bluuebunny/crossref_metadata_2025 huggingface dataset:
The origin and evolution of interstellar organics
Authors: Chiar Jean E. , Pendleton Yvonne J.
Published: October 2008

Over the last decade, we have made great strides in better understanding dust composition and evolution in dense clouds and the diffuse interstellar medium (ISM). Thanks to improvements in IR detector sensitivity on ground-based telescopes and the Spitzer Space Telescope mission, we are no longer limited to a handful of bright background stars in order to study dust composition in quiescent dense clouds and the diffuse ISM. More thorough sampling of lines of sight in these regions has highlighted the dichotomy of the nature and composition of dust in these environments. In addition, successes in recreating interstellar processes and dust-analogs in the laboratory have helped us to understand the differences in dust absorption features we observe in the ISM. In this article, we focus on the organic components of interstellar dust, reviewing past work and highlighting the most recent observations and laboratory experiments.
Dicarbon molecule in the interstellar clouds
Authors: Kaźmierczak Maja , Schmidt Mirosław , Krełowski Jacek
Published: October 2008

We present high-resolution and high signal-to-noise spectroscopic observations of interstellar molecular lines of C2 towards early-type stars. C2 is particularly interesting because it is the simplest multicarbon molecule and its abundances give information on the chemistry of interstellar clouds, especially on the pathway of formation of (hydro)carbon chains and PAHs which may be considered as possible carriers of diffuse interstellar bands (DIBs). Homonuclear diatomic molecules have negligible dipol moments and hence radiative cooling of excited rotational levels may go only trough the slow quadrupole transitions (van Dishoeck & Black 1982). In C2, pumped by galactic average interstellar field rotational levels are excited effectively much above the gas kinetic temperature and a rotational ladder of electronic transitions is usually observed from high rotational levels. Relations between abundances of the dicarbon and other simple interstellar molecules are considered as well.
Organic compounds as carriers of the diffuse interstellar bands
Authors: Sarre Peter J.
Published: October 2008

The diffuse interstellar bands appear as absorption features in spectra of reddened stars and lie mostly in the visible region of the spectrum. The first examples were recorded photographically nearly one hundred years ago and despite a huge amount of observational, theoretical and laboratory effort the spectra remain unassigned. Most researchers believe that organic material is responsible for the absorptions, the most popular form being polycyclic aromatic (hydro)carbon (PAH) structures. This article reviews briefly the main characteristics of the spectrum, describes some current research and outlines some lines of inquiry.
Observing ultraviolet signatures of interstellar organics with theHubble Space Telescope
Authors: Snow Theodore P.
Published: October 2008

TheCosmic Origins Spectrograph(COS) will be more sensitive for ultraviolet spectroscopy than either theGHRSor theSTIS, especially in the far UV where many absorption lines and bands formed by atoms and molecules have electronic transitions from the ground state. Here we outline our plans for using theCOSto observe interstellar gas and dust in the cold ISM, along with a report on the results of preliminary archivalHSTsearch for UV diffuse interstellar bands.
A study of 2175 Å absorption feature with TAUVEX: An Indo-Israeli UV mission
Authors: Muthumariappan C. , Maheswar G. , Eswaraiah C. , Pandey A. K.
Published: October 2008

TAUVEX is an Indo-Israeli collaborative mission to make photometric observations in the UV region. Using the narrowband filters positioned near 2175 Å feature, we plan to construct the UV bump in the extinction curve towards B type stars brighter than mv = 14. Archival data of TD1, Galex missions are used for stars brighter than mv = 10. We sample the distance to obtain the extintion at different location of the local ISM upto 2 kpc. Using a dust model having silicate, graphite and PAH as components, the extinction curve at different location of the Galaxy is fitted to constrain the dust characteristics.
Dehydrogenated coronene cations and interstellar extinction
Authors: Malloci G. , Mulas G. , Cecchi–Pestellini C. , Useli–Bacchitta F. , Bonnamy A. , Joblin C.
Published: October 2008

Dehydrogenated coronene molecules have been proposed as the carrier of the interstellar UV extinction bump and of some diffuse interstellar bands. To test this hypothesis, we have undertaken a combined a) theoretical and b) experimental work on the subject. a) We use the (time–dependent) density functional theory to study the effect of hydrogenation on the UV absorption cross–section of neutral and ionised coronene molecules. b) For the visible and near–UV, these calculations provide useful guidelines to analyse and interpret the electronic spectra obtained with the PIRENEA experimental set-up dedicated to astrochemistry.
Composite interstellar grains and the 2175Å feature
Authors: Vaidya Deepak B. , Gupta Ranjan
Published: October 2008

We use discrete dipole approximation (DDA) to study the scattering properties of composite grains made up of host silicate spheroids and graphite inclusions. We calculate the extinction cross sections of the composite grains in the wavelength region 0.20–0.55 μm and study the extinction of the composite grains as a function of graphite inclusions. We present the composite grain model and discuss the results.
Models and observations of deuterated molecules in protostellar cores
Authors: Roberts H.
Published: October 2008

Measuring the deuterium fractionation in different molecules can allow one to determine the physical conditions in the gas and to differentiate between gas-phase and grain surface chemical processing. Observations of molecular D/H ratios in different species towards the dense gas surrounding low-mass protostars are presented and are compared with model simulations. These consider gas-phase chemistry, accretion and desorption, and reactions on grain surfaces during the initial stages of core collapse.
Complex chemistry in star-forming regions
Authors: Garrod Robin T. , Widicus Weaver Susanna L. , Herbst Eric
Published: October 2008

We present a new gas-grain chemical model that allows the grain-surface formation of saturated, complex, organic species from their constituent functional-groups–basic building blocks that derive from the cosmic ray-induced photodissociation of the granular ice mantles. The surface mobility of the funtional-group radicals is crucial to the reactions, and much of the formation of complex molecules occurs at the intermediate temperatures (~20–40 K) attained during the warm-up of the hot core. Our model traces the evolution of a large range of detected, and as yet un-detected, complex molecules.
Molecular gas dynamics in the Rosette Nebula
Authors: Matthews Henry E. , Dent William R. F.
Published: October 2008

We present observations of the Rosette Nebula and its near environment in the CO 3–2 transition obtained with an angular resolution of 20″. The gas dynamics of the region are complex; we find (1) a ring of gas expanding at about 20 km s−1, (2) a number of collimated outflow sources, and (3) a chain of dust clumps having a velocity gradient along its length.
Molecular evolution in star-forming cores: From prestellar cores to protostellar cores
Authors: Aikawa Yuri , Wakelam Valentine , Sakai Nami , Garrod R. T. , Herbst E. , Yamamoto Satoshi
Published: October 2008

We investigate the molecular abundances in protostellar cores by solving the gas-grain chemical reaction network. As a physical model of the core, we adopt a result of one-dimensional radiation-hydrodynamics calculation, which follows the contraction of an initially hydrostatic prestellar core to form a protostellar core. Temporal variation of molecular abundances is solved in multiple infalling shells, which enable us to investigate the spatial distribution of molecules in the evolving core. The shells pass through the warm region of T ~ 20–100 K in several 104 yr and falls onto the central star in ~100 yr after they enter the region of T > 100 K. We found that the complex organic species such as HCOOCH3 are formed mainly via grain-surface reactions at T ~ 20–40 K, and then sublimated to the gas phase when the shell temperature reaches their sublimation temperatures (T ≥ 100 K). Carbon-chain species can be re-generated from sublimated CH4 via gas-phase and grain-surface reactions. HCO2+, which is recently detected towards L1527, are abundant at r = 100–2,000 AU, and its column density reaches ~1011 cm−2 in our model. If a core is isolated and irradiated directly by interstellar UV radiation, photo-dissociation of water ice produces OH, which reacts with CO to form CO2 efficiently. Complex species then become less abundant compared with the case of embedded core in ambient clouds. Although a circumstellar (protoplanetary) disk is not included in our core model, we can expect similar chemical reactions (i.e., production of large organic species, carbon-chains and HCO2+) to proceed in disk regions with T ~ 20–100 K.
Organic chemistry in circumstellar envelopes: Setting the stage for prebiotic synthesis
Authors: Ziurys Lucy M.
Published: October 2008

One of the few carbon-rich environments found in interstellar space is the ejecta of asymptotic giant branch (AGB) stars. Such material, which forms a circumstellar envelope, becomes enriched in carbon due to “dredge-up” phenomena associated with nucleosynthesis. A unique organic synthesis flourishes in the gas phase in these envelopes, and radio and millimeter observations have identified a wide range of C-bearing compounds, including long acetylenic chains such as HC5N, HC7N, C4H, C6H, C8H, C6H−, C8H−, and C3O. Oxygen-rich envelopes also have a non-negligible carbon chemistry, fostering species such as HCN and HCO+. Phosphorus chemistry appears to be active as well in circumstellar shells, as evidenced by the recent detections of HCP, CCP, and PO. Radio observations also indicate that some fraction of the circumstellar molecular material survives into the planetary nebula stage, and then becomes incorporated into diffuse, and eventually, dense clouds. The complex organic molecules found in dense clouds such as Sgr B2(N) may be the products of “seed” material that can be traced back to the carbon-enriched circumstellar gas.
Organic molecular anions in interstellar and circumstellar environments
Authors: Cordiner M. A. , Millar T. J. , Walsh C. , Herbst E. , Lis D. C. , Bell T. A. , Roueff E.
Published: October 2008

The synthesis of organic molecular anions in TMC-1 and IRC+10216 is investigated. Modelled C2H−, CN−, C3N−, C5N− and C7N− column densities are sufficiently great that these species might be observable in IRC+10216. Density-enhanced shells in the outer envelope of IRC+10216 are found to enhance the C2H− and CN− column densities by shielding these anions from destruction by UV radiation. From a newly-derived upper column density limit of 6.6 × 1010 cm−2 for C2H− in IRC+10216 we deduce the primary production mechanism for this anion to be C2H2 + H− ⇒ C2H− + H2. In TMC-1, due to the low radiative electron attachment rates calculated for C2H−, CN− and CH2CN−, these species have modelled column densities below the detection threshold. They could, however, be produced in reactions we have not yet considered.
Circumstellar H2O in M-type AGB stars
Authors: Maercker Matthias , Schöier Fredrik L. , Olofsson Hans
Published: October 2008

Surprisingly high amounts of H2O have recently been reported in the circumstellar envelope around the M-type AGB star W Hya. However, substantial uncertainties remain, as the required radiative transfer modelling is difficult due to high optical depths, sub-thermal excitation and the sensitivity to the combined radiation field from the central star and dust grains.
Unidentified infrared bands and the formation of PAHs around carbon stars
Authors: Speck Angela , Barlow Mike , Wesson Roger , Clayton Geoff , Volk Kevin
Published: October 2008

Although unidentified infrared bands (UIBs) have been observed in many astrophysical environments, there is one notable exception: carbon (C) stars. Only a handful of C stars have been shown to emit UIBs and most have hot companions. This makes C stars with hot companions an ideal location to investigate the emitters of the UIBs. PAHs are excited by absorption of single photons whose energy is then distributed over the whole molecule. These molecules then emit the energy at the characteristic wavelengths, but the precise wavelengths and strength ratios depend on the size, composition and charge state of the individual PAHs. Furthermore, the wavelength of photons needed to excite PAHs depends on their size and charge state. While small PAHs undoubtedly need higher energy (UV) photons, it has been suggested that large or ionized PAHS (>100 C atoms) can be excited by visible or even near-IR photons. The lack of PAH emission from single carbon stars suggests that either PAHs do not form around C stars or that only small neutral grains form, which cannot be excited by a C star's radiation field.

There are two competing formation mechanisms for PAHs around C stars: (1) “bottom-up” where acetylene molecules react to form aromatic rings, building up to PAHs; or (2) “top-down”, where small carbon grains react with H atoms and desorb PAHs

Using spatially resolved spectroscopic observations from Gemini/Michelle, of five carbon stars with hot companions, we investigate the circumstance under which PAH emission occurs and try to discriminate between formation mechanisms.
Probing chemical processes in AGB stars
Authors: Schöier Fredrik L. , Olofsson Hans
Published: October 2008

We are conducting multi-transition observations of circumstellar line emission from common molecules such as HCN, SiO, CS, SiS and CN for a large sample of AGB stars with varying photospheric C/O-ratios and mass-loss charachteristics. Our recently published results for SiO and SiS clearly show that major constraints on the relative roles of non-equilibrium chemistry, dust condensation, and photodissociation can be obtained from the study of circumstellar molecular line emission. Presented here are also preliminary results based on detailed radiative transfer modelling of HCN line emission.
Aromatic, aliphatic, and the unidentified 21 micron emission features in proto-planetary nebulae
Authors: Hrivnak Bruce J. , Volk Kevin , Geballe T. R. , Kwok Sun
Published: October 2008

Aromatic features at 3.3, 6.2, 7.7, 8.6, 11.3 μm are observed in proto-planetary nebulae (PPNe) as well as in PNe and H ii regions. Aliphatic features at 3.4 and 6.9 μm are also observed; however, these features are often stronger in PPNe than in PNe. These observations suggest an evolution in the features from simple molecules (C2H2) in AGB stars to aliphatics in PPNe to aromatics in PNe. In the same carbon-rich PPNe, a strong, broad, unidentified 21 μm emission feature has been found. We will present recent observations of the aromatic, aliphatic, and 21 μm emission features, along with C2H2 (13.7 μm) and a new feature at 15.8 μm, and discuss correlations among them and other properties of these PPNe.
Mapping the PAHs and H2 in ρ Oph A
Authors: Justtanont Kay , Liseau René , Larsson Bengt
Published: October 2008

We present an ISOCAM-CVF map of the ρ Oph A region, covering 3′ × 3′. For each 6 arcsec2 pixel, we extract the spectrum from 5–15 μm. We determine the fluxes of the main PAH features by fitting Lorentzian profiles to the spectrum. The peaks of the various PAH components correspond well with the known positions of the PDRs in this vicinity. The spectrum in several pixels exhibits strong rotational lines of molecular hydrogen which can be used to derive the physical properties of the cloud. The H2 emission traces the hot gas of the bipolar CO outflow from VLA1623.
Properties of polycyclic aromatic hydrocarbons in the star forming environment in nearby galaxies
Authors: Sakon Itsuki , Onaka Takashi , Kato Daisuke , Kaneda Hidehiro , Kataza Hirokazu , Okada Yoko , Kawamura Akiko , Onishi Toshikazu , Fukui Yasuo
Published: October 2008

We have carried out the mid-infrared slit spectroscopic observations of sources in the LMC and in NGC 6946 with AKARI/IRC. We investigate the properties of the UIR bands in terms of the star forming activities. We find systematically larger ratios of UIR bands in 6–9 μm to 11.2 μm band in active star forming regions than in the quiet regions. This behavior is consistent with the photo-ionization model of PAHs. Our results suggest that the ratios of UIR bands in 6–9 μm to 11.2 μm band can be used as more efficient and vigorous tools to measure the extent of on-going star formation in remote galaxies rather than just the presence or absence of the features themselves.
Detection of the unidentified infrared bands in a filament of the dwarf galaxy NGC1569
Authors: Matsumoto H. , Onaka T. , Sakon I. , Kaneda H.
Published: October 2008

We made near- to mid-infrared imaging and spectroscopic observations of the dwarf galaxy NGC 1569 with the Infrared Camera (IRC) on board AKARI. The unidentified infrared (UIR) band features at 6.2, 7.7, and 11.2 μm, which are generally attributed to polycyclic aromatic hydrocarbons (PAHs), are clearly detected in a structure associated with an Hα filament. The filament is filled with X-ray emission and is thought to be formed by outflow from the galaxy. Since PAHs are destroyed rapidly in hot plasma, it is most likely that PAHs in the filament are produced from fragmentation of large carbonaceous grains in the shock. We also detect excess emission in 2–5 μm in the filament, which may come from very small grains.
Spectra of nearby galaxies measured with a new very broadband receiver
Authors: Narayanan Gopal , Snell Ronald L. , Erickson Neal R. , Chung Aeree , Heyer Mark H. , Yun Min , Irvine William M.
Published: October 2008

Three-millimeter-wavelength spectra of a number of nearby galaxies have been obtained at the Five College Radio Astronomy Observatory (FCRAO) using a new, very broadband receiver. This instrument, which we call the Redshift Search Receiver, has an instantaneous bandwidth of 36 GHz and operates from 74 to 110.5 GHz. The receiver has been built at UMass/FCRAO to be part of the initial instrumentation for the Large Millimeter Telescope (LMT) and is intended primarily for determination of the redshift of distant, dust-obscured galaxies. It is being tested on the FCRAO 14 m by measuring the 3 mm spectra of a number of nearby galaxies. There are interesting differences in the chemistry of these galaxies.
Organic matter in interplanetary dust particles
Authors: Flynn G. J. , Keller L. P. , Wirick S. , Jacobsen C.
Published: October 2008

Anhydrous interplanetary dust particles (IDPs), which are the most mineralogically primitive extraterrestrial materials available for laboratory analysis, contain several percent organic matter. The high O:C and N:C ratios suggest the organic matter in the anhydrous IDPs is significantly less altered by thermal processing than the organic matter in meteorites. X-ray Absorption Near-Edge Structure (XANES) spectroscopy and infrared spectroscopy demonstrate the presence of C=C, most likely as C-rings, C=O, and aliphatic C-H2and C-H3in all the IDPs examined. A D-rich spot, containing material that is believed to have formed in a cold molecular cloud, has C-XANES and infrared spectra very similar to the organic matter in the anhydrous IDPs, possibly indicating a common formation mechanism. However the primitive organic matter in the IDPs differs from the interstellar/circumstellar organic matter characterized by astronomical infrared spectroscopy in the relative strengths of the asymmetric aliphatic C-H2and C-H3absorptions, with the IDP organic having a longer mean chain length. If both types of organic matter originated by the same process, this may indicate the interstellar organic matter has experienced more severe radiation processing than the organic matter in the primitive IDPs.
Unraveling the chemical history of the Solar System as recorded in extraterrestrial organic matter
Authors: Cody George D. , Alexander Conel M. O'D. , Kilcoyne A. L. David , Yabuta Hikaru
Published: October 2008

We have initiated an extensive program of molecular analysis of extraterrestrial organic matter isolated from a broad range of meteorites (spanning multiple classes, groups, and petrologic types), including recent molecular spectroscopic analyses of the organic matter in the Comet 81P/Wild 2 samples. The results of these analyses clearly reveal the signature of multiple reaction pathways that transformed extraterrestrial organic matter away from its primitive roots. The most significant molecular transformation occurred in the post-accretionary phase of the parent body. However, each of the various chemical transformation trajectories point unambiguously back to a common primitive origin. Applying a wide range of spectroscopic techniques we find that the primitive organic precursor is striking in its chemical complexity exhibiting a broad array of oxygen- and nitrogen-bearing functional groups. The π-bonded carbon exists as predominately highly substituted single ring aromatics, there exists no evidence for abundant, large, polycyclic aromatic hydrocarbons (PAHs). We find that the molecular structure of primitive extraterrestrial organics is consistent with synthesis from small reactive molecules, e. g. formaldehyde, whose random condensation and subsequent rearrangement chemistry at low temperatures leads to a highly cross-linked macromolecule.
Organics in meteorites - Solar or interstellar?
Authors: Alexander Conel M. O'D. , Cody George D. , Fogel Marilyn , Yabuta Hikaru
Published: October 2008

The insoluble organic material (IOM) in primitive meteorites is related to the organic material in interplanetary dust particles and comets, and is probably related to the refractory organic material in the diffuse interstellar medium. If the IOM is representative of refractory ISM organics, models for how and from what it formed will have to be revised.
Laboratory experiments as support to the built up of Titan's theoretical models and interpretation of Cassini-Huygens data
Authors: Gazeau Marie-Claire , Benilan Yves , Es-sebbar Et Touhami , Ferradaz Thomas , Hébrard Eric , Jolly Antoine , Raulin François , Romanzin Claire , Guillemin Jean-Claude , Berteloite Coralie , Canosa André , Le Picard Sébastien D. , Sims Ian R.
Published: October 2008

To interpret the concentrations of the products measured in Titan's atmosphere and to better understand the associated chemistry, many theoretical models have been developed so far. Unfortunately, large discrepancies are still found between theoretical and observational data. A critical examination of the chemical scheme included in these models points out some problems regarding the reliability of the description of critical reaction pathways as well as the accuracy of kinetic parameters. Laboratory experiments can be used to reduce these two sources of uncertainty. It can be:

i) experimental simulations: in our laboratory (LISA), representative Titan's simulation experiments are planned to be carried out in a reactor where the initial gas mixture will be exposed, for the first time, to both electrons and photons. Thus, the chemistry between N atoms and CH3, CH2, CH fragments, issued from electron dissociation of N2 and photo-dissociation of CH4 respectively, will be initiated. Thank to a time resolved technique, we will be able to analyse “in situ”, qualitatively and quantitatively, the stable species as well as the short life intermediates. Then, the implied chemistry will be determined precisely, and consequently, its description will be refined in theoretical models. The current status of this program will be given.

ii) specific experiments: they are devoted, for example, to determine kinetic rate constants and low temperature VUV spectra that will be used to feed models and to interpret observational data. Such experiments performed in LISA and in Rennes' laboratory concern polyynes and cyanopolyynes as these compounds could link the gaseous and the solid phase in planetary atmosphere. Results concerning C4H+ hydrocarbons kinetic rate constants and VUV cross section of HC3N and HC5N will be detailed.
The source of heavy organics and aerosols in Titan's atmosphere
Authors: Waite J. H. , Young D. T. , Coates A. J. , Crary F. J. , Magee B. A. , Mandt K. E. , Westlake J. H.
Published: October 2008

Ion-neutral chemistry in Titan's upper atmosphere (~ 1000 km altitude) is an unexpectedly prodigious source of hydrocarbon-nitrile compounds. We report observations from the Cassini Ion Neutral Mass Spectrometer (INMS; Waite et al. 2004) and Cassini Plasma Spectrometer (CAPS; Young et al. 2004) that allow us to follow the formation of the organic material from the initial ionization and dissociation of nitrogen and methane driven by several free energy sources (extreme ultraviolet radiation and energetic ions and electrons) to the formation of negative ions with masses exceeding 10,000 amu.
Possibilities of lightning-induced processes in gas-dusty atmosphere of water-containing bodies of Solar System
Authors: Serozhkin Yuriy
Published: October 2008

Lightning is considered as one of energy sources for synthesis of biochemical compounds. Numerous theoretical and experimental researches of gas-grain chemistry show that chemical reactions on the gas - ice boundary play a considerable role in such synthesis. In this connection the greatest interest represents studying lightning in gas-dusty atmospheres of water-containing bodies (comets, ice satellites of Jupiter and Saturn).
Micro-Raman study of nanodiamonds from Allende meteorite
Authors: Gucsik Arnold , Ott Ulrich , Marosits Edit , Karczemska Anna , Kozanecki Marcin , Szurgot Marian
Published: October 2008

We have studied the Raman spectroscopic signatures of nanodiamonds from the Allende meteorite in which some portions must be of presolar origin as indicated by the isotopic compositions of various trace elements. The spectra of the meteoritic nanodiamond show a narrow peak at 1326 cm−1 and a broad band at 1590 cm−1. Compared to the intensities of these peaks, the background fluorescence is relatively high. A significant frequency shift from 1332 to 1326 cm−1, peak broadening, and appearance of a new peak at 1590 cm−1 might be due to shock effects during formation of the diamond grains. Such changes may have several origins: an increase in bond length, a change in the electron density function or charge transfer, or a combination of these factors. However, Raman spectroscopy alone does not allow distinguishing between a shock origin of the nanodiamonds and formation by a CVD process as is favored by most workers.
Stardust in meteorites: A link between stars and the Solar System
Authors: Zinner Ernst
Published: October 2008

Ultimately, all of the solids in the Solar System, including ourselves, consist of elements that were made in stars by stellar nucelosynthesis. However, most of the material from many different stellar sources that went into the making of the Solar System was thoroughly mixed, obliterating any information about its origin. An exception are tiny grains of preserved stardust found in primitive meteorites, micrometeorites, and interplanetary dust particles. These μm- and sub-μm-sized presolar grains are recognized as stardust by their isotopic compositions, which are completely different from those of the Solar System. They condensed in outflows from late-type stars and in SN ejecta and were included in meteorites, from which they can be isolated and studied for their isotopic compositions in the laboratory. Thus these grains constitute a link between us and our stellar ancestors. They provide new information on stellar evolution, nucleosynthesis, mixing processes in asymptotic giant branch (AGB) stars and supernovae, and galactic chemical evolution. Red giants, AGB stars, Type II supernovae, and possibly novae have been identified as stellar sources of the grains. Stardust phases identified so far include silicates, oxides such as corundum, spinel, and hibonite, graphite, silicon carbide, silicon nitride, titanium carbide, and Fe-Ni metal.
The flux of interstellar particles detected in the Solar System
Authors: Hajduková Mária
Published: October 2008

The present work shows the proportion of interstellar meteors from different mass ranges (exceeding 20 orders of mass scale) detected by various observational techniques. Having analysed the IAU Meteor Data Center, we find that the mass index of interstellar particles continuously increases towards higher masses, but there is a significant change between 10−10 − 10−11 kg. This break is possibly caused by different physical processes leading to different populations of interstellar particles and might be connected with their origin.
The occurence of interstellar meteoroids in the vicinity of the Earth
Authors: Hajduková Mária
Published: October 2008

If interstellar meteors are present among the registered meteor orbits, the distribution of the excesses of their heliocentric velocities should correspond to the distribution of radial velocities of close stars. Hence, for the velocity vi = 20 kms−1 of an interstellar meteor (with respect to the Sun) we obtain a heliocentric velocity vH = 46.6 kms−1 of an interstellar meteor arriving at the Earth. Moreover, a concentration of radiants to the Sun's apex should be observed. An analysis of the hyperbolic meteors among the 4581 photographic orbits of the IAU Meteor Data Center showed that the identification of the vast majority of the hyperbolic orbits in these catalogues has been caused by an erroneous determination of their heliocentric velocity and/or other parameters. Any error in the determination of vH, especially near the parabolic limit, can create an artificial hyperbolic orbit that does not really exist. On the basis of photographic meteors from the IAU MDC, the proportion of possible interstellar meteors decreased significantly (greater than 1 order of magnitude) after error analysis and does not exceed the value 2.5 × 10−4. Neither any concentration of radiants to the Sun's apex, nor any distribution following the motion of interstellar material has been found.
Theoretical PAH emission models for aromatic infrared bands
Authors: Pathak Amit , Rastogi Shantanu
Published: October 2008

Aromatic Infrared Bands (AIBs) show significant profile variations in different astrophysical environments. Theoretical IR data is used to develop emission models to understand these variations. A good match with the observed “7.7” μm feature from different regions is obtained.
Survival of gas phase amino acids and nucleobases in space radiation conditions
Authors: Pilling S. , Andrade D. P. P. , de Castilho R. B. , Cavasso-Filho R. L. , Lago A. F. , Coutinho L. H. , de Souza G. G. B. , Boechat-Roberty H. M. , de Brito A. Naves
Published: October 2008

We present experimental studies on the photoionization and photodissociation processes (photodestruction) of gaseous amino acids and nucleobases in interstellar and interpla-netary radiation analogs conditions. The measurements have been undertaken at the Brazilian Synchrotron Light Laboratory (LNLS), employing vacuum ultraviolet (VUV) and soft X-ray photons. The experimental set up basically consists of a time-of-flight mass spectrometer kept under high vacuum conditions. Mass spectra were obtained using a photoelectron photoion coincidence technique. We have shown that the amino acids are effectively more destroyed (up to 70–80%) by the stellar radiation than the nucleobases, mainly in the VUV. Since polycyclic aromatic hydrocarbons have the same survival capability and seem to be ubiquitous in the ISM, it is not unreasonable to predict that nucleobases could survive in the interstellar medium and/or in comets, even as a stable cation.
Formation of alcohols on ice surfaces
Authors: Cuppen H. M. , Fuchs G. W. , Ioppolo S. , Bisschop S. E. , Öberg K. I. , van Dishoeck E. F. , Linnartz H.
Published: October 2008

As the number of detections of complex molecules keeps increasing, answering the question about their formation becomes more pressing. Many of the saturated organic molecules are found to have a very low gas phase formation rate and are therefore thought to be formed on the icy surfaces of dust grains. In the Sackler Laboratory for Astrophysics we started a systematic study of the surface reaction routes that have been suggested over the years. Here we present the experimental results on the formation of methanol and ethanol by hydrogenation reactions of carbon monoxide and acetaldehyde ice. Computer simulations of the surface processes under similar conditions using the continuous-time random-walk Monte Carlo technique reveal some of the underlying physical processes. A better understanding of the physical conditions in which these molecules are formed can help in the interpretation of the observational results. The CO hydrogenation results will appear in detail in Fuchs et al. (2008). For more details on ethanol formation we refer to Bisschop et al. (2007).
Electronic spectra of carbon chains and rings: Astrophysical relevance?
Authors: Jochnowitz Evan B. , Maier John P.
Published: October 2008

Our research has focused on the measurement of the electronic spectra of unstable molecules which are presumed to be of relevance to astrophysical observations. Among these are the carbon chains and their ions. Thus we have been using and developing a number of spectroscopic methods to determine their spectra in the gas phase, including absorption via cavity ring-down and REMPI methods. The species are produced in supersonic jets coupled with discharge and laser ablation sources. With the successful laboratory detection of the electronic spectra of a number of key species, such as bare carbon chains Cnn=4,5, comparisons with astrophysical data could be made which lead to interesting implications for the future search for the species which could be responsible for the diffuse interstellar bands. Among the recent relevant observations in the laboratory have been the electronic spectra of carbon rings, Cnn=14,18,22, the development of a method to study transitions in mass-selected ions collisionally relaxed to 20 K and held in a 22-pole radiofrequency trap, and the study of metal containing carbon chains.
In situ observation of structural alteration process of filmy quenched carbonaceous composite
Authors: Kumamoto Akihito , Kimura Yuki , Kaito Chihiro , Wada Setsuko
Published: October 2008

The thermal alteration process of filmy quenched carbonaceous composite (filmy QCC) has been studied in situ by high-resolution transmission electron microscopy (HRTEM). HRTEM images of the as-prepared filmy QCC showed the typical amorphous carbon film structure. By heating above 300 °C, the structural alteration takes place. Curled graphene structure started to appear at 300 °C. Distorted onion-like structure similar to dark QCC appeared above 500 to 700 °C. The distorted onion-like structure that appears at 700 °C after heating for 30 minutes also appeared by heating at 450 °C for 2 hours.
Reactions of aromatics in space and connections to the carbon chemistry of Solar System materials
Authors: Bernstein Max
Published: October 2008

Polycyclic aromatic hydrocarbons (PAHs) and related aromatic materials are thought to be the most abudant class of organic carbon in the universe, being present in virtually all phases of the ISM, and abundant in carbonaceous meteorites and asteroid and comet dust. The basic PAH skeleton is proposed to have formed in outflows of carbon rich stars, and isotopic measurements of extraterrestrial graphitic carbon is consistent with this notion. However, functionalized aromatics bearing oxygen atoms, aliphatic domains, and deuterium enrichments have been extracted from meteorites and more recently been measured in IDPs and Stardust retuned comet samples. Exposure of remnant circumstellar PAHs to energetic processing at low temperature in the presense of H2O is the most parsimonious explanation for these observations.

We will present laboratory infrared spectra of various aromatic species and PAH cations in solid H2O under conditions relevant for comparsion to absorptions attributed to PAHs observed towards objects embedded in dense clouds. In addition, we shall describe the reactions of PAHs under these conditions in the lab when they are exposed to energetic processing. Finally, we will propose a mechanism, and make specific predictions regarding the structures and distribution of deuterium that should be observed in extraterrestrial samples if low temperature ice radiation chemistry is playing a role in the formation of the molecules seen in Solar System materials.
Optical and chemical properties of tholins
Authors: Khare Bishun N. , McKay Christopher P. , Cruikshank Dale P. , Sekine Yasuhito , Wilhite Patrick , Ishihara Tomoko
Published: October 2008

For over three decades tholins have been synthesized from mixtures of the cosmically abundant gases CH4, C2H6, NH3, H2O, HCHO, N2, and H2, previously in the Laboratory for Planetary Studies at Cornell University and in recent years at NASA Ames Research Center. The tholin synthesized by UV light or spark discharge on sequential and non-sequential pyrolysis GC-MS revealed hundreds of compounds, and on hydrolysis produced a large number of amino acids including racemic protein amino acids. Optical constants have been measured of many of the tholins, tholins produced from a condensed mixture of water and ethane at 77 K, poly HCN, and Titan tholin produced on electrical discharge through a mixture of 90% N2 and 10% CH4. Its optical constants were measured from soft x-rays to microwave for the first time.

Here we report the absorption properties of Titan tholin that is produced in the temperature range 135 to 178 K where tholins are produced by magnetospheric charged particles, then pass through lower temperature at 70 K and finally to the ground at 95 K. While descending to the ground, it gets coated and processed on the way by other sources of energy such as long UV and cosmic rays. It is therefore expected that the stable products of CH4 photolysis react with Titan tholin to recycle the CH4 supply in Titan's atmosphere. Furthermore, the reactions of gaseous C2H6 with the reactive materials on the surface of the tholin could incorporate atmospheric C2H6 into the tholin and therefore might reduce the deposition rate of C2H6 onto the ground of Titan.
Photochemistry of interstellar/circumstellar ices as a contributor to the complex organics in meteorites
Authors: Nuevo Michel , Sandford Scott A.
Published: October 2008

The UV irradiation of interstellar/circumstellar ice analogs is known to lead to the formation of organic compounds such as amino acids and maybe nucleobases. In this work, the mechanisms of formation and distribution of amino acids, chosen as tracers for the organic compounds formed in such experiments, are studied and compared with meteoritic data.
Radiation chemistry approach to the study of ice analogs
Authors: Colin-Garcia Maria , Negrón-Mendoza Alicia , Ramos-Bernal Sergio
Published: October 2008

The aim of this work is to study the chemistry of the irradiation of frozen solutions of HCN. This compound has been detected in comets and other icy bodies. The CN group might have made its first appearance in the early stages of chemical evolution. Therefore, is behavior under irradiation at low temperature is relevant for chemical evolution studies and icy bodies.
Formation of amino acid precursors with large molecular weight in dense clouds and their relevance to origins of bio-homochirality
Authors: Kobayashi Kensei , Kaneko Takeo , Takano Yoshinori , Takahashi Jun-ichi
Published: October 2008

A wide variety of organic compounds have been found in carbonaceous chondrites and comets, which suggests that extraterrestrial organic compounds could have been an important source of the first terrestrial biosphere. In the Greenberg model, these organic compounds in the small bodies were originally formed in interstellar dusts (ISD) in dense clouds by the action of cosmic rays and ultraviolet light. We irradiated a frozen mixture of methanol, ammonia and water with high-energy heavy ions from an accelerator (“HIMAC” in NIRS, Japan) to simulate the action of cosmic rays in dense clouds. Racemic mixtures of amino acids were detected after hydrolysis of the irradiation products. A mixture of carbon monoxide, ammonia and water also gave such complex amino acid precursors with large molecular weights. When such amino acid precursors were irradiated with circular polarized UV light from a synchrotron, enantiomeric excesses were detected. The yield of amino acids was not largely changed between, before, and after CPL-irradiation. The present results suggest that the seed of homochirality of terrestrial amino acids were originally formed in interstellar space.
High-power laser-plasma chemistry in planetary atmospheres
Authors: Civiš Svatopluk , Juha Libor
Published: October 2008

Large laser sparks created by a single shot of a high-power laser system were used for the laboratory simulation of the chemical consequences of high-energy-density events (lightning, high-velocity impact) in planetary atmospheres, e.g., the early Earth's atmosphere.
Guanine synthesis from interstellar organic molecules as an example of prebiotical chemistry
Authors: Medellin Adriana Patricia Lozano
Published: October 2008

The idea that some nitrogen bases, such as adenine and guanine, are easily formed and can be found in interstellar space is should not be rejected. In fact, they have been found in the soluble fraction of some ancient meteors. It is possible that the “seed” of life had its origin in space, and thanks to Earth conditions, a synergistic interaction ocurred and allowed life to spring forth on our planet.
ATM and Chk2 kinase target the p53 cofactor Strap
Authors: Adams Cassandra J , Graham Anne L , Jansson Martin , Coutts Amanda S , Edelmann Mariola , Smith Linda , Kessler Benedikt , La Thangue Nicholas B
Published: October 2008

The p53 cofactor Strap (stress responsive activator of p300) is directly targeted by the DNA damage signalling pathway where phosphorylation by ATM (ataxia telangiectasia mutated) kinase facilitates nuclear accumulation. Here, we show that Strap regulation reflects the coordinated interplay between different DNA damage‐activated protein kinases, ATM and Chk2 (Checkpoint kinase 2), where phosphorylation by each kinase provides a distinct functional consequence on the activity of Strap. ATM phosphorylation prompts nuclear accumulation, which we show occurs by impeding nuclear export, whereas Chk2 phosphorylation augments protein stability once Strap has attained a nuclear location. These results highlight the various functional roles undertaken by the DNA damage signalling kinases in Strap control and, more generally, shed light on the pathways that contribute to the regulation of the p53 response.
Efficient approaches for characterizing ubiquitinated proteins
Authors: Hjerpe Roland , Rodríguez Manuel S.
Published: October 2008

Post-translational modification of proteins offers a rapid route to change the activity of crucial factors within the cell. One of the more drastic post-translational modifications, in terms of effect on biochemical properties, is the covalent attachment of the small protein ubiquitin, to a target factor. The labile nature of some post-translational modifications puts obstacles in the path of attempting to detect modified species of most proteins. Indeed, ubiquitination can be rapidly reversed by the action of a large family of DUBs (deubiquitinating enzymes), most of which are cysteine proteases. This, taken together with the rapid proteasomal degradation of some species of ubiquitinated proteins, results in difficulties in detecting modified targets. In this review, practical approaches developed for the detection, purification and characterization of ubiquitinated proteins are reviewed. After a brief appraisal of the use of histidine-tagged ubiquitin, focus is placed on development of UBD (ubiquitin-binding domain)–ubiquitin affinity purification.
Analysis of eicosanoids and related lipid mediators using mass spectrometry
Authors: Maskrey Benjamin H. , O'Donnell Valerie B.
Published: October 2008

Eicosanoids are oxidized arachidonate-derived lipids products generated by lipoxygenase, cyclo-oxygenase and cytochrome P450. Their bioactivity is mediated via receptor-dependent mechanisms and they are involved in a diverse array of processes in both health and disease. For many years, GC–MS was the method of choice for eicosanoid analysis, but, more recently, the availability of high-sensitivity electrospray LC (liquid chromatography)–MS/MS (tandem MS) has provided a new approach for quantification, while minimizing sample preparation. The present review summarizes the various methods available for routine quantification of eicosanoids, focusing ultimately on their analysis using a hybrid Q-Trap mass spectrometer.
How Change Does Not Happen: The Impact of Culture on a Submarine Base
Authors: Losekoot Erwin , Leishman Emma , Alexander Matthew
Published: October 2008

This study was part of a Knowledge Transfer Partnership project involving the University of Strathclyde and Royal Navy Base Faslane on the Clyde. The main focus was a market research study to assist in the development of a retail hub for service personnel and civilians to use while on the base. In the course of the study, it was noted how many obstacles to change there were. The researchers have used Johnson's concepts of the cultural web and organisational paradigm to identify what the ‘blockages’ to change are, and suggest a number of possible ways of addressing these issues. The research suggests that this phenomenon may become more common as more public organisations develop partnerships with private organisations, leading to the potential for clashes of corporate and personal cultures.
Effect of molecular weight of poly(N-vinyl carbazole) on photorefractive performances
Authors: Tsutsumi Naoto , Kasaba Hideto
Published: October 2008

We present here the effect of molecular weight of poly(N-vinyl carbazole) (PVCz) on photorefractive performances. Photorefractive composites with higher molecular weight of PVCz led to higher diffraction efficiency and faster speed of grating buildup. The fastest response time of 18 ms (grating buildup speed of 55.6 s−1) was obtained at 45 V μm−1. Higher diffraction efficiency and faster buildup speed of photorefractive composite with higher molecular weight of PVCz was ascribed to the larger Pockels effect due to larger number density of traps. Dimer cation sites preferentially formed along the longer molecular chain in higher molecular weight of PVCz seem to work as effective traps for hole carriers.
Integrated setup for the fabrication and measurement of magnetoresistive nanoconstrictions in ultrahigh vacuum
Authors: Stickler Daniel , Frömter Robert , Li Wei , Kobs André , Oepen Hans Peter
Published: October 2008

A UHV instrument is presented for in situ fabrication of nanostructures and in situ investigation of their magnetoresistance. Nanostructures of diverse shape and size are created from thin films utilizing a focused ion beam. The magnetic nanostructures are contacted via a micromanipulator, which makes it possible to address the individual structures. The system is additionally equipped with a scanning electron microscope column, which is used for damage-free navigation and control of the structuring and contacting. First magnetoresistance measurements of structures carved into a Permalloy film demonstrate the high sensitivity and the flexibility of the new setup.