Metrological role of neutron activation analysis. IB. Inherent characteristics of relative INAA as a primary ratio method of measurement

This is the second part of a paper which deals with the advantages and disadvantages of relative instrumental neutron activation analysis concerning traceability and uncertainty, and the current scope and possible future extensions of neutron activation analysis as a primary ratio method. The first part of this paper has been published in this Journal [1]. Received: 19 March 2001 Accepted: 2 October 2001     

Synthesis and characterization of a new isocyanato carborane anion [7-OCN-7-CB10H12]; study on its reactivity toward amino containing compounds

The new isocyanato carborane anion, [7-OCN-7-CB₁₀H₁₂]⁻ was prepared by the reaction of 7-H₃N-7-CB₁₀H₁₂ with triphosgene in the presence of triethylamine. The structure of this compound was established by ¹H, ¹¹B and ¹³C NMR as well as IR spectroscopy. The reactivigty of this compound with a series of organic amines was investigated. The resulting ureas were obtained in good to excellent yields. This approach is suitable for development of compounds for use in tumor selective Boron Neutron Capture Therapy (BNCT).     

Small-angle neutron-scattering study of concentrated nonionic-amphiphile solutions

The structure of aqueous solutions of two polyoxyethylene non-ionic amphiphiles, C₁₀E₅ and C₈E₄, is studied by small-angle neutron-scattering along isothermal paths crossing the isotropic single-phase region from 0% to 100% amphiphile volume fractions. The scattered intensityI(k) shows a peak at a valuek _m , which grows monotonically as the amphiphile volume fraction increases. The interpretation of the scattering data lead to the following conclusion: as increases the micellar structure becomes less and less sharp, but some orientational correlations between neighboring amphiphile molecules are preserved even in the pure amphiphile phase.     

Phase transition and mixed oxide-proton conductivity in germanium oxy-apatites

La_9.75□_0.25(Ge₆O₂₄)O_2.62 oxy-apatite shows a phase transition from triclinic to hexagonal symmetry at approximately 1020 K that has been characterised by high-temperature synchrotron X-ray and neutron powder diffraction, and ionic conductivity measurements. The crystal structure at 1073 K has been determined from joint Rietveld refinements of synchrotron X-ray and neutron powder diffraction data. The study shows that hexagonal-La_9.75□_0.25(Ge₆O₂₄)O_2.62 contains interstitial oxygen at the position previously reported for other oxy-germanates. Changes in the oxide conductivity associated with this structural transition are discussed. The thermal analyses showed a weight loss on heating close to 600 K very likely due to water release. The synchrotron thermodiffractometric study shows an anomaly in the cell parameters evolution at that temperature, which indicates that this residual water is located into the apatite channels. The electrical characterisation under different atmospheres (dry and wet synthetic air) indicates that there is a significant proton contribution to the overall conductivity below 600 K, mainly under wet atmosphere.     

The Role of Chemistry in the Development of Boron Neutron Capture Therapy of Cancer

A therapeutic method that selectively destroys malignant cells in the presence of normal cells is a highly valued goal of oncologists and the possible salvation of cancer patients afflicted with some incurable forms of the disease. Selective cell destruction is, in principle, possible with a binary therapeutic strategy based upon the neutron capture reaction observed with the ¹⁰B nucleus and a neutron of low kinetic energy (thermal neutron). This nuclear fission reaction produces both ⁴He and ⁷Li⁺ nuclei along with about 2.4 MeV of kinetic energy and weak γ-radiation. Since the energetic and cytotoxic product ions travel only about one cell diameter in tissue one may specify the cell type to be destroyed by placing innocent ¹⁰B nuclei on or within only the doomed cells. This article describes the current status of chemical research aimed at the eventual adoption of this therapeutic method (boron neutron capture therapy or BNCT). The multidisciplinary nature of this research effort involves chemistry, biology, nuclear physics, medicine, and related specialties. Methods devised for bringing ¹⁰B nuclei to tumor cells in therapeutic amounts are correlated with the structure of a generalized cell and the various cellular compartments available for boron localization. The synthesis methods employed for the creation of boron-containing biomolecules and drugs are presented along with representative data concerning their efficacy in tumor localization. The outlook for BNCT is especially bright at this time because of rapid developments in the fields of bioorganometallic chemistry, microbiology, immunology, and nuclear science, to name but a few. Very effective boron delivery vehicles have been demonstrated, and through the interaction of chemistry and biology these species are undergoing further improvement and evaluation of their suitability for BNCT.     

The IINS, IR and DFT studies of hydrogen bonds in 6-Furfuryl and 6-Benzylaminopurines

FTIR and IINS spectra of 6-Furfurylaminopurine (6-FAP) and 6-Benzylaminopurine (6-BAP) taken at different temperatures have been analysed and compared with the spectra calculated by the ab initio DFT/B3LYP method and the semiempirical PM3 method in the isolated molecule approximation, for the tautomers N3-H, N7-H and N9-H, and dimers with hydrogen bonds. For 6-FAP the best agreement between the calculated and experimental (at 20 K) spectra has been found for the N9-H tautomer, whose structure was established by X-ray diffraction. For 6-BAP the analogous agreement for the N9-H tautomer structure has been poor and much better for the N7-H tautomer. The vibrational spectra calculated for dimers of the molecules studied involved in hydrogen bonds, permitted also an interpretation of the bands whose positions and FWHM in the FTIR spectra changed with temperature.     

Small angle neutron scattering studies on nonaqueous dispersions of calcium carbonate Part 2. Determination of the form factor for concentric spheres

Colloidal dispersions of calcium carbonate, stabilised primarily by a surface active agent, in both toluene and dodecane have been examined by small angle neutron scattering. A model has been developed to simulate the scattering behaviour of the particles and is based on the idea of a concentric sphere with a homogeneous layer of adsorbed material surrounding a core particle. Computations based on the model show a wide variation of scattering behaviour with variation of the coherent scattering length of the dispersion medium. These predictions were confirmed by experiment. A method is described for analysis of the experimental data which leads to a determination of the thickness of the adsorbed layer, the radius of the core particle and the standard deviation of core particle radius.     

K3MnH5, das erste salzartige Manganhydrid

K₃MnH₅, the First Salt-like Manganese Hydride K₃MnH₅ and K₃MnD₅ were synthesized by the reaction of potassium hydride (deuteride) with manganese powder under a hydrogen pressure above 3000 bar at 875 K. X-ray investigations on powdered samples and elastic neutron diffraction experiments on the deuterated compound at the time-of-flight spectrometer LAD in the temperature range 5–600 K led to the complete structure determination. The atomic arrangement is isotypic with that of Cs₃[CoCl₄]Cl (space group: 14/mcm, Z = 4). The structure of K₃MnH₅ contains isolated [MnH₄]^2?-tetrahedra and additional hydrogen ions which are exclusively coordinated by potassium cations. The magnetic susceptibilities show Curie-Weiss behaviour. At temperatures below 50 K there are obviously antiferromagnetic interactions.     

Synthese und Struktur von Li3RhH6, einem ternären Hydrid mit isolierten [RhH6]3−-Oktaedern

Synthesis and Structure of Li₃RhH₆ — a Ternary Hydride with Isolated [RhH₆]^3? Octahedra The ternary rhodium hydride Li₃RhH₆ was synthesized by the reaction of lithium hydride with rhodium under a hydrogen pressure of 80 bar. X-ray investigations on powdered samples and an elastic neutron diffraction experiment on the deuterated compound led to the complete structure determination (space group: Pnma, Z = 4). The atomic arrangement is isotypic to the Na₃RhH₆ structure type. The crystal structure contains isolated [RhH₆]^3? octahedra, which are separated by the lithium ions.     

Sol-Gel Routes to Zeolite Membranes and Thin Films

The synthesis of zeolite membranes and thin films using the secondary growth process is briefly described. In this process colloidal zeolite particles (sols) are prepared hydrothermally and then subsequently deposited on substrates to produce uniform layers of controlled thickness, as illustrated with silicalite and zeolite-A. The formation and growth of the zeolite sols has been investigated in situ by small angle neutron scattering (SANS). SANS measurements on silicalite sols at progressively higher concentrations have provided details of the colloid interactions which lead to zeolite gel-layer structures which are uniform and free of defects.