Resistive MHD-equations for Tokamaks with arbitrary β and cross section

The complete set of hydromagnetic equations for the vector potential A and the momentum density a ≡ ?ν is transformed into a form appropriate for toroidal geometry. The toroidal components are represented by the usual poloidal flux functions Ψ and ψ, respectively, for which the equations of motion are derived. The poloidal components A_⊥ and a_⊥ are given by four potentials $\text{Φ}$, U, and φ, u for which we obtain Poisson equations in the poloidal plane. The corresponding source terms define the remaining variables, namely, $\text{Λ = ? · A, Ω = (? × A)}{}_{\mathrm{\zeta }}\text{/R, λ = ? · a, and ω = (? × a)}{}_{\mathrm{\zeta }}\text{/R}$, for which equations of motion are also derived. Finally, we find that in the limit of small toroidicity the scaling laws previously used are not applicable for toroidal geometry, and that the effort to obtain numerical solutions is not dramatically higher than without using any scaling law.     

Noise and amplitude-squeezing performance of two-polarization-mode semiconductor lasers

Using a theoretical semiclassical approach, we study in detail the amplitude fluctuations and correlations of a two-orthogonal polarization-mode semiconductor laser as obtained from a vertical-cavity surface-emitting laser (VCSEL). We demonstrate that there exists the possibility of squeezing in the two-mode regime besides sub-shot-noise emission in the well-known ideal single-mode operation regime. These theoretical results confirm a recent experimental demonstration of the generation of amplitude-squeezed light with VCSEL's.     

Preparation and evaluation of sufficiently homogeneous and stable reference materials for priority hazardous substances in whole water

We have prepared and evaluated three whole water test materials containing eight polycyclic aromatic hydrocarbons (PAHs), six polybrominated diphenyl ethers (PBDEs) and tributyltin (TBT) with respect to homogeneity and short-term stability. The test materials were used as samples in two inter-laboratory comparisons. The materials were composed of natural mineral water and model suspended particulate matter (SPM) containing the target compounds at ng L^?1 levels. The expanded uncertainty of the estimated mass concentrations in the final test materials was obtained by combining contributions from the homogeneity, the stability and the model SPM characterization. The whole water materials were sufficiently homogeneous and stable at 4 °C for their intended use. In total, 12 out of 15 investigated target parameters could be assessed to be present with a relative combined expanded uncertainty below 25 %. The outcome of the two inter-laboratory comparisons confirmed the good quality of the test materials and the level of uncertainties associated with the estimated mass concentrations. These findings are an important contribution towards the development of whole water matrix reference materials certified for PAH, PBDE and TBT in support of the Water Framework Directive of the European Union.     

Über 9β, 10α-Steroide. 2. Mitteilung. Strukturaufklärung von mikrobiologischen Umsetzungsprodukten mit Sauerstoff-Funktion in Stellung 11

The structure and stereochemistry of some 11α- and 11β-hydroxy-9β, 10α(retro)-steroids of the androstane, pregnane and corticoid series, obtained microbiologically, has been elucidated.     

Effects of confined geometry on phase-separated dextran/gelatine mixtures exposed to shear

The effect of shear on aqueous phase-separated dextran/fish gelatine mixtures with a total concentration of 5 and 10% was studied in a confined geometry. It was measured as a function of composition, strain rate and gap size. This was done by using both small-angle light scattering and a shear cell combined with a confocal laser scanning microscope. At a total polymer concentration of 5%, small-angle light scattering results showed that up to 100 s(-1) the deformation of the domains increases with the strain rate. At strain rates less than 100 s(-1), the response of the system to strain is dominated by strain rate-dependent deformation. At a higher strain rate there might be balance between break-up and re-coalescence. At a total concentration of 10%, small effects of the gap size were found. In confined geometry, the coalescence rate was faster than expected from viscous hydrodynamic growth. The microscope images showed that the gelatine-enriched phase forms a wetting layer on the surface of the glass wall. The degree of wetting appears to increase with increasing the strain rate up to 60 s(-1) and decreases again at higher strain rates.     

Dimroth rearrangement of 5-hydrazino-1,2,3-thiadiazoles

The reversible isomerization of 5-hydrazino-1,2,3-thiadiazoles and 1-amino-5-mercapto-1,2,3-triazoles has been established for an ester function at the 4-position ( 4a ? 5a ). Thus, 4a was isolated by reacting 3a with two equivalents of hydrazine, whereas 5a resulted when an excess of hydrazine was used. Acid treatment of 5a yielded 4a again, and its hydrazone 8 was obtained from 5a and benzaldehyde. Compound 5a was also converted into the derivatives 6a, 7, 9 and 10a-c. The less reactive 5-chloro-1,2,3-thiadiazoles 3b,c afforded the bis-heterocycles 6b,c on heating with hydrazine.     

Aqueous sol–gel processing of precursor oxides for ZrW<Subscript>2</Subscript>O<Subscript>8</Subscript> synthesis

This paper describes the synthesis of ZrW₂O₈ by the use of an aqueous citrate-gel method in order to prepare a fine, pure and homogeneous oxide mixture suitable for ceramic processing. The thermal expansion coefficient thus obtained for α-ZrW₂O₈ is −10.6 × 10⁻⁶ °C⁻¹ (50–125 °C) whereas for the β-ZrW₂O₈ a value of −3.2 × 10⁻⁶ °C⁻¹ (200–300 °C) is obtained. The advantages of the use of a sol–gel method is expressed in the very homogeneous end-products. The paper describes crystallographic data, morphological structure and the thermal expansion properties of the ZrW₂O₈ material. Moreover, photoluminescence and photochromic properties specific to the precursor gel are described and analyzed. These effects support our views that the precursors show homogeneity up to nanometer level.