8,256 research outputs found
Some neutron and gamma radiation characteristics of plutonium cermet fuel for isotopic power sources
Gamma and neutron measurements on various types of plutonium sources are presented in order to show the effects of O-17, O-18 F-19, Pu-236, age of the fuel, and size of the source on the gamma and neutron spectra. Analysis of the radiation measurements shows that fluorine is the main contributor to the neutron yields from present plutonium-molybdenum cermet fuel, while both fluorine and Pu-236 daughters contribute significantly to the gamma ray intensities
Particle-core coupling in S 37
R. Chapman et al. ; 8 págs.; 6 figs.; 2 tabs.Excited states of the neutron-rich N=21 S37 nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. The level scheme of S37 was established to an excitation energy of 4196 keV and a number of new transitions were observed, in particular that corresponding to the decay of the proposed Jπ=(11/2-) level at an excitation energy of 2776 keV. The structure of the state is discussed within the context of state-of-the-art shell-model calculations using the SDPF-U effective interaction; the main component of the wave function corresponds to the coupling of the odd 1f7/2 neutron to the first 2+ state of the S36 core. The electromagnetic decay properties of the state are discussed within the context of a particle-core coupling model and the shell model. The other members of the multiplet of states are also discussed. ©2016 American Physical SocietyWe would like to thank the technical staff of the INFN
Legnaro National Laboratory for their support during this experiment.
This work was supported by the EPSRC (U.K). Four
of us (A.H,M.B, K.L.K., and A.P.) would like to acknowledge
the receipt of financial support from EPSRC during the course
of this work. A.J. would like to acknowledge support from
the Spanish Ministerio de EconomÃa y Competitividad under
Contract No. FPA2014-57196-C5-4-P. Z.D. acknowledges
financial support from OTKA Grant No. K100835.Peer Reviewe
Herschel/PACS far-infrared photometry of two z>4 quasars
We present Herschel far-infrared (FIR) observations of two sub-mm bright
quasars at high redshift: SDSS J1148+5251 (z=6.42) and BR 1202-0725 (z=4.69)
obtained with the PACS instrument. Both objects are detected in the PACS
photometric bands. The Herschel measurements provide additional data points
that constrain the FIR spectral energy distributions (SEDs) of both sources,
and they emphasise a broad range of dust temperatures in these objects. For
lambda_rest ~< 20mu, the two SEDs are very similar to the average SEDs of
quasars at low redshift. In the FIR, however, both quasars show excess emission
compared to low-z QSO templates, most likely from cold dust powered by vigorous
star formation in the QSO host galaxies. For SDSS J1148+5251 we detect another
object at 160mu with a distance of ~10 arcseconds from the QSO. Although no
physical connection between the quasar and this object can be shown with the
available data, it could potentially confuse low-resolution measurements, thus
resulting in an overestimate of the FIR luminosity of the z=6.42 quasar.Comment: 4 pages, 3 figures, accepted for publication in the A&A special issue
on Hersche
First in-beam γ -ray study of the level structure of neutron-rich S 39
R. Chapman et al. ; 8 págs.; 6 figs.; 1 tab.The neutron-rich S39 nucleus has been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. Gamma-ray transitions of the following energies were observed: 339, 398, 466, 705, 1517, 1656, and 1724 keV. Five of the observed transitions have been tentatively assigned to the decay of excited states with spins up to (11/2-). The results of a state-of-the-art shell-model calculation of the level scheme of S39 using the SDPF-U effective interaction are also presented. The systematic behavior of the excitation energy of the first 11/2- states in the odd-A isotopes of sulfur and argon is discussed in relation to the excitation energy of the first excited 2+ states of the adjacent even-A isotopes. The states of S39 that have the components in their wave functions corresponding to three neutrons in the 1f7/2 orbital outside the N=20 core have also been discussed within the context of the 0 ω shell-model calculations presented here. ©2016 American Physical SocietyThis work was supported in part by the EPSRC (UK)
and by the European Union under Contract No. RII3-CT-
2004-506065. Five of us (D.O., M.B., A.H., K.K., and A.P.)
acknowledge financial support from the EPSRC. Z.M.W.
acknowledges support from ORSAS and from the University
of the West of Scotland. A.N.D. acknowledges support from
the STFC. A.J. acknowledges financial support from the
Spanish Ministerio de Ciencia e Innovación under Contracts
No. FPA2007-66069 and No. FPA2009-13377-C02-02. Zs.D.
acknowledges financial support from OTKA under Project
No. K100835. S.S. acknowledges support from the Croatian
Science Foundation under Project No. 7194. The contribution
of the accelerator and target-fabrication staff at the INFN
Legnaro National Laboratory is gratefully acknowledged.Peer Reviewe
First in-beam γ -ray study of the level structure of neutron-rich S 39
The neutron-rich S39 nucleus has been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. Gamma-ray transitions of the following energies were observed: 339, 398, 466, 705, 1517, 1656, and 1724 keV. Five of the observed transitions have been tentatively assigned to the decay of excited states with spins up to (11/2-). The results of a state-of-the-art shell-model calculation of the level scheme of S39 using the SDPF-U effective interaction are also presented. The systematic behavior of the excitation energy of the first 11/2- states in the odd-A isotopes of sulfur and argon is discussed in relation to the excitation energy of the first excited 2+ states of the adjacent even-A isotopes. The states of S39 that have the components in their wave functions corresponding to three neutrons in the 1f7/2 orbital outside the N=20 core have also been discussed within the context of the 0 ω shell-model calculations presented here. © 2016 American Physical Society
Particle-core coupling in S 37
Excited states of the neutron-rich N=21 S37 nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. The level scheme of S37 was established to an excitation energy of 4196 keV and a number of new transitions were observed, in particular that corresponding to the decay of the proposed Jπ=(11/2-) level at an excitation energy of 2776 keV. The structure of the state is discussed within the context of state-of-the-art shell-model calculations using the SDPF-U effective interaction; the main component of the wave function corresponds to the coupling of the odd 1f7/2 neutron to the first 2+ state of the S36 core. The electromagnetic decay properties of the state are discussed within the context of a particle-core coupling model and the shell model. The other members of the multiplet of states are also discussed. © 2016 American Physical Society
Improved annotation of 3' untranslated regions and complex loci by combination of strand-specific direct RNA sequencing, RNA-seq and ESTs
The reference annotations made for a genome sequence provide the framework
for all subsequent analyses of the genome. Correct annotation is particularly
important when interpreting the results of RNA-seq experiments where short
sequence reads are mapped against the genome and assigned to genes according to
the annotation. Inconsistencies in annotations between the reference and the
experimental system can lead to incorrect interpretation of the effect on RNA
expression of an experimental treatment or mutation in the system under study.
Until recently, the genome-wide annotation of 3-prime untranslated regions
received less attention than coding regions and the delineation of intron/exon
boundaries. In this paper, data produced for samples in Human, Chicken and A.
thaliana by the novel single-molecule, strand-specific, Direct RNA Sequencing
technology from Helicos Biosciences which locates 3-prime polyadenylation sites
to within +/- 2 nt, were combined with archival EST and RNA-Seq data. Nine
examples are illustrated where this combination of data allowed: (1) gene and
3-prime UTR re-annotation (including extension of one 3-prime UTR by 5.9 kb);
(2) disentangling of gene expression in complex regions; (3) clearer
interpretation of small RNA expression and (4) identification of novel genes.
While the specific examples displayed here may become obsolete as genome
sequences and their annotations are refined, the principles laid out in this
paper will be of general use both to those annotating genomes and those seeking
to interpret existing publically available annotations in the context of their
own experimental dataComment: 44 pages, 9 figure
Composite quasiparticle formation and the low-energy effective Hamiltonians of the one- and two-dimensional Hubbard Model
We investigate the effect of hole doping on the strong-coupling Hubbard model
at half-filling in spatial dimensions . We start with an
antiferromagnetic mean-field description of the insulating state, and show that
doping creates solitons in the antiferromagnetic background. In one dimension,
the soliton is topological, spinless, and decoupled from the background
antiferromagnetic fluctuations at low energies. In two dimensions and above,
the soliton is non-topological, has spin quantum number 1/2, and is strongly
coupled to the antiferromagnetic fluctuations. We derive the effective action
governing the quasiparticle motion, study the properties of a single carrier,
and comment on a possible description at finite concentration.Comment: REVTEX 3.0, 22 pages with 14 figures in the PostScript format
compressed using uufile. Submitted to Phys. Rev. B. The complete PostScript
file including figures can be obtained via ftp at
ftp://serval.berkeley.edu/hubbard.ps . It is also available via www at
http://roemer.fys.ku.dk/recent.ht
Heavy Quarkonium Potential Model and the State of Charmonium
A theoretical explanation of the observed splittings among the P~states of
charmonium is given with the use of a nonsingular potential model for heavy
quarkonia. We also show that the recently observed mass difference between the
center of gravity of the states and the state of
does not provide a direct test of the color hyperfine interaction in heavy
quarkonia. Our theoretical value for the mass of the state is in
agreement with the experimental result, and its E1 transition width is
341.8~keV. The mass of the state is predicted to be 3622.3~MeV.Comment: 15 page REVTEX documen
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