461 research outputs found
Aspect-ratio dependence of the spin stiffness of a two-dimensional XY model
We calculate the superfluid stiffness of 2D lattice hard-core bosons at
half-filling (equivalent to the S=1/2 XY-model) using the squared winding
number quantum Monte Carlo estimator. For L_x x L_y lattices with aspect ratio
L_x/L_y=R, and L_x,L_y -> infinity, we confirm the recent prediction [N.
Prokof'ev and B.V. Svistunov, Phys. Rev. B 61, 11282 (1999)] that the
finite-temperature stiffness parameters \rho^W_x and \rho^W_y determined from
the winding number differ from each other and from the true superfluid density
\rho_s. Formally, \rho^W_y -> \rho_s in the limit in which L_x -> infinity
first and then L_y -> infinity. In practice we find that \rho^W_y converges
exponentially to \rho_s for R>1. We also confirm that for 3D systems, \rho^W_x
= \rho^W_y = \rho^W_z = \rho_s for any R. In addition, we determine the
Kosterlitz-Thouless transition temperature to be T_KT/J=0.34303(8) for the 2D
model.Comment: 7 pages, 8 figures, 1 table. Minor changes to published versio
Socioeconomic inequalities and the equity impact of population-level interventions for adolescent health: an overview of systematic reviews
Objectives: Despite robust evidence on health inequalities in adulthood, less attention has been paid to inequalities in adolescence. The aim of this overview was to examine systematic review (SR) evidence on the equity impact of population-level interventions intended to improve health, happiness and wellbeing for adolescents. Study Design: An overview (review of systematic reviews). Methods: Eleven electronic databases were systematically searched to identify SRs of population-level interventions for adolescent health. A secondary data analysis of socioeconomic inequality was conducted to identify whether SRs reported on primary studies in terms of disadvantage, by measures of socioeconomic status (SES) and by differential effects. Results: 35,310 review titles were screened; 566 full texts were retrieved and 140 SRs met the predefined selection criteria. Differential intervention effects were considered in 42/140 (30%) SRs, 18/140 (13%) reported primary studies using an SES measure and 16/140 (11%) explicitly reported differential effects. 15/140 SRs (11%) explicitly focused on socioeconomic inequalities; of these 4/15 reported differential intervention effects in more detail, 7/15 concluded there was insufficient primary evidence to identify the impact of interventions on socioeconomic inequalities and 4/15 planned to examine differential effects by SES, but this was not reported further. Conclusions: Our overview identifies that there is limited SR evidence on the equity impact of population-level interventions for adolescent health. Strengthening the evidence on whether interventions narrow or widen inequalities for adolescents must be a priority for public health research
A confirmation of agreement of different approaches for scalar gauge-invariant metric perturbations during inflation
We revisit an extension of the well-known formalism for gauge-invariant
scalar metric fluctuations, to study the spectrums for both, the inflaton and
gauge invariant (scalar) metric fluctuations in the framework of a single field
inflationary model where the quasi-exponential expansion is driven by an
inflation which is minimally coupled to gravity. The proposal here examined is
valid also for fluctuations with large amplitude, but for cosmological scales,
where vector and tensor perturbations can be neglected and the fluid is
irrotacional.Comment: Version accepted in EPJC with new title. 11 pages, no figure
Scale invariant scalar metric fluctuations during inflation: non-perturbative formalism from a 5D vacuum
We extend to 5D an approach of a 4D non-perturbative formalism to study
scalar metric fluctuations of a 5D Riemann-flat de Sitter background metric. In
contrast with the results obtained in 4D, the spectrum of cosmological scalar
metric fluctuations during inflation can be scale invariant and the background
inflaton field can take sub-Planckian values.Comment: final version to be published in Eur. Phys. J.
Weighing Melnick 34: the most massive binary system known
Here, we confirm Melnick 34, an X-ray bright star in the 30 Dor region of the Large Magellanic Cloud, as an SB2 binary comprising WN5h + WN5h components. We present orbital solutions using 26 epochs of VLT/UVES spectra and 22 epochs of archival Gemini/GMOS spectra. Radial velocity monitoring and automated template-fitting methods both reveal a similar high-eccentricity system with a mass ratio close to unity, and an orbital period in agreement with the 155.1 ± 1 d X-ray light-curve period previously derived by Pollock et al. Our favoured solution derived an eccentricity of 0.68 ± 0.02 and mass ratio of 0.92 ± 0.07, giving minimum masses of MAsin3(i) = 65 ± 7âMâ and MBsin3(i) = 60 ± 7âMâ. Spectral modelling using WN5h templates with cmfgen reveals temperatures of T ⌠53âkK for each component and luminosities of log(LA/Lâ) = 6.43 ± 0.08 and log(LB/Lâ) = 6.37 ± 0.08, from which BONNSAI evolutionary modelling gives masses of MA = 139+21â18âMâ and MB = 127+17â17âMâ and ages of âŒ0.6 Myr. Spectroscopic and dynamic masses would agree if Mk34 has an inclination of i ⌠50°, making Mk34 the most massive binary known and an excellent candidate for investigating the properties of colliding wind binaries. Within 2â3 Myr, both components of Mk34 are expected to evolve to stellar mass black holes, which, assuming the binary system survives, would make Mk34 a potential binary black hole merger progenitor and a gravitational wave source
Kosterlitz Thouless Universality in Dimer Models
Using the monomer-dimer representation of strongly coupled U(N) lattice gauge
theories with staggered fermions, we study finite temperature chiral phase
transitions in (2+1) dimensions. A new cluster algorithm allows us to compute
monomer-monomer and dimer-dimer correlations at zero monomer density (chiral
limit) accurately on large lattices. This makes it possible to show
convincingly, for the first time, that these models undergo a finite
temperature phase transition which belongs to the Kosterlitz-Thouless
universality class. We find that this universality class is unaffected even in
the large N limit. This shows that the mean field analysis often used in this
limit breaks down in the critical region.Comment: 4 pages, 4 figure
Stability of the lattice formed in first-order phase transitions to matter containing strangeness in protoneutron stars
Well into the deleptonization phase of a core collapse supernova, a
first-order phase transition to matter with macroscopic strangeness content is
assumed to occur and lead to a structured lattice defined by negatively charged
strange droplets. The lattice is shown to crystallize for expected droplet
charges and separations at temperatures typically obtained during the
protoneutronstar evolution. The melting curve of the lattice for small
spherical droplets is presented. The one-component plasma model proves to be an
adequate description for the lattice in its solid phase with deformation modes
freezing out around the melting temperature. The mechanical stability against
shear stresses is such that velocities predicted for convective phenomena and
differential rotation during the Kelvin-Helmholtz cooling phase might prevent
the crystallization of the phase transition lattice. A solid lattice might be
fractured by transient convection, which could result in anisotropic neutrino
transport. The melting curve of the lattice is relevant for the mechanical
evolution of the protoneutronstar and therefore should be included in future
hydrodynamics simulations.Comment: accepted for publication in Physical Review
Self-efficacy of advanced cancer patients for participation in treatment-related decision-making in six European countries:the ACTION study
PURPOSE: Many patients prefer an active role in making decisions about their care and treatment, but participating in such decision-making is challenging. The aim of this study was to explore whether patient-reported outcomes (quality of life and patient satisfaction), patients' coping strategies, and sociodemographic and clinical characteristics were associated with self-efficacy for participation in decision-making among patients with advanced cancer. METHODS: We used baseline data from the ACTION trial of patients with advanced colorectal or lung cancer from six European countries, including scores on the decision-making participation self-efficacy (DEPS) scale, EORTC QLQ-C15-PAL questionnaire, and the EORTC IN-PATSAT32 questionnaire. Multivariable linear regression analyses were used to examine associations with self-efficacy scores. RESULTS: The sample included 660 patients with a mean age of 66 years (SD 10). Patients had a mean score of 73 (SD 24) for self-efficacy. Problem-focused coping (B 1.41 (95% CI 0.77 to 2.06)), better quality of life (B 2.34 (95% CI 0.89 to 3.80)), and more patient satisfaction (B 7.59 (95% CI 5.61 to 9.56)) were associated with a higher level of self-efficacy. Patients in the Netherlands had a higher level of self-efficacy than patients in Belgium ((B 7.85 (95% CI 2.28 to 13.42)), whereas Italian patients had a lower level ((B -7.50 (95% CI -13.04 to -1.96)) than those in Belgium. CONCLUSION: Coping style, quality of life, and patient satisfaction with care were associated with self-efficacy for participation in decision-making among patients with advanced cancer. These factors are important to consider for healthcare professionals when supporting patients in decision-making processes.</p
Relativistic calculation of nuclear transparency in (e,e'p) reactions
Nuclear transparency in (e,e'p) reactions is evaluated in a fully
relativistic distorted wave impulse approximation model. The relativistic mean
field theory is used for the bound state and the Pauli reduction for the
scattering state, which is calculated from a relativistic optical potential.
Results for selected nuclei are displayed in a Q^2 range between 0.3 and 1.8
(GeV/c)^2 and compared with recent electron scattering data. For Q^2 = 0.3
(GeV/c)^2 the results are lower than data; for higher Q^2 they are in
reasonable agreement with data. The sensitivity of the model to different
prescriptions for the one-body current operator is investigated. The off-shell
ambiguities are rather large for the distorted cross sections and small for the
plane wave cross sections.Comment: 8 pages, 3 figure
Non-invasive real-time imaging of reactive oxygen species (ROS) using auto-fluorescence multispectral imaging technique: a novel tool for redox biology
Detecting reactive oxygen species (ROS) that play a critical role as redox modulators and signalling molecules in biological systems currently requires invasive methods such as ROS -specific indicators for imaging and quantification. We developed a non-invasive, real-time, label-free imaging technique for assessing the level of ROS in live cells and thawed cryopreserved tissues that is compatible with in-vivo imaging. The technique is based on autofluorescence multispectral imaging (AFMI) carried out in an adapted fluorescence microscope with an expanded number of spectral channels spanning specific excitation (365 nm-495 nm) and emission (420 nm-700 nm) wavelength ranges. We established a strong quantitative correlation between the spectral information obtained from AFMI and the level of ROS obtained from CellROX staining. The results were obtained in several cell types (HeLa, PANC1 and mesenchymal stem cells) and in live kidney tissue. Additioanly,two spectral regimes were considered: with and without UV excitation (wavelengths > 400 nm); the latter being suitable for UV-sensitive systems such as the eye. Data were analyzed by linear regression combined with an optimization method of swarm intelligence. This allowed the calibration of AFMI signals to the level of ROS with excellent correlation (R = 0.84, p = 0.00) in the entire spectral range and very good correlation (R = 0.78, p = 0.00) in the limited, UV-free spectral range. We also developed a strong classifier which allowed us to distinguish moderate and high levels of ROS in these two regimes (AUC = 0.91 in the entire spectral range and AUC = 0.78 for UV-free imaging). These results indicate that ROS in cells and tissues can be imaged non-invasively, which opens the way to future clinical applications in conditions where reactive oxygen species are known to contribute to progressive disease such as in ophthalmology, diabetes, kidney disease, cancer and neurodegenerative diseases.Abbas Habibalahi, Mahdieh Dashtbani Moghari, Jared M. Campbell, Ayad G. Anwer, Saabah B. Mahbub, Martin Gosnell, Sonia Saad, Carol Pollock, Ewa M. Goldy
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