Structure and Hydrogen Bonding in CaSiD 1+ x : Issues About Covalent Bonding
We report here our high-resolution neutron powder diffraction and neutron vibrational spectroscopy study of ${\mathrm{CaSiD}}_{1+x}$ along with first-principles calculations, which reveal the deuterium structural arrangements and bonding in this novel alloy hydride. Both the structural and spectroscopic results show that, for $xg0$, D atoms start occupying a ${\mathrm{Ca}}_{3}\mathrm{Si}$ interstitial site. The corresponding $\mathrm{Si}\text{\ensuremath{-}}\mathrm{D}$ bond length is determined to be $1.82\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$, fully $0.24\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ larger than predicted by theory. Thus, our neutron measurements are at odds with the strongly covalent $\mathrm{Si}\text{\ensuremath{-}}\mathrm{H}$ bonding in ${\mathrm{CaSiH}}_{1+x}$ that such calculations suggest, a result which may have implications for a number of ongoing studies of metal-hydrogen systems destabilized by Si alloying.
Neutron scattering in materials science 2
A wide range of materials have been examined in the contents of this volume -- polymers, cements, high-{Tc} superconducting oxides and carbides, inorganic glasses, magnetic films, ceramics, and metallic alloys. Large numbers of contributions in some areas often are an indication of progress in newly-developed techniques, or growth in the application of a more established method. As one example of the former, research on surfaces and interfaces has undergone marked growth with the development and availability of neutron reflectometry. This technique, due to the scattering-length differences between isotopes (the proton and deuteron, for example) and the large penetration depth of neutrons, has been developed into an exquisite probe of the internal structure at interfaces, be these buried within a solid or at a solid/liquid interface. Penetration or contrast are also advantages in the use of neutrons for residual stress analysis and small angle scattering. Two sessions were devoted to the latter topic. Additional applications of small angle neutron scattering (SANS) appeared in a session specifically devoted to cementitious materials. The widespread use of neutron powder-profile analysis in chemical crystallography is perhaps not fully represented in the contributions, but the results of Rietveld analysis frequently appear as a means for themore » elucidation of structure-property relationships in a number of the sections devoted to a specific family of materials. Separate abstracts were prepared for some of the papers in this volume.« less
Old topics, old approaches? ‘Reception’ in television studies and music studies
The question of reception is closely linked to the history and the roots of audience studies. But what is ‘reception’ and what exactly does it mean? As audience studies have developed from a contested novelty to a now established academic field, what do we do with a concept that defined our interests in the past and may now be too wide or even obsolete? This article deals with this issue by mapping how the concept of reception was conceptualized and researched in audience studies of the past ten years, with a focus on studies of music and studies of television. We find that in music, strong focus remains on music reception in the context of performances and events, and this lies in contrast to a small number of studies which instead focus on a framework of music in ordinary life and the audiences’ contextual localities. Concerning reception of television, much of the scholarship starts from the cultural studies tradition and looks at television viewing as a means to construct identities. Discussing these findings, we inquire whether the hybridization of media also implies a hybridization of research traditions and methodologies, and what consequences it has for the balance between textual, production and audience approaches.