bluuebunny/crossref_metadata_2025 huggingface dataset:
Organic matter in the Solar System: From colors to spectral bands
Authors: Cruikshank Dale P.
Published: October 2008

The reflected spectral energy distribution of low-albedo, red-colored, airless bodies in the outer Solar System (planetary satellites, Centaur objects, Kuiper Belt objects, bare comet nuclei) can be modeled with spectral models that incorporate the optical properties of refractory complex organic materials synthesized in the laboratory and called tholins. These materials are strongly colored and impart their color properties to the models. The colors of the bodies cannot be matched with plausible minerals, ices, or metals. Iapetus, a satellite of Saturn, is one such red-colored body that is well matched with tholin-rich models. Detection of aromatic and aliphatic hydrocarbons on Iapetus by the Cassini spacecraft, and the presence of these hydrocarbons in the tholins, is taken as evidence for the widespread presence of solid organic complexes aromatic and aliphatic units on many bodies in the outer Solar System. These organic complexes may be compositionally similar to the insoluble organic matter in some classes of the carbonaceous meteorites, and thus may ultimately derive from the organic matter in the interstellar medium.
Organics in the samples returned from comet 81P/Wild 2 by the Stardust Spacecraft
Authors: Sandford Scott A.
Published: October 2008

The Stardust Mission collected samples from Comet 81P/Wild 2 on 2 Jan 2004 and returned these samples to Earth on 15 Jan 2006. After recovery, a six month preliminary examination was done on a portion of the samples. Studies of the organics in the samples were made by the Organics Preliminary Examination Team (PET) - a worldwide group of over 55 scientists. This paper provides a brief overview of the findings of the Organics PET. Organics in the samples were studied using a multitude of analytical techniques including spatial determination of C and heteroatom elemental abundances (STXM), functional group identification (micro-FTIR/Raman, C,N,O-XANES), and specific molecular identification of certain classes of organics (HPLC-LIF, L2MS, TOF-SIMS). Analyses were also made of spacecraft components and environmental samples collected near the recovered returned capsule to assess contamination issues. The distribution of organics (abundance, functionality, and relative elemental abundances of C,N,O) is heterogeneous both within and between particles. They are an unequilibrated reservoir that experienced little parent body processing after incorporation into the comet. Some organics look like those seen in IDPs (and to a lesser extent, meteorites), while new aromatic-poor and highly labile organics, not seen in meteoritic materials, are also present. The organics are O,N-rich compared to meteoritic organics. Some of the organics have an interstellar heritage, as evidenced by D and15N enrichments.
Chemical diversity of organic volatiles among comets: An emerging taxonomy and implications for processes in the proto-planetary disk
Authors: Mumma Michael J.
Published: October 2008

As messengers from the early Solar System, comets contain key information from the time of planet formation and even earlier – some may contain material formed in our natal interstellar cloud. Along with water, the cometary nucleus contains ices of natural gases (CH4, C2H6), alcohols (CH3OH), acids (HCOOH), embalming fluid (H2CO), and even anti-freeze (ethylene glycol). Comets today contain some ices that vaporize at temperatures near absolute zero (CO, CH4), demonstrating that their compositions remain largely unchanged after 4.5 billion years. By comparing their chemical diversity, several distinct cometary classes have been identified but their specific relation to chemical gradients in the proto-planetary disk remains murky. How does the compositional diversity of comets relate to nebular processes such as chemical processing, radial migration, and dynamical scattering? No current reservoir holds a unique class, but their fractional abundance can test emerging dynamical models for origins of the scattered Kuiper disk, the Oort cloud, and the (proposed) main-belt comets. I will provide a simplified overview emphasizing what we are learning, current issues, and their relevance to the subject of this Symposium.
Predominantly left-handed circular polarization in comets: Does it indicate L-enantiomeric excess in cometary organics?
Authors: Rosenbush V. , Kiselev N. , Kolokolova L.
Published: October 2008

Polarimetric observations demonstrated that all comets with significant values of circular polarization show predominantly left–handed circularly polarized light. We discuss the presence of homochiral organics in cometary materials as a source of the observed circular polarization. We have studied the effect of chirality on light–scattering properties of cometary dust considering particles that possess optical activity. Our investigations show that the cometary dust may include optically active materials which can be prebiological homochiral organics.
Solid organics in cometary comae
Authors: Tozzi Gian Paolo , Kolokolova Ludmilla
Published: October 2008

It is known since long ago that in comets a large quantity of organic matter exists in form of grains or is embedded in silicate grains. This was detected in situ by cometary space missions as well as inferred as a distributed source of some molecules observed in comets. Since organic matter is rather volatile, finding slow sublimating grains in comets can be good evidence of organics as a constituent of such grains. Here we describe a method to detect sublimating grains in comets. It consists of specific observations, specific data analysis, and some light-scattering modeling. We detect sublimating grains by measuring the quantity of grains as a function of the nucleocentric distance. Once detected, it is possible to get their photometric characteristics and compare them with the results of light-scattering modeling. The method has been applied to several comets. Sublimating grains were reliably identified for two of them.
Organics in cometary and interplanetary dust
Authors: Levasseur-Regourd A. Chantal , Lasue Jeremie
Published: October 2008

While gaseous carbon-rich species in cometary comae (coming from the nuclei icy component) are extensively studied by spectroscopic remote observations, so-called CHONs dust particles, i. e. organic compounds coming from the nuclei refractory component, have mostly been studied by dust mass spectrometers flying through the comae of comets 1P/Halley and 81P/Wild 2. However, remote observations of the light scattered by dust in cometary comae and in the interplanetary medium, coupled with both numerical and experimental simulations, have recently allowed us to confirm that such particles harbor a significant fraction of absorbing material, presumably consisting of organic compounds (Levasseur-Regourd et al. PSS 2007, Lasue et al. A&A 2007).

We estimate the fraction of absorbing material present in cometary dust for extensively observed comets (e.g., 1P/Halley, C/1995 O1 Hale-Bopp) and in the interplanetary dust (from zodiacal light observations). We also establish that, besides compact particles, fluffy aggregates are definitely present in these media. The properties (e.g., size distribution, morphology, composition) of the cometary and interplanetary dust particles, as inferred from light scattering data analysis, are compared with those of the IDPS collected in the upper Earth atmosphere and of the unique samples returned by the Stardust mission at Wild 2. The results are discussed in terms of the formation of comets in the protosolar nebula, and of the possible survival, at the epoch of late early bombardment, of cometary organics embedded in fluffy aggregates.
Organic molecules in saturnian E-ring particles. Probing subsurface oceans of Enceladus?
Authors: Postberg Frank , Kempf S. , Srama R. , Grün E. , Hillier J. K. , Green S. F. , McBride N.
Published: October 2008

The population of Saturn's outermost tenuous E-ring is dominated by tiny water ice particles, some of which contain organic or mineral impurities. Active cryo-volcanism on the moon Enceladus, embedded in the E-ring, has been known to be a major source of particles replenishing the ring since late 2005. Therefore, particles in the vicinity of Enceladus provide crucial information about the dynamic and chemical processes occurring far below the moon's icy surface.

We present a compositional analysis of thousands of impact ionisation mass spectra of Saturn's E-ring particles, with sizes predominantly below 1 μm, detected by the Cosmic Dust Analyser onboard the Cassini spacecraft. Our findings imply that organic compounds are a significant component of icy particles ejected by Enceladus plumes. Our in situ measurements are supported by detections of other Cassini instruments. They hint at a dynamic interaction of a hot rocky core with liquid water below the icy surface, where the organic molecules are generated. Further insights are expected from two close Enceladus flybys to be performed by Cassini in 2008. Then, for the first time, we will obtain spectra of freshly ejected particles at the traversals through the cryo-volcanic plumes.
The composition of Europa's near-surface atmosphere
Authors: Wong Mau C. , Cassidy Tim , Johnson Robert E.
Published: October 2008

The presence of an undersurface ocean renders Europa as one of the few planetary bodies in our Solar System that has been conjectured to have possibly harbored life. Some of the organic and inorganic species present in the ocean underneath are expected to transport upwards through the relatively thin ice crust and manifest themselves as impurities of the water ice surface. For this reason, together with its unique dynamic atmosphere and geological features, Europa has attracted strong scientific interests in past decades.

Europa is imbedded inside the Jovian magnetosphere, and, therefore, is constantly subjected to the immerse surrounding radiations, similar to the other three Galilean satellites. The magnetosphere-atmosphere-surface interactions form a complex system that provides a multitude of interesting geophysical phenomenon that is unique in the Solar System. The atmosphere of Europa is thought to have created by, mostly, charged particles sputtering of surface materials. Consequently, the study of Europa's atmosphere can be used as a tool to infer the surface composition. In this paper, we will discuss our recent model studies of Europa's near-surface atmosphere. In particular, the abundances and distributions of the dominant O2 and H2O species, and of other organic and inorganic minor species will be addressed.
Titan's surface inventory of organic materials estimated from Cassini RADAR observations
Authors: Lorenz Ralph D.
Published: October 2008

Cassini RADAR observations now permit an initial assessment of the inventory of two classes, presumed to be organic, of Titan surface materials: polar lake liquids and equatorial dune sands. Several hundred lakes or seas have been observed, of which dozens are each estimated to contain more hydrocarbon liquid than the entire known oil and gas reserves on Earth. Dark dunes cover some 20% of Titan's surface, and comprise a volume of material several hundred times larger than Earth's coal reserves. Overall, however, the identified surface inventories (> 3 × 104 km3 of liquid, and >2 × 105 km3 of dune sands) are small compared with estimated photochemical production on Titan over the age of the Solar System. The sand volume is too large to be accounted for simply by erosion in observed river channels or ejecta from observed impact craters. The lakes are adequate in extent to buffer atmospheric methane against photolysis in the short term, but do not contain enough methane to sustain the atmosphere over geologic time. Thus, unless frequent resupply from the interior buffers this greenhouse gas at exactly the right rate, dramatic climate change on Titan is likely in its past, present and future.
Structural, chemical and isotopic examinations of interstellar organic matter extracted from meteorites and interstellar dust particles
Authors: Busemann Henner , Alexander Conel M. O'D. , Nittler Larry R. , Stroud Rhonda M. , Zega Tom J. , Cody George D. , Yabuta Hikaru , Kilcoyne A.L. David
Published: October 2008

Meteorites and Interplanetary Dust Particles (IDPs) are supposed to originate from asteroids and comets, sampling the most primitive bodies in the Solar System. They contain abundant carbonaceous material. Some of this, mostly insoluble organic matter (IOM), likely originated in the protosolar molecular cloud, based on spectral properties and H and N isotope characteristics. Together with cometary material returned with the Stardust mission, these samples provide a benchmark for models aiming to understand organic chemistry in the interstellar medium, as well as for mechanisms that secured the survival of these fragile molecules during Solar System formation. The carrier molecules of the isotope anomalies are largely unknown, although amorphous carbonaceous spheres, so-called nanoglobules, have been identified as carriers. We are using Secondary Ion Mass Spectrometry to identify isotopically anomalous material in meteoritic IOM and IDPs at a ~100-200 nm scale. Organics of most likely interstellar origin are then extracted with the Focused-Ion-Beam technique and prepared for synchrotron X-ray and Transmission Electron Microscopy. These experiments yield information on the character of the H- and N-bearing interstellar molecules: While the association of H and N isotope anomalies with nanoglobules could be confirmed, we have also identified amorphous, micron-sized monolithic grains. D-enrichments in meteoritic IOM appear not to be systematically associated with any specific functional groups, whereas 15N-rich material can be related to imine and nitrile functionality. The large 15N- enrichments observed here (δ15N > 1000 ‰) cannot be reconciled with models using interstellar ammonia ice reactions, and hence, provide new constraints for understanding the chemistry in cold interstellar clouds.
Presolar grains in the Solar System: Connections to stellar and interstellar organics
Authors: Nittler Larry R.
Published: October 2008

A small fraction of primitive meteorites and interplanetary dust particles (IDPs) consists of grains of presolar stardust. These grains have extremely unusual isotopic compositions, relative to all other planetary materials, indicating that they condensed in the outflows and explosions of prior generations of stars (Clayton & Nittler 2004). Identified presolar grain types include silicate, oxide and carbonaceous phases. The latter include graphitic carbon, diamond and SiC. Although many of these phases do not have a direct connection to organic chemistry, this is not true of the graphitic spherules. Many of these, with isotopic compositions indicating an origin in C-rich asymptotic giant branch (AGB) star outflows, have a structure consisting of naonocrystalline cores surrounded by well-graphitized C (Bernatowicz et al. 1996). The cores include isotopically anomalous polycyclic aromatic hydrocarbons (Messenger et al. 1998) and represent a link between molecular chemistry and dust condensation in stellar outflows. Meteorites and IDPs also contain abundant isotopically anomalous organic matter, including distinct organic grains, some of which probably formed in stellar outflows and/or the interstellar medium (ISM) (Busemann et al. 2006, Floss et al. 2004). In some IDPs, deuterium- and 15N-enriched organic matter is closely associated with presolar silicate grains (Messenger et al. 2005, Nguyen et al. 2007), suggesting an association in the ISM prior to Solar System formation.
Formation of biomolecule precursors in space?
Authors: Geppert Wolf D. , Vigren Erik , Hamberg Mathias , Zhaunerchyk Vitali , Kaminska Magdalena , Thomas Richard D. , Österdahl Fabian , Hellberg Fredrik , Ehlerding Anneli , Danielsson Mathias , Larsson Mats
Published: October 2008

The possibility of an extraterrestrial origin of biomolecule building blocks has been a subject of intense discussions for many years. The detection of amino acids in meteorites opens the possibility of a delivery of biomolecules synthesized in the interstellar medium or star-forming regions to the primeval Earth. Whereas it can be doubted if more complex species like amino acids can survive the strong UV radiation in the early Solar System, this does not necessary hold for more primitive precursor molecules like nitriles. These compounds can also be synthesized very efficiently in methane-nitrogen dominated atmospheres like the one present on Titan and the early ages of Earth. This Contribution focuses on the formation and degradation processes of nitriles in interstellar clouds and planetary atmospheres and on their possible role in the generation of biomolecules.
PAHs in Astronomy - A Review
Authors: Salama Farid
Published: October 2008

Carbonaceous materials play an important role in space. Polycyclic Aromatic Hydrocarbons (PAHs) are a ubiquitous component of organic matter in space. Their contribution is invoked in a broad spectrum of astronomical observations that range from the ultraviolet to the far-infrared and cover a wide variety of objects and environments from meteorites and interplanetary dust particles to outer Solar System bodies to the interstellar medium in the local Milky Way and in other galaxies. Extensive efforts have been devoted in the past two decades to experimental, theoretical, and observational studies of PAHs. A brief review is given here of the evidence obtained so far for the contribution of PAHs to the phenomena aforementioned. An attempt is made to distinguish the cases where solid evidence is available from cases where reasonable assumptions can be made to the cases where the presence - or the absence - of PAHs is purely speculative at this point.
Photoproduction of H3+ from gaseous methanol inside dense molecular clouds
Authors: Pilling S. , Andrade D. P. P. , Santos A. C. F. , Boechat-Roberty H. M.
Published: October 2008

We present experimental results obtained from photoionization and photodissociation processes of abundant interstellar methanol (CH3OH) as an alternative route for the production of H3+ in dense clouds. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS) employing soft X-ray and time-of-flight mass spectrometry. Mass spectra were obtained using the photoelectron-photoion coincidence techniques. Absolute averaged cross sections for the production of H3+ due to molecular dissociation of methanol by soft X-rays (C1s edge) were determined. The H3+'s photoproduction rate and column density were been estimated adopting a typical soft X-ray luminosity inside dense molecular and the observed column density of methanol. Assuming a steady state scenario, the highest column density value for the photoproduced H3+ was about 1011 cm2, which gives the ratio photoproduced/observed of about 0.05%, as in the case of dense molecular cloud AFGL 2591. Despite the small value, this represent a new and alternative source of H3+ into dense molecular clouds and it is not been considered as yet in interstellar chemistry models.
Simulation of organic interstellar dust in the laboratory
Authors: Duley Walt W.
Published: October 2008

New techniques for the generation and analysis of carbon nanoparticles (CNPs) have been developed and have resulted in the production of CNP samples whose infrared spectral properties are essentially identical to those observed in interstellar absorption and emission. These particles are of mixed aromatic/aliphatic composition. Spectra of CNPs containing 102–104atoms will be discussed in relation to spectra of interstellar materials. We find that infrared line widths in these samples are typically 10–30 cm−1, but can be as small as 2 cm−1. Simulation of the 3.28 μm feature is shown to yield important new insight into the nature of interstellar CNPs.
Laboratory analogues of hydrocarbonated interstellar nanograins
Authors: Pino T. , Cao A. T. , Carpentier Y. , Dartois E. , d'Hendecourt L. , Bréchignac Ph.
Published: October 2008

Carbonaceous extraterrestrial matter is observed in a wide variety of astrophysical environments. The spectroscopic signatures revealed a large variety of chemical structure illustrating the rich carbon chemistry that occurs in space. In order to produce laboratory analogues of carbonaceous cosmic dust, a new chemical reactor has been built in the Laboratoire de Photophysique Moléculaire. It is a low pressure flat burner providing flames of premixed hydrocarbon / oxygen gas mixtures, closely following the model system used by the combustion community. In such a device the flame is a one-dimensional chemical reactor that offers a broad range of combustion conditions and sampling which allows production of many and various by-products. In the present work, we have studied: i) the infrared transmission spectra of thin film deposit samples whose nature ranges from strongly aromatic to strongly aliphatic materials; ii) the resonant two-photon photoionisation spectra of gas phase PAHs formed in the flame.
A self-perpetuating catalyst for the production of complex organic molecules in protostellar nebulae
Authors: Nuth Joseph A. , Johnson Natasha M. , Manning Steven
Published: October 2008

When hydrogen, nitrogen and CO are exposed to amorphous iron silicate surfaces at temperatures between 500–900 K a carbonaceous coating forms via Fischer-Tropsch type reactions. Under normal circumstances such a coating would impede or stop further reaction. However, we find that this coating is a better catalyst than the amorphous iron silicates that initiate these reactions. Formation of a self-perpetuating catalytic coating on grain surfaces could explain the rich deposits of macromolecular carbon found in primitive meteorites and would imply that protostellar nebulae should be rich in organic material.
Tholins and their relevance for astrophysical issues
Authors: Quirico E. , Szopa C. , Cernogora G. , Lees V. , Derenne S. , McMillan P. F. , Montagnac G. , Reynard B. , Rouzaud J-N , Fray N. , Coll P. , Raulin F. , Schmitt B. , Minard B.
Published: October 2008

Tholins are polymeric hydrogenated carbon nitrides formed from N2:CH4 mixtures exposed to electrical discharges. They are complex disordered solids, and their structural chemistry and formation processes are not yet fully understood. Tholins have been widely adopted as useful analogs of reddish organic solids associated with planetary bodies or in interstellar space (e.g., Titan's aerosols, reddish surfaces of outer objects, interstellar organics, etc.) for fitting astronomical observations. However, there has been little evidence to date that they in fact constitute pertinent model materials, i. e. with chemical structure/composition similar to those presumed to be present in planetary or interstellar organic solids. In this contribution, we first review recent advances made regarding the determination of composition and structure of tholins produced in the laboratory. They point to a high chemical selectivity in the range of functional groups present, the control of unsaturation by nitrogen, and the highly disordered character of the structures. In a second section, we discuss the relationship between chemistry and the optical properties of tholins, and we point out the lack of a unique relationship between the shape and strength of the visible absorption bands and the chemical composition or structure of the model tholins. The tholins exhibit similarities with HCN “polymers”, that are suspected to be present in cometary refractory dust. This points to the existence of possible similar polymerisation processes, and it suggests they could also be used as analogs of N-rich cometary organics. Laboratory-based studies of cometary dust might offer new insights on the “chemical relevancy” of tholins, as combined micro-analytical techniques will allow direct comparison of chemical information between the materials produced. In a third section we present recent results pertaining to the search for such compounds in cometary grains (Stardust grains, interplanetary dust particles - IDPs). We show that some N-rich spots in stratospheric IDPs are rich in cyanide species, but no tholin-like compounds or polymeric HCN have been detected to date.
Quenched carbonaceous composite (QCC) as a carrier of the extended red emission and blue luminescence in the red rectangle
Authors: Wada S. , Mizutani Y. , Narisawa T. , Tokunaga A. T.
Published: October 2008

Filmy-QCC is an organic material synthesized in the laboratory, and it exhibits red photoluminescence (PL). The peak wavelength of the PL ranges from 650 to 690 nm, depending on the mass distribution of polycyclic aromatic hydrocarbon (PAH) molecules, and the emission profile is a good match for that of the extended red emission in the Red Rectangle nebula. The quantum yield of the PL ranges from 0.009 to 0.04. When filmy-QCC is dissolved in cyclohexane, it exhibits blue PL in the wavelength range of 400–500 nm with a quantum yield of 0.12–0.16. The large width of the red PL and the large wavelength difference between the PL of the filmy-QCC as a solid film and in a solution indicate that there is a strong interaction between the components of filmy-QCC. The major components of filmy-QCC are PAHs up to 500 atomic mass units. Our laboratory data suggest that the blue luminescence observed in the Red Rectangle nebula is probably caused by small PAHs in a gaseous state, and the extended red emission is caused by larger PAHs in dust grains.
Laboratory analogs of carbonaceous matter: Soot and its precursors and by-products
Authors: Jäger Cornelia , Mutschke Harald , Llamas-Jansa Isabel , Henning Thomas , Huisken Friedrich
Published: October 2008

Carbonaceous materials have been prepared in the laboratory by laser-induced pyrolysis of a mixture of hydrocarbons under different conditions and laser ablation of graphite in reactive gas atmospheres. We have investigated the soluble and insoluble parts of the condensed carbon powders with several spectroscopic and chromatographic methods in order to obtain information on the composition of the condensate. The results of these experiments have demonstrated that, at temperatures lower than 1700 K, the pyrolysis by-products are mainly PAHs, whereas at higher temperatures fullerenes and polyyne-based compounds are formed. The experimental findings point to different soot formation mechanisms with variable intermediates and end products. It has been found that soot extracts can contain more than 65 different polycyclic aromatic hydrocarbons (PAHs). Eventually, the study of the condensation pathways of soot particles and their precursors and by-products will permit the prediction of the spectral properties of carbonaceous matter in space.
Ion irradiation effects on sooting flames by-products
Authors: Brunetto R. , Pino T. , Dartois E. , Cao A. T. , d'Hendecourt L. , Strazzulla G. , Bréchignac Ph.
Published: October 2008

Carbonaceous extraterrestrial matter is observed in a wide variety of astrophysical environments. Spectroscopic signatures reveal a large variety of chemical structure illustrating the rich carbon chemistry that occurs in space. In order to produce laboratory analogues of the carbonaceous cosmic dust, a new chemical reactor has been built in the Laboratoire de Photophysique Moléculaire. It is a low pressure flat burner providing flames of premixed hydrocarbon/oxygen gas mixtures, closely following the model system used by the combustion community. In such a device the flame is a one-dimensional chemical reactor offering a broad range of combustion conditions and sampling which allows production of many and various by-products. In the present work, we have studied the effect of ion irradiation (200-400 keV), at the Laboratorio di Astrofisica Sperimentale in Catania, on several samples, ranging from strongly aromatic to strongly aliphatic materials. Infrared and Raman spectra were monitored to follow the evolution of the films under study, and characterize the irradiation process-induced modifications.
Irradiation of mixed ices as a laboratory cometary model
Authors: Colin-Garcia Maria , Negrón-Mendoza Alicia , Ramos-Bernal Sergio , Chacon Elizabeth
Published: October 2008

Icy bodies in space are being irradiated continuously by ionizing radiation. Therefore, the transformation of organic molecules trapped in extraterrestrial ices might have been possible. This work studied a bulk irradiation of a mixture of some constituents of cometary nuclei. The results show that the formation of different compounds, among them ammonia, carbon dioxide, amines, ureas, free amino acids, and oligomeric material, yields carboxylic acids, amino acids, and purines upon hydrolysis.
Photodesorption of ices – Releasing organic precursors into the gas phase
Authors: Öberg Karin I. , van Dishoeck Ewine F. , Linnartz Harold
Published: October 2008

A long-standing problem in interstellar chemistry is how molecules can be maintained in the gas phase at the extremely low temperatures in space. Photodesorption has been suggested to explain the observed cold gas in cloud cores and disk mid-planes. We are studying the UV photodesorption of ices experimentally under ultra high vacuum and at astrochemically relevant temperatures (15 – 27 K) using a hydrogen discharge lamp (7-10.5 eV). The ice desorption during irradiation is monitored using reflection absorption infrared spectroscopy and the desorbed species using mass spectrometry. We find that both the UV photodesorption rates and mechanisms are highly molecule specific. CO photodesorbs without dissocation from the surface layer of the ice. N2, which lacks dipole allowed electronic transitions in the range of the lamp, does not photodesorb. CO2 desorbs through dissociation and subsequent recombination from the top few layers of the ice. At low temperatures (15 – 18 K) the derived photodesorption rates are ~ 10−3 for CO and CO2 and < 2 × 10−4 for N2 ice per incident photon.
Electron, proton and ion induced molecular synthesis and VUV spectroscopy of interstellar molecules in the ice phase
Authors: Sivaraman Bhalamurugan , Jheeta Sohan , Mason Nigel , Hunniford Adam , Merrigan Tony , McCullough Bob , Fulvio Daniele , Palumbo Maria Elisabetta , Moore Marla
Published: October 2008

Planets and their moons are constantly subjected to irradiation from both their respective planetary magnetospheres and the solar wind. Energetic particles (electrons, protons and ions) in such radiation may induce complex chemistry within the icy mantles of such bodies, producing many organic compounds. Such processes can be simulated in laboratory experiments. In this report we present recent results from experiments exploring both molecular synthesis and the morphology of such ices.

The morphology of any ice may be characterised by IR and Vacuum Ultra-Violet (VUV) spectroscopy. The latter is particularly useful for studying ices in which infrared inactive molecules like oxygen (O2) are common. We have shown that oxygen forms dimers in typical planetary ices and that, in contrast to previous analysis, many of the chemical reactions within the ice involve such dimer (and larger cluster) chemistry. We also present the results of a series of experiments that explore electron, proton and ion irradiation on Solar System relevant ices such as carbon dioxide (CO2) at different temperatures. Infrared spectra recorded before and after irradiation are used to identify and quantify molecules formed in such irradiation, e. g. ozone. These experiments show that the morphology of the ice plays a critical role in the chemistry.
Hydrogen cyanide polymers connect cosmochemistry and biochemistry
Authors: Matthews Clifford N. , Minard Robert D.
Published: October 2008

To understand the origin of protein/nucleic acid based life as we know it on Earth, we must “follow” the nitrogen. Because of its unique hydrogen bonding characteristics, nitrogen is the key element in catalytic and/or informational proteins and nucleic acids essential to cell function and reproduction. We present evidence that HCN is the original source of prebiotic protein and nucleobase nitrogen. We also present chemically rational models supporting the radical hypothesis that the polymerization of HCN yields ab initio mundi prebiotic protein and polynucleobase macromolecules of sufficient size and complexity to allow the spontaneous generation of pre-RNA World biopolymers capable of catalysis and information transfer.
Laboratory simulation of the evolution of organic matter in dense interstellar clouds
Authors: Mennella Vito
Published: October 2008

Laboratory simulation of interstellar grain processing is a unique tool to better understand the nature and evolution of cosmic dust. In recent years this approach has been crucial to outline a new model of evolution of the aliphatic component of organic matter in the interstellar medium. Here, the results of a recent laboratory research on processing of nano-sized carbon particles by H atoms under simulated dense medium conditions are discussed. The experiments show that the formation of C-H bonds in the aliphatic CH2 and CH3 functional groups does not take place, while the activation of a band at 3.47 μm, due to the C-H stretching vibration of tertiary sp3 carbon atoms, is observed. These results indicate that the assumption about inhibition of aliphatic C-H bond formation in interstellar dense clouds is correct. Moreover, they suggest that carbon grains responsible for the interstellar aliphatic band at 3.4 μm in diffuse regions can contribute to the absorption observed at 3.47 μm in dense clouds.
PP - Organic synthesis of uracil from interstellar organic molecules
Authors: Prieto Jorge Enrique Bueno
Published: October 2008

It is important to say that the formaldehyde and hydrogen cyanide have been detected in the interstellar medium through resonance spectrum emission. Here I describe a way to produce uracil in interstellar space.
BANQUET SPEECH Full Circle: Star Ferry to Stardust
Authors: Matthews Clifford N.
Published: October 2008

Good evening. I'd like to invite you to join me on a journey that could be entitled “Full Circle: Star Ferry to Stardust”. “Star Ferry” represents Hong Kong, my home town, and especially its university - Hong Kong University - as I knew it during the years of World War II. “Stardust” refers to our gathering here to report on our research on possible organic chemistry in space.
Quantitative analysis of snoRNA association with pre‐ribosomes and release of snR30 by Rok1 helicase
Authors: Bohnsack Markus T , Kos Martin , Tollervey David
Published: October 2008

In yeast, three small nucleolar RNAs (snoRNAs) are essential for the processing of pre‐ribosomal RNA—U3, U14 and snR30—whereas 72 non‐essential snoRNAs direct site‐specific modification of pre‐rRNA. We applied a quantitative screen for alterations in the pre‐ribosome association to all 75 yeast snoRNAs in strains depleted of eight putative helicases implicated in 40S subunit synthesis. For the modification‐guide snoRNAs, we found no clear evidence for the involvement of these helicases in the association or dissociation of pre‐ribosomes. However, the DEAD box helicase Rok1 was required specifically for the release of snR30. Point mutations in motif I, but not in motif III, of the helicase domain of Rok1 impaired the release of snR30, but this was less marked than in strains depleted of Rok1, and resulted in a dominant‐negative growth phenotype. Dissociation of U3 and U14 from pre‐ribosomes is also dependent on helicases, suggesting that release of the essential snoRNAs might differ mechanistically from release of the modification‐guide snoRNAs.
Structural and functional analysis of SGT1–HSP90 core complex required for innate immunity in plants
Authors: Kadota Yasuhiro , Amigues Beatrice , Ducassou Lionel , Madaoui Hocine , Ochsenbein Francoise , Guerois Raphaël , Shirasu Ken
Published: October 2008

SGT1 (Suppressor of G2 allele of skp1), a co‐chaperone of HSP90 (Heat‐shock protein 90), is required for innate immunity in plants and animals. Unveiling the cross talks between SGT1 and other co‐chaperones such as p23, AHA1 (Activator of HSP90 ATPase 1) or RAR1 (Required for Mla12 resistance) is an important step towards understanding the HSP90 machinery. Nuclear magnetic resonance spectroscopy and mutational analyses of HSP90 revealed the nature of its binding with the CS domain of SGT1. Although CS is structurally similar to p23, these domains were found to non‐competitively bind to various regions of HSP90; yet, unexpectedly, full‐length SGT1 could displace p23 from HSP90. RAR1 partly shares the same binding site with HSP90 as the CS domain, whereas AHA1 does not. This analysis allowed us to build a structural model of the HSP90–SGT1 complex and to obtain a compensatory mutant pair between both partners that is able to restore virus resistance in vivo through Rx (Resistance to potato virus X) immune sensor stabilization.
Structure of the intracellular domain of the amyloid precursor protein in complex with Fe65‐PTB2
Authors: Radzimanowski Jens , Simon Bernd , Sattler Michael , Beyreuther Konrad , Sinning Irmgard , Wild Klemens
Published: October 2008

Cleavage of the amyloid precursor protein (APP) is a crucial event in Alzheimer disease pathogenesis that creates the amyloid‐β peptide (Aβ) and liberates the carboxy‐terminal APP intracellular domain (AICD) into the cytosol. The interaction of the APP C terminus with the adaptor protein Fe65 mediates APP trafficking and signalling, and is thought to regulate APP processing and Aβ generation. We determined the crystal structure of the AICD in complex with the C‐terminal phosphotyrosine‐binding (PTB) domain of Fe65. The unique interface involves the NPxY PTB‐binding motif and two α helices. The amino‐terminal helix of the AICD is capped by threonine T668, an Alzheimer disease‐relevant phosphorylation site involved in Fe65‐binding regulation. The structure together with mutational studies, isothermal titration calorimetry and nuclear magnetic resonance experiments sets the stage for understanding T668 phosphorylation‐dependent complex regulation at a molecular level. A molecular switch model is proposed.
Modulation of auditory responses by modality-specific attention in rat primary auditory cortex
Authors: Tai Lung-Hao , Zador Anthony
Published: October 2008

How does attention modulate sensory representations? In order to probe the underlying neural mechanisms, we established a simple rodent model of modality-specific attention. Here we describe results of experiments in freely moving rats in which we have used tetrodes to record neural responses in primary auditory cortex (area A1) while subjects performed this behavior.Subjects were first trained to perform distinct auditory and olfactory two alternative forced-choice (2AFC) tasks. Training and testing were conducted in a custom three-poke computer-controlled behavioral apparatus. Subjects initiated trials with a center-poke, which triggered presentation of a tone (either 5 or 15 Hz), an odor (either R(-)-2-Octanol or S(+)-2-Octanol), or both. Subjects responded moving to the left or right poke. Correct responses were rewarded with water. Auditory and olfactory blocks (of 50 trials each) were interleaved in a single session. In auditory blocks, pure tones were either presented with or without a null odor (caproic acid, n=2 and 3 respectively), and subjects were cued to perform the task based on auditory stimuli. In olfactory blocks, both odors and pure tones were presented simultaneously, and subjects were cued to perform the task based on olfactory stimuli.After subjects reached consistent performance on the interleaved blocks, tetrode drives were implanted in primary auditory cortex of the left hemisphere. Single unit responses to tones were heterogeneous, and included transient, sustained, and suppressed. Among 304 responsive units recorded, 19% (58 units) showed modality-specific attentional modulation of at least one of the tone-evoked responses; in most cases, the responses to a particular auditory stimulus was enhanced in the auditory block (or, equivalently, suppressed in the olfactory block). In addition, we also observed modality-specific attentional modulation of the spontaneous activity in similar proportion of units (61 units). Our results suggest that shifting attention from audition to olfaction and back can modulate the activity of single neurons in primary auditory cortex.
Angle Alignment Evokes Perceived Depth and Illusory Surfaces
Authors: Shapley Robert , Maertens Marianne
Published: October 2008

There is a distinct visual process that triggers the perception of illusory surfaces and contours along the intersections of aligned, zigzag line patterns. Such illusory contours and surfaces are qualitatively different from illusory contours of the Kanizsa type. The illusory contours and surfaces in this case are not the product of occlusion and do not imply occlusion of one surface by another. Rather, the aligned angles in the patterns are combined by the visual system into the perception of a fold or a 3-D corner, as of stairs on a staircase or a wall ending on a floor. The depth impression is ambiguous and reversible like the Necker cube. Such patterns were used by American Indian artists of the Akimel O'odham (Pima) tribe in basketry, and also by modern European and American artists like Josef Albers, Bridget Riley, Victor Vasarely, and Frank Stella. Our research aims to find out what manipulations of the visual image affect perceived depth in such patterns in order to learn about the perceptual mechanisms. Using paired comparisons, we find that human observers perceive depth in such patterns if, and only if, lines in adjacent regions of the patterns join to form angles, and also if, and only if, the angles are aligned precisely to be consistent with a fold or 3-D corner. The amount of perceived depth is graded, depending on the steepness and the density of angles in the aligned-angle pattern. The required precision of the alignment implies that early retinotopic visual cortical areas may be involved in this perceptual behavior, but the linkage of form with perceived depth suggests involvement of higher cortical areas as well.
Highly efficient retinal metabolism in cones
Authors: Miyazono Sadaharu , Shimauchi-Matsukawa Yoshie , Tachibanaki Shuji , Kawamura Satoru
Published: October 2008

After bleaching of visual pigment in vertebrate photoreceptors,all-transretinal is reduced toall-transretinol by retinol dehydrogenases (RDHs). We investigated this reaction in purified carp rods and cones, and we found that the reducing activity towardall-transretinal in the outer segment (OS) of cones is >30 times higher than that of rods. The high activity of RDHs was attributed to high content of RDH8 in cones. In the inner segment (IS) in both rods and cones, RDH8L2 and RDH13 were found to be the major enzymes among RDH family proteins. We further found a previously undescribed and effective pathway to convert 11-cisretinol to 11-cisretinal in cones: this oxidative conversion did not require NADP+and instead was coupled with reduction ofall-transretinal toall-transretinol. The activity was >50 times effective than the oxidizing activity of RDHs that require NADP+. These highly effective reactions of removal ofall-transretinal by RDH8 and production of 11-cisretinal by the coupling reaction are probably the underlying mechanisms that ensure effective visual pigment regeneration in cones that function under much brighter light conditions than rods.
Interplay of β2* nicotinic receptors and dopamine pathways in the control of spontaneous locomotion
Authors: Avale Maria Elena , Faure Philippe , Pons Stéphanie , Robledo Patricia , Deltheil Thierry , David Denis J. , Gardier Alain M. , Maldonado Rafael , Granon Sylvie , Changeux Jean-Pierre , Maskos Uwe
Published: October 2008

Acetylcholine (ACh) is a known modulator of the activity of dopaminergic (DAergic) neurons through the stimulation of nicotinic ACh receptors (nAChRs). Yet, the subunit composition and specific location of nAChRs involved in DA-mediated locomotion remain to be established
in vivo
. Mice lacking the β2 subunit of nAChRs (β2KO) display striking hyperactivity in the open field, which suggests an imbalance in DA neurotransmission. Here, we performed the selective gene rescue of functional β2*-nAChRs in either the substantia nigra pars compacta (SNpc) or the ventral tegmental area (VTA) of β2KO mice. SNpc rescued mice displayed normalization of locomotor activity, both in familiar and unfamiliar environments, whereas restoration in the VTA only rescued exploratory behavior. These data demonstrate the dissociation between nigrostriatal and mesolimbic β2*-nAChRs in regulating unique locomotor functions. In addition, the site-directed knock-down of the β2 subunit in the SNpc by RNA interference caused hyperactivity in wild-type mice. These findings highlight the crucial interplay of nAChRs over the DA control of spontaneous locomotion.
mda
-9/Syntenin promotes metastasis in human melanoma cells by activating c-Src
Authors: Boukerche Habib , Su Zao-zhong , Prévot Célia , Sarkar Devanand , Fisher Paul B.
Published: October 2008

The scaffold PDZ-domain containing protein
mda
-9/syntenin functions as a positive regulator of cancer cell progression in human melanoma and other tumors.
mda
-9/Syntenin regulates cell motility and invasion by altering defined biochemical and signaling pathways, including focal adhesion kinase (FAK), p38 mitogen-activated protein kinase (MAPK) and NF-κB, but precisely how
mda
-9/syntenin organizes these multiprotein signaling complexes is not well understood. Using a clinically relevant human melanoma model, we demonstrate that
mda
-9/syntenin physically interacts with c-Src and this communication correlates with an increase in FAK/c-Src complex formation and c-Src activation. Inhibiting
mda
-9/syntenin, using an adenovirus expressing antisense
mda
-9/syntenin or addition of c-Src siRNA, suppresses melanoma cell migration, anchorage-independent growth, and spontaneous tumor cell dissemination
in vivo
in a human melanoma animal metastasis model. These data are compatible with a model wherein interaction of MDA-9/syntenin with c-Src promotes the formation of an active FAK/c-Src signaling complex, leading to enhanced tumor cell invasion and metastatic spread. These provocative findings highlight
mda
-9/syntenin and its interacting partners as promising therapeutic targets for intervention of metastasis.
Functional capacities and sport‐specific skills of 14‐ to 15‐year‐old male basketball players: Size and maturity effects
Authors: Coelho E Silva Manuel J. , Figueiredo António J. , Moreira Carvalho Humberto , Malina Robert M.
Published: October 2008

The aim of the study was to estimate the influence of body size and pubertal status on variation in functional capacities and sport‐specific skills of 59 youth basketball players aged 14.0–15.9 years. Height and mass were measured and stage of pubic hair was assessed at clinical examination. Six tests of functional capacity were evaluated: squat jump, countermovement jump, 60‐s sit‐ups, 2‐kg standing medicine ball throw, hand grip strength, and 20‐m multi‐stage shuttle run. Four basketball skills were tested (shooting, passing, dribbling, and defensive movements). Comparisons between basketball players of different sexual maturity status were performed using analysis of covariance (controlling for chronological age). Functional capacities and basketball skills appeared to be largely independent of pubertal status especially after controlling for variation in body size. Results of multiple linear regressions indicated chronological age as a significant predictor for four items, while maturity status was a significant predictor for only one item. The influence of body mass was negative for two functional indicators (jumping, multi‐stage shuttle run) and two basketball skills (dribbling, defensive movements), but positive for two functional tests of upper body strength (hand grip, ball throw). Height was positively correlated with two specific skills (passing, defensive movements), while a combination of tallness and heaviness was associated with a disadvantage on three functional capacities and two sport‐specific skills.