Magnetic, electronic, and structural characterization of nonstoichiometric iron oxides at the nanoscale

We have investigated the structural, magnetic, and electronic properties of nonstoichiometric iron oxide nanocrystals prepared by decomposition of iron(II) and iron(0) precursors in the presence of organic solvents and capping groups. The highly uniform, crystalline, and monodisperse nanocrystals that were produced enabled a full structural and compositional survey by electron microscopy and X-ray diffraction. The complex and metastable behavior of nonstoichiometric iron oxide (wüstite) at the nanoscale was studied by a combination of Mossbauer spectroscopy and magnetic characterization. Deposition from hydrocarbon solvents with subsequent self-assembly of iron oxide nanocrystals into superlattices allowed the preparation of continuous thin films suitable for electronic transport measurements.     

Zur komplexchemie von 4-zentren-π-systemen : XII. Glyoxaldiiminkomplexe: 1H-nmr-spektren und long range-kopplungen

Glyoxaldiimines (I) RN=CHCH=NR show in the NMR a downfield shift of glyoxalic protons (H_gly) when complexed to

(II: M = Mo, W), but increasing high field shifts when going to

(III) and

complexes (IV). In the tungsten complexes II H_glyW coupling satellites are resolved (J(WH) ≈4–6 Hz); in the phosphine compounds III, IV long range PH_gly coupling is clearly visible. Mechanisms of spinspin interaction are briefly discussed in connection with the EPR results on monoanionic radicals of II–IV.     

Development of a very low energy μ+ beam at PSI

At PSI we are investigating the technique of decelerating an existing very intense secondary beam of surface ⁺ (4 MeV) to an energy of 10 eV using appropriate moderators. These ⁺ can then be used as a source of a tertiary beam of low energy muons with tunable kinetic energy between 10 eV and 10 keV.With a 1000 A layer of solid Argon deposited on an Al substrate we obtain a moderation efficiency (with respect to the number of incoming surface ⁺) of the order of 10^–4.Results of our investigations and the present status of the project are presented together with future plans and possibilities.     

AES investigations of the iron surface composition after laser irradiation under atmospheric conditions

The laser induced modification of iron surfaces with atmospheric species was investigated by means of Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). Different laser systems were used for irradiating iron samples in a wide range of the laser processing parameters up to small foci and ultra short pulses.A nitriding of iron connected with an oxidation of the near surface region was observed in the wavelength range between 193 nm and 10.6 m using large foci (0.1 cm²) and short pulses (10...1400ns). In case of small foci (7·10^–6cm²) with ns-pulses (50 ns) an enrichment of the iron melt with nitrogen and an advanced oxidation of the surrounding area of the laser spot were detected. When using shorter pulses (200 fs, 40 ps) no indications for a nitriding were found.     

Structural analysis of Cryptosporidium parvum.

Cryptosporidium parvum (Apicomplexa, formerly Sporozoa) is the causative agent of cryptosporidiosis, an enteric disease of substantial medical and veterinary importance. C. parvum shows a number of unique features that differ from the rest of the class of coccidea in which it is currently grouped taxonomically. Differences occur in the overall structure of the transmission form and the invasive stages of the parasite, its intracellular location, the presence of recently described additional extracellular stages, the host range and target cell tropism, the ability to autoinfection, the nonresponsiveness to anticoccidial drugs, the immune response of the host, and immunochemical and genetic characteristics. These differences have an important impact on the infectivity, the epidemiology, the therapy, and the taxonomy of the parasite. The present article describes the structural analysis of the parasite using light and electron microscopy with an emphasis on structural details unique to C. parvum.     

Nachweis der Exposition gegen O,O-Dimethyl-O-(3-methyl-4-nitrophenyl)-thiophosphat durch die Bestimmung von p-Nitro-m-kresol im Harn

Zusammenfassung Die spektrophotometrische Bestimmung von p-Nitro-m-kresol bei 400 nm wurde zum Zweck eines frühzeitigen und empfindlichen Nachweises der Exposition, sowie zur Untersuchung des Metabolismus von Metation (Folithion, Sumithion) modifiziert. Nach der sauren Hydrolyse von Harn beseitigt man die Harnpigmente durch Oxydation mit H₂O₂ und durch Abtrennung von p-Nitro-m-kresolat durch Ausschütteln mit Acetonitril aus 5 n Natronlauge. Die Ausbeute der Rückgewinnung bei einer Konzentration von 0,5 ppm p-Nitro-m-kresol betrug 97,3±6,3%, bei 5 ppm 92,6±2,4%. Bei stark pigmentierten Harnen (insbesondere tierischer Herkunft) wird eine weitere Reinigung vorgenommen und zwar durch die Beseitigung der Abbauprodukte mit Oxalatpuffer aus Toluol. Die Ausbeute betrÄgt bei 0,5 ppm 86,5±5,1%, bei 5 ppm 85,2±3,1%. Die untere Bestimmungsgrenze liegt bei 1,5 g p-Nitro-m-kresol in 10 ml Harn (0,15 ppm).

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Summary The early and sensitive detection of an exposure to Metation (Folithion, Sumithion) has been performed by a modified spectrophotometric determination of p-nitro-m-cresol in the urine at 400nm. After acid hydrolysis of the urine the pigments are removed by means of oxidation with H₂O₂ and separation of p-nitro-m-cresol by extraction from 5 N NaOH solution into acetonitrile. The recovery of p-nitro-m-cresol was 97.3±6.3% and 92.6±2.4% with concentrations of 0.5 ppm and 5 ppm, respectively. Further purification is required for highly pigmented urines (especially of animal origin), viz., the removal of decomposition products by extraction from toluene solution into oxalate buffer. 86.5±5.1% and 85.2±3.1% have been recovered with concentrations of 0.5 ppm and 5 ppm, respectively. The lower limit of determination is 1.5 g of p-nitro-m-cresol in 10 ml of urine (0.15 ppm).

     

Natural Occurrence of Enantiomeric and meso-Astaxanthin. 5. Ex wild salmon (Salmo salar and Oncorhynchus)

The configurational isomers of astaxanthin (3,3′-dihydroxy-β,β-carotene-4,4′-dione) from the flesh of salmon (Salmo salar and Oncorhynchus) caught at different places in Europe and Canada were isolated and analyzed as (?)-camphanic acid diesters by means of HPLC. The biological variation in the composition of the configurational isomers in seven fish was surprisingly similar: 78 to 85% of (3S, 3′S)-astaxanthin, 12 to 17% (3R, 3′R)-astaxanthin and 2 to 6% meso-astaxanthin.