On Larkin-Imry-Ma State of 3He-A in Aerogel

Superfluid ³He-A shares the properties of spin nematic and chiral orbital ferromagnet. Its order parameter is characterized by two vectors and . This doubly anisotropic superfluid, when it is confined in aerogel, represents the most interesting example of a system with continuous symmetry in the presence of random anisotropy disorder. We discuss the Larkin-Imry-Ma state, which is characterized by the short-range orientational order of the vector , while the long-range orientational order is destroyed by the collective action of the randomly oriented aerogel strings. On the other hand, sufficiently large regular anisotropy produced either by the deformation of the aerogel or by applied superflow suppresses the Larkin-Imry-Ma effect leading to the uniform orientation of   . The interplay of regular and random anisotropy allows us to study many different effects.      

Polarization of Dielectrics by Acceleration

We argue that acceleration induces electric polarization in usual dielectrics. Both accelerations in superfluid ( and ) participate in the medium polarization. Excitations contribution to the polarization is calculated at low temperatures. Estimates of the effect show order of magnitude agreement with recent experimental results on electric effect of superflow.     

Noise and Sensitivity of Aluminum Kinetic Inductance Detectors for Sub-mm Astronomy

Kinetic inductance detectors are based upon high Q superconducting resonators. We have measured the electrical Noise Equivalent Power (NEP) of 100 nm thick 1/4λ coplanar waveguide Aluminum resonators at 100 mK using phase readout and radius readout. We find that the phase NEP is independent of the Q factor of the resonator, limited by excess noise in the KID and given by NEP at 100 Hz. It increases with roughly f ^−0.5 at lower frequencies. The amplitude NEP is strongly Q factor dependent, limited by the setup noise, nearly frequency independent and as low as NEP for a high Q resonator (Q=454.000). For lower Q resonators the amplitude NEP increases to values equal to or even larger than the phase readout.      

Finite-size Effects on the Thermal Resistivity of 4He Near the Superfluid Transition

We present measurements of the thermal resistivity () near the superfluid transition temperature of ⁴He at saturated vapor pressure and confined in glass capillary arrays with rectangular capillary cross-sections of spacing L = 1 μm, width m, and length mm. We expect the finite-size effect in this rectangular geometry to provide a good approximation to that in the ideal parallel-plate geometry. The data coincide within our resolution with previous measurements for cylindrical capillaries of 1 m radius, indicating that the finite-size scaling-functions for these two geometries are indistinguishable. This stands in contrast to the scaling functions for static properties which, near the transition temperature, depend on the dimensionality of the confinement. The results are consistent with recent Monte Carlo and spin-dynamics simulations, and with renormalization-group calculations for capillaries with square cross section and .     

Turbidity Data of Weightless SF<Subscript>6</Subscript> Near its Liquid–Gas Critical Point

Light transmission measurements performed in SF₆ close to its liquid–gas critical point are used to obtain turbidity data in the reduced temperature range (T is temperature, T _c is the critical temperature). Automatic experiments (ALICE 2 facility) were made at a near critical density, i.e., , in the one-phase homogeneous region, under the microgravity environment of the Mir Space Station ( is the average density, ρ _c is the critical density). The turbidity data analysis verifies the theoretical crossover formulations for the isothermal compressibility and the correlation length ξ. These latter formulations are also used to analyze very near T _c thermal diffusivity data obtained under microgravity conditions by Wilkinson et al. (Phys. Rev. E 57 436, 1998).     

Sound Velocity Measurements in the Low and the High Field Phases of the Nuclear-Ordered bcc Solid 3He in Magnetic Fields

We have measured the temperature and magnetic-field dependences of the sound velocity for one longitudinal and two transverse waves in the low field phase (LFP) and the high field phase (HFP) of nuclear spin ordered bcc solid ³He crystals with a single magnetic domain along the melting curve. From sound velocity measurements for various crystal orientations as a function of the sound propagation direction, we determined the elastic stiffness constants, c _ij (T,B). In the LFP with tetragonal symmetry for the nuclear spin structure, we extracted six nuclear spin elastic stiffness constants Δc _ij ^ℓ (T,0.06 T) from the temperature dependence of the sound velocity at 0.06 T and Δc _ij ^ℓ (0.5 mK,B) from the magnetic-field dependence of sound velocity at 0.5 mK. In the HFP with cubic symmetry for the nuclear spin structure, we extracted three Δc _ij ^h (T,0.50 T) at 0.50 T and Δc _ij ^h (0.5 mK,B) at 0.5 mK. At the first-order magnetic phase transition from the LFP to the HFP at the lower critical field B _c1, large jumps in sound velocities were observed for various crystal directions and we extracted three . Using the thermodynamic relation between Δc _ij and the change in the internal energy for the exchange interaction in this system, ΔU _ex(T,B), Δc _ij are related to the generalized second-order Grüneisen constants Γ _ij ^X ≡∂ ²ln X/∂ ε _i ∂ ε _j as Δc _ij (T,B)=Γ _ij ^X ΔU _ex(T,B), where X represents some physical quantity which depends on the molar volume and ε _j is the j-th component of a strain tensor. In the LFP, the Δc _ij ^ℓ (T,0.06 T) were proportional to T ⁴, and Δc _ij ^ℓ (0.5 mK,B) were proportional to B ². We extracted for the spin wave velocity in the LFP, s ^ℓ , from Δc _ij ^ℓ (T,0.06 T) and for the inverse susceptibility, 1/χ ^ℓ from Δc _ij ^ℓ (0.5 mK,B). In the HFP, Δc _ij ^h (T,0.50 T) were proportional to T ⁴ and Δc _ij ^h (0.5 mK,ΔB) were proportional to ΔB(≡B−B _c1). We obtained for the spin wave velocity in the HFP, s ^h , from Δc _ij ^h (T,0.50 T) and for B _c1 from Δc _ij ^h (0.5 mK,ΔB). The values obtained for and were compared with the Multiple Spin Exchange model (MSE) with three parameters by using analytic expressions for s ^ℓ and χ ^ℓ . The three-parameter MSE does not agree with the observed Δc _ij in the LFP.      

Diffusivity and solubility of oxygen in solid palladium

The solid solubility c _O of oxygen in palladium in equilibrium with gaseous oxygen has been determined from absorption-desorption experiments for temperatures T of 1123 and 1173 K and oxygen partial pressures between 2.7 × 10³ and 4.0 × 10⁴ Pa. The relationship between c _O, and T is given by , where R = 8.314 JK⁻¹ mol⁻¹ is the universal gas constant, ΔH _s = −13.55 kJ/mol denotes the heat of solution of oxygen in palladium and the constant a amounts to or . The diffusion coefficient D _O of oxygen in solid palladium has been determined by incomplete isothermal internal oxidation of Pd–Fe alloys using the data on the oxygen solubility in palladium. The temperature dependence of D _O obeys the Arrhenius equation D _O = D ⁰ exp(−E _d/RT) with pre-exponential factor D ⁰ = 2.33 × 10⁻⁷ m²/s and activation energy of diffusion of oxygen in palladium, E _d = 102.76 kJ/mol     

Three oxidation states and atomic-scale <Emphasis Type="Italic">p–n</Emphasis> junctions in manganese perovskite oxide from hydrothermal systems

Perovskite oxides have provided magical structural models for superconducting and colossal magnetoresistance, and the search for nano-scale and/or atomic-scale devices with particular property by specific preparations in the same systems has been extensively conducted. We present here the three oxidation states of manganese (Mn³⁺, Mn⁴⁺, Mn⁵⁺) in the perovskite oxide, La_0.66Ca_0.29K_0.05MnO₃, which most interestingly shows the rectifying effect as atomic-scale p–n junctions (namely FY-Junctions) of single crystals and films. The family of cubic perovskite oxides were synthesised by the so-called hydrothermal disproportionation reaction of MnO₂ under the condition of strong alkali media. The new concept of the atomic-scale p–n junctions, based on the ideal rectification characteristic of the p–n junctions in the single crystal, basically originates from the structural linkages of [Mn³⁺–O–Mn⁴⁺–O–Mn⁵⁺], where Mn³⁺ and Mn⁵⁺ in octahedral symmetry serve as a donor and an acceptor, respectively, corresponding to the localized Mn⁴⁺ .     

On perfect nonlinear functions (Π)

Perfect nonlinear functions are of importance in cryptography. By using Galois ring, relative trace and investigating the character values of corresponding relative difference sets, we present a construction of perfect nonlinear functions from to , where m′ is a divisor of 2m, and a construction of perfect nonlinear functions from to where 2m is possibly larger than the largest divisor of n. Meanwhile we prove that there exists a perfect nonlinear function from to if and only if p = 2, and there doesn’t exist a perfect nonlinear function from to if m > n and l(l is odd) is self-conjugate modulo 2 ^k (k ≥ 1).      

Nodes of the Gap Function and Anomalies in Thermodynamic Properties of the B-Phase of Superfluid 3He

Departures of thermodynamic properties of the B-phase of three-dimensional superfluid ³He from the predictions of BCS theory are analyzed. Attention is focused on deviations of the ratios and from their BCS values, where is the pairing gap at zero temperature, T_c is the critical temperature, and C_s and C_n are the superfluid and normal specific heats. We attribute these deviations to the momentum dependence of the gap function , which becomes well pronounced when this function has a pair of nodes lying on either side of the Fermi surface. We demonstrate that such a situation arises if the P-wave pairing interaction, evaluated at the Fermi surface, has a sign opposite to that anticipated in BCS theory. Taking account of the momentum structure of the gap function, we derive a closed relation between the two ratios that contains no adjustable parameters and agrees with the experimental data. Some important features of the effective pairing interaction are inferred from the analysis.      

Construction of binary minimal product parity-check matrices

A parity-check matrix H of a given code is called minimal if it has minimum number of nonzero entries among all parity-check matrices representing . Let and be two binary linear block codes with minimal parity-check matrices H ₁ and H ₂, respectively. It is shown that, using H ₁ and H ₂, one can efficiently generate a minimal parity-check matrix for the product code .     

The Two-dimensional Vibrating Reed: A Study of Anisotropic Pinning in High-temperature Superconductors

The pinning of flux lines on point-like defects in superconductors depends on both the magnitude and the symmetry of the order parameter. We study the anisotropy of pinning in untwinned single crystals of YBa₂Cu₃O and crystals of Bi₂Sr₂CaCu₂O employing a modified vibrating reed technique with two degrees of freedom. The pinning potential is calculated for an anisotropic d-wave superconductor in the approximation of a single pancake vortex interacting with a single point defect. The response of the reed to pinning potentials with two- and fourfold symmetry is modeled. The appearance of a twofold symmetry is demonstrated for YBa₂ Cu₃O crystals. The effect of the fourfold symmetric component is masked by flux creep effects in our experiments. Dedicated to Frank Pobell, former editor of JLTP.     

Experimental Observation of 2 – Anion and its para → ortho Conversion in Solid para hydrogen Using High–Resolution ESR Spectroscopy

We present experimental observations and study of in solid parahydrogen. Since the parahydrogen molecule does not produce local magnetic fields, high–resolution ESR spectra of trapped radicals can be observed in the solid parahydrogen matrices. Using this high–resolution ESR spectroscopy, new quartet ESR signals were observed in –rays irradiated solid parahydrogen and assigned as In addition, para– was observed to convert into ortho– on the storage at 4.2 K. On the other hand, ortho–H ₂ molecule converts into para– at cryogenic temperatures. The difference in the conversion between the H ₂ molecule and the anion is explained by the parity conservation law of wavefunctions on exchanging the protons in homonuclear diatomic molecules such as the anion and H ₂ molecule.     

Stability and direct conversion of mineral barite crystals in carbonated hydrothermal fluids

The pseudomorphic replacement of mineral barite (BaSO₄) crystals into barium carbonate was investigated in the present work by using carbonated alkaline hydrothermal fluids. Hydrothermal treatments were carried out over the temperature range from 150 up to 250 °C for intervals between 1 and 192 h, with different filling ratios (40–70%), and molar ratios of 1, 5, and 10. The reaction products were characterized by XRD and SEM techniques. The chemical reactivity of mineral barite crystals was markedly limited at temperatures below 200 °C, and only a tiny BaCO₃ layer on the surface of the original BaSO₄ crystal was formed on the crystal treated for 192 h. The rate of the pseudomorphic conversion of BaSO₄ into BaCO₃, was accelerated by increasing the reaction temperature and the molar ratio . Powder X-ray diffraction results showed that under hydrothermal conditions the replacement of ions by ions, in barite crystals was completed at 250 °C with a molar ratio = 10 for an interval of 192 h, resulting in the Witherite structure. The morphology of the completely converted BaCO₃ at 250 °C in a Na₂CO₃ solution for 192 h, showed that the conversion proceed without severe changes of the original shape and dimension of the original crystal, similar to that observed in mineral pseudomorphic replacement process.     

Excess Volumes, Densities, Speeds of Sound, and Viscosities for the Binary Systems of 1-Octanol with Hexadecane and Squalane at (298.15, 303.15 and 308.15) K

Excess molar volumes, , excess molar isentropic compressibilities, , and deviations of the speeds of sound, u ^D, from their ideal values u ^id in an ideal mixture for binary mixtures of 1-octanol, C₈H₁₇OH, with hexadecane, C₁₆H₃₄, and squalane (2,6,10,15,19,23-hexamethyltetracosane), C₃₀H₆₂, at T = (298.15, 303.15, and 308.15) K and at atmospheric pressure were derived from experimental density, ρ, and speed-of-sound data, u. Viscosity measurements were also carried out for the same mixtures. The Prigogine-Flory-Patterson (PFP) theory has been applied to analyze of these systems. Furthermore, the apparent molar volumes, and apparent molar compressibility, of the components at infinite dilution have been calculated.     

Reference Viscosities of H<Subscript>2</Subscript>, CH<Subscript>4</Subscript>, Ar,and Xe at Low Densities

The zero-density viscosity of hydrogen, methane, and argon was determined in the temperature range from 200 to 400 K, with standard uncertainties of 0.084% for hydrogen and argon and 0.096% for methane. These uncertainties are dominated by the uncertainty of helium’s viscosity , which we estimate to be 0.080% from the difference between ab initio and measured values at 298.15 K. For xenon, measurements ranged between 200 and 300 K and the zero-density viscosity was determined with an uncertainty of 0.11%. The data imply that xenon’s viscosity virial coefficient is positive over this temperature range, in contrast with the predictions of corresponding-states models. Furthermore, the xenon data are inconsistent with Curtiss’ prediction that bound pairs cause an anomalous viscosity decrease at low reduced temperatures. At 298.15 K. the ratios , and were determined with a relative uncertainty of less than 0.024% by measuring the flow rate of these gases through a quartz capillary while simultaneously measuring the pressures at the ends of the capillary. Between 200 and 400 K, a two-capillary viscometer was used to determine with an uncertainty of 0.024% for H₂ and Ar, 0.053% for CH₄, and 0.077% for Xe. From was computed using the values of calculated ab initio. Finally, the thermal conductivity of Xe and Ar was computed from and values of the Prandtl number that were computed from interatomic potentials. These results may help to improve correlations for the transport properties of these gases and assist efforts to develop ab initio two- and three-body intermolecular potentials for these gases. Reference viscosities for seven gases at 100 kPa are provided for gas metering applications.     

Activation kinetics of the As acceptor in HgCdTe

The amphoteric model of As in HgCdTe is the basis of an investigation into how the transfer is achieved under Hg saturation and so obtain a method for calculating optimum annealing times for the transfer. It is concluded that Schaake’s assumption that the transfer, or activation, process is diffusion limited, rather than reaction-rate limited, is a better fit to experimental data. The identification of the Te self-diffusivity in HgCdTe as due to Te _i defects is considered to be incorrect. As a result, Schaake’s activation model can only underestimate the optimum anneal times for activation if the experimentally observed Te self-diffusivity is used. An equation based on experimental activation data is given that permits an estimate of the optimum anneal time to be obtained in HgCdTe layers.     

Partial Molar Volumes and Viscosity B-Coefficients of Nicotinamide in Aqueous Resorcinol Solutions at <Emphasis Type="Italic">T</Emphasis> = (298.15, 308.15, and 318.15) K

Partial molar volumes and viscosity B-coefficients for nicotinamide in (0.00, 0.05, 0.10, 0.15, and 0.20) mol·dm⁻³ aqueous resorcinol solutions have been determined from solution density and viscosity measurements at (298.15, 308.15, and 318.15) K as a function of the concentration of nicotinamide (NA). Here the relation , has been used to describe the temperature dependence of the partial molar volume . These results and the results obtained in pure water were used to calculate the standard volumes of transfer and viscosity B-coefficients of transfer of nicotinamide from water to aqueous resorcinol solutions to study various interactions in the ternary solutions. The partial molar volume and experimental slopes obtained from the Masson equation have been interpreted in terms of solute–solvent and solute–solute interactions, respectively. The viscosity data have been analyzed using the Jones–Dole equation, and the derived parameters B and A have also been interpreted in terms of solute–solvent and solute–solute interactions, respectively, in the ternary solutions.The structure making or breaking ability of nicotinamide has been discussed in terms of the sign of . The activation parameters of viscous flow for the ternary solutions studied were also calculated and explained by the application of transition state theory.     

Interface structure and strain development during compression tests of Al2O3/Nb/Al2O3 sandwiches

The interface structure of an Al₂O₃/Nb/Al₂O₃ sandwich produced by solid-state diffusion bonding was investigated in detail by various transmission electron microscopy (TEM) methods. The joint possessed at one interface a , , and on the other interface a and orientation relationship. At both interfaces, misfit dislocations formed to compensate the lattice mismatch as found by high-resolution transmission electron microscopy (HRTEM). Electron energy-loss near edge structure (ELNES) studies revealed that the interface is terminating with an Al layer resulting in Al–Nb bonds. Identical sandwiches were investigated on the meso- and macroscopic scale by performing compression tests and simultaneously monitoring the strain development at (001)_Nb and crystal faces. The full-field optical strain measurements (FFOM) revealed that the strain is localized at the interfaces when observed at the (001)_Nb face while it is along the maximum shear directions of 36–54° inclined to the interface when observed at the face. The strain localization along a specific maximum shear direction results in the cleavage of Al₂O₃, always initiating from the interface possessing the and orientation relationship.     

Effects of oxygen partial pressure control on the microstructure and PTCR properties of Ho doped BaTiO<Subscript>3</Subscript>

Effects of oxygen partial pressure ( ) control on the electrical properties and microstructural development of (Ba_1-xHo_x)_0.997TiO₃ were studied. An oxidation condition ( ∼ 1.0 atm) was maintained during the heating process, and then the specimen was sintered in a reducing atmosphere ( < 10⁻⁹ atm) at 1350 °C, followed by the annealing process at 1000 °C and = 1 atm. The switching temperature (T_S) from the oxidation atmosphere to the reducing condition was changed from 1100 to 1350 °C. A significant decrease in the room-temperature resisitivity (ρ₂₅) was observed as T_S was increased. The temperature coefficient of resistance (TCR) was independent of the change in T_S, and closed pores decreased with increasing T_S.