103 research outputs found
Measurement of direct neutron capture by neutron-rich sulfur isotopes
Thermal neutron capture cross sections for S(n,)S and
S(n,)S have been measured and spectroscopic factors of
the final states have been extracted. The calculated direct-capture cross
sections reproduce the experimental data.Comment: 4 pages (uses espcrc1.sty), 1 postscript figure (uses psfig),
accepted for publication in Nucl. Phys. A (Suppl.), uuencoded tex-files and
postscript-files available at ftp://is1.kph.tuwien.ac.at/pub/ohu/Stherm.u
Reaction rate for two--neutron capture by He
Recent investigations suggest that the neutrino--heated hot bubble between
the nascent neutron star and the overlying stellar mantle of a type--II
supernova may be the site of the r--process. In the preceding --process
building up the elements to , the He(2n,)He--
and He(,n)Be--reactions bridging the instability gap at
and could be of relevance. We suggest a mechanism for
He(2n,)He and calculate the reaction rate within the
+n+n approach. The value obtained is about a factor 1.6 smaller than
the one obtained recently in the simpler direct--capture model, but is at least
three order of magnitude enhanced compared to the previously adopted value. Our
calculation confirms the result of the direct--capture calculation that under
representative conditions in the --process the reaction path proceeding
through He is negligible compared to He(n,)Be.Comment: 13 pages, 4 postscript figures, to appear in "Zeitschrift f. Physik
A", changed internet address and filename, the uuencoded postscript file
including the figures is available at
ftp://is1.kph.tuwien.ac.at/pub/ohu/twoneutron.u
Reaction rates for Neutron Capture Reactions to C-, N- and O-isotopes to the neutron rich side of stability
The reaction rates of neutron capture reactions on light nuclei are important
for reliably simulating nucleosynthesis in a variety of stellar scenarios.
Neutron capture reaction rates on neutron-rich C-, N-, and O-isotopes are
calculated in the framework of a hybrid compound and direct capture model. The
results are tabulated and compared with the results of previous calculations as
well as with experimental results.Comment: 33 pages (uses revtex) and 9 postscript figures, accepted for
publication in Phys. Rev.
Consistency of the posterior distribution in generalized linear inverse problems
For ill-posed inverse problems, a regularised solution can be interpreted as
a mode of the posterior distribution in a Bayesian framework. This framework
enriches the set the solutions, as other posterior estimates can be used as a
solution to the inverse problem, such as the posterior mean that can be easier
to compute in practice. In this paper we prove consistency of Bayesian
solutions of an ill-posed linear inverse problem in the Ky Fan metric for a
general class of likelihoods and prior distributions in a finite dimensional
setting. This result can be applied to study infinite dimensional problems by
letting the dimension of the unknown parameter grow to infinity which can be
viewed as discretisation on a grid or spectral approximation of an infinite
dimensional problem. Likelihood and the prior distribution are assumed to be in
an exponential form that includes distributions from the exponential family,
and to be differentiable. The observations can be dependent. No assumption of
finite moments of observations, such as expected value or the variance, is
necessary thus allowing for possibly non-regular likelihoods, and allowing for
non-conjugate and improper priors. If the variance exists, it may be
heteroscedastic, namely, it may depend on the unknown function. We observe
quite a surprising phenomenon when applying our result to the spectral
approximation framework where it is possible to achieve the parametric rate of
convergence, i.e the problem becomes self-regularised. We also consider a
particular case of the unknown parameter being on the boundary of the parameter
set, and show that the rate of convergence in this case is faster than for an
interior point parameter.Comment: arXiv admin note: substantial text overlap with arXiv:1110.301
A glossary for research on human crowd dynamics
This article presents a glossary of terms that are frequently used in research on human crowds. This topic is inherently multidisciplinary as it includes work in and across computer science, engineering, mathematics, physics, psychology and social science, for example. We do not view the glossary presented here as a collection of finalised and formal definitions. Instead, we suggest it is a snapshot of current views and the starting point of an ongoing process that we hope will be useful in providing some guidance on the use of terminology to develop a mutual understanding across disciplines.
The glossary was developed collaboratively during a multidisciplinary meeting. We deliberately allow several definitions of terms, to reflect the confluence of disciplines in the field. This also reflects the fact not all contributors necessarily agree with all definitions in this glossary
Geographical gradient of the <em>eIF4E</em> alleles conferring resistance to potyviruses in pea (<em>Pisum</em>) germplasm
<div><p>Background</p><p>The eukaryotic translation initiation factor 4E was shown to be involved in resistance against several potyviruses in plants, including pea. We combined our knowledge of pea germplasm diversity with that of the <i>eIF4E</i> gene to identify novel genetic diversity.</p><p>Methodology/Principal findings</p><p>Germplasm of 2803 pea accessions was screened for <i>eIF4E</i> intron 3 length polymorphism, resulting in the detection of four <i>eIF4E<sup>A-B-C-S</sup></i> variants, whose distribution was geographically structured. The <i>eIF4E<sup>A</sup></i> variant conferring resistance to the P1 PSbMV pathotype was found in 53 accessions (1.9%), of which 15 were landraces from India, Afghanistan, Nepal, and 7 were from Ethiopia. A newly discovered variant, <i>eIF4E<sup>B</sup></i>, was present in 328 accessions (11.7%) from Ethiopia (29%), Afghanistan (23%), India (20%), Israel (25%) and China (39%). The <i>eIF4E<sup>C</sup></i> variant was detected in 91 accessions (3.2% of total) from India (20%), Afghanistan (33%), the Iberian Peninsula (22%) and the Balkans (9.3%). The <i>eIF4E<sup>S</sup></i> variant for susceptibility predominated as the wild type. Sequencing of 73 samples, identified 34 alleles at the whole gene, 26 at cDNA and 19 protein variants, respectively. Fifteen alleles were virologically tested and 9 alleles (<i>eIF4E<sup>A-1-2-3-4-5-6-7</sup></i>, <i>eIF4E<sup>B-1</sup></i>, <i>eIF4E<sup>C-2</sup></i>) conferred resistance to the P1 PSbMV pathotype.</p><p>Conclusions/Significance</p><p>This work identified novel <i>eIF4E</i> alleles within geographically structured pea germplasm and indicated their independent evolution from the susceptible <i>eIF4E<sup>S1</sup></i> allele. Despite high variation present in wild <i>Pisum</i> accessions, none of them possessed resistance alleles, supporting a hypothesis of distinct mode of evolution of resistance in wild as opposed to crop species. The Highlands of Central Asia, the northern regions of the Indian subcontinent, Eastern Africa and China were identified as important centers of pea diversity that correspond with the diversity of the pathogen. The series of alleles identified in this study provides the basis to study the co-evolution of potyviruses and the pea host.</p></div
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