Total cross sections,elastic scattering observables and direct reconstruction of scattering matrix in np Interactions between 0.8 and 1.1 GeV at SATURNE II

Neutron-proton total cross section differences with the beam and target polarizations orientated either transversally or longitudinally with respect to the beam direction, as well as 11 spin dependent elastic scattering observables measured at SATURNE II as a function of energy and angle are presented. A major part of results was measured using the quasimonoenergetic polarized neutron beam and/or the polarized proton target. A small part of data was obtained using a polarized deuteron beam considered as a beam of quasifree neutrons and protons. The present paper represents a review of measured observables. Several sets of present data are compared with results obtained in other laboratories below 0.8 GeV. Imaginary parts of spin dependent forward amplitudes for np scattering and for the isospin stateI=0 were determined. First direct reconstruction of the np scattering matrix at 0.84 GeV is shown.We acknowledge support for this work from J. Arvieux, R. Beurtey, P. Borgeaud, P. A. Chamouard, A. Fleury, E. Heer, J. M. Laget, L. Musílek, L. Price, N. A. Russakovich, J. Saudinos, and J. Tolar. Discussions with J. Franz, J. M. Lagniel, C. Lechanoine-Leluc, G. Milleret, I. Strakovsky, and Y. Terrien have solved several problems. The exploitation of the polarized target owes a lot to G. Guillier, Ph. Marlet and J. Mommejat. We thank T. Lambert, E. Perrin, J. Poupard and J. P. Richeux for their efficient help in preparation of the experiment and the SATURNE II crew for unusual accelerator operations. Finally, we express our gratitude to Françoise Haroutel, who efficiently helped overcome all administrative requirements concerning a large international colaboration. This work was partly supported by the Swiss National Science Foundation and by the US Department of Energy Contract No. W-31-109-ENG-38.     

A slow positron lifetime study of the annealing behaviour of an amorphous silicon layer grown by MBE

We have studied MBE grown amorphous silicon, which was recrystallized at different temperatures for one hour, with a pulsed positron beam. A positron lifetime of 538±10 ps in the as-grown state is attributed to microvoids containing at least 10 vacancies. An incompletely recrystallized sample annealed at 500°C shows an additional long lifetime from ortho-positronium (o-Ps) pick-off annihilation. The o-Ps component disappears for samples, recrystallized at 700°C and above, and the defect lifetime steadily decreases with higher annealing temperature until a value of 310 ps is reached for the layer annealed at 1200°C. This value is explained by positron trapping at dislocations or small vacancy defects stabilized by dislocations or impurities.Paper presented at the 132nd WE-Heraeus-Seminar on Positron Studies of Semiconductor Defects, Halle, Germany, 29 August to 2 September 1994     

Zur Kristallzüchtung von Cadmiumsulfid und anderen II–VI-Verbindungen. IV. Zum Gleichgewicht zwischen Selen und Wasserstoff bei 400°C

The vapour pressure of Hg over HgSe (350–540°C) is determined by the transpiration method using N₂ and H₂ (with and without catalyst) as carrier gases. Evaluation according the equations listed in ?Inhaltsübersicht”? and regarding Se-polymerisation leads to the equilibrium function K_H2Se and to ΔH°₂₉₈ (H₂Se) = 6.4 kcal/mole. The new data are compared with literature values. The equilibrium composition of H₂Se is discussed.     

Preparation of the β3‐Homoselenocysteine Derivatives Fmoc‐β3hSec(PMB)‐OH and Boc‐β3hSec(PMB)‐OH for Solution and Solid‐Phase‐Peptide Synthesis and Selenoligation

The title compounds, 4 and 7 , have been prepared from the corresponding α‐amino acid derivative selenocystine ( 1 ) by the following sequence of steps: cleavage of the Se? Se bond with NaBH₄, p‐methoxybenzyl (PMB) protection of the SeH group, Fmoc or Boc protection at the N‐atom and Arndt–Eistert homologation (Schemes 1 and 2). A β³‐heptapeptide 8 with an N‐terminal β³‐hSec(PMB) residue was synthesized on Rink amide AM resin and deprotected (‘in air’) to give the corresponding diselenide 9 , which, in turn, was coupled with a β³‐tetrapeptide thiol ester 10 by a seleno‐ligation. The product β³‐undecapeptide was identified as its diselenide and its mixed selenosulfide with thiophenol (Scheme 3). The differences between α‐ and β‐Sec derivatives are discussed.     

Finitely cotilting modules

Over an arbitrary ring, we consider cotilting modules endowed with some finiteness conditions. We show that they correspond to pairs of dualities between certain cat-egories consisting of finitely presented modules. This extends the Cotilting Theorem proved by Colby for the noetherian case. The relationship with the cotilting modules studied by Colpi, D'Este, Tonolo and Trlifaj is also discuss.d.     

Detection of Copper Deposition on Anodes of Over-Discharged Lithium Ion Cells by GD-OES Depth Profiling

A method based on glow discharge optical emission spectroscopy (GD-OES) depth profiling is developed to detect copper deposition on graphite electrodes for the first time. Commercial 18650 cells with graphite anodes were subject to Cu dissolution by over-discharge to 0 V. On a first approach, the depth profiles for Cu show significant differences for over-discharged cells compared to a baseline graphite electrode from cells discharged to the end-of-discharge voltage. An accumulation of Cu is found on the anode surface by GD-OES, which is consistent with SEM and EDX. The trend of the total Cu amount is compared with ICP-OES measurements.