1,861 research outputs found
Developing a Web-Based Question-Driven Audience Response System Supporting BYOD
Question-driven Audience Response Systems (ARSs) are in the focus of research since the 1960s. Since then, the technology has changed and therefore systems have evolved too. This work is about conception and implementation of the web-based ARS RealFeedback which uses the principle of bring your own device (BYOD). A state-of-the-art analysis compares the features of existing web-based ARSs. The most important findings are used for the conception and the implementation of the system. Thinking-aloud tests, and the first usages during lectures confirm that the chosen requirements are very significant and valuable for lecturers
Pd-catalyzed enantioselective aerobic oxidation of secondary alcohols: Applications to the total synthesis of alkaloids
Enantioselective syntheses of the alkaloids (-)-aurantioclavine, (+)-amurensinine, (-)-lobeline, and (-)- and (+)-sedamine are described. The syntheses demonstrate the effectiveness of the Pd-catalyzed asymmetric oxidation of secondary alcohols in diverse contexts and the ability of this methodology to set the absolute configuration of multiple stereocenters in a single operation. The utility of an aryne C-C insertion reaction in accessing complex polycyclic frameworks is also described
A Convergent and Enantioselective Synthesis of (+)-Amurensinine via Selective C−H and C−C Bond Insertion Reactions
A convergent and enantioselective synthesis of the natural product amurensinine is described. The synthetic strategy takes advantage of mild and selective C−H and C−C bond insertion reactions, in addition to the palladium-catalyzed aerobic oxidative kinetic resolution recently developed in these laboratories
Molecular and immunological characterization of profilin from mugwort pollen
In late summer in Europe, pollen of mugwort is one of the major sources of atopic allergens. No information about the complete molecular structure of any mugwort allergen has been published so far. Here we report the isolation and characterization of mugwort pollen cDNA clones coding for two isoforms of the panallergen profilin. Thirtysix percent of the mugwort allergic patients tested displayed IgE antibodies against natural and recombinant profilin, and no significant differences were observed in the IgEbinding properties of the isoforms. One profilin isoform was purified to homogeneity and detailed structural analysis indicated that the protein exists in solution as dimers and tetramers stabilized by sulfydryl and/or ionic interactions. Profilin monomers were detectable only after exposure of multimers to harsh denaturing conditions. Dimers and tetramers did not significantly differ in their ability to bind serum IgE from mugwort pollenallergic patients. However, oligomeric forms might have a higher allergenic potential than monomers because larger molecules would have additional epitopes for IgEmediated histamine release. Profilin isolated from mugwort pollen also formed multimers. Thus, oligomerization is not an artifact resulting from the recombinant production of the allergen. Inhibition experiments showed extensive IgE crossreactivity of recombinant mugwort profilin and profilin from various pollen and food extracts
Magnetization Jump in a Model for Flux Lattice Melting at Low Magnetic Fields
Using a frustrated XY model on a lattice with open boundary conditions, we
numerically study the magnetization change near a flux lattice melting
transition at low fields. In both two and three dimensions, we find that the
melting transition is followed at a higher temperature by the onset of large
dissipation associated with the zero-field XY transition. It is characterized
by the proliferation of vortex-antivortex pairs (in 2D) or vortex loops (in
3D). At the upper transition, there is a sharp increase in magnetization, in
qualitative agreement with recent local Hall probe experiments.Comment: updated figures and texts. new movies available at
http://www.physics.ohio-state.edu:80/~ryu/jj.html. Accepted for publication
in Physical Review Letter
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