A molecular structure investigation of the enol and keto tautomers of acetylacetone has been carried out by electron diffraction. It was found that the concentration of the enol form in the sample of the vapor at 105°w as 66 ± 5%. The enol tautomer contains a short internal hydrogen bond, • • O = 2.381 ± 0.020 Á, which appears to be linear and symmetric. The hydrogen bond is part of a planar ring in which the bonded distances,
The (110) faces of lysozyme crystals in their mother liquor have been investigated using an atomic force microscope (AFM) in height mode. Crystal growth and dissolution steps, as well as simultaneous growth and dissolution in pits, have been observed. Screw dislocations were also observed but the fine structure has not yet been investigated. Images that may possess molecular resolution were obtained and compared with theoretical images based on the crystallographic structure and the effects of arbitrary tip profiles. Crystallographic periodicities of 38 and 112 A were observed. A recurring feature is a centered periodic array of minima that may be associated with one of the two nearly planar sheets of molecules present in the crystal that are parallel to the (110) faces.
This book is concerned with factors that affect the way in which sound is reflected from a surface with particular emphasis on those surfaces found in auditoria. The two aspects, absorption and diffusion, are covered but the main novelty is the treatment of diffusion. Both authors have achieved well deserved international recognition for undertaking fundamental research on this topic over the last fifteen years. Trevor Cox has concentrated on the aspects of modelling, prediction and measurement whilst Peter D'Antonio has first hand experience of the application of diffusion in a range of highly significant and high profile projects. The distinct backgrounds of the two authors complement each other well, resulting in a book that will be valuable to both practitioners and researchers.
A surface diffusion coefficient is needed in room acoustics to enable the quality of diffusing surfaces to be evaluated. It may also facilitate more accurate geometric room acoustic models. This paper concentrates on diffusion coefficients derived from free-field polar responses. An extensive set of two-and three-dimensional measurements and predictions was used to test the worth of different diffusion coefficient definitions. The merits and problems associated with these types of coefficients are discussed, and past parameters reviewed. Two new coefficients are described. The new measure based on the autocorrelation function is forwarded as the best free-field coefficient. The strengths and weaknesses of the coefficient are defined.
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