Anitproton-matter interactions in antiproton applications

By virtue of the highly energetic particles released when they annihilate in matter, antiprotons have a variety of potentially important applications. Among others, these include remote 3-D density and composition imaging of the human body and also of thick, dense materials, cancer therapy, and spacecraft propulsion. Except for spacecraft propulsion, the required numbers of low energy antiprotons can be produced, stored, and transported through reliance on current or near term technology. Paramount to these applications and to fundamental research involving antiprotons is knowledge of how antiprotons interact with matter. The basic annihilation process is fairly well understood, but the antiproton annihilation and energy loss rates in matter depend in complex ways on a number of atomic processes. The rates, and the corresponding cross sections, were measured or are accurately predictable only for limited combinations of antiproton kinetic energy and material species

The Combined Release and Radiation Effects Satellite (CRRES) program: A unique series of scientific experiments

The Defense Department and NASA have joined in a program to study the space environment which surrounds the earth and the effects of space radiation on modern satellite electronic systems. The Combined Release and Radiation Effects Satellite (CRRES) will carry an array of active experiments including chemical releases and a complement of sophisticated scientific instruments to accomplish these objectives. Other chemical release active experiments will be performed with sub-orbital rocket probes. The chemical releases will 'paint' the magnetic and electric fields of earthspace with clouds of glowing ions. Earthspace will be a laboratory, and the releases will be studied with an extensive network of ground-, aircraft-, and satellite-based diagnostic instruments. Some of the topics discussed include the following: the effects of earthspace; the need for active experiments; types of chemical releases; the CRRES program schedule; international support and coordinated studies; photographing chemical releases; information on locating chemical releases for observation by the amateur; and CRRES as a program

A System for Coding the Interaction in Focus Groups and Dyadic Interviews

Interaction among participants is the fundamental mechanism that generates data in focus groups. Despite calls for ways to analyze interaction in focus groups, there is still an unmet need to develop such tools. We present a coding system to investigate interaction by emphasizing how participants use the substantive aspects of the topics they discuss. We then apply it to the question of how conversations in dyadic interviews (with two participants) compare to discussions in focus groups (with four or more participants). We find that dyadic interviews are more likely to contain explicit connections to the content of the previous speaker’s statement, and to generate more statements of agreement, indicating a higher degree of mutual attunement. These results demonstrate the effectiveness of our coding system in one particular context. We conclude by considering both the limitations of this system and the possibilities for extending it in future research

Photoacoustic ultrasound sources from diffusion-limited aggregates

Metallic diffusion-limited aggregate (DLA) films are well-known to exhibit near-perfect broadband optical absorption. We demonstrate that such films also manifest a substantial and relatively material-independent photoacoustic response, as a consequence of their random nanostructure. We theoretically and experimentally analyze photoacoustic phenomena in DLA films, and show that they can be used to create broadband air- coupled acoustic sources. These sources are inexpensive and simple to fabricate, and work into the ultrasonic regime. We illustrate the device possibilities by building and testing an optically-addressed acoustic phased array capable of producing virtually arbitrary acoustic intensity patterns in air.Comment: 5 pages, 5 figure

A Systematic Comparison of In-Person and Video-Based Online Interviewing

Due to the increasing popularity of online qualitative interviewing methods, we provide a systematically organized evaluation of their advantages and disadvantages in comparison to traditional in-person interviews. In particular, we describe how individual interviews, dyadic interviews, and focus groups operate in both face-to-face and videoconferencing modes. This produces five different areas for comparison: logistics and budget, ethics, recruitment, research design, and interviewing and moderating. We conclude each section with set of recommendations, and conclude with directions for future research in online interviewing

3D Ultrastructure of the Cochlear Outer Hair Cell Lateral Wall Revealed By Electron Tomography.

Outer Hair Cells (OHCs) in the mammalian cochlea display a unique type of voltage-induced mechanical movement termed electromotility, which amplifies auditory signals and contributes to the sensitivity and frequency selectivity of mammalian hearing. Electromotility occurs in the OHC lateral wall, but it is not fully understood how the supramolecular architecture of the lateral wall enables this unique form of cellular motility. Employing electron tomography of high-pressure frozen and freeze-substituted OHCs, we visualized the 3D structure and organization of the membrane and cytoskeletal components of the OHC lateral wall. The subsurface cisterna (SSC) is a highly prominent feature, and we report that the SSC membranes and lumen possess hexagonally ordered arrays of particles. We also find the SSC is tightly connected to adjacent actin filaments by short filamentous protein connections. Pillar proteins that join the plasma membrane to the cytoskeleton appear as variable structures considerably thinner than actin filaments and significantly more flexible than actin-SSC links. The structurally rich organization and rigidity of the SSC coupled with apparently weaker mechanical connections between the plasma membrane (PM) and cytoskeleton reveal that the membrane-cytoskeletal architecture of the OHC lateral wall is more complex than previously appreciated. These observations are important for our understanding of OHC mechanics and need to be considered in computational models of OHC electromotility that incorporate subcellular features

Analysis induced reduction of a polyelectrolyte

The polymer, poly(diallyldimethylammonium chloride) (PDDA), is shown to undergo chemical change via a reduction mechanism during X-ray analysis. Examination of the N 1s spectrum of PDDA shows a time dependence on the degree of reduction, together with clear amplification of the extent of reduction through the charge compensation system and X-ray irradiation