Homopolar oscillating-disc dynamo driven by parametric resonance

We use a simple model of Bullard-type disc dynamo, in which the disc rotation rate is subject to harmonic oscillations, to analyze the generation of magnetic field by the parametric resonance mechanism. The problem is governed by a damped Mathieu equation. The Floquet exponents, which define the magnetic field growth rates, are calculated depending on the amplitude and frequency of the oscillations. Firstly, we show that the dynamo can be excited at significantly subcritical disc rotation rates when the latter is subject to harmonic oscillations with a certain frequency. Secondly, at supercritical mean rotation rates, the dynamo can also be suppressed but only in narrow frequency bands and at sufficiently large oscillation amplitudes.Comment: 4 pages, 5 figure

Zika virus infection study : clinical and biological description, immunological response description, transmissibility

En 2015, lors de l'émergence du virus Zika en Guyane Française, l'infection étaient encore peu connue. Nous avons suivi une cohorte de 49 patients infectés par ZIKV (RT-PCR positive dans le sang ou les urines) pendant un an.La proportion d’asymptomatiques était moindre que décrite précédemment (27%, IC 95%, 6–61). L’incubation médiane était d’environ neuf jours. Nous avons précisé la description clinique initiale de l'infection à ZIKV, permettant notamment de mieux la discriminer des autres arboviroses (pas ou peu de fièvre, exanthème maculo-papuleux avec prurit et conjonctivite, atteinte articulaire modérée et sans ténosynovite). Le tableau clinique persistait en moyenne 10 jours pour l'atteinte articulaire, 13 jours pour l'exanthème et 19 jours pour l'asthénie. Au-delà du premier mois il n'y avait pas d'évolution chronique ni d'atteinte de la qualité de vie ou de la capacité à travailler. La recherche du virus dans le sang montrait une persistance plus longue dans le compartiment capillaire que dans le sang veineux. Cela était en faveur d'un allongement de l'isolement vectoriel à appliquer aux patients. L’excrétion de ZIKV dans le sperme était plus courte que décrite précédemment, ce qui permettait de raccourcir la durée du port du préservatif au retour de zone à risque. Les cinétiques d’excrétion virale sanguine et urinaire et la sérologie confirmaient une séquence diagnostique en trois temps : RT-PCR ZIKV dans le sang jusqu'à J5 du début des signes, urinaire jusqu'à J10, puis sérologie.In 2015, during the emergence of Zika virus in French Guyana, the infection were still little described. We followed a cohort of 49 ambulatory patients infected with ZIKV (positive RT-PCR in blood or urine) for one year.The proportion of asymptomatics was lower than previously described (27%, 95% CI, 6–61). The median incubation was around nine days. We have clarified the initial clinical description of the ZIKV infection, in particular making it possible to better discriminate it from other arboviruses (no or little fever, maculopapular rash with pruritus and conjunctivitis, moderate joint involvement and without tenosynovitis). Half of the patients had mild neurological damage (reversible areflexia). The clinical picture persisted for an average of 10 days for joint involvement, 13 days for exanthema and 19 days for asthenia. Beyond the first month there was no chronic evolution or impairment of quality of life or ability to work. Testing for virus in blood showed longer persistence in the capillary compartment than in venous blood. This was in favor of lengthening the vector isolation to be applied to patients. The excretion of ZIKV in semen was shorter than previously described, which made it possible to shorten the duration of wearing the condom upon returning from at-risk area. The blood and urine viral excretion kinetics and the serology confirmed a three-step diagnostic sequence: ZIKV RT-PCR in the blood up to D5 of the onset of signs, urine up to D10, then serology

Etude séro-épidémiologique de la rougeole, des oreillons et de la rubéole au sein des candidats à l'engagement de l'armée française

BORDEAUX2-BU Santé (330632101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

A new graphical user interface for fast construction of computation phantoms and MCNP calculations: Application to calibration of in vivo measurement systems

The paper reports on a new utility for development of computational phantoms for Monte Carlo calculations and data analysis for in vivo measurements of radionuclides deposited in tissues. The individual properties of each worker can be acquired for a rather precise geometric representation of his (her) anatomy, which is particularly important for low energy gamma ray emitting sources such as thorium, uranium, plutonium and other actinides. The software discussed here enables automatic creation of an MCNP input data file based on scanning data. The utility includes segmentation of images obtained with either computed tomography or magnetic resonance imaging by distinguishing tissues according to their signal (brightness) and specification of the source and detector. In addition, a coupling of individual voxels within the tissue is used to reduce the memory demand and to increase the calculational speed. The utility was tested for low energy emitters in plastic and biological tissues as well as for computed tomography and magnetic resonance imaging scanning information

Increased risk of severe malaria in travellers during the COVID-19 pandemic

International audienceWe observed an increase in severe cases of falciparum malaria among French service members (who are travellers in endemic areas) in 2020, associated with an increase in the time between onset of symptoms and diagnosis/treatment. The COVID-19 epidemic may have lengthened the malaria diagnosis process, mainly due to clinical similarities

Differential Impact According to Mission’s Operational Intensity on Psychoactive Substance Use: A Retrospective Cohort of French Male Army Service Members

International audienceBackground: Stressful deployments in combat areas are known to increase the risk of substance abuse in military personnel. Objectives: The aim of the study was to compare deployment on stressful, high-intensity missions (HIMs) to deployment on low-intensity missions (LIMs) in order to understand factors associated with substance use variations across the mission. Methods: A retrospective cohort study based on a one-shot self-questionnaire was performed four months after their return on two samples of male French Army service members: one returning from an HIM and one from an LIM. The questionnaire focused on tobacco, alcohol, cannabis, cocaine, and psychoactive medication use at three times: before, during, and after the mission. Results: During an HIM, the frequency of tobacco use increased, alcohol use remained stable – although 38% declared a decrease in consumption – and illicit drug use decreased. During an LIM, tobacco and alcohol use increased, cannabis use remained stable, and only cocaine and medication use decreased. After their return, use levels among both samples reverted to values similar to those reported before the mission, except for a decrease in tobacco use observed at return from an HIM. The main factors perceived as related to variations were stress in an HIM and low cost in an LIM. Conclusions/importance: The study suggests a differential impact of deployment on substance use according to the operational intensity of the mission. Variations in use are predominant during the mission with a washout effect after returning home

Zika Virus Persistence and Higher Viral Loads in Cutaneous Capillaries Than in Venous Blood

We collected venous and capillary serum samples from 21 Zika virus‒infected patients on multiple days after symptom onset and found RNA load was higher and median duration of virus detection significantly longer in capillary than in venous blood. These findings raise questions about the role of the capillary compartment in virus transmission dynamics