Field Measurements and Parameter Calibrations of Propagation Model for Digital Audio Broadcasting in Norway

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Proceedings of the 19th NASA Propagation Experimenters Meeting (NAPEX 19) and the 7th Advanced Communications Technology Satellite (ACTS) Propagation Studies Workshop (APSW 7)

The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. NAPEX 19 was held on 14 Jun. 1995, in Fort Collins, Colorado. Participants included representatives from Canada, Japan, and the United States, including researchers from universities, government agencies, and private industry. The meeting focused on mobile personal satellite systems and the use of 20/30-GHz band for fixed and mobile satellite applications. In total, 18 technical papers were presented. Following NAPEX 19, the Advanced Communications Technology Satellite (ACTS) Propagation Studies Workshop 7 (APSW 7) was held on 15-16 Jun. 1995, to review ACTS propagation activities with emphasis on the experimenters' status reports and dissemination of propagation data to industry

The development of the terrestrial broadcasting networks of the United Kingdom in the twentieth century

This thesis describes an investigation into the evolution of terrestrial broadcasting -a vital new medium that has had an enormous social impact. The approach has been to concentrate upon the research and development needed to plan the intricate radio and television transmitter networks. These processes required national and international agreement on the use of the radio frequency spectrum, and the specification of many hundreds of transmitting stations. They provided the link between the broadcasters and the public, and this work presents a unique illustration of a project which dealt with many novel technical problems whilst accommodating the demands of all those concerned with the exploitation of the medium. The UK became prominent in the field of broadcasting technology, particularly in areas concerned with propagation and service planning. The geographical position of this country between large land and sea masses, the nature of its terrain, meteorology and its population distribution, presented a wide range of distinctive problems. Research in the UK provided valuable evidence for the subsequent planning of services throughout the world, although during the rapid development of broadcasting it was impossible to examine fully all the experimental results which were produced. With resources not previously available, the author - engaged on planning work since the middle of the century - has researched evidence much of which was archived many years ago. It is not simply a work of historical interest, because new information concerning radio propagation has emerged. Its timing is also appropriate, because the beginning of the twenty-first century is witnessing revolutionary changes in broadcasting

Ultra-high-speed imaging of bubbles interacting with cells and tissue

Ultrasound contrast microbubbles are exploited in molecular imaging, where bubbles are directed to target cells and where their high-scattering cross section to ultrasound allows for the detection of pathologies at a molecular level. In therapeutic applications vibrating bubbles close to cells may alter the permeability of cell membranes, and these systems are therefore highly interesting for drug and gene delivery applications using ultrasound. In a more extreme regime bubbles are driven through shock waves to sonoporate or kill cells through intense stresses or jets following inertial bubble collapse. Here, we elucidate some of the underlying mechanisms using the 25-Mfps camera Brandaris128, resolving the bubble dynamics and its interactions with cells. We quantify acoustic microstreaming around oscillating bubbles close to rigid walls and evaluate the shear stresses on nonadherent cells. In a study on the fluid dynamical interaction of cavitation bubbles with adherent cells, we find that the nonspherical collapse of bubbles is responsible for cell detachment. We also visualized the dynamics of vibrating microbubbles in contact with endothelial cells followed by fluorescent imaging of the transport of propidium iodide, used as a membrane integrity probe, into these cells showing a direct correlation between cell deformation and cell membrane permeability

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression