8,261 research outputs found
A critical approach to the concept of a polar, low-altitude LARES satellite
According to very recent developments of the LARES mission, which would be
devoted to the measurement of the general relativistic Lense--Thirring effect
in the gravitational field of the Earth with Satellite Laser Ranging, it seems
that the LARES satellite might be finally launched in a polar, low--altitude
orbit by means of a relatively low--cost rocket. The observable would be the
node only. In this letter we critically analyze this scenario.Comment: LaTex2e, 11 pages, 4 figures, 1 table. Accepted for publication in
Classical and Quantum Gravit
A Magellanic origin for the Virgo substructure
Iorio et al. (2018) mapped out the Milky Way halo using a sample of RR Lyrae
stars drawn from a cross-match of Gaia with 2MASS. We investigate the
significant residual in their model which we constrain to lie at Galactocentric
radii and extend over of the
sky. A counterpart of this structure exists in both the Catalina Real Time
Survey and the sample of RR Lyrae variables identified in Pan-STARRS by
Hernitschek et al. (2016), demonstrating that this structure is not caused by
the spatial inhomogeneity of Gaia. The structure is likely the Virgo Stellar
Stream and/or Virgo Over-Density. We show the structure is aligned with the
Magellanic Stream and suggest that it is either debris from a disrupted dwarf
galaxy that was a member of the Vast Polar Structure or that it is SMC debris
from a tidal interaction of the SMC and LMC ago. If the
latter then the sub-structure in Virgo may have a Magellanic origin.Comment: 9 pages, 7 figures, accepted to MNRAS 31/10/201
The Lense-Thirring effect in the Jovian system of the Galilean satellites and its measurability
In this paper we investigate the possibility of measuring the post-Newtonian
general relativistic gravitomagnetic Lense-Thirring effect in the Jovian system
of its Galilean satellites Io, Europa, Ganymede and Callisto in view of recent
developments in processing and modelling their optical observations spanning a
large time interval (125 years). The present day best observations have an
accuracy between several kilometers to few tens of kilometers, which is just
the order of magnitude of the Lense-Thirring shifts of the orbits of the
Galilean satellites over almost a century. From a comparison between analytical
development and numerical integration it turns out that, unfortunately, most of
the secular component of the gravitomagnetic signature is removed in the
process of fitting the initial conditions. Indeed, an estimation of the
magnitude of the Lense-Thirring effect in the ephemerides residuals is given;
the resulting residuals have a maximum magnitude of 20 meters only (over 125
years).Comment: Latex, 10 pages, 4 tables, 3 figures, 27 references. Invited paper
for a Special Issue of Int. J. Mod. Phys. D on the Lense-Thirring effect, D.
Grumiller edito
On the perspectives of testing the Dvali-Gabadadze-Porrati gravity model with the outer planets of the Solar System
The multidimensional braneworld gravity model by Dvali, Gabadadze and Porrati
was primarily put forth to explain the observed acceleration of the expansion
of the Universe without resorting to dark energy. One of the most intriguing
features of such a model is that it also predicts small effects on the orbital
motion of test particles which could be tested in such a way that local
measurements at Solar System scales would allow to get information on the
global properties of the Universe. Lue and Starkman derived a secular
extra-perihelion \omega precession of 5\times 10^-4 arcseconds per century,
while Iorio showed that the mean longitude \lambda is affected by a secular
precession of about 10^-3 arcseconds per century. Such effects depend only on
the eccentricities e of the orbits via second-order terms: they are, instead,
independent of their semimajor axes a. Up to now, the observational efforts
focused on the dynamics of the inner planets of the Solar System whose orbits
are the best known via radar ranging. Since the competing Newtonian and
Einsteinian effects like the precessions due to the solar quadrupole mass
moment J2, the gravitoelectric and gravitomagnetic part of the equations of
motion reduce with increasing distances, it would be possible to argue that an
analysis of the orbital dynamics of the outer planets of the Solar System, with
particular emphasis on Saturn because of the ongoing Cassini mission with its
precision ranging instrumentation, could be helpful in evidencing the predicted
new features of motion. In this note we investigate this possibility in view of
the latest results in the planetary ephemeris field. Unfortunately, the current
level of accuracy rules out this appealing possibility and it appears unlikely
that Cassini and GAIA will ameliorate the situation.Comment: LaTex, 22 pages, 2 tables, 10 figures, 27 references. Reference [17]
added, reference [26] updated, caption of figures changed, small change in
section 1.
The stellar mass-halo mass relation of isolated field dwarfs: a critical test of CDM at the edge of galaxy formation
We fit the rotation curves of isolated dwarf galaxies to directly measure the
stellar mass-halo mass relation () over the mass range . By accounting for cusp-core
transformations due to stellar feedback, we find a monotonic relation with
little scatter. Such monotonicity implies that abundance matching should yield
a similar if the cosmological model is correct. Using the 'field
galaxy' stellar mass function from the Sloan Digital Sky Survey (SDSS) and the
halo mass function from the Cold Dark Matter Bolshoi simulation, we
find remarkable agreement between the two. This holds down to M, and to M if we
assume a power law extrapolation of the SDSS stellar mass function below M.
However, if instead of SDSS we use the stellar mass function of nearby galaxy
groups, then the agreement is poor. This occurs because the group stellar mass
function is shallower than that of the field below M,
recovering the familiar 'missing satellites' and 'too big to fail' problems.
Our result demonstrates that both problems are confined to group environments
and must, therefore, owe to 'galaxy formation physics' rather than exotic
cosmology.
Finally, we repeat our analysis for a Warm Dark Matter cosmology,
finding that it fails at 68% confidence for a thermal relic mass of keV, and keV if we use the power law extrapolation
of SDSS. We conclude by making a number of predictions for future surveys based
on these results.Comment: 22 pages; 2 Tables; 10 Figures. This is the version accepted for
publication in MNRAS. Key changes: (i) added substantially more information
on the surveys used to measure the stellar mass functions; (ii) added tests
of the robustness of our results. Results and conclusions unchanged from
previously. Minor typos corrected from previous versio
Alpha Lipoic Acid (ALA) effects on subchorionic hematoma. Preliminary clinical results
OBJECTIVE: The clinic use of alpha Lipoic Acid (ALA) is linked to its capability to exert antioxidant effects and, more interestingly, to counteract the pathologic changes of complex networks of cytokines, chemokines and growth factors, restoring their physiological state. The aim of this randomized controlled clinical trial was to test the contribution of oral supplementation of ALA to the standard treatment with Progesterone vaginal suppositories, in healing subchorionic hematomas in patients with threatened miscarriage. Controls were administered only Progesterone suppositories.
PATIENTS AND METHODS: Nineteen pregnant women in the first trimester of gestation, with threatened miscarriage and ultrasound evidence of subchorionic hematoma, were included in the trial and randomly divided in two groups: controls, treated with 400 mg Progesterone (200 mg 2 times per day), given by vaginal suppositories, and case study treated with the same Progesterone dosage, plus ALA, given orally at the dose of 600 mg (300 mg 2 times per day, DAV®, Lo.Li. Pharma srl, Italy). Sixteen patients completed the trial. Treatment was performed until complete resolution of the clinical picture.
RESULTS: In both groups, the subjects improved significantly but, in general, a better and faster evolution in the major signs of threatened miscarriage was observed in the subjects treated with ALA and Progesterone. In these patients, the speed of resorption of subchorionic hematoma was significantly (p ≤ 0.05) superior compared to controls. The ALA and Progesterone group showed a faster decrease or disappearance of all symptoms than that observed in the control group, however the difference was not significant.
CONCLUSIONS: These preliminary results suggest that ALA supplementation significantly contributes to speed up the process of restoration of physiological conditions in threatened miscarriage and ameliorates the medical conditions of both the mothers and the foetus, probably modulating the networks of cytokines, growth factors and other molecules
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