Primary structure of rat pancreatic lipase mRNA

AbstractThe sequence of a rat pancreatic lipase mRNA was determined. The data have been assigned the following accession number, X61925, in the EMBL data library. The total length of the messenger is 1531 nucleotides, plus a poly(A) stretch of about 60 nucleotides. A 72-nucleotides 5′-noncoding region is followed by a 1419-nucleotides open reading frame which encodes a protein of 473 amino acids, including the 17 amino acid signal peptide. The mature enzyme (456 residues) has 6 additional C-terminal amino acids, as compared with the amino acid sequence of pig (direct amino acid sequence), dog, man and rat isoenzyme from Genbank, M58369 (all deduced from the nucleotide sequence). A higher degree of homology exists between the amino acid sequence of rat mature enzyme with those of dog (88%), pig (75%) and man (75%) than with that of rat isolipase (74%)

Performance of hybrid turbulence models in OpenFOAM for numerical simulations of a confined backward-facing step flow at low Prandtl number

/To date, numerical simulation of complex turbulent flows with separation remains challenging. On the one hand,turbulence models in Reynolds-averaged Navier-Stokes (RANS) equations struggle with correctly representing turbulent momentum transfer in such flows, whereas turbulence-resolving techniques such as large-eddy simulations (LES) carry high computational cost on the other hand. Alternatively, hybrid RANS–LES turbulence models promise to deliver scale-resolving accuracy at acceptable computational cost, yet their accuracy remains highly dependent on simulation setup and flow conditions. Here, we investigate hybrid turbulence models readily available in OpenFOAM, and benchmark their performance to Reynolds-averaged approaches and turbulence-resolving high-fidelity reference data for a confined backward-facing step flow at low Prandtl number and relatively low Reynolds number. Although temperature is generally well predicted by all considered setups, a comparison between RANS and LES shows that turbulence resolution can increase the accuracy for the considered flow case. Results show that scale-adaptive simulation techniques do not produce resolved turbulence and fail to outperform the baseline Reynolds-averaged simulations for the considered case. In contrast, detached-eddy variants do resolve turbulence in the separated shear layer, yet some configurations suffer from modeled-stress depletion due to late development of resolved turbulence. A grid coarsening study compares the degradation of accuracy for each approach, showcasing robustness of the standard RANS approach and the good performance of full LES even at surprisingly coarse resolutions. For each grid, the best-performing setup was either a RANS or an LES approach, but never a hybrid turbulence model setup. Finally, a Reynolds-number sensitivity is presented, indicating that resolved turbulence development is promoted at higher Reynolds numbers, thus leading to setups more amenable to hybrid turbulence models. &nbsp

Caractérisation par technique PIV des écoulements moyens et transitoires dans un modèle à eau d'un réacteur de recherche

International audienceLa modélisation physique du circuit primaire d'un nouveau type de réacteur nucléaire apporte des informations importantes au niveau du comportement thermo-hydraulique. Dans le cadre des études R&D pour le réacteur MYRRHA, développé par le centre belge de l'énergie nucléaire (SCK-CEN), un modèle à eau à échelle réduite a été construit à l'Institut von Karman. Des mesures PIV caractérisent l'écoulement dans différents plans du modèle à eau. Pour obtenir des images de qualité dans un environnement présentant aussi peu d'accès optique, une méthodologie a été développée, basée sur l'utilisation d'images de calibration. L'utilisation d'un ensemencement à base de particules fluorescentes a permis également d'augmenter considérablement le rapport signal/bruit. Les résultats sont présentés pour deux modes de fonctionnement du modèle à eau: condition nominale et convection naturelle. Des informations importantes au niveau du champ de vitesse à l'entrée du réacteur et plus particulièrement sur l'importance de la composante radiale de la vitesse ont pu être extraites. Ces données servent à la validation des codes de simulation numérique

Titans metal-poor reference stars II. Red giants and CEMP stars

Representative samples of F-, G-, K-type stars located out of the Solar Neighbourhood has started to be available in spectroscopic surveys. The fraction of metal-poor ([Fe/H]~$\lesssim -0.8$~dex) giants becomes increasingly relevant to far distances. In metal-poor stars, effective temperatures ($T_{\mathrm{eff}}$) based on LTE spectroscopy and on former colour-$T_{\mathrm{eff}}$ relations of still wide use have been reported to be inaccurate. It is necessary to re-calibrate chemical abundances based on these $T_{\mathrm{eff}}$ scales in the multiple available surveys to bring them to the same standard scale for their simultaneous use. For that, a complete sample of standards is required, which so far, is restricted to a few stars with quasi-direct $T_{\mathrm{eff}}$ measurements. We aim at providing a legacy sample of metal-poor standards with proven accurate atmospheric parameters. We add 47 giants to the sample of metal-poor dwarfs of Giribaldi et al. 2021, thereby constituting the Titans metal-poor reference stars. $T_{\mathrm{eff}}$ was derived by 3D non-LTE H$\alpha$ modelling, whose accuracy was tested against interferometry and InfraRed Flux Method (IRFM). Surface gravity (log $g$) was derived by fitting Mg~I~b triplet lines, whose accuracy was tested against asteroseismology. Metallicity was derived using Fe II lines, which was verified to be identical to the [Fe/H] derived from non-LTE spectral synthesis. $T_{\mathrm{eff}}$ from 3D non-LTE H$\alpha$ is equivalent to interferometric and IRFM temperatures within a $\pm$46~K uncertainty. We achieved precision of $\sim$50~K for 34 stars with spectra with the highest S/N. For log $g$, we achieved a total uncertainty of $\pm$0.15~dex. For [Fe/H], we obtained a total uncertainty of $\pm$0.09~dex. We find that the ionization equilibrium of Fe lines under LTE is not valid in metal-poor giants.Comment: Accepted in A&

CFD analysis of interaction effects between vehicles in formation flight for in-air capturing of reusable launchers

Reusing the complex, high performance, high-cost rocket stages and engines by returning them back to their launch site is becoming important not only from economical aspects but also from an ecological point of view. An innovative return mode, ‘in-air capturing (IAC)’, is chosen as it provides potential for a better performance by reducing the overall fuel consumption, when compared to other approaches like vertical landing. In this mode, a winged reusable launcher vehicle (RLV), which has slowed down to subsonic velocity through atmospheric braking is captured using an aircraft and towed back to launch site. First, the vehicles approach each other in a parallel formation with similar velocities by keeping a safe distance between them. During this formation, a capturing device autonomously captures the RLV. Once the connection has been achieved, the captured configuration is pulled up from a gliding flight to cruise flight with a towing aircraft serving as an external propulsion system to the RLV. During these phases, the RLV is exposed to the wake of the towing aircraft and will face disturbances that will likely lead to a reduction in formation envelope. The impact of proximity between the capturing device and the RLV should also be evaluated to investigate the complex interactions which would alter the aerodynamic performances of both vehicles after connection. Moreover, in the next phase, the connected configuration must pull-up from a descent to cruise flight. For this the towing aircraft will be at high angle of attacks leading to strong downwash velocity in the wake that must be studied further. In this work, a full-scale three-dimensional RANS simulation will be performed with the open source CFD code OpenFOAM 6.0 using the k-ω SST turbulence model and a compressible solver rhoSimpleFoam to investigate aforementioned issues. The CFD results will be analysed to gain better insight in the flow field and interaction effects between the three vehicles and their aerodynamic performance used for the flight dynamics simulation of IAC

Mesures de stéréo-PIV dans une cuve agitée

International audienceLes écoulements en cuve agitée se retrouvent dans de nombreuses applications industrielles comme l’agroalimentaire, le pharmaceutique, ou encore l’industrie chimique. Les écoulements présents dans ce type d’installation rotative sont largement tridimensionnels et particulièrement non symétriques lorsque la cuve est munie de contre pales. La modélisation de ces écoulements n’est donc pas aisée, et se complexifie d’autant plus lorsque plusieurs phases coexistent dans la cuve.L’objectif de cette étude conjointe entre l’Institut von Karman et le CETIM est de créer une base de don-nées expérimentale pour la validation des codes numériques destinés à la simulation d’écoulements en cuve agitée. Le projet comprend plusieurs étapes qui vont de mesures en écoulement monophasique, jusqu’à des mesures diphasiques de mélange solide – liquide et liquide – gaz. Cette communication traite des résultats expérimentaux de la première étape qui se focalise sur l’écoulement purement liquide.L’installation expérimentale est une cuve cylindre transparente en Plexiglass dont la hauteur et le diamètre font 638 mm. Elle comprend trois contre-pales, elles aussi en Plexiglass, séparées de 120°, et descendant jusqu’à quelques millimètres de son fond plat. L’axe central de rotation est muni une turbine à 4 pales. Deux turbines, de diamètre égal à 40% de celui de la cuve, sont testées ; la première est constituée de pales à 90°alors que dans la secondes les pales sont inclinées à 45°. La turbine se situe à 30% du fond de cuve.L’étude expérimentale utilise l’eau comme fluide pour les mesures en régime turbulents. Les trois composantes du champ de vitesse dans un plan horizontal situé au milieu des pales, et dans un plan vertical situé en aval d’une contre-pale sont mesurées par application de la stéréo-PIV (SPIV). Les écoulements créés par les deux types de pales avec sans contre-pales, et ce pour trois vitesses de rotation différentes (3 tpm, 15 tpm et 90tpm), sont comparés. L’analyse des mesures SPIV dans le plan horizontal ont nécessité l’implémentation d’un système dynamique de masque afin d’éliminer les erreurs dues à la présence de réflexions de particules sur les pales, du fait de leur caractère transparent.Les champs de vitesse moyen et de l’intensité de turbulence seront présentés. Du fait de la rotation des pales,deux définitions de valeur moyenne seront considérées ; tout d’abord une moyenne sur toutes les images mesurées, puis une moyenne effectuée uniquement sur les images correspondant à une position identique des pales.Enfin, les mesures effectuées à une vitesse de 15 tpm permettront de montrer, via une analyse fréquentielle des champs de vitesse, quelle partie de l’écoulement est directement influencée par la rotation des pales

DYNAMIC MODELLING AND CONTROL OF AN AERODYNAMICALLY CONTROLLED CAPTURING DEVICE FOR ‘IN-AIR-CAPTURING’ OF A REUSABLE LAUNCH VEHICLE

The renewed interest in reusable launch vehicles has fueled the development of many advanced space transportation concepts. An interesting method for recovering rocket stages called ’In-AirCapturing’, has been patented by DLR. The winged stages are captured mid-flight and towed back to the landing site by an aircraft, eliminating the need for an additional propulsion system. A critical procedure in the capturing process involves an aerodynamically controlled capturing device attached by a rope to the towing aircraft, performing an autonomous rendezvous maneuver with the launch vehicle. In this paper, the complex dynamics associated with this phase are modelled and examined. This includes the aerodynamics of the capturing device, external disturbances like the turbulent wake of the aircraft and the flexible dynamics associated with the rope. These effects are combined into a multidisciplinary framework and a preliminary control system is proposed. The final open-loop simulation results provide valuable information about the stability and controllability of the system, which will be used for advanced control design in future work