818 research outputs found
Scalar Casimir effect between two concentric D-dimensional spheres
The Casimir energy for a massless scalar field between the closely spaced two
concentric D-dimensional (for D>3) spheres is calculated by using the mode
summation with contour integration in the complex plane of eigenfrequencies and
the generalized Abel-Plana formula for evenly spaced eigenfrequency at large
argument. The sign of the Casimir energy between closely spaced two concentric
D-dimensional spheres for a massless scalar field satisfying the Dirichlet
boundary conditions is strictly negative. The Casimir energy between D-1
dimensional surfaces close to each other is regarded as interesting both by
itself and as the key to describing of stability of the attractive Casimir
force. PACS number(s): 03.70.+k, 11.10.Kk, 11.10.Gh, 03.65.GeComment: 14 pages. arXiv admin note: substantial text overlap with
arXiv:1207.418
Wavelength Tunability of Ion-bombardment Induced Ripples on Sapphire
A study of ripple formation on sapphire surfaces by 300-2000 eV Ar+ ion
bombardment is presented. Surface characterization by in-situ synchrotron
grazing incidence small angle x-ray scattering and ex-situ atomic force
microscopy is performed in order to study the wavelength of ripples formed on
sapphire (0001) surfaces. We find that the wavelength can be varied over a
remarkably wide range-nearly two orders of magnitude-by changing the ion
incidence angle. Within the linear theory regime, the ion induced viscous flow
smoothing mechanism explains the general trends of the ripple wavelength at low
temperature and incidence angles larger than 30. In this model, relaxation is
confined to a few-nm thick damaged surface layer. The behavior at high
temperature suggests relaxation by surface diffusion. However, strong smoothing
is inferred from the observed ripple wavelength near normal incidence, which is
not consistent with either surface diffusion or viscous flow relaxation.Comment: Revtex4, 19 pages, 10 figures with JPEG forma
Investment Opportunities Forecasting: Extending the Grammar of a GP-based Tool
In this paper we present a new version of a GP financial forecasting tool, called EDDIE 8. The novelty of this version is that it allows the GP to search in the space of indicators, instead of using pre-specified ones. We compare EDDIE 8 with its predecessor, EDDIE 7, and find that new and improved solutions can be found. Analysis also shows that, on average, EDDIE 8's best tree performs better than the one of EDDIE 7. The above allows us to characterize EDDIE 8 as a valuable forecasting tool
Observations of Pauli Paramagnetic Effects on the Flux Line Lattice in CeCoIn5
From small-angle neutron scattering studies of the flux line lattice (FLL) in
CeCoIn5, with magnetic field applied parallel to the crystal c-axis, we obtain
the field- and temperature-dependence of the FLL form factor, which is a
measure of the spatial variation of the field in the mixed state. We extend our
earlier work [A.D. Bianchi et al. 2008 Science 319, 177] to temperatures up to
1250 mK. Over the entire temperature range, paramagnetism in the flux line
cores results in an increase of the form factor with field. Near H_c2 the form
factor decreases again, and our results indicate that this fall-off extends
outside the proposed FFLO region. Instead, we attribute the decrease to a
paramagnetic suppression of Cooper pairing. At higher temperatures, a gradual
crossover towards more conventional mixed state behavior is observed.Comment: Submitted to New Journal of Physics, 13 pages, 4 figure
CeCoIn5 - a quantum critical superfluid
We have made the first complete measurements of the London penetration depth
of CeCoIn5, a quantum-critical metal where superconductivity
arises from a non-Fermi-liquid normal state. Using a novel tunnel diode
oscillator designed to avoid spurious contributions to , we have
established the existence of intrinsic and anomalous power-law behaviour at low
temperature. A systematic analysis raises the possibility that the unusual
observations are due to an extension of quantum criticality into the
superconducting state.Comment: 5 pages, 3 figure
The Association of Neighborhood Social Capital and Ethnic (Minority) Density with Pregnancy Outcomes in the Netherlands
Background: Perinatal morbidity rates are relatively high in the Netherlands, and significant inequalities in perinatal morbidity and mortality can be found across neighborhoods. In socioeconomically deprived areas, ‘Western’ women are particularly at risk for adverse birth outcomes. Almost all studies to date have explained the disparities in terms of individual determinants of birth outcomes. This study examines the influence of neighborhood contextual characteristics on birth weight (adjusted for gestational age) and preterm birth. We focused on the influence of neighborhood social capital – measured as informal socializing and social connections between neighbors – as well as ethnic (minority) density. Methods: Data on birth weight and prematurity were obtained from the Perinatal Registration Netherlands 2000–2008 dataset, containing 97% of all pregnancies. Neighborhood-level measurements were obtained from three different sources, comprising both survey and registration data. We included 3.422 neighborhoods and 1.527.565 pregnancies for the birth weight analysis and 1.549.285 pregnancies for the premature birth analysis. Linear and logistic multilevel regression was performed to assess the associations of individual and neighborhood level variables with birth weight and preterm birth. Results: We found modest but significant neighborhood effects on birth weight and preterm births. The effect of ethnic (minority) density was stronger than that of neighborhood social capital. Moreover, ethnic (minority) density was associated with higher birth weight for infants of non-Western ethnic minority women compared to Western women (15 grams; 95% CI: 12,4/17,5) as well as reduced risk for prematurity (OR 0.97; CI 0,95/0,99). Conclusions: Our results indicate that neighborhood contexts are associated with birth weight and preterm birth in the Netherlands. Moreover, ethnic (minority) density seems to be a protective factor for non-Western ethnic minority women, but not for Western women. This helps explain the increased risk of Western women in deprived neighborhoods for adverse birth outcomes found in previous studies
Outcome measurements following palatal soft tissue graft harvesting : a review
Free gingival graft (FGG) and connective tissue graft (CTG) are two of the most commonly techniques performed in periodontal and peri-implant plastic surgery. Although several outcome measurements have been proposed for evaluation of palatal wound healin
Randomized clinical trial on the survival of lithium disilicate posterior partial restorations bonded using immediate or delayed dentin sealing after 3 years of function
Objectives: The survival and success rate and the quality of survival of partial ceramic restorations bonded employing Immediate (IDS) or Delayed Dentin Sealing (DDS) in vital molar teeth were evaluated in a randomized clinical trial with within-subject comparison study.Materials and methods: 30 patients received two lithium disilicate ceramic (IPS-e.max press, Ivoclar Vivadent) partial restorations on vital first or second molar teeth (N = 60). The two teeth randomly received either IDS (test group, n = 30) or DDS (control group, n = 30). Partial ceramic restorations were luted (Variolink Ultra, Ivoclar Vivadent) two weeks after preparation. Evaluations were performed at 1 week, 12 months and 36 months post-operatively, using qualitative (FDI) criteria. Representative failures were evaluated microscopically (SEM) and by means of simplified qualitative fractography analysis.Results: One absolute failure occurred in the DDS group due to (secondary) caries. The overall survival rate according to Kaplan-Meier after 3 years was 98.3% (FDI criteria score 1-4, n = 59) and the overall success rate was 85% (FDI criteria score 1-3, n = 51), with no significant difference between restorations in the IDS and DDS group (p = 0.32; Kaplan-Meier, Log Rank (Mantel-Cox), CI = 95%). For the quality of the survival, no statistically significant differences were found between IDS and DDS (p = 0.7; Kaplan-Meier, Log Rank (Mantel-Cox), CI = 95%) restorations on any follow-up timepoints for any of the FDI criteria (Wilcoxon, McNemar, p > 0.05).Conclusion: Adhesively luted partial ceramic restorations in vital molar teeth have a good prognosis, however IDS did not show any differences in success and survival rates after 3 years of function.</p
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