First approach to radionuclide mixtures quantification by using plastic scintillators. Influence of the diameter of the plastic beads

Recent studies have evaluated the capability of plastic scintillation (PS) as an alternative to liquid scintillation (LS) in radionuclide activity determination without mixed waste production. In order to complete the comparison, we now assess the extent to which PS can be used to quantify mixtures of radionuclides and the influence of the diameter of the plastic scintillation beads in detection efficiency.

The results show that the detection efficiency decreases and the spectrum shrink to lower energies when the size of the plastic scintillation beads increases, and that the lower the energy of the beta particle, the greater the variation takes place. Similar behaviour has been observed for beta–gamma and alpha emitters.

Two scenarios for the quantification of mixtures are considered, one including two radionuclides (¹⁴C and ⁶⁰Co) whose spectra do not overlap significantly, and the other including two radionuclides (¹³⁷Cs and ⁹⁰Sr/⁹⁰Y), where the spectra of one the isotopes is totally overlapped by the other The calculation has been performed by using the conventional window selection procedure and a new approach in which the selected windows correspond to those with lower quantification errors. Relative errors obtained using the proposed approach (less than 10%) are lower than those of the conventional procedure, even when a radionuclide is completely overlapped, except for those samples with extreme activity ratios that were not included in the window optimization process.     

Comparative validation of amisulpride determination in pharmaceuticals by several chromatographic, electrophoretic and spectrophotometric methods

Depleted uranium (DU) is a by-product of the uranium enrichment process for nuclear fuel. According to the Commission Decision 2002/657/EC, a confirmatory method for the quantification of DU in freeze-dried fish was developed by isotope ratio dynamic reaction cell inductively coupled plasma-mass spectrometry (IR-DRC-ICP-MS). A preliminary study was performed to determine the following parameters: instrumental detection limit (IDL), isotopic ratio measurement limit (IRML), percentage of DU (P(DU)) in presence of natural uranium (NU) and limit of quantification (LoQ(DU)). The analyses were carried out by means of IR-DRC-ICP-MS. Ammonia was the reaction gas used for the dynamic reaction cell. In addition, a sector field inductively coupled plasma mass spectrometer (SF-ICP-MS) was employed to calculate the within-laboratory reproducibility. For the confirmatory method the following parameters were determined: (a) trueness; (b) precision; (c) critical concentrations alpha and beta (CC(alpha), CC(beta)); (d) specificity; (e) stability. Trueness was assessed by using the recovery tests. The recovery and within-laboratory reproducibility were determined by fortifying the blank digested solution of dogfish tissue: six aliquots were fortified at 1, 1.5 and 2 times the LOQ(DU) with 25.0, 37.5 and 50.0 ng L(-1) or 4.16, 6.24, 8.32 microg kg(-1) with a recovery of -8.2, +9.5 and +9.6%, respectively and a within-laboratory reproducibility (three analytical run) of 15.5, 8.0 and 11.0%, respectively. The results for the decision limit and the detection capability were: CC(alpha) = 11.69 ng L(-1) and CC(beta) = 19.8 ng L(-1). The digested solutions resulted to be stable during testing time (60 days) and the method can be considered highly specific as well.     

H/D isotopic recognition in hydrogen bonded systems: H/D isotopic self-organization effects in the IR spectra of the hydrogen bond in 2-methylimidazole crystals

Polarized IR spectra of H12(3)45 2-methylimidazole and of its H1D2(3)45, D1H2(3)45 and D12(3)45 deuterium derivative crystals are reported and interpreted within the limits of the "strong-coupling" theory. The spectra interpretation facilitated the recognition of the H/D isotopic "self-organization" phenomenon, which depends on a non-random distribution of protons and deuterons in the lattices of isotopically diluted crystal samples. The H/D isotopic "self-organization" mechanism engaged all four hydrogen bonds from each unit cell. These effects basically resulted from the dynamical co-operative interactions involving adjacent hydrogen bonds in each hydrogen bond chain. A weaker exciton coupling involved the closely spaced hydrogen bonds; each belonging to a different chain of associated 2-methylimidazole molecules. The high intensity of the narrow band at ca. 1880cm(-1) was interpreted as the result of coupling between the γ(N-H?N) proton bending "out of plane" vibration overtone and the ν(N-H) proton stretching vibration.     

Synthesis, 5-hydroxytryptamine1A receptor affinity and docking studies of 3-[3-(4-aryl-1-piperazinyl)-propyl]-1H-indole derivatives

A series of 3-[3-(4-aryl-1-piperazinyl)-propyl]-1H-indole derivatives (12a-h) was synthesized and evaluated for binding affinity at the human 5-hydroxytryptamine(1A) receptor (5-HT(1A)R) compounds (12b) and (12h) showed the highest 5-HT(1A) receptor affinity (IC(50)=15 nM). Molecular docking studies with all the compounds in a homology model of 5-HT(1A) showed that the main interaction anchoring the ligand in the receptor was a charge-reinforced bond between the protonated nitrogen atom (N-4) of the piperazine ring and Aspartate(3.32).     

Hydrothermal Synthesis and Crystal Structure of Iron Molybdophosphate Fe[Mo_6O_(12)(OH)_3(H_2PO_4)(HPO_4)_2(PO_4)]_2- [Fe(2,2′-bipy)(H_2O)_2]_2[Fe(2,2′-bipy)_3]_2·6H_2O

1 INTRODUCTION Organic-inorganic hybrid materials and polyoxo-metalates have received much attention because of their intriguing structural diversity and potential applications in molecular adsorption, ion exchange, heterogeneous catalysis and nanotech nology as well as in electrical, magnetic and photochemical areas[1, 2]. One of the important ad- vances in the design of new organic-inorganic hybrid materials is utilizing poly- oxometalates’ coordination ability to produce poly- oxoanio…     

The O((1)D) + H2 (X (1)Σ+, v, j) → OH(X (2)Π, v', j') + H((2)S) reaction at low collision energy: when a simple statistical description of the dynamics works

In this communication, we highlight that statistical approaches for chemical reactions describe reasonably well the low energy dynamics of the title process. Consequently, such methods prove to be valuable to compute rate constants from low to room temperatures. Results are compared with experiment and recent precise quantum wave packet calculations [J. Phys. Chem. A, 2009, 113, 5285].     

Monitoring and analytics of semivolatile organic compounds (SVOCs) in indoor air

This paper reviews literature information on the behaviour of semivolatile organic compounds (SVOCs) in the indoor environment, as well as the most likely emission sources. The consecutive stages of analytical procedures used for monitoring SVOCs in indoor environments are described. The most common approaches used for collecting samples from the gas and particulate phases are mentioned. The paper discusses and compares various types of sorbents and filters applied in dynamic, passive and denudational techniques, as well as the techniques used to liberate the SVOCs, including Soxhlet, sonication and microwave extraction. The main advantages and disadvantages of each technique are discussed, together with possible future trends. The approaches commonly used during the final determination step, such as gas chromatography and liquid chromatography, are presented together with their possible drawbacks, and ways of eliminating them are suggested. The review makes brief reference to the effects of human exposure to SVOCs in house dust and discusses the main aspects of the analytical procedures used to monitor the presence of SVOCs in this medium.     

Electroluminescence in ruthenium(II) complexes

We have investigated the electrochemical, spectroscopic, and electroluminescent properties of a family of diimine complexes of Ru featuring various aliphatic side chains as well as a more extended pi-conjugated system. The performance of solid-state electroluminescent devices fabricated from these complexes using indium tin oxide (ITO) and gold contacts appears to be dominated by ionic space charge effects. Their electroluminescence efficiency was limited by the photoluminescence efficiency of the Ru films and not by charge injection from the contacts. The incorporation of di-tert-butyl side chains on the dipyridyl ligand was found to be the most beneficial substitution in terms of reducing self-quenching of luminescence.     

Asymmetric 1,3-dipolar cycloaddition of N-metalated azomethine ylides to methyl (S)-2-(p-tolylsulfinyl)acrylate. Synthesis of optically pure 2,4,5-trisubstituted 2,5-dihydro-1H-pyrroles

The first 1,3-dipolar reaction of azomethine ylides with optically pure vinyl sulfoxide are reported. The presence of the sulfinyl group increase the reactivity of the acrylate moiety as a dipolarophile, and the reactions evolve with complete regio- and endo-selectivities. Nevertheless, mixtures of the two diastereoisomers 4 and 5 (75-88% de) resulting from the anti dipole/s-cis dipolarophile and syn dipole/s-trans dipolarophile approaches, respectively, are obtained. The stereoselectivity can be controlled by using THF or MeCN as solvents or by changing the reaction temperature in MeCN. After separation of the cycloadducts, optically pure 2,5-dihydro-1H-pyrroles are easily obtained by pyrolytic desulfinylation.     

Influence of the Meniscus at the Bottom of the Solid Plate on Imbibition Experiments

The analysis of the experiments on liquid imbibition into porous solids carried out by using the increase of weight technique proves the influence that meniscus formation has on the experimental increase of weight when the bottom of the porous layer is put in contact with the free surface of the liquid used to perform the penetration experiments. This process (meniscus onset) has a temporary dependence due to the change of the distance between the inferior base of the plate and the free surface of the liquid as a result of the imbibition. We have also found the proper experimental conditions under which such temporary dependence can be minimized after a short time after the start of contact between the porous layer and the free surface of the liquid utilized in the penetration procedure. Thus, the weight increase because of the meniscus formation can be assumed as a constant during the greatest part of the experiments, allowing the use of the proper mathematical form of Washburn's equation in order to describe the imbibition of the liquid into the pores of the solid. Copyright 2001 Academic Press.