Alignment of fluorescent molecules vapour-deposited on to highly oriented PTFE substrates

The alignment of six fluorescent materials (p-terphenyl, p-quaterphenyl, p-quinquephenyl, diphenylstilbene, 1,4-bis(2-methylstyryl)benzene, and 1,4-bis-2-(5-phenyloxazolyl)benzene) grown from the vapour phase on to friction-deposited, highly oriented poly(tetrafluoroethylene) (PTFE) films was studied. The dichroic ratio of the fluorescent films produced was determined by polarized spectroscopic fluorescence measurements, and the crystallographic orientation of these materials was determined by transmission electron microscopy. The measured dichroic ratios ranged from 1.7 for diphenylstilbene to 5.0 for the p-quaterphenyl film. Electron diffraction patterns revealed that five of the fluorescent materials grew epitaxially on the single crystal-like PTFE films, the fluorescent crystals adopting particular orientations with respect to the crystallographic planes of PTFE. On the other hand, crystals of 1,4-bis-2-(5-phenyloxazolyl) benzene aligned in a fibre pattern, apparently by a grapho-epitaxial mechanism.     

A Monte Carlo estimation of the marginal distributions in a problem of probabilistic dynamics

Modelling the effect of the dynamic behaviour of a system on its PSA study leads, in a Markovian framework, to a development at first order of the Chapman-Kolmogorov equation, whose solutions are the probability densities of the problem. Because of its size, there is no hope of solving directly these equations in realistic circumstances. We present in this paper a biased simulation giving the marginals and compare different ways of speeding up the integration of the equations of the dynamics.     

Flow-dependent platelet behaviour in blood—material interactions

Platelet activation and adhesion are important parameters characterizing blood compatibility of biomaterials. A platelet transport theory based on convection diffusion, which describes the influence of wall shear rate, platelet concentration, axial position, hematocrit and red cell size, was originally proposed by Turitto and Baumgartner and later expanded by Aarts. This theory was applied in an in vitro perfusion system for three different materials with wall shear rates between 100s^-1 and 4300 s^-1 in order to cover the regions of diffusion controlled, reaction controlled and intermediate platelet adherence. Platelet diffusivity and platelet vessel wall surface reactivity were determined for these cases and the constants m and n were calculated using the relation between platelet diffusivity and shear rate as expressed by the following power law function: D _w=m*y ⁿ _w.     

Extending trouble ticket systems to fault diagnostics

Network management in large heterogeneous communication environments requires the incorporation of more advanced tools than are currently available, especially in the area of fault management. By providing an informational infrastructure for documenting network behavior and maintenance activities, TTSs (trouble ticket systems) have provided some relief for the fault management problem. Researchers have recognized TTSs as a means for realizing more advanced functions in network management platforms to effect automatic trouble ticket generation, fault diagnostics, and the correlation of multiple views network problems and behavior. The authors describe current research trends towards understanding and implementing these advanced functions in a TTS framework     

Potassium uptake and water content in hepatocytes isolated from rat livers preserved in Euro-Collins and UW solutions and after transplantation

Isolated hepatocytes from the rat were used to assess the maintenance of liver cell function in relation to the composition of the preservation medium. After separation by collagenase, they were incubated in Krebs-Ringer-Bicarbonate medium (KRB), Euro-Collins (EC), or University of Wisconsin (UW) solutions. Potassium influx, cell volume, and transaminase release were measured in cells freshly separated from control livers or from livers preserved in vitro up to 12 h in these media or having undergone orthotopic liver transplantation (OLT). While ion exchange levels were retained in all media, cells shrank significantly in UW but were able to restore their volume after 3 h of liver preservation. With regard to in vivo conditions, UW appears to be the best medium to prevent edema and to maintain more stable potassium exchange and enzyme production. These results are of value for liver transplantation in humans.     

Services and applications: requirements and realizations in theUMTS era

The ACTS program is moving the results of the R&D of the parent RACE program nearer to realization through technology and user trials. Particularly in the mobile domain of ACTS, several projects have been investigating the user dimension in the context of the third-generation Universal Mobile Telecommunications Service. Results so far suggest many opportunities to broaden participation, exploit the inherent benefits of the mobile environment, and take advantage of the enormous improvements in wireless communications to realize the potential of global multimedia mobility. This article considers the needs of users for mobile multimedia applications and the consequences of those needs on the equipment, supporting services and teleservices, and communications bearers     

In the beginning [junction transistor]

The junction transistor, technologically the most important solid-state device, invented theoretically by W.B. Shockley on January 23, 1948, brought about the semiconductor revolution. That invention was triggered by the experimental discovery of the point-contact transistor by W. Brattain and J. Bardeen 38 days earlier. Bardeen's notebook entries at Bell Telephone Laboratories for the crucial 100-day period November 21, 1947-February 29, 1948 have been examined to ascertain why this winner of two Nobel Prizes in physics could not invent the junction transistor. It was found that the boundary between the thin p-type inversion layer and the n-type bulk germanium semiconductor in their original point-contact transistor discovery was characterized as a “high resistance boundary” in macroscopic electrical engineering terms by Bardeen, the electrical engineer turned mathematical physicist. Pages from Shockley's notebook are reproduced in full to show what exactly he was thinking on December 16, 1947, the day the point-contact transistor was experimentally discovered by Brattain and Bardeen. The origin of U.S. Patent 2524035 has been traced to the Bell Telephone Laboratories notebook pages of its inventors and examined. It is shown that this patent could not be considered as the first patent describing Shockley's revolutionary theoretical invention of the minority carrier injection concept underlying bipolar transistor action     

Analogue micropowered log-domain tone controller for auditoryprostheses

A micropower tone-control circuit comprising two first-order log-domain filters and a subtractor built with MOS transistors in weak inversion is described. The tone-controller is capable of providing bass cut/boost and treble cut operations. This circuit is being used in new designs of a conventional (acoustic) hearing-aid and cochlear implant