5,698 research outputs found
Classical Cepheids: Yet another version of the Baade-Becker-Wesselink method
We propose a new version of the Baade--Becker--Wesselink technique, which
allows one to independently determine the colour excess and the intrinsic
colour of a radially pulsating star, in addition to its radius, luminosity, and
distance. It is considered to be a generalization of the Balona approach. The
method also allows the function F(CI) = BC + 10 log (Teff) for the class of
pulsating stars considered to be calibrated. We apply this technique to a
number of classical Cepheids with very accurate light and radial-velocity
curves and with bona fide membership in open clusters (SZ Tau, CF Cas, U Sgr,
DL Cas, GY Sge), and find the results to agree well with the reddening
estimates of the host open clusters. The new technique can also be applied to
other pulsating variables, e.g. RR Lyrae and RV Tauri.Comment: 6 pages, 2 figures, 1 table; Submitted to Astrophysical Bulletin,
201
The Standard Model from a New Phase Transition on the Lattice
Several years ago it was conjectured in the so-called Roma Approach, that
gauge fixing is an essential ingredient in the lattice formulation of chiral
gauge theories. In this paper we discuss in detail how the gauge-fixing
approach may be realized. As in the usual (gauge invariant) lattice
formulation, the continuum limit corresponds to a gaussian fixed point, that
now controls both the transversal and the longitudinal modes of the gauge
field. A key role is played by a new phase transition separating a conventional
Higgs or Higgs-confinement phase, from a phase with broken rotational
invariance. In the continuum limit we expect to find a scaling region, where
the lattice correlators reproduce the euclidean correlation functions of the
target (chiral) gauge theory, in the corresponding continuum gauge.Comment: 16 pages, revtex, one figure. Clarifications made, mainly in sections
3 and 6 that deal with the fermion action, to appear in Phys Rev
Domain Walls of D=8 Gauged Supergravities and their D=11 Origin
Performing a Scherk-Schwarz dimensional reduction of D=11 supergravity on a
three-dimensional group manifold we construct five D=8 gauged maximal
supergravities whose gauge groups are the three-dimensional (non-)compact
subgroups of SL(3,R). These cases include the Salam-Sezgin SO(3) gauged
supergravity. We construct the most general half-supersymmetric domain wall
solutions to these five gauged supergravities. The generic form is a triple
domain wall solution whose truncations lead to double and single domain wall
solutions. We find that one of the single domain wall solutions has zero
potential but nonzero superpotential.
Upon uplifting to 11 dimensions each domain wall becomes a purely
gravitational 1/2 BPS solution. The corresponding metric has a 7+4 split with a
Minkowski 7-metric and a 4-metric that corresponds to a gravitational
instanton. These instantons generalize the SO(3) metric of Belinsky, Gibbons,
Page and Pope (which includes the Eguchi-Hanson metric) to the other Bianchi
types of class A.Comment: 23 pages, 1 figure, minor changes, references adde
A randomized study of nutritional supplementation in patients with unilateral wet age-related macular degeneration
The purpose of this study is evaluate the efficacy and safety of medicinal products con-taining the original Age-Related Eye Disease group (AREDS) formulation at doses approved in Europe (EU, control group; n = 59) with a product that adds DHA, lutein, zeaxanthin, resveratrol and hydroxytyrosol to the formula (intervention group; n = 50). This was a multicenter, random-ized, observer-blinded trial conducted in patients aged 50 years or older diagnosed with unilateral exudative Age related Macular Degeneration AMD. At month 12, the intervention did not have a significant differential effect on visual acuity compared with the control group, with an estimated treatment difference in Early Treatment Diabetic Retinopathy Study (ETDRS) of -1.63 (95% CI -0.83 to 4.09; p = 0.192). The intervention exhibited a significant and, in most cases, relevant effect in terms of a reduction in some inflammatory cytokines and a greater improvement in the fatty acid profile and serum lutein and zeaxantin concentration. In patients with unilateral wet AMD, the addition of lutein, zeaxanthin, resveratrol, hydroxytyrosol and DHA to the AREDS EU recommended doses in the short-term did not have a differential effect on visual acuity compared to a standard AREDS EU formula but, in addition to improving the fatty acid profile and increasing carotenoid serum levels, may provide a beneficial effect in improving the proinflammatory and proangiogenic profile of patients with AMD. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
Plasma lipidome and risk of atrial fibrillation: results from the PREDIMED trial
The potential role of the lipidome in atrial fibrillation (AF) development is still widely unknown. We aimed to assess the association between lipidome profiles of the Prevención con Dieta Mediterránea (PREDIMED) trial participants and incidence of AF. We conducted a nested case-control study (512 incident centrally adjudicated AF cases and 735 controls matched by age, sex, and center). Baseline plasma lipids were profiled using a Nexera X2 U-HPLC system coupled to an Exactive Plus orbitrap mass spectrometer. We estimated the association between 216 individual lipids and AF using multivariable conditional logistic regression and adjusted the p values for multiple testing. We also examined the joint association of lipid clusters with AF incidence. Hitherto, we estimated the lipidomics network, used machine learning to select important network-clusters and AF-predictive lipid patterns, and summarized the joint association of these lipid patterns weighted scores. Finally, we addressed the possible interaction by the randomized dietary intervention.Forty-one individual lipids were associated with AF at the nominal level (p < 0.05), but no longer after adjustment for multiple-testing. However, the network-based score identified with a robust data-driven lipid network showed a multivariable-adjusted ORper+1SD of 1.32 (95% confidence interval: 1.16-1.51; p < 0.001). The score included PC plasmalogens and PE plasmalogens, palmitoyl-EA, cholesterol, CE 16:0, PC 36:4;O, and TG 53:3. No interaction with the dietary intervention was found. A multilipid score, primarily made up of plasmalogens, was associated with an increased risk of AF. Future studies are needed to get further insights into the lipidome role on AF.Current Controlled Trials number, ISRCTN35739639
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Direct Observation of Shock-Induced Disordering of Enstatite Below the Melting Temperature
We report in situ structural measurements of shock-compressed single crystal orthoenstatite up to 337 ± 55 GPa on the Hugoniot, obtained by coupling ultrafast X-ray diffraction to laser-driven shock compression. Shock compression induces a disordering of the crystalline structure evidenced by the appearance of a diffuse X-ray diffraction signal at nanosecond timescales at 80 ± 13 GPa on the Hugoniot, well below the equilibrium melting pressure (>170 GPa). The formation of bridgmanite and post-perovskite have been indirectly reported in microsecond-scale plate-impact experiments. Therefore, we interpret the high-pressure disordered state we observed at nanosecond scale as an intermediate structure from which bridgmanite and post-perovskite crystallize at longer timescales. This evidence of a disordered structure of MgSiO3 on the Hugoniot indicates that the degree of polymerization of silicates is a key parameter to constrain the actual thermodynamics of shocks in natural environments. © 2020. The Authors
The contact angle of nanofluids as thermophysical property
Droplet volume and temperature affect contact angle significantly. Phase change heat transfer processes of nanofluids – suspensions containing nanometre-sized particles – can only be modelled properly by understanding these effects. The approach proposed here considers the limiting contact angle of a droplet asymptotically approaching zero-volume as a thermophysical property to characterise nanofluids positioned on a certain substrate under a certain atmosphere.
Graphene oxide, alumina, and gold nanoparticles are suspended in deionised water. Within the framework of a round robin test carried out by nine independent European institutes the contact angle of these suspensions on a stainless steel solid substrate is measured with high accuracy. No dependence of nanofluids contact angle of sessile droplets on the measurement device is found. However, the measurements reveal clear differences of the contact angle of nanofluids compared to the pure base fluid.
Physically founded correlations of the contact angle in dependency of droplet temperature and volume are obtained from the data. Extrapolating these functions to zero droplet volume delivers the searched limiting contact angle depending only on the temperature. It is for the first time, that this specific parameter, is understood as a characteristic material property of nanofluid droplets placed on a certain substrate under a certain atmosphere. Together with the surface tension it provides the foundation of proper modelling phase change heat transfer processes of nanofluids
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
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