3,944 research outputs found
Collinear versus non-collinear magnetic order in Pd atomic clusters: ab-initio calculations
We present a thorough theoretical assessment of the stability of
non-collinear spin arrangements in small palladium clusters. We generally find
that ferromagnetic order is always preferred, but that antiferromagnetic and
non-collinear configurations of different sorts exist and compete for the first
excited isomers. We also show that the ground state is insensitive to the
choice of atomic configuration for the pseudopotential used and to the
approximation taken for the exchange and correlation potential. Moreover, the
existence and relative stability of the different excited configurations also
depends weakly on the approximations employed. These results provide strong
evidence on the transferability of pseudopotential and exchange and correlation
functionals for palladium clusters as opposed to the situation found for the
bulk phases of palladium.Comment: 5 pages, 4 figure
Simultaneous Optical Model Analyses of Elastic Scattering, Breakup, and Fusion Cross Section Data for the He + Bi System at Near-Coulomb-Barrier Energies
Based on an approach recently proposed by us, simultaneous
-analyses are performed for elastic scattering, direct reaction (DR)
and fusion cross sections data for the He+Bi system at
near-Coulomb-barrier energies to determine the parameters of the polarization
potential consisting of DR and fusion parts. We show that the data are well
reproduced by the resultant potential, which also satisfies the proper
dispersion relation. A discussion is given of the nature of the threshold
anomaly seen in the potential
Structural and energetic properties of nickel clusters:
The four most stable structures of Ni clusters with from 2 to 150
have been determined using a combination of the embedded-atom method in the
version of Daw, Baskes and Foiles, the {\it variable metric/quasi-Newton}
method, and our own {\it Aufbau/Abbau} method. A systematic study of
energetics, structure, growth, and stability of also larger clusters has been
carried through without more or less severe assumptions on the initial
geometries in the structure optimization, on the symmetry, or on bond lengths.
It is shown that cluster growth is predominantly icosahedral with of
{\it fcc}, {\it tetrahedral} and {\it decahedral} growth. For the first time in
unbiased computations it is found that Ni is the multilayer (third
Mackay) icosahedron. Further, we point to an enhanced ability of {\it fcc}
clusters to compete with the icosahedral and decahedral structures in the
vicinity of N=79. In addition, it is shown that conversion from the {\it
hcp}/anti-Mackay kind of icosahedral growth to the {\it fcc}/Mackay one occurs
within a transition layer including several cluster sizes. Moreover, we present
and apply different analytical tools in studying structural and energetic
properties of such a large class of clusters. These include means for
identifying the overall shape, the occurrence of atomic shells, the similarity
of the clusters with, e.g., fragments of the {\it fcc} crystal or of a large
icosahedral cluster, and a way of analysing whether the -atom cluster can be
considered constructed from the -atom one by adding an extra atom. In
addition, we compare in detail with results from chemical-probe experiment.
Maybe the most central result is that first for clusters with above 80
general trends can be identified.Comment: 37 pages, 11 figure
Spin-one color superconductivity in compact stars?- an analysis within NJL-type models
We present results of a microscopic calculation using NJL-type model of
possible spin-one pairings in two flavor quark matter for applications in
compact star phenomenology. We focus on the color-spin locking phase (CSL) in
which all quarks pair in a symmetric way, in which color and spin states are
locked. The CSL condensate is particularly interesting for compact star
applications since it is flavor symmetric and could easily satisfy charge
neutrality. Moreover, the fact that in this phase all quarks are gapped might
help to suppress the direct Urca process, consistent with cooling models. The
order of magnitude of these small gaps (~1 MeV) will not influence the EoS, but
their also small critical temperatures (T_c ~800 keV) could be relevant in the
late stages neutron star evolution, when the temperature falls below this value
and a CSL quark core could form.Comment: 7 pages, 7 figures, revised version, accepted for the Conference
Proceedings of "Isolated Neutron Stars: from the Interior to the Surface",
London, 24-28. April 200
Neutron Transfer reactions induced by 8Li on 9Be
Angular distributions for the elastic scattering of 8Li on 9Be and the
neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been
measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for
8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between
the experimental differential cross section and finite-range DWBA calculations
with the code FRESCO. The spectroscopic factors obtained are compared to shell
model calculations and to other experimental values from (d,p) reactions. Using
the present values for the spectroscopic factor, cross sections for the direct
neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the
framework of a potential model.Comment: 24 pages, 8 Figures, submitted as regular article to PR
Subsurface dynamic evaluation to identify old quarries in urban areas : Lisbon city case study
The urban expansion over the last century in Lisbon has created a lot of pressure in the suburbs leading to construction taking place in less favourable terrains. These areas were also occupied by an extensive mining industry, for the extraction of massive limestones for building and ornamental stone that had an important role for the reconstruction of Lisbon after the earthquake of 1755. Due to its heavily urbanized landscape in the last century, the terrain morphology is often changed by non-natural processes such as excavations and landfill deposits and nowadays the exact location where these exploitations took place is unknown leading to potential risk situations for buildings, infrastructures and the local population. The aim of this study was to perform a detailed subsurface dynamic analysis to locate the quarries and their landfill material thickness. For that, cartographic and topographic information dating from 1911, 1950, 1970, 2012 were used to create digital terrain models which allowed the terrain morphology changes
to be identified and the volume of landfill materials to be obtained. This study enables the Town Hall to create constraints in land use in their Master Plan and other planning instruments to reduce cost increases and the risk of hazards.info:eu-repo/semantics/publishedVersio
Novel types of anti-ecloud surfaces
In high power RF devices for space, secondary electron emission appears as
the main parameter governing the multipactor effect and as well as the e-cloud
in large accelerators. Critical experimental activities included development of
coatings with low secondary electron emission yield (SEY) for steel (large
accelerators) and aluminium (space applications). Coatings with surface
roughness of high aspect ratio producing the so-call secondary emission
suppression effect appear as the selected strategy. In this work a detailed
study of the SEY of these technological coatings and also the experimental
deposition methods (PVD and electrochemical) are presented. The coating-design
approach selected for new low SEY coatings include rough metals (Ag, Au, Al),
rough alloys (NEG), particulated and magnetized surfaces, and also graphene
like coatings. It was found that surface roughness also mitigate the SEY
deterioration due to aging processes.Comment: 4 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop
on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba,
Italy; CERN Yellow Report CERN-2013-002, pp.153-15
Impact of the treatment of periodontitis on systemic health and quality of life: A systematic review
AIM: To investigate the effect of treatment of periodontitis on systemic health outcomes, pregnancy complications, and associated quality of life. MATERIALS AND METHODS: Systematic electronic searches were conducted to identify randomized controlled trials with minimum 6-month follow-up and reporting on the outcomes of interest. Qualitative and quantitative analyses were performed as deemed suitable. RESULTS: Meta-analyses confirmed reductions of high-sensitivity C-reactive protein (hs-CRP) [0.56 mg/L, 95% confidence interval (CI) (−0.88, −0.25), p < .001]; interleukin (IL)-6 [0.48 pg/ml, 95% CI (−0.88, −0.08), p = .020], and plasma glucose [1.33 mmol/l, 95% CI (−2.41, −0.24), p = .016], and increase of flow-mediated dilation (FMD) [0.31%, 95% CI (0.07, 0.55), p = .012] and diastolic blood pressure [0.29 mmHg, 95% CI (0.10, 0.49), p = .003] 6 months after the treatment of periodontitis. A significant effect on preterm deliveries (<37 weeks) was observed [0.77 risk ratio, 95% CI (0.60, 0.98), p = .036]. Limited evidence was reported on quality-of-life (QoL) outcomes in the included studies. CONCLUSIONS: Treatment of periodontitis results in systemic health improvements including improvement in cardiometabolic risk, reduction in systemic inflammation and the occurrence of preterm deliveries. Further research is however warranted to confirm whether these changes are sustained over time. Further, appropriate QoL outcomes should be included in the study designs of future clinical trials
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