Microhardness of single crystals of the calomel family

Microhardness of Hg₂Cl₂, Hg₂Br₂ and Hg₂I₂ single crystals has been measured on (001) and (110) faces using the indenter after Vickers. It has been found that the microhardness of the first two homologues differs only slightly whereas the iodide is considerably softer: by about 20% on the (001) face and by about 30% on the (110) face. The average microhardness value, calculated from the values obtained on gradually rotating the indenter over 360° on the (001) face, is for Hg₂Cl₂ and Hg₂Br₂ practically equal to the microhardness of NaCl (20.3 and 19.4 compared to 19.6 · 10⁷ Pa). The average microhardness of the (110) face is for Hg₂Cl₂ and Hg₂Br₂ about 2 × lower and for Hg₂I₂ about 2.6 × lower than that of the (001) face. In the case of Hg₂Cl₂ the microhardness of the (001) face has been also calculated from crystallochemical parameters and the results have been found to be in good agreement with the value obtained experimentally for the orientation of the indenter's diagonal parallel to the [100] direction, where the data is the least influenced by the elasticity of the sample (16.6 compared to 18.6 · 10⁷ Pa).     

Die Diffusion von Wasserstoff in Nickel-Ein- und -Polykristallen bei 60°C

Diffusion of hydrogen in nickel mono- and polycrystals is investigated to find the influence of grain boundaries. The result is that the small differences in the diffusion coefficients cannot unambiguously related to the differences between the polycrystalline material and the monocrystals. The grain boundaries do not influence essentially the mechanism of the diffusion.     

Chiral nematic liquid crystals in cylindrical cavities. A classification of planar structures and models of non-singular disclination lines

Abstract

A part of homotopy theory is applied to classify planar structures in chiral nematic liquid crystals confined to cylindrical cavities. The resulting classification is exact in the approximation of undeformed chiral nematic surfaces. Within this approach the relative stability of possible planar structures with surface and bulk disclination lines is discussed. The number and the shape of these disclinations, which in some cases form spiral structures, are predicted. Further approximate analytical expressions for non-singular director fields close to disclination lines with integral strength are introduced. Our predictions, which are also in agreement with some previously suggested pictures of such director fields, are used to improve stability considerations of the confined planar chiral nematic structures in tubes and droplets.     

Rapid determination of 90Sr in urine samples using AnaLig® Sr-01

This paper describes the use of IBC’s AnaLig^® Sr-01 molecular recognition technology product to effectively and selectively pre-concentrate, separate, and recover strontium from urine samples. This method uses two-stage columns separation consisting of two different commercial products Eichrom’s Pre-filter Material and AnaLig^® Sr-01 column from IBC Advanced Technologies. This method does not involve co-precipitation of strontium as phosphates and oxalates from urine samples. The new rapid method separates strontium-90 with high chemical recovery.     

Beobachtung des Stickstoffstoffwechsels bei Leguminosen mittels 15N

Es war Ziel dieser Arbeit, zu ermitteln, welchen Einfluß höhere Dosen von Stickstoffdüngemitteln in Form von KNO₃ auf die Menge des in der Pflanze fixierten Luftstickstoffs haben. Als Versuchspflanze wählten wir Pferdebohnen (Vicia faba, Chlumetzer Abart) wegen ihrer vielseitigen Verwendung in der Landwirtschaft und ihrer besonderen experimentellen Eignung.     

Analysis of PCBs in Biotic Matrices by Two-Dimensional GC-ECD

Abstract

The suitability of three GC-ECD systems for the separation of a model mixture containing various congeners of PCBs together with persistent chlorinated aromatics (pesticides and their metabolites, industrial chemicals) was tested. Analyses were performed on two parallel capillaries, the stationary phase of one of them was always in routine practice very common 5% phenyl-methylpolysiloxane, the second one was either 50% phenylmethylpolysiloxane or 7% phenyl-7% cyanopropyl-methylpolysiloxane. The number of unresolved (coeluted) analytes was significantly reduced in these systems and thus unbiased quantitation of PCBs and other components used for regulation was possible. The utilization of this type of multidimensional chromatography for rapid and reliable analysis of real samples (fish oil, human fat) was documented.     

Immobilized palladium on surface-modified Fe3O4/SiO2 nanoparticles: as a magnetically separable and stable recyclable high-performance catalyst for Suzuki and Heck cross-coupling reactions

A palladium-based catalyst (Fe₃O₄/SiO₂/HPG–OPPh₂–PNP) supported on chlorodiphenylphosphine-functionalized magnetic nanoparticles was successfully prepared from Fe₃O₄/SiO₂ with sequential attachment of glycerol and chlorodiphenylphosphine, followed by treatment of an ethanolic solution of palladium chloride with hydrazine. The as-prepared catalyst was characterized by ICP-AES, FTIR, XRD, SEM, and TEM. The Fe₃O₄/SiO₂/HPG–OPPh₂–PNP was found as a magnetically separable and highly active catalyst for Suzuki coupling reactions of aryl iodides, bromides, and chlorides as well as Heck reactions of aryl iodides and bromides. Under appropriate conditions, all reactions afforded the desired products in moderate to excellent yields. Moreover, this catalyst can be easily recovered by using a magnetic field and directly reused for at least six cycles without significant loss of its activity.