Etude asympotique d'une marche aléatoire centrifuge

A paraître dans les Annales de l'IHPInternational audienceThe centrifugal random walk is a Markov process in the Euclidean space whose transition probabilities are those of an ordinary symemetric random walk perturbated by a centrifugal drift. We study the behaviour of this process in the mean, in law and on individual trajectories when times goes to infinity

Photometric Mapping with ISOPHOT using the "P32" Astronomical Observation Template

The ``P32'' Astronomical Observation Template (AOT) provided a means to map large areas of sky (up to 45 x 45 arcmin) in the far-infrared (FIR) at high redundancy and with sampling close to the Nyquist limit using the ISOPHOT C100 (3 x 3) and C200 (2 x 2) detector arrays on board the Infrared Space Observatory (ISO). However, the transient response behaviour of the Ga:Ge detectors, if uncorrected, can lead to severe systematic photometric errors and distortions of source morphology on maps. We describe the basic concepts of an algorithm which can successfully correct for transient response artifacts in P32 observations. Examples are given to demonstrate the photometric and imaging performance of ISOPHOT P32 observations of point and extended sources corrected using the algorithm. For extended sources we give the integrated flux densities of the nearby galaxies NGC6946, M51 and M101 and an image of M101 at 100 micron.Comment: 15 pages, 16 figures, published in A&A 410, 107

Plant biodiversity assessment through soil eDNA reflects temporal and local diversity

1. Several studies have shown the potential of eDNA-based proxies for plant identification, but little is known about their spatial and temporal resolution. This limits its use for plant biodiversity assessments and monitoring of vegetation responses to environmental changes. Here we calibrate the temporal and spatial plant signals detected with soil eDNA surveys by comparing with a standard visual above-ground vegetation survey. 2. Our approach compares vegetation in an old-growth boreal forest in southern Norway, surveyed in 100 permanent 1-m2 plots seven times over a 30-year period, with a single soil eDNA metabarcoding-based survey from soil samples collected at the same 100 plots in the year of the last vegetation survey. 3. On average, 60% and 10% of the vascular plants and bryophytes recorded across all vegetation surveys were detected by soil eDNA. Taxa detected by soil eDNA were more representative for the local taxa pool than for the specific plot, and corresponded to those surveyed over the 30-year period although most closely matched the current taxa composition. Soil eDNA detected abundant taxa better than rare ones although both rare taxa and taxa unrecorded by the visual survey were detected. 4. Our study highlights the potential of soil eDNA assessments for monitoring of vegetation responses over broad spatial and temporal scales. The method's ability to detect abundant taxa makes it suitable for assessment of vegetation composition in a specific area and for broad-scale plant diversity assessments

Listeria infection in young infants: results from a national surveillance study in the UK and Ireland.

OBJECTIVES: To describe the epidemiology, age at infection, clinical characteristics and outcome of listeria infection in young infants to inform management and empiric antibiotic choice in young infants. DESIGN: Prospective 2-year surveillance of Listeria monocytogenes infection in young infants detected through the British Paediatric Surveillance Unit 'orange card' system and triangulated with the public health laboratories. SETTING: National population study (England, Wales, Scotland and the Ireland) PATIENTS: All infants under 90 days with proven or probable invasive listeriosis MAIN OUTCOME MEASURES: Incidence, mortality, age of infection, clinical characteristics and outcome RESULTS: During a 2-year period (2017-2019), 27 cases of listeriosis in infants <90 days of age were reported. The incidence of listeriosis in this study was 1.8 per 100 000 live births with 7% mortality (2/27). Nearly all cases presented within the first 24 hours of life (26/27). The majority (20/27, 74%) were born preterm and 16/24 (67%) were born to women from ethnic minority backgrounds. CONCLUSIONS: Invasive listeriosis in young infants in the UK and Ireland is rare and presents early in the neonatal period. National guidelines that recommend the use of amoxicillin as part of empiric regimes for sepsis and meningitis in infants over 1 month of age should be modified

Filling the Infrared Gap: ISO Observations of 1 Jy BL Lacertae Objects

The large majority of BL Lacertae objects belonging to the 1 Jy sample, the class prototype for radio-selected sources, are thought to emit most of their synchrotron power in the far IR band. Ironically, this spectral region is very sparsely sampled, with only a minority of the objects having IRAS data (most of them being upper limits or low-quality detections). We aim at filling this IR gap by presenting new, simultaneous ISOCAM and ISOPHOT observations over the 7 - 200 micron range for half the sample. A measurement of the position of the synchrotron peak frequency, nu_peak, can provide information about particle acceleration mechanisms and constrain the inverse Compton radiation that will be detected by up-coming new gamma-ray missions. We have observed 17 1 Jy BL Lacertae objects with the camera and the photometer on board the Infrared Space Observatory (ISO) satellite. The ISOPHOT data reduction was done employing a novel correction, which mitigates the effect of chopping for faint sources. Using our new ISO data, complemented by nearly-simultaneous radio and optical observations for 10 and 4 objects respectively, and other multi-frequency data, we have built the spectral energy distributions of our sources (plus a previously published one) and derived the rest-frame nu_peak. Its distribution is centered at 10^13 Hz (30 micron) and is very narrow, with 60% of the BL Lacs in the 1 - 3 10^13 Hz range. Given our set of simultaneous infrared data, these represent the best determinations available of the synchrotron peak frequencies for low-energy peaked BL Lacs. A comparison with previous such estimates, based on non-simultaneous optical and near IR data, may indicate strong nu_peak variations in a number of sources, possibly associated with large flares as observed in the high-energy peaked BL Lac MKN 501. (abridged)Comment: 13 pages, 1 figure, accepted for publication in Astronomy & Astrophysic

Minocycline in Severe Cerebral Amyloid Angiopathy: A Single-Center Cohort Study

BACKGROUND: Evidence from animal studies suggests that minocycline may reduce lobar intracerebral hemorrhage (ICH) recurrence in cerebral amyloid angiopathy, possibly by inhibiting perivascular extracellular matrix degradation in cerebral small vessels. There is currently no evidence of its safety or efficacy in humans with cerebral amyloid angiopathy. METHODS AND RESULTS: To provide preliminary data to support future studies of minocycline’s efficacy, the authors performed a retrospective single-center cohort study to assess the incidence of recurrent ICH in patients with an aggressive clinical course of probable cerebral amyloid angiopathy who had been prescribed minocycline off-label via shared decision-making. Crude incidence rate ratios were calculated to compare incidence rates before versus after treatment. Sixteen patients (mean age at minocycline initiation, 66.3±3.5 years; women 62.5%; median of 3 lobar ICHs [range, 1–6]) were initiated on minocycline and followed for a median of 12.4 months (range, 1.8–61.4 months). Adverse events were reported in 4 of 16 patients (gastroenteric, n=3; dizziness, n=1) and were considered mild. ICH incidence sharply increased the year before minocycline initiation compared with the preceding years (2.18 [95% CI, 1.50–3.07] versus 0.40 [95% CI, 0.25–0.60] events per patient-year) and fell to 0.46 (95% CI, 0.23–0.83) events per patient-year afterwards. Incidence rate ratios of recurrent ICH after minocycline was lower (0.21 [95% CI, 0.11–0.42], P<0.0001) compared with the year before initiation. CONCLUSIONS: Minocycline appeared safe and generally tolerated in a small group of patients with clinically aggressive cerebral amyloid angiopathy and was associated with reduced ICH recurrence. Determining whether this reduction represents a biological response to minocycline rather than a regression to the mean, however, will require a future controlled treatment trial

The genomes of two key bumblebee species with primitive eusocial organization

Background: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation