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Littérature scientifique sur le sujet « Interstellar ices. carbon monoxide »

Auteur : Grafiati
Publié le 21 décembre 2024

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Articles de revues sur le sujet "Interstellar ices. carbon monoxide"

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Wang, Jia, Andrew M. Turner, Joshua H. Marks, Chaojiang Zhang, N. Fabian Kleimeier, Alexandre Bergantini, Santosh K. Singh, Ryan C. Fortenberry et Ralf I. Kaiser. « Preparation of Acetylenediol (HOCCOH) and Glyoxal (HCOCHO) in Interstellar Analog Ices of Carbon Monoxide and Water ». Astrophysical Journal 967, no 2 (21 mai 2024) : 79. http://dx.doi.org/10.3847/1538-4357/ad3c3e.

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Abstract Enols—tautomers of ketones or aldehydes—are considered key intermediates in the formation of prebiotic sugars and sugar acids. Although laboratory simulation experiments suggest that enols should be ubiquitous in the interstellar medium, the underlying formation mechanisms of enols in interstellar environments are largely elusive. Here, we present the laboratory experiments on the formation of glyoxal (HCOCHO) along with its ynol tautomer acetylenediol (HOCCOH) in interstellar ice analogs composed of carbon monoxide (CO) and water (H2O) upon exposure to energetic electrons as a proxy for secondary electrons generated from Galactic cosmic rays. Utilizing tunable vacuum ultraviolet photoionization reflectron time-of-flight mass spectrometry, glyoxal and acetylenediol were detected in the gas phase during temperature-programmed desorption. Our results reveal the formation pathways of glyoxal via radical–radical recombination of two formyl (HĊO) radicals, and that of acetylenediol via keto-enol-ynol tautomerization. Due to the abundance of carbon monoxide and water in interstellar ices, glyoxal and acetylenediol are suitable candidates for future astronomical searches. Furthermore, the detection of acetylenediol in astrophysically relevant ices advances our understanding for the formation pathways of high-energy tautomers such as enols in deep space.
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Abplanalp, Matthew J., et Ralf I. Kaiser. « On the formation of complex organic molecules in the interstellar medium : untangling the chemical complexity of carbon monoxide–hydrocarbon containing ice analogues exposed to ionizing radiation via a combined infrared and reflectron time-of-flight analysis ». Physical Chemistry Chemical Physics 21, no 31 (2019) : 16949–80. http://dx.doi.org/10.1039/c9cp01793c.

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Schmidt, Fabian, Petra Swiderek, Tarek Scheele et Jan H. Bredehöft. « Mechanisms of methyl formate production during electron-induced processing of methanol–carbon monoxide ices ». Physical Chemistry Chemical Physics 23, no 20 (2021) : 11649–62. http://dx.doi.org/10.1039/d1cp01255j.

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A novel mechanism is proposed for the electron-induced production of methyl formate from CO and CH3OH which is relevant for interstellar ice chemistry. A key-step in this reaction is the formation of an intermediate CH3OCO radical.
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Kuznetsov, O. V., M. M. Evseev, E. A. Batrakova et I. O. Antonov. « Ionization Energy of Reaction Products in an Ethanol–Carbon Monoxide System in Interstellar Ices ». Bulletin of the Lebedev Physics Institute 51, no 3 (mars 2024) : 77–82. http://dx.doi.org/10.3103/s1068335623601826.

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Pilling, Sergio, Eduardo Seperuelo Duarte, Enio F. da Silveira, Emmanuel Balanzat, Hermann Rothard, Alicja Domaracka et Philippe Boduch. « Radiolysis of ammonia-containing ices by heavy cosmic rays inside dense molecular clouds ». Proceedings of the International Astronomical Union 5, S265 (août 2009) : 442–43. http://dx.doi.org/10.1017/s1743921310001237.

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AbstractWe present experimental studies on the interaction of heavy, highly charged and energetic ions (46 MeV 58Ni13+) with interstellar ammonia-containing (H2O:NH3:CO) ice analog in an attempt to simulate the physical chemistry induced by heavy ion cosmic rays inside dense astrophysical environments. The measurements were performed at the heavy ion accelerator GANIL in Caen, France. In-situ analysis have been performed by a Fourier transform infrared spectrometer. The averaged values for the dissociation cross section of water, ammonia and carbon monoxide are determined and the estimated half life for the studied species inside dense molecular clouds is 2-3 × 106 years. The IR spectra of organic residue produced by the radiolysis have revealed, at room temperature, five bands that are tentatively assigned to vibration modes of the zwitterionic glycine (NH3+CH2COO−).
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Bennett, Chris J., Corey S. Jamieson et Ralf I. Kaiser. « AN EXPERIMENTAL INVESTIGATION OF THE DECOMPOSITION OF CARBON MONOXIDE AND FORMATION ROUTES TO CARBON DIOXIDE IN INTERSTELLAR ICES ». Astrophysical Journal Supplement Series 182, no 1 (15 avril 2009) : 1–11. http://dx.doi.org/10.1088/0067-0049/182/1/1.

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Ioppolo, S., B. A. McGuire, M. A. Allodi et G. A. Blake. « THz and mid-IR spectroscopy of interstellar ice analogs : methyl and carboxylic acid groups ». Faraday Discuss. 168 (2014) : 461–84. http://dx.doi.org/10.1039/c3fd00154g.

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A fundamental problem in astrochemistry concerns the synthesis and survival of complex organic molecules (COMs) throughout the process of star and planet formation. While it is generally accepted that most complex molecules and prebiotic species form in the solid phase on icy grain particles, a complete understanding of the formation pathways is still largely lacking. To take full advantage of the enormous number of available THz observations (e.g.,Herschel Space Observatory, SOFIA, and ALMA), laboratory analogs must be studied systematically. Here, we present the THz (0.3–7.5 THz; 10–250 cm−1) and mid–IR (400–4000 cm−1) spectra of astrophysically-relevant species that share the same functional groups, including formic acid (HCOOH) and acetic acid (CH3COOH), and acetaldehyde (CH3CHO) and acetone ((CH3)2CO), compared to more abundant interstellar molecules such as water (H2O), methanol (CH3OH), and carbon monoxide (CO). A suite of pure and mixed binary ices are discussed. The effects on the spectra due to the composition and the structure of the ice at different temperatures are shown. Our results demonstrate that THz spectra are sensitive to reversible and irreversible transformations within the ice caused by thermal processing, suggesting that THz spectra can be used to study the composition, structure, and thermal history of interstellar ices. Moreover, the THz spectrum of an individual species depends on the functional group(s) within that molecule. Thus, future THz studies of different functional groups will help in characterizing the chemistry and physics of the interstellar medium (ISM).
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Collings, M. P., J. W. Dever, M. R. S. McCoustra et H. J. Fraser. « Implications of Ice Morphology for Comet Formation ». Highlights of Astronomy 13 (2005) : 491–94. http://dx.doi.org/10.1017/s1539299600016397.

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AbstractLaboratory surface science under ultra-high vacuum (UHV) conditions allows us to simulate the growth of ices in astrophysical environments. Using the techniques of temperature programmed desorption (TPD), reflection-absorption infrared spectroscopy (RAIRS) and micro-balance methods, we have studied binary ice systems consisting of water (H2O) and variety of other species including carbon monoxide (CO), at astrophysically relevant conditions of temperature and pressure. We present results that demonstrate that the morphology of water ice has an important influence on the behavior of such systems, by allowing processes such as diffusion and trapping that can not be understood through a knowledge of the binding energies of the species alone. Through an understanding of the implications of water ice morphology on the behavior of ice mixtures in the interstellar environment, additional constraints can be placed on the thermodynamic conditions and ice compositions during comet formation.
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Huang, C. H., A. Ciaravella, C. Cecchi-Pestellini, A. Jiménez-Escobar, L. C. Hsiao, C. C. Huang, P. C. Chen, N. E. Sie et Y. J. Chen. « Effects of 150–1000 eV Electron Impacts on Pure Carbon Monoxide Ices Using the Interstellar Energetic-Process System (IEPS) ». Astrophysical Journal 889, no 1 (24 janvier 2020) : 57. http://dx.doi.org/10.3847/1538-4357/ab5dbe.

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Hasegawa, Takeshi, Hiroto Yanagisawa, Takumi Nagasawa, Reo Sato, Naoki Numadate et Tetsuya Hama. « Infrared Band Strengths of Dangling OH Features in Amorphous Water at 20 K ». Astrophysical Journal 969, no 2 (1 juillet 2024) : 134. http://dx.doi.org/10.3847/1538-4357/ad5318.

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Abstract Infrared (IR) spectra of vapor-deposited amorphous water at low temperatures show two weak peaks at around 3720 and 3696 cm−1 assigned to free-OH stretching modes of two- and three-coordinated water molecules (so-called “dangling” OH bonds), respectively, on the ice surface. A recent JWST observation first succeeded in detection of a potential dangling OH feature at 3664 cm−1 for ices in molecular clouds, highlighting the importance of dangling OH bonds in interstellar ice chemistry. A lack of band strengths of these features at low temperatures restricts the quantification of dangling OH bonds from IR spectra, hindering development of a molecular-level understanding of the surface structure and chemistry of ice. Using IR multiple-angle incidence resolution spectrometry, we quantified the band strengths of two- and three-coordinated dangling OH features in amorphous water at 20 K as being 4.6 ± 1.6 × 10−18 and 9.1 ± 1.0 × 10−18 cm molecule−1, respectively. These values are more than an order of magnitude lower than band strengths of bulk-water molecules in ice and liquid water and are similar to those of H2O monomers confined in solid matrices. Adsorption of carbon monoxide with dangling OH bonds results in the appearance of a new broad dangling OH feature at 3680–3620 cm−1, with a band strength of 1.8 ± 0.1 × 10−17 cm molecule−1. The band strengths of dangling OH features determined in this study advance our understanding of the surface structure of interstellar ice analogs and recent IR observations of the JWST.
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Thèses sur le sujet "Interstellar ices. carbon monoxide"

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Del, Fré Samuel. « Études théoriques de la photodésorption d'analogues de glaces moléculaires interstellaires : application au monoxyde de carbone ». Electronic Thesis or Diss., Université de Lille (2022-....), 2024. http://www.theses.fr/2024ULILR039.

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Des quantités inhabituelles de molécules en phase gazeuse sont détectées dans les régions froides (environ 10 K) du milieu interstellaire (ISM), principalement attribuées à la désorption non thermique de molécules depuis les glaces déposées sur les grains de poussière. En particulier, la désorption induite par les rayons ultraviolets du vide (photodésorption VUV) est considérée comme étant une voie de désorption majoritaire dans les régions de l'ISM dominées par les photons. Les investigations expérimentales ont révélé que dans les glaces pures de monoxyde de carbone (CO), espèce omniprésente dans l'ISM, la photodésorption VUV peut suivre un mécanisme indirect de désorption induite par transition électronique (DIET) pour les photons dont l'énergie est comprise entre 7 et 10 eV. Néanmoins, la compréhension des mécanismes moléculaires sous-jacents reste un sujet de débat scientifique. Dans ce contexte astrochimique, nous présentons une étude théorique combinée utilisant la dynamique moléculaire ab initio (AIMD) basée sur la théorie de la fonctionnelle de la densité (DFT) et des potentiels machine learning (PML) construits avec des réseaux de neurones artificiels (ANN), afin d'étudier la dernière partie du mécanisme DIET dans les glaces amorphes de CO. Ici, une molécule CO hautement excitée vibrationnellement (v = 40) au centre d'un agrégat composé de 50 molécules de CO, initialement optimisé puis thermalisé à 15 K, déclenche, la désorption indirecte de molécules de surface. Nos résultats théoriques révèlent que le processus de désorption consiste en 3 étapes fondamentales qui commence par une attraction mutuelle entre la molécule excitée vibrationnellement et une ou deux molécules voisines, activée par l'étirement de la liaison CO et favorisée par l'effet stérique des molécules environnantes. Cela est suivi par une séquence de transferts d'énergie initiée par une collision, se concluant en la désorption de molécules CO vibrationnellement froides dans 88% des trajectoires AIMD. De plus, les distributions théoriques de l'énergie interne et translationnelle des molécules désorbées concordent remarquablement avec les résultats expérimentaux, ce qui soutient le rôle crucial de la relaxation vibrationnelle dans le processus de désorption. Enfin, les premiers PML construits à partir des simulations AIMD, sont capables d'ajuster avec précision la surface d'énergie potentielle multidimensionnelle du système, permettant de prédire efficacement les énergies des agrégats et les forces atomiques. Les simulations de dynamique moléculaire classique utilisant ces potentiels sont plus de 1800 fois plus rapides que celles basées sur l'AIMD, tout en offrant des précisions similaires à ceux de la DFT
Unusual amounts of gas-phase molecules are detected in the cold regions (around 10 K) of the interstellar medium (ISM), primarily attributed to the non-thermal desorption of molecules from ices deposited on dust grains. In particular, vacuum ultraviolet (VUV) photon-induced desorption (photodesorption) is considered a major desorption pathway in photon-dominated regions of the ISM. Experimental investigations have revealed that in pure carbon monoxide (CO) ices, a ubiquitous species in the ISM, VUV photodesorption can follow an indirect mechanism of desorption induced by electronic transitions (DIET) for photons with energy between 7 and 10 eV. Nevertheless, the understanding of the underlying molecular mechanisms remains a topic of scientific debate. In this astrochemical context, we present a combined theoretical study using ab initio molecular dynamics (AIMD) based on density functional theory (DFT) and machine learning potentials (PML) constructed with artificial neural networks (ANN) to study the final part of the DIET mechanism in amorphous CO ices. Here, a highly vibrationally excited CO molecule (v = 40) at the center of an aggregate initially composed of 50 CO molecules, optimized and then thermalized at 15 K, triggers the indirect desorption of surface molecules. Our theoretical results reveal that the desorption process consists of three fundamental steps, beginning with a mutual attraction between the vibrationally excited molecule and one or two neighboring molecules, activated by CO bond stretching and facilitated by the steric effect of surrounding molecules. This is followed by a sequence of energy transfers initiated by a collision, resulting in the desorption of vibrationally cold CO molecules in 88% of the AIMD trajectories. Additionally, the theoretical distributions of the internal and translational energy of desorbed molecules remarkably match experimental results, supporting the crucial role of vibrational relaxation in the desorption process. Finally, the first PML constructed from AIMD simulations accurately fit the multidimensional potential energy surface of the system, allowing efficient prediction of aggregate energies and atomic forces. Classical molecular dynamics simulations using these potentials are over 1800 times faster than those based on AIMD while offering precision comparable to DFT
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Letzelter, Corinne. « Spectroscopie et photodissociation de la molecule de co : applications astrophysiques ». Paris 6, 1987. http://www.theses.fr/1987PA066182.

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Etude des spectres d'absorption et d'emission de la molecule de co et de ses isotopes dans le domaine 88. 5 nm-125 nm. Les sections efficaces d'absorption des bandes de co entre 88. 5 nm et 115 nm ont ete mesurees en utilisant le rayonnement synchrotron comme source lumineuse. La fluorescence a ete observee dans tout le domaine uv et visible et les rendements de flourescence ont ete determines. La section efficace de photodissociation corespondante est calculee en tenant compte d'un eventuel continuum de dissociation pour lequel une limite de la section efficace d'absorption a ete donnee. Presentation des consequences de ces nouvelles donnees sur la modelisation des nuages interstellaires
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Reynaud, Denis. « Dynamique du gaz interstellaire dans les galaxies spirales barrées : une étude en interférométrie millimétrique de NGC 1530 ». Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10044.

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Les barres jouent probablement un role important dans l'evolution des galaxies. Le potentiel gravitationnel de la barre est capable de concentrer de grandes quantites de gaz interstellaire dans le voisinage du noyau, fournissant ainsi du combustible aux activites nucleaires eventuelles (formation explosive d'etoiles ou disque d'accretion de trou noir). Le gaz tombe vers le centre de la galaxie le long de deux chocs presque paralleles a la barre. Ces chocs sont riches en poussieres et en gaz moleculaire. L'interferometre millimetrique et le telescope de 30m de l'iram ont permis une etude precise du gaz moleculaire dans la barre et le noyau d'une galaxie spirale barree typique, ngc 1530. Dans cette galaxie, nous avons detecte co(1-0) le long de deux bandes formees par les chocs dans le gaz moleculaire. Dans ces bandes, le gaz tombe vers le centre, avec une vitesse de chute typique de 100 kms#-#1. Nous avons montre l'anticorrelation entre le cisaillement du gaz dans ces chocs et l'efficacite de formation d'etoiles en comparant des images h et co. Puis nous avons etudie le centre de cette galaxie a plus haute resolution en #1#2co(1-0), #1#2co(2-1), #1#3co(1-0) et hcn(1-0). Le gaz a un mouvement centripete le long de deux arcs entourant un disque nucleaire gazeux, mais dans ce disque le mouvement est circulaire. Dans le disque, le gaz se distribue suivant un anneau dont les rayons externes et internes correspondent aux resonances interieures de lindblad ou suivant une spirale non resolue. Le disque nucleaire montre une grande quantite de gaz dense tracee par hcn et #1#3co, ainsi qu'une activite de formation d'etoiles intense detectee dans l'emission etendue du continuum centimetrique. Par contre les arcs sont pauvres en gaz dense et forment peu d'etoiles. La formation d'etoiles dans le disque nucleaire peut etre maintenue pendant une longue periode de temps, grace a la grande quantite de gaz moleculaire disponible.
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Jacq, Thierry. « Le survey radiomillimetrique de l'observatoire de bordeaux : le gaz moleculaire interstellaire dans le plan galactique entre l=38 et l=67.5, structure spirale, nuages moleculaires, comparaison entre hi et **(13)co. ch dans le nuage sombre lynds 134 ». Paris 6, 1987. http://www.theses.fr/1987PA066440.

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L'observation radiomillimetrique a 110. 2 ghz du plan galactique a permis d'identifier 181 nuages interstellaires dont certains parametres sont listes. Deux bras spiraux sont mis en evidence: celui de persee d'inclinaison 12**(o) et un bras mineur lie au gaz local et incline de 22**(o). Les donnees moleculaires sont correlees aux donnees hi obtenues a arecibo et les resultats de cette comparaison sont presentes. D'autre part le nuage sombre l 134 est observe a 9 cm en ch et l'abondance relative de ce radical en fonction de la position est determinee
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Pon, Andrew Richard. « Shocks, Superbubbles, and Filaments : Investigations into Large Scale Gas Motions in Giant Molecular Clouds ». Thesis, 2013. http://hdl.handle.net/1828/4553.

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Giant molecular clouds (GMCs), out of which stars form, are complex, dynamic systems, which both influence and are shaped by the process of star formation. In this dissertation, I examine three different facets of the dynamical motions within GMCs. Collapse modes in different dimensional objects. Molecular clouds contain lower dimensional substructures, such as filaments and sheets. The collapse properties of finite filaments and sheets differ from those of spherical objects as well as infinite sheets and filaments. I examine the importance of local collapse modes of small central perturbations, relative to global collapse modes, in different dimensional objects to elucidate whether strong perturbations are required for molecular clouds to fragment to form stars. I also calculate the dependence of the global collapse timescale upon the aspect ratio of sheets and filaments. I find that lower dimensional objects are more readily fragmented, and that for a constant density, lower dimensional objects and clouds with larger aspect ratios collapse more slowly. An edge-driven collapse mode also exists in sheets and filaments and is most important in elongated filaments. The failure to consider the geometry of a gas cloud is shown to lead to an overestimation of the star formation rate by up to an order of magnitude. Molecular tracers of turbulent energy dissipation. Molecular clouds contain supersonic turbulence that simulations predict will decay rapidly via shocks. I use shock models to predict which species emit the majority of the turbulent energy dissipated in shocks and find that carbon monoxide, CO, is primarily responsible for radiating away this energy. By combining these shock models with estimates for the turbulent energy dissipation rate of molecular clouds, I predict the expected shock spectra of CO from molecular clouds. I compare the results of these shock models to predictions for the emission from the unshocked gas in GMCs and show that mid-to-high rotational transitions of CO (e.g., J = 8 to 7), should be dominated by shocked gas emission and should trace the turbulent energy being dissipated in molecular clouds. Orion-Eridanus superbubble. The nearby Orion star forming region has created a large bubble of hot plasma in the local interstellar medium referred to as the Orion-Eridanus superbubble. This bubble is unusual in that it is highly elongated, is believed to be oriented roughly parallel to the galactic plane, and contains bright filamentary features on the Eridanus side. I fit models for a wind driven bubble in an exponential atmosphere to the Orion-Eridanus superbubble and show that the elongation of the bubble cannot be explained by such a model in which the scale height of the galactic disk is the typical value of 150 pc. Either a much smaller scale height must be adopted or some additional physics must be added to the model. I also show that the Eridanus filaments cannot be equilibrium objects ionized by the Orion star forming region.
Graduate
0606
andyrpon@gmail.com
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Livres sur le sujet "Interstellar ices. carbon monoxide"

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Symposium, International Astronomical Union. CO : Twenty-five years of millimeter-wave spectroscopy : proceedings of the 170th Symposium of the International Astronomical Union, held in Tucson, Arizona, May 29-June 5, 1995. Dordrecht : Kluwer Academic Publishers, 1997.

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United States. National Aeronautics and Space Administration. Scientific and Technical Information Branch., dir. Molecular clouds in Orion and Monoceros. [Washington, DC] : National Aeronautics and Space Administration, Scientific and Technical Information Branch, 1986.

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Symposium, International Astronomical Union. CO, twenty-five years of millimeter-wave spectroscopy : Poster presentations, IAU Symposium 170, 29 May-2 June 1995, Tucson, Arizona. [Tucson, Ariz : National Radio Astronomy Observatory, 1997.

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Symposium, International Astronomical Union. CO, twenty-five years of millimeter-wave spectroscopy : Proceedings of the 170th Symposium of the International Astronomical Union, held in Tucson, Arizona, May 29-June 5, 1995. Dordrecht : Kluwer Academic Publishers, 1996.

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Molecular clouds in the Carmina arm. 1986.

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Molecular clouds in Orion and Monoceros. 1986.

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CO : Twenty-Five Years of Millimeter-Wave Spectroscopy (International Astronomical Union Symposia). Springer, 1996.

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Chapitres de livres sur le sujet "Interstellar ices. carbon monoxide"

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Kakkar, Harjasnoor, Berta Martínez-Bachs et Albert Rimola. « An Ab Initio Computational Study of Binding Energies of Interstellar Complex Organic Molecules on Crystalline Water Ice Surface Models ». Dans Computational Science and Its Applications – ICCSA 2022 Workshops, 281–92. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-10562-3_21.

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AbstractThe interstellar medium is extremely heterogeneous in terms of physical environments and chemical composition. Spectroscopic observations in the recent decades have revealed the presence of gaseous material and dust grains covered in ices predominantly of water in interstellar clouds, the interplay of which may elucidate the existence of more than 250 molecular species. Of these species of varied complexity, several terrestrial carbon-containing compounds have been discovered, known as interstellar complex organic molecules (iCOMs) in the astrochemical argot. In order to investigate the formation of iCOMs, it is crucial to explore gas-grain chemistry and in this regard, one of the fundamental parameters is the binding energy (BE), which is an essential input in astrochemical models. In this work, the BEs of 13 iCOMs on a crystalline H2O-ice surface have been computed by means of quantum chemical periodic calculations. The hybrid B3LYP-D3 DFT method was used for the geometry optimizations of the adsorbate/ice systems and for computing the BEs. Furthermore, to refine the BE values, an ONIOM2-like approximation has been employed to obtain them at CCSD(T), which correlate well with those obtained at B3LYP-D3. Additionally, aiming to lower the computational cost, structural optimizations were carried out using the HF-3c level of theory, followed by single point energy calculations at B3LYP-D3 in order to obtain BE values comparable to the full DFT treatment.
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« Chemistry in the Freezer : Making Complex Molecules From Simple Interstellar Ices ». Dans Dust in Galaxies, 132–56. The Royal Society of Chemistry, 2019. http://dx.doi.org/10.1039/9781788015059-00132.

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In darker regions of interstellar clouds, dust grains accumulate layers of simple ices on their surfaces. These ices are composed mainly of water, but also contain carbon monoxide and dioxide, simple hydrides such as methane and ammonia, and a few other species. Many of these icy species are also formed in simple chemical reactions on the surfaces of dust grains and are retained there until the ices are removed. These ice layers are chemically simple, but are the raw material for forming relatively complex molecular species, especially in star-forming regions. The formation of complex species from the simple ice species can be tested in appropriate laboratory experiments and is found to be efficient. It seems likely that most of the more complex species identified in interstellar clouds can be formed in a chemistry based on the ices formed in dark clouds.
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« Interstellar Carbon Monoxide ». Dans The ALMA Telescope, 1–8. Cambridge University Press, 2023. http://dx.doi.org/10.1017/9781009279727.003.

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Actes de conférences sur le sujet "Interstellar ices. carbon monoxide"

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Waller, Michael G., Mark R. Walluk et Thomas A. Trabold. « Towards the Development of a Fuel Cell System for Residential Applications : Propane Reforming via Catalytic Partial Oxidation ». Dans ASME 2014 12th International Conference on Fuel Cell Science, Engineering and Technology collocated with the ASME 2014 8th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fuelcell2014-6431.

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The Environmental Protection Agency (EPA) has estimated that 5% of air pollutants originate from small internal combustion engines (ICE) used in non-automotive applications. While there have been significant advances towards developing more sustainable systems to replace large ICEs, few designs have been implemented with the capability to replace small ICEs such as those used in the residential sector for lawn and garden equipment. Replacing these small residential internal combustion engines presents a unique opportunity for early market penetration of fuel cell technologies. This paper describes the initial efforts to build an innovative residential-scale fuel cell system using propane as its fuel source, and the deployment of this technology in a commonly used device found throughout the U.S. There are three main components to this program, including the development of the propane reforming system, fuel cell operation, and the overall system integration. This paper presents the reforming results of propane catalytic partial oxidation (cPOx). The primary parameters used to evaluate the reformer in this experiment were reformate composition, carbon concentration in the effluent, and reforming efficiency as a function of catalyst temperature and O2/C ratio. When including the lower heating value (LHV) for product hydrogen and carbon monoxide, maximum efficiencies of 84% were achieved at an O2/C ratio of 0.53 and a temperature of 940°C. Significant solid carbon formation was observed at catalyst temperatures below 750°C.
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Baines, Kevin H., et W. Hayden Smith. « Adaptive spectropolarimetric imaging from the Cassini orbiter ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.thn1.

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Ambitious objectives for the NASA/ESA Cassini orbiter/Titan probe mission to the saturnian system include the determination of composition and distribution of material within rings, on satellite surfaces, and within the atmospheres of Saturn and Titan. Dynamic processes which lead to spatial and temporal variations are also to be investigated. Known materials include hydrogen, methane, ammonia, phosphine, germane, and carbon monoxide for Saturn; nitrogen, methane, and higher hydrocarbons for Titan; and water and possibly ammonia ice for the other satellites and rings. Within atmospheres, ammonia (for Saturn) and methane (for Titan) are suspected condensates. Such an assortment of materials in a diverse set of planetary objects calls for versatile yet low power, low mass instrumentation. Polarimetric imagers enable investigations of ices in atmospheres, rings, and satellite surfaces. Acoustooptic tunable filters (AOTFs) specifically enable rapid, high signal-to-noise simultaneous acquisition of orthogonally polarized images in arbitrary spectral bands. Spectral mappers enable the assessment of trace gases within planetary atmospheres. Specifically, digital array scanned interferometers (DASIs) address desired high and low resolution, wide spectral band observations at high throughput, efficiency, and spectral fidelity. AOTFs and DASIs are compact, no moving parts, electronically spectrally adaptive instruments well suited for analyses of material within the saturnian system.
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