The vast transformation of the Roman world at the end of antiquity has been a subject of broad scholarly interest for decades, but until now no book has focused specifically on the Iberian Peninsula ...in the period as seen through an archaeological lens. Given the sparse documentary evidence available, archaeology holds the key to a richer understanding of the developments of the period, and this book addresses a number of issues that arise from analysis of the available material culture, including questions of the process of Christianization and Islamization, continuity and abandonment of Roman urban patterns and forms, the end of villas and the growth of villages, and the adaptation of the population and the elites to the changing political circumstances.
The Greco-Roman world is identified in the modern mind by its cities. This includes both specific places such as Athens and Rome, but also an instantly recognizable style of urbanism wrought in ...marble and lived in by teeming tunic-clad crowds. Selective and misleading this vision may be, but it speaks to the continuing importance these ancient cities have had in the centuries that followed and the extent to which they define the period in subsequent memory. Although there is much that is mysterious about them, the cities of the Roman Mediterranean are, for the most part, historically known. That the names and pasts of these cities remain known to us is the product of an extraordinary process of remembering and forgetting stretching back to antiquity that took place throughout the former Roman world. This volume tackles this subject of the survival and transformation of the ancient city through memory, drawing upon the methodological and theoretical lenses of memory studies and resilience theory to view the way the Greco-Roman city lived and vanished for the generations that separate the present from antiquity.This book analyzes the different ways in which urban communities of the post-Antique world have tried to understand and relate to the ancient city on their own terms, examining it as a process of forgetting as well as remembering. Many aspects of the ancient city were let go as time passed, but those elements that survived, that were actively remembered, have shaped the many understandings of what it was. In order to do so, this volume assembles specialists in multiple fields to bring their perspectives to bear on the subject through eleven case studies that range from late Antiquity to the mid-twentieth century, and from the Iberian Peninsula to Iran. Through the examination of archaeological remains, changing urban layouts and chronicles, travel guides and pamphlets, they track how the ancient city was made useful or consigned to oblivion.
Group I alkoxides are highly active precatalysts in the heterodehydrocoupling of silanes and amines to afford aminosilane products. The broadly soluble and commercially available KOtAmyl was utilized ...as the benchmark precatalyst for this transformation. Challenging substrates such as anilines were found to readily couple primary, secondary, and tertiary silanes in high conversions (>90 %) after only 2 h at 40 °C. Traditionally challenging silanes such as Ph3SiH were also easily coupled to simple primary and secondary amines under mild conditions, with reactivity that rivals many rare earth and transition‐metal catalysts for this transformation. Preliminary evidence suggests the formation of hypercoordinated intermediates, but radicals were detected under catalytic conditions, indicating a mechanism that is rare for Si−N bond formation.
Group I alkoxides and amylates efficiently catalyze the heterodehydrocoupling of challenging silane and amine substrates under mild conditions! This represents one of the most straightforward and accessible methods to form aminosilanes through heterodehydrocoupling! This train is now leaving the station – don't miss it!
Drag reduction by riblets García-Mayoral, Ricardo; Jiménez, Javier
Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences,
04/2011, Letnik:
369, Številka:
1940
Journal Article
Recenzirano
The interaction of the overlying turbulent flow with riblets, and its impact on their drag reduction properties are analysed. In the so-called viscous regime of vanishing riblet spacing, the drag ...reduction is proportional to the riblet size, but for larger riblets the proportionality breaks down, and the drag reduction eventually becomes an increase. It is found that the groove cross section A+g is a better characterization of this breakdown than the riblet spacing, with an optimum . It is also found that the breakdown is not associated with the lodging of quasi-streamwise vortices inside the riblet grooves, or with the inapplicability of the Stokes hypothesis to the flow along the grooves, but with the appearance of quasi-two-dimensional spanwise vortices below y+ 30, with typical streamwise wavelengths . They are connected with a Kelvin-Helmholtz-like instability of the mean velocity profile, also found in flows over plant canopies and other surfaces with transpiration. A simplified stability model for the ribbed surface approximately accounts for the scaling of the viscous breakdown with A+g.
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