5,216 research outputs found
D3 Ì„-branes and gaugino condensation
Anti-D3 branes at the bottom of warped throats, commonly used to uplift the cosmological constant in String-Theory de Sitter proposals, source a plethora of supersymmetry-breaking fluxes, that can interact nontrivially with other ingredients of the flux compactification. In this paper we perform a complex-structure decomposition of these fluxes, and compute the effect of the (0,3) flux component on the stabilization of Kähler moduli via D7-branes gaugino condensation. This allows us to obtain a new constraint on the validity of this stabilization mechanism. This effect does not appear hard to satisfy in de Sitter construction proposals that use long warped throats, but may be problematic in proposals where the warping is small
Properties of the solar neighbor WISE J072003.20-084651.2
The severe crowding towards the Galactic plane suggests that the census of
nearby stars in that direction may be incomplete. Recently, Scholz reported a
new M9 object at an estimated distance d~7 pc (WISE J072003.20-084651.2;
hereafter WISE0720) at Galactic latitude b=2.3 degr.
Our goals are to determine the physical characteristics of WISE0720, its
kinematic properties, and to address the question if it is a binary object, as
suggested in the discovery paper.
Optical and infrared spectroscopy from the Southern African Large Telescope
and Magellan, respectively, and spectral energy distribution fitting were used
to determine the spectral type of WISE0720. The measured radial velocity,
proper motion and parallax yielded its Galactic velocities. We also
investigated if WISE0720 may show X-ray activity based on archival data.
Our spectra are consistent with spectral type L0+/-1. We find no evidence for
binarity, apart for a minor 2-sigma level difference in the radial velocities
taken at two different epochs. The spatial velocity of WISE0720 does not
connect it to any known moving group, instead it places the object with high
probability in the old thin disk or in the thick disk. The spectral energy
distribution fit hints at excess in the 12 and 22 micron WISE bands which may
be due to a redder companion, but the same excess is visible in other late type
objects, and it more likely implies a shortcoming of the models (e.g., issues
with the effective wavelengths of the filters for these extremely cool objects,
etc.) rather than a disk or redder companion. The optical spectrum shows some
Halpha emission, indicative of stellar activity. Archival X-ray observations
yield no detection.Comment: A&A, accepted; 9 pages, 6 figure
High Resolution HDS/SUBARU chemical abundances of the young stellar cluster Palomar 1
Context. Palomar\,1 is a peculiar globular cluster (GC). It is the youngest
Galactic GC and it has been tentatively associated to several of the
substructures recently discovered in the Milky Way (MW), including the Canis
Major (CMa) overdensity and the Galactic Anticenter Stellar Structure (GASS).
Aims. In order to provide further insights into its origin, we present the
first high resolution chemical abundance analysis for one red giant in Pal\,1.
Methods. We obtained high resolution (R=30000) spectra for one red giant star
in Pal\,1 using the High Dispersion Spectrograph (HDS) mounted at the SUBARU
telescope. We used ATLAS-9 model atmospheres coupled with the SYNTHE and WIDTH
calculation codes to derive chemical abundances from the measured line
equivalent widths of 18 among , Iron-peak, light and heavy elements.
Results. The Palomar~1 chemical pattern is broadly compatible to that of the MW
open clusters population and similar to disk stars. It is, instead, remarkably
different from that of the Sagittarius (Sgr) dwarf spheroidal galaxy.
Conclusions. If Pal\,1 association with either CMa or GASS will be confirmed,
this will imply that these systems had a chemical evolution similar to that of
the Galactic disk.Comment: 13 pages, 9 figures, 5 tables. Accepted for publication in Astronomy
and Astrophysics. Minor changes in the tex
A Systematic Review of Sellar and Parasellar Brown Tumors: An Analysis of Clinical, Diagnostic, and Management Profiles
Objective
To systematically review and analyze clinical, diagnostic, and management trends in sellar and parasellar brown tumors reported in existing literature.
Methods
In this systematic review, PubMed, Ovid MEDLINE, Scopus, and Google Scholar databases were searched for reported cases of sellar/parasellar brown tumors. Relevant titles and abstracts were screened in accordance to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol. Articles meeting inclusion criteria were subjected to data extraction, summarization, and analysis. A rare case of parasellar brown tumor was also presented.
Results
Eight reports (including the current report) were eligible for inclusion. Mean patient age was 42.75 years. Reported symptoms included visual disturbances (n = 6), headache (n = 5), fatigue (n = 3), nausea/vomiting (n = 2), chest pain (n = 1), neck pain (n = 1), and dysphagia (n = 1). In cases where computed tomography findings were provided (n = 6), lesions were noted to be expansile and lytic. Lesions were hyperintense on T2-weighted magnetic resonance imaging (66.7%) and demonstrated contrast enhancement (83.3%). Histology unanimously showed multinucleated giant cells in a fibrovascular connective tissue stroma. Dramatic symptom resolution was noted in all patients who underwent resection of the sellar/parasellar brown tumor (n = 4; 50%).
Conclusions
Sellar/parasellar brown tumors are a rare, tertiary manifestation of hyperparathyroidism and can be elusive to diagnose. Diagnosis requires a high index of clinical suspicion in addition to comprehensive biochemical testing, imaging, and histopathologic analysis. Surgical extirpation is favored in cases where the lesion is causing compressive symptoms, or if it is unresponsive to management of hyperparathyroidism
CLASH-VLT: Substructure in the galaxy cluster MACS J1206.2-0847 from kinematics of galaxy populations
In the effort to understand the link between the structure of galaxy clusters
and their galaxy populations, we focus on MACSJ1206.2-0847 at z~0.44 and probe
its substructure in the projected phase space through the spectrophotometric
properties of a large number of galaxies from the CLASH-VLT survey. Our
analysis is mainly based on an extensive spectroscopic dataset of 445 member
galaxies, mostly acquired with VIMOS@VLT as part of our ESO Large Programme,
sampling the cluster out to a radius ~2R200 (4 Mpc). We classify 412 galaxies
as passive, with strong Hdelta absorption (red and blue galaxies, and with
emission lines from weak to very strong. A number of tests for substructure
detection are applied to analyze the galaxy distribution in the velocity space,
in 2D space, and in 3D projected phase-space. Studied in its entirety, the
cluster appears as a large-scale relaxed system with a few secondary, minor
overdensities in 2D distribution. We detect no velocity gradients or evidence
of deviations in local mean velocities. The main feature is the WNW-ESE
elongation. The analysis of galaxy populations per spectral class highlights a
more complex scenario. The passive galaxies and red strong Hdelta galaxies
trace the cluster center and the WNW-ESE elongated structure. The red strong
Hdelta galaxies also mark a secondary, dense peak ~2 Mpc at ESE. The emission
line galaxies cluster in several loose structures, mostly outside R200. The
observational scenario agrees with MACS J1206.2-0847 having WNW-ESE as the
direction of the main cluster accretion, traced by passive galaxies and red
strong Hdelta galaxies. The red strong Hdelta galaxies, interpreted as
poststarburst galaxies, date a likely important event 1-2 Gyr before the epoch
of observation. The emission line galaxies trace a secondary, ongoing infall
where groups are accreted along several directions.Comment: A&A accepted, 19 pages, 30 figures, minor language change
RIXS interferometry and the role of disorder in the quantum magnet BaTiIrO
Motivated by several claims of spin-orbit driven spin-liquid physics in
hexagonal BaTiIrO hosting Ir2O9 dimers, we report on
resonant inelastic x-ray scattering (RIXS) at the Ir L3 edge for different x.
We demonstrate that magnetism in BaTiIrO is governed by an
unconventional realization of strong disorder, where cation disorder affects
the character of the local moments. RIXS interferometry, studying the RIXS
intensity over a broad range of transferred momentum q, is ideally suited to
assign different excitations to different Ir sites. We find pronounced Ir-Ti
site mixing. Both ions are distributed over two crystallographically
inequivalent sites, giving rise to a coexistence of quasimolecular singlet
states on Ir2O9 dimers and spin-orbit entangled j=1/2 moments of 5d
Ir ions. RIXS reveals different kinds of strong magnetic couplings for
different bonding geometries, highlighting the role of cation disorder for the
suppression of long-range magnetic order in this family of compounds.Comment: 12 pages, 9 figure
Recommended from our members
RIXS interferometry and the role of disorder in the quantum magnet Ba3 Ti3-x Irx O9
Motivated by several claims of spin-orbit-driven spin-liquid physics in hexagonal Ba3Ti3-xIrxO9 hosting Ir2O9 dimers, we report on resonant inelastic x-ray scattering (RIXS) at the Ir L3 edge for different x. We demonstrate that magnetism in Ba3Ti3-xIrxO9 is governed by an unconventional realization of strong disorder, where cation disorder affects the character of the local moments. RIXS interferometry, studying the RIXS intensity over a broad range of transferred momentum q, is ideally suited to assign different excitations to different Ir sites. We find pronounced Ir-Ti site mixing. Both ions are distributed over two crystallographically inequivalent sites, giving rise to a coexistence of quasimolecular singlet states on Ir2O9 dimers and spin-orbit-entangled j=1/2 moments of 5d5Ir4+ ions. RIXS reveals different kinds of strong magnetic couplings for different bonding geometries, highlighting the role of cation disorder for the suppression of long-range magnetic order in this family of compounds
Definition, Assessment, and Management of Vitamin D Inadequacy: Suggestions, Recommendations, and Warnings from the Italian Society for Osteoporosis, Mineral Metabolism and Bone Diseases (SIOMMMS)
In the recent years, both the prescriptions of serum 25(OH)D levels assay, and vitamin D supplementation are constantly increasing, as well as the costs to be incurred relating to these specific aspects. As in many other countries, the risk of vitamin D deficiency is particularly high in Italy, as recently confirmed by cohort studies in the general population as well as in patients with metabolic bone disorder. Results confirmed the North-South gradient of vitamin D levels described among European countries, despite the wide use of supplements. Although vitamin D supplementation is also recommended by the Italian Medicine Agency for patients at risk for fragility fracture or for initiating osteoporotic medication, the therapeutic gap for osteoporosis in Italy is very high. There is a consistent proportion of osteoporotic patients not receiving specific therapy for osteoporosis following a fragility fracture, with a poor adherence to the recommendations provided by national guidelines and position paper documents. The failure or inadequate supplementation with vitamin D in patients on antiresorptive or anabolic treatment for osteoporosis is thought to further amplify the problem and exposes patients to a high risk of re-fracture and mortality. Therefore, it is important that attention to its possible clinical consequences must be given. Thus, in light of new evidence from the literature, the SIOMMMS board felt the need to revise and update, by a GRADE/PICO system approach, its previous original recommendations about the definition, prevention, and treatment of vitamin D deficiency in adults, released in 2011. Several key points have been here addressed, such as the definition of the vitamin D status: normality values and optimal values; who are the subjects considered at risk of hypovitaminosis D; opportunity or not of performing the biochemical assessment of serum 25(OH)D levels in general population and in subjects at risk of hypovitaminosis D; the need or not to evaluate baseline serum 25(OH)D in candidate subjects for pharmacological treatment for osteoporosis; how and whether to supplement vitamin D subjects with hypovitaminosis D or candidates for pharmacological treatment with bone active agents, and the general population; how and whether to supplement vitamin D in chronic kidney disease and/or chronic liver diseases or under treatment with drugs interfering with hepatic metabolism; and finally, if vitamin D may have toxic effects in the subject in need of supplementation. © 2022 by the authors
Counting defects with the two-point correlator
We study how topological defects manifest themselves in the equal-time
two-point field correlator. We consider a scalar field with Z_2 symmetry in 1,
2 and 3 spatial dimensions, allowing for kinks, domain lines and domain walls,
respectively. Using numerical lattice simulations, we find that in any number
of dimensions, the correlator in momentum space is to a very good approximation
the product of two factors, one describing the spatial distribution of the
defects and the other describing the defect shape. When the defects are
produced by the Kibble mechanism, the former has a universal form as a function
of k/n, which we determine numerically. This signature makes it possible to
determine the kink density from the field correlator without having to resort
to the Gaussian approximation. This is essential when studying field dynamics
with methods relying only on correlators (Schwinger-Dyson, 2PI).Comment: 11 pages, 7 figures
Geologically recent areas as one key target for identifying active volcanism on Venus
The recently selected NASA VERITAS and DAVINCI missions, the ESA EnVision, the Roscosmos Venera-D will open a new era in the exploration of Venus. One of the key targets of the future orbiting and in situ investigations of Venus is the identification of volcanically active areas on the planet. The study of the areas characterized by recent or ongoing volcano-tectonic activity can inform us on how volcanism and tectonism are currently evolving on Venus. Following this key target, Brossier et al. (2022, https://doi.org/10.1029/2022GL099765) extend the successful approach and methodology used by previous works to Ganis Chasma in Atla Regio. Here we comment on the main results published in Brossier et al. (2022, https://doi.org/10.1029/2022GL099765) and discuss the important implications of their work for the future orbiting and in situ investigation of Venus. Their results add further lines of evidence indicating possibly recent volcanism on Venus
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