954 resultados para Wilson loops


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Both stamped.

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The collection was presented to the British museum (Nat. Hist.) by W. Wilson Saunders.

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Cover title.

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From a comprehensive study of the public addresses of Woodrow Wilson in the period following the outbreak of the war in Europe in August 1914 to the war's conclusion in June 1919, this essay examines Wilson's transformation of the long-held vision of America as merely a great example of liberty to its embodiment as the self-sacrificing champion of liberty. It will demonstrate how this transformation of the American "self" was inextricably connected to a changing image of the war and the construction of an enemy image of the German government.

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A major chemical challenge is the structural mimicry of discontinuous protein surfaces brought into close proximity through polypeptide folding. We report the design, synthesis, and solution structure of a highly functionalized saddle-shaped macrocyclic scaffold, constrained by oxazoles and thiazoles,upporting two short peptide loops projecting orthogonally from the same face of the scaffold. This structural mimetic of two interhelical loops of cytochrome b(562) illustrates a promising approach to structurally mimicking discontinuous loops of proteins.

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Tetrapeptide analogue H-[Glu-Ser-Lys(Thz)]-OH, containing a turn-inducing thiazole constraint, was used as a template to produce a 21-membered structurally characterized loop by linking Glu and Lys side chains with a Val-Ile dipeptide. This template was oligomerized in one pot to a library (cyclo-[1](n), n = 2-10) of giant symmetrical macrocycles (up to 120-membered rings), fused to 2-10 appended loops that were carried intact through multiple oligomerization (chain extension) and cyclization (chain terminating) reactions of the template. A three-dimensional solution structure for cyclo-[1](3) shows all three appended loops projecting from the same face of the macrocycle. This is a promising approach to separating pepticle motifs over large distances.

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Protein-protein interactions are central to all biological processes. The creation of small molecules that can structurally mimic the fundamental units of protein architecture (helices, strands, turns, and their combinations) could potentially be used to reproduce important bioactive protein surfaces and interfere in biological processes. Although this field is still in relative infancy, substantial progress is being made in creating small molecules that can mimic these individual secondary structural elements of proteins. However the generation of compounds that can reproduce larger protein surfaces, composed of multiple structural elements of proteins, has proven to be much more challenging. This presentation will describe some densely functionalised small molecules that do constrain multiple peptide motifs in defined structures such as loop bundles, helix bundles, strand and sheet bundles. An example of a helix bundle that undergoes conformational changes to a beta sheet bundle and aggregates into multi-micron length peptide nanofibre 'rope' will be described.

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Back and von Wright have developed algebraic laws for reasoning about loops in the refinement calculus. We extend their work to reasoning about probabilistic loops in the probabilistic refinement calculus. We apply our algebraic reasoning to derive transformation rules for probabilistic action systems. In particular we focus on developing data refinement rules for probabilistic action systems. Our extension is interesting since some well known transformation rules that are applicable to standard programs are not applicable to probabilistic ones: we identify some of these important differences and we develop alternative rules where possible. In particular, our probabilistic action system data refinement rules are new.