The influence of temperature gradients on the kinetic boundary layer problem for a condensing droplet

We extend an earlier method for solving kinetic boundary layer problems to the case of particles moving in aspatially inhomogeneous background. The method is developed for a gas mixture containing a supersaturated vapor and a light carrier gas from which a small droplet condenses. The release of heat of condensation causes a temperature difference between droplet and gas in the quasistationary state; the kinetic equation describing the vapor is the stationary Klein-Kramers equation for Brownian particles diffusing in a temperature gradient. By means of an expansion in Burnett functions, this equation is transformed into a set of coupled algebrodifferential equations. By numerical integration we construct fundamental solutions of this equation that are subsequently combined linearly to fulfill appropriate mesoscopic boundary conditions for particles leaving the droplet surface. In view of the intrinsic numerical instability of the system of equations, a novel procedure is developed to remove the admixture of fast growing solutions to the solutions of interest. The procedure is tested for a few model problems and then applied to a slightly simplified condensation problem with parameters corresponding to the condensation of mercury in a background of neon. The effects of thermal gradients and thermodiffusion on the growth rate of the droplet are small (of the order of 1%), but well outside of the margin of error of the method.     

Even denominator filling factors in the thermoelectric power of a 2DEG

We have investigated the interaction of phonons with a 2DEG in the FQH regime with phonon drag thermoelectric power (TEP). We find that the TEP at filling factors with the same even denominator is identical and at other even denominator filling factors they differ only by a constant. Assuming these states to be Composite Fermions (CF), we can explain our observations by extending a zero magnetic field theory for phonon drag to the CF-phonon interaction. This analysis is further corroborated by the observed T⁴ dependence of the CF TEP.     

Crossing of shears bands in196Pb

High-spin states in¹⁹⁶Pb have been populated using the reaction¹⁷⁰Er(³⁰Si,4n). The previously observed shears bands in this nucleus have been extended and some of their transitions have been reordered. They now form regular bands with band crossings. One of the bands splits into two pathways at high spin.     

Precipitation and characterization of uniform submicrometer lead titanate particles. Part II: Reaction mechanism

The chemical mechanism of the precipitation of lead titanium peroxohydroxide particles in a solution of nitrilotriacetate (NTA) complexes of lead and titanium peroxo-hydroxide is envisioned as the interaction between cations of lead hydroxide and anions of polymeric titanium peroxo-hydroxide.     

Tetracyclic alkaloids of the sparteine group.1H and13C NMR spectroscopy and conformational analysis

The¹H and¹³C chemical shifts of 11 sparteine derivatives are reported. Substituent and group effects are interpreted in terms of structural properties. The conformational equilibrium of aphyllin is determined.Ruhr-Universität Bochum, Fakultät für Chemie, Bochum, Germany. Universität Hannover, Institut für Organische Chemie, Hannover, Germany (present address). Department of Organic Chemistry, Poznan Academy of Economics, Poznan, Poland. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1026–1033, August, 1995. Original article submitted May 10, 1995.Dedicated to Prof. N. S. Zefirov on the occasion of his 60th birthday.     

Neue Spiroverbindungen aus Cyclophosphazenen und Cyclodi[phosphadiazan]en

New Spiro Compounds from Cyclophosphazenes and Cyclodi[phosphadiazanes] Chlorocyclophosphazenes (Cl₂P = N)₃ and (Cl₂p = N)₄ react with dihydrazidophosphoric acid derivatives in THF in the presence of triethylamine to give the spirocyclic compounds Cl₄N₃P₃(NHN(CH₃))₂P(S)OC₆H₅, Cl₆N₄P₄(NHNH)₂P(S)OC₆H₅. Constitutions have been confirmed by MS, NMR, IR and elemental analysis.     

Optical spectra and laser-induced dissociation of supported Na particles

This paper reports new results on the optical spectra of Na particles and on laser-induced photodissociation of Na atoms from the surface of these particles. In continuation of our earlier studies we have performed experiments to elucidate the mechanism of thenonthermal dissociation process. Furthermore, theoretical calculations have been carried out with the goal to correlate the wavelength dependence of the photodissociation yield with the optical absorption spectra of the metal particles. In addition, manipulation of the size distribution of metal particles on supports is outlined as an application of the effect. This allows for the preparation of very special surfaces with novel physical and chemical properties.     

Frequency domain measurements on Na2B4O7−V2O5 semiconducting glass

Summary Dielectric measurements on Na₂B₄O₇(99.5%)−V₂O₅(0.5%) glass system, in the frequency range 10⁻³ to 10⁴ Hz and temperature range 300 to 500 K, have been carried out. The normalized plots of complex capacitance have shown a single mechanism responsible for conduction for both volume and surface measurements with their close values of activation energies (0.67±0.03) eV and (0.64±0.03) eV, respectively. The low-frequency dispersion (LFD) behaviour has been observed to be perturbed by the presence of more than one competing process. The impedance plots have shown a parallel combination of a capacitor (C) and a resistor (R), with some contribution of a dispersive element due to charge accumulation in the vicinity of the electrodes. The values ofR andC were found to be of the same order of magnitude, for both surface and volume measurements. The observedR has shown a decrease with an increase in temperature due to an increase in mobility of Na⁺ ions, whereasC remains practicaly constant. The complex capacitance surface behaviour is dominated by volume, due to hygroscopy of this glass system.