242 research outputs found
Quasilocalized gravity without asymptotic flatness
We present a toy model of a generic five-dimensional warped geometry in which
the 4D graviton is not fully localized on the brane. Studying the tensor sector
of metric perturbation around this background, we find that its contribution to
the effective gravitational potential is of 4D type (1/r) at the intermediate
scales and that at the large scales it becomes 1/r^{1+alpha}, 0<alpha=< 1 being
a function of the parameters of the model (alpha=1 corresponds to the
asymptotically flat geometry). Large-distance behavior of the potential is
therefore not necessarily five-dimensional. Our analysis applies also to the
case of quasilocalized massless particles other than graviton.Comment: 9 pages, 1 figure; to be published in Phys. Rev.
The complete genome of Burkholderia phenoliruptrix strain BR3459a, a symbiont of Mimosa flocculosa: highlighting the coexistence of symbiotic and pathogenic genes.
Burkholderia species play an important ecological role related to xenobiosis, the promotion of plant growth, the biocontrol of agricultural diseases, and symbiotic and non-symbiotic biological nitrogen fixation. Here, we highlight our study as providing the first complete genome of a symbiotic strain of B. phenoliruptrix, BR3459a (=CLA1), which was originally isolated in Brazil from nodules of Mimosa flocculosa and is effective in fixing nitrogen in association with this leguminous species. Genomic comparisons with other pathogenic and non-pathogenic Burkholderia strains grouped B. phenoliruptrix BR3459a with plant-associated beneficial and environmental species, although it shares a high percentage of its gene repertoire with species of the B. cepacia complex (Bcc) and "pseudomallei" group. The genomic analyses showed that the bce genes involved in exopolysaccharide production are clustered together in the same genomic region, constituting part of the Group III cluster of non-pathogenic bacteria. Regarding environmental stresses, we highlight genes that might be relevant in responses to osmotic, heat, cold and general stresses. Furthermore, a number of particularly interesting genes involved in the machinery of the T1SS, T2SS, T3SS, T4ASS and T6SS secretion systems were identified. The xenobiotic properties of strain BR3459a were also investigated, and some enzymes involved in the degradation of styrene, nitrotoluene, dioxin, chlorocyclohexane, chlorobenzene and caprolactam were identified. The genomic analyses also revealed a large number of antibiotic-related genes, the most important of which were correlated with streptomycin and novobiocin. The symbiotic plasmid showed high sequence identity with the symbiotic plasmid of B. phymatum. Additionally, comparative analysis of 545 housekeeping genes among pathogenic and non-pathogenic Burkholderia species strongly supports the definition of a new genus for the second branch, which would include BR3459a. The analyses of B. phenoliruptrix BR3459a showed key property of fixing nitrogen that together with genes for high tolerance to environmental stresses might explain a successful strategy of symbiosis in the tropics. The strain also harbours interesting sets of genes with biotechnological potential. However, the resemblance of certain genes to those of pathogenic Burkholderia raise concerns about large-scale applications in agriculture or for bioremediation
Complete genome sequence of Burkholderia phenoliruptrix BR3459a (CLA1), a heat-tolerant, nitrogen-fixing symbiont of mimosa flocculosa.
The genus Burkholderia represents a challenge to the fields of taxonomy and phylogeny and, especially, to the understanding of the contrasting roles as either opportunistic pathogens or bacteria with biotechnological potential. Few genomes of nonpathogenic strains, especially of diazotrophic symbiotic bacteria, have been sequenced to improve understanding of the genus. Here, we contribute with the complete genome sequence of Burkholderia phenoliruptrix strain BR3459a (CLA1), an effective diazotrophic symbiont of the leguminous tree Mimosa flocculosa Burkart, which is endemic to South America
Investigación + Creación; proyecto Vestuario, Patrimonio y Comunidad
La investigación+creación es un modelo de generación de nuevo conocimiento más cercano a las áreas creativas, desde allí se plantean proyectos que fundamentan las disciplinas del diseño. Por lo anterior, el gobierno colombiano desde el 2019, crea la primera convocatoria establecida específicamente para ello; InvestigARTE. Uno de los proyectos beneficiarios de dicha iniciativa es el de Vestuario, Patrimonio y Comunidad, el cual busca reconocer los saberes artesanales y tradicionales del quehacer de una de las regiones del país, refiriéndose exclusivamente a productos que tienen que ver con el cuerpo y sus artefactos vestimentarios. Aquí se explicita su proceder y pertinencia
Label-free cell cycle analysis for high-throughput imaging flow cytometry
Imaging flow cytometry combines the high-throughput capabilities of conventional flow cytometry with single-cell imaging. Here we demonstrate label-free prediction of DNA content and quantification of the mitotic cell cycle phases by applying supervised machine learning to morphological features extracted from brightfield and the typically ignored darkfield images of cells from an imaging flow cytometer. This method facilitates non-destructive monitoring of cells avoiding potentially confounding effects of fluorescent stains while maximizing available fluorescence channels. The method is effective in cell cycle analysis for mammalian cells, both fixed and live, and accurately assesses the impact of a cell cycle mitotic phase blocking agent. As the same method is effective in predicting the DNA content of fission yeast, it is likely to have a broad application to other cell types
Characterizing planetary systems with SPIRou: M-dwarf planet-search survey and the multiplanet systems GJ 876 and GJ 1148
SPIRou is a near-infrared spectropolarimeter and a high-precision
velocimeter. The SPIRou Legacy Survey collected data from February 2019 to June
2022, half of the time devoted to a blind search for exoplanets around nearby
cool stars. The aim of this paper is to present this program and an overview of
its properties, and to revisit the radial velocity (RV) data of two multiplanet
systems, including new visits with SPIRou. From SPIRou data, we can extract
precise RVs using efficient telluric correction and line-by-line measurement
techniques, and we can reconstruct stellar magnetic fields from the collection
of polarized spectra using the Zeeman-Doppler imaging method. The stellar
sample of our blind search in the solar neighborhood, the observing strategy,
the RV noise estimates, chromatic behavior, and current limitations of SPIRou
RV measurements on bright M dwarfs are described. In addition, SPIRou data over
a 2.5-year time span allow us to revisit the known multiplanet systems GJ~876
and GJ~1148. For GJ~876, the new dynamical analysis including the four planets
is consistent with previous models and confirms that this system is deep in the
Laplace resonance and likely chaotic. The large-scale magnetic map of GJ~876
over two consecutive observing seasons is obtained and shows a dominant dipolar
field with a polar strength of 30~G, which defines the magnetic environment in
which the inner planet with a period of 1.94~d is embedded. For GJ~1148, we
refine the known two-planet model.Comment: accepted in A&
The SPIRou Legacy Survey Rotation period of quiet M dwarfs from circular polarization in near-infrared spectral lines: I. The SPIRou APERO analysis
Context. The rotation period of stars is an important parameter along with
mass, radius, effective temperature. It is an essential parameter for any
radial velocity monitoring, as stellar activity can mimic the presence of a
planet at the stellar rotation period. Several methods exist to measure it,
including long sequences of photometric measurements or temporal series of
stellar activity indicators. Aims. Here, we use the circular polarization in
near-infrared spectral lines for a sample of 43 quiet M dwarfs and compare the
measured rotation periods to those obtained with other methods. Methods. From
Stokes V spectropolarimetric sequences observed with SPIRou at CFHT and the
data processed with the APERO pipeline, we compute the least squares
deconvolution profiles using different masks of atomic stellar lines with known
Land\'e factor appropriate to the effective temperature of the star. We derive
the longitudinal magnetic field to examine its possible variation along the 50
to 200 observations of each star. For determining the stellar rotation period,
we apply a Gaussian process regression enabling us to determine the rotation
period of stars with evolving longitudinal field. Results. Among the 43 stars
of our sample, we were able to measure a rotation period for 27 stars. For 8
stars, the rotation period was previously unknown. We find a good agreement of
our rotation periods with periods found in the literature based on photometry
and activity indicators and confirm that near-infrared spectropolarimetry is an
important tool to measure rotation periods, even for magnetically quiet stars.
Furthermore, we compute ages for 20 stars of our sample using gyrochronology
Not any type of rice performs equally to improve lactose-induced diarrhea characteristics in rats: is amylose an antidiarrheal factor?
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
A hot mini-Neptune and a temperate, highly eccentric sub-Saturn around the bright K-dwarf TOI-2134
Funding: ACC and TGW acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. RDH is funded by the UK Science and Technology Facilities Council (STFC)’s Ernest Rutherford Fellowship (grant no. ST/V004735/1). SD is funded by the UK Science and Technology Facilities Council (grant no. ST/V004735/1). BSL is funded by a UK Science and Technology Facilities Council (STFC) studentship (ST/V506679/1). This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement SCORE no. 851555).We present the characterisation of an inner mini-Neptune in a 9.2292005±0.0000063 day orbit and an outer mono-transiting sub-Saturn planet in a 95.50+0.36-0.25 day orbit around the moderately active, bright (mv = 8.9 mag) K5V star TOI-2134. Based on our analysis of five sectors of TESS data, we determine the radii of TOI-2134b and c to be 2.69±0.16 R⊕ for the inner planet and 7.27±0.42 R⊕ for the outer one. We acquired 111 radial-velocity spectra with HARPS-N and 108 radial-velocity spectra with SOPHIE. After careful periodogram analysis, we derive masses for both planets via Gaussian Process regression: 9.13+0.78-0.76 M⊕ for TOI-2134b and 41.89+7.69-7.83 M⊕ for TOI-2134c. We analysed the photometric and radial-velocity data first separately, then jointly. The inner planet is a mini-Neptune with density consistent with either a water-world or a rocky core planet with a low-mass H/He envelope. The outer planet has a bulk density similar to Saturn’s. The outer planet is derived to have a significant eccentricity of 0.67+0.05-0.06 from a combination of photometry and RVs. We compute the irradiation of TOI-2134c as 1.45±0.10 times the bolometric flux received by Earth, positioning it for part of its orbit in the habitable zone of its system. We recommend further RV observations to fully constrain the orbit of TOI-2134c. With an expected Rossiter-McLaughlin (RM) effect amplitude of 7.2±1.3 m-1, we recommend TOI-2134c for follow-up RM analysis to study the spin-orbit architecture of the system. We calculate the Transmission Spectroscopy Metric, and both planets are suitable for bright-mode NIRCam atmospheric characterisation.Publisher PDFPeer reviewe
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