Role of correlated two-pion exchange in K+NK^+ N scattering

A dynamical model for S-- and P--wave correlated $2 \pi$ (and $K \bar K$) exchange between a kaon and a nucleon is presented, starting from corresponding $N \bar N \rightarrow K \bar K$ amplitudes in the pseudophysical region, which have been constructed from nucleon, $\Delta$--isobar and hyperon ($\Lambda$, $\Sigma$) exchange Born terms and a realistic meson exchange model of the $\pi \pi \rightarrow K \bar K$ and $K \bar K \rightarrow K \bar K$ amplitude. The contribution in the s--channel is then obtained by performing a dispersion relation over the unitarity cut. In the $\rho$--channel, considerable ambiguities exist, depending on how the dispersion integral is performed. Our model, supplemented by short range interaction terms, is able to describe empirical $K^+ N$ data below pion production threshold in a satisfactory way.Comment: 24 pages, REVTEX, figures available from the author

Quality circle failure and how to avoid it

This paper, which is based on a nationwide postal questionnaire survey and case study work, presents the reasons why quality circles fail. These include rejection of the concept by top management, uncertainties caused by redundancies and company restructuring, labour turnover, lack of cooperation from middle and first line management, failure by circle leaders to find enough time to organise meetings and circles running out of projects to tackle. Opposition from the trade unions is only a minor stumbling block. Adequate facilitation, good circle leadership, continued management support and recognition, maintenance trade union support, and further training over time are the most important company controllable factors which can help to prevent quality circle failure.

Neutron diffraction studies at the Puerto Rico Nuclear center

A neutron diffraction program was initiated recently at the Puerto Rico Nuclear Center. The two double crystal spectrometers in use were assembled with the aid of staff members of the Brookhaven National Laboratory. The first research problem to be completed was a single crystal structure analysis of CaWO4. Choosing the origin at the 4(a) tungsten site in the tetragonal I4 1/a cell, the 16(f) oxygen parameters were found to be as follows : x = 0.2413 ± 0.0005, y = 0.1511 ± 0.0006, z = 0.0861 ± 0.0001. Anisotropic temperature parameters were also determined for all atoms in the least squares analysis of the structure. The magnetic structure of CuSO4 has been determined in a continuation of a study started at Brookhaven in collaboration with Dr. P. J. Brown. Using the Wollan-Koehler-Bertaut notation, the antiferromagnetic spin ordering mode in the orthorhombic Pbnm cell is Ax, i.e., + - +- on the 0 0 0, 0 0 1/2, 1/2 1/2 0, 1/2 1/2 1/2 sites, with the spin axis parallel to a. A moment of approximately 1 μB was found for the Cu2+ ion. The crystal structure of BaNiO2 was re-examined in a neutron powder diffraction study and Lander's x-ray result of a coplanar square coordination of Ni2+ was confirmed. BaNiO2 was also investigated for magnetic order at 4,2 °K but conclusive results have not been obtained. A magnetic transition has been found in Fe2SiO4 in the neighborhood of 30 °K. This compound has an olivine type structure with eight Fe2+ ions in the 4(a) and 4(c) positions of the Pbnm space group. Analysis of the magnetic structure is still in progress, but the dominant mode is C in the W.-K.-B. notation.Un programme de diffraction neutronique a été récemment établi au Centre d'Études Nucléaires de Puerto Rico. Les deux diffractomètres utilisés ont été assemblés avec l'aide de membres du Laboratoire National de Brookhaven. Le premier programme de recherche était l'achèvement de l'analyse de la structure d'un monocristal de CaWO4. En choisissant l'origine au site 4a) des atomes W dans la maille quadratique, groupe I41/a, on trouve les paramètres suivants de l'oxygène dans les sites 16(f) : x = 0,2413 ± 0,0005, y = 0,1511 ± 0,0006, z = 0,0861 ± 0,0001. Les paramètres anisotropes de vibration ont été également déterminés pour tous les atomes dans l'analyse aux moindres carrés de la structure. La structure magnétique de CuSO4 a été déterminée en continuation d'une étude, commencee à Brookhaven en collaboration avec le Dr P. J. Brown. Dans la notation de Wollan-Koehler-Bertaut, le mode de l'ordre antiferromagnétique des spins dans la maille orthorhombique du groupe Pbnm est Ax, c'est-à-dire sur les sites 0 0 0, 0 0 1/2 ; 1/2 1/2 0, 1/2 1/2 1/2, les spins se succèdent dans la suite + - + -, leur axe étant selon a. Un moment d'environ 1 μ B a été trouvé pour l'ion Cu2+. La structure cristalline de BaNiO2 a été réexaminée et le résultat obtenu par Lander aux rayons X d'une coordination carré coplanaire de Ni2+ a été confirmé. On a également cherché un ordre magnétique dans BaNiO2 à 4,2 °K, mais aucun résultat concluant n'a été obtenu. Une transition magnétique a été trouvée dans Fe2SiO4 au voisinage de 30 °K. Ce composé a une structure du type olivine avec huit ions Fe2+ dans les positions 4(a) et 4(c) du groupe d'espace Pbnm. L'analyse de la structure magnétique continue, mais le mode dominant est C dans la notation W.-K.-B