Determination of trace and platinum-group elements in high ionic-strength volcanic fluids by sector-field inductively coupled plasma mass spectrometry (ICP-MS)

The accurate measurement of ultra-trace concentrations of rare metals and platinum group elements in volcanic fluids is complicated by interferences, complex matrices, and preferential element partitioning. We analyzed condensed, high-temperature magmatic fluids collected from Kudryavy volcano (Kurile Islands, Russia) for Be, B, Rb, Sr, Mo, Ru, Rh, Pd, Cd, W, Re, Pt, Pb, Bi, and U using ICP-MS. The samples had three different matrices: 5 mol L^–1 sodium hydroxide (NaOH, pH = 11), gas condensates of sulfuric acid (H₂SO₄, pH = 0), and solid elemental sulfur. Interferences and suppression/enhancement effects were investigated using standards in concentrated NaOH and H₂SO₄ solutions to determine adequate dilution for sample analyses, which then required very low levels of element detection (< 1 μg L^–1 for most elements). Depending on the field sampling technique of volcanic gas vents, our results show significant differences in concentrations of some trace elements due to the precipitation of solid sulfur during gas condensation and variations in element volatility as a function of temperature.     

Incommensurate and commensurate magnetic long-range order in metallic REPd3 compounds of rare earths (RE=Nd,Tb, Dy,Er, Tm,Yb)

Compared to previous bulk magnetic measurements unusual magnetic ordering phenomena were detected by systematic neutron scattering experiments performed in the temperature range of 7 mKT300 K on the series of cubic metallic compounds REPd₃ of the rare earths RE=Nd, Tb, Dy, Er, Tm and Yb. Except for ErPd₃ withT _N =3 K the observed critical temperatures are compatible with the de Gennes scaling. The complexity of long-range magnetic ordering increases with decreasing 4f ⁿ occupancy, ranging from ferro- or ferrimagnetism in YbPd₃ and DyPd₃ via commensurate antiferromagnetic ordering in ErPd₃ and TmPd₃ [k=(1/2, 1/2, 0)] to incommensurate antiferromagnetic ordering of modulated type in TbPd₃ and NdPd₃. Both RKKY interactions, crystalline electric field, hybridization with 4d states of Pd as well as nuclear spin polarization in the case of RE=Nd appear to be of importance for the magnetic properties of REPd₃ systems.     

Improvement of the Froissart-Martin bound for complex scattering angles

Extension of the Froissart-Martin bound for complex scattering angles is improved using the solution of the Dirichlet boundary value problem for doubly connected domain. The Froissart-Martin bound for physical scattering angles is used as input value on one of the two boundaries. The obtained bound is valid in an ellipse smaller than the Lehmann-Martin one. Possiblities of further improvements and applications are discussed. Details will be published elsewhere (Chaichian M., Fischer J., Nelipa N. F.,Vrko I. Preprint of the University of Helsinki, HU-TFT-81-22, to be published).Abstract of the paper presented at the International Symposium Selected Topics in Quantum Field Theory and Mathematical Physics, Bechyn, Czechoslovakia, June 14–19, 1981.     

Ammoxidation of halogen-substituted toluenes on V-P-oxide catalysts

The ammoxidation of various halogen-substituted toluenes on crystalline vanadium phosphate catalysts was investigated. The monophosphates and the NH₄VOP₂O₇ are transformed into new NH₄-containing V-P-oxides. The (VO)₂P₂O₇ used is stable in time on stream. These structures are very active and selective ammoxidation catalysts.

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. NH₄VOP₂O₇ V-P , NH₄. (VO)₂P₂O₇ . .

     

Stress driven shear bands and the effect of confinement on their structures--a rheological, flow visualization, and Rheo-SALS study

An equimolar mixture of a cationic surfactant, cetylperidinium chloride (CPyCl), and salt sodium salicylate (NaSal) forms wormlike micelles in aqueous solutions. Under shear, the solution shows a pronounced shear-thickening behavior, which is coupled with oscillations in shear rate and the apparent viscosity. In this shear-thickening regime shear bands form, which also oscillate in position and intensity. These shear bands are visualized by direct imaging and Rheo-small angle light scattering methods. Temporal intensity fluctuations of the shear bands were evaluated using image analysis. Fourier transformations (FT) of the oscillating shear rate and intensity of the shear bands showed a single dominating frequency in the power spectrum analysis. This characteristic frequency as well as the amplitude of shear rate fluctuation was found to increase with stress. From the rheological and optical measurements, we propose that a stress driven mechanism is responsible for the formation of shear bands. Experiments performed in transparent parallel-plate geometry show dampening of the shear rate oscillations and increase in the characteristic frequency with decrease in the gap. Power spectrum analysis and the SALS measurements confirm the formation of different structures as a function of gap size in the parallel-plate geometry.     

Synthese und Struktur von Silber(II)-tetrafluoroaurat(III) Ag[AuF4]2

Synthesis and Structure of Silver(II) Tetrafluoroaurate(III) Ag[AuF₄]₂ Intensive green single crystals of Ag[AuF₄]₂ can be obtained by heating up micro crystalline Ag[AuF₄]₂ in autoclaves (p(F₂) ～ 200 bar, T ～ 400°C, t ～ 14 d). It crystallizes monoclinic, space group P2₁/n ? C; (No. 14) with a = 522.3(1), b = 1101.3(3), c = 550.5(2) pm, β = 94.98(3), Z = 2 and is isotypic with Pd[AuF₄]₂.