Chemie und Struktur Einiger Spinelle

Zusammenfassung Es gibt viele Varianten in der Feinstruktur von VerbindungenAB ₂O₄ mit Spinellstruktur, wenn die IonenA undB beide zwei-und dreiwertig sein können. Eine systematische Betrachtung zeigt, daß neben den gebräuchlichen kristallographischen Strukturparametern noch 4 oder 5 andere Variablen auftreten können.Für Ferriten wird die Bestimmung einiger dieser Variablen besprochen.

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Chemistry and structure of some spinels

There are many possibilities for the exact crystal structure of compoundsAB ₂O₄ with spinel structure, in which the ionsA andB may both have the valency two or three. It is shown that apart from the normal crystallographic structural parameters at least 4 or 5 other parameters may occur. The determination of some of these in ferrites is discussed.

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Many-to-many location-routing with inter-hub transport and multi-commodity pickup-and-delivery

In this paper, we consider a variant of the many-to-many location-routing problem, where hub facilities have to be located and customers with either pickup or delivery demands have to be combined in vehicle routes. In addition, several commodities and inter-hub transport processes are taken into account. A practical application of the problem can be found in the timber-trade industry, where companies provide their services using hub-and-spoke networks. We present a mixed-integer linear model for the problem and use CPLEX 12.4 to solve small-scale instances. Furthermore, a multi-start procedure based on a fix-and-optimize scheme and a genetic algorithm are introduced that efficiently construct promising solutions for medium- and large-scale instances. A computational performance analysis shows that the presented methods are suitable for practical application.     

In situ activation analysis of marine sediments with252Cf

A seabed nuclear probe has been developed which permits the measurement of up to 33 elements at the parts per thousand to parts per million levels in continental shelf areas. The probe consists of a neutron irradiation source,²⁵²Cf, which neutron activates the elements in the minerals of interest. These resulting radioactive elements emit characteristic gamma radiation which is analyzed in situ in 2- to 10 min counting intervals with a Ge(Li) detector system. Details of the irradiation source, the Ge(Li) detector, and spectra taken in situ in a marine environment are discussed with respect to the detection of the minerals at concentrations of economic interest.     

Isobaric analogue resonances in proton scattering on Ba

Extensive experimental data for the resonance scatttering of protons to the ground state and first excited state in ¹³⁸Ba are presented. A Breit Wigner analysis with a background term of the form Σ_n(a_n/Eⁿ) is performed and the extracted background function is compared with optical-model calculations using the parameters given in a detailed investigation by Perey. Neutron spectroscopic factors calculated in different ways from this data are compared with the corresponding factors from (d, p). An accurate determination of resonance energies for the first two resonances reveals a deviation from a constant Coulomb shift of the order of 10 keV.     

Permeability of oxygen through polycarbonate in water

The permeability of oxygen in water through polycarbonate is observed for thin Makrofol KG and Polyethylenterephthalat (PETP) foils of different thicknesses.

For each thickness the oxygen permeability through the polymer foils has been measured for unirradiated and with a high fluence irradiated foils. It was found that the permeability of oxygen through irradiated Makrofol KG foils is up to a factor of two higher than unirradiated foils.

The foils were irradiated with ⁷⁹Au ions at the energy of 11.65 MeV/u at GSI Darmstadt, Germany.     

High-performance liquid chromatographic method for the determination of alprazolam in plasma using the column-switching technique.

A reversed-phase high-performance liquid chromatographic method is described for the quantitative determination of alprazolam in the plasma of geriatric patients in the presence of 4-hydroxyalprazolam, alpha-hydroxyalprazolam, bromazepam, oxazepam, lorazepam, clobazam, desmethylclobazam, diazepam and desmethyldiazepam. The procedure is based on the enrichment of alprazolam on a PRP-1 pre-column, followed by the transfer of the compound in a forflush mode to the analytical column. Alprazolam can be quantified reliably down to a minimum concentration of 1 ng/ml of plasma.     

Morphology of polyphosphazenes: Oriented and unoriented

The purpose of this work is to obtain a better understanding of the morphology of polyphosphazenes and to establish some general morphological characteristics. Solution cast, stretched and annealed films of poly(bistrifluoroethoxyphosphazene), PBFP, and poly(bisphenoxyphosphazene), PBPP, have been investigated by electron and optical microscopy. Thin and thick films were prepared using different solvents. Films were cast and stretched below as well as above T(1), the thermotropic transition of each polymer. In the case of PBFP its T(1) transition was established through birefringent-temperature measurements and orientational changes were measured as a result of heat cycling stepwise through T(1). Thin specimens were oriented on electron microscope grids using a mechanical stretcher; thicker films were drawn by hand at various temperatures, too. Orientation was effectively induced through casting on hot liquid surfaces at temperatures > T(1). PBPP exhibits a layer (domain) morphology of high crystallinity and orientation under these conditions. Dislocations or stacking faults can be recorded in darkfield in PBPP but the low stability of PBFP to the electron beam does not permit dark-field images to be recorded. Optical microscopy was used to record cast film textures.Paper presented at: Frühjahrstagung der Deutschen Physikalischen Gesellschaft und der Polymer-Gruppe Schweiz, Lausanne 18.–20. März, 1985.Dedicated to Professor H.-G. Kilian's 60th birthday.     

Direct assay techniques for comprehensive radionuclide quantification of radwaste packages

Battelle, Pacific Northwest Laboratories has recently developed, tested and field-demonstrated a technology for the direct assay of transuranic radionuclides (TRU), fission products, and activation products in a variety of radwaste packages generated at commercial nuclear power plants. This technology involves non-destructive passive neutron counting for determination of nanocurie/gram quantities of the TRU radionuclides. Direct gamma spectrometry combined with thermoluminescent dosimetry (TLD) and correlation analysis is also utilized to determine the concentrations of the fission and activation products present in the radwaste packages. Employing counting times of 10 to 20 minutes, a complete analysis of all radionuclides specified for assay by the U.S. Nuclear Regulatory Commission (in 10CFR61) prior to shallow-land disposal of commercial radwastes can be measured at concentrations at least tenfold below the least restrictive Class A waste catagory.