3,940 research outputs found
On the spin-isospin decomposition of nuclear symmetry energy
The decomposition of nuclear symmetry energy into spin and isospin components
is discussed to elucidate the underlying properties of the NN bare interaction.
This investigation was carried out in the framework of the
Brueckner-Hartree-Fock theory of asymmetric nuclear matter with consistent two
and three body forces. It is shown the interplay among the various two body
channels in terms of isospin singlet and triplet components as well as spin
singlet and triplet ones. The broad range of baryon densities enables to study
the effects of three body force moving from low to high densities.Comment: 8 pages, 4 figure
Nuclear Pairing in the T=0 channel revisited
Recent published data on the isoscalar gap in symmetric nuclear matter using
the Paris force and the corresponding BHF single particle dispersion are
corrected leading to an extremely high proton-neutron gap of
MeV at . Arguments whether this value can be reduced due
to screening effects are discussed. A density dependent delta interaction with
cut off is adjusted so as to approximately reproduce the nuclear matter values
with the Paris force.Comment: 4 pages, 4 figure
Specific Heat of a Fractional Quantum Hall System
Using a time-resolved phonon absorption technique, we have measured the
specific heat of a two-dimensional electron system in the fractional quantum
Hall effect regime. For filling factors
and 1/3 the specific heat displays a strong exponential temperature dependence
in agreement with excitations across a quasi-particle gap. At filling factor
we were able to measure the specific heat of a composite fermion
system for the first time. The observed linear temperature dependence on
temperature down to K agrees well with early predictions for a Fermi
liquid of composite fermions.Comment: 4 pages, 4 figures (version is 1. resubmission: Added a paragraph to
include the problems which arise by the weak temperature dependence at \nu =
1/2, updated affiliation
Phonon emission and absorption in the fractional quantum Hall effect
We investigate the time dependent thermal relaxation of a two-dimensional
electron system in the fractional quantum Hall regime where ballistic phonons
are used to heat up the system to a non-equilibrium temperature. The thermal
relaxation of a 2DES at can be described in terms of a broad band
emission of phonons, with a temperature dependence proportional to . In
contrast, the relaxation at fractional filling is characterized by
phonon emission around a single energy, the magneto-roton gap. This leads to a
strongly reduced energy relaxation rate compared to with only a weak
temperature dependence for temperatures 150 mK 400 mK.Comment: 4 pages, 3 figures; 14th International Conference on High Magnetic
Fields in Semiconductor Physics, September 24-29, 2000, Matsue, Japa
PALMA: Perfect Alignments using Large Margin Algorithms
Despite many years of research on how to properly align sequences in the presence of sequencing errors, alternative splicing and micro-exons, the correct alignment of mRNA sequences to genomic DNA is still a challenging task. We present a novel approach based on large margin learning that combines kernel based splice site predictions with common sequence alignment techniques. By solving a convex optimization problem, our algorithm -- called PALMA -- tunes the parameters of the model such that the true alignment scores higher than all other alignments. In an experimental study on the alignments of mRNAs containing artificially generated micro-exons, we show that our algorithm drastically outperforms all other methods: It perfectly aligns all 4358 sequences on an hold-out set, while the best other method misaligns at least 90 of them. Moreover, our algorithm is very robust against noise in the query sequence: when deleting, inserting, or mutating up to 50 of the query sequence, it still aligns 95 of all sequences correctly, while other methods achieve less than 36 accuracy. For datasets, additional results and a stand-alone alignment tool see http://www.fml.mpg.de/raetsch/projects/palma
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