303 research outputs found
K- and L-theory of the semi-direct product of the discrete 3-dimensional Heisenberg group by Z/4
We compute the group homology, the topological K-theory of the reduced
C^*-algebra, the algebraic K-theory and the algebraic L-theory of the group
ring of the semi-direct product of the three-dimensional discrete Heisenberg
group by Z/4. These computations will follow from the more general treatment of
a certain class of groups G which occur as extensions 1-->K-->G-->Q-->1 of a
torsionfree group K by a group Q which satisfies certain assumptions. The key
ingredients are the Baum-Connes and Farrell-Jones Conjectures and methods from
equivariant algebraic topology.Comment: Published by Geometry and Topology at
http://www.maths.warwick.ac.uk/gt/GTVol9/paper37.abs.htm
Computational Analysis of Foil Air Journal Bearings Using a Runtime-Efficient Segmented Foil Model
This contribution is concerned with the development and the implementation of a foil air journal bearing model. For this purpose, the numerical procedure solving the Reynolds equation for compressible fluids has to be coupled to a compliant foil model. The presented beam-based approach is supposed to reproduce most of the experimentally known particularities in the mechanical behavior of the foil structure, while being at least as runtime-efficient as the commonly used simple elastic foundation model. The developed modeling approach will be validated by comparing simulation results to data found with a more complex reference model. In the analysis part, most notably, the top foil compliance is shown to deteriorate the load-carrying capacity of air bearings. Moreover, the influence of the top foil compliance on the dynamics of a rigid rotor supported by two foil air journal bearings will be discussed.</jats:p
TCR-engineered T cells: A model of inducible TCR expression to dissect the interrelationship between two TCRs
TCR gene modified T cells for adoptive therapy simultaneously express the Tg TCR and the endogenous TCR, which might lead to mispaired TCRs with harmful unknown specificity and to a reduced function of TCR-Tg T cells. We generated dual TCR T cells in two settings in which either TCR was constitutively expressed by a retroviral promoter while the second TCR expression was regulable by a Tet-on system. Constitutively expressed TCR molecules were reduced on the cell surface depending on the induced TCR expression leading to strongly hampered function. Besides that, using fluorescence resonance energy transfer we detected mispaired TCR dimers and different pairing behaviors of individual TCR chains with a mutual influence on TCR chain expression. The loss of function and mispairing could not be avoided by changing the TCR expression level or by introduction of an additional cysteine bridge. However, in polyclonal T cells, optimized TCR formats (cysteineization, codon optimization) enhanced correct pairing and function. We conclude from our data that (i) the level of mispairing depends on the individual TCRs and is not reduced by increasing the level of one TCR, and (ii) modifications (cysteineization, codon optimization) improve correct pairing but do not completely exclude mispairing (cysteineization)
Broadband 180 degree universal rotation pulses for NMR spectroscopy designed by optimal control
Broadband inversion pulses that rotate all magnetization components 180
degrees about a given fixed axis are necessary for refocusing and mixing in
high-resolution NMR spectroscopy. The relative merits of various methodologies
for generating pulses suitable for broadband refocusing are considered. The de
novo design of 180 degree universal rotation pulses using optimal control can
provide improved performance compared to schemes which construct refocusing
pulses as composites of existing pulses. The advantages of broadband universal
rotation by optimized pulses (BURBOP) are most evident for pulse design that
includes tolerance to RF inhomogeneity or miscalibration. We present new
modifications of the optimal control algorithm that incorporate symmetry
principles and relax conservative limits on peak RF pulse amplitude for short
time periods that pose no threat to the probe. We apply them to generate a set
of pulses suitable for widespread use in Carbon-13 spectroscopy on the majority
of available probes
Reading Across Cultures: Global Narratives, Hotels and Railway Stations
This is the final version of the article. Available from Springer Verlag via the DOI in this record.This article takes its cue from the English critic, novelist and painter John Berger. He argues that what we know determines what we see. Hotels and railway stations, though they differ in size, design and appearance, are places of temporary national and international congress that are recognized by everyone. They become visible or even iconic once their history or their role is turned into at least part of a wider narrative—in literature, film or in other arts. This provides a representative focus by which we may read a city’s or a nation’s past. In exemplifying such connections I focus first on the long-term history of Friedrichstraße station and some of the surrounding hotels in the context of the history of Berlin, situating them within the national and, by implication, also the international context. Secondly, I will consider the outbreak of the First World War in 1914 as an event in which the role of railway stations generated both personal and collective memories across cultures and over several decades
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