Congruent Temperature Research Articles

Anomalous enhancement of resurgent Na+ currents at high temperatures by SCN9A mutations underlies the episodic heat-enhanced pain in inherited erythromelalgia

Inherited erythromelalgia (IEM), caused by mutations in Nav1.7 channel is characterized by episodic neuropathic pain triggered especially by warm temperature. However, the mechanism underlying the temperature–dependent episodic attacks of IEM remains elusive. We investigated the electrophysiological effect of temperature changes on Nav1.7 channels with three different mutations, p.I136V, p. I848T, and p.V1316A, both in vitro and in vivo. In vitro biophysical studies of the mutant channels show consistent temperature-dependent enhancement of the relative resurgent currents if normalized to the transient currents, as well as temperature-dependent changes in the time to peak and the kinetics of decay of the resurgent currents, but no congruent temperature–dependent changes in steady–state parameters such as shift of activation/inactivation curves and changes of the absolute size of the window or resurgent currents. In vivo nerve excitability tests (NET) in IEM patients reveal the essentially normal indices of NET at a single stimulus. However, there are evident abnormalities if assessed with preconditioning pulses, such as the decrease of threshold elevation in hyperpolarizing threshold electrotonus (50–100 ms), the increase of inward rectification in current–voltage curve, and the increase of refractoriness at the interpulse interval of 2–6 ms in recovery cycle, probably also implicating derangements in temperature dependence of inactivation and of recovery from inactivation in the mutant channels. The pathogenesis of heat–enhanced pain in IEM could be attributed to deranged temperature dependence of Nav1.7 channels responsible for the genesis of resurgent currents.

Importance of point defect reactions for the atomic-scale roughness of III–V nanowire sidewalls

The surface morphology of III–V semiconductor nanowires (NWs) protected by an arsenic cap and subsequently evaporated in ultrahigh vacuum is investigated with scanning tunneling microscopy and scanning transmission electron microscopy. We show that the changes of the surface morphology as a function of the NW composition and the nature of the seed particles are intimately related to the formation and reaction of surface point defects. Langmuir evaporation close to the congruent evaporation temperature causes the formation of vacancies which nucleate and form vacancy islands on {110} sidewalls of self-catalyzed InAs NWs. However, for annealing temperatures much smaller than the congruent temperature, a new phenomenon occurs: group III vacancies form and are filled by excess As atoms, leading to surface AsGa antisites. The resulting Ga adatoms nucleate with excess As atoms at the NW edges, producing monoatomic-step islands on the {110} sidewalls of GaAs NWs. Finally, when gold atoms diffuse from the seed particle onto the {110} sidewalls during evaporation of the protective As cap, Langmuir evaporation does not take place, leaving the sidewalls of InAsSb NWs atomically flat.

Comparative Characteristics of GaAs and InAs Langmuir Evaporation - Monte Carlo Simulation

The process of GaAs and InAs substrates high-temperature annealing under the Langmuir evaporation conditions is studied by Monte Carlo simulation. The temperature range of gallium arsenide and indium arsenide congruent and incongruent evaporation are determined. It was demonstrated that the congruent evaporation temperature Tc is sensitive to the vicinal surface terrace width. The decrease of the terrace width results in a decrease in the congruent evaporation temperature. The Ga and In diffusion lengths along the (111)A and (111)B surfaces at congruent temperatures are estimated. The surface morphology transformation kinetic during high-temperature annealing is analyzed.

Feeling cold is contagious

Seeing someone plunge into an ice-cold bath induces feelings of cold. However, it was recently demonstrated that viewing another's skin temperature change also induces a small congruent temperature change in the observer. This synchronization suggests top-down influences on peripheral temperature regulation mechanisms and lends supports to somatic-simulation theories of inter-subjectivity.

Coesite (SiO 2) as an extreme case of superheated crystal: An X-ray diffraction study up to 1776 K

The dense SiO 2 polymorph coesite has been investigated by X-ray powder diffraction from room temperature up to 1776 K. No phase transition has been detected in this temperature interval. Thermal expansion shows little anisotropy and remains very small since the volume increases by only 1.6% between 300 and 1776 K. As indicated by theoretical simulations, the small dilation results from limited rotations of SiO 4 tetrahedra and also from slight expansion of Si–O bonds. In addition, the results demonstrate that coesite can be kept 900° above its metastable congruent temperature of fusion which is about 875 K. Comparisons with measurements made under the same conditions for quartz and cristobalite indicate that, for SiO 2 polymorphs with 4-fold coordinated Si, crystal structure exerts a smaller influence than melt viscosity on the extent of superheating.

New developments in two-feldspar thermometry

The thermodynamic model of the two-feldspar thermometer has been revised. From recent enthalpy and volume measurements in the (Na,Ca)- and (K,Ca)-feldspar binaries, new interaction parameters have been derived and previous ones have been updated. Entropy parameters have been fitted to the phase equilibrium data of Seck (1971) and Elkins and Grove (1990). The two data sets could be suitably combined into one. Ideal Ab, Or, and An activities have been expressed in terms of both the molecular mixing and Al-avoidance models. Two-feldspar pairs from high-grade metamorphic rocks that cooled slowly under dry conditions suffer from a distinct type of retrograde resetting. Whereas the original An content in both the plagioclase and the alkali feldspar is preserved because the intercrystalline Ca + Al ) (Na,K) + Si diffusion is sluggish, Na and K may be freely exchanged between phases. Mathematical reversal of the Na-K. exchange at constant An yields the temperature at which the two feldspars originally coexisted. The shifts in Ab and Or contents obtained from the reversal reflect the relative plagioclase/alkali feldspar proportions observed in thin sections. Good agreement between calculated and measured ratios was found for feldspar pairs from Sri Lankan granulites. This observation represents a successful test of the reliability of the calculated Ab-Or shifts. In contrast to dry metamorphic rocks, similar application of chemical constraints is not indicated in the case of volcanic rocks. Then the two-feldspar thermometer delivers three, usually incongruent temperatures: T(Ab), T(Or), and T(An). From the abundance of temperatures, Fuhrman and Lindsley (1988) suggested adjusting compositions within assumed chemical uncertainties (e.g., +/-2 mol%) so that congruent temperatures could be obtained. However, the result is not unique. Depending on minute variations in the starting compositions, the temperatures may vary by several tens of degrees. In addition, temperatures vary to a similar extent depending on the type of search algorithm. Therefore, we advise users to completely abandon this practice. Instead, a statistical procedure is suggested: Two-feldspar compositions are randomly generated according to Gaussian distributions with their means at the observed compositions and standard errors chosen according to the quality of the chemical analysis. This procedure returns normally distributed temperatures [T(Ab), T(Or), T(An)] together with means and standard deviations. From the overlap of the three Gaussian curves the question of equilibrium or non-equilibrium crystallization of feldspar pairs may be addressed.

The Cu-Ni-Pd (copper-nickel-palladium) system

The Cu-Ni system [1991Nas] (Fig. 1) is a simple isomorphous system with a possible phase separation below ∼300 °C. The Cu-Pd system [Massalski2] (Fig. 2) is a simple isomorphous system at high temperatures. The fcc (Cu, Pd) phase, however, undergoes transformation below 600 °C to give two phases and with congruent transformation temperatures of 598 and 508 °C, respectively. Between the two phases and two long period superlattice phases with one dimensional (1D) and two dimensional (2D) antiphase domain structures exist. A eutectoid type reaction ↔ (2D) + has been suggested to exist at ∼400 °C. The Ni-Pd system [1991Nas] (Fig. 3) is an isomorphous system with a solidus/liquidus minimum of 1237 °C at 45.4 at.% Pd. At 700 °C the experimental results suggest the possible existence of short range order/clustering in the fcc (Ni, Pd) phase.

Effects of rapid thermal annealing on the optical properties of 1.3 μm InGaAlAs multiquantum wells grown by digital-alloy molecular-beam epitaxy

We investigated the effect of rapid thermal annealing (RTA) on the optical properties of digital-alloy 1.3 μm InGaAlAs multiquantum-well structure grown by molecular-beam epitaxy at RTA temperature (TRTA) in the range of 400 °C–675 °C. Photoluminescence (PL) peak intensity taken at room temperature rose drastically at TRTA above 625 °C, which increased up to ∼500 times larger at TRTA of 650 °C and RTA time of 60 s than that of as-grown sample without any significant shift of PL peak wavelength. This extraordinary increase of PL peak intensity at TRTA⩾625 °C is attributed to the curing of nonradiative centers mainly in InAlAs grown at a lower temperature than its congruent temperature, and partially at the heterointerfaces between InGaAs/InAlAs short-period superlattices.

Atomic hydrogen cleaning, nitriding and annealing InSb (100)

Hydrogen cleaning and nitridation of InSb (100) using radio frequency (r.f.)-generated radicals was investigated using reflection high energy electron diffraction (RHEED), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Hydrogen cleaning was found to remove antimony oxide and carbon contamination even at room temperature (RT) by creating volatile species but did not remove the indium oxide. Hydrogen cleaning at 275°C gave a clean, flat surface which showed a (4×2) In-rich reconstruction, while hydrogen cleaning at temperatures above the maximum congruent temperature of ∼325°C resulted in a surface with a step-terrace structure accompanied by large islands and deep pits. By annealing to 375°C a surface cleaned at 275°C, a surface with a step-terrace structure but no pit or island defects could be obtained. Similar behaviour was observed for nitrided rather than oxidised surfaces.

Phase-diagram study for the Al2O3-CaF2-SiO2 system

Phase relations for the Al2O3-CaF2-SiO2 system were investigated from 1673 to 1723 K. The hotfilament technique was applied to observe a two-liquid region and liquidus for the ternary system. The liquidus saturated with SiO2 was investigated at 1673 K by using the hot-filament technique and the chemical equilibrium technique. In this system, the addition of Al2O3 to the CaF2-SiO2 system reduces the congruent temperature. A small substitution of Al2O3 for CaF2 increases the solubility of SiO2, namely, if the region of liquid phase could be enlarged. These results suggest that Al2O3 would be an effective substitute of CaF2 in slag for steelmaking.

The order-disorder transformation in Ni 3Al and Ni 3AlFe alloys—I. Determination of the transition temperatures and their relation to ductility

A combination of dilatometry and high-temperature diffractometry was used to determine the order-disorder transition temperatures for a series of nickel-aluminum-iron alloys. Extrapolation to zero iron content gave an estimate of the transition temperature for a Ni 77.5Al 22.5 binary alloy: this was 1375°C, just 10°C below the solidus. Further dilatometric runs with several binary Ni-Al alloys, exploiting a new technique of dilatometric curve-fitting, permitted the transition temperature to be plotted as a function of Ni Al ratio. At ~23 at.% Al, the transition temperature crossed over the liquidus temperature; alloys containing less aluminum than this freeze in the disordered form and order on further cooling (sequential ordering); alloys containing more than ~23 at.% Al freeze directly into the ordered form and, unlike the former category, such directly ordered alloys contain no antiphase domains, or very few. Empirical evidence concerning ductility of binary and ternary alloys containing γ′ (Ni 3Al) is reviewed, and some new experiments reported. The tentative conclusion is reached that sequential ordering favors polycrystalline ductility because of the role of antiphase domains in braking dislocations. In this way, the ductile-brittle transition between 24 and 25 at.% Al can be interpreted. The congruent (virtual ordering) temperature of stoichiometric Ni 3Al is estimated to be 1450 ± 10°C, and from this value, the antiphase domain energy on a (111) plane is calculated to be 112 mJ/m 2.

Optimal surface and growth front of III–V semiconductors in molecular beam epitaxy: A study of kinetic processes via reflection high energy electron diffraction specular beam intensity measurements on GaAs(100)

A systematic examination of the influence of each growth parameter on the surface kinetic processes in GaAs molecular beam epitaxy growth has been undertaken employing reflection-high-energy-electron-diffraction intensity dynamics measurement on GaAs(100) As-(2×4) surfaces. It is found that for growth temperature near congruent temperature the recovered growth front of grown GaAs is characterized by the lowest, though metastable, surface step distribution and thus appears optimal for formation of interfaces. The competition between the various growth condition dependent surface kinetic processes and their consequences for the surface and interface morphology are revealed by this systematic study.

Existence of metastable step density distributions on GaAs(100) surfaces and their consequence for molecular beam epitaxial growth

Variations in the static and steady-state specular beam intensity (I0 and IS, respectively) in reflection high-energy electron diffraction from GaAs(100) have been examined as a function of substrate temperature (TS) and As4 pressure in molecular beam epitaxy. At a fixed As4 pressure, regimes of reversible and irreversible behavior of I0 and IS as a function of TS are identified. The irreversible regime of I0 is shown to occur at temperatures close to the congruent temperature. At each temperature in this regime, the existence of smoothest, but metastable, surface step density configuration is demonstrated. The maximum in IS is found to occur in this regime. The surface kinetic processes responsible for this behavior are discussed.

A Technique for Reactant Introduction in Measurement of Rapid Reaction Rates

A simple technique is reported for rapid introduction of solid or liquid reactants into solution for continuous observation of ensuing reactions during ≥1 sec. The accuracy of the method is attested by congruent temperature dependence of the derived rate constants together with those from an independent procedure. The new technique allows measurement of solvolysis reactions considerably faster than those heretofore accessible.