A very-high-energy component deep in the γ-ray burst afterglow.

Gamma-ray bursts (GRBs) are brief flashes of γ-rays and are considered to be the most energetic explosive phenomena in the Universe1. The emission from GRBs comprises a short (typically tens of seconds) and bright prompt emission, followed by a much longer afterglow phase. During the afterglow phase, the shocked outflow-produced by the interaction between the ejected matter and the circumburst medium-slows down, and a gradual decrease in brightness is observed2. GRBs typically emit most of their energy via γ-rays with energies in the kiloelectronvolt-to-megaelectronvolt range, but a few photons with energies of tens of gigaelectronvolts have been detected by space-based instruments3. However, the origins of such high-energy (above one gigaelectronvolt) photons and the presence of very-high-energy (more than 100 gigaelectronvolts) emission have remained elusive4. Here we report observations of very-high-energy emission in the bright GRB 180720B deep in the GRB afterglow-ten hours after the end of the prompt emission phase, when the X-ray flux had already decayed by four orders of magnitude. Two possible explanations exist for the observed radiation: inverse Compton emission and synchrotron emission of ultrarelativistic electrons. Our observations show that the energy fluxes in the X-ray and γ-ray range and their photon indices remain comparable to each other throughout the afterglow. This discovery places distinct constraints on the GRB environment for both emission mechanisms, with the inverse Compton explanation alleviating the particle energy requirements for the emission observed at late times. The late timing of this detection has consequences for the future observations of GRBs at the highest energies.

Multi-material spectral photon-counting micro-CT with minimum residual decomposition and self-supervised deep denoising.

Spectral micro-CT imaging with direct-detection energy discriminating photon counting detectors having small pixel size (< 100×100 µm2) is mainly hampered by: i) the limited energy resolution of the imaging device due to charge sharing effects and ii) the unavoidable noise amplification in the images resulting from basis material decomposition. In this work, we present a cone-beam micro-CT setup that includes a CdTe photon counting detector implementing a charge summing hardware solution to correct for the charge-sharing issue and an innovative image processing pipeline based on accurate modeling of the spectral response of the imaging system, an improved basis material decomposition (BMD) algorithm named minimum-residual BMD (MR-BMD), and self-supervised deep convolutional denoising. Experimental tomographic projections having a pixel size of 45×45 µm2 of a plastinated mouse sample including I, Ba, and Gd small cuvettes were acquired. Results demonstrate the capability of the combined hardware and software tools to sharply discriminate even between materials having their K-Edge separated by a few keV, such as e.g., I and Ba. By evaluating the quality of the reconstructed decomposed images (water, bone, I, Ba, and Gd), the quantitative performances of the spectral system are here assessed and discussed.

Search for Dark Matter Annihilation Signals in the H.E.S.S. Inner Galaxy Survey.

The central region of the Milky Way is one of the foremost locations to look for dark matter (DM) signatures. We report the first results on a search for DM particle annihilation signals using new observations from an unprecedented γ-ray survey of the Galactic Center (GC) region, i.e., the Inner Galaxy Survey, at very high energies (≳100 GeV) performed with the H.E.S.S. array of five ground-based Cherenkov telescopes. No significant γ-ray excess is found in the search region of the 2014-2020 dataset and a profile likelihood ratio analysis is carried out to set exclusion limits on the annihilation cross section ⟨σv⟩. Assuming Einasto and Navarro-Frenk-White (NFW) DM density profiles at the GC, these constraints are the strongest obtained so far in the TeV DM mass range. For the Einasto profile, the constraints reach ⟨σv⟩ values of 3.7×10^{-26} cm^{3} s^{-1} for 1.5 TeV DM mass in the W^{+}W^{-} annihilation channel, and 1.2×10^{-26} cm^{3} s^{-1} for 0.7 TeV DM mass in the τ^{+}τ^{-} annihilation channel. With the H.E.S.S. Inner Galaxy Survey, ground-based γ-ray observations thus probe ⟨σv⟩ values expected from thermal-relic annihilating TeV DM particles.

The morphometric acclimation to depth explains the long-term resilience of the seagrass Cymodocea nodosa in a shallow tidal lagoon.

Cadiz Bay is a shallow mesotidal lagoon with extensive populations of the seagrass Cymodocea nodosa at intertidal and shallow subtidal elevations. This work aims to understand the mechanisms behind the resilience of this species to gradual sea level rise by studying its acclimation capacity to depth along the shallow littoral, and therefore, to gradual variations in the light environment. To address this objective, these populations have been monitored seasonally over a 10 year period, representing the longest seasonal database available in the literature for this species. The monitoring included populations at 0.4, -0.08 and -0.5 m LAT. The results show that C. nodosa has a strong seasonality for demographic and shoot dynamic properties - with longer shoots and larger growth in summer (high temperature) than in winter (low temperature), but also some losses. Moreover, shoots have different leaf morphometry depending on depth, with small and dense shoots in the intertidal areas (0.4 m) and sparse large shoots in the subtidal ones (-0.08 and 0.5 m). These differences in morphometry and shoot dynamic properties, combined with the differences in shoot density, explain the lack of differences in meadow production balance (i.e. meadow growth - meadow losses) between the intertidal (0.4 m) and the deepest population (-0.5 m), supporting the long term resilience of Cymodocea nodosa in Cadiz Bay. This study contributes to the understanding of the mechanisms behind seagrass stability and resilience, which is particularly important towards predicting the effects of climate change on these key coastal ecosystems, and also highlights the value of continuous long-term monitoring efforts to evaluate seagrass trajectories.

Search for γ-Ray Line Signals from Dark Matter Annihilations in the Inner Galactic Halo from 10 Years of Observations with H.E.S.S.

Spectral lines are among the most powerful signatures for dark matter (DM) annihilation searches in very-high-energy γ rays. The central region of the Milky Way halo is one of the most promising targets given its large amount of DM and proximity to Earth. We report on a search for a monoenergetic spectral line from self-annihilations of DM particles in the energy range from 300 GeV to 70 TeV using a two-dimensional maximum likelihood method taking advantage of both the spectral and spatial features of the signal versus background. The analysis makes use of Galactic center observations accumulated over ten years (2004-2014) with the H.E.S.S. array of ground-based Cherenkov telescopes. No significant γ-ray excess above the background is found. We derive upper limits on the annihilation cross section ⟨σv⟩ for monoenergetic DM lines at the level of 4×10^{-28} cm^{3} s^{-1} at 1 TeV, assuming an Einasto DM profile for the Milky Way halo. For a DM mass of 1 TeV, they improve over the previous ones by a factor of 6. The present constraints are the strongest obtained so far for DM particles in the mass range 300 GeV-70 TeV. Ground-based γ-ray observations have reached sufficient sensitivity to explore relevant velocity-averaged cross sections for DM annihilation into two γ-ray photons at the level expected from the thermal relic density for TeV DM particles.

H.E.S.S. Limits on Linelike Dark Matter Signatures in the 100 GeV to 2 TeV Energy Range Close to the Galactic Center.

A search for dark matter linelike signals iss performed in the vicinity of the Galactic Center by the H.E.S.S. experiment on observational data taken in 2014. An unbinned likelihood analysis iss developed to improve the sensitivity to linelike signals. The upgraded analysis along with newer data extend the energy coverage of the previous measurement down to 100 GeV. The 18 h of data collected with the H.E.S.S. array allow one to rule out at 95% C.L. the presence of a 130 GeV line (at l=-1.5°, b=0° and for a dark matter profile centered at this location) previously reported in Fermi-LAT data. This new analysis overlaps significantly in energy with previous Fermi-LAT and H.E.S.S. RESULTS: No significant excess associated with dark matter annihilations was found in the energy range of 100 GeV to 2 TeV and upper limits on the gamma-ray flux and the velocity weighted annihilation cross section are derived adopting an Einasto dark matter halo profile. Expected limits for present and future large statistics H.E.S.S. observations are also given.

Search for Dark Matter Annihilations towards the Inner Galactic Halo from 10 Years of Observations with H.E.S.S.

The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations of DM particles using γ-ray observations towards the inner 300 pc of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic Center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant γ-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section ⟨σv⟩. These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach ⟨σv⟩ values of 6×10^{-26} cm^{3} s^{-1} in the W^{+}W^{-} channel for a DM particle mass of 1.5 TeV, and 2×10^{-26} cm^{3} s^{-1} in the τ^{+}τ^{-} channel for a 1 TeV mass. For the first time, ground-based γ-ray observations have reached sufficient sensitivity to probe ⟨σv⟩ values expected from the thermal relic density for TeV DM particles.

Pollen limitation may be a common Allee effect in marine hydrophilous plants: implications for decline and recovery in seagrasses.

Pollen limitation may be an important factor in accelerated decline of sparse or fragmented populations. Little is known whether hydrophilous plants (pollen transport by water) suffer from an Allee effect due to pollen limitation or not. Hydrophilous pollination is a typical trait of marine angiosperms or seagrasses. Although seagrass flowers usually have high pollen production, floral densities are highly variable. We evaluated pollen limitation for intertidal populations of the seagrass Zostera noltei in The Netherlands and found a significant positive relation between flowering spathe density and fruit-set, which was suboptimal at <1200 flowering spathes m(-2) (corresponding to <600 reproductive shoots m(-2)). A fragmented population had ≈35 % lower fruit-set at similar reproductive density than a continuous population. 75 % of all European populations studied over a large latitudinal gradient had flowering spathe densities below that required for optimal fruit-set, particularly in Southern countries. Literature review of the reproductive output of hydrophilous pollinated plants revealed that seed- or fruit-set of marine hydrophilous plants is generally low, as compared to hydrophilous freshwater and wind-pollinated plants. We conclude that pollen limitation as found in Z. noltei may be a common Allee effect for seagrasses, potentially accelerating decline and impairing recovery even after environmental conditions have improved substantially.

Constraints on an annihilation signal from a core of constant dark matter density around the milky way center with H.E.S.S.

An annihilation signal of dark matter is searched for from the central region of the Milky Way. Data acquired in dedicated on-off observations of the Galactic center region with H.E.S.S. are analyzed for this purpose. No significant signal is found in a total of ∼9 h of on-off observations. Upper limits on the velocity averaged cross section, ⟨σv⟩, for the annihilation of dark matter particles with masses in the range of ∼300 GeV to ∼10 TeV are derived. In contrast to previous constraints derived from observations of the Galactic center region, the constraints that are derived here apply also under the assumption of a central core of constant dark matter density around the center of the Galaxy. Values of ⟨σv⟩ that are larger than 3×10^{-24} cm^{3}/s are excluded for dark matter particles with masses between ∼1 and ∼4 TeV at 95% C.L. if the radius of the central dark matter density core does not exceed 500 pc. This is the strongest constraint that is derived on ⟨σv⟩ for annihilating TeV mass dark matter without the assumption of a centrally cusped dark matter density distribution in the search region.

Acceleration and transport of relativistic electrons in the jets of the microquasar SS 433.

SS 433 is a microquasar, a stellar binary system that launches collimated relativistic jets. We observed SS 433 in gamma rays using the High Energy Stereoscopic System (H.E.S.S.) and found an energy-dependent shift in the apparent position of the gamma-ray emission from the parsec-scale jets. These observations trace the energetic electron population and indicate that inverse Compton scattering is the emission mechanism of the gamma rays. Our modeling of the energy-dependent gamma-ray morphology constrains the location of particle acceleration and requires an abrupt deceleration of the jet flow. We infer the presence of shocks on either side of the binary system, at distances of 25 to 30 parsecs, and that self-collimation of the precessing jets forms the shocks, which then efficiently accelerate electrons.

Search for photon-linelike signatures from dark matter annihilations with H.E.S.S.

Gamma-ray line signatures can be expected in the very-high-energy (E(γ)>100 GeV) domain due to self-annihilation or decay of dark matter (DM) particles in space. Such a signal would be readily distinguishable from astrophysical γ-ray sources that in most cases produce continuous spectra that span over several orders of magnitude in energy. Using data collected with the H.E.S.S. γ-ray instrument, upper limits on linelike emission are obtained in the energy range between ∼ 500 GeV and ∼ 25 TeV for the central part of the Milky Way halo and for extragalactic observations, complementing recent limits obtained with the Fermi-LAT instrument at lower energies. No statistically significant signal could be found. For monochromatic γ-ray line emission, flux limits of (2 × 10(-7) -2 × 10(-5)) m(-2) s(-1) sr(-1) and (1 × 10(-8) -2 × 10(-6)) m(-2) s(-1)sr(-1) are obtained for the central part of the Milky Way halo and extragalactic observations, respectively. For a DM particle mass of 1 TeV, limits on the velocity-averaged DM annihilation cross section ⟨σv⟩(χχ → γγ) reach ∼ 10(-27) cm(3)s(-1), based on the Einasto parametrization of the Galactic DM halo density profile.

Time-resolved hadronic particle acceleration in the recurrent nova RS Ophiuchi.

Recurrent novae are repeating thermonuclear explosions in the outer layers of white dwarfs, due to the accretion of fresh material from a binary companion. The shock generated when ejected material slams into the companion star's wind can accelerate particles. We report very-high-energy (VHE; [Formula: see text]) gamma rays from the recurrent nova RS Ophiuchi, up to 1 month after its 2021 outburst, observed using the High Energy Stereoscopic System (H.E.S.S.). The temporal profile of VHE emission is similar to that of lower-energy giga-electron volt emission, indicating a common origin, with a 2-day delay in peak flux. These observations constrain models of time-dependent particle energization, favoring a hadronic emission scenario over the leptonic alternative. Shocks in dense winds provide favorable environments for efficient acceleration of cosmic rays to very high energies.

Search for a dark matter annihilation signal from the galactic center halo with H.E.S.S.

A search for a very-high-energy (VHE; ≥100 GeV) γ-ray signal from self-annihilating particle dark matter (DM) is performed towards a region of projected distance r∼45-150 pc from the Galactic center. The background-subtracted γ-ray spectrum measured with the High Energy Stereoscopic System (H.E.S.S.) γ-ray instrument in the energy range between 300 GeV and 30 TeV shows no hint of a residual γ-ray flux. Assuming conventional Navarro-Frenk-White and Einasto density profiles, limits are derived on the velocity-weighted annihilation cross section (σv) as a function of the DM particle mass. These are among the best reported so far for this energy range and in particular differ only little between the chosen density profile parametrizations. In particular, for the DM particle mass of ∼1 TeV, values for (σv) above 3×10(-25) cm(3) s(-1) are excluded for the Einasto density profile.

Revealing x-ray and gamma ray temporal and spectral similarities in the GRB 190829A afterglow.

Gamma-ray bursts (GRBs), which are bright flashes of gamma rays from extragalactic sources followed by fading afterglow emission, are associated with stellar core collapse events. We report the detection of very-high-energy (VHE) gamma rays from the afterglow of GRB 190829A, between 4 and 56 hours after the trigger, using the High Energy Stereoscopic System (H.E.S.S.). The low luminosity and redshift of GRB 190829A reduce both internal and external absorption, allowing determination of its intrinsic energy spectrum. Between energies of 0.18 and 3.3 tera-electron volts, this spectrum is described by a power law with photon index of 2.07 ± 0.09, similar to the x-ray spectrum. The x-ray and VHE gamma-ray light curves also show similar decay profiles. These similar characteristics in the x-ray and gamma-ray bands challenge GRB afterglow emission scenarios.

High rate of transmission among contacts in large London outbreak of isoniazid mono-resistant tuberculosis.

BACKGROUND: For a continuing London outbreak of isoniazid mono-resistant tuberculosis (TB), we aimed to determine transmission rates and risk factors for contacts of early cases, in order to inform future guidance on contact tracing. METHODS: Paper-based proformas were completed by TB nurses, and then analysed using EpiInfo/SAS statistical software. RESULTS: Forty community contacts (11%) became cases, 45 (13%) were recommended chemoprophylaxis and 270 (76%) were discharged clear of infection. The highest transmission rate was among contacts exposed to two or more cases (29% became cases) and close contacts of sputum smear-positive cases (22%). Other risk factors were being male and exposure to drug-using cases or cases with prison links. The number needed to be screened (NNS) to detect one case was lowest [5 (95% CI: 4-8)] for contacts of sputum smear-positive pulmonary cases, although the NNS was still only 20 (95% CI:8-72) for casual contacts of smear-positive cases. CONCLUSIONS: Transmission of disease to contacts was high (11%) compared with other documented outbreaks (0.7-2%). The results support recommended guidelines for contact tracing but also provide grounds to recommend, for outbreak cases, screening of casual contacts of smear-positive cases and contacts exposed to more than one case, drug users or prisoners.

Chronic antigenic stimuli as a possible explanation for the immunodepression caused by liver cirrhosis.

The objectives of this work were the analysis of the functional characteristics of circulating monocytes and T lymphocytes in patients with liver cirrhosis, and evaluation of the relationship with an increased exposure to antigens due to bacterial translocation. Forty patients with liver cirrhosis (20 with compensated cirrhosis and 20 with ascitic decompensation) and 20 healthy control subjects were studied. Bacterial translocation was evaluated by serum levels of lipopolysaccharide binding protein (LBP). Macrophage activation was studied by CD40 antigen expression. T lymphocytes were analysed for activation (CD25(+), CD122(+)), effector function (CD8(+)CD45RO(+)CD57(+)), apoptosis (CD95(+)) and regulatory abilities, either by analysis of the membrane expression of co-stimulatory molecules CD80, CD86 and CD28, or by quantification of regulatory T cells CD4(+)CD25(high)forkhead box P3 (FoxP3). The percentage of activated monocytes and T lymphocytes in patients was increased significantly. The proportions of effector senescent cells and of those near to apoptosis were also significantly higher. With respect to these proportions, there were no significant differences between patients in function of the presence or absence of decompensation or in function of the increased or normal values of LBP. Conversely, those patients with elevated levels of LBP presented a significantly higher frequency of regulatory T cells than those with normal levels. In conclusion, patients with liver cirrhosis showed an intensive activation state with a higher percentage of cells committed to activation-induced death, even in non-advanced stages. It is possible that bacterial permeability and endotoxaemia contribute to the expansion of those lymphocyte populations implicated in the prevention of a more severe antigen-induced immunopathology.

Isolation of a T-lymphotropic retrovirus from a patient at risk for acquired immune deficiency syndrome (AIDS).

A retrovirus belonging to the family of recently discovered human T-cell leukemia viruses (HTLV), but clearly distinct from each previous isolate, has been isolated from a Caucasian patient with signs and symptoms that often precede the acquired immune deficiency syndrome (AIDS). This virus is a typical type-C RNA tumor virus, buds from the cell membrane, prefers magnesium for reverse transcriptase activity, and has an internal antigen (p25) similar to HTLV p24. Antibodies from serum of this patient react with proteins from viruses of the HTLV-I subgroup, but type-specific antisera to HTLV-I do not precipitate proteins of the new isolate. The virus from this patient has been transmitted into cord blood lymphocytes, and the virus produced by these cells is similar to the original isolate. From these studies it is concluded that this virus as well as the previous HTLV isolates belong to a general family of T-lymphotropic retroviruses that are horizontally transmitted in humans and may be involved in several pathological syndromes, including AIDS.

Molecular epidemiology of tuberculosis in England, 1998.

SETTING: England. OBJECTIVE: To investigate the proportion of tuberculosis (TB) cases attributable to recent transmission and factors associated with clustering. DESIGN: Demographic, clinical and microbiological surveillance data were collated from all new culture-confirmed cases in 1998. Using insertion sequence (IS) 6110 restriction fragment length polymorphism (RFLP) typing, strains were classified as clustered (identical patterns) or unique and risk factors were determined using multivariable logistic regression. RESULTS: RFLP patterns were available for 2265 of 3713 (61%) cases: 1808 had >or=5 IS6110 copies, while 372 cases were in 152 clusters, giving an estimated proportion due to recent transmission of 12.2%.Pulmonary disease (aOR 1.6; 95%CI 1.1-2.2), previous treatment (aOR 3.7; 2.2-6.5) and homelessness (aOR 5.5; 1.2-24.1) were independent risk factors for clustering. Fourteen per cent of patients of Indian subcontinent origin were clustered compared with 27% of white patients. Many clusters spanned ethnic groups (45%) and geographical regions (47%). CONCLUSION: The calculated proportion of TB cases due to recent transmission is low.Adjusting for missed cases and study duration, it increases to 27.6%. Many cases may arise from reactivation or acquisition outside England. Transmission within England accounted for approximately one in four cases and occurred over wide geographic areas, between ethnic groups and among the homeless. Molecular epidemiology can inform local and national public health action.

Development and validation of baseline, perioperative and at-discharge predictive models for postsurgical prosthetic joint infection.

OBJECTIVES: To develop and validate baseline, perioperative and at-discharge risk-scoring systems for postsurgical prosthetic joint infection (PJI) in patients undergoing arthroplasty. METHODS: A multicentre prospective cohort study of patients undergoing hip and knee arthroplasty was performed. Patients were randomly assigned (2:1) to a derivation cohort (DC) or a validation cohort (VC). Multivariable predictive models of PJI were constructed at baseline (preoperative period), perioperative (adding perioperative variables) and at-discharge (adding wound state at discharge). The predictive ability of the models and scores was evaluated by area under the receiving operating characteristic curves (AUROC). RESULTS: The DC and VC included 2324 and 1245 patients, respectively. Baseline model included total hip arthroplasty (THA), revision arthroplasty (RA), Charlson index and obesity. The AUROC for the score was 0.75 and 0.78 in the DC and VC, respectively. Perioperative model included THA, RA, obesity, National Nosocomial Infections Surveillance (NNIS) index ≥2, significant wound bleeding and superficial surgical site infection; the AUROC was 0.81 and 0.77 in the DC and VC, respectively. The at-discharge model included THA, RA, obesity, NNIS index ≥2, superficial surgical site infection and high-risk wound; the AUROC was 0.82 and 0.84 in the DC and VC, respectively. A score ≥8 points provided 99% negative predictive values for all models. CONCLUSIONS: Simple scores for predicting PJI at three different moments of care in patients undergoing arthroplasty were developed and validated. The scores allow early and accurate identification of high-risk individuals in whom enhanced preventive measures and follow-up may be needed. Further external validation is needed.

[EVAL MATER: Proposal for a paediatric evaluation of linguistic and psychomotor competences during the 1st medical check-up in nursery school]. / EVAL MATER: proposition d'une évaluation pédiatrique des compétences langagières et psychomotrices lors du 1er bilan de santé en école maternelle.

OBJECTIVES: To prevent learning disorders, the authors propose a standardized approach of linguistic competences and psychomotor development in young children. POPULATION AND METHODS: Children were evaluated during the systematic examination that was carried out in nursery school between 3 years and 6 months and 4 years and 6 months of age. 2 investigations were led: investigation of prevalence led in 2660 children and evaluation of performance of the tests in 99 children among them. RESULTS: The statistical analyses of their results made it possible to determine scores helping with the decision of a request for assessment to diagnostic aiming. The sensitivity and the specificity of the tests increased with the age and were better within the framework of the tests of language. This new assessment was appreciated by the doctors users.