117 research outputs found
Phenomenological Tests of Supersymmetric A_4 Family Symmetry Model of Neutrino Mass
Recently Babu, Ma and Valle proposed a model of quark and lepton mixing based
on symmetry. Within this model the lepton and slepton mixings are
intimately related. We perform a numerical study in order to derive the slepton
masses and mixings in agreement with present data from neutrino physics. We
show that, starting from three-fold degeneracy of the neutrino masses at a high
energy scale, a viable low energy neutrino mass matrix can indeed be obtained
in agreement with constraints on lepton flavour violating
and decays. The resulting slepton spectrum must necessarily
include at least one mass below 200 GeV which can be produced at the LHC. The
predictions for the absolute Majorana neutrino mass scale eV
ensure that the model will be tested by future cosmological tests and
searches.
Rates for lepton flavour violating processes
in the range of sensitivity of current
experiments are typical in the model, with BR(\mu \to e \gamma) \gsim
10^{-15} and the lower bound BR. To first
approximation, the model leads to maximal leptonic CP violation in neutrino
oscillations.Comment: 23 pages, 7 figure
Ising model on 3D random lattices: A Monte Carlo study
We report single-cluster Monte Carlo simulations of the Ising model on
three-dimensional Poissonian random lattices with up to 128,000 approx. 503
sites which are linked together according to the Voronoi/Delaunay prescription.
For each lattice size quenched averages are performed over 96 realizations. By
using reweighting techniques and finite-size scaling analyses we investigate
the critical properties of the model in the close vicinity of the phase
transition point. Our random lattice data provide strong evidence that, for the
available system sizes, the resulting effective critical exponents are
indistinguishable from recent high-precision estimates obtained in Monte Carlo
studies of the Ising model and \phi^4 field theory on three-dimensional regular
cubic lattices.Comment: 35 pages, LaTex, 8 tables, 8 postscript figure
Non-linear magnons and exchange Hamiltonians of delafossite proximate quantum spin liquids
Quantum spin liquids (QSL) are theoretical states of matter with long-range
entanglement and exotic quasiparticles. However, they generally elude
quantitative theory, rendering their underlying phases mysterious and hampering
efforts to identify experimental QSL states. Here we study triangular lattice
resonating valence bond QSL candidate materials KYbSe and NaYbSe. We
measure the magnon modes in their 1/3 plateau phase, where quantitative theory
is tractable, using inelastic neutron scattering and fit them using nonlinear
spin wave theory. We also fit the KYbSe heat capacity using high
temperature series expansion. Both KYbSe fits yield the same magnetic
Hamiltonian to within uncertainty, confirming previous estimates and showing
the Heisenberg to be an accurate model for these materials. Most
importantly, comparing KYbSe and NaYbSe shows that smaller -site
Na ion has a larger ratio. However, hydrostatic pressure applied
to KYbSe increases the ordering temperature (a result consistent with
density functional theory calculations), indicating that pressure decreases
. These results show how periodic table and hydrostatic pressure can
tune the YbSe materials in a controlled way.Comment: 7 pages, 7 figures; 4 pages and 7 additional figures of supplemental
informatio
Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns
We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] gsim −1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similar metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution
The VISTA Variables in the Vía Láctea eXtended (VVVX) ESO public survey: Completion of the observations and legacy
© 2024 ESO. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1051/0004-6361/202450584The ESO public survey VISTA Variables in the V\'ia L\'actea (VVV) surveyed the inner Galactic bulge and the adjacent southern Galactic disk from . Upon its conclusion, the complementary VVV eXtended (VVVX) survey has expanded both the temporal as well as spatial coverage of the original VVV area, widening it from to sq. deg., as well as providing additional epochs in filters from . With the completion of VVVX observations during the first semester of 2023, we present here the observing strategy, a description of data quality and access, and the legacy of VVVX. VVVX took hours, covering about 4% of the sky in the bulge and southern disk. VVVX covered most of the gaps left between the VVV and the VISTA Hemisphere Survey (VHS) areas and extended the VVV time baseline in the obscured regions affected by high extinction and hence hidden from optical observations. VVVX provides a deep catalogue of point sources, as well as a band catalogue of variable sources. Within the existing VVV area, we produced a map of the surveyed region by combining positions, distances, and proper motions of well-understood distance indicators such as red clump stars, RR Lyrae, and Cepheid variables. In March 2023 we successfully finished the VVVX survey observations that started in 2016, an accomplishment for ESO Paranal Observatory upon 4200 hours of observations for VVV+VVVX. The VVV+VVVX catalogues complement those from the Gaia mission at low Galactic latitudes and provide spectroscopic targets for the forthcoming ESO high-multiplex spectrographs MOONS and 4MOST.Peer reviewe
Use of mechanical circulatory support in patients with non-ischaemic cardiogenic shock
Aims Despite its high incidence and mortality risk, there is no evidence-based treatment for non-ischaemic cardiogenic shock (CS). The aim of this study was to evaluate the use of mechanical circulatory support (MCS) for non-ischaemic CS treatment.Methods and results In this multicentre, international, retrospective study, data from 890 patients with non-ischaemic CS, defined as CS due to severe de-novo or acute-on-chronic heart failure with no need for urgent revascularization, treated with or without active MCS, were collected. The association between active MCS use and the primary endpoint of 30-day mortality was assessed in a 1:1 propensity-matched cohort. MCS was used in 386 (43%) patients. Patients treated with MCS presented with more severe CS (37% vs. 23% deteriorating CS, 30% vs. 25% in extremis CS) and had a lower left ventricular ejection fraction at baseline (21% vs. 25%). After matching, 267 patients treated with MCS were compared with 267 patients treated without MCS. In the matched cohort, MCS use was associated with a lower 30-day mortality (hazard ratio 0.76, 95% confidence interval 0.59-0.97). This finding was consistent through all tested subgroups except when CS severity was considered, indicating risk reduction especially in patients with deteriorating CS. However, complications occurred more frequently in patients with MCS; e.g. severe bleeding (16.5% vs. 6.4%) and access-site related ischaemia (6.7% vs. 0%).Conclusion In patients with non-ischaemic CS, MCS use was associated with lower 30-day mortality as compared to medical therapy only, but also with more complications. Randomized trials are needed to validate these findings.[GRAPHICS
Association between Use of Enhanced Recovery after Surgery Protocol and Postoperative Complications in Total Hip and Knee Arthroplasty in the Postoperative Outcomes Within Enhanced Recovery after Surgery Protocol in Elective Total Hip and Knee Arthroplasty Study (POWER2)
Importance: The Enhanced Recovery After Surgery (ERAS) care protocol has been shown to improve outcomes compared with traditional care in certain types of surgery.
Objective: To assess the association of use of the ERAS protocols with complications in patients undergoing elective total hip arthroplasty (THA) and total knee arthroplasty (TKA).
Design, Setting, and Participants: This multicenter, prospective cohort study included patients recruited from 131 centers in Spain from October 22 through December 22, 2018. All consecutive adults scheduled for elective THA or TKA were eligible for inclusion. Patients were stratified between those treated in a self-designated ERAS center (ERAS group) and those treated in a non-ERAS center (non-ERAS group). Data were analyzed from June 15 through September 15, 2019.
Exposures: Total hip or knee arthroplasty and perioperative management. Sixteen individual ERAS items were assessed in all included patients, whether they were treated at a center that was part of an established ERAS protocol or not. Main Outcomes and Measures: The primary outcome was postoperative complications within 30 days after surgery. Secondary outcomes included length of stay and mortality. Results: During the 2-month recruitment period, 6146 patients were included (3580 women [58.2%]; median age, 71 [interquartile range (IQR), 63-76] years). Of these, 680 patients (11.1%) presented with postoperative complications. No differences were found in the number of patients with overall postoperative complications between ERAS and non-ERAS groups (163 [10.2%] vs 517 [11.4%]; odds ratio [OR], 0.89; 95% CI, 0.74-1.07; P =.22). Fewer patients in the ERAS group had moderate to severe complications (73 [4.6%] vs 279 [6.1%]; OR, 0.74; 95% CI, 0.56-0.96; P =.02). The median overall adherence rate with the ERAS protocol was 50.0% (IQR, 43.8%-62.5%), with the rate for ERAS facilities being 68.8% (IQR, 56.2%-81.2%) vs 50.0% (IQR, 37.5%-56.2%) at non-ERAS centers (P <.001). Among the patients with the highest and lowest quartiles of adherence to ERAS components, the patients with the highest adherence had fewer overall postoperative complications (144 [10.6%] vs 270 [13.0%]; OR, 0.80; 95% CI, 0.64-0.99; P <.001) and moderate to severe postoperative complications (59 [4.4%] vs 143 [6.9%]; OR, 0.62; 95% CI, 0.45-0.84; P <.001) and shorter median length of hospital stay (4 [IQR, 3-5] vs 5 [IQR, 4-6] days; OR, 0.97; 95% CI, 0.96-0.99; P <.001).
Conclusions and Relevance: An increase in adherence to the ERAS program was associated with a decrease in postoperative complications, although only a few ERAS items were individually associated with improved outcomes
Chemical Tagging in the Sdss-Iii/Apogee Survey: New Identifications of Halo Stars with Globular Cluster Origins
We present new identifications of five red giant stars in the Galactic halo with chemical abundance patterns that indicate they originally formed in globular clusters. Using data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) Survey available through Sloan Digital Sky Survey (SDSS) Data Release 12, we first identify likely halo giants, and then search those for the well-known chemical tags associated with globular clusters, specifically enrichment in nitrogen and aluminum. We find that 2% of the halo giants in our sample have this chemical signature, in agreement with previous results. Following the interpretation in our previous work on this topic, this would imply that at least 13% of halo stars originally formed in globular clusters. Recent developments in the theoretical understanding of globular cluster formation raise questions about that interpretation, and we concede the possibility that these migrants represent a small fraction of the halo field. There are roughly as many stars with the chemical tags of globular clusters in the halo field as there are in globular clusters, whether or not they are accompanied by a much larger chemically untaggable population of former globular cluster stars
The Gaia-ESO Survey: The inner disk, intermediate-age open cluster Trumpler 23
Milky Way open clusters are very diverse in terms of age, chemical
composition, and kinematic properties. Intermediate-age and old open clusters
are less common, and it is even harder to find them inside the solar
Galactocentric radius, due to the high mortality rate and strong extinction
inside this region. NGC 6802 is one of the inner disk open clusters (IOCs)
observed by the -ESO survey (GES). This cluster is an important target
for calibrating the abundances derived in the survey due to the kinematic and
chemical homogeneity of the members in open clusters. Using the measurements
from -ESO internal data release 4 (iDR4), we identify 95 main-sequence
dwarfs as cluster members from the GIRAFFE target list, and eight giants as
cluster members from the UVES target list. The dwarf cluster members have a
median radial velocity of km s, while the giant cluster
members have a median radial velocity of km s and a median
[Fe/H] of dex. The color-magnitude diagram of these cluster
members suggests an age of Gyr, with and
. We perform the first detailed chemical abundance analysis of NGC
6802, including 27 elemental species. To gain a more general picture about
IOCs, the measurements of NGC 6802 are compared with those of other IOCs
previously studied by GES, that is, NGC 4815, Trumpler 20, NGC 6705, and
Berkeley 81. NGC 6802 shows similar C, N, Na, and Al abundances as other IOCs.
These elements are compared with nucleosynthetic models as a function of
cluster turn-off mass. The , iron-peak, and neutron-capture elements
are also explored in a self-consistent way
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