Étude expérimentale des interactions dynamiques aube/carter

Un dispositif expérimental original a été conçu pour simuler les interactions aube/carter pour une gamme de vitesse allant de 60 à 450 m/s. Un banc balistique projette avec précision une éprouvette de matériau abradable (M601) venant impacter une aube à géométrie simplifiée. Les efforts d'interaction sont mesurés par un capteur de force piézoélectrique auquel à été associé un protocole de traitement du signal permettant d'augmenter la bande passante du capteur. Les influences sur l'effort d'interaction de la vitesse, de la profondeur d'incursion et des paramètres d'aube ont été étudiées

Comparative study of meningitis dynamics across nine African countries: a global perspective

<p>Abstract</p> <p>Background</p> <p>Meningococcal meningitis (MM) represents an important public health problem especially in the "meningitis belt" in Africa. Although seasonality of epidemics is well known with outbreaks usually starting in the dry season, pluri-annual cycles are still less understood and even studied. In this context, we aimed at study MM cases time series across 9 sahelo-sudanian countries to detect pluri-annual periodicity and determine or not synchrony between dynamics. This global and comparative approach allows a better understanding of MM evolution in time and space in the long-term.</p> <p>Results</p> <p>We used the most adapted mathematical tool to time series analyses, the wavelet method. We showed that, despite a strong consensus on the existence of a global pluri-annual cycle of MM epidemics, it is not the case. Indeed, even if a clear cycle is detected in all countries, these cycles are not as permanent and regular as generally admitted since many years. Moreover, no global synchrony was detected although many countries seemed correlated.</p> <p>Conclusion</p> <p>These results of the first large-scale study of MM dynamics highlight the strong interest and the necessity of a global survey of MM in order to be able to predict and prevent large epidemics by adapted vaccination strategy. International cooperation in Public Health and cross-disciplines studies are highly recommended to hope controlling this infectious disease.</p

Infectious consequences of hematoma from cardiac implantable electronic device procedures and the role of the antibiotic envelope: A WRAP-IT trial analysis.

Hematoma is a complication of cardiac implantable electronic device (CIED) procedures and may lead to device infection. The TYRX antibacterial envelope reduced major CIED infection by 40% in the randomized WRAP-IT (World-wide Randomized Antibiotic Envelope Infection Prevention Trial) study, but its effectiveness in the presence of hematoma is not well understood.The purpose of this study was to evaluate the incidence and infectious consequences of hematoma and the association between envelope use, hematomas, and major CIED infection among WRAP-IT patients.All 6800 study patients were included in this analysis (control 3429; envelope 3371). Hematomas occurring within 30 days postprocedure (acute) were characterized and grouped by study treatment and evaluated for subsequent infection risk. Data were analyzed using Cox proportional hazard regression modeling.Acute hematoma incidence was 2.2% at 30 days, with no significant difference between treatment groups (envelope vs control hazard ratio [HR] 1.15; 95% confidence interval [CI] 0.84-1.58; P = .39). Through all follow-up, the risk of major infection was significantly higher among control patients with hematoma vs those without (13.1% vs 1.6%; HR 11.3; 95% CI 5.5-23.2; P.001). The risk of major infection was significantly lower in the envelope vs control patients with hematoma (2.5% vs 13.1%; HR 0.18; 95% CI 0.04-0.85; P = .03).The risk of hematoma was 2.2% among WRAP-IT patients. Among control patients, hematoma carried a11-fold risk of developing a major CIED infection. This risk was significantly mitigated with antibacterial envelope use, with an 82% reduction in major CIED infection among envelope patients who developed hematoma compared to control

Relationship between QT interval and outcome in low-flow low-gradient aortic stenosis with low left ventricular ejection fraction

Background QT interval has been shown to be associated with cardiovascular events. There is no data regarding the association between QT interval and left ventricular (LV) function and prognosis in patients with low LV ejection fraction (LVEF), low‐flow, low‐gradient aortic stenosis (LF‐LG AS). We aimed to examine the relationship between corrected QT interval (QT c) and LV function and outcome in these patients. Methods and Results Ninety‐three patients (73±10 years; 74% men) with LF‐LG AS (mean gradient 450 ms in men and >470 ms in women. LV global longitudinal strain was measured by speckle tracking and expressed in absolute value |%|. QT c correlated with the following: global longitudinal strain (r=−0.40, P=0.005), LVEF (r=−0.27, P=0.02), stroke volume (r=−0.35, P=0.007), and B‐type natriuretic peptide (r=0.45, P=0.0006). During a median follow‐up of 2.0 years, 49 patients died. Prolonged QT c was associated with a 2‐fold increase in all‐cause mortality (hazard ratio=2.05; P=0.01) and cardiovascular mortality (hazard ratio=1.89; P=0.04). In multivariable analysis adjusted for EuroSCORE, aortic valve replacement, previous myocardial infarction, LVEF, and ß‐blocker medication, prolonged QT c was independently associated with all‐cause mortality (hazard ratio=2.56; P=0.008) and cardiovascular mortality (hazard ratio=2.50; P=0.02). Conclusions In patients with LF‐LG AS and reduced LVEF, longer QT c interval was associated with worse LV function and increased risk of death. Assessment of QT c may provide a simple and inexpensive tool to enhance risk stratification in LF‐LG AS patients

Analysing Spatio-Temporal Clustering of Meningococcal Meningitis Outbreaks in Niger Reveals Opportunities for Improved Disease Control

Meningococcal meningitis (MM) is an infection of the meninges caused by a bacterium, Neisseria meningitidis, transmitted through respiratory and throat secretions. It can cause brain damage and results in death in 5–15% of cases. Large epidemics of MM occur almost every year in sub-Saharan Africa during the hot, dry season. Understanding how epidemics emerge and spread in time and space would help public health authorities to develop more efficient strategies for the prevention and the control of meningitis. We studied the spatio-temporal distribution of MM cases in Niger from 2002 to 2009 at the scale of the health centre catchment areas (HCCAs). We found that spatial clusters of cases most frequently occurred within nine districts out of 42, which can assist public health authorities to better adjust allocation of resources such as antibiotics or rapid diagnostic tests. We also showed that the epidemics break out in different HCCAs from year to year and did not follow a systematic geographical direction. Finally, this analysis showed that surveillance at a finer spatial scale (health centre catchment area rather than district) would be more efficient for public health response: outbreaks would be detected earlier and reactive vaccination would be better targeted

Measles in Democratic Republic of Congo: an outbreak description from Katanga, 2010--2011

BACKGROUND: The Democratic Republic of Congo experiences regular measles outbreaks. From September 2010, the number of suspected measles cases increased, especially in Katanga province, where Medecins sans Frontieres supported the Ministry of Health in responding to the outbreak by providing free treatment, reinforcing surveillance and implementing non-selective mass vaccination campaigns. Here, we describe the measles outbreak in Katanga province in 2010--2011 and the results of vaccine coverage surveys conducted after the mass campaigns. METHODS: The surveillance system was strengthened in 28 of the 67 health zones of the province and we conducted seven vaccination coverage surveys in 2011. RESULTS: The overall cumulative attack rate was 0.71% and the case fatality ratio was 1.40%.The attack rate was higher in children under 4 and decreased with age. This pattern was consistent across districts and time. The number of cases aged 10 years and older barely increased during the outbreak. CONCLUSIONS: Early investigation of the age distribution of cases is a key to understanding the epidemic, and should guide the vaccination of priority age groups

Recurrent cardiac events in patients with idiopathic ventricular fibrillation, excluding patients with the Brugada syndrome

BACKGROUND: The recurrence of cardiac events in patients with idiopathic ventricular fibrillation (VF) excluding patients with the Brugada syndrome is unclear since this entity remains present in previous studies. METHODS: Since 1992, 18 patients (72% male) with idiopathic VF out of 455 ICD implants were treated with an implantable cardioverter defibrillator (ICD). The mean age at first ICD implantation was 42 ± 14 years. Brugada syndrome, as well as other primary electrical diseases (e.g. long QT), were systematically excluded in all patients by the absence of the typical electrocardiogram (ST elevation in the right precordial leads) at rest and/or after pharmacological tests (ajmaline, flecainide, or procainamide). Recurrence of cardiac events was prospectively assessed. RESULTS: During a mean follow-up period of 41 ± 27 months, VF recurrence with appropriate shock occurred in 7 patients (39%) covering a total of 27 shocks. The median time to first appropriate shock was 12 ± 9 months. There were no deaths. In the electrophysiological study, 39% of patients were inducible, but inducibility failed to predict subsequent arrhythmic events. Forty-four percent of patients suffered 21 inappropriate shocks, which were caused by sinus tachycardia, atrial arrhythmias or lead malfunction. CONCLUSION: Idiopathic ventricular fibrillation patients have a high recurrence rate of potentially fatal ventricular arrhythmias, excluding patients with the Brugada syndrome or other known causes. ICD prevents sudden cardiac death but inappropriate shocks remained a major issue in this young and active population

Beyond the disk: EUV coronagraphic observations of the Extreme Ultraviolet Imager on board Solar Orbiter

Context. Most observations of the solar corona beyond 2 R consist of broadband visible light imagery carried out with coronagraphs. The associated diagnostics mainly consist of kinematics and derivations of the electron number density. While the measurement of the properties of emission lines can provide crucial additional diagnostics of the coronal plasma (temperatures, velocities, abundances, etc.), these types of observations are comparatively rare. In visible wavelengths, observations at these heights are limited to total eclipses. In the ultraviolet (UV) to extreme UV (EUV) range, very few additional observations have been achieved since the pioneering results of the Ultraviolet Coronagraph Spectrometer (UVCS). Aims. One of the objectives of the Full Sun Imager (FSI) channel of the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter mission has been to provide very wide field-of-view EUV diagnostics of the morphology and dynamics of the solar atmosphere in temperature regimes that are typical of the lower transition region and of the corona. Methods. FSI carries out observations in two narrowbands of the EUV spectrum centered on 17.4 nm and 30.4 nm that are dominated, respectively, by lines of FeIX/X (formed in the corona around 1 MK) and by the resonance line of HeII (formed around 80 kK in the lower transition region). Unlike previous EUV imagers, FSI includes a moveable occulting disk that can be inserted in the optical path to reduce the amount of instrumental stray light to a minimum. Results. FSI detects signals at 17.4 nm up to the edge of its field of view (7 R), which is about twice further than was previously possible. Operation at 30.4 nm are for the moment compromised by an as-yet unidentified source of stray light. Comparisons with observations by the LASCO and Metis coronagraphs confirm the presence of morphological similarities and differences between the broadband visible light and EUV emissions, as documented on the basis of prior eclipse and space-based observations. Conclusions. The very-wide-field observations of FSI out to about 3 and 7 R, without and with the occulting disk, respectively, are paving the way for future dedicated instruments