Constraint Molecular Dynamics and results on isotopic distributions produced in heavy ion collision — The Sn + Ni systems

The Constraint Molecular Dynamics approach is illustrated together with calculation on different heavy ion collisions. In particular the charge-mass distribution produced in the collision ¹²⁴Sn + ⁶⁴Ni and ¹¹²Sn + ⁵⁸Ni at 35 MeV/nucleon is discussed. By comparing the Y = (N ? Z)/A distributions for fragments produced in central collisions it results that this observable can be sensitive to the dynamic effects induced on the two systems by the different charge/mass ratio.     

Mössbauer studies of EFG of the different57Fe(57Co)-Oxygen configurations in oriented Y−Ba−Cu−O

We have determined the various parameters of the electric field gradient (EFG) for different Fe-oxygen configurations. This was achieved by analyses of a variety of spectra using a procedure which allows fitting of all spectra of oriented 1-2-3 compounds obtained at different tilt angles β simultaneously, taking into account the degree of texture. The use of a point charge model is invalidated because of the high degree of estimated covalence. The Mössbauer parameters are rationalized. The absence of any observed anisotropy of the mean square displacement of the dopant at the Cu(1) site is rather intriguing.     

Solid-state electrode with a Cu(I)-based membrane hydrophobised by PTFE for the measurement of Cu2+ and I?

The preparation of CuI + Ag₂S and Cu₂[HgI₄] + Ag₂S membranes hydrophobised by PTFE is described. The pressed membranes mounted in a multi-purpose all-solid-state electrode body have been examined as electrochemical sensors for Cu²⁺ and I^– ions. For the electrode with (CuI + Ag₂S + PTFE)-membrane experimental slopes of 29 mV(pCu)^–1 and 62 mV(pI)^–1 were obtained, in good agreement with the theoretical values. For practical measurement in solutions where both Cu²⁺ and I^– can be present, the investigated electrode offers certain advantages in comparison with a commercial Cu-ISE.     

Mechanism of ruthenium tetroxide-catalysed oxidation of aldoses by alkalineN-bromoacetamide

The kinetics of oxidation of three aldoses (glucose, mannose and galactose) byN-bromoacetamide (NBA) in the presence of an alkaline solution of RuO₄ as catalyst and Hg(OAc)₂ as co-catalyst and as a scavenger for bromide have been investigated. The main products of the oxidation are the corresponding aldonic acids. The reaction is zero order with respect to aldose and OH⁻. First order dependence of the reaction on both NBA and RuO₄ at low concentrations shifts to zero order at higher concentrations. Addition of acetamide decreases the reaction rate, while addition of Hg(OAc)₂ has the opposite effect. No significant effect of ionic strength was observed. OBr⁻ is postulated as the reactive oxidising species and a mechanism involving co-catalysis by RuO₄ and Hg^II is proposed. TMC 2588     

Pure and doped lanthanum cobaltites obtained by combustion method

We report the synthesis of La_1−xSr_xCoO₃ nanopowders by solution combustion method using metal nitrates and -alanine (alanine method) or urea (urea method) as fuel. The influence of metal nitrates/organic substance molar ratio and the type of fuel was investigated. The isolated complex precursors were characterized by atomic absorption spectroscopy (AAS), FT-IR spectra and DTA–TG analysis. The La_1−xSr_xCoO₃ (x = 0–0.3) powders were characterized by X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray analysis (SEM–EDX), as well as by specific surface area measurements. XRD patterns indicate the formation of single-phase LaCoO₃ (rhombohedral) when as-synthesized powders were calcined at 873 K, 3 h in the case of the alanine method and at 1073 K, 3 h for urea-based system. Also, strontium doped lanthanum cobaltites obtained by both methods at 1273 K are single phase with rhombohedral perovskite-like structure as XRD data have proved. SEM investigation of pure and doped lanthanum cobaltites reveal that the samples prepared by both methods have fine particles with tendency of agglomerates formation with different shapes, spongy aspect and high porosity. La_1−xSr_xCoO₃ nanopowders obtained by alanine method have larger specific surface area values than those prepared by urea method.     

Solid-state electrode with a Cu(I)-based membrane hydrophobised by PTFE for the measurement of Cu2+ and I−

The preparation of CuI + Ag₂S and Cu₂[HgI₄] + Ag₂S membranes hydrophobised by PTFE is described. The pressed membranes mounted in a multi-purpose “all-solid-state” electrode body have been examined as electrochemical sensors for Cu²⁺ and I^? ions. For the electrode with (CuI + Ag₂S + PTFE)-membrane experimental slopes of 29 mV(pCu)^?1 and 62 mV(pI)^?1 were obtained, in good agreement with the theoretical values. For practical measurement in solutions where both Cu²⁺ and I^? can be present, the investigated electrode offers certain advantages in comparison with a commercial Cu-ISE.     

Multipole plasmon resonances of submicron silver particles

Single crystal, silver particles of 215 +/- 10 nm size were synthesized in solution using the hydrogen reduction method and were characterized by UV-visible extinction spectroscopy and electron microscopy. The extinction spectra reveal the presence of higher order multipoles of the plasmon resonance, such as quadrupole, octupole, and hexadecapole, in addition to the dipole. The formation of higher order multipoles was continuously monitored during the particles growth. Mie extinction calculations were performed and are in good agreement with the measured extinction spectra. The frequency shift of all plasmon modes was measured as a function of the refractive index of the surrounding dielectric medium.