Hydrodynamic heat flow in very dilute superfluid3He-4He mixtures

The superfluid hydrodynamics of heat flow is examined for very small mass concentrationsc of³He in⁴He in an effort to better understand recent results for the effective heat conductivity _eff, which appear to be in conflict with predictions. The full hydrodynamics contains a thermal boundary layer; within this layer the temperature and concentration gradients differ from those in the bulk fluid. An examination of finite heating effects based on the ansatz _eff c ^–p for smallc shows distinctly different behavior for experimental determinations of _eff whenp<1,p=1, andp>1. Thus, finite heating can be used as a probe to evaluate the exponentp.     

<Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">n</Emphasis> junctions in ZnO implanted with group V ions

n-Type ZnO〈Ga〉 films were implanted with 150-keV N⁺ (As⁺) ions to a dose of 7 × 10¹⁵ cm⁻² and then annealed in atomic oxygen at different temperatures. p-Type conductivity was obtained at annealing temperatures in the range 770–870 K. The parameters of the p-type layers were determined by photoluminescence spectroscopy, secondary ion mass spectrometry, and Hall effect measurements. According to the Hall data, the p-type layers had a resistivity of ∼30 Ω cm, carrier mobility of ∼2 cm²/(V s), and carrier concentration of ∼10¹⁸ cm⁻³. The electroluminescence spectra of the p-n junctions produced by ion implantation showed a band at 440 nm, due to recombination via donor-acceptor pairs.     

Reproducibility and stability of N–Al codoped p-type ZnO thin films

Reproducible and stable p-type ZnO thin films have been prepared by the N–Al codoping method. Secondary ion mass spectroscopy measurements demonstrate that N and Al are incorporated into ZnO. The resistivity, carrier concentration, and Hall mobility are typically of 50–100 Ωcm, 1×10¹⁷–8×10¹⁷ cm⁻³, and 0.1–0.6 cm²/Vs, respectively, for the N–Al codoped p-type ZnO films. Hall measurement, X-ray diffraction, and optical transmission were carried out to investigate the changes of the properties with the storage period. Results show that the p-type characteristics of the N–Al codoped ZnO films are of acceptable reproducibility and stability. In addition, the N–Al codoped p-type ZnO films have good crystallinity and optical quality. The properties are time independent.     

Adsorption of p-chlorophenol from aqueous solutions on bentonite and perlite

The adsorption of p-chlorophenol (p-CP) from aqueous solutions on bentonite and perlite was studied. These materials are available in large quantities in Bulgaria. Model solutions of various concentrations (1–50 mg dm⁻³) were shaken with certain amounts of adsorbent to determine the adsorption capacity of p-CP on bentonite and perlite as well. The influence of several individual variables (initial adsorbate concentration, adsorbent mass) on the rate of uptake of the studied compound on the adsorbent was determined by carrying out experiments at different contact times using the batch adsorber vessel designed according to the standard tank configuration. Rapid adsorption was observed 20–30 min after the beginning for every experiment. After that, the concentration of p-CP in the liquid phase remained constant. The adsorption equilibrium of p-CP on bentonite and perlite was described by the Langmuir and the Freundlich models. A higher adsorption capacity was observed for bentonite (10.63 mg g⁻¹) compared to that for perlite (5.84 mg g⁻¹).     

Fermi Liquid Properties of 3He-4He Mixtures

We calculate microscopically the spectrum of a ³ He impurity atom moving in ⁴ He, determine the Fermi-Liquid interaction between ³ He atoms and then calculate the pressure and concentration dependence of the effective mass and the magnetic susceptibility. The long wavelength limit of the spectrum defines the hydrodynamic effective mass. When k 1.7Å^–1 the motion of the impurity is damped due to the decay into a roton and a low energy impurity mode. The calculations of the Fermi-Liquid interaction are based on correlated basis functions (CBF); the relevant matrix elements are determined by the Fermi hypernetted-chain theory. Our theoretical effective masses agree well with recent measurements, ^1,2 but our analysis suggests a new extrapolation to the zero-concentration limit. With that effective mass we also find a good agreement with the measured ³ Landau parameter F ₀ ^a .     

Physical Mechanisms for Effective Mass Enhancement in 3He

We use structural information from simulations and from variational ground state calculations for calculating the effective mass of ³He at zero temperature. It is found that the relatively large effective mass is due to a combination of several physical effects: Density fluctuations cause an effective mass enhancement due to predominantly hydrodynamic backflow. This effect is, around the Fermi momentum, a smooth function of the single particle wave number; its magnitude is consistent with the effective mass of ⁴He impurities in ³He. Spin-fluctuations, on the other hand, cause a pronounced peak of the effective mass around the Fermi wave number. We also find, consistent with earlier work, an instability of the single particle spectrum at about 2.5 k _F, this is due to the coupling to density fluctuations in the maxon region.     

Effect of reduced pressure on oxidation and thermal stability of polycarbosilane-derived SiC fibers

To clarify the effects of reduced pressure on the thermal stability of polycarbosilane-derived SiC fibers (Nicalon, Hi-Nicalon and Hi-Nicalon S), the heat-treatments were conducted at 1623 and 1723 K under total pressures (p _T) of 1–10⁵ Pa. The oxidation behavior and thermal stability of the fibers were investigated through examinations of mass change, grain growth, specific resistivity, fiber morphology and tensile strength. All the fibers were definitely oxidized in the active-oxidation regime at p _T 10² Pa and T = 1723 K. Nicalon and Hi-Nicalon S were subjected to serious degradation of fiber strength. Hi-Nicalon had a strength of 1.2 GPa even after heat-treatment at p _T = 1 Pa.     

Observation of the radiative transitions between 4d9(2D5/2,3/2)5s2nl and 4d105p(2P

Radiative transitions between the 4d ⁹(² D _5/2,3/2)⁵ s ² nl and 4d ¹⁰5p(² P ₁ ^2,3/2/0 )nl autoionization states of the cadmium atom, representing dielectronic recombination satellites of the laser lines of Cd⁺ ion with λ = 325.0 nm (4d ⁹5s ^{2 2} D _3/2 → 4d ¹⁰5p ² P ₁ ^2/0 ) and λ = 353.6 nm (4d ⁹5s ^{2 2} D _3/2 → 4d ¹⁰5p ² P ₃ ^2/0 ), have been observed for the first time in the regime of electron-ion collisions. The energy dependence of the effective cross sections for the electron-impact excitation of satellite lines has been studied in the interval from 7 to 10 eV. The effective cross sections for the excitation of dielectronic recombination satellites are on the order of ∼10⁻¹⁷ cm², which is comparable with the efficiency of excitation of the main laser lines.     

Electrical properties of photodiodes based on <Emphasis Type="Italic">p</Emphasis>-GaSb/<Emphasis Type="Italic">p</Emphasis>-GaInAsSb/<Emphasis Type="Italic">N</Emphasis>-GaAlAsSb heterojunctions

We have studied the electrical characteristics of photodiodes based on p-GaSb/p-GaInAsSb/N-GaAlAsSb heterojunctions and investigated the mechanisms of current transfer in these heterostructures at various temperatures. A comparison of the theoretical results and experimental data showed that the tunneling charge transfer mechanism dominates at low temperatures (T < 150 K) under both forward and reverse bias conditions. The tunneling current becomes a determining factor at an electric field strength in the p-n junction of no less that 10⁵ V/cm, which is related to a small bandgap width of the materials studied and low effective masses of electrons and holes.     

Highly effective phototransducers based on polycrystalline heterostructures of AIIBVI compounds

Thin-film polycrystalline heterostructures based on A^IIB^VI compounds were prepared, and related highly effective surface-barrier phototransducers of the p-Cu_1.8S/n-A^IIB^VI/n-A^IIB^VI type (with a quantum efficiency of ∼0.9) were obtained. The heterostructures are promising materials for the creation of solar cells and UV photodetectors insensitive to the visible light.     

Kolbenmanometer mit Kraftmesszelle zur Kalibrierung sehr kleiner Drücke

Piston gauges are very precise pressure gauges. In the conventional design, the force exerted by the pressure balances the gravitational force on a piston or cylinder. Due to the mass of piston or cylinder, the smallest measurable pressure is limited to a few kPa (a few 10 mbar). The company DH Instruments, Inc. has developed a new piston gauge in which the pressure‐ induced force on the piston is measured by a mass comparator. Thereby, the measuring range is substantially extended towards smaller pressures. The instrument offers a measuring range from 1 Pa to 15 kPa (0,01 mbar to 150 mbar) for gauge and absolute pressure. The resolution is 1 mPa (10^‐5 mbar) and the uncertainty (5 mPa + 3·10^‐5 p). The piston gauge is calibrated through the determination of mass and piston‐cylinder effective area. An automated pressure controller is included in the instrument. Integrated software allows multi‐point calibrations with another device to be run unattended. The system has been used to perform an automatic test of capacitance diaphragm gauges in a variety of ranges.     

A statistical approach to strength evaluation incorporating porosity effect for porous ceramics

ABSTRACT It has not been clear whether the conventional effective volume proposed for dense brittle materials can be applied satisfactorily to the strength evaluation of porous ceramics. In the present study, a modified effective volume was proposed by incorporating the porosity effect in the statistical evaluation of strength properties of porous ceramics. The modified effective volume was derived as the conventional effective volume multiplied by a function of porosity p. In this work, a power function of (1 + p)^a was adopted as the simplest porosity function. To clarify the applicability of the modified effective volume, bending tests were conducted using smooth and notched specimens of 3 wt% MgO partially stabilised zirconia with six different porosities. The porosity dependence appeared in the relation between the conventional effective volume and the mean strength of various zirconia ceramics with different porosities. The exponent a of the porosity function was determined from experimental data obtained by using identically shaped specimens with distinct porosities, and the modified effective volume was calculated for several types of specimens used in the experiments. It was revealed that the mean strength was almost uniquely correlated with the modified effective volume independent of porosity. The experimental correlation verified the applicability of the modified effective volume to strength evaluation of porous ceramics.     

C 1-stably ℒ p shadowable homoclinic classes

Let p be a hyperbolic saddle of diffeomorphism f on closed manifold M and H(p, f) be the homoclinic class associated with it. In this article, we introduce the notion of C ¹-stably ? _p shadowing and prove that if f is C ¹-stably ? _p shadowable on a homoclinic class H(p, f) then, H(p, f) has a dominated splitting. Moreover, we prove that if f is C ¹-stably Lipschitz ? _p shadowable on H(p, f) and H(p, f)-germ of f is expansive then the homoclinic class is hyperbolic.     

Valence Band Structure of Coupled Diluted Magnetic Quantum Dots

The valence band structure of double InAs/GaAs diluted magnetic vertical quantum dots has been studied in the frame of multiband k⋅p calculation. We find that due to anisotropic effective mass, the ground state can be tuned from the characteristic of heavy- to light-hole state through just changing the parameter of quantum coupling between two QDs. We also show how this crossover manifests itself in the p–d exchange interaction between hole and Mn spins.     

Cadmium telluride thin-film detectors of nuclear radiation

Semiconductor detectors for X-ray and γ radiation are developed based on thin cadmium telluride (p-n-CdTe) films possessing a columnar structure. The detector structures are formed on molybdenum substrates by CdTe sublimation and magnetron sputtering of cadmium. The p-CdTe films have a thickness of d=30–150 μm and a resistivity of ρ≥10³–10⁷ Ω cm. The single crystal grains in the films have an average size of 50–100 μm and are oriented perpendicularly with respect to the Mo substrate. In comparison to the usual single crystal CdTe detectors, the proposed thin-film single crystal CdTe detectors possess a more perfect structure, since the grain boundaries act as effective sinks for defects. The energy resolution of the new generation of CdTe detectors reaches ∼5 keV for the 59.6 keV line of ²⁴¹Am at room temperature.     

On the arithmetic of the endomorphisms ring {{\rm End}(\mathbb{Z}_{p} \times \mathbb{Z}_{p^{2}})}

For a prime number p, Bergman (Israel J Math 18:257–277, 1974) established that End(\mathbbZ_p×\mathbbZ_p²){{\rm End}(\mathbb{Z}_{p}\times \mathbb{Z}_{p^{2}})} is a semilocal ring with p ⁵ elements that cannot be embedded in matrices over any commutative ring. We identify the elements of End(\mathbbZ_p ×\mathbbZ_p²){{\rm End}(\mathbb{Z}_{p} \times \mathbb{Z}_{p^{2}})} with elements in a new set, denoted by E _p , of matrices of size 2 × 2, whose elements in the first row belong to \mathbbZ_p{\mathbb{Z}_{p}} and the elements in the second row belong to \mathbbZ_p²{\mathbb{Z}_{p^{2}}}; also, using the arithmetic in \mathbbZ_p{\mathbb{Z}_{p}} and \mathbbZ_p²{\mathbb{Z}_{p^{2}}}, we introduce the arithmetic in that ring and prove that the ring End(\mathbbZ_p ×\mathbbZ_p²){{\rm End}(\mathbb{Z}_{p} \times \mathbb{Z}_{p^{2}})} is isomorphic to the ring E _p . Finally, we present a Diffie-Hellman key interchange protocol using some polynomial functions over E _p defined by polynomials in \mathbbZ[X]{\mathbb{Z}[X]}.     

Structural classification of Quillaja saponins by electrospray ionization ion trap multiple-stage mass spectrometry in combination with multivariate analysis, proof of concept

MS² and MS³ spectra of thirteen previously identified saponin structures from Quillaja saponaria Molina were obtained by electrospray ionization ion trap multiple-stage mass spectrometry (ESI-ITMSⁿ) in positive ion mode. The spectra were analysed by partial least squares regression-discriminant analysis (PLS-DA) yielding a method that can classify the spectra according to saponin structure. For this method a referencing of the m/z axis was essential to obtain a correlation between peaks in the spectra and common structural elements. The MS² and MS³ spectra could be classified according to the structures of the oligosaccharides at C-3 and C-28 of the corresponding saponins. Terminal residues with the same mass, such as β-d-Apif and β-d-Xylp, could also be distinguished. The PLS-DA method was applied on Quillaja saponins separated from a commercial bark extract by reversed-phase chromatography.The method outlined here is applied on a specific group of Quillaja saponins, but can be used on other types of glycoconjugates. Combination of this technique with chromatography would give a very powerful tool for rapid identification of components in complex mixtures.     

Polarization Dependence of the Specific Heat and the Origin of the Effective Mass in Liquid 3He

The enhanced effective mass of liquid ³ He has been alternatively ascribed to the large spin fluctuations in this system (nearly ferromagnetic model) or to local correlations effects (nearly localized model). We recently measured that polarizing liquid ³ He decreases its specific heat. We present our experiment, and discuss its implications in this theoretical context.     

The Characters of a Sylow p-Subgroup of the Group G2(pn), p≠2, 3

 We compute the irreducible complex characters of a Sylow p-subgroup of the Chevalley group G ₂(q), q=p ⁿ , p≠2, 3 and show that the non linear irreducible characters are induced from linear characters of subgroups of order q ⁵ and q ⁴. Received April 6, 1995     

Enhancedp-wave pairing in polarized3He-4He mixtures

The potential model of Bardeen, Baym, and Pines is generalized to describe polarized³He-⁴He-mixtures. The zero-field strength and range of the potential as a function of³He-density and pressure are determined by transport data and, for the first time, the magnetostriction. It is found that at higher pressures the magnetostriction leads to a³He-density-dependence in the strength of the potential, an effect which only negligibly appears when fitting the transport data. The model predicts ap-wave superfluid transition with a transition temperatureT _c ^p which is highest at the maximum solubility. Including the correction for the polarization-dependence of the maximum solubility, a large increase inT _c ^p with polarization is found. The size of the enhancement depends on the zero fieldT _c ^p which in turn depends on which set of normal state data we fit.