Validation Test Cases for Multi-Physic Problems: Application to Magneto-Hydrodynamic Numerical Simulations

In the present paper, some elementary test cases in laminar flow with magnetic forcing terms are analyzed (Hartmann flow, Couette flow, Rayleigh flow); equations of the coupled problem are exposed and analytical solutions are derived in each case, highlighting the relevant non-dimensional number which drives the physics of the problem. Several analytical calculations are then proposed and discussed, in particular in the context of MHD propulsion by a nozzle.Comment: 10

L'instabilité elliptique dans les enveloppes fluides des planètes et des étoiles

Le noyau liquide terrestre, l’atmosphère des planètes gazeuses ou les étoiles sont des exemples de fluides en rotation, au sein desquels des ondes dites inertielles peuvent se propager. Lorsqu’un forçage mécanique est présent (e.g. présence d'une lune, précession de l'axe de rotation), ces ondes peuvent être excitées par résonance directe ou former des résonances paramétriques appelées instabilités inertielles. Si la pertinence de ces résonances ne laisse plus de doute en aéronautique, leurs conséquences dans un contexte astro- ou géophysique soulèvent de nombreuses questions. Au cours de cet exposé, je m’intéresserai d’abord au forçage de marées et à l’instabilité associée, et présenterai les premières simulations de cette instabilité en géométrie ellipsoïdale. Je considérerai ensuite l’interaction de cette instabilité de marées avec différentes complexités géophysiques, par exemple la présence possible de convection thermique, menant à une compétition avec les colonnes de Busse. Bien que les astres synchronisés comme notre Lune actuelle ne puissent exciter d’instabilités de marées, ils présentent un autre forçage, la libration en longitude/latitude. Je montrerai que la libration peut aussi faire résonner des ondes inertielles et ainsi générer des écoulements vigoureux. Enfin, j’aborderai le rôle possible de ces écoulements dans la génération des champs magnétiques planétaires, montrant ainsi qu’ils pourraient être à l’origine du champ magnétique lunaire. Tous les résultats obtenus seront systématiquement replacés dans un contexte naturel, montrant leur possible importance pour les astres telluriques (Terre & Lune primitives, Europe et trois Super-Terres) ou gazeux (étoiles et planètes des systèmes extrasolaires à Jupiters chauds tels que Tau-boo)

Instabilité elliptique sous champ magnétique

Nous présentons une approche théorique, expérimentale et numérique de la dynamique de l'instabilité elliptique dans un fluide tournant conducteur lorsque qu'un champ magnétique est imposé le long de l'axe de rotation. Nous démontrons que le taux de croissance de l'instabilité et le carré de l'amplitude du champ induit diminuent linéairement avec le carré du champ appliqué. Une dynamique non-linéaire particulièrement riche est mise en évidence. Enfin, l'éventualité d'une dynamo par instabilité elliptique est discutée

The great screen anomaly—a new frontier in product discovery through functional metagenomics

Functional metagenomics, the study of the collective genome of a microbial community by expressing it in a foreign host, is an emerging field in biotechnology. Over the past years, the possibility of novel product discovery through metagenomics has developed rapidly. Thus, metagenomics has been heralded as a promising mining strategy of resources for the biotechnological and pharmaceutical industry. However, in spite of innovative work in the field of functional genomics in recent years, yields from function-based metagenomics studies still fall short of producing significant amounts of new products that are valuable for biotechnological processes. Thus, a new set of strategies is required with respect to fostering gene expression in comparison to the traditional work. These new strategies should address a major issue, that is, how to successfully express a set of unknown genes of unknown origin in a foreign host in high throughput. This article is an opinionating review of functional metagenomic screening of natural microbial communities, with a focus on the optimization of new product discovery. It first summarizes current major bottlenecks in functional metagenomics and then provides an overview of the general metagenomic assessment strategies, with a focus on the challenges that are met in the screening for, and selection of, target genes in metagenomic libraries. To identify possible screening limitations, strategies to achieve optimal gene expression are reviewed, examining the molecular events all the way from the transcription level through to the secretion of the target gene product

Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).

Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)

Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.

BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362