Predicting high harmonic ion cyclotron heating efficiency in Tokamak plasmas

Observations of improved radio frequency (rf) heating efficiency in ITER relevant high-confinement (H-)mode plasmas on the National Spherical Tokamak Experiment are investigated by whole-device linear simulation. The steady-state rf electric field is calculated for various antenna spectra and the results examined for characteristics that correlate with observations of improved or reduced rf heating efficiency. We find that launching toroidal wave numbers that give fast-wave propagation in the scrape-off plasma excites large amplitude (～kV?m(-1)) coaxial standing modes between the confined plasma density pedestal and conducting vessel wall. Qualitative comparison with measurements of the stored plasma energy suggests that these modes are a probable cause of degraded heating efficiency.     

Study of local atomic and electronic structure of titanium-containing forsterite based on analysis of X-ray absorption spectra

The local atomic structure of titanium-containing forsterite is investigated based on analysis of X-ray absorption near-edge structure (XANES) spectra. The Ti K-XANES spectra of the mineral under study are calculated for several possible structural models. Theoretical analysis of the X-ray absorption spectra is performed based on the full-potential finite-difference method. The local geometry of the titanium environment is determined by comparing the experimental Ti K-XANES spectrum with the theoretical spectra calculated for different structural models. The structural model where titanium atoms substitute for silicon ones is found to be most likely for titanium-containing forsterite. The calculated partial densities of electron states of titanium near the bottom of the conduction band of titanium-containing forsterite are analyzed.     

Determination of anthocyanins in the urine of patients with colorectal liver metastases after administration of bilberry extract

Anthocyanins possess cancer chemopreventive properties in preclinical models. Their clinical pharmacology is only poorly understood. In this pilot study, anthocyanins and their metabolites were analysed in the urine of two patients with colorectal liver metastases. They received a single dose of 1.88 g standardized bilberry extract (mirtoselect) via either nasogastric or nasojejunal tube intra‐operatively during liver resection. HPLC‐MS/MS and HPLC‐UV analysis showed there were more anthocyanins and metabolites in the urine of the patient who received mirtoselect via the stomach than via the jejunum. This result is consistent with information obtained in rodents which suggests the stomach is the predominant site for anthocyanin absorption. Copyright © 2010 John Wiley & Sons, Ltd.     

Lewis acid-mediated addition of silylated methylenecyclopropane to aldehydes—synthesis of tetrahydrofuran derivatives

Lewis acid-mediated intermolecular addition of silylated methylenecyclopropane to aldehydes provides a novel route to tetrahydrofuran derivatives.     

Iron-57 Mössbauer spectroscopy study of phases in the CaZrTi2−2x Nb x Fe x O7 zirconolite system

Materials of composition CaZrTi_2?2x Nb _x Fe _x O₇ with the fluorite-related zirconolite structure have been prepared. The ⁵⁷Fe Mössbauer spectra show that iron is initially located in the five co-ordinate cation sites. As the iron content increases the iron enters the octahedral sites until, at a composition CaZrTi_0.4Nb_0.8Fe_0.8O₇, ca. 50% of the iron is five co-ordinate and the remainder is located in the octahedral sites.     

Characterisation of the reduction properties of La0.5Sr0.5Fe0.5Co0.5O3

We report here on the characterisation by temperature programmed reduction, ⁵⁷Fe Mössbauer spectroscopy and X-ray absorption spectroscopy of the phases resulting from treatment of the perovskite-related material La_0.5Sr_0.5Fe_0.5Co_0.5O₃ in a flowing 90% hydrogen/10% nitrogen atmosphere. The results show that treatment of La_0.5Sr_0.5Fe_0.5Co_0.5O₃ (which contains approximately 50% Fe⁴⁺ and 50% Fe³⁺) in the flowing 90% hydrogen/10% nitrogen atmosphere at 600°C does not result in the reduction of any of the constituent elements of the material and that the perovskite structure is still retained. The Mössbauer spectrum recorded following heating in the gaseous reducing environment at 1,000°C shows the presence of metallic iron, an Fe³⁺-containing phase with parameters compatible with the presence of SrLaFeO₄ which has a K₂NiF₄-type structure, and a paramagnetic Fe³⁺ phase. The X-ray absorption spectroscopy results show the presence of metallic cobalt. The Mössbauer spectrum recorded following heating at 1,200°C continues to show the Fe³⁺-containing components plus a larger contribution from metallic iron. The X-ray absorption spectroscopy results show the presence of metallic cobalt, SrLaFeO₄, La₂O₃ and SrO.     

A study of the oxidation of europium(II) sulphide by europium-151 Mössbauer spectroscopy

The oxidation of solid europium(II) sulphide under mild conditions has been examined by¹⁵¹Eu Mössbauer spectroscopy. The results show that europium(II) sulphide is remarkably stable to oxidation at 25°C and is only partially converted to Eu³⁺ after exposure to air for four days. Treatment in air at a temperature of 250°C for six hours induces a similar degree of oxidation. The mechanism and kinetics of oxidation of curopium(II) sulphide under mild conditions in the solid state are therefore non-trivial matters.     

Industrial Applications of Mössbauer Spectroscopy

Hyperfine Interactions - The historical development of the use of Mössbauer spectroscopy in industrial applications is briefly outlined. The power of the technique for the study of...     

The Structural Characterization of Tin- and Titanium-Dopedα-Fe2O3Prepared by Hydrothermal Synthesis

The structural characteristics of tin- and titanium-dopedα-Fe₂O₃prepared by hydrothermal methods have been investigated by Rietveld structure refinement of the X-ray powder diffraction data. The analysis reveals that the dopant ions adopt two distinct sites: in addition to partially substituting at the octahedral Fe sites, they also occupy the interstitial octahedral sites which are vacant in theα-Fe₂O₃structure. The structural model deduced involves clusters of three substituted cations and is rational in that it represents microstructural regions of the rutile structure within a matrix ofα-Fe₂O₃.