Über die Dichten von Soda- und Ätznatron lösungen

Ohne Zusammenfassung     

Amorphization of Al32Ge68 in a slow heating run studied by NMR

Amorphization of Al₃₂Ge₆₈ at normal pressure, starting from the thermobarically quenched high-pressure crystalline metallic γ-phase, was studied in a slow heating run by performing NMR field-sweep experiments. In the temperature interval from 77 to 300 K the ²⁷Al central line exhibits a continuous broadening and a positive frequency shift. Close to 300 K rather abrupt changes were observed, where the shift changed its sign, and the line width jumped to its highest value. The discontinuous course of the phase changes indicates that the amorphization process proceeds via a sequence of intermediate metastable states, which can be ‘overheated’ in a slow heating run and consequently transform in an explosion-like manner to the final amorphous state at a well-defined temperature. The frequency shift could be decomposed into the negative second-order quadrupolar shift and the positive Knight shift. The change of the shift sign from positive to negative at 300 K reflects the vanishing tendency of the Knight shift upon heating and is compatible with the conduction-electron localization upon structure amorphization.     

Book rewiev

Howard Anton and Robert C. Busby, John Wiley & Sons, Inc., 2002.     

Magnetic poly(N‐isopropylacrylamide) microspheres by dispersion and inverse emulsion polymerization

The aim of this study was to develop novel thermally responsive polymer microspheres with magnetic properties. Dispersion and inverse emulsion copolymerization of N‐isopropylacrylamide (NIPAAm) and N,N′‐methylenebisacrylamide (MBAAm) was investigated in the presence of γ‐Fe₂O₃ nanoparticles. The resulting microspheres were characterized in terms of morphology, size, polydispersity, iron content, and temperature‐dependent swelling using optical microscopy, transmission electron microscopy, scanning electron microscopy, QELS, and AAS. The effects of several variables, such as the concentration of γ‐Fe₂O₃, MBAAm crosslinking agent, Span 80 surfactant, 2,2′‐azobis(2‐methyloctanenitrile) (AMON) initiator, and polymerization temperature on the properties of the microspheres were studied. Swelling and thermoresponsive behavior of the microspheres containing γ‐Fe₂O₃ nanoparticles were also investigated. The microspheres contained about 8 wt % of iron. The presence of magnetic nanoparticles and their concentration changes did not have any significant effect on the temperature sensitivity of the composites. The particles gradually shrink into an increasingly collapsed state when the temperature is raised to 40 °C since the increase in temperature weakens the hydration and PNIPAAm chains gradually become more hydrophobic, which leads to the collapse of the particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5884–5898, 2007     

Arsenic determination in marine sediment using ultrasound for sample preparation.

This work deals with As determination in marine sediment using ultrasound for sample preparation. It is shown that As can be quantitatively extracted from marine sediment using 20% (v/v) HCl and sonication. The slurry is centrifuged and the analyte is determined in the supernatant by hydride generation atomic absorption spectrometry (HG AAS). A flow injection (FI) system is employed for hydride generation, with 0.5% (m/v) NaBH(4) used as reducdant and a 20% (v/v) HCl used as sample carrier. The limit of quantification is 1.6 microg g(-1) of As, which is based on 800 microl of sample solution and 0.200 g of sample mass in a volume of 50 mL. Certified and non certified marine sediment samples were analyzed; the results were in accordance with the certified or reference values. Speciation analysis by HPLC-ICP-MS showed that As(V) is the only detectable As species present in the supernatant of the centrifuged sample.     

Sur le groupe des homographies et des antihomographies d'une variable complexe

Sans résumé     

On the condensate values in QCD

Conclusions The sets (3) and (4) of condensates have been compared using the QCD sum rules (2) with indefinite weight functions. A bad matching between both sets of condensates and experimental data has been obtained. The standard values (3) appear to be closer to data but some increase ofQ is necessary to improve the agreement. Only higher values ofm ₀ ² could change the results of this analysis. It is interesting that negative values ofm ₀ ² considerably improve the agreement with data; note that this quantity cannot be determined with a sufficient accuracy. We conclude that the QCD sum rules (2) cannot definitely determine a privileged set of condensates.Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday.     

Time structure of iodine laser pulse in the free running mode of operation

Time structure of iodine laser pulse in the free running mode of operation was studied using the power amplifier of laser system PERUN as the laser oscillator. Two characteristic shapes of laser pulse correspond to different regimes of laser operation, the existence of which is ascribed to the critical concentration of I₂ molecules. Simultaneously an additional chemical pumping was proved at least in the initial phase of photodissociation and in a late-time lasing after the end of flashlamps pumping light.