Deuterium quadrupole coupling tensors in methyl halides: Ab initio effective core potential and liquid crystal nuclear magnetic resonance study J. Chem. Phys. 107, 1744 (1997) The quadrupole coupling constant and asymmetry parameter for the deuteron in liquid heavy water was determined using purely theoretical methods. Molecular-dynamics simulations with the ab initio potential-energy surface of Lie and Clementi were used to generate snapshots of the liquid. The electric-field gradient at the deuteron was then calculated for these configurations and averaged to obtain the liquid quadrupole coupling constant. At 300 K a quadrupole coupling constant of 256±5 kHz and an asymmetry parameter of 0.164 ± 0.003 were obtained. The temperature dependence of the quadrupole coupling constant was investigated. Ab initio calculation of the deuterium quadrupole coupling in liquid waterRolf Eggenberger, Stefan Gerber, Hanspeter Huber, Debra Searles, and Marc Welker

Pyracylene (cyclopent[fg\ acenaphthylene, 1) is available in two steps from pyrene and, contrary to previous experience, can be crystallized, stored as a solid, and even sublimed without decomposition. The X-ray structure of 1 exhibits a pronounced alternation of bond lengths along the 12-ir periphery. The absorption spectrum (with transition moment directions) and the photoelectron spectrum of 1 are reported and analyzed. Pyracylene is quite stable to irradiation both as a solid and in solution. Radiationless deactivation of the lowest excited singlet state is very rapid; fluorescence and intersystem crossing yields were below our limits of detection (F < 3 X 10"4, 0T < 2 X 10"2). The lowest triplet state, observed by flash photolysis with a sensitizer (Xmx = 360 nm, e > 104 M"1 cm"1; = 520 nm, t = 7500 M"1 cm"1), is also rather short-lived (r = 4.6 ms). The triplet energy of 1 is bracketed in the range of 103 ± 20 kj mol"1 on the basis of energy-transfer experiments. A major component of flame soots, which had been tentatively attributed to 1 by GC-MS analysis, is shown not to be identical with 1. The heat of formation of 1 is calculated as AfH = 410 kj mol"1 with the MMP2 force field.The literature on pyracylene (cyclopent \fg] acenaphthylene, 1) displays a remarkable dichotomy. On the one hand, 1 is held to be very unstable, a prototype "antiaromatic" molecule with a •This work is part of the Ph. D. thesis of B.F.

Telepathology may be used to provide a frozen section service to hospitals without a department or institute of pathology. We have developed a telepathology system using the commercially available Integrated Services Digital Network (ISDN). The main software and hardware elements of our system are: Apple Macintosh workstations, a program for simultaneous transfer of image, voice and data, and a data bank for storage of patients' data and microscopic images. A picture instrument manager (PIM) makes remote control of microscopes or other instruments possible. The system connects the Department of Pathology of the University of Basel with the Regional Hospital of Samedan, 250 km away, and the Regional Hospital of Burgdorf, 100 km away. During a period of 20 months, frozen sections with the hospitals in Samedan and Burgdorf were performed in 53 patients. Between 54 and 58 s were required for the transfer of a diagnostic 8-bit grey level image containing 341 +/- 26.1 (standard error) kbytes (n = 13) or a diagnostic 24-bit colour image containing 165 +/- 16.9 kbytes (n = 40). Frozen section diagnosis was completed in 20-40 min. True-positive diagnoses of malignant tumours were achieved in 85.7% of cases (sensitivity = 0.857). No false-positive diagnosis was made. In 3 of the 53 cases telepathological diagnosis was not possible for technical reasons.

No abstract

No abstract