43,154 research outputs found
Vertex Detector Cable Considerations
Vertex detector cable requirements are considered within the context of the
SiD concept. Cable material should be limited so that the number of radiation
lengths represented is consistent with the material budget. In order to take
advantage of the proposed accelerator beam structure and allow cooling by flow
of dry gas, pulsed power is assumed. Potential approaches to power
distribution, cable paths, and cable design for operation in a 5 T magnetic
field are described.Comment: 3 pages, 3 figure
Observation of narrow-band noise accompanying the breakdown of insulating states in high Landau levels
Recent magnetotransport experiments on high mobility two-dimensional electron
systems have revealed many-body electron states unique to high Landau levels.
Among these are re-entrant integer quantum Hall states which undergo sharp
transitions to conduction above some threshold field. Here we report that these
transitions are often accompanied by narrow- and broad-band noise with
frequencies which are strongly dependent on the magnitude of the applied dc
current.Comment: 4 pages, 3 figure
Reparameterizing the Birkhoff Polytope for Variational Permutation Inference
Many matching, tracking, sorting, and ranking problems require probabilistic
reasoning about possible permutations, a set that grows factorially with
dimension. Combinatorial optimization algorithms may enable efficient point
estimation, but fully Bayesian inference poses a severe challenge in this
high-dimensional, discrete space. To surmount this challenge, we start with the
usual step of relaxing a discrete set (here, of permutation matrices) to its
convex hull, which here is the Birkhoff polytope: the set of all
doubly-stochastic matrices. We then introduce two novel transformations: first,
an invertible and differentiable stick-breaking procedure that maps
unconstrained space to the Birkhoff polytope; second, a map that rounds points
toward the vertices of the polytope. Both transformations include a temperature
parameter that, in the limit, concentrates the densities on permutation
matrices. We then exploit these transformations and reparameterization
gradients to introduce variational inference over permutation matrices, and we
demonstrate its utility in a series of experiments
Resonance assignments for latherin, a natural surfactant protein from horse sweat
Latherin is an intrinsically surfactant protein of ~23Â kDa found in the sweat and saliva of horses. Its function is probably to enhance the translocation of sweat water from the skin to the surface of the pelt for evaporative cooling. Its role in saliva may be to enhance the wetting, softening and maceration of the dry, fibrous food for which equines are adapted. Latherin is unusual in its relatively high content of aliphatic amino acids (~25Â % leucines) that might contribute to its surfactant properties. Latherin is related to the palate, lung, and nasal epithelium carcinoma-associated proteins (PLUNCs) of mammals, at least one of which is now known to exhibit similar surfactant activity to latherin. No structures of any PLUNC protein are currently available. 15N,13C-labelled recombinant latherin was produced in Escherichia coli, and essentially all of the resonances were assigned despite the signal overlap due to the preponderance of leucines. The most notable exceptions include a number of residues located in an apparently dynamic loop region between residues 145 and 154. The assignments have been deposited with BMRB accession number 19067
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The decay of space charge in a glassy epoxy resin following voltage removal
The PEA technique is used to measure the distribution of space charge in an epoxy resin after polarisation for one week at an applied field of 7.14kV/mm over a range of temperatures. The decay of the space charge is followed for times up to 114 hours after removal of the voltage and analysed in terms of a number of alternative decay mechanisms. It is shown that the rate-determining stage of the decay mechanism is that of a thermally activated process that has been associated with charge de-trapping. At times greater than 102s the de-trapping process behaves as though the space charge field does not exist and the retention time of the space charge depends only upon the depth of the deepest occupied traps and the temperature
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