the different properties and characteristics of the superconducting elements and circuits, a set of quench detectors adapted to their specific tasks has been developed.

'Vanishing' structural effects of temperature in polymer glasses close to the glass-transition temperature

International Nuclear Information System (INIS)

Shantarovich, V.P.; Suzuki, T.; Ito, Y.; Yu, R.S.; Kondo, K.; Yampolskii, Yu. P.; Alentiev, A.Yu.

2007-01-01

Positron annihilation lifetime (PAL) measurements were used for observation of structural effects of temperature in polystyrene (PS), super-cross-linked polystyrene networks (CPS), and in polyimides (PI) below and in the vicinity of glass-transition temperature T g . 'Vanishing' of these structural effects in the repeating cycles of the temperature controlled PAL experiments due to the slow relaxation processes in different conditions and details of chemical structure is demonstrated. Obtained results illustrate complex, dependent on thermal history, inhomogeneous character of the glass structure. In fact, structure of some polymer glasses is changing continuously. Calculations of the number density of free volume holes in these conditions are discussed

Influence of Soil Temperature on Meloidogyne incognita Resistant and Susceptible Cotton, Gossypium hirsutum

OpenAIRE

Carter, William W.

1982-01-01

The degree of resistance by a cotton plant to Meloidogyne incognita is affected by soil temperature, particularly in moderately resistant cultivars, The total number of nematodes in the resistant and moderately resistant rools at 35 C was equal to, or greater than, the number in susceptible roots at 20, 25, or 30 C. A shift in numbers to developing and egg-bearing forms of nematodes in the susceptible cultivar as tentperature increased indicates development was affected by temperature rather ...

Martensitic transition near room temperature and the temperature- and magnetic-field-induced multifunctional properties of Ni49CuMn34In16 alloy

Science.gov (United States)

Sharma, V. K.; Chattopadhyay, M. K.; Khandelwal, A.; Roy, S. B.

2010-11-01

A near room-temperature martensitic transition is observed in the ferromagnetic austenite state of Ni50Mn34In16 alloy with 2% Cu substitution at the Ni site. Application of magnetic field in the martensite state induces a reverse martensitic transition in this alloy. dc magnetization, magnetoresistance and strain measurements in this alloy reveal that associated with this martensitic transition there exist a large magnetocaloric effect, a large magnetoresitance and a magnetic-field temperature-induced strain. This NiMnIn alloy system thus is an example of an emerging class of magnetic materials whose physical properties can be tuned by suitable chemical substitutions, to achieve magnetic-field and temperature-induced multifunctional properties at and around room temperature

Dipolon theory of energy gap parameters at finite temperature and transition temperatures Tc and T* in high-temperature superconductors

International Nuclear Information System (INIS)

Sharma, R.R.

2006-01-01

First temperature dependent regular and pseudo-energy gap parameters and regular and pseudo-transition temperatures arising from the same physical origin have been calculated in the strong coupling formalism. Temperature dependent many-body field-theoretic techniques have been developed, as an extension of our previous zero-temperature formalism, to derive temperature dependent general expressions for the renormalized energy gap parameter Δ(k->,ω), the gap renormalization parameter Z(k->,ω) and energy band renormalization parameter χ(k->,ω) for momentum k-> and frequency ω making use of dipolon propagator and electron Green's function taking into account explicitly the dressed dipolons as mediators of superconductivity, the screened Coulomb repulsion and nonrigid electron energy bands considering retardation and damping effects and electron-hole asymmetry. The theory takes into account all necessary and important correlations. Our self-consistent calculations utilize the previously symmetry predicted two energy gap parameters for superconducting cuprates, one being antisymmetric (''as'') with respect to the exchange of the k x and k y components of vector k-> and the other being symmetric (''s'') with respect to the exchange of k x and k y . Our present temperature dependent self-consistent solutions of the real and imaginary parts of the Δ(k->,ω), Z(k->,ω) and χ(k->,ω) confirm the existence of these two (different) solutions and conclude that the antisymmetric solution of the gap parameter corresponds to the observed regular (''reg'') superconducting energy gap whereas the symmetric solution corresponds to the observed pseudo-(''pse-'') energy gap. Explicit temperature dependent self-consistent calculations have been performed here for Bi 2 Sr 2 CaCu 2 O 8+δ as well as Bi 2 Sr 2 CaCu 2 O 8 giving temperature dependent energy gap parameters and corresponding transition temperatures. The calculated results are consistent with the available experimental

A fully automated temperature-dependent resistance measurement setup using van der Pauw method

Science.gov (United States)

Pandey, Shivendra Kumar; Manivannan, Anbarasu

2018-03-01

The van der Pauw (VDP) method is widely used to identify the resistance of planar homogeneous samples with four contacts placed on its periphery. We have developed a fully automated thin film resistance measurement setup using the VDP method with the capability of precisely measuring a wide range of thin film resistances from few mΩ up to 10 GΩ under controlled temperatures from room-temperature up to 600 °C. The setup utilizes a robust, custom-designed switching network board (SNB) for measuring current-voltage characteristics automatically at four different source-measure configurations based on the VDP method. Moreover, SNB is connected with low noise shielded coaxial cables that reduce the effect of leakage current as well as the capacitance in the circuit thereby enhancing the accuracy of measurement. In order to enable precise and accurate resistance measurement of the sample, wide range of sourcing currents/voltages are pre-determined with the capability of auto-tuning for ˜12 orders of variation in the resistances. Furthermore, the setup has been calibrated with standard samples and also employed to investigate temperature dependent resistance (few Ω-10 GΩ) measurements for various chalcogenide based phase change thin films (Ge2Sb2Te5, Ag5In5Sb60Te30, and In3SbTe2). This setup would be highly helpful for measurement of temperature-dependent resistance of wide range of materials, i.e., metals, semiconductors, and insulators illuminating information about structural change upon temperature as reflected by change in resistances, which are useful for numerous applications.

Niclosamide inhibits epithelial-mesenchymal transition and tumor growth in lapatinib-resistant human epidermal growth factor receptor 2-positive breast cancer.

Science.gov (United States)

Liu, Junjun; Chen, Xiaosong; Ward, Toby; Mao, Yan; Bockhorn, Jessica; Liu, Xiaofei; Wang, Gen; Pegram, Mark; Shen, Kunwei

2016-02-01

Acquired resistance to lapatinib, a human epidermal growth factor receptor 2 kinase inhibitor, remains a clinical problem for women with human epidermal growth factor receptor 2-positive advanced breast cancer, as metastasis is commonly observed in these patients. Niclosamide, an anti-helminthic agent, has recently been shown to exhibit cytotoxicity to tumor cells with stem-like characteristics. This study was designed to identify the mechanisms underlying lapatinib resistance and to determine whether niclosamide inhibits lapatinib resistance by reversing epithelial-mesenchymal transition. Here, two human epidermal growth factor receptor 2-positive breast cancer cell lines, SKBR3 and BT474, were exposed to increasing concentrations of lapatinib to establish lapatinib-resistant cultures. Lapatinib-resistant SKBR3 and BT474 cells exhibited up-regulation of the phenotypic epithelial-mesenchymal transition markers Snail, vimentin and α-smooth muscle actin, accompanied by activation of nuclear factor-кB and Src and a concomitant increase in stem cell marker expression (CD44(high)/CD24(low)), compared to naive lapatinib-sensitive SKBR3 and BT474 cells, respectively. Interestingly, niclosamide reversed epithelial-mesenchymal transition, induced apoptosis and inhibited cell growth by perturbing aberrant signaling pathway activation in lapatinib-resistant human epidermal growth factor receptor 2-positive cells. The ability of niclosamide to alleviate stem-like phenotype development and invasion was confirmed. Collectively, our results demonstrate that lapatinib resistance correlates with epithelial-mesenchymal transition and that niclosamide inhibits lapatinib-resistant cell viability and epithelial-mesenchymal transition. These findings suggest a role of niclosamide or derivatives optimized for more favorable bioavailability not only in reversing lapatinib resistance but also in reducing metastatic potential during the treatment of human epidermal growth factor receptor

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 relaxation and the Kapitza boundary resistance paradox

OpenAIRE

Brink, Alec Maassen van den; Dekker, H.

1994-01-01

The calculation of the Kapitza boundary resistance between dissimilar harmonic solids has since long (Little [Can. J. Phys. 37, 334 (1959)]) suffered from a paradox: this resistance erroneously tends to a finite value in the limit of identical solids. We resolve this paradox by calculating temperature differences in the final heat-transporting state, rather than with respect to the initial state of local equilibrium. For a one-dimensional model we thus derive an exact, paradox-free formula fo...

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

Temperature-dependent vibrational spectroscopy to study order-disorder transitions in charge transfer complexes

Directory of Open Access Journals (Sweden)

Rohan Isaac

2018-02-01

Full Text Available Charge-transfer (CT complexes are a promising class of materials for the semiconductor industry because of their versatile properties. This class of compounds shows a variety of phase transitions, which are of interest because of their potential impact on the electronic characteristics. Here temperature-dependent vibrational spectroscopy is used to study structural phase transitions in a set of organic CT complexes. Splitting and broadening of infrared-active phonons in the complex formed between pyrene and pyromellitic dianhydride (PMDA confirm the structural transition is of the order-disorder type and complement previous x-ray diffraction (XRD results. We show that this technique is a powerful tool to characterize transitions, and apply it to a range of binary CT complexes composed of polyaromatic hyrdocarbons (anthracene, perylene, phenanthrene, pyrene, and stilbene and PMDA. We extend the understanding of transitions in perylene-PMDA and pyrene-PMDA, and show that there are no order-disorder transitions present in anthracene-PMDA, stilbene-PMDA and phenanthrene-PMDA in the temperature range investigated here.

Observing the temperature dependent transition of the GP2 peptide using terahertz spectroscopy.

Directory of Open Access Journals (Sweden)

Yiwen Sun

Full Text Available The GP2 peptide is derived from the Human Epidermal growth factor Receptor 2 (HER2/nue, a marker protein for breast cancer present in saliva. In this paper we study the temperature dependent behavior of hydrated GP2 at terahertz frequencies and find that the peptide undergoes a dynamic transition between 200 and 220 K. By fitting suitable molecular models to the frequency response we determine the molecular processes involved above and below the transition temperature (T(D. In particular, we show that below T(D the dynamic transition is dominated by a simple harmonic vibration with a slow and temperature dependent relaxation time constant and that above T(D, the dynamic behavior is governed by two oscillators, one of which has a fast and temperature independent relaxation time constant and the other of which is a heavily damped oscillator with a slow and temperature dependent time constant. Furthermore a red shifting of the characteristic frequency of the damped oscillator was observed, confirming the presence of a non-harmonic vibration potential. Our measurements and modeling of GP2 highlight the unique capabilities of THz spectroscopy for protein characterization.

Temperature dependency of electrical resistivity of soils; Tsuchi no hiteiko no ondo izonsei ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

Park, S; Matsui, T [Osaka University, Osaka (Japan). Faculty of Engineering; Park, M; Fujiwara, H [Osaka University, Osaka (Japan)

1997-10-22

Kinds of ground materials, porosity, electrical resistivity of pores, degree of saturation, and content of clays are the factors affecting the electrical resistivity of soils. In addition to these factors, the electrical resistivity of soils around hot spring water and geothermal areas depends on the temperature due to fluctuation of cation mobility in the pore water with the temperature. In this paper, the temperature dependency of electrical resistivity of groundwater and soils is investigated by recognizing that of groundwater as that of pore water. As a result, it was found that the electrical resistivity of groundwater becomes lower as increasing the amount of dissolved cation, and that the temperature dependency of electrical resistivity is not significant because of the small mobility of cation. The electrical resistivity of soils was significantly affected by that of pore water, in which the mobility of cation was changed with temperature changes. Accordingly, the temperature dependency of electrical resistivity of soils has a similar tendency as that of groundwater. 5 refs., 9 figs., 2 tabs.

Glass transition temperature of dried lens tissue pretreated with trehalose, maltose, or cyclic tetrasaccharide.

Science.gov (United States)

Kawata, Tetsuhiro; Matsuo, Toshihiko; Uchida, Tetsuya

2014-01-01

Glass transition temperature is a main indicator for amorphous polymers and biological macromolecules as materials, and would be a key for understanding the role of trehalose in protecting proteins and cells against desiccation. In this study, we measured the glass transition temperature by differential scanning calorimetry of dried lens tissues as a model of a whole biological tissue to know the effect of pretreatment by trehalose and other sugars. Isolated porcine lenses were incubated with saline, 100 or 1000 mM concentration of trehalose, maltose, or cyclic tetrasaccharide dissolved in saline at room temperature for 150 minutes. The solutions were removed and all samples were dried at room temperature in a desiccator until no weight change. The dried tissues were ground into powder and placed in a measuring pan for differential scanning calorimetry. The glass transition temperature of the dried lens tissues, as a mean and standard deviation, was 63.0 ± 6.4°C (n = 3) with saline pretreatment; 53.0 ± 0.8°C and 56.3 ± 2.7°C (n = 3), respectively, with 100 and 1000 mM trehalose pretreatment; 56.0 ± 1.6°C and 55.8 ± 1.1°C (n = 3), respectively, with 100 and 1000 mM maltose pretreatment; 60.0 ± 8.8°C and 59.2 ± 6.3°C (n = 3), respectively, with 100 and 1000 mM cyclic tetrasaccharide pretreatment. The glass transition temperature appeared lower, although not significantly, with trehalose and maltose pretreatments than with saline and cyclic tetrasaccharide pretreatments (P > 0.05, Kruskal-Wallis test). The glass transition temperature of the dried lens tissues with trehalose pretreatment appeared more noticeable on the thermogram, compared with other pretreatments. The glass transition temperature was measured for the first time in the dried lens tissues as an example of a whole biological tissue and might provide a basis for tissue preservation in the dried condition.

Citrate increases glass transition temperature of vitrified sucrose preparations

NARCIS (Netherlands)

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

2004-01-01

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

Transitions in aqueous solutions of sucrose at subzero temperatures

Czech Academy of Sciences Publication Activity Database

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

2007-01-01

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

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

International Nuclear Information System (INIS)

Habib, S.; Mottola, E.; Tinyakov, P.

1996-01-01

Winding number transitions in the two-dimensional softly broken O(3) nonlinear σ model are studied at finite energy and temperature. New periodic instanton solutions which dominate the semiclassical transition amplitudes are found analytically at low energies, and numerically for all energies up to the sphaleron scale. The Euclidean period β of these finite energy instantons increases with energy, contrary to the behavior found in the Abelian Higgs model or simple one-dimensional systems. This results in a sharp crossover from instanton-dominated tunneling to sphaleron-dominated thermal activation at a certain critical temperature. Since this behavior is traceable to the soft breaking of conformal invariance by the mass term in the σ model, semiclassical winding number transition amplitudes in the electroweak theory in 3+1 dimensions should exhibit a similar sharp crossover. We argue that this is indeed the case in the standard model for M H W . copyright 1996 The American Physical Society

A Challenge to Improve High-Temperature Platinum Resistance Thermometer

Science.gov (United States)

Tanaka, Y.; Widiatmo, J. V.; Harada, K.; Kobayashi, T.; Yamazawa, K.

2017-05-01

High-temperature standard platinum resistance thermometers (HTSPRTs) are used to interpolate the international temperature scale of 1990 (ITS-90), especially for temperatures between the aluminum and the silver points. For this, long-term stability of the HTSPRT is essential. CHINO R800-3L type SPRT, which has a nominal resistance at the triple point of water (TPW) around 0.25 Ω , is the one developed earlier for the interpolation of the ITS-90 at this temperature range. Further development to this previous model has been carried out for the purpose of improving the thermal stability. The improvement was focused on reducing the effect coming from the difference in thermal expansion between platinum wire and the quartz frame on which the platinum wire is installed. New HTSPRTs were made by CHINO Corporation. Some series of tests were carried out at CHINO and at NMIJ. Initial tests after the HTSPRT fabrication were done at CHINO, where thermal cycles between 500°C and 980°C were applied to the HTSPRTs to see change in the resistances at the TPW (R_{TPW}) and at the gallium point (R_{Ga}). Repeated resistance measurements at the silver point (R_{Ag}) were performed after completing the thermal cycling test. Before and after every measurement at silver point, R_{TPW} was measured, while before and after every two silver point realization R_{Ga} were measured. After completing this test, the HTSPRTs were transported to NMIJ, where the same repeated measurements at the silver point were done at NMIJ. These were then repeated at CHINO and at NMIJ upon repeated transportation among the institutes, to evaluate some effect due to transportation. This paper reports the details of the above-mentioned tests, the results and the analysis.

Monitoring of high temperature zone by resistivity tomography during in-situ heater test in sedimentary soft rocks

International Nuclear Information System (INIS)

Kubota, Kenji; Suzuki, Koichi; Ikenoya, Takafumi; Takakura, Nozomu; Tani, Kazuo

2008-01-01

In-situ heater test has been conducted to evaluate the influence of high temperature in an underground facility at a depth of 50 m. Resistivity monitoring is thought to be effective to map the extent of the high temperature zone. So we have conducted resistivity tomography during the heater test. As a result, low resistivity zone was appeared near the heated area as starting the heating, and the zone was expanded. Resistivity of rock is proportional to resistivity of pore water. It is known that pore water resistivity decreases as the temperature rise. This suggests that high temperature zone is detected and spatial distribution of temperature can be mapped by resistivity tomography. (author)

Method for measuring the resistive transition and critical current in superconductors using pulsed current

International Nuclear Information System (INIS)

McGinnis, W.C.; Jones, T.E.

1993-01-01

A method is described for measuring the intragranular critical current of a granular superconductive material, comprising the steps of: conducting a substantially rectangular electronic pulse through said material so as to conduct a current through said material such that when said intragranular critical current of said material is exceeded, any grains present in said material are in a superconducting state when said current is less than said intragranular critical current, said material having a critical temperature; measuring said current through said material while conducting said pulse; measuring a voltage difference across said material while conducting said pulse; and determining said intragranular critical current through said material by varying said current to discern a current level at which an electrical resistance of said material increases to that of a non-superconducting state as the grains of said material transition from said superconducting to said non-superconducting state

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

Solvent deuteration enhancement of hydrophobicity: DSC study of the inverse temperature transition of elastin-based polypeptides

International Nuclear Information System (INIS)

Chihao Luan; Urry, D.W.

1991-01-01

As previously shown, the polypentapeptide of elastin, (Val 1 -Pro 2 -Gly 3 -Val 4 -Gly 5 ) n or simply poly(VPGVG), undergoes an inverse temperature transition which is seen macroscopically as a phase separation with a dense viscoelastic phase of about 60% water, 40% peptide by weight and which is characterized molecularly by increase in intra- and intermolecular order as evidenced by formation of specific hydrophobic contacts. Furthermore, from an extensive study of polypentapeptides of the composition poly[f x (VPGXG), f v (VPGVG)], where f x + f v = 1 and X is any of the amino acid residues with apolar (hydrophobic) side chains, it has been shown that the temperature of the transition decreases and the heat of the transition increases with increased hydrophobicity. In the present paper differential scanning calorimetry has been utilized to determine the effect of D 2 O on the temperature and heats of the inverse temperature transitions for poly(VPGVG), poly(IPGVG), poly(LPGVG), and poly(VPAVG) and in the latter case in the presence of 0.5 and 1.0 N NaCl and of 1,2, and 3 M urea. In all cases, the effect of D 2 O as compared to H 2 O is to lower the transition temperature about 2 C and to increase the heat of the transition about 10%, and this occurs also in the presence of NaCl, which itself lowers the temperature and increases the heat, and in the presence of urea, which itself raises the temperature and decreases the heat of the transition. It is concluded that the effect of replacement of H 2 O by D 2 O by D 2 O in these polypeptides is to effect a small but consistent increase in the expression of hydrophobicity

The resistivity of Y1Ba2Cu3O7 between 80 K and 1240 K

International Nuclear Information System (INIS)

Fisher, B.; Polturak, E.; Koren, G.; Kessel, A.; Fischer, R.; Harel, L.

1987-01-01

Resistivity measurements between 80-1240 K and dilatometric measurements between 300-1200 K in YBa 2 Cu 3 O 7 are reported. We found that the resistivity increases exponentially with temperature, with different exponents below and above the tetragonal-orthorhombic transition. The thermal expansion coefficient also changes at this transition. We suggest that conduction occurs by tunneling of electrons through potential barriers in the lattice, the width of which increases with temperature. (author)

Temperature decline thermography for laminar-turbulent transition detection in aerodynamics

Science.gov (United States)

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

2017-09-01

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

Anomalous low temperature resistivity in CeCr0.8V0.2Ge3

Science.gov (United States)

Singh, Durgesh; Patidar, Manju Mishra; Mishra, A. K.; Krishnan, M.; Ganesan, V.

2018-04-01

Resistivity (8T) and heat capacity (0T) of CeCr0.8V0.2Ge3 at low temperatures and high magnetic fields are reported. Resistivity curve shows a Kondo like behavior at an anomalously high temperature of 250K. A broad peak at 20K is observed in resistivity. A sharp change in resistivity around 7.3K is due to magnetic ordering mediated by coherence effects. Similar low temperature peak is also observed in heat capacity around 7.2K. A small magnetic field of the order of 1T shifts the peak towards lower temperatures confirming the antiferromagnetic ordering. A broad feature, which appears in resistivity at 20K, is absent in heat capacity. This feature shift towards higher temperatures with magnetic field, and may be due to the partial ferromagnetic ordering or due to geometrical frustration which opposes the magnetic ordering. The system shows a moderate heavy fermion behavior with Sommerfeld coefficient (γ) of 111mJ/mol-K2. Debye temperature of the compound is 250K. Shifting of TN in magnetic fields towards 0K indicates a possibility of quantum criticality in this system.

Temperature influence and reset voltage study of bipolar resistive ...

Indian Academy of Sciences (India)

Moreover, the Cu/ZrO2/ATO device which the ZrO2 thin film annealed at 300 °C can be measured as resistive switching sweeps at 200, 100 and 50 K. It was found that the ratio of off/on reduced when the measured temperature decreased. When the - measurement temperature decreases, on decreases obviously ...

Diffusion barrier coatings for high temperature corrosion resistance of advanced carbon/carbon composites

International Nuclear Information System (INIS)

Singh Raman, K.S.

2000-01-01

Carbon possesses an excellent combination of mechanical and thermal properties, viz., excellent creep resistance at temperatures up to 2400 deg C in non-oxidizing environment and a low thermal expansion coefficient. These properties make carbon a potential material for very high temperature applications. However, the use of carbon materials at high temperatures is considerably restricted due to their extremely poor oxidation resistance at temperatures above 400 deg C. The obvious choice for improving high temperature oxidation resistance of such materials is a suitable diffusion barrier coating. This paper presents an overview of recent developments in advanced diffusion- and thermal-barrier coatings for ceramic composites, with particular reference to C/C composites. The paper discusses the development of multiphase and multi-component ceramic coatings, and recent investigations on the oxidation resistance of the coated C/C composites. The paper also discusses the cases of innovative engineering solutions for traditional problems with the ceramic coatings, and the scope of intelligent processing in developing coatings for the C/C composites. Copyright (2000) AD-TECH - International Foundation for the Advancement of Technology Ltd

Infield X-ray diffraction studies of field and temperature driven structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}

Energy Technology Data Exchange (ETDEWEB)

Shahee, Aga, E-mail: agashahee@gmail.com [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India); Department of Physics, IIT Bombay, Powai, Mumbai 400076 (India); Sharma, Shivani; Singh, K.; Lalla, N.P. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India)

2017-07-15

Highlights: • Temperature and magnetic field driven coupled magneto-structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}. • Microscopic evidence of strong spin-charge-lattice coupling. • Iso-thermal magnetic field driven structure phase transition. • Field-driven structural phase transition origin of observed 1st order type CMR effect. - Abstract: Comprehensive X-ray diffraction (XRD) studies have been performed at different temperature (T) (4.2–300 K) and magnetic field (H) (0–8 T) to understand the evolution of crystal structure of Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ} (NSMO) under non ambient conditions. The T dependent XRD results show the abrupt change in the lattice parameters without any change in lattice symmetry at ∼200 K, which is associated with the first order structural phase transition from ferromagnetic to antiferromagnetic phase. This phase transition is strongly H dependent and shifted to lower temperature (∼150 K) on the application of 8 T field with phase coexistence (high temperature phase ∼18%), even down to 4.2 K. Isothermal XRD results at 150 K under different H clearly illustrate the H induced first order structural phase transition. The critical H at which this phase transformation starts is ∼1 T, with rapid growth above 4 T with hysteretic nature during increasing and decreasing H. These results are supported with the resistivity and magnetoresistance results and affirm the strong spin-lattice coupling in NSMO. Our detail studies reveal the structural correlations to the observed colossal magnetoresistance and magnetocaloric effect in this material.

Predictions of glass transition temperature for hydrogen bonding biomaterials.

Science.gov (United States)

van der Sman, R G M

2013-12-19

We show that the glass transition of a multitude of mixtures containing hydrogen bonding materials correlates strongly with the effective number of hydroxyl groups per molecule, which are available for intermolecular hydrogen bonding. This correlation is in compliance with the topological constraint theory, wherein the intermolecular hydrogen bonds constrain the mobility of the hydrogen bonded network. The finding that the glass transition relates to hydrogen bonding rather than free volume agrees with our recent finding that there is little difference in free volume among carbohydrates and polysaccharides. For binary and ternary mixtures of sugars, polyols, or biopolymers with water, our correlation states that the glass transition temperature is linear with the inverse of the number of effective hydroxyl groups per molecule. Only for dry biopolymer/sugar or sugar/polyol mixtures do we find deviations due to nonideal mixing, imposed by microheterogeneity.

Size dependent hcp-to-fcc transition temperature in Co nanoclusters obtained by ion implantation in silica

International Nuclear Information System (INIS)

Mattei, G.; Maurizio, C.; Fernandez, C Julian de; Mazzoldi, P.; Battaglin, G.; Canton, P.; Cattaruzza, E.; Scian, C.

2006-01-01

In this work we present in situ investigations on the increase of the hcp-to-fcc transition temperature for Co with respect to the bulk value (420 deg. C) when nanoclusters are considered. Starting from Co:SiO 2 composites obtained by ion implantation with average Co cluster size of about 5 nm, a transition temperature between 800 deg. C and 900 deg. C is found upon thermal annealing in vacuum by in situ transmission electron microscopy. Preliminary results on electron irradiation to promote the transition at lower temperatures are presented

Transition temperature to the superconducting phase of QCD at high baryon density

International Nuclear Information System (INIS)

Brown, William E.; Liu, James T.; Ren, Hai-cang

2000-01-01

Recent interest in the study of color superconductivity has focused on the regime of high baryon density where perturbative QCD may be employed. Based on the dominant one-gluon-exchange interaction, both the transition temperature and zero temperature gap have been determined to leading order in the coupling g. While the leading non-BCS behavior T C ∼μg -5 e -κ/g is easily obtained, the pre-exponential factor has proved more difficult to evaluate. Focusing on the transition temperature, we present a perturbative derivation of this factor, exact to leading order in g. This approach is first motivated by the study of a toy model and involves working to second order in the perturbative expansion. We compare this result to the zero temperature gap. Additionally, we extend the analysis to the case of higher angular momentum for longitudinal and transverse quark pairing. (c) 2000 The American Physical Society

Low-Cost, High Glass-Transition Temperature, Thermosetting Polyimide Developed

Science.gov (United States)

Chuang, Kathy C.

1999-01-01

PMR-15 polyimide, developed in the mid-1970's at the NASA Lewis Research Center, is recognized as a state-of-the-art high-temperature resin for composite applications in the temperature range of 500 to 550 F (260 to 288 C). PMR-15 offers easy processing and good property retention at a reasonable cost. For these reasons, it is widely used in both military and commercial aircraft engine components. Traditionally, polyimide composites have been designed for long-term use at 500 to 600 F over thousands of hours. However, new applications in reusable launch vehicles (RLV's) require lightweight materials that can perform for short times (tens of hours) at temperatures between 800 and 1000 F (425 and 538 C). Current efforts at Lewis are focused on raising the use temperature of polyimide composites by increasing the glass-transition temperature of the matrix resins. Achieving this dramatic increase in the upper use temperature without sacrificing polymer and composite processability is a major technical challenge.

Variation of kinetic energy release with temperature and electron energy for unimolecular ionic transitions

International Nuclear Information System (INIS)

Rabia, M.A.; Fahmy, M.A.

1992-01-01

The kinetic energy released during seven unimolecular ionic transitions, generated from benzyl alcohol and benzyl amine have been studied as a function of ion source temperature and ionizing electron energy. Only, the kinetic energy released during H CN elimination from fragment [C 7 H 8 N]+ ion of benzyl amine displays a temperature dependence. For only two transitions, generated from benzyl alcohol, the kinetic energy released show a significant ionizing electron energy dependence. These results may reveal the role of the internal energy of reacting ions in producing the kinetic energy released some transitions produced from benzyl alcohol

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

Science.gov (United States)

Singh, Abhishek; Pandey, Tribhuwan

2014-03-01

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

Multiple magnetic transitions in SmCoAsO

Directory of Open Access Journals (Sweden)

Yongliang Chen

2011-12-01

Full Text Available The magnetic properties of SmCoAsO have been investigated. Our results differ from early observations. Complicated magnetism consists of antiferromagnetic, ferromagnetic, ferrimagnetic and paramagnetic, even diamagnetism at low field has been observed. A metamagnetic transition was observed, resulting from a canting of the spins. The interaction between two Co sublattices with canted-structure might take responsibility for the multiple magnetic transitions. Electrical resistivity data indicate that SmCoAsO is metallic conductor with room temperature resistivity of 0.51669 mΩ-cm. Negative magnetoresistance effect suggests a significant suppression of spin-flip scattering by the applied magnetic field. The magnetic phase diagram has been established.

Uncertainty Analysis of the Temperature–Resistance Relationship of Temperature Sensing Fabric

Directory of Open Access Journals (Sweden)

Muhammad Dawood Husain

2016-11-01

Full Text Available This paper reports the uncertainty analysis of the temperature–resistance (TR data of the newly developed temperature sensing fabric (TSF, which is a double-layer knitted structure fabricated on an electronic flat-bed knitting machine, made of polyester as a basal yarn, and embedded with fine metallic wire as sensing element. The measurement principle of the TSF is identical to temperature resistance detector (RTD; that is, change in resistance due to change in temperature. The regression uncertainty (uncertainty within repeats and repeatability uncertainty (uncertainty among repeats were estimated by analysing more than 300 TR experimental repeats of 50 TSF samples. The experiments were performed under dynamic heating and cooling environments on a purpose-built test rig within the temperature range of 20–50 °C. The continuous experimental data was recorded through LabVIEW-based graphical user interface. The result showed that temperature and resistance values were not only repeatable but reproducible, with only minor variations. The regression uncertainty was found to be less than ±0.3 °C; the TSF sample made of Ni and W wires showed regression uncertainty of <±0.13 °C in comparison to Cu-based TSF samples (>±0.18 °C. The cooling TR data showed considerably reduced values (±0.07 °C of uncertainty in comparison with the heating TR data (±0.24 °C. The repeatability uncertainty was found to be less than ±0.5 °C. By increasing the number of samples and repeats, the uncertainties may be reduced further. The TSF could be used for continuous measurement of the temperature profile on the surface of the human body.

Evidence of a low temperature dynamical transition in concentrated PNIPAM microgels

OpenAIRE

Zanatta, Marco; Tavagnacco, Letizia; Buratti, Elena; Bertoldo, Monica; Natali, Francesca; Chiessi, Ester; Orecchini, Andrea; Zaccarelli, Emanuela

2018-01-01

The occurrence of a dynamical transition at low temperature has been reported in a large number of different proteins. Here we provide the first observation of a "protein-like" dynamical transition in a non-biological aqueous environment. To this aim we exploit the popular colloidal system of poly-N-isopropylacrylamide (PNIPAM) microgels, extending their investigation to unprecedentedly high concentrations. Thanks to the heterogeneous polymeric architecture of the microgels, water crystalliza...

On-line monitoring of resistance of aqueous solutions at high temperature

International Nuclear Information System (INIS)

Hu Shilin; Zhang Pingzhu; Shang Weiguo

1999-01-01

The coulostatic measurement is a fast speed electrochemical test method. By this technology, analyzing Δ E(t)- T curves recorded under coulostatic perturbation, the solution resistance R l , resistance of coated film R f , capacity of coated film C f , Polarization resistance R p and double layer capacity C d are obtained. The resistance variety of 0.05N KCl is measured from room temperature up to 255 deg. C under saturation steam pressure. (author)

Resistive transition for two-dimensional superconductors: Comparison between experiments and Coulomb-gas-model predictions

International Nuclear Information System (INIS)

Minnhagen, P.

1983-01-01

The Coulomb-gas model of vortex fluctuations leads to scaling relations for the resistive transition which can be directly tested by experiments. By analyzing published resistance data, it is shown that there is experimental evidence for the Coulomb-gas scaling relation in the absence of a perpendicular magnetic field. It is also shown that there exists some suggestive support for the Coulomb-gas predictions in the presence of a magnetic field

Charge Berezinskii-Kosterlitz-Thouless transition in superconducting NbTiN films

Energy Technology Data Exchange (ETDEWEB)

Mironov, Alexey Yu.; Silevitch, Daniel M.; Proslier, Thomas; Postolova, Svetlana V.; Burdastyh, Maria V.; Gutakovskii, Anton K.; Rosenbaum, Thomas F.; Vinokur, Valerii V.; Baturina, Tatyana I.

2018-03-06

Three decades after the prediction of charge-vortex duality in the critical vicinity of the two-dimensional superconductor-insulator transition (SIT), one of the fundamental implications of this duality-the charge Berezinskii-Kosterlitz-Thouless (BKT) transition that should occur on the insulating side of the SIT-has remained unobserved. The dual picture of the process points to the existence of a superinsulating state endowed with zero conductance at finite temperature. Here, we report the observation of the charge BKT transition on the insulating side of the SIT in 10 nm thick NbTiN films, identified by the BKT critical behavior of the temperature and magnetic field dependent resistance, and map out the magnetic-field dependence of the critical temperature of the charge BKT transition. Finally, we ascertain the effects of the finite electrostatic screening length and its divergence at the magnetic field-tuned approach to the superconductor-insulator transition.

Effect of hydriding temperature and strain rate on the ductile-brittle transition in β treated Zircaloy-4

International Nuclear Information System (INIS)

Bai, J.B.

1996-01-01

In this paper, the effect of hydriding temperature and strain rate on the ductile-brittle transition in β treated Zircaloy-4 has been investigated. The hydriding temperature used is 700degC, strain rates being 4x10 -4 s -1 and 4x10 -3 s -1 . The results show that at same conditions the ductility of hydrides decreases as the hydriding temperature decreases. There exists a critical temperature (transition temperature) of 250degC for hydriding at 700degC, below which the hydrided specimens (and so for the hydrides) are brittle, while above it they are ductile. This transition temperature is lower than the one mentioned by various authors obtained for hydriding at 400degC. For the same hydriding temperature of 700degC, the specimens tested at 4x10 -3 s -1 are less ductile than those tested at 4x10 -4 s -1 . Furthermore, unlike at a strain rate of 4x10 -4 s -1 , there is no more a clear ductile-brittle transition behaviour. (author)

Magnetic phase transitions and anomalous transport properties in Ca-doped Eu hexaborides

International Nuclear Information System (INIS)

Rhyee, J. S.; Oh, B. H.; Cho, B. K.

2004-01-01

The temperature- and field-dependent magnetization M(T,H), electrical resistivity ρ(T,H), and Hall resistivity ρ xy (T,H) were measured for single crystals of a series of compounds Eu 1,x Ca x B 6 (x =0.0, 0.2, 0.4, 0.6, and 0.9). The ferromagnetic transition temperature of EuB 6 (T c = 12 K) was suppressed with small doping of Ca for Eu 0.8 Ca 0.2 B 6 (T c = 5.5 K) as evidenced by M(T) and a sharp drop in ρ(T). On the other hand, an antiferromagnetic transition was observed, rather than ferromagnetic transition, for Eu 0.6 Ca 0.4 B 6 (T N = 4.5 K) and Eu 0.4 Ca 0.6 B 6 (T N = 3 K). At the same time, a rapid increase of ρ(T) was found at low temperatures (T ≤ 10 K). The upturn of ρ(T) was suppressed with increasing applied magnetic field. From an analysis of the Hall resistivity ρ xy , the anomalous increase of ρ(T) and its suppression were found to be due to the dramatic variations in the charge carrier density n eff (T,H) and the Hall mobility μ H (T,H).

Characterization of frequency-dependent glass transition temperature by Vogel-Fulcher relationship

International Nuclear Information System (INIS)

Bai Yu; Jin Li

2008-01-01

The complex mechanical modulus of polymer and polymer based composite materials showed a frequency-dependent behaviour during glass transition relaxation, which was historically modelled by the Arrhenius equation. However, this might not be true in a broad frequency domain based on the experience from the frequency dependence of the complex dielectric permittivity, which resulted from the same glass transition relaxation as for the complex mechanical modulus. Considering a good correspondence between dielectric and mechanical relaxation during glass transition, the Vogel-Fulcher relationship, previously proposed for the frequency dependence of dielectric permittivity, is introduced for that of the mechanical modulus; and the corresponding static glass transition temperature (T f ) was first determined for polymer and polymer based composite materials. (fast track communication)

Glass transition temperature of PMMA/modified alumina nanocomposite: Molecular dynamic study

OpenAIRE

Mohammadi, Maryam; Davoodi, Jamal; Javanbakht, Mahdi; Rezaei, Hamidreza

2017-01-01

In this study, the effect of alumina and modified alumina nanoparticles in a PMMA/alumina nanocomposite was investigated. To attain this goal, the glass transition behavior of poly methyl methacrylate (PMMA), PMMA/alumina and PMMA/hydroxylated alumina nanocomposites were investigated by molecular dynamic simulations (MD). All the MD simulations were performed using the Materials Studio 6.0 software package of Accelrys. To obtain the glass transition temperature, the variation of density vs. t...

Failure mode transition in AHSS resistance spot welds. Part I. Controlling factors

International Nuclear Information System (INIS)

Pouranvari, M.; Marashi, S.P.H.

2011-01-01

Highlights: → Interfacial to pullout failure mode transition for AHSS RSWs is studied. → An analytical mode is proposed to predict failure mode of AHSS RSWs. → Hardness characteristics of RSWs plays key role in the failure mode transition. - Abstract: Failure mode of resistance spot welds is a qualitative indicator of weld performance. Two major types of spot weld failure are pull-out and interfacial fracture. Interfacial failure, which typically results in reduced energy absorption capability, is considered unsatisfactory and industry standards are often designed to avoid this occurrence. Advanced High Strength Steel (AHSS) spot welds exhibit high tendency to fail in interfacial failure mode. Sizing of spot welds based on the conventional recommendation of 4t 0.5 (t is sheet thickness) does not guarantee the pullout failure mode in many cases of AHSS spot welds. Therefore, a new weld quality criterion should be found for AHSS resistance spot welds to guarantee pull-out failure. The aim of this paper is to investigate and analyze the transition between interfacial and pull-out failure modes in AHSS resistance spot welds during the tensile-shear test by the use of analytical approach. In this work, in the light of failure mechanism, a simple analytical model is presented for estimating the critical fusion zone size to prevent interfacial fracture. According to this model, the hardness ratio of fusion zone to pull-out failure location and the volume fraction of voids in fusion zone are the key metallurgical factors governing type of failure mode of AHSS spot welds during the tensile-shear test. Low hardness ratio and high susceptibility to form shrinkage voids in the case of AHSS spot welds appear to be the two primary causes for their high tendency to fail in interfacial mode.

Heat resistance of Fe-Al intermetallics in the context of selected heat-resistant and hihg-temperature creep resistant steels

Directory of Open Access Journals (Sweden)

P. Baranowski

2009-04-01

Full Text Available Results are hereby presented of heat-resistance tests of two Fe3Al and FeAl intermetallic phase-based alloys in the context of St41k-typeboiler steel and 50H21G9N4 high-temperature creep resistant steel. It has been ascertained that heat resistance of the 50H21G9N4 steeland of the Fe3Al and FeAl intermetallic phase-based alloys significantly exceeds that of the boiler steel tested in the air atmosphere and the atmosphere of a flue gas with CO, CO2, SiO2 content alike. Improvement of these properties depends of exposure conditions. The largest differences have been observed when the tests were carried out in temperature 1023 K and in the flue gas atmosphere. The differences have been more and more noticeable as the exposition duration extended. A tendency has been also recorded of smaller mass decrements of the Fe3Al and FeAl intermetallic phase-based alloys as compared to the 50H21G9N4 steel.

Magnetic phase transitions in Er7Rh3 studied on single crystals

International Nuclear Information System (INIS)

Tsutaoka, Takanori; Obata, Keisuke; Cheyvuth, Seng; Koyama, Keiichi

2014-01-01

Highlights: • Magnetic and electrical properties of Er 7 Rh 3 were studied on single crystals. • The magnetic phase diagram along the c-axis was constructed. • The field-induced magnetic transitions in Er 7 Rh 3 can be explained by the magnetic structure with two magnetic propagation vectors. • The anomalies of electrical resistivity can also be described by the magnetic structure in Er 7 Rh 3 . - Abstract: Magnetic phase transitions in Er 7 Rh 3 with the Th 7 Fe 3 type hexagonal structure have been studied on single crystals by measuring magnetization, magnetic susceptibility and electrical resistivity. Er 7 Rh 3 possesses antiferromagnetic state below T N = 13 K. In the ordered state, the two successive magnetic transitions at T t1 = 6.2 K and T t2 = 4.5 K were observed. Several field-induced magnetic transitions were also observed along the a- and c-axes below T N ; magnetic field H – temperature T phase diagram along the c-axis was constructed. The field-induced magnetic transitions in Er 7 Rh 3 can be explained by the magnetic structure with two magnetic propagation vectors which were derived by the previous neutron diffraction studies. Electrical resistivity shows humps just below the magnetic transition temperatures, T N and T t1 due to the super-zone gap formation at the Fermi level; these anomalies can also be described by the magnetic structure changes in Er 7 Rh 3

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.

Regime transitions in near-surface temperature inversions : a conceptual model

NARCIS (Netherlands)

van de Wiel, B.J.H.; Vignon, E.; Baas, P.; Bosveld, F.C.; de Roode, S.R.; Moene, A.F.; Genthon, C.; van der Linden, Steven J.A.; van Hooft, J. Antoon; van Hooijdonk, I.G.S.

2017-01-01

A conceptual model is used in combination with observational analysis to understand regime transitions of near-surface temperature inversions at night as well as in Arctic conditions. The model combines a surface energy budget with a bulk parameterization for turbulent heat transport. Energy fluxes

Indium tin oxide films prepared by atmospheric plasma annealing and their semiconductor-metal conductivity transition around room temperature

International Nuclear Information System (INIS)

Li Yali; Li Chunyang; He Deyan; Li Junshuai

2009-01-01

We report the synthesis of indium tin oxide (ITO) films using the atmospheric plasma annealing (APA) technique combined with the spin-coating method. The ITO film with a low resistivity of ∼4.6 x 10 -4 Ω cm and a high visible light transmittance, above 85%, was achieved. Hall measurement indicates that compared with the optimized ITO films deposited by magnetron sputtering, the above-mentioned ITO film has a higher carrier concentration of ∼1.21 x 10 21 cm -3 and a lower mobility of ∼11.4 cm 2 V -1 s -1 . More interestingly, these electrical characteristics result in the semiconductor-metal conductivity transition around room temperature for the ITO films prepared by APA.

Investigation into the temperature dependence of isotropic- nematic phase transition of Gay- Berne liquid crystals

Directory of Open Access Journals (Sweden)

A Avazpour

2014-12-01

Full Text Available Density functional approach was used to study the isotropic- nematic (I-N transition and calculate the values of freezing parameters of the Gay- Berne liquid crystal model. New direct and pair correlation functions of a molecular fluid with Gay- Berne pair potential were used. These new functions were used in density functional theory as input to calculate the isotropic- nematic transition densities for elongation at various reduced temperatures. It was observed that the isotropic- nematic transition densities increase as the temperature increases. It was found that the new direct correlation function is suitable to study the isotropic- nematic transition of Gay- Berne liquids. Comparison to other works showed qualitative agreement

Surface electric resistance of YBa2Cu3O7-δ ceramics and its dependence on magnetic field

International Nuclear Information System (INIS)

Gorochev, O.A.; Graboj, I.Eh.; Kaul', A.R.; Mitrofanov, V.P.

1989-01-01

Method of dielectric resonator in the 4.2-300 K temperature range is used to measure surface electric resistance of YBa 2 Cu 3 O 7-δ ceramics samples produced by different technologies. The temperature dependence of surface resistance near transition temperature is calculated. At 77.3 K dependence of electric resistance on external magnetic field at H≤200Oe is determined. Calculated dependence is verified in experiment

Universal linear-temperature resistivity: possible quantum diffusion transport in strongly correlated superconductors.

Science.gov (United States)

Hu, Tao; Liu, Yinshang; Xiao, Hong; Mu, Gang; Yang, Yi-Feng

2017-08-25

The strongly correlated electron fluids in high temperature cuprate superconductors demonstrate an anomalous linear temperature (T) dependent resistivity behavior, which persists to a wide temperature range without exhibiting saturation. As cooling down, those electron fluids lose the resistivity and condense into the superfluid. However, the origin of the linear-T resistivity behavior and its relationship to the strongly correlated superconductivity remain a mystery. Here we report a universal relation [Formula: see text], which bridges the slope of the linear-T-dependent resistivity (dρ/dT) to the London penetration depth λ L at zero temperature among cuprate superconductor Bi 2 Sr 2 CaCu 2 O 8+δ and heavy fermion superconductors CeCoIn 5 , where μ 0 is vacuum permeability, k B is the Boltzmann constant and ħ is the reduced Planck constant. We extend this scaling relation to different systems and found that it holds for other cuprate, pnictide and heavy fermion superconductors as well, regardless of the significant differences in the strength of electronic correlations, transport directions, and doping levels. Our analysis suggests that the scaling relation in strongly correlated superconductors could be described as a hydrodynamic diffusive transport, with the diffusion coefficient (D) approaching the quantum limit D ~ ħ/m*, where m* is the quasi-particle effective mass.

In Situ Observation of Gypsum-Anhydrite Transition at High Pressure and High Temperature

International Nuclear Information System (INIS)

Liu Chuan-Jiang; Zheng Hai-Fei

2012-01-01

An in-situ Raman spectroscopic study of gypsum-anhydrite transition under a saturated water condition at high pressure and high temperature is performed using a hydrothermal diamond anvil cell (HDAC). The experimental results show that gypsum dissolvs in water at ambient temperature and above 496 MPa. With increasing temperature, the anhydrite (CaSO 4 ) phase precipitates at 250–320°C in the pressure range of 1.0–1.5GPa, indicating that under a saturated water condition, both stable conditions of pressure and temperature and high levels of Ca and SO 4 ion concentrations in aqueous solution are essential for the formation of anhydrite. A linear relationship between the pressure and temperature for the precipitation of anhydrite is established as P(GPa) = 0.0068T−0.7126 (250°C≤T≤320°C). Anhydrite remained stable during rapid cooling of the sample chamber, showing that the gypsum-anhydrite transition involving both dissolution and precipitation processes is irreversible at high pressure and high temperature. (geophysics, astronomy, and astrophysics)

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-09-01

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

Phase-insensitive detectors for ac resistance bridges with application to temperature control systems

International Nuclear Information System (INIS)

Duncan, M.G.

1977-01-01

A method of detecting AC resistance bridge error signals with low sensitivity to stray reactances is presented. The detector, which compares magnitudes of two bridge signals, can be used in a fast resistance temperature control to maintain constant resistance to better than 2 ppM at resistances down to 5 milliohms

Wear resistance of AISI 304 stainless steel submitted to low temperature plasma carburizing

Directory of Open Access Journals (Sweden)

Marcos Antônio Barcelos

Full Text Available Abstract Despite the AISI 304 stainless steel has high corrosion/oxidation resistance, its tribological properties are poor, being one of the barriers for use in severe wear applications. Thus, there is a wide field for studying technologies that aim to increase the surface hardness and wear resistance of this material. In this work, hardness and wear resistance for AISI 304 stainless steel submitted to the thermochemical treatment by low temperature plasma carburizing (LTPC in a fixed gas mixture composition of 93% H2 and 7% CH4 are presented. Through the evaluation of the carburizing layers, it was possible to observe a substantial improvement in tribological properties after all temperature and time of treatment. This improvement is directly related to the increase of the process variables; among them temperature has a stronger influence on the wear resistance obtained using LTPC process.

Resistance to antitumor chemotherapy due to bounded-noise-induced transitions

Science.gov (United States)

D'Onofrio, Alberto; Gandolfi, Alberto

2010-12-01

Tumor angiogenesis is a landmark of solid tumor development, but it is also directly relevant to chemotherapy. Indeed, the density and quality of neovessels may influence the effectiveness of therapies based on blood-born agents. In this paper, first we define a deterministic model of antiproliferative chemotherapy in which the drug efficacy is a unimodal function of vessel density, and then we show that under constant continuous infusion therapy the tumor-vessel system may be multistable. However, the actual drug concentration profiles are affected by bounded even if possibly large fluctuations. Through numerical simulations, we show that the tumor volume may undergo transitions to the higher equilibrium value induced by the bounded noise. In case of periodically delivered boli-based chemotherapy, we model the fluctuations due to time variability of both the drug clearance rate and the distribution volume, as well as those due to irregularities in drug delivery. We observed noise-induced transitions also in case of periodic delivering. By applying a time dense scheduling with constant average delivered drug (metronomic scheduling), we observed an easier suppression of the transitions. Finally, we propose to interpret the above phenomena as an unexpected non-genetic kind of resistance to chemotherapy.

Molecular Motion in Polymers: Mechanical Behavior of Polymers Near the Glass-Rubber Transition Temperature.

Science.gov (United States)

Sperling, L. H.

1982-01-01

The temperature at which the onset of coordinated segmental motion begins is called the glass-rubber transition temperature (Tg). Natural rubber at room temperature is a good example of a material above its Tg. Describes an experiment examining the response of a typical polymer to temperature variations above and below Tg. (Author/JN)

Superconducting and charge density wave transition in single crystalline LaPt2Si2

Science.gov (United States)

Gupta, Ritu; Dhar, S. K.; Thamizhavel, A.; Rajeev, K. P.; Hossain, Z.

2017-06-01

We present results of our comprehensive studies on single crystalline LaPt2Si2. Pronounced anomaly in electrical resistivity and heat capacity confirms the bulk nature of superconductivity (SC) and charge density wave (CDW) transition in the single crystals. While the charge density wave transition temperature is lower, the superconducting transition temperature is higher in single crystal compared to the polycrystalline sample. This result confirms the competing nature of CDW and SC. Another important finding is the anomalous temperature dependence of upper critical field H C2(T). We also report the anisotropy in the transport and magnetic measurements of the single crystal.

Halogen effect for improving high temperature oxidation resistance of Ti-50Al by anodization

Science.gov (United States)

Mo, Min-Hua; Wu, Lian-Kui; Cao, Hua-Zhen; Lin, Jun-Pin; Zheng, Guo-Qu

2017-06-01

The high temperature oxidation resistance of Ti-50Al was significantly improved via halogen effect which was achieved by anodizing in an ethylene glycol solution containing with fluorine ion. The anodized Ti-50Al with holes and micro-cracks could be self-repaired during oxidation at 1000 °C. The thickness of the oxide scale increases with the prolonging of oxidation time. On the basis of halogen effect for improving the high temperature oxidation resistance of Ti-50Al by anodization, only fluorine addition into the electrolyte can effectively improve the high temperature oxidation resistance of Ti-50Al.

Determination of Material Properties Near the Glass Transition Temperature for an Isogrid Boom

Science.gov (United States)

Blandino, Joseph R.; Woods-Vedeler, Jessica A. (Technical Monitor)

2002-01-01

Experiments were performed and results obtained to determine the temperature dependence of the modulus of elasticity for a thermoplastic isogrid tube. The isogrid tube was subjected to axial tensile loads of 0-100 lbf and strain was measured at room and elevated temperatures of 100, 120, 140, 160, 180, 190, and 200 F. These were based on tube manufacturer specifying an incorrect glass transition temperature of 210 F. Two protocols were used. For the first protocol the tube was brought to temperature and a tensile test performed. The tube was allowed to cool between tests. For the second protocol the tube was ramped to the desired test temperature and held. A tensile test was performed and the tube temperature ramped to the next test temperature. The second protocol spanned the entire test range. The strain rate was constant at 0.008 in/min. Room temperature tests resulted in the determination of an average modulus of 2.34 x 106 Psi. The modulus decreased above 100 F. At 140 F the modulus had decreased by 7.26%. The two test protocols showed good agreement below 160 F. At this point the glass transition temperature had been exceeded. The two protocols were not repeated because the tube failed.

Glass transition in thaumatin crystals revealed through temperature-dependent radiation-sensitivity measurements

Energy Technology Data Exchange (ETDEWEB)

Warkentin, Matthew, E-mail: maw64@cornell.edu; Thorne, Robert E. [Physics Department, Cornell University, Ithaca, New York (United States)

2010-10-01

Radiation damage to protein crystals exhibits two regimes of temperature-activated behavior between T = 300 and 100 K, with a crossover at the protein glass transition near 200 K. These results have implications for mechanistic studies of proteins and for structure determination when cooling to T = 100 K creates excessive disorder. The temperature-dependence of radiation damage to thaumatin crystals between T = 300 and 100 K is reported. The amount of damage for a given dose decreases sharply as the temperature decreases from 300 to 220 K and then decreases more gradually on further cooling below the protein-solvent glass transition. Two regimes of temperature-activated behavior were observed. At temperatures above ∼200 K the activation energy of 18.0 kJ mol{sup −1} indicates that radiation damage is dominated by diffusive motions in the protein and solvent. At temperatures below ∼200 K the activation energy is only 1.00 kJ mol{sup −1}, which is of the order of the thermal energy. Similar activation energies describe the temperature-dependence of radiation damage to a variety of solvent-free small-molecule organic crystals over the temperature range T = 300–80 K. It is suggested that radiation damage in this regime is vibrationally assisted and that the freezing-out of amino-acid scale vibrations contributes to the very weak temperature-dependence of radiation damage below ∼80 K. Analysis using the radiation-damage model of Blake and Phillips [Blake & Phillips (1962 ▶), Biological Effects of Ionizing Radiation at the Molecular Level, pp. 183–191] indicates that large-scale conformational and molecular motions are frozen out below T = 200 K but become increasingly prevalent and make an increasing contribution to damage at higher temperatures. Possible alternative mechanisms for radiation damage involving the formation of hydrogen-gas bubbles are discussed and discounted. These results have implications for mechanistic studies of proteins and for

Depression of Glass Transition Temperatures of Polymer Networks by Diluents

NARCIS (Netherlands)

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

1983-01-01

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

Correlation of Critical Temperatures and Electrical Properties in Titanium Films

Science.gov (United States)

Gandini, C.; Lacquaniti, V.; Monticone, E.; Portesi, C.; Rajteri, M.; Rastello, M. L.; Pasca, E.; Ventura, G.

Recently transition-edge sensors (TES) have obtained an increasing interest as light detectors due to their high energy resolution and broadband response. Titanium (Ti), with transition temperature up to 0.5 K, is among the suitable materials for TES application. In this work we investigate Ti films obtained from two materials of different purity deposited by e-gun on silicon nitride. Films with different thickness and deposition substrate temperature have been measured. Critical temperatures, electrical resistivities and structural properties obtained from x-ray are related to each other.

Correlated structural and electronic phase transformations in transition metal chalcogenide under high pressure

Energy Technology Data Exchange (ETDEWEB)

Li, Chunyu, E-mail: licy@hpstar.ac.cn, E-mail: yanhao@hpstar.ac.cn; Ke, Feng; Yu, Zhenhai; Chen, Zhiqiang; Yan, Hao, E-mail: licy@hpstar.ac.cn, E-mail: yanhao@hpstar.ac.cn [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 (China); Hu, Qingyang [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 (China); Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 (United States); Zhao, Jinggeng [Natural Science Research Center, Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080 (China)

2016-04-07

Here, we report comprehensive studies on the high-pressure structural and electrical transport properties of the layered transition metal chalcogenide (Cr{sub 2}S{sub 3}) up to 36.3 GPa. A structural phase transition was observed in the rhombohedral Cr{sub 2}S{sub 3} near 16.5 GPa by the synchrotron angle dispersive X-ray diffraction measurement using a diamond anvil cell. Through in situ resistance measurement, the electric resistance value was detected to decrease by an order of three over the pressure range of 7–15 GPa coincided with the structural phase transition. Measurements on the temperature dependence of resistivity indicate that it is a semiconductor-to-metal transition in nature. The results were also confirmed by the electronic energy band calculations. Above results may shed a light on optimizing the performance of Cr{sub 2}S{sub 3} based applications under extreme conditions.

Neutron scattering near the order-disorder transition in Cu3Au: evidence for a lower spinodal temperature

International Nuclear Information System (INIS)

Rogge, R.B.; Gaulin, B.D.; Svensson, E.C.; Hallman, E.D.; Wei, W.

1995-01-01

The binary alloy Cu 3 Au undergoes a first-order phase transition at 667 ± 3 K Within the context of the Landau theory of phase transitions, there exist, in addition to the order-disorder temperature, T c , upper and lower spinodal temperatures, T su and T si . These mark the first temperatures, upon approaching the phase transition from above and below, respectively, at which metastable droplets of the second phase can fluctuate out of the first phase. Until recently, there has, however, been little physical evidence supporting the existence of the spinodal temperatures. Elastic and inelastic neutron-scattering measurements have been carried out on Cu 3 Au over an extended temperature range with particular emphasis on temperatures near T c . The lattice constant data, order-parameter data, and phonon data provided by these measurements all indicate that there are two temperature regimes just below T c with a crossover between these regimes in the range of (T c - 35) to (T c - 25) K. This crossover temperature is interpreted as the lower spinodal temperature of Cu 3 Au. (author)

Effect of thermal phonons on the superconducting transition temperature

International Nuclear Information System (INIS)

Leavens, C.R.; Talbot, E.

1983-01-01

There is no consensus in the literature on whether or not thermal phonons depress the superconducting transition temperature T/sub c/. In this paper it is shown by accurate numerical solution of the real-frequency Eliashberg equations for the pairing self-energy phi and renormalization function Z that thermal phonons in the kernel for phi raise T/sub c/ but those in Z lower it by a larger amount so that the net effect is to depress T/sub c/. (A previous calculation which ignored the effect of thermal phonons in phi overestimated the suppression of T/sub c/ by at least a factor of 3.) It is shown how to switch off the thermal phonons in the imaginary-frequency Eliashberg equations, exactly for Z and approximately for phi. The real-frequency and approximate imaginary-frequency results for the depression of T/sub c/ by thermal phonons are in very satisfactory agreement. Thermal phonons are found to depress the transition temperature of Nb 3 Sn by only 2%. It is estimated that the suppression of T/sub c/ by thermal phonons saturates at about 50% in the limit of very strong electron-phonon coupling

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

Science.gov (United States)

Popova, V A; Surovtsev, N V

2014-09-01

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

Towards an accurate and precise determination of the solid-solid transition temperature of enantiotropic systems

Energy Technology Data Exchange (ETDEWEB)

Herman, Christelle, E-mail: christelle.herman@ulb.ac.b [Universite Libre de Bruxelles, Transfers, Interfaces and Processes Department, Chemical Engineering Unit, 50 Avenue Franklin D-Roosevelt, CP 165/67, 1050 Bruxelles (Belgium); Leyssens, Tom [Universite Catholique de Louvain, Institute of Condensed Matter and Nanosciences, 1 Place Louis Pasteur, 1348 Louvain-La-Neuve (Belgium); Vermylen, Valerie [UCB Pharma, 60 Allee de la Recherche, 1070 Braine l' Alleud (Belgium); Halloin, Veronique; Haut, Benoit [Universite Libre de Bruxelles, Transfers, Interfaces and Processes Department, Chemical Engineering Unit, 50 Avenue Franklin D-Roosevelt, CP 165/67, 1050 Bruxelles (Belgium)

2011-05-15

Research highlights: We test two methods to obtain the solid-solid transition temperature of Etiracetam system, showing two enantiotropically related polymorphs. The first method, based on a thermodynamic development, is sensitive to the correctness of the data required. The second method is an experimental study of the stability thermal range of each morph. We identify the nature of crystals in suspension at equilibrium through Raman analysis. The solid-solid transition temperature is found equal to 303.65 K {+-} 0.5 K. - Abstract: This paper presents two distinct methods for the determination of the solid-solid transition temperature (T{sub tr}) separating the temperature ranges of stability of two crystallographic forms, hereafter called morphs, of a same substance. The first method, based on thermodynamic calculations, consists in determining T{sub tr} as the temperature at which the Gibbs free energies of the two morphs are equal to each other. For this purpose, some thermodynamic characteristics of both morphs are required, such as the specific heat capacities, the melting temperatures and the melting enthalpies. These are obtained using the Differential Scanning Calorimetry (DSC). In the second method, T{sub tr} is determined directly by an experimental study of the temperature ranges of stability of each morph. The three main originalities of the method developed are (i) to prepare samples composed by an isomassic mixture of crystals of both morphs, (ii) to set them in a thermostated and agitated suspension, and (iii) to use an in situ Raman spectroscopic probe for the determination of the crystallographic form of the crystals in suspension at equilibrium. Both methods are applied to determine the solid-solid transition temperature of the enantiotropic system of Etiracetam, and both of its two crystallographic forms so far identified, named morph I and morph II. The first method is shown to be very sensitive to the experimental data obtained by DSC while

Towards an accurate and precise determination of the solid-solid transition temperature of enantiotropic systems

International Nuclear Information System (INIS)

Herman, Christelle; Leyssens, Tom; Vermylen, Valerie; Halloin, Veronique; Haut, Benoit

2011-01-01

Research highlights: → We test two methods to obtain the solid-solid transition temperature of Etiracetam system, showing two enantiotropically related polymorphs. → The first method, based on a thermodynamic development, is sensitive to the correctness of the data required. → The second method is an experimental study of the stability thermal range of each morph. → We identify the nature of crystals in suspension at equilibrium through Raman analysis. → The solid-solid transition temperature is found equal to 303.65 K ± 0.5 K. - Abstract: This paper presents two distinct methods for the determination of the solid-solid transition temperature (T tr ) separating the temperature ranges of stability of two crystallographic forms, hereafter called morphs, of a same substance. The first method, based on thermodynamic calculations, consists in determining T tr as the temperature at which the Gibbs free energies of the two morphs are equal to each other. For this purpose, some thermodynamic characteristics of both morphs are required, such as the specific heat capacities, the melting temperatures and the melting enthalpies. These are obtained using the Differential Scanning Calorimetry (DSC). In the second method, T tr is determined directly by an experimental study of the temperature ranges of stability of each morph. The three main originalities of the method developed are (i) to prepare samples composed by an isomassic mixture of crystals of both morphs, (ii) to set them in a thermostated and agitated suspension, and (iii) to use an in situ Raman spectroscopic probe for the determination of the crystallographic form of the crystals in suspension at equilibrium. Both methods are applied to determine the solid-solid transition temperature of the enantiotropic system of Etiracetam, and both of its two crystallographic forms so far identified, named morph I and morph II. The first method is shown to be very sensitive to the experimental data obtained by DSC

Electrical resistivity of Y(Fe1-x Alx)2 in the spin glass concentration range

International Nuclear Information System (INIS)

Cunha, S.F. da; Souza, G.P. de; Takeushi, A.Y.

1986-01-01

The temperature dependence of the electrical resistivity of the Y(Fe 1-x Al x ) 2 system (0.125 ≤ x ≤ 0.25) was measured. This system exhibits a minimum at low temperatures for the concentration range where the phase diagram presents a spin glass-ferromagnetic transition. A negative temperature coefficient is observed at high temperatures for x > 0.18 and was attributed to the high value of the electrical resistivity in this concentration range. (Author) [pt

Research on the technologies of cracking-resistance of mass concrete in subway station

Science.gov (United States)

Sheng, Yanmin; Li, Shujin; Jiang, Guoquan; Shi, Xiaoqing; Yang, Zhu; Zhu, Zhihang

2018-03-01

This paper takes the theory of multi-field coupling and the model of hydration-temperature-humidity-constraint to assess the effect of cracking-resistance on structural concrete and optimize the controlling index of crack resistance. The effect is caused by structure, material and construction, etc. The preparation technology of high cracking-resistance concrete is formed through the researching on the temperature rising and deformation over the controlling influence of new anti-cracking materials and technologies. A series of technologies on anti-cracking and waterproof in underground structural concrete of urban rail transit are formed based on the above study. The technologies include design, construction, materials and monitoring. Those technologies are used in actual engineering to improve the quality of urban rail transit and this brings significant economic and social benefits.

Host Resistance and Temperature-Dependent Evolution of Aggressiveness in the Plant Pathogen Zymoseptoria tritici

Directory of Open Access Journals (Sweden)

Fengping Chen

2017-06-01

Full Text Available Understanding how habitat heterogeneity may affect the evolution of plant pathogens is essential to effectively predict new epidemiological landscapes and manage genetic diversity under changing global climatic conditions. In this study, we explore the effects of habitat heterogeneity, as determined by variation in host resistance and local temperature, on the evolution of Zymoseptoria tritici by comparing the aggressiveness development of five Z. tritici populations originated from different parts of the world on two wheat cultivars varying in resistance to the pathogen. Our results show that host resistance plays an important role in the evolution of Z. tritici. The pathogen was under weak, constraining selection on a host with quantitative resistance but under a stronger, directional selection on a susceptible host. This difference is consistent with theoretical expectations that suggest that quantitative resistance may slow down the evolution of pathogens and therefore be more durable. Our results also show that local temperature interacts with host resistance in influencing the evolution of the pathogen. When infecting a susceptible host, aggressiveness development of Z. tritici was negatively correlated to temperatures of the original collection sites, suggesting a trade-off between the pathogen’s abilities of adapting to higher temperature and causing disease and global warming may have a negative effect on the evolution of pathogens. The finding that no such relationship was detected when the pathogen infected the partially resistant cultivars indicates the evolution of pathogens in quantitatively resistant hosts is less influenced by environments than in susceptible hosts.

Novel phase transitions in B-site doped manganites

International Nuclear Information System (INIS)

Popovic, Z.V.; Cantarero, A.; Thijssen, W.H.A.; Paunovic, N.; Dohcevic-Mitrovic, Z.; Sapina, F.

2005-01-01

We have examined the infrared reflectivity and the electrical resistivity of La 1- x [Sr(Ba)] x Mn 1- z [Cu(Zn)] z O 3 samples in ferromagnetic metallic and insulator regime. Several phase transitions are observed, the most obvious being the transition from a ferromagnetic metallic to a ferromagnetic insulator phase that is related to the formation of short-range orbitally ordered domains. The temperature T 1 of the phase transition is dependent on doping concentration and for optimally doped samples (∼32% of Mn 4+ ions) we have found T 1 ∼0.93 T C

Epithelial-Mesenchymal Transitions and the Expression of Twist in MCF-7/ADR,Human Multidrug-Resistant Breast Cancer Cells

Institute of Scientific and Technical Information of China (English)

Fei Zhang; Yurong Shi; Lin Zhang; Bin Zhang; Xiyin Wei; Yi Yang; RUi Wang; Ruifang Niu

2007-01-01

OBJECTIVE To study the expression levels of Twist and epithelialmesenchymal transitions in multidrug-resistant MCF-7/ADR breast cancer cells,and to study the relationship between multidrug resistance (MDR) and metastatic potential of the cells.METHODS RT-PCR,immunohislochemical and Western blotting methods were used to examine the changes of expression levels of the transcription factor Twist.E-cadherin and N-cadherin in the MCF-7 breast cancer cell line and its multidrug-resistant variant.MCF-7/ADR.RESULTS In MCF-7 cells,the expression of E-cadherin can be detected,but there is no expression of Twisl or N-cadherin.In MCF-7/ADR cells,E-cadherin expression is lost.bul the expression of two other genes was significantly positive.CONCLUSION Epithelial-mesenchymal transitions induced by Twist,may have a relationship with enhanced invasion and metastatic potential during the development of multidrug-resistant MCF-7/ADR breast cancer cells.

Determination of the glass transition temperature: methods correlation and structural heterogeneity

OpenAIRE

Hutchinson, John M.

2009-01-01

The definition of the glass transition temperature, Tg, is recalled and its experimental determination by various techniques is reviewed. The diversity of values of Tg obtained by the different methods is discussed, with particular attention being paid to Differential Scanning Calorimetry (DSC) and to dynamic techniques such as Dynamic Mechanical Thermal Analysis (DMTA) and Temperature Modulated DSC (TMDSC). This last technique, TMDSC, in particular, is considered in respect of ways in which ...

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.

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

Science.gov (United States)

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

2003-01-01

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

Low temperature resistivity studies of SmB6: Observation of two-dimensional variable-range hopping conductivity

Science.gov (United States)

Batkova, Marianna; Batko, Ivan; Gabáni, Slavomír; Gažo, Emil; Konovalova, Elena; Filippov, Vladimir

2018-05-01

We studied electrical resistance of a single-crystalline SmB6 sample with a focus on the region of the "low-temperature resistivity plateau". Our observations did not show any true saturation of the electrical resistance at temperatures below 3 K down to 70 mK. According to our findings, temperature dependence of the electrical conduction in a certain temperature interval above 70 mK can be decomposed into a temperature-independent term and a temperature-activated term that can be described by variable-range hopping formula for two-dimensional systems, exp [ -(T0 / T) 1 / 3 ]. Thus, our results indicate importance of hopping type of electrical transport in the near-surface region of SmB6.

Using Dopants to Tune Oxygen Vacancy Formation in Transition Metal Oxide Resistive Memory.

Science.gov (United States)

Jiang, Hao; Stewart, Derek A

2017-05-17

Introducing dopants is an important way to tailor and improve electronic properties of transition metal oxides used as high-k dielectric thin films and resistance switching layers in leading memory technologies, such as dynamic and resistive random access memory (ReRAM). Ta 2 O 5 has recently received increasing interest because Ta 2 O 5 -based ReRAM demonstrates high switching speed, long endurance, and low operating voltage. However, advances in optimizing device characteristics with dopants have been hindered by limited and contradictory experiments in this field. We report on a systematic study on how various metal dopants affect oxygen vacancy formation in crystalline and amorphous Ta 2 O 5 from first principles. We find that isoelectronic dopants and weak n-type dopants have little impact on neutral vacancy formation energy and that p-type dopants can lower the formation energy significantly by introducing holes into the system. In contrast, n-type dopants have a deleterious effect and actually increase the formation energy for charged oxygen vacancies. Given the similar doping trend reported for other binary transition metal oxides, this doping trend should be universally valid for typical binary transition metal oxides. Based on this guideline, we propose that p-type dopants (Al, Hf, Zr, and Ti) can lower the forming/set voltage and improve retention properties of Ta 2 O 5 ReRAM.

Glass Transition Temperature Measurement for Undercured Cyanate Ester Networks: Challenges, Tips, and Tricks (Briefing Charts)

Science.gov (United States)

2014-01-29

DISTRIBUTION A: Approved for public release; distribution is unlimited. Thermosetting Polymers Have a TG Envelope – Not Just a TG 4 • The glass transition...glass transition temperature of a thermosetting polymer can vary over a wide range of temperatures depending on how the polymer is processed • A... thermosetting polymer with only one kind of network formation and negligible side reactions, the conversion may be determined at every point in the scan. • By

Development and evaluation of a HEPA filter for increased strength and resistance to elevated temperature

International Nuclear Information System (INIS)

Gilbert, H.; Bergman, W.; Fretthold, J.K.

1992-01-01

We have developed an improved HEPA filter for increased strength and resistance to elevated temperature to improve the reliability of HEPA filters under accident conditions. The improvements to the HEPA filter consist of a silicone rubber sealant and a new HEPA medium reinforced with a glass cloth. Several prototype filters were built and evaluated for temperature and pressure resistance and resistance to rough handling. The temperature resistance test consisted of exposing the HEPA filter to 1,000 scan at 700 degrees F for five minutes. The pressure resistance test consisted of exposing the HEPA filter to a differential pressure of 10 in. w.g. using a water saturated air flow at 95 degrees F. For the rough handling test, we used a vibrating machine designated the Q110. DOP filter efficiency tests were performed before and after each of the environmental tests. In addition to following the standard practice of using a separate new filter for each environmental test, we also subjected the same filter to the elevated temperature test followed by the pressure resistance test. The efficiency test results show that the improved HEPA filter is significantly better than the standard HEPA filter

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

Temperature Effect on the Susceptibility of Methicillin-Resistant Staphylococcus aureus to Four Different Cephalosporins

OpenAIRE

Canawati, Hanna N.; Witte, Joyce L.; Sapico, Francisco L.

1982-01-01

Forty isolates of methicillin-resistant Staphylococcus aureus were tested for in vitro susceptibility to cephalothin, cefamandole, cefotaxime, and moxalactam, using the disk diffusion and microbroth dilution methods at incubation temperatures of 30 and 35°C. Resistance to all four antibiotics was more clearly evident at an incubation temperature of 30°C.

Determination of the glass transition temperature of cyclodextrin polymers.

Science.gov (United States)

Tabary, Nicolas; Garcia-Fernandez, Maria Jose; Danède, Florence; Descamps, Marc; Martel, Bernard; Willart, Jean-François

2016-09-05

The aim of this work was to determine the main physical characteristics of β-cyclodextrin polymers, well known for improving complexation capacities and providing enhanced and sustained release of a large panel of drugs. Two polymers were investigated: a polymer of β-cyclodextrin (polyβ-CD) and a polymer of partially methylated (DS=0.57) β-cyclodextrin (polyMe-β-CD). The physical characterizations were performed by powder X-ray diffraction and differential scanning calorimetry. The results indicate that these polymers are amorphous and that their glass transition is located above the thermal degradation point of the materials preventing their direct observation and thus their full characterization. We could however estimate the virtual glass transition temperatures by mixing the polymers with different plasticizers (trehalose and mannitol) which decreases Tg sufficiently to make the glass transition observable. Extrapolation to zero plasticizer concentration then yield the following Tg values: Tg (polyMe-β-CD)=317°C±5°C and Tg (polyβ-CD)=418°C±6°C. Copyright © 2016 Elsevier Ltd. All rights reserved.

Upper limit on the transition temperature for non-ideal Bose gases

International Nuclear Information System (INIS)

Dai Wusheng; Xie Mi

2007-01-01

In this paper, we show that for a non-ideal Bose gas there exists an upper limit on the transition temperature above which Bose-Einstein condensation cannot occur regardless of the pressure applied. Such upper limits for some realistic Bose gases are estimated

Electric resistance of nickel and niobium in the temperature range of 300-1300 K

International Nuclear Information System (INIS)

Novikov, I.I.; Roshchupkin, V.V.; Mozgovoj, A.G.; Semashko, N.A.

1982-01-01

The results of experimental investigation of nickel and niobium electric resistance on the wire samples by the potentiometric method in the temperature range of 300-1300 K are presented. Experimental data processing by the least square method is carried out; approximating equations of temperature dependence of the nickel and niobium electric resistance are prepared

Rubberlike Dynamics in Sulphur above the λ-Transition Temperature

International Nuclear Information System (INIS)

Monaco, G.; Crapanzano, L.; Crichton, W.; Mezouar, M.; Verbeni, R.; Bellissent, R.; Fioretto, D.; Scarponi, F.

2005-01-01

The high-frequency acoustic dynamics of sulfur across the liquid-liquid, λ transition has been studied using inelastic x-ray scattering. The combination of these high-frequency data with lower frequency, literature data indicates that liquid sulfur develops, in the high-temperature, polymeric solution phase, some characteristic features of a rubber. In particular, entanglement coupling among polymeric chains plays a relevant role in the dynamics of this liquid phase

Effects of ion temperature fluctuations on the stability of resistive ballooning modes

International Nuclear Information System (INIS)

Singh, R.; Nordman, H.; Jarmen, A.; Weiland, J.

1996-01-01

The influence of ion temperature fluctuations on the stability of resistive drift- and ballooning-modes is investigated using a two-fluid model. The Eigenmode equations are derived and solved analytically in a low beta model equilibrium. Parameters relevant to L-mode edge plasmas from the Texas Experimental Tokamak are used. The resistive modes are found to be destabilized by ion temperature fluctuations over a broad range of mode numbers. The scaling of the growth rate with magnetic shear and mode number is elucidated. 13 refs, 4 figs

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

Directory of Open Access Journals (Sweden)

S. Sreehari Sastry

2012-01-01

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

Monitoring of high temperature area by resistivity tomography during in-situ heating test in sedimentary soft rocks

International Nuclear Information System (INIS)

Kubota, Kenji; Suzuki, Koichi; Ikenoya, Takafumi; Takakura, Nozomu; Tani, Kazuo

2009-01-01

One of the major issues in disposal of nuclear waste is that the long term behaviors of sedimentary soft rocks can be affected by various environmental factors such as temperature, mechanical conditions or hydraulic conditions. Therefore, it is necessary to develop a method for evaluating the long term stability of caverns in sedimentary soft rocks as subjected to changes of environment. We have conducted in-situ heating test to evaluate the influence of high temperature to the surrounding rock mass at a depth of 50 m. The well with a diameter of 30 cm and 60 cm of height, was drilled and filled with groundwater. The heater was installed in the well for heating the surrounding rock mass. During the heating, temperature and deformation around the well were measured. To evaluate the influence of heating on sedimentary soft rocks, it is important to monitor the extent of heated area. Resistivity monitoring is thought to be effective to map the extent of the high temperature area. So we have conducted resistivity tomography during the heating test. The results demonstrated that the resistivity of the rock mass around the heating well decreased and this area was gradually expanded from the heated area during the heating. The decreasing rate of resistivity on temperature is correlated to that of laboratory experimental result and existing empirical formula between aqueous solution resistivity and temperature. Resistivity is changed by many other factors, but it is expected that resistivity change by other factors is very few in this test. This suggests that high temperature area is detected and spatial distribution of temperature can be mapped by resistivity tomography. So resistivity tomography is expected to be one of the promising methods to monitor the area heated by nuclear waste. (author)

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)

Fast temperature programming in gas chromatography using resistive heating

NARCIS (Netherlands)

Dallüge, J.; Ou-Aissa, R.; Vreuls, J.J.; Brinkman, U.A.T.; Veraart, J.R.

1999-01-01

The features of a resistive-heated capillary column for fast temperature-programmed gas chromatography (GC) have been evaluated. Experiments were carried out using a commercial available EZ Flash GC, an assembly which can be used to upgrade existing gas chromatographs. The capillary column is placed

Pressure and temperature induced electrical resistance change in nano-carbon/epoxy composites

NARCIS (Netherlands)

Shen, J. T.; Buschhorn, S. T.; De Hosson, J. Th. M.; Schulte, K.; Fiedler, B.

2015-01-01

In this study, we investigate the changes of electrical resistance of the carbon black (CB) and carbon nanotube (CNT) filled epoxy composites upon compression, swelling and temperature variation. For all samples we observe a decrease of electrical resistance under compression, while an increase of

The Effect of Temperature and Host Plant Resistance on Population Growth of the Soybean Aphid Biotype 1 (Hemiptera: Aphididae).

Science.gov (United States)

Hough, Ashley R; Nechols, James R; McCornack, Brian P; Margolies, David C; Sandercock, Brett K; Yan, Donglin; Murray, Leigh

2017-02-01

A laboratory experiment was conducted to evaluate direct and indirect effects of temperature on demographic traits and population growth of biotype 1 of the soybean aphid, Aphis glycines Matsumura. Our objectives were to better understand how temperature influences the expression of host plant resistance, quantify the individual and interactive effects of plant resistance and temperature on soybean aphid population growth, and generate thermal constants for predicting temperature-dependent development on both susceptible and resistant soybeans. To assess indirect (plant-mediated) effects, soybean aphids were reared under a range of temperatures (15-30 °C) on soybean seedlings from a line expressing a Rag1 gene for resistance, and life history traits were quantified and compared to those obtained for soybean aphids on a susceptible soybean line. Direct effects of temperature were obtained by comparing relative differences in the magnitude of life-history traits among temperatures on susceptible soybeans. We predicted that temperature and host plant resistance would have a combined, but asymmetrical, effect on soybean aphid fitness and population growth. Results showed that temperature and plant resistance influenced preimaginal development and survival, progeny produced, and adult longevity. There also appeared to be a complex interaction between temperature and plant resistance for survival and developmental rate. Evidence suggested that the level of plant resistance increased at higher, but not lower, temperature. Soybean aphids required about the same number of degree-days to develop on resistant and susceptible plants. Our results will be useful for making predictions of soybean aphid population growth on resistant plants under different seasonal temperatures. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Low-temperature resistivity anomaly in underdoped Pr0.8Sr0.2MnO3 manganite nanoparticles

International Nuclear Information System (INIS)

Das, Proloy T.; Giri, S.K.; Panda, J.; Taraphder, A.; Nath, T.K.; Nigam, A.K.

2013-01-01

High resolution electrical resistivity measurements were carried out of under-doped Pr 0.8 Sr 0.2 MnO 3 manganite nanoparticles with grain size modulation down to 40 nm in magnetic fields H, from 0 to 9 T in the low temperature regime down to a temperature of 4.2 K. In the temperature range below 80 K, a distinct resistivity minima is observed for all the samples with different particle sizes for all H. While trying to fit low temperature resistivity data with different models for the observed resistivity minima with negative temperature coefficient of resistance (TCR) for all H, it appears that all the data for different particle sizes, can be best described by electron-electron (e-e) interaction effect in comparison with other models, e.g., Kondo model, coulomb blockades etc. The low temperature data for all H have been fitted with an expression containing three terms, namely, residual resistivity, inelastic scattering, e-e interaction and Kondo effects. We conclude that the e-e interaction is the dominant transport mechanism at low temperatures for the observed negative TCR in this strongly disordered nanometric Pr 0.8 Sr 0.2 MnO 3 phase separated manganite system. (author)

Laser beam joining of non-oxidic ceramics for ultra high temperature resistant joints

International Nuclear Information System (INIS)

Lippmann, W.; Knorr, J.; Wolf, R.; Reinecke, A.M.; Rasper, R.

2004-01-01

The excellent technical properties of silicon carbide (SiC) and silicon nitride (Si 3 N 4 ) ceramics, such as resistance to extreme temperatures, oxidation, mechanical wear, aggressive chemical substances and radioactive radiation and also its high thermal conductivity and good temperature-shock resistance, make these ceramics ideally suited for use in the field of nuclear technology. However, their practical use has been limited so far because of the unavailability of effective joining techniques for these ceramics, especially for high temperature applications. A new joining technology (CERALINK registered ) has been developed in a network project which allowed high temperature resistant and vacuum-tight joining of SiC or Si 3 N 4 ceramics. A power laser is used as heat source, which makes it possible to join ceramic components in free atmosphere in combination with a pure oxidic braze filler. As no furnace is necessary, there are no limitations on the component dimensions by the furnace-geometry. During the joining process, the heated area can be limited to the seam area so that this technology can also be used to encapsulate materials with a low melting point. The seam has a high mechanical strength, it is resistant to a wide range of chemicals and radiation and it is also vacuum-tight. The temperature resistance can be varied by variation of the braze filler composition - usually between 1,400 C and >1,600 C. Beside the optimum filler it is also important to select the suitable laser wavelength. The paper will demonstrate the influence of different wave lengths, i. e. various laser types, on the seam quality. Examples are chosen to illustrate the strengths and limitations of the new technology

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.

The High-Temperature Resistance Properties of Polysiloxane/Al Coatings with Low Infrared Emissivity

Directory of Open Access Journals (Sweden)

Jun Zhao

2018-03-01

Full Text Available High-temperature-resistant coatings with low infrared emissivity were prepared using polysiloxane resin and flake aluminum as the adhesive and pigment, respectively. The heat resistance mechanisms of the polysiloxane/Al coating were systematically investigated. The composition, surface morphology, infrared reflectance spectra, and thermal expansion dimension (ΔL of the coatings were characterized by X-ray photoelectron spectroscopy (XPS, field emission scanning electron microscopy (FE-SEM, Fourier transform infrared spectroscopy, and thermal mechanical analysis (TMA, respectively. The results show that thermal decomposition of the resin and mismatch of ΔL between the coating and the substrate facilitate the high temperature failure of the coating. A suitable amount of flake aluminum pigments could restrain the thermal decomposition of the resin and could increase the match degree of ΔL between the coating and substrate, leading to an enhanced thermal resistance of the coating. Our results find that a coating with a pigment to binder ratio (P/B ratio of 1.0 could maintain integrity until 600 °C, and the infrared emissivity was as low as 0.27. Hence, a coating with high-temperature resistance and low emissivity was obtained. Such coatings can be used for infrared stealth technology or energy savings in high-temperature equipment.

Effects of configurational changes on electrical resistivity during glass-liquid transition of two bulk metal-alloy glasses

Energy Technology Data Exchange (ETDEWEB)

Aji, D. P. B.; Johari, G. P., E-mail: joharig@mcmaster.ca [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

2014-12-14

Consequences of increase in structural fluctuations on heating Pd{sub 40}Ni{sub 10}Cu{sub 30}P{sub 20} and Zr{sub 46.75}Ti{sub 8.25}Cu{sub 7.5}Ni{sub 10}Be{sub 27.5} through their glass to liquid transition range were investigated by measuring the electrical resistivity, ρ, an electron scattering property. The temperature coefficient of resistivity (TCR = (1/ρ) dρ/dT) of the liquid and glassy states is negative. The plots of their ρ against T in the T{sub g} (glass to liquid transition) range show a gradual change in the slope similar to the change observed generally for the plots of the density, elastic modulus, and refractive index. As fluctuations in the melt structure involve fewer configurations on cooling, ρ increases. In the energy landscape description, the melt's structure explores fewer minima with decrease in T, vibrational frequencies increase, and electron scattering and ρ increase. Plots of (−dρ/dT) against T resemble the plot of the specific heat of other glasses and show a sub-T{sub g} feature and a rapid rise at T near T{sub g}. Analysis shows that the magnitude of negative TCR is dominated by change in the phonon characteristics, and configurational fluctuations make it more negative. The TCR of the liquid and glassy states seems qualitatively consistent with the variation in the structure factor in Ziman's model for pure liquid metals as extended by Nagel to metal alloys and used to explain the negative TCR of a two-component metal glass.

A portable borehole temperature logging system using the four-wire resistance method

Science.gov (United States)

Erkan, Kamil; Akkoyunlu, Bülent; Balkan, Elif; Tayanç, Mete

2017-12-01

High-quality temperature-depth information from boreholes with a depth of 100 m or more is used in geothermal studies and in studies of climate change. Electrical wireline tools with thermistor sensors are capable of measuring borehole temperatures with millikelvin resolution. The use of a surface readout mode allows analysis of the thermally conductive state of a borehole, which is especially important for climatic and regional heat flow studies. In this study we describe the design of a portable temperature logging tool that uses the four-wire resistance measurement method. The four-wire method enables the elimination of cable resistance effects, thus allowing millikelvin resolution of temperature data at depth. A preliminary two-wire model of the system is also described. The portability of the tool enables one to collect data from boreholes down to 300 m, even in locations with limited accessibility.

Tuning the ferroelectric-to-paraelectric transition temperature and dipole orientation of group-IV monochalcogenide monolayers

Science.gov (United States)

Barraza-Lopez, Salvador; Kaloni, Thaneshwor P.; Poudel, Shiva P.; Kumar, Pradeep

2018-01-01

Coordination-related, two-dimensional (2D) structural phase transitions are a fascinating facet of two-dimensional materials with structural degeneracies. Nevertheless, a unified theoretical account of these transitions remains absent, and the following points are established through ab initio molecular dynamics and 2D discrete clock models here: Group-IV monochalcogenide (GeSe, SnSe, SnTe,...) monolayers have four degenerate structural ground states, and a phase transition from a threefold coordinated onto a fivefold coordinated structure takes place at finite temperature. On unstrained samples, this phase transition requires lattice parameters to evolve freely. A fundamental energy scale J permits understanding this transition, and numerical results indicate a transition temperature Tc of about 1.41 J . Numerical data provides a relation among the experimental (rhombic) parameter 〈Δ α 〉 [Chang et al., Science 353, 274 (2016), 10.1126/science.aad8609] and T of the form 〈Δ α 〉 =Δ α (T =0 ) (1-T /Tc)β , with a critical exponent β ≃1 /3 that coincides with experiment. It is also shown that 〈Δ α 〉 is temperature independent in another theoretical work [Fei et al., Phys. Rev. Lett. 117, 097601 (2016), 10.1103/PhysRevLett.117.097601], and thus incompatible with experiment. Tc and the orientation of the in-plane intrinsic electric dipole can be controlled by moderate uniaxial tensile strain, and a modified discrete clock model describes the transition on strained samples qualitatively. An analysis of out-of-plane fluctuations and a discussion of the need for van der Waals corrections to describe these materials are given too. These results provide an experimentally compatible framework to understand structural phase transitions in 2D materials and their effects on material properties.

Thermal expansion and cooling rate dependence of transition temperature in ZrTiO4 single crystal

International Nuclear Information System (INIS)

Park, Y.

1998-01-01

Thermal expansion in ZrTiO 4 single crystal was investigated in the temperature range covering the normal, incommensurate, and commensurate phases. Remarkable change was found at the normal-incommensurate phase transition (T I ) in all thermal expansion coefficients a, b, and c. The spontaneous strains χ as and χ bs along the a and b axes show linear temperature dependence, while the spontaneous strain χ cs along the c axis shows a nonlinear temperature dependence. Small discontinuity along the c direction was observed at the incommensurate-commensurate transition temperature, T c = 845 C. dT I /dP and dT c /dP depend on the cooling rate

RNA-Seq analysis reveals insight into enhanced rice Xa7-mediated bacterial blight resistance at high temperature.

Directory of Open Access Journals (Sweden)

Stephen P Cohen

Full Text Available Plant disease is a major challenge to agriculture worldwide, and it is exacerbated by abiotic environmental factors. During some plant-pathogen interactions, heat stress allows pathogens to overcome host resistance, a phenomenon which could severely impact crop productivity considering the global warming trends associated with climate change. Despite the importance of this phenomenon, little is known about the underlying molecular mechanisms. To better understand host plant responses during simultaneous heat and pathogen stress, we conducted a transcriptomics experiment for rice plants (cultivar IRBB61 containing Xa7, a bacterial blight disease resistance (R gene, that were infected with Xanthomonas oryzae, the bacterial blight pathogen of rice, during high temperature stress. Xa7-mediated resistance is unusual relative to resistance mediated by other R genes in that it functions better at high temperatures. Using RNA-Seq technology, we identified 8,499 differentially expressed genes as temperature responsive in rice cultivar IRBB61 experiencing susceptible and resistant interactions across three time points. Notably, genes in the plant hormone abscisic acid biosynthesis and response pathways were up-regulated by high temperature in both mock-treated plants and plants experiencing a susceptible interaction and were suppressed by high temperature in plants exhibiting Xa7-mediated resistance. Genes responsive to salicylic acid, an important plant hormone for disease resistance, were down-regulated by high temperature during both the susceptible and resistant interactions, suggesting that enhanced Xa7-mediated resistance at high temperature is not dependent on salicylic acid signaling. A DNA sequence motif similar to known abscisic acid-responsive cis-regulatory elements was identified in the promoter region upstream of genes up-regulated in susceptible but down-regulated in resistant interactions. The results of our study suggest that the plant

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)

Effect of temperature on structure and corrosion resistance for ...

Indian Academy of Sciences (India)

The effect of plating temperatures between 60 and 90◦C on structure and corrosion resistance for elec- troless NiWP coatings ..... which helps to form fine grain. At 80 .... [23] Zhang W X, Jiang Z H, Li G Y and Jiang Q 2008 Surf. Coat. Technol.

Sequential transition of the injury phenotype, temperature-dependent survival and transcriptional response in Listeria monocytogenes following lethal H2O2 exposure.

Science.gov (United States)

Ochiai, Yoshitsugu; Yamada, Fumiya; Yoshikawa, Yuko; Mochizuki, Mariko; Takano, Takashi; Hondo, Ryo; Ueda, Fukiko

2017-10-16

The food-borne pathogen Listeria monocytogenes is present persistently in food processing environments, where this bacterium is exposed to various stress factors, including oxidative stress. This study aimed to elucidate the temperature-dependent response of L. monocytogenes to H 2 O 2 exposure and the phenotypic changes in colony formation by H 2 O 2 -treated bacteria. Survival curves indicated an increase in the resistance to H 2 O 2 in L. monocytogenes as the temperature decreased during the stress exposure procedure. Transcriptional induction of genes with key roles in response to H 2 O 2 , including sigB and kat, was observed at 37°C, but not at 20°C, whereas other stress response genes were induced at both temperatures. Following H 2 O 2 exposure, L. monocytogenes produced small colony phenotypes and the colony size decreased in a stress exposure duration-dependent manner. Resuscitated cells with no ability to form colonies in the absence of sodium pyruvate were also found. Our findings show the possibility that a sequential transition in the injury phenotype from small colony phenotype to resuscitated cells occurred during the course of exposure to H 2 O 2 . The higher H 2 O 2 resistance at 20°C than 37°C suggests further investigation of the response to H 2 O 2 exposure under the lower temperatures, including refrigeration temperature, which may contribute to elucidation of bacterial survival over extended time periods in food-processing environments. Copyright © 2017 Elsevier B.V. All rights reserved.

Temperature- and field-induced structural transitions in magnetic colloidal clusters

Science.gov (United States)

Hernández-Rojas, J.; Calvo, F.

2018-02-01

Magnetic colloidal clusters can form chain, ring, and more compact structures depending on their size. In the present investigation we examine the combined effects of temperature and external magnetic field on these configurations by means of extensive Monte Carlo simulations and a dedicated analysis based on inherent structures. Various thermodynamical, geometric, and magnetic properties are calculated and altogether provide evidence for possibly multiple structural transitions at low external magnetic field. Temperature effects are found to overcome the ordering effect of the external field, the melted stated being associated with low magnetization and a greater compactness. Tentative phase diagrams are proposed for selected sizes.

Numerical simulation of temperature's sensitivity of chamfer hole's resistance on hydraulic step cylinder

International Nuclear Information System (INIS)

Jinhua, Wang; Hanliang, Bo; Wenxiang, Zheng; Jinnong, Yang

2003-01-01

The control rod drive is a very important device for controlling nuclear reactor startup, operation, shut down, and power change. The ability of the control rod drive to move safely and reliably directly relates to reactor safety. The Hydraulic Control Rod Drive System (HCRDS) is a new type of control rod drive system developed by the Institute of Nuclear Energy Technology (INET) of Tsinghua University for Nuclear Heating Reactors. The HCRDS, designed using the hydrodynamic principle, has many advantages, including having the structure complete in the vessel, no possible ejection accident, short drive line, simple movable parts structure and safe shutdown during accidents. The hydraulic step cylinder is the key part for the HCRDS. In the process of reactor startup, the variation of temperature could make the water's density and viscosity change, and the force from the water flow would change accordingly. These factors could influence the performance of the hydraulic step cylinder. In this paper, the temperature sensitivity of the chamfer hole's resistance in the hydraulic step cylinder was studied with the Computational Fluid Dynamics (CFD) program CFX5.5. The results were satisfactory: the discipline of variation of the chamfer hole's resistance with the outer tube's position was the same at different temperatures, the discrepancy of the chamfer hole's resistance was small for the same position at different temperatures, the chamfer hole's resistance decreased gradually with the increase of temperature, and the decrease extent was relatively small

Development of leak detection system using high temperature-resistant microphones

International Nuclear Information System (INIS)

Morishita, Yoshitsugu; Mochizuki, Hiroyasu; Watanabe, Kenshiu; Nakamura, Takahisa; Nakazima, Yoshiaki; Yamauchi, Tatsuya

1995-01-01

This report describes the development and testing of a coolant leak detection system for an inlet feeder pipe of an advanced thermal reactor (ATR) using high temperature-resistant microphones. Such microphones must be resistant to both high temperatures and high radiation doses. Leakage sound characteristics, attenuation of the sound level in a heat insulating box for the inlet feeder pipes, and background noise were investigated using the experimental facility and the prototype ATR 'FUGEN'. The optimum frequency ranges for the microphone were then determined based on the observed leakage sound and background noise. The ability of the microphone to discriminate between leaks and other burst-type noises was also investigated by statistical analyses. Finally, it was confirmed that the present method could detect a leak within a couple of seconds. (author)

M₅Si₃(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

Energy Technology Data Exchange (ETDEWEB)

Tang, Zhihong [Iowa State Univ., Ames, IA (United States)

2007-01-01

Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti₅Si₃-based alloys was investigated. Oxidation behavior of Ti₅Si₃-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti₅Si₃ by nucleation and growth of nitride subscale. Ti₅Si_3.2and Ti₅Si₃C_0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi₂ coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo₃Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo₃Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nb_ss (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L {leftrightarrow} Nb_SS + NbB was determined to occur at 2104 ± 5 C by DTA.

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

DEFF Research Database (Denmark)

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

2005-01-01

Low-temperature water–gas shift reactivity trends on transition metals were investigated with the use of a microkinetic model based on a redox mechanism. It is established that the adsorption energies for carbon monoxide and oxygen can describe to a large extent changes in the remaining activation...

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.

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

A study on the improvement of oxidation resistance of OAE-added stainless steels for high temperature applications

International Nuclear Information System (INIS)

Kim, Dae Hwan; Kim, Gil Moo

1996-01-01

Since the manufacturing temperature of stainless steels is relatively high, oxidation at the elevated temperature becomes important. The chemical and physical properties of the protective oxide film which was formed on the stainless steels at high temperature for the oxidation resistance are important in determining the rate of oxidation and the life of equipment exposed to high temperature oxidizing environments. In this study, the oxidation behavior of STS 309S and STS 409L added by a small amount of oxygen active element(each + 0.5wt% Hf and Y) was studied to improve oxidation resistance. In the cyclic oxidation, while OAE-free specimens showed relatively poor oxidation resistance due to spallations and cracks of Cr-rich oxide layer, OAE-added specimens improved cyclic oxidation resistance assumably due to constant oxidation rate with stable oxide layers at high temperature. Especially Hf improved cyclic oxidation resistance by forming Cr-rich oxide layer preventing internal oxidation in STS 309S. (author)

Rheometrical experiments with monitoring of resistivity: for a better understanding of the solid-fluid transition in clayey landslides

Science.gov (United States)

Carrière, Simon; Bièvre, Grégory; Chambon, Guillaume; Jongmans, Denis; Lebourg, Thomas; Larose, Eric

2015-04-01

Landslides are natural and complex phenomena which affect all types of geological formations and present a large variety of size, morphology and displacements rates. Among these phenomena, flow-like events in clay-rich formations are particularly complex due to the unpredictable acceleration and fluidization that characterize them. Because of their suddenness, such landslides constitute serious threat for population living in these areas. The forecast and the understanding of these events has then been an active topic of research in the scientific community during the past decades. In that respect, rheometrical experiments in the laboratory bring some insight into the processes occurring during the solid-fluid transition. In creep tests, the evolution of the shear strain rate is measured under constant levels of shear stress, allowing to follow changes in apparent viscosity with time and to observe fluidization. Rheometrical oscillatory tests have been designed to capture the evolution of the elastic shear modulus G (and hence the shear wave velocity Vs) during these creep phases. Previous results have shown that Vs exhibits a drop at the solid-fluid transition, with complex time-dependent effects which could lead, under transient loading, to the occurrence of Vs variations prior to the transition. A complementary way to understand the processes is to measure the electrical resistivity during these rheometrical tests. This parameter, which depends on the water content and salinity, as well as on the amount of clay particles, could also exhibit some changes before or during the solid-fluid transition. For that purpose, the metallic plates of the rotational rheometer have been replaced by new ones made in an electrically insulating material (PVC) with a configuration of four inserted circular electrodes. Rheometrical tests made with this new apparatus provide similar rheological results. For the electrical tests, the geometrical factor has been computed using Finite

Magnetic Phase Transitions in NdCoAsO

Energy Technology Data Exchange (ETDEWEB)

McGuire, Michael A [ORNL; Gout, Delphine J [ORNL; Garlea, Vasile O [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); Sales, Brian C [ORNL; Mandrus, David [ORNL

2010-01-01

NdCoAsO undergoes three magnetic phase transitions below room temperature. Here we report the results of our experimental investigation of this compound, including determination of the crystal and magnetic structures using powder neutron diffraction, as well as measurements of electrical resistivity, thermal conductivity, Seebeck coefficient, magnetization, and heat capacity. These results show that upon cooling a ferromagnetic state emerges near 69 K with a small saturation moment of -0.2{micro}{sub B}, likely on Co atoms. At 14 K the material enters an antiferromagnetic state with propagation vector (0 0 1/2) and small ordered moments (-0.4{micro}{sub B}) on Co and Nd. Near 3.5 K a third transition is observed, and corresponds to the antiferromagnetic ordering of larger moments on Nd, with the same propagation vector. The ordered moment on Nd reaches 1.39(5){micro}{sub B} at 300 mK. Anomalies in the magnetization, electrical resistivity, and heat capacity are observed at all three magnetic phase transitions.

Room-Temperature Synthesis of Transition Metal Clusters and Main Group Polycations from Ionic Liquids

OpenAIRE

Ahmed, Ejaz

2011-01-01

Main group polycations and transition metal clusters had traditionally been synthesized via high-temperature routes by performing reactions in melts or by CTR, at room-temperature or lower temperature by using so-called superacid solvents, and at room-temperature in benzene–GaX3 media. Considering the major problems associated with higher temperature routes (e.g. long annealing time, risk of product decomposition, and low yield) and taking into account the toxicity of benzene and liquid SO2 i...

Electric-Field-Driven Dual Vacancies Evolution in Ultrathin Nanosheets Realizing Reversible Semiconductor to Half-Metal Transition.

Science.gov (United States)

Lyu, Mengjie; Liu, Youwen; Zhi, Yuduo; Xiao, Chong; Gu, Bingchuan; Hua, Xuemin; Fan, Shaojuan; Lin, Yue; Bai, Wei; Tong, Wei; Zou, Youming; Pan, Bicai; Ye, Bangjiao; Xie, Yi

2015-12-02

Fabricating a flexible room-temperature ferromagnetic resistive-switching random access memory (RRAM) device is of fundamental importance to integrate nonvolatile memory and spintronics both in theory and practice for modern information technology and has the potential to bring about revolutionary new foldable information-storage devices. Here, we show that a relatively low operating voltage (+1.4 V/-1.5 V, the corresponding electric field is around 20,000 V/cm) drives the dual vacancies evolution in ultrathin SnO2 nanosheets at room temperature, which causes the reversible transition between semiconductor and half-metal, accompanyied by an abrupt conductivity change up to 10(3) times, exhibiting room-temperature ferromagnetism in two resistance states. Positron annihilation spectroscopy and electron spin resonance results show that the Sn/O dual vacancies in the ultrathin SnO2 nanosheets evolve to isolated Sn vacancy under electric field, accounting for the switching behavior of SnO2 ultrathin nanosheets; on the other hand, the different defect types correspond to different conduction natures, realizing the transition between semiconductor and half-metal. Our result represents a crucial step to create new a information-storage device realizing the reversible transition between semiconductor and half-metal with flexibility and room-temperature ferromagnetism at low energy consumption. The as-obtained half-metal in the low-resistance state broadens the application of the device in spintronics and the semiconductor to half-metal transition on the basis of defects evolution and also opens up a new avenue for exploring random access memory mechanisms and finding new half-metals for spintronics.

Novel phase transitions in B-site doped manganites

Energy Technology Data Exchange (ETDEWEB)

Popovic, Z.V. [Institute of Physics, P.O. Box 68, 11080 Belgrade/Zemun (Serbia and Montenegro)]. E-mail: zoran.popovic@phy.bg.ac.yu; Cantarero, A. [Materials Science Institute, University of Valencia, P.O. Box 22085, 46071 Valencia (Spain); Thijssen, W.H.A. [Kamerlingh Onnes Laboratorium, Leiden University, Postbus 9504, 2300 RA Leiden (Netherlands); Paunovic, N. [Institute of Physics, P.O. Box 68, 11080 Belgrade/Zemun (Serbia and Montenegro); Dohcevic-Mitrovic, Z. [Institute of Physics, P.O. Box 68, 11080 Belgrade/Zemun (Serbia and Montenegro); Sapina, F. [Materials Science Institute, University of Valencia, P.O. Box 22085, 46071 Valencia (Spain)

2005-04-30

We have examined the infrared reflectivity and the electrical resistivity of La{sub 1-} {sub x} [Sr(Ba)] {sub x} Mn{sub 1-} {sub z} [Cu(Zn)] {sub z} O{sub 3} samples in ferromagnetic metallic and insulator regime. Several phase transitions are observed, the most obvious being the transition from a ferromagnetic metallic to a ferromagnetic insulator phase that is related to the formation of short-range orbitally ordered domains. The temperature T {sub 1} of the phase transition is dependent on doping concentration and for optimally doped samples ({approx}32% of Mn{sup 4+} ions) we have found T {sub 1}{approx}0.93 T {sub C}.

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

DEFF Research Database (Denmark)

Guo, Huilong; Wang, Jiayi; Zhou, Chengbo

2015-01-01

Deformation and yield induced structure transitions of polyamide 6 (PA6) were detected with the combination of the wide- and small-angle X-ray scattering (WAXS and SAXS) at 30 degrees C below glass transition temperature (T-g) of PA6. During deformation, gamma-alpha phase transition was found...... at elastic stage. The concentrated stress in crystals at elastic stage provided adequate energy for the direct gamma-alpha phase transition under T-g. The force to promote the gamma-phase into a phase directly is insufficient at the yield stage and a transient phase as a compromise was formed. The transient...... phase was confirmed by DSC measurements and assisted the gamma-alpha phase transition indirectly. The gamma-phase slips into incomplete fragments at yield point, and the parts along tensile direction are responsible for the formation of transient phase. The gamma-fragments after yield is oriented...

A Definition of the Magnetic Transition Temperature Using Valence Bond Theory.

Science.gov (United States)

Jornet-Somoza, Joaquim; Deumal, Mercè; Borge, Juan; Robb, Michael A

2018-03-01

Macroscopic magnetic properties are analyzed using Valence Bond theory. Commonly the critical temperature T C for magnetic systems is associated with a maximum in the energy-based heat capacity C p (T). Here a more broadly applicable definition of the magnetic transition temperature T C is described using the spin moment expectation value (i.e., applying the spin exchange density operator) instead of energy. Namely, the magnetic capacity C s (T) reflects variation in the spin multiplicity as a function of temperature, which is shown to be related to ∂[χT(T)]/∂T. Magnetic capacity C s (T) depends on long-range spin interactions that are not relevant in the energy-based heat capacity C p (T). Differences between C s (T) and C p (T) are shown to be due to spin order/disorder within the crystal that can be monitored via a Valence Bond analysis of the corresponding magnetic wave function. Indeed the concept of the Boltzmann spin-alignment order is used to provide information about the spin correlation between magnetic units. As a final illustration, the critical temperature is derived from the magnetic capacity for several molecular magnets presenting different magnetic topologies that have been experimentally studied. A systematic shift between the transition temperatures associated with C s (T) and C p (T) is observed. It is demonstrated that this shift can be attributed to the loss of long-range spin correlation. This suggests that the magnetic capacity C s (T) can be used as a predictive tool for the magnetic topology and thus for the synthetic chemists.

Low temperature magnetoresistance in La1.32Sr1.68Mn2O7 layered manganite under hydrostatic pressure

International Nuclear Information System (INIS)

Kumaresavanji, M.; Fontes, M.B.

2010-01-01

The La 1.32 Sr 1.68 Mn 2 O 7 layered manganite system has been studied by the low temperature electrical resistance and magnetoresistance under hydrostatic pressure up to 25 kbar. We have observe both, a Curie temperature (T C ) and a metal-insulator transition (T MI ) at 118 K in the ambient pressure. The applied pressure shifts the T MI to higher temperature values and induces a second metal-insulator transition (T 2 MI ) at 90 K, in the temperature dependence of resistivity measurements. Also, the pressure suppresses the peak resistance abruptly at T C . When an external field of 5 T is applied, we have observed a large negative magnetoresistance of 300% at the transition temperature and a 128% at 4.5 K. However, the increased pressure decreases the magnetoresistance ratio gradually. When the pressure reaches its maximum available value of 25 kbar, the magnetoresistance ratio decreases at a rate of 1.3%/kbar. From our experimental results, the decrease of magnetoresistance ratio with pressure is explained by the pressure induced canted spin state which is not favor for the spin polarized intergrain tunneling in layered manganites.

Long duration performance of high temperature irradiation resistant thermocouples

International Nuclear Information System (INIS)

Rempe, J.; Knudson, D.; Condie, K.; Cole, J.; Wilkins, S.C.

2007-01-01

Many advanced nuclear reactor designs require new fuel, cladding, and structural materials. Data are needed to characterize the performance of these new materials in high temperature, radiation conditions. However, traditional methods for measuring temperature in-pile degrade at temperatures above 1100 C degrees. To address this instrumentation need, the Idaho National Laboratory (INL) developed and evaluated the performance of a high temperature irradiation-resistant thermocouple that contains alloys of molybdenum and niobium. To verify the performance of INL's recommended thermocouple design, a series of high temperature (from 1200 to 1800 C) long duration (up to six months) tests has been initiated. This paper summarizes results from the tests that have been completed. Data are presented from 4000 hour tests conducted at 1200 and 1400 C that demonstrate the stability of this thermocouple (less than 2% drift). In addition, post test metallographic examinations are discussed which confirm the compatibility of thermocouple materials throughout these long duration, high temperature tests. (authors)

Transition edge sensor series array bolometer

Energy Technology Data Exchange (ETDEWEB)

Beyer, J, E-mail: joern.beyer@ptb.d [Physikalisch-Technische Bundesanstalt (PTB), Abbestrasse 2-12, D-10587 Berlin (Germany)

2010-10-15

A transition edge sensor series array (TES-SA) is an array of identical TESs that are connected in series by low-inductance superconducting wiring. The array elements are equally and well thermally coupled to the absorber and respond to changes in the absorber temperature in synchronization. The TES-SA total resistance increases compared to a single TES while the shape of the superconducting transition is preserved. We are developing a TES-SA with a large number, hundreds to thousands, of array elements with the goal of enabling the readout of a TES-based bolometer operated at 4.2 K with a semiconductor-based amplifier located at room temperature. The noise and dynamic performance of a TES-SA bolometer based on a niobium/aluminum bilayer is analyzed. It is shown that stable readout of the bolometer with a low-noise transimpedance amplifier is feasible.

Transition edge sensor series array bolometer

International Nuclear Information System (INIS)

Beyer, J

2010-01-01

A transition edge sensor series array (TES-SA) is an array of identical TESs that are connected in series by low-inductance superconducting wiring. The array elements are equally and well thermally coupled to the absorber and respond to changes in the absorber temperature in synchronization. The TES-SA total resistance increases compared to a single TES while the shape of the superconducting transition is preserved. We are developing a TES-SA with a large number, hundreds to thousands, of array elements with the goal of enabling the readout of a TES-based bolometer operated at 4.2 K with a semiconductor-based amplifier located at room temperature. The noise and dynamic performance of a TES-SA bolometer based on a niobium/aluminum bilayer is analyzed. It is shown that stable readout of the bolometer with a low-noise transimpedance amplifier is feasible.

Influence of intermartensitic transitions on transport properties of Ni$_{2.16}Mn_{0.84}$Ga alloy

CERN Document Server

Khovailo, V V; Wedel, C; Takagi, T; Abe, T; Sugiyama, K

2004-01-01

Magnetic, transport, and x-ray diffraction measurements of ferromagnetic shape memory alloy Ni$_{2.16}$Mn$_{0.84}$Ga revealed that this alloy undergoes an intermartensitic transition upon cooling, whereas no such a transition is observed upon subsequent heating. The difference in the modulation of the martensite forming upon cooling from the high-temperature austenitic state [5-layered (5M) martensite], and the martensite forming upon the intermartensitic transition [7-layered (7M) martensite] strongly affects the magnetic and transport properties of the alloy and results in a large thermal hysteresis of the resistivity $\\rho$ and magnetization $M$. The intermartensitic transition has an especially marked influence on the transport properties, as is evident from a large difference in the resistivity of the 5M and 7M martensite, $(\\rho_{\\mathrm{5M}} - \\rho_{\\mathrm{7M}})/\\rho _{\\mathrm{5M}} \\approx 15%$, which is larger than the jump of resistivity at the martensitic transition from the cubic austenitic phase ...

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

DEFF Research Database (Denmark)

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

1981-01-01

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

Fracture resistance of asphalt concrete modified with crumb rubber at low temperatures

Directory of Open Access Journals (Sweden)

A. Razmi

2018-05-01

Full Text Available The main objective of this study is to obtain fracture toughness of asphalt concrete modified by Crumb Rubber (CR and Sasobit at low temperatures. First, Bending Beam Rheometer (BBR test was performed on unmodified binder (binder 60/70, binder 60/70 + 3%Sasobit and 20%CR + 3%Sasobit modified asphalt binder to find how each modifier affect asphalt binder stiffness and relaxation rate at low temperatures. Mixed mode I/II fracture tests were conducted by cracked Semi-Circular Bending (SCB specimens and the critical stress intensity factors were calculated for pure mode I, mixed mode I/II and pure mode II conditions. Results of BBR tests indicated that 20%CR + 3%Sasobit reduces stiffness and the m-value increase at low temperatures. As a result, 20%CR + 3%Sasobit has positive effect on low temperatures performance by improving thermal cracking resistance. Also, according to the fracture toughness test results, the Warm Mix Asphalt (WMA mixture containing 20% CR, shows higher resistance against crack growth than WMA mixture. It was found that mixed mode I/II can be more detrimental than pure mode I and II conditions. Keywords: Crumb rubber, Asphalt concrete, Bending Beam Rheometer, Fracture resistance, Semi-circular bending test

Graphene-based mid-infrared room-temperature pyroelectric bolometers with ultrahigh temperature coefficient of resistance.

Science.gov (United States)

Sassi, U; Parret, R; Nanot, S; Bruna, M; Borini, S; De Fazio, D; Zhao, Z; Lidorikis, E; Koppens, F H L; Ferrari, A C; Colli, A

2017-01-31

There is a growing number of applications demanding highly sensitive photodetectors in the mid-infrared. Thermal photodetectors, such as bolometers, have emerged as the technology of choice, because they do not need cooling. The performance of a bolometer is linked to its temperature coefficient of resistance (TCR, ∼2-4% K -1 for state-of-the-art materials). Graphene is ideally suited for optoelectronic applications, with a variety of reported photodetectors ranging from visible to THz frequencies. For the mid-infrared, graphene-based detectors with TCRs ∼4-11% K -1 have been demonstrated. Here we present an uncooled, mid-infrared photodetector, where the pyroelectric response of a LiNbO 3 crystal is transduced with high gain (up to 200) into resistivity modulation for graphene. This is achieved by fabricating a floating metallic structure that concentrates the pyroelectric charge on the top-gate capacitor of the graphene channel, leading to TCRs up to 900% K -1 , and the ability to resolve temperature variations down to 15 μK.

Effect of Contact Pressure on the Resistance Contact Value and Temperature Changes in Copper Busbar Connection

Directory of Open Access Journals (Sweden)

Agus Risdiyanto

2012-12-01

Full Text Available This paper discussed the influence of tightness or contacts pressure on copper busbar joints to determine changes in the value of the initial contact resistance and the maximum temperature at the joint due to high current load. The test sample was copper busbar 3 x 30 mm with configuration of bolted overlapping joint. Increasing contact pressure at the joint was measured to find out its effect on the value of contact resistance. The applied pressure was 6 to 36 MPa. Procedure of contact resistance measurement refer to the ASTM B539 standard using four-wire method. The sample subsequently loaded with the current of 350 A for 60 minutes and the maximum temperature at the joint was measured. The result showed that increasing contact pressure at the busbar joint will reduce the contact resistance and maximum temperature. The increase of contact pressure from 6 to 30 MPa causes decreasing contact resistance from 16 μΩ to 11 μΩ. Further increasing of contact pressure more than 30 MPa did not affect the contact resistance significantly. The lowest temperatur of busbar joint of 54°C was reached at a contact pressure of 36 Mpa.

Effect of temperature on the multi-gap resistive plate chamber operation

International Nuclear Information System (INIS)

Zhao, Y.E.; Wang, X.L.; Liu, H.D.; Chen, H.F.; Li, C.; Wu, J.; Xu, Z.Z.; Shao, M.; Zeng, H.; Zhou, Y.

2005-01-01

In order to obtain a quantitative understanding of the influence of temperature on the multi-gap resistive plate chamber (MRPC) operation, we tested the performance of a 6-gap, 6.1x20 cm 2 active area MRPC with cosmic rays at different temperatures. Results of measurements of noise rate, dark current and detection efficiency are presented

Analytical expressions for transition edge sensor excess noise models

International Nuclear Information System (INIS)

Brandt, Daniel; Fraser, George W.

2010-01-01

Transition edge sensors (TESs) are high-sensitivity thermometers used in cryogenic microcalorimeters which exploit the steep gradient in resistivity with temperature during the superconducting phase transition. Practical TES devices tend to exhibit a white noise of uncertain origin, arising inside the device. We discuss two candidate models for this excess noise, phase slip shot noise (PSSN) and percolation noise. We extend the existing PSSN model to include a magnetic field dependence and derive a basic analytical model for percolation noise. We compare the predicted functional forms of the noise current vs. resistivity curves of both models with experimental data and provide a set of equations for both models to facilitate future experimental efforts to clearly identify the source of excess noise.

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)

Coherence length saturation at the low temperature limit in two-dimensional hole gas

Science.gov (United States)

Shan, Pujia; Fu, Hailong; Wang, Pengjie; Yang, Jixiang; Pfeiffer, L. N.; West, K. W.; Lin, Xi

2018-05-01

The plateau-plateau transition in the integer quantum Hall effect is studied in three Hall bars with different widths. The slopes of the Hall resistance as a function of magnetic field follow the scaling power law as expected in the plateau-plateau transition, and saturate at the low temperature limit. Surprisingly, the saturation temperature is irrelevant with the Hall bar size, which suggests that the saturation of the coherence length is intrinsic.

Temperature Dependence of Interband Transitions in Wurtzite InP Nanowires.

Science.gov (United States)

Zilli, Attilio; De Luca, Marta; Tedeschi, Davide; Fonseka, H Aruni; Miriametro, Antonio; Tan, Hark Hoe; Jagadish, Chennupati; Capizzi, Mario; Polimeni, Antonio

2015-04-28

Semiconductor nanowires (NWs) formed by non-nitride III-V compounds grow preferentially with wurtzite (WZ) lattice. This is contrary to bulk and two-dimensional layers of the same compounds, where only zincblende (ZB) is observed. The absorption spectrum of WZ materials differs largely from their ZB counterparts and shows three transitions, referred to as A, B, and C in order of increasing energy, involving the minimum of the conduction band and different critical points of the valence band. In this work, we determine the temperature dependence (T = 10-310 K) of the energy of transitions A, B, and C in ensembles of WZ InP NWs by photoluminescence (PL) and PL excitation (PLE) spectroscopy. For the whole temperature and energy ranges investigated, the PL and PLE spectra are quantitatively reproduced by a theoretical model taking into account contribution from both exciton and continuum states. WZ InP is found to behave very similarly to wide band gap III-nitrides and II-VI compounds, where the energy of A, B, and C displays the same temperature dependence. This finding unveils a general feature of the thermal properties of WZ materials that holds regardless of the bond polarity and energy gap of the crystal. Furthermore, no differences are observed in the temperature dependence of the fundamental band gap energy in WZ InP NWs and ZB InP (both NWs and bulk). This result points to a negligible role played by the WZ/ZB differences in determining the deformation potentials and the extent of the electron-phonon interaction that is a direct consequence of the similar nearest neighbor arrangement in the two lattices.

Aluminide protective coatings on high–temperature creep resistant cast steel

Directory of Open Access Journals (Sweden)

J. Kubicki

2009-10-01

Full Text Available This paper presents the results of research on aluminide protective coatings manufactured on high–temperature creep resistant cast steel. The main purpose of these coatings is protection against the high temperature corrosion, especially at high carburizing potential atmosphere. Coatings were obtained on cast steel type G–XNiCrSi36–18 with the following methods: pack cementation, paste method, cast method and slurry cementation. The phase composition, thickness and morphology of coatings were determined. Coatings capacity of carbon diffusion inhibition and thermal shocks resistance of coatings were determined with different methods. It was found, that all of the coatings reduce carbon diffusion in different degree and all coatings liable to degradation in consequence cracking and oxidation. Coating life time is mainly dependent on morphology, phase composition and service condition (thermal shocks first of all.

Review of resistance temperature detector time response characteristics. Safety evaluation report

International Nuclear Information System (INIS)

1981-08-01

A Resistance Temperature Detector (RTD) is used extensively for monitoring water temperatures in nuclear reactor plants. The RTD element does not respond instantaneously to changes in water temperature, but rather there is a time delay before the element senses the temperature change, and in nuclear reactors this delay must be factored into the computation of safety setpoints. For this reason it is necessary to have an accurate description of the RTD time response. This report is a review of the current state of the art of describing and measuring this time response

Modeling heat resistance of Bacillus weihenstephanensis and Bacillus licheniformis spores as function of sporulation temperature and pH.

Science.gov (United States)

Baril, Eugénie; Coroller, Louis; Couvert, Olivier; Leguérinel, Ivan; Postollec, Florence; Boulais, Christophe; Carlin, Frédéric; Mafart, Pierre

2012-05-01

Although sporulation environmental factors are known to impact on Bacillus spore heat resistance, they are not integrated into predictive models used to calculate the efficiency of heating processes. This work reports the influence of temperature and pH encountered during sporulation on heat resistance of Bacillus weihenstephanensis KBAB4 and Bacillus licheniformis AD978 spores. A decrease in heat resistance (δ) was observed for spores produced either at low temperature, at high temperature or at acidic pH. Sporulation temperature and pH maximizing the spore heat resistance were identified. Heat sensitivity (z) was not modified whatever the sporulation environmental factors were. A resistance secondary model inspired by the Rosso model was proposed. Sporulation temperatures and pHs minimizing or maximizing the spore heat resistance (T(min(R)), T(opt(R)), T(max(R)), pH(min(R)) and pH(opt(R))) were estimated. The goodness of the model fit was assessed for both studied strains and literature data. The estimation of the sporulation temperature and pH maximizing the spore heat resistance is of great interest to produce spores assessing the spore inactivation in the heating processes applied by the food industry. Copyright © 2011 Elsevier Ltd. All rights reserved.

Aluminide protective coatings on high–temperature creep resistant cast steel

OpenAIRE

J. Kubicki; A. Kochmańska

2009-01-01

This paper presents the results of research on aluminide protective coatings manufactured on high–temperature creep resistant cast steel. The main purpose of these coatings is protection against the high temperature corrosion, especially at high carburizing potential atmosphere. Coatings were obtained on cast steel type G–XNiCrSi36–18 with the following methods: pack cementation, paste method, cast method and slurry cementation. The phase composition, thickness and morphology of coatings were...

Resistance switching in silver - manganite contacts

International Nuclear Information System (INIS)

Gomez-Marlasca, F; Levy, P

2009-01-01

We investigate the electric pulse induced resistance switching in a transition metal oxide-metal contact at room temperature - a non volatile, reversible and multilevel memory device. Using a simple multiterminal configuration, we find that the complementary effect -in which the contact resistance of each pulsed electrode displays variations of opposite sign- is strongly influenced by the history of the pulsing procedure. Loops performed by varying the magnitude and sign of the stimulus at each pulsed electrode allow to disentangle their sole contribution at different stages of the process. Electromigration of oxygen ions and vacancies is discussed as participating at the core of the underlying mechanisms for resistance switching.

Resistance switching in silver - manganite contacts

Energy Technology Data Exchange (ETDEWEB)

Gomez-Marlasca, F [Materia Condensada GIA GAIANN CAC -CNEA, and Instituto de Nanociencia y Nanotecnologia, CNEA, Gral Paz 1499 (1650) San Martin, Pcia. Buenos Aires (Argentina); Levy, P, E-mail: levy@cnea.gov.a

2009-05-01

We investigate the electric pulse induced resistance switching in a transition metal oxide-metal contact at room temperature - a non volatile, reversible and multilevel memory device. Using a simple multiterminal configuration, we find that the complementary effect -in which the contact resistance of each pulsed electrode displays variations of opposite sign- is strongly influenced by the history of the pulsing procedure. Loops performed by varying the magnitude and sign of the stimulus at each pulsed electrode allow to disentangle their sole contribution at different stages of the process. Electromigration of oxygen ions and vacancies is discussed as participating at the core of the underlying mechanisms for resistance switching.

Dependence of defect introduction on temperature and resistivity and some long-term annealing effects

Science.gov (United States)

Brucker, G. J.

1971-01-01

The effort reported here represents data of lithium properties in bulk-silicon samples before and after irradiation for analytical information required to characterize the interactions of lithium with radiation-induced defects in silicon. A model of the damage and recovery mechanisms in irradiated-lithium-containing solar cells is developed based on making measurements of the Hall coefficient and resistivity of samples irradiated by 1-MeV electrons. Experiments on bulk samples included Hall coefficient and resistivity measurements taken as a function of: (1) bombardment temperature, (2) resistivity, (3) fluence, (4) oxygen concentration, and (5) annealing time at temperatures from 300 to 373 K.

Investigate the electrical and thermal properties of the low temperature resistant silver nanowire fabricated by two-beam laser technique

Science.gov (United States)

He, Gui-Cang; Dong, Xian-Zi; Liu, Jie; Lu, Heng; Zhao, Zhen-Sheng

2018-05-01

A two-beam laser fabrication technique is introduced to fabricate the single silver nanowire (AgNW) on polyethylene terephthalate (PET) substrate. The resistivity of the AgNW is (1.31 ± 0.05) × 10-7 Ω·m, which is about 8 times of the bulk silver resistivity (1.65 × 10-8 Ω·m). The AgNW electrical resistance is measured in temperature range of 10-300 K and fitted with the Bloch-Grüneisen formula. The fitting results show that the residue resistance is 153 Ω, the Debye temperature is 210 K and the electron-phonon coupling constant is (5.72 ± 0.24) × 10-8 Ω·m. Due to the surface scattering, the Debye temperature and the electron-phonon coupling constant are lower than those of bulk silver, and the residue resistance is bigger than that of bulk silver. Thermal conductivity of the single AgNW is calculated in the corresponding temperature range, which is the biggest at the temperature approaching the Debye temperature. The AgNW on PET substrate is the low temperature resistance material and is able to be operated stably at such a low temperature of 10 K.

Metal–insulator transition in Ni-doped Na0.75CoO2: Insights from ...

Indian Academy of Sciences (India)

resistivity on lowering the temperature, with the metal-to-insulator transition temperature. (TMIT) increasing with the Ni ... The Ni-doped sample is seen to change over from a metallic to insulating behaviour at ~175 K. The ..... neutron diffraction to look for structural changes, viz., changes in bond lengths and site occupancies ...

Superconductivity and the structural phase transitions in palladium hydride and palladium deuteride

International Nuclear Information System (INIS)

Standley, R.W.

1980-01-01

The results of two experimental studies of the superconducting transition temperature, T/sub c/, of palladium hydride, PdH/sub x/, and palladium deuteride, PdD/sub x/, are presented. In the first study, the superconducting transition temperature of PdH/sub x/(D/sub x/) is studied as a function of H(D) concentration, x, in the temperature range from 0.2 K to 4K. The data join smoothly with those reported previously by Miller and Satterthwaite at higher temperatures, and the composite data are described by the empirical relation T/sub c/ = 150.8 (x-x/sub o/) 2 244 , where x/sub o/ = 0.715 for hydride samples and 0.668 for deuteride samples. The results, when compared with the theoretical predictions of Klein and Papaconstantopoulos, et al., raise questions about the validity of their explanation of the reverse isotope effect, which is based solely on a difference in force constants. In the second study, the effect of the order-disorder structural transition associated with the 50 K anomaly on the superconductivity of PdH/sub x/(D/sub x/) is investigated. Samples were quenched to low temperatures in the disordered state, and their transition temperatures measured. The samples were then annealed just below the anomaly temperature, and the ordering process followed by monitoring the change in sample resistance. The transition temperatures in the ordered state were then measured

Method for preparing high transition temperature Nb.sub.3 Ge superconductors

Science.gov (United States)

Newkirk, Lawrence R.; Valencia, Flavio A.

1977-01-01

Bulk coatings of Nb.sub.3 Ge superconductors having transition temperatures in excess of 20 K are readily formed by a chemical vapor deposition technique involving the coreduction of NbCl.sub.5 and GeCl.sub.4 in the presence of hydrogen. The NbCl.sub.5 vapor may advantageously be formed quantitatively in the temperature range of about 250.degree. to 260.degree. C by the chlorination of Nb metal provided the partial pressure of the product NbCl.sub.5 vapor is maintained at or below about 0.1 atm.

Statistical evaluation of fracture characteristics of RPV steels in the ductile-brittle transition temperature region

International Nuclear Information System (INIS)

Kang, Sung Sik; Chi, Se Hwan; Hong, Jun Hwa

1998-01-01

The statistical analysis method was applied to the evaluation of fracture toughness in the ductile-brittle transition temperature region. Because cleavage fracture in steel is of a statistical nature, fracture toughness data or values show a similar statistical trend. Using the three-parameter Weibull distribution, a fracture toughness vs. temperature curve (K-curve) was directly generated from a set of fracture toughness data at a selected temperature. Charpy V-notch impact energy was also used to obtain the K-curve by a K IC -CVN (Charpy V-notch energy) correlation. Furthermore, this method was applied to evaluate the neutron irradiation embrittlement of reactor pressure vessel(RPV) steel. Most of the fracture toughness data were within the 95 percent confidence limits. The prediction of a transition temperature shift by statistical analysis was compared with that from the experimental data. (author)

Low temperature structural transitions in dipolar hard spheres: The influence on magnetic properties

International Nuclear Information System (INIS)

Ivanov, A.O.; Kantorovich, S.S.; Rovigatti, L.; Tavares, J.M.; Sciortino, F.

2015-01-01

We investigate the structural chain-to-ring transition at low temperature in a gas of dipolar hard spheres (DHS). Due to the weakening of entropic contribution, ring formation becomes noticeable when the effective dipole–dipole magnetic interaction increases. It results in the redistribution of particles from usually observed flexible chains into flexible rings. The concentration (ρ) of DHS plays a crucial part in this transition: at a very low ρ only chains and rings are observed, whereas even a slight increase of the volume fraction leads to the formation of branched or defect structures. As a result, the fraction of DHS aggregated in defect-free rings turns out to be a non-monotonic function of ρ. The average ring size is found to be a slower increasing function of ρ when compared to that of chains. Both theory and computer simulations confirm the dramatic influence of the ring formation on the ρ-dependence of the initial magnetic susceptibility (χ) when the temperature decreases. The rings due to their zero total dipole moment are irresponsive to a weak magnetic field and drive to the strong decrease of the initial magnetic susceptibility. - Highlights: • Found structural chain-to-ring transition at low temperature sheds the light on the no-man's-land of the phase diagram of dipolar hard sphere gas. • Particle concentration plays a crucial part: at high dilution only chains and rings are observed, otherwise different branched structures occur. • The dramatic influence of the ring formation on the concentration dependence of the initial magnetic susceptibility when temperature decreases

Glass Transitions and Low-Frequency Dynamics of Room-Temperature Ionic Liquids

International Nuclear Information System (INIS)

Yamamuro, O.; Inamura, Y.; Hayashi, S.; Hamaguchi, H.

2006-01-01

We have measured the heat capacity and neutrion quasi- and inelastic scattering spectra of some salts of 1-butyl-3-methylimidazolium ion bmim+, which is a typical cation of room-temperature ionic liquids, and its derivatives. The heat capacity measurements revealed that the room-temperature ionic liquids have glass transitions as molecular liquids. The temperature dependence of configurational entropy demonstrated that the room-temperature ionic liquids are 'fragile liquids'. Both heat capacity and inelastic neutron scattering data revealed that the glassy phases exhibit large low-energy excitations usually called 'boson peak'. The quasielastic neutron scattering data showed that so-called 'fast process' appears around Tg as in molecular and polymer glasses. The temperature dependence of the self-diffusion coefficient derived from the neutron scattering data indicated that the orientation of bmim+ ions and/or butyl-groups of bmim+ ions is highly disordered and very flexible in an ionic liquid phase

Corrosion resistant coatings suitable for elevated temperature application

Science.gov (United States)

Chan, Kwai S [San Antonio, TX; Cheruvu, Narayana Sastry [San Antonio, TX; Liang, Wuwei [Austin, TX

2012-07-31

The present invention relates to corrosion resistance coatings suitable for elevated temperature applications, which employ compositions of iron (Fe), chromium (Cr), nickel (Ni) and/or aluminum (Al). The compositions may be configured to regulate the diffusion of metals between a coating and a substrate, which may then influence coating performance, via the formation of an inter-diffusion barrier layer. The inter-diffusion barrier layer may comprise a face-centered cubic phase.

Spatially resolved analysis of resistive switching in transition metal oxide thin films

OpenAIRE

Landrock, Ruth Christine

2011-01-01

The quest for a non-volatile, small and fast computer memory calls for new memory concepts. Resistive Random Access Memory (ReRAM) based on transition metal oxides is an attractive candidate for future computer memories, because it has the potential of a low power consumption combined with fast switching speeds and good scalability. While in general, switching in such systems relies on a local redox reaction, many details are still unknown or under intense discussion. Especially the geometric...

Microstructure and high temperature oxidation resistance of Ti-Ni gradient coating on TA2 titanium alloy fabricated by laser cladding

Science.gov (United States)

Liu, Fencheng; Mao, Yuqing; Lin, Xin; Zhou, Baosheng; Qian, Tao

2016-09-01

To improve the high temperature oxidation resistance of TA2 titanium alloy, a gradient Ni-Ti coating was laser cladded on the surface of the TA2 titanium alloy substrate, and the microstructure and oxidation behavior of the laser cladded coating were investigated experimentally. The gradient coating with a thickness of about 420-490 μm contains two different layers, e.g. a bright layer with coarse equiaxed grain and a dark layer with fine and columnar dendrites, and a transition layer with a thickness of about 10 μm exists between the substrate and the cladded coating. NiTi, NiTi2 and Ni3Ti intermetallic compounds are the main constructive phases of the laser cladded coating. The appearance of these phases enhances the microhardness, and the dense structure of the coating improves its oxidation resistance. The solidification procedure of the gradient coating is analyzed and different kinds of solidification processes occur due to the heat dissipation during the laser cladding process.

Fracture Resistances of Y_2O_3 Particle Dispersion Strengthened 9Cr Steel at Room Temperature and High Temperatures

International Nuclear Information System (INIS)

Yoon, Ji Hyun; Kang, Suk Hoon; Lee, Yongbok; Kim, Sung Soo

2012-01-01

The fracture resistance and tensile properties of Y_2O_3 oxide dispersion strengthened steel containing 9 wt% Cr (9Cr-ODS) were measured at various temperatures up to 700°C. The fracture characteristics were compared with those of commercial E911 ferritic/martensitic steel. The strength of 9Cr-ODS was at least 30% higher than that of E911 steel at the test temperatures below 500°C. The strength difference between the two materials was almost diminished at 700°C. 9Cr-ODS showed cleavage fracture behavior at room temperature and unstable crack growth behaviors at 300°C and 500°C. The J-R fracture resistance of 9Cr-ODS was much lower than that of E911 steel at all temperatures. It was deduced that the coarse Cr_2O_3 particles that were formed during the alloying process provided the crack initiation sites of cleavage fracture in 9Cr-ODS.

Temperature and center-limb variations of transition region velocities

International Nuclear Information System (INIS)

Athay, R.G.; Dere, K.P.

1989-01-01

HRTS data from the Spacelab 2 mission are used to derive the center-limb and temperature variations of the mean velocity and the velocity variance in the solar chromosphere and transition zone. The mean velocity is found to vary much more rapidly from center to limb and with temperature than does the velocity variance. Also, the mean velocity shows a characteristic signature at some magnetic neutral lines in accordance with the findings of Klimchuk (1987) from Solar Maximum Mission (SMM) data. The velocity variance does not show a characteristic signature at the neutral lines but shows an inverse correlation with intensity. The latter is interpreted as reduced velocity variance in strong field regions. The results are discussed in terms of downflow along lines of force in magnetic arcades. 23 refs

Does Brillouin light scattering probe the primary glass transition process at temperatures well above glass transition?

Science.gov (United States)

Voudouris, P; Gomopoulos, N; Le Grand, A; Hadjichristidis, N; Floudas, G; Ediger, M D; Fytas, G

2010-02-21

The primary alpha-relaxation time (tau(alpha)) for molecular and polymeric glass formers probed by dielectric spectroscopy and two light scattering techniques (depolarized light scattering and photon correlation spectroscopy) relates to the decay of the torsional autocorrelation function computed by molecular dynamics simulation. It is well known that Brillouin light scattering spectroscopy (BLS) operating in gigahertz frequencies probes a fast (10-100 ps) relaxation of the longitudinal modulus M*. The characteristic relaxation time, irrespective of the fitting procedure, is faster than the alpha-relaxation which obeys the non-Arrhenius Vogel-Fulcher-Tammann equation. Albeit, this has been noticed, it remains a puzzling finding in glass forming systems. The available knowledge is based only on temperature dependent BLS experiments performed, however, at a single wave vector (frequency). Using a new BLS spectrometer, we studied the phonon dispersion at gigahertz frequencies in molecular [o-terphenyl (OTP)] and polymeric [polyisoprene (PI) and polypropylene (PP)] glass formers. We found that the hypersonic dispersion does relate to the glass transition dynamics but the disparity between the BLS-relaxation times and tau(alpha) is system dependent. In PI and PP, the former is more than one order of magnitude faster than tau(alpha), whereas the two relaxation times become comparable in the case of OTP. The difference between the two relaxation times appears to relate to the "breadth" of the relaxation time distribution function. In OTP the alpha-relaxation process assumes a virtually single exponential decay at high temperatures well above the glass transition temperature, in clear contrast with the case of the amorphous bulk polymers.

The influence of initial temperature on flame acceleration and deflagration-to-detonation transition

International Nuclear Information System (INIS)

Ciccarelli, G.; Boccio, J.L.; Ginsberg, T.

1996-01-01

The influence of initial mixture temperature on deflagration-to-detonation transition (DDT) has been investigated experimentally. The experiments were carried out in a 27-cm-inner diameter, 21.3-meter-long heated detonation tube, which was equipped with periodic orifice plates to promote flame acceleration. Hydrogen-air-steam mixtures were tested at a range of temperatures up to 650K and at an initial pressure of 0.1 MPa. In most cases, the limiting hydrogen mole fraction which resulted in transition to detonation corresponded to the mixture whose detonation cell size, λ, was approximately equal to the inner diameter of the orifice plate, d (e.g., d/λ∼1). The only exception was in dry hydrogen-air mixtures at 650K where the DDT limit was observed to be 11 percent hydrogen, corresponding to a value of d/λ equal to 5.5. For a 10.5 percent hydrogen mixture at 650K, the flame accelerated to a maximum velocity of about 120 m/s and then decelerated to below 2 m/s. This observation indicates that the d/λ = 1 DDT limit criterion provides a necessary condition but not a sufficient one for the onset of DDT in obstacle-laden ducts. In this particular case, the mixture initial condition (i.e., temperature) resulted in the inability of the mixture to sustain flame acceleration to the point where DDT could occur. It was also observed that the distance required for the flame to accelerate to the onset of detonation was a function of both the hydrogen mole fraction and the mixture initial temperature. For example, decreasing the hydrogen mole fraction or increasing the initial mixture temperature resulted in longer transition distances

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

Science.gov (United States)

Davis, Paul M.

2017-05-01

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

Mechanism transition of cell-impedance-controlled lithium transport through Li1-δMn2O4 composite electrode caused by surface-modification and temperature variation

International Nuclear Information System (INIS)

Jung, Kyu-Nam; Pyun, Su-Il

2007-01-01

The mechanism transition of lithium transport through a Li 1-δ Mn 2 O 4 composite electrode caused by the surface-modification and temperature variation was investigated using the galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS) and the potentiostatic current transient technique. From the analyses of the ac-impedance spectra, experimentally measured from unmodified Li 1-δ Mn 2 O 4 and surface-modified Li 1-δ Mn 2 O 4 with MgO composite electrodes, the internal cell resistance of the MgO-modified Li 1-δ Mn 2 O 4 electrode was determined to be much smaller in value than that of the unmodified electrode over the whole potential range. Moreover, from the analysis of the anodic current transients measured on the MgO-modified Li 1-δ Mn 2 O 4 electrode, it was found that the cell-impedance-controlled constraint at the electrode surface is changed to a diffusion-controlled constraint, which is characterised by a large potential step and simultaneously by a small amount of lithium transferred during lithium transport. This strongly suggests that the internal cell resistance plays a significant role in determining the cell-impedance-controlled lithium transport through the MgO-modified Li 1-δ Mn 2 O 4 electrode. Furthermore, from the temperature dependence of the internal cell resistance and diffusion resistance in the unmodified Li 1-δ Mn 2 O 4 composite electrode measured by GITT and EIS, it was concluded that which mechanism of lithium transport will be operative strongly depends on the diffusion resistance as well as on the internal cell resistance

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.

Effect of cooling rate on the transition temperature in Bi-Pb-Sr-Ca-Cu-O system

International Nuclear Information System (INIS)

Wang Yugui; Wang Jinsong; Wang Nanlin; Jiao Xinping; Han Guchang; Chen Zhaojia; Wang Keqin; Wu Xiaoguang

1989-12-01

The resistance and a.c. susceptibility measurement show that cooling rate of the cast-annealing samples in heat treatment process has some effect on the 110K superconducting phase in Bi-Pb-Sr-Ca-Cu-O system. Rapid quenching of the sample in air from 845 deg C causes oxygen deficiency in lattice and brings about a trifling change of unit cell size along c-axis direction. The d.c. magnetization and specific heat anomaly Δc measurements demostrate that fast cooling rate can reduce the transition temperature of high-T c phase and the lower critical field, and weaken the pinning forces for vertex lines. The peak value of specific heat anomaly of the sample with nominal composition of Bi 1.7 Pb 0.3 Sr 2 Ca 2 Cu 4.5 O v is still small in comparison with YBa 2 Cu 3 O 7 . From the magnetization curve the authors estimate that the superconducting volume fraction is about 20%

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.)

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

Science.gov (United States)

Mahato, Somnath; Puigdollers, Joaquim

2018-02-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Zhou, Xianzhong; Matthes, Frank; Bürgler, Daniel E., E-mail: d.buergler@fz-juelich.de; Schneider, Claus M. [Peter Grünberg Institut, Electronic Properties (PGI-6) and Jülich-Aachen Research Alliance, Fundamentals of Future Information Technology (JARA-FIT), Forschungszentrum Jülich, D-52425 Jülich (Germany)

2016-01-15

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2008-09-15

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

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

Science.gov (United States)

He, Ruoying; Weisberg, Robert H.