Synthesis of pentacyclic lα,11-(2-oxethano) steroids

Treatment of a 1α,2α-methyleneandrostan analog (4) with hydrobromic acid/acetic acid gives an apparent intramolecular homoconjugate ring-opening, which serves as the key step in the synthesis of a new type of pentacyclic steroid analogs (2).     

Eigenvalue-Dynamics off the Calogero–Moser System

By finding N(N– 1)/2 suitable conserved quantities, free motions of real symmetric N×N matrices X(t), with arbitrary initial conditions, are reduced to nonlinear equations involving only the eigenvalues of X – in contrast to the rational Calogero-Moser system, for which [X(0),Xd(0)] has to be purely imaginary, of rank one.     

Vacancy-induced states on VC0.80 (110) identified using angle-resolved photoelectron spectroscopy

Angle-resolved photoemission measurements have been performed on the (110) face of a VC_0.80 single crystal using resonance radiation. A vacancy-induced peak is identified at about 1.7 eV below the Fermi energy. Comparison of the experimental peak dispersions with direct transitions between energy bands of VC_1.0 is also made.     

Friedel oscillations around an adatom

Friedel oscillations around an adatom on a metal surface are studied analytically and numerically. Non-linear response and a general surface model potential are used. Parallel to the surface the amplitude of the oscillations goes as r^?5 but any other direction into the metal as r^?3.     

An XPS round robin investigation on analysis of wood pulp fibres and filter paper

X-ray photoelectron spectroscopy (XPS) has been applied to pulp and paper research for decades. However, there has been no attempt to standardise or even systematically compare experimental and analysis procedures, even though it is known that fibrous, nature-derived and insulating fibre materials pose remarkable challenges to reliable surface analysis. The experimental problems are mainly linked with neutralisation, energy resolution, contamination and X-ray induced degradation.We have tested applicability, reliability and reproducibility of XPS analysis on real pulp samples with varying lignin and extractives contents in a small round robin investigation. We also tested the instrumental set-ups with an acetone-extracted filter paper, used as a reference sample. The data, collected at four different laboratories with state-of-the-art instruments indicate that reproducible results can be obtained, despite minor differences in experimental and analysis procedures. However, we found that a specified sample handling procedure and limited X-ray exposure are crucial for reproducible, reliable data.Based on the round robin data we recommend dose restricted monochromatic measurements, a cellulosic in situ reference and a consistent sample handling procedure. The data confirms that a paper-based reference material and the correlation of high-resolution C 1s data with O/C atomic ratios can be used in testing instruments and experimental set-ups for pulp and paper materials.     

Intrinsic surface binding energy shifts in Yb metal

We report on the four-peak structure observed in the region of 4f photoemission in Yb metal, using synchrotron radiation in the energy range 70–200 eV. We conclude, contrary to previous reports, that the doublet associated with surface emissions results from an intrinsic surface shift on clean regions of the surface. We also demonstrate that the observed structure is consistent with earlier XPS measurements, and we set an upper limit on the width of the bulk peaks.     

Elastic and inelastic scattering of 178 MeV protons from 58Ni and 60Ni

The elastic and inelastic scattering of 178 MeV protons from ⁵⁸Ni and ⁶⁰Ni has been studied. Angular distributions were measured for the differential cross sections for elastic scattering as well as inelastic scattering from excited states below about 5 MeV, all with natural parity. For the elastic and for the inelastic scattering from the first excited state (2⁺ in both nuclei, the angular distributions for the polarization were also measured. The measurements extend out to c.m. angles of about 60°, corresponding to a momentum transfer of about 600 MeV/c.The elastic and inelastic scattering data were compared to the results of coupled-channel calculations in the vibrational model using a deformed spin-orbit interaction of the full Thomas form. Good agreement was found in general showing that the main features of the experimental results are well described in this model.     

A multiple grating flame photometer for the simultaneous determination of five elements

A flame emission spectrometer for the simultaneous determination of five elements has been constructed. The instrument is built around a special holographic diffraction grating, built up from several smaller gratings with different ruling characteristics, each covering a different spectral range. It is provided with automatic background correction and a photon counting system. Sensitivity and precision are good. The instrument is compared with other multichannel flame emission systems. Construction of the spectrometer including electronics is described.     

Measurement and calculation of guide vane performance in expanding bends for wind-tunnels

 The design of guide vanes for use in expanding bends was investigated both experimentally and numerically. The primary application in mind is the use of expanding corners in wind-tunnels for the purpose of constructing compact circuits with low losses. To investigate the performance of guide vanes in realistic situations expansion ratios between 1 and 53 were tested in the experiments. These were carried out in an open wind-tunnel specially built for the present purpose. The experimental results demonstrated that suitably designed guide vanes give very low losses and retained flow quality even for quite substantial expansion ratios. For wind-tunnel applications expansion ratios around 1.3 seem appropriate, Optimization of a guide vane design was done using a two-dimensional cascade code, Mises. A new vane optimized for an expansion ratio of 43 gave a two-dimensional total pressure-loss coefficient as low as 0.041 for a chord Reynolds number of 200,000. Received: 7 April 1997/Accepted: 11 August 1997