2,502 research outputs found
Quantum Monte Carlo calculations of neutron-alpha scattering
We describe a new method to treat low-energy scattering problems in
few-nucleon systems, and we apply it to the five-body case of neutron-alpha
scattering. The method allows precise calculations of low-lying resonances and
their widths. We find that a good three-nucleon interaction is crucial to
obtain an accurate description of neutron-alpha scattering.Comment: 4 pages, 2 figures, submitted to Physical Review Letter
Video data modulation study, volume 1 Final report
Video data modulation technique
Neutron Drops and Skyrme Energy-Density Functionals
The J=0 ground state of a drop of 8 neutrons and the lowest
1/2 and 3/2 states of 7-neutron drops, all in an external well, are
computed accurately with variational and Green's function Monte Carlo methods
for a Hamiltonian containing the Argonne two-nucleon and Urbana IX
three-nucleon potentials. These states are also calculated using Skyrme-type
energy-density functionals. Commonly used functionals overestimate the central
density of these drops and the spin-orbit splitting of 7-neutron drops.
Improvements in the functionals are suggested
Field-induced segregation of ferromagnetic nano-domains in PrSrMnO, detected by Mn NMR
The antiferromagnetic manganite PrSrMnO was investigated
at low temperature by means of magnetometry and Mn NMR. A field-induced
transition to a ferromagnetic state is detected by magnetization measurements
at a threshold field of a few tesla. NMR shows that the ferromagnetic phase
develops from zero field by the nucleation of microscopic ferromagnetic
domains, consisting of an inhomogeneous mixture of tilted and fully aligned
parts. At the threshold the NMR spectrum changes discontinuously into that of a
homogeneous, fully aligned, ferromagnetic state, suggesting a percolative
origin for the ferromagnetic transition.Comment: Latex 2.09 language. 4 pages, 3 figures, 23 references. Submitted to
physical Review
A Comparison of Nursing Homes in Rural and Urban Communities in Indiana
The growing number of elderly persons in U.S. society—the “Graying of America”—increases the urgency of making available the resources needed to ensure optimum quality of life for all seniors. When families are no longer able to meet their loved one’s needs, it becomes necessary to consider the possibility of long-term care. Often, families face this decision without the information they need in order to make an informed choice. The researchers utilized a four-tiered categorization to compare nursing homes in most rural, rural, urban and most urban counties in Indiana. The Medicare website (http://www.medicare.gov/) addresses issues of staffing, number of Medicare/Medicaid beds, and quality ratings. The authors discussed implications for elderly residents of rural counties in Indiana and encouraged further research to determine the extent to which their findings may be generalized to the continental U.S
Time-Dependent Current Partition in Mesoscopic Conductors
The currents at the terminals of a mesoscopic conductor are evaluated in the
presence of slowly oscillating potentials applied to the contacts of the
sample. The need to find a charge and current conserving solution to this
dynamic current partition problem is emphasized. We present results for the
electro-chemical admittance describing the long range Coulomb interaction in a
Hartree approach. For multiply connected samples we discuss the symmetry of the
admittance under reversal of an Aharonov-Bohm flux.Comment: 22 pages, 3 figures upon request, IBM RC 1971
Ab initio calculation of the Hoyle state and a new look at clustering in nuclei
I present an ab initio calculation of the spectrum of carbon-12, including
also the famous Hoyle state. Its structure is discussed and a new
interpretation of clustering in nuclear physics is given.Comment: Plenary talk, The Rutherford Centennial Conference on Nuclear
Physics, Manchester, August 8-12, 201
Selecting and implementing overview methods: implications from five exemplar overviews
This is the final version of the article. Available from BioMed Central via the DOI in this record.Background
Overviews of systematic reviews are an increasingly popular method of evidence synthesis; there is a lack of clear guidance for completing overviews and a number of methodological challenges. At the UK Cochrane Symposium 2016, methodological challenges of five overviews were explored. Using data from these five overviews, practical implications to support methodological decision making of authors writing protocols for future overviews are proposed.
Methods
Methods, and their justification, from the five exemplar overviews were tabulated and compared with areas of debate identified within current literature. Key methodological challenges and implications for development of overview protocols were generated and synthesised into a list, discussed and refined until there was consensus.
Results
Methodological features of three Cochrane overviews, one overview of diagnostic test accuracy and one mixed methods overview have been summarised. Methods of selection of reviews and data extraction were similar. Either the AMSTAR or ROBIS tool was used to assess quality of included reviews. The GRADE approach was most commonly used to assess quality of evidence within the reviews.
Eight key methodological challenges were identified from the exemplar overviews. There was good agreement between our findings and emerging areas of debate within a recent published synthesis. Implications for development of protocols for future overviews were identified.
Conclusions
Overviews are a relatively new methodological innovation, and there are currently substantial variations in the methodological approaches used within different overviews. There are considerable methodological challenges for which optimal solutions are not necessarily yet known. Lessons learnt from five exemplar overviews highlight a number of methodological decisions which may be beneficial to consider during the development of an overview protocol.The overview conducted by Pollock [19] was supported by a project grant from the Chief Scientist Office of the Scottish Government. The overview conducted by McClurg [21] was supported by a project grant by the Physiotherapy Research Foundation. The overview by Hunt [22] was supported as part of doctoral programme funding by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care South West Peninsula (PenCLAHRC). The overview conducted by Estcourt [20] was supported by an NIHR Cochrane Programme Grant for the Safe and Appropriate Use of Blood Components. The overview conducted by Brunton [23] was commissioned by the Department of Health as part of an ongoing programme of work on health policy research synthesis.
Alex Pollock is employed by the Nursing, Midwifery and Allied Health Professions (NMAHP) Research Unit, which is supported by the Chief Scientist Office of the Scottish Government. Pauline Campbell is supported by the Chief Nurses Office of the Scottish Government
Many-body effects in 16O(e,e'p)
Effects of nucleon-nucleon correlations on exclusive reactions on
closed-shell nuclei leading to single-hole states are studied using
( MeV, ) as an example. The quasi-hole wave
function, calculated from the overlap of translationally invariant many-body
variational wave functions containing realistic spatial, spin and isospin
correlations, seems to describe the initial state of the struck proton
accurately inside the nucleus, however it is too large at the surface. The
effect of short-range correlations on the final state is found to be largely
cancelled by the increase in the transparency for the struck proton. It is
estimated that the values of the spectroscopic factors obtained with the DWIA
may increase by a few percent due to correlation effects in the final state.Comment: 21 Pages, PHY-7849-TH-9
Quantum Monte Carlo calculations of spectroscopic overlaps in nuclei
We present Green's function Monte Carlo calculations of spectroscopic
overlaps for nuclei. The realistic Argonne v18 two-nucleon and
Illinois-7 three-nucleon interactions are used to generate the nuclear states.
The overlap matrix elements are extrapolated from mixed estimates between
variational Monte Carlo and Green's function Monte Carlo wave functions. The
overlap functions are used to obtain spectroscopic factors and asymptotic
normalization coefficients, and they can serve as an input for low-energy
reaction calculations
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