2,122 research outputs found
Electroinduced two-nucleon knockout and correlations in nuclei
We present a model to calculate cross sections for electroinduced two-nucleon
emission from finite nuclei. Short-range correlations in the wave functions and
meson-exchange contributions to the photoabsorption process are implemented.
Effects of the short-range correlations are studied with the aid of a
perturbation expansion method with various choices of the Jastrow correlation
function. The model is used to investigate the relative importance of the
different reaction mechanisms contributing to the A(e,epn) and A(e,epp)
process. Representative examples for the target nuclei C and O
and for kinematical conditions accessible with contemporary high-duty cycle
electron accelerators are presented. A procedure is outlined to calculate the
two-nucleon knockout contribution to the semi-exclusive (e,ep) cross
section. Using this technique we investigate in how far semi-exclusive
(e,ep) reactions can be used to detect high-momentum components in the
nuclear spectral function.Comment: 51 pages, Latex, uses epsf.sty and elsart.sty, 17 figures (in eps
format
Mean-field calculations of quasi-elastic responses in 4He
We present calculations of the quasi-elastic responses functions in 4He based
upon a mean-field model used to perform analogous calculations in heavier
nuclei. The meson exchange current contribution is small if compared with the
results of calculations where short-range correlations are explicitly
considered. It is argued that the presence of these correlations in the
description of the nuclear wave functions is crucial to make meson exchange
current effects appreciable.Comment: uuencoded file containing 7 LaTex peges plus 3 ps figures. To be
published in Physical Review
Neutrino-nucleus quasi-elastic scattering and strange quark effects
A relativistic distorted-wave impulse-approximation model is applied to
quasi-elastic neutrino-nucleus scattering. The bound state is obtained in the
framework of the relativistic mean field theory and the final state interaction
is taken into account in the scattering state. Results for the charged- and
neutral-current neutrino (antineutrino) reactions on C target nucleus
are presented and the sensitivity of various quantities to the strange quark
content of the nucleon weak current is discussed.Comment: 18 pages, 10 figure
On the role of the effective interaction in quasi-elastic electron scattering calculations
The role played by the effective residual interaction in the transverse
nuclear response for quasi-free electron scattering is discussed. The analysis
is done by comparing different calculations performed in the Random--Phase
Approximation and Ring Approximation frameworks. The importance of the exchange
terms in this energy region is investigated and the changes on the nuclear
responses due to the modification of the interaction are evaluated. The
calculated quasi-elastic responses show clear indication of their sensibility
to the details of the interaction and this imposes the necessity of a more
careful study of the role of the different channels of the interaction in this
excitation region.Comment: 16 pages, 4 Postscript figure
Appointments, pay and performance in UK boardrooms by gender
This article uses UK data to examine issues regarding the scarcity of women in boardroom positions. The article examines appointments, pay and any associated productivity effects deriving from increased diversity. Evidence of gender-bias in the appointment of women as non-executive directors is found together with mixed evidence of discrimination in wages or fees paid. However, the article finds no support for the argument that gender diverse boards enhance corporate performance. Proposals in favour of greater board diversity may be best structured around the moral value of diversity, rather than with reference to an expectation of improved company performance
Reluctant Donors? The Europeanization of International Development Policies in the New Members
The EU played an instrumental role re-starting the international development policies in Central and Eastern European member states, but questions remain about how far this policy area has been Europeanized since accession. Focusing on the Czech Republic, Hungary, Poland and Slovakia, the paper investigates why the new donors have been reluctant to adopt the EU’s development acquis more fully. The paper traces the process of the EU’s development policy rulemaking and subsequent national rule implementation to understand the socialization opportunities these processes offer. The conclusions reveal thrre reasons why socialization has been weak: (1) perceptions among the new member states on the development acquis’ procedural legitimacy; (2) low domestic resonance with the development acquis; and (3) inconsistencies in the activities of norm entrepreneurs. The paper contributes to our understanding of development policy in the EU, in particular how decision making takes place within the Council and its Working Groups post enlargement
Changes in and predictors of length of stay in hospital after surgery for breast cancer between 1997/98 and 2004/05 in two regions of England: a population-based
BACKGROUND
Decreases in length of stay (LOS) in hospital after breast cancer surgery can be partly attributed to the change to less radical surgery, but many other factors are operating at the patient, surgeon and hospital levels. This study aimed to describe the changes in and predictors of length of stay (LOS) in hospital after surgery for breast cancer between 1997/98 and 2004/05 in two regions of England.
METHODS
Cases of female invasive breast cancer diagnosed in two English cancer registry regions were linked to Hospital Episode Statistics data for the period 1st April 1997 to 31st March 2005. A subset of records where women underwent mastectomy or breast conserving surgery (BCS) was extracted (n = 44,877). Variations in LOS over the study period were investigated. A multilevel model with patients clustered within surgical teams and NHS Trusts was used to examine associations between LOS and a range of factors.
RESULTS
Over the study period the proportion of women having a mastectomy reduced from 58% to 52%. The proportion varied from 14% to 80% according to NHS Trust. LOS decreased by 21% from 1997/98 to 2004/05 (LOSratio = 0.79, 95%CI 0.77-0.80). BCS was associated with 33% shorter hospital stays compared to mastectomy (LOSratio = 0.67, 95%CI 0.66-0.68). Older age, advanced disease, presence of comorbidities, lymph node excision and reconstructive surgery were associated with increased LOS. Significant variation remained amongst Trusts and surgical teams.
CONCLUSION
The number of days spent in hospital after breast cancer surgery has continued to decline for several decades. The change from mastectomy to BCS accounts for only 9% of the overall decrease in LOS. Other explanations include the adoption of new techniques and practices, such as sentinel lymph node biopsy and early discharge. This study has identified wide variation in practice with substantial cost implications for the NHS. Further work is required to explain this variation
Antisymmetrized Green's function approach to reactions with a realistic nuclear density
A completely antisymmetrized Green's function approach to the inclusive
quasielastic scattering, including a realistic one-body density, is
presented. The single particle Green's function is expanded in terms of the
eigenfunctions of the nonhermitian optical potential. This allows one to treat
final state interactions consistently in the inclusive and in the exclusive
reactions. Nuclear correlations are included in the one-body density. Numerical
results for the response functions of O and Ca are presented and
discussed.Comment: 45 pages, 3 figure
One Body Density Matrix, Natural Orbits and Quasi Hole States in 16O and 40Ca
The one body density matrix, momentum distribution, natural orbits and quasi
hole states of 16O and 40Ca are analyzed in the framework of the correlated
basis function theory using state dependent correlations with central and
tensor components. Fermi hypernetted chain integral equations and single
operator chain approximation are employed to sum cluster diagrams at all
orders. The optimal trial wave function is determined by means of the
variational principle and the realistic Argonne v8' two-nucleon and Urbana IX
three-nucleon interactions. The correlated momentum distributions are in good
agreement with the available variational Monte Carlo results and show the well
known enhancement at large momentum values with respect to the independent
particle model. Diagonalization of the density matrix provides the natural
orbits and their occupation numbers. Correlations deplete the occupation number
of the first natural orbitals by more than 10%. The first following ones result
instead occupied by a few percent. Jastrow correlations lower the spectroscopic
factors of the valence states by a few percent (~1-3%) and an additional ~8-12%
depletion is provided by tensor correlations. It is confirmed that short range
correlations do not explain the spectroscopic factors extracted from (e,e'p)
experiments. 2h-1p perturbative corrections in the correlated basis are
expected to provide most of the remaining strength, as in nuclear matter.Comment: 25 pages, 9 figures. Submitted to Phys.Rev.
Illness perceptions and explanatory models of viral hepatitis B & C among immigrants and refugees: a narrative systematic review.
© 2015 Owiti et al.; licensee BioMed Central. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain
Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article,
unless otherwise stated.BACKGROUND: Hepatitis B and C (HBV, HCV) infections are associated with high morbidity and mortality. Many countries with traditionally low prevalence (such as UK) are now planning interventions (screening, vaccination, and treatment) of high-risk immigrants from countries with high prevalence. This review aimed to synthesise the evidence on immigrants' knowledge of HBV and HCV that might influence the uptake of clinical interventions. The review was also used to inform the design and successful delivery of a randomised controlled trial of targeted screening and treatment. METHODS: Five databases (PubMed, CINHAL, SOCIOFILE, PsycINFO & Web of Science) were systematically searched, supplemented by reference tracking, searches of selected journals, and of relevant websites. We aimed to identify qualitative and quantitative studies that investigated knowledge of HBV and HCV among immigrants from high endemic areas to low endemic areas. Evidence, extracted according to a conceptual framework of Kleinman's explanatory model, was subjected to narrative synthesis. We adapted the PEN-3 model to categorise and analyse themes, and recommend strategies for interventions to influence help-seeking behaviour. RESULTS: We identified 51 publications including quantitative (n = 39), qualitative (n = 11), and mixed methods (n = 1) designs. Most of the quantitative studies included small samples and had heterogeneous methods and outcomes. The studies mainly concentrated on hepatitis B and ethnic groups of South East Asian immigrants residing in USA, Canada, and Australia. Many immigrants lacked adequate knowledge of aetiology, symptoms, transmission risk factors, prevention strategies, and treatment, of hepatitis HBV and HCV. Ethnicity, gender, better education, higher income, and English proficiency influenced variations in levels and forms of knowledge. CONCLUSION: Immigrants are vulnerable to HBV and HCV, and risk life-threatening complications from these infections because of poor knowledge and help-seeking behaviour. Primary studies in this area are extremely diverse and of variable quality precluding meta-analysis. Further research is needed outside North America and Australia
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