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A distributed time-slot assignment protocol is developed for a mobile multi-hop broadcast packet radio network, using time division multiple access channel access and virtual circuit switching. The protocol eliminates the single point failure mode of centralized network management and the delays of centralized processing. It is applicable to the user-to-user communications functions of such systems as the U. S. Army's enhanced position location and reporting system (EPLRS). The important functions of the distributed protocol, including time-slot assignment, virtual circuit set-up, and network synthesis, are identified, and implementing algorithms are presented and verified. The performance analysis of the protocol is divided into two parts. In this paper, Part 1 of the performance analysis, the capacity of a network using this protocol is studied and a tool is developed to design the network capacity by trading off among the network area, the transmission range, and the number of packet radio units. Since these results are not in closed form, numerical results provide insight into these parameters. In Part 2 the network set-up time and network data rate are analysed and a hierarchical architecture for the distributed protocol is proposed and analysed.

SUMMARY This paper describes how a transmission electron microscope may be used to study rigid body displacements between coincidence related grains. Computer calculations have predicted that such displacements reduce grain boundary internal energy in metals by relieving atomic over-crowding. Displacements are revealed as fringe patterns by a Bloch wave interference mechanism resembling that which gives rise to stacking fault fringes. The sensitivity of the technique in detecting very small displacements and its potential applications are discussed.

In a recent paper Sheinin and Corbett developed a multi-beam dynamical theory of the image contrast expected at coherent twins. They found that the contrast in both bright and dark field is characterised by two sets of interpenetrating thickness fringes. The present paper extends their treatment to consider the contrast expected at any form of coincidence grain boundary and includes the effect of relative translation between the adjacent crystals. It is shown that the images discussed by Sheinin and Corbett correspond to a special diffraction condition and that in general, if a translation is present, the contrast comprises more complicated fringe systems resembling stacking fault like fringes. Furthermore, it is shown that by imaging using (overlapping) diffraction spots common to both crystals any translation at the boundary can be measured. Sheinin and Corbett entwickelten kurzlich eine dynamische Vielstrahl-Theorie des elektronen mikroskopischen Bildkontrastes koharenter Zwillingsgrenzen. Sie fande, das der Kontrast, sohwohl in Hellfeld- wie auch in Dunkelfeld-Beleuchtung, durch zwei sich durchdringende Systeme paralleler Dickenstreifen charakterisiert ist. Diese Behandlung wird auf jede Form von Koinzidenzgrenzen erweitert und schliest die Wirkung relativer Translation zwischen angrenzenden Kristallen ein. Es wird gezeigt, das die Bilder, die von Sheinin und Corbett diskutiert wurden, einer speziellen Beugungsbedingung entsprechen, und das im allgemeinen, wenn Translation mit wirkt, der Kontrast kompliziertere Streifensysteme einschliest, ahnlich jenen von Stapelfehlern. Es wird weiter gezeigt, das mit Hilfe von Bildern, die unter Verwendung von gemeinsamen Beugungspunkten beider Kristalle entstehen, jede Translation an der Grenze gemessen werden kann.

A nine-year-old male Newfoundland-cross was treated with doxorubicin, cyclophosphamide, and methotrexate as adjuvant chemotherapy following the resection of a maxillary osteosarcoma. The dog remained in good health until week 13 of therapy, when he became anorexic, and developed icterus and ascites. Laboratory tests at this time suggested sub-acute hepatic failure and renal failure. Necropsy revealed severe generalized hepatic necrosis with resultant ascites and intestinal haemorrhage. Since there was no evidence on necropsy of an infectious aetiology, and since there was no history of toxin ingestion, methotrexate which is a known hepatotoxin in man, was considered the probable cause of the hepatic necrosis. This side-effect of methotrexate has not previously been reported in the dog, and animals undergoing therapy with the drug should be monitored closely for hepatotoxicity.

SUMMARY This review is concerned with the interpretation of contrast features observed at interphase interfaces using conventional transmission electron microscopy. The principal features which arise are interfacial dislocations and steps, four types of fringes, namely thickness, Δw, displacement and moire fringes, and lattice images. The contrast mechanisms leading to these features are discussed in the framework of the dynamical theory of electron diffraction. In particular, the influence on image contrast of the cyrstal composition and structure, the interfacial configuration and the crystallographic relationship of the two phases in the specimen is considered. In general, electron diffraction in bi-crystalline specimens is complicated, and reliable interpretation can only be carried out when the diffraction conditions have been carefully established. The diffraction conditions most widely used are discussed, and their relative merits compared.

SUMMARY A technique enabling accurate measurements of relative displacements between adjacent coincidence related crystals has been described previously. The technique depends on intensity measurements of stacking-fault-like fringes by comparison of experimental and theoretically simulated fringe profiles. This matching procedure is illustrated in the present work for a (l2l) boundary between twin related aluminium crystals. The main part of the paper describes the application of the technique for measuring excess volume at certain coincidence boundaries, and considers in detail the measurement for (l2l) boundaries. The excess volume per unit area at (l2l) boundaries is found to be 0·02 nm.