236 research outputs found
Mycobacterium tuberculosis proteins involved in cell wall lipid biosynthesis improve BCG vaccine efficacy in a murine TB model
OBJECTIVES: Advances in tuberculosis (TB) vaccine development are urgently required to enhance global disease management. We evaluated the potential of Mycobacterium tuberculosis (M. tb)-derived protein antigens Rv0447c, Rv2957 and Rv2958c to boost BCG vaccine efficacy in the presence or absence of glucopyranosyl lipid adjuvant formulated in a stable emulsion (GLA-SE) adjuvant. METHODS: Mice received the BCG vaccine, followed by Rv0447c, Rv2957 and Rv2958c protein boosting with or without GLA-SE adjuvant 3 and 6 weeks later. Immune responses were examined at given time points. 9 weeks post vaccination, mice were aerosol-challenged with M. tb, and sacrificed at 6 and 12 weeks to assess bacterial burden. RESULTS: Vaccination of mice with BCG and M. tb proteins in the presence of GLA-SE adjuvant triggered strong IFN-γ and IL-2 production by splenocytes; more TNF-α was produced without GLA-SE addition. Antibody responses to all three antigens did not differ, with or without GLA-SE adjuvant. Protein boosting without GLA-SE adjuvant resulted in vaccinated animals having better control of pulmonary M. tb load at 6 and 12 weeks post aerosol infection, while animals receiving the protein boost with GLA-SE adjuvant exhibited more bacteria in the lungs. CONCLUSIONS: Our data provides evidence for developing Rv2958c, Rv2957 and Rv0447c in a heterologous prime-boost vaccination strategy with BCG
Accuracy of syndrome definitions based on diagnoses in physician claims
<p>Abstract</p> <p>Background</p> <p>Community clinics offer potential for timelier outbreak detection and monitoring than emergency departments. However, the accuracy of syndrome definitions used in surveillance has never been evaluated in community settings. This study's objective was to assess the accuracy of syndrome definitions based on diagnostic codes in physician claims for identifying 5 syndromes (fever, gastrointestinal, neurological, rash, and respiratory including influenza-like illness) in community clinics.</p> <p>Methods</p> <p>We selected a random sample of 3,600 community-based primary care physicians who practiced in the fee-for-service system in the province of Quebec, Canada in 2005-2007. We randomly selected 10 visits per physician from their claims, stratifying on syndrome type and presence, diagnosis, and month. Double-blinded chart reviews were conducted by telephone with consenting physicians to obtain information on patient diagnoses for each sampled visit. The sensitivity, specificity, and positive predictive value (PPV) of physician claims were estimated by comparison to chart review.</p> <p>Results</p> <p>1,098 (30.5%) physicians completed the chart review. A chart entry on the date of the corresponding claim was found for 10,529 (95.9%) visits. The sensitivity of syndrome definitions based on diagnostic codes in physician claims was low, ranging from 0.11 (fever) to 0.44 (respiratory), the specificity was high, and the PPV was moderate to high, ranging from 0.59 (fever) to 0.85 (respiratory). We found that rarely used diagnostic codes had a higher probability of being false-positives, and that more commonly used diagnostic codes had a higher PPV.</p> <p>Conclusions</p> <p>Future research should identify physician, patient, and encounter characteristics associated with the accuracy of diagnostic codes in physician claims. This would enable public health to improve syndromic surveillance, either by focusing on physician claims whose diagnostic code is more likely to be accurate, or by using all physician claims and weighing each according to the likelihood that its diagnostic code is accurate.</p
: a data-driven approach to correct for systematics in RV data -- Application to SPIRou data of the planet-hosting M dwarf GJ 251
Context: Recent advances in the development of precise radial velocity (RV)
instruments in the near-infrared (nIR) domain, such as SPIRou, have facilitated
the study of M-type stars to more effectively characterize planetary systems.
However, the nIR presents unique challenges in exoplanet detection due to
various sources of planet-independent signals which can result in systematic
errors in the RV data.
Aims: In order to address the challenges posed by the detection of
exoplanetary systems around M-type stars using nIR observations, we introduce a
new data-driven approach for correcting systematic errors in RV data. The
effectiveness of this method is demonstrated through its application to the
star GJ 251.
Methods: Our proposed method, referred to as (Weighted
principAl comPonent analysIs reconsTructIon), uses a dataset of per-line RV
time-series generated by the line-by-line (LBL) algorithm and employs a
weighted principal component analysis (wPCA) to reconstruct the original RV
time-series. A multi-step process is employed to determine the appropriate
number of components, with the ultimate goal of subtracting the wPCA
reconstruction of the per-line RV time-series from the original data in order
to correct systematic errors.
Results: The application of to GJ 251 successfully
eliminates spurious signals from the RV time-series and enables the first
detection in the nIR of GJ 251b, a known temperate super-Earth with an orbital
period of 14.2 days. This demonstrates that, even when systematics in SPIRou
data are unidentified, it is still possible to effectively address them and
fully realize the instrument's capability for exoplanet detection.
Additionally, in contrast to the use of optical RVs, this detection did not
require to filter out stellar activity, highlighting a key advantage of nIR RV
measurements.Comment: Submitted to A&A. For the publicly available Wapiti code, see
https://github.com/HkmMerwan/wapit
Calcitonin gene-related peptide stimulates proliferation of alveolar epithelial cells
<p>Abstract</p> <p>Background</p> <p>Alveolar epithelial cells are known as progenitor cells for the restoration from the damage in the lung. Calcitonin gene-related peptide (CGRP) has been reported to play an important role in the proliferation of various types of epithelial and endothelial cells. We investigated the effects of CGRP on the proliferation of alveolar epithelial cells <it>in vitro </it>and <it>in vivo</it>.</p> <p>Methods</p> <p>A549 cells were cultured in Dulbecco Modified Eagle Medium with 5% fatal bovin serum for 24 hours, then CGRP was added <it>in vitro</it>. The proliferation of DNA synthesis was measured using 5-bromo-2-deoxyuridine, an analog of thymidine, by enzyme-linked immunosorbent assay.</p> <p>As one intracellular response to CGRP, we examined activation of p44/42- extracellular signal-regulated kinase (ERK) pathway by adding CGRP, using western blotting method.</p> <p>Recombinant adenovirus encoding nuclear-targeted-human ÎČ-CGRP (rhCGRP) was administered into Male Wister rat (n = 5, 10 weeks old) lungs by intratracheal instillation <it>in vivo</it>. 7 days after the administration of CGRP, rat lungs were harvested and histological findings and immunohistochemical staining of proliferating cell nuclear antigen (PCNA) were evaluated to examine cell proliferation.</p> <p>Results</p> <p><it>In vitro </it>study, CGRP increased the proliferation of A549 cells in a dose and time dependent manner. CGRP8-37 (inhibitor of CGRP receptor) decreased CGRP induced proliferation of DNA synthesis. Phosphorylation of ERK pathway was observed within 15 minutes and peaked in one hour. U0126 (inhibitor of ERK pathway) decreased CGRP induced proliferation of DNA synthesis.<it>In vivo </it>study, histological examination of the lung indicated proliferation of alveolar epithelial cells in the rhCGRP-treated group and the nuclei of alveolar epithelial cells were positive for PCNA immunostaining.</p> <p>Conclusion</p> <p>In this study, we conclude that CGRP stimulates proliferation of human alveolar epithelial cells <it>in vivo </it>and <it>in vitro</it>.</p
Monitoring the large-scale magnetic field of AD~Leo with SPIRou, ESPaDOnS and Narval. Toward a magnetic polarity reversal?
One manifestation of dynamo action on the Sun is the 22-yr magnetic cycle,
exhibiting a polarity reversal and a periodic conversion between poloidal and
toroidal fields. For M dwarfs, several authors claim evidence of activity
cycles from photometry and analyses of spectroscopic indices, but no clear
polarity reversal has been identified from spectropolarimetric observations.
Our aim is to monitor the evolution of the large-scale field of AD Leo, which
has shown hints of a secular evolution from past dedicated spectropolarimetric
campaigns. We analysed near-infrared spectropolarimetric observations of the
active M dwarf AD Leo taken with SPIRou between 2019 and 2020 and archival
optical data collected with ESPaDOnS and Narval between 2006 and 2019. We
searched for long-term variability in the longitudinal field, the width of
unpolarised Stokes profiles, the unsigned magnetic flux derived from Zeeman
broadening, and the geometry of the large-scale magnetic field using both
Zeeman-Doppler Imaging and Principal Component Analysis. We found evidence of a
long-term evolution of the magnetic field, featuring a decrease in axisymmetry
(from 99% to 60%). This is accompanied by a weakening of the longitudinal field
(-300 to -50 G) and a correlated increase in the unsigned magnetic flux (2.8 to
3.6 kG). Likewise, the width of the mean profile computed with selected
near-infrared lines manifests a long-term evolution corresponding to field
strength changes over the full time series, but does not exhibit modulation
with the stellar rotation of AD Leo in individual epochs. The large-scale
magnetic field of AD Leo manifested first hints of a polarity reversal in late
2020 in the form of a substantially increased dipole obliquity, while the
topology remained predominantly poloidal and dipolar. This suggests that
low-mass M dwarfs with a dipole-dominated magnetic field can undergo magnetic
cycles.Comment: 26 pages, 18 figures, 8 table
The magnetic field and multiple planets of the young dwarf AU~Mic
In this paper we present an analysis of near-infrared spectropolarimetric and
velocimetric data of the young M dwarf AU Mic, collected with SPIRou at the
Canada-France-Hawaii telescope from 2019 to 2022, mostly within the SPIRou
Legacy Survey. With these data, we study the large- and small-scale magnetic
field of AU Mic, detected through the unpolarized and circularly-polarized
Zeeman signatures of spectral lines. We find that both are modulated with the
stellar rotation period (4.86 d), and evolve on a timescale of months under
differential rotation and intrinsic variability. The small-scale field,
estimated from the broadening of spectral lines, reaches kG. The
large-scale field, inferred with Zeeman-Doppler imaging from Least-Squares
Deconvolved profiles of circularly-polarized and unpolarized spectral lines, is
mostly poloidal and axisymmetric, with an average intensity of G. We
also find that surface differential rotation, as derived from the large-scale
field, is 30% weaker than that of the Sun. We detect the radial
velocity (RV) signatures of transiting planets b and c, although dwarfed by
activity, and put an upper limit on that of candidate planet d, putatively
causing the transit-timing variations of b and c. We also report the detection
of the RV signature of a new candidate planet (e) orbiting further out with a
period of d, i.e., near the 4:1 resonance with b. The RV
signature of e is detected at 6.5 while those of b and c show up at
4, yielding masses of and
Earth masses for b and c, and a minimum mass of
Earth masses for e.Comment: MNRAS, in press (20 pages and 12 figures + 9 pages of supplementary
material
Near-IR and optical radial velocities of the active M-dwarf star Gl 388 (AD Leo) with SPIRou at CFHT and SOPHIE at OHP
Context: The search for extrasolar planets around the nearest M-dwarfs is a
crucial step towards identifying the nearest Earth-like planets. One of the
main challenges in this search is that M-dwarfs can be magnetically active and
stellar activity can produce radial velocity (RV) signals that could mimic
those of a planet.
Aims: We aim to investigate whether the 2.2 day period observed in optical
RVs of the nearby active M-dwarf star Gl 388 (AD Leo) is due to stellar
activity or to a planet which co-rotates with the star as suggested in the
past.
Methods: We obtained quasi-simultaneous optical RVs of Gl 388 from 2019 to
2021 with SOPHIE (R75k) at the OHP in France, and near-IR RV and Stokes V
measurements with SPIRou at the CFHT (R70k).
Results: The SOPHIE RV time-series displays a periodic signal with
2.230.01 days period and 23.60.5 m/s amplitude, which is consistent
with previous HARPS observations obtained in 2005-2006. The SPIRou RV
time-series is flat at 5 m/s rms and displays no periodic signals. RV signals
of amplitude higher than 5.3 m/s at a period of 2.23 days can be excluded with
a confidence level higher than 99%. Using the modulation of the longitudinal
magnetic field (Bl) measured with SPIRou, we derive a stellar rotation period
of 2.23050.0016 days.
Conclusions: SPIRou RV measurements provide solid evidence that the periodic
variability of the optical RVs of Gl 388 is due to stellar activity rather than
to a co-rotating planet. The magnetic activity nature of the optical RV signal
is further confirmed by the modulation of Bl with the same period. The SPIRou
campaign on Gl 388 demonstrates the power of near-IR RV to confirm or infirm
planet candidates discovered in the optical around active stars. SPIRou
observations reiterate how effective spectropolarimetry is at determining the
stellar rotation period.Comment: 25 pages, 23 figures, Accepted by Astronomy and Astrophysic
Optical and near-infrared stellar activity characterization of the early M dwarf Gl~205 with SOPHIE and SPIRou
The stellar activity of M dwarfs is the main limitation for discovering and
characterizing exoplanets orbiting them since it induces quasi-periodic RV
variations. We aim to characterize the magnetic field and stellar activity of
the early, moderately active, M dwarf Gl205 in the optical and nIR domains. We
obtained high-precision quasi-simultaneous spectra in the optical and nIR with
the SOPHIE spectrograph and SPIRou spectropolarimeter between 2019 and 2022. We
computed the RVs from both instruments and the SPIRou Stokes V profiles. We
used ZDI to map the large-scale magnetic field over the time span of the
observations. We studied the temporal behavior of optical and nIR RVs and
activity indicators with the Lomb-Scargle periodogram and a quasi-periodic GP
regression. In the nIR, we studied the equivalent width of Al I, Ti I, K I, Fe
I, and He I. We modeled the activity-induced RV jitter using a
multi-dimensional GP regression with activity indicators as ancillary time
series. The optical and nIR RVs have similar scatter but nIR shows a more
complex temporal evolution. We observe an evolution of the magnetic field
topology from a poloidal dipolar field in 2019 to a dominantly toroidal field
in 2022. We measured a stellar rotation period of Prot=34.40.5 d in the
longitudinal magnetic field. Using ZDI we measure the amount of latitudinal
differential rotation (DR) shearing the stellar surface yielding rotation
periods of Peq=32.01.8 d at the stellar equator and Ppol=45.50.3 d at
the poles. We observed inconsistencies in the activity indicators'
periodicities that could be explained by these DR values. The multi-dimensional
GP modeling yields an RMS of the RV residuals down to the noise level of 3 m/s
for both instruments, using as ancillary time series H and the BIS in
the optical, and the FWHM in the nIR.Comment: 41 pages, 24 figures. Accepted for publication in A&A. Improved
quality of figures and reduced size of Appendi
Homogeneous search for helium in the atmosphere of 11 gas giant exoplanets with SPIRou
The metastable helium triplet in the near-infrared (10833{\AA}) is among the
most important probes of exoplanet atmospheres. It can trace their extended
outer layers and constrain mass-loss. We use the near-infrared high-resolution
spectropolarimeter SPIRou on the CFHT to search for the spectrally resolved
helium triplet in the atmospheres of eleven exoplanets, ranging from warm
mini-Neptunes to hot Jupiters and orbiting G, K, and M dwarfs. Observations
were obtained as part of the SPIRou Legacy Survey and complementary open-time
programs. We apply a homogeneous data reduction to all datasets and set
constraints on the presence of metastable helium, despite the presence of
systematics in the data. We confirm published detections for HAT-P-11b,
HD189733b, and WASP-69b and set upper limits for the other planets. We apply
the p-winds open source code to set upper limits on the mass-loss rate for the
non-detections and to constrain the thermosphere temperature, mass-loss rate,
line-of-sight velocity, and the altitude of the thermosphere for the
detections. We confirm that the presence of metastable helium correlates with
the stellar mass and the XUV flux received by the planets. We investigated the
correlation between the mass-loss rate and the presence of metastable helium,
but it remains difficult to draw definitive conclusions. Finally, some of our
results are in contradiction with previous results in the literature, therefore
we stress the importance of repeatable, homogeneous, and larger-scale analyses
of the helium triplet to obtain robust statistics, study temporal variability,
and better understand how the helium triplet can be used to explore the
evolution of exoplanets.Comment: 28 pages, 13 figures, Accepted in A&A for publicatio
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