Studies on some experimental parameters of radiometric flow injection analysis (RFIA) using137Cs and60Co

A simple radiometric flow injection analyzer with NaI(Tl) detector was used for the study of some experimental parameters of¹³⁷Cs and⁶⁰Co determination. A sample transfer system was developed employing both merging zone and sample injection principle.     

Thermal decomposition of 2,3,5-triphenyl tetrazolium halochromate complexes

Thermal decomposition studies of 2,3,5-triphenyl tetrazolium halochromates have been carried out upto 1000°C at a linear heating rate of 10 deg·min^?1. The complexes undergo two stage decomposition. First one corresponds to the redox decomposition of the complex along with the loss of a phenyl halide molecule and 3/2 mol of oxygen. While, the second step corresponds to the oxidation of the formazan type structure formed in the first step. The first step decomposition follows diffusion controlled reaction mechanism in a sphere governed by the equationg(α)=[1?(1?α)^1/3]². Activation energy and pre-exponential factors have been determined by Coats-Redfern model and Dixit-Ray model. Activation energy decreases as the electronegativity of the halide ion decreases.     

Levels of natural and artifical radioactivity in sediments in the Eastern Black Sea of Turkey

Sediment samples collected from the Eastern Black Sea in 1993 from 15 sampling stations of different depths have been analyzed. Natural and artifical radionuclide activity levels in offshore sediment samples from the Eastern Black Sea in Turkey are reported about seven years after the Chernobyl accident. The purpose of this paper is to follow up the earlier study and present results for the distributions of radionuclides in sediments of the Black Sea.     

Quantitative analysis of sea-bed sediments from Eastern Black Sea by EDXRF spectrometry

Sea-bed sediments from Eastern Black Sea have been analyzed for their Fe, Ba and Sr contents using the methods of standard addition and energy dispersive X-ray fluorescence (EDXRF). Samples were prepared from powder sifted by a 200 mesh sieve. An annular 100 mCi²⁴¹Am radioactive source emitting 59.543 keV photons was used for excitation and a Ge(Li) detector, which has a 190 eV FWHM for 5.9 keV photons was used for intensity measurements. 2048 channels of the MCA are employed for 20 or 30 min. Dried and ground sea-bed sediments are found to contain 2.95–7.50% Fe, 0.032–0.268% Ba and about 73–273 ppm Sr. These results agree with those obtained via atomic absorption methods.     

Radiochemical studies on the separation of cobalt with sodium alginate

⁶⁰Co was used as indicator for studies on the separation of cobalt with sodium alginate. Effect of eight experimental parameters (digestion time, digestion temperature, mode of separation, concentration of reagents, pH, order of heating, ammonia, mixing of reagents) on the precipitation and separation of cobalt alginate have been investigated.     

A further test of the shape and anisotropy of the F---H2 interaction potential

A recently proposed anisotropic potential model for the interaction of a fluorine atom with a hydrogen molecule treated as a rigid rotor analysed by carrying out exact quantum calculations of elastic and rotationally inelastic differential cross sections for comparison with previoully reported F---H₂ and newly measured F---D₂ state selected measurements. The sensitivity of the cross sections to changes of the potential anisotropy and to isotopic substitution is examined. The results provide specific indications on the features of the best potential energy surface in terms of its average ‘size’ and its most likely anisotropy responsible for inelastic rotational excitations occuring at collision energies of about 85 meV.     

Provitamin D and vitamin D isomerizations in the mass spectrometer. Translational energy release and collision-induced dissociation studies

Collision-induced dissociation mass-analysed ion kinetic energy spectrometry and translational energy release studies have established that provitamin D₃ (7-dehydrocholesterol), provitamin D₂ (ergosterol), vitamin D₃ and vitamin D₂ isomerizations in the mass spectrometer occur at the fragment ion level leading to [M? H₂O? CH₃]⁺ ions of identical structure. It was found that the reaction, [M]⁺˙→[M? H₂O]⁺˙, plays a central role in these isomerizations.     

Chelate von Chinolin-8-01-Derivaten. V [I]. Komplexbildung und Extraktion von Nickel mit alkylsubstituierten Chinolin-8-olen

Chelates of 8-Quinolinol Derivatives. V. Coordination and Extraction of Nickel with Alkylsubstituted 8-Quinolinols . The nickel chelates of 2-, 5-, and 7-methyl-8-quinolinols and of a series of 7-alkyl-8-quinolinols were synthesized in the water-free state. Spectroscopic and magnetochemical differences between the compounds with 2-, 5-, and 7-methyl-8-quinolinols were explained by structural peculiarities. For the nickel chelates with 7-alkyl-8-quinolinols a somewhat distorted square-planar structure is supposed. To characterize the influence of substituents the adduct formation with pyridine was studied. For the extraction of nickel with 8-quinolinols the kind of the alkyl or alkenyl substituent in 7-position has no distinct influence on the state of the extraction equilibrium but it impairs the quickness of the extraction with increasing hydrophobicity.     

Experimental and Kinetic Modeling Study of Methanol Ignition and Oxidation at High Pressure

A detailed chemical kinetic model for oxidation of CH₃OH at high pressure and intermediate temperatures has been developed and validated experimentally. Ab initio calculations and Rice–Ramsperger–Kassel–Marcus/transition state theory (RRKM/TST) analysis were used to obtain rate coefficients for , , , and . The experiments, involving CH₃OH/O₂ mixtures diluted in N₂, were carried out in a high‐pressure flow reactor at 600–900 K and 20–100 bar, varying the reaction stoichiometry from very lean to fuel‐rich conditions. Under the conditions studied, the onset temperature for methanol oxidation was not dependent on the stoichiometry, whereas increasing pressure shifted the ignition temperature toward lower values. Model predictions of the present experimental results, as well as rapid compression machine data from the literature, were generally satisfactory. The governing reaction pathways have been outlined based on calculations with the kinetic model. Unlike what has been observed for unsaturated hydrocarbons, the oxidation pathways for CH₃OH under the investigated conditions were very similar to those prevailing at higher temperatures and lower pressures. At the high pressures, the modeling predictions for onset of reaction were particularly sensitive to the reaction.     

Modification of the magnetic properties of a heterometallic wheel by inclusion of a Jahn-Teller distorted Cu(II) ion

An investigation into the physical consequences of including a Jahn-Teller distorted Cu(II) ion within an antiferromagnetically coupled ring, [R(2)NH(2)][Cr(7)CuF(8)((O(2)C(t)Bu)(16))] is reported. Inelastic neutron scattering (INS) and electron paramagnetic resonance (EPR) spectroscopic data are simulated using a microscopic spin Hamiltonian, and show that the two Cr-Cu exchange interactions must be inequivalent. One Cr-Cu exchange is found to be antiferromagnetic and the other ferromagnetic. The geometry of the Jahn-Teller elongation is deduced from these results, and shows that a Jahn-Teller elongation axis must lie in the plane of the Cr(7)Cu wheel; the elongation is not observed by X-ray crystallography, due to positional disorder of the Cu site within the wheel. An electronic structure calculation confirms the structural distortion of the Cu site.