Marangoni convection in molten salts Physical modelling toward lower Prandtl numbers

Marangoni convection is involved in many technological processes. The substances of industrial interest are often governed by diffusive heat transport and their physical modelling is limited with respect to the Prandtl number Pr. The present paper addresses this deficiency. Studies were made on molten salts having Pr values in an intermediate range well below that of the typically employed organics. Since some of the selected species have a relatively high melting point, a high-temperature facility which allows studying thermocapillary convection at temperatures in excess of 1,000°C was built. The results presented here were obtained in a cylindrical geometry, although the equipment that was built is not restricted to this configuration because of its modular construction. Modelled after some applications, the fluid was heated centrically on top. The bulk was embedded in a large thermostatically controlled reservoir so as to establish the lower ambient reference temperature. A characteristic size of the experimental cell was chosen such that, on the one hand, the dynamic Bond number Bo did not become too high; on the other hand, the liquid had to have a certain depth to allow particle image velocimetry. The complicated balance between body forces and thermocapillary forces in the case of intermediate Bo was found to result in a distinct local separation into a bulk motion governed by natural convection with a recirculating Marangoni flow on top. In contrast to low viscosity organics, the vapour pressure of which increases considerably with decreasing Pr, high values of the Marangoni number can be reached. Comparisons of the topology of Marangoni vortices between molten salts with 2.3 ⩽ Pr ⩽ 6.4 and a silicone oil with Pr typically one order of magnitude higher suggest that the regime of non-negligible heat diffusion is entered.     

Test of time-reversal symmetry in the proton-deuteron system

Internal target experiments with high-quality proton beams allow for a new class of experiments providing null tests of time-reversal symmetry in forward scattering. This could yield more stringent limits on T-odd P-even observables. An excellent candidate for such experiments is the proton-deuteron system. This system is analyzed in terms of effective T-violating P-conserving nucleon-nucleon interactions and bounds on coupling strengths that might be expected are given.     

Study of electron bremsstrahlung in strong Coulomb fields at the ESR storage ring

Electron bremsstrahlung has been investigated for collisions of 223.2 MeV/amu He-like uranium ions with N₂ and Ar gaseous targets. The doubly differential cross-sections for bremsstrahlung are compared to the predictions of relativistic first order Born calculations (Bethe-Heitler formula with Elwert correction factor) and to the calculations based on the exact wavefunctions for electrons moving in the external point-Coulomb potential of the projectile. Whereas the “exact” IPA calculations give an improved agreement with experimental data, as compared to the Bethe-Heitler theory, in particular at the end-point region of the bremsstrahlung spectra, discrepancies still remain at lower photon energies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Optimization of natural gas production by waterflooding

This paper discusses optimization of natural gas production using waterflooding of a gas reservoir. The functions governing the rate of gas withdrawal and the rate of water injection control the operation of the reservoir. These, together with volume and mass balance and the ideal gas law, give a simple system of ordinary differential equations modelling the reservoir. We use several physical and economic definitions of an optimal production rate. Under each definition, we establish the optimal controls. The relation between prices of water and natural gas and the optimal controls is discussed.Work performed under the auspices of the Energy Research and Development Administration.     

Electronical tunable millimeterwave oscillators in slotline technique

A new electronical tuning process is proposed for a millimeterwave oscillator in slotline-technique. The circuit used for the GaAs-FET oscillator is realized by a slotline coupler-structure in which the feedback between the resonator and the transistor drain is made by help of electromagnetical field.     

An easy applicable method for the design of asymmetrical finline and slotline tapers

In this paper, some utilities for the developement of asymmetrical circular arc tapes are described. Basing on a polygon-approximation of characteristic impedance a method for to determine the geometrical parameters of the taper is explained. The applicability of the method presented here is proved by extensive measurements.     

The excited states of 85Sr

High resolution γ-ray studies have shown the decay patterns of isomers of ⁸⁵Y to be very complex. A level scheme of ⁸⁵Sr is proposed from the results of γ-γ coincidence measurements. Spin and parity assignments to the levels of ⁸⁵Sr were made on the basis of log ft values, nuclear reaction data and γ-ray branchings. The level scheme is discussed within the theoretical framework of $\text{n(}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?3}}$ cluster properties.     

Zur Komplexbildung von N-(Thiocarbamoyl)benzamidinen

Complex Formation of N-(Thiocarbamoyl) benzamidines N-(Thiocarbamoyl)benzamidines 1 and N-(Thiocarbamoyl)-N′-phenyl-benzamidines 2 form in alcoholic solutions with Ni²⁺, Cu²⁺, Pd²⁺, Co³⁺, and Ag⁺ ions well crystallized chelates 1a ? h and 2a? h , respectively, with N/S coordination. The X-ray photoelectron spectra evidence the NH group as ligator in the case of chelates of 1 and the increased donor capacity compared with the isosteric oxygen ligator atom bound to nickel. This is confirmed by d-¹H-n.m.r. spectroscopy analyzing the value of ΔG_c^≠ for the rotational barrier for the Et₂N group of 1a