Inviscid incompressible limits of the full Navier-Stokes-Fourier system

We consider the full Navier-Stokes-Fourier system in the singular limit for the small Mach and large Reynolds and Peclet numbers, with ill prepared initial data on the three dimensional Euclidean space. The Euler-Boussinesq approximation is identified as the limit system

Involvement of a single periplasmic hydrogenase for both hydrogen uptake and production in some Desulfovibrio species

Au cours de cette étude, nous avons montré que plusieurs bactéries sulfato-réductrices possédant un nombre différent de gènes codant pour des hydrogénases, oxydent le lactate en absence de sulfate lorsqu'elles sont en coculture avec #Methanospirillum hungatei. L'efficacité du transfert d'hydrogène avec la bactérie méthanogène n'est pas corrélée avec le nombre de gènes codant pour l'hydrogénase chez ces bactéries sulfato-réductrices. #Desulfovibrio vulgaris Groningen, qui possède uniquement le gène de l'hydrogénase à nickel-fer (hydrogénase [NiFe]), oxyde l'hydrogène en présence de sulfate et produit de l'hydrogène au cours de la fermentation du pyruvate. L'hydrogénase de #D. vulgaris Groningen a été purifiée et caractérisée. Son poids moléculaire est de 87 kDA et elle est constituée de deux sous-unités différentes (60 et 28 kDa). L'hydrogénase de cette bactérie contient 10,6 atomes de fer, 0,9 atome de nickel et 12 atomes de soufre par molécule et son spectre d'absorption est caractéristique d'une protéine à centre fer-soufre. Les activités catalytiques de consommation et production d'hydrogène sont de 332 et 230 unités/mg de protéine, respectivement. Les cellules de #D. vulgarie Groningen contiennent exclusivement l'hydrogénase [NiFe] quelles que soient les conditions de croissance, ainsi que l'ont montré des études biochimiques et immunologiques. L'immunocytolocalisation de cryosections ultrafines de cellules ayant poussé sur différents milieux indique que l'hydrogénase [NiFe] est localisée dans l'espace périplasmique, le marquage étant plus important sur les cellules cultivées sur H2 et sulfate ou pyruvate seul que sur celles cultivées sur lactate et sulfate. Les résultats nous permettent de conclure que #D. vulgaris Groningen contient une seule hydrogénase de type [NiFe] située dans l'espace périplasmique tel que cela a été décrit chez #D. gigas. (Résumé d'auteur

Stability with respect to domain of the low Mach number limit of compressible viscous fluids

We study the asymptotic limit of solutions to the barotropic Navier-Stokes system, when the Mach number is proportional to a small parameter \ep \to 0 and the fluid is confined to an exterior spatial domain \Omega_\ep that may vary with \ep. As $\epsilon \rightarrow 0$, it is shown that the fluid density becomes constant while the velocity converges to a solenoidal vector field satisfying the incompressible Navier-Stokes equations on a limit domain. The velocities approach the limit strongly (a.a.) on any compact set, uniformly with respect to a certain class of domains. The proof is based on spectral analysis of the associated wave propagator (Neumann Laplacian) governing the motion of acoustic waves.Comment: 32 page

Cross standard form : a solution to improve a given controller with H2 or Hoo specifications

This paper introduces in cross standard form (CSF) as a solution to the inverse optimal control problem. That is, the CSF is a canonical standard problem whose unique H1 or H2 optimal controller is a given controller. From the control design point of view, the general idea is to apply the CSF to a given controller in order to set up a standard problem which can be completed to handle frequency domain H2 or H1 specification. The analytical formulation of the CSF proposed in this paper can be applied to reduced-, full- or augmented-order compensators or two-degree of freedom compensations. Numerical and academic examples are given

Flexible Mode Modelling of the InSight Lander and Consequences for the SEIS Instrument

We present an updated model for estimating the lander mechanical noise on the InSight seismometer SEIS, taking into account the flexible modes of the InSight lander. This new flexible mode model uses the Satellite Dynamics Toolbox to compute the direct and the inverse dynamic model of a satellite composed of a main body fitted with one or several dynamic appendages. Through a detailed study of the sensitivity of our results to key environment parameters we find that the frequencies of the six dominant lander resonant modes increase logarithmically with increasing ground stiffness. On the other hand, the wind strength and the incoming wind angle modify only the signal amplitude but not the frequencies of the resonances. For the baseline parameters chosen for this study, the lander mechanical noise on the SEIS instrument is not expected to exceed the instrument total noise requirements. However, in the case that the lander mechanical noise is observable in the seismic data acquired by SEIS, this may provide a complementary method for studying the ground and wind properties on Mars

Wave: A New Family of Trapdoor One-Way Preimage Sampleable Functions Based on Codes

We present here a new family of trapdoor one-way Preimage Sampleable Functions (PSF) based on codes, the Wave-PSF family. The trapdoor function is one-way under two computational assumptions: the hardness of generic decoding for high weights and the indistinguishability of generalized $(U,U+V)$-codes. Our proof follows the GPV strategy [GPV08]. By including rejection sampling, we ensure the proper distribution for the trapdoor inverse output. The domain sampling property of our family is ensured by using and proving a variant of the left-over hash lemma. We instantiate the new Wave-PSF family with ternary generalized $(U,U+V)$-codes to design a "hash-and-sign" signature scheme which achieves existential unforgeability under adaptive chosen message attacks (EUF-CMA) in the random oracle model. For 128 bits of classical security, signature sizes are in the order of 15 thousand bits, the public key size in the order of 4 megabytes, and the rejection rate is limited to one rejection every 10 to 12 signatures.Comment: arXiv admin note: text overlap with arXiv:1706.0806

RNA polymerase II stalling promotes nucleosome occlusion and pTEFb recruitment to drive immortalization by Epstein-Barr virus

Epstein-Barr virus (EBV) immortalizes resting B-cells and is a key etiologic agent in the development of numerous cancers. The essential EBV-encoded protein EBNA 2 activates the viral C promoter (Cp) producing a message of ~120 kb that is differentially spliced to encode all EBNAs required for immortalization. We have previously shown that EBNA 2-activated transcription is dependent on the activity of the RNA polymerase II (pol II) C-terminal domain (CTD) kinase pTEFb (CDK9/cyclin T1). We now demonstrate that Cp, in contrast to two shorter EBNA 2-activated viral genes (LMP 1 and 2A), displays high levels of promoter-proximally stalled pol II despite being constitutively active. Consistent with pol II stalling, we detect considerable pausing complex (NELF/DSIF) association with Cp. Significantly, we observe substantial Cp-specific pTEFb recruitment that stimulates high-level pol II CTD serine 2 phosphorylation at distal regions (up to +75 kb), promoting elongation. We reveal that Cp-specific pol II accumulation is directed by DNA sequences unfavourable for nucleosome assembly that increase TBP access and pol II recruitment. Stalled pol II then maintains Cp nucleosome depletion. Our data indicate that pTEFb is recruited to Cp by the bromodomain protein Brd4, with polymerase stalling facilitating stable association of pTEFb. The Brd4 inhibitor JQ1 and the pTEFb inhibitors DRB and Flavopiridol significantly reduce Cp, but not LMP1 transcript production indicating that Brd4 and pTEFb are required for Cp transcription. Taken together our data indicate that pol II stalling at Cp promotes transcription of essential immortalizing genes during EBV infection by (i) preventing promoter-proximal nucleosome assembly and ii) necessitating the recruitment of pTEFb thereby maintaining serine 2 CTD phosphorylation at distal regions