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The behavior of a water molecule in Na6[AlSiO4]6 sodalite has been investigated using density functional calculations. The lowest energy position of the molecule is near the plane of the 6-ring window which does not contain a Na ion. The molecule is oriented to form hydrogen bonds with two of the framework oxygens and to interact with a Na ion in a nearby window. In this configuration the energy is 0.58 eV below the energy of the isolated water molecule plus that of anhydrous sodalite. Several tests indicate that most of the binding energy is due to the interaction of the oxygen with the Na ion. An analysis of electronic density for the lowest energy position shows that, when the molecule is put in contact with sodalite, charge is transferred from the water molecule to the spaces between the hydrogen atoms and the framework oxygens and between the water molecule oxygen and the nearest Na framework ion. Other bonding sites are above the plane of a 6-ring window occupied by a Na ion and above a 4-ring window.

Extensive molecular dynamics simulations indicate that for time scales t{lt}{tau}{sub g} , where {tau}{sub g}{proportional_to}N{sup 3{nu}} , the dynamical scaling exponent x=2+{nu}{sub D}/{nu} for a polymer chain in solution is anomalous (x=2 ) in two dimensions, contrary to the well known prediction (x=3 ) of the Zimm model. A numerical solution of the 2D hydrodynamic Zimm model equations, which extends into the regime t{gt}{tau}{sub g} , supports this value, suggesting a breakdown of dynamical scaling in 2D. {copyright} {ital 1997} {ital The American Physical Society}

Writing 〈${\mathit{R}}_{\mathit{N}}^{2}$〉= ${\mathit{AN}}^{2\ensuremath{\nu}}$(1+${\mathit{BN}}^{\mathrm{\ensuremath{-}}{\mathrm{\ensuremath{\Delta}}}_{1}}$+${\mathit{CN}}^{\mathrm{\ensuremath{-}}1}$+\ensuremath{\cdot}\ensuremath{\cdot}\ensuremath{\cdot}) for the mean square end-to-end length 〈${\mathit{R}}_{\mathit{N}}^{2}$〉 of a self-avoiding polymer chain of N links, we have calculated ${\mathrm{\ensuremath{\Delta}}}_{1}$ for the two-dimensional continuum case from a finite perturbation method based on the ground state of Edwards self-consistent solution which predicts the (exact) \ensuremath{\nu}=3/4 exponent. This calculation yields ${\mathrm{\ensuremath{\Delta}}}_{1}$=1/2. A finite-size scaling analysis of data generated for the continuum using a biased sampling Monte Carlo algorithm supports this value, as does a reanalysis of exact data for two-dimensional lattices. \textcopyright{} 1996 The American Physical Society.

Intraoperative somatosensory-evoked potential (SSEP) data were collected prospectively in a consecutive series of patients with an acute lumbar herniated nucleus pulposus (HNP). Each patient underwent an open limited diskectomy, hemilaminotomy, and partial foraminotomy. The sequence of diskectomy and bony decompression was randomized, and the extent of foraminotomy was standardized. SSEP data were recorded after each operative procedure and were coded for blind interpretation. SSEP tracings were compared with each patient's baseline for changes in latency and amplitude. In the overall study, changes in amplitude and latency produced by diskectomy versus bony decompression were not statistically significant. In the six patients with lateral recess stenosis (LRS), a statistically significant reduction in latency was observed after bony decompression (averaging -2.05 ms) compared with diskectomy (-0.62 ms). In patients with underlying LRS and a HNP, minimally invasive techniques addressing the disc only may be inadequate to decompress a lumbar nerve root.

We present the results of a new perturbation calculation in polymer statistics which starts from a ground state that already correctly predicts the long chain length behaviour of the mean square end--to--end distance $\langle R_N^2 \rangle\ $, namely the solution to the 2~dimensional~(2D) Edwards model. The $\langle R_N^2 \rangle$ thus calculated is shown to be convergent in $N$, the number of steps in the chain, in contrast to previous methods which start from the free random walk solution. This allows us to calculate a new value for the leading correction--to--scaling exponent~$\Delta$. Writing $\langle R_N^2 \rangle = AN^{2\nu}(1+BN^{-\Delta} + CN^{-1}+...)$, where $\nu = 3/4$ in 2D, our result shows that $\Delta = 1/2$. This value is also supported by an analysis of 2D self--avoiding walks on the {\em continuum}., Comment: 17 Pages of Revtex. No figures. Submitted to J. Phys. A

The molecular field equations for the allowed spin directions for dimer and trimer molecular species have been solved numerically for a range of values of the exchange and anisotropy interactions and of the applied magnetic field. The results may be used for the evaluation of the exchange and anisotropy constants from high field Mössbauer spectra or for selecting the best conditions for proposed experiments in order to determine these parameters.

Events of the type e/sup +/e/sup -/ ..-->.. e/sup +/e/sup -/eta' (958) have been observed with the Mark II detector at SPEAR by detecting the decay mode eta' ..-->.. rho/sup 0/..gamma... From the observed cross section and known branching fractions of the eta' is GAMMA/sub gammagamma/ = 5.9 +- 1.6 +- 1.2 keV and the total width is GAMMA = 300 +- 90 +- 60 keV (statistical and systematic errors).

Author(s): Shannon, S.R.; Anderson, L.; Bridgewater, A.; Chaffee, R.; Chamberlain, O.; Dahl, O.; Fuzesy, R.; Gorn, W.; Jaros, J.; Johnson, R.; Kenney, R.; Nelson, J.; O'Keefe, G.; Oliver, W.; Papp, J.; Pollard, D.; Pripstein, M.; Robrish, P.; Shapiro, G.; Steiner, H.; Wahlig, M.

The authors have measured the asymmetry in the cross section for the reaction {gamma}p {yields} {pi}{sup +}n between the two stages of polarization of the initial proton normal to the plane of scattering. The initial laboratory photon energies, k, were 5 GeV and 16 GeV, and the regions of momentum transfer, t, covered were 0.14 {le} {radical}-t {le} 1.01 GeV/c and 0.14 {le} {radical}-t {le} 0.78 GeV/c respectively. A butanol polarized target was used with the SLAC 20 GeV/c magnetic spectrometer. The data show a sizeable asymmetry at both 5 GeV and 16 GeV. The 16 GeV data peak at {radical}-t {approx} 0.30 GeV/c with an asymmetry of about -0.70, and the 5 GeV data pak at {radical}-t {approx} 0.80 GeV/c with an asymmetry of about -0.70. The direction of our normal to the scattering plane is along (photon in) x (pion out).

The electromagnetic shower detection system of the Mark II Magnetic Detector consists of ten large lead/liquid argon modules. Eight of these, termed "barrel" modules, are placed outside the aluminum coil which defines the magnetic field volume of the device. The other two, the "end-cap" modules are placed at the ends of the solenoid. The design and construction of the lead assemblies, the tank structure and the cryogenic system will be described, as will the data acquisition electronics. Preliminary results on the performance of the first barrel module will be presented.

In this talk I will report some of the first results from the Mark II experiment at the Stanford Linear Accelerator Center e+e−; storage ring facility SPEAR. The first part will be devoted to a description of the Mark II detector and of its performance. Then I will show preliminary results on a measurement of the inclusive production of baryons \(\left( {p,\,\bar p,\,\Lambda \,and\,\bar \Lambda } \right)\) over the centre-of-mass energy range from 4.5 to 6 GeV in a search for a threshold of charmed baryon production. Data on decays of charmed D mesons have been accumulated at the Ψ ″ (3770) resonance and first results will be given in part three from an analysis of about one-third of the whole data sample. Finally, we have observed, for the first time, evidence for η ′ (958) production in two-photon collisions. We have measured the radiative width of the η ′ through this process as will be discussed in the last part of this talk.