189 research outputs found
Three-nucleon force at large distances: Insights from chiral effective field theory and the large-N_c expansion
We confirm the claim of Ref. [D.R. Phillips, C. Schat, Phys. Rev. C88 (2013)
3, 034002] that 20 operators are sufficient to represent the most general local
isospin-invariant three-nucleon force and derive explicit relations between the
two sets of operators suggested in Refs. [D.R. Phillips, C. Schat, Phys. Rev.
C88 (2013) 3, 034002] and [H. Krebs, A.M. Gasparyan, E. Epelbaum, Phys.Rev. C87
(2013) 5, 054007]. We use the set of 20 operators to discuss the chiral
expansion of the long- and intermediate-range parts of the three-nucleon force
up to next-to-next-to-next-to-next-to-leading order in the standard formulation
without explicit Delta(1232) degrees of freedom. We also address implications
of the large-N_c expansion in QCD for the size of the various three-nucleon
force contributions.Comment: 15 pages, 6 figure
Are Consensus Ratings of Functional Job Analysis Scales More Reliable than Ratings Made by Independent Raters?
This study addresses an open research question in regard to a well-established and widely-used job analysis system, Functional Job Analysis (FJA): Are consensus ratings of the FJA scales more reliable than the independent scale ratings that are the norm in job analysis application and the related research literature? In our experimental study, we found that this is not the case: no significant difference is found between consensus and independent ratings of the FJA scales. The reasons for this finding are explored as well as its relevance to the validity of the FJA system. Implications for other work and job analysis systems are discussed
Multibaryons in the collective coordinate approach to the SU(3) Skyrme model
We obtain the rotational spectrum of strange multibaryon states by performing
the SU(3) collective coordinate quantization of the static multi-Skyrmions.
These background configurations are given in terms of rational maps, which are
very good approximations and share the same symmetries as the exact solutions.
Thus, the allowed quantum numbers in the spectra and the structure of the
collective Hamiltonians we obtain are also valid in the exact case. We find
that the predicted spectra are in overall agreement with those corresponding to
the alternative bound state soliton model.Comment: 16 pages, 1 figur
The nature of the Lambda(1405)
We present here some results supporting the nature of the
resonance as dynamically generated from the meson baryon interaction in coupled
channels and resulting from the superposition of two close-by poles. We find
support for this picture in the reaction,
which shows a different shape than the one obtained from the reaction. We also call the attention to the with in the region, which shows a narrow
peak in the calculations around 1420 MeV. We also report on recent calculations
of the radiative decay of the two states and on reactions to
obtain information on these decay modes. Finally, we present results for the
reaction recently measured at ANKE/COSY and compare
them with theoretical results.Comment: Talk given at the NSTAR2007 Workshop, Bonn September 200
Radiative decays of decuplet hyperons
We calculate the radiative decay widths of decuplet hyperons in a chiral
constituent quark model including electromagnetic exchange currents between
quarks. Exchange currents contribute significantly to the E2 transition
amplitude, while they largely cancel for the M1 transition amplitude.
Strangeness suppression of the radiative hyperon decays is found to be weakened
by exchange currents. Differences and similarities between our results and
other recent model predictions are discussed.Comment: 11 pages, 1 eps figure, revtex, accepted for publication in Phys.
Rev.
Multibaryons with heavy flavors in the Skyrme model
We investigate the possible existence of multibaryons with heavy flavor
quantum numbers using the bound state approach to the topological soliton model
and the recently proposed approximation for multiskyrmion fields based on
rational maps. We use an effective interaction lagrangian which consistently
incorporates both chiral symmetry and the heavy quark symmetry including the
corrections up to order 1/m_Q. The model predicts some narrow heavy flavored
multibaryon states with baryon number four and seven.Comment: 8 pages, no figures, RevTe
Negative Parity 70-plet Baryon Masses in the 1/Nc Expansion
The masses of the negative parity SU(6) 70-plet baryons are analyzed in the
1/Nc expansion to order 1/Nc and to first order in SU(3) breaking. At this
level of precision there are twenty predictions. Among them there are the well
known Gell-Mann Okubo and equal spacing relations, and four new relations
involving SU(3) breaking splittings in different SU(3) multiplets. Although the
breaking of SU(6) symmetry occurs at zeroth order in 1/Nc, it turns out to be
small. The dominant source of the breaking is the hyperfine interaction which
is of order 1/Nc. The spin-orbit interaction, of zeroth order in 1/Nc, is
entirely fixed by the splitting between the singlet states Lambda(1405) and
Lambda(1520), and the spin-orbit puzzle is solved by the presence of other
zeroth order operators involving flavor exchange.Comment: 31 pages, 3 figure
Work factors and psychological distress in nurses' aides: a prospective cohort study
<p>Abstract</p> <p>Background</p> <p>Nurses' aides (assistant nurses), the main providers of practical patient care in many countries, are doing both emotional and heavy physical work, and are exposed to frequent social encounters in their job. There is scarce knowledge, though, of how working conditions are related to psychological distress in this occupational group. The aim of this study was to identify work factors that predict the level of psychological distress in nurses' aides.</p> <p>Methods</p> <p>The sample of this prospective study comprised 5076 Norwegian nurses' aides, not on leave when they completed a mailed questionnaire in 1999. Of these, 4076 (80.3 %) completed a second questionnaire 15 months later. A wide spectrum of physical, psychological, social, and organisational work factors were measured at baseline. Psychological distress (anxiety and depression) was assessed at baseline and follow-up by the SCL-5, a short version of Hopkins Symptom Checklist-25.</p> <p>Results</p> <p>In a linear regression model of the level of psychological distress at follow-up, with baseline level of psychological distress, work factors, and background factors as independent variables, work factors explained 2 % and baseline psychological distress explained 34 % of the variance. Exposures to role conflicts, exposures to threats and violence, working in apartment units for the aged, and changes in the work situation between baseline and follow-up that were reported to result in less support and encouragement were positively associated with the level of psychological distress. Working in psychiatric departments, and changes in the work situation between baseline and follow-up that gave lower work pace were negatively associated with psychological distress.</p> <p>Conclusion</p> <p>The study suggests that work factors explain only a modest part of the psychological distress in nurses' aides. Exposures to role conflicts and threats and violence at work may contribute to psychological distress in nurses' aides. It is important that protective measures against violent patients are implemented, and that occupational health officers offer victims of violence appropriate support or therapy. It is also important that health service organisations focus on reducing role conflicts, and that leaders listen to and consider the views of the staff.</p
The extraordinary evolutionary history of the reticuloendotheliosis viruses
The reticuloendotheliosis viruses (REVs) comprise several closely related amphotropic retroviruses isolated from birds. These viruses exhibit several highly unusual characteristics that have not so far been adequately explained, including their extremely close relationship to mammalian retroviruses, and their presence as endogenous sequences within the genomes of certain large DNA viruses. We present evidence for an iatrogenic origin of REVs that accounts for these phenomena. Firstly, we identify endogenous retroviral fossils in mammalian genomes that share a unique recombinant structure with REVs—unequivocally demonstrating that REVs derive directly from mammalian retroviruses. Secondly, through sequencing of archived REV isolates, we confirm that contaminated Plasmodium lophurae stocks have been the source of multiple REV outbreaks in experimentally infected birds. Finally, we show that both phylogenetic and historical evidence support a scenario wherein REVs originated as mammalian retroviruses that were accidentally introduced into avian hosts in the late 1930s, during experimental studies of P. lophurae, and subsequently integrated into the fowlpox virus (FWPV) and gallid herpesvirus type 2 (GHV-2) genomes, generating recombinant DNA viruses that now circulate in wild birds and poultry. Our findings provide a novel perspective on the origin and evolution of REV, and indicate that horizontal gene transfer between virus families can expand the impact of iatrogenic transmission events
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