Geometric structure and electronic properties of neutral and anionic Fe2C3 and Fe2C4 clusters, as obtained by density-functional calculations

We calculated the geometrical structures and electronic properties of neutral and anionic Fe2Cn clusters (n = 3,4) using a density-functional method that employs linear combinations of atomic orbitals as basis sets, standard nonlocal norm-conserving pseudopotentials, and the generalized gradient approximation to exchange and correlation. We show that the ground-state structures of Fe2C3 and Fe2C4 are essentially the same in the neutral and anionic states, namely, planar rings that feature nonadjacent Fe atoms. For the anionic clusters, these findings contrast with previously published results.     

Trace elements in a profile of the unsaturated zone of the São Paulo Basin

This study comprises Tertiary sediments (clays, silts, and fine clayey sands) from the unsaturated zone of the Experimental Station in the University of São Paulo, taken from a nine meters depth profile; ten samples were separated in bulk and <53 m fractions. Chemical composition was determined by INAA to ascertain the distribution of trace elements throughout the sediment deposition, and to establish the background parameters, useful for mobilization studies of such elements after industrial waste disposal.     

Radionuclide X-ray fluorescence analysis of drinking water using preconcentration of trace metals on chelating cellulose exchanger OSTSORB-OXIN

Determination of Cr, Fe, Cu, Zn and Pb in drinking water preconcentrated on a chelating ion exchanger of Czechoslovak production is described. The analytical system consisted of a radionuclide source²³⁸Pu, a Si/Li semiconductor detector and a multichannel analyzer. Results are compared with trehshold limit values recommended for drinking water.     

A switchable radioactive neutron source: Proof-of-principle

The formation of¹⁶⁰Er,¹⁵⁹Dy and¹⁴⁹Gd employing natural dysprosium as target and its irradiation with α-particles was the objective of this work. This is included in a study performed by our group on excitation functions of induced reactions for charged particles on rare earths. A target with metallic foils of Dy was irradiated in the Isochronous Cyclotron at Karlsruhe (Germany) with incident energy up to 88.5 MeV. Due to the contributions of the precursors in the isobaric chains, we were not able to measure the absolute cross sections. Then, the determination of the cumulative cross sections were carried out. Thick target yields for the production of¹⁶⁰Er,¹⁵⁹Dy and¹⁴⁹Gd are also presented. At present we do not know other publications about the functions studied in this work.     

Monitoring the atmospheric stability by using radon concentration measurements: A study in a Central Italy site

Summary Meteorological and radon concentration data referring to a measurement campaign carried out in Urbino, Central Italy, are reported and discussed. This study presents a method allowing monitoring of the vertical atmospheric stability using continuous measurements of radon gas near ground. In particular radon evidences the presence of temperature inversion such as the formation of the nocturnal stable layer and gives information on the vertical turbulence and the motion of air masses. This technique is very useful in describing the temporal evolution of the pollutants in the atmosphere.     

Thermal behaviourof complexes of antipyrine derivatives Part III.

The thermal behaviour of the mixed-ligand complexes of cobalt(II) and copper(I) ions with antipyrine derivatives of 1,2-ethanediamine or piperazine (BAMP and TAMEN), with water and with 2-mercapto-benzothiazole (Hmbt) was investigated. The complexes contain 2-mercaptobenzothiazole (Hmbt, in the case of cobalt(II) ion) or dimercaptobenzothiazine (mbt–mbt, in the case of copper(I) ion) molecules as ligands and perchlorate (ClO₄^–) or thiocyanate (SCN – ) ion as counterion. By heating, water and ligands release the solid phase at lower temperature. At higher temperatures process of different organic reactions of ligands (e.g. polymerization, polycondensation) could be suggested to interpret the relative high final mass values.     

Determination of nitric acid concentration by using europium ion fluorescence

A method is presented for the determination of 2-10M nitric acid based on the fact that the presence of high nitric acid concentration causes an enhancement of the intensity of some bands in the fluorescence spectra of rare earth ions in solution. The 616-nm band of Eu(3+) shows the most dramatic intensity enhancement with increasing nitric acid concentration. The present method, based on the measurement of the ratio of Eu(3+) fluorescent band intensities is shown to be independent of Eu(3+) concentration and relatively free of interference. This robust method allows the presence of an interferent to be determined from the experimental data.     

Elaboration of a programmed,semi-automated radiochemical processing system for neutron activation analysis of some volatile elements

Based on the method of SAMSAHL a programmed, semi-automated processing system has been developed and tested for the neutron activation analysis of the following elements: As, Se, Sb, Br, Sn and Te. The main characteristics of the procedure are the following: wet ashing of the sample (by means of digestion in a mixture of concentrated sulphuric acid and hydrogen peroxide), bromination, and chlorination. The procedure is controlled via the appropriate dosage of the reagents and a carefully managed thermal balance. The chemical yield and its reproducibility were determined by tracer techniques using exactly the same parameters as for the active runs. According to the results the method can be used for the routine determination of the given elements except antimony. Presented at the 4th Symposium on the Recent Developments in Neutron Activation Analysis, 1975, Cambridge.     

Spectroscopic evidence for the intermediacy of a 6-R-2,4-diazabicyclo-[3.1.0]hex-2-(3)ene in the photoisomerization of 4-R-1,4-(3,4)-dihydropyrimidines

¹H- and ¹³C-nmr spectroscopy is presented showing that photolysis of 4-(p-trifluoromethylphenyl)-1,4-(3,4)-dihydropyrimidine yields 6-(p-trifluoromethylphenyl)-2,4-diazabicyclo[3.1.0]hex-2-(3)ene.     

Appareillage pour la mesure de variations rapides de l'emission d'un gaz radioactif par un solide soumis a un traitement thermique,sous atmosphere controlee

An apparatus is described that enabled us to carry out a quantitative kinetic investigation of rather quick physicochemical transformations of divided solids by means of an emission of radioactive gas, as in the emanation method. Especially the details of the reaction cells are given in which surface area measurements by the BET method are also performed, and of the low volume scintillation chamber. Its high efficiency does not depend on the nature of the gas. The diverse components of the device ensure a good quality of pure atmosphere or vacuum, rapid and precise temperature setting and control, and reproducible sweeping of the radioactive gas escaping from the sample.