The quantitative determination of FeS2 phases in coal by means of57Fe Mössbauer spectroscopy

A knowledge of the concentration of pyrite and marcasite in coals can provide important insight into the genesis of coal deposits. Determinations of the relative amounts of pyrite and marcasite by traditional methods of coal analysis are, however, beset with many difficulties. Using⁵⁷Fe Mössbauer spectroscopy and a mild chemical treatment with hydrofluoric acid, a technique has been devised for the quantitative determination of the relative concentrations of pyrite and marcasite in samples of whole coals or their low-temperature ashes. The sample preparation procedure is comparable to less accurate methods. Good qualitative agreement has been obtained between ore microscopic and Mössbauer spectroscopic techniques for a series of extensively investigated whole coal samples.     

The thermoconvective instability of plane poiseuille flow heated from below: A proposed benchmark solution for open boundary flows

The transient two-dimensional Navier-Stokes and energy equations have been solved numerically for flow in a horizontal channel heated from below in the Boussinesq limit. For the set of dimensionless parameters chosen, the flow consists of periodic transverse travelling waves resulting from a convective instability. The solution is proposed as a benchmark for the application of outflow boundary conditions (OBC) in time-dependent flows with strong buoyancy effects. Richardson extrapolation in both time and space is used in obtaining the solution. Field plots and profiles of velocity, temperature, vorticity and streamfunction at selected axial positions and times are also presented from the finest grid and smallest time step calculation. The calculations have been made on an extended domain so that the effects of OBC used in the present study would be negligible in the test region.     

The conductance of cyclic polyether-cation complexes

Precise conductance measurements are reported for sodium, potassium, and cesium salts in methanol and acetonitrile solutions containing cyclic polyethers dibenzo-18-crown-6 and dicyclohexyl-18-crown-6. Decreases in equivalent conductance caused by the addition of a cyclic polyether to solutions of constant ionic strength were analyzed by nonlinear least squares to give association constants and equivalent conductances of the cation-polyether complex. The selectivity observed for the complexing is a function not only of ionic size but also of solvent.     

Aldol diastereoselection via zirconium enolates. Product-selective,enolate structure independent condensations.

Both($\text{E}$)- and ($\text{Z}$)-zirconium enolates have been shown to undergo selective kinetic aldol condensation to give mainly $\text{erythro}$-β-hydroxy ketones, esters and amides.     

Far-infrared super-radiant laser action in heavy water

Super-radiant output from D₂O pumped by up to 10 J pulses of the CO₂ P(32), R(12) and R(22) laser transitions gave measured energies of 330 mJ, 240 mJ and 120 mJ respectively. In the R(12) case the emission was at 361 μm and 385 μm in the intensity ratio of 1:2, the average power was 1–2 MW and peak powers of about 5 MW were measured.     

Die mechanischen Eigenschaften von Doppeltschicht-Membranen

Ohne Zusammenfassung     

Second order Chebyshev semi-iteration in connection with p-parametric E.A.D.I. schemes

In this paper an analysis of a second order Chebyshev semi-iterative method for the p-parametric E.A.D.I. schemes is presented with a recommendation for the selection of the optimum parameters in order to achieve the maximum rate of convergence.