1,010 research outputs found
Efimov universality with Coulomb interaction
The universal properties of charged particles are modified by the presence of
a long-range Coulomb interaction. We investigate the modification of Efimov
universality as a function of the Coulomb strength using the Gaussian expansion
method. The resonant short-range interaction is described by Gaussian
potentials to which a Coulomb potential is added. We calculate binding energies
and root mean square radii for the three- and four-body systems of charged
particles and present our results in a generalised Efimov plot. We find that
universal features can still be discerned for weak Coulomb interaction, but
break down for strong Coulomb interaction. The root-mean-square radius plateaus
at increasingly smaller values for strong Coulomb interaction and the
probablity distributions of the states become more concentrated inside the
Coulomb barrier. As an example, we apply our universal model to nuclei with an
alpha-cluster substructure. Our results point to strong non-universal
contributions in that sector.Comment: 18 pages, 9 figures, final version (with small orthographical
corrections
Continuum-discretized coupled-channels method for four-body nuclear breakup in He+C scattering
We propose a fully quantum-mechanical method of treating four-body nuclear
breakup processes in scattering of a projectile consisting of three
constituents, by extending the continuum-discretized coupled-channels method.
The three-body continuum states of the projectile are discretized by
diagonalizing the internal
Hamiltonian of the projectile with the Gaussian basis functions. For
He+C scattering at 18 and 229.8 MeV, the validity of the method is
tested by convergence of the elastic and breakup cross sections with respect to
increasing the number of the basis functions. Effects of the four-body breakup
and the Borromean structure of He on the elastic and total reaction cross
sections are discussed.Comment: 5 pages, 6 figures, uses REVTeX 4, submitted to Phys. Rev.
-- coupling in He with the Nijmegen soft-core potentials
The -- coupling in
He is studied with the [ + +
] + [ + + ] + [ + + ] model,
where the particle is assumed as a frozen core. We use the Nijmegen
soft-core potentials, NSC97e and NSC97f, for the valence baryon-baryon part,
and the phenomenological potentials for the parts (=,
, and ). We find that the calculated of He for NSC97e and NSC97f are,
respectively, 0.6 and 0.4 MeV in the full coupled-channel calculation, the
results of which are about half in comparison with the experimental data,
MeV.
Characteristics of the sector in the NSC97 potentials are discussed in
detail.Comment: 18 pages, 4 figure
A robust method for estimating gene expression states using Affymetrix microarray probe level data
<p>Abstract</p> <p>Background</p> <p>Microarray technology is a high-throughput method for measuring the expression levels of thousand of genes simultaneously. The observed intensities combine a non-specific binding, which is a major disadvantage with microarray data. The Affymetrix GeneChip assigned a mismatch (MM) probe with the intention of measuring non-specific binding, but various opinions exist regarding usefulness of MM measures. It should be noted that not all observed intensities are associated with expressed genes and many of those are associated with unexpressed genes, of which measured values express mere noise due to non-specific binding, cross-hybridization, or stray signals. The implicit assumption that all genes are expressed leads to poor performance of microarray data analyses. We assume two functional states of a gene - expressed or unexpressed - and propose a robust method to estimate gene expression states using an order relationship between PM and MM measures.</p> <p>Results</p> <p>An indicator 'probability of a gene being expressed' was obtained using the number of probe pairs within a probe set where the PM measure exceeds the MM measure. We examined the validity of the proposed indicator using Human Genome U95 data sets provided by Affymetrix. The usefulness of 'probability of a gene being expressed' is illustrated through an exploration of candidate genes involved in neuroblastoma prognosis. We identified the candidate genes for which expression states differed (un-expressed or expressed) when compared between two outcomes. The validity of this result was subsequently confirmed by quantitative RT-PCR.</p> <p>Conclusion</p> <p>The proposed qualitative evaluation, 'probability of a gene being expressed', is a useful indicator for improving microarray data analysis. It is useful to reduce the number of false discoveries. Expression states - expressed or unexpressed - correspond to the most fundamental gene function 'On' and 'Off', which can lead to biologically meaningful results.</p
Spin-orbit splitting of 9 Lambda Be excited states studied with the SU_6 quark-model baryon-baryon interactions
The previous Faddeev calculation of the two-alpha plus Lambda system for 9
Lambda Be is extended to incorporate the spin-orbit components of the SU_6
quark-model baryon-baryon interactions. We employ the Born kernel of the
quark-model Lambda N LS interaction, and generate the spin-orbit component of
the Lambda alpha potential by the alpha-cluster folding. The Faddeev
calculation in the jj-coupling scheme implies that the direct use of the
quark-model Born kernel for the Lambda N LS component is not good enough to
reproduce the small experimental value Delta E^exp_{ls}=43 +- 5 keV for the
5/2^+ - 3/2^+ splitting. This procedure predicts three to five times larger
values in the model FSS and fss2. The spin-orbit contribution from the
effective meson-exchange potentials in fss2 is argued to be unfavorable to the
small ls splitting, through the analysis of the Scheerbaum factors for the
single-particle spin-orbit potentials calculated in the G-matrix formalism.Comment: 4 pages, 1 figur
Interaction of hHR23 with S5a. The ubiquitin-like domain of hHR23 mediates interaction with S5a subunit of 26 S proteasome
hHR23B is one of two human homologs of the Saccharomyces cerevisiae
nucleotide excision repair (NER) gene product RAD23 and a component of a
protein complex that specifically complements the NER defect of xeroderma
pigmentosum group C (XP-C) cell extracts in vitro. Although a small
proportion of hHR23B is tightly complexed with the XP-C responsible gene
product, XPC protein, a vast majority exists as an XPC-free form,
indicating that hHR23B has additional functions other than NER in vivo.
Here we demonstrate that the human NER factor hHR23B as well as another
human homolog of RAD23, hHR23A, interact specifically with S5a, a subunit
of the human 26 S proteasome using the yeast two-hybrid system.
Furthermore, hHR23 proteins were detected with S5a at the position where
26 S proteasome sediments in glycerol gradient centrifugation of HeLa S100
extracts. Intriguingly, hHR23B showed the inhibitory effect on the
degradation of (125)I-lysozyme in the rabbit reticulocyte lysate. hHR23
proteins thus appear to associate with 26 S proteasome in vivo. From
co-precipitation experiments using several series of deletion mutants, we
defined the domains in hHR23B and S5a that mediate this interaction. From
these results, we propose that part of hHR23 proteins are involved in the
proteolytic pathway in cells
Variational calculations for the hydrogen-antihydrogen system with a mass-scaled Born-Oppenheimer potential
The problem of proton-antiproton motion in the --
system is investigated by means of the variational method. We introduce a
modified nuclear interaction through mass-scaling of the Born-Oppenheimer
potential. This improved treatment of the interaction includes the nondivergent
part of the otherwise divergent adiabatic correction and shows the correct
threshold behavior.
Using this potential we calculate the vibrational energy levels with angular
momentum 0 and 1 and the corresponding nuclear wave functions, as well as the
S-wave scattering length. We obtain a full set of all bound states together
with a large number of discretized continuum states that might be utilized in
variational four-body calculations. The results of our calculations gives an
indication of resonance states in the hydrogen-antihydrogen system
Benchmark Test Calculation of a Four-Nucleon Bound State
In the past, several efficient methods have been developed to solve the
Schroedinger equation for four-nucleon bound states accurately. These are the
Faddeev-Yakubovsky, the coupled-rearrangement-channel Gaussian-basis
variational, the stochastic variational, the hyperspherical variational, the
Green's function Monte Carlo, the no-core shell model and the effective
interaction hyperspherical harmonic methods. In this article we compare the
energy eigenvalue results and some wave function properties using the realistic
AV8' NN interaction. The results of all schemes agree very well showing the
high accuracy of our present ability to calculate the four-nucleon bound state.Comment: 17 pages, 1 figure
Inclusive and exclusive photoproduction on the deuteron: - and -threshold phenomena
Inclusive and exclusive photoproduction on the deuteron are
investigated theoretically. Modern hyperon-nucleon forces and a recently
updated kaon photoproduction operator for the process are
used. Sizable effects of the hyperon-nucleon final state interaction are found
near the and thresholds in the inclusive reaction.
Angular distributions for the exclusive process show clear final state
interaction effects in certain kinematic regions. Precise data especially for
the inclusive process around the threshold would help to clarify
the strength and property of the interaction.Comment: 14 pages, 10 figure
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