Crossing of shears bands in196Pb

High-spin states in¹⁹⁶Pb have been populated using the reaction¹⁷⁰Er(³⁰Si,4n). The previously observed shears bands in this nucleus have been extended and some of their transitions have been reordered. They now form regular bands with band crossings. One of the bands splits into two pathways at high spin.     

Tetracyclic alkaloids of the sparteine group.1H and13C NMR spectroscopy and conformational analysis

The¹H and¹³C chemical shifts of 11 sparteine derivatives are reported. Substituent and group effects are interpreted in terms of structural properties. The conformational equilibrium of aphyllin is determined.Ruhr-Universität Bochum, Fakultät für Chemie, Bochum, Germany. Universität Hannover, Institut für Organische Chemie, Hannover, Germany (present address). Department of Organic Chemistry, Poznan Academy of Economics, Poznan, Poland. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1026–1033, August, 1995. Original article submitted May 10, 1995.Dedicated to Prof. N. S. Zefirov on the occasion of his 60th birthday.     

Optical spectra and laser-induced dissociation of supported Na particles

This paper reports new results on the optical spectra of Na particles and on laser-induced photodissociation of Na atoms from the surface of these particles. In continuation of our earlier studies we have performed experiments to elucidate the mechanism of thenonthermal dissociation process. Furthermore, theoretical calculations have been carried out with the goal to correlate the wavelength dependence of the photodissociation yield with the optical absorption spectra of the metal particles. In addition, manipulation of the size distribution of metal particles on supports is outlined as an application of the effect. This allows for the preparation of very special surfaces with novel physical and chemical properties.     

Analysis of barbiturates in human serum and urine by high-performance capillary electrophoresis-micellar electrokinetic capillary chromatography with on-column multi-wavelength detection

The analysis of barbiturates in human serum (or plasma) and urine by high-performance capillary electrophoresis-electrokinetic capillary chromatography with on-column fast-scanning multi-wavelength detection is discussed. The use of a buffer of ca. pH 8 and containing sodium dodecyl sulphate provides a medium suitable for fast and high-resolution separations of barbiturates. Seven barbiturates are characterized by their retention and absorption spectra between 195 and 320 nm. Comparison of these computer-stored data with those of unknown samples is shown to allow the identification of barbiturates in samples of patients undergoing pharmacotherapy and in toxicological urine and serum specimens. Three-dimensional electropherograms provide reliable information on the requirement and suitability of sample pretreatment procedures. With urine, extraction of barbiturates prior to analysis is necessary. With human serum several barbiturates, including phenobarbital, are shown to elute in an interference-free window in front of uric acid and the proteins, allowing these substances to be determined by direct sample injection. The need for multi-wavelength detection over a relatively wide wavelength range as a means of peak confirmation in electrokinetic capillary analyses is demonstrated and limitations of this technique for compounds with similar retention behaviour and absorption spectra are discussed.     

First synthesis of magnesacyclopentadienes from acetylenes by treatment with BuMgHlg in the presence of Zr complexes

Treatment of internal acetylenes and allenes with BuMgHlg (Hlg = Cl, Br) in the presence of Cp₂ZrCl₂ selectively leads to the formation of substituted magnesacyclopenta-2,4-dienes and alkylidenemagnesacyclopentenes.     

Roughness reduction in submicron waveguides by low-molecular weight development

Roughness reduction of a submicron waveguide profile in chemically amplified negative resist is here performed by proper selection of an alkali-based developer, taking into account that its smaller molecules lead to smoother resist surface by altering the developing mechanism of aggregate extraction performed with standard quaternary ammonium hydroxide. Roughness is then analyzed by means of classical Atomic Force Microscope inspection; furthermore, a non-invasive line edge roughness analysis approach based on top-down scanning electron microscope acquisition gives comparable results, in terms of standard deviation and molecular aggregate periodicity.