Analysis of the JAXA Nonequilibrium Infrared Emission Spectra for Mars Entry Conditions

International audienceNonequilibrium infrared emission spectra representative of a Mars atmospheric entry mission are modeled using RADIS, a spectral code for CO and CO 2 based on the HITEMP-2010 and CDSD-4000 databases. The modeled experimental data for the free-flow and the forebody radiation were obtained in the JAXA expansion tube facility. In the expanding flow, good agreement with the experimental data can be obtained using a slightly nonequilibrium distribution and a homogeneous flow. The model suggests that all three CO 2 vibration modes share a same vibrational temperature slightly higher than the gas temperature. In the shock layer, the forebody radiation includes both CO 2 and CO emission features. It can be correctly predicted by assuming thermal and chemical equilibrium at 4000 ± 500 K. Nomenclature p = pressure [bar] T r ot = rotational temperature of the gas [K] T tr ans = translational temperature of the gas [K] T vib = vibrational temperature of the gas [K] T vib 1 , T vib 2 , T vib 3 = for CO 2 , temperature of each vibration mode: symmetric, bending and asymmetric vibration, respectively [K] x CO , x CO

Investigation of Infra-red and Nonequilibrium Air Radiation

This report summarizes the results obtained during a research program on the infrared radiation of air plasmas conducted in the High Temperature Gasdynamics Laboratory at Stanford University. This program was intended to investigate the masking of infrared signatures by the air plasma formed behind the bow shock of high velocity missiles. Prior to this work, the radiative emission of air plasmas in the infrared had been the object of few experimental investigations, and although several infrared systems were already modeled in radiation codes such as NEQAIR, measurements were required to validate numerical predictions and indicate whether all transitions of importance were accounted for in the model. The program was further motivated by the fact that 9 excited states (A, B, C, D, B', F, H, and H') of NO radiate in the infrared, especially between 1 and 1.5 microns where at least 9 transitions involving can be observed. Because these IR transitions are relatively well separated from each other, excited NO states concentrations can be easily measured, thus providing essential information on excited-state chemistry for use in optical diagnostics or in electronic excitation model validation. Detailed comparisons between measured and simulated spectra are presented

High-Pressure CO2_2 Dissociation with Nanosecond Pulsed Discharges

The efficiency of the conversion of CO$_2$ into CO with nanosecond repetitively pulsed discharges (NRP) is investigated in a high pressure batch reactor. Stable discharges are obtained at up to 12~bar. By-products of CO$_2$ splitting are measured with gas chromatography. The energy efficiency is determined for a range of processing times, pulse energy, and fill pressures. The energy efficiency is found to be approximately 20% and is only weakly sensitive to the plasma operating parameters, i.e., the extent of CO$_2$ conversion is almost linearly-dependent on the specific energy input. A conversion rate of up to 14% is achieved with an energy efficiency of 23%. For long processing times, a drop in efficiency is observed, due to the increasing significance of recombination reactions, as described by a macroscopic kinetic mechanism. Reaction pathways that are believed to play an important role in nanosecond pulsed discharges are discussed. It appears that vibrational excitation does not play a significant role in CO$_2$ conversion in these types of short-pulse discharge. Results also draw attention to the relative importance of two particular electronic excitation reactions.Comment: 21 pages, 12 figure

Caractérisation spatio-temporelle de NO et température par QCLAS et PLIF dans une post-décharge nanoseconde

International audienc

Abnormal nociception and opiate sensitivity of STOP null mice exhibiting elevated levels of the endogenous alkaloid morphine

<p>Abstract</p> <p>Background-</p> <p>Mice deficient for the stable tubule only peptide (STOP) display altered dopaminergic neurotransmission associated with severe behavioural defects including disorganized locomotor activity. Endogenous morphine, which is present in nervous tissues and synthesized from dopamine, may contribute to these behavioral alterations since it is thought to play a role in normal and pathological neurotransmission.</p> <p>Results-</p> <p>In this study, we showed that STOP null brain structures, including cortex, hippocampus, cerebellum and spinal cord, contain high endogenous morphine amounts. The presence of elevated levels of morphine was associated with the presence of a higher density of mu opioid receptor with a higher affinity for morphine in STOP null brains. Interestingly, STOP null mice exhibited significantly lower nociceptive thresholds to thermal and mechanical stimulations. They also had abnormal behavioural responses to the administration of exogenous morphine and naloxone. Low dose of morphine (1 mg/kg, i.p.) produced a significant mechanical antinociception in STOP null mice whereas it has no effect on wild-type mice. High concentration of naloxone (1 mg/kg) was pronociceptive for both mice strain, a lower concentration (0.1 mg/kg) was found to increase the mean mechanical nociceptive threshold only in the case of STOP null mice.</p> <p>Conclusions-</p> <p>Together, our data show that STOP null mice displayed elevated levels of endogenous morphine, as well as an increase of morphine receptor affinity and density in brain. This was correlated with hypernociception and impaired pharmacological sensitivity to mu opioid receptor ligands.</p

Meteors: A Delivery Mechanism of Organic Matter to the Early Earth

All potential exogenous pre-biotic matter arrived to Earth by ways of our atmosphere, where much material was ablated during a luminous phase called "meteors" in rarefied flows of high (up to 270) Mach number. The recent Leonid showers offered a first glimpse into the clusive physical conditions of the ablation process and atmospheric chemistry associated with high-speed meteors. Molecular emissions were detected that trace a meteor's brilliant light to a 4,300 K warm wake rather than to the meteor's head. A new theoretical approach using the direct simulation by Monte Carlo technique identified the source-region and demonstrated that the ablation process is critical in the heating of the meteor's wake. In the head of the meteor, organic carbon appears to survive flash heating and rapid cooling. The temperatures in the wake of the meteor are just right for dissociation of CO and the formation of more complex organic compounds. The resulting materials could account for the bulk of pre-biotic organic carbon on the early Earth at the time of the origin of life.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43257/1/11038_2004_Article_310535.pd

Dual Action of lysophosphatidate- functionalised titanium: Interactions with human (MG63) osteoblasts and methicillin resistant staphylococcus aureus

© 2015 Skindersoe et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Titanium (Ti) is a widely used material for surgical implants; total joint replacements (TJRs), screws and plates for fixing bones and dental implants are forged from Ti. Whilst Ti integrates well into host tissue approximately 10% of TJRs will fail in the lifetime of the patient through a process known as aseptic loosening. These failures necessitate revision arthroplasties which are more complicated and costly than the initial procedure. Finding ways of enhancing early (osseo)integration of TJRs is therefore highly desirable and continues to represent a research priority in current biomaterial design. One way of realising improvements in implant quality is to coat the Ti surface with small biological agents known to support human osteoblast formation and maturation at Ti surfaces. Lysophosphatidic acid (LPA) and certain LPA analogues offer potential solutions as Ti coatings in reducing aseptic loosening. Herein we present evidence for the successful bio-functionalisation of Ti using LPA. This modified Ti surface heightened the maturation of human osteoblasts, as supported by increased expression of alkaline phosphatase. These functionalised surfaces also deterred the attachment and growth of Staphylococcus aureus, a bacterium often associated with implant failures through sepsis. Collectively we provide evidence for the fabrication of a dual-action Ti surface finish, a highly desirable feature towards the development of next-generation implantable devices

Overview of the coordinated ground-based observations of Titan during the Huygens mission

Coordinated ground-based observations of Titan were performed around or during the Huygens atmospheric probe mission at Titan on 14 January 2005, connecting the momentary in situ observations by the probe with the synoptic coverage provided by continuing ground-based programs. These observations consisted of three different categories: (1) radio telescope tracking of the Huygens signal at 2040 MHz, (2) observations of the atmosphere and surface of Titan, and (3) attempts to observe radiation emitted during the Huygens Probe entry into Titan's atmosphere. The Probe radio signal was successfully acquired by a network of terrestrial telescopes, recovering a vertical profile of wind speed in Titan's atmosphere from 140 km altitude down to the surface. Ground-based observations brought new information on atmosphere and surface properties of the largest Satumian moon. No positive detection of phenomena associated with the Probe entry was reported. This paper reviews all these measurements and highlights the achieved results. The ground-based observations, both radio and optical, are of fundamental imnortance for the interpretatinn of results from the Huygens mission

Prédiction du rayonnement hors équilibre d un plasma d air avec un modèle collisionel-radiatif (Application aux expériences de tubes à choc pour des conditions représentatives d une rentrée sur Terre)

Sous conditions de fort déséquilibre thermodynamique, les populations des états internes émettant dans le VUV et l infrarouge ne suivent plus une distribution de Boltzmann mais sont contrôlés par des processus collisionels et radiatifs. Nous avons développé un nouveau modèle collisionel-radiatif (CR) comprenant les mécanismes d excitation et d ionisation par impact d électrons et de particules lourdes, ainsi que les transitions radiatives. Une revue exhaustive des diverses données expérimentales et théoriques nous a conduit à sélectionner les formulations les plus appropriées. Les transitions radiatives on été traitées via le concept de facteur d échappement, égal à 0 pour les transitions dans le VUV, et à 1 pour les transitions dans l infrarouge, en accord avec les récents calculs de la littérature. Nous avons interfacé notre modèle CR avec un code d écoulement et un code spectral en vue de prédire les luminances récemment mesurées dans le tube à choc EAST de la NASA. Nous avons choisi deux conditions représentatives d une rentrée hypervéloce sur Terre: V=10.6 et 11.12 km/s, à pression p=13.3 Pa. Nous avons comparé les densités d électrons prédites par le modèle d écoulement avec celles extraites des caméras CCD et avons obtenu un excellent accord, validant de fait le modèle d ionisation et nous permettant de déterminer la position du choc. Ensuite, nous avons comparé les profils de luminance prédits par le modèle CR mesurés dans le VUV et l infrarouge avec les données expérimentales et avons obtenu un excellent accord. Nous avons ainsi montré que les collisions par impact de particules lourdes sont cruciales et doivent être déterminés précisément en vue de prédire le flux radiatif dans le VUV, lequel peut représenter 60% du flux total reçu par le vaisseau spatial lors de sa rentrée dans l atmosphère terrestre.Under nonequilibrium, the populations of the electronic states that strongly radiate in the VUV and IR are no longer governed by a Boltzmann distribution but rather by collisional and radiative processes. A new collisional-radiative (CR) model was developed including the key processes chief among them electron-impact excitation and ionization, heavy-particle impact excitation and bound-bound transitions. A comprehensive review of the available experimental and theoretical reaction rates governing these processes was undertaken to produce a reliable set of rates. The bound-bound radiative mechanisms were treated using the escape factor concept, set to zero for VUV lines and set to one for infrared lines, in accordance with literature results. The CR model was interfaced with the a flowfield solver and with a radiation code to predict the nonequilibrium VUV and IR radiation spectra very recently measured in the EAST facility at NASA Ames Research Center. Two shock-tube conditions representative of a Lunar return reentry trajectory were selected: V=10.6 and 11.12 km/s, both at p=13.3 Pa. The electron number density profiles inferred from experiments were compared with the prediction of the flowfield model, showing excellent agreement in trend and absolute magnitude for both freestream conditions, and thus validating the ionization model and providing a way to accurately locate the shock front in the CCD images. Then, the experimental intensity profiles were compared with the prediction of the CR model. Excellent agreement between predicted and measured intensity profiles was obtained for both freestream conditions, when adjusting the heavy-particle impact excitation rate constants of Park (1985), suggesting that the nonequilibrium peak intensities observed in the VUV and IR spectral ranges are controled by heavy-particle impact processes.CHATENAY MALABRY-Ecole centrale (920192301) / SudocSudocFranceF