2,293 research outputs found
The perturbative odderon in elastic p p and p pbar scattering
Different models for the odderon-proton coupling are considered and their
effects on the differential cross section in the dip region in elastic p p and
p pbar scattering are investigated. An allowed range for the size of a possible
diquark cluster in the proton can be obtained from a geometrical model.Comment: Talk presented at the conference QCD 02 in Montpellier, France. 4
pages, 3 figure
Calculation of the separation streamlines of barchans and transverse dunes
We use FLUENT to calculate the wind profile over barchans and transverse
dunes. The form of the streamlines of flow separation at the lee side of the
dunes is determined for a symmetric barchan dune in three dimensions, and for
the height profile of a measured transverse dune field in the Len\c{c}\'ois
Maranhenses.Comment: 6 pages including 5 figures. Proceedings of PSIS 200
Exploring Outliers in Crowdsourced Ranking for QoE
Outlier detection is a crucial part of robust evaluation for crowdsourceable
assessment of Quality of Experience (QoE) and has attracted much attention in
recent years. In this paper, we propose some simple and fast algorithms for
outlier detection and robust QoE evaluation based on the nonconvex optimization
principle. Several iterative procedures are designed with or without knowing
the number of outliers in samples. Theoretical analysis is given to show that
such procedures can reach statistically good estimates under mild conditions.
Finally, experimental results with simulated and real-world crowdsourcing
datasets show that the proposed algorithms could produce similar performance to
Huber-LASSO approach in robust ranking, yet with nearly 8 or 90 times speed-up,
without or with a prior knowledge on the sparsity size of outliers,
respectively. Therefore the proposed methodology provides us a set of helpful
tools for robust QoE evaluation with crowdsourcing data.Comment: accepted by ACM Multimedia 2017 (Oral presentation). arXiv admin
note: text overlap with arXiv:1407.763
Microscopic theory of surface-enhanced Raman scattering in noble-metal nanoparticles
We present a microscopic model for surface-enhanced Raman scattering (SERS)
from molecules adsorbed on small noble-metal nanoparticles. In the absence of
direct overlap of molecular orbitals and electronic states in the metal, the
main enhancement source is the strong electric field of the surface plasmon
resonance in a nanoparticle acting on a molecule near the surface. In small
particles, the electromagnetic enhancement is strongly modified by quantum-size
effects. We show that, in nanometer-sized particles, SERS magnitude is
determined by a competition between several quantum-size effects such as the
Landau damping of surface plasmon resonance and reduced screening near the
nanoparticle surface. Using time-dependent local density approximation, we
calculate spatial distribution of local fields near the surface and enhancement
factor for different nanoparticles sizes.Comment: 8 pages, 6 figures. Considerably extended final versio
Ab-initio study of the relation between electric polarization and electric field gradients in ferroelectrics
The hyperfine interaction between the quadrupole moment of atomic nuclei and
the electric field gradient (EFG) provides information on the electronic charge
distribution close to a given atomic site. In ferroelectric materials, the loss
of inversion symmetry of the electronic charge distribution is necessary for
the appearance of the electric polarization. We present first-principles
density functional theory calculations of ferroelectrics such as BaTiO3, KNbO3,
PbTiO3 and other oxides with perovskite structures, by focusing on both EFG
tensors and polarization. We analyze the EFG tensor properties such as
orientation and correlation between components and their link with electric
polarization. This work supports previous studies of ferroelectric materials
where a relation between EFG tensors and polarization was observed, which may
be exploited to study ferroelectric order when standard techniques to measure
polarization are not easily applied.Comment: 9 pages, 6 figures, 5 tables, corrected typos, as published in Phys.
Rev.
Proton Drip-Line Calculations and the Rp-process
One-proton and two-proton separation energies are calculated for proton-rich
nuclei in the region . The method is based on Skyrme Hartree-Fock
calculations of Coulomb displacement energies of mirror nuclei in combination
with the experimental masses of the neutron-rich nuclei. The implications for
the proton drip line and the astrophysical rp-process are discussed. This is
done within the framework of a detailed analysis of the sensitivity of rp
process calculations in type I X-ray burst models on nuclear masses. We find
that the remaining mass uncertainties, in particular for some nuclei with
, still lead to large uncertainties in calculations of X-ray burst light
curves. Further experimental or theoretical improvements of nuclear mass data
are necessary before observed X-ray burst light curves can be used to obtain
quantitative constraints on ignition conditions and neutron star properties. We
identify a list of nuclei for which improved mass data would be most important.Comment: 20 pages, 9 figures, 2 table
Recovering rearranged cancer chromosomes from karyotype graphs
BACKGROUND: Many cancer genomes are extensively rearranged with highly aberrant chromosomal karyotypes. Structural and copy number variations in cancer genomes can be determined via abnormal mapping of sequenced reads to the reference genome. Recently it became possible to reconcile both of these types of large-scale variations into a karyotype graph representation of the rearranged cancer genomes. Such a representation, however, does not directly describe the linear and/or circular structure of the underlying rearranged cancer chromosomes, thus limiting possible analysis of cancer genomes somatic evolutionary process as well as functional genomic changes brought by the large-scale genome rearrangements. RESULTS: Here we address the aforementioned limitation by introducing a novel methodological framework for recovering rearranged cancer chromosomes from karyotype graphs. For a cancer karyotype graph we formulate an Eulerian Decomposition Problem (EDP) of finding a collection of linear and/or circular rearranged cancer chromosomes that are determined by the graph. We derive and prove computational complexities for several variations of the EDP. We then demonstrate that Eulerian decomposition of the cancer karyotype graphs is not always unique and present the Consistent Contig Covering Problem (CCCP) of recovering unambiguous cancer contigs from the cancer karyotype graph, and describe a novel algorithm CCR capable of solving CCCP in polynomial time. We apply CCR on a prostate cancer dataset and demonstrate that it is capable of consistently recovering large cancer contigs even when underlying cancer genomes are highly rearranged. CONCLUSIONS: CCR can recover rearranged cancer contigs from karyotype graphs thereby addressing existing limitation in inferring chromosomal structures of rearranged cancer genomes and advancing our understanding of both patient/cancer-specific as well as the overall genetic instability in cancer
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