1-(Organosulfonyloxy)-3(1H)-1,2-benziodoxoles: Preparation and Reactions with Alkynyltrimethylsilanes

Organosulfonyloxy derivatives of 1,2-benziodoxol-3(1H)-one (3a-c) and 3,3-bis(trifluoromethyl)-3(1H)-1,2-benziodoxole (5a-c) can be prepared in high yield by the reaction of 1-hydroxybenziodoxoles 1 or 4 and the corresponding sulfonic acids or Me(3)SiOTf in the form of stable, but moderately hygroscopic, microcrystalline solids. Reaction of the triflate derivatives 3a and 5a with alkynyltrimethylsilanes affords either alkynyliodonium triflates 6, or (E)-beta-(trifluoromethanesulfonyloxy)alkenyliodonium triflates 7, while the same reaction in the presence of pyridine selectively gives the respective 1-alkynylbenziodoxoles 8 and 9 in 82-90% yield.     

Mössbauer effect in superconducting tin-europium-molybdenum-sulfides

Mössbauer spectra of¹¹⁹Sn in Sn_1–z Eu _z Mo₆S₈ (z=0, 1/3, 2/3) have been measured in the temperature range 4.9 KT293 K. The spectra consist of a quadrupole doublett with unequal intensities at all temperatures. The Debye-Waller factor, the isomeric shift and the asymmetry of the intensity of the quadrupole components show irregularities between 50 K and 110 K which are interpreted as arising from a structural phase transition. The temperature dependence of the Debye-Waller factor can be approximated by a simple phonon spectrum. No quantitative explanation can be given for the large values of the asymmetry. Evidence is presented that this behavior is connected with the properties of the librational modes of the Mo₆S₈-units in the crystal.     

Eine Schnellmethode zur Furfurolbestimmung

Ohne Zusammenfassung     

Interferometry of pions and kaons in high energy collisions

A hydrodynamic model which reproduces the observed rapidity and transverse momentum spectra of mesons and baryons is applied to the study of Bose-Einstein correlations. The pion correlations are found to be strongly affected by resonance decays, except for pairs of large transverse momenta.For S+S at 200 A GeV, in the central rapidity region the effective longitudinal source radii for pions and kaons differ by a factor of 2, the transverse radii by a factor of 1.3. The lifetime of the source can be extracted from kaon interferometry.     

Giant dielectric constant response of the composites in ternary system CuO-TiO2-CaO

The subsolidus phase relations of the ternary system CuO-TiO₂-CaO sintered at 950 °C in air have been determined by powder X-ray diffraction method. Only one ternary compound CaCu₃Ti₄O₁₂ was found in this system. From room-temperature dielectric property mapping at 10 kHz, a giant dielectric constant (ε_r>10⁴) was observed for most of the ceramic composites in the CuO-rich region and in the region along the CaO-CuO binary line. The composites in the CaCu₃Ti₄O₁₂-rich region were found to give a comparable giant dielectric constant when sintered at 1050 °C. The particular microstructure of larger grains with predominant phase surrounded by smaller grains with the secondary phases was found in such composites with a high dielectric constant. The relations between structures and dielectric properties were investigated. An internal barrier layer capacitance effect is the most probable mechanism to explain this particular dielectric behavior.     

Influence of interparticle interactions on the kinetics of self-assembly and mechanical strength of nanoparticulate aggregates

Computer simulations based on Discrete Element Method have been performed in order to investigate the influence of interparticle interactions on the kinetics of self-assembly and the mechanical strength of nanoparticle aggregates.Three different systems have been considered.In the first system the interaction between particles has been simulated using the JKR (Johnson,Kendall and Roberts) contact theory,while in the second and third systems the interaction between particles has been simulated using van der Waals and electrostatic forces respectively.In order to compare the mechanical behaviour of the three systems,the magnitude of the maximum attractive force between particles has been kept the same in all cases.However,the relationship between force and separation distance differs from case to case and thus,the range of the interparticle force.The results clearly indicate that as the range of the interparticle force increases,the self-assembly process is faster and the work required to produce the mechanical failure of the assemblies increases by more than one order of magnitude.