The science case and challenges of space-borne sub-millimeter interferometry

Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular resolution astrophysics. In both mentioned cases, the angular resolution reached the values of about 10–20 microarcseconds (0.05–0.1 nanoradian). Further developments towards at least an order of magnitude “sharper” values, at the level of 1 microarcsecond are dictated by the needs of advanced astrophysical studies. The paper emphasis that these higher values can only be achieved by placing millimeter and submillimeter wavelength interferometric systems in space. A concept of such the system, called Terahertz Exploration and Zooming-in for Astrophysics, has been proposed in the framework of the ESA Call for White Papers for the Voyage 2050 long term plan in 2019. In the current paper we present new science objectives for such the concept based on recent results in studies of active galactic nuclei and supermassive black holes. We also discuss several approaches for addressing technological challenges of creating a millimeter/sub-millimeter wavelength interferometric system in space. In particular, we consider a novel configuration of a space-borne millimeter/sub-millimeter antenna which might resolve several bottlenecks in creating large precise mechanical structures. The paper also presents an overview of prospective space-qualified technologies of low-noise analogue front-end instrumentation for millimeter/sub-millimeter telescopes. Data handling and processing instrumentation is another key technological component of a sub-millimeter Space VLBI system. Requirements and possible implementation options for this instrumentation are described as an extrapolation of the current state-of-the-art Earth-based VLBI data transport and processing instrumentation. The paper also briefly discusses approaches to the interferometric baseline state vector determination and synchronisation and heterodyning system. The technology-oriented sections of the paper do not aim at presenting a complete set of technological solutions for sub-millimeter (terahertz) space-borne interferometers. Rather, in combination with the original ESA Voyage 2050 White Paper, it sharpens the case for the next generation microarcsecond-level imaging instruments and provides starting points for further in-depth technology trade-off studies.</p

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Vibrational properties of small rhodium clusters: role of magnetism, charge state, and isomerization effects

Extensive density functional theory calculations dedicated to analyze the structure, electronic properties, and vibrational behavior of small and positively charged rhodium clusters are presented. Following the experimental results of Harding et al. [D.J. Harding et al., J. Chem. Phys. 133, 214304-1 (2010)] Rh19+ , Rh11+ , Rh12+ , and Rh13+  clusters are considered and the infrared (IR) spectra for various structural isomers is simulated. The calculations reveal a complex interplay between the distribution and intensity of the IR active frequencies with the atomic structure, magnetism, and charge state of the systems, as well as the crucial role played by high-energy isomers to explain experimental data. Based on a direct comparison between theory and experiment we predict that, for Rh9+, a weighted average of simulated IR spectra corresponding to our lowest energy 9-atom cubic cluster and the closest in energy compact isomer can yield an acceptable agreement between theory and experiment. The possibility of considering mixtures of various IR spectra to explain the measured data is supported by nudged-elastic-band calculations that reveal the existence of inter-conversion processes between different isomers with relatively small energy barriers ( ~0.6 eV). In addition, the recent observation of bi-exponential decays in reactivity experiments of rhodium clusters interacting with N2O species around those sizes also supports this claim. For Rh11+ and Rh12+ clusters, we also obtain that compact high-energy structures with low spin magnetizations are the ones having an IR spectra more in agreement with experiments. Finally for the most common compact and cubic Rh13+  clusters considered in the literature, for which there are no experimental IR spectra to compare with, well defined vibrational features are predicted which could help to identify the atomic configuration of this highly relevant structure

Formation and atomic structure of hierarchical boron nitride nanostructures

"We report a combined experimental and theoretical study of boron nitride (BN) nanostructures synthesized by ball milling methodology. The BN nanostructures were obtained using h-BN powder under low-vacuum conditions and steel balls of different sizes. The HRTEM images of our samples show the formation of spheroidal BN nanoparticles with diameters as small as 7 nm which self-assemble into different hierarchical nanostructures such as two-dimensional layered materials, spheroidal configurations, and one-dimensional solid BN chains. The Raman spectra reveal an intense absorption band in the 300-600 cm1 region, which is absent in the spectra of BN nanotubes, previously synthesized BN nanoparticles, and in all bulk boron nitride polymorphs. Density functional theory calculations show that the Raman spectra are consistent with the formation of fullerene-like BN particles which also exhibit an intense absorption band in the 200-800 cm1 range dominated by a complex mixture of tangential, stretching, and radial breathing modes. Finally, by means of electron-beam irradiation experiments additional structural transformations can be induce on our hierarchical BN particles consisting in the formation of nanoholes of the order of 5 nm. Our here-reported BN nanostructures might lead to a wide range of potential applications.

The science case and challenges of space-borne sub-millimeter interferometry

Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular resolution astrophysics. In both mentioned cases, the angular resolution reached the values of about 10–20 microarcseconds (0.05–0.1 nanoradian). Further developments towards at least an order of magnitude “sharper” values, at the level of 1 microarcsecond are dictated by the needs of advanced astrophysical studies. The paper emphasis that these higher values can only be achieved by placing millimeter and submillimeter wavelength interferometric systems in space. A concept of such the system, called Terahertz Exploration and Zooming-in for Astrophysics, has been proposed in the framework of the ESA Call for White Papers for the Voyage 2050 long term plan in 2019. In the current paper we present new science objectives for such the concept based on recent results in studies of active galactic nuclei and supermassive black holes. We also discuss several approaches for addressing technological challenges of creating a millimeter/sub-millimeter wavelength interferometric system in space. In particular, we consider a novel configuration of a space-borne millimeter/sub-millimeter antenna which might resolve several bottlenecks in creating large precise mechanical structures. The paper also presents an overview of prospective space-qualified technologies of low-noise analogue front-end instrumentation for millimeter/sub-millimeter telescopes. Data handling and processing instrumentation is another key technological component of a sub-millimeter Space VLBI system. Requirements and possible implementation options for this instrumentation are described as an extrapolation of the current state-of-the-art Earth-based VLBI data transport and processing instrumentation. The paper also briefly discusses approaches to the interferometric baseline state vector determination and synchronisation and heterodyning system. The technology-oriented sections of the paper do not aim at presenting a complete set of technological solutions for sub-millimeter (terahertz) space-borne interferometers. Rather, in combination with the original ESA Voyage 2050 White Paper, it sharpens the case for the next generation microarcsecond-level imaging instruments and provides starting points for further in-depth technology trade-off studies.Peer reviewe

Diagnosis and management of asymptomatic bacteriuria in kidney transplant recipients: a survey of current practice in Europe

International audienceBackgroundAsymptomatic bacteriuria is frequent in kidney transplant recipients (KTRs). However, there is no consensus on diagnosis or management. We conducted a European survey to explore current practice related to the diagnosis and management of asymptomatic bacteriuria in adult KTRs.MethodsA panel of experts from the European Renal Association–European Dialysis Transplant Association/Developing Education Science and Care for Renal Transplantation in European States working group and the European Study Group for Infections in Compromised Hosts of the European Society of Clinical Microbiology and Infectious Diseases designed this cross-sectional, questionnaire-based, self-administered survey. Invitations to participate were e-mailed to European physicians involved in the care of KTRs.ResultsTwo hundred and forty-four participants from 138 institutions in 25 countries answered the survey (response rate 30%). Most participants [72% (176/244)] said they always screen for asymptomatic bacteriuria in KTRs. Six per cent (15/240) reported never treating asymptomatic bacteriuria with antibiotics. When antimicrobial treatment was used, 24% of the participants (53/224) said they would start with empirical antibiotics. For an episode of asymptomatic bacteriuria caused by a fully susceptible microorganism and despite no contraindications, a majority of participants (121/223) said they would use a fluoroquinolone (n = 56), amoxicillin/clavulanic acid (n = 38) or oral cephalosporins (n = 27).ConclusionsScreening for and treating asymptomatic bacteriuria are common in KTRs despite uncertainties around the benefits and harms. In an era of antimicrobial resistance, further studies are needed to address the diagnosis and management of asymptomatic bacteriuria in these patients