1,158 research outputs found
Analysis Of Nociceptive Evoked Potentials During Multi-Stimulus Experiments Using Linear Mixed Models
Neural processing of sensory stimuli can be studied using EEG by estimation of the evoked potential using the averages of large sets of trials. However, it is not always possible to include all stimulus parameters in a conventional analysis, since this would lead to an insufficient amount of trials to obtain the evoked potential by averaging. Linear mixed models use dependencies within the data to combine information from all data for the estimation of the evoked potential. In this work, it is shown that in multi-stimulus EEG data the quality of an evoked potential estimate can be improved by using a linear mixed model. Furthermore, the linear mixed model effectively deals with correlation between parameters in the data and reveals the influence of individual stimulus parameters
Ground-state properties of tubelike flexible polymers
In this work we investigate structural properties of native states of a
simple model for short flexible homopolymers, where the steric influence of
monomeric side chains is effectively introduced by a thickness constraint. This
geometric constraint is implemented through the concept of the global radius of
curvature and affects the conformational topology of ground-state structures. A
systematic analysis allows for a thickness-dependent classification of the
dominant ground-state topologies. It turns out that helical structures,
strands, rings, and coils are natural, intrinsic geometries of such tubelike
objects
Back-flow ripples in troughs downstream of unit bars: Formation, preservation and value for interpreting flow conditions
Back-flow ripples are bedforms created within the lee-side eddy of a larger bedform with migration directions opposed or oblique to that of the host bedform. In the flume experiments described in this article, back-flow ripples formed in the trough downstream of a unit bar and changed with mean flow velocity; varying from small incipient back-flow ripples at low velocities, to well-formed back-flow ripples with greater velocity, to rapidly migrating transient back-flow ripples formed at the greatest velocities tested. In these experiments back-flow ripples formed at much lower mean back-flow velocities than predicted from previously published descriptions. This lower threshold mean back-flow velocity is attributed to the pattern of velocity variation within the lee-side eddy of the host bedform. The back-flow velocity variations are attributed to vortex shedding from the separation zone, wake flapping and increases in the size of, and turbulent intensity within, the flow separation eddy controlled by the passage of superimposed bedforms approaching the crest of the bar. Short duration high velocity packets, whatever their cause, may form back-flow ripples if they exceed the minimum bed shear stress for ripple generation for long enough or, if much faster, may wash them out. Variation in back-flow ripple cross-lamination has been observed in the rock record and, by comparison with flume observations, the preserved back-flow ripple morphology may be useful for interpreting formative flow and sediment transport dynamics
On the detectability of the CMSSM light Higgs boson at the Tevatron
We examine the prospects of detecting the light Higgs h^0 of the Constrained
MSSM at the Tevatron. To this end we explore the CMSSM parameter space with
\mu>0, using a Markov Chain Monte Carlo technique, and apply all relevant
collider and cosmological constraints including their uncertainties, as well as
those of the Standard Model parameters. Taking 50 GeV < m_{1/2}, m_0 < 4 TeV,
|A_0| < 7 TeV and 2 < tan(beta) < 62 as flat priors and using the formalism of
Bayesian statistics we find that the 68% posterior probability region for the
h^0 mass lies between 115.4 GeV and 120.4 GeV. Otherwise, h^0 is very similar
to the Standard Model Higgs boson. Nevertheless, we point out some enhancements
in its couplings to bottom and tau pairs, ranging from a few per cent in most
of the CMSSM parameter space, up to several per cent in the favored region of
tan(beta)\sim 50 and the pseudoscalar Higgs mass of m_A\lsim 1 TeV. We also
find that the other Higgs bosons are typically heavier, although not
necessarily much heavier. For values of the h^0 mass within the 95% probability
range as determined by our analysis, a 95% CL exclusion limit can be set with
about 2/fb of integrated luminosity per experiment, or else with 4/fb (12/fb) a
3 sigma evidence (5 sigma discovery) will be guaranteed. We also emphasize that
the alternative statistical measure of the mean quality-of-fit favors a
somewhat lower Higgs mass range; this implies even more optimistic prospects
for the CMSSM light Higgs search than the more conservative Bayesian approach.
In conclusion, for the above CMSSM parameter ranges, especially m_0, either
some evidence will be found at the Tevatron for the light Higgs boson or, at a
high confidence level, the CMSSM will be ruled out.Comment: JHEP versio
Minimizing the stabbing number of matchings, trees, and triangulations
The (axis-parallel) stabbing number of a given set of line segments is the
maximum number of segments that can be intersected by any one (axis-parallel)
line. This paper deals with finding perfect matchings, spanning trees, or
triangulations of minimum stabbing number for a given set of points. The
complexity of these problems has been a long-standing open question; in fact,
it is one of the original 30 outstanding open problems in computational
geometry on the list by Demaine, Mitchell, and O'Rourke. The answer we provide
is negative for a number of minimum stabbing problems by showing them NP-hard
by means of a general proof technique. It implies non-trivial lower bounds on
the approximability. On the positive side we propose a cut-based integer
programming formulation for minimizing the stabbing number of matchings and
spanning trees. We obtain lower bounds (in polynomial time) from the
corresponding linear programming relaxations, and show that an optimal
fractional solution always contains an edge of at least constant weight. This
result constitutes a crucial step towards a constant-factor approximation via
an iterated rounding scheme. In computational experiments we demonstrate that
our approach allows for actually solving problems with up to several hundred
points optimally or near-optimally.Comment: 25 pages, 12 figures, Latex. To appear in "Discrete and Computational
Geometry". Previous version (extended abstract) appears in SODA 2004, pp.
430-43
A high-speed demultiplexer based on a nonlinear optical loop mirror with a photonic crystal fiber
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