High-order harmonic transient grating spectroscopy of SF6 molecular vibrations

special issue : Ultrafast electron and molecular dynamicsInternational audienceStrong field transient grating spectroscopy has shown to be a very versatile tool in time-resolved molecular spectroscopy. Here we use this technique to investigate the high-order harmonic generation from SF6 molecules vibrationally excited by impulsive stimulated Raman scattering. Transient grating spectroscopy enables us to reveal clear modulations of the harmonic emission. This heterodyne detection shows that the harmonic emission generated between 14 to 26 eV is mainly sensitive to two among the three active Raman modes in SF6, i.e. the strongest and fully symmetric nu 1-A1g mode (774 cm-1, 43 fs) and the slowest mode nu5-T2g (524 cm-1, 63 fs). A time-frequency analysis of the harmonic emission reveals additional dynamics: the strength and central frequency of the nu 1 mode oscillate with a frequency of 52 cm-1 (640 fs). This could be a signature of the vibration of dimers in the generating medium. Harmonic 11 shows a remarkable behavior, oscillating in opposite phase, both on the fast (774 cm-1) and slow (52 cm-1) timescales, which indicates a strong modulation of the recombination matrix element as a function of the nuclear geometry. These results demonstrate that the high sensitivity of high-order harmonic generation to molecularvibrations, associated to the high sensitivity of transient grating spectroscopy, make their combination a unique tool to probe vibrational dynamics

HIV-2 diversity displays two clades within group A with distinct geographical distribution and evolution

Genetic diversity of HIV-2 groups A and B has not yet been fully described, especially in a few Western Africa countries such as Ivory-Coast or Mali. We collected 444 pol, 152 vif, 129 env, and 74 LTR sequences from patients of the French ANRS CO5 HIV-2 cohort completed by 221 pol, 18 vif, 377 env, and 63 LTR unique sequences from public databases. We performed phylogenetic reconstructions and revealed two distinct lineages within HIV-2 group A, herein called A1 and A2, presenting non-negligible genetic distances and distinct geographic distributions as A1 is related to coastal Western African countries and A2 to inland Western countries. Estimated early diversification times for groups A and B in human populations were 1940 [95% higher probability densitiy: 1935-53] and 1961 [1952-70]. A1 experienced an early diversification in 1942 [1937-58] with two distinct early epidemics in Guinea-Bissau or Senegal, raising the possibility of group A emergence in those countries from an initial introduction from Ivory-Coast to Senegal, two former French colonies. Changes in effective population sizes over time revealed that A1 exponentially grew concomitantly to Guinea-Bissau independence war, but both A2 and B lineages experienced a latter growth, starting during the 80s economic crisis. This large HIV-2 genetic analysis provides the existence of two distinct subtypes within group A and new data about HIV-2 early spreading patterns and recent epidemiologic evolution for which data are scarce outside Guinea-Bissau

Characterization update of HIV-1 M subtypes diversity and proposal for subtypes A and D sub-subtypes reclassification.

BACKGROUND: The large and constantly evolving HIV-1 pandemic has led to an increasingly complex diversity. Because of some taxonomic difficulties among the most diverse HIV-1 subtypes, and taking advantage of the large amount of sequence data generated in the recent years, we investigated novel lineage patterns among the main HIV-1 subtypes. RESULTS: All HIV full-length genomes available in public databases were analysed (n = 2017). Maximum likelihood phylogenies and pairwise genetic distance were obtained. Clustering patterns and mean distributions of genetic distances were compared within and across the current groups, subtypes and sub-subtypes of HIV-1 to detect and analyse any divergent lineages within previously defined HIV lineages. The level of genetic similarity observed between most HIV clades was deeply consistent with the current classification. However, both subtypes A and D showed evidence of further intra-subtype diversification not fully described by the nomenclature system at the time and could be divided into several distinct sub-subtypes. CONCLUSIONS: With this work, we propose an updated nomenclature of sub-types A and D better reflecting their current genetic diversity and evolutionary patterns. Allowing a more accurate nomenclature and classification system is a necessary step for easier subtyping of HIV strains and a better detection or follow-up of viral epidemiology shifts

Comparison of Patient and Surgeon Expectations of Total Hip Arthroplasty

OBJECTIVES: Analysis of discrepancies between patient and surgeon expectations before total hip arthroplasty (THA) should enable a better understanding of motives of dissatisfaction about surgery, but this question has been seldom studied. Our objectives were to compare surgeons' and patients' expectations before THA, and to study factors which affected surgeon-patient agreement. METHODS: 132 adults (mean age 62.8+/-13.7 years, 52% men) on waiting list for THA in three tertiary care centres and their 16 surgeons were interviewed to assess their expectations using the Hospital for Special Surgery Total Hip Replacement Expectations Survey (range 0-100). Patients' and surgeons' answers were compared, for the total score and for the score of each item. Univariate analyses tested the effect of patients' characteristics on surgeons' and patients' expectations separately, and on surgeon-patient differences. RESULTS: Surgeon and patient expectations' mean scores were high (respectively 90.9+/-11.1 and 90.0+/-11.6 over 100). Surgeons' and patients' expectations showed no systematic difference, but there was little agreement on Bland and Altman graph and correlation coefficient was low. Patients had higher expectations than surgeons for sports. Patients rated their expectations according to trust in physician and mental quality of life, surgeons considered disability. More disabled patients and patients from a low-income professional category were often "more optimistic" than their surgeons. CONCLUSION: Surgeons and patients often do not agree on what to expect from THA. More disabled patients expect better outcomes than their surgeons

Laser-Induced Electron Diffraction in Chiral Molecules

Strong laser pulses enable probing molecules with their own electrons. The oscillating electric field tears electrons off a molecule, accelerates them, and drives them back toward their parent ion within a few femtoseconds. The electrons are then diffracted by the molecular potential, encoding its structure and dynamics with angstrom and attosecond resolutions. Using elliptically polarized laser pulses, we show that laser-induced electron diffraction is sensitive to the chirality of the target. The field selectively ionizes molecules of a given orientation and drives the electrons along different sets of trajectories, leading them to recollide from different directions. Depending on the handedness of the molecule, the electrons are preferentially diffracted forward or backward along the light propagation axis. This asymmetry, reaching several percent, can be reversed for electrons recolliding from two ends of the molecule. The chiral sensitivity of laser-induced electron diffraction opens a new path to resolve ultrafast chiral dynamics

« Bronzes grecs et romains, recherches récentes » — Hommage à Claude Rolley

Philologue, archéologue, historien, spécialiste des bronzes, Claude Rolley, disparu en 2007, occupa une place originale parmi les spécialistes du monde méditerranéen antique. Marqué par la découverte du cratère de Vix (en 1953) qu’il ne cessa d’étudier tout au long de sa carrière, il sut croiser recherches et approches sur les périodes à la fois classique et proto-historique, de la Laconie à la Bourgogne jusqu’à la Grande Grèce. Les bronzes, de toutes dimensions ou origines, dont il tint la chronique pendant près de 25 ans dans la Revue archéologique, étaient pour lui une source de réflexion multiple : stylistique, technique – il prenait en compte aussi bien les questions d’assemblage ou de fonte que la composition chimique des objets –, ou culturelle – ses travaux ont apporté des éclairages décisifs sur la formation des ateliers et la circulation des objets d’un centre de production à l’autre. À l’initiative de plusieurs de ses disciples, un colloque lui a rendu hommage (INHA, 16-17 juin 2009) : les textes qui suivent en sont le fruit

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P &lt; 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men