Stress-induced crossover phenomena in nickel above its Curie point

The temperature dependence of the anisotropic critical scattering of neutrons from a nickel single crystal was observed under the influence of elastic uniaxial mechanical stress of 140 g/mm². The temperature was varied between 10^-4 < τ = [T ? T_c(Δ)]/T_c(0) < 10^-2, and the momentum transfer between 1.4 × 10^-3 < $\text{q = (2π/λ) sin θ < 6.6 × 10}{}^{-3}\text{A}\text{?}{}^{\mathrm{-I}}$. The expected crossover from isotropic (Heisenberg) to anisotropic (XY) behaviour should occur between 10^-5 < τ < 10^-3, in good agreement with the experimental result.     

Mathematical simulation of conjugate turbulent natural convection in an enclosure with local heat source

A numerical analysis of turbulent regimes of the natural convection in a closed rectangular region with heat-conducting walls of finite thickness was carried out in the presence of a locally concentrated heat source under the conditions of the radiative-convective heat exchange with the ambient medium on one of the external boundaries. The mathematical model was constructed on the basis of the Reynolds equations in dimensionless variables stream function — vorticity vector — temperature. Special attention was paid to the investigation of the influence of the Grashof number er 10⁸≤Gr<10¹⁰, of the unsteadiness factor 0< τ <1000, and the thermal conductivity ratio λ _2,1 = 5.7·10⁻⁴, 6.8·10⁻⁵ on both the local and integral characteristics of the problem.     

Influence of Microfields on Coherent Optics Measurements of Electric Field Intensity

The influence of random microfields on measurements of external regular electric field by coherent nonlinear optics is analyzed. At an electron concentration <10¹⁴cm^?3, the influence of microfields may be neglected. Possible separation of inputs from these microfields into the resulting signal is discussed.     

Der Vordurchschlagsstrom im Hochvakuum. I. Die Spannungsabhängigkeit des Stromes bei konstantem Feld

Pre-breakdown currents were measured in the range from 10⁻¹⁷ to 10⁻⁹ A in a vacuum of 10⁻⁹ Torr. The cathode was the extended (100) surface of a nickel single crystal. In the range from 10⁻¹⁵ to 10⁻¹¹ A the current curves could be measured in times ≦ 1 s. It was found that the emission is not constant in times < 1 s. The currents show a fluctuation in times < 1 s which is voltage depending. The average current (measured in times > 1 s) rises with the total voltage at constant field. This is interpreted by a voltage depending work function which varies by the influence of ionic bombardment on adsorbed gas layers. This view is supported by a pronounced effect of oxygen adsorption. The total voltage effect causes a considerably error in the field enhancement factor β and the emitting surface which are calculated from the Fowler-Nordheim plots.     

On Lepton asymmetry and BBN

The strongest available cosmological constraint on lepton asymmetry is L<0.01. We discuss in more detail a BBN model with late ν_e↔ν_s oscillations which is capable of measuring extremely small lepton asymmetry, L>10⁻⁸. This sensitivity is achieved through the influence of small L on the neutrino oscillations, suppressing or enhancing them, and thus decreasing or increasing the primordially produced ⁴He. The cases of asymmetry generated by late resonant electron-sterile oscillations and relic lepton asymmetry are considered. The influence of L on nucleons freezing in pre-BBN epoch is numerically analyzed in the full range of the oscillation parameters for the model and L≥10⁻¹⁰.     

Unsteady conjugate thermogravitational convection in a cylindrical region with local energy source

The mathematical modelling of unsteady regimes of natural convection in a closed cylindrical region with a heat-conducting shell of finite thickness was carried out in the presence of a local heat source under the conditions of convective heat exchange with the ambient medium. The mathematical model was constructed in dimensionless variables “stream function — vorticity vector — temperature” in the cylindrical coordinate system. The influence of the Rayleigh number, 10⁴ ≤ Ra ≤ 10⁶, of the unsteadiness factor 0 < τ < 300, of the thermal conductivity ratio λ _2,1 = 5.7·10⁻⁴, 4.3·10⁻², and the energy source sizes on both local characteristics (streamlines and temperature fields) and on the integral complex (the mean Nusselt number on typical boundaries) was analysed in detail. Thermohydrodynamic peculiarities due to the geometry of the object of research were established.     

Double spin asymmetry in exclusive ρ0 muoproduction at COMPASS

The longitudinal double spin asymmetry A₁ ^ρ for exclusive leptoproduction of ρ⁰ mesons, μ+N→μ+N+ρ, is studied using the COMPASS 2002 and 2003 data. The measured reaction is incoherent exclusive ρ⁰ production on polarised deuterons. The Q² and x dependence of A₁ ^ρ is presented in a wide kinematical range, 3×10^-3<Q²< 7 (GeV/c)² and 5×10^-5<x<0.05. The results presented are the first measurements of A₁ ^ρ at small Q² (Q²< 0.1 (GeV/c)²) and small x (x<3×10^-3). The asymmetry is in general compatible with zero in the whole kinematical range. PACS 13.60.Le; 13.88.+e     

Zusammensetzung und Eigenschaften des natürlich radioaktiven Aerosols

The influence of an electrical field, acting on the deposition of natural radioactive aerosols was investigated. At an over-all aerosol concentration of 10⁴ particles pro cm³ only 3% of the Ra-A-activity exists in an atom-disperse state. 90% of the radon-decay-products are attached on particles with a radius <10^?5 cm. The size-spectrum of natural occurring radioactive aerosol was calculated. The result is in good agreement with experience.     

Control of acceptor doping in MOCVD HgCdTe epilayers

The acceptor doping of mercury cadmium telluride (HgCdTe) layers grown by MOCVD are investigated. (111)HgCdTe layers were grown on (100)GaAs substrates at 350°C using horizontal reactor and interdiffused multilayer process (IMP). TDMAAs and AsH3 were alternatively used as effective p-type doping precursors. Incorporation and activation rates of arsenic have been studied. Over a wide range of Hg_1−xCd_xTe compositions (0.17 < x < 0.4), arsenic doping concentration in the range from 5×10¹⁵ cm⁻³ to 5×10¹⁷ cm⁻³ was obtained without postgrowth annealing. The electrical and chemical properties of epitaxial layers are specified by measurements of SIMS profiles, Hall effect and minority carrier lifetimes. It is confirmed that the Auger-7 mechanism has decisive influence on carrier lifetime in p-type HgCdTe epilayers.     

Minimum metallic conductivity in a thin crystal

Electrical conductivities of thin crystals of Bi₂(Te,S)₃ measured from 4.2°K to 300°K fall into four regions: 1) σ < 1.3×10^?5 S with positive temperature coefficient of conductivity; 2) 1.3×10^?5 S < σ < 1.4×10^?5 S with temperature independent conductivity; 3) 1.4×10^?5 S σ < 4×10^?5 S with negative temperature coefficient of conductivity, and 4) σ > 4×10^?5 S with hardly any temperature dependence. A disproportionately high fraction of samples falls into the second range; 1.3×10^?5 S < σ < 1.4×10^?5 S.     

Pair Interaction Potential of Particles for Two‐Component Plasma

In this work the semiclassical potential for plasma particles pair interactions, which takes into account the diffraction effects due to the uncertainty principle in two‐component plasma (the region of temperatures 10⁴K < T < 10⁸K and densities 10²¹cm^–3 < n ≤ 10²⁴cm^–3), was proposed. The values of this potential were numerically calculated and an interpolation formula was obtained (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A LEED study of adsorbed neon on graphite

Neon monolayers on graphite have been investigated by high resolution LEED in the range 14.5 < T < 7.5 K and 10^?8 < p < 10^?4 Torr. The fluid-solid transition line has the form ln$\text{(}\text{p}\text{Torr}\text{)= ?}\text{A}\text{T + B}\text{,}\text{with}\text{A = 740 ± 45}\text{K and}\text{B = 31.0 ± 2.8}$. The solid is an incommensurate rotated phase whose lattice parameter decreases and rotation angle increases away from the transition line. Comparison is made with other thermodynamic and diffraction studies, and a preliminary phase diagram is constructed. Extrapolation of these data to higher temperatures and pressure suggests that this rotated solid monolayer is stable up to 23–25 K (P = 3?10 Torr) at coverage x = 1, and is stable over the range 0.88 < x < 1.0 at T = 16 K (2 × 10^?7 < p 1.5 × 10^?2 Torr). Extrapolation to lower temperatures gives the 2D triple point pressure in the range p = (0.3?3) × 10^?10 Torr. The steep slope of the fluid-solid transition line is consistent with the fluid phase having a high density (x?0.80) in the temperature range studied.     

Propagation of coherently combined flattened laser beam array in turbulent atmosphere

The analytical expression for the propagation of a flattened laser beam array in a turbulent atmosphere is derived based on extended Huygens–Fresnel principle. The influence of beam order and turbulent atmosphere on beam quality is studied. It is revealed that the beam quality of a coherently combined laser beam array with higher order is better than its lower order counterpart when propagating in free-space, weak and medium turbulence (i.e. C_n²<10^?13 m^?2/3). The beam quality of higher order beam arrays degrades faster as the intensity of turbulence gets stronger. In the case of propagating in strong turbulence, the beam order has no influence on coherently combined beam quality.     

Reactions of initiation of the autoignition of H<Subscript>2</Subscript>–O<Subscript>2</Subscript> mixtures in shock waves

The initiation of the autoignition of hydrogen–oxygen–argon mixtures behind reflected shock waves is studied by absorption and emission spectrophotometry in the temperature range of 960 < T < 1670 K at pressures of ~0.1 MPa. Introduction of Mo(CO)₆ additive in an amount of ~80 ppm made it possible to study the effect of O atoms on the shortening of the ignition delay time of H₂–O₂–Ar mixtures. A kinetic modeling of our own and published experimental data at temperatures of 930 < T < 2500 K and pressures of 0.05 < P < 8.7 MPa enabled to establish how the initiation reactions influence the process of self-ignition and to evaluate the rate constant for one of the initiation reactions: k(H₂ + O₂ → 2OH) = (3 ± 1) × 10¹¹exp(–E _a/RT), cm³ mol^–1 s^–1, where E _a = (40 ± 2) kcal/mol.     

New ways of estimating the energy of pulsed sources,according to the results from recording acoustic waves in the atmosphere

The problem of developing relations that allow us to increase the accuracy of estimates for energy E of a pulsed source of acoustic waves in the atmosphere is solved by generalizing experimental data on time t _R+ of pressure growth to the peak value P ₊ in the first positive phase of acoustic signals from different sources in a wide range of energies (10^?8 < E < 10¹⁰ kg of TNT) and reduced distances (10 < RE ^?1/3 < 4 × 10⁴ m kg^?1/3). In addition to a new way of estimating energy E of a pulsed source, a way of estimating distance R from the source is also proposed. Innovative science also reveals a change in the law of the increase in parameter t _R+ as distance R from a source grows.     

Spectroscopic Studies on the Thermodynamics of L-Cysteine Capped CdSe/CdS Quantum Dots��BSA Interactions

CdSe/CdS quantum dots (QDs) capped with L-cysteine can provide an effective platform for the interactions with bovine serum albumin (BSA). In this study, absorption and fluorescence (FL) spectroscopy were used to study the binding reactions of QDs with BSA, respectively. The binding constant (??10⁴ M^-1) from FL quenching method matches well with that determined from the absorption spectral changes. The modified Stern-Volmer quenching constant (5.23?×?10⁴, 5.22?×?10⁴, and 4.90?×?10⁴ M^-1) and the binding sites (??1) at different temperatures (304 K, 309 K, and 314 K) and corresponding thermodynamic parameters were calculated (?G?<?0, ?H?<?0, and ?S?<?0). The results show the quenching constant is inversely correlated with temperature. It indicates the quenching mechanism is the static quenching in nature rather than dynamic quenching. The negative values of free energy (?G?<?0) suggest that the binding process is spontaneous, ?H?<?0 and ?S?<?0 suggest that the binding of QDs to BSA is enthalpy-driven. The enthalpy and entropy changes for the formation of ground state complex depend on the capping agent of QDs and the protein types. Furthermore, the reaction forces were discussed between QDs and BSA, and the results show hydrogen bonds and van der Waals interactions play a major role in the binding reaction.     

Absolute coverage and isostemc heat of adsorption of deuterium on Pt(111) studied by nuclear microanalysis

The absolute coverage (θ) of deuterium adsorbed on Pt(111) in the ranges 180< T<440 K and 5 × 10^?6 < P < 5 × 10^?2 Pa D₂ has been determined by nuclear microanalysis using the D(³He, p)⁴He reaction. From these data, the isosteric heat of adsorption (E_a) has been determined to be 67 ± 7 kJ mol^?1 at θ ? 0.3. This heat of adsorption yields values of the pre-exponential for desorption (10^?5 to 10^?2 cm² atom^?1 s^?1) that lie much closer to the normal range for a second order process than those determined from previous isosteric heat measurements. The E_a versus θ relationship indicates that the adsorbed D atoms are mobile and that there is a repulsive interaction of 6–8 kJ mol^?1 at nearest neighbour distances. At 300 K the coverage decreases to ? 0.05 monolayer (? 8 × 10¹³ D atoms cm^?2) as P→ 0, apparently invalidating a recent model of site exchange in the adsorbed layer.     

Calculations of mass and moment of inertia for neutron stars

Masses and moments of inertia for slowly-rotating neutron stars are calculated from the Tolman-Oppenheimer-Volkoff equations and various equations of state for neutron-star matter. We have also obtained pressure and density as a function of the distance from the centre of the star. Generally, two different equations of state are applied for particle densities n > 0.47 fm^?3 and n < 0.47 fm^?3.The maximum mass is, in our calculations for all equations of state except for the unrealistic non-relativistic ideal Fermi gas, given by 1.50 M_⊙ < M < 1.82 M_⊙, which agrees very well with “experimental results”. Corresponding results for the maximum moment of inertia are 9.5 × 10⁴⁴ g · cm² < I < 1.58 × 10⁴⁵ g · cm², which also seem to agree very well with “experimental results”. The radius of the star corresponding to maximum mass and maximum moment of inertia is given by 8.2 km < R < 10.0 km, but a smaller central density ρ_c will give a larger radius.     

A design study for an internal gas-jet target for the heavy-ion storage ring CRYRING

This paper presents the design of the internal gas-jet target, CRYJET, which is being constructed for investigations of, e.g., fast ion--atom collisions in the heavy-ion storage and cooler ring CRYRING at the Manne Siegbahn Laboratory, Stockholm University. The goal for the design work was to create an ultra-cold He target (< = 10 mK in the longitudinal direction and 0.5 mK transverse temperature) with a density of ∼ 10¹² atoms/cm³. Care was taken in order to minimize the influence from the jet on the very low background pressure in the storage ring (∼ 10^-11 mbar). The low temperature is essential for the resolution in the experiments. The high density will enable us to get sufficient luminosities for investigations of processes with cross sections down to the 10^-27 cm² range. The gas-jet target will be equipped with two recoil-ion-momentum spectrometers in order to extract detailed information about the collision dynamics. This revised version was published online in August 2006 with corrections to the Cover Date.