Magnetic properties of Nd3+ in Nd−Ba−Cu−O-compounds

Neutron diffraction, neutron spectroscopy and magnetization measurements have been employed to study the structural, electronic, and magnetic behavior of eleven compounds with the general formula Nd_1+y Ca _v Ba_2–y–v Cu₃O _x (0y0.5; 0v0.25; 6x7). The structure turned out to react to oxygen reduction similar as other 123-compounds, yielding discontinuities close to the metal-insulator-transition and the well-known relations of bond lengths as a function ofT _c. The crystalline electric field (CEF) interaction, splitting the 10-fold degenerate ground-state J-multiplet of the Nd³⁺-ions into five doublet states, was investigated by neutron spectroscopy. The derived CEF parameters have been used to determine changes in the electronic surroundings of the Nd³⁺ ions. In addition, with the help of the CEF parameters the thermodynamic magnetic properties of these compounds were calculated which turn out to be in good agreement with the experimental data.     

Characterization and Transport Properties of Surfactant-Templated Silica Layers for Membrane Applications

An intermediate surfactant-templated silica (STS) layer is applied between the supporting mesoporous γ-Al₂O₃ and the amorphous microporous silica overlayer resulting in dual-layered microporous silica membranes for gas separation applications that show improved values for both hydrogen flux and selectivity. Determination of thickness and porosity of as-deposited membrane layers by spectroscopic ellipsometry reveals that the STS layer is present as a distinctive layer of ～20 nm thickness, with penetration up to a depth of ～70 nm into the underlying γ-Al₂O₃support layer, whose thickness and porosity are determined to be 1.3 μm and 50%, respectively.     

Synthesis of benzophenone-containing analogues of phosphatidylcholine

As part of a collaborative study of cellular efflux of cholesterol and phospholipids, photoactivable analogues 4-8 of phosphatidylcholine (PC) having benzophenone groups in the choline moiety and at the end of the C2 and C1 alkyl chains have been synthesized. The efficient preparation via Suzuki coupling of the appropriate long-chain benzophenone-containing carboxylic acid and alcohol and their incorporation by adaptation of known approaches into the acyl- and ether-linked PC analogues 6-8 are described. Development of a method for radiolabeling these PC analogues, via hydrogenation of a double bond in modified side chains, is also described.     

Gaschromatographische Untersuchung der Adsorptionseigenschaften von Silicalit und ZSM-5

High silica molecular sieves (silicalite, ZSM-5) were tested as adsorbents for gas chromatographic trace analysis. Therefore the retention behaviour of low-boiling organic compounds (hydrocarbons, halogenated hydrocarbons, amines, alcohols and ethers) on these materials was investigated. The specific retention volumes at different temperatures have been determined and elution orders and peak shapes were studied. The retention data allow a simple calculation of the breakthrough volumes (dynamic adsorption capacity) and the chromatographic characterisation of the adsorbents. Both nitrogen and oxygen containing compounds could not—or at least unreproducibely—be eluated up to 300°. The elution order and the peak shape of compounds with the same number of carbon atoms but different geometric and electronic structure (e.g.n-butenes;n-hexane, cyclohexane, benzene) can be explained by the action of exclusion effects and different diffusion barriers. On the basis of calculated breakthrough volumes we conclude that silicalite should be useful in the preconcentration of both saturated C₃–C₆ hydrocarbons and C₁–C₂ chlorinated hydrocarbons from gaseous streams.     

Zur reaktion von metall-koordiniertem kohlenmonoxid mit yliden: XXI. Ambidentes verhalten von eisenacyl-phosphor-yliden gegenüber methylfluorsulfonsäureester: Umwandlung in eisenacyl-phosphoniumsalze oder β-phosphoniovinyl- eisenkomplexe

]The reaction of the acyliron phosphorus ylide Cp(CO)₂FeC(O)CHPMe₃ with MeOSO₂F yields the acyliron phosphonium salt [Cp(CO)₂FeC(O)C(Me)- HPMe₃]SO₃F, while Cp(CO)₂FeC(O)C(Me)PEt₃ undergoes exclusively O-alkylation to the complex salt [Cp(CO)₂FeC(OMe)C(Me)PEt₃]SO₃F, (A). The acyliron ylides Cp(CO)₂FeC(O)C(R)PR₃ (R  R′  Me; or R  H, R′  Et) are converted to a mixture of the O- and C-methylated products. According to spectroscopic data and X-ray diffraction analysis of A the O- alkylation products have to be described as phosphoniovinyliron complexes.     

A remark about the justification of the nonlinear Schrödinger equation in quadratic spatially periodic media

We prove the validity of a technical assumption necessary in a proof of the validity of the nonlinear Schr?dinger equation as envelope equation in quadratic spatially periodic media.      

Zur Methylalkoholbestimmung in Formaldehydl?sungen mittels Chroms?ure

Ohne Zusammenfassung     

The β-decay of 22Al

In an experiment performed at the LISE3 facility of GANIL, we studied the decay of ²²Al produced by the fragmentation of a ³⁶Ar primary beam. A β-decay half-life of T_1/2 = 91.1±0.5ms was measured. The β-delayed one- and two-proton emission as well as β-α and β-delayed γ-decays were measured and allowed us to establish a partial decay scheme for this nucleus. New levels were determined in the daughter nucleus ²²Mg. The comparison with model calculations strongly favours a spin-parity of I^π = 4⁺ for the ground state of ²²Al.