123 research outputs found
Orbit determination of Transneptunian objects and Centaurs for the prediction of stellar occultations
The prediction of stellar occultations by Transneptunian objects and Centaurs
is a difficult challenge that requires accuracy both in the occulted star
position as for the object ephemeris. Until now, the most used method of
prediction involving tens of TNOs/Centaurs was to consider a constant offset
for the right ascension and for the declination with respect to a reference
ephemeris. This offset is determined as the difference between the most recent
observations of the TNO and the reference ephemeris. This method can be
successfully applied when the offset remains constant with time. This paper
presents an alternative method of prediction based on a new accurate orbit
determination procedure, which uses all the available positions of the TNO from
the Minor Planet Center database plus sets of new astrometric positions from
unpublished observations. The orbit determination is performed through a
numerical integration procedure (NIMA), in which we develop a specific
weighting scheme. The NIMA method was applied for 51 selected TNOs/Centaurs.
For this purpose, we have performed about 2900 new observations during
2007-2014. Using NIMA, we succeed in predicting the stellar occultations of 10
TNOs and 3 Centaurs between 2013 and 2015. By comparing the NIMA and JPL
ephemerides, we highlighted the variation of the offset between them with time.
Giving examples, we show that the constant offset method could not accurately
predict 6 out of the 13 observed positive occultations successfully predicted
by NIMA. The results indicate that NIMA is capable of efficiently refine the
orbits of these bodies. Finally, we show that the astrometric positions given
by positive occultations can help to further refine the orbit of the TNO and
consequently the future predictions. We also provide the unpublished
observations of the 51 selected TNOs and their ephemeris in a usable format by
the SPICE library.Comment: 12 pages, 9 figures, accepted in A&
Triplicity and Physical Characteristics of Asteroid (216) Kleopatra
To take full advantage of the September 2008 opposition passage of the M-type
asteroid (216) Kleopatra, we have used near-infrared adaptive optics (AO)
imaging with the W.M. Keck II telescope to capture unprecedented high
resolution images of this unusual asteroid. Our AO observations with the W.M.
Keck II telescope, combined with Spitzer/IRS spectroscopic observations and
past stellar occultations, confirm the value of its IRAS radiometric radius of
67.5 km as well as its dog-bone shape suggested by earlier radar observations.
Our Keck AO observations revealed the presence of two small satellites in orbit
about Kleopatra (see Marchis et al., 2008). Accurate measurements of the
satellite orbits over a full month enabled us to determine the total mass of
the system to be 4.64+/-0.02 10^18 Kg. This translates into a bulk density of
3.6 +/-0.4 g/cm3, which implies a macroscopic porosity for Kleopatra of ~
30-50%, typical of a rubble-pile asteroid. From these physical characteristics
we measured its specific angular momentum, very close to that of a spinning
equilibrium dumbbell.Comment: 35 pages, 3 Tables, 9 Figures. In press to Icaru
Analysis of the rotation period of asteroids (1865) Cerberus, (2100) Ra-Shalom, and (3103) Eger - search for the YORP effect
The spin state of small asteroids can change on a long timescale by the
Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, the net torque that arises
from anisotropically scattered sunlight and proper thermal radiation from an
irregularly-shaped asteroid. The secular change in the rotation period caused
by the YORP effect can be detected by analysis of asteroid photometric
lightcurves. We analyzed photometric lightcurves of near-Earth asteroids (1865)
Cerberus, (2100) Ra-Shalom, and (3103) Eger with the aim to detect possible
deviations from the constant rotation caused by the YORP effect. We carried out
new photometric observations of the three asteroids, combined the new
lightcurves with archived data, and used the lightcurve inversion method to
model the asteroid shape, pole direction, and rotation rate. The YORP effect
was modeled as a linear change in the rotation rate in time d\omega /dt. Values
of d\omega/ dt derived from observations were compared with the values
predicted by theory. We derived physical models for all three asteroids. We had
to model Eger as a nonconvex body because the convex model failed to fit the
lightcurves observed at high phase angles. We probably detected the
acceleration of the rotation rate of Eger d\omega / dt = (1.4 +/- 0.6) x
10^{-8} rad/d (3\sigma error), which corresponds to a decrease in the rotation
period by 4.2 ms/yr. The photometry of Cerberus and Ra-Shalom was consistent
with a constant-period model, and no secular change in the spin rate was
detected. We could only constrain maximum values of |d\omega / dt| < 8 x
10^{-9} rad/d for Cerberus, and |d\omega / dt| < 3 x 10^{-8} rad/d for
Ra-Shalom
Comparison of anti-interleukin-5 therapies in patients with severe asthma: global and indirect meta-analyses of randomized placebo-controlled trials
International audienceInconsistent results have been reported regarding IL-5 blockade treatment in asthma. There were no direct between-treatment comparisons. Only differences between each drug and placebo were studied. We identified all RCTs with anti-IL5 treatments for patients with asthma over the 1990-September 2015 period. RCTs were searched on Medline, Cochrane and Embase. At least 50 patients were enrolled in each study. Outcomes considered were exacerbation rate reduction, FEV1 changes, ACQ-5 improvement, adverse events and serious adverse events. A global meta-analysis was first conducted followed by an indirect comparison of each IL-5-targeting drug: benralizumab, reslizumab and mepolizumab. Further eosinophilic subgroup analysis and sensitivity analysis were also conducted in case of heterogeneity. Ten trials involving 3421 patients were eligible for meta-analysis. IL-5 blockade significantly reduced annual exacerbation rates vs. placebo by 40% [29-50] (P < 0.01, I2 = 0.61). ACQ-5 was significantly improved vs. placebo but below the recognized MCID level (-0.31 [-0.41, -0.21], P < 0.01, I2 = 0.11). FEV1 changes from baseline were improved vs. placebo by 0.09 L [0.05-0.12] (P < 0.01, I2 = 0.28). The subgroup analysis identified a slight additional improvement in mean treatment effects in eosinophilic (> 300 mm3 /L) patients with severe asthma. Similar patterns and rates of adverse events and severe adverse events were reported with the three drugs. The data interpretations were not affected by the sensitivity analysis. IL-5 blockade appears to be a relevant treatment strategy to improve severe asthma management, particularly for eosinophilic patients. No clear superiority appeared between the drugs when appropriate doses were compared
Immune sensitization of equine bronchus: glutathione, IL-1β expression and tissue responsiveness
BACKGROUND: Increasing clinical epidemiological and experimental evidence indicates that excess of production of reactive oxygen free radicals (ROS) induced by an oxidative stress is involved in the pathogenesis of a number of human airway disorders, as well as equine recurrent airway obstruction. Free-radicals modulate the activation of transcription factors, such as nuclear factor-(NF)-κB and activator protein (AP)-1, in several different cells. This activation leads to expression of many pro-inflammatory cytokines, including interleukin (IL)-1β. We have hypothesized that equine airway sensitization might induce an oxidative stress and increase the ROS production, which in turn might enhance a production of IL-1β and airway hyperresponsiveness. METHODS: We have examined the effect of passive sensitization on IL-1β mRNA expression and electrical field stimulation (EFS)-induced contraction in equine isolated bronchi, and the potential interference of reduced-glutathione (GSH), an antioxidant, with these responses. Bronchi passively sensitized with serum from animals suffering from heaves and having high total level of IgE, and control tissues, either pretreated or not with GSH (100 μM), were used to quantify IL-1β mRNA. Other tissues were used to study the effect of EFS (3–10–25 Hz). RESULTS: Mean IL-1β mRNA expression was higher in passively sensitized than in control rings. GSH significantly (p < 0.05) reduced the IL-1β mRNA expression only in passively sensitized bronchi. ELF induced a frequency-dependent contraction in both non-sensitized and passively sensitized tissues, with a significantly greater response always observed in sensitized tissues. GSH did not modify the EFS-induced contraction in non-sensitized bronchi, but significantly (p < 0.05) decreased it in passively sensitized tissues. CONCLUSION: Our data indicate that the passive sensitization of equine bronchi induces inflammation and hyperresponsiveness. These effects might be due to an oxidative stress because a pretreatment with GSH decreased the increased IL-1β mRNA expression and responsiveness to EFS of passively sensitized bronchi
The non-convex shape of (234) Barbara, the first Barbarian
Asteroid (234) Barbara is the prototype of a category of asteroids that has
been shown to be extremely rich in refractory inclusions, the oldest material
ever found in the Solar System. It exhibits several peculiar features, most
notably its polarimetric behavior. In recent years other objects sharing the
same property (collectively known as "Barbarians") have been discovered.
Interferometric observations in the mid-infrared with the ESO VLTI suggested
that (234) Barbara might have a bi-lobated shape or even a large companion
satellite. We use a large set of 57 optical lightcurves acquired between 1979
and 2014, together with the timings of two stellar occultations in 2009, to
determine the rotation period, spin-vector coordinates, and 3-D shape of (234)
Barbara, using two different shape reconstruction algorithms. By using the
lightcurves combined to the results obtained from stellar occultations, we are
able to show that the shape of (234) Barbara exhibits large concave areas.
Possible links of the shape to the polarimetric properties and the object
evolution are discussed. We also show that VLTI data can be modeled without the
presence of a satellite.Comment: 10 pages, 6 figure
Corticosteroid suppression of lipoxin A4 and leukotriene B4from alveolar macrophages in severe asthma
<p>Abstract</p> <p>Background</p> <p>An imbalance in the generation of pro-inflammatory leukotrienes, and counter-regulatory lipoxins is present in severe asthma. We measured leukotriene B<sub>4 </sub>(LTB<sub>4</sub>), and lipoxin A<sub>4 </sub>(LXA<sub>4</sub>) production by alveolar macrophages (AMs) and studied the impact of corticosteroids.</p> <p>Methods</p> <p>AMs obtained by fiberoptic bronchoscopy from 14 non-asthmatics, 12 non-severe and 11 severe asthmatics were stimulated with lipopolysaccharide (LPS,10 μg/ml) with or without dexamethasone (10<sup>-6</sup>M). LTB<sub>4 </sub>and LXA<sub>4 </sub>were measured by enzyme immunoassay.</p> <p>Results</p> <p>LXA<sub>4 </sub>biosynthesis was decreased from severe asthma AMs compared to non-severe (p < 0.05) and normal subjects (p < 0.001). LXA<sub>4 </sub>induced by LPS was highest in normal subjects and lowest in severe asthmatics (p < 0.01). Basal levels of LTB<sub>4 </sub>were decreased in severe asthmatics compared to normal subjects (p < 0.05), but not to non-severe asthma. LPS-induced LTB<sub>4 </sub>was increased in severe asthma compared to non-severe asthma (p < 0.05). Dexamethasone inhibited LPS-induced LTB<sub>4 </sub>and LXA<sub>4</sub>, with lesser suppression of LTB<sub>4 </sub>in severe asthma patients (p < 0.05). There was a significant correlation between LPS-induced LXA<sub>4 </sub>and FEV<sub>1 </sub>(% predicted) (r<sub>s </sub>= 0.60; p < 0.01).</p> <p>Conclusions</p> <p>Decreased LXA<sub>4 </sub>and increased LTB<sub>4 </sub>generation plus impaired corticosteroid sensitivity of LPS-induced LTB<sub>4 </sub>but not of LXA<sub>4 </sub>support a role for AMs in establishing a pro-inflammatory balance in severe asthma.</p
A multiwavelength study of Swift GRB 060111B constraining the origin of its prompt optical emission
In this work, we present the results obtained from a multi-wavelength
campaign, as well as from the public Swift/BAT, XRT, and UVOT data of GRB
060111B for which a bright optical emission was measured with good temporal
resolution during the prompt phase. We identified the host galaxy at R~25 mag;
its featureless spectral continuum and brightness, as well as the non-detection
of any associated supernova 16 days after the trigger and other independent
redshift estimates, converge to z~1-2. From the analysis of the early afterglow
SED, we find that non-negligible host galaxy dust extinction, in addition to
the Galactic one, affects the observed flux in the optical regime. The
extinction-corrected optical-to-gamma-ray spectral energy distribution during
the prompt emission shows a flux density ratio =0.01-0.0001
with spectral index , strongly suggesting a
separate origin of the optical and gamma-ray components. This result is
supported by the lack of correlated behavior in the prompt emission light
curves observed in the two energy domains. The properties of the prompt optical
emission observed during GRB 060111B favor interpretation of this optical light
as radiation from the reverse shock in a thick shell limit and in the slow
cooling regime. The expected peak flux is consistent with the observed one
corrected for the host extinction, likely indicating that the starting time of
the TAROT observations is very near to or coincident with the peak time. The
estimated fireball initial Lorentz factor is >260-360 at z=1-2, similar to the
Lorentz factors obtained from other GRBs. GRB 060111B is a rare, good test case
of the reverse shock emission mechanism in both the X-ray and optical energy
ranges.Comment: Accepted for publication in Astronomy and Astrophysics, 15 pages,10
figures and 7 table
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