Flow visualization studies of VTOL aircraft models during Hover in ground effect

A flow visualization study of several configurations of a jet-powered vertical takeoff and landing (VTOL) aircraft model during hover in ground effect was conducted. A surface oil flow technique was used to observe the flow patterns on the lower surfaces of the model. There were significant configuration effects. Wing height with respect to fuselage, the presence of an engine inlet duct beside the fuselage, and nozzle pressure ratio are seen to have strong effects on the surface flow angles on the lower surface of the wing. This test was part of a program to improve the methods for predicting the hot gas ingestion (HGI) for jet-powered vertical/short takeoff and landing (V/STOL) aircraft. The tests were performed at the Jet Calibration and Hover Test (JCAHT) Facility at Ames Research Center

Stopping of Charged Particles in a Magnetized Classical Plasma

The analytical and numerical investigations of the energy loss rate of the test particle in a magnetized electron plasma are developed on the basis of the Vlasov-Poisson equations, and the main results are presented. The Larmor rotation of a test particle in a magnetic field is taken into account. The analysis is based on the assumption that the energy variation of the test particle is much less than its kinetic energy. The obtained general expression for stopping power is analyzed for three cases: (i) the particle moves through a collisionless plasma in a strong homogeneous magnetic field; (ii) the fast particle moves through a magnetized collisionless plasma along the magnetic field; and (iii) the particle moves through a magnetized collisional plasma across a magnetic field. Calculations are carried out for the arbitrary test particle velocities in the first case, and for fast particles in the second and third cases. It is shown that the rate at which a fast test particle loses energy while moving across a magnetic field may be much higher than the loss in the case of motion through plasma without magnetic field.Comment: 14 pages, 3 figures, LaTe

From Bengali to English: sequential bilingualism of a second-generation British Bangladeshi

The paper discusses sequential language acquisition of the researcher's daughter Safa who transformed from a monolingual Bengali speaker to an almost monolingual English speaker in a few months after moving to the UK. Safa was born in Bangladesh and was a monolingual Bengali speaker until she was three years and nine months when the family moved to the UK. Unlike most research on sequential bilingualism, Safa's transition from Bengali to English went through a period of an invented language, which she developed and used for a few months. Safa then underwent language shift as Bengali became her passive language. Safa's loss of fluency in Bengali was mainly due to the absence of Bengali linguistic environment, because her family lived outside the community. Safa's mother's indifference to Bangladeshi ethnicity and her parents’ positive attitude towards Britishness meant that her decline in Bengali did not cause them much concern. Despite the lack of proficiency in Bengali, Safa still retains a strong ethnic Bangladeshi identity. Tabors and Snow’s four-stage developmental process of sequential second-language acquisition has been applied to find the similarities and differences in Safa's case, while language maintenance and shift theories have contributed to the analysis of the process of her language shift

How sailfish use their bills to capture schooling prey

The istiophorid family of billfishes is characterized by an extended rostrum or ‘bill’. While various functions (e.g. foraging and hydrodynamic benefits) have been proposed for this structure, until now no study has directly investigated the mechanisms by which billfishes use their rostrum to feed on prey. Here, we present the first unequivocal evidence of how the bill is used by Atlantic sailfish ( Istiophorus albicans ) to attack schooling sardines in the open ocean. Using high-speed video-analysis, we show that (i) sailfish manage to insert their bill into sardine schools without eliciting an evasive response and (ii) subsequently use their bill to either tap on individual prey targets or to slash through the school with powerful lateral motions characterized by one of the highest accelerations ever recorded in an aquatic vertebrate. Our results demonstrate that the combination of stealth and rapid motion make the sailfish bill an extremely effective feeding adaptation for capturing schooling prey. </jats:p

Lutte contre la pourriture grise (Botrytis cinerea)

S'attaquant surtout aux grappes et aux pédoncules, Botrytis cinerea forme conifidère de Scierotinia fuckeliana, étudié tout d'abord par MULLER-THURGAU (1888), puis par RAVAZ (1895), est fréquemment responsable de dommages relatifs à l'importance ou bien à la qualité des récoltes : nécessité du ciselage des raisins de table pourris, nécessité de l'épluchage des grappes en Champagne, pertes en volume, casse brune des vins (GOUIRAND, 1907), etc... La crainte des dégâts incite en outre souvent les vignerons à vendanger trop tôt au détriment de la qualité. Répandu un peu partout dans la nature, sur les débris végétaux morts, où il vit en saprophyte et s'accommode de conditions très variées, le champignon peut devenir parasite, lorsque les conditions lui sont favorables et ainsi attaquer les tissus vivants : feuilles, rameaux, inflorescence et grappes (VIENNOT BOURGIN, 1960). Pour comprendre les techniques de lutte, il est utile de rappeler brièvement les conditions de développement du champignon au vignoble

Long-term in vivo imaging of translated RNAs for gene therapy.

International audienceTo determine the potential of RNA for transient expression, we followed its translational efficiency and expression kinetics in vivo in mouse skin. Three RNA species were delivered in vivo with differing 5' and 3' ends, as well as with different structures that are known to influence their translation fate, such as an internal ribosome entry site (IRES), a cap or a poly(A) tail. RNAs were transferred by electropermeabilization, and each encoded the firefly luciferase enzyme to allow monitoring of translational efficiency by in vivo bioluminescence imaging. We show that all types of naked RNAs delivered into mouse skin are efficient for transient protein expression in vivo. Expression could be achieved with some differences in efficiency and time course, using either capped/polyadenylated RNAs or RNAs containing HCV IRES structures with or without a poly(A) tail. Our data reveal expression occurring up to 2 weeks, suggesting that electroporated RNA has high stability in vivo, particularly capped and polyadenylated RNAs. Our study shows that RNA molecules are efficient tools for the transient expression of proteins in vivo and that they can be used for therapeutic purposes. Changes in RNA features may be used to modulate both expression efficiency and kinetics